Miscarriage: When a beginning is not a beginning

The “Pregnant Woman” statue
at Ireland Park, Toronto, by Rowan Gillespie

Photo credit: Benson Kua.
[Editor's note: We are pleased to be able to run this post by Dr. Kate Clancy that first appeared at Clancy's Scientific American blog, the wonderful Context and Variation. Clancy is an Assistant Professor of Anthropology at the University of Illinois. She studies the evolutionary medicine of women’s reproductive physiology, and blogs about her field, the evolution of human behavior and issues for women in science. You can follow her on Twitter--which we strongly recommend, particularly if you're interested in human behavior, evolutionary medicine, and ladybusiness--@KateClancy.]
Over the course of my training to become a biological anthropologist with a specialty in women’s reproductive ecology and life history theory, or ladybusiness expert, I have learned a lot about miscarriage. Only it wasn’t miscarriage, it was spontaneous abortion. Except that some didn’t like the term spontaneous abortion and used intrauterine mortality (Wood, 1994). Or fetal loss. Fetal loss is probably the most common.
There is also pregnancy loss (Holman and Wood, 2001). You can use that term, too. Oh, or a Continue reading

Childbirth and C-sections in pre-modern times

[Today's post first appeared at Dr. Kristina Killgrove's blog, Powered by Osteons. Kristina is a bioarchaeologist who studies the skeletons of ancient Romans to learn more about how they lived. Her biography at her blog begins, "When your life's passion is to study dead Romans, you often get asked for your 'origin story,' something that explains a long, abiding and, frankly, slightly creepy love for skeletons." Now that you undoubtedly want to know more, read the rest of her bio here, and then read below to learn why childbirth is so difficult and what the archaeological record has to tell us about outcomes for mother and child in the ancient world. For more about Kristina and her work, you can see her academic Website at Killgrove.org  and find out about her latest research project at RomanDNAProject.org. You can also find her at her G+ page and on Twitter as @BoneGirlPhD.]

Basically since we started walking upright, childbirth has been difficult for women.  Evolution selected for larger and larger brains in our hominin ancestors such that today our newborns have heads roughly 102% the size of the mother’s pelvic inlet width (Rosenberg 1992).

Yes, you read that right. Our babies’ heads are actually two percent larger than our skeletal anatomy


Fetal head and mother’s pelvic inlet width
Photo credit: Evolution-of-man.info

Obviously, we’ve also evolved ways to get those babies out.  Biologically, towards the end of pregnancy, a hormone is released that weakens the cartilage of the pelvic joints, allowing the bones to spread; and the fetus itself goes through a complicated movement to make its way down the pelvic canal, with its skull bones eventually sliding around and overlapping to get through the pelvis.  Culturally, we have another way to deliver these large babies: the so-calledcaesarean section.

Up until the 20th century, childbirth was dangerous.  Even today, in some less developed countries, roughly 1 maternal death occurs for every 100 live births, most of those related to obstructed labor or hemorrhage (WHO Fact Sheet 2010).  If we project these figures back into the past, millions of women must have died during or just after childbirth over the last several millennia.  You would think, then, that the discovery of childbirth-related burial – that is, of a woman with a fetal skeleton within her pelvis – would be common in the archaeological record.  It’s not.

Archaeological Evidence of Death in Childbirth

Two recent articles in the International Journal of Osteoarchaeology start the exact same way, by explaining that “despite this general acceptance of the vulnerability of young females in the past, there are very few cases of pregnant woman (sic) reported from archaeological contexts” (Willis & Oxenham, In Press) and ”archaeological evidence for such causes of death is scarce and therefore unlikely to reflect the high incidence of mortality during and after labour” (Cruz & Codinha 2010:491).

The examples of burials of pregnant women that tend to get cited include two from Britain (both published in the 1970s), four from Scandinavia (published in the 1970s and 1980s), three from North America (published in the 1980s), one from Australia (1980s), one from Israel (1990s), six from Spain (1990s and 2000s), one from Portugal (2010), and one from Vietnam (2011) (most of these are cited in Willis & Oxenham).  Additionally, I found some unpublished reports: a skeleton from Egypt, a body from the Yorkshire Wolds in England, and a skeleton from England.

The images of these burials are impressive: even more than child skeletons, these tableaux are pathos-triggering, they’re snapshots of two lives cut short because of an evolutionary trade-off.


The wide range of dates and geographical areas illustrated in the slideshow demonstrates quite clearly that death of the mother-fetus dyad is a biological consequence of being human.  But what we have from archaeological excavations is still fewer than two dozen examples of possible childbirth-related deaths from all of human history.

Where are all the mother-fetus burials?


As with any bioarchaeological question, there are a number of reasons that we may or may not find evidence of practices we know to have existed in the past.  Some key issues at play in recovering evidence of death in childbirth include:
  • Archaeological Theory and Methodology.  From the dates of discovery of maternal-fetal death cited above, it’s obvious that these examples weren’t discovered until the 1970s.  Why the 70s?  It could be that the rise of feminist archaeology focused new attention on the graves of females, with archaeologists realizing the possibility that they would find maternal-fetal burials.  Or it could be that the methods employed got better around this time: archaeologists began to sift dirt with smaller mesh screens and float it for small particles like seeds and fetal bones.
  • Death at Different Times.  Although some women surely perished in the middle of childbirth, along with a fetus that was obstructed, in many cases delivery likely occurred, after which the mother, fetus, or both died.  In modern medical literature, there are direct maternal deaths (complications of pregnancy, delivery, or recovery) and indirect maternal deaths (pregnancy-related death of a woman with preexisting or newly arisen health problems) recorded up to about 42 days postpartum.  An infection related to delivery or severe postpartum hemorraging could easily have killed a woman in antiquity, leaving a viable newborn.  Similarly, newborns can develop infections and other conditions once outside the womb, and infant mortality was high in preindustrial societies.  With a difference between the time of death of the mother and child, a bioarchaeologist can’t say for sure that these deaths were related to childbirth.  Even finding a female skeleton with a fetal skeleton inside it is not always a clear example, as there are forensic cases of coffin birth or postmortem fetal extrusion, when the non-viable fetus is spontaneously delivered after the death of the mother.
  • Cultural Practices.  Another condition of being human is the ability to modify and mediate our biology through culture.  So the final possibility for the lack of mother-fetus burials is a specific society’s cultural practices in terms of childbirth and burial.  In the case of complicated childbirth (called dystocia in the medical literature), this is done through caesarean section (or C-section), a surgical procedure that dates back at least to the origins of ancient Rome.

Cultural Interventions in Childbirth


It’s often assumed that the term caesarean/cesarean section comes from the manner of birth ofJulius Caesar, but it seems that the Roman author Pliny may have just made this up. The written record of the surgical practice originated as the Lex Regia (royal law) with the second king of Rome, Numa Pompilius (c. 700 BC), and was renamed the Lex Caesarea (imperial law) during the Empire.  The law is passed down through Justinian’s Digest (11.8.2) and reads:

Negat lex regia mulierem, quae praegnas mortua sit, humari, antequam partus ei excidatur: qui contra fecerit, spem animantis cum gravida peremisse videtur.

The royal law forbids burying a woman who died pregnant until her offspring has been excised from her; anyone who does otherwise is seen to have killed the hope of the offspring with the pregnant woman. [Translation mine]
Example of Roman gynaecological equipment: speculum
From the House of the Surgeon, Pompeii (1st c AD)
Photo credit: UVa Health Sciences Library

There’s discussion as to whether this law was instituted for religious reasons or for the more practical reason of increasing the population of tax-paying citizens.  In spite of this law, though, there isn’t much historical evidence of people being born by C-section.  Many articles claim the earliest attested C-section as having produced Gorgias, an orator from Sicily, in 508 BC (e.g., Boley 1991), but Gorgias wasn’t actually born until 485 BC and I couldn’t find a confirmatory source for this claim.  Pliny, however, noted that Scipio Africanus, a celebrated Roman general in the Second Punic War, was born by C-section (Historia Naturalis VII.7); if this fact is correct, the earliest confirmation that the surgery could produce viable offspring dates to 236 BC.


This practice in the Roman world is not the same as our contemporary idea of C-section.  That is, the mother was not expected to survive and, in fact, most of the C-sections in Roman times were likely carried out following the death of the mother.  Until about the 1500s, when the French physician François Rousset broke with tradition and advocated performing C-sections on living women, the procedure was performed only as a last-ditch effort to save the neonate.  Some women definitely survived C-sections from the 16th to 19th centuries, but it was still a risky procedure that could easily lead to complications like endometritis or other infection.  Following advances in antibiotics around 1940, though, C-sections became more common because, most importantly, they were much more survivable.


Caesarean Sections and Roman Burials


Roman relief showing a birthing scene
Tomb of a Midwife (Tomb 100), Isola Sacra
Photo credit: magistrahf on Flickr

In spite of the Romans’ passion for recordkeeping, there’s very little evidence of C-sections.  It’s unclear how religiously the Lex Regia/Caesarea was followed in Roman times, which means it’s unclear how often the practice of C-section occurred.  Would all women have been subject to these laws?  Just the elite or just citizens?  How often did the section result in a viable newborn?  Who performed the surgery?  It probably wasn’t a physician (since men didn’t generally attend births), but a midwife wouldn’t have been trained to do it either (Turfa 1994).


Whereas we can supplement the historical record with bioarchaeological evidence to understand Romans’ knowledge of anatomy, their consumption of lead sugar, or the practice of crucifixion, this isn’t possible with C-sections – the surgery is done in soft tissue only, meaning we’d have to find a mummy to get conclusive evidence of an ancient C-section.

We can make the hypothesis, though, that because of the Lex Regia/Caesarea, we should findno evidence in the Roman world of a woman buried with a fetus still inside her.  This hypothesis, though, is quickly negated by two reported cases – one from Kent in the Romano-British period and one from Jerusalem in the 4th century AD. The burial from Kent hasn’t been published, although there is a photograph in the slide show above.

Interestingly, the Jerusalem find was studied and reported by Joe Zias, who also analyzed theonly known case of crucifixion to date.  Zias and colleagues report on the find in Nature(1993) and in an edited volume (1995), but their primary goal was to disseminate information about the presence of cannabis in the tomb (and its supposed role in facilitating childbirth), so there’s no picture and the information about the skeletons is severely lacking:

We found the skeletal remains of a girl (sic) aged about 14 at death in an undisturbed family burial tomb in Beit Shemesh, near Jerusalem.  Three bronze coins found in the tomb dating to AD 315-392 indicate that the tomb was in use during the fourth century AD.  We found the skeletal remains of a full-term (40-week) fetus in the pelvic area of the girl, who was lying on her back in an extended position, apparently in the last stages of pregnancy or giving birth at the time of her death… It seems likely that the immature pelvic structure through which the full-term fetus was required to pass was the cause of death in this case, due to rupture of the cervix and eventual haemorrhage (Zias et al. 1993:215).

Both Roman-era examples involve young women, and it is quite interesting that they were already fertile.  Age at menarche in the Roman world depended on health, which in turn depended on status, but it’s generally accepted that menarche happened around 14-15 years old and that fertility lagged behind until 16-17, meaning for the majority of the Roman female population, first birth would not occur until at least 17-19 years of age (Hopkins 1965, Amundsen & Diers 1969).  These numbers have led demographers like Tim Parkin (1992:104-5) to note that pregnancy was likely not a major contributor to premature death among Roman women.  But the female pelvis doesn’t reach skeletal maturity until the late teens or early 20s, so complications from the incompatibility in pelvis size versus fetal head size are not uncommon in teen pregnancies, even today (Gilbert et al. 2004).

More interesting than the young age at parturition is the fact that both of these young women were likely buried with their fetuses still inside them, in direct violation of the Lex Caesarea.  So it remains unclear whether this law was ever prosecuted, or if the application of the law varied based on location (these young women were both from the provinces), social status (both young women were likely higher status), or time period.  Why wasn’t medical intervention, namely C-section, attempted on these young women?  It’s possible that further context clues from the cemeteries and associated settlements could give us more information about medical practices in these specific locales, but neither the Zias articles nor the Kent report make this information available.

Childbirth – Biological or Cultural?

Childbirth is both a biological and a cultural process.  While biological variation is consistent across all human populations, the cultural processes that can facilitate childbirth are quite varied.  The evidence that bioarchaeologists use to reconstruct childbirth in the past includes skeletons of mothers and their fetuses; historical records of births, deaths, and interventions; artifacts that facilitate delivery; and context clues from burials.  The brief case study of death in childbirth in the Roman world further shows that history alone is insufficient to understand the process of childbirth, the complications inherent in it, and the form of burial that results.  In order to develop a better understanding of childbirth through time, it’s imperative that archaeologists pay close attention when excavating graves, meticulously document their findings, and publish any evidence of death in childbirth.



Further Reading:
ResearchBlogging.orgReferences:

This post was chosen as an Editor's Selection for ResearchBlogging.orgD.W. Amundsen, & C.J. Diers (1969). The age of menarche in Classical Greece and Rome. Human Biology, 41 (1), 125-132. PMID: 4891546.


J.P. Boley (1991). The history of caesarean section. Canadian Medical Association Journal, 145 (4), 319-322. [PDF]


S. Crawford (2007). Companions, co-incidences or chattels? Children in the early Anglo-Saxon multiple burial ritual.  In Children, Childhood & Society, S. Crawford and G. Shepherd, eds.  BAR International Series 1696, Chapter 8. [PDF]

C. Cruz, & S. Codinha (2010). Death of mother and child due to dystocia in 19th century Portugal. International Journal of Osteoarchaeology, 20, 491-496. DOI: 10.1002/oa.1069.

W. Gilbert, D. Jandial, N. Field, P. Bigelow, & B. Danielsen (2004). Birth outcomes in teenage pregnancies. Journal of Maternal-Fetal and Neonatal Medicine, 16 (5), 265-270. DOI:10.1080/14767050400018064.

K. Hopkins (1965). The age of Roman girls at marriage. Population Studies, 18 (3), 309-327. DOI: 10.2307/2173291.


E. Lasso, M. Santos, A. Rico, J.V. Pachar, & J. Lucena (2009). Postmortem fetal extrusion. Cuadernos de Medicina Forense, 15 (55), 77-81. [HTML - Warning: Graphic images!]

T. Parkin (1992).  Demography and Roman society.  Baltimore: Johns Hopkins University Press.

K. Rosenberg (1992). The evolution of modern human childbirth. American Journal of Physical Anthropology, 35 (S15), 89-124. DOI: 10.1002/ajpa.1330350605
J.M. Turfa (1994). Anatomical votives and Italian medical traditions. In: Murlo and the Etruscans, edited by R.D. DePuma and J.P. Small. University of Wisconsin Press.


C. Wells (1975). Ancient obstetric hazards and female mortality. Bulletin of the New York Academy of Medicine, 51 (11), 1235-49. PMID: 1101997.

A. Willis, & M. Oxenham (In press). A Case of Maternal and Perinatal Death in Neolithic Southern Vietnam, c. 2100-1050 BCE. International Journal of Osteoarchaeology, 1-9. DOI:10.1002/oa.1296.


J. Zias, H. Stark, J. Seligman, R. Levy, E. Werker, A. Breuer & R. Mechoulam (1993). Early medical use of cannabis. Nature, 363 (6426), 215-215. DOI: 10.1038/363215a0.

J. Zias (1995). Cannabis sativa (hashish) as an effective medication in antiquity: the anthropological evidence. In: S. Campbell & A. Green, eds., The Archaeology of Death in the Ancient Near East, pp. 232-234.

Note: Thanks to Marta Sobur for helping me gain access to the Zias 1995 article, and thanks toSarah Bond for helping me track down the Justinian reference.

Pregnancy 101: On the cervical mucus plug and why I’ve never been more happy to hold something so disgusting in my hand

Like the eye of Sauron drawn to the One Ring, one cannot resist looking at the mucus plug.
June 3rd, 2007 fell on a Sunday. I awoke that morning feeling disappointed that I was still pregnant. My due date had come and gone and, honestly, I was sick of being a human incubator. I had enough of the heartburn, involuntary peeing, and the overall beached-whale feeling. The baby in utero was resting comfortably on my sciatic nerve, and I could barely walk. And perhaps even more important was the fact that I just wanted to finally meet the child I had grown from just a few cells!

Feeling like it would never come to be, I slowly waddled into the bathroom and somehow negotiated the tall edge of the bathtub in order to take a shower. As I stood allowing the hot water to pour down my back, I looked down at the giant watermelon growing from my abdomen and literally began to beg. “Little baby, please please PLEASE make your way out today!” Right at that moment, and I kid you not, my cervix released my mucus plug and deposited it into the palm of my hand.

Video of a mucus plug being poked and prodded with tweezers. Watch at your own risk.
Suddenly, I saw the light at the end of the pregnancy tunnel. I excitedly called for my husband. “Jim! You have to come see this!!” He came running in as he was already on edge, given the circumstances. “My mucus plug came out! Do you want to see it?” As much as he tried to resist looking at something that was potentially grotesque (and it was), instinct overrode logic. His actions did not match the words coming out of his mouth, which were along the lines of “hell no!” and, like Sauron responding to the wearing of the ring, his eyes were slowly drawn down to what was gently wobbling in the palm of my hand.   

The human eye is poised for setting its gaze upon things that are aesthetically pleasing and the mere mention of the word “mucus” could potentially elicit a queasy feeling in one’s gut. However, mucus plays a significant biological role in our bodies. In general, the mucus serves as a physical barrier against microbial invaders (bacteria, fungi, viruses) and small particulate matter (dust, pollen, allergens of all kinds). Protective mucus membranes line a multitude of surfaces in our bodies, including the digestive tract, the respiratory pathway, and, of course, the female reproductive cavity.

But when it comes to matters of ladybusiness, the function of mucus goes beyond that of a microbial defense system. Produced by specialized cells lining the cervix, which is the neck of the uterus and where the uterus and vagina meet, mucus also plays a role in either facilitating or preventing sperm from traveling beyond the vagina and into the upper reproductive tract.

For instance, cervical mucus becomes thinner around the time of ovulation, providing a more suitable conduit for sperm movement and swimming (presumably toward the egg). Furthermore, some components from this so-called “fertile” cervical mucus actually help prolong the life of sperm cells. Conversely, after the ovulation phase, normal hormonal fluctuations cause cervical mucus to become thicker and more gel-like, acting as a barrier to sperm. This response helps to prepare the uterus for pregnancy if  fertilization happens.

During pregnancy, a sustained elevation of a hormone called progesterone causes the mucus-secreting cells in the cervix to produce a much more viscous and elastic mucus, known as the cervical mucus plug. In non-scientific terms, the mucus plug is like the cork that keeps all of the bubbly baby goodness safe from harmful bacteria. It is quite large, often weighing in around 10 g (0.35 oz) and consists mostly of water (>90%) that contains several hundred types of proteins. These proteins do many jobs, including immunological gatekeepers, structural maintenance, regulation of fluid balance, and even cholesterol metabolism (cholesterol is an ever important component of healthy fetal development).
As a woman nears the end of a pregnancy, the cervix releases the mucus plug as it thins out in preparation for birth. Often, the thinning of the cervix can release some blood into the mucus plug, which is why some describe the loss of the mucus plug as a “bloody show.” However, losing the mucus plug is not necessarily an indication that labor is starting. Activities like sex or an internal cervical examination can cause the mucus plug to dislodge. It can fall out hours, days, or even weeks before labor begins. In my case, the loss of my mucus plug was associated with the onset of labor, which is why I have never been so happy to hold something so disgusting in my hand. 


Last week, I told the story of my two births, including the loss of my mucus plug, at an event called The Story Collider. I described the mucus plug as “a big hot gelatinous mess.” I pushed it a bit further by providing the following graphic imagery: “Picture a Jell-O jiggler, but instead of brightly colored sugar, it’s made up of bloody snot.” I was pleased with the audience response, which mostly consisted of animated face smooshing accompanied by grossed-out groans and sighs. For the rest of the evening, I heard people call to me from all over the bar by screaming “MUCUS PLUG!!!” Given the importance of the mucus plug during pregnancy (and mucus in general) combined with its comedic potential, its no wonder that it was a hit. Go mucus!


Jeanne Garbarino, Double X Science biology editor

References

Kamran Moghissi, Otto W. Neuhaus, and Charles S. Stevenson. Composition and properties of human cervical mucus. I. Electrophoretic separation and identification of proteins.. J Clin Invest. 1960 September; 39(9): 1358–1363.

Lee DC, Hassan SS, Romero R, Tarca AL, Bhatti G, Gervasi MT, Caruso JA, Stemmer PM, Kim CJ, Hansen LK, Becher N, Uldbjerg N. Protein profiling underscores immunological functions of uterine cervical mucus plug in human pregnancy. J Proteomics. 2011 May 16;74(6):817-28. Epub 2011 Mar 23.

Ilene K. Gipso. Mucins of the human endocervix. Frontiers in Bioscience 2001 October; 6, d1245-1255.

Merete Hein MD, Erika V. Valore MS, Rikke Bek Helmig MD, PhD, Niels Uldbjerg MD, PhD, Tomas Ganz PhD, MD. Antimicrobial factors in the cervical mucus plug. American Journal of Obstetrics and Gynecology 2002 July Volume 187, Issue 1, 137-144

Naja Becher, Kristina Adams Waldorf, Merete Hein & Niels Uldbjerg. The cervical mucus plug: Structured review of the literature. Acta Obstetricia et Gynecologica. 2009; 88: 502_513

Mother’s Day: Part of me forever

Always a part of each other. (Source)

Double X Science’s Chris Gunter, science education and outreach editor, wrote this wonderful post for the Last Word on Nothing. We are featuring it here for Mother’s Day because, as she writes, if you’re a mother, you and your child are part of each other forever–and this time, we mean in a scientific sense.
Source.
This summer I put my Lilkid, as I call him online, on the school bus for the first time ever. Evidently I have “socialized” him enough with other lilkids, because he got on without a backwards glance, ignoring his mother getting all teary and father waving goodbye. He chose a seat and then mouthed through the window with a huge grin, “MOM! I am ON THE SCHOOL BUS! And IT HAS NO SEAT BELTS!!!”
When you have a kid, people tell you various clichés about how your child will be part of you forever. Ladies, in your case, it’s true, and it’s supported by science.
Thanks to a phenomenon called fetal microchimerism, a mother can carry cells from her fetus in her own body for many years after the pregnancy ends. Particularly in the last two decades, microchimerism has been recognized as the norm rather than the exception. We now know that, instead of being separate systems, the mother and fetus leave a number of permanent marks on each other through the trafficking of cells back and forth over the placenta. Fetal stem cells make their way into the mother’s bloodstream and even into her bone marrow, sometimes contributing to her blood supply for the rest of her life.
Source.
Like many parts of having a kid, the consequences of this microchimerism are both good and bad. Fetal cells have been found at sites of injury in the mother while she’s pregnant, or even years later in liver injuries or appendicitis cases, apparently drawn by damage and participating in repair or regeneration. Good news! Fetal cells have also been found in breast cancers much later, again seeming to try and repair the tissue. Thanks, kid!
But the presence of fetal cells is also invoked as the reason why women have more autoimmune disorders, including lupus and thyroiditis, during and years after pregnancy. Immunologists think that this happens essentially because Mom’s immune system eventually realizes that these fetal cells don’t belong to her own body, and attacks them as a result. Hmmm, not great. [However, at least you have some more scientific basis if you hear yourself telling your child, “You are KILLING me!”]
Source.
In fact, testing women’s cells for the presence of the Y chromosome — the “male” chromosome, which females shouldn’t carry — uncovers it in about 30% of the bone marrow of grown women and 47% of cardiac aortas. Even among women who have truly never had a reportable pregnancy, 7% or more would test positive for XY cells. Doubling those numbers to account for fetuses of both sexes further supports the idea that many pregnancies go undetected. It’s not just the mothers standing with me at the bus stop who are microchimeric; these problems and benefits apply to more women than we think.
So as I watched Lilkid pull away into a new stage of independence, this geeky scientist thought about how his cells would literally be part of my body forever, for both good and more challenging times. Then the straight Mom kicked in with a host of more mundane worries: “Great — now I have to go look into this ‘no seat belt on the bus’ thing. Did I pack enough snacks for him to eat?” And so on as the school bus drove off for the first of many mornings.
_____________
Chris Gunter is a geneticist and the Director of Research Affairs at the HudsonAlpha Institute for Biotechnology in Huntsville, Alabama, and a DXS editor. 

As Seen on TV! Restoring Hair with LASERS!!!!!!

The author’s rapidly-expanding forehead.

Anyone who watches TV, reads magazines, or flips through catalogs has seen some interesting products. Maybe they seem plausible to you, maybe they don’t. However, a little investigation shows they are based less on science and well…actually working, and more on wishful thinking. At worst they’re actual con-jobs, designed to separate you from your money as efficiently as possible (which I guess is a certain standard of success). As a result, we at Double X Science bring you “As Seen on TV!” In these features, we’ll look at some of the products shilled on talk shows and infomercials, items lurking between the articles you read in magazines, or things you might find on the shelves of the stores where you shop.

I admit it, I’m a balding dude. My forehead is gradually taking over my entire scalp, replacing my formerly thick and curly hair with a vast expanse of pink skin. Yes, dear readers: My hair was once so thick and curly that, when I wore it long and in a ponytail, ladies would ask me for my secret. (The answer: Wash it every other day with some brand of cheap shampoo and let it air dry. Don’t tell.) I don’t like the fact of my impending baldness, so I’m sympathetic toward defoliation-sufferers who want to bring their hair back at any cost.

On the other hand, I don’t think I’ll invest in any of the hair restoration products advertised in the SkyMall catalog I picked up on my flight to my brother’s wedding in San Francisco. I counted seven products in this single catalog promising to restore hair in one way or another, either reversing baldness or filling in thin patches on the scalp –- and that doesn’t include hair-coloring, extensions, or other options. I won’t cover all of them, but no fewer than three products pledge to bring hair back through the magic of lasers.

Ah, lasers. They may not have the mystique of magnets or the nous of “natural”, but they are a frequent ingredient in modern snake oil. (Come to think of it, one of the hair-restoration products may have contained snake oil. I don’t want to ask.) But while lasers can help correct nearsightedness in some cases, perform minimally invasive surgeries, and remove hair, color my scalp skeptical about their ability to restore hair.

First, a disclaimer: I’m not a biologist, a doctor, medical researcher, or in any field related to those. I’m a physicist, so the closest I ever get professionally to this topic is the “no-hair” theorem in black hole physics. The “no-hair” theorem says that black holes have very few distinguishing characteristics: only mass and rotational rate (and technically electric charge as well, though it’s hard to build up enough charge to make a difference). The analogy is that, if all humans were completely hairless, we would have a lot fewer ways to tell each other apart. In other words, this ain’t my area, so bear (bare) with me!

Night on Baldhead Mountain

Hair loss can occur for a wide variety of reasons: chemotherapy, a number of unrelated diseases, even stress. However, as humans (both men and women!) age, we all tend to lose our hair to some degree. The effect is most pronounced in male pattern baldness (a bare patch on the top of the head merging over time with the growing forehead to leave a fringe around the edges of the scalp) or female pattern baldness (a general loss of hair at the top of the scalp). However, past the age of 80, nearly everyone starts losing hair, regardless of genetics, diet, or health.

The reasons, as with so many other things, are hormonal. Hair production is governed by sex hormones: most famously testosterone, but also a less well-known cousin known as dihydrotestosterone (DHT). In some people, DHT commands the follicles — the small organs in the skin that produce and feed hair — to shrink, producing ever-finer hair until they cease operating entirely. Thus, gradual hair loss of the usual (as opposed to disease- or circumstance-derived) variety is generally preceded by the hair itself becoming thinner and fuzzier.

My naive understanding of the biology of hair loss leads me to suspect that since hormones are the culprit behind hair loss, then any hair restoration should address those hormones in some way. That alone makes me suspicious of the laser-based products SkyMall peddles. To see why, let’s look at lasers themselves.

Lasers (without sharks)

The word “laser” began as an acronym: Light Amplification by the Stimulated Emission of Radiation. The details could be an Everyday Science or Double Xplainer post in their own right, but here’s the short version. The lasers used in the SkyMall products are LED lasers, meaning they are based on the underlying physics as LED lights. An electric current kicks electrons or other electric charge carriers from one type of material to another across a junction. The excess energy the electric charge sheds during this process is given off in the form of a photon, a particle of light. Since the same amount of energy is involved every time, light from LEDs is nearly monochromatic, meaning it is almost purely one color.

The “amplification” part of the name comes by putting the LED into a special kind of cavity with reflective walls. These walls set up standing waves for the light, which interfere constructively like vibrations in a guitar string, making them brighter. However, unlike guitar strings, the production of the light in lasers is a self-feeding process, resulting in the different parts of the system synchronizing until they emit photons in concert with each other. It’s really interesting stuff, and while it’s somewhat complicated, there’s nothing really mysterious or magical about it, any more than magnets are magical.

In fact, LED lasers are so unmagical that you can buy them as cat toys. LED lasers are the inner workings of laser pointers, which you can buy very inexpensively at any number of shops.

The smell of frying follicles

One of three laser-based hair-restoration products from SkyMall.
This one features built-in headphones, so you can at least listen
to music while you sit around looking like a fool. However,
I recommend a cheaper set of headphones, since the $700
price tag is a bit steep, and you’d get the same result with
regards to hair restoration.
Laser hair removal uses intense lasers to selectively heat the follicles in the skin, hopefully avoiding damage to the rest of the skin. This process can slow down hair growth and cause the hair to fall out of the treated follicles, but it doesn’t always actually stop it: the treatment must be continued for a long term. Basically, the laser is damaging the follicle.

As you can imagine, that also makes me skeptical that lasers can stimulate new hair growth. Lasers produce light…and that’s it! In addition to the usual red lasers like in laser pointers, manufacturers also make infrared lasers, which are useful for surgery. While we perceive infrared as heat (which is why sunshine feels warm), I don’t think merely warming the scalp is going to make hair grow faster, or else you wouldn’t need lasers at all — an electric blanket would do just as well. Too much heating and we’re back at laser hair removal.

Similarly, visible-light lasers like the kind that seem to be in these SkyMall products simply produce red light. Because ordinary light bulbs produce a broad range of colors (white light is a mixture of all the visible-light wavelengths), sitting under a desk lamp would expose your scalp to red light. Yes, it wouldn’t be as intense as lasers, but you could do the same trick with a laser pointer from Schtaples (the Scmoffice Schmupply Schtore), provided you have the patience to hold it against your scalp for long periods of time.

The author engages in home laser hair restoration, while his cats
meow around his feet.
So, to summarize:
  • Hair loss in its most common forms is hormonal, so it’s unclear to me that light (whether laser or otherwise) has anything to do with it. Hair removal can be achieved with lasers, but that involves causing damage to hair follicles, not using anything intrinsic to light.
  • Lasers are simply very monochromatic light sources, that use synchronization of atoms on the microscopic level to do their business. There’s nothing in a laser that isn’t in ordinary light bulbs, though you can make things far more intense with a laser. However, high intensity brings us back to laser hair removal, not restoration.
  • As always, if a product sounds miraculous, it’s probably bunkum. If all it took to regrow hair was a glorified laser pointer, nobody would be bald! LED lasers are cheap and ubiquitous; we could all restore our hair without paying a company $700 (and listen to the music on inexpensive headphones, to boot).
Now if you’ll pardon me, I’ll get back to shining this laser pointer at my scalp.

Biology Explainer: The big 4 building blocks of life–carbohydrates, fats, proteins, and nucleic acids

The short version
  • The four basic categories of molecules for building life are carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates serve many purposes, from energy to structure to chemical communication, as monomers or polymers.
  • Lipids, which are hydrophobic, also have different purposes, including energy storage, structure, and signaling.
  • Proteins, made of amino acids in up to four structural levels, are involved in just about every process of life.                                                                                                      
  • The nucleic acids DNA and RNA consist of four nucleotide building blocks, and each has different purposes.
The longer version
Life is so diverse and unwieldy, it may surprise you to learn that we can break it down into four basic categories of molecules. Possibly even more implausible is the fact that two of these categories of large molecules themselves break down into a surprisingly small number of building blocks. The proteins that make up all of the living things on this planet and ensure their appropriate structure and smooth function consist of only 20 different kinds of building blocks. Nucleic acids, specifically DNA, are even more basic: only four different kinds of molecules provide the materials to build the countless different genetic codes that translate into all the different walking, swimming, crawling, oozing, and/or photosynthesizing organisms that populate the third rock from the Sun.

                                                  

Big Molecules with Small Building Blocks

The functional groups, assembled into building blocks on backbones of carbon atoms, can be bonded together to yield large molecules that we classify into four basic categories. These molecules, in many different permutations, are the basis for the diversity that we see among living things. They can consist of thousands of atoms, but only a handful of different kinds of atoms form them. It’s like building apartment buildings using a small selection of different materials: bricks, mortar, iron, glass, and wood. Arranged in different ways, these few materials can yield a huge variety of structures.

We encountered functional groups and the SPHONC in Chapter 3. These components form the four categories of molecules of life. These Big Four biological molecules are carbohydrates, lipids, proteins, and nucleic acids. They can have many roles, from giving an organism structure to being involved in one of the millions of processes of living. Let’s meet each category individually and discover the basic roles of each in the structure and function of life.
Carbohydrates

You have met carbohydrates before, whether you know it or not. We refer to them casually as “sugars,” molecules made of carbon, hydrogen, and oxygen. A sugar molecule has a carbon backbone, usually five or six carbons in the ones we’ll discuss here, but it can be as few as three. Sugar molecules can link together in pairs or in chains or branching “trees,” either for structure or energy storage.

When you look on a nutrition label, you’ll see reference to “sugars.” That term includes carbohydrates that provide energy, which we get from breaking the chemical bonds in a sugar called glucose. The “sugars” on a nutrition label also include those that give structure to a plant, which we call fiber. Both are important nutrients for people.

Sugars serve many purposes. They give crunch to the cell walls of a plant or the exoskeleton of a beetle and chemical energy to the marathon runner. When attached to other molecules, like proteins or fats, they aid in communication between cells. But before we get any further into their uses, let’s talk structure.

The sugars we encounter most in basic biology have their five or six carbons linked together in a ring. There’s no need to dive deep into organic chemistry, but there are a couple of essential things to know to interpret the standard representations of these molecules.

Check out the sugars depicted in the figure. The top-left molecule, glucose, has six carbons, which have been numbered. The sugar to its right is the same glucose, with all but one “C” removed. The other five carbons are still there but are inferred using the conventions of organic chemistry: Anywhere there is a corner, there’s a carbon unless otherwise indicated. It might be a good exercise for you to add in a “C” over each corner so that you gain a good understanding of this convention. You should end up adding in five carbon symbols; the sixth is already given because that is conventionally included when it occurs outside of the ring.

On the left is a glucose with all of its carbons indicated. They’re also numbered, which is important to understand now for information that comes later. On the right is the same molecule, glucose, without the carbons indicated (except for the sixth one). Wherever there is a corner, there is a carbon, unless otherwise indicated (as with the oxygen). On the bottom left is ribose, the sugar found in RNA. The sugar on the bottom right is deoxyribose. Note that at carbon 2 (*), the ribose and deoxyribose differ by a single oxygen.

The lower left sugar in the figure is a ribose. In this depiction, the carbons, except the one outside of the ring, have not been drawn in, and they are not numbered. This is the standard way sugars are presented in texts. Can you tell how many carbons there are in this sugar? Count the corners and don’t forget the one that’s already indicated!

If you said “five,” you are right. Ribose is a pentose (pent = five) and happens to be the sugar present in ribonucleic acid, or RNA. Think to yourself what the sugar might be in deoxyribonucleic acid, or DNA. If you thought, deoxyribose, you’d be right.

The fourth sugar given in the figure is a deoxyribose. In organic chemistry, it’s not enough to know that corners indicate carbons. Each carbon also has a specific number, which becomes important in discussions of nucleic acids. Luckily, we get to keep our carbon counting pretty simple in basic biology. To count carbons, you start with the carbon to the right of the non-carbon corner of the molecule. The deoxyribose or ribose always looks to me like a little cupcake with a cherry on top. The “cherry” is an oxygen. To the right of that oxygen, we start counting carbons, so that corner to the right of the “cherry” is the first carbon. Now, keep counting. Here’s a little test: What is hanging down from carbon 2 of the deoxyribose?

If you said a hydrogen (H), you are right! Now, compare the deoxyribose to the ribose. Do you see the difference in what hangs off of the carbon 2 of each sugar? You’ll see that the carbon 2 of ribose has an –OH, rather than an H. The reason the deoxyribose is called that is because the O on the second carbon of the ribose has been removed, leaving a “deoxyed” ribose. This tiny distinction between the sugars used in DNA and RNA is significant enough in biology that we use it to distinguish the two nucleic acids.

In fact, these subtle differences in sugars mean big differences for many biological molecules. Below, you’ll find a couple of ways that apparently small changes in a sugar molecule can mean big changes in what it does. These little changes make the difference between a delicious sugar cookie and the crunchy exoskeleton of a dung beetle.

Sugar and Fuel

A marathon runner keeps fuel on hand in the form of “carbs,” or sugars. These fuels provide the marathoner’s straining body with the energy it needs to keep the muscles pumping. When we take in sugar like this, it often comes in the form of glucose molecules attached together in a polymer called starch. We are especially equipped to start breaking off individual glucose molecules the minute we start chewing on a starch.

Double X Extra: A monomer is a building block (mono = one) and a polymer is a chain of monomers. With a few dozen monomers or building blocks, we get millions of different polymers. That may sound nutty until you think of the infinity of values that can be built using only the numbers 0 through 9 as building blocks or the intricate programming that is done using only a binary code of zeros and ones in different combinations.

Our bodies then can rapidly take the single molecules, or monomers, into cells and crack open the chemical bonds to transform the energy for use. The bonds of a sugar are packed with chemical energy that we capture to build a different kind of energy-containing molecule that our muscles access easily. Most species rely on this process of capturing energy from sugars and transforming it for specific purposes.

Polysaccharides: Fuel and Form

Plants use the Sun’s energy to make their own glucose, and starch is actually a plant’s way of storing up that sugar. Potatoes, for example, are quite good at packing away tons of glucose molecules and are known to dieticians as a “starchy” vegetable. The glucose molecules in starch are packed fairly closely together. A string of sugar molecules bonded together through dehydration synthesis, as they are in starch, is a polymer called a polysaccharide (poly = many; saccharide = sugar). When the monomers of the polysaccharide are released, as when our bodies break them up, the reaction that releases them is called hydrolysis.

Double X Extra: The specific reaction that hooks one monomer to another in a covalent bond is called dehydration synthesis because in making the bond–synthesizing the larger molecule–a molecule of water is removed (dehydration). The reverse is hydrolysis (hydro = water; lysis = breaking), which breaks the covalent bond by the addition of a molecule of water.

Although plants make their own glucose and animals acquire it by eating the plants, animals can also package away the glucose they eat for later use. Animals, including humans, store glucose in a polysaccharide called glycogen, which is more branched than starch. In us, we build this energy reserve primarily in the liver and access it when our glucose levels drop.

Whether starch or glycogen, the glucose molecules that are stored are bonded together so that all of the molecules are oriented the same way. If you view the sixth carbon of the glucose to be a “carbon flag,” you’ll see in the figure that all of the glucose molecules in starch are oriented with their carbon flags on the upper left.

The orientation of monomers of glucose in polysaccharides can make a big difference in the use of the polymer. The glucoses in the molecule on the top are all oriented “up” and form starch. The glucoses in the molecule on the bottom alternate orientation to form cellulose, which is quite different in its function from starch.

Storing up sugars for fuel and using them as fuel isn’t the end of the uses of sugar. In fact, sugars serve as structural molecules in a huge variety of organisms, including fungi, bacteria, plants, and insects.

The primary structural role of a sugar is as a component of the cell wall, giving the organism support against gravity. In plants, the familiar old glucose molecule serves as one building block of the plant cell wall, but with a catch: The molecules are oriented in an alternating up-down fashion. The resulting structural sugar is called cellulose.

That simple difference in orientation means the difference between a polysaccharide as fuel for us and a polysaccharide as structure. Insects take it step further with the polysaccharide that makes up their exoskeleton, or outer shell. Once again, the building block is glucose, arranged as it is in cellulose, in an alternating conformation. But in insects, each glucose has a little extra added on, a chemical group called an N-acetyl group. This addition of a single functional group alters the use of cellulose and turns it into a structural molecule that gives bugs that special crunchy sound when you accidentally…ahem…step on them.

These variations on the simple theme of a basic carbon-ring-as-building-block occur again and again in biological systems. In addition to serving roles in structure and as fuel, sugars also play a role in function. The attachment of subtly different sugar molecules to a protein or a lipid is one way cells communicate chemically with one another in refined, regulated interactions. It’s as though the cells talk with each other using a specialized, sugar-based vocabulary. Typically, cells display these sugary messages to the outside world, making them available to other cells that can recognize the molecular language.

Lipids: The Fatty Trifecta

Starch makes for good, accessible fuel, something that we immediately attack chemically and break up for quick energy. But fats are energy that we are supposed to bank away for a good long time and break out in times of deprivation. Like sugars, fats serve several purposes, including as a dense source of energy and as a universal structural component of cell membranes everywhere.

Fats: the Good, the Bad, the Neutral

Turn again to a nutrition label, and you’ll see a few references to fats, also known as lipids. (Fats are slightly less confusing that sugars in that they have only two names.) The label may break down fats into categories, including trans fats, saturated fats, unsaturated fats, and cholesterol. You may have learned that trans fats are “bad” and that there is good cholesterol and bad cholesterol, but what does it all mean?

Let’s start with what we mean when we say saturated fat. The question is, saturated with what? There is a specific kind of dietary fat call the triglyceride. As its name implies, it has a structural motif in which something is repeated three times. That something is a chain of carbons and hydrogens, hanging off in triplicate from a head made of glycerol, as the figure shows.  Those three carbon-hydrogen chains, or fatty acids, are the “tri” in a triglyceride. Chains like this can be many carbons long.

Double X Extra: We call a fatty acid a fatty acid because it’s got a carboxylic acid attached to a fatty tail. A triglyceride consists of three of these fatty acids attached to a molecule called glycerol. Our dietary fat primarily consists of these triglycerides.

Triglycerides come in several forms. You may recall that carbon can form several different kinds of bonds, including single bonds, as with hydrogen, and double bonds, as with itself. A chain of carbon and hydrogens can have every single available carbon bond taken by a hydrogen in single covalent bond. This scenario of hydrogen saturation yields a saturated fat. The fat is saturated to its fullest with every covalent bond taken by hydrogens single bonded to the carbons.

Saturated fats have predictable characteristics. They lie flat easily and stick to each other, meaning that at room temperature, they form a dense solid. You will realize this if you find a little bit of fat on you to pinch. Does it feel pretty solid? That’s because animal fat is saturated fat. The fat on a steak is also solid at room temperature, and in fact, it takes a pretty high heat to loosen it up enough to become liquid. Animals are not the only organisms that produce saturated fat–avocados and coconuts also are known for their saturated fat content.

The top graphic above depicts a triglyceride with the glycerol, acid, and three hydrocarbon tails. The tails of this saturated fat, with every possible hydrogen space occupied, lie comparatively flat on one another, and this kind of fat is solid at room temperature. The fat on the bottom, however, is unsaturated, with bends or kinks wherever two carbons have double bonded, booting a couple of hydrogens and making this fat unsaturated, or lacking some hydrogens. Because of the space between the bumps, this fat is probably not solid at room temperature, but liquid.

You can probably now guess what an unsaturated fat is–one that has one or more hydrogens missing. Instead of single bonding with hydrogens at every available space, two or more carbons in an unsaturated fat chain will form a double bond with carbon, leaving no space for a hydrogen. Because some carbons in the chain share two pairs of electrons, they physically draw closer to one another than they do in a single bond. This tighter bonding result in a “kink” in the fatty acid chain.

In a fat with these kinks, the three fatty acids don’t lie as densely packed with each other as they do in a saturated fat. The kinks leave spaces between them. Thus, unsaturated fats are less dense than saturated fats and often will be liquid at room temperature. A good example of a liquid unsaturated fat at room temperature is canola oil.

A few decades ago, food scientists discovered that unsaturated fats could be resaturated or hydrogenated to behave more like saturated fats and have a longer shelf life. The process of hydrogenation–adding in hydrogens–yields trans fat. This kind of processed fat is now frowned upon and is being removed from many foods because of its associations with adverse health effects. If you check a food label and it lists among the ingredients “partially hydrogenated” oils, that can mean that the food contains trans fat.

Double X Extra: A triglyceride can have up to three different fatty acids attached to it. Canola oil, for example, consists primarily of oleic acid, linoleic acid, and linolenic acid, all of which are unsaturated fatty acids with 18 carbons in their chains.

Why do we take in fat anyway? Fat is a necessary nutrient for everything from our nervous systems to our circulatory health. It also, under appropriate conditions, is an excellent way to store up densely packaged energy for the times when stores are running low. We really can’t live very well without it.

Phospholipids: An Abundant Fat

You may have heard that oil and water don’t mix, and indeed, it is something you can observe for yourself. Drop a pat of butter–pure saturated fat–into a bowl of water and watch it just sit there. Even if you try mixing it with a spoon, it will just sit there. Now, drop a spoon of salt into the water and stir it a bit. The salt seems to vanish. You’ve just illustrated the difference between a water-fearing (hydrophobic) and a water-loving (hydrophilic) substance.

Generally speaking, compounds that have an unequal sharing of electrons (like ions or anything with a covalent bond between oxygen and hydrogen or nitrogen and hydrogen) will be hydrophilic. The reason is that a charge or an unequal electron sharing gives the molecule polarity that allows it to interact with water through hydrogen bonds. A fat, however, consists largely of hydrogen and carbon in those long chains. Carbon and hydrogen have roughly equivalent electronegativities, and their electron-sharing relationship is relatively nonpolar. Fat, lacking in polarity, doesn’t interact with water. As the butter demonstrated, it just sits there.

There is one exception to that little maxim about fat and water, and that exception is the phospholipid. This lipid has a special structure that makes it just right for the job it does: forming the membranes of cells. A phospholipid consists of a polar phosphate head–P and O don’t share equally–and a couple of nonpolar hydrocarbon tails, as the figure shows. If you look at the figure, you’ll see that one of the two tails has a little kick in it, thanks to a double bond between the two carbons there.

Phospholipids form a double layer and are the major structural components of cell membranes. Their bend, or kick, in one of the hydrocarbon tails helps ensure fluidity of the cell membrane. The molecules are bipolar, with hydrophilic heads for interacting with the internal and external watery environments of the cell and hydrophobic tails that help cell membranes behave as general security guards.

The kick and the bipolar (hydrophobic and hydrophilic) nature of the phospholipid make it the perfect molecule for building a cell membrane. A cell needs a watery outside to survive. It also needs a watery inside to survive. Thus, it must face the inside and outside worlds with something that interacts well with water. But it also must protect itself against unwanted intruders, providing a barrier that keeps unwanted things out and keeps necessary molecules in.

Phospholipids achieve it all. They assemble into a double layer around a cell but orient to allow interaction with the watery external and internal environments. On the layer facing the inside of the cell, the phospholipids orient their polar, hydrophilic heads to the watery inner environment and their tails away from it. On the layer to the outside of the cell, they do the same.
As the figure shows, the result is a double layer of phospholipids with each layer facing a polar, hydrophilic head to the watery environments. The tails of each layer face one another. They form a hydrophobic, fatty moat around a cell that serves as a general gatekeeper, much in the way that your skin does for you. Charged particles cannot simply slip across this fatty moat because they can’t interact with it. And to keep the fat fluid, one tail of each phospholipid has that little kick, giving the cell membrane a fluid, liquidy flow and keeping it from being solid and unforgiving at temperatures in which cells thrive.

Steroids: Here to Pump You Up?

Our final molecule in the lipid fatty trifecta is cholesterol. As you may have heard, there are a few different kinds of cholesterol, some of which we consider to be “good” and some of which is “bad.” The good cholesterol, high-density lipoprotein, or HDL, in part helps us out because it removes the bad cholesterol, low-density lipoprotein or LDL, from our blood. The presence of LDL is associated with inflammation of the lining of the blood vessels, which can lead to a variety of health problems.

But cholesterol has some other reasons for existing. One of its roles is in the maintenance of cell membrane fluidity. Cholesterol is inserted throughout the lipid bilayer and serves as a block to the fatty tails that might otherwise stick together and become a bit too solid.

Cholesterol’s other starring role as a lipid is as the starting molecule for a class of hormones we called steroids or steroid hormones. With a few snips here and additions there, cholesterol can be changed into the steroid hormones progesterone, testosterone, or estrogen. These molecules look quite similar, but they play very different roles in organisms. Testosterone, for example, generally masculinizes vertebrates (animals with backbones), while progesterone and estrogen play a role in regulating the ovulatory cycle.

Double X Extra: A hormone is a blood-borne signaling molecule. It can be lipid based, like testosterone, or short protein, like insulin.

Proteins

As you progress through learning biology, one thing will become more and more clear: Most cells function primarily as protein factories. It may surprise you to learn that proteins, which we often talk about in terms of food intake, are the fundamental molecule of many of life’s processes. Enzymes, for example, form a single broad category of proteins, but there are millions of them, each one governing a small step in the molecular pathways that are required for living.

Levels of Structure

Amino acids are the building blocks of proteins. A few amino acids strung together is called a peptide, while many many peptides linked together form a polypeptide. When many amino acids strung together interact with each other to form a properly folded molecule, we call that molecule a protein.

For a string of amino acids to ultimately fold up into an active protein, they must first be assembled in the correct order. The code for their assembly lies in the DNA, but once that code has been read and the amino acid chain built, we call that simple, unfolded chain the primary structure of the protein.

This chain can consist of hundreds of amino acids that interact all along the sequence. Some amino acids are hydrophobic and some are hydrophilic. In this context, like interacts best with like, so the hydrophobic amino acids will interact with one another, and the hydrophilic amino acids will interact together. As these contacts occur along the string of molecules, different conformations will arise in different parts of the chain. We call these different conformations along the amino acid chain the protein’s secondary structure.

Once those interactions have occurred, the protein can fold into its final, or tertiary structure and be ready to serve as an active participant in cellular processes. To achieve the tertiary structure, the amino acid chain’s secondary interactions must usually be ongoing, and the pH, temperature, and salt balance must be just right to facilitate the folding. This tertiary folding takes place through interactions of the secondary structures along the different parts of the amino acid chain.

The final product is a properly folded protein. If we could see it with the naked eye, it might look a lot like a wadded up string of pearls, but that “wadded up” look is misleading. Protein folding is a carefully regulated process that is determined at its core by the amino acids in the chain: their hydrophobicity and hydrophilicity and how they interact together.

In many instances, however, a complete protein consists of more than one amino acid chain, and the complete protein has two or more interacting strings of amino acids. A good example is hemoglobin in red blood cells. Its job is to grab oxygen and deliver it to the body’s tissues. A complete hemoglobin protein consists of four separate amino acid chains all properly folded into their tertiary structures and interacting as a single unit. In cases like this involving two or more interacting amino acid chains, we say that the final protein has a quaternary structure. Some proteins can consist of as many as a dozen interacting chains, behaving as a single protein unit.

A Plethora of Purposes

What does a protein do? Let us count the ways. Really, that’s almost impossible because proteins do just about everything. Some of them tag things. Some of them destroy things. Some of them protect. Some mark cells as “self.” Some serve as structural materials, while others are highways or motors. They aid in communication, they operate as signaling molecules, they transfer molecules and cut them up, they interact with each other in complex, interrelated pathways to build things up and break things down. They regulate genes and package DNA, and they regulate and package each other.

As described above, proteins are the final folded arrangement of a string of amino acids. One way we obtain these building blocks for the millions of proteins our bodies make is through our diet. You may hear about foods that are high in protein or people eating high-protein diets to build muscle. When we take in those proteins, we can break them apart and use the amino acids that make them up to build proteins of our own.

Nucleic Acids

How does a cell know which proteins to make? It has a code for building them, one that is especially guarded in a cellular vault in our cells called the nucleus. This code is deoxyribonucleic acid, or DNA. The cell makes a copy of this code and send it out to specialized structures that read it and build proteins based on what they read. As with any code, a typo–a mutation–can result in a message that doesn’t make as much sense. When the code gets changed, sometimes, the protein that the cell builds using that code will be changed, too.

Biohazard!The names associated with nucleic acids can be confusing because they all start with nucle-. It may seem obvious or easy now, but a brain freeze on a test could mix you up. You need to fix in your mind that the shorter term (10 letters, four syllables), nucleotide, refers to the smaller molecule, the three-part building block. The longer term (12 characters, including the space, and five syllables), nucleic acid, which is inherent in the names DNA and RNA, designates the big, long molecule.

DNA vs. RNA: A Matter of Structure

DNA and its nucleic acid cousin, ribonucleic acid, or RNA, are both made of the same kinds of building blocks. These building blocks are called nucleotides. Each nucleotide consists of three parts: a sugar (ribose for RNA and deoxyribose for DNA), a phosphate, and a nitrogenous base. In DNA, every nucleotide has identical sugars and phosphates, and in RNA, the sugar and phosphate are also the same for every nucleotide.

So what’s different? The nitrogenous bases. DNA has a set of four to use as its coding alphabet. These are the purines, adenine and guanine, and the pyrimidines, thymine and cytosine. The nucleotides are abbreviated by their initial letters as A, G, T, and C. From variations in the arrangement and number of these four molecules, all of the diversity of life arises. Just four different types of the nucleotide building blocks, and we have you, bacteria, wombats, and blue whales.

RNA is also basic at its core, consisting of only four different nucleotides. In fact, it uses three of the same nitrogenous bases as DNA–A, G, and C–but it substitutes a base called uracil (U) where DNA uses thymine. Uracil is a pyrimidine.

DNA vs. RNA: Function Wars

An interesting thing about the nitrogenous bases of the nucleotides is that they pair with each other, using hydrogen bonds, in a predictable way. An adenine will almost always bond with a thymine in DNA or a uracil in RNA, and cytosine and guanine will almost always bond with each other. This pairing capacity allows the cell to use a sequence of DNA and build either a new DNA sequence, using the old one as a template, or build an RNA sequence to make a copy of the DNA.

These two different uses of A-T/U and C-G base pairing serve two different purposes. DNA is copied into DNA usually when a cell is preparing to divide and needs two complete sets of DNA for the new cells. DNA is copied into RNA when the cell needs to send the code out of the vault so proteins can be built. The DNA stays safely where it belongs.

RNA is really a nucleic acid jack-of-all-trades. It not only serves as the copy of the DNA but also is the main component of the two types of cellular workers that read that copy and build proteins from it. At one point in this process, the three types of RNA come together in protein assembly to make sure the job is done right.


 By Emily Willingham, DXS managing editor 
This material originally appeared in similar form in Emily Willingham’s Complete Idiot’s Guide to College Biology

Pregnancy 101: My placenta looked like meatloaf, but I wasn’t about to eat it.

By Jeanne Garbarino, Biology Editor
An historic view interpretation of the placenta (source). 

She gave me a few minutes to meet my daughter before she reeled me back into a state that was my new reality.  “You’re not finished Jeanne.  You still need to birth your placenta.”  What?!?! More pushing? But I was lucky and the efforts required to bring my placenta ex vivo were minimal. 

This is the second placenta my body helped make.  OK,
so it doesn’t EXACTLY look like meatloaf…  

The idea of a placenta, which is the only human organ to completely and temporarily develop after birth, was fascinating.  That thing sitting in a rectangular periwinkle bucket was what allowed me to grow another human.. inside of my body!  There was no way I was not going to check it out, as well as create a permanent record of its relatively short-lived existence. 

My first impression was that it looked like “meatloaf.”  Not necessarily a well made meatloaf, but perhaps one that is made by my mother (sorry mom).  But, alas, chaos reigned and I wasn’t able to really take a good look.  However, for my second birth and hence second placenta, my midwife indulged me with a more detailed look and a mini-lesson.   

Baby’s eye view:
Where geekling deux spent 39 weeks and 4 days. 

Her gloved hands, still wet with my blood and amniotic fluid, slid into the opening that was artificially created with a tool resembling a crocheting needle.  She opened the amniotic sac wide so I could get a baby’s eye view of the crimson organ that served as a nutritional trading post between me and my new bundle of joy. 

She explained that the word “placenta” comes from from the Greek word plakoeis, which translates to “flat cake” (however, I’m sure if my mom’s meatloaf was more common in ancient Greece, the placenta would be named differently).   “It’s one of the defining features of being a mammal,” she explained as I was working on another mammalian trait – getting my baby to nurse for the first time.

That was about all I could mentally digest at the time, but still, more than three years later, the placenta continues to fascinate me, mostly due to the fact that it is responsible for growing new life.  It’s a natural topic for this long overdue Pregnancy101post, so let’s dive in!
Development of the placenta
It all starts when a fertilized egg implants itself into the wall of the uterus.  But, in order to fully understand how it works, we should start with an overview of the newly formed embryo. 

The very early stages of us (and many other things that are alive).
The trophoblast invades the uterus,
leading to implantation of the blastocyst.

As soon as a male sperm cell fuses with a female egg cell, fertilization occurs and the cells begin to multiply.  But, they remain contained within a tiny sphere.  As the cells continue to divide, they are given precise instructions depending on their location within that sphere, and begin to transform into specific cell types.  This process, which is called cellular differentiation, actually seals the fate every cell in our body, sort of like how we all have different jobs – some of us are transport things, some of us are involved in policing the neighborhoods, some of us build structures, some of us communicate information, some of us deal with food, some of us get rid of waste, etc.  Every cell gets a job (it’s the only example of 100% employment rates!).

Now back to the cells in the fertilized egg.  As they start to learn what their specific job will be, the cells within the sphere will start to organize themselves.  After about 5 days after fertilization, the sphere of cells becomes something called a blastocyst, which readies itself for implantationinto the wall of the uterus. 

The act of implantation is largely due to the cells found on the perimeter of the blastocyst sphere.  These cells, collectively known as the trophoblast, release a very important hormone – human chorionic gonadotropin (hCG) – that tells the uterus to prepare for it’s new tenant.  (If you recall, hCG is the hormone picked up by pregnancy tests.)  Around day 7, the trophoblast cells start to invade the lining of the uterus, and begin to form the placenta.  It is at this point that pregnancy officially begins.  (Here is a cool video, created by the UNSW Embryology Department, showing the process of implantation.)

Structure of the placenta

Eventually the trophoblast becomes the recognizable organ that is the placenta.  Consider the “flat cake” analogy, with the top of the cake being the fetal side (the side that is in contact with the baby), and the bottom of the cake being the maternal side (the side that is in contact with the mother).     

Cross section of the placenta: Blood vessels originating from the fetus sit in a pool
of maternal blood, which is constantly replenished my maternal arteries and veins.
The red represents oxygenated blood, and the blue represents de-oxygenated blood.

Projecting from the center of the fetal side of the placenta are two arteries and one vein, coiled together in a long, rubbery rope, often bluish-grey in color.   This umbilical cord serves as the tunnel through which nutrients and waste are shuttled, and essentially serves to plug the baby into the mother’s metabolic processes.  At the umbilical cord-placenta nexus, the umbilical cord arteries and vein branch out into a network of blood vessels, which further divide into a tree-like mass of vessels within the placenta. 

These tree-like masses originating from the umbilical cord (and thus fetus) sit in a cavity called the intervillous space, and are bathed in nutrient-rich maternal blood.  This maternal blood, which provides the fetus with a means for both nutrient delivery and waste elimination, is continually replenished via a network of maternal arteries and veins that feed into the intervillous space.  Furthermore, these arteries and veins help to anchor the placenta into the uterine wall.  One of the most interesting aspects about the mother-feus relationship is that the blood vessel connection is indirect.  This helps to prevent a detrimental immune response, which could lead to immunological rejection of the fetus (sort of like how a transplanted organ can become rejected by the recipient).  
Functions of the placenta

Just like a plant needs sunlight, oxygen, and water to grow, a baby needs all sorts of nutrients to develop.  And since a baby also produces waste, by nature of it being alive and all, there is an absolute requirement for waste removal.  However, because we can’t just give a developing fetus food or a bottle, nor are we able to change diapers in utero, the onus lies completely on the biological mother. 

This is where the placenta comes in. Because the fetus is plugged into the circulatory system of the mother via the umbilical cord and placenta, the fetus is provided with necessary nutrients and a mechanism to get rid of all the byproducts of metabolism.  Essentially, the placenta acts as a waitress of sorts – providing the food, and cleaning it all up when the fetus is done eating. 

But it’s not just about nutrition and waste.  The placenta also serves as a hormone factory, making and secreting biological chemicals to help sustain the pregnancy.  I mentioned above that the placenta produces hCG, which pretty much serves as a master regulator for pregnancy in that it helps control the production of maternally produced hormones, estrogen and progesterone.  It also helps to suppress the mother’s immunological response to the placenta (along with other factors), which cloaks the growing baby, thereby hiding it from being viewed as a “foreign” invader (like a virus or bacteria). 

Another hormone produced by the placenta is human placental lactogen (hPL), which tells the mother to increase her mammary tissue.  This helps mom prepare for nursing her baby once it’s born, and is the primary reason why our boobs tend to get bigger when we are pregnant.  (Yay for big boobies, but my question is, what the hell transforms our rear ends into giant double cheeseburgers, and what biological purpose does that serve??  But I digress…)

Despite the fact that the mother’s circulatory system remains separate from the baby’s circulatory system, there are a clear mixing of metabolic products (nutrients, waste, hormones, etc).  In essence, if it is in mom’s blood stream, it will very likely pass into baby’s blood stream.  This is the very reason that pregnant mothers are strongly advised to stay away from cigarettes, drugs, alcohol, and other toxic chemicals, all of which can easily pass through the placental barrier lying between mother and fetus.  When moms do not heed this warning, the consequences can be devastating to the developing fetus, potentially leading to birth defects or even miscarriage.        

There are also situations that could compromise the functions of the placenta – restriction of blood supply, loss of placental tissue, muted placental growth, just to name a few – reducing the chances of getting and/or staying pregnant.  This placental insufficiency is generally accompanied by slow growth of the uterus, low rate of weight gain, and most importantly, reduced fetal growth.     

And it’s not just the growth of the placenta that is important – where the placenta attaches to the uterus is also very important.  When the placenta grows on top of the opening of the birth canal, the chances for a normal, vaginal birth are obliterated.  This condition, known as placenta previa, is actually quite dangerous and can cuase severe bleeding in the third trimester.  0.5% of all women experience this, and it is one of the true medical conditions that absolutely requires a C-section. 

Then, there is the issue of attachment.  If the placenta doesn’t attach well to the uterus, it could end up peeling away from the uterine wall, which can cause vaginal bleeding, as well as deprive the baby from nutrient delivery and waste disposal.  This abruption of the placenta  is complicated by the use of drugs, smoking, blood clotting disorders, high blood pressure, or if the mother has diabetes or a history of placental abruption. 

Conversely, there are times when the blood vessels originating from the placenta implant too deeply into the uterus, which can lead to a placenta accreta.  If this occurs, the mother generally delivers via C-section, followed by a complete hysterectomy. 

Cultural norms and the placenta

There are many instances where the placenta plays a huge role in the culture of a society.  For instance, both the Maori people of New Zealand and the Navajopeople of Southwestern US will bury the placenta.  There is also some folklore associated with the placenta, and several societies believe that it is alive, pehaps serving as a friend for the baby.   But the tradition that seems to be making it’s way into the granola culture of the US is one that can be traced back to traditional Chinese practices: eating the placenta. 

Placentophagy, or eating one’s own placenta, is very common among a variety of mammalian species.  Biologically speaking, it is thought that animals that eat their own placenta do so to hide fresh births from predators, thereby increasing the chances of their babies’ survival.  Others have suggested that eating the nutrient-rich placenta helps mothers to recover after giving birth.

However, these days, a growing number of new mothers are opting to ingest that which left their own body (likely) through their own vaginas.  And they are doing so though a very expensive process involving dehydrating and encapsulating placental tissue.  

Why would one go through this process?  The claims are that placentophagy will help ward of post partum depression, increase the supply of milk in a lactating mother, and even slow down the ageing process.  But, alas, these are some pretty bold claims that are substantiated only by anecdata, and not actual science (see this).

So, even though my placentas looked like meatloaf, there was no way I was eating them.  If you are considering this, I’d approach the issue with great skepticism.  There are many a people who will take advantage of maternal vulnerabilities in the name of cold hard cash.  And, always remember, if the claims sound to good to be true, they probably are!   


Thanks for tuning into this issue of Pregnancy101, and enjoy this hat, and a video!

Source


Are your children always on your mind? They may be IN your mind

Hmm. Do I have any cells in there?
On Mother’s Day this year, we told you why, if you have biological children, those children are literally a part of you for life thanks to a phenomenon called microchimerism. When a woman is pregnant, some of the fetal cells slip past the barrier between mother and fetus and take up residence in the mother. What researchers hadn’t turned up in humans before now was that some of those cells can end up in the mother’s brain. Once there, according to a study published today in PLoS ONE, they can stick around for decades and, the researchers suggest, might have a link to Alzheimer’s disease. Note that is a big “might.”

The easiest way to tell if a fetal cell’s made it into a maternal tissue is to look for cells carrying a Y chromosome or a Y gene sequence (not all fetuses developing as male carry a Y chromosome, but that’s a post for another time). As you probably know, most women don’t carry a Y chromosome in their own cells (but some do; another post for another time). In this study, researchers examined postmortem brain tissue from 26 women who had no detectable neurological disease and 33 women who’d had Alzheimer’s disease; the women’s ages at death ranged from 32 to 101. They found that almost two thirds (37) of all of the women tested had evidence of the Y chromosome gene in their brains, in several brain regions. The blue spots in the image below highlight cells carrying these “male” genes a woman’s brain tissue.

Photo Credit: Chan WFN, Gurnot C, Montine TJ, Sonnen JA, Guthrie KA, et al. (2012)
Male Microchimerism in the Human Female Brain. 
PLoS ONE 7(9): e45592. doi:10.1371/journal.pone.0045592

The researchers also looked at whether or not these blue spots were more (or less) frequent in the brains of women with Alzheimer’s disease compared to women who’d had no known neurological disease. Although their results hint at a possible association, it wasn’t significant. Because the pregnancy history of the women was largely unknown, there’s no real evidence here that pregnancy can heighten your Alzheimer’s risk or that being pregnant with or bearing a boy can help or hinder. As I discuss below, you can end up with some Y chromosome-bearing cells without ever having been pregnant.

Also, age could be an issue. Based on the reported age ranges of the group, the women without Alzheimer’s were on average younger at death (70 vs 79), with the youngest being only 32 (the youngest in Alzheimer’s group at death was 54). No one knows if the women who died at younger ages might later have developed Alzheimer’s. 

Indeed, most of this group–Alzheimer’s or not–had these Y-chromosome cells present in the brain. The authors say that 18 of the 26 samples from women who’d had no neurologic disease were positive for these “male” cells–that’s 69%–while 19 of the 33 who had Alzheimer’s were. That’s 58%. In other words, a greater percentage of women who’d not had Alzheimer’s in life were carrying around these male-positive cells compared to women who had developed Alzheimer’s. The age difference might also matter here, though, if these microchimeric cells tend to fade with age, although the researchers did get a positive result in the brain of a woman who was 94 when she died.

Thus, the simple fact of having male-positive cells (ETA: or not enough of them) in the brain doesn’t mean You Will Develop Alzheimer’s, which is itself a complex disease with many contributing factors. The researchers looked at this potential link because some studies have found a higher rate of Alzheimer’s among women who’ve been pregnant compared to women who have not and an earlier onset among women with a history of pregnancy. The possible reasons for this association range from false correlation to any number of effects of pregnancy, childbearing, or parenting.

Nothing about this study means that migration of fetal cells to the brain is limited to cells carrying Y chromosomes. It’s just that in someone who is XX, it’s pretty straightforward to find a Y chromosome gene. Finding a “foreign” X-linked gene in an XX person would be much more difficult. Also, a woman doesn’t have to have borne a pregnancy to term to have acquired these fetal cells. As the authors observe, even women without sons can have these Y-associated cells from pregnancies that were aborted or ended prematurely or from a “vanished” male twin in a pregnancy that did go to term. 

In fact, a woman doesn’t even have to have ever been pregnant at all to be carrying some cells with Y chromosomes. Another way you can end up with Y chromosome cells in an XX chromosome body is–get this–from having an older male sibling who, presumably, left a few cellular gifts behind in the womb where you later developed. As the oldest sibling, I can only assume I could have done the same for the siblings who followed me. So, if you’ve got an older sibling and have been pregnant before–could you be a double microchimera? 

But wait. You could even be a triple microchimera! This microchimerism thing can be a two-way street. If you’re a woman with biological children, those children already carry around part of you in the nuclear DNA you contributed and all of the mitochondria (including mitochondrial DNA) in all of their cells. Yes, they get more DNA from you than from the father. But they might also be toting complete versions of your cells, just as you have cells from them, although fetus–>mother transfer is more common than mother–>fetus transfer. The same could have happened between you and your biological mother. If so, a woman could potentially be living with cells from her mother, older sibling, and her children mixed in with her own boring old self cells.

The triple microchimera thing might be a tad dizzying, particularly the idea that you could be walking around with your mother’s and sibling’s cells hanging out in You, a whole new level of family relationships. But if you’re a biological mother, perhaps you might find it comforting to know that a cellular part of you may accompany your child everywhere, even as your child is always on your mind–and possibly in it, too.