Genetic Variation of a Bacterial Pathogen within Individuals with Cystic Fibrosis Provides a Record of Selective Pressures

            In the paper from Lieberman et al, the bacterial pathogen B. dulosa was studied to find out whether mutations within the bacteria’s genome led to a genetic fix in the population or resulted in more genetic diversity. The two different models the hypothesis was based on were the dominant-lineage model, which suggested that that the presence of more beneficial mutations would eventually select for superior dominant lineages of genes, and the diverse-community model, which stated that adaptive lineages reached an intermediate frequency in the population, leading to general genetic diversity with many coexisting gene lineages. The study that the researchers conducted found that the B. dulosa that colonized in the patients with cystic fibrosis had been colonizing with multiple genetic lineages for at least 5 years, showing that they had been developing like that for quite some time. They additionally found that many of the selective pressures acting on the pathogens were the same across all of the patients, showing that the diverse mutations were fairly stable across the sample population. Overall, the study’s support of the diverse-community model allowed them to conclude that in bacterial populations, the beneficial mutations that emerge and compete with each other actually prevent any one dominant lineage from becoming fixed in the population, and rather evolve together to fight off common selective forces. 

Human Physique and Sexual Attractiveness

What makes a person attractive? How do we rate the attractiveness of a female or male counter parts comparable to another’s? In the study by Dixson et. Al. relates human physique to how sexual attractive the opposite sex was. They hypothesizes that evolution has left physical markers for the reproductive qualities for potential mates for those of European ancestry.  People of New Zealand and California were asked to complete 5 studies that related an particular physical trait to sexual attractiveness. the Frist study woman rated muscularity of males to their attractiveness and in the second study the measures the amount of pubic hair on the chest and the genitals to attractiveness. Study three tested penis sizes that the attractiveness of the male. This study showed that on average women thought that the largest penis was rated the most attractive, then the medium or the smaller sized penis. The fourth and last study was comparing the curves and skin color of an female, respectively. The studies showed that men attractiveness toward an female slightly curvy and light-skinned woman preferred in both New Zealand and California.

Does alcohol truly prevent coronary heart disease?

Everyone can enjoy a glass of wine or even an cold glass of beer, but does alcohol consumption provide more the just an way to unwind. According to a recent article by Mukamal et. Al. a two alcoholic beverages a day can lower a person chances of getting coronary heart diseases.

Several studies have indicated that moderate drinkers have a lower risk of both nonfatal myocardial infraction and fetal heart diseases than people who abstain from alcohol. Mukamal et. Al has compiled information from 42 peer-reviewed published studies in to a single analysis whose purpose is to answer this issue. The article goes in brief details of the many hypothesis and studies conducted up until now that have supported and even falsified that alcohol reduces getting coronary heart diseases.  Their finding proved that while alcohol consumption deceases person chances of contracting a heart related problem alcohol also increases the levels of certain molecules that promote heart diseases. Through meta-analysis of people who drink alcohol regularly, Rimm and colleagues (1999) found that alcohol lowered important factors in atherosclerosis, inflammation, and thrombosis such as high-density lipoprotein cholesterol (HDL-C) otherwise known as the “Good Choloesterol”. The studies showed that 30 grams of alcohol or about two drinks per day increases the levels of HDL-C similar in strength to gemfibrozil, a prescription medication that is used to treat patient with high levels of cholesterol and is accounted for a 16.8% decrease in in the risk of coronary heart diseases. While the studies show so proven benefits, alcohol can also increase levels of triglyceride by about 5.7percent, with can increase an chances of devolving heart diseases by a 4.6% increase.

Whether alcohol decrease the risk of developing a coronary heart diseases is up the reader, especially since there is an 50-50 percent chance of lower your own risk of heart disease. However drinking in moderation is always still the preferred way to go.

Racial differences in blood clotting

I found this article extremely interesting while I was writing my paper. This article focused on the differences between clotting factors of African Americans and European-descent American. The article driven their research on how it can improve medications and even lead to personalized medication in the future for heart related problems.

African Americans have a greater chance of incidence of heart attacks then White patients and lower survival rates, with is 21/2 times lower then whites. This difference has lead researchers to study the differences between African American that can contribute to higher incidence of heart disease. Despite the traditional differences such as socioeconomic status, diet, and environment, researchers at Thomas Jefferson University found that African American have an more potent blood clotting factor then Caucasians. In the experiment, Bray et.Al. took blood samples from 154 subjects( 70 blacks and 84 whites) and tested the blood clotting affinity. They found that that Blacks blood clots faster because of the clotting agent PAR4. PAR4 bind more thrombin, a blood platelet activator, faster then other agents in Whites. Another gene called PCTP, which mediates platelet activation of the PAR4 was another difference between clot formation of blacks and whites. PCTP was expressed higher in black then in whites.

This new research present new way of thinking about prescriptions. Many blood thinners work by targeting the PAR gene family to prevent blood clotting. However in Blacks that have PAR4 genes are unaffected by drugs currently on the market.  In class we have often talked about individualized treatments an I think that this article is strong evidence that support the idea of individualized medicine in the future.

Leonard C Edelstein, Lukas M Simon, Raúl Teruel Montoya, Michael Holinstat, Edward S Chen, Angela Bergeron, Xianguo Kong, Srikanth Nagalla, Narla Mohandas, David E Cohen, Jing-fei Dong, Chad Shaw, Paul F Bray. Racial differences in human platelet PAR4 reactivity reflect expression of PCTP and miR-376c. Nature Medicine, 2013; DOI: 10.1038/nm.3385


Melanin: Animals Vs. Insects.

In my presentation, I talked about the roles of melanin in human, mostly focusing on the compound’s protective properties from UVA and UVB rays. I mentioned slightly that melanin is found in all types of animal and even insects. Since I did not go into further details within my presentation, I want to bring this article on the blog to open up this topic for discussion.

This article, written by Manickam Sugumaran, compares the properties for melanin production in animals verses melanin production in insects. The article details the processes and the distinct types of protein factors for melanogenesis. Through the presentation I discussed human, which is responsible of hair, eye, and skin color.  Eumelanin is produced from the hydroxylation of tyrosine by tyrosine. Insects contain produce their melanin through an different process, which employs phenoloxidase and dopachrome( decarboxylating) isomerase for melanin production. Since the pathways for creating melanin is significant different between animals and insects, Sugumaran says that the advantages of are also an mirror to these differences.

In insects, phenoloxidase and melanin has many functions, Sugumaran talks about the major three physiologically important biochemical processes. The first is sclerotization of the insect cuticle. Sclerotization is the transformation of the soft and pale cuticle (outer shell of the insect) into a hard exoskeleton. If the exoskeleton does not harden and dry quickly the insect will die of dehydration. The second hypothesis is insect immunity. Insects lack immunoglobulin, and melanin forms a second line of defense (first being the exoskeleton) that traps pathogens by depositing melanin on the forging object. The melanin goes through the phenoloxidases cascade, which prevents the multiplication and the growth of the parasite. The last hypothesis is healing injury. Melanin and phenoloxidase is uses a clotting factor in insects to prevent the lost of haemolymph. Here we see major differences between melanin in animals and insect, but yet understand why has evolution left such differences.

This is a good article to start off with the continuation of the advantages of melanin from the oral presentation. It also offers new material for discussion on why melanin productions was conserved by yet has different advantages in various organisms.


Tsetse Fly Genome Sequenced

The genome of the tsetse fly has recently been sequenced and the success has been gaining attention in mainstream media through the New York Times and National Geographic. Why is the tsetse fly important and what’s so special about its genome? The tsetse fly transmits human African trypanosomiasis, commonly known as “sleeping sickness.” Trypanosomiasis is a vector-borne parasitic disease with two main types, depending on the parasite (Tranosoma brucei gabiense causes 98% of cases, trpanosoma brucei rhodesiense causes the other 2%). Trypoanosomiasis occurs in 36 Sub-Saharan African countries where tsetse flies are found. Animals can also be affected by tyrpanosomiasis, and can serve as reservoirs for human pathogen parasites. Thus, animal husbandry is more difficult in areas with tsetse flies, which are mostly rural.

There are many interesting discoveries about tsetse flies that have been made in the process of sequencing its genome. For example, female tsetse flies give birth to one larva at a time and only produce about 8-10 offspring during their life span, unlike mosquitoes that can produce about a thousand offspring. Therefore, eliminating one female tsetse fly can have a big effect on the population, according to Dr. Serap Aksoy of the Yale School of Public Health. Even though tsetse flies feed on blood, females nourish their young in the womb with milk, a surprising characteristic that somewhat resembles mammalian care for offspring.

The Aksoy lab at Yale is responsible for sequencing the tsetse fly genome. They hope that this will aid current control methods and lead to the development of new strategies to reduce or even eliminate the transmission of trypanosomiasis in Sub-Saharan Africa. One line of attack is targeting the single gene that regulates milk production in female flies. The idea is that less milk will cause the flies to be less fertile. Other possibilities are vaccines and/or repellants that target specific aspects of the tsetse fly genome.

Depression as an evolutionary strategy for defense against infection

The main question of this article is: “Despite its negative consequences, why does depression persist in the population?” The article introduces the “infection-defense hypothesis” of depression, which proposes that moods—with their ability to orchestrate a wide array of physical and behavioral responses—have played an adaptive role throughout human history by helping individuals fight existing infections, as well as helping both individuals and their kin avoid new ones. In contrast to many previous evolutionary theories of depression, the infection-defense hypothesis takes into account and helps to integrate a large and growing body of evidence linking depression to inflammation and immune function, and helps to explain depression’s association with a vast array of conditions and illnesses such as nutritional deficiencies, seasonal changes, hormonal fluctuations, and chronic diseases. The article also notes several predictions for the infection-defense hypothesis. Predictions include: (1) most signs and symptoms of depression will aid the immune system’s ability to fight infections, by performing one or more of the following functions, (2) many types of infectious diseases will be associated with depressive symptoms, (3) depressed individuals will tend to have elevated rates of infection and/or immune alteration, (4) medical, environmental, and physiological conditions that increase immune vulnerability, or that increase exposure to infection, will also be associated with increased rates of depression, (5) there are bidirectional processes that communicate between the nervous and immune systems and provide mechanisms for infections, immune processes, and mood to influence one another, and (6) moods provide an implicit mechanism for cost-benefit analysis of an individual’s optimal responses to environmental challenges and the organisms’ immune status, helping to regulate the timing and intensity of infection-defense responses. Considerable evidence exists to support each of these predictions. The infection-defense hypothesis and in particular, the notion that moods may serve as a behavioral defense against infection, can possibly play a role in understanding the causes, treatment, and prevention of depression.


“Even More Scared” The Effect of Childbirth Reality Shows on Young Women’s Perceptions of Birth

During class, we went into discussion, briefly, about childbirth and cesarean

Sections. Our talks leaned on the class’s anxiety towards giving birth in the near future. Giving birth is a serious and stressful matter, however almost a full 100% of the class expressed their pressing fears in delivering a child. Lauren Elizabeth Rink at the University of Michigan went to address this growing anxiety about birth in the United States. Her thesis focused on the effects of the media, particularly television reality shows, on young woman’s perception of childbirth.


In Rink’s thesis she hypothesis that the increasing anxiety experienced by younger woman, about 18-22 years of age, is do in large because of the media representations of childbirth. Rink describes woman who are pregnant and planning of starting a family as “high information seekers”. As so, they turn to media sources such as television, the Internet, video’s, and books to learn about childbirth. It is this imperative, in Rink’s opinion, to study the effects of birth reality show like Lifetime’s One Born Every Minute on undergraduate women’s perception of childbirth. In this study, undergraduate female students (n=78) from the University of Michigan participate in pre and post survey after watching One Born Every Minute. Her finding founding were that after watching One Born Every Minute, student anxiety of having high risks births greatly increased. Through the surveys, Rink also found that the increase in television media seems to created “norms” about childbirth that limits different birthing options available. Such options as midwifery and natural Births are minimized because they are not shown a frequently as medicalization. I found this paper very interesting because it continued from our talk in class.

The Drunken Monkey Hypothesis

The topic I chose for my oral presentation recently came back in the news, with the publication of the book The Drunken Monkey: Why We Drink and Abuse Alcohol by Dr. Robert Dudley, a professor of biology at the University of California Berkeley. The book goes into greater detail about the hypothesis I discussed in class about alcoholism stemming from the consumption of fermented fruit. The theory, which Dudley refers to as a the “Drunken monkey hypothesis,” proposes that our tendency to favor alcoholic drinks and become addicted to them stems from the fact that humans have developed a powerful sensory bias towards alcohol that relates it to nutritional reward. As detailed in an article in The Huffington Post by Dudley, titled “How Evolution Explains Why Humans Drink and Abuse Alcohol.” Primates would have eaten fruit living in more tropical climates, which would have exposed them to more rapidly ripening fruit that contains ethanol due to fermentation. The consumption of these fruits by primates and our subsequent evolution from them suggest that we may have developed a genetic adaptation that primes us to want to consume more of it. It makes sense that early primates would have been drawn to this as a food source in the first place – fruit flies were the first ones to figure out that the smell of alcohol indicated a good source of calories, and alcohol stimulates feeding in modern humans through the aperitif effect (apéritifs are alcoholic drinks that are served before meals to stimulate the appetite).

The drunken monkey hypothesis points toward an evolutionary mismatch in humans with our modern consumption of much higher levels and concentrations of alcohol, especially with the evolutionarily recent process of distillation. Animals in the wild do not get drunk, since fruit contain very low levels of alcohol. But it leaves humans with the evolutionary results of being drawn to alcoholic substances.

Synopsis for Setchell

The article’s main question is: “what is the influence of major histocompatibility complex (MHC) on patterns of reproduction in the mandrill? The study also looked into the possibility of whether or not the males had a reproductive advantage via either superior competitive ability or via female choice within-male MHC diversity. This study is innovative because this particular study contained a large dataset, involving reproduction over multiple years for a long-lived species. This study was also the first to demonstrate a reproductive advantage associated with MHC dissimilarity in a polygynous species with high levels of male-male competition. This study supported previous studies showing significantly higher rate of nonsynonymous than synonymous substitutions within the mandrill DRB.

This study was done on a large, semi-free-ranging population of mandrills, at the Centre International de Recherches Médicales, Franceville. Observations of the female reproductive status, births, injuries, and disappearance were made daily. DNA was extracted from blood samples obtained during annual captures of the colony for genetic analysis. MHC-DRB genotyping was also conducted for 155 of the population. The overall genetic similarity between genotypes of two individuals was estimated in order to determine whether reproduction was biased towards unrelated partners. Measures of MHC dissimilarity were also calculated for each potentially reproductive dyad in order to determine whether reproduction was biased towards partners with dissimilar MHC genotypes. Various statistical analyses were done in order to answer questions such as, “does overall genetic dissimilarity influence reproduction?” or “does male genotype influence reproduction?”

After genetic analysis, the results suggest that the MHC sequences are capable of providing resistance to pathogens, and thus might be the foundation of MHC- associated mate choice. The results showed that that pedigree relatedness, overall genetic dissimilarity, MHC dissimilarity and male genotype all influenced reproduction in this mandrill colony. Results also showed that male rank was by far the strongest influence on reproduction in males, with alpha males being 18 times more likely to sire a given offspring than nonalpha males.

The findings show that MHC-associated mate choice may be more widespread than previously thought. The findings also suggest that individual genetic characteristics in mandrills may be linked to male vigour and further studies can be taken on to investigate whether microsatellite heterozygosity or MHC diversity are linked to better condition or reduced susceptibility to disease.