BioQuakes

AP Biology class blog for discussing current research in Biology

Author: covalentbond

Does the aging process influence changes on a cellular level or do changes on a cellular level influence the aging process?

wrinkles

How do humans age? While we are “programmed to die,” there doesn’t seem to be one thing that causes our death by “old age.” For example, one way we carry out our own deaths is found on the cellular level, where we accumulate mutations in the DNA repair process and the cells themselves die, or the enter senescence (non-replicating state) as they age. These processes occur at several different times, overlapping and alternating. Therefore, what appears to be the best time to intervene in order to promote healthy aging? No one knows, but they do know what DNA becomes extremely damaged as time goes on and has an incredible impact on our aging process. The cells have sooner suicide dates where they undergo apoptosis more rapidly than normal, and the loss of too many cells can cause tissue atrophy and dysfunction. In addition to creating a lack of cells, the damaged DNA can even shift epigenetic markers.

Typically, epigenetic marks shift in tumor cells, which can lead to cancerous cells. However, in the early 1990s at Johns Hopkins University, Jean-Pierre Issa was studying changes in DNA methylation in colon cancer cells when he observed shifts in epigenetic markers over time, but not only in tumor cells; he found that (to a lesser degree) these shifts were occurring in healthy cells as well. After mapping DNA methylation in human cells, we know that some areas of the genome become hypermethylated with age while others exhibit reduced methylation. These changes typically occur through DNA replication or DNA damage repair because the histone modifications are not always perfectly reproduced and in order to repair damaged DNA, repair proteins must remove the epigenetic marks to access the damaged genetic material to repair it, and once completed, the epigenetic marks can be omitted or misplaced. These epigenetic alterations have been linked to a reduced regenerative capacity of stem cells with age, and bring up a valuable question:

“Is this an epiphenomenon that happens just because we age, or is it actually causing symptoms or diseases of aging and limiting life span?”

Article source: http://www.the-scientist.com/?articles.view/articleNo/42280/title/How-We-Age/

Why don’t women see themselves as brilliant?

640px-Kalpana_Chawla,_NASA_photo_portrait_in_orange_suit

Why is the population of women in physics, engineering, music composition, etc. so sparse? It might have to do with current stereotypes.

Up until relatively recently, women were not in the academic work place’ men dominated all of the academic, intelligent, and advanced jobs. However, today, over 50% of molecular biology and 60% of comparative literature degrees go to women. But where are all of the women in political science and philosophy?

Research shows that careers that focus on brilliance tend to have fewer women in it. In other words, jobs that emphasize knowledge you “can’t be taught” are typically filled with men. Sarah-Jane Leslie and Andrei Cimpian became interested in gender representation in fields that focused on talent versus fields that focused on hard work. They surveyed other potential explanations, gender differences at the upper end of the intelligence scale, and how men and women differ in how they think. They hypothesized that women might not be able to work a certain schedule and therefore not have enough time required for certain academic fields, fields which are extremely selective should have more men than women, and men are better at abstract thinking and women are better at emotional understanding. They tested these hypotheses with surveys that ranked reactions to a statement from strongly agree to strongly disagree (Likert scale), collected and compared GRE scores, and included statements that assessed how much participants though thinking abstractly or emotionally was important in their academic field.

Leslie and Cimpian concluded that stereotypes about women (and also African-Americans) undermine their representation in certain jobs because they subconsciously do not feel fit to be in that field. Other factors include schedule flexibility or harassment in the work environment, but above all, it’s all about attitude, not aptitude.

Why do you think women don’t see themselves as brilliant, even though they may be well aware of their intellectual abilities?

https://www.sciencenews.org/blog/scicurious/attitude-not-aptitude-may-contribute-gender-gap?tgt=nr

Diet Tip #1: Hang Out with Skinny People and Go on a Low Calorie Diet

labrat

Microbiomes are incredibly vast and mysterious; we don’t quite know how they work. However, with a few experiments, we have come to a few conclusions.

1) Microbiomes determine your weight.

Scientists extracted bacteria from the intenstines of human twins, one lean and one larger. The injected these microbiomes into twin mice. The mouse who received the large twin’s microbiome gained fat and the mouse who received the lean twin’s microbiome remained small.

2) Fat microbiomes can be influenced by a skinny microbiome.

A fat mouse placed in a cage of skinny mice lost weight.*

3) Skinny microbiomes cannot be changed.

A skinny mouse placed in a cage of fat mice remained skinny.*

4) With the correct diet, you can become skinny.

Fat mice eating healthy food made them skinny but when they ate junk food, they stayed fat. A different group of scientists replicated this experiment with overweight humans and a low calorie diet. Their microbiotic diversity was low and increased significantly, leading to weight loss.

5) Diet does not affect skinny people.

Regardless of which diet the skinny mice ate, they stayed skinny. A different group of scientists replicated this experiment with skinny people and a low calorie diet. Their microbiotic diversity was already high and did not change much.

*read the full study here

Why?

Fat microbiomes tend to be more efficient at extracting nutrients from food and storing the excess, so whenever someone with an efficient microbiome eats, he/she stores a lot of the nutrients. Skinny microbiomes, on the other hand, are not as efficient at extracting nutrients so there is less energy to store after a meal. Going on a low calorie diet if you want to lose weight could solve the problem because whatever can be extracted from the food will be used for day to day functions. Considering that skinny people already are not extremely efficient at extracting nutrients, a low calorie diet will not necessarily cause any significant changes.

This source performed a study (humans) where they discovered that obese people typically have lower genetic diversity than lean people. Obese people who went on a low calorie diet had a higher genetic diversity at the end of the experiment than those who did not go on a low calorie diet, and obese people who continued to have a low genetic diversity gained significantly more weight over nine years. Lean people who went on a low calorie diet did not have a significant increase in microbiotic diversity compared to lean people who did not go on that diet. However, this correlation does not imply causation because some obese people have a high genetic diversity. Scientists believe that a low genetic diversity is linked to metabolic disorders, which could cause obesity, but that obesity in and of itself is not always caused by low genetic diversity.

Whenever you touch, breathe, or eat something, bacteria is entering your body and interacting with the native bacteria. So, when fat mice interact with skinny mice, it’s possible that the fat mice pick up diverse bacteria from skinny mice, contributing to their increase in microbiotic diversity, and when skinny mice interact with fat mice, they can’t lose genetic diversity but also have nothing really to gain from mice with low genetic diversity.

Conclusion: If you have a metabolic disorder, it could be beneficial to surround yourself with skinny people and eat low calorie foods because you’re more likely to absorb diverse types of bacteria while also storing less energy from food.

Are Antibiotics Killing More Than Just Infections?

What are in your antibiotics?

We all take antibiotics. Staph infections, Strep throat, etc. and they get the job done. Within two or three days, sometimes a week, you’re cured and infection-free. But is that really best for us?

Microbiomes are what make us so unique and individual. In fact, we have more bacteria cells that human cells in a 10 to 1 ratio. We have different microbiomes for different parts of the body; our mouth has a different microbiome than our skin microbiome which has a different microbiome than our gut microbiome. We can influence our microbiomes by what we eat, or rather they influence us based on what we eat. As part of an evolutionary benefit, our microbiomes adapt to newly introduced food within days, which we previously thought took years to change. In other words, if you didn’t eat carrots for three years and sporadically ate carrots one day, your microbiome would activate bacteria that was previously dormant to digest the carrots within days. Think for a moment: a bacteria your body hadn’t made in three years is suddenly recolonized and active in helping you digest within a few days. It’s truly amazing! However, the rest depends on how you were born.

If you were vaginally born, your first encounter with bacteria (bacteria from the placenta is still controversial as to whether babies acquire some of their intestinal bacteria before birth) was in the birth canal, which is exactly where you get your microbiota colonies from. If you were Cesarean born, you might find that you have a higher chance of chronic conditions like asthma or Celiac’s disease simply because you received your mother’s skin microbiome instead of her vaginal microbiome. If you were not breast fed, you are more likely to contract similar conditions because breast milk contains nutrients that cannot be broken down by your digestive track. Rather, they surpass your digestive track and nourish microbiota. Formulas were unaware of this and therefore did not contain everything necessary for your microbiota health, but formulas have been making adaptions to fully mimic these qualities of breast milk.

Say you did all of the right things: you eat whole, unprocessed foods that can nourish your microbiome, you were vaginally born and you were breastfed. It’s completely possible that you have a wonderful, flourishing microbiome. However, you likely do not.  Processed foods do not contain enough prebiotic nutrients (food for microbes). Although one associates Western civilization with nutrition and health, we are actually considered “impoverished” in the world of microbiomes.

The big problem with the Western diet is that it doesn’t feed the gut, only the upper G I. All the food has been processed to be readily absorbed, leaving nothing for the lower G I. But it turns out that one of the keys to health is fermentation in the large intestine. Stephen O’Keefe

Those with no contact to the Western world and its medicine, pesticides, sterility and processed foods have a rich and diverse microbiome. Not to mention the growth hormone in cows, which changes the microbiota for a hastened growth as well as the metabolism of the liver. They even stimulate an increase in body fat. Western medicine, however, affects us in less visible manner. Our antibiotics are too strong for our own good; they destroy the pathogenic bacteria, yes, but they also destroy the health-promoting ones. Therefore, some argue that we should improve our diagnostics to prescribe fewer and narrow-spectrum antibiotics to kill the harmful bacteria while reducing the collateral damage. (Dr. Blaser) These heavy duty antibiotics not only destroy the healthy, diverse microbiota, but have a permanent effect if used for a second course; the microbiome will bounce back but it will not be able to return to its original state. In addition to this, antibiotics have been trying to eliminate H. pylori since 1983 when they found it could lead to stomach cancer or peptic ulcers, when in fact its disappearance could be contributing to acid reflux and obesity. Due to our continual efforts to eliminate H. pylori from the microbiome, it is unlikely that we will see it in upcoming microbiomes due to antibiotics, and “each generation is [already] passing on fewer of this microbes.” Prevotella, for example, is a gut bacteria extremely difficult to find in Western society but relatively common in underdeveloped countries. One woman had unusually high levels of this bacteria in her microbiome, but after one course of antibiotics for oral surgery, her wonderful microbiome was reduced to the average American bacterial standards. 

One of the more striking results from the sequencing of my microbiome was the impact of a single course of antibiotics on my gut community. My dentist had put me on a course of Amoxicillin as a precaution before oral surgery. (Without prophylactic antibiotics, of course, surgery would be considerably more dangerous.) Within a week, my impressively non-Western “alpha diversity” — a measure of the microbial diversity in my gut — had plummeted and come to look very much like the American average. My (possibly) healthy levels of prevotella had also disappeared, to be replaced by a spike in bacteroides (much more common in the West) and an alarming bloom of proteobacteria, a phylum that includes a great many weedy and pathogenic characters, including E. coli and salmonella. What had appeared to be a pretty healthy, diversified gut was now raising expressions of concern among the microbiologists who looked at my data.

Her bacterial composition will return to something that somewhat resembles her original microbiome, but every course after that will decrease potential microbial recovery and also decrease invasion resistance (keeps pathogens from gaining a toehold by occupying potential niches or otherwise rendering the environment inhospitable to foreigners e.g. H. pylori regulates stomach acid to make the environment unfavorable to other bacteria that wants to colonize; vaginal pH is kept low so the environment is too acidic for foreign bacteria to colonize, etc.) So the next time you take an antibiotic, ask yourself: what am I doing to my microbiome?

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