When you look at it, your brain is in a series of complex change: gazing makes your brain secrets a large amount of oxytocin that makes you  get closer. At the same time, the oxytocin in its brain is increasing, making the same impact…

“It”I mention here is dog.  Journal“Science”has published a study in recent year, that points out that gazing behavior between owners and dogs produce a positive feedback of oxytocin secretion, which makes dogs become human’s best friends. Wolves, who rarely engage in eye contact with their human handlers, seem resistant to this effect. Hence, oxytocin not only become the connection of people’s love, but also produce the love over species.

What is oxytocin?

In 1906, the renowned British physiologist Sir Henry H Dale discovered a type of hormone facilitating uterine contractions. He named it “oxytocin”. In 1909, the clinical potential of Dale’s seminal findings on oxytocin was realized by the celebrated British obstetrician and gynecologist William Blair Bell. Bell claimed that oxytocin could not only rapidly facilitated uterine contractions to assist in fetal delivery, but also prevented postpartum hemorrhage, and provided considerable relief for male and female patients suffering from severe constipation. In the early 1950s, American biochemist Vincent du Vigneaud identified the nine-amino acid sequence of oxytocin, and synthesized this polypeptide hormone for the first time. This work represented the first characterization and synthesis of a neuropeptide and resulted in a Nobel Prize in Chemistry for du Vigneaud in 1955. (More details about oxytocin in http://jop.sagepub.com/content/27/3/231.full)

Oxytocin is normally produced by the paraventricular nucleus of the hypothalamus and released by the posterior pituitary. Both male and female can secrete oxytocin. After releasing, a part of oxytocin reaches periphery tissue through blood circulation, and the rest passing hemato encephalic barrier, enters the central nervous system and functions as a neurotransmitter.

Oxytocin’s functions

Oxytocin influence several aspects of individual behaviors. The studies in early stage mostly focus on its impact of maternal behavior. A study shows that there is a positive correlation between oxytocin throughout pregnancy and maternal-fetal attachment. In other words, if mother has high levels of oxytocin, she would do more intimate behaviors, such as hug. Besides this, oxytocin affects couple relationship. Because the couples who absorb oxytocin have less conflicts and more positive communications. Additionally, previous studies have shown oxytocin increases trust among people.

It is very interesting that oxytocin can also affect some animals. Microtus ochrogaster release oxytocin that stimulates dopamine during mating, so they can maintain monogamy. However, microtus montanus, which has similar genes with microtus orhrogaster, doesn’t release oxytocin and dopamine, so this species maintains group marriage.

Then we go back to the study at Azabu University in Sagamihara, Japan, which was published in “Science”. The result finds that gazing from pet dogs made high levels of oxytocin contents in owner’s urine samples, and vice versa. Therefore, the relationship between owners and pet dogs becomes closer and closer. This positive feedback loop, he says, may have played a critical role in dog domestication. In this study, the dogs were males and females, spayed, neutered and intact. The breeds included Golden retrievers, standard poodles, miniature Dachshunds, miniature Schnauzers, a Jack Russell Terrier, and two mixed breed. So the samples are very representative. And I think the conclusion is convincing.

So that human and dogs become good friend is not a coincidence. What’s more, in my opinion, my dog is as my “fur baby”, do you?

Source1 Source2 Source3 Source4 Source5 Source6 Source7 Source8

Pic1 Pic2 Pic3

As we know, our daily diet can affect our health. Today, vegetable, green food becomes the synonym of healthy food. People start to modify their diets that eat more vegetables and less meat. What’s more, many choose to become vegetarians. Approximately six to eight million adults in the United States eat no meat, fish, or poultry, according to a Harris Interactive poll commissioned by the Vegetarian Resource Group, a nonprofit organization that disseminates information about vegetarianism. Several million more have eliminated red meat but still eat chicken or fish. About two million have become vegans, forgoing not only animal flesh but also animal-based products such as milk, cheese, eggs, and gelatin.

However, a research group in Austria set off an alarm bell for vegetarians: be a vegetarian is not healthier. Its results showed that a vegetarian diet is associated with poorer health (higher incidences of cancer, allergies, and mental health disorders), a higher need for health care, and poorer quality of life. In detail, the analysis shows that in the frequency of chronic diseases, significantly higher cancer incidence rates in vegetarians than in subjects with other dietary habits. Also, vegetarians suffer largely more often from anxiety disorder and/or depression. Additionally, they have a poorer quality of life in terms of physical health, social relationships, and environmental factors. This study contains the large sample size, the matching according to age, sex, and socioeconomic background, and the standardized measurement of all variables. And they consider the influence of weight and lifestyle factors on health, such as physical exercise and smoking behavior. So this study actually avoid confounding variables. But it has only shown that Austrian adults who consume a vegetarian diet are less healthy, have a lower quality of life, and also require more medical treatment. Moreover, we still need a more in-depth analysis of the health effects of different dietary habits.

I have heard that there is a connection between infertility and vegetarianism. A research group in University of Munich had this kind of study. They found that vegetarians in their samples has possibility that cause changes in hormone levels. To be specific, vegetarian’s diet easily cause deficiency of protein and fat, which influence fertilization. But the result may cause by confounding variables. For example, because diets of vegetarians are relatively simple, vegetarians are easier to get disturbances in estrogen levels, which influence fertilization, than non-vegetarians. However, this phenomenon unusually exits clinically. Also, it’s hard to consider other factors except diet, such as congenital defects, reproductive system inflammation, age and psychological state. It cannot state whether a causal relationship exists, but describe ascertained associations

What’s more, a vegetarian diet can be lacking in certain key nutrients, if not well planned. For instance, vegetarian should eat more to maintain healthy and get enough protein. Vegetarians and vegans also need to prioritize their intake of iron, calcium, vitamin B12, and zinc. Vitamin D and omega-3 fatty acid supplementation may also be necessary.

Eventually, I’d like to say that be a vegetarian is not the only way to keep healthy. Especially sometimes false belief in vegetarianism can even cause adverse effects. So, trying to balance nutrition, maintain healthy daily routine and exercise is the suitable to keep healthy.

If someone want to become a vegetarian, he or she actually requires planning and knowledge of plant-based nutrition. Here are some resources that can help:

American Dietetic Association www.eatright.org

The Vegetarian Resource Group www.vrg.org

Source1 Source2 Source3

pic1 pic2

In State College, I always think that the air here is pretty fresh, and I feel very comfortable with blue sky, white clouds and beautiful sunshine. However, in North China, the outside environment is totally different. A large blanket of brown haze has settled over North China, especially in the big cities because industries emit in the air pollutant. In the daily life, many people choose to wear masks  outside and have air home purifiers to protect their respiratory tracts and lungs. Under this condition, can haze affects people’s mood?

Many people may have the experience that often feel cheerful on sunny days and feel down on dreary days. If this experience appears frequently, even affect normal activities, people should pay attention and find a psychiatrist to consult that whether they have SAD. SAD, seasonal affective disorder is a type of depression that occurs during the same season each year. If you have SAD, your symptoms would start in the fall, and continue into the winter months, sapping your energy and making you feel moody. But, you will feel much better in spring and summer. The specific cause of seasonal affective disorder remains unknown. Some factors that may come into play include: circadian rhythm, serotonin levels, and melatonin levels. To be specific, the period of sunlight reduce in fall and winter. This decrease in sunlight may disrupt body’s internal clock and lead to feelings of depressions. Also, reduced sunlight can cause a drop in serotonin which affects mood, and may trigger depression. Lastly, the change in season can disrupt balance of the body’s level of melatonin, which plays a role in mood and sleep patterns. The study scientists did in Ohio State University prefers the third factor, the level of melatonin.

Three people suicided, in Beijing, China, in one day of 2014 when Beijing was in a pollutionhaze. So, can haze cause seasonal affective disorder, and then induce suicide? Vice professor Jie Zhong in Psychology of Peking University said that although melatonin levels are related to depression, this kind of influence usually exist in the high latitude regions having polar daylight and polar night, such as Russia, Norway and Denmark. Therefore, he said that haze is just an excuse for depression. From my perspective, this conclusion has no any evidence or experiment to support, so it is not convincing.

Now can we believe that haze has no any relation with depression? No. Scientists have studied the topic of relationship between mood and suicide since the beginning of 20th century. The purpose of that study was to evaluate the hypothesis that sunshine exposure may trigger suicidal behavior. Hence they found that sunshine may have a triggering effect on suicide, and suggests further research in the field of sunshine-regulated hormones, particularly melatonin.

An article published in International Journal of Biometeorology in 2013, studied the citizens in Be’er Sheva, Israel.The main objective of this study was to evaluate the role of the concentration of solid air-suspended particles (SSP) in the incidence of mental disorders. In this area, the desert air streams  which bring with an increased concentration of SSP, appear to be complicated stressors that can excite the multiple breaches in psychological state of weather sensitive persons ( such as ideation, mental derangement, depression, nervous tension, and emotional conflicts). Some of these reactions have several accompanying effects, such as a higher prevalence of attempted suicide consistently associated with depression or violation of routine behavior and nervous tension followed by serious consequences in mental dysfunctions.

What’s more, a research group from Canada and a research group from Seoul National University have done similar studies. The results from Canadian research group indicate a potential association between air pollution and emergency department visits for suicide attempts by collecting emergency visit data in a hospital in Vancouver, Canada. The study in SNU is called “Long-Term Fine Particulate Matter Exposure and Major Depressive Disorder in a Community-Based Urban Cohort”. And its subjects are 560 elders in a local welfare house. Its result is that long-term PM2.5 exposure increased the risk of MDD among the general population. But in my opinion, the subjects limit to some extent the generalization of the findings made in the study.  So we can only regard it as a reference.

From here we see that there is some correlations between haze and depressive disorder, but we cannot conclude that haze can induce or lead to depressive disorder. We need more specific and rigorous experiments to find the causality. However, in some degrees, people cannot ignore this possibility.

Source1 Source2 Source3 Source4 Source5 Source6 Source7

Pic1 Pic2

  Do you believe that “ for every extra 10cm (4in) of height, when fully grown, the risk of developing cancer increased by 18% in women and 11% in men”? It sounds unbelievable, but according to a large sample and long-term experiment in Sweden, it is true.

At the 54th Annual European Society for Paediatric Endocrinology Meeting, researchers from  the Karolinska Institutet (one of the largest and most prestigious medical universities in the world )and University of Stockholm showed that cancer risk has been found to increase with height in both Swedish men and women. They examined 5.5 million men and women in Sweden, born between 1938 and 1991 and with adult heights ranging between 3.3 feet and 7.4 feet, and followed the group of individuals from 1958 or from the age of 20 until the end of 2011. Then the scientists got the conclusion which I show above. What’s more, they demonstrated that taller women had a 20% greater risk of breast cancer development, while both men and women have the increased risk of developing melanoma by approximately 30% per 10 cm of height. Study lead author Dr. Emelie Benyi of Karolinska Institutet said that their study is the largest study performed on linkage between height an cancer including both male and female.

Does this mean that great height is the direct cause of development of cancer? Certainly, not! First, the cause of cancer is multifactorial. Although height might be a reason, but is very difficult to predict what is the impact on cancer risk at the individual level. Second, the study only included the sample of men and women in Sweden. To be specific, the data on adult heights was collected from the Swedish Medical Birth, the Swedish Conscription, and the Swedish Passport Registers, whereas the cancer data was retrieved from the Swedish Cancer Register. That “ taller people are more likely to develop cancer” cannot represent the whole population of human. Third, it is possible that the confounding variable exists. It is unclear so far if they also have a higher risk of dying from cancer or have an increased mortality overall, as Dr. Emelie Benyi said. Fourth, it could be a file drawer problem.

Although it seems that height and cancer risk are fairly clearly linked, tall people don’t have to be too worried about these results. “Height itself is not a risk factor, but it really appears to be a marker for one or more exposures that influence cancer risk.” said Geoffrey C. Kabat, a senior epidemiologist in the department of epidemiology and population health at the Albert Einstein College of Medicine of Yeshiva University in New York.

Many factors can influence our heights.( For example, the nutrition we intake in childhood, the amount of foods we consumed in childhood can influence heights.) Therefore we have several possible explanation for the correlation between heights and cancer risks. Growth factor is a circulating level of protein which is influenced by exercises, stress, body mass index and nutrition. It is associated with both increased height and cancer risk. So taller people (while young) are exposed to higher levels of growth factors, which could possibly promote cancer development.  Also, taller people simply have a larger number of cells in their bodies that then could potentially transform into cancer. Because cancer means that some of the body’s cells begin to divide without stopping and spread into surrounding tissues. (much information about cancer in cancer.gov)So it is easy to understand that the more cells you have, the much number of cells might be abnormal. A third possible explanation is that taller individuals have a higher caloric intake, which has also previously been linked to cancer. These explain why heights and cancer risks relate each other.

Additionally, the impact of height that increases the risk of cancer is actually smaller than we think. Cancer Research UK scientists have studied in this relative risk. “The researchers found that every extra 10cm (or 4 inches) of height was associated with a 17 per cent higher risk of the disease. Drinking alcohol increases breast cancer risk: every extra unit per day increases the risk by 12 per cent (and a large glass of wine is about three units). Comparing that to the effect of weight, the risk for women with the highest BMIs is 40 per cent higher than for the slimmest women. Having children also has an effect. Women with no children have a 43 per cent higher risk of this disease than those who have had children.” So in comparison with these risks, the influence of high is not large. (If you want to learn more about it, click the following link Height and cancer risk – the long and short of it)

Now we have no clear conclusion about cancer risk and height. Please do not worry about your height. To reduce risk of cancer, there are many important thing to do, such as giving up smoking, cutting down on alcohol, and adopting a healthy diet and lifestyle.

Source1 Source2 Source3 Source4 Source5 Source6

Pic1 Pic2 Pic3

We always hear that someone says, “ I can feel your pain” in our daily life. Is it just an expression of sympathy or is it real that people carry other’s pain as if it was their own?

Before I talk about this topic, I’d like to share the recent scientific news first. A new study in rodents suggest that mice feel each other’s pain. “Healthy mice living in the same room with mice experiencing pain are up to 68% more sensitive to pain themselves, regardless of their stress levels, according to the new study, which found that mice could scent when their fellows were suffering.” After the study, the researchers at Oregon Health & Science University in Portland thought that smell might be the massager.

(If you are interested in this study, you can click the following link: Social transfer of pain in mice) Then we can get a conclusion that feeling other’s pain is not only an expression of sympathy but also a real biological phenomenon. Although it is too early to these findings to humans, there is growing evidence that people also share their pain.

Then we go back to the topic.

The way the brain perceives pain

If we would like to understand or explain that we can feel other’s pain, we should know how our brain process pain. Actually the determinants of pain are varies. In 1968, Melzack and Casey studies that the concept of pain as a perception, has sensory, motivational, and cognitive determinants. So when these three factors work, we get the sense of pain that is an adaptive process that is a warning of actual or potential injury.

With the development of brain imaging technique (such as PET or fMRI), cognitive neuroscientists found that different pains can cause some same activations in our brain structure, so called “pain matrix”. Figure 2 outlines the regions that are generally shown to be activated in functional imaging studies of pain. Pain matrix involves the parts that process the cognition of pain like the primary sensory cortex and the parts that trigger the emotional responses of pain like anterior cingulate cortex. It is possible that due to the activity of pain matrix, we can feel other’s pain when we see they are suffered. 

Do we feel pain differently when see other’s pain?

Let’s assume that when seeing other’s pain, we would trigger our pain matrix. So can we distinguish the pain that we actually get by body damaging and the pain from seeing other’s pain? Professor Singer and other researchers in the University of Zurich had a fMRI research in 2004. Volunteers experienced a painful stimulus and compared it to that elicited when they observed a signal indicating that their loved one was receiving a similar pain stimulus.(The specific study is in this link: Empathy for Pain Involves the Affective but not Sensory Components of Pain) Then they conclude that the neural substrate for empathic experience does not involve the entire “pain matrix.” So it is obvious that “self” pain and “other” pain are different, and other’s pain always trigger only the part that cause people have emotional responses of pain in our brain but not the part means that we are actually suffered.

If we just simply conclude by one study, it is largely possible that it has file drawer problem. Then I find another study from Alessio Avenanti in Nature Neuroscience shows that people have an actual physical reaction when observing others being injured or expressing pain. So at least, we can reject the null hypothesis that there is no relationship between self feelings and other’s pain, and accept the alternative hypothesis that people can feel other’s pain.

Why we can feel other’s pain?

Empathy helps us to understand feelings and inner states of mind of others and to share experiences, needs, beliefs and goals. Humans can generally empathize with others and imagine what another person is going through. The reason we have empathy is that we have a system called “synaesthesia for pain” . In synaesthesia for pain a person not only empathy with another’s pain but experiences the observed or imagined pain as if it was their own. Mirror-touch synesthesia is one type of synaesthesia for pain.It is related to the activity of mirror neurons, according to International Encyclopedia of the Social & Behavioral Sciences, which provides a correspondence in the neural activation during the actual execution of an action and the observation of other person’s action and this system is supposed to allow several key social processes, such as understanding other persons’ intentions and behaviors, as well as self-awareness and learning through imitation. So if we observe someone suffering physical pain, the pain is “mirrored” through our sensation. Some people have an unusually strong ability to empathize with others. And children with asperger syndrome are less capable of empathy.

Lastly, there are still many theories about mirror neuron system debated. Scientist cannot get a final conclusion. Hence we need more meta-analysis, peer reviews and researches.

I think mirror-touch synesthesia (if it really exists) help people more considerate about the feelings of others, and more adaptive in the society. Feeling other’s pain is not a bad thing.

pic1 pic2

Source1 Source2 Source3 Source4  Source 5

Anger is one of the basic emotional reaction. When I wake up in the morning especially when I have to take class in the 8 a.m., I feel a little bit grumpy, angry. At that time, I always tell my roommate “don’t talk to me.” It is kind of uncomfortable. But It seems that the only reason is that I didn’t have enough time to sleep. In order to let me feel better in the morning, I do some researches about this
question.

According to the article of Daily Mail, on average, people have black moods at least two mornings a week. It is easily understandable that if people have a bad attitude about the day, they may have black moods.  Alice D. Domar, Ph.D., executive director of the Domar Center for Mind/Body Health, argues that people just feel grumpy in few days of a week because they are not looking forward to working. In other words, if there are not enough things which can bring joy and happiness to people, they will feel bad. So having a happy life could help improve the happiness of your morning Also, these black moods could be associated with not getting enough rest and being tired, bad night’s sleep.

However, Allison G. Harvey, Ph.D, professor of psychology at the University of California, Berkeley and director of the Golden Bear Sleep and Mood Research Clinic, indicates that “The process of waking up is slow — not like a light switch, much slower,” and “These feelings are not pleasant, but do not necessarily indicate having had a poor night of sleep.” The reason is connected to sleep inertia. This term given in 1976 means that a transitional period of grogginess between waking and being full awake. Transition between sleep mode and awake mode actually lasts a long time. Because when we wake up, our brain-stem arousal systems are instantly activated. But our cortical regions, especially the part of the brain involved in decision-making and self-control, need to take longer to work. According to a neuroscientist and chronobiology expert, Kenneth Wright,“ Cognition is best several hours prior to habitual sleep time, and worst near habitual wake time.” What he said can explain why in the early morning, our memory, reaction time and ability to deal with problems suffer.

Also, morning depression is also associated with the setting of our internal alarm clock—our circadian rhythm. If there are difference between our actually required wake-up time and our natural wake-up time depended on our circadian rhythm, we would feel uncomfortable. The circadian rhythm is affected by some specific hormones, such as cortisol and melatonin. To be specific, cortisol can make people energetic and active in the daytime and melatonin can makes people tired and sleepy at night. Thus, if our circadian rhythm is disrupted, our body physically starts to produce hormones at the wrong time. So this will affect negatively not only on our health but also on our emotion.

Luckily, the effects of sleep inertia and circadian rhythm can be changed according to Kenneth P. Wright Jr.’s experiment. So people, in order to avoid black moods in the morning, can make a certain lifestyle to regulate and stabilize circadian rhythm. For example, going to bed and get up at certain times, doing exercise frequently, and eating regularly are helpful. So the sleep-wake cycle can synchronize with the body clock.

Reference:

Source1 Source2 Source3 Source4

Picture1 Picture2

Hearing the same joke, some people laugh until they cry, but some people do not have any reaction. Watching a tearjerker, some people cry throughout, but some people can still laugh. What cause these difference? It is easy for us to combine these reactions with cultural factors, personal experience and personality. Actually, they are not all the answers for this question.

Recently, a paper published in “Emotion” shows that genes may affect emotional expression. The present research examined the effect of the 5-HTTLPR polymorphism in the serotonin transporter gene on objectively coded positive emotional expressions. By the way, Researchers commonly report it with two variations in
humans: the short allele (“s”) and the long allele (“l”). Three studies with independent samples of participants were conducted. To be specific, study 1 examined young adults watching still cartoons; study 2 examined young, middle-aged, and older adults watching a thematically ambiguous yet subtly amusing film clip; and study 3 examined middle-aged and older spouses discussing an area of marital conflict (that typically produces both positive and negative emotion).

I want to introduce the way researchers code participants’ emotional expressions. It is named Facial Action Coding System (FACS). FACS is a research tool useful for measuring any facial expression a human being can make. It is an anatomically based system for comprehensively describing all observable facial movement. So it helps researchers to test and analyze objectively without experimenter effect.

After analysis of three studies, results showed that the short allele of 5-HTTLPR predicted heightened positive emotional expressions. To sum up, people with “s” allele (genotype is ss or sl) are more sensitive and more easily to affect by environment, experience and stimulus. In order words, the more “s” alleles people have, the more times they laugh.

If you think this research is not very convincing, I find another paper published in 2012 having the similar conclusion. The researchers identified 77 pertinent effect sizes on 9361 subjects from 30 reports, providing data for two meta analyses on the moderating role of 5HTTLPR when it comes to the impact of the environment on development. According to this research, “we found 41 effect sizes (N = 5863) for the association between negative environments and developmental outcomes with or without significant moderation by 5HTTLPR genotype and 36 effect sizes (N = 3498) for the potentially 5HTTLPR-moderated association between positive environments and developmental outcomes”. Then they got a result that people with “s” allele, called them ss/sl carriers were significantly more vulnerable to negative environments than ll carriers, which support the diathesis-stress model. These children are easy to have emotional disorder in adolescence if they would face unfortunate experience. Controversially, they also benefit more if they could grow up in healthy and warm environment. So this result just fits in the previous experiment’s conclusion.

Although we get the conclusion, we still have a lot of space to explore in the neurobiological mechanism to find the specific results. But at least now we know that laugh or not can be caused by our genes, which I never imagine before. So next time when you see someone appears distant to you, it may not mean that he or she doesn’t like you, but means that he or she doesn’t have many “s” alleles. ?

Source1 Source2 Source3

pic1 pic2 pic3

I think you may hear of that someone says “people who are blood group A are mosquitoes’ magnets”, or someone mention that O type of blood always attract mosquitoes. Many of my friends have complained that their own blood types are mosquitoes’ favorite, but they have different types of blood，including A, B, O and AB (covering all types of blood). Certainly, some people are badly bitten by the mosquitoes especially in the summer. Is it because there is a specific type of blood attracting mosquitoes mostly?

In order to find the correlation or relationship between mosquitoes and blood types, some scientists did the experiment which had been published in “Nature “in 1972. The experimenters chose pairs of subjects who contrasted in ABO blood group statues to see whether physiological factors could affect the selection of human hosts for feeding by mosquito. To be specific, 102 subjects put their arms into a box which contained 20 female mosquitoes during the ten minutes’ testing time. Analysis of the blood group data reveals that the mosquitoes preferentially selected hosts of blood group O. However, the basis of this result is not obvious, although they took more than 100 times experiments (repeated experiments). Additionally, this experiment was done in the seventies of last century, the period that people had still explored mosquitoes. So this conclusion is not very convincing.

Before I try to explain the reason that mosquito like some certain types of blood, I’d like to find out that what in our body attract mosquitoes, like the heat we release， chemical components of our sweat, or something else.

Actually among these factors, CO2 (carbon dioxide) is the main clue for mosquito to find you. The airflow of CO2 can largely help mosquito to find direction and lock target. In field experiment, mosquito trap containing CO2 can trap more than 8 to 45 times of numbers of mosquitoes than mosquito trap without containing CO2. Although different types of mosquitoes may have a little difference, they usually depend on CO2 to find targets. Cooperating with 1-octen-3-ol and lactic acid (a component of human sweat), mosquitoes are easier to find targets. DEET, (N,N-diethyl-meta-toluamide) the world’s most widely used topical insect repellent, with broad effectiveness against most insects, strongly inhibits the co-receptor of mosquitoes so that DEET can work well.

So a man dripping with sweat are mosquitoes favorite because their sweat and CO₂ releasing by gasping for breath have fatal attraction for mosquitoes. Also, people with faster metabolism rate easily attract mosquitoes.

Now let’s go back to the experiment I mention above. The leader of the experiment in 1972 is Corinne Shear Wood, a pioneering medical anthropologist. She did other experiments to improve the existed experiment and eliminate confounding variables, just like the experiment we saw in the SC200 class which repeating and modifying to get real conclusion. In the experiment, she segmented the landing and blood meal of mosquitoes; on close examination, she also chose the test sample with different skin pigmentation, age, sex, skin temperature, degrees of subcutaneous fat and relative nutritional status. But none of these factors could be demonstrated to be acting as host determinants. In “New Evidence for a Late Introduction of Malaria into the New World”, she points out that the result of investigation suggest that a factor which has definite attraction or repulsion value to the mosquito is related, to statistically significant degree, to the subject’s ABO blood-group status. In conclusion, it reveals that the hosts with blood-group O are often chosen by mosquito. And blood-group O has more dominant attraction than blood group A and B.

After 20 years, in 2004 Japanese scientist Yoshikazu Shirai had started to study this question again. He did three different studies that are landing preference among ABO blood groups, among secretors or nonsecretors, and among ABH antigens. He got the result that despite differences in the methods used in these studies, the landing preferences are the same; that is, O > B > AB > A. It seems that we have already gotten correct answer. But, actually, not. His experiment has different result with Wood’s. In his result, although O has much attraction than A, O doesn’t have more obvious attraction than B and AB. In addition, according to his report, Shirai said “ even the landing tests on ABH antigens do not provide an explanation for the landing preference among ABO blood groups, and there may be other unknown influences underlying the differences of ABO landing preference. In fact, ABH antigens are thought to exist on human skin in low concentrations, and we suppose that mosquitoes cannot perceive them.”

In a short, he thought that his report could not prove that blood group affect mosquito feeding habits because of the lack of clear preference among human blood groups exhibited in his study.

To sum up, currently our studies about blood groups and mosquito feeding habits are superficial. It is probably because we don’t have large sample size, or we cannot control many confounding variables. So now we don’t have exactly causal relation between blood group and mosquito feeding habits.

Source1

Source2

Source3

Source4

Source5

pic1

pic2

pic3

Have you ever experienced that you pick up the food dropping on the floor and keep eating it? Yes, I have. Because I think I pick up them immediately and it seems that food looks good. Also, I’ve heard of “three-second rule”, which also has other names like “five-second rule” or “ten- second rule” — food (or sometimes cutlery) dropped on the ground will not be significantly contaminated with bacteria if it is picked up within three (or five or ten) seconds of being dropped. In my memory, this rule comes from Japan. And before I searching the background of this rule, I believe this rule is real and scientific.

However, in fact, this rule is just created by a girl of the Chicago High School for Agricultural, Jillian Clarke who was the winner of Public Health of the 2004 Ig Nobel Prize. A report of DailyMail pointed out that the researchers of Manchester Metropolitan University tested five food items, which were bread with jam, cooked pasta, ham, a plain biscuit and dried fruit, to see whether the three-second rule could be true. They dropped these food items on the floor and left them for 3, 5, and 10 seconds intervals to see whether the items will sustain bacterial growth in the interval. Both the ham, a salty product, and the sugary bread and jam fared well in the test. After the study, researchers found that the food with a high salt or sugar content were safer to eat after being retrieved, as is less chance of harmful bacteria surviving on such items. Thus, the report think that three-second rule fit the food containing the most sugar and salt.

Does it mean that three second rule real? From my perspective, No! I think although there is a research show the conclusion, it still has possibility that the study is false positive. Because the research was only done by once, which means there is no repeated experiment. Also, there is no other report or study supporting this conclusion. What’s more, even though the research shows that the condition of food with high salt and sugar doesn’t fit the environment for bacteria to reproduce
, dropped food would be sticked by the bacteria on the floor. So the existed bacteria also harm to human body. Hence, the the transfer of bacteria between floor and food is also very important.

Rutgers researchers also do the research in order to turn out bacteria may transfer to candy that has fallen on the floor no matter how fast you pick it up. “The researchers tested four surfaces — stainless steel, ceramic tile, wood and carpet — and four different foods (watermelon,
bread, bread and butter, and gummy candy). They also looked at four different contact times — less than one second, five, 30 and 300 seconds. They used two media — tryptic soy broth orpeptone buffer — to grow Enterobacter aerogenes, a nonpathogenic “cousin” of Salmonella naturally occurring in the human digestive system.” After replicating 128 scenarios 20 times each, which means they yielded 2560 measurements (enough repeated experiment!!!) They got the result that watermelon had been contaminated most heavily and gummy candy has been contaminated least heavily. This result demonstrates that moisture is the key factor of transfer of bacteria from surfaces to food appears. Donald Schaffner, professor and extension specialist in food science, said “Bacteria don’t have legs, they move with the moisture, and the wetter the food, the higher the risk of transfer. Also, longer food contact times usually result in the transfer of more bacteria from each surface to food.” In addition, they got an unexpected result that the topography of the surface and food also play an important role in bacterial transfer. The flatter floor makes more bacteria transfer successfully. So although longer contact time results in more bacterial transfer, it also shows other factors, like moisture, topography of the floor and food can affect the contamination of food.

So I think if you want to keep healthy, you’d better not believe three-second rule and five-second rule.

Source1

Source2

Source3

Pic1

Pic2

Pic3

Pic4

I’m from China. My roommate also comes from China， but more accurately she comes from Szechuan Province. Have you heard of Szechuan in southwestern China? Maybe not. But you probably know that there is a restaurant in the downtown named “Little Szechuan”. The most common favor of “Little Szechuan” cuisine is hot and spicy. I think Szechuan Cuisine is the most popular cuisine in China. Not only in China, but also around the world, many people enjoy eating hot and spicy food like chili peppers. According to psychologist Paul Rozin of the University of Pennsylvania, about a third of the people around the world eat hot peppers every single day. When I eat spicy food, my mouth feels like it’s on fire. It sounds terrible, but actually I like that feeling. So why people like hot and spicy food?

Let’s talk about spiciness. Spiciness, is not a taste or a flavor, like sweet, salty or sour. Spiciness is pain. According to the science of spiciness of TED-Ed Original, the chemical compounds in spicy foods can activate the type of sensory neurons called polymodal nociceptors which are in mouth and nose. When people eat chili pepper, you have the feeling that it’s on fire is because your brain thinks it’s burning. Eating spicy food just likes torturing ourselves. This makes me more confused that it seems that people enjoying spicy food are masochistically inclined.

I have found many different views about the reasons people like spiciness. According to James Gorman’s article, some professionals think that people like chilies due to their benefits which can help people lower blood pressure, have antimicrobial effects and increase salivation so that people have good appetite.  Some experts have different opinions that the pain brought by spiciness can kill other pains. The views should be supported by experiments so we can say that the conclusion can show the causal relation between chilies and other pains. So I find a research which is a file drawer about how chilies can be used to treat pain. Chili peppers’ heat comes from capsaicin which is a compound produced to prevent the peppers from fungal attack. The summary shows that capsaicin helps to reduce pain in part by depleting body’s supply of substance P which is a chemical component of nerve cells which connected to pain signal in the brain. What’s more, it also works by de-sensitizing sensory receptors in the skin.

But all I mentioned about are about the physical benefits but not about personal preference. So I think perhaps, people enjoy chilies because chilies have addictive properties. However, my idea refuses by Dr. Rozin who I have introduced above.

“If humans were becoming addicted to chili peppers, ‘then the animals in Mexico would also like it, because they have that system and they eat hot peppers all the time,’ says Rozin. ‘But they don’t like it which makes me think that there’s something more human about it.’”

What’s more, Dr. Rozin argues that our ability to enjoy experiences that logic says it is an example of a hedonic reversal that it is the word hedonic coming from the Ancient Greek hēdonikos, meaning pleasure. This only happens in human because the feelings of aversion and pleasure overlap largely in human brains. Thus, they both release some chemicals makes people happy. So actually because our most intricate mind and most complex brain, a large part of people enjoy spiciness.

As a result, I think that’s very magic that people enjoy the pain, chilies because we regard this pain as pleasure.

If you are interested in this topic, you can see more in Paul Rozin’s research. This is  the link of his reasearch. http://chemse.oxfordjournals.org/content/6/1/23.short

Source：

source1

source2

source3

Pic:

pic1

pic2

When I think about genetically modified crops, there are several question appearing in my brain. Are they healthy for people to eat? Are some blogs which argue that genetically modified crops are harmful true? Can we eat genetically modified crops every day? Knowing nothing about genetically modified crops make me a little scared about them. So I decide to learn more about them.

After searching I find that, as David H. Freedman said, the large majority of the exploration on genetically modified crops suggests that they are safe to eat and that they have the potential to feed millions of people worldwide who currently go hungry. In order to find the risks and benefits of GM (genetically modified) crops, scientists have to do a set of accurate researches and analysis. The GM food is a high-risk experiment conduct by our scientists; the GM technology may a big break though in scientific world but when it comes to the food safety for human species. The GM crops may not cause some problem right now but in the few hundreds of years once when irreversible recessive mutation massively occur in human DNA; the extinction of human will come in the near future. But, to some extent, only if we handle the GM technology correctly. This technology will lead to another new evolution.

Recently most of corn and soybeans grown in U.S. are genetically modified. The benefits of GM crops greatly outweigh the health risks, which maintain theoretically. As David Zilberman who is a U.C. Berkeley agricultural and environmental economist said, the GM crops utilization “has lowered the price of food” and “it has increased farmer safety by allowing them to use less pesticide. It has raised the output of corn, cotton and soy by 20 to 30 percent, allowing some people to survive who would not have without it. If it were more widely adopted around the world, the price [of food] would go lower, and fewer people would die of hunger.” David Schubert, an Alzheimer’s researcher who heads the Cellular Neurobiology Laboratory at the Salk Institute for Biological Studies in La Jolla, Calif indicates that there are many different methods for a well-characterized gene to get into the genome of some target plants.

However, it doesn’t mean that GM crops do not have any negative effects. Actually we just don’t have enough evidence of their risks. From SC200, we learn that it is very difficult to prevent from all confounding variables. So if people want to know about the long-term effects of GM foods, they have to avoid many confounding factors such as the underlying genetic variability in foods and the problems in evaluating the influence of foods. What’s more, more recent, more complex GM foods are more difficult to evaluate. And it is hard to predict their spontaneous impacts.

According to The State of Food and Agriculture 2003-2004, the main food safety concerns associated with transgenic products and foods derived from them relate to the possibility of increased allergens, toxins or other harmful compounds; horizontal gene transfer particularly of antibiotic-resistant genes; and other unintended effects. Many of these concerns also apply to crop varieties developed using conventional breeding methods and grown under traditional farming practices. So as a conclusion, scientists still need to assess that whether GM crops have direct and indirect health benefits.

Source:

Source1 Source2 Source3 picture1 picture2

Do you often bite your nails? Many nail biters want to quit this habit, so do I. Because this is disgusting for other people to watch, ruining the appearance of hands, and even eating myself. I’ve tried to quit it several times, but I have never succeeded.

Actually, people have bite nails for millennia. Cleanthes, the ancient Greek philosopher, was said to be addicted to biting his nails. Now, according to Joseph Stromberg’s article, the small-scale studies indicate about 20 percent or so of adults bite regularly, which would suggest a large amount of people do it.

So what is the reason that people bite nails? Are nail biters weaker willed? Or are we more neurotic? Some psychological researches could be answers to my questions.

First, (medical name for excessive nail biting is “onychophagia”) some psychologists argue that nail biters can be “pathological groomers” for whom normal grooming behaviors, such as pulling hair or picking skin. In other words, they have been out of control. American Psychiatric Association’s DSM puts pathological grooming in the same category as another disorder, obsessive compulsive disorder, OCD. Carol Mathews, a psychiatrist at the University of California, San Francisco, studies in pathological grooming which is known as dermatillomania. According to what she said, pathological groomers are behaviors that stem from normal grooming — the kind of thing that most animals do and is evolutionarily adaptive. However, she also believes that they just become automatic behaviors that have no relationship to external stimuli at all, which means that biting nails and OCD are in common.

Second, Recently psychologists have a more convincing theory of nail biting, that biting nails can give biters pleasure and relaxation so they can escape from pressure temporarily. According to the argument of Fred Penzel, a psychologist who specializes in helping patients deal with nail biting and other body-focused repetitive disorders,  biting nail helps biters to calm down. So to say, nails biting is like nicotine, having two effects which one is stimulating under certain situations and the other is relaxing in other else situations.

Third, there is increasing evidence showing that people who uncontrolledly bite their nails and do other similar behaviors, which I mentioned above, are often perfectionists and their actions may help them soothe boredom, irritation and dissatisfaction. From SC200, I learn that correlation doesn’t equal to causation. So although I cannot say that biting nails causes perfectionism or perfectionism leads to biting nails, they probably have some relationships. A new study supports this theory. To be specific, the researchers randomly surveyed 48 subjects, half of whom had these disorders and half of whom did not, on their organizational behavior and ability to regulate their emotions. Those having the defined as organizational perfectionists, who have a tendency to over plan, overwork themselves and are easy to get frustrated without high levels of activity. Therefore, nail biting may arise from perfectionism.

There are still some other arguments about nail biting, such as under-feeding or over-feeding, breast-feeding too long, or problematic relationship with your mother due to oral fixation, linked to myriad causes. Also, Sigmund Freud said that excessive nursing as a baby lead people to become orally receptive that means that people just simply love putting things in their mouths.

I think there is nothing wrong with biting nails. Many people derive pleasure from biting their nail; biting nails relieves stress; nail biters work well under pressure. Additionally, it is funny but true that nail biting boosts your immune system. (Though biting fingernails isn’t the cleanest of habits, it has been linked to certain health benefits. Biting nails makes newer germs get into body, so it can keep our immune system actively fending off bacteria and make it strengthener.) So biters do not need to quit this habit.

Source:

Source1

Source2

Source3

Source4

Source5

Pic1

What do stars look like? My first reaction is that star is star-shaped, a shape has five points. It is probably a mathematic question. Because we can draw a continues line into a five-pointed star, which is very convenient and efficient. But actually stars are big balls of gas, giving off heat and light. Therefore, most of stars is not star-shaped, but spherical.

So why we always draw stars with points? The answer is a little surprising that we see stars as pointy. What’s more, the images captured by telescope show that star is pointy. This is the image of the cluster Westerlund 2 from NASA/ESA Hubble Space Telescope. It is not because the stars have points. Actually, the accuracy of pictures could be affected by several optical phenomena since pictures just record object’s images in several different mediums by some apparatus.

This NASA/ESA Hubble Space Telescope image of the cluster Westerlund 2 and its surroundings has been released to celebrate Hubble’s 25th year in orbit and a quarter of a century of new discoveries, stunning images and outstanding science. The image’s central region, containing the star cluster, blends visible-light data taken by the Advanced Camera for Surveys and near-infrared exposures taken by the Wide Field Camera 3. The surrounding region is composed of visible-light observations taken by the Advanced Camera for Surveys.

As we know, light is a wave. When a wave encounters an obstacle or a slit, diffraction occurs. To be specific, when light from a distant source passes through a hole or around an object, its waves are reflected or bent a little and interfere with each other. So the passing light leaves an imprint of the hole or object. When the object is a straight line, it spreads the light out into a perpendicular series of dashes. So if we use camera focusing on a point light when there is an obstacle between light source and photographic plate, the photo would represent that a line, brighter in the center and darker in the two edges, is perpendicular to the point light. When the object is a cross, it creates two perpendicular series of dashes. What’s more, circles can lead to concentric rings and hexagons can cause six-pointed stars. We can find that the photo Hubble Space Telescope taken is very similar to diffraction pattern. Since Hubble Space Telescope has four struts in order to support its small secondary mirror, and their imprint causes the four-pointed stars in its photos.

As a result, we see the pointed stars due to the lack of apparatus. However, before invention of camera and telescope, human draw stars with points according to Uranometria, the short title of a star atlas produced by Johann Bayer in 1603.

The reason is very simple. Because human’s optical structure, our eyes have defect. So to say, our crystalline lenses is camera lens, our iris is aperture, and our retina is imaging device. In detail, our lenses are not very perfect, having subtle structural imperfections called suture lines. Light passes the imprint making those imperfections leave. So when light reaches our retina, it shows that it is star-shaped. Additionally, during the lifetime, the surface patterns of human’s lenses have changed more and more complexly. Consequently, our optical structure would cause diffraction. The researchers of Instituto de Optica Daza de Valdés confirmed this statement. They utilized a set of complex mechanics to record what was happen after the green light reaching a human’s eye left a light spot in the retina. The light spot was exactly star-shaped.

That people used to draw shapes with five or six or more points to represent stars is not the reason that stars are star-shape. Different image of object is due to the interfere of light and imperfections of optical structures. Although scientifically most stars just like our star, sun are spherical, we still look stars with points. “Twinkle, twinkle, little star. How I wonder what you are.” Next time when we look at star, we already know that actually it is scientifically acceptable that we see stars with star-shaped but without spherical.

Source and credits:

Source1

Source2

Source3

Picture1

Picture2

Picture3

Picture4

Picture5