Why

Why do insects stop 'breathing'? To avoid damage from too much oxygen, say researchers

A new study investigating the respiratory system of insects may have solved a mystery that has intrigued physiologists for decades: why insects routinely stop breathing for minutes at a time. Challenging previous theories, researchers at UC Irvine and Humboldt University propose that insects such as grasshoppers, moths, butterflies, some types of fruit flies, beetles and bugs close off th...

Biologists discover why 10% of Europeans are safe from HIV

Biologists at the University of Liverpool have discovered how the plagues of the Middle Ages have made around 10% of Europeans resistant to HIV. Scientists have known for some time that these individuals carry a genetic mutation (known as CCR5-delta32) that prevents the virus from entering the cells of the immune system but have been unable to account for the high levels of the gene in Scandinavi...

Why are coyotes getting more aggressive?

Coyotes tend to avoid human contact. But recently, coyotes have been getting increasingly aggressive in the eastern United States, including southeastern New York state, attacking neighborhood pets on the fringe of urban and suburban areas. "This kind of aggressive behavior is usually the last stage before coyotes actually start attacking humans -- such as small children that are perceived...

Monkeypox mystery: New research may explain why 2003 outbreak in the US wasn't deadly

An outbreak of 72 cases of monkeypox in the United States during the summer of 2003 didn't produce a single fatality, even though the disease usually kills 10 percent of those infected. In this month's issue of Virology, researche...

New research shows why too much memory may be a bad thing

New research from Columbia University Medical Center may explain why people who are able to easily and accurately recall historical dates or long-ago events, may have a harder time with word recall or remembering the day’s current events. They may have too much memory ?making it harder to filter out information and increasing the time it takes for new short-term memories to be processed and store...

Why were the HIV prevention trials in commercial sex workers abandoned?

One promising approach to help stem the global HIV epidemic is to give commercial sex workers an HIV medication (such as the drug tenofovir) before they have high risk sex in the hope of reducing their chances of becoming infected, an approach called "pre-exposure prophylaxis" (PREP). But activist groups, including Act Up-Paris have "halted the progress of at least two important clinical trials o...

Discovery suggests why stem cells run through stop signs

Everyone knows that stem cells are controversial. Many people know that stem cells can grow into virtually any cell type found in the body, from a red blood cell to a muscle cell to a brain cell. But no one really knows why stem cells continue to divide and renew themselves long after the point where other cells stop dividing. Now scientists at Northwestern University and the University of...

Why do aneurysms form? New studies suggest leading role for white blood cells

Each year, 200,000 Americans find out that the largest blood vessel in their body, the aorta, may burst open at any time. About 20,000 die suddenly from such a rupture. And another 36,000 have surgery to repair or replace the swelling section of aorta before time runs out. But despite the deadly toll of this condition, called abdominal aortic aneurysm or AAA ("triple A"), experts know very...

Researchers discover why melanoma is so malignant

About 60,000 Americans will be diagnosed with melanoma this year, says the American Cancer Society, and 10,000 of those cases will be fatal. If not caught in the early stages, melanoma can be a particularly virulent form of cancer, spreading through the body with an efficiency that few tumors possess. Now, researchers at Whitehead Institute for Biomedical Research have discovered one of the reaso...

Why Christmas trees are not extinct

Conifers such as Christmas trees suffer a severe plumbing problem. The "pipes" that carry water through firs, pines and other conifers are 10 times shorter than those in flowering trees. But a University of Utah study suggests why conifers not only survive but thrive: efficient microscopic valves let water flow through conifers about as easily as it flows through other trees. "When you are...

Noise And Delays Explain Why Some Genes Oscillate In Activity

If you snooze, you lose those uncomely grayish-brown crescents below your eyes. If you don't snooze, you lose a lot more. The body can't fight off infection, the muscles can't regenerate as quickly, the mind can't learn new words, and the eyes can't focus on the road. You also gain things: a bad mood and increased risk for diabetes, high blood pressure, and heart problems. Indeed, the effects of...

Why we give: New study finds evidence of generosity among our early human ancestors

A groundbreaking new study examines the origins of holiday giving and finds that our early human ancestors were frequently altruistic. "Reciprocity is arguably the foundational basis of cooperation in humans," writes Michael Gurven (University of California ?Santa Barbara). "A core feature of reciprocity is the contingent relationship between acts of giving and receiving among social part...

The reason why antiviral therapy can't annihilate HIV infection, and what to do about it

Antiviral therapy has been used to suppress HIV replication and has dramatically improved the clinical course of disease in affected patients. But the existence of viral reservoirs precludes the complete elimination of HIV from treated patients. In a new study appearing on November 1 in The Journal of Clinical Investigation, Tae-Wook Chun and colleagues from the NIH offer new insight into the er...

Why the Amazon rainforest is so rich in species

Tropical areas of south and central America such as the Amazon rainforest are home to some 7500 species of butterfly compared with only around 65 species in Britain. UCL scientists have ruled out the common theory that attributed this richness of wildlife to climate change, in a paper published on 7th December by the journal Proceedings of the Royal Society B (Biological Sciences). Instea...

Engineers discover why toucan beaks are models of lightweight strength

As a boy growing up in Brazil 40 years ago, Marc A. Meyers marveled at the lightweight toughness of toucan beaks that he occasionally found on the forest floor. Now a materials scientist and professor of mechanical and aerospace engineering at UCSD's Jacobs School of Engineering, Meyers said makers of airplanes and automobiles may benefit from the first ever detailed engineering analysis of touca...

Newly identified mechanism helps explain why people of African descent are more vulnerable to TB

A team of scientists has identified a cellular mechanism that may help explain the puzzle of why people of African descent are more susceptible to tuberculosis infection and why, once infected, they develop more severe states of the disease than whites. The team includes researchers from University of California, Los Angeles (UCLA), and Harvard School of Public Health (HSPH). The paper will appea...

Cell barrier shows why bird flu not so easily spread among humans

Although more than 100 people have been infected with the H5N1 avian influenza virus, mostly from close contact with infected poultry, the fact that the virus does not spread easily from its pioneering human hosts to other humans has been a biomedical puzzle. Now, a study of cells in the human respiratory tract reveals a simple anatomical difference in the cells of the system that makes it...

Why nerve cells work faster than the theory allows

With accuracy unknown until now, researchers from the Max Planck Institute for Dynamics and Self-Organization and the Bernstein Center for Computational Neuroscience in Göttingen together with the neurophysiologist Maxim Volgushev from the Ruhr-Universität Bochum have analyzed, by which rules, the nerve cells in the cerebral cortex decide to send out impulses. They surprisingly found, that...

Brain differences could explain why males and females experience pain relief differently

A study conducted by investigators at Georgia State University and the Atlanta-based Center for Behavioral Neuroscience (CBN) reports that anatomical and functional differences in the brain may explain sex differences in the experience of pain and in the effects of certain drugs on pain. The finding, reported in the April 13 issue of the Journal of Comparative Neurology, is the first rep...

Scientists discover why cornea is transparent and free of blood vessels, allowing vision

Scientists at the Harvard Department of Ophthalmology's Schepens Eye Research Institute and Massachusetts Eye and Ear Infirmary (MEEI) are the first to learn why the cornea, the clear window of the eye, is free of blood vessels--a unique phenomenon that makes vision possible. The key, say the researchers, is the unexpected presence of large amounts of the protein VEGFR-3 (vascular endothelial gro...

Evolutionary forces explain why women live longer than men

Despite research efforts to find modern factors that would explain the different life expectancies of men and women, the gap is actually ancient and universal, according to University of Michigan researchers. "Women live longer in almost every country, and the sex difference in lifespan has been recognized since at least the mid-18th century," said Daniel J. Kruger, a research scientist in...

Why mice don't get cancer of the retina

Humans are more susceptible to developing the eye cancer retinoblastoma than mice because, unlike humans, mice can compensate for the loss of activity of a gene critical to normal retinal development , according to results of a study by investigators at St. Jude Children's Research Hospital. The study, published today in the open access journal BMC Biology, explains why humans with a defective co...

Why we could all do with a siesta

The Spaniards may have been right all along ?a siesta after a hearty lunch is natural, new research suggests. The findings ?published in the scientific journal Neuron this week ?have implications for treating obesity and eating...

A reason why video games are hard to give up

Kids and adults will stay glued to video games this holiday season because the fun of playing actually is rooted in fulfilling their basic psychological needs. Psychologists at the University of Rochester, in collaboration with Immersyve, Inc., a virtual environment think tank, asked 1,000 gamers what motivates them to keep playing. The results published in the journal Motivation and Emoti...

Why Popeye only has eyes for spinach

Eating spinach could protect your eyes from the leading cause of blindness in western society, say experts at The University of Manchester. Spinach and some other vegetab...

Researchers examine why food tastes bad to chemotherapy recipients

About two million cancer patients currently receiving certain drug therapies and chemotherapy find foods and beverages to have a foul metallic flavor, according to a medical study. In general, more than 40 percent of hospitalized patients suffer from malnutrition due to taste and smell dysfunction. "Unfortunately, these problems that impact nutrition and quality of life are underestimated...

PNAS study reveals why organs fail following massive trauma

Massive trauma, say from a sabertooth tiger attack, meant immediate death for the primitive human. Modern man is more likely to survive severe injury caused by a car crash, gunshot or fall thanks to high-tech emergency medicine. Unfortunately, the body does not know what to do when it survives an injury that would have been fatal until recently in human evolution. Nearly one third of the time, m...

Why do insects like to eat some plants more than others?

In a study appearing in the forthcoming issue of The American Naturalist, Tom E. X. Miller, Andrew J. Tyre, and Svata M. Louda (all of the University of Nebraska, Lincoln) examined herbivore dynamics, specifically why plants aren't all eaten at the same rate. Plant-insect ecologists typically attribute the differences to variation in the nutritional quality or defective chemistry of plant...

Why do some queen bees eat their worker bee's eggs?

Worker bees, wasps, and ants are often considered neuter. But in many species they are females with ovaries, who although unable to mate, can lay unfertilized eggs which turn into males if reared. For some species, such as bumble bees, this is the source of many of the males in the species. But in others, like the honeybee, workers "police" each other ?killing eggs laid by workers or confronting...

Why do cold animals make bigger babies?

Reproduction involves a critical decision: Should an organism invest energy in a few large offspring or many small ones? In a new study from The American Naturalist, Michael Angilletta (Indiana State University), Chris Oufiero (University of California, Riverside), and Adam Leaché (University of California, Berkeley) used a new statistical approach that can test multiple theories at the same time...

Why don't all moles progress to melanoma?

Everyone has moles. Most of the time, they are nothing but a cosmetic nuisance. But sometimes pigment-producing cells in moles called melanocytes start dividing abnormally to form a deadly form of skin cancer called melanoma. About one in 65 Americans born this year will be diagnosed with melanoma at some point during their lifetime. Scientists know that 30 percent of all melanomas begin...

Researchers to study why dead zone returned to Lake Erie

A $2.5 million grant will fund a 5-year study examining why dead zones have returned to Lake Erie, and researchers hope the findings will allow them to detect the cause and stop the spread before the fishery and tourism industries suffer. "This is a very serious problem," said University of Michigan's Donald Scavia, professor in the School of Natural Resources and Environment, and lead in...

Why is the heart heart-shaped?

How does the heart attain its characteristic shape? Shape may be sculpted by cell movement, cell division, or changes in cell size and shape, all of which can be influenced by the local environment. The heart appears as a simple tube early in development; later, the tube walls bulge outward to form the cardiac chambers. In a new study published online in the open access journal PLoS Biol...

Why doesn't the immune system attack the small intestine?

Answering one of the oldest questions in human physiology, researchers at Dana-Farber Cancer Institute have discovered why the body's immune system - perpetually on guard against foreign microbes like bacteria ?doesn't attack tissues in the small intestine that harbor millions of bacteria cells. In a study in the February issue of Nature Immunology, and which is currently available on the...

Why aren't humans furry? Stone-Age moms could be the answer

Medical Hypotheses, an Elsevier publication, has announced the winner of the 2006 David Horrobin Prize for medical theory. Written by Judith Rich-Harris, author of The Nurture Assumption and No Two Alike, the article, "Parental selection: a third selection process in the evolution of human hairlessness and skin color" was judged to best embody the spirit of the journal. The £1,000 prize, launched...

Penn study on olfactory nerve cells shows why we smell better when we sniff

Unlike most of our sensory systems that detect only one type of stimuli, our sense of smell works double duty, detecting both chemical and mechanical stimuli to improve how we smell, according to University of Pennsylvania School of Medicine researchers in the March issue of Nature Neuroscience. This finding, plus the fact that both types of stimuli produce reaction in olfactory nerve cel...

Eating with our eyes: Why people eat less at unbused tables

People watching the Super Bowl who saw how much they had already eaten -- in this case, leftover chicken-wing bones -- ate 27 percent less than people who had no such environmental cues, finds a new Cornell study. The difference between the two groups -- those eating at a table where leftover bones accumulated compared with those whose leftovers were removed -- was greater for men than for...

The penalty of having a sister -- why sibling sex matters for male saiga antelopes

Having a twin sister could put male saiga antelopes at a reproductive disadvantage, says new research published today. The study shows that male twins with a sister are born lighter than those with a brother, making them smaller than the optimal size for males. The research also shows that saigas are the supermums of the hoofed animal world with no other similar species investing more in their o...

UCLA study uncovers clues for why Graves' disease attacks the eyes

UCLA researchers have uncovered new clues that may explain why Graves?disease (GD) attacks the muscle tissue behind the eyes, often causing them to bulge painfully from their sockets, as in the late actor Marty Feldman. Scientists at UCLA’s Jules Stein Eye Institute and Harbor-UCLA Medical Center discovered defects in the infection-fighting T-cells of GD patients?immune systems. Reported...

Why do oysters choose to live where they could be eaten?

There are many reasons why living in dense groups with others of your own kind is a good idea. Oftentimes, aggregations of a species serve as protection from predators and harsh environments or may be beneficial to future reproductive success. However, in the case of oyster larvae, the selection of a place to call home can be a life or death decision. According to an article in the May edi...