Friday, July 6, 2012
Get them some sleep, scientists say of young delinquents
Juvenile delinquency among high school students may be partly linked to lack of sleep, researchers have found based on a new study.
Although a handful of past studies have suggested such a link could exist, little detailed information exists. The new analysis found that more serious forms of delinquency appear to become more common in relation to the severity of youngsters’ sleep deficit.
The study re-examined 15-year-old data from the National Longitudinal Study of Adolescent Health, a federally funded project that surveyed adolescent health in the United States in relation to a variety of risky behaviors.
The survey sample used for the study on sleep and delinquency encompassed 14,382 high school students—half male, half female, 63.5 percent white.
Students who slept seven or fewer hours nightly reported “significantly more property delinquency,” such as vandalism or theft, than students who slept the recommended eight to 10 hours, the authors of the new study reported. The findings appear in the Oct. 10 issue of the Journal of Youth and Adolescence.
Those who slept five or fewer hours per night, meanwhile, “reported significantly more violent delinquency,” wrote the researchers, Samantha Clinkinbeard and colleagues at the University of Nebraska at Omaha.
“Lack of sleep has been linked to a wide range of negative developmental outcomes,” but “largely overlooked among researchers interested in adolescent delinquency,” the group wrote.
Although the study couldn’t demonstrate that insufficient snoozing caused delinquency rather than, for example, the other way around, “the findings suggest that sleep is an important, and overlooked, dimension of delinquent behavior,” the researchers wrote. They argued that this aspect deserves further investigation.
The study didn’t determine whether insomnia, home environment or other factors caused the sleep shortage possibly linked to delinquency. But a smaller study, published in last December’s issue of the Journal of Genetic Psychology, found that “possible insomnia” predicted smoking, delinquency and drinking-and-driving among high schoolers.
“Sleep and other relevant health behaviors [should] be considered in the context of more comprehensive approaches to delinquency prevention and intervention,” Clinkinbeard and colleagues wrote.
Tiny bugs have own personalities despite being clones, scientists say
Tiny green insects known as pea aphids have individual behavior patterns, or “personalities,” despite being clones of one another, scientists say. The researchers found differences in the way each individual responds to a threat.
The study was part of a “burgeoning” of scientific interest in animal personality variation, noted the investigators, with the University of Osnabrueck, Germany. But despite this trend, they added, few studies have been done on invertebrates, or simple animals without backbones.
Studies on “clonal invertebrates,” which are all genetically identical and would thus be expected to show limited differences in behavior, are “nonexistent,” they added, reporting their findings in the March 1 online issue of the journal Developmental Psychobiology.
“This is surprising given the obvious advantages of using invertebrates/clones to tackle the crucial question why such consistent behavioral differences exist,” they went on. Personality differences not attributable to genes are generally presumed to be due to the environment in which an organism formed, though there is also a growing appreciation of epigenetic factors—chemical differences that are not genetic, but that influence gene activity.
Pea aphids, scientifically named Acyrthosiphon pisum, are pale little insects typically less than a sixth of an inch (half a centimeter) long that feed on pea plants and their relatives. A cluster of aphids infesting a given plant is typically a genetically identical, or clonal, group produced by one mother without sex, although aphids can also reproduce sexually at certain phases.
When a pea aphid is threatened by a predator—of which the species has several including wasps and grubs—it gives off a chemical alarm signal that alerts nearby aphids. They may respond in several ways: they can walk away, drop off the plant or seemingly ignore the signal. The researchers, Wiebke Schuett and colleagues, found that pea aphids can be divided into one of three categories: consistent “droppers,” consistent “non-droppers,” and some that behave unpredictably.
In experiments, “manipulations of early environmental conditions had little qualitative impact on such patterns,” the researchers wrote. Although the reasons for the differences are unclear, the findings may be important for future studies of personality variation and its evolutionary and ecological consequences, they added.
Researchers seek to understand how animals develop different “personalities” in part because they want to understand how humans do so. Animals are used as model organisms because they are often simpler and easier to experiment on. For instance, animals may be bred differently to examine resulting differences in behavior, and the early life environment of a test animal can be controlled and examined.
Studies have found that 20 to 50 percent of the variation in animal personality traits is genetic, according to researchers with the Netherlands Institute of Ecology and the Max Planck Institute for Ornithology in Germany, who reviewed the subject for the December issue of the journal Philosophical Transactions of the Royal Society B.
“Development and learning” dominate the rest of this variation, they added. But “one of the main questions that still remains unresolved is why variation in personality exists and how this is maintained… Molecular genetic research on animal personality is still in its infancy.”
Human ancestor ate bark, study finds
Next time you’re grumbling about a stale cookie or a steak that tastes “like cardboard,” count yourself lucky that you’re not Australopithecus sediba, the human ancestor who ate bark.
At least, that’s what scientists say about A. sediba, a short, gangly South African species from two million years ago. Their study indicates the creature targeted trees, bushes and fruits for its diet, chomping on harder foods than other other known early hominids, or human ancestors.
Virtually all others that have been tested from Africa—including Paranthropus boisei, dubbed “Nutcracker Man” thanks to its massive jaws and teeth—focused more on grasses and sedges, according to anthropology doctoral student Paul Sandberg of the University of Colorado Boulder, a co-author of the new study.
The findings were published in the June 27 online edition of the research journal Nature.
Scientists analyzed the A. sediba diet by zapping fossilized teeth with a laser, said Sandberg. The laser breaks off telltale carbon from the enamel of teeth, so researchers can pinpoint which types of plants the carbon comes from. The results show which of two groups of plants were consumed: so-called “C3” plants like trees, shrubs and bushes preferred by A. sediba, and “C4” plants like grasses and sedges consumed by many other early hominids.
The teeth from both A. sediba individuals analyzed had levels of C3 outside the range of all 81 previously tested hominids, the researchers reported. “The lack of any C4 evidence, and the evidence for the consumption of hard objects, are what make the inferred diet of these individuals compelling,” said Sandberg.
“It is an important finding because diet is one of the fundamental aspects of an animal, one that drives its behavior and ecological niche. As environments change over time because of shifting climates, animals are generally forced to either move or to adapt to their new surroundings,” said Sandberg.
The researchers concluded that bark and other “fracture-resistant” foods were at least a seasonal part of the A. sediba diet. Some modern apes and their relatives eat bark and woody tissues, which contain protein and sugars. The diet of A. sediba may have been similar to that of today’s African savanna chimpanzees, Sandberg said.
A unique aspect of the project was the analysis of microscopic, fossilized particles of plant tissue known as phytoliths trapped in ancient tooth tarter, a hardened form of dental plaque, said study co-author Amanda Henry of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
“The fact that these phytoliths are preserved in the teeth of two-million-year-old hominids is remarkable and speaks to the amazing preservation at the site,” said Sandberg. “The phytolith data suggest the A. sediba individuals were avoiding the grasses growing in open grasslands that were abundant in the region at the time.” A third, independent line of study—analyzing microscopic pits and scratches on A. sediba teeth, which reveal what they were eating shortly before death—also confirmed at least one of the hominids was eating hard foods, said Sandberg.
How tomatoes lost their flavor
Breeders have unknowingly bred the flavor out of tomatoes by favoring those with a nice uniform color, scientists are reporting.
It’s hoped the finding could help growers recapture the old, sweet flavor of tomatoes—which, as they sit on supermarket shelves today, often seem not to taste much different from the packaging they sit in.
The finding, reported in the June 29 issue of the journal Science, could have implications for the U.S. tomato industry, which harvests over 15 million tons of the fruit yearly for processing and fresh-market sales.
“This information… provides a strategy to recapture quality characteristics that had been unknowingly bred out of modern cultivated tomatoes,” said Ann Powell, a biochemist at the University of California Davis and one of the lead authors of the study.
For about 70 years, breeders have selected tomato varieties with uniformly light green fruit before ripening. These tomatoes then turn red evenly as they ripen, and they look nice in a supermarket display. Powell and colleagues say the gene at the heart of uniform ripening codes for the production of a molecule called GLK2, which is a transcription factor, meaning it governs genetic activity.
GLK2 boosts the fruit’s capacity for photosynthesis, the process of converting sunlight to sugars, Powell and colleagues found. The molecule also aids the production of lycopene, a health promoting compound. But the uniform-ripening mutation disables GLK2, the researchers found. This leads to inferior development of photosynthesis-enabling cellular structure called choloroplasts, and in turn, lower production of key ingredients that give tomatoes their sweetness.
Researchers at the university began studying the genes influencing tomato development and ripening after screening tomato plants for certain transcription factors that might play a role in both color and quality. They were particularly interested in tomatoes they saw that were unusually dark green before ripening. Partnering with researchers at Cornell University in New York and in Spain, who were mapping regions of the tomato genome, the scientists discovered two transcription factors, GLK1 and GLK2, that control the development of chloroplasts.
The researchers scoured a collection of mutant and wild species of tomatoes established at UC Davis by the late Professor Charles Rick beginning in the 1950s. They discovered that dark green tomatoes that naturally produce GLK2 produced ripe fruit with more sugars or soluble solids, important for processing tomatoes, as well as more lycopene.
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