Yearly Archives: 2007

Yup, it’s Monday evening:
Light Activates Output from Evening Neurons and Inhibits Output from Morning Neurons in the Drosophila Circadian Clock:

Living organisms have evolved circadian clocks that anticipate daily changes in their environment. Their clockwork is fully endogenous, but can be reset by external cues. (Light is the most efficient cue.) The circadian neuronal network of the fruit fly (Drosophila) brain perceives light through the visual system and a dedicated photoreceptor molecule, cryptochrome. Flies exhibit a bimodal locomotor activity pattern that peaks at dawn and dusk in light-dark conditions. These morning and evening activity bouts are controlled by two distinct neuronal clocks in the fly brain. By using flies with a deficient cryptochrome pathway, we have uncovered an unexpected role for light in the circadian system. In addition to synchronizing the two oscillators to solar time, light also controls their behavioral output. The morning oscillator can periodically rouse the fly when in constant darkness, but not in constant light, whereas the evening oscillator can do the same in constant light, but not in constant darkness. This suggests the existence of a light-dependent switch between oscillators that appears to require the visual system. Such a mechanism likely contributes to better separate the active periods of the fly at dawn and dusk, and may help the animal to adapt to seasonal changes in day length.

How Can We Draw the Line between Clinical Care and Medical Research:

A Policy Forum published in this month’s PLoS Medicine highlights an issue that the PLoS Medicine editors have often debated: when research takes place within the context of clinical care, how can we distinguish which activities constitute care, and which research? The World Medical Association Code of Medical Ethics declares that a physician must always “act in the patient’s best interest when providing medical care” [1]. Yet increasingly physicians also undertake research, which involves possibly unknown risks and benefits. These risks, and the uncertainty of benefit, might therefore conflict with a patient’s best interests.

Bioclocks Work By Controlling Chromosome Coiling:

There is a new twist on the question of how biological clocks work. In recent years, scientists have discovered that biological clocks help organize a dizzying array of biochemical processes in the body. Despite a number of hypotheses, exactly how the microscopic pacemakers in every cell in the body exert such a widespread influence has remained a mystery.
Now, a new study provides direct evidence that biological clocks can influence the activity of a large number of different genes in an ingenious fashion, simply by causing chromosomes to coil more tightly during the day and to relax at night.

Is The Beauty Of A Sculpture In The Brain Of The Beholder?:

Is there an objective biological basis for the experience of beauty in art? Or is aesthetic experience entirely subjective? This question has been addressed in a new article by Cinzia Di Dio, Emiliano Macaluso and Giacomo Rizzolatti. The researchers used fMRI scans to study the neural activity in subjects with no knowledge of art criticism, who were shown images of Classical and Renaissance sculptures.

Carnivorous Plants Use Pitchers Of ‘Slimy Saliva’ To Catch Their Prey:

Carnivorous plants supplement the meager diet available from the nutrient-poor soils in which they grow by trapping and digesting insects and other small arthropods. Pitcher plants of the genus Nepenthes were thought to capture their prey with a simple passive trap but in a paper in PLoS One, Laurence Gaume and Yoel Forterre, a biologist and a physicist from the CNRS, working respectively in the University of Montpellier and the University of Marseille, France show that they employ slimy secretions to doom their victims.

Horses Disperse Alien Plants Along Recreational Trails:

Plant invasions are rapidly becoming a threat to wildlands. One of the ways these aliens are dispersed is through large mammals that forage and excrete seeds in new locations. A new study has found horses to be a source of dispersal along recreational trails in Colorado.

Polar Bears Threatened By Hunting Policy Favoring The Killing Of Male Bears:

Policies that encourage hunters to go after male polar bears in order to conserve females, could make it harder for the animals to find mates. University of Alberta researchers determined there is a critical threshold in the male-to-female ratio. Below it, their model predicts a sudden and rapid collapse in fertilization rates.

Giant Fossil Sea Scorpion Bigger Than Man:

The discovery of a giant fossilised claw from an ancient sea scorpion indicates that when alive it would have been about two and a half meters long, much taller than the average man.

Unraveling the Silky Spider Web:

Web-making spiders employ a host of silk glands to synthesize a variety of silk filaments with different mechanical properties. Although it is widely believed that the aciniform glands are one such silk factory, there has been no hard evidence linking aciniform-derived proteins and silk –until now.

There are 34 articles published in PLoS ONE this week. As always, look around, read, rate, comment, annotate…. Here are my picks for the week (no need to repeat the dinosaur paper here, of course):
A Viscoelastic Deadly Fluid in Carnivorous Pitcher Plants:

Carnivorous pitcher plants supplement their nutrient intake by trapping and digesting insects in what were thought to be passive pitfall traps. But in this study, the authors show that the pitchers of plants Nepenthes rafflesiana in fact employ highly specialized secretions to doom their victims. They show that this fluid, even when diluted, has the perfect viscoelastic properties to prevent the escape of any small creatures that come into contact with it.

The Golden Beauty: Brain Response to Classical and Renaissance Sculptures:

Speculation and debate often surround the question of whether the experience of beauty in art is based upon objective biological factors or individual subjective perception. In this study, a group of researchers attempted to answer this question by measuring brain activity in people who were exposed to original and modified images of masterpieces of Classical and Renaissance sculpture. The results suggest that in naïve art observers, a sense of beauty is determined by both objective beauty and emotional experiences.

The Effect of Real-World Personal Familiarity on the Speed of Face Information Processing:

In this study, Balas and colleagues investigated whether people’s ability to process basic information about other individuals’ faces (for example, making a decision on the individual’s gender, identity, or orientation of the image) is affected by whether they know that person. The results showed, surprisingly, that real-world familiarity with an individual helps a person to process visual cues relating to that individual faster, even if identity is not required for performing that task. These findings highlight the importance of experience and familiarity in determining visual recognition processes.

Reappraisal of Vipera aspis Venom Neurotoxicity:

The variation of venom composition with geography is an important aspect of intraspecific variability in the Vipera genus, although causes of this variability remain unclear. The diversity of snake venom is important both for our understanding of venomous snake evolution and for the preparation of relevant antivenoms to treat envenomations. A geographic intraspecific variation in snake venom composition was recently reported for Vipera aspis aspis venom in France. Since 1992, cases of human envenomation after Vipera aspis aspis bites in south-east France involving unexpected neurological signs were regularly reported. The presence of genes encoding PLA2 neurotoxins in the Vaa snake genome led us to investigate any neurological symptom associated with snake bites in other regions of France and in neighboring countries. In parallel, we used several approaches to characterize the venom PLA2 composition of the snakes captured in the same areas. We conducted an epidemiological survey of snake bites in various regions of France. In parallel, we carried out the analysis of the genes and the transcripts encoding venom PLA2s. We used SELDI technology to study the diversity of PLA2 in various venom samples. Neurological signs (mainly cranial nerve disturbances) were reported after snake bites in three regions of France: Languedoc-Roussillon, Midi-Pyrénées and Provence-Alpes-Côte d’Azur. Genomes of Vipera aspis snakes from south-east France were shown to contain ammodytoxin isoforms never described in the genome of Vipera aspis from other French regions. Surprisingly, transcripts encoding venom neurotoxic PLA2s were found in snakes of Massif Central region. Accordingly, SELDI analysis of PLA2 venom composition confirmed the existence of population of neurotoxic Vipera aspis snakes in the west part of the Massif Central mountains. The association of epidemiological studies to genetic, biochemical and immunochemical analyses of snake venoms allowed a good evaluation of the potential neurotoxicity of snake bites. A correlation was found between the expression of neurological symptoms in humans and the intensity of the cross-reaction of venoms with anti-ammodytoxin antibodies, which is correlated with the level of neurotoxin (vaspin and/or ammodytoxin) expression in the venom. The origin of the two recently identified neurotoxic snake populations is discussed according to venom PLA2 genome and transcriptome data.

Season of Birth and Dopamine Receptor Gene Associations with Impulsivity, Sensation Seeking and Reproductive Behaviors:

Season of birth (SOB) has been associated with many physiological and psychological traits including novelty seeking and sensation seeking. Similar traits have been associated with genetic polymorphisms in the dopamine system. SOB and dopamine receptor genetic polymorphisms may independently and interactively influence similar behaviors through their common effects on the dopaminergic system. Based on a sample of 195 subjects, we examined whether SOB was associated with impulsivity, sensation seeking and reproductive behaviors. Additionally we examined potential interactions of dopamine receptor genes with SOB for the same set of traits. Phenotypes were evaluated using the Sociosexual Orientation Inventory, the Barratt Impulsivity Scale, the Eysenck Impulsivity Questionnaire, the Sensation Seeking Scale, and the Delay Discounting Task. Subjects were also asked about their age at first sex as well as their desired age at the birth of their first child. The dopamine gene polymorphisms examined were Dopamine Receptor D2 (DRD2) TaqI A and D4 (DRD4) 48 bp VNTR. Primary analyses included factorial gender×SOB ANOVAs or binary logistic regression models for each dependent trait. Secondary analysis extended the factorial models by also including DRD2 and DRD4 genotypes as independent variables. Winter-born males were more sensation seeking than non-winter born males. In factorial models including both genotype and season of birth as variables, two previously unobserved effects were discovered: (1) a SOB×DRD4 interaction effect on venturesomeness and (2) a DRD2×DRD4 interaction effect on sensation seeking. These results are consistent with past findings that SOB is related to sensation seeking. Additionally, these results provide tentative support for the hypothesis that SOB modifies the behavioral expression of dopaminergic genetic polymorphism. These findings suggest that SOB should be included in future studies of risky behaviors and behavioral genetic studies of the dopamine system.

‘Noah’s Flood’ Kick-started European Farming?:

The flood believed to be behind the Noah’s Ark myth kick-started European agriculture, according to new research by the Universities of Exeter, UK and Wollongong, Australia. New research assesses the impact of the collapse of the North American (Laurentide) Ice Sheet, 8000 years ago. The results indicate a catastrophic rise in global sea level led to the flooding of the Black Sea and drove dramatic social change across Europe.

Earliest Chocolate Drink Of The New World:

The earliest known use of cacao–the source of our modern day chocolate–has been pushed back more than 500 years, to somewhere between 1400 and 1100 B.C.E., thanks to new chemical analyses of residues extracted from pottery excavated at an archaeological site at Puerto Escondido in Honduras. The new evidence also indicates that, long before the flavor of the cacao seed (or bean) became popular, it was the sweet pulp of the chocolate fruit, used in making a fermented (5% alcohol) beverage, which first drew attention to the plant in the Americas.

Octopus And Kin Inspire New Camouflage Strategies For Military Applications:

Researchers are studying the remarkable shape- and color-changing abilities of the octopus and its close relatives in an effort to understand one of nature’s most remarkable feats of camouflage and self-preservation.

New Evidence For Female Control In Reproduction:

Adding another layer of competition to the mating game, scientists are reporting possible biochemical proof that the reproductive system of female mammals can “sense” the presence of sperm and react to it by changing the uterine environment. This may be the molecular mechanism behind post-copulatory sexual selection, in which females that have mated with several partners play a role in determining which sperm fertilizes their egg.

Earlier Bites By Uninfected Mosquitoes Boost West Nile Deaths In Lab Mice:

There’s one more reason to try to avoid being bitten by mosquitoes, scientists have discovered: bites from mosquitoes that aren’t infected by the West Nile virus may make the disease worse in people who acquire it later from West Nile-infected mosquitoes.

Sunbathing Tree Frogs’ Future Under A Cloud:

Animal conservationists in Manchester are turning to physics to investigate whether global warming is responsible for killing sun-loving South American tree frogs.

Like Father, Like Son: Attractiveness Is Hereditary:

Sexy dads produce sexy sons, in the insect world at least. While scientists already knew that specific attractive traits, from cricket choruses to peacocks’ tails, are passed on to their offspring, the heritability of attractiveness as a whole is more contentious. Now, new research by the University of Exeter shows that attractiveness is hereditary.

Evolution Is Deterministic, Not Random, Biologists Conclude From Multi-species Study:

A multi-national team of biologists has concluded that developmental evolution is deterministic and orderly, rather than random, based on a study of different species of roundworms.

Greg Laden explains.
Telecommuting Has Mostly Positive Consequences For Employees And Employers:

Telecommuting is a win-win for employees and employers, resulting in higher morale and job satisfaction and lower employee stress and turnover. These were among the conclusions of psychologists who examined 20 years of research on flexible work arrangements.

Yes, I know. It’s true.
Gene In Male Fish Lures Females Into Sex:

A gene has been found in male cichlid fish that evolved to lure female fish so that male cichlids can deposit sperm in the females mouths. A study in the online open access journal BMC Biology reveals that the gene is associated with egg-like markings on the fins of cichlid fishes and uncovers the evolutionary history of these markings, which are central to the success of the fishes’ exotic oral mating behaviour.

Evolutionary Biology Research On Plant Shows Significance Of Maternal Effects:

When habitat changes, animals migrate. But how do immobile organisms like plants cope when faced with alterations to their environment? This is an increasingly important question in light of new environmental conditions brought on by global climate change.

Monday night is the time when new articles on PLoS Medicine and PLoS Biology get published. My picks for this week:
Who Needs Cause-of-Death Data:

More than half of the world’s deaths pass by undocumented as to cause. Whilst the appropriate focus of health services may well be the care of the living, consistent and reliable cause-of-death data also constitute a crucial and major resource for health planning and prioritisation, and their lack in many settings is a major concern.

Complex Regulation of cyp26a1 Creates a Robust Retinoic Acid Gradient in the Zebrafish Embryo:

The formation of gradients of morphogens, signaling molecules that determine cell fates in a concentration-dependent manner, is a fundamental process in developmental biology. Several morphogens pattern the anterior-posterior (head to tail) axis of the vertebrate nervous system, including the vitamin A derivative, retinoic acid (RA) and fibroblast growth factors (Fgfs). However, it remains unclear how the activities of such morphogen gradients are coordinated. We have addressed this question by combining genetic experiments in zebrafish and computational analyses. We show that RA acts as a graded signal over long distances and that its gradient is shaped, to a large extent, by local control of RA degradation. In particular, RA promotes and Fgf suppresses RA degradation, thereby linking the shapes of RA and Fgf gradients. Computational models suggest that this linkage helps make RA-mediated patterning robust to changes in the rate at which RA is synthesized (which may vary with levels of dietary vitamin A) as well as in the size and shape of the embryo during development. Analogous regulatory loops may be used for similar purposes in other tissues in which RA and Fgfs interact, as well as in other morphogen systems.

Hormone Of Darkness: Melatonin Could Hurt Memory Formation At Night:

What do you do when a naturally occurring hormone in your body turns against you? What do you do when that same hormone – melatonin – is a popular supplement you take to help you sleep? A University of Houston professor and his team of researchers may have some answers.

Self-organized Traffic Light Control System Could Improve Traffic Flow 95 Percent:

Traffic flows account for as much as one-third of global energy consumption. But unconventional changes in managing traffic flow could significantly reduce such waste and lower harmful CO2 emissions, says Dirk Helbing.

Genital Arousal Disorder Adversely Impacts Women’s Lives:

New research shows that women suffering from Persistent Genital Arousal Disorder (PGAD), a condition marked by unprovoked, intrusive and persistent sensations of genital arousal that are unrelieved by one or several orgasms, are likely to experience a variety of associated psychological conditions. Women who have this rare and often distressing condition often experience related depression, anxiety, panic attacks and frequently show a past history of sexual victimization.

Using Neural Signals To Predict Sensory Decisions:

The rodent whisker sensory system is particularly intriguing because it is “active”: the animal generates sensory signals by palpating objects through self-controlled whisker motion (just as we move our fingertips along surfaces to measure their tactile features).

Delay In Autumn Color Caused By Increased Carbon Dioxide Not Global Warming:

The delay in autumnal leaf coloration and leaf fall in trees is caused by rising levels of carbon dioxide (CO2) in the atmosphere and not by increased global temperatures, suggests a new study by researchers at the University of Southampton.

Zeroing In On Cellular Machinery That Enables Neurons To Fire:

If you ever had a set of Micronauts — toy robots with removable body parts — you probably had fun swapping their heads, imagining how it would affect their behavior. Scientists supported by the National Institutes of Health have been performing similar experiments on ion channels — pores in our nerve cells — to sort out the channels’ key functional parts.

Mud, Mud, Glorious Mud?:

Mother bats know exactly what’s good for them and their young: During pregnancy and lactation female bats are in great need of minerals. Dr. Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research and colleagues found out how fruit-eating bats in the Ecuadorian rainforest cover their mineral requirements.

Trumpeter Swans Re-established In Ontario, Canada:

Originally native to Ontario, the trumpeter swan disappeared from Eastern Canada early in the 20th century. Restoration efforts were initiated in the early 1980s to reintroduce the trumpeter swan to its former range. Through conservation efforts the Ontario population has reached 1000, with at least 131 breeding pairs, and the future looks bright.

Your Homework: come up with a set of experiments that can be published in a single paper that can reasonably cite all the above studies.