Dependence receptors: Mechanisms of an announced death

Dependence receptors form a family of functionally related receptors which are all able to induce two completely opposite intracellular signals depending on the availability of their ligand. Indeed, in its presence, they mediate a positive, classical signal transduction of survival, differentiation or migration but without it, they trigger a negative signal which leads to cell death. The molecular mechanisms involved in triggering cell death in the absence of ligand are starting to be unravelled: dependence receptors are recruited at well-defined domains at the plasma membrane, they trigger cell death through a monomeric form, they are cleaved by caspases and they recruit a caspase activating complex.     

Development of path stereotypy in a single day in rats on a multiple-T maze

Humans and animals trained on sequential reaction tasks show decreases in reaction time and increases in anticipatory movements even long after they have ceased to make errors. Humans show these changes even when they do not explicitly recognize that they performed a repeating sequence. We have developed a task which rats learn to perform error-free quickly, but in which they continue to show path-refinement on a single day. This task may enable the study of performance strategy changes occurring within a single day.     

Seasonality and reproduction in aphids

Aphids are short-lived and occupy habitats which vary in quality in both time and space. They exploit their ephemerally nutritious habitats by rapidly producing many small offspring when conditions are good, and fewer, larger offspring when conditions are poor, at which time they also divert more of their resources into fat storage. Aphids of each of the generations which make up a life cycle have specific reproductive strategies adapted to the conditions they are most likely to encounter, that is they anticipate the predictable seasonal trends in habitat quality.     

Reproductive behaviour of the Grey seal (Halichoerus grypus) on Sable Island, Nova Scotia

We describe an unusual mating system, observed in a land-breeding colony of Grey seal, Halichoerus grypus , in the western Atlantic. Males and females begin to visit the breeding beach about a week before the season begins, but none stay ashore for long until the first pup is born. The cows are gregarious, probably return to the same part of the beach to give birth from one year to the next, and tend to remain in the general vicinity of the birth site during their two and a half week sojourn ashore. Within these limits, however, they are quite mobile, and the size, location and composition of the temporary aggregations which they form vary from one day to the next. The cows become thinner and more sedentary as oestrus approaches, but otherwise they give no overt signs of receptivity. The males do not defend territories, nor do they form dominance hierarchies. Instead, they compete for tenure, the right to remain within the shifting population of females. Tenured bulls directly test the receptivity of nearby cows from time to time, and they continually manoeuvre in ways which maximize their chances of being next to cows which are either in oestrus or likely to become so in the near future. Bulls which fail to establish themselves amongst females try to intercept cows as they are leaving for the sea at the end of their season, but their reproductive success, estimated in several ways, is significantly lower than that of bulls with tenure.
The system would be adaptive for seals which breed on the pack ice, but it is unique amongst land-breeding pinnipeds. If, as some circumstantial evidence suggests, Grey seals were originally pack-ice breeders, the persistence of such a system in a land-breeding colony raises some interesting questions about the plasticity of mating behaviour.     

Cell traction models for generating pattern and form in morphogenesis

During early development migratory mesenchymal cells navigate to distant sites where they aggregate to form a variety of embryonic organ rudiments. We present here a new model for mesenchymal cell morphogenesis based on the mechanical interaction between motile cells and their extracellular environment. The model is based on two properties of motile cells: (a) they are capable of generating large traction forces which can deform the extracellular matrix through which they move, and (b) the deformations they produce in their environment affect the direction of their movements. We derive field equations which describe the motion of cells in an elastic extracellular matrix and show that these equations can generate a variety of spatial patterns, such as the formations of skin organ primordia, especially feather germs, cartilage condensation patterns which presage bone formation in limb development, and melanocyte density patterns which form animal coat patterns.Support for this work was provided by NSF Grant # MCS-8110557 [GFO]     

'Friendship' for fitness in chimpanzees?

It has been repeatedly suggested that primates trade social services for fitness benefits in their relationships with the opposite sex. We tested this proposal in a colony of captive chimpanzees, Pan troglodytes, by examining behavioural data on grooming, agonistic support and food sharing in relation to genetically established paternity. We found no support for the notion of trade. First, males did not sire more offspring with females that they actively groomed more frequently, that they supported more often or with which they shared food more frequently. Correspondingly, females did not give birth to more offspring sired by males from which they received more services. Second, males that showed more affiliative behaviour towards females in general did not sire more progeny. Furthermore, females did not bear more offspring sired by males to which they themselves directed more sociopositive behaviour. Results from this captive colony are compatible with those reported for chimpanzees under natural conditions. Copyright 1999 The Association for the Study of Animal Behaviour.     

Optimal Outbreeding and the Development of Sexual Preferences in Japanese Quail

Adult male Japanese quail and, to a lesser extent, adult females were likely to approach a member of the opposite sex which they had not seen before in preference to one with which they grew up. However, they only did this if the group in which they were reared when young contained a particular number of the opposite sex: two females in the case of males and three males in the case of females. The result is explained in terms of the likelihood of the novel member of the opposite sex being slightly different from those with which the birds grew up. If the number of individuals of the opposite sex is small, a novel one is likely to be unacceptably strange, and if the number is high any novel bird from a limited laboratory stock is likely to resemble one or other of the familiar birds. A functional explanation for the quail's behaviour in terms of optical outbreeding is discussed.     

Spatio-temporal patterns generated by Salmonella typhimurium.

We present experimental results on the bacterium Salmonella typhimurium which show that cells of chemotactic strains aggregate in response to gradients of amino acids, attractants that they themselves excrete. Depending on the conditions under which cells are cultured, they form periodic arrays of continuous or perforated rings, which arise sequentially within a spreading bacterial lawn. Based on these experiments, we develop a biologically realistic cell-chemotaxis model to describe the self-organization of bacteria. Numerical and analytical investigations of the model mechanism show how the two types of observed geometric patterns can be generated by the interaction of the cells with chemoattractant they produce.     

Aestivo-hibernal reproductive diapause in Drosophila moriwakii: flight as a controlling factor

Drosophila moriwakii Okada & Kurokawa (Diptera; Drosophilidae) generally has only one generation per year and enters aestivo-hibernal reproductive diapause in Sapporo, northern Japan, but a small fraction of the population produced a second generation in summer at a place where breeding resources were abundant. In this species, diapause seems to be controlled by flight activity. When flies were cultured in cages in which they were able to fly freely, they entered diapause irrespective of photoperiod, but they did not do so at long daylengths when cultured in small vials in which they were prevented from flying. Furthermore, flies with wings removed did not enter diapause at long daylengths even if they were cultured in the cages.     

QUESTIONABLE COMPENSATION CLAIMS—Principles of Special Examination

In deciding a disputed claim of disability arising from occupation, physicians should ascertain whether a patient''s medical history has any bearing on the disability; they should attempt psychologic evaluation of the patient as it may reflect on the conditions they observe in physical examination; they should investigate symptoms complained of by the patient rather than accept them as prima facie evidence of disability; and they must have knowledge of the extent to which an injury can cause disability.It is urged that standards of physical ability and disability, as well as of other physical factors which may affect compensation claims, be established by organized research.     

Computerized comparison of imaging in scintigraphy; physiopathological applications

The authors describe a method of treating scintigraphic data with which they can correctly compare images of a structure that were obtained in different conditions. This method comprises two steps which are fully computerized. During the first one known as the "registration" step and intended to make a comparison possible they maximise a new similarity criterion by a series of random trials in a five parameter space. During the second, which is the actual comparison, they use an appropriate statistical test to recognise those homologous pixels with a significantly different contents which will be the only ones retained to build up the final image. They give then two examples of what the method brings in the medical field which are the detection of adenomatous parathyroid glands and the follow-up of lung perfusion in case of embolism.     

Questionable compensation claims; principles of special examination

In deciding a disputed claim of disability arising from occupation, physicians should ascertain whether a patient's medical history has any bearing on the disability; they should attempt psychologic evaluation of the patient as it may reflect on the conditions they observe in physical examination; they should investigate symptoms complained of by the patient rather than accept them as prima facie evidence of disability; and they must have knowledge of the extent to which an injury can cause disability. It is urged that standards of physical ability and disability, as well as of other physical factors which may affect compensation claims, be established by organized research.     

Phagocytosis: latex leads the way

Phagocytosis is the process that cells have evolved to internalise large particles such as mineral debris, which they store, or apoptotic cells and pathogens, which they have the capacity to kill and degrade. However, several important pathogens can suppress these killing functions and survive and multiply within phagosomes, causing disease. Recent advances in phagosome biology have been made possible largely by a model system that uses inert latex beads. The ability to purify latex bead-containing phagosomes has opened the door to allow comprehensive biochemical analyses and functional assays to study the molecular mechanisms governing phagosome function. These approaches have led to unique insights directly relevant for the understanding of the biology of intracellular pathogens and the ways by which they subvert their hosts.     

The Neural Mechanisms of Re-Experiencing Mental Fatigue Sensation: A Magnetoencephalography Study

There have been several studies which have tried to clarify the neural mechanisms of fatigue sensation; however fatigue sensation has multiple aspects. We hypothesized that past experience related to fatigue sensation is an important factor which contributes to future formation of fatigue sensation through the transfer to memories that are located within specific brain structures. Therefore, we aimed to investigate the neural mechanisms of fatigue sensation related to memory. In the present study, we investigated the neural activity caused by re-experiencing the fatigue sensation that had been experienced during a fatigue-inducing session. Thirteen healthy volunteers participated in fatigue and non-fatigue experiments in a crossover fashion. In the fatigue experiment, they performed a 2-back test session for 40 min to induce fatigue sensation, a rest session for 15 min to recover from fatigue, and a magnetoencephalography (MEG) session in which they were asked to re-experience the state of their body with fatigue that they had experienced in the 2-back test session. In the non-fatigue experiment, the participants performed a free session for 15 min, a rest session for 15 min, and an MEG session in which they were asked to re-experience the state of their body without fatigue that they had experienced in the free session. Spatial filtering analyses of oscillatory brain activity showed that the delta band power in the left Brodmann’s area (BA) 39, alpha band power in the right pulvinar nucleus and the left BA 40, and beta band power in the left BA 40 were lower when they re-experienced the fatigue sensation than when they re-experienced the fatigue-free sensation, indicating that these brain regions are related to re-experiencing the fatigue sensation. Our findings may help clarify the neural mechanisms underlying fatigue sensation.     

Chimpanzees use self-distraction to cope with impulsivity

It is unknown whether animals, like humans, can employ behavioural strategies to cope with impulsivity. To examine this question, we tested whether chimpanzees (Pan troglodytes) would use self-distraction as a coping strategy in a situation in which they had to continually inhibit responses to accumulating candies in order to earn a greater amount of those rewards. We tested animals in three conditions in which they were sometimes given a set of toys and were sometimes allowed physical access to the accumulating candies. Chimpanzees allowed the rewards to accumulate longer before responding when they could divert their attention to the toys, and they manipulated the toys more when the candies were physically accessible. Thus, chimpanzees engaged in self-distraction with the toys when such behaviour was most beneficial as a coping mechanism.     

The response of willow grouse chicks to auditory stimuli 1. Preference for hen grouse calls

Willow grouse (Lagopus lagopus lagopus) chicks newly hatched from mechanically incubated eggs were exposed to different combinations of sounds in a heated runway. They approached a loudspeaker playing grouse hen calls, which they had never heard, in preference to one playing the noise of the hatching machine from which they had just been removed. Similarly they preferred the hen call to another novel sound. When the three sounds were played singly instead of in pairs, only the hen call was approached.     

Abortion Rights along the Irish-English Border and the Liminality of Women’s Experiences

My research in European abortion laws and restrictions focuses on the migration of thousands of Irish women who travel to England each year to access safe and legal abortion services. This article is an investigation of the Irish-English border as a symbol for reproductive freedom and the new value systems in which Irish women participate when they cross its boundary. I provide a brief history of abortion law in the Republic of Ireland and Northern Ireland and emphasize a specific case in which border crossing was severely restricted for a young rape victim desiring an abortion. Additionally, my research examines women’s experiences of liminality as they cross the Irish-English border and the complex, conflicting emotions that they may feel as they travel abroad. In particular, I address a recent pro-choice initiative by a Dutch organization called Women on Waves, which sent a ship converted into a reproductive clinic to Dublin to provide services to Irish women. The ship, which has since sailed to Poland and Portugal to offer further assistance to women in countries with bans on abortion, complicates the notion of crossing concrete national lines as it moves throughout international waters.     

Attractiveness qualifies the effect of observation on trusting behavior in an economic game

Recent studies show that subtle cues of observation affect cooperation even when anonymity is explicitly assured. For instance, recent studies have shown that the presence of eyes increases cooperation on social economic tasks. Here, we tested the effects of cues of observation on trusting behavior in a two-player Trust game and the extent to which these effects are qualified by participants' own attractiveness. Although explicit cues of being observed (i.e., when participants were informed that the other player would see their face) tended to increase trusting behavior, this effect was qualified by the participants' other-rated attractiveness (estimated from third-party ratings of face photographs). Participants' own physical attractiveness was positively correlated with the extent to which they trusted others more when they believed they could be seen than when they believed they could not be seen. This interaction between cues of observation and own attractiveness suggests context dependence of trusting behavior that is sensitive to whether and how others react to one's physical appearance.     

Some Implications of Medical Beliefs and Practices for Social Anthropology

A people's medical beliefs and practices persist because they answer instrumental and moral imperatives, and they are empirically effective. This is not the same thing as saying that they are effective from the standpoint of Western medical notions or that they always bring the results for which people hope. The empirical effectiveness of these practices has important ontological consequences, since it enables sickness episodes to communicate and confirm ideas about the real world.     

Reasons for failure of antihypertensive treatment.

One hundred patients whose hypertension was originally well controlled were carefully screened when a routine clinic visit showed that their blood pressure was above 170/100 mm Hg. Simple misconceptions accounted for 75 failures: 38 did not know they had to continue their drugs, 14 thought they should not take antihypertensive drugs if they had not had a meal, 13 did not know which drugs controlled their blood pressure, and 10 believed it was better not to take their drugs on clinic days. Eleven patients were using racemic alpha-methyldopa, which was ineffective; 11 others said they could not afford the drugs; only three intentionally stopped their drugs because of unpleasant side effects. Patients need to be thoroughly informed about their treatment and the number of drugs kept to a minimum.