Arginine vasopressin and a vasopressin antagonist peptide: Opposite effects on extinction of active avoidance in rats

Systemic injection of arginine vasopressin (AVP) (1 μ/rat) significantly prolonged extinction of a pole-jump, active avoidance response in rats; lateral ventricular injection of 1000-fold less AVP (1 ng/rat) produced similar results. A new AVP analogue, [1-deaminopenicillamine-2-(O-methyl)-tyrosine]arginine vasopressin (dPTyr-(Me)AVP), is known to antagonize behavioral and vascular effects of exogenous AVP at molar ratios of 5:1. At a dose of 100 μ/rat (subcutaneously) dPTyr-(Me)AVP produces, by itself, a behavioral effect opposite to that of exogenous AVP, namely a facilitation of extinction. Injections of dPTyr-(Me)AVP into the lateral ventricle were ineffective except at a dose of 10 μg/rat. These results confirm previous reports of the effect of vasopressin on delaying extinction of avoidance behavior, but suggest a site of action distant from the lateral ventricle.     

Progesterone's effects on the psychology of disease avoidance: support for the compensatory behavioral prophylaxis hypothesis

In the human menstrual cycle, luteal phase immunomodulation prevents the maternal immune system from attacking the half-foreign blastocyst should conception occur, thereby facilitating implantation and development. However, tolerance of the conceptus comes at the cost of increased vulnerability to infection. The compensatory behavioral prophylaxis hypothesis (Fessler, 2001; Fessler & Navarrete, 2003) holds that evolved psychological mechanisms enhance avoidance of potential contaminants during periods of reproductive immunomodulation so as to decrease the likelihood of infection. Because such immunomodulation is triggered by progesterone, this hormone is predicted to correspondingly enhance behavioral prophylaxis and the motivational states underlying it. We investigated specific domains of disease avoidance psychology in a nonclinical sample of women (n = 120) by measuring salivary progesterone in naturally cycling women. We find that progesterone correlates directly with the degree to which women report emotions, thoughts, and behaviors consonant with enhanced prophylaxis.     

Demographic stochasticity, allee effects, and extinction: the influence of mating system and sex ratio

Demographic stochasticity has a substantial influence on the growth of small populations and consequently on their extinction risk. Mating system is one of several population characteristics that may affect this. We use a stochastic pair-formation model to investigate the combined effects of mating system, sex ratio, and population size on demographic stochasticity and thus on extinction risk. Our model is designed to accommodate a continuous range of mating systems and sex ratios as well as several levels of stochasticity. We show that it is not mating system alone but combinations of mating system and sex ratio that are important in shaping the stochastic dynamics of populations. Specifically, polygyny has the potential to give a high demographic variance and to lower the stochastic population growth rate substantially, thus also shortening the time to extinction, but the outcome is highly dependent on the sex ratio. In addition, population size is shown to be important. We find a stochastic Allee effect that is amplified by polygyny. Our results demonstrate that both mating system and sex ratio must be considered in conservation planning and that appreciating the role of stochasticity is key to understanding their effects.     

Health and the avoidance of macroparasites: a preliminary cross-cultural study

Some evolutionary explanations of cross-cultural differences propose that human personality is caused by pathogen stress. Both xenophobia and ethnocentrism evolved under conditions with high parasite prevalence. Further, inter-individual variation in disgust or fear of parasites is expected to be influenced by human health, where healthy people should express lower disgust sensitivity to parasites. We examined inter-individual variation of children’s fear, disgust and self-perceived danger between two distinct cultures differing in overall pathogen prevalence. We found that children were able to distinguish between disease-relevant and disease-irrelevant groups of invertebrates and that children in regions with high pathogen prevalence expressed greater fear, disgust and self-perceived danger of all animals, irrespective of disease threat. After controlling for confounding factors, better health of children was associated with lower perceived danger of disease-relevant animals. Gender differences were found only in conditions with low pathogen stress. Our results support the idea that cross-cultural differences in human perception of animals are mediated by pathogen threat. Further research is necessary to investigate causal relationship between human health and avoidance of potentially hazardous animals.     

Independently evolved jamming avoidance responses employ identical computational algorithms: a behavioral study of the African electric fish,Gymnarchus niloticus

An African electric fish, Gymnarchus, and a South American electric fish, Eigenmannia, are believed to have evolved their electrosensory systems independently. Both fishes, nevertheless, gradually shift the frequency of electric organ discharge away when they encounter a neighbor of a similar discharge frequency. Computational algorithms employed by Gymnarchus for this jamming avoidance response have been identified in this study for comparison with those of extensively studied Eigenmannia.

1. Gymnarchus determines whether it should raise or lower its discharge frequency based solely upon the signal mixture of its own reafferent and the exafferent signal from a neighbor, and does not internally refer to the pacemaker command signal which drives its own discharge.
2. The signal mixture is analyzed in terms of the time courses of amplitude modulation and phase modulation at each area of the body surface.
3. Phase of the signal mixture at each area is compared with that of another area for the detection of phase modulation.
4. Unambiguous information necessary for the jamming avoidance response is extracted by integrating information from all body areas each of which yields ambiguous information.
5. These computational features are identical to those of Eigenmannia, suggesting that the neural circuit for jamming avoidance responses may have evolved from preexisting mechanisms for electrolocation in both fishes.

     

Hunting to extinction: biology and regional economy influence extinction risk and the impact of hunting in artiodactyls

Half of all artiodactyls (even-toed hoofed mammals) are threatened with extinction, around double the mammalian average. Here, using a complete species-level phylogeny, we construct a multivariate model to assess for the first time which intrinsic (biological) and extrinsic (anthropogenic and environmental) factors influence variation in extinction risk in artiodactyls. Globally artiodactyls at greatest risk live in economically less developed areas, have older weaning ages and smaller geographical ranges. Our findings suggest that identifying predictors of threat is complicated by interactions between both biological and anthropogenic factors, resulting in differential responses to threatening processes. Artiodactyl species that experience unregulated hunting live in significantly less economically developed areas than those that are not hunted; however, hunted species are more susceptible to extinction if they have slower reproductive rates (older weaning ages). In contrast, risk in non-hunted artiodactyls is unrelated to reproductive rate and more closely associated with the economic development of the region in which they live.     

The influence of metabolic cost upon the level and precision of behavioral thermoregulation in an eurythermic lizard

The mean TB of G. coeruleus in each condition was positively correlated to the length of reinforcement, whereas the shuttle rate was inversely correlated to the length of reinforcement. The precision of TB regulation and the total metabolic expenditures of lizards did not vary significantly for different reinforcement regimes at the same ambient temperature. Eurythermality in G. coeruleus is caused by variations in preferred body temperature and not by fluctuations in TB around the particular regime body temperature.     

Special feature for the Olympics: effects of exercise on the immune system: overtraining effects on immunity and performance in athletes

Overtraining is a process of excessive exercise training in high-performance athletes that may lead to overtraining syndrome. Overtraining syndrome is a neuroendocrine disorder characterized by poor performance in competition, inability to maintain training loads, persistent fatigue, reduced catecholamine excretion, frequent illness, disturbed sleep and alterations in mood state. Although high-performance athletes are generally not clinically immune deficient, there is evidence that several immune parameters are suppressed during prolonged periods of intense exercise training. These include decreases in neutrophil function, serum and salivary immunoglobulin concentrations and natural killer cell number and possibly cytotoxic activity in peripheral blood. Moreover, the incidence of symptoms of upper respiratory tract infection increases during periods of endurance training. However, all of these changes appear to result from prolonged periods of intense exercise training, rather than from the effects of overtraining syndrome itself. At present, there is no single objective marker to identify overtraining syndrome. It is best identified by a combination of markers, such as decreases in urinary norepinephrine output, maximal heart rate and blood lactate levels, impaired sport performance and work output at 110% of individual anaerobic threshold, and daily self-analysis by the athlete (e.g. high fatigue and stress ratings). The mechanisms underlying overtraining syndrome have not been clearly identified, but are likely to involve autonomic dysfunction and possibly increased cytokine production resulting from the physical stress of intense daily training with inadequate recovery.     

How river structure and biological traits influence gene flow: a population genetic study of two stream invertebrates with differing dispersal abilities

1. Determined by landscape structure as well as dispersal‐related traits of species, connectivity influences various key aspects of population biology, ranging from population persistence to genetic structure and diversity. Here, we investigated differences in small‐scale connectivity in terms of gene flow between populations of two ecologically important invertebrates with contrasting dispersal‐related traits: an amphipod (Gammarus fossarum) with a purely aquatic life cycle and a mayfly (Baetis rhodani) with a terrestrial adult stage. 2. We used highly polymorphic markers to estimate genetic differentiation between populations of both species within a Swiss pre‐alpine catchment and compared these results to the broader‐scale genetic structure within the Rhine drainage. Landscape genetic approaches were used to test for correlations of genetic and geographical structures and in‐stream barrier effects. 3. We found overall very weak genetic structure in populations of B. rhodani. In contrast, G. fossarum showed strong genetic differentiation, even at spatial scales of a few kilometres, and a clear pattern of isolation by distance. Genetic diversity decreased from downstream towards upstream populations of G. fossarum, suggesting asymmetric gene flow. Correlation of genetic structure with landscape topography was more pronounced in the amphipod. Our study also indicates that G. fossarum might be capable of dispersing overland in headwater regions and of crossing small in‐stream barriers. 4. We speculate that differences in dispersal capacity but also habitat specialisation and potentially the extent of local adaptation could be responsible for the differences in genetic differentiation found between the two species. These results highlight the importance of taking into account dispersal‐related traits when planning management and conservation strategies.     

The influence of environment and life-history traits on the distribution of genes and individuals: a comparative study of 11 rainforest trees

This study investigates patterns of genetic connectivity among 11 co-distributed tropical rainforest tree species from the genus Elaeocarpus across a biogeographic barrier, the Black Mountain Corridor (BMC) in the Australian Wet Tropics (AWT). We analysed a combination of allelic and flanking region sequence data from microsatellite markers, and evaluated the relative influence of environmental preferences and functional traits on genetic diversity and gene flow. The results indicate that only in three species geographic structuring of haplotype distribution reflects a north vs. south of the BMC pattern. Environmental factors linked with altitude were recognized as affecting genetic trends, but the selective processes operating on upland species appear to be associated with competitiveness and regeneration opportunities on poor soil types rather than climate variables alone. In contrast to previous observations within southeastern Australian rainforests, genetic differentiation in the AWT appears to be associated with small-fruited rather than large-fruited species, highlighting how external factors can influence the dispersal dimension. Overall, this study emphasizes the importance of considering functional and environmental factors when attempting generalizations on landscape-level patterns of genetic variation. Understanding how plant functional groups respond to environmental and climatic heterogeneity can help us predict responses to future change.     

Long term neurological and behavioral effects of graded perinatal asphyxia in the rat

Perinatal hypoxic-ischemic states can cause irreversible damage to the brain, ranging from minimal brain dysfunction to death. Only few studies have been reported describing neurological, cognitive and behavioral deficits following perinatal asphyxia. We therefore decided to study long term effects of perinatal asphyxia in a well-documented animal model resembling the clinical situation. Caeserean section in rats was performed and the pups, still in the uterus horns, were placed into a water bath at 37 degrees C for periods of 5-20 min; pups were then given to surrogate mothers and examined at three month of age. Examinations consisted of a battery of motor and reflex tests, Morris water maze, multiple T-maze, elevated plus maze and open field studies. No abnormalities were found in rats even with long periods of perinatal asphyxia by neurological examination, in the open field and in mazes. Interestingly, in the elevated plus maze rats with long lasting exposure to hypoxia (15 and 20 min of asphyxia) showed reduced anxiety-related behavior. This finding may be relevant for the explanation of anxiety related disorders in adulthood with a tentative history in the perinatal period.     

The behavioral effects of a single adverse exposure in a number of rat generations: the role of maternal glucocorticoids]

The ionizing irradiation of rat fetuses during the last third of intrauterine development increased blood corticosterone level adulthood and decreased the open field locomotion of their adult offsprings of the next first nonirradiated generation. Treatment of the pregnant rats with glucocorticoids also decreased the offspring locomotion. Irradiation of fetuses in the middle of embryogenesis decreased blood corticosterone level in adulthood and shortened the open-field freezing reaction of their adult offsprings of the next first nonirradiated generation. Adrenalectomy of females before mating decreasing the blood corticosterone level had a similar effect on freezing duration of their adult offsprings. Irradiation of the ancestors within the last third of their intrauterine development had no effect on blood corticosterone level of their adult offsprings of the first generation and produced no behavioral alterations in their descendants of the next second nonirradiated generation. Irradiation of the ancestors in the middle of their embryogenesis decreased the stress-induced corticosterone response in their adult offsprings of the first generation and increased rearings and locomotion in their descendants of the next second nonirradiated generation. The data suggest that a single noxious treatment may have behavioral effects throughout two consequent generations of rats. Mother's glucocorticoid hormones may be one of the factors which transmit the effect.