A yeast in the stomach of the mouse

Summary The high incidence (100 %) ofTorulopsis pintolopesi in the stomach of the mouse and the absence of any type of inflammatory response show the existance of an adaptation between the yeast and the mouse. This is in agreement with the opinion ofParle that the yeast belongs to the normal flora of the digestive tract. According to our studiesT. pintolopesi is an acidophilic species which is a normal host in the stomach and a transient organism in the intestine.     

Interspecific Interactions Between Cebus capucinus and Other Species: Data from Three Costa Rican Sites

Capuchins exhibit considerable cross-site variation in domains such as foraging strategy, vocal communication and social interaction. We report interactions between white-faced capuchins (Cebus capucinus) and other species. We present comparative data for 11 groups from 3 sites in Costa Rica that are ecologically similar and geographically close, thus reducing the likelihood that differences are due solely to genetic or ecological differences. Our aim is to document both the range of variation and common elements across sites and situations. We also consider factors that contribute to the variation or consistency or both, including social learning, local ecology, and temperament. We consider 4 categories of allospecifics: (1) vertebrate prey, (2) potential predators, (3) feeding competitors, and (4) neutral species. Although we cannot rule out local differences in ecology, our data suggest that social learning may account for at least some cross-site differences in behavior toward allospecifics. Our strongest finding is that boldness, aggression and pugnacity are displayed consistently across sites, groups and circumstances, even in interactions with neutral species, which reflects a critical aspect of species-specific temperament in Cebus capucinus that has been evolutionarily developed and reinforced through highly opportunistic foraging, strong predator defense, and active hunting. We suggest directions for future research, particularly in regard to primate temperament as an evolved trait with consequences for fitness.     

Virulence in malaria: an evolutionary viewpoint

Malaria parasites cause much morbidity and mortality to their human hosts. From our evolutionary perspective, this is because virulence is positively associated with parasite transmission rate. Natural selection therefore drives virulence upwards, but only to the point where the cost to transmission caused by host death begins to outweigh the transmission benefits. In this review, we summarize data from the laboratory rodent malaria model, Plasmodium chabaudi, and field data on the human malaria parasite, P. falciparum, in relation to this virulence trade-off hypothesis. The data from both species show strong positive correlations between asexual multiplication, transmission rate, infection length, morbidity and mortality, and therefore support the underlying assumptions of the hypothesis. Moreover, the P. falciparum data show that expected total lifetime transmission of the parasite is maximized in young children in whom the fitness cost of host mortality balances the fitness benefits of higher transmission rates and slower clearance rates, thus exhibiting the hypothesized virulence trade-off. This evolutionary explanation of virulence appears to accord well with the clinical and molecular explanations of pathogenesis that involve cytoadherence, red cell invasion and immune evasion, although direct evidence of the fitness advantages of these mechanisms is scarce. One implication of this evolutionary view of virulence is that parasite populations are expected to evolve new levels of virulence in response to medical interventions such as vaccines and drugs.     

Imperfect vaccination: some epidemiological and evolutionary consequences

An aim of some vaccination programmes is to reduce the prevalence of an infectious disease and ultimately to eradicate it. We show that eradication success depends on the type of vaccine as well as on the vaccination coverage. Vaccines that reduce the parasite within-host growth rate select for higher parasite virulence and this evolution may both increase the prevalence of the disease and prevent disease eradication. By contrast, vaccines that reduce the probability of infection select against virulence and may lead more easily to eradication. In some cases, epidemiological feedback on parasite evolution yields an evolutionary bistable situation where, for intermediate vaccination coverage, parasites can evolve towards either high or low virulence, depending on the initial conditions. These results have practical implications for the design and use of imperfect vaccines in public- and animal-health programmes.     

Nerve dependency in scarless fetal wound healing

The human fetus is capable of healing cutaneous wounds without scar up to the third trimester of development This process of tissue repair is more akin to newt limb regeneration than classic adult scar forming wound repair. Regeneration of the newt limb is dependent on neural input in its early stages. This study was an attempt to determine whether a similar dependence on neural input exists for mammalian fetal wounds to heal without scar. The left hind limb of six fetal lambs was denervated during the early second trimester of development (day 55; term = 145 days). Two weeks after denervation, the animals were again exposed to create bilateral incisional and 6-mm-diameter excisional wounds on their innervated right and denervated left lower extremities. Five days after creation of these defects, the wounds were examined for alterations in repair. Four fetal lambs survived, and three were suitable for evaluation. There were marked alterations in wound healing seen after denervation. Excisional wounds on the innervated side contracted and decreased their surface area by 14 percent. In contrast, the denervated wounds not only failed to contract, but increased in size by 60 percent. Changes in the incisional wounds were equally distinctive. Innervated incisional wounds healed completely without scar and had a wound breaking strength comparable to that of normal skin (Table I). In contrast, two of the three denervated incisional wounds dehisced and failed to heal, even in the regions where the skin was approximated by suture. The third denervated incisional wound did heal but with a significant amount of scar. Electron microscopy confirmed this finding by clearly demonstrating thickened and irregular collagen deposition in the extracellular matrix of all the denervated incisional specimens. In summary, like the regenerating newt limb, scarless fetal skin wound repair requires neural stimulation for tissue regeneration to occur. Therefore, in the mammal, the primary regulator for this unique type of tissue repair may have a central neural, rather than a local, tissue origin.     

TAP score: torsion angle propensity normalization applied to local protein structure evaluation

Background  

Experimentally determined protein structures may contain errors and require validation. Conformational criteria based on the Ramachandran plot are mainly used to distinguish bet ween distorted and adequately refined models. While the readily available criteria are sufficient to detect totally wrong structures, establishing the more subtle differences between plausible structures remains more challenging.