vFLIP protects PC-12 cells from apoptosis induced by Sindbis virus: implications for the role of TNF-alpha.

Sindbis virus (SV) is an alphavirus used as a model for studying the pathogenesis of viral encephalitis. In this study we examined the effects and the mechanisms involved in the apoptosis induced by SV in PC-12 cells, and the role of a vFLIP in this process. Infection of PC-12 cells with a neurovirulent strain of SV, SVNI, induced cell apoptosis. Overexpression of vFLIP encoded by the HHV-8 or treatment with a caspase-8 inhibitor inhibited cell apoptosis. SVNI induced an increase in the expression of tumor necrosis factor alpha (TNF-alpha), and pre-treatment of the cells with an anti-TNF-alpha blocking antibody or with soluble TNF-alpha receptor abrogated the apoptotic effect of SVNI. Moreover, TNF-alpha R1 knockout mice were more resistant to the cytopathic effects of the virus as compared to control animals. Our results indicate that the apoptosis induced by SVNI is mediated by activation of caspase-8, and that TNF-alpha plays an important role in the apoptotic response.     

Reconsidering diversity–productivity relationships: directness of productivity estimates matters

Despite extensive research efforts, the controversy over diversity–productivity (D–P) patterns in natural communities still looms large. Recent meta‐analyses suggest that unimodal D–P relationships tend to pre‐dominate in plant studies, while positively linear relationships are more common in animal studies. These patterns, however, are based on studies in which productivity is estimated either directly, based on the biomass or energy of the studied organisms, or indirectly, according to the productivity of lower trophic levels, and various surrogates. Our analysis shows that the distribution of D–P patterns is sensitive to the directness of productivity estimates in animal studies but not in plant studies. Analysis of D–P patterns should be based on direct productivity estimates of the studied organisms, especially in comparative meta‐analyses of communities from multiple trophic levels, where productivity is often affected nonlinearly by indirect factors or when complex feedback interactions are expected between productivity and diversity.     

Sensitive In Situ Monitoring of a Recombinant Bioluminescent Yersinia enterocolitica Reporter Mutant in Real Time on Camembert Cheese

Bioluminescent mutants of Yersinia enterocolitica were generated by transposon mutagenesis using a promoterless, complete lux operon (luxCDABE) derived from Photorhabdus luminescens, and their production of light in the cheese environment was monitored. Mutant B94, which had the lux cassette inserted into an open reading frame of unknown function was used for direct monitoring of Y. enterocolitica cells on cheeses stored at 10°C by quantifying bioluminescence using a photon-counting, intensified charge-coupled device camera. The detection limit on cheese was 200 CFU/cm². Bioluminescence of the reporter mutant was significantly regulated by its environment (NaCl, temperature, and cheese), as well as by growth phase, via the promoter the lux operon had acquired upon transposition. At low temperatures, mutant B94 did not exhibit the often-reported decrease of photon emission in older cells. It was not necessary to include either antibiotics or aldehyde in the food matrix in order to gain quantitative, reproducible bioluminescence data. As far as we know, this is the first time a pathogen has been monitored in situ, in real time, in a “real-product” status, and at a low temperature.     

RNA bulge entropies in the unbound state correlate with peptide binding strengths for HIV-1 and BIV TAR RNA because of improved conformational access.

For the binding of peptides to wild-type HIV-1 and BIV TAR RNA and to mutants with bulges of various sizes, changes in the DeltaDelta G values of binding were determined from experimental K d values. The corresponding entropies of these bulges are estimated by enumerating all possible RNA bulge conformations on a lattice and then applying the Boltzmann relationship. Independent calculations of entropies from fluctuations are also carried out using the Gaussian network model (GNM) recently introduced for analyzing folded structures. Strong correlations are seen between the changes in free energy determined for binding and the two different unbound entropy calculations. The fact that the calculated entropy increase with larger bulge size is correlated with the enhanced experimental binding free energy is unusual. This system exhibits a dependence on the entropy of the unbound form that is opposite to usual binding models. Instead of a large initial entropy being unfavorable since it would be reduced upon binding, here the larger entropies actually favor binding. Several interpretations are possible: (i) the higher conformational freedom implies a higher competence for binding with a minimal strain, by suitable selection amongst the set of already accessible conformations; (ii) larger bulge entropies enhance the probability of the specific favorable conformation of the bound state; (iii) the increased freedom of the larger bulges contri-butes more to the bound state than to the unbound state; (iv) indirectly the large entropy of the bound state might have an unfavorable effect on the solvent structure. Nonetheless, this unusual effect is interesting.     

Neuroleptics and Dopamine Transporters

The effects of neuroleptic treatments on dopamine transporters and on dopamine receptors was investigated in the forebrain of adult rats treated for 21 days with either haloperidol, clozapine or saline. The dopamine D₁receptors, labeled with [³H]SCH23390, increased in nucleus accumbens, latero-dorsal rostral neostriatum and substantia nigra, after clozapine but not haloperidol. The dopamine D₂receptors, studied with [³H]raclopride, increased in nucleus accumbens and in dorsolateral, ventro-medial and dorso-medial quadrants of the rostral neostriatum after either haloperidol or clozapine treatments, and also in latero-ventral rostral neostriatum but only after haloperidol. Haloperidol also up-regulated D₂receptors in rostral and caudal neostriatum, but clozapine produced a more uneven increase, especially in caudal neostriatum. In contrast, the densities of dopamine uptake sites, or transporters, labeled with [^I25I]RTI-121, remained unchanged after both neuroleptic treatments. The observation that dopamine transporters are resistant to treatments that modify D₁and D₂receptors indicates that these uptake sites can probably be ruled out as the target of neuroleptic drugs, and that dopamine receptor up-regulations can indeed occur independently of the densities of nerve endings at the terminal fields of innervation.     

The beach‐spawning California grunion Leuresthes tenuis eats and digests conspecific eggs

Apparent egg cannibalism was investigated in the beach‐spawning California grunion Leuresthes tenuis. Three hypotheses were tested to determine whether L. tenuis regularly consumes and efficiently digests conspecific eggs. First, examination of the gut contents of adults collected at four spawning sites over two seasons showed that the intestines of most fish from all the sites (57–87%, n ≥ 30, each site) contained L. tenuis eggs. The two other hypotheses focused on digestion of the eggs. First, the force required to crush cannibalized eggs was significantly less than that for uncannibalized eggs (fertilized or unfertilized), indicating that ingestion weakens the egg chorions. Second, conspecific eggs fed to fish held in the laboratory visibly degraded as they passed through the gut. The eggs lost c. half of their protein content and about two‐thirds of their lipid content as they passed from proximal to distal regions of the gut, indicating that digestion occurred. Digestive enzyme activities of the gut further confirmed that L. tenuis can break down the contents of ingested eggs. Trypsin activity decreased and aminopeptidase activity increased posteriorly along the gut, whereas amylase and lipase activities exhibited less clear patterns by gut region. As far as is known, this study is the first to show that L. tenuis is an egg cannibal.     

Empathy as a driver of prosocial behaviour: highly conserved neurobehavioural mechanisms across species

Empathy reflects the natural ability to perceive and be sensitive to the emotional states of others, coupled with a motivation to care for their well-being. It has evolved in the context of parental care for offspring, as well as within kinship bonds, to help facilitate group living. In this paper, we integrate the perspectives of evolution, animal behaviour, developmental psychology, and social and clinical neuroscience to elucidate our understanding of the proximate mechanisms underlying empathy. We focus, in particular, on processing of signals of distress and need, and their relation to prosocial behaviour. The ability to empathize, both in animals and humans, mediates prosocial behaviour when sensitivity to others'' distress is paired with a drive towards their welfare. Disruption or atypical development of the neural circuits that process distress cues and integrate them with decision value leads to callous disregard for others, as is the case in psychopathy. The realization that basic forms of empathy exist in non-human animals is crucial for gaining new insights into the underlying neurobiological and genetic mechanisms of empathy, enabling translation towards therapeutic and pharmacological interventions.     

Biochemical Characterization of Branched Chain Amino Acids Uptake in Trypanosoma cruzi

Trypanosoma cruzi is the etiological agent of Chagas disease. During its life cycle, it alternates among vertebrate and invertebrate hosts. Metabolic flexibility is a main biochemical characteristic of this parasite, which is able to obtain energy by oxidizing a variety of nutrients that can be transported from the extracellular medium. Moreover, several of these metabolites, more specifically amino acids, have a variety of functions beyond being sources of energy. Branched chain amino acids (BCAA), beyond their role in ATP production, are involved in sterol biosynthesis; for example, leucine is involved as a negative regulator of the parasite differentiation process occurring in the insect midgut. BCAA are essential metabolites in most nonphotosynthetic eukaryotes, including trypanosomes. In view of this, the metabolism of BCAA in T. cruzi depends mainly on their transport into the cell. In this work, we kinetically characterized the BCAA transport in T. cruzi epimastigotes. Our data point to BCAA as being transported by a single saturable transport system able to recognize leucine, isoleucine and valine. In view of this, we used leucine to further characterize this system. The transport increased linearly with temperature from 10 to 45 °C, allowing the calculation of an activation energy of 51.30 kJ/mol. Leucine uptake was an active process depending on ATP production and a H⁺ gradient, but not on a Na⁺ or K⁺ gradient at the cytoplasmic membrane level.