Effects of EEG of the osmotic opening of the blood-brain barrier in rats

EEG activity was recorded in rats submitted to osmotic opening of the BBB by intracarotid mannitol infusion.This procedure produced an immediate short-lasting depression of the EEG and a tardive paroxysmal EEG activity. Both these phenomena were more relevant on the ipsilateral hemisphere. In some instances a tonico-clonic seizure was recorded.Pre-treatment with diazepam abolished the occurrence of the tardive EEG and behavioral modifications.In accord with previous findings, focal seizure activity is likely to be responsible for the metabolic abnormalities associated with osmotic opening of the BBB. This preparation therefore produces in the brain unphysiological states in respect to local metabolism and electrical function.     

Enzymatic variability among Brazilian Pythium insidiosum isolates

BackgroundPythium insidiosum is an oomycete classified in the kingdom Stramenopila. P. insidiosum hyphae are not able to initiate infection without the secretion of hydrolytic enzymes, which are considered an important factor in microbial virulence.AimsTo evaluate the extracellular enzymatic activity of 14 Brazilian P. insidiosum isolates and a standard strain (ATCC 58637) by the API-ZYM System screening method.MethodsZoospores were grown in RPMI 1640 broth, and 65 μL of the liquid phase were inoculated in each cupule of the API-ZYM strips.ResultsDifferences in the enzymatic activities were observed among the isolates, although phosphohydrolases and ester hydrolases were conspicuous among all isolates. β-glucosidase was also present in most of the isolates. Enzymatic activities of α-glucosidase and chymotrypsin were not observed, differing from a previous study involving Australian isolates and intracellular enzymes.ConclusionsThe discrepancy in the enzymatic profile observed among Brazilian P. insidiosum isolates reflects the phenotypic variations found in susceptibility tests.     

Differential expression of interferon responsive genes in rodent models of transmissible spongiform encephalopathy disease

Background

Alzheimer's disease (AD) is characterized by a decline in cognitive function and accumulation of amyloid-β peptide (Aβ) in extracellular plaques. Mutations in amyloid precursor protein (APP) and presenilins alter APP metabolism resulting in accumulation of Aβ42, a peptide essential for the formation of amyloid deposits and proposed to initiate the cascade leading to AD. However, the role of Aβ40, the more prevalent Aβ peptide secreted by cells and a major component of cerebral Aβ deposits, is less clear. In this study, virally-mediated gene transfer was used to selectively increase hippocampal levels of human Aβ42 and Aβ40 in adult Wistar rats, allowing examination of the contribution of each to the cognitive deficits and pathology seen in AD.

Results

Adeno-associated viral (AAV) vectors encoding BRI-Aβ cDNAs were generated resulting in high-level hippocampal expression and secretion of the specific encoded Aβ peptide. As a comparison the effect of AAV-mediated overexpression of APPsw was also examined. Animals were tested for development of learning and memory deficits (open field, Morris water maze, passive avoidance, novel object recognition) three months after infusion of AAV. A range of impairments was found, with the most pronounced deficits observed in animals co-injected with both AAV-BRI-Aβ40 and AAV-BRI-Aβ42. Brain tissue was analyzed by ELISA and immunohistochemistry to quantify levels of detergent soluble and insoluble Aβ peptides. BRI-Aβ42 and the combination of BRI-Aβ40+42 overexpression resulted in elevated levels of detergent-insoluble Aβ. No significant increase in detergent-insoluble Aβ was seen in the rats expressing APPsw or BRI-Aβ40. No pathological features were noted in any rats, except the AAV-BRI-Aβ42 rats which showed focal, amorphous, Thioflavin-negative Aβ42 deposits.

Conclusion

The results show that AAV-mediated gene transfer is a valuable tool to model aspects of AD pathology in vivo, and demonstrate that whilst expression of Aβ42 alone is sufficient to initiate Aβ deposition, both Aβ40 and Aβ42 may contribute to cognitive deficits.     

At the boundary between biological and cultural evolution: the origin of surname distributions

Surnames and non-recombining alleles are inherited from a single parent in a highly similar way. A simple birth-death model with mutations can accurately describe this process. Exponentially growing and constant populations are investigated, and we study how different compositions of the founder populations can be observed in present-day diversity distributions. We analyse different quantities in the statistically stationary state, both through analytic and numerical methods. Our results compare favourably to field data for family sizes in several countries. We discuss the relationship between the distribution of surnames and the genetic diversity of a population.     

Efficacy of hyaluronic acid binding assay in selecting motile spermatozoa with normal morphology at high magnification

Background  

The present study aimed to evaluate the efficacy of the hyaluronic acid (HA) binding assay in the selection of motile spermatozoa with normal morphology at high magnification (8400x).     

Increased concentrations of IL-18 and uric acid in sickle cell anemia: contribution of hemolysis, endothelial activation and the inflammasome

Sickle cell anemia (SCA) is a common, severe monogenetic disorder characterized by chronic hemolysis, frequent infections, a chronic inflammatory state and recurrent occlusions of the microcirculation, resulting in painful crises, organ damage and premature death. This study evaluated associations between serum levels of IL-18, uric acid, hemolytic markers, and inflammatory molecules in SCA patients. A cross-sectional study was performed including 45 SCA patients (median age of 20.5 years) without general symptoms and who had not undergone blood transfusions. Inclusion criteria for the steady-state SCA patients were the absence of hospitalization and the absence of infections. Interleukin-18 and uric acid levels were correlated closely with markers of hemolysis, endothelial dysfunction and others cytokines levels. These findings suggest probable influences of IL-18 and uric acid in the pathophysiology of vascular occlusion in SCA. Additional studies should be performed to characterize similar prognosis markers and possible therapeutic targets.     

Songbird genetic diversity is lower in anthropogenically versus naturally fragmented landscapes

Natural habitats, and the populations they sustain, are becoming increasingly fragmented by human activities. Parallels between ‘true’ islands and ‘habitat’ islands suggest that standing levels of individual genetic diversity in naturally fragmented populations may predict the genetic fate of their anthropogenically fragmented counterparts, but this hypothesis remains largely untested. We compared neutral-locus genetic diversity of individual song sparrows (Melospiza melodia) breeding in a naturally fragmented landscape (small coastal islands) to that of song sparrows in similar-sized ‘urban islands’ separated by roads and housing developments rather than by water. Individuals on coastal islands were more heterozygous and less inbred than those in urban islands. Estimates of population genetic structuring (assessed by pairwise genetic differentiation and Bayesian clustering methods) and contemporary dispersal (based on assignment tests) revealed little structure within either landscape, suggesting that lack of connectivity at the geographic scale we investigated cannot explain the reduced heterozygosity of urban birds. However, within-site genetic similarity was higher in the urban than the coastal landscape. Assuming that historic genetic diversity was similar in these two environments, our findings suggest that anthropogenically fragmented populations may lose genetic diversity faster than their naturally fragmented counterparts.     

REPRODUCTIVE CONFLICT IN BUMBLEBEES AND THE EVOLUTION OF WORKER POLICING

Worker policing (mutual repression of reproduction) in the eusocial Hymenoptera represents a leading example of how coercion can facilitate cooperation. The occurrence of worker policing in “primitively” eusocial species with low mating frequencies, which lack relatedness differences conducive to policing, suggests that separate factors may underlie the origin and maintenance of worker policing. We tested this hypothesis by investigating conflict over male parentage in the primitively eusocial, monandrous bumblebee, Bombus terrestris. Using observations, experiments, and microsatellite genotyping, we found that: (a) worker‐ but not queen‐laid male eggs are nearly all eaten (by queens, reproductive, and nonreproductive workers) soon after being laid, so accounting for low observed frequencies of larval and adult worker‐produced males; (b) queen‐ and worker‐laid male eggs have equal viabilities; (c) workers discriminate between queen‐ and worker‐laid eggs using cues on eggs and egg cells that almost certainly originate from queens. The cooccurrence in B. terrestris of these three key elements of “classical” worker policing as found in the highly eusocial, polyandrous honeybees provides novel support for the hypothesis that worker policing can originate in the absence of relatedness differences maintaining it. Worker policing in B. terrestris almost certainly arose via reproductive competition among workers, that is, as “selfish” policing.     

Brood‐parasite‐induced female‐biased mortality affects songbird demography: negative implications for conservation

Parasites, of all sorts, can profoundly affect host population dynamics. Parasites commonly cause sex‐biased mortality and this can add to their impact. Female‐biased mortality in particular can destabilize dynamics and promote population collapse. We previously reported in a correlative study that brown‐headed cowbird Molothrus ater brood parasitism of song sparrows Melospiza melodia appears to cause female‐biased host nestling mortality. Here, we report results from ‘infestation’ and ‘de‐infestation’ experiments designed to test whether brood parasitism causes female‐biased mortality, and we document the resulting demographic impact using a simulation model. Experimental cowbird infestation of song sparrow nests halved the proportion of female host nestlings (0.31±0.07 vs 0.59±0.06; infested vs unparasitized nests at day 6) replicating the halving reported in naturally cowbird‐parasitized nests (0.28±0.01 vs 0.57±0.05; parasitized vs unparasitized). De‐infestation of naturally cowbird‐parasitized nests in turn wholly eliminated any effect on the proportion of female host nestlings (0.53±0.13 vs 0.54±0.06; de‐infested vs unparasitized) confirming that brood parasitism is the cause. This halving of the proportion of females fledging is likely to be as significant as nest predation in affecting population dynamics, based on the elasticities derived from our demographic model (–0.50 vs –0.59). Experimental infestation reduced the testosterone levels, begging behaviour, and body mass of six day old female host nestlings, whereas males were largely unaffected, suggesting that it is the exacerbation of intra‐brood competition that may be primarily responsible for the resulting female‐biased mortality. The brown‐headed cowbird is invasive in most of North America and has been implicated in regional population declines of many native species. We suggest that female‐biased host offspring mortality is likely to be commonplace among the 144 host species the cowbird successfully parasitizes, and we discuss the negative implications for songbird conservation, given the projected demographic impact.