Chronic carbon monoxide enhanced IbTx-sensitive currents in rat resistance pulmonary artery smooth muscle cells

Exogenous carbon monoxide (CO) can induce pulmonary vasodilation by acting directly on pulmonary artery (PA) smooth muscle cells. We investigated the contribution of K+ channels to the regulation of resistance PA resting membrane potential on control (PAC) rats and rats exposed to CO for 3 wk at 530 parts/million, labeled as PACO rats. Whole cell patch-clamp experiments revealed that the resting membrane potential of PACO cells was more negative than that of PAC cells. This was associated with a decrease of membrane resistance in PACO cells. Additional analysis showed that outward current density in PACO cells was higher (50% at +60 mV) than in PAC cells. This was linked to an increase of iberiotoxin (IbTx)-sensitive current. Chronic CO hyperpolarized membrane of pressurized PA from -46.9 +/- 1.2 to -56.4 +/- 2.6 mV. Additionally, IbTx significantly depolarized membrane of smooth muscle cells from PACO arteries but not from PAC arteries. The present study provides initial evidence of an increase of Ca2+-activated K+ current in smooth muscle cells from PA of rats exposed to chronic CO.     

Corticosterone shifts reproductive behaviour towards self-maintenance in the barn owl and is linked to melanin-based coloration in females

Trade-offs between the benefits of current reproduction and the costs to future reproduction and survival are widely recognized. However, such trade-offs might only be detected when resources become limited to the point where investment in one activity jeopardizes investment in others. The resolution of the trade-off between reproduction and self-maintenance is mediated by hormones such as glucocorticoids which direct behaviour and physiology towards self-maintenance under stressful situations. We investigated this trade-off in male and female barn owls in relation to the degree of heritable melanin-based coloration, a trait that reflects the ability to cope with various sources of stress in nestlings. We increased circulating corticosterone in breeding adults by implanting a corticosterone-releasing-pellet, using birds implanted with a placebo-pellet as controls. In males, elevated corticosterone reduced the activity (i.e. reduced home-range size and distance covered within the home-range) independently of coloration, while we could not detect any effect on hunting efficiency. The effect of experimentally elevated corticosterone on female behaviour was correlated with their melanin-based coloration. Corticosterone (cort-) induced an increase in brooding behaviour in small-spotted females, while this hormone had no detectable effect in large-spotted females. Cort-females with small eumelanic spots showed the normal body-mass loss during the early nestling period, while large spotted cort-females did not lose body mass. This indicates that corticosterone induced a shift towards self-maintenance in males independently on their plumage, whereas in females this shift was observed only in large-spotted females.     

Pleiotropy in the melanocortin system: expression levels of this system are associated with melanogenesis and pigmentation in the tawny owl (Strix aluco)

The adaptive function of melanin‐based coloration is a long‐standing debate. A recent genetic model suggested that pleiotropy could account for covariations between pigmentation, behaviour, morphology, physiology and life history traits. We explored whether the expression levels of genes belonging to the melanocortin system (MC1R, POMC, PC1/3, PC2 and the antagonist ASIP), which have many pleiotropic effects, are associated with melanogenesis (through variation in the expression of the genes MITF, SLC7A11, TYR, TYRP1) and in turn melanin‐based coloration. We considered the tawny owl (Strix aluco) because individuals vary continuously from light to dark reddish, and thus, colour variation is likely to stem from differences in the levels of gene expression. We measured gene expression in feather bases collected in nestlings at the time of melanin production. As expected, the melanocortin system was associated with the expression of melanogenic genes and pigmentation. Offspring of darker reddish fathers expressed PC1/3 to lower levels but tended to express PC2 to higher levels. The convertase enzyme PC1/3 cleaves the POMC prohormone to obtain ACTH, while the convertase enzyme PC2 cleaves ACTH to produce α‐melanin‐stimulating hormone (α‐MSH). ACTH regulates glucocorticoids, hormones that modulate stress responses, while α‐MSH induces eumelanogenesis. We therefore conclude that the melanocortin system, through the convertase enzymes PC1/3 and PC2, may account for part of the interindividual variation in melanin‐based coloration in nestling tawny owls. Pleiotropy may thus account for the covariation between phenotypic traits involved in social interactions (here pigmentation) and life history, morphology, behaviour and physiology.     

Population genetics of the American eel (Anguilla rostrata): FST = 0 and North Atlantic Oscillation effects on demographic fluctuations of a panmictic species

We performed population genetic analyses on the American eel (Anguilla rostrata) with three main objectives. First, we conducted the most comprehensive analysis of neutral genetic population structure to date to revisit the null hypothesis of panmixia in this species. Second, we used this data to provide the first estimates of contemporary effective population size (N_e) and to document temporal variation in effective number of breeders (N_b) in American eel. Third, we tested for statistical associations between temporal variation in the North Atlantic Oscillation (NAO), the effective number of breeders and two indices of recruit abundance. A total of 2142 eels from 32 sampling locations were genotyped with 18 microsatellite loci. All measures of differentiation were essentially zero, and no evidence for significant spatial or temporal genetic differentiation was found. The panmixia hypothesis should thus be accepted for this species. N_b estimates varied by a factor of 23 among 12 cohorts, from 473 to 10 999. The effective population size N_e was estimated at 10 532 (95% CI, 9312–11 752). This study also showed that genetically based demographic indices, namely N_b and allelic richness (Ar), can be used as surrogates for the abundance of breeders and recruits, which were both shown to be positively influenced by variation during high (positive) NAO phases. Thus, long‐term genetic monitoring of American glass eels at several sites along the North American Atlantic coast would represent a powerful and efficient complement to census monitoring to track demographic fluctuations and better understand their causes.     

Population structure,relative growth and morphological sexual maturity of the snapping shrimp Alpheus brasileiro Anker, 2012 (Caridea: Alpheidae) from the south-eastern coast of Brazil

The present study investigated the population structure of the snapping shrimp Alpheus brasileiro. We tested the hypotheses that the sex ratio of the population differs from the expected 1:1 and that the growth pattern differs between adults and juveniles and between sexes. Reproductive period, juvenile recruitment and morphological sexual maturity were estimated. Samples were collected in two periods. The first sampling occurred bimonthly from March 2013 to January 2014. The second sampling occurred monthly from April 2015 to March 2016. The population structure was determined based on the size-frequency distribution of different demographic categories. To analyse the relative growth, we measured the second pleuron length, major cheliped propodus length, major cheliped propodus width, major cheliped propodus height, appendix interna length, appendix masculina length. The results showed that the sex ratio did not differ from 1:1 (male:female). Reproduction and juvenile recruitment were continuous throughout the study period. The analysis of relative growth confirmed the hypothesis that males and females, and juveniles and adults, have different growth patterns, indicating distinct strategies of energy allocation. The estimated carapace length at the onset of morphological sexual maturity was 4.9?mm in males and 4.7?mm in females. The results obtained in this study are probably related to the monogamous social behaviour of A. brasileiro. Monogamy can influence demographic parameters such as sex ratio and the size at which males and females reach morphological sexual maturity.     

A distinctive fungal community inhabiting cryoconite holes on glaciers in Svalbard

Cryoconite holes on glacier surfaces are ice-cold hot spots of microbial diversity and activity but still little is known about their fungal inhabitants. We provide the first report of distinctive fungal communities in cryoconite debris from three valley glaciers at Kongsfjorden, Svalbard. Multivariate analysis of terminal-restriction fragment length polymorphism (T-RFLP) profiles of rRNA ITS amplicons revealed that quite distinct fungal communities were found in cryoconite holes compared with soils from adjacent moraine and tundra sites, and that communities on glaciers with contrasting ice-surface hydrology also differed. Most of the fungi cultured from cryoconite sediment were basidiomycetous yeasts or filamentous Ascomycota (Helotiales/Pleosporales). The latter included aeroaquatic fungi, such as Articulospora and Varicosporium, implying a role for these important freshwater decomposers in the carbon dynamics of cryoconite holes. Matching of the dominant peaks from T-RFLP analysis to predicted peaks of cultured isolates confirmed the abundance of these aeroaquatic fungi but also revealed that most of the dominant T-RFLP peaks did not match any cultured isolates. Considering the prevalence and endangerment of glacial environments worldwide, these findings would suggest that their potential as reservoirs of fungal diversity should not be overlooked.     

Ketogenic Diet Increases Glutathione Peroxidase Activity in Rat Hippocampus

Ketogenic diets have been used in the treatment of refractory childhood epilepsy for almost 80 years; however, we know little about the underlying biochemical basis of their action. In this study, we evaluate oxidative stress in different brain regions from Wistar rats fed a ketogenic diet. Cerebral cortex appears to have not been affected by this diet, and cerebellum presented a decrease in antioxidant capacity measured by a luminol oxidation assay without changes in antioxidant enzyme activities—glutathione peroxidase, catalase, and superoxide dismutase. In the hippocampus, however, we observed an increase in antioxidant activity accompanied by an increase of glutathione peroxidase (about 4 times) and no changes in lipoperoxidation levels. We suggest that the higher activity of this enzyme induced by ketogenic diet in hippocampus might contribute to protect this structure from neurodegenerative sequelae of convulsive disorders.