Trophic niche width,offspring condition and immunity in a raptor species

Strategies developed by organisms to maximize foraging efficiency have a strong influence on fitness. The way in which the range of food resources is exploited has served to classify species, populations and individuals from more specialist (narrow trophic niche) to more generalist (broad trophic niche). Recent studies have provided evidence that many of the considered generalist species/populations are actually composed of different specialist individuals (individual specialization). Even the existence of generalism as an adaptive strategy has been questioned. In this study, we investigated the relationship between trophic niche width, individual quality and offspring viability in a population of common kestrel Falco tinnunculus during 4 years. We showed that the diet of kestrels varied significantly among years and that individuals of better quality fed their offspring with a higher diversity of prey species and a higher amount of food. Moreover, body condition and immune response of nestlings were positively correlated with diversity of prey delivered by parents. Our study suggests that generalism has the potential to increase fitness and that broadening the trophic niche may be an adaptive strategy in unpredictable environments.     

Eleven ancestral gene families lost in mammals and vertebrates while otherwise universally conserved in animals

Background  

Gene losses played a role which may have been as important as gene and genome duplications and rearrangements, in modelling today species' genomes from a common ancestral set of genes. The set and diversity of protein-coding genes in a species has direct output at the functional level. While gene losses have been reported in all the major lineages of the metazoan tree of life, none have proposed a focus on specific losses in the vertebrates and mammals lineages. In contrast, genes lost in protostomes (i.e. arthropods and nematodes) but still present in vertebrates have been reported and extensively detailed. This probable over-anthropocentric way of comparing genomes does not consider as an important phenomena, gene losses in species that are usually described as "higher". However reporting universally conserved genes throughout evolution that have recently been lost in vertebrates and mammals could reveal interesting features about the evolution of our genome, particularly if these losses can be related to losses of capability.     

Effect of phospholipid surface charge on the conductance and gating of a Ca2+-activated K+ channel in planar lipid bilayers

Summary A Ca-activated, K-selective channel from plasma membrane of rat skeletal muscle was studied in artificial lipid bilayers formed from either phosphatidylethanolamine (PE) or phosphatidylserine (PS). In PE, the single-channel conductance exhibited a complex dependence on symmetrical K⁺ concentration that could not be described by simple Michaelis-Menten saturation. At low K⁺ concentrations the channel conductance was higher in PS membranes, but approached the same conductance observed in PE above 0.4m KCl. At the same Ca²⁺ concentration and voltage, the probability of channel opening was significantly greater in PS than PE. The differences in the conduction and gating, observed in the two lipids, can be explained by the negative surface charge of PS compared to the neutral PE membrane. Model calculations of the expected concentrations of K⁺ and Ca²⁺ at various distances from a PS membrane surface, using Gouy-Chapman-Stern theory, suggest that the K⁺-conduction and Ca²⁺-activation sites sense a similar fraction of the surface potential, equivalent to the local electrostatic potential at a distance of 9 Å from the surface.     

Circadian variation of rectal temperature in newborn sheep

In adult animals, body temperature shows a 24 h rhythm that is endogenously generated. We examined the existence of 24 h rhythms of temperature in 10 newborn sheep. Four newborns, aged 5 to 28 days were kept with their mothers under nycthemeral conditions, and the remaining 6 lambs, aged 21 to 43 days, were kept with their mothers in constant light from day 3 after birth. Experiments were performed with both groups of lambs in the laboratory. Additional experiments were performed with the 6 lambs kept under constant light while they were in the pen with their mothers to rule out artifacts due to manipulation or artificial feeding. During the experiments done in the laboratory, the lambs were kept blindfolded in a canvas sling and were fed baby formula approximately every four hours (lambs kept under nycthemeral conditions) or every hour (constant light lambs). Lights were on in the room during the whole experiment. Temperature in the room was maintained at 18 +/- 0.1 degrees C (mean +/- SEM). In the experiments done in the pen, animals remained with the mother and room temperature was not controlled. In all experiments, rectal temperature was hourly measured for 24 h with a thermocouple inserted in the lamb's rectum and connected to a Philipp Schenk digital recorder. Lambs kept under nycthemeral conditions show a variation of mean rectal temperature (t degree) with a period of 24 h, that fits a cosine function (P less than 0.001): Rectal t degree (degree C) = 40.6 + 0.4 cos [15 (t-16.22)]. The mesor is 40.6, the amplitude 0.4, and the acrophase expressed in h is 16.22 (n = 4). Lambs kept under constant light show a variation of rectal temperature with a period of 24 h, independently of whether the measurements were done in the laboratory or in the pens. The acrophases varied widely in these animals, when the acrophase were synchronized so theta = 2400, mean rectal temperature showed a variation with a period of 24 h that fits the equation (P less than 0.001): Rectal t degree (degree C) = 39.5 + 0.18 cos [15 (t-0.23)]. The presence of a 24 h rhythm of rectal t degree in lambs kept under nycthemeral conditions, and its persistence in lambs kept under constant light suggests that the rhythm of rectal temperature observed in the newborn lamb is a true circadian rhythm.(ABSTRACT TRUNCATED AT 400 WORDS)     

Alternative Fecal Indicators and Their Empirical Relationships with Enteric Viruses,Salmonella enterica,and Pseudomonas aeruginosa in Surface Waters of a Tropical Urban Catchment

The suitability of traditional microbial indicators (i.e., Escherichia coli and enterococci) has been challenged due to the lack of correlation with pathogens and evidence of possible regrowth in the natural environment. In this study, the relationships between alternative microbial indicators of potential human fecal contamination (Bacteroides thetaiotaomicron, Methanobrevibacter smithii, human polyomaviruses [HPyVs], and F+ and somatic coliphages) and pathogens (Salmonella spp., Pseudomonas aeruginosa, rotavirus, astrovirus, norovirus GI, norovirus GII, and adenovirus) were compared with those of traditional microbial indicators, as well as environmental parameters (temperature, conductivity, salinity, pH, dissolved oxygen, total organic carbon, total suspended solids, turbidity, total nitrogen, and total phosphorus). Water samples were collected from surface waters of urban catchments in Singapore. Salmonella and P. aeruginosa had significant positive correlations with most of the microbial indicators, especially E. coli and enterococci. Norovirus GII showed moderately strong positive correlations with most of the microbial indicators, except for HPyVs and coliphages. In general, high geometric means and significant correlations between human-specific markers and pathogens suggest the possibility of sewage contamination in some areas. The simultaneous detection of human-specific markers (i.e., B. thetaiotaomicron, M. smithii, and HPyVs) with E. coli and enterococcus supports the likelihood of recent fecal contamination, since the human-specific markers are unable to regrow in natural surface waters. Multiple-linear-regression results further confirm that the inclusion of M. smithii and HPyVs, together with traditional indicators, would better predict the occurrence of pathogens. Further study is needed to determine the applicability of such models to different geographical locations and environmental conditions.     

Environment-Related Adaptive Changes of Gut Commensal Microbiota Do not Alter Colonic Toll-Like Receptors but Modulate the Local Expression of Sensory-Related Systems in Rats

Pathogenic and protective roles have been attributed to gut commensal microbiota (GCM) in gastrointestinal inflammatory and functional disorders. We have shown that the adaptation to a new environment implies specific changes in the composition of GCM. Here we assessed if environment-related adaptive changes of GCM modulate the expression of colonic Toll-like receptors (TLRs) and sensory-related systems in rats. Adult male SD rats were maintained under different environmental conditions: barrier-breed-and-maintained, barrier-breed adapted to conventional conditions or conventional-breed-and-maintained. Fluorescent in situ hybridization and real-time quantitative PCR (qPCR) were used to characterize luminal ceco-colonic microbiota. Colonic expression of TLR2, TLR4, TLR5, and TLR7, cannabinoid receptors (CB1/CB2), μ-opioid receptor (MOR), transient receptor potential vanilloid (TRPV1, TRPV3, and TRPV4), protease-activated receptor 2 (PAR-2), and calcitonin gene-related peptide were quantified by RT-qPCR. CB1, CB2 and MOR expression, was evaluated also by immunohistochemistry. In rats, housing-related environmental conditions induce specific changes of GCM, without impact on the expression of TLR-dependent bacterial recognition systems. Expression of sensory-related markers (MOR, TRPV3, PAR-2, and CB2) decreased with the adaptation to a conventional environment, correlating with changes in Bacteroides spp., Lactobacillus spp., and Bifidobacterium spp. counts. This suggests an interaction between GCM and visceral sensory mechanisms, which might be part of the mechanisms underlying the beneficial effects of some bacterial groups on functional and inflammatory gastrointestinal disorders.     

GnRH-induced cytosolic calcium oscillations in pituitary gonadotrophs: phase resetting by membrane depolarization.

Cultured rat pituitary gonadotrophs under whole-cell voltage clamp conditions respond to the hypothalamic hormone GnRH with synchronized oscillatory changes in both cytosolic Ca2+ concentration ([Ca2+]i) and [Ca2+]i-activated, apamin-sensitive K+ current (IK(Ca)). We found, and report here for the first time, that in GnRH-stimulated cells a brief depolarizing pulse can elicit a transient [Ca2+]i rise similar to the endogenous cycle. Furthermore, Ca2+ entry during a single depolarizing pulse was found to shift the phase of subsequent endogenous [Ca2+]i oscillations, which thereafter continue to occur at their previous frequency before the pulse. Application of two consecutive depolarizing pulses showed that the size of the [Ca2+]i rise evoked by the second pulse depended on the time lapsed between two consecutive pulses, indicating that each endogenous or evoked [Ca2+]i rise cycle leaves the Ca2+ release mechanism of the gonadotroph in a refractory state. Recovery from this condition can be described by an exponential function of the time lapsed between the pulses (time constant of ca. 1 s). We propose that the underlying mechanism in both refractoriness after endogenous cycles and phase resetting by a brief pulse of Ca2+ entry involves the InsP3 receptor-channel molecule presumed to be located on the cytosolic aspect of the endoplasmic reticulum membrane.