Pressor, tachycardic and feeding responses in conscious rats following i.c.v. administration of dynorphin. Central blockade by opiate and alpha 1-receptor antagonists

Experiments were designed to determine the hemodynamic responses of conscious, unrestrained rats given intracerebroventricular (i.c.v.) injections of dynorphin A-(1-13) and the possible central receptor mechanisms mediating those changes. Male Sprague-Dawley rats (300 gb. wt.) received i.c.v. injections (by gravity flow in a total volume of 3 or 5 microliter) of control solutions of sterile saline (SS) or dimethylsulfoxide (DMSO) or 1.5, 3.0 or 6.1 nmol of dynorphin A-(1-13). Blood pressure and heart rate changes were monitored over 2 h after administration; as well, feeding activity was visually assessed and scored over this period. Other groups of conscious rats were pretreated i.c.v. with equimolar doses (3.0-24.4 nmol) of specific receptor antagonists (naloxone HCl, phentolamine HCl, propranolol HCl, yohimbine HCl or prazosin HCl) 10 min before subsequent i.c.v. administration of SS or DMSO/SS or 6.1 nmol of dynorphin A-(1-13). I.c.v. injection of dynorphin A-(1-13) caused a dose-related pressor response, associated temporally with tachycardia. As well, dynorphin evoked feeding activity and some grooming, which occurred when the rats were hypertensive and tachycardic and decreased as heart rate and blood pressure returned to control levels. I.c.v. pretreatment studies indicated that naloxone HCl (12.2 nmol), phentolamine HCl (12.2 nmol) and prazosin HCl (6.1 nmol) blocked the pressor response, tachycardia as well as feeding activity of rats subsequently given dynorphin. The results suggest the pressor and tachycardic effects of conscious rats following i.c.v. dynorphin administration may, in part, be due to behavioral activation (feeding). As well, these data indicate that both opioid as well as alpha 1-adrenergic receptors within the CNS are involved in mediating the pressor, tachycardic and feeding responses of conscious rats given i.c.v. injections of dynorphin A.     

Tumor necrosis factor-alpha convertase (ADAM17) mediates regulated ectodomain shedding of the severe-acute respiratory syndrome-coronavirus (SARS-CoV) receptor, angiotensin-converting enzyme-2 (ACE2)

Angiotensin-converting enzyme-2 (ACE2) is a critical regulator of heart function and a cellular receptor for the causative agent of severe-acute respiratory syndrome (SARS), SARS-CoV (coronavirus). ACE2 is a type I transmembrane protein, with an extracellular N-terminal domain containing the active site and a short intracellular C-terminal tail. A soluble form of ACE2, lacking its cytosolic and transmembrane domains, has been shown to block binding of the SARS-CoV spike protein to its receptor. In this study, we examined the ability of ACE2 to undergo proteolytic shedding and investigated the mechanisms responsible for this shedding event. We demonstrated that ACE2, heterologously expressed in HEK293 cells and endogenously expressed in Huh7 cells, undergoes metalloproteinase-mediated, phorbol ester-inducible ectodomain shedding. By using inhibitors with differing potency toward different members of the ADAM (a disintegrin and metalloproteinase) family of proteases, we identified ADAM17 as a candidate mediator of stimulated ACE2 shedding. Furthermore, ablation of ADAM17 expression using specific small interfering RNA duplexes reduced regulated ACE2 shedding, whereas overexpression of ADAM17 significantly increased shedding. Taken together, these data provided direct evidence for the involvement of ADAM17 in the regulated ectodomain shedding of ACE2. The identification of ADAM17 as the protease responsible for ACE2 shedding may provide new insight into the physiological roles of ACE2.     

Phylogenetic analysis of a novel sulfate-reducing magnetic bacterium, RS-1, demonstrates its membership of the δ-Proteobacteria

Abstract Most of the 16S ribosomal RNA gene of a sulfate-reducing magnetic bacterium, RS-1, was sequenced, and phylogenetic analysis was carried out. The results suggest that RS-1 is a member of the δ-Proteobacteria, and it appears to represent a new genus. RS-1 is the first bacterium reported outside the α-Proteobacteria that contains magnetite inclusions. RS-1 therefore disrupts the correlation between the α-Proteobacteria and possession of magnetite inclusions, and that between the δ-Proteobacteria and possession of greigite inclusions. The existence of RS-1 also suggests that intracellular magnetite biomineralization is of multiple evolutionary origins.     

Evolution of animal genitalia: morphological correlates of fitness components in a water strider

Rapid divergence of male genitalia is one of the most general evolutionary trends in animals with internal fertilization, but the mechanisms of genital evolution are poorly understood. The current study represents the first comprehensive attempt to test the main hypotheses that have been suggested to account for genital evolution (the lock-and-key, sexual selection and pleiotropy hypotheses) with intraspecific data. We measure multivariate phenotypic selection in a water strider species, by relating five different components of fitness (mating frequency, fecundity, egg hatching rate, offspring survival rate and offspring growth rate) to a suite of genital and non-genital morphological traits (in total 48). Body size had a series of direct effects in both sexes. Large size in females was positively related to both fecundity and egg hatching rate. There was positive sexual selection for large size in males (mating frequency), which to some extent was offset by a reduced number of eggs laid by females mated to large males. Male genitalic morphology influenced male mating frequency, but the detected directional selection on genitalia was due to indirect selection on phenotypically correlated non-intromittent traits. Further, we found no assortative mating between male intromittent genitalia and female morphology. Neither did we find any indications of male genitalia conveying information of male genetic quality. Several new insights can be gained from our study. Most importantly, our results are in stark disagreement with the long standing lock-and-key hypothesis of genital evolution, as well as with certain models of sexual selection. Our results are, however, in agreement with other models of sexual selection as well as with the pleiotropy hypothesis of genital evolution. Fluctuating asymmetry of bilaterally symmetrical traits, genital as well as non-genital, had few effects on fitness. Females with low fluctuating asymmetry in leg length produced offspring with a higher survival rate, a pattern most proba bly caused by direct phenotypic maternal effects. We also discuss the relevance of our results to sexual conflict over mating, and the evolution of sexual traits by coevolutionary arms races between the sexes.     

The use of principal component analysis for the modelling of high performance liquid chromatography

Principal component analysis (PCA) was used to analyse the behaviour of a chromatographic separation as its scale increased. Three 4.6 mm diameter columns identical in every respect except for column length (25, 15 and 5 cm), were used to generate the data from a test system based on the reversed-phase HPLC separation of crude erythromycin on a polystyrene matrix (PLRP 1000) having a particle diameter of 8 mu;m and a pore diameter of 100 nm. The species were separated with an isocratic solvent composed of 45/55 acetonitrile/water at about pH 7. An experimental design technique was used to investigate the effects of four process variables (load volume, load concentration, temperature and pH of buffer) on the chromatogram shapes. Following appropriate pre-processing of the chromatographic data, subsets of critical chromatograms were selected which sufficiently characterised the entire data set. From this subset, the corresponding runs were performed on the different sized columns and principal component models were generated for each. At 5 and 15 cm a single principal component was sufficient to characterise all the variance in the chromatograms which the range of process variables introduced, but at 25 cm two principal components were required, particularly to characterise the chromatograms with small loads. Excellent correlations were observed between the first principal components at the three scales. The possibility of predicting the separations on the 25 cm column from an analysis of the separations observed at 5 cm was investigated. The study revealed that good predictions could be made at high loads (>92%) , but the model was not effective at low loads because of the need to incorporate a second principal component which was not defined by the range of variables applied to the 5 cm column.     

Effects of dispersal mode on the environmental and spatial correlates of nestedness and species turnover in pond communities

Advances in metacommunity theory have made a significant contribution to understanding the drivers of variation in biological communities. However, there has been limited empirical research exploring the expression of metacommunity theory for two fundamental components of beta diversity: nestedness and species turnover. In this paper, we examine the influence of local environmental and a range of spatial variables (hydrological connectivity, proximity and overall spatial structure) on total beta diversity and the nestedness and turnover components of beta diversity for the entire macroinvertebrate community and active and passively dispersing taxa within pond habitats. High beta diversity almost entirely reflects patterns of species turnover (replacement) rather than nestedness (differences in species richness) in our dataset. Local environmental variables were the main drivers of total beta diversity, nestedness and turnover when the entire community was considered and for both active and passively dispersing taxa. The influence of spatial processes on passively dispersing taxa, total beta diversity and nestedness was significantly greater than for actively dispersing taxa. Our results suggest that species sorting (local environmental variables) operating through niche processes was the primary mechanism driving total beta diversity, nestedness and turnover for the entire community and active and passively dispersing taxa. In contrast, spatial factors (hydrological connectivity, proximity and spatial eigenvectors) only exerted a secondary influence on the nestedness and turnover components of beta diversity.     

Proof-of-concept human laboratory study for protracted abstinence in alcohol dependence: effects of gabapentin

There is a need for safe medications that can effectively support recovery by treating symptoms of protracted abstinence that may precipitate relapse in alcoholics, e.g. craving and disturbances in sleep and mood. This proof-of-concept study reports on the effectiveness of gabapentin 1200 mg for attenuating these symptoms in a non-treatment-seeking sample of cue-reactive, alcohol-dependent individuals. Subjects were 33 paid volunteers with current Diagnostic and Statistical Manual of Mental Disorders-IV alcohol dependence and a strength of craving rating 1 SD or greater for alcohol than water cues. Subjects were randomly assigned to gabapentin or placebo for 1 week and then participated in a within-subjects trial where each was exposed to standardized sets of pleasant, neutral and unpleasant visual stimuli followed by alcohol or water cues. Gabapentin was associated with significantly greater reductions than placebo on several measures of subjective craving for alcohol as well as for affectively evoked craving. Gabapentin was also associated with significant improvement on several measures of sleep quality. Side effects were minimal, and gabapentin effects were not found to resemble any major classes of abused drugs. Results suggest that gabapentin may be effective for treating the protracted abstinence phase in alcohol dependence and that a randomized clinical trial would be an appropriate next step. The study also suggests the value of cue-reactivity studies as proof-of-concept screens for potential antirelapse drugs.