alpha-Tocopherol and protein kinase C inhibition enhance platelet-derived nitric oxide release.

Platelet activation is tightly regulated by products of the endothelium and platelets including nitric oxide (NO). Excess vascular oxidative stress has been associated with impaired NO release, and antioxidant status has been shown to alter endothelium-derived NO bioactivity. Although physiological levels of a-tocopherol are known to inhibit platelet function, the effect of a-tocopherol on platelet NO release is unknown. Loading platelets with physiologic levels of a-tocopherol increased platelet NO production approximately 1.5-fold (Pa-tocopherol, platelet NO release increased 50% (Pa-Tocopherol-loaded platelets also produced 74% less superoxide as compared with control (Pa-tocopherol inhibited PKC-dependent eNOS phosphorylation as determined by immunoprecipitation. Lastly, platelets isolated from NOS3-deficient mice released 80% less superoxide as compared with control animals (P=0.011), and incubation of NOS III-deficient platelets with 500 mM a-tocopherol only caused a modest additional decrease in platelet superoxide release (NS). Thus, a-tocopherol appears to enhance platelet NO release both in vitro and in vivo through antioxidant- and PKC-dependent mechanisms.     

Global transcriptional response of pig brain and lung to natural infection by Pseudorabies virus

Background  

Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult.     

Temperature responses of tropical to warm temperateCladophora species in relation to their distribution in the North Atlantic Ocean

The relationship between distribution boundaries and temperature responses of some North AtlanticCladophora species (Chlorophyta) was experimentally examined under various regimes of temperature, light and daylength. Experimentally determined critical temperature intervals, in which survival, growth or reproduction was limited, were compared with annual temperature regimes (monthly means and extremes) at sites inside and outside distribution boundaries. The species tested belonged to two phytogeographic groups: (1) the tropical West Atlantic group (C. submarina: isolate from Curaçao) and (2) the amphiatlantic tropical to warm temperate group (C. prolifera: isolate from Corsica;C. coelothrix: isolates from Brittany and Curaçao; andC. laetevirens: isolates from deep and shallow water in Corsica and from Brittany). In accordance with distribution from tropical to warm temperate regions, each of the species grew well between 20–30°C and reproduction and growth were limited at and below 15°C. The upper survival limit in long days was <35°C in all species but high or maximum growth rates occurred at 30°C.C. prolifera, restricted to the tropical margins, had the most limited survival at 35°C. Experimental evidence suggests thatC. submarina is restricted to the Caribbean and excluded from the more northerly American mainland and Gulf of Mexico coasts by sporadic low winter temperatures in the nearshore waters, when cold northerly weather penetrates far south every few years. Experimental evidence suggests thatC. prolifera, C. coelothrix andC. laetevirens are restricted to their northern European boundaries by summer temperatures too low for sufficient growth and/or reproduction. Their progressively more northerly located boundaries were accounted for by differences in growth rates over the critical 10–15°C interval.C. prolifera andC. coelothrix are excluded or restricted in distribution on North Sea coasts by lethal winter temperatures, again differences in cold tolerance accounting for differences in their distribution patterns. On the American coast, species were probably restricted by lethal winter temperatures in the nearshore and, in some cases, by the absence of suitable hard substrates in the more equable offshore waters. Isolates from two points along the European coast (Brittany, Corsica) ofC. laetevirens showed no marked differences in their temperature tolerance but the Caribbean and European isolates ofC. coelothrix differed markedly in their tolerance to low temperatures, the lethal limit of the Caribbean isolate lying more than 5°C higher (at ca 5°C).     

Mitochondrial heteroplasmy and DNA barcoding in Hawaiian <Emphasis Type="Italic">Hylaeus</Emphasis> (<Emphasis Type="Italic">Nesoprosopis</Emphasis>) bees (Hymenoptera: Colletidae)

Background  

The past several years have seen a flurry of papers seeking to clarify the utility and limits of DNA barcoding, particularly in areas such as species discovery and paralogy due to nuclear pseudogenes. Heteroplasmy, the coexistence of multiple mitochondrial haplotypes in a single organism, has been cited as a potentially serious problem for DNA barcoding but its effect on identification accuracy has not been tested. In addition, few studies of barcoding have tested a large group of closely-related species with a well-established morphological taxonomy. In this study we examine both of these issues, by densely sampling the Hawaiian Hylaeus bee radiation.     

Histogenesis of the pituitary in rainbow trout (Salmo gairdneri) in different ambient salinities with particular reference to the rostral pars distalis

Summary The pituitary gland is first evident in rainbow trout two weeks before hatching. Differentiation of prolactin and ACTH cells is not marked until 3–4 days after hatching when the follicular arrangement of the prolactin cells become apparent. There is no difference in the time of development of either prolactin or ACTH cells in larvae reared in different ambient salinities despite marked changes in tissue ion and water content. This suggests that prolactin and ACTH do not play the osmo- and iono-regulatory roles in larval rainbow trout that they are considered to play in adult salmonids.The work was supported by a grant-in-aid of research from the National Research Council of Canada     

Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium

Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel.     

Does RU486 modify hormonal responses to handling stressor and cortisol treatment in fed and fasted rainbow trout?

This study examines the effect of the steroid analogue, RU486, on the physiological responses of fed and chronically fasted rainbow trout to an acute handling stressor. This potent ligand of the glucocorticoid receptor was administered as a slow-release implant either alone, or in combination with cortisol. There were temporal changes in plasma cortisol concentrations following administration of cortisol implants in both fed and fasted trout. By day 14, plasma cortisol levels in fed fish were similar in all treatment groups, but in fasted fish, the effect of cortisol administration on plasma cortisol concentrations was still evident; RU486 administered with cortisol, did not affect this response. Cortisol administration also elicited a small, but significant increase in plasma GH concentrations in fed rainbow trout and in plasma glucose concentrations in fasted animals. RU486-treatment prevented these responses. Conversely, whereas RU486 alone had no effect on hepatic 5'-monodeiodinase activity, when administered with cortisol it enhanced the marked suppressive effect of cortisol evident in both fed and fasted groups, suggesting that it may exert an interactive effect with cortisol on this process. Stressor-related changes in plasma cortisol, glucose, GH and thyroid hormone concentrations were evident in both fed and fasted groups; however, there was no evidence of a suppressive effect of RU486 treatment on any of the measured plasma parameters. Although RU486 did not prevent the stressor-related changes, the post-stressor cortisol profiles in RU-treated trout were extremely erratic compared with the oil-treated controls. This implies a disturbance of the normal interactions of the components of the hypothalamus-pituitary-interrenal tissue axis.     

Coupling non‐invasive physiological assessments with telemetry to understand inter‐individual variation in behaviour and survivorship of sockeye salmon: development and validation of a technique

Approximately 200 km from the mouth of the Fraser River, British Columbia, Canada, adult sockeye salmon Oncorhynchus nerka , were gastrically implanted with radio transmitters without anaesthetic. Subsets of the transmitter implanted fish were also biopsied which included drawing blood from the caudal peduncle (3 ml), removal of gill tissue (0·03 g) and quantification of energetic status using a microwave fat meter. Several experiments were used to test the hypothesis that the biopsy had a negligible effect on the subsequent survival and migratory behaviour of transmitter implanted fish. In the first experiment, no difference was found in the survival (both 100%) or tag retention (both 100%) between the two treatment groups (transmitter implanted with and without biopsy) when fish were held in pens for 24 h in the marine environment. Similarly, in other experiments where fish were released to the ocean to resume their migratory journey, no statistical differences were found in the travel times of fish in the two treatment groups, or in the proportion of fish that passed in‐river telemetry checkpoints. These results indicated that the handling and biopsy methods produced similar levels of mortality and tag retention as the telemetry treatment alone and that any changes in behaviour between the two treatment groups did not adversely affect migration time. Based upon the evidence provided from the biotelemetry of >300 adult sockeye salmon, it was felt that this general type of approach could be applicable to other fish species.     

Trafficking of L-triiodothyronine between ovarian fluid and oocytes of rainbow trout (Oncorhynchus mykiss)

The study examines the dynamics of thyroid hormone (TH) trafficking between rainbow trout (Oncorhynchus mykiss) oocytes and ovarian fluid (OF) to explore the processes involved in the transfer of hormone to the oocytes. We also examined the effects of enhancing oocyte T(3) content and subsequent embryo survival. Oocytes incubated in OF alone had significant losses of THs within 12 h, whereas the T(3) content of oocytes retained in T(3)-enriched OF (10 and 100 microg ml(-1)) was significantly elevated in a dose-dependant manner within 3 h. When transferred to non-supplemented OF, the T(3) content of the 10 micro ml(-1) treatment group decreased significantly within 24 h with a concomitant significant increase in OF T(3) concentration. Although there was no significant change in the 100 microg ml(-1) treatment group the significant increase in the OF T(3) concentration was evidence for marked T(3) efflux during this period. These findings provide evidence for the independent trafficking of T(3) based on concentration gradients across the oocyte cell membrane, and suggest that it is not vitellogenin-dependent. Fertilization of in ovo T(3)-supplemented oocytes resulted in a small, albeit significant, increase in mortality rate, but there was no significant effect of treatment on embryo growth rates up to the hatching stage of development.