Plasma selenium levels in healthy blood bank donors in the central-eastern part of Belgium

Graphite furnace atomic absorption spectrometry, with Zeeman background correction and after improved matrix modification, was used to measure the plasma selenium content of healthy blood bank donors in the central part of Belgium.

The mean plasma selenium concentration of 80 men and 80 women was 79.7±4.4 ng/mL with a range of 55.0–117.4 ng/mL.

There was no gender difference observed. Plasma selenium level was significantly highest for the adult group, aged 45–64 years, compared to the others, except the young adults (18–24 years).

The mean plasma selenium concentration measured corresponded well with literature data for Belgium. The obtained values were found to be in the medium range, compared with recent literature values for the European countries.     

Modulation of K+ channels by hydrogen peroxide.

External application of hydrogen peroxide (H2O2) was found to inhibit the time-dependent fast inactivation process of three cloned voltage-gated K+ channels expressed in Xenopus oocytes: KShIIIC, KShIIID and HukII. As expected from kinetic models where some channels are still opening while a significant fraction of channels is already inactivated there was a large increase in current magnitude concomitant to inactivation block. The channels otherwise functioned normally. The effects of H2O2 were specific (other cloned voltage-gated K+ channels were not affected), and reversible, the currents returned to normal upon removal of the H2O2. H2O2 is produced during normal metabolism; it could act as a modulator of excitability through effects on K+ channels if effective local concentrations are reached in neuronal regions close to the channel. KShIIIC and KShIIID currents are very similar to an O2-sensitive K+ current present in type I cells of the carotid body which is believed to underlie the modulation of excitability of these cells by changes in arterial O2 pressure. H2O2 has been proposed as an intermediary between O2 and cellular response in the carotid body; our results provide support for this model.     

Managing anabolic steroids in pre-hibernating Arctic ground squirrels: obtaining their benefits and avoiding their costs

Androgens have benefits, such as promoting muscle growth, but also significant costs, including suppression of immune function. In many species, these trade-offs in androgen action are reflected in regulated androgen production, which is typically highest only in reproductive males. However, all non-reproductive Arctic ground squirrels, irrespective of age and sex, have high levels of androgens prior to hibernating at sub-zero temperatures. Androgens appear to be required to make muscle in summer, which, together with lipid, is then catabolized during overwinter. By contrast, most hibernating mammals catabolize only lipid. We tested the hypothesis that androgen action is selectively enhanced in Arctic ground squirrel muscle because of an upregulation of androgen receptors (ARs). Using Western blot analysis, we found that Arctic ground squirrels have AR in skeletal muscle more than four times that of Columbian ground squirrels, a related southern species that overwinters at approximately 0°C and has low pre-hibernation androgen levels. By contrast, AR in lymph nodes was equivalent in both species. Brain AR was also modestly but significantly increased in Arctic ground squirrel relative to Columbian ground squirrel. These results are consistent with the hypothesis that tissue-specific AR regulation prior to hibernation provides a mechanism whereby Arctic ground squirrels obtain the life-history benefits and mitigate the costs associated with high androgen production.     

Effects of chronic uridine treatment on regional neuropeptide and tyrosine hydroxylase-like immunoreactivities in the brain of 12 month-old male rats

Uridine was administered in the drinking water (0.5 mg/ml) in adult 6 month-old rats for 6 months. The mean daily dose of uridine was 12.5 mg/rat. The effects of this treatment on tyrosine hydroxylase, galanin, somatostatin, neuropeptide Y and cholecystokinin-like immunoreactivities were studied by means of semiquantitative immunocytochemistry using the peroxidase-antiperoxidase procedure in combination with image analysis. A decrease of somatostatin, cholecystokinin and galanin-like immunoreactivities in nerve terminals was observed in various brain areas of 12 month-old animals compared with 3 month-old animals, while the levels of tyrosine hydroxylase-like immunoreactivity were unchanged. Uridine-treated animals showed a decrease of galanin, neuropeptide Y and cholecystokinin-like immunoreactivities in nerve terminals of some diencephalic areas and an increase of cholecystokinin-like immunoreactivity in nerve terminals of most of the telencephalic brain areas in comparison with vehicle treated animals of the same age. It is suggested that the pyrimidine nucleoside uridine can affect the synthesis and/or degradation of mRNAs involved in the synthesis of neuropeptides via direct nuclear actions and/or indirect actions involving effects on receptor activated phosphoinositide metabolism. Uridine offers a new way to modulate central peptide synapses.