Enhancement of 3H-phenytoin binding by diazepam and (+)bicuculline

3H-Phenytoin binding to the particulate fraction of rat wholebrain homogenate was studied using the filter assay technique. It was found that diazepam and (+)bicuculline methobromide caused a concentration-dependent enhancement of the total binding of 3H-phenytoin, whereas GABA and (-)bicuculline methobromide (the inactive bicuculline isomer) had no effect. In subsequent competition experiments (labelled versus unlabelled phenytoin), it was found that the presence of a potentiating concentration of diazepam transformed the biphasic phenytoin competition isotherm into a simple curve with a Hill coefficient of approximately one, and a Ki of 110 nM.     

Cimetidine and ranitidine in duodenal ulcer.

Two histamine H2 antagonists, cimetidine and ranitidine, given in doses of 1 g daily and 200 mg daily to 18 and 20 patients respectively proved equivalent in promoting healing of duodenal ulcer. No adverse effects occurred during the trial, though serum urea and creatinine concentrations tended to rise slightly during treatment with cimetidine but not ranitidine. Choice between the two drugs is likely to be influenced by overall patterns of adverse effects rather than considerations of individual potency.     

Nucleoside triphosphate requirements for superoxide generation and phosphorylation in a cell-free system from human neutrophils. Sodium dodecyl sulfate and diacylglycerol activate independently of protein kinase C.

The NADPH-oxidase of human neutrophils can be activated in a cell-free system comprised of plasma membrane, cytosol, and an anionic amphiphile such as arachidonate or sodium dodecyl sulfate (SDS). Recently, we showed that diacylglycerol acts synergistically with SDS in the cell-free system to stimulate superoxide generation, with concurrent phosphorylation of a 47-kDa cytosolic protein which is thought to be a component of the oxidase (Burnham, D. N., Uhlinger, D. J., and Lambeth, J. D. (1990) J. Biol. Chem. 265, 17550-17559). We report herein that when undialyzed cytosol is used along with either SDS alone or SDS plus diacylglycerol as activators, adenosine 5'-(gamma-thio)triphosphate (ATP gamma S) and guanosine 5'-(gamma-thio)triphosphate (GTP gamma S) both stimulated superoxide generation several fold, yielding about the same maximal velocity. ATP and GTP showed lower levels of stimulation. Stimulation by ATP gamma S and GTP gamma S was nonadditive, and showed a 5-7-fold greater specificity for GTP gamma S. ATP gamma S stimulation was inhibited by the nucleoside diphosphate (NDP) kinase inhibitor UDP. In contrast, when extensively dialyzed cytosol was used, most of the stimulation by ATP gamma S was lost, while most of that by GTP gamma S was retained. Addition of GDP restored the ability of ATP gamma S to stimulate, consistent with NDP kinase-catalyzed formation of GTP gamma S from ATP gamma S plus GDP. This activity was demonstrated directly in both cytosol and plasma membrane. Using undialyzed cytosol, phosphorylation of p47 showed a similar nonspecificity for nucleoside triphosphates, due to NDP kinase activity, but revealed the expected ATP specificity when dialyzed cytosol was used. Neither ATP gamma S nor GTP gamma S were good substrates for protein phosphorylation. Under a variety of conditions, phosphorylation of p47 or other neutrophil proteins failed to correlate with oxidase activation. The present studies indicate that SDS and diacylglycerol stimulation of superoxide generation in the cell-free system is independent of protein kinase C or other protein kinase activity, and suggest a novel role for diacylglycerol in cell regulation.     

Benzodiazepine Receptor Binding Following Amygdala-Kindled Convulsions: Differing Results in Washed and Unwashed Brain Membranes

The binding of [3H]flunitrazepam and [3H]RO5-4864 was measured in unwashed brain homogenates and in extensively washed brain membranes from amygdala-kindled and "yoked" control rats sacrificed 2 weeks following the sixth stage 5 convulsion. In unwashed homogenates, [3H]flunitrazepam binding was reduced in both the hypothalamus and ipsilateral right cortex of kindled rats (unchanged in other areas). In washed brain membranes, [3H]flunitrazepam binding was unaltered in these regions; it was bilaterally elevated, however, in both the amygdala and hippocampus (unchanged in other areas). In washed membranes, the in vitro addition of gamma-aminobutyric acid enhanced [3H]flunitrazepam binding to a similar extent in kindled and control membranes. These data indicate that the type of benzodiazepine binding abnormality observed after kindling depends on the type of tissue preparation employed in the assay procedure.     

Myxococcal predation of the cyanobacterium Phormidium luridum in aqueous environments

Two strains of Myxococcus xanthus, and a strain of Myxococcus fulvus were compared with respect to their ability to entrap and lyse trichomes of the cyanobacterium Phormidium luridum var. olivaceae. All of these isolates form colonial aggregates and spherules in either axenic culture with a tryptone-salts medium or in a mixed culture with viable cyanobacterial cells as the sole source of nutrients. Light microscopy showed evidence of swarming activity on the surface of all three myxococci with the accompanying formation of fruiting structures. Extended incubation of mixed cultures showed the myxococci to be capable of long-term control of the cyanobacterial population with predator-prey population cycling occurring on average every 9 days. Serial transfer of mixed cultures into either fresh autotrophic medium or cyanobacterial cultures of 10⁷ per ml showed the persistence of predatory activity. Myxococcal densities were shown to return repeatedly to initial virulent levels. Predator inoculum levels could be reduced to 50 cells per 100 ml in a cyanobacterial culture of 10⁷ per ml. These in vitro data enhance the potential of the myxococcus predatory colony as a biological control agent for in situ cyanobacteria.     

Vitamin D status and determinants of deficiency in non-supplemented athletes during the winter months in Tunisia

Recent reports suggest that hypovitaminosis D in athletes is as common as in the general population. This study was devised to examine vitamin D status and determinants of deficiency in athletes living in a sunny country (Tunisia). One hundred and fifty national elite athletes, training outdoors (n = 83) or indoors (n = 67), were enrolled from January to February 2012. Plasma 25-hydroxyvitamin D was measured by radioimmunoassay. Concentrations were between 50 and 75 nmol · l^-1 in 21.3% of participants, between 25 and 50 nmol · l^-1 in 55.3% of participants and <25 nmol · l^-1 in 14.7% of participants. The concentrations were significantly lower in indoor athletes than outdoor athletes (36.2±19.0 nmol · l^-1 vs. 49.1±19.2 nmol · l^-1; p < 0.001). In multivariate analysis, vitamin D deficiency (25-hydroxyvitamin D <50 nmol · l^-1) was associated with indoor sports [multi-adjusted odds ratio (95% confidence interval), 5.03 (1.64-15.4); p = 0.005], female gender [3.72 (1.44-9.65); p = 0.007] and age < 18 years [2.40 (1.01-5.85); p = 0.05]. Athletes living in sun-rich environments are exposed to a high risk of vitamin D inadequacy. Given the importance of vitamin D in health and athletic ability, targeting sufficient levels of plasma 25-hydroxyvitamin D in athletes is well justified.     

Genetics of plumage color in the Gyrfalcon (Falco rusticolus): analysis of the melanocortin-1 receptor gene

Genetic variation at the melanocortin-1 receptor (MC1R) gene is correlated with melanin color variation in a few reported vertebrates. In Gyrfalcon (Falco rusticolus), plumage color variation exists throughout their arctic and subarctic circumpolar distribution, from white to gray and almost black. Multiple color variants do exist within the majority of populations; however, a few areas (e.g., northern Greenland and Iceland) possess a single color variant. Here, we show that the white/melanic color pattern observed in Gyrfalcons is explained by allelic variation at MC1R. Six nucleotide substitutions in MC1R resulted in 9 alleles that differed in geographic frequency with at least 2 MC1R alleles observed in almost all sampled populations in Greenland, Iceland, Canada, and Alaska. In north Greenland, where white Gyrfalcons predominate, a single MC1R allele was observed at high frequency (>98%), whereas in Iceland, where only gray Gyrfalcons are known to breed, 7 alleles were observed. Of the 6 nucleotide substitutions, 3 resulted in amino acid substitutions, one of which (Val(128)Ile) was perfectly associated with the white/melanic polymorphism. Furthermore, the degree of melanism was correlated with number of MC1R variant alleles, with silver Gyrfalcons all heterozygous and the majority of dark gray individuals homozygous (Ile(128)). These results provide strong support that MC1R is associated with plumage color in this species.