Starch Binding Domain-containing Protein 1/Genethonin 1 Is a Novel Participant in Glycogen Metabolism

Stbd1 is a protein of previously unknown function that is most prevalent in liver and muscle, the major sites for storage of the energy reserve glycogen. The protein is predicted to contain a hydrophobic N terminus and a C-terminal CBM20 glycan binding domain. Here, we show that Stbd1 binds to glycogen in vitro and that endogenous Stbd1 locates to perinuclear compartments in cultured mouse FL83B or Rat1 cells. When overexpressed in COSM9 cells, Stbd1 concentrated at enlarged perinuclear structures, co-localized with glycogen, the late endosomal/lysosomal marker LAMP1 and the autophagy protein GABARAPL1. Mutant Stbd1 lacking the N-terminal hydrophobic segment had a diffuse distribution throughout the cell. Point mutations in the CBM20 domain did not change the perinuclear localization of Stbd1, but glycogen was no longer concentrated in this compartment. Stable overexpression of glycogen synthase in Rat1WT4 cells resulted in accumulation of glycogen as massive perinuclear deposits, where a large fraction of the detectable Stbd1 co-localized. Starvation of Rat1WT4 cells for glucose resulted in dissipation of the massive glycogen stores into numerous and much smaller glycogen deposits that retained Stbd1. In vitro, in cells, and in animal models, Stbd1 consistently tracked with glycogen. We conclude that Stbd1 is involved in glycogen metabolism by binding to glycogen and anchoring it to membranes, thereby affecting its cellular localization and its intracellular trafficking to lysosomes.     

Impact on energy metabolism of quantitative and functional cyclosporine-induced damage of kidney mitochondria

In this study we have measured, under experimental conditions which maintained efficient coupling, respiratory intensity, respiratory control, oxidative phosphorylation capacity and protonmotive force. Succinate cytochrome-c reductase and cytochrome-c oxidase activities were also studied. These investigations were carried out using kidney mitochondria from cyclosporine-treated rats (in vivo studies) and from untreated rats in the presence of cyclosporine (in vitro studies). Inhibition of respiratory intensity by cyclosporine did not exceed 21.1% in vitro and 15.9% in vivo. Since there was no in vitro inhibition of succinate cytochrome-c reductase and cytochrome-c oxidase activities, the slowing of electron flow observed can be interpreted as a consequence of an effect produced by cyclosporine between cytochromes b and c₁. Cyclosporine had no effect on respiratory control either in vitro or in vivo. Statistically significant inhibition of the oxidative phosphorylation was observed both in vitro (6.6%) and in vivo (12.1%). Moreover, cyclosporine did not induce any change of membrane potential either in vivo or in vitro. Our findings show that cyclosporine is neither a protonophore, nor a potassium ionophore. In cyclosporine-treated rats we noticed a decrease of protein in subcellular fraction, including the mitochondrial fraction. The role of the inhibition respiratory characteristics by cyclosporine in nephrotoxicity in vivo must take account of these two parameters: inhibition of the respiratory characteristics measured in vitro and diminution of mitochondrial protein in cyclosporine-treated rats.     

Intracellular and Extracellular pH and Ca Are Bound to Control Mitosis in the Early Sea Urchin Embryo via ERK and MPF Activities

Studies aiming to predict the impact on marine life of ocean acidification and of altered salinity have shown altered development in various species including sea urchins. We have analyzed how external Na, Ca, pH and bicarbonate control the first mitotic divisions of sea urchin embryos. Intracellular free Ca (Ca_i) and pH (pH_i) and the activities of the MAP kinase ERK and of MPF regulate mitosis in various types of cells including oocytes and early embryos. We found that intracellular acidification of fertilized eggs by Na-acetate induces a huge activation of ERK at time of mitosis. This also stops the cell cycle and leads to cell death, which can be bypassed by treatment with the MEK inhibitor U0126. Similar intracellular acidification induced in external medium containing low sodium or 5-(N-Methyl-N-isobutyl) amiloride, an inhibitor of the Na⁺/H⁺ exchanger, also stops the cell cycle and leads to cell death. In that case, an increase in Ca_i and in the phosphorylation of tyr-cdc2 occurs during mitosis, modifications that depend on external Ca. Our results indicate that the levels of pH_i and Ca_i determine accurate levels of Ptyr-Cdc2 and P-ERK capable of ensuring progression through the first mitotic cycles. These intracellular parameters rely on external Ca, Na and bicarbonate, alterations of which during climate changes could act synergistically to perturb the early marine life.     

Digest: The contribution of historical climate events in shaping the modern latitudinal diversity gradient of ancient reptiles

It is recognized that biodiversity changes across the planet latitudinally; however, the timing of and reasons for diversity loss at higher latitudes are not well understood. Meseguer and Condamine investigate phylogenies and fossil evidence of reptilian species and determine that global warming and cooling events allowed asymmetric extinction and dispersion across latitudes, suggesting a hypothesis where climate profoundly shapes the latitudinal diversity gradient in certain taxa.     

Dynamic and temporal structure of the troglobitic beetle Speonomus hydrophilus (Coleoptera: Bathyscimae)

The population ecology of the beetle Speonomus hydrophilus , occurring both in caves (reduced fluctuations in many abiotic parameters) and under the deepest layer of soil in mountains (MSS, more exposed to climatic variations), was studied in four habitats in the French central Pyrenees We have assessed some of the characteristics of the environment where these populations occur c g physical data (altitude and exposure), geologic data (nature of the parent-rock) and abiotic parameters (temperature with its seasonal fluctuations) and we investigated the relative importance of environmental structure and ecological characteristics on the temporal organization of S hydrophilus and the troglobitic fauna which cohabits The climatic study shows the existence of an annual thermal cycle which is regular and well marked for the MSS habitats but slightly out of phase with the surface cycle These periodic variations however slight may be stressful for troglobitic species In the MSS populations, the phenology of the entire community is reflected in the pattern seen in Speonomus The analysis of faunal profiles shows that samples follow the same seasonal succession during the annual cycle A potential seasonal rhythm of emergence may reflect a seasonal rhythm of vitellogenesis which produces a rhythm of egg-laying     

Simultaneous radioimmunoassay of progesterone, androst-4-enedione, pregnenolone, dehydroepiandrosterone and 17-hydroxyprogesterone in specific regions of human brain

Simultaneous determination of progesterone, androst-4-enedione, pregnenolone, dehydroepiandrosterone (DHEA) and 17-hydroxyprogesterone has been developed for human cerebral tissue. Before immunoassay, steroids were separated on a Celite column with propylene glycol as stationary phase with hexane containing increasing proportions of dichloromethane as mobile phase. This system allowed separation of steroids of similar polarity, especially of pregnenolone and progesterone. The brain regions studied cortex (prefrontal, parietal and temporal), cerebellum and corpus callosum, were obtained after autopsy from 9 women and 1 man between 76 and 93 years of age. Steroids were found in all regions. The overall concentrations expressed in nmol/kg of tissue were: 10.1, 7.6, 120.7, 19.6 and 10.4 respectively, for progesterone, androst-4-enedione, pregnenolone, dehydroepiandrosterone and 17-hydroxyprogesterone, corresponding to 7.3, 4.9, 74, 6.5 and 9.2 times the plasma levels. These very high concentrations, not previously described in human brain tissue, pose the question of the existence of local biosynthetic pathways independent of the peripheral endocrine gland system as well as that of progressive accumulation of steroids over a lifetime. Concentrations of each steroid in each subject varied little among the various brain regions studied, but there was much variation among the subjects with respect to the concentrations of a given steroid.     

Influence of a prolonged tamoxifen administration on steroidogenesis by incubated rat testes

Tamoxifen was administered i.m. for 9 days to adult male rats in a daily dose of 100 micrograms or 1 mg. The treatment resulted in a significant reduction of the plasma levels of testosterone and LH, without modification of the plasma levels of FSH and of the testes weight. Upon incubation, the testes from the tamoxifen-treated rats produced less testosterone and 7 alpha-hydroxytestosterone, but metabolized [4-14C]testosterone in the same way as the control animals. Small doses of hCG (0.5 i.u. for 9 days) were unable to modify the tamoxifen effect on the testicular function, while tamoxifen significantly inhibited the increase of the plasma levels of testosterone induced by the administration of moderate doses of hCG (1.5 i.u. or 2.5 i.u. for 9 days) to hypophysectomized rats. Tamoxifen treatment, however, did not modify significantly the reactivity of the testes towards high doses of hCG (10 i.u.), administered either 2 h before sacrifice or for 9 days. It is concluded that a prolonged administration of tamoxifen in the rat has, besides an indirect effect resulting from a decrease of the LH levels, a direct inhibitory influence on the testicular testosterone formation, which can be reversed by high doses of hCG.     

Influence of neonatal androgenization on the testicular steroidogenesis in the adult rat

The in vitro testicular steroidogenesis of male rats, androgenized on the third postnatal day by a single injection of 1 mg testosterone propionate, was investigated when the animals were 100 days old. The neonatal androgenization resulted in a 25% lower testes weight, significantly increased plasma levels of FSH (P less than 0.01) and LH (P less than 0.02), and normal levels of testosterone. Although the testes were hypotrophic, the incubation of the testes pairs yielded the same amounts of testosterone, 7 alpha-hydroxytestosterone and 5 alpha-androstane-(3 alpha + 3 beta), 17 beta-diol as in the control animals. However, the steroidogenic response to an acute hCG stimulation was reduced. From incubations of testes homogenates with various labelled steroid precursors it could be inferred that the activity of the 17 alpha-hydroxylase, the 3 beta-hydroxysteroid dehydrogenase-isomerase and the 17 beta-hydroxysteroid dehydrogenase, expressed per unit of incubated protein, was significantly increased in the testes of the androgenized rats. These data indicate that the basal steroidogenesis in neonatally androgenized male rats is maintained by an increased synthesis per unit of tissue, possibly under influence of an increased gonadotrophic stimulus, but that the maximum steroidogenic capacity is reduced.