Effect of naloxone and beta-casomorphin on the hypothalamic-pituitary-luteinizing hormone axis in vitro.

The effect of naloxone and beta-casomorphin on luteinizing hormone (LH) release from pituitary cell aggregates, obtained by three-dimensional culture, with or without mediobasal hypothalamic fragments was studied in vitro. Short-term naloxone perifusion at a concentration of 10(-5)M did not modify either basal or LHRH-stimulated LH release from the pituitary cell aggregates. In contrast, a 12-min naloxone perifusion at the same concentration caused an increase in LH release in the mediobasal hypothalamic-pituitary cell aggregate axis. This increase was rapid (12-16 min after time pulse), marked [up to 10 times (p less than 0.004) the initial base line], short (return to the base line secretion 32-40 min after the beginning of the time pulse) and dose-dependent, with a rise greater than 1000% at a concentration of 10(-4) (p less than 0.006). The same effect was observed when a second pulse was applied 48 min after the first one. LH release induced by naloxone was antagonized 56 +/- 2% (p less than 0.03) by beta-casomorphin (an exogenous opiate) at a concentration of 10(-5) M. beta-casomorphin alone did not modify LH basal secretion, but inhibited 25.1 +/- 2.4% (p less than 0.008) LH release enhanced by LHRH. These results indicate that naloxone, an opiate antagonist, markedly increases LH release via a mu-type opioid receptor mechanism at the hypothalamic level only, during short-term exposure.     

Les prélèvements testiculaires dans les azoospermies sécrétoires: le point de vue du Biologiste de la Reproduction sur la lecture du prélèvement

The prognosis of severe male sterility (nonobstructive azoospermia) has considerably improved over recent years with the introduction of ICSI. The human reproduction biologist actively collaborates with the surgeon in the search for and extraction of sperm from testicular tissue (TESE). The presence of the biologist during surgery is mandatory to guide exploration and to avoid an excessive number of biopsies. Sperm extraction is performed in the laboratory by mechanical extraction with fine forceps. Enzymatic extraction with collagenase IV can be used in cases of nonobstructive azoospermia to optimize tissue dispersion and to improve retrieval of mature cells. The use of only one fraction (50%) of Pure Sperm (JC Diffusion, Lyon France) limits the loss of spermatozoa. to optimize the results in cases of akinesia, it may be useful to induce sperm motility by pentoxifylline or perform in vitro culture for three days. Sperm cryopreservation is compulsory in the case of nonobstructive azoospermia. This allows programming of TESE for a different time from that of ICSI. All results obtained with cryopreserved testicular sperm, in recent years, are encouraging. It is also recommended to freeze several small fractions of sperm in order to limit the number of surgical procedures on the testicle. This article presents the results of our experience in 36 cases of nonobstructive azoospermia. Extraction was negative in 13 cases (36%), similar to the rate reported in the literature.     

Premiere decouverte en Europe Sud-occidentale de Praeovibos priscus (Mammalia,Artiodactyla, Ovibovinae) dans le gisement pleistocene moyen ante-risseien de la Caune de l'Arago (Tautavel,Pyrenees-Orientales,France)

Teeth, cranial and postcranial skeletton of Praeovibos were sampled from the sediments of the Caune de l'AragoCave. This material is enough to recognize the anatomical relationships between Praeovibos and Ovibos. Praeovibos is discovered for the first time in France and in South Western Europe also. The problem of the correlation of the whole European Middle Pleistocene is approached from a different point of view.     

The yeast ATP synthase subunit 4: structure and function

The structure of ATP synthase subunit 4 was determined by using the oligonucleotide probe procedure. This subunit is the fourth polypeptide of the complex when classifying subunits in order of decreasing molecular mass. Its relative molecular mass is 25 kDa. The ATP4 gene was isolated and sequenced. The nucleotide sequence predicts that subunit 4 is probably derived from a precursor protein 244 amino acids long. Mature subunit 4 contains 209 amino acid residues and the predicted molecular mass is 23250 kDa. Subunit 4 shows homology with the b-subunit of Escherichia coli ATP synthase and the b-subunit of beef heart mitochondrial ATP synthase. By using homologous transformation, a mutant lacking wild subunit 4 was constructed. This mutant is devoid of oxidative phosphorylation and F1 is loosely bound to the membrane. Our data are in favor of a structural relationship between subunit 4 and the mitochondrially-translated subunit 6 during biogenesis of F0.     

Chimeric analysis of the small GTPase RacE in cytokinesis signaling in Dictyostelium discoideum

RacE is a small GTPase required for cytokinesis in Dictyostelium discoideum. To investigate RacE's potential binding and signaling interfaces that allow its function in cytokinesis, 10 different chimeras were created between RacE and the closely related small GTPase, RacC. RacE/RacC chimeras, containing various combinations of four RacE regions, E I-IV: E-I (aa 1-67), E-II (aa 68-124), E-III (aa 125-184), and E-IV (aa 185-223), were tested for their ability to rescue the multinucleated, cytokinesis-defective phenotype of RacE null cells grown in suspension. Regions E-II and E-IV were essential but not sufficient for the rescue of RacE null cells. These two regions, in combination with either region E-1 or E-III, resulted in rescue. Results presented here suggest that region E-II contains a crucial, yet incomplete, binding site. Regions E-I or E-III separately provide additional, necessary elements for RacE's function. The extended E tail of RacE (E-IV) may act as a 'sensor' of the bound nucleotide state of RacE and facilitate GDP to GTP exchange (possibly through interactions with a GEF molecule), thereby resulting in activation of RacE. This study provides new evidence for small GTPases engaging several distinct protein interfaces to mediate signaling in various cellular processes.