Plasma and liver selenium levels in the rat during supplementation with 0.5, 2, 6, and 15 ppm selenium in drinking water

Plasma and liver selenium of Wistar rats were determined after 1, 3, and 6 mo supplementation with 0.5, 2, 6, or 15 ppm selenium as sodium selenite in drinking water. Plasma selenium was not different from control values at additional intake of 0.5 ppm but increased above usual levels at higher intakes. A highly significant correlation was observed between the total quantity of selenium ingested and plasma selenium after 1 mo treatment (r=0.99,p<0.01), but was less pronounced after 3 and 6 mo (0.94,p<0.05, and 0.78,p<0.05, respectively). The decrease in plasma selenium with time of treatment was more pronounced at higher intakes. There was also a highly significant correlation between total selenium intake and liver selenium concentration (r=0.99,p<0.01) after 1 mo of treatment, but this time liver selenium did not change with time, and the correlation remained highly significant throughout the investigation. Liver selenium therefore appears as a more sensitive and more representative measure of selenium intake than plasma selenium. Most supplements did not affect body weight and survival of animals, except when the diet was supplemented with 15 ppm for 6 mo; however, alterations in biochemical parameters concerning lipid status and hepatic function were observed at levels above 2.0 ppm.     

Rank relations among sisters in semi-free-ranging Barbary macaques (Macaca sylvanus)

Although semi-free-ranging Barbary macaque females are able to outrank older females from lower-ranking matrilines (matrilineal rank acquisition), they do not systematically outrank their older sisters, as is known to be the case for semi-free-ranging rhesus monkeys (Macaca mulatta) and Japanese macaques (Macaca fuscata). We test the hypothesis that differences in the support received by younger sisters against their older sisters and against older lower-ranking females might account for this interspecific difference. Thirty-one sister dyads, members of a group of 109 Barbary macaques living at La Montagne des Singes, France, were observed during 16 months. The results indicate that (1) all females were dominant to their younger sisters, and the latter were never observed to challenge their older sisters; (2) younger sisters received as much kin support against their older sisters as against older lower-ranking females; (3) only very young females received support from their kin against their older sisters; (4) younger sisters received much more support from nonkin females against lower-ranking females than against their older sisters; and (5) Barbary macaque females appear to be supported against their older sisters less frequently than rhesus macaque females are. We conclude that the lack of nonkin support is the main factor accounting for the failure of younger sisters to outrank their older sisters in Barbary macaques. Initially this might result from kin support not being sufficient to induce younger sisters to challenge and to solicit support against their older sisters.     

Contrasting effects of PACAP and carbachol on [Ca]i and inositol phosphates in human neuroblastoma NB-OK-1 cells

The effects of PACAPs on [Ca²⁺]_i were compared to those of carbachol in human neuroblastoma NB-OK-1 cells. PACAP(1–27) and PACAP(1–38) increased [Ca²⁺]_i in a biphasic manner: a transient rise and a secondary plateau. The transient phase reflected the mobilization of [Ca²⁺]_i pool(s) via the inositol phosphate pathway. The modest sustained plateau required extracellular Ca²⁺. Carbachol also increased [Ca²⁺]_i in a biphasic manner, but it mobilized intracellular Ca²⁺ pool(s) with a higher efficacy than PACAPs, then greatly increased Ca²⁺ entry, this being accompanied by a more marked and prolonged elevation of IP₃ and IP₄ than with PACAPs. It is likely that cAMP-mediated phosphorylations due to PACAPs facilitated desensitization at the PACAP receptor-phospholipase C level, so that there was less Ca²⁺ handling through PACAP receptors than with muscarinic M₁ receptors.     

Development and validation of a high-performance liquid chromatographic method for the determination of methocarbamol in human plasma

An isocratic HPLC method was developed and validated for the quantitation of methocarbamol in human plasma. Methocarbamol and internal standard in 200 μl of human plasma were extracted with ethyl acetate, evaporated to dryness and reconstituted in water. Separation was achieved on a reversed-phase C₁₈ column with a mobile phase of methanol—0.1 M potassium phosphate monobasic—water (35:10:55, v/v/v). The detection was by ultraviolet at 272 nm. Linearity was established at 1–100 μg/ml (r > 0.999). The limit of quantitation was designed as 1 μg/ml to suit pharmacokinetic studies. Inter-day precision and accuracy of the calibration standards were 1.0 to 3.6% coefficients of variance (C.V.) and −2.0 to +1.6% relative error (R.E.). Quality controls of 3, 20 and 70 μg/ml showed inter-day precision and accuracy of 2.5 to 3.6% C.V. and −0.9 to −0.4% R.E. Recovery of methocarbamol was 91.4–100.3% in five different lots of plasma. The method was shown to be applicable on different brands of C₁₈ columns.     

Renal eicosanoids and blood pressure in genetically hypertensive rats of the lyon strain

The present paper reviews the evidence for a possible involvement of renal eicosanoids in the pathophysiology of high blood pressure in genetically hypertensive rats of the Lyon strain. Both in vivo and in vitro experiments suggest that an increased ability to synthesize the vasoconstrictor prostaglandin H₂ and/or thromboxane A₂ in renal vessels (1) acts as an autocrine amplifier of pressor agents and (2) may contribute to resetting the pressure natriuresis curve which is a prerequisite for the development and maintenance of hypertension.     

The Presence of (+)-S-Adenosyl-l-Methionine in the Rat Brain and Its Lack of Effect on Phenylethanolamine N-Methyltransferase Activity

Abstract: (+)-S-Adenosyl- l -methionine [(+)-SAM] was isolated from rat brain and was quantified by HPLC followed by UV spectrophotometric measurements and by ¹H-NMR. Its estimated ratio in brain is 3% of total SAM. Because of its commercial unavailability, (+)-SAM was also prepared from chemically synthesized SAM by separation of the two diastereoisomers on a preparative reverse-phase Nucleosil C8 column. The (+) diastereoisomer thus obtained was then assayed in vitro both as an inhibitor and a substrate of phenylethanolamine N -methyltransferase. Enzymatic activity was measured by HPLC analysis. It was shown that (+)-SAM has no effect on phenylethanolamine N -methyltransferase activity; therefore, it is unlikely that (+)-SAM plays any possible role in regulation of adrenaline synthesis in the brain.     

Gonadal sex differentiation in Alligator mississippiensis,a species with temperature-dependent sex determination

Temperature of egg incubation determines sex in Alligator mississippiensis hatchlings. To define the timing and morphology of sexual differentiation, alligator gonads were examined histologically and ultrastructurally throughout embryogenesis. At the male-producing temperature (33° C), the onset of testis differentiation occurred in most embryos during developmental stages 21–22, when a number of somatic cells in the medulla of the gonad became enlarged, forming presumptive Sertoli cells. Some enlarged somatic cells were also observed at the female-producing temperature (30° C) during gonadogenesis, but they were less widespread than at 33° C. Ovarian differentiation at 30° C began slighlty later, during stage 22–23, and was characterised by proliferation of germs cells in the cortex of the gonad. Testis formation in alligators may depend upon presumptive Sertoli cells differentiating prior to a critical event in embryogenesis, such as germ cell proliferation and meiosis. If follows that ovary formation occurs if this requirement is not met, as at lower incubation temperatures.     

Genetic analysis of Cln/Cdc28 regulation of cell morphogenesis in budding yeast.

The CLN1, CLN2 and CLN3 gene family of G1-acting cyclin homologs of Saccharomyces cerevisiae is functionally redundant: any one of the three Cln proteins is sufficient for activation of Cdc28p protein kinase activity for cell cycle START. The START event leads to multiple processes (including DNA replication and bud emergence); how Cln/Cdc28 activity activates these processes remains unclear. CLN3 is substantially different in structure and regulation from CLN1 and CLN2, so its functional redundancy with CLN1 and CLN2 is also poorly understood. We have isolated mutations that alter this redundancy, making CLN3 insufficient for cell viability in the absence of CLN1 and CLN2 expression. Mutations causing phenotypes specific for the cell division cycle were analyzed in detail. Mutations in one gene result in complete failure of bud formation, leading to depolarized cell growth. This gene was identified as BUD2, previously described as a non-essential gene required for proper bud site selection but not required for budding and viability. Bud2p is probably the GTPase-activating protein for Rsr1p/Bud1p [Park, H., Chant, I. and Herskowitz, I. (1993) Nature, 365, 269-274]; we find that Rsr1p is required for the bud2 lethal phenotype. Mutations in two other genes (ERC10 and ERC19) result in a different morphogenetic defect: failure of cytokinesis resulting in the formation of long multinucleate tubes. These results suggest direct regulation of diverse aspects of bud morphogenesis by Cln/Cdc28p activity.     

Topoisomerase activity associated with SV40 large tumor antigen.

Purified preparations of simian virus 40 (SV40) large tumor antigen (LT) from three different sources, including LT expressed from a recombinant baculovirus, were found to relax negatively supercoiled cyclic DNA molecules, whether or not they contained SV40 sequences. Relaxation was stimulated by MgCl2 but not by ATP, and inhibited by camptothecin, suggesting the involvement of an enzymatic activity similar to that of topoisomerase I (topo I). However, the pH requirements for relaxation by respectively LT and topo I are different. Also, antibodies reacting with LT inhibited relaxation by preparations of LT but not topo I, whereas antibodies inhibiting relaxation by topo I had no effect on relaxation by LT. Reconstruction experiments suggested that both procedures used to purify LT, immunoaffinity chromatography and DEAE-Sepharose chromatography, separate topo I from LT. Finally, relaxing activity was found in over 40 preparations of LT, and in the few instances where activity could not be found, it probably had been lost during storage, rather than absent from the start. Whereas these results seem to exclude that the activity being detected is that of a contaminant of LT, they would be consistent with this activity being that of a stable topo-LT complex, or else intrinsic to LT itself.     

High prevalence of a point mutation in the porphobilinogen deaminase gene in Dutch patients with acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant disease characterized by a deficiency of porphobilinogen deaminase (PBGD). Up to now 14 different mutations have been described. In an effort to investigate the molecular epidemiology of AIP we have undertaken a systematic study of different exons of the PBGD gene from a large number of unrelated patients. Here, exon 8 from 82 unrelated Dutch and French AIP patients was examined using single strand confirmation polymorphism analysis (SSCP) after polymerase chain reaction (PCR) amplification. A single base mutation, C to T, at position 346 of the sequence coding for PBGD was observed in 15 Dutch families but in only 1 French family. A simple PCR assay is described to facilitate the diagnosis of this common mutation at the DNA level.