Production of enterotoxin A by supposedly nonenterotoxigenic Staphylococcus aureus strains.

The production of staphylococcal enterotoxins A (SEA) and B (SEB) was studied by inoculating six well-defined staphylococcal collection strains into cow's, goat's, or sheep's milk (individually or as a 50% mixture of cow's + goat's or cow's + sheep's), into brain heart infusion, and into a medium generally used to enhance the synthesis of enterotoxins (3+3 medium). Four of the strains used are considered to be SEB producers, another is considered an SEA producer, and the remaining strain is nonenterotoxigenic but produces large quantities of staphylococcal protein A. Staphylococcal protein A masked the results in most cases. Only one strain secreted exclusively SEB, while the other three SEB producers synthesized SEA in different amounts. We conclude that enterotoxin production depends on the natural substrate and may differ from the results obtained when the strain is grown on cellophane over agar to determine its toxigenicity.     

Relationship between a 47-kDa cytoplasmic membrane polypeptide and nitrate transport in Anacystis nidulans

The polypeptide composition of cytoplasmic membranes of the cyanobacterium Anacystis nidulans changes in response to variations in the nitrogen source available to the cells, differing specifically in the amount of a polypeptide of 47-kDa molecular mass. Synthesis of the polypeptide and expression of nitrate transport activity are repressed by ammonium. Transfer of ammonium-grown cells to a medium containing nitrate as the sole nitrogen source results in parallel development of the 47-kDa polypeptide and nitrate transport activity of the cells. These results suggest the involvement of the 47-kDa cytoplasmic membrane polypeptide in nitrate transport by A. nidulans.     

Meristem transformation of sunflower via Agrobacterium

Summary For transformation of sunflower (Helianthus annuus L. cv. Zebulon), shoot apical meristems were dissected from seeds and cocultivated with a disarmed Agrobacterium tumefaciens strain harboring a binary vector carrying genes encoding GUS- and NPTII-activity. The influence of the media conditions, the time of cocultivation and the stage of the developing seed on shoot development and meristem transformation was analysed. Transformants were selected by their ability to grow on kanamycin. Transformation was confirmed by assays for GUS and NPTII. GUS-positive shoots were rooted on rockwool and transferred to soil. Transformation of shoot meristem cells occurred at low frequencies. Chimaeric expression of the two genes was observed in transformed plants. Integration of the foreign DNA in the sunflower genome was confirmed with the polymerase chain reaction.Abbreviations GUS ß-Glucuronidase - NPTII Neomycin phosphotransferase II     

Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae

The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text.     

Prothymosin alpha expression is associated to cell division in rat testis

Summary Using immunohistochemical methods, we have investigated the cellular distribution of prothymosin alpha (ProT) in adult rat testis. A policlonal antibody raised against thymosin alpha 1 conjugated to keyhole limpet hemocyanin was used. ProT immunoreactivity was observed in the cytoplasm and nucleus of spermatogonia and primary spermatocytes in initial phases of the first meiotic division, preleptotene, leptotene and zygotene. However, in pachytene phase they already showed a weak or negative staining. On the other hand, secondary spermatocytes, spermatids, spermatozoa and Sertoli cells were not stained. Based on this fact we suggest that ProT is present in the proliferative cycle in the final steps of G₁ phase, throughout the S and G₂ phases and in initial steps of the prophase.     

Insulin-stimulated alpha-(methyl)aminoisobutyric acid uptake in skeletal muscle. Evidence for a short-term activation of uptake independent of Na+ electrochemical gradient and protein synthesis.

1. The present study was designed to explore the mechanisms by which insulin stimulates system A of amino acid transport in extensor digitorum longus (EDL) muscles, by using a system A analogue, alpha-(methyl)aminoisobutyric acid (MeAIB). 2. Insulin stimulation of MeAIB uptake was noted after only 30 min of incubation and was maximal at 60 min. Kinetics of the insulin effect on MeAIB uptake were characterized by an increased Vmax. without modification of Km for MeAIB. 3. Incubation of EDL muscles with cycloheximide for 90 min did not modify MeAIB uptake in either the presence or the absence of insulin, indicating the independence of insulin action from protein synthesis de novo. Incubations for 180 min with cycloheximide caused a decrease in basal MeAIB uptake; however, the percentage stimulation of amino acid transport by insulin was unaltered. Basal MeAIB uptake was increased by incubation for 180 min, but under these conditions no change in the percentage effect of insulin was found. 4. Ouabain, gramicidin D, or both, markedly decreased basal MeAIB uptake by EDL muscle, but the percentage effect of insulin was unaltered. 5. We conclude that insulin action on amino acid transport through system A in muscle is rapid, is characterized by an increased Vmax., and is independent of protein synthesis de novo and the Na+ electrochemical gradient. Our data are compatible with insulin acting directly on the system A transporter.     

Effect of pectin on pectinases in autolysis of Botrytis cinerea

Pectic activity in autolyzed cultures of Botrytis cinerea in a medium with and without pectin was similar, but in the medium with pectin maximal activities occurred in younger cultures. The pectic activities found were polygalacturonase, polymethylgalacturonase, endo activity (pectin as substrate) and pectin lyase. The molecular weights of polygalacturonase, polymethylgalacturonase and endo activity (pectin as substrate) were 36000, 33000 and 30200 daltons respectively, and the molecular weight of pectin lyase was 18200 daltons. By gel electrophoresis four different pectic activities were detected, three in the top of the gel and one in the bottom. Two enzymes were characterized, the polygalacturonase activity (first band in the top) inhibited by Ca⁺⁺ and the pectin lyase activity (in the bottom) which was not inhibited by Ca⁺⁺. These enzymes are not induced by the presence of pectin in the medium during degradation of Botrytis cinerea.     

Regional brain GABA metabolism and release during hepatic coma produced in rats chronically treated with carbon tetrachloride

Hepatic coma was induced in rats chronically treated with CCl₄, by means of a single injection of ammonium acetate. The activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T), as well as the synaptosomal uptake and release of [³H]GABA, were measured in the following brain areas of the comatose rats: cortex, striatum, hypothalamus, hippocampus, midbrain and cerebellum. Hepatic coma was associated with a general decrease of GAD activity, whereas GABA-T activity was diminished only in the hypothalamus, striatum and midbrain. During hepatic coma, the K⁺-stimulated [³H]GABA release was notably diminished in the striatum and cerebellum, whereas a significant increase was observed in the hippocampus. [³H]GABA uptake increased in most regions after CCl₄ treatment, independently of the presence of coma. The results indicate that GABAergic transmission seems to be decreased in most cerebral regions during hepatic coma.     

Asymmetric incorporation of [14C]cyanate and of fluorescein isothiocyanate in mamillary body of conditioned rats

A marked decrease in overall learning capacity has been observed in rats injected with cyanate. Therefore it was of interest to test whether learning influenced carbamylation of brain proteins. Incorporation of [¹⁴C]cyanate into proteins of the mamillary body was selectively modified following operant conditioning of the rat, so that trained rats showed an asymmetric image with higher levels of incorporation in the right side than in the left side, as compared to control rats. These results were confirmed using fluorescein isothiocyanate. The asymmetry persisted once the learning had been well established.     

Livestock production in central Mali: Reproductive performance and reproductive wastage in ruminants in the agro-pastoral system

Results of a 7-yr field study and a 3-yr slaughterhouse study into reproductive performance and reproductive wastage of ruminants in central Mali are reported. Cattle had delayed age at first puberty (40), long calving intervals (644) and produced few young (3.02) per lifetime. Goats and sheep first conceived at about 11 mo, had shorter parturition intervals (298 and 280 d) but also produced few young (2.64 and 1.92) per lifetime. Conceptions showed a strong seasonality in cattle and mainly occurred during and shortly after the short rainy season. Seasonality was less marked in small ruminants, but most females conceived before the rains. However, maximum litter sizes were associated with late-rain and post-rain conceptions. Early embryonic wastage did not appear to be a major problem but abortions, stillbirths and heavy preweaning mortality were sources of loss of reproductive potential. Additionally at a secondary (government controlled) abattoir, 15.0 % of cows, 31.7 % of goats and 20.0 % of sheep that were slaughtered were found to be pregnant.