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121.
A study of the monomeric chromophore of the oligopeptides netropsin (1), distamycin III (2), and distamycin V (3) by polarization spectroscopy techniques and molecular orbital calculations is reported. Linear dichroism spectra of the monomeric model compounds 1-methyl-2(ethylcarbamoyl)-4-acetamido-pyrrole (4) and 1-methyl-2(ethylcarbamoyl)-pyrrole (5) dissolved and oriented in lyotropic and thermotropic liquid crystals provide, together with the magnetic CD spectra, experimental checks of the theoretical calculations. The polarization directions of the investigated transition obtained by these means in this study allow us to build up in the following paper the exciton states of (1)-(3) and these provide a stereochemical interpretation of the flow linear dichroism spectra of the complexes of DNA with (2) and (3). 相似文献
122.
123.
Seven dogs were subjected 30 min to ligation of the thoracic aorta and were then kept alive 6-7 days after the ligature had been removed. Their spinal cord and brain stem were treated by the Nauta-Gygax method and the extent and appearance of preterminal and terminal degeneration of certain ascending spinal systems were analysed. In the medulla oblongata region, marked degenerating fibres from the lower thoracic and lumbosacral cord segments were found in the nucleus tractus spinalis nervi trigemini. Preterminal and terminal degenerating fibres were visualized in the caudal part of the trigeminal nuclear complex. Comparison with the literature showed these to be previously unknown projections with a relationship to the nucleus tractus spinalis nervi trigemini. 相似文献
124.
Rhodotorula minuta produced 16% ofd-mannitol and 3% ofd-arabinitol when cultivated ond-ribose, 4% of mannitol and 11% of arabinitol when grown ond-xylose, 5% ofd-mannitol and 5% ofd-arabinitol when grown ond-arabinose, and 5% ofd-mannitol and 6% ofd-arabinitol when cultivated ond-lyxose. 相似文献
125.
High-performance liquid chromatography was used to estimate 3-ketolactose and 3-ketosucrose in cultures of agrobacteria. The
activities of enzymes that convert the disaccharide substrate were evaluated during batch cultivation ofAgrobacterium tumefaciens on sucrose, maltose, and lactose. The highest activity of glucoside 3-dehydrogenase and a slight activity of disaccharide-hydrolyzing
enzymes were found in cells grown on lactose. Nongrowing cells converted lactose to 3-ketolactose faster than immobilized
cells did. Immobilization of cells into polysaccharide gels did not stabilize the activity of glucoside 3-dehydrogenase. Glutaraldehyde
cross-linking of the cell content led to an inactivation of the respiratory chain but Fe3+ could be used as an electron acceptor. Cells treated with glutaraldehyde converted lactose faster than nongrowing ones but
the activity of glucoside 3-dehydrogenase was not stable. 相似文献
126.
Production of enterotoxin A by supposedly nonenterotoxigenic Staphylococcus aureus strains. 总被引:1,自引:1,他引:0 下载免费PDF全文
E Gomez-Lucía J Goyache J A Orden J L Blanco J A Ruiz-Santa-Quiteria L Domínguez G Surez 《Applied microbiology》1989,55(6):1447-1451
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. 相似文献
127.
Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae 总被引:1,自引:0,他引:1
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. 相似文献
128.
E. Rosón R. Gallego T. García-Caballero E. P. Heimer A. M. Felix F. Domínguez 《Histochemistry and cell biology》1990,94(6):597-599
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. 相似文献
129.
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. 总被引:1,自引:1,他引:0 下载免费PDF全文
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. 相似文献
130.
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. 相似文献