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61.
The non-heterocystous cyanobacterium Oscillatoria sp. strain 23 fixes nitrogen under aerobic conditions. If nitrate-grown cultures were transferred to a medium free of combined nitrogen, nitrogenase was induced within about 1 day. The acetylene reduction showed a diurnal variation under conditions of continuous light. Maximum rates of acetylene reduction steadily increased during 8 successive days. When grown under alternating light-dark cycles, Oscillatoria sp. fixes nitrogen preferably in the dark period. For dark periods longer than 8 h, nitrogenase activity is only present during the dark period. For dark periods of 8 h and less, however, nitrogenase activity appears before the beginning of the dark period. This is most pronounced in cultures grown in a 20 h light – 4 h dark cycle. In that case, nitrogenase activity appears 3–4 h before the beginning of the dark period. According to the light-dark regime applied, nitrogenase activity was observed during 8–11 h. Oscillatoria sp. grown under 16 h light and 8 h dark cycle, also induced nitrogenase at the usual point of time, when suddenly transferred to conditions of continuous light. The activity appeared exactly at the point of time where the dark period used to begin. No nitrogenase activity was observed when chloramphenicol was added to the cultures 3 h before the onset of the dark period. This observation indicated that for each cycle, de novo nitrogenase synthesis is necessary. 相似文献
62.
The determination of enzymatic activities in cell-free extracts of Acidaminococcus fermentans and Peptostreptococcus asaccharolyticus led to a refined scheme for the pathway of glutamate fermentation via (R)-2-hydroxyglutarate to acetate and butyrate. From the ratio of these products the amount of ATP generated by substrate level phosphorylation was calculated. Growth experiments with the organisms including Clostridium symbiosum and Clostridium tetanomorphum indicated that a sodium gradient contributed additional energy for growth. The high growth yields found in organisms containing the biotin dependent sodium pump glutaconyl-CoA decarboxylase could be reduced by the sodium ionophor monensin. In P. asaccharolyticus energy equivalent up to 0.6 mol ATP per mol of glutaconyl-CoA decarboxylated was conserved via the Na+ gradient. The data may explain the growth promoting effects of monensin in cattle. 相似文献
63.
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65.
Mariann Thymann Bernadette Hoste Wolfgang Scheffrahn Jacques Constans Hartwig Cleve 《Human genetics》1985,69(3):224-227
Summary The proteins of three anodal Gc1 variants, Gc 1A16, 1A11, and 1A17, are characterized by the most acidic isoelectric points observed so far among the different Gc mutants. Stepwise removal of N-acetylneuraminic acid (NANA) by treatment with neuraminidase was performed to estimate the degree of sialilation of these Gc variants. The results indicate that both proteins, the anodal and the cathodal component of these Gc 1 mutants, carry sialic acid residues. This observation is remarkable in so far as usually only the anodal component of the Gc 1 protein contains NANA and only a single residue. From the experiments carried out it can be deduced that Gc 1A16 has two NANA residues in the anodal and one NANA residue in the cathodal component. Gc 1A16 was found in four members of three generations in a Danish family; the variant segregated as a Mendelian trait. More difficult to interprete are the results obtained with the variants Gc 1A11 and Gc 1A17. Gc 1A11 probably has three NANA residues in the anodal and two NANA residues in the cathodal component. Gc 1A11 has been observed in two mother-child pairs and is presumably also a simple genetic trait. Gc 1A17 has also several NANA residues in both Gc proteins; it is suggested that the anodal component has either three or four NANA residues and the cathodal component either two or three NANA residues. Family information on this variant is not yet available. 相似文献
66.
Albrecht Guhlmann Wolfgang Hagmann Dietrich Keppler 《Prostaglandins & other lipid mediators》1987,34(1)
N-Acetyl-leukotriene E4, the end product of leukotriene C4 metabolism in the mercapturic acid pathway, was rapidly eliminated from the blood circulation into the bile of rats. Part of the N-acethyl-leukotriene E4 secreted from bile into the intestine undewent enterohepatic circulation. Leukotriene absorption occurred from the small intestine and from the colon. Biliary and urinary excretion within 5.5 h amounted to 15 and 2%, respectively, of the intraduodenally administered N-acetyl- H leukotriene E4 in animals anesthetized with ketamine. HPLC analyses indicated that 35% of the biliary radioactivity corresponded to unchanged N-acetyl- H leukotriene E4, while 65% in bile and 100% in urine were polar metabolites. Enterohepatic circulation extends the biological half-life of N-acetyl-leukotriene E4. 相似文献
67.
Dewsbury, D. A., ed. (1985): Foundations of comparative psychology (Zur Geschichte der vergleichenden Psychologie). Benchmark Papers in Behavior Series. Toates, F. (1986): Motivational systems (Antriebe). Le Magnen, J. (1986): Hunger. Rosenblatt, J. S., C. Beer, M.-C. Busnel, & P. J. B. Slater, eds. (1985): Advances in the study of behavior. Dickerson, J. W. T., & H. McGurk, eds. (1982): Brain and behavioural development. Interdisciplinary perspectives on structure and function (Gehirn und Verhaltensentwicklung). Bisping, R. (1985): Gedächtnisübertragung bei Goldfischen. Experimentelle Untersuchungen in der “shuttle-box” mit besonderer Berücksichtigung des Problems der Reizspezifität unter einer Rot-Grün-Diskriminationsbedingung (Memory transfer in goldfish). Nachtigall, W. (1984): Erfinderin Natur: Konstruktionen der belebten Welt (Natural constructions). Rasch und Röhring Verlag, Hamburg und Zürich. 相似文献
68.
Prof. Dr. med. Wolfgang Schulze Martin Riemer Uwe Rehder Karl-Heinz Höhne 《Cell and tissue research》1986,244(1):1-8
Summary With the use of a digital image-processing method three-dimensional reconstructions of the arrangement of spermatocytes in human seminiferous tubules were performed. With this method it was possible to investigate the cellular distribution in the tubule in nearly any given perspective and projection. In addition, by means of simple mathematical procedures, such as by transformation of Cartesian coordinates into cylindrical coordinates, it was possible to vary the shape of a reconstruction, i.e., to convert the cylindrical image of a tubular portion into a right-angled r--z-representation.The present work not only confirms the existence of a complex helical plan of organization of the human seminiferous epithelium but also provides further aspects of the phenomenon of physiological germ-cell loss and its integration into the kinetics of spermatogenesis.Dedicated to Prof. E.C. Roosen-Runge, Seattle, on the occasion of his 75th birthday 相似文献
69.
James P. Chalcroft Harald Engelhardt Wolfgang Baumeister 《Archives of microbiology》1986,144(3):196-200
The regular surface layer of Pseudomonas acidovorans was investigated by computer processing of a series of tilted view electron micrographs, and a reconstruction of the three-dimensional structure was obtained. The pattern is tetragonal and consists of massive identical subunits, block-like in face-view, which interlock loosely in a simple cobblestone pattern. The square unit cell has a lattice constant of 11 nm. The surface layer pattern of P. acidovorans appears to be more dependent on the underlying membrane for maintaining its integrity than those so far studied in other bacteria. 相似文献
70.
Cells of a mutant in vivo subline of the Ehrlich-Lettré mouse ascites tumour (ELAT) were converted to growth in suspension culture. Kinetic analysis revealed the selective character of the conversion process; without a detectable adaptation period, a fraction of about 2 × 10-5 of the explanted cells continued to grow in vitro. the resulting, mutant Ehrlich-Lettré ascites cell strain was designated HD33 and propagated uninterruptedly from 1974 on. the corresponding in vivo ELAT subline HD33 was derived from the HD33 ascites cell strain by intraperitoneal retransplantation. In HD33 cell suspension cultures, the population doubling time, the average intermitotic interval, as determined by videomonitoring, and the average duration of the cell cycle, as determined from percentage of labelled mitoses (PLM) data, were all measured at 15 hr. Cell loss and quiescent compartments were insignificant. the duration of the G1 phase was effectively zero. Both PLM data and [3H]/[14C] thymidine double-labetling measurements revealed an S-phase duration of between 11 and 12 hr. the G2 phase lasted 3–5 hr. The HD33 strain differs from comparable suspension strains of wild-type Ehrlich ascites cells in the insignificant role of density-dependent inhibition in growth, and the striking prolongation of the S phase which is associated with an excessive, cytoplasmic storage of glycogen by the mutant cells. 相似文献