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41.
42.
The kinetics of simultaneous mineralization of p-nitrophenol (PNP) and glucose by Pseudomonas sp. were evaluated by nonlinear regression analysis. Pseudomonas sp. did not mineralize PNP at a concentration of 10 ng/ml but metabolized it at concentrations of 50 ng/ml or higher. The Ks value for PNP mineralization by Pseudomonas sp. was 1.1 micrograms/ml, whereas the Ks values for phenol and glucose mineralization were 0.10 and 0.25 micrograms/ml, respectively. The addition of glucose to the media did not enable Pseudomonas sp. to mineralize 10 ng of PNP per ml but did enhance the degradation of higher concentrations of PNP. This enhanced degradation resulted from the simultaneous use of glucose and PNP and the increased rate of growth of Pseudomonas sp. on glucose. The Monod equation and a dual-substrate model fit these data equally well. The dual-substrate model was used to analyze the data because the theoretical assumptions of the Monod equation were not met. Phenol inhibited PNP mineralization and changed the kinetics of PNP mineralization so that the pattern appeared to reflect growth, when in fact growth was not occurring. Thus, the fitting of models to substrate depletion curves may lead to erroneous interpretations of data if the effects of second substrates on population dynamics are not considered. 相似文献
43.
Gas exchange studies in two Portuguese grapevine cultivars 总被引:8,自引:0,他引:8
M. Manuela Chaves Peter C. Harley John D. Tenhunen Otto L. Lange 《Physiologia plantarum》1987,70(4):639-647
Gas exchange characteristics of leaves of Vitis vinifera L. cvs Tinta Amarela and Periquita, two grapevine cultivars grown in distinct climatic regions of Portugal, were studied under natural and controlled conditions. Daily time courses of gas exchange were measured on both a hot, sunny day and a cooler, partly cloudy day. Responses of net photosynthesis to irradiance and internal partial pressure of CO2 , were also obtained. A strong correlation between net photosynthesis (PN ) and leaf conductance (gs ) was found during the diurnal time courses of gas exchange, as well as a relatively constant internal partial pressure of CO2 (Pi ), even under non-steady-state conditions. On the cloudless day, both PN and gs were lower in the afternoon than in the morning, despite similar conditions of leaf temperature, air to leaf water vapor deficit and irradiance. The response curves of net photosynthesis to internal CO2 showed linearity up to pi values of 50 Pa, possibly indicating a substantial excess of photosynthetic capacity. When measured at low partial pressures of O2 (1 kPa), PN became inhibited at high CO2 levels. Inhibition of PN at high CO2 was absent under normal levels of O2 (21 kPa). Significant differences in gas exchange characteristics were found between the two cultivars, with T. Amarela having higher rates under similar measurement conditions. In particular, the superior performance of T. Amarela at high temperatures may represent adaptation to the warmer conditions at its place of origin. 相似文献
44.
Taurine entered the alga Chlorella fusca Shihira et Krauss strain 21l-8b via a pH and energy-dependent system ("permease"). Transport followed triphasic kinetics from 10−6 to 10−2 M with Km values for taurine of 5.4 × 10−5 , 4.1 × l0−4 and l.5 × 10−3 M. This uptake system was specific for sulfonic acids and showed no affinity for α- and β -amino acids or Na+ ; thus the permease of C. fusca is different from all known taurine transport systems with respect to structural specificity and lack of Na+ -dependence. Uptake was not observed in sulfate-grown algae but developed as a response to sulfate limitation within 2 h. Sulfate addition caused a rapid decline in taurine transport capacity. Labeled taurine was rapidly metabolized in C. fusca to sulfate and ethanolamine, suggesting oxidative hydrolysis as the mechanism of C-S bond cleavage. Further incorporation of these catabolic products in C - and S -metabolism was demonstrated. Taurine catabolism was also detected in other green algae and some cyanobacteria. 相似文献
45.
46.
A. E. Melchinger H. H. Geiger G. Seitz G. A. Schmidt 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(3):339-345
Summary Three-way cross means were predicted with formulae involving linear functions of general (GCA) and specific combining ability (SCA) effects estimated from single-cross factorials between genetically divergent populations. Data from an experiment with 66 single-cross and 66 three-way cross forage maize (Zea mays L.) hybrids was used for comparing the prediction formulae. The genotypic correlation (r) between observed and predicted three-way crosses increased with increasing , the weighting factor of SCA effects, for plant height and ear dry matter (DM) content. It displayed slightly convex curves for total and stover DM yield, ear percentage, and metabolizable energy content of stover. For Jenkins' method B, r was considerably less than 1.0 for all traits, indicating the presence of epistasis. The square root of heritability (h) of the predicted means decreased with increasing , the reduction being small with a greater number of test environments. Using the product r·h as a criterion of efficiency, none of the prediction methods was consistently superior and the differences among them were rather small (< 7.5%) for all traits, irrespective of the number of test environments. We recommend evaluating the GCA of a greater number of lines from each parent population in testcrosses with a small number of elite lines from the opposite population. All possible three-way or double crosses between both sets of lines should be predicted by Jenkins's method C. This procedure allows one to select with a higher intensity among the predicted hybrids and thus should increase the genetic gain.Extended version of a paper (Geiger et al. 1986) read at the sixth meeting of the EUCARPIA Section Biometrics in Plant Breeding held at Birmingham, UK, July 28–August 1, 1986 相似文献
47.
A Schmidt B Crisp D Krause R H Silverman R B Herberman J R Ortaldo 《Natural immunity and cell growth regulation》1987,6(1):19-27
Pretreatment of human large granular lymphocytes (LGL) or unseparated peripheral blood mononuclear cells with interferon (IFN) resulted in a significant augmentation of natural killer (NK) activity. This increase was paralleled by an increase in the 2'-5'A synthetase activity. In order to investigate the possibility that IFN might be inducing augmentation of NK cells via the 2'-5'A pathway, we tested the effects of nonphosphorylated core material [(A2'p)2A] and of the triphosphorylated form of the 2'-5'A [ppp(A2'p)2A]. The core material had no detectable effect on NK activity. In contrast, when experiments were performed with the triphosphorylated form of 2'-5'A, NK activity was stimulated. In order to achieve activation, permeabilization of LGL with calcium chloride was necessary and, under these conditions, a dose-dependent augmentation of NK activity was seen. However, the calcium treatment had considerable toxic effects on basal levels of NK activity. Collectively, these results suggest that IFN may be inducing augmentation of NK activity via the 2'-5'A pathway. Further studies will be necessary to determine the effects of IFN and/or 2'-5'A on subsequent activation steps in the process leading to cytotoxicity by NK cells. 相似文献
48.
The metabolism of sulfide, sulfur, and acetate by Beggiatoa alba was investigated under oxic and anoxic conditions. B. alba oxidized acetate to carbon dioxide with the stoichiometric reduction of oxygen to water. In vivo acetate oxidation was suppressed by sulfide and by several classic respiratory inhibitors, including dibromothymoquinone, an inhibitor specific for ubiquinones. B. alba also carried out an oxygen-dependent conversion of sulfide to sulfur, a reaction that was inhibited by several electron transport inhibitors but not by dibromothymoquinone, indicating that the electrons released from sulfide oxidation were shuttled to oxygen without the involvement of ubiquinones. Intracellular sulfur stored by B. alba was not oxidized to sulfate or converted to an external soluble form under aerobic conditions. On the other hand, sulfur stored by filaments of Thiothrix nivea was oxidized to extracellular soluble oxidation products, including sulfate. Sulfur stored by filaments of B. alba, however, was reduced to sulfide under short-term anoxic conditions. This anaerobic reduction of sulfur was linked to the endogenous oxidation of stored carbon and to hydrogen oxidation. 相似文献
49.
Interaction of small dermatan sulfate proteoglycan from fibroblasts with fibronectin 总被引:20,自引:7,他引:13
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G Schmidt H Robenek B Harrach J Gl?ssl V Nolte H H?rmann H Richter H Kresse 《The Journal of cell biology》1987,104(6):1683-1691
Immunogold labeling was used to localize the core protein of small dermatan sulfate proteoglycan (DS-PG) on the surface of cultured human fibroblasts. At 4 degrees C, DS-PG core protein was uniformly distributed over the cell surface. At 37 degrees C, gold particles either became rearranged in form of clusters or remained associated with fibrils. Double-label immunocytochemistry indicated the co-distribution of DS-PG core protein and fibronectin in the fibrils. In an enzyme-linked immunosorbent assay, binding of DS-PG from fibroblast secretions and of its core protein to fibronectin occurred at pH 7.4 and at physiological ionic strength. Larger amounts of core protein than of intact proteoglycan could be bound. Fibronectin peptides containing either the heparin-binding domain near the COOH-terminal end or the heparin-binding NH2 terminus were the only fragments interacting with DS-PG and core protein. Competition and replacement experiments with heparin and dermatan sulfate suggested the existence of adjacent binding sites for heparin and DS-PG core protein. It is hypothesized that heparan sulfate proteoglycans and DS-PG may competitively interact with fibronectin. 相似文献
50.