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131.
Ca2+ - and Mg2+ -stimulated ATPase activity of the microsomal fraction of shoots and roots and the temperature dependence of the Ca2+ -stimulated ATPase activity of the shoot of plants of two genotypes of Plantago major ssp. major L., one originating from an exposed and the other from a shaded habitat, were followed at two levels of irradiance. In addition the responses of these parameters were studied after transfer of the plants from one light condition to the other. The capacity and the optimum temperature of shoot ATPase activity were affected by irradiance during growth, in contrast to the root ATPase activity. Generally, no plastic adaptive response of the measured characteristics was observed after transfer of the plants. The remaining plasticity or stability of plant characteristics could not be interpreted as adaptive; the adaptive plastic responses were confined to the seedling stage of individuals of both genotypes. Possible mechanisms involved in plastic and adaptive responses and including phytochrome are discussed. 相似文献
132.
Low‐dose,continuous enzyme replacement therapy ameliorates brain pathology in the neurodegenerative lysosomal disorder mucopolysaccharidosis type IIIA
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133.
134.
Ingrid?A.?van de?LeemputEmail author Terry?P.?Hughes Egbert?H.?van?Nes Marten?Scheffer 《Coral reefs (Online)》2016,35(3):857-865
The prevalence of alternate stable states on coral reefs has been disputed, although there is universal agreement that many reefs have experienced substantial losses of coral cover. Alternate stable states require a strong positive feedback that causes self-reinforcing runaway change when a threshold is passed. Here we use a simple model of the dynamics of corals, macroalgae and herbivores to illustrate that even weak positive feedbacks that individually cannot lead to alternate stable states can nonetheless do so if they act in concert and reinforce each other. Since the strength of feedbacks varies over time and space, our results imply that we should not reject or accept the general hypothesis that alternate stable states occur in coral reefs. Instead, it is plausible that shifts between alternate stable states can occur sporadically, or on some reefs but not others depending on local conditions. Therefore, we should aim at a better mechanistic understanding of when and why alternate stable states may occur. Our modelling results point to an urgent need to recognize, quantify, and understand feedbacks, and to reorient management interventions to focus more on the mechanisms that cause abrupt transitions between alternate states. 相似文献
135.
Ida J. van der Klei Joanna Rytka Wolf H. Kunau Marten Veenhuis 《Archives of microbiology》1990,153(5):513-517
The parental strain (A+T+) of Saccharomyces cerevisiae and mutants, deficient in catalase T (A+T–), catalase A (A–T+) or both catalases (A–T–), grew on ethanol and oleic acid with comparable doubling times. Specific activities of catalase were low in glucose- and ethanol-grown cells. In the two oleic acid-grown A+-strains (A+T+ and A+T–) high catalase activities were found; catalase activity invariably remained low in the A–T+ strain and was never detected in the A–T– strain. The levels of -oxidation enzymes in oleic acid-grown cells of the parental and all mutant strains were not significantly different. However, cytochrome C peroxidase activity had increased 8-fold in oleic acid grown A– strains (A–T+ and A–T–) compared to parental strain cells. The degree of peroxisomal proliferation was comparable among the different strains. Catalase A was shown to be located in peroxisomes. Catalase T is most probably cytosolic in nature and/or present in the periplasmic space. 相似文献
136.
Prof. Dr. M. F. El Etreby H. M. Beier W. Elger A. -T. Mahrous M. Töpert 《Cell and tissue research》1983,229(1):61-73
Summary Using the immunoperoxidase technique and specific goat antiserum to uteroglobin, selective immunochemical staining products are localized in the epididymal epithelium of the caput and proximal corpus region, at the adluminal border of the cauda epididymidis and, as well known, in epithelial cells of the endometrium of pregnant and progesterone-treated rabbits. Specific staining is also seen on spermatozoa. A uteroglobin-like antigen has been similarly localized in alveolar and bronchial epithelial cells of the lung. Testis, prostate, seminal vesicle and ductus deferens do not seem to contain in their tissues immunoreactive uteroglobin-like antigens. Similarly, the uterus and ductus epididymidis of immature rabbits are devoid of immunoreactivity. The presence of uteroglobin-like antigens in tissues other than the endometrium, particularly the ductus epididymidis, stimulates new discussions on the function of this protein in reproductive physiology and fertility research. 相似文献
137.
138.
Localization of Glucose Oxidase and Catalase Activities in Aspergillus niger 总被引:2,自引:0,他引:2
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The subcellular localization of glucose oxidase (EC 1.1.3.4) in Aspergillus niger N400 (CBS 120.49) was investigated by (immuno)cytochemical methods. By these methods, the bulk of the enzyme was found to be localized in the cell wall. In addition, four different catalases (EC 1.11.1.6) were demonstrated by nondenaturing polyacrylamide gel electrophoresis of crude extracts of induced and noninduced cells. Comparison of both protoplast and mycelial extracts indicated that, of two constitutive catalases, one is located outside the cell membrane whereas the other is intracellular. Parallel with the induction of glucose oxidase, two other catalases are also induced, one located intracellularly and one located extracellularly. Furthermore, lactonase (EC 3.1.1.17) activity, catalyzing the hydrolysis of glucono-δ-lactone to gluconic acid, was found to be exclusively located outside the cell membrane, indicating that gluconate formation in A. niger occurs extracellularly. 相似文献
139.
We have studied methanol-utilization in a peroxisome-deficient (PER) mutant of Hansenula polymorphoa. In spite of the fact that in carbon-limited chemostat cultures under induced conditions the enzymes involved in methanol metabolism were present at wild-type (WT) levels, this mutant is unable to grow on methanol as a sole carbon and energy source. Addition of methanol to glucose-limited (SR=12.5mM) chemostat cultures of the PER mutant only resulted in an increase in yield when small amounts were used (up to 22.5 mM). At increasing amounts however, a gradual decrease in cell density was observed which, at 80 mM methanol in the feed, had dropped below the original value of the glucose-limited culture. This reduction in yield was not observed when increasing amounts of formate instead of methanol were used as supplements for the glucose-limited mutant culture and also not in WT cells, used as control in these experiments. The effect of addition of methanol to a glucose-limited PER culture was also studied in the transient state during adaptation of the cells to methanol. The enzyme patterns obtained suggested that the ultimate decrease in yield observed at enhanced methanol concentrations was due to an inefficient methanolmetabolism as a consequence of the absence of peroxisomes. The absence of intact peroxisomes results in two major problems namely i) in H2O2-metabolism, which most probably is no longer mediated by catalase and ii) the inability of the cell to control the fluxes of formaldehyde, generated from methanol. The energetic consequences of this metabolism, compared to the WT situation with intact peroxisomes, are discussed.Abbreviations AO
alcohol oxidase
- DHAS
dihydroxyacetone synthase
- WT
wild-type
- PER
peroxisome-deficient
- GSH
reduced glutathione
- GSSG
glutathione disulphide 相似文献
140.
Nocloprost was administered to 3 groups of 4 pregnant guinea pigs intravenously and subcutaneously in a dose of 30 micrograms/kg and intragastrically in a dose of 100 micrograms/kg. Plasma nocloprost levels were measured at defined times up to 24 h p. adm. with a specific radioimmunoassay and induction of abortion monitored simultaneously. In one animal per group uterus pressure was recorded continuously up to 8 hours p.adm. Animals were sacrificed 7 days p.adm. and the number and state of fetuses in utero evaluated. Systemic availability of unchanged drug was 100% after intravenous (AUCi.v. = 8.6 +/- 2.0 ng h/ml) and subcutaneous (AUCs.c. = 11.5 +/- 1.2 ng h/ml) administration and approximately 30% after intragastric administration (AUCi.g. = 8.9 +/- 2.0 ng h/ml). The incidence of abortion after intragastric administration corresponded to that after subcutaneous administration. After intravenous injection the abortion rate was somewhat less, indicating that equal AUC-values do not necessarily indicate identical pharmacological effects. 相似文献