Small doses of β-endorphin (10?11?10?5M) decrease corticosterone production of zona fasciculata cells but fail to influence steroid production of zona glomerulosa cells. 10?4M β-endorphin increases corticosterone production of both zones. The stimulating effect of ACTH on zona fasciculata corticosterone- and zona glomerulosa aldosterone production was decreased by β-endorphin (10?9?10?7M). Conclusion: β-endorphin might modulate both basal and ACTH stimulated corticosterone secretion. 相似文献
In order to distinguish between the regulatory effects of oxygen tension and light intensity on cytochrome c oxidase protein and enzymatic activity cells of Rhodobacter capsulatus were shifted from phototrophic (anaerobic, light) growth to aerobic-light, aerobic-dark and to anaerobic-dark conditions, respectively. During shift-experiments the formation of oxidase protein and regulation of oxidase activity was followed by immunological and enzymatic means. The results support the idea, that the formation of oxidase protein is regulated by oxygen tension and light intensity changes, whereas the regulation of oxidase activity seems only to be correlated to the oxygen tension. A DNA sequence involved in the oxygen-dependent regulation of cytochrome oxidase could be identified in the regulation-deficient oxidase mutant H41 of R. capsulatus. Immunological investigations of cytochrome c2 from mutant H41 demonstrated at the same time the participation of the c2-polypeptide in the regulation of cytochrome c oxidase.Abbreviations Bchl
bacteriochlorophyll
- CIE
crossed immuno-electrophoresis
- DMSO
dimethyl sulfoxide 相似文献
Patients with pulmonary hypertension due to chronic bronchitis may improve during long-term treatment with oxygen. The methods of administration which are currently available are expensive and present practical difficulties. The Rimer-Birlec domiciliary oxygen concentrator produces an oxygen concentration of 92% at a flow of 21./min. It has been used successfully in a patient''s home but further use will require an increase in mechanical reliability and a decrease in noise. In view of its convenience and the economic advantages the oxygen concentrator is an important advance in treatment with oxygen and could prove to be the method of choice in the home. 相似文献
The activity of rat liver malic enzyme shows a marked increase when the animals are maintained on a restricted protein diet. Of the NADP-linked dehydrogenases tested (malic enzyme, glucose-6-phosphate dehydrogenase, and isocitrate dehydrogenase), the response is confined only to malic enzyme. Dietary sucrose is not required for the increase in activity, but elevated dietary levels of this disaccharide increase hepatic malic enzyme regardless of dietary protein. Glucose-6-phosphate dehydrogenase activity is increased by dietary sucrose provided adequate dietary protein is supplied. The specificity of the response to lowered dietary protein shown by malic enzyme suggests that the control of the hepatic enzyme is mediated by processes different from those controlling the activity of glucose-6-phosphate dehydrogenase. 相似文献
Hypervirulent K. pneumoniae (hvKp) is a distinct pathotype that causes invasive community-acquired infections in healthy individuals. Hypermucoviscosity (hmv) is a major phenotype associated with hvKp characterized by copious capsule production and poor sedimentation. Dissecting the individual functions of CPS production and hmv in hvKp has been hindered by the conflation of these two properties. Although hmv requires capsular polysaccharide (CPS) biosynthesis, other cellular factors may also be required and some fitness phenotypes ascribed to CPS may be distinctly attributed to hmv. To address this challenge, we systematically identified genes that impact capsule and hmv. We generated a condensed, ordered transposon library in hypervirulent strain KPPR1, then evaluated the CPS production and hmv phenotypes of the 3,733 transposon mutants, representing 72% of all open reading frames in the genome. We employed forward and reverse genetic screens to evaluate effects of novel and known genes on CPS biosynthesis and hmv. These screens expand our understanding of core genes that coordinate CPS biosynthesis and hmv, as well as identify central metabolism genes that distinctly impact CPS biosynthesis or hmv, specifically those related to purine metabolism, pyruvate metabolism and the TCA cycle. Six representative mutants, with varying effect on CPS biosynthesis and hmv, were evaluated for their impact on CPS thickness, serum resistance, host cell association, and fitness in a murine model of disseminating pneumonia. Altogether, these data demonstrate that hmv requires both CPS biosynthesis and other cellular factors, and that hmv and CPS may serve distinct functions during pathogenesis. The integration of hmv and CPS to the metabolic status of the cell suggests that hvKp may require certain nutrients to specifically cause deep tissue infections. 相似文献
Shifts from ornamental fish tanks to functional reef ecosystem aquaria has led to unprecedented pressure on marine invertebrate fisheries. The Caribbean blue-legged hermit crab (Clibanarius tricolor) is among the species targeted for functional reef tanks, valued for its role as an aquarium cleaner. Little is known about the biology of the species or the genetic landscape in which the increased collecting is happening. Here, we investigate the phylogeographic history and genetic diversity of C. tricolor through analysis of mitochondrial (CO1, 16S) and nuclear (H3) DNA. We test whether phylogeographic breaks for other invertebrates structure the genetic diversity of C. tricolor and explore additional factors that may govern structure, such as reproductive strategy, life history, habitat preference, adult mobility, demographic history, and vicariance events. Based on these three markers, we find high genetic diversity and connectivity and find no evidence to support the tested barriers as relevant to gene flow for C. tricolor. Rather, mitochondrial and nuclear markers infer high genetic diversity, panmixia, and demographic expansion during the Pleistocene. Our finding of panmixia makes it difficult to identify source or sink populations, but the absence of hierarchical structure inferred from mtDNA and nuDNA markers we use, high levels of genetic diversity and homogeneity for these same markers, and advantageous life history traits suggest C. tricolor is not currently at special risk; however, geographically restricted haplotypes and limitations within our study prevent us from making a strong conclusion about the sustainability of the fishery. Our work on the Caribbean blue-legged hermit crab highlights the importance of acquiring basic information on exploited species and reiterates that common regional forces may not equally impact connectivity among co-distributed species.
Most bacteria at certain stages of their life cycle are able to move actively; they can swim in a liquid or crawl on various surfaces. A typical path of the moving cell often resembles the trajectory of a random walk. However, bacteria are capable of modifying their apparently random motion in response to changing environmental conditions. As a result, bacteria can migrate towards the source of nutrients or away from harmful chemicals. Surprisingly, many bacterial species that were studied have several distinct motility patterns, which can be theoretically modeled by a unifying random walk approach. We use this approach to quantify the process of cell dispersal in a homogeneous environment and show how the bacterial drift velocity towards the source of attracting chemicals is affected by the motility pattern of the bacteria. Our results open up the possibility of accessing additional information about the intrinsic response of the cells using macroscopic observations of bacteria moving in inhomogeneous environments. 相似文献