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51.
The rpf gene cluster of Xanthomonas campestris pv. campestris is involved in the co-ordinate positive regulation of the production of extracellular enzymes and the extracellular polysaccharide xanthan. Several of the rpf genes are involved in a regulatory system involving the small diffusible molecule DSF (for diffusible signal factor). Synthesis of DSF requires RpfF, and a two-component sensory transduction system involving RpfC has been implicated in the perception of the signal and signal transduction. Here we show that mutations in both rpfF and rpfC lead to reductions in the levels of cyclic glucan. The levels of cyclic glucan synthetase in membrane preparations from rpfF and rpfC mutants were, however, unaltered from the wild-type. Similar alterations in the level of cyclic glucan without changes in cyclic glucan synthetase activity were seen when wild-type bacteria were exposed to osmotic stress. These results extend the range of cellular functions subject to regulation by the rpf genes and DSF system.  相似文献   
52.
The ultrastructure of inner capsule cells of the vertebrate muscle spindle was studied by transmission electron microscopy and compared with that of homologous cells in the tendon organ. Aside from variations in their complexity and pattern of organization, cells of the inner capsule in these two sensory receptors exhibited marked similarities in fine structure. The virtual absence of basal lamina in the region of the nucleated soma as well as on the branching cytoplasmic extensions of these cells was noted. In the inner capsule of both end organs, three kinds of intercellular specialization were encountered. Cell processes were typically linked together at multiple sites by intermediate junctions. In addition, focal points of membrane fusion between two or more cellular profiles were identified as tight junctions. In more extensive regions of plasma membrane overlap, gap junctions were also discerned. It seems probable that these sites along the inner capsule represent areas of mechanical and electrical linkage, enabling contiguous cells to function as a synchronous unit. Tight junctions may also provide the inner capsular sheath with specific permeability-barrier characteristics. Elements of the Golgi complex and associated presecretory vesicles and cytoplasmic granules were prominent. Their presence implicates these cells in the elaboration of the paracellular connective-tissue matrix occupying the intracapsular spaces of both receptors. The close resemblance of these cells to endoneurial fibroblasts of peripheral nerve and to hyalocytes of the vitreous body is emphasized. It is likely that, regardless of species examined, cells of the inner capsule in both receptors play an overall protective role in the formation, maintenance and regulation of their luminal paracellular contents.  相似文献   
53.
Total and tartrate-labile serum acid phosphatase levels were compared in patients with and without prostates, and in 12 patients before and after cystoprostatectomy. Absence of the prostate seems to make no significant difference to the levels of serum acid phosphatase. There is no justification for referring to the tartrate-labile serum acid phosphatase as “prostatic acid phosphatase.” A substantial incidence of marginally raised levels of serum acid phosphatase in each group of patients suggests that the upper limit of normal for the total serum acid phosphatase should be taken as 5 K.A.u.  相似文献   
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This paper discusses treatment implications of comorbid psychopathology in the context of American Indian and Alaska Native culture and in the context of the Indian Health Service's Mental Health and Alcohol and Substance Abuse Program Branches. Treatment of comorbidity in this population is a particularly difficult problem due to numerous barriers to treatment and a poorly defined treatment system. As in other clinical populations, these patients are high utilizers of the limited treatment services available, but may not receive the type of treatment they need. After describing the extent of comorbidity in this population, we present an historical perspective of mental illness that provides an Indian's view of why we are where we are today in treating these problems. Next, we discuss Western and traditional treatment implications for comorbidity among adults and adolescents. Finally, we suggest directions for future research in this area.  相似文献   
56.
A significantly greater rise in carboxyhaemoglobin concentration in response to smoking a single cigarette was shown in pregnant (3-9% increase) as opposed to non-pregnant (2-1% increase) women. This was more pronounced when anaemia was present (5-0% increase) and appeared to be inversely related to the haemoglobin concentration. We suggest that the risks to the fetus may be particularly increased when anaemia complicates pregnancy in women who smoke cigarettes.  相似文献   
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Topographical control of cell behaviour. I. Simple step cues   总被引:5,自引:0,他引:5  
The photolithographic techniques of the microelectronics industry have allowed us to fabricate patterned plastic substrata to investigate contact guidance of animal tissue cells. The reactions of cells to single steps on a substratum were examined using time-lapse videorecording and scanning electron microscopy. BHK cells and chick embryonic neural cell processes exhibited gradual inhibition of crossing steps with a concomitant increase in alignment at steps dependent on increasing step height. Comparison of these cells' reactions, with those of chick heart fibroblasts and rabbit neutrophils, at a 5 micron step revealed that the influence of topography is also dependent on cell type, the neutrophils being relatively unaffected. The presence of an adhesive difference at a series of steps altered BHK cells' reactions such that the frequency of crossing was dependent on the direction of approach to a step. Although our data are consistent with Dunn & Heath's proposal (1976) that the inflexibility of the cytoskeleton of a moving cell's protrusion is the cellular property determining such reactions to topography, we have found that, on encountering a topographical feature, the response of a cell may be predictable on a probabilistic basis, i.e. the topographical feature reduces the probability of a cell making a successful protrusion and contact in a given direction, that even the largest features tested did not act as absolute barriers to cell locomotion since a small proportion of a population of cells were able to overcome them, and that other guidance cues could significantly alter a cell's response. Even in situations where it is not the primary cue in directing cell locomotion, topographical control may be an important factor during morphogenesis since it must, at the very least, influence the efficiency of other cues.  相似文献   
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The crowns of several teeth of a captive killer whale, particularly on the mandible, were worn to the level of the pulp cavities by biting a cement structure in the pool. Food plugging partially vacant pulp cavities created intense vascularization, inflammation, and eventually a systemic focus for infection. This trauma correlated with an elevated white blood cell count. Haematology was restored to normal following regular care for the worn teeth. Patent drainage of the pulp cavity was maintained through routine brushing with a large-scale toothbrush. Administration of antibiotics was not necessary in controlling the white blood cell count.  相似文献   
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