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1.
Cultured astrocytes from a syncytium after maturation 总被引:2,自引:0,他引:2
The formation of functional gap junctions between astrocytes was investigated during differentiation of these cells in culture. Precursor cells of GFA (glial fibrillary acidic) protein-positive astrocytes were cultured in a chemically defined medium as a homogeneous population. These cells were rarely coupled to one neighbour, as revealed by electrical and dye coupling and never formed a large syncytium, as investigated by injection and spread of Lucifer Yellow. Differentiation with respect to GFA protein accumulation can be induced in these cells by culturing in horse serum-containing medium. The formation of functional junctions developed within 2 weeks in about 20% of the cells. Coupled cells formed a large syncytium. When the astrocytes were co-cultured with primary cerebellar cells (consisting predominantly of small neurons) after the switch to serum-containing medium the percentage of coupled astrocytes increased to about 65%. Again the coupled cells formed a large syncytium. Since no physical contact was possible between the astrocyte cultures and the primary cerebellar cells the stimulation of coupling had to be signalized by soluble factor(s). 相似文献
2.
Free and polymerized tubulin in cultured bone cells and Chinese hamster ovary cells: the influence of cold and hormones 总被引:1,自引:1,他引:0
A low pH method of liposome-membrane fusion (Schneider et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:442) was used to enrich the mitochondrial inner membrane lipid bilayer 30-700% with exogenous phospholipid and cholesterol. By varying the phospholipid-to- cholesterol ratio of the liposomes it was possible to incorporate specific amounts of cholesterol (up to 44 mol %) into the inner membrane bilayer in a controlled fashion. The membrane surface area increased proportionally to the increase in total membrane bilayer lipid. Inner membrane enriched with phospholipid only, or with phospholipid plus cholesterol up to 20 mol %, showed randomly distributed intramembrane particles (integral proteins) in the membrane plane, and the average distance between intramembrane particles increased proportionally to the amount of newly incorporated lipid. Membranes containing between 20 and 27 mol % cholesterol exhibited small clusters of intramembrane particles while cholesterol contents above 27 mol % resulted in larger aggregations of intramembrane particles. In phospholipid-enriched membranes with randomly dispersed intramembrane particles, electron transfer activities from NADH- and succinate-dehydrogenase to cytochrome c decreased proportionally to the increase in distance between the particles. In contrast, these electron- transfer activities increased with decreasing distances between intramembrane particles brought about by cholesterol incorporation. These results indicate that (a) catalytically interacting redox components in the mitochondrial inner membrane such as the dehydrogenase complexes, ubiquinone, and heme proteins are independent, laterally diffusible components; (b) the average distance between these redox components is effected by the available surface area of the membrane lipid bilayer; and (c) the distance over which redox components diffuse before collision and electron transfer mediates the rate of such transfer. 相似文献
3.
Synthesis of intrathecal interferon in systemic lupus erythematosus with neurological complications.
Intrathecal synthesis of interferon in the absence of viral or bacterial infection was detected during the occurrence of neurological complications in two patients with systemic lupus erythematosus. The interferons displayed characteristics similar to those observed in the sera of patients with the disease. No interferon inducing activity was detected in the cerebrospinal fluid or serum of the two patients. These observations support the hypothesis of a localised mechanism of interferon induction in systemic lupus erythematosus which includes the interaction of lymphocytes with damaged tissues. 相似文献
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Chloragogen cells, subserving ion exchange and electron accepting functions, were studied in Tubifex tubifex after insecticide treatment. Chloragogen cells were strongly influenced by in vivo carbofuran poisoning. The first alterations in the chloragogen cells became activated, both the formation and release of the chloragosomes reached a high rate. The released chloragosomes were phagocytosed by the amoebocytes. At an advanced stage of the toxication a heavy loading of the apical cytoplasm of chloragogen cells with lipid droplets, finally degenerative changes both in the chloragogen cells and amoebocytes were observed. Possible mechanisms of the carbofuran toxication and of the protective function of chloragogen cells in T. tubifex are discussed. 相似文献
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John A. Nyakatura Vivian R. Allen Jonas Laustr?er Amir Andikfar Marek Danczak Hans-Jürgen Ullrich Werner Hufenbach Thomas Martens Martin S. Fischer 《PloS one》2015,10(9)
Orobates pabsti, a basal diadectid from the lower Permian, is a key fossil for the understanding of early amniote evolution. Quantitative analysis of anatomical information suffers from fragmentation of fossil bones, plastic deformation due to diagenetic processes and fragile preservation within surrounding rock matrix, preventing further biomechanical investigation. Here we describe the steps taken to digitally reconstruct MNG 10181, the holotype specimen of Orobates pabsti, and subsequently use the digital reconstruction to assess body mass, position of the centre of mass in individual segments as well as the whole animal, and study joint mobility in the shoulder and hip joints. The shape of most fossil bone fragments could be recovered from micro-focus computed tomography scans. This also revealed structures that were hitherto hidden within the rock matrix. However, parts of the axial skeleton had to be modelled using relevant isolated bones from the same locality as templates. Based on the digital fossil, mass of MNG 10181 was estimated using a model of body shape that was varied within a plausible range to account for uncertainties of the dimension. In the mean estimate model the specimen had an estimated mass of circa 4 kg. Varying of the mass distribution amongst body segments further revealed that Orobates carried most of its weight on the hind limbs. Mostly unrestricted joint morphology further suggested that MNG 10181 was able to effectively generate propulsion with the pelvic limbs. The digital reconstruction is made available for future biomechanical studies. 相似文献
10.
Franz Peter Fischer Christina Miltz Ingrid Singer Geoffrey A. Manley 《Journal of morphology》1992,213(2):225-240
The starling cochlea was studied with TEM at four locations along the basilar papilla to investigate gradients in morphological features over the papilla's length and width. Hair cell shape changes continuously from neural to abneural and from basal to apical. Unlike the situation in mammals, there are no distinct populations of hair cells; the previously described types (tall hair cells and short hair cells) are merely extremes in a continuum. Contacts between THC are a normal feature. Except at the base of the papilla, SHC have very large cuticular plates, suggesting a micromechanical function for these cells. In contrast to the THC, the SHC normally completely lack afferent innervation; this indicates that their function is restricted to within the basilar papilla itself. © 1992 Wiley-Liss, Inc. 相似文献