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1.
Proteolytic maturation of insulin is a post-Golgi event which occurs in acidifying clathrin-coated secretory vesicles 总被引:48,自引:0,他引:48
The direct identification of the intracellular site where proinsulin is proteolytically processed into insulin has been achieved by immunocytochemistry using an insulin-specific monoclonal antibody. Insulin immunoreactivity is absent from the Golgi stack of pancreatic B-cells and first becomes detectable in clathrin-coated secretory vesicles released from the trans Golgi pole. Clathrin-coated secretory vesicles transform into mature noncoated secretory granules which contain the highest concentration of insulin immunoreactive sites. Maturation of clathrin-coated secretory vesicles is accompanied by a progressive acidification of the vesicular milieu, as evidenced by a cytochemical probe that accumulates in acidic compartments whereupon it can be revealed by immunocytochemistry. Thus packaging of the prohormone in secretory vesicles, and acidification of this compartment, are critical steps in the proper proteolytic maturation of insulin. 相似文献
2.
Summary Internal fertilization is demonstrated in the priapulid wormTubiluchus philippinensis by the electron microscopic observation of sperm in the urogenital duct of female animals. This finding is of interest in that all other members of this group thus far examined have exhibited external fertilization. 相似文献
3.
Oxygen concentration regulates EGF-induced proliferation and EGF-receptor down regulation 总被引:2,自引:0,他引:2
D A Wing G D Talley T G Storch 《Biochemical and biophysical research communications》1988,153(3):952-958
Reducing oxygen from 20% to 2.5% increases EGF-induced DNA synthesis and cell proliferation in cultures of human diploid fibroblasts. Reducing oxygen also changes the pattern of EGF binding to the cell surface. The loss of surface binding that follows EGF attachment to cells in 20% oxygen does not occur in 2.5% oxygen. 相似文献
4.
The feeding appendages ofAlvinella pompejana obtained from a deep-sea hydrothermal vent environment are described. They are characterized by a ciliated groove, the cells of which have a very distinctive ultrastructure, by groups of bipolar receptor cells and by several kinds of gland cells. Among these, one cell type is in an upside down position suggesting a function completely different from other epidermal secretory cells. The gills differ considerably from the feeding appendages on the basis of their ultrastructure. Their epidermis is very irregular in height; basal infoldings give the blood access to a space coming very near to the external medium. The blood vascular system is open. On the other hand, the gills ofAmphicteis gunneri are not effective sites of gas exchange, since their columnar epithelium is underlain with muscle cells. The cells composing the feeding appendages and gills ofAlvinella pompejana are characterized by ultrastructurally very different mitochondria. 相似文献
5.
Calcium alters the acyl chain composition and lipid fluidity of rat hepatocyte plasma membranes in vitro 总被引:1,自引:0,他引:1
Calcium ion decreases the lipid fluidity of isolated rat hepatocyte plasma membranes by modulating the activity of membrane enzymes which alter the lipid composition. To explore the mechanism of the effect of the cation, eight fluorophores were used to assess lipid fluidity via estimations of either steady-state fluorescence polarization or excimer fluorescence intensity. The results demonstrate that the reduction in fluidity occurs in the hydrophobic interior of the bilayer and that both the dynamic and static (lipid order) components of fluidity are affected by treatment with calcium. Analysis of the membrane lipids demonstrates that calcium treatment decreases the arachidonic acid content of the polar lipid fraction and, thereby, reduces the double-bond index of the fatty acids. This change in composition, which is expected to reduce the lipid fluidity, may result from activation by calcium of the endogenous hepatocyte plasma membrane phospholipase A2. 相似文献
6.
Summary Under conditions of food deprivation, the hindgut epithelium of the experimental animals (Mesidotea entomon, Oniscus asellus, Porcellio scaber) undergoes ultrastructural changes. After the application of different diets it was demonstrated that this part of the alimentary canal contains nutrients, though it is lined by a cuticle. Experimental evidence for the formation of glycogen from glucose offered as the only diet comes from autoradiographic experiments. Amino acids, too, were detected in the hindgut cells soon after refeeding. Lipids, on the other hand, which are first absorbed by the large cells of the midgut glands, were not found in the hindgut epithelium. The existence of lipid inclusions in the hindgut epithelium some weeks after refeeding, however, supports the hypothesis that lipids reach the epithelial cells of the hindgutvia midgut glands and hemolymph. 相似文献
7.
E. Nevo A. Beiles D. Kaplan N. Storch D. Zohary 《Plant Systematics and Evolution》1986,153(3-4):141-164
Genetic diversity and structure of populations of the wild progenitor of barleyHordeum spontaneum in Iran was studied by electrophoretically discernible allozymic variation in proteins encoded by 30 gene loci in 509 individuals representing 13 populations of wild barley. The results indicate that: a)Hordeum spontaneum in Iran is extremely rich genetically but, because of predominant self-pollination, the variation is carried primarily by different homozygotes in the population. Thus, genetic indices of polymorphismP-1% = 0.375, range = 0.267–0.500, and of genetic diversity,He = 0.134, range = 0.069–0.198, are very high. b) Genetic differentiation of populations includes clinal, regional and local patterns, sometimes displaying sharp geographic differentiation over short distances. The average relative differentiation among populations isGst = 0.28, range = 0.02–0.61. c) A substantial portion of the patterns of allozyme variation in the wild gene pool is significanctly correlated with the environment and is predictable ecologically, chiefly by combinations of temperature and humidity variables. d) The natural populations studied, on the average, are more variable than two composite crosses, and more variable than indigenous land races of cultivated barely,Hordeum vulgare, in Iran. — The spatial patterns and environmental correlates and predictors of genetic variation ofH. spontaneum in Iran indicate that genetic variation in wild barley populations is not only rich but also at least partly adaptive. Therefore, a much fuller exploitation of these genetic resources by breeding for disease resistance and economically important agronomic traits is warranted. 相似文献
8.
Zoomorphology - Die licht- und elektronenmikroskopische Untersuchung der Prosomadrüsen der Spinnmilben Bryobia praetiosa, Bryobia rubrioculus und Tetranychus urticae (Tetranychidae,... 相似文献
9.
Zusammenfassung Das Epithel der Kopfanhänge von elf marinen und Süßwasserprosobranchiern besteht aus prismatischen bis kubischen Stützzellen mit meist dichtem Mikrovillussaum und z.T. Pigmentgranula sowie Sinneszellen, die fast immer in Form sekundärer Sinneszellen vorliegen; nur bei Patella coerulea kommen vermutlich auch primäre Sinneszellen vor. Ihr Zytoplasma ist apikal durch glattwandige E. R.-Zisternen, helle Bläschen und Mikrotubuli gekennzeichnet. Außerdem tragen diese Zellen Zilien und stehen basal mit Nervenendigungen in Kontakt, die sich in drei Gruppen einteilen lassen: 1. Vermutlich cholinerge Endigungen mit optisch leeren Bläschen (Ø 600–800 Å). 2. Endigungen mit dense core vesicles (Ø 1000–1100 Å). Die Annahme, daß diese Endigungen biogene Amine enthalten, wird durch fluoreszenzmikroskopische Befunde gestützt. 3. Endigungen mit großen (Ø 3000–4000 Å) neurosekretorischen Elementargranula.
Structure and innervation of the cephalic tentacles of Prosobranch molluscs
Summary The epithelium of the cephalic tentacles of eleven marine and freshwater prosobranch snails consists of villus bearing supporting cells, which partly contain pigment granules, and sensory cells, which occur in form of secondary sensory cells with the exception of Patella coerulea which presumably possesses primary sensory cells. These receptor cells are characterized as chemoreceptors by apical cilia, smooth surfaced E.R., microtubulues and empty vesicles. At their bases they are in close contact with nerve endings which can be classified in three groups: 1. presumably cholinergic endings with clear vesicles (Ø 600–800 Å). 2. endings with dense core vesicles (Ø 1000–1100 Å). The assumption that these endings contain biogenic amines is supported by positive fluorescence microscopical tests. 3. Endings with big (Ø 3000–4000 Å) neurosecretory elementary granules.
Herrn Prof. Dr. W. Bargmann danke ich für die Überlassung eines Arbeitsplatzes im Anatomischen Institut Kiel. 相似文献
10.