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  • 1
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In the normal histogenesis of mouse retina localized distribution of acid phosphatase positive granules has been seen around the photoreceptor cell nuclei along the outer limiting membrane. These granules disappear during the development of the rod elements. Temporarily increased activity is also seen along the nuclei of the inner layer adjacent to and in the course of the development of the outer and the inner plexiform layers. Within the inner nuclear layer, the cells at the outer and inner rows develop localized acid phosphatase positive granules which persist in the adult retina. Ganglion cells and the layer of nerve fibres show little change. In the pigment epithelium the enzyme gradually increases. In mice, homozygous for the retinal degeneration gene, degenerating photoreceptor cell nuclei, characterized by perinuclear acid phosphatase staining, can be detected before morphological signs of degeneration. Increased frequency of such nuclei and intensity of staining are recorded with the progress of degeneration. Enzyme activity in the photoreceptor cells, within the inner nuclear layer and in the degenerating photoreceptor cell nuclei is demonstrable using naphthol substrates but not β-glycerophosphate. Positive reaction with β-glycerophosphate is obtained in these sites in the presence of dimethyl sulphoxide. Existence of differential permeability among the retinal lysosomes is tentatively suggested.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During the post-natal development of the retina in mice, macrophages which are selectively stained for N-Acetyl-β-glucosaminidase enter the retina through the vascular route. Most of these cells finally occupy the outer and the inner levels of the inner nuclear layer adjoining the plexiform layers and are transformed into very small cells which persist in the adult retina without further change. In mice with hereditary retinal degeneration (rd rd) these β-glucosaminidase positive macrophages enter the outer nuclear layer of the retina, soon after the onset of degeneration undergo extensive hypertrophy and rapidly phagocytize the degenerating photoreceptor cells. After the digestion of the ingested materials the enzyme activity is very much reduced and the cells become smaller in size. They eventually acquire the morphological features seen in the normal retina.
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  • 3
    ISSN: 1432-0568
    Keywords: Retina ; Mouse ; Photoreceptors ; Differentiation ; rd Mutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mice, homozygous for the mutant gene rd show selective degeneration of the photoreceptor cells after their initial differentiation. Phenotypic expression in the mutant and in normal mice was studied by light and electron microscopy. The sequential emergence of developmental deviations in the mutant retina falls into three categories. First, predegenerative differences are manifest within the photoreceptor cells during 4–8 days after birth in retarded growth of the inner segments, reduced outer segment production, delayed development of the outer plexiform layer and slower segregation of the perikarya. Next, degenerative changes are recognized from 6 day onwards with swelling and vacuolization of the Golgi cisternae in the inner segments followed by cytolytic alterations affecting the ultrastructure of the entire cell. Lastly, with increasing loss of photoreceptor cells post-degenerative effects are seen in deepening of the basal infoldings and microvilli of the pigment epithelium and increase of Müller's fibres. The progress of degeneration in the mutant retina corresponds to the phase of rapid growth of the Golgi apparatus and rod outer segments in the normal retina. The role of the Golgi apparatus in the differentiation of the photoreceptor cells and its relation to the expression of the rd gene are discussed.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 152 (1960), S. 131-136 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The cellular configuration of a hydra is dissociated under the pressure of a cover-glass and the different cell types are isolated and observed in hanging drop chamber. 2. With the exception of certain cnidoblasts, all the cells are rounded after dissociation of which only the nutritive muscular cells of the endoderm show amoeboid movement. 3. Pseudopodium originates as ectoplasmic out-pushing in which endoplasm flows in afterwards. Pseudopodia are thrown from all sides of the cell. 4. The details of intra-cellular contents in the different cell-types are described. 5. The nature of surface rigidity, attachment and cell shape before and after dissociation have been discussed in relation to the animal form and morphallactic power of hydra.
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We have examined cyclic GMP concentrations, guanylate cyclase activities, and cyclic GMP phosphodiesterase (PDE) activities in developing retinas of congenic mice with different allelic combinations at the retinal degeneration (rd) and retinal degeneration slow (rds) loci. Although guanylate cyclase activities were found to be uniformly low in the mutant retinas, striking differences in PDE activity and cyclic GMP levels were observed in retinas of the various genotypes. Homozygous rds mice, which lack receptor outer segments, showed reduced retinal PDE activity and cyclic GMP concentration in comparison to normal animals. In heterozygous rds/+ mice with abnormal outer segments, the levels were intermediate. In retinas of homozygous rd mice, PDE activity was lower than in rds retinas and cyclic GMP levels were much higher. In mice homozygous for both rd and rds genes, retinal PDE activities were even lower than in single homozygous rd mice; the cyclic GMP level reached the same high value as in the rd animals, persisted for a longer time at this high level, and did not correlate with the rate of photoreceptor cell loss. Thus, a marked variation in PDE activity appears to be the major manifestation of abnormal outer segment differentiation and eventual degeneration of photoreceptor cells in these neurological mutants. An increased cyclic GMP level seems to be an essential corollary in the expression of the rd gene even in the absence of outer segments, but it appears unlikely that an abnormally high nucleotide level in itself causes photoreceptor cell death.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 47 (1960), S. 263-263 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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