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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 173 (1982), S. 197-202 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using light and electron microscopy we found that the manatee retina has both rodlike and conelike photoreceptors in accord with its diurnal behavior pattern. Outer segment disks in both cell types appear to be enclosed along most of their length within the plasma membrane. The synaptic terminals are simple, with small, superficial postsynaptic contacts. The cones have long inner segments, short, conical outer segments and terminals with numerous synaptic ribbons and deeply embedded postsynaptic elements. There are two cone subclasses that may subserve color vision. Morphometry shows that there are more ganglion cells of small size ventrally, and that the thickness of the nerve fiber layer there is reduced, suggesting the presence of a specialized visual area in the retina. However, there were no pronounced differences in cone cell density in any of the regions examined.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 39 (1989), S. 139-151 
    ISSN: 0730-2312
    Keywords: calcium ; Fura-2 ; growth factors ; competence ; PDGF ; autoradiography ; digital image analysis ; FGF ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Although increased free intracellular calcium (Cai) may be one of the main regulators of cell growth and differentiation, studies in cell populations have implied that not all growth factors produce Cai increases. In order to examine in more detail whether Cai increases were related to mitogenesis, we used digital image analysis of intracellular Fura-2 fluorescence to measure Cai in individual BALB/c 3T3 cells stimulated with either platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF). We found that PDGF induced larger and more prolonged Cai increases than FGF did, but that both growth factors induced an initial rapid increase in Cai (〈 2 min) followed by a later sustained increase (〉 20 min). Only the prolonged Cai increase required extracellular calcium. Following PDGF treatment (1-8 units/ml), the percentage of cells with a large peak Cai increase (〉 twofold) correlated with the percentage of cells made competent (subsequent growth in 1% platelet-poor-plasma). In contrast, purified bovine basic FGF (200-800 pg/ml) and recombinant human acidic FGF (10-300 ng/ml) produced peak Cai increases that were not directly correlated with mitogenesis. In addition, concentrations of intracellular Quin 2 that inhibited Cai transients also inhibited PDGF stimulation but not FGF stimulation of mitogenesis. Thus, Cai increases are necessary for mitogenesis in BALB/c 3T3 cells stimulated by PDGF, but not that stimulated by FGF.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 168 (1981), S. 51-71 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The topography and histology of the skin of the naked mole (Heterocephalus glaber) have been correlated with its behavior. The integument is exceptionally loose, thereby reducing integumentary stresses when the animal is digging and moving in narrow tunnels. It also allows the position of the nasolabial sensory patch to change. This patch is exposed to mechanical stimuli when Heterocephalus moves along the tunnel, but becomes partially shielded by a transient buccal evagination, the formation and function of which are here described. Most of the differentiated patches of the skin lie in the cranial and anogenital regions. The eyes are microphthalmic and nearly completely closed by the nonmobile eyelids; there is no pinna, hair-coat or sweat glands.The epidermis is of variable thickness; in some places it has only one layer of cells. The detached epidermal cells penetrate the dermis irregularly.The epidermis of Heterocephalus is specialized by modifications of its germinative stratum, equivalent to an epidermosis, the syndrome of which consists of reduction of all types of epidermal buddings - pilogenetic and adenogenetic - as well as those which have a mechanical significance.
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  • 14
    ISSN: 0730-2312
    Keywords: avian embryo ; peripheral nervous system ; neural crest ; cell-adhesion ; cell migration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The peripheral nervous system derives mainly from the neural crest both in the head and trunk. Using markers such as fibronectin (FN), neural cell-adhesion molecule (NCAM), the nuclcolar marker for quail cells in chimaeric embryos, and NC-1, a monoclonal antibody specific to crest cells and their neural derivatives, we have attempted to reconstruct the processes that lead to the formation of peripheral ganglia. Our observations allow us to propose a model of the formation of ganglia based on morphogenetic movements and on variations of crest cell adhesiveness. In most cases, crest cells migrate in morphologically defined and transient pathways that lead them to their final site of arrest; these pathways are always associated with FN, which appears necessary for crest cell attachment and movement in vitro. The directionality of crest cell migration is probably dictated by the cells' motile properties and population pressure in restricted areas suitable for cell movement. The disappearance of the pathways and of the substrate necessary for migration while the population is rapidly dividing may be responsible for the aggregation of crest cells in the case of the sensory ganglia. To the contrary, the aggregation of crest cells into autonomic ganglia (sympathetic, enteric, aid ciliary ganglia) does not seem to obey the same rules, no disappearance of the substratum or of the pathways being obvious; rather, their formation seems correlated with the de novo synthesis of adhesive molecules such as NCAM.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 56 (1994), S. 469-479 
    ISSN: 0730-2312
    Keywords: inducible v-sis (PDGF-B) ; signal transduction ; Egr-1 protein ; mutant Ras ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The early growth response gene, Egr-1, is up-regulated transiently by mitogens and many other simuli in all cells tested. Using NIH3T3 cells conditionally expressing v-sis from a metallothionein promoter, we show that the addition of Zn2+ stimulates the production of PDGF-B(v-sis) and elicits the expression of Egr-1 in a dose-dependent and time-regulated manner. The signal is likely independent of protein kinase C, but depends on tyrosine kinase and other kinase activities and is mediated by c-Ha-Ras since the presence of dominant-negative mutants of Ras and Raf abrogates the induction of Egr-1 expression by Zn2+. Transiently activated Ras expression in NIH3T3 cells also stimulates the transient expression of Egr-1, but cells that constitutively express Rass do not have elevated levels of Egr-1. Transient assays also demonstrated that Zn2+ or activated Ras expression stimulated the activity of a 950 bp Egr-1 promoter-reporter gene construct and this is abrogated in the presence of mutant Ras and Raf. The accumulated data show that Egr-1 gene expression is regulated by multiple mechanisms, as would be needed for putative role in Cell proliferation, in suppression of transformation and in differentiation.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 139 (1989), S. 398-406 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although variability in the duration of the cell cycle is thought to reflect growth-regulatory processes that control cell cycle progression, the precise timing of the variable period within the GI phase of the cell cycle has not been defined. In particular, the timing of cell cycle variability in relation to the cell's commitment (R point) to the initiation of DNA synthesis remains controversial. In order to investigate cell cycle variability, indirect immunofluorescence was used to measure the formation of the primary cilium as a possible marker of G1 events in both stimulated quiescent and exponentially growing cells. The primary cilium, an internal “9 + 0” nonmotile structure formed by one of the interphase centrioles, was first detected in postmitotic BABL/c 3T3 cells 5 hr before the initiation of DNA synthesis, an interval similar to that for the reassembly of the primary cilium in serum-stimulated quiescent fibroblasts. This similarity in the timing of ciliation suggests that serum-stimulated quiescent cells reenter the cell cycle in early G1 and recapitulate much of G1. Moreover, the rate of cilia formation in both postmitotic and serum-stimulated quiescent cells was identical to the rate of DNA synthesis initiation. Thus, cell cycle variability occurs before ciliation in both stimulated quiescent and exponentially growing cells. Furthermore, since ciliation also precedes the R point, variability in the centriole cycle occurs before the R point and thus may reflect processes controlling the cell's commitment to the initiation of DNA synthesis.
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  • 17
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Amphotropic murine leukemia virus pseudotypes of murine sarcoma viruses containing theras or mos oncogenes were constructed to permit efficient introduction of the sarcoma virus genome into early-passage human umbilical vein endothelial cells. The resulting cell lines were morphologically and phenotypically unchanged, retaining properties characteristic of differentiated endothelial cells. For example, the cells in a Kirsten sarcoma virus-modified line were found to biosvnthesize and secrete von Willebrand factor in both a constitutive and regulated manner, and they contained ultrastructurally identifiable Weibel-Palade bodies, an endothelial cell-specific organelle. In contrast to the parent cultures, sarcoma virus-modified cells were able to proliferate indefinitely in culture. Examination of both Kirsten sarcoma and Moloney leukemia virus-modified lines indicated that the immortalized cells retained a diploid female karyotype after over 18 months in culture. In addition, the sarcoma virus-modified cells were able to grow independently of added endothelial cell growth factor. This growth factor autonomy does not appear to be due to autocrine production of a biologically cross-reactive growth factor. These immortal, virus-modified endothelial cells express large amounts of sarcoma virus-specific mRNA but no detectable helper virus or transforming virus activity. This technique for immortalization of primary human cells without alteration of the differentiated characteristics of the cell type is readily applied to a variety of human cell types. Moreover, the ability to separate the immortalizing and transforming activities of viral oncogenes should provide further understanding as to mechanisms of oncogene action.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 14 (1992), S. 861-867 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 2 (1985), S. 29-33 
    ISSN: 0741-0581
    Keywords: Ultramicrotomy ; Ceramic ; Alumina ; TEM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A technique was developed to aid in the interpretation of nucleation and growth characteristics of otherwise electron-opaque Al2O3 particles. The technique involved embedding a dense collection of particles in an Epon mixture and sectioning with a diamond knife on an ultramicrotome. Serial sections were utilized to obtain three-dimensional information. It was found that ultramicrotomy does not introduce artifacts in ceramics which would otherwise affect measurements of the crystallite size or phase fraction, nor does it affect the crystallographic data significantly.It was observed that α-Al2O3 nucleated at the surface of isolated particles and in the neck region of sintered particles. Other data, obtained from diffraction and in situ hot-stage studies, indicated that each polycrystalline α-Al2O3 particle transformed to a nearly single crystal of γ-Al2O3, which extended into adjacent particles under favorable circumstances.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 8 (1988), S. 137-158 
    ISSN: 0741-0581
    Keywords: Kaposi's sarcoma ; Lymphoma ; Histology ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Malignancies frequently arise in patients infected with human immunodeficiency virus (HIV), including those patients classified as having the acquired immunodeficiency syndrome (AIDS). Currently, Kaposi's sarcoma and certain types of lymphoma are considered to develop as a result of HIV infection, and other cancers have also been reported in these patients. For the most part, ultrastructural study of HIV-associated malignancies has been limited to Kaposi's sarcoma; the ultrastructural features of the epidemic form of this disease are generally the same as those of the classical form. The occurrence of these cancers in HIV-infected individuals appears to be related to the immunodeficiency caused by this virus, but the basic etiologic mechanisms remain unknown. In general, only palliative treatments are presently available for HIV-associated malignancies.
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