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  • Cell & Developmental Biology  (6)
  • 1980-1984  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Sensitivity of excision repair in normal human, xeroderma pigmentosum variant and Cockayne's syndrome fibroblasts to inhibition by cytosine arabinoside (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 108 (1981), S. 163-173 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Inhibition of the gap-filling, polymerizing step of excision repair by 1-β-D-arabinofuranosylcytosine (ara-C) after irradiation with ultraviolet light in human diploid fibroblasts resulted in the formation of persistent DNA strand breaks in G1, G2, and plateau phase cells, but not in S phase cells. Addition of hydroxyurea to ara-C resulted in partial inhibition of repair in S phase cells. These observations can be explained either in terms of changing roles in repair for different DNA polymerases throughout the cell cycle or by the presence of a pool of deoxycytidine nucleotides during S phase equivalent to an external source of deoxycytidine at 50 μM concentration. A similar concentration dependence on ara-C was observed for inhibition of repair in normal human, xeroderma pigmentosum (XP) variant, and Cockayne's syndrome cells. Ara-C produced a similar number of breaks in normal and Cockayne's syndrome cells but slightly more in XP variant cells. Exonuclease III and S1 nuclease independently both degraded about 50% of the 3H-thymidine incorporated into repaired regions in the presence of ara-C. Sequential digestion with both enzymes degraded nearly 90% of the repaired regions. These observations can be explained if excision repair proceeds by displacing the damaged strand so that both the 3H-labeled patch and the damaged region are still ligated to high molecular weight DNA and compete for the same complementary strand during in vitro incubation with the nucleases. The amount of 3H-thymidine incorporated in DNA by repair decreased with increasing concentrations of ara-C and hydroxyurea, suggesting that the incomplete patches became shorter under these conditions. Extrapolation of the digestion kinetics with exonuclease III permits an estimate of the normal patch size of about 100 nucleotides, consistent with previous estimates.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041080207
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  • 2
    Electronic Resource
    Electronic Resource
    Metabolic requirements for maintenance of the chlortetracycline-labeled pool of membrane-bound calcium in human neutrophils (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 117 (1983), S. 415-422 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human neutrophils labeled with chlortetracycline (CTC), commonly used as a probe of membrane-bound calcium, release lysosomal enzymes and exhibit a rapid decrease in fluorescence when exposed to the chemotactic peptide fMet-Leu-Phe or the lectin Con A. This decrease has been attributed to the release of calcium from a membrane-associated “trigger pool.” The nature of this putative pool has been further characterized by examining the effects of various inhibitors on the CTC fluorescence response and lysosomal enzyme release from stimulated neutrophils. These agents included inhibitors of glycolysis (2-deoxyglucose and iodoacetate), an uncoupler of oxidative-phosphorylation (KCN), and a sulfhydryl inhibitor (N-ethylmaleimide). Resting neutrophils, labelled with CTC demonstrated an enhanced decay of baseline fluorescence when exposed to 2-deoxyglucose or iodoacetate. This suggested that the pool of membrane-bound calcium labeled by this probe was maintained by glycolytic metabolism. Furthermore, 2-deoxyglucose and iodoacetate inhibited both the stimulated decrease in CTC fluorescence and lysosomal enzyme release induced by fMet-Leu-Phe and Con A in a time-dependent manner. KCN did not inhibit either response to stimulation, but did retard the recovery of CTC fluorescence observed when fMet-Leu-Phe was used as the stimulus. High concentrations of N-ethylmaleimide (100 μM) completely inhibited both the CTC fluorescence response and lysosomal enzyme release almost immediately; low concentrations of N-ethylmaleimide (30 μM) inhibited lysosomal enzyme release in a time-dependent manner without significantly affecting changes in CTC fluorescence. These results are consistent with the hypothesis that CTC serves as a probe of membrane-bound “trigger” calcium, the release of which is dependent upon intact glycolysis and is a requirement for lysosomal enzyme release.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041170317
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of phagocytosis on guinea pig granulocyte membrane markers (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 102 (1980), S. 71-80 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The internalization of membrane markers during phagocytosis was followed in guinea pig granulocytes as a function of the extent of particle ingestion. The plasmalemma was carefully labeled with diazotized 35S-sulfanilate, or by treatment with periodate and sodium 3H-borohydride. These treatments provided general membrane markers. More specific markers used were 5′-nucleotidase, neuraminidase-releasable membrane sialate, and concanavalin A binding sites. In all cases except the last, internalization of membrane was directly determined on isolated phagosomes; disappearance of binding sites from the cell surface was followed in the last instance. Both phagosomal levels and disappearance from the surface were measured in the case of 5′-nucleotidase, permitting balance studies. Phagocytosis was determined as uptake of paraffin emulsions labeled with Oil-Red 0. “Marker/particle” ratios were determined as the percent external marker internalized per mg paraffin ingested.The “marker/particle” ratios for cells with chemically labeled membranes were considered to reflect random internalization of membrane entities. Colchicine had no effect on those ratios. Internalization of 5′-nucleotidase and neuraminidase-releasable sialate gave “marker/particle” ratios similar to those of the random markers, and these increased in the presence of colchicine. Concanavalin A binding sites did not appear to be removed from the cell surface in the absence of colchicine, but disappearance was observed in its presence. Control experiments indicated that these changes due to colchicine must be very cautiously interpreted. Our results differ from those obtained by others, and the reasons due to species, cell type, experimental design, etc. are discussed. Maximal particle uptake was computed to require internalization of one-fifth to one-third of the total external membrane of the cells - based on the assumption of random internalization of markers.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041020111
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  • 4
    Electronic Resource
    Electronic Resource
    The cellular basis of self renewal in culture by human acute myeloblastic leukemia blast cell progenitors (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 102 (1980), S. 217-222 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Blast cells from patients with Acute Myeloblastic Leukemia (AML) were separated according to cell size using velocity sedimentation under unit gravity. Fractions obtained in this way were plated in methyl cellulose with a growth stimulator present in media conditioned by leukocytes in the presence of phytohemagglutinin (PHA-LCM). Colonies of blast cells form under these conditions. Pooled cell suspensions from such colonies were plated in microwells; the plating efficiency of such suspensions is a measure of blast progenitor self-renewal occurring in the original blast colonies. Self-renewal assays on each fraction indicated that self renewal among blast progenitors is heterogeneously distributed with subpopulations differing in renewal capacities. The results are consistent with the view that blast cell subpopulations in AML undergo a series of transitions associated with decreasing self renewal capacity, analogous to that observed in normal hemopoiesis, where proliferative capacity decreases with increasing differentiation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041020213
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence of phospholipase A2 in the sea urchin egg: Its possible involvement in the cortical granule reaction (1984)
    New York, NY : Wiley-Blackwell
    Gamete Research 9 (1984), S. 329-338 
    Details
    ISSN: 0148-7280
    Keywords: cortical granule reaction ; phospholipase A2 ; quinacrine ; sea urchin ; fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Fertilization of the sea urchin egg involves an exocytotic event known as the cortical granule reaction (CGR). In many cell systems, phospholipase A2 is implicated in regulation of the secretory event. Indirect evidence suggests that phospholipase A2 mediates the CGR; however, there has been no direct demonstration of phospholipase A2 activity in the sea urchin egg. We report here evidence of phospholipase A2 activity in egg homogenate of the sea urchin Lytechinus pictus. The enzyme was calcium-dependent and had a pH optimum near the intracellular pH of the unfertilized egg. Neither exogenous calmodulin nor trifluoperazine had any apparent effect on enzyme activity. Quinacrine, a phospholipase A2 inhibitor, blocked the enzyme activity in the egg homogenate. In intact eggs, quinacrine blocked the CGR in a dose-dependent, egg-concentration-dependent manner. The inhibitory effect of quinacrine on the CGR could not be overcome by the phospholipase A2 activator melittin or by the calcium ionophore A23187. Quinacrine did not inhibit sperm-egg binding or sperm incorporation. These results lend further support to the hypothesis that phospholipase A2 is involved in the CGR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120090308
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  • 6
    Electronic Resource
    Electronic Resource
    Normal levels of zinc and sulfhydryls in morphologically abnormal populations of spermatozoa from moderately zinc-deficient rats (1984)
    New York, NY : Wiley-Blackwell
    Gamete Research 9 (1984), S. 375-386 
    Details
    ISSN: 0148-7280
    Keywords: rat ; zinc-deficient ; sperm ; dense fibers ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Zinc is required for spermatogenesis in mammals and is concentrated in the dense outer fibers of the sperm tail, where it is associated with cysteine-rich protein. To investigate the effects of marginal zinc deficiency upon dense fiber formation and upon sperm quality in general, weanling Sprague-Dawley rats were administered a commercial low-zinc diet, supplemented with phytate, for approximately 60 days, and were compared with controls fed the same diet plus 50 ppm zinc in their drinking water. The following characteristics of the zinc-deficient rats were significantly lower than in the controls: body weight, testis weight, epididymis weight, seminal vesicle weight, sperm content of the cauda epididy-midis, sperm motility, testis zinc, and hair zinc. By contrast, the levels of sperm zinc and sperm sulfhydryls were the same in the zinc-deficient and control rats. The zinc-deficient rats displayed a highly variable spectrum of sperm defects, which included decapitation, disorganized and redundant tail elements, and superfluous cytoplasm. However, abortive dense fiber development was only rarely observed. Apparently, even when availability of zinc is limited and reduced sperm production ensues, elaboration of dense fibers rich in zinc and sulfhydryls continues to be obligatory for the completion of spermiogenesis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120090403
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