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  • Artikel  (211)
  • Cell & Developmental Biology  (211)
  • 1970-1974  (166)
  • 1935-1939  (45)
  • 1
    Digitale Medien
    Digitale Medien
    Calcium-mediated effects of calcitonin on cyclic AMP formation and lymphoblast proliferation in thymocyte populations exposed to prostaglandin E1Issued as NRCC 12843. (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 80 (1972), S. 315-328 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The calcitonin (SCT) from salmon ultimobranchial bodies which (like mammalian calcitonins) lowers the plasma calcium concentration in mammals can also affect cyclic AMP (cyclic adenosine 3′,5′-monophosphate) metabolism and proliferation of lymphoblasts in normal and prostaglandin E1 (PGE1)-treated rat thymocyte populations in three different ways. In the first case, low concentrations (0.5-5.0 ng per milliliter) of SCT lower (by a calcium-mediated process) the ability of PGE1 to transiently increase cyclic AMP synthesis, but the reduced surge of cyclic AMP production is still ample to stimulate lymphoblasts in the cell population to initiate deoxyribonucleic acid (DNA) synthesis. Secondly, these low SCT concentrations affect the eventual progression of the PGE1-stimulated, DNA-synthesizing lymphoblasts into mitosis by a calcium-mediated process. Depending on the extracellular calcium concentration and the magnitude of the initial increment in the intracellular cyclic AMP content, SCT can either promote or inhibit the progression of the stimulated cells into mitosis. SCT's third action is a rapid (within 5 minutes), calcium-independent elevation of the cellular cyclic AMP content in otherwise untreated thymic lymphocyte populations exposed to a very high concentration (100 ng per milliliter) of the hormone. This early, transient rise in the cyclic AMP level is followed by a calcium-dependent increase in lymphoblast proliferation. An attempt is made to interrelate and explain the different actions of SCT on cyclic AMP metabolism and mitogenesis.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040800302
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  • 2
    Digitale Medien
    Digitale Medien
    Concanavalin A and the initiation of thymic lymphoblast DNA synthesis and proliferation by a calcium-dependent increase in cyclic GMP levelIssued as N.R.C.C. No. 14254. (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 84 (1974), S. 445-457 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Exposure of a thymic lymphocyte population (suspended in serum-free synthetic medium) to the phytomitogen concanavalin A (Con A) causes brief (within the first 8 to 12 minutes) rises in the cellular contents of cyclic AMP and cyclic GMP. However, the rise in the cyclic GMP level is calcium (extracellular)-dependent, but the cyclic AMP rise is not. These changes are followed during the next hour by the initiation of DNA synthesis by a large fraction of the lymphoblast subpopulation which, like the preceding cyclic GMP rise, is calcium-dependent. The stimulated lymphoblasts eventually progress into mitosis. Additional observations indicate that Con A operates by sensitizing lymphoblasts to calcium ions which, in turn, cause the initiation of DNA synthesis by a process mediated by cyclic GMP, but not cyclic AMP.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040840312
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  • 3
    Digitale Medien
    Digitale Medien
    The influence of calcium on the cyclic AMP-mediated stimulation of DNA synthesis and cell proliferation by prostaglandin E1Issued as NRCC no. 12621. (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 79 (1972), S. 353-362 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Prostaglandin type E1 (PGE1) rapidly stimulates cyclic AMP formation and the initiation of deoxyribonucleic acid (DNA) synthesis in rat thymic lymphocytes suspended in vitro by reactions which are not affected by wide variations in the extracellular calcium concentration. On the other hand, the operation of the associated reaction(s) responsible for the subsequent progression of the stimulated cells into mitosis is profoundly affected by the extracellular calcium level. If the maximum intracellular cyclic AMP concentration is in the lower range of stimulatory values (e.g., 150 × 10-8 picomoles per cell as produced by an exposure to 0.5 μg of PGE1 per milliliter of medium), an extracellular calcium concentration of 0.5 to 1.0 mM is needed to obtain maximum cell proliferation, but not the maximum stimulation of DNA synthesis. Contrariwise, if the cellular cyclic AMP content is raised to a much higher level (260 × 10-8 picomoles per cell) by exposure to a greater PGE1 concentration (5.0 μg per millilter), cell proliferation is maximally stimulated in calcium-free medium and increasing the extracellular calcium concntration above 0.2 mM actually prevents the stimulation of cell proliferation (but does not affect the stimulation of DNA synthesis). Thus, the ultimate translation of PGE1's early cyclic AMP-mediated reactions into increased cell proliferation is determined by both the intracellular cyclic AMP level and the extracellular calcium concentration.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040790305
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  • 4
    Digitale Medien
    Digitale Medien
    The roles of calcium and cyclic AMP in the stimulatory action of parathyroid hormone on thymic lymphocyte proliferationIssued as NRCC 12299 (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 78 (1971), S. 355-368 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Both the parathyroid hormone (PTH) and the calcium ion increase the cellular content of cyclic adenosine 3′,5′-monophosphate (cyclic AMP), promote the initiation of deoxyribonucleic acid synthesis and stimulate the proliferation of rat thymocytes maintained in vitro. The ability of cyclic AMP to serve as the mediator of the mitogenic actions of both PTH and calcium is established by the fact that cyclic AMP itself stimulates cell proliferation in the absence of PTH and extracellular calcium. Neither PTH nor calcium appear to raise the cellular cyclic AMP level by increasing the nucleotide's synthesis by adenylate cyclase (formerly adenyl cyclase); PTH concentrations as high as 50 μg per ml of medium do not increase the enzyme's activity (in the presence or absence of calcium) and mitogenic calcium concentrations inhibit it. PTH also does not directly affect isolated thymocyte phosphodiesterase, but mitogenic calcium levels inhibit the enzyme's activity. Additional experiments show that it is calcium which raises the cyclic AMP level in cells treated with PTH, and some possible calcium-mediated mechanisms by which the hormone could elevate the cellular cyclic AMP levels are discussed. Thus, the mitogenic action of PTH is primarily mediated by calcium while cyclic AMP is the ultimate implementor of the hormonal action. However, calcium has a dual role and evidence is presented which indicates that besides raising the cellular cyclic AMP level, it also controls the operation of cyclic AMP's mitogenic end-reaction.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040780305
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of tolbutamide on the metabolism of Tetrahymena (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 83 (1974), S. 275-286 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Tolbutamide partially inhibited the growth but increased the glycogen content of Tetrahymena pyriformis in logarithmically growing cultures. Tolbutamide slightly increased 14CO2 production from [1-14C] and [6-14HC] glucose and [2-14C] pyruvate, but had little effect on the oxidation of [1-14C] acetate when any of these substrates were added to the proteose-peptone medium in which the cells had been grown. Measurement of 14CO2 production from [1-14C] and [2-I4C]-glyoxylate showed that this substrate was primarily oxidized via the glyoxylate cycle, with little if any oxidation occurring via the peroxisomal glyoxylate oxidase. Addition of tolbutamide inhibited the glyoxylate cycle as indicated by a marked reduction in label appearing in CO2 and in glycogen from labeled acetate. In control cells, addition of acetate strongly inhibited the oxidation of [2-14C]-pyruvate whereas addition of pyruvate had little effect on the oxidation of [1-14C]-acetate. Acetate was more effective than pyruvate in preventing the growth inhibitory and glycogen-increasing effects of tolbutamide. The data suggest that one effect of tolbutamide may be to interfere with the transfer of isocitrate and acetyl CoA across mitochondrial membranes.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040830215
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  • 6
    Digitale Medien
    Digitale Medien
    The ability of calcium to change cyclic AMP from a stimulator to an inhibitor of thymic lymphoblast proliferationIssued as NRCC 13130. (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 81 (1973), S. 241-250 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Calcium is a major regulator of thymic lymphoblast proliferation in vivo and in vitro. The proliferative activity of the lymphoblasts in thymic lymphocyte (thymocyte) populations in vitro is both constant and low in the presence of calcium concentrations between 0 and 1.0 mM, but higher concentrations increase proliferation by an endogenous cyclic AMP-mediated promotion of the initiation of DNA synthesis.Lower concentrations (10-7 to 10-5 M) of exogenous cyclic AMP (but not 5′-AMP) stimulate lymphoblast proliferation in a low-calcium (0.5 mM) medium, but higher concentrations do not. However, all exogenous cyclic AMP concentrations between 10-7 and 10-3 M (but again not 5′-AMP) block the stimulation of lymphoblast proliferation in a high-calcium (1.5 mM) medium. Exogenous cyclic AMP does not prevent calcium from “activating” lymphoblasts, but it reversibly blocks the reaction responsible for the initiation of DNA synthesis in these stimulated cells. Finally, cyclic AMP's inhibitory action, in contrast to its stimulatory action in low-calcium medium, is not specific for the cyclic nucleotide since a low, non-mitogenic concentration of cyclic GMP also prevents calcium from stimulating DNA synthesis and cell proliferation.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040810212
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  • 7
    Digitale Medien
    Digitale Medien
    Calcium-dependent stimulation by a phorbol ester (PMA) of thymic lymphoblast DNA synthesis and proliferationIssued as NRCC No. 13507. (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 82 (1973), S. 151-156 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: PMA (phorbol myristate acetate, i.e., 12-0-tetradecanoyl-phorbol-13-acetate) a tumor-promoting ester from croton oil, at its most effective concentration of 0.05 μg per milliliter, rapidly (within one hour) induces a large fraction of the lymphoblasts in suspended thymic lymphocyte populations to start making DNA, and these stimulated cells later progress into mitosis. This stimulatory PMA action is probably mediated by calcium because it disappears when calcium is omitted from the medium, and PMA strikingly increases the sensitivity of the lymphoblasts to calcium's stimulatory action.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040820203
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  • 8
    Digitale Medien
    Digitale Medien
    The possible mediation by cyclic AMP of the stimulation of thymocyte proliferation by vasopressin and the inhibition of this mitogenic action by thyrocalcitoninIssued as NRCC 11451. (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 76 (1970), S. 65-76 
    Details
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Lysine vasopressin (antidiuretic hormone), like cyclic adenosine 3',5'-monophosphate (cyclic AMP), rapidly (in less than 1 hour) stimulates the initiation of deoxyribonucleic acid synthesis and thereby increases the flow of cells into mitosis in rat thymic lymphocyte populations in vitro. This mitogenic action of vasopressin, again like that of cyclic AMP, is potentiated by caffeine, an inhibitor of the intracellular phosphodiesterase which catalyzes the degradation of cyclic AMP. On the other hand, vasopressin's mitogenic action (also like that of cyclic AMP) is blocked by imidazole, an activator of cyclic nucleotide phosphodiesterase activity. The hormone, thyrocalcitonin (calcitonin) which is known to block the cyclic AMP-mediated mitogenic effect of parathyroid hormone by interfering with cyclic AMP action, also blocks the mitogenic action of vasopressin. The inhibitory effects of imidazole and thyrocalcitonin on vasopressin's mitogenic action are both overcome by the phosphodiesterase inhibitor, caffeine. It is concluded from these observations that the mitogenic action of vasopressin is mediated by cyclic AMP.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jcp.1040760110
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  • 9
    Digitale Medien
    Digitale Medien
    A gross study of the compartmentalized stomach of two new-world camelids, the llama and guanaco (1971)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 134 (1971), S. 399-423 
    Details
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: The llama and guanaco stomach consisted of three compartments. A transverse pillar divided the large, first compartment into cranial and caudal sacs. Both sacs contained recessed glandular saccules. The saccules in the caudal sac were everted during the gastric contraction cycle. The non-recessed surfaces of this compartment were covered by stratified squamous epithelium.The first compartment communicated on the right with a smaller, reniform second compartment. Except on the lesser curvature, this compartment contained deep cells which were lined by a papillated glandular mucosa.The ventricular groove, defined by a single muscular lip, coursed along the cranial sac of the first compartment, over the lesser curvature of the second compartment, and terminated at the tubular passage to the third compartment.The initial four-fifths of the elongate third compartment contained mucigenous glands like those found in the saccules and cells of the first and second compartment Proper gastric glands and pyloric glands were confined to the terminal one-fifth of the third compartment.Attempts to homologize the compartments of the camelid stomach with those of the Pecora or so-called advanced ruminants were unsuccessful. The results of this study and concurrent physiologic investigations indicated that the processes of ruminant digestion can operate within wide anatomic boundaries, and that the camelid stomach with its extensive glandular mucosa is adapted for greater digestive efficiency than the advanced ruminant stomach.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jmor.1051340403
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  • 10
    Digitale Medien
    Digitale Medien
    Surface pits in the family esocidae.This work was supported by a grant from the Fisheries Research Board of Canada, and grant A-1705 from the National Research Council of Canada.This paper is part of dissertation submitted by the senor author in partial fulfilment of the requirements for a Ph.D. in the Department of Zoology, University of Toronto. I. Structure and types (1973)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 141 (1973), S. 307-320 
    Details
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: In Esox americanus and Esox niger (Esocidae) there are two types of surface pits, sensory and nonsensory. Both types of pits are morphologically very similar and are associated with modified (cardioid) scales. The pits are distinguished by the presence and absence respectively of neuromasts. Ultrastructure of the neuromasts indicates that they are basically similar to previously described neuromasts. However, the hair cells have crystalline-like deposits in the nuclear region. The nonsensory pit contains a small group of distinct epidermal cells, called central cells. These cells occupy a central position in the pit, similar to that of the neuromasts in the sensory pit. The central cells are unlike any cell types described for fishes, and on an ultrastructural basis no function can be ascribed to them and the significance of the nonsensory pit is unknown.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/jmor.1051410306
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