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  • 1
    Electronic Resource
    Electronic Resource
    Spermatogenesis and spermiogenesis in Ascaris lumbricoides Var. suum (1977)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 154 (1977), S. 317-337 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Reorganization of the prophase I nucleus marks the beginning of the first meiotic division. A pair of centrioles is present at each pole at metaphase I and mitochondria are not observed in the spindle area. A chromosomal pellicle, which resembles a kinetochore plate but has no apparent association with microtubules, surrounds each autosome at metaphase I and II. The sex body lags behind the autosomes at anaphase I and segregates differentially to one daughter cell. Mitochondria and a pair of centrioles are present in the spindle during the second meiotic division. Localized condensation of chromatin and fusion of the condensed chromatin of the secondary spermatocyte telophase nucleus results in a compact spermatid nucleus. Loss of spermatid cytoplasm is effected by the ejection of a cytophore vesicle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051540302
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  • 2
    Electronic Resource
    Electronic Resource
    Chromatin diminution in early embryogenesis of Ascaris lumbricoides L. var. suum (1977)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 152 (1977), S. 141-151 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The occurrence of chromatin diminution in early Ascaris lumbricoides L. embryos has been studied in detail, and it is shown that it is possible to preselect three characteristic types of mitoses: pre-diminution, diminution, and post-diminution mitosis. The first three embryonic mitotic divisions are of the pre-diminution type. Chromatin diminution occurs after the third mitosis, but there is a variation from embryo to embryo as to whether or not chromosomal diminution occurs during the fourth, fifth, and six divisions. However, the seventh embryonic division, which gives rise to an eight-cell embryo, always exhibits chromatin diminution. Subsequent mitoses of somatic cells already in the diminished state are of the post-diminution type of mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051520202
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  • 3
    Electronic Resource
    Electronic Resource
    Oocyte development in the mouse: An ultrastructural comparison of oocytes isolated at various stages of growth and meiotic competence (1978)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 156 (1978), S. 209-235 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: An ultrastructural comparison of mouse oocytes isolated at various stages of growth and meiotic competence has been carried out. Progressive changes in the nucleoli, ribosomes, mitochondria, endoplasmic reticulum, Golgi complex, and other organelles and inclusions of the oocyte have been examined as a function of oocyte size by transmission electron microscopy. The observations presented support the idea that growth of the mammalian oocyte involves not just tremendous enlargement of the cell, but extensive alterations in its overall metabolism as reflected in the ultrastructure of the oocyte at various stages of growth.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051560206
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence contrary to the protein error hypothesis for in vitro senescence (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 87 (1976), S. 3-13 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose-6-phosphate dehydrogenase (G-6-PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 ± 1%, S.E.), in comparison with that in 19 old cultures (4.9 ± 1%, S.E.). Old cultures had ceased active cell division (49-60 doublings); DNA replication, measured by [3H] thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5-22 doublings) had a [3H] thymidine labeling index of 75-85%. Titration of G-6-PD activity in extracts of young and old cells with neutralizing antibody directed specifically against G-6-PD failed to detect an increment of enzymatically defective G-6-PD in old cells. The thermostability studies were capable of detecting altered G-6-PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G-6-PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G-6-PD from the thermolabile mutant and G-6-PD inactivated with N-ethylmaleimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040870103
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  • 5
    Electronic Resource
    Electronic Resource
    Growth and biochemical characteristics of a detachment variant of CHO cellsBy acceptance of this article for publication, the publisher recognizes the Government's (license) rights in any copyright and the Government and its authorized representatives have unrestricted right to reproduce in whole or in part said article under any copyright secured by the publisher. (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 90 (1977), S. 375-385 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A variant subline of Chinese hamster cells (line CHO) was isolated that had increased resistance to detachment from the substratum. Comparisons between parental and variant cells of the complex carbohydrates liberated during trypsin detachment showed that the variant cells synthesized little or no hyaluronic acid. These cells also had reduced amounts of other complex carbohydrates in the cell periphery. However, parental and variant cells did not differ in morphology, growth control, or cyclic AMP concentration. Profound changes in the physical and chemical nature of the cell periphery, in themselves, evidently are insufficient to cause changes in many aspects of cell behavior.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040900302
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of dopamine on prostaglandin E1-elicited electrophysiological changes in a neuronal somatic cell hybrid (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 98 (1979), S. 11-16 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: PGE1 elicited a slow, dose-dependent membrane depolarization with an increase in membrane conductance in the somatic cell hybrid TCX11. The ED 50 was 1-2 × 10-8 M with maximal responses at 1-5 × 10-7 M. Dopamine (DA) reversed the effect of PGE1 and caused the membrane potential and resistance to return to control levels. Chronic exposure of cells (measured in minutes) to DA alone would not cause this hyperpolarization. 5-HT was also tested and failed to consistently reverse the PGE1 effects. Chlorpromazine antagonized the effects of DA on the PGE1 response. The electrophysiological results reported here using TCX11 cells are discussed in light of previously reported biochemical results describing interactions of PGE1 and DA, and the electrophysiological effects of DA alone.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040980103
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  • 7
    Electronic Resource
    Electronic Resource
    Cell cycle control by Ca++-ions in mouse 3T3 cells and in transformed 3T3 cells (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 98 (1979), S. 31-39 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Total cellular calcium levels do not change when 3T3-4a cells stop proliferating due to serum depletion, or when serum-arrested quiescent cells are incubated for up to 44 hours in calcium-deficient medium (∼10 μM Ca++). Upon stimulation with dialyzed serum cells enter S and progress through at least one cycle even at extremely low calcium levels in the culture medium (≥10 μM). Cells divide until a final cell density is attained which is proportional to the calcium concentration in the medium and cells reversibly arrest in G1. Cells which arrested in G1 in medium containing ≤26 μM Ca++ in the presence of excess serum can be stimulated to enter S in response to added calcium after a prereplicative phase of 14 to 16 hours. Serum does not affect 45Ca-uptake in these cells. Benzo[a]pyrene transformed 3T3 (BP3T3) cells have a 100-200 times lower Ca++-requirement than 3T3 cells but arrest in G1 at low Ca++ levels. In contrast, SV40-virus transformed 3T3 (SV3T3) cells that grow without restriction in monolayer cultures have even lower Ca++-requirements for growth than BP3T3 cells and have no Ca++-sensitive restriction point. Therefore, 3T3 and BP3T3 cells have retained the capacity to sense intracellular Ca++-pool sizes and to arrest in G1 at subthreshold cellular Ca++-levels.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040980105
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  • 8
    Electronic Resource
    Electronic Resource
    Growth control in primary fetal rat liver cells in culture (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 85 (1975), S. 113-123 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Primary fetal rat liver cells cultured in medium deficient in, but not free of, arginine in the presence of dialyzed fetal calf serum grow until the final cell density is attained and cells become quiescent in the G0 phase of the cell cycle. When growing cells are transferred into arginine free medium, cells become reversibly arrested in G0. Fetal rat liver cells can be induced to synthesize DNA by addition of high levels of arginine to serum free medium. Low arginine levels in the culture medium do not induce cell growth unless serum is present. Serum stimulates arginine uptake in fetal rat liver cells suggesting that serum growth factor(s) act by increasing intracellular arginine levels high enough to initiate the growth cycle. Fractionation of fetal calf serum by gel filtration on G-200 Sephadex yields a partially purified arginine uptake stimulating activity which is eluted from the column in the same fractions that contain fetal rat liver cell growth promoting activity. Insulin induces DNA synthesis in quiescent fetal rat liver cells. Glucagon reverses the stimulatory effects of insulin. N6,O2-Dibutyryl adenosine 3′:5′-cyclic monophosphoric acid (But2c-AMP) (10-4 M) and theophilline (10-3 M) inhibit arginine uptake and the initiation of DNA synthesis by serum. The role of arginine in the control of DNA synthesis in fetal rat liver cells and the mechanism of action of serum growth factors are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040850112
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  • 9
    Electronic Resource
    Electronic Resource
    Purine uptake by azaguanine-resistant chinese hamster cells (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 89 (1976), S. 209-217 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In this study the resistance of a number of lines of Chinese hamster ovary cells to azaguanine is examined. Those which are drug resistant by virtue of a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT) fail to take up any exogenous hypoxanthine or azaguanine. A second class of drug resistant cells which grow in the reverse selective HAT medium and have levels of HPRT in the range of the wild type parent line take up these purines at lower rates than the non-resistant cells and incorporate smaller amounts of them into trichloracetic acid-insoluble constituents. The results suggest that their basis for resistance resides in lowered incorporation of azaguanine into DNA and RNA, possibly due to a mofified HPRT molecule which accepts hypoxanthine, but not azaguanine as a substrate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040890204
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of a depolarizing dopamine response in a vertebrate neuronal somatic cell hybrid (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 91 (1977), S. 103-118 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The physiology and pharmacology of a depolarizing dopamine response was studied in the vertebrate neuronal somatic cell hybrid TCX11. The average resting membrane potential was -50 mV (S.D. = ±7) with a membrane resistance of 40.5 mOhms (S.D. = ±8) as determined from intracellular recordings. Depolarizing current pulses did not elicit an action potential. Cells displayed a linear current-voltage relationship when artificially depolarized up to +30 mV. Iontophoretically applied dopamine elicited a depolarizing response with a conductance increase and a reversal potential of -15 mV (S.D. = ±4.7). Experiments altering medium ion concentrations demonstrated the conductance increase was to sodium and most likely potassium. The dopamine agonist ET495 (Piribedil) and the analogue epinine mimicked dopamine, while closely related biogenic amines, with the exception of noradrenaline, elicited no response. Apomorphine also elicited a depolarizing response but was much less efficacious than Piribedil. Noradrenaline was less potent than dopamine and appeared to act at the dopamine receptor. Methylation (3-methoxytyramine) or absence of the 3-hydroxy group (tyramine) of dopamine resulted in total loss of activity. The dopamine antagonists chlorpromazine, trifluoperazine, promazine, and bulbocapnine reversibly blocked the response to dopamine at medium concentrations less than 5 μM. The adrenergic antagonist phentolamine blocked the response while phenoxybenzamine only reduced the response at higher concentrations. The acetylcholine antagonists α-bungarotoxin, hexamethonium, and scopolamine did not block the dopamine response. Both d-tubocurarine and atropine acted as antagonists.Collectively, these results demonstrate the presence of a receptor on a cultured cell line that is specific for dopamine, mediates a depolarizing and conductance increase response to dopamine, and displays the pharmacology most closely associated with dopamine receptors.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1040910111
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