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  • Life and Medical Sciences  (4)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 115 (1964), S. 419-445 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 70 (1967), S. 179-186 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous studies have demonstrated that a consistent maximum number of polytenic replication cycles occurs in the salivary gland nuclei of a wild-type strain of D. melanogaster. Since that number is achieved within the larval period, the DNA synthesis of the prepupal period is believed to be that of propagation of the final cycle. Photometric determinations have been made, in this study, of the salivary gland nuclei of larvae and prepupae of the tu-h strain in which the larval period has been extended as a consequence of delay or failure of pupation. The DNA values indicate that a higher maximum number of polytenic replications is achieved in such nuclei. It is inferred, thereby, that initiation of polytenic replication is a function of the larval state and, since it is terminated by the intervention of metamorphosis, a hormonal dependence is suggested.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 70 (1967), S. 187-190 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A comparison has been made, by Feulgen photometry, of the polytene nuclei of the salivary glands of a wild-type strain of Drosophila melanogaster grown at 17°C and 25°C, respectively. Despite the fact that the time period of the larval stage was more than doubled at the lower temperature, the DNA values were the same in magnitude and similar in distribution of replication classes at each of the stages studied. The data have been interpreted as indicating that, so long as the larval state prevails, initiation of polytenic replication occurs upon completion of the previous cycle.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 18 (1987), S. 179-190 
    ISSN: 0148-7280
    Keywords: phosphorylated protamines ; sperm chromatin condensation ; spermiogenesis ; motile spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The basic nuclear proteins of a fraction of elongating spermatids from human tests and of a fraction of motile spermatozoa from the ejaculate, separated by ion-exchange chromatography, were compared. Analysis by acetic acid-urea polyacrylamide gel electrophoresis (PAGE) showed that, in both fractions, four proteins of lower mobility were coeluted with protamine 1 by 23% guanidinium chloride (GuCI) while protamine 2 alone was eluted by 50% GuCI. Treatment with alkaline phosphatase identified those four proteins as phosphorylated protamines, and cyanogen bromide (CNBr) treatment of the dephosphorylated protamines distinguished them as variants of protamine 2 and not of protamine 1. Thus far, phosphorylated forms of protamine 1 have not been detected in either spermatids or spermatozoa. Those observations indicate that protamine 2 functions in the cycle of phosphorylation-dephosphorylation, which is essential to the process of sperm chromatin condensation, while the role of protamine 1 in human spermiogenesis is not yet defined.The presence of phosphorylated protamine in motile, presumably mature spermatozoa appears to be characteristic of human sperm but not of the sperm of other mammals and is probably the basis for the heterogeneity of chromatin condensation frequently observed in human spermatozoa.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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