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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 2 (1979), S. 125-135 
    ISSN: 0148-7280
    Keywords: oogenesis ; oocyte growth ; Xenopus laevis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: When female Xenopus laevis are injected with [3H]-vitellogenin or [14C] N-acetyl glucosamine, most of the labeled material becomes associated three days later with oocytes having a diameter of 0.9-1.1 mm; smaller and larger oocytes are less labeled. With time, the pattern of labeling shifts to larger oocytes, indicating that those oocytes initially labeled continue to grow. We have measured such shifts as a function of time to provide estimates for oocyte growth rates from the end of stage III (diameter = 0.6 mm) to stage VI (diameter = 1.2 mm). The total time required for oocytes to progress through this size increase is 16-24 weeks in unstimulated females and 9-12 weeks in human chorionic gonadotropin (hCG)-stimulated females. The fastest rate of growth occurs from mid-stage IV (approximately 0.8 mm diameter) until midstage V (1.2 mm diameter), which corresponds to the period of most pronounced vitellogenin uptake. The relative proportion of oocytes within this size range is also reduced, as predicted under steady-stage conditions. Evidence is also presented which indicates that the steady-state level of full-grown oocytes is maintained by a combination of replenishment and atresia. These results provide the first description of the kinetics of oocyte growth in X laevis females maintained under normal laboratory conditions and should be useful for any considerations of macromolecular events occurring during oogenesis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 101-112 
    ISSN: 0197-8462
    Keywords: 60-Hz electric fields ; rats ; behavior ; teratology ; growth ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A series of three experiments was performed to determine the effects of 30-day exposures to uniform 60-Hz electric fields (100 kV/m) on reproduction and on growth and development in the fetuses and offspring of rats. In the first experiment, exposure of females for 6 days prior to and during the mating period did not affect their reproductive performance, and continued exposure through 20 days of gestation (dg) did not affect the viability, size, or morphology of their fetuses. In the second experiment, exposure of the pregnant rat was begun on 0 dg and continued until the resulting offspring reached 8 days of age. In the third experiment, exposure began at 17 dg and continued through 25 days of postnatal life. In the second and third experiments, no statistically significant differences suggesting impairment of the growth or survival of exposed offspring were detected. In the second experiment, a significantly greater percentage of the exposed offspring showed movement, standing, and grooming at 14 days of age than among-sham-exposed offspring. There was a significant decrease at 14 days in the percentage of exposed offspring displaying the righting reflex in the second experiment and negative geotropism in the third experiment. These differences were all transient and were not found when the animals were tested again at 21 days of age. Evaluation of the reproductive integrity of the offspring of the second experiment did not disclose any deficits.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 40 (1995), S. 481-489 
    ISSN: 1040-452X
    Keywords: Xenopus oocyte ; Interspersed RNA ; Translation ; Oligodeoxynucleotides ; RNA binding protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: It has been shown that about two thirds of Xenopus oocyte or sea urchin egg cytoplasmic poly(A)+ RNA contains interspersed repetitive sequences. The functional significance of this interspersed RNA has remained unknown. Here the function of a subfamily of interspersed RNA (XR family; McGrew and Richter, 1989: Dev Biol 134:267-270) in Xenopus oocytes was studied. We found that the elimination of T7 XR (one of the two complementary strands of the XR repeat) interspersed RNA by complementary oligodeoxynucleotides significantly inhibited protein synthesis. On the other hand, the injection of in vitro synthesized T7 XR RNA stimulated translation. Moreover, the insertion of the T7 XR RNA sequence into globin mRNA repressed the translation of the globin mRNA. In order to explain these results, we analyzed interactions between the XR interspersed RNA and oocyte proteins. We found that the major XR RNA binding proteins were p56 and p60, which could be the known mRNA “masking” proteins that bind mRNA and inhibit translation. Further, a 42 kD protein has been identified that appears to bind T7 XR RNA relatively specifically, although it interacts with mRNA with a lower affinity. Based on all of these data, we have proposed that interspersed RNA may be involved in regulating translation by competing with mRNA to interact with certain proteins that can regulate translation. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 77 (1971), S. 61-70 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Full-grown ovarian oocytes removed from non-hormone-treated Rana pipiens females exhibit a low level of protein synthesis, the rate of which is dependent upon the ionic environment. The highest rates of protein synthesis in these oocytes are obtained in media containing either a divalent cation (Ca++ or Mg++) or high levels of K+. The dependence of protein synthesis on ionic environment persists through about the first 18-24 hours of maturation (at 18°C). Normal maturation of oocytes in vitro also has specific ionic requirements for the first 24 hours. In this case, the process requires high ionic strength (T/2 = 1.0-1.2) and divalent cations. The kinetics of K+ exchange suggest that K+ exists in the ovarian oocyte in two compartments; one in equilibrium with the exogenous medium and freely exchangeable; the other in equilibrium with the exogenous medium and freely exchangeable; the other in equilibrium with the first internal compartment and only very slowly exchangeable. The slowly exchangeable (bound) compartment contains about 95% of all endogenous K+. In hormone stimulated oocytes, the kinetics of K+ exchange are essentially the same. Oocyte adaptation to ionic environment is discussed as a possible regulatory mechanism during maturation.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 80 (1972), S. 339-345 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Although it is well known that thymus function changes with age, it is not known whether these changes are associated with specific thymocyte populations. Since one criterion of specificity is cell size, we studied the size distribution of thymocytes from mice 0.5 days to 30.5 months of age. Body weight, thymus weight, and thymocyte yield were also measured. The mean cell volume of thymocytes from 8.5 to 13 week old mice was 326 μ3, with two detectable subpopulations. Mean thymocyte size was found to change with age. During the first postnatal week, the mean cell volume of the whole thymocyte population increased from 200 to 350 μ3, and the percentage of large cells increased greatly and constituted 90% of the whole population at four days of age. A rather slow decline in mean cell volume with some fluctuation occurred throughout the remaining life span, and at 30.5 months the mean had dropped to about 190 μ3. We suggest on the basis of these data that large thymocytes are involved in the contribution of the thymus to early postnatal development of the immune system and that the age-related functional capacity of the thymus is related to the size of the thymocyte population.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 121 (1984), S. 13-20 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Hemopoietic stem cells may give rise to progeny like themselves or undergo determination; this event is followed by a series of maturation divisions ending in proliferatively inert but functional cells. In normal hemopoiesis and acute leukemia stem cell renewal is not exact; proliferative capacity is lost gradually. As a consequence, clonal populations cannot be continued indefinitely. Postdeterministic differentiation normally leads to cellular diversity; following transformation this diversity is increased, with the production of blast cells together with one or more myelopoietic lineage. The blasts are heterogeneous both in their proliferative capacity and their phenotypes, as determined using immunologically defined markers. Both self-renewal and determination are considered to be irreversible in vivo. By contrast, in continuous myelopoietic cell lines self-renewal is sufficiently precise to confer immortality on the populations. Furthermore, both determination and renewal may in some instances be reversible. The differences between normal or leukemic hemopoiesis in vivo and continuous lines in culture limits the value of the latter for studies of normal blood formation or the clonal hemopathies.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 113 (1982), S. 103-111 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 127 (1986), S. 229-236 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Four T-cell and two B-cell lines from patients with lymphoblastic leukemia were examined with a panel of monoclonal antibodies for a variety of lineage and differentiation stage-associated antigens during growth in liquid suspension. In five of the lines, markers normally associated with the granulopoietic lineage were found and the level of expression of these markers varied during culture. The sixth line, MOLT-3, was examined in more detail. Using clonal selection it was found that phenotypic heterogeneity could readily be obtained and that subclones could be acquired that expressed a wide range of markers, typically in reproducible kinetic patterns, that were not detected on the parent clone. Previous results were confirmed showing that treatment with the drug 5-azacytidine (5-aza) prior to selection promoted the expression of the granulopoietic lineage associated antigen 80H.5 on MOLT-3 subclones; however, treatment with 5-aza appeared to inhibit substantially the expression of other novel markers by subclones following a second selection compared to untreated controls. It appears that the expression of markers normally associated with other lineages on leukemic lymphoblasts (lineage infidelity) may be characteristic of such lines and that phenotypically variant subclones expressing lineage infidelity can readily be obtained by clonal selection.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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