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  • 1
    Electronic Resource
    Electronic Resource
    Time Course and Localization of the Effects of Estrogen on Glutamic Acid Decarboxylase Activity (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 34 (1980), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Two approaches were used in an attempt to characterize the effect of estrogen on glutamic acid decarboxylase (GAD) [EC 4.1.1.15] activity in ovariectomized rats. In the first experiment, estradiol-17β (E2) was unilaterally implanted in one of five different brain areas. After 3 days of estrogen exposure, the animals were sacrificed, and GAD activity in the substantia nigra (SN) and ventral tegmental region (VTR) was measured. Estrogen implanted into the preoptic area and the ventromedial nucleus was ineffective, as were implants of cholesterol, regardless of implant site. However, GAD activity was decreased in the SN when E2 was implanted into the caudate nucleus or amygdala and in the VTR when implanted into the nucleus accumbens septi. Furthermore, this decrease in GAD activity occurred only in the implanted side. In the second experiment, the time course of changes in GAD activity was measured in ovariectomized rats given a single systemic injection of either 8μg estradiol benzoate (EB) or oil. Rats were sacrificed at 0, 12, 29, or 53 h postinjection. It was found that GAD activity in the SN was maximally suppressed 29 h after EB, whereas decreased GAD activity in the VTR was apparent 12 h after EB but had returned to normal by 29 h. Oil injections had no significant effect on GAD activity. These results suggest that there may be two separate and distinct γ-aminobutyric acid pathways, which are differentially responsive to estrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1980.tb09648.x
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  • 2
    Electronic Resource
    Electronic Resource
    NEUROENDOCRINE FACTORS IN EXPERIMENTAL CARCINOGENESIS (1969)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 164 (1969), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1969.tb14066.x
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  • 3
    Electronic Resource
    Electronic Resource
    Unilateral lesions of the hamster suprachiasmatic nuclei: evidence for redundant control of circadian rhythms (1984)
    Springer
    Journal of comparative physiology 154 (1984), S. 221-232 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Several properties of vertebrate circadian rhythms can be attributed to the behavior of an underlying pacemaker system which is composed of two separate but mutually interacting circadian oscillators. As originally formulated, the model for such a pacemaker system proposed that two oscillators or populations of oscillators have different properties, specifically in their responses to light (Pittendrigh 1974; Pittendrigh and Daan 1976b). We have tested the proposition that the right and left suprachiasmatic nuclei (SCN) of the golden hamster contribute in different ways to the regulation of circadian rhythmicity by measuring the wheel-running activity rhythms of hamsters with lesions to either the right or left SCN. Although effects of unilateral or other partial SCN lesions on pacemaker properties were observed, these effects were not different in hamsters receiving right- or left-side lesions. More specifically: (1) free-running period (τ) in constant light was shorter in lesioned hamsters irrespective of the side lesioned (Fig. 3a), and the total amount of SCN destruction was found to correlate with τ (Fig. 4). (2) Phase-angle difference (Ψ) of some lesioned hamsters (both right- and left-side) during entrainment to L∶D, 14∶10 was significantly more positive than that of controls (Fig. 3b). (3) The rate of phase-shift following a shift of the light/dark cycle was not different in hamsters with right- or left-side lesions (Fig. 3c). And (4) the simultaneous expression of different circadian periods, similar to ‘splitting’, was observed in hamsters with unilateral lesions (Fig. 5). It is concluded that the right and left SCN are similar in their contributions to the control of circadian rhythmicity and that there is as yet no evidence for the permanent loss of multioscillator properties resulting from the destruction of only one of the two SCN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00604987
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  • 4
    Electronic Resource
    Electronic Resource
    Development of hamster circadian rhythms: Role of the maternal suprachiasmatic nucleus (1988)
    Springer
    Journal of comparative physiology 162 (1988), S. 601-610 
    Details
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During development, the circadian rhythms of rodents become entrained to rhythmicity of the mother. Rhythms in behavior and in neuroendocrine function are regulated by a circadian pacemaker thought to be located within the suprachiasmatic nucleus (SCN) of the hypothalamus. Evidence indicates that this pacemaker begins to function and to be entrained by maternal rhythms before birth. Although the maternal rhythms which mediate prenatal entrainment of the fetal circadian pacemaker have not been identified, it is likely that they are regulated by the maternal SCN. The role of the maternal SCN in entrainment of the offspring was examined in Syrian hamsters (Mesocricetus auratus) by measuring the activity/rest rhythms of pups. Using the synchrony among the rhythms of pups within a litter as an indication that the pups had been entrained, the effect on entrainment of ablating the maternal SCN was determined. Lesions of the maternal SCN which were performed early in gestation (day 7) and which destroyed at least 75% of the SCN were found to disrupt the normal within litter synchrony among pups, indicating interference with the normal mechanism of entrainment. The effect of lesions on day 7 of gestation could mean that the maternal SCN is important for entrainment of the pups before birth, after birth, or during both of these times. To determine if the maternal SCN is specifically important for prenatal entrainment, lesions were performed two days before birth on day 14 of gestation. Lesions of the maternal SCN on day 14 were not as disruptive as were lesions on day 7. This suggests that the maternal SCN is important between days 7 and 14 of gestation and that the synchrony normally observed at weaning is already established, in part, on or before day 14 of gestation. This further suggests that an entrainable circadian pacemaker is present in the fetus only two weeks after fertilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01342635
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructural differentiation of Leydig cells in the fetal and postnatal hamster testisSupported in part by U.S.P.H.S. grants HD 05727 and HD 01182. (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 178 (1974), S. 551-565 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Leydig cells appear in the hamster testis between 12 and 13 days gestation. The cells are round to oval, with prominent lipid droplets, abundant smooth endoplasmic reticulum, large mitochondria with tubular cristae and well developed Golgi complexes. Cells of this type are found in pairs and groups around interstitial blood vessels during the last three days of gestation and up to the fourth day after birth, when regressive changes begin to appear. During the second postnatal week, most cells in the interstitial regions are undifferentiated, with only a few scattered partially differentiated Leydig cells remaining. The time during which fully differentiated Leydig cells are present encompasses the period of sexual differentiation of the reproductive ducts and the critical period for differentiation of sexual behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091780304
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  • 6
    Electronic Resource
    Electronic Resource
    Localization of the neural control of luteinization in the feminine male rat (FALE)Supported by grant HD-01182 from the U. S. Public Health Service. (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 157 (1967), S. 63-69 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Castration of the male rat during the first three days of life allows retention of the cyclic pattern of gonadotrophin release with which the male is born. Since the neonatally castrated male shares several endocrine characteristics with the female, the terms feminine male or FALE have been employed to identify these animals. Twenty-seven of 28 FALES developed corpora lutea (CL) in ovarian transplants provided no other treatment was initiated. In contrast, exposure to constant illumination, suprachiasmatic lesions, or transection of anterior hypothalamic pathways prevented CL formation in 18 of 20 FALES. These findings support the concept that the preoptic-anterior hypothalamic region is an essential component of the neural mechanism which regulates the cyclic luteinization of ovarian grafts in the FALE. Since the FALE is a male rat in which differentiation has not been permitted to occur, it is suggested that sexual differentiation of the normal male hypothalamus consists of an alteration in function of this preoptic system.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091570110
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  • 7
    Electronic Resource
    Electronic Resource
    Localization of hypothalamic regulation of anterior pituitary functionOriginal research from the author's laboratory supported by grant HD-01182 from the USPHS, and by a grant from the Ford Foundation. (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 129 (1970), S. 219-222 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001290210
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