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  • 1
    Electronic Resource
    Electronic Resource
    Occurrence of preantral intra-ovarian oocyte release in the rat and the Syrian hamster (Mesocricetus auratus) (1982)
    Springer
    Anatomy and embryology 165 (1982), S. 169-175 
    Details
    ISSN: 1432-0568
    Keywords: Ovary ; Oocyte ; Follicles ; Rat ; Syrian Hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Serial sections of 62 rat ovaries and 66 ovaries from Syrian hamsters (Mesocricetus auratus) have been examined by light microscopy. The relative and absolute percentage of preantral intra-ovarian oocyte release (PIOR) was recorded. PIOR was incomplete when the rupture of the basal membrane was not followed by the release of the oocyte from its preantral follicle into the ovarian stroma; conversely, a PIOR was regarded to the complete if the oocyte was released from the preantral follicle into the adjacent stroma. PIOR occurred in 23% of rat ovaries and in 32% of hamster ovaries; meiosis was not resumed. In rat ovaries the frequency of complete PIOR was 71%; the oocyte disappeared quickly after its release and herniated granulosa cells could invade capillaries. By contrast, incomplete PIOR was prevalent in hamster ovaries (67%); oocytes survived in the interstitial cortical tissue after the disappearance of their granulosa and theca cells (“free oocytes”). It is concluded that PIOR reflects the onset of follicular atresia and that different local factors are probably responsible for species differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305475
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preantral intra-ovarian oocyte release in the white-footed mouse, Peromyscus leucopus (1982)
    Springer
    Cell & tissue research 226 (1982), S. 461-464 
    Details
    ISSN: 1432-0878
    Keywords: Ovary ; Oocyte ; Oocyte release ; Corpus luteum ; Peromyscus leucopus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Adult white-footed mice, Peromyscus leucopus, were kept either in long photoperiod (LP; LD 16:8) or in short photoperiod (SP; LD 8∶16) for six weeks. Ovaries were serially sectioned and examined histologically. Preantral follicles were observed to release their oocyte into the ovarian stroma. This phenomenon is termed “preantral intra-ovarian oocyte release (PIOR)”. The first step in PIOR appeared to be the interruption of the basal membrane and the thecal layer. PIOR was considered incomplete when the oocyte was retained in the follicular compartment. PIOR was complete when granulosa cells were seen to be herniated and the oocyte released either into the interstitial cortical tissue or into a corpus luteum. During incomplete PIOR signs of atresia were increased, whereas during complete PIOR they were decreased. Resumption of meiosis was not seen. PIOR was observed in 19.5 % of the ovaries after LP and in 18.8 % of the ovaries after SP. PIOR is regarded as a sign of follicular atresia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218373
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Regularly scheduled, day-time, slow-onset 60 Hz electric and magnetic field exposure does not depress serum melatonin concentration in nonhuman primates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 111-118 
    Details
    ISSN: 0197-8462
    Keywords: baboon (Papio cynocephalus) ; cannula ; electric field ; magnetic field ; pineal gland ; radioimmunoassay ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Experiments conducted with laboratory rodents indicate that exposure to 60 Hz electric fields or magnetic fields can suppress nocturnal melatonin concentrations in pineal gland and blood. In three experiments employing three field-exposed and three sham-exposed nonhuman primates, each implanted with an indwelling venous cannula to allow repeated blood sampling, we studied the effects of either 6 kV/m and 50 μT (0.5 G) or 30 kV/m and 100 μT (1.0 G) on serum melatonin patterns. The fields were ramped on and off slowly, so that no transients occurred. Extensive quality control for the melatonin assay, computerized control and monitoring of field intensities, and consistent exposure protocols were used. No changes in nocturnal serum melatonin concentration resulted from 6 weeks of day-time exposure with slow field onset/offset and a highly regular exposure protocol. These results indicate that, under the conditions tested, day-time exposure to 60 Hz electric and magnetic fields in combination does not result in melatonin suppression in primates. © 1995 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250160711
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Rapid-onset/offset, variably scheduled 60 Hz electric and magnetic field exposure reduces nocturnal serum melatonin concentration in nonhuman primates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 16 (1995), S. 119-122 
    Details
    ISSN: 0197-8462
    Keywords: baboon (Papio cynocephalus) ; intermittent ; irregular ; pineal gland ; transient ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Experiments with rodents indicate that power-frequency electric field (EF) or magnetic field (MF) exposure can suppress the normal nocturnal increase in melatonin concentration in pineal gland and blood. In a separate set of three experiments conducted with nonhuman primates, we did not observe melatonin suppression as a result of 6 weeks of day-time exposure to combined 60 Hz electric and magnetic fields (E/MF) with regularly scheduled “slow” E/MF onsets/offsets. The study described here used a different exposure paradigm in which two baboons were exposed to E/MF with “rapid” E/MF onsets/offsets accompanied by EF transients not found with slowly ramped E/MF onset/offset; profound reductions in nocturnal serum melatonin concentration were observed in this experiment. If replicated in a more extensive experiment, the observation of melatonin suppression only in the presence of E/MF transients would suggest that very specific exposure parameters determine the effects of 60 Hz E/MF on melatonin. © 1995 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250160712
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    Paper (German National Licenses)
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