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  • 1
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In a previous report (Zenzes et al., 1978 b) it was shown that dissociated ovarian cells of newborn rats in vitro, if exposed to H-Y antigen, reorganize into testicular structures. The current study was designed to see whether this morphological conversion also results in a functional conversion. The LH/hCG receptor was used as a parameter characteristic for the newborn testis, but not for the newborn ovary. In the converted ovary, the LH/hCG receptor becomes detectable a few hours after onset of the culture and remains continuously present afterward. The appearance of this receptor may be due to a hormone-like action of H-Y antigen.
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  • 2
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The Ag-AS method, developed by Goodpasture and Bloom (1975) stains transcriptionally active nucleolus organizer regions (NORs) on the chromosomes and in the interphase nuclei. Metaphases and interphase nuclei of early mouse embryos (unfertilized eggs, pronucleus stages, 2-, 4-, 8-cell stages, and morulae) were subjected to silver-staining. First staining of a single chromosome bearing an NOR was observed at the 2-cell stage. At the 4-cell stage 4–6 chromosomes, and at the 8-cell stage invariably all the 6 chromosomes known to bear NORs, respond positively to silver-staining. These results indicate that during mouse embryogenesis ribosomal RNA genes start to function at the 2-cell stage. The polar body does not respond to silver-staining, which supports the view that the polar body genome remains inactive.
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Pre- and postmeiotic stages of male gametogenesis of 10 different vertebrate species belonging to mammals, birds, amphibians, and fishes were subjected to the Ag-AS staining technique (Goodpasture and Bloom, 1975). A uniform pattern of silver-staining is observable during spermatogenesis of the different vertebrate species. Silver-staining is present in spermatogonia and during the whole period of meiotic prophase, but totally absent during diakinesis and metaphase II of meiosis. In early spermatids silver-staining reappears and only disappears around the beginning of elongation of the spermatid nucleus. Since the Ag-AS technique is believed to stain only transcriptionally active nucleolus organizer regions, our findings indicate that ribosomal RNA genes become reactivated in the haploid spermatid.
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  • 4
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary While it has been shown previously (Zenzes et al., 1978; Ohno et al., 1978) that when dissociated testicular cells are exposed to anti-H-Y antiserum in vitro they are prevented from reorganizing into testicular structures, forming ovarian follicular structures instead, the most conclusive evidence for the action of H-Y antigen would be the conversion of ovarian cells into testicular organization. Testing for H-Y antigen of the medium collected from cultivated testicular cells revealed a positive reaction. Dissociated ovarian cells of newborn rats cultivated in this medium reorganize into testicular structures. It is concluded that H-Y antigen is responsible for this histomorphologic change.
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  • 5
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Silver-staining in the nuclei and chromosomes of spermatogenesis of four species of mammals (Man, Mus musculus, Rattus norvegicus, and Cavia cobaya) was investigated qualitatively and quantitatively. These species show a very similar pattern of activity of the nucleolus organizer regions (NORs) during the various stages of spermatogenesis. Silver precipitates are detectable in growing spermatogonia and up until the pachytene stage of meiotic prophase. During the meiotic metaphases I and II and during interkinesis silver-stainability disappears completely. A resumption of silverstainability occurs in round spermatids indicating a postmeiotic reactivation of NORs. This process does not persist beyond the early elongation phase. The quantitative determination of the silver-covered areas in relation to the total nuclear areas reveals minor differences between the species investigated with regard to the times and extents of maximum activation. The known localizations of the NORs in the karyotypes of the species investigated was confirmed using metaphase-preparations derived from somatic tissues.
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  • 6
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The g-factors of the 11/2− states in145, 147, 149Eu were measured by the TDPAD method in metallic Sm-targets. The temperature dependence of the paramagnetism in the system145EuSm follows strictly a Curie-Weiß law Beff=B0[1+¯C/(T-θ)] with C=−50(2)K and θ=−29(5)K. Extrapolation to T→∞ yields g(145Eu)=+1.356(8), g(147Eu)=+1.28(1) and g(149Eu)=+1.27(5). In addition, the quadrupole coupling constantν Q=12.5(5) MHz, and a lower limit for the paramagnetic relaxation time τ = 1 us was determined at room temperature for the 11/2− state of145Eu in Sm. Extensive studies of the anomaly of magnetic moments in the vicinity of the closed neutron shells N=50 and N=126 have unambiguously revealed an anomaly of the proton gl factor of δgl≈0.1 [1]. In the present letter we report on a similar investigation for the closed neutron shell N=82. For this purpose the g-factors of the first excited 11/2− states in the rare earth isotopes145, 147, 149Eu were measured. Due to paramagnetic effects, a measurement of nuclear g-factors in the rare earth region requires the investigation of the paramagnetic behaviour of the probe atoms in the chosen target material. The g-factors in145,147,149Eu were measured by the method of the time differential perturbed angular distribution (TDPAD) of the deexcitationγ-rays. The 11/2− states in145Eu(EX=716 keV, T1/2=0.49 gms) and in149Eu(EX=497 keV, T1/2=2.43 μs) were populated and aligned by the nuclear reaction144,148sm(d,n)145,149Eu with the pulsed deuteron beam (Ed=11 MeV) of the Erlangen tandem accelerator. Enriched metallic Sm targets of 89%144Sm and 95%148Sm were used. The 11/2− state in147Eu(EX=625 keV, T1/2=0.77 μs) was excited by the reaction147Sm(p,n)147Eu with a pulsed proton beam (Ep=10 MeV) using a 93% enriched147Sm target. A detailed description of the experimental set-up and the evaluation procedure for the present TDPAD measurements is given in ref. [2]. The deexcitation γ-rays of the isomeric Eu states were detected by two NaJ(T1) detectors encompassing an angle of Δθ=90°, and placed in a plane perpendicular to the external applied magnetic field direction. The magnetic field was calibrated by measuring the very precisely known g-factor of the isomeric 5/2+ state of19F in a BaF2 target. The Sm targets were mounted either in an oven for the high-temperature measurements or into a copper cooling-rod for temperatures down to liquid nitrogen.
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  • 7
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Theg-factor of the first excited state in the odd-odd nucleus138La (E x=73 keV,I π,T 1/2=116 ns) was measured by the time-differential perturbed angular distribution (TDPAD) method. The result, corrected for Knight shift and diamagnetic shielding, isg=+0.962±0.016. This value can be fairly well reproduced using the additivity relation for magnetic moments, empirical values for the odd-proton and odd-neutrong-factors, and an experimentally deduced wave function for the 3+ state.
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  • 8
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Genic activity in tetraploid members of the amphibian speciesOdontophrymus americanus is reduced to that of diploid ones. Loss of ribosomal genes, a mechanism suggested by others as a means of decreasing genetic activity, could be ruled out. The diploids and the tetraploids have almost identical proportions of their genomes complementary to (28s+18s) ribosomal RNA.
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  • 9
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rat ovary is insensitive to luteinizing hormone and human chorionic gonadotrophin till to the 8th to 10th day of postnatal development. This insensitivity is due to the lack of a specific hormone receptor.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 33 (1977), S. 1397-1398 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Hemigonadectomy in 9-day-old female rats results in a drastic increase in the weight and the number of HCG-binding sites of the remaining ovary during further development. However, on a per mg basis of ovarian weight, the number of HCG-receptors is identical in hemicastrated and control rats.
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