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  • Electronic Resource  (7)
  • 1985-1989  (5)
  • 1975-1979  (2)
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  • Electronic Resource  (7)
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  • 1
    Electronic Resource
    Electronic Resource
    Crystal data for PbGe[Ge3O9](h) (1979)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 12 (1979), S. 421-422 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Trilling crystals of PbGe[Ge3O9](h) were grown from the melt by spontaneous crystallization. The crystals develop pseudo-trigonal-prismatic habit. The unit cell is monoclinic but pseudo-rhombohedral. The probable space groups are C2/m, C2 or Cm. The lattice constants of the reduced monoclinic unit cell are a = 7.331 (7), b = 11.455 (3), c = 6.831 (6) Å, β = 141.97 (13)°. Dx = 6.029 Mg m-3 for Z = 2 formula units. The lattice constants of the pseudo-rhombohedral setting are a1 = a2 = 6.800 (6), a3 = 6.831 (6) Å, = β = 115.13 (19), γ = 114.76 (18)° and Z = 1. X-ray powder data are given. Improved crystal data of PbGe[Ge3O9](t) are also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889879012887
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    HF sputtered indium oxide films doped with tin (1978)
    Springer
    Applied physics 16 (1978), S. 381-390 
    Details
    ISSN: 1432-0630
    Keywords: 73 ; 72.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Indium-tin-oxide films (ITO films) sputtered in Ar-atmosphere with and without addition of oxygen reveal an irreversible increase in conductivity during annealing in vacuum. This annealing process increases drastically the density of free electrons, while the Hall mobility changes only slightly. Below the annealing temperature the temperature dependence of the conductivity is reversible. In films with low density of free electrons, which behave like non-degenerated semiconductors, two activation energies for the mobility could be found. The irreversible changes, observed during annealing in the vacuum, are explained by diffusion of oxygen from the interior of the film to the surface, followed by desorption of the oxygen from the surface into the vacuum. The excess oxygen in the non-stoichiometric films plays the role of electron traps. The irreversible effects during annealing in the vacuum are partly reversible in the long run. If the annealed films are exposed to oxygen or air their conductivity decreases because of diffusion of oxygen from the surface into the film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885863
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Development of the first meiotic prophase stages in human fetal oocytes observed by light and electron microscopy (1987)
    Springer
    Human genetics 〈Berlin〉 77 (1987), S. 223-232 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The development of the first meiotic prophase stages was studied in two series of human female embryos and fetuses aborted for social reasons. The first series (64 embryos or fetuses aborted at 6–24 weeks of gestation) was used mainly to perfect the methods applied to obtain chromosome preparations and synaptonemal complex spreads. The second series (37 embryos or fetuses aborted at 9–24 weeks of gestation) was used to establish the timing and to charcterize the different stages of prophase I. Leptotene-zygotene figures were observed in some embryos at 10 weeks of gestation. Typical zygotene figures were seen at 11–22 weeks. Pachytenes were first observed at 12–13 weeks, and the proportion of these figures was usually lower than 40%. Diplotenes were seen in fetuses with a gestational age of 14 weeks or more. The duration of the process in the human female is thus about 3–4 weeks, a similar period to that described for the male.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284474
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  • 4
    Electronic Resource
    Electronic Resource
    Nucleolar structures in chromosome and SC preparations from human oocytes at first meiotic prophase (1989)
    Springer
    Human genetics 〈Berlin〉 82 (1989), S. 147-153 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We describe a comparative study of the behavior of nucleolar structures and their relationship with nucleolar chromosomes and synaptonemal complexes at first meiotic prophase of human oocytes in an attempt to elucidate the nature of this cellular organization and to learn more about maternal nondisjunction. The number of main nucleoli varies along the different stages of prophase I and is usually low. It shows an increase from leptotene to pachytene and a decrease from pachytene to diplotene related to a decrease and an increase of main nucleoli volume, respectively. The methodology employed has enabled us to analyze in detail dark bodies, round bodies, dense bodies, and main nucleoli in chromosome or synaptonemal complex spreads. The relationship between nucleolar chromosomes or synaptonemal complexes and the nucleoli implies the existence, in a very reduced space, of chromosomal regions that contain homologous sequences and that are often unpaired. This situation may facilitate the production of heterologous pairing and chromosomal exchanges between nonhomologous chromosomes and finally result in aneuploidy. THus, the situation explained above together with the differences between the oocyte and spermatocyte NOR cycles could be one of the reasons for the higher incidence of aneuploidies of maternal origin at meiosis I.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00284048
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  • 5
    Electronic Resource
    Electronic Resource
    A qualitative study on vanadate effects in the tetrahydrofolate-dependent formate transfer in vitro and in vivo in mice (1987)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 336 (1987), S. 111-116 
    Details
    ISSN: 1432-1912
    Keywords: Vanadate ; Formate ; In vivo drug metabolism ; Tetrahydrofolate ; [14C]CO2 Exhalation analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Parenteral administration of sodium vanadate (NaVO3, 22 mg/kg b.w., i.p.) to mice depresses the oxidation rate of [14C]formate to [14C]CO2, as determined by radioactive breath analysis. The heavy metal-induced inhibition is relatively fast in onset, fairly intense (up to 80% inhibition), of short duration (about 2 h) and strongly correlated to the presence of vanadate (in the pentavalent state) in plasma. The [14C]CO2 exhalation rate from [14C]bicarbonate is less affected by vanadate in vivo, thereby suggesting a specific interference of vanadium in the intermediate step of formate oxidation to HCO3 −. In vitro in mouse liver cytosolic fractions vanadate inhibits the enzymatic transfer of formate to tetrahydrofolic acid. The inhibition is accomplished by a vanadate-dependent oxidative degradation of tetrahydrofolate. In contrast, the concentrations of N5-methyltetrahydrofolate, dihydrofolate and folate remain unchanged upon in vitro-exposure to vanadate. The in vitro studies thus might explain the observed inhibition of formate oxidation to carbon dioxide in vivo by a vanadate-evoked depletion of its biological carrier tetrahydrofolic acid. Whether the interference in tetrahydrofolate metabolism also occurs under in vivo conditions, remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177760
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of hypotonic treatment on the morphology of meiotic stages I. Prophase of the first meiotic division of male mice, man and Locusta migratoria (1986)
    Springer
    Genetica 69 (1986), S. 19-26 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Male mice were treated with hydroxyurea (HU) to obtain a restricted germ cell population and a sequential analysis of the first meiotic prophase was performed. The results from HU-treated mice were compared with those from untreated mice, human and grasshopper material with and without hypotonic treatment. In hypotonically treated material the three subclasses of diffuse stages were obvious in all species investigated. In material not treated hypotonically the different classes of prophase stages showed a more gradual course, there was a tendency towards less spreading of the bivalents and no pronounced diffuse substages could be found. The first desynaptic stage in this material could be recognized in most cases as wellspread classical ‘pachytene’ like bivalents with a pronounced double-threaded structure. The more advanced desynaptic stage in untreated material resembled the diffuse stage as found in plant meiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122930
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  • 7
    Electronic Resource
    Electronic Resource
    The influence of hypotonic treatment on the morphology of meiotic stages II. Prophase of the first meiotic division of female mice up to dictyotene (1986)
    Springer
    Genetica 70 (1986), S. 161-165 
    Details
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Various investigations of prophase of the first meiotic division of female mice showed different results with respect to the appearance of those stages during ovarian development. It was not clear up to now whether in oocytes, in addition to the dictyotene stage, there exists a diffuse diplotene stage as can be found during male meiosis. In this study the morphology of meiotic prophase stages was compared in preparations of oocytes with and without hypotonic pretreatment. There appears to be a strong effect of hypotonic treatment on the morphology of different meiotic prophase stages and there is a striking resemblance with meiotic stages from male material which was treated similarly. From the results of hypotonically untreated ovarian material it was obvious that early desynaptic stages could be confused with pachytene. In addition, it was demonstrated that there exists a diffuse (diplotene) stage with a duration of approximately 3 days before dictyotene stage. The possible function of the diffuse stage is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122182
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