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  • 1
    Electronic Resource
    Electronic Resource
    Differences in genetic backgrounds affecting gonadal differentiation between two local populations of the Japanese wrinkled frog (Rana rugosa) (1998)
    Springer
    Anatomy and embryology 198 (1998), S. 141-148 
    Details
    ISSN: 1432-0568
    Keywords: Key words XX/XY type ; Sex chromosome ; Gonochorism ; Testis ; Ovary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Gonadal differentiation in two local populations – Hamakita and Hiroshima – of the Japanese wrinkled frog (Rana rugosa) was examined from hatching to the end of metamorphosis. The Hamakita male has X and Y chromosomes distinguishable morphologically from each other, while X and Y chromosomes in the Hiroshima male cannot be distinguished morphologically. In the two populations, primordial gonads differentiated into testes or ovaries by stage I of Taylor and Kollros, and larvae at stage XXV – the end of metamorphosis – possessed definitive testes or ovaries. However, immature testes at stages II–III in the Hiroshima population showed a higher incidence of testes with ovarian characteristics – meiotic figures and gonadal cavities – than those in the Hamakita population. In addition, proliferative activities in the testicular cells of the immature testes in the Hiroshima population were very low. On the other hand, there were no remarkable differences in the histological processes of ovary development between the two populations. Intraspecific hybridization between females of the Hamakita population and males of the Hiroshima population retarded testis differentiation after stage XV, while the reciprocal hybridization showed normal gonadal sex differentiation and development. These observations suggest that R. rugosa, possessing heteromorphic sex chromosomes in the male, establishes firm gonochorism, where the feminization involves the suppression of testis differentiation, and that masculinization is performed by resistance to this suppression as well as active proliferation of testicular cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050172
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  • 2
    Electronic Resource
    Electronic Resource
    Crystal structure of poly(p-benzamide) (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1135-1143 
    Details
    ISSN: 0887-6266
    Keywords: poly(p-benzamide), crystal structure of ; crystal structure of poly(p-benz-amide) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Redetermination of the crystal structure of poly(p-benzamide) was made by using newly collected intensity data. The molecular conformation is TCTC, where the internal rotation angles about the N—C bond of the amide group and about the virtual bond of N-phenyl-C are T (trans) and C (cis) conformations, respectively. Two molecular chains pass through a rectangular unit cell with dimension, a = 7.75 Å, b = 5.30 Å, c (fiber axis) = 12.87 Å, and the space group, P212121-D42. The reflection observed at the spacing of 010 may be attributed to the reflection due to another crystal polymorph or the diffuse scattering due to disorder. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310909
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure of isotactic poly(4-methyl-1-pentene) (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 131-142 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal structure of isotactic poly(4-methyl-1-pentene) was determined by x-ray analysis. The unit cell is tetragonal, P4b2, with α = 18.70 Å and c (fiber axis) = 13.68 Å; it contains four molecular chains each consisting of seven monomeric units in the fiber period. The molecular conformation is essentially a (7/2) helix, but deviates slightly from the uniform (7/2) helix. The unusual low density is discussed from the structural point of view.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180160112
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