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  • 1
    Electronic Resource
    Electronic Resource
    Comparative studies on the histology of the ovotestis in Hypselodoris tricolor and Godiva banyulensis (Gastropoda, Opisthobranchia), with special reference to yolk formation (1986)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 188 (1986), S. 105-118 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The histology of the ovotestis was studied by light and electron microscopy in two nudibranch gastropod species. While in Hypselodoris tricolor the ovotestis is intimately associated with the digestive gland tissue, the large gonadal mass of Godiva banyulensis is placed freely in the haemocoele. This fact results in great histological differences between both species.As is common among Mollusca, the immature yolk granule in Hypselodoris and Godiva presumably originates from membrane-rich cytoplasmic inclusions, which we have termed dense multivesicular bodies. Such inclusions consist of an outer membrane enclosing membrane remnants and a granular, electron-dense material. These elements are accumulated and mixed in the center of the dense multivesicular body and could be actually transformed into the paracrystalline core of the immature yolk granule, the cortex of which is made up of part of the central accumulation materials that have not spread into the crystal. During vitellogenesis, some mitochondria are subjected to a process of transformation affecting mainly their inner membrane (including mitochondrial cristae) and matrix. However, the conversion of modified mitochondria into yolk precursors, as reported for other gastropod species, could not be determined with absolute certainty on the basis of our observations on static material.The mature yolk granule consists of a central paracrystalline core, similar in structure to that of the immature yolk granule, and a peripheral membranous cortex, which seems to spread centripetally, thus permitting the crystal to grow. The cortical material consumed in synthesizing the central core appears to be restored by addition of degenerative mitochondria to the yolk granule surface.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051880110
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  • 2
    Electronic Resource
    Electronic Resource
    SnS—Sno2 conversion of chemically deposited SnS thin films (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 1 (1992), S. 117-121 
    Details
    ISSN: 1057-9257
    Keywords: Tin(II) sulphide ; Tin(IV) oxide ; Photoconductor ; Air annealing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The thermal decomposition of chemically deposited SnS thin films to SnO2 films by air annealing at temperatures up to 400°C is discussed. The conversion of a 0.7 μm thick SnS thin film to an SnO2 film involves the creation of non-stoichiometric SnS, SnS + SnS2 mixed phase and non-stoichiometric SnO2 (i.e. SnO2 — x), as concluded from X-ray diffraction patterns, optical transmission spectra and electrical characteristics. The SnO2 thin films obtained in this manner are photoconductive, with a lowest sheet resistance (in the dark) of about 105 Ω/□ and an activation energy (Ea) of 0.1 eV for the electrical conductivity observed for the SnS films annealed at 325°C. This was found as the onset temperature for conversion of the SnS + SnS2 phase to the non-stoichiometric SnO2 - x film. Elevation of the annealing temperature to 400°C results in an elevation of the sheet resistance to about 109 Ω/□ with the value of Ea at 1.3 eV, indicating an improvement in the degree of stoichiometry.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/amo.860010303
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear morphogenesis during spermiogenesis in the nudibranch molluscHypselodoris tricolor (Gastropoda, opisthobranchia) (1986)
    New York, NY : Wiley-Blackwell
    Gamete Research 13 (1986), S. 159-171 
    Details
    ISSN: 0148-7280
    Keywords: nudibranch ; spermiogenesis ; nuclear morphogenesis ; chromatin condensation ; manchette ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: An electron microscope study was carried out on Hypselodoris tricolor spermatids to describe the development of the nuclear morphogenesis and investigate the possible cause(s) of the change in the shape of the spermatid nucleus during spermiogenesis. Three different stages may be distinguished in the course of the nuclear morphogenesis on the basis of the morphology and inner organization of the nucleus. Stage 1 spermatid nuclei are spherical or ovoid in shape and the nucleoplasm finely granular in appearance. Stage 2 nuclei exhibit a disc- or cup-shaped morphology, and the chromatin forms short, thin filaments. During stage 3, a progressive nuclear elongation takes place, accompanied by chromatin rearrangement, first into fibers and then into lamellae, both formations helically oriented. A row of microtubules attached to the nuclear envelope completely surrounds the nucleus. Interestingly, the microtubules always lie parallel to the chromatin fibers adjacent to them. Late stage 3 spermatids show the highest degree of chromatin condensation and lack the manchette at the end of spermiogenesis. Our findings indicate the existence of a clear influence exerted on the chromatin by the manchette microtubules, which appear to be involved in determining the specific pattern of chromatin condensation in Hypselodoris tricolor.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120130209
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray diffraction study of poly(p-phenylene). Part I. Variation of crystallite size with annealing temperature (1990)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 41 (1990), S. 152-155 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Linienprofilanalyse der (hk0)-Reflexe von gesintertem Poly(p-phenylen) wird vorgestellt. Die Maxima der Weitwinkelröntgenbeugung wurden analysiert, um die mittlere Größe der kohärent streuenden Bereiche in Abhängigkeit von der Temperatur TA zu untersuchen. Die Ergebnisse zeigen, daß die Querabmessung der kohärent streuenden Bereiche bis TA = 300°C zuerst leicht zunimmt und dann für TA 〉 300°C stark anwächst. Dies hängt mit der Umordnung starrer Ketten aus den ungeordneten in kristalline Bereiche zusammen. Das Fehlen einer Röntgenkleinwinkelstreuung stützt die Annahme einer eingefrorenen nematischen flüssig-kristallinen Struktur, die etwa 40% des Materials umfaßt.
    Notes: A line profile analysis of the (hk0) reflections of sintered poly(p-phenylene) is presented. The wide angle X-ray diffraction maxima were analyzed to study the average size of the coherently diffracting domains as a function of annealing temperature TA. The results show that the lateral size of the coherently diffracting domains increase first slightly for TA 〈 300°C and then rapidly for TA 〉 300°C. This is related to a rearrangement of rigid chains from disordered into the crystalline regions. The absence of SAXS supports the view of a nematic frozen-in liquid crystalline structure contributing to about 40% of the material.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1990.010410303
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  • 5
    Electronic Resource
    Electronic Resource
    Eine kurze Synthese von [3-15N]-3′-Azido-3′-desoxythymidin (N3-markiertes AZT) über 3-Nitro-AZTDiese Arbeit wurde von der Dirección General de Investigación Cientifica y Técnica (Grants PB86-0137 und PB89-0277 an die Universitat de Barcelona sowie Grant PB90-0605 für V. T. und J. L. C.) gefördert: V. B. und X. A. danken dem Ministerio de Education y Ciencia für Stipendien. (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 106 (1994), S. 2535-2537 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19941062318
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  • 6
    Electronic Resource
    Electronic Resource
    A Short Route to [3-15N]-3′-Azido-3′-deoxythymidine (N3-Labeled AZT) via 3-Nitro-AZTThis research was supported by the Dirección General de Investigatión Científica y Técnica (Grants PB86-0137 and PB89-0277 to the Universität de Barcelona, and Grant PB90-0605 to the Universitat Politècnica) and by the Ministerio de Educatión y Ciencia (fellowships to V. B. and X. A). (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 33 (1995), S. 2454-2455 
    Details
    ISSN: 0570-0833
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199424541
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetic study of the reaction between iodide and N-chloramines (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 28 (1996), S. 391-396 
    Details
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We carried out a kinetic study of the reaction between iodide ion and various primary N-chloramines and found it to be first-order in the latter. Experiments also showed the rate constant for the reaction to be directly proportional to the iodide and hydrogen ion concentrations. The influence of the buffer concentration reveals the presence of general acid catalysis processes. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/kin.8
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  • 8
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    Soil microbial biomass and nitrogen mineralization rates along an altitudinal gradient on the Cofre de Perote Volcano (Mexico): The importance of landscape position and land use (2012)
    Wiley-Blackwell
    Details
    Publication Date: 2012-09-26
    Description: ABSTRACT A study was conducted to examine the responses of microbial activity and nitrogen (N) transformations along an altitudinal gradient. The gradient was divided into three parts. Three areas were sampled: upper part (UP): coniferous forest, corn field, and abandoned corn field; middle part (MP): tropical cloud forest, grassland, and corn field (COL); and lower part (LP): tropical deciduous forest and sugarcane. The results showed that soil microbial biomass carbon (C) and basal respiration were significantly higher in MP and UP than in LP, whereas the microbial quotient (C mic /C org ) was higher in LP and MP than in UP. The metabolic quotient ( q CO 2 ) was similar among gradient parts evaluated. Net N mineralization, ammonification, and nitrification rates were higher in UP than MP and LP. We found that in UP, the forest conversion to cropland resulted in no significant differences in microbial activity and N transformation rates between land uses. In MP, microbial biomass C, ammonification, and net N mineralization rates decreased significantly with conversion to cropland, but C mic /C org and nitrification were higher in COL. Basal respiration and q CO 2 were significantly lower in COL when compared with other land uses. In LP, lower microbial biomass C, C mic /C org , and nitrification rates but higher ammonification and net N mineralization rates were observed in tropical deciduous forest than in sugarcane. No significant differences in basal respiration and q CO 2 were found between uses of LP. Clearly, then, soil organic C is not equally accessible to the microbial community along the gradient studied. Copyright © 2012 John Wiley & Sons, Ltd.
    Print ISSN: 1085-3278
    Electronic ISSN: 1099-145X
    Topics: Geography , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley-Blackwell
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  • 9
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    Codon Usage Bias and Effective Population Sizes on the X Chromosome versus the Autosomes in Drosophila melanogaster (2013)
    Oxford University Press
    Details
    Publication Date: 2013-03-21
    Description: Codon usage bias (CUB) in Drosophila is higher for X-linked genes than for autosomal genes. One possible explanation is that the higher effective recombination rate for genes on the X chromosome compared with the autosomes reduces their susceptibility to Hill–Robertson effects, and thus enhances the efficacy of selection on codon usage. The genome sequence of D. melanogaster was used to test this hypothesis . Contrary to expectation, it was found that, after correcting for the effective recombination rate, CUB remained higher on the X than on the autosomes. In contrast, an analysis of polymorphism data from a Rwandan population showed that mean nucleotide site diversity at 4-fold degenerate sites for genes on the X is approximately three-quarters of the autosomal value after correcting for the effective recombination rate, compared with approximate equality before correction. In addition, these data show that selection for preferred versus unpreferred synonymous variants is stronger on the X than the autosomes, which accounts for the higher CUB of genes on the X chromosome. This difference in the strength of selection does not appear to reflect the effects of dominance of mutations affecting codon usage, differences in gene expression levels between X and autosomes, or differences in mutational bias. Its cause therefore remains unexplained. The stronger selection on CUB on the X chromosome leads to a lower rate of synonymous site divergence compared with the autosomes; this will cause a stronger upward bias for X than A in estimates of the proportion of nonsynonymous mutations fixed by positive selection, for methods based on the McDonald–Kreitman test.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    The Relation between Recombination Rate and Patterns of Molecular Evolution and Variation in Drosophila melanogaster (2014)
    Oxford University Press
    Details
    Publication Date: 2014-03-22
    Description: Genetic recombination associated with sexual reproduction increases the efficiency of natural selection by reducing the strength of Hill–Robertson interference. Such interference can be caused either by selective sweeps of positively selected alleles or by background selection (BGS) against deleterious mutations. Its consequences can be studied by comparing patterns of molecular evolution and variation in genomic regions with different rates of crossing over. We carried out a comprehensive study of the benefits of recombination in Drosophila melanogaster , both by contrasting five independent genomic regions that lack crossing over with the rest of the genome and by comparing regions with different rates of crossing over, using data on DNA sequence polymorphisms from an African population that is geographically close to the putatively ancestral population for the species, and on sequence divergence from a related species. We observed reductions in sequence diversity in noncrossover (NC) regions that are inconsistent with the effects of hard selective sweeps in the absence of recombination. Overall, the observed patterns suggest that the recombination rate experienced by a gene is positively related to an increase in the efficiency of both positive and purifying selection. The results are consistent with a BGS model with interference among selected sites in NC regions, and joint effects of BGS, selective sweeps, and a past population expansion on variability in regions of the genome that experience crossing over. In such crossover regions, the X chromosome exhibits a higher rate of adaptive protein sequence evolution than the autosomes, implying a Faster-X effect.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
    Published by Oxford University Press
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