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  • Articles  (26)
  • Cell & Developmental Biology  (13)
  • Industrial Chemistry  (13)
  • Wiley-Blackwell  (26)
  • 1990-1994  (13)
  • 1970-1974  (13)
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  • Articles  (26)
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  • Wiley-Blackwell  (26)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 203 (1990), S. 151-164 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Crocodilians and birds are the extant representatives of a monophyletic taxon known as archosaurs. Their limbs are highly derived in terms of reduction in number of skeletal elements in both the carpus and the tarsus. It is necessary to have a detailed description of crocodilian limb ontogeny to address the evolutionary issue dealing with the origin and organization of the avian limb. In this paper, we present an analysis of the early development of the crocodilian limb skeleton. Contrasting with earlier observations, we redefine the number and composition of carpal, tarsal, and phalangeal elements. This ontogenetic information is then used to introduce a revision of the homologies of the skeletal elements in the crocodilian limb. Some invariances are pointed out in the developmental organization of tetrapod limbs and this evidence serves to readdress several issues concerning the evolution of the avian limb. We present further embryological data in support of the hypothesis that digits 2-3-4 are the components of the wing skeleton in birds. In general, our comparative survey indicates that the elements that appear late in ontogeny are the ones lost in phylogeny. By comparing turtle (primitive) limb development with crocodilian and bird development, we propose a hypothesis in which the derived skeletal patterns found in crocodilians and birds have originated by a heterochronic process of paedomorphosis.
    Additional Material: 8 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 214 (1992), S. 269-285 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fibula reduction is a key feature of avian limb evolution. In a combined comparative and experimental approach the present study analyses the trends of fibula reduction in extant birds and their developmental basis. The study of 55 species of birds reveals four different types of tibiotarsus-to-fibula relationships. Extremely small fibulae are associated with two types of limb modification: (1) elongations of the limb primarily affect the tibiotarsus, increasing its length more than that of the fibula; (2) miniaturizations of the limb reduce both tibiotarsus and fibula length, but are reglarly associated with structural reductions of the distal parts of the fibula. True structrual reductions are distinguished from relative size reductions. The specific features of fibula reduction are analyzed through experimental mesenchyme excisions in chick limb buds. The methodical variation of experimental parameters resolves a long-standing controversy about the effects of mesenchyme reductions on the patterns of skeletal formation. Mesenchyme excisions are shown to have unequal effects on the two zeugopod bones, affecting the fibula to a greater degree than the tibiotarsus. Several of the features seen in birds with advanced fibula reductions are paralleled by the effects of mesenchyme reductions. The consequences of this differential susceptibility of the skeletal blastemata are discussed both in terms of pattern formation in limb development and in terms of its bearing on the patterns of evolutionary limb reduction. It is concluded that thresholds of cell number and blastema size in development constrain the patterns of phenotypic variation in avian limbs. © 1992 Wiley-Liss, Inc.
    Additional Material: 12 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 261-271 
    ISSN: 1040-452X
    Keywords: Immunocytochemistry ; Ultrastructure ; Perichromatin granules ; Interchromatin granules ; Mouse spermatids ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the ultrastructural distribution of heterogeneous nuclear ribonucleoproteins (hnRNPs), small nuclear ribonucleoproteins (snRNPs), and ribosomal proteins during mouse spermatogenesis and spermiogenesis by means of specific antibodies and immunocytochemistry.All the above components were detectable from primary spermatocytes until the spermatid elongation phase, when the RNA synthetic activity is known to cease. Ribosomal protein (P1/P2 and L7) labeling disappeared as early as during the acrosome phase, and nucleoli were no longer labeled even during the cap phase. The nucleoplasmic structures labeled with the different anti-nucleoplasmic RNP immunoprobes corresponded, until the acrosome phase, to those previously observed as targets of the same antibodies in the nucleoplasm of somatic cell nuclei. Clusters of interchromatin granules of spermatocyte and early spermatid nuclei exhibit some labeling for hnRNP when compared with nuclei of Sertoli cells or previously analyzed liver or tissue culture cells, where these structural constituents usually remain weakly labeled or unlabeled.In spermatids in step 10, another type of nuclear granule, resembling perichromatin granules, but occurring in aggregates, can be observed. These structural constituents were labeled with antibodies recognizing nucleoplasmic snRNP antigens and therefore suggesting a non-nucleolar origin of these granules.Finally, we have observed nucleoplasmic areas of fibrogranular material, occurring only in primary spermatocytes. These components were labeled with anti-ribosomal protein antibodies but did not contain either hnRNPs or snRNPs. © 1993 Wiley-Liss, Inc.
    Additional Material: 15 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 23 (1992), S. 334-352 
    ISSN: 1059-910X
    Keywords: Identified neurons ; Quantification ; Rotating/tilting ; Synaptic contacts ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: With the classical Golgi techniques, numerous types of neurons can be distinguished in the cerebral cortex, each with a specific dendritic geometry and pattern of axonal ramifications. In the present review we describe two techniques which allow quantification of synapses on identified neurons: (1) Golgi-rapid impregnation-gold toning-electron microscopy, and (2) Golgi-Kopsch impregnation-gold toning-electron microscopy in combination with staining of the tissue with ethanolic phosphotungstic acid (E-PTA). Both techniques were applied on neurons in the visual cortex of young and adult rabbits. By means of rotating and tilting specimens in the electron microscope, the nondistinctive ultrastructure of obliquely sectioned synapses can be circumvented, leading to precise estimates of asymmetrical vs. symmetrical synapses without complete reconstruction of the neuron. © 1992 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 25 (1990), S. 42-44 
    ISSN: 1040-452X
    Keywords: Ovary transfer ; Mice ; Transgenic offspring ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Female transgenic mice may be unable to reproduce successfully if the product encoded by the transgene results in pathological changes or affects the fertility of the mouse. To approach this problem, we have produced chimaeras by transferring the ovaries of transgenic mice into normal mice of the same strain. Such chimaeras will be an ideal tool for investigating the interactions between transgenic ovaries and normal mice or vice versa. Here we show that, using this method, we were able to get large numbers of transgenic offspring even from founder transgenic female mice that were themselves infertile as a result of the overexpression of growth hormone genes. Although none of the ovary recipients were given immunosuppressant treatment, 60% of the recipients had biologically active ovaries over a mean period of about 100 days.
    Additional Material: 2 Tab.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 29 (1991), S. 259-270 
    ISSN: 1040-452X
    Keywords: Sperm motility ; Fish ; Motility ; Sperm ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Carp semen obtained from isolated fish after hormonal stimulation was highly variable in terms of volume of semen, osmotic pressure of the seminal plasma, and sperm capacity to move. Moreover, this last parameter was unstable when the spermatozoa were kept within the seminal plasma, and the present work was designed to investigate and possibly correct this phenomenon. Sperm potential movement was the major parameter studied and was measured by the percentage of motile cells in a final 3,000-fold dilution in a medium of low osmotic pressure in which sperm movement is known to occur (Morisawa and Suzuki, Science 210:1145-1147, 1980). This was completed with occasional measurements of flagellar beat frequencies and demembranation-reactivation of axonemal movement. The results showed that sperm potential movement was preserved upon dilution of the semen into cold 200 mM KCl medium and that semen of initially “poor” quality or spermatozoa that had lost their capacity to move during storage in the semen recovered gradually their potential movement during incubation at 2°C in the same medium. The K+ dependence for both the conservation and the regeneration of sperm capacity to move showed a minimal requirement of 50 mM KCl in media of high osmotic pressure. Na+ ions had similar properties but not divalent cations. The K+ activation was not pH dependent between pH 9.03 and 6.04. Whatever the functional state of live spermatozoa, demembranation-reactivation occurred in ATP-Mg2+. It is concluded that, with dilution of the semen in appropriate conditions, carp spermatozoa retain or acquire potential movement and therefore are a lower vertebrate spermatozoa model available year-round. In addition, obtaining potentially nonmotile sperm and reversion in vitro might be useful to study the control of in vitro maturation.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 43 (1971), S. 616-619 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Es wird ein neuer Kalorimeter-Typ beschrieben, der auf dem Wärmeflußprinzip beruht und sich sowohl zur absoluten als auch differentiellen Messung von Verbrennungs-wärmen eignet. Aufgrund ihrer großen Empfindlichkeit gestattet die Meßanordnung Wärmenengen von ca. 200mJ - entsprechend der Verbrennungswärme von etwa 50 bis 100 μg Substanz - mit einer Genauigkeit von ± 0, 75% zu ermitteln. Die Bildungsenthalpie von Wolframtrioxid konnte durch kalorimetrische Messung der Verbrennungswärme von Substanzmengen von ca. 50 μg (W-Draht) neu bestimmt werden.
    Additional Material: 3 Ill.
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  • 8
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In einem nichtthermischen Plasma werden aktive Spezies erzeugt, die zu chemischen Reaktionen führen. Im Hinblick hierauf läßt sich eine Optimierung entwickeln, die noch keine speziellen Eigenschaften des Plasmas enthält. Als erster Optimierungsschritt wird gefordert, daß der Anteil der elektrischen Leistung für die Aufheizung des Gases vernachlässigbar ist gegenüber dem Anteil für die Erzeugung der aktiven Spezies. Dies ist oberhalb eines kritischen Wertes des Energieverlustfaktors für die Elektronen gegeben. Als nächster Optimierungsschritt wird eine möglichst hohe Produktionsrate der angeregten Atome verlangt. Für Felder oberhalb des kritischen Wertes ist dies gleichbedeutend mit der Forderung nach einer hohen elektrischen Leistungsdichte. In den meisten nichtthermischen Plasmen läßt sich der erste Optimierungsschritt realisieren. Weitere Optimierungsschritte müssen für die einzelnen Entladungstypen getrennt diskutiert werden. Besondere Bedeutung kommt dabei der Gasströmung durch das Plasma zu.
    Additional Material: 9 Tab.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 45 (1973), S. 1436-1447 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 15 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 46 (1974), S. 655-655 
    ISSN: 0009-286X
    Keywords: Polymerisation ; Emulsion ; Vinylchlorid ; Polyvinylchlorid ; Kinetik ; Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
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