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  • Life and Medical Sciences  (51)
  • crystal structures  (10)
  • Wiley-Blackwell  (61)
  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 4 (1974), S. 97-105 
    ISSN: 0045-205X
    Schlagwort(e): Life and Medical Sciences
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Zusätzliches Material: 16 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 29 (1991), S. 259-270 
    ISSN: 1040-452X
    Schlagwort(e): Sperm motility ; Fish ; Motility ; Sperm ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: 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.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 261-271 
    ISSN: 1040-452X
    Schlagwort(e): Immunocytochemistry ; Ultrastructure ; Perichromatin granules ; Interchromatin granules ; Mouse spermatids ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: 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.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 23 (1992), S. 334-352 
    ISSN: 1059-910X
    Schlagwort(e): Identified neurons ; Quantification ; Rotating/tilting ; Synaptic contacts ; Electron microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Allgemeine Naturwissenschaft
    Notizen: 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.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 25 (1990), S. 42-44 
    ISSN: 1040-452X
    Schlagwort(e): Ovary transfer ; Mice ; Transgenic offspring ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: 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.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 40 (1995), S. 345-354 
    ISSN: 1040-452X
    Schlagwort(e): Signal transduction ; α-subunit ; β-subunit ; Peptide antisera ; Flagellum ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Heterotrimeric G proteins play important roles as signal transducing components in various mammalian sperm functions. We were interested in the distribution of G proteins in human sperm tails. Prior to membrane preparation, spermatozoa were separated from contaminating cells which are frequently present in human ejaculates. Enriched human sperm tail membranes were generated by using hypoosmotic swelling and homogenization procedures. Antisera against synthetic peptides were used to identify G proteins in immunoblots. AS 8, an antiserum directed against an amino acid sequence that is found in most G protein α-subunits, and A 86, which detects all known pertussis toxin-sensitive α-subunits, reacted specifically with a 40-kDa protein. Antisera against individual G protein α-subunits failed to detect any specific antigens in enriched tail membranes AS 36, recognizing the ã2-subunit of G proteins, identified a 35-kDa protein in sperm tail membranes. Antisera against the 36-kDa β1-subunit did not detect any relevant proteins in the membrane fraction. Neither G protein α-subunits nor G protein β-subunits were found in the cytosol. ADP ribosylation of spermatozoal membrane or cytosolic proteins revealed no pertussis toxin-sensitive α-subunits. However, membrane preparations of nonpurified human spermatozoa contained α2 subunits, as shown immunologically and by ADP ribosylation; they most probably derived from somatic cells which are frequently present in human ejaculates. Our results stress the fact that spermatozoa need to be purified before sperm membrane preparation to avoid misinterpretations caused by contaminating cells. Furthermore, we suggest that G proteins in membranes of human sperm tails belong to a novel subtype of G protein α-subunits; the putative β-subunit was identified as a β2-subunit. © 1995 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 214 (1992), S. 269-285 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 203 (1990), S. 151-164 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: 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.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 114 (1983), S. 328-338 
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: A cloned strain of bovine vascular endothelial cells with a finite in vitro lifespan was treated with benzo(a)pyrene (BP) after approximately 75% of its lifespan was completed. Untreated cultures of this strain senesced upon serial subcultivation and contained large, nondividing cells. In three out of seven trials, BP treatment produced transformed cells appeared in the cultures concomitant with the senescence of the parent cells. All transformed cell lines examined exhibited indefinite lifespans and altered karyotypes. Two of the lines retained most of the characteristics of normal endothelial cells, except that one became aneuploid and the other polyploid, Neither of these lines formed tumors when inoculated into nude mice. The remaining two lines retained mostly diploid kayotypes, but a high percentage of cells contained Robertsonian translocations. In one line cell volume was markedly reduced. In addition, these lines grew in multilayers, were anchorage independent, and proliferated in medium containing 0.5% serum. When 107 cells of these lines were injected into nude mice, tumors appeared within 1 week and were identified as malignant hemangioendotheliomas of bovine origin.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 132 (1987), S. 453-462 
    ISSN: 0021-9541
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Cytogenetic evaluation of serially subcultivated human endothelial cells revealed significant differences between cultures derived from fetal umbilical cords and cultures derived from various vessel sites in adults. A rapid increase in the prevalence of polyploid cells, to levels of 100% in many cases, was detected in human umbilical vein endothelial cell cultures but not in endothelial cell cultures from adult vessels. Because the development of polyploidy has been viewed as one signpost of in vitro senescence, it may be that these in vitro observations of high levels of polyploidy are a reflection of the fact that umbilical tissue is at the end of its in vivo developmental lifespan when studied. Consistent karyotypic alterations also were observed in two clones from adult human abdominal aorta, even though these cultures exhibited low percentages of polyploid cells. Cultures of one clone exhibited a trisomy of chromosome 11, on which there are at least three onc gene loci, and a deletion of chromosome 13 through band q14. A loss of band 13q14 is a prezygotic chromosomal lesion known to predispose to retinoblastoma. In the other clone, two cell populations were observed, and each displayed a chromosomal abnormality A trisomy of the long arm of chromosome 2 was noted in one cell population via a marker chromosome involving 2 and 14. The other cell population exhibited an abnormality of chromosome 2. Neither of these karyotypic alterations was detected in the parent culture from which the clones were derived. The results reported in this study have both practical and theoretical implications. The high incidence of polyploidy in serially cultivated umbilical cultures as well as the occurrence of chromosomal changes in umbilical and aortic cultures testify to the need for cytogenetic monitoring of cell cultures even though they are derived from presumably normal tissue. Cytogenetic changes in the endothelium may be important in atherogenesis and other pathologic states. The conversion of diploid endothelial cells into polyploid endothelial cells may provide a convenient model cell system for studying mechanisms of the development of polyploidy in cells and their relationship to in vitro senscence.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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