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  • Life and Medical Sciences  (257)
  • Wiley-Blackwell  (257)
  • Cambridge University Press
  • International Union of Crystallography (IUCr)
  • Wiley
  • 1990-1994  (257)
  • 1960-1964
  • 1950-1954
  • 1994  (126)
  • 1992  (131)
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  • Wiley-Blackwell  (257)
  • Cambridge University Press
  • International Union of Crystallography (IUCr)
  • Wiley
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  • 1990-1994  (257)
  • 1960-1964
  • 1950-1954
Year
  • 1
    Electronic Resource
    Electronic Resource
    Nongenomic regulation of extracellular matrix events by vitamin D metabolites (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 56 (1994), S. 331-339 
    Details
    ISSN: 0730-2312
    Keywords: 1,25-(OH)2D3 ; 24,25-(OH)2D3 ; matrix vesicles ; nongenomic regulation ; extracellular matrix ; alkaline phosphatase ; phospholipase A2 ; Protein kinase C ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Vitamin D metabolites appear to regulate chondrocytes and osteoblasts via a combination of genomic and nongenomic mechanisms. Specificity of the nongenomic response to either 1,25-(OH)2D3 or 24, 25-(OH)2D3 may be conferred by the chemical composition of the target membrane and its fluid mosaic structure, by the presence of specific membrane receptors, or by the interaction with classic Vitamin D receptors. Nongenomic effects have been shown to include changes in membrane fluidity, fatty acid acylation and reacylation, arachidonic acid metabolism and prostaglandin production, calcium ion flux, and protein kinaase C activity. Chondrocytes metabolize 25-(OH)D3 to 1,25-(OH)2D3 and 24,25-(OH)2D3; production of these metabolites is regulated by both growth factors and hormones and is dependent on the state of cell maturation. 1,25-(OH)2D3 and 24,25-(OH)2D3 may interact directly with extracellular matix vesicles to regulate their function in the matrix, including protease activity, resulting in matrix modefication and calcification. Isolated matrix vesicles, produced by growth zone chondrocytes, can activate latent transforming growth factor-β when incubated with exogenous 1,25-(OH)2D3. These observations suggest that nongenomic regulation of martix vesicle structure and function may be a mechanism by which mesenchymal cells, like osteoblasts and chndrocytes, may modulate events in the extracellular matrix at sites distant from the cell surace.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240560309
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  • 2
    Electronic Resource
    Electronic Resource
    Heparin inhibition of autonomous growth implicates amphiregulin as an autocrine growth factor for normal human mammary epithelial cells (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 153 (1992), S. 103-111 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Normal human mammary epithelial cells (HMECs) proliferate in a serum-free defined growth medium in the absence of epidermal growth factor (Li and Shipley, 1991). Amphiregulin (AR) is a heparin-regulated, EGF-like growth factor. Our observation that one strain of HMECs produce AR mRNA (Cook et al., 1991a) stimulated us to determine whether AR expression was a common phenomenon in HMECs and whether AR could act as an autocrin growth factor to support the EGF-independent growth of these cells. In this study, we detected high levels of AR expression in four separate HMEC strains while one immortal mammary cell line (HBL-100) and six mammary tumor-derived cell lines had low to undetectable levels of AR. The EGF-indendent growth of HMECs was blocked by the addition of heparin or a monoclonal anti-RGF receptors antibody to the culture medium, implication AR as an autocrine growth mediator. This hypothesis is further supported by the fact that medium conditioned by HMECs contains secreted AR protein. A mammary tumor-derived cell line, Hs578T, which proliferates in an EGF-independent manner, does not express detectable levels of AR and is not growth inhibited by heparin. Examination of the same cell types for expression of transforming growth factor type-alpha (TGF-α) mRNA revealed coordinate expression of AR and TGF-α in these cells. These data suggest that both AR and TGF-α mRNA are produced in much greater abundance by normal HMECs than in tumor-derived cells in culture, and that AR is an important autostimulatory factor for the growth of normal HMECs. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041530114
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  • 3
    Electronic Resource
    Electronic Resource
    Increase in copy number of an integrated vector during continuous culture of Hansenula polymorpha expressing functional human haemoglobin (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 10 (1994), S. 1569-1580 
    Details
    ISSN: 0749-503X
    Keywords: Hansenula ; haemoglobin ; integration ; continuous culture ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Recombinant human haemoglobin A (rHbA) was produced by a leucine-requiring strain of Hansenula polymorpha which had been transformed with an integration vector containing the Saccharomyces cerevisiae LEU2 gene and cDNAs for the expression of α and β globin each driven by the H. polymorpha MOX promoter. After 40 generations in a chemostat it was found that the integrated vector had become amplified in the host strain. In some cases this led to an increase in LEU2 gene dosage, but a loss of globin expression cassettes. In other cases the globin gene dosage also increased. These changes coincided with an increase in rHbA production in the culture, which was reversed when the dilution rate was increased. Isolates from a chemostat culture producing elevated levels of rHbA were grown in fed-batch fermentations, resulting in higher productivities than when inoculated with the parent strain. The rHbA produced was purified and characterized. Oxygen binding studies and electrospray mass spectrometry showed that the rHbA had been processed and assembled correctly, and behaved as a fully functional co-operative tetramer.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320101206
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  • 4
    Electronic Resource
    Electronic Resource
    Methylation of the 5′ flanking sequences of the ribosomal DNA in human cell lines and in a human-hamster hybird cell line (1992)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 50 (1992), S. 357-362 
    Details
    ISSN: 0730-2312
    Keywords: rDNA ; lymphoblastoid ; methylation ; hypermethylation ; DNA ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In human lymphoplastoid cell line (Z83) in which rDNA genes on chromosomes 22 are amplified but transcribed at a low level, immunocytological studies with antibodies to 5 methylcytidine provided evidence for hypermethylation of the rDNA. The extent of methylation of the 5′ flanking sequence of the ribosomal DNA was examined by comapring the size of restriciton fragments obtained by digestion of genomic DNA with EcoRI and Hpall or EcoRI and Mpsl. Southern blots indicated hypermethylation of the 5′ flanking sequences of many copies of rRNA genes in these cells, but not in a control lymphoblastoid cell line without rDNA amplification. Results obtained with somatic hybird human-hamster cell line, in which the rRNA genes on the single human chromosomes 22 are inactive, showed that only a small fraction of the CCGG sites in the 5′ flanking sequences of the transcriptionally silent rRNA genes in this hybird were methylated. Since inactive rRNA genes can show such a minimal level of methylation, it is likely that the extreme hypermethylation of the apmlified rRNA genes in Z83 association with their inactivation rather than following it. © 1992 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240500404
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  • 5
    Electronic Resource
    Electronic Resource
    Visual demonstration of the limb-forming zone in the chick embryo lateral plate (1992)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 213 (1992), S. 305-316 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The present study was undertaken to determine whether a visible Wolffian ridge, distinct from the lateral fold, can be identified in chick embryos. Ectoderm thickness was measured in stage 11-17 chick embryos. There was a general trend, from thin ectoderm in the midline, to an ectodermal thickening over the somites, intermediate mesoderm, and lateral plate. Other embryos were cut from the yolk, pinned out, and photographed. The lateral fold was then eliminated, and the embryo was rephotographed. The photographs reveal a definite opaic zone, distinct from the lateral fold, in stage 11-18 chick embryos. Furthermore, there is a direct correlation between the opacity of this cellular band and the limb-forming potential of grafted wing, flank, and leg regions (see Stephens et al., '89). At stages 11-14, the wing, flank, and leg exhibit a uniform opacity, and a uniform capacity for limb formation when grafted to a host celom. From stage 15 to stage 18, the opacity in the flank diminishes, and its limb-forming capability disappears. This study demonstrates the presence of an opaic zone, which we have called the limb-forming zone (LFZ) along the lateral side of early chick embryos, which is independent of the lateral fold, is not as extensive as the lateral plate, and is not simply associated with ectodermal thickening, but which is directly correlated with limb-forming potential in the lateral plate. © 1992 Wiley-Liss, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052130304
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  • 6
    Electronic Resource
    Electronic Resource
    Negative regulation of gene expression by TGF-β (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 32 (1992), S. 111-120 
    Details
    ISSN: 1040-452X
    Keywords: Metalloproteinase ; Stromelysin ; Protooncogenes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Stromelysin gene expression is transcriptionally activated by a number of growth factors (e.g., EGF and PDGF), tumor promoters (e.g., TPA), and oncogenes (e.g., ras, src) through an AP-1-dependent mechanism. TGF-β repression of stromelysin induction is mediated at the level of transcription by an element located at position -709 in the rat stromelysin promoter referred to as the TGF-β inhibitory element (TIE). A TIE-binding protein complex is induced by treatment of rat fibroblasts with TGF-β. This protein complex contains the protooncogene c-fos, and induction of c-fos by TGF-β is required for the repressive effects of TGF-β on stromelysin gene expression. Interestingly, c-fos induction is also required for stimulation of stromelysin expression by EGF in rat fibroblasts. Preliminary studies suggest that differential regulation of members of the jun family of early-response genes may explain this apparent paradox and determine whether stromelysin is induced or repressed by growth factors. TGF-β stimulation therefore initiates a cascade of events that results in a specific pattern of gene expression: the direct stimulation of early-response genes can lead to subsequent induction or repression of other genes.Growth factor regulation of matrix metalloproteinases appears to play a role in embryonic development in the morphogenesis of the murine lung. Treatment of embryonic lungs in organ culture with the growth factors EGF or TGF-β results in stimulation of growth and inhibition of branching morphogenesis. A similar inhibition of branching was observed when these lung rudiments were treated with the matrix metalloproteinase collagenase. Most interestingly, the effects of EGF and TGF-β can be completely reversed by the tissue inhibitor of metalloproteinases, TIMP. TGF-β has the opposite effect on growth of murine lung rudiments - growth is inhibited in a dose-dependent manner. This example illustrates a potential role for growth factor regulation of matrix-degrading metalloproteinases in complex developmental processes. © 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080320206
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  • 7
    Electronic Resource
    Electronic Resource
    Interactions between brain mitochondria and cytoskeleton: Evidence for specialized outer membrane domains involved in the association of cytoskeleton-associated proteins to mitochondria in situ and in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 27 (1994), S. 233-261 
    Details
    ISSN: 1059-910X
    Keywords: Brain mitochondria ; Microtubules ; Neurofilaments ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The surface distribution of several proteins (porin, hexokinase, and two proteins associated with microtubules or actin filaments) on the outer membrane of brain mitochondria was analyzed by immunogold labelling of purified mitochondria in vitro. The results suggest the existence of specialized domains for the distribution of porin in the outer mitochondrial membrane. Similarities between the distribution of porin and the distribution of microtubule-associated proteins bound in vitro to mitochondria suggested that mitochondria and microtubules interact by binding microtubule-associated proteins to porin-containing domains of the outer membrane. This hypothesis was supported by biochemical studies on outer mitochondrial proteins involved in in vitro binding of cytoskeleton elements. In vitro interactions between mitochondria and microtubules or neurofilaments were analyzed by electron microscopy. These studies revealed cross-bridging between the outer membrane of mitochondria and the two cytoskeleton elements. Cross-bridging was influenced by ATP hydrolysis and by several proteins associated with the surface of mitochondria or with microtubules. In addition, unidentified proteins which were recognized by antibodies to all intermediate filaments subunits were associated either with the mitochondrial surface or with microtubules. This data suggest the participation of additional cytoplasmic proteins in the interactions between cytoskeleton elements and mitochondria. © 1994 Wiley-Liss, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070270305
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  • 8
    Electronic Resource
    Electronic Resource
    Sperm capacitation in the domestic cat (Felis catus) and leopard cat (Felis bengalensis) as studied with a salt-stored zona pellucida penetration assay (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 200-207 
    Details
    ISSN: 1040-452X
    Keywords: Protein-free medium ; BSA ; In vitro sperm penetration ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The ability of domestic cat or leopard cat spermatozoa to penetrate zonae pellucidae (ZP) of salt-stored, domestic cat oocytes was examined as an assay for sperm capacitation. Ovarian oocytes were recovered after ovariectomy and matured in vitro for 18-36 h. Following removal of cumulus cells, the oocytes were used fresh, or stored (4°C, 0.5-24 weeks) in a HEPES-buffered hypertonic salt solution. Electroejaculated, washed sperm (2-4 × 106 sperm/ml) were preincubated for 1.0 h (38°C, 5% CO2 in air) and then co-incubated (2 × 105 sperm/ml) with fresh or stored oocytes for 6.0 h. Gametes were incubated in a protein-free, modified Tyrode's solution (TLP-PVA) or in the same medium containing 4.0 mg/ml bovine serum albumin (BSA; TALP-PVA). Treatments were compared for percentage ZP penetration (defined as sperm heads reaching more than halfway through the ZP) as an index of sperm capacitation. In both the domestic cat and leopard cat, there was no difference (P 〉 0.05) in sperm penetration of fresh ZP (domestic cat, 42.5 ± 5.4%; leopard cat, 38.6 ± 2.8%) or stored ZP (domestic cat, 32.4 ± 4.2%; leopard cat, 27.6 ± 2.3%). Sperm incubated in protein-free medium (TLP-PVA) were less capable (P〈0.05) of ZP penetration (domestic cat, 14.6 ± 5.9%; leopard cat, 7.9 ± 3.0%) than sperm incubated in medium TALP-PVA containing BSA (domestic cat, 60.3 ± 5.9%; leopard cat, 58.4 ± 3.0%). These data indicate that (1) albumin facilitates capacitation and ZP penetrating ability of cat spermatozoa; (2) domestic cat ZP appear to lack a block to heterospecific penetration by “foreign” (leopard cat) sperm; and (3) penetration of stored domestic cat ZP can be used as an index of sperm capacitation in the domestic cat and the leopard cat.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080310307
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of gonadotropins upon the incidence and kinetics of meiotic maturation of macaque oocytes in vitro (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 467-472 
    Details
    ISSN: 1040-452X
    Keywords: Oocyte maturation ; Germinal vesicle breakdown ; Polar body ; LH/FSH ; Macaque ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The specific aim of this study was to determine the effects of gonadotropins in vitro upon the incidence of and precise time interval to germinal vesicle breakdown (GVB) and extrusion of the first polar body (PB1) in oocytes from nonstimulated rhesus monkeys. Cumulus-enclod germinal vesicle (GV) stage oocytes from 10 normal, cycling rhesus monkeys in the follicular phase of the menstrual cycle were cultured with either: (1) 1.0 μg/ml human follicle-stimulating hormone (hFSH), (2) 10 μg/ml human luteinizing hormone (hLH), (3) 1.0 μg/ml hFSH and 10 μg/ml hLH, or (4) no gonadotropins (controls). Oocytes (n = 234) were examined at 3-hr intervals from 0 to 21 hr and at 4-hr intervals from 24 to 52 hr for GVB and PB1. Neither the incidence of GVB (hFSH: 63.5%; hLH: 56.1%; both gonadotropins: 63.1%; no gonadotropins: 53.6%) nor extrusion of PB1 (hFSH: 41.3%; hLH: 36.4%; both gonadotropins: 36.9%; no gonadotropins; 31.9%) differed (P 〉 0.05) among treatments. The time to GVB was accelerated (P 〈 0.05) by gonadotropins (hFSH: 10.8 ± 1.7 hr; hLH: 10.1 ± 1.8 hr; both gonadotropins: 8.8 ± 1.1 hr) when compared to controls (17.4 ± 2.0 hr). However, the time interval to extrusion of PB1 did not differ (P 〉 0.05) among treatments (hFSH: 32.3 ± 1.2 hr; hLH: 35.1 ± 1.4 hr; both gonadotropins: 35.2 ± 1.3 hr; no gonadotropins: 34.1 ± 1.2 hr). The mean interval to extrusion of PB1 was 34.1 ± 0.6 hr. In conclusion, GVB and PB1 extrusions appear to be, in part, independently regulated events in macaque oocytes matured in vitro since the timing of PB1 extrusion is not tightly coupled with the onset of GVB. Although the developmental potential of oocytes may be enhanced by gonadotropins, alternative approaches must be developed to improve the poor competence of oocytes from nonstimulated monkeys to mature in vitro. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370415
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  • 10
    Electronic Resource
    Electronic Resource
    Three-dimensional structure of lung elastin demonstrated by scanning electron microscopy/stereo-pair images (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 254-261 
    Details
    ISSN: 1059-910X
    Keywords: TEM ; Formic acid ; Alkali ; Freeze-drying ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The aim of this study was to expose the inflated 3-D structure of lung elastin. Formic acid digestion followed by freeze-drying unveiled the lamellar framework. The 3-D structure of elastin was well preserved within the alveolar septa and ducts, as demonstrated by scanning electron microscopy/stereo-pair photography. Elastin fibers are seen in the alveolar septa, which are continuous with the lamellae. The removal of collagen fibers and cells by formic acid was visualised as a function of time: The optimum was 48 hours. Transverse sections still retained some collagen fibrils and partially digested cells in addition to elastin as shown by transmission electron microscopy (TEM). Forme acid digestion followed by critical point drying caused damage to the lamellar structures and they appeared to collapse. Sodium hydroxide digestion combined with freeze-drying did not preserve the 3-D lamellar structure of elastin, but converted it into flat ribbonlike bands. The main structures remaining following alkali treatment were identified by TEM as collagen fibrils well preserved in their original locations. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290312
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