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  • Life and Medical Sciences  (131)
  • ASTRONOMY
  • SOLAR PHYSICS
  • Wiley-Blackwell  (131)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 153 (1992), S. 103-111 
    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.
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  • 2
    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.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 213 (1992), S. 305-316 
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 32 (1992), S. 111-120 
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 200-207 
    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.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 49 (1992), S. 259-265 
    ISSN: 0730-2312
    Keywords: heme ; heme oxygenase ; mRNA ; environmental agents ; metalloporphyrins ; lipopolysaccharide ; acute phase ; Hep3B ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In situ hybridization and Northern analysis of heme oxygenase (HO) mRNA was used to determine the induction and expression of HO by various environmental agents. Exposure of Hep3B cells to hemin (10 μM) for as little as 5 min resulted in significant production of HO transcripts and mRNA expression as seen by in situ hybridization. We followed the pattern of HO transcript accumulation by heme and results indicate that the peak of induction of HO by heme was reached between 10 and 20 minutes. Other metalloporphyrins were all effective in inducing HO mRNA after 1 h exposure. On the other hand, CoCl2 caused accumulation of HO mRNA at a later time than seen with the metalloporphyrins. However, lipopolysaccharide (LPS) gave a more immediate effect on HO induction which was somewhat similar to heme in its time course. Direct measurements of HO activity revealed that enzyme activity could be detected after about 20 min exposure to hemin, and this activity was inhibited by tin protoporphyrin (SnPP). The different pattern of HO mRNA induction by LPS as contrasted with CoCl2 suggests that LPS may act through a different translational factor, or stimulate free radical formation and the subsequent release of heme and induction of HO. These results indicate that heme causes accumulation of HO mRNA by a different mechanism than that of CoCl2. Finally, LPS shares a concomitant effect on induction of HO as an acute phase reactant type protein.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 8-16 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In investigating the role of cell-extracellular matrix interactions in cell adhesion and growth control, the effects of heparin on cell-collagen interactions were examined. Exponentially growing Balb/c-3T3 fibroblasts were radiolabelled with 3H-thymidine and detached from tissue culture surfaces using EDTA, and cell attachment to various types of collagen substrata was assayed in the presence or absence of heparin or other glycosaminoglycans (GAGs) or dextran sulfate (40 K). Cells attached readily (70-90%) to films of types I and V, but not to type III collagen. The number of cells bound to types I and V collagen films was inhibited by 10-50% when heparin was present from 0.1-100 μg/ml. Cell-collagen attachment was also inhibited by dextran sulfate, and to a lesser extent by dermatan sulfate, but chondroitin sulfates A and C and hyaluronic acid showed no effect. Heparin was active even at early time points in the adhesion assay, suggesting it may disrupt cell-collagen attachment. To study the effects of heparin in modulating cell growth on collagen, growth arrested cells cultured on type I collagen films were serum stimulated in the presence of heparin or other GAGs for 3 days. Growth was inhibited (〉 40%) only by heparin and dextran sulfate. Interaction of heparin fragments (Mr ≤ 6KD) with type I collagen was analyzed by affinity co-electrophoresis (Lee and Lander, 1991) and showed higher affinity heparin binding to native as compared with denatured collagen. These data suggest that sites within native collagen may mediate Balb cell-collagen and heparin-collagen interactions, and such interactions may be relevant towards understanding heparin's antiproliferative activity in vivo and in vitro.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 211 (1992), S. 295-306 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Histology, histochemistry, and biochemistry of the oviduct change seasonally in relationship to the annual ovarian cycle of Calotes versicolor. Histological changes show distinct changes in various components of the infundibulum, uterus and vagina of the oviduct. The active phase in the oviduct cycle of C. versicolor is relatively long, extending from April to October. Histochemical results of the oviduct during the breeding season show PAS-positive glycosaminoglycans in the mucosal epithelium as well as the presence of hydroxysteroid dehydrogenases, esterase, and intense acid phosphatase activity in the uterine glands. Biochemically alkaline and acid phosphatase show marked cyclic changes in the infundibulum and uterus respectively during the oviduct cycle. Greater activity was observed during the breeding season. β-Glucuronidase, on the other hand, shows an inverse relationship with the oviduct cycle being most active during the regressive phase and least at the time of reproductive phase.
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  • 9
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The liver of the cobia, Rachycentron canadum, was examined by gross dissection, histological, and ultrastructural procedures. Other visceral organs were examined by histological techniques only. Unique perivenous smooth muscle cords are associated with veins in these systems, but they are particularly prominent in their association with the hepatic portal veins and their numerous intrahepatic branches. The perivenous smooth muscle cords accompany tributaries of the portal veins to the junction of the venules with the hepatic sinusoids. The reciprocal contraction and relaxation of various segments of the smooth muscle cords appear to result in pooling of blood in temporary reservoirs and in its transport to various regions of the organ. This process might apply to other organ systems as well. Possibly this unique relationship of the smooth muscle cords with veins functions in a diving reflex. Triads are occasionally encountered in the cobia liver. © 1992 Wiley-Liss, Inc.
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  • 10
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The feline anterior sartorius is a long strap-like muscle composed of short muscle fibers. Nerve branches that enter this muscle contain the axons of motor units whose constituent muscle fibers are distributed asymmetrically within the muscle. In the present study, twitch and tetanic isometric contractions were evoked by stimulating individual nerve branches while muscle force was recorded and intramuscular length changes were monitored optically by the movement of reflective markers on the muscle. Contractions elicited by stimulating the parent nerve produced little change in the positions of the surface markers. Contractions elicited by stimulating the proximally or distally directed nerve branches caused the muscle to shorten at the end closest to the nerve branch and lengthen at the opposite end. Some muscles were supplied by a centrally directed nerve branch whose stimulation produced variable effects: in some cases a portion of the muscle shortened whereas the rest lengthened, but in other cases, the positions of the surface markers showed little change. The intramuscular length changes produced by stimulating single nerve branches were greater during isometric contractions at short whole-muscle lengths than at long whole-muscle lengths. The twitch and tetanic length-tension relationships obtained by stimulating the individual nerve branches were not congruent with the length-tension relationship produced when the parent nerve was stimulated. At short whole-muscle lengths, stimulation of a single nerve branch generated only a small fraction of the force that could be generated by the muscle when the parent nerve was stimulated. As whole-muscle length increased, an increased fraction of total muscle force could be generated by stimulating a single nerve branch. The results suggest that a complex relationship between passive and active elements contributes to the total muscle force and depends on the distribution of active and passive muscle units throughout the muscle. © 1992 Wiley-Liss, Inc.
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