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  • ASTROPHYSICS  (177)
  • Life and Medical Sciences  (151)
  • SPACE VEHICLES
  • 1990-1994  (328)
  • 1970-1974
  • 1990  (328)
  • 1
    Electronic Resource
    Electronic Resource
    Tissue plasminogen activator messenger RNA levels increase in cultured human endothelial cells exposed to laminar shear stress (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 143 (1990), S. 364-371 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Fluid shear stress can stimulate secretion of tissue plasminogen activator (tPA) by cultured human endothelial cells, while plasminogen activator inhibitor type-1 secretion remains unstimulated. To determine whether hemodynamically induced changes in tPA messenger RNA (mRNA) levels also occur, primary cultures from the same harvst of primary human umbilical vein endothelial cells were either maintained in stationary culture or exposed to arterial levels of shear stress (25 dynes/cm2) for 24 hours. Total cellular RNA was isolated from the shear stressed and stationary cultures and the relative levels of tPA mRNA and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA were determined using a coupled reverse transcriptase/polymerase chain reaction method. As indicated by the amount of amplification product, tPA mRNA levels were many fold higher (〉 10) in endothelial cells subjected to shear stress for 24 hours than in stationary controls. In contrast, mRNA levels for GAPDH were similar in control and shear stressed cells. The constancy of the measured GAPDH signal indicated that the tPA response was a selective effect of fluid shear stress. When a similar polymerase chain reaction method was used, the mRNA levels of basic fibroblast growth factor (bFGF) were found not to vary in comparison to GAPDH mRNA after 24 hours of shear stress. These results indicate that enhancement of the fibrinolytic potential of endothelial cells in response to hemodynamic forces could involve transcriptional events.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041430222
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  • 2
    Electronic Resource
    Electronic Resource
    Morphologic changes in human carcinoma cells (A-431) stimulated by epidermal growth factor: Effect of cholesterol and low-density lipoproteins on the ruffling response (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 458-468 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Stimulation of A-431 carcinoma cells with epidermal growth factor (EGF) causes dramatic morphologic responses including ruffling, rounding, and bulk-phase pinocytosis. In attempts to explore the mechanisms responsible for changes in plasmalemma topography. we have investigated the effects of exogenous sterols thought to alter membrane fluidity.Light and scanning electron microscopy revealed a time- and concentration-dependent inhibition of ruffling (〉 90%) by cholesterol. This effect could be duplicated by preincubation of the cells with comparable levels of low-density lipoproteins (LDL). EGF-stimulated bulk-phase endocytosis also is inhibited by treatment with cholesterol. No alteration of EGF binding, kinase stimulation, or internalization was detected in cells incubated in cholesterol-enriched medium (175 μg/ml in 0.5% ethanol), nor did cholesterol or LDL have any effect on EGF-stimulated rounding.Morphometry of electron micrographs from cholesterol-treated cells revealed a selective depletion of interdigitating lateral surface membrane that normally appears to be recruited to generate apical ruffles. Thus, the sterol inhibition of ruffling may be due to redistribution of plasmalemma rather than to changes in membrane viscosity. Together with previous observations, these data suggest that EGF-stimulated ruffling and bulk-phase pinocytosis are related phenomena, whereas EGF-stimulated cell rounding is an independent process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041420304
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  • 3
    Electronic Resource
    Electronic Resource
    Identification and purification of the cell surface glycoprotein homologous to PsA in different species of cellular slime mold on the basis of a shared carbohydrate epitope (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 11 (1990), S. 484-491 
    Details
    ISSN: 0192-253X
    Keywords: Dictyostelium ; glycosylation ; cell adhesion ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The monoclonal antibodies MUD1 and MUD50 recognize peptide and carbohydrate epitopes, respectively, on the Dictyoste-lium discoideum developmentally regulated cell surface glycoprotein PsA. PsA is a putative pre-spore cell adhesion molecule during the slug stage and is anchored to the cell membrane via a phos-phatidylinositol glycan. Here we report on the presence of a PsA-like homolog in several Dictyo-stelium species. The MUD1 epitope is mostly confined to the D. discoideum complex, and only one non-D. discoideum strain reacted strongly with this antibody. By contrast, the mAb MUD50 recognises a homologous molecule in several Dictyostelium species that do not react with MUD1. With mAb MUD50 immunoaffinity chromatography, it was possible to purify and obtain an amino-terminal sequence for the PsA homolog from the Dictvoste-lium sp. strain ZA3A and from one strain of D. pur-pureum.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020110525
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  • 4
    Electronic Resource
    Electronic Resource
    Early embryo development in the Siberian hamster (Phodopus sungorus) (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 224-229 
    Details
    ISSN: 1040-452X
    Keywords: Preimplantation embryo ; Blastocyst ; Trophoblast ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Development of preimplantation embryos of the Siberian hamster (Phodopus sungorus) in vivo and in vitro was examined. The timing of early development in vivo was found to be slower than that reported for the golden hamster. Progression through the cleavage stages, cavitation, and hatching from the zona pellucida occurred later, with blastocyst formation beginning on the afternoon of day 4 and uterine attachment occurring early on day 5. In vitro, morulae, and early blastocysts collected on day 4 and cultured in serum-containing medium formed expanded blastocysts and some began to hatch from the zona pellucida. With extended culture, blastocysts attached and formed trophoblast outgrowths. Outgrowth was characterized by an initial migration of small cells from the blastocyst, followed by formation of a sheet of trophoblast giant cells. Differences in the morphology of outgrowth between the hamster and mouse suggest that further comparative studies with the Siberian hamster may be useful.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080270307
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of cold shock and phospholipase A2 on intact boar spermatozoa and sperm head plasma membranes (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 143-149 
    Details
    ISSN: 1040-452X
    Keywords: Fertility ; Ca2+ uptake ; Head plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Head plasma membranes (HPM) isolated from cryopreserved boar spermatozoa show an excessive fluidization (Buhr et al., Gamete Res 23:441-449, 1989), which might be involved in the loss of fertility. The current study assessed the ability of cold shock (5°C) and phospholipase A2 (PA2) to duplicate these effects on membrane structure and to affect 45Ca2+ uptake and gross morphological characteristics of whole, fresh boar sperm. The HPM from cold-shocked sperm showed a significantly greater rate of fluidization over time than did HPM from control sperm. Addition of PA2 (bee or snake venom, 0.1 or 10.0 ng/ml) to HPM from control sperm caused fluidization similar to cold shocking, but to a lesser degree (P 〈 0.05). Cold-shocked intact sperm exhibited severe acrosomal disruption, loss of motility, and increased 45Ca2+ uptake relative to control sperm. Addition of PA2 (bee or snake venom, 0.1, 1.0., 10.0, and 1,000 ng/ml) to control sperm had not effect on gross morphology or motility while maintaining or increasing sperm extrusion of 45Ca2+. Therefore, although PA2 can, to some extent, duplicate the effects of cold shock on HPM molecular organization, its lipid hydrolytic action is insufficient to cause all the gross disruptions of severe thermal shock. Both PA2 and cold shock disrupted HPM structure, but only cold shock increased 45Ca2+ uptake, suggesting that cold shock may be increasing 45Ca2+ uptake in areas other than the head. Cold shock disrupts sperm on three levels; membrane molecular organization, intracellular Ca2+ regulation, and gross morphology/motility.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080260208
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of microinjection and two types of electrical stimuli on bovine sperm-hamster egg penetration (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 27 (1990), S. 163-167 
    Details
    ISSN: 1040-452X
    Keywords: Electrofusion ; Electroporation ; In vitro fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: These experiments were designed to test the effects of an electrofusion and an electroporation pulse on bovine sperm-hamster egg development. In experiment 1, single motile sperm were injected into the perivitelline space of each egg. A 4,500 V/cm, 30 μsec fusion pulse (FP) was applied while sperm-egg membrane contact was maintained. It was observed that single motile sperm were rendered immotile immediately after FP application whereas nonpulsed single motile sperm remained motile for up to 36 h postinjection. In addition, both motile and sanicated spermatozoa were injected directly into the ooplasm prior to receiving an FP to determine whether the FP was detrimental to sperm viability. In experiment 2, to induce the acrosome reaction, an 1,150 V/cm electroporation pulse was applied to washed bovine sperm suspended in TALP medium containing 5 mM Ca2+. Treated and nontreated sperm were coincubated with zona-free hamster ova, and sperm-penetrating ability was measured. Results from experiment 1 indicate that FP failed to induce sperm-egg fusion (0/69). FP did not, however, inhibit decondensation or pronuclear formation of sperm injected into hamster egg ooplasm. Single motile sperm injected into the ooplasm resulted in development of both pulsed (19/28) and nonpulsed (21/28) groups. Sonicated tail-free sperm heads injected into the ooplasm resulted in no detectable difference between treated (18/30) and nontreated (19/30) groups. In experiment 2, treatment of sperm with electroporation pulse +5 mM Ca2+ increased zona-free hamster ova penetration scores over nontreated sperm within bulls (P 〈 .05). These results indicate that an electroporation pulse in conjunction with high Ca2+ rather than an electrofusion pulse facilitates sperm penetration and early development.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080270212
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  • 7
    Electronic Resource
    Electronic Resource
    Golgi study of the anterior dorsal ventricular ridge in a lizard. I. neuronal typology in the adult (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 203 (1990), S. 293-300 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using Golgi techniques we have studied neuronal cell types in the anterior dorsal ventricular ridge (ADVR) of the adult lizard Gallotia galloti. Multipolar, bitufted, and juxtaependymal neuronal forms were found. The multipolar and bitufted neurons are present in both the periventricular and central ADVR zones. Multipolar neurons can be subdivided into multipolar neurons with polygonal somata and four to six main dendritic trunks and multipolar neurons with pyramidal somata and three or more dendritic trunks. The former are the cells most frequently impregnated in the ADVR. In the population of bitufted neurons, we distinguish subtypes I, II, and III according to the number of dendritic trunks that emerge from the somata. Juxtaependymal neurons are restricted to a cell-poor zone, adjacent to ependymal cells. Their dendrites either are orientated parallel to the ventricular surface or extend into the periventricular zone. The dendrites of ADVR neurons have pedunculated spines with knob-like tips. However, such spines do not appear on the somata or on the primary dendritic trunks. The number of spines is scarce or moderate. The periventricular neuronal clusters contain two to five cells. The morphology of these neurons is mainly multipolar, but we also found some bitufted neurons.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052030304
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  • 8
    Electronic Resource
    Electronic Resource
    SV40 T antigen alone drives karyotype instability that precedes neoplastic transformation of human diploid fibroblasts (1990)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 42 (1990), S. 13-31 
    Details
    ISSN: 0730-2312
    Keywords: immortalization ; chromosome damage ; SV40 ; simian virus 40 ; large T antigen ; karyotype instability ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: To define the role of SV40 large T antigen in the transformation and immortalization of human cells, we haye constructed a plasmid lacking most of the unique coding sequences of small t antigen as well as the SV40 origin of replication. The promoter for T antigen, which lies within the origin of replication, was deleted and replaced by the Rous sarcoma virus promoter. This minimal construct was co-electroporated into normal human fibroblasts of neonatal origin along with a plasmid containing the neomycin resistance gene (neo). Three G418-resistant, T antigen-positive clones were expanded and compared to three T antigen-positive clones that received the pSV3neo plasmid (capable of expressing large and small T proteins and having two origins of replication). Autonomous replication of plasmid DNA was observed in all three clones that received pSV3neo but not in any of the three origin minus clones. Immediately after clonal expansion, several parameters of neoplastic transformation were assayed. Low percentages of cells in T antigen-positive populations were anchorage independent or capable of forming colonies in 1% fetal bovine serum. The T antigen-positive clones generally exhibited an extended lifespan in culture but rarely became immortalized. Large numbers of dead cells were continually generated in all T antigen-positive, pre-crisis populations. Ninety-nine percent of all Tantigen-positive cells had numerical or structural chromosome aberrations. Control cells that received the neo gene did not have an extended life span, did not have noticeable numbers of dead cells, and did not exhibit karyotype instability. We suggest that the role of T antigen protein in the transformation process is to generate genetic hypervariability, leading to various consequences including neoplastic transformation and cell death.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240420103
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  • 9
    Electronic Resource
    Electronic Resource
    Golgi study of the anterior dorsal ventricular ridge in a lizard. II. Neuronal cytodifferentiation (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 203 (1990), S. 301-310 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of the morphologic features of neurons in the anterior dorsal ventricular ridge (ADVR) has been followed in Golgi preparations from the lizard Gallotia galloti between embryonic stage 32 and post-eclosion stages of specimens 3.6-4.5 cm in length. The differentiation sequence of multipolar and bitufted neurons was established. Dendritic growth cones are present after stage 34. Filiform dendritic processes are replaced later on by spines. Clusters of neurons first appear at stage 39 in the periventricular zone, the cells becoming Golgi-impregnated in pairs. After hatching, the number of impregnated cells per cluster increases.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052030305
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  • 10
    Electronic Resource
    Electronic Resource
    Solubilization and characterization of a lactogenic receptor from human placental chorion membranes (1990)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 43 (1990), S. 1-15 
    Details
    ISSN: 0730-2312
    Keywords: placentae ; prolactin ; growth hormone ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Prolactin has wide range of actions, including osmoregulation and the control of mammary gland development and lactation. These effects are mediated through a high-affinity cell surface receptor, which has been well characterized in a number of animal tissues. The molecular characteristics of the human receptor are unknown, however. The present studies were initiated, therefore, to determine the binding and molecular characteristics of the lactogenic receptor of human placental chorion membranes. Subcellular fractionation studies showed that the bulk of the receptor sedimented in the microsomal fraction at 45,000gav. Endogenous ligand was dissociated from the receptor with 3.5 M MgCl2 or 0.05 M acetate buffer (pH 4.8) with preservation of binding activity. The microsomal receptor bound human growth hormone (hGH), human prolactin(hPRL), ovine prolactin (oPRL), and human placental lactogen (hPL) but not non-primate growth hormones, indicating a narrow specificity for lactogenic hormones. The binding was only partially reversible in agreement with the know binding kinetics of animal lactogenic receptor. The receptor was solubilized with 45% yield from the microsomes using 16 mM 3-[(3-cholamidopropyl)dimethylammonio]-l-propane sulphonate (CHAPS) detergent-250 mM NaCL, and the binding activity was fully restored by a two-fold dilution in the binding reaction to reveal a KD of 0.8 nM for hGH and a binding capacity of 200 fmol of specifically bound hGH per mg of microsomal protein. Gel filtration chromatography indicated the minimum molecular weight of the ligand-receptor complex was approximately 60,000 daltons, and sodium dodecyl sulphate polyacrylaminde gel electrophoresis (SDS-PAGE) of covalently cross-linked 125I-hGH-receptor complexes revealed a molecular size of 58,000 daltons. When account was taken of the contribution of the ligand, a molecular weight of 36,000 for the receptor's binding domain was obtained. These data indicate that the chorion lactogenic receptor has very similar binding and molecular characteristics to the lactogenic receptors from other mammalian species. Chorion membranes are thus a convenient source of material for the further purification and characterization of the human lactogenic receptor.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240430102
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