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  • Life and Medical Sciences  (135)
  • FLUID MECHANICS AND HEAT TRANSFER  (65)
  • Biochemistry and Biotechnology  (50)
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  • 1985-1989  (255)
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  • 1988  (255)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 32 (1988), S. 993-1000 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monoclonal antibodies are being manufactured for clinical trials in suspension culture at the 1300-L scale. Suspension culture offers some advantages relative to high-density mammalian cell culture methods; in particular, the ability to closely monitor the behavior of cells in a homogeneous environment. Computer control and on-line mass spectrography of exit gases provide instantaneous information about the culture metabolic activity. Air sparging and agitation by marine impeller provide aeration sufficient to maintain a constant dissolved oxygen tension at cell concentrations up to 5.0 × 106 cells/mL without causing apparent cell damage.
    Additional Material: 8 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 321-327 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A combination of ionic strength reduction and diafiltration of Trichoderma reesei cellulate complex through a hollow fiber apparatus of 5000 molecular weight (MW) cutoff and subsequent passage of filtrate over a Spherogel-TSK 3000-SW column provided extracts that had the ability to generate microfibrils in filter paper and to disrupt filter paper and corn leaf tissue. Milligram quantities of material obtained from these extracts released small amounts of soluble carbohydrate from filter paper, required ferric iron for increased activity, and contained amino acids. Short fiber formation and disruption of filter paper during interaction with these extracts was enhanced by prior acid treatment and eliminated by prior base treatment. The amount of soluble carbohydrate hydrolyzed in 24 h from filter paper by whole cellulase complex was not changed by first disrupting the substrate with the extracts.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0749-503X
    Keywords: Single-cell proteins ; Saccharomyces cerevisiae ; fragile mutants ; srb1 ; lysis ; polyploids ; protein extracts ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: A series of prototrophic fragile strains of different ploidy (2n, 3n and 4n) has been genetically constructed on the basis ofhalopoid srb1 containing segregants of the fragile Saccharomyces cerevisiae mutant VY 1160. The strains have been characterized by several criteria. In regard to generation time, biomass yield, and nucleic acids content of the cells, the tetraploid srb1 homozygous hybrid is indistinguishable from an industrial strain of S. cerevisiae. However, it is characterized by a higher protein content. Unlikely any other laboratory or industrial strains, the original mutant and these hybrids possess an ability for lysis upon suspension in hypotonic solutions. The dependence of the percentge of lysed cells on the growth phase and concentration of osmotic stabilizer in the medium has been investigated. The quantity of proteins in the soluble fractions obtained after lysis of these strains by osmotic shock has been determined. These hybrids can be considered as a potential industrial source of potentials for nutritional purposes.
    Additional Material: 7 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 11 (1988), S. 318-325 
    ISSN: 0886-1544
    Keywords: actin ; contractile proteins ; microvilli ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The mammalian genome contains 20-30 genes encoding a family of actins. To date, however, only six proteins (four muscle and two nonmuscle isoforms) encoded by this multigene complex have been identified. We have isolated two actins from the brush border of rat intestinal epithelial cells that have isoelectric points and N-terminal peptides characteristic of the cytoplasmic β- and γ-actins. However, using a panel of actin-specific monoclonal antibodies, we show that these actins contain a set of epitopes that distinguishes them from any of the known cytoplasmic or muscle isoforms. These unique actins share features of both the nonmuscle and muscle isoforms, suggesting that they represent an intermediate in the evolution of the specialized muscle actins.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 1 (1988), S. 11-17 
    ISSN: 1040-452X
    Keywords: GH1 ; GH2 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We report the primary structures of two mRNA species (GH1 and GH2), each predicted from the cloned cDNA and genomic gene sequences, that encode growth hormone in rainbow trout (Salmo gairdneri). Both GH1 and GH2 mRNA contain open reading frames comprising 630 nucleotides and encode 210 amino acid residues, of which 11 are variant. The translated regions of mRNA are flanked by a short 5′-untranslated sequence, which is highly conserved, and a relatively long 3′-untranslated sequence, which is highly divergent. The differences at the 3′-untranslated regions suggest that the GH1 and GH2 mRNA originate from different loci. RNA blot analysis of trout pituitary RNA using an oligonucleotide probe specific for the GH2 sequence indicates that the cloned gene is expressed. The GH1 and GH2 mRNA likely are transcribed from two distinct loci, which were duplicated during tetraploidization of the salmonid genome between 50 and 100 million years ago.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Nuclear and cytoplasmic volume changes as well as the elimination of residual spermatid cytoplasm were investigated in the red-ear turtle (Pseudemys scripta) and the rooster (Gallus domesticus). Nuclei of newly formed spermatids which were originally centrally located became eccentrically located within the cell in both species. Shortly thereafter the nuclear pole of the spermatid was found situated within deep crypts of a Sertoli cell. The cytoplasm of elongating spermatids was displaced along the nonacrosomal region of the nucleus and the proximal flagellum. In both species sheetlike Sertoli cell processes indented spermatid cytoplasm adjacent to the nucleus and appeared to segregate small packets of the cytoplasm. In the turtle, these packets of cytoplasm were separated from the spermatid. In both the turtle and rooster, a portion of the spermatid cytoplasm was displaced forward over the acrosomal region of the spermatid to resemble a hood. As spermatids were transported to the seminiferous tubular lumen, cytoplasmic lobes which projected forward of the spermatid head were formed by preferential flow of cytoplasm into one aspect of the cytoplasmic hood. In both species, at sperm release the cytoplasmic lobe was disengaged from the spermatid head to form a large residual body that was internalized and degraded within the Sertoli cell. Medium-sized cytoplasmic lobes were pinched from the head and neck region of the turtle and rooster spermatids, respectively. In the turtle, small-sized mitochondrial-rich cytoplasmic fragments budded from the caudal head and midpiece of the spermatids and were phagocytosed by the Sertoli cell. Thus, cytoplasmic elimination occurred through (1) segregation of cytoplasmic packets by Sertoli penetrating processes (turtle), (2) elimination of large and medium-sized residual bodies from the head (turtle and bird), and (3) budding of small mitochondrial-rich cytoplasmic fragments from the region of the midpiece (turtle). In the turtle a 79% reduction in total cell volume occurred during spermiogenesis which was the result of an 84% cytoplasmic reduction and a 78% nuclear reduction. During spermiogenesis, the rooster lost 97% of its total cell volume due to a 97% cytoplasmic volume change and a 96% nuclear volume change.
    Additional Material: 31 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 198 (1988), S. 165-177 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The process involved in the reduction of both nuclear and cytoplasmic volume was investigated in the bluegill (Lepomis macrochirus), a teleost fish. Young spermatids contained centrally positioned nuclei which, with time, moved toward the cell surface to become eccentrically positioned. Chromatin condensation was initiated from a region near the implantation fossa, whereas at the opposite pole of the nucleus an area sparse in heterochromatin (clear area) was noted. The nuclear membrane lying adjacent to the clear area dissolved and subsequently reformed, yielding a nucleus with a reduced volume. During this process, packets of cytoplasm surrounded by a double membrane were formed along the future midpiece. The packets of cytoplasm migrated toward the cell surface, protruded from the surface, and were extruded into the spermatocyst lumen. These structures, termed residual bodies, were subsequently endocytosed, accumulated into large phagocytic vocuoles, and eventually degraded by the nearby Sertoli cell. When the spermatocyst ruptured, spermatozoa containing sparse cytoplasm were released into the excurrent duct system. During spermiogenesis, both the nuclear and cytoplasmic volumes decreased substantially (80%, 92% respectively) leading to an overall 87% reduction in total cell volume.
    Additional Material: 19 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 796-801 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Techniques for the immobilization of bovine carbonic anhydrase (BCA) on porous silica beads and graphite are presented. Surface coverage on porous silica beads was found to be 1.5 × 10-5 mmol BCA/m2, and on graphite it was 1.7 × 10-3 mmol BCA/m2 nominal surface area. Greater than 97% (silica support) and 85% (graphite support) enzyme activity was maintained upon storage of the immobilized enzyme for 50 days in pH 8 buffer at 4°C. After 500 days storage, the porous silica bead immobilized enzyme exhibited over 70% activity. Operational stability of the enzyme on silica at 23°C and pH 8 was found to be 50% after 30 days. Catalytic activity expressed as an apparent second-order rate constant K′Enz for the hydrolysis of p-nitrophenyl acetate (p-NPA) catalyzed by BCA immobilized on silica beads and graphite at pH 8 and 25°C is 2.6 × 102 and 5.6 × 102 M-1s-1 respectively. The corresponding KENZ value for the free enzyme is 9.1 × 102 M-1s-1. Activity of the immobilized enzyme was found to vary with pH in such a manner that the active site pK, on the porous silica bead support is 6.75, and on graphite it is 7.41. Possible reasons for a microenvironmental influence on carbonic anhydrase pKa, are discussed. Comparison with literature data shows that the enzyme surface coverage on silica beads reported here is superior to previously reported data on silica beads and polyacrylamide gels and is comparable to an organic matrix support. Shifts in BCA-active site pKa values with support material, a lack of pH dependent activity studies in the literature, and differing criteria for reporting enzyme activity complicate literature comparisons of activity; however, immobilized BCA reported here generally exhibits comparable or greater activity than previous reports for immobilized BCA.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 134 (1988), S. 220-228 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mitogen c stimulation of quiescent human fibroblasts (HSWP) with serum or a mixture of growth factors (consisting of vasopressin, bradykinin, EGF, and insulin) stimulates the release of inositol phosphates, mobilization of intracellular Ca, activation of Na/H exchange and subsequent incorporation of [3H]-thymidine. We have determined previously that pretreatment with the tumor-promoting phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) inhibits mitogen-stimulated Na influx in HSWP cells. We report herein that TPA pretreatment also substantially inhibits the mitogen-stimulated release of inositol phosphates in HSWP cells. Half maximal inhibition of mitogen-stimulated inositol phosphate release occurs at 1-2 nM TPA. Treatment of cells with TPA alone has no effect on inositol phosphate release. The effect of TPA pretreatment on inositol phosphate release induced by individual growth factors has also been determined. Orthovanadate, reported by Cassel et al. (1984) to increase Na/H exchange in A431 cells, has been demonstrated to stimulate both Na influx and inositol phosphate release in HSWP cells. TPA pretreatment also inhibits both orthovanadate-stimulated inositol phosphate release and Na influx. In addition, Orthovanadate was determined to increase intra-cellular Ca activity by mobilizing intracellular calcium stores, as determined with the fluorescent intracellular calcium probe fura-2. TPA pretreatment blocks orthovanadate stimulated mobilization of intracellular Ca stores. It appears clear that in HSWP cells pretreatment of cells with phorbol ester is capable of artificially desensitizing the early cellular responses to mitogenic stimuli (growth factors, orthovanadate) by blocking the signal transduction mechanism involved at a point prior to the release of inositol phosphates. We hypothesize that in HSWP cells the normal desensitization of both inositol phosphate release and Na/H exchange is mediated via activation of protein kinase C subsequent to the stimulus-mediated activation of phospholipase C and release of protein kinase C activator diacylglycerol. However it is interesting to note that TPA-mediated inhibition of these early responses in HSWP cells does not inhibit their ability to be stimulated to incorporate [3H]-thymidine. These results are contrasted with those obtained in WI-38 cells. A cell-type in which (1) orthovanadate does not stimulate inositol phosphate release, (2) TPA has minimal or no inhibitory effect on early growth factor induced cellular responses (i.e., inositol phosphate release, intracellular Ca mobilization, activation of Na/H exchange), (3) TPA stimulates Na/H exchanger activity, without activating inositol phosphate release, and (4) TPA promotes (unlike in HSWP cells) the incorporation of [3H]-thymidine.
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 137 (1988), S. 448-454 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Slow Ca-action potentials (CaAP) were studied in normal human skeletal muscle fibers obtained during surgery (fibers with both ends cut). Control studies also were carried out with intact as well as cut rat skeletal muscle fibers. Experiments were performed in hypertonic Cl-free saline with 10 or 84 mM Ca and K-channel blockers; muscles were preincubated in a saline containing Cs and tetraethylammonium. A current-clamp technique with two intracellular microelectrodes was used. In human muscle, 14.5% of the fibers showed fully developed CaAPs, 21% displayed nonregenerative Ca responses, and 64.5% showed only passive responses; CaAPs were never observed in 10 mM Ca. In rat muscle, nearly 90% of the fibers showed CaAPs, which were not affected by the cut-end condition. Human and rat muscle fibers had similar membrane potential and conductance in the resting state. In human muscle (22-32± C, 84 mM Ca), the threshold and peak potential during a CaAP were + 26 ± 6 mV and + 70 ± 3 mV, respectively, and the duration measured at threshold level was 1.7 ± 0.5 sec. In rat muscle, the duration was four times longer During a CaAP, membrane conductance was assumed to be a leak conductance in parallel with a Ca and a K conductance. In human muscle (22-32° C, 84 mM Ca, 40 μS, fiber diameter), values were 0.4 ± 0.1 μS, 1.1 ± 0.7 μS, and 0.9 ± 0.4 μS, respectively. Rat muscle (22-24° C, 84 mM Ca) showed leak and K conductances similar to those found in human fibers. Ca-conductance in rat muscle was double the values obtained in human muscle fibers.
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