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  • Polymer and Materials Science  (316)
  • Life and Medical Sciences  (117)
  • Organic Chemistry  (38)
  • Genetics  (11)
  • Wiley-Blackwell  (471)
  • 1990-1994  (467)
  • 1980-1984
  • 1915-1919  (1)
  • 1890-1899  (3)
  • 1991  (467)
  • 1940
  • 1916  (1)
  • 1895  (3)
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  • 1990-1994  (467)
  • 1980-1984
  • 1915-1919  (1)
  • 1890-1899  (3)
  • 1940-1944  (12)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Comparative kinetics of short and long sperm in sperm dimorphic Drosophila species (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 269-274 
    Details
    ISSN: 0886-1544
    Keywords: minor and major waves ; beat frequeney ; wave propagation velocity ; coiling diameter ; storage effect ; differential behaviour ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: All species of the Drosophila obscura group exhibit within-ejaculate sperm length dimorphism. The present work is a contribution to the understanding of sperm competition through a comparative study of sperm kinetic parameters in four of these species. Videomicrographic observations at 200 frames per second of sperm from males and females, out of the storage organ, prior or after storage were made. Drosophila sperm display both major and minor waves. The former is analysed by measuring coiling diameter (μm) and the latter by recording both beat frequency (s-1) and wave propagation velocity (μm·s-1). Results show that the ‘behaviour’ of short and long spermatozoa noticeably differ: short sperm kinetics remains unaltered after storage while both major and minor waves of long spermatozoa are markedly modified. Thus, evidence is provided here of a sort of “differential activation” which is assumed to result in different survival abilities of short and long sperm within the storage organ of females.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970190405
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  • 2
    Electronic Resource
    Electronic Resource
    Crystallinity and lateral crystallite size of different UHMW PE materials (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 863-866 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Nascent high-molecular-weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70-75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molecular weight of the sample and the higher the activity of the used catalyser. A melting / recooling treatment results in a reduction of crystallinity by about 15-25% and disappearance of the triclinic phase. Further, an irreversible conversion of nascent orthorhombic extended chain crystallites to orthorhombic folded chain crystallites of increased lateral dimensions and crystalline perfections takes place during the melting / recooling treatment. The results are compared to those obtained for lower-molecular-weight PE samples and for high-strength / modulus PE fibers of different origins.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420332
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of spermatogenic cell populations at specific stages of differentiation in the human (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 30 (1991), S. 275-282 
    Details
    ISSN: 1040-452X
    Keywords: Human testis ; Cell separation ; Elutriation ; Spermatid ; Ultrastructure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Studying biochemical events in human spermatogenesis requires separated populations of spermatogenic cells. Dissociation of these cells was performed by a Trypsin-DNAse method adapted from the technique used for rodents. Cell separation was performed by centrifugal elutriation. Seven populations were collected, one further purified by Percoll gradient centrifugation, giving nine different cell populations. The efficiency of the cell separation was evaluated by phase contrast microscopy, flow cytometric DNA analysis, and electron microscopy. Five populations were enriched in spermatids: two in round spermatids (87% and 73%), another in round (52%) and elongating (44%) spermatids, another constituted by 80% elongating spermatids, and the last by 90% elongated spermatids. Two of the four remaining populations were enrichied in primary spermatocytes (74% and 54%); another population was the upper part of the Percoll gradient and constituted cytoplasmic lobes and residual bodies (89%); the last population was made up of various cells, with no specific enrichment. Electron microscopic observations revealed good preservation of the separated cells; only the flagella from elongated spermatids were lost. Furthermore, an unusual pattern of nucleoplasm distribution during stages 2-4 of spermatid differentiation was observed and its signification is discussed with regard to the shape of the human spermatozoon.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080300316
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of charge density and steric factor of aminated chloromethyl polystyrene homologs in bilirubin adsorption (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 2483-2488 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Bilirubin, a bile pigment, was studied for its extent of adsorption on substituted aminechloromethyl polystyrene by UV spectrophotometry. By performing simple displacement reactions on chloromethyl polystyrene with secondary and tertiary amines, the amount of charge density and steric factor on substituted nitrogen atom have been varied. Adsorption isotherms of bilirubin at 0°C by different amine-chloromethyl polystyrene homologs suggest the existence of electrostatic interaction of polymeric resin with bilirubin moiety. Results of adsorption of bilirubin to polymeric resin have shown that the extent of adsorption of bilirubin depends on the unit charge, and on the structure of the substituted amine-chloromethyl polystyrene. The effects of porosity of resin on bilirubin adsorption have also been discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420913
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  • 5
    Electronic Resource
    Electronic Resource
    Developmental protein synthesis is required for the transcription of Dictyostelium prespore genes (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 12 (1991), S. 113-122 
    Details
    ISSN: 0192-253X
    Keywords: Dictyostelium discoideum ; cyclo heximide ; emetine ; protein synthesis ; mRNA accu mulation ; transcription ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: It has been established previ- ously that the maintenance of expression of pre-spore-specific genes of Dictyostelium discoideum is prevented by the translational inhibitor cyclohex- imide. The drug had no effect upon the level of transcripts of the other genes examined, prestalk-specific or cell type-nonspecific. However, the interpretation of this result is open to question, because of possible nonspecific effects of cyclo-heximide. We have now characterized the cellular specificity and temporal profiles of mRNA accumu- lation of additional Dictyostelium cDNA clones, and have examined other inhibitors of in vivo protein synthesis. Four structurally and mechanistically distinct translational inhibitors each prevented the reaccumulation of prespore transcripts in cyclic AMP-primed, disaggregated amoebae. These results establish the importance of developmental protein synthesis in the accumulation of prespore gene transcripts. Nuclear run-on transcription assays were used to learn whether protein synthesis is required primarily for mRNA synthesis or transcript stability. A transcriptional time course first demonstrated that the abundance of these cell-specific transcripts during development mirrors their rates of synthesis. Significantly, the protein synthesis requirement of the prespore genes examined also occurs at the level of mRNA transcription, implying the existence of one or more developmentally regulated transcriptional activators.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020120119
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  • 6
    Electronic Resource
    Electronic Resource
    The synthesis of soluble, substituted silane high polymers by Wurtz coupling techniques (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 813-824 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Wurtz-type coupling of a number of representative classes of substituted dichlorosilane monomers was investigated in considerable detail. Low temperature polymerization techniques, including ultrasonic activation, were also studied. Similarly, the effect of dipolar additives on the polymerization process was examined. The conclusions drawn from these studies provide some insight into the selection of useful polymerization conditions for the conversion of various monomer types into linear high polymers.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290604
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and properties of polyethersulphone-polydimethyisiloxane block copolymers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 193-200 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High molecular weight alternating block copolymers of polyethesulphone (PES) and polydimethylsiloxane (PDMS) were prepared by the condensation of dimethylamino-terminated PDMS oligomers and hydroxy-terminated PES oligomers in 1,2-dichlorobenzene. Microphase separation of the block copolymers at exceptionally short block lengths was observed by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The Si—O—C intersegment linkage in these materials appeared to display poor hydrolytic stability which is contrary to results obtained for other block copolymers.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290206
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of graft copolymers of rigid-rod poly(p-phenylenebenzobisimidazole) (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 121-125 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290114
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of plasma polymerized hydrocarbons using CP-MAS 13C-NMR (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1801-1805 
    Details
    ISSN: 0887-624X
    Keywords: Carbon-13 NMR ; plasma polymerization ; thin films ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma polymerized hydrocarbons made from ethane and methane were produced under different reactor conditions and probed by solid-state carbon-13 nuclear magnetic resonance (13C-NMR) with cross-polarization and magic-angle sample spinning. NMR experiments provided structural information about the plasma polymers. The conditions of low power, high hydrocarbon gas flow rate, and no added hydrogen gas appeared to give the highest amount of nonprotonated sp3 hybridized carbons in the films for the reactor design used. The use of methane or ethane as reactor gas did not affect plasma polymer structure significantly.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080291212
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  • 10
    Electronic Resource
    Electronic Resource
    Association of vanadate-sensitive Mg2+-ATPase and shape change in intact red blood cells (1991)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 46 (1991), S. 284-290 
    Details
    ISSN: 0730-2312
    Keywords: erythrocytes ; magnesium ; echinocyte ; calcium ; plasma membrane ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Intact human erythrocytes, initially depleted of Mg2+ by EDTA incubation in the presence of A23187, exhibit Mg2+-dependent phosphate production of around 1.5 mmol per liter cells · h, half-maximally activated at around 0.4 mM added free Mg2+. This appears to correspond to Mg2+-stimulated adenosine triphosphatase (Mg2+-ATPase) activity found in isolated membranes, which is known to have a similar activity and affinity for Mg2+. Vanadate (up to 100 μM) inhibited Mg2+-dependent phosphate production and ATP breakdown in intact cells. Over a similar concentration range vanadate (3-100 μM) transformed intact cells from normal discocytes to echinocytes within 4-8 h at 37°C, and more rapidly in Mg2+-depleted cells. The rate of Ca2+-induced echinocytosis was also enhanced in Mg2+-depleted cells. These results support previous studies in erythrocyte ghosts suggesting that vanadate-induced shape change is associated with inhibition of Mg2+-ATPase activity localized in the plasma membrane of the red blood cell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240460403
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