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  • Polymer and Materials Science  (845)
  • Life and Medical Sciences  (368)
  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of poly-L-lysine with controlled low molecular weight (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 3893-3906 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Carboxy-(N∊-benzyloxycarbonyl)-L-lysine anhydride (Z-L-lysine NCA) was polymerized in dimethylformamide with triethylamine, diethylamine or hexylamine as initiator, at varying molar ratios of NCA to initiator (M/I ratio). After removal of the protecting Z-group the resulting poly-L-lysine was characterized with 1H NMR and MALDI TOF MS. Both diethylamine- and hexylamine-initiated polymerization yielded poly-L-lysine in which the initiators were incorporated at the carboxylic end of the polymer. This indicates that the NCA polymerization occurred exclusively via nucleophilic attack of the initiator on the monomer. On the other, hand, when triethylamine was used as the initiator, poly-L-lysine was obtained in which no triethylamine-derived end group could be detected by MS. These polymer chains are most likely end-capped with an N-acyl-2,5-dioxopiperazine group at the carboxylic end of the polymer. Incorporation of diethylamine and hexylamine allowed determination of the degree of polymerization (DP) of the obtained polymers by 1H NMR. The DP depended linearly on the M/I ratio, for both diethylamine and hexylamine, with higher DPs for the diethylamine-initiated poly-L-lysine at equal M/I ratio.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021981211
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  • 2
    Electronic Resource
    Electronic Resource
    PML-containing nuclear bodies: Their spatial distribution in relation to other nuclear components (1996)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 63 (1996), S. 280-291 
    Details
    ISSN: 0730-2312
    Keywords: nuclear bodies ; PML ; confocal microscopy ; image restoration ; RNA ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The PML protein is a human growth suppressor concentrated in 10 to 20 nuclear bodies per nucleus (PML bodies). Disruption of the PML gene has been shown to be related to acute promyelocytic leukaemia (APL). To obtain information about the function of PML bodies we have investigated the 3D-distribution of PML bodies in the nucleus of T24 cells and compared it with the spatial distribution of a variety of other nuclear components, using fluorescence dual-labeling immunocytochemistry and confocal microscopy. Results show that PML bodies are not enriched in nascent RNA, the splicing component U2-snRNP, or transcription factors (glucocorticoid receptor, TFIIH, and E2F). These results show that PML bodies are not prominent sites of RNA synthesis or RNA splicing. We found that a large fraction of PML bodies (50 to 80%) is closely associated with DNA replication domains during exclusively middle-late S-phase. Furthermore, in most cells that we analysed we found at least one PML body was tightly associated with a coiled body. In the APL cell line NB4, the PML gene is fused with the RARα gene due to a chromosomal rearrangement. PML bodies have disappeared and the PML antigen, i.e., PML and the PML-RAR fusion protein, is dispersed in a punctated pattern throughout the nucleoplasm. We showed that in NB4 cells the sites that are rich in PML antigen significantly colocalize with sites at which nascent RNA accumulates. This suggests that, in contrast to non-APL cells, in NB4 cells the PML antigen is associated with sites of transcription. The implications of these findings for the function of PML bodies are consistent with the idea that PML bodies are associated with specific genomic loci. © 1996 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Surface analysis of monomolecular layers with time-of-flight SIMS (1990)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 16 (1990), S. 216-217 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740160145
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  • 4
    Electronic Resource
    Electronic Resource
    Transforming growth factor-β in the early mouse embryo: Implications for the regulation of muscle formation and implantation (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 14 (1993), S. 212-224 
    Details
    ISSN: 0192-253X
    Keywords: Embryonic stem cells ; differentiation ; organogenesis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In a search for functions of transforming growth factor-β during early embryonic development we used two different experimental approaches. In the first we made use of embryonic stem (ES) cells. ES cells in culture differentiate to derivatives of all three germ layers and mimic some aspects of organogenesis when grown as aggregates in suspension to form embryoid bodies. Differentiation procedes further when the embryold bodies attach to suitable substrates. Muscle and neuronal cells are among the most readily identified cell types then formed. We examined the effect of all-trans retinoic acid (RA) and members of the transforming growth factor-β family(TGF-βl, TGF-β2) under these conditions in an assay where single aggregates formed in hanging microdrops in medium supplemented with serum depleted of lipophilic substances which would include retinoids. Endoderm-like cells formed under all conditions tested. RA at concentrations of 108 M and 107 M induced the formation of neurons but in the absence of RA or at concentrations up to 10-9 M, neurons were not observed. Instead, beating muscle formed in about one-third of the plated aggregates; this was greatly reduced when RA concentrations increased above 10-9 M. Immunofluorescent staining for muscle specific myosin showed that two muscle cell types could be distinguished: elongated, non-contractile myoblasts and mononucleate flat cells. The mononucleate flat cells appeared to correspond with rhythmically contracting muscle. The number of non-contractile myoblasts increased 3-fold over controls in the presence of 10-9 M RA. TGF-βs increased the number of contractile and non-contractile muscle cells by a factor 3 to 7 over controls, depending on the TGF-β isoform added and the muscle cell type formed. TGF-β2 also invariably increased the rate at which contracting muscle cells were first observed in replated aggregates. The stimulatory effect of TGF-βs on the formation of mononucleate flat cells was completely abrogated by RA at 10-9 M while the number of myoblasts under similar conditions was unchanged. These data suggest that a complex interplay between retinoids and TGF-β isoforms may be involved in regulation of differentiation in early myogenesis.In the second approach, neutralizing polyclonal rabbit antibodies specific for TGF-β2 were injected into the cavity of mouse blastocysts 3.5 days post coitum (pc). After 1 day in culture, embryos were transferred to pseudopregnant females. The number of decidua, embryos and resorptions were counted at day 8.5-9.5 pc. Control antibody injected embryos implanted with high efficiency (87%) compared with anti-TGF-β2 injected embryos which implanted with an efficiency of only 43%. If empty decidua (resorptions) were included, the overall recovery was 71% and 32% for control and experimental embryos, respectively. Embryos that were recovered showed no overt macroscopic abnormalities. These results together impiy functions for TGF-βs in implantation as well as in later development of the embryo. © 1993Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020140308
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  • 5
    Electronic Resource
    Electronic Resource
    Seeded emulsion polymerization of butylacrylate: “Zero-one or pseudo-bulk?” (1996)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 47 (1996), S. 441-449 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the emulsion polymerization of butyl acrylate at 20°C in Smith-Ewart interval III were investigated using a redox initiator system peroxodisulfate-bisulfite-copper. The aim of this work was to obtain more basic knowledge about the kinetic behavior of the butyl acrylate system. Monomer conversion into polymer was based on gravimetrically calibrated online densitometry. The experimentally obtained conversion versus time curves for these seeded reactions were fitted by a linear regression procedure (slope and intercept) as well as by a nonlinear regression procedure based upon zero-one kinetics. The conclussion is that the emulsion polymerization of butyl acrylate may reflect zero-one kinetics up to a particle size of approximately 130 nm. The rate coefficients for entry and exit can be obtained fairly accurately with the slope and intercept procedure and with the nonlinear regression method if the propagation rate coefficient is accurately known. However, this is not the case. Therefore the development of universal procedures for obtaining the propagation rate coefficients is essential, since this parameter is of paramount importance in all further model calculations concerning emulsion polymerization.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1996.010471004
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  • 6
    Electronic Resource
    Electronic Resource
    Development of macromolecular prodrugs of the antitumor antibiotic adriamycin (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 9 (1985), S. 175-178 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.020091985125
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  • 7
    Electronic Resource
    Electronic Resource
    Emulsion co- and terpolymerization of styrene, methyl methacrylate, and methyl acrylate. I. Experimental determination and model prediction of composition drift and microstructure in batch reactions (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 935-947 
    Details
    ISSN: 0887-624X
    Keywords: emulsion copolymerization ; terpolymerization ; composition drift ; chemical composition distribution ; gradient polymer elution chromatography ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In Part I of this series the reactivity ratios of the comonomer pair methyl acrylate-methyl methacrylate were determined with low-conversion bulk polymerizations. It was shown that the binary reactivity ratios of the systems styrene-methyl acrylate, styrene-methyl methacrylate, and methyl acrylate-methyl methacrylate describe composition drift in low-coversion bulk terpolymerizations with these monomers reasonably well. A computer model was developed to simulate the composition drift in emulsion co- and terpolymerizations. The composition drift in two batch emulsion copolymerization systems (styrene-methyl acrylate and methyl acrylate-methyl methacrylate) and one emulsion terpolymerization system (styrene-methyl acrylate-methyl methacrylate) was investigated both experimentally and with the model. Experimental results were compared with model calculations. The copolymer chemical composition distributions (CCD) were determined with gradient polymer elution chromatography (GPEC®). This technique was also used for the first time to obtain information about the extent of composition drift in emulsion terpolymerizations. Cumulative terpolymer compositions were determined with 3H-NMR as a function of conversion and with this information the three-dimensional CCD was obtained. The composition drift was analyzed with respect to free radical copolymerization kinetics (reactivity ratios) and monomer partitioning. It was shown that in most emulsion copolymerizations the composition drift is mainly determined by the reactivity of the monomers and to a lesser extent by monomer partitioning, except in systems where there is a large difference in water solubility. The model predictions for cumulative terpolymer composition as a function of conversion and the three-dimensional terpolymer CCD showed excellent agreement with the experiments. The GPEC® elution chromatogram of the terpolymer was found to be in accordance with the predicted CCD and the experimentally determined CCD. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Nuclear transfer and electrofusion in bovine in vitro-matured/in vitro-fertilized embryos: Effect of media and electrical fusion parameters (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 36 (1993), S. 307-312 
    Details
    ISSN: 1040-452X
    Keywords: Micromanipulation ; IVM oocytes ; IVM/IVF donor embryos ; Cytochalasin B ; Nocodazole ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In this study, micromanipulation and electrofusion conditions for the cloning of in vitro-produced bovine embryos (here after termed IVM/IVF embryos) derived from in vitro-matured (IVM) and in vitro-fertilized (IVF) oocytes were established. The effect of DC field strength on the fusion rate was tested in a model system using pronuclear stage embryos in which a cytoplasmic vesicle was removed and reinserted. Efficient fusion (80%) was obtained by applying a pulse of 1.75 kV/cm for 40 μsec. In vitro development of manipulated pronuclear stage embryos was as efficient as that of unmanipulated control embryos. Different fusion media were compared in the cloning procedure, using IVM oocytes as recipients and blastomeres from day 6 IVM/IVF donor embryos. Zimmermann cell fusion medium reduced the lysis of nuclear transfer embryos compared to F300 (5% vs. 25%). The effects of drugs disrupting the microfilaments and microtubuli were determined. Neither the addition of cytochalasin B (CCB) for 1 hr in the postfusion medium nor incubation of donor blastomeres with nocodazole had a significant effect on the fusion or cleavage rate of the nuclear transfer embryos. Additional experiments demonstrated that there was no difference in developmental potential between nuclear transfer embryos allowed to develop in vitro or in vivo and that the embryos gave a 15% pregnancy rate in recipient cattle. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080360304
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  • 9
    Electronic Resource
    Electronic Resource
    Distribution of the intermediate filament proteins vimentin, keratin, and desmin in the bovine ovary (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 41 (1995), S. 459-467 
    Details
    ISSN: 1040-452X
    Keywords: Vimentin ; Keratin ; Desmin ; Immunohis-tochemistry ; Ovary ; Bovine ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The distribution of the intermediate filament (IF) proteins desmin, keratin, and vimentin was studied immunohistochemically in bovine ovaries. Special attention was paid to granulosa cells to examine possible marked changes of IF distribution in relation to folliculogenesis during ovarian development. Therefore, ovaries were used from fetuses from 3 months of gestation onward, calves, heifers, and cows. In all ovaries, desmin immunoreactivity was restricted to smooth muscle cells in blood vessel walls. Keratin appeared a characteristic of the ovarian surface epithelium. Co-localization of keratin and vimentin was observed in the epithelium of rete ovarii tubules in fetuses and calves, and in cortical cord epithelium and pregranulosa cells of primordial follicles in fetuses at 3-7 months of gestation. Vimentin was demonstrated in endothelium and in fibroblasts. In addition, vimentin immunoreactivity was present in granulosa cells of primary, secondary, and antral follicles. In antral follicles, these granulosa cells mainly had an elongated appearance and either contained an oblong or a round nucleus. Those with an oblong nucleus were characteristic for atretic antral follicles. In nonatretic follicles, numerous vimentin immunore-active, elongated granulosa cells with a round nucleus were observed, especially in the peripheral granulosa layer and in small (〈3 mm in diameter) antral follicles. Additionally, in antral follicles, protrusions of vimentin-positive corona radiata cells were observed, that penetrated the zona pellucida to contact the oocyte. The data show that the distribution of vimentin containing IFs is associated with various aspects of granulosa cell activity, as mitosis, atresia, and intercellular transport. © 1995 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080410408
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  • 10
    Electronic Resource
    Electronic Resource
    Ultrastructural evidence for the axonal localization of caudodorsal cell hormone mRNA in the central nervous system of the mollusc Lymnaea stagnalis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 25 (1993), S. 12-18 
    Details
    ISSN: 1059-910X
    Keywords: In situ hybridization ; Digoxigenin ; Electron microscopy ; Cryosections ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The technique of in situ hybridization has been used to evaluate the expression of an ovulation hormone mRNA (caudodorsal cell hormone; CDCH) in the central nervous system (CNS) of the mollusc Lymnaea stagnalis. Hybridization with radioactive as well as with nonradioactive labeled oligonucleotide and plasmid probes revealed a specific labeling on cell bodies of caudodorsal cells (CDCs), which are known to produce CDCH, on the light microscopical level. In addition, specific labeling was observed outside the cell bodies, as far as the cerebral commissure, where CDCH is released in the haemolymph. To investigate whether these signals represent an axonal localization of the CDCH mRNA, we performed in situ hybridization at the electron microscopical (EM) level. The results showed an intraaxonal localization of CDCH mRNA with digoxigenin labeled oligonucleotide and plasmid probes. Gold labeling was observed in secretion granules, and double labeling experiments showed that these granules also contain CDCH. This specific intragranular localization suggest that CDCH mRNA is transported through the axon and released by exocytosis in the haemolymph. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070250104
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