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  • 1
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 19 (1982), S. 171-178 
    ISSN: 0730-2312
    Keywords: glycoproteins ; cell surface recognition ; affinity adsorption ; amino acid compositions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Pichia amethionina is a heterothallic yeast isolated from necrotic cactus tissue. Haploid cells of opposite mating type, designated a and α, agglutinate strongly when mixed. The agglutination factors of the two cell types have been solubilized from the cell walls by β-glucanase digestion and then partially purified by affinity adsorption to the opposite cell type and by gel filtration. From α-cells was obtained a large, heat-stable glycoprotein with the ability to agglutinate a-cells. This α-agglutinin was inactivated by mercaptoethanol, probably because the recognition sites are linked to the glycoprotein core by disulfide bonds. Digestion of a-cells with β-glucanase released a large heat-labile glycoprotein that did not agglutinate α-cells but did inhibit agglutination of a-cells by α-agglutinin. Subtilisin digestion of this a-factor released a carbohydrate-free protein of 27,000 daltons that retained the biological activity of the factor. These agglutination factors are sex- and species-specific and are not found on the surface of heterozygous diploid cells.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 32 (1986), S. 113-123 
    ISSN: 0730-2312
    Keywords: tyrosine kinase ; phosphorylation ; mitochondria ; serum step-down ; human fibroblast ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A tyrosine protein kinase activity has been detected in the mitochondrial fraction purified from human fibroblasts. By enzymatic and sedimentation analysis this activity appeared to be localized in the mitochondrial outer membrane. Mitochondrial tyrosine phosphorylation was strictly dependent on the presence of Mn2+ ions. An inverse relationship between cell proliferation and mitochondrial protein phosphorylation on tyrosine residues has been found: a marked increase in the mitochondrial tyrosine kinase activity occurred when a significant reduction in the growth rate followed serum step-down. In mitochondria purified from resting cells, a protein band with apparent molecular weight of 50 kd appeared to be phosphorylated on tyrosine.
    Additional Material: 6 Ill.
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  • 3
    ISSN: 0192-253X
    Keywords: 5-Azacytidine ; DNA methylation ; Plant tumorogenesis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The phenomenon of habituotion is considered in plant tissue cultures to be a real process of chemical tumorogenesis: the cultures acquire the capacity of autonomous growth in a hormone-free medium under the influence of a variety of chemical and physical agents. Treatments with 5-azacytidine (AzaC) of in vitro cultured cells of the Nicotiana glauca × N. langsdorffii nontumorous hybrid (NNT)during the culture cycle led to the induction of a habituated phenotype. The repetitive DNA sequences showed a significant lower level of endogenous methylation in the treated cells in comparison with the normal ones. It is worth noting that it was impossible until now to habituate this strain by conventional methods and that the treatments were effective only in the first 5 days of subculturing; various evidence (cytological and biochemical) pointed out a phenomenon of DNA amplification, occurring in the same period. Moreover, analysis of DNA from control and treated cells shows the induction of variations in the endogenous methylation pattern by AzaC in a critical period of cell culture. These results suggest that demethylation can act as a switch from hormone-dependent to autonomous proliferation by activation of genes coding for or regulating the synthesis of growth factors.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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