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The production of d-aminoacylase by Alcaligenes denitrificans and Alcaligenes faecalis has been studied. The enzyme was inducibly produced and N-acetyl-d-leucine and N-acetyl-d-valine were the most effective inducers. d-methionine, d-valine, d-phenylalamine and d-leucine were produced by the enzymic hydrolysis of the appropriate N-acetyl-d-amino-acids with whole cell biomass. The hydrolysis of N-acetyl-d-methionine by A. denitrificans and N-acetyl-d-valine by A. faecalis was preferential. Maximum yields of d-methionine and d-valine were 94.3 and 84.7% at a specific product formation rate of 20.10 and 19.19 μmol min−1 mg−1 of wet cells at 20 mM substrate concentration and 5 mg ml−1 of cell density. 相似文献
23.
F F Smith J R Mertz I Krebs L L Tres C B Chae Z Zakeri J Engelhardt D Hoover M Tenniswood A L Kierszenbaum 《Molecular reproduction and development》1992,33(4):363-372
We have previously reported that a heterodimeric protein secreted by rat Sertoli cells is antigenically related to a protein associated with outer dense fibers of the sperm tail. Therefore, we have explored the possibility that Sertoli and spermatogenic cells express a similar gene encoding a homologous protein. A Sertoli cell heterodimeric protein cDNA probe recognizes specific mRNA in pachytene and round spermatids fractionated by centrifugal elutriation; however, this specific mRNA was less prominent than in cultured Sertoli cells. In agreement with these observations, in situ hybridization experiments show that Sertoli cells are predominantly engaged in active heterodimeric protein mRNA synthesis, while meiotic prophase spermatocytes and spermatids also show significant but less abundant specific mRNA. Immunoblotting experiments demonstrate that, while Sertoli cells synthesize a heterodimeric protein consisting of two disulfide-linked components with molecular masses of 45 and 35 kD, both primary spermatocytes and round spermatids synthesize single 30 kD monomers not associated by disulfide linkage but recognized by antisera to Sertoli cell heterodimeric protein. Immunoblotting and immunogold electron microscopic studies show that antisera to Sertoli cell heterodimeric protein recognize a protein associated with outer dense fibers. This immunoreactivity was abolished by a 5-min pronase treatment, without affecting the integrity of outer dense fibers. Results of this study and previous studies demonstrate that both Sertoli and spermatogenic cells express a similar gene and that an antigenically related product encoded by this gene becomes associated with outer dense fibers during their assembly at spermiogenesis. 相似文献
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25.
G. Ricci L. Volpi L. Pasquali L. Petrozzi G. Siciliano 《Journal of biological physics》2009,35(4):317-336
Astrocytes have long been considered as just providing trophic support for neurons in the central nervous system, but recently
several studies have highlighted their importance in many functions such as neurotransmission, metabolite and electrolyte
homeostasis, cell signaling, inflammation, and synapse modulation. Astrocytes are, in fact, part of a bidirectional crosstalk
with neurons. Moreover, increasing evidence is stressing the emerging role of astrocyte dysfunction in the pathophysiology
of neurological disorders, including neurodegenerative disease, stroke, epilepsy, migraine, and neuroinflammatory diseases. 相似文献
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Résumé Nous avons montré par une technique autoradiographique que les ions Cl– et Na+ sont concentrés dans les cellules à chlorure de la branchie d'anguille adaptée à l'eau de mer. La signification de cette accumulation ionique plus marquée vers le pôle apical de ces cellules a été discutée par rapport à l'excrétion branchiale de ces ions en eau de mer.
Autoradiographic localization of Cl– and Na+ ions in the chloride cells of sea water adapted eel (Anguilla anguilla L.) gills
Summary With an autoradiographic technique Cl– and Na+ ions have been shown to be localized in the chloride cells of sea water eel gills. The significance of this accumulation, more marked towards the apical pole of these cells, is discussed with regard to branchial excretion of these ions in sea water.相似文献
28.
[3H]Dihydroergocryptine ([3H]DHE) was shown to bind to sites in membranes from neuroblastoma X glioma hybrid cells (NG 108-15) that had the characteristics expected of alpha-adrenergic receptors. The binding was saturable with 0.3 pmol [3H]DHE bound per mg of protein and of high affinity, with an apparent dissociation constant (KD) of 1.8 nM. The specificity of the binding site for various ligands was more similar to that of alpha 2 receptors than to that of alpha 1. No specific binding of [3H]WB-4101 was found in the membranes derived from NG 108 cells. This finding also indicated that the [3H]DHE binding site in the cell is the alpha 2 receptor. GTP lowered the affinity of agonists for the [3H]DHE binding site, although the nucleotide hardly affected the affinity of antagonists including [3H]DHE. 相似文献
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Multiple forms of amylase in leaf extracts: electrophoretic transfer of the enzyme forms into amylose-containing polyacrylamide gels 总被引:1,自引:0,他引:1
A method for the analysis of multiple forms of glucan-degrading enzymes is described. The procedure consists of the separation of the proteins by electrophoresis or isoelectric focusing in glucan-free polyacrylamide gels followed by the nondenaturing electrophoretic transfer into a second polyacrylamide layer which contains immobilized glucans. The method combines the resolving power of electrophoretic separations in glucan-free media with the sensitivity of amylase activity detection in amylose-containing polyacrylamide gels. The procedure is especially useful when samples containing low amylase activity, but a large number of multiple enzyme forms, are to be analyzed. 相似文献