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891.
Compositional constraints and genome evolution 总被引:31,自引:0,他引:31
892.
Giacomo Carrea Roberto Bovara Renato Longhi Roberto Barani 《Enzyme and microbial technology》1984,6(7):307-311
12-Ketochenodeoxycholic acid, an essential intermediate in the synthesis of chenodeoxycholic acid, has been enzymatically prepared from dehydrocholic acid. The specific reduction of dehydrocholic with NADH was catalysed by 3α-hydroxysteroid dehydrogenase (3α-hydroxysteroid: NAD(P)+ oxidoreductase, EC 1.1.1.50) and 7α-hydroxysteroid dehydrogenase (7α-hydroxysteroid:NAD+ 7-oxidoreductase, EC 1.1.1.159). Cofactor regeneration was obtained through the formate dehydrogenase (formate:NAD+ oxidoreductase, EC 1.2.1.2) catalysed oxidation of formate. Complete transformation of dehydrocholic acid to the 12-keto derivative was achieved with a coenzyme turnover number up to 1200. No steroid by-products were detected by high performance liquid chromatography and thin layer chromatography. The process yielded 9 g product l?1 in 66–84 h. The high purity of the enzymatically prepared 12-ketochenodeoxycholic acid should drastically reduce the formation of the toxic by-product lithocholic acid, which occurs in the synthesis of chenodeoxycholic acid when using chemical methods alone. 相似文献
893.
A. Campisi M. Renis A. Russo V. Sorrenti C. Di Giacomo C. Castorina A. Vanella 《Neurochemical research》1992,17(12):1201-1205
Transglutaminases, calcium-dependent thiol enzymes, may be involved in cellular growth control and differentiation, having an intracellular regulatory role in some post-traslational modifications found in various classes of proteins. In order to elucidate the involvement of this class of enzymes in cellular differentiation processes, we have assayed transglutaminase activity in primary and subcultured rat glial cells. Reduced activity was found from 3rd to 5th passage. In the 5th passage the activity was some 50% of that found in the primary cultures and was not restored by addition of 10 M retinoic acid. The decrease of TGase activity, observed during serial passages, could represent an early metabolic alteration related to cell dedifferentiation and loss of growth control. In fact, the subcultured cells may have undergone a disarranged state, as confirmed by a decrease in GFAP-stained cells and glutamine synthetase activity, respectively, immunocytochemical and biochemical markers of astroglial cells. 相似文献
894.
Dr. Peter P. Li Stavroula Andreopoulos Chun C. Wong Giacomo G. Vecil Jerry J. Warsh 《Neurochemical research》1995,20(10):1249-1255
Postnatal development of Go isoforms in rat cerebral cortex was studied by SDS-PAGE and immunoblotting. When rat cerebral cortical membranes were resolved on separating gels containing 9% acrylamide and 8 M urea, three electrophoretically distinct Go-immunoreactive proteins were evident. Comparison of their electrophoretic mobilities and partial tryptic digest pattern with recombinant Go1 or Go1-specific antibody revealed that the slowest and intermediate-migrating bands represent unmodified and fatty acylated forms of Go1 protein, respectively. The fastestmigrating band corresponds to Go2. While the fatty acylated form of Go1 is the predominant species, its appearance paralleled that observed for Go2 in developing rat cortex. Perinatal hypothyroidism induced by methimazole treatment did not significantly alter the appearance of cerebral cortical Go1 and Go2 between days 1 and 22 postpartum. Our findings support the earlier idea that heterogeneity of Go proteins in mammalian brain is likely the result of different co- or post-translational processings of each splice variant of Go. While the appearance of Go isoforms is developmentally regulated, they likely do not play an obligatory role in neonatal brain development. Alternatively, the expression of Go isoforms in developing rat cortex may be controlled by an intrinsic signal(s) that is independent of the thyroid status. 相似文献
895.
Epithelial V-like Antigen (EVA), a Novel Member of the Immunoglobulin Superfamily, Expressed in Embryonic Epithelia with a Potential Role as Homotypic Adhesion Molecule in Thymus Histogenesis 总被引:3,自引:0,他引:3 下载免费PDF全文
Maria Guttinger Francesca Sutti Maddalena Panigada Simona Porcellini Barbara Merati Margherita Mariani Tambet Teesalu G. Giacomo Consalez Fabio Grassi 《The Journal of cell biology》1998,141(4):1061-1071
Thymus development depends on a complex series of interactions between thymocytes and the stromal component of the organ. To identify regulated genes during this codependent developmental relationship, we have applied an RNA fingerprinting technique to the analysis of thymus expansion and maturation induced in recombinase-deficient mice injected with anti-CD3 antibodies. This approach led us to the identification of a gene encoding a new member of the immunoglobulin superfamily, named epithelial V-like antigen (EVA), which is expressed in thymus epithelium and strongly downregulated by thymocyte developmental progression. This gene is expressed in the thymus and in several epithelial structures early in embryogenesis. EVA is highly homologous to the myelin protein zero and, in thymus-derived epithelial cell lines, is poorly soluble in nonionic detergents, strongly suggesting an association to the cytoskeleton. Its capacity to mediate cell adhesion through a homophilic interaction and its selective regulation by T cell maturation might imply the participation of EVA in the earliest phases of thymus organogenesis. 相似文献
896.
Salvatore Fasulo Aurelio Licata Antonia Contini Luigi Ainis Angela Mauceri Giacomo Zaccone 《Acta zoologica》1991,72(4):217-222
Abstract Various horseradish peroxidase-conjugated lectins have been used for the ultrastructural localization of carbohydrate moieties of glycoconjugates on plasma membranes of the surface cells of Blennius sanguinolentus epidermis. Concanavalia ensiformis (Con A), Arachis hypogaea (PNA), Pisum sativum (PSA) and Ulex europaeus (UEA I) lectins bind only to the outermost plasma membranes, the glycocalyx and the intercellular spaces of the surface cells. Other lectins applied, such as Triticum vulgare (WGA), Glycine max (SBA) and Griffonia simplicifolia (GS I), presenting GlcNAc and GaINAc specificity, reacted with the plasma membranes of basolateral domains and gave an attenuated reaction with the outermost plasma membranes. The results suggest that regional differences exist in the distribution patterns of GlcNAc and GalNAc-terminating glycoconjugates. The possible implication of the polarized expression of these glycoconjugates in ion transport is discussed. 相似文献
897.
S. Francesco Retta Fiorella Balzac Piercarlo Ferraris Alexey M. Belkin Reinhard Fssler Martin J. Humphries Giacomo De Leo Lorenzo Silengo Guido Tarone 《Molecular biology of the cell》1998,9(4):715-731
The β1-integrin cytoplasmic domain consists of a membrane proximal subdomain common to the four known isoforms (“common” region) and a distal subdomain specific for each isoform (“variable” region). To investigate in detail the role of these subdomains in integrin-dependent cellular functions, we used β1A and β1B isoforms as well as four mutants lacking the entire cytoplasmic domain (β1TR), the variable region (β1COM), or the common region (β1ΔCOM-B and β1ΔCOM-A). By expressing these constructs in Chinese hamster ovary and β1 integrin-deficient GD25 cells (Wennerberg et al., J Cell Biol 132, 227–238, 1996), we show that β1B, β1COM, β1ΔCOM-B, and β1ΔCOM-A molecules are unable to support efficient cell adhesion to matrix proteins. On exposure to Mn++ ions, however, β1B, but none of the mutants, can mediate cell adhesion, indicating specific functional properties of this isoform. Analysis of adhesive functions of transfected cells shows that β1B interferes in a dominant negative manner with β1A and β3/β5 integrins in cell spreading, focal adhesion formation, focal adhesion kinase tyrosine phosphorylation, and fibronectin matrix assembly. None of the β1 mutants tested shows this property, indicating that the dominant negative effect depends on the specific combination of common and B subdomains, rather than from the absence of the A subdomain in the β1B isoform. 相似文献
898.
Bucci I Napolitano G Giuliani C Lio S Minnucci A Di Giacomo F Calabrese G Sabatino G Palka G Monaco F 《Biological trace element research》1999,67(3):257-268
In subjects affected by trisomy 21 (Down syndrome), hypothyroidism is the most common endocrinological deficit. Plasma zinc
levels, which are commonly detected below the normal range in Down patients, are related to some endocrinological and immunological
functions; in fact, zinc deficiency has been shown to impair immune response and growth rate. Aims of this study were to evaluate
(1) the role of zinc deficiency in subclinical hypothyroidism and (2) thyroid function changes in Down children cyclically
supplemented with zinc sulfate. Inverse correlations have been observed between age and triiodotironine (T3) and between zinc
and thyroid-stimulating hormone (TSH); higher TSH levels have been found in hypozincemic patients at the beginning of the
study. After 6 mo of supplementation, an improvement of thyroid function (TSH levels: 3.96 ± 1.84 vs 2.64 ± 1.33 mUI/mL basally
and after 6 mo, respectively) was observed in hypozincemic patients. In the second cycle of supplementation, a similar trend
of TSH was observed. At the end of the study, TSH significantly decreased in treated hypozincemic subjects (4.48 ± 1.93 vs
2.96 ± 1.20 mUI/mL) and it was no longer different in comparison to normozincemic patients. We suggest zinc supplementation
to the diet in hypozincemic Down children as a simple and useful therapeutic tool. 相似文献
899.
Angela Chiavegato Marta Scatena Marleen Roelofs Paolo Ferrarese Paolo Pauletto Giacomo Passerini-Glazel Francesco Pagano Saverio Sartore 《Experimental cell research》1993,207(2)
The differentiation patterns of smooth muscle cells (SMC) in rabbit bladder during development and in the hypertrophic response to partial outflow obstruction induced in adult animals were evaluated by biochemical and immunochemical techniques and by using a panel of monoclonal antibodies specific for desmin, vimentin, α-actin of smooth muscle (SM) type, SM myosin, and nonmuscle (NM) myosin isoforms. Desmin and SM α-actin were homogeneously distributed in SMC of developing, adult, and obstructed bladders. Conversely, marked changes in the ratio and antigenicity of SM myosin isoforms were observed by SDS electrophoresis and Western blotting, respectively. In particular, the 205 K (SM1) isoform was down-regulated with development whereas the 200 K (SM2) isoform was up-regulated around 7 days after birth and down-regulated in the obstructed bladder. Vimentin was expressed in SMC of the fetal bladder and declined markedly during postnatal, physiological hypertrophy of SMC, which occurs concomitantly with diminution of DNA synthesis. This polypeptide became detectable, however, in SMC of obstructed bladders. The 196 K (NM) myosin isoform recognized by NM-A9 antibody, present only in endothelium of blood vessels and in mucosa of normal fetal and adult bladders, became expressed in detrusor muscle, when SMC underwent a process of pathological hypertrophy. The reexpression of vimentin and the de novo appearance of NM myosin isoform in hypertrophic bladders can be reversed when the tissue mass is reduced, such as in bladders after 1-month recovery from partial obstruction. Thus, a specific NM myosin isoform can be used as a marker of SMC hypertrophy in obstructed bladder. In addition, the combined use of anti-vimentin and NM-A9 antibodies can distinguish between SMC which are in the physiological or in the pathological condition of adaptive bladder hypertrophy. 相似文献
900.
Roberto Bovara Giacomo Carrea Gianluca Ottolina Sergio Riva 《Biotechnology letters》1993,15(9):937-942
Summary The Vmax and KM of various forms of lipase from Pseudomonas cepacia (powder, adsorbed onto Celite or covalently linked to polyethylene glycol) were determined in organic solvents preequilibrated to water activities (a
w) from <0.1 to 0.84. The model reaction was the transesterification between n-octanol and vinyl butyrate. It was found that KM for the nucleophile increased with increasing a
w for all three lipase forms. Vmax increased with increasing a
w for polyethylene glycol-lipase, whereas there was an optimum at intermediate a
w values (0.11 – 0.38) for lipase powder and Celite-immobilized lipase. 相似文献