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1.
2.
Acceptor-donor relationships in the transglutaminase-mediated cross-linking of lens beta-crystallin subunits 总被引:4,自引:0,他引:4
Following the isolation of the N epsilon-(gamma-glutamyl)lysine-containing polymers from human cataracts, our efforts were directed to induce such cross-links experimentally in rabbit lens, and evidence was obtained for the selective reactivities of certain beta-crystallin subunits in this transglutaminase-catalyzed event. In the present work, we examined the enzymatic cross-linking of purified crystallins individually (alpha, beta H, beta L, and gamma) and in combinations, with particular emphasis on forming the approximately 55K dimer. This species was the primary product in the cross-linking of beta H-crystallins; beta L also reacted with transglutaminase. Neither alpha- nor gamma-crystallins formed appreciable amounts of cross-linked structures with transglutaminase. Dansylcadaverine, known to compete against the reactive lysines of proteins in forming N epsilon-(gamma-glutamyl)lysine cross-bridges, was shown to inhibit the generation of dimeric and higher ordered oligomers from beta H and beta L. The fluorescent amine specifically labeled only two subunits in beta H (approximately 29-30K and approximately 26K) and one in beta L (approximately 26K), identifying these substrates as possessing transglutaminase-reactive endo-gamma-glutaminyl residues. An antiserum to bovine beta Bp recognized the approximately 23K subunit of rabbit beta-crystallins and also the approximately 55K dimer, suggesting that the approximately 23K protein participates as a lysine donor in generating the cross-linked dimer with transglutaminase. Inasmuch as the same antiserum reacts with an approximately 50K material reported to appear in increasing amounts with age in human lens, the results lend added support to the physiological significance of transglutaminase in the aging of lens. 相似文献
3.
J. L. Campo T. Velasco 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,77(4):561-567
Summary Effects of errors in estimates of the genetic correlation on the accuracy of unrestricted, optimum, and desired gains selection indices were examined experimentally in Tribolium castaneum. Three lines were selected for three generations for pupal weight at 21 days and adult weight at 31 days, using unrestricted (I9), optimum (O9), and desired gains (G9) index selection methods. The genetic correlation between pupal and adult weights in the base population was 0.95. The optimum index was designed to set the response of pupal weight by a fixed amount, while in the desired gains index the responses of pupal and adult weights were specified as being equal to 31. Three other indices were constructed using a deliberately incorrect genetic correlation (0.25), i.e., unrestricted (I2), optimum (O2), and desired gains (G2). Responses observed in unrestricted index lines (I9 versus I2) and optimum index lines (O9 versus O2) did not differ significantly, even though lines I9 and I2 differed in a practical sense. Responses in desired gains index lines (G9 versus G2) differed significantly. Responses obtained for aggregate genotype (pupal weight + adult weight) and for the component traits were greater in line I9 than those obtained in line I2. Responses obtained in the O9 and O2 lines for pupal and adult weights were similar, while those obtained in the G9 and G2 lines were similar for pupal weight but not (P<0.05) for adult weight. Therefore, underestimation of the genetic correlation seems to affect the efficiency of a desired gains index more than that of unrestricted or optimum indices. 相似文献
4.
C Beas-Zárate A R del Angel Meza A Morales-Villagran A Feria Velasco 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1988,89(2):173-177
1. Endogenous serotonin (5-HT), 5-hydroxyindol acetic acid (5-HIAA) content and exogenous 5-HT uptake (Km and Vmax) were measured in different brain regions (cerebellum, diencephalon, brain stem and telencephalon) of rats fed with a corn diet and restricted protein (8%) diet during 6 weeks. 2. A reduction of 5-HT levels was found in all regions studied of animals fed a corn diet, whereas, 5-HIAA was only decreased in brain stem and diencephalon. 3. An important increase in Km and Vmax were registered in brain stem and diencephalon of protein restricted animals, whereas, an increase of 5-HT uptake affinity in cerebellum, brain stem and telencephalon (35, 42 and 33% respectively) was observed. Simultaneously, under corn diet conditions, the Vmax decreased 40, 30 and 34% respectively in those regions. 4. It is suggested that the brain stem was the more sensitive area under nutritional restricted conditions and the development of some possible compensatory mechanisms of the 5-HTergic system is discussed. 相似文献
5.
In order to characterize the mechanism of activation of the enzyme 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine:acetyl-CoA acetyltransferase (EC 2.3.1.67) which is the limiting step in the regulation of the synthesis of the potent inflammatory mediator 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; homogenates from human polymorphonuclear leukocytes were incubated in the presence of the catalytic subunit of cyclic AMP-dependent protein kinase and in the presence of a partially purified phospholipid sensitive, calcium-dependent protein kinase (PrKC). The first kinase was found to enhance up to 3-fold acetyltransferase activity in a dose- and time-dependent manner. In homogenates from PMN previously stimulated with complement-coated zymosan particles, the decay of acetyltransferase activity was partially prevented by the addition of soybean trypsin inhibitor and almost completely inhibited when the homogenates were supplemented with inhibitors of alkaline phosphatase such as 50 mM KF and 100 microM paranitrophenylphosphate. Under these conditions it was possible to initiate the decay of acetyltransferase activity by adding an excess of alkaline phosphatase. Preincubation of PMN with 12-O-tetradecanoylphorbol-13-acetate previous or simultaneously to the addition of ionophore A23187 reduced the increase in acetyltransferase produced by ionophore A23187, whereas the generation of superoxide anions was enhanced. Addition of partially purified PrKC to homogenates from ionophore A23187-stimulated PMN, reduced acetyltransferase activity by 63%, whereas only a 16% inhibition was observed on homogenates from resting PMN. These data indicate the modulation of acetyltransferase activity in human polymorphonuclear leukocytes by a phosphorylation-dephosphorylation mechanism linked to cyclic AMP-dependent protein kinase. Phospholipid sensitive, calcium-dependent protein kinase seems not to be involved in the mechanism of activation, but, most probably, in the generation of negative activation signals. 相似文献
6.
Protein kinase C from small intestine epithelial cells 总被引:1,自引:0,他引:1
G Velasco C F Iglesias P Domínguez F Barros S Gascón P S Lazo 《Biochemical and biophysical research communications》1986,139(3):875-882
Protein kinase C activity has been identified in cytosolic and membrane fractions from rat and rabbit small intestine epithelial cells. The cytosolic fraction comprised about the 75% of total activity. Protein kinase C activity was resolved from other protein kinase activities by ion exchange chromatography. Phosphatidylserine or phosphatidylinositol were required for protein kinase C to be active. In addition, the activity was enhanced by the presence of a diacylglycerol. Diolein and dimyristin were the most effective (13-14 fold activation). In the presence of phosphatidylserine and diolein, the Ka for activation by Ca2+ was 10(-7)M. The phorbol ester TPA substituted for diacylglycerol in activating protein kinase C. Brush border and basolateral membranes contained protein kinase C activity, although the specific activity of the basal lateral membranes was four-fold higher than the specific activity of the brush border membranes. The presence of PKC in small intestine epithelial cells might have important implications in the Ca2+ mediated control of ionic transport in this tissue. 相似文献
7.
Formation of a 55 000-weight cross-linked beta crystallin dimer in the Ca2+-treated lens. A model for cataract 总被引:2,自引:0,他引:2
Incubation of lens in Ca2+-containing media, considered by several investigators to be a useful model of cataract formation, gave rise to significant alterations in the covalent structures of various proteins. In rabbit lens, when sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used after reduction of disulfides in urea, the most readily observable changes were (i) disappearance of 210K, 95K, and 60K proteins, (ii) modifications of alpha crystallin subunits, (iii) alterations of beta H crystallins, and (iv) de novo production of 55K and higher molecular weight polymers. The addition of leupeptin inhibited the disappearances of 210K, 95K, and 60K proteins and the alteration of alpha crystallins, suggesting that all these were caused by a Ca2+-activated protease. The proteolytically sensitive 60K species was identified as vimentin, a component of intermediate filaments. Formation of the 55K material and of higher molecular weight polymers during Ca2+ treatment of the lens could be prevented by histamine, a compound known to inhibit the transglutaminase-mediated cross-linking of proteins by epsilon-(gamma-glutamyl)lysine peptide bonds in other biological systems. It could also be shown by immunoblotting that an antibody raised against the 55K material reacted selectively with beta crystallins of normal lens. This indicates that the 55K product is in all likelihood an essential intermediate toward higher polymers and that the 55K product is a cross-linked dimer of certain polypeptides of beta crystallin.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
8.
Maria V. Croce Marcela Fejes Norma Riera D. A. Minoldo Amada Segal-Eiras 《Cancer immunology, immunotherapy : CII》1985,20(1):91-95
Summary A total of 122 sera from acute lymphoblastic leukemia (ALL) patients were analyzed for circulating immune complexes (CIC) by two methods: the 125I-C1q binding assay and the polyethylene glycol precipitation test (PEG). The results were correlated with induction, remission and relapse stages of the disease. Using the first method the levels of CIC in induction were 15.18±9.15, with 19/29 positive cases (65.50%), P<0.001 compared with controls. In the remission phase the levels were 9.02±5.62, 11/45 (24.49%) nonsignificant P value, and in relapse they were 16.14±11.17 28/48 (58.33%) P<0.001. The PEG precipitation test results were: 0.33±0.10, 8/22 (36.36%); 0.24±0.11, 10/48 (20.83%) and 0.28±0.10, 6/28 (21.42%), respectively. Thus the values of CIC as measured by PEG in the three clinical of phases ALL did not differ significantly from controls. This contrasts with results obtained by the radioiodinated C1q binding assay, where the incidence of positive values was significantly higher in induction and in relapse and lower in the remission phase. These observations were extended in sequential vertical studies performed in a group of patients. These results suggest that raised CIC detected by the 125I-C1q method may reflect a progressive state in ALL and that quantitation of these immune complexes may provide an adequate biochemical marker for prognosis. 相似文献
9.
The present paper describes growth dynamics in a natural bed of the resource luga negra (Sarcothalia crispata) in Guapilinao, southern Chile (41°57 S, 73°31 W). This resource is currently harvested and exported as raw material for the production of carrageenan. Seasonal variation in biomass, frond size, density and phenology was determined by periodic sampling. Natural recruitment was evaluated on different substrata added to the field; at the same time, substrata were inoculated under greenhouse conditions. Results showed that luga negra has seasonal growth: biomass increased from a minimum in spring to a maximum in mid to late summer. On the other hand, density was minimal in winter (200 ind. m–2) and increased to 2000 ind. m–2 in late spring. Peak abundance of mature tetrasporic fronds occurred in late summer, whereas that of cystocarpic fronds occurred in winter. Recruitment began in summer and extended into winter. Survival on different substrata were compared. Gametophytes had better survival rates on clam shells and 5 mm rope while tetrasporophytes had the best survival rate on clam shells and secondarily on boulders. 相似文献
10.