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排序方式: 共有245条查询结果,搜索用时 15 毫秒
1.
Biosynthesis of immunoglobulin A (IgA). Secretion and addition of carbohydrate to monomer and polymer forms of a mouse myeloma protein 总被引:9,自引:3,他引:6
Cell suspensions of mouse plasma-cell tumour MOPC 315 secreting predominantly IgA (immunoglobulin A) monomer and dimer were incubated with radioactive leucine, mannose, galactose and fucose for various periods of time. The amounts of secreted and intracellular immunoglobulins were measured by co-precipitation with specific antibody, and the molecular species present were assessed by electrophoresis in polyacrylamide gels. Analysis of the secreted myeloma protein demonstrated that monomer and dimer IgA molecules are identical with respect to carbohydrate composition and rate of secretion. Within the cell, the myeloma protein is almost entirely accounted for by monomer units which either leave the cell as such or are polymerized with the addition of J chain close to the time of secretion. The results support the concept of a stepwise addition of carbohydrate residues to IgA immunoglobulin during the process of secretion. Similar patterns of carbohydrate assembly were found for the monomer or dimer molecules. Mannose residues are added at an early stage, whereas fucose is added close to the time of secretion. Galactose is also added early, but some may also be incorporated at a later stage. Control of IgA polymerization is considered unlikely to reflect regulation at the level of carbohydrate addition, and it is suggested that the critical controlling factor is the J chain. 相似文献
2.
Induction of expression of protein disulphide-isomerase during lymphocyte maturation stimulated by bacterial lipopolysaccharide 总被引:2,自引:0,他引:2
Protein disulphide-isomerase (PDI) activity, and the level of immunodetectable PDI protein, were monitored in splenic lymphocytes and in BCL1 cells during culture in the presence of various activating factors. Bacterial lipopolysaccharide stimulated induction of PDI in splenic B cells and BCL1 cells. The time-course and specificity of induction indicated that the increase in expression of PDI is closely coupled to the final stages of B cell differentiation into antibody-producing plasma cells. The system will prove valuable in studies on the control of expression of PDI. 相似文献
3.
Angelo N. Belcastro Wade Parkhouse Goeff Dobson James S. Gilchrist 《Molecular and cellular biochemistry》1988,83(1):27-36
The purpose of this study was to examine the Ca2+-Mg2+ myofibrillar ATPase and protein composition of cardiac and skeletal muscle following strenuous activity to voluntary exhaustion. Sprague-Dawley rats (200 g) were assigned to a control and exercised group, with the run group completing 25 m·min–1 and 8% grade for 1 hour. Following activity, the myocardial Ca2+–Mg2+ myofibrillar ATPase activity -pCa relationship had undergone a rightward shift in the curve. Electrophoretic analysis revealed a change in the pattern of cardiac myofibrillar protein bands, particularly in the 38–42 Kdalton region. Enzymatic analysis of myofibrillar proteins from plantaris muscle, revealed no change in Ca2+ regulation following exercise. Electronmicrographic and electrophoretic analysis revealed extensively disrupted sarcomeric structure and a change in the ratio of several plantaris myofibrillar proteins. No difference was observed for myosin: Actin: tropomyosin ratios; however a dramatic reduction in 58 and 95 Kdalton proteins were evident. The results indicate that prolonged running is associated with similar responses in cardiac and skeletal muscle myofibrillar protein compositions. The abnormalities in myofibrillar ultrastructure may implicate force transmission failure as a factor in exercised-induced muscle damage and/or fatigue. 相似文献
4.
Parkhouse W. S.; McKenzie D. C.; Hochachka P. W.; Ovalle W. K. 《Journal of applied physiology》1985,58(1):14-17
The in vitro deproteinized vastus lateralis muscle buffer capacity, carnosine, and histidine levels were examined in 20 men from 4 distinct populations (5 sprinters, 800-m runners; 5 rowers; 5 marathoners; 5 untrained). Needle biopsies were obtained at rest from the vastus lateralis muscle. The buffer capacity was determined in deproteinized homogenates by repeatedly titrating supernatant extracts over the pH range of 7.0-6.0 with 0.01 N HCl. Carnosine and histidine levels were determined on an amino acid AutoAnalyzer. Fast-twitch fiber percentage was determined by staining intensity of myosin adenosinetriphosphatase. High-intensity running performance was assessed on an inclined treadmill run to fatigue (20% incline; 3.5 m X s-1). Significantly (P less than 0.01) elevated buffer capacities, carnosine levels, and high-intensity running performances were demonstrated by the sprinters and rowers, but no significant differences existed between these variables for the marathoners vs. untrained subjects. Low but significant (P less than 0.05) interrelationships were demonstrated between buffer capacity, carnosine levels, and fast-twitch fiber composition. These findings indicate that the sprinters and rowers possess elevated buffering capabilities and carnosine levels compared with marathon runners and untrained subjects. 相似文献
5.
6.
D C McKenzie L S Goodman C Nath B Davidson G O Matheson W S Parkhouse P W Hochachka P S Allen C Stanley W Ammann 《Journal of applied physiology》1991,70(6):2650-2655
Six male Quechua Indians (34.0 +/- 1.1 yr, 159.5 +/- 2.1 cm, 60.5 +/- 1.6 kg), life-long residents of La Raya, Peru (4,350-m altitude with an average barometric pressure of 460 Torr), were studied using noninvasive methods to determine the structural and functional changes in the cardiovascular system in response to a 6-wk deacclimation period at sea level. Cardiac output, stroke volume, and left ventricular ejection fractions were determined using radionuclide angiographic techniques at rest and during exercise on a cycle ergometer at 40, 60, and 90% of a previously determined maximal O2 consumption. Subjects at rest were subjected to two-dimensional and M-mode echocardiograms and a standard 12-lead electrocardiogram. Hemoglobin and hematocrit were measured on arrival at sea level by use of a Coulter Stacker S+ analyzer. After a 6-wk deacclimation period, all variables were remeasured using the identical methodology. Hemoglobin values decreased significantly over the deacclimation period (15.7 +/- 1.1 to 13.5 +/- 1.2 g/dl; P less than 0.01). The results indicate that the removal of these high-altitude-adapted natives from 4,300 m to sea level for 6 wk results in only minor changes to the cardiac structure and function as measured by these noninvasive techniques. 相似文献
7.
Comparison of antibody response and antigen recognition was made by ELISA and western-blot analysis in pig experimental infections by T-1 and T-3 Spanish Trichinella isolates. Two groups of Iberian pigs were experimentally infected with 150 larvae/kg body weight of GM-1 and C-76 Spanish Trichinella isolates as representatives of T-1 and T-3 gene pools respectively. Antibody levels and antigen recognition were measured on days -14, 0, 6, 16, 20, 27, 34, 49, 63 and 82 after infection by ELISA and western-blotting assays. Antibody response against C-76 infection was significantly delayed and lower than against GM-1. The two Trichinella isolates were indistinguishable, however, by western blotting analysis, although recognition of larval antigens was quantitatively higher than adult ones. Interestingly, the principle larval antigenic components recognized by pigs were those recognized by the monoclonal anti-sera NIM-M1. Finally, there were no serological patterns indicative of the stage of infection ("antibody windows") discriminating, for example between early versus late infections. 相似文献
8.
Cloning of a species-specific DNA probe from Onchocerca gibsoni 总被引:1,自引:0,他引:1
A genomic library of Onchocerca gibsoni has been prepared in the vector lambda-gt10 and has been screened for specific DNA sequences by hybridization with radiolabelled total genomic DNA from a number of Onchocerca species. A clone--fOGI--has been isolated which does not interact with DNA prepared from O. gutturosa, O. lienalis, O. ochengi, O. cervicalis or O. volvulus (both Liberian and Mexican isolates). In addition, no hybridization is observed with host (cattle) DNA. fOGI can detect as little as 100-200 pg of O. gibsoni DNA. It is thus concluded that fOGI has the sensitivity to detect microfilariae of O. gibsoni found in the skin of cattle and the specificity to differentiate them from closely related species living in the same environment. 相似文献
9.
Non-covalent interactions result in aggregation of surface antigens of the parasitic nematode Trichinella spiralis. 总被引:4,自引:0,他引:4
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Surface antigens of three stages of the nematode worm Trichinella spiralis has been labelled with iodine and examined by sodium dodecyl sulphate (SDS)/polyacrylamide-gel electrophoresis under reducing and non-reducing conditions. A variety of interactions were defined: the infective larva surface antigens formed a spectrum of aggregates from 50kDa to greater than 1000kDa from subunits of 47kDa and 90kDa; in the adult worms of 60kDa complex arose fron interaction between two dissimilar molecules of 40kDa and 20kDa; the new-born larvae components formed homologous dimers from a 58kDa molecule. Aggregating molecules were adherent to lentil lectin-Sepharose and are therefore glycoproteins. The interactions observed were completely abolished by boiling in SDS/mercaptoethanol, but only partially destroyed by boiling in SDS/iodoacetamide. Based upon this, the associations can be characterized as non-covalent, but disulphide-bond-dependent. It is suggested, but not proved, that the aggregates arise from strong non-covalent hydrophobic interaction sites which are stabilized by intrachain disulphide bonds in the molecules concerned. 相似文献
10.
Questionnaires were sent to all 2348 doctors who had graduated from medical schools in England, Scotland, and Wales in 1974 asking about their career preferences. Most were in their second preregistration post, and the response rate was 86-1%. The most popular first choice of career was general practice (665 of the responders; 32-9%), followed by medicine (454; 22-5%), surgery (321; 15-9%), and paediatrics (129; 6-4%). Only 507 of the responders (25-1%), however, stated that their preference was "definite". First choices differed widely between men and women graduates and between graduates of different medical schools. 相似文献