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81.
Elaine K. Perry Elizabeth Marshall Janet Kerwin Carthage J. Smith † Sabiha Jabeen Anthony V. Cheng Robert H. Perry† 《Journal of neurochemistry》1990,55(4):1454-1456
Senile dementia of Lewy body type is characterized clinically by a relatively acute onset of fluctuating memory loss and confusion, frequently accompanied by visual hallucinations. Neurochemical analyses of temporal cortex has revealed a distinction between hallucinating and nonhallucinating patients in both cholinergic and monaminergic transmitter activities. In contrast with the cholinergic enzyme choline acetyltransferase, which was more extensively reduced in hallucinating individuals, serotonergic S2 receptor binding and both dopamine and serotonin metabolites were significantly decreased in nonhallucinating cases. These results suggest that an imbalance between monaminergic and cholinergic transmitters is involved in hallucinogenesis in the human brain. 相似文献
82.
83.
S Marshall 《The Journal of biological chemistry》1989,264(4):2029-2036
When adipocytes were exposed to [3H]leucine for times ranging from 5 to 180 s, leucine was found to enter cells rapidly and equilibrate with the cell interior within 5 s. After an additional 15-30 s [3H]leucine was incorporated into nascent protein, and the rate of incorporation was linear for up to 6 h in both control and insulin-treated cells. Since treatment of adipocytes with 10 ng/ml insulin enhanced the rate of leucine incorporation 2-3-fold with minimal or no effect on the rate of protein degradation or leucine uptake, we conclude that the predominant effect of insulin is on enhancement of protein synthesis. To assess the time required for insulin to stimulate protein synthesis, we preincubated cells with 10 ng/ml of insulin for various times from 2 to 30 min and then measured [3H]leucine incorporation into protein during a 4-min assay. These results revealed that the insulin stimulation of protein synthesis is rapid (t 1/2 of 4.4 min), but 9-fold slower than insulin activation of glucose transport (t 1/2 less than 0.5 min under identical conditions). In contrast to the rapidity of insulin activation, we found that deactivation proceeded at much slower rates (t 1/2 of 32 and 21 min for protein synthesis and glucose transport, respectively). Desensitization of the glucose transport system has previously been shown to occur after adipocytes are exposed to high glucose and insulin. To examine the specificity of desensitization, we treated cells for 6 h with 20 mM glucose and 25 ng/ml insulin and then examined insulin sensitivity and maximal insulin responsiveness of both the glucose transport and protein synthesis systems. After treatment, the glucose transport was markedly insulin-resistant (60% loss in maximal insulin responsiveness and a marked loss in insulin sensitivity), whereas the protein synthesis system exhibited neither diminished insulin responsiveness nor loss of insulin sensitivity. In fact, insulin sensitivity actually increased, as indicated by the finding that less insulin was required to stimulate protein synthesis (insulin ED50 values of 0.25 and 18 ng/ml at 0 and 6 h of treatment). From these studies we conclude that desensitization of the glucose transport system by glucose and insulin treatment appears to be specific for this particular effector system and does not reflect a state of generalized cellular insulin resistance. 相似文献
84.
S Rodriguez de Cordoba P Marshall P Rubinstein 《Journal of immunology (Baltimore, Md. : 1950)》1989,142(3):836-841
To characterize the molecular polymorphism of the DP alpha and DP beta gene products, the HLA-DP molecules expressed by more than 200 cell lines were individually immunoprecipitated by using the mAb B7/21 and their neuraminidase-treated DP alpha and DP beta chains analyzed in IEF gels. These cell lines, most of them from members of 32 families, allowed the definition, by segregation analysis, of the IEF patterns of the DP polypeptide chains encoded by 129 distinct haplotypes. Both DP alpha and DP beta chains display polymorphic IEF-banding patterns. Two DP alpha (A and B) and seven DP beta (A, B, C, D, E, F, and G) IEF variants were characterized. The DP alpha B variant was found in linkage disequilibrium with both DP beta B and DP beta D. Linkage disequilibrium was also encountered with alleles at the DR and DQ loci. Finally, the correlations between the IEF DP alpha and DP beta variants and the primed lymphocyte test-defined HLA-DP specificities were determined by using a panel of 24 primed lymphocyte test-typed cell lines. 相似文献
85.
D J Haisenleder G A Ortolano D Jolly A C Dalkin T D Landefeld W W Vale J C Marshall 《Life sciences》1990,47(19):1769-1773
Serum inhibin and FSH and FSH beta subunit mRNA levels were measured at 3h intervals throughout the 4 day estrous cycle in female rats and hourly between 1000 and 2400 h of proestrus. On proestrus, serum inhibin concentrations fell during the late morning-early afternoon, then increased transiently during the late afternoon gonadotropin surges. Inhibin levels decreased during the late evening of proestrus, coincident with the FSH surge-related rise in FSH beta mRNA levels. Serum inhibin remained relatively stable during estrus and early metestrus, but rose during the late evening of metestrus and remained elevated until early diestrus. FSH beta mRNA levels were elevated on late estrus and early metestrus and declined during the evening of metestrus as serum inhibin levels increased. These data show that concentrations of serum inhibin change during the estrous cycle and that a general inverse relationship exists between serum inhibin and FSH levels and FSH beta mRNA concentrations in the pituitary. This suggests that inhibin may inhibit FSH beta gene expression and FSH secretion during the 4 day cycle in female rats. 相似文献
86.
Substrate kinetics of the tonoplast h-translocating inorganic pyrophosphatase and its activation by free mg 下载免费PDF全文
To clarify the kinetic characteristics and ionic requirements of the tonoplast H+-translocating inorganic pyrophosphatase (H+-PPiase), PPi hydrolysis and PPi-dependent H+ transport were studied in tonoplast vesicles isolated from leaf mesophyll tissue of Kalanchoë daigremontiana Hamet et Perrier de la Bâthie. The tonoplast H+-PPiase showed an absolute requirement for a monovalent cation and exhibited hyperbolic kinetics with respect to cation concentration. H+-PPiase activity was maximal in the presence of K+ (K50 approximately 3 millimolar), with PPi-dependent H+ transport being more selective for K+ than PPi hydrolysis. When assayed in the presence of 50 millimolar KCl at fixed PPi concentrations, H+-PPiase activity showed sigmoidal kinetics with respect to total Mg concentration, reflecting a requirement for a Mg/PPi complex as substrate and free Mg2+ for activation. At saturating concentrations of free Mg2+, H+-PPiase activity exhibited Michaelis-Menten kinetics towards MgPPi2− but not Mg2PPi, demonstrating that MgPPi2− was the true substrate of the enzyme. The apparent Km (MgPPi2−) for PPi hydrolysis (17 micromolar) was significantly higher than that for PPi-dependent H+ transport (7 micromolar). Free Mg2+ was shown to be an allosteric activator of the H+-PPiase, with Hill coefficients of 2.5 for PPi hydrolysis and 2.7 for PPi-dependent H+ transport. Half-maximal H+-PPiase activity occurred at a free Mg2+ concentration of 1.1 millimolar, which lies within the range of accepted values for cytosolic Mg2+. In contrast, cytosolic concentrations of K+ and MgPPi2− appear to be saturating for H+-PPiase activity. We propose that one function of the H+-PPiase may be to act as an ancillary enzyme that maintains the proton-motive force across the vacuolar membrane when the activity of the tonoplast H+-ATPase is restricted by substrate availability. As ATP levels decline in the cytosol, free Mg2+ would be released from the MgATP2− complex, thereby activating the tonoplast H+-PPiase. 相似文献
87.
J. D. Karron D. L. Marshall D. M. Oliveras 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,79(4):457-460
Summary To estimate the numbers of sporophytic S-alleles in two adjacent populations of wild radish, we performed 701 reciprocal crosses among 50 individuals. Each cross was replicated five times in each direction. Sixteen plants were fully intercompatible, indicating the presence of at least 32 S-alleles in the two populations. A minimum of 22 S-alleles occur in a single population. The frequency of incompatibility was significantly higher for within-population crosses (14.5%) than for between-population crosses (7.8%). This suggests that the two populations differ in the composition and frequency of alleles at the S-locus. 相似文献
88.
Defective intracellular transport and processing of CFTR is the molecular basis of most cystic fibrosis. 总被引:113,自引:0,他引:113
S H Cheng R J Gregory J Marshall S Paul D W Souza G A White C R O'Riordan A E Smith 《Cell》1990,63(4):827-834
The gene associated with cystic fibrosis (CF) encodes a membrane-associated, N-linked glycoprotein called CFTR. Mutations were introduced into CFTR at residues known to be altered in CF chromosomes and in residues believed to play a role in its function. Examination of the various mutant proteins in COS-7 cells indicated that mature, fully glycosylated CFTR was absent from cells containing delta F508, delta 1507, K464M, F508R, and S5491 cDNA plasmids. Instead, an incompletely glycosylated version of the protein was detected. We propose that the mutant versions of CFTR are recognized as abnormal and remain incompletely processed in the endoplasmic reticulum where they are subsequently degraded. Since mutations with this phenotype represent at least 70% of known CF chromosomes, we argue that the molecular basis of most cystic fibrosis is the absence of mature CFTR at the correct cellular location. 相似文献
89.
C P Ponting S K Holland S A Cederholm-Williams J M Marshall A J Brown G Spraggon C C Blake 《Biochimica et biophysica acta》1992,1159(2):155-161
A complete understanding of the accelerating mechanisms of plasminogen activation and fibrinolysis necessarily requires structural information on the conformational forms of plasminogen. Given the absence of high-resolution structural data on plasminogen the use of lower resolution approaches has been adopted. Two such approaches have previously indicated a compact conformation of Glu-plasminogen (Tranqui, L., Prandini, M., and Chapel, A. (1979) Biol. Cellulaire, 34, 39-42; Bányai, L. and Patthy, L. (1985) Biochim. Biophys. Acta, 832, 224-227) whereas a third has suggested a fairly extended conformation (Mangel, W., Lin, B. and Ramakrishnan, V. (1990) Science, 248, 69-73). Native Glu-plasminogen has been investigated using small-angle X-ray scattering (SAXS) experiments. It is concluded that this molecule in solution is compact (radius of gyration, RG 3.05 +/- 0.02 nm and maximum intramolecular distance, Im 9.1 +/- 0.3 nm) and that the data are consistent with the right-handed spiral structure observed using electron microscopy by Tranqui et al. (1979). A spiral structure of native plasminogen would have important implications for the conformational response of plasminogen to fibrin and concomitant stimulation of plasminogen activation. 相似文献
90.
Pyruvate kinase (EC 2.7.1.40) from aggregating Dictyostelium discoideum cells has been purified to homogeneity. It has a monomeric molecular weight of 66kD and is tetrameric in low ionic strength buffers. The enzyme is not regulated by fructose 1,6-bisphosphate or by alanine and appears to resemble the M1 isoenzyme from rat liver most closely, although its activity is not inhibited by ATP. 相似文献