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1.
Membrane-bound immunoglobulin (mIg) is the antigen receptor on B lymphocytes mediating early events in antigen presentation and signal transduction. Wild-type human mIgM constructs transfected into the murine B-cell lymphoma A20 are expressed as transmembrane proteins with antigen presentation and signaling functions comparable to the endogenous mIgG2A; the transfected wild-type mIgM is internalized rapidly after anti-Ig cross-linking. Transfected constructs lacking the normal three-amino acid cytoplasmic tail are expressed exclusively as phosphatidylinositol-linked proteins, lack both antigen presentation and signal transduction functions, and are internalized slowly following anti-Ig binding. The molecular mass of the cytoplasmic tail-deleted phosphatidylinositol-linked Ig molecule is consistent with cleavage of the transmembrane residues during processing. Cytoplasmic domains may therefore regulate the mode of expression of membrane proteins and thereby influence their functional capabilities.  相似文献   
2.
The genetic diversity of a clonal sedge (Tertraria capillaris) was assessed using isozyme analysis of 11 loci. Of 29 enzyme systems tested, eight were selected which gave interpretable bands with consistently good resolution. Though seedlings of the species are rarely observed in nature, isozyme analysis showed that for the study transects containing 100 sample plants, the majority of plants at the site were sexually rather than clonally derived. Young plants generated from embryos grown in vitro from excised seeds showed a high level of genetic diversity which could account for the genetic diversity measured in the parent population. In terms of restoration of the species, 85% of the assessed genetic diversity at the study site could be retained if 25 T. capillaris plants were taken at random. The study illustrates how genetic assessment coupled with tissue culture methods provides a feasible model for the recovery of most of the assessed local genetic diversity of a clonal species.  相似文献   
3.
Interferon Regulatory Factors (IRFs) play fundamental roles in dendritic cell (DC) differentiation and function. In particular, IRFs are critical transducers of TLR signaling and dysregulation in this family of factors is associated with the development of autoimmune disorders such as Systemic Lupus Erythematosus (SLE). While several IRFs are expressed in DCs their relative contribution to the aberrant phenotypic and functional characteristics that DCs acquire in autoimmune disease has not been fully delineated. Mice deficient in both DEF6 and SWAP-70 (= Double-knock-out or DKO mice), two members of a unique family of molecules that restrain IRF4 function, spontaneously develop a lupus-like disease. Although autoimmunity in DKO mice is accompanied by dysregulated IRF4 activity in both T and B cells, SWAP-70 is also known to regulate multiple aspects of DC biology leading us to directly evaluate DC development and function in these mice. By monitoring Blimp1 expression and IL-10 competency in DKO mice we demonstrate that DCs in these mice exhibit dysregulated IL-10 production, which is accompanied by aberrant Blimp1 expression in the spleen but not in the peripheral lymph nodes. We furthermore show that DCs from these mice are hyper-responsive to multiple TLR ligands and that IRF4 plays a differential role in in these responses by being required for the TLR4-mediated but not the TLR9-mediated upregulation of IL-10 expression. Thus, DC dysfunction in lupus-prone mice relies on both IRF4-dependent and IRF4-independent pathways.  相似文献   
4.
S-Nitrosylation is a post-translational modification on cysteine(s) that can regulate protein function, and pannexin 1 (Panx1) channels are present in the vasculature, a tissue rich in nitric oxide (NO) species. Therefore, we investigated whether Panx1 can be S-nitrosylated and whether this modification can affect channel activity. Using the biotin switch assay, we found that application of the NO donor S-nitrosoglutathione (GSNO) or diethylammonium (Z)-1–1(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA NONOate) to human embryonic kidney (HEK) 293T cells expressing wild type (WT) Panx1 and mouse aortic endothelial cells induced Panx1 S-nitrosylation. Functionally, GSNO and DEA NONOate attenuated Panx1 currents; consistent with a role for S-nitrosylation, current inhibition was reversed by the reducing agent dithiothreitol and unaffected by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a blocker of guanylate cyclase activity. In addition, ATP release was significantly inhibited by treatment with both NO donors. To identify which cysteine residue(s) was S-nitrosylated, we made single cysteine-to-alanine substitutions in Panx1 (Panx1C40A, Panx1C346A, and Panx1C426A). Mutation of these single cysteines did not prevent Panx1 S-nitrosylation; however, mutation of either Cys-40 or Cys-346 prevented Panx1 current inhibition and ATP release by GSNO. This observation suggested that multiple cysteines may be S-nitrosylated to regulate Panx1 channel function. Indeed, we found that mutation of both Cys-40 and Cys-346 (Panx1C40A/C346A) prevented Panx1 S-nitrosylation by GSNO as well as the GSNO-mediated inhibition of Panx1 current and ATP release. Taken together, these results indicate that S-nitrosylation of Panx1 at Cys-40 and Cys-346 inhibits Panx1 channel currents and ATP release.  相似文献   
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6.
The occurrence of hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase in adult Hymenolepis diminuta was demonstrated. This activity was negligible in the cestode's cytosolic fraction but was noted when the mitochondrial or microsomal fraction served as the enzyme source. The predominant localization of HMG-CoA reductase activity was with the microsomal fraction. This fraction did not contain appreciable mitochondrial contamination based on the distribution of marker enzymes. The enzymatic nature of HMG-CoA conversion to mevalonic acid by either fraction was apparent because the reaction was heat labile and responded linearly to time of assay and protein content. The enzymatic reduction of HMG-CoA absolutely required NADPH when either fraction was assayed. The lesser activity of the mitochondrial fraction was membrane-associated. The predominant localization of HMG-CoA reductase activity with microsomal membranes and its separation with the membranous component of the mitochondrial fraction suggest that mitochondrial activity reflects the presence of microsomal membranes. In its predominant localization and pyridine nucleotide requirement, the cestode's HMG-CoA reductase activity resembles that of mammalian systems. The finding of HMG-CoA reductase provides an enzymatic mechanism for the intermediate conversion of HMG-CoA to mevalonic acid that would be needed for acetate-dependent isoprenoid lipid synthesis by adult H. diminuta.  相似文献   
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8.
In an initial trial of glibenclamide in the treatment of maturity onset diabetes mellitus 28 patients were treated for up to one year and no toxic effects or side-effects were encountered. The hypoglycaemic potency of this drug is such that 5 mg. of glibenclamide corresponds to about 1,500 mg. of tolbutamide and 375 mg. of chlorpropamide.  相似文献   
9.
Roots of Vitis vinifera L., were treated with benzyladenine when the plant shoots were 38 cm long. Seventy-two hours after benzyladenine treatment, apical or basal leaves on separate shoots were exposed to 14CO2. Control shoots received 14CO2 but no benzyladenine. Application of benzyladenine directed 14C-photosynthate to roots, but a small amount of radioactivity was detected in the shoot tip when 14CO2 was administered to an apical leaf. Distribution of radioactivity among the sugar, organic acid, and amino acid fractions was altered by benzyladenine treatment. In all parts of plants with roots treated with benzyladenine and apical leaf fed 14CO2, the percentage of the total label in the sugar fraction comprised of fructose was generally more than twice that in control plants.  相似文献   
10.
Ilia from a known sex, race, and age sample of fetal and infant skeletons from the collections of the Smithsonian Institution were evaluated for six metric and one nonmetric characters. Three indices calculated from the measurements were analyzed. The nonmetric trait was examined for fit with known sex. The three indices failed to show significant sex differences. The nonmetric trait, Auricular Surface Elevation, proved dependable (91% accurate) for the male Fetal and Six Month age groups.  相似文献   
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