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1.
HbA1c is the most prevalent of the minor human hemoglobins. It is formed by the nonenzymatic addition of glucose to the alpha-amino group of the beta chain by an initial condensation reaction and a subsequent intermolecular Amadori rearrangement. We have developed a method of analysis which utilizes high performance liquid chromatography to follow the formation of HbA1c and greatly simplifies the determination of the kinetic parameters associated with this reaction. This has allowed us to study the effects of several Hb ligands, including the hydrogen ion, on the kinetics of this glycosylation reaction. Both the initial condensation reaction and the subsequent rearrangement are shown to exhibit acid catalysis, but the rate of the condensation step is limited by the extent of protonation of the alpha-amino group. The variation in kinetic parameters as a function of hydrogen ion concentration has allowed us to determine the probable reaction mechanism of HbA1c formation by comparison to previously reported model systems of Schiff base formation and Amadori rearrangement. The formation of pre-HbA1c from deoxy-Hb shows an increased forward rate when compared to oxy-Hb. The presence of physiologic concentrations of CO2 causes a proportional decrease in both k1 and k-1. 2,3-Diphosphoglycerate causes a significant increase in the keq of the formation reaction. The effects of CO and the substitution of L-glucose for D-glucose are not significant. 相似文献
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A gene encoding the endogenous superantigen Mlsc, which deletes Tcrb-V3+ T cells in the NOD inbred mouse strain, was found to co-segregate with Mtv-3 on chromosome 11. This identifies a fourth gene encoding a deletion ligand for Tcrb-V3+ T cells and extends recently published observations in support of the hypothesis that a number of endogenous superantigens are the products of Mtv proviruses.
Address correspondence and offprint requests to : K. Tomonari. 相似文献
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A plant collected in South Africa in the early 1960's has been considered an intergeneric hybrid with the parental taxa beingRuspolia hypocrateriformis (Vahl)Milne-Redhead var.australis
Milne-Redhead andRuttya ovata
Harv. The intermediate morphology of the plant provided the strongest evidence of its hybrid origin. The natural hybrid, named formally as ×Ruttyruspolia
A. Meeuse & de Wet, is highly sterile. Crosses between the two presumed parental taxa produced two plants that are very similar to the putative natural hybrid. We had examined the presumed parental species and the natural and artificial hybrids using enzyme electrophoresis. The two parental species are highly differentiated at genes specifying soluble enzymes; they have a genetic identity of 0.51. They have no common alleles at two genes, and contain alternative alleles in very different frequencies at two loci.Ruttya andRuspolia exhibit both unique and common alleles at two additional genes. The natural and artificially produced plants of ×Ruttyruspolia are identical electrophoretically and contain alleles unique to each of the parental species at two genes. In addition, individuals of ×Ruttyruspolia combine alternative high frequency alleles from each parent at two loci. Allozymes provide strong confirming evidence for the hybrid origin of naturally occurring ×Ruttyruspolia because the products of specific alleles either unique to or highly characteristic of the two putative parental taxa are found combined in ×Ruttyruspolia. 相似文献
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A total of 34 isolates ofListeria monocytogenes were tested against ampicillin, cephalothin, chloramphenicol, erythromycin, tetracycline, and penicillin-G using the Autobac 3-h AIS and the Autobac 5-h MIC procedures. The results were compared to susceptibility category interpretations and MICs determined using the Sceptor system. With the Sceptor System, all isolates were interpreted to be moderately susceptible to ampicillin and penicillin-G, and susceptible to the four other antibiotics. With the Autobac AIS, all isolates were interpreted to be susceptible to all the antibiotics except penicillin-G. All but one of the 34 isolates were interpreted to be resistant to penicillin-G with the Autobac AIS test. The remaining isolate was interpreted to be indeterminant. The Autobac AIS test was unsatisfactory for determining the susceptibility ofL. monocytogenes isolates to penicillin-G. The Autobac MIC results correlated well with the MIC results of the Sceptor system provided that the Autobac was programmed as though it were testing enterococci. The Autobac MIC reported penicillin-G MICs in units per milliliter and required the use of a conversion factor to obtain micrograms per milliliter, and did not allow for the testing of erythromycin. The Autobac MIC susceptibility category interpretations must not be used, as they were derived from an outdated susceptibility standard. The Autobac MIC test may be used if the limitations given above are observed. 相似文献
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Isolation of single taste cells from lingual epithelium 总被引:1,自引:0,他引:1
A method is described for obtaining large numbers of isolatedtaste cells with identified polarity from lingual epithelium.The procedure involves incubating lingual epithelium in collagenase,staining the apical surface with fluorescein-conjugated wheatgerm agglutinin (FTTC-WGA), peeling non-gustatory surface epitheliumfrom the underlying taste buds and connective tissue, and dissociatingisolated taste buds with Ca2+-free saline. Isolated taste cellsretain their characteristic morphology for at least 30 min afterdissociation, and the apical specialization can be identifiedas a single patch of fluorescence usually located at the tipof an elongate process. Isolated taste cells are amenable tostudy with the patch-clamp technique, and whole-cell patch-clamprecordings show that isolated taste cells have membrane propertiessimilar to taste cells of intact lingual epithelium. Evidenceis presented that FITC-WGA staining does not alter the voltage-dependentionic currents of the taste cell membrane. 相似文献
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Malgorzata Schmidt Desirée Du Sart Paul Kalitsis Margaret Leversha Sue Dale Leslie Sheffield Daniela Toniolo 《Human genetics》1991,86(5):519-521
Summary We have analysed two duplications of the X chromosome in male patients using chromosome replication and DNA methylation patterns as determinants of the functional status of the duplicated segments. In both cases, the large duplicated regions, Xq12-q22 and Xq26.3-qter, were not inactivated. A review of previously reported male cases revealed that these duplications were also not subject to inactivation. Taken together, the examined duplications cover almost the entire X chromosome except the pericentromeric region and Xq25–26. Thus, most regions of the X chromosome can be present in two functional copies without lethal consequences. 相似文献
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H Y Ahn L F Sue J K Ma C A Pinkstaff R S Pore D O Overman C J Malanga 《Biochimica et biophysica acta》1988,966(1):122-132
The ability of the isolated gill epithelium of Mytilus edulis to incorporate [14C]glucosamine as a precursor in the biosynthesis and secretion of mucous glycoproteins was investigated. Localization of mucous cells in the gill filament was achieved using histochemical staining techniques. Mucus cells containing neutral and acidic mucins were found in the lateral region, whereas mucus cells containing primarily neutral or sulfated mucins were found in the abfrontal region. Autoradiographic results showed that in both regions, the mucous cells were rich in content of the incorporated radiolabel. The secreted glycoproteins containing the incorporated radiolabel were analyzed by column chromatography using Bio-Gel P-2 and P-6. Two populations of the glycoproteins differing in molecular size were isolated. Upon alkaline reductive borohydride cleavage of the O-glycosidic linkages of the high molecular weight protein, about 70% of the radiolabel and 85% of the carbohydrate content were removed from the protein. The alkaline borohydride cleavage resulted in the formation of at least six oligosaccharide chains of various lengths of sugar units. Gas chromatographic analysis of the carbohydrate composition shows that the glycoproteins contain N-acetylglucosamine, N-acetylgalactosamine, and galactose, fucose, and mannose as the neutral monosaccharides. The above results indicate that the isolated gill epithelium of M. edulis is capable of incorporating [14C]glucosamine in the synthesis of secretable mucin-type glycoproteins. 相似文献