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C Hulbert

Publications and source records attributed to C Hulbert.

4 recordsLinked to original sources
PubMed1991

Dynamic changes in 13C NMR spectra of intact hearts under conditions of varied metabolite enrichment.

Dynamic changes in 13C NMR signal from enriched glutamate pools within hearts have been examined under varied conditions of metabolite pool size and fractional enrichment. Relative signal intensities of 13C-enriched glutamate isotope isomers were similar within spectra from both intact hearts and corresponding in vitro samples. The parameters used to assess metabolic activity with 13C NMR proved independent of fractional enrichment and pool size. The data show the importance of acknowledging unlabeled, 13C NMR invisible metabolites.

Animals↗
PubMed1989

Human insulin autoantibody fine specificity and H and L chain use.

Fine specificity and H and L chain isotypes of insulin autoantibodies in sera from 11 subjects were examined. None of these 11 subjects was treated with exogenous insulin. Two patterns of fine specificity were found. In one, the autoantibodies were specific for human insulin, with a requirement for threonine at B30. The conservative substitution in pork insulin (threonine to alanine) abrogated IgG binding by these sera. Insulin autoantibodies in other sera cross-reacted with beef, pork, and human insulin; not requiring threonine at B30. Reciprocal competitive inhibition experiments showed that epitopes recognized by the human specific insulin autoantibodies were exclusively on the B chain, whereas the cross-reactive sera contain autoantibodies that recognize both the B chain and combinatorial (A and B chain) epitopes. The fine specificity of cross-reactive insulin autoantibodies are thus similar to insulin antibodies from insulin-treated subjects. When IgG subclasses and L chains of insulin autoantibodies were examined, however, restricted C region usage was found. The hierarchy was IgG3 greater than G1 greater than G2 greater than G4; with one subclass dominant in each serum, although others were used. L chain use was similarly restricted. There was no correlation between isotype and fine specificity or between H and L chain type. It is concluded that heterogeneity of insulin autoantibodies is restricted. The response is probably more oligo- or pauciclonal than insulin antibody from insulin-treated subjects.

Amino Acid Sequence↗
PubMed1989

Factors affecting the insulin autoantibody ELISA.

IgG antibodies to insulin are present in insulin-treated patients and are detected in the prodrome of untreated type I diabetes. Sporadic reports of autoantibodies to insulin suggest that they are also present in other disorders. To establish the incidence of insulin autoantibodies in other endocrine and autoimmune diseases an ELISA was used to examine sera from 529 subjects with no prior insulin therapy. These untreated patients included: normal controls (adults and children), newly-diagnosed type I diabetes, first-degree relatives of diabetics, type II diabetes, Graves' hyperthyroidism, and systemic lupus erythematosus. As a positive control group, 280 insulin-treated patients were studied. Measurement of IgG antibodies by direct binding to insulin coated plates was complicated by differences between adult and pediatric populations and by overlap of binding between treated and untreated subjects. Competitive inhibition with excess soluble human insulin overcame these problems and permitted identification of insulin specific binding. Using this approach insulin antibodies were most frequent in insulin-treated diabetics (98%) and in type I diabetics (37%) prior to treatment. The absolute numbers of subjects with insulin autoantibody in the other groups differed depending upon whether a cut-off for binding (mean + 2SD of controls) or for insulin inhibition of binding (45%) was used. Regardless of the criteria used there were subjects (2-24%) in all groups tested with circulating insulin-specific IgG autoantibody detected by ELISA. These low level antibodies detected in solid phase assays may be part of the normal immune repertoire.

Adolescent↗