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Biomedical subjects

R Flückiger

Publications and source records attributed to R Flückiger.

66 records · Page 4Linked to original sources
PubMed1984

Nonenzymatic glycosylation of basement membrane collagen in diabetes mellitus.

For a better understanding of the processes leading to diabetic microangiopathy, type IV collagen from kidneys of patients with long-term diabetes was compared with the collagen from kidneys of sex- and age-matched controls. Type IV collagen from diabetic kidneys revealed no abnormalities in amino acid composition, hydroxylation of proline and lysine, enzymatic glycosylation of hydroxylysine, and immunological reactivity with several monoclonal and polyclonal, anti-type IV collagen antibodies. However, ketoamine-linked hexose, resulting from the nonenzymatic condensation of glucose with lysyl or hydroxylysyl residues, was 1.7-fold higher in diabetic type IV collagen. The stoichiometry of this modification was estimated to be 1-2 residues of hexose per triple helical molecule (Mr 380,000). This small amount of ketoamine-linked hexose might hardly have an effect on the function and turnover of type IV collagen, unless it is bound to a crucial site along the collagen molecule. The nonenzymatic glycosylation of collagen might therefore be a mere consequence of the metabolic disturbances, rather than the primary cause for the late complications of diabetes mellitus.

Amino Acid Sequence↗
PubMed1984

Quantitation of glycosylated hemoglobin by boronate affinity chromatography.

Total hemoglobin glycosylation and the contribution of glycosylation at the N-terminus of the beta-chains and at "non"-beta-N-terminal positions were quantitated by use of boronate affinity and ion exchange chromatography. Glycohemoglobin (y) was found to correlate linearly (y = 1.92x + 0.53; r = 0.96) with HbA1c (x) and to contain approximately 50% beta-N-terminally glycosylated hemoglobin. This result is in agreement with the binding on boronate agarose of the various hemoglobin components resolved by cation exchange chromatography. An amount of glycohemoglobin similar to that of HbA1c was isolatable from HbA. A slope of less than 2 results because HbA1c is retained only to 93% and the intercept of the regression line reflects the partial adherence (65%) of HbA1a + b to the resin. These results confirm the occurrence of significant "non"-beta-N-terminal glycosylation and show that under optimal chromatographic conditions total glycohemoglobin can be determined with boronate affinity chromatography.

Borohydrides↗
PubMed1984

Measurement of receptor induced changes in intracellular free calcium in human platelets.

The intracellular free calcium concentration plays a key role as second messenger in the regulation of cellular reactions. Post-receptor events can be investigated by measurement of free calcium concentration in cells. Our experience in measuring the intracellular free calcium concentration in platelets with the use of the fluorescent indicator quin-2-tetraacetoxymethyl- ester is described. Possible pitfalls in the preparation procedures of the platelets are discussed as well as critical steps and the limitations of the quin-2-method. The methodological approach is demonstrated by the presentation of an investigation with the adenylate cyclase inhibitors adenosine-5'-diphosphate and epinephrine as well as their interrelationship. The potentiation effect of epinephrine to adenosine 5'-diphosphate on platelet function such as aggregation is accompanied by a potentiation of the effect of these two platelet activators in elevating the intracellular free calcium concentration. Adenosine 5'-diphosphate elevates intra-platelet free calcium alone, whereas epinephrine acting through stimulation of the alpha2-receptor needs another permissive factor to immediately elevate the intra-platelet free calcium.

Adenosine Diphosphate↗
PubMed1979

Glycosylated hemoglobins: increased glycosylation of hemoglobin A in diabetic patients.

The components of the hemoglobin-A1 fraction--hemoglobins A1a--c--arise from nonenzymatic glycosylation of hemoglobin A at the beta-chain N-terminal amino groups and can be resolved from hemoglobin A by cation exchange chromatography. Glycosylation can also occur at the alpha-chain N-terminals as well as the epsilon-amino groups of lysine residues of both alpha- and beta-chains; this results in glycosylated species appearing in the hemoglobin-A fraction. In this study, we determined the extent of hemoglobin-A glycosylation using a colorimetric chemical method specific for the detection of ketoamine-linked hexoses in proteins. We demonstrate increased glycosylation of the main hemoglobin-A fraction in diabetic patients, which correlates significantly (r = 0.72, P less than 0.001) with the hemoglobin-A1 percentage determined by column chromatography in the corresponding hemolysates. This finding provides the basis for the application of this chemical procedure to the measurement of total glycosylation of hemoglobin.

Chemical Phenomena↗
PubMedDate not supplied

Glycosylation of variant hemoglobins in normal and diabetic subjects.

The extent of in vivo glycosylation of variant hemoglobins was examined in individuals with S-, C-, and D-trait. Chromatographic estimates of glycosylation for nondiabetic individuals with S-trait were significantly lower than those for nondiabetic black subjects with normal hemoglobin (P < 0.001). However, chemical determinations of glycosylation (thiobarbituric acid or TBA technique) were similar for these groups (P > 0.10). The chromatographic elution pattern of hemoglobin S (HbS) was determined, and on this basis an adjustment procedure was performed for chromatographic data. A regression line was calculated for the relationship between chromatographic and colorimetric estimates of glycosylated hemoglobin in S-trait individuals with and without diabetes. The slope of this line was significantly different (P < 0.001) from that for the relationship in individuals with normal hemoglobin. However, after adjustment of chromatographic values from S-trait individuals, the slopes were similar (P < 0.10). Findings from individuals heterozygous for HbC and D were similar to those for individuals with S-trait. These data indicate that the extent of glycosylation of HbS, C, and D is similar to that of HbA in both the normoglycemic and hyperglycemic range. The TBA technique is the most direct method for determining the extent of glycosylation in individuals with HbS, C, or D. However, adjustment of column chromatographic values is feasible.

Adult↗