Susceptibility of different rat tissues to non-enzymatic protein glycosylation in experimental diabetes.

Hyperglycemia was induced in Sprague-Dawley rats by alloxan and maintained for 2, 6 and 10 weeks without insulin treatment. Levels of glycosylated plasma proteins, hemoglobin and glycosylated tissue proteins of aorta, heart, kidney, liver and brain were estimated at these intervals. Protein glycosylation was observed to increase linearly as a function of period of hyperglycemia in all the tissues studied, except brain, in the following order: aorta > heart > kidney > liver. Protein glycosylation, leading to formation of covalently modified advanced glycosylated products and protein-protein adducts, may reflect disposition of these tissues to diabetic complications.

Interaction of human alpha fetoprotein with bilirubin.

Human alpha fetoprotein (AFP) binds bilirubin with an affinity somewhat lower than albumin. Free bilirubin was found to have an extinction maximum at 440 nm with an extinction coefficient of 4.97 x 10(4) M-1cm-1. AFP binding with the bile pigment elicits a blue shift while albumin interaction produced red spectral shift.

Development of an inexpensive and rapid two site microenzyme linked immunosorbent assay kit for human alpha fetoprotein.

Laboratory scale development of a two site micro enzyme linked immuno assay kit is described. The kit comprises rabbit anti human alphafetoprotein (AFP), anti human AFP IgG peroxidase conjugate and standard AFP. All the above reagents were prepared in the laboratory. The kit is eminently suitable for early screening of blood sample of pregnant women for neural tube defects of their fetuses and for the quantitation of AFP as a tumor marker. The assay kit was used to determine AFP in 76 sera from women at different stages of pregnancy. During 1st trimester AFP level was 18 to 119 ng/ml, during 2nd trimester the concentration varied from 85 to 302 ng/ml and during 3rd from 103 to 580 ng/ml. No evidence for maternal antibody to AFP was found. The above data agree with AFP level in pregnant women reported by earlier workers, using RIA or ELISA. The present ELISA kit would hopefully be much cheaper than internationally available ELISA kits for human AFP.

Alpha fetoprotein levels in newborn infants with reference to sex, gestational age and birth weight.

Alpha fetoprotein (AFP) concentration was higher in the mature full term male infants than age matched females. An inverse correlation, at birth, between cord serum AFP level and duration of pregnancy was observed. In contrast no correlation between body weight and AFP levels exists in babies of either sex at identical gestational age.

Ontogeny of insulin-receptor interaction: correlation with circulatory insulin levels.

Interaction of [125I]-insulin with intact hepatocytes and its correlation with circulatory insulin level was examined. The hepatocytes from new-born rats bound lowest amount of [125I]-insulin (1.39±0.41 pM/mg cell protein) when circulatory insulin level was high (8±1.5 μU/ml). Hepatocytes from 7 day and 21 day old animals demonstrated a more or less similar relationship, Cells from 31 day old animals exhibited maximum insulin binding, activity (5.13±0.18.pM/mg cell protein) against a low serum insulin level (4.25±0.25 μU/ ml). Scatchard analysis of insulin binding shows that the affinity is higher in the hepatocytes from new-born animals than in the hepatocytes of 31 day old animals. Higher binding observed in the latter case may be due to a greater number of binding sites. Hepatocytes from one year old rats bound very little insulin (2.50±0.36 pM/mg cell protein) against a high circulatory insulin level (9.25±0.85 μU/ml). In view of these results, it appears that the down-regulation hypothesis holds true during ontogeny too.