The needs for dietary zinc are adequately met by most fully breast-fed infants despite relatively low zinc intakes in relation to estimated requirements. The objective of this study was to use stable isotope techniques to evaluate how zinc retention is achieved in normal fully breast-fed infants. Nine male infants, aged 2-5 mo, were fed expressed human milk labeled with 70Zn over a 24-h period. Complete fecal collections were obtained for 8 d. On d 4-7, a metabolic period was initiated which included test weighing and milk sampling, to measure zinc intake, and daily urine collections. Isotopic enrichment of fecal and urine samples was determined by fast atom bombardment mass spectrometry. Results included a mean (+/- SD) dietary zinc intake of 17.8 +/- 6.6 mumol/d; fractional absorption of 0.54 +/- 0.075; and total absorbed zinc of 9.5 +/- 3.5 mumol/d. Mean endogenous fecal zinc, determined on seven infants by isotope dilution, was 4.7 +/- 2.3 mumol/d, which resulted in a mean net absorption of 4.8 +/- 3.4 mumol/d. The results of the study indicated that, for fully breast-fed infants, it is the combination of a relatively high fractional absorption and efficient conservation of intestinal endogenous zinc that results in zinc retention adequate to meet the demands of growth in the face of modest intake.

To establish the prevalence of proinsulin-specific antibodies in diabetic patients, thirty serum sampies were analyzed.Among the insulin-treated group, proinsulin antibodies were demonstrated in 20 cases (80%) by the significant binding of 1251-bovine proinsulin to the sera pretreated with excess of insulin and reduced binding when these sera were preincubated with unlabelled bovine proinsulin. Five other sera (20%) bound tracer pro insulin, but did not bind significantly after preincubation with insulin indicating tbat only cross-reacting insulin antibodies were present and there were no detectable proinsulin antibodies. Sera from five diet-controlled patients bad no antibodies. IntroduetionComrnercia! preparations of insulin contain variable amounts of proinsulin and related substances (Steiner, HaI/und, Rubenstein, Cho and Bayliss 1968, Chance 1972) which have been shown to have significant immunogenicity in anima! experiments (Rubenstein, Steiner, Lawrence and Kirsteins 1969, Kerp 1971, Schlichtkrull, Brange, Christiansen, Hallund, Heding and Jorgensen 1972. I t is very likely that the daily administration of proinsulin, present in therapeutic insulin will induce proinsulin-specific antibodies in diabetie patients. Although a small concentration of such antibodies have been demonstrated in a pooled human sera (Kerp, Steinhilber and Kasemir 1970), their ineidence in the individual patients remains uninvestigated.The purpose of this report is to establish the prevalence of proinsulin-specific antibodies in diabetic patients. Materials and MethodsFisher Endocrinology Laboratories, Chicago) were purified by gel filtration (Sephadex G-50, 0.5 x 20 in. column, borate buffer pH 7.4) and diluted to 0.2 ng/mL The same preparations of labelIed tracers were used for alI the tests.80vine proinsulin (lot no. 615-10708-212-2) and insulin (lot no. 615-10828-244) were supplied by Dr. R. Chance, Lilly Research Laboratories, Indianapolis. These proteins were dissolved in borate buffer, pH 7.4, containing 1% bovine serum albumin (Mann Laboratories, New York) and diluted to 500 ng/mL Anti-human immunoglobulin serum (AHI-RS) was prepared by hyperimmunizing rabbits to purified plasma Cohn fraction 11. This sera reacted strongly with both the antigenie types K and A light chains and was therefore a polyvalent anti-immunoglobulin (Feinstein, Rapaport and Chong 1969). A seven-fold concentration of this sera produced maximal precipitation of immunoglobulins.Detection of proinsulin and insulin antibodies: Two sets of tubes, each containing 0.1 ml of diluted (1: 16) serum were preincubated for 20 hr at 4 0 C with 0.1 ml of buffer, insulin (500 ng/mq or proinsulin (500 ng/ml). To one set of tubes, 0.1 ml of I 51-bovine proinsulin (0.2 ng/ml) and to the other set, 0.1 ml of 12SI_bovine insulin (0.2 !Jg/ml) were added. Tubes were reincubated for 40 hr at 4 0 C. To precipitate the immune complexes, 0.1 ml of AHI-RS 0:2) was then added. Forty hours later precipitate was filtered and washed on oxoid membrane (Amersham Searle). The radi...

ceUular hypersensitivity in diabetes meUitus. Experimental induction of anti-pancreatic, cellular hypersensitivity and associated morphological B-cell changes in the rat. Acta allerg.

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