Effect of lactose on mineral absorption in preterm infants.

To determine whether a reduction of dietary lactose affects mineral absorption in preterm infants, a controlled, randomized, 72-hour balance study was conducted with very low birth weight infants (birth weights less than 1400 gm) fed Similac Special Care formula with a 50:50 carbohydrate blend of glucose polymers and lactose (n = 8) or a nearly identical formula with 100% carbohydrate as lactose (n = 10). The studies were conducted after at least 3 consecutive days of full oral feeds at a mean age of approximately 23 days. There was no difference between groups in percentage of apparent absorption of calcium, phosphorus, magnesium, zinc, copper, or manganese. Retention of these nutrients was similar to or greater than that which occurs in utero. Calcium absorption was 75% of intake. These results indicate that reducing the lactose content of premature-infant formulas to 50% of the carbohydrate does not impair mineral absorption.

Trace element metabolism in the fetus and neonate.

The effects of trace metal nutrition on the fetus and neonate have been described. Since very little research has been done with the human fetus and neonate, much of our knowledge must be extrapolated from animal studies. In addition, most of the work centres around the effects of copper and zinc nutrition. Nutritional requirements (when known) for both enteral and total parenteral feeding of certain trace metals, as well as the bioavailability, have been discussed. Finally, methods of assessment of trace metal nutritional status have been discussed. These include direct measurement of metal concentrations and determination of biochemical indicators, such as metal-dependent enzyme activities--both of which are static indicators of nutritional status, and functional assessment of nutritional status which is a dynamic measure of trace metal nutrition and includes tests measuring the effects of metal nutrition on the function of cells, tissues, organs, and the host in general.

Kinetic nephelometric determination of transthyretin and retinol-binding protein in neonatal serum.

We have developed a kinetic immunonephelometric method for the determination of retinol-binding protein and modified the method of Jacob et al (Clin Chem 1983; 29: 564) for the determination of transthyretin (prealbumin) in neonatal serum specimens from small, premature infants. The methodologies allow detection of 17.5 mg/l transthyretin and 1.7 mg/l retinol-binding protein in 25 microliter of serum. Between-run precision studies using pooled neonatal serum gave CV values of 3% and 5-6% for transthyretin and retinol-binding protein, respectively. Results obtained for neonatal specimens using this method agreed well with those obtained for the same specimens using radial immunodiffusion. Mean (SD) serum concentrations for 39 neonatal specimens were 100.4 (46.6) and 26.3 (10.8) mg/l for transthyretin and retinol-binding protein, respectively.