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Glucose production and oxidation were measured in ventilated preterm appropriate-for-gestational-age and small-for-gestational-age infants on the first day of life. Using a new technique of NaH13CO3infusion followed by a [U-13C]glucose infusion, we measured glucose oxidation rates without measuring the CO2production rate. Infants were studied at 18 ± 4 h (mean ± 1 SD) of life and received parenterally administered glucose only (4.2 ± 0.5 mg·kg−1· min−1). In 13 of 16 patients, the glucose production rate exceeded 1.0 mg·kg−1·min−1. Infants born from mothers who had been receiving steroids antenatally had higher glucose production rates (2.3 ± 1.1 mg·kg−1·min−1) compared with infants from mothers who had not (1.1 ± 0.8 mg · kg−1· min−1, p= 0.036). The glucose oxidized (2.9 ±1.0 mg · kg−1· min−1) was lower than the amount of glucose infused (p = 0.005) and was not different for appropriate-for-gestational-age and small-for-gestational-age infants. Plasma levels of glucose, insulin, glucagon, and total IGF-I were not correlated with glucose metabolism on the first day of life. Total IGF-II levels were negatively correlated with the rate of glucose appearance. We conclude that preterm infants on the first day of life receiving a glucose infusion of 4.2 mg · kg−1· min−1continue to produce glucose. The glucose oxidation rate is lower than the glucose infusion rate and the contribution of glucose oxidation to the total energy expenditure is limited.

Androgen insensitivity syndrome (AIS) is an X-linked disorder in which defects in the androgen receptor gene have prevented the normal development of both internal and external male structures in 46,XY individuals. This survey reports the analysis of 11 AIS subjects. The androgen receptor gene of these subjects was analyzed using polymerase chain reaction (PCR)-single-strand conformation polymorphism analysis and sequencing or sequencing of PCR-amplified androgen receptor gene fragments alone. In total, 10 single base changes and one partial gene deletion were detected. Seven single base changes resulted in an amino acid change, one resulted in the introduction of a premature stop codon, one event represented a single base insertion resulting in a frame-shift, and one single base change affected a donor splice site. The androgen receptor protein in genital skin fibroblasts from several patients was studied with respect to molecular mass after immunoprecipitation and SDS-PAGE. Two patients expressed a truncated receptor protein in agreement with the established genomic mutation. Pedigree analysis was performed to identify possible carriers for the syndrome in families of AIS patients using single-strand conformation polymorphism and restriction site analysis of PCR products. In one case, the polymorphic (CAG)n(CAA) repeat in exon 1 encoding a polyglutamine stretch was used to identify the mutant allele in a family with X-linked partial androgen insensitivity before the identification of the actual genomic mutation. PCR-single-strand conformation polymorphism analysis proved to be a fast and reliable technique to screen for androgen receptor gene mutations and to study the androgen receptor gene of family members of AlS-affected individuals.

Measurements of whole-body protein turnover in preterm infants have been made using different stable isotope methods. Large variation in results has been found, which could be due to different clinical conditions and/or the use of different tracers. We studied 14 appropriate for gestational age and nine small for gestational age orally fed preterm infants using [15N]glycine and [1-13C]leucine simultaneously, which allowed us to make a comparison of commonly used methods to calculate whole-body protein turnover. Whole-body protein turnover was calculated from 15N enrichment in urinary ammonia and urea after [15N]-glycine administration and from the 13C enrichment in expired CO2after administration of [1-13C]leucine. Enrichment of α-ketoisocaproic acid after [1-13C]leucine constant infusion was measured as a direct parameter of whole-body protein turnover. Group means for whole-body protein turnover using [15N]glycine or [1-13C]leucine ranged from 10 to 14 g.kg-1.d-1, except when using the end product method that assumes a correlation between leucine oxidation and total nitrogen excretion. We found very low 15N enrichment of urinary urea in the majority of small for gestational age infants. These infants also had a lower nitrogen excretion in urine and oxidized less leucine. Nitrogen balance was higher in small for gestational age infants (416 pm 25 mg±kg-1d-1) compared with appropriate for gestational age infants (374 pm 41 mg±kg-1d-1, p= 0.003). [15N]Glycine does not seem to exchange its label with the body nitrogen pool to a significant degree and is therefore not always suitable as a carrier for 15N in protein turnover studies in premature infants.

The aim of this longitudinal study was to examine vitamin D metabolism in exclusively breast-fed infants. The four common vitamin D metabolites—25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D 1,25(OH)2D, 24,25-dihydroxyvitamin D 24,25(OH)2D, and 25,26-dihydroxyvitamin D 25,26(OH)2D—as well as vitamin D binding protein (DBP) were determined simultaneously in mothers and their children from delivery to several months of age. Maternal blood samples, drawn approximately 6 wk before the expected date of delivery, were also analyzed. At delivery, total vitamin D metabolites in maternal and fetal plasma were closely correlated, maternal levels being higher. Unbound (free) vitamin D metabolite concentrations were higher in fetal than in maternal plasma, with the exception of free 1,25(OH)2D levels, which were equal. This suggests a rapid placental transfer of 1,25(OH)2D. 24,25(OH)2D and 25,26(OH)2D levels both in mothers and children were closely correlated with the precursor sterol 25OHD. For 1,25(OH)2D, no correlation could be demonstrated with any of the other vitamin D metabolites. DBP concentrations in maternal plasma at the time of delivery were about twice the mean adult reference value. In cord blood, DBP levels were in the lower part of the adult reference range. Maternal total 1,25(OH)2D levels, which were twice the reference mean during pregnancy, fell sharply after delivery but free 1,25(OH)2D levels much less. Analogous to the biochemical changes in the mother, the infants' DBP levels fell after birth, as a result of the sudden disappearance of the estrogen stimulus. At the same time, the mineral supply via the placenta was cut off. These two factors are probably responsible for a stimulus to 1,25(OH)2D synthesis (and/ or inhibition of 1,25(OH)2D degradation), resulting in a sharp increase of 1,25(OH)2D and an even stronger increase of free 1,25(OH)2D. Concentrations of 25OHD and 1,25(OH)2D in breast milk were low. Such water-soluble metabolites as 25OHD-glucuronides were not detected. Judged by plasma 25OHD levels, the vitamin D stores of most children born to mothers with normal vitamin D status are depleted approximately 8 wk after delivery. Therefore, supplementation with an appropriate dose of vitamin D shortly after birth seems advisable, especially in winter.

Plasma selenium concentration and glutathione peroxidase activity in red blood cells were determined in subjects from different age groups. The selenium level (mean ± SD) found in infancy (0 to 6 months) was 2 ± 0.6 /μg/dl, with the lowest value of 1 /μg/dl observed in a 4- month-old infant. These levels were significantly lower (p<0.001) than the value of 9.5 ± 1.1 /μg/dl found in the adult group and 7.7 ± 1.3 μg/dl found in the group of older children (2 to 15 yr). Younger children (6 to 24 months of age) had intermediate levels of 5 ± 1.2 /μg/dl. When the data were plotted on a logarithmic scale as a function of age, the figure shows clearly that the plasma selenium levels increase steadily with age throughout life after an initial drop at 60 to 90 days. There was a satisfactory correlation between the plasma selenium concentration and the enzyme glutathione peroxidase activity in the red blood cells (Spearman's ρ0.45, p<0.005). Although very low selenium values were observed, the enzyme glutathione peroxidase activity remained above 10 U/g hemoglobin (with only one exception) in all patients.