Biomedical subjects
K Simmer
Publications and source records attributed to K Simmer.
Maternal zinc and intrauterine growth retardation.
The levels of zinc in plasma, erythrocytes, polymorphonuclear (PMN) and mononuclear (MN) white cells were measured after delivery in women giving birth to appropriate-for-gestational-age (AGA) babies (group I mothers), or small-for-gestational-age (SGA) babies (group II mothers) and in non-pregnant controls. Mean maternal plasma zinc and albumin levels 24-48 h after delivery were lower than in controls, but PMN and MN zinc levels were unchanged. PMN zinc levels were lower than those of MN cells. PMN and MN zinc levels were significantly lower in group II mothers than in group I, irrespective of smoking habits. There were no racial differences in peripheral white cell zinc levels. PMN, and to a lesser degree MN, zinc levels were lower in smoking than in non-smoking mothers. Erythrocyte zinc did not correlate with other zinc measurements nor with the size of the babies. Fetal erythrocyte zinc levels were one-third of maternal levels. A combination of smoking and/or low PMN zinc levels selects 85% of mothers having small-for-gestational-age babies.
Zinc in the fetus and newborn.
The growing fetus and infant are at risk of becoming deficient of zinc, an adequate supply of which is essential for normal growth and development. Mild maternal zinc depletion was strongly associated with intrauterine growth retardation. Low levels of zinc in maternal plasma and poor placental perfusion reduced the materno-fetal transfer of zinc. Mean maternal dietary intake of zinc was 60% recommended daily allowance and mothers of small-for-gestational-age (SGA) babies consumed significantly less zinc than mothers of appropriate-for-gestational-age babies. In addition, iron/folate supplements, which are often routinely prescribed during pregnancy, despite dietary intakes of iron and folate being adequate, significantly decreased the oral bio-availability of zinc in pregnant women. Zinc supplementation may be beneficial to women at risk of delivering SGA babies. Zinc requirements and interactions are also important to consider when designing mineral supplements for preterm babies, infant formulae and food fortification in developing countries.
Placental handling of zinc in the guinea pig.
The distribution of zinc between the mother and the fetoplacental unit, and its placental transfer, were studied using stable and isotopic zinc in unanaesthetized pregnant guinea pigs and an in situ perfusion preparation. The concentration of stable zinc in fetal plasma and skeletal muscle was higher than that in the maternal tissues: 2.0 compared with 1.4 micrograms/ml and 84 with 49 ng/mg dry weight, respectively. The placenta and maternal and fetal liver had similar zinc concentrations: 90, 75 and 88 ng/mg dry weight, respectively. The ability of the placenta to concentrate 65Zn, measured 1 h after a single intravenous injection into the unanaesthetized mother, was comparable with that of the maternal liver. Maternal-fetal mass transfer of zinc was directly related to maternal plasma zinc concentrations from 0.7 to 24.1 micrograms/ml (b = 2 ng X min-1 X g-1 X microgram-1, r = 0.92). At physiological plasma levels, the calculated transfer would supply the fetus with 0.12 mg zinc/day, similar to the accretion rate over the last trimester. Placental transfer of zinc was not influenced by the concentration of zinc in the placental perfusate. Extraction of zinc from the perfusate was also slow, and partly by absorption. Maternofetal transfer of zinc was directly related to both uterine and umbilical blood flows. The high concentration of zinc in the syncytium, relative to both maternal and fetal plasma levels, suggests active uptake at the maternal surface, combined with a slow release into the fetus, down a concentration gradient.
Prostaglandin production and zinc depletion in human pregnancy.
An association between zinc depletion and intrauterine growth retardation might occur through disturbed prostaglandin (PG) synthesis. The zinc content and PG metabolism of leucocytes from control, nonpregnant women and mothers 24-48 h after delivery, were measured and related to fetal growth and maternal smoking. Mothers of small for gestational age babies had lower polymorphonuclear and mononuclear cell zinc contents than mothers of appropriate for gestational age babies or nonpregnant controls. Monocytes were the major leucocytes producing PGs. Mothers of small for gestational age babies had higher PGE2:F2 alpha ratios than mothers of appropriate for gestational age babies. PGF2 alpha production and PGE2:F2 alpha ratio were correlated with tissue zinc status. Monocytes from nonsmokers tended to produce more PGs than those from smokers but the differences were not significant. Mild maternal zinc depletion is not significantly sufficient to alter absolute PG production, but is associated with altered differential production of PGs in human leucocytes. Zinc depletion or malnutrition may contribute to intrauterine growth retardation by affecting placental and/or umbilical PG production.
Gastric pneumatosis in neonates: revisited.
Pneumatosis intestinalis, found commonly in neonatal necrotising enterocolitis (NEC), can occur in any part of the gastrointestinal tract, from the oesophagus to the rectum. Gastric pneumatosis, defined as air within the wall of the stomach, however, is an extremely rare sign during infancy and is usually secondary to gastric outlet obstruction. The clinical course and outcome of a neonate with gastric pneumatosis associated with NEC is reported along with a brief review of the literature. The findings illustrate that gastric pneumatosis can be the presenting feature of fulminant NEC and may indicate widespread, severe gastrointestinal insult.
Home oxygen therapy after preterm birth in Western Australia.
OBJECTIVES: To review our management of infants discharged home receiving supplemental oxygen. Stable preterm infants receive low flow O(2) by nasal cannulae aiming for SaO(2) of > or = 95%. Oxygen-dependent infants must pass an air test (ability to maintain SaO(2) > 80% during 4 h disconnection from oxygen) before discharge home with supplemental oxygen. A sleep study is performed before nocturnal O(2) is ceased. METHODS: Infants less than 33 weeks gestational age (GA) who were admitted January 1999-June 2001 and discharged home with supplemental oxygen were identified through the databases and medical records of the King Edward Memorial/Princess Margaret Hospitals. The data collected were compared with an audit performed a decade earlier. RESULTS: Ninety-three infants were discharged home with supplemental oxygen between 1999 and 2001 (10% neonatal intensive care unit admissions less than 33 weeks GA; median GA 26 weeks (interquartile range 25-28). All infants had an air test before discharge: 63% failed the first air test and 30% at least two air tests. The median delay between the first air test and discharge was 2 weeks. The median postmenstrual age at discharge was 40 weeks gestation (interquartile range 38-41). Ninety infants had a sleep study before nocturnal oxygen was ceased and nine failed the first sleep study. Hospital readmission rate was 60%. More preterm infants (less than 33 weeks) were discharged with supplemental oxygen in 1999-2001 (10%, n = 96 in 1999-2001) than in 1987-1992 (2.5%, n = 53) and this was associated with an earlier discharge (40 vs 44 weeks postmenstrual age), lower oxygen requirements at discharge (60 vs 125 mL/min), earlier discontinuation of daytime and nocturnal oxygen (1 vs 4 months postmenstrual age and 2.5 vs 6 months postmenstrual age) and no increase in readmission rate (64% vs 60%). The incidence of bronchopulmonary dysplasia for these infants has remained stable at 20%. CONCLUSION: Our home oxygen programme, based on an air test predischarge and a sleep study prediscontinuation of nocturnal oxygen, facilitates early discharge home. Our data suggest that over the last decade, bronchopulmonary dysplasia is associated with less impairment in lung function. Further evidence from randomized clinical trials is required to determine optimal target range for oxygen saturation in preterm infants.