Environmental lead exposure, maternal thyroid function, and childhood growth

Prenatal and early-life exposure to lead is hypothesized to have a range of adverse effects on childhood health. Drawing on data collected from a population-based prospective cohort study of a highly exposed town and a low exposed town in Kosovo, Yugoslavia we assessed whether elevated maternal blood lead (BPb) concentrations during pregnancy were associated with reduced childhood measures of attained height and BMI or growth rate, and whether the associations, if any, were mediated by maternal thyroid hormone concentration at mid-pregnancy. There was no association between blood lead levels and height or BMI in either town. However, increased maternal thyroid hormone was unexpectedly associated with reduced attained childhood height, and growth rate of height from 6.5 to 10 years, in the low-exposure town. We examine potential reasons for this unexpected inverse association.     

Comparison of dimercaptosuccinic acid and calcium disodium ethylenediaminetetraacetic acid versus dimercaptopropanol and ethylenediaminetetraacetic acid in children with lead poisoning

Objectives: To compare the response to dimercaptopropanol (BAL) and calcium disodium ethylenediaminetetraacetic acid (EDTA) versus orally administered meso-2,3-dimercaptosuccinic acid (DMSA) and EDTA in children with lead poisoning.Methods: Retrospective review of medical records of children admitted to MetroHealth Medical Center with a whole blood lead (BPb) concentration of 2.17 μmol/L (45 μg/dl) or more (or less than 2.17 μmol/L and not a candidate for outpatient oral chelation) and treated with BAL + EDTA or DMSA + EDTA. In each group, the mean BPb values at the end of therapy and at 14 and 33 days after chelation were compared with pretreatment BPb by the Wilcoxon signed-rank test, whereas the Mann-Whitney U test was used to compare percentage change from pretreatment at each follow-up day between the two groups.Results: Twenty-three children received BAL + EDTA and 22 received DMSA + EDTA.The BPb values (mean ± SD) at the end of therapy and at 14 and 33 days after chelation were significantly lower than pretreatment in both groups (BAL + EDTA: 17 ± 10, 34 ± 7, 36 ± 11 vs 58 ± 14 μg/dl, p <0.02, 0.01, 0.001, respectively; DMSA + EDTA: 10 ± 4, 30 ± 10, 30 ± 14 vs 50 ± 10 μg/dl, p <0.01, 0.001, 0.01, respectively). The percentage reduction (mean ± SD) in BPb from pretreatment at the end of therapy and on days 14 and 33 after chelation did not differ between the groups (BAL + EDTA: −71.2% ± 19.8%, −40.2% ± 13.8%, −37.1% ± 17%; DMSA + EDTA: −79.9% ± 8.7%, −38.3% ± 21.6%, −37% ± 32%; p >0.20). Elevation of alanine aminotransferase and vomiting during therapy were observed more frequently in the BAL + EDTA group compared with the DMSA + EDTA group.Conclusions: Treatment with DMSA or BAL combined with EDTA results in a comparable reduction in BPb. (J Ppediatr 1997;130:966-71)     

铅污染区儿童血铅与锌原卟啉、红细胞参数相关性研究

目的探讨铅污染区儿童血铅与锌原卟啉、红细胞参数相关性。方法对云南某县铅锌矿区和县城非铅锌矿区2～9岁儿童共464人进行血铅(BPb)水平、红细胞参数及锌原卟啉(ZPP)水平调查,按血铅水平分为高、低血铅组并进行血Pb与红细胞参数(RBC、HB、HCT、MCV、MCH、MCHC、RDW)及ZPP相关性分析。结果儿童血铅浓度均值154.4ugL,铅中毒率79.1%,ZPP均值2.7uggHb。血铅>250ugL时,血铅与红细胞参数具有相关性(RR:0.637)。高铅组血铅水平与RBC、ZPP有较强相关性(r分别为:-0.975、0.957)。RBC随血铅水平增高呈高度负相关,血铅水平<200ugL时,与ZPP无相关性。血铅水平达～250ugL、～300ugL、～350ugL时,血铅与ZPP具有较强相关性(r分别为:0.567、0.93、0.886)并呈高度正相关。结论随血铅水平的增高,RBC与血铅呈高度负相关,当血铅水平>250ugL时,血铅与ZPP具有高度正相关性,而当血铅水平<200ugL时,与ZPP相关关系不密切,因此ZPP不能作为铅中毒筛查指标。     

Gestational lead exposure selectively decreases retinal dopamine amacrine cells and dopamine content in adult mice

Gestational lead exposure (GLE) produces supernormal scotopic electroretinograms (ERG) in children, monkeys and rats, and a novel retinal phenotype characterized by an increased number of rod photoreceptors and bipolar cells in adult mice and rats. Since the loss of dopaminergic amacrine cells (DA ACs) in GLE monkeys and rats contributes to supernormal ERGs, the retinal DA system was analyzed in mice following GLE. C57BL/6 female mice were exposed to low (27 ppm), moderate (55 ppm) or high (109 ppm) lead throughout gestation and until postnatal day 10 (PN10). Blood [Pb] in control, low-, moderate- and high-dose GLE was ≤ 1, ≤ 10, ~ 25 and ~ 40 μg/dL, respectively, on PN10 and by PN30 all were ≤ 1 μg/dL. At PN60, confocal-stereology studies used vertical sections and wholemounts to characterize tyrosine hydroxylase (TH) expression and the number of DA and other ACs. GLE dose-dependently and selectively decreased the number of TH-immunoreactive (IR) DA ACs and their synaptic plexus without affecting GABAergic, glycinergic or cholinergic ACs. Immunoblots and confocal revealed dose-dependent decreases in retinal TH protein expression and content, although monoamine oxidase-A protein and gene expression were unchanged. High-pressure liquid chromatography showed that GLE dose-dependently decreased retinal DA content, its metabolites and DA utilization/release. The mechanism of DA selective vulnerability is unknown. However, a GLE-induced loss/dysfunction of DA ACs during development could increase the number of rods and bipolar cells since DA helps regulate neuronal proliferation, whereas during adulthood it could produce ERG supernormality as well as altered circadian rhythms, dark/light adaptation and spatial contrast sensitivity.     

Galton's midparent height revisited

Galton (Journal of the Anthropological Institute of Great Britain and Ireland, 15, 246-263, 1886) defined midparent height as the average of the two parental heights. An alternative is to average the parental heights after converting them to standard deviation scores (SDSs). The aim of the paper is to compare the two midparent height calculations, and to see if they explain the imputation procedure used by Galton to adjust for the difference in adult height between daughters and sons. He multiplied daughters' heights by 1.08 before averaging them with sons' heights. Using data from 17 national height references it is shown that this procedure is equivalent to averaging the height SDSs of the sons and daughters. It demonstrates that midparent height SDS obtained by averaging the height SDSs of the two parents is a valid alternative to conventional midparent height.