Biomonitoring lead exposure with δ-aminolevulinate dehydratase (ALA-D) activity ratios

Summary The occupational or environmental exposure of selected populations to lead, either alone or in combination with other metals, was monitored using ratios of the activity of the erythrocytic enzyme -aminolevulinate dehydratase. The results obtained have reaffirmed earlier findings that this test affords several significant advantages over the use of the enzyme's activity value measured at a set pH value and other types of activity ratios to assess lead exposure. Furthermore, the activity ratios' proven sensitivity, reliability, reproducibility, specificity and stability warrant that they be considered as viable alternatives to the more widely accepted diagnostic criteria of lead intoxication namely zinc protoporphyrin and lead levels in blood.     

Effects of lead,copper, and zinc on the rat's lactate dehydrogenase in vivo and in vitro

Following subacute intoxication of rats with Pb-, Cu-, and Zn-salts (separately or in mixture) for 5 weeks, the chelating agent D-penicillamine was administered for 3 weeks. In the course of the 3-month experiment, lactate dehydrogenase (LDH) was estimated in serum and in cytoplasmic fraction of the kidney. Pb²⁺ treatment resulted in an increase of LDH activity, Cu²⁺ in a slight decrease, whereas Zn²⁺ had no effect, respectively. Mixture of these metals caused a significant rise in the enzymatic activity. Seven weeks after the stoppage of the administration of toxic substances, altered LDH activity, both in serum and in kidney returned to normal. D-penicillamine treatment was found to accelerate a restoration of the enzyme activity.In the experiments in vitro, Cu²⁺ inhibited significantly the kidney LDH activity, Pb²⁺ and Zn²⁺ being 100- and 400-times less efficient, respectively. Cu²⁺ inhibition was reversed by D-penicillamine, whereas inhibition of LDH by Zn²⁺ or Pb²⁺ was irreversible.     

Motor nerve conduction velocity in asymptomatic lead workers

Summary No difference was found between the nerve conduction velocities of the ulnar nerve of 32 lead exposed workers in the mill of a lead-zinc mine, compared to that of a control group of 14 persons. The lead exposure period was 2–37 months (mean: 12.9 months).The blood lead of the exposed group was as an average (± SD): 53 ± 16 g per 100 ml compared to 11 ± 4 g per 100 ml for the control group.Further studies are needed to establish a possible dose-time-response relationship for the possible, subclinical neuropathy found by some investigators.     

Reversal learning deficits in young monkeys exposed to lead.

The reversal learning capacity of young rhesus monkeys in visual discrimination tasks was examined during daily exposure to dietary lead acetate throughout the first year of life. While not affected in physical development, all lead-treated monkeys showed performance deficits on reversal learning tasks. These deficits were independent of lead-induced changes in motivation. Over a series of problems, the overall learning rate of monkeys with blood lead concentrations in the range of 70-90 microgram/dl was retarded, which resulted partly from a pronounced difficulty in attaining criterion on the first of a series of reversals within a given problem. This latter deficit resulted from an increase in errors, balks, and total trials to criterion on the first reversal. Monkeys exposed to blood lead concentrations of 40-60 microgram/dl required significantly more trials to finish all problems, but did not show the first-reversal deficit. Theoretical implications of these data were discussed.     

清远地区孕妇及其新生儿血铅含量分析

目的了解清远市孕妇及其新生儿血铅水平的现状与相关因素。方法选取1364对孕妇及其新生儿静脉血采用BH2100型原子吸收光谱法进行血铅含量的测定并对铅中毒的相关因素的调查。结果孕妇血铅中毒率26％，中位教76.8μg／L，新生儿中毒率27．5％，中位数80．6μg／L，孕妇血铅与新生儿铅含量正相关性(P＜0．05)调查表66.7％的铅中毒孕妇有相关因素。结论孕妇血铅含量高低与其新生的血铅值呈正相关且由于胎儿期生长发育需求，铅高于母亲。     

新生儿脐血铅含量与神经行为发育的关系

目的 :探讨孕期低水平铅暴露下 ,脐血血铅含量对新生儿神经行为发育的影响。方法 :随机选择 2 0 0 3年 1～4月出生足月新生儿 135例。以脐血铅作为孕期铅暴露的指标 ,新生儿神经行为发育 (NBNA)评分作为效应指标 ,采用描述性分析方法评价二者之间的相关性。结果 :高暴露组和低暴露组在新生儿主动肌张力、神经行为发育总评分上差异有显著性 (P<0 .0 5 ) ,原始反射评分差异有非常显著性 (P<0 .10 ) ,在新生儿行为能力、被动肌张力、一般估价上差异无显著性。结论 :孕期低水平铅暴露对新生儿神经行为发育影响明显。     

儿童铅暴露相关危险因素Logistic逐步回归分析

目的:了解珠江三角洲中心地区儿童铅暴露水平及相关因素。方法:对1 866例1-3岁入托体检儿童进行静脉血铅、锌、钙、铁、铜、锰测定,并做铅暴露危险因素问卷调查。结果:儿童血铅水平均数为116.72 μg／L,≥100 μg／L者占48.77％,年龄、喜饮罐装饮料、母亲职业、居住的楼龄及楼层、居住环境是儿童铅暴露的危险因素,血锌是保护因素。结论:环境铅污染是儿童铅暴露的主要来源,环境污染对儿童已构成严重的威胁,应引起社会的关注。     

铅对小鼠海马[Ca2+]的影响及L型钙通道的作用

目的　探讨铅对分离的小鼠海马细胞内游离钙的影响及其及L型钙通道的作用。方法　采用低浓度胰蛋白酶消化法分离小鼠海马细胞 ,并以莹光指标剂 (Fura 2 )作Ca2 荧光探针 ,用双波长荧光法测定海马细胞 [Ca2 ] i。结果　铅可致分离的小鼠海马细胞 [Ca2 ] i 升高 [由静息时的 (2 0 3 4± 10 86)nmol L升至 (4 2 3 3± 19 2 6)nmol L] ,而不论胞外是否有钙 ;铅可抑制钾诱发海马细胞 [Ca2 ] i 升高 ,尼莫地平可加强这种抑制作用 ,而BayK864 4则可部分消除这种抑制作用。结论　铅可致分离的小鼠海马细胞 [Ca2 ] i 升高作用与胞内钙库释放有关 ;铅的抑制钾诱发海马细胞 [Ca2 ] i 升高作用与其抑制L型钙通道有关。     

发育期铅染毒对大鼠学习和记忆的持续性效应

目的研究不同发育期铅染毒对大鼠学习和记忆的持续性效应。方法大鼠分别在断乳前和断乳后进行铅染毒，分别测试20、40和60天龄大鼠Y迷宫学习、短时记忆和长时记忆能力。结果(1)断乳前铅染毒组大鼠20天龄时，0、10min和24h逃避达标率显著低于对照组；停止染毒40d后，10min逃避达标率与对照组相比，差异无显著性；但0min和24h逃避达标率显著低于对照组。(2)断乳后，铅染毒组大鼠0min和24h逃避达标率显著低于对照组，24h逃避达标率显著高于断乳前铅染毒组。结论(1)断乳前铅染毒可损伤大鼠的空间学习、短时和长时记忆能力；停止染毒后短时记忆可得到恢复，而学习和长时记忆的损伤仍持续存在。(2)断乳后铅染毒可损伤大鼠的空间学习和长时记忆能力，但损伤较断乳前铅染毒轻。