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J J Chisolm

Publications and source records attributed to J J Chisolm.

At least 55 records · Page 3Linked to original sources
PubMed1977

Is lead poisoning still a problem?

Today, health professionals are concerned about whether asymptomatic or mildly symptomatic increases in lead absorption in preschool children is one of the important factors causing minimal brain dysfunction, which only becomes evident later during the school years. This concern arises, in part, because current screening data show that 5 to 10% of the children tested recently in the United States have a degree of increase in lead absorption sufficient to cause metabolic derangement in heme synthesis, but insufficient, with rare exception, to cause classical acute clinical symptoms of plumbism. These screening data are disturbing because similar increases in lead absorption in suckling (but not older) experimental animals have been shown in some studies to be followed by the delayed appearance of subtle deficits in learning ability and aberrations in behavior. Derangement of hemoglobin synthesis is the first adverse effect of increased lead absorption now detectable. Intervention on the basis of the first or critical effect of a toxic agent before more serious effects occur has advantages from the viewpoint of preventive medicine. Current CDC guidelines for prevention of childhood lead poisoning are based on this concept and recommend the use of micro-scale erythrocyte protoporphyrin tests in conjunction with micro blood lead tests for early detection of children with disturbed heme synthesis caused by lead.

Aminolevulinic Acid↗
PubMed1976

Lead poisoning: altered urinary catecholamine metabolites as indicators of intoxication in mice and children.

Whether neuropsychological impairment occurs in children with increased lead absorption who are without clinical symptoms is of current concern. This tissue, which involves potentially large numbers of children, remains unresolved, in part because of the lack of sensitive biochemical indicators of the effects of lead on the nervous system. In experimental subclinical lead poisoning in mice, significant increases in homovanillic acid and vanillylmandelic acid have been found in brain and urine. In children with increased lead absorption, these acids were meaured in urine collected quantitatively under controlled dietary conditions; preliminary results show fivefold increases in the daily output of these compounds. These data suggest that the altered catecholamine metabolism also occurs in children.

Animals↗
PubMed1975

Dose-effect and dose-response relationships for lead in children.

Lead absorption and prevention of the serious effects of lead re-examined from the viewpoints of the critical organ and clinical effect concepts and the associated dose-effect and dose-response relationships. If the critical organ is the first affected and the critical effect is the first measurable adverse effect, intervention on this basis should prevent the occurrence of later, more serious effects. In the range of lead absorption of greatest current pediatric concern (blood lead in the range of 50 to 80 mug/dl), blood lead values are not a good predictor of critical effect, whereas chelatable lead is significantly and linearly related to evidence of critical effect on hemoglobin synthesis in the bone marrow. Erythrocyte protoporphyrin and delta-aminolevulinic acid and coproporphyrin in urine are indicators of this effect. The dose-response concept provides a better way of viewing the relationship between blood lead and measures of adverse effect than do the classifications of "sensitivity," "specificity", "false negatives," and "false positives," which are often employed in the evaluation of screening tests. The dose-response concept recognizes the uniqueness of the individual and the presence of susceptible and resistant individuals in heterogeneous population groups. With the dose-response concept, individuals may be identified as reactors or nonreactors, according to whether they exhibit a particular effect. Among the various indicators of lead's critical (or first) effect on hemoglobin synthesis, erythrocyte protoporphyrin potentially is the most practical for monitoring children at high risk for plumbism.

Adolescent↗
PubMed1975

Indicators of internal dose of lead in relation to derangement in heme synthesis.

Simultaneous measurements of Pb-B, Pb-U, chelatable lead, ALA-U and EP have been made in a group a asymptomatic children with increased lead absorption. Although the group is small, the results are internally consistent and show linear dose-effect relationships between Pb-U and chelatable lead (indicators of dose) and ALA-U and EP (indicators of lead's effect on heme synthesis). The data show, however, that Pb-B in a rather narrow range (48-68 mug Pb) is not a reliable indicator of the internal dose of lead. These results, as well as others, raise questions concerning the validity of relying exclusively on Pb-B in the clinical management of groups such as young children in old houses and lead-exposed workmen who are at increased risk for plumbism; The results suggest that chelatable lead is most closely related to lead's inhibitory effect on heme synthesis and that, biologically, it may serve as the best "chemical biopsy" of soft tissue lead concentration; A simple AAS method for measureing chelatable lead in urine is described; A new wet digestion technique which is compatible with ASV is also described. EP is apparently a better predictor of chelatable lead than Pb-B. Micro tests for EP, especially the zinc protoporphyrin fraction, are simple and highly useful in monitoring long-term trends in soft tissue levels in individual patients.

Aminolevulinic Acid↗
PubMed1974

Variations in hematologic responses to increased lead absorption in young children.

In the study of human populations, much emphasis is placed on the concentration of lead in whole peripheral blood. There is a considerable body of evidence which indicates that this measurement reflects recent and current assimilation of lead. While broad ranges in blood lead concentration have been associated with differing risks of toxicity for groups, it is not a precise index of adverse effect per se, even at elevated levels. Within the red blood cell itself there is not a close association between the concentration of lead and such adverse metabolic effects as the increased loss of potassium caused by lead. Above the apparent "threshold zone" of approximately 30-50 mug Pb/100 ml whole blood, equivalent metabolic effects on heme synthesis may be seen over an interval of at least 20 mug Pb/100 ml whole blood. This variation will be examined with particular reference to the interrelationship between the concentrations of lead and protoporphyrin in peripheral blood. The data indicate that limitations in both precision and accuracy of measurement account for a relatively small fraction of the observed variations. Together with other experimental and clinical information, they suggest that concurrent dietary deficiency of iron may be one of the important modifying factors in the responses of subjects with increased lead absorption. It is suggested that suspected adverse effects upon the various organ systems associated with increased lead absorption be measured directly and that the CaEDTA mobilization test for lead should be more fully explored as a measure of the "metabolically active" fraction of the total body lead burden.

Child, Preschool↗
PubMed1971

Lead poisoning.

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Child↗