Studies in the Biology of Metals

Abstract

Our study of the effect of the lead ion on the development of the chick embryo has brought out the following facts: 1. Gross growth is retarded. 2. Somite growth is retarded to a degree greater than that exhibited by body length and width. 3. The head and optic anlagen are regions of particular sensitivity. Their differential development is markedly inhibited. From the purely biological point of view these results are in line with the findings of Child (10) and his school as to the sensitivity of the head end of rapidly growing organisms to harmful influences, and with those of Stockard (11) as to the peculiar sensitivity of the optic anlagen. It is almost too well known to need repetition that the head region and the somites of embryos are specific areas of intense growth by increase in cell number. Therefore, turning from the general to the particular, the differential retardation of these regions which is caused by lead, is evidence justifying the conclusion that it is areas of rapid growth by cell proliferation which are selectively inhibited by this metallic ion.

Effects of lead exposure on pregnancy outcome and the fetal brain of squirrel monkeys.

“…However, it has recently been produced by the intraperitoneal administration of lead to guinea pigs (I I). Indications of brain-growth retardation were also found in a study on chickens (17) and, indirectly, in the often reported general fetal growth retardation (= fetal or neonatal body weight reduction) following lead exposure. The reduction of the head circumference of the surviving offspring in the present study was not statistically significant, but it corresponded well with the magnitude of the prenatal maternal mean PbB values.…”

“…Low mean hemoglobin values were noted for three of the pregnant monkeys (table 3, monkeys 4, 9 and II). Coulter counting on pregnancies 9-12, at about [14][15][16][17] weeks of pregnancy, showed the erythrocytes to be normocytic and normochromic, while the hematocrit in pregnancies 9 and 11 was decreased, compared to that of the controls (table 2). However, the low hemoglobin levelsfor monkeys 4,9 and 11 rose to normal (143-144 gil) four, one, and one week, respectively, after the end of pregnancy/exposure.…”

“…The mean head circumference, at a postnatal age of 14 weeks, for the five surviving lead-exposed offspring was 15.8 (range [15][16][17] em, compared to 16.8 (range [16][17][18] cm (N = 10) for a group of offspring born over the same period of time in the unexposed control group. This reduction was not statistically significant.…”

Principles of geochemical prospecting

“…Some ions are freely admitted and others are impeded to a greater or lesser degree, an effect that is apparently due largely to the pH of the cell sap within the root tip. Lead, for example, is an element that is apparently largely immobilized by precipitation in the cell walls and nuclei of the roots of some plants (Hammett, 1928). Thus, toxic excesses of lead may not reach the active centers of growth in the upper parts of the plant.…”