Evidence for dietary essentiality of lithium in the rat.

The purpose of this study was to determine the dietary essentiality of lithium (Li) in rats. In three experiments, two types of diets were fed during growth, reproduction, and lactation. In the first experiment, dams were maintained on a corn-based diet containing 2 ng or 500 ng (controls) Li/g through five successive periods of pregnancy and lactation. The offspring of dams fed the low-Li diet had significantly lower weaning weights (p = 0.011), and the percent weaned was lower (p = 0.094) than that of controls. In the second experiment, rats were maintained through three generations on a rice-based diet containing 0.6 ng Li/g, or the control (500 ng/g) diet. There was a significant effect of Li level on litter size (p = 0.017) and litter wt at birth (p = 0.006) in the third generation. The overall effect through three generations on litter wt at birth approaches statistical significance (p = 0.086). In the third experiment, third-generation rats were continued on the respective rice-based diets with three levels of dietary sodium, the normal level, one-half, and four times that level. The litter size and birth wt were significantly lower (p = 0.0030 and 0.0038, respectively) among the low-Li dams that consumed the normal and high-sodium levels compared to those that consumed the low-sodium diets. The interaction of Li and sodium as regards litter wt at birth approached significance (p = 0.083). Various tissues of the rats in the third experiment were analyzed for Li. It seems likely that Li exerts an essential nutrient role for the rat.

The design of cost-effective air quality monitoring networks.

A statistical measure of information content is used as a means for assessing the effectiveness of a particular monitoring network configuration. This measure is directly related to the precision with which the network can estimate the level of air quality in the region. Each potential site in the network can contribute to an increase in the overall precision of the estimate. The amount of increase is determined by the degree of dependence, displayed by observed pollutant concentrations, between potential sites.A statistical procedure is used to combine the observed pollution dynamics and the measurement network in order to assess network effectiveness. An iterative application of this procedure leads to the design of the most effective network subject to a specified budget constraint.

Mineral analysis of ancient Peruvian hair.

Ancient Peruvian hair has been excavated from a series of archaeological sites on the Peruvian coast. After careful cleaning, examination by scanning electron microscopy revealed most of the samples to be in a state of preservation comparable to modern hair. No evidence of pathological conditions was observed. Trace metal composition was determined by atomic absorption and flame emission spectrophotometry and nitrogen by Kjeldahl analysis, producing the following results: (1) nitrogen is lost with time, while all other tested minerals except zinc and copper showed irregular increases; (2) relatively high chromium levels may indicate that diabetes was not present in the samples; and (3) no consistent trend in the ratio of calcium to strontium was found through time and across corresponding dietary shifts.