Mercury and Selenium in Blood and Epidermis of Bottlenose Dolphins (Tursiops truncatus) from Sarasota Bay, FL: Interaction and Relevance to Life History and Hematologic Parameters

Blood and epidermal biopsies from free-ranging Tursiops truncatus captured and released during either summer or winter health assessments in Sarasota Bay, FL, were evaluated for concentrations of mercury, selenium, stable isotopes (δ¹³C and δ¹⁵N), and blood glutathione peroxidase activity in conjunction with routine hematology and serum chemistry panels. Major objectives were to: 1) quantify and describe relationships among mercury, selenium, glutathione peroxidase, and stable isotopes of C and N in blood and epidermis; 2) elucidate major parameters that influence blood mercury and glutathione peroxidase activity; 3) relate measures of tissue mercury, selenium, and glutathione peroxidase to specific ecological, hematological, morphological, or life history parameters, including season, sex, age, and trophic level. Mercury in both tissues examined is almost exclusively methylmercury. Epidermal concentrations of mercury and selenium reflect their respective amounts in blood, albeit at several times blood concentrations of mercury. The strong association between blood mercury and serum selenium, in conjunction with a lack of significant correlation between blood mercury and glutathione peroxidase, implies that a substantial proportion of blood mercury is affiliated with another selenium-containing moiety or is related to recent dietary intakes (e.g., trophic level, intensive fish consumption). Circulating blood mercury may be described in terms of serum selenium concentration, along with interaction terms among serum selenium, blood δ¹⁵N, and age. Current selenium concentrations in Sarasota Bay dolphins appear adequate for maintenance of blood glutathione peroxidase activity. However, dolphins evidently are subject to seasonal exacerbation of oxidative stress, which might render them more vulnerable to toxic effects of mercury. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Bone remodeling rates and skeletal maturation in three archaeoloqical skeletal populations

Cortical bone remodeling rates for rib samples from three archaeological populations and a modern autopsy sample were determined using an algorithm developed by Frost. (Frost [1987a] Calcif. Tissue Res. 3:211–237). When plotted against the relative antiquities for population samples, histomorphometric variables; i.e., activation frequency (μ _rc, net bone formation (_netV_f,r,t), and mean annual bone formation rate (V_f,r,t), exhibit a concordant trend of increased cortical bone remodeling activity levels over time. Two intensive foraging populations, Windover and Gibson, are similar for all bone remodeling parameters and have the lowest remodeling activity levels among the samples. The more recent Ledders sample, which is reported to practice agricultural subsistence, is consistently intermediate between these and a modern autopsy sample. Although there appear to be differences in bone formation rates among the populations, it is concluded that these differences cannot be attributed to differences in bone remodeling rates among the populations, but rather are reflecting different effective ages of adult compacta for their ribs. These findings suggest that the earlier populations, particularly Windsor and Gibson, appear to have reached skeletal maturity at an older age than observed for modern. © 1995 Wiley-Liss, Inc.     

Archaeology and Human Evolution

Archaeology is the study of human behavior through material culture, the things we rely on for survival. Behavioral change was likely a driving factor in the evolution of our species, and archaeology therefore plays a central role in understanding human origins from the beginning of the known archaeological record some 2.5 million years ago. From its origins to subsequent diversification, the material record of human behavioral innovation provides an essential learning tool for understanding human behavioral diversity and also serves as a gateway to critical thinking in education.     

In vivo reversal of glutathione deficiency and susceptibility to in vivo dexamethasone-induced apoptosis by N-acetylcysteine and L-2-oxothiazolidine-4-carboxylic acid, but not ascorbic acid, in thymocytes from gamma-glutamyltranspeptidase-deficient knockout mice.

Cellular glutathione is released during apoptosis and may play a role in the regulation of the mitochondrial permeability transition pore. The question of whether only cytosolic glutathione is important in apoptosis, or whether mitochondrial glutathione also plays a role, was investigated using gamma-glutamyltranspeptidase-deficient knockout mice. Thymocytes from these mice were found to have both glutathione pools diminished and they were more susceptible to dexamethasone (DEX)-induced apoptosis. Supplementation with N-acetylcysteine (NAC) and L-2-oxothiazolidine-4-carboxylic acid replenished both glutathione pools and provided protection from apoptosis. Ascorbate supplementation was beneficial to the mitochondrial glutathione pool, but apoptosis was not prevented. NAC supplementation caused an increase in reactive oxygen species formation and cardiolipin oxidation, but had no adverse affect on the amount of apoptotic cells. Our results suggest that the glutathione status is an important factor in apoptosis and indirect evidence indicates that the cytosolic pool of glutathione may be important in DEX-induced apoptosis, with mitochondrial events being secondary, and may reflect the execution phase.     

Comparing the Powers of the Wald-Wolfowitz and Kolmogorov-Smirnov Tests

The Wald-Wolfowitz test and the Kolmogorov-Smirnov test are two well-known tests which can be used to test for differences between two population distributions, where these distributions could differ in means, variances or shapes. This paper compares the simulated power of the Wald-Wolfowitz test to that of the Kolmogorov-Smirnov test in several situations. Differences in location only, differences in variance only, and differences in both location and variance are considered. In most cases, equal sample sizes of 10 and 20 are used.