Histologic findings in free-ranging Sarasota Bay bottlenose dolphin (Tursiops truncatus) skin: mercury, selenium, and seasonal factors.

Full-thickness epidermal biopsy samples were collected from free-ranging common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida, USA. Season (summer or winter) of collection, mercury (Hg) concentration, and selenium (Se) concentration were compared to histologic parameters. Epidermal Hg concentration was positively related to age (P<0.001) and negatively related to height of the stratum spinosum (P<0.05). The mitotic index and heights of the stratum externum and intermedium were lower in summer than in winter (P<0.01). Transmission electron microscopic examination revealed variation in the diameters (60-138 nm) and arrangements of collagen fibers, regardless of age or concentrations of Hg and Se. The significance of the variation in height of the stratum spinosum and the perivascular collagen degeneration to dolphin health need further investigation.

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 (d(13)C and d(15)N), 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 d(15)N, 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.

Essential and non-essential elements in eight tissue types from subsistence-hunted bowhead whale: nutritional and toxicological assessment.

OBJECTIVES: To assess essential/non-essential elements in bowhead whale. STUDY DESIGN: Analyzes of tissues for key elements and comparing them to published food guidelines. METHODS: Using national and international guidelines calculate percent (%) "Recommended Daily Allowance" of essential elements in 100 g portion of bowhead tissues. For non-essential elements, determine maximal tissue consumption based on average element concentrations and provisional tolerable weekly intake; and minimal risk level. RESULTS: Liver and kidney are rich in essential/non-essential elements and have the greatest concentration of cadmium (Cd) among tissues studied, while mercury (Hg), lead (Pb) and arsenic (As) are relatively low. Kidney of bowhead whale is consumed in very limited amounts (limited tissue mass compared to muscle and maktak); liver is consumed rarely. Other tissues, except blubber, are excellent sources of many essential elements, without the abundance of liver and kidney Cd. CONCLUSIONS: Renal Cd concentrations are most restrictive for consumption on a tissue mass basis. Better understanding of Cd bioavailability, food processing, and actual consumption rates and patterns, are critical to providing improved guidance. Compared to store-bought meat, bowhead whale had comparable concentrations of elements in the tissues studied, with a few noted differences. The occasional blubber substitute, Crisco, was nearly devoid of trace element content.

Role of mitochondrial DNA in toxic responses to oxidative stress.

Mitochondria are at the crossroads of several crucial cellular activities including: adenosine triphosphate (ATP) generation via oxidative phosphorylation; the biosynthesis of heme, pyrimidines and steroids; calcium and iron homeostasis and programmed cell death (apoptosis). Mitochondria also produce considerable quantities of superoxide and hydrogen peroxide (H2O2) that in conjunction with its large iron stores can lead to a witch's brew of reactive intermediates capable of damaging macromolecules. Mitochondrial DNA (mtDNA) represents a critical target for such oxidative damage. Once damaged, mtDNA can amplify oxidative stress by decreased expression of critical proteins important for electron transport leading to a vicious cycle of reactive oxygen species (ROS) and organellar dysregulation that eventually trigger apoptosis. Oxidative stress is associated with many human disorders including: cancer, cardiovascular disease, diabetes mellitus, liver disease and neurodegenerative disease. This article reviews the evidence that oxidative damage to mtDNA can culminate in cell death and thus represents an important target for therapeutic intervention in a number of human diseases.

Circumpolar pattern of mercury and cadmium in ringed seals.

Mercury (Hg) and cadmium (Cd) concentrations in ringed seal liver and kidney were compared from 11 locations across the Arctic, from Alaska, Canada, Greenland, Svalbard to the White Sea. Adult and sub adult seals were evaluated separately to account for age accumulations of Hg and Cd. Only recently (1995-2001) collected samples were included to minimize influence of changes over time. The Hg and Cd concentrations in ringed seal liver and kidney differed significantly among the studied locations. The Hg concentrations in liver of ringed seals was highest in the western Canadian Arctic locations, while Cd in liver was highest in the eastern Canadian and West Greenland locations. In general, Hg and Cd concentrations in liver and kidney were significantly higher in adult ringed seals than in sub adults and the circumpolar patterns were most pronounced in adult ringed seals. The Hg and Cd concentrations in kidney of ringed seals in general supported the geographical pattern found in livers although the coverage was more limited. The most likely explanation for the observed circumpolar pattern appears mainly to be related to natural geological differences in mineral (Hg and Cd) among regions.

Distribution of inorganic mercury in liver and kidney of beluga and bowhead whales through autometallographic development of light microscopic tissue sections.

Inorganic mercury was localized through autometallography (AMG) in kidney and liver of free-ranging, subsistence-harvested beluga (Delphinapterus leucus: n = 20) and bowhead (Balaena mysticetrus: n = 5) whales. AMG granules were not evident in bowhead tissues, confirming nominal mercury (Hg) concentrations (range = 0.011 to 0.038 microg/g ww for total Hg). In belugas, total Hg ranged from 0.30 to 17.11 and from 0.33 to 82.47 microg/g ww in liver and kidney, respectively. AMG granules were restricted to cortical tubular epithelial cytoplasm in belugas with lower tissue burdens; whales with higher tissue burdens had granules throughout the uriniferous tubular epithelium. In liver, AMG granular densities differed between lobular zones, concentrating in stellate macrophages and bile cannalicular domains of hepatocytes. AMG granules aggregated in periportal regions in belugas with lower hepatic Hg concentrations, yet among whales with higher Hg, AMG granule deposition extended to pericentral and midzonal regions of liver lobules. Mean areas occupied by AMG granules correlated well with hepatic Hg concentrations and age. In beluga livers, AMG staining density was not associated with lipofuscin quantity (an index of oxidative damage). Occasionally, AMG granules and lipofuscin were colocalized, but more often were not, implying that Hg was not a prominent factor in hepatic lipofuscin deposition in belugas.