965 resultados para Christian converts from Judaism.
Resumo:
The limited knowledge and/or the inability to control physiological condition parameters that influence the fate of organohalogen contaminants (OHCs) has been the foremost confounding aspect in monitoring programs and health risk assessments of wild top predators in the Arctic such as the polar bear (Ursus maritimus). In the present comparative study, we used a potential surrogate Canoidea species for the East Greenland polar bear, the captive sledge dog (Canis familiaris), to investigate some factors that may influence the bioaccumulation and biotransformation of major chlorinated and brominated OHCs in adipose tissue and blood (plasma) of control (fed commercial pork fat) and exposed (fed West Greenland minke whale (Balaenoptera acutorostrata) blubber) adult female sledge dogs. Furthermore, we compared the patterns and concentrations of OHCs and their known or suggested hydroxylated (OH) metabolites (e.g., OH-PCBs) in sledge dogs with those in adipose tissue and blood (plasma) of East Greenland adult female polar bears, and blubber of their main prey species, the ringed seal (Pusa hispida). The two-year feeding regime conducted with sledge dogs led to marked differences in overall adipose tissue (and plasma) OHC residue accumulation between the control and exposed groups. Characteristic prey-to-predator OHC bioaccumulation dynamics for major PCB and PBDE congeners (patterns and concentrations) and biotransformation capacity with respect to PCB metabolite formation and OH-PCB retention distinguished, to some extent, captive sledge dogs and wild polar bears. Based on the present findings, we conclude that the use of surrogate species in toxicological investigations for species in the Canoidea family should be done with great caution, although they remain essential in the context of contaminants research with sensitive arctic top carnivore species such as the polar bear.
Resumo:
The enhanced accumulation of organic matter in Eastern Mediterranean sapropels and their unusually low d15N values have been attributed to either enhanced nutrient availability which led to elevated primary production and carbon sequestration or to enhanced organic matter preservation under anoxic conditions. In order to evaluate these two hypothesis we have determined Ba/Al ratios, amino acid composition, N and organic C concentrations and d15N in sinking particles, surface sediments, eight spatially distributed core records of the youngest sapropel S1 (10-6 ka) and older sapropels (S5, S6) from two locations. These data suggest that (i) temporal and spatial variations in d15N of sedimentary N are driven by different degrees of diagenesis at different sites rather than by changes in N-sources or primary productivity and (ii) present day TOC export production would suffice to create a sapropel like S1 under conditions of deep-water anoxia. This implies that both enhanced TOC accumulation and d15N depletion in sapropels were due to the absence of oxygen in deep waters. Thus preservation plays a major role for the accumulation of organic-rich sediments casting doubt on the need of enhanced primary production for sapropel formation.