The development of functional digestive and metabolic organs in turbot,Scophthalmus maximus

The functional status of organ systems involved into the processing of exogenous food is critical for the survival and growth of fish early life stages. The present study on laboratory-reared larval turbot, Scophthalmus maximus, provides an overview on the ontogeny of structure and functions involved in digestion, absorption and metabolism of nutrients. At start of exogenous feeding the intestine of larval turbot is anatomically differentiated, with enterocytes displaying an adult-type ultrastructure and being able to process lipids. At the microvillous border of the enterocytes, enzymes of contact digestion such as aminopeptidase are found. The ultrastructure of the exocrine pancreatic cells is fully differentiated from hatching onwards. Likewise, substantial activities of trypsin-type proteases are present. A stomach anlage exists in first-feeding larvae; however, the stomach becomes functional (appearance of gastric glands and pepsin secretion) only during metamorphosis. Liver parenchymal cells already display a functional ultrastructure during the endotrophic phase; with onset of exogenous feeding they develop pronounced diet-related changes of their energy stores. Larval respiration is not executed by the gills since respiratory surface of these structures develops only towards metamorphosis. The energy generation of larval muscle tissue depends on aerobic metabolism, whereas glycolytic activities start to increase at metamorphosis. In conclusion, two important patterns can be recognized in the development of turbot larvae: (1) The structure/function is differentiated at hatching or at the onset of exogenous feeding (afterwards it experiences mainly quantitative but not qualitative growth, i.e., intestine, exocrine pancreas, liver); or (2) the structure/function is absent in larvae and develops only during metamorphosis (i.e., gills, glycolytic muscle metabolism, stomach).     

Influence of platinum, palladium and rhodium as compared with cadmium, nickel and chromium on cell viability and oxidative stress in human bronchial epithelial cells

The platinum group elements (PGE) Pt, Pd and Rh are increasingly emitted into the environment by automobile catalytic converters. Whereas the biological availability of PGE to plants and animals has been demonstrated, only few studies concentrate on the influence of PGE on a cellular level. The effects of Pt, Pd and Rh compared with Cd, Ni and Cr on cell viability and oxidative stress response using soluble metal salts were studied in the human bronchial epithelial cell line BEAS-2B. Whilst Rh(III) showed little influence, both Pt(II) and Pt(IV) as well as Pd(II) had significant effects on cell viability at levels comparable to Cd(II) and Cr(VI). Arranging metal species in order of increasing toxicity as determined by LC50 yields: Rh(III)=1.2 mmol/L相似文献   

Klimaänderung—Was weiß die Wissenschaft?

In the Intergovernmental Panel for Climate Change (IPCC), scientists worldwide are working on a holistic view of climate development. This accommodates highly complex interactions between natural occurrences, their effects and human activity as far as possible. Uncertainties are expressed in terms of confidence levels. The Third Assessment Report presents the following cases: Human activities have generally increased the atmospheric concentrations of green-house gases and their radiative forcings during the 20^th century. The resulting radiative forcing is positive (warming) with a small uncertainty range; that from the direct aerosol effects is negative (cooling) and smaller; whereas the negative forcing from the indirect effects of aerosols (clouds and water cycle) might be large but is not well quantified. An increasing body of observations gives a collective picture of a warming earth and other changes in the climate system. Observed changes in regional climate during the past 50 years have affected biological and hydrological systems in many parts of the world. There are preliminary indications that social and economic systems have also been affected. Local, regional and global environmental problems are often interlinked in ways that, in total, affect the sustainable satisfaction of human needs. The Projections of all SRES scenarios show an increase of the globally averaged surface temperature within the 21^st century at a rate which is very likely to be without precedent during at least the last 10,000 years, based on paleoclimate data. Adaptation is a necessary strategy at all scales to complement climate change mitigation efforts. Together they can contribute to sustainable development objectives.