Strana 1 od 64 výsledky
Two 4-nitrobenzyl derivatives, 2-fluoroethyl 4-nitrobenzyl carbonate 1 and 4-nitrobenzyl N-2-fluoroethyl carbamate 2, were radiolabeled with (18)F and evaluated for imaging tumor hypoxia with positron emission tomography. Although good tumor uptake was observed for [(18)F]1 and [(18)F]2 (>2.5%ID/g
Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ238U values of marine limestones as a
Explaining the ~5-million-year delay in marine biotic recovery following the latest Permian mass extinction, the largest biotic crisis of the Phanerozoic, is a fundamental challenge for both geological and biological sciences. Ocean redox perturbations may have played a critical role in this delayed
The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ34S data from sections spanning the Late Triassic-Early Jurassic transition, which document synchronous large positive excursions on a global
Late Permian reefs of the Capitan complex, west Texas; the Magnesian Limestone, England; Chuenmuping reef, south China; and elsewhere contain anomalously large volumes of aragonite and calcite marine cements and sea-floor crusts, as well as abundant microbial precipitates. These components strongly
We present a framework for interpreting the carbon isotopic composition of sedimentary rocks, which in turn requires a fundamental reinterpretation of the carbon cycle and redox budgets over Earth's history. We propose that authigenic carbonate, produced in sediment pore fluids during early
Naked carp (Gymnocypris przewalskii), endemic to the saline-alkaline Lake Qinghai, have the capacity to tolerate combined hypoxia and high alkalinity. This study evaluated the effect of the interaction between carbonate alkalinity and hypoxia on ammonia excretion and blood gas variation in naked
The terminal Ediacaran Period witnessed the decline of the Ediacara biota (which may have included many stem-group animals). To test whether oceanic anoxia might have played a role in this evolutionary event, we measured U isotope compositions (δ238U) in sedimentary carbonates from the Dengying
BACKGROUND
Dacryoconarids are extinct marine zooplankton known from abundant, globally distributed calcite microfossils in the Devonian, but their shell stable isotope composition has not been previously explored. Devonian stable isotope stratigraphy is currently limited to less common invertebrates
Understanding how rising temperatures, ocean acidification, and hypoxia affect the performance of coastal fishes is essential to predicting species-specific responses to climate change. Although a population's habitat influences physiological performance, little work has explicitly examined the
The effects of various levels of hypoxia (PWO2 ranging from 10 to 60 Torr) on arterial blood gases (PaO2 and PaCO2) and acid-base status were investigated in trout at 15 degrees C. The hypoxic responses of two stocks of trout living in natural waters having very different levels of NaCl (1.0
To examine factors determining the haemodynamic and metabolic responses to treatment of diabetic ketoacidosis with alkali, groups of anaesthetised and ventilated rats with either diabetic ketoacidosis (mean arterial pH 6.86-6.96, mean arterial blood pressure 63-67 mm Hg) or hypovolaemic shock due to
Dimethyl carbonate (DMC) is a widely used industrial chemical, which may be increasingly used in the future. However, its toxicity profile remains largely unknown. The present study was designed to investigate the effects of DMC exposure on the ovaries and the effect of autophagy activation on
Lactate concentrations were measured in the shell and plasma of the turtle Chrysemys picta bellii after 3 months of submergence anoxia at 3°C and during and after 9 days of submergence anoxia at 10°C. Liver and skeletal muscle lactate levels were also measured in control and anoxic animals
Freshwater turtles as a group are more resistant to anoxia than other vertebrates, but some species, such as painted turtles, for reasons not fully understood, can remain anoxic at winter temperatures far longer than others. Because buffering of lactic acid by the shell of the painted turtle is