Renal oxygenation during the early stages of adenine-induced chronic kidney disease

To assess whether renal hypoxia is an early event in adenine-induced chronic kidney disease, adenine (100 mg) or its vehicle was administered to male Sprague-Dawley rats by daily oral gavage for 7 days. Kidney oxygenation was assessed by 1) blood oximetry and Clark electrode in thiobutabarbital-anesthetized rats, 2) radiotelemetry in unanesthetized rats, and 3) expression of hypoxia-inducible factor (HIF)-1α and HIF-2α protein. After 7 days of treatment, under anesthesia, renal O2 delivery was 51% less, whereas renal O2 consumption was 65% less, in adenine-treated rats than in vehicle-treated rats. Tissue Po2 measured by Clark electrode was similar in the renal cortex but 44% less in the medulla of adenine-treated rats than in that of vehicle-treated rats. In contrast, in unanesthetized rats, both cortical and medullary tissue Po2 measured by radiotelemetry remained stable across 7 days of adenine treatment. Notably, anesthesia and laparotomy led to greater reductions in medullary tissue Po2 measured by radiotelemetry in rats treated with adenine (37%) than in vehicle-treated rats (16%), possibly explaining differences between our observations with Clark electrodes and radiotelemetry. Renal expression of HIF-1α was less after 7 days of adenine treatment than after vehicle treatment, whereas expression of HIF-2α did not differ significantly between the two groups. Renal dysfunction was evident after 7 days of adenine treatment, with glomerular filtration rate 65% less and serum creatinine concentration 183% greater in adenine-treated rats than in vehicle-treated rats. Renal cortical tissue hypoxia may not precede renal dysfunction in adenine-induced chronic kidney disease and so may not be an early pathological feature in this model.

Energy metabolism in rat testis after 137Cs incorporation

Testis tissue energy metabolism was investigated in experiments on albino rats by the polarographic method with using of Clark electrode upon 137Cs incorporation. Speed changes are revealed in all metabolic conditions such as oxidation under endogenous and exogenous substrates, uncoupling of oxidative phosphorylation, and decrease share of the fatty acids role in testicular tissue energy production.

Non-obvious Problems in Clark Electrode Application at Elevated Temperature and Ways of Their Elimination

Well-known cause of frequent failures of closed oxygen sensors is the appearance of gas bubbles in the electrolyte. The problem is traditionally associated with insufficient sealing of the sensor that is not always true. Study of a typical temperature regime of measurement system based on Clark sensor showed that spontaneous release of the gas phase is a natural effect caused by periodic warming of the sensor to a temperature of the test liquid. The warming of the sensor together with the incubation medium causes oversaturation of electrolyte by dissolved gases and the allocation of gas bubbles. The lower rate of sensor heating in comparison with the medium reduces but does not eliminate the manifestation of this effect. It is experimentally established, that with each cycle of heating of measuring system up to 37°C followed by cooling the volume of gas phase in the electrolyte (KCl; 60 g/L; 400 μL) increased by 0.6 μL approximately. Thus, during just several cycles it can dramatically degrade the characteristics of the sensor. A method was developed in which the oxygen sensor is heated in contact with the liquid, (depleted of dissolved gases), allowing complete exclusion of the above-mentioned effect.

Calibration, Response, and Hysteresis in Deep-Sea Dissolved Oxygen Measurements

Accurately measuring the dissolved oxygen concentration in the ocean has been the subject of considerable research. Traditionally, the calibration and correction of profiling oxygen measurements has centered on static, steady-state errors, leaving dynamic or time-dependent errors in the sensor response largely untreated. This study evaluates a reengineered Sea-Bird Electronics dissolved-oxygen Clark electrode (SBE 43) and demonstrates the characterization of sensor time response over oceanographic temperatures and pressures as well as treating a time-dependent, pressure-induced effect observed as hysteresis, most notably in deep-ocean oxygen profiles. The effects of temperature and pressure on sensor response are measured separately and then combined into an expression for evaluating an in situ time constant. The physics of the pressure-induced hysteresis in oxygen sensors are discussed and modeled for many individual sensors in several locations throughout the world’s oceans. This effort reduces the underlying uncertainty of Clark oxygen sensors to approximately 0.1% of the measured signal, which is equivalent to the accuracy of the chemical calibration standard.