Elongated conductive structures in detonation soot of high explosives.

High values of electrical conductivity are obtained at the detonation of condensed high explosives with the formula C a H b N c O d . Such values can be explained only in the framework of the contact conductivity hypothesis. In this case, the conductivity is provided by elongated highly-conductive structures which penetrate the whole space of the detonation wave. This work is devoted to the investigation of the detonation soot of high explosives with a significant carbon content in order to discover elongated structures supporting the contact conductivity hypothesis.

Quantitative estimation of transmembrane ion transport in rat renal collecting duct principal cells.

Kidney collecting duct principal cells play a key role in regulated tubular reabsorption of water and sodium and secretion of potassium. The importance of this function for the maintenance of the osmotic homeostasis of the whole organism motivates extensive study of the ion transport properties of collecting duct principal cells. We performed experimental measurements of cell volume and intracellular sodium concentration in rat renal collecting duct principal cells from the outer medulla (OMCD) and used a mathematical model describing transmembrane ion fluxes to analyze the experimental data. The sodium and chloride concentrations ([Na+]in = 37.3 ± 3.3 mM, [Cl-]in = 32.2 ± 4.0 mM) in OMCD cells were quantitatively estimated. Correspondence between the experimentally measured cell physiological characteristics and the values of model permeability parameters was established. Plasma membrane permeabilities and the rates of transmembrane fluxes for sodium, potassium and chloride ions were estimated on the basis of ion substitution experiments and model predictions. In particular, calculated sodium (PNa), potassium (PK) and chloride (PCl) permeabilities were equal to 3.2 × 10-6 cm/s, 1.0 × 10-5 cm/s and 3.0 × 10-6 cm/s, respectively. This approach sets grounds for utilization of experimental measurements of intracellular sodium concentration and cell volume to quantify the ion permeabilities of OMCD principal cells and aids us in understanding the physiology of the adjustment of renal sodium and potassium excretion.

Regulatory volume decrease of rat kidney principal cells after successive hypo-osmotic shocks.

Outer Medullary Collecting Duct (OMCD) principal cells are exposed to significant changes of the extracellular osmolarity and thus the analysis of their regulatory volume decrease (RVD) function is of great importance in order to avoid cell membrane rupture and subsequent death. In this paper we provide a sub-second temporal analysis of RVD events occurring after two successive hypo-osmotic challenges in rat kidney OMCD principal cells. We performed experimental cell volume measurements and created a mathematical model based on our experimental results. As a consequence of RVD the cell expels part of intracellular osmolytes and reduces the permeability of the plasma membrane to water. The next osmotic challenge does not cause significant RVD if it occurs within a minute after the primary shock. In such a case the cell reacts as an ideal osmometer. Through our model we provide the basis for further detailed studies on RVD dynamical modeling.