Potassium transport in isolated cerebral microvessels from the rat

Microvessels have been prepared from the gray matter of a rat brain by a technique involving density gradient centrifugation. A suspension of these vessels, largely capillaries, was incubated in vitro in order to investigate K transport. The flux of K (as 86Rb) into and out of endothelial cells was estimated. Potassium influx was sensitive to temperature and pH of the medium, and was markedly inhibited by 1 mM ouabain (45%). Ouabain did not inhibit K efflux, as anticipated, when Na-K pumps are mainly located on the abluminal plasma membrane of the endothelial cell. The ouabain-sensitive K influx was measured at varying external concentrations of K. The Km of ouabain-sensitive K influx was 2.95 mM, which is similar to the affinity of the transport carrier of K, found in in vivo studies of K efflux from brain to the blood system. Both 1 mM furosemide and 5 mM barium chloride inhibited part of the ouabain-insensitive K influx. Potassium efflux was not influenced by furosemide, but was somewhat reduced by barium chloride. Noradrenalin (10(-3) mM) and histamine (0.1 mM) did not significantly affect the influx of K.

Multipoint kinetic methods evaluated for quantitation of theophylline with prosthetic group label immunoassay

We describe the development and evaluation of a multipoint kinetic approach to the measurement and data-processing steps in immunoassays. Nonlinear regression methods are used to fit data obtained during the kinetic phase of the immunochemical reaction to a model that represents the kinetic behavior of the total system. This approach is evaluated for quantitation of theophylline with a new reaction system in which FAD is the label in a homogeneous reaction system. Competition for antibody binding sites between drug and labeled drug is monitored by the activity of glucose oxidase (EC 1.1.3.4) generated by the reaction of unbound label with apoglucose oxidase. The process is fit well by a parallel first-order/zero-order model and regression methods are used to predict steady-state velocities from non-steady-state portions of the response. One fitting method yields results in about 3 min after mixing, as compared with longer than 8 min for single-point fixed-time methods. Steady-state velocities vary linearly with theophylline concentration.

Multipoint kinetic methods evaluated for quantitation of theophylline with prosthetic group label immunoassay

We describe the development and evaluation of a multipoint kinetic approach to the measurement and data-processing steps in immunoassays. Nonlinear regression methods are used to fit data obtained during the kinetic phase of the immunochemical reaction to a model that represents the kinetic behavior of the total system. This approach is evaluated for quantitation of theophylline with a new reaction system in which FAD is the label in a homogeneous reaction system. Competition for antibody binding sites between drug and labeled drug is monitored by the activity of glucose oxidase (EC 1.1.3.4) generated by the reaction of unbound label with apoglucose oxidase. The process is fit well by a parallel first-order/zero-order model and regression methods are used to predict steady-state velocities from non-steady-state portions of the response. One fitting method yields results in about 3 min after mixing, as compared with longer than 8 min for single-point fixed-time methods. Steady-state velocities vary linearly with theophylline concentration.

Participation of regional sympathetic outflows in the centrogenic pulmonary pathology

In anesthetized and vagotomized rats, a mechanical cerebral compression (CC) evoked systemic arterial hypertension (SAH) and pulmonary venous hypertension (PVH) followed by massive pulmonary hemorrhagic edema (PHE). The hemodynamic and pulmonary changes induced by CC were more pronounced in the right heart bypass (RHB) preparation (venous return to reservoir and constant pulmonary inflow). Additional observations in RHB included a marked reduction in reservoir volume (RV) without significant change in pulmonary vascular resistance (PVR). In either natural circulation or RHB, an upper thoracic sympathectomy did not affect the SAH, RV reduction, and PVR change, but reduced the PVH and PHE by approximately one-third. Such effects were not attributed to cardiac denervation, because beta 1-adrenergic blockade (metaprolol) did not alter the CC-induced PHE. Splanchnic denervation greatly diminished the SAH and prevented the RV reduction, PVH, and PHE. The results suggest that the centrogenic PHE is initiated from an intense arteriolar constriction, principally in the splanchnic beds. The latter causes left heart failure leading to volume and pressure loading and blood loss in the lungs. Direct sympathetic impulses to the lungs do not affect the PVR and RV changes and are not essential for the genesis of PHE. However, they may alter the vascular compliance and thereby exacerbate the PVH and PHE when passive accumulation of blood is produced in the lungs.