The small regulatory RNA SyR1/PsrR1 controls photosynthetic functions in cyanobacteria.

Little is known so far about RNA regulators of photosynthesis in plants, algae, or cyanobacteria. The small RNA PsrR1 (formerly SyR1) has been discovered in Synechocystis sp PCC 6803 and appears to be widely conserved within the cyanobacterial phylum. Expression of PsrR1 is induced shortly after a shift from moderate to high-light conditions.

Comparison of four experimental techniques for studying drug absorption kinetics in the anesthetized rat in situ.

Theophylline absorption kinetics were determined using in situ perfusion techniques. The objectives of this study were to obtain information on the effective permeability constant (ke) of theophylline and its variance during the course of an experiment, and to study the dependence of ke on the experimental technique used. Four in situ intestinal perfusion techniques were compared in the rat: single-pass perfusion, recirculating perfusion, oscillating perfusion, and the closed loop method.

Absorption of Etoposide (VP-16-213) from the Small Intestine of the Rat. The Potential Role of Mucus as an Absorption Rate Limiting Barrier.

The absorption of etoposide (VP-16-213) was investigated in a perfused intestinal loop. The absorbed amount of drug was determined by collecting the blood draining the loop via cannulation of the efferent jejunal vein. The absorption rate of VP-16-213 strongly depended on the composition of the perfusion medium.

Influence of bloodflow on the absorption of theophylline from the jejunum of the rat.

The influence of the jejunal bloodflow on the absorption of theophylline was investigated. The bloodflow through a segment under investigation was varied by changing the systemic blood pressure by means of a donor blood infusion into the jugular vein or by an infusion of isoprenaline or levarterenol into a femoral vein, and was measured by collecting the venous outflow from the intestinal segment. Above a bloodflow of approximately 0.

Non-enhancement of sodium cromoglycate intestinal absorption by quaternary ammonium ions. An effect of salt on ion-pair formation?

Studies on the nature of rat small intestine perfusates indicate that this environment is thermodynamically unfavourable for the production of ion pairs between cromoglycate and alkylbenzyldimethylammonium ions. This is suggested as being the reason why, unlike previously found for ocular absorption of cromoglycate, these quaternary ammonium ions do not alter cromoglycate intestinal absorption.