Fungal products. Part XVII. Microbiological hydroxylation of gibberellin A9 and its methyl ester

Angiotensin II (A II) and analogues were tested for their ability to restore electrical and mechanical activity to cardiac muscle preparations in which the fast Na+ channels had been inactivated by partial depolarization (22-27 mM K+) or by tetrodotoxin (TTX). The partially depolarized or TTX-blocked preparations were chosen because under these conditions electrical and mechanical responses are primarily Ca2+ -dependent. In depolarized rabbit right atria, A II restored spontaneous mechanical and electrical activity (measured by both intracellular and extracellular recording techniques). The frequency of action potential discharge was concentration-dependent; the threshold concentration of A II was 10(-10) M, the ED50 was 8 X 10(-9) M, and the maximum effect was observed at 5 X 10(-8) M. In contrast, depolarized guinea pig atria were insensitive to A II, Sar1-angiotensin II, and des-Asp1-angiotensin II, even at concentrations as high as 10(-5) M. Rabbit papillary muscle (TTX-blocked), embryonic (18-day) chick heart (partially depolarized) and chick heart reaggregates (TTX-blocked) responded similarly to rabbit atria in that A II (9.6 X 10(-7) M) restored both electrical and mechanical activity. We found that in these preparations the action of A II was unaffected by propranolol (5.0 X 10(-6) M to 5.0 X 10(-5) M) but was blocked by Mn2+ (10(-3) M), D-600 (1 X 10(-7) g/ml) and the specific A II antagonists Sar1-Ala8-angiotensin II (P-113) (5.0 X 10(-5) M) and Sar1-Ile8-angiotensin II (5.28 X 10(-5) M). We conclude that the positive inotropic effect of A II on the myocardium is due to its ability to increase transmembrane ion movements in or through the cell membrane. The ability of Mn2+ and D-600 to block this effect suggests that this ion movement is via the so-called "slow channels."     

An electrophoretic analysis of RNA synthesis in normal and lobeless Ilyanassa embryo

A primary infection with schistosoma mansoni, of 5 or more weeks duration, stimulated a high level of resistance to a challenge infection in the WO outbred strain of golden hamster. In sharp contrast, the LGN strain showed no statistically significant immunity to reinfection in most experiments and where detected the level of resistance was only about half that observed in the WO strain. Immunity to reinfection was assayed with the lung recovery method which assesses resistance a few days after challenge and with the conventional perfusion assay which measures immunity 6 weeks after challenge. Wide differences in the immune response to S. mansoni in different strains of the same host species have not been reported previously.     

Regulation of nitrogen catabolic enzymes in chick liver -- effects of amino acids

It is well-known that in the chick, dietary protein increases the levels of several hepatic enzymes that are involved in nitrogen metabolism and excretion. However, the biochemical mechanism of this response is essentially unknown. The experiments presented in this paper show that the chick is responding to alpha-amino nitrogen and not to any specific amino acid. Furthermore, it is shown that this system responds to endogenous sources of nitrogen as well as dietary protein and that the xanthine dehydrogenase response involves regulation of enzyme synthesis without changing the rate of degradation.     

Clinical experience using a small-gauge needle for arterial puncture

The present study was undertaken to ascertain the feasibility of using a 25-gauge needle for arterial punctures. A total of 11,500 arterial punctures were performed over the past four years by this technique without any major complication. Repeated arterial punctures were well tolerated by all patients, and the necessity for indwelling arterial catheters was almost totally eliminated during this period of study.     

Amplified migration inhibition effect

Upon exposure to specific antigen in tissue culture, sensitive lymphocytes released macrophage migration inhibition factor and other lymphokines into the supernatant culture medium. Migration of peritoneal macrophages from nonsensitive animals was inhibited in the presence of such supernatants. However, with previous techniques it was found that an inhibitory effect was present at only low low titers (less than 10(2)). It is therfore of great interest that by increasing cellular density, the total number of cells being kept constant, inhibitory activity can be amplified by a factor as great as 10(10). This amplification was observed only when lymphocytes and macrophages were loosely packed, as by spontaneous sedimentation in a conical test tube. The effect was abolished by dispersing the cell suspension in a flat-bottomed flask or, alternatively, by shaking the test tube so that intimate prolonged intercellular contact was prevented.     

Attaching community psychiatric nurses to general practice

A scheme for attachment of psychiatric nurses from hospital to group practice in Oxford is described. One community psychiatric nurse can work satisfactorily with eight general practitioners covering a population of about 18,000. From analysis of a working year, it is concluded that this arrangement improves the care of patients in the community by providing psychiatric help at times when it was previously unavailable or unacceptable.The implications of such a scheme for the workings of the primary health care team and the hospital psychiatric service are considered, and a case is made for a further study involving a comparison between practices with and without the attachment of a community psychiatric nurse.     

Reversible binding of chlorpromazine to brain tubulin

Isolated lamb hearts perfused at 13degrees C. with acellular perfusates developed progressive intersitital edema and a rise in vascular resistance. They did not exhbit any electrical or mechanical activity. In contrast, hearts perfused with whole fresh blood remained well preserved, had no edema or change in vascular resistance, and contracted vigorously while being perfused at 10degrees and 13degrees C. This study was designed to determine which particular component(s) of whole blood contributed to improved cardiac preservation. Isolated lamb hearts were perfused for 18 hours at 13degrees C. with plasma containing platelets and some or no red blood cells. Continuously fresh plasma was obtained from a donor animal by means of a flow-through centrifuge. Hearts perfused at 13degrees C. with fresh plasma of either low or high platelet count contracted during the initial 2 to 4 hours of the perfusion only and were as poorly preserved as hearts perfused with acellular microfiltered plasma. A hematocrit value of 2 to 5 per cent in the plasma perfusate resulted in the hearts being preserved almost as well as with fresh whole blood; they showed a forceful cardiac activity at 13degrees C., there was no edema, the vascular resistance was stable, and after rewarming they had good ventricular function. The improvement in cardiac preservation brought about by addition of a minimal amount of red blood cells suggests a specific effect of erythrocytes on the cardiac microcirculation.