Case note descriptions of the placenta: are they worthwhile?

In 429 placentae, measurements were made of weight, diameter, shape, eccentricity of the cord and weight and length of the cord, and the results were compared with Apgar score of the infant at birth and its standardized birth weight. There was no evidence that cord eccentricity, placental shape or "thickness", or the dimensions of the cord had any significant relation to the growth of the fetus or its condition at birth. The value of routine recording of crude measurements and qualitative assessments of the placenta in case notes is questioned.

Micromethod for the assay of renin of seven species

Renin was extracted and purified from human, dog, hog, rat, beef, rabbit and sheep kidneys. The renin "concentration" of these preparations was determined and expressed in international (Goldblatt) units by measuring the pressor effect produced by intravascular injection into normal dogs of a permanent colony. The renin "activity" was determined by bioassay, in the rat, of the angiotensin produced by incubation in vitro with renin substrate prepared from the serum of nephrectomized dogs. The rate of angiotensin formation was proportional to the concentration of renin, independent of the substrate concentration, and rather similar for renin of all seven species (mean rate = 55 x 10(4) ng angiotensin/unit renin/16 hrs). Due to this uniformity, either of the two international reference preparations of renin (human or hog) from the World Health Organization can serve as an internal standard in the assay of reninof each of the seven species, to express their concentration in terms of the international unit. Renin substrate from hog plasma was suitable for the assay of human, dog and hog renin (mean rate = 55 x 10(4)). However, it reacted much more slowly with the renin of rat, beef, rabbit and sheep (mean rate = 9 x 10(4)) and was, therefore, less suitable for their assay.

A model for therapeutic interventins on established coronary atherosclerosis in a nonhuman primate

The observations so far conducted in cynomologus monkeys on semipurified diets containing butter and cholesterol suggest that this nonhuman primate is an excellent model for studying the therapy of established coronary atherosclerosis. (1) This species is available at a reasonable cost and can be kept in captivity in good health for prolonged periods of time. (2) It readily accepts semipurified diets with a percentage composition similar to that of human diets in the U.S. (3) Ingestion of these diets leads quite rapidly (around 6 months) to moderate coronary atherosclerosis. More prolonged feeding leads to lesions which are histologically very similar to those in man. (4) The distribution of lesions in the main coronary arteries is similar to that in man. (5) Methods to quantify the coronary lesions are available. (6) The diets can be so modified that cholesterol levels closely resemble those in hypercholesterolemic man. (7) The monkeys are amenable to several therapeutic regimens which show promise of arresting the progress or inducing the regression of the coronary lesions.

Kinetics of renin-antirenin reaction: micromethods for the assay of renin and antirenin

Indirect micromethods were designed for the assay of human renin (lower limit 0.25 times 10-4 U and of antirenin to human renin (lower limit 3 times 10-4 U), with the rat used for the bioassay of the angiotensin produced by the action of renin on renin substrate. This made possible the assay of unusually small amounts (0.01 mu1) of serum for antirenin. The Michaelis-Menten concept of a dissociating complex can be applied to the antireninrenin reaction: the rate constants for the formation and for the breakdown of the complex were k1 equal to 1.65 (ml/U antirenin per min) and k3 equal to 1.97 times 10-3 (U inactivated renin/U antirenin per min), respectively; the apparent Michaelis constant was 12 times 10-4 (U renin/ml). A second method of analysis was also applied by assuming the formation of a rather tight complex, with antirenin functioning as an irreversible inactivator of renin. Both methods of analysis yielded practically the same rate constant (k1 equal to 1.65 and k1 equal to 1.71), but the treatment according to the Michaelis-Menten equation affords a slightly better fit of the experimental data (accuracy equal to plus or minus 15.5 percent) than the second method of calculation (accuracy equal to plus or minus 21.6 percent).

Release of antirenin to human renin by anaphylactic shock or by antihypertensive agents

In dogs that have had repeated intravascular injections of small doses of human renin, even for long periods, the development of antirenin to human renin in the blood has not been previously noted, and their pressor response (30 mmHg) to 1 U of human renin has remained unchanged for years. In such dogs, however, a profound, abrupt fall of the systemic blood pressure, due to an anaphylactic reaction to human renin, or to the infusion of depressor agents, such as Arfonad, histamine, or diazoxide, resulted in the appearance in the blood of an inhibitor specific for human renin. This inhibitor was suddenly released into the blood-stream from the tissues in which it presumably had been stored, and it persisted, in a relatively high concentration, in some animals for months. It did not occur in dogs that had not previously received many injections of human renin. This study has shown that the inhibitor has all of the properties of antirenin to human renin. It abolished the pressor response to hog, dog, and rat renin or to angiotensin and norepinephrine. It inactivated human renin, but not dog renin, duringits incubation with renin substrate to form angiotensin.

Studies on renin. I. Purification of dog renin and micromethod for the determination of renin in dog serum and tissues

Dog renin was produced with a yield of 1.1 Goldblatt units (GU)/g renal tissue and with a specific activity of 1.3 GU/mg protein, i.e., a specific activity 10-16 times higher than that of previous preparations. This renin, free of angiotensinase and of anaphylactoid substances, was used to study the effects of prolonged infusion of renin in normal conscious dogs and as a standard for the bioassay of renin. A simplified method was designed for the indirect assay of canine renin. After prolonged incubation, the angiotensin produced was determined by bioassay in the rat, and the final estimate was expressed as the concentration of renin, in terms of GU, with an accuracy of ± 12.8%. The lower sensitivity of the assay is 1.0 x 10 -5 GU/ml; this limit permits an estimate of the endogenous renin in 0.1 ml of normal dog serum or in 0.005 mg of normal canine renal tissue. The sensitivity of this bioassay is, therefore, within the range found in seven radioimmunoassays (0.26 x 10 -5 GU/ml to 6.2 x 10 -5 GU/ml), and compared with the previous direct bioassay of renin in the dog the sensitivity is approximately 100,000-fold greater. By reference to an internationally accepted unit of renin, the Goldblatt unit, it was possible to recalculate and compare directly the results obtained in seven laboratories on the concentration of renin in blood, renal lymph, and various other tissues. This unified method for the evaluation of renin assays has made possible the determination of the rate of release of renin from the kidneys and the minimum rate of infusion of renin capable of producing persistent appreciable elevation of blood pressure.

Polykaryocytosis and replication of mouse hepatitis virus in peritoneal macrophages

Results of this investigation indicated that the infectivity titre of mouse hepatitis virus decreased after 6 hour incubation at 37°. Nutrient fluids from infected macrophage cultures retained pathogenicity in vivo and the ability to form polykaryons in vitro. Electron microscope studies of polykaryons formed from infected macrophage cultures showed the presence of virus-like particles in the cytoplasm. From the study, it was concluded that polykaryon formation in infected macrophage cultures resulted from an active viral agent.