Hemodynamic changes in placenta, myometrium and heart after administration of the uterine relaxant ritodrine.

The action of the uterine relaxant ritodrine on placental, myometrial and cardiac blood pools has been examined during spontaneous and oxytocin-induced uterine activity. 113mIndium was injected intravenously and the blood pools were measured by recording gamma-activity externally. After i.v. injection of Ritodrine, the typical blood pool changes in labor were inhibited. Thereafter, placental and myometrial blood pools increased more than due to inhibition of labor alone. Simultaneously, there was a corresponding decrease in cardiac blood pool indicating an increase in cardiac output. The rapid inflow of blood in the uteroplacental region after Ritodrine indicates an improved hemodynamic situation. This action could be of benefit in emergency situations in a hyperactive ischaemic uterus during labor.

[The action of Buphenin on uteroplacental haemodynamics (author's transl)]. / Effets de la buphénine sur l'hémodynamique utéro-placentaire.

The action of buphenin, a uterine relaxant from the group of adrenergic beta-mimetics, was examined on the blood pools of placenta, myometrium and heart, in 10 pregnant women. The method consisted of an i.v. injection of the radioisotope 113m-Indium and of registering the blood pools by external measurement of the gamma-activity. buphenin caused an increase in placental and myometrial blood pools with a corresponding decrease in cardiac blood pool. These changes were observed in all the cases examined and occurred whether the uterus had previously been inactive or in labour. The changes in blood pool were dependent on the dose of buphenin administered but there was no relationship apparent between the degree of pool changes and severity of pregnancy complication prevailing.

Actions of the uterine relaxant, fenoterol, on uteroplacental hemodynamics in human subjects.

The action of fenoterol, a uterine relaxant of the adrenergic beta-mimetic group of drugs, has been investigated on placental, myometrial, and cardiac blood pools. 113mIndium was injected intravenously and the blood pools were measured by recording gamma activity externally. In eight cases with oxytocin-induced labor, fenoterol inhibited the typical blood pool changes of labor, i.e., contraction-synchronized decrease of placental and myometrial blood pools with increase in cardiac blood pool. Furthermore, fenoterol produced an increase in placental and myometrial pools with corresponding decrease of cardiac blood pool. These changes were observed consistently. In four other cases, of which three had spontaneous labor, similar effects were observed. The possible mechanisms of hemodynamic action of fenoterol, with reference to uterine relaxation, are discussed.

Ultrastructural localization of calcitonin in the parafollicular cells of pig thyroid gland with cytochrome c-labeled antibody fragments.

Parafollicular cells in mammalian thyroid glands are thought to be responsible for the secretion of calcitonin. In this study, calcitonin was localized in pig thyroid gland by an indirect immunocytochemical technique using rabbit antiserum directed against synthetic porcine calcitonin for the first step, and sheep Fab fragments prepared against rabbit Fab and coupled to cytochrome c for the second step. The antigenic determinants of calcitonin were present only in the parafollicular cells, whose secretory granules were heavily labeled. Labeling of the cytoplasmic matrix is thought to indicate a possible leakage of the polypeptide from the granules. A striking observation was the complete absence of labeling in the cisternae of the rough-surfaced endoplasmic reticulum and of the Golgi apparatus. It is concluded that the secretory granules of parafollicular cells contain calcitonin; the mechanism of synthesis of this peptide is not clearly understood.

Ultrastructural localization of intracellular antigen using enzyme-labeled antibody fragments.

The efficiency of small enzyme-labeled tracers for the demonstration of intracellular antigen was investigated in tissues fixed with picric acid-formaldehyde. The influence of fixation on the immunological activity was tested in vitro by radial immunodiffusion. The experimental model consisted of newborn pig jejunum after absorption of ferritin from the intestinal lumen. Ferritin was located after 1 hr in vacuoles scattered in the cytoplasm of the absorptive cells and represented an easily recognizable intracellular antigen. After immunohistochemical treatments with antiferritin preparations, the distribution of labeling enzyme reaction product was examined by morphometry. The ratio of the labeled volume to the total volume of vacuoles containing ferritin indicated the degree of specific labeling of the antigen. In both direct and indirect methods, the degree of labeling was low when enzyme-labeled immunoglobulin G was the tracer. With antigen binding fragments (Fab), the labeling was significantly increased. In the indirect method, the degree of labeling was influenced by the first-step reagents. Onlywhen the serum titer was optimum was a high degree of labeling obtained. With antigen binding fragments or papain-digested serum the effect of the titer was negligible and maximum labeling was achieved. In both methods, with peroxidase as the labeling enzyme, a diffuse nonspecific deposition of reaction product was observed. This could be avoided by using cytochrome c instead.