Interactions between amphetamine and reserpine in vitro

Resumen Se estudia en el conducto deferente aislado de rata la respuesta a la reserpina después de la estimulación del preparado con anfetamina. En estas condiciones, la reserpina produce una contracción que es proporcional a las concentraciones de anfetamina y reserpina utilizadas, y es máxima para una concentración de reserpina de 2,5×10^–5 g/ml, para ser luego decreciente cualquiera que sea la concentración de anfetamina que se haya empleado previamente. Se discuten los posibles mecanismos que regulan la respuesta a la reserpina después de la anfetamina.     

In vitro studies on bilirubin transport by the small intestine of the rat

Resumen Se estudió el transporte de bilirrubina no conjugada en asas intestinales aisladas y perfundidas de rata. Los resultados indican un pasaje bidireccional con la probable participación de un mecanismo de difusión simple.

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This work was supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas, República Argentina, National Institutes of Health, Bethesda (Md., USA) and Ministerio de Salud Publica y Bienestar Social de la Provincia de Santa Fé (Republica Argentina).     

Nodal signalling in the epiblast patterns the early mouse embryo.

Shortly after implantation the mouse embryo comprises three tissue layers. The founder tissue of the embryo proper, the epiblast, forms a radially symmetric cup of epithelial cells that grows in close apposition to the extra-embryonic ectoderm and the visceral endoderm. This simple cylindrical structure exhibits a distinct molecular pattern along its proximal-distal axis. The anterior-posterior axis of the embryo is positioned later by coordinated cell movements that rotate the pre-existing proximal-distal axis. The transforming growth factor-beta family member Nodal is known to be required for formation of the anterior-posterior axis. Here we show that signals from the epiblast are responsible for the initiation of proximal-distal polarity. Nodal acts to promote posterior cell fates in the epiblast and to maintain molecular pattern in the adjacent extra-embryonic ectoderm. Both of these functions are independent of Smad2. Moreover, Nodal signals from the epiblast also pattern the visceral endoderm by activating the Smad2-dependent pathway required for specification of anterior identity in overlying epiblast cells. Our experiments show that proximal-distal and subsequent anterior-posterior polarity of the pregastrulation embryo result from reciprocal cell-cell interactions between the epiblast and the two extra-embryonic tissues.     

Pineal indols and testosterone affect exploratory activity of male rats

The testosterone level has an inverse relation to activity in the open-field test. This is more important in red light than in white light. Pineal indols do not disturb this action. Some of these results are consistent with the assumption that androgens play a role on the exploratory activity of adult subjects.     

Biliary excretion of sulfobromophthalein in isolated perfused livers from normal and spironolactone-treated rats

Summary Bile flow and biliary excretion of sulfobromophthalein (BSP) was examined in isolated perfused livers from normal and spironolactone(SP)-treated rats. BSP biliary excretion contributed to the bile production in both groups. Moreover SP increased BSP biliary excretion but transfer of dye from plasma into liver was not affected.Acknowledgments. This work was supported by a grant from Consejo Nacional de Investigaciones Científicas y Técnicas República Argentina (EFIHER-CONICET). Isolated rat liver preparations were performed by Miss Graciela Patricia Rodriguez. The assistance of Carlos Guillermo Grieve is also gratefully acknowledged.     

Effects of intracerebroventricular injections of angiotensin II on prolactin plasma levels in the Rhesus monkey

Summary Intracerebroventricular injections of angiotensin II (A II) induced a sharp and dose-dependent increase in plasma prolactin (PRL) levels in the awake Rhesus monkey. Our results suggest that in primates, A II may be involved in the mechanisms controlling PRL secretion.Acknowledgments. We thank Mrs. J. Arsaut and D. Verrier for excellent technical assistance. This work was supported by grants from INSERM (CRL No. 78.1.2656), DGRST (77.7.9654) and CNRS (ERA 493).     

Effect of phosphate omission on glucose-induced insulin release in vitro

Summary In the isolated perfused rat pancreas, omission of extracellular phosphate (H₂PO ₄ ^– significantly reduces the insulin secretion in response to 16.7 mM glucose.