The skin from four species of North American tree frogs (Hylidae) was found in vitro, to be remarkably permeable to water in the presence or absence of the neurohypophysial hormone vasotocin. This property was, however, only seen in preparations from the ventral integument; osmotic water movement across the dorsal skin was negligible. The ionic permeability, reflected by the electrical resistan...

1. Surface-labelling of starch granules by tritiation seems feasible, and a technique is described that could be useful in structure determination. The impurities that are produced must be taken into account but the fact that a high polymer can be successfully tritiated seems very promising. 2. The surfaces of corn-starch granules must contain both amylose and amylopectin.

Indicator dilution techniques were used to determine the vascular and extravascular volumes of the normal human kidney. Renal volumes were corrected to 1.73 m and refer to one kidney. The renal blood volume (VI0) averaged 34.8 ±3.1 ml; the water contained in the distribution volume of labeled inulin (ViX") averaged 48.8 ± 9.0 ml, and that of tritiated water (VTHO) 152 ± 20 ml. VIN-"' was used a...

Methyl esters of polyunsaturated fatty acids labeled with tritium were prepared by partial stereoselective reduction of the corresponding acetylenic esters with tritiated disiamylborane, followed by protonolysis with tritiated acetic acid. The labeling was strictly specific, and the tritium atoms were located only at the carbon atoms forming the unsaturated bond(s). Synthesis of some tritiated ...

The effects of somatostatin on the release of tritiated dopamine (DA) formed continuously from tritiated tyrosine were studied in vitro in superfused striatal slices and in vivo in both caudate nuclei and both substantiae nigrae of halothane-anesthetized cats using a push-pull cannula technique. Somatostatin (3 X 10(-10) to 3 X 10(-7) M) increased the spontaneous tritiated dopamine release from...

An in vivo system for studying arterial transport was developed which utilized the rabbit carotid artery perfused in vivo with Dulbecco's modified Eagle's medium containing 125I-labeled albumin, [3H]-3-methyl-d-glucose, or tritiated water. The appearance of labeled materials in jugular venous blood was measured serially over 4 hours. Vascular integrity was assessed by scanning electron and tran...

The incorporation of tritiated thymidine into DNA molecules was studied by electr.:m microscopic autoradiography. To make autoradiogram in electron microscopic level, DNA was extracted from rat ascites hepatoma (AH 130) cells after in vitro incubation with tritiated thymidine. Extracted DNA samples were rotary shadowed with platinum palladium and covered with emulsion. Silver grains demonstrate...