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The gravity and complexity of problems encountered in the management of patients bleeding severely from the upper gastrointestinal tract have prompted numerous studies of the factors involved.1-7 Many diverse approaches toward the treatment of such patients have resulted. Since the criteria of "massive hemorrhage" and the indications for operative treatment have not been uniform, it is difficult to draw firm conclusions from these reports. A few common factors have emerged. The patient who bleeds acutely, and who may present with a normal hemoglobin and hematocrit in the face of a 30% or greater reduction in blood volume, requires earlier and more aggressive therapy than one who bleeds slowly enough to permit some compensatory hemodilution. The patient who has serious concomitant disease is in far greater jeopardy from hemorrhage than an otherwise healthy person who suffers loss of blood to the same extent. Early surgical intervention appears helpful, especially when

Twelve 8-substituted analogs of cyclic AMP were tested on excised guinea pig trachea and rat portal vein; cyclic AMP, dibutyryl cyclic AMP, and theophylline were similarly tested. The 8-benzylthio, 8-methylthio, 8-azido, and 8-thio derivatives of cyclic AMP were among the most potent relaxants of both tracheal and venous smooth muscle. Each of these four analogs was: (a) more potent than dibutyryl cyclic AMP, but less potent than theophylline, on excised trachea; and (b) roughly equipotent to or less potent than either dibutyryl cyclic AMP or theophylline on excised vein. Several other 8-substituted derivatives of cyclic AMP, as well as cyclic AMP itself, were inactive as relaxants at concentrations of 400 μg/ml.In general, the decreasing order of relaxant activity among the groups of 8-substituted analogs of cyclic AMP was 8-thio>8-oxo>8-amino.

Sulfate particles with diameters of less than 1.7 microns contribute approximately 40 percent by weight to total sulfate particulate in Pittsburgh air. The irritant nature of these particles and their small size and associated long atmospheric residence time, as well as the short half-life of sulfur dioxide in the atmosphere, suggest that particulate sulfate may be a better indicator of atmospheric pollution than sulfur dioxide.

The DDT associated with samples of airborne particulates was measured by gas chromatography. Because of possible vaporization of DDT during sampling, concentrations reported represent minimum values but demonstrate that DDT can be present in an urban atmosphere that is distant from any large-scale agricultural activity.