Inhibition of hypoxic pulmonary vasoconstriction by dipyridamole is not platelet mediated

Dipyridamole, which is known to alter platelet function, has also been shown to reduce hypoxic pulmonary vasoconstriction. This latter effect could result from dipyridamole either acting on a platelet-mediated system, or acting directly on pulmonary vascular smooth muscle. To investigate these two possibilities, normal dogs were compared with dogs rendered thrombocytopenic by a platelet antiserum. Compared with the hypoxic pressor response before drug treatment, the hypoxic response following dipyridamole was only 32% as great in the normal dogs and only 38% as great in the thrombocytopenic dogs. Thus, dipyridamole was no less effective in reducing the hypoxic pressor response in the virtual absence of platelets. This supports a direct effect of dipyridamole on pulmonary vascular smooth muscle, which could be mediated by an increase in adenosine levels.     

Determination of molecular weight, isoelectric point, and glycoprotein moiety for the principal skin test-reactive component of histoplasmin

A purified component designated HPD (histoplasmin-purified derivative) dII was isolated from two different cru-e histoplasmin lots by a combination of gel filtration and polyacrylamide disc electrophoresis (Sprouse, 1969). A 0.05-mug portion of HPD dII was reactive and specific in detection of delayed hypersensitivity in guinea pigs experimentally infected with Histoplasma capsulatum. The objective of this study was to characterize this skin test-reactive component for (i) homogeneity, (ii) molecular weight, (iii) isoelectric point, and (iv) composition. Sephadex chromatography, polyacrylamide disc electrophoresis, sucrose density gradient ultracentrifugation, acid and heat denaturation, and immunoelectrophoresis indicate that HPD dII is (i) homogeneous, (ii) of approximately 12,000 molecular weight, and (iii) a glycopeptide of approximately 60% carbohydrate and 40% proteinaceous composition. The marked acid and heat stability exhibited by the compound probably is attributable to the prominent carbohydrate moiety in the molecule. Isoelectric focusing indicated an isoelectric point of 5.68. This would suggest that dII is an acidic compound with either predominance of acidic amino acid residues in the molecule or, more probably, an abundance of electron donors in the carbohydrate moiety. In summary, HPD dII appears to be a glycopeptide of approximately 12,000 molecular weight, reactive in elicitation of delayed hypersensitivity of histoplasmosis.     

Esophageal perforation. An unusual presentation with a benign clinical course

A case of esophageal perforation occurring in a 75-year-old man is presented. The clinical presentation was benign and the diagnosis of esophageal perforation was made incidental to an upper gastrointestinal barium examination. Conservative management consisting of nasogastric suctioning, antibiotics and antacids was effective in minimizing the clinical course. This represents a rare instance of a successful nonsurgical approach to esophageal perforation.     

Metabolism of glucose, fructose and lactate in vivo in chronically cannulated foetuses and in suckling lambs

1. Chronically cannulated sheep foetuses and suckling lambs were injected with 14C-labelled glucose, fructose or lactate, and sequential blood samples taken under conditions of minimal stress and without anaesthesia. 2. Gluconeogenesis from lactate was not detectable in foetal sheep, but the pathway was active in suckling lambs. 3. Fructose utilization rates were low in foetal sheep, with no measurable conversion into glucose or lactate. 4. The high rates of irreversible loss of both glucose and lactate in the foetus were decreased in suckling lambs. Radioactivity from labelled glucose entered both the lactate and fructose pools in foetal sheep, and entered the lactate pool in suckling lambs. 5. A model is proposed in which carbon flow between glucose, fructose and lactate has been quantified in foetal sheep.