To define the histology of the columnarlined esophagus, we obtained esophageal biopsies from various levels with manometric control from 11 patients. There were three types of columnar epithelia above the lower esophageal sphincter: atrophic gastric-fundic-type epithelium with parietal and chief cells; junctional-type epithelium with cardiac mucous glands; and distinctive specialized columnar epithelium with a villiform surface, mucous glands and intestinal-type goblet cells. When present, specialized columnar epithelium was always the most proximal, and gastric fundic epithelium the most distal epithelium. Junctional epithelium was interposed between gastric fundic and specialized columnar or squamous epithelium. Four patients had unequivocal esophagitis in squamous epithelium, but its presence and severity did not correlate with inflammation in or length or type of distal columnar epithelium. Histoligic study of the columnar-lined esophagus demonstrated a spectrum of epithelial patterns. This heterogeneity helps to explain prior discrepant reports.

A B S T R A C T We investigated the effect of pyridoxine administration in three patients with homocystinuria due to cystathionine synthase deficiency. The drug decreased the plasma concentration and urinary excretion of methionine and homocystine and the urinary excretion of homolanthionine and the homocysteine-cysteine mixed disulfide. Urinary cystine rose somewhat. Oral methionine tolerance tests before and during the patients' response to pyridoxine indicated that during response they remained deficient in their capacity to convert the sulfur of methionine to inorganic sulfate, although this capacity increased somewhat. During pyridoxine response only, the methionine loads caused increased homocystinuria. There was no indication that pyridoxine stimulated an alternate pathway of metabolism. The values for specific activity of cystathionine synthasz in liver biopsy specimens from two patients in pyridoxine response were 3 and 4% of the mean control value. When these patients were not receiving pyridoxine, comparable values were 2 and 1%, respectively. The hepatic enzyme activity of the mutant patients was similar to normal enzyme activity with respect to trypsin activation, heat inactivation, and stabilization by pyridoxal phosphate. Approximate estimates were made of the relation between total body capacity to metabolize methionine and hepatic cystathionine synthase activity. These estimates suggested that because of the large normal reserve capacity of cystathionine synthase, a few per cent residual activity is sufficient to metabolize the normal dietary load of methionine. Thus, small increases in residual capacity may be of major physiological importance. However, many liver biopsies would be required to establish unequivocally that such changes were due to the administration of a particular therapeutic agent rather than to biological variation. All the

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Cholografin and Renografin 76 were studied to determine their effects on platelet function. In vitro platelet aggregation was significantly inhibited by at least 3.4 micron/ml Cholografin and 19.5 micron/ml Renografin 76. Patients who received Cholografin for intravenous cholangiography, and Renografin 76 for non-cardiac angiography, had low levels of plasma contrast agent, and hemostasis was clinically unimpaired. Patients who received Renografin 76 for cardiac angiography had inhibition of platelet aggregation at high levels of plasma contrast agent; there was no correlation with prolonged bleeding times, or with bleeding complications. High levels of plasma contrast agent may inhibit platelet aggregation in vitro and in vivo, although this may not be associated with clinically significant bleeding.