Graft-versus-host-like colitis associated with malignant thymoma.

A case of a patient with a malignant thymoma who developed an unusual form of colitis is reported. The patient was a previously healthy 20-year-old man who was referred to the Johns Hopkins Medical Institution for biopsy and resection of a mediastinal mass, which proved to be a malignant thymoma. During this hospitalization and subsequently, the patient developed severe chronic diarrhea, the etiology of which remained uncertain after routine work-up, including cultures. Colonoscopic biopsies revealed only minimal inflammation but numerous, prominent apoptotic lesions within crypt epithelium, suggestive of an autoimmune or graft-versus-host-like colitis. The patient, who was immunocompetent and human immunodeficiency virus (HIV) negative, had no known risk factors for graft-versus-host-disease (e.g., no blood transfusions, no transplantation history before diarrheal episodes). Stool cultures for pathogenic bacteria and viruses were negative. The diarrhea and histologic findings eventually improved with steroid therapy yet returned on recurrence of the thymoma. This unusual form of colitis has not been previously reported to be associated with thymoma and is interesting in light of the role the thymus plays in immune regulation.

Collagenous colitis in setting of nonsteroidal antiinflammatory drugs and antibiotics.

Collagenous colitis is a clinicopathologic syndrome characterized by chronic watery diarrhea and a mucosal inflammatory process with increased subepithelial collagen band on colonic biopsy. This disorder occurs primarily in females, and the etiology is unknown. We report the atypical presentation of collagenous colitis in two older-aged men following prolonged use of nonsteroidal antiinflammatory agents and short-term use of antibiotics. Although one patient had colonic pseudomembranes, neither patient had microbiological evidence of C. difficile toxin or infection. A variety of medications were initially given to these patients without resolution of diarrhea. Only after the diagnosis of collagenous colitis was made and antiinflammatory drugs directed at the colitis given did the diarrhea abate. These cases illustrate an unusual presentation of collagenous colitis with possible implications for pathogenesis.

Computed tomography of angioedema of small bowel due to reaction to radiographic contrast medium.

Although urticaria and facial and peripheral edema are well recognized idiosyncratic reactions to ionic contrast medium, to our knowledge, isolated angioedema of the small bowel has not been reported previously. We present a case of acute onset of small bowel edema and ascites during the infusion of iodiated contrast medium.

Microvascular repair following local crush and avulsion vascular injury.

A model has been developed demonstrating intimal damage resulting from a combined crush and avulsion injury to the femoral artery of the rat. Revascularization after traumatization is accomplished with microvascular anastomosis of the severed ends. Vascular patency rates at 2 and 7 days postoperatively are low (0-25%) in comparison with control groups (90-100%). A high correlation is found between patency tests performed at 20 minutes and at 2 days after blood flow re-establishment. Systemically administered heparin improves traumatized-vessel patency dramatically.

Stoichiometry of proton movements coupled to ATP synthesis driven by a pH gradient in Streptococcus lactis.

An electrochemical potential difference for H+ was established across the plasma membrane of the anaerobe Streptococcus lactis by addition of sulfuric acid to cells suspended in potassium phosphate at pH 8 along with valinomycin or permeant anions. Subsequent acidification of the cell was measured by the distribution of salicyclic acid. A comparison between cells treated or untreated with the inhibitor N,N'-dicyclohexylcarbodiimide was used to reveal that portion of net proton entry attributable to a direct coupling between H+ inflow and synthesis of ATP catalyzed by the reversible proton-translocating ATPase of this microorganism. When the imposed electrochemical proton gradient was below 180-190 mV, proton entry was at the rate expected of passive flux, for both control cells and cells treated with the ATPase inhibitor, However, at higher driving force acidification of control cells was markedly accelerated, coincident with ATP synthesis, while acidification of cells treated with the inhibitor continued at the rate characteristic of passive inflow. This observed threshold (180-190 mV) was identified as the reversal potential for this H+ "pump". Parallel measurements showed that the free energy of hydrolysis for ATP in these washed cells was 8.4 kcal/mole (370mV). The comparison between the reversal (threshold) potential and the free energy of hydrolysis for ATP indicates a stoichiometry of 2 H+/ATP for the coupling of proton movements to ATP formation in bacteria.