Isao Tamura

The mechanism of conversion of xanthine dehydrogenase to oxidase and the role of the enzyme in reperfusion injury.

In 1968 Delia Corte and Stirpe reported that mammalian xanthine oxidase was originally a dehydrogenase, and was converted to the oxidase by modification of the enzyme protein during extraction or purification (Delia Corte and Stirpe, 1968, 1972). This conversion occurs either reversibly by sulfhydryl oxidation, or irreversibly by proteolysis (Delia Corte and Stirpe, 1968, 1972; Stirpe and Delia Corte, 1969; Waud and Rajagopalan,1976; Nakamura and Yamazaki, 1982; Ikegami and Nishino, 1986; Saito and Nishino, 1989). Although the mammalian enzyme is easily converted from the dehydrogenase to the oxidase, the enzyme can be purified in a reversible form by careful purification procedures (Waud and Rajagopalan,1976; Nakamura and Yamazaki, 1982; Ikegami and Nishino, 1986; Saito and Nishino, 1989). The dehydrogenase form has very low oxidase activity (3–4% of dehydrogenase activity) when enzyme activity is determined by the standard assay system, but detailed kinetic analysis shows that even the dehydrogenase has an appreciable amount of oxidase activity. Table 1 shows the kinetic parameters obtained from rat liver xanthine dehydrogenase and oxidase (Saito and Nishino, 1989). For the dehydrogenase, the Vmax value for dehydrogenase activity has about four times higher than the value for oxidase activity. The Km value for oxygen of the dehydrogenase is five times higher than that of the oxidase. The oxidase activity of the dehydrogenase is almost completely inhibited by NAD. While dehydrogenase activity of the oxidase type is almost negligible, the Vmax value for oxidase activity of this form is similar to that of the dehydrogenase form for dehydrogenase activity, indicating the same rate limiting step of urate release from the enzyme. It should be noted that the dehydrogenase produces more ratio of O2 formation than the oxidase if NAD is absent. However, O2 is almost completely inhibited in the presence of NAD. In contrast to the mammalian enzyme, conversion of the dehydrogenase form to the oxidase form has never been reported for the avian enzyme, but the reactivity of chicken liver xanthine dehydrogenase with oxygen is similar to that of rat liver xanthine dehydrogenase.

SEGMENTAL MEDIOLYTIC ARTERIES : A CASE REPORT WITH REVIEW OF THE LITERATURE

Summary Segmental mediolytic arteritis is a very rare vascular disease which causes sudden intraabdominal hemorrhage. The disease is characterized by degeneration of the arterial media, followed by aneurysmal dilatation and rupture of the involved artery. Up to now, only 13 cases have been reported, and this unique disease is not fully recognized among general pathologists and physicians. Here, we present a case of segmental mediolytic arteritis involving the propria hepatic artery, which resulted in intraabdominal hemorrhage, and consequently hypovolemic circulatory disturbance. Histologically, the rupture focus showed degeneration and desquamation of the intima and media with fibrin-like material covering the exposed adventitia. Inflammatory infiltrates were only noted in the rupture focus as a secondary reactive change. Other than the rupture focus, there were two foci showing similar findings. This disease has rarely been reported and is seldom recognized as a cause of arterial rupture. In cases of sudden intraabdominal hemorrhage, segmental mediolytic arteritis should be considered as a possible cause in addition to atherosclerotic and mycotic aneurysm, traumatic injury and vasculitis syndromes.

MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY FOR AFFERENT LOOP SYNDROME

In April 2006, a 70-year-old man who had undergone a subtotal gastrectomy with Billroth II reconstruction for a benign peptic ulcer in 1955 and cholecystectomy for gallstones in 2005 was admitted to our hospital complaining of abdominal pain, distention and vomiting. Physical examination showed a large cystic abdominal mass with tenderness in the epigastrium. The results of laboratory tests showed serum amylase (AMY) of 518 IU/L, alanine aminotransferase of 641 IU/L, aspartate aminotransferase of 1198 IU/L, lactate dehydrogenas (LDH) of 378 IU/L and white blood cell of 5100/lL. Computed tomography (CT) examination showed fluid-filled loops of bowel (Fig. 1a). The superior mesenteric vessels were displaced anteriorly (Fig. 1a). These findings strongly suggested the diagnosis of afferent loop syndrome.1,2 MRCP clearly showed a long complex afferent loop course with an abrupt cut-off at the site of the gastrojejunostomy anastomosis (Fig. 2).

Cystic lesion of the buttock communicating with the lateral side of the posterior urethra.

We report a case of a congenital cystic lesion of the right buttock without cutaneous or rectal fistula. The cystic lesion communicated with the right lateral side of the posterior urethra via a fistulous tract.

Laparoscopic surgery using a newly designed suction lifter.

The authors describe a simple and available abdominal wall-lift technique for endoscopic surgery that involves a new suction lifter that they designed for laparoscopic surgery. Since July 1998, the authors have used this technique successfully in eight patients with appendicitis, in one patient with a perforated duodenal ulcer, and in one patient with an adenoma of the ascending colon.