Keiji Nishimaki

Enhanced Embryonic Nonmuscle Myosin Heavy Chain Isoform and Matrix Metalloproteinase Expression in Aortic Abdominal Aneurysm With Rapid Progression

Abdominal aortic aneurysms (AAAs) are characterized by structural deterioration of aortic wall leading to progressive dilatation. The histopathological changes in AAAs are particularly evident within the elastic media, which is normally comprised mainly of vascular smooth muscle cells (SMCs). There are vascular myosin heavy chain (MHC) isoforms; SM2 is specifically expressed in differentiated SMCs and SMemb is a nonmuscle-type MHC abundantly expressed in SMCs of the fetal aorta with an immature phenotype. Although AAA altered expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), pathophysiological role of SMC phenotypic modulation in the AAA progression remains uncertain. To determine whether phenotypic modulation in vascular SMCs contributes to arterial medial degeneration, we examined MHC expression in SMCs of AAA. Aortic specimens were obtained from patients with slowly progressed AAA (n = 12) and rapidly progressed AAA (n = 5), and compared with normal aortic tissue (n = 3). Immunohistochemical staining was performed for detection of SMemb, SM2, MMP (types 2 and 9) and TIMP (types 1 and 2). Faint SMemb and abundant SM2 were observed in normal aorta, while the balance shifted to SMemb predominance in AAAs. Compared with slowly progressed AAA tissue, rapidly expanded AAA tissue demonstrated marked increases in SMemb expression with suppressed SM2. Predominant SMemb expression indicates presence of phenotypic modulated SMCs and enhanced MMP; while abundant TIMP was seen in mature SMCs expressing SM2. SMemb expression is markedly increased in AAA with MMP enhancement, and a significant imbalance between SMemb and SM2 results in rapid progression of AAA.

Lipid peroxidation and antioxidant activities in regenerating liver after partial hepatectomy in splenectomized rats

Lipid peroxidation, antioxidant activities, and total fatty acids were investigated in the regenerating liver after partial hepatectomy in splenectomized male Wistar rats. The lipoperoxide levels were significantly lower in the splenectomized rats than in the non-splenectomized rats. The hepatic superoxide dismutase (SOD) activity was significantly higher in the splenectomized rats than in the controls, whereas the α-tocopherol content, and the activities of glutathione (GSH) peroxidase and catalase did not differ so widely between splenectomized and nonsplenectomized rats. In both groups, the fatty acid composition of the total lipids was not so different in the early stages of hepatic regeneration after partial hepatectomy, but it was noted that in the later stages of hepatic regeneration, polyunsaturated fatty acids tended to increase in the splenectomized rats. These results suggest that splenectomy attenuates lipid peroxidation, and tends to increase in polyunsaturated fatty acids in the remnant liver after partial hepatectomy, which may be attributable to high SOD activity, the maintenance of α-tocopherol, and the remaining activities of GSH peroxidase and catalase.

Free radicals in reperfusion injury after acute aortic occlusion

This investigation aims to evaluate the role of free radicals and the influence of radical scavengers in reperfusion injury of the skeletal muscle in male Wistar rats. Various parameters, including tissue blood flow, serum and calf muscle tissue levels of thiobarbituric acid (TBA) reactants, and the water content of calf muscles, were measured in the experimental setting, where infrarenal abdominal aorta was occluded for two hours followed by reperfusion with and without intraperitoneal administration of radical scavengers (superoxide dismutase or catalase). The rats were divided into four groups: group A: single laparotomy; group B: two-hour occlusion; group C: two-hour occlusion with superoxide dismutase; group D: two-hour occlusion with catalase. The increases in both serum and calf muscle tissue levels of TBA reactants following reperfusion were diminished in groups C and D as compared with those in group B. The water content of calf muscles showed a significant increase after reperfusion in group B, whereas it did not change in group D. The calf muscle tissue blood flow after reperfusion was significantly lower in group C than that in group B. These results indicate that oxygen-derived free radicals may be responsible for reperfusion injury in the lower extremity and that the attenuated blood flow during reperfusion produced by these scavengers seems to play an important role in reducing lipid peroxidation . In a clinical setting, limiting the rate of reperfusion blood flow may reduce the reperfusion injury in skeletal muscle.

Exogastrically Developed Pedunculated Epithelioid Leiomyoma of the Stomach

Epithelioid leiomyomas of the gastrointestinal tract are difficult to diagnose before surgery and their malignancy is not readily evaluated. The tumor is of smooth muscle origin, arising from the muscularis propria, and frequently develops in the gastrium, occasionally extending into the gastrocolic ligament or greater omentum. Malignancy is evaluated from the numbers of mitotic cells per 50 high power fields. However, even a tumor with few mitoses may metastatize. Thus, we propose that the malignancy of the tumor should be decided in terms of location, size, pattern of growth, invasion of the mucosa, cellularity, mitotic rate, and anaplasia. We reported a case of epithelioid leiomyoma that was pedunculated, with exogastric expansion. The literature is reviewed.

The Role of Neostigmine in Development of Acute Gastric Mucosal Lesion in Dogs with Live Bacterial Flora-Induced Shock

SummaryThe factors that frequently cause the development of acute gastric mucosal lesions (AGML) were studied in 37 mongrel dogs. Bacterial shock was induced by bolus injection of E. coli live bacterial flora (1010 cells/kg body weight) under parietal cell-stimulated condition by intravenous administration of 0.008 mg/kg per hour of pentagastrin. In addition, 0.01 mg/kg per hour of neostigmine sulfate was administered intravenously during the experiment. Frequent development of AGML was observed in the neostigmine-administered canines without significant changes in the gastric corporal and antral tissue blood flow. In the neostigmine-administered group, AGML was observed in the antrum, although in the other group AGML was mostly observed in the corpus. These results suggest that a neostigmine-induced systemic vagostimulated condition by intravenous administration of neostigmine plays an important role in the development of AGML in dogs subjected to bacterial shock.