Kyoichi Nakamura

Early loss of myocardial myoglobin detected immunohistochemically following occlusion of the coronary artery in rats

The time course of the loss of myoglobin from the rat ventricular myocardium in the early phase of ischemia was studied with the use of an immunohistochemical technique and an image analyzer. The loss of myoglobin, as an index of myocardial injury, was evident in the left ventricular subendocardium as early as 0.5 hr after occlusion of the left main coronary artery. A clear-cut demarcation of the myoglobin-depleted area helped quantification of the injured areas with an image analyzer. The area with depleted myoglobin became transmural and reached maximum after 2 and 3 hr of occlusion, respectively. Electron microscopic observation of the myoglobin-depleted region revealed amorphous dense bodies in the mitochondria, indicating irreversible damage to the myocardial cells. On the other hand, no irreversible changes could be detected with hematoxylin-eosin stain until 6 hr after the start of the ischemia, and the distinction between the reversible and irreversible areas was unclear. We suggest that depletion of myoglobin from the myocardium serves as a marker for irreversible ischemic injury. Quantitative assessment of the injured areas by immunohistochemical staining for myoglobin together with an image analyzer could be of great value for the evaluation of early ischemic myocardial damage.

Primary Gastric Malignant Lymphoma: A Morphological and Immunohistochemical Study of 38 Cases

Thirty eight cases of primary gastric malignant lymphoma were studied morphologically and immunohistochemically. The Working Formulation was used for classification of non‐Hodgkins lymphoma (1). The results indicated that 37 cases were non‐Hodgkins lymphoma while the remaining case was Hodgkins disease. Thirty‐three cases (89%) of non Hodgkins lymphoma were considered to be of B cell origin and 2 cases (5%) of histiocytic origin. No case was considered to be of T cell origin. We suggest that the majority of primary gastric malignant lymphomas are derived from follicular center cells, and that gastric plas‐macytoma is not as rare as previously described. Acta Pathol Jpn 39: 229–234, 1989.

Objective Quantification of Grade of Atypia in Epithelial Tumors of the Stomach by Image Processing

An image processing technique to extract tubular and nuclear areas from histological specimens stained with hematoxylin was established. Two indices representing tubular density and nucleus‐to‐cytoplasm ratio of glands were examined in intestinal‐type tumor of the stomach. In specimens clearly stained with hematoxylin, significant differences of brightness among nuclei, cytoplasm and stroma can be obtained. Image processing by computer enabled us to identify nuclei, cytoplasm and stroma by utilizing the differences of brightness among them. Both indices tended to increase with severity of histological atypia and their values in the tubular adenoma group were significantly different from those in the tubular adenocarcinoma group (P< 0.05). Therefore, these two indices could be regarded as valid and objective measures of the grade of histological atypia. Eighty‐four percent of tubular adenoma and tubular adenocarcinoma cases were classified correctly with the discriminant formula and critical value calculated from the two indices on the basis of measurement of the images magnified by 40 times. There is, however, still a non‐negligible overlap of discriminant scores between the tubular adenoma group and tubular adenocarcinoma group. More indices representing histological atypia will be required to allow objective differential diagnosis between malignant and benign lesions.

Chronic toxicity of charred fish meat in Wistar rats

An experiment was performed on Wistar rats to examine the possible carcinogenic effects of charred fish meat. Each group (of 30 male rats each) was fed one of the following diets: the standard diet mixed with 50% charred fish meat (Group 1), the standard diet mixed with 25% charred fish meat (Group 2), the standard diet alone (Group 3), or the 1-methyl-3-nitro-1-nitrosoguanidine (MNNG) treatment in drinking water (Group 4); this last group served as positive control. The animals were observed for two years. No significant incidences of tumors were recorded. However, there were statistically significant incidences of nonspecific pathological lesions of the glandular stomach, such as erosion, regeneration, and hyperplastic epithelium. Also, an atypical epithelium of the stomach was found incidentally in two animals (Groups 1 and 2); this might suggest a premalignant condition.