No abstract

We investigated the potential toxicity of gum ghatti, which is added to food for emulsifying, thickening, and stabilizing, after 4 weeks of repeated oral administration at a dose of 8000 mg/kg/day to male and female SD rats. Although food consumption was significantly reduced in males in the gum ghatti group compared with those in the distilled water group from Day 18 onwards, the change was minor, there was no pathological evidence of digestive tract abnormalities, and there were no significant changes in body weight; therefore, the change in food consumption was judged to be of no toxicological significance. Hematology and blood biochemistry revealed statistically significant differences in some parameters between the gum ghatti group and the distilled water group. These changes were all within the normal range of physiological variation and therefore were not considered to represent the effects of gum ghatti. In addition, general signs, body weight, and pathology showed no changes in either sex attributable to gum ghatti. Thus, all changes observed were of no toxicological significance and within the normal range of physiological variation, suggesting gum ghatti has no toxic effects in rats.

In peripheral tissues, cells are maintained in the interstitial fluid that flows from capillaries to lymph system. However, the brain has no lymphatic capillaries, and the actual state of the interstitial fluid has long been unknown. Recently, a glymphatic system has been proposed in which part of the cerebrospinal fluid flowing on the surface of brain tissue enters the brain parenchyma via the peri-arterial space, becomes interstitial fluid, and then flows out again from the peri-venous space. Brain injury due to head contusion or stroke is thought to impair the intracerebral circulation and aggravate the extracellular environment, but the actual situation is unknown. Therefore, in this study, we examined the effects of focal brain tissue damage on intracerebral circulation using the light-injured mouse, an originally developed closed head injury model. In light-injured mice, the injury-making process does not affect intracerebral circulation because the cranium is maintained. However, this method has quantitative problems, so we developed a method to image cerebrospinal fluid and blood vessels from the surface of the cerebral cortex. After examining different injury sites and different time periods after injury, it was found that intracerebral circulation was reduced to the same extent on the ipsilateral and contralateral sides of the injury at one-week post-injury. This intracerebral circulatory deficit was still partially present at four-weeks post-injury. These results indicate that the intracerebral circulation is extensively impaired by local injury and neurodegenerative diseases.

The pathological effects of copper deficiency (COD) are well known. However, the pathogenesis of cardiomyopathy resulting from COD remains unclear. In this study, aimed to elucidate the pathogenesis of COD-induced cardiomyopathy by examining the morphology of the cardiovascular system in copper-deficient rats using histopathology, immunohistochemistry, and scanning and transmission electron microscopy. Changes detected in the myocardium and interstitium were consistent with those reported for COD. Morphological changes included mesh-like changes in the capillary endothelial cells that appear to be a novel finding in COD-induced cardiomyopathy. These changes are hypothesized to result from abnormal vascular remodeling following damage to the basement membrane and due to the mechanical effects of myocardial contractions. Although cardiomyopathy may be associated with microcirculatory disorders arising from these lesions, further investigations are necessary to demonstrate a causal relationship between the pathogenesis of cardiomyopathy and the contribution of these lesions to disease progression.

Spontaneous hemangiosarcoma in young rats is rare. In this report, we describe a case of a spontaneous hemangiosarcoma in the spleen and liver of young rats. At necropsy, multiple pale red masses were observed in the spleen. Histopathologically, solid growth and haphazardly arranged neoplastic cells were observed, although no characteristic growth pattern was observed. In contrast, irregularly sized small slit-shaped spaces containing erythrocytes were found among the neoplastic cells. Reticular fibers incompletely surrounding the neoplastic cells were observed by silver staining. Immunohistochemistry revealed that the neoplastic cells were positive for vWF and CD34. Electron microscopic examination revealed that the neoplastic cells had erythrocytes in the lumen and Weibel-Palade bodies in the cytoplasm and were arranged along a discontinuous basal lamina. These features indicate that the tumor originated from vascular endothelial cells. Based on these results, the tumor was diagnosed as a hemangiosarcoma in the spleen and liver.