Evaluation of potential activity of luseogliflozin on vascular proliferation in the mesenteric lymph node with or without vascular tumors in Sprague-Dawley rats in a carcinogenicity study

Morphological analysis of patchy thickening and reddish discoloration of active hair growth areas in the skin of New Zealand White rabbits

Patchy thickening and reddish discoloration of active hair growth areas of skin in rabbits are occasionally found, and this gross feature could affect precise evaluation when conducting a dermal irritation test. Since little is known about the mechanism of this phenomenon, we examined the dorsal skin of New Zealand White rabbits morphologically and immunohistochemically in order to identify the possible mechanism responsible for developing these skin changes in relation to the hair cycle. Skin samples from 4 rabbits were divided into three groups (5 samples/group) based on their macroscopic characteristics: a thickened skin, erythematous skin, and smooth skin group. Histomorphological examination revealed that the percentage of hair follicles in the anagen phase, hair follicle length, hair follicle area, and proliferating cell nuclear antigen-positive cells in the hair follicles were greater in the thickened skin and erythematous skin groups than in the smooth skin group. Unlike mice and rats, the dermis was nearly adjacent to the muscular layer with a thin hypodermis, and the whole lengths of hair follicles in the anagen phase were located in the dermis in the rabbit skin. These results suggest that large hair follicles in the anagen phase compressed the surrounding dermis; therefore, the skin was grossly raised and showed thickening. A higher number of CD31-positive blood vessels, suggesting the occurrence of angiogenesis, was observed around the hair follicles in the erythematous skin group, and they seemed to affect the reddish discoloration of skin noted grossly.

Metastatic hemangiosarcoma of the liver in a young rat

Spontaneous hemangiosarcoma is generally uncommon in rats. Furthermore, there are only a few case reports in young rats. This report describes a spontaneous hemangiosarcoma in a young 7-week-old rat. At necropsy, no remarkable changes were noted in any organs including the liver. Histopathologically, multifocal small tumors were located mainly in the perilobular region of the liver. The tumors comprised polygonal to short spindle-shaped cells that showed cellular atypia and local infiltration. In the foci, there were blood-filled spaces lined by spindle-shaped cells. Reticular fibers, which were loosely connected together and formed an irregular network within the foci, were noticed with Azan and silver stain. Immunohistochemistry revealed that tumor cells expressed vascular endothelial cell markers: von willebrand factor and CD34, respectively. These features indicate that the tumor originated from vascular endothelial cells. Although the primary lesion was uncertain, the foci were all small and multicentrically located mainly in the perilobular region, indicating that the liver lesion likely formed by hematogenic metastasis. Taken together, we diagnosed this case as a metastatic hemangiosarcoma.