A thymus szerkezete a huszonegyedik század elején

The classical histological features of the thymus are the cortex and medulla, the Hassall’s bodies as well as the lobules. Anti-pan-cytokeratin immunocytochemistry shows that the keratin staining pattern of the cortical and medullary epithelial cells is different. The medulla is further compartmentalized: it consists of keratin-positive network and keratin-negative areas. Histology of the keratin-negative area is identical with the connective tissue of the septae. The basal lamina is continuous at the capsule and septae, but it becomes discontinuous at the border between the keratin-positive network and keratin-negative area. This immunohistochemical finding is the first histological sign, which may explain that the medulla has no blood-thymus barrier. The supporting tissue of the keratin-negative area is identical with that of the septae. The connective tissue of thymic capsule and septae develops from the cranial neural crest cells, therefore we hypothesize that the keratin-negative area has neural crest origin. Blood vessels of the thymic medulla localize in the keratin-negative area. Every emigrating or immigrating immunologically competent cells should enter the keratin-negative area, therefore this area is the transit zone of the thymus. The hematoxylin-eosin staining of the thymus shows that the thymic cortico-medullary border does not represent cellular background. However, the border between keratin-positive network and keratin-negative area is determined by cellular identity (epithelial and mesenchymal tissues). Therefore, it can be assumed that the real histological and functional border is the border between the keratin-positive network and the keratin-negative area. Orv Hetil. 2019; 160(5): 163–171.

Mesenchymal Stem Cells with Enhanced Bcl-2 Expression Promote Liver Recovery in a Rat Model of Hepatic Cirrhosis

Background/Aims: Mesenchymal stem cell (MSC) transplantation has emerged as an option for the treatment of chronic hepatic cirrhosis, while its therapeutic efficacy could be improved. The bcl-2 gene is anti-apoptotic and can help cell survival and proliferation. Therefore, we explored whether transplanted MSCs with enhanced bcl-2 expression may be beneficial in the treatment of experimental cirrhosis in rats. Methods: MSCs were isolated from rat bone marrow, expanded in vitro and transfected with adeno-associated virus (AAV) engineered the bcl-2 gene (AAV-bcl-2). Rats with cirrhosis induced by carbon tetrachloride (CCl4) were treated with AAV-bcl-2 infected BMSCs-AAV-bcl-2, with the cells traced in vivo post transplantation. Liver pathology and function were evaluated 7, 14, 21, and 28 days post transplantation, respectively. Results: On day 7 post transplantation, the infused AAV-bcl-2 had integrated into the hepatocyte-like cells (HLCs) that expressed albumin (ALB), Cytokeratin 18 (CK18), and hepatocytes nuclear factor 4a (HNF4a). On day 28 post transplantation, rats in the cirrhosis + BMSCs-AAV-bcl-2 group showed the most dense HLCs, highest mRNA and protein levels of ALB, CK18, and HNF4a, compared to the other groups. Their liver function recovered most rapidly in 4 week observation, while histological sign of cirrhosis remained at the end of this period. Conclusion: BMSCs over expressing bcl-2 gene showed better survival, and enhanced the differentiation into hepatocytes-like cells, and appeared to promote the recovery of liver function in rats with experimental cirrhosis.

The Role of White Blood Cells in Post-Mortem Wounds

Walcher in 1936 pointed out the importance of studying a lesion microscopically in order to distinguish between ante-mortem and post-mortem injuries. According to him and to many other authors (Raekallio, 1984; Ojala et al., 1969; Fatteh, 1966) leucocytic reaction is the earliest histological sign of inflammation, and it is the most reliable sign of the vitality of wounds. The pavementation (also known as margination) of the vascular endothelium of white blood cells, and the beginning of their extravasation, may be seen during the first hour (Ojala et al., 1969), 6 hours (Malik, 1970), 8 hours (Fatteh, 1966) or 8–16 hours (Raekallio, 1964) after the injury. Profuse bleeding and fibrin deposition are no longer regarded as necessarily signs of vitality of wounds. (Shapiro and Robertson, 1962; Laiho, 1967), yet the behaviour of white blood cells in post-mortem wounds remains unknown. It was therefore decided to study the effects of chemotactic materials injected intradermally and in the anterior abdominal wall in dead rats. The experimental findings are presented, along with discussion, and a review of the literature.

Histopathological changes in the pancreas of laboratory rats

'Chronic relapsing pancreatitis' was seen in 81 per cent of 108 rats of 3 inbred strains. Clinically, even in advanced cases, there were no symptoms of disease and the physical status of the animals was satisfactory. The least histological sign of involvement was a decrease or loss of cytoplasmic basophilia in acinar cells in some lobules, and infiltration of the intralobular connective tissue by mononuclear cells. More severe forms of the disease were characterized by flattening of the epithelium of acini by 'microcystic-transformation' of the gland, and fatty atrophy. Fibrosis of the connective tissue and dilatation of the ducts were usual events. In few cases 'polyarteritis-like' lesions of the arteries of the pancreas were observed. Microbiological investigation of the aetiology is in progress.