The periodic acid-silver methenamine method and the periodic acid-thiocarbohydrazide-silver proteinate method have been used for the demonstration of carbohydrates in various plant and animal tissues. The comparison of the results obtained with both methods indicates that the periodic acid-thiocarbohydrazide-silver proteinate method is more specific and gives better quality pictures than the PA-silver methenamine method. It is pointed out that adequate controls are necessary for a valid cytochemical interpretation of the results. With the PA-thiocarbohydrazide-silver proteinate method, no positively stained structure can be assumed to be of carbohydrate nature unless it is found unstained in non-oxidized thiocarbohydrazide-silver proteinate treated sections. Both methods have their limitations and do not demonstrate the total carbohydrate amount in tissue sections.

Hormone production was studied in situ by immunocytochemical methods in 20 pituitary adenomas. Special attention was given to 13 adenomas removed from acromegalic patients. Out of them, 6 had mild to moderate hyperprolactinemia. Immunohistochemistry revealed PRL-containing cells without any close relationship with high PRL serum level in 6 patients. Double immunogold staining revealed mammosomatotrope cells characterized by simultaneous presence of GH and PRL in the same granules in 2 patients. Since mammosomatotropes have never been demonstrated in the normal pituitary, our results probably signify gene dysregulation in pituitary cells of those acromegalic patients.

The modifications of mouse mast cells incubated in solutions of polylysine at two different concentrations are studied. At higher dose (0.5 mg/ml), the polycation has evident toxic effects. At lower dose (0.5 micrograms/ml), it induces some modifications of the granule morphology. Cytochemical reactions to demonstrate polyanions, basic proteins and organic bases are used to study the granule content. A polylysine treatment promotes the release of basic groups (vaso-amines) and sulphydryl-containing compounds (basic protein) from the mast cell granules. On the contrary, polyanions remain in the cells and correspond to the granule matrix persisting after amino-liberator treatment.

Fractionated whole-body irradiation induces thymic lymphomas in most of treated C57Bl/Ka mice. The cellular events occurring during the latency period consist of the emergence of preleukaemic cells and of marked alterations to the T-cell lineage and the microenvironment within the thymus. The proportions of the various thymocyte subsets are modified, suggesting a blockage in the normal differentiation process. Thymic epithelial cells are functionally modified, leading to decreased interactions with immature thymocytes. Interestingly, bone marrow grafting early after irradiation, which inhibits the development of lymphomas, induces the disappearance of preleukaemic cells from the thymus, whereas thymocyte subpopulations and thymic epithelium are restored. Interferon gamma and tumor necrosis factor alpha also prevent the onset of lymphomas. Studies on the effect of bone marrow transplantation and cytokine inoculation in split-dose irradiated mice should allow characterization of the factors that modulate the progression of preleukaemic cells towards the neoplastic state.

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