No abstract

The quantitative method of measuring fibroblart precursors in populations of hcmatopoietic cella dcmonstrates that their concentration in blood doea not depend on the number of heart puncturw during blood collection. This meana that fibroblaat colonies, originating in monolayer culturw of blood cella, develop from circulating blood ah. From the indices of aH-thymidine labeling it is calculated that the mean generation time for fibroblasts in seven and llday cultures is 34 to 43 hours and that the proliferative pool in fibroblast colonier ia not less than 84 and 79 per cent respectively. The concentration of fibroblast precursors among nucleated cells of peripheral blood of guinea pigs ranges between 0.2 and 2 x 1 4 6 .

Bone formation in organ cultures of intact marrow fragments from mouse is described. Marrow explants were cultured on the top surface of a millipore filter at a gas-liquid interface. Observations with both light- and electron microscopes demonstrated the formation of a well-organised trabecular matrix lined with osteoblast-like cells. The tissue and cells were positive for alkaline-phosphatase activity. Large amounts of thick, well-banded collagen fibrils and matrix vesicles typical of those found in bone were present. The tissue became mineralised in the presence of 10 mM Na-beta-glycerophosphate; in its absence a similar trabecular matrix developed but mineralisation did not take place.

Sera from healthy people and from patients with schizophrenia were heated at 560 for 30 min and then kept at 4'. These sera were then tested for cytotoxicity and by the indirect immunofluorescerice method with thymocytes, bone-marrow cells, and lymph-node cells of adult C3H mice. The cytotoxicity index for mouse thymocytes of sera from 60 healthy donors ranged from 0.00 to 0.4, with an average of 0.08. That of sera from 35 patients with schizophrenia ranged from 0.29 to 0.91, with an average of 0.71. The cytotoxicity index for mouse bone-marrow cells of sera from healthy donors ranged from 0.03 to 0.23, whereas that of sera from patients with schizophrenia ranged from 0.00 to 0.14. Sera of patients at dilutions of 1: 8-1:32 displayed immunofluorescence of almost 100% of thymocytes and 58-78% of lymphocytes, whereas sera of healthy donors displayed none. We thus conclude that the sera of patients with schizophrenia contain antibodies against thymic antigens localized on thymocytes and thymus-derived lymphocytes.

Livers from 17to 20-day CBA mouse embryos were maintained for three weeks in organ culture. During this period, hematopoiesis continued; morphologically recognizable cells were identified until day 24 and hematopoietic cells with colony forming ability were present until day 23. The method appears to hold promise for studies of hematopoietic differentiation in vitro.