SummaryOsteopetrotic (op/op) mice have a severe deficiency of osteoclasts, monocytes, and peritoneal macrophages because of a defect in the production of functional macrophage colony-stimulating factor (M-CSF) resulting from a mutation within the M-CSF gene. In this study, we examined whether daily 5-,ug injections of purified recombinant human M-CSF (rhM-CSF) for 14 d would cure these deficiencies in the mutant mice. Monocytes in the peripheral blood of the oplop mice were significantly increased in number after subcutaneous injections of the factor two or three times a day. In contrast, osteopetrosis in the long bones of op/op mice was completely cured by only one injection of rhM-CSF per day. Bone trabeculae in the diaphyses were removed . Many osteoclasts were detected on the surface of bone trabeculae in the metaphyses . Although development of tooth germs ofuninjected oplop mice was impaired, rhM-CSF injection restored the development ofmolar tooth germs and led to tooth eruption as a consequence ofthe recovery ofbone-resorbing activity. These results demonstrate that M-CSF is one ofthe factors responsible for the differentiation of osteoclasts and monocyte/macrophages under physiological conditions.

SummarySevere deficiency of osteoclasts, monocytes, and peritoneal macrophages in osteopetrotic (op/op) mutant mice is caused by the absence of functional macrophage colony-stimulating factor (M-CSF). To clarify the role of M-CSF in the osteoclast differentiation, we established a clonal stromal cell line OP6L7 capable of supporting hemopoiesis from newborn op/op mouse calvaria . Although very few macrophages appeared in the cocultures of bone marrow cells and OP6L7 cells, a 50-fold larger number of macrophages was detected in the day 7 cocultures when purified recombinant human M-CSF (rhM-CSF) was exogenously supplied . Tartrate-resistant acid phosphatase (TRACP; a marker enzyme of osteoclasts)-positive cells appeared only when bone marrow cells were cultured in contact with OP6L7 cells and both rhM-CSF and lot, 25 (OH)2D3 were added. The TRACK positive cells became multinucleated with increasing time in culture and expressed the cfmsIM-CSF receptor. These results indicate that both contact with stromal cells and M-CSF are requisite for osteoclast differentiation under physiological conditions .

Oral inoculation of human rotavirus MO strain (serotype 3) into 5-dayold BALB/c mice cause gastroenteritis characterized by diarrhea. Clinical symptoms, histopathological changes in the small intestine, and the detection of rotavirus antigen in enterocytes were all characteristic of rotavirus-induced gastroenteritis. Using this small animal model, passive protection of suckling mice against human rotavirus infection was achieved with the use of immunoglobulin (IgY) from the yolks of eggs of rotavirus-immunized hens. When IgY against a rotavirus strain homotypic to the challenge virus (MO strain) was administered in the mice, complete protection against rotavirus infection was achieved. On the other hand, with oral administration of IgY against a heterotypic strain (serotype 1 , Wa strain), a lower protective effect was nevertheless obtained. The four different strains of human rotavirus (Wa, KUN, MO, and ST3) were inactivated in vitro by treatment with PSK, a protein-bound polysaccharide preparation, in a dose-dependent manner . Oral administration of 2.5 mg of PSK caused a therapeutic effect on experimentally MO-infected suckling mice. The antiviral effect of PSK was indicated by the reduction of the duration of diarrhea.

SummaryThe preadipose cell line, PA6, can support long-term hemopoiesis. Frequency of the hemopoietic stem cells capable of sustaining hemopoiesis in cocultures of bone marrow cells and PA6 cells for 6 wk was 1/5.3 x 10 4 bone marrow cells. In the group of dishes into which bone marrow cells had been inoculated at 2.5 x 10 4 cells/dish, 3 of 19 dishes (16%) contained stem cells capable of reconstituting erythropoiesis of WBB6FI-kV/W ~ mice, indicating that PA6 cells can support the proliferation of primitive hemopoietic stem cells. When the cocultures were treated with an antagonistic anti-c-kit monoclonal antibody, ACK2, only a small number of day 12 spleen colony-forming units survived; and hemopoiesis was severely reduced. However, when the cocultures were continued with antibody-free medium, hemopoiesis dramatically recovered. To examine the proliferative properties of the ACK2-resistant stem cells, we developed a colony assay system by modifying our coculture system. Sequential observations of the development of individual colonies and their disappearance demonstrated that the stem cells having higher proliferative capacity preferentially survive the ACK2 treatment. Furthermore, cells of subclones of the PA6 clone that were incapable of supporting long-term hemopoiesis expressed mRNA for the c-kit ligand. These results suggest that a mechanism(s) other than that involving c-kit receptor and its ligand plays an important role in the survival and proliferation of primitive hemopoietic stem cells.

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