The effects of N4-behenoyl-1-beta-D-arabinofuranosylcytosine (BH-AC) on the cell cycle of murine leukemic cells (L 1210 cells) were compared with those of 1-beta-D-arabinofuranosylcytosine (ara-C), known to be effective for acute leukemia. In a cytokinetic study, a combination of Feulgen microcytofluorometry and tritiated thymidine autoradiography (3H-TdR ARG) was used to measure DNA content and to determine DNA synthesis simultaneously in a single cell. Administration of 200 mg/kg of BH-AC significantly prolonged the survival time of mice bearing L 1210. In addition, the cells in the G1 + S1 phases increased with time, accounting for 94.4 per cent of all cells measured at 48 h after the administration, compared to 73.7 per cent before administration. On the other hand, following the administration of 86 mg/kg of ara-C (equivalent to 200 mg/kg of BH-AC), the percentage of cells in the S1 + S2 phases increased maximally to 75.9 per cent at 18 h. Cytokinetic studies further showed that BH-AC administration blocks DNA synthesis of the cells in the S-phase for a longer period than does ara-C. These results suggest that the prolonged inhibition by BH-AC on DNA synthesis allows cells to accumulate in the S-phase to a greater degree.

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Inhibins in the male Göttingen miniature pig: Leydig cells are the predominant source of inhibin B.

The expression of inhibin subunits in the testes of the Göttingen miniature pig was examined by in situ hybridization and immunohistochemistry. In addition, the major forms were determined by enzyme-linked immunosorbent assay (ELISA). Strong positive immunostaining for the inhibin alpha subunit was observed in Sertoli and late-stage germ cells, but it was weak in Leydig cells. However, Leydig cells showed strong positive staining for the betaA subunit, but Sertoli cells and spermatogonia showed a weak reaction. Strong positive immunostaining for the betaB subunit was observed in Leydig cells but spermatogonia showed weak staining for it. In contrast to the staining specificity of inhibin alpha and betaA subunits, the betaB subunit did not exhibit positive staining in Sertoli cells. In situ hybridization revealed that although the a subunit mRNA signal was highly expressed in all cell types, the reaction appeared to be stronger in Sertoli cells and spermatogonia than in Leydig cells. betaA subunit mRNA expression was somewhat identical to that of the alpha subunit, however, germ cells showed a weak stain for it. A strong, positive mRNA signal for the betaB subunit was confined to Leydig cells and late-stage germ cells. ELISA results showed that concentrations of inhibin B and inhibin pro-alphaC were high in the circulation and testes. In contrast, inhibin A levels in both plasma and testes were undetectable. The present results strongly suggest that inhibin B is the major form of circulating inhibin and that Leydig cells are the predominant source of this dimeric inhibin in male Göttingen miniature pigs. Furthermore, the germ cells also appear to be an important source of circulating inhibins.

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