There are a large number of αemitters with long-life in nuclear materials inventories and nuclear waste around the world, including Pu and minor actinides (Np, Am, and Cm). 1,2 These long-lived actinides are suggested to be separated than being immobilized in mineral-based ceramics to prevent the migration of radionuclide in the biosphere. 3 Monazite has been proposed as the potential actinides host-matrices owing to its excellent long-term stability. 4-6 An 3+ PO 4 monazite waste forms can be easily obtained from Pu to Es by wet or dry chemistry methods. 7 In contrast, some front actinides (from Th to Np) with the stable tetravalent oxidation state require a coupled substitution of divalent cation for their incorporation in monazite by solid state sintering methods. According to the description by Podor, 8 the formation of M 3+ 1−2x Ca 2+x An 4+x PO 4 (An 4+ = Pu 4+ , U 4+ , Th 4+ ) monazite is restricted by the

It was speculated that vasectomy might induce hyperplasia of Leydig cells associated with atrophy of seminiferous tubules, but estimates of the Leydig cell number were lacking in previous studies. This study aimed to test the speculation by determining the numerical change of Leydig cells and other interstitial cells after a vasectomy that induced spermatogenic damage. Twelve adult Japanese white rabbits and twelve mature Sprague-Dawley rats were subjected to a unilateral vasectomy away from the scrotum. Six months (rabbits) or thirty-seven days (rats) postoperation, testes on both sides were removed and methacrylate sections prepared. The total numbers (per testis) of all nuclei in the testicular interstitial tissue were estimated with a stereological technique -the optical disector. The results showed that marked spermatogenic damage associated seminiferous tubular atrophy on the vasectomized side occurred in 7 (rabbits) or 5 (rats) of the 12 animals. For the rabbit, the total numbers of myoid cells or leukocytes on the vasectomized side (compared with the contralateral nonvasectomized side) were unchanged but those of Leydig cells and other interstitial cells increased significantly by 41% and 52%, respectively, (a) with the increase in the testis with spermatogenic damage appearing to be larger than that in the testis without spermatogenic damage and (b) without significant increase in the total volume of the interstitium. For the rat, there were no significant differences in the total numbers of any cell type. In conclusion, hyperplasia or hyperproliferation of the interstitial cells, which might be a result of increased intra-testicular pressure for long, was possible postvasectomy, but it might not be indicative of a better function of the cells.