Strain Differences in Sensitivity to the Promoting Effect of Sodium L-Ascorbate in a Two-stage Rat Urinary Bladder Carcinogenesis Model

Rat strain differences in sensitivity to the promoting effect of sodium L-ascorbate (SA) on the development of urinary bladder tumors were investigated. In experiment 1, WS/Shi (WS), ODS/Shi-od/od (ODS), and LEW/Crj (LEW) rats were initiated with 0.05% N -butyl- N -(4-hydroxybutyl)-nitrosamine (BBN) in their drinking water and subsequently given basal Oriental MF diet (M) with or without a 5% SA supplement. In LEW rats the SA treatment increased the induction of neoplastic lesions in the urinary bladder, whereas WS and ODS animals proved unresponsive to its promoting effects. In experiment 2, WS and F344 rats were maintained on two kinds of commercial basal diets, M and CLEA CA-1 (C), during administration of SA, since dietary factors can influence promoting effects. Feeding M during the promotion period in F344 rats yielded significantly more neoplastic lesions than feeding C, but in WS rats no such dietary influence was apparent. In experiment 3, strain differences in biosynthesis of α-2u-globulin (α_2u-g) were assessed because both α_2u-g in the urine and administration of sodium salts of organic acids such as SA have been reported to be involved in tumor promotion. Immunohistochemical analysis of renal tubules and Western blotting analysis of urine revealed the presence of α_2u-g in all three strains examined. These data suggest that differences in susceptibility to promotion are due to genetic factors rather than dietary factors and the ability to synthesize . α_2u-g.     

Ultrastructural Study of Melanocytic Lesions in Albino Guinea Pigs Induced with 7,12-Dimethyl-Benzanthracene

We studied the fine structure of benign, premalignant and malignant melanocytic lesions induced in Dunkin—Hartley guinea pigs by means of topical application of 7,1 2-dimethyl-benzanthracene (DMBAI. The most noteworthy characteristics of the atypical melanocytes (melanocytic dysplasia and melanomas) were the variable morphology and structure, and, in particular, the aberrant character of the melanosomes. The melanocytes presented irregularity of nuclear outlines with requent lobulation. The heterochromatin was usually found in thick clumps reinforcing the nuclear membrane, and the nucleoli were usually multiple. The melanosomes were ellipsoidal and spherical with a pattern that was lamellar, concentric, incomplete, and even microgranular and microvesicular. The melanization was usually in thick, irregular clumps. Melanosome complexes were always present.     

125I对大鼠甲状腺致瘤作用的病理研究

本文报道用雄Wistar大鼠,腹腔注射不同活度的¹²⁵I后,观察两年的结果。6个实验组动物甲状腺所受剂量分别为187、129、94、56、18,8和9,3Gy。实验结果表明l 18,8～9dGy可能是¹²⁵I的最适致癌剂量范围;56Gy可能是最适致癌剂量;9,3Gy组与对照组差别不明显。推测¹²⁵I在18,8Gy以下可能有一不致癌的剂量限值。当¹²⁵I剂量大于129Gy时甲状腺发生退行性变。¹²⁵I诱发的甲状腺癌以滤泡性腺癌和髓样癌为主。电镜观察证明,除髓样癌发自滤泡旁细胞外,其它良性瘤和恶性瘤均发自甲状腺滤泡上皮细胞。