Effect of vitamin A on epitheliomesenchymal interaction during odontogenesis and oncogenesis in NMU-treated hamster.

1) nmu诱导的下颌切牙牙体发育障碍表现为发育不全，从牙釉质色素缺失、牙釉质发育不全到牙釉质缺失、牙本质形成不规则发育不全。这些变化在视黄醇棕榈酸酯（RP）加NMU治疗的动物中比单独使用NMU治疗的动物更为明显。2) RP与NMU联合使用时，牙源性上皮细胞巢在切牙区增生并形成牙本质发育不良的频率增加。3) RP + nmu处理的仓鼠，牙本质形成的牙源性上皮发生肿瘤改变的频率和程度均增加。4)在nmu处理的仓鼠中，过量的β -胡萝卜素轻微地阻止了牙生成的干扰，牙源性上皮的非典型增殖和上皮成分的角化。5) NMU抑制成釉细胞的分化，但未阻止成牙釉质细胞的分化和前成釉细胞与成牙釉质细胞之间的细胞间接触。RP和β -胡萝卜素不能阻止nmu诱导的成釉细胞分化抑制，但可以抑制nmu诱导的牙源性上皮角质化。RP + NMU治疗诱导牙本质形成的牙源性上皮不典型增生是由于抑制了鳞状皮化生和上皮角化。6) RP + NMU治疗可降低牙龈或前胃上皮肿瘤侵袭的发生率。7) β -胡萝卜素对牙龈鳞状细胞癌的肿瘤生长有中等抑制作用，对前胃鳞状细胞癌的肿瘤生长有轻微抑制作用。8)大剂量β -胡萝卜素诱导nmu处理的仓鼠胆管腺纤维化样增生和腺胃粘膜下层梭形细胞增生。

1) NMU-induced disturbances in odontogenesis of the cut mandibular incisors was hypoplasia ranging in extent from loss of pigment of enamel and enamel hypoplasia to loss of enamel and irregular hypoplastic dentin formation. These changes of the incisors were more prominent in animals treated with retinol palmitate (RP) plus NMU than those in the animals treated with NMU alone.2) When RP was administered in combination with NMU,there was an increase frequency of odontogenic epithelial cell nests' proliferation with dysplastic dentin formation at the incisal region.3) In RP plus NMU-treated hamsters, the frequency and degree of neoplastic changes of the odontogenic epithelium with dentin formation were increased.4) In NMU-treated hamsters, an excess of beta-carotene slightly prevented the disturbances in odontogenesis, atypical proliferation of odontogenic epithelium, and keratinization of epithelial component.5) NMU inhibited ameloblast differentiation, whereas, the differentiation of odontoblasts and cell-to-cell contact between preameloblasts and odontoblasts were not prevented. RP and beta-carotene did not prevent NMU-induced inhibition of ameloblast differentiation but inhibited NMU-induced keratinization of odontogenic epithelium. Atypical proliferation of odontogenic epithelium with inductive dentin formation caused by RP + NMU treatment resulted from the inhibition of squamous metaplasia with keratinization of the epithelium.6) RP plus NMU treatment resulted to a decrease in incidence of neoplastic invasion of the epithelium in the gingiva or forestomach.7) beta-carotene has moderate suppressive effect on tumor growth of the gingival squamous cell carcinoma and slight effect on squamous cell carcinoma of the forestomach.8) Administration of large quantity of beta-carotene induced adenofibrosislike proliferation of the bile ducts and proliferation of spindle-shaped cells in the submucosa of the glandular stomach in NMU-treated hamsters.