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To investigate molecular mechanisms of growth control by diets, we examined the effects of nutrition on the expression of c-myc and insulin-like growth factor-1 (IGF-1) genes in the liver of growing rats. In the first study, rats were fed either a 24% casein, 24% zein or protein-free diet, or were starved for 3 d. The levels of the two mRNAs in the tissues were then determined by Northern blot hybridization. In the liver, levels of the two mRNAs varied in a reciprocal anner in response to changes in either quantity or quality of diet. The expression of c-myc mRNA was greatly enhanced by consumption of the protein-free diet or by starvation, whereas the IGF-1 mRNA levels were reduced markedly by consumption of the zein diet or the protein-free diet or by starvation. In another study, the casein and zein diets were fed to rats that had been adapted to a 2-h meal-feeding pattern, first with nonpurifled diet for 10 d and then with the protein-free diet for 3 d before the experiment. In rats fed casein, the level of c-myc mRNA decreased 75% within 8 h after consumption of the casein diet, whereas the IGF-1 mRNA level increased 100% during that period. Consumption of the zein diet did not affect the level of either mRNA. Because quantity of food intake did not differ between the rats fed casein and those fed zein, expression of the two genes in the liver was affected by the quality of the protein consumed. These results indicate that quality and quantity of diets changed the expression of c-myc and IGF-1 genes and thus demonstrate the possibility that nutrition not only supplies material for body components but also affects the signal transduction for growth in young growing rats.

One of the tools to test an in vitro hypothesis in vivo is transgenic/gene targeting technology. Transgenic technology provides many advantages such as: (1) the study of specific gene function as systemic and developmental effects; and (2) testing of specific gene function chronically. nevertheless, one disadvantage of this technology is the difficulty in tissue-specific targeting of the transgenic expression. Another useful tool is the in vivo gene transfer approach. Therefore, we tested a potential novel model for the study of transgene expression and knock-out using antisense technology. Here, we have demonstrated that incubation of hemagglutinating virus of Japan (HVJ)-liposome complex containing FITC-labeled oligonucleotides in the amniotic fluid of fetal rats resulted in the nuclear localization of fluorescence in the skin (epidermis and dermis). Similarly, transfection of beta-galactosidase gene resulted in positive staining in several surface layers of the skin. Thus, local gene or antisense oligonucleotide transfer approach into the skin may be useful for studying the role of autocrine/paracrine mediators and treating diseases.

In AKR/J mice inoculated intraperitoneally with protoscoleces of Echinococcus multilocularis, the oral administration of alpha-difluoromethylornithine (DFMO) in drinking water had no obvious effect on the development of hydatid cysts. The DFMO treatment also caused no apparent depletion of three major polyamines (putrescine, spermidine, and spermine) in the cysts, although a slight reduction in the putrescine level was detected. The failure of DFMO treatment to reduce the growth of cysts in mice may result from the absence of ornithine decarboxylase in the parasite.

A new method was developed for the assay of ornithine decarboxylase (ODC)-antizyme complex, in which alpha-difluoromethylornithine (DFMO)-inactivated ODC was used to release active ODC competitively from the complex. ODC-antizyme complex was present in the extracts of hepatoma tissue-culture (HTC) cells and of ODC-stabilized variant HMOA cells, in much larger amounts in the latter. Cellular amounts of the complex fluctuated after a change of medium in a similar manner in HTC and HMOA cells, increasing during the period of ODC decay. After treatment with cycloheximide, the decay of ODC-antizyme complex in HMOA cells was more rapid than the decay of free ODC, but it was much slower than the decay of free ODC or complexed ODC in HTC cells. Administration of putrescine caused a rapid increase in the amount of ODC-antizyme complex in both HTC and HMOA cells, but nevertheless the decay of total ODC (free ODC plus ODC-antizyme complex) was more rapid with putrescine than with cycloheximide. These results suggested the possibility that ODC is degraded through complex-formation with antizyme. In contrast with complexed antizyme, free antizyme was not stabilized in HMOA cells.