Histological and ultrastructural changes induced by selenium in early experimental gastric carcinogenesis

AIM： To investigate the effect and significance of selenium in early experimental gastric carcinogenesis. METHODS： Weaning male Wistar rats were divided randomly into normal control group, experiment control group, low selenium （2 mg/L） group and high selenium （4 mg/L） group. Wistar rat gastric carcinogenesis was induced by N-methyl-N-nitro-N-nitroso guanidine （MNNG） （20 mg/kg） gavage dally for 10 d. Na2SeO3 was given by piped drinking 1 wk prior to MNNG gavage. The rats were killed at the 43^rd wk. The surface characteristics of gastric mucosa were observed with naked eyes. Histopathologic changes of rat gastric mucosa were observed by HE staining and AB-PAS methods. The changes of cellular ultrastructure were observed under transmission electron microscope. Statistical analysis was carried out by SPSS. RESULTS： The incidence rate of gastric mucosa erosion, hemorrhage and intestinal metaplasia was 0, 45.5%, 66.7%, and 92.9%, respectively （92.9% vs 45.5%, P〈0.05） in the normal control group, experiment control group, low selenium group, and high selenium group. Leiomyoma formed in the process of inducement of rat gastric carcinoma. Dietary Na2SeO3 （2 and 4 mg/L） slightly increased the incidence rate of leiomyoma （0.23%, 46.6%, and 46.6%）. gastric mucosa did not change in the course of rat gastric carcinogenesis. Dietary Na2SeO3 by pipe drinking could expand the intracellular secretory canaliculus of parietal cells and increase the number of endocrine cells and lysosomes. CONCLUSION： Dietary Na2SeO3 by pipe drinking aggravates gastric erosion, hemorrhage and promotes intestinal metaplasia of gastric mucosa. The mechanism may be related with the function of parietal cells.

The Variability of the Narrow-line Seyfert 1 Galaxies from the Pan-STARRS's View

By means of the data sets from the Pan-STARRS1 survey, we have systematically examined the relationship between the variability characteristics and the physical parameters of the largest NLS1 galaxy sample up to now.The results are summarized as follows:(1). We find significant anti-correlations between variability amplitude and absolute magnitude in g, r, i, z and y bands, which are consistent with the results in previous works.(2) The correlations between the variability amplitude in optical band and many physical parameters(e.g., λL(5100 A),black hole mass, Eddington ratio, R;and R;) are investigated. The results show the variability amplitude is significantly anti-correlated with L(5100 A), MBH, Eddington ratio and R_(4570), but positively correlated with R;.The relation could be explained by the simple standard accretion disk model.(3) We further investigate the relationship between optical variability and radio luminosity/radio-loudness. The results present weak positive correlation in g and r bands, but insignificant correlation in i, z and y bands. The large error of the approximate fraction of the host galaxy in i, z and y bands may lead to insignificant correlations.