Effect of pH on anisotropic gelation of DNA induced by aluminum cations.

To investigate the effects of pH on the structure and the properties of DNA anisotropic gels and their growth process, we have observed the morphology of DNA anisotropic gel films prepared from DNA solutions with various initial pH, and measured the pH dependences of the shrinking ratio, the birefringence, and the relaxation modulus of the gel as well as the time courses of the gel front and pH-change front lines. The gel films prepared from DNA solutions with high pH have inhomogeneous macroscopic structure, large shrinking ratio, and high optical anisotropy whereas those prepared from DNA solutions with low pH have homogeneous macroscopic structure, small shrinking ratio, and low optical anisotropy. The difference observed at different pH is attributed to the difference in the interaction between DNA molecules and aluminum cations. The time courses of the gel front and pH-change front lines were analyzed with theories based on assumptions for each condition. Both two-stage dynamics observed under high initial pH and one-stage dynamics under low initial pH were explained consistently with the theories.

Bio-kinetics of radon ingested from drinking water.

Previous studies have identified the stomach as the most significant organ for the dose from ingested radon. An important factor in dosimetric modelling is the rate of radon loss from the stomach. In the present study, two subjects who ingested radon-rich water were measured using a NaI(Tl) detector fixed over the stomach. The counting rates for 214Pb and 214Bi peak regions were plotted as a function of time after ingestion. These data were interpreted using a compartment model that expressed biokinetics of radon and its progeny. The model was fitted to the experimental data by changing biokinetic parameters such as the rate of radon loss from the stomach. Previous models for dosimetric purposes often assumed that the half-time for radon loss from the stomach is below 20 min. The present results, however, suggest that a part of radon stayed longer in the stomach than expected in the previous models.

Physical growth and retinopathy in preterm infants: involvement of IGF-I and GH.

GH and IGF-I are important for physical growth. We measured serum levels of these factors in preterm infants. The study population (n = 81) was divided into three groups according to the gestational age. We evaluated differences in serum GH and IGF-I levels among groups with regard to physical growth and development of retinopathy of prematurity. Serum GH levels in extremely preterm infants born at <28 wk of gestational age were significantly higher than levels in those born between 28 and 34 wk at 1 and 2 mo of age. In contrast, serum IGF-I levels in extremely preterm infants remained low, whereas those in the other two groups gradually increased. Evaluation of the effects of GH and IGF-I on physical growth in very low birth weight infants (<1500 g) showed that IGF-I concentrations were positively related to physical growth for several months after birth, whereas no relationship was observed between GH and physical growth. Multivariate analysis demonstrated that high GH concentration at 1 mo of age was significantly associated with development of severe retinopathy of prematurity. In conclusion, persistent low serum IGF-I levels may explain the slow physical growth during neonatal life, and exposure of high GH may cause, at least in part, severe retinopathy of prematurity in preterm infants.

[Therapeutic trial for promotion of fecal excretion of PCDFs and PCBs by the administration of cholestyramine in Yusho patients].

Any effective therapy for elimination of causal agents remaining in Yusho patients was not found until now. To know the profile of fecal excretion of polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs), the amounts of PCDFs and PCBs in the stool of six Yusho patients with the typical symptoms were determined. The stool samples of Yusho patients were collected in 1989. PCDFs, i.e., 2,3,7,8-tetrachlorodibenzofuran (TCDF), 2,3,4,7,8-pentachlorodibenzofuran (PnCDF), 1,2,3,4,7,8- and 1,2,3,6,7,8-hexachlorodibenzofurans (HxCDFs), 1,2,3,4,6,7,8-heptachlorodibenzofuran (HpCDF) and octachlorodibenzofuran (OCDF) were detected in all of the samples. PCDFs found in the stool samples were mostly PnCDF and HxCDFs. Of PCDFs detected, PnCDF and HxCDFs contributed to 42 +/- 4.7% and 43 +/- 5.5% as mean +/- SE, respectively. The fecal excretion of PnCDF and HxCDFs in Yusho patients was 720 +/- 490 pg/day and 790 +/- 620 pg/day as mean +/- SE, respectively. On the other hand, the fecal excretion of PnCDF and HxCDFs in normal controls was 32 +/- 13 pg/day and 47 +/- 5.2 pg/day as mean +/- SE, respectively. The fecal excretion of PnCDF and HxCDFs in Yusho patients was about 23 times and 17 times each higher than that in normal controls. The fecal excretion of PCBs in Yusho patients and normal controls was 400 +/- 430 ng/day and 150 +/- 39 ng/day, respectively, as mean +/- SE. In order to promote the excretion of these toxic chemicals in the stool of Yusho patients, the patients were continuously administered with cholestyramine, an anion exchange resin, at a dose of 4 g, 3 times a day, for 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

[Concentration profile of PCBs in the digestive tract of rat fed with cholestyramine and rice bran fiber diet].

The aim of this study is to examine the inhibitory effect of rice bran fiber (RBF) and cholestyramine for intestinal absorption of polychlorinated biphenyls (PCBs). Sixteen rats were orally given at the dose of 100 mg of PCBs per kg of the animal, and were divided into four groups (A-D): Rats in each group were housed with the normal diet for the first 7 days, and subsequently, were given with the same diet as control for group A, with the diet containing 10% RBF for group B, with the diet containing 5% cholestyramine for group C and with the combined diet containing 10% RBF and 5% cholestyramine for group D for the next 10 days. All rats were sacrificed on the 17th day after PCBs administration, and PCBs in contents of the digestive tracts were determined: small and large intestine resected was divided into two parts each of the same length, and the contents were chemically analyzed to determine PCBs. PCBs concentration in rats of group A decreased in order of upper portions (1.0 microgram/g) and then lower (0.6 microgram/g) of small intestine, and upper (0.5 microgram/g) and then lower (0.4 microgram/g) of large intestine. Decreasing the PCBs concentration might be due to re-absorption in the intestine. In the case of groups B-D, PCBs concentration was in order of upper and then lower of small intestine, and large intestine. It was indicated that PCBs re-absorption in intestine is inhibited by the intake of RBF, cholestyramine, and RBF and cholestyramine.

Breaking action of ascorbic acid on nucleic acids.

The lowering of the viscosity of DNA solution was caused by the action of AsA or EA and facilitated in the presence of CU2+. However, the action of AsA-3-P was very weak. By sucrose density gradient centrifugation, it was observed that single- and double-strand scissions of DNA were provoked by AsA or EA and enhanced with Cu2+, while only a single-strand scission was caused by AsA-3-P and Cu2+. Similar action of AsA or AsA-3-P was also observed for RNA. Thus, the result indicates that the enediol group of AsA takes an essential part in the breakage of nucleic acids, and Cu2+ enhances the action. It was shown that Apu was mainly decomposed by AsA, whereas Apy not, suggesting that some pyrimidine cluster may be one of the regions attacked by AsA. During the reaction with DNA, the reducing activity of AsA decreased first to some extent and then increased, whereas the reducing activity of AsA-3-P was much lower than that of AsA and decreased steadily. The priming activity of DNA for DNA polymerase was changed after treatment with AsA according to the condition. It was enhanced when DNA was treated under mild conditions but decreased with severer action.