Biomedical subjects
Publications and source records attributed to Shinobu Tanaka.
Surveyor nuclease, a single-strand-specific endonuclease that cleaves DNA at the 3' side of a base-mismatch site in both DNA strands, can be used for genotyping of SNPs by preparing two different types of a heteroduplex: one from mutant DNA fragments and the other from a mixture of wild-type and mutant fragments. We show an example of this technique and propose that it can be used with some advantages instead of RFLP analysis.
The present study investigated the effects of Ginkgo biloba extract and its flavonoid fractions on alpha-amylase and alpha-glucosidase activity in vitro. Ginkgo biloba extracts and their flavonoid fraction significantly inhibited alpha-amylase and alpha-glucosidase activity in vitro. Furthermore, Ginkgo biloba extracts and their flavonoid fraction reduced the elevation of rat plasma glucose level after oral administration of various saccharinity agents. In addition, we examined the effects of the flavonoid fraction isolated from Ginkgo biloba extracts on the plasma glucose level in streptozotocin-induced diabetic rats. When flavonoid fractions were orally administered to the rats three times daily for 9 days, plasma glucose concentrations were decreased compared with those in the water treatment group. Furthermore, flavonoid fractions reduced the elevation of rat plasma glucose levels after oral administration of sucrose and glucose in streptozotocin-induced diabetic rats.
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Determination of the biochemical components in erythrocytes should provide unique pathophysiological information. We optimized a simple alcohol binding method for the selective removal of hemoglobins from hemolysates, and enabled simultaneous determination of several components in erythrocytes using commercially available assay kits in an automated analyzer. Venous blood was collected in a vacutainer containing lithium heparin. The washed cells were hemolyzed with distilled water, frozen, and then thawed. Nine volumes of the hemolysates were mixed with one volume of Tris-HCl buffer. One volume of n-butanol was then added to nine volumes of the buffered hemolysates. After vigorous mixing, the mixture of n-butanol and hemolysates was left to stand. The butanol-bound hemoglobins were precipitated by centrifugation, and the clear supernatant below the butanol layer was applied directly to an automated analyzer. Using sera, we determined the effects of the hemoglobin removal procedures on the chemical analytes. Sufficient recovery was noted in most analytes, except for several enzyme activities and lipids. Accordingly, we determined five components present in erythrocytes: creatine, potassium, magnesium, and aspartate aminotransferase as well as superoxide dismutase activities in healthy subjects. We suggest that our simple method is applicable to the simultaneous determination of erythrocyte components in routine laboratory tests.
Membrane orientation induced by an alternating electric field has been examined for the L-enantiomer and racemic dipalmitoylphosphatidylcholine (DPPC) bilayers. The orientation effect was measured by bending curvature of hairpin-like deformation of the multilamellar cylindrical tubes with varying field-strength, frequency and tube size. It has been observed that both L- and DL-DPPC tubes are similar in the profiles of field-strength dependence and frequency dependence on the curvature deformation, but different in the deformed curvatures. DL-DPPC tubes deform largely as compared with L-DPPC tubes. The square of the deformed curvature of DL-DPPC tubes is larger than that of L-DPPC by about 37% on average. The result indicates that the racemic membrane is responsive to the electric field as compared with the L-enantiomer membrane. This suggests that a hybrid arrangement of head groups of the racemic lipid leads an effective response of the membrane due to the head group orientation.
Previous reports have shown that the liver-type glucose transporter GLUT2 gene expression is upregulated in the liver of obese and diabetic animals and in human subjects. This phenomenon is correlated with an increased glucose output from the liver; however, the regulatory mechanism is not clear. To investigate the relationship between hepatic steatosis, frequently found in obese and diabetic patients, and GLUT2 gene expression, we developed an oleic acid-induced in vitro fatty liver model. Lipid-accumulated cells morphologically mimicking hepatic steatosis were successfully induced in the human HepG2 cell line by 24-h culture with oleic acid at 1 mM. The cells with steatosis showed increased levels of intracellular triglycerides and apolipoprotein B, which were reduced in the presence of bezafibrate at 100 &mgr;g/ml. GLUT2 mRNA expression estimated by semi-quantitative reverse transcription polymerase chain reaction was increased in the cells with steatosis. Bezafibrate inhibited GLUT2 mRNA expression in the cells with and without steatosis. These results suggest that hepatic steatosis causes the enhancement of hepatic GLUT2 mRNA expression, which may be associated with gluconeogenesis and insulin resistance.
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