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Biomedical subjects

L Y Lin

Publications and source records attributed to L Y Lin.

69 records · Page 4Linked to original sources
PubMed1987

Isocratic high-performance liquid chromatographic separation and multiple-wavelength ultraviolet detection of aldicarb and its soil degradation products. Optimization of stationary phase selectivity.

The unique selectivities which can be generated through optimization of stationary/mobile phase combinations have been applied to the development of an isocratic, reversed-phase high-performance liquid chromatographic method for the separation of aldicarb and its primary soil degradation products. The method utilizes a cyanopropyl bonded stationary phase and water-acetonitrile mobile phase and is capable of separating aldicarb and its various sulfoxide, sulfone and oxime derivatives in less than 10 min. When combined with multiple-wavelength UV detection and an appropriate preconcentration step, this method can in principle be applied to the routine monitoring of aldicarb and its soil derivatives in water at concentrations less than 1 microgram/l.

Aldicarb↗
PubMed1986

Quantitation of chick tissue zinc-metallothionein by gel electrophoresis and silver stain enhancement.

Discontinuous gradient gel electrophoretic systems were developed to quantitate zinc-metallothionein (Zn-MT) in chick tissues, liver and pancreas. Gels were stained with Coomassie Blue initially, then enhanced by silver stain. At least 4 micrograms of Zn-MT could be detected after Coomassie Blue stain, and 1 microgram Zn-MT detected following silver stain enhancement. Significant linearity (correlation coefficient = 0.99) of a standard curve was established in the Coomassie Blue stained gels. The results of our experiment suggest that electrophoretic analysis is a simple and feasible method for the quantitation and identification of Zn-MT in chick tissues.

Animals↗
PubMedDate not supplied

Hydroxyl radical mediated demethylenation of (methylenedioxy)phenyl compounds.

The oxidative demethylenation reactions of (methylendioxy)phenyl compounds (MDPs), (methylenedioxy)benzene (MDB), (methylenedioxy)amphetamine (MDA), and (methylenedioxy)methamphetamine (MDMA), were evaluated by using two hydroxyl radical generating systems, the autoxidation of ascorbate in the presence of iron-EDTA and the iron-catalyzed Haber-Weiss reaction conducted by xanthine/xanthine oxidase with iron-EDTA. Reaction products generated when MDB, MDA, and MDMA were incubated with the ascorbate or xanthine oxidase system were catechol, dihydroxyamphetamine (DHA), and dihydroxymethamphetamine (DHMA), respectively. The reaction required the presence of either ascorbic acid or xanthine oxidase. Levels of each catechol increased in proportion to ferric ion concentration and were suppressed by desferrioxamine B methanesulfonate (desferal). Catalase (CAT) inhibited the oxidation by the ascorbate system whereas superoxide dismutase (SOD) had little effect. The addition of hydrogen peroxide to the reaction mixture stimulated the oxidation, but the reaction was not initiated by hydrogen peroxide alone, suggesting that hydrogen peroxide acts as a precursor of hydroxyl radical. SOD and CAT suppressed the demethylenation reactions in the xanthine oxidase system. Hydroxyl radical scavenging agents such as ethanol, benzoate, DMSO, and thiourea effectively inhibited the oxidation by both systems. Urea, which has little effect on hydroxyl radical, was without any effect. These results indicated that hydroxyl radical can effect the cleavage of methylenedioxy group on MDPs.

3,4-Methylenedioxyamphetamine↗
PubMedDate not supplied

Enzymatic and chemical demethylenation of (methylenedioxy)amphetamine and (methylenedioxy)methamphetamine by rat brain microsomes.

The metabolism of (methylenedioxy)amphetamine (MDA) and (methylenedioxy)methamphetamine (MDMA) was examined in microsomal preparations from rat brains. The products generated from MDA and MDMA were identified as dihydroxyamphetamine (DHA) and dihydroxymethamphetamine (DHMA), respectively. The demethylenation reaction required NADPH and was strongly inhibited by CO/O2 (4:1 v/v), suggesting that the formation of DHA and DHMA is mediated by cytochrome P450. The conversion was inhibited by desipramine, imipramine, and methimazole, whereas SKF-525A and alpha-naphthoflavone had little effect. Lineweaver-Burk plots of MDA and MDMA demethylenation were biphasic in both cases, indicating that multiple isozymes may participate in the oxidation. The microsomal preparation showed no significant stereoselectivity in the demethylenation of either MDA or MDMA. Catechol formation differed with the incubation buffer and was 2.6 times greater when phosphate rather than HEPES buffer was used. This difference disappeared, however, when desferrioxamine B methanesulfonate (desferal) and hydroxyl radical (.OH) scavenging agents were added to either buffer. The demethylenation was also sensitive to catalase and was stimulated by the addition of ferric ion and EDTA to the microsomal incubation mixture. These results indicate that the demethylenation of MDA and MDMA by rat brain microsomes has a cytochrome P450-mediated component as well as a chemical component involving .OH.

3,4-Methylenedioxyamphetamine↗
PubMedDate not supplied

Effects of cortisol and salinity challenge on water balance in developing larvae of tilapia (Oreochromis mossambicus).

Effects of exogenous cortisol on drinking rate and water content in developing larvae of tilapia (Oreochromis mossambicus) were examined. Both freshwater- and seawater-adapted larvae showed increases in drinking rates with development. Drinking rates of seawater-adapted larvae were about four- to ninefold higher than those of freshwater-adapted larvae from day 2 to day 5 after hatching. Seawater-adapted larvae showed declines in drinking rate and water content at 4 and 14 h, respectively, after immersion in 10 mg L(-1) cortisol. In the case of freshwater-adapted larvae, the drinking rate decreased after 8 h of cortisol immersion, while the water content did not show a significant change even after 32 h of cortisol immersion. In a subsequent experiment of transfer from freshwater to 20 ppt (parts per thousand, salinity) seawater, immersion in 10 mg L(-1) cortisol for 8-24 h enhanced the drinking rate in larvae at 4 h after transfer, but no significant difference was found in water contents between cortisol-treated and control groups following transfer. These results suggest that cortisol is involved in the regulation of drinking activity in developing tilapia larvae.

Adaptation, Physiological↗
PubMedDate not supplied

Regulation of drinking rate in euryhaline tilapia larvae (Oreochromis mossambicus) during salinity challenges.

Euryhaline tilapia larvae are capable of adapting to environmental salinity changes even when transferred from freshwater (FW) to seawater (SW) or vice versa. In this study, the water balance of developing tilapia larvae (Oreochromis mossambicus) adapted to FW or SW was compared, and the short-term regulation of drinking rate of the larvae during salinity adaptation was also examined. Following development, wet weight and water content of both SW- and FW-adapted larvae increased gradually, while the dry weight of both group larvae showed a slow but significant decline. On the other hand, the drinking rate of SW-adapted larvae was four- to ninefold higher than that of FW-adapted larvae from day 2 to day 5 after hatching. During acute salinity challenges, tilapia larvae reacted profoundly in drinking rate, that is, increased or decreased drinking rate within several hours while facing hypertonic or hypotonic challenges, to maintain their constancy of body fluid. This rapid regulation in water balance upon salinity challenges may be critical for the development and survival of developing larvae.

Adaptation, Physiological↗
PubMedDate not supplied

Modification of morphology and function of integument mitochondria-rich cells in tilapia larvae (Oreochromis mossambicus) acclimated to ambient chloride levels.

Similar to those of the gills of adults, three types of mitochondria-rich (MR) cells with different morphologies of apical surfaces (wavy convex, shallow basin, and deep hole) were identified on the integument of freshwater-acclimated tilapia larvae (Oreochromis mossambicus). The object of this study is to test the hypothesis that these subtype cells may represent MR cells equipped with variable efficiencies in Cl(-) uptake. Larvae acclimated to low-Cl(-) =0.001-0.007 mM) water developed higher densities of MR cells than those acclimated to high-Cl(-) =7.3-7.9 mM) water. The percentage of wavy-convex-type cells in total MR cells was higher in low-Cl(-)-acclimated larvae than in high-Cl(-)-acclimated larvae, which displayed only deep-hole type. In addition, Cl(-) influx rates of whole larva measured with (36)Cl(-) showed a coincident correlation with MR cell densities, that is, low-Cl(-) larvae displayed higher Cl(-) influx rates than did high-Cl(-) larva, suggesting that tilapia larvae develop a higher density of MR cells with larger apical surfaces (wavy-convex type) to boost Cl(-) uptake in Cl(-)-deficient water. The distinct types of apical surfaces may represent different phases of MR cells that possess different efficiencies of Cl(-) uptake. Increased apical membrane surface areas of MR cells may provide larvae with rapid regulation of Cl(-) before new MR cells differentiate.

Animals↗
PubMedDate not supplied

Esthetic overdenture for a patient with possible Seckel syndrome.

This is a case report of a 21-year-old with possible Seckel syndrome (bird-headed dwarfism), micrognathia, microdontia, severe bony undercuts, and periodontal disease who sought treatment at a university dental clinic. Treatment included extractions, periodontal therapy, retention of premolars with sealants, and overdentures with resilient soft liners. A limited review of Seckel syndrome literature is included. The modification of existing dental materials and procedures required for successful functional and esthetic results are discussed.

Abnormalities, Multiple↗
PubMedDate not supplied

[Educational effects of a short-term diabetes camp for children].

A Diabetes camp provides children with fun and educational experience. Seventeen diabetic school children (12 boys and 5 girls) participated in a short-term diabetes camp from April 16 to 17, 1988. Their ages ranged from 8.5 to 13.2 years with an average of 11.3 +/- 1.5 (mean +/- SD) years. The duration of their diabetes varied from 0.05 to 5.3 years with an average of 2.7 +/- 3.3 years. The camp staff consisted of a pediatric endocrinologist, 3 nurses, 4 dietitians, 3 social workers, 4 assistant diabetes educators, and 2 counsellors who were specialized in music and recreational activities. The children's abilities in managing their diabetes were assessed by using a scoring system before and after the camping. Wilcoxon matched-pairs signed-rank tests with significance levels set at p < 0.05 (two-tailed) were conducted to determine whether there were any significant changes in the results from pre- and postcamp assessments. The children showed significant improvement in using glucose-monitoring devices, drawing insulin, injecting insulin, and choosing the right exchange of food with the p values of less than 0.05, 0.01, 0.01, and 0.01 respectively. We concluded that this short-term diabetes camp was educational for school children with diabetes. The campers improved their knowledge and skill in management of diabetes.

Adolescent↗