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Biomedical subjects

J X Huang

Publications and source records attributed to J X Huang.

29 records · Page 2Linked to original sources
PubMed1987

Adsorption isotherms on high-performance liquid chromatographic sorbents. II. Proteins on cation exchangers with silica support.

Adsorption isotherms of proteins were measured by frontal chromatography in a miniaturized chromatographic system with short, narrow-bore columns. The adsorbents were microparticulate, macroporous siliceous cation exchangers, used in the high-performance liquid chromatography of proteins, and the range of mobile phase compositions was similar to that used in elution chromatography for their separation. Adsorption of protein on the wetted stainless-steel parts of the system was reduced by coating the metal surface with a hydrophilic polymer layer. The adsorption isotherms of proteins were concave down and, in most cases, well represented by the Langmuir model. However, the data could also be fitted with reasonable accuracy to the isotherm equation by Jovanović. Although the siliceous cation exchangers were of different provenance, the isotherms of the proteins were similar. Isotherms measured by the shake-flask method were found to be identical with those obtained by frontal chromatography.

Chromatography, High Pressure Liquid↗
PubMed1985

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. II. Retention behavior, quantitative structure-retention relationships and octanol-water partition coefficients.

The retention behavior of methoxy-substituted p-benzoquinones and the corresponding hydroquinones in reversed-phase chromatography was examined on octylsilica and two octadecylsilica stationary phases and with five hydroorganic mobile phases containing acetonitrile, methanol or tetrahydrofuran and additionally in most cases (NH3OH)3PO4 used as a reducing and buffering agent. The retention order of benzoquinones and hydroquinones was the same on each stationary phase with either methanol or acetonitrile as the organic modifier. On the other hand, minor differences in the retention order were observed with the various stationary phases. In all cases, satisfactory quantitative structure-retention relationships (QSRRs) were found and the data suggest that the differences in the retention behaviour of octadecylsilicas used in this study are silanophilic interactions which, together with solvophobic interaction contribute to the retention of these eluites. Further analysis showed that QSRRs of sterically crowded molecules must take into account reduced surface area available for binding. The retention data obtained with use of aqueous tetrahydrofuran as mobile phase failed to give rise to satisfactory QSRRs. This was attributed to selective solvation of eluite by tetrahydrofuran and/or nearly equipotent binding of eluite and tetrahydrofuran to stationary phase.

Benzoquinones↗
PubMed1985

Effects of cadmium on cadmium smelter workers.

The effects of cadmium on 65 workers in a cadmium-refining plant in the People's Republic of China were investigated. The average airborne cadmium oxide concentrations ranged from 0.004 to 0.187 mg/m3 at most worksites. Except for some vague symptoms and reports of anosmia, no significant abnormalities were found in the clinical examinations. The level of cadmium in the blood and urine was increased in the majority of the cadmium-exposed subjects. Nine cases (13.8%) with suspected or mild renal tubular damage were found in this study.

Adolescent↗
PubMed1984

High-performance liquid chromatography of substituted p-benzoquinones and p-hydroquinones. I. Interplay of on-column redox reaction and the chromatographic retention process.

Chromatograms exhibiting unusual elution profiles were obtained in the reversed-phase chromatography of methoxy-substituted hydroquinones with hydro-organic mobile phases. The dependence of the elution profiles on the flow-rate and the mass of injected sample indicated that peaks were caused by the interplay of the chromatographic retention process and the concomitant oxidation of hydroquinones in the chromatographic column. The reaction was first investigated in free solution and the first-order rate constants and equilibrium constants were estimated for the oxidation of 2-methoxy-, 2,5-dimethoxy-, 2,6-dimethoxy-, 2,3,5-trimethoxy- and 2,3,5,6-tetramethoxyhydroquinones. The effect of Fe3+ and Cu2+ on the oxidation of 2,6-dimethoxyhydroquinone was also examined and it was found that Fe3+ caused a ten-fold increase in the reaction rate. The oxidation of 2-methoxy- and 2,6-dimethoxyhydroquinones in the chromatographic column showed first-order and zerothorder kinetic behavior at low and high sample loads, respectively. Such change in reaction order is typical for heterogeneous reactions that follow Langmuir-Hinshelwood kinetics and suggests the existence of catalytically active sites on the silica. Upon purging the columns with EDTA, on-column oxidation of the hydroquinones was attenuated so that no reaction zones appeared on the chromatogram. Subsequent loading of the column with Fe3+, however, gave rise to broad reaction zones and possibly to total conversion of the hydroquinones to benzoquinones in the column. In all cases investigated the rate of oxidation was much higher in the column than in free solution. On the basis of the results obtained here, heavy mental-catalyzed reaction at the stationary phase surface is proposed to be the dominant mechanism for the oxidation reaction examined here.

Benzoquinones↗
PubMedDate not supplied

Respiratory symptoms and pulmonary function among Chinese rice-granary workers.

The authors conducted a cross-sectional study of 474 rice-granary workers and 235 non-granary worker controls in a rural area near Shanghai, the People's Republic of China. Responses to a respiratory-symptom questionnaire and pre- and post-shift spirometry were obtained for all subjects. Area sampling was performed for total and vertically elutriated (</= 15 micrometer) dust levels. Total dust levels were high, ranging from 6.6 mg/m(3) to 59.8 mg/m(3), with vertical elutriated dust concentrations ranging from 2.0 to 10. 4 mg/m(3). The granary workers reported significantly more respiratory symptoms, including chronic cough, sputum production, chronic bronchitis, grain fever (ODTS), and nasal and skin irritation. Grain dust and tobacco smoking were more than additive for the prevalence of chronic cough and chronic bronchitis. After adjusting for confounders, the granary workers had lower mean FEV&inf1;/FVC values both pre- and post-shift, indicating an association between chronic grain-dust exposure and chronic airway obstruction. The results suggest that exposure to rice dust can induce pulmonary responses similar to those observed with exposures to other types of grains.

Acute Disease↗