Biomedical subjects

Zhi Su

Publications and source records attributed to Zhi Su.

23 records · Page 2Linked to original sources

PubMed2003

New trends in the development of occupational exposure limits for airborne chemicals in China.

Occupational exposure limits (OELs) are well established in many countries, which serve occupational professionals as benchmarks of industrial hygiene practice at workplaces worldwide. Starting in the mid-1950s, the central government of China began promulgating OELs for hazardous substances at workplaces. This paper discusses the historical basis, philosophical principles and schematic protocols of developing and setting OELs in China. The underlying principles include: (1) protection of human health being the first and the most important criterion; (2) the use of quantitative epidemiological studies in humans being given top priority; (3) integration and full use of all information sources, including animal experimental data for new chemicals or chemicals with new toxicity concerns; (4) considerations of socioeconomic and technological feasibilities in the country; and (5) amending existing standards based on new evidence. The strategy of the World Health Organization's "Two-step Procedure" is applied to convert health-based recommendations to law-based operational OELs, with considerations for national technological and socioeconomic conditions and priorities. As a result of the recent passage of the new law Occupational Diseases Prevention and Control Act of the People's Republic of China (ODPCAct), an official document Occupational Exposure Limits for Hazardous Agents in the Workplace containing a comprehensive list of new and amended OELs has been issued, which has now become one of the most essential regulations affiliated with the ODPCAct. This paper provides a brief summary of the salient features of the new law ODPCAct and the principles and processes of developing or amending OELs. This paper also discusses the challenges that lie ahead in enforcing the new regulations in China.

Air Pollutants, Occupational↗

PubMed2003

Effects of FK506 on [Ca2+]i differ in mouse and rabbit ventricular myocytes.

FK506 binding proteins (FKBPs 12 and 12.6) interact with ryanodine receptor (RyR) and modulate its functions. FK506 binds to and reverses effects of FKBP on RyR, thus increasing RyR sensitivity to Ca2+, decreasing RyR cooperativity, and increasing RyR open probability. FK506 would thus be expected to have an effect on excitation-contraction coupling, but which of these FK506 effects predominates and how the [Ca2+]i transient would be altered are difficult to predict. FK506 has been reported to increase the [Ca2+]i transient in rat myocytes, but effects in other species have not been described. We compared the effects of FK506 on [Ca2+]i transients, L-type Ca2+ channel and Na/Ca exchange currents, membrane potential, and sarcoplasmic reticulum (SR) Ca2+ content in adult mouse and rabbit ventricular myocytes (VM). FK506 (10 microM) increased the [Ca2+]i transient in mouse VM (656 +/- 116 to 945 +/- 144 nM, p < 0.001) but decreased the amplitude of [Ca2+]i transients in rabbit VM (627 +/- 61 to 401 +/- 37 nM, p < 0.001). Similar effects were observed with rapamycin. The effects of FK506 and rapamycin on [Ca2+]i transients in VM of both species were reversible upon washout. FK506 did not alter SR Ca2+ content in mouse VM (0.79 +/- 0.1 versus 0.78 +/- 0.1 pC/pF) but reduced the SR Ca2+ content in rabbit VM (0.43 +/- 0.05 versus 0.30 +/- 0.04 pC/pF, P < 0.05) [pC = the integral (pA. s) of the caffeine-induced inward I(Na/Ca) normalized by cell capacitance (pF)]. FK506 had no effects on membrane potential, I(Ca,L) and outward I(Na/Ca) in either mouse or rabbit VM. These results indicate that alteration of the functions of RyR by FK506-mediated dissociation of FKBP from RyR has different species-dependent effects on SR Ca2+ load and thus [Ca2+]i transients. This difference may result from the fact that [Na+]i is low in rabbit myocytes, allowing extrusion by Na+/Ca2+ exchange of Ca2+ released by FK506-induced dissociation of FKBP12.6 from SR RyR.

Animals↗

PubMed2003

[Effect of the polymorphism of myeloperoxidase gene on the risk of benzene poisoning].

OBJECTIVE: To study the relationship between the polymorphism myeloperoxidase (MPO) gene and the genetic susceptibility to benzene toxicity in workers exposed to benzene and in patients with benzene poisoning. METHODS: Using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) techniques, the genotypes' polymorphism of MPO gene in 35 patients with chronic benzene poisoning, 46 workers exposed to benzene from the same workplace (as exposed control) and 26 controls were analyzed. RESULT: There were three (G/G, G/A and A/A) genotypes in the region of 463 bp upstream of MPO gene. The distribution frequency in G/G wild-type genotype in patients was 27.4% more than that in the exposed workers. The risk of benzene-hematotoxicity in those with G/G genotype was 2.8-fold higher than G/A + A/A genotype (OR = 2.835, 95% CI: 1.065 - 7.549, P < 0.05). The polymorphism of myeloperoxidase was not associated with gender specific. CONCLUSION: In the same benzene-exposed environment, the subjects with MPO-463 G/G genotype may be more susceptible to benzene toxicity.

Adult↗

PubMedDate not supplied

The [3H]dofetilide binding assay is a predictive screening tool for hERG blockade and proarrhythmia: Comparison of intact cell and membrane preparations and effects of altering [K+]o.

INTRODUCTION: The human ether-a-go-go-related gene (hERG) encodes a potassium channel responsible for the cardiac delayed rectifier current (IKr) involved in ventricular repolarization. Drugs that block hERG have been associated with QT interval prolongation and serious, sometimes fatal, cardiac arrhythmias (including torsade de pointes). While displacement of [3H]dofetilide, a potent methanesulfonanilide hERG blocker, from cells heterologously expressing hERG has been suggested as a screening assay, questions have been raised about its predictive value. METHODS: To validate the utility of this assay as a screening tool, we performed a series of saturation and competition binding studies using [3H]dofetilide as ligand and either intact cells or membrane preparations from HEK 293 cells stably transfected with hERG K+ channels. The object of these experiments was to (1) compare binding Ki values for 22 hERG blockers using intact cells or membrane homogenates to determine whether maintaining cell integrity enhanced assay reliability; (2) evaluate the ability of different K+ concentrations (2, 5, 10, 20, and 60 mM) to modulate hERG binding; and (3) to establish the predictive value of the assay by comparing Ki values from binding studies at 5 and 60 mM [K+]o to functional IC50 values for hERG current block using 56 structurally diverse drugs. RESULTS: We found (a) comparable Ki values in the intact cell and isolated membrane binding assays, although there were some differences in rank order; (b) increasing [K+]o lowered the Kd and increased the Bmax for [3H]dofetilide, particularly in the membrane assay; and (c) good correlation between binding Ki values and functional IC50 values for hERG current block. DISCUSSION: In conclusion, increasing K+ concentrations results in an increase in both [3H]dofetilide affinity for hERG and available binding sites, particularly when using membrane homogenates. There are no meaningful differences between Ki values when comparing intact cell versus membrane assay, neither are there meaningful trends with increasing [K+]o within assays. There is good correlation between binding Ki values and functional (whole-cell patch clamp) IC50 values at both 5 and 60 mM K+ concentrations (R2 values of .824 and .863, respectively). The simplicity, predictability, and adaptability to high-throughput platforms make the [3H]dofetilide membrane binding assay a useful tool for screening and ranking compounds for their potential to block the hERG K+ channel.

Anti-Arrhythmia Agents↗

PubMedDate not supplied

Occupational health and safety legislation and implementation in China.

This article reviews the current statistics of employment and work-related injuries and illness in China, as well as the history of occupational health and safety legislation in the country. Comprehensive, newly promulgated workplace health and safety legislation is described, and the specific responsibilities of employers, government agencies, trade unions, and employees are detailed. The government's implementation plan for this and prior legislation is also outlined.

China↗