PubMed Health⌕ Search

Biomedical subjects

R H Wong

Publications and source records attributed to R H Wong.

9 recordsLinked to original sources
PubMed2000

Increased lymphocyte sister chromatid exchange frequency in workers with exposure to low level of ethylene dichloride.

The genotoxicity of low-level exposure to ethylene dichloride (EDC) and vinyl chloride monomer (VCM) in humans is not clear. We used lymphocyte sister chromatid exchange (SCE) frequency as a parameter to investigate the genotoxicity of low level EDC and VCM in VCM-manufacturing workers. The SCE frequency was determined for 51 male workers with exposure to VCM and/or EDC and for 20 male workers devoid of such exposure. Epidemiological data were obtained by questionnaire, and included history of smoking, drinking, and any medication taken, as well as a detailed occupational history. Personal- and area-sampling and analysis were conducted in order to calculate the time-weighted average (TWA) contaminant-exposure level corresponding to different job categories. Moderate EDC exposure around 1 ppm corresponded to a significantly greater SCE frequency than was the case for the low EDC exposure group (p<0.01). However, VCM exposure of similar level was not associated with increased SCE. We conclude that EDC may cause genotoxicity at a relatively low level of exposure.

Adult↗
PubMed1998

Effects on sister chromatid exchange frequency of aldehyde dehydrogenase 2 genotype and smoking in vinyl chloride workers.

Vinyl chloride monomer (VCM) is a human carcinogen. However, the exact mechanism of carcinogenesis remains unclear. VCM may be metabolized by cytochrome P450 2E1 (CYP2E1), aldehyde dehydrogenase 2 (ALDH2) and glutathione S-transferases (GSTs). Thus workers with inherited variant metabolic enzyme activities may have an altered risk of genotoxicity. This study was designed to investigate which risk factors might affect sister chromatid exchange (SCE) frequency in polyvinyl chloride (PVC) workers. Study subjects were 44 male workers from three PVC factories. Questionnaires were administered to obtain detailed histories of cigarette smoking, alcohol consumption, occupations, and medications. SCE frequency in peripheral lymphocytes was determined using a standardized method, and CYP2E1, GSTM1, GSTT1 and ALDH2 genotypes were identified by the polymerase chain reaction (PCR). Analysis revealed that smoking status and exposure to VCM were significantly associated with increased SCE frequency. The presence of ALDH2 1-2/2-2 genotypes was also significantly associated with an elevation of SCE frequency (9. 5 vs. 8.1, p<0.01). However, CYP2E1, GSTM1 or GSTT1 genotypes were not significantly associated with SCE frequency. When various genotypes were considered together, combination of CYP2E1 c1c2/c2c2 with ALDH2 1-2/2-2 showed an additive effect on SCE frequency. Similar results were also found for the combination of smoking with CYP2E1, or smoking with ALDH2. These results suggest that VCM workers with ALDH2 1-2/2-2 genotypes, who also smoke, may have increased risk of DNA damage.

Adult↗
PubMed1998

Chinese herbal medicine, sibship, and blood lead in children.

OBJECTIVES: Risk factors for increased blood lead concentration (BPb) has been investigated. However, the effect of sibship and Chinese herbal medicine on BPb has not been systematically studied. In this study BPb data from voluntary testing was used to determine if Chinese herbal medicine and sibship were associated with BPb. METHODS: 319 children aged 1-7 were tested for BPb. Meanwhile, parents were interviewed to obtain information including consumption of Chinese herbal medicine, living environment, lifestyle, and sibship of the children tested. RESULTS: The mean (SD) BPb of 319 preschool children was 4.4 (2.4) micrograms/dl. The consumption of Ba-baw-san (a Chinese herbal medicine) was significantly associated with increased BPb in children (p = 0.038). Further multivariate regression analysis of BPb in 50 pairs of siblings showed the factors of being brothers explained 75% of variation for BPb, and being sisters and brother-sister explained 51% and 41% of variation respectively. CONCLUSION: Chinese herbal medicine and children's play patterns within the family expressed in different types of sibship are the main determinants of low concentrations of BPb in preschool children of Taiwan.

Age Factors↗
PubMed1997

Biphasic emetic response of cyclophosphamide in the ferret.

Cyclophosphamide (177 mg/kg, IV: n = 8) produced a biphasic emetic response in the ferret with a mean +/- SE of 23.3 +/- 4.0 emetic episodes during a 4-h observation period. The emetic profile of cyclophosphamide showed a first phase with 18.6 +/- 3.9 episodes and a second phase with 4.7 +/- 1.2 episodes. Ondansetron (0.07 and 0.13 mg/kg, IV) and droperidol (0.25 and 0.79 mg/kg, IV) significantly reduced the number of emetic episodes in the first phase. Metoclopramide (2.24, 4.08, and 7.07 mg/kg, IV) also significantly reduced the number of emetic episodes in the first phase, and the dose of 7.07 mg/kg completely prevented emetic episodes in the second phase. In addition, ondansetron-treated ferrets (0.04, 0.07, and 0.13 mg/kg, IV) had a significant increase in the number of emetic episodes in the second phase.

Animals↗
PubMed1997

The effect of seating force and die spacing on pulpward cementation pressure transmission: a laboratory study.

Pulpward pressure transmission during crown cementation occurs via the dentinal tubules. The present study investigated the effect of crown seating forces and the effect of increasing the die spacing on pulpward pressure transmission. Twenty upper premolars were prepared with 1 mm shoulder margins for non-precious metal full crowns. A 0-104 kPa pressure transducer (Mediamate EA, Data Instruments, Baltimore, MD, USA) was connected, via the sectioned root of the premolar, to the pulp chamber which was perfused with saline at 83 kPa driven by nitrogen gas, for two hours prior to cementation. Crowns with 2 or 6 layers of die-spacing were seated with 25 N or 100 N force using zinc-phosphate cement. The pressure transducer was connected to a Wheatstone bridge (Measurements Group, Instruments Division) and the extent of crown seating and output from the pressure transducer was recorded. Results indicate that 25 N seating force produced a lower mean pulpward pressure (41 +/- 54 Pa) compared to the 100 N seating force (251 +/- 276 Pa). Seating was significantly improved with 6 layers of die-spacing (seating discrepancy 18 +/- 12 mm) compared with 2 layers (139 +/- 111 mm). It is concluded that a higher seating force increases pulpward pressure transmission. Increasing die spacing improved crown seating but did not affect the amount of pressure transmitted.

Adolescent↗
PubMed1995

Efficacy of Chinese acupuncture on postoperative oral surgery pain.

One of the challenges of acupuncture research is designing appropriate control groups. To address this problem, after surgical third molar extractions 19 patients were randomly assigned to an acupuncture group (n = 11) or a placebo acupuncture group (n = 8). The length of time for reaching moderate pain and pain intensity after oral surgery were recorded by standard patient self-report. The results indicated that subjects treated with acupuncture reported longer pain-free duration times (mean, 181 versus 71 minutes; p < or = 0.046) and experienced less pain intensity than those who received placebo acupuncture. This study provides a model for an acupuncture control that could examine the placebo effect in clinical acupuncture research.

Acupuncture Analgesia↗
PubMed1995

Electroacupuncture reduces morphine-induced emesis in ferrets: a pilot study.

We treated morphine-induced emesis in ferrets with electroacupuncture (EA) for five minutes at the acupuncture point Neiguan (P6) using two different frequencies of stimulation: 1.0 Hz and 5.0 Hz (n = 5 ferrets per group). Both EA treatments reduced the number of emetic episodes (39% reduction of episodes, p < or = 0.05 at 1.0 Hz; 43% reduction of episodes, p < or = 0.05 at 5.0 Hz) and prolonged the onset time of emesis as compared with control receiving no EA. This model demonstrates that under these conditions EA is effective as an antiemetic against morphine in the ferret and may allow for further studies on the mechanisms of acupuncture and emesis.

Analgesics, Opioid↗
PubMed1989

Porphyria cutanea tarda and AIDS.

Two male patients, each of whom had one or more risk factors for human immunodeficiency virus, subsequently developed findings of porphyria cutanea tarda preceding diagnosis of acquired immune deficiency syndrome (AIDS).

Acquired Immunodeficiency Syndrome↗