2000 Vol. 13, No. 2
2000, 13(2): 85-89.
The mean lead levels in the maternal blood, cord blood, breast milk and placental tissue, were 0.63 μmol/L (13.2 μg/dL), 0.33 μmol/L (6.90 μg/dL), 4.74 μg/L and 0.86 μmol/kg (17.85 μg/100g) respectively for 165 parturient women occupationally non-exposed to lead in 2 hospitals in Shanghai. No significant difference was found between maternal age groups for these indicators. However, the lead levels in the cord blood and breast milk increased with the lead level in the maternal blood, with coefficient of correlation of 0.714 (P＜0.0001) and 0.353 (P＜0.01) respectively. The mean concentration of lead in breast milk for 12 occupationally lead exposed women was 52.7 μg/L, which was almost 12 times higher than that for the occupationally non-exposed population. These results suggested that transfer of lead via placenta prenatally and breast milk postnatally were possible and might pose a potential health hazard to the fetuses and the neonates.
2000, 13(2): 90-96.
One of the most potent rodenticides is 2-fluoroacetamide (2-FA). Toxicity of this chemical is well documented. However, its inhalation toxicity data is not available in the literature. Hence, acute inhalation toxicity study was carried out by exposing male and female rats to aerosols of 2-FA at different concentrations for 4 h in a dynamically operated whole body inhalation exposure chamber. During and after the inhalation exposure the rats were less active, and showed mild tremors and convulsions. At higher concentrations the rats died after 2-3 days. The estimated 4-h LC50 for male and female rats was 136.6 and 144.5 mg·m-3 respectively. Exposure to 0.7 LC50 for 4 h duration showed an increase in the liver weight of male and female rats 7 days after exposure. Various haematological and biochemical variables determined were within the normal limits. However, histological findings showed injured lung as indicated by desquamation and necrosis of the epithelium of the respiratory tract. Marked hypertrophy of hepatocytes displaying strong acidophilic granulated cytoplasm was observed. Focal dilatation of renal proximal tubules in kidney with cytoplasmic vacuolation, and irregularly placed pyknotic nuclei were seen. The present study shows that 2-FA is a highly toxic chemical through the inhalation route based on the LC50 value. Consequently necessary precautions should be taken during its handling.
The Identification and Toxicity of the Microcystin in the Waterbloom Obtained From an Eutrophied Lake
2000, 13(2): 97-104.
The water of "J" lake has been seriously eutrophied; concentration of total nitrogen (TN), total phosphorus (TP) and chlorophyll a were all far above the 3rd level of the National Standard of Ground Water of China. The concentration of microcystin (MCYST) of the water at one site (M) was 1865 μg/l. There were 2.36μg MCYST-LR per mg dry waterbloom powder.
2000, 13(2): 105-116.
To study the effect of dietary fatty acid on the colon tumorigenesis induced by methyl nitrosourea in rats, male SD rats were fed five semi-synthetic diets composed of different proportions of beef tallow, soybean oil, alkana oil, corn oil and fish oil for 180 days. The experimental groups were injected with a solution of methyl nitrosourea in phosphate buffer intraperitoneally once a week for six weeks. The control groups were injected with phosphate buffer solution only. The incidence of colon cancer, the avergage volume of the tumors, proliferation cell nuclear antigen, cell kinetics, membrane lipid fluidity, alkaline phosphatase activities and the content of prostaglandin E2 in colon mucosa and the fatty acid of testis pad fat were measured at the end of the experiment. The results showed that the incidence of colon cancer and the average volume of tumors in animals fed with diets composed mainly of beef tallow, soybean oil or alkana oil were significantly higher than those that were fed fish oil. The most effective anticancer diet in our study contained saturated fatty acid, monounsaturated fatty acid and polyunsaturated fatty acid of fish oil in the proportion of 13.9%, 16.4% and 68.8% respectively. Inhibition of colon tumorigenesis appeared to be related to the regulation of membrane lipid fluidity, and a decrease in the proliferation of cell nuclear antigen in colon cells. In addition, a decrease was noted in the number of cells in S phase and alkaline phosphatase activity, along with inhibition of arachidonic acid products and a corresponding decrease in the amount of prostaglandin E2.
2000, 13(2): 117-121.
The earthworm Metaphire posthuma were used as a model to assess the toxic potential of cadmium incorporated into the soil by environmental or human activities. The retention period of neutral red in the lysosomes of the coelomocytes was used as a biomarker. The viability of harvested coelomocytes by a non-invasive extrusion protocol was 93% with no alteration by the dye during experimentation. The control cells retained dye for 119 and 121 min in normal soil and KCl, respectively, whereas a linear decline in the retention time in the treated earthworm coelomocytes was observed. This illustrated that the presence of cadmium caused damage to the lysosomes of the coelomocytes.
Effect of Nicotinamide on 12-O-tetradecanoyl-phorbol-13-acetate Exposed Mouse Skin Endonuclease Activity and DNA Synthesis
2000, 13(2): 122-130.
Nicotinamide (NA), a relatively nontoxic compound, has been shown to inhibit tumor development, induce differentiation, increase the sensitization of the anticancer drug resistant cancer cells and is being used in different skin ailments. But there are not many reports on its mechanism of action. Here we report that NA induced endonuclease activity. This endonuclease induction by NA appeared to be dose dependent and a function of time. As evident by the use of modifiers of DNase I, this endonuclease appeared to be like DNase type I. Increased [3H] thymidine incorporation in DNA in the presence of NA is possibly a consequence of increased 3-OH'nicks due to increased DNA fragmentation by increased endonuclease activity. The present results would be of help in the better understanding of the mechanism of NA action and its improved use in cancer control.
2000, 13(2): 131-139.
To further reveal the risks of heroin abuse to human body, and to determine the injuries of oxidation, peroxidation and lipoperoxidation induced by nitric oxide and other free radicals to heroin abusers, we determined and compared plasma values of lipoperoxides (LPO), nitric oxide (NO), vitamin C (VC), vitamin E (VE), β-carotene (β-CAR) and erythrocyte values of LPO, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in 114 heroin abusers and 100 healthy volunteers. Using linear regression and correlation as well as stepwise regression and correlation, we also analyzed the effect of the abusing duration, and daily abusing quantity on the above-mentioned biochemical parameters in the heroin abusers. The results showed that, compared with the healthy volunteer groups, the average plasma values of LPO, and NO, and the average erythrocyte value of LPO in the heroin abuser group were significantly increased (P＜0.0001), and the average plasma values of VC, VE, and β-CAR and the average erythrocyte values of SOD, CAT, and GSH-Px were significantly decreased (P＜0.0001). Analysis of linear regression and correlation showed that with prolonged heroin abusing and with increased daily quantity in the heroin abusers, the plasma values of LPO, and NO, and the erythrocyte value of LPO were gradually increased (P＜0.001), whereas the plasma values of VC, VE, and β-CAR and the erythrocyte values of SOD, CAT, and GSH-Px were gradually decreased (P＜0.001). Analysis of stepwise regression and correlation indicated that the plasma values of NO, VC and VE were closely correlated with the abusing duration and daily abusing quantity. These results indicate that the balance between oxidation and antioxidation in the heroin abusers was seriously disturbed, and the injuries induced by nitric oxide and other free radicals, through oxidation, peroxidation and lipoperoxidation to the bodies of heroin abusers exacerbated. It is therefore necessary that in abstaining from heroin dependence, the heroin abusers should acquire sufficient quantities of antioxidants such as VC, VE and β-CAR.
2000, 13(2): 140-147.
The study investigated the burden of smear-positive pulmonary TB and its infectivity, using DALY (Disability-Adjusted Life Year) as an indicator. An assumed cohort of 2000 cases was set up based on the age-specific incidence of 794 newly registered smear positive cases of TB in Beijing in 1994. Prognostic trees and model diagrams of infectivity under natural history and DOTS (Direct Observed Treatment, Short-course) strategy were established according to the epidemiological evidence. The results show that 29.6% of DALYs would be neglected if the burden caused by the infectivity was not considered. The results also show that DOTS strategy may reduce 97.3% of the number of potential cases infected, 92.9% of DALYs related to TB-patients themselves, and 99.9% of DALYs caused by TB's infectivity as well.
The Prevalence of NIDDM and IGT and Related Factors Among Residents in Some Areas of Hubei Province, China
2000, 13(2): 148-153.
The epidemiological survey of prevalence of NIDDM (non-insulin dependent diabetes mellitus) and IGT(impaired glucose tolerance)was conducted among 9450 residents aged 25～70 in some areas of Hubei Province, China. The results show that NIDDM and IGT prevalences are 2.62% and 4.48%, respectively. There is no significant difference between male and female (P>0.05). The NIDDM prevalence in cities is slightly higher than that in countryside, but the difference is not significant (P>0.05). However, the IGT prevalence in city is significantly higher than that in countryside (P<0.01). The prevalence of both NIDDM and IGT is increasing along with the age of the population. It is also significantly related to the family history of NIDDM, hypertension, and high body mass index (BMI). By using stepwise logistic regression to analyse the risk factors of NIDDM, age (OR=1.86),BMI(OR=2.69), family history (OR=2.84) and hypertension (OR=2.23) entered the model (significance level is α=0.05).