Occupational risks for primary liver cancer in Shanghai, China

Using occupational data for over 3,400 primary liver cancer cases diagnosed between 1980 and 1984 reported to the Shanghai Cancer Registry, and employment information from the 1982 census for the Shanghai population, standardized incidence ratios were computed to generate leads to occupational risks of liver cancer. Among men, a statistically significant excess number of cases was observed for chemical processors, textile workers, wood workers, blacksmiths and machine-tool operators, and material handlers and dock workers. Increased incidence of liver cancer also was observed among female transport equipment operators. These findings indicate that a number of similar occupations are associated with increased risk of primary liver cancer in western countries and China. Although causal inferences cannot be drawn from these data, our study adds to the limited evidence of the potential role of occupational exposures in liver carcinogenesis.

Prior medical conditions and the risk of adult leukemia in Shanghai, People's Republic of China

A population-based case-control interview study of 486 adult leukemia cases and 502 healthy controls was carried out in Shanghai, People's Republic of China during 1987-89 to evaluate the etiologic role of prior medical conditions, medications, and diagnostic X-rays. Risks were examined separately for 236 cases with acute non-lymphocytic leukemia (ANLL), 79 with chronic myeloid leukemia (CML), 81 with acute lymphocytic leukemia (ALL), and 21 with chronic lymphocytic leukemia (CLL). Little difference was found between cases and controls for prior history of diabetes, hypertension, allergic conditions, most medications, and diagnostic X-rays. A few significant associations were observed for appendectomy, tuberculosis, and for several other chronic disorders with specific leukemia cell types, but the odds ratio estimates for most of these ranged from two to three and, with the exception of the two specified above, were based generally on five or fewer exposed controls. In contrast to an association with childhood leukemia in Shanghai, prior use of chloramphenicol was not linked with ANLL or other forms of adult leukemia. Further research is needed to clarify the relation of specific medical conditions and exposures with particular subtypes of leukemia, and to examine reasons for the low incidence of CLL in China and other Asian populations.

Physical activity and risk of endometrial cancer

In a population-based case-control study of endometrial cancer, we interviewed 268 cases and an equal number of matched controls regarding physical activity at work and outside of work. We also obtained self-ratings of overall physical activity levels. The results showed that nonretired women holding sedentary jobs or those reporting sedentary life-styles were at somewhat increased risk of endometrial cancer. The associations remained unchanged after adjustment for caloric intake and body mass index. Although an effect of physical inactivity on endometrial cancer risk is biologically plausible, our results show some inconsistencies, such as a lack of elevation in risk among women who were physically inactive outside of work.

Incidence trends for cancers of the breast, ovary, and corpus uteri in urban Shanghai, 1972-89

Incidence data from the Shanghai (People's Republic of China) Cancer Registry were used to assess the temporal trends of three major female cancers during 1972-89. Rates for cancers of the breast, corpus uteri and, to a lesser extent, ovary rose over the study period. The increases in breast and ovarian cancer were most pronounced among women under age 50, whereas those for corpus uteri cancer were restricted generally to those aged 55 to 69 years. When considered by cohort year of birth, risk of breast and ovarian cancers rose among women born since 1925 and 1935, respectively, but little evidence of cohort effect was apparent for corpus uteri cancer. Potential explanations for these patterns are explored.

Occupational physical activity and the incidence of cancer of the breast, corpus uteri, and ovary in Shanghai

BACKGROUND

A sedentary life style has been consistently associated with an increased risk of colon cancer, but the evidence for its association with breast and other gynecologic cancers is limited.

METHODS

Occupational information for 3783 incident patients with cancer (breast, 2736; corpus uteri, 452; and ovary, 595) whose disease was diagnosed during the period 1980-1984 was compared with 1982 census data on employment in Shanghai urban areas. The standardized incidence ratios (SIR) of these cancers were estimated for each occupational group classified by job titles and physical activity levels.

RESULTS

A significantly increased incidence of breast cancer was found among professionals (SIR = 158), government officials (SIR = 131), and clerical workers (SIR = 143); the incidence was reduced among service workers (SIR = 87) and craftsmen (SIR = 91). Occupational physical activity, as measured by sitting time and energy expenditure, was inversely related to breast cancer incidence, with SIR of 127-131 for inactive jobs (sedentary or low-energy expenditure) and 79-93 for active jobs (long periods of standing or high energy expenditure). Similar associations, although to a lesser extent, were also seen for cancer of the corpus uteri and ovary.

CONCLUSIONS

Women with low physical activity occupations had an increased incidence of cancer of the breast, corpus uteri, and ovary; the incidence was reduced among women with high-activity jobs. These findings were consistent with observations from earlier studies and provided further evidence that physical activity may lower the risk of these female hormone-dependent cancers.

Cancer incidence trends in urban Shanghai, 1972-1989

Incidence data pertaining to more than 250,000 cancer cases diagnosed during the years 1972-1989 among residents of urban Shanghai, China, were analyzed to determine the relative importance of the various malignancies and to discover changes over time. In the most recent 3-year period, lung cancer was the most frequent cancer among men (57.0 per 100,000 person-years, age-adjusted world standard), followed by cancers of the stomach (50.1), liver (29.6), esophagus (13.3), colon (11.2) and rectum (9.4). Among women, breast cancer leads (25.1), followed by cancers of the stomach (23.2), lung (18.8), liver (10.9), colon (10.2) and rectum (7.3). The most impressive increases in incidence rates from 1972-74 to 1987-89 were observed for cancers of the gallbladder (119% and 101% among men and women, respectively), colon (85% and 78%), and brain and other nervous system (71% and 60%). In addition, increases of 20-50% occurred for cancers of the pancreas, male lung, female breast, corpus uteri, kidney, and for non-Hodgkin's lymphoma. Rates declined notably for cancers of the esophagus (-54% and -53%), cervix uteri (-86%), and to a lesser extent (10-20%) cancers of the male stomach and liver. These observed trends can be explained only partly by improvements in cancer diagnosis and completeness of the cancer registry, and most likely reflect changes in the prevalence of risk factors in this population.

Serum micronutrients and the subsequent risk of oral and pharyngeal cancer

To investigate the relationship between serum micronutrients and the subsequent risk of oral and pharyngeal cancer, a nested case-control study was conducted within a cohort of 25,802 adults in Washington County, MD, whose blood samples were collected in 1974 and stored at -70 degrees C for subsequent assays. The serum levels of nutrients in 28 individuals who developed oral and pharyngeal cancer during 1975 to 1990 were compared with levels in 112 matched controls. Serum levels of all individual carotenoids, particularly beta-carotene, were lower among subjects who developed oral and pharyngeal cancer. The risks of this malignancy decreased substantially with increasing serum level of each individual carotenoid. Persons in the highest tertile of total carotenoids had about one-third the cancer risk as those in the lowest tertile. High serum levels of alpha-tocopherol also were related to a low oral cancer risk in later years, but the risks were elevated significantly with increasing serum levels of gamma-tocopherol and selenium. The findings from this study are consistent with many previous epidemiological investigations of dietary factors for oral and pharyngeal cancer and provide further evidence for the potential role of carotenoids and alpha-tocopherol in the chemoprevention of these malignancies.

Physical activity and occupational risk of colon cancer in Shanghai, China

Using occupational data for over 2000 colon cancer cases diagnosed between 1980 and 1984 in Shanghai, and employment information from the 1982 census for the Shanghai population, standardized incidence ratios (SIR) were computed for occupational groups classified by job types and physical activity levels. Men employed in occupations with low physical activity levels had modest but significantly elevated risks of colon cancer. SIR for jobs with low activity based on sitting time was 121 (95% confidence interval, Cl: 108-135) and based on energy expenditure was 126 (95% Cl: 115-138). Corresponding SIR for women were 99 (95% Cl: 83-118) and 113 (95% Cl: 100-127). The data were also used to screen for specific occupations with elevated SIR to generate leads to occupational colon cancer. Increased incidence was observed for professional and other white collar workers, and male chemical processors and female textile workers. The findings add to the emerging evidence that workplace activity may influence the risk of this common cancer.

A population-based case-control study of dietary factors and endometrial cancer in Shanghai, People's Republic of China

The relation between diet and endometrial cancer was examined in a population-based case-control study conducted in Shanghai, People's Republic of China, between 1988 and 1990, involving interviews with 268 cases and 268 controls aged 18-74 years. The subjects' usual dietary intake of 63 major foods during the previous 10 years (disregarding any recent changes) was measured by means of a structured quantitative food questionnaire. Although women in the highest quartile of total caloric intake had a 2.1-fold increased risk of endometrial cancer, risk varied according to the source of calories. The highest quartiles of caloric intake from fat and protein were associated with odds ratios of 3.9 and 3.1, respectively, while calories from carbohydrates, the major contributor of total calories in this population, were not related to risk. The association of fat and protein with endometrial cancer risk was confined to foods of animal origin in the diet. After adjustment for age, body mass index (weight (kg)/height (m)2), and number of pregnancies, odds ratios were 3.5 (95% confidence interval (CI) 2.0-6.0) and 3.0 (95% CI 1.7-5.1) for women in the highest quartiles of intake of animal fat and animal protein, respectively. Food group analyses showed a similar pattern, with high consumption of meat, eggs, and fresh fish being associated with elevated risks. After adjustment for total calories, no significant association of risk was found with intake of vegetables or dark green/yellow vegetables, or with estimated carotene intake, although fruit and allium vegetables were associated with some reduction in risk. These results suggest that diets rich in animal fat and animal protein may play an important role in the etiology of endometrial cancer.

Correlations of colon cancer mortality with dietary factors, serum markers, and schistosomiasis in China

To determine correlates of the geographic variation in colon cancer mortality within China, dietary variables, biochemical markers, and other factors from an ecological survey in 49 Chinese rural counties were examined. High consumption of animal foods, salt-preserved vegetables, and beer was associated with increased mortality of colon cancer, whereas the rates were significantly inversely related with intake of green vegetables. Serum levels of total cholesterol, urea nitrogen, and lipid peroxide were positively correlated with colon cancer mortality, after adjustment for each other and for other blood nutrients. No appreciable associations, however, were found between colon cancer and serum levels of beta-carotene, alpha-tocopherol, vitamin C, and selenium. In addition, prevalence of schistosomiasis was significantly correlated with increased colon cancer mortality. This ecological study indicates that observations from earlier analytic investigations in Western societies may apply to a Chinese rural population and suggests that schistosomiasis and dietary factors may contribute to the remarkable geographic variation of colon cancer in China.

Molecular cloning and expression ofBacillus subtilis bglS gene inSaccharomyces cerevisiae

A 2.7-kb EcoRI DNA fragment carrying a Bacillus subtilis endo-beta-1,3-1, 4-glucanase gene (bglS) from the E. coli plasmid pFG1 was cloned into an Escherichia coli/yeast shuttle vector to construct a hybrid plasmid YCSH. The hybrid plasmid was used to transform Saccharomyces cerevisiae, and the bglS gene was expressed. Variation between levels of bglS gene expression in S. cerevisiae was about 2.3-fold, depending on the orientation of the 2.7-kb DNA fragment. Assay of substrate specificity and optimal pH of the enzyme demonstrated that the enzyme encoded by YCSH (bglS) was identical with that found in B. subtilis, but the expression level of bglS gene in S. cerevisiae (YCSH) was much lower than that in E. coli (YCSH).

A population-based case-control study of cancers of the nasal cavity and paranasal sinuses in Shanghai

A population-based case-control study of cancer of the nasal cavity and sinuses, involving interviews of 60 incident cases and 414 controls, was conducted in Shanghai. Cigarette smoking was associated with a mild elevation in risk of squamous-cell carcinoma but not cancers of other cell types. Occupational exposures to wood and silica dusts and to petroleum products, and the use of wood and straw as cooking fuel, were linked to moderate increases in risk, while 4-fold or greater increases were associated with a history of chronic nasal diseases, including those occurring 10 or more years prior to cancer diagnosis. Dietary analyses revealed a significant protective effect of consumption of allium vegetables, oranges and tangerines, with a 50% reduced risk of nasal cancer among individuals in the highest intake group of these foods. Consumption of salt-preserved vegetables, meat and fish was associated with a significantly increased risk of nasal cancer in a dose-response fashion, with a 5-fold excess observed for the heaviest intake of these salted foods. These findings suggest that dietary factors may contribute to the development of nasal cancer.

Risk factors for renal-cell cancer in Shanghai, China

A population-based case-control study of 154 histologically verified renal-cell cancer patients and 157 controls was performed in Shanghai, China, an area with low rates for this tumor. Elevated risks were observed for cigarette smoking (odds ratio (OR) = 2.3; 95% confidence interval (CI): 1.1 to 4.9), and for increasing categories of body weight and meat consumption, while reduced risks were seen for increasing categories of fruit and vegetable intake. An increased risk was also observed for regular use of phenacetin-containing analgesics (OR = 2.3; 95% CI:0.7 to 7.0). These findings are consistent with earlier studies in Western countries, and indicate that many of the same etiologic factors for renal-cell cancer operate in low- and high-risk societies.

Occupational risks for nasopharyngeal cancer in Shanghai

To investigate occupational determinants of nasopharyngeal cancer (NPC) in the urban area of Shanghai, occupational information for 996 incident NPC patients diagnosed during 1980 to 1984 was compared with 1982 census data on employment. Standardized incidence ratios for NPC were estimated for broad and detailed occupational classifications. For the broadest level of classification, no excess risk was observed among craftmen and related manufacturing workers, but within this group significant excess risks were observed for specific occupations of textile weavers and knitters; metal smelting, converting, and refining furnacemen; boiler firemen; blacksmiths, hammersmiths, and forging-press operators; bakers, pastry cooks, and confectionery makers; welders and flame-cutters; and metal grinders, polishers, tool sharpeners, and machine-tool operators. Some of these findings are new; others are consistent with previous studies in other areas of the world. This study provides further evidence for the role of occupational factors in NPC.

Risk factors for oral and pharyngeal cancer in Shanghai, with emphasis on diet

A population-based case-control study of oral and pharyngeal cancer was conducted in Shanghai, China, from 1988 to 1990, in which 204 (115 male, 89 female) incident cases and 414 (269 male, 145 female) controls were interviewed. Cigarette smoking and alcohol consumption, as well as occupational exposures to asbestos and to petroleum products and the use of kerosene stoves in cooking, were associated with increased risk of oral and pharyngeal cancer. In addition, more cases than controls reported having chronic oral diseases and false teeth. Dietary intakes of 42 major foods and selected salt-preserved or deep-fried foods during the past 10 years, ignoring any recent changes, were measured by a structured quantitative food questionnaire. After adjusting for known etiological factors, risks decreased with increasing intake of fruits, particularly oranges and tangerines, and some vegetables, including dark yellow vegetables and Chinese white radish. Men in the highest tertile of intake of these fruits and vegetables had about 30-50% the risk of those in the lowest tertile, with a less pronounced effect among women. A new finding was an excess risk associated with high consumption of salt-preserved meat and fish. The findings from this study provide further evidence that dietary factors play an important role in the development of oral and pharyngeal cancer.

[Preliminary study on the effect of endothelin on the contraction of isolated rat pulmonary artery and its mechanism]

Experiment was performed on the rings of right pulmonary artery (PA) taken from male Wistar rats. Each ring was suspended in an organ bath (37 degrees C) containing Krebs solution, gassed with 95% O2-5% CO2 (pH7.40). The changes of vascular tension were measured. The contraction of PA to endothelin (ET) (10(-9) mol/L) and the effects of 764-3 (50, 100, 200, 300 micrograms/ml as a scavenger of superoxide anion), verapamil (3 x 10(-6) mol/L) NDGA, indomethacin, atropine, phentolamine, propranolol, ketanserin tartrate and diethylcarbamazine on the ET-induced contraction were investigated. The results indicated that ET can induce a potent and sustained contraction of PA, inhibited by verapamil and 764-3, but unaffected by inhibitors of cyclooxygenase, lipoxygenase, leukotrienes systhetase or adrenergic, serotonergic, cholinergic receptors. It is suggested that the influx of extracellular Ca2+ and the production of superoxide anion might be involved in the ET-induced contraction. Arachidonate metabolism and receptors mentioned above probably didn't participate in the responses.

Diet and other risk factors for laryngeal cancer in Shanghai, China

A population-based, case-control study of laryngeal cancer was conducted in Shanghai, China, during 1988-1990, in which 201 incident cases (177 males, 24 females) and 414 controls (269 males, 145 females) were interviewed. Cigarette smoking was the major risk factor, accounting for 86% of the male and 54% of the female cases. After adjusting for smoking, there was little increase in risk associated with drinking alcoholic beverages. Among men, cases more often reported occupational exposures to asbestos and coal dust. A protective effect was associated with the intake of fruits (particularly oranges and tangerines), certain dark green/yellow vegetables, and garlic, but there was an increased risk with the intake of salt-preserved meat and fish. The findings suggest that risk factors for laryngeal cancer in Shanghai resemble those in Western countries, and they provide further evidence that dietary factors play an important etiologic role.

Relation of obesity and body fat distribution to endometrial cancer in Shanghai, China

In a case-control study involving 268 cases of endometrial cancer and an equal number of population controls, we assessed the relationship of risk to body weight and fat distribution, examining weight at various ages and current anthropometric measurements. Weight gain during later adulthood and resultant high body masses were important risk predictors, indicating that obesity is an important risk factor, even in an area where the prevalence of obesity and incidence of endometrial cancer are low. Certain fat distribution patterns were related to risk of endometrial cancer independent of general obesity. In particular, fat deposits on the trunk were associated with elevated risks, with the odds ratio for the highest versus lowest quartile of subscapular skinfolds remaining significant even after adjustment for body mass index (odds ratio = 2.9; 95% confidence interval, 1.1-7.3). Central versus peripheral obesity, as measured by the subscapular:triceps ratio, also was related to increased risk, although the association failed to remain significant after adjustment for body mass (highest to lowest quartile, odds ratio = 1.7). In contrast, upper body obesity, as assessed by the waist:thigh ratio, was unrelated to risk. These results support the need for future studies assessing the relationship of hormonal and other biological parameters of fat distribution to assist in identifying causal mechanisms for this tumor.

Pharmacologic and radioligand binding studies of 1,4-dihydropyridines in rat cardiac and vascular preparations: stereoselectivity and voltage dependence of antagonist and activator interactions

The pharmacologic and radioligand-binding properties of 1,4-dihydropyridines in an activator (Bay K 8644) and an antagonist (nifedipine) series were studied in rat tail artery, heart membrane, and neonatal rat ventricular myocytes. The S-enantiomers of the activator series contracted rat tail artery in the presence of 15 mM K+ (EC50 values of 10(-8) to 10(-5) M). (S)-Bay K 8644 (I) and its o-difluoromethoxy analog (III) were the most potent members of the activator series examined. The abilities of the activators to stimulate maximum tension response of the artery differed with structure; thus, the efficacy of (S)-Bay K 8644 was 70% that of the analog lacking the 3-carbomethoxy group. The R-enantiomers of the activator series and a series of achiral nifedipine analogs were inhibitory in the same tissue. The intact-cell binding assay revealed the binding affinities of 1,4-dihydropyridine antagonists in depolarized cells (50 mM K+) to be higher than those in polarized cells (5 mM K+). The ratio KD (polarized)/KD (depolarized) was 77 for nifedipine (IC50 = 5.4 x 10(-9) M) but was only 2.9 for the weak 3-methoxy nifedipine analog (IC50 = 4.8 x 10(-6) M); an approximately linear relationship exists between this ratio and the antagonist potency. In marked contrast, and in confirmation of previous work [Mol. Pharmacol. 35:541-552 (1989)], the binding affinities of activators were not significantly affected by membrane potential, regardless of potency. We conclude that the S-enantiomers of Bay K 8644 analogs are activators with different potency and efficacy and that the R-enantiomers are antagonists, that the binding of 1,4-dihydropyridine antagonists is voltage dependent, whereas binding of the activators is not, and that the voltage-dependence of binding of the antagonists is correlated with the potency of the antagonist.

Human studies with the chelating agents, DMPS and DMSA

Meso-2,3-dimercaptosuccinic acid (DMSA) is bound to plasma albumin in humans and appears to be excreted in the urine as the DMSA-cysteine mixed disulfide. The pharmacokinetics of DMSA have been determined after its administration to humans po. For the blood, the tmax and t1/2 were 3.0 h + 0.45 SE and 3.2 h + 0.56 SE, respectively. The Cmax was 26.2 microM + 4.7 SE. To determine whether dental amalgams influence the human body burden of mercury, we gave volunteers the sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (DMPS). The diameters of dental amalgams of the subjects were determined to obtain the amalgam score. Administration of 300 mg DMPS by mouth increased the mean urinary mercury excretion of subjects over a 9 h period. There was a positive correlation between the amount of mercury excreted and the amalgam score. DMPS might be useful for increasing the urinary excretion of mercury and thus increasing the significance and reliability of this measure of mercury exposure. DMSA analogs have been designed and synthesized in attempts to increase the uptake by cell membranes of the DMSA prototype chelating agents. The i.v. administration of the monomethyl ester of DMSA, the dimethyl ester of DMSA or the zinc chelate of dimethyl DMSA increases the biliary excretion of platinum and cadmium in rats.

Bladder cancer and occupation in Shanghai, 1980-1984

To investigate occupational determinants of bladder cancer in the urban area of Shanghai, occupation and industry information for 1,219 incident bladder cancer cases diagnosed during the period 1980 to 1984 were compared with 1982 census data on employment. Standardized incidence ratios (SIR) for bladder cancer were estimated for occupation and industry classifications. Significant excess risks were observed for plastic products workers (male: SIR = 432; female: SIR = 368); textile bleachers, dyers, and finishers (male: SIR = 169); metal refining and processing workers (male: SIR = 139; female: SIR = 197); petroleum refining workers (male: SIR = 2152); railway engine drivers and firemen (male: SIR = 683); and workers employed in industries of apparel and other textile products manufacturing (female: SIR = 204); paper processing (male: SIR = 146; female: SIR = 226); organic chemical manufacturing (male: SIR = 186); plastic product manufacturing (male: SIR = 218; female: SIR = 272); and metallurgy (male: SIR = 107; female: SIR = 561). This study indicates that many of the industries and occupations that are responsible for increased risk throughout the world are also associated with occupational bladder cancer in Shanghai.

Pharmacological, radioligand binding, and electrophysiological characteristics of FPL 64176, a novel nondihydropyridine Ca2+ channel activator, in cardiac and vascular preparations

The pharmacological, radioligand binding, and electrophysiological properties of FPL 64176, a new nondihydropyridine Ca2+ channel activator, were studied in rat tail artery, cardiac membranes, and A7r5 smooth muscle cells. FPL 64176 induced a contractile response, with an EC50 value of 2.11 x 10(-7) M. The maximum tension response to FPL 64176 was approximately 2-fold higher than that to (S)-Bay K 8644. FPL 64176 showed no significant inhibitory activity at concentrations up to 10(-5) M. The Ca2+ channel antagonists nifedipine, verapamil and diltiazem noncompetitively antagonized and completely relaxed the responses induced by FPL 64176. IC50 values of these three drugs were 5.22 x 10(-9), 1.31 x 10(-7), and 1.95 x 10(-7) M, respectively, for relaxing submaximum contractile responses to FPL 64176 (5 x 10(-7) M). The washout time for FPL 64176 was about 40 min, which was much longer than that for (S)-Bay K 8644 (within 1 min). FPL 64176 weakly inhibited (+)-[3H]PN 200-110, [3H]D888, and [3H]TA-3090 binding in rat cardiac membranes, with IC50 values of 1.04 x 10(-5) M and 7.03 x 10(-6) M for inhibition of (+)-[3H]PN 200-110 and [3H]TA-3090 binding, respectively, and with 23% inhibition of [3H]D888 binding at a FPL 64176 concentration of 1 x 10(-5) M. Dissociation kinetics of the three radioligands were allosterically accelerated by FPL 64176. Electrophysiological studies on the A7r5 smooth muscle cell line directly confirmed a large (approximately 14-fold) stimulatory effect on L-type Ca2+ current amplitude. The results suggest that FPL 64176 is a new type of Ca2+ channel activator with higher efficacy and a mechanism and site of action that are distinct from those for (S)-Bay K 8644.

Thermodynamic and kinetic aspects of agonist and antagonist binding to 1,4-dihydropyridine receptors

The kinetic and equilibrium binding properties of the 1,4-dihydropyridine activator [3H](-)-S-Bay K 8644 and the antagonist [3H](+)-PN 200-110 were determined in rat heart membrane particulate preparations at temperatures between 4 and 37 degrees C. The binding of [3H](-)-S-Bay K 8644 was temperature-dependent with a single binding site with KD = 3.57 nM and Bmax = 330 fmol/mg.protein at 25 degrees C. The association and dissociation rate constants were 3.4 x 10(7) min-1 M-1 and 0.095 min-1 respectively at 25 degrees C and decreased slightly at lower temperatures. In contrast, [3H](+)-PN 200-110 bound to high (KD(H) = 0.032 nM, Bmax(H) = 316 fmol/mg.protein) and low affinity sites (KD(L) = 27.6 nM and Bmax(L) = 6432 fmol/mg.protein) at 25 degrees C in rat heart preparation. A similar two-site binding of [3H](+)-PN 200-110 was found in rat brain preparation, but only a single binding site was detected in rat skeletal muscle. Binding of [3H](+)-PN 200-110 to the high and low affinity sites in cardiac membranes was sensitive and insensitive respectively to temperature. Association and dissociation rates of [3H](+)-PN 200-110 at the high affinity binding sites were best fitted as mono-exponential functions. Association and dissociation rates of [3H](+)-PN 200-110 were 3.94 x 10(8) min-1 M-1 and 7.86 x 10(-3) min-1 at 25 degrees C. The association rate varied only slightly (3-fold), but the rate of dissociation decreased significantly (200-fold) with temperature from 37 to 4 degrees C. Thermodynamic analysis of equilibrium binding showed that the binding of activator was enthalpy driven, whereas the binding of antagonist to the high affinity site was both entropy- and enthalpy-driven and to the low affinity site was totally entropy-driven.

A population-based case-control study of endometrial cancer in Shanghai, China

A case-control study of 268 patients with endometrial cancer and 268 population controls was conducted during 1988-1990 in Shanghai, China, to evaluate etiologic factors in a population whose risk had not been substantially altered by the use of exogenous estrogens. In spite of this, the major risk factors resembled those found in other studies. The risk of endometrial cancer was significantly elevated among nulligravidas (OR = 5.4, 95% CI = 2.0-14.6) and decreased with number of pregnancies (p less than 0.01). Late age at menopause was associated with increased risk, while early age at menarche was unrelated. Use of oral contraceptives for more than 2 years was associated with a reduction in endometrial cancer risk (OR = 0.4, 95% CI = 0.1-1.2), while short-term use of oral contraceptives and other methods of contraception were unrelated. Obesity was a strong predictor of risk, with women in the highest quartile of weight having 2.5 times the risk of those in the lowest quartile. In contrast to many other studies, cigarette smokers were at elevated risk (OR = 1.7, 95% CI = 0.9-3.0). Risk was also elevated among women reporting a history of gall-bladder disease, polycystic ovaries, menstrual symptoms, and non-estrogen hormone use.

Choroid plexus protects cerebrospinal fluid against toxic metals

Although heavy metal ions are known to be toxic to the central nervous system (CNS), the mechanisms by which the CNS may protect itself from initial challenges of such toxic ions is unknown. The choroid plexus is the principal site of formation of the cerebrospinal fluid (CSF) which bathes the brain. We have determined in rats and rabbits that after intraperitoneal administration of lead, cadmium, mercury, and arsenic compounds, these toxic metal ions accumulated in the lateral choroid plexus at concentrations of Pb, Hg, and As that were 70-, 95-, and 40-fold higher, respectively, than those found in the CSF. Cd was not detected in the CSF. In addition, concentrations of these heavy metal ions were found to be many fold greater in the choroid plexus than in the brain or blood. The accumulation of Pb in the choroid plexus was dose-dependent and time-related. When the choroid plexus was preincubated, in vitro, with ouabain (1.5 mM), the uptake of Cd from the CSF side of the choroid plexus was inhibited 57%. Cadmium metallothionein was not found in the choroid plexus. Whereas the concentration of reduced glutathione in the choroid plexus was less than that in the brain cortex, the concentration of cystine was fourfold greater. The lateral choroid plexus sequesters Pb, Cd, As, and Hg. It appears to be one of the important mechanisms that protects the CSF and the brain from the fluxes of toxic heavy metals in the blood.

Interactions of analogs of the 1,4-dihydropyridine tiamdipine in cardiac and smooth muscle

Two series of 1,4-dihydropyridines related to tiamdipine, 2-(2-aminoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6- methyl-4-(3-nitrophenyl)-1,4-dihydropyridine, have been evaluated for their pharmacologic and radioligand binding properties in smooth and cardiac muscle. In the tiamdipine series the influence of phenyl ring substitution, 3-Cl, 3-MeO and 3-CF3, was greatly reduced relative to the N-formyl and neutral nifedipine derivatives. Consistent with our previous observations onset and offset of action were greatly reduced by the presence of the amine side chain. In tiamdipine analogs also bearing an asymmetric substituent at C-2, chirality at C-4 was determinant for activity.

Determination and metabolism of dithiol chelating agents. VII. Biliary excretion of dithiols and their interactions with cadmium and metallothionein

N-(2,3-Dimercaptopropyl) phthalamidic acid (DMPA), meso-dimercaptosuccinic acid (DMSA), and 2,3-dimercapto-1-propanesulfonic acid (DMPS) are dithiol chelating agents with antidotal activity for lead, mercury, arsenic, and other heavy metals. The biliary excretion of these compounds was studied in male Sprague-Dawley rats. After iv administration of DMPA, 72% of the injected dose was recovered in the bile. Half of the recovered DMPA was in the unaltered form (parent compound) and the other half was in the altered form (parent compound recovered after chemical reduction by DTT). An altered, presumably disulfide, form of DMPS was found in the bile. Neither unaltered nor altered DMSA was detected in the bile. DMPA (0.10 mmol/kg), given to rats 3 days after exposure to Cd, elicited within 30 min a 20-fold increase in biliary Cd excretion. The increase of biliary Cd by DMPA was dose-related and not due to an increase of bile flow rate. DMSA and DMPS did not significantly affect the biliary excretion of Cd. Incubation of DMPA or DMSA with Cd-saturated metallothionein (MT) resulted in the removal of Cd from MT. DMPA was more active than DMSA in this respect. The evidence strongly supports the mechanism that the increase of biliary cadmium following DMPA administration is the result of DMPA entering cells and mobilizing and removing the cadmium from MT. The removal of cadmium from metallothionein by dithiol chelating agents provides another dimension to their mechanisms of action and may provide an important new tool for the study of cadmium as well as metallothionein.

The interactions of 1,4-dihydropyridines bearing a 2-(2-aminoethylthio)methyl substituent at voltage-dependent Ca2+ channels of smooth muscle, cardiac muscle and neuronal tissues

The Ca2+ channel antagonistic potencies of tiamdipine [2-(2-aminoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6-m ethyl-4-(3- nitrophenyl)-1,4-dihydropyridine] and nifedipine [2,6-dimethyl-3,5-dicarbomethoxy-4-(2-nitrophenyl)-1,4-dihydrop yri dine] analogs bearing phenyl ring substituents were studied using pharmacologic and radioligand binding techniques. Additionally, analogs of tiamdipine possessing (2-aminoethylthio)methyl-, (2-acetamidoethylthio)methyl- and (2-pyrrolidinylmethylthio)methyl- groups at the C2 position of the 1,4-dihydropyridine ring have been studied. Tiamdipine and nifedipine analogs inhibited K(+)-induced contractile responses in rat tail artery. IC50 values of 4-phenyl ring substituted 2-(2-aminoethylthio)methyl tiamdipine analogs ranged from 10(-7) mol/l to 10(-8) mol/l. However, the corresponding 4-phenyl ring substituted nifedipine analogs covered a wider range of potency from 10(-6) mol/l to 10(-9) mol/l. KI values of the corresponding tiamdipine analogs for the inhibition of specific [3H]PN 200-110 [(+)-[3H]isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5- methoxycarbonyl-2,6-dimethyl-3-pyridinecarboxylate] binding ranged from 10(-7) mol/l to 10(-9) mol/l in guinea pig ileal and rat heart membranes and rat brain synaptosomes. The two stereoisomers of tiamdipine and its analog 2-(2-acetamidoethylthio)methyl-3-carboethoxy-5-carbomethoxy- 6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine, and the four stereoisomers of 2-(2-pyrrolidinylmethylthio)methyl-3-carboethoxy-5-carbom eth oxy-6-methyl-4-(3- nitrophenyl)-1,4-dihydropyridine showed high stereoselectivity ratios of approximately (-)/(+) = 100 and 1000 in pharmacologic and binding experiments, respectively. The inhibitory actions of 2-(2-aminoethylthio)methyltiamdipine analogs against K(+)-induced contractile responses in rat tail artery developed very slowly requiring at least 2 h for maximum effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination and metabolism of dithiol chelating agents. VIII. Metal complexes of meso-dimercaptosuccinic acid

Metal complexes of meso-dimercaptosuccinic acid (DMSA) with Pb2+, Cd2+, and Hg2+ were studied by potentiometric and infrared methods. This dimercapto metal-binding agent was found to form complexes whose structures are dependent on the metal ion to be complexed. In the cases of Pb2+ and Cd2+, one oxygen and one sulfur act as the donor atoms; in the case of Hg2+, two sulfur atoms act as the donors. The solubilities of all metal chelates were found to be pH dependent. Complexes of cadmium and lead are insoluble in the pH range 1.0 to 7.1, but are solubilized when the noncoordinated sulfhydryl and carboxylic acid groups are ionized. The mercury complex is insoluble in the pH range 1.0 to 3.0. It dissolves when one of the noncoordinated carboxylic acid groups is ionized. The dimethyl ester of meso-DMSA (DiMe-meso-DMSA) was synthesized and its acid dissociation constants were determined (pK1 = 6.38 and pK2 = 8.00). Esterification of the carboxyl groups of meso-DMSA changes its coordination properties in that the two sulfur atoms of DiMe-meso-DMSA are used to coordinate with Hg2+, Cd2+, or Pb2+. Esterification of meso-DMSA also changes its biological properties. DiMe-meso-DMSA, when given to rats 3 days after Cd administration, greatly increased the excretion of Cd via bile. In contrast, meso-DMSA was devoid of such activity.

A population-based case-control study of childhood leukemia in Shanghai

A population-based case-control interview study of 309 childhood leukemia cases and 618 healthy population control children was conducted in urban Shanghai, China. Like some studies in other countries, excess risks for both acute lymphocytic leukemia (ALL) and acute nonlymphocytic leukemia (ANLL) were associated with intrauterine and paternal preconception diagnostic x-ray exposure, and with maternal employment in the chemical and agricultural industries during pregnancy. ANLL was linked to maternal occupational exposure to benzene during pregnancy, whereas both ALL and ANLL were significantly associated with maternal exposure to gasoline and the patient's prior use of chloramphenicol. New findings, previously unsuspected, included an association of ANLL with younger maternal age at menarche (odds ratio [OR] = 4.3; 95% confidence interval (CI) = 1.3-13.9); a protective effect for long-term (greater than 1 year) use of cod liver oil containing vitamins A and D for both ALL (OR = 0.4; 95% CI = 0.2-0.9) and ANLL (OR = 0.3; 95% CI = 0.1-1.0); and excess risks of ANLL among children whose mothers were employed in metal refining and processing (OR = 4.6; 95% CI = 1.3-17.2) and of ALL associated with maternal occupational exposure to pesticides (OR = 3.5; 95% CI = 1.1-11.2). No relationships were found with late maternal age, certain congenital disorders, or familial occurrence, which have been related to childhood leukemia in other studies. In contrast with other reports, an excess of leukemia, primarily ANLL, occurred among second or later-born rather than firstborn children.

Occupation and lung cancer in Shanghai: a case-control study

Occupation was evaluated as a potential risk factor for lung cancer as part of a large population based case-control study conducted in the ten urban districts of Shanghai. A total of 733 newly diagnosed cases of male lung cancer and 760 controls selected from the general population was interviewed to obtain lifetime occupational histories and information on smoking and other factors. Of the approximately 25 major industrial titles examined, significantly raised risks, adjusted for smoking, were found for employment in agricultural production (odds ratio (OR) = 1.6, 95% confidence interval (CI) = 1.0-2.6). A concomitant increase was detected for farmers (OR = 1.6, 95% CI = 1.0-2.5) when 35 major occupational titles were examined. There was a 70% excess among workers in the chemical industry (OR = 1.7, 95% CI = 0.9-3.1) and a significant decrease among textile industry workers (OR = 0.7, 95% CI = 0.5-1.0). Raised risks of 30% to 80% were associated with reported job exposures to wood and coal dusts, smoke from burning fuels, and chemical fumes. Employment categories were also examined for 672 cases and 735 controls among women, but small numbers in many of the industrial and occupational categories precluded detailed analyses. The largest excess risk among women (OR = 5.1, 95% CI 1.3-23.5) was among glass products workers. Although cigarette smoking was the dominant cause of lung cancer among men and a significant risk factor among women in Shanghai, these findings suggest the importance of certain workplace exposures and offer leads to occupational carcinogens.

Lung cancer and smoking in Shanghai

A case-control study involving interviews with 733 male and 672 female incident lung cancer patients and 1495 population-based controls revealed that cigarette smoking is the dominant cause of lung cancer among men in urban Shanghai. All of the principal cell types were affected, with clear trends of rising risk with increasing intensity and duration of smoking. Far fewer women smoked cigarettes, but the overall risk patterns resembled those among males. Among women, however, smoking accounted for only about one-quarter of all lung cancers and less than 10% of lung adenocarcinomas. The findings lay to rest any doubts about the health hazards of smoking Chinese cigarettes, although smoking is not responsible for the high rates of adenocarcinoma reported among Chinese women.

Potential-dependent interactions of nitrendipine and related 1,4-dihydropyridines in functional smooth muscle preparations

Interaction of nitrendipine and other Ca2+ channel antagonists including nifedipine, diltiazem, and D600 with intestinal smooth muscle was shown to depend on membrane potential. In the absence of extracellular Ca2+, guinea pig ileal longitudinal muscle does not contract and can be incubated at various K+ concentrations in the presence or absence of antagonist. Preincubation with elevated K+ prior to admission of Ca2+ and challenge with K+ to a total of 100 mM increased the activity of the antagonist. The IC50 for nitrendipine incubated in the presence of 5 mM K+ was 5.36 X 10(-9) M and in the presence of 40 mM K+ was 0.53 X 10(-9) M. Other 1,4-dihydropyridines showed similar potency shifts.

Lung cancer among Chinese women

A case-control study involving interviews with 672 female lung cancer patients and 735 population-based controls was conducted to investigate the high rates of lung cancer, notably adenocarcinoma, among women in Shanghai. Cigarette smoking was a strong risk factor, but accounted for only about one-fourth of all newly diagnosed cases of lung cancer. Most patients, particularly with adenocarcinoma, were life-long non-smokers. The risks of lung cancer were higher among women reporting tuberculosis and other pre-existing lung diseases. Hormonal factors were suggested by an increased risk associated with late menopause and by a gradient in the risk of adenocarcinoma with decreasing menstrual cycle length, with a 3-fold excess among women who had shorter cycles. Perhaps most intriguing were associations found between lung cancer and measures of exposure to cooking oil vapors. Risks increased with the numbers of meals cooked by either stir frying, deep frying or boiling; with the frequency of smokiness during cooking; and with the frequency of eye irritation during cooking. Use of rapeseed oil, whose volatiles following high-temperature cooking may be mutagenic, was also reported more often by the cancer patients. The findings thus confirm that factors other than smoking are responsible for the high risk of lung cancer among Chinese women and provide clues for further research, including the assessment of cooking practices.

Decreased risk of lung cancer in the cotton textile industry of Shanghai

The relationship between lung cancer risk and work in the cotton textile industry was investigated in a large population-based case-control study in urban Shanghai, where the industry is a major employer of men and women. Personal interviews obtained occupational, smoking, and other information from 1405 newly diagnosed lung cancer cases and 1495 controls. A significantly low risk of lung cancer was associated with cotton textile employment [odds ratio (OR) = 0.7,95% confidence interval (CI) = 0.6-0.9]. In men, the decreased risk was observed among both smokers (OR = 0.7, 95% CI = 0.5-1.1) and nonsmokers (OR = 0.3, 95% CI = 0.1-1.0). In women, the risk was also decreased regardless of smoking status (OR = 0.8, 95% CI = 0.4-1.6 among smokers; OR = 0.9, 95% CI = 0.6-1.2 among nonsmokers). In both sexes, the reductions in risk tended to be greater for lung cancer cell types other than adenocarcinoma. Low risks were found regardless of occupations within the cotton textile industry; the OR for workers in textile processing who potentially had greater dust exposure was 0.8 (95% CI = 0.6-1.2), whereas the OR for those in other industry jobs was 0.7 (95% CI = 0.4-1.0). There was little difference in risk according to self-reported exposure to textile dust, and no clear trend with duration of employment or dust exposure. Reasons for the reduced risk of lung cancer in cotton textile workers without a dose response are unclear, although several methodological explanations were considered. The findings, however, appear consistent with prior epidemiological studies and are interesting in light of speculation about tumor-inhibitory factors, such as bacterial endotoxins, that are found in dusts from cotton and other fiber crops.

Lung cancer and prior tuberculosis infection in Shanghai

In a population-based case-control study of lung cancer in Shanghai involving interviews during 1984-86 with 1,405 cancer patients and 1,495 controls, a significant 50% elevation in the risk of lung cancer, adjusted for cigarette smoking, was observed among persons who had a history of tuberculosis. Among those diagnosed with tuberculosis within the past 20 years, the risk exceeded 2.5-fold. In males the lung cancers tended to occur on the same side as the previous tuberculosis infection. For both sexes, the effect of recent tuberculosis was most apparent for adenocarcinoma and peripheral tumours. No relationship was found between lung cancer risk and the type of tuberculosis therapy, including use of isoniazid. The findings suggest that tuberculosis may predispose to lung cancer, with the association most apparent among recent survivors of the infection.