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.