Cancer risk in offspring of male pesticide applicators in agriculture in Sweden.

AIMS: To explore cancer risk from date of birth until 1994 in children, born 1958 or later, of Swedish male pesticide applicators. METHODS: Records of male pesticide applicators licensed 1965-76 were linked to the Multigeneration Register. The records of their offspring were then linked to the Swedish Cancer Registry and the Cause of Death Register. RESULTS: In total 51 cases of cancer were observed, which is significantly lower than the expected 73.0 (standardised incidence ratio (SIR) 0.70, 95% CI 0.52 to 0.92). Tumours of the nervous system was most common, amounting to 20 cases, 39% of all cancer cases (SIR 1.01, 95% CI 0.62 to 1.56). A statistically significant reduced risk for leukaemia was found (SIR 0.43, 95% CI 0.19 to 0.86). For non-Hodgkin's lymphoma, three cases were observed and 4.8 expected (SIR 0.63, 95% CI 0.13 to 1.83). For Hodgkin's disease, five cases were observed versus 3.7 expected (SIR 1.36, 95% CI 0.44 to 3.17). Two cases of testicular cancer were observed and 1.7 expected (SIR 1.19, 95% CI 0.13 to 4.28). CONCLUSIONS: None of the a priori hypotheses of increased risk of tumours of the nervous system, kidney cancer, leukaemia, lymphoma, soft tissue sarcoma, and testicular cancer in children of male pesticide applicators could be confirmed.

Effects of isoenergetic overfeeding of either carbohydrate or fat in young men.

Ten pairs of normal men were overfed by 5 MJ/d for 21 d with either a carbohydrate-rich or a fat-rich diet (C- and F-group). The two subjects in each pair were requested to follow each other throughout the day to ensure similar physical activity and were otherwise allowed to maintain normal daily life. The increase in body weight, fat free mass and fat mass showed great variation, the mean increases being 1.5 kg, 0.6 kg and 0.9 kg respectively. No significant differences between the C- and F-group were observed. Heat production during sleep did not change during overfeeding. The RQ during sleep was 0.86 and 0.78 in the C- and F-group respectively. The accumulated faecal loss of energy, DM, carbohydrate and protein was significantly higher in the C- compared with the F-group (30, 44, 69 and 51% higher respectively), whereas the fat loss was the same in the two groups. N balance was not different between the C- and F-group and was positive. Fractional contribution from hepatic de novo lipogenesis, as measured by mass isotopomer distribution analysis after administration of [1-(13)C]acetate, was 0.20 and 0.03 in the C-group and the F-group respectively. Absolute hepatic de novo lipogenesis in the C-group was on average 211 g per 21 d. Whole-body de novo lipogenesis, as obtained by the difference between fat mass increase and dietary fat available for storage, was positive in six of the ten subjects in the C-group (mean 332 (SEM 191)g per 21 d). The change in plasma leptin concentration was positively correlated with the change in fat mass. Thus, fat storage during overfeeding of isoenergetic amounts of diets rich in carbohydrate or in fat was not significantly different, and carbohydrates seemed to be converted to fat by both hepatic and extrahepatic lipogenesis.

[Effects of excessive isocaloric intake of either carbohydrate or fat on body composition, fat mass, de novo lipogenesis and energy expenditure in normal young men]. / Virkninger af isokalorisk overindtagelse af kulhydrat eller fedt på legemsvaegt, fedtmasse, de novo lipogenese og energiomsaetning hos normale unge maend.

Ten pairs of normal young men were overfed by 5 MJ per day for 21 days with either a carbohydrate-rich or a fat-rich diet (C- and F-group). The two subjects of a pair were requested to follow each other throughout the day to ensure similar physical activity. The increase in body weight and fat mass were not significantly different between the C- and the F-group. Heat production during sleep did not change during overfeeding. The accumulated faecal loss of energy, dry matter, carbohydrate and protein was significantly higher in the C- than in the F-group. Hepatic de novo lipogenesis was 212 g per 21 days in the C-group and was too low to be determined in the F-group. Whole body de novo lipogenesis was positive in six of the ten subjects in the C-group (mean: 332 g per 21 days). It is concluded that the increase in body weight and fat mass during overfeeding of isocaloric amounts of diets rich in carbohydrate or in fat was not significantly different, and that surplus of carbohydrate seemed to be converted to fat both by hepatic and extrahepatic de novo lipogenesis.

Risk of colorectal and other gastro-intestinal cancers after exposure to nitrate, nitrite and N-nitroso compounds: a follow-up study.

N-nitroso compounds are potent carcinogens detected in foodstuffs. The importance of dietary nitrosamines in relation to human cancer development is, however, uncertain. We studied the relationship between intake of nitrates, nitrites and N-nitrosodimethylamine (NDMA) and risk of cancers of the gastro-intestinal tract in a cohort of 9,985 adult Finnish men and women. During a follow-up period of up to 24 years, 189 gastro-intestinal cancer cases were diagnosed in the cohort, initially free from cancer. Intake of nitrate, nitrite and NDMA were estimated, based on food-consumption data from a 1-year dietary history interview covering the total diet of the participants. A significant positive association was observed between intake of NDMA and subsequent occurrence of colorectal cancer with a relative risk (RR) between the highest and lowest quartiles of intake of 2.12 [95% confidence interval (CI) 1.04-4.33]. Of various sources of N-nitroso compounds, intake of smoked and salted fish was significantly (RR = 2.58, 95% CI 1.21-5.51) and intake of cured meat was non-significantly (RR = 1.84, 95% CI 0.98-3.47) associated with risk of colorectal cancer. No similar association was observed for intake of other fish or other meat. No significant associations were observed between NDMA intake and cancers of the head and neck combined or of the stomach or between nitrate or nitrite intake and risk of cancers of the gastro-intestinal tract. Our results are in line with the idea that N-nitroso compounds can induce colorectal cancer in humans.

Regulation of glycogen accumulation in L6 myotubes cultured under optimized differentiation conditions.

The differentiation of the L6 myogenic cell line was enhanced by the addition of dexamethasone, retinoic acid, insulin-like growth factor I (IGF-I), and creatine. Spontaneous contractions appeared from day 10 or 11 and persisted to day 14 or 15. Glucose transport was increased by insulin (100 nM) and IGF-I (5 nM) by approximately 60%. The highest level of glycogen was measured in myotubes differentiated under the influence of a combination of 5 nM dexamethasone, 100 nM retinoic acid, 5 nM IGF-I, and 10 mM creatine with glucose as substrate. The glycogen accumulation rate was constant from 0 to 2 h of incubation and decreased gradually to zero at 4 h. From 0 to 0.5 h of the glycogen accumulation, the glycogen synthase a (GSa) activity was 30-35% of the total activity, with a subsequent gradual decline to 2.5% after 6 h. The glycogen phosphorylase a (GPha) activity was constant at approximately 80% from 0 to 0.5 h, increasing to approximately 100% after 6 h. The activity ratio of GSa to GPha decreased about sixfold without significant change in the rate of glycogen accumulation. This indicates that factors other than phosphorylation/dephosphorylation play a decisive role in the regulation of glycogen metabolism in L6 myotubes. Intracellular glucose (glucosei) and glucose 6-phosphate (G-6-P) may be such factors. The observed values of these parameters may in fact explain an activation of GSa (G-6-P) and an inhibition of GPha (glucosei).

Prostate cancer in pesticide applicators in Swedish agriculture.

BACKGROUND: The use of chemicals in agriculture has been associated with elevated risks of prostate cancer. The aim of this study was to analyze prostate cancer risk in a cohort of 20,025 pesticide applicators in agriculture licensed between 1965-1976. METHODS: The cohort was followed up in the Swedish Cancer Register from date of licence until death of December 31, 1991. The mean follow-up time was 21.3 years. RESULTS: We found a statistically significant increased risk of prostate cancer with 401 cases observed compared to 355 expected, with a standardized incidence ratio (SIR) of 1.13 (95% confidence interval: 1.02-1.24). There were 7 cases among those born in 1935 or later, and the SIR was 2.03 (0.82-4.19). For those born earlier than 1935 the SIR was 1.12 (1.01-1.24). CONCLUSIONS: These findings of a statistically significant increased risk of prostate cancer, together with recent results from other studies, imply a relationship between agrochemicals or other risk factors in the environment of farmers and prostate cancer.

Effect of fasted and fed conditions of protein turnover in perfused cultured hepatocytes.

In vivo studies of protein turnover in the fasted to fed transition have shown conflicting results. In the present study, protein turnover was investigated in primary cultures of rat hepatocytes, perfused for 48 h under conditions simulating portal vein concentrations of amino acids and hormones in the fasted or fed state. The rate of protein degradation was about 40% lower under fed than under fasted conditions. This difference was maintained for 36 h of perfusion. Transition from fasted to fed conditions showed an immediate decrease in the degradation rate to that exhibited by cultures perfused under fed conditions. After 24 h of perfusion, the rate of synthesis was 50% higher with a fed medium, and transition from fasted to fed conditions resulted in a 50% increase in the synthesis rate. Dose-response relationships for insulin showed effects on protein turnover in the insulin concentration range below the physiologic range. It is concluded that protein degradation as well as protein synthesis in the fasted to fed transition is regulated mainly by the amino acid concentrations.

Pesticides and cancer.

Epidemiologic evidence on the relationship between chemical pesticides and cancer is reviewed. In animal studies, many pesticides are carcinogenic, (e.g., organochlorines, creosote, and sulfallate) while others (notably, the organochlorines DDT, chlordane, and lindane) are tumor promoters. Some contaminants in commercial pesticide formulations also may pose a carcinogenic risk. In humans, arsenic compounds and insecticides used occupationally have been classified as carcinogens by the International Agency for Research on Cancer. Human data, however, are limited by the small number of studies that evaluate individual pesticides. Epidemiologic studies, although sometimes contradictory, have linked phenoxy acid herbicides or contaminants in them with soft tissue sarcoma (STS) and malignant lymphoma; organochlorine insecticides are linked with STS, non-Hodgkin's lymphoma (NHL), leukemia, and, less consistently, with cancers of the lung and breast; organophosphorous compounds are linked with NHL and leukemia; and triazine herbicides with ovarian cancer. Few, if any, of these associations can be considered established and causal. Hence, further epidemiologic studies are needed with detailed exposure assessment for individual pesticides, taking into consideration work practices, use of protective equipment, and other measures to reduce risk.

Dietary intakes of nitrate, nitrite and NDMA in the Finnish Mobile Clinic Health Examination Survey.

Concern about potential health hazards of nitrate, nitrite and N-nitroso compounds necessitates calculations of exposures to these compounds and their distribution in normal populations. This study describes dietary intake of nitrate (NO3-), nitrite (NO2-) and N-nitrosodimethylamine (NDMA) among 5304 adult men and 4750 women, who participated in the Finnish Mobile Clinic Health Examination Survey in 1967-72. Food consumption data for each individual over the preceding year were collected by a dietary history interview. Intakes of nitrate, nitrite and NDMA from vegetables, fruits, cheese, meat and fish products were calculated using available values mainly derived from Finland and other countries in northern Europe. Nitrate and nitrite from drinking water were not included in the study. Mean daily dietary intake of nitrate was 77 mg, of nitrite 5.3 mg, and of NDMA 0.05 microgram respectively. Intake of NDMA from beer, estimated in a part of the study population, was 0.07 microgram per day. More than 90% of dietary nitrate was derived from vegetables, including potatoes. Nitrite was mainly provided by cured meat products. Cured meat products and smoked and salted fish were important food sources of NDMA. The total daily intake of nitrate was similar in men and women, whereas intakes of nitrite and NDMA were higher in men than in women. The diet of farmers was characterized by lower amounts of nitrate, nitrite and NDMA, whereas white collar workers and those employed in industry had higher intakes. Current smokers were exposed to higher dietary intakes of nitrate, nitrite and NDMA than non-smokers. Intakes of dietary nitrate, nitrite and NDMA estimated on an individual level are suggested to be useful in evaluating the health effects of these compounds in epidemiological studies.

[Low cancer risk among female agricultural workers]. / Låg cancerrisk bland kvinnliga lantbrukare.

In a cohort study of cancer incidence, 50,682 women registered in the 1970 Swedish census as engaged in agriculture were followed up in the national Cancer- Environment Register from 1971 to 1987. Instead of the expected incidence of 5,273 cases, a total of only 4,474 cases were found, yielding a significantly reduced standardised incidence ratio (SIR) of 0.85. Thus, site specific SIRs were also significantly reduced for cancer of the breast (0.83), cervix uteri (0.40), lung (0.46), urinary tract (0.57), and several other sites.

Cancer risks among male farmers in Sweden.

We have conducted a cohort study of cancer risks among 140,208 Swedish farmers in order to compare their cancer risks with those of the general male population. Since there were no individual data regarding exposure to agricultural chemicals and acquiring such data was not realistic, we obtained crude and hypothetical estimates for exposure by dividing the data into time periods, year-of-birth cohorts and geographical areas. The cohort was followed-up in the Cancer Environment Register from 1 January 1971 either until death or until 31 December 1987. The relative risk was computed as the ratio of the observed and expected number of cases (SIR = standardized incidence ratio). A total of 15,040 cases were observed vs 18,918 expected, resulting in a statistically significant decreased SIR of 0.80 (95% confidence interval: 0.78-0.81). The SIR was significantly decreased for several cancer sites, and the lowest value was found for tongue, lung, oesophagus, liver and urinary organs, which is in agreement with other studies on cancer risks among farmers. Other major cancer sites with decreased SIRs were the colon, rectum, pancreas and kidney. Lip cancer and multiple myeloma showed statistically significant increased risks. SIRs for stomach cancer, prostate cancer, skin carcinoma, malignant melanoma, tumours in connective tissue or muscle, malignant lymphomas and leukaemia were all close to unity, which is not consistent with several other studies that have shown increased risks for these sites. For malignant lymphomas the SIR increased over time, though not significantly, and was highest among younger farmers. The SIR for non-Hodgkin lymphoma was lowest in the northernmost region. This gives some support to the hypothesis that there is an association between non-Hodgkin lymphoma and exposure to pesticides and other agricultural chemicals. It is of note that the SIR for multiple myeloma was significantly increased in those parts of Sweden where the use of pesticides has been less frequent and in lower amounts.

Cancer risks among female farmers in Sweden.

There are few studies on cancer risks among female farmers, particularly on breast cancer and cancer in female genital organs. We have conducted a cohort study of cancer risk among 50,682 women with occupations in agriculture according to the Swedish 1970 census. The cohort was followed up in the nationwide, population-based, Cancer-Environment Register from 1 January 1971 until death or until 31 December 1987. Expected number of cases was based on annual cancer incidence in five-year age groups. The standardized incidence ratio (SIR) was computed as the ratio between observed and expected number of cases. A total of 4,474 cases of cancer were observed in the cohort from 1971 until 1987 cf 5,273 expected, resulting in a significantly decreased SIR of 0.85 (95 percent confidence interval [CI] = 0.82-0.87). SIR for breast cancer was significantly decreased (0.83, CI = 0.78-0.88), as was the SIR for cervix uteri (0.40, CI = 0.31-0.50). For the other female genital organs, SIR was close to one. Other cancer sites with significantly decreased SIRs were: colon (0.90, CI = 0.81-1.00); rectum (0.86, CI = 0.74-1.00); lung (0.46, CI = 0.37-0.57); kidney (0.81, CI = 0.68-0.97); urinary organs (0.57, CI = 0.45-0.72); connective tissue and muscle (0.62, CI = 0.39-0.95); and non-Hodgkin's lymphomas (0.78, CI = 0.63-0.96).

Metabolism of thapsigargin in rat hepatocytes.

The cytotoxicity, uptake, and metabolism of thapsigargin, an inhibitor of the Ca(2+)-ATPases of the sarco- and endoplasmatic reticulum (the SERCA-family), were investigated in suspensions of rat hepatocytes using [3H]thapsigargin labeled at C-8. No effect was observed on the lactate dehydrogenase leakage from the cells or in glucose formation when hepatocytes were incubated with 0.5-25 microM thapsigargin. At 25 microM [3H]thapsigargin the initial rate of uptake into the cells was 471 nmol/10(8) cells/min. Thapsigargin metabolism followed first-order kinetics, with an initial rate of metabolism at 25 microM of 65 nmol/10(8) cells/min. The much faster uptake than metabolism suggests that thapsigargin probably is bound to cellular proteins or trapped in cellular membranes. The metabolites were characterized by normal and reversed phase TLC and by positive and negative FAB/ms. Two labeled products were identified when cells were incubated with 25 microM [3H]thapsigargin. The first product formed was desoctanoyl-thapsigargin, followed by formation of desacyl-thapsigargin. Thapsigargin metabolism was strongly inhibited by diethyl p-nitrophenyl phosphate, indicating that the deacylation of the compound is catalyzed by microsomal carboxylesterases. Upon prolonged incubation, a volatile, tritiated compound appeared, possibly water, due to oxidation of the alcohol group at C-8 of thapsigargin.

Cytoprotective effect of tocopherols in hepatocytes cultured with polyunsaturated fatty acids.

When highly unsaturated fatty acids are added to cell cultures, it can become important to include antioxidants in the culture medium to prevent cytotoxic peroxidation. To find an optimal antioxidant for this purpose, the effect of 50 microM alpha-tocopherol, gamma-tocopherol, alpha-tocopheryl acetate, alpha-tocopheryl acid succinate, or alpha-tocopheryl phosphate, or of 1 microM N,N'-diphenyl-1,4-phenylenediamine, was investigated with respect to the agent's ability to prevent lactate dehydrogenase leakage in long-term rat hepatocyte cultures supplemented with 0.5 mM highly unsaturated fatty acids. Formation of thiobarbituric acid reactive substances in the cultures was also measured. alpha-Tocopheryl acid succinate was found to be the most effective cytoprotective compound, followed by N,N'-diphenyl-1,4-phenylenediamine, alpha-tocopherol, gamma-tocopherol and alpha-tocopheryl acetate, and alpha-tocopheryl phosphate was without effect.

Quantification of protein turnover in primary cultures of rat hepatocytes.

1. A radioactive tracer method, based on [3H]valine, for determination in parallel experiments of degradation of cellular proteins and synthesis of both cellular and secreted proteins in cultured rat hepatocytes was developed with special emphasis on methods of calculation, the number of protein pools and maintenance of nitrogen balance. 2. An extracellular concentration of 2 mM valine ensured a specific activity of the precursor pool for protein synthesis, which was constant during the experimental period and practically identical to that of extracellular valine. 3. Amino acid concentrations in the culture medium used were not rate-limiting for the synthesis of proteins. 4. The rate of labelling of the cellular protein pool during 8 days was in accordance with first-order saturation kinetics, which together with a constant ratio between labelling of soluble and membrane bound proteins, is compatible with a single pool of cellular proteins. 5. Protein degradation can be accurately measured by the release from prelabelled proteins of [3H]valine in the presence of 2 mM extracellular valine, if a 1 h chasing period is included in the experimental design. 6. The constancy of the degradation constant (kd) during protein labelling for up to 8 days, is in accordance with the existence of only one pool of cellular protein. 7. The cultured hepatocytes were in nitrogen balance during the experimental period of 8 days as reflected in a constant protein content per cell. The absolute rates of degradation and synthesis of cellular protein were identical, which confirm the validity of the method described.

Absence of glycogen cycling in cultured rat hepatocytes.

Glycogen synthesis and degradation were studied in cultured rat hepatocytes prelabeled by incubation with [14C]glucose or [14C]galactose. During prelabeling about 75% of the accumulated glycogen was synthesized from glucose and about 25% from gluconeogenic precursors. Following the labeling period, glycogen synthesis and degradation were estimated at 5 and 12.5 mM glucose and varying concentrations of insulin and glucagon. At 12.5 mM glucose and 10 nM insulin the accumulation of glycogen was comparable to in vivo values, whereas the level of radioactivity in prelabeled glycogen remained constant. Further addition of 0.1 nM glucagon resulted in constant values of both content and radioactivity of glycogen. Increasing the concentration of glucagon to 10 nM resulted in a parallel decrease of content and radioactivity in glycogen. At 5 mM glucose, 10 nM insulin, and 0.1 nM glucagon both the content and the radioactivity of glycogen were constant, whereas addition of 10 nM glucagon resulted in a parallel decrease of content and radioactivity of glycogen, which was 64% higher than that observed with 12.5 mM glucose. In the absence of insulin, prostaglandin D2 had effects similar to those of 10 nM glucagon, whereas no effects was observed in the presence of insulin. From these results and from calculated rates of glucose 6-phosphate formation, it is concluded that the rate of glycogen degradation is less than 10% of the rate of synthesis under conditions favoring glycogen accumulation. At conditions favoring glycogen degradation (10 nM insulin plus 10 nM glucagon or prostaglandin in the absence of insulin) no synthesis could be detected. Results from cells prelabeled with [14C]galactose suggested that glycogen degradation is not an absolutely ordered process, but that some random degradation takes place.

Inhibition of fatty acid synthesis in rat hepatocytes by exogenous polyunsaturated fatty acids is caused by lipid peroxidation.

Rat hepatocyte long-term cultures were utilized to investigate the impact of different polyunsaturated fatty acids (PUFA) on the insulin-induced de novo fatty acid synthesis in vitro. The addition of 0.5 mM albumin-complexed oleic, linoleic, columbinic, arachidonic, eicosapentaenoic or docosahexaenoic acid resulted in a marked suppression of fatty acid synthesis. By evaluation of cell viability (determined as the leakage of lactate dehydrogenase (LDH) it turned out, that the antioxidant used (50 microM alpha-tocopherol phosphate) had a low antioxidant activity, resulting in cytotoxic effects by the peroxidized PUFA. Arachidonic acid and eicosapentaenoic acid showed a dose- and time-dependent cytotoxicity. Two other antioxidants: 50 microM alpha-tocopherol acid succinate and 1 microM N,N'-diphenyl-1,4-phenylenediamine, both proved more efficient than alpha-tocopherol phosphate. There was a significant correlation between LDH-leakage and inhibition of fatty acid synthesis. Lipid peroxidation, measured as thiobarbituric acid-reactive substances, also showed a significant correlation with the degree of inhibition of fatty acid synthesis. Furthermore, PUFA had no inhibitory effect on fatty acid synthesis when peroxidation was minimized by the use of proper antioxidants. These data indicate that PUFA in vitro inhibit the insulin-induced de novo fatty acid synthesis in hepatocytes from starved rats, due to cytotoxic effects caused by lipid peroxidation.