Altered enzyme activities of xenobiotic biotransformation in kidneys after subchronic administration of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) to rats

Activities of the xenobiotic metabolizing enzymes were measured in the liver, kidney, duodenum and lung microsomes and cytosol fractions of Wistar rats after subchronic administration of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a potent bacterial mutagen in chlorinated drinking water. MX was administered by gavage at the dose level of 30 mg/kg for 18 weeks (low dose), or at the dose level which was raised gradually from 45 mg/kg for 7 weeks via 60 mg/kg for 2 weeks to a clearly toxic dose of 75 mg/kg for 5 weeks (high dose). Microsomal and cytosolic preparations were made and the activities of 7-ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-dealkylase (PROD), NADPH-cytochrome-c-reductase, UDP-glucuronosyltransferase (UDPGT) and glutathione-S-transferase (GST) were measured. Kidneys were affected most. A dose-dependent decrease was observed in EROD (90% in males, 80% in females at the high dose) and in PROD (58% in females, at the high dose) in kidneys. An increase was, however, detected in kidney NADPH-cytochrome-c-reductase (66% in females at high dose), UDPGT (89% in males and 97% in females at high dose) and GST activities (56% in males and 50% in females at high dose). MX caused only a few changes in the enzyme activities of the liver. The EROD activity was decreased 25% to 37%, both in the livers of males and females, but the total content of P450s was not altered. Hepatic GST activity was elevated in females in a dose-dependent manner (31% and 44%). GST activity was elevated in duodenum in females (59%) at the high dose. There were no marked changes in the enzyme activities in the lungs. MX was a weak inhibitor of EROD activity both in the liver and kidney microsomes in vitro, decreasing the EROD activity by 53% and 43%, respectively at the concentration of 0.9 mM. The results indicate that MX decreases the activity of phase I metabolism enzymes, but induces phase II conjugation enzyme activities, particularly in kidneys in vivo. It is possible that these changes contribute to metabolism of MX in kidneys and renders them susceptible to MX in the course of repeated exposure.     

Pharmacokinetics in Rat of 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a Drinking Water Mutagen,after a Single Dose

Abstract: The pharmacokinetics of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) was evaluated after a single oral or intravenous administration in the rats using ¹⁴C-labelled compound. Twenty to 35% of the dose was absorbed into circulation from the gastrointestinal tract as assessed from the excretion in urine. The mean elimination half-life of the radioactivity in blood (T_1/2 k₁₀) was 3.8 hr. Traces of radioactivity remained in the blood for several days. The tissues lining the gastrointestinal and urinary tract, kidneys, stomach, small intestines and urinary bladder contained the highest radioactivity. The activity declined slowest in the kidneys. Urine was the main excretion route. Seventy-seven % of the total amount excreted appeared in urine in 12 hr and 90% in 24 hr. No radioactivity was exhaled in air suggesting that elimination through respiration did not occur. After an intravenous administration of ¹⁴C-MX, the T_1/2 k₁₀, was much longer, 22.9 hr, and the total elimination half-life (T_1/2 β), 42.1 hr. The results indicate that MX is absorbed from the gastrointestinal tract to a considerable degree and it is excreted in urine very rapidly. A fraction of MX or its metabolites is retained in blood for a longer period of time. The pharmacokinetics of MX does not suggest extensive cumulation of MX in tissues after continuous exposure.     

Exposure to natural fluoride in well water and hip fracture: a cohort analysis in Finland.

In the retrospective cohort study based on record linkage, the authors studied a cohort of persons born in 1900-1930 (n = 144,627), who had lived in the same rural location at least from 1967 to 1980. Estimates for fluoride concentrations (median, 0.1 mg/liter; maximum, 2.4 mg/liter) in well water in each member of the cohort were obtained by a weighted median smoothing method based on ground water measurements. Information on hip fractures was obtained from the Hospital Discharge Registry for 1981-1994. No association was observed between hip fractures and estimated fluoride concentration in the well water in either men or women when all age groups were analyzed together. However, the association was modified by age and sex so that among younger women, those aged 50-64 years, higher fluoride levels increased the risk of hip fractures. Among older men and women and younger men, no consistent association was seen. The adjusted rate ratio was 2.09 (95% confidence interval: 1.16, 3.76) for younger women who were the most exposed (>1.5 mg/liter) when compared with those who were the least exposed (< or =0.1 mg/liter). The results suggest that fluoride increases the risk of hip fractures only among women.     

Wine and good subjective health

The association of subjective, self-rated suboptimal (average or poor) health with the intake of beer, wine, and liquor and alcohol intoxication was examined in a general population sample in Finland in 1992. The odds ratios were adjusted for several possible confounders with the use of logistic regression analysis. Compared with subjects who drank no wine, suboptimal health was less frequent among both men and women who imbibed 1-4 drinks of wine, and more common among men who consumed > or = 10 drinks of wine or liquor. Moderate wine drinking seems to be related to good self-rated health.     

Pre-operative serum level of tumour-associated trypsin inhibitor and residual turnour size as prognostic indicators in Stage III epithelial ovarian cancer

Objective To evaluate the use of the pre-operative tumour-associated trypsin inhibitor (TATI) level and residual tumour size at primary surgery as a prognostic indicators for patients with Stage III epithelial ovarian cancer.
Design Retrospective cohort study.
Setting Department of Obstetrics and Gynaecology, University Hospital, Helsinki, Finland.
Participants Ninety-eight women with Stage III ovarian cancer.
Methods TATI was measured by radioimmunoassay from serum samples obtained within one week before surgery. A cutoff value of 22 μg/L was used. Multivariate analysis included pre-operative TATI level, age, histologic grade and histologic type. Mantel-Cox test was used for calculating statistical significance of differences in survival between groups.
Main outcome measures Cumulative five-year survival, pre-operative serum TATI level and residual tumour size.
Results Surgery was optimal (residual tumour size ≤ 2 cm) in 55 patients and suboptimal (residual tumour size > 2 cm) in 43. Pre-operative TATI level ≤ 22 μg/L predicted better prognosis both in patients with optimal and suboptimal surgery compared with patients with pre-operative TATI level > 22 μ/L. Patients with optimal surgery and a pre-operative TATI > 22 μg/L had a twofold relative risk of death compared with those with a pre-operative TATI ≤ 22 μg/L. The cumulative survival was less than three years for patients with suboptimal surgery and pre-operative TATI > 22 μg/L.
Conclusions Pre-operative serum TATI in combination with residual tumour size may be useful in stratifying patients with Stage III ovarian cancer into different categories in randomised treatment trials.     

Smoking, alcohol use, and physical activity: a 13-year longitudinal study ranging from adolescence into adulthood.

PURPOSE: To assess the associations among smoking, alcohol use, and physical activity, and to assess how the health behaviors predict changes in other health behaviors from adolescence to adulthood. METHODS: Subjects were the participants of the North Karelia Youth Project study from six schools in Eastern Finland. At the baseline in 1978 they were 13-year-olds (n = 903) and in the last of the six surveys in 1993 they were 28-year-olds. This study uses the data from three surveys in which the participants were 15-, 21-, and 28-year olds. The response rate was 71% in the last survey. Data were analysed by SPSS software. RESULTS: Smoking prevalence was highest at the age of 21 years and alcohol use at the age of 28 years. The prevalence of leisure-time physical activity did not change much over time. Smoking and alcohol use correlated positively for each survey. Smoking correlated negatively with leisure-time physical activity. The best predictors for each health behavior were the same behaviors measured before, but smoking had the strongest level of continuity. In addition, alcohol use at the age of 15 years predicted smoking at the ages of 21 years and 28 years, but smoking in adolescence did not predict alcohol use in adulthood. CONCLUSIONS: Smoking was associated with both alcohol use and physical activity and therefore has a central role among health behaviors. Smoking and alcohol use were particularly clearly related from adolescence to adulthood. Smoking behavior was the most constant behavior.     

Cardiac arrest and left ventricular fibrosis in a Finnish family with the lamin A/C mutation

Introduction: We screened the candidate genes from a Finnish family in which the mother was resuscitated from ventricular fibrillation and the daughter died suddenly without any prior cardiac symptoms.
Methods and Results: In addition to screening of potential structural gene mutations, phenotyping of the proband and medico-legal autopsy of the victim of the sudden death, including histopathological examinations, were performed. Genetic screening revealed an R541C mutation in the lamin A/C gene both in the proband and her daughter. None of the 16 first- or second-degree relatives, or 96 unrelated healthy subjects, carried the same mutation. In the proband, the size and the global function of the left ventricle (LV) were normal, but a local hypokinesia and thinning of inferoposterior area of the LV were seen in 2D echocardiography and magnetic resonance imaging. Coronary angiogram and the results of the electrophysiological study were normal. Autopsy of the victim of sudden death showed localized thinning and fibrosis in the inferoposterior area of the LV, with only minimal fibrosis in the right ventricle and no abnormalities in the interventricular septum.
Conclusion: These observations indicate that a fatal or near-fatal cardiac arrhythmia can be the first clinical manifestation of a "de novo" mutation R541C of the lamin A/C gene. Replacement of cardiac myocytes by fibrosis seems to be the predominant pathologic-anatomic finding.     

Five-year trend in serum HDL-lipoprotein cholesterol in the Finnish population aged 25-64 years. A suggestion of an increase

High density lipoprotein cholesterol (HDLC) was measured in the population surveys carried out in Finland in 1982 and 1987. The mean (+/- SD) of HDLC for men aged 25-64 years was 1.23 +/- 0.32 mmol/l in 1982 and 1.30 +/- 0.33 mmol/l in 1987, the increase being 5.7%. Respective values in women were 1.46 +/- 0.33 mmol/l and 1.58 +/- 0.35 mmol/l, an increase of 8.2%. The increase was significantly greater in women than in men (P less than 0.001). The prevalence of low HDLC (less than or equal to 0.9 mmol/l) fell from 13.5 to 9.6% in men and from 3.2 to 1.4% in women. Factors associated with low HDLC were the history of ischemic heart disease (IHD), diabetes and hypertension in both sexes and the positive family history of IHD in women. Subjects with low HDLC also had higher body mass index (BMI), waist-hip ratio and serum total cholesterol (TC) concentration than subjects with normal HDLC. Changes in BMI, waist-hip ratio, alcohol intake, leisure time physical activity, prevalence of smoking or in the dietary variables recorded, did not explain the increase in HDLC.     

Functional Characterization and Categorization of Missense Mutations that Cause Methylmalonyl‐CoA Mutase (MUT) Deficiency

Methylmalonyl‐CoA mutase (MUT) is an essential enzyme in propionate catabolism that requires adenosylcobalamin as a cofactor. Almost 250 inherited mutations in the MUT gene are known to cause the devastating disorder methylmalonic aciduria; however, the mechanism of dysfunction of these mutations, more than half of which are missense changes, has not been thoroughly investigated. Here, we examined 23 patient missense mutations covering a spectrum of exonic/structural regions, clinical phenotypes, and ethnic populations in order to determine their influence on protein stability, using two recombinant expression systems and a thermostability assay, and enzymatic function by measuring MUT activity and affinity for its cofactor and substrate. Our data stratify MUT missense mutations into categories of biochemical defects, including (1) reduced protein level due to misfolding, (2) increased thermolability, (3) impaired enzyme activity, and (4) reduced cofactor response in substrate turnover. We further demonstrate the stabilization of wild‐type and thermolabile mutants by chemical chaperones in vitro and in bacterial cells. This in‐depth mutation study illustrates the tools available for MUT enzyme characterization, guides future categorization of further missense mutations, and supports the development of alternative, chaperone‐based therapy for patients not responding to current treatment.