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Biomedical subjects

Y Thomassen

Publications and source records attributed to Y Thomassen.

At least 55 records · Page 3Linked to original sources
PubMed1993

Urinary mercury excretion in chloralkali workers after the cessation of exposure.

Seventeen former chloralkali workers were followed through the regular determination of urinary mercury for nearly two years after the cessation of exposure to mercury vapor in a study of the time course of urinary mercury elimination. Their duration of exposure ranged from 3 d to 35.5 years. A one-compartment model for urinary mercury elimination was applied. The urinary mercury concentration declined at a rate indicating a half-time of 91 d. When corrected for an individual base-line level of urinary mercury resulting from sources of mercury intake not related to work, the half-time was 72.4 [95% confidence interval (95% CI) 63.2-81.7] d, with a mean elimination rate constant of 0.011 (95% CI 0.008-0.013).d-1. The day-to-day variability of the urinary mercury concentration averaged 22%, expressed as the coefficient of variation between urine samples delivered on three consecutive days.

Adolescent↗
PubMed1992

Speciation of mercury in human whole blood by capillary gas chromatography with a microwave-induced plasma emission detector system following complexometric extraction and butylation.

Methyl- and inorganic mercury were extracted from human whole blood samples, as their diethyldithiocarbamate complexes, into toluene and butylated by using a Grignard reagent. The mercury species were then separated by gas chromatography (on a 12 m non-polar DB-1 capillary column) and detected by a microwave-induced plasma atomic emission spectrometric (GC-MPD) system. The accuracy and precision of the proposed method were established by the analysis of Seronorm lyophilized human whole blood standards for methyl- and inorganic mercury. No statistical difference (t-test) between the sum of these two species determined by the GC-MPD based method and the recommended total mercury concentrations in the Seronorm samples was observed. Results for the determination of methyl- and inorganic mercury in 60 controls and 90 previously occupationally exposed (to inorganic mercury) workers are presented to illustrate the practical utility of the proposed method. No significantly elevated inorganic mercury concentrations between the two groups were evident.

Chromatography, Gas↗
PubMed1992

Dental amalgam and mercury.

The mercury concentrations in blood (HgB) and urine (HgU) samples, and in exhaled air (HgAir) were measured in 147 individuals from an urban Norwegian population, using cold vapour atomic absorption spectrometry. The study aimed to estimate the mercury exposure from the dental restorations, by correlating the data to the presence of amalgam restorations. Mean values were HgB = 24.8 nmol/l, HgU = 17.5 nmol/l and HgAir = 0.8 micrograms/m3. HgU correlated with HgAir, and both HgU and HgAir with the number of amalgam restorations, amalgam restored surfaces and amalgam restored occlusal surfaces. HgB showed poor correlation to HgU and HgAir and the presence of amalgam restorations. A differentiation of the mercury absorption due to exposure from dental amalgams and from the dietary intake, necessitates measurements of both organic and inorganic mercury in the plasma, and in the erythrocytes. The results suggest that individuals with many amalgam restorations, i.e., more than 36 restored surfaces, absorb 10-12 micrograms Hg/day.

Adolescent↗
PubMed1992

Aluminum metabolism and bone histology after kidney transplantation: a one-year follow-up study.

Parathyroid activity, bone aluminum (Al) metabolism, bone histology, and clinical bone disease were studied in 55 successfully grafted kidney recipients at transplantation (Tx) and after 1 yr of immunosuppression with a low dose corticosteroid and a high dose cyclosporin-A regimen. Symptoms of Al-related bone disease disappeared after Tx. Serum Al and stainable bone Al decreased. The rate of Al removal from the bone surfaces was independent of graft function (creatinine range, 62-415 mumol/L) and bone turnover. Osteoblast activity and bone formation rate increased, while mineralization lag time normalized. Indices of bone resorption remained elevated, indicating persisting hyperparathyroidism. Eighteen percent of the recipients had posttransplant hypercalcemia, most likely caused by incomplete involution of hyperplastic parathyroid glands, while 53% had normocalcemic hyperparathyroidism related to impaired graft function. Cortical thickness decreased, while cancellous bone volume remained stable after Tx; both indices correlated significantly at follow-up with their respective values at Tx. None of 46 radiologically examined recipients had aseptic bone necrosis 1 yr after Tx.

Adolescent↗
PubMed1992

Reduced concentration of hepatic alpha-tocopherol in patients with alcoholic liver cirrhosis.

The concentration of alpha-tocopherol was measured in liver biopsy specimens obtained from 83 patients with alcoholic and non-alcoholic liver diseases. The mean hepatic vitamin E content (as alpha-tocopherol) was significantly lower in 23 patients with alcoholic cirrhosis (17.6 +/- 12.1 nmol/mg wet weight liver), compared with 12 patients with normal liver histology (39.2 +/- 29.7 nmol/mg, P less than 0.01). The mean serum concentration of alpha-tocopherol was lower in patients with alcoholic cirrhosis (13.9 +/- 7.0 mumol/l) than in individuals with alcoholic fatty liver (21.3 +/- 9.3 mumol/l, P less than 0.01) and patients with normal liver histology (23.4 +/- 11.6 mumol/l, P less than 0.01). A decreased ratio of serum alpha-tocopherol/total serum lipids was also observed in patients with alcoholic cirrhosis, compared with patients with normal liver histology (P less than 0.05). There was a significant correlation between concentrations of alpha-tocopherol in liver and serum (r = 0.43, P less than 0.001). Furthermore, serum alpha-tocopherol correlated with retinol (r = 0.53, P less than 0.001), selenium (r = 0.45, P less than 0.001), and albumin (r = 0.37, P less than 0.001) in serum. We suggest that the reduced content of hepatic alpha-tocopherol observed in some patients may play a role in ethanol-induced lipid peroxidation.

Adolescent↗
PubMed1991

High serum selenium concentrations in reindeer breeding Lappish men.

This study investigated the relationship of serum selenium to its dietary sources in a group of Lappish men and a control population. Lappish men had higher serum selenium concentrations than non-Lappish men (1.79 vs 1.58 mumol/1; p = 0.003). Serum selenium correlated positively with consumption of reindeer meat, age and cholesterol. In linear regression models, however, being Lappish was the most significant predictor of high serum selenium. Lappish men ate more reindeer meat (p = 0.001) and less fish (p = 0.013) than men in the control group. Consumption of reindeer meat was also correlated with higher serum cholesterol levels. We conclude that high serum selenium concentrations in Lappish men may be important since low mortality from cancer is reported in this group.

Adult↗
PubMed1990

Levels of selenium and antioxidative enzymes following occupational exposure to inorganic mercury.

Levels of selenium and mercury in blood and urine were analysed in 37 male workers exposed to elemental mercury vapour in a chloralkali plant and in 39 unexposed controls of the same age. Mean urinary Hg was 223 nmol l-1 (15 nmol/mmol creatinine) in the exposed group and 26 nmol l-1 (2.0 nmol/mmol creatinine) in the controls. Mean blood and plasma Hg levels were 46 and 36 nmol l-1, respectively, in the exposed group, as compared with 17 and 7 nmol l-1 in the controls. The concentrations of Se in plasma and erythrocytes did not differ between the two groups. Urinary Se levels were, however, slightly but significantly lower in the exposed group (median values 23 vs 29 nmol/mmol creatinine), and there was a negative correlation between urinary Se and plasma Hg in the exposed group. This may be due to a retention of Se in the kidneys. In a subgroup of exposed workers and controls, glutathione peroxidase, superoxide dismutase and catalase were also analysed. No differences were found between the groups with respect to these antioxidative enzymes. The effect on Se status of moderate Hg exposure seems to be of minor clinical importance.

Adult↗
PubMed1990

Selenium concentrations in the human thyroid gland.

Recently, we found that prediagnostic serum selenium concentration was significantly lower for cases developing thyroid cancer (n = 43) than for controls. We assumed that redistribution of serum selenium into the affected tissue took place in the prediagnostic period. The present study was carried out to determine the physiological concentration of selenium in the thyroid, since very few data are available in the literature. The concentrations of selenium in the thyroid (n = 45) and liver samples from Norwegians who had died because of acute illness or accidents were determined by hydride generation atomic absorption spectrometry. The mean selenium concentration was found to be 0.72 +/- 0.44 microgram/g in the thyroid and 0.45 +/- 0.11 microgram/g in the liver tissue. The surprisingly high concentration of selenium in apparently normal thyroids indicates that selenium has important functions in this organ. The remarkably broad range, together with the observation that no significant correlation exists between thyroid and liver concentrations, suggest that factors other than the selenium status are important determinants for the selenium concentration in the thyroid gland. This observation is consistent with our hypothesis that in carcinogenesis, prediagnostic processes influence the serum-/thyroid-ratio of selenium.

Adult↗
PubMed1990

Fluoride, aluminum, and phosphate kinetics in cryolite workers.

Exposure to cryolite (Na3AlF6) dust may result in skeletal fluorosis. Eight male workers at a cryolite concentrator participated in a 4-day study after 5 days of vacation. Dust exposures were 0.16 to 21.2 mg/m3. Urine was collected before work began and during two 4-hour periods. Preshift urine fluoride concentrations increased during the week. Fluoride concentrations in postshift urine and serum both correlated with the dust exposures. Serum fluoride concentrations decreased with a half-life of 3.3 to 6.9 hours after work. Fluoride clearance was 40.5 to 76.5 mL/min at urinary flow rates of 0.89 to 2.21 mL/min. Serum aluminum concentrations varied without relation to the exposure, but the urinary aluminum excretion correlated with the fluoride levels. Preshift serum-phosphate concentrations increased significantly during the week, possibly indicating changes in mineral metabolism. For monitoring of individual uptake of cryolite dust, serum fluoride measurements are most useful.

Aluminum↗
PubMed1990

The determination of copper in human liver biopsy specimens by cup-in-tube ETAAS.

A method for the direct determination of copper in human liver biopsy specimens is described. The addition of a mixed Mg-Pd nitrate modifier is shown effectively to delay the volatilization of copper both from aqueous standards and the powered NISTBovine Liver to an appearance time comparable with the solid biopsy specimens. Calibration against solid liver reference materials is preferable compared with aqueous copper standard solutions. A number of copper absorption lines provide a wide range of sensitivities; the less sensitive Cu-line 222.6 nm was found optimal in the determination of copper concentrations in the range of 20-200 mg/kg in liver biopsy specimens. The copper concentrations measured in liver biopsy specimens from patients suffering from sclerosing cholangitis were considerably higher than those reported for a group of healthy persons.

Animals↗
PubMed1989

Prediagnostic serum selenium in a case-control study of thyroid cancer.

Sera from 43 persons who developed thyroid cancer on an average 4.8 years after blood sampling were compared with sera from controls. Three controls per case matched for sex, age, place of residence and year of blood sampling, with regard to serum selenium and serum copper. Cases were significantly lower in serum selenium than controls, and the estimated odds ratio of thyroid cancer increased from 1 for levels greater than or equal to 1.65 mumol/l, to 6.1 for levels 1.26-1.64 mumol/l, to 7.7 for levels less than or equal to 1.25 mumol/l. When time from blood sampling to diagnosis of the case was considered, it could be shown that the protective effect of high serum selenium concentrations was restricted to the last (less than 7) years prior to the diagnosis of thyroid cancer. The serum selenium concentration of cases tended to decrease relative to controls the shorter time was from blood sampling to the diagnosis. There was no difference between cases and controls with regard to serum copper.

Adenocarcinoma↗
PubMed1989

Polyamines and other accessory sex gland secretions in human seminal plasma 8 years after vasectomy.

In 56 males, vasectomized 8 years previously, and in 56 age-matched non-vasectomized controls, a number of secretory products of prostatic, seminal vesicular and epididymal/testicular origin were used to monitor post-operative changes in accessory sex gland function. Significant reductions were observed in seminal plasma volume (3.0 vs 4.9 ml, P less than 0.01), and the total ejaculate contents of zinc (5.1 vs 9.7 mumol, P less than 0.01), magnesium (10.6 vs 26.5 mumol, P less than 0.01), PAP (371 vs 1260 IU, P less than 0.005) and citric acid (76.7 vs 127.9 mumol, P less than 0.05), indicating a major impact on secretions of prostatic origin. Unaltered PGE-1 (54.3 vs 53.2 micrograms, P less than 0.95) and fructose (3.9 vs 4.5 mumol, P greater than 0.1) indicated no effects on the secretory function of the seminal vesicles. A marked reduction was demonstrated in the ejaculatory contents of the polyamines, spermidine (366 vs 650 nmol, P less than 0.005) and spermine (5435 vs 11 804 nmol, P less than 0.05) but not their acknowledged precursor, putrescine, which is also of prostatic origin.

Acid Phosphatase↗
PubMed1988

Gastrointestinal absorption and urinary excretion of aluminium in patients with predialysis chronic renal failure.

In a randomized cross-over study, serum and urinary aluminum (A1) was measured in 8 patients with predialysis chronic renal failure. Samples were taken after ingestion of an A1-containing phosphate binder (ACPB) with either water or 7% citric acid, and A1 was analyzed by electrothermal atomic absorption spectrometry. Both serum levels and urinary excretion of A1 increased markedly after ingestion of ACPB with citric acid. Only urinary A1 excretion increased significantly after ACPB with water. Citric acid alone caused no change in serum concentration or urinary excretion of A1. The serum A1 increase after ACPB with citric acid indicates that absorption of A1 is taking place in both upper and lower intestines. Marked individual variations in gastrointestinal A1 absorption, independent of kidney function, were seen after intake of ACPB with citric acid. These variations could not be predicted from changes in serum concentrations or from urinary excretion of A1 after intake of ACPB with water. Intake of ACPB caused a significant decrease in serum phosphate.

Adult↗
PubMed1988

Seasonal variations in serum aluminum concentrations.

During 1984 and 1985 we performed frequent measurements of serum aluminum (Al) in patients with moderate chronic renal failure, and healthy controls, all living in the Oslo region. The results demonstrated seasonal variations with high levels in the autumn. During the peak periods serum Al increased by a factor greater than four. Outside the peaks patients using Al-containing phosphate binders had higher serum Al levels than non-users, a difference not seen during the peaks. Serum Al levels were unrelated to parathyroid hormone (PTH) concentrations and to calcitriol intake. Urinary excretion and the glomerular filtration rate was stable during the period with high serum Al in the autumn 1984. Increased gastrointestinal absorption of Al, possibly caused by a waterborne factor with chelating properties, may explain the seasonal variations.

Adult↗
PubMed1988

Serum selenium concentration associated with risk of cancer.

The association between serum selenium concentration and risk of cancer was studied in a nested case control study. Case control pairs came from a population of 9364 people examined in 1979. During the six year follow up, 60 men and women aged between 20-54 at the time of blood sampling, who had been free of malignant disease, developed cancer. The mean serum selenium concentration of 1.56 mumol/l (123.2 micrograms/l) in patients was not significantly different from that in controls (1.63 mumol/l (128.7 micrograms/l]. The difference in mean selenium concentration was largest and most significant for haematological malignancies alone. The difference in selenium concentrations in cases of fatal cancer compared with controls was significant (p less than 0.01). The risk of developing adenocarcinomas does not seem to be influenced by serum selenium concentration.

Adenocarcinoma↗
PubMed1987

The Tromsø Heart Study: serum selenium and risk of myocardial infarction a nested case-control study.

The association between serum selenium concentration and the risk of myocardial infarction was studied in a nested case-control study. Altogether 59 men, initially free of disease, aged 28-54 at the time of blood sampling, died suddenly or experienced a fatal or non-fatal myocardial infarction during a six year follow-up period. Case-control pairs came from a population of 9364 persons examined in 1979-80 in the second Tromsø Heart Study. No significant difference was observed between serum selenium in cases and controls (p = 0.34). The major determinants of myocardial infarction and sudden death were raised levels of serum cholesterol and triglycerides (p less than or equal to 0.001) and high systolic blood pressure (p less than 0.05). Thus, in this population with intermediate selenium intake, low serum selenium is not associated with an excess risk of myocardial infarction.

Adult↗
PubMed1987

The Tromsø Heart Study: relationships between the concentration of selenium in serum and risk factors for coronary heart disease.

The association between the concentration of selenium in serum and risk factors for cardiovascular disease was studied in 467 apparently healthy men and women. The concentration of selenium in serum was significantly higher in men than in women (1.63 versus 1.51 mumol/L) (p less than 0.001). A statistically significant positive correlation between serum selenium concentration and total cholesterol was found in women, but not in men. No other statistically significant correlations were observed with the major risk factors for coronary heart disease. There were indications that high consumption of fish, coffee and bread were associated with increased serum selenium levels, but the differences did not reach statistical significance. Our findings suggest that serum selenium concentrations in the range 1.2-2.0 mumol/L are not associated with major risk factors for cardiovascular disease.

Adult↗