Biomechanical, biochemical and structural correlations in immature and mature rabbit articular cartilage.

OBJECTIVE: The structure and composition of articular cartilage change during development and growth. These changes lead to alterations in the mechanical properties of cartilage. In the present study, biomechanical, biochemical and structural relationships of articular cartilage during growth and maturation of rabbits are investigated. DESIGN: Articular cartilage specimens from the tibial medial plateaus and femoral medial condyles of female New Zealand white rabbits were collected from seven age-groups; 0 days (n=29), 11 days (n=30), 4 weeks (n=30), 6 weeks (n=30), 3 months (n=24), 6 months (n=24) and 18 months (n=19). The samples underwent mechanical testing under creep indentation. From the mechanical response, instantaneous and equilibrium moduli were determined. Biochemical analyses of tissue collagen, hydroxylysylpyridinoline (HP) and pentosidine (PEN) cross-links in full thickness cartilage samples were conducted. Proteoglycans were investigated depth-wise from the tissue sections by measuring the optical density of Safranin-O-stained samples. Furthermore, depth-wise collagen architecture of articular cartilage was analyzed with polarized light microscopy. Finite element analyses of the samples from different age-groups were conducted to reveal tensile and compressive properties of the fibril network and the matrix of articular cartilage, respectively. RESULTS: Tissue thickness decreased from approximately 3 to approximately 0.5mm until the age of 3 months, while the instantaneous modulus increased with age prior to peak at 4-6 weeks. A lower equilibrium modulus was observed before 3-month-age, after which the equilibrium modulus continued to increase. Collagen fibril orientation angle and parallelism index were inversely related to the instantaneous modulus, tensile fibril modulus and tissue thickness. Collagen content and cross-linking were positively related to the equilibrium compressive properties of the tissue. CONCLUSIONS: During maturation, significant modulation of tissue structure, composition and mechanical properties takes place. Importantly, the present study provides insight into the mechanical, chemical and structural interactions that lead to functional properties of mature articular cartilage.

Selenium in pregnancy: is selenium an active defective ion against environmental chemical stress?

Transportation of selenium from mother to fetus and its possible effects on mother's zinc, copper, cadmium, and mercury levels were studied together during the first trimester and at term in 216 mothers. Mothers came from three geographical places with different selenium intakes. The role of selenium as a biomarker for the vital function was estimated by studying the associations between tissue or blood selenium content and placental cytochrome P450 enzyme activities and the newborn's birth weight. Regardless of the selenium intake of the mothers, higher concentrations were found in the cord blood than in mother's blood reflecting active transportation of selenium to the fetus. Active smoking was associated with higher placental selenium concentrations like it is associated with higher placental zinc concentrations. When the cadmium concentrations were high in placenta, as in smokers, the transfer of selenium from blood to placenta was increased, decreasing the selenium levels in blood. On the other hand, the high selenium concentrations in blood were connected to lower cadmium concentrations in placenta also in nonsmokers. Selenium had correlations with copper and zinc. ECOD activity in placental tissue, mercury in mothers' hair, mothers' age, and selenium concentrations in cord blood and placental selenium all seem to have connections with xenobiotic-metabolizing enzymes linked effects among mothers. These data suggest that selenium has an active role in the mother's defense systems against the toxicity of environmental pollutants and the constituents of cigarette smoke.

Effect of supplementation with organic selenium on mercury status as measured by mercury in pubic hair.

The purpose of this study was to evaluate the effect of four months of yeast-based selenium supplementation on selenium and mercury status in subjects with low serum selenium. The study was carried out in Rakvere, Estonia. Pubic hair mercury, serum selenium and blood selenium concentrations in 23 subjects (serum selenium < 90 micrograms/l) were investigated before and after selenium supplementation. Thirteen subjects were randomized into the selenium supplementation group and ten into the placebo group. The selenium supplementation group received daily 100 micrograms of selenomethionine. Selenium supplementation reduced pubic hair mercury level by 34% (p = 0.005) and elevated serum selenium by 73% and blood selenium by 59% in the supplemented group (p < 0.001 for both). The study indicates that mercury accumulation in pubic hair can be reduced by dietary supplementation with small daily amounts of organic selenium in a short range of time.

Mercury accumulation and accelerated progression of carotid atherosclerosis: a population-based prospective 4-year follow-up study in men in eastern Finland.

Basic research and our previous studies have suggested that mercury exposure enhances lipid peroxidation and the risk of myocardial infarction, but there are no studies concerning the association between mercury accumulation and atherosclerosis. We therefore investigated whether high hair mercury content is associated with accelerated progression of carotid atherosclerosis, determined by ultrasonographic assessment of common carotid intima-media thickness (IMT), in a prospective study among 1014 men aged 42-60 years. In a linear regression model adjusting for other atherosclerotic risk factors, high hair mercury content was one of the strongest predictors of the 4-year increase in the mean IMT (P2.81 microg/g (fifths) had an IMT increase of 0.105, 0.102, 0.113, 0.107 and 0.140 mm/4 years, respectively (P=0.041 for heterogeneity between groups). The IMT increase was 0.034 mm/4 years (31.9%) greater in the highest fifth than in the other fifths (P<0.05 for the difference). These findings suggest that mercury accumulation in the human body is associated with accelerated progression of carotid atherosclerosis.

Mercury-binding capacity of organic and inorganic selenium in rat blood and liver.

The mercury-binding capacity of seleno-DL-methionine and selenium dioxide was assessed in male Wistar rats. Mercury was supplied as fish loaves made of northern pike or rainbow trout. We used a selenium concentration of 3.4 mg/kg fish, about sixfold compared to the equivalent quantity of mercury. Seleno-DL-methionine had a tendency to increase both methyl mercury and total mercury in blood, although it also seemed to reduce the proportion of methyl mercury of total mercury. Selenium dioxide lowered mercury levels by 24-29% both in the blood and in the liver of rats that were fed with northern pike.

Trends in the concentrations of mercury, copper, zinc and selenium in inhabitants of north-eastern Finnish Lapland in 1982-1991. A pilot study.

The heavy industry on the Murmansk region in Russia is releasing huge amounts of waste into the air, including heavy metals and sulphur compounds. To investigate the temporal trend in exposure to certain heavy metals among the inhabitants of north-eastern Finland, a pilot study was carried out involving serum and hair samples from group of 11 persons monitored in Ivalo in 1982 and 1991. A further 6 persons residing near the Russian border in Nellim and 10 adults and 2 children residing in the Sevettijärvi-Näätämö area also participated in 1991. In addition, serum and hair samples were also obtained from controls residing in the Helsinki area. Total mercury content, determined by flow injection analysis and the amalgam system, pointed to a decrease in concentrations in the hair of inhabitants of Ivalo, whereas mercury concentrations were found to be higher in those residing near the Russian border. The mercury concentrations in the hair of northern inhabitants were about 4 times greater than those in the hair of the people from southern Finland on average. No trend towards an increase or decrease was found in copper and zinc concentrations in hair and serum as determined by atomic absorption spectrometry in employing the flame technique. Selenium has been thought to act as an antagonist to the heavy metal mercury. The addition of selenium to fertilisers began in Finland in 1984, but such fertilisers have not been used widely in Lapland. Selenium concentrations, determined by flameless atomic absorption spectrometry, showed an increase with time in the inhabitants of northern Finland. Selenium concentrations were higher in the residents of Lapland than in the southern Finns, but this difference occurred after the addition of selenium to fertilisers has begun to be less common.

Intake of mercury from fish, lipid peroxidation, and the risk of myocardial infarction and coronary, cardiovascular, and any death in eastern Finnish men.

BACKGROUND: Even though previous studies have suggested an association between high fish intake and reduced coronary heart disease (CHD) mortality, men in Eastern Finland, who have a high fish intake, have an exceptionally high CHD mortality. We hypothesized that this paradox could be in part explained by high mercury content in fish. METHODS AND RESULTS: We studied the relation of the dietary intake of fish and mercury, as well as hair content and urinary excretion of mercury, to the risk of acute myocardial infarction (AMI) and death from CHD, cardiovascular disease (CVD), and any cause in 1833 men aged 42 to 60 years who were free of clinical CHD, stroke, claudication, and cancer. Of these, 73 experienced an AMI in 2 to 7 years. Of the 78 decreased men, 18 died of CHD and 24 died of CVD. Men who had consumed local nonfatty fish species had elevated hair mercury contents. In Cox models with the major cardiovascular risk factors as covariates, dietary intakes of fish and mercury were associated with significantly increased risk of AMI and death from CHD, CVD, and any death. Men in the highest tertile (> or = 2.0 micrograms/g) of hair mercury content had a 2.0-fold (95% confidence interval, 1.2 to 3.1; P = .005) age- and CHD-adjusted risk of AMI and a 2.9-fold (95% CI, 1.2 to 6.6; P = .014) adjusted risk of cardiovascular death compared with those with a lower hair mercury content. In a nested case-control subsample, the 24-hour urinary mercury excretion had a significant (P = .042) independent association with the risk of AMI. Both the hair and urinary mercury associated significantly with titers of immune complexes containing oxidized LDL. CONCLUSIONS: These data suggest that a high intake of mercury from nonfatty freshwater fish and the consequent accumulation of mercury in the body are associated with an excess risk of AMI as well as death from CHD, CVD, and any cause in Eastern Finnish men and this increased risk may be due to the promotion of lipid peroxidation by mercury.

High-performance liquid chromatographic assay of platelet-produced thromboxane B2.

A method for the routine determination of platelet-produced thromboxane B2 (TXB2) from human serum is presented. To induce the secretion of thromboxane A2 from the platelets, blood is kept at 37 degrees C for 30 min before serum is separated. Serum is prepurified through small reversed-phase columns and TXB2 is analysed by reversed-phase high-performance liquid chromatography. A column-switching technique is used to remove the interfering compounds present in serum. The detection limit with standard solution is 30 ng per injection. The method was applied to the measurement of platelet-produced TXB2 serum from 1040 men. The mean TXB2 was 247 +/- 134 ng/ml in the serum of men who had not used prostaglandin inhibitors, and 208 +/- 123 ng/ml in the serum of men who had used a prostaglandin inhibitor during a two-week period before blood sampling.

HDL, HDL2, and HDL3 subfractions, and the risk of acute myocardial infarction. A prospective population study in eastern Finnish men.

BACKGROUND: We investigated the association of cholesterol concentrations in serum high density lipoprotein (HDL) and its subfractions HDL2 and HDL3 with the risk of acute myocardial infarction in 1,799 randomly selected men 42, 48, 54, or 60 years old. METHODS AND RESULTS: Baseline examinations in the Kuopio Ischaemic Heart Disease Risk Factor Study were done during 1984-1987. In Cox multivariate survival models adjusted for age and examination year, serum HDL cholesterol of less than 1.09 mmol/l (42 mg/dl) was associated with a 3.3-fold risk of acute myocardial infarction (95% confidence intervals [CI], 1.7-6.4), serum HDL2, cholesterol of less than 0.65 mmol/l (25 mg/dl) was associated with a 4.0-fold risk of acute myocardial infarction (95% CI, 1.9-8.3), and serum HDL3 cholesterol of less than 0.40 mmol/l (15 mg/dl) was associated with a 2.0-fold (95% CI, 1.1-4.0) risk of acute myocardial infarction. Adjustments for obesity, ischemic heart disease, other cardiovascular disease, maximal oxygen uptake, systolic blood pressure, antihypertensive medication, serum low density lipoprotein cholesterol, and triglyceride concentrations reduced the excess risks associated with serum HDL, HDL2, and HDL3 cholesterol in the lowest quartiles by 52%, 48%, and 41%, respectively. Additional adjustments for alcohol consumption, cigarettes smoked daily, smoking years, and leisure time energy expenditure reduced these excess risks associated with low HDL, HDL2, and HDL3 cholesterol levels by another 26%, 24% and 21%, respectively. CONCLUSIONS: Our data confirm that both total HDL and HDL2 levels have inverse associations with the risk of acute myocardial infarction and may thus be protective factors in ischemic heart disease, whereas the role of HDL3 remains equivocal.

Effects of antioxidant supplementation on platelet function: a randomized pair-matched, placebo-controlled, double-blind trial in men with low antioxidant status.

We investigated the effect on platelet function of supplementing men with low antioxidant status with 600 mg ascorbic acid, 300 mg alpha-tocopherol, 27 mg beta-carotene, and 75 micrograms selenium in yeast daily. Eighty men were randomly assigned in pairs (matched for smoking, baseline antioxidant status, and time and day of entry) by use of a double-blind design to receive supplement or placebo for 5 mo. Compared with 39 control subjects, 39 antioxidant-supplemented men experienced the following net reductions during the double-blind period: 20% (P = 0.012) in serum lipid peroxides, 24% (P = 0.035) in ADP-induced platelet aggregation, 42% (P = 0.040) in the rate of ATP release during aggregation, 51% (P = 0.018) in serum (platelet-produced) thromboxane B2, and 29% (P = 0.024) in plasma beta-thromboglobulin concentration. The data support our hypothesis that antioxidant supplementation of men with low antioxidant status and high fat intake reduces lipid peroxidation, the capacity of platelets to aggregate and to produce thromboxane A2, and in vivo platelet activation.

Interactions of serum copper, selenium, and low density lipoprotein cholesterol in atherogenesis.

OBJECTIVE: To investigate the interactions between serum copper, selenium, and low density lipoprotein cholesterol concentrations with regard to the progression of carotid atherosclerosis. DESIGN: Longitudinal study of a cohort of middle aged men followed up for 24 months. SETTING: Epidemiological survey of the population of seven communities in eastern Finland. SUBJECTS: 126 men aged 42, 48, 54, or 60 at examination randomly selected from a population based sample of 2682 men. MAIN OUTCOME MEASURES: Increase in maximal carotid intima media thickness. RESULTS: The mean increase in the maximal common carotid intima media thickness after two years was greater in men with high serum copper concentrations (0.16 mm compared with 0.08 mm in men with concentrations less than 17.6 mumol/l; p = 0.010), those with low serum selenium concentrations (0.15 mm compared with 0.09 mm in men with concentrations greater than or equal to 1.40 mumol/l; p = 0.035), and those with raised serum low density lipoprotein cholesterol concentrations (0.15 mm compared with 0.08 mm in men with concentrations less than 4.0 mmol/l; p = 0.032) after adjustment for age and cigarette pack years in a three way analysis of covariance. A raised serum low density lipoprotein concentration was associated with accelerated progression of atherosclerosis only in men with higher than median serum copper concentrations (net difference 0.22 mm; p less than 0.001 for two way interaction), and this synergism was even more pronounced in men with serum selenium concentrations below the median value (net difference 0.41 mm; p = 0.042 for three way interaction). CONCLUSION: These data provide evidence of a synergistic effect of copper (a pro-oxidant), a low serum concentration of selenium (a cofactor of an enzyme that scavenges free radicals), and low density lipoprotein cholesterol concentration in atherogenesis.

Dose responses in platelet fatty acid composition, aggregation and prostanoid metabolism during moderate freshwater fish diet.

The dose responses in platelet fatty acid composition, aggregation and thromboxane production and in plasma prostacyclin level during moderate freshwater fish diet was studied in healthy male students (n = 100). There were four fish diet groups eating 0.9, 1.5, 2.3 or 3.8 fish-containing meals per week for 12 weeks. The meals provided about 0.25, 0.5, 0.6 or 1.1 g n-3 fatty acids per day, respectively. The increase of n-3 at the expense of n-6 fatty acids in total platelet lipids took place already with 1.5 weekly fish meals (0.5 g n-3 fatty acids/d). Most of the observed changes in platelet fatty acids were seen already after 5 weeks. ADP-and collagen-induced platelet aggregation was measured from controls and 1.5 and 3.8 fish meals per week groups. The maximum platelet aggregation values of the group with the highest fish intake were significantly lower than in the controls at the end of dietary period. A tendency towards reduced platelet aggregability was observed also in the group eating 1.5 fish meals per weeks. Thromboxane B2 and 6-keto-PGF1 alpha were determined from controls and two groups with highest fish intake. The highest intake was needed to decrease the thromboxane B2 production of clotted blood and the plasma 6-keto-PGF1 alpha concentration. A positive correlation between ADP-induced aggregation and thromboxane B2 production was found. These results show that platelet characteristics can already be modified with a very moderate freshwater fish intake.

Risk factors for carotid atherosclerosis: the Kuopio Ischaemic Heart Disease Risk Factor Study.

We assessed the severity of carotid atherosclerosis in 412 men from eastern Finland aged 42, 48, 54 or 60 years at examination with B-mode ultrasonography in 1987 in the Kuopi ischaemic Heart Disease Risk Factor Study (KIHD). Thirty-seven per cent of participants had intimal-medial thickening, 10% had plaques and 2% had stenosis. Age (P less than 0.001), cigarette-years (P less than 0.001), serum LDL cholesterol (P = 0.005), low income (P = 0.020) and low alcohol consumption (P = 0.048) had significant partial associations with the severity of carotid atherosclerosis. A linear regression model including these variables and plasma fibrinogen (NS) and serum HDL-cholesterol (NS) accounted for 33% of the variation in atherosclerosis severity. Our data provide further evidence on the role of smoking and LDL-cholesterol in atherosclerosis.

Prevalence of carotid atherosclerosis and serum cholesterol levels in eastern Finland.

We investigated the prevalence of carotid atherosclerosis and its association with serum lipoprotein cholesterol fractions in 412 Eastern Finnish men ages 42, 48, 54, or 60 years who were examined between February and December 1987 in the Kuopio Ischaemic Heart Disease Risk Factor Study. Carotid atherosclerosis was assessed with high-resolution B-mode ultrasonography. Of the participants, 37% had thickening of the intimal or medial layer of the arterial wall, 10% had plaques, 2% had stenosis in the right or left common carotid artery or in the carotid bifurcation, and only 51% were free of any detectable carotid atherosclerosis. The prevalence of atherosclerosis was 14.1%, 32.0%, 67.7%, and 81.9% in the four age groups, respectively. The mean age-adjusted serum low density lipoprotein (LDL) cholesterol concentration was 3.67 mmol/l (142 mg/dl) in men free of carotid atherosclerosis and 4.02 mmol/l (155 mg/dl) in those with at least intimal thickening (p = 0.003 for difference). The mean age-adjusted serum cholesterol concentration in the high density lipoprotein (HDL) fraction was 1.34 mmol/l (52 mg/dl) in the atherosclerosis-free and 1.27 mmol/l (49 mg/dl) in the atherosclerotic men (p = 0.029 for difference). There was a similar difference in both the serum HDL2 and the HDL3 cholesterol levels. Serum LDL and HDL (inverse) cholesterol were significant determinants of severity of carotid atherosclerosis in a multivariate regression model adjusting for age, obesity, plasma fibrinogen, cigarette-years, and duration of hypertension. Our data reveal the high prevalence of atherosclerosis in middle-aged Eastern Finnish men and provide further evidence of the roles of LDL and HDL cholesterol in atherosclerosis.

Blood pressure, dietary fats, and antioxidants.

We investigated the association of dietary fatty acids and antioxidants with blood pressure in 722 eastern Finnish men aged 54 y, examined in the Kuopio Ischaemic Heart Disease Risk Factor Study in 1984-86. Men with self-reported hypertension or cerebrovascular disease or under antihypertensive medication were excluded. Allowing for the major anthropometric, dietary, medical, and psychological determinants of blood pressure in multivariate regression analyses, both plasma ascorbic acid (p = 0.0008) and serum selenium (p = 0.0017) concentrations had a moderate, independent inverse association, estimated dietary intake of saturated fatty acids had a positive association (p = 0.013), and estimated dietary intake of linolenic acid had an inverse (p = 0.048) association with the mean resting blood pressure. The marked elevation of blood pressure at the lowest levels of plasma ascorbic acid and serum Se concentrations supports the hypothesis that antioxidants play a role in the etiology of hypertension.

Boreal freshwater fish diet modifies the plasma lipids and prostanoids and membrane fatty acids in man.

The effect of fish diet on 43 healthy male students was studied. They ate a fish-containing meal for 15 weeks on an average of 3.7 times per week. Twenty-one of them voluntarily restricted their lipid intake while the rest ate normally. Controls continued their usual eating habits (19 students). The meals consisted of Finnish freshwater fish (87%) (vendace, pike, perch and rainbow trout) and brackish water fish (13%) (Baltic herring) that provided about 1 g of omega-3 polyunsaturated fatty acids per day (0.25 g eicosapentaenoic acid and 0.55 g docosahexaenoic acid). During the diet, omega-3 fatty acids increased in erythrocyte ghosts and platelets at the expense of omega-6 fatty acids. The concentration of serum cholesterol diminished in those fish consumers who lowered their lipid intake. Apolipoprotein A1 and B were lowered in both fish-consuming groups. Triglyceride levels also showed a tendency to decrease. The formation of thromboxane B2 during incubation of whole blood decreased in both fish-consuming groups. The decrease of plasma 6-keto-PGF1 alpha was not statistically significant, if compared with the controls. The results obtained indicate that a moderate intake of fish-containing meals has some beneficial effects on the plasma lipid and prostanoid metabolism, when coronary heart disease risk factors are considered.

Relationship of serum selenium and antioxidants to plasma lipoproteins, platelet aggregability and prevalent ischaemic heart disease in Eastern Finnish men.

In a cross-sectional population study of 1132 unselected Eastern Finnish men aged 54 years, serum selenium concentration had a weak positive association with plasma HDL cholesterol (standardised partial regression coefficient, beta = 0.061, P = 0.019) and a fairly strong inverse relationship (beta = -0.223, P less than 0.001) with the extent of ADP-induced platelet aggregation. Neither plasma ascorbate concentration nor alpha-tocopherol to total cholesterol ratio had any association with plasma lipoproteins, platelet aggregability or prevalent ischaemic heart disease (IHD). When a covariance-correction was applied, men with ischaemic ECG findings at exercise had a lower mean serum selenium than others (81.5 micrograms/l vs. 85.9 micrograms/l, P less than 0.01 for difference). This difference was equally large for men with neither symptoms nor previous diagnosis of IHD.