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Biomedical subjects

J C Hansen

Publications and source records attributed to J C Hansen.

At least 127 records · Page 7Linked to original sources
PubMed1986

Sister chromatid exchange (SCE) in Greenlandic Eskimos. Dose-response relationship between SCE and seal diet, smoking, and blood cadmium and mercury concentrations.

The mutagenicity of the chromosomes of the peripheral lymphocytes of 147 Greenlandic Eskimos living in the district of Angmagssalik, Greenland, and in Denmark, was evaluated by means of the sister chromatid exchange (SCE) test. Thirty cells from each person were examined. The purpose of the investigation was to determine if there was any relationship between mutagenic activity and diet, and hence the elements selenium, cadmium, mercury and lead. The probands were divided into three groups according to their intake of seal meat or industrially prepared food: group 1, those eating seal at least six times per week; group 2, two to five times per week; and group 3 once each week or not at all. The statistical analysis was performed by means of multiple linear regression analyses, with diet, living district, sex, age, tobacco smoking, and blood lead and mercury concentrations as variables. Forty-eight percent of the variation in SCE could be explained by differences in diet, living district, age, and tobacco consumption. Groups 1 and 2 had a 1.7 and 0.65 times higher SCE/cell, respectively, than group 3. For every additional 10 years of age of the probands, the SCE/cell increased by 0.4, and for every 10 g of tobacco smoked per day the SCE/cell was 0.7 higher compared to non-smokers. When priority was given to blood Hg concentration in the calculation, 16.3% of the total variation in SCE/cell could be explained. An increase in the blood Hg concentration of 10 micrograms l-1 corresponded to an increase of 0.3 SCE/cell. In 92 individuals blood Se and Cd concentrations were also analysed. The variables, tobacco smoking, diet, living district and Cd explained 53% of the total variation in SCE. Giving priority to the blood Hg and Cd concentrations, explained 21.4% of the total variation in SCE/cell. An increase of 10 micrograms l-1 in blood Cd and Hg corresponded to an increase in SCE/cell of 0.7 and 0.2, respectively. No influence on the SCE/cell could be attributed to the blood Pb and Se concentrations. Evaluated by the SCE test, seal diet, smoking, living district and blood Hg and Cd concentrations all contribute to mutagenicity in Greenlandic Eskimos, with seal diet as the most important of the factors examined.

Adult↗
PubMed1986

GNP and LTC team.

Explore the source record for details and available documents.

Geriatric Nursing↗
PubMed1985

Conformational and electrostatic properties of unoccupied and liganded estrogen receptors determined by aqueous two-phase partitioning.

The technique of aqueous two-phase partitioning (ATPP) has been used to characterize conformational and electrostatic properties of unoccupied and liganded rat uterine estrogen receptors. The adaptation of the hydroxylapatite receptor assay with ATPP systems has permitted estrogen receptor (ER) partition coefficients to be accurately determined, even when the partitioning process results in significant loss of ER binding capacity. The pH and salt dependences of estrogen receptor partition coefficients indicate that the theory governing partitioning behavior can be accurately applied to partitioning data obtained with crude cytosols. This technique has revealed a ligand-induced change in the properties of the unoccupied receptor that precedes the process of heat-induced transformation in vitro. The difference in partitioning behavior between unoccupied and nontransformed estrogen receptor is observed in all combinations of buffers and salts tested and is of equal magnitude as the difference between partition coefficients of nontransformed and transformed ER. The partition coefficients of both unoccupied and nontransformed ER are constant over the ER concentration range in which binding cooperativity has been previously demonstrated. The combined effects of salt and pH on ER partition coefficients indicate a pI of approximately 5.5 for both unoccupied and nontransformed estrogen receptors. However, the partition coefficients at the pI differ. It is concluded that estradiol binding to its unoccupied receptor results in a change in surface properties of the ER monomer that is independent of receptor transformation and makes the receptor less hydrophobic.

Animals↗
PubMed1985

Selenium treatment in rheumatoid arthritis.

A low selenium level has been reported in rheumatoid arthritis and juvenile chronic arthritis. Selenium is an essential part of the enzyme glutathione peroxidase, which catabolizes peroxides, compounds which are suggested to be of pathogenetic importance in rheumatic diseases. To assess a possible antirheumatic effect of selenium, 40 patients with active RA were included in a 6-month double-blind clinical study of selenium versus placebo. The patients in the selenium group were given daily supplements of 256 micrograms selenium in selenium-enriched yeast. Although concentrations of selenium in serum and erythrocytes increased considerably, no significant antirheumatic effect of selenium could be demonstrated.

Arthritis, Rheumatoid↗
PubMed1985

Low selenium level in severe rheumatoid arthritis.

Serum selenium concentrations were measured in 87 patients with rheumatoid arthritis. The serum selenium levels of the whole group of patients was significantly reduced (70.2 +/- 13.3 micrograms/l, p less than 0.001) when compared with the reference material (79.8 +/- 10.6 micrograms/l). However, the reduction was not equally pronounced in three groups of patients representing different courses of the disease. One group with an active, disabling disease of long duration had a very reduced serum selenium level (63.7 +/- 14.1 micrograms/l, p less than 0.001). Another group, with a protracted but mild disease had a slightly reduced level (74.1 +/- 10.8 micrograms/l, p less than 0.01), and a group with mild disease of short duration had a slightly but not significantly reduced selenium level (75.9 +/- 10.8 micrograms/l, p less than 0.1). Significant correlation was found between serum selenium and the number of joints with limitation of motion, number of joints with active arthritis, haemoglobin concentration and IgG concentration. No correlation was found between serum selenium and disease duration, morning stiffness, ESR, C-reactive protein, rheumatoid factor titre, serum albumin, IgM and IgA. Selenium is part of the enzyme glutathione peroxidase that catabolizes peroxides which are suggested to be actively involved in inflammation. A low selenium level may thus be a further factor in the pathogenesis of rheumatoid arthritis.

Adult↗
PubMed1985

Cadmium concentrations in blood samples from an East Greenlandic population.

An analysis for cadmium was made of 101 human blood samples from the district of Angmagssalik, East Greenland, and 29 from East Greenlanders living temporarily in Copenhagen. No relationship could be found between concentrations of blood cadmium and ethnic origin (Eskimos--Danes), sex, age or amount of seal eaten. Only smoking habits were reflected, as a median of 2.2 micrograms/l was found in smokers and 1.1 in non-smokers. Since analyses of organs from seals have suggested that the WHO provisional, tolerable weekly intake is exceeded by a factor as high as 10 as a result of seal eating, it is surprising that seal eating is without any effect on the blood concentration.

Animals↗
PubMed1984

Selenium and its interrelation with mercury in wholeblood and hair in an East Greenlandic population.

138 Blood samples and 12 hair samples from the district of Angmagssalik, East Greenland, have been analysed for selenium and mercury. It was found that selenium like mercury, was absorbed in accordance with the amount of marine food eaten. The mean blood concentration in the group eating most marine food was 173 and 186 micrograms Hg/1 for men and women, respectively, while in the group eating the lowest quantity of marine food, the mean values were 86 and 118 micrograms Hg/1. In blood, the selenium and mercury did not correlate in individuals, but only in groups according to eating habits. On a molar basis, selenium is present in blood in excess as compared to mercury, while the opposite is the case for hair. It is concluded that only part of the selenium interacts with mercury, and that blood, but not hair, reflects present dietary intake. The righ supply of selenium in relation to mercury exposure through the traditional arctic food is probably able to alleviate the hazards from dietary mercury exposure.

Adult↗
PubMed1984

Event-related brain potentials reveal similar attentional mechanisms during selective listening and shadowing.

The properties of linguistic attention were examined by recording event-related brain potentials (ERPs) to probe stimuli mixed with dichotically presented prose passages. Subjects either shadowed (repeated phrase by phrase) or selectively listened to one passage while ERPs were recorded from electrodes overlying midline sites, left-hemisphere speech areas, and corresponding areas of the right hemisphere. Mixed with each voice (a male voice in one ear, a female voice in the other) were four probe stimuli: digitized speech sounds (but or /a/ as in father) produced by the same speaker and tone bursts at the mean fundamental and second formant frequencies of that voice. The ERPs elicited by the speech probes in the attended ear showed an enhanced negativity, with an onset at 50 ms-100 ms and lasting up to 800 ms-1,000 ms, whereas the ERPs to the second formant probes showed an enhanced positivity in the 200 ms-300 ms latency range. These effects were comparable for shadowing and selective listening conditions and remained stable over the course of the experiment. The attention-related negativity to the consonant-vowel-consonant probe (but) was most prominent over the left hemisphere; other probes produced no significant asymmetries. The results indicate that stimulus selection during linguistic attention is specifically tuned to speech sounds rather than simply to constituent pure-tone frequencies or ear of entry. Furthermore, it appears that both attentional set and stimulus characteristics can influence the hemispheric utilization of stimuli.

Adolescent↗
PubMed1983

Human exposure to heavy metals in East Greenland. I. Mercury.

The concentration of mercury in 178 blood samples and 32 hair samples from the Angmagssalik district in East Greenland has been determined. For Greenlanders mercury concentrations are highly dependent on the amount of seal eaten. In the most heavily exposed group (eating more than six meals of seal per week), a significant positive correlation between blood mercury and age was demonstrated. No differences according to sex were demonstrated when the mean values were corrected for influence of age. In the most heavily exposed group, a mean value of 62.5 micrograms Hg/l was found, while in the group eating 1 meal of seal or less per week, the mean value was 22.2 micrograms Hg/l. In the control group consisting of Danes living temporarily in the district, the mean blood mercury concentration was 5.8 corresponding to the fact that they eat seal only occasionally. Hair mercury concentrations were found to correlate well with blood mercury concentrations (r=0.9222). The hair/blood ratio was estimated to 289. It is concluded that the present relatively high mercury exposure in Greenland does not exert any immediate risk of intoxication to the adult population, but supplementary investigation on fetal exposure is needed.

Adult↗