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Biomedical subjects

H J Mason

Publications and source records attributed to H J Mason.

16 recordsLinked to original sources
PubMed1992

Longitudinal studies of exposure to cadmium.

Measurements of urinary proteins, blood and urinary cadmium, and in vivo kidney and liver cadmium have been made for a group of workers at several times between 1981 and 1990. The possibility of the introduction of measurement artifacts due to the use of different in vivo measurement systems has been assessed and is considered to be small. Changes in cadmium body burden with time have been studied in relation to kidney function. The results suggest several interesting patterns, although more data are needed to elucidate these further. They do, however, show the effectiveness of good hygiene in the workplace.

Body Burden↗
PubMed1991

Occupational mercury vapour exposure and testicular, pituitary and thyroid endocrine function.

We have investigated the pituitary-testicular axis in a well-characterized population which was occupationally exposed to mercury vapour. Thyroid stimulating hormone and prolactin were also measured as indices of thyroid and pituitary endocrine function. We found no relation between blood or urine mercury levels or length of occupational exposure with any measurement of endocrine function. A small, but statistically significant negative correlation between serum sex-hormone binding globulin and the duration of occupational exposure to mercury was found. The physiological significance of this result is unclear.

Adolescent↗
PubMed1990

Effect of occupational lead exposure on serum 1,25-dihydroxyvitamin D levels.

The effects of lead exposure on serum 1,25-dihydroxyvitamin D levels and calcium homeostasis have been studied in 63 males occupationally exposed to the metal in the UK. The exposure indices used were blood lead, reflecting short-term exposure, and an in vivo X-ray fluorescence measurement of tibia lead which reflects cumulative lead exposure. Serum 1,25-dihydroxyvitamin D levels were higher than those in a referent population, who were non-occupationally exposed to lead, and were correlated with both blood lead and tibia lead. Multiple regression analysis suggested that blood lead was the variable responsible for the increase in serum 1,25-dihydroxyvitamin D. There were no other abnormalities in calcium metabolism associated with the degree of lead exposure.

Alanine↗
PubMed1990

Occupational cadmium exposure and testicular endocrine function.

Cadmium is known to cause testicular necrosis in several animal species, although there is little data on its possible effects in humans. We have investigated the effect of occupational cadmium exposure on the pituitary-testicular endocrine axis, as measured by serum testosterone, luteinizing hormone (LH) and follicular-stimulating hormone (FSH), in a well-characterized population occupationally exposed to cadmium. Over 60% of all workers, who had been exposed to cadmium oxide fumes for longer than a year, in a single factory, since 1926, were studied. Integrated cadmium exposure estimates were constructed for each subject from atmospheric measurements, together with other available company data, and these exposure estimates were validated by in-vivo neutron activation analyses of liver cadmium burdens. The lack of testicular endocrine effects was in contrast to significant dose-related changes in renal glomerular and tubular function demonstrated in the same population.

Adult↗
PubMed1990

Chronic occupational lead exposure and testicular endocrine function.

The effects of moderate lead exposure on testicular endocrine function were evaluated in a group of 90 males who were occupationally exposed to inorganic lead. Lead concentrations in blood and bone were measured as indices of short-term and long-term, cumulative exposure, respectively. The results of this study show that the lead exposure levels encountered in the UK at present may result in a subclinical increase in follicle stimulating hormone (FSH), which is related to blood lead levels. This suggest that lead may be causing some subclinical primary damage to the seminiferous tubules in the testes. However, at blood lead levels of less than 47 micrograms dl-1 this effect on serum FSH is not apparent. There was no significant effect on serum testosterone concentrations or the free testosterone index. The mean luteinizing hormone (LH) level in the exposed group was found to be lower than in the control population. However, there appeared a confoundingly significant positive correlation between serum luteinizing hormone levels and the length of occupational lead exposure within the exposed group.

Adolescent↗
PubMed1989

Intra-individual variation in plasma and erythrocyte cholinesterase activities and the monitoring of uptake of organo-phosphate pesticides.

The measurement of plasma and erythrocyte cholinesterase activities is used to monitor absorption of anti-cholinesterase organo-phosphorus compounds. A fall in an individual's enzyme activity signifies excessive exposure if it is clearly greater than the normal intra-individual variation found in unexposed subjects. The extent of normal variation in enzyme activity as measured is dependent on both the true intra-individual biological variation and the precision of the method used. This report defines normal variation in plasma and erythrocyte cholinesterase activity using the assay developed and used routinely in our laboratory. We have also defined the relation between the precision of the assay used by a laboratory and the sensitivity with which a significant depression in successive enzyme measurements can be detected. This allows occupational physicians, who use cholinesterase measurements to monitor organo-phosphate exposure, to establish percentage depressions from their method precision data that may possibly indicate organo-phosphate uptake between successive enzyme measurements. We have calculated that, with our analytical precision, percentage drops between two successive measurements that are greater than 15 and 7.5 per cent for the plasma and erythrocyte enzymes respectively suggest significant organo-phosphorus absorption in pesticide workers.

Cholinesterase Inhibitors↗
PubMed1988

Relations between liver cadmium, cumulative exposure, and renal function in cadmium alloy workers.

Detailed biochemical investigations of renal function were made on 75 male workers exposed to cadmium and an equal number of referents matched for age, sex, and employment status. The exposed group consisted of current and retired workers who had been employed in the manufacture of copper-cadmium alloy at a single factory in the United Kingdom for periods of up to 39 years and for whom cumulative cadmium exposure indices could be calculated. In vivo measurements of liver and kidney cadmium burden were made on exposed and referent workers using a transportable neutron activation analysis facility. Significant increases in the urinary excretion of albumin, retinol binding protein, beta 2 microglobulin, N-acetylglucosaminidase (NAG), alkaline phosphatase, gamma-glutamyl transferase and significant decreases in the renal reabsorption of calcium, urate, and phosphate were found in the exposed group compared with the referent group. Measures of glomerular filtration rate (GFR) (creatinine clearance, serum creatinine, and beta 2 microglobulin) indicated a reduction in GFR in the exposed population. Many of these tubular and glomerular function indicators were significantly correlated with both cumulative exposure index and liver cadmium burden. Using cumulative exposure index and liver cadmium as estimates of dose, a two phase linear regression model was applied to identify an inflection point signifying a threshold level above which changes in renal function occur. Many biochemical variables fitted this model; urinary total protein, retinol binding protein, albumin, and beta 2 microglobulin gave similar inflection points at cumulative exposure levels of about 1100 y.micrograms/m3 whereas changes in the tubular reabsorption of urate and phosphate occurred at higher cumulative exposure indices. Measures of GFR, although fitting the threshold model did not give well defined inflection points. Fewer variables fitted the two phase model using liver cadmium; those that did gave threshold levels in the range 20.3-55.1 ppm. When cadmium workers with cumulative exposure indices of less than 1100 y.micrograms/m3 were compared with their respective referents only serum beta 2 microglobulin and urinary NAG were significantly increased in the exposed group and these differences were not related to the degree of cadmium exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

Alloys↗
PubMedDate not supplied

In vivo neutron activation analysis of organ cadmium burdens. Referent levels in liver and kidney and the impact of smoking.

In vivo neutron activation measurements of liver and kidney cadmium have been made in 77 exposed workers and 101 referents. Cadmium levels were higher in exposed workers than in referents; both in liver, 25.7 cf. 0.6 micrograms/g, and kidney, 17.9 cf. 2.7 mg. The 19 referents who never smoked had lower mean organ cadmium burdens than the other referents, the difference achieving statistical significance in the kidney, p less than .01. Cigarette smoking was estimated to increase cadmium body burden by 370 +/- 140 micrograms/pack year. These referent cadmium levels are similar to, although slightly below, previous in vivo and autopsy data.

Body Burden↗