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Biomedical subjects

A C Cantrell

Publications and source records attributed to A C Cantrell.

13 recordsLinked to original sources
PubMed1997

Semen quality and fertility of men employed in a South African lead acid battery plant.

Previous studies of the associations of measures of occupational lead exposure with measures of semen quality and infertility among male workers have produced conflicting results. The current study was undertaken to examine these associations among a population of workers with a broad range of measures of current and historical lead exposure. Ninety-seven lead-exposed workers from a South African lead acid battery facility provided semen samples that were analyzed for sperm density, sperm count, sperm motility, sperm morphology, and presence of antisperm antibodies. Questionnaire data were collected for reported histories of sub- or infertility. Current blood leads ranged from 28 to 93 micrograms/dl. Semen lead ranged from 1 to 87 micrograms/dl. Reasonably consistent and significant associations were found between an increased percentage of sperm with abnormal morphology and higher measures of current blood lead, cumulative blood lead, and duration of exposure. An increased percent of immotile sperm was associated only with zinc protoporphyrin (ZPP) among the lead exposure measures. There were no associations of sperm density or sperm count with any of the lead exposure measures. A weak association of increased percent of sperm with antisperm antibodies with increased semen lead was present. There were no consistent associations of measures of lead exposure with measures of fertility or procreativity. This study, while supporting the association of lead exposure with increased risk of abnormal sperm morphology seen in some previous studies, does not lend support to previously reported associations of sperm density or count or infertility with measures of lead exposure. However, the relatively high range of current blood leads, high prevalence of abnormalities in semen quality, and the lack of a control population, suggest that these negative findings should be interpreted with caution.

Cross-Sectional Studies↗
PubMed1996

Biological indicators of exposure to total and respirable aluminium dust fractions in a primary aluminium smelter.

OBJECTIVES: The study attempts to define biological indicators of aluminium uptake and excretion in workers exposed to airborne aluminium compounds in a primary aluminium smelter. Also, this study defines the total and respirable aluminium dust fractions in two different potrooms, and correlates their concentrations with biological indicators in this group of workers. METHODS: Air was sampled at defined work sites. Non-destructive and conventional techniques were used to find total and respirable aluminium content of the dust. Blood and urine was collected from 84 volunteers employed at various work stations throughout the smelter and from two different cohorts of controls matched for sex, age, and socioeconomic status. Aluminium in serum samples and urine specimens was measured by flameless atomic absorption with a PE 4100 ZL spectrometer. RESULTS: The correlation of aluminium concentrations in serum and urine samples with the degree of exposure was assessed for three arbitrary exposure categories; low (0.036 mg Al/m3), medium (0.35 mg Al/m3) and high (1.47 mg Al/m3) as found in different areas of the smelter. At medium and high exposure, the ratio of respirable to total aluminium in the dust samples varied significantly. At high exposure, serum aluminium, although significantly raised, was still within the normal range of an unexposed population. The workers with low exposure excreted aluminium in urine at levels significantly higher than the controls, but still within the normal range of the population. However, potroom workers with medium and high exposure had significantly higher urinary aluminium than the normal range. CONCLUSIONS: It is concluded that only urinary aluminium constitutes a practical index of occupational exposure at or above 0.35 mg Al/m3, and that the respirable fraction of the dust may play a major role in the biological response to exposure to aluminium in a smelter environment.

Adult↗
PubMed1995

Membrane potential of rat hepatoma cells in culture: influence of factors affecting amino acid transport.

The effect has been studied of various media, hormones and of amino acids on the membrane potential of rat hepatoma cells in culture measured by microelectrode impalement. Cells in Eagle's minimal essential medium plus 5% serum had a value which varied daily from about 5-8 mV, inside negative. The membrane potential of rat hepatocytes was measured to be 8.7 +/- 0.2 mV, inside negative. The membrane potential of the hepatoma cells was decreased by insulin and increased by glucagon. Membrane potential was unaffected by change of medium to Hanks' or Earle's balanced salt solutions or deprivation of serum. It was, however, reduced in cells in phosphate-buffered saline and by reduction of pH. The former effect was shown to be due to the higher [Na+] of phosphate-buffered saline as opposed to the other media. Addition of alanine, glycine, serine, proline and methylaminoisobutyrate all reduced membrane potential by 2-3 mV. Smaller decreases were seen with methionine, leucine and phenylalanine, but none with glutamine, threonine, BCH (2-aminonorborane-2-carboxylic acid) and D-alanine. The results are compared with the effects of similar conditions on aminoisobutyrate uptake. Whilst there was a correlation under some conditions there was not under others. It is concluded that for the hepatoma cells factors additional to the membrane potential must exert some influence on the capacity for amino acid transport.

Amino Acids↗
PubMed1988

Properties of membrane bound ferrochelatase purified from baboon liver mitochondria.

1. Baboon ferrochelatase was purified to apparent homogeneity. 2. The pH optimum was 7.85 and the pI 5.3. 3. The estimated molecular weight was 205 K made up by two 50 + 60 K heterodimers. 4. The Km values for proto- and mesoporphyrin were 18.5 and 10.8 microM with iron as co-substrate. With cobalt as co-substrate the Km values were 34.5 and 10.4 microM, respectively. The mean Km value for iron was 2.2 microM while cobalt acted as a complete inhibitor. 5. Lead played a dual role that of both pseudo substrate and inhibitor. As shown by inhibitor kinetics, Pb acted as a two-step two-site parabolic competitive inhibitor. The mean Ki value at low Pb levels was 0.65 mM and at high levels 0.17 mM. 6. Substrate inhibition occurred above 36 microM for proto- and 44 microM for mesoporphyrin with iron as co-substrate. For iron, with mesoporphyrin as co-substrate it occurred above 29 microM.

Animals↗
PubMed1981

Attempts to demonstrate short-term metabolic effects of vinyl chloride in normal rat liver.

The present study examines whether VCM or one of its metabolites, chloracetaldehyde, has a short-term effect on cell metabolism. ATP, ADP, and AMP levels were measured in regenerating rat liver after 4 and 16 hours. No change in the levels of these nucleotides was evident after i.v. injection of VCM immediately after partial hepatectomy. A second technique, that of measuring transmembrane potentials with microelectrodes, was applied both to cells in rat liver slices and pulmonary alveolar macrophages. The addition of VCM and chloracetaldehyde with the electrodes in position in rat liver slices had no significant effect on transmembrane potentials. The same was true for a series of measurements on macrophages before and after addition of the test chemicals. It therefore appears that VCM does not alter general cell metabolism but could act on a specific intracellular target.

Adenine Nucleotides↗
PubMed1977

The effect of zinc and pH on the behaviour of delta-aminolevulinic acid dehydratase activity in baboons exposed to lead.

Four adult male baboons (Papio ursinus) were exposed to a cloud of lead oxide dust to induce changes in the status of delta-aminolevulinic acid dehydratase (ALAD). Enzyme activity fell rapidly to a steady state as blood lead levels rose above normal. Exogenous zinc was shown to activate the enzyme, and the antagonistic effect of zinc on in vivo and in vitro lead inhibition was demonstrated for baboons. In baboons not exposed to lead dust, ALAD showed an activity optimum at pH 7-1 which shifted to pH 6-8 with in vitro addition of lead. In baboons exposed to lead dust, with raised blood lead, activity optima were observed at pH 6-8 and 6-2, while the optimum at pH 7-1 was absent.

Animals↗
PubMed1976

The in vitro effect of zinc on the inhibition of human delta-aminolevulinic acid dehydratase by lead.

The antagonistic effect of zinc on inhibibition of human aminolevulinic acid dehydratase (ALAD) by lead was examined in vitro. The phenomenon was studied at pH 6.5-7.5 . Zinc and lead were added at concentrations ranging from physiological levels to levels far in excess of those expected in heavy industrial exposure. ALAD activity of normal blood assayed in the presence of zinc was unaffected by exogenous lead if the added zinc concentration was above 0.53 mmol/l blood, or double the normal endogenous level, and was of the order found in heavy industrial exposure to zinc. In this case, ALAD assay values were appreciably raised and might have fallen into the normal range in spite of a dangerous total blood lead of over 0.0048 mmol/l. When zinc was added in vitro to blood from a worker with a blood lead level of 0.0043 mmol/l the ALAD values obtained were also raised and did not reflect the dangerous level of lead in the patient.

Environmental Exposure↗
PubMedDate not supplied

Reaction of colloidal silica with membranes of intact mammalian cells.

Colloidal silical particles were produced at a size that permitted reaction with human erythrocytes and rat macrophages without affecting cell integrity. Binding of colloid was shown by increased electrophoretic mobility of red cells and also resulted in changes in the surface topography of red cells as seen with scanning electron microscopy. The degree to which colloid binds to red cells was determined by microprobe analysis of single intact cells. Furthermore, the capacity of red cells to bind silica was increased if sialic acid residues were removed enzymatically from the cell surface.

Animals↗