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Biomedical subjects

T M Florence

Publications and source records attributed to T M Florence.

At least 19 recordsLinked to original sources
PubMed1995

The role of free radicals in disease.

Evidence is accumulating that most of the degenerative diseases that afflict humanity have their origin in deleterious free radical reactions. These diseases include atherosclerosis, cancer, inflammatory joint disease, asthma, diabetes, senile dementia and degenerative eye disease. The process of biological ageing might also have a free radical basis. Most free radical damage to cells involves oxygen free radicals or, more generally, activated oxygen species (AOS) which include non-radical species such as singlet oxygen and hydrogen peroxide as well as free radicals. The AOS can damage genetic material, cause lipid peroxidation in cell membranes, and inactivate membrane-bound enzymes. Humans are well endowed with antioxidant defences against AOS; these antioxidants, or free radical scavengers, include ascorbic acid (vitamin C), alpha-tocopherol (vitamin E), beta-carotene, coenzyme Q10, enzymes such as catalase and superoxide dismutase, and trace elements including selenium and zinc. The eye is an organ with intense AOS activity, and it requires high levels of antioxidants to protect its unsaturated fatty acids. The human species is not genetically adapted to survive past middle age, and it appears that antioxidant supplementation of our diet is needed to ensure a more healthy elderly population.

Aging↗
PubMed1994

Toxicity of nickel ores to marine organisms.

Queensland Nickel proposes to import New Caledonian (Ballande) and Indonesian (Gebe) nickel ores, one option being ship-to-barge transfer in Halifax Bay, North Queensland. Because small amounts of ore may be split during the unloading and transfer operations, it was important to investigate the potential impact of the spilt ore on the ecological health of the Bay. Long-term leaching of the ores with seawater showed that only nickel and chromium (VI) were released from the ores in sufficient concentrations to cause toxicity to a range of marine organisms. The soluble fractions of nickel and chromium (VI) were released from the ores within a few days. Nickel, chromium (VI) and the ore leachates showed similar toxicity to the juvenile banana prawn Penaeus merguiensis, the amphipod Allorchestes compressa and both temperature (22 degrees C) and tropical (27 degrees C) strains of the unicellular marine alga Nitzschia closterium. In a series of 30-day sub-chronic microcosm experiments, juvenile leader prawns Penaeus monodon, polychaete worms Galeolaria caespitosa and the tropical gastropod Nerita chamaeleon were all very resistant to the nickel ores, with mortality unaffected by 700 g ore per 50 l seawater. The growth rate of the leader prawns was, however, lower than that of the controls. From these data, a conservative maximum safe concentration of the nickel ores in seawater is 0.1 g l-1. The nickel ore was not highly toxic and if spilt in the quantities predicted, would not have a significant impact on the ecological health of the Bay.

Animals↗
PubMed1994

Percutaneous absorption of inorganic lead compounds.

In vivo experiments with the stable lead isotope, 204Pb, have confirmed that inorganic lead compounds can be absorbed through the skin. Three different analytical techniques--thermal ionization mass spectrometry, inductively coupled plasma mass spectrometry and anodic stripping voltammetry--showed that lead, as lead nitrate or lead acetate, was rapidly absorbed through the skin and detectable in sweat, blood and urine within 6 h of skin application. Of the 4.4 mg of lead applied to the skin in one experiment, 1.3 mg was absorbed within 24 h. Initial rapid uptake was probably via sweat glands and hair follicles, followed by slower absorption via the transepidermal route. While increases in 204Pb concentration and abundance were observed, no increase in total lead in blood or urine was found. It is possible that the physicochemical form of skin-absorbed lead partitions strongly into extracellular fluid, but has a low affinity for erythrocytes. There was no significant difference in uptake of lead into erythrocytes (in vitro) from normal saline, synthetic sweat or sauna sweat. Ultrafiltration of sweat showed that up to 70% of lead in sweat was associated with > 30,000 MW particles. It is possible that percutaneous absorption of lead could contribute significantly to lead body burden, particularly from occupational exposure to lead in dust. Moreover, because lead absorbed through the skin was only just detectable in blood, and blood lead is the main criterion by which industry determines exposure, skin-absorbed lead may remain undetected.

Humans↗
PubMed1992

Determination of trace element speciation and the role of speciation in aquatic toxicity.

Knowledge of trace element speciation in waters is essential to an understanding of aquatic toxicity and bioaccumulation, as well as to the partitioning of elements between water and colloidal and particulate phases. In natural waters, only very small percentages of the dissolved heavy metals, such as copper, lead cadmium or zinc, are present as free (aquo) metal ion; most of the metal is adsorbed to colloidal particles or combined in complexes. For aquatic toxicity studies, the aim of the speciation measurement is to determine the fraction of total dissolved metal (the 'toxic fraction') that will react with, and be transported across, a biological membrane such as a fish gill. In this review, a range of trace element speciation techniques is discussed and compared. A simple anodic stripping voltammetric method is recommended for the measurement of the fraction of electroactive metal in a sample, i.e. the fraction of total dissolved metal that can be deposited into a mercury electrode at the natural pH of the sample. The electroactive fraction is believed to approximate the toxic fraction. A rapid ion exchange method, suitable for field use, is proposed for the determination of the toxic fraction of copper in waters.

Adsorption↗
PubMed1992

Platinum in the human diet, blood, hair and excreta.

Baseline levels of platinum in the blood, hair and urine of 21 adults from Sydney, Australia, and three adults from the relatively unpolluted area of Lord Howe Island, Australia, were determined by adsorptive voltammetry. The median concentrations of platinum in samples from residents in Sydney were: whole blood, 0.56 microgram Pt l-1; hair, 3.84 micrograms Pt kg-1; urine, 0.18 microgram Pt l-1 (0.23 microgram Pt g creatinine). Samples from residents of Lord Howe Island had platinum levels that were within the range of values of the corresponding samples from Sydney residents. For faeces samples, the median platinum concentration was 10.5 micrograms kg-1 FW. The excretion of platinum over a 4-day period was measured in one adult male. Urinary excretion of platinum was between 0.76 and 1.07 micrograms Pt day-1 and in faeces it was between 0.61 and 0.73 microgram Pt day-1. The concentrations of platinum in a range of foodstuffs from Sydney were between 8.11 micrograms kg-1 FW for liver and 0.13 microgram kg-1 FW for full-cream milk. This information as well as the amounts of these foods in hypothetical diets for Australians was used to calculate the total dietary intake of platinum. The average diet of a Sydney adult contains 1.44 micrograms of platinum per day (adult male, 1.73 micrograms Pt day-1; adult female, 1.15 micrograms Pt day-1). The uptake of dietary platinum from the gut was estimated to be at least 42% and, therefore, diet appears to make a substantial contribution to total platinum intake.

Adult↗
PubMed1992

Trace element speciation by anodic stripping voltammetry.

The effects of a range of complexing agents and a detergent on the stripping process in anodic stripping voltammetry (ASV) were compared by using both differential-pulse and d.c. techniques. The detergent and most of the ligands, added after deposition was complete, seriously affected the height of the differential-pulse waves, and fulvic acid even decreased the area of the d.c. stripping peak. In order to obtain a correlation between ASV-labile metal measurements and bioassays, it is important that complexing agents in the sample solution affect only the deposition stage, and not the stripping stage in ASV. In order to achieve this result, the double acidification technique is recommended, where a voltammogram is recorded with deposition at the natural pH of the sample, but with stripping carried out at pH less than 2, then a second voltammogram run on the same solution, but with both deposition and stripping effected at pH less than 2. Excellent agreement was obtained between ASV-labile metal measured by the double acidification method and algal assays for a variety of natural and synthetic waters.

Electrochemistry↗
PubMed1990

Determination of platinum in blood by adsorptive voltammetry.

This work describes a sensitive method for the determination of platinum in blood, which can be used for determining the natural levels of platinum in human blood, for monitoring patients treated with platinum cytotoxic drugs, and for monitoring occupational exposure to these drugs and other platinum compounds. The method involves dry ashing of blood samples in a muffle furnace and determination of platinum by adsorptive voltammetric (AV) measurement of the catalytic reduction of protons by the platinum-formazone complex. The detection limit for a 100-microL sample of blood is 0.017 micrograms/L, with a recovery of 94% and a relative standard deviation of 7% at a platinum level of 1 microgram/L. By using this method, the natural levels of platinum in human blood were found to be in the range 0.1-2.8 micrograms/L (median = 0.6 micrograms/L). These results were verified by inductively coupled plasma mass spectrometry (ICP-MS) with blood prepared by wet ashing and using gold as an internal standard.

Electrochemistry↗
PubMed1990

Influence of complexing agents and surfactants on metal speciation analysis in road runoff.

A combination of medium exchange and sample acidification techniques is used to enable the calculation of the individual effects of complexing agents and surfactants on the deposition and stripping steps in anodic stripping voltammetry for copper, lead and cadmium in road and urban runoff. A simple acidification procedure is presented for determination of the toxic fraction.

Benzopyrans↗
PubMed1989

Manganese in scalp hair: problems of exogenous manganese and implications for manganese monitoring in Groote Eylandt Aborigines.

The use of scalp hair to monitor manganese was studied as part of an investigation of manganese intoxication amongst a group of Aborigines living on manganese-rich soil on Groote Eylandt, in the Northern Territory of Australia. High scalp-hair manganese values were due largely to manganese from exogenous sources. Manganese (IV) dioxide in dust, trapped in hair, was reduced by the components of sweat, leading to the diffusion of manganese (II) into the hair shaft. At least 15 micrograms Mn g-1 hair could be incorporated into hair via this exogenous route. To overcome the problems of manganese contamination, the ability of a number of leaching agents to remove exogenous manganese selectively from hair was tested. Measurements of manganese along the length of hair strands were extrapolated back to zero length to estimate the amount of manganese in the hair as it emerged from the scalp. Using this extrapolation technique, Aborigines on Groote Eylandt had a mean scalp-hair manganese of 16 ppm. Aborigines in non-manganese areas had 2 ppm manganese in hair. Caucasians living in the same manganese-rich area had 2.5 ppm manganese in hair, compared to 0.5 ppm manganese in non-manganese areas. Measurements of manganese in hair and blood of Groote Eylandt Aborigines showed that the population had a high exposure to manganese, but did not distinguish between those individuals affected/unaffected by the neurological condition, Groote Eylandt Syndrome.

Australia↗
PubMed1989

Manganese catalysis of dopamine oxidation.

Manganese catalysis of the oxidation of dopamine by air was studied as part of an investigation of possible manganese intoxication amongst a group of Aborigines living on manganese-rich soil on Groote Eylandt, in the Northern Territory of Australia. Manganese significantly increased the oxidation rate of dopamine, and the manganese complexes with some purines were especially efficient catalysts. An oxidation mechanism, involving a manganese(II)/(III) redox couple and a semiquinone free radical intermediate, is proposed. Stoichiometric hydrogen peroxide was produced by the oxidation, and the oxidation products of dopamine were highly toxic to the marine diatom Nitzschia closterium. Hydrogen peroxide and the superoxide radical did not oxidize dopamine at physiological pH. Some electrophilic compounds, including ascorbic acid, dehydroascorbic acid and thiamine, effectively inhibited dopamine oxidation. The Groote Eylandt Aborigines are likely to be deficient in ascorbic acid (vitamin C) and thiamine (vitamin B1), and these deficiencies, as well as their lifestyle, may predispose them to manganese intoxication.

Catalysis↗
PubMed1988

The use of sweat to monitor lead absorption through the skin.

It is usually assumed that lead can be absorbed through the skin only if it is present as an organolead compound such as tetraethyllead or lead naphthanate. It has been found, however, that finely-powdered lead metal or lead nitrate solution placed on the skin results in rapid absorption of lead, and transport of the metal around the body. The absorbed lead appears in sweat and saliva, but not in blood or urine. The application of 6 mg of lead as 0.5 M lead nitrate to the left arm resulted in an increase in lead concentration in pilocarpine-induced iontophoresis sweat samples taken from the right arm, from an initial value of 15-25 micrograms Pbl-1 to greater than 300 micrograms Pbl-1 after 2 days. Saliva lead increased from 2.5 to 15 micrograms Pbl-1 in the same period. The rate of lead absorption through the skin increases with increased sweating of the skin. Since no measurable increase in blood lead has been found, the lead must be transported in the plasma and rapidly concentrated into the extracellular fluid pool (sweat and saliva), without significant uptake by the erythrocytes, and with a very low transient concentration in the plasma. Workers occupationally exposed to lead have extremely high levels of lead in sweat even though their lead in blood is only moderately elevated. Lead absorbed through the skin may be eliminated via sweat and other extracellular fluids, and hence not be as great a health hazard as ingested lead, but this will need to be proved by further studies.

Environmental Pollution↗
PubMed1988

A comparative study of copper, lead, cadmium and zinc in human sweat and blood.

Zinc, cadmium, lead and copper in sweat from 24 male and 39 female volunteers were determined by anodic stripping voltammetry. Sweating was induced on the forearms by pilocarpine iontophoresis. Average values found for zinc, cadmium, lead and copper in sweat from males were 181 (range 25-863), 1.4 (less than 0.5-10), 41 (6-87) and 103 (less than 5-673) micrograms l-1, respectively. Zinc in sweat from females was significantly higher than in sweat from males (331 micrograms l-1, range 87-836 micrograms l-1), while sweat copper and sweat lead in females were lower (29 micrograms Cu l-1, range less than 5-146 micrograms Cu l-1 and 24 micrograms Pb l-1, range less than 5-66 micrograms Pb l-1). Those taking oral contraceptives showed increased sweat copper concentrations (94 micrograms Cu l-1, range less than 5-480 micrograms Cu l-1) and sweat lead concentrations (36 micrograms Pb l-1, range less than 5-70 micrograms Pb l-1). There was no sex-based difference for copper in sauna-induced sweat. Metal concentrations in sweat were compared with ceruloplasmin, alkaline phosphatase, and total and mobile copper and zinc concentrations in serum in males and females.

Cadmium↗
PubMed1987

The determination of trace metals in sweat by anodic stripping voltammetry.

Sweating was induced on the forearm of subjects by pilocarpine iontophoresis, and the sweat collected on a small membrane filter. Zinc, cadmium, lead and copper were then determined in the filter by anodic stripping voltammetry (ASV) using one of two alternative techniques: leaching the filter with a supporting electrolyte (0.1 M NaNO3/0.002 M HNO3), followed by ASV of the leachate; or, direct ASV analysis of the trace metals in the membrane filter using a novel thin-layer cell. Average values found for zinc, cadmium, lead and copper in sweat from males were (micrograms 1-1): 720, less than 3, 15 and 80, respectively. Copper in sweat from females was lower (23 micrograms l-1) than for males, although use of oral contraceptives appeared to increase copper concentration.

Electrochemistry↗