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Biomedical subjects

R W Mayes

Publications and source records attributed to R W Mayes.

35 records · Page 2Linked to original sources
PubMed1992

Development of a laboratory method to predict rapidly the availability of radiocaesium.

A simple extraction procedure has been developed to assess rapidly the probable extent of the transfer of radiocaesium into ruminant food products soon after a nuclear accident. The in vitro extractions were validated against true absorption measurements of different forms of radiocaesium in the sheep gut. Extractions were performed on a range of different radiocaesium sources. Some of these sources were artificial (ionic radiocaesium adsorbed onto bentonite, silica spheres and filter-papers) and others were environmentally contaminated [silt from the Ravenglass Estuary contaminated by effluent from British Nuclear Fuels Limited (BNFL) Sellafield, and upland grass and heather contaminated by Chernobyl fallout]. Laboratory experiments concentrated primarily on the use of simple inorganic extractants in competitive ion-exchange processes. Of the reagents used, 0.1 mol dm-3 stable caesium chloride solution was the most effective extractant. The proportion of radiocaesium extracted by 0.1 mol dm-3 caesium chloride correlated well with measurements of true absorption. Extracting radiocaesium using 0.1 mol dm-3 caesium chloride proved to be an inexpensive and rapid method of predicting the availability of radiocaesium for absorption in the ruminant gut, giving results within 24 h. Further extractions were carried out using cellulase/pepsin simulated digestions and ovine rumen fluid. Results suggested that the availability of radiocaesium from some inorganic sources may be underestimated using such techniques.

Accidents↗
PubMed1991

Chloroquine distribution in postmortem cases.

Chloroquine concentrations in blood and tissues were examined in overdose and non-overdose cases to determine appropriate ranges for interpretation. Twenty-nine literature overdose cases and 8 non-overdose literature cases were compared with this laboratory's findings. The results indicate significant postmortem redistribution of chloroquine. Combining this laboratory's results and the literature results indicates that using a liver concentration of 150 mg/kg as a cutoff between overdose and non-overdose concentrations properly identified 30 of the 34 published cases containing liver chloroquine and 19 of the 20 presented cases.

Accidents, Aviation↗
PubMed1991

The toxicological examination of the victims of the British Air Tours Boeing 737 accident at Manchester in 1985.

The results of toxicological analyses of the body fluids of the victims from the accident involving the British Air Tours Boeing 737 in August 1985 are presented for carboxyhemoglobin, cyanide, and volatiles. All the victims except one had raised concentrations of carbon monoxide. All the victims had raised concentrations of cyanide. All the victims showed the presence of volatile substances in the blood. Autopsies revealed that all the victims had carbon particles in the trachea and bronchi. Thus, all the victims must have inhaled fire products in the burning aircraft cabin. Six victims had concentrations of carbon monoxide or cyanide in the blood that were neither fatal nor incapacitating; therefore, it is reasonable to suggest that these six victims survived for a comparatively short time and that there may have been other causes, in addition to toxic fumes, for their deaths. The other 48 victims must have survived long enough in the fire to accumulate incapacitating or fatal concentrations of carbon monoxide or cyanide or both. The effects of these substances found in the blood of each of the 48 victims must have combined to produce an insurmountable impediment to escape from the aircraft.

Accidents, Aviation↗
PubMed1989

The quantification of dietary intake, digestion and metabolism in farm livestock and its relevance to the study of radionuclide uptake.

The transfer coefficient and biological half-life have been widely used to describe the uptake of radionuclides by farm animals. However, these parameters may be inadequate, for they take little account of the effects of the processes occurring in the animal upon the behaviour of a radionuclide. The aim of this paper is to review techniques which could be used to study the uptake of dietary radionuclides by farm animals. The main factors affecting uptake can be categorised in terms of intake, digestion and absorption, and metabolism. The estimation of the intake of a radionuclide by grazing animals is difficult. Intake estimation by determining amounts of standing herbage before and after grazing is rarely a valid method because of herbage growth. Methods based on animal measurements have wider application. Many intake methods give short-term estimates (measured over a few hours), whereas for most radionuclide studies, longer-term estimates (over days or weeks) are required. The most suitable methods use indigestible markers to determine the output of faeces and the digestibility of grazed herbage. Considerable variability in the distribution of radionuclides may exist among different plant species. To accurately estimate radionuclide intake on mixed pastures it is necessary to determine the plant species composition of the diet of animals; present methods may be inadequate and new techniques may be required. If contaminated, the drinking-water intake by animals would need to be determined. The processes of digestion (the physical disintegration and chemical breakdown by gut microbes and secreted enzymes) may affect the radionuclide uptake by an animal. Other factors, including the chemical form of the radionuclide, rate of passage of material along the gut, degree of incorporation into microbial tissue, and the absorption mechanism might also affect the degree to which the radionuclide can cross the gut wall. The apparent absorption coefficient (apparent digestibility) has been widely used in nutritional studies to quantify net uptake of a component from the gut. However, as this parameter does not adequately indicate the ability of a substance to cross the gut wall, its value in radionuclide uptake studies is rather limited. More useful, since it gives an indication of transfer across the wall of the gut, is the true absorption coefficient. The use of animals with cannulae in the digestive tract, allows the quantitative measurement of digestion and absorption in the different functional parts of the gut. The metabolism of absorbed substances by an animal involves transport (through the circulatory system), uptake into tissue cells, modification by biochemical reactions, and excretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal Feed↗
PubMed1989

A possible method for estimating the true absorption coefficient for radiocaesium in ruminants.

A method has been described for estimating the true absorption coefficient for radiocaesium. The ratio of the excretion of 137Cs in the faeces to that excreted in the urine was estimated in housed ewes and lambs offered a radiocaesium-free diet for 16-22 days, after previously grazing a pasture contaminated with Chernobyl fall-out. There was a two-fold range in the faeces:urine excretion ratio. The ratios obtained were used to estimate the the faecal 137Cs of endogenous origin from the urinary excretion rates of ewes given diets contaminated with radiocaesium from Chernobyl or from marine effluent from BNFL, Sellafield, and hence the true absorption coefficient could be determined. The observed variations in faeces:urine excretion ratios had little effect upon the estimates of true absorption coefficient.

Accidents↗
PubMed1989

Transfer of radiocesium from different environmental sources to ewes and suckling lambs.

Indoor experiments are described that compare the transfer of radiocesium to ewe and lamb tissues from different sources. Lactating ewes were fed either perennial ryegrass contaminated by Chernobyl fallout, or saltmarsh vegetation contaminated by marine discharges from the Sellafield reprocessing plant. The transfer to ewe tissues and milk was greater from the Chernobyl contaminated herbage than from saltmarsh vegetation. Lambs receiving a mixture of vegetation and milk were given radiocesium from one of the two vegetation sources or from milk obtained from the experimental ewes. Transfer to lamb tissues declined in the order milk greater than Chernobyl fallout greater than Sellafield discharge. The radiocesium transfer to lamb tissues exceeded that to ewe tissues. Transfer coefficients for 137Cs in the Chernobyl fallout were higher than most previously published figures at 0.12 d kg-1 for ewe muscle and 0.50 d kg-1 for lamb muscle. The transfer coefficient for 137Cs from ewe milk to lamb muscle was 1.20 d kg-1.

Accidents↗
PubMed1984

Applications of gas chromatographic head space analysis to aviation accident toxicology.

The use of head space sampling in conjunction with gas chromatography has proved a useful technique for analyzing aviation accident post mortem material for ethanol, carbon monoxide, and volatile contaminants. An account of the experience of the technique to date at the Royal Air Force Institute of Pathology and Tropical Medicine is given, and the problems and advantages associated with the method are discussed.

Accidents, Aviation↗
PubMed1982

Lack of allergic reactions in workers exposed to Pruteen (bacterial single-cell protein).

Men exposed to high concentrations of bacterial single-cell protein (Pruteen) dust have complained of "sticky eyes" and influenza-like symptoms. Over four years, surveillance of a work force of 70 men with a programme that included a respiratory health questionnaire, skin prick testing, serum testing for precipitating antibodies, lung function measurements, and chest radiography has shown no evidence of allergic reaction or of exposure-related deterioration in lung function. The symptoms experienced may be attributable to exposure to lipopolysaccharide. The results show that Pruteen can be produced and handled without adverse effects on health, provided that adequate measures are taken to prevent exposure to high concentrations of dust.

Animal Feed↗
PubMed1982

The extraction and identification of drugs in aviation toxicology.

The drug screen as used in Aviation Pathology is unique in toxicological analysis in that it seeks to identify the whole range of clinical drugs at or below therapeutic levels. Recently the introduction of proteolytic enzymes has enabled more efficient extraction of drugs from tissues. The measurement of the Gas Chromatographic Retention Index can provide an important parameter in the identification of drug substances.

Aerospace Medicine↗
PubMed1977

Occupational vitiligo induced by p-tert-butylphenol, a systemic disease?

Vitiligo, morphologically indistinguishable from true vitiligo, was detected in 54 of 198 men exposed to p-tert-butylphenol (P.T.B.P.) during its manufacture. There is evidence that P.T.B.P. caused vitiligo by a systemic mechanism and that the severity of the disease was related to the intensity of exposure. No association with autoimmune disease was found. Screening for other possible associated disorders revealed mildly abnormal liver-function tests in 6 workers: liver biopsy confirmed liver damage. Of the 144 men exposed to P.T.B.P. who did not have vitiligo, only 2 had any abnormal liver-function tests. It seems possible that the liver damage is related to P.T.B.P.

Chemical Industry↗
PubMed1973

Extraction of cartilage protein-polysaccharides with inorganic salt solutions.

1. Bovine nasal cartilage was extracted with inorganic salt solutions of various ionic strengths. The efficiency of extraction of protein-polysaccharide from the tissue was determined for each extraction. The results confirm and enlarge earlier observations (Sajdera & Hascall, 1969). 2. The chloride salts of lanthanide metals extract high yields of protein-polysaccharide from the tissue at much lower concentrations than was achieved with univalent and bivalent salts. 3. The lanthanum salt of extracted protein-polysaccharide precipitates when the concentration of LaCl(3) is decreased. Precipitation is complete in the presence of 0.05m-LaCl(3). This finding is relevant to the interpretation of earlier observations on the effect of LaCl(3) on elastic recovery of articular cartilage after compression (Sokoloff, 1963). 4. A linear relationship was found between the concentration at which a particular salt is maximally effective in solubilizing protein-polysaccharide from the tissue and the enthalpy of hydration of the cation of the salt. On the basis of this relationship a hypothesis is proposed to explain the characteristic protein-polysaccharide-extraction profiles exhibited by inorganic salt solutions.

Animals↗
PubMed1973

The composition of cartilage proteoglycans. An investigation using high- and low-inonic-strength extraction procedures.

1. A proteoglycan fraction (the proteoglycan subunit fraction) was prepared from extracts, with 0.15m-KCl (low-ionic-strength) and 0.5m-LaCl(3), 2.0m-CaCl(2) and 4.0m-guanidinium chloride (high-ionic-strength), of bovine nasal cartilage by equilibrium-density-gradient centrifugation, essentially as described by Hascall & Sajdera (1969). 2. The use of different centrifugation times showed that near-equilibrium conditions were reached by 48h for the fractions prepared from the high-ionic-strength extracts. The fraction isolated from the low-ionic-strength extract required a longer centrifugation time to reach equilibrium conditions. 3. The composition of the proteoglycan fractions from the various extracts was compared by analyses of their carbohydrate and amino acid contents. Difference indices were calculated from the amino acid analysis to compare the degree of compositional relationship between the protein components of the proteoglycans. 4. Small compositional differences were found between the proteoglycans isolated from the various high-ionic-strength extracts. The protein content of the fractions from the CaCl(2) extract and the guanidinium chloride extract showed the greatest difference in this respect, although their amino acid analysis was similar. 5. The proteoglycan fraction isolated from the low-ionic-strength extract shows marked differences in composition from the fractions isolated from the high-ionic-strength extracts. Its protein and glucosamine contents were lower whereas its hexuronic acid and galactosamine contents were higher than those of the latter. It also exhibits major differences in its amino acid composition. The glucosamine:galactosamine ratio of the fraction from the low-ionic-strength extract indicates that it may be an almost exclusively chondroitin sulphate-proteoglycan. Its analysis correlates closely with that of a low-molecular-weight proteoglycan isolated from pig laryngeal cartilage by Tsiganos & Muir (1969). 6. The proteoglycan fractions from both the low- and high-ionic-strength extracts migrate as a single band in zone electrophoresis carried out in a sucrose-density gradient at both pH3.0 and pH7.0, although each showed evidence of band widening during the electrophoresis. All the proteoglycan fractions migrated with the same electrophoretic mobility at pH3.0, irrespective of the differences in composition between them. 7. The differences between the proteoglycans from the low- and high-ionic-strength extracts are discussed and the view is advanced that they may be due to association between predominantly chondroitin sulphate-proteoglycans and a keratan sulphate-enriched proteoglycan species.

Amino Acids↗