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Biomedical subjects

J Addison

Publications and source records attributed to J Addison.

At least 19 recordsLinked to original sources
PubMed1998

The management of minor traumatic brain injury.

Minor traumatic brain injury accounts for the majority of the one million head trauma attendances at A&E departments in the United Kingdom. Guidelines have been established listing criteria for skull films, admission to hospital, computed tomography, and neurosurgical consultation. These are currently undergoing revision and were the subject of a satellite symposium to the J Douglas Miller memorial meeting held in October 1996 in Edinburgh. In the East Anglia Region the current guidelines have been issued as memo-cards for A&E officers. The aim of admission is to observe for deterioration, predominantly caused by intracranial haematomas. The indicators for the development of such lesions are an impaired level of consciousness and presence of a skull fracture. Such patients should therefore undergo regular and frequent neurological observations, and be admitted for at least 12 hours. Following discharge, routine follow up should be considered to identify and treat patients with postconcussion symptoms and signs. The possible way forward for the management of these patients is adopting a greater emphasis on preventative aspects, and establishing, implementing, and auditing evidence based guidelines. Improved teaching in the form of formal induction seminars and computerised teaching aids is required, and a better understanding of the aetiology and treatment of the postconcussion syndrome.

Brain Injuries↗
PubMed1998

Posterior vertebral rim fractures.

Fracture of the posterior vertebral endplate is a cause of low back pain in adolescents and young adults. Clinically it resembles an acute disc prolapse with low back pain and radiculopathy, but may present with neurogenic claudication due to spinal stenosis in older patients. The lesions may be incidental findings. Plain radiographs are diagnostic in about 40% of cases. CT shows the fracture fragment and vertebral defect in most cases but the fracture fragment may be overlooked on MRI. Accurate diagnosis is essential as the surgical technique for disc herniation is inadequate for endplate fractures. In this pictorial essay we review the imaging findings.

Humans↗
PubMed1995

Vermiculite: a review of the mineralogy and health effects of vermiculite exploitation.

Vermiculite is a mica-type mineral that is being used in increasing quantities for insulation, in composite cements, and in horticulture. No serious health risks have been found resulting from the exposure to vermiculite alone nor are any anticipated in view of its long-term chemical durability, even with respect to fibers of vermiculite. Vermiculite ores may contain a variety of other minerals including asbestos, which, if present in significant quantities, could pose a health risk to producers and end users. A variety of regulations are in place that should prevent inadvertent exposure to asbestos in vermiculites, but great care is needed if true asbestos hazards are to be correctly identified. At the same time, vermiculites containing any of a variety amphibole minerals should not be excluded from use because of mistaken identification of these minerals as asbestos. A variety of test methods that have been developed are described and recommendations are made with respect to appropriate action levels for asbestos in vermiculites or other raw materials.

Aluminum Silicates↗
PubMed1994

Use of the short-term inflammatory response in the mouse peritoneal cavity to assess the biological activity of leached vitreous fibers.

We used a special-purpose glass microfiber sample, Johns-Manville Code 100/475, to study the effects of various acid and alkali treatments on biological activity as assessed by inflammation in the mouse peritoneal cavity, the leaching of Si, and the phase contrast optical microscopy (PCOM) fiber number. We used mild and medium treatments with oxalic acid and Tris buffer and harsh treatment with concentrated HCl and NaOH. Mild oxalic acid and Tris treatment for 2 weeks had no effect on any of the end-points, but prolonging the mild oxalic acid treatment time to 2 months reduced the biological activity and the fiber number. Medium oxalic acid treatment reduced the biological activity and the fiber number and caused a loss of Si. Medium Tris alkali treatment reduced the PCOM-countable fibers and the biological activity but did not cause a substantial loss of Si. Harsh treatment with strong HCl did not affect the fiber number or cause leaching but the biological activity was reduced; strong NaOH reduced the fiber number and biological activity, and caused marked leaching of Si. The medium oxalic acid conditions (pH 1.4) were more acid than those found in lung cells but produced the same effects (reduction in fiber number and biological activity) as the more physiological mild treatment (pH 4.0), when prolonged. This study suggests that medium oxalic acid treatment can be used as a short-term assay to compare loss of Si, reduction in fiber number, and change in biological activity of vitreous fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Lung content analysis of cases occupationally exposed to chrysotile asbestos.

The lung contents of six workers who had been occupationally exposed to chrysotile asbestos were examined. Five were lung cancer cases from Quebec, Canada. The sixth, an American worker who had developed pleural mesothelioma, was particularly interesting, with the lung content strikingly distinct from the Canadian cases; chrysotile, the predominant fiber in his lung, was present at a concentration 300 times that of the average total fiber content in the Canadian cases. The fiber length distribution of the chrysotile recovered from the U.S. mesothelioma case was indistinguishable from that of chrysotile specimens known to produce mesotheliomas in rats. It was also found that the characteristics of the calcium-magnesium-iron silicate fibers present in all six cases were not readily comparable to tremolite asbestos specimens known to induce mesotheliomas in animals.

Asbestos, Serpentine↗
PubMed1993

Asbestos fibers in parenteral medication.

The adequacy of current regulations for the control of particulate matter in injectable medicines has been brought into question by a recent television program which reported that asbestos fibers had been found in a number of such preparations. The fibers were identified as chrysotile, which occurs very widely as a secondary mineral in rocks, and is almost ubiquitous among minerals derived from natural erosion. Fibers are found in almost all drinking water and air samples unrelated to any contamination of fiber resulting from industrial exploitation. Because of this, even extreme laboratory precautions may fail to eliminate every fine fiber. A normal person living in an urban environment inhales about 10(5) asbestos fibers daily and ingests 10(10). There is evidence that a small proportion of these fibers regularly enters the circulation, and some fibers may be excreted in the urine. Elimination also occurs because retained chrysotile fibers fragment and disappear relatively quickly from human tissues, probably through macrophage action. Fiber length and dose are also important in disease causation. Established evidence on fiber length, durability, and quantitative exposure required for disease production does not indicate that the fibers reported to have been found in parenteral preparations constitute any hazard.

Asbestos↗
PubMed1991

Variations in the carcinogenicity of tremolite dust samples of differing morphology.

Six samples of tremolite of different morphological type were prepared as dusts of respirable size and used in intraperitoneal injection studies in rats. Three "asbestiform" tremolites produced mesotheliomas in almost all animals, although with significantly different tumor-induction periods. A brittle type of fibrous tremolite which, when manipulated to prepare "respirable dust," produced a sample with relatively few asbestiform fibers remaining nonetheless produced tumors in 70% of rats. Two samples of nonfibrous tremolite produced respirable dust samples containing numerous elongated fragments with aspect ratios greater than 3:1, which therefore fitted the definition of respirable fibers. Both these samples produced relatively few tumors, although one had more long "fibers" than did the brittle tremolite that produced 70% of tumors. This study has therefore demonstrated that different morphologic forms of tremolite produce dusts with very different carcinogenic potential. Carcinogenicity does not depend simply on the number of elongated particles injected, and we need to develop methods of distinguishing carcinogenic tremolite fibers from relatively innocuous tremolite dusts, with similar numbers of elongated particles of similar aspect ratios.

Animals↗
PubMed1990

Analysis of amphibole asbestos in chrysotile and other minerals.

Chrysotile asbestos and many other mineral raw materials contain amphibole minerals which may be asbestiform. There is currently no analytical method which will detect the presence of amphibole at sufficiently low limits to preclude the possibility of inadvertent exposure of persons handling these materials to hazardous airborne fibre concentrations. A method of chemical digestion of chrysotiles has been tested with regard to the determination of their tremolite contaminant content and this has been applied to a range of chrysotile and other minerals. The method improves the sensitivity of the amphibole analysis at least 10-fold giving detection limits of 0.01-0.05% in chrysotile by X-ray diffractometry (XRD). The difficulties arising from compositional and morphological variations are discussed in the context of the potential hazards from airborne fibres and the relative values of analyses by XRD, infrared spectrophotometry (IR) and electron microscopy. It is concluded that XRD and IR are useful as screening methods for the detection of amphibole in chrysotile but other materials should be analysed by optical or electron microscopy.

Asbestos↗
PubMed1989

Comparative studies of airborne asbestos in occupational and non-occupational environments using optical and electron microscope techniques.

We have compared asbestos fibre and general fibre counts from scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with fibre counts from phase-contrast optical microscope (PCOM) methods. Three different types of sample have been evaluated: laboratory-prepared samples of different fibre types; chrysotile asbestos textile factory samples; and non-occupational and environmental samples from sites where asbestos might be found. TEM produced total fibre number assessments which were greater than those found with SEM which, in turn, produced fibre counts greater than those obtained with the PCOM. However, when fibres longer than 5 microns were alone counted, the two electron microscope (EM) methods provided similar results. This indicates that TEM is advantageous in comparison with SEM when counting or sizing short fibres and has no advantage for fibres longer than 5 microns. For fibres longer than 5 microns in both the laboratory-prepared and asbestos factory samples, the EM asbestos counts were higher than the PCOM fibre counts, the ratios depending on the fibre type in the case of the former. The PCOM fibre counts in samples from the non-occupational situations were shown to be poor predictors of airborne asbestos fibre concentrations determined by EM. This was mainly due to the presence of high and variable proportions of non-asbestos fibres in these samples. It is concluded that, in order to convert EM asbestos fibre concentrations (greater than 5 microns) to equivalent PCOM asbestos concentrations, they should be divided by 4.0 for chrysotile and 1.7 for amphibole asbestos.

Air Pollutants↗
PubMed1988

Growth of rat osteoblast-like cells in a lipid-enriched culture medium and regulation of function by parathyroid hormone and 1,25-dihydroxyvitamin D.

To examine the role of lipid metabolism in the growth and function of osteoblast-like cells, we studied ROS 17/2.8 osteosarcoma cells and primary cultures of rat calvarial osteoblasts during growth in a serum-free medium supplemented by purified human lipoproteins or by liposomes. Increase in ROS cell number was measured in sparse (1-5 X 10(3)/cm2) cultures over 6-8 days. Liposomes (0-300 micrograms/ml) and high (HDL), low (LDL), and very low density (VLDL) lipoprotein fractions (0-300 micrograms apoprotein) markedly stimulated cell growth. Cells plated at 5 X 10(3)/cm2 achieved growth rates in the presence of LDL or HDL comparable to 10% fetal bovine serum. Serum-free culture with exogenous lipid maintained the response of cell cyclic AMP accumulation to parathyroid hormone. Cyclic AMP response to parathyroid hormone was enhanced by glucocorticosteroid, and was attenuated by 1,25-dihydroxyvitamin D (1,25(OH)2D) with an EC50 (10(-10) M) comparable to that previously observed in serum-cultured cells (J. Biol. Chem. 258:736, 1985). 1,25(OH)2D also increased the alkaline phosphatase activity in ROS cells cultured in lipid-supplemented serum-free culture. Lipoproteins or liposomes also markedly enhanced the proliferative response of sparse cultures of normal rat osteoblasts to polypeptide mitogens.

Animals↗
PubMed1986

Effects of the inhalation of dusts from calcium silicate insulation materials in laboratory rats.

The effects of respirable dust from three commercially produced calcium silicate insulation materials were examined in laboratory rats by long-term inhalation and injection techniques. These calcium silicate products have been used as replacements for asbestos in the insulation of the engine rooms of ships, and the particle size distribution of the dust clouds generated for the experimental study closely matched those found in ships during the installation of this type of material. One year of exposure to a dust cloud of 10 mg/m3 of respirable dust had no discernible effect on the length of survival of treated animals compared to controls. No pulmonary lesions were found that appeared associated with the inhalation of calcium silicate per se, but one sample did contain significant amounts of quartz and this did produce a few small pulmonary nodules. While two small pulmonary neoplasms, one malignant and one benign, were found in dusted animals, neither was the cause of death, and the incidence was not significantly different from the control group where no tumors were found. One peritoneal mesothelioma was found in an animal from one of the inhalation groups, but this was considered to be a spontaneous tumor as none of over 100 animals injected intraperitoneally with 25 mg of calcium silicate developed these tumors. While the white blood cell count of dusted animals, compared to controls, was significantly raised in all treated groups at the end of the dusting period, these figures were within the published normal ranges for laboratory rats. It was concluded that the three tested calcium silicate products were harmless to the rats of this species at the doses tested.

Animals↗
PubMed1986

Silicosis in barium miners.

Four men who mined barytes in Scotland and who developed pneumoconiosis are described. Three developed progressive massive fibrosis, from which two died; and one developed a nodular simple pneumoconiosis after leaving the industry. The radiological and pathological features of the men's lungs were those of silicosis and high proportions of quartz were found in two of them post mortem. The quartz was inhaled from rocks associated with the barytes in the mines. The features of silicosis in barium miners are contrasted with the benign pneumoconiosis, baritosis, that occurs in workers exposed to crushed and ground insoluble barium salts. Diagnostic difficulties arise when silicosis develops in workers mining minerals known to cause a separate and benign pneumoconiosis. These difficulties are compounded when, as not infrequently happens, the silicotic lesions develop or progress after exposure to quartz has ceased.

Aged↗
PubMed1986

Elevated serum chromogranin A concentrations in small-cell lung carcinoma.

Serum chromogranin A concentrations measured by radioimmunoassay in patients with small-cell lung carcinoma were compared with values from healthy adults and patients with non-small-cell lung carcinoma or chronic obstructive pulmonary disease. The mean (+/- SE) level was significantly higher (p less than or equal to 0.02) in patients with small-cell lung carcinoma (815 +/- 290 ng/mL, n = 46) than in normal controls (123 +/- 6 ng/mL, n = 20) or patients with chronic obstructive pulmonary disease (169 +/- 18 ng/mL, n = 39), lung adenocarcinoma (180 +/- 22, ng/mL, n = 62), large-cell lung carcinoma (183 +/- 23 ng/mL, n = 18), or lung epidermoid carcinoma (203 +/- 37 ng/mL, n = 78). The mean concentration in extensive-stage small-cell lung carcinoma (1155 +/- 449 ng/mL, n = 29) was significantly greater (p = 0.026) than in limited disease (234 +/- 56 ng/mL, n = 17). Elevated serum chromogranin A values were seen in 53% of patients with limited and 72% with extensive disease. Four patients originally classified as having non-small-cell lung carcinomas with raised chromogranin A levels were subsequently found to have mixed small-cell and non-small-cell tumors. Serum chromogranin A concentrations may be a useful marker of small-cell lung carcinoma disease activity.

Adult↗