Biomedical subjects
Publications and source records attributed to J S Crowther.
A course on food safety for nutritionists has been developed in Indonesia through collaboration between government, industry, academia and international agencies. By teaching the basic principles of the subject it equips the participants to recommend foods that are safe as well as nutritious.
A sensitive radioimmunoassay for the detection of botulinum toxin, produced by Clostridium botulinum, was developed. This employs homogeneous botulinum neurotoxin type A and its 125I-labelled derivative of high specific radioactivity, rather than its complex with haemagglutinin as used hitherto. The sensitivity of the assay is 1 ng of neurotoxin per ml, which is equivalent to 80 LD50 units (half-lethal doses) in mice. Neurotoxin and its complex with haemagglutinin were measurable with equal sensitivity when using antibodies against botulinum neurotoxin type A. Specificity of the assay was demonstrated by the lack of response to type B and E botulinum toxins and to heat-inactivated botulinum toxin or extracts of Clostridium sporogenes strain BL46, which contains many surface antigenic determinants common to Clostridium botulinum. Using appropriate conditions, neurotoxin added to fish extract could be quantified accurately, proportionality being observed between the amounts of standard toxin added. In addition, the amounts of toxin species produced by culturing Clostridium botulinum in canned fish was measurable; the values obtained were comparable to those observed by the mouse bioassay. Moreover, the fish samples gave a dose-response curve in the competition radioimmunoassay which was paralleled by the response of botulinum neurotoxin standards. This assay offers the most sensitive, reliable immunological method available for the quantitation of molecular forms of botulinum toxin. As the technique can be used with unpurified fish extracts, it should be widely applicable to different types of samples contaminated with botulinum toxin; furthermore, the clinical diagnosis of human botulism could be substantiated with this method.
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In a study of three socio-economic groups in Hong Kong, the high income group had a high faecal concentration of bile acids, especially the dihydroxy bile acids, compared to the low income group. The faecal bile acids were also more highly degraded. The faecal flora contained more bacteroides and fewer eubacteria. Very few of the clostridia able to dehydrogenate the steroid nucleus were isolated. An epidemiological study based on street blocks indicated that the high income group also have a higher incidence of cancer of the large bowel and of the breast. The results are discussed in terms of theories on the aetiology of large bowel cancer.
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Five patients with progressive fibrotic lung disease are described. The dominant symptom was slowly increasing dyspnoea, and cough and sputum were not prominent. Marked weight loss was also a feature. There was severe restrictive impairment of ventilation with normal arterial gas tensions. The changes were confined to the upper parts of the lung in some but others had more generalized disease. The duration has varied so far from two to 17 years. The lung changes are considered to be due to dense progressive fibrosis. Necropsy in two confirmed this. Histologically there was monotonous fibrosis with lymphoid collections and secondary bronchiectasis, a picture similar to that found in association with ankylosing spondylitis. None of these patients had joint disease. Tuberculosis was excluded as a cause by exhaustive bacteriological tests and the failure of chemotherapy to stop deterioration. All other recognized types of infective and non-infective progressive lung fibrosis were also excluded, and this is not considered to be a variant of cryptogenic fibrosing alveolitis. Though these patients have many features in common they do not necessarily have the same pathogenesis. They are presented as an encouragement to further study.
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The consumption of a chemically defined diet altered both the faecal flora and faecal steroids. Enterobacteria increased while enterococci and other lactic acid bacteria decreased in number. No other obvious change occurred. However, the alteration in the degree of degradation of the faecal neutral steroids may reflect some alteration in the anaerobic flora. Total excretion of both acid and neutral steroids was also reduced. On cessation of the diet both faecal flora and faecal steroids reverted to levels before the diet.
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