Biomedical subjects
Publications and source records attributed to S J Baker.
Airborne lead has been measured at four urban, one semi-urban and one rural site in Wales during 1984, 1985 and 1986 to assess the effect of the reduction in lead additives in petrol which was required by an EC Directive at the beginning of 1986. The results showed a 52-61% fall in air lead in accord with the 63% reduction in petrol lead.
The morphology of the epithelium overlying human colonic mucosal lymphoid follicles has been studied by electron microscopy. Epithelial crypts stop at the edge of the follicle and the centre is covered by a single layer of enterocytes. Numerous lymphocytes and, occasionally, other mononuclear cells, are associated with these enterocytes. The lymphocytes are situated in the intercellular spaces, invaginate the lateral cell wall and ultimately appear to be completely surrounded by the enterocyte. When the lymphocyte is near the centre of the enterocyte there is usually little change in enterocyte morphology, but when the lymphocyte is near the apical surface of the enterocyte, the latter closely resembles the membranous epithelial cells ('M' cells) of human small intestine. It is probable that, as with the 'M' cells in the small intestine, these colonic 'M' cells have an antigen sampling function. Their presence may explain the localization of the early lesions of some colonic inflammatory diseases, including Crohn's disease. They may also provide a portal of entry for some rectally-transmitted viral infections.
An epidemic of acute diarrhea in a village in southern India in 1972 was associated with a high rate of isolation of enteric pathogenic bacteria from the patients and lasted for three months. There was no significant association between the prevalence of enteroviruses or parasites and cases of diarrhea. The epidemic started as a common-source outbreak due to the contamination of well water, and there were many secondary cases probably due to a person-to-person spread. The illness did not produce chronic diarrhea or malabsorption.
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A man with a gastrojejunostomy and intestinal malabsorption was found to be excreting large numbers of coronavirus-like particles in his stools over a period of at least eight months. Coronavirus-like particles were found in vesicles in degenerating jejunal enterocytes in all of five jejunal biopsies. In a review of electron micrographs, similar structures were found in biopsies from three of 12 patients with classical chronic tropical sprue and in one patient with a sprue-like syndrome associated with agammaglobulinaemia. The hypothesis is advanced that infection with this virus may produce enterocyte damage and may be one cause of the syndrome of tropical sprue.
The minimal daily requirement of dietary vitamin B12 is defined as that amount which must be ingested in the diet to prevent the occurrence of megaloblastosis, anemia, or other manifestations of vitamin B12 deficiency. An attempt has been made to define this requirement by studying hematological responses to varying amounts of the vitamin in five south Indian subjects with vitamin B12 deficiency anemia (one due to gastric atrophy and four due to dietary deficiency). Amounts ranging from 0.07 to 0.25 micrograms of dietary vitamin B12 were shown to be inadequate but amounts ranging from 0.3 to 0.65 microgram were adequate or possibly more than adequate. It is concluded that the minimal daily requirement of dietary vitamin B12 for the average south Indian adult is in the region of 0.5 microgram/day and that an intake of 1.0 microgram/day would cover the needs of the vast majority of the population and allow a wide margin of safety.
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In man, physiological amounts of vitamin B12 (cyanocobalamin) are absorbed by the intrinsic factor mediated mechanism exclusively in the ileum. Human faeces contain appreciable quantities of vitamin B12 or vitamin B12-like material presumably produced by bacteria in the colon, but this is unavailable to the non-coprophagic individual. However, the human small intestine also often harbours a considerable microflora and this is even more extensive in apparently healthy southern Indian subjects. We now show that at least two groups of organisms in the small bowel, Pseudomonas and Klebsiella sp., may synthesise significant amounts of the vitamin.
The aerobic and anaerobic bacterial flora grown from 40 human jejunal aspirates were compared with the flora grown from an intestinal mucosal biopsy obtained simultaneously from the same level. In four paired samples the flora was identical; in nine the flora differed by only one organism. In six pairs the flora differed by two organisms, and in 11 pairs by three or more organisms. In nine pairs the jejunal aspirate grew only one organism or was sterile, but the biopsy showed considerable numbers of organisms. In one pair the jejunal aspirate grew organisms, but there was no growth from the biopsy. It is apparent that for adequate bacteriological study of the intestine, the flora at both sites should be investigated.
The effects of an intensive 4 week Alpine climbing expedition on percentage body fat, absolute body fat and lean body mass was investigated in 14 adult male students. Anthropometric measures were taken on two occasions during the training period prior to the expedition, twice during the expedition and finally eight weeks after the expedition had returned home. There was a 3% reduction in percentage body fat between the first testing occasion and the fourth taken towards the end of the expedition. Over the same interval there was a mean reduction of 2.6 kg in absolute body fat and a reduction in lean body mass of 2.47 kg. All three criterion mean values on the final testing session returned to or exceeded those taken on session one.
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1. The effect of fortification of food with iron to provide 10 mg elemental Fe/child per d was studied in preschool children maintained on a cereal diet, over a 5-month period. 2. The absorption of 5 mg Fe as ferrous sulphate mixed in one meal was 3.3% of the test dose and when 3.3 mg was given with each of three meals over a 2 d period the corresponding value was 4.8%. 3. The mean absorption of a test dose of ferrous ascorbate studied in twenty-four children midway through the trial was 42%. 4. The only beneficial effect of Fe fortification in this time-period in the experimental group was the prevention of the decrease in packed cell volume which occurred in the control groups.
1. A study was conducted in two centres in southern and northern India of the effects of the addition of ascorbic acid and protein supplements to iron, pteroyglutamic acid and cyanocobalamin, in the prophylaxis and treatment of anaemia of pregnancy. 2. A dose of 500 mg ascorbic acid/d had no beneficial effect. Women who received 15 g calcium caseinate/d showed a superior haematological response. The reasons for this are unknown, but are more likely attributable to an increased absorption of the supplemental iron than to the correction of a protein deficiency.
1. The relative efficacy of oral and parenteral iron administration in the prophylaxis and treatment of Fe-deficiency anaemia of pregnancy has been studied. 2. Intravenous administration of Fe by total dose infusion of Fe dextran was not superior to oral Fe 120 mg/d, 6 d/week for 10-12 weeks. 3. Intramuscular Fe dextran, 100 mg twice per week for 10-12 weeks, produced a significantly greater rise in mean haemoglobin concentration than oral Fe therapy. 4. The superiority of intramuscular Fe as compared with intravenous Fe is probably related to the different handling of the Fe dextran by the reticulo-endothelial system. 5. In spite of the better response to intramuscular Fe dextran, it is not recommended for public health practice because of the risks associated with its use and the much higher cost of the preparation and its delivery.
Since 1949, the World Health Organization, recognizing the public health importance of nutritional anemia, has sponsored efforts directed towards its understanding and control. During this period, often as a result of the work of the Organization, advances have been made in many areas. Basic understanding of iron, folate and vitamin B12 nutrition, and the various factors which may influence the availability and requirements of these factors, has greatly increased. Surveys in a number of countries have highlighted the widespread prevalence of nutritional anemia, particularly in developing countries. The major factor responsible is a deficiency of iron, whith folate deficiency also playing a role in some population groups, especially in preganant women. There is increasing evidence that anemia adversely affects the health of individuals and may have profound socioeconomic consequences. Control of nutritional anemia is possible by providing the deficient nutrient(s) either as therapeutic supplements or by fortification of commonly used foodstuffs. Some control programs are reviewed and suggestions for further action outlined. The Organization still has an important role to play in this field, encouraging the development of control programs and providing advice and technical assistance ot member countries.
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