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Biomedical subjects

O M Wrong

Publications and source records attributed to O M Wrong.

At least 37 records · Page 2Linked to original sources
PubMed1978

Effect of lactulose on ammonia production in a fecal incubation system.

An in vitro fecal incubation system was used to demonstrate how lactulose influences ammonia metabolism in the colon. Lactulose and other fermentable substrates (glucose, mannitol, and sorbitol), pH and organic acid were varied independently so that their different effects could be determined. Fermentable substrate caused a fall in ammonia concentration during the period of fermentation. Acidification to pH 5.0 or less, with hydrochloric acid or a lactic-acetic acid mixture, significantly reduced ammonia generation, but unlike fermentable substrates, did not lower the existing ammonia concentration. The lactic-acetic acid mixture did not reduce ammonia generation significantly below that found with acidification by hydrochloric acid. The effect of lactulose in reducing ammonia concentration is attributed to its role as a bacterial substrate in either increasing bacterial assimilation of ammonia or reducing deamination of nitrogenous compounds. The effect of low pH in reducing generation of ammonia appears to be part of a general reduction in bacterial metabolism.

Ammonia↗
PubMed1976

Generation of ammonia from non-urea sources in a faecal incubation system.

1. A 25% faecal suspension in sodium chloride solution, incubated anaerobically at 37 degrees C for 48 h, showed excellent survival of all the main groups of faecal bacteria. 2. All faecal incubation systems studied generated large amounts of ammonia, particularly those in which bacterial counts fell during incubation. As normal faeces contain negligible amounts of urea this ammonia must have been generated from sources other than urea. 3. Ammonia was also generated by faeces delivered by sodium chloride enema, and by ileostomy fluid, indicating that the phenomenon is not confined to distal colonic contents. 4. Ammonia generation by incubated faeces was inhibited by prior autoclaving of the sample, but not by sterilization with gamma-irradiation. 5. Generation of ammonia by incubated stool was accompanied by release of large amounts of organic anion and a fall in pH. 6. These observations are interpreted as evidence that ammonia generated within the colon in situ is not derived exclusively from urea, but also from bacterial deamination of amino acids, peptides and proteins. Simultaneously bacterial activity generates large amounts of organacid. The presence of living bacteria is not essential for ammonia generation, provided that bacterial enzymes are present. 7. Bacterial generation of organic solute in faeces which have left the body is sufficiently rapid to cast serious doubts on the validity of faecal centrifugation, or other time-consuming techniques involving lengthy handling of faeces, as methods of obtaining extracellular faecal fluid for measurements of organic constituents or ammonia.

Adult↗
PubMed1975

Assessment of urine-concentrating ability in man: effect of fludrocortisone and urea in enhancing response to vasopressin.

1. Healthy subjects, given a long-acting preparation of vasopressin intramuscularly, excreted a significantly less concentrated urine than when subjected to fluid deprivation for 28 h. 2. When fludrocortisone, a potent mineralocorticoid, was given in addition to vasopressin the urine was not significantly less concentrated than after fluid deprivation. 3. Oral urea-loading also enhanced the urine-concentrating power of vasopressin but its effect was less marked than that of fludrocortisone. Oral urea did not increase further the urine concentration achieved by combined fludrocortisone and vasopressin. 4. Renal concentrating power was assessed in fourteen patients with renal disease and impaired concentrating ability. Fludrocortisone significantly enhanced the urine concentration achieved by vasopressin alone and the resultant urine was not significantly less concentrated than that achieved by fluid deprivation. 5. The action of fludrocortisone in enhancing the urine-concentrating effect of vasopressin is similar to that of aldosterone and is probably due to the increased sequestration of solute in the renal medulla, caused by increased reabsorption of sodium chloride in the ascending limb of the loop of Henle. 6. In the clinical assessment of renal concentrating power, the combined use of fludrocortisone and vasopressin has potential advantages over established methods.

Adolescent↗
PubMed1975

The incorporation of ammonia nitrogen into albumin in man: the effects of diet, uremia and growth hormone.

15 N-ammonium chloride was given orally to 17 individuals in 20 studies. Retention of 15N by those with normal renal function was inversely proportional to the protein intake; enrichment of albumin with 15N increased during protein restriction. Protein restriction appeared to be a more potent stimulus to the synthetic use of ammonia than a large pool of urea nitrogen. Both retention of isotope and enrichment of albumin decreased when a high protein diet was given. Enrichment of albumin with 15N in response to 10 or 20 mg of growth hormone daily was similar to that in healthy individuals on a 20 g protein diet for 3 weeks. The relevance of these findings to the nutritional potential of recycled urea nitrogen is discussed.

Adult↗
PubMed1973

Observations upon ammonia absorption from the human ileum.

Experiments have been performed upon the absorption of ammonia and hydrazine from different solutions instilled into a human ileal sac with an exteriorized stoma. Ammonia and hydrazine absorption was greater from solutions of higher pH. It is concluded that non-ionic diffusion plays an important role in ammonia absorption from the human ileum.

Adult↗
PubMed1972

Faecal ammonia and pH during lactulose administration in man: comparison with other cathartics.

The effect of lactulose on faecal pH and ammonia has been studied in three normal subjects with the aid of dialysis of faeces in vivo. Observations were also made with sodium sulphate and the two hexahydric alcohols, mannitol and sorbitol, given in doses sufficient to cause a similar increase in stool weight. All four cathartics rendered the stool more acid, but there was no increase in the concentration of faecal ammonia. Lactulose, despite increasing faecal volume, did not cause an increase in the absolute amount of ammonia lost in the faeces, but the other purgatives did show a modest rise. The results are inconsistent with the theory that lactulose benefits the clinical picture of portosystemic encephalopathy by trapping ammonia in an acid stool. An alternative suggestion is advanced, namely, that any cathartic (including lactulose) reduces ammonia absorption from the colon by decreasing colonic transit time, and so reducing the amount of ammonia generated by autolysis of colonic bacteria.

Adult↗