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Biomedical subjects

M Walker

Publications and source records attributed to M Walker.

At least 559 records · Page 31Linked to original sources
PubMed1980

Transit of a meal through the stomach, small intestine, and colon in normal subjects and its role in the pathogenesis of diarrhea.

A method for measuring the transit time of a meal, containing sausages, mashed potato, baked beans, and a pineapple custard dessert, through the gastrointestinal tract was evaluated in 14 healthy volunteers. Gastric emptying was determined by incorporating a radioactive marker in the meal and counting over the surface of the stomach using a crystal scintillation detector. Small intestinal transit time was determined by measuring breath hydrogen excretion and by estimating the radioactivity over the cecum. Finally, whole gut transit time was measured by incorporating radiopaque plastic markers or carmine red in the meal and estimating the appearance of these markers in the stool. Our results showed that measurements of small intestinal transit time were reproducible and in the majority of subjects the increase in hydrogen excretion occurred at the same time as the increase in radioactive counts over the surface of the cecum. The passage of the first marker in the stool coincided with the appearance of carmine red. There were no significant correlations between small intestinal transit time and whole gut transit time or the half time for gastric emptying. Incorporation of 10, 25, and 40 g lactulose into our standard meal in place of sucrose increased the rate of transit through the small intestine but did not significantly alter the rate of gastric emptying or the whole gut transit time. Total stool weight for 48 hr after ingestion of the meal was inversely related to whole gut transit time but not to small intestinal transit time suggesting that the tendency to develop diarrhea in response to a meal containing unabsorbable carbohydrate depends more on the lack of colonic accommodation than on the rate of small intestinal transit. Finally, there was no significant correlation between the measurements of small intestinal transit time after a drink of lactulose and the transit time of a meal in the same subjects.

Adult↗
PubMed1979

Electrophysiological and electron-microscopical correlations with fluid and electrolyte secretion in rabbit ileum.

1. The effects of theophylline and triaminopyrimidine on the passive permeability of Na+ and Cl- across sheets of rabbit ileum treated with 0.1 mM-ouabain were examined by determining the NaCl: mannitol dilution potentials, K+:Na+; choline: Na+ and SO24-:Cl- biionic potentials. The results indicate (a) that triaminopyrimidine reduces paracellular Na+ and K+ permeability without affecting Cl- permeability and (b) that theophylline increases Cl- permeability without affecting Na+ permeability and (c) that neither theophylline nor triaminopyrimidine interfere with each other's action. This is further evidence consistent with separate routes for paracellular Na+ and Cl- movement. 2. Electrical resistance changes across sheets of actively transporting rabbit ileum were measured as a function of time in various conditions. Theophylline has a biphasic effect on resistance. Initially it decreases resistance from 56 omega cm2 (control) to 40 omega cm2. In the ensuing 30 min, resistance rises to 50 omega cm2; whereas it falls to 30 omega cm2 in controls. When theophylline is present, with triaminopyrimidine, or with galactose, no secondary rise in tissue resistance occurs. The initial decrease in resistance is consistent with a theophylline-dependent increase in Cl- conductance and the secondary rise in resistance may be attributed to collapse of the lateral intercellular space following leakage of NaCl and fluid into the mucosal solution. 3. Electron microscopy of glutaraldehyde-fixed tissue confirms the above views, since, with theophylline present, the lateral intercellular spaces are collapsed and with both triaminopyrimidine and theophylline, or both theophylline and 20 mM-galactose present the spaces remain open. 4. It is shown in the Discussion that the theophylline- or choleragen induced increase in passive Cl- permeability of the mucosal border is the only requirement necessary to explain the increase in electrogenic Cl- secretion, the increase in short-circuit current, as well as neutral secretion of NaCl and net fluid secretion.

Animals↗
PubMed1978

Esophageal deviation in four English Bulldogs.

Regurgitation, vomiting, and aspiration pneumonia in 4 young male English Bulldogs were attributed to esophageal deviation that was demonstrated by esophageal radiography. A genetic relationship among these dogs was not determined. Exploratory thoractomy, performed in 2 dogs, demonstrated an apparent compression of the esophagus by the left subclavian artery and brachiocephalic artery at the level of the 2nd and 3rd intercostal spaces. This apparent compression correlated with the roentgen location of esophageal deviation. Surgical redirection of the left subclavian artery resulted in immediate and long-lasting remission of clinical signs.

Animals↗
PubMed1978

Isolation of rotavirus from foals with diarrhoea.

A rotavirus, morphologically similar to other known rotaviruses, was demonstrated in the faeces of 5 foals with diarrhoea on two properties. Four of these 5 samples produced specific intracytoplasmic fluorescence in cell culture when reacted with calf rotavirus antiserum conjugate. Sixteen affected foals from both properties were depressed, did not suckle and became recumbent. Most had a watery diarrhoea which lasted for 3 days and resulted in some dehydration and loss of body condition. Sick foals were separated from their mothers following the onset of diarrhoea and given fluid therapy and antibiotics, but despite these measures 4 of 12 affected foals on one property died. Acute and convalescent sera were collected from 6 foals, and in each case a rise in the titres of complement fixing and neutralising antibodies was demonstrated. Faecal filtrates containing foal rotaviruses were fed to gnotobiotic piglets and the effects compared with those of other rotaviruses. Viral isolates from both properties produced an asymptomatic infection in piglets. This contrasts with the other rotaviruses isolated in Australia that have been shown to cause diarrhoea in gnotobiotic piglets.

Animals↗
PubMed1978

Multiple births and visible birth defects in 13,000 consecutive deliveries in one Ghanaian hospital.

The analysis of the data from this study, though not complete, has shown the following: 1) High rates of plural births may be expected in Ghanaian populations (3.21% for twins, 0.05% for triplets). 2) Hellin's law relating to the incidence of multiple births has been found to apply to a Ghanaian population. 3) Our data show that maternal age and parity have considerable effect on twinning. 4) Multiple pregnancies may not, in themselves, constitute a risk to the mother. On the other hand, the birthweight of the babies may be the cause of hazard at childbirth.

Adolescent↗
PubMed1977

Potassium-renin-aldosterone relationships during the first year of life.

In order to gain insight into factors controlling aldosterone secretion during the first year of life, we studied the relationships between PRA, serum potassium, sodium, and serum aldosterone levels. While we found a dissociation during the early neonatal period, there was a high degree of correlation between serum aldosteron, PRA, and serum potassium by 3 to 12 months of age. This suggests that aldosterone secretion in the 3- to 12-month-old child, as in adults, is regulated by the circulating levels of potassium and angiotensin II.

Aldosterone↗
PubMed1976

Isoantiserum-augmented development of lymphocyte-mediated cytotoxicity.

Passive administration of anti-P-814 isoantiserum (IS) with P-815 mastocytoma was shown to augment the development of T-lymphocyte-mediated cytotoxicity (LMC). The LMC activity augmented by IS was specific to immunizing tumor cells, but required the simultaneous administration of P-815 tumor cells and anti-P-815 serum, suggesting that the antigen-antibody complex is involved in the development of specific cytotoxic T cells. The serum component responsible for augmented development of LMC activity appeared to be IgM in that the augmenting activity fractionated in the void volume of a G-200 Sephadex column and appears very early after immunization. Our experimental results suggest the development of specific T-cell cytotoxicity can be directly regulated by specific IgM antibodies.

Animals↗
PubMed1975

Pyruvate kinase deficiency anemia with terminal myelofibrosis and osteosclerosis in a beagle.

A 15-month-old male Beagle with chronic hemolytic anemia was found to have erythrocytic pyruvate kinase deficiency and, terminally, myelofibrosis and osteosclerosis. The dog's erythron was studied by procedures that enabled close comparison with congenital hemolytic anemia (pyruvate kinase deficiency) of Basenji dogs. The affected dog's sire, dam, and one littermate--each clinically and hematologically normal--were found to have 50% reduction in erythrocytic pyruvate kinase (PK) activity.

Ancylostomiasis↗
PubMed1975

REM sleep reduction effects on depression syndromes.

Thirty-four endogenous and 18 reactive, depressed patients (hospitalized and nonschizophrenic) were treated in a double-blind, crossover study of the hypothesis that rapid eye movement (REM) sleep reduction (by awakenings) relieves depression. In the endogenous group-but not in the reactive group-subjects deprived of REM sleep for three weeks improved significantly more than control subjects awakened from non-REM sleep. Therapeutic efficacy of REM sleep reduction appeared similar to reported efficacy of imipramine hydrochloride treatment of depression. Eight of nine endogenous patients, unimproved by REM sleep deprivation, did not improve with imipramine. Results suggested (1) that substantial REM sleep reduction has antidepressant activity, and (2) since imipramine and other drug antidepressants reduce REM sleep much more so than nonantidepressant drugs, that an antidepressant "mechanism" of drugs resides in their capacity to substantially reduce REM sleep.

Adjustment Disorders↗