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Biomedical subjects

J Rask-Madsen

Publications and source records attributed to J Rask-Madsen.

At least 127 records · Page 7Linked to original sources
PubMed1976

Congenital chloridorrhoea. A question of reversed brush border transport processes and varying junctional tightness.

The surprising results of intestinal perfusion studies in an 8-month-old child with congenital chloridorrhoea offered a unique opportunity not only to elucidate the underlying defect, but also to test the adequacy of proposed models for normal intestinal transport. In ileum Na, K and Cl as well as water were secreted and HCO3 absorbed. Lumen was 91 mV negative to blood. Only Cl was transported against both electrical and chemical gradients, but discrepancies between observed and predicted Na flux ratios suggested the presence of a Na-absorbing mechanism as well. Mucosa was impermeable to Cl from the lumen side. 2.5 mM glycochenodeoxycholic acid (GCDC) mediated Na and water absorption and abolished any transport of Cl. PD was -95 mV. In colon a similar pattern was observed and mucosa to serosa fluxes of Cl were abnormally low. Rectal PD was -116 mV. GCDC made the epithelium more absorptive in function, but contrary to ileum the effect was due to an increase of Na and Cl fluxes from mucosa to serosa. The patient was at that time in severe electrolyte imbalance. He was reinvestigated three months later when he was in a good clinical condition with normal serum electrolytes. Net transfer of electrolytes and water and bidirectional fluxes of Cl and K were unchanged while bidirectional Na fluxes had increased considerably and PD decreased to -18 mV. Rectal PD was -45 mV. In jejunum water and electrolyte transport were normal and PD -3 mV. It is tentatively concluded that the abnormal transport in ileum is due to an inversion of the brush border transport processes, which also satisfies the paradoxical effects of GCDC. Furthermore, Na and Cl seem to migrate through separate pathways. A varying degree of junctional tightness, which is almost completely cationic, may be responsible for the functional differences observed in resonse to improvement of the general electrolyte status.

Biological Transport, Active↗
PubMed1975

Electrical polarization of rectal mucosa and excretion of tetrahydroaldosterone in patients with cystic fibrosis of pancreas and in normal subjects.

The electrical potential difference (PD) across the rectal wall was measured in 26 patients with cystic fibrosis of pancreas (CFP) and in 18 healthy subjects. The PDs obtained in normal children were identical to those previously obtained in normal adults. A significantly greater dispersion of the values was observed in CFP. When the patients were divided into groups according to metachromasia in fibroblast cultures, the mean PD was increased only in the ametachromatic group. True enough, this observation suggests a difference between various forms of CFP, distinguished by metachromasia, and thus is a further indication of the heterogeneity of the disease. The greater abnormalities in metachromasia negative patients may, however, be due solely to the fact that these patients are more severely affected by the disease. The urinary excretion of tetrahydroaldosterone in patients was within the ranges obtained in controls, which excludes the possibility of secondary hyperaldosteronism as the source of increased PD. No evidence was provided in favour of a basic defect in the intestinal transport of Na+ or Cl minus, but K+ concentrations in faecal fluids of patients were significantly lower than in controls. The equilibrium concentration of K+ could be accounted for by simple passive diffusion, suggesting that the epithelium behaved inertly with respect to this ion in CFP.

Adolescent↗
PubMed1973

Sieving characteristics of inflamed rectal mucosa.

The sieving characteristics of the normal and inflamed rectal mucosa are studied in three healthy volunteers and five patients with ulcerative colitis. Following rectal instillation of (125)I-polyvinylpyrrolidone (PVP), the molecular size distribution of labelled PVP in urine samples was determined by Sephadex gel filtration. The results of the study suggest that the increased permeability of the inflamed rectal mucosa to electrolytes and small hydrophilic compounds is due primarily to ultrastructural changes since only the low molecular fractions of PVP were found in the urine.

Cell Membrane Permeability↗
PubMed1973

Rectal hyperpolarization following intestinal bypass for obesity.

The electrical potential difference across the rectal mucosa in six shunt-operated women was compared with that obtained in 26 normal females. The potential difference was considerably increased in all the patients, whereas the plasma concentrations and the transmural fluxes of sodium, chloride, and potassium were within normal ranges. Based on measurements of plasma renin and plasma aldosterone concentrations in three of the patients, the possibility of secondary hyperaldosteronism could be ruled out.

Adult↗
PubMed1972

Lithium-induced hyperpolarization of the human rectum in vivo.

The transmucosal potential difference across the rectal mucosa was measured in 30 healthy subjects and in 13 psychiatric patients on lithium treatment for manic-depressive psychosis. It was significantly greater in the lithium-treated patients. A highly significant correlation was found between the potential difference and the serum lithium, and in all eight patients in whom it was measured before and one week after starting lithium treatment a rising potential difference was found. This phenomenon may possibly be explained in terms of resistance of the rectal mucosa to vasopressin.

Bipolar Disorder↗