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M N Eade

Publications and source records attributed to M N Eade.

17 recordsLinked to original sources
PubMed1992

Escherichia coli enterotoxin (STa) binds to receptors, stimulates guanyl cyclase, and impairs absorption in rat colon.

To determine the contribution of the colon in Escherichia coli heat-stable enterotoxin-mediated diarrheal disease, toxin binding, guanyl cyclase activation, and toxin-induced water flux in the rat colon and ileum were compared. Scatchard analysis suggested a single class of heat-stable enterotoxin receptors with an affinity constant of binding of 10(9) L/mol in both colonocytes and ileocytes; however, the number of toxin receptors per cell was 3.5-fold greater in coloncytes than ileocytes (8.32 +/- 1.33 x 10(5) vs. 2.33 +/- 0.28 x 10(5) receptors per cell; P = 0.02). Heat-stable enterotoxin stimulated guanyl cyclase activation in an identical dose-dependent manner in proximal colonic and ileal membranes, with similar sensitivity and maximum response. Heat-stable enterotoxin also inhibited net water flux to a similar degree in both colon and ileum (-47.8 vs. -48.4 microL.cm-1.h-1, respectively) at a dose of 8 nmol/L. At this dose in the colon, because of a higher baseline of absorption, absorption continued, but at a diminished level. At this dose in the ileum, heat-stable enterotoxin induced net secretion. These data are consistent with the concept that heat-stable enterotoxin-induced diarrheal disease results from a decreased absorptive capacity in the colon in the face of increased small intestinal fluid secretion.

Analysis of Variance↗
PubMed1990

No evidence of a countercurrent multiplier in the intestinal villus of the dog.

The hypothesis that a countercurrent multiplier within the intestinal villus increases osmolality in the distal villus tip was tested. Total sodium, potassium, and water content of intestinal tissue samples was measured. The results showed no significant difference in the total Na plus K concentration (millimoles per kilogram H2O +/- SEM) between the villi tips (185.1 +/- 7.7), whole villi (179.8 +/- 5.4), or intestine minus villi (177.2 +/- 1.7). In contrast, in the kidney (where the existence of a countercurrent multiplier has been demonstrated), the renal medulla had a total Na plus K concentration of 284 +/- 17.1 that was significantly more than the renal cortical concentration of 163 +/- 3.1. Villous tissue osmolality should be in osmotic equilibrium with intestinal luminal fluid. Sampling of intestinal luminal fluid revealed a total Na plus K concentration of 145-165 mmol/kg H2O, a figure compatible with normal luminal osmolality of 280-320 mosmol/kg H2O. These results deny the existence of a countercurrent multiplier in the intestinal villus of the dog.

Animals↗
PubMedDate not supplied

Intestinal blood flow in the dog measured by indicator fractionation without tissue samples.

1. A modification of Sapirstein's indicator fractionation technique for measurement of intestinal blood flow has been studied and evaluated in the dog. 2. The concentration of 42K within the intestinal wall was measured simultaneously by a tissue assay procedure and by use of a miniature Geiger-Müller tube within the intestinal lumen. Both methods gave similar results under a wide variety of conditions. 3. Isotope measurement by the Geiger-Müller tube technique obviates the need for tissue samples to be taken and would permit repeat measurements of intestinal blood flow in the same animal.

Animals↗
PubMedDate not supplied

Measurement of 42K concentration in the mucosal portion of the intestine without tissue samples: an approach to the measurement of mucosal blood flow in the dog.

1. The concentration of 42K within the jejunal mucosa was measured by intraluminal miniatrue Geiger-Müller tubes shieleded with platinum foil. 2. Isotope concentration measured by tissue assay of jejunal mucosa gave similar results to that obtained by the Geiger-Müller tubes. 3. Isotope measurement by shielded Geiger-Müller tubes obviates the need for tissue samples and permits repeat measurement in the same animal. This should find physiological application in measuring the mucosal portion of total intestinal blood flow by the indicator fractionation technique.

Animals↗