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Biomedical subjects

M Jodal

Publications and source records attributed to M Jodal.

At least 109 records · Page 6Linked to original sources
PubMed1979

Effects of cholera toxin on villous tissue osmolality and fluid and electrolyte transport in the small intestine of the cat.

The effects of cholera toxin on tissue osmolality and on net transport rates of water, sodium, chloride and potassium as well as on unidirectional fluxes of water and sodium were studied in vivo. In all experiments the toxin caused a net secretion of water, sodium, chloride and potassium. The unidirectional sodium transport from tissue to lumen was increased while the flux in the opposite direction was reduced 180 min after cholera toxin instillation. Cholera toxin produced only a small reduction in the villous tissue hyperosmolality, created by the intestinal countercurrent exchanger. This reduction was far too small to explain the observed net secretion of fluid and solutes induced by the cholera toxin. Other mechanisms underlying the cholera secretion are discussed.

Animals↗
PubMed1978

Tissue osmolality in intestinal villi during luminal perfusion with isotonic electrolyte solutions.

A cryoscoptic technique has been developed that makes it possible to determine tissue osmolality in the core of the intestinal villi. During absorption from an isotonic electrolyte solution containing glucose an osmolality gradient was demonstrated from tip to base of the villi in both the jejunum and the ileum. The tissue osmolality at the villous tips was measured to 1 000-1 200 mOsm/kg H2O while the osmolality at the villous base was approximately isotonic with plasma. Increasing intestinal blood flow by i.a. administration of a vasodilator drug, or making the intestine ischemic by clamping the intestinal vascular supply while supplying the mucosa with oxygen, markedly decreased tissue osmolality. Substituting all sodium ions with choline in the luminal perfusate abolished almost completely the tissue hyperosmolality and the intestine became a secretory organ. These observations are consistent with the view that the observed villous tissue hyperosmolality was created by a countercurrent multiplication of sodium chloride. The physiological implications of this mechanism is discussed and it is, among other things, proposed that the hyperosmolar region represents the hyperosmotic compartment necessary for explaining intestinal water absorption.

Animals↗
PubMed1978

The effects of cholera toxin on intramural blood flow distribution and capillary hydraulic conductivity in the cat small intestine.

Blood flow distribution to the mucosa-submucosa and to the muscularis in the cat small intestine was investigated with a 85Kr elimination technique before and after exposing the intestinal mucosa for 30 min to cholera enterotoxin. In all experiments the toxin induced an intestinal secretion. Concomitantly, total intestinal blood flow was increased to a level 50 per cent above control 3 h after exposure. This vasodilatation reflected a doubling of mean blood flow in the mucosa--submucosa while muscularis blood flow remained unchanged. In another series of experiments the effect of cholera toxin on intestinal capillary hydraulic conductivity was investigated by determining the capillary filtration coefficient (CFC). A slight increase in CFC was noted during the 3 h observation period but this was not more pronounced than would have been expected from the concomitant vasodilatation. It is concluded that hemodynamic changes in the intestinal mucosa may be one of the several factors that probably are involved in the pathogenesis of cholera.

Animals↗
PubMed1978

Nervous release of vasoactive intestinal polypeptide in the gastrointestinal tract of cats: possible physiological implications.

1. The release of vasoactive intestinal polypeptide (VIP) into blood from the gastrointestinal tract was studied when eliciting autonomic nervous effects known to be mediated via non-adrenergic, non-cholinergic nerve fibres. All studies were performed on animals given atropine. 2. Electrical stimulation of the low threshold vagal fibres to the stomach did not significantly change gastric volume or VIP concentration in the venous effluent from the stomach. Stimulating the high threshold fibres, on the other hand, produced a gastric relaxation concomitant with a significant increase of venous plasma VIP concentrations. When eliciting a similar vagal relaxation of the stomach by distending a balloon the oesophagus a significant increase of venous plasma VIP concentration was also recorded. 3. Mechanical stimulation of the mucosa of the small bowel increased intestinal blood flow and a significant increase of venous plasma VIP concentration was observed. 4. Stimulation of the pelvic nerves to the colon produced a transient vasodilation and a significant increase of VIP in the venous effluent from the large bowel. A maintained vasodilation in the colon was induced by mechanically stimulating the rectal mucosa. This vascular response was accompanied by a significant raise of venous plasma VIP concentration. 5. The results demonstrate that all the studied nervous effects known to be mediated via non-adrenergic, non-cholinergic nerve fibres were accompanied by significant increases of the VIP concentration in the venous effluent. The possible physiological implications of these findings are discussed and it is proposed that VIP may be a neurotransmitter in the gastrointestinal tract.

Adrenergic Fibers↗
PubMed1978

Evidence for the existence of a countercurrent exchanger in the small intestine in man.

The vasculature in the human villus forms vascular loops by the supplying arterial vessel and the draining capillaries and/or veins. This study reports two experimental observations that strongly suggest that these vascular loops function as countercurrent exchangers. (1) The elimination of intraarterially injected 85Kr from the human small bowel exhibits an initial very rapid component of the type earlier reported in the feline gut. This component in all probability reflects the extravascular "shunting" in the exchanger of the injected radioactive tracer. (2) When exposing the intestinal mucosa to an isotonic electrolyte solution containing glucose, an osmolality gradient from the tip to the base of the human villi was demonstrated, the tips having an osmolality of around 700 milliosmoles per kg H2O. This hyperosmolality is created by the exchanger acting as a countercurrent multiplier.

Colon↗
PubMed1977

Significance of enzyme release from ischemic isolated rat heart.

Whole-heart ischemia has been induced in isolated working rat heart. The distribution of the reduced coronary flow was even, as judged by 3H-antipyrine autoradiographs. Reducing the coronary flow resulted in myocardial ischemia, as indicated by a lowered tissue content of glycogen, ATP and creatine phosphate and accumulation of lactate. After a reperfusion period of 30 min there was a restoration of glycogen, ATP and creatine phosphate for hearts that were ischemic for 5 and 10 min, with a concomitant normalization of tissue lactate. Hearts that were ischemic for 30 min did not show restoration of high energy phosphates and glycogen. There was a leakage of ASAT, CK and LD in all groups of hearts, suggesting that a release of these enzymes does not necessarily indicate an irreversibly damaged myocardial cell.

Adenosine Triphosphate↗
PubMed1977

The importance of the intestinal countercurrent exchanger for 85Kr absorption from the feline gut.

The rate of 85Kr absorption from the feline gut was studied at varying intestinal blood flows induced by i.a. infusions of a vasodilator drug or by lowering arterial inflow pressure. The effects on rate of absorption of distending the intestine by increasing intraluminal pressure from 0-1 to 5-7 cm H2O as well as of augmenting the rate of luminal perfusion of the 85Kr solution were also investigated. Distending the small bowel increased rate of 85Kr absorption at all levels of intestinal blood flow except at the very low and the very high blood flow rates. Decreasing blood flow by lowering of arterial perfusion pressure decreased the rate of absorption from the distended gut while it had no effect in the collapsed small intestine. Increasing the rate of luminal perfusion enhanced the rate of 85Kr absorption at all blood flow levels except at the lowest ones. The results are discussed with regard to villous hemodynamics, intestinal countercurrent exchange and intraluminal concentration gradients in the lumen. It is concluded that the countercurrent exchanger represents, under physiological conditions, the major limiting factor for the absorption of lipophilic solutes such as 85Kr.

Animals↗
PubMed1976

Colonic blood flow in cat and man as analyzed by an inert gas washout technique.

An inert gas elimination technique for studying blood flow and flow distribution in the colon was developed on the cat and applied to patients during abdominal surgery. The method involves recording of the elimination of intra-arterially injected 85Kr from a colonic segment whereby the gamma- and beta-radiation of the tracer is registered simultaneously by a scintillation detector and Geiger-Muller tube, respectively. Total blood flow was determined from the recording of gamma-radioactivity using a modification of Zierler's formula, and muscularis blood flow as calculated according to Kety from the mono-exponential elimination recorded by the Geiger-Muller tube. The relative weights of the muscularis and mucosa-submucosa were determined from dissections or histological sections. With these weights and total and muscularis blood flows, flow in the mucosa-submucosa was calculated. Total colonic blood flow was 18 +/- 2 ml per min and 100 g of colonic tissue (mean +/- SE; n = 21). In the muscularis layer blood flow amounted to 11 +/- 1 ml per min and 100 g of muscularis tissue (n = 12), and flow in the mucosa-submucosa was calculated to be 28 +/- 5 ml per min and 100 g of mucosal-submucosal tissue. A major fraction (66 +/- 6%) of total blood flow was distributed to the mucosa-submucosa. As total colonic blood flow was enhanced the increase in flow was diverted only to the mucosa-submucosa. The feline and human large bowel exhibited great qualitative and quantitative circulatory similarities.

Animals↗
PubMed1976

Blood flow in the small intestine of cat and man as analyzed by an inert gas washout technique.

Using a recently developed 85Kr-elimination technique, blood flow and flow distribution of the human small intestine have been investigated in patients during abdominal surgery. Total intestinal blood flow was estimated to be 38 +/- 4 ml per min and 100 g of intestinal tissue (mean +/- SE: n = 19), jejunal blood flow being slightly higher than ileal. In 14 of these patients muscularis blood flow was determined to be 21 +/- 2 ml per min and 100 g of muscularis tissue and mucosal-submucosal blood flow was calculated to be 51 +/- 6 ml per min and 100 g of mucosal-submucosal tissue. Seventy-five +/- 3% of total blood flow was distributed to the mucosa-submucosa and the remaining 25 +/- 3% to the muscularis. It was demonstrated that an increasing fraction of flow was diverted to the mucosa-submucosa with enhanced total intestinal blood flow. The human gut exhibited great qualitative and quantitative circulatory similarities with the feline small intestine.

Animals↗
PubMed1975

A method for the continuous study of net water transport in the feline small bowel.

A new perfusion technique has been developed for the study of net water transport across the intestinal epithelium in vivo. The lumen of an isolated intestinal segment is steadily perfused with a solution of known composition in a closed perfusion system with a reservoir large enough to prevent recirculation. The intestinal segment may be enclosed in a plethysmorgraph. Changes in the perfused volume is recorded by a volume transducer coupled to the recirculating system via a T-tube. If no motility occurs, the changes of the perfusion volume reflects net water transport across the intestinal epithelium. A quantitative comparison of this technique with the convention polyethylene glycol method revealed no significant difference. The plethysmorgraphic method also makes it possible to quantify the net water absorption via lymph and blood.

Animals↗