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W von Engelhardt

Publications and source records attributed to W von Engelhardt.

At least 55 records · Page 3Linked to original sources
PubMed1986

pH-microclimate at the luminal surface of the intestinal mucosa of guinea pig and rat.

Segments of guinea pig jejunum, proximal and distal colon and of rat jejunum were superfused either in vivo or in vitro with different electrolyte solutions. The pH in the bulk phase solution and at the surface of the epithelium was measured with two different types of glass pH-microelectrodes, a pointed tip (Hinke-type) and a flat membrane electrode (Dubuisson-type); both types of electrodes gave the same results. The existence of a pH-microclimate at the surface of the mucosa was demonstrated under both in vivo and in vitro conditions. In vivo the pH-microclimate was stable and virtually independent of changes in the luminal bulk phase pH. When the bulk phase pH of the guinea pig colon was changed between pH 5 and pH 8.6, the mean pH in the microclimate was 7.08 +/- 0.15 (n = 163) in the proximal colon and 6.91 +/- 0.14 (n = 75) in the distal colon. In the guinea pig jejunum pH in the microclimate was 7.37 +/- 0.21 (n = 10) while the luminal pH was 7.27 +/- 0.10. Under in vitro conditions, the pH in the microclimate was more acidic (guinea pig jejunum delta pH 0.93, rat jejunum delta pH 0.40, guinea pig proximal colon delta pH 0.22). Addition of glucose (10 mM) or short-chain fatty acids (80-90 mM) to the luminal solution or replacement of sodium by lithium did not influence the pH in the microclimate significantly. Also the addition of acetazolamide, amiloride, SITS or sodium deoxycholate to the luminal solution, did not affect the pH in the microclimate in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Potassium microclimate at the mucosal surface of the proximal and the distal colon of guinea pig.

K+ concentrations were measured with K+ sensitive liquid ion exchanger microelectrodes in situ and in vitro in the mucus layer at the luminal cell surface of the proximal and the distal colon in guinea pig. In a first series of experiments K+ concentrations were increased in the luminal solution from 0 to 70 mmol X l-1; the serosal K+ concentrations were kept in vitro at 5.4 mmol X l-1. In the proximal colon mean K+ concentration in the microclimate was in vitro 7.9 +/- 3.5 mmol X l-1, and independent from mucosal concentrations. In the distal colon in vitro, and in situ in the proximal as well as in the distal colon, K+ concentrations in the microclimate were increased slightly when K+ concentrations were elevated in the luminal solution up to 70 mmol X l-1. In a second series of in vitro studies K+ concentrations were also altered in the serosal fluid. In the proximal and in the distal colon K+ concentrations increased linearly with elevated K+ concentrations in the serosal solutions. A temporarily interrupted mucosal blood flow resulted in a significant increase in the K+ concentration in the microclimate. A paracellular shunt pathway and a high preepithelial diffusion barrier for K+ would explain the observed K+ concentrations in the microclimate at the luminal cell surface.

Animals↗
PubMed1986

Retention of fluid and particles in the digestive tract of the llama (Lama guanacoe f. glama).

The retention times of fluid and particles of different lengths were measured in the digestive tract of the llama. PEG was used as a fluid marker; hay particles were labelled with cerium or samarium and the samples were determined by neutron activation analysis. In compartments 1 and 2 the retention time of fluid (9.7 hr) was significantly shorter than that of particles having a length of 0.2-1.0 cm (19.2 hr) and 2.5-4.0 cm (25.0 hr). In the intestine slightly significant differences in the retention times of fluid (20.1 hr) and particles (26.2 hr) were seen. In the whole digestive tract retention times were 36.2 hr for fluid, 52.0 hr for smaller particles and 59.9 hr for larger particles.

Animals↗
PubMed1985

Control of stomach motility in the llama (Lama guanacoe f. glama).

Manometric and electromyographic recordings of stomach motility were made in five conscious llamas to investigate the influence of distension of the stomach compartments, of temporary cervical vagal blockade and the influence of atropine, acetylcholine and adrenaline. The frequency of A-contractions was slowed by distension of the canal joining compartment 2 (C2) and compartment 3 (C3), or of the proximal region of C3, and either increased and/or reduced by distension of the distal region of C3 or the hind stomach. The number of B-contractions in a cycle was increased according to the degree of distension of the cranial sac of compartment 1 (C1). B-contractions were also induced by distension of the canal or proximal region of C3 and were inhibited by distension of the distal region of C3 or the hind stomach. Contractions of C3 were not influenced by distension of C1 or C2 but were inhibited by distension of the canal, while distension within C3 caused a local excitation and an inhibition both proximal and distal to the point of stimulation. The hind stomach was only affected by local stimuli. Temporary vagal blockade abolished all contractions of C1, C2, and the canal and C3, but had little effect on the motility of the hind stomach. Infusion of atropine (0.01 mg/kg), acetylcholine (7-33 micrograms/kg . min) and adrenaline (0.3 micrograms/kg . min) inhibited motility in all stomach compartments except the hind stomach where acetylcholine was stimulatory. It is concluded that while the hind stomach may have intrinsic motility, the contractions of C1, C2, the canal and C3 of the llama stomach are dependent upon a vagal motor nerve supply and that the pattern of contractions observed is regulated at least partially according to the individual degree of distension of each of the stomach compartments.

Acetylcholine↗
PubMed1984

Structure of zonulae occludentes and the permeability of the epithelium to short-chain fatty acids in the proximal and the distal colon of guinea pig.

Absorption of short-chain fatty acids has been studied in the proximal and the distal colon of anaesthetized guinea pigs. Segments were perfused with a solution similar in chemical composition to that of normal colonic fluids. In the proximal colon the permeability of the mucosa was similar for acetate, propionate and butyrate. For acetate the permeability was significantly higher in the proximal than in the distal colon, and the reverse was seen for butyrate. In the distal colon the short-chain fatty acids seem to be absorbed mainly in the undissociated form due to their lipid solubility; a paracellular pathway for the dissociated molecules is of no major importance. In the proximal colon, on the other hand, a considerable portion of acetate and propionate disappears in the ionized form. Light microscopy (semithin sections) and electron microscopy (freeze-fracture replicas) showed remarkable morphological differences between the proximal and the distal colon. "Leaky spots" with only few strands were present in the zonulae occludentes between the epithelial cells at the surface of the proximal colon. In the distal colon the junctions between the cells were more compact, and significantly more strands separated the lumen from the intercellular space. These results suggest that short-chain fatty acids could be absorbed by a paracellular pathway in the proximal colon, and not in the distal colon. In the proximal colon the number of strands of the zonulae occludentes between surface cells and that between cryptal cells was similar. On the contrary, in the distal colon significantly more strands were present between surface cells than between cryptal cells. Morphological and physiological considerations suggest that absorption of short-chain fatty acids in the crypts is negligible.

Animals↗
PubMed1984

Urea secretion into the colon of sheep and goat.

Total urea entry rate into the body pool and urea hydrolysis rate (transfer of endogenous urea into the total gastrointestinal (g.i.) tract) were obtained after single intravenous injections of [14C]urea and from renal urea excretion in sheep and goat. Secretion of endogenous urea into the colon was estimated from the appearance of urea N in the temporarily isolated and perfused colon. Rate of urea secretion into the colon was rather small (0.10-0.31 mmol . h-1). It was only 0.3-1.1% of urea entry rate, or 0.4-7% of urea hydrolysis rate. Urea secretion into the colon increased linearly with increase of plasma urea concentration. Dietary conditions and short-chain fatty acid concentrations in colonic contents had no significant effect on the permeability of the colonic epithelium for urea.

Animals↗
PubMed1983

Stimulatory effect of short chain fatty acids on the epithelial cell proliferation in rat large intestine.

1. Short chain fatty acids [SCFA: acetate 75, propionate 35, butyrate 20 (microM)] introduced intraluminally into the colon increased the mitotic index and the labeling index of the large intestinal epithelial cells within 60 min in fasted rats. 2. Epithelia that lacked direct contact with SCFA were also stimulated. 3. SCFA did not have such a stimulatory effect either in vagotomized rats or in sympathectomized rats. 4. These results suggest that SCFA stimulate epithelial cell proliferation in the large intestine of fasted rats via the autonomic nervous system.

Animals↗
PubMed1982

[Absorption of isosorbide dinitrate in guinea-pig intestine and in the colon of sheep (author's transl)].

Segments of the intestine of anaesthetized guinea-pigs and the colon of conscious sheep were perfused with saline containing 0.1--25 mg/l 1,4:3,6-dianhydrosorbitol-2,5-dinitrate (isosorbide dinitrate, ISDN). The increase in ISDN uptake was linearly related to its concentration. Absorption was rapid. In the jejunum and the ileum of guinea-pig, 7% of perfused ISDN was absorbed per 10 cm of intestine in the proximal and 15% in the distal colon, respectively. In the total colon of sheep, 83% disappeared during the perfusion. Per unit of length, surface or dry weight of mucosa the net flux of ISDN in the small intestine was only half that in the colon. Absorption from the colon per unit of wet weight of the gut was only slightly higher compared to the small intestine. 1 h after the infusion of 14C-labelled ISDN into the large intestine of sheep filled with normal contents 14C-activity was detected in the plasma, a maximum was reached after 4 h. Renal excretion of ISDN or its 14C-labelled metabolites was parallel to the ISDN concentration in blood. Microbial degradation of ISDN to CO2 in colon contents was insignificant.

Animals↗
PubMed1981

Luminal mucin in the large intestine of mice, rats and guinea pigs.

The luminal and epithelial mucin was studied histochemically in the large intestine of mice (Mus musculus), rats (Rattus rattus) and guinea pigs (Cavia porcellus) using freeze-substitution and vapor-fixation methods. Neutral mucin decreased and acid mucin increased in the epithelium from the cecum to the distal colon. Vacuolated cells contained more acid mucin than goblet cells. Luminal mucin always contained neutral mucin, which formed the main constituents in the cecum and in the proximal colon. Sialo-mucin increased from the cecum to the distal colon. Sulfo-mucin appeared only in the distal colon. Except in the cecum a luminal mucin layer (LML) was found at the epithelial surface. In the proximal colon LML was not entirely continuous and varied in composition and thickness (182.4 +/- 170.1, 150.5 +/- 110.4, 30.0 +/- 28.9 (micrometer), in mice, rats and guinea pigs, respectively), and contained many bacteria. In the distal colon LML was compact, homogeneous and thin (33.6 +/- 18.8, 16.1 +/- 7.3, 29.1 +/- 20.0 (micrometer), in mice, rats and guinea pigs, respectively) containing few bacteria. Possible functions of the luminal mucin and their regional differentiations were discussed.

Animals↗
PubMed1981

Influence of short-chain fatty acids and osmolality on mucin release in the rat colon.

The influence of short-chain fatty acids (SCFA) and osmolality on mucin release in the rat colon was studied histochemically by determining number of stained mucin-containing cells. SCFA did not significantly influence the number of cells staining for mucin. Hypertonic solutions (360 mosm/l) did not affect mucin release in the proximal colon, but stimulated mucin release in the distal colon. Solutions of lower osmolality (300 or 250 mosm/l) caused a considerable release of mucin from goblet cells as well as vacuolated cells in both the proximal and the distal colon; the lower the osmolality, the more mucin was released. The mucosa of the distal colon was conspicuously affected by solutions of lower osmolality. The influence of osmolality on mucin release was entirely local.

Animals↗
PubMed1981

Absorption of Na, H ions and short chain fatty acids from the sheep colon.

The interrelationship between the absorption of Na, H ions and short chain fatty acids (SCFA) and the secretion of HCO3 in the sheep colon was studied using an in vivo perfusion technique. 1. Under control conditions net SCFA absorption was 62.9 +/- 6.1 mmol . h-1, net Na absorption 49.8 +/- 7.6 mmol . h-1. HCO3 accumulated in the colon lumen at a rate of 5.1 +/- 2.9 mmol . h-1. 2. When 30, 50, or 70% of the Na in the perfusion solution were replaced by Li, Na transport was gradually inhibited and even abolished when 70 mmol . 1(-1) of Li were present. SCFA absorption also decreased, however, to a lower degree. 3. Net Na transport was higher in the presence than in the absence of SCFA. This difference disappeared when Na transport was inhibited by Li. 4. HCO3 accumulation in the colon lumen significantly increased with increasing Li concentrations up to a maximum of 21.7 +/- 7.1 mmol . h-1 when 50% of Na were replaced by Li, however, only in the presence of SCFA. 5. Neither increasing Li concentrations nor the presence or absence of SCFA influenced the H ion disappeared from the perfusion solution. 6. These results indicate that net absorption of Na and SCFA in sheep colon are closely linked to the availability of H ions.

Absorption↗
PubMed1980

The fine structure of the stomach mucosa of the Llama (Llama guanacoe). II. The fundic region of the hind stomach.

The epithelium of the fundic region mucosa of the hind stomach in the Llama guanacoe has been studied using morphological and histochemical methods. Morphology suggests that solute and water absorption may occur in the epithelium of the surface and of the foveolae, although this absorption can not be estimated because of the extensive secretion of the gastric glands. The same cells of the surface and foveolar epithelium show numerous secretory granules. The glands reveal neck cells, chief cells, a large number of oxyntic cells, four types of endocrine cells (A-like, ECL, D and EC), brush cells and wandering cells. PAS and Alcian blue reactions for light microscopy suggest a secretion of neutral and acidic mucosubstances in the surface and foveolar epithelium, of neutral mucosubstances only in the neck cells. Periodic acid-thiocarbohydrazide silver proteinate (PA-TCH-SP) reaction for electron microscopy confirms the presence of neutral mucosubstances within the secretory granules of the surface, foveolar and neck epithelial cells. In all these cells, the reaction product is also evident within sacculi and vesicles of the maturing surface of the Golgi apparatus. A positive PA-TCH-SP reaction also occurs on the membrane (and not on the contents) of the Golgi apparatus (maturing surface) and of the secretory granules of the chief cells as well as on the membrane of the Golgi apparatus and of apical vesicles and tubules of the oxyntic cells. In addition, silver granules slightly enhance the electron desity of the contents of the secretory granules in the endocrine cells. Morphological and histochemical findings are discussed and compared with results described by others for monogastric mammals.

Aminosalicylic Acid↗