Compensation by the residual intestine after intestinal resection in the rat. II. Influence of postoperative time interval

The sequence of events which comprise the early response of the residual intestine to 70% resection of the combined jejunum and ileum was investigated. Animals were killed at 2,4,6,8, and 12 postoperative days. Marked increases in DNA synthesis expressed as disintegraions per minute per crypt, cells per cyrypt column, labeled cells per crypt column, thickness of intestinal wall components, and cells per villus column were apparent as early as 2 to 4 postoperative days. By 12 days, the values had reached the 30-day postoperative levels found in earlier experiments, indicating that a new steady state had already been reached. Jejunal and ileal crypts responded nearly the same during the first 12 days with their sizes increasing to about 150% of control values. However, although jejunal villus cell counts increased to 125% of controls, the ileal villus cell counts increased to 180% of controls, indicating that the sizes of the two crypt and villus epithelial cell populations are independently controlled.

Pacinian corpuscles and their relationship to the lymphatic system

By means of well-roven methods of investigation the Pacinian corpuscles in the meso-jejunum of the cat were injected with vital stains (patent blue violet and Japanese ink), and the transport of dyestuffs through the lymphatic system established.

Functional and structural characteristics of the jejunum and ileum in the dog and the rat

The dog jejunum is a much denser tissue than the ileum, with a greater weight per unit length and higher proportion of mucosal tissue. Morphometric analysis reveals longer and wider villi, deeper crypts and larger enterocytes in the jejunal mucosa. Uptake of phenylalanine or beta-methyl-glucoside by tissue slices in vitro is slightly greater in jejunal than in ileal tissue. The levels of acid phosphatase and alkaline phosphatase in the individual enterocytes are significantly greater in the jejunum, according to quantitative histochemical analysis. The absorption of water, sodium, potassium, chloride and glucose in vivo is significantly smaller in the jejunal than in ileal loops, particularly when expressed in terms of unit mucosal weight. Sodium and water absorptions are stimulated by glucose at both sites, but the stimulation is significantly greater in the ileum. Opposite results have been obtained in rats where the transport of phenylalannie in vitro is greater in the ileum, but water, electrolyte and glucose absorption in vivo is greater in the jejunum.

Clinical involvement of mesenteric and antimesenteric borders of small bowel loops. I. Normal pattern and relationships

Anatomic features of the mesentery, as it contributes to the characteristic course and coiled nature of small bowel loops, are analyzed in detail. An understanding of the anatomic definition and relationships of the loops of small intestine permits roentgen identification of their mesenteric and antimesenteric borders. It is established that (a) the concave margin of a small bowel loop, facing toward the axis of the root of the mesentery, is the mesenteric border; and (b) the convex margin of a small bowel loop, facing away from the axis of the root of the mesentery, constitutes the antimesenteric border. The ability to distinguish between the mesenteric and antimesenteric borders of small bowel loops further refines the capabilities of radiologic diagnosis in a variety of intraabdominal disease processes.

The mechanism for small-bowel adaptation in lactating rats

1. To study the relative contributions of luminal nutrition, bile and pancreatic secretions and hormonal factors in intestinal adaptation, lactation hyperphagia was chosen as a model for increased luminal nutrition, either alone (intestinal transection control group) or in combination with (i) exclusion of bile and pancreatic secretions from the jejunum (by transposition of the jejunum above the Ampulla of Vater) or (ii) exclusion of bile, pancreatic secretions and exogenous luminal nutrition from the jejunum (proximal Thiry-Vella by-pass group). 2. The results confirm that in lactation there is mucosal hyperplasia with increases in villus height and crypt depth, and in small-bowel wet and defatted dry-tissue weights per unit length of intestine. 3. There are corresponding changes in absorptive function with increased glucose and water absorption per unit length of intestine. 4. These structural and functional adaptive changes are proportionately greater in ileum than in jejunum. 5. The exclusion of exogenous luminal nutrition, bile and pancreatic secretions from the jejunum did not diminish the degree of intestinal mucosal hyperplasia and functional adaptation seen in lactation. 6. Diversion to the ileum of greater than normal amounts of bile, pancreatic secretions and luminal nutrition did not further increase the degree of mucosal hyperplasia and enhanced absorption seen in the lactating intestinal transection control group. 7. Unlike other models of intestinal adaptation, the changes in small-bowel mucosal structure and function seen in lactation are probably due to hormonal factors.

Hydrolysis of peptides within lumen of small intestine

The quantitative significance of intraluminal peptide hydrolases in the terminal stages of peptide digestion has been investigated, and the precise origins of these enzymes have been determined. Intestinal contents and mucosae were obtained from rats anethetized with ether. Experiments carried out on pancreaticobiliary secretions and germfree rats show that pancreatic and bacterial enzymes do not contribute significantly toward the luminal digestion of dipeptides. Chemical assay data, thermostability studies, and examination of electrophoretic mobilities of luminal peptide hydrolases indicate that jejunal enzymes originate predominantly from the cytoplasm of intestinal mucosal cells, whereas the brush border of muosal cells is a major source of the enzymes in the ileum. With glycl-L-phenylalanine and L-phenylalanyl-glycine as substrates, jejunal luminal activity was less than 2.6% of mucosal activity. Brush-border peptide hydrolase activity in ileal contents, however, was 11.9% and 40.7% of mucosal brush-border activity for the two substrates. Luminal enzymes thus play an insignifcant role in the terminal digestion of peptides in the jejunum, but have a much more important role in the ileal digestion of peptides.

[Comparison of different morphometric methods to estimate the surface of the rat intestinal mucosa. Their relationship to intestinal function (author's transl)]

In contrast to the human small intestine with predominantly fingerlike villi, trapezoid forms are encountered in the small bowel of the rat. For this reason, it is doubtful whether it is sufficient to measure the villus height alone as a representative parameter for the assessment of the villus surface. In this study, the method developed by Clarke is employed to calculate the villus surface per unit area of intestine. The data obtained by this method are compared with those estimated planimetrically. Correlations were then established between the absorptive capacity and enzymatic activity of the intestinal mucosa on the one hand, and the villus height or the villus area obtained by each method on the other hand. Under our experimental conditions--a hyperregenerative transformation of the intestinal mucosa caused by chronic exposure to glucagon--the results indicate that the calculated villus surface per unit area of small intestine correlates better than the villus height with the functional parameters of the intestinal mucosa.

The effect of partial starvation and glucagon treatment on intestinal villus morphology and cell migration

Male Sprague-Dawley rats were either treated with repeated ip injections of glucagon every 6 hr or partially starved. After 7 days of partial starvation or 5 days of glucagon injections, a time period shown previously to induce increased transport, all animals were sacrificed and a segment of jejunum was removed, fixed in formalin, sectioned, and dipped in Kodak NTB-2 liquid emulsion. After 8 weeks of exposure the autoradiographs were developed; assessments of villus height and crypt depth and measurements of length of the column of exposed grains were made in a calibrated microscope. The mean villus length in both semistarved and glucagon-treated groups was found to be significantly reduced (p less than 0.001) when compared to control animals. The crypt-to-villus ratio was found to be unaltered by either treatment modality. The rate of cell migration was diminished by both partial starvation and glucagon treatment, but only glucagon therapy was found to cause a significant (p less than 0.01) reduction in the rate of cell movement when compared to controls.

[Perfecting of a technic for the in vivo study of intestinal absorption of monosaccharides in rats]

A method for in vivo perfusion of isolated jejunal and ileal loops with catheterisation of the efferent veins is described in the rat. The haemodynamical, histological results and the steadiness of D-glucose absorption showed that there functional ability was preserved at least during one hour. D-glucose is absorbed faster by the jejunal than the ileal portion in the rat.

[Quantification of the three-dimensional structure of jejunal mucosa in healthy subjects and patients with coeliac disease (author's transl)]

Jejunal biopsies of 10 normal subjects and 7 patients with coeliac disease were analysed quantitatively using the microdissection technique described by Clarke. Mucosal surface in the healthy upper jejunum was increased 8.3 +/- 1.1 times, the number of villi per mm2 intestine being 18.2 +/- 2.1. The ratio of the number of crypts per villi was 10.7 +/- 2.3. Mucosal transformation in coeliac disease was associated with a decrease in villi and crypts per mm2 intestine as well as in mucosal surface and an increase in crypt depth and number of mitotic figures per crypt. There was a highly significant linear correlation between villous height and mucosal surface per mm2 intestine (r = 0.93).

The time-course of changes in mucosal architecture and epithelial cell production and cell shedding in the small intestine of the rat fed after fasting

Rats were starved for 3 days, then either allowed access to food or continued in starvation. The following measurements on the upper jejunum were made on groups of refed and starved rats at nine time intervals after refeeding: villus height, crypt depth, crypt/villus ration, rate of cell production per crypt, and number of epithelial cells shed per villus in 5 minutes. Villus height increased 2 hours after refeeding, while crypt depth changed less dramatically. Crypt/villus ratio was unchanged. The number of shed epithelial cells per villus was reduced below the starved level for 4 hours after refeeding, and did not rise significantly above the starved level until 9 hours; the rate of cell production was not significantly increased until 12 hours after refeeding. No evidence for a reserve of cells in G2 was found, and the 3 hour lag between the rise in cell shedding and the increase in cell production would probably not give enough time for cells in G1 to pass through S and G2. It is concluded that these observations do not support the hypothesis that increased cell shedding from the top of the villus stimulates increased cell production in the crypts of Lieberkuhn.

Effect of Klebsiella pneumoniae enterotoxin on intestinal transport in the rat

The effects on intestinal transport of either a semipurified preparation of enterotoxin elaborated by Klebsiella pneumoniae or similaryly prepared control material were tested by marker perfusion studies in the small intestine of rats. At a concentration of 2 mg/ml, the enterotoxin produced net secretion of water, Na, and Cl in both jejunal and ileal segments; HCO3 transport was not affected. Net secretion was evident within 30 min after intorduction of the toxin and was maximal after 90 min. The addition of 56 mM glucose to the enterotoxin-containing perfusion fluid resulted in reversal of water and Na transport to net absorption in both intestinal segments. The enterotoxin also produced a significant depression of xylose absorption in both the jejunum and ileum but did not affect the absorption of either glucose or L-leucine. Intestinal structure was not altered after perfusion of the toxin but insillation of approximately one-quarter of the total perfusion dose into a ligated jejunal loop for 18 h produced fluid secretion and structural abnormalities. These observations confirm the fact that other species of coliform bacteria in addition to tescherichia coli are capable of elaborating an enterotoxin. Such species commonly contaminate the small intestine of persons with tropical sprue and it is suggested that chronic exposure of the intestinal mucosa to the enterotoxin elaborated by these bacteria may be a factor in the pathogenesis of intestinal abnormalities in thid disorder.

The nutritive effect of glucose on the structure and function of jejunal self-emptying blind loops in the rat

In an attempt to obtain further information on the influence of the intestinal contents on the development of mucosal structure and function, self-emptying blind loops of rat jejunum were constructed, and the oral end was exteriorized with a stoma to permit infusion of different solutions into the loop. Ringer solution or media containing glucose or galactose was instilled into the loops three times daily for 27 days before functional and structural examination of the loops. The body weight and food intake of the animals did not differ significantly from one group to another. Treatment with glucose, but not with galactose or Ringer solution alone, induced a significant increase in the villus height. Disaccharidase but not dipeptidase activity was concomitantly increased. Infusion of glucose or galactose both led to an increase in the transport capacity of the loop, as determined by glucose absorption in vivo. These results indicate that glucose has a nutritive effect, probably due to its intracellular metabolism, which is responsible for the structural alterations observed. On the other hand, the increase in transport capacity may be attributed to substrate-induced stimulation of the specific monosaccharide transport system in the epithelial cell.

Histological development of the thymic and intestinal lymphoid tissue of the horse

The basic components of the immune system, and the defence mechanisms in the gastrointestinal tract, are briefly reviewed. Histological studies in 84 equine foetuses showed that lymphoid cells begin populating the thymic primordium at 11-12 weeks, the mesenteric lymph nodes at 13 weeks, the spleen at 25 weeks and the intestinal lamina propria at 13-14 weeks' gestation. Lymphocytes were seen in the intestinal epithelium very early in gestation. Histological signs of response to antigenic stimulation were seen in five foetuses, indicating that the horse is likely to be capable of mounting an immune response in utero. The changing status of the foal as it becomes fully immunocompetent is discussed.

Mechanisms of lipid loss from the small intestinal mucosa

Many water-soluble compounds have been shown to pass from the small intestinal mucosa into the lumen. In this work, the loss of lipids from the mucosa was investigated by perfusion experiments in rats, using 0-15M NaCl or buffer solutions over range of pH, with or without the addition of 5-7 or 11-4mM taurocholic acid. Perfusates were extracted for the estimation of individual lipids and for DNA, which is a measure of cell loss. The results suggest that free fatty acids reach the lumen by diffusion and that their solubility in the luminal fluid is a factor determining their rate of loss. Triglycerides, cholesterol, phosphatidyl ethanolamine, and phosphatidly choline are present onlyas the result of desquamation of mucosal cells.

Effect of pentagastrin on small bowel structure and function in the rat

Since chronic pentagastrin stimulates pancreatic and proximal duodenal growth (15), we studied jejunal structure and function following subcutaneous pentagastrin (2 mg-100 g-1 day-1). After 15 days, macroscopic enlargement was confined to the proximal duodenum with a significant increase in wet weight (from 231 +/- SEM 6 to 308 +/- 13 mg) but there was no significant difference in wet and defatted dry intestinal weights, histological measurements of villous height and mucosal thickness or in glucose absorption per unit length of distal duodenum and proximal jejunum. Since chronic pentagastrin causes parietal cell hyperplasia and hypersecretion of gastric acid, the results suggest that the adaptive changes seen in the jejunum after ileectomy are neither mediated by gastrin nor by factors present in gastric secretions.

Intestinal intubation in the unanaesthetised miniature pig: technique for sampling and measurement of gut length per fistulam

Techniques have been developed and are described for the surgical preparation of long-term jejunal and ileal fistulas in miniature swine and for the management and restraint of the fistulated swine for laboratory investigation. An apparatus and procedure is described for per fistulam intubation which allows sampling of intestinal contents at any site in the jejuno-ileum of the unanaesthetised pig. A comparison between in vivo intestinal length, measured by intubation between jejunal and ileal fistulas, and post mortem intestinal length demonstrates that, as in the human, the intestine becomes remarkably elongated after death.