Morphology and enzyme aktivity in rat small intestinal epithelium 6 and 12 hrs. after an alkylating agent (cyclophosphamide).

Six and twelve hours after a single i.p. dose of cyclophosphamide (100 mg/kg body weight) the activity of different "brush border enzymes" (maltase, sucrase lactase, alkaline phosphatase, gamma-glutamyl transferase) and of a lysosomal enzyme (acid phosphatase) did not change. In vivo absorption of galactose was not diminished by the treatment. The pattern of response to cyclophosphamide seems to be different in SPF and GF rats. The response of crypt epithelium (cell number, mitotic number, mitotic frequency) was more pronounced in the SPF rats, whereas the villus height only decreased in the GF rats.

[The barrier-function of the gastrointestinal (author's transl)]. / Die Barrierefunktion des Magen-Darm-Trakts.

The present review tries to coordinate anatomical barriers and the biochemical and immunological events controlling and even preventing the entry of substances from the external environment into the extra- and intra-cellular space of the body. A selection of diseases with disturbance of the "barrier function" is included.

Starvation and sucrose activity in small intestinal mucosa. An evaluation of different tissue preparations and reference systems.

Starvation for 48 hrs reduced the activity of sucrase referred to unit length in rat proximal small intestine by approximately 30%, irrespective of whe her mucosal scrapings, isolated villus epithelial cells or brush border membranes were investigated. Sucrase activity referred to unit weight, unit protein or to unit DNA of intestinal epithelium did not change.

Effect of starvation on small intestinal enzyme activity in germ-free rats.

Starvation overnight and starvation for 48 h reduced the weight and the protein content of mucosal scrapings, but only minimally reduced the DNA content of the mucosal scrapings. The activity of sucrase and maltase was reduced by both periods of starvation. The activity of lactase and of acid and alkaline phosphatase, however, was less subject to starvation. There were striking differences in the response to starvation between the proximal, mid and distal third of the small intestine. The importance of the proper reference system was discussed.

[Cytostatica and small intestine (author's transl)]. / Zytostatika und Dünndarm.

Cytostatica not only suppress proliferation in tumor cells but it also checks proliferation in small intestinal epithelium. The consequence is cell reduction and damage resulting in a diminished function. Because of the high reserve capacity of the small intestinal epithelium, clinical signs of diminished function are mostly seen after repeated high doses or one extremely high doses of Cytostatica. Although there is abundant information on the effect of Cytostatica on the small intestinal epithelium (cell turnover, morphology, digestive enzymes and absorption) there are other areas that are as urgent for the interested clinician to work on: 1. Would it be possible to coincide the dose and dosage rate with the cell cycles to reduce the chance of damage to small intestinal epithelium? 2. Which role has the luminal content when there is damage from Cytostatica? Is it possible to concentrate on changing the luminal contents (antibiotics, "elemental diet", cultivate desirable microflora, etc.) Therefore diminishing the damage from Cytostatica? 3. How would Cytostatica influence the barrier function on the intestinal wall? Should the patient on Cytostatica therapy receive special protection against intestinal infection? 4. Does Cytostatica affect the biotransformation in the small intestinal epithelium, especially when taken orally? How important is this biotransformation in small intestinal epithelium damaged by Cytostatica therapy? 5. What factors determine the regeneration of the small intestinal epithelium after Cytostatica damage?

The effect of a single dose of cyclophosphamide on the jejunum of specified pathogenfree and germfree rats.

After a single dose of cyclophosphamide (100 mg/kg) cell proliferation in the jejunum of the rat decreased within the first 24 h and returned to the initial level after 48 h. Under the influence of cyclophosphamide, an increased cell loss in germfree rats could be observed. Villus height and villus cell count tended to decrease. Changes in disaccharidase activity in mucosal scrapings with respect to protein and DNA content could not be demonstrated. An influence of presence or absence of bacterial flora could be observed.

[Partially mechanized determination of protein and desoxyribonucleic acid in the mucosa of the small intestine on microliter scale]. / Teilmechanisierte Bestimmung des Proteins und der Desoxyribonukleinsäure im Mikrolitermassstab in der Dünndarmschleimhaut

The protein determination method according to Lowry and the DNA test according to Schneider were adapted to a microliter scale thus rendering feasible serial determinations with an adequate degree of accuracy. The criteria for reliability (precision within the series and day after day) are sufficient.

An experimental model for measuring intestinal permeability.

In the nonanesthetized rat, the jejunal permeability to four simultaneously administered molecules, mannitol, phenol red, inulin and PVP, was measured by analyzing blood, serum, urine and duodenal fluid for these compounds. Of the molecules which had entered the body, approximately 50% were found in the urine, another 50% in the extracellular space and only about 1% were excreted into the duodenal juice. The intracellular content of the molecules is not accounted for in these numbers. The rate of permeation decreased with increasing molecular weight of the substances. EDTA (25 mmol/l) and deoxycholate (5 mmol/l) increased the jejunal permeability for these molecules but not for mannitol. The alterations in mucosal cell turnover and morphology induced by hydroxyurea did not change jejunal permeability for mannitol and phenol red at any time. 24 and 48 h following hydroxyurea, jejunal permeability for inulin and PVP was decreased.

Intestinal morphology and cell production rate in aging rats.

Age-related changes in the gut were investigated in male gnotobiotic rats, living in a controlled and constant environment until death. Parameters of the regenerative compartment of the jejunum and ileum were the cell production rate (measured by a stathmokinetic technique), the number of crypts, and the crypt:villus ratio. Parameters of the functional compartment were the average surface area of the villi, height and broadness of villi, etc. Age did not change the size of individual villi or crypts or the cell production rate. The number of crypts and, to the same extent, the number of villi increased with age, indicating a continuation of mucosal growth up to an age of 2 yr.

Analysis of the effects of food and of digestive secretions on the small intestine of the rat: III. Mucosal mass, activity of brush border enzymes, and in vivo absorption of galactose, sodium, and potassium.

A modified Roux-en-y repositioning of rat proximal small intestine resulted in a gut segment (A) exposed only to digestive secretions, but not to food and a gut segment (B) exposed to food, stomach juice and by reflux only to digestive secretions, and a third segment (C) exposed to both, food and digestive secretions. The changes in segment A were qualitatively very similar to those occurring after removal of luminal nutrition (intravenous feeding, self-emptying blind loop, and Thiry Vella loop). These findings support the hypothesis that the presence of luminal nutrition is a major factor regulating mucosal mass and enzyme activity in rat proximal small intestine. The changes in the luminal environment in segment B caused an increase in mucosal mass (in the proximal half only), an increase in sucrase activity which paralleled the increase in mucosal mass, and no change in activity of alkaline phosphatase which in fact was a decrease in activity ;at the cellular level'. Later on the net absorption of sodium and potassium was improved and the disappearance of galactose was unchanged when referred to unit length of small intestine.In segment C there was a small increase in mucosal mass, an increase in activity only for alkaline phosphatase, and an improvement of the net absorption of sodium without changes in the disappearance of galactose. These changes were compatible with a more proximal promotion of a distal gut segment.

An experimental model for studies on the effects of food and digestive secretions on the digestive-absorptive capacity of rat small intestine.

At an average of 32 days after a modified Roux-en-y repositioning of rat small intestine, the mucosal mass, mucosal composition, in vivo absorption of galactose and the activity of maltase, sucrase and alkaline phosphatase were measured. In the gut segment with digestive secretions but without food (A) the only change was a decrease of sucrase activity which occurred most probably at the cellular level. In the gut segment with food and gastric juice and a reflux of digestive secretions (B) complex changes took place. An increase in mucosal mass was not accompanied by an increase in galactose absorption. There was a high increase of sucrase activity, a moderate increase of maltase activity and a tendency of the alkaline phosphatase activity to decrease. The changes (increase in mucosal mass and total enzyme activity, but no changes in activity at the cellular level) in the segment exposed to both digestive secretions and food (C) were compatible with a more proximal promotion of a distal gut segment.

[Effect of osmolality on the gastrointestinal permeation of various carbohydrates in healthy persons]. / Einfluss der Osmolalität auf die gastrointestinale Permeation verschiedener Kohlenhydrate am Gesunden.

The effect of a high osmotic solution on active and passive sugar permeation was investigated in 19 healthy volunteers. The reduced rate of active sugar absorption (3-O-MG and xylose) out of a high osmotic solution was interpreted as a consequence of an impaired emptying of the stomach. The increased passive permeation of intact disaccharides applied in hyperosmolar solution demonstrates an increased gastrointestinal permeability. Intubation studies suppose increased disaccharide absorption out of hyperosmolar solution in the stomach, i.e. high osmolar solutions increase gastric mucosal permeability.

Acute distal intestinal obstruction in gnotobiotic rats. Intestinal morphology and cell renewal.

1. Complete mechanical obstruction of the distal small intestine was produced in gnotobiotic rats. 72 h after the operation small intestinal morphology and epithelial cell renewal were investigated proximal and distal to the site of obstruction. 2. Proximal to the site of obstruction there were minor changes in villus height, base length and in villus cell number, a large increase in depth and diameter of the crypts and an approximately threefold increase in cell renewal. 3. Distal to the site of obstruction there were no differences between the intestines of rats with obstruction and controls. 4. The apparent lack of secretion by the goblet cells and the reduced number of intraepithelial leucocytes suggest that the barrier function of the small intestine is impaired in obstruction.

Analysis of the effects of food and of digestive secretions on the small intestine of the rat. 1. Mucosal morphology and epithelial replacement.

A modified Roux-en-Y repositioning of rat small intestine was performed so that the proximal segment of bowel (A) received only bile and pancreastic secretions, the second (B) received food direct from the stomach, and these two segments drained into a third (C). Four to five weeks after operation, cell production was assessed by injection of vincristine into operated, sham-operated and unoperated rats, and counts of blocked metaphases were made on isolated microdissected crypts. Villus height, crypt depth, and the number of crypts per villus (crypt/villus ratio) were also measured. Most of segment A showed no significant differences from sham-operated intestine, although the normal proximo-distal gradient of villus height was abolished. At the distal end (near the anastomosis with segments B and C), crypt depth and cell production were increased. The villus height gradient in segment B was also abolished, although crypt depth and cell production were significantly increased, especially at the proximal end. Crypt/villus ratio was also increased. Segment C showed all the characteristics of small bowel promoted to a more proximal position: increased villus height, crypt depth and cell production. Increased crypt/villus ratio was also observed. These results are discussed in terms of the role of food and of digestive secretions in the control of mucosal morphology and epithelial replacement.

Measurement of enzyme activity and substrates in intestinal mucosa. Evaluation of a system for quality control in clinical and experimental gastroenterology.

Widely used methods in diagnostical and experimental gastroenterology like measuring the protein-and DNA-content and the activity of alkaline phosphatase and sucrase of intestinal mucosa were adapted to a microliter system and partly automatized. With "artificial" control material a system for statistical quality control was established. Lastly the results on up to three years experience with this control system were presented showing an imprecision within run below 5% and an in-imprecision between run below 8% in all methods.

Effect of dietary bulk on small intestinal morphology and cell renewal in the rat.

Feeding an elemental diet (Vivonex) to rats over 9 days causes a decrease in the rate of cell renewal and a reduction in villus size in both the jejunum and ileum, as compared with rats fed regular chow. The addition of bulk to elemental diet cannot prevent the reduction in villous size, but it can cause a small increase in the rate of cell renewal, which is still much lower than that in chow-fed rats. The serum gastrin level of rats fed the elemental diet is about one-third of the level found in chow-fed rats, and it is not changed by the addition of bulk.

Elimination of low molecular weight polyethylene glycol 400 in the urine following an oral load, as a measure of intestinal permeability.

After an oral load of 10 g polyethylene glycol, its concentration in the urine was measured by gas chromatography. The coefficient of variation of the imprecision between run was about 11%. The urinary excretion was 25% of the administered dose with a coefficient of variation of the interindividual variation 26% and the intraindividual variation between 13% and 29%.