Exteriorized Loop Research Articles

Dose-survival characteristics of epithelial cells of mouse intestinal mucosa.

The experiments reported here were aimed at determining the dose-survival characteristics of the epithelial cells that form the mucosal lining of the small intestine of the mouse. When a loop of small intestine is exposed to a suitably chosen dose of x rays and examined about thirteen days later, discrete islands of regenerating epithelium may be seen in an area otherwise completely ulcerated. It is assumed that each island, or nodule, of epithelium arises from a single proliferative cell surviving within a mucosal crypt and that such cells survive independently. Therefore, the dose-survival relation determined from nodule counts represents the dose survival for single cells. Materials and Methods Female hybrid (CDF1) mice aged thirteen to eighteen weeks were used. The strain was an arbitrary choice, but the age range was suggested by the relatively uniform response observed in this strain after twelve weeks of age when radiation-induced gut death was the end-point studied (1). Mice are anesthetized by an intraperitoneal injection of pentobarbital sodium (approximately 80 mg/kg body weight). A length of small intestine from the jejunum and upper ileum is then exteriorized and laid on a thin Lucite platform as a semicircular loop having a radius of approximately 1.3 cm. The remainder of the mouse is housed in a protective lead box during irradiation. The middle 90° of the exteriorized loop is shielded from above and below by arcs of lead during a preliminary exposure of the two lateral 45° segments. The shields are then removed, and the experimental dose is given to the whole 180° of exposed intestine. The preliminary doses are selected so that the total dose to the lateral segments is about 3,000 R—sufficient to depopulate the mucosal surface. In this way cell survivors in the experimental area are isolated from unirradiated epithelium during the thirteen-day period of post-irradiation regrowth. X rays are generated by two opposed tubes operated at 200 kVp, 15 mA, each filtered by 0.25 mm Cu + 0.55 mm Al giving an h.v.l. of 0.9 mm Cu. The dose rates in midfield were 730 and 140 R/ minute at target separations of 50 and 108 cm respectively. When the total dose was divided into two fractions, the first was always 700 R given at 140 R/min. to the whole abdomen with head, thorax, tail, and most of one femur shielded. For single exposures or the second of a two-dose regime, the exteriorized loop was irradiated with the target separation reduced to 50 cm to give an exposure rate of 730 R/min. During all irradiations the animals are anesthetized and positioned in a Lucite box through which oxygen is ventilated at about 5 to 6 volume changes per minute. Thirteen days after irradiation the animals are sacrificed and the irradiated segments of intestine removed, cleaned, and fixed in Bouin's solution. The number of nodules is counted at a magnification of ×6 to ×15, using a stereoscopic dissecting microscope.

Recovery of the Intestinal Mucosa in the Rat after X-Irradiation of the Exteriorized Intestine

We have previously reported on the effect of irradiating an exteriorized loop of rat intestine with a dose of 1000 R (1). Our observations extended to 72 hours after irradiation, when the damage to the epithelial cells lining the jejunal crypts and villi was severe with complete loss of the villous structures. We therefore decided to study the recovery process after this dose of radiation to assess when it took place and whether evidence of residual damage could be observed. There is considerable variation on these points in the literature. One group of workers found that after a dose of 900 R to an exteriorized loop of rat intestine only transitory changes were present initially, with no residual damage at a later period (2). On the other hand, another group found that after a dose of 1000 R to an exteriorized loop of rat intestine there was gross damage at 5 days, which gave rise to late radiation changes (3). The interpretation of the effects of irradiation is complicated by our inability to differentiate between the consequences of damage to the gut and the changes that result from repair processes. Though both processes no doubt occur concurrently, only the predominant one at a given moment is cited in this study, as this simplification is considered justifiable under present circumstances.

Procedure for Exteriorizing the Carotid Artery in the Bovine

Abstract A surgical procedure for making a permanent exteriorized loop in the carotid artery of the bovine is described. Eight of nine operations were successful and the vessels remained in place even under frequent bleeding. It was found that animals could be trained for sampling from the carotid loop with much less disturbance than by rectal puncture of the internal iliac, prepubic or the middle coccygeal arteries. Thus, sampling from the carotid gave much more reliable values for detecting respiratory alkalosis in cattle under heat stress.

Changes in the intestinal mucosa of the sheep following death by humane killer.

IN the course of an investigation of the changes in composition of the digesta along the alimentary tract of the sheep1, it was noted that there was a considerable addition of nitrogen to the chyme in the most proximal quarter of the small intestine. The nitrogen content in the remaining quarters fell off distally until the abomasal level was attained in the fourth quarter. It was noted from in vivo studies on fistulated animals, and in those with exteriorized loops of the small intestine within the first two feet or so of the pylorus, that this addition of nitrogen did not occur to the same extent as in the shot sheep. Lignin was used as a reference substance to assess these changes.

Physiologic Observations on a Segment of Normal Human Jejunum

Summary Numerous studies have been made on an exteriorized human loop of jejunum (Tables 1, 2). As a result of these studies further trial of calcium as an antispasmodic is indicated. A dissimilarity of action between ephedrine, epinephrine is demonstrated. Further information about the site of action of Etamon is presented.

Volatile fatty acids in portal blood of sheep.

VOLATILE fatty acids—chiefly acetic, propionic and butyric acids—are formed as a result of the fermentation processes in the rumen of sheep and are absorbed through its wall. With the purpose of investigating the concentration of these acids and other constituents in the portal blood during a digestion cycle, that is, the 12-hour period after feeding, a slightly modified London canula was fixed adjacent to the main trunk of the portal vein of two sheep1, which had previously been provided with a rumen canula and an exteriorized loop of the carotid artery. The feed, which consisted of 125 gm. chopped hay, 200 gm. linseed meal and 15 gm. blood meal, was given every 12 hours2, and all was consumed within an hour. The total amount of volatile fatty acids in rumen liquor was determined by steam distillation, and separated into acetic, propionic and butyric plus higher acids using the chromatographic technique of Elsden3. For determination of total volatile acids in blood a modification of the method of McClendon4 was adopted. Blood-sugar estimations were carried out according to Somogyi5 with an accuracy of ±0·11 m.mol. per litre.

The effect of elevated metabolism on rate of intestinal contractions

1. Thyroid extract, in doses sufficient to elevate metabolism fifty per cent, does not alter the rate of contraction in exteriorized intestinal loops in dogs (Fig. 1) except in a segment just above the ileocecal valve (Fig. 2). 2. Alpha 1, 2, 4 dinitrophenol, in doses sufficient to elevate metabolism over 200–500% does not increase the rate of contraction (Fig. 3) in exteriorized intestinal loops in dogs. 3. Feeding reactions are poor with both these drugs.

Role of the small intestine during emesis

Intestinal activity precedes the act of vomiting when studied in exteriorized loops (7). It is suggested tentatively that this activity is antiperistaltic.

Influence of cathartics on the activity of small intestine

Although the various cathartics influence the amplitude and character of contractions in exteriorized loops of small intestine they fail to change the rate. After administration of magnesium sulfate the feeding responses are suppressed. Of the drugs studied cascara sagrada disturbs activity (motility and feeding responses) least.

The gastro-ileac reflex: Further experimental observations

The activity of exteriorized loops of jejunum, ileum and colon in continuity in trained dogs was studied in relation to feeding.

The activity of the lower part of the lleum of the dog in relation to the ingestion of food

The activity of exteriorized loops of the lower part of the ileum in continuity, enclosed in bipedicled tubes of skin, was studied in the dog in relation to the ingestion of food. A regular cycle of activity was noted in the normal animal: namely, a rapid motor response to feeding, followed by prolonged activity which gradually diminished until, after forty-eight hours of fasting, the activity was extremely feeble.

An experimental study of the rhythmic contractions in the small intestine of the dog

Exteriorized loops were prepared at various levels in the small bowel of trained dogs and the occurrence and rate of rhythmic contractions noted. Rhythmic contractions were found to be a relatively rare form of movement in these preparations, occurring in about 2 per cent of all tracings. The remaining 98 per cent of the tracings was occupied by irregular types of segmentation, peristaltic and tonus waves. The rate of rhythmic contractions was a constant for any given loop with a variation of plus or minus one contraction per minute. The rate of any given loop was found to be a function of its distance from the pylorus, the loop at the highest level having the highest rate, that at the lowest level having the lowest rate. The rate was not affected by fasting, feeding or sleep, except that in the recently fed animal, rhythmic contractions were less commonly observed than in the fasting animal. The rate was unaffected by degenerative vagal and splanchnic section.

Improvements in the operative treatment of carcinoma of the large bowel

Attention is directed to the advantages of a type of a single stage abdominoperineal proctosigmoidectomy with perineal colostomy or perineal anus, which may hospitalize the patient only two or three weeks. Peritonization of denuded areas in the abdomen and the formation of a pelvic diaphragm of peritoneum have been found to be unnecessary. The chief cause of death is peritonitis resulting from the spread of bacteria from infected tissue about the cancer, and especially the dissemination of bacteria through retained avascular and necrotic bowel, measures to avoid which are mentioned. In anastomosis of the colon there is need of the more enduring silk or alloy wire sutures and questionable suture lines should be guarded by overlying “lamp chimney” drains. Oblique muscle splitting incisions are of great advantage in many of the Mikulicz type of resections. The exteriorized loop is best removed at the first stage and tubes tied into the ends of the bowel should remain external to the level of the skin. Incision with follow-up wire suture should supplant the clamp in division of the spur as this enables the bowel ends to be united early and painlessly, saving the patient much discomfort and hospitalization. A modification of the Mikulicz operation may be used for high rectosigmoid growths with the advantage of preserving the normal sphincteric control.