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Ultrastructural Changes in the Small Intestines of Rats With Self-Filling Blind Loops
Vol. 67 , ~ o.l Print ed in U.S.A .
GASTROENTEROLOGY 67:646- 651. 1974 Copyright © 1974 by Th e Willia ms & Wilkins Co.
ULTRASTRUCTURAL CHANGES IN THE SMALL INTESTINES OF RATS WITH SELF-FILLING BLIND LOOPS MICHAEL GRACEY, M .D. , F .R.A.C . P. , JOHN PAPADIMITRIOU, M . R.C . PATH. , AND GEOFFREY BowER, M . B . , M.R.A.C . P.
Gastroenterological Research Unit, Princess Margaret Children's Medical Research Foundation, and th e Department of Pathology , School of Medicin e, Univ ersity of W estern Australia , Perth, Western Australia
Ultrastructural abnormalities were found commonly in the small intestinal epithelium of a series of rats with surgically induced intestinal stasis, although the villous architecture and epithelial cell structure appeared normal by conventional light microscopy. The ultrastructural changes included variable degrees of distortion and denudation of microvilli, swelling, and vesiculation of mitochondria, accumulation oflipid droplets in the apical portions of enterocytes, and distortion of Golgi material. The changes were patchy, but occurred in approximately 10 to 35% of enterocytes examined from the midvillus region of these animals. It is suggested that these abnormalities may contribute to intestinal malabsorption which occurs as a consequence of bacterial contamination of the upper gut . It has been widely accepted that bacterial contamination of the upper gut is not accompanied by changes in villous architecture or epithelial cell structure, although infiltration of the underlying lamina propria by inflammatory cells is usual. 1' 4 Some authors , however, have noted histological abnormalities in patients with intestinal stasis 5 • 6 and have suggested that these might be of functional significiance .6 It might be anticipated that more detailed information about the structure of enterocytes could be obtained by electron microscopy, and two recent studies have shown evidence of ultrastructural damage in patients 7 and experimental animalss with bacterial overgrowth in the proximal gut . These two studies were very
limited . The clinical study 7 involved only 3 patients, while the experimental one s involved only 3 animals . In particular, the previous experimental investigation reported abnormalities only in the blind loops and jejunum distal to this . This study confirms and extends this earlier works in which ultrastructural damage in the small intestinal epithelium was found in rats with a self-filling jejunal blind loop, and supports the possibility that such changes may be pertinent to the production of malabsorption in the presence of chronic microbial contamination of the upper gut.
Materials and Methods
Adult Wistar rats, weighing 150 to 200 g, and bred from a long-established colony in the Received October 25, 1973. Accepted March 28, University of Western Australia, were used throughout . Under open ether anesthesia, a 1974. Address requests for reprints to: Dr. Michael segment of upper jejunum was selected, and a Gracey, Gastroenterological Research Unit, Princess self-filling blind loop approximately 8 em long Margaret Children's Medical Research Foundation, was constructed surgically using the technique described by Cameron et a!. 9 Intestinal continu· Perth, Western Australia . Dr. Gracey is the Adolph Basser Research Fellow of ity was maintained by making a side-to-end the Royal Australasian College of Physicians. anastomosis . Studies were performed in 6 con646
October 1974
ULTRASTRUCTURAL CHANGES IN BLIND-LOOP RATS
trol animals and 6 experimental animals which were housed and fed identically after recovery from operation. In control animals, duplicate specimens were obtained from jejunum approximately 20 to 25 em from the duodenojejunal junction; in the operated animals specimens were obtained, in duplicate, from (1) the blind loop, (2) jejunum 5 em proximal to the junction with the loop, and (3) jejunum 5 em distal to the loop. All specimens were coded, examined, and reported without knowledge of their origin. Light microscopy. Specimens for light-microscopic examination were fixed in formol-saline and carefully orientated before mounting and staining with hematoxylin and eosin. Scanning electron microscopy. Specimens were washed in buffered saline and then fixed in cold 3% glutaraldehyde in 0.1 M cacodylate buffer (pH 7 .4) for 16 to 18 hr. They were then washed in fresh buffer, dehydrated in graded solutions of ethanol, and allowed to dry in air. When dry, the specimens were coated, while on a rotating stage, with a layer of gold-palladium of approximately 40 to 50 /.LID in thickness. They were then placed on a JSM scanning electron microscope, tilted 45° to the scanning beam, and examined at an accelerating voltage of 25 kv. Micrographs were taken on Kodak Panatomic X film . Transmission electron microscopy. Specimens were fixed in cold 3% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) at 4 C for 16 to 18 hr. They were then postfixed in 1% osmium tetroxide in 0.1 M cacodylate buffer at 4 C for 1 hr, dehydrated in graded solutions of ethanol , and embedded in Araldite . Eight to 10 Araldite blocks were prepared and examined from each tissue sample. The embedded tissue was examined under a dissecting microscope and trimmed by hand. Particular care was taken to avoid the tips of villi and to select midzone areas of villi for inclusion in the final block face. Sections were cut on an LKB ultramicrotome stained with lead hydroxide, and examined on a JEM-T6 or a Philips 300 electron microscope .
Results Light microscopy. No abnormality of the villous architecture or epithelial cell structure was detected by light microscopy in mucosa from the blind loop or the proximal or distal jejunum of operated animals. There was, however, a moderate degree of infiltration of the lamina propria, particularly by plasma cells and lymphocytes, and some reduction in the villus to crypt ratio.
647
Mucus-secreting goblet cells were more numerous than normal, especially in tissue from the blind loops. Scanning electron microscopy. At low magnification, the morphological pattern of the epithelium from blind loop and proximal and distal gut revealed a predominantly "broad leaf" pattern indistinguishable from control specimens (fig. 1). Transmission electron microscopy. Structurally abnormal enterocytes were detected in all samples of mucosa from the blind loop animals . This was in contrast to the control animals in which abnormalities were only very occasionally found and occurred in 2 to 5% of cells. The distribution of lesions in the operated animals was patchy, and their frequency was variable in individual sections, occurring in 10 to 35% of cells. Lesions were more common in specimens from the blind loop rather than from afferent or efferent jejunum . However, significant abnormalities were found in each region and they were qualitatively similar. Representative lesions are shown in figures 2 to 5. Affected cells showed a variable degree of damage to the microvillous surface ranging from virtual denudation (fig. 2) to minor distortion of microvillous shape. Intermediate changes were common, especially blebbing of the luminal surface of enterocytes (fig. 3) and swelling and ballooningofthe microvilli (fig. 4). Abnormalities were more numerous closer to the apical sections rather than the basal sections. The terminal web region displayed some loss and disarrangement of fibrillar components (figs. 3 and 4). Mitochondria were swollen and numerous small vesicles were visible throughout the apical cytoplasm (fig. 4). Lipid droplets were common, particularly in the apical portion of the cyotplasm. Numerous electron-dense cells were seen in which there were few or distorted microvilli, swollen mitochondria, prominent, enlarged, and distorted Golgi material and apical nuclei (fig. 5). Only minimal changes were seen in cells in the intestinal crypts. Many contained apical centrioles, numerous electron-dense bodies, especially in the apical region of the
FIG. 1. Scanning electron micrograph of the epithelial surface of a blind jejunal loop. A normal " broad leaf' pattern of mucosal architecture is displayed ( x 160) .
FIG. 2. Transmission electron micrograph of the apical portion of an absorptive cell in the midzone of a villus in a blind jejunal loop. Loss of microvilli is obvious, and the few which are remaining are distorted and irregular. Numerous lipid droplets are visib le (arrows) ( x 16,400).
FIG. 3. Transmission electron micrograph of the ap ical surface of an enterocyte in the midzone of a villus in a blind jejunal loop. The surface of the enterocyte shows blebbing which has replaced the normal microvillar structure ( x 23, 160).
6-!8
.
.
FIG. 4. Transmission electron micrograph of the apical portion of an enterocyte in the midzone of a villus in a blind jejunal loop. The microvilli are swollen and ballooned . The enterocytic mitochondria are swollen and many vacuoles are present in the cytoplasm ( x 19, 700).
FIG. 5. Transmission electron micrograph of the apical portion of enterocytes in the midzone of a villus in a blind jejunal loop. Two enterocytes are electron-dense, possess few microvilli, and display swollen mitochondria, distorted Golgi material, and enlarged vesicles ( x 21,180). 649
650
GRACEY ET AL.
Vol. 67, No.4
cell, while the terminal web region was troenteritis have recently been shown to poorly formed and traversed by a loose have deleterious effects on intestinal funcmesh of numerous fine filaments . tion, 13 and it would seem possible that these substances may also cause ultraDiscussion structural effects. The possibility remains, This study indicates that ultrastructural of course, that several interrelated factors abnormalities occur in the small intestinal may operate simultaneously. epithelium as a result of bacterial contamiThe contribution of the ultrastructural nation of the upper gut, thus confirming abnormalities found in this study to the and extending recent experimental 8 and occurrence of diarrhea and intestinal malclinical studies. 7 In the present studies, absorption in patients with bacterial overextensive damage to microvillous and cyto- growth in the upper gut is uncertain. It plasmic portions of enterocytes was found seems likely that it is relevant to impaired in specimens of jejunum from rats with a carbohydrate absorption which occurs in self-filling jejunal blind loop, while light adults, 14 and more particularly , in infants .8 and scanning electron-microscopic appear- It is possible that a similar effect on water ances of the cells were essentially normal. and other small water-soluble molecules The changes were most numerous in tissue occurs . Ament et al. 7 have suggested that from the loop, but present and qualita- the ultrastructural lesions contribute to tively similar in jejunum proximal to and diarrhea by delaying the exit of chylomidistal from the loop. crons from damaged enterocytes. This conThe pathogenetic significance of these cept may be somewhat supported by the findings is obscure . Ament et al. 7 found findings in this study of many 1ipid dropultrastructural abnormalities in 3 patients lets in affected enterocytes. These possibilwith intestinal stasis and considered them ities require additional investigation . relevant to the production of intestinal malabsorption in the "contaminated REFERENCES small-bowel syndrome," and likely to be induced by the presence of excessive con- 1. Donaldson RM Jr: Studies on the pathogenesis of centrations of deconjugated bile salts in steatorrhoea in the blind loop syndrome. J Clin this situation. It is interesting that the Invest 44:1815-1825, 1965 degree of damage found in this study was 2. Paulk EA Jr, Farrar WE Jr: Diverticulosis of the small intestine and megaloblastic anemia. Am J most marked in the blind loop rather than Med 37:473- 480, 1964 afferent or efferent jejunum, since the concentration of intra! uminal deconjugated 3. Rubin CE, Dobbins WO III: Peroral biopsy of the small intestine. A review of its diagnostic usefulbile salts in highest in this region in this ness. Gastroenterology 49:676-697, 1965 experimental modeJ.B Furthermore, similar 4. Tabaqchali S, Hatzioannou J , Booth CC: Bileultrastructural changes can be induced salt deconjugation and steatorrhoea in patients experimentally by feeding a deconjugated with the stagnant-loop syndrome . Lancet 2:12-16, bile salt orally 10 or by perfusion of the 1968 small intestine with deconjugated bile salt 5. Paulley JW: The jeunal mucosa in malabsorptive states with high bacterial counts. In Malabsorp· in vivo; these expermiments were accomtion . Edited by RH Girdwood, AN Smith. Pfizer panied by inhibitory effects on intestinal Monograph, University of Edinburgh Press, 1969 active transport. 11 • 12 These findings would p171- 176 seem to support the suggestion of Ament 6. Schiffer LM, Faloon WW, Chodos RB, et al: 7 and his colleagues that the changes are Malabsorption syndrome associated with intesti· caused by deconjugated bile salts, alnal diverticulosis. Gastroenterology 42:63-68, though other possibilities could be consid1962 ered. Bacterial invasion seems unlikely; it 7. Ament ME, Shimoda SS , Saunders DR, et a!: was found only rarely in Ament's 7 patients, Pathogenesis of steatorrhea in three cases of small and was not observed in this study. Bacteintestinal stasis syndrome. Gastroenterology 63:728-747, 1972 rial toxins isolated from patients with gas-
October 1974
ULTRASTRUCTURAL CHANGES IN BLIND-LOOP RATS
8. Gracey M , Burke V, Oshin A, et al: Bacteria, bile salts and intestinal monosaccharide malabsorption. Gut 12:683-692, 1971 9. Cameron DG, Watson GM, Witts LJ: The experimental production of macrocytic anaemia by operations on the intestinal tract. Blood 4:803-815, 1949 10. Gracey M , Papadimitriou J, Burke V, et al: Effects on small-intestinal function and structure induced by feeding a deconjugated bile salt. Gut 14:519-528, 1973 II. Gracey M , Burke V, Oshin A: The effect of bile
651
salts on intestinal sugar transport in vivo. Scand J Gastroenterol 6:273-276, 1971 12. Harries JT, Sladen GE: The effects of different bile salts on the absorption of fluid, electrolytes and monosaccharides in the small intestine of the rat in vivo. Gut 13:596-603, 1972 13. Gorbach SL, Khura na CM: Toxigenic Escherichia coli . A cause of infantile diarrhea in Chicago. N Eng! J M ed 287:791-795, 1972 14. Donaldson RM Jr: Role of enteric micro-organisms in malabsorption . Fed Proc 26:1426-1431 , 1967
GASTROENTEROLOGY 67:646- 651. 1974 Copyright © 1974 by Th e Willia ms & Wilkins Co.
ULTRASTRUCTURAL CHANGES IN THE SMALL INTESTINES OF RATS WITH SELF-FILLING BLIND LOOPS MICHAEL GRACEY, M .D. , F .R.A.C . P. , JOHN PAPADIMITRIOU, M . R.C . PATH. , AND GEOFFREY BowER, M . B . , M.R.A.C . P.
Gastroenterological Research Unit, Princess Margaret Children's Medical Research Foundation, and th e Department of Pathology , School of Medicin e, Univ ersity of W estern Australia , Perth, Western Australia
Ultrastructural abnormalities were found commonly in the small intestinal epithelium of a series of rats with surgically induced intestinal stasis, although the villous architecture and epithelial cell structure appeared normal by conventional light microscopy. The ultrastructural changes included variable degrees of distortion and denudation of microvilli, swelling, and vesiculation of mitochondria, accumulation oflipid droplets in the apical portions of enterocytes, and distortion of Golgi material. The changes were patchy, but occurred in approximately 10 to 35% of enterocytes examined from the midvillus region of these animals. It is suggested that these abnormalities may contribute to intestinal malabsorption which occurs as a consequence of bacterial contamination of the upper gut . It has been widely accepted that bacterial contamination of the upper gut is not accompanied by changes in villous architecture or epithelial cell structure, although infiltration of the underlying lamina propria by inflammatory cells is usual. 1' 4 Some authors , however, have noted histological abnormalities in patients with intestinal stasis 5 • 6 and have suggested that these might be of functional significiance .6 It might be anticipated that more detailed information about the structure of enterocytes could be obtained by electron microscopy, and two recent studies have shown evidence of ultrastructural damage in patients 7 and experimental animalss with bacterial overgrowth in the proximal gut . These two studies were very
limited . The clinical study 7 involved only 3 patients, while the experimental one s involved only 3 animals . In particular, the previous experimental investigation reported abnormalities only in the blind loops and jejunum distal to this . This study confirms and extends this earlier works in which ultrastructural damage in the small intestinal epithelium was found in rats with a self-filling jejunal blind loop, and supports the possibility that such changes may be pertinent to the production of malabsorption in the presence of chronic microbial contamination of the upper gut.
Materials and Methods
Adult Wistar rats, weighing 150 to 200 g, and bred from a long-established colony in the Received October 25, 1973. Accepted March 28, University of Western Australia, were used throughout . Under open ether anesthesia, a 1974. Address requests for reprints to: Dr. Michael segment of upper jejunum was selected, and a Gracey, Gastroenterological Research Unit, Princess self-filling blind loop approximately 8 em long Margaret Children's Medical Research Foundation, was constructed surgically using the technique described by Cameron et a!. 9 Intestinal continu· Perth, Western Australia . Dr. Gracey is the Adolph Basser Research Fellow of ity was maintained by making a side-to-end the Royal Australasian College of Physicians. anastomosis . Studies were performed in 6 con646
October 1974
ULTRASTRUCTURAL CHANGES IN BLIND-LOOP RATS
trol animals and 6 experimental animals which were housed and fed identically after recovery from operation. In control animals, duplicate specimens were obtained from jejunum approximately 20 to 25 em from the duodenojejunal junction; in the operated animals specimens were obtained, in duplicate, from (1) the blind loop, (2) jejunum 5 em proximal to the junction with the loop, and (3) jejunum 5 em distal to the loop. All specimens were coded, examined, and reported without knowledge of their origin. Light microscopy. Specimens for light-microscopic examination were fixed in formol-saline and carefully orientated before mounting and staining with hematoxylin and eosin. Scanning electron microscopy. Specimens were washed in buffered saline and then fixed in cold 3% glutaraldehyde in 0.1 M cacodylate buffer (pH 7 .4) for 16 to 18 hr. They were then washed in fresh buffer, dehydrated in graded solutions of ethanol, and allowed to dry in air. When dry, the specimens were coated, while on a rotating stage, with a layer of gold-palladium of approximately 40 to 50 /.LID in thickness. They were then placed on a JSM scanning electron microscope, tilted 45° to the scanning beam, and examined at an accelerating voltage of 25 kv. Micrographs were taken on Kodak Panatomic X film . Transmission electron microscopy. Specimens were fixed in cold 3% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) at 4 C for 16 to 18 hr. They were then postfixed in 1% osmium tetroxide in 0.1 M cacodylate buffer at 4 C for 1 hr, dehydrated in graded solutions of ethanol , and embedded in Araldite . Eight to 10 Araldite blocks were prepared and examined from each tissue sample. The embedded tissue was examined under a dissecting microscope and trimmed by hand. Particular care was taken to avoid the tips of villi and to select midzone areas of villi for inclusion in the final block face. Sections were cut on an LKB ultramicrotome stained with lead hydroxide, and examined on a JEM-T6 or a Philips 300 electron microscope .
Results Light microscopy. No abnormality of the villous architecture or epithelial cell structure was detected by light microscopy in mucosa from the blind loop or the proximal or distal jejunum of operated animals. There was, however, a moderate degree of infiltration of the lamina propria, particularly by plasma cells and lymphocytes, and some reduction in the villus to crypt ratio.
647
Mucus-secreting goblet cells were more numerous than normal, especially in tissue from the blind loops. Scanning electron microscopy. At low magnification, the morphological pattern of the epithelium from blind loop and proximal and distal gut revealed a predominantly "broad leaf" pattern indistinguishable from control specimens (fig. 1). Transmission electron microscopy. Structurally abnormal enterocytes were detected in all samples of mucosa from the blind loop animals . This was in contrast to the control animals in which abnormalities were only very occasionally found and occurred in 2 to 5% of cells. The distribution of lesions in the operated animals was patchy, and their frequency was variable in individual sections, occurring in 10 to 35% of cells. Lesions were more common in specimens from the blind loop rather than from afferent or efferent jejunum . However, significant abnormalities were found in each region and they were qualitatively similar. Representative lesions are shown in figures 2 to 5. Affected cells showed a variable degree of damage to the microvillous surface ranging from virtual denudation (fig. 2) to minor distortion of microvillous shape. Intermediate changes were common, especially blebbing of the luminal surface of enterocytes (fig. 3) and swelling and ballooningofthe microvilli (fig. 4). Abnormalities were more numerous closer to the apical sections rather than the basal sections. The terminal web region displayed some loss and disarrangement of fibrillar components (figs. 3 and 4). Mitochondria were swollen and numerous small vesicles were visible throughout the apical cytoplasm (fig. 4). Lipid droplets were common, particularly in the apical portion of the cyotplasm. Numerous electron-dense cells were seen in which there were few or distorted microvilli, swollen mitochondria, prominent, enlarged, and distorted Golgi material and apical nuclei (fig. 5). Only minimal changes were seen in cells in the intestinal crypts. Many contained apical centrioles, numerous electron-dense bodies, especially in the apical region of the
FIG. 1. Scanning electron micrograph of the epithelial surface of a blind jejunal loop. A normal " broad leaf' pattern of mucosal architecture is displayed ( x 160) .
FIG. 2. Transmission electron micrograph of the apical portion of an absorptive cell in the midzone of a villus in a blind jejunal loop. Loss of microvilli is obvious, and the few which are remaining are distorted and irregular. Numerous lipid droplets are visib le (arrows) ( x 16,400).
FIG. 3. Transmission electron micrograph of the ap ical surface of an enterocyte in the midzone of a villus in a blind jejunal loop. The surface of the enterocyte shows blebbing which has replaced the normal microvillar structure ( x 23, 160).
6-!8
.
.
FIG. 4. Transmission electron micrograph of the apical portion of an enterocyte in the midzone of a villus in a blind jejunal loop. The microvilli are swollen and ballooned . The enterocytic mitochondria are swollen and many vacuoles are present in the cytoplasm ( x 19, 700).
FIG. 5. Transmission electron micrograph of the apical portion of enterocytes in the midzone of a villus in a blind jejunal loop. Two enterocytes are electron-dense, possess few microvilli, and display swollen mitochondria, distorted Golgi material, and enlarged vesicles ( x 21,180). 649
650
GRACEY ET AL.
Vol. 67, No.4
cell, while the terminal web region was troenteritis have recently been shown to poorly formed and traversed by a loose have deleterious effects on intestinal funcmesh of numerous fine filaments . tion, 13 and it would seem possible that these substances may also cause ultraDiscussion structural effects. The possibility remains, This study indicates that ultrastructural of course, that several interrelated factors abnormalities occur in the small intestinal may operate simultaneously. epithelium as a result of bacterial contamiThe contribution of the ultrastructural nation of the upper gut, thus confirming abnormalities found in this study to the and extending recent experimental 8 and occurrence of diarrhea and intestinal malclinical studies. 7 In the present studies, absorption in patients with bacterial overextensive damage to microvillous and cyto- growth in the upper gut is uncertain. It plasmic portions of enterocytes was found seems likely that it is relevant to impaired in specimens of jejunum from rats with a carbohydrate absorption which occurs in self-filling jejunal blind loop, while light adults, 14 and more particularly , in infants .8 and scanning electron-microscopic appear- It is possible that a similar effect on water ances of the cells were essentially normal. and other small water-soluble molecules The changes were most numerous in tissue occurs . Ament et al. 7 have suggested that from the loop, but present and qualita- the ultrastructural lesions contribute to tively similar in jejunum proximal to and diarrhea by delaying the exit of chylomidistal from the loop. crons from damaged enterocytes. This conThe pathogenetic significance of these cept may be somewhat supported by the findings is obscure . Ament et al. 7 found findings in this study of many 1ipid dropultrastructural abnormalities in 3 patients lets in affected enterocytes. These possibilwith intestinal stasis and considered them ities require additional investigation . relevant to the production of intestinal malabsorption in the "contaminated REFERENCES small-bowel syndrome," and likely to be induced by the presence of excessive con- 1. Donaldson RM Jr: Studies on the pathogenesis of centrations of deconjugated bile salts in steatorrhoea in the blind loop syndrome. J Clin this situation. It is interesting that the Invest 44:1815-1825, 1965 degree of damage found in this study was 2. Paulk EA Jr, Farrar WE Jr: Diverticulosis of the small intestine and megaloblastic anemia. Am J most marked in the blind loop rather than Med 37:473- 480, 1964 afferent or efferent jejunum, since the concentration of intra! uminal deconjugated 3. Rubin CE, Dobbins WO III: Peroral biopsy of the small intestine. A review of its diagnostic usefulbile salts in highest in this region in this ness. Gastroenterology 49:676-697, 1965 experimental modeJ.B Furthermore, similar 4. Tabaqchali S, Hatzioannou J , Booth CC: Bileultrastructural changes can be induced salt deconjugation and steatorrhoea in patients experimentally by feeding a deconjugated with the stagnant-loop syndrome . Lancet 2:12-16, bile salt orally 10 or by perfusion of the 1968 small intestine with deconjugated bile salt 5. Paulley JW: The jeunal mucosa in malabsorptive states with high bacterial counts. In Malabsorp· in vivo; these expermiments were accomtion . Edited by RH Girdwood, AN Smith. Pfizer panied by inhibitory effects on intestinal Monograph, University of Edinburgh Press, 1969 active transport. 11 • 12 These findings would p171- 176 seem to support the suggestion of Ament 6. Schiffer LM, Faloon WW, Chodos RB, et al: 7 and his colleagues that the changes are Malabsorption syndrome associated with intesti· caused by deconjugated bile salts, alnal diverticulosis. Gastroenterology 42:63-68, though other possibilities could be consid1962 ered. Bacterial invasion seems unlikely; it 7. Ament ME, Shimoda SS , Saunders DR, et a!: was found only rarely in Ament's 7 patients, Pathogenesis of steatorrhea in three cases of small and was not observed in this study. Bacteintestinal stasis syndrome. Gastroenterology 63:728-747, 1972 rial toxins isolated from patients with gas-
October 1974
ULTRASTRUCTURAL CHANGES IN BLIND-LOOP RATS
8. Gracey M , Burke V, Oshin A, et al: Bacteria, bile salts and intestinal monosaccharide malabsorption. Gut 12:683-692, 1971 9. Cameron DG, Watson GM, Witts LJ: The experimental production of macrocytic anaemia by operations on the intestinal tract. Blood 4:803-815, 1949 10. Gracey M , Papadimitriou J, Burke V, et al: Effects on small-intestinal function and structure induced by feeding a deconjugated bile salt. Gut 14:519-528, 1973 II. Gracey M , Burke V, Oshin A: The effect of bile
651
salts on intestinal sugar transport in vivo. Scand J Gastroenterol 6:273-276, 1971 12. Harries JT, Sladen GE: The effects of different bile salts on the absorption of fluid, electrolytes and monosaccharides in the small intestine of the rat in vivo. Gut 13:596-603, 1972 13. Gorbach SL, Khura na CM: Toxigenic Escherichia coli . A cause of infantile diarrhea in Chicago. N Eng! J M ed 287:791-795, 1972 14. Donaldson RM Jr: Role of enteric micro-organisms in malabsorption . Fed Proc 26:1426-1431 , 1967