Use of microspheres to measure small intestinal villus blood flow in the dog.

The accuracy of using 7- to 10-micron microspheres to measure blood flow to dog small intestinal villi was studied. These spheres appear to pass unimpeded through the afferent arterioles of the villus and lodge at the villus tip because 1) virtually all villus spheres were located at the tip, 2) flow determined by visually counting spheres did not differ significantly from flow determined from radioactivity of the sheared-off villus layer, 3) the size distribution of spheres in the villus and subvillus layers was virtually identical to that administered, indicating no premature impaction of the larger spheres, and 4) spheres lodging in the submucosa during vasoconstriction did not subsequently migrate to the villi during vasodilatation. Studies with 25-micron spheres indicated that 28% of the 7- to 10-micron spheres shunted through vessels greater than 10 micron. Double isotope studies showed that lodges spheres do not migrate and that the injection of 2--4 X 10(6) spheres does not alter villus flow. Thus, 7- to 10-micron microspheres pass to and lodge in villus vessels in proportion to capillary flow and should provide an accurate estimate of villus nutrient blood flow.     

Morphogenesis of fetal rat duodenal villi

To study the structural features of fetal rat duodenal mucosa associated with histogenesis of villi, duodena from 15- to 19-day fetuses were examined by light and electron microscopy. The duodenal epithelium of 15-to 18-day fetuses was stratified. Distinctive junctional complexes associated with membrane-bounded vesicles and cilia-like structures were seen in the deeper epithelial layers at 15 and 16 days. Small lumina, designated “secondary lumina,” lined with a variable number of microvilli developed between epithelial cells at these junctional complexes during the sixteenth through eighteenth days. Degenerative changes and exfoliation of superficial epithelial cells were obvious in 17- and 18-day fetuses. In 18-day fetuses, aggregates of mesenchyme had invaginated the basal aspect of the stratified epithelium. Concomitantly, the number of epithelial layers overlying these mesenchymal projections was decreased. In 19-day fetuses, well formed, short duodenal villi lined by a simple columnar epithelium which included goblet and endocrine cells were evident. Injection of ferritin into the main duodenal lumen of 17-day fetuses failed to reveal continuity between the main lumen and the secondary lumina. However, continuity between many secondary lumina and the main lumen was demonstrated in 18-day fetuses. Thus, major morphological features associated with villus formation in fetal rat duodenum include: (1) formation of many secondary lumina in primitive stratified epithelium, (2) eventual fusion of these lumina with the main duodenal lumen, by their continued growth coupled with exfoliation of degenerating superficial layers and (3) upward growth of mesenchyme towards the lumen as cell exfoliation and expansion of secondary lumina take place.     

Factors influencing villus size in the small intestine of adult rats as revealed by transposition of intestinal segments

As an index of villus size, the number of epithelial cells per representative villus section was counted in longitudinal sections of the rat small intestine. Villus size was found to decrease gradually along the length of the small intestine, with villi being nearly three times as large in upper duodcnum as in terminal ileum. The influence of various surgical operations on villus size was then examined. In ileal segments inserted into the jejunum, villi enlarged to the size of local jejunal villi. In jejunal segments inserted into the ileum, villi decreased almost to the size of local ileal villi. Thus, villus size was influenced by the environment, that is, most probably by the different types of chyme in jejunum and ileum. In duodenal segments inserted into the ileum, villi did not decrease in size, and distally located ileal villi enlarged. This and other experiments indicated that the duodenum produced secretions which not only neutralized the villus-reducing effect of the ileal environment, but also exerted a potent villus-enlarging effect. Pyloric secretions had a similar villus-enlarging effect. Segments of intestine were made into blind sacs by closing their proximal end and joining their distal end to the colon, so as to remove the influence of the chyme. Villus size decreased in sacs of jejunum and lower duodenum (without the duodenal papilla), but increased in sacs of ileum. Thus in the three types of sacs, there was a tendency for villi to acquire an intermediate size. In conclusion, an intermediate villus size, which is postulated to exist in chyme-free, non-functional intestine, would normally be modified by two types of factors: villusenlarging factors present mainly in pyloric and duodenal secretions, and villus-reducting factors present in the ileal chyme. Interaction between these factors would result in the gradient of villus size along the small intestine.     

Structural and cellular adaptation of duodenal iron uptake in rats maintained on an iron-deficient diet

Iron deficiency induced in rats maintained on a commercial diet with a low iron content has been used to investigate adaptive mechanisms that enhance duodenal iron uptake. These adaptive changes have been divided into those that result from changes in villus surface area (structural adaptation) and those that reflect changes in the way individual enterocytes express iron transport function (cellular adaptation). Cellular adaptation was assessed by carrying out microdensitometry of autoradiographs prepared from duodenal tissue previously incubated for 5 min in 200 micromol/l 59Fe2+-ascorbate. Structural adaptation was studied by performing image analysis of microdissected and sectioned villi. Cellular adaptation involved increased iron uptake by enterocytes present in the lower villus. Thus iron deficiency resulted in a threefold enhanced expression of uptake in the lower 100 microm villus (3.9+/-2.4 versus 12.6+/-1.5 arbitrary units, P<0.001). Maximal uptake was reached in the upper region of both control and iron-deficient villi, but iron deficiency had no effect on cellular uptake at this part of the villus. Structural adaptation involved the lengthening (+16%, P<0.05) and broadening (+14%) of villi in the duodenum of iron-deficient rats. The resultant expansion in villus area caused a further increase in uptake that was mostly expressed in the upper villus. Maximal uptake corrected for structure occurred in the middle third of villi from control and iron-deficient rats. Cellular plus structural adaptation produced a twofold increase in iron uptake. More than half of this effect was caused by changes in villus structure. [3H]Thymidine labelling experiments revealed a slightly earlier expression of enterocyte iron uptake in iron deficiency.     

Morphological effects of a large single dose of cycloheximide on the intestinal epithelium of the rat

Adult male rats received 15 mg/kg cycloheximide and the subsequent morphological effects at three and six hours after injection were evaluated using histometry, light and electron microscopy, histological demonstration of terminal web and acid phosphatase, and radioautography with tritiated thymidine. Rapid atrophy of the villi took place, progressing from the villus tip by premature exfoliation of epithelial cells. The crypts also diminished by random exfoliation of many crypt cells and by partial or complete disintegration. Mitosis and epithelial cell migration were absent. By six hours, the area occupied by the villi and the crypts per unit length of histological section was decreased by about 70–90% in most of the small intestine but only by about 40–60% in the duodenum and the terminal ileum. In the upper half of the villi, the epithelium was strongly positive for acid phosphatase and contained large numbers of round bodies resembling primary lysosomes. In the lower half, the microvillous border and terminal web were found to be disrupted. Animals receiving only 5 mg/kg cycloheximide also showed the atrophy of villi and crypts, and the round bodies resembling lysosomes. Evidence from several sources has indicated that protein synthesis in normal villus epithelial cells subsides toward the villus tip and becomes minimal at exfoliation. At exfoliation, proteins responsible for epithelial cohesion probably fail because they are no longer replenished. Cycloheximide appears to accelerate this process.     

Stereomicroscopic and ultrastructural characterization of propionitrile-induced duodenal ulcer in the rat

Acute duodenal ulcer produced by subcutaneous injection of propionitrile in rats was studied by stereo, light, and electron microscopy in order to gain insight into the localization and mechanism of initial cell injury. Stereomicroscopy revealed an initial fissuring and splitting of the tips of the villus folds within 4 hours after two injections of propionitrile. This was followed by sloughing of the epithelium, shortening and effacement of the villus folds, and within 24 hours the appearance of discrete ulcers in the mucosa of the proximal duodenum. In most of the rats, two ulcers developed: the first and larger ulcer was on the antimesenteric side of the duodenum, and the other, a small and more superficial one, was on the opposite wall. Ultrastructural lesions appeared in the absorptive epithelial cells of the proximal duodenum within 5 hours following a single dose of propionitrile. The cytoplasmic changes of cellular injury were preceded and/or accompanied by beading and loss of microvilli. The initiation of propionitrile-induced alterations at the tip of the villi in the proximal duodenum suggests that the ulcerogenic agent acts from the luminal side of the duodenum and probably originates from the stomach.     

Microangioarchitecture of the guinea pig common bile duct and duodenal papilla: A scanning electron and light microscopic study

Background: The microvascular pattern of the duodenal papilla is unknown. Since the duodenal papilla is located in the transition zone between the stomach and duodenum, and because it regulates bile transfer into the duodenum, a particular microangioarchitecture can be expected. Therefore, we examined the microvasculature of the papilla using guinea pigs as a model. Methods: The microvascularization of the duodenal papilla and common bile duct was studied in 26 adult guinea pigs (Cavia porcellus), using scanning electron microscopy of microvascular corrosion casts and critical point dried specimens, and light microscopy of tissue sections. Results: The duodenal papilla is located in the cranial portion of the duodenum, approximately 5 mm beyond the pyloric valve. At the most luminal aspect of the cast papilla, ring-shaped capillaries, resembling those of the cast gastric mucosa, are present. Deeper parts of the papilla are provided with villi. Subepithelial capillaries of the papilla are 15 μm thick in average. These capillaries have a dual blood supply either via the straight long arterioles arising from the submucosa or by the pericryptal capillaries. The common bile duct comprises numerous mucoid glands with their pits surrounded by ring-shaped capillaries in corresponding casts. Conclusions: The special arrangement of different capillary patterns, together with their luminal size and the dual blood supply, favor their protective role from the gastric chyme. © 1994 Wiley-Liss, Inc.     

Influence of bile and pancreatic secretions on the size of the intestinal villi in the rat

Along the rat small intestine, the size of the villi gradually decreases from a maximum in the duodenum to less than half of this size in the terminal ileum. In previous work, various villus enlarging and reducing factors present in the intestinal chyme were found to control villus size. A villus enlarging factor which appeared to reach the intestine through the duodenal papilla was presently investigated. Transplants of duodenal papilla, together with a small segment of the duodenum, were made to isolated ileal segments and to the lower ileum. At both sites, the transplants elicited a marked villus enlargement within a month. A previous finding was that villus size decreased in isolated duodenal segments unless the duodenal papilla was present. In the next experiments, the bile-drainage was diverted from the duodenal papilla by implanting the bile duct into an isolated ileal segment which in turn was joined to the colon. The duodenal papilla which now transmitted only pancreatic secretions was then transplanted to the ileum. The bile caused only moderate villus enlargement in the ileal segments whereas marked villus enlargement took place in the ileum receiving the pancreatic secretions. It was concluded that a villus enlarging influence reached the intestine through the duodenal papilla. The pancreatic secretions appeared to play a major role in this influence.     

Laser-Doppler measurements of concentration and velocity of moving blood cells in rat cerebral circulation

In brain cortex all capillaries are perfused with plasma at anyone time while the flow of blood cells is heterogenous. Increased blood flow is associated with increased number of moving erythrocytes in the microcirculation, while capillary recruitment in its classical anatomical sense appears not to exist in the brain. Modulation of the concentration of flowing erythrocytes may influence the oxygen supply to the tissue. Therefore, we examined the possibility that laser-Doppler flowmetry (LDF) could be used to quantify changes in the microvascular concentration of moving blood cells (CMBC) and blood cell velocity (< v >) by comparing LDF measurements with electromagnetic flow measurements in vitro, and confocal laser-scanning microscopy in vivo in the brain of anaesthetized male Wistar rats. In vitro measurements showed that CMBC was affected by changes in haematocrit, while < v > correlated almost linearly with blood cell velocity measured electromagnetically within a relevant physiological range. In vivo studies during hypercapnia (Paco ₂ from 39 ± 4 to 66 ± 5 mmHg) with confocal laser scanning microscopy disclosed a 39 ± 10% increase of cortical capillary erythrocytes, while CMBC measured with LDF increased by 37 ± 5%. Erythrocyte flow velocity in brain cortex capillaries increased by 65 ± 17% with confocal microscopy as compared to 72 ± 8% with LDF. Local electrical stimulation of cerebellar cortex, and application of adenosine or sodium-nitroprusside, increased CMBC and < v > simultaneously, while during hypercapnia the < v > increase preceded the CMBC increase by 30 s. The CMBC rise rapidly reached a steady state in response to all types of stimulation, while < v > continued to increase during the major part, or the entire stimulation period. In conclusion, our data support the hypothesis that LDF may be useful for haemodynamic studies of brain microcirculation.     

Methionine accumulation in villi isolated from maturing rat intestine

1. This study compares the absorption rates of methionine in 15-day-old rats (preweaned) and 30-day-old rats (post-weaned), and the effect of varying initial substrate concentration on the absorption rate of methionine in tissue removed from specific sites in the small intestine.2. The experiments utilize a new in vitro method, the villus technique, permitting evaluation of the mucosal (villus) absorptive cells separated from the relatively non-transporting muscle and connective tissue components (non-villus tissue).3. When the villus technique was used in a comparative age study of absorption by jejunal and duodenal tissue, it was found that at initial methionine concentrations below 1.0 mM, no difference in the transport rate between preweaned and post-weaned animals was observed.4. However, in preweaned animals, methionine transport is faster in the ileum than in the jejunum or duodenum.5. With initial methionine concentration greater than 1.0 mM, duodenal and jejunal villi from preweaned animals transport methionine better than villi from older animals.6. At these higher methionine concentrations there is a slightly better transport by ileal villi from 30-day-old rats than in the younger group.7. With increasing initial concentration of methionine, physiological changes are shown to occur during maturation because transport rates into villi of mature duodenal and jejunal tissues are slower than into similar tissue from preweaned rats.8. The underlying physiological changes responsible for the transport rate differences are not known.9. The results reported indicate that following maturation, the absorbing mucosal cells from the duodenum, jejunum and ileum have an equal capacity for methionine accumulation.10. The apparent localization of the major amino acid transport to the ileum as reported by others may be an artifact reflecting the inclusion of an undetermined amount of non-absorbing muscle mass in the calculation of intestinal transport.     

丹参对胃和十二指肠粘膜微循环血流和胃液分泌的影响

采用幽门结扎灌流法及氢气清除技术连续动态地观察了丹参注入前后,大鼠胃液分泌量、胃总酸度和胃及十二指肠粘膜血流量的改变,以深入探讨丹参的抗消化性溃疡,保护胃肠粘膜的作用机制。结果表明:丹参注入后40min左右,胃泌素刺激引起的胃液分泌亢进和胃酸排出增多均受到明显的抑制,效应持续120min以上;丹参注入20min左右,胃体和十二指肠粘膜的血流量分别增加了29.8%和43.7%(P<0.01)。在胃泌素引起最大胃液分泌亢进的同时,可伴有粘膜血流增多的趋势,但无统计学意义;上述结果提示,丹参能减少胃液的分泌和H~+的分泌,但其对胃肠粘膜的保护作用主要是借助改善粘膜的血液灌流而完成的。     

Milk lipid absorption and chylomicron production in the suckling rat

Structural correlates of milk lipid absorption and chylomicron production were studied in 10-day-old suckled rats. The gastric and duodenal contents and duodenal mucosae were examined with the light and electron microscopes. In the gastric lumen the milk lipid globule cores were smooth, circular and uniformly electron opaque. Many membranes and lamellar structures with a trilaminar and multilamellar appearance were adherent to the peripheries of the cores. In the central duodenal lumen the milk lipid globule cores were also smooth, circular and uniformly electron opaque. Very few milk lipid globules in the duodenal lumen showed adherent membranes or lamellae. Membrane fragments and lamellae were present in the lumen separate from the milk lipid globules. In the duodenal lumen between villi the milk lipid globules had multiple electron lucent indentations of the core. It is believed that the irregular peripheries of the milk lipid globule cores are the result of lipolysis within the duodenal lumen acting at the milk lipid globule surface. This lipolysis of triacylglycerol would produce amphiphilic lipids which may result in the electron lucent spaces at the milk lipid globule periphery. The absorptive epithelial cells along the length of the duodenal villus varied in structure relative to their position at the tip, middle, or base of the villus. Typical mid-villus epithelial cells contained lipid droplets averaging 0.3-μm diameter in the smooth and rough endoplasmic reticulum and in Golgi complexes in the apical cytoplasm. Villus tip and villus base cells contained large lipid droplets between 7–16 μm. Only a few 0.3-μm lipid droplets were present within these cells. These large lipid droplets appeared to be accumulations of triacylglycerol present in the apical cytoplasm associated with lamellar and membranous structures. Numerous chylomicrons were present between epithelial cells located in the middle region of the villus while significantly fewer chylomicrons were seen between epithelial cells at the tip and base of the villus. These observations suggest that the cells at the middle of the duodenal villus of suckling rats were more efficient in the production of chylomicron triacylglycerol derived from incoming milk triacylglycerol than cells at the tip and base of the villus.     

Role of villus microcirculation in intestinal absorption of glucose: coupling of epithelial with endothelial transport

Capillaries in jejunal villi can absorb nutrients at rates several hundred times greater (per gram tissue) than capillaries in other tissues, including contracting skeletal muscle and brain. We here present an integrative hypothesis to account for these exceptionally large trans-endothelial fluxes and their relation to epithelial transport. Equations are developed for estimating concentration gradients of glucose across villus capillary walls, along paracellular channels and across subjunctional lateral membranes of absorptive cells. High concentrations of glucose discharged across lateral membranes to subjunctional intercellular spaces are delivered to abluminal surfaces of villus capillaries by convection-diffusion in intercellular channels without significant loss of concentration. Post-junctional paracellular transport thus provides the series link between epithelial and endothelial transport and makes possible the large trans-endothelial concentration gradients required for absorption to blood. Our analysis demonstrates that increases of villus capillary blood flow and permeability-surface area product (PS) are essential components of absorptive mechanisms: epithelial transport of normal digestive loads could not be sustained without concomitant increases in capillary blood flow and PS. The low rates of intestinal absorption found in anaesthetised animals may be attributed to inhibition of normal villus microvascular responses to epithelial transport.     

Milk lipid absorption and chylomicron production in the suckling rat.

Structural correlates of milk lipid absorption and chylomicron production were studied in 10-day-old suckled rats. The gastric and duodenal contents and duodenal mucosae were examined with the light and electron microscopes. In the gastric lumen the milk lipid globule cores were smooth, circular and uniformly electron opaque. Many membranes and lamellar structures with a trilaminar and multilamellar appearance were adherent to the peripheries of the cores. In the central duodenal lumen the milk lipid globule cores were also smooth, circular and uniformly electron opaque. Very few milk lipid globules in the duodenal lumen showed adherent membranes or lamellae. Membrane fragments and lamellae were present in the lumen separate from the milk lipid globules. In the duodenal lumen between villi the milk lipid globules had multiple electron lucent indentations of the core. It is believed that the irregular peripheries of the milk lipid globule cores are the result of lipolysis within the duodenal lumen acting at the milk lipid globule surface. This lipolysis of triacylglycerol would produce amphiphilic lipids which may result in the electron lucent spaces at the milk lipid globule periphery. The absorptive epithelial cells along the length of the duodenal villus varied in structure relative to their position at the tip, middle, or base of the villus. Typical mid-villus epithelial cells contained lipid droplets averaging 0.3-micrometer diameter in the smooth and rough endoplasmic reticulum and in Golgi complexes in the apical cytoplasm. Villus tip and villus base cells contained large lipid droplets between 7-16 micrometers. Only a few 0.3-micrometer lipid droplets were present within these cells. These large lipid droplets appeared to be accumulations of triacylglycerol present in the apical cytoplasm associated with lamellar and membranous structures. Numerous chylomicrons were present between epithelial cells located in the middle region of the villus while significantly fewer chylomicrons were seen between epithelial cells at the tip and base of the villus. These observations suggest that the cells at the middle of the duodenal villus of suckling rats were more efficient in the production of chylomicron triacylglycerol derived from incoming milk triacylglycerol than cells at the tip and base of the villus.     

Differences in the development of jejunum and ileum as observed in fetal rat intestinal isografts. Possible implications related to the villus size gradient

Previous studies have shown that villus size in the small intestine decreases from the duodenum toward the ileum. Villus-enlarging and villus-reducing factors have been found in the gastric, pancreatic, and duodenal secretions, and in bile (Altmann and Leblond, ′70; Altmann, ′74). We here explore the role of intrinsic factors present in the individual sections of the small intestine by following the development of villus height in fetal (21-day old) jejunal and ileal segments implanted under the kidney capsule of syngeneic adult rats. Twenty-eight and 45 days after implantation, the jejunal villi contained significantly more columnar epithelial cells than did the ileal villi, but the jejunoileal gradient was even greater in small intestine of corresponding ages, developing in situ. Our experiments, thus, show that the jejunoileal gradient is already programmed in rats 1 day before birth, while other factors contribute postnatally to regulation of its magnitude.     

Placental development in the mongolian gerbil (Meriones unguiculatus). II. From the establishment of the labyrinth to term

Placental development was studied in 24 gerbils from day 13 to term. Allantoic mesoderm contacts and vascularizes the chorionic-trager plate of germinal cytotrophoblast on day 13. Soon villous extensions penetrate the plate, carrying with them a covering of three layers of trophoblast derived from it. As the villi elongate, clumps of germinal cytotrophoblast are carried peripherally by them. Further development of each villus results in a cylindrical mesenchymal core with a central arteriole, and radially arranged branching lamellar extensions carrying capillaries derived from the villus arteriole. Germinal cytotrophblast clusters disappear near term, but some indication always remains of the trilaminar covering of the villus and its lamellae. A typical countercurrent blood flow pattern occurs. The trophospongium is derived from the ectoplacental cone and the mesometrial surface of the germinal cytotrophoblastic plate. Although a few clusters of small cells occur, it is essentially a giant cell trophospongium and never contains cells resembling the clear cells of the rat. Late in pregnancy it becomes much reduced in thickness. The unique subplacental gland begins to degenerate soon after placental establishment and is gone by the last half of pregnancy. The metrial gland begins development at midterm and becomes a solid mass of cells filling the perivascular space of the mesometrial triangle at term.     

Intestinal villus blood flow measured with carbon monoxide and microspheres.

The purpose of the present study was to compare the small intestinal blood flow that equilibrates with luminal CO (FLco) with simultaneous determinations of villus blood flow measured by a recent modification of the microsphere technique. These studies, carried out in rabbits, showed that FLco closely correlated (r = 0.83) with villus flow measured with microspheres over a three-fold range of flows, and the mean rate of flow to the villi by both techniques was about 0.08 ml/min X g of intestine. Thus, FLco appears to be a measure of villus blood flow. Based on previous studies of inert gas uptake from the rabbit small intestine, it appears that absorption of readily diffusible substances in the rabbit can be represented by a simple two-component model: a flow-limited component in which substances equilibrate with villus blood flow and are carried away without subsequent countercurrent exchange, and a diffusion-limited component which presumably represents uptake by the blood flow of the crypt region or submucosa.     

Developmental changes in rhesus monkey placental villi and cell columns

Summary Developing rhesus monkey placentas were analyzed by scanning electron microscopy with special attention directed toward defining stages in the development of the villus branches. The initial phase in formation of villi was the conversion of reticulated trabeculae of syncytial trophoblast into chorionic villi by growth and proliferation of cell columns of cytotrophoblast. These villi were stout and unbranched. The second phase of development appeared to be the longitudinal splitting of the villi and cell columns to form groups of parallel branches but there was a common insertion of these into the basal plate. The third phase in formation of villi, which appeared to begin at about the same time as the longitudinal splitting occurred, was the outgrowth of largediameter side branches in a zone nearer the chorionic plate. At about 38–40 days of gestation the next stage in villus formation occurred, characterized by the emergence of numerous, small syncytial sprouts. Continued proliferation of villi at later stages of gestation resulted in a decreased diameter of the terminal villi and an increasing complexity in the course of fetal capillaries.     

Carbonic anhydrase in the normal rat stomach and duodenum and after treatment with omeprazole and ranitidine

A low pH in the lumen of the stomach and duodenum stimulates gastroduodenal mucosal secretion of bicarbonate, particularly in the duodenum. Long-term deprivation of this acid stimulus might affect the ability of the mucosa to secrete bicarbonate, with a consequent decrease in mucosal protection against the acid. This could occur by 'down-regulation' of carbonic anhydrase (CA) activity in the bicarbonate-transporting cells. Levels of CA activity and amounts of CA isoenzymes in rat gastric and duodenal mucosa were determined by biochemical assay and histochemical and immunohistochemical staining. Control animals and animals pre-treated for 4-6 weeks with the histamine H2-receptor antagonist ranitidine (600 mg kg-1 daily) or the H+,K+-ATPase inhibitor omeprazole (28 mg kg-1 daily) were examined. Both drugs are potent inhibitors of gastric secretion of acid. Both gastric and duodenal mucosal total CA activity and the distribution of isoenzymes were very similar in control animals and animals treated with these drugs. In the stomach, CA II was found in the surface epithelial and parietal cells. In the duodenum both CA I and CA II were observed. The staining for CA I was restricted to a small number of villus cells which looked like ordinary duodenal enterocytes. CA II in the duodenum was found in all villus cells, except the goblet cells. The staining decreased gradually from the top to the bottom of the villi and was absent in the crypts. Duodenal bicarbonate secretion is dependent on mucosal CA activity, and the distribution of CA II thus suggests that this alkaline secretion is of villous rather than cryptal origin.     

Measurements of intestinal villi non-specific and ulcer-associated duodenitis-correlation between area of microdissected villus and villus epithelial cell count.

Measurements of villus height, villus area, together with counts of epithelial cells in individual villi, were performed on endoscopic duodenal biopsies from five groups of patients: controls, ulcer-associated duodenitis, mild and severe non-specific (non-ulcerative) duodenitis, cimetidine healed ulcer-associated duodenitis and cimetidine healed non-specific duodenitis. The objectives of the study were two-fold: to establish if epithelial cell count correlated with simpler measurements of villus height or area; and to compare the findings in ulcer-associated and in non-specific duodenitis. Villus area correlated well with epithelial cell count per villus (r = 0.96); villus height correlated less well (r = 0.66). When compared with controls, there was a significant decrease in the epithelial cell count per villus in ulcer-associated and severe non-specific duodenitis, but this was confined to the visually inflamed area of the duodenal bulb. After healing of inflammation with cimetidine villus height, area, and epithelial cell count returned to values similar to those in controls. This study confirms that the effects of ulcer-associated and severe non-specific duodenitis on duodenal villi are identical.