Lower Ileum Research Articles

Bacteria isolated from the duodenum, ileum, and cecum of young chicks.

Facultatively anaerobic and strictly anaerobic bacteria colonizing the intestinal tracts of 14-day-old chicks fed a corn-based diet were enumerated, isolated, and identified. Colony counts from anaerobic roll tubes (rumen fluid medium) or aerobic plates (brain heart infusion agar) recovered from homogenates of the duodenum, upper and lower ileum, and cecum varied appreciably among samples from individual birds. Anaerobic and aerobic counts from the duodenum and ileum were similar. Anaerobic counts were highest from the cecum (0.7 X 10(11) to 1.6 X 10(11)/g of dry tissue) and exceeded aerobic plate counts by a factor of at least 10(2). Facultatively anaerobic groups (Streptococcus, Staphylococcus, Lactobacillus, and Escherichia coli) comprised the predominant flora of the duodenum and ileum, although large numbers of anaerobes (9 to 39% of the small intestine isolates), represented by species of Eubacterium, Propionibacterium, Clostridium, Gemmiger, and Fusobacterium, were also recovered. Strict anaerobes (anaerobic gram-positive cocci, Eubacterium, Clostridium Gemmiger, Fusobacterium, and Bacteriodes) made up nearly the entire microbial population of the cecum. Scanning electron microscopy of the intestinal epithelia of chicks revealed populations of microbes on the duodenal, ileal, and cecal mucosal surfaces.

Proposed Life Cycle of Eimeria Zuernii

SUMMARY Ten bull calves, three months old or less, were infected with oocysts of Eimeria zuernii. At post-mortem examination large schizonts were found in the lower ileum and small schizonts were present in the colon and caecum. Gametogony occurred in the colon and caecum. The life cycle of E. zuernii apparently contains at least two schizogonous generations before gametogony.

Protohemin in bile during primate development

Protohemin is excreted in biles of primate fetuses and premature newborns. It also was found in relatively large quantities in the lower ileum and mesenteric lymph-nodes of newborn primates.

Distribution of small bowel tumors

We have studied the anatomic distribution of 784 small bowel carcinomas and have analyzed available epidemiologic data to determine the relation of these rare cancers to other gastrointestinal tumors and to diet. The anatomic distribution of small bowel cancer in unusual: most tumors occur in the duodenum or proximal jejunum, relatively few tumors occur in the central bowel, and only in the lower ileum do the expected number of tumors appear. Review of available epidemiologic data shows a correlation between small bowel cancer and lower, but not upper gastrointestinal cancer. The incidence of small bowel cancer is positively correlated with protein and fat consumption.

Molybdate and tungstate transfer by rat ileum competitive inhibition by sulphate

For both MoO 4 2− and WO 4 2− the maximum rate of uptake by the small intestine of the rat (studied in vitro using the everted sac technique) occurs in the lower ileum. Kinetic constants, derived by a least squares procedure, are compared with those previously obtained for SO 4 2− transport. For both V and K a , SO 4 2− > MoO 4 2− > WO 4 2− , with only small differences between sacs IV and V. Mutual inhibition of MoO 4 2− and WO 4 2− transport and inhibition of both by SO 4 2− are competitive processes. This is shown by the generally good agreement between K a values and derived K i values and by V values in the presence and absence of the inhibiting species. The three ions SO 4 2−, MoO 4 2− and WO 4 2− are probably transferred across the intestine by a common carrier system. Implications for the sulphate-molybdenum interaction in molybdosis are discussed.

Effects of Diets Containing Dried Whey on the Lactase Activity of the Small Intestinal Mucosa and the Contents of the Small Intestine and Cecum of the Pig

Two studies were conducted to establish the effects of dietary lactose supplied from dried whey on the lactase activity in the contents of the small intestine and cecum as well as the mucosa of the small intestine. In the first study, feeding 0, 10, 25, or 40% dried whey for 120 days did not alter the mucosal lactase specific activity (mumoles galactose released/mg protein) in the duodenum, upper jejunum, or lower ileum. In the second study, total lactase activity in the small intestine was estimated from the total activity found in 10-cm segments of each meter of small intestine. Feeding a diet containing 40% whey continuously from weaning at 5 weeks of age or from 12 weeks of age did not alter the total lactase activity of pigs killed at 21 weeks of age. Dietary lactose tended to increase the lactase activity in the contents of the cecum and small intestine, but the increases were not always statistically significant. In the second study, Chester White pigs had approximately threefold greater mucosal lactase activities than that of Hampshires. These two breeds may be suitable models for detailed studies into the relationships between lactase deficiency and lactose intolerance.

Effect of Soy Sterols on Intestinal Absorption and Secretion of Cholesterol and Bile Acids in the Chick

Twenty-day-old chicks were fed for 7 days a diet containing 0.5% cholesterol, with or without \% soy sterols. During the last 4 days, yttrium-91 was in cluded in the diet to serve as a nonabsorbable reference substance for the determination of rates of net absorption and secretion of cholesterol and bile acids. Dietary soy sterols reduced the size of the liver plasma cholesterol pool, decreased the daily net absorption of both cholesterol and bile acids between the duodenum and lower jejunum and also depressed their daily endogenous secretion into the duodenum. In addition, soy sterols exerted a marked inhibitory action on the absorption of steroids between the lower jejunum and the lower ileum. The reduced ileal absorption accounted entirely for the effect of soy sterols on the overall net absorption of cholesterol, which dropped from 22% in the cholesterol group to 6% in the group receiving soy sterols. Overall net absorption was less for phytosterols than for cholesterol, campesterol being taken up to a greater extent than stigmasterol and AŸ-sitosterol. J. Nutr. 104: 1086-1090, 1974.

On Some Anoplocephaline Cestodes from Pikas, Ochotona spp. (Lagomorpha), in Nepal, with the Description of Ectopocephalium abei gen. et sp. n.

Three species of anoplocephaline cestodes, Anoplocephalinae gen. et sp. indet., Schizorchis cf. altaica Gvozdev, 1951, and Ectopocephalium abei gen. et sp. n., are reported from pikas, Ochotona roylei (Ogilby) and 0. macrotis (Giinther), from central Nepal. The taxonomic status of Schizorchis esarsi Lovekar et al., 1972, and of Schizorchodes dipodomi Bienek and Grundmann, 1972, is discussed, with the conclusion that both species belong in the subfamily Linstowiinae, near the genus Atriotaenia Sandground, 1926. Ectopocephalium gen. n. is distinguished from other genera in the subfamily Anoplocephalinae by the modified anterior portion of the strobila, which is embedded in the tissue of the sacculus rotundus (lower ileum) of the host, and by the arrangement of the genital organs. The attachment of E. abei and the consequent tissue response are described, and the zoogeography of cestodes in pikas is briefly discussed. During March-July 1968, a biological survey of Nepal was undertaken by an expedition from the University of Hokkaido, with support of the Hokkaido University Himalayan Committee. The objectives included an investigation of the small mammals of the region, under the direction of Dr. Hisashi Abe, of Hokkaido University, who kindly made available to us a large series of preserved carcasses for parasitological examination. Information concerning the taxonomy and ecology of these mammals has been published by Abe (1971). Among the preserved materials was a series of pikas, Ochotona spp., from which we obtained anoplocephaline cestodes representing three species. One of these exhibited a combination of characters that was unlike any within the genera recognized in the subfamily Anoplocephalinae. The results of the study of these cestodes are reported in the present

Coccidiosis of Lambs. III. The Reaction of the Small Intestinal Mucosa to Experimental Infections with E. arloingi “B” and E. crandallis

SUMMARY Experimental coccidia-free lambs were infected with pure cultures of E. arloingi “B” and E. crandallis. The infections gave rise to a tissue reaction in the upper and lower ileum respectively. A lesion similar to that of the “flat mucosa” was produced in areas of the intestine which had a high density of parasites. A similar reaction, without any overt mucosal surface changes, was produced in areas of low parasite density. The two species of coccidia together successfully colonized the whole length of the small intestine, and the results are discussed in relation to observations in field lambs and other experimental coccidial infections of lambs and chickens.

Postprandial concentrations of free and conjugated bile acids down the length of the normal human small intestine.

Small intestinal samples were obtained by intubation from multiple sites along the small intestine in 11 subjects with no known gastrointestinal disease eating a normal diet and at laparotomy in a further three subjects. Free (unconjugated) bile acids were consistently demonstrated in ileal samples, and occasionally in lower jejunal samples, by thin-layer chromatography, supplemented in some cases by gas/liquid chromatography and by infrared spectroscopy. The free bile acid concentration, measured enzymically following thin-layer chromatography, reached a maximum (1 mM) in the lower ileum, where it represented half the total bile acid concentration. Following ampicillin, the concentration of free bile acids decreased markedly, suggesting that they resulted from bacterial deconjugation; at the same time the total bile acid concentration increased, suggesting impaired absorption due to the reduced concentration of the more rapidly absorbed free bile acids. Our results indicate that the presence of free bile acids in lower jejunal and ileal samples is a normal finding, and cannot be taken as evidence of abnormal bacterial overgrowth. They also suggest that bacterial deconjugation at these sites may be a factor contributing to the remarkable efficiency of bile salt reabsorption.

Ontogeny of the Bovine Immune Response

The ontogenesis of the bovine immune response was studied in three embryos (<40 days) and 106 fetuses of various ages. In the absence of overt antigenic stimulation, fetuses had lymphoid development of the thymus at 42 days of gestation, the spleen was structurally present at 55 days, and certain peripheral lymph nodes were present at 60 days. Mesenteric lymph nodes were structurally present by 100 days of gestation, and lymphoid tissue of the gastrointestinal tract, particularly the lower ileum, was observed in histologic sections of a 175-day fetus with a bacterial infection. Pyroninophilic cells, plasma cells, and germinal centers were present in lymph node sections of antigenically stimulated fetuses. Lymphoid tissue developed more rapidly in fetuses with bacteria, viral antigens, or apparent maternal red-blood-cell antigens than in the normal fetus. Thymic and splenic indices reached maximal values in the 205- to 220-day fetal age group. Immunoglobulin M (IgM)-containing cells were first observed, by immunofluorescence, in a single fetus at 59 days of gestation. Immunoglobulin G (IgG)-containing cells were observed at 145 days of gestation in one fetus with a bacterial and viral infection. IgM-containing cells were observed in 36 fetuses and IgM and IgG cells were present in seven fetuses. Spleen, lymph nodes, thymus, bone marrow, and liver of one fetus from a dam with lymphosarcoma had immunoglobulin-containing cells. Hemal lymph nodes, blood (buffy coat), Peyer patches, and heart and lung sections from fetuses with immunoglobulin-containing cells in spleen or lymph node did not have immunoglobulin-containing cells. Antigens of the virus of bovine virus diarrhea-mucosal disease (BVD) were detected in one fetus, and antigens of infectious bovine rhinotracheitis (IBR) virus were detected in three fetuses; however, viruses were not isolated in primary bovine embryonic kidney cells. Two of the three fetuses with IBR virus antigens had neutralizing serum antibody titers to IBR virus. Bacteria including Escherichia coli, Lactobacillus sp. and Mima polymorpha var. oxidans were isolated from four fetuses. Antibodies that caused the agglutination of maternal red blood cells were present in 8 of 20 bovine fetal serum samples. The antibodies were 2-mercaptoethanol sensitive and partially heat resistant (56 C for 30 min). The ontogeny of the bovine immune response and human immune response were compared, and it was suggested that the similarities were primarily due to the two species having the same approximate gestation period of 280 days.

An experimental study of intestinal movement (author's transl)

Experimental studies were performed on the mechanism of intestinal movement electromyographically. The action potentials were recorded from intestinal wall of mongrel dogs with various surgical conditions. Frequency of spike-burst was investigated as a pattern of electromyogram.In control group, frequency of spike-burst of upper jejunum was 17.6 cycles/min. and lower ileum was 12.9 cycles/min.Changes of spike-burst frequency with transection and end-to-end anastomosis were observed. Proximal to the anastomosis, the average frequency was 17.5 cycles/min and distal to it fell in 13.4 cycles/min. The recovery to normal frequency was incomplete even 14 months after operation.The transection of intestinal tract has brought the decrease of spike-burst frequency in its distal portion, but no considerable changes were observed in further transection of its distal canal.The frequency of spike-burstwas not at all affected by the section of nerves in mesentery.Thelongitudinal section was ineffective to produce the change of spike-burst frequency.

Changes in the distribution and chemical composition of Hymenolepis diminuta, and the intestinal nutritional gradients of uninfected and parasitized rats following a glucose meal.

1. The protein nitrogen, carbohydrate and amino acid contents of the rat duodenum, jejunum, upper and lower ileum have been determined for up to 3 hr following the feeding of a glucose-containing test diet.2. The changes in distribution of Hymenolepis diminuta within the intestine and the changes in worm total nitrogen and carbohydrate have been followed over the same period following the same diet.3. The glucose and TCA-soluble carbohydrate contents of the uninfected gut were approximately double those of the parasitized animals.

Immunity to cholera: antibody response in the lower ileum of the rabbit.

Extracts were prepared of whole tissue of the lower ileum, of cells separated by the citrate method, and of mucosal tissue of the muscularis after the removal of cells; all tissues were taken from rabbits immunized by parenteral and/or intraintestinal routes with cell-free supernatant of peptone-water cultures of Vibrio cholerae. Before preparation of extracts, the bowel section was washed with isotonic saline. The tissue and cell extracts, and wash, together with serum, were titrated for antitoxic and vibriocidal antibody. All showed the presence of antitoxic and complement-dependent vibriocidal antibody. Antibody activity was precipitated by 50 96 saturation with ammonium sulfate, and the recovery of precipitable protein was the same for all extracts, about 0.2 mg/cm of bowel. The antibody content ranged from 1,261 units of antitoxin/mg in tissue extract to 85 units/mg in wash. Antibody occurred in a concentration gradient from tissue to lumen, and vibriocidal antibody was more readily released from cells than was antitoxin. IgG and IgA, but not IgM, were found by immunoelectrophoresis to be present in extracts of tissues and cells and in wash. Cholera is an infection in which the causative

Effects of fasting on intestinal transfer of sugars and amino acids in vitro.

1. Transfer of sugars, amino acids and fluid and metabolism of glucose were studied with everted sacs of small intestine prepared from fed and 3-day fasted rats.2. In the absence of glucose there was some evidence for increased intestinal transfer of sugars and amino acids in fasted animals. In the presence of glucose there was in general decrease in transfer of amino acids and fluid.3. In fasted animals glucose transfer was reduced except in the lower ileum, and there was a general reduction in glucose metabolism.4. Because of the large reduction in gut weight in fasted animals, expressing transfer on a weight basis is considered not to be a valid procedure in studying the effects of fasting on intestinal transfer.5. The results have been discussed in relation to effects of fasting on energy availability, efficiency of transfer mechanisms, permeability of the intestine and the value of in vitro methods in the study of physiological absorption.

Infectivity, Growth, Development, Excystation and Transplantation of Zygocotyle lunata (Trematoda) in the Chick

Twenty-three chicks, each fed 10 cysts of Zygocotyle lunata in 3% NaHCO:~, were infected with a total of 85 worms (1 to 9/host), recovered only in the ceca 1 to 120 days postexposure. Body length increased slowly until the 5th day, and then rapidly until the 20th, followed by a slow increase to an average of 5 mm by the 120th day. Gonadal differentiation was evident by the 4th day and eggs appeared in the uterus by the 12th. Excystation occurred in the chick intestine, probably the lower ileum, but not in a surgically isolated chick cecum. Excysted metacercariae transplanted to the chick rectum migrated to the ceca. Zygocotyle lunata (Diesing, 1836) parasitizes the ceca of a variety of birds and mammals and has been maintained in sheep, rats, and ducks in the laboratory (Hall, 1927; Price, 1928; Willey, 1941). Adults can be surgically implanted into the cecum of a rat, and metacercariae placed there excyst (Bacha, 1960, 1962). Willey (1941) reported sexual maturation of Z. lunata within 41 to 44 days in ducks and 46 to 61 days in rats but Bacha (1960) found eggs in the uterus of a 17-day-old worm from the rat. This paper reports use of the domestic chick for the first time in studies on infectivity, growth, development, excystation, and transplantation of this trematode. MATERIALS AND METHODS Cercariae shed by naturally infected Helisomna trivolvis (Say) from Lake Warren, Bucks County, Pa., encysted on finger bowls containing pond water. Cysts 1 to 10 days old, well within the Received for publication 8 August 1969. * Supported by NIH Grant AI-06835. viability period (Willey, 1941), were scraped from bowls, and 10 pretreated in 3% NaHCO. for 30 to 60 min (Bacha, 1964) were fed in 1 to 3 ml of the bicarbonate to each of 23 1to 3-day-old domestic chicks which were necropsied 1 to 120 days later. Worms were pipetted into hot AFA (Fried, 1962), stained in Gower's (1939) carmine, cleared in terpineol, and mounted in Permount. Criteria of growth were length measurements of uncurled specimens (Fried, 1962). In excystation studies, the right cecum and a 2-inch strip of lower ileum were removed from Host A and 10 cysts placed into each organ. After the open ends were ligated with silk thread, the preparation was placed in a finger bowl containing 150 ml Tyrode's at 37 C and examined 4 hr later. Host B was prepared for surgery (Fried and Vonroth, 19618) and the right cecum was ligatured close to the ileocecal valve. After the cecal apex was severed, 10 cysts were implanted and the opening sutured; thie chick was necropsied 5 hr after surgery. Ten cysts were implanted into the rectum of Host C which was necropsied 5 hr later. Hosts D to J (Table II) were fed 10 to 50 cysts each and necropsied 0.5 to 15 hr postexposure. Four excysted metacercariae from Host I and 3 from Host F (Table II) were implanted into the recta of chicks K and L which were necropsied 3 days later. This content downloaded from 207.46.13.51 on Sun, 19 Jun 2016 07:40:07 UTC All use subject to http://about.jstor.org/terms FRIED-BIOLOGY OF ZYGOCOTYLE LUNATA (TREMATODA) IN THE CHICK 45

Electrical activity of small intestinal smooth muscle

Intestinal slow waves occur spontaneously and continuously in most mammalian species studied, including man, regardless of the presence or absence of contractions. They originate in the longitudinal muscle. Spikes may or may not occur during slow wave depolarization. Spikes initiate contractions, the maximal frequency of which is equal to the frequency of slow waves. Slow waves seem to provide a timing mechanism which allows spiking and subsequent contractions only at regular intervals. Slow waves are conducted from longitudinal to circular muscle along interconnecting strands of muscle fibers, thereby coordinating contractions in the two layers. The frequency of intestinal slow waves is amazingly constant in any one part of the gut; it averages 11.8 cycles per minute in human duodenum and declines to 9.0 cycles per minute in lower ileum. The negative aboral frequency gradient is stepwise, with variable lengths of intestine operating at successively lower frequencies. Within each constant frequency region, slow waves seem to be conducted aborally from a pacemaker, and apparent conduction times can be measured as the lag between corresponding points on waves recorded from two sites along the gut. However, conduction may be more apparent than real. Slow waves may originate from all cells or groups of cells in the longitudinal muscle, which would then act as a long series of oscillators. Coupling of these oscillators so that the faster ones drive the slower ones would result in many of the features of slow wave activity in the intestine. Apparent conduction times may simply represent the phase lag between a driving and a driven oscillator. The well known coordination between contractions in the gastric antrum and those in the duodenal bulb can be explained by the presence of attenuated gastric slow waves a short distance into the duodenal bulb. In this region, the duodenal slow waves are superimposed on gastric waves resulting in augmentation of those duodenal waves directly after antral activity. These augmented waves are more likely to result in spikes and, therefore, contractions of the duodenal bulb than are the ordinary duodenal slow waves. Transection (with healed end to end anastomosis) or merely damage to the myenteric plexus abolishes coupling along the chain of slow wave oscillators so that aboral regions are no longer driven by higher frequency regions oral to the injury. The maximal frequency of contraction is, therefore, decreased below such an injury. Frequency of slow waves within a segment of gut with damaged myenteric plexus is even lower than it is aboral to such a segment. The myenteric plexus is apparently involved somehow in coupling of slow wave activity along the gut and in establishing the uncoupled spontaneous frequency of slow waves. Feeding has no effect on frequency of slow waves but does lead to an increased percentage of slow waves having spikes, and, therefore, a decrease in the amount of time the gut is mechanically quiescent. Analysis of electrical spiking provides a convenient means of following the effects of feeding on intestinal contractions. A number of studies on patients with a variety of disorders have been reported but no diagnostic value of electroenterography has been established, although its use at surgery to determine the extent of irreversible bowel damage may prove to be useful.

Primary gastrointestinal tract lymphoma in childhood.

We have recently reviewed the experience of the Hospital for Sick Children, Toronto, The Princess Margaret Hospital, and the Department of Radiotherapy, Toronto General Hospital, with malignant lymphoma in childhood (patients less than 16 years of age at time of diagnosis) (1, 2). Of 196 children who presented in the years 1930 to 1965, 75 had Hodgkin's disease, and 121 had lymphosarcoma, reticulum-cell sarcoma, or other malignant lymphoma. In Hodgkin's disease no child presented with the primary site in the gastrointestinal tract, but of the 121 children with other malignant lymphomas (Table I) 56 presented with abdominal symptoms and signs. Of these, 55 required a laparotomy to establish the diagnosis. The laparotomy findings in 40 cases indicated the primary site of origin to be gut. In one instance the lesion has been reclassified as pseudolymphoma of the small intestine (3). Ten of the remaining 39 cases have previously been reviewed (4). We present this analysis because a marked improvement in survival is apparent in our recent experience with this uncommon and usually fatal tumor. Clinical Data (a) Age and Sex: The age distribution is seen in Figure 1. There is a peak incidence in the age range of 5 to 8 years. Boys outnumbered girls in a ratio of 9:1. The age distribution of the survivors follows the incidence pattern. (b) Mode of Presentation: These children presented with abdominal pain and vomiting, most often as episodes of small bowel obstruction of greater or less degree. In over half of the cases a definite mass was palpable in mid or right abdomen. Fifteen children presented with intussusception and one with a perforated viscus. The diagnosis of primary malignant lymphoma of gut is not easily made preoperatively. Eight of our children had had prior surgery, 2 for reduction of an intussusception and 6 on a diagnosis of appendicitis or appendiceal abscess, without the lymphomatous nature of their disease being appreciated. (c) Stage at Diagnosis—Early Stage: In 20 children the laparotomy findings indicated that the lymphoma was limited to a segment of gut plus or minus the associated mesenteric nodes only. This group is defined as having “early stage” disease. Late Stage: In 19 children the disease was more extensive. Most often, spread was to the para-aortic and retroperitoneal nodes by implants and plaques in mesentery or peritoneum, or by direct infiltration of structures adjacent to the primary tumor. In all these children the primary involvement of gut dominated the clinical picture at laparotomy. This group of patients is defined as having “late stage” disease. (d) Primary Site: In 35 of the 39 children the primary site was in the lower ileum, cecum, appendix, ascending colon, or some combination of these sites (Table II). Treatment (a) Surgery: The diagnosis is made at laparotomy, often for an acute abdomen at a time when malignant tumor is not anticipated.

Activity, Concentration, and Lumen-Blood Electrochemical Potential Difference of Calcium in the Intestine of the Laying Hen

The driving forces for the intestinal absorption of calcium, consisting of the chemical and electrical gradients between the intestinal lumen and circulation, were evaluated in the laying hen. Those forces were related to the in vivo calcium absorption. The concentration and activity of calcium in ultrafiltrates made from the intestinal contents, were found to be dependent on dietary calcium level and source. Of the calcium sources tested, calcium sulfate supported the highest concentration and activity of calcium in the various intestinal segments. Only part of the variation in those parameters could be explained on the basis of corresponding variations in intralumenal pH. Comparison of the fraction of active calcium (activity/concentration) in the ultrafiltrates, with the theoretical activity coefficient, suggested that most of the ultrafilterable calcium in blood plasma was ionic, but that a considerable portion of the ultrafilterable calcium in the intestine was in a complexed form. The transmural electrical potential (PD) in the laying fowl was similar to that of other animals; it was lowest in the lower jejunum and highest in the colon. The electrochemical potential difference (ECPD) of calcium was calculated from the PD and the activities of blood plasma and intestinal contents. Due to a lower activity of calcium and a high PD in the lower ileum and colon, the ECPD was unfavorable for absorption of calcium in those segments as compared with the duodenum and jejunum. This coincided with an absence of any net calcium absorption in those posterior segments. The differences in the ECPD, could only partially account for the difference among the segments in the in vivo calcium absorption. The possibility of absorption of complexed calcium is discussed.

Cholesterol synthesis in the squirrel monkey: relative rates of synthesis in various tissues and mechanisms of control

Cholesterol synthesis has been extensively investigated in various tissues of lower mammals; however, there is little specific information concerning cholesterologenesis in the primate. Furthermore, experiments in whole animals suggest that important differences may exist in the features of cholesterologenesis in the dog and rat versus the monkey and man. Using the new world squirrel monkey, therefore, we performed the present studies to determine the rates of cholesterologenesis in various tissues per unit weight, to define the relative rates of whole organ synthesis, and to evaluate the operation of control mechanisms in these tissues.In control animals fed a low cholesterol chow diet, the liver and ileum were the two most active sites for cholesterologenesis followed, in order, by the colon, esophagus, and proximal small bowel. Rates of synthesis in 10 other tissues tested were considerably lower than these found in the gastrointestinal tract. When rates of whole organ synthesis were calculated, three tissues, i.e., liver, bowel, and skin, accounted for 92% of the total demonstrable synthetic activity.Following cholesterol feeding utilizing either a solid chow or liquid formula diet, marked suppression of hepatic cholesterologenesis occurred while synthesis in other organs remained essentially unaltered. Similarly, fasting animals for periods up to 96 hr resulted in suppression of synthesis in the liver, but not in various levels of the intestine. Finally, biliary diversion for 48 hr caused a twofold increase in hepatic cholesterologenesis and a six- to eightfold increase in sterol synthesis in the small but not the large intestine.