Ascorbic acid prevents the dose-dependent inhibitory effects of polyphenols and phytates on nonheme-iron absorption.

The effects of maize-bran phytate and of a polyphenol (tannic acid) on iron absorption from a white-bread meal were tested in 199 subjects. The phytate content was varied by adding different concentrations of phytate-free and ordinary maize bran. Iron absorption decreased progressively when maize bran containing increasing amounts of phytate phosphorous (phytate P) (from 10 to 58 mg) was given. The inhibitory effect was overcome by 30 mg ascorbic acid. The inhibitory effects of tannic acid (from 12 to 55 mg) were also dose dependent. Studies suggested that greater than or equal to 50 mg ascorbic acid would be required to overcome the inhibitory effects on iron absorption of any meal containing greater than 100 mg tannic acid. Our findings indicate that it may be possible to predict the bioavailability of iron in a diet if due account is taken of the relative content in the diet of the major promoters and inhibitors of iron absorption.

Effect of traditional oriental soy products on iron absorption.

The effect of a variety of traditional oriental unfermented and fermented soy products on iron absorption was evaluated in 242 Indian women. When compared with a soy-flour meal containing an equal amount of protein, iron absorption was found to be significantly improved with silken tofu, natto, tempeh, rice miso, barley miso, and soybean miso. This improvement could not be adequately explained except with reference to changes in the protein composition of the products. The protein fraction profiles of the soy products were obtained by size-exclusion high-performance liquid chromatography. An inverse relationship between food iron absorption and the high-molecular-weight fraction of the soy products was demonstrated (r = 0.66, p = 0.01). However, anomalous results obtained with three products (sufu, tempeh, and fully hydrolyzed isolated soy protein) did not make it possible to reach firm conclusions concerning the effect of the protein fraction of soy on iron bioavailability.

The promotive effect of soy sauce on iron absorption in human subjects.

The effects on iron absorption of a traditionally fermented Japanese soy sauce added to soy and rice meals were assessed. The addition of soy sauce to a soy flour meal could not overcome the strong inhibition of iron absorption (geometric mean absorption 7.2 per cent with soy sauce vs. 8.7 per cent without, P = 0.5). However, soy sauce added to a rice meal instead of soy flour significantly improved the geometric mean iron absorption (13.9 per cent with soy sauce vs. 5.2 per cent with soy flour, P = 0.002) and had a promotory effect on absorption from a rice meal alone (11.4 per cent with soy sauce vs. 3.5 per cent without, P = 0.0002). Although soy sauce contains appreciable amounts of organic acids, the addition of 340 mg lactic acid to rice did not enhance iron absorption (3.1 per cent with lactic acid vs. 2.2 per cent without, P = 0.11). The promotory effect of soy sauce on iron absorption appears to be due not only to its lack of soy protein content but may also be due to the presence of fermentation products other than organic acids.

Factors involved in the regulation of iron transport through reticuloendothelial cells.

The effects of various maneuvers on the handling of 59Fe-labeled heat-damaged red cells (59Fe HDRC) by the reticuloendothelial system were studied in rats. Raising the saturation of transferrin with oral carbonyl iron had little effect on splenic release of 59Fe but markedly inhibited hepatic release. Splenic 59Fe release was, however, inhibited by the prior administration of unlabeled HDRC or by the combination of carbonyl iron and unlabeled HDRC. When carbonyl iron was administered with unlabeled free hemoglobin, the pattern of 59Fe distribution was the same as that observed when carbonyl iron was given alone. 59Fe ferritin was identified in the serum after the administration of 59Fe HDRC but the size of the fraction was not affected by raising the saturation of transferrin. Sizing column analyses of tissue extracts from the spleen at various times after the administration of 59Fe HDRC revealed a progressive shift from hemoglobin to ferritin, with only small amounts present in a small molecular weight fraction. The small molecular weight fraction was greater in hepatic extracts, with the difference being marked in animals that had received prior carbonyl iron. The increased hepatic retention of 59Fe associated with a raised saturation of transferrin was reduced by a hydrophobic ferrous chelator (2,2'-bipyridine), a hydrophilic ferric chelator (desferrioxamine), and an extracellular hydrophilic ferric chelator (diethylene-triaminepentacetic acid). Transmembrane iron transport did not seem to be a rate-limiting factor in iron release, since no differences in 59Fe membrane fractions were noted in the different experimental settings. These findings are consistent with a model in which RE cells release iron from catabolized red cells at a relatively constant rate. When the saturation of transferrin is raised, a significant proportion of the iron is transported from the spleen to the liver either in small molecular weight complexes or in ferritin. Although a saturated transferrin had no effect on the release of iron from reticuloendothelial cells, prior loading with HDRC conditions them to release less iron.

The acute and long-term effect of balloon sphincteroplasty on papillary structure in pigs.

BACKGROUND: Balloon dilation or sphincteroplasty is emerging as a potentially safe and effective alternative to sphincterotomy in the management of bile duct stones. However, concerns related to the possible development of fibrosis or papillary stenosis led us to investigate the acute and long-term effects of balloon sphincteroplasty on papillary structure. METHODS: Sixteen pigs (45 to 50 kg) underwent transduodenal cannulation of the bile duct while under general anesthesia. Balloon sphincteroplasty was performed in 10 pigs to a diameter of 8 mm at a pressure of 10 atm. Sphincterotomy was carried out in 3 pigs while 2 other untreated pigs acted as controls. Eleven animals were sacrificed at intervals from 15 to 120 minutes after balloon sphincteroplasty or sphincterotomy. The remaining 5 animals were sacrificed between 6 and 12 weeks later. Histologic sections through the papilla were assessed for evidence of morphologic changes. RESULTS: When compared with controls, sections taken 15 to 120 minutes after balloon sphincteroplasty showed a progressive increase in acute inflammation extending transmurally. Intramucosal, but no transmural, hemorrhage was noted. No architectural distortion or smooth muscle disruption was observed in contrast to the transmural hemorrhage, smooth muscle disruption, and mucosal necrosis seen following sphincterotomy. After 6 to 12 weeks, mild chronic inflammation with follicular hyperplasia was present but no smooth muscle disruption or fibrosis was observed. CONCLUSION: Balloon sphincteroplasty causes an acute transmural inflammatory response and chronic follicular hyperplasia but is not associated with fibrosis or altered papillary architecture.

Pancreatic duct: MR cholangiopancreatography with a three-dimensional fast spin-echo technique.

PURPOSE: To determine the role of three-dimensional fast spin-echo magnetic resonance (MR) cholangiopancreatography in the evaluation of the normal and abnormal pancreatic duct. MATERIALS AND METHODS: A non-breath-hold MR cholangiopancreatographic technique with use of a body coil was compared with direct pancreatography performed with endoscopic retrograde cholangiopancreatography in 37 patients. RESULTS: MR cholangiopancreatograms of satisfactory quality were obtained in 92% of patients. Sensitivity for detection of pancreatic duct dilatation (n = 15) was 100% and 87% (observers 1 and 2, respectively). Among patients with pancreatic duct strictures (n = 8), 75% of the strictures were detected; there was a single false-positive finding. Specificity for both observers was 69% for the maximum intensity projection reconstructions and increased to 81% with review of the source images. Four of six cases of pancreas divisum (67%) and two cases of pancreatic duct stones were demonstrated. Interobserver agreement was moderate to substantial, as assessed with kappa-analysis. CONCLUSION: MR cholangiopancreatography can accurately demonstrate the normal pancreatic duct as well as various pancreatic duct abnormalities.

Magnetic resonance cholangiography: comparison with endoscopic retrograde cholangiopancreatography.

BACKGROUND & AIMS: Magnetic resonance cholangiography (MRC) is a noninvasive diagnostic modality capable of producing high-quality images of the biliary tree. The purpose of this study was to determine in a prospective, blinded fashion the sensitivity and specificity of three-dimensional fast spin-echo (3D FSE) MRC for the evaluation of biliary tract abnormalities. METHODS: Forty-six patients referred for elective direct cholangiography (45 endoscopic retrograde cholangiopancreatography and 1 percutaneous transhepatic cholangiography) were studied prospectively with 3D FSE MRC during a 1-year period. All images were interpreted blindly by two radiologists. The presence of dilatation, strictures, and intraductal abnormalities was recorded. Sensitivity and specificity of 3D FSE MRC were determined using findings on direct cholangiography as the gold standard. RESULTS: MRC images of diagnostic quality were obtained in 44 (95.7%) of the patients. Sensitivity for the detection of bile duct dilatation (n = 27), biliary strictures (n = 10), and intraductal abnormalities (n = 7) was 96.3%, 90%, and 100%, respectively. In addition, the MRC showed 16 of 17 patients with normal bile ducts (specificity, 94.1%). CONCLUSIONS: MRC has a very high sensitivity and specificity in the evaluation of the biliary tract. Based on these data, we believe that the efficacy of MRC using 3D FSE is sufficient to warrant its use in the routine diagnosis of biliary tract disease.

IL-8 secretion and neutrophil activation by HT-29 colonic epithelial cells.

This study examines the ability of HT-29 human colonic epithelial cells to stimulate neutrophil migration and adhesion. Interleukin-8 (IL-8), a potent neutrophil chemoattractant, was detected in conditioned media from both unstimulated (1.1 ng/ml) and IL-1 beta-stimulated (16.1 ng/ml) HT-29 cultures. Conditioned medium from IL-1 beta-exposed HT-29 cells stimulated neutrophil migration (395% of control, P < 0.01), and this effect was completely inhibited by anti-IL-8 antibody. HT-29 medium also induced shedding of neutrophil L-selectin and increased expression of neutrophil CD11/CD18 adhesion receptors. Coculture of HT-29 cells with human endothelial cell monolayers resulted in increased neutrophil transendothelial migration (169% of control, P < 0.01), which was blocked by both anti-IL-8 and anti-CD18 antibody. Northern hybridization analysis demonstrated increased levels of mRNA for IL-8 and intercellular adhesion molecule-1 (ICAM-1) in cytokine-treated HT-29 cells. Cytokine stimulation of HT-29 monolayers was also associated with increased neutrophil adhesion to these cells. Neutrophil-HT-29 cell adhesion was blocked by monoclonal antibodies to neutrophil CD18 or to ICAM-1 on the HT-29 cells (86% and 56% inhibition, respectively, P < 0.01 for both). These data suggest that IL-8 secretion by activated colonic epithelial cells may contribute to neutrophil extravasation and tissue infiltration in intestinal inflammation.