Serological survey of Australian native reptiles for exposure to ranavirus.

Ranaviruses have been isolated from many ectothermic vertebrates, and serological surveys of both amphibians and reptiles have shown the presence of ranaviral antibodies in a proportion of these populations. An enzyme-linked immunosorbent assay (ELISA) was developed to measure serum antibodies against ranavirus in Australian reptiles. The ELISA was validated with serum from challenge trials with Bohle iridovirus (BIV) in 6 reptilian species. A preliminary sero-survey of northern Queensland riparian reptile fauna (saw-shelled turtles Myuchelys latisternum, Krefft's river turtles Emydura macquarii krefftii, freshwater crocodiles Crocodylus johnstoni, as well as the snakes Boiga irregularis, Dendrelaphis punctulatus, Tropidonophis mairii, Morelia spilota, Liasis childreni and L. fuscus) revealed evidence of past exposure to Bohle iridoviral antigens in part of the population at several locations sampled. Furthermore, in Krefft's river turtles and freshwater crocodiles, a statistically significant trend was apparent for larger reptiles to be more likely to have BIV-reactive sera than smaller individuals. The use of adult tortoise populations as sentinels can assist in monitoring the presence of BIV in northern Australian freshwater streams, and thereby the potential dangers to native fauna from this agent.

Increased intestinal permeability and Parkinson disease patients: chicken or egg?

UNLABELLED: Gastrointestinal involvement is a frequent and early event in the course of Parkinson Disease (PD), and may have a prominent role in the early pathophysiology of the disease. On the other hand, derangement in intestinal permeability could also result from the involvement of the gastrointestinal tract over the course of the disease. PATIENTS AND METHODS: The intestinal permeability of 12 non-selected PD patients was studied using a validated, non-invasive test; these results were compared to predefined age-adjusted reference values. RESULTS: 4/12 PD patients had abnormal gastrointestinal permeability; two had both an abnormal lactulose/mannitol ratio and an abnormal sucrose concentration, and two an isolated abnormal result. An increased lactulose/mannitol ratio is consistent with defect of either the enterocytes or the tight junctions between them. CONCLUSION: Intestinal permeability is increased in a significant proportion of unselected PD patients with minimal gastrointestinal symptoms. The significance of this finding needs to be further evaluated.

Gastrointestinal symptoms in Parkinson disease: clinical aspects and management.

Although it is now generally recognized that the clinical spectrum of Parkinson disease (PD) is broader than its defining motor aspects, its various non-motor symptoms are often not routinely assessed in the clinical setting. As most of these symptoms are amenable to treatment, improved recognition would lead to more comprehensive management of the disease, and ultimately improve the quality of life for PD patients. In an attempt to increase the general awareness of physicians caring for these patients, this article focuses on the clinical manifestations and treatment of the gastrointestinal symptoms most commonly experienced by PD patients, as well as on the gastrointestinal side effects of antiparkinsonian treatments.

Reducing small intestinal permeability attenuates colitis in the IL10 gene-deficient mouse.

BACKGROUND: Defects in the small intestinal epithelial barrier have been associated with inflammatory bowel disease but their role in the causation of disease is still a matter of debate. In some models of disease increased permeability appears to be a very early event. The interleukin 10 (IL10) gene-deficient mouse spontaneously develops colitis after 12 weeks of age. These mice have been shown to have increased small intestinal permeability that appears early in life. Furthermore, the development of colitis is dependent upon luminal agents, as animals do not develop disease if raised under germ-free conditions. AIMS: To determine if the elevated small bowel permeability can be prevented, and if by doing so colonic disease is prevented or attenuated. METHODS: IL10 gene-deficient (IL10(-)/(-)) mice) were treated with AT-1001 (a zonulin peptide inhibitor), a small peptide previously demonstrated to reduce small intestinal permeability. Small intestinal permeability was measured, in vivo, weekly from 4 to 17 weeks of age. Colonic disease was assessed at 8 weeks in Ussing chambers, and at 17 weeks of age inflammatory cytokines and myeloperoxidase were measured in the colon. Colonic permeability and histology were also endpoints. RESULTS: Treated animals showed a marked reduction in small intestinal permeability. Average area under the lactulose/mannitol time curve: 5.36 (SE 0.08) in controls vs 3.97 (SE 0.07) in the high-dose AT-1001 group, p<0.05. At 8 weeks of age there was a significant reduction of colonic mucosal permeability and increased electrical resistance. By 17 weeks of age, secretion of tumour necrosis factor alpha (TNFalpha) from a colonic explant was significantly lower in the treated group (25.33 (SE 4.30) pg/mg vs 106.93 (SE 17.51) pg/ml in controls, p<0.01). All other markers also demonstrated a clear reduction of colitis in the treated animals. Additional experiments were performed which demonstrated that AT-1001 was functionally active only in the small intestine. CONCLUSIONS: This work suggests that increased intestinal permeability may be an important aetiological event in the development of colitis in IL10(-)/(-) mice.

Predicting relapse in Crohn's disease: a biopsychosocial model.

BACKGROUND: Crohn's disease (CD) is a chronic relapsing inflammatory bowel disorder. Both biological and psychosocial factors may modulate the illness experience. AIM: The aim of this study was to identify clinical, biological and psychosocial parameters as predictors of clinical relapse in quiescent CD. METHODS: Patients in medically induced remission were followed prospectively for 1 year, or less if they relapsed. Disease characteristics were determined at baseline. Serum cytokines, anti-Saccharomyces cerevisiae antibodies, C-reactive protein (CRP), erythrocyte sedimentation rate and intestinal permeability were measured every 3 months. Psychological distress, perceived stress, minor life stressors and coping strategies were measured monthly. A time-dependent multivariate Cox regression model determined predictors of time to relapse. RESULTS: 101 patients (60 females, 41 males) were recruited. Fourteen withdrew and 37 relapsed. CRP (HR = 1.5 per 10 mg/l, 95% CI 1.1 to 1.9, p = 0.007), fistulising disease (HR = 3.2, 95% CI, 1.1 to 9.4, p = 0.04), colitis (HR = 3.5 95% CI 1.2 to 9.9, p = 0.02) and the interaction between perceived stress and avoidance coping (HR = 7.0 per 5 unit increase for both scales, 95% CI 2.3 to 21.8, p = 0.003) were predictors of earlier relapse. CONCLUSIONS: In quiescent CD, a higher CRP, fistulising disease behaviour and disease confined to the colon were independent predictors of relapse. Moreover, patients under conditions of low stress and who scored low on avoidance coping (ie, did not engage in social diversion or distraction) were least likely to relapse. This study supports a biopsychosocial model of CD exacerbation.

Indwelling urethral versus suprapubic catheters in nursing home residents: determining the safest option for long-term use.

BACKGROUND: The incidence of infectious complications has not been previously compared for two types of common urinary catheters used in the long-term care setting: indwelling urethral catheters and suprapubic catheters. AIM: To compare catheter-associated urinary tract infection (CAUTI) rates and multidrug-resistant organism (MDRO) colonization between nursing home residents with indwelling urethral and suprapubic catheters. METHODS: Participants included 418 nursing home residents with an indwelling device enrolled in a previously published prospective targeted infection prevention study conducted between 2010 and 2013. Resident age, gender, function, comorbidities, and information on infections, antibiotic use, and recent hospitalizations were obtained at study enrolment, day 14, and every 30 days thereafter for up to one year. Microbiological samples were obtained from several anatomic sites at each visit. Cox proportional hazard models were adjusted for facility-level clustering and other covariates. FINDINGS: In all, 208 study participants had an indwelling urinary catheter, contributing 21,700 device-days; 173 (83%) with a urethral catheter, 35 (17%) with a suprapubic catheter. After covariate adjustment, the suprapubic group had a lower incidence of CAUTI (6.6 vs 8.8 per 1000 device-days; P = 0.05), were half as likely to be hospitalized (hazard ratio (HR) = 0.46; P < 0.01) and were 23% less likely to have had antibiotics in the past 30 days (HR = 0.77; P = 0.02). Among residents catheterized ≥90 days, the mean number of MDROs isolated in the suprapubic group was significantly higher than in the urethral group (0.57 vs 0.44; P = 0.01). Ciprofloxacin-resistant Gram-negative bacilli were frequent in both groups. CONCLUSION: Residents with a suprapubic catheter may have fewer CAUTIs, less hospitalization and less antibiotic use, but are more likely colonized with MDROs.

Kinetic constants for receptor-dependent and receptor-independent low density lipoprotein transport in the tissues of the rat and hamster.

In this study, carried out in the rat and hamster, the receptor-dependent low density lipoprotein (LDL) transport process in each organ was characterized in terms of its maximal uptake rate (Jm) and Michaelis constant (Km), while the rate of receptor-independent uptake was defined in terms of its proportionality constant (P). The highest Jm values of 50-126 micrograms/h per g were found in the liver and endocrine glands in both species and receptor-dependent uptake also was detected in other organs like spleen, kidney, and intestine. The Km values were essentially the same in all of the organs and equaled approximately 90 mg/dl in both species. The receptor-independent uptake constants also were similar in the two species and were highest in the spleen, liver, and intestine. From these values for Jm, Km, and P, it was possible to construct theoretical curves that predict the plasma LDL-cholesterol concentration and fractional catabolic rate given any alteration in LDL-cholesterol production or the magnitude of receptor-dependent LDL transport in any organ of the rat or hamster.

Glucose transport and microvillus membrane physical properties along the crypt-villus axis of the rabbit.

Both transport function and microvillus membrane physical properties evolve as the enterocyte matures and migrates up the crypt-villus axis. We isolated enriched fractions of villus tip, mid-villus, and crypt enterocytes from which microvillus membrane vesicles were prepared. Using this material we characterized the alterations that occur in microvillus membrane fluidity as the rabbit enterocyte matures and correlated these with kinetic studies of glucose transport. With increasing maturity the microvillus membrane becomes more rigid due to both an increase in the cholesterol/phospholipid ratio and alterations in individual phospholipid subclasses. Maximal rates of glucose transport were greatest in microvillus membrane vesicles prepared from mature cells. However, the glucose concentration producing half-maximal rates of transport (Km) was significantly lower in crypt microvillus membrane vesicles, suggesting that a distinct glucose transporter existed in crypt enterocytes. This distinction disappeared when differences between membrane lipid environments were removed. By fluidizing villus-tip microvillus membrane vesicles, in vitro, to levels seen in the crypt microvillus membrane, we observed a reduction in the Km of this transport system. These data suggest that the kinetic characteristics of the sodium-dependent glucose transporter are dependent upon its local membrane environment.

The safety, tolerance, pharmacokinetic and pharmacodynamic effects of single doses of AT-1001 in coeliac disease subjects: a proof of concept study.

BACKGROUND: Lifelong adherence to a strict gluten-free diet is the cornerstone of coeliac disease treatment. Elucidation of disease pathogenesis has created opportunities for novel therapeutic approaches to coeliac disease. AT-1001 is an inhibitor of paracellular permeability whose structure is derived from a protein secreted by Vibrio cholerae. AIM: To determine the safety and tolerability of 12 mg doses of AT-1001 in coeliac disease subjects challenged with gluten. METHODS: An in-patient, double-blind, randomized placebo-controlled safety study utilizing intestinal permeability, measured via fractional excretions of lactulose and mannitol, as an exploratory measure of drug efficacy. RESULTS: Compared to placebo, no increase in adverse events occurred in patients exposed to AT-1001. Following acute gluten exposure, a 70% increase in intestinal permeability was detected in the placebo group, while none was seen in the AT-1001 group. Interferon-gamma levels increased in four of seven patients (57%) of the placebo group, but only in four of 14 patients (29%) of the AT-1001 group. Gastrointestinal symptoms were more frequently detected in the placebo group when compared to the AT-1001 group (P = 0.018). CONCLUSIONS: AT-1001 is well tolerated and appears to reduce intestinal barrier dysfunction, proinflammatory cytokine production, and gastrointestinal symptoms in coeliacs after gluten exposure.

Intestinal mucosal dysfunction and infection during remission-induction therapy for acute myeloid leukaemia.

Intestinal barrier function was prospectively examined in the course of a clinical trial evaluating the efficacy and safety of lisofylline for reducing cytotoxic therapy-induced intestinal epithelial damage-related infectious morbidity in patients receiving standard remission-induction therapy for acute myeloid leukaemia. The absorption and permeation of oral D-Xylose, lactulose and mannitol were measured weekly from baseline until marrow recovery in adult recipients of idarubicin plus cytarabine for untreated acute myeloid leukaemia. These studies were correlated with non-haematologic chemotherapy-related toxicities reflecting mucosal damage, including nausea, vomiting, stomatitis, diarrhoea, abdominal pain and systemic infection. D-xylose absorption decreased and lactulose:mannitol ratio reflecting intestinal permeability increased from baseline until the second and third week after the beginning of the treatment followed by recovery. These measures correlated with infection rates, nausea, vomiting, diarrhoea and increased blood product utilization. Lisofylline was associated with increased intestinal permeability, nausea, vomiting and infection-related morbidity despite a reduction in the duration of neutropaenia. These surrogates of intestinal barrier function correlated well with clinically important outcomes despite the failure to demonstrate reduced morbidity with lisofylline and represent useful objective outcome measurements for future clinical trials of products for the amelioration of the effects of cytotoxic therapy on the intestinal mucosa.

Lipid permeability of rat jejunum and ileum: correlation with physical properties of the microvillus membrane.

It is now generally accepted that dietary lipids permeate through the cholesterol-phospholipid bilayer of the intestinal microvillus membrane during the process of intestinal absorption. Therefore, it has been assumed that rates of lipid permeation depend upon the physical properties of the microvillus membrane. In this study the lipid permeability properties of the microvillus membrane were compared in two regions of the intestine, jejunum and ileum. Since the jejunum is exposed to the majority of dietary lipid it would be reasonable to suppose that it would be more efficient at lipid absorption. The ileum was found to be less permeable to all fatty acids examined and this could be correlated with increased rigidity of ileal microvillus membrane vesicles measured with multiple fluorescent probes. Differences in membrane fluidity were found in both the outer third and central regions of the bilayer. When measurements of membrane fluidity were performed either in the presence or the absence of fatty acids, it could be demonstrated that these acids perturb the physical properties of the outer region or the membrane. Therefore, this suggests that the rate-limiting step in fatty acid permeation may be localized to the outer third of the bilayer. Pharmacologic or dietary manipulations attempting to alter rates of lipid permeability should, therefore, be directed towards altering the physical properties of this region of the microvillus membrane.

Lipid permeability of the intestinal microvillus membrane may be modulated by membrane fluidity in the rat.

Fatty acids and cholesterol permeate across the intestinal microvillus membrane at rates dictated by the hydrophobicity of the permeating lipid and the permeability properties of the microvillus membrane. A theory has evolved suggesting that the chemical composition and physical properties of the microvillus membrane are important in determining microvillus membrane lipid permeability in vivo. This communication reports a test of this hypothesis. To compare in vivo membrane lipid permeability within the same intestinal region, but under conditions were membrane physical properties were radically altered, rats were fed an inhibitor of cholesterol synthesis. This resulted in the replacement of 87-90% of membrane cholesterol with its' precursor, 7-dehydrocholesterol. Marked changes in membrane physical properties were observed, including a reduction in the static and dynamic component of membrane fluidity within the jejunal microvillus membrane. These changes were limited primarily to the outer regions of the bilayer. Associated with these alterations was a pronounced reduction in membrane lipid permeability. Therefore, microvillus membrane lipid permeability, in vivo, appears to be correlated with physical properties of the bilayer, especially those of the superficial regions.

Erythrocyte membrane fluidity in malignant hyperthermia.

Malignant hyperthermia (MH) is a rare but serious complication of general anesthesia that potentially carries a high mortality and morbidity. It is associated with excessive release of calcium into skeletal muscle following exposure to certain drugs, including the volatile general anesthetics. Since these are recognized membrane fluidizing agents it has been speculated that this condition might represent a generalized defect in membrane physical properties either at rest or inducible by fluidizing agents. If this hypothesis were found to be correct, malignant hyperthermia might conveniently be detected by examining membrane physical properties of easily accessible cells rather than the cumbersome method of muscle biopsy currently employed. To test this hypothesis we identified patients proven to be susceptible to MH by muscle biopsy and a cohort of patients not susceptible to MH as defined by negative muscle biopsy testing. Erythrocytes were isolated from both groups and membrane physical properties examined using conventional, widely available, steady-state fluorescence polarization techniques. Erythrocyte membranes were evaluated with multiple probes both in the basal condition and following fluidization with either increasing temperature or two concentrations of a fluidizing alcohol. We report, contrary to previous publications, that no discernable differences were detectable between MH-positive or negative patients. Thus, we find no evidence for a generalized membrane defect in MH and conclude that the determination of erythrocyte membrane physical properties, by these techniques, are of no use in the preoperative screening for this disorder.

Oxidative and drug-induced alterations in brush border membrane hemileaflet fluidity, functional consequences for glucose transport.

Oxidation of biological membranes has been suggested as a major pathological process in a variety of disease states including intestinal ischemia and inflammatory bowel disease. Previous studies on the small intestinal brush border membrane have shown that part of the decrease in the activity of the Na(+)-dependent glucose transporter (SGLT1) observed after oxidation could be secondary to the derangement in membrane fluidity that accompanied oxidative damage. The present study examined the relationship between oxidative-induced hemileaflet fluidity alterations and the resultant change in Na(+)-dependent glucose transport activity. To address this issue, in vitro oxidation of guinea pig brush border membrane vesicles was induced by incubation of the vesicles with ferrous sulfate and ascorbate. We found that oxidation decreased the fluidity of both the outer and inner hemileaflets, the decrease being greater in the outer leaflet. Moreover, the preferential alteration in hemileaflet fluidity was accompanied by a decrease in glucose transport. However, when membrane perturbing agents such as hexanol and A(2)C were used to restore membrane fluidity to levels comparable to controls, rates of glucose transport could not be interpreted in terms of variation of bulk membrane fluidity or variation in fluidity of any specific membrane leaflet. On the basis of these experiments, we propose that previous studies that reported coincidental alteration in membrane fluidity and glucose transport cannot be interpreted on the basis of bulk fluidity or hemileaflet fluidity.

Proline transport across the intestinal microvillus membrane may be regulated by membrane physical properties.

There is now abundant evidence that integral membrane protein function may be modulated by the physical properties of membrane lipids. The intestinal brush border membrane represents a membrane system highly specialized for nutrient absorption and, thus, provides an opportunity to study the interaction between integral membrane transport proteins and their lipid environment. We have previously demonstrated that alterations in this environment may modulate the function of the sodium-dependent glucose transporter in terms of its affinity for glucose. In this communication we report that membrane lipid-protein interactions are distinctly different for the proline transport proteins. Maximal transport rates for L-proline by either the neutral brush border or imino transport systems are reduced 10-fold when the surrounding membrane environment is made more fluid over the physiological range that exists along the crypt-villus axis. Furthermore, in microvillus membrane vesicles prepared from enterocytes isolated from along the crypt-villus axis a similar gradient exists in the functional activity of these transport systems. This would imply that either the functional activity of these transporters are regulated by membrane physical properties or that the synthesis and insertion of these proteins is coordinated in concert with membrane physical properties as the enterocyte migrates up the crypt-villus axis.

Capsaicin effects on non-neuronal plasma membranes.

Capsaicin has been touted as a pharmacological tool specific for sensory afferent neurons and is widely used in neurophysiological studies. However, we have recently demonstrated that in concentrations commonly employed within the gastrointestinal tract, capsaicin inhibits platelet aggregation to at least three different stimuli. Since this was observed in a nerve free system it raised the question of how specific capsaicin is. In this communication we report that capsaicin has profound effects on physical properties of non-neuronal cell plasma membranes. These effects were observed while measuring the effect of capsaicin upon the fluidity of both intact cell membranes and a variety of purified membrane preparations. Membrane fluidity was assessed with the fluorescent probes diphenylhexatriene (DPH) and its trimethylamino derivative TMA-DPH and demonstrated concentration-dependent capsaicin effects. Furthermore, the effects were cell specific and for full expression required both intact cells and a non-lipid extractable component of the plasma membrane. These non-neuronal effects must be carefully considered when contemplating the explanation for capsaicin-induced effects.

The anti-oxidant properties of 5-aminosalicylic acid.

Oxidative damage to biological membranes is an important cause of tissue injury in inflammatory bowel disease. 5-Aminosalicylic Acid (5ASA) has therapeutic efficacy in Ulcerative colitis, which may be based on its antioxidant properties. We used Parinaric acid as a fluorescent marker of oxidation in an intestinal microvillous brush border membrane preparation. Various concentrations of the antioxidants 5ASA, ascorbate, and tocopherol were added, and oxidation was initiated from within the membrane by 2,2' azobis (2.4-dimethylvaleronitrile) (AMVN) and from solution by 2,2' azobis (2-amidinopropane) hydrochloride (AAPH). Tocopherol was able to inhibit oxidation from either source. Ascorbate was only able to inhibit oxidation initiated from solution. 5ASA was able to inhibit oxidation initiated from either site, and was more effective than tocopherol against AAPH, but similarly effective against AMVN. We postulate that water soluble 5ASA preferentially associates with membrane surface, allowing chain-breaking antioxidant activity when peroxidation is initiated within the membrane. Likewise, it is effective against aqueous oxidants because its position allows it to interact with AAPH before lipid peroxidation can be initiated as well as breaking the lipid peroxidation chain once it is initiated. This dual capacity may be important for therapeutic effect of 5ASA and may suggest other candidate antioxidants for clinical trials.

Gastric tolerance of high-dose pulse oral prednisone in multiple sclerosis.

BACKGROUND: Prednisone and methylprednisolone are well absorbed orally and have lower treatment costs than IV methylprednisolone, but concern that low-dose corticosteroid may cause increased disease activity and that high oral doses may cause gastric ulceration inhibits use of oral therapy for MS attacks. METHODS: Gastric mucosal injury, detected by measurement of gastric permeability, was examined after five alternate day doses of IV methylprednisolone (1 g) or oral prednisone (1,250 mg) in 21 patients with MS. A triple sugar test solution was consumed at bedtime, and urine was collected overnight. Urine sugar concentrations were determined by high-pressure liquid chromatography. Gastric permeability was expressed as total mg of sucrose excreted. RESULTS: Seventeen patients completed the protocol (12 oral, 5 IV). Baseline sucrose excretion was normal in all. Both groups demonstrated an increase in gastric permeability after steroid treatment, but there was no difference between the two groups (95% CI 95 to 91 mg, p = 0.96). After treatment, three (25%) patients in the oral group, and two (40%) patients the IV group, had modestly abnormal gastric permeability (95% CI 34 to 64%, P = 0.6). CONCLUSIONS: Short-term high-dose oral prednisone is not associated with greater gastric damage, as measured with permeability tests, than IV methylprednisolone. High-dose oral prednisone should be considered a first-line treatment option for MS attacks.

On the in vitro vasoactivity of bile acids.

We compared the vasorelaxant action of nine different bile acids and correlated their vasorelaxant activity with their individual indices for hydrophobicity or lipophilicity. Vasorelaxant activity correlated with the relative lipid solubility of bile acids with lipophilic bile acids exhibiting the greatest vasorelaxant activity with modest to no vasorelaxant activity exhibited by hydrophilic bile acids. We also investigated whether bile acid-induced vasorelaxation is mediated by antagonism of a prototypal contractile receptor, the alpha(1)-adrenoceptor, by stimulation of a bile acid surface membrane receptor, by the release of endothelium-derived relaxant factors, by promoting the generation of reactive oxygen species and increasing the extent of lipid peroxidation, or by modifying membrane fluidity. Lipophilic bile acids induce vasorelaxation possibly by antagonizing alpha(1)-adrenoceptors, a phenomenon that manifests itself as a lowering of the affinity of vascular alpha(1)-adrenoceptors. Bile acid-induced vasorelaxation was not dependent upon stimulation of a bile acid surface membrane receptor or the release of endothelium-derived relaxant factors. Lipophilic bile acids can also increase the extent of lipid peroxidation with a subtle reduction in the fluidity of rat vascular smooth muscle membranes not associated with loss of membrane cholesterol or phospholipid. We have concluded that lipophilic bile acids are non-selective vasorelaxants whose mechanism of action is a multifaceted process involving antagonism of contractile surface membrane receptors possibly effected by an increased extent of lipid peroxidation and/or membrane fluidity but occurs independent of the release of endothelial-derived relaxant factors or stimulation of a surface membrane bile acid binding site.

Intestinal permeability and postheparin plasma diamine oxidase activity in the prediction of Crohn's disease relapse.

A method of detecting presymptomatic relapse of Crohn's disease could allow for the selective use of maintenance or intensified medical therapy in those with an increased risk of relapse. The aim of this study was to evaluate three potential laboratory markers of relapse: intestinal and gastroduodenal permeability and plasma diamine oxidase activity. Intestinal permeability (lactulose/mannitol test), gastroduodenal permeability (urinary sucrose excretion), and postheparin plasma diamine oxidase activity were serially measured in 61 adults with Crohn's disease in remission (CDAI <150) for at least 30 days. Subjects were followed periodically for clinical relapse (CDAI >150 and increased by at least 100 points or the need for steroids or surgery). Fourteen patients (23%) relapsed. A cut-off of 0.030 for the lactulose/mannitol ratio was defined. Those with ratios above the cutoff had a 7.0 times greater risk of relapse (p<0.001). Three subjects who went from a normal ratio to an abnormal ratio relapsed, whereas none of 32 subjects with a repeatedly normal ratio relapsed. Sucrose excretion and plasma diamine oxidase activity did not predict relapse. Serial testing of intestinal permeability, but not of gastroduodenal permeability or plasma diamine oxidase activity, was useful in predicting relapse in asymptomatic patients.