The Function, Underlying Mechanism and Clinical Potential of Exosomes in Colorectal Cancer.

Colorectal cancer (CRC) is a lethal malignancy worldwide. Exosomes are extracellular vesicles derived from the endosomal pathway of nearly all cells and can be found in body fluids. They can be considered an intercellular system in the human body that can mediate near- and long-distance intercellular communication due to their features and functions. Investigations have revealed that exosomes are participated in different processes, physiologically and pathologically, especially in cancer. However, the clinical value of exosomes and their mechanisms of action in CRC are unclear and have not been systematically assessed. The purpose of this review is to discuss how exosomes play a role in the occurrence and development of CRC, with a particular focus on the functions and underlying mechanisms of tumor-derived exosomes as well as non-tumor-derived exosomes. We also describe the evidence that exosomes can be used as diagnostic and prognostic markers for CRC. In addition, the possibilities of exosomes in CRC clinical transformation are also discussed.

Comprehensive Modeling in Predicting Biodiesel Density Using Gaussian Process Regression Approach.

In this study, four Gaussian process regression (GPR) approaches by various kernel functions have been proposed for the estimation of biodiesel density as the functions of pressure, temperature, molecular weight, and the normal melting point of fatty acid esters. Comparing the actual values with GPR outputs shows that these approaches have good accuracy, but the performance of the rational quadratic GPR model is better than others. In this GPR model, RMSE = 0.47, MSE = 0.22, MRE = 0.04, R 2 = 1, and STD is equal to 0.3. In addition, for the first time, this study shows that the effective parameters affect the biodiesel density. According to this analysis, it was shown that among the input parameters, pressure has the greatest effect on the target values with a relevancy factor of 0.59. This study can be used as a suitable and valuable work/tool for chemical and petroleum engineers who attempt environment protection and recovery improvement.

Managing cognitive load in simulations: exploring the role of simulation technologists.

BACKGROUND: Facilitating simulation is a complex task with high cognitive load. Often simulation technologists are recruited to help run scenarios and lower some of the extraneous load. We used cognitive load theory to explore the impact of technologists on instructors, identifying sources of instructor cognitive load with and without technologists present. METHODS: Data were collected from 56 simulation sessions for postgraduate emergency medicine residents. Instructors delivered 14 of the sessions without a technologist. After each session, the instructor and simulation technologist (if present) provided quantitative and qualitative data on the cognitive load of the simulation. RESULTS: Instructors rated their cognitive load similarly, regardless of whether simulation technologists were present. However, the composition of their cognitive load differed. Instructors experienced reduced cognitive load related to the simulator and technical resources when technologists were present. Qualitative feedback from instructors suggested real consequences to these differences in cognitive load in (1) perceived complexities in running the scenario, and (2) observations of learners. CONCLUSION: We provide evidence that simulation technologists can remove some of the extraneous load related to the simulator and technical resources for the instructor, allowing the instructor to focus more on observing the learner(s) and tailoring the scenario to their actions.

CONTEXTE: Faciliter la simulation est une tâche complexe qui comporte une charge cognitive élevée. Des technologues en simulation sont souvent recrutés pour aider à exécuter des scénarios et à alléger la charge extrinsèque. Nous avons utilisé la théorie de la charge cognitive pour explorer l'impact des technologues sur les instructeurs, en identifiant les sources de la charge cognitive de l'instructeur avec et sans la présence du technologue. MÉTHODES: Les données ont été recueillies à partir de 56 ateliers de simulation auprès des résidents en médecine d'urgence. Les instructeurs ont animé 14 de ces ateliers sans technologue. Après chaque session, l'instructeur et le technologue en simulation (s'il était présent) ont fourni des données quantitatives et qualitatives sur la charge cognitive associée à la simulation. RÉSULTATS: Les instructeurs ont évalué leur charge cognitive de façon similaire indépendamment de la présence du technologue en simulation. Cependant, la composition de leur charge cognitive était différente. Les instructeurs ont subi une moindre charge cognitive liée au simulateur et aux ressources techniques en présence des technologues. La rétroaction qualitative des instructeurs a suggéré des conséquences réelles liées aux différences de charges cognitives concernant (1) les complexités perçues en exécutant le scénario, et (2) les observations des apprenants. CONCLUSION: Nous fournissons des données probantes suggérant que les technologues en simulation puissent éliminer une partie de la charge extrinsèque liée au simulateur et aux ressources techniques, ce qui permet à l'instructeur de se concentrer davantage sur l'observation de l'apprenant et d'adapter le scénario à leurs actions.

Bacteroides fragilis polysaccharide A is necessary and sufficient for acute activation of intestinal sensory neurons.

Symbionts or probiotics are known to affect the nervous system. To understand the mechanisms involved, it is important to measure sensory neuron responses and identify molecules responsible for this interaction. Here we test the effects of adding Lactobacillus rhamnosus (JB-1) and Bacteroides fragilis to the epithelium while making voltage recordings from intestinal primary afferent neurons. Sensory responses are recorded within 8 s of applying JB-1 and excitability facilitated within 15 min. Bacteroides fragilis produces similar results, as does its isolated, capsular exopolysaccharide, polysaccharide A. Lipopolysaccharide-free polysaccharide A completely mimics the neuronal effects of the parent organism. Experiments with a mutant Bacteroides fragilis devoid of polysaccharide A shows that polysaccharide A is necessary and sufficient for the neuronal effects. Complex carbohydrates have not been reported before as candidates for such signalling between symbionts and the host. These observations indicate new neuronal targets and invite further study of bacterial carbohydrates as inter-kingdom signalling molecules between beneficial bacteria and sensory neurons.

Psychoactive bacteria Lactobacillus rhamnosus (JB-1) elicits rapid frequency facilitation in vagal afferents.

Mounting evidence supports the influence of the gut microbiome on the local enteric nervous system and its effects on brain chemistry and relevant behavior. Vagal afferents are involved in some of these effects. We previously showed that ingestion of the probiotic bacterium Lactobacillus rhamnosus (JB-1) caused extensive neurochemical changes in the brain and behavior that were abrogated by prior vagotomy. Because information can be transmitted to the brain via primary afferents encoded as neuronal spike trains, our goal was to record those induced by JB-1 in vagal afferents in the mesenteric nerve bundle and thus determine the nature of the signals sent to the brain. Male Swiss Webster mice jejunal segments were cannulated ex vivo, and serosal and luminal compartments were perfused separately. Bacteria were added intraluminally. We found no evidence for translocation of labeled bacteria across the epithelium during the experiment. We recorded extracellular multi- and single-unit neuronal activity with glass suction pipettes. Within minutes of application, JB-1 increased the constitutive single- and multiunit firing rate of the mesenteric nerve bundle, but Lactobacillus salivarius (a negative control) or media alone were ineffective. JB-1 significantly augmented multiunit discharge responses to an intraluminal distension pressure of 31 hPa. Prior subdiaphragmatic vagotomy abolished all of the JB-1-evoked effects. This detailed exploration of the neuronal spike firing that encodes behavioral signaling to the brain may be useful to identify effective psychoactive bacteria and thereby offer an alternative new perspective in the field of psychiatry and comorbid conditions.

Intestinal serotonin release, sensory neuron activation, and abdominal pain in irritable bowel syndrome.

OBJECTIVES: Serotonin (5-hydroxytryptamine, 5-HT) metabolism may be altered in gut disorders, including in the irritable bowel syndrome (IBS). We assessed in patients with IBS vs. healthy controls (HCs) the number of colonic 5-HT-positive cells; the amount of mucosal 5-HT release; their correlation with mast cell counts and mediator release, as well as IBS symptoms; and the effects of mucosal 5-HT on electrophysiological responses in vitro. METHODS: We enrolled 25 Rome II IBS patients and 12 HCs. IBS symptom severity and frequency were graded 0-4. 5-HT-positive enterochromaffin cells and tryptase-positive mast cells were assessed with quantitative immunohistochemistry on colonic biopsies. Mucosal 5-HT and mast cell mediators were assessed by high-performance liquid chromatography or immunoenzymatic assay, respectively. The impact of mucosal 5-HT on electrophysiological activity of rat mesenteric afferent nerves was evaluated in vitro. RESULTS: Compared with HCs, patients with IBS showed a significant increase in 5-HT-positive cell counts (0.37 ± 0.16% vs. 0.56 ± 0.26%; P=0.039), which was significantly greater in patients with diarrhea-predominant IBS vs. constipation-predominant IBS (P=0.035). Compared with HCs, 5-HT release in patients with IBS was 10-fold significantly increased (P < 0.001), irrespective of bowel habit, and was correlated with mast cell counts. A significant correlation was found between the mucosal 5-HT release and the severity of abdominal pain (r(s)=0.582, P=0.047). The area under the curve, but not peak sensory afferent discharge evoked by IBS samples in rat jejunum, was significantly inhibited by the 5-HT3 receptor antagonist granisetron (P<0.005). CONCLUSIONS: In patients with IBS, 5-HT spontaneous release was significantly increased irrespective of bowel habit and correlated with mast cell counts and the severity of abdominal pain. Our results suggest that increased 5-HT release contributes to development of abdominal pain in IBS, probably through mucosal immune activation.

Luminal administration ex vivo of a live Lactobacillus species moderates mouse jejunal motility within minutes.

Gut commensals modulate host immune, endocrine, and metabolic functions. They also affect peripheral and central neural reflexes and function. We have previously shown that daily ingestion of Lactobacillus reuteri (LR) for 9 d inhibits the pseudoaffective cardiac response and spinal single-fiber discharge evoked by visceral distension, and decreases intestinal motility and myenteric AH cell slow afterhyperpolarization (sAHP) by inhibiting a Ca-activated K (IK(Ca)) channel. We tested whether luminal LR could acutely decrease motility in an ex vivo perfusion model of naive Balb/c jejunum. Live LR dose dependently decreased motor complex pressure wave amplitudes with 9- to 16-min onset latency and an IC(50) of 5 × 10(7) cells/ml Krebs. Heat-killed LR or another live commensal, Lactobacillus salivarius, were without effect. The IK(Ca) channel blocker TRAM-34, but neither the opener (DCEBIO) nor the hyperpolarization-activated cationic channel inhibitor ZD7288 (5 µM) (or TTX 1 µM), mimicked the LR effect on motility acutely ex vivo. We provide evidence for a rapid, strain-specific, dose-dependent action of a live Lactobacillus on small intestinal motility reflexes that recapitulates the long-term effects of LR ingestion. These observations may be useful as a first step to unraveling the pathways involved in bacteria to the nervous system communication.

Lactobacillus reuteri enhances excitability of colonic AH neurons by inhibiting calcium-dependent potassium channel opening.

Probiotics are live non-pathogenic commensal organisms that exert therapeutic effects in travellers' diarrhea, irritable bowel syndrome and inflammatory bowel disease. Little is known about mechanisms of action of commensal bacteria on intestinal motility and motility-induced pain. It has been proposed that probiotics affect intestinal nerve function, but direct evidence for this has thus far been lacking. We hypothesized that probiotic effects might be mediated by actions on colonic intrinsic sensory neurons. We first determined whether sensory neurons were present in rat colon by their responses to chemical mucosal stimulation and identified them in terms of physiological phenotype and soma morphotype. Enteric neuron excitability and ion channel activity were measured using patch clamp recordings. We fed 10(9)Lactobacillus reuteri (LR) or vehicle control to rats for 9 days. LR ingestion increased excitability (threshold for evoking action potentials) and number of action potentials per depolarizing pulse, decreased calcium-dependent potassium channel (IK(Ca)) opening and decreased the slow afterhyperpolarization (sAHP) in sensory AH neurons, similar to the IK(Ca) antagonists Tram-34 and clotrimazole. LR did not affect threshold for action potential generation in S neurons. Our results demonstrate that LR targets an ion channel in enteric sensory nerves through which LR may affect gut motility and pain perception.

Lactobacillus reuteri ingestion prevents hyperexcitability of colonic DRG neurons induced by noxious stimuli.

Lactobacillus species ingestion can decrease autonomic responses and spinal fiber discharge to nociceptive colorectal distension (CRD), even in the absence of inflammation. The present study aimed to determine whether dorsal root ganglion (DRG) somas could be a locus where the antinociceptive probiotic may have an effect. Healthy rats were fed with Lactobacillus reuteri or vehicle control for 9 days whereupon they were anesthetized, and intermittent distal colonic CRD at 80 mmHg distension was either performed for 1 h or not. The animals were immediately euthanized and patch-clamp recordings taken after isolation and overnight culture from those DRG that projected to the distal colon. CRD decreased the threshold for action potential generation and increased the number of spikes discharged during a standard depolarizing test stimulus, and this effect was blocked by prior probiotic ingestion. The increase in excitability was paralleled by an increase in DRG capacitance, which was not altered by Lactobacillus reuteri ingestion. CRD did not increase tissue weight or myeloperoxidase activity. We suggest that the effects of CRD may have been caused by activity-dependent neurotransmission between DRG somas. CRD evoked increases in action potential upstroke speed, which suggests that it may also have led to augmentation of sodium channel conductances. Probiotic ingestion may have interfered with this hypothetical mechanism since it blocked the effect of CRD on the action potential.

In situ recording from gut pacemaker cells.

Interstitial cells of Cajal (ICC) associated with the myenteric plexus of the small intestine are crucial players in gut physiology performing pacemaker functions and directing peristalsis and segmentation. ICC have been studied after chemical isolation and under culture conditions, but concerns that these methods affect the intrinsic properties have hindered progress in our understanding of ICC. To overcome this problem, we have developed a method to obtain electrophysiological recordings from ICC in situ. The critical feature is the ability to make high resistance seals onto cells that are embedded within tissue to obtain patch clamp recordings. Our first results show a prominent presence of a chloride channel, one of the proposed ICC pacemaker channels. The developed method can be applied to auxiliary cells of the enteric nervous system such as glial cells or fibroblasts and will be ideal for the study of cell-cell communication in tissue.

Mast cell-dependent excitation of visceral-nociceptive sensory neurons in irritable bowel syndrome.

BACKGROUND & AIMS: Intestinal mast cell infiltration may participate to abdominal pain in irritable bowel syndrome (IBS) patients. However, the underlying mechanisms remain unknown. We assessed the effect of mast cell mediators released from the colonic mucosa of IBS patients on the activation of rat sensory neurons in vitro. METHODS: Colonic mast cell infiltration and mediator release were assessed with quantitative immunofluorescence and immunoenzymatic assays. The effect of mucosal mediators was tested on mesenteric sensory nerve firing and Ca(2+) mobilization in dorsal root ganglia in rats. RESULTS: Mediators from IBS patients, but not controls, markedly enhanced the firing of mesenteric nerves (14.7 +/- 3.2 imp/sec vs 2.8 +/- 1.5 imp/sec; P < .05) and stimulated mobilization of Ca(2+) in dorsal root ganglia neurons (29% +/- 4% vs 11% +/- 4%; P < .05). On average, 64% of dorsal root ganglia responsive to mediators were capsaicin-sensitive, known to mediate nociception. Histamine and tryptase were mainly localized to mucosal mast cells. IBS-dependent nerve firing and Ca(2+) mobilization were correlated with the area of the colonic lamina propria occupied by mast cells (r = 0.74; P < .01, and r = 0.78; P < .01, respectively). IBS-dependent excitation of dorsal root ganglia was inhibited by histamine H(1) receptor blockade and serine protease inactivation (inhibition of 51.7%; P < .05 and 74.5%; P < .05; respectively). CONCLUSIONS: Mucosal mast cell mediators from IBS patients excite rat nociceptive visceral sensory nerves. These results provide new insights into the mechanism underlying visceral hypersensitivity in IBS.

Characterization of myenteric sensory neurons in the mouse small intestine.

We recorded from myenteric AH/Dogiel type II cells, demonstrated mechanosensitive responses, and characterized their basic properties. Recordings were obtained using the mouse longitudinal muscle myenteric plexus preparation with patch-clamp and sharp intracellular electrodes. The neurons had an action potential hump and a slow afterhyperpolarization (AHP) current. The slow AHP was carried by intermediate conductance Ca2+ -dependent K+ -channel currents sensitive to charybdotoxin and clotrimazole. All possessed a hyperpolarization-activated current that was blocked by extracellular cesium. They also expressed a TTX-resistant Na+ current with an onset near the resting potential. Pressing on the ganglion containing the patched neuron evoked depolarizing potentials in 17/18 cells. The potentials persisted after synaptic transmission was blocked. Volleys of presynaptic electrical stimuli evoked slow excitatory postsynaptic potentials (EPSPs) in 9/11 sensory neurons, but 0/29 cells received fast EPSP input. The slow EPSP was generated by removal of a voltage-insensitive K+ current. Patch-clamp recording with a KMeSO4-containing, but not a conventional KCl-rich, intracellular solution reproduced the single-spike slow AHPs and low input resistances seen with sharp intracellular recording. Cell-attached recording of intermediate conductance potassium channels supported the conclusion that the single-spike slow AHP is an intrinsic property of intestinal AH/sensory neurons. Unitary current recordings also suggested that the slow AHP current probably does not contribute significantly to the high resting background conductance seen in these cells. The characterization of mouse myenteric sensory neurons opens the way for the study of their roles in normal and pathological physiology.

Vagal influences over mast cells.

The established microanatomical association of rat intestinal mucosal mast cells (IMMC) and mucosal nerves raises the possibility that there is crosstalk between mast cells and extrinsic nerves that connect to the CNS. The idea of mast cell-CNS interactions is supported by the demonstration that rat mast cell protease II (RMCPII), found predominantly in IMMC, can be conditionally released by pairing an audio-visual cue with antigen challenge. That the vagus nerve is involved in the IMMC-nerve axis was further demonstrated in a series of our studies showing that: (a) vagal afferents penetrate the small intestinal mucosa and contact IMMC; (b) vagotomy causes a reduction in IMMC density, suggesting a trophic relationship (typical of nerve-target interactions); and (c) stimulation of the cervical vagus causes an increase in histamine and serotonin in IMMC. To further investigate the IMMC-nerve axis in a model of post-inflammatory bowel disorders, infection with Nippostrongylus brasiliensis (Nb) was used to demonstrate an increase in mast cell numbers in the intestinal mucosa and mucosal nerve remodelling with hyperinnervation. Administration of Nb antigen resulted in dramatic increases in mesenteric afferent nerve firing in Nb infected rats, that was absent in sham animals. Moreover, challenge of post-Nb rats with 2-methyl-5HT caused increased mesenteric afferent firing, indicating that vagal afferent innervation remains intact in the post-infection state. These data suggest a functional connection between mast cells and extrinsic afferent nerves. Nb infection provides a useful model of altered communication between IMMCs, peripheral nerves and the CNS, as may occur in post-inflammatory disease states. Since a close anatomical relationship has also previously been demonstrated between nerves and IMMC in humans, further understanding the mast cell-nerve axis may be of critical importance in the development of treatments for various human disease states, including functional bowel disorders.

Structure-activity relationship of an alpha-toxin Bs-Tx28 from scorpion (Buthus sindicus) venom suggests a new alpha-toxin subfamily.

Scorpion venoms are among the most widely known source of peptidyl neurotoxins used for callipering different ion channels, e.g., for Na(+), K(+), Ca(+) or Cl(-). An alpha-toxin (Bs-Tx28) has been purified from the venom of scorpion Buthus sindicus, a common yellow scorpion of Sindh, Pakistan. The primary structure of Bs-Tx28 was established using a combination of MALDI-TOF-MS, LC-ESI-MS, and automated Edman degradation analysis. Bs-Tx28 consists of 65 amino acid residues (7274.3+/-2Da), including eight cysteine residues, and shows very high sequence identity (82-94%) with other long-chain alpha-neurotoxins, active against receptor site-3 of mammalian (e.g., Lqq-IV and Lqh-IV from scorpions Leiurus sp.) and insect (e.g., BJalpha-IT and Od-1 from Buthotus judaicus and Odonthobuthus doriae, respectively) voltage-gated Na(+) channels. Multiple sequence alignment and phylogenetic analysis of Bs-Tx28 with other known alpha- and alpha-like toxins suggests the presence of a new and separate subfamily of scorpion alpha-toxins. Bs-Tx28 which is weakly active in both, mammals and insects (LD(50) 0.088 and 14.3microg/g, respectively), shows strong induction of the rat afferent nerve discharge in a dose-dependent fashion (EC(50)=0.01microg/mL) which was completely abolished in the presence of tetrodotoxin suggesting the binding of Bs-Tx28 to the TTX-sensitive Na(+)-channel. Three-dimensional structural features of Bs-Tx28, established by homology modeling, were compared with other known classical alpha-mammal (AaH-II), alpha-insect (Lqh-alphaIT), and alpha-like (BmK-M4) toxins and revealed subtle variations in the Nt-, Core-, and RT-CT-domains (functional domains) which constitute a "necklace-like" structure differing significantly in all alpha-toxin subfamilies. On the other hand, a high level of conservation has been observed in the conserved hydrophobic surface with the only substitution of W43 (Y43/42) and an additional hydrophobic character at position F40 (L40/A/V/G39), as compared to the other mentioned alpha-toxins. Despite major differences within the primary structure and activities of Bs-Tx28, it shares a common structural and functional motif (e.g., transRT-farCT) within the RT-CT domain which is characteristic of scorpion alpha-mammal toxins.

Gastrointestinal dysmotility in patients with acute pancreatitis.

BACKGROUND AND AIMS: Gut-origin bacterial translocation is one of the major causes of pancreatic necrotic tissue infection in patients with severe acute pancreatitis (SAP). The gastrointestinal dysmotility is supposed to be the fundamental event in this process. To test this hypothesis, alteration of colonic transit time (CTT) in patients with acute pancreatitis (AP) was investigated. In order to evaluate the possible mechanisms involved in gastrointestinal dysmotility, changes of serum motilin (MTL), cholecystokinin (CCK) and vasoactive intestinal peptide (VIP) in patients with AP were also measured. METHODS: Twenty-four non-consecutive patients with AP and 25 controls were included in this study. The diagnosis of AP was based upon clinical features, biochemical indices and radiological investigation. The severity of AP at admission was evaluated according to the APACHE-II and Balthazar computed tomography (CT) scoring system. Total and segmental CTT in patients with AP and in controls were determined by ingestion of radiopaque markers (Sitzmarks(R)) according to the modified Metcalf's method. Meanwhile, serum MTL and CCK were assessed using radioimmunoassay (RIA), and serum VIP was measured by using ELISA in this study. RESULTS: Compared to the controls, the total CTT and segmental CTT (mainly right and left hemicolon) were prolonged significantly in 10 patients with SAP and 14 patients with MAP; P < 0.05. Moreover, the total CTT and segmental CTT were markedly more delayed in patients with SAP than in patients with MAP; P < 0.05. The concentrations of serum MTL and CCK were significantly decreased in both MAP and SAP patients compared with those in controls (P < 0.01). There was no significant differences in serum MTL and CCK levels between the SAP and MAP groups; P > 0.05. In addition, the concentration of serum VIP was increased in AP patients, and it reached statistical significance in patients with SAP (P < 0.05). CONCLUSIONS: In conclusion, gastrointestinal dysmotility often occurred in patients with AP, especially more severely in SAP patients. One of the possible mechanisms might be related to the synergic actions of gut hormones, such as MTL, CCK and VIP.

Growth hormone downregulated the excessive apoptosis of ileal intestinal epithelial cells in rats during the early course of acute necrotizing pancreatitis.

INTRODUCTION: Growth hormone (GH) has beneficial effects in protecting the intestinal barrier integrity of rats with acute necrotizing pancreatitis (ANP), and the balance between apoptosis and proliferation of intestinal epithelium is one of the key factors in maintenance of the intestinal barrier homeostasis. AIM: To evaluate further the effect of GH on cell apoptosis of intestinal epithelium in rats with ANP. METHODOLOGY: Seventy-two rats were randomly divided into 3 groups: sham operation (SO) group (n = 24); ANP group (n = 24); and ANP with GH treatment group (n = 24). ANP in rats was established by injection of 5% sodium taurocholate into the biliopancreatic duct, and laparotomized animals without induction of ANP (sham operation) served as controls. The rats in the GH treatment group received human recombinant GH (0.75 U/kg body weight) subcutaneously once, immediately after operation. The segment of ileum was removed and the detached epithelial cells of ileum were harvested at 3 hours, 6 hours, 12 hours, and 24 hours after operation. Apoptosis of intestinal epithelium was studied by DNA gel electrophoresis, fluorescein isothiocyanate (FITC)-labeled annexin V and propidium iodide (PI) staining under flow cytometry, and the terminal deoxynucleotidyl transferase-mediated d-UTP-biotin nick end labeling (TUNEL) histochemical method. RESULTS: All specimens harvested at different time points from rats with ANP showed a marked DNA ladder pattern after agarose gel electrophoresis, in comparison with those in the SO group, indicating DNA fragmentation appeared at the early stage in the ANP group. However, a DNA ladder pattern was seen only at 3 hours after operation in the GH-treated rats. The apoptotic percentage assayed by flow cytometry with use of an annexin V kit at 6 hours in the ANP group was significantly higher than in the control group (80% +/- 9% versus 28% +/- 6%; p < 0.01) and was decreased markedly in the GH treatment group (27% +/- 15% versus 80% +/- 9%, p < 0.01). The apoptotic index, studied by the TUNEL method, was obviously higher in the ANP group than in the control group (3 hours: 18 +/- 4 versus 6 +/- 2; 6 hours: 20 +/- 3 versus 8 +/- 2; 12 hours: 15 +/- 2 versus 11 +/- 1; 24 hours: 14 +/- 2 versus 5 +/- 1; p < 0.01), whereas the apoptotic index in the GH treatment group decreased at 3 hours and 6 hours (10 +/- 2 versus 18 +/- 4; 10 +/- 2 versus 20 +/- 3; p < 0.01). The same results were achieved for the apoptotic index of villi tips in the three groups. CONCLUSION: Apoptosis is a principle model of intestinal epithelial cell death at the early stage of ANP, and GH may downregulate the apoptosis significantly. This action probably is involved in the mechanisms contributing to the protective effects of GH on intestinal barrier integrity in ANP.