Sucralose enhances GLP-1 release and lowers blood glucose in the presence of carbohydrate in healthy subjects but not in patients with type 2 diabetes.

BACKGROUND/OBJECTIVE: Artificial sweeteners were thought to be metabolically inactive, but after demonstrating that the gustatory mechanism was also localized in the small intestine, suspicions about the metabolic effects of artificial sweeteners have emerged. The objective of this study was to determine the effect of artificial sweeteners (aspartame and sucralose) on blood glucose, insulin, c-peptide and glucagon-like peptide-1 (GLP-1) levels. SUBJECTS/METHODS: Eight newly diagnosed drug-naive type 2 diabetic patients (mean age 51.5±9.2 years; F/M: 4/4) and eight healthy subjects (mean age 45.0±4.1 years; F/M: 4/4) underwent 75 g oral glucose tolerance test (OGTT). During OGTT, glucose, insulin, c-peptide and GLP-1 were measured at 15- min intervals for 120 min. The OGTTs were performed at three settings on different days, where subjects were given 72 mg of aspartame and 24 mg of sucralose in 200 ml of water or 200 ml of water alone 15 min before OGTT in a single-blinded randomized order. RESULTS: In healthy subjects, the total area under the curve (AUC) of glucose was statistically significantly lower in the sucralose setting than in the water setting (P=0.002). There was no difference between the aspartame setting and the water setting (P=0.53). Total AUC of insulin and c-peptide was similar in aspartame, sucralose and water settings. Total AUC of GLP-1 was significantly higher in the sucralose setting than in the water setting (P=0.04). Total AUC values of glucose, insulin, c-peptide and GLP-1 were not statistically different in three settings in type 2 diabetic patients. CONCLUSIONS: Sucralose enhances GLP-1 release and lowers blood glucose in the presence of carbohydrate in healthy subjects but not in newly diagnosed type 2 diabetic patients.

Effect of vitamin D deficiency and replacement on endothelial functions in Behçet's disease.

OBJECTIVES: Endothelial dysfunction is previously demonstrated in Behçet's disease (BD) and vitamin D is implicated to affect endothelial functions. We aimed to evaluate the status of serum 25(OH)Vit D3 levels and its association with disease activity, endothelial function and carotis intima media thickness (CIMT) in patients with BD. METHODS: Thirty-six BD (F/M: 22/14, mean age: 39.6 years) patients and 51 healthy controls (F/M: 28/23, mean age: 34.5 years) were studied. Rheumatoid arthritis (RA) (n=33) patients (F/M: 26/7, mean age: 50.82 years) were also enrolled, as a disease control group. Endothelial function was evaluated by brachial artery flow mediated dilatation (FMD) and CIMT with B-Mode ultrasound. The vitamin D-deficient BD patients received 1000 IU Vitamin D3 daily for 3 months. RESULTS: Less than 50 nmol/L levels of 25(OH) Vit D3 were present in 61.1% (n=22) of BD and 35.3% (n=18) of HC (serum 25(OH)Vit D3 levels: BD: 44.5 (9-112) vs HC: 56 (14-125) nmol/lt, p=0.01). CIMT and FMD were also significantly different between BD and HC [0.56 (0.35-9.26) vs. 0.39 (0-0.52) and 5.20 (0.56-30.58) vs. 9.04 (-6.9-34.17), p=0.001 and p=0.02, respectively]. However, no correlation was observed between 25(OH)VitD3 levels and CIMT or FMD (r=0.6, p=0.7 and r=0.03, p=0.8, respectively) at baseline. CIMT measurements improved after replacement therapy (0.56 vs. 0.49, p=0.02), FMD measurements also improved, but not reaching statistical significance (5.2 vs. 8.28, p=0.06). CONCLUSIONS: A high presence of vitamin D deficiency was observed in BD patients from Turkey and replacement of vitamin D had favourable effects on endothelial function.

The effect of azithromycin on reactive oxygen species in rosacea.

BACKGROUND: Recent evidence suggests that inflammation in rosacea is associated with generation of reactive oxygen species (ROS) that are released by inflammatory cells. The efficacy of current therapeutic agents for rosacea such as tetracyclines and metronidazole has also been attributed to their antioxidant properties. Recently, a macrolide antibiotic, azithromycin, has been found to be an effective alternative in the treatment of rosacea. AIM: We planned a study to evaluate the antioxidant effects of azithromycin on ROS in rosacea. We compared basal ROS concentrations measured in the facial skin of patients with rosacea with the post-treatment levels and with those of healthy controls. METHODS: Facial skin biopsies of 17 papulopustular patients with rosacea and 25 healthy controls were taken. Rosacea patients were assigned to receive oral azithromycin 500 mg on three consecutive days each week for 4 weeks. The total number of inflammatory lesions (the sum of papules and pustules) on the face of each patient with rosacea was counted at each visit. The luminol- and lucigenin-enhanced chemiluminescence (CL) levels of patients with rosacea were measured before and after 4 weeks of treatment and compared with those of healthy controls. RESULTS: Rosacea patients had higher ROS levels than healthy controls (P < 0.001). A statistically significant decrease of both luminol- and lucigenin-enhanced CL levels were observed in patients with rosacea after treatment with azithromycin (t = 4.602, P < 0.001; vs. t = 4.634, P < 0.001, respectively). CONCLUSION: Rosacea patients have higher ROS levels than healthy controls. The results of our study support the antioxidant properties of azithromycin in rosacea.

The effect of economic status on height, insulin-like growth factor (IGF)-I and IGF binding protein-3 concentrations in healthy Turkish children.

OBJECTIVES: The effect of economic status (ES) on growth, insulin-like growth factor (IGF)-I and IGF-binding protein (IGFBP)-3 in healthy children is not well characterized. We aimed to study the interrelationship between height, weight, IGF-I, IGFBP-3, mid-parental height (MPH) and ES. DESIGN/SUBJECTS: Eight hundred and fourteen healthy children (428 boys, 386 girls; age 3-18 years) were classified according to income of the families as low, middle and high. Standard deviation scores (SDSs) of height, weight, MPH, IGF-I and IGFBP-3 were compared between the groups. The combined effect of these parameters and ES on height SDS was investigated with complex statistical models. RESULTS: There was a significant trend for height and weight SDSs to increase with higher income levels in boys, but not in girls. Body mass index (BMI) SDSs were similar in three groups. There was a general trend for MPH SDS to increase with income levels in both sexes. In boys, IGF-I SDS was significantly higher in high ES group than low ES. In girls, IGFBP-3 SDSs were significantly higher in high ES group than in middle ES group. For both genders, height SDS was highly correlated with weight SDS and moderately correlated with BMI SDS, MPH SDS and IGF-1 SDS. All correlations were significant and positive. Complex models showed that MPH (19%), IGF-I (13%) and ES (3%) in boys, and MPH (16%) and IGF-I (7%) in girls have significant contribution to height SDSs. CONCLUSIONS: ES per se, independent of overt malnutrition, affects height, weight, IGF-I and IGFBP-3 with some gender differences in healthy children. Influence of income on height and weight show sexual dimorphism, a slight but significant effect is observed only in boys. MPH is the most prominent variable effecting height in healthy children. Higher height and MPH SDSs observed in higher income groups suggest that secular trend in growth still exists, at least in boys, in a country of favorable economic development.

The effect of postmenopausal hormone therapy with or without folic acid supplementation on serum homocysteine level.

OBJECTIVE: To evaluate the effects of postmenopausal hormone therapy (HT) with or without the addition of folic acid (FA) on serum homocysteine levels in a randomized, placebo-controlled design. Additionally, a non-randomized control group with no treatment was included. METHODS: Forty non-hysterectomized healthy postmenopausal women were randomly allocated to receive either oral continuous combined HT (0.625 mg conjugated equine estrogen with 2.5 mg medroxyprogesterone acetate daily) and oral folic acid (5 mg/day, n = 20) or HT and placebo (n = 20) for 3 months. A control group (n = 15) did not receive any study medication and was followed in the same manner. The fasting total serum homocysteine level was measured by fluorescence polarization immunoassay with a sensitivity of < 0.5 micromol/l. Serum levels of folate, estrogen and lipid profile were also followed. RESULTS: The mean age of the postmenopausal women was 52 +/- 6 years. Baseline homocysteine level was the highest in the HT + FA group (9.96 +/- 2.82 micromol/l), compared to HT + placebo (9.64 +/- 1.89 micromol/l) and control groups (9.01 +/- 1.83 micromol/l) (ANCOVA, p = 0.022). Low baseline folate and vitamin B12 levels contributed significantly to the high level of baseline homocysteine in the HT + FA group. The addition of FA to HT led to a significant decrease in the serum homocysteine level from the baseline level of 9.96 +/- 2.82 micromol/l to the final level of 8.92 +/- 2.53 micromol/l (p = 0.023). On the other hand, HT alone (HT + placebo group) significantly increased the serum homocysteine level from 9.64 +/- 1.89 micromol/l to 10.22 +/- 1.77 micromol/l without a decline in serum folate level (p = 0.045). The serum homocysteine level in the control group did not change significantly (from 9.01 +/- 1.83 micromol/l to 9.58 +/- 2.05 micromol/l, p = 0.29). CONCLUSIONS: Three months of oral continuous combined HT increased the fasting total serum homocysteine level without affecting the serum folate level. Lowering the homocysteine level in postmenopausal woman on HT is achievable by folic acid supplementation.

Inhibition of gastric emptying by acarbose is correlated with GLP-1 response and accompanied by CCK release.

We investigated the effect of acarbose, an alpha-glucosidase and pancreatic alpha-amylase inhibitor, on gastric emptying of solid meals of varying nutrient composition and plasma responses of gut hormones. Gastric emptying was determined with scintigraphy in healthy subjects, and all studies were performed with and without 100 mg of acarbose, in random order, at least 1 wk apart. Acarbose did not alter the emptying of a carbohydrate-free meal, but it delayed emptying of a mixed meal and a carbohydrate-free meal given 2 h after sucrose ingestion. In meal groups with carbohydrates, acarbose attenuated responses of plasma insulin and glucose-dependent insulinotropic polypeptide (GIP) while augmenting responses of CCK, glucagon-like peptide-1 (GLP-1), and peptide YY (PYY). With mixed meal + acarbose, area under the curve (AUC) of gastric emptying was positively correlated with integrated plasma response of GLP-1 (r = 0.68, P < 0.02). With the carbohydrate-free meal after sucrose and acarbose ingestion, AUC of gastric emptying was negatively correlated with integrated plasma response of GIP, implying that prior alteration of carbohydrate absorption modifies gastric emptying of a meal. The results demonstrate that acarbose delays gastric emptying of solid meals and augments release of CCK, GLP-1, and PYY mainly by retarding/inhibiting carbohydrate absorption. Augmented GLP-1 release by acarbose appears to play a major role in the inhibition of gastric emptying of a mixed meal, whereas CCK and PYY may have contributory roles.

Nitric oxide and endothelin relationship in intestinal ischemia/reperfusion injury (II).

Endothelins ( ETs ) are potent vasoconstrictors derived from vascular endothelium. They have primary roles in many pathophysiologic states including ischemia/reperfusion (I/R) injury. The relationships between nitric oxide (NO) and ETs are still under investigation. In this study on rats we want to focus on the interaction of NO and ET especially in I/R injury. For this purpose ET-1 and PD-156252, a nonselective ET receptor blocker, were given in a mesenteric I/R model and reactive oxygen species were detected directly using chemiluminescence of the ileal tissue. ET administrations to sham and I/R groups caused significant increases in NO concentrations whereas, in terms of peroxynitrite, which is a highly reactive group of free radicals, its increasing effects were seen only in I/R groups. This suggests that in I/R where superoxide levels increase together with NO, the conversion to peroxynitrite is likely and this effect is augmented with ET administration. On the other hand PD administration decreases superoxide and thereby peroxynitrite levels and this study shows that the effect of PD-156252 is established through this mode of action. These data suggest therapeutic approaches that may be beneficial in the treatment of I/R injury.

Different kinds of reactive oxygen and nitrogen species were detected in colon and breast tumors.

Several studies have shown the involvement of reactive oxygen species (ROS; O2*-, hypochlorite, hydroxyl radical, hydrogen peroxide) in carcinogenesis. With certain pathologies, nitric oxide (NO) is formed and can interact with superoxide radical (O2*-) resulting in the propagation of the highly reactive species, peroxynitrite. In order to study the molecular mechanisms underlying the ability of reactive oxygen and nitrogen species (RONS) to mediate carcinogenesis, we have measured ROS, NO, and peroxynitrite content of cancerous tissues obtained from colon and breast carcinoma cases by chemiluminescence technique. All ROS were significantly increased in cancerous colon tissues with hypochlorite making the most important contribution and suggesting the role of inflammatory cells. NO was also increased and the peroxynitrite concentration was higher in cancerous samples. For breast carcinoma cases, only O2*- was significantly increased. Hypochlorite was not detected excluding the contribution of inflammatory cells. NO concentrations were not significantly different, therefore, ROS might originate by change in the redox state of the tissue.

Estrogens ameliorate remote organ inflammation induced by burn injury in rats.

OBJECTIVE AND DESIGN: The present study was designed to investigate the role of sex steroids in burn-induced remote organ injury. MATERIAL OR SUBJECTS: Male Wistar albino rats were given burn trauma (n=39), and underwent castration or sham operation at 2 h following the burn injury. TREATMENT: Rats were injected sc with either 17beta estradiol benzoate (E2, 10 mg/kg) or an androgen receptor blocker cyproterone acetate (CPA, 25 mg/kg) or vehicle, immediately after burn and at 12 h. METHODS: At 24 h of burn insult, rats were decapitated. Blood samples for RIA of testosterone, estradiol and tumor necrosis factor (TNF)-alpha and the tissue samples for myeloperoxidase activitiy (MPO) were taken. ANOVA student's t test was used for statistical analysis. RESULTS: Castration, antiandrogen and E2 treatments increased plasma estradiol levels and depressed burn-induced elevation in serum TNF-alpha levels. In the liver and lung, burn-induced increase in MPO was reduced by E2 and castration, while CPA was effective in reducing neutrophil infiltration only in the liver. CONCLUSION: We propose that treatment with estrogens or antiandrogens might be applicable in clinical situations to ameliorate systemic inflammation induced by burn.

Effect of mitochondrial electron transport chain inhibitors on superoxide radical generation in rat hippocampal and striatal slices.

In this study, we have compared the generation of superoxide radical in rat hippocampal and striatal slices in the presence of specific mitochondrial electron transport chain (ETC) inhibitors (complexes I and III) under control and depolarization conditions [incubation in artificial cerebrospinal fluid (ACSF) or depolarizing ACSF (dACSF), respectively]. Superoxide radical generation was increased in both ACSF- and dACSF-incubated hippocampal and striatal slices when rotenone and antimycin A were added to the incubation medium. The increase in superoxide radical was dependent on the concentration of ETC inhibitors under control, but not depolarization conditions. Rotenone was found to be more effective than antimycin A in producing superoxide radical from hippocampal and striatal slices. Our results also showed that hippocampal slices were more sensitive to ETC inhibitors compared with striatal slices. Thus, different regions of the brain seem to differ in their capacity to generate free radicals and vulnerability to oxidative stress conditions. This difference should be considered in developing therapeutic modalities against oxidative stress-related disorders and neurodegeneration.

Endothelin-1-induced PMN infiltration and mucosal dysfunction in the rat small intestine.

The objectives of this study were to characterize the effects of endothelin (ET)-1 on intestinal mucosal parameters and to assess the contribution of polymorphonuclear leukocytes (PMNs), intercellular adhesion molecule-1 (ICAM-1), and a platelet-activating factor (PAF) to the mucosal dysfunction induced by ET-1. Different concentrations of ET-1 (100, 200, and 400 pmol/kg) were infused into the superior mesenteric artery for 10 min, and tissue samples were obtained 30 min after terminating the infusion. ET-1 administration significantly elevated tissue myeloperoxidase activity, plasma carbonyl content, and tissue chemiluminescence intensity, indicating that ET-1 produces PMN infiltration and oxidant stress. Blood-to-lumen clearance of (51)Cr-EDTA significantly increased after ET-1 infusion (400 pmol/kg). Monoclonal antibodies against ICAM-1 (1A29, 2 mg/kg), antineutrophil serum, and PAF antagonist (WEB-2086, 10 mg/kg) attenuated the mucosal barrier dysfunction induced by ET-1. Overall, our data indicate that ET-1 causes PMN accumulation, oxidant stress, and mucosal dysfunction in the rat small intestine and that ET-1-induced mucosal dysfunction involves a mechanism that includes a role for PMNs, ICAM-1, and PAF.

The effects of free oxygen radical scavenger and platelet-activating factor antagonist agents in experimental acute pancreatitis.

This study was done to evaluate the possible preventive effects of reactive oxygen species (ROS) scavenger agent desferrioxamine (DFX) and platelet-activating factor (PAF) antagonist agent ginkgo biloba (GB) in an experimental acute pancreatitis model. Seventy-eight CD-1 mice were divided into six groups consisting of 10-13 mice. Induction of pancreatitis was achieved by cerulein injection in groups 2-5. The first group was control, whereas DFX and GB were used alone or in combinations as preventive agents in groups 3-5. DFX or GB were injected to the mice in groups 6 and 7 to evaluate any toxic effect. The assessment of the pancreatic edema and inflammation, the measurement of the amylase and the pancreatic weight and the measurement of the pancreatic tissue oxidative capacity by chemiluminescence method were the parameters to evaluate pancreatitis. Although the results indicate DFX and GB alone or in combinations have significant preventive roles, this was not a complete prevention.

The effects of thromboxane synthase inhibition on reperfusion injury and endothelin-1,2 levels in allograft kidney transplantation in rats.

Thromboxane A2 is a proaggregative vasoconstrictor that is synthesized and released in reperfusion injury. We aimed to investigate the effects of thromboxane synthase inhibitor, UK 38485, on endothelin-1,2 (ET) response of the renal endothelium and lipid peroxidation and protein oxidation in the early period of kidney transplantation. Four groups (n=8 in group IV and n=10 in the others) [corrected] of Sprague-Dawley rats were designed as Group I (sham nephrectomy), Group II (autotransplantation), Group III (allotransplantation) and Group IV (allotransplantation group in which the allografts were perfused with UK 38485. All subjects underwent right nephrectomy after transplantation. The grafts were flushed with 4 ml of ice-cold Ringer's lactate and in Group IV 10 microg of UK 38485 was added into the solution for each kidney. In allotransplantation groups, the kidneys were harvested from allogeneic white Wistar albino rats. The kidney grafts were allowed 120 min of reperfusion after 40 min of cold ischemic period. ET-1,2 plasma concentrations in the renal vein blood and diene conjugates (DC), hydroxyalkanals (HAA), hydroxyalkenals (HAE) and malondialdehyde (MDA) levels as the products of lipid peroxidation, protein carbonyls and protein sulfhydryls as the indicators of protein oxidation were analyzed in kidney tissue. Plasma ET-1,2 concentrations increased significantly in Group II and Group III (P<0.01) when compared to Group I but decreased in Group IV in comparison with Group III (P<0.05). DC, HAA, HAE and MDA levels increased in Groups II and III (P<0.001). Significant protein oxidation occurred only in Group III (P<0.01). Perfusion of the allografts with UK 38485 prevented lipid peroxidation and protein oxidation in Group IV. Histopathological changes were mild in the last group. We concluded that, in kidney transplantation, local administration of UK 38485 has cytopreservative effects on the allografts and this effect can be related to ET-1,2 concentrations.

Role of nitric oxide in indomethacin-induced gastric mucosal dysfunction in the rat.

The present study was undertaken to explore the role of nitric oxide (NO) in the pathogenesis of experimental non-steroidal anti-inflammatory drug (NSAID)-induced gastropathy. We assessed the role of NO inhibition and donation in indomethacin-induced gastric mucosal dysfunction. The stomach was perfused with vehicle (control) for 20 min, followed by indomethacin (10 mg ml-1 in 1 25 % sodium bicarbonate, pH 8 4) for 120 min. NG-nitro-L-arginine methyl ester (L-NAME, 5 and 10 mg kg-1, I.V. bolus), L-arginine, D-arginine (100 mg kg-1 I.V. bolus, 10 mg kg-1 h-1, 2 h infusion) and the NO donor glyceryl trinitrate (GTN) were given at the same time (20, 40 and 80 microg kg-1 min-1, 15 min infusion) as perfusion with indomethacin was started. Epithelial permeability was quantified by measuring blood-to-lumen clearance of 51Cr-labelled EDTA. Indomethacin caused a 20-fold increase in 51Cr-EDTA leakage compared with that of the control group. Treatment with L-NAME or L-arginine did not affect the indomethacin-induced alterations in mucosal permeability. Administration of GTN (20 microg kg-1 min-1) significantly reduced the indomethacin-induced mucosal dysfunction. By contrast, higher doses of GTN (80 microg kg-1 min-1) exacerbated epithelial dysfunction induced by indomethacin. Elevated levels of carbonyls and myeloperoxidase (MPO) observed after indomethacin administration were significantly reduced, to the control values, when GTN (20 microg kg-1 min-1) was administered along with indomethacin. These data suggest that NO from exogenous sources can exert a dual action on the integrity of the gastric mucosa challenged by indomethacin. Low doses of GTN can prevent mucosal dysfunction induced by indomethacin, while higher doses of GTN may exacerbate the increases in epithelial permeability.

Oxygen radicals and nitric oxide in rat mesenteric ischaemia-reperfusion: modulation by L-arginine and NG-nitro-L-arginine methyl ester.

1. The aims of the present study were to detect changes in superoxide anion (O2.-), nitric oxide (NO) and other reactive oxygen species (ROS) directly by measurement of chemiluminescence (CL) and to investigate the role of L-arginine, a nitric oxide synthase (NOS) substrate, and NG-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, together with their molecular enantiomers D-arginine and D-NAME, in a rat mesenteric ischaemia-reperfusion (I/R) model. 2. Seventy-nine female Wistar albino rats were divided into eight groups. The first three groups underwent sham operation; group 1 was the control group, group 2 received L-arginine and group 3 received L-NAME. Ischaemia was produced in the remaining five groups by ligation of the superior mesenteric artery for 30 min followed by 60 min reperfusion. Group 4 rats were control I/R rats and groups 5-8 received either L-arginine, L-NAME, D-arginine or D-NAME, respectively. 3. Both luminol and lucigenin CL was significantly increased in I/R groups compared with sham-operated groups. L-Arginine significantly reduced CL measurements. D-Arginine was also protective, but not as much as L-arginine. Both L- and D-arginine had in vitro O2.- (-)scavenging potential, as tested by the xanthine-xanthine oxidase system. NG-Nitro-L-arginine methyl ester decreased lipid peroxidation values in addition to reducing CL measurements. Nitric oxide concentrations were significantly increased in I/R groups in comparison with sham-operated groups. Peroxynitrite formation was increased by I/R. Treatment with L-NAME was beneficial by reducing NO concentrations in the reperfused ileum. 4. In our I/R model, O2.-, NO and other ROS were increased. Although NOS inhibitors were effective in reducing oxidative damage, increasing NO concentrations with L-arginine was also beneficial, presumably due to the ability of L-arginine to inhibit phagocyte adherence and its radical scavenging potential. In fact, NO may have different effects in terms of tissue injury or protection depending on the concentration of oxygen and the haemodynamic state of the tissue.

Measurement of reactive oxygen species by chemiluminescence in diet-induced atherosclerosis: protective roles of vitamin E and probucol on different radical species.

We have investigated the effects of a high-cholesterol diet on the production of different reactive oxygen species in rabbit aortic rings and evaluated the protective effects of vitamin E and probucol in preventing peroxidative changes. Twenty-five male albino rabbits were divided into five groups. Control rabbits were fed a vitamin E-poor rabbit chow. Rabbits in the second group were given a vitamin E-poor diet supplemented with 2% cholesterol. Other groups received either 50 mg/kg vitamin E, 1% probucol, or both, in addition to 2% cholesterol for 4 weeks. Reactive oxygen species formation in aortic rings was measured by enhanced chemiluminescence using luminol and lucigenin. (The results were given as cpm/mg wet weight.) Further differentiation of radical species involved in luminol-enhanced chemiluminescence was performed using sodium azide and L-nitroarginine, a selective inhibitor of nitric oxide production. Our results indicated that cholesterol feeding increased lucigenin and luminol chemiluminescence, where the contribution of free radicals inhibited by sodium azide (radicals originating from endothelial cells or from phagocytes) were 53% and peroxynitrite 24%. Both vitamin E and probucol were effective as scavengers of free radicals, but the effect of vitamin E was more pronounced. In conclusion, the present study demonstrated excessive generation of reactive oxygen species within the atherosclerotic vessel. Peroxidative changes could be prevented by vitamin E and probucol treatment, but vitamin E seemed to be more efficient.

Early detection of peritonitis in continuous ambulatory peritoneal dialysis patients by use of chemiluminescence: evaluation of diagnostic accuracy by receiver-operating characteristic curve analysis.

Continuous ambulatory peritoneal dialysis (CAPD) is now a widely accepted treatment for end-stage renal disease. However, the high incidence of peritonitis is a major complication of CAPD. Polymorphonuclear leukocytes (PMNs) play a major role in antimicrobial response of the host. During phagocytosis, the PMNs undergo a striking increase in oxidative metabolism, known as the respiratory burst, and emit light as chemiluminescence (CL). CL is thus a sensitive measure of PMN oxidative potential and correlates well with antimicrobial activity. In view of the observation of increased susceptibility to infection in CAPD patients, we have studied lucigenin- and luminol-enhanced CL in peritoneal fluids of these patients and assessed the diagnostic accuracy of these tests by ROC curve analysis. ROC curves showed diagnostic accuracies for both tests that were superior to counts of PMNs in the dialysis fluid (P <0.001). At selected cutoff values of 150000 cpm/vial for lucigenin CL and 600000 cpm/vial for luminol CL, sensitivities were 100%. Specificities for lucigenin and luminol CL were 89% and 80%, respectively. Our results suggest that CL measurements can be used as an early marker for the presence of infection in CAPD patients.

Adenosine protects against indomethacin-induced gastric damage in rats.

This study examines the putative gastroprotective effect of adenosine on indomethacin-induced gastric lesions and the possible mechanisms involved. After 24 hr of starvation, the rats were treated either with indomethacin (Indo; 25 mg/kg, subcutaneously) alone or adenosine + Indo (Ado; 7.5 mg/kg, subcutaneously, three times a day), or the vehicle (5% NaHCO3, subcutaneously). The length of hemorrhagic lesions in the stomachs was expressed as the lesion index. The tissue-associated myeloperoxidase (MPO) activity and protein oxidation were measured in gastric tissue samples. Formation of reactive oxygen species in gastric tissues was measured by using luminol- and lucigenin-enhanced chemiluminescence. In other groups of rats, gastric mucosal permeability and gastric acid output were performed following the same treatment regimens. The gastric mucosal permeability was measured by determination of [51Cr]EDTA clearance in a perfused stomach preparation and gastric acid secretion studies were performed following pylorus ligation. The lesion index, the increase in lucigenin-enhanced chemiluminescence, and the increase in gastric mucosal permeability in Indo-treated rats were reversed by Ado pretreatment. Ado pretreatment also prevented the increase in gastric acid output and gastric volume in Indo-treated rats. Thus, these findings implicate that exogenous adenosine has a protective role on indomethacin-induced gastric lesions, possibly by inhibiting gastric hyperacidity and reactive oxygen formation and by preventing disruption of the mucosal integrity.

Nitric oxide and endothelin relationship in intestinal ischemia/reperfusion injury.

Gastrointestinal mucosal blood flow is dependent on a balanced release of vasoactive substances from endothelium. Nitric oxide (NO) may increase the flow by vasodilatation and/or antiaggregation whereas endothelin (ET) may decrease it by vasoconstriction and aggregation. NO and ET may have counterbalancing effects on each other in tissue damage. In order to test this hypothesis, in this study on rats, L-arginine to increase NO levels and N(G)-nitro-L-arginine methyl esther (L-NAME) to decrease NO levels have been used in an intestinal ischemia/ reperfusion (I/R) injury model and portal vein ET response was evaluated. Lipid peroxidation product measurements and chemiluminescence (CL) studies were also carried out in ileal tissue samples. Intestinal I/R injury caused an increase in portal venous ET levels with levels of 9.4+/-0.5 fmol/ml in sham operation and 14.8+/-1.6 fmol/ml in I/R group. ET level of L-NAME-sh group was lower than that of sham-operated group and also ET level of L-NAME-I/R group was lower than that of I/R group. This yielded the conclusion that inhibition of NO synthesis decreases portal venous ET levels in this model. Increased NO production by L-arginine caused increased ET levels in sham operated groups but this effect was not observed in I/R injury state. This study also showed that inhibition of NO synthesis has a protective role by reducing the reperfusion damage in this model. It is likely that NO and ET have a feedback effect on each other both under physiologic conditions and I/R injury.

The functional assessment of autotransplanted splenic tissue by its capacity to remove oxidatively modified erythrocytes.

Free radicals and reactive oxygen species have been implicated in the pathogenesis of a variety of hematologic diseases and erythrocyte aging. Aged erythrocytes are removed from the circulation primarily by the spleen. In this study, we aimed to determine the functional effectiveness of autotransplanted splenic tissue by its capacity to remove oxidatively modified erythrocytes from the circulation. Our experimental model in rats includes splenectomy with autotransplantation of 80% of the excised splenic tissue into the omental pouch. In this model, free radical damage was estimated by different parameters of lipid peroxidation such as carbonyl content and thiobarbituric acid reactive substances (TBARS), together with Heinz body formation. Our results have shown that splenic autotransplantation was effective in removing oxidatively modified, aged erythrocytes from the circulation.