Protective effect of Irsogladine on monochloramineinduced gastric mucosallesions in rats:a comparative study with rebamipide

AIM To examine the effect of irsogladine, a novel antiulcer drug, on the mucosal ulcerogenic response to monochloramine (NH 2Cl) in rat stomach, in comparison with rebamipide, another antiulcer drug with cytoprotective activity. METHODS AND RESULTS Oral administration of NH 2Cl (120*!mM) produced severe hemorrhagic lesions in unanesthetized rat stomachs. Both irsogladine ( 1*!mg/*!kg - 10*!mg/*!kg , po ) and rebamipide ( 30*!mg/*!kg - 100*!mg/*!kg , po ) dose dependently prevented the development of these lesions in response to NH 2Cl, the effect of irsogladine was significant at 3*!mg/*!kg or greater, and that of rebamipide only at 100*!mg/*!kg . The protective effect of irsogladine on NH 2Cl induced gastric lesions was significantly reduced by N G nitro L arginine methyl ester (L NAME) but not by indomethacin, while that of rebamipide was significantly mitigated by indomethacin but not by L NAME. Topical application of NH 2Cl (20*!mM) caused a marked reduction of potential difference (PD) in ex vivo stomachs. This PD reduction was not affected by mucosal application of irsogladine, but significantly prevented by rebamipide. The mucosal exposure to NH 4OH (120*!mM) also caused a marked PD reduction in the ischemic stomach (bleeding from the carotid artery), resulting in gastric lesions. These ulcerogenic and PD responses caused by NH 4OH plus ischemia were also significantly mitigated by rebamipide, in an indomethacin sensitive manner, while irsogladine potently prevented such lesions without affecting the PD response, in a L NAME sensitive manner. CONCLUSION These results suggest that ① NH 2Cl generated either exogenously or endogenously damages the gastric mucosa, ② both irsogladine and rebamipide protect the stomach against injury caused by NH 2Cl, and ③ the mechanism underlying the protective action of irsogladine is partly mediated by endogenous nitric oxide, while that of rebamipide is in part mediated by endogenous prostaglandins.

Monochloramine for Remediation of <i>Legionella</i>Only in Domestic Hot Water Systems: An Iron Fist in a Velvet Glove

Monochloramine is a well-known disinfectant for drinking water with several advantages over chlorine and chlorine dioxide. With these two biocides, monochloramine is included in the US-EPA list of disinfectants for drinking water. At the beginning of XXI century, epidemiological studies demonstrated its superior ability to control Legionella in hot water health-care premises. In 2005 a research program started to set up a reliable and effective method to produce monochloramine directly in domestic hot water systems, at the safest concentration and without accumulation of by-products. Results of these researches, which has been carried out with the collaboration of Italian and American Institutions showed that monochloramine can be safely and reliably prepared and that it is the best approach to Legionella remediation in health-care facilities.

Continuous Disinfection by Monochloramine on Domestic Hot Water System of Health-care Facilities for the Control of Legionella Contamination in Italy

Backgroud： The prevention of Legionella spp. colonization of water distribution systems is a critical issue in healthcare settings and only an effective disinfection of water systems and appropriate environmental surveillance strategies allow to prevent nosocomial legionellosis. Methods： Due to the temporary effectiveness （increase of the temperature of water in boilers and shock hyperchlorination）, the high costs （point-of-use water filters） or the ineffectiveness （hydrogen peroxide, H202） of the previous control procedures, 3 devices （one for each hot water loop） continuously injecting monochloramine have been installed in two different Italian hospitals heavily contaminated by Legionellapneumophila SG3 and SG6. Aim： To evaluate the efficacy of continuous disinfection by monochloramine for control of Legionella on domestic hot water （DHW） distribution system of health-care facilities. Findings： One month after the disinfection of DHW with monochloramine, the load ofL. pneumophila SG3 and SG6 （previous mean count ranging from 103 to 105 CFU/L）, as well as the Heterotrophic Plate Count （HPC） （previous mean count ranging from 〉 10^2 to 〉 10^4 CFU/mL）, decreased at undetectable levels in 100% of the sampling points in the two hospitals. Conclusion： The results suggest that continuous injection of monochloramine on DHW systems can fully control L. pneumophila and HPC in contaminated hospitals since the beginning of its application.

Formation Characteristics of N-Nitrosodimethylamine during Chloramines of PolyDADMAC

Interactions of chloramine with organic nitrogen compounds during purification of water for drinking may generate carcinogenic N-nitrosodime-thylamine (NDMA) as byproduct, and it has been found that cationic amine-based water treatment polymers may be one of the important precursors of NDMA. We have analyzed experimentally the influence rule of NDMA formation during chlorination and disinfection, in order to provide technical support for reducing or even avoiding the formation of NDMA. The formation characteristics of nitrosamines during the chlorination of poly-diallyldimethylammonium chloride (polyDADMAC) have been studied during our experiments. The results show that the type of chlorinating agent is crucial for the generation of NDMA;if pH = 7, NDMA has the great potential formation;the NDMA potential formation increases with temperature. The yield of NDMA will be higher as the concentration of monochloramine is 1.5 to 2.5 times of the precursor;the variation of polymer with reaction time can explain the concentration of NDMA in terminal water of pipe network is higher than that in drinking water.

The Spatial Distribution of Nitrite Concentrations in a Large Drinking Water Distribution System in Finland

Nitrite in drinking water is a potential health hazard and monitoring its concentrations in distributed water is of paramount importance. When monochloramine is used in secondary disinfection in drinking water distribution systems (DWDSs), nitrite is often formed by nitrification in the biofilm on the inner surface of distribution pipes. This article attempts to identify areas with a risk of increased nitrite concentrations as well as the main reasons leading to nitrite occurrence in a large urban DWDS in Finland using spatial inspection of obligatory monitoring data. Nitrification was found to occur throughout the study area, though nitrite was not increased everywhere. Instead, nitrite was increased close to the water treatment plants (WTPs) and was connected to fresh drinking water than stagnant drinking water. Temperature effects on nitrite concentrations were surprisingly insignificant, even though it is well known that nitrification reactions are affected by temperature. The temperature dependence of ammonium and total residual chlorine was more significant than the dependence of nitrite. The findings of this study emphasize the need to monitor nitrite concentrations close to WTPs.

Impact of chlorine exposure time on disinfection byproduct formation in the presence of iopamidol and natural organic matter during chloramination

Chloramines,in practice,are formed onsite by adding ammonia to chlorinated drinking water to achieve the required disinfection.While regulated disinfection byproducts(DBPs)are reduced during chloramine disinfection,other DBPs such as iodinated(iodo-)DBPs,that elicit greater toxicity are formed.The objective of this study was to investigate the impact of prechlorination time on the formation of both halogen-specific total organic halogen(TOX)and iodo/chlorinated(chloro-)DBPs during prechlorination/chloramination in source waters(SWs)containing iopamidol,an X-ray contrast medium.Barberton SW(BSW)and Cleveland SW(CSW)containing iopamidol were prechlorinated for 5–60 min and afterwards chloraminated for 72 hr with ammonium chloride.Chlorine contact time(CCT)did not significantly impact total organic iodine(TOI)concentrations after prechlorination or chloramination.Concentrations of total organic chlorine(TOCl)formed during prechlorination did not significantly change regardless of pH and prechlorination time,whileTOClappearedtodecreaseafter 72 hrchloraminationperiod.Dichloroiodomethane(CHCl_2I)formation during prechlorination did not exhibit any significant trends as a function of p H or CCT,but after chloramination,significant increases were observed at pHs 6.5 and 7.5 with respect to CCT.Iodo-HAAs were not formed during prechlorination but were detected after chloramination.Significant quantities of chloroform(CHCl_3)and trichloroacetic acid(TCAA)were formed during prechlorination but formation ceased upon ammonia addition.Therefore,prechlorination studies should measure TOX and DBP concentrations prior to ammonia addition to obtain data regarding the initial conditions.

Factors affecting the formation of trihalomethanes in the presence of bromide during chloramination

The effects of the concentration of dissolved total organic carbon (TOC), the TOC/Br- ratio, bromide ion levels, the chlorine to ammonia-N ratio (Cl:N), the monochloramine dose and the chlorine dose on the formation of trihalomethanes (THMs) (including chloroform, bromodichloromethane, chlorodibromomethane, and bromoform) from chlorination were investigated using aqueous humic acid (HA) solutions. The profile of the chloramine decay was also studied under various bromide ion concentrations. Monochloramine decayed in the presence of organic material and bromide ions. The percentage of chloroform and brominated THMs varied according to the TOC/Br- ratio. Total THMs (TTHMs) formation increased from 112 to 190 μg/L with the increase concentrations of bromide ions from 0.67 to 6.72 mg/L, but the chlorine-substituted THMs were replaced by bromine-substituted THMs. A strong linear correlation was obtained between the monochloramine dose and the formation of THMs for Cl:N ratios of 3:1 and 5:1. These ratios had a distinct effect on the formation of chloroform but had little impact on the formation of bromodichloromethane or chlorodibromomethane. The presence of bromide ions increased the rate of monochloramine decay.

Insight into the formation of iodinated tr ihalomethanes dur ing chlor ination,monochloramination, and dichloramination of iodide-containing water

In this study, the formation of iodinated trihalomethanes(I-THMs) was systematically evaluated and compared for three treatment processes-(i) chlorination,(ii) monochloramine, and(iii) dichloramination-under different p H conditions. The results demonstrated that ITHM formation decreased in the order of monochloramination > dichloramination > chlorination in acidic and neutral p H. However, the generation of I-THMs increased in the dichloramination < chlorination < monochloramination order in alkaline condition. Specifically, the formation of I-THMs increased as p H increased from 5 to 9 during chlorination and monochloramination processes, while the maximum I-THM formation occurred at pH 7 during dichloramination. The discrepancy could be mainly related to the stability of the three chlor(am) ine disinfectants at different p H conditions. Moreover, in order to gain a thorough insight into the mechanisms of I-THM formation during dichloramination, further investigation was conducted on the influencing factors of DOC concentration and Br/Imolar ratio. I-THM formation exhibited an increasing and then decreasing trend as the concentration of DOC increased from 1 to 7 mg-C/L, while the yield of I-THMs increased with increasing Br/Imolar ratio from 5:0 to 5:10. During the three processes mentioned above, similar I-THM formation results were also obtained in real water, which indicates that the excessive generation of I-THMs should be paid special attention during the disinfection of iodide-containing water.