Hydrogen peroxide stimulates rat colonic prostaglandin production and alters electrolyte transport.

The changes in short circuit current (electrogenic Cl- secretion) of rat colon brought about by xanthine/xanthine oxidase in the Ussing chamber were inhibited by catalase and diethyldithiocarbamate, but not by superoxide dismutase. These results, the reproduction of the response with glucose/glucose oxidase and with exogenous H2O2, and the lack of effect of preincubation with deferoxamine or thiourea implicate H2O2, and not O2- or OH., as the important reactive oxygen metabolite altering intestinal electrolyte transport. 1 mM H2O2 stimulated colonic PGE2 and PGI2 production 8- and 15-fold, respectively, inhibited neutral NaCl absorption, and stimulated biphasic electrogenic Cl secretion with little effect on enterocyte lactic dehydrogenase release, epithelial conductance, or histology. Cl- secretion was reduced by cyclooxygenase inhibition. Also, the Cl- secretion, but not the increase in prostaglandin production, was reduced by enteric nervous system blockade with tetrodotoxin, hexamethonium, or atropine. Thus, H2O2 appears to alter electrolyte transport by releasing prostaglandins that activate the enteric nervous system. The change in short circuit current in response to Iloprost, but not PGE2, was blocked by tetrodotoxin. Therefore, PGI2 may be the mediator of the H2O2 response. H2O2 produced in nontoxic concentrations in the inflamed gut could have significant physiologic effects on intestinal water and electrolyte transport

Immune system control of rat and rabbit colonic electrolyte transport. Role of prostaglandins and enteric nervous system.

Le système immunitaire comme le système nerveux et endocrinien intestinal, peut être un système régulateur important du transport intestinal de l'eau et des électrolytes à l'état normal et dans les états pathologiques

Cyclospora: an enigma worth unraveling.

In part, Cyclospora cayetanensis owes its recognition as an emerging pathogen to the increased use of staining methods for detecting enteric parasites such as Cryptosporidium. First reported in patients in New Guinea in 1977 but thought to be a coccidian parasite of the genus Isospora, C. cayetanensis received little attention until it was again described in 1985 in New York and Peru. In the early 1990s, human infection associated with waterborne transmission of C. cayetanensis was suspected; foodborne transmission was likewise suggested in early studies. The parasite was associated with several disease outbreaks in the United States during 1996 and 1997. This article reviews current knowledge about C. cayetanensis (including its association with waterborne and foodborne transmission), unresolved issues, and research needs

Cryptosporidium Species and Subtypes and Clinical Manifestations in Children, Peru

One-sentence summary for table of contents: Different genotypes and subtypes are linked to different clinical manifestations

Cryptosporidium parvum, molecular environmental detection and implications

Cryptosporidiosis is a major cause of diarrheal illness worldwide and characterized by several daily bowel movements, resulting in fluid loss and dehydration. Two species, Cryptosporidium hominis and C. parvum are the main causative agents in human infection. Complicating matters for disinfection, epidemiology, and treatment studies, C. parvum isolates infect multiple mammalian species while C. hominis solely infects humans. The purpose of this dissertation was to: (1) develop a C. parvum PCR based detection method and discuss its limitations; and (2) to extend current epidemiological and molecular data rationalizing the multiple C. parvum host specific infectivity patterns. To fulfill these two objectives, three separate experiments were designed and executed. The results from which are included in the appendix as peer reviewed published manuscripts and are the basis of this dissertation. The first manuscript outlines the use and validation of microscopic micromanipulation to isolate and deliver low numbers of C. parvum oocysts to a test vial of interest. In addition, a nested PCR primer set was developed targeting the 18S rRNA and tested for sensitivity using micromanipulation and specificity using isolated DNA from multiple different species. It was determined that micromanipulation is an accurate technique able to deliver low numbers of oocysts to a test vial of interest. The nested PCR protocol had LLOD, in replicates of 50 and laboratory grade water, of 100% with ten oocysts and 38% with a single oocyst. The second manuscript compared detection efficiencies of the EPA Method 1623 with the nested PCR protocol outlined in the first manuscript. Both methods had equal detection efficiencies giving positive detection at the five-oocyst level. In addition, non-specific PCR amplification results generated during the study revealed specificity issues that have implications effecting past, current and future molecular detection validation processes. The final manuscript describes nucleotide and deduced amino acid differences between the C. parvum and C. hominis attachment/invasion surface proteins Cpgp 40/15, p23, and GP900. This information has implications explaining host-specificity differences observed among Cryptosporidium spp

Developing Monitoring Methods for Leptasterias spp. as Sentinel Species in Detecting Local Environmental Changes

Leptasterias spp., a six-rayed sea star, is found in rocky intertidal habitats ranging from Alaska to central California. Leptasterias spp. can be monitored on a broad scale throughout their range by a variety of means using timed counts and random plot censusing in order to detect both large-scale and local-level changes in the environment due to climate change, land-based human activity, or other environmental events. Leptasterias brood their young externally until the embryos grow into fully developed juveniles. These juveniles disperse by crawling away, limiting their dispersal potential. This localized dispersal provides an opportunity to use Leptasterias spp. as sentinel species of local environmental health across a broad geographic range. We aim to develop an effective method for monitoring these small brooding sea stars along a heterogeneous coastline. We describe two methods for monitoring Leptasterias spp. populations that take into account the patchy distribution patterns of the species in multiple habitat types. Variable sized plots, line transects, and timed counts were used. Monitoring sites were strategically chosen for assessing environmental factors including temperature and terrestrial runoff nearest to San Francisco Bay. Split into two categories of habitat type, beach and tide pool habitat, sites were censused using methods that maximize accuracy of sampling efforts in determining population sizes