We have developed FISH probes specific for the family Helicobacteraceae as well as two individual Helicobacter species. This study will allow the future use of the FISH to better understand host-pathogen interactions in vitro.

Natural colonization with different Helicobacter species was found in IL-10-/- mice within the same breeding colony. The severity of typhlocolitis differed according to the colonizing Helicobacter species. Furthermore, the rate of typhlocolitis development in IL-10-/- mice naturally colonized with Helicobacter species was significantly slower than that reported in experimentally infected mice.

The inflammatory bowel diseases are considered an abnormal host immune response to an environmental stimulus. Evidence suggests a role for intestinal bacteria in initiating and/or providing an ongoing stimulus for inflammation in inflammatory bowel disease. Helicobacter pylori is the major cause of active chronic gastritis and peptic ulcers in humans and has been linked to gastric carcinoma and lymphoma. Studies in various animal models, particularly mice, have identified enterohepatic Helicobacter species that are capable of causing hepatitis and enterocolitis. We hypothesize that Helicobacter species may have a role in maintaining inflammation in humans with inflammatory bowel disease. In order to investigate this, biopsy specimens were obtained from patients with and without inflammatory bowel disease. DNA was extracted from the tissues and subjected to PCR with primers designed to detect the ribosomal DNA of members of the Helicobacter species. DNA from six biopsy samples from 60 inflammatory bowel disease patients tested positive. This included 5 of 33 ulcerative colitis patients that were positive compared to 0 of 29 age-matched controls (P < 0.04). Sequencing of the bands produced by PCR amplification revealed >99% homology with H. pylori. These results indicate that a member of the Helicobacter species may be involved in some cases of ulcerative colitis.

Sequential effects are ubiquitous in decision-making, but no more than in the absolute identification task where participants must identify stimuli from a set of items that vary on a single dimension. A number of competing explanations for these sequential effects have been proposed, and recently Matthews and Stewart [(2009a). The effect of inter-stimulus interval on sequential effects in absolute identification. The Quarterly Journal of Experimental Psychology, 62, 2014-2029] showed that manipulations of the time between decisions is useful in discriminating between these accounts. We use a Bayesian hierarchical regression model to show that inter-trial interval has an influence on behaviour when it varies across different blocks of trials, but not when it varies from trial to trial. We discuss the implications of both our and Matthews and Stewart's results on the effect of inter-trial interval for theories of sequential effects.