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Using immune electron microscopy, an attempt has been made to visualise viral particles in Crohn's disease tissue and faeces. No particles resembling viruses were observed, but in the absence of a specific antiserum a negative result does not exclude the presence of a virus, particularly if it is sparsely distributed. Compared with controls, an abundance of a 12 nm particle was found in all Crohn's disease tissue and one small intestinal lymphoma. This particle has been identified as ferritin and is unlikely to be of aetiological significance.

Immunohistochemical studies using an antiserum to a pure porcine vasoactive intestinal peptide, possessing no cross reactivity against the related hormones glucagon, secretin, and gastrin-inhibitory peptide, revealed a wide distribution of vasoactive intestinal peptide cells throughout the entire length of the mammalian and avian gut. The highest numbers of cells were present in the small intestine and more particularly in the large intestine in all species investigated. Three types of endocrine cell in the mammalian gut are sufficiently widely distributed to be considered as the sites for production of vasoactive intestinal peptide. In the avian gut there are only two identifiable cell types. Sequential immunofluorescence and silver staining showed, in the bird, that the enterochromaffin (EC) cell was not responsible. This procedure could not be used in our mammalian gut samples but here serial section immunofluorescence for enteroglucagon and vasoactive intestinal peptide indicated that the two cells were not identical and that each was differently localized in the mucosa. These results leave the D cell of the Wiesbaden classification as the most likely site for the production of vasoactive intestinal peptide. The final identification must come from successful immune electron cytochemistry but this has not yet been achieved.

The effects of intravenous infusions of prostaglandins (PGs) F2 alpha(0-4 or 0-8 mug kg-1 min-1) or E2 (0-08 or 0-1 mug kg-1 min equals1) on net colonic movement of water and electrolytes and on ileal flow were measured in eight healthy males by simultaneous ileal and colonic perfusion. Ileal flow was increased by PGF2 alpha (six subjects) from a mean of 1-69 ml min-1 to 4-63 ml min-1 (P smaller than 0-01); it also increased in the two subjects given PGE2. Colonic absorptive function was not significantly diminished by either prostaglandin. These results suggest that diarrhoea due to prostaglandins originates in the small intestine.

A mycobacterial aetiology for Crohn's disease (CD) has been suggested. Slow growing mycobacteria indistinguishable from M paratuberculosis, the causative agent of enteritis in ruminants (Johne's disease) have been isolated from CD tissues. We have used cloned genomic DNA probes derived from a CD isolated mycobacteria strain Ben, to investigate the presence of mycobacterial DNA sequences in CD tissues. DNA was extracted from total tissue from 17 CD and four control gut specimens. DNA was digested with restriction endonucleases, electrophoresed and transferred to nylon membranes by Southern blotting and hybridised to radiolabelled DNA probes. No mycobacterial DNA was detected in any tissue sample studied. Reconstitution experiments with known numbers of in vitro cultured mycobacteria showed sensitive detection of mycobacterial DNA. DNA extracted from mouse liver, infected with M lepraemurium revealed a strong hybridisation signal and showed the applicability of the experimental approach to the detection of mycobacterial DNA in naturally infected tissues. The results do not provide evidence for the involvement of mycobacteria in the pathogenesis of CD but do not exclude the possibility of low levels of infection in subsets of intestinal cells with spheroplast or cell wall deficient forms of mycobacteria.

Indirect evidence has suggested that circulating trophic factor(s) are involved in intestinal adaptation. A 3T3 fibroblast cell culture system was used to more directly delineate the presence of such factors. Rats were divided into four groups; C-unop, those undergoing no surgery, S, those in which a dorsal slit was made; C-op, those in which the peritoneum was incised; and R, those undergoing 80% intestinal resection. At the time of death at 24 hours, one week and two weeks postoperative, stimulation of DNA synthesis in the 3T3 cells was noted after incubation with platelet free plasma from the C-op and R groups, and simultaneously an increase in ileal DNA specific activity occurred. Characterisation of the plasma fraction with growth factor activity revealed it to have a MW of greater than 6,000 and less than 14,000 d. The factor(s) was resistant to reduction with DTT, and was partially inactivated by heating to 60 degrees C. The use of 3T3 cell growth factor assay system allows further characterisation of circulating factors involved in intestinal adaptation.

A hormone-secreting renal tumour that affected small bowel structure, motility, and function has been described by Gleeson et al (1971). The present studies show that the large amount of glucagon-like immunoreactivity which could be extracted from this tumour had the molecular weight, action on plasma insulin and glucose in vivo, and immunological reactions of the gut hormone enteroglucagon. This is the first enteroglucagonoma to be reported.

Small intestinal samples were obtained by intubation from multiple sites along the small intestine in 11 subjects with no known gastrointestinal disease eating a normal diet and at laparotomy in a further three subjects. Free (unconjugated) bile acids were consistently demonstrated in ileal samples, and occasionally in lower jejunal samples, by thin-layer chromatography, supplemented in some cases by gas/liquid chromatography and by infrared spectroscopy. The free bile acid concentration, measured enzymically following thin-layer chromatography, reached a maximum (1 mM) in the lower ileum, where it represented half the total bile acid concentration. Following ampicillin, the concentration of free bile acids decreased markedly, suggesting that they resulted from bacterial deconjugation; at the same time the total bile acid concentration increased, suggesting impaired absorption due to the reduced concentration of the more rapidly absorbed free bile acids. Our results indicate that the presence of free bile acids in lower jejunal and ileal samples is a normal finding, and cannot be taken as evidence of abnormal bacterial overgrowth. They also suggest that bacterial deconjugation at these sites may be a factor contributing to the remarkable efficiency of bile salt reabsorption.