Robert Begbie

NUTRITIONAL INFLUENCES ON INTERACTIONS BETWEEN BACTERIA AND THE SMALL INTESTINAL MUCOSA

Type-I fimbriae . Fimbrial serotypes associated with diarrhoea1 disease . Fimbrial adhesins associated with Helicobacter pylori . .

Expression of differentiated functions in the developing porcine small intestine

Abstract Heterologous cDNA clones were used as hybridization probes to define the temporal expression of intestinal functions during fetal and postnatal development in the pig. Northern hybridization analysis revealed the presence of the mRNAs for the cellular retinol binding protein CRBP II, for the digestive enzyme aminopeptidase N, and for the microvillar proteins villin and ezrin in the small intestine of both weaned and 40-day fetal pigs. The presence of these mRNAs suggests that at the end of the first third of gestation the pig fetal intestine is already exhibiting some characteristics of a differentiated epithelium. The mRNAs for the two fatty acid-binding proteins I-FABP and L-FAPB, both involved in the metabolism of long chain fatty acids, were detected only in the intestinal mRNA extracted from weaned animals, while that for the cellular retinol-binding protein CRBP I was expressed only in the fetal tissue. The temporal limits of expression of intestinal genes in the pig epithelium seem therefore more easily defined than in other experimental animals with shorter times of fetal development. To isolate pig genes expressed at different developmental stages during intestinal epithelial cell differentiation, a cDNA library was constructed from poly(A) + RNA extracted from mature pig intestine. This library was employed in the isolation of clones encoding CRBP II and L-FABP. The nucleotide sequence of the two pig cDNA clones was determined, and the sequences of the deduced proteins compared with their homologues from other species. The results of this analysis showed that the two pig clones share a high level of homology with human and rat homologues both at the DNA and at the protein level.

Escherichia coli K88 receptor expression in intestine of disease-susceptible weaned pigs

A challenge trial was carried out in which Escherichia coli O157 K88ac was administered to a litter of weaned pigs and the development of the disease monitored over a five-day experimental period. The eight animals in the trial were assigned to two groups depending on whether they exhibited disease symptoms. Six pigs developed diarrhoea and two appeared unaffected; these were designated as the test (or K88-susceptible) group and the control (or K88-resistant) group, respectively. The animals were euthanised and the intestine was removed and sections processed for brush border membrane vesicle preparation. Microscopic and biochemical assays were undertaken on tissue samples from each animal and a strong correlation was observed between the expression of a glycoprotein receptor complex associated with the brush border membrane and the development of disease symptoms. Further investigation revealed the presence of an analogous glycoprotein complex in the K88-resistant group which did not bind the K88-fimbriae antigen. These results suggest that genetic differences in the glycosyl moieties of the receptor complex provide the basis for disease susceptibility to K88-positive E. coli.

S10.17 Identification of specific receptors in the piglet intestine forEscherichin coli K88 fimbriae

The recently published X-ray structure of the heat-labile enterotoxin from E. coli (1), and its complex with lactose (2), and the three-dimensional structure of the natural receptor GM1, derived from NMR (3) and molecular modeling, has enabled us to perform docking experiments using computer graphics in combination with energy minimization and molecular dynamics. A description of the binding surfaces and important binding characteristics, such as hydrophobic and hydrogen bond interactions, will be given. Only minor differences in conformation were found between the complexed molecules and the respective free molecules. Comparative docking experiments using various isoreceptors, for which binding data and three-dimensional models exist ((4) and references therein), explain the variation in toxin affinity found for these structures. 1. Sixma, T. K., Pronk, S. E., Kalk, K. H., Wartna, E. S., van Zanten, B. A. M., Witholt, B. and Hol, W. G. J. (1991) Nature, 351, 371 -377 .2 . Sixma, T. K., Pronk, S. E., Kalk, K. H., van Zanten, B. A. M., Berghuis, A. M. and Hol, W. G. J. (1992) Nature, 355, 561-56. 3. Acquotti, D., Poppe, L., Dabrowski, J., von der Lieth, C.-W., Sonnino, S. and Tettamanti, G. (1990) J. Am. Chem. Soe., 112, 7772-7778. 4./~ngstr6m, J., Teneberg, S. and Karlsson, K.-A. (1993) submitted.