The involvement of 5-hydroxytryptamine (5-HT) and 5-HT3 receptors and prostaglandin E2 (PGEz) in Salmonella Typhimurium-induced fluid accumulation in the porcine small intestine was investigated. Salmonella Typhimurium (10' and 10" cfu) and cholera toxin (CT; 20pg) were instilled for 8 and 11 h in ligated loops in the porcine jejunum and ileum. Fluid accumulation and concentrations of Na+, K f , C1-, 5-HT and PGE2 in the fluid accumulated in the loops were measured. The fluid accumulation was also measured when Salmonella Typhimurium (10'' cfu) and CT (20 pg) were instilled for 8 h in ligated loops in jejunum and ileum in pigs given subcutaneous injections of saline or the 5-HT3 receptor antagonist ondansetron (200 pg/kg). Salmonella Typhimurium (10" cfu) and CT both induced fluid accumulation in jejunum and ileum after 8 and 11 h. Both treatments also induced an increase in luminal release of 5-HT and PGE2. The accumulated fluid was iso-osmotic and hyperosmotic in CT-and Salmonella Typhimurium-treated loops, respectively. Ondansetron reduced the Typhimuriuminduced fluid accumulation in both jejunum and ileum by c. 40%, while it failed to reduce the response to CT. These results demonstrate that 5-HT and PGEz are released and 5-HT3 receptors activated in the secretory pathway of Typhimurium in the porcine small intestine.

The effect of age on the secretory response of pig small intestine to in vivo challenge by cholera toxin (CT) was investigated. The small intestine of 14-day-old pigs was more sensitive to CT challenge than that of 14-wk-old animals. In the 14-day jejunum CT-induced fluid secretion was five times that observed in the 14-wk tissue. Similarly, the 14-day ileum produced a fourfold higher secretion than the 14-wk ileum, although the magnitude of ileal secretion was markedly lower than that observed in the jejunum at the same CT dose. This reduced response to CT with age was not due to a reduced secretory capacity of the tissue, since supramaximal doses of prostaglandin E2 and theophylline induced a similar response in tissue from both age groups in vitro. We conclude that these results are consistent with the hypothesis that an antisecretory factor, which naturally inhibits fluid losses in enterotoxigenic diarrhea, is produced in older animals.

The difficulties in experimentally establishing patent intestinal infections with the pig large roundworm Ascaris suum make transfer of adult or larval stages a potentially important method of inducing this infection. Adult worms and 10-day-old larvae were transferred by stomach tube to untreated pigs and pigs treated with the gastric acid pump inhibitor omeprazole, as well as surgically directly into the small intestine of pigs. Transfer of adult worms resulted in patent infections with comparable worm survival rates in all 3 recipient groups but with a nonsignificant decrease in egg production after transfer to untreated pigs. Thus, it is possible with oral transfer of adult worms to achieve infections with more or less known numbers and sexes of the parasites, as well as producing patent infections in hosts that have never experienced a hepato-tracheal migration. Whereas the orally transferred 10-day-old L3/L4 larvae did not establish well, surgical transfer of larvae to helminth-naive recipient pigs resulted in high recovery rates 1 wk after transfer in 3 out of 5 pigs.

Summary Eleven mares were induced to ovulate by treatment with 3,000 iu hCG and subsequently inseminated with frozen‐thawed semen. The time of ovulation was determined by transrectal ultrasonography of the ovaries performed every 4 h. At different times after ovulation ova were collected from oviducts removed by surgery through a flank incision under general anaesthesia. The presumed fertilised ova were cultured for 20 min in a medium containing [3H]uridine, fixed, embedded in Epon, semithin‐sectioned and processed for autoradiography. Selected semithin sections were re‐embedded and processed for transmission electron microscopy. Spherical, paternal and maternal pronuclei were observed within 12 h after ovulation, and by 19 h the pronuclei had migrated to close apposition. The 2‐cell stage was seen within 34 h and a major activation of RNA synthesis was detected at 64 h after ovulation in 4 blastomeres of a 6‐cell embryo, suggesting maternal‐embryonic transition apparently occurs at the 4th cell cycle.

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