Technical and surgical aspects of continuous vascular access in freely moving small animals.

Many systems and techniques for continuous vascular access in small animals have been described. Problems with these systems have included (1) insufficient free movement, (2) sepsis, (3) high cost, (4) complicated construction, (4) thrombosis, and (5) dislocations of the intravenous catheter. The described operative techniques and a new experimental setup overcome these complications. The apparatus involves a swivel that is connected with an intravenously placed polyurethane catheter. A leather harness on the back of the animal is connected with the end of the swivel joint via a silicone tube in which the intravenous catheter runs to the swivel. The swivel, a modified conventional glass syringe, is positioned in ball bearings and a Johnson joint. The swivel, ball bearings, and Johnson joint are counterbalanced and can move up and down. When this system was used, the catheters functioned well for as long as 28 days, with a mean duration of 24.4 +/- 1.8 days (n = 420). Five catheter dislocations resulted from harness failure, and three dislocations were caused by animals twisting. All animals gained weight (3.53 +/- 0.37 gm/day (mean +/- SEM)). The rotary portion of the swivel and the Johnson joint secure stressless movement of the animal, avoiding twisting and dislocation of the catheter, which overcomes typical problems of existing methods. The low thrombogenicity of the polyurethane catheter also reduces complications. A further advantage is low cost, because prefabricated, reusable materials are used.

Distribution of gastrointestinal hormones in the adaptive response after small bowel transplantation.

Enteroendocrine regulatory peptides may play an important role in the adaptation of small bowel mucosa, and it is likely that they act interdependently with neural and luminal stimuli. We assessed their action in rats by morphometric evaluation of enteroendocrine cells after heterotopic accessory small bowel transplantation (SBT), in which the graft is shunted off from the intestinal passage and is entirely deprived of neural connections, and after orthotopic SBT with normal intestinal passage. Sections of the jejunum and the ileum of the graft were immunostained with antibodies to cholecystokinin (CKK), neurotensin (NT) and vasoactive intestinal peptide (VIP). The amount and distribution of positive cells was assessed semiquantitatively. Three weeks after SBT in the heterotopic graft there was a marked decrease in CCK and NT positive cells and VIP positive fibres in the entire organ, compared with the controls. Histological examination revealed that villi and crypts had atrophied. After orthotopic SBT the number of CCK and NT positive cells increased and exceeded normal values by 20-40%. VIP positive fibres did not reach normal amounts. No mucosal atrophy was detected. These findings support the view that the intrinsic neurohormonal system is reestablished in the grafted small bowel and that enteroendocrine regulatory peptides may act as trophic factors that are responsible for adaptation after SBT.