Chronic cannulation in the small intestine of feral pigeons (Columba livia) to assess bioavailability

We improved a method of chronic duodenal cannulation to study intestinal transport of solutes in an in vivo model (pigeon, Columba livia). A hypoallergenic cannula was inserted into the proximal part of the small intestine of pigeons and used for solution administration. Recovery from surgery was extremely rapid and animals started eating and drinking within a day. After surgery, the body mass of cannulated pigeons was stable, and no adverse effects in the weight could be detected. The method is simple, economical and useful to determine intestinal bioavailability of solutes, for nutritional and ecological studies, in intact animals without influence of anesthesia.

Ovine toxoplasmosis

SUMMARYCongenital infection with Toxoplasma gondii is an important cause of abortion in sheep worldwide. The cat is the definitive host of the parasite, and infected cats may shed millions of oocysts in their faeces resulting in extensive environmental contamination and an important source of infection for grazing herbivorous animals. Studies looking at development of specific antibodies in sheep, as an indicator of exposure to T. gondii, have shown that there is an increase in seroprevalence associated with age indicating that most infections in sheep occur following birth. The stage of gestation when transplacental transmission of T. gondii to the developing foetus occurs is critical in determining the clinical outcome. The importance of endogenous transplacental transmission in persistently infected ewes and its clinical importance is a subject of current debate. Ewes infected prior to mating develop immune responses that help protect against disease in a subsequent pregnancy and also against experimental challenge administered during pregnancy. Both innate and adaptive immune responses are activated following T. gondii infection and experiments involving the chronic cannulation of peripheral lymph nodes in sheep have allowed the dynamics of the immune responses to be analysed in real time. A live vaccine, Toxovax® is the only commercially available vaccine worldwide to protect against congenital toxoplasmosis.

A method for sampling representative muscular venous blood during exercise in rats

A technique for chronic cannulation of the muscular branch of the femoral vein in the rat is described. The method was validated by the application of vascular corrosion casts and comparative analysis of lactate concentration with mixed venous blood and arterial samples taken through the cannulas during lower hindlimb muscle contraction in anaesthetized rats.

A simple method for chronic cannulation of the portal vein in intact unrestrained rats

A simple new method is described for chronic cannulation of the portal vein in rats. A Silastic catheter (0.64 mm OD) with an internal metallic leader is directly inserted in the junction of the two small ileal veins. The catheter is advanced into the mesenteric vein to the portal vein. Then the leader is removed and the catheter tunneled out the back of the neck. This method allows for the measurement of portal vein pressure, direct injection of substances in the portal vein, or blood samples for at least 1 wk in intact unrestrained rats. Validation included the presence of elevated portal vein pressure in portal hypertensive rats compared with normal rats and the absence of clot development in the portal vein. This method should help provide a better understanding of hepatic physiology and pharmacology in normal and disease states.

In vivo analysis of partitioning of cardiac output between systemic and central venous sinus circuits in rainbow trout: a new approach using chronic cannulation of the branchial vein

Freshwater-acclimated rainbow trout were chronically and non-occlusively cannulated in the dorsal aorta (DA), sinus venosus (SV) and branchial vein (BV), the latter returning the blood perfusing the central venous sinus (CVS) of the gill after being shunted away from the systemic circuit. After recovery, blood samples from these three sites were analysed for haematocrit (Hct) and [Hb]. Branchial venous blood was found to have considerably lower Hct and [Hb] (Hct = 3.5 +/− 3.1%; [Hb] = 1.04 +/− 0.75 g 100 ml-1) than systemic blood (DA: Hct = 24.3 +/− 8.9%, [Hb] = 6.54 +/− 2.90 g 100 ml-1; SV: Hct = 23.1 +/− 8.8%, [Hb] = 6.15 +/− 2.55 g 100 ml-1; means +/− S.D. N = 8), which strongly suggests that plasma skimming occurred at arteriovenous anastomoses and arterioles draining into the CVS. The partitioning of cardiac output, calculated on the basis of the [Hb] data, showed that the systemic flow accounted for 93 +/− 4.6% (N = 7) of the total cardiac output with only 7 +/− 4.7% of cardiac output being diverted into the CVS, thus bypassing the systemic vasculature. Previous results using in vitro experiments are compared with the present data in an evaluation of the usefulness of the isolated perfused gill and head preparations in the experimental analysis of circulatory physiology in fish gills.

A method to study pulmonary vascular response in the conscious newborn piglet

New methods for chronic instrumentation of the newborn piglet are described, which allow continuous monitoring of not only pressures in the pulmonary artery and aorta but also in the left and right atria, pulmonary vein, as well as main branch pulmonary artery flows. Changes in pulmonary vascular tone to short-acting vasoactive agents can be recognized by redistribution of flow between lungs and localized to the precapillary vessels or pulmonary veins. Furthermore, vasoactive response in small pulmonary veins may be investigated as well as selective metabolic studies across the right lung. Methods are also described for the chronic cannulation of the neck vessels permitting repeated introduction of catheters on separate study days in the conscious piglet. The pulmonary circulation of the piglet constricts briskly to moderate hypoxemia ([Formula: see text], 1 Torr = 133.32 Pa) with little change in cardiac output or systemic resistance. The piglet demonstrated responses to dilator and constrictor prostaglandins generally similar to the lambs and other species. None of these agents significantly affect pulmonary venous tone.

Aldosterone regulates salivary sodium secretion in cattle

ABSTRACT Intravenous infusion of aldosterone (10 μg/kg body wt per h for 5 h) in four 2-month-old calves decreased salivary and urinary sodium (Na+) concentration and increased salivary potassium (K+) concentration without modifying salivary flow or urinary K+ concentration. Intravenous angiotensin II infusion (0·3 μg/kg body wt per min for 1 h) in four Na+-replete 16-month-old bulls decreased salivary Na+ concentration and increased that of K+. It also increased plasma cortisol and plasma aldosterone concentrations, and decreased plasma renin activity (PRA). In four 16-month-old bulls Na+ deficiency (induced by chronic cannulation of the righ parotid duct and loss of saliva for 5 days) had similar effects to those observed following aldosterone infusion in calves: a decrease in salivary Na+/K+ ratio. This decrease was associated with an increase in PRA and an increase in plasma aldosterone concentration. In these animals a close positive relationship was observed between PRA and plasma aldosterone concentration (r = 0·91; n = 20; P < 0·01). Thus in cattle, during Na+ deficiency, the effect of aldosterone on parotid glands participates in the regulation of Na+ metabolism. J. Endocr. (1986) 108, 405–411