BIOMEDICAL MODELS

Swine are commonly used in cardiovascular research because swine and humans share important anatomic and physiologic characteristics. Their hearts are approximately the same size, and coronary blood flow, hemodynamic and myocardial contractility, development of atherosclerosis are analogous (Stanton and Mersmann, 1986). Consequently, swine are used to study congenital heart disease (Gillette et al., 1991; Mitchell et al., 1994; Swindle et al., 1992), myocardial infarction (Bloor et al., 1992), hemodynamics and shock (Hannon, 1992; Hoban et al., 1992), development of interventional radiology devices including balloon catheters and intravascular stents (Gal and Isner, 1992; White et al., 1992), hypertension (Zambraski et al., 1992), cardiopulmonary bypass and anesthesia (Cameron et al., 1992; Weiskopf et al., 1992), heart failure (Hendrick et al., 1990), and atherosclerosis (Lee et al., 1986).



Swine are also used extensively for nutritional studies because their digestive physiology is similar to humans. Because they are omnivores, swine will readily consume a variety of nutritional supplements and test substances (Swindle et al., 1988). They have also been used for many other studies related to nutrition, including total parenteral nutrition, lipid metabolism, diabetes, alcoholism, gastric ulceration, and splanchnic blood flow (Cohen et al., 1992; Laber-Laird et al., 1992; Tumbleson, 1986).



Organ transplantation studies have been performed using the swine heart (Hall et al., 1986), liver (Flye, 1992), kidney (Pennington, 1992), pancreas (Koyama et al., 1986), and intestine (Pritchard et al., 1986). Many of these organ transplantation studies have been related to immunologic aspects of transplants, including the development of transgenic animals that would be immunologically accepted by humans (Sachs, 1992).



Other studies have involved wound healing and plastic and reconstructive surgery (Kerrigan et al., 1986), fetal surgery (Randall, 1986), and pharmacology and toxicology (Kurihara-Bergstrom et al., 1986; Feletou and Teisseire, 1992). Reproductive physiology and endocrine functions have also been studied (Tumbleson, 1986).



Swine are used extensively in surgical training classes for health care practitioners. Initially they were used to train medical students and residents in surgical skills ( and Bobbie, 1983) but are now used extensively to train graduate physicians, nurses, and technical staff' in endoscopic and stapling surgical techniques, laser surgery, and microsurgery.



When comparing studies using swine, the differences in physiology, genotype, and phenotype and in maturity at a given body weight need to be considered, not only among breeds, but among breeds from different producers. It is best to use the same breed and age, however, this is not always possible. In order to make hemodynamic comparisons, values should be indexed to body weight in kilograms or body surface area. Because of varying growth rates among breeds, animals may differ in age and maturity at the same weight. This factor should also be considered when comparing data (Smith et al., 1990; Smith et al., in press). Genotype matching has become increasingly important in achieving reproducibility among animals.



Anesthesia, analgesia, and surgical care are important subjects and have received much attention in the literature. Reviews on these important subjects are available (Riebold and Thurmon, 1986; Smith et al., in press; Swindle et al., 1988).