Female Minipigs Research Articles

Brain and heart membrane fatty acid composition in miniature swine fed diets containing corn and menhaden oils

Thirty-six female minipigs, from 4.7–10.6 years old, were fed corn oil (CO) and/or menhaden oil (MO) in diets containing 0, 0.75, or 15% MO and sufficient CO to provide 15% total oil for 6 months. Half the animals were made hypercholesterolemic by feeding them a 13% lard, 2% cholesterol diet for 2 months prior to the experimental feeding period. Samples were taken from the same location in each animal from forebrain, caudate nucleus, cerebellum, and heart to isolate brain synaptosomes and heart plasma membranes. Pretreatment of the minipigs with cholesterol had no effect on the fatty acid composition of the fractions isolated and their membrane fluidity. Despite MO feeding, the long chain n-3 fatty acids were low in the heart plasma membranes compared to heart tissue homogenates from the same animals. Minipigs fed 15% MO showed significant increases in synaptosomal eicosapentaenoate (EPA) and docosapentaenoate (DPA). Docosahexaenoate (DHA) was incorporated into synaptosomes in animals fed 0.75% MO, at concentrations significantly higher than in the CO-fed pigs. Pigs fed 15% MO showed significantly lower brain DHA than those fed CO. The synaptosomal data for the pigs fed the various diets suggest that metabolic synthesis from linolenate, 18:3(n-3), may be a more important source of brain DHA than diet, but that dietary n-6 n-3 ratios and levels of 18:3(n-3), EPA, DPA and DHA may require careful attention. The fatty acid changes did not affect fluidity determined by fluorescence anisotropy of diphenylhexatriene or its polar derivatives.

Characterization of the P450 system in Göttingen minipigs.

It is essential to establish the activity and regulation of the cytochrome P450 system of species selected for toxicological and pharmacological studies. The minipig has become a popular substitute for the traditional non-rodent species although little information is available on its P450 system. The total P450 and the enzyme activity of the most important drug-metabolizing isoenzymes: CYP1A2, CYP2C19, CYP2D6, CYP2E1 and CYP3A4 were measured in liver microsomes from 4 minipigs and 8 conventional pigs of both sexes. Immunochemical levels were determined for 4 of teh isoenzymes. The total P450 activity was slightly higher in minipigs compared to conventional pigs but no sex difference was detected. CYP1A2 activity (7-ethoxyresorufin) was 4 times higher in female minipigs than in male minipigs. The activity in male minipigs was almost identical to the activity in conventional pigs. The activity of CYP2E1 (chlorzoxazone) was 4 times higher in female than in male minipigs and 2 times higher in female than in male conventional pigs. No activity of CYP2D6 (debrisoquine) and CYP2C19 (mephenytoin) could be detected. The CYP3A4 activity (testosterone) detected in minipigs was higher than the activity in conventional pigs. A weak sex difference was seen in both strains. Western blotting using anti-human CYP2E1 and CYP3A4 confirmed the results obtained in the enzyme activity assays, while only CYP1A2 correlated with the activity in the conventional strain. The total P450 enzyme activity was close to the levels reported for human beings, as were the activities of CYP2E1 and CYP3A4.

Evaluation of optimal stent size after endourologic incision of ureteral strictures.

The stent size necessary to promote optimal ureteral healing after an endoureterotomy is not known. We compared healing of an endoureterotomy over a 7F indwelling ureteral stent with healing over a 14F endopyelotomy stent. A midureteral stricture was created in each of 25 anesthetized female minipigs using an electrified stone basket passed retrograde. Six weeks later, the stricture was incised with a 24F cutting balloon device. Twenty pigs were randomized to receive a 7F or a 14F stent; four control pigs received neither incisions nor stents. At 1 week, a radiograph was performed to confirm proper stent position, and the stents were removed. At 3 months, a retrograde ureterogram was performed, and the ureters were examined grossly and harvested for histologic studies. Two of the ten pigs in each study group developed a recurrent stricture. The use of a 14F stent provided no advantage over the use of a smaller, more easily positioned 7F stent.

28-Day continuous dosing study in minipigs with a SALATRIM structured triacylglycerol composed of stearate, acetate, and propionate

SALATRIM 23SO lot A026 belongs to a family of structured triacylglycerols with lower caloric availability than corn oil. Male and female minipigs were divided into five groups of four pigs of each sex and fed diets containing 0%, 3%, 6%, and 10% SALATRIM or 10% corn oil, as a reference for the high fat content of the SALATRIM diets, for 28 days. Diets were supplemented with 2% corn oil to ensure adequate essential fatty acid availability. No effects on body weight, feed consumption, clinical observations, hematology, serum chemistry, bone mineral content, serum and liver levels of fat-soluble vitamins, and organ weights were detected. Focal hepatocellular vacuolation was observed in treated and control groups. The incidence was similar among groups

Acute methanol toxicity in minipigs

The pig has been proposed as a potential animal model for methanol-induced neuro-ocular toxicosis in humans because of its low liver tetrahydrofolate levels and slower rate of formate metabolism compared to those of humans. To examine the validity of this animal model, 12 4-month-old female minipigs (minipig YU) were given a single oral dose of water or methanol at 1.0, 2.5, or 5.0 g/kg body wt by gavage (n = 3 pigs/dose). Dose-dependent signs of acute methanol intoxication, which included mild CNS depression, tremors, ataxia, and recumbency, developed within 0.5 to 2.0 hr, and resolved by 52 hr. Average maximum methanol concentrations in plasma, of 3100 +/- 700 (SD), 6200 +/- 2300, and 15,200 +/- 900 micrograms/ml were reached within 0.5 to 4 hr following methanol administration in animals given 1.0, 2.5, or 5.0 g methanol/kg, respectively. The mean initial elimination half-lives of methanol were 9.0 +/- 1.6, 22.4 +/- 6.1, and 18.9 +/- 4.3 hr, for 1, 2.5, and 5.0 g/kg doses, respectively. In 3 minipigs, a transient increase in plasma formate concentration (1.74-3.40 mEq/liter vs control = 0.5 +/- 0.3 mEq/liter) occurred 4 to 30 hr following methanol administration. Methanol- and formate-dosed pigs did not develop optic nerve lesions, toxicologically significant formate accumulation, or metabolic acidosis. Based on results following a single dose, female minipigs do not appear to be overtly sensitive to methanol and thus may not be a suitable animal model for acute methanol-induced neuro-ocular toxicosis.

Acute Methanol Toxicity in Minipigs

The pig has been proposed as a potential animal model for methanol-induced neuro-ocular toxicosis in humans because of its low liver tetrahydrofolate levels and slower rate of formate metabolism compared to those of humans. To examine the validity of this animal model, 12 4-month-old female minipigs (minipig YU) were given a single oral dose of water or methanol at 1.0, 2.5, or 5.0 g/kg body wt by gavage (n = 3 pigs/dose). Dose-dependent signs of acute methanol intoxication, which included mild CNS depression, tremors, ataxia, and recumbency, developed within 0.5 to 2.0 hr, and resolved by 52 hr. Average maximum methanol concentrations in plasma, of 3100 ± 700 (SD), 6200 ± 2300, and 15,200 ± 900 μg/ml were reached within 0.5 to 4 hr following methanol administration in animals given 1.0, 2.5, or 5.0 g methanol/kg, respectively. The mean initial elimination half-lives of methanol were 9.0 ± 1.6, 22.4 ± 6.1, and 18.9 ± 4.3 hr, for 1, 2.5, and 5.0 g/kg doses, respectively. In 3 minipigs, a transient increase in plasma formate concentration (1.74–3.40 mEq/liter vs control = 0.5 + 0.3 mEq/liter) occurred 4 to 30 hr following methanol administration. Methanol- and formate-dosed pigs did not develop optic nerve lesions, toxicologically significant formate accumulation, or metabolic acidosis. Based on results following a single dose, female minipigs do not appear to be overtly sensitive to methanol and thus may not be a suitable animal model for acute methanol-induced neuroocular toxicosis.

Influence of clofibrate on the plasma lipoprotein pattern and on the lipid content and protein and collagen synthesis in atherosclerotic coronary arteries and abdominal aorta from hypercholesterolemic mini-pigs

The influence of clofibrate on the plasma lipoprotein pattern in hyperlipidemic mini-pigs was studied and an attempt was made to characterize the type of atherosclerosis produced in this animal model. Thirty-two female mini-pigs of the Göttingen strain were used. Experimental hypercholesterolemia and atherosclerosis were produced in 16 of the animals by adding 11.2% egg yolk and 0.5% cholesterol to the diet for 14 months. In groups of 8 normolipidemic and 8 hyperlipidemic animals clofibrate was added in a dose of 2 g per animal and day. The remaining 8 animals of each category served as controls. Two months of clofibrate treatment normalized the plasma cholesterol in the hyperlipidemic group mainly by reducing the elevated LDL-cholesterol fraction. In normolipidemic animals clofibrate significantly reduced the HDL-cholesterol. At the end of the treatment period the animals were slaughtered and autopsied. The right coronary artery and normal and atherosclerotic pieces of the abdominal aorta were taken for biochemical analysis. There was a marked accumulation of free and esterified cholesterol in the right coronary artery from hyperlipidemic animals. Clofibrate treatment significantly reduced the content of esterified cholesterol in this vessel. Atherosclerotic pieces from the abdominal aorta were also rich in free and esterified cholesterol and showed a higher rate of proline and hydroxyproline incorporation than the adjacent normal tissue. The contents of proline and hydroxyproline were relatively unchanged, however, suggesting that there may be an increased turnover of protein and collagen synthesis rather than an increased total protein and collagen production. Histological examination of the atherosclerotic plaques revealed a markedly thickened intima rich in fibroblasts, macrophages, foam cells an collagen fibers. Areas of necrosis and calcification were also observed. It is suggested that the atherosclerosis produced in the aorta in hyperlipidemic mini-pigs is of a lipid-rich, proliferative, collagen-synthesizing type with features of necrosis and calcification.

Experimental Electrical Stimulation of the Bladder Using a New Device

Repeated bladder contractions were evoked during a six month period in three unanaesthetized female minipigs by using unipolar carbon fiber electrodes embedded in the bladder wall adjacent to the ureterovesical junction. In contrast to bipolar and direct bladder muscle stimulation unipolar electrodes at each ureterovesical junction evoked bladder pressure increase similar to those produced in previous investigations in dogs. Sacral nerve stimulation of S2 evoked bladder contraction at a minimal current. Microscopic examination revealed no cellular reactions to the carbon fibers but a subcutaneous reaction to the receivers was seen and was thought to be due to mechanical irritation. The clinical implication of the findings is discussed.

Experimental electrical stimulation of the bladder using a new device.

Repeated bladder contractions were evoked during a six month period in three unanaesthetized female minipigs by using unipolar carbon fiber electrodes embedded in the bladder wall adjacent to the ureterovesical junction. In contrast to bipolar and direct bladder muscle stimulation unipolar electrodes at each ureterovesical junction evoked bladder pressure increase similar to those produced in previous investigations in dogs. Sacral nerve stimulation of S2 evoked bladder contraction at a minimal current. Microscopic examination revealed no cellular reactions to the carbon fibers but a subcutaneous reaction to the receivers was seen and was thought to be due to mechanical irritation. The clinical implication of the findings is discussed.

Influence of age and sex on composition and lipid fluidity in miniature swine plasma lipoproteins

Age- and sex-related differences were observed in the plasma cholesterol level, the plasma concentrations of certain lipoprotein components, and the HDL lipid phase fluidity in miniature swine from post-weaning (6 weeks) through puberty (6 months), maturity (2–6 years), and old age (10–12 years). Age effects were more dominant in the males, with VLDL protein; LDL protein, triacylglycerol, and phospholipid; and HDL triacylglycerol, phospholipid, cholesterol, and polyunsaturated fatty acids showing statistically significant negative correlations with age. These effects were not observed in females. HDL cholesterol was positively correlated with age in females. Total plasma cholesterol decreased with age in males only, but plasma triacylglycerol was not influenced by age in either sex. Higher concentrations of all lipoprotein lipids were observed in the female minipigs regardless of age. HDL lipids became less fluid with age in the males alone suggesting a physical chemical basis for the lower incidence of heart disease among females. The more fluid HDL circulating in the female may be more capable of mobilizing peripheral tissue cholesterol for catabolism thus protecting her from developing atherosclerotic lesions.