Research applications using pigs

Sirtuins, a key regulator of ageing and age-related neurodegenerative diseases

Sirtuins are Nicotinamide Adenine Dinucleotide (NAD+) dependent class ІΙΙ histone deacetylases enzymes (HDACs) present from lower to higher organisms such as bacteria (Sulfolobus solfataricus L. major), yeasts (Saccharomyces cerevisiae), nematodes (Caenorhabditis elegans), fruit flies (Drosophila melanogaster), humans (Homo sapiens sapiens), even in plants such as rice (Oryza sativa), thale cress (Arabidopsis thaliana), vine (Vitis vinifera L.) tomato (Solanum lycopersicum). Sirtuins play an important role in the regulation of various vital cellular functions during metabolism and ageing. It also plays a neuroprotective role by modulating several biological pathways such as apoptosis, DNA repair, protein aggregation, and inflammatory processes associated with ageing and neurodegenerative diseases. In this review, we have presented an updated Sirtuins and its role in ageing and age-related neurodegenerative diseases (NDDs). Further, this review also describes the therapeutic potential of Sirtuins and the use of Sirtuins inhibitor/activator for altering the NDDs disease pathology.

Animal Models Reflecting Chronic Obstructive Pulmonary Disease and Related Respiratory Disorders: Translating Pre-Clinical Data into Clinical Relevance

Chronic obstructive pulmonary disease (COPD) affects the lives of an ever-growing number of people worldwide. The lack of understanding surrounding the pathophysiology of the disease and its progression has led to COPD becoming the third leading cause of death worldwide. COPD is incurable, with current treatments only addressing associated symptoms and sometimes slowing its progression, thus highlighting the need to develop novel treatments. However, this has been limited by the lack of experimental standardization within the respiratory disease research area. A lack of coherent animal models that accurately represent all aspects of COPD clinical presentation makes the translation of promising in vitrodata to human clinical trials exceptionally challenging. Here, we review current knowledge within the COPD research field, with a focus on current COPD animal models. Moreover, we include a set of advantages and disadvantages for the selection of pre-clinical models for the identification of novel COPD treatments.

Use of a modified passive leg-raising maneuver to predict fluid responsiveness during experimental induction and correction of hypovolemia in healthy isoflurane-anesthetized pigs

OBJECTIVE To evaluate the use of a modified passive leg-raising maneuver (PLRM) to predict fluid responsiveness during experimental induction and correction of hypovolemia in isoflurane-anesthetized pigs. ANIMALS 6 healthy male Landrace pigs. PROCEDURES Pigs were anesthetized with isoflurane, positioned in dorsal recumbency, and instrumented. Following induction of a neuromuscular blockade, pigs were mechanically ventilated throughout 5 sequential experimental stages during which the blood volume was manipulated so that subjects transitioned from normovolemia (baseline) to hypovolemia (blood volume depletion, 20% and 40%), back to normovolemia, and then to hypervolemia. During each stage, hemodynamic variables were measured before and 3 minutes after a PLRM and 1 minute after the pelvic limbs were returned to their original position. The PLRM consisted of raising the pelvic limbs and caudal portion of the abdomen to a 15° angle relative to the horizontal plane. RESULTS Hemodynamic variables did not vary in response to the PLRM when pigs were normovolemic or hypervolemic. When pigs were hypovolemic, the PLRM resulted in a significant increase in cardiac output and decrease in plethysomographic variability index and pulse pressure variation. When the pelvic limbs were returned to their original position, cardiac output and pulse pressure variation rapidly returned to their pre-PLRM values, but the plethysomographic variability index did not. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested a modified PLRM might be useful for identification of hemodynamically unstable animals that are likely to respond to fluid therapy. Further research is necessary to validate the described PLRM for prediction of fluid responsiveness in clinically ill animals.

The Yucatan Minipig Temporomandibular Joint Disc Structure-Function Relationships Support Its Suitability for Human Comparative Studies

Frequent involvement of the disc in temporomandibular joint (TMJ) disorders warrants attempts to tissue engineer TMJ disc replacements. Physiologically, a great degree of similarity is seen between humans and farm pigs (FPs), but the pig's rapid growth confers a significant challenge for in vivo experiments. Minipigs have a slower growth rate and are smaller than FPs, but minipig TMJ discs have yet to be fully characterized. The objective of this study was to determine the suitability of the minipig for TMJ studies by extensive structural and functional characterization. The properties of minipig TMJ discs closely reproduced previously reported morphological, biochemical, and biomechanical values of human and FP discs. The width/length dimension ratio of the minipig TMJ disc was 1.95 (1.69 for human and 1.94 for FP). The biochemical evaluation revealed, on average per wet weight, 24.3% collagen (22.8% for human and 24.9% for FP); 0.8% glycosaminoglycan (GAG; 0.5% for human and 0.4% for FP); and 0.03% DNA (0.008% for human and 0.02% for FP). Biomechanical testing revealed, on average, compressive relaxation modulus of 50 kPa (37 kPa for human and 32 kPa for FP), compressive instantaneous modulus of 1121 kPa (1315 kPa for human and 1134 kPa for FP), and coefficient of viscosity of 13 MPa·s (9 MPa·s for human and 3 MPa·s for FP) at 20% strain. These properties also varied topographically in accordance to those of human and FP TMJ discs. Anisotropy, quantified by bidirectional tensile testing and histology, again was analogous among minipig, human, and FP TMJ discs. The minipig TMJ's ginglymoarthrodial nature was verified through cone beam computer tomography. Collectively, the similarities between minipig and human TMJ discs support the use of minipig as a relevant model for TMJ research; considering the practical advantages conferred by its growth rate and size, the minipig may be a preferred model over FP.

Can we induce osteoporosis in animals comparable to the human situation?

Osteoporosis is a chronic systemic bone disease of growing relevance due to the on-going demographic change. Since the underlying regulatory mechanisms of this critical illness are still not fully understood and treatment options are not satisfactorily resolved, there is still a great need for osteoporosis research in general and animal models in particular. Ovariectomized rodents are standard animal models for postmenopausal osteoporosis and highly attractive due to the possibility to specifically modify their genetic background. However, some aspects can only be addressed in large animal models; such as metaphyseal fracture healing and advancement of orthopedic implants. Among other large animal models sheep in particular have been proven invaluable for osteoporosis research in this context. In conclusion, today we are able to influence the bone metabolism in animals causing a more or less pronounced systemic bone loss and structural deterioration comparable to the situation found in patients suffering from osteoporosis. However, there is no perfect model for osteoporosis, but a variety of models appropriate for answering specific questions. Though, the appropriateness of an animal model is not only defined in regard to the similarity to human physiology and the disease itself, but also in regard to acquisition, housing requirements, handling, costs, and particularly ethical concerns and animal welfare.

Aflatoxin B1 Suppressed T-Cell Response to Anti-pig-CD3 Monoclonal Antibody Stimulation in Primary Porcine Splenocytes: A Role for the Extracellular Regulated Protein Kinase (ERK1/2) MAPK Signaling Pathway

The aim of the present study is to investigate whether aflatoxin B1 (AFB1)-induced immunotoxicity is associated with oxidative stress and the expression of extracellular regulated protein kinases (ERK) 1/2. The primary splenocytes isolated from healthy pigs were activated and proliferated by anti-pig-CD3 monoclonal antibodies (mAb) in the present experiment, which is an antigen-specific stimulant. Results indicated that cell proliferation and interleukin-2 (IL-2) production were significantly suppressed by AFB1 from 4 to 8 μg/mL in a dose-dependent manner compared to the control group. Furthermore, AFB1 significantly increased malondialdehyde (MDA) levels, decreased reduced glutathione (GSH) and total superoxide dismutase levels, and up-regulated p-ERK1/2 expression in the activated splenocytes. N-Acetyl-l-cysteine blocked anti-CD3-induced T-cell suppression by AFB1 through increasing intracellular concentrations of GSH levels, decreasing MDA levels, and down-regulated p-ERK1/2 expression, respectively. Inhibition of the ERK1/2 expression by ERK-specific iRNA attenuated the decrease of T-cell proliferation and IL-2 production induced by AFB1. It was concluded that AFB1 inhibits anti-CD3-induced lymphocyte proliferation and IL-2 production by the oxidative stress mediated ERK1/2 MAPK signaling pathway.

Estudo ultrassonográfico morfométrico do fígado e trato biliar de suínos submetidos a obstrução biliar experimental

OBJETIVO: Comparar as alterações anatômicas decorrentes de um quadro de icterícia obstrutiva experimental induzida em suínos nos períodos pré e pós-operatório por meio de exame ultrassonográfico. MATERIAIS E MÉTODOS: Seis suínos da raça Landrace, com 36 dias de idade, foram submetidos a obstrução biliar completa mediante ligadura do ducto colédoco por cirurgia videolaparoscópica. RESULTADOS: Não ocorreram dificuldades na execução dos procedimentos obstrutivos e a recuperação cirúrgica foi eficiente. Decorridos sete dias, os animais apresentaram icterícia, bilirrubinúria e acolia fecal. O exame ultrassonográfico comparativo permitiu visualizar hepatomegalia, colecistomegalia e aumento no calibre do ducto colédoco em todos os animais, assim como alterações decorrentes da colestase. A avaliação morfométrica revelou aumento significativo nos diâmetros da vesícula biliar e do lobo hepático lateral esquerdo. CONCLUSÃO: Os suínos representam um modelo experimental adequado de icterícia obstrutiva, e o exame ultrassonográfico demonstrou-se sensível e relevante no diagnóstico das alterações decorrentes de obstrução biliar extra-hepática nesses animais.

Comparative study between ligature with thread or metallic clamping by means of laparoscopy with the purpose of experimental biliary obstruction in swines

PURPOSE

To induce a total extra-hepatic obstructive jaundice in swines, by ligation of the common bile duct by laparoscopic surgery.

METHODS

Eight swines of the Landrace race, 36-day-old, originated from the same matrix, distributed in two groups. Group A: was used titanium metal clip to the common bile duct ligation in three animals; group B: were ligated with 2-0 cotton thread in five animals.

RESULTS

The ligation of the biliary ducts was performed successfully in all animals, with easy identification of the common bile duct by laparoscopy. There weren't difficulties in the procedures, mainly due to the increased surgical field provided by the excellent quality of light and image of the appliance. The clinical signs of jaundice were evident in the animals in seven days. In group A, two animals showed bile duct perforation near the clip, probably due to ischemic necrosis, progressing to peritonitis and death. In group B, five animals showed obstructive jaundice without any amendment.

CONCLUSION

Under the conditions of this study, we therefore recommend the use of unabsorbed wires to experimental biliary obstruction, in order to avoid complications, such as ischemia and necrosis, followed by perforation of the wall of the bile ducts.

T-2 toxin induced Salmonella Typhimurium intoxication results in decreased Salmonella numbers in the cecum contents of pigs, despite marked effects on Salmonella-host cell interactions

The mycotoxin T-2 toxin and Salmonella Typhimurium infections pose a significant threat to human and animal health. Interactions between both agents may result in a different outcome of the infection. Therefore, the aim of the presented study was to investigate the effects of low and relevant concentrations of T-2 toxin on the course of a Salmonella Typhimurium infection in pigs. We showed that the presence of 15 and 83 μg T-2 toxin per kg feed significantly decreased the amount of Salmonella Typhimurium bacteria present in the cecum contents, and a tendency to a reduced colonization of the jejunum, ileum, cecum, colon and colon contents was noticed. In vitro, proteomic analysis of porcine enterocytes revealed that a very low concentration of T-2 toxin (5 ng/mL) affects the protein expression of mitochondrial, endoplasmatic reticulum and cytoskeleton associated proteins, proteins involved in protein synthesis and folding, RNA synthesis, mitogen-activated protein kinase signaling and regulatory processes. Similarly low concentrations (1-100 ng/mL) promoted the susceptibility of porcine macrophages and intestinal epithelial cells to Salmonella Typhimurium invasion, in a SPI-1 independent manner. Furthermore, T-2 toxin (1-5 ng/mL) promoted the translocation of Salmonella Typhimurium over an intestinal porcine epithelial cell monolayer. Although these findings may seem in favour of Salmonella Typhimurium, microarray analysis showed that T-2 toxin (5 ng/mL) causes an intoxication of Salmonella Typhimurium, represented by a reduced motility and a downregulation of metabolic and Salmonella Pathogenicity Island 1 genes. This study demonstrates marked interactions of T-2 toxin with Salmonella Typhimurium pathogenesis, resulting in bacterial intoxication.

The mycotoxin deoxynivalenol potentiates intestinal inflammation by Salmonella typhimurium in porcine ileal loops

Background and Aims

Both deoxynivalenol (DON) and nontyphoidal salmonellosis are emerging threats with possible hazardous effects on both human and animal health. The objective of this study was to examine whether DON at low but relevant concentrations interacts with the intestinal inflammation induced by Salmonella Typhimurium.

Methodology

By using a porcine intestinal ileal loop model, we investigated whether intake of low concentrations of DON interacts with the early intestinal inflammatory response induced by Salmonella Typhimurium.

Results

A significant higher expression of IL-12 and TNFα and a clear potentiation of the expression of IL-1β, IL-8, MCP-1 and IL-6 was seen in loops co-exposed to 1 µg/mL of DON and Salmonella Typhimurium compared to loops exposed to Salmonella Typhimurium alone. This potentiation coincided with a significantly enhanced Salmonella invasion in and translocation over the intestinal epithelial IPEC-J2 cells, exposed to non-cytotoxic concentrations of DON for 24 h. Exposure of Salmonella Typhimurium to 0.250 µg/mL of DON affected the bacterial gene expression level of a limited number of genes, however none of these expression changes seemed to give an explanation for the increased invasion and translocation of Salmonella Typhimurium and the potentiated inflammatory response in combination with DON.

Conclusion

These data imply that the intake of low and relevant concentrations of DON renders the intestinal epithelium more susceptible to Salmonella Typhimurium with a subsequent potentiation of the inflammatory response in the gut.

Microdialysis as a method for biochemical and physiological studies of the porcine and human disc

At present, no minimally invasive technique exists for the continuous evaluation of the biochemistry of animal and human intervertebral discs, but for research purposes microdialysis may be such a new technique. Thus, the aims of this study were to (1) evaluate if microdialysis can be used successfully in lumbar porcine disc and (2) develop a suitable procedure for the application of microdialysis in the human disc. Conventional specific pathogen-free pigs were used to evaluate cannulation (n = 2) and then insertion of a 10 mm microdialysis membrane, including recovery of a dialysate from the nucleus pulposus (n = 6). The procedure was performed immediately after euthanasia and aided by fluoroscopy to guide the needle and confirm catheter placement. Access to lumbar porcine disc was obtained with an 18 G 2 in. needle applied at a 35-45 degrees angle from the sagittal plane, and took less than 8 min to perform. At a 0.5 microL/min flush rate, dialysates could be recovered and analysable amounts of glucose, lactate and pyruvate were obtained. In one human cadaver, the L4-L5 disc was accessed by a 19 G 3 in. needle inserted at a 35-40 degrees angle. It was possible to apply 10 mm as well as 30 mm microdialysis membranes in the nucleus. In both species the position of the membranes was verified by direct fluoroscopy and with contrast fluid. The results obtained from porcine and human cadavers are promising, and encourage further in vivo studies using microdialysis technique on intervertebral discs.

Expression and immunogenicity of the mycobacterial Ag85B/ESAT-6 antigens produced in transgenic plants by elastin-like peptide fusion strategy

This study explored a novel system combining plant-based production and the elastin-like peptide (ELP) fusion strategy to produce vaccinal antigens against tuberculosis. Transgenic tobacco plants expressing the mycobacterial antigens Ag85B and ESAT-6 fused to ELP (TBAg-ELP) were generated. Purified TBAg-ELP was obtained by the highly efficient, cost-effective, inverse transition cycling (ICT) method and tested in mice. Furthermore, safety and immunogenicity of the crude tobacco leaf extracts were assessed in piglets. Antibodies recognizing mycobacterial antigens were produced in mice and piglets. A T-cell immune response able to recognize the native mycobacterial antigens was detected in mice. These findings showed that the native Ag85B and ESAT-6 mycobacterial B- and T-cell epitopes were conserved in the plant-expressed TBAg-ELP. This study presents the first results of an efficient plant-expression system, relying on the elastin-like peptide fusion strategy, to produce a safe and immunogenic mycobacterial Ag85B-ESAT-6 fusion protein as a potential vaccine candidate against tuberculosis.

Gene expression analysis of a porcine native abdominal aortic aneurysm model

INTRODUCTION

We sought to characterize the gene expression patterns occurring during the development of aneurysms in the native porcine aorta.

METHODS

In Yorkshire swine, the infrarenal aorta was balloon dilated and infused with a solution of type I collagenase/pancreatic porcine elastase (16,000 U/1,000 U). Aneurysmal and control aortic samples were obtained at 1 (n = 3), 2 (n = 6), and 4 (n = 5) weeks following aneurysm induction. RNA was isolated, converted to biotin-modified antisense RNA and hybridized to porcine genome arrays. Aneurysmal and control gene intensities were compared using the 2-sample-for-means z-test. P < .01 was considered statistically significant.

RESULTS

Extracellular matrix remodeling genes that were upregulated in aneurysmal compared with control tissue included matrix metalloproteinase-1, -2, -3, and -9; MT-MMP; cathepsin-D, -H, -K, and -S; tissue inhibitor of metalloproteinase-1; and collagen I-alpha1 chain (P < .01). Elastin exhibited temporally downregulated gene expression (P < .01). Inflammatory genes that were upregulated included intercellular adhesion molecule-2, tumor necrosis factor-alpha, interleukin (IL)-1 beta, IL-10, chemokine receptor-4, and tissue plasminogen activator (P < .01). Atherosclerosis and cancer genes that were upregulated included apolipoprotein E, acyl-CoA binding protein, friend leukemia virus integration-1, and E26 transformation-specific sequence (P < .01).

CONCLUSION

The porcine model replicates the gene expression patterns that are observed during the development of aneurysms in human studies as well as in rodent models. The porcine model thereby represents a novel method to study the impact of endovascular, cell-based, and other therapeutic interventions on AAA pathophysiology.

Review of nonprimate, large animal models for osteoporosis research

Large animal models are required for preclinical prevention and intervention studies related to osteoporosis research. The challenging aspect of this requirement is that no single animal model exactly mimics the progression of this human-specific chronic condition. There are pros and cons associated with the skeletal, hormonal, and metabolic conditions of each species that influence their relevance and applicability to human physiology. Of all larger mammalian species, nonhuman primates (NHPs) are preeminent in terms of replicating important aspects of human physiology. However, NHPs are very expensive, putting them out of reach of the vast majority of researchers. Practical, cost-effective alternatives to NHPs are sought after among ungulate (porcine, caprine, and ovine) and canine species that are the focus of this review. The overriding caveat to using large lower-order species is to take the time in advance to understand and appreciate the limitations and strengths of each animal model. Under these circumstances, experiments can be strategically designed to optimize the potential of an animal to develop the cardinal features of postmenopausal bone loss and/or yield information of relevance to treatment.

In vitro culturing of porcine tracheal mucosa as an ideal model for investigating the influence of drugs on human respiratory mucosa

It has been previously shown that fresh mucosa from different mammals could serve as raw material for in vitro culturing with the differentiation of cilia, which are the most important morphological structures for the function of the mucociliary system. Increasing legal restrictions on the removal of human tissue and changing surgical techniques have led to a lack of fresh human mucosa for culturing. Most of the animals that have been used as donors up to now are genetically not very close to human beings and must all be sacrificed for such studies. We, therefore, established a modified system of culturing mucosa cells from the trachea of pigs, which is available as a regular by-product after slaughtering. With respect to the possibility of developing “beating” cilia, it could be shown that the speed of cell proliferation until adhesion to the coated culture dishes, the formation of conjunctions of cell clusters and the proliferation of cilia were comparable for porcine and human mucosa. Moreover, it could be demonstrated that the porcine cilia beat frequency of 7.57 ± 1.39 Hz was comparable to the human mucosa cells beat frequency of 7.3 ± 1.4 Hz and that this beat frequency was absolutely constant over the investigation time of 360 min. In order to prove whether the reaction to different drugs is comparable between the porcine and human cilia, we initially tested benzalkonium chloride, which is known to be toxic for human cells, followed by naphazoline, which we found in previous studies on human mucosa to be non-toxic. The results clearly showed that the functional and morphological reactions of the porcine ciliated cells to these substances were similar to the reaction we found in the in vitro cultured human mucosa.

Ingestion of deoxynivalenol (DON) contaminated feed alters the pig vaccinal immune responses

Deoxynivalenol (DON), a mycotoxin produced by some Fusarium species, is a frequent contaminant of cereals. This toxin is known to modulate the immune function but only few studies have investigated the effect of DON on the vaccinal immune response. In the present experiment, 24 pigs received for 9 weeks either control feed or feed naturally contaminated with 2.2-2.5 mgDON/kg feed. At days 4 and 15 of the experiment, the animals were subcutaneously immunized with ovalbumin. Consumption of DON-contaminated diet does not have a major effect on the hematological and biochemical blood parameters. By contrast, ingestion of DON significantly affects the global and the specific immune response of the pigs. In the serum, DON increases the concentration of total IgA and, in vaccinated animals, DON also increases the concentration of ovalbumin-specific IgA and IgG. DON does not modulate lymphocytes proliferation after mitogenic stimulation but the toxin had a biphasic effect on lymphocyte proliferation after antigenic stimulation (up-regulation at day 21 and down-regulation at day 35-49). Because cytokines play a key role in immunity, the expression levels of TGF-beta, IFN-gamma, IL-4 and IL-6 were measured, by RT-PCR in the spleen, the ileum and the mesenteric lymph node of the animals at the end of the experiment. In the mesenteric lymph node, a significantly lower expression of both TGF-beta and IFN-gamma mRNA expression levels is observed in animals feed with DON when compared with control piglets. Taken together, our data indicate that DON alters the vaccinal immune response. These results may have implications for humans and animals consuming DON-contaminated food or feed as breakdown in vaccinal immunity may lead to the occurrence of disease even in properly vaccinated populations.

Effects of extradural morphine on end-tidal isoflurane concentration and physiological variables in pigs undergoing abdominal surgery: a clinical study

OBJECTIVE

To evaluate the effects of preoperative extradural morphine on the end-tidal isoflurane (Fe'ISO) concentration and on physiological variables in pigs undergoing abdominal surgery.

STUDY DESIGN

Prospective, randomized, blinded study.

ANIMALS

Fourteen healthy pigs (20 +/- 4 kg) undergoing intestinal cannulation.

MATERIALS AND METHODS

Anaesthesia was induced with a combination of medetomidine (50 microg kg(-1)) and tiletamine-zolazepam (2.5 mg kg(-1)) injected intramuscularly, and was maintained with isoflurane in air and oxygen (FiO(2) = 50% O(2)). In the first group, morphine (0.1 mg kg(-1)) was administered extradurally before surgery. The second group received an equivalent volume of extradural saline as control. During the experiment, heart and respiratory rates, mean arterial blood pressure, tidal volume and minute ventilation were recorded every 10 minutes. The concentration of Fe'ISO was adjusted, according to the depth of anaesthesia, by an experienced animal nurse. Within treatment groups, time-related changes in Fe'ISO and physiological variables were analysed using a repeated measurement anova. Differences in data between treatment groups were analysed at specific time points using a Mann-Whitney U-test. Results are presented as mean +/- SD; p < 0.05 was considered as significant.

RESULTS

After the onset of action of the morphine, the Fe'ISO required to maintain anaesthesia was significantly lower in the extradural morphine group compared with control. During the expected maximal effect of the drug, Fe'ISO was significantly lower in the morphine group (0.6 +/- 0.2%) than in the control group (0.9 +/- 0.2%). The decrease in Fe'ISO indicated that the onset of action of morphine was approximately 30 minutes after injection. No significant differences in other clinical variables were found between the groups.

CONCLUSION

Pigs that received extradural morphine before abdominal surgery achieved surgical anaesthetic depth at a lower Fe'ISO concentration.

CLINICAL RELEVANCE

Extradural morphine allows abdominal surgery to be performed at a lower Fe'ISO concentrations.

The fatty acid pattern of dietary fat influences the oral bioavailability of the flavonol quercetin in pigs

We have shown recently that dietary fat content influences the bioavailability of the flavonol quercetin. In the present study, the influence of the fatty acid pattern of dietary fats on the oral bioavailability of quercetin was investigated. Quercetin (30 micromol/kg body weight) was administered to growing pigs (n 6) in test meals consisting either of 200 g of a standard pig diet (2% crude fat) or of the same diet supplemented with 15 g fat/100 g diet using either medium-chain (MCT) or long-chain fatty acid triacylglycerols (LCT). Blood samples were drawn repeatedly over a period of 24 h and analysed by HPLC. In addition, the influence of the different diets on gastric emptying was investigated in rats. In pigs, the bioavailability of quercetin was measured by quantifying its plasma metabolites with an intact flavonol structure. Bioavailability was enhanced by 38% (P<0.05) and 12% (P>0.05) after intake with the MCT and LCT diets, respectively, compared to the standard diet. Maximum plasma concentrations of quercetin were reached significantly later with the MCT diet than with the LCT or the standard diet (P<0.05). No differences in dry matter of the gastric content were observed 60 min after intake of the experimental diets in rats. Thus, administration of quercetin together with a diet containing MCT fat enhances the bioavailability of the flavonol. Absorption of quercetin was delayed significantly with this diet. However, this was probably not due to slower gastric emptying of the MCT diet.

Mycotoxin fumonisin B1 increases intestinal colonization by pathogenic Escherichia coli in pigs

Fumonisin B(1) (FB(1)) is a mycotoxin that commonly occurs in maize. FB(1) causes a variety of toxic effects in different animal species and has been implicated as a contributing factor of esophageal cancers in humans. In the present study, we examined the effect of dietary exposure to FB(1) on intestinal colonization by pathogenic Escherichia coli associated with extraintestinal infection. Three-week-old weaned pigs were given FB(1) by gavage as a crude extract or as a purified toxin at a dose of 0.5 mg/kg of body weight daily for 6 days. On the last day of the toxin treatment, the pigs were orally inoculated with an extraintestinal pathogenic E. coli strain. All animals were euthanized 24 h later, necropsies were performed, and tissues were taken for bacterial counts and light microscopic examination. Ingestion of FB(1) had only a minimal effect on animal weight gain, did not cause any macroscopic or microscopic lesions, and did not change the plasma biochemical profile. However, colonization of the small and large intestines by an extraintestinal pathogenic E. coli strain was significantly increased. Our results show that FB(1) is a predisposing factor to infectious disease and that the pig can be used as a model for the study of the consequences of ingesting mycotoxin-contaminated food.

The bioavailability of quercetin in pigs depends on the glycoside moiety and on dietary factors

Recent investigations suggest that the bioavailability of quercetin depends on the glycoside moiety of the quercetin glycosides present in the diet. In this study, we compared the oral bioavailability of quercetin from quercetin aglycone and two different quercetin glycosides in pigs. Pigs were equipped with permanent catheters in the jugular and portal veins. After consumption of a test meal containing the respective compounds, blood samples were drawn repeatedly over a period of 24 h and analyzed by HPLC. In a first set of experiments, pigs received a single oral dose of 148 micromol/kg body (equivalent to 50 mg/kg) provided as quercetin aglycone, quercetin-3-O-glucoside (Q3G) or quercetin-3-O-glucorhamnoside (rutin) as part of their diet. The main metabolite in plasma was always conjugated quercetin, whereas free quercetin was not detected in either the jugular or the portal blood. For Q3G and rutin, the relative total bioavailability of quercetin (i.e., conjugated quercetin and conjugated methylethers of quercetin) was 148% (P = 0.07) and 23% (P < 0.05), respectively, compared with quercetin aglycone. In another experiment with a dose of 29.6 micro mol/kg (equivalent to 10 mg/kg), the relative total bioavailability of Q3G was 167% compared with the aglycone (P < 0.05). Bioavailability of Q3G was significantly higher when the test meal was ground beef rather than the standard ration. Our results indicate that the bioavailability of quercetin from quercetin glycosides is determined by a complex interdependence between the chemical form of the flavonols and dietary factors.

Histamine H3 receptor activation inhibits neurogenic sympathetic vasoconstriction in porcine nasal mucosa

Histamine release from mast cells is a primary mediator of rhinorrhea, nasal mucosal swelling, increased secretion, sneezing, pruritus and congestion that occur in allergic rhinitis. It is well known that histamine H(1) receptor antagonists inhibit the itch and rhinorhea, but do not block the allergic nasal congestion. A growing body of evidence shows that in addition to histamine H(1) receptors, activation of H(3) receptors may contribute to the procongestant nasal actions of histamine. Activation of the prejunctional histamine H(3) receptor modulates sympathetic control of nasal vascular tone and resistance. The present study was conducted to further characterize the role of histamine H(3) receptors on neurogenic sympathetic vascular contractile responses in isolated porcine nasal turbinate mucosa. We presently found that the histamine H(3) receptor agonist, (R)-alpha-methylhistamine (10-1000 nM), inhibited electrical field stimulation-induced sympathetic vasomotor contractions in a concentration-dependent fashion. Pretreatment with either of the selective histamine H(3) receptor antagonists, thioperamide and clobenpropit, blocked the sympathoinhibitory effect of (R)-alpha-methylhistamine in porcine turbinate mucosa. The effect of compound 48/80, an agent that elicits the release of endogenous histamine from mast cells on nasal sympathetic contractile responses, was also tested. The action of compound 48/80 to release mast cell-derived histamine in the nose mimics many of the nasal responses associated with allergic rhinitis, extravascular leakage and decreased nasal patency. We presently found that compound 48/80 also inhibited the electrical field stimulation-induced sympathetic response. Pretreatment with the H(3) receptor antagonist clobenpropit blocked the sympathoinhibitory action of compound 48/80 on sympathetic contractile responses in nasal mucosa. Taken together, these studies indicate that histamine H(3) receptors modulate vascular contractile responses by inhibition of noradrenaline release from sympathetic nerve terminals in nasal mucosa. It is further suggested that histamine H(3) receptors may play a role in the regulation of vascular tone and nasal patency in allergic nasal congestive disease.

Predominance of delta-opioid-binding sites in the porcine enteric nervous system

The antidiarrheal and constipating actions of opioids are mediated in part by enteric neurons, which lie within the wall of the small intestine and colon, but the differential expression of specific, high-affinity opioid-binding sites in ganglionated plexuses within functionally distinct intestinal segments has not been examined. We determined the saturation binding characteristics under Na+-free conditions of the nonselective opioid receptor (OPR) ligand [3H][(5alpha,7alpha)-17-(cyclopropylmethyl)-4,5-epoxy-18,19-dihydro-3-hydroxy-6-methoxy-alpha, alpha-dimethyl-6,14-ethenomorphinan-7-methanol] (diprenorphine) and the respective delta-, kappa-, and mu-OPR ligands [3H]naltrindole, D-(5alpha,7alpha,8beta)-(-)-N-methyl-N-[7-(1-pyrrolidinyl)-1-oxoaspiro-(4,5)dec-8-yl]benzeneacetamide ([3H]U-69,593), and [3H][D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) in neuronal membranes isolated from myenteric and submucosal plexuses of porcine small intestine and colon. Naloxone-displaceable [3H]diprenorphine-binding sites (KD values ranging from 0.2-0.5 nM and Bmax = 50-95 fmol/mg of protein) were found in both subregions from all gut segments examined. High-affinity [3H]naltrindole sites (KD = 60-140 pmol) were at highest densities (approximately 60 fmol/mg of protein) in submucosal plexus of the ileum and distal colon myenteric plexus and were at lowest densities (8-9 fmol/mg of protein) in the submucosal plexuses of cecum and distal colon. [3H]U-69,593 sites (KD = 0.3-4 nM) were present only in the myenteric plexuses of all segments examined, with highest densities in cecum and proximal colon (44-47 fmol/mg of protein). [3H]DAMGO-binding sites were expressed at relatively low densities in the enteric plexuses of all gut regions. These results indicate that delta-OPRs predominate in the porcine enteric nervous system with a more circumscribed expression of kappa- and mu-OPRs.

Ex vivo assessment of immunosuppression in undiluted whole blood from pigs dosed with tacrolimus (FK506)

To assess the duration of immunosuppression in FK506-dosed pigs, an undiluted whole blood assay was established to measure reactivities of T cells in their physiological milieu. PMA and ionomycin were shown to induce IL-2 production in swine blood. The IC50 of FK506 in inhibiting IL-2 production in whole blood and isolated PBMC stimulated with PMA and ionomycin measured 1.2 and 0.04 nM, respectively. These data underscore the influence of red blood cells and plasma proteins on drug potency. IL-2 levels were determined in blood drawn immediately before and 1, 24, 48, and 72 h after iv dosing. For pigs dosed with 0.05 mg/kg, 50% recovery of IL-2 production was observed at 16 h and 100% at 35 h after dosing. For pigs dosed with 0.15 mg/kg, 50% recovery was observed at 38 h and 100% at 72 h. Blood concentrations of FK506 at 50 and 100% recovery of IL-2 production measured 10.8 and 2.2 nM for pigs dosed with 0.05 mg/kg and 6.1 and 1.1 nM for pigs dosed with 0.15 mg/kg, respectively. These concentrations are severalfold higher than predicted from the IC50 of FK506 for inhibiting IL-2 production in the whole blood assay. These data suggest that the true potency of FK506 in blood after dosing is influenced by additional factors, which could include plasma protein binding, the presence of active or interfering metabolites, serum interfering factors, and sequestration of drug in blood cells. Our results demonstrate the utility of an undiluted whole blood assay for assessing the duration of immunosuppression in drug-dosed animals and emphasize the importance of assessing drug potency in the whole blood environment ex vivo.