Murine norovirus (MNV) has recently been recognized as a widely prevalent viral pathogen in mouse colonies and causes disease and mortality in mice with impaired innate immunity. We tested the hypothesis that MNV infection would alter disease course and immune responses in mice with inflammatory bowel disease (IBD). FVB.129P2-Abcb1a^tm1Bor N7 (Mdr1a–/–) mice develop spontaneous IBD that is accelerated by infection with Helicobacter bilis. As compared with controls, Mdr1a–/– mice coinfected with MNV4 and H. bilis showed greater weight loss and IBD scores indicative of severe colitis, demonstrating that MNV4 can modulate the progression of IBD. Compared with controls, mice inoculated with MNV4 alone had altered levels of serum biomarkers, and flow cytometric analysis of immune cells from MNV4-infected mice showed changes in both dendritic cell (CD11c⁺) and other nonT cell (CD4⁻ CD8⁻) populations. Dendritic cells isolated from MNV4-infected mice induced higher IFNγ production by polyclonal T cells in vitro at 2 d after infection but not at later time points, indicating that MNV4 infection enhances antigen presentation by dendritic cells early after acute infection. These findings indicate that acute infection with MNV4 is immunomodulatory and alters disease progression in a mouse model of IBD.

Infection with Helicobacter species is endemic in many animal facilities and may alter the penetrance of inflammatory bowel disease (IBD) phenotypes. However, little is known about the relative pathogenicity of H. typhlonius, H. rodentium, and combined infection in IBD models. We infected adult and neonatal IL10^–/– mice with H. typhlonius, H. rodentium, or both bacteria. The severity of IBD and incidence of inflammation-associated colonic neoplasia were assessed in the presence and absence of antiHelicobacter therapy. Infected IL10^–/– mice developed IBD with severity of noninfected (minimal to no inflammation) < H. rodentium < H. typhlonius < mixed H. rodentium + H. typhlonius (severe inflammation). Inflammation-associated colonic neoplasia was common in infected mice and its incidence correlated with IBD severity. Combined treatment with amoxicillin, clarithromycin, metronidazole, and omeprazole eradicated Helicobacter in infected mice and ameliorated established IBD in both infected and noninfected mice. Infection of IL10^–/– mice with H. rodentium, H. typhlonius, or both organisms can trigger development of severe IBD that eventually leads to colonic neoplasia. The high incidence and multiplicity of neoplastic lesions in infected mice make this model well-suited for future research related to the development and chemoprevention of inflammation-associated colon cancer. The similar antiinflammatory effect of antibiotic therapy in Helicobacter-infected and -noninfected IL10^–/– mice with colitis indicates that unidentified microbiota in addition to Helicobacter drive the inflammatory process in this model. This finding suggests a complex role for both Helicobacter and other intestinal microbiota in the onset and perpetuation of IBD in these susceptible hosts.

Mice that constitutively express the human interleukin 6 (huIL6) protein from a heritable transgene (H2-L^d-IL-6) express high levels of the acute-phase reactant, serum amyloid protein A, a liver-derived apoprotein of high-density lipoprotein that is the precursor of AA amyloid. Typically at approximately 5 mo of age B6(C)-Tg(H2-L^d-IL-6)Kish (H2/huIL-6) animals begin to develop splenic deposits of AA amyloid, which progress to involve the liver, kidney, and vasculature, ultimately resulting in death due to severe systemic AA amyloidosis at 8 to 9 mo of age. These mice provide a robust model in which to study novel therapeutic and diagnostic imaging agents for AA amyloidosis. We recently have noted a change in onset of spontaneous disease, as evidenced by 2 female transgenic mice that were found moribund at only 5 mo of age. Extensive hepatosplenic amyloid deposits in both mice were identified and quantified by single-photon emission computed tomography, which further revealed heterogeneous distribution of radiotracer in the spleen indicating a distinction between amyloid-laden red pulp and the disease-free lymphoid follicles. The AA nature of the deposits was evidenced immunohistochemically and by mass spectrometric analyses of extracted amyloid fibrils. Our studies have documented the manifestation of early-onset, severe, spontaneous AA amyloidosis in 2- to 5-mo-old H2/huIL-6 mice; we hypothesize that this disease is due to genetic rather than environmental factors.

The petit rat (pet/pet) is a recently discovered semilethal mutant dwarf. The neonatal pet/pet rats had a low body weight and small thymus and testis. During the first 3 d after birth, 50% of the male and 80% of the female pet/pet pups were lost or found dead. Surviving pet/pet rats showed marked retardation of postnatal growth, and their body weights were 41% (female rats) and 32% (male rats) of those of normal rats at the adult stage. The pet/pet rats exhibited proportional dwarfism, and their longitudinal bones were shorter than those of controls without skeletal malformations. Most organs of male pet/pet rats, especially the thymus, testis, adipose tissue surrounding the kidney, and accessory sex organs, weighed markedly less at 140 d of age than did those of their normal counterparts. The thymus of pet/pet rats was small with abnormal thymic follicles. Testes from pet/pet rats exhibited 2 patterns of abnormal histology. Spermatogenesis was present in testes that were only slightly anomalous, but the seminiferous tubules were reduced in diameter. In severely affected testes, most of the seminiferous tubules showed degeneration, and interstitial tissue was increased. Plasma growth hormone concentrations did not differ between pet/pet and normal male rats. The dwarf phenotype of pet/pet rats was inherited as an autosomal recessive trait. These results indicate that the pet/pet rat has a semilethal growth-hormone-independent dwarf phenotype that is accompanied by thymic and testicular anomalies and low birth weight.

The Komeda miniature rat Ishikawa (KMI) is a spontaneous animal model of dwarfism caused by a mutation in Prkg2, which encodes cGMP-dependent protein kinase type II (cGKII). This strain has been maintained as a segregating inbred strain for the mutated allele mri. In this study, we characterized the phenotype of the KMI strain, particularly growth traits, craniofacial measurements, and organ weights. The homozygous mutant (mri/mri) animals were approximately 70% to 80% of the size of normal, heterozygous (mri/+) animals in regard to body length, weight, and naso-occipital length of the calvarium, and the retroperitoneal fat of mri/mri rats was reduced greatly. In addition, among progeny of the (BN×KMI-mri/mri)F1×KMI-mri/mri backcross, animals with the KMI phenotype (mri/mri) were easily distinguished from those showing the wild-type phenotype (mri/+) by using growth traits such as body length and weight. Genetic analysis revealed that all of the backcrossed progeny exhibiting the KMI phenotype were homozygous for the KMI allele in the 1.2-cM region between D14Rat5 and D14Rat80 on chromosome 14, suggesting strongly that mri acts in a completely recessive manner. The KMI strain is the first and only rat model with a confirmed mutation in Prkg2 and is a valuable model for studying dwarfism and longitudinal growth traits in humans and for functional studies of cGKII.

Porcine models have become increasingly popular in cardiovascular research. The standard farm pig rapidly increases in body weight and size, potentially confounding serial measurements of cardiac function and morphology. We developed an adult porcine model that does not show physiologic increases in heart mass during the study period and is suitable for long-term study. We compared adult minipigs with the commonly used adolescent Yorkshire swine. Myocardial infarction was induced in adult Göttingen minipigs and adolescent Yorkshire swine by occlusion of the left anterior descending coronary artery followed by reperfusion. At 8 wk after infarction, the left ventricular ejection fraction was 34.1 ± 2.3% in minipigs and 30.7 ± 2.0% in Yorkshire swine. The left ventricular end-diastolic mass in Yorkshire pigs assessed by magnetic resonance imaging increased 17 ± 5 g, from 42.6 ± 4.3 g at week 1 after infarction to 52.8 ± 6.6 g at week 8, whereas it remained unchanged in minipigs. Cardiac anatomy and physiology in adult minipigs were evaluated invasively by angiography and noninvasively by Multidetector Computed Tomography and by Magnetic Resonance Imaging at 1.5 T and 3 T prior to myocardial infarction and during folow-up. This porcine heart failure model is reproducible, mimics the pathophysiology in patients who have experienced myocardial infarction, and is suitable for imaging studies. New heart failure therapies and devices can be tested preclinically in this adult animal model of chronic heart failure.

The objective of this study was to demonstrate that Bama miniature pigs are a suitable experimental animal model for the evaluation of drugs for man. To this end, in vitro lovastatin metabolism at the minipig liver microsomal level and in vivo pharmacokinetics were studied. Results were compared with those obtained from humans. Our data indicate that the main metabolites and enzyme kinetic parameters of lovastatin metabolism are similar in pigs and humans. Triacetyloleandomycin, a specific inhibitor of human CYP3A4, inhibited the metabolism of lovastatin in pig and human liver microsomes. In addition, the pharmacokinetic parameters and absolute bioavailability suggested that the absorption and elimination of lovastatin in Bama miniature pigs were similar to those in humans. Lovastatin was distributed across many organs in pigs, but the highest levels were found in the stomach, intestines, and liver. Within 96 h, 7% and 82% of the given dose was excreted in the urine and feces, respectively. In addition, no significant species differences in the plasma protein binding ratio of lovastatin and the rates of lovastatin hydrolysis to β-hydroxyacid lovastatin were apparent. From these results, we conclude that Bama miniature pigs are suitable for use in drug evaluation studies.

Gender differences, sex steroid effects, and sex-specific candidate therapeutics in ischemic stroke have been studied in rodents but not in nonhuman primates. In this feasibility study (n = 3 per group), we developed a model of transient focal cerebral ischemia in adult male and female rhesus macaques that consistently includes white matter injury. The animals also were used to determine whether gender-linked differences in histopathologic outcomes could be evaluated in this model in future, larger preclinical trials. Histologic brain pathology was evaluated at 4 d after 90 min of reversible occlusion of the middle cerebral artery (MCA). MCA occlusion was accomplished by using a transorbital approach and temporary placement of an aneurysm clip. Male and female rhesus macaques 7 to 11 y of age were studied. Baseline and intraischemic blood glucose, systolic blood pressure, heart rate, oxygen saturation, end-tidal CO₂, and rectal temperatures were not different among groups. The variability in injury volume was comparable to that observed in human focal cerebrovascular ischemia and in other nonhuman primate models using proximal MCA occlusion. In this small sample, the volume of injury was not different between male and female subjects, but observed variability was higher in female caudate nucleus, putamen, and hemisphere. This report is the first to compare cerebral ischemic outcomes in female and male rhesus macaques. The female rhesus macaque ischemic stroke model could be used after rodent studies to provide preclinical data for clinical trials in women.

A retrospective study using maternal and birth statistics from an open, captive rhesus macaque colony was done to determine the effects of parity, exposure to simian retrovirus (SRV), housing, maternal parity, and maternal birth weight on infant birth weight, viability and gestation length. Retrospective colony statistics for a 23-y period indicated that birth weight, but not gestation length, differed between genders. Adjusted mean birth weights were higher in nonviable infants. Mothers positive for SRV had shorter gestations, but SRV exposure did not affect neonatal birth weights or viability. Infants born in cages had longer gestations than did those born in pens, but neither birth weight nor viability differed between these groups. Maternal birth weight did not correlate with infant birth weight but positively correlated with gestation length. Parity was correlated with birth weight and decreased viability. Increased parity of the mother was associated with higher birth weight of the infant. A transgenerational trend toward increasing birth weight was noted. The birth statistics of this colony were consistent with those of other macaque colonies. Unlike findings for humans, maternal birth weight had little predictive value for infant outcomes in rhesus macaques. Nonviable rhesus infants had higher birth weights, unlike their human counterparts, perhaps due to gestational diabetes occurring in a sedentary caged population. Similar to the situation for humans, multiparity had a protective effect on infant viability in rhesus macaques.

Transgenic mice, although useful for analyses of gene function, can present unanticipated phenotypic manifestations, including behavioral problems, that may not be directly associated with the gene of interest but rather due to the complex interplay inherent in genomes. These unexpected events can present unique insight into gene function, leading to an advantage in some situations, yet in others can confound interpretation and compromise usefulness of the transgenic line. Here we document that short-term supplementation with S-adenosyl methionine (SAM)—a nutriceutical known to regulate neurotransmitter levels, improve working memory, and reduce aggression—reduced handling- and startling-induced seizures that otherwise precluded behavioral analyses in a transgenic line. This effect lasted for at least 1 mo after withdrawal of SAM and allowed mice to be used in standard maze analyses. These findings suggest that short-term administration of a neurotropic nutriceutical may provide a functional rescue for behavioral studies in an otherwise intractable transgenic mouse line as well as improve the welfare of similar lines.