Segmented filamentous bacteria (SFB) are commensal bacteria that were first identified in the ilea of mice and rats. Morphologically similar bacteria occur in a broad range of host species, but all strains have been refractory to in vitro culture thus far. Although SFB were once considered innocuous members of the intestinal microbiota of laboratory rodents, they are now known to affect the development of the immune system in rodents and, subsequently, the phenotype of models of both enteric and extraintestinal disease. Therefore, SFB represent long-recognized commensal bacteria serving as an intercurrent variable in studies using rodent models of disease. Here we describe the basic biology of SFB and discuss the immunologic and physiologic effects of colonization with SFB, with particular attention to their effects on rodent models of disease. In addition, we propose that SFB represent only the 'tip of the iceberg' in our understanding of the influence of the microbiota on model phenotypes. As next-generation sequencing techniques are increasingly used to investigate organisms that are refractory to culture, we are likely to identify other commensal microbes that alter the models we use. This review underscores the need to characterize such host–microbe interactions, given that animal research represents a critical tool that is particularly vulnerable to scrutiny in an era of decreasing financial resources and increasing accountability for the use of animal models.

Urinary biomarkers may offer a more sensitive and less invasive means to monitor kidney disease than traditional blood chemistry biomarkers such as creatinine. CD1^pcy/pcy (pcy) mice have a slowly progressive disease phenotype that resembles human autosomal dominant polycystic kidney disease with renal cyst formation and inflammation. Previous reports suggest that dietary protein restriction may slow disease progression in mice and humans with polycystic kidney disease. Accordingly, we fed pcy mice either a standard chow (22.5% protein) or a protein-restricted (11.5% soy-based protein) diet from weaning until 34 wk of age. Every 6 wk we measured markers of kidney disease, including serum creatinine, BUN, and serum albumin as well as urinary monocyte chemoattractant protein 1 (MCP1), microalbumin, and specific gravity. Progression of kidney disease was equivalent for both diet groups despite dietary protein restriction. Urinary biomarkers proved useful for early detection of disease, in that urinary microalbumin was elevated as early as 22 wk of age and urinary MCP1 was increased by 28 wk of age, whereas increases in serum creatinine and BUN were detected later (at 34 wk of age) in both diet groups. Thus, urinary microalbumin and MCP1 analyses provided earlier, noninvasive indicators for detection of kidney disease and disease progression in pcy mice than did serum creatinine and BUN.

Dietary deficiency of ω3 fatty acid during development leads to impaired cognitive function. However, the effects of multiple generations of ω3 fatty-acid deficiency on cognitive impairment remain unclear. In addition, we sought to test the hypothesis that the cognitive impairments of ω3 fatty-acid–deficient mice are mediated through the arachidonic acid–cyclooxygenase (COX) pathway. To address these issues, C57BL/6J mice were bred for 3 generations and fed diets either deficient (DEF) or sufficient (SUF) in ω3 fatty acids. At postnatal day 21, the F3 offspring remained on the dam's diet or were switched to the opposite diet, creating 4 groups. In addition, 2 groups that remained on the dam's diet were treated with a COX inhibitor. At 19 wk of age, spatial-recognition memory was tested on a Y-maze. Results showed that 16 wk of SUF diet reversed the cognitive impairment of F3 DEF mice. However, 16 wk of ω3 fatty-acid–deficient diet impaired the cognitive performance of the F3 SUF mice, which did not differ from that of the F3 DEF mice. These findings suggest that the cognitive deficits after multigenerational maintenance on ω3 fatty-acid–deficient diet are not any greater than are those after deficiency during a single generation. In addition, treatment with a COX inhibitor prevented spatial-recognition deficits in F3 DEF mice. Therefore, cognitive impairment due to dietary ω3 fatty-acid deficiency appears to be mediated by the arachidonic acid–COX pathway and can be prevented by 16 wk of dietary repletion with ω3 fatty acids or COX inhibition.

Three breeding colonies of Myd88^–/– mice had a history of significant morbidity and mortality. Although strain-specific poor reproductive performance might explain neonatal death and dystocia, mice were found dead or required euthanasia because of moribundity, distended abdomen, head tilt, and seizures. Histopathology results included bacteremia, placentitis, metritis, peritonitis with abscess formation, and suppurative meningoencephalitis. Intralesional gram-negative coccobacilli were present, often in extremely high number. Cultures of samples of the cardiac blood of a mouse and from water-bottle sipper tubes provided to some affected mice grew Pseudomonas aeruginosa. In addition, affected tissues from 2 mice and feces from a third tested PCR-positive for P. aeruginosa. Although the mice had received autoclaved reverse-osmosis–purified drinking water, we suspect that the mice were inoculated with P. aeruginosa through contaminated sipper tubes. Because of the deficiency in most of the Toll-like receptor signaling pathways, these Myd88^–/– mice were unlikely to have developed competitive innate and adaptive immune responses, resulting in bacterial infections. These clinical cases underscore the importance of understanding how genotype, phenotype and environment affect animal health. Sound husbandry and experimental practices are needed to prevent the exposure of immuno-deficient mice to pathogens.

Three mice (2 male, 1 female; age, 5 to 16 mo) from a mouse line transgenic for keratin 14 (K14)-driven LacZ expression and on an outbred Crl:CD1(ICR) background, were identified as having distended abdomens and livers that were diffusely enlarged by numerous cysts (diameter, 0.1 to 2.0 cm). Histopathology revealed hepatic cysts lined by biliary type epithelium and mild chronic inflammation, and confirmed the absence of parasites. Among 21 related mice, 5 additional affected mice were identified via laparotomy. Breeding of these 5 mice (after 5 mo of age) did not result in any offspring; the K14 mice with polycystic livers failed to reproduce. Affected male mice had degenerative testicular lesions, and their sperm was immotile. Nonpolycystic K14 control male mice bred well, had no testicular lesions, and had appropriate sperm motility. Genetic analysis did not identify an association of this phenotype with the transgene or insertion site.

The objective of this study was to investigate the effects of liraglutide, an analog of human glucagon-like peptide 1 (GLP1), on WBN/Kob-Lepr^fa (fa/fa) rats, which spontaneously develop type 2 diabetes mellitus with pancreatic disorder and obesity. Male fa/fa rats (age, 7 wk) were allocated into 4 groups and received liraglutide (37.5, 75, 150 μg/kg SC) or saline (control group) once daily for 4 wk. All rats in the control group became overweight and developed hyperglycemia as they aged. Although the rats given liraglutide showed a dose-dependent reduction in food intake, no significant effects on body weight or fat content occurred. In the liraglutide groups, the development of hyperglycemia was suppressed, even as plasma insulin concentrations increased in a dose-dependent manner. Intravenous glucose tolerance testing of the liraglutide-treated rats confirmed improvement of glucose tolerance and enhanced insulin secretion. Histologic examination revealed increased numbers of pancreatic β-cell type islet cells and increased proliferation of epithelial cells of the small ducts in the liraglutide-treated groups. Although our study did not reveal a significant decrease in obesity after liraglutide administration, the results suggest a marked antidiabetic effect characterized by increased insulin secretion in fa/fa rats with pancreatic disorders.

Many studies of the response of colonic tumors to therapeutics use tumor multiplicity as the endpoint to determine the effectiveness of the agent. These studies can be greatly enhanced by accurate measurements of tumor volume. Here we present a quantitative method to easily and accurately determine colonic tumor volume. This approach uses a biocompatible alginate to create a negative mold of a tumor-bearing colon; this mold is then used to make positive casts of dental stone that replicate the shape of each original tumor. The weight of the dental stone cast correlates highly with the weight of the dissected tumors. After refinement of the technique, overall error in tumor volume was 16.9% ± 7.9% and includes error from both the alginate and dental stone procedures. Because this technique is limited to molding of tumors in the colon, we utilized the Apc^Pirc/+ rat, which has a propensity for devel- oping colonic tumors that reflect the location of the majority of human intestinal tumors. We have successfully used the described method to determine tumor volumes ranging from 4 to 196 mm³. Alginate molding combined with dental stone casting is a facile method for determining tumor volume in vivo without costly equipment or knowledge of analytic software. This broadly accessible method creates the opportunity to objectively study colonic tumors over time in living animals in conjunction with other experiments and without transferring animals from the facility where they are maintained.

Baboons provide a natural model of epilepsy. However, spontaneous seizures are usually sporadic, brief, and may not be observed. We hypothesized that various types of craniofacial trauma (CFT) may serve as reliable markers for epilepsy. We evaluated the type, demographics, and clinical significance of CFT in a large baboon colony. CFT was categorized according to somatotopic location, propensity to recur, and association with witnessed seizures or abnormal EEG findings. We divided the baboons with CFT into 2 groups: those with known histories of seizures (CFT+Sz, n = 176) and those without seizure histories (CFTonly; n = 515). In CFT+Sz baboons, the 568 injuries identified included periorbital (57%), scalp (27%), muzzle (12%), and facial (4%) injuries; multiple somatotopic locations or body parts were affected in 21 baboons. The most common CFT injuries associated with seizures were periorbital and scalp lesions (43% for each region). Compared with those in CFTonly animals, EEG abnormalities, including interictal epileptic discharges (IED) and photosensitivity were more prevalent in the CFT+Sz group, particularly among baboons with periorbital or scalp injuries. Compared with CFT+Sz animals, CFTonly baboons tended to have later onset and less frequent recurrence of CFT but higher prevalence of muzzle and tooth injuries. IED and photosensitivity were less prevalent in the CFTonly than the CFT+Sz group, with periorbital injuries carrying the highest and muzzle injuries the lowest association with IED or photosensitivity in both groups. Therefore, CFT in general and periorbital injuries in particular may be markers for seizures in baboons.

Retinoic acid is a widely used factor in both mouse and human embryonic stem cells. It suppresses differentiation to mesoderm and enhances differentiation to ectoderm. Fibroblast growth factor 2 (FGF2) is widely used to induce differentiation to neurons in mice, yet in primates, including humans, it maintains embryonic stem cells in the undifferentiated state. In this study, we established an FGF2 low-dose-dependent embryonic stem cell line from cynomolgus monkeys and then analyzed neural differentiation in cultures supplemented with retinoic acid and FGF2. When only retinoic acid was added to culture, neurons differentiated from FGF2 low-dose-dependent embryonic stem cells. When both retinoic acid and FGF2 were added, neurons and astrocytes differentiated from the same embryonic stem cell line. Thus, retinoic acid promotes the differentiation from embryonic stem cells to neuroectoderm. Although FGF2 seems to promote self-renewal in stem cells, its effects on the differentiation of stem cells are influenced by the presence or absence of supplemental retinoic acid.

Superficial decidualization of the endometrial stroma is an essential feature of the implantation stage of pregnancy in rhesus macaques and other primates. Decidualization involves proliferation of the endometrial stromal cells, with differentiation into morphologically distinct decidual cells. Previous reports involving nonpregnant rhesus monkeys have described local- ized and widespread endometrial decidualization in response to administration of progesterone and synthetic progestogens. Ectopic decidua or 'deciduosis' describes the condition in which groups of decidual cells are located outside of the endometrium, most often in the ovaries, uterus and cervix but also in various other organs. In humans, most cases of deciduosis are associated with normal pregnancy, and ectopic decidua can be found in the ovary in nearly all term pregnancies. Here we describe pronounced endometrial decidualization in 2 rhesus macaques. Both macaques had been treated long-term with medroxyprogesterone acetate for presumed endometriosis, which was confirmed in one of the macaques at postmortem examination. In one animal, florid extrauterine and peritoneal serosal decidualization was admixed multifocally with carcinomatosis from a primary colonic adenocarcinoma. Cells constituting endometrial and serosal decidualization reactions were immunopositive for the stromal markers CD10, collagen IV, smooth muscle actin, and vimentin and immunonegative for cytokeratin. In contrast, carcinomatous foci were cytokeratin-positive. To our knowledge, this report describes the first cases of serosal peritoneal decidualization in rhesus macaques. The concurrent presentation of serosal peritoneal decidualization with carcinomatosis is unique.