A review of high-resolution X-ray computed tomography and other imaging modalities for small animal research.

Dedicated high-resolution small animal systems have recently emerged as important new tools for laboratory animal research. These imaging systems permit researchers to noninvasively screen animal models for mutations or pathologies and to monitor disease progression and response to therapy. The authors survey various small animal imaging modalities, including MRI, PET, SPECT, and microCT, and discuss several representative microCT mouse imaging studies.

Body condition scoring: comparing newly trained scorers and micro-computed tomography imaging.

A Body Condition Scoring (BCS) protocol is an easily learned tool that can be used as a means of body condition assessment for random populations of mice. Here, the authors use X-ray computed tomography technology to show that BCS is a quick and effective method for evaluating parameters such as muscle thickness and fat, and that the method is equally as accurate when employed by newly trained or expert scorers.

Spontaneous inflammatory bowel disease in multiple mutant mouse lines: association with colonization by Helicobacter hepaticus.

BACKGROUND: Both genetic and microbial factors are thought to play a role in the development of inflammatory bowel disease (IBD): however, no causative microbial agent has been clearly defined for humans or animals. Normal flora or previously unrecognized intestinal pathogens may contribute to the development of disease in susceptible hosts. A newly recognized murine Helicobacter, H. hepaticus, causes hepatitis in mice and in one strain of mice is linked to liver cancer. This study investigates the association between colonization of the lower intestinal tract of multiple genetically altered lines of mice with H. hepaticus, and the occurrence of IBD. MATERIALS AND METHODS: Rectal prolapse noted clinically in multiple genetically altered mouse lines was evaluated for the presence of H. hepaticus and histologic evidence of IBD. Fifty-five mice representing 11 different genetic alterations were evaluated. RESULTS: H. hepaticus was detected in 85% of mutant mice with rectal prolapse. Histologic evidence of proliferative typhlitis, colitis or proctitis was present in 65% of the animals examined, 89% of which were positive for H. hepaticus as detected by species specific PCR. CONCLUSION: The presence of H. hepaticus in association with IBD in multiple lines of genetically altered mice suggests further studies are needed to test experimentally the role H. hepaticus plays in the development of IBD in susceptible mice. Additionally, specific mutant mouse lines infected with H. hepaticus in this study may provide additional models for elucidation of microbial and genetic factors in the pathogenesis of IBD.

Inflammatory bowel disease: an immunity-mediated condition triggered by bacterial infection with Helicobacter hepaticus.

Inflammatory bowel disease (IBD) is thought to result from either an abnormal immunological response to enteric flora or a normal immunological response to a specific pathogen. No study to date has combined both factors. The present studies were carried out with an immunologically manipulated mouse model of IBD. Mice homozygous for the severe combined immunodeficiency (scid) mutation develop IBD with adoptive transfer of CD4+ T cells expressing high levels of CD45RB (CD45RB(high) CD4+ T cells). These mice do not develop IBD in germfree conditions, implicating undefined intestinal flora in the pathogenesis of lesions. In controlled duplicate studies, the influence of a single murine pathogen, Helicobacter hepaticus, in combination with the abnormal immunological response on the development of IBD was assessed. The combination of H. hepaticus infection and CD45RB(high) CD4+ T-cell reconstitution resulted in severe disease expression similar to that observed in human IBD. This study demonstrates that IBD develops in mice as a consequence of an abnormal immune response in the presence of a single murine pathogen, H. hepaticus. The interaction of host immunity and a single pathogen in this murine system provides a novel model of human IBD, an immunity-mediated condition triggered by bacterial infection.

Helicobacter rodentium sp. nov., a urease-negative Helicobacter species isolated from laboratory mice.

A spiral-shaped bacterium with bipolar, single, nonsheathed flagella was isolated from the intestines of laboratory mice. The organism grew at 37 and 42 degrees C under microaerobic and anaerobic conditions, did not hydrolyze urea, was weakly positive for catalase and oxidase, reduced nitrate to nitrite, did not hydrolyze indoxyl acetate or hippurate, and was resistant to cephalothin and nalidixic acid. This is the first urease-negative, murine Helicobacter spp. isolated from intestines. Also, Helicobacter pullorum and this bacterium are unique among the genus Helicobacter in having nonsheathed flagella. The new bacterium appears to be part of the normal intestinal flora; although its pathogenic potential is unknown, this organism was also isolated from scid mice with diarrhea that were co-infected with Helicobacter bilis. On the basis of 16S rRNA gene sequence analysis data and biochemical and phenotypic criteria, the new organism is classified as a novel helicobacter, for which we propose the name Helicobacter rodentium. The type strain is MIT 95-1707 (= ATCC 700285).

Microbiologic, radiographic, and anatomic study of the nasolacrimal duct apparatus in the rabbit (Oryctolagus cuniculus).

This study was motivated by the sporadic observation of epiphora in two male rabbits. The epiphora was unilateral and not associated with conjunctivitis or Pasteurella infection. To characterize the cause of epiphora, we studied 15 specific-pathogen-free New Zealand White rabbits. This study group was composed of the two affected males, four unaffected males, and nine unaffected females. Clinical evaluation consisted of bacterial culture of conjunctival specimens, examination of conjunctival scrapings for chlamydial inclusions, culture and cytologic examination of specimens from the nasolacrimal duct, plain and contrast radiography, latex casting, histologic examination, and the Schirmer tear test. Important differences found in the rabbits with epiphora included an opalescent, gritty, nasolacrimal duct flush fluid and marked unilateral dilatation of the duct proximal to a dorsal flexure at the caudal limit of the incisor tooth root. The flush solution from one affected rabbit cleared with ether, suggesting the presence of triglycerides or cholesterol. The organisms most commonly isolated from the conjunctiva were Moraxella sp., Oligella urethralis, Staphylococcus aureus, coagulase-negative Staphylococcus sp., and Streptococcus viridans. The organisms most commonly isolated from the nasolacrimal duct flush fluid were Moraxella sp., S. viridans, and Neisseria sp. Culture of the nasolacrimal duct flush fluid yielded microorganisms more consistently than did culture of the conjunctival specimens. All microorganisms isolated from affected rabbits also were isolated from unaffected rabbits. There was no apparent contribution of microorganisms to the development of epiphora, and Schirmer tear test results for affected animals were within the range seen in unaffected animals. Occlusion of the nasolacrimal duct was presumed to be attributable to fat droplets. This study augments the existing literature and represents the first report of anomalous nasolacrimal duct anatomic features in the rabbit.

Characterization of dermatologic changes in geriatric rhesus macaques.

Nonhuman primates are frequently used for aging studies. We observed a high prevalence of skin disease among a group of geriatric rhesus monkeys (mean age = 25 years; n = 9) used in aging behavioral studies. Gross and histopathologic changes in the skin of these geriatric rhesus were compared with skin from control adult monkeys (mean age = 10; n = 4) and sun-exposed monkeys (mean age = 11; n = 4) to characterize age-related skin changes. Biopsy specimens were taken from four specified skin locations (lateral to bridge of nose, ventral midline, dorsal midline, perineal area) and from additional areas where skin lesions were present. Samples were routinely processed and evaluated by light microscopy. Blood samples were collected and tested for estrogen, thyroid-stimulating hormone, triiodothyronine thyroxine, and cortisol levels. The axilla was swabbed and samples were obtained for bacterial culturing. All nine of the geriatric monkeys had notable dermal lesions, while one of the control monkeys and one of the sun-exposed monkeys had abnormal findings. Major gross findings included increased areas of erythematous skin, wrinkling, focal skin scaling, thinning of hair, foot calluses, and exudative lesions. Histologic skin changes included subacute dermatitis, acanthotic dermatitis, and a lesion resembling an early solar lentigo in the sun-exposed animal. These changes were not associated with hormonal abnormalities or bacterial pathogens. Histologic changes are compatible with nonspecific skin changes observed in elderly humans. This study establishes a baseline of dermatologic changes of the aging rhesus macaque.

Evaluation of various oral antimicrobial formulations for eradication of Helicobacter hepaticus.

Helicobacter hepaticus colonizes the cecum and colon of several strains of mice from a variety of commercial suppliers, persistently infects mice, causes chronic hepatitis, is linked to hepatic tumors in A/JCr mice, and has been associated with inflammatory bowel disease of athymic and scid mice. For this reason, eradication of the organism from infected mouse colonies is desirable. We recently reported that amoxicillin or tetracycline-based triple therapy (amoxicillin or tetracycline in combination with metronidazole and bismuth) given by oral gavage 3 times daily for 2 weeks eradicated H. hepaticus in 8- to 10-week-old A/JCr mice. To establish a more convenient therapy regimen for eradicating H. hepaticus, we evaluated water and dietary administration of various antibiotic combinations in A/JCr and DBA/2 mice naturally infected with H. hepaticus. The A/JCr male mice received amoxicillin-based triple therapy in drinking water or by oral gavage, or received tetracycline-based triple therapy in the drinking water. The DBA/2J female mice received amoxicillin-based triple therapy in a specially formulated dietary wafer or by oral gavage, or received enrofloxacin in drinking water. All treatments were given for a 2-week period. Control animals received no treatment. One month after treatment, H. hepaticus was recovered from the liver, cecum, or colon of A/JCr control mice and mice receiving amoxicillin- or tetracycline-based triple therapy in drinking water but not in mice receiving amoxicillin-based triple therapy by oral gavage. Helicobacter hepaticus was not recovered from DBA/2J mice receiving amoxicillin-based triple therapy in dietary wafer or by oral gavage but was recovered from control mice and 7 of 10 mice receiving enrofloxacin in drinking water. Results indicate that amoxicillin-based triple therapy administered in the diet or by oral gavage is effective in eradicating H. hepaticus. Antibiotics administered in the water, however, were not effective in eradicating the organism.

Evaluation of antibiotic therapies for eradication of Helicobacter hepaticus.

The newly recognized murine pathogen Helicobacter hepaticus is known to colonize the ceca and colons of several strains of mice from a variety of commercial suppliers. Additionally, the organism persistently infects mice, causes a chronic hepatitis, and is linked to hepatic tumors in the A/JCr inbred mouse strain. For this reason, eradication of the organism from infected mouse colonies is desirable. Treatment modalities for eradication of H. hepaticus from the gastrointestinal system consisted of oral administration of various antibiotic combinations previously evaluated for eradication of experimental H. felis gastric infection in mice. A/JCr mice (8 to 10 weeks old) naturally infected with H. hepaticus were divided into six treatment groups of 10 animals each. Animals received monotherapy of amoxicillin, metronidazole, or tetracycline or triple therapy of amoxicillin-metronidazole-bismuth (AMB) or tetracycline-metronidazole-bismuth (TMB). All medications were administered by oral gavage three times daily for 2 weeks. One month after the final treatment, mice were euthanatized and livers, ceca, and colons were cultured for H. hepaticus. All untreated control animals had H. hepaticus isolated from the cecum and/or colon. H. hepaticus was not recovered from the livers, ceca, or colons of the AMB or TMB treatment groups. All animals receiving the various antibiotic monotherapies had H. hepaticus isolated from the cecum and colon. We conclude that at the doses and the route evaluated, AMB and TMB triple therapies are effective for eradication of H. hepaticus in 8- to 10-week old A/JCr mice.

Absence of glomerulonephritis in guinea pigs deficient in the fourth component of complement.

Genetically determined deficiencies of the early components of the classical complement pathway (C1, C4, C2) or of the third component of complement (C3) in both human beings and experimental animals are known to be associated with renal disease, including glomerulonephritis. The current study was performed to examine the C4-deficient (C4D) guinea pig for the presence of renal disease. Eighteen C4D animals and 17 control animals (Crl:Hartley) (divided by sex into four age categories) were examined. Light microscopic examination revealed no differences in mesangium, glomerular cellularity, thickness of capillary loops, or presence of epithelial crescents in the kidneys of C4D guinea pigs as compared with control animals. Electron microscopic examination did not reveal glomerular or tubular immune complex deposits in either C4D or control animals. C4D guinea pigs apparently do not demonstrate glomerulonephritis.