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Indirect mouse model for the evaluation of potential antiviral compounds: results with Venezuelan equine encephalomyelitis virus.

An indirect mouse model was utilized to evaluate the antiviral activity of several compounds against Venezuelan equine encephalomyelitis (VEE) virus infection in mice. Mice were given various dosages of lysine-stabilized polyriboinosinic acid-polyribocytidylic acid, a tilorone analogue, kethoxal, or mepacrine before and/or shortly after receiving one of several dose levels of attenuated strain TC-83 VEE virus. Twenty-one days later, the same mice were rechallenged intracranially with virulent Trinidad donkey strain VEE virus. Susceptibility to rechallenge was interpreted as evidence of drug effectiveness in completely preventing the initial immunizing virus infection. In contrast, if a drug lacked antiviral effectiveness, the initial attenuated infection stimulated sufficient immunity to protect mice against the virulent rechallenge. Both of the interferon inducers, lysine-stabilized polyriboinosinic acid-polyribocytidylic acid and tilorone analogue 11,567, possessed significant (P < 0.01) antiviral activity based upon this indirect model, whereas mepacrine and kethoxal were inactive. Results using the indirect method were confirmed by using the conventional direct method for evaluating the effectiveness of potentially useful antiviral compounds. The indirect mouse model described should prove useful for studying drug efficacy against certain viruses that are lethal only by intracranial inoculation.

Animals

Echinococcus granulosus: development of an intermediate host mouse model for use in vaccination studies.

A mouse model has been developed to evaluate potential protective antigens which could render intermediate hosts resistant to a challenge infection with Echinococcus granulosus eggs. DBA/2J, CBA/J, Balb/cJ, C57/B16J and CF-1 mice were initially infected orally and parenterally with eggs, hatched eggs or activated oncospheres. Generally less than 1% of the oral dose established as cysts. Mean cysts counts were increased when Balb/cJ mice were injected intraperitoneally or intravenously with activated oncospheres. A challenge regime using 600 activated oncospheres injected intraperitoneally into adult Balb/cJ mice was subsequently adopted yielding means of 15-51 cysts per mouse. When activated oncospheres were injected intraperitoneally into Balb/cJ, DBA/2J and CF-1 mice, cysts were restricted to the peritoneal cavity. Activated oncospheres injected intravenously, however, lodged almost exclusively in the lung and thoracic cavity, except in DBA/2J mice where 55% lodged in the liver. This anatomical localization enabled the outcome of prior infection and challenge to be monitored separately. Prior infection rendered Balb/cJ mice fully resistant to subsequent challenge.

Animals

Retinal Proteome Profiling of Inherited Retinal Degeneration Across Three Different Mouse Models Suggests Common Drug Targets in Retinitis Pigmentosa.

Inherited retinal degenerations (IRDs) are a leading cause of blindness among the population of young people in the developed world. Approximately half of IRDs initially manifest as gradual loss of night vision and visual fields, characteristic of retinitis pigmentosa (RP). Due to challenges in genetic testing, and the large heterogeneity of mutations underlying RP, targeted gene therapies are an impractical largescale solution in the foreseeable future. For this reason, identifying key pathophysiological pathways in IRDs that could be targets for mutation-agnostic and disease-modifying therapies (DMTs) is warranted. In this study, we investigated the retinal proteome of three distinct IRD mouse models, in comparison to sex- and age-matched wild-type mice. Specifically, we used the Pde6&#x3b2;Rd10 (rd10) and RhoP23H/WT (P23H) mouse models of autosomal recessive and autosomal dominant RP, respectively, as well as the Rpe65-/- mouse model of Leber's congenital amaurosis type 2 (LCA2). The mice were housed at two distinct institutions and analyzed using LC-MS in three separate facilities/instruments following data-dependent and data-independent acquisition modes. This cross-institutional and multi-methodological approach signifies the reliability and reproducibility of the results. The large-scale profiling of the retinal proteome, coupled with in&#xa0;vivo electroretinography recordings, provided us with a reliable basis for comparing the disease phenotypes and severity. Despite evident inflammation, cellular stress, and downscaled phototransduction observed consistently across all three models, the underlying pathologies of RP and LCA2 displayed many differences, sharing only four general KEGG pathways. The opposite is true for the two RP models in which we identify remarkable convergence in proteomic phenotype even though the mechanism of primary rod death in rd10 and P23H mice is different. Our data highlights the cAMP and cGMP second-messenger signaling pathways as potential targets for therapeutic intervention. The proteomic data is curated and made publicly available, facilitating the discovery of universal therapeutic targets for RP.

Animals

Production of toxic shock syndrome toxin 1 in a mouse model of Staphylococcus aureus abscess formation.

A mouse model of abscess formation is described in which toxic shock syndrome toxin 1 (TSST-1) is produced by Staphylococcus aureus in vivo. Mice injected intravenously with S. aureus developed renal abscesses within 4-7 days. Kidneys excised from infected mice were cultured quantitatively, and extracts from the kidneys were assayed for TSST-1 with use of a competitive enzyme-linked immunosorbent assay. Animals with less than 10(7) S. aureus/g of kidney had less than 6 ng of TSST-1/mL of extract. Toxin levels ranged from less than 6 ng/mL to 271 ng/mL in kidney extracts from mice with greater than 10(7) S. aureus/g of kidney. Urine from infected mice also contained measurable levels of TSST-1 (range, less than 6-728 ng/mL). Mice developed serum antibodies to TSST-1 by 2 weeks after challenge. Serum samples collected 5-7 days after bacterial challenge did not show biochemical changes typical of a toxic shock-like illness in these animals.

Abscess

Natural history of chronic Staphylococcus epidermidis foreign body infection in a mouse model.

The development and characterization of a mouse model of chronic Staphylococcus epidermidis foreign body infection was done with two clinical isolates that differed in degree of extracellular slime production. Segments of Silastic catheters bearing preformed S. epidermidis biofilms were implanted intraperitoneally, and mice were assessed after 3 and 6 months. Both test strains of S. epidermidis persisted at the implant site through the 6-month follow-up in 80% of the mice, regardless of the degree of slime production. There was no evidence of overt animal morbidity, and microbiologic assessment of other peritoneal sites did not reveal dissemination of bacteria from the infected focus. In comparison with control mice, animals harboring chronic foreign body infection presented marked peripheral neutrophilia and mild anemia.

Animals

Effects of antiinflammatory agents on chronic Salmonella typhimurium infection in a mouse model.

Anti-inflammatory corticosteroids have been demonstrated to lower the resistance of the host to a range of infections in several different animal models. We have adapted the mouse model for Salmonella typhimurium infection, using a subcutaneous inoculation of 10(4) organisms in CBA/Ca mice. The chronic infection was potentiated by treatment with hydrocortisone given orally in the diet for up to 4 weeks, beginning on day 30 after infection. A dose of 25 mg/kg of body weight resulted in 100% mortality from Salmonella infection within 24 days of beginning hydrocortisone treatment. Nonsteroid drugs, indomethacin and a trial agent BW 755C, were compared with the corticosteroid in this model. No mortality was recorded during the 4 weeks of drug treatment in these groups. Fecal samples were monitored weekly, and drug-related effects on the normal fecal flora were observed. The kinetics of S. typhimurium infection were followed in both fecal and organ samples for the duration of the experiments. The model is useful for the determination of the lowered resistance of the host to infection after drug treatment and specifically demonstrated here the potential of the trial drug BW 755C as an active anti-inflammatory agent without one of the undesirable side effects of corticosteroids.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz

Interactions between Trichomonas vaginalis and vaginal flora in a mouse model.

To study the role of vaginal flora and pH in the pathogenesis of Trichomonas vaginalis, an intravaginal mouse model of infection was established. By employing this model, the vaginal flora and pH of mice could be monitored for changes caused by the parasite. As a baseline, the endemic vaginal flora of BALB/c mice was examined first and found to consist mainly of Staphylococcus aureus and Enterococcus species (32-76%). Lactobacilli and enteric bacilli were moderate (16-32%) in their frequency of isolation, and the prevalence of both anaerobic species and coagulase-negative staphylococci was low (4-16%). Vaginal pH was recorded at 6.5 +/- 0.3. Estrogenization, which was required for a sustained T. vaginalis infection, did not significantly alter vaginal flora; however, a slight rise in the number of bacterial species isolated per mouse and a drop in vaginal pH (6.2 +/- 0.5) were observed. Trichomonas vaginalis-infected mice did not appear to show significant changes in vaginal flora although vaginal pH was slightly increased. This mouse model could have applications in both immunologic and pathogenic studies of T. vaginalis and, with further modifications, aid in the study of protist-bacterial interactions.

Animals

Mouse model for Pneumocystis carinii pneumonia that uses natural transmission to initiate infection.

Animal models for Pneumocystis carinii, for the most part, have been limited to immunosuppressed rats and ferrets, while a dependable mouse model has been more difficult to develop. A P. carinii mouse model has now been established with several strains of mice, including C3Heb/FeJ, C3HeN, BALB/c, DBA/2N, and BALB/c nu/nu (athymic). In lieu of using invasive methods for initiating P. carinii infections, mice harboring P. carinii transmitted the disease to mice without latent infection via short-term cohabitation. After the exposure period, the seed mice were sacrificed to confirm the presence of acute P. carinii pneumonia. Acute infections in recipient mice developed at approximately 7 to 8 weeks, while control unseeded littermates remained uninfected. All recipient mice and their littermates were maintained in isolation hoods to eliminate the possibility of exposure to other sources of P. carinii. This approach allows investigators to consistently transmit P. carinii to mice and to select the strain of mouse desired for use in a particular study. The results presented here suggest that more attention should be given to the potential for patient-to-patient transmission of P. carinii in immunocompromised patients such as those with AIDS.

Animals

Development of a mouse model to estimate the potency of the diphtheria toxoid component of diphtheria-tetanus and diphtheria-tetanus-pertussis vaccines.

A mouse model to estimate the potency of the diphtheria toxoid component in diphtheria-tetanus vaccines and diphtheria-tetanus-pertussis vaccines has been developed as an alternative to the conventional method of testing in guinea-pigs. Optimal conditions with regard to dose, route and period of immunization have been standardized. The maximum levels of antitoxin were detected five weeks after vaccination and the s.c. route was found to be optimal. Potency data have been compared with other studies in mouse models and with those obtained by the conventional method in guinea-pigs.

Animals

A mouse model for the study of necrotizing enterocolitis.

A mouse model for the study of necrotizing enterocolitis is presented. It is a model of temporary intestinal ischemia and consists of occluding both superior mesenteric vessels with a bulldog clamp for varying periods of time. The resultant lesions resemble the intestinal lesions seen in necrotizing enterocolitis in respect to the gradual development of the necrotizing lesions and their patchy distribution. We also studied the effect of intravenous saline and low molecular weight dextran in preventing the development of these ischemic lesions. In moderate ischemia, saline and dextran show a similar protective effect, and in severe ischemia, both show a protective effect, with dextran being more effective than saline.

Animals

A mouse model of coxsackievirus myocarditis.

OBJECTIVE: To develop a mouse model of coxsackievirus B3 (CVB3) myocarditis. DESIGN: Preliminary studies have indicated that mice infected with CVB3 alone erratically responded with viral myocarditis. Prospective evaluation of the effect of cyclophosphamide at two time intervals resulted in consistency for the development of myocarditis. ANIMALS: Juvenile five- to nine-week-old male mice CD-1 type (Charles River Canada Limited). INTERVENTIONS: Infection with coxsackie B3 enterovirus. Pretreatment with cyclophosphamide two days and 4 h before inoculation of 0.2 or 0.15 mg/g. Animals were killed seven, nine, 28 and 63 days post infection. MAIN RESULTS: Following cyclophosphamide conditioning, a tissue response infection with CVB3 was uniformly observed. Virus, however, was infrequently recovered from the myocardium whereas myocarditis became chronic after 28 days. CONCLUSIONS: Pretreatment of juvenile mice with cyclophosphamide results in a reproducible model of viral myocarditis with chronic changes in the myocardium.

Animals

Evaluation of the neurotoxicity of dapsone in the mouse model.

Effect of DDS was studied using the mouse model. It was observed that DDS did not have any neurotoxic effect. On the contrary it showed a protective action towards the nerve, when administered in the early stages following definite establishment of nerve lesions.

Animals

Histopathologic-microbiologic correlates of invasiveness in a mouse model of ascending unobstructed urinary tract infection.

To clarify the usefulness of histopathology in evaluating invasiveness during acute cystitis and pyelonephritis in a mouse model of urinary tract infection, findings from bladder and kidney sections of mice inoculated transurethrally with Escherichia coli were compared with results of bladder, kidney, spleen, and blood cultures and with changes in peripheral blood leukocyte counts. All of the 14 bladder histopathologic abnormalities evaluated were significantly associated with a positive bladder culture, and 7 were associated with splenic infection. Histopathologic features of cystitis were present in some culture-negative bladders. Eleven of 12 renal histopathologic abnormalities evaluated were significantly associated both with a positive kidney culture and with splenic infection, and two correlated with the development of peripheral leukocytosis. Histopathologic features of pyelitis and nephritis permitted culture-positive kidneys to be categorized as exhibiting colonization only, pyelitis only, or pyelitis plus frank nephritis and demonstrated that some culture-negative kidneys exhibit signs of pyelitis and nephritis. These findings suggest that detailed, semiquantitative histopathologic evaluation can add to quantitative cultures in the assessment of bacterial urovirulence in the mouse model of ascending urinary tract infection.

Animals

Transgenic mouse model: a new approach for the investigation of endocrine pancreatic B-cell growth.

The transformation and adaptation of pancreatic insulin-producing (B) cells has been studied in a transgenic mouse model using a panel of antisera recognising peptides and general neuroendocrine markers at both light and electron microscopical levels. Stages of tumour genesis in the transgenic mouse model from hyperplasia to neoplasia, have been compared with human B-cell tumours. A normal complement of peptide containing cells was seen in the transgenic mouse pancreas, but cells containing pro-insulin-derived peptides became more numerous as hyperplasia commenced. The transgenic mouse tumours were composed of B cells, although 30-35% of the tumours were also found to contain PP cells--a finding which is directly comparable with that in human insulin-producing tumours. NSE, 7B2 and chromogranin immunoreactivities were found in most cells from all the tumours examined. Antisera to PGP 9.5, a novel marker for elements of the neuroendocrine system, were found to stain hyperplastic and neoplastic B-cells intensely. In contrast, normal mouse B-cells did not show PGP 9.5 immunoreactivity thus it appears that PGP 9.5 is differentially expressed in transformed and/or growing mouse B-cells and hence may be used as an indicator in studies of early tumour growth.

Adenoma, Islet Cell

Effect of thyroid hormone and sex status on epidermal growth factor concentrations in the submandibular gland of a congenitally hypothyroid mouse model.

Studies were performed to explore the role of thyroid hormone and sex status on epidermal growth factor concentrations in the submandibular gland of a congenitally hypothyroid mouse model designated hyt/hyt. The animals were studied at 20, 30 and 40 days of postnatal age. The euthyroid animals were homozygous or heterozygous for the hypothyroid gene. The homozygous euthyroid animals displayed a pattern of submandibular gland epidermal growth factor concentrations similar to those previously described in other mouse species and showed the expected sex differences. The hypothyroid animals had measurable but very low submandibular gland epidermal growth factor concentrations without sexual dimorphism. Serum thyroxine concentrations in the heterozygotes were comparable to those in the homozygous euthyroid animals, yet the animals had a delayed increase in epidermal growth factor concentrations combined with a later expression of female-male differences. The timing of the sex differences in submandibular gland epidermal growth factor concentrations followed a pattern similar to that seen for the timing of the first litter in these three genetically distinct groups. This infers the timing of the onset of puberty and suggests a role of androgens in the changes seen in epidermal growth factor concentrations. We conclude that thyroid hormone and sex status in this mouse model influence the pattern and concentrations of submandibular gland epidermal growth factor concentrations.

Animals

Revisiting endothelial tropism of SARS-CoV-2 using a cell-specific hACE2 mouse model.

UNLABELLED: Severe COVID-19 is frequently associated with vascular complications, raising ongoing debate about whether SARS-CoV-2 can directly infect endothelial cells and thereby contribute to disease pathogenesis. Although endothelial cells express angiotensin-converting enzyme 2 (ACE2), the in vivo relevance of endothelial-restricted viral tropism remains unclear. To directly assess the consequences of endothelial-restricted SARS-CoV-2 tropism in vivo, we generated a transgenic mouse model expressing human ACE2 under control of the endothelial-specific Cdh5 promoter (Cdh5-hACE2). Despite confirmed pulmonary endothelial expression and protein presence of hACE2, SARS-CoV-2 infection of Cdh5-hACE2 mice did not induce clinical illness, detectable viral replication, immune cell influx in the lung, or histopathological abnormalities in the lung or brain. These findings indicate that endothelial-restricted SARS-CoV-2 tropism alone is insufficient to drive productive infection and clinical disease in vivo, suggesting that endothelial involvement in COVID-19 likely arises in the context of broader cellular infection or systemic host responses rather than from primary endothelial infection. IMPORTANCE: Although SARS-CoV-2 primarily infects the upper and lower airways, COVID-19 was quickly recognized as a multi-organ disease, in which vascular complications are a recurring feature. This has raised the possibility that direct infection of endothelial cells contributes to disease pathogenesis. However, whether vascular injury arises from productive endothelial infection or instead represents a secondary consequence of systemic inflammation remains unresolved. To directly disentangle these possibilities and define the in vivo consequences of endothelial-restricted viral tropism, we generated a transgenic mouse model expressing human ACE2 under the control of the endothelial-specific Cdh5 promoter (Cdh5-hACE2).

Animals

Experimental nude mouse model of human colorectal cancer liver metastases.

A nude mouse model (BALB/c) was established for investigating the production of hepatic metastases by human colorectal carcinoma (HCC) cells. The malignant potentials of 3 different HCCs derived from a primary tumor (HCC-P4733), a lymph node metastasis (HCC-M14328), and a hepatic metastasis (HCC-M1410) were investigated following implantation into the spleens of athymic nude mice. Cells of the HCC-M1410 line produced extensive liver tumors in all mice by 30 days after injection. Cells of the HCC-M14328 and HCC-P4733 lines produced few liver tumors in the inoculated mice and then only after a 90-day period. Isozyme and karyotype analyses ascertained the human origin of all the tumors. Studies with [125I]IdUrd-labeled HT-29 carcinoma cells suggested that tumor cells reached the liver shortly after injection into the spleen. Thus the production of HCC tumors in livers of nude mice was determined by the ability of HCC cells to proliferate in the liver parenchyma rather than by the ability of the cells to reach the liver. The results suggest that the intrasplenic injection of HCC cells can provide a valuable model for the study of the biology and therapy of the liver metastases.

Animals

S-adenosylmethionine protects against acetaminophen hepatotoxicity in two mouse models.

Because S-adenosylmethionine promotes synthesis of hepatic glutathione in chronic liver disease and is well tolerated in man, we investigated its use as an antidote to acetaminophen hepatotoxicity in two mouse models. In C57Bl6 mice, deaths were abolished by S-adenosylmethionine given within 1 hr of 3.3 mmol/kg body wt acetaminophen (0 of 32 vs. 13 of 49, p less than 0.005) and reduced if given 2 to 5 hours after acetaminophen administration (4 of 42 vs. 13 of 49, p less than 0.01). Mixed disulfate/tosylate salt of S-adenosylmethionine abolished mortality in C3H mice given 2 mmol/kg body wt acetaminophen (0 of 24 vs. 4 of 18; p less than 0.05). In both mouse models, S-adenosylmethionine reduced depletion of plasma (median = 20.8 mumol/L vs. 14.6 mumol/L) and liver glutathione (198% vs. 100%; p less than 0.05), liver damage and release of AST after acetaminophen administration. Pretreatment with buthionine sulfoximine, which inhibits glutathione synthesis, abolished the beneficial effect of S-adenosylmethionine on survival and plasma glutathione level. S-adenosylmethionine reduces acetaminophen hepatotoxicity by metabolism of the active moiety to glutathione. This benefit may last as long as 5 hr after acetaminophen ingestion.

Acetaminophen