Outbred Laboratory Mice Research Articles

Retinal neuroanatomy of two emerging model organisms, the spiny mouse (Acomys dimidiatus) and the Mongolian gerbil (Meriones unguiculatus)

Current research using animal models to investigate retinal cell biology and model retinal degenerative diseases largely utilize small mammals that are nocturnal and lack the ability to restore lost vision. In contrast, the Mongolian gerbil (Meriones) is a diurnal rodent with good photopic vision, and the spiny mouse (Acomys) is a small desert-dwelling rodent with remarkable regenerative capabilities. The goal of this study was to identify antibodies that detect retinal cell classes in Meriones and Acomys, and to describe the retinal anatomy of these two species in comparison to outbred laboratory mice (Mus musculus). Immunohistochemistry was performed on retinal sections with antibodies for various retinal cell types. Sections were imaged by light, fluorescence, and confocal microscopy. Cell density, morphology, and placement were compared between species qualitatively and quantitatively. Our analyses revealed a classic assembly of retinal cells in Meriones and Acomys, with a few deviations compared to Mus. Meriones displayed the highest density of cones and Acomys the lowest. A higher density of bipolar cell bodies in the proximal portion of the inner nuclear layer was observed in both Acomys and Meriones compared to Mus, and both species exhibited an increase in amacrine cell density compared to Mus. Our results provide a foundation for future research into the visual system adaptations of these interesting species.

Functional semi-finished fish product evaluation: organoleptic and evidence in vivo

Introduction The development of functional products is a new promising trend in the modern food industry. The research aims to confirm the quality indicators, efficacy and safety for living organisms of the developed functional semi-finished fish product—raw smoked sausage. The research was aimed at studying the characteristics of the semi-finished product obtained, including its organoleptic properties. However, it was also important to test the properties of the probiotic component added to the developed product and its effects in vivo on mice to verify the efficacy and safety of the E. coli 64 G strain. Methods Organoleptic and histological assessments of the product were performed. A series of experiments were also conducted to assess the product’s safety and functional properties. For this purpose, Enteracol was fed to white outbred laboratory mice with different concentrations of the active ingredient ( Escherichia coli 64G strain). Organoleptic properties of the proposed product, such as smell, consumer view, and balanced taste, demonstrated high consumer qualities of the crude smoked sausage with a probiotic component. Results The results of the controlled prospective study confirmed that the product is safe and non-toxic to living organisms: mice state alive after consuming a created meal. At the same time, assessing the product’s antagonistic activity revealed its high protective effect (85%–100% survival rate of animals in the experimental groups compared to the control with 100% mortality). Discussion The proposed product has a stimulating effect on an organism and demonstrates the antagonistic activity against pathogenic and opportunistic bacteria established in the Enterobacteriaceae family members. The next step will be a long-term study of the product’s stimulating effect to prove its positive impact on the body.

Research of dynamics of monovalent ions in urine at various stages of urolithiasis development in in vivo experiment

Introduction. Experimental model of intraperitoneal injection of sodium oxalate is one of the most promising and practical models of oxalate urolithiasis in rodents.Purpose of the study. To describe the urolithiasis progression in experimental animals with regard to the changes in the ion balance at various stages of pathology formation.Materials and methods. We treated male ICR (CD‑1) outbred laboratory mice with a single injection of sodium oxalate (NaOx) to perform nephrolithiasis modeling. The ionic composition of urine and blood serum in the control and experimental groups was examined by capillary electrophoresis. The presence of oxalate crystals in the urine sediment and histological data can assess the severity of the pathology.Results and conclusions. Increase of the level of Na and Ca ions and decrease of the level of K, NH4, Mg ions was observed in 4 hours and 24 hours after intraperitoneal injection of sodium oxalate, that can be regarded as a depression of tubular reabsorption and secretion.

Protein coding variation in the J:ARC and J:DO outbred laboratory mouse stocks provides a molecular basis for distinct research applications.

Outbred laboratory mice (Mus musculus) are readily available and have high fecundity, making them a popular choice in biomedical research, especially toxicological and pharmacological applications. Direct high throughput genome sequencing (HTS) of these widely used research animals is an important genetic quality control measure that enhances research reproducibility. HTS data have been used to confirm the common origin of outbred stocks and to molecularly define distinct outbred populations. But these data have also revealed unexpected population structure and homozygosity in some populations; genetic features that emerge when outbred stocks are not properly maintained. We used exome sequencing to discover and interrogate protein-coding variation in a newly established population of Swiss-derived outbred stock (J:ARC) that is closely related to other, commonly used CD-1 outbred populations. We used these data to describe the genetic architecture of the J:ARC population including heterozygosity, minor allele frequency, LD decay, and we defined novel, protein-coding sequence variation. These data reveal the expected genetic architecture for a properly maintained outbred stock and provide a basis for the on-going genetic quality control. We also compared these data to protein-coding variation found in a multiparent outbred stock, the Diversity Outbred (J:DO). We found that the more recently derived, multiparent outbred stock has significantly higher interindividual variability, greater overall genetic variation, higher heterozygosity, and fewer novel variants than the Swiss-derived J:ARC stock. However, among the novel variants found in the J:DO stock, significantly more are predicted to be protein-damaging. The fact that individuals from this population can tolerate a higher load of potentially damaging variants highlights the buffering effects of allelic diversity and the differing selective pressures in these stocks. While both outbred stocks offer significant individual heterozygosity, our data provide a molecular basis for their intended applications, where the J:DO are best suited for studies requiring maximum, population-level genetic diversity and power for mapping, while the J:ARC are best suited as a general-purpose outbred stock with robust fecundity, relatively low allelic diversity, and less potential for extreme phenotypic variability.

Morphology of the testes of animals during estrogen injection in the prenatal period

The aim of the study was to investigate the morphological changes in the testes of the offspring of white non-pedigreed laboratory mice when the synthetic oestrogen analogue synestrol was prenatally injected to the mother. After fertilization, the females were divided into 2 groups which received a single intramuscular injection of the synthetic oestrogen analogue synestrol on day E 11.5 of gestation at the same time of the day. The intact group was not exposed to any treatment. The experimental group was exposed to synestrol, a synthetic oestrogen analogue, as a 2% oil solution at a dose of 40 µg/kg (C-40). The results of morphometric analysis of testes of descendants of white outbred laboratory mice after prenatal single injection of synthetic oestrogen analogue synestrol in a dose of 40 µg/kg showed morphological changes in the organ parenchyma, manifested as decrease in mean number of Sertoli cells (C-40) 17.4±1.1 compared to intact group 20.8±1.9; decrease in mean number of spermatogonia (C-40) 24.4±1.1 compared to intact group, decrease in mean number of spermatozoa (C-40) 178.0±4.2 compared to intact group 196.6±5.3. There was observed a change in the endocrine apparatus of testes, expressed as a decrease in the mean area of Leydig cell nuclei in the intact group of 6,72±1,78. Prenatal effects of synestrol revealed in an experimental model, allow us to use it to search for means of postnatal developmental testicular dysfunction correction as well as to develop optimal doses of oestrogenic preparations during pregnancy.

Unifying Virulence Evaluation in Toxoplasma gondii: A Timely Task.

Toxoplasma gondii, a major zoonotic pathogen, possess a significant genetic and phenotypic diversity that have been proposed to be responsible for the variation in clinical outcomes, mainly related to reproductive failure and ocular and neurological signs. Different T. gondii haplogroups showed strong phenotypic differences in laboratory mouse infections, which provide a suitable model for mimicking acute and chronic infections. In addition, it has been observed that degrees of virulence might be related to the physiological status of the host and its genetic background. Currently, mortality rate (lethality) in outbred laboratory mice is the most significant phenotypic marker, which has been well defined for the three archetypal clonal types (I, II and III) of T. gondii; nevertheless, such a trait seems to be insufficient to discriminate between different degrees of virulence of field isolates. Many other non-lethal parameters, observed both in in vivo and in vitro experimental models, have been suggested as highly informative, yielding promising discriminatory power. Although intra-genotype variations have been observed in phenotypic characteristics, there is no clear picture of the phenotypes circulating worldwide; therefore, a global overview of T. gondii strain mortality in mice is presented here. Molecular characterization has been normalized to some extent, but this is not the case for the phenotypic characterization and definition of virulence. The present paper proposes a baseline (minimum required information) for the phenotypic characterization of T. gondii virulence and intends to highlight the needs for consistent methods when a panel of T. gondii isolates is evaluated for virulence.

The New Dipeptide TSPO Ligands: Design, Synthesis and Structure-Anxiolytic Activity Relationship.

The translocator protein (TSPO, 18 kDa) plays an important role in the synthesis of neurosteroids by promoting the transport of cholesterol from the outer to the inner mitochondrial membrane, which is the rate-limiting step in neurosteroidogenesis. Stimulation of TSPO by appropriate ligands increases the level of neurosteroids. The present study describes the design, synthesis and investigation of anxiolytic-like effects of a series of N-acyl-tryptophanyl-containing dipeptides. These novel dipeptide TSPO ligands were designed with the original drug-based peptide design strategy using alpidem as non-peptide prototype. The anxiolytic activities were investigated in Balb/C mice using the illuminated open-field and elevated plus-maze tests in outbred laboratory mice ICR (CD-1). Dipeptide GD-102 (N-phenylpropionyl-l-tryptophanyl-l-leucine amide) in the dose range of 0.01–0.5 mg/kg intraperitoneally (i.p.) has a pronounced anxiolytic activity. The anxiolytic effect of GD-102 was abolished by PK11195, a specific TSPO antagonist. The structure–activity relationship study made it possible to identify a pharmacophore fragment for the dipeptide TSPO ligand. It was shown that l,d-diastereomer of GD-102 has no activity, and the d,l-isomer has less pronounced activity. The anxiolytic activity also disappears by replacing the C-amide group with the methyl ester, a free carboxyl group or methylamide. Consecutive replacement of each amino acid residue with glycine showed the importance of each of the amino acid residues in the structure of the ligand. The most active and technologically available compound GD-102, was selected for evaluation as a potential anxiolytic drug.

Rapid genotype imputation from sequence without reference panels.

Inexpensive genotyping methods are essential for genetic studies requiring large sample sizes. In human studies, array-based microarrays and high-density haplotype reference panels allow efficient genotype imputation for this purpose. However, these resources are typically unavailable in non-human settings. Here we describe a method (STITCH) for imputation based only on sequencing read data, without requiring additional reference panels or array data. We demonstrate its applicability even in settings of extremely low sequencing coverage, by accurately imputing 5.7 million SNPs at a mean r2 of 0.98 in 2,073 outbred laboratory mice (0.15X sequencing coverage). In a sample of 11,670 Han Chinese (1.7X), we achieve accuracy similar to alternative approaches that require a reference panel, demonstrating that this approach can work for genetically diverse populations. Our method enables straightforward progression from low-coverage sequence to imputed genotypes, overcoming barriers that at present restrict the application of genome-wide association study technology outside humans.

Regional variations in the distributions of small intestinal intraepithelial lymphocytes (IELs) in outbred laboratory mice ( Mus musculus domesticus) and the inbred strain of mice established from Japanese fancy mice ( Mus musculus molossinus)

Previously, we reported regional variations in small intestinal IELs of mice. In this study, we examined the regional variations of IELs in outbred laboratory mice (ddY: Mus musculus domesticus) and the inbred strain of mice established from Japanese fancy mice (JF1: Mus musculus molossinus). IELs were isolated from the proximal, middle and distal parts of the small intestine and analyzed by flow cytometry. The percentages of γδ T cells and αβ T cell subset of extrathymic origin were higher in the proximal part while the percentages of αβ T cell subset(s) of thymic origin were higher in the distal part in both ddY and JF1 mice. Such trends in regional variations of IELs were almost the same as those found in the inbred strains of laboratory mice in our previous reports. This strongly suggests that these regional variations of IELs may be common phenomena in Mus musculus species.

Biological and genetic characterisation of Toxoplasma gondii isolates from chickens ( Gallus domesticus) from São Paulo, Brazil: unexpected findings

In spite of a wide host range and a world wide distribution, Toxoplasma gondii has a low genetic diversity. Most isolates of T. gondii can be grouped into two to three lineages. Type I strains are considered highly virulent in outbred laboratory mice, and have been isolated predominantly from clinical cases of human toxoplasmosis whereas types II and III strains are considered avirulent for mice. In the present study, 17 of 25 of the T. gondii isolates obtained from asymptomatic chickens from rural areas surrounding São Paulo, Brazil were type I. Antibodies to T. gondii were measured in 82 chicken sera by the modified agglutination test using whole formalin-preserved tachyzoites and mercaptoethanol and titres of 1:10 or more were found in 32 chickens. Twenty-two isolates of T. gondii were obtained by bioassay in mice inoculated with brains and hearts of 29 seropositive (≥1:40) chickens and three isolates were obtained from the faeces of cats fed tissues from 52 chickens with no or low levels (<1:40) of antibodies. In total, 25 isolates of T. gondii were obtained by bioassay of 82 chicken tissues into mice and cats. All type I isolates killed all infected mice within 4 weeks whereas type III isolates were less virulent to mice. There were no type II strains. Tissue cysts were found in mice infected with all 25 isolates and all nine type I isolates produced oocysts. Infected chickens were from localities that were 18–200 km apart, indicating no common source for T. gondii isolates. This is the first report of isolation of predominantly type I strains of T. gondii from a food animal. Epidemiological implications of these findings are discussed.

An experimental and theoretical study of the dynamics of a mouse – nematode (Heligmosomoides polygyrus) interaction

The population dynamics of outbred laboratory mice in indoor enclosures in the absence and presence of a naturally transmitted direct life-cycle nematode Heligmosomoides polygyrus Dujardin 1845 were reported previously. This manuscript presents further information on the age and sex structure of the populations, results of experiments designed to estimate the density-dependent effect of the parasite on host survival and reproduction, and a mathematical model of both uninfected and infected mouse populations. In the uninfected mouse population, survival of female mice was age- and density-independent, survival of male mice was age-dependent and density-independent, and recruitment was density-dependent. Independent experiments revealed that the parasite had no density-dependent effect on mouse reproduction, but had density-dependent effects on both acute and chronic survival of mice. An age-structured Leslie matrix model captured the exponential growth and plateau of the uninfected mouse population. Modification of the model to incorporate the effects of the parasite provided a good fit to the data from the infected populations, supporting the hypothesis that density-dependent effects of the parasite on host survival could lead to regulation of host abundance.

The growth of infant mice at two temperatures.

Summary. Mice, Mus musculus, were bred in permanently mated pairs, in two environments, at 21° C and −3° C, respectively. Observations on strain A2G/Tb are described in detail; others studied were strain C57BL/Tb, outbred laboratory mice, and wild mice bred in the laboratory. Second to fourth litters were observed at birth, 10 days and 21 days. Most deaths were due to losses of whole litters. Mortality was higher at −3° C than at 21° C, but not among A2G/Tb mice of a stock bred for many generations in the cold. Litter weights at birth, for a given litter size, were unaffected by cold, but there were fewer large litters at −3° C than at 21° C; hence mean litter weight at birth was lower in the cold. At 10 and 21 days, litter weights, except those of strain C57BL/Tb, were lower in the cold at most litter sizes. Individual weight at 3 weeks was unaffected by number of litter mates at litter sizes around the mode, and declined only at high litter sizes; hence the sizes of most litters were within the range which allowed most growth. The findings illustrate the importance of the uterine environment in determining litter size and survival in the nest.

Total reproductive performance of captive house mice at two temperatures

Wild house mice, Mus musculus L., were trapped on a farm, and bred in the laboratory at two environmental temperatures, 21°C and −3°C. The reproductive performance of 12 pairs of the second generation reared in the laboratory was recorded to the age of two years; ten pairs of the first generation were transferred to −3°C at mating, and were similarly observed for two years. The wild mice at 21°C resembled inbred laboratory mice in litter size and the weight of young at three weeks, but produced many more litters: nestling mortality was about 16%. The fertility of the wild mice was, however, inferior to that of some outbred laboratory mice. At −3°C the number of litters per pair was about half that at 21°C, and nestling mortality was over 50 % losses were mainly of whole litters. Litters at birth tended to be larger at −3°C; the young aged three weeks were heavier in the cold environment. At birth, fifth litters were largest at 21°C, and fourth litters at −3°C. Weights of individual young aged three weeks tended to rise with parity in both temperatures. Some mice, in both temperatures, continued to produce litters for the full two years.