The effect of transportation stress on splenic natural killer cell activity in C57BL/6J mice

Splenic natural killer cell activity and plasma corticosterone levels were measured in air- and truck-transported C57BL/6J mice (Mus musculus) on days 0, 1, 3 and 5 post-arrival. These data are important in determining adequate stabilization periods for transported animals before studies involving natural killer cells are begun. Three control groups (phosphate buffered saline, polyinosinic-polycytidylic acid, and hydrocortisone injected mice) were stabilized in the animal facilities 3 weeks before the start of experiments. Natural killer activity in transported mice was reduced significantly (p less than 0.05) on day 0 and returned to normal levels by 24 hours. Plasma corticosterone levels were increased significantly (p less than 0.005) on day 0 and returned to control levels by day 1, correlating inversely with splenic natural killer activity. This study indicates that stress resulting from transportation causes a short-term decrease in the splenic natural killer cell activity of mice, and this decrease may be related to the increased plasma corticosterone levels induced by the stressful event. We conclude that mice should be stabilized at least 24 hours before experiments involving the natural killer cell system are begun.     

Mechanisms of depression of splenic natural killer cell function in C57BL/6 mice infected with Leishmania donovani

C57BL/6 mice chronically infected with the protozoan parasite Leishmania donovani exhibit profoundly depressed splenic natural killer (NK) cell activity as measured by in vitro cytolysis of lymphoma target cells. Injection of infected mice with an interferon (IFN) inducer or in vitro treatment of infected splenocytes with IFN, a phorbol ester, or indomethacin failed to restore their NK activity to the degree shown by age-matched, uninfected mice. Fractionation of infected splenocytes by nylon wool, Sephadex G-10, or carbonyl iron and magnetism treatments was also unable to effect an increase in NK activity. Addition of infected splenocytes to uninfected ones in in vitro NK assays suppressed the NK activity of the latter, and the suppression could be partially or wholly abrogated by prior fractionation of infected splenocytes by the methods noted above. In vitro treatment of infected splenocytes with concanavalin A revealed the presence of NK activity in these cell populations. The results indicate that splenocytes in L. donovani-infected mice become insensitive to IFN stimulation; and the impairment of another, possibly IFN-independent pathway of NK-cell activation may also contribute to the observed L. donovani-induced depression in splenic NK activity in C57BL/6 mice.     

Embryonic stem cells derived from C57BL/6J and C57BL/6N mice

Mouse embryonic stem (ES) cells with the C57BL/6 genetic background allow the generation of knockout mice without the need to backcross to C57BL/6. However, C57BL/6 ES cells whose pluripotency after homologous recombination has been confirmed are not yet available from public cell banks. To facilitate the use of ES cells derived from C57BL/6 sublines in both biologic and medical research, we demonstrated that the use of knockout serum replacement as a medium supplement and 8-cell blastomeres as recipient embryos allowed establishment of ES cells and production of germline chimeric mice, respectively. Under effective conditions, a large number of ES cell lines were established from C57BL/6J and C57BL/6N blastocysts. The majority of ES cells in many cell lines obtained from both strains showed a normal chromosome number. Germline chimeric mice were generated from C57BL/6J and C57BL/6N ES cells. Finally, the ES cell line B6J-S1UTR, derived from C57BL/6J, was used for successful production of gene knockout mice. C57BL/6J ES (B6J-S1UTR and B6J-23UTR) and C57BL/6N ES (B6N-22UTR) cells are available from the cell bank of the BioResource Center at RIKEN Tsukuba Institute (http://www.brc.riken.jp/lab/cell/english/).     

Effect of chronic corticosterone application on depression‐like behavior in C57BL/6N and C57BL/6J mice

Many studies using genetic mouse models are performed with animals on either one of the two closely related genetic backgrounds, C57BL/6J or C57BL/6N. These strains differ only in a few genetic loci, but have some phenotypic differences that also affect behavior. In order to determine the effects of chronic stress hormone exposure, which is relevant for the pathogenesis of psychiatric disorders, we investigated here the behavioral manifestations of long‐term increase in corticosterone levels. Thus, male mice from both sub‐strains were subcutaneously implanted with corticosterone (20 mg) or placebo pellets that released the hormone for a period of 21 days and resulted in significantly elevated plasma corticosterone levels. Corticosterone significantly increased food intake in B6N, but not in B6J mice. At various time points after pellet implantation, we performed tests relevant to activity and emotional behaviors. B6J mice displayed a generally higher activity in the home cage and the open field. Corticosterone decreased the activity. In B6N mice, corticosterone also decreased sucrose preference, worsened the coat state and increased forced swim immobility, while it had no effect in the B6J strain. Altogether, these results indicate that B6N mice are more sensitive to some of the effects of chronic corticosterone treatment than B6J mice.     

Differences in anxiety-related behavior between apolipoprotein E-deficient C57BL/6 and wild type C57BL/6 mice

The influence of ApoE gene deletion on the anxiety state has not been previously investigated. The elevated plus maze was used in this study to determine differences in anxiety-related behavior between apoE-deficient and wild type C57BL/6 mice. The apoE-deficient mice demonstrated less anxiety on the elevated plus maze by spending more time in the open arms of the elevated plus maze compared to wild type mice (p<0.001). Additionally, female apoE-deficient mice visited the open arm of the maze more often than their apoE-deficient male counterpart (p<0.05). The anxiety state and/or sex are possible variables to be considered when designing physiological and/or behavioral studies involving mice that are apoE-deficient.     

A multi-mineral natural product inhibits liver tumor formation in C57BL/6 mice

C57BL/6 mice were maintained for up to 18 months on high-fat and low-fat diets with or without a multi-mineral supplement derived from the skeletal remains of the red marine algae Lithothamnion calcareum. Numerous grossly observable liver masses were visible in animals on the "western-style" high-fat diet sacrificed at 12 and 18 months. The majority of the masses were in male mice (20 out of 100 males versus 3 out of 100 females; p = 0.0002). There were more liver masses in animals on the high-fat diet than on the low-fat diet (15 out of 50 on high-fat versus 5 out of 50 on low-fat; p = 0.0254). The multi-mineral supplement reduced the number of liver masses in mice on both diets (3 out of 25 male mice in the low-fat diet group without the supplement versus 1 out of 25 mice with supplement; 12 of 25 male mice in the high-fat diet group without the supplement versus 3 of 25 mice with supplement [p = 0.0129]). Histological evaluation revealed a total of 17 neoplastic lesions (9 adenomas and 8 hepatocellular carcinomas), and 18 pre-neoplastic lesions. Out of eight hepatocellular carcinomas, seven were found in unsupplemented diet groups. Steatosis was widely observed in livers with and without grossly observable masses, but the multi-mineral supplement had no effect on the incidence of steatosis or its severity. Taken together, these findings suggest that a multi-mineral-rich natural product can protect mice against neoplastic and pre-neoplastic proliferative liver lesions that may develop in the face of steatosis.     

Substrains matter in phenotyping of C57BL/6 mice

The inbred mouse strain C57BL/6 has been widely used as a background strain for spontaneous and induced mutations. Developed in the 1930s, the C57BL/6 strain diverged into two major groups in the 1950s, namely, C57BL/6J and C57BL/6N, and more than 20 substrains have been established from them worldwide. We previously reported genetic differences among C57BL/6 substrains in 2009 and 2015. Since then, dozens of reports have been published on phenotypic differences in behavioral, neurological, cardiovascular, and metabolic traits. Substrains need to be chosen according to the purpose of the study because phenotypic differences might affect the experimental results. In this paper, we review recent reports of phenotypic and genetic differences among C57BL/6 substrains, focus our attention on the proper use of C57BL/6 and other inbred strains in the era of genome editing, and provide the life science research community wider knowledge about this subject.     

Delayed matching-to-position performance in C57BL/6N mice

Delayed matching-to-sample is one of the most frequently employed behavioral tasks for assessing spatial working memory in animals. Although the advantages of the task have been widely acknowledged and it is used in the study of a variety of species, its application to mice has been rare. In the present study, we reported the efficacy of a delayed matching-to-position task in C57BL mice lever-pressing in an operant-conditioning chamber. Each trial started with the press of a back lever, followed by the presentation of either a left or right front lever. When the ratio requirement for presses to the front lever (sample) was met, a delay interval started. Delay interval continued until the mice made the first response after the elapse of the programmed delay interval. This was followed by the presentation of a choice of left or right front levers. The choice of the same front lever as the sample was reinforced, whereas the other was not. The proportion of correct choices showed a delay-dependent decrement. A higher ratio of response requirement to the sample resulted in increased accuracy, but the duration of the intertrial interval had no effect. Preceding trials also influenced response accuracy, indicating proactive interference. Overall, the results replicated the effects of parametric manipulations reported in other species, and thus, our findings validate the efficacy of the task for assessing spatial working memory in laboratory mice.     

Mast cells and macrophages in normal C57/BL/6 mice

Mast cells and macrophages have an important role in immunity and inflammation. Because mice are used extensively for experimental studies investigating immunological and inflammatory responses, we examined mast cell and macrophage distribution in normal murine tissues. Mast cells were abundant in the murine dermis, tongue, and skeletal muscle but were rarely found in the heart, lung, spleen, kidney, liver, and the bowel mucosa. In contrast, dogs exhibited large numbers of mast cells in the lung parenchyma, liver, and bowel. Some murine dermal mast cells had long cytoplasmic projections filled with granular content. Mouse mast cells demonstrated intense histamine immunoreactivity and were identified with histochemical enzymatic techniques for tryptase and chymase. Macrophages, identified using the monoclonal antibody F4/80, were abundant in the spleen, lung, liver, kidney, and bowel but relatively rare in the heart, tongue, and dermis. Using a nuclease protection assay we investigated mRNA expression of stem cell factor (SCF), a crucial survival factor for mast cells, and the macrophage growth factors macrophage colony stimulating factor (M-CSF) and granulocyte macrophage colony stimulating factor (GM-CSF). Stem cell factor mRNA was highly expressed in the murine lung. Relatively low levels of SCF mRNA expression were found in the tongue and earlobe, which are tissues containing a high number of mast cells. Macrophage CSF and GM-CSF mRNA was highly expressed in the lung and spleen. The murine heart, an organ with a low macrophage content, expressed high levels of M-CSF but negligible levels of GM-CSF mRNA. Constitutive growth factor mRNA expression in murine tissues without significant populations of mast cells and macrophages may suggest an alternative role for these factors in tissue homeostasis.     

Genetic variation in C57BL/6 ES cell lines and genetic instability in the Bruce4 C57BL/6 ES cell line

Genetically modified mouse strains derived from embryonic stem (ES) cells are powerful tools for gene function analysis. ES cells from the C57BL/6 mouse strain are not widely used to generate mouse models despite the advantage of a defined genetic background. We assessed genetic variation in six such ES cell lines with 275 SSLP markers. Compared to C57BL/6, Bruce4 differed at 34 SSLP markers and had significant heterozygosity on three chromosomes. BL/6#3 and Dale1 ES cell lines differed at only 3 SSLP makers. The C2 and WB6d ES cell lines differed at 6 SSLP markers. It is important to compare the efficiency of producing mouse models with available C57BL/6 ES cells relative to standard 129 mouse strain ES cells. We assessed genetic stability (the tendency of cells to become aneuploid) in 110 gene-targeted ES cell clones from the most widely used C57BL/6 ES cell line, Bruce4, and 710 targeted 129 ES cell clones. Bruce4 clones were more likely to be aneuploid and unsuitable for ES cell-mouse chimera production. Despite their tendency to aneuploidy and consequent inefficiency, use of Bruce4 ES cells can be valuable for models requiring behavioral studies and other mouse models that benefit from a defined C57BL/6 background. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Adrenal function and the effect of a high-fat diet on C57BL/6J and C57BL/6J-ob/ob mice.

In C57BL/6J mice and the ob/+ and ob/ob mutants total plasma corticosterone levels were found to be statistically different. In C57BL/6J mice the level was 1.9 +/- 0.2 mug/100 ml plasma, in ob/+ mice 8.6 +/- 1.6 mug/100 ml and in ob/ob mice 13.7 +/- 1.5 mug/100 ml. The percentage of protein-bound corticosterone as well as the free endogenous corticosterone levels were also different. Feeding a high-fat diet to young C57BL/6J and C57BL/6J-ob/ob mice for a period of 4 weeks had no effect upon blood glucose, plasma insulin and plasma corticosterone levels. The significantly higher increase in body weight of the high-fat diet groups of both lines of mice was mainly due to fat cell hypertrophy.     

Effect of kaempferol on IgE-mediated anaphylaxis in C57BL/6 mice and LAD2 cells

BackgroundImmunoglobulin E (IgE)-mediated mast cell (MC) activation is crucial in multiple allergic diseases. Parkinson disease protein 7 (DJ-1) and Lyn kinase were reported as the receptor-proximal events in IgE receptor (FcεRI) signals in human MC. Kaempferol, a natural flavonol mainly derived from the rhizome of traditional Chinese herb Kaempferia galanga L. (Zingiberaceae), has been known to inhibit allergic reactions, but it was limited to the receptor-distal signals on rat basophilic leukemia cells. A thorough investigation of the inhibitory effects of kaempferol on human MC has not been done.PurposeTo investigate the inhibitory effects of kaempferol on IgE-mediated anaphylaxis in vivo and in human MCs, as well as the mechanism underlying its effects, especially the receptor-proximal signals.MethodsIgE-mediated passive cutaneous anaphylaxis and systemic anaphylaxis model were applied to elucidate the antiallergic activity of kaempferol in vivo. The degranulation assay, calcium imaging, the release of cytokines and chemokines on the laboratory of allergic disease 2 (LAD2) cells were used to evaluate the antiallergic effect of kaempferol in vitro. Western blot analysis was performed to investigate the DJ-1/Lyn signaling pathway and downstream molecules. Kinase activity assay, immunofluorescence, and molecular docking were conducted to confirm the influence of kaempferol on DJ-1/Lyn molecules.ResultsKaempferol dose-dependently attenuated ovalbumin/IgE-induced mice paw swelling, primary MC activation from paw skin, as well as rehabilitated the hypothermia, and reduced the serum concentrations of histamine, tumor necrosis factor-alpha, interleukin-8, and monocyte chemo-attractant protein-1. Additionally, kaempferol suppressed IgE-mediated LAD2 cell degranulation and calcium fluctuation. Remarkably, kaempferol was found to bind with DJ-1 protein, and initially prevented DJ-1 from translocating to the plasma membrane, thereby inhibited full activation of Lyn, and eventually restrained those receptor-distal signaling molecules, involved Syk, Btk, PLCγ, IP3R, PKC, MAPKs, Akt and NF-κB.ConclusionKaempferol could be used as a DJ-1 modulator for preventing MC-mediated allergic disorders through attenuating Lyn activation.     

Epstein-Barr virus nuclear antigen 1 does not cause lymphoma in C57BL/6J mice

To test whether transgenic Epstein-Barr virus nuclear antigen 1 (EBNA1) expression in C57BL/6 mouse lymphocytes causes lymphoma, EBNA1 expressed in three FVB lineages at two or three times the level of latent infection was crossed up to six successive times into C57BL/6J mice. After five or six crosses, 14/36, (38%) EBNA1 transgenic mice, 11/31 (36%) littermate EBNA1-negative controls, and 9/25 (36%) inbred C57BL/6J mice housed in the same facility had lymphoma. These data indicate that EBNA1 does not significantly increase lymphoma prevalence in C57BL/6J mice.     

Supernumerary ovarian grafts in aging C57BL/6J mice reveal complexities in the neuroendocrine impairments of acyclic mice

Determinants of the age-related acyclic state, persistent vaginal cornification (PVC), were studied in reproductively senescent mice using a 2-stage ovarian transplantation procedure, whereby ovaries from young mice were grafted to older mice without removing their autogenous ovaries until 8 wk later. In contrast to the usual ("1-stage") procedure, in which the autogenous ovaries are removed at the time of grafting, the 2-stage approach is postulated to circumvent potential effects of the reduction in steroids during the ovariprival phase prior to vascularization of the grafted ovary, which may reverse age-related hypothalamic-pituitary impairments. The 2-stage transplantation procedure was validated in young C57BL/6J mice. Estrous cycles were not disrupted by removal of the autogenous ovaries 8 wk after the grafting, indicating that grafted ovaries began functioning before or within days after ovariectomy. No difference in estrous cycle frequency or distribution was detected between the young mice with 2-stage and those with 1-stage transplants for at least 3 mo after removal of the autogenous ovaries. Most older (15- to 18-mo-old) mice with PVC (70%) remained acyclic after receiving young ovaries by either the 1-stage or the 2-stage procedure, indicating that extra-ovarian, presumably neuroendocrine, impairments are sufficient to maintain acyclicity in most older mice once it is initiated. However, 30% of the older mice from each transplantation group began cycling after receiving young ovaries by either the 1-stage or 2-stage procedure, as observed before 1-stage transplants. Therefore, cycle reactivation was not a result of the transient ovariprival phase incurred during 1-stage transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-related fibrillar deposits in brains of C57BL/6 mice

The present article reviews findings regarding the age-related occurrence of clusters of unusual granules in the brains of C57BL/6 (B6) mice and discusses the potential relevance of this phenomenon as a model of specific aspects of brain aging in humans. The granules occur predominatly in the hippocampus of B6 mice and represent aggregations of fibrillar material that are mostly associated with astrocytes. The deposits become evident at about 4 to 6 mo of age, and increase markedly in both number and size thereafter. Similar structures have been observed in adult senescence accelerated mice (SAM) and have been noted, although very rarely, in older mice from other strains. The deposits appear to manifest dominant genetic heritability. Heparan sulfate proteoglycan and laminin or related molecules have been identified as components of the granular material. Although the deposits do not represent senile plaques with β-amyloid deposition, they might mimic the deposition of extracellular matrix molecules that is thought to be an early event in amyloidogenesis in the aged brain and in Alzheimer's disease.     

Self-mutilation of the penis in C57BL/6N mice

A major cause of male reproductive failure in a C57BL/6N mouse production colony is self-inflicted mutilation of the penis. The extent of the damage ranged from loss of the distal end to loss of the entire penis. From January 1974 to August 1976, 645 adult male mice with mutilated penis were removed from this colony--where the monthly census was 9500 mice, mated 1 male to 4 females using a continuous mating system. On necropsy, it was observed that the substance blocking the urethra in the penile stump resulted in urine retention, grossly distending the urinary bladder. Proteus mirabilis and other bacteria isolated from the urethral plugs were considered secondary invaders.