Spontaneous B-cell lymphoma in the cranial mediastinal lymph node of an aged male C57BL/6J mouse.

B-cell lymphoma is generally observed in the spleen, mesenteric lymph nodes, and Peyer's patches in aged mice and rarely appears in other organs. Herein, we report a case of spontaneous B-cell lymphoma originating from the cranial mediastinal lymph node in a male 75-week-old C57BL/6J mouse. Macroscopically, a white mass was found at the base of the heart with no connection to the thymus. Microscopic examination revealed a solid proliferation of tumor cells with large nuclei at the center of the mass. Some macrophages, normal-sized lymphocytes, and lymphatic sinuses were found in both central and peripheral areas. Immunohistochemical analysis showed positive staining for cluster of differentiation 19, paired box protein 5, immunoglobulin M, and Ki-67 but not for cytokeratin AE1/AE3. These findings were not completely consistent with the established mouse lymphoma classification, leading to a diagnosis of B-cell lymphoma originating from the cranial mediastinal lymph node. This case report is the first to document a B-cell lymphoma in the cranial mediastinal lymph nodes in an aged C57BL/6J mouse.

Combination of pathological, biochemical and behavioral evaluations for peripheral neurotoxicity assessment in isoniazid-treated rats.

In drug development, assessment of non-clinical peripheral neurotoxicity is important to ensure human safety. Clarifying the pathological features and mechanisms of toxicity enables the management of safety risks in humans by estimating the degree of risk and proposing monitoring strategies. Published guidelines for peripheral neurotoxicity assessment do not provide detailed information on which endpoints should be monitored preferentially and how the results should be integrated and discussed. To identify an optimal assessment method for the characterization of peripheral neurotoxicity, we conducted pathological, biochemical (biomaterials contributing to mechanistic considerations and biomarkers), and behavioral evaluations of isoniazid-treated rats. We found a discrepancy between the days on which marked pathological changes were noted and those on which biochemical and behavioral changes were noted, suggesting the importance of combining these evaluations. Although pathological evaluation is essential for pathological characterization, the results of biochemical and behavioral assessments at the same time points as the pathological evaluation are also important for discussion. In this study, since the measurement of serum neurofilament light chain could detect changes earlier than pathological examination, it could be useful as a biomarker for peripheral neurotoxicity. Moreover, examination of semi-thin specimens and choline acetyltransferase immunostaining were useful for characterizing morphological neurotoxicity, and image analysis of semi-thin specimens enabled us to objectively show the pathological features.

Oral Function and the Oral Microbiome in the Elderly in the Kyotango Area.

INTRODUCTION: Prevention of tooth loss contributes to an extended life expectancy, namely longevity. Aging-related oral hypofunction, including tooth loss, markedly increases the risks of functional disorder and mortality. Dysbiosis of the oral microbiome has recently been associated with various diseases, such as liver cirrhosis, pancreatic cancer, colorectal cancer, and inflammatory bowel disease. Therefore, the relationship between the oral microbiome and systemic health has been attracting increasing attention. In the present study, we examined oral function and the oral microbiome in the elderly in a world-leading longevity area. MATERIALS AND METHODS: An oral examination, chewing ability/tongue-lip motor function/saliva tests, and a metagenomic analysis with a 16S rRNA gene-targeting next-generation sequencer were conducted on 78 subjects aged ≥80 years. Twenty-six healthy individuals aged between 20 and 39 years were also investigated as controls. The data obtained were statistically analyzed. The protocol of the present study was approved by the Ethics Review Board of our university (ERB-C-885). RESULTS: Chewing ability, tongue-lip motor function, and saliva volume were normal in elderly subjects with a current tooth number ≥20, but were significantly lower in those with a current tooth number <20. The oral microbiome in elderly subjects with a current tooth number ≥20 and young controls differed from that in elderly subjects with a current tooth number <20. CONCLUSION: Tooth number ≥20 in elderly subjects in the longevity area contributed to the maintenance of both oral function and the diversity of the oral microbiome.

Flow cytometric detection and microscopic observation of activated eosinophils in peripheral blood.

Eosinophils possess highly electron-dense granules with crystal-like structures and are characterized as high side scatter (SSC) areas by flow cytometry analysis. Eosinophils with low SSC features have been noted in extremely rare cases; however, the underlying cause remains unclear. Eosinophils in the low SSC area were analyzed using microscopy. A transmission electron microscope revealed the loss of crystal-like structures in granules with low electron density and piecemeal degranulation, which was undetectable by May-Grünwald-Giemsa staining. Based on the results of flow cytometry, May-Grünwald-Giemsa staining and transmission electron microscopy, SSC values could help potentially detect crystal-like structures and piecemeal degranulation eosinophils.

Coagulation assay discrepancies in Japanese patients with non-severe hemophilia A.

Patients with non-severe hemophilia A often show discrepancies in factor VIII (FVIII) activity. However, information on variant-specific coagulation assay characteristics in Japanese patients is limited. Pathogenic variants were classified into three groups, thrombin-cleavage site (TC), A1-A2-A3 interface (IF), and non-discrepant, with reference to previous studies. Cutoff values for the one-stage assay (OSA)/chromogenic substrate assay (CSA) ratio, which is suitable for distinguishing discrepancies, were determined for all five aPTT reagents. TGA and CWA parameters and bleeding scores were compared between groups. Two of the 39 patients with non-severe hemophilia A (5%) were classified as TC, 10 (26%) as IF, and 27 (69%) as non-discrepant. The OSA/CSA cutoff values between the groups varied widely by aPTT reagent and tended to be relatively low compared to previous studies. As an indicator of bleeding tendency, TGA had a low correlation coefficient for the IF variant, but this was not significant and was comparable to FVIII activity and CWA. Moreover, various parameters and bleeding tendency differed among patients with the same variants. Thus, our findings suggest that it is difficult to adequately assess the bleeding tendency of individual patients, even with the various assessments currently available.

Karnovsky's fixative prevents artifacts appearing as vacuolation derived from tissue processing in kidneys treated with antisense oligonucleotide.

Antisense oligonucleotide (ASO) therapies have been identified as a new treatment modality for intractable diseases. In kidneys treated with ASOs, vacuoles, in addition to basophilic granules, are often observed in the proximal tubules. Some reports have described that these vacuoles are likely to be a secondary phenomenon resulting from the extraction of ASOs during tissue processing. In this study, we compared renal morphology after fixation with Karnovsky's fixative or 4% paraformaldehyde phosphate buffer (PFA) with that of 10% neutral-buffered formaldehyde solution (NBF). Female Sprague-Dawley rats, intravenously treated four times with 50 mg/kg locked nucleic acid containing antisense oligonucleotides (LNA-ASOs) for 1 or 2 weeks, were examined. Microscopically, vacuoles and basophilic granules in the proximal tubules were observed in the kidneys fixed with NBF. Basophilic granules are indicative of the accumulation of ASOs. Moreover, some of the vacuoles also contained faint basophilic granules, suggesting that the vacuoles were relevant to the accumulation of ASOs. Although moderate vacuolation was observed in the proximal tubules, the majority of the vacuolated epithelia were negative for kidney injury molecule-1 on immunohistochemical staining. Vacuoles in the proximal tubules were not observed in samples subjected to Karnovsky's fixation, although basophilic granules were observed. In samples subjected to PFA fixation, vacuoles and basophilic granules were observed in the proximal tubules, similar to those in samples subjected to NBF fixation. Overall, our findings demonstrated the possibility of overestimation of vacuolation due to artifacts during tissue processing when using conventional NBF fixation. Karnovsky's fixative is considered a useful alternative for distinguishing artificial vacuoles from true nephrotoxicity.

Spontaneous ovarian choriocarcinoma in a young ICR mouse.

This paper describes the spontaneous ovarian choriocarcinoma observed in a young female Crl:CD1 (ICR) mouse. The mouse was sacrificed at 8 weeks of age after oral administration of a compound for 2 weeks. The left ovary was found to be cystically enlarged with dark red hemorrhaging. The cystic mass contained abundant blood plasma and erythrocytes. At the peripheral regions of the mass, large pleomorphic tumor cells with bizarre shaped nuclei were detected. Tumor cells contained a single large nucleus and abundant eosinophilic to amphophilic cytoplasm. Histopathology of the tumor cells resembled that of trophoblastic giant cells. Therefore, the observed ovarian lesion was diagnosed as a choriocarcinoma. No microscopic lesions were observed in the right ovary or other reproductive organs. Ovarian choriocarcinoma was considered to be of non-gestational origin. This is the first report of ovarian choriocarcinoma in a young ICR mouse.

Spontaneous hyaline glomerulopathy in a young Slc:ICR mouse.

Hyaline glomerulopathy is a type of glomerular lesion that occurs in aging mice. Spontaneous hyaline glomerulopathy is rare in young mice. Here, we report spontaneous hyaline glomerulopathy in a young adult (15-week-old) ICR mouse. Necropsy revealed discoloration and roughness of the kidney surface. Microscopically, diffuse glomerular lesions were prominent. Amorphous, eosinophilic materials were deposited globally in the glomeruli. The mesangial region was expanded; however, the mesangial cells showed no proliferation. Thickening of the Bowman's capsule with proliferation of parietal epithelial cells was observed. Glomerular deposits were strongly positive for anti-IgM, anti-IgG, and periodic acid-Schiff stain and were stained red by Masson's trichrome stain. The deposits were negative for anti C3 and stained negatively with Congo red stain. Periodic acid methenamine silver and electron microscopy revealed glomerular deposits limited to intraglomerular capillaries. Based on the histological features, we diagnosed this lesion as hyaline glomerulopathy. This case could improve our understanding of spontaneous lesions in toxicological and pharmacological studies.

MEAF6 is essential for cell proliferation and plays a role in the assembly of KAT7 complexes.

Myst family genes encode lysine acetyltransferases that mainly mediate histone acetylation to control transcription, DNA replication and DNA damage response. They form tetrameric complexes with PHD-finger proteins (Brpfs or Jades) and small non-catalytic subunits Ing4/5 and Meaf6. Although all the components of the complex are well-conserved from yeast to mammals, the function of Meaf6 and its homologs has not been elucidated in any species. Here we revealed the role of Meaf6 utilizing inducible Meaf6 KO ES cells. By elimination of Meaf6, proliferation ceased although histone acetylations were largely unaffected. In the absence of Meaf6, one of the Myst family members Myst2/Kat7 increased the ability to interact with PHD-finger proteins. This study is the first indication of the function of Meaf6, which shows it is not essential for HAT activity but modulates the assembly of the Kat7 complex.

Quantification of histopathological findings using a novel image analysis platform.

Digital pathology, including image analysis and automatic diagnosis of pathological tissue, has been developed remarkably. HALO is an image analysis platform specialized for the study of pathological tissues, which enables tissue segmentation by using artificial intelligence. In this study, we used HALO to quantify various histopathological changes and findings that were difficult to analyze using conventional image processing software. Using the tissue classifier module, the morphological features of degeneration/necrosis of the hepatocytes and muscle fibers, bile duct in the liver, basophilic tubules and hyaline casts in the kidney, cortex in the thymus, and red pulp, white pulp, and marginal zone in the spleen were learned and separated, and areas of interest were quantified. Furthermore, using the cytonuclear module and vacuole module in combination with the tissue classifier module, the number of erythroblasts in the red pulp of the spleen and each area of acinar cells in the parotid gland were quantified. The results of quantitative analysis were correlated with the histopathological grades evaluated by pathologists. By using artificial intelligence and other functions of HALO, we recognized morphological features, analyzed histopathological changes, and quantified the histopathological grades of various findings. The analysis of histopathological changes using HALO is expected to support pathology evaluations.

Comparison of changes in urinary and blood levels of biomarkers associated with proximal tubular injury in rat models.

To investigate useful biomarkers associated with proximal tubular injury, we assessed changes in levels of a focused set of biomarkers in urine and blood. Male rats administered a single dose or four doses of gentamicin (GM, 240 mg/kg/day) or a single dose of cisplatin (CDDP, 5 mg/kg) were euthanized on days 2 (the day after initial dosing) 5, or 12. At each time point, histopathological examination of the kidney and immunohistochemistry for biomarkers, kidney injury molecule-1 (Kim-1), lipocalin (NGAL), clusterin (CLU), cystatin C (CysC) and ß2-microglobulin (ß2M) were performed. Biomarker levels were measured in urine and blood. In both treatment groups, degenerated/necrotic proximal tubules and regenerated tubules were mainly observed on days 5 and 12, respectively. At the same time as these tubular injuries, urinary Kim-1, CysC and ß2M levels were increased. Moreover, urinary levels of CysC and ß2M in GM-treated animals and Kim-1 in CDDP-treated animals increased (on day 2) prior to tubular injury on day 5. This was considered to reflect the characteristics of drug toxicity. Although almost all of the biomarkers in blood were not sufficiently sensitive to detect proximal tubular injury, urinary and plasma ß2M levels simultaneously increased. Therefore, in addition to urinary Kim-1, CysC and ß2M levels, plasma ß2M levels were also considered useful for detecting proximal tubular injury.

Kinetics of drug selection systems in mouse embryonic stem cells.

BACKGROUND: Stable expression of transgenes is an important technique to analyze gene function. Various drug resistance genes, such as neo, pac, hph, zeo, bsd, and hisD, have been equally used as selection markers to isolate a transfectant without considering their dose-dependent characters. RESULTS: We quantitatively measured the variation of transgene expression levels in mouse embryonic stem (mES) cells, using a series of bi-cistronic expression vectors that contain Egfp expression cassette linked to each drug resistant gene via IRES with titration of the selective drugs, and found that the transgene expression levels achieved in each system with this vector design are in order, in which pac and zeo show sharp selection of transfectants with homogenously high expression levels. We also showed the importance of the choice of the drug selection system in gene-trap or gene targeting according to this order. CONCLUSIONS: The results of the present study clearly demonstrated that an appropriate choice of the drug resistance gene(s) is critical for a proper design of the experimental strategy.

Th2 cytokine-mediated methimazole-induced acute liver injury in mice.

Drug-induced liver injury (DILI) is a major safety concern in drug development and clinical practice. The pathogenesis of DILI usually involves the participation of the parent drug or metabolites that either affect cellular function or elicit an immune response. However, the mechanisms leading to DILI are unknown in most cases. Methimazole (MTZ) is used as an antithyroid drug and is well known to have induced liver injuries such as cholestatic hepatitis in a small number of human cases. Immune-mediated reactions were also suggested to play a role in MTZ-induced acute liver injury, but the mechanism underlying this process has not been elucidated. To address this issue, we measured plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, hepatic glutathione levels, hepatic expression of CD4⁺ Th cell-related transcriptional factors, cytokines and chemokines, plasma interleukin (IL)-4 levels and histopathological changes in the liver following MTZ (450 mg kg⁻¹ , p.o.) administration in mice. The hepatic expression of mRNA for Th2 cell-related factors, such as GATA-binding protein, macrophage inflammatory protein-2 (MIP-2) and plasma IL-4 levels, as well as plasma AST and ALT levels, was significantly increased in mice treated with MTZ. These changes were markedly enhanced by pre-treatment with L-buthionine sulfoximine (3 mmol kg⁻¹, i.p.) and MTZ (15 mg kg⁻¹, p.o.). Neutralization of IL-4 using a monoclonal anti-mouse IL-4 antibody (100 µg/mouse, single i.p.) suppressed the hepatotoxic effect of MTZ. In conclusion, this report is the first to demonstrate that Th2 cytokine-mediated immune responses are involved in MTZ-induced acute liver injury in mice.

Gene expression in livers of BALB/C and C57BL/6J mice fed a high-fat diet.

We previously demonstrated that high-fat diet (HFD)-induced hepatic lipid accumulation is more severe in BALB/c mice than in C57BL/6J (B6) mice. To understand the changes in liver metabolism, we studied blood chemistry, gene expression, and histopathological changes of the liver in nine-week HFD-fed BALB/c and B6 mice and one- or four-week HFD-fed BALB/c mice. Serum total cholesterol and triglyceride levels were significantly increased in all HFD-fed groups, and one- and four-week HFD-fed BALB/c groups, respectively. Histopathology revealed that vacuolation of hepatocytes was severe in nine-week HFD-fed BALB/c mice, although it was less severe in the other groups. Microarray analysis of mRNA expression of nine-week HFD-fed BALB/c mice showed up-regulation of genes involved in fatty acid uptake and biosynthesis, such as Cd36, Acaca, Acly, and Fasn. Some changes were observed in the one- and four-week HFD-fed BALB/c groups and the nine-week HFD-fed B6 group, however these changes in mRNA expression were not so marked. In conclusion, the fatty accumulation observed in BALB/c mice may be caused, at least in part, by up-regulation of fatty acid uptake and biosynthesis. Cd36, Acaca, Acly and Fasn may be involved in these metabolic processes.

Etv2/ER71 induces vascular mesoderm from Flk1+PDGFRα+ primitive mesoderm.

Etv2 (Ets Variant 2) has been shown to be an indispensable gene for the development of hematopoietic cells (HPCs)/endothelial cells (ECs). However, how Etv2 specifies the mesoderm-generating HPCs/ECs remains incompletely understood. In embryonic stem cell (ESC) differentiation culture and Etv2-null embryos, we show that Etv2 is dispensable for generating primitive Flk-1(+)/PDGFRα(+) mesoderm but is required for the progression of Flk-1(+)/PDGFRα(+) cells into vascular/hematopoietic mesoderm. Etv2-null ESCs and embryonic cells were arrested as Flk-1(+)/PDGFRα(+) and failed to generate Flk-1(+)/PDGFRα(-) mesoderm. Flk-1(+)/Etv2(+) early embryonic cells showed significantly higher hemato-endothelial potential than the Flk-1(+)/Etv2(-) population, suggesting that Etv2 specifies a hemato-endothelial subset of Flk-1(+) mesoderm. Critical hemato-endothelial genes were severely down-regulated in Etv2-null Flk-1(+) cells. Among those genes Scl, Fli1, and GATA2 were expressed simultaneously with Etv2 in early embryos and seemed to be critical targets. Etv2 reexpression in Etv2-null cells restored the development of CD41(+), CD45(+), and VE-cadherin(+) cells. Expression of Scl or Fli1 alone could also restore HPCs/ECs in the Etv2-null background, indicating that these 2 genes are critical downstream targets. Furthermore, VEGF induced Etv2 potently and rapidly in Flk-1(+) mesoderm. We propose that Flk-1(+)/PDGFRα(+) primitive mesoderm is committed into Flk-1(+)/PDGFRα(-) vascular mesoderm through Etv2 and that up-regulation of Etv2 by VEGF promotes this commitment.

Spontaneous poorly differentiated carcinoma with cells positive for vimentin in a salivary gland of a young rat.

Spontaneous salivary gland tumors in rats are rare. The authors report a poorly differentiated carcinoma of a submandibular gland in a ten-week-old rat that was positive for vimentin. Microscopically, the neoplastic cells showed a diffuse growth pattern in most areas of the tumor mass and a nestlike structure in a part of the peripheral area. Immunohistochemically, the cells were positive for keratin and vimentin but not for alpha-smooth muscle actin. Ultrastructurally, desmosome-like structures were observed. Based on these findings, the tumor was diagnosed as a poorly differentiated carcinoma. The origin of the neoplastic cells would be either acinar or ductal cells. This suggests that acinar or ductal cells have the potential to transform into vimentin-expressing cells.

The effect of fasting on hepatic lipid accumulation and transcriptional regulation of lipid metabolism differs between C57BL/6J and BALB/cA mice fed a high-fat diet.

The effects of fasting on hepatic lipid metabolism in mice fed a high-fat diet (HFD) are still unclear. After fasting, the degree of hepatic lipid accumulation differs between HFD-fed C57BL/6J (B6) and BALB/cA (BALB/c) mice. It is not clear whether this difference is due to sensitivity to fasting or HFD. The aim of this study is to elucidate this difference among strains. After nine weeks of HFD feeding, both B6 and BALB/c mice showed moderate hepatic steatosis. However, after a subsequent twenty-hour fast, the hepatic lipid accumulation was markedly decreased in B6 but not in BALB/c mice. Moreover, the mRNA expression of a transcription factor, Srebp1(regulates hepatic lipid metabolism), and its target genes-malic enzyme, acetyl-CoA carboxylase, fatty acid synthase(regulate fatty acid synthesis), and glycerol-3-phosphate acyltransferase(regulates triacylglycerol synthesis)-were more markedly reduced in B6 than BALB/c mice. In conclusion, fasting may modify hepatic lipid accumulation in HFD-fed B6 and BALB/c mice differently. The difference may be partly owing to a marked downregulation of the expression of some lipid-metabolism-related genes in B6 mice. These results suggest that fasting per se has a significant effect on hepatic lipid accumulation in mouse strains. SREBP1 might play a role in this fasting effect.

Multiple mesoderm subsets give rise to endothelial cells, whereas hematopoietic cells are differentiated only from a restricted subset in embryonic stem cell differentiation culture.

In the developing mouse, vascular endothelial cell (EC) and hematopoietic cell (HPC) lineages are two initial cell lineages that diverge from mesodermal cells, which have been roughly subdivided into three subtypes according to their geographical location: the organizer, embryonic mesoderm in the primitive streak, and extraembryonic mesoderm during gastrulation. Although the initial progenitors that become the two lineages appear in both vascular endothelial growth factor receptor 2(+) (VEGFR2(+)) lateral and extraembryonic mesoderm, little is known about the underlying molecular events that regulate the derivation of ECs and HPCs. Here, we describe an experimental system consisting of two types of embryonic stem cell lines capable of distinguishing between organizer and the middle section of the primitive streak region. Using this system, we were able to establish a defined culture condition that can separately induce distinct types of mesoderm. Although we were able to differentiate ECs from all mesoderm subsets, however, the potential of HPCs was restricted to the VEGFR2(+) cells derived from primitive streak-type mesodermal cells. We also show that the culture condition for the progenitors of primitive erythrocytes is separated from that for the progenitors of definitive erythrocytes. These results suggest the dominant role of extrinsic regulation during diversification of mesoderm.

Histopathological characteristics of Kupffer cells and ito cells in the porcine and bovine liver.

We previously reported that no Kupffer cells reacted with the antibody against lysozyme, and Ito cells contained a large cytoplasmic vacuole in the feline liver. In this report, we further examined the characteristics of porcine and bovine hepatic non-parenchymal cells. In the liver of both animals, Kupffer cells were positive for lysozyme, and cytoplasmic vacuoles in Ito cells were small. The histopathological characteristics of porcine and bovine hepatic non-parenchymal cells were different from those of the feline liver.

Involvement of sex, strain and age factors in high fat diet-induced obesity in C57BL/6J and BALB/cA mice.

Although a number of obesity animal models have been reported, each model possesses different characteristics of obesity, suggesting care should be taken in choosing an animal model suitable for the experimental purpose. In this report, we fed 4-(young) and 52-week-old (middle-aged) C57BL/6J (B6) and young BALB/cA (BALB/c) mice with a high fat diet (HFD) for 9 weeks, and investigated the clinical and histological characteristics of obesity. In BALB/c mice, males gained more body weight and body fat weight and had higher energy intake than females by HFD feeding. Comparing the effect of HFD feeding between the strains of mice, BALB/c male mice accumulated more hepatic lipid than B6 male mice. In addition, middle-aged B6 mice increased the ratio of fat to body weight and hepatic lipid accumulation more than young mice. In conclusion, the characteristics of obesity induced by HFD feeding were influenced by the sex, strain and age of mice. Sex steroid hormones, hepatic lipid metabolism and systemic metabolism might be involved in these factors. The basic data in this study will be useful for the development of animal models of high fat diet-induced obesity.