A Case Report of a Malignant Fibrous Histiocytoma in a T-cell Receptor β Chain and p53 Double-knockout Mouse

A subcutaneous tumor was found in the right abdomen of a 16-week-old male TCRβ and p53 double-knockout mouse. The tumor had indistinct borders with the surrounding tissue. The cut surface after formalin fixation was pale yellowish white, partially dark red and partly white. Histologically, the tumor was composed of three distinct regions. The first region showed pleomorphic cells arranged in sheets. The second region showed spindle cells arranged in interlacing fascicles. The final region contained a mixture of the above mentioned two types of cells. Furthermore, a small amount of collagen fibers, round cells, multinucleated giant cells, and cells with eosinophilic granules were observed between these tumor cells. Immunohistochemical examination and electron microscopy identified that the pleomorphic cells and spindle cells were histiocytes and fibroblasts, respectively, and that the round cells were undifferentiated mesenchymal cells. Based on these findings, the tumor was diagnosed as a malignant fibrous histiocytoma

Spontaneous Cardiac Hypertrophy in a Crl:CD(SD) Rat

Cardiac hypertrophy was observed in a 9-week-old Crl:CD(SD) rat that died unexpectedly. The animal was allocated to the control group of a toxicity study, and no abnormalities in its general conditions, body weight or food intake were observed. Necropsy revealed an increase in heart weight. Gross examination indicated cardiac enlargement with thickening of the right and left ventricular walls. Histopathological examination revealed hypertrophy of the cardiomyocytes in the right and left ventricular walls and the interventricular septum. Electron microscopic examination indicated bizarre nuclei and accumulation of an increased number of various sizes of mitochondria in the perinuclear region of the hypertrophied myocytes. Hypertrophied myocytes connected by intensely folded intercalated disks were also observed. Based on these findings, the animal was diagnosed with cardiac hypertrophy. This is the first case report of cardiac hypertrophy in this strain

Microscale spatial analysis provides evidence for adhesive monopolization of dietary nutrients by specific intestinal bacteria

<div><p>Each species of intestinal bacteria requires a nutritional source to maintain its population in the intestine. Dietary factors are considered to be major nutrients; however, evidence directly explaining the <i>in situ</i> utilization of dietary factors is limited. Microscale bacterial distribution would provide clues to understand bacterial lifestyle and nutrient utilization. However, the detailed bacterial localization around dietary factors in the intestine remains uninvestigated. Therefore, we explored microscale habitats in the murine intestine by using histology and fluorescent <i>in situ</i> hybridization, focusing on dietary factors. This approach successfully revealed several types of bacterial colonization. In particular, bifidobacterial colonization and adhesion on granular starch was frequently and commonly observed in the jejunum and distal colon. To identify the bacterial composition of areas around starch granules and areas without starch, laser microdissection and next-generation sequencing-based 16S rRNA microbial profiling was performed. It was found that <i>Bifidobacteriaceae</i> were significantly enriched by 4.7 fold in peri-starch areas compared to ex-starch areas. This family solely consisted of <i>Bifidobacterium pseudolongum</i>. In contrast, there was no significant enrichment among the other major families. This murine intestinal <i>B</i>. <i>pseudolongum</i> had starch-degrading activity, confirmed by isolation from the mouse feces and <i>in vitro</i> analysis. Collectively, our results demonstrate the significance of starch granules as a major habitat and potential nutritional niche for murine intestinal <i>B</i>. <i>pseudolongum</i>. Moreover, our results suggest that colonizing bifidobacteria effectively utilize starch from the closest location and maintain the location. This may be a bacterial strategy to monopolize solid dietary nutrients. We believe that our analytical approach could possibly be applied to other nutritional factors, and can be a powerful tool to investigate <i>in vivo</i> relationships between bacteria and environmental factors in the intestine.</p></div

<i>Bifidobacterium</i> accumulated onto starch granules in broad regions of the murine intestinal tract.

<p>(a, b) Cross section of murine jejunum stained by Bif153 (green), Eub338 (red), Lab158 (blue), and Lugol’s solution. Bif153-positive bifidobacteria preferentially colonized onto starch granules (arrowhead) in the presence of jejunal-dominant lactic acid bacteria. (c,d) Cross section of murine colon stained by Bif153 (green), Erec482 (red), Clept1240 (blue), and Lugol’s solution. Similar to the jejunum, Bif153-positive bifidobacteria preferentially colonized starch granule surfaces (arrowhead) in the presence of colonic-dominant bacteria, <i>Clostridium</i> cluster XIVa and XIVb and <i>Clostridium leptum</i> subgroup. Images are representative of at least 7 individual mice. (a,c) Fluorescence microscopy. (b,d) Bright-field microscopy. Bars = 20 μm.</p

Murine intestinal tract filled with indigenous bacteria and food residue.

<p>(a–e) Cross section of murine colon and digesta. (b) and (d) are magnified images of (a) and (c), respectively. (b) Mucus layer surrounding the mucosa (arrow) and food residues, including plant tissues (arrowhead), in the digesta were visualized by Alcian blue-PAS staining. (d) Intestinal bacteria were visualized by hematoxylin-eosin staining. (e) Structures stained with hematoxylin-eosin were labeled by FISH using a universal bacterial probe Eub338 (green) and DAPI (red). Images are representative of at least 3 individual mice. Bars = 200 μm (a), 100 μm (b), 20 μm (c), 10 μm (d, e).</p

<i>Bifidobacterium pseudolongum</i> accumulates onto dietary starch granules in a species-specific manner.

<p>(a,b) Intestinal contents in the peri-starch areas (St) and ex-starch areas (Ex) were collected from sections of the murine colon using LMD and subjected to NGS-based 16S rRNA microbial profiling. The results of 6 mice were shown at the family level. (b) Mean ± SD is shown. *; significantly different between peri-starch and ex-starch (p<0.05, two-tailed paired t-test). (c) <i>B</i>. <i>pseudolongum</i> around a starch granule stained by Bpl190 (red), Bif153 (green), and Eub338 (blue) (arrowhead). Images are representative of 3 individual mice. Bars = 20 μm.</p

The isolated murine <i>Bifidobacterium pseudolongum</i> shows amylolytic activity.

<p>(a) A modified GAM agar plate was stained by Lugol’s solution. Starch in agar was degraded around colonies. (b) Before staining. 4121; <i>B</i>. <i>animalis</i> subsp. <i>lactis</i>, type strain YIT 4121, 4102; <i>B</i>. <i>pseudolongum</i> subsp. <i>pseudolongum</i>, type strain YIT 4102, 4101; <i>B</i>. <i>pseudolongum</i> subsp. <i>globosum</i>, type strain YIT 4101, #1–9; Isolates identified as <i>B</i>. <i>pseudolongum</i>. (See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0175497#pone.0175497.t001" target="_blank">Table 1</a>).</p

Structures colonized by bacteria in the digesta.

<p>(a,b) Cross section of murine jejunum stained by Eub338 (green) and DAPI (red). Bacteria accumulate around granular structures with a diameter of approximately 5–15 μm (arrowhead). (c,d) Cross section of murine cecum stained by Eub338 (green) and DAPI (red). Inner area of plant cell wall was filled with bacteria. Images are representative of at least 7 individual mice. (a,c) Fluorescence microscopy. (b,d) Bright-field images. Bars = 20 μm.</p