Rodents exhibit diverse morphological and ecological adaptations across species, making them important species for considering the evolutionary background of morphological traits. Although the splenic artery has been described in various rodent species, interspecific comparisons remain difficult due to a lack of uniformity in anatomical descriptions. We therefore traced the ramification patterns of the splenic artery in 15 rats (Rattus norvegicus), 15 degus (Octodon degus), and 10 red-bellied squirrels (Callosciurus erythraeus) using standardized anatomical criteria to enable rigorous interspecific comparisons. In all degus and red-bellied squirrels, the splenic artery was the first independent branch of the celiac artery, while in 73% of rats, the splenic artery emerged as one of the trifurcated branches of the celiac artery. The splenic artery of red-bellied squirrels exhibited the highest average number of divisions before entering the splenic parenchyma compared to the other two species, resulting in the highest average number of splenic branches. Further, the average number of gastric branches, including the short gastric and gastroepiploic arteries, was highest in red-bellied squirrels and lowest in rats. The differences in branching patterns of the splenic artery among three rodent species, as revealed in this study, are expected to provide clues to understanding species differences in ramification patterns of the splenic artery in rodents.

Mammalian embryos possess undifferentiated gonads and primordial male and female reproductive tracts. In males, sex-determining region of the Y chromosome (Sry) triggers the differentiation of gonadal supporting cell precursors into Sertoli cells. In C57BL/6N-XY^POS (B6N-XY^POS) mice, a model of disorders of sex development, Sry expression is delayed relative to wild-type B6N mice, and several reproductive tract malformations have been reported. In this study, we investigated the developmental stage and regions at which reproductive tract development fails in B6N-XY^POS. In B6N-XY^POS at 15.5 days post-coitum (dpc), the number of seminiferous tubules showed no difference from B6N, but seminiferous tubules with closed at both ends appeared. In B6N-XY^POS with bilaterally developed ovaries or testes, significant disorders were observed only in the female reproductive tract. B6N-XY^POS ovotestes showed impaired testis differentiation in the cranial and caudal regions, not only in fetuses but also in adults. In female B6N-XY^POS with bilaterally or unilaterally formed ovaries, the Müllerian ducts opened into the urogenital sinus at 15.5 dpc; however, at postnatal day 1, one individual exhibited a uterus with a closed region, and many adult females formed an edematous uterus. These results suggest that impaired cranial testis differentiation may disrupt the connection between the seminiferous tubules and the rete testis. They also suggest that Müllerian duct formation is initially completed even in female B6N-XY^POS with an edematous uterus, but that the duct closes abnormally between 15.5 dpc and birth.

We morphologically examined 148 fecal samples of pheasants reared at farms and zoos in Japan by the sugar flotation method to evaluate infection with gastrointestinal parasites, including Eimeria species. Eimeria oocysts, Capillariid eggs, and Ascaridia/Heterakis eggs were detected in 76.2%, 49.0%, and 26.5%, respectively. These results suggest that these parasites seem to be widespread in pheasants in Japan.

A 12-year-old spayed female Korean shorthair cat was evaluated for mediastinal and cervical masses. A serum biochemistry analysis revealed hypercalcemia and hypophosphatemia, with normal parathyroid hormone (PTH) levels. Diagnostic imaging showed multicystic cervical and mediastinal masses with increased opacity in the left caudal lung field, suggestive of partial lung collapse. Abdominal imaging was unremarkable. Cytology of the mediastinal mass suggested an epithelial or neuroendocrine tumor. Hypercalcemia remained unresolved following bisphosphonate therapy; the cat was euthanized 290 days after presentation. Postmortem examination revealed multicystic cervical and mediastinal masses with hemorrhage and necrosis. Histopathology showed neoplastic epithelial cells with cystic degeneration and lymphatic invasion in cervical and mediastinal masses. Immunohistochemistry confirmed PTH expression, establishing the chief cell parathyroid carcinoma. To our knowledge, this case represents a suspected ectopic feline parathyroid chief cell carcinoma with extensive cystic change and metastatic features.

An 11-year-old castrated male mixed-breed cat presented with a 2-week history of lethargy and anorexia. Abdominal ultrasonography revealed jejunal thickening and adjacent masses. As fine-needle aspiration cytology and PCR for antigen receptor gene rearrangement of the masses suggested small T-cell lymphoma, resection biopsy was performed. Based on histopathology and immunohistochemistry, a diagnosis of small T-cell lymphoma with prominent lymphoid follicle formation and concurrent large B-cell lymphoma was made. Postoperative chemotherapy with chlorambucil and prednisolone was performed. The cat survived for 728 days since initial presentation, with no recurrence of clinical signs or ultrasonographic abnormalities. To the best of our knowledge, this is the first report describing a feline case of intestinal small T-cell lymphoma with prominent lymphoid follicle formation and concurrent intestinal large B-cell lymphoma.

An elderly, spayed female Maltese dog (10 years 3 months, 2.2 kg) presented with hyporexia, weight loss, polydipsia, and a staggering gait. Serum biochemistry analysis revealed increased aspartate aminotransferase, alanine transaminase, ammonia (226 μg/dL), and fasting total bile acids (130 μmol/L). Contrast-enhanced CT showed multiple clusters of contrast enhancement within the hepatic parenchyma; however, discrete shunt vessels could not be clearly identified, and a definitive diagnosis could not be established based on CT alone. Intraoperative jejunal venous portography revealed numerous microvascular clusters connecting portal branches to the hepatic vein and caudal vena cava. The portal pressure was 7 mmHg. Based on these findings, multiple intrahepatic portosystemic shunts (MIPSS) were diagnosed, and medical management was selected.

Our strain of inbred PVG-RT7b (PVG.7b) rats was at risk of failing to be maintained owing to frequent neonatal death. Only 23.5% of mothers succeeded in nurturing their offspring at the first parturition. Furthermore, mothers failing to nurture their offspring at first parturition also failed in the second one. Here, we investigated the cause of frequent neonatal deaths in PVG.7b rats. Exchanging newborn offspring between PVG.7b and Wistar-Imamichi (WI) rats. resulted in 80.0% of WI mothers succeeding in nurturing PVG.7b offspring, whereas only 18.2% of PVG.7b mothers succeeded in nurturing WI offspring. These findings indicate that the neonatal mortality of PVG.7b is due to maternal factors rather than inherent offspring issues. Additionally, we examined the mammary glands of PVG.7b immediately after the second parturition. PVG.7b rats, which initially failed to nurture, exhibited normal mammary gland development and milk production after the second birth. These results suggested that neonatal death is due to maternal behavior. Moreover, we investigated the nurturing ability of PVG.7b rats nurtured by WI foster mothers (PVG.7b ^Infant/WI) or born and nurtured from WI recipients after embryo transfer (PVG.7b ^ET/WI). Only 26.1% of PVG.7b ^Infant/WI mothers succeeded in nurturing their offspring, compared to 63.6% of PVG.7b ^ET/WI mothers. However, only 20.0% of PVG.7b mothers born and nursed by PVG.7b ^ET/WI succeeded in nurturing their offspring. These results suggest that the fetal environment influences the nurturing ability of PVG.7b rats.

We aimed to evaluate the efficacy and safety of a modified injectable anesthesia protocol combining dexmedetomidine, midazolam, and butorphanol (dMMB) compared with the conventional medetomidine-based protocol (MMB) in C57BL/6J mice. Animals were assigned to three groups (n=5 per group for each sex): MMB (0.5/4.0/5.0), dMMB (0.25/4.0/5.0), and dMMB (0.1/6.0/10.0) mg/kg. We assessed anesthetic induction and recovery times, depth scores, heart rate, SpO₂, and body temperature, and administered atipamezole 40 min post-anesthesia to evaluate temperature recovery. Blood glucose levels were also measured. Both dMMB protocols produced anesthetic effects comparable to MMB, but recovery was significantly faster than MMB. Duration of surgical anesthesia in males (mean ± 95% confidence interval) was 141 ± 11 min for MMB, 112 ± 8 min for dMMB (0.25/4.0/5.0), and 89 ± 10 min for dMMB (0.1/6.0/10.0). In females, durations were 109 ± 43 min, 76 ± 12 min, and 78 ± 16 min, respectively. In addition, hypothermia was less severe, particularly with the lowest dexmedetomidine dose (0.1/6.0/10.0). Furthermore, females had a significantly shorter duration of surgical anesthesia than males. Blood glucose levels increased under all anesthetic protocols, with males showing higher values than females, while no significant differences among anesthetic protocols were detected in either sex. No additional adverse effects were observed. These findings indicated that low-dose dexmedetomidine-based anesthesia provides effective sedation while improving safety by reducing hypothermia and facilitating rapid recovery.

Agouti-dominant spotting (Ads) is a novel mutant mouse that was spontaneously isolated from KOR1/Stm (KOR1), an inbred strain derived from a Japanese wild mouse. Heterozygous Ads mice exhibit dominant white-spotting on the dorsal coat, whereas homozygous mice display embryonic lethality. We generated [Ads×C57BL/6J (B6)]F₁ (F₁), F₂ and [B6×(Ads×B6)]N₂ (N₂) mice to investigate the inheritance patterns of the Ads phenotype. The segregation ratio did not conform to the theoretical values expected for a simple autosomal dominant inheritance pattern with recessive embryonic lethality, as there was a reduced number of individuals exhibiting white-spotting in F₂ (χ²=29.07, P<0.0001) and N₂ (χ²=5.79, P=0.016). Genome-wide linkage analysis revealed that the Ads locus was located within the interval between D4Mit288 (56.8-Mb) and D4Mit69 (136.1-Mb) on chromosome 4. Further fine mapping using additional N₂ and N₃ progeny and markers narrowed the Ads locus to the genomic interval between Dhcr24 (106.4-Mb) and D4Mit199 (111.7-Mb). Among the genes encoded within this genomic interval, we predicted that the mago homolog, exon junction complex core component (Magoh), was the most promising candidate gene for Ads, as its null mutations have been reported to cause a white-spotting phenotype in Mos2 mice. However, no mutations were identified in the coding region of Magoh in Ads mice, suggesting that the causative mutation for the white-spotting phenotype may reside in a cis-regulatory region of Magoh or in another novel gene within the interval.

A 12-year-8-month-old neutered male cat presented with multiple nail bed masses and an ulcerative lip lesion. PCR identified Felis catus papillomavirus type 3 (FcaPV3) in the nail masses and type 4 (FcaPV4) in the lip lesion. Histopathology revealed basosquamous cell carcinoma (BSCC) in the digits and Bowenoid in situ carcinoma (BISC) in the lip. Immunohistochemistry showed that tumor cells in both BSCC and BISC were positive for p16 and p63 and weakly positive for pRb; p53 was negative in BSCC but weakly positive in BISC. In situ hybridization confirmed FcaPV3 and FcaPV4 E6 genes in digital and lip tumors, respectively. Over 6 months, viral sequencing showed 23 nucleotide changes in FcaPV3, suggesting viral evolution. This is the first report of distinct malignant epithelial tumors independently induced by FcaPV3 and FcaPV4 in a cat.

Hypertension is associated with impaired central autonomic regulation and remains a major risk factor for cardiovascular diseases. The nucleus tractus solitarius (NTS) in the medulla oblongata plays a critical role in blood pressure control via glutamatergic neurotransmission from peripheral baroreceptors. Previous studies have shown that intracisternal administration of Group II metabotropic glutamate receptor (mGluR2/3) agonists attenuates hypertension; however, the clinical applicability of this invasive approach is limited. The present study investigated whether systemic administration of a selective mGluR2/3 agonist, LY 379268, can modulate central blood pressure regulation and attenuate hypertension. LY 379268 was administered intravenously to spontaneously hypertensive rats (SHRs). In anesthetized conditions, arterial blood pressure and heart rate were continuously recorded and dose–response effects were evaluated. In conscious conditions, LY 379268 were administered into the tail vein of control SHRs or SHRs with intact (Sham) or preoperatively transected baroreceptor information (Sino-Aortic Denervation, SAD), and blood pressure was periodically measured by the tail-cuff method. A dose-dependent reduction in arterial blood pressure without significant changes in heart rate was observed up to moderate doses (10 μg/kg), showing bell-shape response. Similarly, aforementioned dose of LY 379268 i.v. injection decreased blood pressure in control or Sham-SHRs but not in SAD-SHRs in conscious condition. In addition, intravenous Evans blue injection demonstrated increased permeability of the blood-brain-barrier in the NTS. These findings indicate that systemic activation of mGluR2/3 can attenuate hypertension by modulating central autonomic regulation via access to the NTS. Intravenous administration of mGluR2/3 agonists may represent a minimally invasive strategy for targeting central mechanisms underlying hypertension.

Replication of Senecavirus A (SVA) generates intact virions and empty capsids, some of which disassemble into pentamers. To enable precise quality control of SVA intact viral antigen, we established a double-antibody sandwich ELISA to quantify intact SVA virions and virus-like particles (VLPs). The assay employs a conformation-specific nanobody (SV1) as the capture antibody, which binds both virions and VLPs, and a His-tagged nanobody (SVH1) as the detection antibody. Using purified virions as standards, the assay demonstrated a limit of detection (LOD) of 9.7 ng/mL, with a linear range spanning from 9.7 ng/mL to 1.25 μg/mL. Critically, it showed no cross-reactivity with pentamers and other viral particles, including foot-and-mouth disease virus (FMDV), porcine circovirus type 2 (PCV2), porcine parvovirus (PPV), classical swine fever virus (CSFV), and encephalomyocarditis virus (EMCV). The coefficients of variation (CV) were <10% for both intra-batch and inter-batch analyses. Validation against sucrose density gradient centrifugation (SDGC) confirmed concordant results. Applied to vaccine development, the ELISA quantified a 36% antigen loss in SVA VLPs after emulsification. In summary, this method provides a rapid, specific tool for SVA vaccine standardization.

Parapoxvirus infections caused by bovine papular stomatitis virus (BPSV) and pseudocowpox virus (PCPV) are globally distributed zoonoses in ruminants. Although parapoxviruses have been isolated and genetically characterized in several regions of Japan, no sequence data are available from Hokkaido, which has the country’s largest cattle population. Consequently, the genetic characteristics of strains circulating in Hokkaido remain unclear. This study analyzed the genetic relationships and molecular epidemiology of 11 BPSV and two PCPV strains isolated in Hokkaido between 2005 and 2022. Full-length sequences of open reading frames (ORF) 11 and 32 were determined and compared with previously reported strains. The deduced amino acid identities of ORF11 ranged from 95 to 100% among 11 BPSV strains and 98% between the two PCPV strains. ORF32 amino acid identities among BPSV strains ranged from 88% to 100%. This study reports the first ORF32 sequences of Japanese parapoxviruses. Phylogenetic analysis based on ORF11 showed that 10 BPSV strains formed a single cluster, whereas one strain was distinct; the two PCPV strains also formed separate clusters. ORF32 analysis indicated that most BPSV strains clustered together, except for one strain with an amino acid deletion. Comparisons with domestic and foreign strains demonstrated that ORF11 is highly conserved, whereas ORF32 exhibits greater genetic diversity, supporting its suitability for molecular epidemiological analysis. These findings indicate that genetically related parapoxviruses are circulating in Hokkaido.

In 2025, an outbreak of equine influenza occurred among draft horses at Obihiro Racecourse in Hokkaido, Japan. The number of horses showing clinical signs increased dramatically in April. The proportion affected was significantly higher in 2-year-olds than in older groups. The proportion that developed fever during the outbreak was significantly higher than that observed among Thoroughbreds during the 2007 outbreak. In non-epidemic periods, the geometric mean hemagglutination inhibition antibody titer of 2-year-old draft horses was significantly lower than that of 2-year-old Thoroughbreds. These draft horses had received fewer vaccinations than the Thoroughbreds. Less frequent vaccination likely led to a lower antibody titer and a higher final attack rate in the 2-year-olds and in the overall draft horse population.

An adult male Sunda pangolin (Manis javanica) exhibited thickened, hyperkeratotic skin between dorsal scales. Initial wound management led to temporary resolution, but a proliferative, hemorrhagic mass developed 11 weeks later. Histopathological examination confirmed squamous cell carcinoma (SCC). Surgical excision followed by cryotherapy was performed. Despite histological evidence of complete tumor ablation, the animal’s condition deteriorated due to secondary infection and poor wound healing. This case highlights the diagnostic and therapeutic challenges of managing SCC in pangolins due to their unique integumentary anatomy. This is the first documented case of cutaneous SCC in a Sunda pangolin and expands the known disease spectrum in this critically endangered species.

A captive male Japanese raccoon dog (Nyctereutes procyonoides viverrinus) presented with medial shoulder luxation. The animal had previously undergone left hindlimb amputation following a traffic accident and exhibited severe dysfunction of the right hindlimb due to chronic medial patellar luxation (MPL), resulting in forelimb-dependent ambulation. Closed reduction was unsuccessful, so external skeletal fixation was applied to achieve stabilization through periarticular fibrosis. The animal resumed weight-bearing shortly after surgery, and the fixator was safely removed under light sedation six weeks later. This case highlights the effectiveness of external skeletal fixation as a minimally invasive treatment for shoulder luxation in raccoon dogs.

A 9-year-old male Asian small-clawed otter (Aonyx cinereus) kept at NIFREL exhibited acute left hindlimb lameness. Under general anesthesia, physical examination revealed a positive cranial drawer sign on the left stifle, and cranial tibial displacement with osteoarthritic changes was observed on the stifle radiograph, leading to a diagnosis of cranial cruciate ligament (CCL) injury. The left hindlimb lameness improved with conservative management consisting of meloxicam and exercise restriction. Over a follow-up period of 953 days, the left gait remained stable with minimal radiographic progression of degenerative joint disease. In Asian small-clawed otters, this case adds to the limited body of knowledge on CCL injuries and demonstrates the viability of conservative treatment depending on clinical presentation.