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Topic:Histopathology

Histopathology in horses involves the microscopic examination of tissue samples to study the manifestations of disease. This field provides insights into the structural and cellular changes that occur in equine tissues as a result of various pathological conditions. Common applications of histopathology in equine medicine include the diagnosis of neoplastic, inflammatory, and degenerative diseases. Techniques such as tissue staining and immunohistochemistry are employed to identify specific cellular components and pathological markers. This page aggregates peer-reviewed research studies and scholarly articles that explore the methodologies, findings, and implications of histopathological investigations in equine health.
Chronic hepatitis in horses with persistent equine hepacivirus infection.
Equine veterinary journal    December 25, 2025   Volume 58, Issue 2 444-457 doi: 10.1111/evj.70124
Jager MC, Luethy D, Shallop S, Cathcart J, Divers TJ, Tan JY, Beasley EM, Johnson P, Leduc L, Smith C, Jamieson CA, Magdesian KG, Van de Walle GR....Equine hepacivirus (EqHV) is closely related to hepatitis C virus (HCV), which causes persistent infection and chronic hepatitis in people. Information on persistent EqHV infection and hepatitis is limited. Objective: To report 19 cases of chronic hepatitis and persistent EqHV infection. Methods: Mixed retrospective and prospective case series. Methods: Inclusion criteria were: (1) chronic hepatitis, defined as persistently increased serum liver biomarkers, increased serum liver biomarkers accompanied by histopathological evidence of chronicity, for example, fibrosis, or both; (2) positive ser...
Beneath the surface: gut microbes, cyathostomins and resident immune cells – Characterising the baseline.
International journal for parasitology    December 7, 2025   104755 doi: 10.1016/j.ijpara.2025.11.007
Yerlikaya Z, Miranda-CasoLuengo R, Jahns H, Byrne O, Meijer WG, Mulcahy G, Walshe N.Cyathostomins are the most prevalent and currently considered the most pathogenic gastrointestinal nematodes in horses. Their life cycle includes an encystment phase within the large intestinal mucosa, where up to 90 % of the total worm burden resides. Clinical disease ranges from chronic protein-losing enteropathy to acute, sometimes fatal, typhlocolitis. Despite their significance, the ecological interplay between cyathostomins, the host immune response, and the gut microbiota remains poorly understood. To our knowledge, this is the first study to investigate these interactions at the mucos...
Histomorphometric characterization of the endometrium in mules (Equus mulus): An approach to endometritis/endometrosis.
Animal reproduction science    December 2, 2025   Volume 284 108056 doi: 10.1016/j.anireprosci.2025.108056
Mules (Equus mulus), as sterile hybrids between mares and donkeys, present a unique uterine morphology and physiology that remains poorly characterized. This study provides the first histomorphometric evaluation and transcriptional profiling of the endometrium in adult mules. To achieve this, endometrial biopsies were analysed using quantitative stereology, histological classification (Kenney-Doig system), and qPCR of key immune-related and fibrotic genes. Histometric analyses revealed that the stratum spongiosum was the predominant component of the mule endometrium (mean volume density: 84.7â...
Generalized steatitis in a miniature horse filly with laminitis and a positive outcome at 18-month follow-up.
The Canadian veterinary journal = La revue veterinaire canadienne    December 1, 2025   Volume 66, Issue 12 1292-1296 
Johnson A, Karam B, Schroeder O, McKaig L, Loesch K.A 12-month-old miniature horse filly was presented because of laminitis, suspected lymphangitis, and pyrexia. Although the filly's initial physical examination and diagnostic tests suggested an infectious etiology, ultrasonographic findings were suspicious for generalized steatitis. This was confirmed histopathology. The filly experienced full recovery with continued resolution of clinical signs at 18 mo after presentation. This case included aspects similar to those of previously reported clinical presentations, as well as long-term follow-up in a breed that is not overrepresented, providing...
Thyroid Disease in Horses-Retrospective Case Series on Patients Examined for Thyroid Disease in an Equine University Clinic (2009-2024).
Veterinary sciences    November 27, 2025   Volume 12, Issue 12 1127 doi: 10.3390/vetsci12121127
Stoeckle SD, Stage HJ, Gehlen H.Thyroid diseases in horses are rare and pose challenges for veterinarians due to the complexity of clinical and diagnostic approaches. This retrospective case series describes cases of equine thyroid disease in a referral hospital population. Files of horses examined for suspected thyroid disease at an equine university clinic between 2009 and 2024 were reviewed. Data from nine horses examined for suspected thyroid disease, including signalment, clinical presentation, laboratory results, imaging findings, fine needle aspirates, biopsies, diagnoses, and treatments, were summarised. Diagnoses in...
Outbreak of digital extensor dysfunction compatible with acquired equine polyneuropathy observed for the first time in Iceland.
Acta veterinaria Scandinavica    November 26, 2025   Volume 67, Issue 1 50 doi: 10.1186/s13028-025-00835-4
Björnsdóttir S, Sigurðardóttir ÓG, Oddsdóttir C, Reynisdóttir I, Hanche-Olsen S, Gröndahl G.Acquired equine polyneuropathy is a neuromuscular syndrome characterized by digital extensor dysfunction, primarily affecting the pelvic limbs, with consistent, repeated knuckling. Despite being recognized as an emerging disease in Scandinavia since 1995, the aetiology remains unknown, and cases have been limited to Norway, Sweden, and Finland. Methods: On a combined breeding and training farm in Iceland, 30 out of 145 horses (21%) presented with acute pelvic weakness, pelvic limb digital extensor dysfunction, knuckling and/or recumbency, from May to August 2019. The affected horses, aged 2-9Â...
Fibrocartilaginous Emboli in a 15-Year-Old Pony Mare.
Veterinary medicine and science    November 14, 2025   Volume 11, Issue 6 e70699 doi: 10.1002/vms3.70699
Kyle-LaBell E, Andersson A, Baughman B.Fibrocartilaginous embolic myelopathy (FCE) was diagnosed in a 15-year-old pony mare by histopathologic examination of the spinal cord. The horse was euthanized and submitted for necropsy following focal seizures and lateral recumbency for approximately 12 h. Histopathology of spinal cord segments C5-C7 revealed severe ischemic myelomalacia with intravascular amorphous material that stained positive with Alcian Blue, consistent with cartilaginous matrix. These features in addition to the acute onset of clinical signs are characteristic for FCE. This case report describes the clinical and histo...
Granulosa cell tumor in Arabian mares: prevalence, risk factors, clinical and histopathological findings and outcome of surgical removal.
Frontiers in veterinary science    November 13, 2025   Volume 12 1689782 doi: 10.3389/fvets.2025.1689782
Derar D, Ali A, Al-Sobayil F, Refaai W.Granulosa cell tumors (GCTs) represent the most common ovarian neoplasms in mares, yet data on their epidemiology, risk factors, and clinical outcomes in Arabian horses are limited. Understanding their prevalence and diagnostic features is crucial for improving fertility management in this breed. Unassigned: Clinical records from 807 Arabian mares housed on 35 stud farms in central Saudi Arabia were retrospectively reviewed to determine the prevalence of GCT and potential risk factors, including age, parity, and anabolic steroid use. Twenty-four confirmed cases were further investigated using ...
Behavioral and orthopedic issues in geldings with Postcastration adhesions: A retrospective study of 35 cases.
Research in veterinary science    September 23, 2025   Volume 196 105910 doi: 10.1016/j.rvsc.2025.105910
Domańska-Kruppa N, Benoit P, Żukiewicz-Benoit K, Domino M, Kliczkowska K, Szubart M, Stefanik E.Limited data is available on the diagnostic and therapeutic methods for pathologies caused by scarring after castration. It is well recognized that specific behaviors or untypical hindlimb lameness may be observed in geldings with gelding scars and adhesions caused by spermatic cord remnants after castration OBJECTIVES: To describe how to diagnose movement disorders associated with excessive adhesions caused by spermatic cord remnant after castration and to present a successful surgical treatment method. Methods: To assess the impact of gelding scars on horses' movement and behavior, medical r...
Cone beam computed tomographic myelography in horses with cervical vertebral compressive myelopathy.
Equine veterinary journal    September 18, 2025   doi: 10.1111/evj.70094
González-Medina S, Barrett MF, Aboellail TA, Nelson BB, Nout-Lomas YS.While computed tomographic (CT) myelography is increasingly available and has been evaluated in alive horses, objective criteria for diagnosing cervical vertebral compressive myelopathy (CVCM) are lacking. Objective: To establish morphometric dimensions of the cervical vertebral canal and spinal cords from horses with CVCM and compare those to unaffected horses with the use of cone beam CT (CBCT). Methods: Prospective observational study. Methods: Four control horses and ten horses with CVCM underwent diagnostic imaging and histopathology. Morphometric measurements were obtained from cervical ...
Equine maxillofacial intraosseous cystic lesions: a retrospective study of 17 cases.
Frontiers in veterinary science    September 10, 2025   Volume 12 1644866 doi: 10.3389/fvets.2025.1644866
Kelley JL, Rawlinson JE, Bell CM.Cystic and pseudocystic masses of the equine maxilla and mandible are rare lesions that result in clinically significant morbidity and/or mortality for the patient. Previous literature consists of case reports or case series. Few studies have addressed the variety of cystic lesions and comparative features. The aim of this study was to retrospectively describe the clinical signs, imaging findings, histopathologic diagnoses, treatments, and clinical outcomes for cystic masses in the equine maxilla and mandible. Unassigned: Cases were recruited from six sources including a pathology laboratory, ...
Equine Sarcoid Arising From the Medial Caruncle With Invasion of the Third Eyelid in a Quarter Horse Gelding.
Veterinary ophthalmology    September 4, 2025   Volume 29, Issue 2 e70074 doi: 10.1111/vop.70074
Plotsker NM, Taylor R, Coffin HR, Beatty A, Newbold G, Knickelbein KE.To describe the clinical and histologic features of a sarcoid arising from the medial caruncle with spread to the third eyelid of a horse. Methods: A 20-year-old Quarter Horse gelding. Methods: An incisional biopsy of the medial caruncle mass was initially performed, with histopathology suggesting a sarcoid or other spindle cell neoplasm. The mass grew rapidly following the biopsy, expanding to affect the third eyelid and adjacent superior palpebral conjunctiva. A complete third eyelid and medial caruncle excision with resection of affected palpebral conjunctiva and adjunctive cryotherapy was ...
[Unilateral leiomyoma in the spermatic cord – a reason for intermittent colic in stallions?].
Tierarztliche Praxis. Ausgabe G, Grosstiere/Nutztiere    September 2, 2025   Volume 53, Issue 4 272-279 doi: 10.1055/a-2638-4414
Hegger A, Köhne M, Gerhauser I, Görgens A.A 19-year-old Oldenburg stallion was presented multiple times over the course of several months with recurrent colic signs. At each examination, an enlargement of the scrotum was noted, which could not be further specified by palpation and ultrasonographic examination. The increase in circumference was noted both on palpation and on inspection and the size remained unchanged throughout. No special findings were noted during the general examination and the special examination of the colic patient. A few months after the first onset of symptoms, a chicken egg-sized mass was palpated on the right...
Imaging Findings of Congenital Distal Interphalangeal Joint Dysplasia in a 3-Month-Old Friesian Foal. Giessen EJM, Stas EKL, Grinwis GCM, Veraa S.A 3-month-old Friesian colt presented with severe, progressive distal limb lameness in two limbs. Radiographic and postmortem full-body CT imaging revealed severe articular deforming osteolysis and osteoproliferation at the dorsodistal navicular bone margin and the adjacent distal phalanx proximo-palmar/proximo-plantar margin in two limbs, with the remainder of the distal interphalangeal joint being unaffected. Multiple other joints showed small osteolytic subchondral defects. Postmortem histopathological examination confirmed focal joint disease of both distal interphalangeal joints, without ...
Neoplastic and non-neoplastic swellings of the external genitalia in horses and donkeys: clinical, histopathological, and treatment outcomes.
Frontiers in veterinary science    August 5, 2025   Volume 12 1613601 doi: 10.3389/fvets.2025.1613601
El-Shafaey ES, Hamed M, Amin Y, Alkhodair KM, Shousha S, Aljazzar A, El Sebaei MG, Mosbah E.External genitalia swellings represent diagnostic and treatment challenges in equids. Thus, the present study aimed to describe the clinical, histopathological, and treatment outcomes of external genitalia swellings in horses and donkeys. Unassigned: Seventy-five equids (49 horses and 26 donkeys) from 6 months to 8 years were enrolled based on the clinical evidence of external genital swellings. The descriptive details, including sex, age, lesion location, and treatment outcomes, for each case were recorded and analyzed. Unassigned: Twenty forms of external genital swellings were recorded ...
Histological Study of the Normal Proximal Third Interosseus Muscle Enthesis in the Equine Pelvic Limb.
Anatomia, histologia, embryologia    July 29, 2025   Volume 54, Issue 4 e70059 doi: 10.1111/ahe.70059
Joostens Z, Audigié F, de la Rebière de Pouyade G, Garigliany MM, Busoni V.In human medicine, the enthesis, or tendon-to-bone insertion, is generally considered a linked entity or 'enthesis organ' and plays a crucial biomechanical role. This study aimed to histologically assess the equine proximal third interosseus muscle (suspensory ligament) enthesis in 10 pelvic limbs from 7 horses. The area of the proximal third interosseus muscle enthesis was divided into 6 compartments based on post-mortem computed tomography and prepared for histology using haematoxylin/eosin and trichrome staining. The proximal third interosseus muscle enthesis showed a fibrocartilaginous nat...
Gastric Candidiasis in Five Horses: A Case Series.
Microorganisms    July 25, 2025   Volume 13, Issue 8 1746 doi: 10.3390/microorganisms13081746
Neira-Egea P, Alamar Malvoisin C, de la Cuesta-Torrado M, Bautista-Erler C, Vitale V, Jolly S, Cesarini C. spp. are ubiquitous yeasts that are part of most mammals' microbiota and can become opportunistic pathogens under predisposing conditions. Interestingly, recent studies in human medicine report an increased abundance of spp. in association with inflammatory bowel disease (IBD). Gastrointestinal candidiasis has been primarily reported in neonatal foals, but not in adult horses. The aim of this study is to describe the morphological, histopathological, and microbiological features of gastric lesions associated with infiltration in five horses referred to two tertiary hospitals for different r...
Histopathological and molecular evaluation of hydatid cysts according to necropsy findings of 52 equids in Türkiye.
Journal of helminthology    July 24, 2025   Volume 99 e82 doi: 10.1017/S0022149X25100552
Celik F, Karabulut B, Uslug M, Cankaya E, Eroksuz Y, Simsek S. is a parasitic cestode primarily maintained within an equine-canine life cycle, with horses, donkeys, mules, and other ungulates serving as intermediate hosts. Although has historically been considered non-zoonotic, recent molecular studies suggest that this assumption may need to be reevaluated. This study aimed to investigate the presence and molecular characterization of in equids from Türkiye. A retrospective analysis of 52 equine necropsies performed between 2020 and 2025 identified hydatid cysts in one Arabian horse and two donkeys. Gross and histopathological examination confirmed t...
Arteritis, aneurysm and thromboembolic colic caused by migration of Strongylus vulgaris larvae in equids.
Journal of equine veterinary science    July 9, 2025   Volume 152 105650 doi: 10.1016/j.jevs.2025.105650
Souto EPF, Dantas VW, Oliveira AM, Garcia DS, Vilela VLR, Neto EGM, Mota RA, Dantas AFM.Strongylus vulgaris remains a significant cause of disease in equids, especially in regions with insufficient deworming practices. Objective: To describe the epidemiological, clinical, pathological, and parasitological findings of vascular and extravascular lesions associated with S. vulgaris in equids. Methods: A retrospective analysis was conducted on necropsy reports from equids examined at the Animal Pathology Laboratory, Federal University of Campina Grande (2000-2024), targeting cases of vascular lesions associated with S. vulgaris. Epidemiological, clinical, and pathological findings we...
Multi-Detector Helical Computed Tomography, Transrectal Ultrasonography, and Histology of the Sacroiliac Joint: A Comparative Study in Adult Warmblood Horse Cadavers.
Animals : an open access journal from MDPI    July 7, 2025   Volume 15, Issue 13 1995 doi: 10.3390/ani15131995
Mathys RA, Schmitz TR, Geyer H, Borel N, Hilbe M, Ohlerth S, Bischofberger AS.This study described, assessed and correlated ultrasonographic, computed tomographic, and histological findings in the sacroiliac joints of adult Warmblood horse cadavers. In total, 25 joints from 15 horses were examined post-mortem using transrectal ultrasonography and helical computed tomography. Findings on computed tomography were graded in the caudal joint third (caudally) and for the entire joint as mild, moderate, or severe. In total, 11 joints from nine horses were evaluated histologically. All joints (100%) showed abnormalities on computed tomography, and 92% (23/25) displayed abnorma...
Bilateral testicle teratoma in an equine fetus: a rare case.
Journal of equine veterinary science    June 23, 2025   105633 doi: 10.1016/j.jevs.2025.105633
Nieman RT, Lamim LI, Del Fava C.Fetal loss in mares can result from a range of causes, including infectious agents or noninfectious conditions such as neoplasia, which may originate from either the fetus or the dam. Among neoplastic conditions, teratomas are rarely reported and, to date, have not been described in the equine fetal testis. Teratomas arise from the partial differentiation of pluripotent germ cells and may occur in young and adult horses, typically in cryptorchid testes. Their gross and histopathological features vary widely between cases. This report describes a rare case of bilateral fetal testicular teratoma...
Equine Veterinarian Perspectives on Mucocutaneous Tumors in Horses: A Survey-Based Study in Portugal.
Animals : an open access journal from MDPI    June 23, 2025   Volume 15, Issue 13 1853 doi: 10.3390/ani15131853
Pimenta J, Cotovio M.This study explores equine veterinarians' clinical practices regarding mucocutaneous tumors, based on a survey conducted among members of the Portuguese Association of Equine Veterinarians, and examines their perceptions of owner and buyer concerns regarding these tumors. Veterinarians expressed significantly greater concern about squamous cell carcinoma (SCC) during routine examinations ( < 0.001) compared to sarcoids and melanomas. Concern over sarcoids was significantly greater during pre-purchase evaluations compared to routine clinical exams ( = 0.03). For melanomas, a trend toward inc...
Equine sarcoids from Southern Italy: Molecular and Histopathological characterization.
Research in veterinary science    June 19, 2025   Volume 193 105777 doi: 10.1016/j.rvsc.2025.105777
Martano M, Montagnaro S, Power K, Cuccaro B, Cutarelli A, Maiolino P, Restucci B.This study investigated the presence of δ bovine papillomaviruses (BPV-1, BPV-2, BPV-13, BPV-14) in equine skin lesions from Southern Italy, focusing on equine sarcoids and their histopathological correlations. 63 equine skin samples were analysed using PCR and sequencing for BPV detection, and their histopathological features were assessed. BPV DNA was detected in 69.84% of the samples, with BPV-1 and BPV-2 being the most prevalent genotype, followed by BPV-13, while BPV-14 was not detected. BPV DNA was also found in non-sarcoid tumours and non-neoplastic conditions. Histopathological analys...
Structure Function Relationships in the Aging Superficial Digital Flexor Tendon: Implications for Injury.
The Veterinary clinics of North America. Equine practice    June 14, 2025   Volume 41, Issue 2 239-250 doi: 10.1016/j.cveq.2025.04.001
Zamboulis DE, Thorpe CT.The high stresses and strains experienced by the superficial digital flexor tendon (SDFT) make it prone to age-related injury. The SDFT exhibits cellular and structural specializations, localized to the interfascicular matrix (IFM), enabling it to resist its extreme mechanical environment. With aging, these specializations are lost, impacting the ability of the tendon to withstand repeated loading. Within the IFM, there is loss of mechanical properties and organization accompanying cell senescence and a decreased resolution of inflammation. Developing therapeutics to reverse these changes may,...
Sudden death in a Thoroughbred stallion: cardiac tamponade due to transverse aortic rupture with bone metaplasia and calcification.
Journal of equine science    June 12, 2025   Volume 36, Issue 2 75-79 doi: 10.1294/jes.36.75
Maeda Y, Kanno C, Sugiyama M, Yamamoto R, Sato S, Ando R, Noda R, Kawaguchi H, Takahashi F.A 17-year-old Thoroughbred stallion died suddenly after grazing. Necropsy revealed massive hemorrhage in the pericardial sac, suggesting cardiac tamponade. Aortic perforation was observed at the aortic origin, and hemorrhage was observed in and around the epicardium. Superficial observation of the aortic lumen revealed a transverse tear of the aortic wall at the bases of the right semilunar valve and septal semilunar valve. Fibro-osseous changes with calcification were histopathologically observed at the site of the rupture. A nodular goiter was observed in the left thyroid gland. The horse di...
Sinonasal angiofibroma in a horse.
Journal of comparative pathology    May 13, 2025   Volume 219 88-90 doi: 10.1016/j.jcpa.2025.05.003
Schollmeyer M, Liebler-Tenorio EM, Felton C, Kohl S, Ulrich R.A 34-year-old Haflinger gelding presented with a unilateral, expansile, intranasal mass that regrew after partial excision. After euthanasia, a large pedunculated mass that originated from the left caudal maxillary sinus and obliterated the left nasal cavity was seen by radiological and macroscopic examination. Histopathology revealed a poorly cellular, expansile, well-vascularized neoplasm composed of a loosely arranged meshwork of spindle cells and collagen fibres. Spindle cells were immunopositive for alpha-smooth muscle actin and occasionally for vimentin, whereas endothelial cells immunol...
First report on equine papillomavirus type 1 in Arabian horses in Saudi Arabia: Clinical, histopathological, and molecular characterization.
Open veterinary journal    April 30, 2025   Volume 15, Issue 4 1798-1802 doi: 10.5455/OVJ.2025.v15.i4.32
Al-Hammadi MA.Equine papillomavirus type 1 (EcPV-1) causes cutaneous papillomatosis in horses, which is characterized by benign, proliferative epithelial lesions. Despite its global presence, the prevalence and characterization of EcPV-1 in Arabian horses in Saudi Arabia have not been previously reported. Unassigned: This study is the first to identify and comprehensively analyze EcPV-1 in four Arabian horses presenting with multiple raised, verrucous lesions around the muzzle and lips. Unassigned: This study involved clinical examination, skin biopsy collection, histopathological examination, and molecular...
Chronic idiopathic myopathy in Icelandic horses: A case series.
Equine veterinary journal    April 24, 2025   Volume 57, Issue 5 1341-1346 doi: 10.1111/evj.14519
Hansen S, Hopster-Iversen C, Berg L, Fjeldborg J, Massey C, Piercy RJ, Carstensen H.Exertional myopathies are recognised as a cause of poor performance in equines. In Icelandic horses presenting reduced performance and/or multi-limb lameness, no specific myopathy has been identified. Objective: To characterise the clinical presentation and histopathological findings in muscle biopsy samples from Icelandic horses demonstrating poor performance. Methods: Case series. Methods: Phenotypic characteristics, clinical examination and diagnoses of 17 Icelandic horses were studied. All horses had a resting serum creatine kinase (CK) and aspartate transaminase activities measured, and C...
Histological and morphometric changes in cardiac conduction fibers after spontaneous myocardial infarction in horses and dogs.
Veterinary world    April 19, 2025   Volume 18, Issue 4 827-836 doi: 10.14202/vetworld.2025.827-836
Gómez-Torres F, Ballesteros-Acuña L, Ruíz-Sauri A.Arrhythmic sudden cardiac death in dogs and horses often results from ventricular arrhythmia secondary to myocardial damage. Despite this, limited data exist on the histomorphometric changes in cardiac conduction fibers (CCFs) and cardiac conduction cells (CCCs) following spontaneous myocardial infarction (MI). This study aimed to characterize morphometric and histological alterations in conduction fibers and their junctions with cardiomyocytes in infarcted hearts of horses and dogs. Unassigned: Ten hearts from horses and 10 from dogs that had died suddenly were examined. Histological and immu...
Assessing Cadmium Levels in Horses Imported from the European Union and Slaughtered in Italy.
Veterinaria italiana    April 14, 2025   Volume 61, Issue 2 doi: 10.12834/VetIt.3692.31893.2
Dimuccio MM, Ceci E, Bonerba E, Celentano FE, De Marzo P, Leone R, Sportelli S, Bozzo G.The aim of this study was to evaluate cadmium (Cd) concentrations in horses imported from various European Union countries and slaughtered in Italy. In addition, we assessed the potential correlation between Cd levels in tissues and organs, and Cd-related gross and histological lesions. The animals were divided into six groups based on age and geographical origin. Among the 430 animals examined, gross renal lesions were observed in only two kidney samples from Polish horses, which also had the highest Cd concentrations: 9.1 mg/kg w/w and 8.23 mg/kg w/w, respectively. Further histological a...