Histology in horses involves the microscopic examination of tissues to understand their structure and function. This field of study provides insights into the cellular composition and architecture of equine tissues, aiding in the diagnosis of diseases and the assessment of tissue health. Histological analysis is used to identify pathological changes, such as inflammation, neoplasia, or degenerative conditions, by examining tissue samples obtained through biopsies or necropsies. Common tissues studied in equine histology include skin, muscle, bone, and internal organs. This page compiles peer-reviewed research studies and scholarly articles that explore histological techniques, findings, and their applications in equine veterinary medicine.
Swerczek TW.Small but significant numbers of primary and secondary spermatocytes and spermatids have been observed in the semen of some Thoroughbred stallions. Extensive histological examination of the testes of affected animals has not been undertaken but in one young stallion which died as the result of a leg injury, the premature dehiscence of these cells seemed to be related to segmental defects within the seminiferous tubules. The causes of lesions leading to premature shedding of germ cells are discussed.
Steven DH, Samuel CA.The study of the equine placenta, which began in Venice in 1598, has a long but discontinuous history. Early observations were purely morphological, but new techniques have stimulated a broader and more functional approach. Histological and ultrastructural observations at various stages of pregnancy have shown that the fetal side of the placenta comes to acquire certain features in common with the air-blood barrier of the mammalian lung. These changes may reflect the increasing O2 requirements of the fetus as gestation proceeds.
Hernández-Jáuregui , González-Angulo A.Electron microscopy and immunofluorescence techniques were used to study the various epithelial cells in the endometrial cups of ten pregnant mares, and in the uterine epithelium of one non-pregnant mare. Evidence was obtained which suggested that epithelial gland cells within the endometrial cups, as distinct from the hypertrophied decidual-like cells in the cup, may synthesize PMSG. The suggestion does not agree with the findings of other workers in the fetal origin (chorionic girdle cells) of this gonadotrophin.
Moor RM, Allen WR, Hamilton DW.Biochemical and morphological studies were carried out to determine the origin and histogenesis of endometrial cups in mares. A wide range of fetal and maternal tissues were cultured in vitro and their ability to secrete gonadotrophin (PMSG) was monitored. High levels of PMSG were produced in culture only by cells from the restricted area of the equine trophoblast known as the chorionic girdle which is an annular band of highly specialized cells at the junction of the allantois and the regressing yolk sac. The morphological appearance of girdle cells after cultivation in vitro and after alloge...
Hay MF, Allen WR, Lewis IM.Graafian follicles of various sizes obtained from mares at different stages of the oestrous cycle were examined histologically and histochemically for delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity and related enzymes. The 3beta-HSD activity was not found in the theca interna of any follicles but was present in the membrana granulosa of well-vascularized large follicles in the late luteal phase of the cycle and at oestrus. These findings indicate that pregnenolone cannot be converted into progesterone in the theca interna. It is suggested that this conversion occurs in the memb...
Flood PF, Marrable AW.The distribution of several hydroxysteroid dehydrogenases (HSD) was examined in a variety of equine placental and fetal tissues. The main points of interest were: (a) the lack of dehydrogenase activity in the gonad, (b) the appearance of a variety of HSDs in the trophoblast as early as 13 days of gestation, (c) the histochemical similarity between the cells of the trophoblast and the endometrial cup, and (d) the restriction of the strong endometrial 17beta-HSD reaction to those parts of the uterine epithelium directly apposed to the trophoblast.
Hay MF, Allen WR.Gonadal tissue obtained at about 50-day intervals from Days 60 to 300 of gestation was examined histologically, histochemically and in the electron microscope. The marked enlargement of the gonads (ovaries or testes) reached a peak around Day 250 and was caused by hypertrophy and hypoplasia of interstitial cells. These cells had all the ultrastructural characteristics of a steroid-secreting cell but delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) was not detected at any stage of their development. There was no significant change in the ultrastructure of the interstitial cells between Day...
Guseĭnov TS.The investigation was performed on 35 corpses of men, 8 corpses of cats, 7--of pigs and 5--of horses. The following methods were used: polychrome injection of arteries, veins, lymph capillaries and vessels, macro-microdissection, staining after van Gieson and with hematoxylin-eosin, impregnation with 0,25--1% solution of silver nitrate, dehydration and clearing, calculation of thickness of loops per 1 mm2 and their depth by means of ocular micrometer. The lymphatic bed of the serous membrane was established to be better developed in representatives of carnivora (cats) and omnivora (pigs), than...
Baker JR, Leyland A.In a histological survey of 244 tumerous growths from 155 horses, the tumours commonly found were fibromas, squamous cell carcinomas, sarcoids and papillomas, most frequently affecting the skin, external genitalia, eye and orbit. The histological features that differentiate fibroblastic citaneous growths are detailed so that the clinical behaviour of these distinct neoplasms can be studied.
Ricketts SW.The author describes a technique for obtaining endometrail biopsy specimens from mares. the noraml cyclincal histology of the endometrium and anarbitarry classification histology of the endometrium and an arbitarary classification of the histopathology seen in endometrial biopsy speciemens. Previous literature on the subject is cited. Results of endometrial biopsies taken by the author from 134 barren mares, with histories of subfertility are descirbed and classified. The use of the technique and the interpretationof its find ings in relation to reproductive performance is discussed.
Mackenzie CD.The basic components of the immune system, and the defence mechanisms in the gastrointestinal tract, are briefly reviewed. Histological studies in 84 equine foetuses showed that lymphoid cells begin populating the thymic primordium at 11-12 weeks, the mesenteric lymph nodes at 13 weeks, the spleen at 25 weeks and the intestinal lamina propria at 13-14 weeks' gestation. Lymphocytes were seen in the intestinal epithelium very early in gestation. Histological signs of response to antigenic stimulation were seen in five foetuses, indicating that the horse is likely to be capable of mounting an imm...
Ramadan RO.The clinical features and pathology of an ocular melanoma in a young born-grey mare are described. The tumour, possibly arising on the cornea, invaded the eye and extra-orbital muscles. Histologically; it consisted predominantly of spindle-shaped and polygonal cells containing melanin.
Godbout M, Vargas A, Hélie P, Bullone M, Lavoie JP.To use a biopolymer delivery system to investigate the ability of interleukin (IL)-4 to recruit neutrophils into subcutaneous tissues of equids. Methods: 16 horses and 2 ponies. Methods: Animals were assigned to 3 experiments (6/experiment). Effects of recombinant equine (Req) IL-4 (100, 250, or 500 ng/site) versus a positive control (ReqIL-8; 100 ng, 250 ng, or 1 μg/site) and a negative control (Dulbecco PBSS or culture medium) on neutrophil chemotaxis were assessed after SC injection into the neck with an injectable biopolymer used as the vehicle. Tissue samples including the biopolymer plu...
Martinelli MJ, Baker GJ, Clarkson RB, Eurell JC, Pijanowski GJ, Kuriashkin IV, Carragher BO.To expand our current knowledge and to establish limits of correlation between signal intensities of the magnetic resonance (MR) image and actual macroscopic and microscopic anatomic features of the imaged structures of the equine metacarpophalangeal joint (MCPJ). Methods: The right MCPJ was obtained from 4 adult horses that were euthanatized for reasons unrelated to the musculoskeletal system. Methods: The distal portion of the right forelimbs was collected from 4 equine cadavers. The bones were drilled to provide fixed reference points and examined by MR imaging. After imaging, the joints we...
Collar EM, Zavodovskaya R, Spriet M, Hitchens PL, Wisner T, Uzal FA, Stover SM.To gain insight into the pathophysiology of equine lumbar vertebral fractures in racehorses. Objective: To characterise equine lumbar vertebral fractures in California racehorses. Methods: Retrospective case series and prospective case-control study. Methods: Racehorse post mortem reports and jockey injury reports were retrospectively reviewed. Vertebral specimens from 6 racehorses affected with lumbar vertebral fractures and 4 control racehorses subjected to euthanasia for nonspinal fracture were assessed using visual, radiographic, computed tomography and histological examinations. Results: ...
Hay AN, Witonsky SG, Lindsay DS, LeRoith T, Zhu J, Kasmark L, Leeth CM. is a ubiquitous parasite in the eastern United States, which is the principal causative agent in the neurologic disorder equine protozoal myeloencephalitis (EPM). While much is known about this protozoa's life cycle in its natural host, the opossum (), little is known of how it acts in the aberrant equine host, which displays a high incidence of exposure with a relatively low rate of morbidity. For this study, we employed the popular interferon gamma knockout mouse model to determine the potential for recrudescence of infection after treatment with the anticoccidial drug diclazuril. Mice wer...
Enders AC, Jones CJ, Lantz KC, Schlafke S, Liu IK.Invasion of trophoblast cells of the chorionic girdle into the endometrium and their subsequent dependence as endometrial cup cells on the maternal vascular system are unique features of equine gestation. This study of exocrine secretion by the endometrial glands and endocrine secretion by the cup cells was initiated to examine the relationships between and the effects of two disparate epithelial cell types sharing the endometrium. Endometrial cups were examined from day 36 to day 83 of gestation by light and electron microscopy, and immunohistochemical and lectin analysis. As the cup cells in...
Barasa A, Dazia S, Canavese B, Modica R.The dental pulp of 34 horses aged between 4 months and 20 years has been studied on India ink injected and on paraffin embedded specimens. The pulp dimensions of the first and especially of the second dentition decrease with age. This reduction is accompanied by pronounced changes of structure; the mucous connective tissue becomes a dense, irregular connective tissue. The vessels are numerous and make a network particularly rich at the margins of the pulp; they diminish with advancing age. The reduction of the pulp volume and the regression of its vascular network are particularly pronounced a...
Alitalo I, Kärkkäinen M.Ataxia caused by a focal compression of the cervical spinal cord was diagnosed in four young standardbred trotting horses. Diagnosis was verified by myelography. Changes in the cervical vertebral column were studied using microradiographic and histologic methods. In the vertebrae involved, there was irregularity of the cartilaginous growth zone, cracks with a loose fragment and disturbance in the enchondral ossification. These changes resemble osteochondrosis. Porous appearance in lateral and ventral funiculi as well as mural calcified plaques in the small vessels of the white matter were foun...
Barnard K, Leadon DP, Silver IA.Collagen, elastin and structural glycoprotein content of the lungs of 38 fetal and neonatal foals, 8 of which were showing dysmaturity or convulsive syndrome, were measured by standard biochemical means. Glycoprotein content showed little or no change between 100 and 340 days of gestation; elastin remained constant from 100 to about 260 days when there was an exponential increase up to the time of birth, while collagen content rose linearly from 100 days to birth. In dysmature animals there was significantly less collagen in the lungs at birth but the difference in elastin content between the ...
Ludewig T.Glomus organs (Hoyer-Grosser's organs) were frequently found in the corium and the subcutis of the skin of the equine and bovine mammary gland. They were most frequently situated in the border zone between the stratum profundum and the stratum superficiale corii. These specialized vascular structures (arterio-venous anastomosis) were present in all investigated skin areas. Although the glomus organs varied in size and shape, they possessed common histologic structures: an arteriole entered the connective capsule of the glomus and divided into strongly convoluted arterio-venous channels; the ar...
Rijkenhuizen AB, Nèmeth F, Dik KJ, Goedegebuure SA, Van den Brom WE.Clinical, radiographical, scintigraphical and histological effects on the navicular bone after resection of the medial and lateral palmar digital arteries in the pastern of one forelimb in ponies are evaluated. The acute disruption of the main blood supply of the distal extremity causes lameness due to the suddenness of the resection in which the collateral circulation is insufficiently developed. Because of the compensatory collateral circulation, no permanent symptoms of ischaemia occur despite the partial resection of both palmar digital arteries. Histologically the percentage of relative o...
Dagleish MP, Pemberton AD, McAleese SM, Thornton EM, Miller HR, Scudamore CL.Equine alpha-1-proteinase inhibitor (API) consists of three, occasionally four, serum glycoproteins. This study investigated the immunohistochemical localisation of equine API in paraformaldehyde fixed, paraffin embedded equine tissue samples of liver, lung, stomach, pancreas, jejunum and colon in five horses using affinity purified sheep polyclonal and protein A purified mouse monoclonal antibodies, whose specificities were verified by Western blotting. Exposing tissue sections to boiling citrate buffer greatly enhanced antigen recovery and improved immunostaining with both antibodies, result...
O'Brien M, Mochel JP, Kersh K, Wang C, Troy J.Pain management is critical to equine welfare with non-steroidal anti-inflammatory drugs (NSAID) commonly used in horses. However, systemic NSAID use is limited by harmful gastrointestinal and renal side effects. Intravenous regional limb perfusion (IVRLP) is a technique used in horses that produces high, local antibiotic concentrations while limiting systemic circulation. NSAID-IVRLP would be a novel method of local pain management while limiting systemic NSAID side effects. To date, NSAID-IVRLP administration has not been reported in horses. This study aimed to identify the pharmacokinetics ...
Sjöberg I, Law E, Södersten F, Höglund OV, Wattle O.A 3D printed self-locking device made of polydioxanone (PDO) was developed to facilitate a standardized ligation technique. The subcutaneous tissue reaction to the device was evaluated after implantation in ten horses of mixed age, sex and breed and compared to loops of poly(lactic-co-glycolic acid) (PLGA). In two of the horses, the implants were removed before closing the skin. The appearance of the implants and surrounding tissue was followed over time using ultrasonography. Implants were removed after 10 and 27 (± 1) days for histologic examination. Results: On macroscopic inspection at ...
Labens R, Raidal S, Borgen-Nielsen C, Pyecroft S, Pant SD, De Ridder T.Topical wound treatments rely on carrier formulations with little to no biological impact. The potential for a common vehicle, a propylene glycol (PG) gel, to affect wound healing measures including microbiota is not known. Microbiome characterization, based on next generation sequencing methods is typically performed on tissue or directly obtained wound fluid samples. The utility for primary wound dressings to characterize equine wound microbiota in the context of topical treatments is currently unknown. This investigation reports the topical effect of an 80% PG based gel on wound healing and...
Kramer AJ, Meziara Wilson T, Kimura S, Groover E, DeLeon-Carnes M, Neto RLALT.A 23-y-old gelding was presented to a veterinary teaching hospital with a history of chronic, refractory diarrhea. Clinically, the horse was in poor body condition, with a thickened and corrugated large intestine identified by transcutaneous abdominal ultrasonography. At postmortem examination following euthanasia, the large colon and cecum had segmental thickening of the intestinal wall with innumerable mucosal ulcers and prominent polypoid mucosal masses. Many mesenteric and hepatic lymph nodes were enlarged. Histology revealed granulomatous and ulcerative typhlocolitis and granulomatous lym...
Hewitt-Dedman CL, Kershaw LE, Schwarz T, Del-Pozo J, Duncan J, Daniel CR, Cillán-García E, Pressanto MC, Taylor SE.Magnetic resonance spectroscopy (MRS) has been used to investigate metabolic changes within human bone. It may be possible to use MRS to investigate bone metabolism and fracture risk in the distal third metacarpal/tarsal bone (MC/MTIII) in racehorses. Objective: To determine the feasibility of using MRS as a quantitative imaging technique in equine bone by using the H spectra for the MC/MTIII to calculate fat content (FC). Methods: Observational cross-sectional study. Methods: Limbs from Thoroughbred racehorses were collected from horses that died or were subjected to euthanasia on racecourses...
Watkins A, Engiles J, Long A, Brandly J, Hopster K.Large colon volvulus is a cause of colic in horses with high morbidity and mortality when not promptly treated. More treatment options are needed to improve the outcome of these cases by protecting against the damage caused by ischaemia and reperfusion injury. Objective: To determine the effect of preconditioning with dexmedetomidine prior to induction of ischaemia-reperfusion (IR) injury in a large colon volvulus model in the horse. Methods: Randomised blinded in vivo experiments. Methods: Horses received either a dexmedetomidine (DEX) or saline (CON) constant rate infusion (CRI) immediately ...
Labordère AL, Ruzickova P, Kamus LJ, Beauchamp G, Malo A, Richard H, Laverty S.To evaluate vascularity of the synovial membrane covered septum (SMS) separating the tarsocrural (TC) and proximal intertarsal (PIT) joints (Part 1) and compare two methods of transection, electrosurgical or Ferris Smith rongeur (FS rongeur) (Part 2). Methods: Experimental study. Methods: Part 1, 10 SMS (n = 5 horses). Part 2, six horses (n = 12 tarsi). Methods: In part 1, SMS harvested postmortem were each divided into eight regions of interest (ROIs), processed for histology, and immunostained with anti-α-actin antibody for blood vessel identification. Vascular density was calculate...
Cuccato M, Bertuglia A, Divari S, Brambilla E, Grieco V, Bollo E, Scaglione FE.An aborted female foal was submitted for necropsy. During the gross examination, the ovaries were pale, grayish, and enlarged (6 × 5 cm), with a well-developed vascular structure surrounding the external surface; the cut surface of the ovaries showed a brownish parenchyma with white follicular areas mainly localized in the peripheral region. The ovaries were fixed for histological investigations. The histological evaluation of the ovaries showed polygonal-shaped cells with abundant cytoplasm and round or oval nuclei, arranged in cords of single cells. The tissue architecture was characterized...
Tippen SP, Metzger CE, Sacks SA, Allen MR, Mitchell CF, McNulty MA.Bisphosphonates are widely used in equine athletes to reduce lameness associated with skeletal disorders. Widespread off-label use has led to concern regarding potential negative effects on bone healing, but little evidence exists to support or refute this. Objective: To investigate the influence of clinically relevant doses of tiludronate on bone remodelling and bone healing. Methods: Randomised, controlled in vivo experiments. Methods: Each horse had a single tuber coxae biopsied (Day 0), then were divided into a treatment (IV tiludronate) or control (IV saline) group. Treatments were admini...
Dubuc J, Schneider MJ, Dubuc V, Richard H, Pinsard M, Bancelin S, Legare F, Girard C, Laverty S.Investigate meniscal extracellular matrix degradation. Equine menisci ( = 34 from 17 horses) were studied. Site-matched sections were cut and scored from three regions (ROIs; = 102) and stained for histology, proteoglycan (safranin O and fast green), aggrecan, and collagen cleavage (NITEGE, DIPEN, and C1,2C antibodies, respectively). Picrosirius red and second harmonic generation microscopy were performed to investigate collagen ultrastructure. A total of 42 ROIs met the inclusion criteria and were included in the final analysis. The median (range) ROI histological score was 3 (0-9), providin...
Stedman JM, Lutter JD, Hallman C, Laverty S, Richard H, Santschi EM.High-field MRI of the equine stifle provides high-resolution information about soft tissues that is useful in the diagnosis of stifle lameness. The aim of this prospective anatomic study was to describe the appearance, position, size, and shape of the equine femorotibial ligaments, meniscal ligaments, and menisci using 3 Tesla MRI under extended, extended-loaded, and flexed conditions. Additionally, histologic examination of the collateral and cruciate ligaments (CLs) of a single stifle was performed to compare with MRI images. In extension, mild variations in MRI signal intensity were apparen...
Asgenbaatar N, Yi M, Wang X, Ulaangerel T, Shen Y, Wen X, Du M, Dong X, Mengkh Y, Dugarjav M, Bou G.The preparation of paraffin sections is an important experimental technique in animal histological research, and key factors that determine the quality of a section include the dehydration time, waxing time, and drying temperature of the paraffin section. Paraffin sections obtained from testis tissue of adult horses exhibited higher quality with clear tissue structure and complete cell morphology after they underwent gradient dehydration for 6 hours, were immersed in wax for 60 minutes, and were dried in a 75-degree oven for 15 minutes. The detailed, optimized procedures that are developed in ...
Lin ST, Foote AK, Bolas NM, Sargan DR, Murray RC.Information regarding the histopathology of the proximal phalanx (P1) sagittal groove in racehorses is limited. Twenty-nine cadaver limbs from nine Thoroughbred racehorses in racing/race-training underwent histological examination. Histological specimens of the third metacarpal/metatarsal (MC3/MT3) parasagittal grooves and P1 sagittal grooves were graded for histopathological findings in hyaline cartilage (HC), calcified cartilage (CC), and subchondral plate and trabecular bone (SCB/TB) regions. Histopathological grades were compared between (1) fissure and non-fissure locations observed in a ...
Korim F, Revajová V, Koľvek F, Bujňák L, Hreus S, Všianský D.The parotid duct has been reported to be the most common site of sialoliths in horses. In this case report, we described the first confirmed case of the equine sialolithiasis in Slovakia. The work was aimed to describe the transcutaneous approach to removing the sialolith, which manifested as a hard painless mass in the area of the maxillary cheek teeth, in a 14-year-old Slovakian warmblood mare. Pathological-anatomical and histological examination after extirpation confirmed the presence of parotid duct ectasia resulting from calculus. The mineral composition of the sialolith was determined w...
Okudaira M, Cresswell EN, Wollman CW, McDonough SP, Engiles JB, Reesink HL.To describe the development and maturation of equine proximal sesamoid bones (PSBs) in fetuses and young horses using radiography, microcomputed (micro)-CT, and histology. Methods: A descriptive study. Forelimb PSBs from 12 equids ranging in age from 105 days of gestation to 540 days postgestation were evaluated. Radiography was used for preliminary assessment of metacarpophalangeal joint and PSB mineralization, and micro-CT imaging was performed to assess mineralized PSBs. Tissue volume, bone volume fraction, height, width, depth, trabecular thickness, and anisotropy were quantified from midp...
Chiara M, Mariaelena C, Alessandro C, Davide B, Lavinia C, Paola MM, Barbara L, Chiara DP, Flagiello F, Pia PM.The advanced-PRF+ (A-PRF+) is a platelet concentrate, showing a higher concentration of growth factors, an increased number of cells and looser structure of the fibrin clot than leukocyte-PRF. A high variability in the size of PRF associated with patients, haematological features and centrifugation protocols was reported. The aims of this study were to evaluate the feasibility of A-PRF+ production in the field and the correlation between haematological parameters, macroscopic and microscopic features in equine A-PRF+. Samples from twenty Standardbred horses (3-7 years) were harvested with gla...
Fukuda K, Mita H, Kuroda T, Tamura N, Kuwano A, Sato F, Takahashi T.To clarify the anti-inflammatory effect of platelet lysate (PL) on equine persistent synovitis by using a model of synovitis induced by monoiodoacetic acid (MIA). Methods: Nonseptic synovitis was induced by administering MIA into both antebrachiocarpal joints of 6 clinically healthy horses on day 0. On days 23, 30, and 37, carpal circumference measurement and synovial fluid collection for assays (leucocytes, LDH, tumor necrosis factor-α, and TGF-β1) were performed, after which PL was injected into 1 antebrachiocarpal joint and saline into the contralateral joint. Synovium and synovial fluid ...
Damone J, Bass L, Gadomski B, Rao S, Frank C, Moorman VJ.The equine digital cushion (DC) has been a poorly understood structure regarding its mechanical properties and composition. The objective of this study was to develop a sampling technique and to compare the biomechanical and histologic properties of DC between lame and non-lame forelimbs. Both forefeet from horses with induced carpal lameness were radiographed prior to humane euthanasia. Radiographs were used to guide sample collection of two, post-mortem, midline DC samples, palmar and dorsal, via an 8mm biopsy punch. Samples were subjected to compressive testing to determine elastic modulus....
Peretti JC, Dos Santos AB, Davi Dos Santos E, Machado TP, Pescador CA, Quillas LJA, Milani VM, Picetti TS, da Motta AC.Lymphoma is the most common tumor of hematopoietic origin in horses. The course of the disease and clinical signs vary greatly, depending on tumor location and extent. The aim of this report is to describe the occurrence of T-cell-rich oral large B-cell lymphoma with marked local infiltration in a 25-year-old Crioula mare. The mare showed an increase in volume on the right side of its face, dyspnea, anorexia, and progressive weight loss. The clinical assessment showed that the lesion was located in the rostral and caudal sinuses and was markedly invasive to adjacent structures. The autopsy rev...
