Effect of lactic acid addition to equine whole blood on platelet aggregation measured by impedance aggregometry.

BACKGROUND: Acidemia in sick or injured horses is often due to lactic acid accumulation. Alterations in platelet function and hemostasis are among numerous deleterious effects caused by decreased physiologic pH. OBJECTIVES: We aimed to evaluate the effect of hyperlactatemia and resultant acidemia on platelet aggregation in equine whole blood using impedance aggregometry. METHODS: Platelet aggregation was measured using the Multiplate analyzer in whole blood from 34 healthy horses at baseline and after in vitro addition of lactic acid to adjust the pH. Platelet aggregation of each sample was quantified by the area under the curve measurement reported by the Multiplate system. The association between platelet aggregation and pH was analyzed using a linear mixed-effects model. The association of baseline platelet aggregation with hematocrits (Hcts), white blood cell (WBC) counts, and platelet counts was evaluated using Pearson's correlations. RESULTS: There was a significant association between acidemia and decreased platelet aggregation. No significant correlations were detected between platelet aggregation and Hct, WBC count, or platelet count. Platelet aggregation measured in healthy horses using the Multiplate analyzer showed substantial variation between animals. CONCLUSIONS: Acidemia caused by the addition of lactic acid to equine whole blood was associated with a mild though statistically significant decrease in platelet aggregation. In conjunction with other factors, this change may contribute to morbidity-related disorders of hemostasis, although its precise clinical relevance is uncertain.

Nonclassified Lymphoma as a Cause of Radial Nerve Paralysis in a Horse.

A 4-year-old American Quarter Horse gelding was evaluated for acute non-weight-bearing lameness of the right thoracic limb with swelling in the right shoulder region. Physical examination revealed radial nerve paralysis of unknown etiology. The primary differential diagnosis was musculoskeletal trauma. Ultrasonography of the right shoulder region identified a heterogeneous mass that extended from the point of the shoulder to the thoracic inlet. Cytologic analysis of fluid collected by fine needle aspirate of the mass was consistent with large cell lymphoma. Based on the cytological findings, locally invasive neoplasia was diagnosed and considered the likely cause of the radial nerve paralysis. Because of the poor prognosis, the horse was euthanized, and postmortem examination confirmed the diagnosis of a nonclassified large cell lymphoma that extended from the deep tissues of the right pectoral muscle group into the thoracic inlet and pleural cavity, as well as the right brachial plexus. The mass in the region of the brachial plexus encompassed and mechanically compressed all of the nerves within the area, resulting in the clinical sign of radial nerve paralysis. Although neoplasia as a cause of radial nerve paralysis is rare, it should be considered as a differential diagnosis, regardless of age.

Hemoabdomen secondary to high grade lymphoma.

A 10-year-old castrated male Labrador retriever dog was presented for evaluation of a right elbow mass. Mandibular lymphadenopathy was noted on physical examination. Following sudden death after discharge, a necropsy was performed. Cause of death was determined to be due to hemoabdomen secondary to high grade lymphoma.

Hémoabdomen secondaire à un lymphome de haut grade. Un chien mâle Labrador retriever castré âgé de 10 ans a été présenté pour l'évaluation d'une masse au coude droit. Une lymphadénopathie mandibulaire a été observée à l'examen physique. Après une mort soudaine consécutive au congé, une nécropsie a été réalisée. La cause de la mort a été déterminée comme étant un hémoabdomen secondaire à un lymphome de haut grade.(Traduit par Isabelle Vallières).

Novel Biomarkers of Human GM1 Gangliosidosis Reflect the Clinical Efficacy of Gene Therapy in a Feline Model.

GM1 gangliosidosis is a fatal neurodegenerative disease that affects individuals of all ages. Favorable outcomes using adeno-associated viral (AAV) gene therapy in GM1 mice and cats have prompted consideration of human clinical trials, yet there remains a paucity of objective biomarkers to track disease status. We developed a panel of biomarkers using blood, urine, cerebrospinal fluid (CSF), electrodiagnostics, 7 T MRI, and magnetic resonance spectroscopy in GM1 cats-either untreated or AAV treated for more than 5 years-and compared them to markers in human GM1 patients where possible. Significant alterations were noted in CSF and blood of GM1 humans and cats, with partial or full normalization after gene therapy in cats. Gene therapy improved the rhythmic slowing of electroencephalograms (EEGs) in GM1 cats, a phenomenon present also in GM1 patients, but nonetheless the epileptiform activity persisted. After gene therapy, MR-based analyses revealed remarkable preservation of brain architecture and correction of brain metabolites associated with microgliosis, neuroaxonal loss, and demyelination. Therapeutic benefit of AAV gene therapy in GM1 cats, many of which maintain near-normal function >5 years post-treatment, supports the strong consideration of human clinical trials, for which the biomarkers described herein will be essential for outcome assessment.

Decreased hematopoietic progenitor cell mobilization in pearl mice.

Neutropenia is common to both Hermansky-Pudlak syndrome type 2 and canine cyclic hematopoiesis (CH) which are caused by mutations in the AP3B1 gene. The purpose of this study was to determine if pearl mice were neutropenic. Complete blood counts (CBCs) and bone marrow differential counts, colony forming unit (CFU) assay, bone marrow lineage negative (lin(-)), Sca(+) and c-kit(+) cells (LSK cells), bone marrow elastase, myeloperoxidase, and cathepsin G enzyme activity were compared in C57Bl6 (Bl/6) and pearl mice. Stress granulopoiesis was evaluated following 200 mg/kg cyclophosphamide or 1 mg/kg bortezomib administration and by limiting dilution bone marrow transplantation. The CBCs and CFUs were determined in Bl/6 and pearl mice following AMD3100 or granulocyte colony-stimulating factor (G-CSF) administration. Pearl mice were not neutropenic and did not have cyclic neutropenia. Bone marrow elastase, myeloperoxidase, and cathepsin G enzyme activity were similar in pearl and Bl/6 mice. The numbers of CFU-G, CFU-GEMM, and LSK cells were increased moderately in pearl mice. Stress granulopoiesis was similar in Bl/6 and pearl mice. CFU assays and CBCs performed on Bl/6 and pearl mice administered AMD3100 resulted in similar results. However, normal mice administered G-CSF had higher peripheral blood neutrophil counts and greater CFU numbers compared with pearl mice. Unlike patients with HPS-2 and dogs with CH, pearl mice did not have neutropenia or CH but had decreased hematopoietic progenitor cell and granulocyte mobilization in response to G-CSF.

Botryoid nuclei in the peripheral blood of a dog with heatstroke.

An EDTA-anticoagulated blood sample collected from a 1.5-year-old, intact male, English Bulldog was submitted for a CBC. The CBC data and blood smear evaluation revealed borderline high hematocrit (54%, reference interval 37-55%), inappropriate rubricytosis, moderate leukopenia due to both mature neutropenia and lymphopenia, and mild thrombocytopenia. Numerous leukocytes showed evidence of karyolysis, pyknosis, and karyorhexis, and apoptotic bodies were frequent in the background. Many neutrophils had botryoid nuclei characterized by increased numbers of nuclear segments radially arranged with spoke-like, delicate chromatin filaments connecting the segments centrally. The finding of botryoid nuclei and inappropriate rubricytosis was indicative of severe hyperthermia, such as heatstroke. The dog had been exercised a long time during conditions of high temperature and humidity until he collapsed. The dog was diagnosed with severe heatstroke, hypovolemic shock, disseminated intravascular coagulation, and multiorgan dysfunction syndrome. Despite aggressive treatment, the patient died of cardiopulmonary arrest. Botryoid nuclei are frequent in people with heatstroke. In the authors' experience, botryoid nuclei are seen commonly in dogs with heatstroke, but they have never been reported in veterinary medicine. The presence of petechiation with only mild thrombocytopenia and inappropriate rubricytosis also is suggestive of heatstroke and manifests ongoing life-threatening vascular derangement.

Multifocal cutaneous histiocytic sarcoma in a young dog and review of histiocytic cell immunophenotyping.

A 9-month-old male Great Dane had progressive generalized nodular dermatopathy for several months. There were > 100 raised, alopecic, firm, painful nodules throughout the skin. Aspirates from several lesions yielded moderate numbers of irregularly round or polygonal to spindle-shaped cells with mild to moderate anisocytosis and few inflammatory cells, and the cytologic interpretation was proliferation of mesenchymal or histiocytic cells. On histopathologic examination, nodules were composed of densely packed sheets of round to spindle-shaped cells with mild anisokaryosis and low mitotic activity. Multifocal histiocytic sarcoma with a spindle-cell pattern was diagnosed based on morphologic features and intense expression of CD18. Additional immunophenotypic analysis on frozen sections of tissue confirmed the diagnosis of histiocytic sarcoma; expression of CD18, CD45, CD1a, CD11b, and CD11c, limited expression of Thy-1 (CD90) and CD80, and lack of expression of CD4, CD11d, and CD86 indicated that the cells were likely interstitial dendritic cells; a review of reactive and neoplastic dendritic cells is provided. Based on staging, internal organs were not affected. Sequential treatment with lomustine and doxorubicin failed to prevent progression of the cutaneous lesions, and the dog died 3 months after initial diagnosis. At necropsy, a focus of neoplastic cells was present in one lymph node, but except for skin other organs were not involved. The clinical presentation of histiocytic sarcoma may be unusual, and neoplastic cells may lack overt features of malignancy on cytologic and histopathologic examination. In some instances, immunophenotyping is required to differentiate histiocytic sarcoma from other histiocytic disorders.

Glanzmann thrombasthenia in a 17-year-old Peruvian Paso mare.

A 17-year-old Peruvian Paso mare was evaluated for bilateral epistaxis that had been present for at least 3 years. The mare had mild anemia, platelet count within the reference interval, unremarkable coagulation times, and a negative Coggins test. On endoscopic examination, structural abnormalities were not observed in the nasal cavities, pharynx, larynx, trachea, or either guttural pouch, but petechiation was noted in the nasal mucosa. Additional tests revealed prolonged cutaneous bleeding time, normal concentration of von Willebrand factor antigen, an abnormal clot retraction test, and failure of plalelet aggregation in response to agonists, suggesting a functional disorder of platelets. Genetic analysis indicated the horse was homozygous for a 10-base-pair deletion that included the last 3 base pairs of exon 11 and the first 7 base pairs of intron 11 of the gene encoding glycoprotein IIb. The diagnosis was Glanzmann thrombasthenia (GT) caused by a structural defect in glycoprotein IIb. GT is an autosomal recessive disorder caused by a defect in the glycoprotein IIb-IIIa complex on platelet surfaces. Separate genes encode each glycoprotein, and mutations in either gene can result in GT. This case of GT is unique given the age of the mare at the time of diagnosis. We conclude that GT, although an inherited disorder, should be considered in horses with suspected dysfunctional platelets, regardless of age.