Feline Platelets Research Articles

Evaluation of clopidogrel response in healthy cats using a novel viscoelastic test and thromboelastography.

Cats with cardiomyopathy face an increased risk of arterial thromboembolism (ATE). Although clopidogrel is frequently utilized to mitigate this risk, feline responses to this therapy exhibit variability. This study evaluated 2 viscoelastic devices, thromboelastography (TEG) and Viscoelastic Coagulation Monitor (VCM), for monitoring clopidogrel in cats in comparison to light transmission aggregometry (LTA). Twenty-eight healthy cats received clopidogrel for 7 days. Blood was collected at baseline and after treatment for analysis by TEG, VCM, and LTA. On LTA, maximum amplitude, slope, and area under the curve (AUC) significantly decreased after treatment (p < 0.0001). On VCM, maximum clot firmness (MCF) significantly increased after treatment (p = 0.002). On TEG, R-time significantly prolonged (p = 0.024), while K and alpha angle significantly changed (p = 0.0002 and p = 0.0014, respectively). There was a moderate negative correlation between TEG R-time and LTA AUC (r = -0.39, p = 0.042). Eight cats were identified as non-responders to clopidogrel. Of the 8 non-responders, 6 (75%) had shortened R time after treatment. VCM appeared to be less discriminatory in identifying non-responders. LTA remained the gold standard of monitoring clopidogrel treatment in cats. Unexpected changes on VCM and TEG were likely related to high interindividual and assay variability and increased sensitivity of feline platelets. R-time on TEG may have potential utility for point-of-care monitoring of clopidogrel response in cats.

Kanamycin treated-ethylenediamine tetraacetic acid (EDTA)-dependent pseudothrombocytopenia in blood specimen of cats

Background: Pseudothrombocytopenia is a commonly obtained false negative result when analyzing feline platelet count by automated machine. It is related to ethylenediamine tetra-acetic acid (EDTA), a widely utilized anticoagulant in blood collection tube, resulting in EDTA-dependent pseudothrombocytopenia (EDTA-PTCP). Aim: To investigate whether treated with kanamycin enhanced the quantity of platelet aggregations in feline blood specimens collected using EDTA-PTCP. Methods: Thirty-one blood samples were obtained using EDTA tubes. The complete blood count was analyzed using automated Mindray-BC-5000Vet. Both Manual cell counts and thin blood smears were performed to estimate the amount of RBC, WBC and platelets as well as to evaluate the severity scores of platelet clumping, respectively. Comparisons were made between those pre-treated and treated with kanamycin in EDTA tube. Results: There were significantly different mean platelet counts in the samples before and after they were treated with kanamycin, both on automated (156.6  76.4 vs 260.3  115.5; p &lt; 0.001) and manual (168.5  92.1 vs 262.8  119.6; p &lt; 0.001) readings, with a 95% confidence interval (CI) of 0.19 (0.022–0.365). Conclusion: This study suggests that in clinical laboratory practice, kanamycin should be added to feline blood specimens with EDTA-PTCP.

Effects of orally administered pimobendan on platelet function in healthy adult cats.

Several phosphodiesterase inhibitors have demonstrable antiplatelet actions when administered to human patients. Concentration-dependent inhibition of feline platelet aggregation by pimobendan has been previously demonstrated in vitro. However, there are no published reports characterizing the effect of oral pimobendan, administered at therapeutic doses, on platelet function in cats. This study aimed to evaluate the effect of orally administered pimobendan on platelet function in healthy adult cats. 6 healthy purpose-bred adult cats. Cats were administered pimobendan orally at a dosage of 0.625 mg/cat (low-dose) twice daily for 1 week, followed by 1.25 mg/cat (high-dose) twice daily for 1 week. Venous blood sampling for platelet testing and plasma drug concentration occurred at baseline, 1 hour postdose on the eighth day of treatment with low-dose pimobendan, 1 hour postdose on the eighth day of treatment with high-dose pimobendan, and after a 1-week washout period. Platelet function was assessed by whole blood aggregometry and by use of a platelet function analyzer (PFA-100®). Friedman tests were used to compare platelet function parameters among the 4 sampling timepoints. After 1 week of treatment, median (range) plasma pimobendan concentrations were 15.1 ng/mL (6.89-20.2 ng/mL) and 32.8 ng/mL (23.3-44.8 ng/mL) in cats receiving low-dose and high-dose pimobendan, respectively. No significant differences in PFA closure time or any aggregometry variable were found among the treatment conditions. Pimobendan was not associated with measurable inhibition of platelet function when administered orally to healthy adult cats at 2 clinically relevant dosages.

Synergistic inhibitory effects of clopidogrel and rivaroxaban on platelet function and platelet-dependent thrombin generation in cats.

Dual antithrombotic treatment (DAT) with clopidogrel and rivaroxaban sometimes is prescribed to cats with hypertrophic cardiomyopathy at risk of thromboembolism. To date, no studies have evaluated their combined effects on platelet function. Evaluate the safety of DAT in healthy cats and compare, ex vivo, platelet-dependent thrombin generation and agonist-induced platelet activation and aggregation in cats treated with clopidogrel, rivaroxaban, or DAT. We hypothesized that DAT would safely modulate agonist-induced platelet activation and aggregation more effectively than single agent treatment. Nine apparently healthy 1-year-old cats selected from a research colony. Unblinded, nonrandomized ex vivo cross-over study. All cats received 7 days of rivaroxaban (0.6 ± 0.1 mg/kg PO), clopidogrel (4.7 ± 0.8 mg/kg PO), or DAT with defined washout periods between treatments. Before and after each treatment, adenosine diphosphate (ADP)- and thrombin-induced platelet P-selectin expression was evaluated using flow cytometry to assess platelet activation. Platelet-dependent thrombin generation was measured by fluorescence assay. Platelet aggregation was assessed using whole blood impedance platelet aggregometry. No cats exhibited adverse effects. Of the 3 treatments, only DAT significantly decreased the number of activated platelets (P = .002), modulated platelet activation in response to thrombin (P = .01), dampened thrombin generation potential (P = .01), and delayed maximum reaction velocity (P = .004) in thrombin generation. Like clopidogrel, DAT inhibited ADP-mediated platelet aggregation. However, rivaroxaban alone resulted in increased aggregation and activation in response to ADP. Treatment combining clopidogrel and rivaroxaban (DAT) safely decreases platelet activation, platelet response to agonists, and thrombin generation in feline platelets more effectively than monotherapy with either clopidogrel or rivaroxaban.

Amikacin prevents platelet aggregation in feline venous blood samples.

Physiologically, feline platelets are more reactive and prone to aggregation, which interferes with platelet counts using automated counters and manual methods. The use of aminoglycoside amikacin in association with EDTA has proven to be efficient in preventing platelet aggregates in cases of pseudo thrombocytopenia (PTP) in people. This study evaluated the efficacy of amikacin in preventing platelet aggregation in EDTA-containing feline blood samples and investigated the possible effects on hematologic measurands. Blood samples (1.0mL) collected from 100 healthy cats were stored in two EDTA tubes: 0.5mL in a microtube containing 10μL of 250mg/mL amikacin (EDTA-AMK group) and 0.5mL in a microtube containing only K2 EDTA 10% (EDTA group). A CBC was executed with an automated impedance blood analyzer, and a microscopic examination of the blood smears was performed. Platelet clumps were observed in 56% of samples from the EDTA group and 5% of samples from the EDTA-AMK group. Platelet counts (PLT), plateletcrit (PCT), and WBC counts were significantly higher (P<.001) in the EDTA-AMK group compared withi the EDTA group. Amikacin prevents platelet aggregation in feline venous blood samples and does not cause clinically relevant changes in other hematologic measurands. To our knowledge, this is the first report showing the use of amikacin in preventing platelet aggregation in feline blood samples. Based on this study, amikacin could be added to EDTA collection tubes for complete blood counts in cats.

Assessment of P2Y12 Inhibition by Clopidogrel in Feline Platelets Using Flow Cytometry Quantification of Vasodilator-Stimulated Phosphoprotein Phosphorylation.

The primary objective of this study was to evaluate a novel flow cytometry-based assay of quantifying platelet phosphorylation of vasodilator-stimulated phosphoprotein (P-VASP) in cats that received clopidogrel treatment. Eight healthy cats received 18.75 mg PO q24h of clopidogrel for 7 days. Prior to and after clopidogrel treatment, blood was collected for ADP-induced light transmission aggregometry (LTA) and P-VASP measurement by flow cytometry. Flow cytometry measurement of P-VASP levels was used to derive platelet reactivity index (PRI) before and after clopidogrel treatment. Based on P-VASP and LTA findings, platelet response to ADP was significantly attenuated after 7 days of clopidogrel treatment. By eliciting the competing platelet pathways of P2Y12 and cAMP using ADP and PGE1, respectively, ADP had no effect on P-VASP levels following clopidogrel treatment (p = 0.94). Clopidogrel also significantly decreased PRI from 28.84 ± 28.52% to 1.69 ± 12.39% (p = 0.0078). PRI on day 8 correlated moderately with the degree of slope inhibition on LTA (r = −0.4, p = 0.4). Flow cytometry analysis of P-VASP is effective at monitoring the inhibitory effects of clopidogrel on feline platelets.

Effects of imidazoline and nonimidazoline α-adrenoceptor agonists and antagonists, including xylazine, medetomidine, dexmedetomidine, yohimbine, and atipamezole, on aggregation of feline platelets.

To examine the effects of imidazoline and nonimidazoline α-adrenergic agents on aggregation of feline platelets. Blood samples from 12 healthy adult cats. In 7 experiments, the effects of 23 imidazoline and nonimidazoline α-adrenoceptor agonists or antagonists on aggregation and antiaggregation of feline platelets were determined via a turbidimetric method. Collagen and ADP were used to initiate aggregation. Platelet aggregation was not induced by α-adrenoceptor agonists alone. Adrenaline and noradrenaline induced a dose-dependent potentiation of ADP- or collagen-induced aggregation. Oxymetazoline and xylometazoline also induced a small potentiation of ADP-stimulated aggregation, but other α-adrenoceptor agonists did not induce potentiation. The α2-adrenoceptor antagonists and certain imidazoline α-adrenergic agents including phentolamine, yohimbine, atipamezole, clonidine, medetomidine, and dexmedetomidine inhibited adrenaline-potentiated aggregation induced by ADP or collagen in a dose-dependent manner. The imidazoline compound antazoline inhibited adrenaline-potentiated aggregation in a dose-dependent manner. Conversely, α1-adrenoceptor antagonists and nonimidazoline α-adrenergic agents including xylazine and prazosin were ineffective or less effective for inhibiting adrenaline-potentiated aggregation. Moxonidine also was ineffective for inhibiting adrenaline-potentiated aggregation induced by collagen. Medetomidine and xylazine did not reverse the inhibitory effect of atipamezole and yohimbine on adrenaline-potentiated aggregation. Adrenaline-potentiated aggregation of feline platelets may be mediated by α2-adrenoceptors, whereas imidazoline agents may inhibit in vitro platelet aggregation via imidazoline receptors. Imidazoline α-adrenergic agents may have clinical use for conditions in which there is platelet reactivity to adrenaline. Xylazine, medetomidine, and dexmedetomidine may be used clinically in cats with minimal concerns for adverse effects on platelet function.

The feline blood film.

Practical relevance: Many veterinary practices have invested in quality automated hematology instruments for use in-house. However, regardless of their specific choice of analyzer, there are important hematology findings that can only be determined by microscopic examination of stained blood films. For this reason, and also for the purpose of quality control for the analyzer, a quick blood film review should be performed alongside every automated complete blood count. Even those practices that submit their blood samples to outside diagnostic laboratories for evaluation, still require the capability to examine stained blood films in emergency situations. Series outline: This is the second of a two-part article series that aims to familiarize the practitioner with normal findings on feline blood films, with a particular focus on unique features in the cat, as well as to assist with interpretation of common abnormalities. Part 2 focuses on the morphology of feline leukocytes and platelets in health and disease. Evidence base: The information and guidance offered is based on the published literature and the author's own extensive clinical pathology research.

Platelet Activation and Clopidogrel Effects on ADP-Induced Platelet Activation in Cats with or without the A31P Mutation in MYBPC3.

BackgroundClopidogrel is commonly prescribed to cats with perceived increased risk of thromboembolic events, but little information exists regarding its antiplatelet effects.ObjectiveTo determine effects of clopidogrel on platelet responsiveness in cats with or without the A31P mutation in the MYBPC3 gene. A secondary aim was to characterize variability in feline platelet responses to clopidogrel.AnimalsFourteen healthy cats from a Maine Coon/outbred mixed Domestic cat colony: 8 cats homozygous for A31P mutation in the MYPBC3 gene and 6 wild‐type cats without the A31P mutation.MethodsEx vivo study. All cats received clopidogrel (18.75 mg PO q24h) for 14 days. Before and after clopidogrel treatment, adenosine diphosphate (ADP)‐induced P‐selectin expression was evaluated. ADP‐ and thrombin‐induced platelet aggregation was measured by optical aggregometry (OA). Platelet pVASP and ADP receptor response index (ARRI) were measured by Western blot analysis.ResultsPlatelet activation from cats with the A31P mutation was significantly (P = .0095) increased [35.55% (18.58–48.55) to 58.90% (24.85–69.90)], in response to ADP. Clopidogrel treatment attenuated ADP‐induced P‐selectin expression and platelet aggregation. ADP‐ and PGE 1‐treated platelets had a similar level of pVASP as PGE 1‐treated platelets after clopidogrel treatment. Clopidogrel administration resulted in significantly lower ARRI [24.13% (12.46–35.50) to 11.30% (−7.383 to 23.27)] (P = .017). Two of 13 cats were nonresponders based on OA and flow cytometry.Conclusion and Clinical ImportanceClopidogrel is effective at attenuating platelet activation and aggregation in some cats. Cats with A31P mutation had increased platelet activation relative to the variable response seen in wild‐type cats.

Study on the kinetics and influence of feline platelet aggregation and deaggregation.

BackgroundFeline platelets are prone to clumping after blood collection, rendering the determination of accurate platelet counts difficult for clinical laboratories and resulting in a high incidence of pseudothrombocytopenia in feline haematology reports. No information is available about the kinetics of platelet aggregate formation in feline ethylenediaminetetraacetic acid blood and the course of platelet counts over a clinically relevant time period. The aim of the present study was to determine platelet counts in healthy cats over a time period of 24 h after blood collection at 9 time points; to assess potential effects of platelet aggregates, anaesthesia and bleeding conditions on feline platelets and white blood cell counts; and finally, to investigate if glucose concentration is associated with the presence of aggregates. From 30 clinically healthy cats, blood samples were analysed at 9 different time points using two different haematology instruments (using fluorescence and impedance-based flow cytometry) in the counting chamber and by blood smear evaluation.ResultsFourteen of the 30 samples were thrombocytopenic at one to 8 time points after collection as analysed on a fluorescence flow cytometry haematology analyser. At the 24-h timepoint, all thrombocytopenic samples had returned to normal platelet counts. Seventeen of the 30 samples showed platelet aggregates in the counting chamber. Significant differences in platelet counts were associated with the presence and size of aggregates and time since bleeding. No statistically significant differences in counts were found with regard to the quality of blood collection or the use of anaesthesia. Platelet aggregation and, therefore, pseudothrombocytopenia occurred in 57 % of the investigated samples at different time points.ConclusionFor the first time, deaggregation of feline platelet aggregates could be demonstrated as a reversible effect of platelet aggregation. For clinical laboratories or veterinarians, it may be helpful to rerun feline samples with pseudothrombocytopenia to obtain a more reliable platelet count. The quality of blood collection seems not to be causative for platelet aggregation. Blood smear evaluation is absolutely indicated in cases when haematology instruments give PLT counts below the reference interval.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-015-0590-7) contains supplementary material, which is available to authorized users.

Effective prevention of pseudothrombocytopenia in feline blood samples with the prostaglandin I2 analogue Iloprost.

BackgroundIn vitro platelet aggregation in feline blood samples is a well-known phenomenon in veterinary clinical laboratories resulting in high numbers of pseudothrombocytopenia. Several attempts have been made to prevent or dissolve platelet aggregates in feline blood samples and to increase the reliability of feline platelet counts. Prostaglandin I2 (PGI2) is the most powerful endogenous inhibitor of platelet aggregation but unstable. Iloprost is a stable PGI2 analogue. The aims of the present study were (1) to evaluate the anti-aggregatory effect of Iloprost on feline platelet counts and to determine a useful concentration to inhibit platelet aggregation in EDTA samples from clinically healthy cats, (2) to investigate the effect of Iloprost on hematological blood parameters, and (3) to determine stability of Iloprost in K3-EDTA tubes for up to 16 weeks. From 20 clinically healthy cats blood was drawn from the jugular vein and immediately distributed in a 1.3 ml K3-EDTA tube, and two 1.3 ml K3-EDTA tubes containing 20 ng and 200 ng Iloprost, respectively. A complete blood cell count was performed on the Sysmex XT-2000iV and the Mythic 18 on eight consecutive time points after collection. Blood smears were evaluated for the presence of PLT aggregates.ResultsIn the absence of Iloprost, pseudothrombocytopenia was observed in 50 % of the investigated samples that led to significantly decreased optical PLT counts by a mean of 105 x103/μl, which could be prevented by the addition of 1 μL (20 ng) Iloprost leading to an increase in PLT counts by a mean of 108 x103/μl.ConclusionThis is the first study showing an anti-aggregatory effect of the PGI2-analogue Iloprost in feline EDTA blood. In all clinically healthy cats investigated, pseudothrombocytopenia was prevented by adding Iloprost to EDTA tubes prior to blood collection. Furthermore, Iloprost was very useful in preventing falsely increased WBC counts in samples with platelet aggregates analyzed on impedance-based hematological instruments. Iloprost is preferable to PGI2 or PGE1 due to its stability and easy and safe handling properties. Cytological evaluations of blood smears as well as other hematological parameters were not influenced to a clinically significant degree by the presence of Iloprost.

Reducing error in feline platelet enumeration by addition of Iloprost to blood specimens: comparison to prostaglandin E1 and EDTA.

Prostaglandin E1 (PGE1) and Iloprost inhibit platelet aggregation and should prevent or minimize preanalytic error with feline platelet enumeration. The objective was to compare the relative effectiveness in reducing errors in platelet enumeration by adding Iloprost to feline EDTA blood specimens in comparison to adding PGE1 or EDTA alone. In addition, a grading system for platelet aggregation in blood smears was evaluated for effectiveness in predicting prominent errors and compared to ADVIA's PLT-CLM flag. Finally, the use of plateletcrit in feline blood with platelet aggregation was evaluated. Blood specimens from 35 cats were included. Blood was collected into EDTA tubes with or without Iloprost or PGE1, and was rapidly mixed. Platelet count (PLT), plateletcrit (PCT), mean platelet volume (MPV), and platelet flags were determined with an ADVIA 2120. Manual PLT was performed with a Leucoplate stain. PLT was determined by an IDEXX VetAutoread hematology analyzer (QBC). Neither addition of Iloprost nor PGE1 to EDTA blood specimens completely prevented platelet aggregation. Iloprost-treated specimens had the least severe aggregation. PGE1 was better than EDTA alone. Significant errors in PLT results were consistently identified by the grading system. ADVIA's PLT-CL flag usually predicted significant errors in PLT. QBC PLT results showed high imprecision. Manual PLT error was smaller than ADVIA PLT in EDTA specimens with aggregation. Adding Iloprost to feline blood specimens improved platelet enumeration accuracy. A grading system for severity of platelet aggregation and usually the ADVIA's PLT-CL alarm predicted specimens with significant errors in platelet enumeration.

Enumeration of feline platelets in ethylenediamine tetra-acetic acid anticoagulated blood with the ADVIA 2120 system and two manual methods

A manual method (Thrombo-TIC; Bioanalytic GmbH, Umkirch/Freiburg, Germany) was advertised to disaggregate platelet clumps and to make human platelets spherical to improve platelet enumeration. The current study's hypothesis was that this method would perform better than current methods for feline blood anticoagulated with ethylenediamine tetra-acetic acid (EDTA), which often contains platelet aggregates. Platelet concentrations (PLTs) were determined in 21 feline blood samples by 3 methods. Thrombo-TIC was compared to the manual method (Leucoplate; Sobioda, Montbonnot-Saint-Martin, France) currently used in the authors' laboratory along with an ADVIA 2120 (Siemens AG, Eschborn, Germany) optical platelet concentration. Feline blood samples often contained platelet aggregates. ADVIA flagged for platelet aggregates in 11 of the 21 feline blood samples, and examination of blood smear revealed platelet aggregates in 14 of the 21 samples. The hemocytometers displayed more platelet aggregates with the Thrombo-TIC method than with Leucoplate. The method giving the greatest PLT was considered most accurate. The Leucoplate median PLT (238 × 10(9)/1) was greater than Thrombo-TIC (202 × 10(9)/1) or ADVIA (157 × 10(9)/1). Intra-assay precision was determined for the 3 methods using the 21 feline blood samples. Median Thrombo-TIC and Leucoplate precision (7.4% and 7.3% coefficient of variation [CV], respectively) were similar and not much worse than ADVIA (5.9% CV). The Thrombo-TIC method did not appear to perform better than the current manual method (Leucoplate). Leucoplate appeared least affected by platelet aggregation in feline blood. The ADVIA automated PLT appeared to be most negatively affected by platelet aggregation. The Thrombo-TIC method did not appear to prevent platelet aggregation in feline EDTA blood samples and, thus, is not recommended for such use.

Ultrastructural characteristics of fibrin clots from canine and feline platelet concentrates activated with calcium gluconate or calcium gluconate plus batroxobin

BackgroundThe aim of this study was to use transmission electron microscopy to describe the ultrastructural characteristics of clots obtained from canine and feline platelet concentrates (PC) that had been activated with calcium gluconate (CG) or CG plus batroxobin (CGB). Platelets from fibrin clots were classified according their morphological changes. The area of the intercellular space (μm2), the area of the fibrin fibers (μm2), and the width of the fibrin fibers (μm) were determined for the dog clots. The platelet area (μm2), the area of fibrin fibers (μm2), the ratio of the minor and major axes of platelets, the ratio of the major and minor axes of platelets, and the number of α-granules found within platelets were measured for the cat clots.ResultsCat platelets displayed full activation. Dog platelets displayed lysis with loss of normal architecture. In both species, a statistically significant difference was found (P < 0.01) between the fibrin fiber measurements in the PC clots activated with CG and CGB.ConclusionsThe findings suggest that activation with CG caused platelet alpha granules to release their contents. In cats, fibrin production was greater when the PC was activated with CG. In dogs, activation with CG produced thick fibrin fibers.

Validation of the Celltac alpha automated hematology analyzer for canine and feline blood samples

Small hematology analyzers for veterinary practices improve point-of-care diagnostic testing for companion animals. Validation of these instruments is needed to ensure the accuracy of results. The objective was to validate the Celltac alpha hematology analyzer for feline and canine blood samples. Canine and feline blood samples were analyzed on a Celltac alpha and a Sysmex XT-2000iV. Manual methods were used for the WBC differential count, PCV, and feline platelet (PLT) count. Flagging and precision of the new instrument were analyzed. Correlation and Bland-Altman analyses were used to compare the methods. A total of 623 blood samples (363 canine, 260 feline) were analyzed. Within-batch precision of the Celltac showed acceptable coefficients of variation (CV) for WBC count (< 4%), PLT count (< 8%), hemoglobin (HGB) concentration (< 3%), and HCT (< 3%), while precision was poor for leukocyte subpopulations. HGB concentration and WBC count had good agreement between the methods. CV for the granulocyte (GRAN) count was 2-9% in cats and 6-29% in dogs. CV for the lymphocyte (LYM) count was 8-20% in cats and 13-51% in dogs. Negative bias and a proportional systematic error were apparent for PLT count, feline HCT, and eosinophil count. Analytical error flags and incomplete results were reported for 11.8% of canine and 25.4% of feline samples. Leukocytosis and leukopenia were reliably detected by the Celltac alpha. The instrument provided acceptable results for total WBC count, GRAN count, HGB concentration, and HCT in canine blood samples, but PLT count was systematically overestimated. In feline blood samples, both low and high PLT counts were inaccurate and a proportional systematic error for HCT led to overestimation of this variable. Imprecision for WBC differential counts was high.

Evaluation of the effect of calcium gluconate and bovine thrombin on the temporal release of transforming growth factor beta 1 and platelet-derived growth factor isoform BB from feline platelet concentrates.

BackgroundThere are not reported regarding the protocols for obtaining platelet concentrates (PC) in cats for medical purposes. The objectives of this study were: 1) to describe a manual method for producing two kinds of PC in cats (PC-A and PC-B), 2) to describe the cellular population of the PC, 3) to measure and compare the effect of calcium gluconate (CG) and bovine thrombin (BT) on the temporal release of transforming growth factor beta 1 (TGF-β1) and platelet-derived growth factor type BB (PDGF-BB) at 3 and 12 hours post-activation and 4) to establish correlations between the cellular population of both PCs and the concentration of growth factors (GF). Blood samples were taken from 16 cats for complete blood count, plasma collection and PC preparation. The PC were arbitrarily divided into two fractions, specifically, PC-A (lower fraction) and PC-B (upper fraction).ResultsThe platelet counts were significantly different (P<0.05) between the PC and whole blood but not between the PC fractions. The TGF-β1 concentration efficiencies for PC-A and PC-B activated with CG were 42.86% and 46.54%, and activated with BT were 42.88% and 54.64%, respectively. The PDGF-BB concentration efficiencies for PC-A and PC-B activated with CG were 61.36% and 60.61%, and activated with BT were 65.64% and 72.12%, respectively. The temporal release of GFs showed no statistically significant difference (P>0.05) between the activating substances at the time or for any PC fraction.ConclusionsWhatever the activation means, these preparations of cat PC provide significant concentrations of platelets and GFs for possible clinical or experimental use.

Lack of inhibitory effect of acetylsalicylic acid and meloxicam on whole blood platelet aggregation in cats

To determine the effects of acetylsalicylic acid (ASA) and meloxicam on feline platelet aggregation and associated platelet thromboxane production and serotonin release. Prospective interventional study. University research facility. Eight healthy male castrated domestic short hair cats from a research colony. Oral medications were administered to 8 cats for 14 days in a randomized, placebo-controlled, crossover design. Treatment groups included: aspirin (ASA) (5 mg/kg q 48 h), meloxicam (0.05 mg/kg q 24 h), and placebo (0.5 mL of water q 24 h). Thromboxane assays (TXB(2) ) and whole blood (impedance) aggregometry (WBA) were performed on samples collected before drug administration, and on days 7, 15, and 17, using adenosine diphosphate (ADP; 10 μM) and collagen (5 μg/mL) as agonists for WBA. Serotonin release was assayed on postaggregation plasma. Oral mucosal bleeding time (OMBT) and complete blood cell counts were measured on days 0 and 15. Neither medication affected WBA at any time point. OMBT decreased in the ASA group relative to baseline. No differences were detected in WBA and OMBT baseline between any groups. No difference was detected in serotonin secretion at any time point. TXB(2) was significantly decreased in the ASA group at all times after initiation of treatment but no change was noted in the meloxicam or placebo groups. At the doses studied, neither meloxicam nor ASA had an inhibitory effect on WBA or OMBT in cats. Thromboxane concentrations were significantly decreased with ASA treatment.

Evaluation of the Mythic 18 hematology analyzer for use with canine, feline, and equine samples

The Mythic 18 is a fully automated hematology bench-top analyzer using impedance technology for a complete blood cell count (CBC) and a 3-part white blood cell count (WBC) differential. The purpose of the current study was to evaluate the Mythic for assessment of agreement, precision, linearity, carry-over, stability, and usability under practice conditions. Ethylenediamine tetra-acetic acid-blood samples from 122 dogs, 140 cats, and 123 horses were analyzed with the Mythic and reference methods (Sysmex XT-2000iV, manual hematocrit, and microscopic WBC differentiation). Pearson's coefficient of correlation, Passing-Bablok regression analysis, and Bland-Altman difference plots were performed to determine agreement. For precision, standard deviation and coefficients of variation were calculated. Linearity was determined according to Emancipator-Kroll. Red blood cell parameters showed excellent correlation and small biases, except for red cell distribution width and mean corpuscular hemoglobin concentration. Total WBC correlated excellently in canine and equine and very well in feline samples. In 23 feline specimens with platelet aggregates, the Mythic overestimated WBC. In all 3 species, absolute granulocyte counts correlated excellently. Equine lymphocyte counts showed good correlation whereas canine and feline lymphocyte counts correlated poorly. Feline platelets showed good correlation with a negative bias. The instrument showed good to excellent precision. The whole 3-part differential was found to be accurate in horses. In dogs and cats, absolute granulocyte counts were reliable. As with all impedance-based hematological instruments, evaluation of a blood smear is absolutely indicated to check for the presence of platelet aggregates, to verify WBC differentiation, and to identify possible abnormalities.

Distribution of the Feline Calicivirus Receptor Junctional Adhesion Molecule A in Feline Tissues

Junctional adhesion molecule A (JAM-A) is an immunoglobulin superfamily protein that plays an important role in the assembly and maintenance of tight junctions and the establishment of epithelial cell polarity. The feline JAM-A (fJAM-A) is a functional receptor for feline calicivirus (FCV). Among natural diseases associated with FCV infection, isolates that cause oral vesicular disease are detected in epithelial cells; however, isolates that cause systemic disease are detected in multiple cell types. The distribution of an FCV receptor or receptors in feline tissues is relevant to viral pathogenesis in that it should reflect the wide latitude of clinical sequelae associated with FCV infection. The authors examined the expression of feline JAM-A in the cat by using confocal immunofluorescence localization on normal tissues, with special regard to tissue targets of naturally occurring FCV. As described in the human and the mouse, fJAM-A was widely distributed in feline tissues, where it localized at cell-cell junctions of epithelial and endothelial cells. fJAM-A was highly expressed on feline platelets, with lower levels of expression on feline peripheral blood leukocytes. Additionally, FCV infection of a feline epithelial cell monolayer causes redistribution of fJAM-A to the cytosol of infected cells. It is reasonable to propose that the spectrum of lesions caused by FCV reflects disruption of intercellular junctions that rely on fJAM-A function and tight junctional integrity.

Feline platelet counting with prostaglandin E1 on the Sysmex XT‐2000iV

The large size of many feline platelets and the high frequency of platelet aggregation often results in falsely low platelet counts in this species. A combination of optical platelet counting to detect even large platelets and the use of prostaglandin E1 (PGE1) to inhibit platelet clumping may increase the accuracy of feline platelet counting. The objective of this study was to compare platelet counts in feline whole blood samples with and without the addition of PGE1 and using different analytical methods in a clinical setting. Platelet counts were determined in 10 feline patients in a referral veterinary hospital using 2 sample types (EDTA, EDTA with PGE1) and 2 methods of analysis (optical counting [PLT-O] and impedance counting [PLT-I]) on the Sysmex XT 2000 iV analyzer. All PGE1-PLT-O samples had platelet counts of >200 x 10(9)/L. Mean platelet count using PGE1-PLT-O (410,256+/-178 x 10(9)/L) was significantly higher (P<.03) compared with PGE1-PLT-I (256+/-113 x 10(9)/L), EDTA-PLT-O (238+/-107 x 10(9)/L), and EDTA-PLT-I (142+/-84 x 10(9)/L) methods. Depending on the method, platelet counts in 2 to 7 of 10 cats were <200 x 10(9)/L when PGE1-PLT-O was not used. A slightly increased platelet count in response to treatment of a feline patient with thrombocytopenia would have been missed without use of PGE1-PLT-O. Using PLT-O analysis on EDTA samples containing PGE1 provides higher, and therefore likely more accurate, feline platelet counts in a clinical setting.