Platelets Of Dogs Research Articles

Molecular detection and risk factors for Anaplasma platys infection in dogs from Egypt

BackgroundAnaplasma platys is a tick-borne bacterium which infects blood platelets of dogs, causing canine cyclic thrombocytopenia. The disease is distributed worldwide, particularly in the tropics and subtropics, but information on the epidemiology of A. platys infection in dogs is fragmentary in many countries, including Egypt. In this study, we investigated the prevalence and risk factors associated with A. platys infection in dogs from Egypt.MethodsA conventional PCR targeting a fragment of the 16S rRNA gene of A. platys was used to screen 500 dogs from five North Egyptian governorates. DNA sequencing and phylogenetic analysis were performed for one of the positive samples.ResultsThe overall prevalence of A. platys in the studied dogs was 6.4%. Females of the German shepherd breed without veterinary care had higher odds for A. platys positivity. High tick infestation and lack of anti-tick treatment were also identified as risk factors for A. platys infection. Phylogenetic analysis revealed that the sequence obtained herein was closely related to sequences from Egypt, South Africa and Uruguay.ConclusionsThis is the first large-scale epidemiological study of A. platys in Egypt, where female German shepherd dogs without veterinary care, as well as dogs with high tick infestation and without anti-tick treatment are at a higher risk of infection.Graphical abstract

Platelet proteome changes in dogs with congestive heart failure

BackgroundPlatelets play a central role in the development of cardiovascular diseases and changes in their proteins are involved in the pathophysiology of heart diseases in humans. There is lack of knowledge about the possible role of platelets in congestive heart failure (CHF) in dogs. Thus, this study aimed to investigate the changes in global platelet proteomes in dogs with CHF, to clarify the possible role of platelets in the physiopathology of this disease. Healthy-dogs (n = 10) and dogs with acute CHF due to myxomatous mitral valve disease (MMVD, n = 10) were used. Acute CHF was defined based on the clinical (increased respiratory rate or difficulty breathing) and radiographic findings of pulmonary edema. Dogs Blood samples were collected into tubes with acid-citrate-dextrose, and platelet-pellets were obtained by centrifuge and washing steps. Platelet-proteomes were identified using LC-MS based label-free differential proteome expression analysis method and matched according to protein database for Canis lupus familiaris.ResultsTotally 104 different proteins were identified in the platelets of the dogs being 4 out of them were significantly up-regulated and 6 down-regulated in acute CHF dogs. Guanine-nucleotide-binding protein, apolipoproteins (A-II and C-III) and clusterin levels increased, but CXC-motif-chemokine-10, cytochrome-C-oxidase-subunit-2, cathepsin-D, serine/threonine-protein-phosphatase-PP1-gamma-catalytic-subunit, creatine-kinase-B-type and myotrophin levels decreased in acute CHF dogs. These proteins are associated with several molecular functions, biological processes, signaling systems and immune-inflammatory responses.ConclusionThis study describes by first time the changes in the protein composition in platelets of dogs with acute CHF due to MMVD. Our findings provide a resource for increase the knowledge about the proteome of canine platelets and their roles in CHF caused by MMVD and could be a tool for further investigations about the prevention and treatment of this disease.

Surface immunoglobulins of erythrocytes and platelets in dogs naturally infected by Rangelia vitalii

Rangelia vitalii is a protozoan of the Babesiidae family that parasitizes domestic and wild dogs in South American countries. The main laboratory findings in blood samples from animals infected by R. vitalii are anemia and thrombocytopenia. The aim of this study was to detect IgM and IgG immunoglobulins on the surface of red blood cells and platelets, as well as to determine the percentage of reticulated platelets and reticulocytes in dogs naturally infected by R. vitalii. Blood samples from twenty dogs seen at the Veterinary Hospital of the Federal University of Santa Maria (UFSM) were divided into two groups: the diseased group consisted of blood samples from 10 animals with the diagnosis of rangeliosis, and the healthy group (control) consisted of samples from 10 healthy animals. All diseased dogs showed normocytic normochromic anemia but showed no differences (p > 0.05) in reticulocyte counts compared to healthy dogs. Moreover, IgM and IgG immunoglobulins were detected on the surface of the plasma membrane of red blood cells from both groups, but the amounts did not differ between groups (p > 0.05). Thrombocytopenia in infected animals was classified as severe. The percentage of reticulated platelets was higher (p < 0.001) in diseased dogs than in healthy animals. Diseased animals showed more IgM immunoglobulins bound to the surface of platelets than did the healthy group (p < 0.001). However, the amount of IgG bound to the surface of platelets was not different between groups. In conclusion, we showed that R. vitalii caused immune-mediated thrombocytopenia since IgM immunoglobulins were found on the surface of platelets of diseased dogs. We suggest that the binding of immunoglobulins on platelet surfaces contributes to early destruction of these cells and, consequently, alterations in hemostasis. An increase in reticulated platelets was noted in response to thrombocytopenia, indicating active thrombopoiesis.

Neonatal Anaplasma platys infection in puppies: Further evidence for possible vertical transmission

Anaplasma platys, the aetiological agent of infectious canine cyclic thrombocytopaenia, infects platelets of dogs, usually causing mild or asymptomatic disease. Although A. platys is transmitted by ticks, as for other Anaplasma species, alternative modes of transmission may be involved. The aim of the present study was to evaluate the occurrence of A. platys infection in litters of puppies, which could suggest possible vertical transmission. Twelve litters, together with the respective bitches, were included in the study for the detection of A. platys DNA by PCR, followed by sequencing. Five puppies, from 2/4 litters <28 days of age, tested positive for A. platys DNA. No puppies from eight litters 1–3 months of age tested positive for A. platys DNA. The identical sequences (16S rRNA and gltA partial gene), the absence of ticks on puppies at the time of collection and the young age of the five infected puppies suggest vertical transmission of A. platys. This mode of transmission might contribute to the maintenance and spread of the pathogen in canine populations.

Efeitos de diferentes doses de hiclato de doxiciclina nos parâmetros hematológicos de cães com erliquiose

Resumo: Este estudo objetivou comparar os efeitos de duas doses de hiclato de doxiciclina sobre a contagem de hemácias, concentração de hemoglobina, hematócrito, contagem de leucócitos e plaquetas de cães com erliquiose. Foram estudados os grupos I, composto por cães saudáveis (n=6), negativos na sorologia para Ehrlichia canis e Leptospira spp., na PCR em tempo real para E. canis e Anaplasma platys e na semi–nested PCR para Babesia canis; grupos II (n=6) e III (n=6), compostos por cães com história clínica sugestiva, sorologia e/ou PCR em tempo real positivas para E. canis, e negativos na pesquisa de anticorpos anti-Leptospira spp., na PCR em tempo real para A. platys e na semi–nested PCR para B. canis. Os cães doentes foram tratados com hiclato de doxiciclina via oral a cada 12 horas por 30 dias (5 mg/kg, grupo II; 10 mg/kg, grupo III). Hemogramas foram feitos antes, decorridos 15 dias e aos 10 dias após o término dos tratamentos. Não houve diferenças entre os grupos nos tempos avaliados quanto às variáveis hemácias, hemoglobina, hematócrito e leucócitos. Observou-se diferença quanto aos trombócitos entre o grupo I e os grupos II e III (p&lt;0,0001) no início do estudo. Aos 15 dias de tratamento, a média do grupo III foi menor que dos grupos I (p=0,008) e II (p=0,0007), indicando persistência da trombocitopenia, ausente no grupo II. Não houve diferença entre os grupos no tempo final, sugerindo que ambos os tratamentos promoveram aumento da contagem de plaquetas em cães naturalmente infectados por E. canis.

Anaplasma platys Immunoblot Test Using Major Surface Antigens.

Anaplasma platys is an uncultivable tick-borne obligatory intracellular bacterium, which is known to infect platelets of dogs. A. platys causes infectious canine cyclic thrombocytopenia in subtropical and tropical regions throughout the world. Several cases of human infection with A. platys infection have also been reported. However, seroprevalence of A. platys exposure and infection has not been determined in most of the regions, in part, due to lack of a simple and reliable assay method. Furthermore, A. platys antigens recognized by dogs are unknown. We previously sequenced gene encoding A. platys major outer membrane proteins P44 and Omp-1X. In the present study, we obtained purified recombinant A. platys P44 and Omp-1X proteins, and using them as antigens in immunoblotting examined seroreactivity in dogs. Of 34 specimens from Venezuela where A. platys infection was previously reported, 25 specimens (73.5%) reacted to rAplP44 and/or rAplOMP-1X. Neither Anaplasma phagocytophilum-seropositive (N = 10) nor A. phagocytophilum-seronegative canine specimens (N = 10) from the geographic regions where A. platys infection has never been reported, reacted rAplP44 or rAplOMP-1X. The result indicates a high A. platys seroprevalence rate in tested dogs from Venezuela and suggests that the immunoblot analysis based on recombinant A. platys major outer membrane proteins can provide a simple and defined tool to enlighten the prevalence of A. platys infection.

Plasma and platelet serotonin concentrations in healthy dogs and dogs with myxomatous mitral valve disease

ObjectivesSerotonin has been implicated in canine myxomatous mitral valve disease (MMVD); however, the sources of serotonin have not been fully elucidated. This study compared the concentration of serotonin in plasma and platelets of normal healthy small breed dogs with predisposition to MMVD and dogs with naturally occurring MMVD. Animals43 small-breed client-owned dogs with an approximate weight of <10 kg and age of 6 years or above were divided into 2 groups: a healthy control group (n = 20) and a group with echocardiographic evidence of MMVD (n = 23). Methods5 ml samples of blood were collected. Plasma and platelets were separated by centrifugation and assayed for serotonin measured by enzyme linked immunosorbent assay (ELISA). ResultsMedian plasma serotonin concentration was not significantly different (p = 0.3630) between normal healthy dogs (3.7 ng/ml) and dogs with MMVD (4.3 ng/ml). Males had higher plasma serotonin concentration than females (4.7 and 2.9 ng/ml respectively, p = 0.0043). Platelet serotonin concentration was not different between healthy dogs and dogs with MMVD (128.6 ng/109 platelets and 176.6 ng/109 platelets respectively, p = 0.4575). Age, echocardiographic indices and platelet count showed no correlation with plasma or platelet serotonin concentration. ConclusionsCirculating plasma serotonin is unlikely a major source of serotonin signaling in canine MMVD. Platelets could be a source of serotonin in canine MMVD through platelet adhesion to the mitral valve; however, the amount of serotonin stored in platelets of healthy dogs and dogs with MMVD is not different.

Anaplasma platys in Bone Marrow Megakaryocytes of Young Dogs

Anaplasma platys is an obligate intracellular rickettsial pathogen that infects platelets of dogs, forming basophilic intracellular morulae. In the present report, cellular inclusions were documented in bone marrow thrombocyte precursors of two young naturally infected dogs, indicating that A. platys can infect megakaryocytes and promegakaryocytes.

Infection-associated platelet dysfunction of canine platelets detected in a flow chamber model

BackgroundIn the present study, the influence of bacterial infection, lipopolysacharides (LPS) and hydroxyethyl starch (HES) on platelet function in a parallel plate flow chamber were measured. Experiments were performed with non-activated and protease-activating-receptor (PAR) 4 agonist activated platelets. Comparative measurements were in vivo capillary bleeding time, platelet function analyzer and impedance aggregometry.ResultsPAR 4 agonist did not increase platelet adhesion of platelets from dogs with bacterial inflammation in the flow chamber in contrast to platelets of healthy dogs. Except from impedance aggregometry with lower sensitivity and specificity, PFA did not detect platelet dysfunctions in dogs with infection. In vitro addition of LPS or HES significantly reduced platelet covered area after PAR-activation.ConclusionsThe flow chamber detects platelet dysfunctions in dogs with inflammatory diseases. In vitro addition of LPS highlights the inhibiting effect of bacterial wall components on platelet function. Platelet dysfunction induced by infection could possibly also be diagnosed after treatment of sepsis with colloids has commenced. The flow chamber could be a useful tool to detect sepsis associated platelet dysfunction given that larger prospective trials confirm these findings from a proof of concept study.

Assessment of serotonin in serum, plasma, and platelets of aggressive dogs

Abstract Canine aggression is the most common reason for the referral of dogs to behavior practices. In addition, dog bites represent an important problem for public health and animal welfare. The serotonergic system is believed to play an important role in modulating aggression. The aim of the present study was (1) to assess the suitability of different types of blood samples for measuring circulating serotonin in canine clinical studies, and (2) to investigate the relationship between the serotonergic system and canine aggression. The assessment of serotonin was simultaneously carried out in serum, plasma, and platelets of 28 aggressive and 10 nonaggressive dogs with an enzyme immunoassay technique. The mean serotonin concentration in aggressive dogs was significantly lower than in nonaggressive dogs in all the assayed samples. These findings suggest an inverse relationship between the activity of the serotonergic system and canine aggression. Considering the simplicity of the methodology, the authors propose sampling serum as the most suitable method for measuring circulating serotonin in dogs.

Activities of ectonucleotidases and adenosine deaminase in platelets of dogs experimentally infected with Rangelia vitalii

Rangeliosis is a disease which affects dogs in Brazil, caused by a piroplasm known as Rangelia vitalii. This disease causes a lot of clinico-pathological features, including the coagulation disorders associated with bleeding. The cause of these changes has not yet been determined. Considering the association of purinergic system and hemostasis this study aimed to evaluate the activity of enzymes that hydrolyze ATP, ADP and AMP; and deamination of adenosine in platelets from dogs experimentally infected with R. vitalii. For this study, 12 healthy young dogs (females) were used, separated in two groups. Group A (n=5) were uninfected controls, and group B were experimentally infected with R. vitalii (n=7). After being inoculated with R. vitalii-infected blood, animals were monitored by blood smear examinations, which showed intra-erythrocytic forms of the parasite after five days post-inoculation (PI). Blood samples were collected to quantitate and separate platelets (Day 0, 12 and 21 PI) and to measure the enzymatic activities (Day 12 and 21 PI). The activity of NTPDase, 5′-nucleotidase and adenosine deaminase (ADA) was measured in platelets. A reduction (P<0.01) in the number of platelets was observed in R. vitalii-infected blood at Days 12 and 21 PI. At Day 12 PI, a reduction (P<0.01) in the hydrolysis of ATP, ADP and AMP, and deamination of adenosine was observed in dogs infected with R. vitalii. At Day 21 PI the ADA activity remained decreased, unlike the activity of NTPDase which increased (P<0.05). Based on these results we can conclude that ATP, ADP and AMP hydrolysis and adenosine deamination were altered in platelets of R. vitalii-infected dogs. Considering the importance of the purinergic system in hemostasis, it is believed that those changes contribute to the coagulation disorders and bleeding observed in R. vitalii-infected dogs and discussed in this manuscript.

Platelet hyperfunction in dogs with malignancies.

In vitro platelet aggregometry was performed on whole blood samples from 59 dogs with malignancies and 24 control dogs. Three reagents were used for the aggregation studies: collagen, arachidonic acid, and adenosine diphosphate (ADP). The parameters measured to evaluate response to collagen included delay in the aggregation response, slope of the aggregation curve, maximum aggregation, and adenosine triphosphate (ATP) secretion. The platelets of dogs with malignancies exhibited significantly (P < .05) shorter delays in the aggregation response, higher maximum aggregation, and higher ATP secretion when compared to control dogs. For the weaker reagents, ADP and arachidonic acid, the lowest concentration resulting in aggregation was determined. Platelets of dogs with malignancies tended to aggregate in response to lower concentrations of ADP than did those of controls (P < .05). The response of platelets to the concentrations of arachidonic acid employed in this study was poor, with few samples achieving measurable aggregation. The findings of this study suggest that dogs with malignancies have hyperaggregable platelets.

In vivo Effect of Monoclonal Antibodies Against the Platelet GPIIb/IIIa

Anti-human GPIIb/IIIa mouse monoclonal antibodies, NNKY2-11 and NNKY2-18, reacted with platelets of dogs, cats and monkeys as well as humans. These antibodies inhibited the platelet aggregations of humans and animals in vitro. In this report, we injected NNKY2-11 and NNKY2-18 intravenously into dogs and examined the effects of the monoclonal antibodies on dog platelets in vivo. When 100μg/kg of NNKY2-11 (IgG2a) were injected into dogs, platelet aggregation was inhibited partially and no change in circulating platelet counts occurred. When 200-300μg/kg of the antibody was infused, the number of circulating platelets decreased rapidly to the level of 5, 000/μl, followed by the recovery to the original level in a time-dependent fashion. Infusion of NNKY2-18 (IgG 1) also caused the partial inhibition of aggregation and the decrease of platelet counts similarly. When NNKY2-11-F (ab′) 2 was injected into dogs, platelet aggregation was inhibited similarly to intact IgG, and thrombocytopenia was observed. When NNKY2-11-Fab was injected, a slight inhibition of aggregation was obtained, but thrombocytopenia was not observed.

Platelet aggregation studies in dogs with acute Ehrlichia platys infection

SUMMARY Ten adult dogs (5 Beagles and 5 mixed-breed dogs) were inoculated IV with canine platelets containing Ehrlichia platys. Inclusions and morulae of E platys developed in platelets of infected dogs at 10 to 14 days after inoculation, followed by marked thrombocytopenia at 14 to 21 days. Parasitemia and marked thrombocytopenia recurred at 24 to 28 days after inoculation. Increased numbers of megakaryocytes were observed in marrow aspirate smears from infected dogs, indicative of regenerative thrombocytopenia. Prior to infection, platelet-rich plasma from these dogs was determined to have similar aggregatory response to arachidonate. After infection with E platys, the aggregatory response of platelet-rich plasma to collagen or 3 dilutions of adenosine diphosphate was evaluated. A statistically significant (P &lt; 0.05) inhibition of platelet aggregatory response to the lowest dilution of adenosine diphosphate was detected for mixed-breed dogs, whereas aggregation responses were unchanged in Beagles. Results indicate that platelet activation may occur in dogs with acute ehrlichial infection.

Some Monoclonal Anti-human-platelet Antibodies Recognize Dog Platelets as Antigens

Among monoclonal antibodies reacting to platelets, some GPIIb/IIIa antibodies have been reported to react to the platelets of different animals.In this study, we searched for common antigens for platelets of dogs and humans, using 11 monoclonal anti-human-platelet antibodies. By flow cytometry, we examined the reactivity of various monoclonal antibodies to dog platelets. Anti-GPIIb/IIIa antibody NNKY2-11 reacted with about 80%, NNKY2-18 about 50%, CD9 antibody NNKY1-19 about 60%, and MALL13 about 95% of dog platelets, indicating that these monoclonal antibodies recongnize a common antigen in the platelet membranes of dog and human. These anti-GPIIb/IIIa antibodies also inhibited the ADP and collagen aggregation of dog platelets but significantly. When dog platelets were treated with EDTA, the reactivity of the anti-GPIIb/IIIa antibodies decreased significantly. It suggested that the structure of the epitope recognized is dipendent upon Ca++, similar to the human platelet GPIIb/IIIa. However, dog platelets did not show an increase in antibody reactivity upon activation. Autoradiography showed that the antigen recognized by NNKY2-11 on the dog platelet membrane is not exactly the same as GPIIb/IIIa of human platelets. The CD9 antibody MALL13 aggregated dog platelets.We suggest that these monoclonal antibodies may be useful studying platelet function in dogs.

Mechanisms of vascular graft thrombosis: Role of altered canine platelet sensitivity to thromboxane

Using the standard turbidimetric method of platelet aggregation and quantitation of platelet secretion with 14C-Serotonin, we have examined the responsiveness of the platelets of mongrel dogs to arachidonic acid (AA), and the thromboxane agonist U46619 in the presence and absence of a subthreshold concentration of epinephrine. In response to stimulation with 750 μM AA, the platelets of 18 dogs produced irreversible aggregation (Group I), the platelets of 22 dogs showed, at most, reversible aggregation (Group II), while the platelets of 8 dogs demonstrated no aggregatory response (Group III). In the presence of AA and a subthreshold concentration of epinephrine (0.5 μM), the platelets of all three groups demonstrated enhanced aggregatory and secretory responses although the extent of 14C-Serotonin secretion differed significantly between all three groups. These in vitro differences in platelet aggregation correlate with the in vivo deposition of platelets onto synthetic vascular grafts and the maintenance of graft patency. When stimulated with 0.5 μM U46619 and a subthreshold concentration of epinephrine, the platelets of 97% Group I dogs and 75% of Group II dogs exhibited irreversible aggregation, while the platelets of all Group III dogs showed only reversible aggregation. In addition, significant differences in the extent of 14C-Serotonin secretion to this combination of agonists were observed between groups. Further examination of the specific effects of U46619 on canine platelets revealed that although the aggregatory and secretory responses to U46619 vary between the different canine platelet populations, the threshold concentration of U46619 required to produce platelet shape change is identical among all groups. Quantitation of the stable metabolite of AA produced via the cyclooxygenase pathway, thromboxane B 2(TxB 2), revealed no significant differences in the production of TxB 2 by the platelets of these different populations upon stimulation with AA. Our results suggest that the mechanisms underlying the differences in responsiveness of canine platelets to AA, are likely due to differences in sensitivity of canine platelets to TxA 2, and may be localized to the mechanism responsible for mediating platelet aggregation and secretion in response to TxA 2.

Abnormal release of storage pool adenine nucleotides from platelets of dogs affected with basset hound hereditary thrombopathy

Platelets from dogs affected with Basset Hound Hereditary Thrombopathy (BHT), have a thrombasthenia-like aggregation defect but release storage pool ATP in quantities not significantly different from normal controls or BHT heterozygotes when stimulated with 1×10 −5M ADP and 0.22 U/ml thrombin. However, the release occurs so rapidly in the BHT platelets stimulated with ADP that it is complete in approximately one-sixth of the time required for release from normal control and heterozygote platelets. Sequential electron micrographs reveal early release of BHT dense body constituents 30 seconds after stimulation with 1×10 −5M ADP while resting BHT morphology is indistinguishable from normal control animals.

Platelet adhesion to foreign surfaces under controlled conditions of whole blood flow: human vs rabbit, dog, calf, sheep, pig, macaque, and baboon.

Our results reveal significant differences between mammalian species with respect to platelet adhesion to foreign surfaces exposed to heparinized, flowing blood. In particular, we have demonstrated the following: 1) At a surface shear rate characteristic of shear rates in mammalian arteries, human platelet adhesion (and that of calf, baboon, macaque, hog or sheep) is negligible in comparison to dog or rabbit platelet adhesion after 10 mins of blood flow. 2) The species differences are biomaterial dependent: the human-dog difference is present with Cuprophan or Avcothane, but absent with compressed Gore-Tex or fluorinated ethylcellulose. (The platelets of humans and dogs adhere to comparable degrees on the latter 2 biomaterials.) 3) With Cuprophan and recirculated blood, the human-dog difference persists at 30 and 180 mins. 4) By means of videomicroscopy, the species differences are unlikely only to be an artifact of the possible formation and embolization of surface-adherent aggregates. Tests for the thromboresistance of candidate biomaterials and for platelet adhesion under controlled flow conditions must therefore begin to take into account differences between humans and other species.

Platelet Aggregation Induced by DAS in Vitro: Some Investigations on Its Mechanism of Action

SummaryThe effect of the depressor active substance (DAS) on platelets of men, cats, pigs, dogs, rats, and rabbits has been studied by the method of Born (1962). DAS was found to induce platelet aggregation only in human and feline platelet rich plasma (PRP). Nevertheless, there are some striking similarities between platelet aggregation induced by DAS and ADP (i.e. inhibition by the same compounds, such as adenosine, tosylarginine methylester, or p-chloromercuribenzoic acid). The species specifity and a marked tachyphylactic action on platelets of both species makes DAS clearly discernible from all the other aggregation inducing substances which have been studied so far. From additional experiments there is evidence that DAS acts on human and cat platelets via a release reaction of cellular substances known to enhance platelet aggregation in a second phase. This process is strongly dependent on the presence of Ca++.

Type I (brain type) creatine phosphokinase (CPK) activity in rat platelets

Studies on the difference in creating phosphokinase (CPK) activity of platelet-rich-plasma and platelet suspension before and after freezing and thawing demonstrated the presence of CPK activity in rat and rabbit platelets but not in the platelets of dogs, monkeys and humans. The CPK activity of rat and rabbit platelets was 61 ± 18 mU/10 8 platelets and 88 ± 23 mU/10 8 platelets respectively. The Type I (brain type) isoenzyme of CPK was found in rat platelets.