Normal Platelet Size Research Articles

Increased Platelet Aggregation Response in Cavalier King Charles Spaniels with Mitral Valve Prolapse

Mitral valve prolapse (MVP) is a fundamental feature of myxomatous mitral valve disease in the dog. In humans, primary MVP is associated with increased platelet reactivity. In Cavalier King Charles Spaniels (CKCS), a breed predisposed to myxomatous mitral valve disease, there is a high prevalence of hypomagnesemia and platelet anomalies, such as thrombocytopenia and ma‐crothrombocytosis. The objective of this study was to evaluate platelet aggregation responses in CKCS and to determine the relationship between the platelet aggregation response and serum magnesium concentration, MVP, mitral regurgitation (MR), and platelet count. In 19 CKCS with MVP and 7 control dogs (not CKCS), the platelet aggregation response to 3 different agonists was compared. The CKCS with > 100,000 platelets/μL (n = 10) had a significantly higher maximum aggregation response with regard to all tested agonists than the CKCS with < 100,000 platelets/μL (n = 9) and control dogs (n = 7). The CKCS with < 100,000 platelets/μL had a platelet aggregation response similar to the control dogs. There was no correlation between degree of MVP and platelet aggregation response. Platelet diameter increased (P= .006) and serum magnesium concentration decreased (P= .04) with lower platelet concentration. In conclusion, CKCS with MVP appeared to separate into 2 groups—1 group with < 100,000 platelets/μL, normal platelet aggregation, low serum magnesium concentration, and enlarged platelets, and another group with >100,000 platelets/μL, increased platelet aggregation, and normal serum magnesium concentration and platelet size.

Increased platelet aggregation response in Cavalier King Charles Spaniels with mitral valve prolapse.

Mitral valve prolapse (MVP) is a fundamental feature of myxomatous mitral valve disease in the dog. In humans, primary MVP is associated with increased platelet reactivity. In Cavalier King Charles Spaniels (CKCS), a breed predisposed to myxomatous mitral valve disease, there is a high prevalence of hypomagnesemia and platelet anomalies, such as thrombocytopenia and macrothrombocytosis. The objective of this study was to evaluate platelet aggregation responses in CKCS and to determine the relationship between the platelet aggregation response and serum magnesium concentration, MVP, mitral regurgitation (MR), and platelet count. In 19 CKCS with MVP and 7 control dogs (not CKCS), the platelet aggregation response to 3 different agonists was compared. The CKCS with >100,000 platelets/microL (n = 10) had a significantly higher maximum aggregation response with regard to all tested agonists than the CKCS with <100,000 platelets/microL (n = 9) and control dogs (n = 7). The CKCS with <100,000 platelets/microL had a platelet aggregation response similar to the control dogs. There was no correlation between degree of MVP and platelet aggregation response. Platelet diameter increased (P = .006) and serum magnesium concentration decreased (P = .04) with lower platelet concentration. In conclusion, CKCS with MVP appeared to separate into 2 groups--1 group with <100,000 platelets/microL, normal platelet aggregation, low serum magnesium concentration, and enlarged platelets, and another group with >100,000 platelets/microL, increased platelet aggregation, and normal serum magnesium concentration and platelet size.

Autosomal dominant thrombocytopenia: incomplete megakaryocyte differentiation and linkage to human chromosome 10

We studied a large kindred with nonsyndromic autosomal dominant thrombocytopenia to define the phenotype and used genomic linkage analysis to determine the locus of the abnormal gene. Affected family members are characterized by lifelong moderate thrombocytopenia (mean = 42.7 × 109/L) with moderate propensity toward easy bruising and minor bleeding. Megakaryocytes are present in bone marrow with reduced frequency, and there are no apparent abnormalities of myeloid or erythroid cells. This type of inherited thrombocytopenia has no evident association with hematopoietic malignancy or progression to aplastic anemia. In the past, members of this family have failed therapeutic trials of immunosuppression and splenectomy. In our investigation, we found that affected individuals had normal platelet size compared with unaffected family members and modestly increased thrombopoietin levels. Hematopoietic colony assays from bone marrow and peripheral blood demonstrated that megakaryocyte precursors (CFU-Mk) were dramatically increased in both number and size in affected individuals. Bone marrow cells grown in liquid culture with thrombopoietin failed to develop polyploid cells greater than 8N. Also, electron microscopy demonstrated that megakaryocytes from an affected individual had markedly delayed nuclear and cytoplasmic differentiation. Genome-wide linkage analysis established a single locus for the disease gene on the short arm of chromosome 10 with a maximum 2-point lod score of 5.68 (at θ = 0). By recruiting additional family members, the genomic region was narrowed to 17 centimorgans. We conclude that a gene in this locus plays an important role in megakaryocyte endomitosis and terminal maturation.

Autosomal dominant thrombocytopenia: incomplete megakaryocyte differentiation and linkage to human chromosome 10

AbstractWe studied a large kindred with nonsyndromic autosomal dominant thrombocytopenia to define the phenotype and used genomic linkage analysis to determine the locus of the abnormal gene. Affected family members are characterized by lifelong moderate thrombocytopenia (mean = 42.7 × 109/L) with moderate propensity toward easy bruising and minor bleeding. Megakaryocytes are present in bone marrow with reduced frequency, and there are no apparent abnormalities of myeloid or erythroid cells. This type of inherited thrombocytopenia has no evident association with hematopoietic malignancy or progression to aplastic anemia. In the past, members of this family have failed therapeutic trials of immunosuppression and splenectomy. In our investigation, we found that affected individuals had normal platelet size compared with unaffected family members and modestly increased thrombopoietin levels. Hematopoietic colony assays from bone marrow and peripheral blood demonstrated that megakaryocyte precursors (CFU-Mk) were dramatically increased in both number and size in affected individuals. Bone marrow cells grown in liquid culture with thrombopoietin failed to develop polyploid cells greater than 8N. Also, electron microscopy demonstrated that megakaryocytes from an affected individual had markedly delayed nuclear and cytoplasmic differentiation. Genome-wide linkage analysis established a single locus for the disease gene on the short arm of chromosome 10 with a maximum 2-point lod score of 5.68 (at θ = 0). By recruiting additional family members, the genomic region was narrowed to 17 centimorgans. We conclude that a gene in this locus plays an important role in megakaryocyte endomitosis and terminal maturation.

Analysis of X-chromosome inactivation and presumptive expression of the Wiskott-Aldrich syndrome (WAS) gene in hematopoietic cell lineages of a thrombocytopenic carrier female of WAS

We report on a thrombocytopenic female belonging to a pedigree with the Wiskott-Aldrich syndrome (WAS). Restriction fragment length polymorphism (RFLP) analysis with probe M27 beta, closely linked to the WAS gene, demonstrated that she is a carrier of WAS. Both small-sized and normal-sized platelets were present, suggesting that, unlike the vast majority of WAS carriers, she does not manifest nonrandom X-chromosome inactivation in the thrombopoietic cell lineage. Study of X-chromosome inactivation by means of RFLP and methylation analysis demonstrated that the pattern of X-chromosome inactivation was nonrandom in T lymphocytes, but random in granulocytes. While this is the first complete report on the occurrence of thrombocytopenia in a carrier female of WAS as the result of atypical lyonization, it also suggests that expression of the WAS gene occurs at (or extends up to) a later stage than the multipotent stem cell along the hematopoietic differentiation pathway.

Platelets of the Wistar Furth rat have reduced levels of alpha-granule proteins. An animal model resembling gray platelet syndrome.

Rats of the Wistar Furth (WF) strain have hereditary macrothrombocytopenia (large mean platelet volume [MPV] with increased platelet size heterogeneity and reduced platelet count). Ultrastructural studies suggest that this anomaly results from erratic subdivision of megakaryocyte cytoplasm into platelets. In this study, we have examined protein profiles of platelets of WF rats for biochemical abnormalities associated with this anomaly. Marked decreases in protein bands with an Mr of 185, 57, 53, 16, 13, and 8 kd were observed in one-dimensional reduced SDS-PAGE gels in WF platelets compared with platelets of Wistar, Long Evans, and Sprague-Dawley rats. These proteins were released into the supernatant when washed platelets were treated with thrombin suggesting that they were alpha-granule proteins. These abnormalities were not present in offspring of crosses between Wistar Furth and Wistar rats; however, they were present in platelets of offspring with large MPV derived from backcrosses of (WF X Wistar) F1 males to WF females, but not in backcross offspring with normal platelet size. Immunoblotting confirmed decreased levels of thrombospondin, fibrinogen, and platelet factor 4 in WF platelets. Electron microscopic examination revealed that platelet alpha granules were usually smaller in Wistar Furth than in Wistar rats. In addition, immunogold electron microscopy demonstrated that the surface connected canalicular system of the large Wistar Furth platelets, contained dense material composed of alpha-granule proteins, not present in Wistar platelets. From these results, we conclude that the Wistar Furth rat platelet phenotype of large mean platelet volume and decreased levels of alpha-granule proteins represents an animal model resembling gray platelet syndrome. The autosomal recessive pattern of inheritance of the large MPV phenotype and platelet alpha-granule protein deficiencies suggests that a component common to both formation of platelet alpha granules, and subdivision of megakaryocyte cytoplasm into platelets, is quantitatively or qualitatively abnormal in Wistar Furth rat megakaryocytes and platelets.

Variation in Surface Platelet Glycoprotein lb Expression in Bernard-Soulier Syndrome

Seven patients with Bernard-Soulier syndrome (BSS) and 15 presumed heterozygotes of BSS from four families are presented. Evaluation of their platelet membranes was performed by an enzyme-linked radioimmunosorbent assay (ELISA) technique including monoclonal antibodies specific for glycoprotein (GP) Ib and GPIIb/IIIa. Analyses of platelets from the patients revealed 6-33% of the normal GPIb concentration; siblings showed nearly equal amounts of this component. One of the relatives had 44% of the normal level, while 85-98% (mean 92%) of the normal GPIb content was observed in the remaining relatives. Normal or slightly elevated levels of GPIIb/IIIa were detected in the patients as well as in the relatives. All relatives had normal platelet count, size distribution, bleeding time, and ristocetin-induced platelet aggregation. The patients and their relatives may account for a biological variation in GPIb expression or may represent a variant type of BSS.

凝集塊のある濃厚血小板の機能について

Platelet size distribution and aggregation response were studied in platelet concentrates (PCs) containing platelet aggregates. Both normal and abnormal platelet size distribution were observed. As the number of clumps in PC increased, abnormal size distribution patterns also increased. As size distribution became abnormal, aggregability to thrombin decreased. Passage of PC through microaggregate filters did not affect platelet functions.These in vitro results indicate that some PCs, containing platelet aggregates can be used for transfusions while others can not. The selection of the proper PC can be judged by the number of clumps, and more exactly, by platelet size distribution. PCs of normal size distribution can be used for transfusion provided adequate blood filters are employed.

Platelet-Associated Immunoglobulin, Platelet Size, and the Effect of Splenectomy in the Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome (WAS) thrombocytopenia is frequently improved by splenectomy, although the mechanism of the thrombocytopenia and its resolution are unknown. Previous studies in two patients have shown that mean platelet volume, which is characteristically reduced in WAS, increased along with platelet count postsplenectomy. Additional studies in a limited number of patients have also demonstrated that platelet-associated immunoglobulin G (PAIgG) is elevated presplenectomy, but to date no postsplenectomy data have been reported. The present study was performed to more fully evaluate the effect of splenectomy on platelet volume and PAIgG in WAS. Before splenectomy, mean platelet volume was reduced but platelet size was broadly distributed with substantial overlap of the normal range. PAIgG was significantly elevated in 13 of 14 presplenectomy WAS patients (means = 78.9 fg per platelet) and fell to normal levels postoperatively (means = 4.0 fg per platelet). Platelet count and clinical status improved postsplenectomy, and mean platelet volume and platelet volume distribution returned to the normal range. WAS subjects who relapsed with recurrent thrombocytopenia redeveloped elevated PAIgG but maintained normal platelet size. The spleen appears to play a critical role in a process that may be immunologically mediated and results in reduced platelet size.

Platelet dysfunction in patients with vitamin B12 deficiency.

10 cases of pernicious anaemia are reported in which 6 had abnormal aggregation with epinephrine, 3 with fibrinogen, 2 with ADP, and 2 with ristocetin. 5 patients had thrombocytopenia and 3 of these had a prolongation of the bleeding time. These abnormalities were normalized after vitamin B12 treatment. After treatment, platelet size changed toward a smaller diameter, but platelet size, however, was not significantly different from the normal platelet size distribution.

Microscopic Platelet Size and Morphology in Various Hematologic Disorders

Microscopic evaluation of apparent platelet size and morphology was examined in a variety of hematologic disorders. The time of preparation of the blood smear was important. An artifactual increase in platelet size was noted on blood films from 20 normal individuals that were prepared either immediately or 180 min after venipuncture. The clearest differentiation of patient categories was obtained with smears prepared 60 min after venipuncture using blood anticoagulated with K3EDTA. Under these conditions, normal size and morphology values were found in thrombocytopenic patients with aplasia or with increased splenic pooling. In contrast, large size values were a reliable finding in idiopathic thrombocytopenic purpura patients, whose platelet counts were less than 50,000/microleter. Large size values were also noted in patients with infiltrated bone marrows or myeloproliferative syndromes regardless of the platelet count. The last two groups usually showed abnormal platelet morphology with greater than 10% hypogranular platelets. Normal platelet size and morphology were observed in patients with iron-deficiency and megaloblastic anemias and in patients with idiopathic thrombocytopenic purpura and systemic lupus erythematosus who had normal platelet counts.

Microscopic platelet size and morphology in various hematologic disorders

Microscopic evaluation of apparent platelet size and morphology was examined in a variety of hematologic disorders. The time of preparation of the blood smear was important. An artifactual increase in platelet size was noted on blood films from 20 normal individuals that were prepared either immediately or 180 min after venipuncture. The clearest differentiation of patient categories was obtained with smears prepared 60 min after venipuncture using blood anticoagulated with K3EDTA. Under these conditions, normal size and morphology values were found in thrombocytopenic patients with aplasia or with increased splenic pooling. In contrast, large size values were a reliable finding in idiopathic thrombocytopenic purpura patients, whose platelet counts were less than 50,000/microleter. Large size values were also noted in patients with infiltrated bone marrows or myeloproliferative syndromes regardless of the platelet count. The last two groups usually showed abnormal platelet morphology with greater than 10% hypogranular platelets. Normal platelet size and morphology were observed in patients with iron-deficiency and megaloblastic anemias and in patients with idiopathic thrombocytopenic purpura and systemic lupus erythematosus who had normal platelet counts.