Search

The most commonly ordered test used for managing patients worldwide is the hemogram, with or without the review of a peripheral smear. The measured features in a standard hemogram has undergone modification of the over the last 30 years with an expansion to the panel of tests. The initial hemogram was the hemoglobin, hematocrit, and total white cell count, to which platelet count, lymphocytes and neutrophils were added as the necessary vital dye stains and the resolution were substantially improved. The revolutionary Coulter principle used impedance of the cells passing through a narrow window. Newer instruments may used both impedance and/or flow cytometric principles. Yet the accurate identification of reticulocytes, measurement of cellular hemoglobin, measurement of immature granulocytes, lymphoid or myeloblasts, identification of clumped platelets interfering with identification of large platelets were all challenges to overcome. The hemogram provides a vital window to visualize the cellular changes associated with the production, release or suppression of the formed elements from the blood forming organ to the circulation. In this chapter, we shall not be concerned with the specific use of the hemogram in assessing disorders to the coagulation pathways or its use in detection of hematological and non-hematological tumors. Rather in the hemogram we can view data reflective of a broad spectrum medical conditions affecting most patients presenting to a physician who are then referred to a specialist for example in hematology-oncology or infectious diseases.

Background: The Sysmex XT-2000iV is a laser-based, flow cytometric hematology system that has been introduced for use in large and referral veterinary laboratories. Objective: The purpose of this study was to validate the Sysmex XT-2000iV for counting erythrocytes, reticulocytes, platelets, and total leukocytes in blood from ill dogs, cats, and horses. Methods: Blood samples from diseased animals (133 dogs, 65 cats, and 73 horses) were analyzed with the Sysmex XT-2000iV and the CELL-DYN 3500. Manual reticulocyte counts were done on an additional 98 canine and 14 feline samples and manual platelet counts were done on an additional 73 feline and 55 canine samples, and compared with automated Sysmex results. Results: Hemoglobin concentration, RBC counts, and total WBC counts on the Sysmex were highly correlated with those from the CELL-DYN (r≥0.98). Systematic differences occurred for MCV and HCT. MCHC was poorly correlated in all species (r=0.33–0.67). The Sysmex impedance platelet count in dogs was highly correlated with both the impedance count from the CELL-DYN (r=0.99) and the optical platelet count from the Sysmex (r=0.98). The Sysmex optical platelet count included large platelets, such that in samples from cats, the results agreed better with manual platelet counts than with impedance platelet counts on the Sysmex. Canine reticulocyte counts on the Sysmex correlated well (r=0.90) with manual reticulocyte counts. Feline reticulocyte counts on the Sysmex correlated well with aggregate (r=0.86) but not punctate (r=0.50) reticulocyte counts. Conclusion: The Sysmex XT-2000iV performed as well as the CELL-DYN on blood samples from dogs, cats, and horses with a variety of hematologic abnormalities. In addition, the Sysmex detected large platelets and provided accurate reticulocyte counts.

A VLS-like mechanism is illustrated of how 3-Cu-layer Bi-HTSC (high temperature superconductor) is slowly formed from precursors by small, Bi/Pb rich, liquid droplets migrating over growing platelets, depositing ledges (steps) of product in their wakes. The difficulty of obtaining a pure 3-layer, i.e. without syntactic intergrowths, is explained.

Background: Many Cavalier King Charles Spaniel (CKCS) dogs are affected by an autosomal recessive dysplasia of platelets resulting in fewer but larger platelets. The IDEXX Vet Autoread (QBC) hematology analyzer directly measures the relative volume of platelets in a blood sample (plateletcrit). We hypothesized that CKCS both with and without hereditary macrothrombocytosis would have a normal plateletcrit and that the QBC results would better identify the total circulating volume of platelets in CKSC than methods directly enumerating platelet numbers. Objectives: The major purpose of this study was to compare the QBC platelet results with platelet counts from other automated and manual methods for evaluating platelet status in CKCS dogs. Methods: Platelet counts were determined in fresh EDTA blood from 27 adult CKCS dogs using the QBC, Sysmex XT-2000iV (optical and impedance), CELL-DYN 3500, blood smear estimate, and manual methods. Sysmex optical platelet counts were reanalyzed following gating to determine the number and percentage of normal- and large-sized platelets in each blood sample. Results: None of the 27 CKCS dogs had thrombocytopenia (defined as

SummaryExtinction (E) or light transmission measurements of platelet suspensions have been widely used to evaluate platelet structure and aggregation for platelet populations of varying mean platelet size (V). However, useful comparisons of platelet suspensions from donors having abnormally-sized platelets with those from healthy controls require a knowledge of the dependence of E on V. We have analyzed the extinction per platelet (e) as a function of the geometric scattering cross-section of equivalent spheres, V2/3, related to the apparent mean platelet optical efficiency, k. Such an analysis using data previously reported by Holme et al., for healthy controls and a variety of platelet-associated disorders showed e/V2/3 or k to be constant over an eight-fold variation in V. The outstanding exception was platelet suspensions from myeloproliferative disorder patients (MPD) which showed ˜25% reduction in k values. When we analyzed e/V2/3 data for differentsized platelet subpopulations which were isolated by elutriation from healthy donors, we found that k doubled with a doubling in V from small to large platelets. It appears that the use of aggregometry devices with wide light acceptance angles yields k values for platelets which are insensitive to variations in V, but rather are sensitive to the expected variations in refractive index associated with distinct platelet internal composition and organization expected for different-sized normal subpopulations and “diseased” platelets as found in MPD. We relate these observations to photometric studies of platelet heterogeneity and of aggregation of platelets with different V and k values.

Las enfermedades genéticas plaquetarias son desórdenes heterogéneos, algunos de ellos muy raros, que se presentan en la medicina clínica, caracterizados por trobocitopenia, plaquetas grandes (macrotrombocitopenias) y signos variables de hemorragia, así como trombosis en otros casos. La patogénesis y patofisiología es bastante desconocida y el propósito de este artículo es proveer una estructura lógica que resuma el conocimiento actual. Abreviaturas: PQ, plaquetas.

Platelets play a crucial role in the pathophysiology of atherothrombotic disease and are involved in the early thromboembolic phase of ischaemic stroke. Large platelets are known to be more active. We hypothesized that thrombomegaly would be limited to patients with cortical infarction as compared with patients with lacunar infarcts, and that it would be associated with functional outcome. Mean platelet volume (MPV) and platelet count (PC) were studied in 167 hospitalized patients with stroke within 48 h of symptom onset, and 65 age, gender and race matched controls. Stroke was clinically and radiologically sub-typed. MPV was significantly higher in patients with ischaemic stroke than the control group: mean (SD) 7.35 (1.05) vs 7.09 (0.74) fl, 2 P = 0.04; this difference could be explained by MPV being higher in patients with cortical stroke: 7.46 (1.00) fl, 2 P = 0.039, but not lacunar infarction: 7.14 (1.16) fl, 2 P = 1.0. No difference was seen in PC between ischaemic patients and controls: 231 (82) 10(9)/l vs 236 (54) 10(9)/l, 2 P = 0.63. MPV did not change at 3 months post-stroke in surviving patients with ischaemic stroke: 7.39 (1.03) fl vs 7.34 (0.97) fl, 2 P = 0.53. Patients who were dead or dependent at 3 months had a significantly higher baseline MPV and a tendency to a lower PC than those who returned to independence. MPV and PC were not altered in patients with primary intracerebral haemorrhage. No differences in red cell volume was observed. Platelet volume is elevated in acute ischaemic stroke, a finding that persists at 3 months post-stroke and is limited to patients with cortical infarction. Thrombomegaly is a risk factor for a poor outcome after ischaemic stroke.

Objective: To report a case of chromosome 22q11.2 deletion presenting with large platelets, platelet dysfunction, immune-mediated thrombocytopenia and neutropenia, in addition to other features of the disease. Case Presentation and Intervention: The patient presented in the neonatal period with tetralogy of Fallot, subtle dysmorphic features and thrombocytopenia. Fluorescent in situ hybridization analysis confirmed the diagnosis of chromosome 22q11.2 deletion. Further investigations showed immune thrombocytopenia and neutropenia in addition to reduced expression of platelet GPIb and abnormal platelet aggregation studies. CD4:CD8 ratio was reversed. His cardiac abnormality was successfully corrected surgically. He had mild recurrent bacterial infections. Recurrent epistaxis was becoming increasingly more severe, and he had cognitive developmental and speech delay. His serum calcium, phosphorus and parathormone have remained normal. Conclusions: Immune thrombocytopenia can coexist with macrothrombocytopenia and platelet dysfunction in chromosome 22q11.2 deletion and may present with significant bleeding episodes.

Background: The ADVIA 120 is a laser-based hematology analyzer with software applications for animal species. Accurate reference values would be useful for the assessment of new hematologic parameters and for interlaboratory comparisons. Objective: The goal of this study was to establish reference intervals for CBC results and new parameters for RBC morphology, reticulocytes, and platelets in healthy dogs and cats using the ADVIA 120 hematology system. Methods: The ADVIA 120, with multispecies software (version 1.107-MS), was used to analyze whole blood samples from clinically healthy dogs (n=46) and cats (n=61). Data distribution was determined and reference intervals were calculated as 2.5 to 97.5 percentiles and 25 to 75 percentiles. Results: Most data showed Gaussian or log-normal distribution. The numbers of RBCs falling outside the normocyticnormochromic range were slightly higher in cats than in dogs. Both dogs and cats had reticulocytes with low, medium, and high absorbance. Mean numbers of large platelets and platelet clumps were higher in cats compared with dogs. Conclusions: Reference intervals obtained on the ADVIA 120 provide valuable baseline information for assessing new hematologic parameters and for interlaboratory comparisons. Differences compared with previously published reference values can be attributed largely to differences in methodology.

Low platelet counts (< 150 x 10(9)/litre) have been measured by autoanalyser in cavalier King Charles spaniels with a wide range of diseases. However, the direct examination of blood smears revealed adequate numbers of platelets but many abnormally large platelets and it was not clear whether the large platelets were the result of disease or a breed abnormality. The numbers and diameters of the platelets in a group of clinically normal King Charles spaniels and a group of other breeds were measured by autoanalyser and manually. The automated platelet counts were lower in the King Charles spaniels than in the other breeds (P < 0.01), but the manual counts were similar. The platelet diameter was greater in the cavalier King Charles spaniels (median values 2.5 to 3.75 microns, P < 0.001) than the other breeds (median values 1.25 to 2.5 microns) and had a bimodal distribution with peaks at 1.25 to 2.5 microns and 3.75 to 5 microns. No clinical evidence of platelet dysfunction was detected. These findings indicate that cavalier King Charles spaniels may have large platelets which could lead to the erroneous diagnosis of thrombocytopenia by automated haematological analysis.

Frequencies of reticulated platelets (RP) and large platelets (LP) among circulating platelets can now be simultaneously determined using the R-3000 automated reticulocyte counter (Sysmex, Kobe, Japan) equipped with special software. We measured frequencies of RP and LP in patients with idiopathic thrombocytopenic purpura (ITP, acute type n = 5; chronic type n = 39), and healthy normal controls (n = 20). In ITP patients, the platelet-associated IgG (PAIgG) level was also determined. Both RP and LP were significantly higher in chronic ITP patients than those in normal volunteers, and interestingly, the LP in acute ITP was significantly lower than that in chronic ITP although there was no significant difference in RP between acute and chronic ITP. Furthermore, we analyzed the changes in both RP and LP during the clinical course of ITP to monitor the therapeutic effect in 2 patients. An elevation of RP with a steep slope prior to a decrease in the platelet count level was observed. The RP significantly correlated with the PAIgG level. Simultaneous measurement of RP and LP may be helpful for the diagnosis of chronic ITP, for the differentiation of acute from chronic type and for the control of the efficacy of management in ITP, since RP seems to reflect the disease activity of ITP.

The spleen contains about one third of total body platelets, which are relatively larger and hemostatically more active. Since voluntary apnea triggers splenic contraction we evaluated whether breath-holding impacts on circulating platelets. 18 trained divers and 24 untrained persons, 6 of whom had been splenectomized performed five successive maximal apneas, separated by 2 min periods. The venous samples, taken at baseline, immediately after each apnea and up to 60 min after the last apnea, were analyzed for platelet count, corrected for changes in total protein concentration, and mean platelet volume. Apneas did not affect platelet count, while the mean platelet volume increased significantly in trained divers, maximally for 9.3% (p=0.02), non-significantly in intact untrained persons (3.1%, p=0.1) and stayed unchanged in splenectomized persons. Breath-holding initiates the increase of large platelets in circulation. Hypothetically, these results can explain the increased risk of thromboembolic events in obstructive sleep apnea.

A case of hereditary thrombocytopenia with large platelets (familial macrothrombocytopenia, FM) is reported. Studies on the platelets from the propositus showed decreased glycosylation of platelet membrane glycoprotein IV, which would distinguish the case from other FM previously described.

Abstract 1097 The immature platelet fraction (IPF) is a useful parameter indicating thrombopoietic activity to differentiate the causes of thrombocytopenia. We previously reported that the percentage of IPF (%IPF) is negatively correlated to the platelet count among ITP patients, and not among myelodysplastic syndrome (MDS) patients. We also noticed that some MDS patients exhibited extremely high %IPF values, which were dissociated from the percentages of reticulated platelets (%RP) measured by flow cytometry. Such discrepancies were also observed in hereditary macrothrombocytopenias, which are sometimes difficult to be distinguished from ITP, because ITP also exhibits increased number of reticulated platelets in a slightly larger size. Once misdiagnosed, a hereditary macrothrombocytopenia patient might be subjected to an invasive treatment such as splenectomy. In order to avoid such mistreatments, a clear marker to differentiate macrothrombocytopenia is desperately needed. In this study, we investigated the IPF values of 16 individuals from 12 families with various hereditary macrothrombocytopenia in order to clarify whether the IPF could be a useful marker to distinguish macrothrombocytopenia from ITP, and examined the IPF during EDTA aggregation and cold-storage to elucidate how platelet size may affect the IPF value. The IPF values were about 5 times higher in MYH9 disorders (%IPF 48.0 ± 1.8) and about 1.5 times higher in other macrothrombocytopenias (%IPF 17.0 ± 2.2) than immune thrombocytopenic patients with similar platelet counts (%IPF 9.3 ± 0.4). These results suggested that the platelet size can affect the IPF value. However it still remains the possibility that some factors specific to these macrothrombocytopenias other than the platelet size might make an influence on the IPF, because the characteristic of large platelets in hereditary macrothrombocytopenia has not been fully understood, and no one knows whether large platelets are functionally identical to normal platelets except for the size. In order to exclude the possibility, we next examined the changes of IPF values during EDTA aggregation and cold-storage. The IPF was significantly increased during storage in a time dependent manner along with forming platelet clumps. The IPF was strongly influenced by a few tiny platelet aggregates rather than other platelet indices, such as mean platelet volume (MPV), platelet-large cell ratio (P-LCR) and platelet distribution width (PDW). In conclusion, the IPF is susceptible to the platelet size, and could be a useful parameter for screening of macrothrombocytopenia from ITP. Disclosures: No relevant conflicts of interest to declare.

The measurement of the number of platelets larger than 3 microns (megathrombocyte index) is the first element in the evaluation of thrombocytopenia. This is currently performed by counting the number of large platelets on the peripheral blood film. The MPV (mean platelet volume) is an automated measurement of the platelet volume. This study examines the mean values, correlations, sensitivity, specificity and the receiver operating characteristic curve (comparison of two tests) to determine which of these tests better separates the production state. For increased vs. decreased production, the MPV was 10.0 + 1.9 fL and 8.0 + 1.5 fL (P < .0001) respectively and the megathrombocyte index (MEGA) was 19.0 + 17.6% and 11.5 + 14.9% (P < .007) respectively. The correlation with the state of production was better for MPV (R = .47) than for MEGA (R = .20). For the MPV a sensitivity of 80% occurred with the MPV ⩾ 8.4 fL with a specificity of 71%. For a MEGA ⩾ 6%, the sensitivity was 80% but the specificity was 43%. For any MPV the sensitivity and specificity were better than for any MEGA. The Receiver Operating Characteristic Curve demonstrated that the MPV is a better test than the MEGA for separating the production into increased and decreased states. The MPV is a better test than the MEGA and will add to, but not replace, examination of the peripheral blood film in the diagnosis of thrombocytopenia. © 1993 Wiley-Liss, Inc.

Severe gangrenous mastitis due to Staphylococcus aureus infection was diagnosed in a 7 year-old intact female beagle which was presented with swelling of mammary glands after dystocia. Leukocytosis (25,200-48,600/microliters), decreased platelets (107,000-179,000/microliters), and abnormal platelet pattern continued during the critical condition. Consistent with platelet pattern, large platelets were observed in the blood smear. The number of leukocytes and platelets rapidly returned to normal during treatment, and the platelet pattern was also restored. The number and pattern of platelet may provide a clue for the evaluation of the clinical condition and/or severity of the lesions in the dog with mastitis.

Mean platelet volume (MPV) was determined on whole blood and platelet concentrates (PC) prepared from units of the same blood, as well as on samples of venous blood taken from donors before plateletpheresis and on PC collected by Spectra (COBE Laboratories Ltd) and CS-3000 (Baxter Healthcare Ltd) cell separators. The mean (+/- SD) MPV for PC prepared from blood (7.18 +/- 0.76 fl, n = 12) was significantly lower than that for whole blood (8.32 +/- 0.72 fl, P < 0.02) suggesting significant separation of young, large and dense platelets together with the red cells. In contrast, the mean MPV for PC collected with Spectra and CS-3000 cell separators was 8.48 +/- 0.52 fl (n = 20) and 8.94 +/- 0.60 fl (n = 12), respectively, and was significantly higher (P < 0.01) than that determined in venous blood samples of donors taken before plateletpheresis (7.76 +/- 0.74 fl and 8.12 +/- 0.62 fl respectively). This indicates preferential separation of large platelets, which are by inference, of better quality, into PC.

We experienced a case in which yeasts in blood sample from a patient with cervical cancer with hepatic metastasis and multiple intraperitoneal cysts interfered with platelet morphology flag in automated blood analyzer. The peripheral blood smear was performed to confirm the flag and revealed intracellular and extracellular yeasts, which were subsequently identified as Candida parapsilosis by blood culture. (Korean J Clin Microbiol 2009;12:138-140)

Giant platelet syndrome is a group of unique disorders characterized by the presence of abnormally large platelets, and usually accompanied by thrombocytopenia. Most cases of giant platelets are encountered in idiopathic thrombocytopenic purpura(ITP). In contrast, inherited giant platelet disorders, a group of heterogeneous diseases, are rare. Bernard-Soulier syndrome and its variants, and MYH9 related diseases have been defined at the molecular level. Abnormalities in transcription factors are implicated in a couple of macrothrombocytopenia syndromes. However, the molecular defects are unknown in gray platelet syndrome. It is important to make a proper diagnosis of congenital macrothrombocytopenia to avoid unnecessary medications and potentially dangerous treatment for presumed ITP

20 out of 50 patients with well-functioning renal allograft displayed at least one platelet count below 110×109/1 (mean -2 SD of controls). For estimation of platelet production during thrombocytopenic episodes, the percentage of large platelets in the peripheral blood was determined which revealed an inverse relationship (p

A form of von Willebrand's disease has been described with enhanced ristocetin-induced platelet aggregation and anodal migration of the factor VIII/von Willebrand factor protein (type IIb). We studied two families with this form of von Willebrand's disease and macrothrombocytopenia. We have found that these platelets bind more of the normal and intermediate-sized multimers of the factor VIII/von Willebrand factor than normal platelets. Analysis of the binding data show an increased affinity of these vWd platelets for the factor VIII/von Willebrand factor. These findings are consistent with an increased number of platelet receptors, which, either by their native topography or migration on the platelet surface, bind factor VIII/von Willebrand factor protein with greater affinity than normal platelets, platelets of other vWd patients, and large platelets of other etiologies.

A method for the separation of platelets on the basis of their volume has been developed using counterflow centrifugal elutriation (CCE).Human peripheral blood platelets were eluted into nine fractions and four types of pattern of the eluted platelets from CCE were observed (Fig. 3), For measurenment of pletelet diameter a flow cytometry was used, and the diameters are given as the mean channel of foward scatter. The smallest-size platelets had a mean channel of 118±7.3. Each succesive fraction had a progressively lager mean channel. The mean channel for the largest-sized platelets, designated fraction 9, was 146±6.8 (Fig. 5).The nine platelet fractions were separated into small platelets (fraction 2-4) and large platelets (fraction 7-9).Transmission electron microscopy demonstrated that small platelets had a mean diameter of 2.1±0.48μm and large platelets had a mean diameter of 3.1±0.48μm. The large platelets possessed a number of granules and mitochondria in the cytoplasm than that of the small platelets (Table 1).Platelet function was measured by ADP and collagen-induced aggregation. For analysis, height of aggregation curve (h), slope in aggregation curve (θ), and lag time in aggregation time were observed (Fig. 8). No significant difference between small and large platelets in aggregation was found (Table 2).

2 members of a family, a child and his father, showed a combined morphological abnormality of leukocytes and platelets. The abnormality consisted of the presence of pseudodrumsticks in the neutrophils and of large platelets. One or more than one pseudodrumstick was present in about 40% of neutrophils. Leukocyte count, differential count and enzymatic stains were normal. Large platelets constituted about 25% of the platelet population. 1 patient also had mild thrombocytopenia which appeared to be unrelated to the basic defect since it appeared after a parotitis infection. Platelet function was normal but for a moderate prolongation of the bleeding time in the patient who had mild thrombocytopenia. No chromosomal abnormality was present in the propositi. The condition seems different from other leukocyte and platelet abnormalities so far described.

SummaryThe bleeding time is shortened and the mean platelet volume is increased in the acute phase of myocardial infarction. In this follow-up study we repeated the measurement of the bleeding time, the platelet count and the platelet volume distribution in 18 patients who had suffered from a definite acute myocardial infarction two years before and in 16 control patients who had been admitted with chest pain but no definite myocardial infarction at that time. At the time of follow-up the bleeding time was significantly lengthened in the myocardial infarction group (median values = 169 s and 209 s respectively), whereas it had shortened in the control group (median values = 258 s and 228 s respectively). Comparison of the platelet volume distribution curves of the myocardial infarction patients at time of infarction and 2 years later revealed a significantly higher percentage of small platelets and significantly lower percentages of both medium-sized and large platelets at the time of infarction. These changes in the platelet volume distribution could indicate consumption of medium-sized and large platelets at the time of myocardial infarction. None of the measured variables predicted which of the patients with acute myocardial infarction would subsequently re-infarct or die. In the patients studied with definite ischaemic heart disease (n = 26) a significant negative correlation between bleeding time and mean platelet volume was found. The shortened bleeding time in myocardial infarction is related to the acute event itself or preceeds it, but is reversed two years later.

Since heterogeneity of circulating platelets is present, we have analyzed what kind of platelets and what factors in platelets do play an important role in thrombogenesis. Using 51 healthy young men and women (22.2±4.6 years in mean±SD), 17 patients in acute stage of thrombosis such as myocardial infarction or cerebral thrombosis (The two-week period following the onset of thrombosis was called the acute stage), 19 patients in the recovery stage of thrombosis and 8 DIC patients, their platelet volume, aggregability and adenine nucleotides content were measured. In healthy volunteers, platelet count was 30.1±5.9×104/μl, platelet mode volume was 4.21±0.56, mean volume was 5.32±0.42 and median volume was 4.66±0.47μ3. There was a significant correlation between platelet mode volume and 5 minutes aggregation induced by 3μM ADP (r=0.375, p

Theories for the blue phase proposed recently by Brazovskii and Dmitriev and by Hornreich and Shtrikman predict that this phase can exist only for cholesterics of sufficiently short pitch. In this article we demonstrate this dependence upon pitch through microscopic observations of three sets of binary mixtures, one set consisting of mixtures of cholesterics of opposite chirality and the other two consisting of cholesteric-nematic mixtures. In the course of these studies we have developed techniques for growing particularly large platelets of the blue phase. We present photographs of these platelets demonstrating, for the first time, the optical anisotropy of the blue phase, which is evident when the platelets are sufficiently large. Characteristic twinning patterns are also evident in the photographs.

1. In a healthy infant and a healthy adult not a change of blood platelets was seen on an administration of a large amount of vitamin B. 2. B-avitaminotic infants fed on human milk negative to Arakawa's reaction showed an anemia and thrombocytosis. 3. When vitamin B was administered to babies and their mothers, blood platelet count showed a decrease, and anemia began to recover in parallel with an increase in the intensity of Arakawa's reaction. 4. There were some cases in which platelet count returned to normal in spite of the fact that Arakawa's reaction of mother's milk remained negative. This is not strange if Takamatsu's10) and others' works are taken into consideration. 5. Blood platelets decrease more rapidly on an administration of vitamin B to both infants and their mothers than on an administration to the former only. 6. As to the classification of platelets, large platelets showed a decrease at first and small platelets began to increase and then returned to the normal ratio of platelets on vitamin B administration.

Five female members of a family manifesting a dominantly inherited bleeding disorder were investigated for coagulation and platelet abnormalities. A long bleeding time, mild thrombocytopenia, large platelets, low platelet factor-3 activity (PF-3), and low factor VIII levels were found in the proband. Long bleeding times, low PF-3, and low factor VIII levels were found in various combinations in the four other family members studied. PF-3 was abnormal by three techniques in the proband and could be corrected by adding ADP. Her platelets and those of one other member did not aggregate when exposed to collagen. The proband’s platelets did not release ADP on collagen exposure. The severity of bleeding was proportional to the number of laboratory abnormalities in the individual’s studied. The findings in this family overlap both hereditary thrombopathia and von Willebrand’s disease and were quite variable between family members. It appears that there exists a spectrum of dominant hereditary bleeding disorders with abnormalities in the platelets or factor VIII levels or both, with variable expressivity in family members.

Results of 123 cases without special complications will be summar-ized. 1. Red cell. count was 5, 094, 4, 869 and 4, 632 thousands in the cases of strongly Arakawa-positive, intermediate, and completely or almost completely Arakawa-negative group respectively. 2. Blood platelet count was 307, 395 and 495 thousands in the cases of strongly Arakawa-positive, intermediate, and completely, or almost completely Arakawa-negative group respectively. 3. As to Horwitz's classification of blood platelets, the percentage of the sum of spindle-shapped and small platelets and pathologi cal large platelets was larger according as Arakawa's reaction became weaker. 4. In the cases in which infants and/or their mothers had been' taking vitamin B, blood platelet count was within the normal limits, while red cell count and classification of blood platelets still remained in the count corresponding to that of the intermediate group of Ara kawa's reaction.

I have obtained the following summary by investigating 237 cases. 1. The mean value of red cell count is 5, 210, 000 in healthy suck-lings and 5, 180, 000 per cmm. in healthy children and adults. 2. Anemia occurs in the cases of sucklings nourished with milk negative to Arakawa's reation-B-avitaminotic sucklings. 3. Platelet count is 299, 000 per cmm. in normal sucklings and 251, 000 in healthy adults and children. 4. The average blood platelet count is 291, 363 and 400 thousands according as Arakawa's reaction becomes weaker. 5. Blood platelet count in avitaminosis B is 477 thousands and this is larger than that of Arakawa-negative group. 6. In the Horwitz classification of blood platelets, normal limits are from 19% to 24 in small platelets and up to 5 in large plate-lets. 7. The ratio of blood platelets in sucklings 2 months old or under is 27.9:68.6:3.5. Both counts of large and small platelets are larger than in older sucklings. 8. The ratio of large platelets is 1:2:3 in percentage and 1:3.7:5 in absolute count according as Arakawa's reaction becomes weaker. 9. In the beginning of B-avitaminosis, blood platelet count shows a slight rise with an increase of small platelets, in the next stage platelet count becomes larger and at the same time large platelets begin to increase and in the manifest stage of avitaminosis B an increase of large platelets becomes remarkable besides the above mentioned chan-ges. 10. Sucklings nourished with human milk negative to Araka-wa's reaction are more or less inclined to a state of B-avitaminosis. 11. It is important to examine not only the platelet count but also its classification in avitaminosis B for the purpose of diagnosis and treatment.

SummaryThe collagen-induced response of free platelets during aggregation was measured with an electronic particle size analyzer. Aggregation was induced in platelet-rich plasma by 0.05 mg/mL collagen. The reaction was followed turbidimetrically and samples for electronic particle size analysis were obtained during aggregation.Free platelet number decreased rapidly after the addition of collagen. This decrease preceded detectable changes in transmittance and a significant reduction in free platelet number was measured during the classical lag phase. In addition, the size distribution of free platelets at variotrs times after the addition of collagen was not significantly altered indicating that large platelets are not preferentially involved in collagen-induced aggregation.

It has been shown that large platelets are hemostatically more active than the smaller ones. We therefore studied the relationship between the mean platelet volume and the percentage of micro- and mega-thrombocytes measured by a Coulter counter S plus II, and the bleeding tendency in 57 unselected patients with a platelet count below 50 X 10(9)/l. We found no significant differences for any of these parameters between patients without and those with mild or severe bleeding tendency. This also held true when patients with a possible platelet dysfunction or with coagulation abnormalities were excluded. We conclude that platelet volume analysis in unselected patients with severe thrombocytopenia is not helpful in the prediction of their risk of bleeding.

Platelet von Willebrand factor (vWf) was compared to its plasma counterpart. The platelet vWf was different from plasma vWf in that the multimeric organization was different, larger multimers were present, and the ratio of vWf activity to antigen was higher. Platelet and plasma vWf were similar in their antigenic reactivity in the electroimmunoassay and by liquid phase radioimmunoassay. The amount of vWf activity in large platelets was significantly higher than in normal platelets while the antigen content, although somewhat higher, was not significant. These studies show differences between normal platelet and plasma vWf, and also suggest that platelet size must be considered when platelet vWf is measured in disease states.

Two cases of von Willebrand disease (vWD) associated with familial thrombocytopenia were reported. The proband (daughter) and her father showed thrombocytopenia with large platelets and decreased von Willebrand factor activity (VIIIR:WF). Factor VIII procoagulant activity (VIII:C) and factor VIII-related antigen (VIIIR:AG) were normal, but both patients revealed an increased ristocetin-induced platelet aggregation and a qualitative abnormality of the factor VIII protein, which was characterized by fast electrophoretic mobility of VIIIR:AG and an abnormal elution of factor VIII-related activities on Sepharose 2B. DDAVP was hemostatically effective even in this thrombocytopenic patient undergoing a dental extraction.

The presence of “giant” platelets in peripheral circulating blood can be associated with many hematologic disorders. With an automated cell-counting instrument such as the Technicon® H6000, the presence of abnormally large platelets can be detected by examination of the leukocyte X-Y display of the peroxidase channel. When an abnormal pattern is discovered, the patient’s blood can then be examined by preparation of a blood smear to confirm the presence of giant platelets. This can be a beneficial and efficient screening of routine complete blood counts for the possible presence of many hematologic disorders using this automated cell-counting instrument in the hematology laboratory.

Summary. Serial platelet counts and measurements of mean platelet volume have been performed on patients who became thrombocytopenic during open heart surgery. The results show that large platelets are released from the bone marrow during the 48 hours following the operation as a primary response to an acute increase in demand. During this period there is only a gradual recovery of the platelet count. In the subsequent days there is an acceleration of platelet production and a simultaneous reduction in platelet volume. These results suggest a change in the nature of the stimulus following the initial postoperative period, indicating a close relationship between platelet size and the total platelet count. Platelet size, therefore, may not be wholly dependent upon either megakaryocytic heterogeneity or platelet age.

Previous studies have shown that cryopreservation of normal platelets induces a reduction in the contents of secretion granules, the generation of thromboxane B2, and aggregability. The present study investigates whether these changes in the total population occur to the same extent in four size-dependent subpopulations with mean platelet volumes of 4.2, 5.7, 8.0, and 11.1 microns 3, obtained by counterflow centrifugation. Cryopreservation reduced the contents of the alpha granule markers and the generation of thromboxane B2 in the platelets from the four fractions to the same extent as in the platelets from the total suspension. Maximal aggregation of the platelets in response to collagen was measured by optical aggregation. The average decrease in light transmission after freezing was 47 +/- 3 percent (SEM) for the platelets in the total population, 40 +/- 3 percent for the largest platelets, and 65 +/- 5 percent for the smallest platelets, which indicates that aggregability was better preserved in the larger platelets than in the smaller cells. It is possible that, in the smallest platelets, a decrease in thromboxane generation of approximately 70 percent becomes rate-limiting for aggregation. Further improvements in the clinical use of freeze-preserved platelets may be sought in the preparation of concentrates with relatively high counts of large platelets.

Platelet volume and count were measured by aperture impedance techniques in rats during acute thrombocytopenia 2, 6, 12 and 24 h and 3, 6, 9 and 11 days after a single injection of anti-platelet serum (APS). Platelet volume heterogeneity was quantified by four statistical parameters: the measure of central tendency, dispersion, asymmetry and convexity. None of the volume distributions, including the controls, was log Gaussian. Mean platelet volume increased for the first 6 h post APS and then started to decrease although the platelet count had not started to rise. There was an initial increase, followed by a smooth decrease to control values, in the coefficient of variation (suggesting an initial increased dispersion about the mean platelet volume) with concomitant decreases in asymmetry and convexity. In contrast the age of the platelets immediately after the APS injection must have a decreased dispersion about the mean age compared with control values. These facts are used to show that young platelets are not synonymous with large platelets even under the stress of acute thrombocytopenia and support the concept that thrombopoiesis is the dominant factor in determining platelet volume heterogeneity.

With a view to throwing some light on the age characteristics of platelets released into the blood in response to short-term physical exercise, we conducted exercise experiments on 23 healthy subjects previously injected with different platelet populations labelled with 111In and 51Cr. Based on comparative platelet kinetic studies of pre- and post-exercise platelets and on exercise experiments carried out while labelled-platelet populations of different age composition were circulating, we cannot support the concept that the platelets released into the blood in response to exercise are enriched with young platelets. In addition, we found that simultaneously-injected large and small platelets were released to the same extent in response to exercise, but that the sequestration patterns of large and small platelets seem to be different.

An excellent correlation was obtained between the percentage of large platelets, or megathrombocytes, and the number of bone-marrow megakaryocytes in 115 patients with both thrombocytopeni...

To see whether selective consumption of either small or large platelets occurs during haemostasis in vivo the mean platelet volume was studied in six patients who developed thrombocytopenia after trauma. The mean platelet volume at the onset of thrombocytopenia was significantly lower than that on admission (p less than 0.01): selective loss of large platelets had occurred.

Large platelets, or megathrombocytes, have been shown to be young platelets recently released from the marrow. The percentage of megathrombocytes was measured in patients with clinical dis...