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Biomedical subjects

G Escolar

Publications and source records attributed to G Escolar.

At least 37 records · Page 2Linked to original sources
PubMed2001

Prohemorrhagic potential of dipyrone, ibuprofen, ketorolac, and aspirin: mechanisms associated with blood flow and erythrocyte deformability.

Dipyrone, ibuprofen, ketorolac, and aspirin were tested in a well-defined perfusion system (shear rates: 300/s, 800/s, and 1,800/s). Whole blood samples were treated with the drugs at analgesic doses and platelet interaction with damaged subendothelium was measured. All the drugs fully inhibited platelet cyclooxygenase, as assessed by classic aggregometry. Perfusion studies showed that there was a general tendency to reduce the percentage of large aggregates (thrombus; %T), to increase the percentage of adhered platelets (adhesion; %A), and to reduce the height of thrombi with respect to control. Aspirin significantly increased %A and reduced %T at all shear rates tested, whereas dipyrone had the same effect at 800/s, and ketorolac and ibuprofen at 1,800/s. In addition, aspirin significantly reduced erythrocyte deformability with respect to the other drugs. In conclusion, under our experimental conditions, aspirin showed the most remarkable effects on platelet function, closely followed by dipyrone. The effects of ketorolac were moderate, whereas ibuprofen had a minor impact on platelet function.

Analysis of Variance↗
PubMed2001

Uremic medium disturbs the hemostatic balance of cultured human endothelial cells.

We have investigated the ability of serum from uremic patients to modify the thrombogenic properties of the endothelium. The effects of uremic medium on the morphology of endothelial cells (ECs), and their resistance to flow was analyzed. The influence of uremic media on the reactivity of the extracellular matrix (ECM) generated by ECs towards normal platelets was evaluated in a parallel-plate perfusion chamber. Exposure of ECs to uremic medium resulted in abnormal cell morphology and signs of an accelerated growth. Detachment of ECs exposed to circulating blood was increased when cells had been grown with media supplemented with uremic serum (21% vs. 14% non exposed). Platelet deposition was significantly elevated on ECMs generated in the presence of uremic media (uremicECMs) (p<0.01 vs. control studies). Effects of uremic serum were not observed at short incubation periods (5 h) but were evident after 24 or 72 h of incubation. Northern blot analysis revealed increased expression of tissue factor (TF) mRNA in ECs exposed to uremic conditions. Immunocytochemical methods detected an augmented expression of TF antigen on uremic ECMs. Incubation of ECMs with an antibody to human tissue factor prevented the increase in platelet deposition observed in uremic ECMs, suggesting that the presence of TF in ECM could be responsible for the enhanced platelet deposition. Results from our study indicate that uremic medium impairs the antithrombotic functions of cultured endothelial cells.

Biological Factors↗
PubMed2001

Comparison of the effects of human erythrocyte ghosts and intact erythrocytes on platelet interactions with subendothelium in flowing blood.

We investigated whether ghosts behaved similarly to intact erythrocytes to maintain regular primary hemostasis under flow conditions. To this end we performed perfusion experiments with whole blood in which erythrocytes were replaced by pink ghosts, and platelet interaction with the subendothelial surface of a damaged vessel was morphometrically evaluated. The same objective was sought by means of studies with a platelet function analyzer (PFA-100(TM) instrument). Perfusions performed with control blood reconstituted with intact erythrocytes gave rise to 0.4+/-0.2% contact but not spread platelets, 10.8+/-3.4% adhering and spread platelets, 16.3+/-4.6% platelets in thrombi, with 27.5+/-7.4% of the surface covered. Even though the average diameter of the ghosts was smaller than that of intact erythrocytes (5.3 microm vs. 7.7 microm), the values obtained in perfusions performed with ghosts were similar to those of the erythrocyte controls. Studies performed with the PFA-100(TM) analyzer were consistent with those observed in perfusion studies. The viscosity of control blood was compared with that of blood reconstituted with ghosts. At shear rates lower than 450 s(-1), the viscosity of the ghost samples was higher than that of the controls, but the difference progressively decreased as shear rate increased up to 750 s(-1) (3.61+/-0.15 and 3.71+/-0.17 cP, respectively). In conclusion, the results of our study showed that ghosts behaved similarly to intact erythrocytes in maintaining a normal platelet interaction with digested subendothelium, under conditions of moderate shear rate and constant hematocrit (40%). The rheological activity of ghosts, bodies that are metabolically less active, was sufficient for them to satisfactorily act as substitutes for intact erythrocytes in our system.

Blood Viscosity↗
PubMed2000

Antiplatelet effects of sodium nitroprusside in flowing human blood: studies under normoxic and hypoxic conditions.

We explored the ability of sodium nitroprusside to modify adhesive and cohesive function of platelets in flowing blood, under normoxic and hypoxic conditions. Aliquots of both untreated and sodium nitroprusside-treated blood were prepared for studies of: (1) platelet aggregation in plasma; (2) erythrocyte deformability; (3) platelet interaction with damaged subendothelium, by using a well-defined perfusion system; and (4) blood gasometry in the perfused samples. Results showed that sodium nitroprusside-treated blood always showed a totally inhibited arachidonic acid-induced platelet aggregation in plasma, as well as significantly increased erythrocyte deformability (0.44+/-0.09 up to 0.66+/-0.05; p<0.05). However, treatment with sodium nitroprusside did not modify the pattern of platelet interaction with subendothelium (percentage of contact, adhesion, thrombus, and covered surface) with respect to untreated blood, under any of the shear rates used (300, 800, and 1800 seconds(-1)), although it significantly reduced the height of thrombi (9.8+/-0.4 vs. 8.3+/-0.4 microm; p<0.05). Hypoxic conditions did not have a noticeable effect in modifying antiplatelet effects of sodium nitroprusside. Additionally, the presence of sodium nitroprusside impaired the normal oxygenation of the blood during perfusion. pO2 in control untreated samples rose from 40.3+/-5.0 mm Hg perfusions to 100.4+/-12.5 mm Hg but remained at 66.3+/-6.3 mm Hg in sodium nitroprusside-treated blood (p<0.05). Our results did not show a significant effect of sodium nitroprusside in the modulation of platelet interaction with subendothelium. The marginal reduction in the thrombi height could be related to rheological interference of increased erythrocyte deformability.

Blood Gas Analysis↗
PubMed2000

The 4G/5G polymorphism of the type 1 plasminogen activator inhibitor gene and thrombosis in patients with antiphospholipid syndrome.

OBJECTIVE: To investigate the relationship between the 4G/5G polymorphism of the type 1 plasminogen activator inhibitor (PAI-1) gene and thrombotic manifestations in patients with antiphospholipid syndrome (APS). METHODS: We studied a total of 247 patients included in the following 4 groups: 70 patients with primary APS, 104 patients with systemic lupus erythematosus (40 with antiphospholipid antibodies [aPL] and clinical [secondary] APS, 13 with aPL but without clinical APS, and 51 with neither detectable aPL nor a history of thrombosis), 14 asymptomatic individuals with aPL, and 59 patients with thrombosis but without known thrombosis risk factors. A control group of 100 healthy individuals was also analyzed. PAI-1 4G/5G polymorphism was determined by polymerase chain reaction and endonuclease digestion. RESULTS: The allele frequency of 4G/5G in controls was 0.47/0.53. There were no differences in allele distribution among patient groups or between patients and controls. However, a higher frequency of the 4G allele was observed in APS patients with versus those without thrombosis (0.57 versus 0.39; P < 0.05) (odds ratio [OR] 2.83, 95% confidence interval [95% CI] 1.18-6.76). This higher frequency of the 4G allele was attributable to the higher frequency in patients with versus those without arterial thrombosis (0.64 versus 0.43; P < 0.01) (OR 5.96, 95% CI 1.67-21.32), while patients with venous thrombosis had an allele distribution similar to that of those without venous thrombosis (0.49 versus 0.50; P not significant). There was a trend toward higher PAI-1 antigen and activity levels in APS patients and controls with the 4G/4G genotype, but this did not reach statistical significance. CONCLUSION: The presence of the 4G allele of the 4G/5G polymorphism of the PAI-1 gene may be an additional risk factor for the development of arterial thrombosis in APS.

Adult↗
PubMed2000

[Effect of cyclooxygenase inhibition on the adaptation of coronary blood flow to tachycardia].

BACKGROUND: The role of different endothelium-derived vasoactive substances in the regulation of coronary circulation during tachycardia is not well defined. In order to elucidate the contribution of prostacyclin to the adaptation of coronary blood flow to tachycardia, the effect of meclofenamate, a cyclooxygenase inhibitor on the coronary blood flow response to rapid atrial pacing was analyzed in a porcine model. METHODS: A group of seventeen pigs were instrumented for coronary blood flow, aortic pressure and atrial pacing. Heart rate was increased by 20 beats every 5 minutes. Coronary blood flow and aortic pressure were measured, and coronary resistance calculated, basally and at each pacing interval, before and after saline serum (n = 6), meclofenamate 5 mg/kg, i.v. (n = 7) or meclofenamate 35 mg/kg, i.v. (n = 4). RESULTS: Neither saline nor meclofenamate modified the normal increase of coronary blood flow provoked by rapid atrial pacing (163 +/- 28% increase before versus 172 +/- 29% after saline; 159 +/- 21% increase before versus 161 +/- 22% after meclofenamate low doses and 201 +/- 39% before vs 172 +/- 36 after meclofenamate high doses). There were no differences in the response of coronary vascular resistance to tachycardia before and after meclofenamate (44% reduction vs 40% respectively). CONCLUSION: Cyclooxygenase blockade does not modify the response of coronary circulation to rapid atrial pacing, suggesting that prostacyclin does not play a limiting role in the regulation of coronary blood flow during tachycardia in this model.

Animals↗
PubMed2000

Abnormal platelet cytoskeletal assembly in hemodialyzed patients results in deficient tyrosine phosphorylation signaling.

BACKGROUND: Uremic patients have a bleeding tendency associated with a platelet dysfunction. We evaluated the impact of a repeated hemodialysis procedure on primary hemostasis by analyzing different aspects of platelet activation in uremic patients. METHODS: Studies were performed in (1) eight patients with end-stage renal disease before the hemodialysis program was initiated and after initiating hemodialysis treatment, and in (2) eight patients on maintenance hemodialysis who were transferred to continuous ambulatory peritoneal dialysis. Studies included routine platelet aggregations and evaluation of platelet-subendothelium interactions under flow conditions. Contractile proteins and tyrosine phosphorylation associated with the cytoskeleton were analyzed, before and after thrombin activation of platelets, by electrophoresis after Triton X-100 extraction. RESULTS: No changes in the clinical parameters analyzed were observed among the different study groups. Aggregation and platelet adhesion only improved when patients were shifted from hemodialysis to continuous ambulatory peritoneal dialysis (P < 0.05 for both percentage of surface covered by platelets and aggregate formation). The association of cytoskeletal proteins in platelets from patients under hemodialysis treatment was statistically decreased with respect to the corresponding values in platelets from patients not subjected to dialysis (P < 0.01 for actin). However, after two months on peritoneal dialysis, these values increased to almost control values (P < 0.001 for actin, vs. hemodialysis). Similarly, translocation of tyrosine-phosphorylated proteins to the cytoskeletal fraction was impaired in platelets from hemodialyzed patients, and it recovered partially after the patients transferred to continuous ambulatory peritoneal dialysis. CONCLUSIONS: Our present data support the concept that repeated platelet stress during hemodialysis has a deleterious effect on the organization of platelet cytoskeleton, which seems to impair the translocation of signal transduction proteins within platelets compromising the platelet function in uremia.

Adult↗
PubMed2000

Effects of the addition of second-messenger effectors to platelet concentrates separated from whole-blood donations and stored at 4 degrees C or -80 degrees C.

BACKGROUND: Platelet concentrates (PCs) are currently stored at 22 degrees C under continuous agitation. Because of the potential risk of the overgrowth of bacteria in case of contamination, PC shelf life is limited to 5 days. A mixture of second-messenger effectors is being evaluated to determine if it has benefits for cold liquid storage and cryopreservation of platelets. STUDY DESIGN AND METHODS: PCs separated from whole-blood donations by the buffy coat method were randomly assigned (n = 6 each) to be stored for 5 days at 22 degrees C under continuous agitation or at 4 degrees C after treatment with a platelet storage medium (ThromboSol, LifeCell Corp. ). PCs were also cryopreserved with 6-percent DMSO (final concentration) or with ThromboSol plus 2-percent DMSO (final concentration) (TC). After storage, platelets were analyzed by flow cytometry, transmission electron microscopy, and aggregation and perfusion techniques. RESULTS: Cold liquid storage of ThromboSol-treated platelets resulted in a lower binding of coagulation factor Va on the platelet surface than on platelets stored at 22 degrees C. In transmission electron microscopy, a conversion to spherical morphology was seen in the case of cold liquid storage. No difference between ThromboSol-treated platelets stored at 4 degrees C and platelets stored at 22 degrees C was seen in perfusion studies. Cryopreservation in the presence of TC prevented the reduction in glycoprotein Ib and IV expression on platelet surface that is seen in 6-percent DMSO-cryopreserved platelets. Platelets cryopreserved in TC covered, by thrombus, a significantly greater percentage of the perfused surface after the freezing and thawing process. CONCLUSION: ThromboSol-treated PCs separated from whole-blood donations by the buffy coat method, stored at 4 degrees C for 5 days, or cryopreserved in the presence of TC, maintained in vitro functional activity comparable to that achieved by current methods of storage, although discoid morphology was not preserved during cold liquid storage with ThromboSol.

Bacteria↗
PubMed2000

Alterations in cytoskeletal organization and tyrosine phosphorylation in platelet concentrates prepared by the buffy coat method.

BACKGROUND: Numerous morphologic and biochemical changes occurring during platelet storage may result in the impairment of platelet function. STUDY DESIGN AND METHODS: The effect of preparation and storage conditions on platelet function was analyzed through evaluation of cytoskeletal organization and signaling mechanisms involved in the activation of platelets by thrombin. Samples of platelets prepared by the buffy coat method were obtained before and after the platelet concentrates were prepared during storage for 1, 3, and 5 days. Thrombin-induced aggregation was monitored, and changes in the organization of proteins in the cytoskeleton were analyzed by gel electrophoresis. For the analysis of tyrosine phosphorylation, proteins were transferred to nitrocellulose membranes and probed with a specific antibody. RESULTS: The aggregation and the cytoskeletal organization induced by thrombin activation were markedly impaired immediately after preparation of platelet concentrates, although they normalized after the first 24 hours of storage and decreased progressively after 3 days of storage. Results in tyrosine phosphorylation paralleled those obtained with cytoskeletal organization, except for samples obtained immediately after processing to obtain platelet concentrates. CONCLUSION: These data indirectly suggest that the stress induced by the preparation method has an activating effect on platelet function that may imply a delayed platelet response to further stimuli. This effect may result in a deficient redistribution of signaling molecules within platelets.

Blood Platelets↗
PubMed2000

Infusible platelet membranes improve hemostasis in thrombocytopenic blood: experimental studies under flow conditions.

BACKGROUND: The potential hemostatic effect of infusible platelet membranes (IPM; Cyplex, Cypress Bioscience) prepared from outdated human platelets is investigated. STUDY DESIGN AND METHODS: Increasing concentrations of IPM were added to blood samples anticoagulated with low-molecular-weight heparin, in which platelets and WBC counts had been experimentally reduced by a filtration procedure. Thrombocytopenic blood with IPM was circulated in a perfusion chamber at various shear rates (300, 600, and 1200/sec(-1)), and platelet and fibrin deposition on the surface of a damaged vessel was measured. Prothrombin fragments 1 and 2 (F1+2) levels were also monitored. RESULTS: Under conditions of severe thrombocytopenia (<6000 platelets/microL) IPM did not increase platelet deposition. However, a dose-dependent increase in fibrin deposition was observed with concentrations of IPM ranging from 0.5 to 2 mg per kg in perfusions at 300 and 600 per sec(-1) (p<0.05 vs. thrombocytopenic blood). Experimental studies performed under conditions of moderate thrombocytopenia and higher shear rates (25, 000-30,000 platelets/microL; at 600 and 1200/sec(-1)) showed that IPM concentrations equivalent to 0.5 or 1 mg per kg improved fibrin deposition (33.5 +/- 9.5% and 37.7 +/- 12.8%, respectively, vs. 22.7 +/- 5.2% in controls) and also promoted a moderate increase in platelet deposition, with a concomitant significant increase in the size of platelet aggregates (p<0.05). Exposure of thrombocytopenic blood to a damaged vessel resulted in an increase of F1+2 levels from 0.8 +/- 0.15 to 1.7 +/- 0.22 nM at 300 per sec(-1) and 1.94 +/- 0.46 nM at 600 per sec(-1). Postperfusion levels of F1+2 after the addition of IPM were always similar to levels in untreated controls. CONCLUSION: IPM promotes local procoagulant activity at sites of vascular damage under conditions of severe and moderate thrombocytopenia. IPM also appears to facilitate platelet cohesive functions under conditions of moderate thrombocytopenia.

Blood Platelets↗
PubMed2000

Clopidogrel: a selective inhibitor of platelet ADP receptors.

Platelets play a key role in the development of ischemic complications in the arterial circulation. Antiplatelet therapy has proven effective in the treatment and prevention of ischemic events. Numerous clinical studies have confirmed the therapeutic efficacy of aspirin to such a point that this antiplatelet agent has become the gold standard in clinical practice. Clopidogrel is a thienopyridine compound that inhibits platelet aggregation by selectively binding to adenylate cyclase-coupled ADP receptors. Results of a large, double-blind, randomized study (CAPRIE) confirm that administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischemic stroke, myocardial infarction or vascular death. The present article highlights the importance of activation of platelets through ADP receptors and reviews the pharmacology and clinical studies of clopidogrel, a selective inhibitor of these mechanisms.

Journal Article↗
PubMed2000

Eptifibatide: a cyclic peptide that selectively inhibits platelet glycoprotein IIb/IIIa.

Platelets play a key role in the pathogenesis of coronary syndromes. Glycoprotein IIb/IIIa (GPIIb/ IIIa), also known as integrin alpha(IIb)beta(3), facilitates platelet aggregation through the binding of fibrinogen. In recent years, GPIIb/IIIa has become the target of new therapeutic strategies aimed at improving the efficacy of current antiplatelet therapy. Eptifibatide is a small cyclic heptapeptide that has shown high specificity and affinity for GPIIb/IIIa and has a short plasma half-life with a rapid onset of antiplatelet action and rapid reversibility of action when treatment is stopped. Two large clinical trials (IMPACT II and PURSUIT) have demonstrated that eptifibatide significantly reduced coronary events in patients without increasing the risk of bleeding complications. Eptifibatide appears to be a more refined alternative to current antithrombotic therapies.

Journal Article↗
PubMed2000

Adherence of platelets under flow conditions results in specific phosphorylation of proteins at tyrosine residues.

Collagen is a powerful platelet activating agent that promotes adhesion and aggregation of platelets. To differentiate the signals generated in these processes we have analyzed the tyrosine phosphorylation occurring in platelets after activation with collagen in suspension or under flow conditions. For the suspension studies, washed platelets were activated with different concentrations of purified type I collagen (ColI). Studies under flow conditions were performed using two different adhesive substrata: ColI and endothelial cells extracellular matrix (ECM). Coverslips coated with ColI or ECM were perfused through a parallel-plate perfusion chamber at 800 s(-1) for 5 min. After activation of platelets either in suspension or by adhesion, samples were solubilized and proteins were resolved by electrophoresis. Tyrosine-phosphorylated proteins were detected in immunoblots by specific antibodies. Activation of platelet suspensions with collagen induced tyrosine phosphorylation before aggregation could be detected. Profiles showing tyrosine-phosphorylated proteins from platelets adhered on ColI or on ECM were almost identical and lacked proteins p95, p80, p66, and p64, which were present in profiles from platelets activated in suspension. The intensity of phosphorylation was quantitatively weaker in those profiles from platelets adhered on ECM. Results from the present work indicate that activation of platelets in suspension or by adhesion induces differential tyrosine phosphorylation patterns. Phosphorylation of proteins p90 and p76 may be related to early activation events occurring during initial contact and spreading of platelets. Considering that adhesion is the first step of platelet activation, studies on signal transduction mechanisms under flow conditions may provide new insights to understand the signaling processes taking place at earliest stages of platelet activation.

Blotting, Western↗
PubMed2000

Thrombin facilitates primary platelet adhesion onto vascular surfaces in the absence of plasma adhesive proteins: studies under flow conditions.

BACKGROUND AND OBJECTIVE: The effect of local and circulating thrombin on platelet adhesion onto vascular surfaces was explored in the absence of plasma adhesive proteins using flow conditions. DESIGN AND METHODS: To study the local effects of thrombin, denuded rabbit aorta segments were incubated with thrombin concentrations of 0.001, 0.01 and 0.1 U/mL. To evaluate the effects of circulating thrombin, the same concentrations were added to perfusates consisting of washed platelets and washed red blood cells suspended in a human albumin solution (5%). In some experiments, purified von Willebrand's factor (vWF) (Haemate-P) was added to the perfusates (0. 8 U/mL of vWF, final concentration). A humanized chimeric antibody to the GPIIb-IIIa complex (Reopro) was used to determine the role of this glycoprotein on platelet adhesion under the conditions described. The effect of blocking GPIb was also assessed. Perfusions were carried out at 800 s(-1) for 10 min. The interaction of platelet with the vessel surface was morphometrically evaluated and expressed as percentage of surface coverage (%SC). Changes in the surface expression of the major platelet antigens were also analyzed by flow cytometry. RESULTS: Incubation of subendothelial surfaces with thrombin enhanced platelet deposition with respect to control levels (increases in SC of 64%, 79% and 86% with 0.001, 0.01 and 0.1 U/mL of thrombin, respectively). Low concentrations of thrombin (0.001 and 0.01 U/mL) incorporated in the perfusates resulted in a similar pro-adhesive effect (increases in SC of 64% and 71%, respectively) while the highest concentration (0.1 U/mL) failed to produce a pro-adhesive effect due to the augmented formation of platelet aggregates with subsequent thrombocytopenia (15+/-1 vs. 160+/-5x10(9) plt/L in the perfusates). Similar results were obtained when VWF was present in the perfusate. Reduction of platelet deposition by blockade of GPIIb-IIIa (to 5.3+/-0.7%) was partially restored by thrombin. Blockade of GPIb prevented platelets from adhering even when thrombin was present (%SC of 2.0+/-0.8%). No significant changes in the distribution of platelet membrane glycoproteins during perfusion experiments were detected. INTERPRETATION AND CONCLUSIONS: Our results suggest that thrombin facilitates primary platelet adhesion onto vascular surfaces even in the absence of plasma adhesive proteins. This effect seems to be mainly dependent on the GPIb/vWF axis.

Animals↗
PubMed2000

Differential aspects of the glycoprotein Ib-von Willebrand factor axis in human and pig species.

BACKGROUND AND OBJECTIVE: The role of glycoprotein Ib (GPIb) in platelet adhesion to subendothelium is well established in human species. However, the interaction of GPIb and von Willebrand factor (VWF) in a widely used experimental model in thrombosis research, that of the pig, has not been clearly elucidated. We investigated the differences between human and pig species in the GPIb/VWF axis in several ways. DESIGN AND METHODS: Standard aggregometry and perfusion studies with circulating blood were applied to isolated platelets or to blood reconstituted with isolated platelets, VWF and red blood cells from the different species. Platelet aggregation to VWF in the presence of either ristocetin or botrocetin was tested. RESULTS: Human VWF and ristocetin did not agglutinate pig platelets. However, botrocetin was capable of agglutinating pig platelets. In perfusion studies (800 s(-1), 10 min), washed platelets from both species were suspended in albumin solutions containing human VWF (hVWF) or porcine VWF (pVWF) and red blood cells from the corresponding species. Reconstituted blood with high concentrations of pVWF (> or =0.25 U/mL) caused severe thrombocytopenia during the perfusion procedure when added to human platelets. Nevertheless, lower concentrations (< or =0.1 U/mL) promoted the formation of large aggregates. Under our experimental conditions, hVWF poorly supported pig platelet adhesion. INTERPRETATION AND CONCLUSIONS: In conclusion, pVWF may support human platelet adhesion and even promote aggregation, while hVWF can only partially facilitate pig platelet adhesion. Minimal concentrations of pVWF could facilitate the interaction of human platelets with subendothelium, increasing their adhesive and aggregating capabilities. Understanding the molecular differences of the GPIb-VWF axis in different species may prove useful for developing therapeutic strategies aimed at preventing excessive platelet deposition on damaged vascular surfaces.

Animals↗
PubMed2000

Platelet ultrastructural morphometry for diagnosis of partial delta-storage pool disease in patients with mild platelet dysfunction and/or thrombocytopenia of unknown origin. A study of 24 cases.

BACKGROUND AND OBJECTIVE: Exact diagnosis is sometimes difficult in patients presenting with a slight bleeding diathesis, prolonged bleeding times, non-specific aggregometric abnormalities, and/or mild thrombocytopenia. The objective of this study was to evaluate the use of platelet ultrastructural morphometry in detecting a partial d-storage pool disease in such patients. DESIGN AND METHODS: Platelets from 52 patients and 15 controls were fixed immediately in glutaraldehyde in White's saline without anticoagulant and processed for transmission electron microscopy. Using computer-assisted morphometry, the size and shape of the platelets were measured, as were the size and number per platelet of the dense- and a-granules. Ultrastructural morphology of the above and other intraplatelet structures was observed. RESULTS: Twenty-four cases were diagnosed as having a partial d-storage pool disease. Mean platelet area (2.28 microm(2)) and maximum diameter (2.58 microm) were significantly greater in patients than in control subjects (1.64 microm(2) and 2. 25 microm, respectively) but discoid shape was preserved. Mean dense-granule number was decreased, both per platelet and per microm(2) of platelet area (patients 0.22 and 0.09; controls 0.42 and 0.24). Seven patients also had a marked decrease in a-granules, resulting in a significantly lower mean number of granules per microm(2 )(patients 2.43; controls 3.15). Additionally, the patients' platelets had significant increases in both lipid droplets and surface-connected canalicular system. INTERPRETATION AND CONCLUSIONS: A partial dense-granule deficiency, sometimes associated with partial a-granule deficiency, should be borne in mind faced with patients who have a slight bleeding diathesis, non-specific platelet dysfunction tests and/or mild thrombocytopenia of unknown origin. Platelet ultrastructural morphometry is useful in diagnosing this condition.

Adolescent↗