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J Bozzo

Publications and source records attributed to J Bozzo.

32 records · Page 2Linked to original sources
PubMed1996

Activated protein C inhibits thrombus formation in a system with flowing blood.

We studied the effect of increasing concentrations of protein C (PC) and activated protein C (APC) on haemostasis in an in vitro thrombosis model. Blood from healthy donors was anticoagulated with citrate-phosphate-dextrose (final citrate concentration 19 mM) or a low molecular weight heparin (LMWH, 20 IU/ml). Enzymatically denuded rabbit aorta segments were exposed to flowing blood for 10 min in an annular perfusion chamber. PC and APC were added to the perfusate immediately prior to exposure. In citrated blood at a shear rate of 800/s, PC and APC induced a statistically significant decrease in platelet deposit at 16 micrograms/ml and 32 micrograms/ml. In perfusions performed with blood anticoagulated with LMWH, there was no effect on platelet deposition at 16 and 32 micrograms/ml either at shear rates of 300/s or 800/s. Addition of PC showed no effect on fibrin deposition at a shear rate of 300/s; in contrast, a nonstatistically significant 40% reduction was seen at a shear rate of 800/s, compared to controls. Addition of APC caused a 100% reduction in fibrin formation at 16 and 32 micrograms/ml at both shear rates studied. PC and APC inhibited platelet deposition on the exposed subendothelial surface, in a dose-dependent manner. Effects of PC and APC on platelet function might be mediated through inhibition of thrombin generation at the platelet microenvironment.

Animals↗
PubMed1996

Red blood cell aggregability is increased by aspirin and flow stress, whereas dipyridamole induces cell shape alterations: measurements by digital image analysis.

We evaluated the influence of pretreatment with aspirin in vitro, alone or combined with dipyridamole, on red cell aggregability. Samples were tested before and after being exposed to well-defined flow conditions. An aggregation rate was estimated through digital analysis of light microscopy images. Red cells of untreated blood that had been exposed to flow showed a higher aggregation rate (38.54 +/- 1.63 vs. 27.52 +/- 1.36; P < 0.05). This effect was not observed in the absence of platelets. Treatment with aspirin induced a high aggregation rate, with or without exposure to flow conditions. Dipyridamole alone or combined with aspirin provoked echinocytosis, disturbing the rouleaux arrangement (rates ranging from 11.25 +/- 1.91 - 13.62 +/- 1.62). Washing red cells after treatment restored about 90% of echinocytes to their biconcave shape, but aggregation rate did not recover in parallel. These results highlight the influence of red cell-platelet interactions in the regulation of haemostasis and show how therapeutic agents can interfere with rheological phenomena.

Aspirin↗
PubMed1996

[Erythrocytes modulate the anti-aggregation effect of aspirin and dipyridamole. Study under static conditions and in a flow system].

PURPOSE: The modulating role played by red cells on platelet function is well known, yet its mechanism of action in the presence of antiaggregating agents is not clearly defined. We tried to assess the influence of aspirin (ASA) or dipyridamole (DIP) treated red cells on platelet aggregation in plasma, with the samples in static conditions and under flow in a perfusion system. MATERIAL AND METHODS: Platelet-rich plasma (PRP) was adjusted to 4 x 10(9)/L. Red cells were washed with a 0.9% sodium chloride and 5mM glucose solution, then resuspended in PRP until a 40% haematocrit was attained. The drugs were added separately or together and the mixture was incubated for 10 minutes at 37 degrees C. Three series of tests were carried out: a) with reconstituted blood; b) with red cells alone; c) with the red cells washed in a 10-fold volume so as to eliminate all the drugs. The samples were divided in two parts: one was let to rest and the other was circulated through a perfusion system with a peristaltic pump. Simultaneous tests with untreated red cells and PRP were run as control in each session. A multichannel aggregameter was used to assess platelet aggregation according to Born's turbidimetric method. Variance analysis (ANOVA) or Student's t test were used for the statistical evaluation. RESULTS: Platelets attained from control samples under flow conditions showed partial inhibition of the maximal aggregation (58.02 +/- 9.92%). The inhibitory power of ASA was higher than that of DIP in all cases. Aggregation was totally inhibited by ASA from the beginning in treated whole blood, but the inhibitory effect appeared later when working with red cells alone, suggesting that red cells must retain part of the drug, which cannot exert its effect until it has been released after several minutes. The inhibition of platelet aggregation when working with washed treated red cells was more effective under flow conditions, chiefly with combined treatment with ASA+DIP. CONCLUSION: These studies stress the importance of flow conditions in the red cells-platelets interaction and in the regulation of the therapeutic agents used to modify platelet function.

Adenosine Diphosphate↗
PubMed1995

Platelet concentrates promote procoagulant activity: evidence from experimental studies using a perfusion technique.

BACKGROUND: Evaluation of the hemostatic effectiveness of platelet transfusions is difficult. Perfusion methods have been employed to test the quality and function of platelet concentrates, allowing differentiation between platelet-platelet and platelet-surface interactions. STUDY DESIGN AND METHODS: A study was performed to investigate platelet adhesive and cohesive properties as well as the formation of fibrin when aliquots of platelet concentrates were added to thrombocytopenic blood. Blood previously anticoagulated with low-molecular-weight heparin (20 U/mL) underwent platelet and white cell reduction by filtration. Perfusates were prepared by adding to filtered blood platelets obtained from standard concentrates (stored for 1, 3, and 5 days). The final platelet count in these perfusates was standardized at 80,000 per microL. After perfusions, platelet-subendothelium interaction and fibrin formation were analyzed morphometrically. Results were always compared with those obtained in unfiltered blood (> 150,000 platelets/microL). RESULTS: A slight impairment in the ability of stored platelets to interact with the subendothelium was noticed during the storage period. However, the presence of fibrin was significantly greater than that observed in studies with unfiltered blood (Day 1 = 23.48 +/- 9.43%*; Day 3 = 26.99 +/- 6.74%*; Day 5 = 17.95 +/- 9.06% vs. unfiltered blood = 12.60 +/- 3.08%; *p < 0.05). The lower platelet counts (80,000/microL) in the perfusates containing platelets from concentrates could account for the reduced platelet-subendothelium interactions, but they cannot explain the increments in fibrin formation. CONCLUSION: While the preparation and storage of platelets have a detrimental effect on platelet adhesiveness, such procedures can positively influence the platelet procoagulant activity necessary to platelet hemostasis.

Animals↗
PubMed1995

Reduced red cell deformability associated with blood flow and platelet activation: improved by dipyridamole alone or combined with aspirin.

OBJECTIVES: To explore the role of blood flow in red blood cell deformability and determine whether it is associated with the release of ATP by red cells. METHODS: A perfusion system was employed to mimic the blood flow conditions. Red cell treatment in vitro with dipyridamole or aspirin, either alone or combined, was performed either on red cells alone prior to blood reconstitution or on already reconstituted blood. Blood viscosity at shear rates of 90 and 450 s-1 was measured, before and after perfusion, by means of a cone/plate viscometer. Red cell deformability was estimated as the magnitude of the slope between these two values of viscosity. ATP level in platelet-free plasma was measured by the firefly luciferase assay, and was used to monitor dipyridamole-induced blockade of ATP efflux by red cells. RESULTS: In control experiments, red cells became more rigid after perfusion (slope values: 0.62 +/- 0.09 vs 0.40 +/- 0.04; P < 0.05). Absence of platelets or treatment of red cells with aspirin and/or dipyridamole prevented dipyridamole prevented the increased stiffness of red cells observed after exposure of blood to flow conditions. Moreover, a significant increase in red cell deformability was observed when blood was treated with dipyridamole alone or combined with aspirin (0.69 +/- 0.07 and 0.65 +/- 0.05 respectively vs. 0.40 +/- 0.04; P < 0.05). Treatment with dipyridamole alone or combined with aspirin caused a decrease in ATP levels. Statistical significance was reached when red cells alone were treated with dipyridamole alone (45.8 +/- 2.8 vs. 173.3 +/- 47.6 ng ATP/ml; P < 0.05). CONCLUSIONS: Flow stress induced a decrease in red cell deformability probably linked to platelet activation. Treatment with dipyridamole alone or associated with aspirin eliminated the effect of flow, increasing red cell deformability. Under our experimental conditions, modifications could not be ascribed to red cell-released ATP. Our results emphasize the importance of blood flow conditions to evaluate RBC deformability.

Adenosine Triphosphate↗
PubMed1994

Influence of co-incubation and cell number of platelets and polymorphonuclear leukocytes in cellular inhibition and activation phenomena.

Evidence indicates that complex interactions occur between blood platelets and polymorphonuclear leukocytes (PMN) referring to both activation and inhibition phenomena. We studied the influence of co-incubating activated PMN and platelets at varying cell counts in the production of two active metabolites, thromboxane A2 (TxA2) measured as thromboxane B2 (TxB2) and platelet activating factor (PAF). The decrease observed in the quantity of TxA2 synthesized by 2 x 10(8) platelets/ml in the presence of physiological PMN counts clearly indicates an inhibitory effect of PMN in AA-derived metabolites. This suggests there is an influence of PMN-released products on activated platelets, decreasing their capacity to synthesize TxA2. Moreover, we found that the addition of platelets, which do not make measurable quantities of PAF, to PMN suspensions significantly decreased the capacity of PMN to synthesize this mediator. Together with this inhibiting action we also observed an activating effect, in such a way that the more PMN were added to platelet suspensions the more TxA2 was produced. Conversely, the maximal amounts of PAF were synthesized when the highest platelet count suspensions were added to PMN. In summary, the results we present here clearly show cellular interactions between platelets and PMN that directly influence the amounts of metabolites synthesized by both cells.

Blood Platelets↗
PubMed1993

Platelet adhesivity to subendothelium is influenced by polymorphonuclear leukocytes: studies with aspirin and salicylate.

Interactions between blood platelets and polymorphonuclear leukocytes (PMN) influence cell reactivity. We have examined the effects of inhibiting platelet and PMN cyclooxygenase and lipoxygenase pathways, by treatment with aspirin (ASA) and salicylate (SAL) on platelet-vessel wall interaction studied under flow conditions by means of an annular chamber perfusion system. We have also measured the levels of cyclooxygenase-derived metabolites during perfusion. Perfusates were prepared with untreated and ASA- or SAL-treated PMN or platelets. Our results demonstrated that blockage of the lipoxygenase pathway in PMN significantly increased platelet thrombus formation and favored the production of thromboxane B2 (TxB2) during perfusion, whereas inhibition of cyclooxygenase pathway in PMN had no effect either on platelet deposition or on TxB2 levels. In contrast, blockage of platelet cyclooxygenase, which caused almost total inhibition of TxB2, enhanced platelet adhesion and did not modify platelet thrombus formation. These results suggest that under dynamic conditions cooperative metabolic mechanisms between platelets and PMN directly influence platelet interaction with vascular subendothelium.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

[Potentiation of the antiplatelet effect of dipyridamole and aspirin by erythrocytes. Study under flow conditions].

PURPOSE: To assess, by means of a morphometric method, the interaction of platelets with subendothelium, as induced by perfusion with the Baumgartner system, and to compare the antiplatelet effect of acetylsalicylic acid (ASA) and dipyridamole (DIP) and the combination of both drugs. MATERIAL AND METHODS: Blood samples were drawn from healthy volunteers and platelet-rich plasma specimens were prepared at a concentration of 4 x 10(8)/mL. Abdominal aorta segments were obtained from New Zealand rabbits, they being deprived of endothelium by alpha-chymotrypsin. Red cells and platelets were separately or conjointly treated on reconstituted whole blood using ASA and DIP at therapeutic doses, separately or in association. Perfusion experiences were carried out in Baumgartner's annular chamber. Upon finishing the studies, the aorta segments were morphometrically evaluated by an optic analysis system attached to a computer with an automatic image recognition programme. The statistical analysis was performed with Student's t test, differences between groups of p < 0.05 being assigned significance. RESULTS: Treatment with the association ASA-DIP was the only one to significantly reduce interaction, as both the size of aggregates and the extent of the covered surface decreased when whole blood was treated, and only the covered surface did when red cells were separately treated. When treating only platelets, the reduction of aggregates had no significance. CONCLUSION: The synergism of ASA and DIP in antiplatelet therapy was confirmed, as well as the important enhancing effect exerted by red cells.

Adenosine↗
PubMedDate not supplied

Preparations of synthetic phospholipids promote procoagulant activity on damaged vessels: studies under flow conditions.

BACKGROUND: The possibility of developing synthetic platelet substitutes that could promote hemostasis with prolonged shelf-life and increased safety is an appealing one. STUDY DESIGN AND METHODS: Preparations containing synthetic phospholipids were incorporated into blood samples (1.15 mg/mL) in which platelets and white cell counts had been experimentally reduced by a filtration procedure. Vesicles containing phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), or combinations of PC and PE and of PC and PS were tested in this system. Blood was recirculated (10 min; shear rate, 250/sec) through a perfusion chamber containing vascular segments. The ability of the various phospholipid preparations to promote fibrin formation on the damaged subendothelium was evaluated morphometrically and expressed as the percentage of fibrin coverage. Generation of thrombin in the system was monitored through the measurement of prothrombin fragments 1 and 2. RESULTS: Vesicles containing PC, PI, PE:PC (1:1), or PS:PC (1:3) increased fibrin deposition on the subendothelium (64.5 +/- 9.8%, 32.7 +/- 6.3%, 58.3 +/- 6.5%, and 46.6 +/- 15.2%, respectively; p < 0.01 vs. 11.5 +/- 1.2% in thrombocytopenic blood). Vesicles containing PE, PS, or PS:PC (3:1) did not show procoagulant effect. CONCLUSION: Synthetic phospholipid preparations promote a local procoagulant activity at sites of vascular damage when they are incorporated into thrombocytopenic blood maintained under flow conditions.

Animals↗
PubMedDate not supplied

Bringing decision support to nurse managers.

Modern hospital nursing management requires timely and accurate information to allow nurse managers to adjust resources to patient requirements. We report an experience using production theory to provide the framework for the development of Decision Support Objects: graphic displays of nursing hours budgeted, scheduled, and worked within institution-specific control limits. Every month, nurse managers follow an analytic algorithm to understand nursing resources and trends on their units. Exception reporting closes the accountability loop. The essentials of education for nurse managers include skill training in the use of the decision-support tools and supportive lecture/seminars for understanding the managerial implications of using them.

Algorithms↗
PubMedDate not supplied

Effect of anticoagulants on activation of polymorphonuclear leukocytes induced by shear stress.

We analyzed how actin polymerization, CD11b expression and homotypic aggregation could be used as markers to study leukocyte activation. Leukocytes were obtained from blood anticoagulated with: citrate, unfractioned heparin (UH) and low molecular weight heparin (LMWH). Flow cytometry was used to study actin polymerization and expression of CD11b after leukocyte exposure to shear stress. Leukocyte aggregation was microscopically assessed. Shear increased both actin polymerization and expression of CD11b in citrated blood (100.1&#x00B1;7.1 vs. 85.8&#x00B1;8.5 p&#x003C; 0.05 and 53.5&#x00B1;3.5 vs. 20.7&#x00B1;5.1; p&#x003C; 0.005 respectively). These parameters remained unmodified in UH samples. Using both anticoagulants together, we observed increase in CD11b expression induced by shear stress (59.3&#x00B1;2.1 vs. 25.1&#x00B1;11.0; p&#x003C; 0,05). LMWH samples showed higher basal levels of actin polymerization and CD11b expression than citrated samples (237&#x00B1;40.8, vs. 85.8&#x00B1;8.5 p&#x003C; 0.05 and 47.8&#x00B1;2.6, vs. 20.7&#x00B1;5.1; p&#x003C; 0.005) but no changes induced by shear were observed. When LMWH was used in combination with citrate we observed a decrease in basal activation and significant modifications in CD11b expression induced by shear stress (80.0&#x00B1;4.1 vs. 50.4&#x00B1;2.7). Leukocyte aggregation was modified by UH at basal levels and by LMWH after shear stress. These results indicate that exposure to shear stress results in leukocyte activation. The choice of anticoagulant is a crucial factor in studies of leukocyte function.

Journal Article↗
PubMedDate not supplied

Nursing resource definition in DRGs. RIMS/Nursing Acuity Project Group.

The use of traditional nurse-specific patient classification/acuity systems for staffing are obsolete as they do not interact with other elements of hospital information systems (HIS). In the face of rapidly advancing managed care penetration the challenge for nursing has become the capability to measure and manage cost, quality, and outcomes by integrating nursing resource information into the standard HIS spawned by DRGs. Earlier efforts to quantify nursing relative intensity measures and correlate them with DRGs were not successful. New health care software technology (as well as combined financial and clinical department support) can now provide integrated clinical information and financial information by DRG for each patient's clinical record. Expert clinician medical-surgical and ICU nursing panels were empowered to evaluate and arrive at group consensus placing designated DRGs in clusters according to their average nursing care resource requirements. The method was tested and validated.

Activities of Daily Living↗
PubMedDate not supplied

Inhibition of fibrin deposition on the subendothelium by a monoclonal antibody to polymorphonuclear leukocyte integrin CD11b. Studies in a flow system.

BACKGROUND AND OBJECTIVE: The development of prothrombotic and procoagulant states may be regulated by direct platelet-leukocyte contact mediated by membrane receptors. We have investigated the role of CD11b integrin in polymorphonuclear leukocytes (PMN) on fibrin formation and platelet reactivity with vascular subendothelium. METHODS: Studies were carried out following a well-established perfusion model, employing either citrated blood, where fibrin formation is blocked, or blood anticoagulated with low molecular weight heparin, which allows thrombin and fibrin formation. Isolated PMN or platelets were treated with specific monoclonal antibodies to CD11b or to CD62P, respectively, and incorporated in reconstituted blood. RESULTS: Treatment of PMN with anti-CD11b significantly decreased the percentage of surface covered with a thick layer (> 5 microns) of fibrin (34.8 +/- 3.3% vs 53.3 +/- 4.9% in control, p < 0.05); it also reduced the average height of fibrin layer and the number of adherent leukocytes (7.9 +/- 1.2 microns vs 10.6 +/- 1.4 microns in control, p < 0.05; and 87 +/- 8 PMN/mm2 vs 186 +/- 25 PMN/mm2 in control, p < 0.05) respectively. Treatment of PMN with CD11b did not significantly affect the attachment of platelets onto the subendothelium when using citrated blood, though a slight decrease in platelet adhesion was observed in the heparinized samples. Treatment of platelets with anti-CD62P did not significantly modify any of the parameters studied. INTERPRETATION AND CONCLUSIONS: Our results indicate that PMN have a role in promoting fibrin deposition under flow conditions, through the participation of CD11b integrin. Under our experimental conditions, this effect does not seem to be influenced by CD62P expressed on activated platelets.

Animals↗