Search PubMed⌕ Search

Biomedical subjects

J Bozzo

Publications and source records attributed to J Bozzo.

At least 19 recordsLinked to original sources
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↗
PubMed1999

Assessment of potential thrombogenicity of coagulation factor IX concentrates in an in vitro model of human thrombogenesis.

We have investigated the potential use of perfusion techniques in the evaluation of the thrombogenic profile of factor IX concentrates. Blood from healthy donors was anticoagulated with low molecular weight heparin and incubated with one of the following: (a) diluent (DIL); (b) a prothrombin complex concentrate (PCC); (c) an intermediate-purity concentrate (FIX/X); or (d) a high-purity concentrate (HPFIX). The thrombogenic potential was assessed as: (1) fibrin formation on subendothelium (Baumgartner's perfusion) and (2) prothrombin activation fragment 1+2 (F1+2, nM) determination. The percentage of fibrin deposition on the subendothelium was only significantly increased after incubation with PCC (62.0+/-3.6% vs. DIL 35.0+/-6.1%;p<0.05). None of the FIX concentrates modified platelet interaction versus control blood (DIL: 26.7+/-2.1%). F1+2 baseline values in anticoagulated blood were 0.6+/-0.1 nM. Preperfusion levels of F1+2 reached values of 4.4+/-0.1 nM for PCC and 5.4+/-0.1 nM for FIX/X. After perfusion, F1+2 values were 2.7+/-0.2 nM for DIL, 5.6+/-0.1 nM for PCC and FIX/X, and 3.3+/-0.2 nM for HPFIX. While measurement of F1+2 was influenced by residual contaminants present in the concentrates, the morphometric evaluation of fibrin deposition on perfused vascular surfaces could be more closely related to the net thrombogenic profile of each FIX preparation.

Animals↗
PubMed1999

Impaired antiplatelet effects of aspirin associated with hypoxia and ATP release from erythrocytes. Studies in a system with flowing human blood.

BACKGROUND: We have explored how hypoxic conditions may affect the antiplatelet effects of aspirin. MATERIALS AND METHODS: For this purpose, a perfusion system containing a damaged vessel segment was modified in order to induce hypoxia (low Po2) in flowing blood. Blood samples were incubated with 50 mumol L-1 aspirin and divided into two aliquots, one being perfused under standard conditions (normoxic) and the other under hypoxic conditions. The interaction of platelets with the subendothelium was morphometrically evaluated. RESULTS: In studies with untreated blood under normoxic conditions, platelet interaction with the subendothelium was 0.3 +/- 0.1% of contact, 5.3 +/- 1.6% of adhesion, 24.3 +/- 3.3% of thrombus and 29.9 +/- 2.7% of total covered surface. Aspirin-treated blood perfused under normoxic conditions showed a marked decrease in thrombus with a concomitant increase in both platelet adhesion and covered surface percentages. However, when aspirin-treated blood was perfused under hypoxic conditions, platelet interaction was not significantly different from that observed in untreated blood. Hypoxia induced a 10-fold increase in ATP release from erythrocytes in the perfusates. If apyrase was added to the perfusates, ATP release was prevented and aspirin effects were evident again. CONCLUSION: Our results suggest that, under hypoxic conditions, the presence of aspirin would not help to inhibit further platelet activation.

Adenosine Triphosphate↗
PubMed1998

Using hospital data systems to find target populations: new tools for clinical nurse specialists.

A newly appointed diabetes clinical nurse specialist/nurse practitioner at Yale-New Haven Hospital was charged with redesigning the diabetes nursing role. For help, she turned to a special information management service within the Nursing and Operational Finance departments. This article describes the project that used an integrated financial and clinical information system to locate and characterize adult patients with diabetes mellitus. Patients with principal and secondary diagnoses of diabetes were identified by ICD-9-CM codes and tracked across inpatient and outpatient services. These data were used to identify opportunities for case management and for managing the costs related to diabetes care. The data also supported proposals made by the clinical nurse specialist/nurse practitioner to management to allocate clinical resources for the care of patients with diabetes. When the clinical wisdom of advanced practice nurses is joined with nursing information management expertise and technology, opportunities for understanding and advancing nursing's work are revealed.

Adult↗
PubMed1998

Platelet-leukocyte activation during hemodialysis detected with a monoclonal antibody to leukocyte integrin CD11b.

Platelet activation is commonly monitored with a battery of monoclonal antibodies against different platelet epitopes with controversial results. The transient expression of platelet markers and their role mediating interactions with other cells could easily explain these discrepancies. The present study has evaluated whether the analysis of a leukocyte activation antigen (CD11b) could provide more reliable results than detection of platelet activation markers. Cytometric techniques with specific monoclonal antibodies were used to compare the reliability of platelet and leukocyte markers to detect activation. Modifications in the presence of platelet glycoproteins GPIb (CD42b), GPIIIa (CD41) and GPIV (CD36), expression of specific platelet markers (P-selectin (CD62P) and lysosomal protein (CD63)) and leukocyte integrin (CD11b) were assessed during hemodialysis. Platelet antigens remained in uremic patients at levels similar or slightly above those detected in a group of healthy subjects. Modifications of platelet antigens during hemodialysis produced inconclusive results. However, numbers of leukocytes expressing CD11b increased progressively during hemodialysis (17.2 +/- 5.1% at 15 min and 21.3 +/- 6.6% at 2 h, p < 0.05, vs. baseline 6.9 +/- 0.2%). The hemodialysis procedure caused an increased formation of leukocyte-platelet aggregates. Detection of leukocyte CD11b may be a useful marker of overall cellular activation during the hemodialysis procedure.

Aged↗
PubMed1998

Understanding nursing resources in intensive care: a case study.

OBJECTIVE: We describe the use of a measurement of nursing acuity in an ICU based on data from an integrated clinical and financial information system to shed light on the problem of a perceived change in the work of the unit. SETTING: A surgical-neurosurgical ICU in a teaching hospital with more than 800 beds. DESIGN: Changes in the work of nursing, defined by nursing acuity and by case mix and use of ancillary services in this unit for an 18-month period, were reviewed. RESULTS: The caseload was unpredictable. The lack of a systematic pattern of use of hospital resources burdened the nurses. CONCLUSION: For the first time at this institution, timely clinical and financial information has been brought together in an understandable format that can be used to explain trends and variances, to plan for the future, and to manage for cost and quality. The model for information management described here might serve other hospitals as well.

Connecticut↗
PubMed1998

Building a nursing management analysis capacity in a teaching hospital.

The authors describe one institution's efforts to create the capacity to use standard hospital information systems to address clinical and operational nursing questions. This work involved not only technical aspects of information management system creation but also building the human currency to make the information available and useful. Because the information available to nursing comes from the same data sources that feed operational management and finance departments, nursing can now speak in the same language at the policy tables.

Budgets↗
PubMed1997

In vitro evaluation of the hemostatic effectiveness of non viable platelet preparations: studies with frozen-thawed, sonicated or lyophilized platelets.

OBJECTIVES: Because of the limited life span of platelets in regular storage systems, we were interested in investigating the effects on hemostasis of nonliving platelet derivatives. METHODS: We evaluated the effects of different platelet preparations on primary hemostasis in a well-established perfusion model. Studies were carried out with blood anticoagulated with low molecular weight heparin. Similar amounts of frozen-thawed, sonicated or lyophilized platelets were added to normal blood or to blood which had been experimentally depleted of platelets. Platelet interaction with the subendothelium and fibrin deposition were morphometrically evaluated. RESULTS: Addition of nonviable platelet preparations to thrombocytopenic blood always promoted a statistically significant increase in the deposition of fibrin on the subendothelium, but only lyophilized platelets retained some ability to interact with the subendothelium. Flow cytometry studies demonstrated the presence of GPIb, GPIIIa and P-selectin on lyophilized platelets. CONCLUSIONS: Preparations containing nonviable platelets may still retain some hemostatic properties.

Animals↗
PubMed1997

[Comparative efficiency of 1 direct and 2 indirect methods for the detection of differences in erythrocyte aggregation, in normal blood and in blood with echinocytosis].

BACKGROUND: There are many different methods for assessing red cell aggregation, but they have been evaluated in isolated form. The aim of this work was to compare the efficacy and reliability of three different methods for evaluating red cell aggregation. MATERIAL AND METHODS: Blood was drawn on trisodium citrate, and after removal of platelet-rich plasma, the red cell were washed with sodium chloride, and blood was reconstituted until a haematocrit of 40% was achieved. Aspirin or dipyridamole were added, the latter for inducing echinocyte formation. Three methods of assessment of red cell aggregation were used; two of them, indirect, were based upon blood viscosimetry under shear rates indices, and sedimentation rate of centrifuged blood. The third, direct method was based on microscope observation of aggregation and digital analysis of its images for statistical evaluation. Both descriptive methods and analysis of variance were used. RESULTS: The addition of aspirin and dipyridamole increased blood viscosity with respect to the control (p < 0.001 and p < 0.005, respectively), thus showing increased red cell aggregation. Sedimentation rate was also increased, with, statistical significance in the case of dipyridamole (p < 0.05). Digital analysis of images showed significant increase of red cell aggregation with aspirin (37.48 +/- 2.16 vs 27.99 +/- 1.55 in controls, p < 0.05). The presence of dipyridamole-induced echinocytes impeded an adequate evaluation of red cell aggregation indices. CONCLUSION: It was included from these studies that blood viscosimetry proved to be as efficient as digital analysis of images for assessing the differences in red cell aggregation. Nevertheless, microscope examination was necessary for a correct evaluation of this phenomenon, and the presence of echinocytes invalidated any attempt to compare red cell aggregation with respect to normal blood.

Aspirin↗
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↗