A needleless closed system device (CLAVE) protects from intravascular catheter tip and hub colonization: a prospective randomized study

Hub colonization and subsequent intraluminal progression due to frequent opening and manipulation of intravenous systems is the cause of many catheter-related infections (CRI). A prospective, comparative, randomized study was performed to assess a new closed-needleless hub device (CLAVE) compared with conventional open systems (COS). End-points were hub and skin colonization, catheter tip colonization, catheter-related bloodstream infection (CRBSI) and number of accidental needlesticks. All cultures were processed following standard semiquantitative microbiological techniques. The study involved patients who underwent heart surgery over an 11-month period in a post-surgical ICU. During the study period, 352 patients underwent major heart surgery and 1774 catheters were inserted. Overall, 865 catheters in 178 patients were allocated to the CLAVE system and 909 catheters in 174 patients to COS. The groups were similar regarding underlying conditions and risk factors for infection. Comparison of endpoint results in CLAVE and COS groups was as follows: incidence density per 1000 catheter-days of tip colonization: 59.2 versus 83.6 (P=0.003); of hub colonization: 7.56 versus 24.66 (P=0.0017); of skin colonization: 41.5 versus 58.9 (P=0.038); and of CRBSI 3.78 versus 5.89 (P=0.4). There was one accidental needlestick and one catheter-related prosthetic endocarditis in the COS group. Multivariate analysis showed that CLAVE use was an independent protective factor for tip colonization. CLAVE offered significant protection from catheter-tip and hub colonization.

Prevalence of diabetes mellitus and related conditions in a south Texas Mexican American sample

The prevalence of self-reported diabetes mellitus in a Mexican American sample population living in Hidalgo County in south Texas was examined along with risk for related sequelae. Data from a stratified random sample of 849 Mexican American men and women ages 45 and older were examined. A subsample of 193 diabetics was compared to 656 nondiabetics with respect to hospitalization, reasons for hospitalization, and other related medical conditions. The prevalence of self-reported diabetes for both men and women was 25.9%. Hospitalization rates for diabetics over a 1-year period and a 5-year period were significantly higher than nondiabetics. Hypertension, cardiac problems, amputations, kidney or urinary problems, eye problems, and joint and bone problems were significantly more common in the diabetics sample than in the nondiabetic sample. The data indicate that diabetes in Mexican Americans may be undertreated in south Texas.

[Reoperations of myocardial revascularization]

Coronary by-pass grafting is a well established procedure for ameliorating ischemic coronary disease. From time to time it is necessary to re-operate these patients. The objective of our paper is to present our experience in this field. Retrospective analysis of 128 patients operated on between February 1978 and November 1996, has been analyzed. The mean age was 57.4 +/- 0.7 years. 77.2 +/- 5 months elapsed between operations. Stable angina (20.4%) or unstable angina (76.3%), myocardial infarction (48%) and congestive heart failure (17%) were the predominant clinical manifestations.

RESULTS

Hospital mortality was 10.9% (14 patients) and in the follow-up there were 16 deaths (14%). Perioperative myocardial infarction was the main cause of in-hospital mortality. In the follow-up there were 4 deaths due to myocardial infarction and another 4 patients died from neoplasms. Perioperative myocardial infarction was present in 9.3% (12 patients)

IN CONCLUSION

a) Re-do coronary by-pass grafting is still a good procedure for solving myocardial ischemia in spite of a higher mortality and morbidity than in the original operation. b) There is no progression in the number of patients according to our experience, probably due to better techniques and the frequent actions by an intervention cardiologist. c) The long-term results are good enough, but with a higher mortality.

Macrosocial and environmental influences on minority health

Ethnic minority populations show patterns of health, health care use, and mortality that differ from the overall U.S. population. Each of the broad groups of minorities (Asian Hispanic, Native, and African Americans) has a unique background of sociocultural factors that influence these patterns. Thus, the larger social environment for ethnic populations, including political, environmental, historical, and economic factors, is a major variable in possible health outcomes. The individual portions in this panel report of the conference seek to identify such factors for each ethnic group and to suggest those macrosocial influences that are most important for observed health effects.

A deleterious effect of aspirin on the antithrombotic properties of endothelial cells is not observed with platelets previously exposed to aspirin: studies in a flow system

We have explored both the independent and combined effects of aspirin on cultured endothelial cells and platelets, and its influence on platelet deposition onto an extracellular matrix. Blood was circulated through a flat perfusion chamber with two coverslips placed sequentially with respect to blood flow. The first coverslip (upstream) was covered with a cultured endothelial cell monolayer, and the second (downstream) coated with extracellular matrix obtained after endothelial cell removal. Platelet interaction was measured on the second coverslip. Treatment of endothelial cells on the first coverslip with 100 μM aspirin strongly reduced 6-keto-PGF(1a) levels recovered in the perfusates (118.3 ± 35.8 vs 1038.0 ± 308.5 pg/ml) and significantly increased platelet deposition on the downstream coverslip (% covered surface: 38.6 ± 6.4% vs 14.6 ± 1.8%; P < 0.001). Increased platelet deposition (% covered surface: 24.9 f 3.1%; P < 0.01) was observed in perfusions performed with blood containing aspirinized platelets, in the presence of intact endothelial cells. Treatment with aspirin of both platelets and endothelial cells had no additional effect on platelet adherence. Pretreatment of cultured endothelial cells with aspirin did not influence the adhesive properties of their underlying extracellular matrix. Our results indicate that, although endothelial cell cyclooxygenase is important in regulating platelet adhesion, its blockade seemed to have minimal effect on platelet deposition once platelet-cyclooxygenase was already inhibited.

Macrosocial and environmental influences on minority health

Ethnic minority populations show patterns of health, health care use, and mortality that differ from the overall U.S. population. Each of the broad groups of minorities (Asian Hispanic, Native, and African Americans) has a unique background of sociocultural factors that influence these patterns. Thus, the larger social environment for ethnic populations, including political, environmental, historical, and economic factors, is a major variable in possible health outcomes. The individual portions in this panel report of the conference seek to identify such factors for each ethnic group and to suggest those macrosocial influences that are most important for observed health effects.

Massive calcification of the left atrium: surgical implications

BACKGROUND

Massive calcification of the atrial walls ("porcelain atrium") is a rare condition that usually has been reported as an incidental radiologic findings.

METHODS

Between January 1988 and June 1993, 971 patients underwent valvular operation at our institution; 21 patients showed extensive calcification of the left atrium. In 8 patients the calcification was massive, involving almost all the atrial surface. The diagnoses were established by radiology and were confirmed at operation. The mean age of these patients (4 men, 4 women) was 55 +/- 9.6 years. All had rheumatic valve disease, were on atrial fibrillation, and had undergone at least one operation previously. Pulmonary artery pressure was severely increased, even up to systemic levels, in all patients except 1. Total endoatriectomy of the left atrium and mitral valve replacement were performed. No patient was lost during the follow-up.

RESULTS

Hospital mortality rate was 12.5% (1 patient) and 2 patients died in the late postoperative period. None of these deaths are attributable to the surgical procedure.

CONCLUSIONS

In toto endoatriectomy of a massively calcified atrium is an easy to perform technique that helps to replace the mitral valve and close the atrial wall.

[Expression of von Willebrand's disease in endothelial cord cell from a type 1 patient. Discrepancies between clinical manifestations and laboratory tests]

PURPOSE

The reactivity of subendothelium generated by endothelial cells attained from the umbilical cord of a newborn girl from a patient with type I von Willebrand's disease was evaluated.

MATERIAL AND METHODS

Platelet adhesiveness was assessed by means of "ex vivo" blood perfusion systems (shearing coefficients from 300 to 1,300 s-1), on umbilical artery subendothelium and over the extracellular matrix (ECM) generated by cultured endothelial cells attained from the umbilical cord of a newborn baby from a type I von Willebrand mother.

RESULTS

By means of an ELISA technique, a significant reduction of both the vWF secreted into the culture (p < 0.05) and of that associated with ECM (p < 0.05) was noticed. The two subendothelial surfaces examined supported a lesser extent of platelet adhesion than the control surfaces from healthy individuals in the perfusion tests at 1,300 s-1 (p < 0.05). The experimental results did not agree with the lack of clinical manifestations and laboratory abnormalities in the propositus at age 3.

CONCLUSIONS

These findings suggest that the endothelial cells cultured from the tissues of a newborn baby from a type I von Willebrand woman expressed less vWF, at the same time confirming the importance of vWF bound to connective tissue in sustaining platelet adhesion. The data attained here illustrate the complex model of inheritance of moderate von Willebrand's disease, along with the technical limitations of cell culture studies. Such observations must be borne in mind whenever any experimental approach is performed with material attained from ill-differentiated tissues such as the umbilical cord vein.

Thoracic aneurysm as a cause of chyluria: resolution by surgical treatment

A 37-year-old man who had suffered a thoracic trauma presented night release of whitish urine 2 years later. Thoracic computed tomography and aortography demonstrated an aneurysm of the thoracic aorta. Lymphography confirmed the compression of the thoracic duct by the aneurysm. After surgical repair the patient has remained asymptomatic.

Cardiac surgery in patients under chronic hemodialysis

A total of 15 chronic renal failure patients on hemodialysis therapy underwent some kind of cardiovascular surgery between August 1984 and March 1993. Ten had a valve abnormality, and the remaining five had coronary artery disease. All of them were hemodialyzed the day before surgery and 24-48 h after the operation. Eleven recovered well after surgery, four died of septic shock: two of these were in septic shock prior to surgery; one was in acute congestive heart failure, and one was operated during an acute myocardial infarction. All operative deaths occurred in the patients who underwent non-elective surgery or were preoperatively in New Heart Association (NYHA) class IV. The factors having an impact on morbidity and mortality seem to be more related to the previous clinical situation and to the urgency of the operation than to the status of chronic renal failure. An early and adequate assessment of the candidates, when possible avoiding emergency surgery and acute left ventricular dysfunction, as well as careful management during cardiopulmonary bypass procedures (CPB) and the immediate post-surgical period will certainly improve the result of cardiac surgery in these patients, making it similar to those who are not in chronic renal failure.

[The contribution and usefulness of routine intraoperative transesophageal echocardiography in cardiac surgery. An analysis of 130 consecutive cases]

PURPOSE

To assess the value of routine intraoperative transesophageal echocardiography (TEE) in unselected patients (P) undergoing cardiac surgery.

DESIGN

Routine intraoperative TEE in unselected patients undergoing cardiac surgery and evaluation of its usefulness and contribute to a successful surgery.

PATIENTS

In-hospital patients from cardiology, cardiac surgery and intensive care departments of a general hospital classified as a reference medical centre in cardiovascular pathology.

MATERIAL AND METHODS

From February 1994 to May 1994 an intraoperative TEE was routinely performed in patients undergoing cardiac surgery. A total of 130 TEE studies were made corresponding to 128 patients, 69 males and 61 females, with a mean age of 49.4 +/- 12.1 years. Indications for surgery were as following: a) Coronary artery bypass grafting (C.A.B.G.)-39; b) Valvular surgery-76; c) C.A.B.G. and valvular surgery-5; d) Thoracic aorta pathology associated or not to aortic valve surgery and/or coronary arteries re-implantation-6; e) Other-4. TEE performed using either a monoplane, biplane or multiplane probe and the images acquisition was made before thoracotomy and cardiopulmonary bypass (CPB) and after CPB with hemodynamic stabilization.

RESULTS

Pre CPB imaging yielded unsuspected findings in 11 P (8.5%) that changed the planned surgery in 7 cases (5.4%). Post CPB echo study, which was performed after hemodynamic stabilization, modified the surgical strategy in 13 cases (10.9%) avoiding 1 predetermined surgical procedure (tricuspid ring annuloplasty) and a new surgery in another case, leading to a 3 non-predetermined surgical procedures (by showing significative tricuspid regurgitation), to a further surgery in the same valve in 6 patients (mitral paravalvular leak with significative regurgitation in 1P, another mitral prosthesis dysfunction in 1P, residual mitral valve insufficiency after mitral valve repair in 3 P and aortic prosthesis dysfunction in 1 P), to a intraaortic counterpulsation balloon device in 1 P and to new CPB due to an insufficient extraction of calcified pericardium in one case of constrictive pericarditis. In 23 cases (17.7%) TEE has modified the anesthetic procedure by demonstrating signs of hemodynamic changes before Swan-Ganz catheter, thus prompting changes in the administrations of fluids and either in inotropic or vasodilator agents. In total, intraoperative TEE has changed the surgical and/or anesthetic plan in 43 cases (33.0%). There was no difficulties or complications related to the procedure.

CONCLUSION

These data indicate that intraoperative TEE is useful in formulating the surgical plan and assessing immediate operative results as well as a guide to anesthetic procedures. Its high rentabillity in modifying the surgical and/or anesthetic plans lead us to believe that it must be used as a routine procedure in patients undergoing cardiac surgery.

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.

[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.

Platelets lacking functional CD36 (glycoprotein IV) show reduced adhesion to collagen in flowing whole blood

A parallel-plate perfusion chamber has been used to evaluate the contribution of the adhesive membrane glycoprotein CD36 (GPIV) to platelet adhesion on type I collagen in flowing whole blood at a shear rate of 800 s-1. In one series of experiments, reconstituted normal blood (hematocrit 0.4; platelet count 1.5 x 10(5)/microL) was prepared from washed red blood cells, plasma, and washed platelets that had been incubated with Fab fragments of a monospecific polyclonal anti-CD36 antibody (50 micrograms/mL, 30 minutes, 37 degrees C). Percent surface coverage of collagen-coated coverslips using reconstituted blood with antibody-blocked platelets, as compared with paired reconstituted controls (100%), was 50% at 2 minutes, 87% at 5 minutes, and 90% at 10 minutes. Further studies were performed by perfusion of whole blood from a healthy donor of the Naka-negative phenotype, whose platelets constitutively lack CD36, over collagen-coated coverslips. In this case, percent surface coverage was 55% of normal controls at 2 minutes, 76% of controls at 5 minutes, and 72% of controls at 10 minutes. In both preparations, platelets lacking functional CD36 had a statistically significant decrease (P < .005) in adhesion after 2 minutes and 10 minutes perfusion but not at 5 minutes. These results show that functional CD36 facilitates the rapid adhesion of platelets to collagen and that this effect is seen at the earliest time points of their interaction.

Interleukin 1-induced cancer cell/endothelial cell adhesion in vitro and its relationship to metastasis in vivo: role of vessel wall 13-HODE synthesis and integrin expression

Previously, we have demonstrated that stimulation of endothelial cells (ECs) with interleukin-1 alpha (IL-1 alpha) enhances the synthesis and expression of the vitronectin receptor (VnR), promotes VnR-dependent adhesion of human A549 adenocarcinoma cells to ECs, and is associated with decreased EC 13-hydroxyoctadecadienoic acid (13-HODE) synthesis in vitro. To determine whether these observations are relevant in vivo, we examined the acute retention and subsequent metastasis of intravenously-injected B16F10 melanoma cells in murine lungs, in relation to vessel wall 13-HODE. In C57BL/6 mice pretreated with IL-1 alpha, vessel wall 13-HODE was decreased and B16F10 lung entrapment and metastasis were increased. The latter two events were blocked by pretreating the animals with the GRGDS peptide. These data suggest a relationship between vessel wall 13-HODE synthesis, adhesion molecule expression, and adhesion of B16F10 cells to the endothelium.

[Effect of PAF (platelet-activating factor) on hemostasis. Studies on endothelial cells and platelets]

PURPOSE

To evaluate the direct action of PAF on the pro-coagulant activity of cultured vascular endothelial cells; to analyse by photometric methods the thrombogenic effect of PAF on platelets, and to assess platelet deposition on vascular endothelium.

MATERIAL AND METHODS

Human endothelial cells were isolated from umbilical cord vein and incubated for three minutes at 22 degrees C with different PAF concentrations (10(9) M to 10(-7) M) in order to assess the influence of this lipidic mediator on the procoagulant activity of the cells. The effect of PAF on platelet aggregation was assessed by aggregation studies using arachidonic acid (AA) and different PAF and Lyso-PAF concentrations (10(-8) M to 10(-4) M). Serotonin (5-HT) release was tested in platelet rich plasma (PRP) samples highly sensitive to PAF. PRP samples were incubated for 30 minutes at 22 degrees C with 100 microCi 3H-5-HT. Platelets were activated with 10(-7) M to 10(-9) M PAF concentrations, the percentage of 3H-5-HT released into the extra-platelet medium being calculated. Baumgartner's continuous perfusion model was used to study platelet deposition on the vascular endothelium. The morphometric evaluation was carried out by a planimeter assembled to a data processor with a programme devised for analysing the platelet-subendothelium interaction.

RESULTS

Evaluation of the procoagulant activity on the cell surface: The expression of the procoagulant activity showed no variations with respect to the controls under different concentrations of PAF. Platelet aggregation and release studies: Normal values of platelet aggregation (80% to 100%) were found when using AA, however, there were great case to case variations under different PAF concentrations. Serotonin release was less marked than aggregation itself. The use of Lyso-PAF failed to elicit platelet aggregation and serotonin release in any case. Morphometric evaluation: The results attained showed that perfusion carried out with 10(-8) M PAF concentration showed contact, adhesiveness and thrombus formation figures similar to those of control perfusion.

CONCLUSIONS

Human platelets are not too sensitive to PAF activity, only high PAF concentrations being capable of inducing platelet aggregation and 5-HT release with ample variability. This suggests the existence of a heterogeneous platelet population with PAF receptors. Low PAF concentrations do not modify the haemostatic function, and only those PAF concentrations inducing maximal release and aggregations could reduce the interaction of platelets with vascular subendothelium and the formation of thrombi.

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.

[The effect of low-dose acetylsalicylic acid on platelet aggregation parameters in vitro]

In order to elucidate whether a single dose of 150 mg acetylsalicylic acid three times a day, provokes significant changes into platelet aggregation, we analyzed a group of 50 patients who underwent coronary revascularization. During 48 hours before surgery, all patients received 100 mg dipyridamole orally every 6 hours and 1 hour after the end of the operation 100 mg dipyridamole via nasogastric tube. Patients were then randomized into three groups to receive 3 times a day a capsule containing: 50 mg acetylsalicylic acid, 50 mg acetylsalicylic acid plus 75 mg dipyridamole or placebo. Before the antiplatelet therapy was started, the day of the operation and 5 days after the onset of the treatment, blood samples were taken to determine platelet aggregation (turbidimetric technique) and the thromboxane A2 liberation. The three groups were comparable for all the studied clinical and angiographic variables. Preoperative dipyridamole did not provoke significant changes in platelet aggregation (acetylsalicylic acid group 86.5 +/- 10% vs 71 +/- 28.8%; acetylsalicylic acid + dipyridamole group 81.5 +/- 7.8% vs 75.3 +/- 22.7%; placebo group 83.7 +/- 8.9% vs 70 +/- 21.5%). After 5 days of treatment with acetylsalicylic acid, both groups under active treatment showed a significant (p less than 0.001) decrease of aggregability (acetylsalicylic acid 12.8 +/- 4.4%; acetylsalicylic acid + dipyridamole 20.5 +/- 17%; placebo 72 +/- 21.5%).(ABSTRACT TRUNCATED AT 250 WORDS)

[The midterm (6 years) clinical results of the Carpenter-Edwards supra-annular bioprosthesis]

We present here the clinical results with a second-generation porcine bioprosthesis, the Carpentier-Edwards supra-annular valve (CESA). Two-hundred and twenty-two CESA bioprostheses were implanted in 189 patients during a four-year period (from 1984 to 1987), either as an isolated procedure or associated to mitral or tricuspid repair. The mid-term clinical results have been evaluated after a mean follow-up of 3.4 years, being 96% complete. There were 16 in-hospital deaths (8.4%) and 6 late, potentially valve-related, cardiac deaths (1.1% patients/year). Overall, 86.7 +/- 2% of the patients were free from cardiac death at 6 years (95.1 +/- 2% of the patients surviving the operative period). Linearized rates of valve related complications were the following: 1.4% patients/year for thromboembolism (including valve thrombosis), 0.5% patients/year for treatment-related hemorrhage and 0.7% patients/year for endocarditis. We did not found any case of either intrinsic or extrinsic valve failure, unrelated to infection of thrombosis. Two patients were reoperated, one because of valve thrombosis and the other due to prosthetic valve endocarditis (reoperation rate of 0.3% patients/year). When lethal and nonlethal valve-related complications (including in-hospital deaths) were considered all together, 75.8 +/- 8.4% of the patients remained alive and free of morbid events at 6 years. When patients were grouped according to the valve replaced (aortic, mitral and multiple), best results were found with patients submitted to isolated aortic valve replacement. We conclude that the CESA bioprosthesis has an excellent mid-term clinical performance. However, longer follow-up is necessary to know if improvement in valve design and manufacturing results in increased valve durability.

Dipyridamole induces changes in the thrombogenic properties of extracellular matrix generated by endothelial cells in culture

Dipyridamole (DIP) is a drug widely used as an antiplatelet agent, which also has effects on endothelial cells. In this study, the effects of treating confluent endothelial cell monolayers (EC) with DIP on EC viability (trypan blue exclusion test) and metabolic activity (3H-thymidine incorporation) were examined. Platelet reactivity of the extracellular matrix (ECM) produced by untreated and DIP-treated ECs was determined morphometrically by a perfusion technique. Levels of ECM-associated von Willebrand factor (vWF) and fibronectin (FN) were also quantified (ELISA). The present results indicate that treatment of EC with 10 microM DIP did not reduce EC viability but that the incorporation of labelled nucleotides was significantly decreased (p less than 0.01). Platelet deposition onto the ECM generated by DIP-treated cells, perfused at a shear rate of 1300 sec-1, differed significantly with respect to controls (p less than 0.05), and platelet adhesion was also reduced (25% less, p less than 0.05). This effect was shear rate dependent, as no differences were noted when the ECMs were perfused at 300 sec-1 shear rate. Levels of VWF and FN associated with ECM remained unchanged with respect to controls. These results suggest that treatment with DIP alters EC metabolic activity, which in turn, influences the reactivity of the ECM generated by treated cells.

Platelet adhesion to exposed endothelial cell extracellular matrixes is influenced by the method of preparation

The relative thrombogenicity of extracellular matrixes (ECMs) produced by cultured human umbilical endothelial cells (ECs) was studied under flow conditions. ECMs were prepared using a number of physical and chemical methods, and their reactivity toward platelets was morphometrically evaluated. von Willebrand factor (vWF), fibronectin (FN), and 13-hydroxy-9-cis,11-trans-octadecadienoic acid (13-HODE) were also determined. We found that platelet adhesion to ECMs differed significantly, both quantitatively and qualitatively, with the method of ECM preparation. Mechanically prepared ECM exposed a less thrombogenic surface compared with ECM prepared by chemical methods (platelet-covered surface of 20% and 50%, respectively). Evaluation of the ECM components vWF, FN, and 13-HODE showed significant changes, both in their concentrations and distribution patterns, depending on the method of ECM preparation. The decrease measured in the levels of ECM-associated vWF (from 108 to 9.2 ng/10(4) cells) and the minor changes observed in the distribution pattern of subendothelial FN did not appear to be sufficient to explain the altered platelet adhesion observed in our model. This suggests that the amount of 13-HODE probably associated to the remaining ECs present in the mechanically exposed ECM could be one factor that specifically contributed to the nonthrombogenic state of these preparations. We conclude that the degree of ECM reactivity toward platelets is dependent on the method of ECM preparation and that this is related to the removal of specific EC/ECM components that modulate their thromboresistant/thrombogenic properties. This fact should be taken into account when ECMs produced by cultured ECs are used in platelet adhesion studies.

Comparison between human umbilical artery and rabbit abdominal aorta as substrata for platelet adhesion and platelet thrombus formation under flow conditions

Rabbit abdominal aortas and human umbilical arteries are currently used as substrata for the study of platelet adhesion and aggregate formation under flow conditions. Using immunohistochemical and ultrastructural methods, we have analyzed both vessel surfaces. The reactivity towards platelets of the subendothelium (SE) exposed on these vessels after mechanical or enzymatic digestion (alpha-chymotrypsin) was morphometrically quantified and the nature of the interaction studied in the electron microscope. After mechanical damage, the ultrastructural study of rabbit aortas showed a clearly defined internal elastic lamina (IEL). In contrast, umbilical vessels lacked a consistent IEL and masses of amorphous material often located deeper in the media were the main constitutents of the SE. Immunohistochemical labeling of the von Willebrand factor bound to both types of vessel differed considerably. Quantification of platelet interactions after perfusion of citrated blood showed qualitative differences between mechanically damaged rabbit or human vessels. Enzymatic digestion produced a more thrombogenic surface on rabbit aortas (p less than 0.01 vs. nondigested), but decreased their reactivity towards platelets on umbilical arteries (p less than 0.01 vs. nondigested). The ultrastructural study of the interacting platelets revealed that aggregates, when present, were found on the extracellular matrix underlying endothelial cells of rabbit aortas, but interacting with fibrillar structures probably derived from cell elements of the media in the case of umbilical arteries. These findings indicate that rabbit aortas and umbilical arteries possess structural characteristics that result in different thrombogenic properties with respect to circulating platelets.

[Update on the role of vascular, plasmatic and cellular components in the regulation of the interaction of platelets with the subendothelium]

The interaction of platelets (Plts) with subendothelium (SE) or with extracellular matrices (ECM) generated by endothelial cells was studied under flow conditions. The role of: a) platelet membrane glycoproteins (GPS) or subunits; b) plasma adhesive proteins such as von Willebrand factor (VWF) and fibronectin (Fn); and c) structural proteins of the SE such as laminin (Lm). Specific antibodies or purified proteins were added to the perfusates. GPS. Monoclonal antibodies (MoAb) directed against distinct epitopes of the GPIIb-IIIa affected in different manner the deposition of platelets. MoAb EDU3 decreased (p less than 0.01) the surface of the vessel covered by platelets (% CS) and increased the presence of platelets in contact (% C) with the SE. MoAb C17 did not modify the % CS but altered the morphological characteristics of the aggregates. A monoclonal antibody against GPIIb, decreased the % CS (p less than 0.01) without influencing % C; VWF. A linear progression of the % CS was observed for VWF levels ranging from 0.1 to 0.6 U/mL. A plateau was reached for concentrations of vWF above 0.6 U/mL; Fn. Perfusions in which blood was reconstituted with Fn-depleted plasma showed the cooperation of this protein facilitating Plt-Plt interaction. No statistical differences were observed in the % CS when ECM were incubated with a MoAb against Fn (3E3); Lm. The % CS decreased statistically (p less than 0.01) when SE or ECM were incubated with an antibody to Lm. These results show the critical role of vascular, plasmatic and cellular components in the maintenance of and adequate platelet function.

The role of platelets in cancer metastasis

Clinical, experimental and ultrastructural studies strongly suggest a role for platelets in metastatic dissemination. Several mechanisms have been proposed to explain the potential contribution of blood platelets to the metastatic cascade. Experimentally, many tumour cells of either animal or human origin have the capacity to activate platelets, although the mechanisms by which malignant cells exert this effect is not yet fully understood. Possible mechanisms include: (1) generation of thrombin; (2) activation by ADP; (3) release of cathepsin B; (4) eicosanoid metabolism. A number of observations also indicated that tumour-cell-induced platelet aggregation required specific receptor sites. We have shown that platelet glycoprotein GPIb and the complex GPIIb/IIIa are necessary for tumour-cell-induced platelet aggregation. We and others reported the isolation of a microparticulate aggregating material from different types of tumour cell lines. This material has been identified as a sialolipoprotein complex which possesses tissue-factor-like activity. The role of sialic acid in the metastatic potential of cells is also believed to be important and may partly modulate their interactions with platelets. In vivo, rheological factors may also regulate the interactions of tumour cells with blood and vascular structures and an alternative approach to the evaluation of platelet-tumour-cell interaction under dynamic conditions has been the use of perfusion systems. Thus, we have established the crucial role of Ca2+ in supporting tumour-cell-platelet activation and subsequent thrombus formation. More recently we investigated the patterns of adhesion of a highly metastatic human adenocarcinoma of the lung to exposed extracellular matrix generated by human vascular endothelial cells in culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective and adjustable pericardial flap to protect internal mammary artery grafts

We describe the surgical technique of a localized and adjustable pericardial flap to protect internal mammary artery grafts. This flap allows selective pulmonary retraction, maintains pleural integrity, and saves most of the pericardium for later closure. This technique has proved to be simple and highly effective. We have used it in 80 patients and have not had any related complications.

[Long-term experience with multivalve replacement with the Medtronic-Hall mechanical prosthesis]

During the period from January to September 1986, 182 Medtronic-Hall (M-H) heart valve prostheses were implanted in 89 patients, mainly because of rheumatic valve disease (68.5%). The patients were divided in two groups. Group I consisted of 83 patients with aortic and mitral valve replacement. Six patients with tricuspid valve replacement plus aortic and/or mitral valve replacement constituted group II. In group I the majority of the patients (86.7%) were in functional class III or IV (NYHA). Twenty three patients had undergone at least one previous cardiac operation. Hospital mortality was 6.02% (5/83). In group II the patients were in functional class III or IV (NYHA). Hospital mortality was 33.3% (2/6). Death occurred in the operating room in only one instance. Follow-up was completed in 98.9% and extended from 27 months to 8 years (348.7 patient years in group I and 23.08 patient years in group II). The overall 5 and 8 years actuarial survival, freedom of thromboembolism and freedom from endocarditis rates in group I were: 80.8 +/- 4.4% and 72.7 +/- 5.2%; 89.8 +/- 4% and 85.8 +/- 4.7%; 94.8 +/- 1.2 and 93.1 +/- 1.7%. In group II, actuarial studies were not carried out because of the scanty number of cases. There were another complications in group I: haemorrhage due to anticoagulation in 6 cases, hemolysis in 8 instances and periprosthetic leaks in 2 cases. There were no cases of structural failure. We conclude that after 8 years of follow-up the M-H valve prosthesis shows an excellent clinical performance and mechanical reliability, and the incidence of valve-related complications was in the low range of that reported with other mechanical prostheses.

Uremic platelets have a functional defect affecting the interaction of von Willebrand factor with glycoprotein IIb-IIIa

Uremic patients have an impaired platelet function that has been related to membrane glycoprotein (GP) abnormalities. Using a perfusion system, we have studied the interaction of normal and uremic platelets with vessel subendothelium (SE) under flow conditions. Reconstituted blood containing washed platelets, purified von Willebrand factor (vWF) (1 U/mL), and normal washed red blood cells was exposed to de-endothelialized rabbit segments for 10 minutes at two different shear rates (800 and 1,600 seconds-1). In some experiments a monoclonal antibody to the GPIIb-IIIa complex (EDU3) was added to the perfusates. With normal platelets, the percentage of the vessel covered by platelets (%CS) was 23.1% +/- 3.7% at 800 seconds-1 and 30% +/- 4.3% at 1,600 seconds-1. Platelets were observed in contact or forming monolayers on vessel SE. EDU3 inhibited the spreading of normal platelets. The %CS (11.1% +/- 3.3%) was statistically decreased (P less than .01) and most of the platelets were observed in contact with the vessel surface. These data indicate that, under flow conditions, the interaction of vWF with GPIIb-IIIa can support the spreading of normal platelets in the absence of exogenous fibrinogen. Under the same experimental conditions, the interaction of uremic platelets with SE was markedly impaired at both shear rates studied (P less than .01 v normal platelets). The presence of EDU3 did not modify the interaction of uremic platelets. These results confirm the impairment of the platelet adhesion observed in uremic patients. Furthermore, they indicate the presence of a functional defect in the interaction of vWF with GPIIb-IIIa. The fact that perfusions with normal and uremic platelets in the presence of an antibody to the GPIIb-IIIa complex did not show any differences gives indirect evidence on a functionally normal interaction vWF/GPIb in uremic patients.

Regulation of tumor cell adhesion by intracellular 13-HODE: 15-HETE ratio

We performed studies to determine whether tumor cells (TCs) produce 13-hydroxyoctadecadienoic acid (13-HODE) and 15-hydroxyeicosatetraenoic acid (15-HETE), and to determine the relationship between TC and endothelial cell (EC) 13-HODE and 15-HETE synthesis, and TC adhesion to ECs and their underlying extracellular matrix (ECM). We measured (1) the amounts and ratios of 13-HODE: 15-HETE in three different human TC lines and in three different murine TC lines under basal and stimulated conditions; and (2) the relationship between 13-HODE synthesis and cAMP levels in TCs and ECs. Under basal conditions, TCs produced both 13-HODE and 15-HETE, the intracellular ratios of which correlated with TC adhesivity. Stimulation of the TCs with the chemotactic tripeptide, N-formyl-methionyl-leucyl-phenylalanine, decreased 13-HODE synthesis, and increased 15-HETE synthesis and TC adhesion to ECs and to their ECM. Alternatively, enhancing 13-HODE synthesis in either TCs or ECs (by elevating the resting levels of intracellular cAMP) was associated with decreased TC adhesion to ECs and ECM. These results suggest that intracellular 13-HODE: 15-HETE ratio in TCs regulates TC adhesivity, and that an alteration in 13-HODE: 15-HETE ratio will markedly influence TC adhesion.

Flow capacity of the human retrograde internal mammary artery: surgical considerations

The diastolic flow of the retrograde internal mammary artery (IMA) was calculated in 30 patients and compared with the expected coronary flow of the left ventricle and that of specific branches. Arterial pressure and free flow were measured in the proximal and distal IMA as well as in the superior epigastric and musculophrenic arteries. Systolic and mean arterial pressure were significantly higher in the proximal IMA than in any other site, but diastolic pressure was comparable. Overall and diastolic antegrade IMA flows (77 +/- 6 and 44 +/- 3 mL/min) were significantly greater than the retrograde flows through the distal IMA (18.5 +/- 2 and 11.5 +/- 1 mL/min), musculophrenic artery (13.3 +/- 1 and 7.9 +/- 1 mL/min), and superior epigastric artery (5.3 +/- 0.4 and 3.1 +/- 0.2 mL/min). Only patient-size-related variables correlated significantly with retrograde IMA flow. Diastolic retrograde IMA flow represented 8.5% +/- 0.6% of the expected left ventricle coronary flow and in 12 patients (40%) was greater than the expected flow of at least one posteroinferior coronary artery. Based on these data, the retrograde IMA may adequately perfuse the posterior descending or other posterolateral coronary branches in select patients. Previous measuring of the retrograde flow is mandatory.

[Variations in the thrombogenic properties of the extracellular matrix produced by endothelial cells in consecutive passages]

Cultured endothelial cells are currently used as a model for the study of the interaction of platelets with the vascular wall under flow conditions. Little is known about the influence of cell-culture conditions on the preservation of the original characteristics of primary tissues. In our study, the reactivity of platelets towards extracellular matrices produced by endothelial cells from different passage numbers was morphometrically evaluated. The presence and distribution of the extracellular von Willebrand factor was analyzed by immunofluorescent techniques. Morphology of endothelial cells in culture varied dramatically along the culture and polymorphism increased clearly at fourth or fifth passages. Extracellular matrix thrombogenicity decreased significantly from the fifth passage number. Simultaneously, von Willebrand factor distribution in ECM changed its typical pattern. Our results confirm that the extracellular matrix produced by human umbilical vein derived-endothelial cells constitutes a good model for the study of platelet adhesion onto vascular subendothelium. The limited viability of ECs and the variation in the thrombogenic properties of ECM formed after multiple passages must be taken into account when these cells or their products are used in experimental research.

A rapid embedding procedure for the study of platelet interactions with extracellular matrices in a flowing system. Effect of aspirin on platelet activity

The cultured endothelial cell (EC) is currently used as a model for the study of the interaction of platelets with the vascular wall. Described is a method for rapid quantitative and qualitative evaluation of platelet interactions with extracellular matrices (ECM) produced by human cultured ECs growing on plastic coverslips. Morphometric calculations can be performed on the same perfused coverslips. A very good correlation (r = 0.96) was found between results of a morphometric method en face and those obtained from analysis of cross sections of the perfused coverslips. A shear rate-dependent increase on platelet deposition onto ECMs was observed with both morphometric procedures. The method is sensitive enough to detect drug-related changes of platelet function. An impairment of the interaction of platelets with the ECM was observed when blood obtained from healthy volunteers who took 500 mg aspirin/day for five days was perfused. Aspirin showed a marked effect, decreasing platelet spreading onto the subendothelium (p less than 0.05). The embedding method described benefits from the use of plastic coverslips that are easily detected from the glycol methacrylate compound used for the embedding procedure. Quantitative analysis en face (covered surface) and qualitative evaluation of platelet interactions (contact, adhesive and aggregated platelets) in cross sections are performed on the same coverslip. This embedding procedure provides a useful tool for the study not only of platelet interactions with ECMs but also for the investigation of interactions of blood elements with other cultured cells.

Differential localization of von Willebrand factor, fibronectin and 13-HODE in human endothelial cell cultures

Von Willebrand factor (vWF), fibronectin (FN) and 13-hydroxy-octadecadienoic acid (13-HODE) are known to influence the regulation of the adhesive properties of vascular surfaces. In the present study vWF, FN and 13-HODE were comparatively localized in endothelial cells (EC) and in the extracellular matrix (ECM) produced by EC. An indirect immunofluorescent technique was applied to coverslips containing human EC cultures previously fixed and permeabilized following different procedures: A. Alcohol/acetone; B. Paraformaldehyde alone and C. Paraformaldehyde followed by Triton X-100. vWF was observed inside EC (A), on the ECM produced by EC (B) or in EC and ECM (C) depending on the fixation procedures used. FN was mainly localized in the ECM despite the fixation procedures employed. FN was only seen in relation to cell bodies after strong permeabilization (A). Under our experimental conditions 13-HODE was never found in ECM. This latter antigen was observed randomly dispersed in those preparations fixed with alcohol/acetone, indicating that it is probably extracted by this fixative. 13-HODE was detected in granular shaped structures in EC after permeabilization with detergent (C). These results suggest that the cellular localization of vWF and FN is compatible with an adhesive role related to the abluminal side of ECs. 13-HODE was readily observed after mild permeabilization. This finding would be morphologically consistent with its contribution to the regulation of the vessel wall thromboresistance.

Cyclic AMP regulation of endothelial cell triacylglycerol turnover, 13-hydroxyoctadecadienoic acid (13-HODE) synthesis and endothelial cell thrombogenicity

The 15-omega-lipoxygenase enzyme in endothelial cells metabolizes endogenous linoleic acid (18:2) into 13-hydroxyoctadecadienoic acid (13-HODE) under basal conditions, i.e., in unstimulated endothelial cells. 13-HODE is thought to regulate the non-adhesivity of the endothelium, contributing to vessel wall/blood cell biocompatibility. We performed experiments, therefore, to determine the relationship between basal levels of cAMP, 13-HODE synthesis, and platelet/endothelial cell adhesion. We found that 13-HODE synthesis increased with elevated cAMP levels and that the elevated 13-HODE levels correlated with increased 18:2 turnover in the triacylglycerol pool. In contrast, neither 18:2 nor arachidonic acid (20:4) turnover in the phospholipid nor prostacyclin (PGI2) production were changed with elevated cAMP levels. Platelet/endothelial cell adhesion was inversely proportional to 13-HODE synthesis. We conclude that intracellular 13-HODE influences platelet/vessel wall interactions, is synthesized from 18:2 released from the endogenous triacylglycerol pool, and that this pathway is modulated by intracellular cAMP levels.

Interleukin-1 increases tumor cell adhesion to endothelial cells through an RGD dependent mechanism: in vitro and in vivo studies

The effects of human recombinant interleukin-1 alpha and beta (rIL-1 alpha; rIL-1 beta) on the adhesion of human A549 lung carcinoma cells and M6 melanoma cells (TC) to human endothelial cells (HECs) in vitro were studied, and on TC/lung entrapment in vivo. In vitro, there was a significant increase in TC/HEC adhesion to HECs pretreated for 4 h with rIL-1 alpha or rIL-1 beta. The effects of rIL-1 alpha and beta on TC/HEC adhesion were time dependent and reached a plateau within 4-6 h. TC/HEC adhesion was not blocked when measured in the presence of antibodies to either fibronectin, glycoprotein IIb/IIIa, anti-ICAM, or anti-LFA. However, enhanced TC/HEC adhesion was completely blocked in the presence of the peptide, GRGDS. In vivo, pretreatment of nude mice for 4 h with rIL-1 alpha (given i.p. before i.v. injection of TCs) enhanced TC retention in the lung 24 h later. Our data demonstrate that IL-1 enhances TC adhesion to the vascular surface both in vitro and in vivo, suggesting that IL-1 can facilitate the metastatic process.

[Myocardial revascularization: isoflurane and halothane. Our experience]

The use of isofluorane in coronary patients has been questioned due to the coronary steal syndrome that this agent is said to produce with changes in the myocardial lactate extraction, ST segment changes or T wave inversion. Three hundred fifty nine patients underwent coronary revascularization were studied. The anaesthesia was carried out with halothane (146 patients) or isofluorane (213 patients) as volatile agents of a balanced anesthetic technique based on high doses of narcotics. We found no correlation between the use of isofluorane and ST changes or T wave inversion. The appearance of myocardial infarction between the 2 groups was also no statistically difference (p = 0.61).

Platelet and shear rate promote tumor cell adhesion to human endothelial extracellular matrix--absence of a role for platelet cyclooxygenase

Blood platelets are thought to be involved in certain aspects of malignant dissemination. To study the role of platelets in tumor cell adherence to vascular endothelium we performed studies under static and flow conditions, measuring tumor cell adhesion in the absence or presence of platelets. We used highly metastatic human adenocarcinoma cells of the lung, cultured human umbilical vein endothelial cells (ECs) and extracellular matrices (ECM) prepared from confluent EC monolayers. Our results indicated that under static conditions platelets do not significantly increase tumor cell adhesion to either intact ECs or to exposed ECM. Conversely, the studies performed under flow conditions using the flat chamber perfusion system indicated that the presence of 2 x 10(5) pl/microliters in the perfusate significantly increased the number of tumor cells adhered to ECM, and that this effect was shear rate dependent. The maximal values of tumor cell adhesion were obtained, in presence of platelets, at a shear rate of 1,300 sec-1. Furthermore, our results with ASA-treated platelets suggest that the role of platelets in enhancing tumor cell adhesion to ECM is independent of the activation of the platelet cyclooxygenase pathway.

Influence of shear stress on tumor-cell adhesion to endothelial-cell extracellular matrix and its modulation by fibronectin

The interaction of malignant cells with blood-vessel endothelial cells and their underlying basement membrane is an important step in the development of secondary metastases. We investigated the interactions of highly metastatic human tumor cells, the A-549 adenocarcinoma of the lung, with cultured endothelial cells (EC) and their extracellular matrix (ECM). We studied the adhesion patterns of the A-549 tumor cells to EC and ECM under static and flow conditions. Our results provide evidence that tumor-cell adhesion depends not only on the characteristics of the tumor cells themselves, but also on the properties of the EC and ECM. Our results also indicate that tumor-cell adhesion to ECM is shear-rate-dependent, and that it is partially modulated by fibronectin. Moreover, our results suggest that the arg-gly-asp (RGD) common adhesion receptor site is also involved in the adhesion of the A-549 cells to EC and ECM.

Differential effects of interleukin-1 and formylmethionylleucylphenylalanine on chemotaxis and human endothelium adhesivity for A549 tumor cells

We investigated the effects of formylmethionylleucylphenylalanine (FMLP), interleukin-1 alpha (IL1 alpha) and interleukin-1 beta (IL1 beta) on tumor cell chemotaxis and tumor cell/endothelial cell adhesion. Chemotaxis of A549 human lung carcinoma cells was measured as the number of tumor cells which migrated across a nitrocellulose filter in a Boyden chamber. Tumor cell/endothelial cell adhesion was measured as the number of 125IUdR tumor cells adherent to monolayers of endothelial cells. Confluent monolayers of human umbilical endothelial cells were incubated from 10 to 240 minutes with FMLP, monocyte-derived interleukin-1, or recombinant IL1 alpha or IL1 beta. The endothelial cells were washed and then incubated with 125IUdR-tumor cells. Thirty minutes later the number of adherent tumor cells was assessed isotopically. Our results demonstrate that (a) interleukin-1 but not FMLP, has chemotactic activity for tumor cells, and (b) both FMLP and interleukin-1 enhance tumor cell adhesion to the endothelium independent of any chemotactic activity. Furthermore, we demonstrate that IL1 alpha and IL1 beta have different effects on tumor cell/endothelial cell adhesion, and raise the possibility that IL1 alpha but not IL1 beta is continuously synthesized and stored within the endothelium. We postulate that IL1 alpha and IL1 beta influence tumor cell/endothelial cell adhesion independent of chemotaxis through the expression of adhesive receptors on the endothelial cell surface.

Endothelium and underlying membrane reactivity with platelets, leukocytes and tumor cells: regulation by the lipoxygenase-derived fatty acid metabolites, 13-HODE and HETES

We hypothesize that the ratio of intracellular 13-hydroxy-octadeca-dienoic acid (13 HODE) and hydroxy-eicosatetraenoic acid (5-, 12- and/or 15-HETE) influences the expression or presentation of adhesive moieties on platelets, leukocytes, malignant cells and endothelial cells, thereby influencing their subsequent adhesive interactions. Thus, we demonstrate that under unstimulated conditions, these cells preferentially synthesize linoleic acid via their lipoxygenase enzymes into 13-HODE, the intracellular level of which is associated with limited or no cell adhesion, while following stimulation, the same cells preferentially metabolize arachidonic acid via the lipoxygenase enzyme into HETEs, the production of which is associated with enhanced adhesion. Which metabolite is synthesized by these cells and the subsequent adhesivity of these cells appear to be dependent upon both the intracellular level of cAMP and the ratio of linoleic and arachidonic acid substrates. This suggests that manipulation of this ratio will have significant effects on the adhesive events involved in the pathogenesis of thrombosis, inflammation and metastasis.

Asialo von Willebrand factor enhances platelet adhesion to vessel subendothelium

Native von Willebrand factor (N-vWF) binds to platelets activated by thrombin, ADP or ristocetin. Asialo vWF (As-vWF) induces platelet aggregation in absence of platelet activators. N-vWF mediates platelet adhesion to vessel subendothelium at high shear rates. We have investigated the role of As-vWF in supporting platelet deposition to rabbit vessel subendothelium at a shear rate of 2,000 sec-1, using the Baumgartner perfusion system. We have studied the effects of the addition of As-vWF (from 2 to 12 micrograms/ml) to perfusates consisting of washed red blood cells, 4% human albumin and washed platelets. Our results show a significant increase in platelet deposition on subendothelium (p less than 0.01) in perfusions to which As-vWF had been added. Blockage of the platelet glycoproteins Ib and IIb/IIIa (GPIb and GPIIb/IIIa) by specific monoclonal antibodies (LJIb1 and LJCP8, respectively) resulted in a decrease of platelet deposition in both types of perfusates prepared with N-vWF and As-vWF. Our results indicate that As-vWF enhances platelet deposition to vessel subendothelium under flow conditions. Furthermore, they suggest that this effect is mediated by the binding of As-vWF to platelet membrane receptors, which in turn, promote platelet spreading and adhesion to the subendothelium.

Binding of 13-HODE and 5-, 12- and 15-HETE to endothelial cells and subsequent platelet, neutrophil and tumor cell adhesion

Some studies report that endothelial cells preferentially take up the lipoxygenase-derived arachidonic acid metabolite, 5-hydroxyeicosatetraenoic acid (5-HETE), released from stimulated leukocytes (polymorphonuclear leukocytes, PMNs), whereas others report that endothelial cells preferentially take up 12-HETE released from platelets. The biological relevance of these observations, however, is unknown. Recently, we and others have found that, under basal conditions, endothelial cells, PMNs and tumor cells metabolize linoleic acid via the lipoxygenase enzyme to 13-hydroxyoctadecadienoic acid (13-HODE). We propose that endogenous levels of these metabolites regulate blood-vessel wall cell adhesion. In this study, we have measured (1) the relative binding of 5-, 12- and 15-HETE, and 13-HODE to endothelial cell monolayers, and (2) their effects on endothelial cell adhesivity with platelets, PMNs and tumor cells. There was a dose-related and specific binding of 5-[3H]HETE to endothelial cells but no binding of 12- or 15-HETE or 13-HODE. Platelet or PMN adhesion to endothelial cells was unaffected by the 5-HETE binding, but tumor cell adhesion was blocked by 40% (P less than 0.01). Interestingly, preincubation of endothelial cells with 13-HODE, 12-HETE or 15-HETE decreased platelet adhesion to endothelial cells (P less than 0.05), even though these metabolites did not bind to the endothelial cells. We conclude that 5-HETE preferentially binds to endothelial cells and interferes with a specific receptor for tumor cells, whereas the other metabolites neither bind to cells nor affect cell adhesion.

Platelet contribution to the formation of metastatic foci: the role of cancer cell-induced platelet activation

Platelets are thought to be involved in the development of blood borne metastasis. Ultrastructural and experimental studies demonstrate that association between tumor cells and platelets with subsequent activation of the coagulation cascade takes place in malignancy. Several hypotheses have been proposed to explain the mechanisms by which tumor cells activate platelets including generation of thrombin, ADP release and involvement of arachidonate metabolism. Perfusion studies with human homologous systems showed that intact tumor cells and tumor cell microvesicles were able to induce platelet thrombogenicity under defined flow conditions. The presence of divalent cations and plasma factors was necessary for the cancer cells to exert their activating capacity. These results suggest a role for platelets in the development of secondary metastasis as well as in the thrombotic events of malignancy.

Fibronectin is required for platelet adhesion and for thrombus formation on subendothelium and collagen surfaces

Fibronectin (FN) plays a role in several adhesion mediated functions including the interaction of platelets with subendothelium. We investigated the role of plasma FN in platelet adhesion and platelet thrombus formation under flow conditions. We used two different perfusion models: the annular chamber with alpha-chymotrypsin-treated rabbit vessel segments, and the flat chamber with coverslips coated with fibrillar purified human collagen type III. Perfusates consisted of washed platelets and washed RBCs, suspended in normal or FN-depleted plasma. Perfusions were carried out for ten minutes at shear rates of 300 or 1,300 s-1. Platelet deposition and thrombus dimensions were evaluated morphometrically by a computerized system. We found that depletion of plasma fibronectin significantly reduced the percentage of total coverage surface and percentage of platelet thrombus, at both shear rates studied, and in both perfusion systems (P less than .01) (P less than .01). The dimensions of the platelet thrombi formed in perfusions at high shear rate were also significantly reduced in perfusions carried out with FN depleted plasma (P less than .01). Addition of purified FN to FN-depleted perfusates restored all values to those measured in the control perfusions. These results indicate that plasma FN is required for platelet aggregate and thrombus formation following adhesion under flow conditions.

Tumor-cell-induced platelet aggregation is a glycoprotein-dependent and lipoxygenase-associated process

To characterize the platelet receptor sites and the platelet metabolic pathways involved in tumor-cell-induced platelet aggregation, we have used a homologous system consisting of human platelets and 2 tumor cell lines of human origin, which activate platelets through different mechanisms. Preincubation of platelets with an MAb against platelet glycoprotein Ib partially blocked tumor-cell-induced platelet aggregation, and preincubation of platelets with an MAb against the glycoprotein complex GPIIb/IIIa totally blocked the aggregation induced by the 2 tumor-cell lines. No inhibitory effect was found when platelets were treated with PAF-receptor antagonists or with specific peptides which block the platelet sites involved in bacterially induced platelet aggregation. Compounds which raised intra-platelet cAMP levels inhibited tumor-cell-induced platelet aggregation in a dose-related manner. Inhibition of cyclo-oxygenase by aspirin which blocked TxB2 formation by platelets did not inhibit platelet aggregation induced by tumor cells whereas the BW755 compound which inhibits cyclo- and lipoxygenase blocked platelet aggregation. These results demonstrate that tumor-cell-induced platelet aggregation is a glycoprotein-dependent and a lipoxygenase-associated phenomenon.