In vitro study of magnetic resonance imaging artefacts of six supraglottic airway devices.

We investigated the artefacts created during magnetic resonance imaging by five different laryngeal mask airways: the Classic (cLMA); the LMA ProSeal; the LMA Unique; the Ambu Disposable Laryngeal Mask; the LMA Supreme; and one other supraglottic airway device, the i-gel supraglottic airway. The devices were placed on top of and inside a phantom simulator to resemble the position in vivo. The artefacts with the cLMA, Unique and Supreme were similar and related to ferromagnetic material in the pilot balloon valve. Artefacts were more prominent with the ProSeal. There were no artefacts with the Ambu Disposable Laryngeal Mask or the i-gel.

Cell surface sialylation of two human tumor cell lines and its correlation with their platelet-activating activity.

The relationship between cell surface sialylation and platelet-activating activity was studied in two tumor cell lines of human origin, the SKNMC neuroblastoma line and the U87MG glioblastoma line. Their platelet-activating activity was evaluated in two different experimental systems, one that measures platelet aggregation and the other that quantifies platelet thrombus formation on vascular subendothelium under flow conditions. Our results demonstrate that, for the SKNMC line, the loss of 30% of surface sialic acid induced a significant reduction in its platelet-activating capacity. Upon recultivation desialylated SKNMC cells did not regenerate surface sialic acid and did not restore their initial values of platelet aggregation and platelet thrombus formation. Conversely, removal of 35% sialic acid from the surface of U87MG cells did not affect their pattern of platelet activation in either system tested. These results demonstrate that there is a correlation between cell surface sialylation and the capacity of SKNMC cells to activate platelets. The lack of effect of desialylation on U87MG-induced platelet activation indicates that different surface components may be the modulators of the interactions of these tumor cells with platelets. Our results support the hypothesis that heterologous mechanisms regulate platelet-tumor cell interactions and that tumor cell sialic acid may be only one of the aspects involved in such interactions.

Inhibitory effects of dipyridamole on growth, nucleoside incorporation, and platelet-activating capability in the U87MG and SKNMC human tumor cell lines.

The effects of dipyridamole on tumor cell function were examined in cultures of two lines of human origin, the SKNMC neuroblastoma line that activates platelets by a mechanism which is dependent on the release of adenosine 5'-diphosphate and the U87MG glioblastoma line that induces platelet activation by the generation of thrombin. Cells grown in the presence of dipyridamole at 1 microM showed greater than 80% inhibition of uptake of adenosine, thymidine, and uridine with both lines. At 5 microM tumor cell growth was inhibited by 70% (U87MG) and 90% (SKNMC) but without concomitant cytotoxicity as determined by clonogenic assay (50% inhibitory concentration approximately 20 microM). At 10 microM dipyridamole cyclic adenosine 3':5'-monophosphate levels increased 150% with both cell lines but no changes above baseline values were seen at 2.5 microM. The two cell lines showed different responses to being cultured in the presence of dipyridamole in terms of their ability to subsequently activate platelets. U87MG cells cultured in 10 microM dipyridamole showed a doubling of the lag time as compared with cells grown in the absence of dipyridamole but with full aggregation; with SKNMC cells the aggregation rate was reduced and cells grown in 10 microM dipyridamole showed no reversible first wave, a 5-fold increase in lag time and a 75% inhibition in total aggregation. Since therapeutic doses of dipyridamole result in plasma concentrations of approximately 3.5 microM these results suggest that potential antimetastatic effects of dipyridamole could be direct arising from inhibition of important steps in tumor cell metabolism or indirect by suppressing one or more of the mechanisms involved in the ability of tumor cells to activate platelets.

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.

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.

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.

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.

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.

Platelet activation induced by a human neuroblastoma tumor cell line is reduced by prior administration of ticlopidine.

Ticlopidine (250 mg twice daily) was administered to human volunteers for seven days and the response of their heparinized platelet-rich plasma to SKNMC (ADP-dependent) human neuroblastoma cells was examined. The first wave of platelet aggregation, characteristic of ADP-dependent human tumor cell lines, was completely abolished but was replaced by a lag period prior to the onset of aggregation. In the Baumgartner perfusion apparatus there was a marked inhibition in the thrombus generated by the presence of SKNMC cells with a concomitant increase in the percentage of surface coverage. These results suggest that the administration of ticlopidine could be useful to prevent some of the steps of metastatic dissemination in which activated platelets may play a role.

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.

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.

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.

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.

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.

Ticlopidine inhibits platelet thrombus formation studied in a flowing system.

We have studied the effect of ticlopidine on platelet function. This effect was assessed by aggregation studies and by the Baumgartner perfusion system as an ex vivo approach to study modifications in the interaction of platelets with vascular subendothelium. Platelets from volunteers, that were given 250 mg of ticlopidine twice a day showed a significantly decreased aggregation of platelets induced by several agonists. In the perfusion studies a marked reduction in the parameters that measure platelet interaction with subendothelium was also observed. The decrease in thrombus formation, and the diminished size of platelet aggregates, clearly indicated that ticlopidine impaired platelet-platelet interaction in this experimental flowing system. Our results suggest that ticlopidine is a potent inhibitor of platelet function and that its antiplatelet activity might be related to the mechanisms that regulate the interaction between platelets at the membrane level.

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.

Sex-related differences in the effects of aspirin on the interaction of platelets with subendothelium.

Using the Baumgartner perfusion technique, marked sex-related differences in the extent of platelet-subendothelium interaction and in the effect of aspirin (ASA) have been observed. The administration of ASA (150 mg daily for 15 days) to two groups of healthy volunteers, one composed of males and the other of females, proved to block the generation of TXB2 in both cases. The basic pattern of platelet subendothelium interaction, however, was found to be markedly different in both groups studied. In men, aspirin treatment induced a significant reduction in the percentage of platelet thrombi, whereas in women, post ASA values remained at the same level as in control experiments. These results show that in the Baumgartner perfusion system women display a less thrombogenic tendency than men and that 150 mg of ASA administered daily are effective in reducing the extent of platelet-subendothelium interaction in the male group but not in the female group. These findings could explain the absence of benefit observed for women in clinical trials with aspirin.

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.

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 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.