Biomedical subjects

W Seeger

Publications and source records attributed to W Seeger.

At least 271 records · Page 15Linked to original sources

PubMed1991

Omega-oxidized leukotriene B4 detected in the broncho-alveolar lavage fluid of patients with non-cardiogenic pulmonary edema, but not in those with cardiogenic edema.

Leukotriene (LT) generation has been implicated in the pathogenesis of the acute respiratory distress syndrome, ARDS. In the present study, we analysed broncho-alveolar lavage fluids of patients on mechanical ventilation because of ARDS (17 samples taken from 9 patients) or because of cardiogenic edema (8 samples taken from 6 patients) and of healthy volunteers (10 samples from different donors). LTs were separated as methylated and non-methylated compounds using different HPLC procedures, and were identified by chromatographic mobility, on-line UV-spectrum analysis and post HPLC immunoreactivity. In the lavage samples of the healthy volunteers and the patients with cardiogenic edema, no LTs were detected by these techniques (detection limit congruent to 0.1-0.2 ng/ml lavage fluid). By contrast, in 15 out of 17 samples from patients with ARDS LTB4 or its metabolites 20-OH-LTB4 and 20-COOH-LTB4 were detected. The endproduct of omega-oxidation, 20-COOH-LTB4, represented the quantitatively predominant compound, detected in the range of 0.3-2.6 ng/ml perfusate. We conclude that the chemotactic agent LTB4 may be involved in the amplification of inflammatory events encountered in ARDS, and that the oxidized metabolites of LTB4 are particularly suitable for monitoring lung leukotriene generation under conditions of neutrophil efflux and oxidative stress.

Adult↗

PubMed1991

Leukotrienes and ARDS.

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Bronchoalveolar Lavage Fluid↗

PubMed1991

[The comparative measurement of the bone marrow dose in quantitative computed tomography (QCT), dual-photon radiography (DPX) and conventional x-rays of the LS].

One of the issues in the discussion on the best method for measuring the bone mineral content is the relevance of the applied dose. We used highly sensitive thermoluminescent dosimeters (TLD) to directly compare bone marrow doses in a human phantom. DPX gave a bone marrow dose in the lumbar spine of 4 mu Gy, in QCT the dose corrected to the same amount of irradiated marrow was about 1 mGy. This value is in the same range as conventional a.p. plus lateral view x-rays of the lumbar spine. Corrected to the total body dose, the QCT dose is as low as 10% of the yearly background irradiation. It should therefore be radiobiologically irrelevant.

Absorptiometry, Photon↗

PubMed1991

Induction of vascular injury by Pseudomonas aeruginosa cytotoxin in rabbit lungs is associated with the generation of different leukotrienes and hydroxyeicosatetraenoic acids.

Pseudomonas aeruginosa cytotoxin, a transmembrane pore-forming protein, causes an increase in pulmonary microvascular permeability with subsequent lung edema formation, possibly related to the induction of arachidonic acid (AA) lipoxygenase products. To investigate this, isolated rabbit lungs were perfused with cytotoxin-containing buffer (6.5 and 13 micrograms of toxin/ml). A severalfold increase in the capillary filtration coefficient was induced, both preceded and accompanied by a marked time- (15-60 min) and dose-dependent release of cysteinyl leukotrienes (LT), LTB4, and 5-, 12-, and 15-hydroxyeicosatetraenoic acids (HETEs) into the lung perfusate. In the bronchoalveolar lavage fluid, corresponding AA-derived products were detected; the total sum of HETEs surpassed that of cysteinyl LTs in this compartment. The lipoxygenase inhibitors AA861 (10 microM) and nordihydroguaiaretic acid (100 microM) and EGTA (5 mM) suppressed the intravascular and alveolar liberation of all 5-lipoxygenase-derived AA metabolites, paralleled by a marked reduction and retardation of microvascular permeability increase (AA861). It thus seems that Pseudomonas cytotoxin induces generation of LTs and HETEs in rabbit lungs that may contribute to the development of pulmonary microvascular injury evoked by this bacterial agent.

Animals↗

PubMed1991

The dorsolateral, suboccipital, transcondylar approach to the lower clivus and anterior portion of the craniocervical junction.

The authors review their experience with a dorsolateral approach to the anterior rim of the foramen magnum and adjacent region. The operative technique includes exposure of the vertebral artery at C1, partial resection of the occipital condyle and lateral atlantal mass, and extradural drilling of the jugular tubercle. This approach has been applied in six patients who harbored intradural space-occupying lesions located ventral to the lower brain stem. Excision of the neoplasm was virtually total in all but one patient, in whom biopsy was the primary goal of the intervention. No morbidity and no mortality were associated with this approach. The main advantage of the dorsolateral, suboccipital, transcondylar route is the direct view it offers to the anterior rim of the foramen magnum without requiring brain stem retraction.

Adult↗

PubMed1991

Neutrophil passage through isolated perfused rabbit lungs.

Kinetics of polymorphonuclear leukocyte (PMN) lung passage were investigated in ex vivo isolated and ventilated left rabbit lungs, perfused with buffer solution at physiological flow rate. 111In-labeled PMNs of rabbit or human origin were injected into the pulmonary artery, and the first fraction of PMNs that rapidly passed the lung together with coinjected erythrocytes, was collected separately for external radioactivity counting. Washout of initially retained PMNs from the lung was monitored by use of a sodium-iodide detector. Recirculation of cells was avoided by insertion of a filter in the perfusion circuit. A fraction of 16.6 +/- 1.3% of rabbit PMNs rapidly passed the lung vasculature, followed by an exponential washout of initially retained PMNs [half-time (t50) of lung transit 8.1 +/- 0.6 min]. Slightly higher t50 (12.2 +/- 1.0 min) was obtained upon use of human PMNs. Reduction in flow by 50% caused a marked prolongation of PMN transit (t50 = 27.8 +/- 5.1 min), whereas increase in flow to 150% only insignificantly decreased t50. Rise in pulmonary venous pressure to 5 and 8 mmHg caused retardation of PMN lung transit (t50 = 15.3 +/- 0.6 and 31.6 +/- 3.6 min). Preincubation of PMNs with 2 ng/ml endotoxin for 1 h induced marked delay in PMN washout (t50 = 26.1 +/- 2.8 min). In conclusion, single-pass PMN kinetics in isolated lungs correspond to in vivo studies previously reported, thus allowing elucidation of PMN-endothelial interactions in an intact lung vasculature under standardized conditions.

Animals↗

PubMed1991

Amplification of LTB4 generation in AM-PMN cocultures: transcellular 5-lipoxygenase metabolism.

The generation of arachidonic acid (AA) metabolites by human polymorphonuclear leukocytes (PMN) and by rabbit alveolar macrophages (AM) was investigated and compared with that produced under conditions of coculture. Incubation of PMN with the calcium ionophore A23187 resulted in rapid generation of leukotriene (LT) B4 and its omega-oxidation products, paralleled by substantial secretion of 5-hydroxyeicosatetraenoic acid (HETE) and intact LTA4. Rapid LTA4 decay to nonenzymatic hydrolysis products in the extracellular space ensued. Exogenous AA, offered simultaneously with the ionophore, markedly increased 5-lipoxygenase product formation. Incubation of AM with A23187 evoked protracted generation of LTB4 in the absence of omega-oxidation, with concomitant liberation of 5-HETE, 15-HETE, free AA, and minor amounts of AA cyclooxygenase products. Exogenously offered LTA4 was avidly taken up and converted into LTB4 by these cells. Costimulation of AM and PMN with the ionophore resulted in an approximately 2.5-fold increase in the generation of LTB4 and its metabolites (compared with the summed amounts of the isolated cell experiments), whereas 5-HETE and nonenzymatic LTA4, hydrolysis product formation were markedly reduced. This change in metabolite profile was dependent on the AM-to-PMN ratio. Acetylsalicylic acid increased 5-lipoxygenase product formation in the coculture studies but not in the isolated cell experiments. AA prelabeling of either PMN or AM resulted in radioactivity detection in all AA lipoxygenase products except for 15-HETE.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Intravascular anti-IgE challenge in perfused lungs: mediator release and vascular pressor response.

Intravascular application of goat anti-rabbit immunoglobulin E (IgE) was used to stimulate parenchymal mast cells in situ in perfused rabbit lungs. Sustained pulmonary arterial pressure rise was evoked in the absence of lung vascular permeability increase and lung edema formation. Early prostaglandin (PG) D2 and histamine release into the perfusate was documented, accompanied by more sustained liberation of cysteinyl leukotrienes (LT), LTB4, and PGI2. The quantities of these inflammatory mediators displayed the following order: histamine greater than cysteinyl-LT greater than PGI2 greater than LTB4 greater than PGD2. Pressor response and inflammatory mediator release revealed corresponding bell-shaped dose dependencies. Cyclooxygenase inhibition (acetylsalicylic acid) suppressed prostanoid generation, increased LT release, and did not substantially affect pressor response and histamine liberation. BW755 C, a cyclo- and lipoxygenase inhibitor, blocked the release of cysteinyl-LT and markedly reduced the liberation of the other inflammatory mediators as well as the pressor response. The H1-antagonist clemastine caused a moderate reduction of the anti-IgE-provoked pressure rise. We conclude that intravascular anti-IgE challenge in intact lungs provokes the release of an inflammatory mediator profile compatible with in situ lung parenchymal mast cell activation. Pulmonary hypertension represents the predominant vascular response, presumably mediated by cysteinyl-LT and, to a minor extent, histamine liberation.

Animals↗

PubMed1991

Human leukoagglutinating antibody evokes cooperative leukotriene synthesis in pulmonary microvasculature. Model of transfusion-related acute lung injury.

Leukoagglutinating antibodies have been implicated in the development of transfusion-related acute lung injury. In the present study, human neutrophil leukotriene generation was provoked by an anti-5b immunoglobulin G, isolated from a multiparous donor plasma that caused noncardiogenic lung edema during transfusion therapy. In 5b-positive polymorphonuclear neutrophils (PMNs), the antibody stimulated marked arachidonic acid metabolism, dependent on the presence of plasma as the complement source. Quantity and profile of lipid mediators (leukotriene B4 and its omega-oxidation products, 5-hydroxyeicosatetraenoic acid, and nonenzymatic hydrolysis products of leukotriene A4) corresponded to those repeatedly described after PMN in vitro stimulation with the artificial calcium ionophore A23187. Anti-5b challenge of PMNs sequestered in the microvasculature of perfused rabbit lungs did, however, induce a markedly modified metabolite profile. Nonenzymatic hydrolysis products of leukotriene A4 were not detected, and 5-hydroxyeicosatetraenoic acid was markedly reduced. In contrast, cysteinyl leukotrienes were measured as predominant compounds, with rapid appearance of leukotriene C4 and more protracted generation of leukotriene E4. Leukotriene B4 and its omega-oxidation products were released with similar kinetics, but in lower amounts, as compared with the isolated PMN stimulation. Anti-5b challenge of PMNs coincubated with pulmonary artery endothelial cells in vitro, but not stimulation of either cell type alone, provoked marked generation of cysteinyl leukotrienes. These findings suggest modulation of PMN 5-lipoxygenase metabolism in favor of leukotriene A4 transfer to adjacent acceptor cells with subsequent enzymatic conversion to cysteinyl leukotrienes under conditions of lung vascular sequestration. Endothelial cells appear to serve as predominant cooperative cells under circumstances of blood-free lung perfusion. PMN-related transcellular eicosanoid synthesis may be involved in the pathogenesis of transfusion-evoked acute lung injury.

Acute Disease↗

PubMed1991

Lung vascular injury after administration of viable hemolysin-forming Escherichia coli in isolated rabbit lungs.

Escherichia coli hemolysin, a transmembrane pore-forming exotoxin, is considered an important virulence factor. In the present study, the possible significance of hemolysin production was investigated in a model of septic lung failure through infusion of viable bacteria in isolated rabbit lungs; 10(4) to 10(7) E. coli/ml perfusate caused a dose- and time-dependent appearance of hemolysin, accompanied by release of potassium, thromboxane A2, and PGI2 into the perfusate. Concomitantly, marked pulmonary hypertension developed. Inhibitor studies suggested that the pressor response was predominantly mediated by pulmonary thromboxane generation. Administration of hemolysin-forming E. coli additionally caused a protracted, dose-dependent increase in the lung capillary filtration coefficient, followed by severe edema formation. The permeability increase was independent of lung prostanoid generation. An E. coli strain that releases an inactive form of hemolysin completely failed to provoke the described biophysical and biochemical responses. Preapplication of 2 x 10(8) human granulocytes was without effect in the present experimental model. We conclude that the hemolysin produced by low numbers of E. coli organisms can provoke thromboxane-mediated pulmonary hypertension and severe vascular leakage. E. coli hemolysin and, possibly, other related cytolysins may thus contribute directly to the pathogenesis of acute respiratory failure under conditions of sepsis or pneumonia.

6-Ketoprostaglandin F1 alpha↗

PubMed1991

Adenosine diphosphate-ribosylation of G-actin by botulinum C2 toxin increases endothelial permeability in vitro.

The endothelial cytoskeleton is believed to play an important role in the regulation of endothelial permeability. We used botulinum C2 toxin to perturb cellular actin and determined its effect on the permeability of endothelial cell monolayers derived from porcine pulmonary arteries. The substrate for botulinum C2 toxin is nonmuscle monomeric actin which becomes ADP-ribosylated. This modified actin cannot participate in actin polymerization and, in addition, acts as a capping protein. Exposure of endothelial cell monolayers to botulinum C2 toxin resulted in a dose- (3-100 ng/ml) and time-dependent (30-120 min) increase in the hydraulic conductivity and decrease in the selectivity of the cell monolayers. The effects of C2 toxin were accompanied by a time- and dose-dependent increase in ADP-ribosylatin of G-actin. G-Actin content increased and F-actin content decreased time- and dose-dependently in C2 toxin-treated endothelial cells. Phalloidin which stabilizes filamentous actin prevented the effects of botulinum C2 toxin on endothelial permeability. Botulinum C2 toxin induced interendothelial gaps. The effects occurred in the absence of overt cell damage and were not reversible within 2 h. The data suggest that the endothelial microfilament system is important for the regulation of endothelial permeability.

Actins↗

PubMed1991

Escherichia coli hemolysin is a potent inductor of phosphoinositide hydrolysis and related metabolic responses in human neutrophils.

Escherichia coli hemolysin (Hly) is a proteinaceous pore-forming exotoxin that probably represents a significant virulence factor in E. coli infections. We investigated its influence on human polymorphonuclear neutrophils (PMN), previously identified as highly susceptible targets. Hly provoked rapid secretion of elastase and myeloperoxidase, generation of superoxide, and synthesis of platelet-activating factor (PAF) and lyso-PAF. Concomitantly, marked phosphatidylinositol (PtdIns) hydrolysis with sequential appearance of the inositol-phosphates, inositol-phosphates, inositol triphosphate, diphosphate, and monophosphate, respectively, and formation of diacylglycerol, occurred. The metabolic responses displayed distinct bell-shaped dose dependencies, with maximum events noted at low toxin concentrations of 0.1-0.5 hemolytic units per milliliter. PtdIns hydrolysis and metabolic responses elicited by Hly exceeded those evoked by optimal concentrations of formylmethionyl-leucyl phenylalanine, PAF, leukotriene B4, A23187, or staphylococcal alpha-toxin. The toxin-induced effects were sensitive toward modulators of PMN stimulus transmission pathways (pertussis toxin, the kinase C inhibitor H7, and phorbol myristate acetate "priming"). We conclude that the marked capacity of low doses of Hly to elicit degranulation, respiratory burst, and lipid mediator generation in human PMN probably envolves signal transduction via PtdIns hydrolysis.

Bacterial Proteins↗

PubMed1991

Inhibition of cytoskeletal rearrangement by botulinum C2 toxin amplifies ligand-evoked lipid mediator generation in human neutrophils.

Botulinum C2 toxin, a binary toxin that ADP-ribosylates nonmuscle G-actin, was used as a selective tool to evaluate the role of actin-dependent cytoskeletal rearrangement in ligand-evoked lipid mediator generation. Human neutrophils (PMN) were preincubated with varying concentrations of the toxin for 30 min. Lipoxygenase products of arachidonic acid were measured by chromatographic techniques in the presence of exogenous arachidonic acid to probe PMN 5-lipoxygenase activity. Formation of platelet-activating factor (PAF) was assayed by the bioincorporation of [3H]acetate. Stimulation was performed with the soluble chemotactic ligands formyl-methionyl-leucyl-phenylalanine (FMLP) and PAF, as well as opsonized zymosan. PMN pretreatment with C2 toxin in the range between 200/400 and 800/1600 ng/ml C2I/II caused a dose-dependent suppression of the basal F-actin content and of stimulus-induced actin assembly. Phosphoinositide hydrolysis (measured as liberated inositol phosphates) and PAF generation in response to FMLP and exogenous PAF were markedly increased at these toxin doses. Minor C2 toxin concentrations (range, approximately 25/50 to 200/400 ng/ml C2I/II) were sufficient to amplify stimulus-induced formation of leukotriene B4 and its omega-oxidation products, nonenzymatic hydrolysis products of leukotriene A4, and 5-hydroxyeicosatetraenoic acid (5-HETE). With increasing toxin doses, leukotriene generation declined and 5-HETE became the predominant metabolite. In contrast to the soluble ligands, the zymosan-effected generation of PAF and leukotrienes was dose-dependently inhibited by C2 toxin concentrations of greater than 200/400 ng/ml, paralleled by a loss of motile and phagocytotic functions in these cells. We conclude that selective inhibition of actin assembly amplifies PAF and 5-lipoxygenase product formation in response to soluble chemoattractants with distinct dose dependences. The augmentation of PAF generation may be linked to amplified second messenger levels at higher doses of C2 toxin, whereas the sensitivity of the 5-lipoxygenase metabolism to low concentrations may indicate toxin effect on a small, functionally specified, actin pool. The present data support an important role of cytoskeletal rearrangement in temporal and/or spatial limitation of chemoattractant-evoked PMN activation.

Arachidonate 5-Lipoxygenase↗

PubMed1990

Inflammatory lipid mediator generation elicited by viable hemolysin-forming Escherichia coli in lung vasculature.

Escherichia coli hemolysin, a transmembrane pore-forming exotoxin, is considered an important virulence factor for E. coli-related extraintestinal infections and sepsis. The possible significance of hemolysin liberation for induction of inflammatory lipid mediators was investigated in isolated rabbit lungs infused with viable bacteria (concentration range, 10(4)-10(7)/ml). Hemolysin-secreting E. coli (E. coli-Hly+), but not an E. coli strain that releases an inactive form of the exotoxin, induced marked lung leukotriene (LT) generation with predominance of cysteinyl LTs. Eicosanoid synthesis was not inhibited in the presence of plasma with toxin-neutralizing capacity. Pre-application of 2 x 10(8) human granulocytes, which sequestered in the lung microvasculature, caused a severalfold increase in leukotriene generation in response to E. coli-Hly+ challenge both in the absence and presence of plasma. Data are presented indicating neutrophil-endothelial cell cooperation in arachidonic acid lipoxygenase metabolism as an underlying mechanism. We conclude that liberation of hemolysin from viable E. coli induces marked lipid mediator generation in lung vasculature, which is potentiated in the presence of neutrophil sequestration and may contribute to microcirculatory disturbances during the course of severe infections.

Animals↗

PubMed1990

Reproduction of transfusion-related acute lung injury in an ex vivo lung model.

Leukoagglutinins are implicated in transfusion-related acute lung injury (TRALI). In the present study, severe lung vascular leakage was reproduced by application of a leukoagglutinating antibody of anti-5b specificity in an ex vivo lung model. The antibody originated from a multiparous donor-plasma, observed to cause noncardiogenic edema during transfusion therapy. Heated full plasma (anti-5b-titer 1/128) or purified immunoglobulin G fraction was used for the studies. Ex vivo isolated rabbit lungs were perfused with albumin buffer, and human granulocytes (PMN) were admixed to the recirculating perfusate. In presence of anti-5b antibody plus 5b-positive PMN plus rabbit plasma as complement-source, severe lung edema occurred after a latent period of 3 to 6 hours. Pulmonary artery pressure was only transiently and moderately increased, and the leakage reaction could be traced back to a several-fold increase in lung vascular permeability. In contrast, no vascular leakage was noted in lungs perfused in the absence of anti-5b antibody, PMN, or rabbit plasma. Moreover, no permeability increase occurred on use of 5b-negative PMN. This reproduction of TRALI in an ex vivo lung model corroborates the role of leukoagglutinating antibodies in initiating PMN-dependent respiratory distress and suggests a contribution of concomitant complement activation.

Agglutinins↗

PubMed1990

Influence of microvascular adherence on neutrophil leukotriene generation. Evidence for cooperative eicosanoid synthesis.

Profile and quantity of leukotriene (LT) and hydroxyeicosatetraenoic acid (HETE) generation upon selective stimulation of isolated polymorphonuclear neutrophils (PMN) compared with neutrophils in a model of pulmonary leukostasis were investigated. Freshly prepared human PMN (2 x 10(8) were injected into the pulmonary artery of isolated, ventilated, and bloodfree perfused rabbit lungs, resulting in nearly quantitative sticking in the microvasculature. The sequestered neutrophils and, in parallel, aliquots of isolated PMN were stimulated with mAb in the presence of C, known to activate PMN arachidonate metabolism via formation of membrane attack complexes. In the isolated cells, a typical LT profile including LTB4 and its omega-oxidation products, 5-HETE and nonenzymatic hydrolysis products of LTA4 was evoked. The latter indicate secretion of LTA4 in considerable amounts. In the model of pulmonary leukostasis, no nonenzymatic LTA4-derivatives were detected, coincident with a predominance of cysteinyl-LT. This finding gives indirect evidence for an efficient LTA4-transfer between PMN feeder cells and vascular acceptor cells with glutathione-S-transferase activity. Moreover, a threefold increase in the total amount of LTA4-derived products was noted in the model of leukostasis, paralleled by a marked decrease in 5-HETE liberation. This effect was further enhanced by inhibition of lung cyclooxygenase. These findings were corroborated in a homologous system, in which rabbit PMN, sticking in the rabbit lung microvasculature, were stimulated with calcium-ionophore A23187. Collectively, these data suggest a complex interaction between microvascular tissue and adhering neutrophils in LT synthesis, involving transcellular LTA4-shift, modulation of the PMN 5-lipoxygenase pathway, and amplification of LT generation. These findings may be relevant for inflammatory events with neutrophils involved.

Animals↗

PubMed1990

Effect of increased donor age on kidney transplant outcome.

Donors over the age of 50 years provided kidneys for 28 of our 226 recipients (12.4%) transplanted from January 1, 1987 to December 31, 1988. Immediate function following transplantation occurred in 36% of the kidneys from donors both over and under the age of 50. The overall 3-month graft survival rate for transplants from donors over 50 years was 89%, compared with 78% for transplants from donors under 50 years (p greater than 0.05). Thus kidneys from well-selected older donors make an important contribution to the total pool of organs available for transplantation.

Age Factors↗

PubMed1990

Surfactant abnormalities and adult respiratory failure.

Surfactant abnormalities have been implicated in the development of the acute respiratory distress syndrome in adults. Experimental studies show that surfactant inhibition by protein-leak into the alveolar space is of major importance under these circumstances. Fibrin(ogen)-surfactant-interaction appears to contribute to disturbances of surfactant function with subsequent alveolar instability and ventilation-perfusion-mismatch. In a prospective study in severely injured patients, the surfactant in serially obtained bronchoalveolar lavage fluids was investigated. An early leakage of plasma proteins into the alveolar space was noted in those patients, who developed severe ARDS. Moreover, deterioration of surfactant function was markedly more pronounced in those patients than in trauma victims who developed only mild pulmonary dysfunction. In addition to the protein-leakage, a progressive decrease of the surfactant-specific dipalmitoyl-phosphatidylcholine was noted, significantly correlated with the deterioration of surfactant function and the severity of respiratory failure. In conclusion, experimental and clinical studies show surfactant abnormalities in the adult respiratory distress syndrome. Plasma protein-leakage and progressive alteration of alveolar type II surfactant secretion appear to be of major importance.

Adult↗