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V J Bom

Publications and source records attributed to V J Bom.

33 records · Page 2Linked to original sources
PubMed1993

The release of endotoxin from antibiotic-treated Escherichia coli and the production of tumour necrosis factor by human monocytes.

The influence of antibiotic-induced release of endotoxin from in-vitro grown Escherichia coli on the production of tumour necrosis factor-alpha (TNF) by human monocytes was studied. Antibiotics tested were: cefuroxime (7.5 and 75 mg/L); ceftazidime (10 and 100 mg/L); aztreonam (10 and 100 mg/L); imipenem (10 and 100 mg/L); and tobramycin (8 mg/L). The effect of the combination of cefuroxime plus tobramycin, and the effect of taurolidine, an endotoxin-binding agent, on TNF production was also tested. After incubation for 4 h, all antibiotic-treated cultures (high-dose) induced a similar rise in extracellular TNF production when compared to the controls. However, after incubation for 24 h, a significant rise in TNF production was noticed in the cefuroxime and aztreonam-treated cultures (6440 and 5969 ng/L, respectively) compared to the ceftazidime and imipenem-treated cultures (846 and 381 ng/L, respectively). The cefuroxime-induced release of TNF could be reduced by addition of tobramycin (from 6440 to 1615 ng/L). Similar differences in TNF production were noticed in cell-associated TNF. Dose-response curves did not demonstrate differences in TNF production in aztreonam or imipenem-treated cultures. However, for both cefuroxime and ceftazidime-treated cultures, low-dose treatment resulted in significantly higher production of TNF. The differences in TNF production between these antibiotics could be explained by the production of filaments following treatment with cefuroxime, aztreonam and low-dose ceftazidime, resulting in late bacterial lysis with high levels of endotoxin, whereas treatment with imipenem or high-dose ceftazidime resulted in the formation of spheroplasts, resulting in early lysis of the bacteria and much lower levels of endotoxin. The addition of taurolidine to either imipenem or aztreonam-treated cultures prevented a rise in TNF production as a result of nearly complete neutralization of the released endotoxin. It was concluded that the observed differences in TNF production by human monocytes in vitro were related to differences in the mechanisms and amount of antibiotic-induced release of endotoxin.

Anti-Bacterial Agents↗
PubMed1993

The clinical expression of hereditary protein C and protein S deficiency: a relation to clinical thrombotic risk factors and to levels of protein C and protein S?

We investigated 103 first-degree relatives of 13 unrelated protein C or protein S deficient patients to assess the role of additional thrombotic risk factors and of protein C and protein S levels in the clinical expression of hereditary protein C and protein S deficiency. Fifty-seven relatives were protein C (37) or protein S deficient (20). Thromboembolic events occurred in 30% of protein C deficient and in 35% of protein S deficient persons, compared with 3% and 0% in their normal controls respectively (P < 0.05). In protein C deficient persons, the median thromboembolic event-free survival was 55 years, while in protein S deficiency this interval was 33 years (P = 0.047). In the protein C deficient group 64% of the initial events occurred spontaneously, as did 71% in the protein S deficient group. Recurrent thromboembolic events were more often associated with concomitant risk factors than the initial events: 64% and 50% in persons with protein C or protein S deficiency respectively. These findings suggest a substantial role for these risk factors in triggering thromboembolic events in deficient persons. Protein C antigen and protein S antigen levels were similar in symptomatic and asymptomatic deficient persons. Total, but not free, protein S antigen levels were significantly higher in symptomatic protein C deficient persons, as were protein C antigen and activity levels in symptomatic protein S deficient ones. The clinical implication of this finding is not yet clear.

Adolescent↗
PubMed1992

Patterns of cytokines, plasma endotoxin, plasminogen activator inhibitor, and acute-phase proteins during the treatment of severe sepsis in humans.

OBJECTIVE: To study the patterns of plasma concentrations of endotoxin, tumor necrosis factor-alpha (TNF), interleukin-6 (IL-6), plasminogen activator inhibitor-1, C-reactive protein, and serum amyloid A during the treatment of human sepsis. DESIGN: A prospective case series study. SETTING: ICU of the Department of Internal Medicine, University Hospital Groningen, The Netherlands. PATIENTS: Twenty consecutive patients (11 female, 9 male, mean age 67 yrs) with clinically defined sepsis. Eighteen patients were admitted from the outpatient emergency ward; two patients were already inpatients. The control group (n = 7) comprised patients with nonseptic shock. MEASUREMENTS AND MAIN RESULTS: Ten (50%) septic patients had detectable endotoxemia (greater than 5 (ng/L). TNF concentrations on admission were increased in 94% of the septic patients, whereas IL-6 and plasminogen activator inhibitor plasma concentrations were increased in all septic patients. The septic group showed significantly (p less than .05) higher concentrations of TNF, IL-6, plasminogen activator inhibitor-1, C-reactive protein, and serum amyloid A compared with the nonseptic patients. In the septic group, we found a correlation of both IL-6 and plasminogen activator inhibitor concentrations with severity of illness (r2 = .33, p less than .05; r2 = .22, p less than .05, respectively). After the start of antibiotic treatment, high concentrations of TNF and plasminogen activator inhibitor persisted in the nonsurvivors in contrast to decreasing concentrations in most of the survivors. After an initial increase in seven patients, IL-6 concentrations decreased in all septic patients and also in nonsurvivors. CONCLUSIONS: This study confirms previous findings that: a) TNF is a major mediator involved in the pathogenesis of septic shock; b) plasminogen activator inhibitor activity is significantly increased in septic patients and might be involved in the pathogenesis of disseminated intravascular coagulation associated with sepsis; and c) IL-6 is involved in the pathophysiology of septic shock, although further studies are needed to determine whether IL-6 is directly involved in mediating the lethal complications of septic shock or whether it should be considered an "alarm hormone" that reflects endothelial cell injury. Our findings also suggest that the concentrations and trends of these mediators during treatment are valuable for monitoring septic patients.

Acute-Phase Proteins↗
PubMed1992

Complement activation and the production of inflammatory mediators during the treatment of severe sepsis in humans.

Sepsis or septic shock is frequently associated with activation of the complement system, coagulation and fibrinolytic changes and the release of several cytokines. In this study we analyzed the relation of complement activation to the inflammatory mediators, hemodynamic and biochemical parameters and severity of illness and outcome in 20 consecutive patients with clinically defined sepsis. Levels of C3a and C3d were elevated in 90% of the patients (median levels 0.19 mg/l and 8.6 mg/l respectively) in comparison to 14% and 42%, respectively of 7 patients with non-septic shock. Levels of C4 were decreased in only 1 of the 20 septic patients. Levels of TNF and IL-6 were elevated in 94% and 100% of the patients, Levels of TNF and IL-6 were elevated in 94% and 100% of the patients, respectively (median levels 122 ng/l and 1300 U/ml) and were clearly interrelated (r = 0.67, p less than 0.01). C3a levels correlated with the APACHE II score (r = 0.57, p less than 0.05) and high C3a levels were associated with fatal outcome (p less than 0.05). C3a was also correlated inversely with mean arterial pressure (r = 0.50, p less than 0.01). Levels of complement C3a and C3d significantly correlated with levels of plasminogen activator inhibitor-1 (PAI) and correlated inversely with AT-III levels. We found no correlation between these complement products and leukocyte counts or lactate levels, nor was there a correlation between C3a or C3d and the cytokines TNF and IL-6. Levels of C3a and C3d did not decrease significantly during the first 24 h of treatment, in contrast to a clear decrease in IL-6 levels in all patients and a decrease in TNF in the surviving patients. TNF levels remained stable or increased in the non-survivors. We conclude that both the complement system and the cytokine system are involved in the pathogenesis of septic shock and may be involved in the development of some of the fatal complications like hypotension and disseminated intravascular coagulation.

Aged↗
PubMed1991

Extrinsic activation of human coagulation factors IX and X on the endothelial surface.

In previous kinetic studies, the catalytic efficiency of the activation of human coagulation factors IX and X by factor VIIa in the presence of purified tissue factor apoprotein was found to be essentially equal. These activation reactions were now studied on the surface of human umbilical vein endothelial cells. The cells were stimulated with endotoxin to express tissue factor. This tissue factor activity was saturable with factor VIIa and could be inhibited by rabbit antibodies against human tissue factor apoprotein. Only stimulated cells supported factor VIIa activity. No difference in the reactivity of factor VII and VIIa was observed in the presence of factor X, due to rapid feedback activation of factor VII by factor Xa. However, the activation of factor IX by factor VII shows a 10 min lag-phase, which reflects that the activation of factor VII by factor IXa is a less efficient process. The kinetic parameters for the factor VIIa dependent activation of factor IX and factor X on the endothelial surface were: Km 0.09 microM, Vmax 0.13 pmol/min, and Km 0.071 microM, Vmax 0.41 pmol/min, respectively. The same ratio between the Vmax for factor X and factor IX activation was observed as in a cell free system. However, the Km of factor IX was 4-fold higher on the endothelial surface than in the cell free system. Together, these kinetic parameters will favour factor X activation 5-fold over factor IX activation at physiological concentrations of these proteins. The activation of factor X by factor VIIa on the endothelial surface was characterized by a short lag-phase, which was absent in factor IX activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Apoproteins↗
PubMed1991

Effects of different types and combinations of antimicrobial agents on endotoxin release from gram-negative bacteria: an in-vitro and in-vivo study.

Total and free endotoxin release in time from cultures of Escherichia coli by different antibiotics was studied in vitro for 4 h in relation to the antibiotic effect on viable counts and morphological features of the test cultures. The most rapid fall in viable counts was seen after treatment with imipenem or the combination of imipenem with tobramycin, accompanied by an early, but minimal increase (1.8-fold) of the total (free plus cell-bound) endotoxin level at 1 h. Total endotoxin levels increased approximately 5-fold upon incubation with ceftazidime, tobramycin or the combination of tobramycin with cefuroxime, whereas incubation with cefuroxime or aztreonam alone caused a late 22-and 49-fold increase in total endotoxin, respectively, at 4 h. In chloramphenicol treated cultures there was still an increase in viable counts during therapy, resulting in an ultimately 78-fold increase of mean levels of total endotoxin. Free endotoxin levels increased approximately 6-fold within 1 h upon treatment with imipenem, alone or in combination with tobramycin, or ceftazidime as the result of rapid lysis of bacteria. Treatment with cefuroxime or aztreonam induced a relatively late but much higher release of free endotoxin (118-and 222-fold, respectively), which was due to the formation of long filamentous structures during the first 2 h of incubation and eventually cell lysis. Both tobramycin and the combination of tobramycin with cefuroxime caused a more gradual rise in free endotoxin, with a +/- 15-fold increase in free endotoxin at 4 h. In chloramphenicol treated cultures, as in the control cultures, the level of free endotoxin remained proportional to the amount of viable organisms. We also studied plasma endotoxin levels in 20 patients with septic shock. 10 out of these 20 patients had a detectable endotoxemia (greater than 5 ng/l) on admission. We describe the patterns of plasma endotoxin in these patients during the first 24 h of antibiotic treatment. We conclude that, in the in-vitro study, values of total endotoxin, free endotoxin, and the rate of release of endotoxin varies with the antibiotic used. We also demonstrate that in patients under treatment for septic shock endotoxin release can be related to the administration of antibiotics.

Aged↗
PubMed1990

Coagulation factor abnormalities as possible thrombotic risk factors after Fontan operations.

Severe thromboembolism occurred in 3 of 37 patients who had undergone Fontan-type operations for correction of congenital heart defects several months to years after the operation. The patients were screened for coagulation factor abnormalities to find out whether known prothrombotic risk factors could explain the high frequency of thromboembolism. 63 abnormalities were found in 24 of the 37 patients. The commonest and most pronounced abnormality was deficiency of protein C, a known risk factor. Concentrations of antithrombin III and factors II and X were significantly lower in protein-C-deficient patients than in those with normal protein C concentrations. These findings suggest that the high thrombotic risk in these patients is caused or at least associated with an imbalance between procoagulant and anticoagulant factors.

Adolescent↗
PubMed1990

Extrinsic activation of human blood coagulation factors IX and X.

We studied activation of human coagulation factors IX and X by factor VIIa in the presence of calcium ions, phospholipid (phosphatidylserine/phosphatidylcholine, 50/50, mol/mol) and purified tissue factor apoprotein. Activation of factor IX and factor X was found to occur without a measurable lag-phase and hence initial rates of factor IXa and factor Xa formation could be determined. Like previously observed for the activation of factor X, the activation of factor IX was saturable with respect to factor VIIa, tissue factor apoprotein and phospholipid. The results suggested that in the presence of a Ca2+ ions the same ternary complex of factor VIIa-tissue factor apoprotein-phospholipid is responsible for the activation of factor IX and factor X. Both the apparent Km of 22 nM-factor IX and the apparent Kcat of 28 min-1 were about 3-fold lower than the corresponding parameters of factor X activation by this complex. Hence, the catalytic efficiency (Kcat/Km) of factor IX and factor X activation was about equal. However, the two substrates inhibited the activation of each other by competition for the same catalytic sites. The apparent Kinh of factor IX for inhibition of extrinsic factor X activation is 30 nM. The apparent Kinh of factor X for inhibition of extrinsic factor IX activation is 116 nM. From these kinetic data it was calculated that at plasma concentration of factors IX and X, the rate of extrinsic factor IX activation would be half the rate of factor X activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Apoproteins↗
PubMed1990

The contributions of Ca2+, phospholipids and tissue-factor apoprotein to the activation of human blood-coagulation factor X by activated factor VII.

In the extrinsic pathway of blood coagulation, Factor X is activated by a complex of tissue factor, factor VII(a) and Ca2+ ions. Using purified human coagulation factors and a sensitive spectrophotometric assay for Factor Xa, we could demonstrate activation of Factor X by Factor VIIa in the absence of tissue-factor apoprotein, phospholipids and Ca2+. This finding allowed a kinetic analysis of the contribution of each of the cofactors. Ca2+ stimulated the reaction rate 10-fold at an optimum of 6 mM (Vmax. of 1.1 x 10(-3) min-1) mainly by decreasing the Km of Factor X (to 11.4 microM). In the presence of Ca2+, 25 microM-phospholipid caused a 150-fold decrease of the apparent Km and a 2-fold increase of the apparent Vmax. of the reaction; however, both kinetic parameters increased with increasing phospholipid concentration. Tissue-factor apoprotein contributed to the reaction rate mainly by an increase of the Vmax., in both the presence (40,500-fold) and absence (4900-fold) of phospholipid. The formation of a ternary complex of Factor VIIa with tissue-factor apoprotein and phospholipid was responsible for a 15 million-fold increase in the catalytic efficiency of Factor X activation. The presence of Ca2+ was absolutely required for the stimulatory effects of phospholipid and apoprotein. The data fit a general model in which the Ca2(+)-dependent conformation allows Factor VIIa to bind tissue-factor apoprotein and/or a negatively charged phospholipid surface resulting into a decreased intrinsic Km and an increased Vmax. for the activation of fluid-phase Factor X.

Apoproteins↗
PubMed1986

Immunoradiometric assays for human coagulation factor VII using polyclonal antibodies against the Ca(II)-dependent and Ca(II)-independent conformation.

Human coagulation factor VII is a trace plasma protein belonging to the vitamin K-dependent factors. Two specific and sensitive immunoradiometric assays for factor VII were developed using immunopurified rabbit antibodies against the Ca(II)-independent and Ca(II)-dependent conformation of factor VII. Both assays were insensitive to the activation state of factor VII. The distribution of factor VII antigen was studied in 40 healthy individuals and the antigen level in normal plasma was calculated to be 0.52-0.62 micrograms/ml. The two assays were used in a comparative study of factor VII procoagulant activity and factor VII antigen in patients treated with oral anticoagulants.

Animals↗
PubMed1986

Application of factor VII-Sepharose affinity chromatography in the purification of human tissue factor apoprotein.

Coagulation factor VII covalently coupled to Sepharose proved to be an effective binding ligand for human tissue factor apoprotein, the specific cofactor of factor VII for the activation of factor X and IX. This interaction is completely calcium-dependent and the calcium ions cannot be replaced by magnesium or barium ions. The binding of the apoprotein to immobilized factor VII seems to be independent of the presence of phospholipid. When factor VII-Sepharose column chromatography is combined with a mild extraction procedure, tissue factor apoprotein could be purified approximately 40,000-fold from an acetone powder of human brain. SDS-PAA gel electrophoresis revealed that with this simple purification scheme human tissue factor apoprotein can be purified to apparent homogeneity and that the apoprotein migrates at a molecular weight of 47,000. The isolated human protein is heterogeneously glycosylated; the two different forms of the apoprotein function as cofactor of factor VII in the activation of both factor X and factor IX.

Brain↗
PubMed1985

Determination of plasma protein S--the protein cofactor of activated protein C.

Protein S, an important cofactor of activated protein C, and C4b-binding protein were purified from human plasma. Specific antibodies against the purified proteins were raised in rabbits and used for the development of immunologic assays for these proteins in plasma: an immunoradiometric assay for protein S (which measures both free protein S and protein S complexed with C4b-binding protein) and an electroimmunoassay for C4b-binding protein. Ranges for the concentrations of these proteins were established in healthy volunteers and patients using oral anticoagulant therapy. A slight decrease in protein S antigen was observed in patients with liver disease (0.78 +/- 0.25 U/ml); no significant decrease in protein S was observed in patients with DIC (0.95 +/- 0.25 U/ml). Criteria were developed for the laboratory diagnosis of an isolated protein S deficiency.

Anticoagulants↗
PubMedDate not supplied

Pharmacokinetics of human recombinant tissue-type plasminogen activator, administered intra-abdominally, in a rat peritonitis model.

Human recombinant tissue-type plasminogen activator (rtPA), administered intraperitoneally, may promote intra-abdominal fibrinolysis in peritonitis, thereby preventing adhesion and abscess formation. The pharmacokinetics of a single intraperitoneal dose of 0.5 or 2.0 mg/ml human rtPA were assessed in rats with fecal peritonitis and related to their endogenous tPA and plasminogen activator inhibitor (PAI) activity. Endogenous PAI activity was strongly elevated both in peritoneal fluid and in plasma, whereas tPA activity was only slightly increased in the peritoneal fluid. Both doses of rtPA significantly enhanced fibrinolytic activity of the peritoneal fluid up to 24 h in a dose-dependent manner. However, tPA activity was lower than calculated from the tPA antigen levels and the specific activity of rtPA in the fluid of rats with peritonitis. Plasma tPA activity was low at both doses. A single dose of 0.5 or 2.0 mg/ml rtPA can raise fibrinolytic activity in the abdominal cavity up to 24 h. High endogenous peritoneal PAI levels may adversely effect intra-abdominal use of human rtPA in peritonitis.

Animals↗