Search PubMed⌕ Search

Biomedical subjects

J van der Meer

Publications and source records attributed to J van der Meer.

At least 73 records · Page 4Linked to original sources
PubMed1997

Fragmin in unstable angina pectoris or in non-Q-wave acute myocardial infarction (the FRIC study). Fragmin in Unstable Coronary Artery Disease.

The safety and efficacy of weight-adjusted, low-molecular-weight heparin (dalteparin) was compared with that of unfractionated heparin during 6 days of treatment in 1,482 patients with unstable angina or non-Q-wave myocardial infarction. Dalteparin, at a lower dose, was compared with placebo during the following 39 days. No significant outcome difference was found between the 2 treatment regimens in the unblinded phase (days 1-6). Between days 6-45 the rates of death, myocardial infarction, and recurrence of angina were comparable between the active treatment and placebo groups. The results suggest that twice-daily administration of subcutaneous dalteparin may be an effective and safe alternative to unfractionated heparin during the acute phase of unstable coronary artery disease. Prolonged treatment with dalteparin at a lower once-daily dose did not confer any additional benefit over aspirin (75-165 mg) alone.

Angina, Unstable↗
PubMed1997

Comparison of low-molecular-weight heparin with unfractionated heparin acutely and with placebo for 6 weeks in the management of unstable coronary artery disease. Fragmin in unstable coronary artery disease study (FRIC)

BACKGROUND: Low-molecular-weight heparin has a number of pharmacological and pharmacokinetic advantages over unfractionated heparin that make it potentially suitable, when used in combination with aspirin, for the treatment of unstable coronary artery disease. METHOD AND RESULTS: Patients with unstable angina or non-Q-wave myocardial infarction (1482) were included in the study, which had two phases. In an open, acute phase (days 1 to 6), patients were assigned either twice-daily weight-adjusted subcutaneous injections of dalteparin (120 i.u./kg) or dose-adjusted intravenous infusion of unfractionated heparin. In the double-blind, prolonged treatment phase (days 6 to 45), patients received subcutaneously either dalteparin (7500 i.u. once daily) or placebo. During the first 6 days, the rate of death, myocardial infarction, or recurrence of angina was 7.6% in the unfractionated heparin-treated patients and 9.3% in the dalteparin-treated patients (relative risk, 1.18; 95% confidence interval [CI], 0.84 to 1.66). The corresponding rates in the two treatment groups for the composite end point of death or myocardial infarction were 3.6% and 3.9%, respectively (relative risk, 1.07; 95% CI, 0.63 to 1.80). Revascularization procedures were undertaken in 5.3% and 4.8% of patients in unfractionated heparin and dalteparin groups, respectively (relative risk, 0.88; 95% CI, 0.57 to 1.35). Between days 6 and 45, the rate of death, myocardial infarction, or recurrence of angina was 12.3% in both the placebo and dalteparin groups (relative risk, 1.01; 95% CI, 0.74 to 1.38). The corresponding rates for death or myocardial infarction were 4.7% and 4.3% (relative risk, 0.92; 95% CI, 0.54 to 1.57). Revascularization procedures were undertaken in 14.2% and 14.3% of patients in the placebo and dalteparin groups, respectively. CONCLUSIONS: Our results add to previous evidence suggesting that the low-molecular-weight heparin dalteparin administered by twice-daily subcutaneous injection may be an alternative to unfractionated heparin in the acute treatment of unstable angina or non-Q-wave myocardial infarction. Prolonged treatment with dalteparin at a lower once-daily dose in our study did not confer any additional benefit over aspirin (75 to 165 mg) alone.

Adult↗
PubMed1997

[Thrombotic thrombocytopenic purpura in 13 Dutch centres: treatment and longterm follow-up].

OBJECTIVE: Analysis of the incidence, treatment modalities and disease course of thrombotic thrombocytopenic purpura (TTP) in the Netherlands. DESIGN: Retrospective follow-up study. SETTING: 13 centres in the Netherlands. METHODS: Regarding all patients admitted between 1-1-1979 and 1-1-1992 to one of 13 Dutch haematological centres, in whom the diagnosis of TTP was made for the first time, information was gathered from the medical records and from the patients own physicians on patient characteristics at presentation and the occurrence of relapse or death. The follow-up period tended on 1-4-1995. RESULTS: A total of 65 patients with newly diagnosed TTP were identified: 0.34 per 1,000,000 persons a year (95% confidence interval (95%-CI): 0.26-0.45), increasing to 0.83 in the last year of the study. Forty-six (95%) patients were treated with fresh frozen plasma: 18 (28%) by plasma infusion and 44 (68%) by plasma exchange; 48 (74%) (additionally) received corticosteroids. All 52 patients (80%) who survived the first four weeks after admission reached complete remission. Twelve patients with relapsing TTP underwent splenectomy in remission. The 5-year survival rate was 77% (95% CI: 66-87) and the 5-year relapse-free survival rate 38% (95% CI: 25-52). Cardiac symptoms, severe thrombocytopenia and a high serum LDH were risk factors for acute mortality, but no risk factors for relapse or late-occurring death could be identified. CONCLUSION: TTP is a rare disease which is increasingly being recognized. Plasma exchange and corticosteroids are the most frequently used therapies. The disease has a high mortality rate in the acute phase of the disease.

Adolescent↗
PubMed1997

Concentration-dependent changes of PCB patterns in fish-eating mammals: structural evidence for induction of cytochrome P450.

Data sets on CB concentrations in fish-eating mammals from five laboratories were combined to test and refine a pharmacokinetic model. Clear differences in PCB patterns were observed between species. The ability to metabolize chlorobiphenyl (CB) congeners with vicinal H-atoms only in the ortho- and meta-positions and with one ortho-chlorine substituent generally increased in the order otter < cetaceans (harbor porpoise, common dolphin) < phocid seals (harbor and grey seal), but the metabolism of congeners with vicinal H-atoms in the meta- and para-positions and with two ortho-chlorines increased in the order cetaceans < seals < otter. Both categories of congeners are probably metabolized by different families of cytochrome P450 (1A and 2B) of which levels apparently differed between the cetaceans, the pinnipeds, and the otter. Within-species CB patterns differed in a concentration-dependent manner. The induction of cytochrome P450 enzymes offers the most likely explanation for this phenomenon, but starvation could have a similar effect on occasion.

Animals↗
PubMed1997

Soluble interleukin 2 receptor and soluble CD8 levels in previously treated human immunodeficiency virus-negative hemophiliacs multiply transfused with a monoclonal antibody-purified factor VIII concentrate.

BACKGROUND: Serum levels of the soluble interleukin 2 receptor (sIL-2R) and soluble CD8 (sCD8) may be used as markers of T-cell activation. The course of serum levels of sIL-2R and sCD8 in hemophiliacs who were treated first with an intermediate-purity factor VIII concentrate and then with a monoclonal antibody (MoAb)-purified factor VIII concentrate are reported. STUDY DESIGN AND METHODS: Serum samples taken before the administration of the MoAb-purified concentrate and after 2 and 5 years of its administration to 20 human immunodeficiency virus-negative patients with hemophilia A were analyzed. Eighteen healthy age-matched men were used as controls. RESULTS: The sIL-2R and sCD8 levels were higher in patients treated with intermediate-purity concentrates than in controls (p = 0.006 and p = 0.0005, respectively). The sIL-2R levels showed a decrease after 5 years of treatment with the MoAb-purified concentrate (p = 0.018 for the difference between 2 and 5 years), to levels that were not significantly different from those in controls. Although sCD8 levels tended to decrease at 5 years (p = 0.09, for the difference between 2 and 5 years), they remained higher than those in controls (p = 0.0005 and p = 0.0016 at 2 and 5 years, respectively). The ratio of sCD8 and sIL-2R tended to increase between 2 and 5 years (p = 0.07). The sIL-2R and sCD8 levels were not related to the numbers of T-lymphocytes and HLA-DR-positive T-lymphocytes in peripheral blood. Nor was a relation demonstrated between sIL-2R levels and CD4-positive cell numbers or between sCD8 levels and CD8-positive cell numbers. Although a relation with chronic hepatitis C cannot be excluded, it seems more likely that changes in sIL-2R levels are due to the use of the MoAb-purified concentrate. CONCLUSION: Elevated levels of sIL-2R and sCD8 were found in multiply transfused human immunodeficiency virus-negative hemophiliacs. After treatment was changed to the use of a MoAb-purified concentrate. sIL-2R levels decreased. These findings suggest a change in immune stimulation that is remarkable, because signs of activation in the effector phase seem to have continued despite normalization in the proliferative phase.

Adult↗
PubMed1997

A simple procedure for in situ immunolabeling, embedding and sectioning of layers of cultured endothelial and smooth muscle cells for both light and electron microscopy.

We present a simple procedure for in situ immunolabeling, embedding and sectioning of layers of cultured endothelial and smooth muscle cells for both light and electron microscopy. Endothelial and smooth muscle cells were seeded in tissue culture chambers/slides precoated with 30% (w/v) gelatin drops fixed with 0.5% glutaraldehyde. Live endothelial cell layers were labeled with an antibody against the surface membrane protein, anti-CD13. After labeling, the cell layers were fixed and separated from the chambers/slides by lifting all of the samples with a spatula. Sections (1-2 mm) were cut, embedded and processed further for light or electron microscopy. Because of the delicate cell layers and the importance of preserving maximum integrity, labeling was performed under standard culture conditions and treated in situ during the entire procedure. Moreover, the small chamber size of the tissue culture dishes generated the additional advantages of requiring only a limited number of cells, small volumes of media, and little antibody.

Endothelium, Vascular↗
PubMed1997

Blood interaction with a Bioline heparin coated HIA-VAD: a study on calves.

The blood compatibility of ventricular assist devices developed by the Helmholtz Institute Aachen (HA-VAD's) was tested on calves. Seven calves received a non-coated HIA-VAD (control) and three a Bioline heparin coated device. The circulatory support of these HIA-VAD's lasted one week. Mechanical blood cell trauma estimated by hematocrit (Hct), hemoglobin (total Hb) and free plasma hemoglobin (free Hb) levels did not differ in either group. All HIA-VAD's in the control group remained thrombus free, except on one occasion when an inflow cannula was obstructed by a thrombus located in the tip. After circulatory support, the animals in this group seemed clinically healthy. However, thrombus formation was observed in the three heparin coated HIA-VAD's. One animal in this group died from complications after re-operation for pneumothorax on the fifth day of support, whereas the other two animals seemed clinically healthy. In these three animals, a strong decrease in platelet numbers was measured even after 24 hours of support which recovered after 72 hours. This decrease in platelet numbers was associated with a lower degree of platelet aggregation ability stimulated by ADP (p < 0.05). Fibrin(ogen) degradation products (FDP) increased significantly immediately after the implantation procedure (p < 0.05). Fibrinogen levels initially decreased during the implantation procedure, but increased thereafter in both groups. The FDP levels remained high in this group, although the FDP levels in both groups were decreased after the implantation procedure. The ex vivo measured circulating heparin levels were lower in the heparin coated HIV-VAD group despite the equally administrated heparin doses in both animal groups. No differences were measured in either group with regard to white blood cell (WBC) numbers and complement hemolytic activity (CH50). Despite these hemostatic changes, no mechanical trauma could be demonstrated after seven days of circulatory support.

Animals↗
PubMed1996

Effects of hyperthermic isolated limb perfusion with recombinant tumor necrosis factor alpha and melphalan on the human fibrinolytic system.

This study was undertaken to determine the effects on systemic fibrinolysis of hyperthermic isolated limb perfusion with recombinant tumor necrosis factor alpha (r-TNF-alpha) and melphalan, with or without pretreatment with recombinant IFN-gamma (r-IFN-gamma). Twenty patients were treated with r-TNF-alpha and melphalan; four patients, treated with melphalan only, served as controls. Of the twenty patients treated with both r-TNF-alpha and melphalan, eight received r-IFN-gamma for two days before the perfusion and as a bolus into the perfusion circuit. A significant leak of r-TNF-alpha from the perfusion circuit to the systemic circulation was observed in all r-TNF-alpha-treated patients (mean maximum TNF-alpha, 87,227 ng/liter versus 31 ng/liter in controls; P < 0.002). In these patients, but not in controls, there was an almost instantaneous rise in systemic tissue plasminogen activator activity (from 0.26 to 5.28 IU/ml in 90 min), causing activation of fibrinolysis. After a delay of 90 min, plasminogen activator inhibitor-1 (PAI-1) antigen rose to high levels in the r-TNF-alpha-treated group (mean maximum PAI-1, 1652 ng/ml versus 211 ng/ml in controls; P < 0.02), associated with a sharp decrease of tissue plasminogen activator activity and a slower decrease of plasminogen-antiplasminogen complexes (from 5.28 to 0.02 IU/ml in 2 h and from 1573 to 347 micrograms/liter in 22 h, respectively). No additional effect of IFN-gamma pretreatment on fibrinolysis could be demonstrated. These results suggest that in isolated limb perfusion with r-TNF-alpha and melphalan an initial activation of systemic fibrinolysis, induced by leakage of r-TNF-alpha from the perfusion circuit, is set off by a subsequent inhibition of the fibrinolytic system by PAI-1. This large increase in PAI-1 could place the patient at risk for deposition of microthrombi in the systemic circulation.

Antineoplastic Agents↗
PubMed1996

Association of smooth muscle cell tissue factor with caveolae.

There is still no satisfactory explanation for the low catalytic activity of tissue factor (TF)/factor VII(a) complexes towards coagulation factor X, as found on the apical surface side of cell layers. It has been hypothesized that TF exists in a latent form. Layers of cultured human smooth muscle cells, constitutively expressing TF, were immunogold-labeled for TF in situ and processed for electron microscopy. We showed that, besides internalization and accumulation in lysosomal-like structures, TF remained associated with noncoated, flask-shaped microinvaginations of the plasma membrane. These invaginations were identified as caveolae. In regions in which intercellular contacts were interrupted, more TF-positive caveolae were observed. Enzymatically detached smooth muscle cells exhibited a similar enlargement of caveolar structures. Concomitantly, an increase of catalytic activity of apically formed TF/VIIa complexes towards factor X was found on the suspended cells. We speculate that caveolae-associated TF may function as a latent pool of procoagulant activity, which can rapidly be activated at sites in which vessel wall integrity is lost.

Blood Coagulation↗