PubMed Health⌕ Search

Biomedical subjects

J Heitz

Publications and source records attributed to J Heitz.

At least 19 recordsLinked to original sources
PubMed2004

In situ analysis of metal melts in metallurgic vacuum devices by laser-induced breakdown spectroscopy.

We report on rapid in situ analysis of liquid metal melts under reduced ambient pressure by laser-induced breakdown spectroscopy (LIBS) using a transportable system. LIBS denotes a method in which characteristic optical emission line intensities of excited species in laser-generated plasma plumes are used for a quantitative chemical analysis of target materials. It is a fast, noncontact method that can be carried out under various atmospheric conditions, allowing large working distances between the sample under investigation and the detection system. For these reasons, LIBS is applicable in particular for process control in metallurgy under reduced ambient pressure. This was demonstrated for two types of vacuum devices under production conditions at a steel mill. The results of these experiments, including calibration curves for Cr, Ni, and Mg in liquid steel, are presented. The influence of variations in the ambient pressure on the results of the LIBS analysis is discussed within the frame of a generalized shock-wave model for the expansion of the laser-induced plasma plume.

Journal Article↗
PubMed2003

Cell adhesion on polytetrafluoroethylene modified by UV-irradiation in an ammonia atmosphere.

We report on the modification of polytetrafluoroethylene (PTFE) by exposure to the ultraviolet (UV) light of a Xe(2)*-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. Typical treatment times were up to 30 min. Subsequently, the samples were grafted with the amino acid alanine from an aqueous solution. The samples were characterized by means of optical transmission spectroscopy, laser-induced fluorescence and contact-angle measurements. We studied the adhesion of rat aortic smooth muscle cells (SMC) and mouse fibroblasts (3T3 cells) to the modified polymer samples using an in vitro technique, where the population density and spread of adhering cells is determined 24 h after seeding by image analysis. For both cell types the exposure of PTFE to UV-light in an ammonia atmosphere resulted in a significant increase in the number of adhering cells and in the size of their spreading area. The grafting with alanine enhanced this effect. Additional experiments with human endothelial cells (HEC) also demonstrated improved adhesion to modified PTFE. Thus, PTFE modified by our method appears to be a promising material for fabrication of artificial vascular prostheses and implants or for cultivation of skin substitutes.

3T3 Cells↗
PubMed2003

Adhesion and proliferation of human endothelial cells on photochemically modified polytetrafluoroethylene.

We studied the adhesion and proliferation of human endothelial cells on photochemically modified polytetrafluoroethylene samples. The polymer surfaces were modified by exposure to the ultraviolet light of a Xe(2)(*)-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. Treatment times were between 10 and 20 min. The endothelial cell density was determined 1, 3 and 8 days after seeding by image analysis. Surface modification of the samples resulted in a significant increase in the number of adhering cells and in the formation of a confluent cell layer after 3-8 days. The results were comparable than those obtained on polystyrene Petri dishes, which are used as standard substrates in cell cultivation. Thus modified PTFE appears to be a promising material for the fabrication of artificial vascular prostheses coated with endothelial cells.

Biocompatible Materials↗
PubMed1992

Blood rheology in acute myocardial infarction: effects of high-dose i.v. streptokinase compared to placebo.

To compare the haemorheological effects of an i.v. infusion of 1.5 MU of streptokinase with placebo, we investigated the time course of plasma fibrinogen concentration and the haemorheologic parameters plasma viscosity, erythrocyte aggregation and whole blood viscosity at different shear rates during the early phase of acute myocardial infarction until week 3 in 38 unselected patients from the ISAM and ISIS-2 study. Within 3 h, streptokinase led to a near afibrinogenaemia lasting for more than 24 h. Concomitantly, with streptokinase we found a reduction of plasma viscosity, erythrocyte aggregation and whole blood viscosity, whereas with placebo, values showed a slight increase, resulting in significant differences between the groups within the first 2 days. Thereafter, both groups showed an increase in all parameters, values reaching a maximum after 1 week. The streptokinase-induced reduction in blood viscosity may lead to an improvement in microcirculation in the infarction area during the early phase, whereas the hyperviscosity observed independently of therapy after 1 week may lead to an impairment of microcirculation.

Adult↗
PubMed1990

Outcome prediction models on admission in a medical intensive care unit: do they predict individual outcome?

Prospectively acquired data from 941 patients staying greater than 24 h in a medical ICU were analyzed to determine the relevance of scoring on ICU admission by the following methods of outcome prediction: Acute Physiology and Chronic Health Evaluation (APACHE II), Simplified Acute Physiology Score (SAPS), and Mortality Prediction Model (MPM). Analysis was performed separately for all patients (group A) and for a subsample (group B), obtained by excluding coronary care patients. Calculation of risk and classification of patients were carried out as recommended in the literature for MPM, APACHE II, and SAPS. In group A, sensitivities (correct prediction of hospital mortality) were 44.7%, 51.1%, and 21.2% and specificities (correct prediction of survival) were 84.5%, 85.4%, and 96.8%, respectively; overall correct classification rates were 73.3%, 75.8%, and 75.6%. In group B, sensitivities were slightly higher, but total correct classification rates did not reach group A levels. Goodness-of-fit testing showed low levels of fit for all methods in both groups. Application of APACHE II to diagnostic subgroups, using disease-adapted risk calculations, revealed marked inconsistencies between the estimated risk and the observed mortality. We conclude that the estimation of risk on admission by the three methods investigated might be helpful for global comparisons of ICU populations, although the lack of disease specificity reduces their applicability for severity grading of a given illness. The inaccuracy of these methods makes them ineffective for predicting individual outcome; thus, they provide little advantage in clinical decision-making.

Female↗
PubMed1990

[The protease inhibitor gabexate mesilate in experimentally-induced acute pancreatitis with early gram-negative infection in the Göttingen minipig: therapeutic efficacy and effects on blood coagulation and fibrinolysis].

Due to its biochemical properties, the newly developed low-molecular protease inhibitor gabexate mesilate is assumed to be efficient in the treatment of complicated acute pancreatitis. This thypothesis was tested using the model of the experimental taurocholate pancreatitis with early artificial E. coli infection in Göttingen mini pigs. Either gabexate mesilate or a placebo was given intravenously 150 min after induction of pancreatitis in a dosage of 2 mg/kg b.w. and h. Median survival time was 15 h in the gabexate mesilate treated animals (n = 7) as compared to 34 h in the placebo group (n = 7); this difference was not significant. The application of gabexate mesilate had no influence on the increased coagulation activity (decrease of prothrombin time, antithrombin III and platelet count) nor on the additional hyperfibrinolysis with concomitant decrease of plasminogen and antiplasmin. Prothrombin time and antithrombin III were less distinctly decreased in the placebo group; decrease of platelet count was more pronounced. On the basis of this study the hypothesis is not confirmed that treatment with gabexate mesilate for necrotizing experimental pancreatitis with additional gram-negative infection has a therapeutic efficiency.

Acute Disease↗
PubMed1989

[Acute myocardial infarct: aspects of changed mortality at the intensive care unit. Results of a prospective study from 1985 to 1987].

Between 1975 and 1987 the mortality rate among 3143 patients with acute myocardial infarction admitted to an intensive care unit fell from 25% to below 10%. Among 829 patients examined prospectively during three consecutive years, the rate was 12.5% in 1985, 13.1% in 1986, and 9.3% in 1987 (mean of 11.6%). In addition to higher age, other risk factors were identified (mortality in brackets): female sex (14.6%), heart failure (20.6%), and diabetes (19.7%). Hypertension (11.2%) and previous infarct (12.8%) had no influence on mortality rate. The mortality rate was significantly reduced (P less than 0.0003) among 290 patients who had received intravenous fibrinolytic treatment, but this effect was marked only among women, elderly patients and those without risk factors. It is concluded that many measures had led to the observed reduction in acute death rate to about 10%. It is not yet possible to determine which of the different interventions played a part.

Age Factors↗
PubMed1989

Quinine dosage in severe malaria with renal failure necessitating haemodialysis.

For therapy of severe malaria with renal failure, a 2/3 reduction in the usual intravenous dose of quinine is recommended (600 mg per 24 h instead of 600 mg per 8 h). Two patients with severe malaria and renal failure requiring dialysis have been treated. The half-life was not prolonged (15 h). Quinine proved to be nondialysable. It was shown that this dose of quinine tended to lead to a low level in blood (under 10 mg.l-1). A normal dose of quinine (2 x 15 mg/kg per day) is therefore recommended for malaria therapy, even in cases with renal failure requiring haemodialysis, in order to attain the desired plasma level (5 to 15 mg.l-1).

Chromatography, High Pressure Liquid↗
PubMed1989

Treatment of carbamazepine poisoning by combined hemodialysis/hemoperfusion.

A severe carbamazepine intoxication in a 45-year-old woman was treated with combined hemodialysis/hemoperfusion. The ingested dose was estimated as 4-36 g. Serum carbamazepine levels were determined by fluorescence polarization immunoassay. The detoxication was performed 18 h after admission and resulted in a 50 percent reduction in serum drug levels accompanied by rapid clinical improvement.

Carbamazepine↗
PubMed1983

Intravenous short-term infusion of streptokinase in acute myocardial infarction.

Short-term i.v. infusion of streptokinase was performed in 93 patients within 6 hours after the onset of acute myocardial infarction. Twenty-six patients underwent angiography in the acute phase (group A) and 52 underwent angiography in the fourth week only (group B); 15 patients had no angiography. Seven patients died during the hospital stay and six suffered nonfatal reinfarctions. There were no bleeding complications. In 11 of 21 group A patients, occluded coronary arteries were opened within 1 hour after the streptokinase infusion was started. In 84% of groups A and B, the infarct-related coronary artery was patent in the fourth week. In 75% of the patent arteries, the residual luminal diameter stenosis was less than 70%. According to serial serum CK-MB curves, recanalization was achieved mostly within 1-2 hours. Myocardial salvage was indicated by improvement in local contraction disorders in the recanalized group A patients and by the significant relationship between infarct size and time from symptom onset to treatment in group B. These data suggest that a high-dose, short-term, i.v. infusion of streptokinase is a safe and efficient method of restoring coronary blood flow. Expeditious initiation of i.v. streptokinase infusion is a critical determinant for early recanalization and salvage of myocardium. Patients with thrombotically subtotal occlusion probably receive the most benefit. Evaluation of the true impact on survival and myocardial function will require controlled clinical trials.

Adult↗
PubMed1982

Radiation effect on partially synchronized Yoshida sarcoma cells.

Yoshida sarcoma cells, which have the same growth characteristics as ascites cells in the mouse and in cell suspension, were partially synchronized in vitro by means of excess thymidine (0.1 mM thymidine for 18 h). The growth of non-synchronized cultures was inhibited by irradiation, the degree depending on the dose of radiation. At the same time, a 50% inhibition in vivo (380 rad) and in vitro (480 rad) was determined. The incorporation of 3H-thymidine into the DNA is inhibited by 10-32%, depending on the radiation dose. The mitotic index decreases 2 h after irradiation by a dose-dependent amount. A mitotic maximum develops later; the delay is dose-dependent. Partially synchronized cells were irradiated in the G1/S-, G2-, and G1-phase. As compared to the 3H-thymidine incorporation and the mitotic index there were no significant differences between the cultures which were irradiated in the individual phases of the non-synchronized control cultures. The cultures which were irradiated in the G2-phase, however, showed a significantly reduced growth in vivo after 48 h. If the cells were cultured for more than 72 h after irradiation, the differences between the cultures irradiated in the G2-phase and the other phases were reduced.

Animals↗
PubMed1982

[Systemic thrombolysis with short-term streptokinase infusion in acute myocardial infarct].

Within 6 hours after the onset of acute myocardial infarction, 93 patients received a brief high-dose intravenous infusion of streptokinase, 49 patients received 500,000 IU within 30 min and 44 patients received 1,500,000 IU within 60 min. 26 patients had angiography in the acute phase, after 24 hours, and in the 4th week; 52 patients had angiography in the 4th week only; and 15 had no angiography. 7 patients died in hospital and 6 suffered a nonfatal reinfarction. There were no complications with bleeding. In 52% of cases, reopening of an occluded infarct vessel was achieved within 1 hour of the beginning of treatment. During the 4th week after infarction a patent infarct vessel was found in 84%, and 58% had a residual stenosis less than 70%. In contrast, in a control group that received no streptokinase treatment, 25% had a patent infarct vessel and 4% had a residual stenosis less than 70%. Indicative for salvage of ischemic myocardium are a significant improvement in local contraction disorders between the acute phase and the 4th week and a significant correlation between infarct size in the 4th week and beginning of treatment after onset of symptoms. 1. It may be concluded that: brief intravenous infusion of streptokinase results in restoration of blood flow in an infarcted coronary artery in a high percentage of cases; the shorter thrombus-lysis time with intracoronary streptokinase infusion could be made up for by the earlier initiation of intravenous streptokinase treatment; and a conclusive randomized trial is needed to ascertain the true impact of a brief high-dose intravenous infusion of streptokinase on mortality and morbidity following acute myocardial infarction.

Adult↗