Biomedical subjects

W Burger

Publications and source records attributed to W Burger.

At least 19 recordsLinked to original sources

PubMed2007

[Experience with new teaching methods and testing in psychiatric training].

In 1999, the Charité Medical University in Berlin, Germany, implemented a reformed medical study course (RMSC) along with traditional undergraduate medical education. The RMSC is characterized by problem-based learning (PBL), training in communication skills with "simulated patients", and interdisciplinary seminars. The curriculum is organized into blocks according to organ system and age (period od life). In a new intensive 4-week psychiatric block, 4th-year students get practical experience in psychiatric wards. Furthermore, PBL groups and workshops are offered that focus on frequent psychiatric disorders. By providing interactive courses with simulated patients, students are intensively trained in taking psychiatric histories and in generating psychopathological findings. Defined learning objectives are tested using multiple-choice items and objectively structured clinical examinations at semester end. First positive results indicate that this course represents an appropriate and practicable curriculum for teaching psychiatry in Germany.

Education, Medical↗

PubMed2006

[The Berlin reformed medical curriculum at the Charité. Experiences with the first cohort].

At the end of the 2004 summer term the first students of the Berlin reformed curriculum finished their education and took their first state examination. With regard to the questions to be answered by the "Berlin Model" the results of the first cohorts were presented and discussed. Overall the Berlin curriculum was successful. The results led to some important considerations concerning adaptation by other faculties, the requirements to start off a problem-based curriculum or an enlargement of the class.

Curriculum↗

PubMed2006

On the fracture of a zirconia ball head.

Y-TZP ball heads were introduced into the market in 1985. Since then these components have had wide diffusion in hip replacements, due to their good mechanical performance and reliability. Namely, only a few papers were published up to year 2000 reporting failures of Y-TZP ball heads. The worldwide recall in August 2001 of some Y-TZP batches changed this situation. This paper analyse the material of a ceramic ball head that fractured in vivo 34 months after surgery. The retrieved fragments were submitted for visual inspection, fractographic analysis by optical microscopy, X-ray diffractometry, and FEG-SEM ceramography analysis. The results obtained show that the hydrothermal stability of the material had only a secondary role in the fracture. The literature reporting on failures of THR making use of Y-TZP ball heads is discussed.

Biocompatible Materials↗

PubMed2005

Low-dose aspirin for secondary cardiovascular prevention - cardiovascular risks after its perioperative withdrawal versus bleeding risks with its continuation - review and meta-analysis.

OBJECTIVES: Low-dose aspirin given for secondary prevention of cardiovascular disease is frequently withdrawn prior to surgical or diagnostic procedures to reduce bleeding complications. This may expose patients to increased cardiovascular morbidity and mortality. Aim of the study was to review and quantify cardiovascular risks because of periprocedural aspirin withdrawal and bleeding risks with the continuation of aspirin. METHODS: We screened MEDLINE (January 1970-October 2004) with additional manual cross-referencing for clinical studies, surveys on the opinions of doctors and guidelines. RESULTS: Studies reporting the relative risk of acute cardiovascular events after aspirin withdrawal when compared with its continuation were not found. However, retrospective investigations revealed that aspirin withdrawal precedes up to 10.2% of acute cardiovascular syndromes. The time interval between discontinuation and acute cerebral events was 14.3 +/- 11.3 days, 8.5 +/- 3.6 days for acute coronary syndromes, and 25.8 +/- 18.1 days for acute peripheral arterial syndromes (P < 0.02 versus acute coronary syndromes). On aspirin-related bleeding risks, we obtained 41 (12 observational retrospective, 19 observational prospective, 10 randomized) studies, reporting on 49 590 patients (14 981 on aspirin). Baseline frequency of bleeding complications varied between 0 (skin lesion excision, cataract surgery) and 75% (transrectal prostate biopsy). Whilst aspirin increased the rate of bleeding complications by factor 1.5 (median, interquartile range: 1.0-2.5), it did not lead to a higher level of the severity of bleeding complications (exception: intracranial surgery, and possibly transurethral prostatectomy). Surveys amongst doctors on the management of this problem demonstrate wide variations. Available guidelines are scarce and in part contradictory. CONCLUSIONS: Only if low-dose aspirin may cause bleeding risks with increased mortality or sequels comparable with the observed cardiovascular risks after aspirin withdrawal, it should be discontinued prior to an intended operation or procedure. Controlled clinical studies are urgently needed.

Acute Disease↗

PubMed2004

Fracture of a Y-TZP ceramic femoral head. Analysis of a fault.

We studied factors contributing to the initiation of fracture and failure of a zirconia ceramic femoral head. The materials retrieved during a revision total hip replacement were submitted to either visual, stereomicroscopic and scanning electron microscopy (SEM) or SEM and energy-dispersive X-ray analysis. X-ray diffraction was performed in order to investigate the extent of tetragonal to monoclinic phase transition. Histological examination was performed on the periprosthetic tissues. The results showed that failure was due to the propagation during clinical use of defects which may have been introduced into the material during the processing of the ceramic, rather than those intrinsic to zirconia. The literature relating to previous failures of zirconia components is reviewed.

Ceramics↗

PubMed2003

[Schooling, living conditions and study motivation of students partaking in the traditional or reformed course of instruction at the Charité (Hospital)].

BACKGROUND: There are two different tracks in undergraduate medical education at the Charité, a traditional (TT) one and a reformed one (RT) which was implemented in 1999. We report a survey reflecting on possible differences between students joining the two tracks. METHODS: During the winter term 2001/02 a questionnaire was sent to all 223 newly enrolled medical students. Three groups were distinguished: those following either the traditional or the reformed course (TT or RT), or those who followed the TT, although they had applied for it, because there were not enough vacancies in the RT. PARTICIPANTS: 150 (63% female; average age: 21.5 years) of 223 first year medical students. RESULTS: Applicants for the RT did not differ significantly from those of the other groups with respect to school-leaving grades, their choice of main courses at school an their motivation to study medicine. But they differed in the demands that they placed on their instruction. The wish for a good practical medical training, advancing their individual potential and the ability to select for themselves any instructional priorities were of greater importance for those choosing the RT than those who preferred the TT. More students of the RT than the TT would again have chosen to study medicine and less often stated that they had considered giving up their medical course. CONCLUSION: Students have different expectations concerning medical curricula. The possibility to choose between different ways of studying may help to meet different expectations.

Adult↗

PubMed2003

Increased release of IL-12p70 by monocytes after periodontal therapy.

OBJECTIVES: It has been suggested that periodontal inflammation may result in an altered immune response. The peripheral immune capacity in periodontitis patients can be investigated using lipopolysaccharide (LPS)-stimulated whole blood cell cultures (WBCC), known to reflect the behavior of monocytes in particular. A previous study in our laboratory revealed that monocytes in the stimulated cultures from periodontitis patients behaved functionally different compared with controls. The present study investigated whether this different response of periodontitis patients' monocytes is intrinsic or acquired. MATERIAL AND METHODS: The release of inflammatory mediators was measured in Escherichia coli LPS-stimulated WBCC from 12 periodontitis patients before and after periodontal therapy. In addition, the total leukocyte and leukocyte differentiation counts were also determined in the patients before and after therapy. RESULTS: The levels of interleukin (IL)-12p70 in cell culture supernatants increased two times and those of prostaglandin E2 showed a trend towards reduction after therapy, whereas the levels of IL-1beta, IL-6, IL-8, IL-10, IL-12p40 and tumor necrosis factor-alpha did not change. The total number of white blood cells was decreased after periodontal therapy. CONCLUSIONS: After periodontal therapy, the functional phenotype of the peripheral blood monocytes from patients was reconstituted, resembling that of subjects without periodontitis.

Adult↗

PubMed2002

Use of barrier membranes and systemic antibiotics in the treatment of intraosseous defects.

OBJECTIVES: Current literature is ambivalent on the use of barrier membranes for regeneration of intraosseous defects. One of the reasons for unpredictable results may be related to infection before, during and after the surgical procedure. Therefore, the purpose of the present controlled study was to evaluate both the use of membranes (MEM) and antibiotics (AB), separately and in combination. METHODS: In all, 25 patients with two intraosseous periodontal defects each were randomized in two groups: AB+ group receiving systemic antibiotics (n = 13) and AB- group without antibiotics (n = 12). After raising flaps and after debridement, both defects in each patient were covered by a bioresorbable membrane (MEM+). However, just before suturing the flaps in a coronal position, the membrane over one of the two defects was removed at random (MEM-). This protocol resulted in four groups of defects: (i). MEM- AB-; (ii). MEM+ AB-; (iii). MEM- AB+; (iv). MEM+ AB+. Patients were monitored clinically and microbiologically for 1 year. Data were analyzed in repeated measures ancova's and adjusted means for clinical variables were obtained from the final statistical model. RESULTS: Reduction in probing pocket depth (PPD) at 12 months postoperatively varied between 2.54 and 3.06 mm between the four treatment modalities, but overall no main effect of MEM or AB was found. Gains in probing attachment level (PAL) at 12 months postoperatively varied between 0.56 and 1.96 mm for the 4 treatments. In the overall analysis for PAL, no main effect of MEM or AB was found. Gains in probing bone level (PBL) 12 months postoperatively ranged from 1.39 to 2.09 mm between the treatment groups. Again, overall, no main effects of MEM or AB were found for PBL. Explorative statistical analyses indicated that smoking and not MEM or AB is a determining factor for gain in PBL (P = 0.0009). Nonsmokers were estimated to gain 2.04 mm PBL compared to 0.52 mm in smokers. The prevalence of several periodontal pathogens, at the day of surgery or postoperatively, and specific defect characteristics, were not determining factors for gain in PAL and PBL. CONCLUSIONS: Neither the application of barrier membranes nor the use of systemic antibiotics showed an additional effect over control on both soft and hard tissue measurements in the treatment of intraosseous defects. In contrast, smoking was a determining factor severely limiting gain in PBL in surgical procedures aimed at regeneration of intraosseous defects.

Abscess↗

PubMed2001

The relation between medical education and the medical profession's world view.

Thinking in medicine is still dominated by the cartesian view of science of the past centuries, dividing individuals into the reasoning mind (res cogitans) and an objective body as part of all non-subjective things of the world (res extensa). This classical scientific paradigm does not take into account the influence the observer exerts on the observed phenomena. Applying this paradigm to medical research and education has consequences regarding the relationship between physicians and patients as well as between medical teachers and their students. An improvement of medical education towards a broader understanding of complex illnesses with their psychosocial implications must be based on philosophical and epistemological issues. The requirements of modern medicine cannot just be met by adding more psycho-social content to somatic medical education or by changing the didactic approach without reflection on the underlying concepts and the relation of the human being to his world.

Attitude of Health Personnel↗

PubMed2001

Influence of right ventricular pre- and afterload on right ventricular ejection fraction and preload recruitable stroke work relation.

When right ventricular (RV) afterload is abnormally increased, it correlates inversely with right ventricular ejection fraction (RVEF). We tested, whether this would be different with normal afterload. Additionally, we investigated whether previous studies on the slope of RV preload recruitable stroke work (SW) relation, which used rather non-physiological measures to change RV preload, could be transferred to more physiological loading conditions. RV volumes were determined by thermodilution in 16 patients with stable coronary artery disease and normal pulmonary artery pressure (PAP) at rest. Pre- and afterload were varied by body posture, nitroglycerin (NTG) application and by exercise at different body positions. At rest, the change from recumbent to sitting position decreased PAP, cardiac index (Ci), RV diastolic and systolic volumes, and RVEF. Additionally, mean pulmonary artery pressure (MPAP) correlated positively with both RVEF and cardiac index. After correction for mathematical coupling, the RV preload recruitable SW relation was: right ventricular stroke work index (RVSWi) (103 erg m-2)= 8.1 x (RV end-diastolic volume index -4.9), with n=96, r=0.57, P< or =0.001. Exercise abolished this correlation and led to an inverse correlation between RV end-systolic volume (ESV) and RVSW. In conclusion, (i) RVEF correlates positively with RV afterload when afterload varies within normal range; (ii) the slope of the RV preload recruitable SW relation, which is obtained at steady state under normal loading conditions, is substantially flatter than previously described for dynamic changes of RV preload. With increasing afterload, preload loses its determining effect on RV performance, while afterload becomes more important. This puts earlier assumptions of an afterload independent RV preload recruitable SW relation into question.

Aged↗

PubMed2000

Effect of atenolol and celiprolol on acetylcholine-induced coronary vasomotion in coronary artery disease.

Earlier studies have reported on the potentiated muscarinic vasoconstriction of intracoronary acetylcholine after metoprolol application in patients with coronary artery disease. The present study investigated the effect of celiprolol, atenolol, and placebo on acetylcholine-induced vasomotion in patients with coronary artery disease. Furthermore, direct effects on coronary vasomotion and on hemodynamics were evaluated. Acetylcholine (intracoronary concentrations of 6.3x10(-7), 2.0x10(-6), and 6.3x10(-6) M) was given before and after double-blind celiprolol (0.30 mg/kg IV), atenolol (0.15 mg/kg IV), or placebo in 3x12 patients. Vasomotion was investigated by quantitative coronary angiography in proximal and distal segments of epicardial coronary arteries, and by the determination of the coronary resistance index based on Doppler-flow measurements. The investigated drugs had no direct affect on the diameter of the epicardial coronary arteries. However, celiprolol, in contrast to atenolol, significantly reduced systemic vascular resistance (change after atenolol: from 1,855+/-308 to 2,161+/-550 dyne s cm(-5); celiprolol: 1,691+/-435 to 1,411+/-343 dyne s cm(-5); and placebo: 1,722+/-215 to 1,710+/-213 dyne s cm(-5), p<0.001) and the coronary resistance index (change after atenolol: 2.52+/-3.58 to 2.86+/-4.24; celiprolol: 2.70+/-1.55 to 2.49+/-2.26; and placebo: 1.97+/-1.35 to 1.92+/-1.25, p<0.01). Celiprolol, atenolol, and placebo did not have different effects on acetylcholine-induced coronary vasomotion of epicardial conductance vessels (diminution of proximal lumen diameter before/after atenolol: 0.42+/-0.39/0.44+/-0.39 mm; celiprolol: 0.32+/-0.26/0.30+/-0.24 mm; and placebo: 0.36+/-0.29/0.43+/-0.40 mm) and of coronary resistance vessels (reduction of coronary resistance index before/after atenolol: 1.95 +/-4.74/ 1.92+/-3.74; celiprolol: 0.98+/-0.73/1.41+/-1.50; and placebo: 1.16+/-1.29/1.16+/-1.04). In contrast to atenolol, celiprolol possesses vasodilative properties in systemic and coronary resistance vessels. There was no direct effect on the diameter of conductance vessels. Acetylcholine-induced coronary vasomotion both in conductance and resistance vessels was not influenced by the beta blockers that were studied. This suggests that atenolol and celiprolol do not influence endothelium-dependent, nitric oxide related vasomotion.

Acetylcholine↗

PubMed1999

The histidine-rich protamine from ostrich and tinamou sperm. A link between reptile and bird protamines.

We have characterized for the first time the proteins of two different species of palaeognathous birds, Struthio camelus australis (ostrich) and Nothoprocta perdicaria sanborni (Chilean tinamou). Similar to what had been previously reported in neognaths, the electrophoretic mobility, amino acid composition, and primary structure of the main protamine (P-II) component of these two species of birds are similar. However, in contrast to neognathous birds, the protamines from paleognaths display a higher electrophoretic mobility and a significantly different amino acid composition and protein sequence. The sperm and the main protamine component P-II from the ostrich reveal structural and compositional characteristics intermediate between neognathous birds and reptiles. The marked differences between the protamines and sperm structure of neognaths and paleognaths provide support to a phylogenetic relationship between neornithine birds in which these two groups represent two separate phylogenetic lines. Furthermore, these results shed some additional light on the controversial origin of birds. They provide further molecular support to the fossil record that suggests that reptiles and birds are closely related.

Alligators and Crocodiles↗

PubMed1999

In vitro evaluation of the mutagenic and carcinogenic power of high purity zirconia ceramic.

Tetragonal zirconia polycrystal (TZP) is a new interesting ceramic for the manufacture of medical devices. Its wide use in orthopedic and odontoiatric implants was limited till now by the high chemical and radiochemical impurities of the raw materials. Purification processes now available allow to obtain high purity ceramic grade powders suitable for TZP ceramics manufacture, even if their possible mutagenic and transforming effects are still unclear. The aim of this work is to study in vitro the mutagenic and oncogenic effects of a new zirconia ceramic stabilized by yttria (Y-TZP). This ceramic was sintered from high purity powders obtained by a process developed under a project carried out within the Brite EuRam programme. For comparison, ceramics made from unpurified zirconia powder were also tested. Fibroblasts irradiated by a linear accelerator were used as positive control. The results obtained show that Y-TZP ceramic does not elicit either mutagenic or transforming effect on C3H/10T(1/2) (10T(1/2)) cells and demonstrate that ceramic from high purity powders can be considered suitable for biomedical applications from the point of view of the effects of its radioactive impurity content.

Animals↗

PubMed1999

Sulfonylureas and ischaemic preconditioning; a double-blind, placebo-controlled evaluation of glimepiride and glibenclamide.

AIMS: Glimepiride is a new sulfonylurea for diabetes treatment which is supposed to impact less on extra-pancreatic ATP-dependent K+ channels than the conventional drug glibenclamide. This study was performed to evaluate whether this results in a better maintenance of ATP-dependent K+ channel mediated ischaemic myocardial preconditioning. METHODS AND RESULTS: In a double-blind placebo-controlled study the period of total coronary occlusion during balloon angioplasty of high grade coronary artery stenoses was used as a model to compare the effects of both drugs. Quantification of myocardial ischaemia was achieved by recording the intracoronary ECG and the time to the occurrence of angina during vessel occlusion. All patients underwent three dilatations. The first dilatation (dilatation 1) served to determine the severity of ischaemia during vessel occlusion. During dilatation 2, baseline values were recorded. Thereafter, glimepiride (15 patients: 1.162 mg), glibenclamide (15 patients: 2.54 mg) or placebo (15 patients) were intravenously administered over 12 min. Dilatation 3 started 10 min after the beginning of the drug administration. Mean ST segment shifts in the placebo group decreased by 35% (dilatation 2: 0.23; dilatation 3:0.15 mV; CI -0.55 to 0.00 mV; P=0.049). A similar reduction also occurred in the glimepiride group, in which repetitive balloon occlusion led to a 34% reduction (dilatation 2: 0.35; dilatation 3: 0.23 mV; CI -0.21 to -0.02 mV; P=0.01). There was little influence however, on mean ST segment shifts in the glibenclamide group (dilatation 2 and dilatation 3: 0.24 mV; CI -0.10 to 0.25 mV; P=0.34). Accordingly, time to angina during balloon occlusion slightly increased (by 30%) in the placebo group (dilatation 2: 37 s; dilatation 3: 48 s; CI 0.0 to 15.0 s; P=0.16); increased by 13% in the glimepiride group (dilatation 2: 40 s; dilatation 3: 45 s; CI 0.0 to 14.0 s; P=0023); and remained unchanged in the glibenclamide group (dilatation 2 and dilatation 3: 30 s; CI -7.5 to 7.5 s; P=0.67). CONCLUSION: These results show that glimepiride maintains myocardial preconditioning, while glibenclamide might be able to prevent it.

Adult↗

PubMed1999

Outpatient coronary angiography with 4 French catheters.

The early 4 French (Fr), pre-formed, Judkins coronary catheters had unsatisfactory maneuverability due to reduced torque stability. Technical innovations have led to improved 4 Fr catheters. This prospective study evaluates the safety and feasibility of the 4 Fr Quick Care Infinity catheter (Cordis, Miami, Florida). Within a series of 2,366 patients investigated for suspected coronary artery disease, 302 were selected for outpatient treatment according to the guidelines for outpatient catheterization. Fluoroscopy time was 2.8 +/- 2.5 minutes. It was not necessary to change to larger catheters in any patient. After sheath removal, hemostasis was achieved within 14 +/- 8 minutes. Strict bed rest lasted 181 +/- 65 minutes; patients were discharged 303 +/- 76 minutes after arterial puncture. Sixteen of the 302 patients (5.3%; 95% confidence interval (CI): 3.1-7.9%) changed to inpatient treatment for reasons unrelated to the arterial access. Eight patients (2.6%; CI: 1.1-5.1%) required one night of hospitalization for control of hematoma. The following morning, vessel murmur, pain, and large hematoma (more than 10 cm diameter) occurred in 1 (0.3%), 6 (2.0%), and 6 (2.0%) patients, respectively. This necessitated hospital admission in 2 patients (0.7%; CI: 0.0-2.3%) for up to 2 days. Major entry site complications requiring blood transfusion or surgery did not occur (CI: 0.0-0.3%). It was concluded that outpatient catheterization for coronary artery disease using the new 4 French catheters is feasible and can be rapidly and safely performed in a selected patient population.

Adult↗

PubMed1999

Collagen application for sealing of arterial puncture sites in comparison to pressure dressing: a randomized trial.

UNLABELLED: One-hundred patients undergoing routine diagnostic or interventional catheterization were randomly assigned to receive either percutaneously applied collagen (group A; n = 50) or conventional pressure dressing (group B; n = 50) for sealing of the femoral artery. Clinical variables were comparable in both groups. The heparin dose was 100 IU/kg in 30 patients and 200 IU/kg in 20 patients of either group. The average compression time was 4.3 minutes in group A and 42.3 minutes in group B (p < 0.001). Bleeding was not observed in group A but was observed in 6/50 patients in group B. The time to ambulation was 6.4 hours (range: 4-12 hours) in group A and 21.6 hours (range: 10-48 hours) in group B (p < 0.001). Hematomas with a diameter of > 6 cm developed in 4/50 patients in group A and in 11/50 patients in group B (p < 0.05). Blood transfusion or surgical interventions were not required and there was no loss of ankle pulses in either group. CONCLUSION: Percutaneously applied collagen reduced compression time and duration of bedrest after diagnostic catheterization and PTCA. Despite earlier ambulation, the incidence of bleeding was lower with collagen than with conventional pressure dressing.

Aged↗

PubMed1998

Y-TZP ceramics for artificial joint replacements.

Due to their excellent mechanical properties, Yttria-stabilized Tetragonal Zirconia Polycrystal ceramics (Y-TZP) are used in ball heads for Total Hip Replacements. It is known that Y-TZP materials may show strength degradation due to ageing or to hydrothermal treatment. Also high wear of UHMWPE sockets coupled to steam sterilized Y-TZP ball heads after a short implantation period was recently reported. This effect may be related to ball head surface phase transformation, due to corrosive attack. The aim of this study is the evaluation of Y-TZP ceramics stability. Y-TZP made out of Yttria coated powders were aged at 140 degrees C under 0.2 MPa water pressure, in Ringer's solution at 37 degrees C, in NZW rabbits. Samples made out Yttria coated powders show lower strength degradation than samples made out coprecipitated powders, and UHMWPE discs coupled to Y-TZP rings made out coated powders do not show increase in wear after repeated sterilization cycles of the ceramic rings.

Animals↗

PubMed1998

Total synthesis of 25-hydroxy-16,23E-diene vitamin D3 and 1 alpha,25-dihydroxy-16,23E-diene vitamin D3: separation of genomic and nongenomic vitamin D activities.

Separation of genomic and nongenomic vitamin D activities was achieved by structural modification of 1,25-dihydroxy vitamin D3 by introduction of 16 and 23E double bonds. The modified compound 3, lacking a 1 alpha-hydroxy group, exhibits only nongenomic activity. Its 1 alpha-hydroxy relative 4 expresses fully both genomic and non-genomic activities. A total synthesis of analogues 3 and 4 is described.

Animals↗