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Biomedical subjects

F Köhler

Publications and source records attributed to F Köhler.

At least 19 recordsLinked to original sources
PubMed2005

Femtosecond formation of coupled phonon-plasmon modes in InP: Ultrabroadband THz experiment and quantum kinetic theory.

The ultrafast transition of an optical phonon resonance to a coupled phonon-plasmon system is studied. After 10-fs photoexcitation of i-InP, the buildup of coherent beats of the emerging hybrid modes is directly monitored via ultrabroadband THz spectroscopy. The anticrossing is mapped out as a function of time and density. A quantum kinetic theory of microscopic carrier-carrier and carrier-LO-phonon interactions explains the delayed formation of the collective modes. The buildup time is quantitatively reproduced to scale with the oscillation cycle of the upper branch of the coupled resonance.

Journal Article↗
PubMed2005

Downregulation of Apaf-1 and caspase-3 by RNA interference in human glioma cells: consequences for erucylphosphocholine-induced apoptosis.

Erucylphosphocholine (ErPC) exerts strong anticancer activity in vivo and in vitroand induces apoptosis even in chemoresistant glioma cell lines. We investigated the contribution of Apaf-1 and caspase-3 to the apoptotic response to ErPC using RNA interference (RNAi) in human glioblastoma cells. We could demonstrate that human glioma cell lines are susceptible to RNAi. Apaf-1 and caspase-3 are amenable to specific small interfering RNA (siRNA)-induced degradation resulting in a reduction of protein levels to 8-33% (Apaf-1) and to 30-50% (caspase-3). Transfection of siRNA directed to Apaf-1 and caspase-3 specifically reduced caspase-3 processing induced by ErPC treatment and yielded a reduction in cells that undergo ErPC-induced apoptosis to 17-33% (Apaf-1) and to 38-50% (caspase-3). The caspase-3 siRNA experiments were corroborated in caspase-3-deficient and -reconstituted MCF-7 breast cancer cells. Survival assays and morphological observations revealed that caspase-3 reconstitution significantly sensitized MCF-7 cells to ErPC. Exploring the caspase cascade responsible for ErPC-induced apoptosis MCF-7 cells provided evidence that caspase-3 is required for the activation of caspases-2, -6 and -8 and also participates in a feedback amplification loop. Our results provide evidence that Apaf-1 and caspase-3 are major determinants of ErPC-induced apoptosis and the possible use of ErPC in a clinical setting is discussed.

Apoptosis↗
PubMed2004

[Health telematics/telemedicine in the republic of Estonia].

The people of Estonia, who until their independence had been systematically deprived of all forms of information, have shown a ready acceptance of the use of information technology in all areas of life. This environment and an excellent IT infrastructure have since the beginning of the new century provided favourable conditions for developing various individual projects in telemedicine. At the core of current telemedical applications in Estonia is the BITNET Project (in neurology, general medicine), built up with Swedish cooperation, and three German-Estonian projects (in telecardiology and telepathology). These projects are accompanied by studies of their cost-effectiveness. They constitute the basis for the plan that routine telemedical services be taken over by the Estonian health insurance. Differing from the situation in the Scandinavian countries, which have had an effective national telemedical service for over ten years, the special feature of telematrics in Estonia is its international networking with foreign centres of excellence. This has its origin in the aim of Estonian health policy to ensure medical services within its own country in all branches of medicine.

Cost-Benefit Analysis↗
PubMed2004

[The Estonian Genome Project in the context of European genome research].

It is the aim of the Estonian Genome Project to establish a database which compiles phenotype and genotype data of a large part of the Estonian population. The Gene Bank will only be used for scientific and public health research. Researchers hope that it will help identify disease genes and prepare the ground for the personalized medicine of the future. Additionally, the project will improve Estonian's international competitiveness in high technology and have a strong educational effect on the population. The legal framework, the Human Genes Research Act, was passed by the Estonian parliament in December 2000. It had been drafted by a group of experts who took into account all available international guidance documents on genetic research. With the pilot project involving three selected regions successfully finished, the main project has now started.

Databases, Nucleic Acid↗
PubMed2004

[Interventional cardiology in Latvia from 1993 to 2003].

A nationale programme for combatting cardiovascular diseases is being implemented in Letvia. A milestone was reached in 1993 with the establishment of a Letvian Centre for Cardiology. Within 10 years the only cardiac catheterization unit in the country has developed into a centre of excellence. But to meet the cardiological needs for all of Letvia requires at least three additional units for left heart catheterization and one for paediatric a cardiac catheterization.

Adult↗
PubMed2002

[Impact of the DRG system for subacute and rehabilitative treatment in Sydney, New South Wales, Australia].

The forthcoming introduction of a DRG system in Germany has entailed numerous uncertainties for the agencies involved, for medical and care staff as well as all others having to do with the health care system, the patients included. As had previously been the case in other countries, this innovation is going to effect major changes in Germany as well. Notwithstanding, efforts to enhance specific, efficient and quality-assured medical care can, and are intended to, be undertaken in the future as well. This short report summarizes the impact introduction of a DRG system has had at the interface between acute care and subsequent rehabilitation in Sydney, New South Wales; concluding, future developments are outlined.

Aftercare↗
PubMed2001

[Pregnancy and congenital heart defects].

With advanced diagnostic and therapeutic techniques in pediatric cardiology and cardiac surgery, pregnancy can be an option for patients with congenital heart disease. A low overall maternal mortality and a healthy pregnancy require interdisciplinary cooperation between the cardiologist, obstetrician and general practitioner caring for the mother. Treatment and outcome will depend on the type of cardiac malformation, on the functional impairment of the maternal heart (heart failure and/or cyanosis) and on the status of the fetus, with evidence of a better outcome for patients treated in specialized centers. However, even with recent advances in treatment, for women with primary pulmonary hypertension, Eisenmenger's syndrome, left heart obstruction of Marfan syndrome, pregnancy remains associated with a high maternal mortality. Therefore, these are conditions in which pregnancy is still absolutely contraindicated and a patient should be counselled to terminate the pregnancy. The risk of an inherited recurrence of a congenital heart disease is difficult to assess in an individual case because the majority of cardiac malformations are caused by multifactored variables. But for some types of malformations (i.e., atrioventricular canal, Morbus Fallot) the incidence of cardiac malformation in the offspring of affected parents is slightly higher compared to the general population. Consequently, all patients with congenital heart disease should be offered genetic counselling and fetal echocardiography. In general, pregnancy in women with congenital heart disease has no significant long-term adverse effects and a second pregnancy is possible in the majority of the cases.

Female↗
PubMed1999

Characterization of the DNA-binding and dimerization properties of the nuclear orphan receptor germ cell nuclear factor.

The orphan receptor germ cell nuclear factor (GCNF) is a member of the superfamily of nuclear receptors. During development, GCNF exhibits a restricted brain-specific expression pattern, whereas GCNF expression in the adult is germ cell specific. Therefore, the receptor may participate in the regulation of neurogenesis and reproductive functions. No natural GCNF target gene has yet been identified, but recent data demonstrate specific and high-affinity binding of GCNF either to the direct repeat DNA element AGGTCAAGGTCA (DR0) or to extended half-sites, such as TCAAGGTCA. In this study, we show that murine GCNF (mGCNF) can bind as a homodimer to extended half-sites, thus describing a novel property within the nuclear receptor superfamily. Homodimeric binding to extended half-sites requires the presence of a dimerization function within the mGCNF DNA-binding domain (DBD) and a novel dimerization surface encompassing the putative helix 3 and the helix 12 region of the mGCNF ligand-binding domain (LBD). In addition, the mGCNF LBD has the potential to adopt different conformations with distinct dimerization properties. The helix 12 region of the mGCNF LBD not only regulates the switch between these dimerization conformations but also dictates the DNA-binding behavior and transcriptional properties of the different dimerization conformations. In summary, our findings describe unique DNA-binding and dimerization properties of a nuclear receptor and suggest a novel mechanism that allows mGCNF to modulate target gene activity.

Amino Acid Sequence↗
PubMed1997

Surgical removal of atrial septal defect occlusion system-devices.

OBJECTIVE: Since 1976 a number of similar transvenous atrial septal defect occlusion systems have been developed and applied to prevent surgical intervention with extracorporeal circulation and the complications involved. One of them is the so called atrial septal defect occlusion system (ASDOS-device; Dr Ing Osypka, Germany). METHOD AND RESULTS: In our institution, eight ASDOS-devices were implanted in adults during the last year. In six individual cases, these devices were explanted because of thrombosis, residual shunts, deformations of the umbrella, disconnection of the system and atrial perforation with hemopericard. This occured 17-380 days after the implant. The surgical removal was uncomplicated in all cases. CONCLUSIONS: Because the complication rate of the ASDOS-device was unacceptably high, surgical repair was preferred.

Adult↗
PubMed1996

The multi-dimensionality of the FIM motor items precludes an interval scaling using Rasch analysis.

Rasch analysis scaling is said to produce an interval scale of Functional Independence Measure (FIM) motor function items. Rasch analysis requires that the data to be analysed represent the influence of a single underlying unidimensional variable. A unidimensional interval scale of activities of daily living means that a person who can perform the most difficult item on a scale can also perform the easiest item. For a FIM motor function interval scale, the ability to climb stairs would imply necessarily and ability to eat normally. As this need not be the case, the FIM motor items do not constitute an adequate interval scale. Eating and walking are different activities, and a unidimensional construct linking them is unsatisfactory. A principal components analysis of the admission FIM motor function items of 515 consecutive patients admitted to an inpatient rehabilitation unit revealed that more than one significant factor was necessary to explain the variance in scores. The counter-factual and statistical evidence argues that a unidimensional construct does not underly the FIM motor function items, and the use of Rasch analysis will not lead to a description of interval properties of the FIM motor function items.

Activities of Daily Living↗
PubMed1995

[Venous angioplasty and Wallstent implantation in emergency treatment of superior vena cava syndrome caused by tumor].

HISTORY AND CLINICAL FINDINGS: A 58-year-old man was hospitalized because of threatened asphyxia resulting from massive obstruction to neck vein flow and increased venous markings over the ventral and dorsal thorax. The previous year he had received radiotherapy (total of 55.8 Gy) for squamous cell carcinoma in the right upper lobe of the lung (primary stage T2 N2 M0). The signs of venous congestion had developed over several months. TESTS: Emergency phlebography demonstrated obstruction to superior vena cava (SVC) flow by tumour compression. TREATMENT AND COURSE: It was possible to pass the SVC obstruction with a hydrophilic guide-wire and then perform a balloon angioplasty, followed later by implantation of two intraluminal expandable stents ("Wallstent"). The dyspnoea quickly improved after the successful recanalization. The day after the intervention palliative radiotherapy of the SVC obstruction was begun. But increased venous markings over the thorax recurred, but without dyspnoea, after 4 1/2 months free of signs of venous congestion. Repeat phlebography again demonstrated complete obstruction of the SVC by the tumour. Recanalization by balloon angioplasty was again achieved. CONCLUSIONS: This case underlines the value of percutaneous balloon angioplasty with stent implantation as supplementary treatment in the late stages of SVC obstruction by tumour.

Angioplasty, Balloon↗