Search PubMed⌕ Search

Biomedical subjects

B Hofmann

Publications and source records attributed to B Hofmann.

At least 19 recordsLinked to original sources
PubMed2006

[The endovenous laser therapy of varicose veins--substantial innovation or expensive playing?].

INTRODUCTION: The aim of the study was to evaluate the efficiency of the endovenous use of laser for treatment of varicose veins. In particular the influence of laser energy on the perivenous temperature, the postoperative clinical and duplex ultrasound course was taken into account. METHOD: The patients were divided into two groups. In 33 cases the laser therapy was used without perivenous liquid protection. In 30 cases a 0.9 % NaCl solution has been injected around the vein. The laser used was a 980 nm diode laser (Ceralas D 980, Biolitec AG, Bonn). The pulse-mode procedure has been applied for triggering the laser impulse (1.5 s pulse length, 1.5 s pause with a 3 mm withdrawal of the laser fibre. The laser energy was 15 watt. 20 cm distal to the saphenofemoral or saphenopopliteal junction a thermo unit measured continuously the perivenous temperature. Clinical and duplex ultrasound checks were carried out before and on the day of the operation. Further checks followed on the first and tenth day after the operation and 8 weeks and 6 months afterwards. RESULTS: The perivenous temperature prior to ELT was 31.3 degrees C, then dropping after the injection of the NaCl solution by 3.4 degrees C. During the ELT the temperature rose by 10.0 degrees C without and by 5.5 degrees C with infiltration. The rise in temperature happened only 3 cm before the tip of the laser fibre arrived at the thermo unit and fell quite rapidly. 98 % of the veins showed within the time period of 2 to 14 months an effective occlusion controlled by duplex ultrasound without refluxing segments. All operations were out-patient treatments. The patients were able to take up work after 1 to 7 days. CONCLUSION: The endovenous laser treatment is an innovative method for the treatment of varicose veins. Considering the mid-term subjective and objective outcomes this method can not only compete with the conventional surgery but has proved to be superior as regards the recurrence rate and patient's comfort. The study presented here, did not find a risk of damage to surrounding non-target tissue.

Adolescent↗
PubMed2006

Alveolar rhabdomyosarcoma of the clivus with intrasellar expansion: Case report.

Rhabdomyosarcomas are common tumors of the head and neck region in children. However, a primarily intracranial localization of this tumor entity is rare. We report on a 3-year-old boy presenting with double vision due to left VI (th) nerve palsy. No other neurological deficits were recognized by clinical inspection. MRI scans visualized an enhancing mass lesion in the upper clivus compressing the cavernous sinus and the pituitary gland. Transsphenoidal biopsy was performed and histopathological examination as well as molecular diagnostics confirmed the diagnosis of an alveolar rhabdomyosarcoma (ARMS). Staging identified a metastatic lesion in the fourth thoracic vertebra resulting in the diagnosis of stage IV disease. Treatment modality included stereotactic radio- and chemotherapy.

Abducens Nerve Diseases↗
PubMed2006

Analysis and cryopreservation of hematopoietic stem and progenitor cells from umbilical cord blood.

BACKGROUND: Umbilical cord blood (UCB) is an important source of hematopoietic stem and progenitor cells (HSC/HPC) for the reconstitution of the hematopoietic system after clinical transplantation. Cryopreservation of these cells is critical for UCB banking and transplantation as well as for research applications by providing readily available specimens. The objective of this study was to optimize cryopreservation conditions for CD34+ HSC/HPC from UCB. METHODS: Cryopreservation of CD34+ HSC/HPC from UCB after mononuclear cell (MNC) preparation was tested in a research-scale setup. Experimental variations were concentration of the cryoprotectant, the protein additive and cell concentration. In addition, protocols involving slow, serial addition and removal of DMSO were compared with standard protocols (fast addition and removal of DMSO) in order to avoid osmotic stress for the cryopreserved cells. Viability and recoveries of MNC, CD34+ cells and total colony-forming units (CFU) were calculated as read-outs. In addition, sterility testing of the collected UCB units before further processing was performed. RESULTS: The optimal conditions for cryopreservation of CD34+ HPC in MNC preparations were 10% DMSO and 2% human albumin at high cell concentrations (5 x 10(7) MNC/mL) with fast addition and removal of DMSO. After cryopreservation using a computer-controlled freezer, high viabilities (89%) and recoveries for CD34+ cells (89%) as well as for CFU (88%) were observed. Microbial contamination of the collected UCB samples was reduced to a rate of 6.4%. DISCUSSION: Optimized cryopreservation conditions were developed for UCB MNC in respect of the composition of the cryosolution. In addition, our results showed that fast addition of DMSO is essential for improved cryopreservation and post-thaw quality assessment results, whereas the speed of DMSO removal after thawing has little influence on the recoveries of CD34+ cells and CFU.

Antigens, CD34↗
PubMed2005

Filter Buffy Coats (FBC): a source of peripheral blood leukocytes recovered from leukocyte depletion filters.

In compliance with federal regulations, blood banks routinely use leukocyte depletion filters to eliminate contaminating leukocytes from blood products such as red blood cell and platelet concentrates. We developed and optimized conditions to elute leukocytes adsorbed to these filters; resulting in leukocyte suspensions which we termed Filter Buffy Coats (FBCs). These Filter Buffy Coats can replace standard buffy coats for various research applications. After optimizing both the filter elution medium as well as elution protocols, we compared commonly used leukocyte depletion filters from four different manufacturers. Relative fractions as well as total recoveries of leukocyte subsets, such as lymphocytes, monocytes and granulocytes, found in Filter Buffy Coats were identified and compared among the filters as well as to standard buffy coats and whole blood. Flow cytometric analysis of Filter Buffy Coats confirmed the presence of T- and B-lymphocytes, NK cells and monocytes. Furthermore, a significant quantity of CD34(+) hematopoietic stem or progenitor cells (HSC/HPC) was detected in Filter Buffy Coats prepared from different filters, thus making FBCs a valuable source for research on HSC/HPC. Colony assays revealed that most of these CD34(+) cells are functional. Using immunomagnetic cell sorting (MACS), we isolated a variety of leukocyte populations from FBC mononuclear cells (Filter-PBMCs) including T lymphocytes (CD4(+), CD8(+), CD3(+)), B lymphocytes (CD19(+)), NK cells (CD56(+)), HSC/HPC (CD34(+), CD133(+)) or dendritic cells (BDCA-4(+)). Functional properties of Filter-PBMCs, as well as of some of these isolated leukocyte populations, were confirmed using standard assays. In summary, Filter Buffy Coats are a valuable and convenient source of different peripheral leukocyte populations and can replace standard buffy coat preparations for research applications.

Antigens, CD↗
PubMed2005

Characterisation of operation conditions and online monitoring of physiological culture parameters in shaken 24-well microtiter plates.

A new online monitoring technique to measure the physiological parameters, dissolved oxygen (DO) and pH of microbial cultures in continuously shaken 24-well microtiter plates (MTP) is introduced. The new technology is based on immobilised fluorophores at the bottom of standard 24-well MTPs. The sensor MTP is installed in a sensor dish reader, which can be fixed on an orbital shaker. This approach allows real online measurements of physiological parameters during continuous shaking of cultures without interrupting mixing and mass transfer like currently available technologies do. The oxygen transfer conditions at one constant shaking frequency (250 1/min) and diameter (25 mm) was examined with the chemical sulphite oxidation method. Varied filling volumes (600-1,200 microL) of Escherichia coli cultures demonstrated the importance of sufficient oxygen transfer to the culture. Cultures with higher filling volumes were subjected to an oxygen limitation, which influenced the cell metabolism and prolongated the cultivation time. The effects could be clearly monitored by online DO and pH measurements. A further study of different media in an E. coli fermentation elucidated the different growth behaviour in response to the medium composition. The MTP fermentations correlated very well with parallel fermentations in shake flasks. The new technique gives valuable new insights into biological processes at a very small scale, thus enabling parallel experimentation and shorter development times in bioprocessing.

Cell Culture Techniques↗
PubMed2005

Ethics of palliative surgery in patients with cancer.

BACKGROUND: Surgery is an important palliative method for patients with advanced malignant disease. In addition to concerns related to clinical decision making, various moral challenges are encountered in palliative surgery. Some of these relate to the patients and their illness, others to the surgeons, their attitudes, skills and knowledge base. METHOD AND RESULTS: Pertinent moral challenges are addressed and analysed with respect to prevailing perspectives in normative ethics. The vulnerability of patients with non-curable cancer calls for moral awareness. Demands regarding sensibility and precaution in this clinical setting represent substantial challenges with regard to the 'duty to help', benevolence, respect of autonomy and proper patient information. Moreover, variations in definition of palliative surgery as well as limited scientific evidence with respect to efficacy, effectiveness and efficiency pose methodological and moral problems. Therefore, a definition of palliative surgery that addresses these issues is provided. CONCLUSION: Both surgical skill and much moral sensibility are required to improve palliative care in surgical oncology. This should be taken into account not only in clinical practice but also in education and research.

Beneficence↗
PubMed2005

Bilateral subdural haematomata and lumbar pseudomeningocele due to a chronic leakage of liquor cerebrospinalis after a lumbar discectomy with the application of ADCON-L gel.

The anti-adhesion gel ADCON-L has been available since the end of the 1990s. During disc surgery it can be applied to the spinal nerve roots and the dura mater spinalis in order to inhibit fibroblast migration and thus avoid postoperative adhesions or excessive keloids, respectively. Due to the way ADCON-L works, inadvertent, intraoperational dural lesions may stay open much longer than usual because ADCON-L inhibits the natural healing process. Possible consequences are a chronic leakage of cerebrospinal fluid in combination with intracranial hypotension syndrome. We report on a patient who underwent lumbar disc surgery with application of ADCON-L gel. Postoperatively he suffered from acute headache, nausea, and vomiting. A lumbar pseudomeningocele was demonstrated on magnetic resonance imaging (MRI). Furthermore, cranial MRI revealed bilateral, chronic subdural haematomata which indicated intracranial hypotension syndrome or continuous leakage of cerebrospinal fluid at the lumbar site. With conservative treatment the problems were gradually reduced and eventually the subdural haematomata were no longer detected. The pseudomeningocele persisted over a 4 month period of observation. Because of the complications we found, the local application of ADCON-L during lumbar disc surgery should be critically evaluated.

Brain↗
PubMed2001

[Physician as a body technician].

"The physician as a technician" is a metaphor for a significant critique of modern medicine. This article approaches some of these critiques. The notion of medicine as an art is sometimes used to remind us of and in praise of the non-technical aspects of medicine. After indicating some difficulties with modern conceptions of medicine as art, I bring in the ancient concept of art, "téchnê", arguing that it avoids some of the difficulties of the modern art concept. Téchnê actually integrates the scientific, technical and normative aspects of medicine and gives a positive interpretation of the claim that the physician has become a technician. The concept provides medicine with a fruitful framework for understanding both technology and philosophy.

Concept Formation↗
PubMed2001

Production of selenomethionine-labelled proteins using simplified culture conditions and generally applicable host/vector systems.

The amino acid analogue selenomethionine (SeMet) is shown to be efficiently incorporated into recombinant proteins expressed in Escherichia coli grown in a simple minimal medium without the addition of synthetic amino acids. Furthermore, satisfactory SeMet incorporation is obtained with a methionine-prototrophic strain transformed with commonly used vector systems. As examples, purified tryparedoxin 1 from Crithidia fasciculata, alkylhydroperoxide reductase (AhpC) from Mycobacterium marinum and the 16-kDa antigen from M. tuberculosis are shown to be efficiently labelled with SeMet, using the culture conditions and the host/vector systems described here. Enzymatic analysis reveals no differences between native and SeMet-labelled tryparedoxin 1 enzyme. Both proteins yield crystals under similar conditions. The culture conditions and host vector systems described greatly facilitate selenium-labelling of proteins for 3-D structure determination.

Animals↗
PubMed2001

Early experience with a quadrileaflet stentless mitral valve.

BACKGROUND: Presently no ideal prosthesis for mitral valve replacement exists. The quadrileaflet mitral valve (SJM-Quattro-MV; St. Jude Medical, Inc, St. Paul, MN) is a chordally supported stentless bioprosthesis. Due to its specific geometry it seems to be particularly suited for mitral valve replacement. METHODS: From March 1999 to October 2000, 12 patients (ages 71+/-2 years) received the SJM-Quattro-MV. Six patients suffered from valvular stenosis and 6 patients from incompetence. Preoperatively, all patients were in New York Heart Association functional class III, with left ventricular ejection fraction amounts of 54%+/-17%. RESULTS: Eleven patients received a medium size SJM-Quattro-MV and one patient received a large size SJM-Quattro-MV. Cross-clamp time was 99.8+/-4.9 minutes. Additional procedures were coronary artery bypass grafting (n = 3) and left atrial microwave ablation (n = 2). Postoperative mortality (n = 1) was procedure related. At follow-up of 11.6+/-5.4 months, all patients were well, the transvalvular pressure gradient was 5.0+/-1.4 mm Hg, and the effective orifice area 2.7+/-0.2 cm2. CONCLUSIONS: Our preliminary experiences with the SJM-Quattro-MV presented good clinical results and promoted an optimistic way of thinking about the further development of these valve prostheses.

Aged↗
PubMed2001

Complexity of the concept of disease as shown through rival theoretical frameworks.

The concept of disease has been the subject of a vast, vivid and versatile debate. Categories such as "realist", "nominalist", "ontologist", "physiologist", "normativist" and "descriptivist" have been applied to classify disease concepts. These categories refer to underlying theoretical frameworks of the debate. The objective of this review is to analyse these frameworks. It is argued that the categories applied in the debate refer to profound philosophical issues, and that the complexity of the debate reflects the complexity of the concept itself: disease is a complex concept, and does not easily lend itself to definition.

Disease↗
PubMed2001

On the value-ladenness of technology in medicine.

The objective of this article is to analyse the value-ladenness of technology in the context of medicine. To address this issue several characteristics of technology are investigated: i). its interventive capacity, ii). its expansiveness and iii). its influence on the concept of disease, iv). its generalising character, v). its independence of the subjective experience of the patient. By this analysis I hope to unveil the double face of technology: Technology has a Janus-face in modern medicine, and the opposite of its factual face is evaluative.

Ethics↗
PubMed2001

The paradox of health care.

The term "paradox" signifies a contradiction of some sort. Modern health care appears to be rich in contradictions, and it is claimed to be paradoxical in a number of ways. In particular health care is held to be a paradox itself: it is supposed to do good, but is accused of doing harm. The objective of this article is to investigate whether the concept of paradox can serve as a framework for analysing pressing problems in modern health care. To pursue this, three distinctive levels of paradox are identified: resolvable paradoxes, antinomies and aporias. The analysis reveals that when facing the challenges of modern health care the focus of attention should be to resolve the resolvable paradoxes, to acknowledge the antinomies and to learn to live with the aporias.

Attitude to Health↗
PubMed2001

GABA(A)-receptor expression in glioma cells is triggered by contact with neuronal cells.

The expression of functional GABA(A)-receptors in glioma cells correlates with low malignancy of tumours and cell lines from glioma lack these receptors. Here we show that contact with neurons induces the expression of functional GABA(A)-receptors. C6 and F98 glioma cell lines were labelled by recombinant expression of enhanced green fluorescent protein injected into rat brain and studied in acute slices after two to three weeks of tumour growth. The cells responded to GABA or the specific agonist, muscimol with a current typical for GABA(A)-receptors, as studied with the patch-clamp technique. To get insight into the mechanism of GABA(A) receptor induction, the C6 or F98 cells were co-cultured with neurons, astrocytes, oligodendrocytes and microglia. Glioma cells expressed functional GABA(A) receptors within 24 h only in cultures where physical contact to neurons occurred. Activation of GABA(A)-receptors in the co-cultures attenuated glioma cell metabolism while blockade of the receptors increased metabolism. We conclude that with this form of interaction, neurons can influence tumour behaviour in the brain.

Action Potentials↗
PubMed2001

Structure of fibroblast growth factor 9 shows a symmetric dimer with unique receptor- and heparin-binding interfaces.

Fibroblast growth factors (FGFs) constitute a family of at least 20 structurally related heparin-binding polypeptides active in regulating cell growth, survival, differentiation and migration. FGF9, originally discovered as a glia-activating factor, shares 30% sequence identity with other FGFs and has a unique spectrum of target-cell specificity. FGF9 crystallized in the tetragonal space group I4(1), with unit-cell parameters a = b = 151.9, c = 117.2 A. The structure of the glycosylated protein has been refined to an R value of 21.0% with R(free) = 24.8%) at 2.6 A resolution. The four molecules in the asymmetric unit are arranged in two non-crystallographic dimers, with the dimer interface composed partly of residues from N- and C-terminal extensions from the FGF core structure. Most of the receptor-binding residues identified in FGF1- and FGF2-receptor complexes are buried in the dimer interface, with the beta8-beta9 loop stabilized in a particular conformation by an intramolecular hydrogen-bonding network. The potential heparin-binding sites are in a pattern distinct from FGF1 and FGF2. The carbohydrate moiety attached at Asn79 has no structural influence.

Amino Acid Sequence↗
PubMed2001

Structures of tryparedoxins revealing interaction with trypanothione.

Tryparedoxins (TXNs) catalyse the reduction of peroxiredoxin-type peroxidases by the bis-glutathionyl derivative of spermidine, trypanothione, and are relevant to hydroperoxide detoxification and virulence of trypanosomes. The 3D-structures of the following tryparedoxins are presented: authentic tryparedoxin1 of Crithidia fasciculata, CfTXN1; the his-tagged recombinant protein, CfTXN1H6; reduced and oxidised CfTXN2, and an alternative substrate derivative of the mutein CfTXN2H6-Cys44Ser. Cys41 (Cys40 in TXN1) of the active site motif 40-WCPPCR-45 proved to be the only solvent-exposed redox active residue in CfTXN2. In reduced TXNs, its nucleophilicity is increased by a network of hydrogen bonds. In oxidised TXNs it can be attacked by the thiol of the 1N-glutathionyl residue of trypanothione, as evidenced by the structure of 1N-glutathionylspermidine-derivatised CfTXN2H6-Cys44Ser. Modelling suggests Arg45 (44), Glu73 (72), the Ile110 (109) cis-Pro111 (110)-bond and Arg129 (128) to be involved in the binding of trypanothione to CfTXN2 (CfTXN1). The model of TXN-substrate interaction is consistent with functional characteristics of known and newly designed muteins (CfTXN2H6-Arg129Asp and Glu73Arg) and the 1N-glutathionyl-spermidine binding in the CfTXN2H6-Cys44Ser structure.

Amino Acid Sequence↗