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Biomedical subjects

K M Müller

Publications and source records attributed to K M Müller.

At least 55 records · Page 3Linked to original sources
PubMed2001

Saline-irrigated, cooled-tip radiofrequency ablation is an effective technique to perform the maze procedure.

BACKGROUND: We evaluated the effectiveness of the saline-irrigated-cooled-tip-radiofrequency ablation (SICTRA) to produce linear intraatrial lesions. METHODS: Thirty patients with chronic atrial fibrillation and mitral valve disease were consecutively randomized to have mitral valve operation either with a Maze procedure (group A) or without (group B). Intraatrial linear lesions were made with an SICTRA catheter (20 to 32 W; 200 to 320 mL/h saline). An echocardiography and 24-hour electrocardiogram were obtained 12 months postoperatively. RESULTS: The cumulative frequencies of sinus rhythm in group A and B were 0.80 and 0.27 (p < 0.01). Restored biatrial contraction was present in 66.7% (6 of 9) of the group A patients in sinus rhythm. One patient from each group received a permanent pacemaker because of bradycardia. A fatal renal bleeding and mediastinitis occurred in 2 group A patients, 6 weeks postoperatively. One group A patient had sudden cardiac death at home, 4 months after operation. One patient from each group had lethal respiratory failure, 7 and 10 months after operation. Survival after 12 months for group A and B was 73% and 93% (p = 0.131). CONCLUSIONS: The SICTRA appeared to be an effective technique to perform the Maze procedure.

Aged↗
PubMed2001

[Biodegradation of a PTFE prosthesis].

Processes of biodegradation of PTFE--as they were not seen before for this type of graft--are demonstrated by clinical examples. As it is possible to subsume these results to regularly described processes of incorporation of alloplastic material, it is to be expected that there will be more cases than those observed by us up to now.

Aged↗
PubMed2001

A structural and phylogenetic analysis of the group IC1 introns in the order Bangiales (Rhodophyta).

Our previous study of the North American biogeography of Bangia revealed the presence of two introns inserted at positions 516 and 1506 in the nuclear-encoded SSU rRNA gene. We subsequently sequenced nuclear SSU rRNA in additional representatives of this genus and the sister genus Porphyra in order to examine the distribution, phylogeny, and structural characteristics of these group I introns. The lengths of these introns varied considerably, ranging from 467 to 997 nt for intron 516 and from 509 to 1,082 nt for intron 1506. The larger introns contained large insertions in the P2 domain of intron 516 and the P1 domain of intron 1506 that correspond to open reading frames (ORFs) with His-Cys box homing endonuclease motifs. These ORFs were found on the complementary strand of the 1506 intron in Porphyra fucicola and P. umbilicalis (HG), unlike the 516 intron in P. abbottae, P. kanakaensis, P. tenera (SK), Bangia fuscopurpurea (Helgoland), and B. fuscopurpurea (MA). Frameshifts were noted in the ORFs of the 516 introns in P. kanakaensis and B. fuscopurpurea (HL), and all ORFs terminated prematurely relative to the amino acid sequence for the homing endonuclease I-Ppo I. This raises the possibility that these sequences are pseudogenes. Phylogenies generated using sequences of both introns and the 18S rRNA gene were congruent, which indicated long-term immobility and vertical inheritance of the introns followed by subsequent loss in more derived lineages. The introns within the florideophyte species Hildenbrandia rubra (position 1506) were included to determine relationships with those in the Bangiales. The two sequences of intron 1506 analyzed in Hildenbrandia were positioned on a well-supported branch associated with members of the Bangiales, indicating possible common ancestry. Structural analysis of the intron sequences revealed a signature structural feature in the P5b domain of intron 516 that is unique to all Bangialean introns in this position and not seen in intron 1506 or other group IC1 introns.

Amino Acid Sequence↗
PubMed2001

[Morphological changes after lung trauma].

Post traumatic pleuro-pulmonary lesions can be divided into 3 phases: Acute phase I--several days to one week--with superficial pleuro-pulmonary defects as a main cause for pneumo-hematothorax, intrapulmonary hematoma from rhexis bleeding of parenchymal vessels, tearing of bronchi and vessels. Latency phase II--1-4 weeks with complications caused by inflammatory overlap, contusion pneumonia, development of fistulae, internal aspiration. Late phase III--1 month to years--special variant of rounded hematoma, pleural inflammation for example in fistulae up to scarring fibrosis. Inflammatory complications and development of ARDS with subsequent complications in the traumatically pre-damaged pulmonary organ.

Follow-Up Studies↗
PubMed2000

Histopathologic findings of lung carcinoma in German uranium miners.

BACKGROUND: This study evaluates the histopathology of lung carcinoma in relation to underground radon exposure. METHODS: Two hundred forty uranium miners of the former Wismut Company in Eastern Germany with histologically or cytologically confirmed primary lung carcinoma were recruited from 3 study clinics between 1991 and 1995. Information on smoking history was obtained by personal interviews, whereas job histories were derived from original payrolls provided by the Wismut Company. Quantitative estimates of occupational radon exposure were based on a job-exposure matrix. RESULTS: Squamous cell carcinoma (SqCC) was the predominant cell type (43%), followed by adenocarcinoma (AC; 26%), small cell lung carcinoma (SCLC; 23%), and other cell types (8%). Nearly all patients were smokers. Time since first occupational exposure was 42 years on average, the mean cumulative radon exposure 506 working level months. Adenocarcinoma appeared to be more likely than both SCLC and SqCC among miners with low cumulative radiation exposure, long time since first exposure, an older age at diagnosis, and among ex- and never-smokers. In current smokers, lung carcinomas developed at a much lower level of radiation exposure than in ex- and never-smokers. The increase in the relative frequency of SCLC and SqCC at the expense of AC with increasing cumulative radiation exposure was more pronounced among ex- and never-smokers and seemed to be masked among current smokers. CONCLUSION: The authors' data suggest that all cell types were associated with radon exposure, but high radiation exposure tended to increase the proportion of SCLC and SqCC.

Adenocarcinoma↗
PubMed2000

Coronary morphologic findings after stent implantation.

Clinical studies demonstrated a reduction of acute complications by high-pressure stenting. This study was performed to correlate the histomorphologic changes of the vessel wall after coronary stenting with stent expansion pressure. We studied the effects of intravital and postmortem stenting on coronary morphology in human hearts. Artifact-free analysis and morphometry of the artery segments' cross section was performed after plastic resin embedding and cutting and grinding sectioning. By comparing intra- and postmortem findings we demonstrated that postmortem stent implantation can serve as an adequate model to study the mechanical effects of coronary stenting. A consistent histologic feature was eccentric stent expansion. Larger calcified areas of the vessel wall were not deformed by implanted stents. The highest degree of vessel injury and deformation was apparent in anatomically "nondiseased" or only slightly fibrotic parts of the arterial wall. Dissections were predominantly located directly adjacent to calcified plaques and appeared as "half-moon"-like tears reaching into the arterial media. A statistically significant stent lumen gain was found when the implantation pressure was increased up to 15 atm. Stent symmetry was not influenced by the applied implantation pressure but depended mostly on local coronary morphology. Thus, increasing implantation pressures during coronary stenting seemed to improve the stenting result up to 15 atm. When applying histomorphologic criteria, the higher pressures (>15 atm) did not cause further optimization of stent expansion. Morphometric analysis of stents implanted postmortemly and intravitally revealed comparable results. Postmortem stenting seems to be an appropriate model for studying stent expansion and stenting results in human coronary arteries.

Aged↗
PubMed2000

A heterodimeric coiled-coil peptide pair selected in vivo from a designed library-versus-library ensemble.

Novel heterodimeric coiled-coil pairs were selected simultaneously from two DNA libraries using an in vivo protein-fragment complementation assay with dihydrofolate reductase, and the best pair was biophysically characterized. We randomized the interface-flanking e and g positions to Gln, Glu, Arg or Lys, and the core a position to Asn or Val in both helices simultaneously, using trinucleotide codons in DNA synthesis. Selection cycles with three different stringencies yielded sets of coiled-coil pairs, of which 80 clones were statistically analyzed. Thereby, properties most crucial for successful heterodimerization could be distinguished from those mediating more subtle optimization. A strong bias towards an Asn pair in the core a position indicated selection for structural uniqueness, and a reduction of charge repulsions at the e/g positions indicated selection for stability. Increased stringency led to additional selection for heterospecificity by destabilizing the respective homodimers. Interestingly, the best heterodimers did not contain exclusively complementary charges. The dominant pair, WinZip-A1B1, proved to be at least as stable in vitro as naturally occurring coiled coils, and was shown to be dimeric and highly heterospecific with a K(D) of approximately 24 nM. As a result of having been selected in vivo it possesses all characteristics required for a general in vivo heterodimerization module. The combination of rational library design and in vivo selection presented here is a very powerful strategy for protein design, and it can reveal new structural relationships.

Amino Acid Sequence↗
PubMed2000

Expression of endothelial cell adhesion molecules on heart valves: up-regulation in degeneration as well as acute endocarditis.

Inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha), as well as shear stress, cause endothelial cells (ECs), to undergo not only functional alterations but also structural reorganizations, which contribute to vascular leakage. Like ECs of the human aorta, ECs on heart valves are exposed to extreme shear stress. However, while ECs expression of cell adhesion molecules (CAMs) in large vessels has been widely studied, it seems that there are no such studies on ECs of heart valves, although this knowledge might be important for our understanding of the aetiological aspects of local inflammatory responses. Using immunohistochemistry, this study characterized the CAM expression of ECs on degenerative, mostly calcified heart valves and on heart valves with florid endocarditis. As expected, the constitutively expressed molecules (ICAM-1, CD34, CD31) were found both on degenerative and on inflamed valves. Furthermore, marked expression of E-selectin and VCAM-1 was found not only on inflamed valves, but also on larger portions of the degenerative valves with no morphological evidence of inflammation. This striking finding might help to explain why patients with fibrotic heart valves are susceptible to recurrent endocarditis. Why the endothelial activation markers E-selectin and VCAM-1 are expressed on degenerative heart valves requires further investigation.

Acute Disease↗
PubMed2000

Natural killer cells activate human dermal fibroblasts.

Human dermal fibroblasts (HDF) undergo activation and secrete cytokines when cocultured with T cells. Here, we identify potent activators of HDF among human peripheral CD2(+)-lymphocytes. Populations with strong HDF activating capacity consisted essentially of cells with a natural killer (NK) surface marker phenotype (CD3(-), CD4(-), CD8(-), CD56(+)). Addition of these cells to HDF resulted in rapid increase of intracellular free calcium concentrations as an early rapid cell activation signal. Upregulation of mRNA encoding for the inflammatory cytokines IL-1 beta and IL-6 as well as for chemokines IL-8 and MCP-1 was detected after cells were cocultured. Elevated concentrations of IL-6 and IL-8 were found in coculture supernatants of HDF and NK-cells. Skin-homing NK cells leaving the blood-stream during an inflammatory skin reaction might therefore represent potent activators of local inflammatory cytokine and chemokine production.

CD2 Antigens↗
PubMed2000

Pathology of small-cell lung cancer.

The morphological differentiation between small-cell and non-small-cell lung cancer has great prognostic and therapeutic significance for the patient. Malignant lung tumors are now classified according to the new 1999 WHO/IASLC classification of lung and pleural tumors. The variant of heterogeneously differentiated "combined small-cell carcinoma" can be distinguished from classical small-cell carcinoma, whereas the subtype of "intermediate cell carcinoma" is no longer used. Together with "large-cell neuroendocrine carcinomas" and typical or atypical carcinoid tumors, small-cell lung cancers are currently histogenetically categorized as neuroendocrine lung tumors. In contrast to large-cell neuroendocrine carcinoma, the immunohistochemical demonstration of neuroendocrine differentiation is not a prerequisite for the diagnosis of small-cell lung cancer. Although electron-microscopical, immunohistochemical, and molecular-biological findings have considerably increased our understanding of the pathogenesis and progression of malignant lung tumors, routine pathological-anatomical diagnostics are still decisively based on light-microscopical evaluation of tissue samples.

Carcinoma, Small Cell↗
PubMed2000

[Malignant mesothelioma of the pleura, pericardium and peritoneum. 1: Etiology, pathogenesis, pathology].

The incidence of primary malignant neoplasms of the pleura, the pericardium and the peritoneum in Germany has been rising since about the mid-1980s. A continuing rise is expected until about 2020, predominantly due to the peak of asbestos processing in Germany between 1965 and 1980. About 90% of the mesotheliomas stored in the files of the German Mesothelioma Registry in Bochum are asbestos related and therefore possibly due to occupational exposure that may be compensated by the professional associations. More than 500 mesotheliomas annually can be diagnosed in the German Mesothelioma Registry. In this first part of the series on mesotheliomas, current concepts on etiology and pathogenesis as well as diagnostic procedures and standards are discussed. At the present, specific chromosomal or genetic defects that constantly give rise to a mesothelioma are not known. The initiation and progression of malignant mesotheliomas is a highly complex mechanism that is based on individual genetic alterations. A reliable diagnosis is the basis for therapeutic, prognostic and medicolegal consequences; in general, it can be achieved by thoracoscopic inspection with selected biopsy. Surgery may gain a more important role in the therapy of malignant tumors of serosal membranes not only in palliative, but also in potential curative approaches if the diagnosis can be made at earlier tumor stages.

Animals↗
PubMed2000

[Changes in differentiation of small cell lung cancer after chemotherapy].

We reexamined biopsy and resection specimens from seven patients with histologically established primary diagnosis of small-cell lung cancer (SCLC) which showed previously undetected adenocarcinomatous differentiation after chemotherapy. Adenocarcinoma was diagnosed in the same part of the lung as was SCLC before treatment in five cases and in contralateral location in two. Two tumors showed heterogeneous differentiation with small-cell and adenocarcinomatous components, and five had only adenocarcinoma. The interval between histological evidence of SCLC and adenocarcinoma was 3 months-5 years. From the specific findings in the respective patients we can offer two possible explanations for changing differentiation in SCLC after chemotherapy: (a) a primarily heterogeneously differentiated tumor with selection of adenocarcinomatous component under chemotherapy, and (b) an independently developed adenocarcinoma after successful chemotherapy of SCLC, as patients with treated SCLC are known to have an increased risk of non-SCLC. However, therapy-induced alteration of differentiation seems much more unlikely. These findings should be considered in diagnosis and therapy of SCLC to allow early and appropriate reaction to non-SCLC components.

Adenocarcinoma↗
PubMed2000

[Pathology and molecular biology of lung cancer].

Therapy and prognosis of lung cancer depend crucially on tumor size, tumor stage, and the histomorphological tumor type at the time of primary diagnosis. A tumor weighing only 1 g and barely detectable by clinical examination consists of about 1 x 10(9) tumor cells. The primary histological diagnosis is generally based on small biopsies 1-2 mm in diameter, which allow the assessment of only a few up to some hundred tumor cells in a section of 4 microns. Until 20 years ago light microscopic and histochemical investigations were the basis for sophisticated morphological tumor diagnosis. In recent years electron microscopy, immunohistochemistry, cytometry, and molecular biology have extended our knowledge of the complex tumor biology, with the range of phenotypes and genotypes indicating enormous tumor heterogeneity. The value, expressiveness, and prognostic importance of these laborious and expensive techniques must be examined in studies, keeping in mind new aspects of tumor classification. Histological and cytological findings are still the decisive basis for the primary diagnosis of the pathologist in any given case.

Biopsy↗
PubMed2000

[Sideroelastosis of pulmonary vessels after welder dust exposure].

Sideroelastosis pulmonum was first described by Ceelen (1931) and Gellerstedt (1939), mentioning an idiopathic type, but also vascular alterations in chronic pulmonary congestion. We analysed the question wether secondary sideroelastosis can be demonstrated also in lungs after previous welder dust exposure. Lung samples of 43 patients and deceased with various exposure periods to welder dust were investigated. On each sample, light microscopical, scan electron microscopical and energy dispersive x-ray micro analyses (EDX) were performed. In six samples (14%) vascular alterations in the area of denaturated elastic fibres with siderophilic "impregnation" were seen, corresponding to the features described by von Ceelen and Gellerstedt. Giant cell or granulomatous reactions, however, were present only in exceptional cases. This phenomenon was seen mostly in cases of marked local siderin deposits and reactive fibrosis. Using EDX, a number of metals characteristic for welder dust (Al, Ti, Cr, Ni) as well as iron were found in siderophages. No other metal than iron was detected in siderophilic elastic fibres using EDX. Causal pathogenetically, a correlation between increased iron uptake connected with welding particles and sideroelastosis of the vessel walls has to be established. However, in formal pathogenesis, other factors such as local perfusion disturbances due to fibrotic processes after exposure to harmful substances must be taken into consideration.

Dust↗
PubMed2000

Computed chest tomography in an animal model for decompression sickness: radiologic, physiologic, and pathologic findings.

This study was conducted to investigate the early pulmonary effects of acute decompression in an animal model for human decompression sickness by CT and light microscopy. Ten test pigs were exposed to severe decompression stress in a chamber dive. Three pigs were kept at ambient pressure to serve as controls. Decompression stress was monitored by measurement of pulmonary artery pressure and arterial and venous Doppler recording of bubbles of inert gas. Chest CT was performed pre- and postdive and in addition the inflated lungs were examined after resection. Each lung was investigated by light microscopy. Hemodynamic data and bubble recordings reflected severe decompression stress in the ten test pigs. Computed tomography revealed large quantities of ectopic gas, predominantly intravascular, in three of ten pigs. These findings corresponded to maximum bubble counts in the Doppler study. The remaining test pigs showed lower bubble grades and no ectopic gas by CT. Sporadic interstitial edema was demonstrated in all animals--both test and control pigs--by CT of resected lungs and on histologic examination. A severe compression-decompression schedule can liberate large volumes of inert gas which are detectable by CT. Despite this severe decompression stress, which led to venous microembolism, CT and light microscopy did not demonstrate changes in lung structure related to the experimental dive. Increased extravascular lung water found in all animals may be due to infusion therapy.

Acute Disease↗