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F Neumann

Publications and source records attributed to F Neumann.

At least 37 records · Page 2Linked to original sources
PubMed1999

A three-dimensional model for arterial tree representation, generated by constrained constructive optimization.

The computational method of constrained constructive optimization (CCO) has been generalized in two important respects: (1) arterial model trees are now grown within a convex, three-dimensional piece of tissue and (2) terminal flow variability has been incorporated into the model to account for the heterogeneity of blood flow observed in real vascular beds. Although no direct information from topographic anatomy enters the model, computer-generated CCO trees closely resemble corrosion casts of real arterial trees, both on a visual basis and with regard to morphometric parameters. Terminal flow variability was found to induce transitions in the connective structure early in the trees' development. The present generalization of CCO offers--for the first time--the possibility to generate optimized arterial model trees in three dimensions, representing a realistic geometrical substrate for hemodynamic simulation studies. With the implementation of terminal flow variability the model is ready to simulate processes such as the adaptation of arterial diameters to changes in blood flow rate or the formation of different patterns of angiogenesis induced by changing needs of blood supply.

Algorithms↗
PubMed1999

Dentin dysplasia type I--a case report.

A case report on dentin dysplasia type I, a congenital disease (autosomal dominant gene defect) affecting deciduous and permanent teeth, is depicted including representations of clinical and histological features, X-ray and CT-findings. Therapy includes extraction of all teeth, ectomization of cystic alteration, revision of paranasal sinus. Aesthetic and functional rehabilitation by means of insertion of a complete denture was achieved.

Adult↗
PubMed1999

Retrospective analysis of the frequency and recognition of adverse drug reactions by means of automatically recorded laboratory signals.

AIMS: To estimate the frequency of adverse drug reactions (ADRs) identified through the use of automatic signals generated from laboratory data (ALS) in hospitalised patients. To determine the frequency of spontaneous recognition of these ADRs by the attending physicians and to assess the potential value of ALS for detection of ADRs. METHODS: Laboratory results of patients hospitalised in a nine bed medical ward were automatically recorded over a period of 17 months. Values exceeding defined boundaries were used as ALS. Charts of every third patient were analysed retrospectively with regard to adverse drug related reactions and causality was evaluated as well as whether the ADR had been recognised during the period of hospitalisation. RESULTS: The charts and ALS of 98 patients were analysed. In 18 cases a drug-related adverse reaction was probable. Awareness to the reaction by the treating physicians was evident in 6 out of these 18 ADRs. Approximately 80% of the ADRs were considered predictable. Three ADRs were regarded as serious. CONCLUSIONS: Adverse drug reactions are common and often preventable. Only one third of ADRs which could have been detected through ALS were recognised by the attending physicians. An increased doctor's awareness of the frequency of drug related abnormal laboratory results by means of ALS is likely to increase the recognition rate of ADRs and might help to prevent them.

Adult↗
PubMed1999

Exploitation of the antibody repertoire of cancer patients for the identification of human tumor antigens.

The screening of tumor-derived expression libraries for antigens which are recognized by high titered IgG antibodies present in autologous sera of the cancer patients by SEREX (serological identification of antigens by recombinant expression cloning) allows for the systematic identification of antigens in human cancers. SEREX has led to the definition of a plentitude of new tumor antigens in many different tumor entities. The majority of the antigens are encoded by hitherto unknown genes and can be grouped into different classes of antigens. The abundance of serologically defined human tumor antigens is not only of relevance for tumor biology and serodiagnosis of cancer, but also facilitates the identification of proteins recognized by tumor specific T lymphocytes, thus providing a molecular basis for polyvalent peptide-based and gene-therapeutic vaccine strategies in a wide variety of human neoplasms.

Antibodies, Neoplasm↗
PubMed1998

Morphometry of human coronary arterial trees.

BACKGROUND: Some groups, including ours, have been generating arterial tree models using constrained constructive optimization (CCO). Arterial trees have been grown to arbitrary resolution without input of anatomical data. We performed this study to learn about the shortcomings that might have resulted from neglecting the anatomical data in CCO models. METHODS: In a total of 450 segments obtained from 4 human cast hearts, the ratio ofbifurcating daughter segment radii (O < Sbif = r(2)/r(1) < 1) was examined, which corresponds to the split of the total flow of the mother segment. For any complete bifurcation, where the radii of the parent segments and the radii of daughters were known, the area expansion ratio was computed (Aexp = [r(1)2 + r(2)2]/r(parent)2). RESULTS: The bifurcating ratio was found to be distributed in a nonnormal fashion, with a median of 0.76. The average area expansion ratio Aexp, characterizing the change of cross-sectional area of the vasculature from proximal to distal, was 0.93+/-0.26. The 'rate of branching' (d(i)/(d(0)) was defined by the segment diameter relative to the diameter of the root segment. Averaging the rate of branching over segments within each bifurcation level resulted in a decreasing function of bifurcation level. CONCLUSIONS: This article provides new experimental data on branching geometry of coronary arteries (i.e., the trees evaluated in this study are purely delivering rather than conveying). Based on these facts, we suggest that the analytical bifurcation law in CCO might be replaced by the bifurcation rule obeyed on a stochastic basis only.

Anthropometry↗
PubMed1998

Analysis of left ventricular function after emergency coronary artery bypass grafting for life-threatening ischaemia following primary revascularization.

OBJECTIVE: Severe ischemic injury in the first few hours following primary revascularization necessitates acute reoperation. To study the effect of emergency coronary artery bypass grafting, we followed 18 patients for up to 8 years, relating their changes of global and regional myocardial function during the acute event and after secondary revascularization to final outcome. METHODS: A total of 16 patients with coronary artery bypass grafting (CABG) and 2 PTCA were treated for coronary heart disease between 1989 and 1993 and experienced life-threatening ischemic events (94% cardiogenic shock, 39% ventricular fibrillation, 67% ischemic electrocardiograph (ECG) changes) within 2.3+/-1.6 h after primary revascularization. Reoperation was carried out 1.0+/-1.3 h after the occurrence of acute ischemia. Serial echoes were obtained during the acute event and after reoperation as well as during the follow-up period. RESULTS: Of the 18 patients, 8 are currently alive, 5 died within 30 days and 4 within the 1st year. There was one late death 5 years after surgery. Global and regional wall motion was evaluated using short axis views of transesophageal echoes taken during the acute event and after secondary revascularization, and compared with transthoracic echoes in long-term survivors up to 5 years after surgery. During the acute event left ventricular ejection fraction (LVEF) was reduced in 83% of the patients and improved significantly after reoperation (chi2 = 11.74, df= 2, P < 0.01). As to regional wall motion, 50% of the segments in non-revascularized areas remained abnormal. Regional wall motion after reoperation was significantly better in the surviving patients compared with patients dying in the post-operative course (chi2 = 6.23, df= 1, P < 0.05). The revascularization score ( > 75%) of abnormal contracting segments during the acute ischemic event was a significant determinant for long-term survival. CONCLUSION: We conclude that patient outcome is determined by the severity of regional wall motion abnormality during the acute ischemic event, the aggressiveness of the attempt to revascularize these perfusion territories and their improvement after revision. Long-term survival reflects, therefore, the extent of emergency revascularization and therefore the ability to identify ischemic perfusion territories for surgical strategy planning.

Aged↗
PubMed1998

Outer radius-wall thickness ratio, a postmortem quantitative histology in human coronary arteries.

Although the anatomy, histology and pathology of human coronary arteries have been studied extensively, little is known about the functional relationship between vessel radius and wall thickness. It is the purpose of this study to present detailed measurements and to describe this relationship covering the range from the feeding coronary artery to the arterioles. Human hearts of 10 adults less than 36 +/- 3 years old were investigated immediately postmortem. Ten cubic tissue blocks, measuring about 10 mm in length on each side, were dissected from the left ventricular wall. After fixation by immersion, 15-microm sections were prepared and outer and inner perimeters of 52 arterial segments were digitalized. Vessel radius and wall thickness were calculated and plotted to show their relationship over the whole range of vessel calibers. Outer vessel radii ranged from 100 to 3,000 microm and wall thickness from 80 to 800 microm. Plotting the outer vessel radius against the wall thickness, the data points were found to cluster around a straight line. A significant correlation between the two parameters was found (R2 = 0.79). This mathematical correlation and the good agreement of the presented results with data from other species indicate a common physiologic concept.

Adult↗
PubMed1998

Biochemical markers of perioperative myocardial ischemia in patients with coronary artery bypass grafting.

Aims of the study: The evaluation of significant perioperative ischemic processes after coronary artery bypass grafting from postoperative ECG, creatine kinase (CK) and CK iso-enzyme MB remains unreliable and, hence, insufficient. Additional, early available biochemical markers could improve the diagnostics of ischemia. Methods: In 86 patients with multiple vessel disease, activity of serum CK and CK-MB as well as mass of CK-MB, myoglobin and troponin-T were analyzed before and after surgery. Twelve-lead electrocardiograms were evaluated before surgery, 3h postoperatively, and before discharge from hospital. Results: In patients with signs of perioperative ischemia in the 3-hour ECG, primary postoperative peak values of myoglobin and CK were distinctly higher than in patients without signs of ischemia, with median values of 1437 ng/ml vs. 986 ng/ml for myoglobin and of 632 U/l vs. 481 U/l (n.s.) for CK. Sensitivity and specificity of myoglobin were 64 % and 69 %, followed by CK with 61 % and 62 %, respectively. Conclusions: Myoglobin, indicating the risk of perioperative ischemia approximately 45 minutes after declamping of the aorta, is suggested as a candidate for early available routine monitoring.

Journal Article↗
PubMed1997

Anatomical variability and functional ability of vascular trees modeled by constrained constructive optimization.

The aim of this study was to investigate the extent that functional capability of vascular trees is related to anatomical variability. To these ends we used the method of Constrained Constructive Optimization (CCO) to generate optimized computer models of coronary arterial trees. All these model trees were optimized according to the same principle under equal boundary conditions of pressures and flows. However, by stochastically casting the locations of the terminal segments, different tree structures were generated, each of which conformed to the same boundary conditions. The structural variability of these models was interpreted as the correlate of the anatomical variability found in real arterial trees. The advantage that computer model trees are known in numerical detail was exploited to perform comprehensive and exact classifications of all segments into bifurcation levels, STRAHLER orders and composite vessels, and to compute the area expansion ratio. The unexpected result was that, despite striking visual differences in anatomical structure, the model trees were almost identical with regard to functional performance. We conclude that models optimized on the computer for a given perfusion task show little differences in their morphometric parameters even if they differ considerably regarding the course of the large vessels.

Computer Simulation↗
PubMed1997

Constitutive expression of human ribosomal protein L7 arrests the cell cycle in G1 and induces apoptosis in Jurkat T-lymphoma cells.

Protein L7 is involved in translational control in eucaryotic cells as indicated by its association with ribosomes, its capability to inhibit specifically the cell-free translation of distinct mRNAs, and its interference with the synthesis of two major nucleus-associated proteins in L7 cDNA-transfected Jurkat T-lymphoma cells [F. Neumann et al. (1995) Nucleic Acids Res. 23, 195]. In this report we show that the constitutive expression of protein L7 in Jurkat cells leads to an arrest in G1 of the cell cycle and induces apoptosis as a consequence of cell-to-cell contact. Treatment of the L7 transfectants with the inhibitor of translation cycloheximide, at doses which do not affect untransfected cells, enhances their sensitivity to the induction of apoptosis. These results suggest that L7 can interfere with the translation of proteins which control cell cycle progression and/or the initiation of the apoptotic pathways.

Apoptosis↗
PubMed1997

Distribution and structure of vagal afferent intraganglionic laminar endings (IGLEs) in the rat gastrointestinal tract.

Intraganglionic laminar endings (IGLEs) are special terminal structures of vagal afferent fibers and have been demonstrated in the myenteric plexus of esophagus and stomach. In order to quantitatively map their presence and distribution over the entire gastrointestinal tract, including the small and large intestines, vagal afferents were anterogradely labeled in vivo by microinjections of the fluorescent carbocyanine dye DiI into the left or right nodose ganglion of adult male rats. In the most successfully labeled cases the highest density of IGLEs was found in the stomach, with about half to one-third of the myenteric ganglia receiving at least one IGLE. The proportion of myenteric ganglia innervated by IGLEs decreased in the small intestine; however, because of its large surface area this gut segment was estimated to contain the highest total number of IGLEs. Both the cecum and colon also contained significant numbers of IGLEs. In the stomach, this vagal afferent innervation by IGLEs was more or less lateralized, with less than 20% of labeled IGLEs found on the contralateral side with respect to the injection. The left/ventral vagus contributed a larger proportion of IGLEs to the proximal duodenum, while the right/dorsal vagus contributed a larger proportion of IGLEs to the distal duodenum and jejunum. Laser scanning confocal microscopy on select specimens revealed further structural details. The parent axon typically formed two or more branches that flanked the ganglia laterally, and in turn produced numerous highly arborizing laminar terminal branches that covered one or both flat sides of the ganglion in a dome-like fashion. The similar distribution patterns and structural details suggest a uniform function for the IGLEs throughout the gastrointestinal tract, but there is as yet no clear proof for any of the hypothesized roles as specialized mechanosensors or local effector terminals.

Animals↗
PubMed1997

Limited bifurcation asymmetry in coronary arterial tree models generated by constrained constructive optimization.

Models of coronary arterial trees are generated by the algorithm of constrained constructive optimization (CCO). In a given perfusion area a binary branching network of straight cylindrical tubes is generated by successively adding terminal segments to the growing structure. In each step the site of connection is chosen according to an optimization target function (total intravascular volume), and in any stage of development the tree fulfills physiologic boundary conditions (constraints involving pressures, flows and bifurcation rules). CCO generates structures which in many aspects resemble real coronary arterial trees, except for very asymmetric bifurcations, occurring when a large branch gives off a tiny terminal segment. In the present work we evaluate an additional constraint within CCO, namely imposing a limit on the asymmetry of bifurcations during the construction process. Model trees are grown with different limits imposed, and the effects on structure are studied both phenomenologically and via statistical descriptors. As the limit to asymmetry is tightened, blood is conveyed to the perfusion sites via detours rather than directly and the comparison with measured data shows that the structure to change from a conveying to a delivering type of function. Simultaneously total intravascular volume, surface and sum of segments' lengths increase. It is shown why and how local bifurcation asymmetry is able to determine the global structure of the optimized arterial tree model. Surprisingly, the pressure profile from inlet to terminals, being a functional characteristic, remains unaffected.

Algorithms↗
PubMed1996

Mass spectrometric identification of leucine zipper-like homodimer complexes of the autoantigen L7.

The eucaryotic protein L7 has been shown to associate in the cytoplasm with the large subunit of ribosomes and to interact specifically with as yet unknown cognate sites of mRNA, thereby inhibiting cell-free translation (Neumann, F., Hemmerich, P., von Mikecz, A., Peter, H. H., and Krawinkel, U.(1995) Nucleic Acids Res. 23, 195-202). The N-terminal region of protein L7 contains a sequence motif similar to the leucine zipper domain of eucaryotic transcription factors, which promotes dimerization through alpha-helical coiled coil formation. Using electrospray-ionization mass spectrometry as a method of molecular specificity, we have directly identified the dimeric complexes comprising the leucine zipper-like region of protein L7 and have determined the dissociation constant of L7 homodimers in an affinity binding assay. We also demonstrate the high content of alpha-helicity of the dimer by circular dichroism spectra and computer-based structure simulation and show that the leucine zipper region of protein L7 is fully sufficient to mediate the inhibition of cell-free mRNA translation. A structural basis for the function of L7 to regulate translation is discussed. From the present results we conclude that L7 interacts with double stranded mRNA in a similar fashion as leucine zipper proteins with specific cognate sites on double stranded DNA.

Amino Acid Sequence↗
PubMed1996

Structural quantification and bifurcation symmetry in arterial tree models generated by constrained constructive optimization.

Arterial tree models are generated by Constrained Constructive Optimization according to minimum intravascular volume. These models, which have been shown to adequately reproduce pressure profiles and branching angles, are analysed topologically and geometrically in order to investigate how structure influences the functional capabilities. Therefore, the number of bifurcation levels and STRAHLER orders was evaluated for the complete trees as well as for subtrees of all possible sizes. Bifurcation symmetry, being a particular aspect of structure, was found to be higher in the smaller than in the larger subtrees. This confirms a more delivering type of function for the small subtrees, as expected from intuitive arguments. Conversely, lower symmetry in larger subtrees relates to their conveying type of function. Moreover, different shapes of the tissue to be perfused lead to different symmetry properties of optimized tree models.

Algorithms↗
PubMed1996

Perioperative myocardial injury with different modes of antegrade and retrograde cardioplegic delivery.

The effect of three cardioplegic protocols on perioperative myocardial injury was studied in 62 coronary artery bypass grafting (CABG) patients randomized into three groups with either antegrade or retrograde cold blood cardioplegia, or coronary sinus occlusion during antegrade supply. During the aortic cross-clamp time anterior and posterior septal temperatures were recorded, indicating the distribution of cardioplegic solution within the myocardium. Serum creatine kinase (CK), CK-isoenzyme MB and myoglobin as well as 12-lead electrocardiograms (ECG) were analyzed. Statistical analysis showed no effect of the cardioplegic protocol, whereas the patient's preoperative status, aortic cross-clamp time and intraoperative myocardial temperature had significant (P < 0.05) effects on immediate postoperative CK and CK-MB enzyme release. Creatine kinase-MB peak values were significantly increased in patients with major vessel disease and reduced left ventricular function (92 +/- 53 U/l versus 67 +/- 25 U/l). Both CK and CK-MB values were significantly higher in patients with aortic cross-clamp times of more than 1 h than in patients with shorter clamping times (661 +/- 188 and 78 +/- 40 U/l versus 500 +/- 200 and 57 +/- 24 U/l). Patients with 22 +/- 3 degrees C myocardial temperature before terminal cardioplegia had significantly elevated CK as compared to patients with temperatures of 15 +/- 2 degrees C (665 +/- 185 U/l versus 510 +/- 211 U/l). However, enzyme peak values had only poor predictive power for postoperative ECG changes, suggesting that enzyme peaks were not necessarily a sign of perioperative ischemia. Patients with major vessel disease and reduced myocardial function, with aortic cross-clamp time of more than 1 h and/or inadequate intraoperative myocardial cooling may be highly susceptible to global ischemia and operative procedures, and therefore show elevated peak enzyme levels shortly after surgery. In contrast, elevated myoglobin peaks within 1 h after aortic declamping were significantly correlated to perioperative signs of transient ischemia (P < 0.02).

Aged↗
PubMed1996

[Acute renal failure--differential diagnosis and therapeutic procedure].

Acute renal failure accompanied by an increase in retention parameters and oligo-anuria is a common medical problem. The most important medical task in nephrology is a fast diagnostic differentiation between prerenal-, renal- and postrenal failure. Using simple techniques such as case history, medical examination, ultrasound and specific analysis of serum and urine, it is possible to obtain a relatively certain diagnosis. Radiographic techniques with radiocontrast agents are contraindicated because of nephrotoxic side effects. The treatment of acute renal failure is based on the underlying disease. Apart from symptomatic treatment, there are only very few medications available to improve the excretory kidney function and diuresis. Complications like hyperkalemia, hyperhydration, metabolic acidosis and uremia require early renal replacement therapy. Especially in cases of extreme hyperkalemia, an immediate beginning of therapy is important. In the medical practice, emphasis should be placed upon the prevention of renal failure.

Acute Kidney Injury↗
PubMed1995

Human ribosomal protein L7 inhibits cell-free translation in reticulocyte lysates and affects the expression of nuclear proteins upon stable transfection into Jurkat T-lymphoma cells.

Eucaryotic ribosomal protein L7 carries a 'Basic-Region-Leucine-Zipper (BZIP)'-like region which mediates high-affinity binding to mRNA and 28S rRNA and formation of homodimers [P. Hemmerich et al. (1993) Nucleic Acids Res. 21, 223-231). Its biological function is unknown as yet and no direct L7-equivalent in procaryotes has been found. In this report we show that eucaryotic L7 specifically inhibits the cell-free translation of reporter mRNAs. The interaction of L7 with mRNA is an essential step in this reaction which is inhibitable by antibodies directed against the BZIP-like region of L7, and by competitors of mRNA binding. L7-mediated inhibition of cell-free translation of polyA+ RNA from Jurkat T-lymphoma cells is selective in that the synthesis of a major 46 kD protein is suppressed. Upon stable transfection of L7 cDNA into Jurkat lymphoma cells two major proteins disappear, namely one nuclear protein and one which associates with the nucleus. Our data suggest a regulatory role of protein L7 in the eucaryotic translation apparatus.

Amino Acid Sequence↗