Biomedical subjects
Publications and source records attributed to Thomas Bartsch.
We establish a hierarchical ordering of periodic orbits in a strongly coupled multidimensional Hamiltonian system. Phase space structures can be reconstructed quantitatively from the knowledge of periodic orbits alone. We illustrate our findings for the hydrogen atom in crossed electric and magnetic fields.
A time-dependent no-recrossing dividing surface is shown to lead to a new criterion for identifying reactive trajectories well before they are evolved to infinite time. Numerical dynamics simulations of a dissipative anharmonic two-dimensional system confirm the efficiency of this approach. The results are compared to the standard fixed transition state dividing surface that is well-known to suffer from recrossings and therefore requires trajectories to be evolved over a long time interval before they can reliably be classified as reactive or nonreactive. The moving dividing surface can be used to identify reactive trajectories in harmonic or moderately anharmonic systems with considerably lower numerical effort or even without any simulation at all.
BACKGROUND: For many patients with severe peripheral arterial occlusion disease (PAOD) an interventional or surgical treatment is not feasible. The regenerative potential of adult autologous mononuclear stem cells could contribute to neoangiogenesis. PATIENTS AND METHODS: Ten patients with severe PAOD were included. The walking distance was < 200 m and no interventional or surgical treatment was possible. After harvesting of 80 ml of bone marrow the mononuclear cell fraction was separated. Thereafter, intraarterial (10 ml into the common femoral artery) and intramuscular (5 ml into the muscles of the thigh and the lower leg) transplantation of the cell suspension was performed. RESULTS: After 2 months the walking distance was enhanced significantly in all patients. Furthermore, a significant improvement of ankle-brachial index at rest, capillary-venous oxygen saturation and parameters of venous occlusion plethysmography was seen. No complications or side effects could be monitored. CONCLUSION: These results demonstrate, that the combined intraarterial and intramuscular transplantation of autologous adult bone marrow stem cells leads to a significant improvement of perfusion indices in patients with severe PAOD.
BACKGROUND AND PURPOSE: Bone marrow-derived circulating progenitor cells (BM-CPCs) are mobilized in adult peripheral blood (PB) during the acute myocardial infarction (AMI) period and contribute to the regeneration of infarcted myocardium. In this study, the influence of physical training on the mobilization and the migratory activity of the BM-CPCs as well as on the left ventricular function (LVEF) after AMI was examined. PATIENTS AND METHODS: 26 patients with AMI were analyzed in two groups. The first group comprised 17 patients with standardized exercise training for 3 weeks 14 +/- 4 days after AMI, the second group nine control subjects without exercise training. PB concentrations of CD34/45+ and CD133/45+ were measured by FACS. The migratory activity of BM-CPCs was analyzed by migration assay. B-type natriuretic peptide (BNP) in PB and the functional investigations spiroergometry (VO2 and PaO2) and stress echocardiography (LVEF) were determined in both groups. RESULTS: A significant increase in both concentrations, CD34/45+ and CD133/45+, as well as in migratory capacity of BM-CPCs was found after 3 weeks of exercise training, which was significantly decreased 3 months after completion of exercise training. No significant difference was observed in the control group without exercise training. In the functional investigations a significant increase in VO2 as well as PaO2 was shown spiroergometrically after exercise training. There was no difference in stress echocardiographic LVEF at rest in both groups. On the other hand, interestingly, the findings showed that the increase of LVEF at peak stress was significantly higher after exercise training as compared to the control group. Moreover, a significant decrease in BNP values was found after exercise training as well as 3 months after AMI. No difference was found in the control group. CONCLUSION: This study demonstrates that exercise training for 3 weeks after AMI leads to a significant mobilization as well as increase of functional activation of BM-CPCs in humans. Moreover, regular exercise training might contribute to the positive effects on the regenerative potency after AMI.
Classical transition state theory (TST) is the cornerstone of reaction-rate theory. It postulates a partition of phase space into reactant and product regions, which are separated by a dividing surface that reactive trajectories must cross. In order not to overestimate the reaction rate, the dynamics must be free of recrossings of the dividing surface. This no-recrossing rule is difficult (and sometimes impossible) to enforce, however, when a chemical reaction takes place in a fluctuating environment such as a liquid. High-accuracy approximations to the rate are well known when the solvent forces are treated using stochastic representations, though again, exact no-recrossing surfaces have not been available. To generalize the exact limit of TST to reactive systems driven by noise, we introduce a time-dependent dividing surface that is stochastically moving in phase space, such that it is crossed once and only once by each transition path.
OBJECTIVES: Stem cell therapy may be useful in chronic myocardial infarction (MI); this is conceivable, but not yet demonstrated in humans. BACKGROUND: After acute MI, bone marrow-derived cells improve cardiac function. METHODS: We treated 18 consecutive patients with chronic MI (5 months to 8.5 years old) by the intracoronary transplantation of autologous bone marrow mononuclear cells and compared them with a representative control group without cell therapy. RESULTS: After three months, in the transplantation group, infarct size was reduced by 30% and global left ventricular ejection fraction (+15%) and infarction wall movement velocity (+57%) increased significantly, whereas in the control group no significant changes were observed in infarct size, left ventricular ejection fraction, or wall movement velocity of infarcted area. Percutaneous transluminal coronary angioplasty alone had no effect on left ventricular function. After bone marrow cell transplantation, there was an improvement of maximum oxygen uptake (VO2max, +11%) and of regional 18F-fluor-desoxy-glucose uptake into infarct tissue (+15%). CONCLUSIONS: These results demonstrate that functional and metabolic regeneration of infarcted and chronically avital tissue can be realized in humans by bone marrow mononuclear cell transplantation.
BACKGROUND: The diabetic foot mainly depends on painless pressure lesions, which are based on diabetic polyneuropathy and microangiopathy. In these cases the regenerative potential of adult autologous mononuclear stem cells could serve as causal therapy. HISTORY AND CLINICAL FINDINGS: A 63-year-old patient with long-lasting type 2 diabetes mellitus suffers from a reduced walking distance of 200 m and a therapy-refractory ulcer at the right ball of the great toe. Therefore, the authors have decided to perform a combined intraarterial and intramuscular transplantation of stem cells into the right limb for the first time on this disease. THERAPY AND RESULTS: After harvesting of bone marrow the mononuclear cell fraction was separated (157 x 10(6) cells). Thereafter, the fractional intraarterial and intramuscular transplantation of the cell suspension was performed (10 ml each). Already 8 weeks later, the ulcer healed completely, after 6 months the walking distance increased by > 100%, on venous occlusion plethysmography the arterial blood circulation at rest increased by 23% and the reactive hyperemia by 56%. CONCLUSION: The combined intraarterial and intramuscular transplantation of autologous bone marrow stem cells could constitute a novel, clinically feasible and safe therapy for patients with diabetic foot syndrome. The success of this approach may be ascribed to microangiogenesis and to an anti-inflammatory effect of the transplanted stem cells.
Transition state theory overestimates reaction rates in solution because conventional dividing surfaces between reagents and products are crossed many times by the same reactive trajectory. We describe a recipe for constructing a time-dependent dividing surface free of such recrossings in the presence of noise. The no-recrossing limit of transition state theory thus becomes generally available for the description of reactions in a fluctuating environment.