Urethral erosion of tension-free vaginal tape.
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Female↗
Biomedical subjects
S C Müller
Publications and source records attributed to S C Müller.
Light-triggered pH banding profile in Chara cells revealed with a scanning pH microprobe and its relation to self-organization phenomena.
When exposed to light, Characean cells develop a pattern of alternating alkaline and acid bands along the cell length. The bands were identified with a tip-sensitive antimony pH microelectrode positioned near one end of Chara internode at a distance of 50-100 microm from the cell wall. The stage with Chara cell was moved along its longitudinal axis at a computer-controlled speed (100 or 200 microm s(-1)) relative to the pH probe over a distance of 50 mm. Under sufficient uniform illumination of the cell (from 100 to 2.5 Wm(-2)), the homogeneous pH distribution becomes unstable and a banding pattern is formed, the spatial scale of which decreases with the light intensity. If the cell is locally illuminated, bands are formed only in the region of illumination. It is shown that the inhibition of cyclosis by cytochalasin B leads to the disappearance of the banding pattern. The addition of ammonium (weak base) inhibited the banding pattern, whereas acetate (weak acid) alleviated the inhibitory effect of ammonium and restored the pH banding. A model explaining the observed phenomena is formulated in terms of proton concentration outside and bicarbonate concentration inside the cell. It contains two diffusion equations for the corresponding ions with nonlinear boundary conditions determined by ion transport processes across the cell membrane. The model qualitatively explains most of the experimental observations. It describes the dependence of the pattern characteristics on the light intensity and reveals the role of cyclosis in this phenomenon.
Antimony↗
Spiral wave dynamics under feedback derived from a confined circular domain.
Spiral waves are induced in a thin layer of the light-sensitive Belousov-Zhabotinsky reaction and controlled by a time-dependent uniform illumination. The intensity of the illumination is taken to be proportional to the average wave activity observed within a circular domain of the reaction layer. Stabilization and destabilization of spiral waves, as well as the existence of additional types of attractors, are demonstrated. A simple mathematical description is proposed in order to explain the existence of the attractors and the dependence of their size on the time delay in the feedback loop.
Journal Article↗
Transitions between orbits of resonance attractors for spiral waves.
Spiral waves rotating in a thin layer of the light-sensitive Belousov-Zhabotinsky reaction can be controlled by the application of short light pulses at instants corresponding to the passage of a wave front through a measuring point. It is shown that such a feedback results in a drift of the spiral wave core along a discrete set of stable circular orbits centered at the measuring point, in good quantitative agreement with the theory of the resonance attractor recently developed. Variations of parameters in the feedback loop initiate transitions between orbits of different size. Thus a spiral wave drift can be induced along a snail-shaped trajectory with permanently growing distance from the measuring point.
Journal Article↗
Comparative study on photosynthetic activity of chloroplasts in acid and alkaline zones of Chara corallina.
A novel experimental approach has been applied to investigate the relationship between pH banding in Chara cells and photosynthetic activity of chloroplasts located in cell regions adjacent to acid and alkaline bands. The combination of pH microelectrode technique with pulse amplitude modulation (PAM) microfluorimetry enabled parallel measurements of longitudinal pH profiles and chlorophyll fluorescence yield in acid and alkaline zones of individual Chara cells. The scanning with a pH-microelectrode along the cell length revealed the light-dependent pH pattern, i.e., alternating acid and alkaline bands with pH differences as large as 2 - 3 pH units. In parallel, measurements of chlorophyll fluorescence yield under actinic light were performed using PAM microfluorometry. It was found that the effective photochemical yield of photosystem II is substantially higher in acid than in alkaline zones. The results clearly show that the banding pattern is not confined solely to the plasmalemma but is also exhibited in alternating photosynthetic performance of the underlying chloroplast layer. Apparently, the acid regions enriched with CO2 ensure sufficient flow of this substrate to the Calvin cycle reactions, thus promoting the photosynthetic rate, whereas the alkaline zones devoid of CO2 favor radiative losses of absorbed solar energy in chloroplasts.
Chloroplasts↗
Spatio-temporal dynamics in glycolysis.
During the glycolytic degradation of sugar in a thin layer of yeast extract, travelling waves of NADH and protons can be generated that carry a state of high enzymatic activity through the system. The controlled initiation of such waves with an activator of the enzyme phosphofructokinase (PFK) and the influence of various salts and co-factors on the propagation dynamics are investigated. Furthermore a first study of the dispersion of waves is presented. The experimental characterisation of this in vitro system contributes to unravelling the possible role of glycolysis for biological information processing. In this context, the provision of chemically available energy in the absence of compartmentation by glycolysis is of primary importance.
Glycolysis↗
Drugs in liver disease and during albumin dialysis -MARS.
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Anti-Bacterial Agents↗
Low urethral pressure profile--clinical implications.
The clinical impact of urethral pressure profilometry (UPP) has been a main urological topic over the past three decades. Exaggerated expectations and differing techniques with incongruent results caused a controversial appearance. However, since the UPP is the only method to measure directly aspects of the urethral closure function, all types of sphincteric urinary incontinence represent indications for this measurement. Based on long-term experience this paper aims to discuss the various complexes regarding the urethral pressure profilometry. The significance of the urethral closure function for urinary continence and the urodynamic relevance of active and passive pressure transmission are described. In addition, clinical implications in terms of therapeutic strategies to treat urinary stress incontinence with regards to a low urethral pressure profile are presented.
Female↗
pH oscillations in the hemin-hydrogen peroxide-sulfite reaction.
Oscillatory behaviour in the pH value has been observed during the oxidation of sulfite by hydrogen peroxide mediated by hemin, a well known enzyme model compound, in a continuous-flow stirred tank reactor. The dynamics of this reaction has been studied for a variety of flow rates of the reactants. As the flow rates increase, the oscillations evolve from relaxation oscillations to more complex shapes, displaying, among others, bursting behaviour. A reaction mechanism is proposed that involves the autocatalytic oxidation of HSO3- by H2O2, while slow equilibria between different pH-dependent forms of hemin account for the feedback loop which gives rise to oscillatory dynamics. It is shown in experiments that no participation of CO2 is required for oscillations to occur.
Catalysis↗
Image processing techniques applied to excitation waves in the chicken retina.
Image processing techniques are described in detail that are used to gain information about the dynamics of wave propagation in excitable media. We focus on a phenomenon called spreading depression (SD) observed in the chicken retina, but the techniques described here concern a large variety of excitable systems. Despite the impressive progress both in SD research of the past 50 years and, during nearly the same period, in the theory of self-organization of wave patterns, there is still little mutual overlap. However, the increasing demands for understanding complex systems, like neuronal tissue, require such theoretical concepts. Arguments are given why the chicken retina is a nearly perfect experimental system for assessing and further developing these concepts.
Animals↗
Improving cystine stone therapy: an in vitro study of dissolution.
OBJECTIVES: To perform an in vitro study analyzing the possibilities in therapeutic strategies for an effective treatment of cystine stones. METHODS: Artificial stones made of cystine [Bon(n)-Stones] with a ball-shaped size of 0.9 cm in diameter were used. Chemolysis of artificial cystine stones with different solvents (artificial urine, physiologic sodium chloride solution, acetylcysteine, tris-(hydroxymethylene)-aminomethane [THAM], and combinations of these) was investigated. An experimental arrangement with computer-assisted online measurement of data simulating the physiologic conditions in the upper urinary tract at varying pH values was used. RESULTS: All solutions showed a statistical improvement in the solubility of cystine stones compared with artificial urine and physiologic sodium chloride solution. The combination of THAM (pH 10) and 2% acetylcysteine was most effective (1 3.91 +/- 1.73 mg/hr) and demonstrated a 41 -fold higher ability to dissolve cystine calculi compared with artificial urine. CONCLUSIONS: Our data indicate that local chemolysis with special solutions is an effective treatment modality in cystine stone therapy.
Acetylcysteine↗
Does the migraine aura reflect cortical organization?
Individuals suffering from classical migraine report an astonishing diversity of migraine auras. A frequently reported symptom is a visual hallucination known as fortification illusion (FI). Here we demonstrate that the typical zig-zag pattern of the FI can be reproduced using experimental data of orientation maps of the primary visual cortex (V1) assuming that a continuous excitation front propagates across V1. We put forward a model in which the cortical neurons within this excitation wave are activated sufficiently to contribute to conscious perception. It is shown that the discontinuous repetitive nature of the zig-zag pattern of the FI can reflect the specific layout of visual cortical orientation maps. Additionally, dynamic features of the FI are predicted based on our model.
Animals↗
Chemolysis of artificial cystine stones (BON(N)-STONES) in vitro using a new dissolution device: first results.
BACKGROUND AND PURPOSE: The treatment of cystine stones is a clinical problem. This in vitro study was performed to establish an experimental system that enables standardized and reproducible investigations on chemolysis of cystine stones to look for an improvement of dissolution strategies. MATERIALS AND METHODS: Artificial spherical stones made of cystine (BON(N)-STONES) with a diameter of 0.9 cm were used. A new dissolution device was developed simulating the physiological conditions in the upper urinary tract with computer-assisted online measurement of data. For chemolysis of artificial cystine stones, different solvents (artificial urine, physiologic sodium chloride solution, 2 % acetylcysteine, 8.4 % sodium bicarbonate solution, THAM, and combinations) were used. RESULTS: Chemolysis is an effective tool in the management of cystine stone disease. Statistical analysis showed significant differences (p < or = 0.05) for all solutions compared with artificial urine alone. A combination of THAM at pH 10 with acetylcysteine (2%) showed a 48-fold stronger ability to dissolve cystine calculi than did artificial urine. CONCLUSION: By performing standardized in vitro investigations, new basics to improve the dissolution of cystine stones have been developed. It is recommended to use artificial stones made of cystine and a dissolution device simulating physiological conditions for investigations on chemolysis in the future.
Acetylcysteine↗
Elimination of spiral waves in cardiac tissue by multiple electrical shocks.
We study numerically the elimination of a spiral wave in cardiac tissue by application of multiple shocks of external current. To account for the effect of shocks we apply a recently developed theory for the interaction of the external current with cardiac tissue. We compare two possible feedback algorithms for timing of the shocks: a "local" feedback algorithm 11 (using an external electrode placed directly on the tissue) and a "global" feedback algorithm 22 (using the electrocardiogram). Our main results are: application of the external current causes a parametric resonant drift similar to that reported in previous model computations; the ratio of the threshold of elimination of the spiral wave by multiple shocks to the threshold of conventional single shock defibrillation in our model for cardiac tissue is about 0.5, while earlier, less realistic models predicted the value about 0.2; we show that an important factor for successful defibrillation is the location of the feedback electrode and the best results are achieved if the feedback electrode or the ECG lead is located at the boundary (or edge) of the cardiac tissue; the "local" and the "global" feedback algorithms show similar efficiency.
Algorithms↗
Influence of alkaline solutions on chemolitholysis and lithotripsy of uric acid stones. An in vitro study.
OBJECTIVES: This study was performed to look for an improvement of therapeutic strategies with regard to the treatment of uric acid stones using artificial stones made of uric acid (BON(N)-STONES) which are comparable to their natural counterparts. MATERIALS AND METHODS: Using an experimental arrangement simulating the physiological conditions in the upper urinary tract the efficacy of different alkaline solutions and artificial urine in dissolving artificial uric acid stones (BON(N)-STONES) was investigated. The dissolution of natural uric acid stones was measured and investigations on shock wave lithotripsy (SWL) combined with initial chemolytic treatment of the stones were performed. RESULTS: The efficacy of alkaline solutions, especially THAM at a pH of 10, in dissolving artificial uric acid stones was demonstrated. The investigations on SWL showed a significant improvement on stone comminution of artificial uric acid stones after initial chemolytic treatment with THAM. CONCLUSIONS: New basics to improve dissolution of uric acid stones have been developed by performing standardized in vitro investigations. The suggestion was confirmed that stone fragility and thus SWL can be improved by varying the physical properties of uric acid stones through initial treatment with THAM solution.
Lithotripsy↗
Salvage surgery of chemorefractory germ cell tumors with elevated tumor markers.
PURPOSE: We evaluated the prognostic criteria for salvage surgery in patients with persistent marker elevation after chemotherapy for metastatic germ cell tumors. MATERIALS AND METHODS: Of 125 men who underwent post-chemotherapeutic resection of residual tumors 30 had persistent marker elevation at surgery. This group was subdivided into 17 patients with no evidence of disease, 7 dead of disease and 6 others. Outcome analysis was performed in the subgroups with regard to preoperative and postoperative parameters. Mean followup was 120.3 months (range 1 to 228) after surgery. RESULTS: Of the 30 patients 17 (57%) with persistently elevated tumor markers after chemotherapy were long-term survivors after salvage surgery. Overall persistent viable cancer and teratomatous elements were identified in 64% and 11% of cases, respectively. Significantly more patients died of disease who had a poor prognosis according to International Germ Cell Cancer Collaborative Group guidelines. Embryonal carcinoma was the predominant initial histology in this group and residual disease was more often located at various sites, for example the viscera, with a lower chance of complete surgical resection. Marker status before surgery, and chemotherapeutic pretreatment and postoperative histological findings did not differ significantly in patients with no evidence of disease and those dead of disease. CONCLUSIONS: Salvage surgery results in long-term success in greater than 50% of patients. Complete resection is the most important single parameter for a favorable outcome. Even patients with visceral metastasis benefit from surgery. Our data do not justify omitting surgery in certain subgroups.
Biomarkers, Tumor↗
Acoustic and mechanical properties of artificial stones in comparison to natural kidney stones.
PURPOSE: Standardized and reproducible artificial kidney stone models are important for performing comparative studies of different lithotripsy modalities. The acoustic and mechanical properties of renal calculi dictate the manner by which stones interact with the mechanical stresses produced by shock wave lithotripsy (SWL) or intracorporeal lithotripsy modalities. We have developed a novel artificial kidney stone model that is made of natural substances found in real kidney stones. These stone models appear to be much closer in physical properties to natural kidney stones than previously used stone models. MATERIALS AND METHODS: The acoustic and mechanical properties of six groups of artificial stone models were compared to corresponding natural stones of similar compositions. Moreover, three groups of artificial stone models made of plaster-of-Paris were compared to their natural counterparts. In terms of acoustic properties, stone density was measured using a pycnometer based on Archimedes' principle, whereas longitudinal and transverse (or shear) wave propagation speeds were measured using an ultrasound pulse transmission technique. These values were used to calculate wave impedance and dynamic mechanical properties (bulk modulus, Young's modulus, and shear modulus) of the stones. The microhardness of the stones was measured and the effect of composition on stone fragility was evaluated. RESULTS: Artificial stones, when compared to natural stones of similar composition, showed similar trends in longitudinal and transverse wave speeds, wave impedance, and dynamic elastic moduli. However, values for the artificial stones were uniformly low compared to those of natural stones, suggesting that these artificial stones may be more amenable to shock wave fragmentation. The results of SWL on stone fragmentation of artificial and natural stones also revealed similar trends with the exception of artificial cystine stones which were found to be the most resistant to shock wave fragmentation. CONCLUSIONS: The results indicate that the physical properties of artificial stones made of natural stone materials are comparable to renal calculi of the same chemical composition. The data suggests that these stone phantoms are suitable for performing standardized and reproducible in vitro investigations, especially with regards to fragility of kidney stones of different chemical compositions during SWL.
Acoustics↗