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Biomedical subjects

M Möller

Publications and source records attributed to M Möller.

At least 19 recordsLinked to original sources
PubMed2006

Use of thermal and visible imagery for estimating crop water status of irrigated grapevine.

Achieving high quality wine grapes depends on the ability to maintain mild to moderate levels of water stress in the crop during the growing season. This study investigates the use of thermal imaging for monitoring water stress. Experiments were conducted on a wine-grape (Vitis vinifera cv. Merlot) vineyard in northern Israel. Irrigation treatments included mild, moderate, and severe stress. Thermal and visible (RGB) images of the crop were taken on four days at midday with a FLIR thermal imaging system and a digital camera, respectively, both mounted on a truck-crane 15 m above the canopy. Aluminium crosses were used to match visible and thermal images in post-processing and an artificial wet surface was used to estimate the reference wet temperature (T(wet)). Monitored crop parameters included stem water potential (Psi(stem)), leaf conductance (g(L)), and leaf area index (LAI). Meteorological parameters were measured at 2 m height. CWSI was highly correlated with g(L) and moderately correlated with Psi(stem). The CWSI-g(L) relationship was very stable throughout the season, but for that of CWSI-Psi(stem) both intercept and slope varied considerably. The latter presumably reflects the non-direct nature of the physiological relationship between CWSI and Psi(stem). The highest R(2) for the CWSI to g(L) relationship, 0.91 (n=12), was obtained when CWSI was computed using temperatures from the centre of the canopy, T(wet) from the artificial wet surface, and reference dry temperature from air temperature plus 5 degrees C. Using T(wet) calculated from the inverted Penman-Monteith equation and estimated from an artificially wetted part of the canopy also yielded crop water-stress estimates highly correlated with g(L) (R(2)=0.89 and 0.82, respectively), while a crop water-stress index using 'theoretical' reference temperatures computed from climate data showed significant deviations in the late season. Parameter variability and robustness of the different CWSI estimates are discussed. Future research should aim at developing thermal imaging into an irrigation scheduling tool applicable to different crops.

Air↗
PubMed2006

Non-invasive detection of fluorescence from exogenous chromophores in the adult human brain.

This is the first report on results proving that fluorescence of exogenous dyes inside the human brain can be excited and detected non-invasively at the surface of the adult head. Boli of indocyanine green (ICG) were intravenously applied to healthy volunteers, and the passage of the contrast agent in the brain was monitored by detecting the corresponding fluorescence signal following pulsed laser excitation at 780 nm. Our hypothesis that the observed fluorescence signal contains a considerable cortical fraction was corroborated by performing measurements with picosecond temporal resolution and analyzing distributions of times of arrival of photons, hence taking advantage of the well-known depth selectivity of that method. Our experimental findings are explained by Monte Carlo simulations modeling the head as a layered medium and taking into account realistic bolus kinetics within the extra- and intracerebral compartment. Although a particular non-specific dye (ICG) was used, the results clearly demonstrate that fluorescence-mediated imaging of the adult human brain is generally feasible. In particular, we will discuss how these results serve as proof of concept for non-invasive fluorescence brain imaging and may thus open the door towards optical molecular imaging of the human brain.

Adult↗
PubMed2006

[Calcinosis cutis in Albright hereditary osteodystrophy: pseudohypoparathyroidism type Ia].

Albright hereditary osteodystrophy (AHO) is characterized by a symptom complex including short stature, brachymetacarpia, obesity, round facies, cutaneous osteomas, and mental retardation. AHO is caused by mutations in the GNAS-gene localized on chromosome 20 encoding for Gsalpha protein, a signal transducer of endocrine pathways. Therefore, AHO is often associated with endocrinopathy such as pseudohypoparathyroidism or hypothyroidism. A nine-month-old boy presented with typical features of this syndrome. The diagnosis was confirmed by biochemical and molecular analyses. An unusual feature was calcinosis cutis at such an early age, which led to extensive differential diagnostic procedures.

Calcinosis↗
PubMed2005

[Comparison of methods for quantification of MVOC in indoor environments].

For several years now, MVOC have been regarded as indicators for microbial growth in indoor environments. Until now, a direct correlation between the occurrence of microfungi and MVOC could not be shown in scientific investigations. One reason may be that different analytical methods were applied, and moreover they were not validated sufficiently. The present investigation aimed to test the comparability of both methods (Tenax adsorption/thermal desorption; charcoal adsorption/elution). It turned out that with both methods comparable results can be achieved if the technical handling of the calibration is standardized to a wide extent. Thus, highest demands have to be made on quality assurance. Therefore, it is necessary to formulate technical regulations for the quantification of MVOC.

Air Pollutants, Occupational↗
PubMed2005

Precision of intracellular calcium spike timing in primary rat hepatocytes.

Extracellular stimuli are often encoded in the frequency, amplitude and duration of spikes in the intracellular concentration of calcium ([Ca2+]i). However, the timing of individual [Ca2+]i-spikes in relation to the dynamics of an extracellular stimulus is still an open question. To address this question, we use a systems biology approach combining experimental and theoretical methods. Using computer simulations, we predict that more naturalistic pulsed stimuli generate precisely-timed [Ca2+]i-spikes in contrast to the application of constant stimuli of the same dose. These computational results are confirmed experimentally in single primary rat hepatocytes upon alpha1-adrenergic stimulation. Hormonal signalling in analogy to neuronal signalling thus has the potential to make use of temporal coding on the level of single cells. The [Ca2+]i-signalling cascade provides a first example for increasing the information capacity of an intracellular regulatory signal beyond the known coding mechanisms of amplitude (AM) and frequency modulation (FM).

Algorithms↗
PubMed2005

Refugia, dispersal and divergence in a forest archipelago: a study of Streptocarpus in eastern South Africa.

We describe a scenario of plant speciation across a relict forest archipelago in South Africa involving Pleistocene habitat expansion-contraction cycles, dispersal and adaptation to lower temperatures. This is the first population level study using molecular data in South African forests and has significant implications for conservation efforts in this area. Populations of the mesophytic forest floor herbs Streptocarpus primulifolius sensu lato and Streptocarpus rexii were sampled throughout their range in the naturally fragmented forests of eastern South Africa in order to investigate population genetic and phylogenetic patterns within the species complex, using nuclear microsatellites, nuclear ribosomal ITS (internal transcribed spacer) sequences and chloroplast genome sequences. S. primulifolius harbours high levels of genetic diversity at both the nuclear (mean HE = 0.50) and the chloroplast level (each population fixed for a unique haplotype). This is consistent with populations of these coastal species being Pleistocene relicts. In contrast, populations of S. rexii in cooler habitats at higher altitudes and lower latitudes harbour little or no nuclear genetic diversity (mean HE = 0.09) and most share a common chloroplast haplotype. The split of S. rexii from populations intermediate between the two species (S. cf. primulifolius) occurred between 0 and 0.44 million years ago according to the calibrated ITS phylogeny of the taxa. The low genetic diversity and homogeneity of S. rexii is congruent with this species having reached its current range during the Holocene. We found no evidence of monophyly of any of the taxa in this study, which we consider a consequence of recent evolution in a fragmented habitat.

Conservation of Natural Resources↗
PubMed2004

Bed-side assessment of cerebral perfusion in stroke patients based on optical monitoring of a dye bolus by time-resolved diffuse reflectance.

We present a minimally invasive optical method, that is, multi-channel time-domain diffuse near-infrared reflectometry of the head to assess cerebral blood perfusion that is applicable at the bed-side and repetitively at short intervals. Following intravenous injection of an ICG bolus, its transit through intra- and extracerebral tissue is monitored based on changes in moments of distributions of times of flight of photons, recorded with a 4-channel instrument simultaneously on both hemispheres. In healthy volunteers, we found that variance of distributions of times of flight of photons is well suited to assess latency and initial slope of the increase in absorption of intracerebral tissue due to the bolus. We successfully applied our method in two patients demonstrating a reversible cerebral perfusion deficit in an ischemic stroke patient who was treated by thrombolysis and in another patient with a permanent impaired unilateral perfusion due to ipsilateral internal carotid artery occlusion. In either case, we observed a difference in bolus transit time between the hemispheres. In the stroke patient, this difference resolved when re-evaluated 1 day after thrombolysis. The study demonstrates the necessity of a technique with sub-nanosecond time resolution to allow for depth discrimination if clinical perfusion monitoring of cerebrovascular diseases is addressed by optical methods.

Adult↗
PubMed2004

Real time fMRI: a tool for the routine presurgical localisation of the motor cortex.

In patients with brain lesions adjacent to the central area, exact preoperative knowledge of the spatial relation of the tumour to the motor cortex is of major importance. Many studies have shown that functional magnetic resonance imaging (fMRI) is a reliable tool to identify the motor cortex. However, fMRI data acquisition and data processing are time-consuming procedures, and this prevents general routine clinical application. We report a new application of real time fMRI that allows immediate access to fMRI results by automatic on-line data processing. Prior to surgery we examined ten patients with a brain tumour adjacent to the central area. Three measurements were performed at a 1.5-T Magnetom Vision Scanner (Siemens, Forchheim, Germany) on seven patients and at a 1.5-T Intera Scanner (Philips, Best, The Netherlands) on three patients using a sequential finger-tapping paradigm for motor cortex activation versus at rest condition. Blood oxygen level-dependant (BOLD) images were acquired using a multislice EPI sequence (16 slices, TE 60, TR 6000, FOV 210x210, matrix 64x64). The central sulcus of the left hemisphere could be clearly identified by a maximum of cortical activity after finger tapping of the right hand in all investigated patients. In eight of ten patients the right central sulcus was localised by a signal maximum, whereas in two patients the central sulcus could not be identified due to a hemiparesis in one and strong motion artefacts in the second patient. Finger tapping with one side versus rest condition seems to result in more motion artefacts, while finger tapping of the right versus the left hand yielded the strongest signal in the central area. Real time fMRI is a quick and reliable method to identify the central sulcus and has the potential to become a clinical tool to assess patients non-invasively before neurosurgical treatment.

Adult↗
PubMed2004

Influence of vegetation on the environmental partitioning of DDT in two global multimedia models.

Two multimedia models are used to investigate the effect of a vegetation compartment on the environmental partitioning of dichlorodiphenyltrichloroethane (DDT): a steady-state unit world model using global averages of vegetation cover and land-to-sea ratio and a dynamic model with latitudinal zones and zone-specific vegetation types and annual temperature courses. The vegetation compartment represents canopies of deciduous and coniferous forests and blades of grasses; the organic carbon content of the vegetation-covered soil is higher than in the bare soil. In the steady-state model, transfer from the air to the vegetation and the underlying soil as well as revolatilization from the foliage and reduced deposition to the soil is observed, depending on the chemical's degradation rate constant in vegetation and the deposition velocities of the gaseous and particle-bound fractions. In both models, a significant effect of the organic carbon content of the vegetation-covered soil increasing the effect of the vegetation compartment is observed. In the steady-state model, the changes in the DDT concentrations in air do not exceed 7% difference between the cases with and without vegetation; the soil concentrations differ by maximally a factor of 2.7. In the spatially and temporally resolved model, however, air concentration differences up to 90% are observed, depending on the type and amount of vegetation in the latitudinal zones. Long-range transport is less pronounced in the model with vegetation.

DDT↗
PubMed2004

Conformational dynamics of single molecules visualized in real time by scanning force microscopy: macromolecular mobility on a substrate surface in different vapours.

We describe a technique to visualize and effect in real time motion and conformational transitions of single macromolecules. Two steps are involved. First, scanning force microscopy (SFM) was applied to detect in situ conformational transitions of single polymer molecules adsorbed on a substrate surface. Secondly, these changes were induced by controlled variations of environmental conditions in a microscope environmental chamber. In particular, we have revealed that exposure of a substrate with adsorbed macromolecules to vapours of different nature was able to increase molecular mobility and to stimulate conformational transitions of the polymer chains on the surface. Realization of SFM observation in a variable vapour environment was not as difficult as in liquid media. Variations of the vapour composition affected the oscillation dynamics of the cantilever with the scanning probe only to a small extent, and did not impede continuation of the scanning procedure. In fact, the characteristic times of the observed conformational changes were large enough (minutes to dozens of minutes) for sampling images repeatedly. Although recording of an SFM image was slow and required several minutes, we were able to visualize step-by-step the successive stages of the slow conformational transformation of the macromolecules adhering to the substrate, i.e. to investigate a molecular response to the environment changes in real time. Here, we studied the reversible collapse-decollapse transitions of cylindrical poly(methacrylate)-graft-poly(n-butyl acrylate) brush-like macromolecules exposed to different vapours. Single macromolecules on mica tended to assume a compacted globular conformation when exposed to the vapour of compounds, which due to their amphiphilic nature adsorb on mica and lower the surface energy of the substrate (e.g. alcohols). By contrast, the macromolecules adopted extended two-dimensional worm-like conformations in the vapours of compounds having high values of surface tension (such as water). In our opinion, the reason for the observed tendency was a competition in spreading on the substrate surface between the macromolecules and the co-adsorbed vapour molecules. If the brush-like macromolecules succeeded in the spreading, they acquired an extended conformation. Otherwise they collapsed to globuli in order to reduce the surface area per macromolecule. Thus, the enhanced mobility of synthetic macromolecules on a substrate observed in a vapour environment in combination with the possibility to manipulate the macromolecular conformation via changes in a vapour phase and the ability to visualize the transitions of the macromolecules individually, provides challenging prospects for SFM studies on the dynamics of single molecules under applied external stimuli.

Journal Article↗
PubMed2004

Cylindrical molecular brushes under poor solvent conditions: microscopic observation and scaling analysis.

Axial contraction of cylindrical molecular brushes of polymethylmethacrylate was observed by static light scattering and scanning force microscopy. Single brush molecules were visualized as worm-like particles whose length was almost three times shorter than the contour length of the backbone. A somewhat larger length was measured by light scattering in a good solvent. A scaling approach has been used to analyze the driving forces for the axial contraction and the conformation of the molecular brushes.

Adsorption↗
PubMed2003

[Defecation problems following radical perineal prostatectomy. A prospective study].

PURPOSE: The true incidence of bowel symptoms prior to radical prostatectomy, as evaluated by a differentiated questionnaire, is unknown. We therefore performed a prospective study on patients who were scheduled for radical perineal prostatectomy. MATERIAL AND METHODS: A total of 67 patients with cT1-cT3, N0, M0 prostate cancer underwent an extrafascial, radical, perineal prostatectomy. The patients received a questionnaire prior to surgery as well as 6 months and 12 months after surgery. This took into account demographic data, stool symptoms (Kelly questionnaire) and questions concerning bladder function (ICS male continence questionnaire). The questionnaires were evaluated by three of the authors not involved in patient care. RESULTS: The mean age of the patients was 64 years. The PSA range was 0.9-55.6 ng/ml (mean 12.7 ng/ml). There were 47 pT2, 19 pT3 and a single pT4 tumour. A total of 59 patients had a Gleason score of 6 or less. Positive surgical margins were present in four patients. The 12 months follow-up questionnaire could be evaluated for 82% of the patients (n=55). In addition, 46 patients answered the questionnaire at 6 months post-surgery. Three or more problems in relation to bowel movements were reported preoperatively by 21% of the patients. Straining with bowel emptying was the symptom which was indicated most often. Stool smearing was reported by 13% of patients at least once or twice monthly. In addition, 6% of patients reported that they had difficulties in differentiating soft stool from gas. After 1 year, seven (13%) of the patients reported stool smearing which was not present prior to surgery. Six of these patients observed this problems only once or twice a month. Only one patient had stool smearing once a week. Two patients reported urgency, two had a decreased warning time and one reported decreased sensibility. Two patients used protective pads. The most frequent symptom reported postoperatively was straining with bowel emptying (24% preoperatively and 16% postoperatively). CONCLUSION: It is evident that men scheduled for radical prostatectomy already have significant stool problems preoperatively. Newly developed, postoperative stool smearing on a daily basis occurred extremely seldom. They same is true for the discrimination between soft stool and gas. From our point of view, it is important to use the extrasphincteric approach to the prostate described by Young. Furthermore, the pubo-anal sling should be preserved.

Constipation↗
PubMed2003

[Treatment of sudden hearing loss through Fibrinogen/LDL-apheresis. A prospective, randomized multicenter trial].

INTRODUCTION: Sudden sensorineural hearing loss (SSHL) is thought to be of various origins. Disturbances of microcirculation, autoimmune pathology and viral infection are among the most likely causes. Acute reduction of plasma fibrinogen and serum LDL positively influences hemorheology and endothelial function and might thus be an effective therapy for SSHL. OBJECTIVE: To test the hypothesis that fibrinogen/LDL-apheresis is as effective or superior to conventional therapy with plasma expanders and prednisolone in the treatment of SSHL. DESIGN: controlled, prospective, randomized, multicenter trial. SETTING AND PATIENTS: 201 patients were recruited from 01/2000 to 6/2001 at the University Clinics of Munich, Berlin, Hamburg and Bochum. Inclusion criteria was sudden sensorineural hearing loss of unknown origin within 6 days of onset. INTERVENTIONS: Single fibrinogen/ LDL-apheresis infusion of prednisolone (250 mg, tapered by 25 mg daily), hydroxyethyl starch (500 ml, 6%) and pentoxifylin (400 mg/day). MAIN OUTCOMES: Improvement of pure tone thresholds 48 h after onset of therapy. RESULTS: Over all improvement of pure tone thresholds in the fibrinogen/ LDL-apheresis treated patients is slightly but not significantly better than in the standard therapy group. After 48 h, 50% speech perception in the fibrinogen/ LDL-apheresis group (21.6+/-20.1 dB) is significantly (p<0.034) better than in the standard group (29.3+/-29.4 dB). Patients with plasma fibrinogen levels of more than 295 mg/dl have a substantial and significantly (p<0.005) better improvement of speech perception (15.3+/-17.3 dB) than standard treated patients (6.1+/-10.4 dB). CONCLUSIONS: Fibrinogen/LDLapheresis is at least equally effective compared to prednisolone treatment in sudden hearing loss. Selected patients with plasma fibrinogen of more than 295 mg/dl improve significantly better when treated with fibrinogen/LDLapheresis.

Adolescent↗
PubMed2003

The use of Geographic Information System (GIS) in the frame of the contingency plan implemented during the 1999-2001 avian influenza (AI) epidemic in Italy.

A Geographic Information System (GIS) is a very powerful and flexible software tool for effective management of spatially referenced data (e.g., geodata). Coupling database and GIS technology provides the tools for a detailed analysis of spatial patterns and distributions in veterinary applications. A specific veterinary GIS (VetGIS) toolbox was developed to perform the calculation of indices such as Lorenz curve, GINI index, and a kernel-based animal density estimation. This software was employed for the analysis and management of avian influenza in Italy during the 1999-2000 epidemic.

Animals↗
PubMed2002

Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects.

The radiative and nonradiative decay rates of lissamine dye molecules, chemically attached to differently sized gold nanoparticles, are investigated by means of time-resolved fluorescence experiments. A pronounced fluorescence quenching is observed already for the smallest nanoparticles of 1 nm radius. The quenching is caused not only by an increased nonradiative rate but, equally important, by a drastic decrease in the dye's radiative rate. Assuming resonant energy transfer to be responsible for the nonradiative decay channel, we compare our experimental findings with theoretical results derived from the Gersten-Nitzan model.

Biophysical Phenomena↗
PubMed2002

Oxidation-resistant gold-55 clusters.

Gold nanoparticles ranging in diameter from 1 to 8 nanometers were prepared on top of silicon wafers in order to study the size dependence of their oxidation behavior when exposed to atomic oxygen. X-ray photoelectron spectroscopy showed a maximum oxidation resistance for "magic-number" clusters containing 55 gold atoms. This inertness is not related to electron confinement leading to a size-induced metal-to-insulator transition, but rather seems to be linked to the closed-shell structure of such magic clusters. The result additionally suggests that gold-55 clusters may act as especially effective oxidation catalysts, such as for oxidizing carbon monoxide.

Journal Article↗
PubMed2002

Calf muscle function after Achilles tendon rupture. A prospective, randomised study comparing surgical and non-surgical treatment.

In a prospective, randomised, multicentre study, 112 patients with Achilles tendon rupture (ATR) were allocated to surgical treatment (n=59), followed by early functional rehabilitation using a brace, and non-surgical treatment (n=53), i.e. eight weeks of plaster treatment. In this study, the results of the isokinetic muscle strength evaluation are presented for contractions in both the concentric and the eccentric mode, plantar flexion and dorsiflexion, two angular velocities and three different positions of the subject. The heel-raise test for endurance, maximum calf circumference and tendon width were also evaluated. The re-rupture rate was 20.8% in the non-surgically-treated group and 1.7% in the surgically-treated group. No significant differences were found between the treatment groups in terms of the isokinetic strength measurements and the endurance test among the patients who did not sustain a re-rupture. If a re-rupture is avoided, both surgical and non-surgical treatment for ATR produce good functional outcome; however, the muscle function was not restored after two years in either group.

Achilles Tendon↗