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Biomedical subjects

S Brandt

Publications and source records attributed to S Brandt.

At least 19 recordsLinked to original sources
PubMed2005

Determination of alveolar-capillary O2 partial pressure gradient by using 15NO.

We propose an approach for determining the alveolar-mean capillary oxygen (O(2)) partial pressure gradient to evaluate the efficiency of O(2) equilibration between alveolar space and pulmonary capillary blood. For this purpose, measurements of the pulmonary [(15)N]nitric oxide diffusing capacity are to be interpolated into the recording of O(2) consumption. We expect the O(2) partial pressure gradient amounting to 3.3 mmHg for breathing room air at rest, a third of that commonly given. The simplicity of our method allows its application to children or even artificially ventilated patients. Therefore, it will enable a new insight into pulmonary O(2) equilibration.

Humans↗
PubMed2004

Mucoceles of the sphenoid sinus.

PURPOSE: Mucoceles of the sphenoid sinus represent 1-2% of all paranasal sinus mucoceles. The aim of this paper is to report our experiences in patients with mucoceles of the sphenoid sinus. PATIENTS AND METHOD: In a period of 4 years, we observed six patients in whom a mucocele of the sphenoid sinus was suggested pre- or intraoperatively. Symptoms and signs included headache, visual loss and palsies of the III and VI cranial nerve. All patients were investigated by MRI and/or CT. Imaging findings were compared with operative and/or histological findings. RESULTS: In three cases there were simple mucoceles, in one case we found a tumour (nasopharyngeal carcinoma) associated mucocele and in two cases, malignant tumours (carcinoma, chordoma) imitated a mucocele. The diagnosis of simple mucoceles was no problem at all by imaging. Difficulties made the two malignant tumours and the tumour associated mucocele. In the first two cases, repeated histological samples were necessary to make the final diagnosis. CONCLUSION: Mucoceles of the sphenoid sinus should be investigated and handled very carefully with regard to differential diagnoses and tumour associated cases.

Adult↗
PubMed2004

Pulmonary 15NO uptake in interstitial lung disease.

Because lung nitric oxide (NO) diffusing capacity (DL) represents alveolar-capillary gas diffusion, we queried as to whether disturbances of pulmonary gas exchange in interstitial lung disease (ILD) are appropriately reflected by using NO. In this pilot study, we applied the (15)N-labeled stable isotope (15)NO (relative abundance 0.37% of total NO) in order to ignore the endogenous NO production. In 10 ILD-outpatients, we measured DL (15)NO by performing the single-breath method. Lung function parameters as well as arterial oxygen partial pressure (PaO(2)) were also tested. Values of DL (15)NO ranged within 50-151 ml (15)NO/(mmHg min). Ratios of DL (15)NO/reference were between 43 and 108% of predicted data as taken from our previous work on healthy volunteers [Eur. J. Physiol. 446 (2003) 256]. We found a significant reduction of DL (15)NO/reference in five patients. Additionally, values of PaO(2) were significantly correlated to ratios of DL (15)NO/reference (adjusted R2 +/-SEE=0.407+/-8.051). In conclusion, (15)NO represents an appropriate indicator gas for reflecting an ILD-induced impairment of alveolar-capillary gas exchange.

Adult↗
PubMed2004

[Indications of HR-CT in the early postoperative phase of stapedotomy].

PURPOSE: This is an analysis of high-resolution computed tomography (HR-CT) performed in patients with and without symptoms after stapes surgery during the early postoperative phase. MATERIALS AND METHODS: We examined 37 patients who underwent stapes surgery between January 1995 and December 2000. HR-CT of the temporal bone was performed in axial and coronal planes with 1-mm-slice thickness and table feed. A reoperation was performed in 7 patients. CT findings were compared with clinical follow up and surgical findings. RESULTS: All patients showed postoperative opacification of the tympanic cavity and external auditory canal as well as partial opacification of the mastoid on CT scans. A dislocation of the prosthesis was found in 11 cases and air bubbles were seen in the vestibule of 5 patients. In one case, small bone fragments were detected in the vestibule. In 6 of 7 cases, CT results were confirmed by retympanotomy. CONCLUSIONS: Due to overlapping of normal and pathological findings in the early postoperative period, indications for HR-CT are limited in this period.

Adult↗
PubMed2003

Pulmonary 15NO uptake in man.

Nitric oxide (NO) is commonly thought to reveal more precise values of pulmonary gas uptake through alveolar-capillary membranes (DL) than the normally used carbon monoxide (CO). Since such measurements are influenced by a significant endogenous NO delivery within human airways, we propose the use of the naturally occurring (15)N-labelled stable nitric oxide isotope (15)NO. It occurs with a relative abundance of 0.37% of the dominating isotope (14)NO. Therefore, the endogenous (15)NO production can be neglected. In the present pilot study we demonstrate the workability of (15)NO in determining DL in healthy individuals. In seven female and 15 male volunteers, averaged values of DL increase with increasing mean alveolar volume as well as individual body height ( P=0.000001). Due to the very high significance level obtained from the multiple regression analysis, we conclude that the application of (15)NO establishes a novel approach to calculate standard values of DL. Such calculations can be employed to predict a reference for patients who suffer from pulmonary diffusion limitation.

Adolescent↗
PubMed2003

[Atraumatic retroperitoneal hemorrhage--interdisciplinary and differential diagnostic considerations based on a case report].

The differential-diagnostic strategy and the order of precedence of most diverse radiologic diagnostic procedures are discussed based on a case of retroperitoneal bleeding. Apart from iatrogen-caused bleedings, the therapeutic anticoagulant therapy in the context of the patient's disease, haemodialysis or a rare, spontaneously-occurring retroperitoneal bleeding play a substantial role. In the order of precedence of radiologic diagnostic procedures for fast diagnosis of a retroperitoneal haematoma, the abdomen CT-scan is the preferred method.

Aged↗
PubMed2001

Amino acid analysis in five pooled single plant cell samples using capillary electrophoresis coupled to laser-induced fluorescence detection.

In this study 21 amino acid standards, samples of pure phloem sap and samples of pooled mesophyll cells were derivatized with fluorescein isothiocyanate, separated by capillary electrophoresis and detected with laser-induced fluorescence at 488 nm. Two different background electrolytes, a sodium borate buffer containing sodium dodecyl sulfate and a sodium borate buffer containing alpha-cyclodextrin, were used for the separation. Using the sodium dodecyl sulfate buffer, 14 amino acid standards could be separated, spiking identified 12 amino acids in pure phloem sap and 13 amino acids in pooled mesophyll cells. With the alpha-cyclodextrin containing background electrolyte, a resolution of 20 amino acid standards could be attained, 17 amino acids in pure phloem sap and 10 amino acids in mesophyll cells could be assigned. Leucine and isoleucine comigrated in both buffer systems. All separations were performed with a voltage of +20 kV and completed within 30 min. The detection limits obtained were in the fmol range for the sodium dodecyl sulfate and in the pmol range for the alpha-cyclodextrin background electrolyte. Compared to the one published capillary electrophoresis-based method for the determination of amino acids from few plant cells, the procedure described here allows very high sensitivity due to the use of laser-induced fluorescence detection and opens the possibility to dilute and measure pl samples with an fully automated, commercially available CE system.

Amino Acids↗
PubMed2001

Representational overlap of adjacent fingers in multiple areas of human primary somatosensory cortex depends on electrical stimulus intensity: an fMRI study.

Functional magnetic resonance imaging (fMRI) was used to examine the influence of non-painful electrical stimulus intensity on the BOLD response in human primary somatosensory cortex (SI). In ten healthy subjects, index and middle finger of the right hand were stimulated separately at two different stimulus intensities. The activated volume of single finger representations as well as the volume of representational overlap of the two activations increased following an increase in stimulus intensity. This effect was seen in two different subdivisions of SI, one in the depth of the central sulcus, presumably corresponding to Brodmann area (BA) 3b, and one on the crown of the postcentral gyrus, presumably corresponding to BA 1/2. Relative overlap (ratio of overlap volume to volume of individual finger representation) was larger in BA 1/2 than in BA 3b. Additionally, in both areas relative overlap increased significantly from low to high stimulus intensity. Relative overlap did not change when different correlation thresholds were employed arguing against an unspecific 'spillover effect'. Analysis of signal intensity time courses indicated that the response difference to high versus low stimulus strength was not present during the initial seconds of stimulation, during which both led to a similar signal intensity increase. Only during the following maintenance level of the response did the response to high stimulus intensity reach a significantly higher plateau level than the one due to low intensity stimulation, an effect which was present in both areas, BA 3b and BA 1/2, respectively.

Adult↗
PubMed2001

Multiphase method for automatic alignment of transmission electron microscope images using markers.

In order to successfully perform the 3D reconstruction in electron tomography, transmission electron microscope images must be accurately aligned or registered. So far, the problem is solved by either manually showing the corresponding fiducial markers from the set of images or automatically using simple correlation between the images on several rotations and scales. The present solutions, however, share the problem of being inefficient and/or inaccurate. We therefore propose a method in which the registration is automated using conventional colloidal gold particles as reference markers between images. We approach the problem from the computer vision viewpoint; hence, the alignment problem is divided into several subproblems: (1) finding initial matches from successive images, (2) estimating the epipolar geometry between consecutive images, (3) finding and localizing the gold particles with subpixel accuracy in each image, (4) predicting the probable matching gold particles using the epipolar constraint and its uncertainty, (5) matching and tracking the gold beads through the tilt series, and (6) optimizing the transformation parameters for the whole image set. The results show not only the reliability of the suggested method but also a high level of accuracy in alignment, since practically all the visible gold markers can be used.

Automation↗
PubMed2001

Automatic alignment of transmission electron microscope tilt series without fiducial markers.

Accurate image alignment is needed for computing three-dimensional reconstructions from transmission electron microscope tilt series. So far, the best results have been obtained by using colloidal gold beads as fiducial markers. If their use has not been possible for some reason, the only option has been the automatic cross-correlation-based registration methods. However, the latter methods are inaccurate and, as we will show, inappropriate for the whole problem. Conversely, we propose a novel method that uses the actual 3D motion model but works without any fiducial markers in the images. The method is based on matching and tracking some interest points of the intensity surface by first solving the underlying geometrical constraint of consecutive images in the tilt series. The results show that our method is near the gold marker alignment in the level of accuracy and hence opens the way for new opportunities in the analysis of electron tomography reconstructions, especially when markers cannot be used.

Animals↗
PubMed2000

Grazing collisions of black holes via the excision of singularities.

We present the first simulations of non-head-on (grazing) collisions of binary black holes in which the singularities are excised from the simulation. Initially equal mass m black holes (spinning or not) are separated by approximately 10m and with impact parameter approximately 2m. Evolutions to t approximately 35m are obtained where two separate horizons are present for t approximately 3.8m; then a single enveloping horizon forms indicating that the holes merged. Apparent horizon area estimates suggest gravitational radiation of about 2%-3% of the total mass. The evolutions end after a moderate amount of time because of instabilities.

Journal Article↗
PubMed2000

Spiral computed tomography before and after cricothyroid approximation.

Cricothyroid approximation raises the vocal pitch by simulating the contraction of the cricothyroid muscle with sutures. The aim of this study was to determine the role of spiral computed tomography (CT) in patients scheduled for cricothyroid approximation. Twenty-nine transsexual patients were examined with spiral CT before and after laryngoplastic surgery. Computed tomography findings were correlated with phoniatric findings in all patients. The average reduction of the cricothyroid distance was 6 mm (range 2-10 mm). The vocal pitch elevation was more remarkable in the patient group with greater reduction of the cricothyroid distance. Computed tomography accurately determines the cricothyroid distance before and after surgery and is an ideal method for follow-up purposes, especially when there is a postoperative reversion towards a lower pitch. In addition, CT provides important data as to the most appropriate extent and site of intracordal intervention to be done for a desired pitch elevation.

Adult↗
PubMed2000

Value of spiral CT in patients with cricothyroid approximation.

Cricothyroid approximation raises the vocal pitch by simulating contraction of the cricothyroid muscle with sutures. The aim of this study was to determine the role of spiral CT in patients scheduled for cricothyroid approximation. 29 transsexual patients were examined with spiral CT prior to and after laryngoplastic surgery. CT findings were correlated with phonographic findings in all patients. The average reduction of the cricothyroid distance was 6 mm (range 2-10 mm). Vocal pitch elevation was greatest in patients with the largest reduction of the cricothyroid distance. CT accurately determines the cricothyroid distance prior to and after surgery and is an ideal method for follow-up, especially in post-operative reversion towards a lower pitch. In addition, CT provides important data in determining the most appropriate extent and site of intracordal intervention to achieve a desired pitch elevation.

Adult↗
PubMed2000

Vertigo after stapes surgery: the role of high resolution CT.

CT findings in patients with vertigo after stapes surgery include a prosthesis shaft entering the vestibule and compressing the saccule, a complete dislocation of the stapes prosthesis, air bubbles and fluid collections within the vestibule and outside the oval window indicating a perilymphatic fistula, and bony fragments leading to compression of the basal saccule. Although immediate post-operative vertigo is often transient, patients with persistent or recurrent vertigo should be imaged as high resolution CT will determine the underlying cause in the majority of cases.

Fistula↗
PubMed1999

Adsorption capacity as a key parameter for enzyme induction and pentachlorophenol degradation in Mycobacterium chlorophenolicum PCP-1.

Adsorption of pentachlorophenol (PCP) on induced cells of Mycobacterium chlorophenolicum PCP-1 and its influence on enzyme induction and PCP degradation of this strain were studied. Compared to non-induced cells, induced degrading cells had a lower adsorption capacity (q(ads)), particularly at prolonged induction and low PCP concentration. Unlike the effects of pH and biomass concentration previously reported for non-induced cells, the variation of q(ads) of induced cells was associated with changes of both the capacity and intensity constants of the Freundlich equation which was used to describe PCP adsorption on M. chlorophenolicum PCP-1. This indicated changes of cell surface properties during enzyme induction and PCP degradation. The latter was shown in turn to be affected by several parameters such as PCP concentration, pH value and induction time. Interestingly, irrespective of the pH and PCP concentration, the specific PCP degradation rate (q(t)(PCP)) at a given induction time was found to be solely a function of q(ads), revealing that adsorption capacity is an inherent key parameter for enzyme induction and PCP degradation. Based on this knowledge, a kinetic model was developed for q(t)(PCP) which used only q(ads) and induction time as variables. The model considered inhibition of PCP on both enzyme induction and enzyme activity and described the experimental data at different PCP concentrations and pH values well. q(ads) also turned out to be a useful criterion for choosing optimum induction concentration of PCP. Irrespective of pH and biomass concentration, an initial adsorption capacity of 2-3 micromol PCP/g cells was found to be optimum for enzyme induction in M. chlorophenolicum PCP-1.

Adsorption↗