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Biomedical subjects

A Gerlach

Publications and source records attributed to A Gerlach.

At least 19 recordsLinked to original sources
PubMed2006

Real-time observation of structural and orientational transitions during growth of organic thin films.

We study kinetically controlled orientational and structural transitions of molecular thin films during growth in situ and in real time, using diindenoperylene (DIP) as an example. By time-resolved surface-sensitive x-ray scattering (out of plane and in plane), we follow the organic molecular beam deposition of DIP on silicon oxide, on stepped sapphire, and on rubrene as an organic model surface. We identify transitions for the few-monolayer (ML) regime, as well as for thick (several 10's of ML) films. We show that the differences in the interaction of DIP with the substrate change the thickness as well as temperature range of the transitions, which include (transient) strain, subtle changes of the orientation, as well as complete reorientation. These effects should be considered rather general features of the growth of organics, which, with its orientational degrees of freedom, is qualitatively different from growth of inorganics.

Journal Article↗
PubMed2006

Structure of a beta-sheet model system in the gas phase: analysis of the fingerprint region up to 10 microm.

In this communication we report on the conformational analysis of side-chains in the beta-sheet model system (Ac-Phe-OMe)(2) by applying IR/R2PI (infrared/resonant 2-photon ionisation) spectroscopy in the fingerprint region up to 10 microm, where in order to get information in this spectral region an extension of our new high energy and narrow band-width nanosecond IR laser system is presented.

Amino Acids↗
PubMed2006

Anomalous roughness evolution of rubrene thin films observed in real time during growth.

We study the growth and structure of thin films of the organic semiconductor rubrene during organic molecular beam deposition (OMBD) on silicon oxide in situ and in real time using X-ray scattering. Using in situ grazing incidence diffraction (GID) we find a small degree of local order but an otherwise largely disordered structure, consistent with out of plane scans. Monitoring the surface morphology in real time during growth, we find relatively smooth films (surface roughness sigma below approximately 15 A for thicknesses up to at least 600 A) and a significant delay before the onset of roughening. This anomalous roughening in the beginning and crossover to normal roughening later during growth may be related to conformational changes of rubrene in the early stages of growth.

Naphthacenes↗
PubMed2006

[Characterization and staging of renal tumors: significance of MRI diagnostics].

PURPOSE: Retrospective evaluation of MRI in the diagnosis of renal masses and determination of the correlation of MRI with histology or follow-up. MATERIALS AND METHODS: 46 consecutive patients (13 female, 33 male, mean age 64.7 yrs) with suspected renal tumors were examined with a 1.5 T MR scanner using a standardized protocol (TSE T2fs, 2DGRE T1, dynam. ce3DGRE T1fs, ce2DGRE T1fs, ce3DGRE urogram). RESULTS: 142 renal lesions were found with diameters of < 2 cm up to 14 x 18 cm. A primary classification as solid and cystic lesions was performed according to MRI criteria. In 29 cases we found lesions bilaterally, in 17 patients only in one kidney, and in four cases we found multifocal renal tumors unilaterally (n = 3) or bilaterally (n = 1). In 22 patients with renal tumors, cystic lesions could be seen as well. In 19 cases these were uncomplicated cysts, and in 3 cases these were complicated cysts. 35/43 lesions were histologically proven solid vascularized tumors (29 renal cell carcinomas, 6 urothelial carcinomas), five additional masses with tumor signs in MRI appeared to be progressive during follow-up thus suggesting malignancy, and one case was a multifocal bilateral renal tumor. 3/43 lesions were initially reported as being suspected of malignancy but were proven during follow-up or histologically to be benign. Tumor thrombus was depicted in MRI in the renal vein in 5 cases, stretching into the IVC in 4 cases and proven histologically in 4 and 3 cases, respectively. Of these solid masses, 99 cystic lesions could be differentiated clearly in MRI (88 simple cysts, 11 complicated cysts) that remained unchanged during follow-up (6 - 65 months) or were proven to be cysts histologically. In 17 cases these cysts were bilateral, in 19 cases unilateral, and 33 kidneys showed multicystic changes. In characterizing renal masses, MRI showed a positive predictive value of 93 % for the diagnosis of a malignant tumor. The T-stage of histologically proven renal cell carcinomas using MRI was correct in 89 %. CONCLUSIONS: MRI is a valid modality for characterizing and staging renal masses using a suitable sequence protocol that includes dynamic ce studies. Venous tumor invasion can be depicted safely. MRI can be employed alternatively to state-of-the-art ceCT and additionally to CT in unclear cases.

Adult↗
PubMed2006

Molecular cytogenetic identification and characterization of a de novo supernumerary neocentromeric derivative chromosome 13.

We report a young girl with microphthalmia, conductive deafness, aortic isthmus stenosis, laryngomalacia, and laryngeal stenosis carrying a de novo supernumerary neocentromeric derivative chromosome 13. For the precise identification and characterization of the eu- and heterochromatic content of the marker chromosome, straightforward molecular cytogenetic analyses were performed, such as chromosome microdissection, FISH with different probes (e.g. wcp, alphoid centromeric probes, BAC), centromere-specific multicolor FISH (cenM-FISH), and multicolor banding (MCB). The analyses demonstrated that the marker consisted of an inverted duplication (partial tetrasomy) of the distal portion of chromosome 13 that was separated from the endogenous chromosome 13 centromere. Using an all-centromere probe and multicolor cenM-FISH, no alpha-satellite DNA hybridization signal was detectable on any portion of the derivative chromosome. The presence of a functional and active neocentromere on the derivative chromosome 13 was confirmed by positive immunofluorescence signals with CENP-C antibodies. BAC-FISH confirmed the cytogenetic localization of the neocentromere in band 13q31.3. Thus the patient had a mosaic conventional karyotype mos 47,XX,+inv dup(13)(qter-->q21.3::q21.3-->q31.3-->neo-->q31.3-->qter)[6]/46,XX [49].

Abnormalities, Multiple↗
PubMed2005

Structures and rearrangement reactions of 4-aminophenol(H2O)1+ and 3-aminophenol(H2O)1+ clusters.

In this paper the structures of 4-aminophenol(H2O)1+ and 3-aminophenol(H2O)1+ clusters are investigated in molecular beam experiments by different IR/UV-double resonance techniques as well as the mass analyzed threshold ionization spectroscopy yielding both inter- and intramolecular vibrations of the ionic and neutral species. Possible structures are extensively calculated at the level of density functional theory (DFT) or at the ab initio level of theory. From the experimental and theoretical investigations it can be concluded that in the case of 4-aminophenol(H2O)1 one O-H...O hydrogen-bonded structure exists in the neutral cluster but two structures containing either an O-H...O or a N-H...O hydrogen-bonded arrangement are observed in the spectra of the ionic species. This observation is a result of an intramolecular rearrangement reaction within the ion which can only take place if high excess energies are used. A reaction path via the CH bonds is calculated and explains the experimental observations. In the case of 3-aminophenol(H2O)1+ only one O-H...O bound structure is observed both in the neutral and ionic species. Ab initio and DFT calculations show that due to geometrical and energetical reasons a rearrangement cannot be observed in the 3-aminophenol(H2O)1+ cluster ion.

Journal Article↗
PubMed2005

First systematic CGH-based analyses of ancient DNA samples of malformed fetuses preserved in the Meckel Anatomical Collection in Halle/Saale (Germany).

We present the first data on our comparative genomic hybridization (CGH)-based strategy for the analysis of ancient DNA (aDNA) samples extracted from fetuses preserved in the Meckel Anatomical Collection in Halle, Germany. The collection contains numerous differently fixed ancient samples of fetal malformations collected from the middle of the 18th to the early 19th century. The main objective of this study is to establish a "standard" aDNA extraction and amplification protocol as a prerequisite for successful CGH analyses to detect or exclude chromosomal imbalances possibly causative for the malformations described for the fetuses.

Congenital Abnormalities↗
PubMed2004

[Contrast-enhanced MR angiography (CEMRA) in peripheral arterial occlusive disease (PAOD): conventional moving table technique versus hybrid technique].

PURPOSE: In peripheral arterial occlusive disease (PAOD), angiographic evaluation of the entire aortopedal arterial system is mandatory. In a randomized study, two different protocols of CEMRA were evaluated prospectively to compare their diagnostic quality and clinical usefulness. PATIENTS AND METHODS: 80 patients (males n = 60, females n = 20, median age = 70 years, diabetics n = 27) with PAOD were examined with a 1.5 T system (40 mT/m) using a dedicated phased array peripheral vascular coil. Protocol A consisted of a single injection of Gd-BOPTA with consecutive craniocaudal image acquisition and protocol B of two injections, with the first injection of Gd-BOPTA followed by image acquisition of the popliteocrural and pedal segments and the second injection followed by acquiring the aortoiliac and femoral segments (hybrid technique). The evaluation of the arterial system was directed to the iliac, femoral, popliteocrural and pedal arteries. RESULTS: The visualization of the entire aortopedal vascular system was of diagnostically good or satisfactory quality in 16 of 40 patients using protocol A and in 29 of 40 patients using protocol B (iliac 40 vs. 37, femoral 40 vs. 40, popliteocrural 35 vs. 37, pedal 16 vs. 29); without the pedal station the number increased to 35 of 40 patients for both protocols. The reason of diagnostic limitations was an arteriovenous overlap in 24 of 80 cases, with 19 of 40 cases for protocol A and 5 of 40 for protocol B, located exclusively in the cruropedal region. CONCLUSION: Moving table hybrid CEMRA is superior to conventional technique in craniocaudal direction by producing less venous overlap of arteries and is especially more suitable for the diagnostic evaluation of the cruropedal region.

Adult↗
PubMed2002

[Lab-On-A- Chip--systems for biomedical research and diagnosis].

In today's biomedical research and diagnosis, a number of substances and agents have to be checked. Frequently, plastic micro titer plates are used for this purpose as large-area test platforms. For the first time, plastic micro titer plates with 96 identical microfluidic labon-a-chip structures for simultaneous capillary electrophoresis (CE) have now been produced using microtechnical fabrication methods. Such structures are suited for e.g. the separation of biomolecules. In completely sealed microfluidic channel systems, smallest sample volumes can be processed, separated, mixed with other substances, or detected. Due to the small channel dimensions, these microfluidic systems are characterized by very small sample volumes needed.

Biomedical Research↗
PubMed2001

Modafinil for excessive daytime sleepiness in myotonic dystrophy.

The authors conducted an open-label trial of modafinil for excessive daytime sleepiness in myotonic dystrophy. Eleven patients were evaluated: two were not treated because of obstructive sleep apnea, and nine received 200 to 400 mg modafinil/day for an average of 16.4 weeks. There were no major side effects. Average sleep latency as measured by the Multiple Sleep Latency Test increased from 7.3 to 22.7 minutes ( p = 0.00013), and average Epworth Sleepiness Scale score decreased from 13.25 to 7.75 (p = 0.01028). Modafinil shows evidence of effectiveness for excessive daytime somnolence in myotonic dystrophy and should be investigated further.

Adult↗
PubMed2000

An immobilized homogeneous catalyst for efficient and selective hydrogenation of functionalized aldehydes, alkenes, and alkynes

An immobilized cationic rhodium(I) catalyst bearing the diphosphine 1,1'-bis(diisopropylphosphino)ferrocene (DiPFc, 1) allows efficient and chemoselective hydrogenation of a range of functionalized aldehydes, as well as alkenes and alkynes, under mild conditions. This heterogenized catalyst system is convenient to prepare, is stable to air and moisture over extended periods, and is readily recycled.

Journal Article↗
PubMed2000

Practical and highly enantioselective ring opening of cyclic meso-anhydrides mediated by cinchona alkaloids.

The cinchona alkaloid-mediated opening of prochiral cyclic anhydrides in the presence of methanol leading to optically active hemiesters is described. Very structurally diverse anhydrides are converted into their corresponding methyl monoesters, and either enantiomer can be obtained with up to 99% ee by using quinine or quinidine as directing additive. After the reaction, the alkaloids can be recovered almost quantitatively and reused without loss of enantioselectivity. Additionally, a catalytic protocol which permits the substoichiometric use of quinidine in the presence of easily accessible pentamethylpiperidine (pempidine) is presented.

Anhydrides↗
PubMed1997

[MR angiography using Gd-DTPA in staging of abdominal aortic aneurysm: a correlation with DSA and CT].

PURPOSE: To evaluate a contrast-enhanced (CE) MRA sequence for staging AAA. METHODS: In 24 patients (male = 20, female = 4, age = 44-81 y) with known AAA the abdominal aorta and its branches including the iliac arteries were imaged, using a 3D GRE-FISP sequence (1.5 T, TR/TE/FA = 25/6/35, slab = 100-140 mm, 32 part., FOV = 440-450 mm, matrix = 256 x 256) during an i.v. infusion of 40 ml of gadopentate dimeglumine. In addition, representative axial single slices (2D breath hold FLASH-sequence. TR/TE/FA = 82/5/30) were acquired following contrast application. MR-results were correlated with i.a. DSA and CT studies. RESULTS: With CE-MRA, AAA (n = 24) and iliac aneurysms (n = 17) could be evaluated in all cases (sens. = 100%, spec. = 100%) including luminal patency and mural thrombus. 50/54 renal arteries could be identified, 4/6 accessory renal arteries (sens. = 66.6%, spec. = 100%), 8/9 renal artery stenoses > 50% (sens. = 88.8%, spec. = 89.3%), 1/1 renal artery occlusion and 7/8 iliac artery stenoses > 50% (sens. = 87.5%, spec. = 97.5%) were depicted correctly. Proximal portion of sup. mes. art. could be detected and evaluated in 21/24 cases. Quantitative determination of therapeutically relevant vascular parameters using MRA was comparable to DSA and CT. CONCLUSION: CE-MRA is a useful method for staging of AAA and may become the method of choice when ultrafast MR techniques are used.

Adult↗
PubMed1997

[Percutaneously implanted permanent vena cava filter: follow-up of 117 consecutive patients].

PURPOSE: Retrospective review of indication, insertion technique and problems, complications and effectiveness of 5 different filter designs implanted during a period of 5 years. MATERIALS, PATIENTS AND METHODS: We inserted one Filcard-filter, 4 Antheor DC 3 perm.-filters, 17 Trigon/Cardial-filters, 28 Titan-Greenfield-filters (modified hook) and 65 LGM 30 D/U Vena Tech-filters via a femoral (n = 111) or a jugular (n = 4) approach in 115 of 117 patients. Indication was acute deep thrombosis of the iliac or femoral vein with and without pulmonary embolism (PE) in patients with contraindication to, or unsuccessful, anticoagulation therapy or lysis. Follow-up was possible in 92 patients. RESULTS: In two of 117 patients the filter could not be implanted due to dissection of the left iliac vein. In the other 115 patients we achieved an orthograde position of the filter in 78%, 22% of the filters tilted more than 15 zero and 25% had been opened incompletely. We noticed late filter dislocation in 4 cases, deep vein thrombosis of the access vein in two cases, one haematoma of the insertion site, three asymptomatic perforations of filter struts through the caval wall, 14 filter induced thromboses of the vena cava (15.2%) and 13 recurrent PE (14.1%), fatal in 5 cases (5.4%). CONCLUSION: The implantation of vena caval filters as a prophylaxis of PE is easy and of low risk. Because of the relatively high rate of recurrent PE (14.1%) in our series after implantation, the effectiveness must be judged critically.

Adult↗
PubMed1995

[Rational diagnosis of traumatic aortic rupture].

The traumatic aortic rupture has an extremely high spontaneous mortality rate. Important for surviving the trauma is a fast and efficient diagnostic procedure. The suspected diagnosis results from relatively typical criteria in the chest radiograph, especially the continuous widening of the mediastinum. The diagnostic procedure of 26 patients with polytrauma, abnormal chest radiograph and further examinations (intra-arterial digital subtraction angiography [i.a.DSA]: n = 10, contrast-enhanced CT: n = 19, CT and DSA: n = 5) was reviewed. Six patients had an aortic rupture. In 4 patients the diagnosis was confirmed by angiography, in 2 patients by surgery. The specificity was 100% for DSA and 40% for CT. To ensure the suspected diagnosis of a traumatic aortic rupture we therefore primarily recommend angiography. Whenever CT is performed in case of head injury, a CT of the thorax can be added in order to exclude mediastinal bleeding and to reduce the need for angiography.

Adolescent↗