Search PubMed⌕ Search

Biomedical subjects

T Vogt

Publications and source records attributed to T Vogt.

At least 37 records · Page 2Linked to original sources
PubMed2003

Identification of differentially expressed genes in models of melanoma progression by cDNA array analysis: SPARC, MIF and a novel cathepsin protease characterize aggressive phenotypes.

Currently, the scale and consistency of changes of gene expression profiles in models of melanoma progression are largely unknown. Therefore, we investigated siblings of cell lines or malignant melanomas (MM), which have been selected by nude mouse passages for (a). increased tumorigenicity (local ECM-independent growth), (b). metastatic potential, or (c). selected for increase invasiveness using the Boyden chamber. cDNA array analysis surveying more than 27.000 transcripts per cell line showed that 1.5-2.8% of all detectable transcripts were consistently differentially regulated during selection process in those models. Using array analysis, we identified 33 individual transcripts that exhibited significant differential hybridization paralleling the increased aggressiveness of the selected progeny. Because some of those genes could play a significant functional role in the progression of MM, we additionally proved their regulative pattern using Northern blotting. Among others, progressive overexpression of osteonectin/SPARC, a angiogenesis, was found in the selected offspring from all three experimental models and may therefore be considered as a potential marker for aggressive MM as well a promising therapeutic target. We further show that the selection of MM cells for increased ECM-independent local growth was accompanied by overexpresssion of macrophage migration inhibiting factor (MIF), an important modulator of both cell cycle progression and angiogenesis, and cathepsin Z, a novel member of the family of matrix degrading proteinases.

Animals↗
PubMed2003

The scattering of guided waves in partly embedded cylindrical structures.

The scattering of ultrasonic guided waves at a point where a free cylindrical waveguide enters an embedding material is investigated. A modal solution that is valid when the guided waves are incident from the free section of the waveguide is developed. It is shown that in this case it is valid to consider only the modal fields over the cross section of the waveguide, neglecting the fields in the embedding material. As an application, the scattering of the lowest-order longitudinal mode in a cylindrical waveguide, L(0,1), is examined in detail. As well as considering epoxy resin as an embedding material, the case where the embedding material is replaced by a perfectly rigid boundary is discussed. The latter gives some insight into the role of nonpropagating and inhomogeneous waveguide modes in the scattering process. The results from the modal solution are validated using Finite Element modeling, very good agreement being obtained.

Journal Article↗
PubMed2003

Cure monitoring using ultrasonic guided waves in wires.

The possibility of using ultrasonic guided waves for monitoring the cure process of epoxy resins is investigated. The two techniques presented use a wire waveguide which is partly embedded in the resin. The first technique is based on the measurement of attenuation due to leakage of bulk waves into the resin surrounding the waveguide. The second technique measures the reflection of the guided wave that occurs at the point where the waveguide enters the resin. Both the attenuation and the reflection coefficient change significantly during cure, and the numerical methods to relate these to the material properties of the curing resin are presented in this paper. The results from the modeling are experimentally verified and show good agreement. The applicability of each testing method is discussed, and typical cure-monitoring curves are presented.

Journal Article↗
PubMed2002

Structure of intercalated Cs in zeolite ITQ-4: an array of metal ions and correlated electrons confined in a pseudo-1D nanoporous host.

The presence of Cs+ ions in the pseudo-1D nanopores of zeolite ITQ-4, Si32O64, is confirmed by x-ray diffraction and atomic pair distribution function analysis. Inside the nanopores the Cs+ ions are found to assemble in zigzag chains and thus form an extended, positively charged sublattice providing charge balance for a low-density electron gas also confined to the nanopores.

Journal Article↗
PubMed2002

Unraveling the symmetry of the hole states near the Fermi level in the MgB2 superconductor.

We use x-ray absorption spectroscopy (XAS) and electron energy loss spectroscopy (EELS) to study the fine structure at the K edge of boron in MgB(2). We observe in XAS a peak of width 0.7 eV at the edge threshold, signaling a narrow energy region with empty boron p states near the Fermi level. The changes in the near edge structure observed in EELS with direction of the momentum transfer imply that these states have p(x)p(y) symmetry. Our observations are consistent with electronic structure calculations indicating a narrow energy window of empty p(x)p(y) states that falls to zero at 0.8 eV above the Fermi level. The disappearance of the p(x)p(y) feature in EELS at grain boundaries suggests that this signature may become powerful in probing superconductivity at nanoscale.

Journal Article↗
PubMed2002

Clinical outcome and predictive value of electrodiagnostics in endoscopic carpal tunnel surgery.

Forty-three patients (50 hands) with clinically and electrophysiologically confirmed carpal tunnel syndrome were included in a prospective study to determinate the clinical outcome and electrophysiological recovery of the median nerve after endoscopic transection of the transverse carpal ligament (TCL). Evaluation included a questionnaire for symptoms, physical examination, grip force measurements, and electrophysiological testing before surgery and at weeks 4 and 20 after surgery. As compared to the preop baseline, the rates of permanent paraesthesia, pain, the presence of Tinel's sign, and thenar atrophy decreased significantly. The majority (94%) of the patients had no residual disturbances and were satisfied with the results. Complications were observed in 4.5%, and the treatment had to be changed to an open release. Nerve conduction studies (NCS) showed significant improvement, but many were still abnormal after 4 months. Since failure of improvement could not be predicted by the electrophysiological data, monitoring the postoperative nerve conduction is not very sensitive in characterising the individual clinical course. Our patients were in hospital for 3.3 days. The time of return to work differed between patients that were self employed (4.3 days) and those working as employees (19 days).

Adult↗
PubMed2002

Hepatic veno-occlusive disease (VOD) with complete occlusion of liver venules after tandem autologous stem cell transplantation-- successful treatment with high-dose methylprednisolone and defibrotide.

Veno-occlusive disease (VOD) is a life-threatening complication following allogeneic or autologous stem cell transplantation. We report on a patient with a high grade B-cell lymphoma who presented 28 days after the second autologous stem cell transplantation with weight gain, ascites, hyperbilirubinemia, and liver venules occlusion as demonstrated by sonography. Starting with high-dose methylprednisolone treatment followed by defibrotide maintenance therapy the patient showed dramatic complete response of VOD, resulting in a normal sonography of the liver and normalization of laboratory values. The response of the occlusion of nearly all liver venules underlines the value of anti-inflammatory treatment combined with new thrombolytic medication such as defibrotide for the treatment of severe VOD.

Adult↗
PubMed2002

[Psoriatic onycho-pachydermo- periostitis].

We report about a patient with a 2 year history of palmo-plantar psoriasis and psoriatic involvement of the nails. Within six months he developed a psoriatic onychodystrophy and painful swellings of the toes and fingers. X-rays revealed acral lamellar periostitis. The case of this patient represents a rare variety of psoriatic arthritis: The psoriatic onycho-pachydermo-periostitis. After a 6 week therapy with methotrexate (15mg per week) the nails began to grow regularly. Therefore, in cases of psoriasis with unusual symptoms of psoriatic arthritis the psoriatic onycho-pachydermo-periostitis should be included in differential diagnosis and therapy.

Adult↗
PubMed2002

Deep-brain stimulation for Parkinson's disease.

Deep brain simulation (DBS) is a powerful new therapeutic approach for patients with Parkinson's disease. However, patient selection is critical for a valuable therapeutic result. Dopa sensitivity of the target symptoms, severe disability and low neurosurgical risks are among the major criteria for this indication. Other criteria like age or cognition must still be addressed in future prospective studies. The preferred target for DBS in PD is the subthalamic nucleus for various good reasons. However, prospective studies for this procedure are lacking and some clinical problems may be more easily solved with targeting the internal pallidum or the thalamus. Despite major progress in this field, much work remains to be done.

Electric Stimulation Therapy↗
PubMed2002

Practical importance of neuroprotection in Parkinson's disease.

Consensus could be reached that there is overwhelming evidence of preclinical neuroprotection. However, the evidence of neuroprotection/neurorescue under clinical conditions is limited. Lessons from clinical trials designed to show neuroprotection (selegiline, amantadine, dopamine agonists) demonstrate that with the drugs available neuroprotection/neurorescue has to start as early as possible. A PET-controlled clinical trial with ropinirole shows that there seems to be a good chance for neuroprotection in the early phase of Parkinson's disease in patients treated from the very beginning of the disease while there is no such benefit in patients with a late start of a neuroprotective therapeutic strategy. Also long-term clinical neuroprotection cannot be reached. Complicating factors to demonstrate clinical neuroprotection are discussed.

Amantadine↗
PubMed2002

Glass classification by linear discriminant analysis of LA-ICP-MS data.

The classification of pharmaceutical and common glasses (ampoules, infusion bottles, cylinders, lead crystal and bottle glass) has been performed means by of chemometric methods. For this purpose intensity data of glass examinations received by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were applied. A Nd:YAG laser with 10 Hz repetition rate in the Q-switch mode at its 4th harmonic (266 nm) was used to get mass spectrometric data of the glasses. 13 isotopes (= variables) were used for measurements (7Li, 11B, 23Na, 24Mg, 27Al, 28Si, 39K, 42Ca, 47Ti, 57Fe, 123Sb, 137Ba, 207Pb). The glass samples represented four types of glasses: 1. borosilicate glass (type "Duran") 2. borosilicate glass (type "Fiolax") 3. soda-lime glass 4. lead glass. Calculations were made by using the SAS statistical software. All results were obtained on the assumption that the underlying data are normally distributed. By applying linear discriminant data analysis a classification of all types of the glasses was possible (13 variables included). The use of the method of "stepwise discriminant analysis" reduced the minimal required number of variables to eight. All types of glasses could be distinguished faultlessly. Besides a graphic system consisting of the isotopes 24Mg-47Ti-137Ba was developed. By means of this system optical distinction of glass classes was possible. The developed method allows to distinguish several types of pharmaceutical and common glasses on the basis of intensity data of mass spectrometric measurement without calibration experiments and linear regression.

Algorithms↗
PubMed2001

Optical response of high-dielectric-constant perovskite-related oxide.

Optical conductivity measurements on the perovskite-related oxide CaCu3Ti4O12 provide a hint of the physics underlying the observed giant dielectric effect in this material. A low-frequency vibration displays anomalous behavior, implying that there is a redistribution of charge within the unit cell at low temperature. At infrared frequencies (terahertz), the value for the dielectric constant is approximately 80 at room temperature, which is far smaller than the value of approximately 10(5) obtained at lower radio frequencies (kilohertz). This discrepancy implies the presence of a strong absorption at very low frequencies due to dipole relaxation. At room temperature, the characteristic relaxation times are fast (less than or approximately 500 nanoseconds) but increase dramatically at low temperature, suggesting that the large change in dielectric constant may be due to a relaxor-like dynamical slowing down of dipolar fluctuations in nanosize domains.

Journal Article↗
PubMed2001

Transition from the layered Sr2RhO4 to the monodimensional Sr4RhO6 phase.

Study of the structural changes occurring during the reduction process of the Sr2RhO4+delta, (214), n=1 term of the Ruddlesden and Popper series, shows that for delta <0.02 values, this material dissociates into the Sr4RhO6 (416) monodimensional phase, alpha = infinity, beta = 0 compound of the (A3B2O6)alpha-(A3B3O9)beta family, and Rh metal. During the first stage, this process occurs by the formation of an intergrowth between the (214) and (416) materials which can be only detected by high resolution electron microscopy and is easily interpreted on the basis of the structural relationship established between them. Further reduction allows the segregation of both phases as separated entities, which coexist with Rh metal. The dissociation process is reversible and, under oxidizing conditions, a layered material with anionic composition delta =0.06 is always obtained. This behaviour seems to be a general way of accommodating the compositional changes in layered A2BO4 phases where the B cation is always in a octahedral environment. The structural mechanism of this transformation is proposed, and the structural relationship between these two low-dimensional oxides is established.

Journal Article↗