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Biomedical subjects

B Frick

Publications and source records attributed to B Frick.

At least 37 records · Page 2Linked to original sources
PubMed2002

Moderate hyperhomocysteinaemia and immune activation in Parkinson's disease.

Moderate hyperhomocysteinaemia has been linked to an increased risk for cardiovascular diseases. Increased homocysteine concentrations may follow folate depletion due to insufficient dietary intake of the vitamin, but there is also some indication that immune activation could play a role. In this preliminary study, homocysteine, folate, and vitamin B(12) concentrations were measured in 19 patients with Parkinson's disease, 61-90 years of age, and compared to a healthy control group of similar age and to neopterin concentrations as an indicator of immune activation. A subgroup of patients presented with increased homocysteine and low folate concentrations. Homocysteine levels correlated inversely with vitamins folate and B(12) and positively with neopterin concentrations. Disturbed homocysteine metabolism in Parkinson's disease may be associated with vitamin deficiency and with immune system activation which may underlie folate depletion.

Aged↗
PubMed2002

Frequency of the Amsterdam criteria in a regional German cohort of patients with colorectal cancer.

Estimates of the colon cancer burden associated with hereditary nonpolyposis colorectal cancer (HNPCC) vary from less than 1 % to more than 5 %. Amsterdam criteria fulfilled within a kindred (classic Amsterdam and Amsterdam II criteria) are widely used to identify patients prone to HNPCC. The present study was initiated to assess the frequency of the Amsterdam criteria within a regional German cohort of 207 patients with a history of colorectal cancer (CRC). Data on individual and family cancer histories were available in 154 patients (73 women, 81 men; mean age at diagnosis 62.4 +/- 13.3 years). A total of 843 first degree relatives have been identified within the kindreds of whom 121 had verified cancers. In 28 of 154 families (18 %), at least one first degree relative of the index patient had CRC. With respect to a typical family history, five kindreds (3.2 %) were likely to suffer from HNPCC on a clinical basis (4 kindreds met the classic Amsterdam criteria and one kindred the Amsterdam II criteria). Testing for microsatellite instability could additionally be performed in 4 of 5 patients who met the Amsterdam criteria and revealed DNA instability in 3 cases. Moreover, a missense mutation of MSH2 (Gly965Asp) was detected in one patient with microsatellite instability. Based on the classic Amsterdam and Amsterdam II criteria approximately 3 % of a regional German cohort of patients with CRC are likely to suffer from HNPCC. However, the final diagnosis of HNPCC can only be established by detection of pathogenic germline mutations within the DNA mismatch repair genes.

Adult↗
PubMed2001

Photoinduced dynamics in a photosensitive side chain polymeric liquid crystal by quasielastic and inelastic neutron scattering.

We report the first study by inelastic (INS) and quasielastic neutron scattering of photoinduced changes in the reorientational and vibrational dynamics of a liquid crystalline side chain polymer. We use the cis-trans photoisomerization transition to take the system out of equilibrium and determine the quasielastic (QE) and inelastic scattering laws on two distinct time windows, corresponding to the time-of-flight (IN6) and backscattering (IN16) spectrometers at Institut Laue Langevin (ILL) (Grenoble). Our investigation was focused on the dynamics of the coupling between the mesogenic side chains and the polymeric main chain, which is connected to the extensive optical writing and memory effects that have been demonstrated in this complex material. We report data on the QE broadening and Debye-Waller factors, as a function of temperature across the glass transition (T(g)=293 K). We also studied the dynamical coupling of side and main chains. We report photoinduced changes on the static structure factor, on the purely elastic scattering fraction, on the low frequency vibrational dynamics (around the boson peak region). In particular, we find that on the space-time scales accessible to the INS techniques there is a time structure in the coupling, and that over longer times and distances the two dynamics are decoupled.

Journal Article↗
PubMed1999

Brillouin and Umklapp scattering in polybutadiene: comparison of neutron and x-ray scattering.

We report a comparison of high resolution inelastic x-ray Brillouin scattering to coherent inelastic neutron scattering for amorphous deuterated polybutadiene, done for one temperature in the glass phase and another one in the melt. The x-ray scattering proves to be by far the better technique for such a polymer within its present resolution bounds. The neutron scattering allows one to extend these measurements to a much better resolution, showing an additional quasielastic signal in the melt. The results suggest x-ray measurements at higher momentum transfer, to see whether they are complementary to neutrons.

Journal Article↗
PubMed1998

Investigation of the Dielectric beta-Process in Polyisobutylene by Incoherent Quasielastic Neutron Scattering.

Recently by dielectric spectroscopy a new secondary relaxation process in polyisobutylene (PIB) was detected showing all the signatures of a Johari-Goldstein relaxation [Richter, D; Arbe, A.; Colmenero, J.; Monkenbusch, M.; Farago, B.; Faust, R. Macromolecules 1998, 31, 1133]. Using high resolution neutron backscattering, we investigated the quasielastic neutron spectra from protonated PIB which are related to this process as a function of momentum transfer and temperature. In addition we studied the elastically scattered intensity over a wide temperature range. After multiple scattering corrections all results can be described consistently in terms of a local jump process with the distribution parameters from the dielectric beta-relaxation. The spatial extent of the associated protonic motion was determined to be d = 2.7 Å. A comparison with the existing body of data for PIB leads to the conclusion that the dielectric beta-process and the earlier found delta-process must be identical, thereby revising the assignment of the delta-process as due to methyl group rotation. Finally, we remark on aspects of the relation between quasielastic coherent and incoherent scattering and address the seemingly contradictory result of different length scales revealed for the same process with the two techniques.

Journal Article↗
PubMed1992

[Hemobilia as a rare cause of gastrointestinal bleeding].

In a 67-year-old man with upper abdominal and gastrointestinal bleeding gastroscopy revealed a duodenal ulcer which was initially taken to be the source of the bleeding. But subsequent retrograde cholangiography demonstrated nearly complete occlusion of the right hepatic duct and a suspicious tumour-like structure. At laparotomy a tumour was excluded and the supplying artery to the ulcer was ligated to arrest the bleeding. Gastrointestinal bleeding recurred postoperatively so that selective angiography of the hepatic artery had to be performed. This demonstrated an aneurysm of a branch of the hepatic artery near the hilus. No further bleeding occurred after its embolization. Haemobilia is a rare cause of upper abdominal bleeding and may be difficult to diagnose, except by selective imaging techniques.

Aged↗