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Biomedical subjects

R Beck

Publications and source records attributed to R Beck.

At least 37 records · Page 2Linked to original sources

[Retinal diseases with primary pulmonary hypertension].

BACKGROUND: Primary pulmonary hypertension (PPH) is a rare but fatal disease that results in right heart failure from idiopathic occlusion of the pulmonary arteries. Patients develop stagnation of venous pressure. PPH occurs most commonly in young and middle-aged women and the mean survival time from onset of symptoms is 2-3 years. The aetiology of PPH is unknown, although familial occurrence of the disease suggests a genetic predisposition. Pulmonary transplantation is reserved for patients who fail medical therapy. Pathophysiologically, PPH is a functional and structural alteration of the pulmonary blood vessels. METHODS: The authors retrospectively reviewed the clinical records of three patients (mean age 34 years) diagnosed with PPH and retinal diseases. RESULTS: All three patients developed central retinal vein occlusion (CRVO). One patient developed a neovascular glaucoma and on the other eye a serous retinal detachment with uveal effusion. A few months after the central vein obstruction was diagnosed two patients died as a result of PPH. CONCLUSIONS: The elevated venous pressure found in PPH is responsible for decreased choroidal perfusion and reduced venous blood outflow from the eye. This would explain the clinical findings of serous retinal detachment and central retinal vein occlusion in these patients.

Adult↗

Wheeze monitoring in children for assessment of nocturnal asthma and response to therapy.

The utilisation of nocturnal wheeze monitoring and quantification for assessment of asthma activity was studied in symptomatic school-aged children before and during treatment. Twelve children 6-14 yrs of age with mild or moderate untreated asthma were studied at home three times: before, 48 h and 6 weeks into treatment with 5 mg montelukast daily. Lung sounds were recorded overnight by an automatic wheeze detection device (PulmoTrack). Per cent wheezing within each respiratory cycle was calculated every 30 s throughout the night and a Nocturnal Wheeze Index (NWI) was calculated for the total night. The results were compared with spirometric indices (forced expiratory volume in one second (FEV1), forced vital capacity), bronchial reactivity (provocative concentration causing a 20% fall in FEV1 by adenosine 5'-monophosphate (PC20)) and daily symptom scores, performed in parallel at each stage of the study. The pretreatment NWI was 814+/-898 (mean+/-SD), which declined to 318+/-199 2 days after onset, and to 137+/-101 after 6 weeks of treatment. The NWI in seven healthy children was 47+/-43. The FEV1, PC20 and symptom scores improved in parallel. Wheeze monitoring provides quantitative and noninvasive information about the extent of nocturnal wheezing in children, correlates well with conventional indices of asthma activity and can assist in assessing efficacy of treatment.

Acetates↗

The reaction gammap-->pi0gamma'p and the magnetic dipole moment of the Delta+ 1232 resonance.

The reaction gammap-->pi(0)gamma'p has been measured with the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI for energies between sqrt[s]=1221-1331 MeV. The cross section's differential in angle and energy have been determined for the photon gamma' in three bins of the excitation energy. This reaction channel provides access to the magnetic dipole moment of the Delta(+)(1232) resonance and, for the first time, a value of mu(Delta(+))=[2.7(+1.0)(-1.3)(stat)+/-1.5(syst)+/-3(theor)]mu(N) has been extracted.

Journal Article↗

In-medium modifications of the pipi interaction in photon-induced reactions.

Differential cross sections of the reactions (gamma,pi(0)pi(0)) and (gamma,pi(0)pi(+/-)) have been measured for several nuclei (1H,12C, and (nat)Pb) at an incident-photon energy of E(gamma)=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the pipi invariant-mass distribution is found in the pi(0)pi(0) channel. This dependence is not observed in the pi(0)pi(+/-) channel and is consistent with an in-medium modification of the pipi interaction in the I=J=0 channel. The data are compared to pi-induced measurements and to calculations within a chiral-unitary approach.

Journal Article↗

Helicity amplitudes A1/2 and A3/2 for the D13(1520) resonance obtained from the gamma-->p-->-->ppi(0) Reaction.

The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.

Journal Article↗

Neutron polarizabilities investigated by quasifree Compton scattering from the deuteron.

Measuring Compton scattered photons and recoil neutrons in coincidence, quasifree Compton scattering by the neutron has been investigated at MAMI (Mainz) at theta(lab)(gamma) = 136 degrees in an energy range from 200 to 400 MeV. From the data a polarizability difference of alpha(n)-beta(n) = 9.8+/-3.6(stat)+2.1-1.1(syst)+/-2.2(model) in units of 10(-4) fm(3) has been determined. In combination with the polarizability sum alpha(n)+beta(n) = 15.2+/-0.5 deduced from photoabsorption data, the first precise results for the neutron electric and magnetic polarizabilities, alpha(n) = 12.5+/-1.8(stat)+1.1-0.6(syst)+/-1.1(model) and beta(n) = 2.7-/+1.8(stat)+0.6-1.1(syst)-/+1.1(model), are obtained.

Journal Article↗

Test of low-energy theorems for 1H(--> gamma, pi(0))(H)in the threshold hegion.

The photon asymmetry in the reaction 1H(--> gamma,pi(0))(1)H close to threshold has been measured for the first time with the photon spectrometer TAPS using linearly polarized photons from the tagged-photon facility at the Mainz Microtron MAMI. The total and differential cross sections were also measured simultaneously with the photon asymmetry. This allowed determination of the S-wave and all three P-wave amplitudes. The values obtained at threshold are E(0+) = [-1.33+/-0.08(stat)+/-0.03(syst)] x 10(-3)/m(pi(+)), P(1) = [9.47 +/- 0.08(stat) +/- 0.29(syst)] x 10(-3)q/m(2)(pi(+)), P(2) = [-9.46 +/- 0.1(stat) +/- 0.29(syst)] x 10(-3)q/m(2)(pi(+)), and P(3) = [11.48 +/- 0.06(stat) +/- 0.35(syst)] x 10(-3)q/m(2)(pi(+)).

Journal Article↗

Molecular pathogenesis of Epstein-Barr virus associated posttransplant lymphomas: new insights through latent membrane protein 1 fingerprinting.

BACKGROUND: Fingerprint amino acid patterns within the carboxy terminus of the latent membrane protein (LMP1) oncoprotein of Epstein-Barr virus (EBV) allow individual strain identification at the molecular level. LMP1 is expressed in the tumor cells of EBV-associated posttransplant lymphomas (PTLs) and the LMP1 genome is also identified in lymphocytes of most donors of allogeneic bone marrow. Therefore, LMP1 genotyping in donor lymphocytes and PTL tumor cells, together with sex chromatin determination of tumor cells, allows to determine the origin of PTL tumor cells and the origin of individual EBV strains harboured by them. METHODS: We traced the origin of aggressive PTLs occurring in six patients after allogeneic T cell-depleted stem cell transplantation (allo-SCT). DNA was extracted from donor lymphocytes and PTLs of recipients and amplified with LMP1-specific primers in each case. A comparative sequence analysis of the fingerprint LMP1 region identified in donor lymphocytes and lymphoma was performed. RESULTS: One lymphoma of donor origin occurred after highly selected CD34+ PBSCT and contained the same LMP1 genotype as the donor lymphocytes. Three lymphomas of recipient origin had deletions within the carboxy terminus of LMP1, not identified in the donor strains. All lymphomas occurred in the setting of allo-SCT and had a rapid clinical course. CONCLUSIONS: These results show that highly selected CD34+ PBSCT does not protect against transfer of EBV positive founder cells of donor type PTL and that, after allo-SCT, recipient type PTLs are not uncommon. Outgrowth of recipient type lymphoma may be favoured by LMP1 deletion variant strains present in recipient lymphocytes.

Adult↗

Direct observation of a rho decay of the D13(1520) baryon resonance.

The reaction gammap-->pi(+)pi(0)n has been measured at MAMI for photon energies up to 820 MeV. Invariant mass spectra of the particles in the final state (pi(+)n), (pi(0)n), (pi(+)pi(0)) have been determined for several bins of incident photon energy. Differences in pi(+)pi(0) and simultaneously measured pi(0)pi(0) invariant mass distributions are assigned to a rho branch of the D13(1520) nucleon resonance.

Journal Article↗

In-medium properties of the D13(1520) nucleon resonance.

The in-medium properties of the D13(1520) nucleon resonance were studied via photoproduction of pi(0) mesons from nuclei (C, Ca, Nb, Pb) with the TAPS detector at the Mainz Microton accelerator. The inclusive (single and multiple pion production) data disagree with model predictions which explain the disappearance of the second resonance bump in total photoabsorption via a medium modification of the D13-->Nrho decay. The exclusive single pi(0) production data show no broadening of the resonance structure beyond Fermi smearing. Both results together cast doubt on attempts to explain the vanishing of the second resonance bump for nuclei by a broadening of the D13 resonance.

Journal Article↗

[Orbital space-occupying lesions. Practical aspects of imaging].

During the period 1992-1998,we diagnosed orbital tumors in 23 cases at the MLU Halle-Wittenberg. In the intraconal compartment we mostly saw cavernous hemangiomas and neurogenic tumors. Lymphomas and a primary meningioma were located in the extraconal space. Beneath the periosteum, bony processes, tumors of the sinuses, dermoid-and epidermoid-cysts normally occur, but we only observed metastases and hematomas. Furthermore,tumors of the lacrimal gland and inflammatory lesions were diagnosed. Orbital tumors are uncommon lesions, whose location in the orbit gives an important hint to differential diagnosis, because a high percentage of various pathologies is located in special compartments of the orbit. According to our results,the MRI-scan is usually sufficient for differentiation and for preoperative planning in order to reduce the X-ray dose of the lens. CT-scans with contrast are sometimes necessary for examining bone destroying processes and for planning the surgical approach to removing the tumor. X-rays of the skull widely lost their importance in the exact diagnostic of orbital tumors. B-scan ultrasonic imaging is reserved for screening and follow-up examination. Despite the use of MRI and CT scanning, the histological examination remains necessary.

Combined Modality Therapy↗

[Measuring corneal volume. A possible quality parameter in cataract surgery?].

BACKGROUND: Phacoemulsification of the lens induces changes in the inner corneal architecture. This study quantified the corneal pre- and postoperative volumes. METHODS: Corneal volume was measured by noninvasive corneal topography using Orbscan. Following phacoemulsification with lens implantation, 56 eyes of 55 persons were examined by three Orbscan tests: preoperatively and 6 h and 24 h after cataract surgery. Healon was used as viscoelastic medium. RESULTS: The mean corneal volume in the 3-mm central corneal diameter was 4.64 mm3 preoperatively, 5.36 mm3 6 h postoperatively, and 5.05 mm3 24 h postoperatively. Corneal volume thus increased by 0.72 mm3 within 6 h after phacoemulsification and decreased by 0.31 mm3 over the following 18 h. CONCLUSION: Orbscan offers a noninvasive method for obtaining useful and accurate information in defining the corneal volume. This method may represent a new parameter for describing the function of corneal endothelial cells in cataract surgery.

Adult↗

Inhibition of lens epithelial cell adhesion by the calcium antagonist Mibefradil correlates with impaired integrin distribution and organization of the cytoskeleton.

BACKGROUND: Posterior capsule opacification is the most common complication of primary cataract surgery and is caused by migration and proliferation of residual lens epithelial cells onto the posterior capsule. Interfering with the mechanisms involved in cell adhesion is a suitable approach to prevent posterior capsule opacification. METHODS: Mibefradil, a T-type calcium-channel blocker, was used to examine the influence on adhesion-mediating mechanisms in human lens epithelial cells derived from cataract surgery. Adhesion was evaluated by light microscopy on the anterior capsules. Expression of integrin receptors was studied by flow cytometry. The influence on the distribution of integrin receptors on the cell surface and the organization of the cytoskeleton was examined by immunofluorescence using a confocal microscope. RESULTS: The calcium-channel blocker Mibefradil inhibited cell adhesion on the anterior capsule wall at concentrations between 10 and 100 pNM. The cells expressed the integrin subunits beta1 and alpha3. Mibefradil distinctly impaired the distribution of these integrins on the cell surface in culture. The cells express the cytoskeletal components actin, vimentin and, very weakly, cytokeratin. The structural organization of the actin filaments and vimentin was strongly disrupted with pronounced fragmentation of the actin filaments in the presence of the calcium-channel blocker. CONCLUSION: The results suggest that the inhibition of cell adhesion by the calcium-channel blocker Mibefradil involves the impairment of integrin-mediated mechanisms. The use of this calcium antagonist appears to be a suitable therapeutic approach to prevent posterior capsule opacification.

Calcium Channel Blockers↗

Analysis of aqueous humour proteins of eyes with and without pseudoexfoliation syndrome.

UNLABELLED: Pseudoexfoliation syndrome (PEX) has been suggested to represent a blood-aqueous barrier impairment leading to a higher protein content in aqueous humour of eyes with PEX. However, the nature of a prospective PEX protein has not yet been described. We set out to reevaluate protein content and examine protein composition for prospective PEX protein candidates in aqueous humour of eyes with PEX syndrome. Aqueous humour of 52 patients with PEX and 38 without PEX signs was sampled during cataract or glaucoma surgery. Total aqueous protein concentration in the samples was analysed in 43 PEX specimens and 32 non-PEX specimens according to Bradford. Aqueous protein composition of all samples was determined by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS PAGE) and silver staining. Screening for amyloids was performed in nine PEX samples and six non-PEX samples by Congo Red staining and polarised light microscopy. Aqueous protein concentration was not significantly increased in PEX eyes in comparison with non-PEX eyes. Furthermore, we could not detect any characteristic difference in protein band sizes of the two groups after SDS PAGE. However, we were able to show the presence of amyloid exclusively in aqueous humour of PEX patients. CONCLUSION: our results do not confirm a generally higher protein concentration in pseudoexfoliation syndrome eyes. This does not necessarily contradict a blood-aqueous barrier impairment but illustrates the variance in protein concentration between and within the two groups. No characteristic protein band allocatable to pseudoexfoliation syndrome proteins could be detected in any of the samples. However, our findings support the theory that the pseudoexfoliation syndrome is associated with an amyloid of a serum protein.

Aged↗

[Effect of intraocular lens design on posterior capsule opacification: an in-vitro model].

BACKGROUND: The development of posterior capsule opacification (PCO) is one of the commonest complications of modern cataract surgery. The various designs of intraocular lenses (IOL) seem to exert a barrier effect on the proliferation and migration of lens epithelial cells and the following development of PCO. METHODS: We set up a cell culture model (advanced 3D capsular bag model) and investigated six differently designed IOL made of different materials as to their effect on cell proliferation. Proliferation and migration of the cells were analysed and documented over a period of 28 days. A cell viability test using the LIVE/DEAD kit (Molecular Probes) was carried out at the end of the investigation. RESULTS: In all tests, lens epithelial cells adhered to and migrated onto the capsular bag. During the culture period, lens epithelial cells migrated only to the optical rim of two of the implanted IOL. On the other four, lens epithelial cells migrated further and covered the whole optical area of the IOL. CONCLUSIONS: Certain lens designs seem to have a reducing effect on the development of PCO. Our advanced in vitro capsular bag model is a suitable cell culture model for the investigation of the reducing effect of various IOL on the development of PCO.

Cataract↗

Erosion of belief and disbelief: effects of religiosity and negative affect on beliefs in the paranormal and supernatural.

The authors investigated the effects of religiosity and negative affect on beliefs in the paranormal and supernatural among 94 undergraduate students enrolled in psychology classes at a small, private U.S. university. They hypothesized that religiosity would predict differential beliefs in the supernatural versus the paranormal but that negative affect would attenuate these beliefs. In addition, the authors predicted that belief in the supernatural and negative affect would interact to predict belief in the paranormal. Overall, the results were consistent with predictions. The religious participants were skeptical of paranormal phenomena but were accepting of supernatural phenomena. In addition, increased reports of negative affect over the preceding year appeared to attenuate belief in the supernatural for the religious participants. By contrast, for the nonreligious participants, increased belief in both the supernatural and paranormal was predicted when reports of negative affect were high. Finally, the interaction of supernatural belief and negative affect significantly predicted belief in the paranormal.

Adult↗