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U Weber

Publications and source records attributed to U Weber.

At least 73 records · Page 4Linked to original sources
PubMed1999

Design and construction of a ripple filter for a smoothed depth dose distribution in conformal particle therapy.

The ripple filter was designed to broaden the Bragg maximum of carbon beams for the raster-scan technique, a special type of tumour-conformal ion beam treatment. In this technique the target volume is divided into individual layers that are treated sequentially by varying the energy from the accelerator stepwise. Because the unmodified Bragg maximum has a small half-width, below 1 mm for small energies (< 160 MeV u(-1)), homogeneous irradiation at small penetration depths of 2-6 cm can only be obtained by using a large number of energy steps. If the energy step is too large, ripples are produced in the superimposed depth dose distribution. The ripple filter widens a Bragg peak to a Gaussian peak with a half-width of more than 2 mm. This helps to smooth the extended Bragg peak and to reduce the number of energy steps required by a factor of two to three, leading to significantly shorter overall irradiation times and a higher particle fluence per layer. The ripple filter consists of a 2 mm thick Plexiglass (PMMA) plate with a periodic structure of fine grooves. It can be mounted 60 cm upstream of the patient as a stationary device, because the fine structure of the grooves is completely washed out by the lateral scattering of the beam.

Algorithms↗
PubMed1999

Minor role of Cl- secretion in non-cystic fibrosis and cystic fibrosis human nasal epithelium.

Na+ and Cl- currents were studied in primary cultures of human nasal epithelium derived from non-cystic fibrosis (non-CF) and cystic fibrosis (CF) patients. We found that Na+ absorption dominates transepithelial transport and the Na+ current contains an amiloride-sensitive and amiloride-insensitive component. In non-CF tissue both components contribute about equally to the entire short-circuit current (ISC), whereas in CF tissues the major part of the current is amiloride-sensitive. Na+ removal reduced ISC to values close to zero. Several Cl- channel blockers were used to identify the remaining tiny Na+-independent current. Under unstimulated, physiological conditions in the presence of Cl- on both sides and amiloride on the apical side of the epithelium diphenylamine-2-carboxic acid (DPC), 4,4'-diisothiocyanatostilbene-2, 2'- disulfonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) failed to induce clearcut inhibition of ISC. cAMP as well as ATP did not affect ISC either in CF or in non-CF epithelia. Reduction of apical Cl- increased ISC and depolarized transepithelial potential; however, the observed increase was insensitive to DIDS, DPC and NPPB. From these data we conclude that Cl- conductances in primary cultures of human nasal epithelium derived from CF patients as well as from non-CF patients are present only in low numbers or do not contribute significantly to transepithelial ion transport.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1999

Cisapride versus placebo for 8 weeks on glycemic control and gastric emptying in insulin-dependent diabetes: a double blind cross-over trial.

In insulin-dependent diabetes mellitus, slow gastric emptying may make absorption unpredictable and foster glycemic instability. Cisapride accelerates emptying, but controlled long term studies are scarce, and effects on glycemic control unknown. We investigated, in patients with insulin-dependent diabetes mellitus and unstable glycemia, the effects of 10 mg cisapride 4 times daily for 8 weeks vs. placebo on glycemic control and gastric emptying under random, cross-over, double blind conditions. In 14 patients with delayed and 9 with nondelayed emptying, blood glucose variability over 28-week treatment periods separated by a 4-week wash-out and gastric emptying of a semisolid 1168-kJ meal immediately after the treatment periods were assessed. Cisapride did not affect glycemic control [SD of within-patient mean blood glucose, 4.2 mmol/L +/-0.1 (+/- SEM) vs. 4.0+/-0.1 mmol/L after placebo; hemoglobin A1c, 8.3+/-0.2% vs. 8.5+/-0.2%]. Emptying was faster after cisapride than after placebo in 8 of 14 patients with delayed vs. 7 of 9 with nondelayed emptying (P = NS) and in 11 of 15 without vs. 4 of 8 with cardiovascular autonomic neuropathy (P = NS). Autonomic neuropathy prevailed in 7 of 14 patients with delayed and 1 of 9 with nondelayed emptying. Blood glucose immediately before and during assessment of emptying was unrelated to the emptying rate, whereas blood glucose increases over fasting levels were greater with faster emptying (P<0.002). In conclusion, cisapride's effects were not different from those of placebo on glycemic control and gastric emptying, it did not differently affect patients with delayed vs. nondelayed emptying, and it slightly accelerated emptying (P = NS) in patients without, but not in those with, cardiovascular autonomic neuropathy. Blood glucose levels before and during assessment of emptying did not affect emptying, but the glucose rise over fasting levels was greater with faster emptying.

Adult↗
PubMed1999

Sec61beta, a subunit of the protein translocation channel, is required during Drosophila development.

We have identified and isolated mutations in the first Drosophila gene encoding a subunit of the Sec61 protein translocation channel, DSec61beta. While neither the Saccharomyces cerevisiae Sec61beta nor its functional Escherichia coli homologue are essential for viability or for protein translocation, we show that DSec61beta is essential for embryonic development. Homozygous mutant embryos die at the end of embryogenesis and are impaired in the secretion of cuticle proteins from the epidermis. DSec61beta germ line clones, result in defects in dorso-ventral patterning of the egg and are consistent with affected secretion of the protein Gurken from the oocyte to the follicle cells. Clonal analyses in the imaginal discs reveal defects in adult structures, including rhabdomere morphogenesis and a reduction of the size of tarsal segments in the leg. This is the first in vivo study of a component of the protein translocation machinery in higher eukaryotes, and illustrates how a protein that has an inessential, kinetic function in single-cell organisms can become critical for the complex development of a multicellular organism.

Alleles↗
PubMed1999

Immunohistological analysis of cytokine expression in human osteoarthritic and healthy cartilage.

OBJECTIVE: To investigate osteoarthritic cartilage in comparison to normal cartilage in humans for the presence of the most relevant cytokines/growth factors known to be important for degradation and formation of new cartilage. METHODS: Cartilage from knee or hip joints was obtained from 10 patients with osteoarthritis (OA) and from 7 age matched control patients with intact cartilage. Additionally, normal cartilage from 2 young patients (12 and 17 years old) was obtained after knee traumas. Immunohistological staining of cartilage sections was performed using antibodies for the following cytokines/growth factors: tumor necrosis factor alpha (TNF-alpha), interleukin 1alpha (IL-1alpha), IL-1beta, interferon-gamma, IL-6, IL-4, IL-10, transforming growth factor beta1 (TGF-beta1), insulin-like growth factor I (IGF-I), IGF-II, platelet derived growth factor AA (PDGF-AA), and PDGF-BB. RESULTS: Immunohistochemical stainings were positive for all cytokines in OA cartilage, while only a faint or no staining was found in healthy cartilage. Activated chondrocytes expressing most of the cytokines were located in the middle and partly in the lower layer of cartilage, with the exception of IGF-I, which was expressed exclusively in the upper cartilage layer close to the surface. More chondrocytes stained positive for TNF-alpha than for IL-1, and expression of the degrading cytokine TNF-alpha was inversely correlated to the expression of the regulatory cytokines IL-4, IL-10, and TGF-beta. CONCLUSION: The most relevant cytokines known to be involved in cartilage metabolism are produced by chondrocytes themselves. They are upregulated in OA cartilage, suggesting that they serve some regulatory function and could be a target for future treatment.

Adolescent↗
PubMed1999

[Loading on internal spinal fixation devices].

The loads acting on internal spinal fixation devices were measured for different activities in ten patients using telemeterized bisegmental implants. The highest loads were found for walking and lateral bending of the upper body while standing. When bending forwards the upper body, the fixator loads were only slightly altered. The forces and moments were not higher during sitting than during standing. Therefore, sitting should be allowed for patients with instrumented spines as soon as getting up is allowed. The forces and moments in the fixators were often altered due to anterior interbody fusion. Especially in patients with degenerative instability, the implant loads were higher after anterior interbody fusion than before. Braces were not able to markedly reduce the fixator loads. Therefore, it does not seem helpful to brace patients after mono- or bisegmental stabilization of the thoracic or lumbar spine.

Braces↗
PubMed1999

Comparison of 3,000 IU aXa of the low molecular weight heparin certoparin with 5,000 IU aXa in prevention of deep vein thrombosis after total hip replacement. German Thrombosis Study Group.

BACKGROUND: The aim of this randomized, double-blind and prospective clinical trial was to investigate whether an increase of the conventional daily dosage (3,000 IU aXa) of the low molecular weight heparin certoparin up to 5,000 IU aXa/day might lower the incidence of deep vein thrombosis (DVT) in patients undergoing elective hip surgery. METHODS: The main criterium of this trial was the incidence of DVT diagnosed by bilateral ascending venography, which was performed either if DVT was clinically suspected or in each remaining patient between the 12th and the 14th postoperative day. A total number of 172 patients were enrolled to receive the conventional dosage of 3,000 IU aXa (Mono-Embolex NM) and 169 patients to receive the high dosage form (5,000 IU aXa) once daily. The mean age (+/-SD) was 69.6+/-9.5 and 67+/-11.7 years. RESULTS: No relevant differences were found concerning predisposing risk factors. The duration of surgery was 93+/-25.2 and 88+/-21.4 min (mean+/-SD). Surgical type and approach were not different between the groups. Deep vein thrombosis was detected in 17 patients (9.9%) in the conventional dose group and in 16 patients (9.5%) in the high dose group (intent-to-treat analysis; n.s.). The rate of bleeding complications was not significantly different except the cell saver volumes (770+/-136 vs 475+/-186 ml; p<0.001). No significant difference was found in the serious adverse event reporting along the lines of EC-GCP (10 vs 8 events; p=0.65). CONCLUSIONS: This clinical trial confirmed that the conventional dosage (3,000 IU aXa/day) of certoparin ensures maximal antithrombotic activity.

Adult↗
PubMed1999

[The operative therapy of distal unstable radius fractures with dorsal and palmar plates. A retrospective study with respect to the DASH-score system].

The distal radius fracture is the most common human skeletal injury. Predominantly woman in the 6th to 7th decade are found. There is a high correlation to the post menopause high turn over osteoporosis and its negative calcium balance. Due to the various multifactoral radius fracture combinations is a detailed classification with its correlated treatment important. The operative intervention in the past played a secondary roll. The newest concepts demand an exact reconstruction of the articulating surfaces through closed reposition and K-wire support, screw osteosynthesis, external fixation and its combinated forms. The posttraumatical joint changes with secondary palmar and dorsal dislocation of the radius base after reduction caused the exact therapy scheme with respect to the AO-classification to be developed. In the clinic and policlinic Oskar-Helene-Heim of the Free University in Berlin 213 patients were surgicly treated on distal radius fractures either from volar or dorsaly with a plate osteosynthesis between 1988-1998. In cases of multidirectionional fractures with compression of the articular surfaces we combined a bicortal bone block or spongiosa to support and to avoid the secondary dislocation and thus arthrosis. The study was divided in three sections, beginning with the clinical inspection. Further followed the X-ray evaluation and the assessment of the DASH-scores.

Aged↗
PubMed1999

[Medical rehabilitation in long-term disability].

UNLABELLED: Based on data from a prospective observational cohort study the following article attempts to answer two key questions of rehabilitation research in Germany: (1) What are the utilization rates of rehabilitation measures in patients with long-term work-incapacity due to low-back pain? (2) In this group of patients: does participation in rehabilitation programs correlate with return to work? Patients with long-term work-incapacity due to low-back pain report a severely impaired health status (measured by FFbH, SF-36, numeric rating scale for pain intensity) which calls for comprehensive medical treatment and rehabilitation. 40.5% of study patients received first time medical rehabilitation between three months and one year after the beginning of long-term work-incapacity, 20.5% between one year and two years after the beginning of long-term work-incapacity. These figures were not influenced by age. Considering the severity of impairment we judge these rates as being quite low. There was no positive correlation found between utilization of medical rehabilitation measures or any other medical treatment and return to work. A positive correlation was observed for utilization of first time medical rehabilitation between three months to one year after the beginning of long-term work-incapacity and functional capacity. This effect was demonstrable for patients 50 years of age or younger. CONCLUSIONS: (1) In our cohort utilization of medical rehabilitation measures in patients with low-back pain and long-term work-incapacity is quite low. This suggests a considerable amount of underutilization. (2) In order to avoid underutilization the process of accessing medical rehabilitation within the German health care system should be critically reviewed. (3) In the given context of high unemployment rates and the German early pensioning system the use of "return to work" as the main criterion to judge effectiveness of rehabilitation measures remains debatable.

Adult↗
PubMed1998

Clinical relevance of accuracy of pedicle screw placement. A computed tomographic-supported analysis.

STUDY DESIGN: The location of pedicle screws (n = 244) and the increase in the pedicle diameter were determined by computed tomography after screw removal in 50 patients with 360 degrees lumbar fusions. The neurologic findings were examined before and after surgery. OBJECTIVES: To evaluate the correlation between the accuracy of pedicle screw placement and preoperative and postoperative neurologic findings. SUMMARY OF BACKGROUND DATA: Incorrect placement of pedicle screws that was detected by computed tomography has been published in several studies. Simultaneous pathologic neurologic deficits are thought to be created by an eccentric screw track. METHODS: Two observers controlled the screw tracts and pedicle diameters. The results were compared with preoperative and postoperative neurologic findings. RESULTS: Fifty-nine percent (144 of 244) of screws were placed centrally in the pedicle. More than half of the eccentric screws (100, 41%; medial 79, 32.4%; lateral 21, 8.6%) penetrated the pedicle wall less than 2 mm (51; 20.9%). In only one patient (0.5%) a radicular irritation was found without objective electrophysiologic correlation when the screw was more than 6 mm medial to the pedicle wall. After screw removal, an insignificant increase in the size of the pedicle diameter in L1-S1 was noted. CONCLUSIONS: Experienced surgeons implant pedicle screws with an accuracy of approximately 80%. The accuracy could be improved by using image-guided insertion equipment. The neurologic symptoms are rarely influenced by an eccentric pedicle screw tract even if penetration of the pedicle wall is more than 6 mm. The results stress the importance of preoperative planning (pedicle diameter, pedicle angle, screw length) when implanting transpedicular fixators.

Bone Screws↗
PubMed1998

Globus sensation: pharyngoesophageal function, psychometric and psychiatric findings, and follow-up in 88 patients.

BACKGROUND: The globus sensation has been widely regarded as psychogenic, but organic disorders were found to be etiologically significant. OBJECTIVE: To investigate the structural, functional, psychological, and psychiatric factors possibly eliciting the globus sensation and influencing its course. METHODS: Eighty-eight patients, 67 women and 21 men (aged 22-71 years), referred to 2 tertiary care centers underwent history taking, otolaryngological examination, pharyngoesophageal videofluoroscopy and manometry, psychosocial evaluation, psychometric tests, psychiatric interview, and when indicated, esophagogastroduodenoscopy, esophageal bolus transport, gastroesophageal reflux, and gastric emptying studies. According to revealed disorders, therapy was initiated, and the outcome was studied. RESULTS: Only 15 patients had normal pharyngoesophageal function; of these 15, 6 had chronic tonsillitis or pharyngitis, 3 had thyroid adenomata, 4 had cervical spondylosis, and 1 each had dry oropharyngeal mucosa and chronic bronchitis. Of the other 73 patients, 2 had pharyngeal dysfunction, 24 had achalasia, 1 had diffuse esophageal spasms, 3 had "nutcracker esophagus," 30 had nonspecific esophageal motor disorders, and 13 had gastroesophageal reflux. Psychometry revealed no more anxiety and depression than in general medical outpatients. Of 58 patients interviewed, 37 met criteria for psychiatric disorders. Psychometric scores and psychiatric characteristics were unrelated to the sensation's course. Therapy was recommended, but only 26 patients were treated accordingly; 22 received nonspecific treatment. Follow-up 3 to 59 months later revealed that the sensation had vanished in 13 patients who had received specific treatment, 5 who had received nonspecific treatment, and 6 who had received no treatment; it was alleviated in 10 who had received specific treatment, 13 who had received nonspecific treatment, and 9 who had received no treatment; and it was unchanged in 3 who had received specific treatment, 5 who had received nonspecific treatment, and 23 patients who had received no treatment. CONCLUSIONS: Pharyngoesophageal disorders may be sensed only vaguely, inducing the globus sensation. Psychological and psychiatric characteristics could be relevant to the discomfort experienced but are unlikely to be etiologically significant.

Adult↗
PubMed1998

High-Resolution High-Count-Rate X-ray Spectroscopy with State-of-the-Art Silicon Detectors.

For the European X-ray multi-mirror (XMM) satellite mission and the German X-ray satellite ABRIXAS, fully depleted pn-CCDs have been fabricated, enabling high-speed low-noise position-resolving X-ray spectroscopy. The detector was designed and fabricated with a homogeneously sensitive area of 36 cm(2). At 150 K it has a noise of 4 e(-) r.m.s., with a readout time of the total focal plane array of 4 ms. The maximum count rate for single-photon counting was 10(5) counts s(-1) under flat-field conditions. In the integration mode more than 10(9) counts s(-1) can be detected at 6 keV. Its position resolution is of the order of 100 micro m. The quantum efficiency is higher than 90% from carbon K X-rays (277 eV) up to 10 keV. New cylindrical silicon drift detectors have been designed, fabricated and tested. They comprise an integrated on-chip amplifier system with continuous reset, on-chip voltage divider, electron accumulation layer stabilizer, large area, homogeneous radiation entrance window and a drain for surface-generated leakage current. At count rates as high as 2 x 10(6) counts cm(-2) s(-1), they still show excellent spectroscopic behaviour at room-temperature operation in single-photon detection mode. The energy resolution at room temperature is 220 eV at 6 keV X-ray energy and 140 eV at 253 K, being achieved with Peltier coolers. These systems were operated at synchrotron light sources (ESRF, HASYLAB and NLS) as X-ray fluorescence spectrometers in scanning electron microscopes and as ultra low noise photodiodes. The operation of a multi-channel silicon drift detector system is already foreseen at synchrotron light sources for X-ray holography experiments. All systems are fabricated in planar technology having the detector and amplifiers monolithically integrated on high-resistivity silicon.

Journal Article↗
PubMed1998

Phrenic nerves and diaphragms in sudden infant death syndrome.

Disturbances of the respiratory system may be an important factor in the cascade of events leading to sudden infant death syndrome (SIDS). Even though the diaphragm is the major respiratory muscle in infants, little is known about alterations of this muscle and of the phrenic nerve in SIDS. In the present study, diaphragms and phrenic nerves of 24 SIDS infants and seven controls were analyzed. Morphometric analysis revealed only slightly larger cross sectional areas of phrenic nerve axons but no increase in myelin sheath thickness in SIDS cases. However, in one SIDS case, myelinated nerve fibre density was severely reduced. Using electron microscopy, several nerve fibres of SIDS infants showed focal accumulations of neurofilaments. Muscle fibre diameters in SIDS diaphragms were significantly larger compared to controls (P < 0.0001). However, in almost all SIDS and control cases, axons and myelin sheaths were artificially swollen, and acute segmental muscle fibre ruptures and contracture bands were found. These prominent nonspecific ultrastructural alterations should advise caution in the interpretation of morphometric data. Thus, in some cases exemplified by one case of the present series, decreased density of phrenic nerve myelinated axons might contribute to SIDS. Still, the present results indicate that development of phrenic nerves and diaphragms is not delayed in most SIDS infants.

Autopsy↗
PubMed1998

[Is subjective health status a good predictor of work resumption?].

The aim of the study is to investigate how persons with long term work-disability due to low back pain assess their health status and how the subjective health measurement influence work resumption (n = 663). Information on their subjective health status at 42 days after start of work-disability is set in relation to the outcomes "Continued work disability after 84 days" versus "work resumption". Bi- and multivariate analysis show that information on the subjective health status and the subjective work prognosis differs between both groups already after 42 days. The results show that the subjective health status in connection with the subjective work prognosis is a good predictor for "Non-resumption of work", but not a sufficiently good predictor for "Resumption to work".

Adolescent↗
PubMed1998

[Microsurgery].

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Humans↗