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Biomedical subjects

Ulrich Weber

Publications and source records attributed to Ulrich Weber.

7 recordsLinked to original sources
PubMed2007

Does chemotherapy impair the bone healing and biomechanical stability of vascularized rib and fibula grafts?

The purpose of this study was to observe the impact of chemotherapy on the healing and biomechanical properties of vascularized bone grafts. Ten male beagle dogs were divided into two experimental groups: a chemotherapy group (CH) and control group (C). Group CH received adjuvant and neo-adjuvant chemotherapy. Each animal of both groups underwent the following operative procedures. The 5th and 7th rib were removed and replaced by vascularized pedicle transfers of the adjacent 4th and 8th rib. Additionally, a free fibular flap was elevated and retransferred to the same anatomic position. The rate of bony union on plain x-ray was 100 percent in group C, 30 percent in the vascularized rib, and 80 percent in the fibula grafts of group CH. Microangiography demonstrated no avascular bone segments in group C and in the fibula flaps of group CH. The vascularized ribs of group CH presented with 20 percent avascular bone segments. Biomechanical tests focusing on the durability of the vascularized grafts against bending and torsion forces demonstrated a reduction of the average maximum bending times by 17 percent and 23.9 percent compared to the controls ( P < 0.05). The twisting times were reduced by 13.8 percent (n.s.) and 32.5 percent ( P < 0.05). The data demonstrated a clear worsening in bone healing and stability after simulated adjuvant and neo-adjuvant chemotherapy. Thus, a large animal model was established for the further determination of the effects of chemotherapy on different vascularized bone transfers.

Angiography↗
PubMed2006

Impact of radiation therapy on healing and stability of vascularized bone grafts in a dog model.

The purpose of the study was to observe the impact of radiation therapy on healing and biomechanical properties of vascularized bone grafts, and thus to establish an appropriate large animal model. Ten male beagles were divided into two experimental groups: radiation (R) and control (C). The left 5th to 7th ribs of the animals of group R were irradiated 3 and 2 weeks preoperatively, using a dose of 8 Gy each time. Each animal of both groups underwent the following operative procedures. The 5th and 7th ribs were removed, and the 5th rib was replaced by a vascularized pedicle transfer of the 4th rib. The 7th rib was reconstructed using a pedicle transplant of the 8th rib. The 5th and 7th ribs were used as nonvascularized bone grafts to replace the donor sites of the 4th and 8th ribs, respectively. Group R received two further irradiation cycles 2 and 3 weeks postoperatively. The vascularized rib grafts of group R demonstrated a higher number of delayed unions in plain x-rays and avascular bone segments in microangiography than the control group. The presence of vital osteocytes in histology was not significantly different between groups. Biomechanical tests focusing on the durability of vascularized ribs against bending and torsion forces demonstrated a reduction of average maximum bending moments by 56.6% after radiation compared to controls (P < 0.05). Twisting moments were reduced by 47.6% (P < 0.05). The data demonstrate a significant worsening in bone healing and stability after pre- and postoperative radiation therapy to the wound bed and bone grafts. Thus, a large animal model is established for further determination of different strategies of radiotherapy in combination with vascularized bone transfers.

Animals↗
PubMed2005

Linear optics controlled-phase gate made simple.

Linear optics quantum logic gates are the best tool to generate multiphoton entanglement. Simplifying a recent approach, we were able to implement the conditional phase gate with only one second-order interference at a polarization dependent beam splitter, thereby significantly increasing its stability. The improved quality of the gate is evaluated by analyzing its entangling capability and by performing full process tomography. The achieved results ensure that this device is well suited for implementation in various multiphoton quantum information protocols.

Journal Article↗
PubMed2005

Experimental analysis of a four-qubit photon cluster state.

Linear-optics quantum logic operations enabled the observation of a four-photon cluster state. We prove genuine four-partite entanglement and study its persistency, demonstrating remarkable differences from the usual Greenberger-Horne-Zeilinger (GHZ) state. Efficient analysis tools are introduced in the experiment, which will be of great importance in further studies on multiparticle entangled states.

Journal Article↗
PubMed2005

Ankylosing spondylitis and heart abnormalities: do cardiac conduction disorders, valve regurgitation and diastolic dysfunction occur more often in male patients with diagnosed ankylosing spondylitis for over 15 years than in the normal population?

The objective of this study was to determine the rate of selected cardiac pathologies (conduction disorders, valve regurgitation and diastolic dysfunction) in patients with long-standing ankylosing spondylitis (AS) and compare the results with the prevalence in the normal population. A rheumatologic (structured questionnaire interview) and cardiac evaluation (resting electrocardiography and echocardiography) was performed in 100 male subjects with AS and a disease duration of more than 15 years. The rates for conduction disorders, aortic and mitral valve regurgitation and diastolic dysfunction were compared with the corresponding results in the literature among the normal population. In patients with long-standing AS there was no increased rate for valve regurgitation (mitral and aortic valve) and for arrhythmia. Diastolic dysfunction occurred more often in patients with long-standing AS. However, this might be caused by the presence of other cardiovascular risk factors such as age and hypertension. According to these results, a cardiologic evaluation with echocardiography should not be recommended routinely in patients with long-standing AS. To confirm these results, a large prospective study with patients with long-standing AS and with a matched control group should be performed in the future.

Adult↗
PubMed2003

[Neuroendocrine tumors of visual system--Merkel cell carcinoma].

PURPOSE: To describe cases of Merkel cell carcinoma. Belonging to the APUD-system tumors, the highly malignant Merkel cell carcinoma affects in 10% the ocular adnexes, 50-60% of the patients develop a metastasis to the lymph nodes, and the five year survival rate is only 38%. 30% of the tumors recur after one year. MATERIAL AND METHODS: In the last eight years the Merkel cell carcinoma was diagnosed in four patients and was treated by wide resection, radiotherapy and cytostatic drugs. Histological and immunohistological examination was performed. RESULTS: In three cases the carcinoma was diagnosed in the upper lid and in one case in the eyebrow. Two patients could not be cured. Characteristic is clinical uniform appearance of the tumor as painless, reddish nodule with smooth surface, telangiectatic blood vessels, fast growing and fast leading to metastasis. Furthermore, the histological characteristics of the tumor were found as well as NSE, S100 proteins and neuroendocrine granula, which allow to classify to the APUD--system and to distinguish from the more benign tumors. CONCLUSIONS: As neuroendocrine tumor the Merkel cell carcinoma represents a high malignant tumor in ophthalmology. The certain diagnosis is only made by histological and immunohistological examination. A full-thickness resection followed by radiation, should be performed as soon as possible.

Aged↗