Hydrogenation properties of supported nanosized gold particles.
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Journal Article↗
Biomedical subjects
C Mohr
Publications and source records attributed to C Mohr.
[Therapeutic facial surgery possibilities for orbital tumors].
Based on a large experience of more than 400 orbital tumours which were treated operatively, the surgical strategies are described in detail. A surgical approach including the temporary removal of one or more bony orbital walls provided excellent exposure of the intraorbital structures. Using microsurgical techniques for tumour removal the surgical morbidity could be minimized. Subsequent refixation of the osteotomized orbital bones with microplates and screws and skin incisions within the hair bearing parts of the skull resulted in excellent postoperative function and cosmesis. For many malignant orbital tumours definitive cure can only be achieved by an orbital exenteration procedure. An individually tailored surgical and reconstructive strategy (if possible preservation of eyelid skin, tarsal and bulbar conjunctiva) gives a significant benefit, as well with respect to function as to the esthetic outcome of the patient.
Follow-Up Studies↗
Clostridium innocuum: a glucoseureide-splitting inhabitant of the human intestinal tract.
Glycosylureides were recently described as non-invasive markers of intestinal transit time. The underlying principle is an enzymatic splitting of (13)C-labelled ureides by intestinal bacteria. The (13)CO(2) released from the urea moiety of the glycosylureides can be measured in breath samples when the ingested tracer substrate reaches the caecum that is colonised with microbes. To date, the microbes that degrade glycosylureides are unknown. In order to identify the glucoseureide (GU)-splitting bacteria, 174 different strains of intestinal microbes obtained from five healthy adults were checked for their ability to degrade GU. The results of the microbial cultures and thin layer chromatography revealed that GU was exclusively degraded by Clostridium innocuum, belonging to the normal human intestinal microflora. C. innocuum probably synthesises a yet unknown enzyme that splits the glucose-urea bond. We suggest that the term glucoseureidehydrolase is the appropriate designation for this enzyme.
Adolescent↗
[Prosthetic-implantology defect treatment concept for oral rehabilitation of the mandibular area after tumor treatment].
Between 1988 and 1997, tumor resection was carried out in 18 irradiated patients group 1: 36-72 Gy. 83 implants) and 22 nonirradiated patients (group 2: 92 implants) in the mandible and floor of the mouth, and these patients subsequently underwent mandibular endosseous implant rehabilitation. A total of 23 patients were treated with exclusively implant-supported prostheses, and 16 with implant tissue-supported constructions. Between 1988 and 1991, group 1 and 2 patients received implant tissue-supported prostheses (using two to four implants). Due to prosthesis-related pressure lesions, the strategy has now been changed. Since 1992, group 1 patients have received exclusively implant-supported prostheses (using five to six implants), while group 2 patients have received implant tissue-supported constructions (using four implants). Special criteria for the success of implant-supported maxillofacial prosthetics were drawn up. With an average follow-up period of 37 months 160 fixtures (91%) were clinically osseointegrated. Both types of restoration provided sufficient oral rehabilitation. However, only completely implant-supported prostheses avoided soft tissue ulcers. The overall success rate was about 77% after 7 years in group 1 and about 87% after 9 years in group 2. With regard to implants placed after strategy change, the 5-year success rate was approximately 86% (group 1) and 94% (group 2). In irradiated patients, an exclusively implant-supported prosthesis without any mucosal contact (thus avoiding soft tissue ulcers with a potential to develop osteoradionecrosis) should therefore be fabricated. Implant tissue-supported restoration is also possible in nonirradiated oral cancer patients.
Adult↗
Compact organization of rRNA genes in the filamentous fungus Ashbya gossypii.
The rDNA cluster in the phytopathogenic fungus Ashbya gossypii consists of approximately 50 tandem repeat units of 8197 bp. Each unit carries a gene for the 35S pre-rRNA, processed into 18S, 5.8S and 25S rRNA, and a divergently transcribed gene for 5S rRNA. The well-characterized rDNA of the yeast Saccharomyces cerevisiae is the only other example of a completely sequenced rDNA unit (9137 bp) carrying both a 35S pre-rRNA and a 5S rRNA gene. The coding regions for the 5S, 5.8S, 18S and 25S rRNAs are 95-100% identical whereas transcribed and non-transcribed spacers show 43-66% sequence identity. Functionally characterized rDNA and rRNA elements of S. cerevisiae can be unambiguously recognized in the A. gossypii sequence, including the RNA polymerase-I transcription start site, two Reb1p enhancer binding sites and numerous recognition sequences for rRNA modification and processing. In addition to these functionally characterized sequences eight highly conserved elements from 10 to 71 bp were detected in the over 600-bp transcribed region upstream of the 18S rRNA gene which most likely play as yet uncharacterized functions at the DNA or RNA level. In addition to this work we started to identify A. gossypii homologs of S. cerevisiae nucleolar proteins involved in rDNA maturation.
Amino Acid Sequence↗
Breaking the bad news: dilemmas in shared decision-making in medical practice.
In a review of the literature, very little empirically based research was uncovered to guide the practice of health professionals who need to tell their patients bad news and help them to decide on their preferred treatment option. Various practising styles and guidelines are presented, and ethical and crosscultural challenges discussed. An enormous amount of research still needs to be done to discover the least stressful ways of dealing with these issues in health care settings.
Communication↗
Neural command of electromotor output in mormyrids
The electric discharge of mormyrid fish has an irregular pattern controlled by the electromotor command nucleus in the medulla. Anatomical studies suggest that much of the descending information integrated by the command nucleus comes from the diencephalic precommand nucleus. But field potentials related to the motor command occur later in the precommand nucleus than in the command nucleus, suggesting that they are a corollary rather than a cause of electromotor command initiation. Recorded extracellularly, certain precommand nucleus units fire spontaneously between electromotor commands but pause briefly following each command; others units fire a burst of spikes only during the post-command pause. The firing frequency of the former is correlated with the duration of the interval between successive electromotor commands when the fish is discharging at more than approximately 5 Hz. The post-command pause in spontaneous firing is due to corollary-discharge-mediated feedback inhibition, probably generated by the activity of the bursting units that fire only during this period. Precommand nucleus neurons are activated by electrosensory input, and stimulation of the precommand nucleus modulates the endogenous pattern of electromotor command. We propose that the irregular rhythm of the motor command depends largely on the integration of descending information of various origins, conveyed via the precommand nucleus to the command nucleus, and that this process is regulated by corollary discharge feedback inhibition to the precommand nucleus.
Journal Article↗
Potent dipeptide inhibitors of the pp60c-src SH2 domain.
The design, synthesis, and evaluation of dipeptide analogues as ligands for the pp60c-src SH2 domain are described. The critical binding interactions between Ac-Tyr-Glu-N(n-C5H11)2 (2) and the protein are established and form the basis for our structure-based drug design efforts. The effects of changes in both the C-terminal (11-27) and N-terminal (51-69) portions of the dipeptide are explored. Analogues with reduced overall charge (92-95) are also investigated. We demonstrate the feasibility of pairing structurally diverse subunits in a modest dipeptide framework with the goal of increasing the druglike attributes without sacrificing binding affinity.
Crystallography, X-Ray↗
The formation of a covalent complex between a dipeptide ligand and the src SH2 domain.
The X-ray crystal structure of the src SH2 domain revealed the presence of a thiol residue (Cys 188) located proximal to the phosphotyrosine portion of a dipeptide ligand. An aldehyde bearing ligand (1) was designed to position an electrophilic carbonyl group in the vicinity of the thiol. X-ray crystallographic and NMR examination of the complex formed between (1) and the src SH2 domain revealed a hemithioacetal formed by addition of the thiol to the aldehyde group with an additional stabilizing hydrogen bond between the acetal hydroxyl and a backbone carbonyl.
Aldehydes↗
[Orbital decompression in treatment of endocrine orbitopathy].
Graves' ophthalmopathy (Graves' disease) is a grave, rare immunological inflammatory reaction of the postorbital connective, adipose and ocular muscle tissue. Graves' disease occurs only within the scope of immunothyropathies and constitutes the most frequently encountered extrathyroidal manifestation. Typical symptoms are a result of the volume increase of the postbulbar connective and adipose tissue and of the interstitial swelling of the ocular muscles. Clinically, we find a spectrum of increasingly grave changes in the orbita, such as infiltration of the eyelid and connective tissue, exophthalmos, swelling of the muscles, damage to the cornea and involvement of the optic nerve with loss of vision. Regarding functional impairment of the optic nerve (optic nerve compression), orbita decompression represents an operative ultima ratio. Between January 1992 and April 1997, 11 patients (22 orbitae) from a group of more than 600 patients with Graves' disease with vision involvement were treated surgically. All treatment data were documented prospectively. Surgical intervention was performed only in cases where a progressive loss of vision existed in spite of retrobulbar irradiation and high-dose glucocorticoid therapy. Surgical therapy consisted of decompression of the medial, inferior and lateral orbital wall and of the orbital contents via combined bi-coronary and anterior access. The long-term results demonstrated improved vision conditions with 17 of the 22 eyes operated on. Parameters such as vision, exophthalmos, VEP, motility, double vision and field of vision were documented pre- and post-operatively. The prediction of post-operative deviations of the bulb axis was limited, and these were rectified through secondary displacements of the ocular muscle. No complications worth mentioning were encountered. In extreme events of therapy-resistant Graves' ophthalmopathies with progressive loss of vision, the three-wall decompression method has proved to be the correct one.
Adult↗
[Interdisciplinary surgical therapy of tumors of the frontal skull base].
Most tumors of the anterior cranial base invade both the intra- and extracranial regions at the borderline of the cranial and facial skeleton. In surgical treatment of these lesions, combined craniofacial approaches are applied in accordance with the anatomical conditions. Surgery is performed by an interdisciplinary team of neurosurgeons and maxillofacial surgeons. To evaluate the effectiveness and the complications of this surgical concept, the data of 58 patients treated over a 10-year period were collected. In these patients, 60 operations were performed, including two operations for tumor recurrence. In 38 cases, complete tumor removal was achieved. One patient died in the early postoperative period because of pulmonary embolism. Significant neurological deficits occurred in three patients. In most cases, postoperative complications and functional disability were both due to intradural invasion of the tumor. Nevertheless, in the majority of the cases radical tumor removal is achieved with acceptable morbidity when microsurgical techniques are applied for the resection of the intradural tumor. Both the meticulous repair of dural defects and the reconstruction of the anterior cranial base and orbit contribute distinctly to a reduction in the rate of postoperative complications and to acceptable cosmetic results.
Adolescent↗
[Reconstruction of the frontobasal skull after tumor operations and trauma. Transplant selection and functional outcome].
Defects of the frontoorbital complex subsequent to extensive tumor surgery or severe trauma often result in aesthetic and functional disharmonies. The long-term results of rehabilitation related to different materials and techniques are the subject of this study. From 1974 to 1996 altogether 127 patients with bony defects of the orbit and/or the skull base underwent surgery. All patients' data were documented prospectively from 1984 onwards. The results following reconstruction with autologous calvarian transplants in 52 patients were compared to those of a control group which received iliac bone or PMMA implants. Eighty-one bony defects (64%) resulted from tumor resection; 37 patients (29%) suffered from the effects of trauma. In 67 cases (53%) reconstruction was performed primarily, in 51 cases (40%) secondarily. Free or pedicled soft-tissue transplants were necessary in order to separate the orbit and the neurocranium in 26% of the defects. On the other hand, small, isolated defects of the orbital roof (7%) were left without any reconstructive procedure. Contrary to the iliac bone grafts, the calvarian transplants resisted secondary resorption. Postoperative infections appeared in two cases; loss of transplants was avoided entirely in the group of calvarian reconstructions in contrast to the alloplasts. The selection of a suitable donor site area and rigid fixation with microplates led to excellent esthetic results even in cases with large defects.
Adolescent↗
An efficient motion estimator with application to medical image registration.
Image registration is a very important problem in computer vision and medical image processing. Numerous algorithms for registering single and multi-modal image data have been reported in these areas. Robustness as well as computational efficiency are prime factors of importance in image data registration. In this paper, a robust/reliable and efficient algorithm for estimating the transformation between two image data sets of a patient taken from the same modality over time is presented. Estimating the registration between two image data sets is formulated as a motion-estimation problem. We use a hierarchical optical flow motion model which allows for both global as well as local motion between the data sets. In this hierarchical motion model, we represent the flow field with a B-spline basis which implicitly incorporates smoothness constraints on the field. In computing the motion, we minimize the expectation of the squared differences energy function numerically via a modified Newton iteration scheme. The main idea in the modified Newton method is that we precompute the Hessian of the energy function at the optimum without explicitly knowing the optimum. This idea is used for both global and local motion estimation in the hierarchical motion model. We present examples of motion estimation on synthetic and real data (from a patient acquired during pre- and post-operative stages) and compare the performance of our algorithm with that of competing ones.
Algorithms↗
Peptide ligands of pp60(c-src) SH2 domains: a thermodynamic and structural study.
Thermodynamic measurements, structural determinations, and molecular computations were applied to a series of peptide ligands of the pp60(c-src) SH2 domain in an attempt to understand the critical binding determinants for this class of molecules. Isothermal titration calorimetry (ITC) measurements were combined with structural data derived from X-ray crystallographic studies on 12 peptide-SH2 domain complexes. The peptide ligands studied fall into two general classes: (1) dipeptides of the general framework N-acetylphosphotyrosine (or phosphotyrosine replacement)-Glu or methionine (or S-methylcysteine)-X, where X represents a hydrophobic amine, and (2) tetra- or pentapeptides of the general framework N-acetylphosphotyrosine-Glu-Glu-Ile-X, where X represents either Glu, Gln, or NH2. Dipeptide analogs which featured X as either hexanolamine or heptanolamine were able to pick up new hydrogen bonds involving their hydroxyl groups within a predominantly lipophilic surface cavity. However, due to internal strain as well as the solvent accessibility of the new hydrogen bonds formed, no net increase in binding affinity was observed. Phosphatase-resistant benzylmalonate and alpha,alpha-difluorobenzyl phosphonate analogs of phosphotyrosine retained some binding affinity for the pp60(c-src) SH2 domain but caused local structural perturbations in the phosphotyrosine-binding site. In the case where a reversible covalent thiohemiacetal was formed between a formylated phosphotyrosine analog and the thiol side chain of Cys-188, deltaS was 25.6 cal/(mol K) lower than for the nonformylated phosphotyrosine parent. Normal mode calculations show that the dramatic decrease in entropy observed for the covalent thiohemiacetal complex is due to the inability of the phosphotyrosine moiety to transform lost rotational and translational degrees of freedom into new vibrational modes.
Amino Acid Sequence↗
Orbital exenteration: surgical and reconstructive strategies.
BACKGROUND: Radical exenteration procedures, which include the removal of orbital content and eyelids, result in serious functional limitations, especially with respect to eating and speaking. Therefore we have recently changed our surgical concept. METHODS: Seventy-seven patients underwent orbital exenteration during the 20-year period from 1974 to 1995 at the Department of Maxillofacial Surgery, Essen University. The simultaneous removal of periorbital bone was performed in 45 of these cases. RESULTS: The 1-year survival rate was 89%, the 5-year rate was 63% and the 10-year rate was 48%. The surgical approach, the amount of resected orbital tissue and the reconstructive procedure have been adapted to the individual needs, depending on the location and extent of the tumor. Subsequently, the surgical morbidity has decreased. DISCUSSION: Detailed consideration of all clinical and histological findings is essential before surgery, in order to prevent a higher rate of recurrence following these modified operations.
Adolescent↗
[Report on the 27th Annual Meeting of the German-Austrian-Swiss Working Group for Tumors of the Maxillofacial Area].
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Austria↗
[Outcome of Van der Meulen columellar extension in bilateral lip-jaw-palate clefts].
A total of 42 patients were operated on for secondary columellar elongation at the Department for Cranio-maxillofacial Surgery in Essen, Germany, from 1990 to 1996. The procedures were carried out because of nasal deformity in bilateral cleft lips (n = 35) or unilateral cleft lips (n = 7). The well-established drawbacks of Millard's forked flap technique, especially the resulting unfavourable scars at the lip columellar angle and the unpredictable, more conspicuous scar formations within the upper lip gave rise to an intensive search for an alternative surgical technique in our clinic. Since 1995 we have undertaken 14 secondary columellar elongations by means of Van der Meulen's three dimensional Z-plasty at the alar rim. Avoiding reopening of the lip we were able to lengthen the columella and project the nasal tip forward between 3 mm and 8 mm in all patients without introducing additional visible scars. The procedure led to an improved contour of the nasal tip, the alar rims and the nostrils. Nevertheless, we observed secondary broadening and shortening of the elongated columella in two children. This complication could subsequently be avoided by postoperative application of a nostril splint. The results confirm the effectiveness of the described technique for moderate columellar lengthening. The postoperative application of nostril splints is mandatory.
Adolescent↗
[Primary soft tissue coverage and specific after-care of endosseous implants in pre-irradiated orbits].
After orbital exenteration and high- dose irradiation (60 Gy on average), 17 endosseous implants were placed periorbitally in 5 patients. No hyperbaric oxygen therapy was performed. All implants were primarily covered with regional or free flaps. After second-stage surgery and aesthetic rehabilitation with an external maxillofacial prosthesis, the pocket depth and implant stability (periotest) were checked, an occipitonasomental radiograph was taken and the soft tissue assessed in short recall intervals. When the implant was uncovered, osseointegration was stable. Within a follow-up period of 35 months, no fixation had failed. In two patients, peri-implant inflammation (microbiologically confirmed Staphylococcus aureus) occurred, which was clinically only determined by soft tissue oedema and rubor. The results demonstrate primary soft tissue covering as essential for non-irritating implant osseointegration in the irradiated orbita. In extraoral implants the clinical estimation of the peri-implant soft tissue, including a microbiological examination, is required for early detection of peri-implant inflammation in order to avoid secondary implant failure. In contrast, periotest and pocket depth are not relevant in recognizing an ensuing peri-implant inflammation.
Adult↗