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Biomedical subjects

W Braun

Publications and source records attributed to W Braun.

At least 55 records · Page 3Linked to original sources
PubMed1997

Bile acid concentrations in serum and duodenal aspirates of healthy preterm infants: effects of gestational and postnatal age.

In 41 healthy human-milk-fed preterm infants the preprandial total bile acid (BA) concentrations in serum and duodenal juice were simultaneous measured during the first 60 days of life. The infants were subdivided into four groups according to their gestational age: 6 infants with a gestational age of 27 and 28 weeks, 7 infants with a gestational age of 29 and 30 weeks, 21 infants with a gestational age of 31 and 32 weeks and 7 infants with a gestational age of 33 and 34 weeks. The BA levels were enzymatically determined using 3-alpha-hydroxysteroid dehydrogenase. In the duodenal juice, cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid and lithocholic acid were separately quantified by thin-layer chromatography. During the first month of life, the serum BA concentrations increased significantly with postnatal age (p < 0.01) but remained nearly constant during the second month of life. In the duodenal aspirates, the BA concentrations increased continuously up to the end of the observations period (p < 0.001). In the duodenal aspirates, the CA/CDCA ratio was high immediately after birth and decreased significantly with increasing postnatal age (p < 0.001). During the first weeks of life, the BA levels were preferentially conjugated with taurine, but in spite of the taurine-rich diet during the whole observation period the taurine/glycine ratio decreased with postnatal age (p < 0.001). In all samples of duodenal juice, the sum of primary BA was > 98% of total 3-alpha-hydroxy-BA. These data indicate that the establishment of an intestinal microbial flora necessary for intestinal BA transformation and the development of the enterohepatic BA circulation lasts some months of postnatal life. The serum BA concentration reflects hepatic synthesis, intestinal absorption, renal excretion and hepatocellular transport into bile in a very complex way which may limit the diagnostic value of serum BA during this time. Additionally, a duodenal BA concentration below 4 mmol/l, as found in this study during the first 2 weeks of life, may be of clinical importance due to its possible effects on fat absorption.

Aging↗
PubMed1997

[Approach-related results following acetabular fractures].

Acetabular fractures are severe injuries. Making a diagnosis and deciding on therapy are difficult because of the complexity of the anatomic structure and because of the soft tissues. Choosing the most suitable approach is the most important problem when deciding on the operative treatment. Besides standard approaches (Kocher/Langenbeck, ilioinguinal and extended iliofemoral), the "Maryland approach" has been established in the last few years. Modifying the steps of preparation, it is possible to begin the operation with a Kocher/Langenbeck approach (with variation on where the skin incision is made) and to extend the approach step by step to achieve optimal exposure. Here we describe the results of acetabular fractures treated between 1989 and 1994 (n = 159) in our clinic related to the surgical approach. The "modified Maryland approach" as used in our clinic, starts with exposure of the dorsal column, offering the possibility of a universal exposure.

Acetabulum↗
PubMed1996

Tumorous calcinosis: a disease of its own?

Tumorous calcinosis has been considered as a disease of its own. A survey of the literature shows that only its clinical and radiological appearances are universally agreed upon, while its epidemiology and etiology are still under discussion. A genetic disorder, recurrent soft-tissue microtrauma and terminal renal failure have been put forward as causes. All of them may lead to a localized or generalized disturbance of the calcium-phosphate metabolism, which in turn could produce tumorous calcinosis. Therefore, tumorous calcinosis should be regarded as a rare manifestation of a metabolic disorder rather than a disease of own.

Adult↗
PubMed1996

[Tumoral calcinosis--an independent disease?].

Tumoral calcinosis has up to date been considered as an independent disease. The survey of the literature shows that only its clinical and radiological appearance are generally accepted while its epidemiology and etiology are still under discussion. A genetical disorder, recurrent soft tissue microtrauma or terminal renal failure are blamed to cause tumoral calcinosis. All these causes may lead to localized or generalized disturbance of the calcium-phosphate-metabolism which in turn causes tumoral calcinosis. Therefore tumoral calcinosis should be regarded as a rare symptom of a metabolic disorder rather than an independent disease. Clinical appearance and treatment of two cases of tumoral calcinosis are reported followed by a review of the literature.

Adult↗
PubMed1996

Intraarticular distal humerus fractures. Factors affecting functional outcome.

In intraarticular fractures of the distal humerus, full functional recovery is difficult to obtain. Even if stable anatomic reconstruction of the articular surface is achieved by open reduction and internal fixation, nerve lesions, joint stiffness, and heterotopic bone formation may spoil the functional result. Ninety-nine consecutive fractures were treated by open reduction and internal fixation and studied retrospectively to determine factors influencing outcome. Followup examination of 77 cases showed 52% excellent and good late results. Twenty-six patients had nerve injuries. The rate of heterotopic bone formation was 49%. Open fractures and polytraumatized patients had less favorable results. Early operations within 24 hours resulted in significantly less heterotopic bone formation and better overall function that did delayed treatment. Careful examination of nervous deficits and early stable internal fixation with routine exposure of the ulnar nerve is therefore recommended in the management of this injury.

Adolescent↗
PubMed1995

Automated assignment of simulated and experimental NOESY spectra of proteins by feedback filtering and self-correcting distance geometry.

A new method for automatically assigning proton-proton NOESY spectra is described and demonstrated for simulated and experimental spectra of the proteins dendrotoxin K, alpha-amylase inhibitor tendamistat and the DNA-binding domain of the 434 repressor protein. The method assigns the NOESY spectrum and calculates three-dimensional protein structures simultaneously, using a list of proton chemical shifts and 3JNH alpha coupling constants. An ensemble of structures is iteratively calculated by self-correcting distance geometry from unambiguous and selected ambiguous NOESY cross peaks. New structure based filters recognize the correct constraints from the ambiguous cross peak list. For the first round of assignment neither a preliminary initial structure nor a sufficient set of unambiguous NOESY cross peaks is needed. The method can also be applied to cross peak lists containing hundreds of noise peaks. For an assumed tolerance of +/- 0.01 ppm in the chemical shifts of the peak positions, only about 10% of the NOESY cross peaks can be unambiguously assigned based on their chemical shifts alone. Our automated method assigned about 80% of all cross peaks with this chemical shift tolerance, and 95 to 99% of the assignments were correct. The average pairwise RMSD for the backbone atoms of the ten best final structures is about 1.5 A in all three proteins and the previously determined NMR solution structures are always embedded in this structure bundle. We regard our method as a highly practical tool for automatic calculation of three-dimensional protein structures from NMR spectra with minimal human interference.

Computer Simulation↗
PubMed1995

Electronic Band Structure of Monolayer Bi on GaP(110).

The two-dimensional electronic band structure of monolayer Bi on GaP(110) has been mapped using angle-resolved UV photoelectron spectroscopy (ARUPS) with synchrotron radiation. Surface photovoltage effects are corrected for by simultaneous second-order core spectroscopy. From valence-band spectra along the four symmetry directions of the surface Brillouin zone at three photon energies it is possible to distinguish three states as surface related. The topmost band is found to be inside the fundamental band gap, at ca 0.75 eV above the bulk valence-band maximum. Comparison with other V/III-V(110) systems shows that this system is not significantly different, despite the relatively large size of the Bi atoms with respect to the GaP lattice; in a selective comparison with InP and GaAs it would appear that Bi-substrate anion bonding is a more important factor than strain.

Journal Article↗
PubMed1995

Predicting the helix packing of globular proteins by self-correcting distance geometry.

A new self-correcting distance geometry method for predicting the three-dimensional structure of small globular proteins was assessed with a test set of 8 helical proteins. With the knowledge of the amino acid sequence and the helical segments, our completely automated method calculated the correct backbone topology of six proteins. The accuracy of the predicted structures ranged from 2.3 A to 3.1 A for the helical segments compared to the experimentally determined structures. For two proteins, the predicted constraints were not restrictive enough to yield a conclusive prediction. The method can be applied to all small globular proteins, provided the secondary structure is known from NMR analysis or can be predicted with high reliability.

Amino Acid Sequence↗
PubMed1995

Three-dimensional structure and actions of immunosuppressants and their immunophilins.

The use of the immunosuppressant drug cyclosporin A (CsA) as a biochemical tool to study the signal transduction pathway in T cells has led to the discovery of a first family of immunosuppressant-binding proteins or "immunophilins," the cyclophilins (Cyp). Another, chemically unrelated immunosuppressant molecule, FK506, was then found to be related to a second class of immunophilins, the FK506-binding proteins (FKBPs). This paper reviews the existing structural information on these immunophilins in the context of present knowledge of the biochemical mechanisms for immunosuppression. The formation of Cyp-CsA and FKBP-FK506 complexes, and the subsequent specific interaction of these complexes with the serine/threonine phosphatase calcineurin (CN), are key steps in the cascade of events that result in the desired immunosuppression. Knowledge of the conformation of the Cyp-CsA-CN and FKBP-FK506-CN ternary complexes is of significant biomedical interest, because mimics of the composite contact surfaces of, for example, Cyp-CsA or FKBP-FK506, could provide immunosuppressant drugs with improved pharmacological profiles.

Amino Acid Isomerases↗
PubMed1995

[What are the advantages of UTN (unreamed tibial nail) in open tibial fractures?].

The AO-unreamed tibial nail (UTN) is an alternative to external fixation in the treatment of open tibial fractures. In order to compare the two implants we did a retrospective study. 70 unselected cases of open tibial fractures were treated by either method. 35 patients with primary UTN were compared to another 35 patients with primary external fixator. Demographic data, localisation and classification of fractures and soft tissue trauma showed no differences between the two groups. The main complications in UTN-group were hardware problems, in external fixator-group infections. Following UTN-treatment duration of first hospital stay and whole fracture treatment were shortened with earlier full weight bearing and fracture healing. Our study shows advantages in the treatment of open tibial fractures using the UTN compared to the external fixation.

Adolescent↗
PubMed1995

[Pediatric femoral shaft fracture: effect of treatment procedure on results with reference to somatic and psychological aspects].

When treating femoral shaft fractures in children both somatic (axial/rotational misalignment) and psychological sequelae of the treatment have to be taken into consideration. We performed a retrospective study on the somatic and psychological outcome in 38 children under the age of 10 years with femoral fractures from 1989 to 1991. Twenty-four were treated conservatively (i.e. by traction), while 14 had surgery. Average time in hospital was significantly shorter in the operative group (9 days) than in the conservative group (37 days). The rate of rotational misalignment > 10 degrees was 14% after operation and 45% after traction. Psychological evaluation revealed a positive influence on intellectual development in 21% of conservatively treated children but there were disturbances in motor development (37%), family environment (17%) and general health (25%) in this group. Operative treatment was superior in causing no adverse effects in these fields. We therefore recommend surgery for femoral fractures in children older than 3 years.

Adaptation, Psychological↗
PubMed1995

[Late results of central talus injuries].

From 1982 to 1992 we treated 66 talar injuries at our institution, 44 of which were central fractures (25 talar neck fractures, 17 corpus fractures, 1 comminuted fracture and 1 complete dislocation of the intact talus). In 77% of patients additional injuries were present; 34% were polytraumatized. In 41 patients (93%) clinical and radiological follow-up was possible after an average of 6.3 years. All displaced fractures were treated by open reduction (84%) and, usually, screw fixation, 41% of these within 6 h after the accident. Only 1 required an osteotomy of the medial malleolus, and in 4 a cancellous bone graft was performed. Non-displaced fractures were treated by plastering and partial weight-bearing for an average of 3.1 months. This regime made it possible to contain the rate of aseptic necrosis of the talar body at 12%. The infection rate was 5%. Degenerative changes of the tibiotalar and subtalar joints were seen in 34%. Although there were no cases of non-union and only 2 of malunion, we observed only 6 patients (15%) with complete functional recovery (painfree, normal gait, full professional and recreational activities). A good result (start-up pain, slight limp) was seen in 15 (37%), and a fair result (pain on walking, but normal gait) was achieved in 7 (17%). We observed 13 patients (32%) who had pain on walking and/or at rest and a definite limp at follow-up examination. The average time off work was 8.7 (2.3-26) months. A poor result was associated with additional injuries and subtalar osteoarthritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

[Closed tibial fracture--reamed or unreamed intramedullary nailing. A clinical study].

When comparing the unreamed tibial nail (UTN) with the external fixator in the treatment of open tibial fractures the UTN has shown advantages. Whether we can find these advantages also in the treatment of closed tibial fractures using the UTN instead of a reamed system should be clarified in the following study. We compared 35 UTN treated patients with 35 patients that were treated with a reamed A0-universal tibial nail. Both groups showed no differences in age, sex, etiology and severity of trauma. The fractures were classified by the A0-classification of fractures and the soft tissue damage by the classification of Tscherne and Oestern. The length of mean hospital stay, the time of partial weight bearing and the duration of fracture healing, were shorter using the UTN. 5 of 9 complications using the UTN were immanent to the system (deformation of the locking screws). The other complications were 2 axis shifts, 1 compartment syndrome and 1 pseudarthrosis. The other group showed 1 hematoma, 1 axis shift, 1 compartment syndrome, 2 thromboembolic complications, 2 infections and 3 cases of pseudarthrosis. We think that there is an advantage to use an UTN instead of a reamed nailing system in treatment of closed tibial fractures.

Adult↗
PubMed1994

Conformational polymorphism of cyclosporin A.

BACKGROUND: Cyclosporin A (CsA) is a cyclic undecapeptide fungal metabolite with immunosuppressive properties, widely used in transplant surgery. It forms a tight complex with the ubiquitous 18 kDa cytosolic protein cyclophilin A (CypA). The conformation of CsA in this complex, as studied by NMR or X-ray crystallography, is very different from that of free CsA. Another, different conformation of CsA has been found in a complex with an antibody fragment (Fab). RESULTS: A detailed comparison of the conformations of experimentally determined structures of protein-bound CsA is presented. The X-ray and NMR structures of CsA-CypA complexes are similar. The Fab-bound conformation of CsA, as determined by X-ray crystallography, is significantly different from the cyclophilin-bound conformation. The protein-CsA interactions in both the Fab and CypA complexes involve five hydrogen bonds, and the buried CsA surface areas are 395 A2 and 300 A2, respectively. However, the CsA-protein interactions involve rather different side chain contacts in the two complexes. CONCLUSIONS: The structural results presented here are consistent with CypA recognizing and binding a population of CsA molecules which are in the required CypA-binding conformation. In contrast, the X-ray structures of the Fab complex with CsA suggest that in this case there is mutual adaptation of both receptor and ligand during complex formation.

Amino Acid Isomerases↗