Search PubMed⌕ Search

Biomedical subjects

M Neuburger

Publications and source records attributed to M Neuburger.

At least 19 recordsLinked to original sources
PubMed2003

[Vertical infraclavicular blockade of the brachial plexus (VIP). A modified method to verify the puncture point under consideration of the risk of pneumothorax].

INTRODUCTION: The vertical infraclavicular blockade of the brachial plexus (VIP) according to Kilka et al.is a technique which has gained more importance over the past years. This method distinguishes itself from other periclavicular techniques by a very low risk of pneumothorax (0.2%), which seems to be increased with asthenic patients. METHODS: In the study presented we examined 52 patients undergoing a vertical infraclavicular blockade of the brachial plexus, for an alternative method to determine the puncture point. With 31 of the 52 patients, who had a small distance (<20 cm) between the landmarks jugulum and anterior process of the acromion, the puncture point was moved 0.3 cm in a lateral direction for each centimeter less than 20 cm. Additionally we determined the "finger-point", i.e. the medial margin of the anesthetist's index finger, placed in the gap between the M. deltoideus and M. pectoralis with the finger tip touching the clavicle. RESULTS: In 54% of the patients, the "finger-point" corresponded to the measured puncture point. In 46% of the patients, these points varied by a maximum of 1 cm in the lateral or medial direction. In 53% of the patients, the plexus could be found at the measured puncture point,which applied especially to the patients with a small distance between the leading points (<20 cm) and as a consequence a lateralized puncture point. If a correction of the puncture point was necessary to find the plexus, the correction by skin movement would always be in the direction of the "finger-point". CONCLUSIONS: As a consequence, we assume that if the distance between the leading points jugulum and ventral process of acromion is smaller than 20 cm, the puncture point for a vertical infraclavicular blockade of the brachial plexus should be lateralized as described above; additionally, the "finger-point" should be determined in order to verify the puncture point and to finally give an idea of the direction, in case of a possible need for correcting the puncture point.

Adult↗
PubMed2001

[Psammous desmo-osteoblastoma of the right maxilla. Case report and differential diagnosis of a rare tumor].

CASE REPORT: We report the case of a 9-year-old female patient with a moderate swelling of the right maxilla. A tumor was diagnosed by conventional X-ray within the region of tooth 17 in the right tuber maxillae. The histological diagnosis after biopsy of the lesion was "fibrous dysplasia Jaffe-Lichtenstein". One year later, the tumor was still growing, and computed tomography was carried out. The first histological diagnosis was confirmed by another biopsy; the differential diagnosis was "ossifying fibroma". In the following years, the tumor grew and expanded into the right orbit and maxilla. Four years after the first diagnosis the tumor was removed operatively. DIFFERENTIAL DIAGNOSIS OF THE OPERATIVE SPECIMEN: The histology showed round, partially trabecular or calcified bodies, known as psammoma-like ossicles. Therefore, in light of the clinical course and the radiographic appearance, the correct diagnosis was "psammous desmo-osteoblastoma". DISCUSSION: The psammous desmo-osteoblastoma and its differential diagnosis are discussed in this article.

Child↗
PubMed2001

[Electric nerve stimulation in relation to impulse strength. A quantitative study of the distance of the electrode point to the nerve].

In the present study the difference of the distances of the tip of the needle to the nerve at similar current intensities but different pulse widths (100 microseconds vs. 1000 microseconds) were determined by means of 20 blockades of the sciatic nerve using the transgluteal approach of Labat. Comparable current intensities at different pulse widths (100 microseconds vs. 1000 microseconds) were compared in the same way, using the same position of the needle. At a pulse width of 100 microseconds and a current intensity of 0.30 mA, the tip of the needle is on an average of 5.0 mm closer to the nerve than with a pulse width of 1000 microseconds and a comparable current intensity of 0.28 mA (difference statistically highly significant; p < 0.005). The comparison of the current intensities at different pulse widths at the same needle-position shows that the difference of the current intensities becomes lower when approaching the nerve. At the most distant point measured in this study, a current intensity of 0.94 mA at 100 microseconds corresponds to an aquivalent current of 0.30 mA at 1000 microseconds (difference 0.64 mA); after an approach of 5.0 mm to the sciatic nerve, this difference is significantly lower (0.30 mA at 100 microseconds, 0.11 mA at 1000 microseconds, difference 0.18 mA; p < 0.01). This means that the control of peripheral nerve stimulation is superior at a pulse width of 100 microseconds because a similar distance corresponds to a greater difference of the current. The success rate of the blockade was 95% at a current of 0.30 mA at 100 microseconds. Nerve lesions or other complications have not been seen. In conclusion, safe and successful nerve blocks in patients without polyneuropathia using the peripheral nerve stimulation seems to be obtained at a current intensity of about 0.30 mA at a pulse width of 100 microseconds.

Adolescent↗
PubMed2001

[Biometric data on risk of pneumothorax from vertical infraclavicular brachial plexus block. A magnetic resonance imaging study].

In the present study 48 sagittal and transversal magnetic resonance images of volunteers were examined for biometric data concerning risk of pneumothorax at the vertical infraclavicular blockade (VIP) of the brachial plexus. With a correct puncture the plexus can be reached after 3 cm. The shortest way to the lung is 5.3 cm (3.1-8.7 cm) at a incorrect medial angle of puncture of 46.3 degrees (35-58 degrees). While moving the angle of puncture at a minimum of 24.1 degrees (1-51 degrees) in a medial direction, a depth of 6.1 cm (4-8.9 cm) has to be reached for fatal lung puncture. The puncture point has to be determined 2.8 cm (0-4.1 cm) towards the midline of the body to have a pleura connection by a strictly vertical puncture at 6 cm (4-8.9 cm). In asthenic women, shorter distances were obtained. A considerable lower deviation can lead to pleural damage (7.5 degrees; 4.7 cm). The plexus is very close to the skin surface (1.6-3 cm). In one case, the risk for pneumothorax could be measured even with the correct puncture technique. Overall, the VIP is a very safe method for brachial plexus anaesthesia with regard to the risk of pneumothorax. In asthenic women, the risk seems to be higher but can be minimised by reducing the maximum puncture depth.

Brachial Plexus↗
PubMed2001

The glycine decarboxylase system: a fascinating complex.

The mitochondrial glycine decarboxylase multienzyme system, connected to serine hydroxymethyltransferase through a soluble pool of tetrahydrofolate, consists of four different component enzymes, the P-, H-, T- and L-proteins. In a multi-step reaction, it catalyses the rapid destruction of glycine molecules flooding out of the peroxisomes during the course of photorespiration. In green leaves, this multienzyme system is present at tremendously high concentrations within the mitochondrial matrix. The structure, mechanism and biogenesis of glycine decarboxylase are discussed. In the catalytic cycle of glycine decarboxylase, emphasis is given to the lipoate-dependent H-protein that plays a pivotal role, acting as a mobile substrate that commutes successively between the other three proteins. Plant mitochondria possess all the necessary enzymatic equipment for de novo synthesis of tetrahydrofolate and lipoic acid, serving as cofactors for glycine decarboxylase and serine hydroxymethyltransferase functioning.

Amino Acid Oxidoreductases↗
PubMed2000

[Late spreading of tuberculosis in tubercular spondylitis].

HISTORY AND ADMISSION DIAGNOSIS: A 65-year-old man, known to have had a gastric ulcer and chronic rheumatoid arthritis as well as alcohol and nicotine abuse, was admitted because of suspected endocarditis. Physical examination revealed marked pain on pressure over the throacic spine. Vesicular breath sounds were reduced over the entire thorax and there was a systolic murmur over Erb's point (above the right clavicle). There was a purulent bursitis over the olecranon. INVESTIGATIONS: Abnormal laboratory tests were: elevated C-reactive protein, elevated leucocyte count (up to 33 thousand during the hospital stay). Smears from the bursitis and blood cultures revealed Staph. aureus. Computed tomography demonstrated a fracture of the 7th thoracic vertebra with a paravertebral abscess. Echocardiography showed anatherosclerotic aortic valve with floating particles. DIAGNOSIS, TREATMENT AND COURSE: Treatment of the suspected staphylococcal bacteraemia with purulent bursitis, spondylitis and aortic valvar endocarditis was begun with broad-spectrum antibiotics, but the patient soon developed a severe acute respiratory distress syndrome and he died of multi-organ failure. Autopsy revealed as cause of death left heart failure with aortic valvar endocarditis and gelatinour pneumonia caused by late tubercular dissemination from the tubercular spondylitis. CONCLUSION: Tuberculosis can be a life-threatening infection. Uncharacteristic history and extrapulmonary manifestations can make it very difficult to arrive at the correct diagnosis.

Aged↗
PubMed2000

Combined structural and biochemical analysis of the H-T complex in the glycine decarboxylase cycle: evidence for a destabilization mechanism of the H-protein.

The lipoate containing H-protein plays a pivotal role in the catalytic cycle of the glycine decarboxylase complex (GDC), undergoing reducing methylamination, methylene transfer, and oxidation. The transfer of the CH(2) group is catalyzed by the T-protein, which forms a 1:1 complex with the methylamine-loaded H-protein (Hmet). The methylamine group is then deaminated and transferred to the tetrahydrofolate-polyglutamate (H(4)FGlu(n)) cofactor of T-protein, forming methylenetetrahydrofolate-polyglutamate. The methylamine group is buried inside the protein structure and highly stable. Experimental data show that the H(4)FGlu(n) alone does not induce transfer of the methylene group, and molecular modeling also indicates that the reaction cannot take place without significant structural perturbations of the H-protein. We have, therefore, investigated the effect of the presence of the T-protein on the stability of Hmet. Addition of T-protein without H(4)FGlu(n) greatly increases the rate of the unloading reaction of Hmet, reducing the activation energy by about 20 kcal mol(-1). Differences of the (1)H and (15)N chemical shifts of the H-protein in its isolated form and in the complex with the T-protein show that the interaction surface for the H-protein is localized on one side of the cleft where the lipoate arm is positioned. This suggests that the role of the T-protein is not only to locate the tetrahydrofolate cofactor in a position favorable for a nucleophilic attack on the methylene carbon but also to destabilize the H-protein in order to facilitate the unlocking of the arm and initiate the reaction.

Amino Acid Oxidoreductases↗
PubMed2000

[Pneumothorax in vertical infraclavicular block of the brachial plexus. Review of a rare complication].

A 50 year old female patient received anaesthesia of the arm by the vertical infraclavicular blockade of the plexus brachialis (VIP). Postoperatively an ipsilateral pneumothorax occurred complicated by pleural effusion and a contralateral bronchopneumonia, which resolved completely after treatment. The blockade of the plexus was performed correctly, failures in determining the correct point of needle insertion could be excluded. Therefore a pneumothorax has to be regarded as a specific complication of the VIP, which might occur despite correct technique, and requires that the patient be informed of this eventuality. Nevertheless, the VIP is an important method due to its high success rate concerning blockade of the musculocutaneous nerve and tolerance of tourniquet. The risk of a pneumothorax is about 0.2 to 0.7%.

Arm↗
PubMed2000

Prognostic significance of nuclear DNA content in chondrosarcoma.

Chondrosarcoma is the second most frequent primary malignant tumor of bone. Many of these tumors represent histopathologic borderline cases. In this study, DNA ploidy status, 2c deviation index (2cDI), and DNA malignancy grade (DNA-MG; based on the variation of nuclear DNA content of tumor cells around the normal DNA [2c] peak) were examined for their diagnostic and prognostic value in comparison with conventional histopathologic grading. Twenty-two paraffin-embedded samples were available for histopathologic investigation and for quantitative cytophotometric DNA determination of Feulgen-stained nuclei. Clinicopathologic parameters and prognosis were analyzed over a maximum follow-up period of 252 months. Nineteen of 22 (86%) chondrosarcomas showed aneuploid DNA content. 2cDI (r =.58, P <.01) and DNA-MG (r =.58; P <.01) correlate with the histopathologic grading. Significant correlation between the 2cDI (P <.01) and DNA-MG (P <.025) and the overall survival was found. Ploidy did not influence the overall survival rate. In metastasis-free patients, the 2cDI and DNA-MG gave better prognostic information than conventional histopathologic grading. When patients developed metastasis, however, histopathologic grading was the prognostic parameter of choice. Cytometric DNA measurement provide additional objective information regarding the diagnosis and prognosis of chondrosarcomas, even more than that obtained by conventional histopathologic grading, and may be helpful in planning the treatment.

Adult↗
PubMed2000

Interaction between the lipoamide-containing H-protein and the lipoamide dehydrogenase (L-protein) of the glycine decarboxylase multienzyme system 2. Crystal structures of H- and L-proteins.

The glycine decarboxylase complex consists of four different component enzymes (P-, H-, T- and L-proteins). The 14-kDa lipoamide-containing H-protein plays a pivotal role in the complete sequence of reactions as its prosthetic group (lipoic acid) interacts successively with the three other components of the complex and undergoes a cycle of reductive methylamination, methylamine transfer and electron transfer. With the aim to understand the interaction between the H-protein and its different partners, we have previously determined the crystal structure of the oxidized and methylaminated forms of the H-protein. In the present study, we have crystallized the H-protein in its reduced state and the L-protein (lipoamide dehydrogenase or dihydrolipoamide dehydrogenase). The L-protein has been overexpressed in Escherichia coli and refolded from inclusion bodies in an active form. Crystals were obtained from the refolded L-protein and the structure has been determined by X-ray crystallography. This first crystal structure of a plant dihydrolipoamide dehydrogenase is similar to other known dihydrolipoamide dehydrogenase structures. The crystal structure of the H-protein in its reduced form has been determined and compared to the structure of the other forms of the protein. It is isomorphous to the structure of the oxidized form. In contrast with methylaminated H-protein where the loaded lipoamide arm was locked into a cavity of the protein, the reduced lipoamide arm appeared freely exposed to the solvent. Such a freedom is required to allow its targeting inside the hollow active site of L-protein. Our results strongly suggest that a direct interaction between the H- and L-proteins is not necessary for the reoxidation of the reduced lipoamide arm bound to the H-protein. This hypothesis is supported by biochemical data [Neuburger, M., Polidori, A.M., Piètre, E., Faure, M., Jourdain, A., Bourguignon, J., Pucci, B. & Douce, R. (2000) Eur. J. Biochem. 267, 2882-2889] and by small angle X-ray scattering experiments reported herein.

Amino Acid Oxidoreductases↗
PubMed2000

Interaction between the lipoamide-containing H-protein and the lipoamide dehydrogenase (L-protein) of the glycine decarboxylase multienzyme system. 1. Biochemical studies.

Lipoamide dehydrogenase or dihydrolipoamide dehydrogenase (EC 1.8.1. 4) is the E3-protein component of the mitochondrial 2-oxoacid dehydrogenase multienzyme complexes. It is also the L-protein component of the glycine decarboxylase system. Although the enzymology of this enzyme has been studied exhaustively using free lipoamide as substrate, no data are available concerning the kinetic parameters of this enzyme with its physiological substrates, the dihydrolipoyl domain of the E2 component (dihydrolipoyl acyltransferase) of the 2-oxoacid dehydrogenase multienzyme complexes or the dihydrolipoyl H-protein of the mitochondrial glycine decarboxylase. In this paper, we demonstrate that Tris(2-carboxyethyl)phosphine, a specific disulfide reducing agent, allows a continuous reduction of the lipoyl group associated with the H-protein during the course of the reaction catalysed by the L-protein. This provided a valuable new tool with which to study the catalytic properties of the lipoamide dehydrogenase. The L-protein displayed a much higher affinity for the dihydrolipoyl H-protein than for free dihydrolipoamide. The oxidation of the dihydrolipoyl H-protein was not affected by the presence of structurally related analogues (apoH-protein or octanoylated H-protein). In marked contrast, these analogues strongly and competitively inhibited the decarboxylation of the glycine molecule catalysed by the P-protein component of the glycine decarboxylase system. Small unfolded proteolytic fragments of the H-protein, containing the lipoamide moiety, displayed Km values for the L-protein close to that found for the H-protein. On the other hand, these fragments were not able to promote the decarboxylation of the glycine in the presence of the P-protein. New highly hydrophilic lipoate analogues were synthesized. All of them showed Km and kcat/Km values very close to that found for the H-protein. From our results we concluded that no structural interaction is required for the L-protein to catalyse the oxidation of the dihydrolipoyl H-protein. We discuss the possibility that one function of the H-protein is to maintain a high concentration of the hydrophobic lipoate molecules in a nonmicellar state which would be accessible to the catalytic site of the lipoamide dehydrogenase.

Amino Acid Oxidoreductases↗
PubMed1999

X-Ray Structure of a Heterochiral, Sulfoximine-Stabilized Dilithiomethane Derivative.

A distorted Li(6)O octahedron in the center and four geminal dilithiated sulfoximine units characterize a tetrameric aggregate of the chiral sulfoximine-stabilized dilithiomethane derivative 3, a previously unknown reaction intermediate in asymmetric dianion chemistry. A comparison with the crystal structure of the monolithiated parent 2, formed by the treatment of 1 with nBuLi, allows a rationalization of the second lithiation.

Journal Article↗
PubMed1999

Structural and functional characterization of H protein mutants of the glycine decarboxylase complex.

The mitochondrial glycine decarboxylase complex (GDC) consists of four component enzymes (P, H, T, and L proteins) involved in the breakdown of glycine. In order to investigate structural interactions involved in the stabilization of the methylamine-loaded H protein (a transient species in the GDC reaction), we designed several mutants of H apoprotein. Structural analysis of the wild-type and mutants of H apoprotein emphasized the necessity to carefully assess, by biophysical techniques, the correct folding of mutated proteins prior to investigate their biochemical properties. The correctly folded wild-type and mutants of H apoprotein were in vitro lipoylated and then characterized in the context of GDC reaction by studying the reconstituted complex and partial reactions. We showed that Val(62) and Ala(64), surrounding the lipoyl-lysine, play an important role in the molecular events that govern the reaction between P and H protein but do not intervene in the recognition of the binding site of lipoic acid by lipoyl ligase. The biochemical results obtained with the HE14A mutant of H protein pointed out the major role of the Glu(14) amino acid residue in the GDC catalysis and highlighted the importance of the ionic and hydrogen bounds in the hydrophobic cleft of H protein for the stabilization of the methylamine-loaded lipoyl arm.

Amino Acid Oxidoreductases↗
PubMed1999

Investigation of the local structure and dynamics of the H subunit of the mitochondrial glycine decarboxylase using heteronuclear NMR spectroscopy.

The lipoate-dependent H protein plays a pivotal role in the catalytic cycle of the glycine decarboxylase complex (GDC), undergoing reducing methylamination, methylene transfer, and oxidation. The local structure and backbone dynamics of the methylamine-loaded H (Hmet), oxidized H (Hox), and H apoprotein (Hapo) have been investigated in solution. Filtered NOESY experiments using a [13C]Hmet as well as comparison of the heteronuclear shifts between the Hox and Hmet proteins demonstrate that the methylamine group is located inside a cleft of the protein. Furthermore, this group appears to be locked in this configuration as indicated by the high value of the activation energy (37 kcal/mol) of the global unloading reaction and by its restricted mobility, deduced from 13C relaxation measurements. Comparisons of the 1H and 15N chemical shifts and 15N relaxation in the three forms suggest that part of the lipoyl-lysine arm interacts with the protein polypeptide in the Hox and Hmet. The major change induced by the loading of the methylamine group concerns the C-terminal helix whose mobility becomes completely restricted compared to those of the Hox and Hapo. This C-terminal helix exhibits different reorientational characteristics in the three forms, which can be explained in the Hapo by a model consisting of a twisting motion about an axis passing through the helix. Our results indicate that the model of a freely swinging arm proposed for other lipoate-containing proteins is not acceptable in solution for the GDC. The implication of this observation in terms of the mechanism of the interaction of the H protein with the T protein, its physiological partner during the catalytic cycle, is discussed.

Amino Acid Oxidoreductases↗
PubMed1999

Biochemical dissection of photorespiration.

Progress has been made in the understanding of photorespiration and related proteins (Rubisco, glycolate oxidase and glycine decarboxylase) in the context of recent structural information. Numerous shuttles exist to support transamination, ammonia refixation and the supply or export of reductants generated or consumed (via malate-oxaloacetate shuttles) in the photorespiratory pathway. A porin-like channel that is anion selective represents the major permeability pathway of the peroxisomal membrane.

Alcohol Oxidoreductases↗
PubMed1999

Memory of Chirality in Photochemistry.

The helical-chiral character of the diradical intermediate 2, which cyclizes quicker than it equilibrates, explains the memory effect of chirality that occurs during the enantioselective photocyclization of alanine derivative 1 to give the proline derivative 3. Ts=H(3)CC(6)H(4)SO(2).

Journal Article↗