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Biomedical subjects

V Braun

Publications and source records attributed to V Braun.

At least 145 records · Page 8Linked to original sources
PubMed1993

[Computerized tomography and craniocerebral trauma].

Computed tomography (CT) is now the standard neuroradiological examination for patients with major head injuries, although conventional X-ray of the skull should not be neglected. Whereas the latter only shows such skull pathology as fractures or intracranial air following a basal fracture, CT clearly visualizes intracranial pathology. It allows differentiation between haematoma and contusion, between localized oedema and generalized brain swelling; CT is therefore indicated in every patient with disturbed consciousness, focal neurological signs, and/or secondary clinical impairment, and also in all drunken patients with head injury. In a patient with impaired consciousness and focal neurological deficit the probability of a pathologic CT is 85%. An extracerebral haematoma is often present, which needs urgent evacuation. A modern, non-expensive communications system using a standard telephone line enables hospitals without a neurosurgical unit to send CT pictures that are difficult to interpret to a neurosurgeon and to discuss them on-line by telephone. This system has now been in operation for over 2 years and has improved the care of patients with head injury in our region. It is highly efficient and reliable and improves cooperation between distant hospitals. It also helps to avoid unnecessary transfers, which are not only expensive but may even harm a critically ill patient.

Brain Concussion↗
PubMed1993

[Results of 100 consecutively operated patients with acoustic neuroma].

The results from 100 patients with 103 acoustic neurinomas who were operated on between February 1979 and April 1992 are presented. All patients were placed in the half-sitting position and operated on by the same surgeon using the suboccipital-trans-meatal approach. Postoperative facial nerve function was good in 56%, moderate in 20% and poor in 24% of our patients. Preservation of useful hearing was achieved in 21%: the smaller the tumor, the better the functional result. However, the early symptoms of acoustic neuromas (tinnitus, dizziness, feeling of unsteadiness) were only slightly improved by the operation. The result concerning tinnitus seemed to be better after sacrificing the cochlear nerve. The number of patients with ataxia increased postoperatively, although objective ataxia decreased. Dizziness improved regardless of the tumor size.

Auditory Threshold↗
PubMed1992

Serratia marcescens forms a new type of cytolysin.

Most Serratia marcescens strains produce a new type of cytolysin (hemolysin) which is also found in other Serratia species. The hemolytic polypeptide ShlA (M(r) 162 101) is secreted across the outer membrane through the help of the ShlB protein which also involves conversion of an inactive precursor in an hemolytically active form. Both proteins are synthesized with signal sequences which are released during export across the cytoplasmic membrane. Mutants expressing inactive ShlB derivatives are impaired in activation and secretion suggesting a tight coupling between both processes. The region of ShlA for activation and secretion is confined to the N-terminal 16% of the polypeptide which contains the sequence NPNG which is also found in the Proteus hemolysin, the Bordetella pertussis filamentous hemagglutinin and two highly expressed outer membrane proteins of Haemophilus influenzae. Substitution of the first asparagine (N) residue by isoleucine converts the Serratia hemolysin into an inactive secretion incompetent form. It is concluded that this region is recognized by ShlB for activation and secretion of ShlA. The Serratia hemolysin forms defined pores in erythrocyte membranes.

Amino Acid Sequence↗
PubMed1992

8-Azido-ATP labelling of the FecE protein of the Escherichia coli iron citrate transport system.

The iron(III) transport system via citrate displays the characteristics of a binding protein-dependent transport mechanism through the cytoplasmic membrane. One of the five transport proteins, FecE, contains the two motifs found in ATP-binding proteins. Cloned overexpressed FecE was photoaffinity-labelled with [32P]8-azido-ATP. Labelling was inhibited by 1 mM ATP, ADP, GTP and less by CTP, demonstrating the specificity of the reaction. It is suggested that ATP is the principal energy source for iron(III) citrate transport through the cytoplasmic membrane of Escherichia coli.

Adenosine Triphosphate↗
PubMed1992

Spasmodic torticollis: severe compression neuropathy in rami dorsales of cervical nerves C1-6.

In 28 patients with spasmodic torticollis dorsal branches of the cervical nerves C1-6, and in 25 of these patients fascicles of the contralateral accessory nerve were investigated by light and electron microscopy. Significant changes were noted in 15 patients. The alterations were not seen or were less prominent in the 5 control cases studied for comparison. Semiquantitative evaluation of light microscopic findings revealed in 12 cases prominent and numerous Renaut bodies; in 9 cases evidence of regeneration (in 3 of these postoperatively); and in 11 cases disproportionately thin myelin sheaths in relation to axon calibers. In conjunction with endoneurial edema and thickening of the perineurium, these changes were suggestive of compression neuropathy. Whether these changes were the cause, or a side effect of the abnormal muscle contractions in spasmodic torticollis could not be elucidated. Peripheral nerve compression, however, may trigger abnormal activity in the peripheral part of the involved interneuronal circuits and may, thus, be considered as one of the many possible causes of spasmodic torticollis.

Adult↗
PubMed1992

An aspartate deletion mutation defines a binding site of the multifunctional FhuA outer membrane receptor of Escherichia coli K-12.

The FhuA protein of the outer membrane serves as a receptor for phages T5, T1, and phi 80, for colicin M, for the antibiotic albomycin, and for ferrichrome and related siderophores. To identify protein regions important for the multiple FhuA activities, fhuA genes of spontaneous chromosomal mutants which expressed wild-type amounts of the FhuA protein were sequenced. A mutant which was partially T5 sensitive but impaired in all other functions was missing aspartate residue 348 of the mature protein as a result of a three-base deletion. This aspartate residue is part of the hydrophilic sequence Asp-Asp-Glu-Lys. Replacement by site-specific mutagenesis of each of the Asp residues by Tyr, of Glu by Val, and of Lys by Met reduced FhuA activity but less than the Asp deletion did. Ferrichrome inhibited binding of phage phi 80 and of colicin M to these mutants in an allele-specific manner. A completely resistant derivative of the Asp deletion mutant contained, in addition, a leucine-to-proline substitution at position 106 and eight changed bases, converting at positions 576 to 578 an Arg-Pro-Leu sequence to Ala-Arg-Cys. The latter mutations and the Leu-to-Pro replacement alone did not alter sensitivity to the phages but reduced sensitivity to colicin M and albomycin 10- to 1,000-fold. The proline replacements probably disturb FhuA conformation and, in concert with the Asp deletion, inactivate FhuA completely. It is concluded that the Asp deletion site defines a region of FhuA which directly participates in binding of all FhuA ligands. Growth promotion studies on iron-limited media revealed that certain siderophores of the hydroxamate type, such as butylferrichrome, ferrichrysin, and ferrirubin, are taken up not only via FhuA but also via the FhuE outer membrane receptor protein.

Amino Acid Sequence↗
PubMed1992

In vitro activation of the Serratia marcescens hemolysin through modification and complementation.

The hemolytic activity of Serratia marcescens is determined by two polypeptides, termed ShlA and ShlB. ShlA is synthesized as an inactive precursor (ShlA*) and secreted with the help of ShlB, which is located in the outer membrane. In this study, it is shown that a cell lysate containing ShlB as well as partially purified ShlB converted ShlA* to the active ShlA hemolysin. ShlA remained active after removal of ShlB by column chromatography. In contrast to the stable modification of ShlA* by ShlB, a reversible activation was achieved by adding to ShlA* an N-terminal fragment of ShlA (ShlA16), consisting of 269 amino acid residues of ShlA and 18 residues of the vector. The nonhemolytic ShlA16 complemented ShlA* only when it was synthesized in an ShlB-producing cell. A deletion derivative of ShlA*, lacking residues 4 to 117, was complemented by ShlA16 but not activated by ShlB. Activation of ShlA* by ShlB at 4 degrees C proceeded at a much slower rate than complementation by ShlA16. It is concluded that ShlA* is modified by ShlB. ShlA16 modified by ShlB complements the missing modification of ShlA* in trans. Modification by ShlB occurs in the N-terminal part of ShlA*, which is also the reaction in vivo which results in active ShlA hemolysin in the culture supernatant. The HpmA hemolysin of Proteus mirabilis, which is very similar to ShlA, was also activated in vitro by ShlB and complemented by ShlA16.

Chromosome Deletion↗
PubMed1992

Membrane topology of the Escherichia coli ExbD protein.

The ExbD protein is involved in the energy-coupled transport of ferric siderophores, vitamin B12, and B-group colicins across the outer membrane of Escherichia coli. In order to study ExbD membrane topology, ExbD-beta-lactamase fusion proteins were constructed. Cells expressing beta-lactamase fusions to residues 53, 57, 70, 76, 78, 80, 92, 121, and 134 of ExbD displayed high levels of ampicillin resistance, whereas fusions to residues 9 and 19 conferred no ampicillin resistance. It is concluded that the only hydrophobic segment of ExbD, encompassing residues 23 to 43, forms a transmembrane domain and that residues 1 to 22 are located in the cytoplasm and residues 44 to 141 are located in the periplasm.

Ampicillin↗
PubMed1992

Iron transport systems of Serratia marcescens.

Serratia marcescens W225 expresses an unconventional iron(III) transport system. Uptake of Fe3+ occurs in the absence of an iron(III)-solubilizing siderophore, of an outer membrane receptor protein, and of the TonB and ExbBD proteins involved in outer membrane transport. The three SfuABC proteins found to catalyze iron(III) transport exhibit the typical features of periplasmic binding-protein-dependent systems for transport across the cytoplasmic membrane. In support of these conclusions, the periplasmic SfuA protein bound iron chloride and iron citrate but not ferrichrome, as shown by protection experiments against degradation by added V8 protease. The cloned sfuABC genes conferred upon an Escherichia coli aroB mutant unable to synthesize its own enterochelin siderophore the ability to grow under iron-limiting conditions (in the presence of 0.2 mM 2.2'-dipyridyl). Under extreme iron deficiency (0.4 mM 2.2'-dipyridyl), however, the entry rate of iron across the outer membrane was no longer sufficient for growth. Citrate had to be added in order for iron(III) to be translocated as an iron citrate complex in a FecA- and TonB-dependent manner through the outer membrane and via SfuABC across the cytoplasmic membrane. FecA- and TonB-dependent iron transport across the outer membrane could be clearly correlated with a very low concentration of iron in the medium. Expression of the sfuABC genes in E. coli was controlled by the Fur iron repressor gene. S. marcescens W225 was able to synthesize enterochelin and take up iron(III) enterochelin. It contained an iron(III) aerobactin transport system but lacked aerobactin synthesis. This strain was able to utilize the hydroxamate siderophores ferrichrome, coprogen, ferrioxamine B, rhodotorulic acid, and schizokinen as sole iron sources and grew on iron citrate as well. In contrast to E. coli K-12, S. marcescens could utilize heme. DNA fragments of the E. coli fhuA, iut, exbB, and fur genes hybridized with chromosomal S. marcescens DNA fragments, whereas no hybridization was obtained between S. marcescens chromosomal DNA and E. coli fecA, fhuE, and tonB gene fragments. The presence of multiple iron transport systems was also indicated by the increased synthesis of at least five outer membrane proteins (in the molecular weight range of 72,000 to 87,000) after growth in low-iron media. Serratia liquefaciens and Serratia ficaria produced aerobactin, showing that this siderophore also occurs in the genus Serratia.

Bacterial Outer Membrane Proteins↗
PubMed1992

Iron(III) hydroxamate transport in Escherichia coli K-12: FhuB-mediated membrane association of the FhuC protein and negative complementation of fhuC mutants.

Iron(III) hydroxamate transport across the cytoplasmic membrane is catalyzed by the very hydrophobic FhuB protein and the membrane-associated FhuC protein, which contains typical ATP-binding domains. Interaction between the two proteins was demonstrated by immunoelectron microscopy with anti-FhuC antibodies, which showed FhuB-mediated association of FhuC with the cytoplasmic membrane. In addition, inactive FhuC derivatives carrying single amino acid replacements in the ATP-binding domains suppressed wild-type FhuC transport activity, which arose either from displacement of active FhuC from FhuB by the mutated FhuC derivatives or from the formation of mixed inactive FhuC multimers between wild-type and mutated FhuC proteins. Inactive FhuC derivatives containing internal deletions and insertions showed no phenotypic suppression, indicating conformational alterations that rendered the FhuC derivatives unable to displace wild-type FhuC. It is concluded that the physical interaction between FhuC and FhuB implies a coordinate activity of both proteins in the transport of iron(III) hydroxamates through the cytoplasmic membrane.

ATP-Binding Cassette Transporters↗
PubMed1991

Transport of iron across the outer membrane.

The TonB protein is involved in energ-coupled receptor-dependent transport processes across the outer membrane. The TonB protein is anchored in the cytoplasmic membrane but exposed to the periplasmic space. To fulfill its function, it has to couple the energy-providing metabolism in the cytoplasmic membrane with regulation of outer membrane receptor activity. Ferrichrome and albomycin transport, uptake of colicin M, and infection by the phages T1 and phi 80 occur via the same receptor, the FhuA protein in the outer membrane. Therefore, this receptor is particularly suitable for the study of energy-coupled TonB-dependent transport across the outer membrane. Ferrichrome, albomycin and colicin M bind to the FhuA receptor but are not released into the periplasmic space of unenergized cells, or tonB mutants. In vivo interaction between FhuA and TonB is suggested by the restoration of activity of inactive FhuA proteins, bearing amino acid replacements in the TonB box, by TonB derivatives with single amino acid substitutions. Point mutations in the fhuA gene are suppressed by point mutations in the tonB gene. In addition, naturally occurring degradation of the TonB protein and its derivatives is preferentially prevented in vivo by FhuA and FhuA derivatives where functional interaction takes place. It is proposed that in the energized state, TonB induces a conformation in FhuA which leads to the release of the FhuA-bound compounds into the periplasmic space. Activation of FhuA by TonB depends on the ExbBD proteins in the cytoplasmic membrane. They can be partially replaced by the TolQR proteins which show strong sequence similarity to the ExbBD proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Outer Membrane Proteins↗
PubMed1991

[Preservation of hearing and facial nerve function in surgery for acoustic neuroma].

The results concerning the preservation of hearing and facial nerve function in 71 patients with 74 acoustic neuromas operated on from 1979 to 1990 are presented. All patients have been operated on in half-sitting position by one surgeon using the suboccipital-transmeatal approach. Postoperative facial nerve function was good (House degree I or degrees II) in 42/73 patients (58%), moderate (House degrees III or degrees IV) in 13/37 (18%), and poor (House degrees V or degrees VI) in 18/73 (24%). Preservation of useful hearing was achieved in 17%. The smaller the tumour and the easier the preparation the better was the functional result. Beside anatomic integrity of nerves and endolymphatic system the internal auditory artery as the most important vessel for the inner ear blood supply should be respected. The cochlear nerve intact in 47 patients we only found one case with recurrent tumour in a patient with neurofibromatosis 2. Preservation of the cochlear nerve did not have an increased risk of tumour recurrence in our group of patients.

Adolescent↗
PubMed1991

Binding of the immunity protein inactivates colicin M.

Colicin M (Cma) displays a unique mode of action in that it inhibits peptidoglycan and lipopolysaccharide biosynthesis through interference with bactoprenyl phosphate recycling. Protection of Cma-producing cells by the immunity protein (Cmi) was studied. The amount of Cmi determined the degree of inhibition of in vitro peptidoglycan synthesis by Cma. In cells, immunity breakdown could be achieved by overexpression of the Cma uptake system. Full immunity was restored after raising the cmi gene copy number. In sphaeroplasts, Cmi was degraded by trypsin, but this could be prevented by the addition of Cma. The N-terminal end includes the only hydrophobic amino acid sequence of Cmi, suggesting a function in anchoring of Cmi in the cytoplasmic membrane. It is proposed that Cmi does not act catalytically but binds Cma at the periplasmic face of the cytoplasmic membrane, thereby resulting in Cma inactivation. Two other possible modes of colicin M immunity, interference of Cmi with the uptake of Cma, and interaction of Cmi with the target of Cma, were ruled out by the data.

Amino Acid Sequence↗
PubMed1991

The tonB gene of Serratia marcescens: sequence, activity and partial complementation of Escherichia coli tonB mutants.

The TonB protein plays a key role in the energy-coupled transport of iron siderophores, of vitamin B12, and of colicins of the B-group across the outer membrane of Escherichia coli. In order to obtain more data about which of its particular amino acid sequences are necessary for TonB function, we have cloned and sequenced the tonB gene of Serratia marcescens. The nucleotide sequence predicts an amino acid sequence of 247 residues (Mr 27,389), which is unusually proline-rich and contains the tandem sequences (Glu-Pro)5 and (Lys-Pro)5. In contrast to the TonB proteins of E. coli and Salmonella typhimurium, translation of the S. marcescens TonB protein starts at the first methionine residue of the open reading frame, which is the only amino acid removed during TonB maturation and export. Only the N-terminal sequence is hydrophobic, suggesting its involvement in anchoring the TonB protein to the cytoplasmic membrane. The S. marcescens tonB gene complemented an E. coli tonB mutant with regard to uptake of iron siderophores, and sensitivity to phages T1 and phi 80, and to colicins B and M. However, an E. coli tonB mutant transformed with the S. marcescens tonB gene remained resistant to colicins Ia and Ib, to colicin B derivatives carrying the amino acid replacements Val/Ala and Val/Gly at position 20 in the TonB box, and they exhibited a tenfold lower activity with colicin D. In addition, the S. marcescens TonB protein did not restore T1 sensitivity of an E. coli exbB tolQ double mutant, as has been found for the overexpressed E. coli TonB protein, indicating a lower activity of the S. marcescens TonB protein. Although the S. marcescens TonB protein was less prone to proteolytic degradation, it was stabilized in E. coli by the ExbBD proteins. In E. coli, TonB activity of S. marcescens depended either on the ExbBD or the TolQR activities.

Amino Acid Sequence↗
PubMed1991

Selective peripheral denervation in patients with spasmodic torticollis.

The results of selective peripheral denervation of the involved muscles in 35 patients with spasmodic torticollis are reported. We modified the operation first described by Bertrand. Follow-up was 3 months to 2.5 years in 34/35 patients. 73% noticed a significant improvement or disappearance of dystonia and pain following surgery and physiotherapy for 3 months postoperatively. Selective peripheral denervation is recommended for patients with spasmodic torticollis of at least 1-2 years duration which is resistant to conservative treatment. It may also be used in patients who do not respond to injection of botulinum A toxin or who develop resistance to this kind of therapy.

Follow-Up Studies↗
PubMed1991

Pore-forming bacterial protein hemolysins (cytolysins).

Protein toxins forming pores in biological membranes occur frequently in Gram-positive and Gram-negative bacteria. They kill either bacteria or eukaryotic cells (at most, a few seem to act on both groups of organisms). Most of the toxins affecting eukaryotes have clearly been shown to be related to the pathogenicity of the producing organisms. Toxin formation frequently involves a number of genes which encode the toxin polypeptide as well as proteins for toxin activation and secretion. Regulation of toxin production is usually coupled with that of the synthesis of a number of other virulence factors. Iron is the only known environmental factor that regulates transcription of a number of toxin genes by a Fur repressor-type mechanism, as has been originally described in Escherichia coli. Interestingly, the thiol-activated hemolysins (cytolysins) of Gram-positive bacteria contain a single cysteine which can be replaced by alanine without affecting the cytolytic activity. The Gram-negative hemolysins (cytolysins) are usually synthesized as precursor proteins, then covalently modified to yield an active hemolysin and secreted via specific export systems, which differ for various types of hemolysins.

Amino Acid Sequence↗
PubMed1990

Iron (III) hydroxamate transport into Escherichia coli. Substrate binding to the periplasmic FhuD protein.

Due to its extreme insolubility, Fe3+ is not transported as a monoatomic ion. In microbes, iron is bound to low molecular weight carriers, designated siderophores. For uptake into cells of Escherichia coli Fe3+ siderophores have to be translocated across two membranes. Transport across the outer membrane is receptor-dependent and energy-coupled; transport across the cytoplasmic membrane seems to follow a periplasmic binding protein-dependent transport mechanism. In support of this notion we demonstrate specific binding of the Fe3+ hydroxamate compounds ferrichrome, aerobactin, and coprogen, which are transported via the Fhu system, to the periplasmic FhuD protein, and no binding of the transport inactive ferrichrome A, ferric citrate, and iron sulfate. About 10(4) ferrichrome molecules were bound to the FhuD protein of cells which overproduced plasmid-encoded FhuD. Binding depended on transport across the outer membrane mediated by the FhuA receptor and the TonB protein. Binding to FhuD was supported by the exclusive resistance of FhuD to proteinase K in the presence of the transport active hydroxamates. The overproduced precursor form of the FhuD protein was not protected by the Fe3+ hydroxamates indicating a conformation different to the mature form. The FhuD protein apparently serves as a periplasmic carrier for Fe3+ hydroxamates with widely different structures.

Bacterial Proteins↗