Search PubMed⌕ Search

Biomedical subjects

W Stender

Publications and source records attributed to W Stender.

17 recordsLinked to original sources
PubMed1990

Ventral interbody spondylodesis using a new plug-shaped implant.

A new technique for interbody lumbar spondylodesis using a new cancellous metal, plug-shaped construct was performed in 35 cases with spondylolisthesis or lumbar instability. All of these patients have had severe low-back pain for years, some with radicular symptoms and had been treated unsuccessfully for years. In a follow-up study, 28 of these patients were examined after a time-period of 4 to 24 months. According to objective criteria, the clinical results were good in 19 cases, moderate in five cases and poor in one case. The patients' own judgement about the success of the operation was somewhat different: 17 patients judged their condition as good, six as moderate and two as poor. For three patients the follow-up examination was so close to surgery that no judgement can be made. We saw postoperative complications in two cases: one was a fracture of the implant, the other was a deep vein thrombosis. Since the first reports about ventral spondylodesis by CAPENER [4] and BURNS [2] in the years 1932 and 1933 this surgical technique has been under discussion worldwide. This discussion even increased after HORMON [10] published some reports about his experience with this operative treatment in 1948. Since that time, many techniques for the intercorporal fusion of the spine have been reported. These include tibial or iliac bone grafts, sometimes fixed with screws or plates [6, 9, 12, 17, 20]. This article now describes the new surgical technique for ventral spondylodesis, using a new implant for the interbody fusion of the lumbar and sacral spine. In addition, we describe the indications for ventral spondylodesis and report the results of a rather small follow-up study.

Adult↗
PubMed1983

The quaternary structure of Escherichia coli RNA polymerase studied with (scanning) transmission (immuno)electron microscopy.

A model for the quaternary structure of Escherichia coli RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) is presented. It is based on results from classification of profiles of enzyme molecules, and from application of immuno electron microscopy. Classification of molecules, prepared with the single carbon layer technique, was first achieved for images recorded in dark field with the scanning transmission electron microscope and later on for images recorded in bright-field transmission electron microscopy. It results in five approximately equally sized groups, containing about 80% of the core enzyme profiles. Holoenzyme profiles can be grouped into the same classes, and have approximately the same dimensions (9 nm X 16 nm). Based on the shapes and sizes of the classified profiles, a tentative model for core enzyme has been constructed. Correlation of shadow projections of this model, with the distributions of attachment sites of antibodies against alpha, beta, beta' and sigma over the profiles, has led to models for core and holoenzyme in which the subunits are localized. The model is compared with literature data on the quaternary structure of RNA polymerase.

Bacterial Proteins↗
PubMed1980

Sequence-specific interaction of sigma subunit of E. coli RNA polymerase with DNA.

The interaction of sigma subunit of E. coli RNA polymerase with DNA, either double or single-stranded, and with two inhibitors of RNA synthesis was investigated by using antibodies directed against the subunit. Free sigma subunit was shown to interact with poly(dA), poly(dT), poly(dAC).poly(dGT), T7 DNA and, to a lesser degree, with lambda DNA. When the sigma subunit forms part of the holo enzyme, sigma also interacts with poly(dG).poly(dC). Rifampicin and streptolydigin interact with sigma in the holo enzyme and with free and core bound sigma subunit, respectively. The results suggest that sigma recognizes mainly AC-GT-sequences in double-stranded DNA. The findings are correlated with the base composition in RNA polymerase binding regions of promoters and suggest at least a general interaction between sigma subunit and single-stranded DNA in open complexes.

Complement Fixation Tests↗
PubMed1980

Antibodies against the subunits of E. coli RNA polymerase as probes for subunit-specific binding of DNA and other ligands.

Antibodies against the isolated subunits alpha, beta, and beta' of DNA-dependent RNA polymerase from E. coli have been prepared. They have been used to compare the extent of antibody-binding, as measured by complement fixation, to the isolated subunits and to the intact enzyme, in the absence and presence of ligands, such as inhibitors, nucleotides, nucleosides, oligo- and poly-nucleotides, and DNA of different composition. In many cases the results show a subunit-specific dependence of complement fixation upon the presence of a ligand and suggest a functional topography of the interaction between the subunits alpha, beta, and beta' of RNA polymerase and defined nucleotide sequences and small ligands.

Antibodies, Bacterial↗
PubMed1979

Quaternary structure of DNA-dependent RNA polymerase from Escherichia coli. Measurement of distances by fluorescence energy transfer.

Distances between the subunits in Escherichia coli RNA polymerase (core and holo enzyme) and the rifamycin binding site have been determined using the nonradiative energy transfer technique. The appropriate donor and acceptor labels have been chosen in order to optimize the spectral overlap and maximize the energy transfer. Spacer linked derivatives of rifamycin SV possessing nitrobenzo-oxadiazole groups (energy acceptor) were synthesized for this purpose. The donor label, acetylaminoethylaminonaphthalene sulfonate, was introduced into the intact enzyme, and the subunits were separated. Enzyme molecules selectively labelled on one kind of subunit were produced by mixed reconstitution techniques employing labelled and non labelled subunits. The labelled beta'-subunit could not be prepared in sufficient amounts. Energy transfer distances between the enzyme-bound rifamycin derivative and the subunits were determined to be approximately 5.9 nm for sigma, 7.2 nm for alpha 2 and 6.1 nm for beta.

Chemical Phenomena↗
PubMed1976

Dissociation kinetics of complexes between the antibiotic rifamycin and DNA-dependent RNA polymerase from Escherichia coli.

Phosphocellulose chromatography was employed to measure the binding of 3-(2-[14C]acetamidoethyl)-thiorifamycin(abbreviated[14C]AcNHEtS-Rif) to RNA polymerase core enzyme. The technique yielded a correct value for the stoichiometry of interaction. The same method was successfully applied to an investigation of the dissociation kinetics of the [14C]AcNHEtS-Rif - core-polymerase complex. We observed biphasic dissociation kinetics not in agreement with the existence of one single first-order dissociation step. Assuming two independent dissociation reactions, rate constants have been evaluated differing roughly by 10-fold (1.7 X 10(-3) s-1 and 1.5 X 10(-4) s-1 at 25 degrees C). The ratio of the amplitudes of the biphasic dissociation kinetics changed with temperature. The kinetic data are interpreted as indirect evidence for the existence of two enzyme species differing in their dynamic properties with respect to the binding of the antibiotic rifamycin. Our data furthermore lend support to the assumption that the two enzyme forms are in equilibrium. The observed sigmoidal dependence of the dissociation rate on temperature could indicate a conformational transition of RNA core polymerase with a transition midpoint at around 20 degrees C. The dye, rose bengal, was found to be as effective as AcNHEtS-Rif itself as a competing agent. The dissociation kinetics of the [14C]-AcNHEtS-Rif - core-polymerase complex in the presence of an excess of the dye rose bengal were found to be very similar to those measured in the presence of AcNHEtS-Rif. This could mean that rose bengal and AcNHEtS-Rif compete for the same site at RNA core polymerase. The dissociation of the ternary complex [14C]AcNHEtS-Rif - core-polymerase - poly[d(A-T)] was followed by gel filtration. Up to the extent of dissociation measured, the reaction appeared to follow first-order kinetics. The dissociation rate constant was calculated to be 1.7 X 10(-4) s-1. Experiments to determine the effect of the antibiotic streptolydigin on the dissociation kinetics of the [14C]AcNHEtS-Rif - core-polymerase complex have not led to conclusive results.

Binding Sites↗
PubMed1975

The modification of DNA-dependent RNA polymerase from Escherichia coli by an alkylating derivative of rifamycin SV.

3-(2-Bromo[1-14C]acetamidoethyl)-thio-rifamycin SV, abbreviated BrAcNEtS-Rif, and alkylating derivative of rifamycin SV was synthesized. A four-fold excess of BrAcNEtS-Rif inhibited the enzymic activity of RNA polymerase from Escherichia coli to 97%. Incubation of RNA polymerase with Br[14C]AcNEtS-Rif led to covalent substitution. The reaction of Br[14C]AcNEtS-Rif with enzyme at a ratio of 1.4:1 and a concentration of 63 nM was found to proceed with a half life of 1 h at 37 degrees C. The enzyme could be protected from reaction with BrAcNEtS-Rif by either rifampicin or the hybrid [poly(dT)]-[r(Ap)5a]. The modification of holoenzyme by Br[14C]AcNEtS-Rif in the presence of p-hydroxymercuribenzene sulfonic acid (pOH-HgBzSO3H) or 4 M LiCl occurred with faster kinetics and led to a higher degree of substitution. Reaction of Br[14C]AcNEtS-Rif with RNA polymerase core enzyme caused predominant substitution of subunit beta. In the case of RNA polymerase holenzyme the radioactive substituents were evenly distributed between subunits beta and sigma. Apparently the topology of the rifamycin binding site of holoenzyme, similarly to core enzyme, precludes attacks of nucleophilic functions from beta' and alpha, but it allows nucleophilic functions from subunits beta and sigma to react with equal probability on BrAcNEtS-Rif. In the presence of a 20-fold excess of pOH-HgBzSO3H, the modification of holoenzyme was drastically altered. Virtually all substitution took place on subunit beta', very little on beta and none on subunits sigma and alpha.

Alkylating Agents↗
PubMedDate not supplied

VD hotline: an evaluation.

A VD hotline started in January 1973 at Monmouth Medical Center, Long Branch, N.J., was evaluated with the following results. Hotline operators handled 260 calls in 1973. The typical caller was a 20-year-old employed male who heard about the hotline from a friend, wanted information about clinic hours and costs, and had questions about symptoms of venereal disease. At Monmouth Medical Center, venereal disease patients who go to the emergency room receive specific diagnosis and therapy, and in the clinic they receive broader medical care. The hotline encourages patients to go to the clinic or to their private physicians. Visits to Monmouth Medical Center for venereal disease increased during the second half of 1972 from 356 to 545 (53%). For the emergency room alone, the rise was 17% and for the clinic, 68%. There was an increase of 20% in the number of patients treated in the emergency room, but the number treated in the clinic leveled. Thus, there was a substantial increase in visits, especially to the clinics where the most care is provided, and a modest increase in treated patients. The causal contribution of the hotline to these increases cannot be stated with certainty. The cost of operating the hotline was $14.70 per call. While high, it might be defended on the basis of avoiding the higher costs of untreated disease. The cost can be reduced by making the hotline serve multiple health purposes. The hotline appeared useful but costly. This retrospective evaluation was hampered by the unavailability of some critical data.

Adolescent↗