Alternating copolymerization of butadiene and propene with the catalyst VO(ONeo)2 Cl/Al(i-C4H9)3, 1

The influence of basic reaction parameters—the ratio of catalyst components, the composition of the monomer mixture and the temperature—on the progress of the copolymerization, the molecular weight and the molecular weight distribution as well as on the composition of the copolymers obtained is reported. Conversion data for the variation of the mole ratio of comonomers show a maximum for an [Al]/[V] mole ratio of approximately 7, whereas the molecular weight of copolymers is not significantly influenced. An increase in the molecular weight of the copolymers can be obtained by an increase of butadiene content in the monomer mixture. However, there is also an increasing incorporation of butadiene into the copolymer. Raising the temperature from ?60°C to 0°C results in a significant decrease in molecular weight, whereas the composition of the copolymers is not significantly changed.     

Effects of acamprosate on memory in healthy young subjects

OBJECTIVE: Several studies have shown acamprosate (calciumacetylhomotaurinate) to increase abstinence rates in weaned alcoholics. Chronic alcoholics often suffer from cognitive deficits. Since acamprosate appears to interact with N-methyl-D-aspartate (NMDA) receptors, a subclass of glutamate receptors playing an important role in learning and memory processes, this study was performed in order to investigate different cognitive functions during administration of acamprosate. METHOD: A randomized, double-blind, cross-over, placebo-controlled design, involving 12 healthy male volunteers was used. Acamprosate 2 g daily per os or placebo were administered for 7 days respectively, with a wash-out interval of 21 days between phases. Mood and different memory functions (i.e., working memory, delayed recall, recognition tasks) were assessed. RESULTS: It was shown that a dose of acamprosate 2 g/day for 7 days may produce an impairment in delayed free recall. Recognition tasks, short term working memory and mood were not altered. CONCLUSIONS: The present study supports the hypothesis that acamprosate impairs memory functions. This is in keeping with the concept of acamprosate acting as NMDA receptor antagonist. The limitations of the study are discussed.     

Extracorporeal CO2 removal as bridge to lung transplantation in life‐threatening hypercapnia

In patients awaiting lung transplantation (LTX), adequate gas exchange may not be sufficiently achieved by mechanical ventilation alone if acute respiratory decompensation arises. We report on 20 patients with life‐threatening hypercapnia who received extracorporeal CO₂ removal (ECCO2‐R) by means of the interventional lung assist (ILA®, Novalung) as bridge to LTX. The most common underlying diagnoses were bronchiolitis obliterans syndrome, cystic fibrosis, and idiopathic pulmonary fibrosis, respectively. The type of ILA was pumpless arteriovenous or pump‐driven venovenous (ILA activve®, Novalung) in 10 patients each. ILA bridging was initiated in 15 invasively ventilated and five noninvasively ventilated patients, of whom one had to be intubated prior to LTX. Hypercapnia and acidosis were effectively corrected in all patients within the first 12 h of ILA therapy: PaCO₂ declined from 109 (70–146) to 57 (45–64) mmHg, P < 0.0001; pH increased from 7.20 (7.06–7.28) to 7.39 (7.35–7.49), P < 0.0001. Four patients were switched to extracorporeal membrane oxygenation due to progressive hypoxia or circulatory failure. Nineteen patients (95%) were successfully transplanted. Hospital and 1‐year survival was 75 and 72%, respectively. Bridging to LTX with ECCO2‐R delivered by arteriovenous pumpless or venovenous pump‐driven ILA is feasible and associated with high transplantation and survival rates.     

Vapour-liquid equilibria and segment-molar excess gibbs free energies of concentrated poly(butyl methacrylate) solutions

Solvent activities were measured by an isopiestic sorption technique for solutions of poly(butyl methacrylate) and poly(tert-butyl methacrylate), respectively, in various solvents between 323 K and 373 K (or 403 K). The experimental data were reduced to segment-molar excess Gibbs free energies and to χ-functions. There is a clear difference in the thermodynamic behaviour of both polymers in their corresponding solutions due to the steric effect of the tert-butyl group. The chain-of-rotators equation-of-state model was used to calculate the thermodynamic quantities applying a group-contribution approach. In general, good agreement can be observed between experimental and calculated results.     

Diffuse perineuronal nets and modified pyramidal cells immunoreactive for glutamate and the GABA(A) receptor alpha1 subunit form a unique entity in rat cerebral cortex

Perineuronal nets (PNs) consisting of polyanionic chondroitin sulfate proteoglycans (CSPG) and other extracellular matrix components create an exceptional microenvironment around certain types of neurons. In rat neocortex, three types of PNs can be distinguished after staining with Wisteria floribunda agglutinin (WFA) by their different morphological structure: lattice-like PNs associated with subpopulations of nonpyramidal neurons, weakly labeled PNs showing a pyramidal morphology, and diffuse PNs that possess a thick, strongly labeled matrix sheath located mainly in layer VIb above the white matter. The type of neuron surrounded by diffuse nets has not been described so far. This study is focused on the cytochemical and morphological characteristics of neurons associated with diffusely contoured PNs in rat parietal cortex using immunocytochemical staining, intracellular injection, and retrograde tracing methods. Cells surrounded by diffuse PNs were glutamate-immunoreactive in contrast to nonpyramidal, net-associated neurons that showed immunoreactivity for GABA, the calcium-binding protein parvalbumin and the potassium channel subunit Kv3.1b. Both groups of PN-ensheathed cells were mostly immunoreactive for the GABA(A) receptor alpha1 subunit. Lucifer Yellow-injected neurons surrounded by diffuse PNs displayed the morphological properties of modified pyramidal cells with intracortical main axons. Many neurons with diffuse PNs were retrogradely labeled over a long distance after Fluoro-Gold tracer injection in the parietal cortex, but remained unlabeled after intrathalamic injection. We conclude that neurons associated with diffuse PNs are a subpopulation of glutamatergic modified pyramidal cells that could act as excitatory long-range intracortically projecting neurons.     

Determination of hemisphere dominance for language: comparison of frontal and temporal fMRI activation with intracarotid amytal testing

The reliability of frontal and temporal fMRI activations for the determination of hemisphere language dominance was evaluated in comparison with intracarotid amytal testing (IAT). Twenty-two patients were studied by IAT (bilateral in 13, unilateral in 9 patients) and fMRI using a paradigm requiring semantic decisions. Global and regional (frontal and temporoparietal) lateralisation indices (LI) were calculated from the number of activated (r>0.4) voxels in both hemispheres. Frontolateral activations associated with the language task were seen in all patients, temporoparietal activations in 20 of 22. Regional LI corresponded better with IAT results than global LI. Frontolateral LI were consistent with IAT in all patients with bilateral IAT (including three patients with right dominant and one patient with bilateral language representation) and were not conflicting in any of the patients with unilateral IAT. Temporoparietal LI were discordant with IAT in two patients with atypical language representation. In the determination of hemisphere dominance for language, regional analysis of fMRI activation is superior to global analysis. In cases with clear-cut fMRI lateralisation, i.e. consistent lateralised activation of frontal and temporoparietal language zones, IAT may be unnecessary. FMRI should be performed prior to IAT in all patients going to be operated in brain regions potentially involved in language.     

Botulinum toxin treatment of cocontractions after birth-related brachial plexus lesions

The authors studied botulinum toxin type A therapy of severe biceps-triceps cocontractions after nerve regeneration following birth-related brachial plexus lesions. Six children (age, 2 to 4 years) were treated two to three times over a period of 8 to 12 months with 40 mouse units of botulinum toxin at two sites of the triceps muscle. Elbow range of motion improved from 0 to 25 to 50 deg to 0 to 25 to 100 deg (p < 0.05), and muscle force of elbow flexion increased from a mean of Medical Research Council classification 1.7 to 3.7 (p < 0.05). After a 1-year follow-up, there was no clinical recurrence.     

Acamprosate reduces motor cortex excitability determined by transcranial magnetic stimulation

Acamprosate is effective in reducing alcohol intake in weaned alcoholics. We were interested if acamprosate had an effect on the excitability of cortical motoneurons determined by transcranial magnetic stimulation (TMS). We studied 12 male healthy volunteers (mean age 29.5 years, SD = 4.8) who were either treated with 6 tablets of acamprosate (each containing 333 mg verum) per day or placebo (randomized cross-over design) for 1 week. TMS was performed after each treatment session including a paired stimulation paradigm. Motor evoked potentials (MEPs) of the placebo and verum group did not differ with respect to paired stimulation. However, motor threshold increased in the acamprosate group (verum: 61.5% (SD = 7.9) vs. placebo: 58.9% (SD = 8.8), p = 0.036). We conclude that acamprosate leads to a hypoexcitability of the motor cortex. This might be due to subcortical mechanisms, e.g. thalamocortical pathways since intracortical inhibition and facilitation was not affected.