A real-time drawing study of melt-crystallized ultra-high molecular weight polyethylene. Comparison with conventional X-ray results

In the past morphological changes, caused by uni-axial drawing of flexible polymers have been studied mostly under conditions, quite different from the drawing conditions. This could give rise to certain artefacts, leading to mis-interpretations. Up to now very little was known about this possibility. Therefore, X-ray patterns obtained by conventional drawing studies and by real-time X-ray drawing studies are compared in this paper. It will be shown, that although some results on melt-crystallized polyethylene discussed here show indeed small differences, conventional X-ray studies can be used without any problem for qualitative studies. However, studies of deformation phenomena in elastic deformable regions as well as quantitative X-ray studies require real-time measurements.     

A novel case of infantile sacral teratoma and a constitutional t(12;15)(q13;q25) pat

Cytogenetic analysis of peripheral lymphocytes of an infantile patient with a sacral teratoma revealed a constitutional translocation (12;15)(q13;q25) pat. The same translocation was found in four additional relatives. Loss of heterozygosity analysis of the patient's tumor material showed retention of both translocation-derived chromosomes. Since allelic loss in the 12q13 region has been observed in germ cell tumors, we hypothesize that disregulation of genes located at or near the 12q13 breakpoint may be related to the development of this sacral teratoma. As a first step towards the identification of these genes, a 12q13 genomic contig that spans the breakpoint has been constructed.     

Evaluation of the Etest ESBL and the BD Phoenix,VITEK 1, and VITEK 2 automated instruments for detection of extended-spectrum beta-lactamases in multiresistant Escherichia coli and Klebsiella spp

Seventy-four isolates of multiresistant Escherichia coli and Klebsiella spp. recovered during a 3-year period and 17 control strains with genotypically identified beta-lactamases were tested for the production of extended-spectrum beta-lactamases (ESBLs) by using the Etest and the VITEK 1, VITEK 2, and Phoenix automated instruments. The use of the Etest was evaluated by investigating its accuracy in detecting the ESBLs of the control strains and by comparing interpretation results of laboratory technicians and experts. The accuracy of the Etest was 94%. With the Etest as the reference for the clinical strains and the genotype as the reference for the control strains, the automated instruments detected the ESBLs with accuracies of 78% (VITEK 2), 83% (VITEK 1), and 89% (Phoenix). No significant difference between the systems with regard to the control strains was detected. The VITEK 2 did, however, perform less well than the Phoenix (P = 0.03) on the collection of clinical isolates, mainly because of its high percentage of indeterminate test results (11%). No significant difference between the performances of the VITEK 1 and either the VITEK 2 or the Phoenix was found. However, because of its associated BDXpert system the Phoenix showed the best performance. The Etest was found to be an accurate test but was limited by its indeterminate results (4%), its inability to differentiate between K1 hyperproduction and ESBLs, questionable guidelines concerning mutants inside the inhibition zones, and the inability of the technicians to recognize subtle zone deformations.     

Non-synaptic release of [3H]noradrenaline in response to oxidative stress combined with mitochondrial dysfunction in rat hippocampal slices

Brain ischemia is frequently associated with oxidative stress in the reperfusion period. It is known that noradrenaline (NA) is released in excess under energy deprivation by the sodium-dependent reversal of the monoamine carrier. However, it is not known how oxidative stress affects NA release in the brain alone or in combination with energy deprivation. As a model of oxidative stress, the effect of H(2)O(2) (0.1-1.5 mM) perfusion was investigated in superfused rat hippocampal slices. It elicited a dose-dependent elevation of the release of [(3)H]NA and its tritiated metabolites as well as a simultaneous drop in the tissue energy charge. Mitochondrial inhibitors, i.e. rotenone (10 microM), and oligomycin (10 microM) in combination, also decreased the energy charge, but they had only a mild effect on [(3)H]NA release. However, when H(2)O(2) was added together with oligomycin and rotenone their effect on [(3)H]NA release was greatly exacerbated. H(2)O(2) and mitochondrial inhibitors also induced an increase in [Na(+)](i) in isolated nerve terminals, and their effect was additive. The effect of H(2)O(2) on tritium release was temperature-dependent. It was also attenuated by the glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (30 microM) and (+/-)-2-amino-5-phosphonopentanoic acid (10 microM), by the nitric oxide synthase inhibitors, N omega-nitro-L-arginine methyl ester (100 microM), or 7-nitroindazole (50 microM) and by the vesicular uptake inhibitor tetrabenazine (1 microM). Our results suggest that oxidative stress releases glutamate followed by activation of postsynaptic ionotropic glutamate receptors that trigger nitric oxide production and results in a flood of NA from cytoplasmic stores. The massive elevation of extracellular NA under conditions of oxidative stress combined with mitochondrial dysfunction may provide an additional source of highly reactive free radicals thus initiating a self-amplifying cycle leading to neuronal degeneration.     

Synaptic integration in rat frontal cortex shaped by network activity

Neocortical neurons in vivo are embedded in networks with intensive ongoing activity. How this network activity affects the neurons' integrative properties and what function this may imply at the network level remain largely unknown. Most of our knowledge regarding synaptic communication and integration is based on recordings in vitro, where network activity is strongly diminished or even absent. Here, we present results from two complementary series of experiments based on intracellular in vivo recordings in anesthetized rat frontal cortex. Specifically, we measured 1) the relationship between the excursions of a neuron's membrane potential and the spiking activity in the surrounding network and 2) how the summation of several inputs to a single neuron changes with the different levels of its membrane potential excursions and the associated states of network activity. The combination of these measurements enables us to assess how the level of network activity influences synaptic integration. We present direct evidence that integration of synaptic inputs in frontal cortex is linear, independent of the level of network activity. However, during periods of high network activity, the neurons' response to synaptic input is markedly reduced in both amplitude and duration. This results in a drastic shortening of its window for temporal integration, requiring more precise coordination of presynaptic spike discharges to reliably drive the neuron to spike under conditions of high network activity. We conclude that ongoing activity, as present in the active brain, emphasizes the need for neuronal cooperation at the network level, and cannot be ignored in the exploration of cortical function.     

The M2 selective antagonist AF-DX 116 shows high affinity for mnscarine receptors in bovine tracheal membranes

Summary We have characterized the muscarine receptors in bovine tracheal and left ventricular membranes using ³H-dexetimide/pirenzepine and ³H-dexetimide/AF-DX 116 competition studies. Pirenzepinc exhibited low (M₂) affinity binding to both preparations; K _d was 590 nM in left ventricle and 463 nM in trachea. AF-DX 116 exhibited high (M₂) affinity binding to left ventricle (K _d = 95.6 nM); in tracheal membranes it bound with high (M₂) affinity (K _d = 40.7 nM) to 74% of the receptors and with low (M₃) affinity (K _d = 2.26 M) to 26% of the receptors. It is concluded that bovine tracheal muscle membranes contain a heterogeneous population of muscarine binding sites, the majority having M₂ (heart) subtype characteristics and being located on the smooth muscle membranes; a minority having M₃ (exocrine gland) subtype characteristics and presumed to be located in submucosal glands. This is the first report of high affinity binding of AF-DX 116 to non-cardiac peripheral muscarine receptors. Send offprint requests to A. F. Roffel at the above address     

Characterization of the muscarinic receptor subtype(s) mediating contraction of the guinea-pig lung strip and inhibition of acetylcholine release in the guinea-pig trachea with the selective muscarinic receptor antagonist tripitramine

1. The muscarinic receptor subtypes mediating contraction of the guinea-pig lung strip and inhibition of the release of acetylcholine from cholinergic vagus nerve endings in the guinea-pig trachea in vitro have previously been characterized as M₂-like, i.e. having antagonist affinity profiles that are qualitatively similar but quantitatively dissimilar compared to cardiac M₂ receptors. The present study sought to establish definitely the identity of these receptor subtypes by using the selective muscarinic receptor antagonist, tripitramine. Guinea-pig atria and guinea-pig trachea (postjunctional contractile response) were included for reference.
2. It was found that tripitramine antagonized methacholine-induced contractions of the guinea-pig lung strip with a pK_B value of 8.76±0.05. Both the parallel shifts of the concentration-response curves and the slope of the Schild plot being not significantly different from unity (when antagonist preincubation was for 2 h) indicated the involvement of a single population of receptors in the contractile response. From the pK_B values obtained with tripitramine and a range of other selective muscarinic receptor antagonists (cf. Roffel et al., 1993), this single population of receptors can only be classified as M₂-like.
3. Tripitramine antagonized methacholine-induced negative chronotropic and inotropic responses in guinea-pig right and left atria with apparent pK_B values of 9.4–9.6. However, such values were only obtained when antagonist preincubation was relatively long and/or antagonist concentration relatively high (e.g. with 1 h at 100 or 300 nM but 3 h at 30 nM). It thus appears that low concentrations of tripitramine do not readily equilibrate with M₂ receptors in guinea-pig atria nor with M₂-like receptors in the guinea-pig lung strip.
4. Tripitramine increased electrical field stimulation-induced cholinergic twitch contractions in guinea-pig trachea in concentrations of 0.3–100 nM, by blocking prejunctional muscarinic inhibitory autoreceptors; with higher concentrations, twitch contractions were progressively diminished, as a result of blocking postjunctional M₃ receptors (apparent pK_B value 6.07±0.15). The pEC₂₀ value (−log concentration that increases twitch by 20% of maximum) was 8.29±0.08, which would suggest that M₄ receptors are involved in this response.
5. Oxotremorine-induced inhibition of the release of prelabelled [³H]-acetylcholine from guinea-pig trachea, under conditions where there is no auto-feedback, was blocked by tripitramine (2 h preincubation) with a pK_B value of 8.56±0.06. The slope of the corresponding Schild plot was not significantly different from unity, which together with the parallel shifts of the concentration-response curves indicated the involvement of a single muscarinic receptor subtype.
6. Since the pK_B value for tripitramine at prejunctional receptors in guinea-pig trachea is in between the affinities towards M₂ and M₄ receptors, correlation plots were constructed to compare the pK_B values obtained with tripitramine and a range of other selective muscarinic receptor antagonists (cf. Kilbinger et al., 1995) to reported affinities at M₁–M₄ receptors. This showed rather similar distribution patterns of the data points around the line of equality in the case of M₂ and M₄ receptor subtypes. However, the correlation coefficient was markedly better for M₂ (0.9667) than for M₄ (0.5976). Since recent evidence suggests that M₄ receptors are not expressed in cholinergic nerves from guinea-pig trachea, it is concluded that prejunctional muscarinic autoinhibitory receptors in this tissue exhibit an atypical M₂ type character, with a pharmacological profile distinct from cardiac M₂ receptors.

     

Severe micrognathia, cleft palate, absent olfactory tract, and abnormal rib development: cerebro-costo-mandibular syndrome or a new syndrome?

We report on a family in which two sibs had apparently absent ribs and severe micrognathia on prenatal ultrasonography. The pregnancies were terminated at 19 and 12 weeks of gestation, respectively. Autopsy findings in the first fetus (19 weeks of gestation) included severe micrognathia, a U-shaped defect of the soft palate, marked postnuchal edema, absent olfactory bulbs, and cribriform plate and rib abnormalities. The ribs consisted of cartilage anteriorly, with only a small amount of fibrous tissue present laterally and posteriorly. The second fetus (12 weeks gestation) had agnathia, with a large U-shaped defect in the soft palate. There was moderate postnuchal edema. The ribs were unossified and there were gaps in the cartilage where primitive mesenchyme was present posteriorly and laterally. These findings are consistent with a severe form of cerebro-costo-mandibular syndrome. The early fetal histopathology of both cases suggests a possible mechanism by which the characteristic "rib gaps" of cerebro-costo-mandibular syndrome may develop, with evidence for abnormal function of a gene or genes involved in regulation of rib chondrogenesis.