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Selected AbstractsSpectro-temporal sound density-dependent long-term adaptation in cat primary auditory cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2008Boris Gourévitch Abstract Sensory systems use adaptive strategies to code for the changing environment on different time scales. Short-term adaptation (up to 100 ms) reflects mostly synaptic suppression mechanisms after response to a stimulus. Long-term adaptation (up to a few seconds) is reflected in the habituation of neuronal responses to constant stimuli. Very long-term adaptation (several weeks) can lead to plastic changes in the cortex, most often facilitated during early development, by stimulus relevance or by behavioral states such as attention. In this study, we show that long-term adaptation with a time course of tens of minutes is detectable in anesthetized adult cat auditory cortex after a few minutes of listening to random-frequency tone pips. After the initial post-onset suppression, a slow recovery of the neuronal response strength to tones at or near their best frequency was observed for low-rate random sounds (four pips per octave per second) during stimulation. The firing rate at the end of stimulation (15 min) reached levels close to that observed during the initial onset response. The effect, visible for both spikes and, to a smaller extent, local field potentials, decreased with increasing spectro-temporal density of the sound. The spectro-temporal density of sound may therefore be of particular relevance in cortical processing. Our findings suggest that low stimulus rates may produce a specific acoustic environment that shapes the primary auditory cortex through very different processing than for spectro-temporally more dense and complex sounds. [source] Upregulation of [3H]methyllycaconitine binding sites following continuous infusion of nicotine, without changes of ,7 or ,6 subunit mRNA: an autoradiography and in situ hybridization study in rat brainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2002Manolo Mugnaini Abstract It is well established that exposure of experimental animals to nicotine results in upregulation of the ,4,2-subtype of neuronal nicotinic acetylcholine receptors (nAChRs). The aim of this study was to determine the effect of nicotine on the levels of ,7-nAChRs in rat brain, for which only partial information is available. Rats were infused with nicotine (3 mg/kg/day) or saline for 2 weeks and their brains processed for receptor autoradiography with [3H]methyllycaconitine (MLA), a radioligand with nanomolar affinity for ,7-nAChRs. In control rats binding was high in hippocampus, intermediate in cerebral cortex and hypothalamus, and low in striatum, thalamus and cerebellum. There was high correlation between the distribution of [3H]MLA binding sites and ,7 subunit mRNA (r = 0.816). With respect to saline-treated controls, nicotine-treated rats presented higher [3H]nicotine binding in 11 out of 15 brain regions analysed (average increase 46 ± 6%). In contrast, only four regions showed greater [3H]MLA binding, among which the ventral tegmental area (VTA) and cingulate cortex (mean increase 32 ± 3%). No changes in ,7 mRNA levels were observed after nicotine treatment. Similarly, there was no variation of ,6 subunit transcript in the VTA, a region which may contain MLA-sensitive (non-,7)-,6*-nAChRs (Klink et al., 2001). In conclusion, nicotine increased [3H]MLA binding, although to a smaller extent and in a more restricted regional pattern than [3H]nicotine. The enhancement of binding was not paralleled by a significant change of ,7 and ,6 subunit transcription. Finally, the present results provide the first anatomical description of the distribution of [3H]MLA binding sites in rat brain. [source] FROM MICRO- TO MACROEVOLUTION THROUGH QUANTITATIVE GENETIC VARIATION: POSITIVE EVIDENCE FROM FIELD CRICKETSEVOLUTION, Issue 10 2004Mattieu Bégin Abstract . -Quantitative genetics has been introduced to evolutionary biologists with the suggestion that microevolution could be directly linked to macroevolutionary patterns using, among other parameters, the additive genetic variance/ covariance matrix (G) which is a statistical representation of genetic constraints to evolution. However, little is known concerning the rate and pattern of evolution of G in nature, and it is uncertain whether the constraining effect of G is important over evolutionary time scales. To address these issues, seven species of field crickets from the genera Gryllus and Teleogryllus were reared in the laboratory, and quantitative genetic parameters for morphological traits were estimated from each of them using a nested full-sibling family design. We used three statistical approaches (T method, Flury hierarchy, and Mantel test) to compare G matrices or genetic correlation matrices in a phylogenetic framework. Results showed that G matrices were generally similar across species, with occasional differences between some species. We suggest that G has evolved at a low rate, a conclusion strengthened by the consideration that part of the observed across-species variation in G can be explained by the effect of a genotype by environment interaction. The observed pattern of G matrix variation between species could not be predicted by either morphological trait values or phylogeny. The constraint hypothesis was tested by comparing the multivariate orientation of the reconstructed ancestral G matrix to the orientation of the across-species divergence matrix (D matrix, based on mean trait values). The D matrix mainly revealed divergence in size and, to a much smaller extent, in a shape component related to the ovipositor length. This pattern of species divergence was found to be predictable from the ancestral G matrix in agreement with the expectation of the constraint hypothesis. Overall, these results suggest that the G matrix seems to have an influence on species divergence, and that macroevolution can be predicted, at least qualitatively, from quantitative genetic theory. Alternative explanations are discussed. [source] Effect of Clostridium perfringens epsilon toxin on MDCK cellsFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2001Erika Borrmann Abstract Epsilon toxin is one of the major lethal toxins produced by Clostridium perfringens type D and B. It is responsible for a rapidly fatal disease in sheep and other farm animals. Many facts have been published about the physical properties and the biological activities of the toxin, but the molecular mechanism of the action inside the cells remains unclear. We have found that the C. perfringens epsilon toxin caused a significant decrease of the cell numbers and a significant enlargement of the mean cell volume of MDCK cells. The flow cytometric analysis of DNA content revealed the elongation of the S phase and to a smaller extent of the G2+M phase of toxin-treated MDCK cells in comparison to untreated MDCK cells. The results of ultrastructural studies showed that the mitosis is disturbed and blocked at a very early stage, and confirmed the toxin influence on the cell cycle of MDCK cells. [source] Distribution of minke whales in the Bellingshausen and Amundsen Seas (60°W,120°W), with special reference to environmental/physiographic variablesFISHERIES OCEANOGRAPHY, Issue 3 2000Fujio Kasamatsu The relationship between the distribution of minke whales (Balaenoptera acutorostrata) in the Bellingshausen and Amundsen Seas (longitude between 60°W and 120°W), and environmental and physiographic variables (sea-surface temperature, sea-ice extension, and sea-floor-slope type), was studied to determine whether these environmental and physical factors affect the distribution and density of minke whales. The analysis was based on sightings data obtained from the 1989/90 and 1982/83 IWC/IDCR cruises. The mean sea-surface temperatures for comparable areas were significantly higher in 1989/90 (2.04°C) than in 1982/83 (1.12°C), and the area where the sea-surface temperature was greater than 1°C in the 1989/90 study was approximately twice that of the 1982/83 study. Additionally, during the surveys, the extent of the sea ice in 1989/90 was less than that in 1982/83, with the mean ice edge about 92.6 km (50 nautical miles; 1 nautical mile ,1.852 km) farther south in 1989/90 than in 1982/83. This is consistent with the sea ice extent observed in winter, when the sea ice extent was less in 1989 than in 1982. The distribution of minke whales was substantially different between the two surveys, with the density and abundance of minke whales being greater in 1982/83 than in 1989/90. The warmer sea-surface temperatures, fewer cold-water intrusions, and the smaller extent of sea ice in 1989/90 may be related to the difference in distribution of minke whales from 1982/83, possibly owing to the shift in availability of prey. [source] Effects of Saccharide Set Retarders on the Hydration of Ordinary Portland Cement and Pure Tricalcium SilicateJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Linghong Zhang The effects of aliphatic sugar alcohols (e.g., threitol, xylitol, sorbitol) on the hydration of tricalcium silicate (C3S) and ordinary portland cement (OPC) were investigated and compared with those of sucrose, a well-established cement set retarder. Only sugar alcohols which contain threo diol functionality retarded the setting of C3S and OPC, their efficacy increasing with the number of threo hydroxy pairs and, to a smaller extent, with the overall population of hydroxy groups. None, however, were as effective as sucrose. The initial and final setting times increased exponentially with the concentration of saccharide, although the hydration of OPC was less inhibited than that of C3S. Saccharides function as "delayed accelerators," that is, cement hydration is first inhibited and then proceeds faster than in saccharide-free cement. This behavior is consistent with the theory that the induction period is controlled by slow formation and/or poisoning of the stable calcium silicate hydrate (CSH) nuclei. The early inhibiting influence of saccharides on CSH precipitation is apparently stronger than on the growth of crystalline calcium hydroxide. Saccharides did not negatively affect the degree of hydration and compressive strength of fully set OPC paste; on the contrary, sorbitol yielded modest increases. [source] State of the art in restless legs syndrome therapy: Practice recommendations for treating restless legs syndromeMOVEMENT DISORDERS, Issue S18 2007Wolfgang H. Oertel MD Abstract Dopaminergic agents are the best-studied agents and are considered first-line treatment of restless legs syndrome (RLS). Extensive data are available for levodopa, pramipexole, and ropinirole, which have approval for the indication RLS, and to a smaller extent for cabergoline, pergolide, and rotigotine. Apart from one recent study, comparing two active drugs (levodopa and cabergoline), no comparative studies have been published. The individual treatment regimen with the most appropriate agent concerning efficacy and side effects has to be selected by the treating physician. On the basis of these clinical trials and expert opinion of the authors, a treatment algorithm is proposed to support the search for the optimal individual treatment. Opioids and anticonvulsants such as gabapentine are second-line options in individual patients. Iron substitution is justified in people with iron deficiency related RLS (ferritin concentration lower than 50 ,g/L). © 2007 Movement Disorder Society [source] Na+ -H+ exchanger 3 (NHE3) is present in lipid rafts in the rabbit ileal brush border: a role for rafts in trafficking and rapid stimulation of NHE3THE JOURNAL OF PHYSIOLOGY, Issue 2 2001Xuhang Li 1Rabbit ileal Na+ -absorbing cell Na+ -H+ exchanger 3 (NHE3) was shown to exist in three pools in the brush border (BB), including a population in lipid rafts. Approximately 50 % of BB NHE3 was associated with Triton X-100-soluble fractions and the other ,50 % with Triton X-100-insoluble fractions; ,33 % of the detergent-insoluble NHE3 was present in cholesterol-enriched lipid microdomains (rafts). 2The raft pool of NHE3 was involved in the stimulation of BB NHE3 activity with epidermal growth factor (EGF). Both EGF and clonidine treatments were associated with a rapid increase in the total amount of BB NHE3. This EGF- and clonidine-induced increase of BB NHE3 was associated with an increase in the raft pool of NHE3 and to a smaller extent with an increase in the total detergent-insoluble fraction, but there was no change in the detergent-soluble pool. In agreement with the rapid increase in the amount of NHE3 in the BB, EGF also caused a rapid stimulation of BB Na+ -H+ exchange activity. 3Disrupting rafts by removal of cholesterol with methyl-,-cyclodextrin (M,CD) or destabilizing the actin cytoskeleton with cytochalasin D decreased the amount of NHE3 in early endosomes isolated by OptiPrep gradient fractionation. Specifically, NHE3 was shown to associate with endosomal vesicles immunoisolated by anti-EEA1 (early endosomal autoantigen 1) antibody-coated magnetic beads and the endosome-associated NHE3 was decreased by cytochalasin D and M,CD treatment. 4We conclude that: (i) a pool of ileal BB NHE3 exists in lipid rafts; (ii) EGF and clonidine increase the amount of BB NHE3; (iii) lipid rafts and to a lesser extent, the cytoskeleton, but not the detergent-soluble NHE3 pool, are involved in the EGF- and clonidine-induced acute increase in amount of BB NHE3; (iv) lipid rafts and the actin cytoskeleton play important roles in the basal endocytosis of BB NHE3. [source] Aerodynamics of the Human Larynx During Vocal Fold Vibration,THE LARYNGOSCOPE, Issue 12 2005Randall L. Plant MD Abstract Objectives: The goal of this study was to comprehensively analyze the influence of aerodynamics on laryngeal function. Three specific aspects were considered: 1) a multidimensional comparison of the interaction of subglottic pressure, sound intensity, and fundamental frequency; 2) examination of instantaneous changes in subglottic pressure during each glottic cycle; and 3) determination of the threshold subglottic pressure for vocal fold vibration and its dependence on other aerodynamic factors. Study Design: Prospective study with six healthy individuals without history of voice disorders. Methods: The subjects vocalized the vowel sound /i/ with a variety of different intensities, pitch, and sound intensity. Subglottic air pressure, fundamental frequency, sound intensity, and the electroglottography signal were simultaneously measured. Results: Linear relationships were seen in all subjects between subglottic air pressure and sound intensity, although there were large variations in the slopes of these relationships. Rapid variations in subglottic pressure during each glottic cycle were detected, corresponding to the opening of the vocal folds with each individual vibration. Threshold pressures for vocal fold vibration were dependent primarily on sound intensity and fundamental frequency and tended to be higher at vibration onset than at offset. Conclusion: The larynx responded in a predictable pattern to general aerodynamic forces, but there was tremendous variability in its specific behavior. Fundamental frequency and sound intensity tended to increase with subglottic air pressure, but that relationship was not seen consistently in all subjects. The relationship between subglottic air pressure and sound intensity was usually linear, unlike the exponential relationship seen in previous studies. Subglottic pressure was noted to undergo rapid change with each glottic cycle in some, but not all, subjects and was most strongly affected by average subglottic pressure. Phonation threshold air pressure was influenced by the sound intensity and, to a smaller extent, by the fundamental frequency of the voiced sound. [source] Daclizumab, an efficient treatment for steroid-refractory acute graft- versus -host diseaseBRITISH JOURNAL OF HAEMATOLOGY, Issue 3 2006Pierre Bordigoni Summary In a phase II study, daclizumab was given as single second-line agent to 62 patients with steroid-refractory acute graft- versus -host disease (aGVHD). Complete resolution of aGVHD was achieved in 68·8% of patients. This response rate was significantly associated with a lower number of involved organs and smaller extent of skin involvement. The 4-year event-free survival (EFS) was 54·6%. Grade ,III aGVHD, ,2 involved organs at baseline and patient age >18 years were independently associated with lower EFS. Daclizumab could be a suitable alternative treatment for aGVHD, particularly when limited to the skin or gastrointestinal tract. [source] | |||||||||||||