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Slow Recovery (slow + recovery)
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] Quantitative evaluation of strategies for erosion control on a railway embankment batterHYDROLOGICAL PROCESSES, Issue 17 2001Y. Gyasi-Agyei Abstract Strategies for erosion control on a railway embankment batter (side slope) are quantitatively evaluated in this paper. The strategies were centred on control (,do nothing' treatment), grass seeding, gypsum application, jute mat (an erosion control blanket) placement and planting hedgerows of Monto vetiver grass. Rainfall and runoff were monitored at 1 min intervals on 10 m wide embankment batter plots during 1998 and 1999. Total bedload and suspended sediment eroded from the plots were also measured but only for a group of storm events within sampling intervals. It has been demonstrated that vetiver grass is not cost-effective in controlling erosion on railway batters within Central Queensland region. Seeding alone could cause 60% reduction in the erosion rate compared with the control treatment. Applying gypsum to the calcium-deficient soil before seeding yielded an additional 25% reduction in the erosion rate. This is the result, primarily, of 100% grass cover establishment within seven months of sowing. Therefore, for railway embankment batter erosion control, the emphasis needs to be on rapid establishment of 100% grass cover. For rapid establishment of grass cover, irrigation is necessary during the initial stages of growth as the rainfall is unpredictable and the potential evaporation exceeds rainfall in the study region. The risk of seeds and fertilizers being washed out by short-duration and high-intensity rainfall events during the establishment phase may be reduced by the use of erosion control blankets on sections of the batters. Accidental burning of grasses on some plots caused serious erosion problems, resulting in very slow recovery of grass growth. It is therefore recommended that controlled burning of grasses on railway batters should be avoided to protect batters from being exposed to severe erosion. Copyright © 2001 John Wiley & Sons, Ltd. [source] An audit designed to assess the need for planned pretreatment PEG placement in patients with stage III & stage IV oral cancerJOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 6 2004F.R. Dawson Background:, Nutritional support is a crucial and challenging part of treatment for patients with oral cancer. The aim of this audit was to assess the need for planned pretreatment percutaneous endoscopic gastrostomy (PEG) placement in this group of patients and to assess diet consistency as a predictor of poor outcomes. Method:, This was a retrospective study of 77 consecutive patients with stage III and IV squamous cell carcinoma of the oral cavity treated by radical surgery and post-operative radiotherapy between January 1999 and December 2001. Information was taken from dietitians' records. Patients were divided into two groups according to survival: group 1 (40 patients) comprised nonsurvivors and group 2 (37 patients), survivors. All patients were enterally fed post-operatively. After approximately 10 days, swallowing was assessed and, if deemed competent, patients progressed to a fluid diet. Tube feeding was gradually reduced and then stopped when oral nutrition was sufficient to maintain weight. Patients progressed to soft diet as they were able. During radiotherapy, liquid diet or tube feeding was instigated as required. Results:, In group 1, 65% required tube feeding for less than 30 days (mean 17 days), 20% for 31,100 days (mean 51 days) and 15% for over 100 days (mean 231 days). The overall mean length of tube feeding was 97 days. Thirty-eight per cent of nonsurvivors developed recurrence and went on to subsequent operations necessitating further tube feeding for an average of 129 days. In group 2, 70% were tube fed for less than 30 days (mean 11 days), 14% for between 31,100 days (mean 43 days), and 17% for more than 100 days. The overall mean length of tube feeding was 72 days. The dietary consistency of nonsurvivors was worse than survivors throughout treatment. At first presentation, only 37% of nonsurvivors managed a normal diet, 8% managed a near normal diet and 3% required tube feeding, whereas 48% of survivors managed a normal diet and 16% a near normal diet. At 1 year, there was a significant difference between the two groups' diets. No patients in group 1 managed a normal or near normal diet, whilst 62% required tube feeding. In group 2, 12 and 32% managed a normal and near normal diet, respectively and only 9% required or wished to remain on tube feeding to supplement their diet. Five per cent of patients in this group remained nil by mouth due to fistula. Conclusion:, Deciding whether a patient has a naso-gastric tube, PEG or radiologically inserted gastrostomy tube placed can be a difficult decision. However, a gastrostomy should be considered prior to treatment in patients whose diet is of poor consistency at presentation or who have an inadequate oral intake to maintain or increase weight and in those with a fistula, expected slow recovery of swallowing function, for example, pharyngeal tumour or undergoing brachytherapy or chemoradiotherapy. [source] Bird responses to fire severity and time since fire in managed mountain rangelandsANIMAL CONSERVATION, Issue 3 2010P. Pons Abstract Broom matorrals are subjected to extensive burning in the Pyrenees to improve grazing value, despite being a habitat of conservation interest in Europe. Our aim here is to evaluate the impact of such management practices over the long term, and of fire severity over the short term, on avifauna. Bird-habitat stations were distributed in broom shrublands from a few months to 51 years after fire, at 1400,2100 m a.s.l. Overall, shrub cover was the main habitat variable affecting the bird community composition. The abundance trends of bird species for half a century after fire were varied, but population recovery seemed slower (especially in the Dartford warbler Sylvia undata) than it had been reported at a lower altitude. Three species of European conservation concern (Alauda arvensis, Lullula arborea and Lanius collurio) showed abundance peaks at 10,19 years after fire. This time interval showed the highest species richness, abundance and conservation value, whereas shrub cover continued to increase afterwards. The bird assemblage tended to impoverish with increasing fire severity in the first year after a fire. Our results emphasize: (1) the slow recovery of bird community of burnt mountain shrublands; (2) the need for long-term biodiversity assessments to help improve planning of fire intervals at different altitudes; (3) the relevance of reducing fire severity due to its impact on fauna. [source] Sodium channel inactivation defects are associated with acetazolamide-exacerbated hypokalemic periodic paralysisANNALS OF NEUROLOGY, Issue 3 2001Saïd Bendahhou PhD A novel mutation in a family with hypokalemic periodic paralysis is described. The mutation R672S is located in the voltage sensor segment S4 of domain II in the SCN4A gene encoding the human skeletal muscle voltage-gated sodium channel. Functional expression of the R672S channels in human embryonic kidney 293 cells revealed a small but significant hyperpolarizing shift in the steady-state fast inactivation, and a dramatic enhancement in channel slow inactivation. These two defects are mainly due to a slow recovery of the mutant channels from fast and/or slow inactivation. Our data may help explain the mechanism underlying hypokalemic periodic paralysis and the patient's worsening from acetazolamide. [source] Biological and technical evaluation of the potential of marine and anadromous fish species for cold-water maricultureAQUACULTURE RESEARCH, Issue 2 2002N R Le François Abstract Concern about the overexploitation of wild aquatic resources, the slow recovery of the groundfish fisheries and the need to encourage the diversification of the mariculture industry of the province of Quebec (Canada) all provided strong incentive to explore the potential of a wide selection of marine and anadromous fish species for cold-water mariculture. Starting from a list of over 45 indigenous fish species of potential commercial interest, a biotechnical review was initiated. Technical sheets for each species were produced and aquaculture-based selection criteria covering three aquaculture approaches of development (complete life cycle, on-growing and stock enhancement) were examined. Species were ranked according to their degree of suitability for the given biological parameters. The final classification analysis within the complete life cycle production strategy positioned the Atlantic wolffish as the top candidate species (91%) followed by the spotted wolffish and Arctic charr (87%). Growth rate, optimal growth temperature, duration of the weaning period, minimal lethal temperature, larval size and feed requirements were the determining criteria. The on-growing scenario final results ranked Arctic charr first (84%) followed by Atlantic cod (79%) and Atlantic halibut (74%) mostly owing to their growth rate at low temperature and optimal growth temperature criteria. Stock enhancement programmes should concentrate their efforts on the striped bass (56%), the haddock (54%) and the Atlantic sturgeon (34%) based on their growth rate, fishery status, landing price and the availability of impact studies. [source] Haemodynamic action of B-type natriuretic peptide substantially outlasts its plasma half-life in conscious dogsCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 5-6 2003Colleen J Thomas Summary 1.,The objective of the present study was to determine the plasma half-life of B-type natriuretic peptide (BNP) in conscious dogs after intravenous administration and to compare this with its haemodynamic effects. In six chronically instrumented dogs, plasma BNP concentrations were measured under basal conditions, during a constant infusion of canine BNP-32 (10 pmol/kg per min; 25 min) to steady state and at nominated time points up to 75 min after stopping the infusion. Concomitant, continuous measurements of mean arterial blood pressure (MAP), heart rate (HR), central venous pressure (CVP) and mesenteric blood flow (MBF) were obtained. 2.,Baseline plasma BNP levels were 15.0 ± 2.3 fmol/mL and rose approximately 10-fold to 159 ± 23 fmol/mL after 20,25 min BNP infusion. When the infusion was turned off, plasma BNP levels declined in a biphasic manner, with an initial half-life of 1.57 ± 0.14 min and a terminal half-life of 301 ± 85 min. The metabolic clearance rate of BNP was 2.29 ± 0.34 L/min. 3.,The infusion of BNP reduced MAP (approximately 10%), CVP (approximately 65%) and MBF (approximately 25%), whereas haematocrit (approximately 4%) and mesenteric vascular resistance (MVR) increased (approximately 40%; all P < 0.05). Plasma BNP levels returned to baseline by 20 min after BNP infusion had been stopped, whereas none of the haemodynamic variables returned to normal by this time. Mean arterial pressure returned to resting levels within 10,15 min after plasma BNP returned to normal. However, CVP, haematocrit and MBF remained substantially below baseline values for more than 20 min after circulating BNP levels had returned to pre-infusion levels. Of these, only mesenteric vascular changes were returned to baseline within 60 min of plasma BNP levels normalizing. 4.,These results demonstrate that the removal of BNP from the canine circulation is rapid, similar to observations made regarding the metabolism of circulating atrial natriuretic peptide in dogs. The half-life of BNP in dogs was shorter than that in rats, sheep or humans. However, the haemodynamic actions of BNP substantially outlasted its plasma half-life. Whether this disparity in plasma level and haemodynamic activity of BNP reflects long-lasting activation of second messenger systems or slow recovery from the hydraulic changes at the capillary level, reflected in the haematocrit and CVP, remains to be answered. [source] | |||||||||||||