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Heat Rate (heat + rate)
Selected AbstractsCardiac basal metabolism: energetic cost of calcium withdrawal in the adult rat heartACTA PHYSIOLOGICA, Issue 3 2010P. Bonazzola Abstract Aim:, Cardiac basal metabolism upon extracellular calcium removal and its relationship with intracellular sodium and calcium homeostasis was evaluated. Methods:, A mechano-calorimetric technique was used that allowed the simultaneous and continuous measurement of both heat rate and resting pressure in arterially perfused quiescent adult rat hearts. Using pharmacological tools, the possible underlying mechanisms related to sodium and calcium movements were investigated. Results:, Resting heat rate (expressed in mW g,1dry wt) increased upon calcium withdrawal (+4.4 ± 0.2). This response was: (1) unaffected by the presence of tetrodotoxin (+4.3 ± 0.6), (2) fully blocked by both, the decrease in extracellular sodium concentration and the increase in extracellular magnesium concentration, (3) partially blocked by the presence of either nifedipine (+2.8 ± 0.4), KB-R7943 (KBR; +2.5 ± 0.2), clonazepam (CLO; +3.1 ± 0.3) or EGTA (+1.9 ± 0.3). The steady heat rate under Ca2+ -free conditions was partially reduced by the addition of Ru360 (,1.1 ± 0.2) but not CLO in the presence of EGTA, KBR or Ru360. Conclusion:, Energy expenditure for resting state maintenance upon calcium withdrawal depends on the intracellular rise in both sodium and calcium. Our data are consistent with a mitochondrial Ca2+ cycling, not detectable under normal calcium diastolic levels. The experimental condition here analysed, partially simulates findings reported under certain pathological situations including heart failure in which mildly increased levels of both diastolic sodium and calcium have also been found. Therefore, under such pathological conditions, hearts should distract chemical energy to fuel processes associated with sodium and calcium handling, making more expensive the maintenance of their functions. [source] Accelerator adsorption onto carbon nanotubes surface affects the vulcanization process of styrene,butadiene rubber compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009A. De Falco Abstract The multiwalled carbon nanotubes (MWCNT) filled styrene,butadiene rubber (SBR) composites were prepared by incorporating MWCNT in a SBR/toluene solution and subsequently evaporating the solvent. These composites have shown a significant improvement in Young's modulus and tensile strength with respect to SBR gum without sacrificing high elongation at break. However, this improvement is less than expected at the higher filler content. Then, the influence of low concentrations of MWCNT on the vulcanization process of the SBR composites was studied by means of rheometer torque curves, swelling measurements, differential scanning calorimeter (DSC) analysis, and Fourier transform infrared (FTIR) spectroscopy. Also, their thermal degradation was studied by thermogravimetric analysis (TGA). It has been noticed that MWCNT affects the cure kinetics of SBR gum matrix reducing all parameters, i.e., the total heat rate and order of the reaction, scorch delay, maximum torque, and crosslink density. This effect increases as MWCNT content does, and it was attributed to the adsorption of the accelerator employed in the vulcanization (N -tert-butyl-benzothiazole-2-sulfenamide) onto the MWCNT surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Increased arterial pressure is not predictive of haemodynamic instability in patients undergoing adrenalectomy for phaeochromocytomaACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2009C. LENTSCHENER Background: Pre-operative hypotensive drugs are assumed to have dramatically decreased operative mortality and morbidity in patients undergoing phaeochromocytoma removal only in non-controlled studies. We evaluated the predictive value of pre-operative high systolic arterial pressure (SAP) on intra- and post-operative haemodynamic instability, in 96 patients undergoing laparoscopic adrenalectomy for phaeochromocytoma. Methods: Ninety-six consecutive patients underwent laparoscopic adrenalectomy for phaeochromocytoma. Pre-operative SAP was not systematically normalised, provided that increased SAP was clinically tolerated. Intravenous nicardipine, esmolol and norepinephrine were intraoperatively titrated to treat SAP increase >150 mmHg, tachycardia >90,110/min, arrhythmia or SAP decrease under 90 mmHg, respectively. Volume expanders were not systematically administered. Patients with increased and normal pre-operative SAP were compared with respect to (a) nicardipine, esmolol and norepinephrine requirement, (b) highest intraoperative SAP and heat rate, (c) lowest intraoperative SAP, (d) duration of surgery and (e) norepinephrine requirement following tumour removal. Results: Groups did not differ significantly with respect to data defined as being indicative of perioperative haemodynamic instability (all P values>0.05). Discussion: As previously demonstrated, in patients undergoing phaeochromocytoma removal, perioperative haemodynamic changes are mainly due to catecholamine release during tumour manipulation, and to the decrease in catecholamine level following tumour removal. Whether pre-operative hypotensive drugs are likely to alter these changes remains questionable. Conclusion: For most patients scheduled for laparoscopic phaeochromocytoma removal, surgery can be carried out without systematic pre-operative arterial pressure normalisation. [source] Uptake and diverse effects of polycyclic aromatic hydrocarbons on the metabolic activity of Elliptio complanata measured by calorespirometryENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2001Marcos A. Cheney Abstract Polycyclic aromatic hydrocarbons (PAHs) are important contaminants of world water resources, with effects on aquatic life. Metabolic responses to short-term acute toxicities of naphthalene, anthracene, and chrysene were investigated in the freshwater bivalve mollusk Elliptio complanata using differential scanning calorespirometry coupled with uptake and scanning electron microscopy. Comparing the uptakes of naphthalene, anthracene, and chrysene with that of inulin, which is known to occupy only extracellular space, showed that all compounds studied were taken up. The PAHs studied had diverse effects on the metabolic activity of E. complanata. Naphthalene and, to a lesser degree, chrysene caused stimulation of heat rates, possibly due to uncoupling of oxidative metabolism. Differential scanning calorespirometry coupled with studies of rates of oxygen consumption by the gill tissue exposed to the PAHs showed similar diverse patterns of respiratory rate stimulation and inhibition. Analysis of results of scanning electron microscopy suggested that irreversible damage to the gill tissue occurred in the presence of anthracene but not in the presence on naphthalene or chrysene. The batch calorespirometric method coupled with uptake and spectroscopy proved to be a useful technique to assess the toxicity of PAHs on the control of energy flux in gills of a freshwater bivalve mollusk. [source] | ||||||||||