Morphometrical features of left atrial appendage in the AF patients subjected to left atrial appendage closure

Background: This study aimed to evaluate the morphometrical features of left atrial appendage (LAA) in patients with atrial fibrillation, subjected to left atrial appendage percutaneous closure (LARIAT) for stroke prevention. Materials and methods: Computed tomography (CT) scans of 51 patients with atrial fibrillation subjected to LARIAT procedure were comparatively evaluated with 50 patients with sinus rhythm (control group). Three-dimensional (3D) reconstructions were created using volume-rendering for evaluation. Results: No differences were found in LAA types of distribution (cauliflower: 25.5 vs. 34.0%, chicken wing: 45.1 vs. 46.0%, windsock: 29.4 vs. 20.0%, all p>0.05) between groups. However, the study group was characterized by LAAs with a lower number of lobes. The LAA orifice anteroposterior and transverse diameters (19.3±4.12 vs. 17.2±4.0mm, p=0.01 and 25.1±5.1 vs. 20.5±4.4mm, p=0.001), orifice area (387.2±133.9 vs. 327.1±128.3mm2, p=0.02) and orifice perimeter (70.2±12.5 vs. 61.2±11.6mm, p=0.04) was significantly larger in atrial fibrillation patients. More oval LAA orifices was found in atrial fibrillation group (94.0 vs. 70.4%, p=0.001). No statistically significant differences were found in LAA body length (47.4±15.4 vs. 43.7±10.9mm, p=0.17), body width (24.7±5.6 vs. 24.4±5.8mm, p=0.81), and chamber depth (17.7±3.5 vs. 16.5±3.8mm, p=0.11). Calculated LAA ejection fraction was significantly lower in study group compared to healthy patients (16.4±14.9 vs. 48.2±12.9%, p=0.001). Conclusions: Important morphometrical differences in LAA orifice have been found, which was significantly larger and more oval in patients with atrial fibrillation compared to healthy controls. Although no difference in LAA body type and size was observed; the LAA ejection fraction was significantly lower in atrial fibrillation rhythm patients

Inactivation and tachyphylaxis of heat-evoked inward currents in nociceptive primary sensory neurones of rats

Membrane currents evoked by repeated noxious heat stimuli (43–47 °C) of 3 s duration were investigated in acutely dissociated dorsal root ganglion (DRG) neurones of adult rats. The heat stimuli generated by a fast solution exchanger had a rise time of 114 ± 6 ms and a fall time of 146 ± 13 ms.When heat stimuli were applied to heat-sensitive small (≤ 32·5 μm) DRG neurones, an inward membrane current (Iheat) with a mean peak of 2430 ± 550 pA was observed (n = 19). This current started to activate and deactivate with no significant latency with respect to the heat stimulus. The peak of Iheat was reached with a rise time of 625 ± 115 ms. When the heat stimulus was switched off Iheat deactivated with a fall time of 263 ± 17 ms.During constant heat stimulation Iheat decreased with time constants of 4–5 s (inactivation). At the end of a 3 s heat stimulus the peak current was reduced by 44 ± 5 % (n = 19).Current-voltage curves revealed outward rectifying properties of Iheat and a reversal potential of −6·3 ± 2·2 mV (n = 6). Inactivation was observed at all membrane potentials investigated (−80 to 60 mV); however, inactivation was more pronounced for inward currents (37 ± 5 %) than for outward currents (23 ± 6 %, P < 0·05).When neurones were investigated with repeated heat stimuli (3 to 5 times) of the same temperature, the peak current relative to the first Iheat declined by 48 ± 6 % at the 3rd stimulus (n = 19) and by 54 ± 18 % at the 5th stimulus (n = 4; tachyphylaxis).In the absence of extracellular Ca2+ (buffered with 10 mm EGTA) inactivation (by 53 ± 6 %) and tachyphylaxis (by 42 ± 7 % across three stimuli) were still observed (n = 8). The same was true when intracellular Ca2+ was buffered by 10 mm BAPTA (inactivation by 49 ± 4 %, tachyphylaxis by 52 ± 7 % across three stimuli; n = 13). Thus, inactivation and tachyphylaxis were mainly independent of intra- and extracellular Ca2+.These results indicate that inactivation and tachyphylaxis of heat-evoked inward currents can be observed in vitro, similar to adaptation and suppression of action potential discharges elicited by comparably fast heat stimuli in vivo. Whereas the voltage dependence of Iheat resembles that of capsaicin-induced membrane currents (ICaps), the independence of inactivation and tachyphylaxis of Iheat from calcium is in clear contrast to ICaps. A similar difference in calcium dependence of inactivation has been reported between heat-evoked and capsaicin-induced currents through the cloned capsaicin receptor channel VR1. Thus, the properties of Iheat and of VR1 largely account for the adaptation and suppression of heat-evoked nociceptor discharges

Effects of Speed-Dependent Treadmill training and Rhythmic Auditory-Cued Overground Walking on Gait and Balance Function and Fall Risk in Individuals with idiopathic Parkinson\u27s Disease: A Randomized Controlled Trial

PURPOSE: This single-blinded, randomized controlled study examined the immediate effects of interval-based and progressive speed-dependent treadmill training (SDTT) and rhythmic auditory-cued (RAC) overground training protocols on gait and balance function and fall risk in individuals with Parkinson’s Disease (PD). SUBJECTS: Twenty participants with idiopathic PD were randomly assigned into either SDTT (n=10) or RAC (n=10). METHODS AND MATERIALS: Training consisted of 30-minute sessions, 3x/week for 6 weeks. Dependent measures included comfortable and fast gait speed (CGS, FGS), Functional Gait Assessment (FGA), 6-Minute Walk Test (6MWT), Berg Balance Scale (BBS), Rapid Step-Up Test (RST), and NeuroCom Sensory Organization Test (SOT), Motor Control Test (MCT), and Limits of Stability (LOS). ANALYSES: Paired t-test and independent t-tests analyzed within and between group training effects. RESULTS: The within-group training effects revealed statistically significant gains in CGS (p = 0.013), 6MWT (p = 0.007) and FGA (p = 0.003) for the RAC group, and in FGS (p = 0.012), 6MWT (p = 0.027) and FGA (p =0.000) for the SDTT group. Within-group training effects revealed statistically significant improvements in BBS (p = 0.017), RST (p = 0.037) and SOT Composite score (p = 0.049) for the RAC group, and in RST (p = 0.045), LOS Composite- EPE (p =0.046), and SOT Composite score (p =0.019) for the SDTT group. No statistically significant differences in training effects were found between-groups. CONCLUSIONS: These results provide evidence that SDTT and RAC protocols produced significant short-term improvements in gait and balance function in a PD cohort of community ambulators

Capacitative Ca2+ entry is graded with degree of intracellular Ca2+ store depletion in bovine vascular endothelial cells

In endothelial cells, release of Ca2+ from endoplasmic reticulum (ER) Ca2+ stores activates Ca2+ influx via the capacitative Ca2+ entry (CCE) pathway. In cultured bovine pulmonary artery endothelial cells, we investigated the relationship between intracellular Ca2+ store load and CCE activity, as well as the kinetics of CCE activation and deactivation, by simultaneously measuring changes in [Ca2+]i and unidirectional manganese (Mn2+) entry through the CCE pathway.Submaximal concentrations of ATP caused quantal release of Ca2+ from the ER, resulting in a dose-dependent depletion of Ca2+ stores and acceleration of Mn2+ entry. Mn2+ entry rate, as a measure of CCE activity, was graded with the amount of released Ca2+. Maximal activation of CCE did not require complete store depletion.Slow depletion of the ER by exposure to the ER Ca2+ pump inhibitor cyclopiazonic acid resulted in a delayed activation of CCE, revealing a temporal dissociation between release of Ca2+ from intracellular stores and activation of CCE.During [Ca2+]i oscillations, at frequencies higher than 0·5 spikes min−1, each Ca2+ spike resulted in a progressive acceleration of CCE without leading to oscillations of Ca2+ entry. In contrast, low frequency [Ca2+]i oscillations were paralleled by transient CCE that was activated and deactivated with each Ca2+ spike, resulting in an oscillatory pattern of Ca2+ entry.It is concluded that CCE is a rapidly activating process which is graded with store depletion and becomes fully activated before complete depletion. The duration of CCE activation correlates with the degree of store depletion and the time that is required to refill depleted stores. Overall, a mechanism of graded CCE prevents exhaustion of intracellular Ca2+ reserves and provides an efficient way to respond to variable degrees of intracellular store depletion

Hydrocracking of Maya Vacuum Residue with NiMo Catalysts Supported on Mesoporous Alumina and Silica–Alumina

Hydrocracking of heavy oils poses greater challenges than that of lighter feeds in terms of catalyst properties and resistance to deactivation. The development of larger pore size catalysts may be beneficial to improve their effectiveness toward cracking the larger molecules present in these feedstocks. Mesoporous alumina and mesoporous silica–alumina (MSA) with different textural properties were used as supports to prepare NiMo-based catalysts. These catalysts were tested in the hydrocracking of a vacuum residue (VR) from Maya crude oil and compared against a commercial Al₂O₃ catalyst. The conversion of VR and asphaltenes into lighter hydrocarbons obtained with supports and catalysts was determined, and the coke deposition process was studied. The in-house developed catalysts were utilized for two consecutive runs with fresh feed to evaluate coke deposition during reutilization of the materials. It was found that coke deposition occurred mainly in the first run, with carbonaceous deposits stabilizing for all the catalysts during their reutilization. Reaction temperature had an important impact on conversions and product distributions, with higher reaction temperatures accounting for higher VR and asphaltene conversions at the expense of a large increase in gas yields. Although the NiMo/Al₂O₃ catalyst achieved similar VR conversion to the other catalysts, it displayed higher asphaltene conversion with lower coke deposition and a reduced gas yield. The effectiveness of this catalyst can be attributed to its larger pores that can allow better diffusion of asphaltene molecules than MSA or NiMo/MSA as well as the commercial catalyst