Monitoring the wild black bear's reaction to human and environmental stressors

<p>Abstract</p> <p>Background</p> <p>Bears are among the most physiologically remarkable mammals. They spend half their life in an active state and the other half in a state of dormancy without food or water, and without urinating, defecating, or physical activity, yet can rouse and defend themselves when disturbed. Although important data have been obtained in both captive and wild bears, long-term physiological monitoring of bears has not been possible until the recent advancement of implantable devices.</p> <p>Results</p> <p>Insertable cardiac monitors that were developed for use in human heart patients (Reveal® XT, Medtronic, Inc) were implanted in 15 hibernating bears. Data were recovered from 8, including 2 that were legally shot by hunters. Devices recorded low heart rates (pauses of over 14 seconds) and low respiration rates (1.5 breaths/min) during hibernation, dramatic respiratory sinus arrhythmias in the fall and winter months, and elevated heart rates in summer (up to 214 beats/min (bpm)) and during interactions with hunters (exceeding 250 bpm). The devices documented the first and last day of denning, a period of quiescence in two parturient females after birthing, and extraordinary variation in the amount of activity/day, ranging from 0 (winter) to 1084 minutes (summer). Data showed a transition toward greater nocturnal activity in the fall, preceding hibernation. The data-loggers also provided evidence of the physiological and behavioral responses of bears to our den visits to retrieve the data.</p> <p>Conclusions</p> <p>Annual variations in heart rate and activity have been documented for the first time in wild black bears. This technique has broad applications to wildlife management and physiological research, enabling the impact of environmental stressors from humans, changing seasons, climate change, social interactions and predation to be directly monitored over multiple years.</p

Effect of three anaesthetic techniques on isometric skeletal muscle strength

Background. Our aim was to quantify human involuntary isometric skeletal muscle strength during anaesthesia with propofol, sevoflurane, or spinal anaesthesia using bupivacaine. Methods. Thirty‐three healthy patients undergoing anaesthesia for elective lower limb surgery were investigated. Twenty‐two patients received a general anaesthetic with either propofol (n=12) or sevoflurane (n=10); for the remaining 11 patients spinal anaesthesia with bupivacaine was used. We used a non‐invasive muscle force assessment system before and during anaesthesia to determine the contractile properties of the ankle dorsiflexor muscles after peroneal nerve stimulation (single, double, triple, and quadruple stimulation). We measured peak torques; contraction times; peak rates of torque development and decay; times to peak torque development and decay; half‐relaxation times; torque latencies. Results. Males elicited greater peak torques than females, medians 6.3 vs 4.4 Nm, respectively (P=0.0002, Mann‐Whitney rank‐sum test). During sevoflurane and propofol anaesthesia, muscle strength did not differ from pre‐anaesthetic values. During spinal anaesthesia, torques were diminished for single‐pulse stimulation from 3.5 to 2.0 Nm (P=0.002, Wilcoxon signed rank test), and for double‐pulse from 7.6 to 5.6 Nm (P=0.02). Peak rates of torque development decreased for single‐pulse stimulation from 113 to 53 Nm s-1 and for double pulse from 195 to 105 Nm s-1. Torque latencies were increased during spinal anaesthesia. Conclusions. At clinically relevant concentrations, propofol and sevoflurane did not influence involuntary isometric skeletal muscle strength in adults, whereas spinal anaesthesia reduced strength by about 20%. Muscle strength assessment using a device such as described here provided reliable results and should be considered for use in other scientific investigations to identify potential effects of anaesthetic agents. Br J Anaesth 2004; 92: 367-7

Enhancement of K+ conductance improves in vitro the contraction force of skeletal muscle in hypokalemic periodic paralysis

An abnormal ratio between Na+ and K+ conductances seems to be the cause for the depolarization and paralysis of skeletal muscle in primary hypokalemic periodic paralysis. Recently we have shown that the k+ channel opener cromakalim hyperpolarizes mammalian skeletal muscle fibers. Now we have studied the effects of this drug on the twitch force of muscle biopsies from normal and diseased human skeletal muscle. Cromakalim had little effect on the twitch force of normal muscle whereas it strongly improved the contraction force of fibers from patients suffering from hypokalemic periodic paralysis. Recordings of intracellular K+ and Cl- activities in human muscle and isolated rat soleus muscle support the view that cromakalim enhances the membrane K+ conductance (gK+). These data indicate that K+ channel openers may have a beneficial effect in primary hypokalemic periodic paralysis

Left Ventricular Trabeculations Decrease the Wall Shear Stress and Increase the Intra-Ventricular Pressure Drop in CFD Simulations

The aim of the present study is to characterize the hemodynamics of left ventricular (LV) geometries to examine the impact of trabeculae and papillary muscles (PMs) on blood flow using high performance computing (HPC). Five pairs of detailed and smoothed LV endocardium models were reconstructed from high-resolution magnetic resonance images (MRI) of ex-vivo human hearts. The detailed model of one LV pair is characterized only by the PMs and few big trabeculae, to represent state of art level of endocardial detail. The other four detailed models obtained include instead endocardial structures measuring ≥1 mm2 in cross-sectional area. The geometrical characterizations were done using computational fluid dynamics (CFD) simulations with rigid walls and both constant and transient flow inputs on the detailed and smoothed models for comparison. These simulations do not represent a clinical or physiological scenario, but a characterization of the interaction of endocardial structures with blood flow. Steady flow simulations were employed to quantify the pressure drop between the inlet and the outlet of the LVs and the wall shear stress (WSS). Coherent structures were analyzed using the Q-criterion for both constant and transient flow inputs. Our results show that trabeculae and PMs increase the intra-ventricular pressure drop, reduce the WSS and disrupt the dominant single vortex, usually present in the smoothed-endocardium models, generating secondary small vortices. Given that obtaining high resolution anatomical detail is challenging in-vivo, we propose that the effect of trabeculations can be incorporated into smoothed ventricular geometries by adding a porous layer along the LV endocardial wall. Results show that a porous layer of a thickness of 1.2·10−2 m with a porosity of 20 kg/m2 on the smoothed-endocardium ventricle models approximates the pressure drops, vorticities and WSS observed in the detailed models.This paper has been partially funded by CompBioMed project, under H2020-EU.1.4.1.3 European Union’s Horizon 2020 research and innovation programme, grant agreement n◦ 675451. FS is supported by a grant from Severo Ochoa (n◦ SEV-2015-0493-16-4), Spain. CB is supported by a grant from the Fundació LaMarató de TV3 (n◦ 20154031), Spain. TI and PI are supported by the Institute of Engineering in Medicine, USA, and the Lillehei Heart Institute, USA.Peer ReviewedPostprint (published version

Long-Range a-Synchronization as Control Signal for BCI: A Feasibility Study

First published February 7, 2023Shifts in spatial attention are associated with variations in α band (α, 8–14 Hz) activity, specifically in interhemispheric imbalance. The underlying mechanism is attributed to local α-synchronization, which regulates local inhibition of neural excitability, and frontoparietal synchronization reflecting long-range communication. The direction-specific nature of this neural correlate brings forward its potential as a control signal in brain-computer interfaces (BCIs). In the present study, we explored whether long-range α-synchronization presents lateralized patterns dependent on voluntary attention orienting and whether these neural patterns can be picked up at a single-trial level to provide a control signal for active BCI. We collected electroencephalography (EEG) data from a cohort of healthy adults (n = 10) while performing a covert visuospatial attention (CVSA) task. The data show a lateralized pattern of α-band phase coupling between frontal and parieto-occipital regions after target presentation, replicating previous findings. This pattern, however, was not evident during the cue-to-target orienting interval, the ideal time window for BCI. Furthermore, decoding the direction of attention trial-by-trial from cue-locked synchronization with support vector machines (SVMs) was at chance level. The present findings suggest EEG may not be capable of detecting long-range α-synchronization in attentional orienting on a single-trial basis and, thus, highlight the limitations of this metric as a reliable signal for BCI control.This research was supported by the Agència de Gestió d’Ajuts Universitaris i de Recerca Generalitat de Catalunya Grant 2017 SGR 1545. This project has been co-funded with 50% by the European Regional Development Fund under the framework of the FEDER Operative Programme for Catalunya 2014-2020 Ministerio de Ciencia e Innovación (Ref: PID2019-108531GB-I00 AEI/FEDER)

Mitral leaflet anatomy revisited

ObjectiveThe aims of this work were to employ functional imaging capabilities of the Visible Heart laboratory and endoscopic visualization of mitral valves in perfusion-fixed specimens to better characterize variability in mitral valve leaflet anatomy and to provide a method to classify mitral leaflets that varies from the current nomenclature.MethodsWe gathered functional endoscopic video footage (11 isolated reanimated human hearts) and static endoscopic anatomical images (38 perfusion-fixed specimens) of mitral leaflets. Commissure and cleft locations were charted using Carpentier's accepted description.ResultsAll hearts had 2 commissures separating anterior and posterior leaflets. “Standard” clefts separating P1/P2 were found in 66% of hearts (n = 25), and standard clefts separating P2/P3 were present in 71% of hearts (n = 27). “Deviant” clefts occurred in each region of the anterior leaflet (A1, A2, A3), and their relative occurrences were 5%, 8%, and 13% (n = 2, 3, 5), respectively. Deviant clefts were found in posterior leaflets: 13.2% in P1 (n = 5), 32% in P2 (n = 12), and 21% in P3 (n = 8).ConclusionsHumans elicit complex and highly variable mitral valve anatomy. We suggest a complementary, yet simple nomenclature to address variation in mitral valve anatomy by describing clefts as either standard or deviant and locating regions in which they occur (A1 to A3 or P1 to P3)