Resurgent sodium current promotes action potential firing in the avian auditory brainstem

Abstract

Auditory brainstem neurons are functionally primed to fire action potentials (APs) at markedly high-rates in order to rapidly encode acoustic information of sound. This specialization is critical for survival and the comprehension of behaviourally relevant communication functions, including sound localization and understanding speech in noise. Here, we investigated underlying ion channel mechanisms essential for high-rate AP firing in neurons of the chicken nucleus magnocellularis (NM) – the avian analog of bushy cells of the mammalian anteroventral cochlear nucleus. In addition to the established function of high-voltage activated potassium channels, we found that resurgent sodium current (I_NaR) plays a role in regulating rapid firing activity of late-developing (embryonic [E] days 19–21) NM neurons. I_NaR of late-developing NM neurons showed similar properties with mammalian neurons in that its unique mechanism of an "open channel block state" facilitated the recovery and increased the availability of sodium (Na_V) channels after depolarization. Using a computational model of NM neurons, we demonstrated that removal of I_NaR reduced high-rate AP firing. We found weak I_NaR during a prehearing period (E11-12), which transformed to resemble late-developing I_NaR properties around hearing onset (E14-16). Anatomically, we detected strong Na_V1.6 expression near maturation, which became increasingly less distinct at hearing onset and prehearing periods, suggesting that multiple Na_V channel subtypes may contribute to I_NaR during development. We conclude that I_NaR plays an important role in regulating rapid AP firing for NM neurons, a property that may be evolutionarily conserved for functions related to similar avian and mammalian hearing.

This article is protected by copyright. All rights reserved

from Physiology via xlomafota13 on Inoreader http://ift.tt/2AiMOhD
via IFTTT

Control networks and hubs

Abstract

Executive control functions are associated with frontal, parietal, cingulate, and insular brain regions that interact through distributed large-scale networks. Here, we discuss how fMRI functional connectivity can shed light on the organization of control networks and how they interact with other parts of the brain. In the first section of our review, we present convergent evidence from fMRI functional connectivity, activation, and lesion studies that there are multiple dissociable control networks in the brain with distinct functional properties. In the second section, we discuss how graph theoretical concepts can help illuminate the mechanisms by which control networks interact with other brain regions to carry out goal-directed functions, focusing on the role of specialized hub regions for mediating cross-network interactions. Again, we use a combination of functional connectivity, lesion, and task activation studies to bolster this claim. We conclude that a large-scale network perspective provides important neurobiological constraints on the neural underpinnings of executive control, which will guide future basic and translational research into executive function and its disruption in disease.

from Physiology via xlomafota13 on Inoreader http://ift.tt/2ihu0e3
via IFTTT

Molecular adaptations of adipose tissue to 6 weeks of morning fasting vs daily breakfast consumption in lean and obese adults

Abstract

This experiment assessed molecular responses of human subcutaneous abdominal adipose tissue (SCAT) to 6 weeks of morning fasting. Forty-eight, healthy lean (n = 29) and obese (n = 20) adults provided SCAT biopsies before and after six weeks of morning fasting (FAST; 0 kcal until 1200 h) or daily breakfast consumption (BFAST; ≥700 kcal before 1100 h). Biopsies were analysed for mRNA levels of selected genes, and GLUT4 and Akt protein content. Basal and insulin-stimulated Akt activation and tissue glucose uptake rates were also determined. In lean individuals, lipid turnover and insulin signalling genes (ACADM and IRS2) were upregulated with FAST versus BFAST [1.14 (95%CI: 0.97 to 1.30) versus 0.80 (95%CI: 0.64 to 0.96), P = 0.007 and 1.75 (95%CI: 1.33 to 2.16) versus 1.09 (95%CI: 0.67 to 1.51), P = 0.03, respectively). In obese individuals, no differential (FAST versus BFAST) expression was observed in genes involved in lipid turnover (all P > 0.1). GLUT4, Akt protein content and insulin-stimulated Akt phosphorylation were unaffected by FAST versus BFAST in both lean and obese cohorts (all P > 0.1). Lower insulin-stimulated glucose uptake rates in obese versus lean individuals were eradicated when normalised to whole-body fat mass (P = 0.416). We conclude that morning fasting upregulates lipid turnover genes in SCAT of lean individuals. Secondly, altered SCAT insulin sensitivity with morning fasting is unlikely to be explained by signalling proximal to Akt. Finally, lower insulin-stimulated SCAT glucose uptake rates in obese individuals are proportional to whole-body fat mass, suggesting a compensatory downregulation, presumably to prevent excessive de novo lipogenesis in adipose tissue. This trial was registered as ISRCTN31521726.

This article is protected by copyright. All rights reserved

from Physiology via xlomafota13 on Inoreader http://ift.tt/2neZEdG
via IFTTT

Gait performance and foot pressure distribution during wearable robot-assisted gait in elderly adults

A robotic exoskeleton device is an intelligent system designed to improve gait performance and quality of life for the wearer. Robotic technology has developed rapidly in recent years, and several robot-assist...

from Rehabilitation via xlomafota13 on Inoreader https://jneuroengrehab.biomedcentral.com/articles/10.1186/s12984-017-0333-z
via IFTTT

Effect of EMG-triggered neuromuscular electrical stimulation with bilateral arm training on hemiplegic shoulder pain and arm function after stroke: a randomized controlled trial

Hemiplegic shoulder pain is a frequent complication after stroke, leading to limited use of the affected arm. Neuromuscular electrical stimulation (NMES) and transcutaneous electrical nerve stimulation (TENS) ...

from Rehabilitation via xlomafota13 on Inoreader http://ift.tt/2zNlScH
via IFTTT

Anesthetic management of a parturient with hemolysis, elevated liver enzyme levels, and low platelet syndrome complicated by renal insufficiency and coagulopathy

Jinguo Wang, Na Wang, Wei Han, Zhanyang Han

Anesthesia: Essays and Researches 2017 11(4):1126-1128

The objective of this study is to describe the anesthetic management of a parturient with hemolysis, elevated liver enzyme levels, and low platelet (HELLP) syndrome and renal insufficiency. A 28-year-old female patient, gestational age of 35 weeks, with hypertensive crisis (blood pressure 190/110 mmHg), was admitted for an emergency cesarean section after diagnosis of HELLP syndrome and renal insufficiency. We performed total intravenous general anesthesia with rapid sequence induction. During the surgical procedure, reduced urine output and coagulopathy were detected. After the treatments of transfusion, diuresis, and anticoagulation, the surgery finished uneventfully. The patient was taken to the Intensive Care Unit without extubation and discharged on the 6th postoperative day. This case report revealed a successful anesthetic management applied to a pregnant woman with HELLP syndrome complicated by renal insuffciency and coagulopathy. There are several case reports about HELLP syndrome, but the patient in this paper is complicated with renal insuffciency and coagulopathy which made the treatment diffcult to handle.

from Anaesthesiology via xlomafota13 on Inoreader http://www.aeronline.org/text.asp?2017/11/4/1126/207075
via IFTTT

Intravenous dexmedetomidine infusion compared with that of fentanyl in patients undergoing arthroscopic shoulder surgery under general anesthesia

Mona Hossam Eldin Abdel Hamid

Anesthesia: Essays and Researches 2017 11(4):1070-1074

Background: Anesthesia for arthroscopic shoulder surgery is challenging due to the need for oligaemic surgical field as well as a good postoperative recovery profile. Aim: The present study was prospective, randomized to evaluate the efficacy of dexmdetomidine infusion compared to that of fentanyl in patients undergoing arthroscopic shoulder surgery under general anesthesia. Patients and Methods: A total of 60 patients aged from thirty to fifty years, American Society of Anesthesiologists Class I/II of either sex for arthroscopic shoulder surgery, were included. The patients were divided into two groups of 30 patients each. Group I received dexmedetomidine loading 1 μg/kg over 10 min followed by maintenance 0.5 μg/kg/h and Group II Fentanyl loading 1 μg/kg followed by maintenance 0.5 μg/kg/h. Measurements: Hemodynamic readings (Heart rate HR, and mean arterial blood pressure MAP) were recorded after the start of the study drug infusion (T1), after intubation (T2), then every 15 minutes till the end of surgery (T15, T30, T45, T60, T75, T90). In the PACU , MAP, and HR were recorded on arrival, after 30 min, 1 hr, and 2 hrs (R0, R30, R1 hr, R2 hr) Postoperative analgesia was assessed by visual analogue scale (VAS), Modified Observers's Assessment of Alertness and Sedation OAA/S was recorded on arrival to PACU. Results: This study showed that in the dexmedatomidine group there was statistically significant decrease of MAP and HR after drug infusion up to two hours in the recovery period, more sedation, better control of pain and surgeon satisfaction. Conclusion: Iv infusion of dexamedatomidine may be an attractive option during arthroscopic shoulder surgery as it provided a better hypotensive anesthesia by lowering MAP and HR which leads to better surgical field and surgeon satisfaction than iv infusion fentanyl along with a better postoperative VAS.

from Anaesthesiology via xlomafota13 on Inoreader http://www.aeronline.org/text.asp?2017/11/4/1070/216038
via IFTTT