On Spin Dependence of Relativistic Acoustic Geometry

This work makes the first ever attempt to understand the influence of the black hole background space-time in determining the fundamental properties of the embedded relativistic acoustic geometry. To accomplish such task, the role of the spin angular momentum of the astrophysical black hole (the Kerr parameter $a$ -- a representative feature of the background black hole metric) in estimating the value of the acoustic surface gravity (the representative feature of the corresponding analogue space time) has been investigated for axially symmetric inflow of hydrodynamic fluid onto a rotating black hole. Since almost all astrophysical black holes are supposed to posses some degree of intrinsic rotation, the influence of the Kerr parameter on classical analogue models is very important to understand. For certain values of the initial boundary conditions describing the aforementioned flow, more than one acoustic horizons, namely two black hole type and one white hole type, may form, where the surface gravity may become formally infinite at the acoustic white hole. The connection between the corresponding analogue Hawking temperature with astrophysically relevant observables associated with the spectral signature has been discussed.Comment: 22 pages, 11 figures, Comments welcom

Kappa-Opioid Receptors in the Caudal Nucleus Tractus Solitarius Mediate 100 Hz Electroacupuncture-Induced Sleep Activities in Rats

Previous results demonstrated that 10 Hz electroacupuncture (EA) of Anmian acupoints in rats during the dark period enhances slow wave sleep (SWS), which involves the induction of cholinergic activity in the caudal nucleus tractus solitarius (NTS) and subsequent activation of opioidergic neurons and μ-receptors. Studies have shown that different kinds of endogenous opiate peptides and receptors may mediate the consequences of EA with different frequencies. Herein, we further elucidated that high-frequency (100 Hz)-EA of Anmian enhanced SWS during the dark period but exhibited no direct effect on rapid eye movement (REM) sleep. High-frequency EA-induced SWS enhancement was dose-dependently blocked by microinjection of naloxone or κ-receptor antagonist (nor-binaltorphimine) into the caudal NTS, but was affected neither by μ- (naloxonazine) nor δ-receptor antagonists (natatrindole), suggesting the role of NTS κ-receptors in the high-frequency EA-induced SWS enhancement. Current and previous results depict the opioid mechanisms of EA-induced sleep

Mitochondrial lipoylation integrates age-associated decline in brown fat thermogenesis.

Thermogenesis in brown adipose tissue (BAT) declines with age; however, what regulates this process remains poorly understood. Here, we identify mitochondria lipoylation as a previously unappreciated molecular hallmark of aged BAT in mice. Using mitochondrial proteomics, we show that mitochondrial lipoylation is disproportionally reduced in aged BAT through a post-transcriptional decrease in the iron-sulfur (Fe-S) cluster formation pathway. A defect in the Fe-S cluster formation by the fat-specific deletion of Bola3 significantly reduces mitochondrial lipoylation and fuel oxidation in BAT, leading to glucose intolerance and obesity. In turn, enhanced mitochondrial lipoylation by α-lipoic acid supplementation effectively restores BAT function in old mice, thereby preventing age-associated obesity and glucose intolerance. The effect of α-lipoic acids requires mitochondrial lipoylation via the Bola3 pathway and does not depend on the anti-oxidant activity of α-lipoic acid. These results open up the possibility to alleviate the age-associated decline in energy expenditure by enhancing the mitochondrial lipoylation pathway