Heating-free, room-temperature operation of a radiofrequency-to-light signal transducer with a membrane oscillator and a built-in metasurface mirror

We present an electro-mechano-optical radiofrequency (rf)-to-light signal transducer robust against laser heating and thus operational at room temperature. A metal-free, low-loss metasurface mirror and an aluminum electrode made separately on a Si3N4 membrane oscillator comprise a chain of electro-mechanical and opto-mechanical systems, mediating electrical and optical signals through the (2,2)-mode characteristic oscillation. We demonstrate up-conversion of rf signals at 175.2 MHz by 6 orders of magnitude in frequency to an optical regime with the transfer efficiency of 2.3×10-9, also showing stable operation due to reduced laser heating of the mirror.

New bulk liquid membrane oscillator composed of two coupled oscillators with diffusion-mediated physical coupling

A new type of bulk liquid membrane system, which represents the first example of a bulk liquid membrane oscillator characterised by the presence of two coupled oscillators, is described. When the benzyldimethyltetradecylammonium chloride surfactant undergoes an oscillatory mass transfer through a nitromethane liquid membrane, a new liquid layer (phase X) appears between the membrane and the acceptor phase. Kinetic analysis provides evidence that the whole system is composed of two coupled oscillators with diffusion-mediated physical coupling. The first component oscillator (based on nitromethane) of lower frequency delivers the driving material to the second one (phase X-based oscillator) leading to additional higher frequency oscillations. A new molecular mechanism is proposed for interpreting the experimental observations. The results might enhance understanding of intercellular communication in biology, where periodic signalling is more efficient than any other type of signalling mode.

Kisspeptin-10 Facilitates a Plasma Membrane-Driven Calcium Oscillator in Gonadotropin-Releasing Hormone-1 Neurons

Kisspeptins, the natural ligands of the G-protein-coupled receptor (GPR)-54, are the most potent stimulators of GnRH-1 secretion and as such are critical to reproductive function. However, the mechanism by which kisspeptins enhance calcium-regulated neuropeptide secretion is not clear. In the present study, we used GnRH-1 neurons maintained in mice nasal explants to examine the expression and signaling of GPR54. Under basal conditions, GnRH-1 cells exhibited spontaneous baseline oscillations in intracellular calcium concentration ([Ca2+]i), which were critically dependent on the operation of voltage-gated, tetrodotoxin (TTX)-sensitive sodium channels and were not coupled to calcium release from intracellular pools. Activation of native GPR54 by kisspeptin-10 initiated [Ca2+]i oscillations in quiescent GnRH-1 cells, increased the frequency of calcium spiking in oscillating cells that led to summation of individual spikes into plateau-bursting type of calcium signals in a subset of active cells. These changes predominantly reflected the stimulatory effect of GPR54 activation on the plasma membrane oscillator activity via coupling of this receptor to phospholipase C signaling pathways. Both components of this pathway, inositol 1,3,4-trisphosphate and protein kinase C, contributed to the receptor-mediated modulation of baseline [Ca2+]i oscillations. TTX and 2-aminoethyl diphenylborinate together abolished agonist-induced elevation in [Ca2+]i in almost all cells, whereas flufenamic acid was less effective. Together these results indicate that a plasma membrane calcium oscillator is spontaneously operative in the majority of prenatal GnRH-1 neurons and is facilitated by kisspeptin-10 through phosphatidyl inositol diphosphate hydrolysis and depolarization of neurons by activating TTX-sensitive sodium channels and nonselective cationic channels. GnRH-1 neurons exhibit a spontaneously active calcium oscillator, dependent on tetrodotoxin-sensitive sodium conductance. Kisspeptin-10/GPR54, via phosphatidyl inositol diphosphate 2 hydrolysis, utilizes these channels and non-selective cationic channels.