Non-technical summary We have investigated the mechanisms underlying the response of cells to pulsed infrared radiation (IR, ∼1862 nm) using the neonatal rat ventricular cardiomyocyte as a model. n = 12), an inhibitor of the mitochondrial Na + /Ca 2+ exchanger (mNCX), (2) Ruthenium Red (40 μM, n = 13), an inhibitor of the mitochondrial Ca 2+ uniporter (mCU), and (3) 2-aminoethoxydiphenylborane (10 μM, n = 6), an IP 3 channel antagonist. Ryanodine blocked the spontaneous [Ca 2+ ] i transients but did not alter the IR-evoked events in the same cells. This pharmacological array implicates mitochondria as the major intracellular store of Ca 2+ involved in IR-evoked responses reported here. Results support the hypothesis that 1862 nm pulsed IR modulates mitochondrial Ca 2+ transport primarily through actions on mCU and mNCX.

Non-technical summary It has been shown previously that application of short pulses of optical energy at infrared wavelengths can evoke action potentials in neurons and mechanical contraction in cardiac muscle cells. Optical stimuli are particularly attractive because of the ability to deliver focused energy through tissue without physical contact or electrical charge injection. Here we demonstrate efficacy of pulsed infrared radiation to stimulate balance organs of the inner ear, specifically to modulate the pattern of neural signals transmitted from the angular motion sensing semicircular canals to the brain. The ability to control action potentials demonstrates the potential of pulsed optical stimuli for basic science investigations and future therapeutic applications. AbstractThe present results show that the semicircular canal crista ampullaris of the toadfish, Opsanus tau, is sensitive to infrared radiation (IR) applied in vivo. IR pulse trains (∼1862 nm, ∼200 μs pulse −1 ) delivered to the sensory epithelium by an optical fibre evoked profound changes in phasic and tonic discharge rates of postsynaptic afferent neurons. Phasic afferent responses to pulsed IR occurred with a latency of <8 ms while tonic responses developed with a time constant (τ) of 7 ms to 10 s following the onset or cessation of the radiation. Afferents responded to direct optical radiation of the sensory epithelium but did not respond to thermal stimuli that generated nearly equivalent temperature increases of the whole organ. A subset of afferent neurons fired an action potential in response to each IR pulse delivered to the sensory epithelium, at phase-locked rates up to 96 pulses per second. The latency between IR pulses and afferent nerve action potentials was much greater than synaptic delay and spike generation, demonstrating the presence of a signalling delay interposed between the IR pulse and the action potential. The same IR stimulus applied to afferent nerve axons failed to evoke responses of similar magnitude and failed to phase-lock afferent nerve action potentials. The present data support the hypothesis that pulsed IR activates sensory hair cells, thus leading to modulation of synaptic transmission and afferent nerve discharge reported here.

A microchip was applied to electrically depolarize rat pheochromocytoma (PC12) cells and to simultaneously detect exocytotic catecholamine release amperometrically. Results demonstrate exocytosis elicited by flowing cells through an electric field generated by a potentiostat circuit in a microchannel, as well as exocytosis triggered by application of an extracellular voltage pulse across. Electrical finite element model (FEM) analysis illustrated that larger cells experienced greater depolarizing excitation from the extracellular electric fields due to the smaller shunt path and higher resistance to current flow in the channel around the cell. Consistent with these simulations, data recorded from cell clusters and large cells exhibited increased release rates relative to data from the smaller cells. Overall, the system was capable of resolving single vesicle quantal release, in the zeptomole range, as well as the kinetics associated with the vesicle fusion process. Analysis of spike population statistics suggested detection of catecholamines from multiple release sites around the cells. The potential for such a device to be used in flow cytometry to evoke and detect exocytosis was demonstrated.

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Particle and cell counting is used for a variety of applications including routine cell culture, hematological analysis, and industrial controls [1][2][3][4][5] . A critical breakthrough in cell/particle counting technologies was the development of the Coulter technique by Wallace Coulter over 50 years ago. The technique involves the application of an electric field across a micron-sized aperture and hydrodynamically focusing single particles through the aperture. The resulting occlusion of the aperture by the particles yields a measurable change in electric impedance that can be directly and precisely correlated to cell size/volume. The recognition of the approach as the benchmark in cell/particle counting stems from the extraordinary precision and accuracy of its particle sizing and counts, particularly as compared to manual and imaging based technologies (accuracies on the order of 98% for Coulter counters versus 75-80% for manual and vision-based systems). This can be attributed to the fact that, unlike imaging-based approaches to cell counting, the Coulter Technique makes a true three-dimensional (3-D) measurement of cells/particles which dramatically reduces count interference from debris and clustering by calculating precise volumetric information about the cells/particles. Overall this provides a means for enumerating and sizing cells in a more accurate, less tedious, less time-consuming, and less subjective means than other counting techniques 6 .Despite the prominence of the Coulter technique in cell counting, its widespread use in routine biological studies has been prohibitive due to the cost and size of traditional instruments. Although a less expensive Coulter-based instrument has been produced, it has limitations as compared to its more expensive counterparts in the correction for "coincidence events" in which two or more cells pass through the aperture and are measured simultaneously. Another limitation with existing Coulter technologies is the lack of metrics on the overall health of cell samples. Consequently, additional techniques must often be used in conjunction with Coulter counting to assess cell viability. This extends experimental setup time and cost since the traditional methods of viability assessment require cell staining and/or use of expensive and cumbersome equipment such as a flow cytometer.The Moxi Z mini automated cell counter, described here, is an ultra-small benchtop instrument that combines the accuracy of the Coulter Principle with a thin-film sensor technology to enable precise sizing and counting of particles ranging from 3-25 microns, depending on the cell counting cassette used. The M type cassette can be used to count particles from with average diameters of 4 -25 microns (dynamic range 2 -34 microns), and the Type S cassette can be used to count particles with and average diameter of 3 -20 microns (dynamic range 2 -26 microns). Since the system uses a volumetric measurement method, the 4-25 microns corresponds to a cell volume range of 34 -8,180 fL and the 3 -...