Hair cell maturation is differentially regulated along the tonotopic axis of the mammalian cochlea

Sound amplification within the mammalian cochlea depends upon specialized hair cells, the outer hair cells (OHCs), which possess both sensory and motile capabilities. In various altricial rodents, OHCs become functionally competent from around postnatal day 7 (P7), before the primary sensory inner hair cells (IHCs), which become competent at about the onset of hearing (P12). The mechanisms responsible for the maturation of OHCs and their synaptic specialization remain poorly understood. We report that spontaneous Ca2+ activity in the immature cochlea, which is generated by CaV1.3 Ca2+ channels, differentially regulates the maturation of hair cells along the cochlea. Under near‐physiological recording conditions we found that, similar to IHCs, immature OHCs elicited spontaneous Ca2+ action potentials (APs), but only during the first few postnatal days. Genetic ablation of these APs in vivo, using CaV1.3−/− mice, prevented the normal developmental acquisition of mature‐like basolateral membrane currents in low‐frequency (apical) hair cells, such as IK,n (carried by KCNQ4 channels), ISK2 and IACh (α9α10nAChRs) in OHCs and IK,n and IK,f (BK channels) in IHCs. Electromotility and prestin expression in OHCs were normal in CaV1.3−/− mice. The maturation of high‐frequency (basal) hair cells was also affected in CaV1.3−/− mice, but to a much lesser extent than apical cells. However, a characteristic feature in CaV1.3−/− mice was the reduced hair cell size irrespective of their cochlear location. We conclude that the development of low‐ and high‐frequency hair cells is differentially regulated during development, with apical cells being more strongly dependent on experience‐independent Ca2+ APs

Development of a Telemetry Unit for Wireless Monitoring of Bone Strain

Computational Infrastructure and Informatics Poster SessionA telemetry unit designed to monitor strain in bones is presented. This unit allows studying the relationship between bone load and bone mass in scenarios that were not possible with current setup. The current measuring setup employs a bench top load instrument and a data acquisition unit to read the output of strain gage sensors attached to the ulna of a mouse. Although precise, this setup is bulky and requires complete immobilization of the mouse. The telemetry unit developed by the authors replaces the data acquisition unit in the current setup and is able to wirelessly transmit the readings of the strain gage to a remote computer. The telemetry unit makes possible the collection of bone strain data in scenarios where the mouse is free to move or while performing fatigue-inducing exercises. The unit has been designed around an ultra low-power microcontroller (MSP430). The microcontroller makes the design highly flexible and programmable. The telemetry unit also includes a high-performance instrumentation amplifier to amplify the strain gage output. The gain and offset of the amplifier are digitally set by the microcontroller eliminating the use of manual potentiometers. The board has an expansion connector that allows up to 16 additional strain gages to be connected to the unit and incorporates a low-power radio transceiver operating in the 2.4 GHz ISM band. The data transmitted by the unit is received by a base station connected to a computer via a USB cable. The telemetry unit has been tested in a lab setting and is able to transmit the strain data at distances greater than 20 m while consuming less than 30 mW of power. This low power consumption allows the unit to be powered by a micro-battery weighting less than 3 grams. The telemetry unit can be used in other biomedical applications such as in the monitoring of orthopedic implants and can be easily configured to use other type of sensors

Herschel Far-Infrared and Sub-millimeter Photometry for the KINGFISH Sample of Nearby Galaxies

New far-infrared and sub-millimeter photometry from the Herschel Space Observatory is presented for 61 nearby galaxies from the Key Insights on Nearby Galaxies: A Far-Infrared Survey with Herschel (KINGFISH) sample. The spatially-integrated fluxes are largely consistent with expectations based on Spitzer far-infrared photometry and extrapolations to longer wavelengths using popular dust emission models. Dwarf irregular galaxies are notable exceptions, as already noted by other authors, as their 500um emission shows evidence for a sub-millimeter excess. In addition, the fraction of dust heating attributed to intense radiation fields associated with photo-dissociation regions is found to be (21+/-4)% larger when Herschel data are included in the analysis. Dust masses obtained from the dust emission models of Draine & Li are found to be on average nearly a factor of two higher than those based on single-temperature modified blackbodies, as single blackbody curves do not capture the full range of dust temperatures inherent to any galaxy. The discrepancy is largest for galaxies exhibiting the coolest far-infrared colors.Comment: Accepted for publication in Ap

Neurophysiology

Contains reports on four research projects.Bell Telephone Laboratories, IncorporatedThe Teagle Foundation, IncorporatedNational Science Foundatio

Benefits of Turbid River Plume Habitat for Lake Erie Yellow Perch (Perca flavescens) Recruitment Determined by Juvenile to Larval Genotype Assignment

Nutrient-rich, turbid river plumes that are common to large lakes and coastal marine ecosystems have been hypothesized to benefit survival of fish during early life stages by increasing food availability and (or) reducing vulnerability to visual predators. However, evidence that river plumes truly benefit the recruitment process remains meager for both freshwater and marine fishes. Here, we use genotype assignment between juvenile and larval yellow perch (Perca flavescens) from western Lake Erie to estimate and compare recruitment to the age-0 juvenile stage for larvae residing inside the highly turbid, south-shore Maumee River plume versus those occupying the less turbid, more northerly Detroit River plume. Bayesian genotype assignment of a mixed assemblage of juvenile (age-0) yellow perch to putative larval source populations established that recruitment of larvae was higher from the turbid Maumee River plume than for the less turbid Detroit River plume during 2006 and 2007, but not in 2008. Our findings add to the growing evidence that turbid river plumes can indeed enhance survival of fish larvae to recruited life stages, and also demonstrate how novel population genetic analyses of early life stages can contribute to determining critical early life stage processes in the fish recruitment process

Factors affecting ammonium uptake in streams - an inter-biome perspective

The Lotic Intersite Nitrogen experiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes. 2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of \u275~-ammonium and downstream measurements of 15N-ammonium concentration. 3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake. 4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa). 5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake

The emission by dust and stars of nearby galaxies in the Herschel KINGFISH survey

Using new far-infrared imaging from the Herschel Space Observatory with ancillary data from ultraviolet (UV) to submillimeter wavelengths, we estimate the total emission from dust and stars of 62 nearby galaxies in the KINGFISH survey in a way that is as empirical and model independent as possible. We collect and exploit these data in order to measure from the spectral energy distributions (SEDs) precisely how much stellar radiation is intercepted and re-radiated by dust, and how this quantity varies with galaxy properties. By including SPIRE data, we are more sensitive to emission from cold dust grains than previous analyses at shorter wavelengths, allowing for more accurate estimates of dust temperatures and masses. The dust/stellar flux ratio, which we measure by integrating the SEDs, has a range of nearly three decades (from 10(-2.2) to 10(0.5)). The inclusion of SPIRE data shows that estimates based on data not reaching these far-IR wavelengths are biased low by 17% on average. We find that the dust/stellar flux ratio varies with morphology and total infrared (IR) luminosity, with dwarf galaxies having faint luminosities, spirals having relatively high dust/stellar ratios and IR luminosities, and some early types having low dust/stellar ratios. We also find that dust/stellar flux ratios are related to gas-phase metallicity ((log(f(dust)/f(*)) over bar) = -0.66 +/- 0.08 and -0.22 +/- 0.12 for metal-poor and intermediate-metallicity galaxies, respectively), while the dust/stellar mass ratios are less so (differing by approximate to 0.2 dex); the more metal-rich galaxies span a much wider range of the flux ratios. In addition, the substantial scatter between dust/stellar flux and dust/stellar mass indicates that the former is a poor proxy of the latter. Comparing the dust/stellar flux ratios and dust temperatures, we also show that early types tend to have slightly warmer temperatures (by up to 5 K) than spiral galaxies, which may be due to more intense interstellar radiation fields, or possibly to different dust grain compositions. Finally, we show that early types and early-type spirals have a strong correlation between the dust/stellar flux ratio and specific star formation rate, which suggests that the relatively bright far-IR emission of some of these galaxies is due to ongoing (if limited) star formation as well as to the radiation field from older stars, which is heating the dust grains

Far-Infrared Line Imaging of the Starburst Ring in NGC 1097 with the Herschel/PACS Spectrometer

NGC 1097 is a nearby SBb galaxy with a Seyfert nucleus and a bright starburst ring. We study the physical properties of the interstellar medium (ISM) in the ring using spatially resolved far-infrared spectral maps of the circumnuclear starburst ring of NGC 1097, obtained with the PACS spectrometer on board the Herschel Space Telescope. In particular, we map the important ISM cooling and diagnostic emission lines of [OI] 63 $\mu$m, [OIII] 88 $\mu$m, [NII] 122 $\mu$m, [CII] 158 $\mu$m and [NII] 205 $\mu$m. We observe that in the [OI] 63 $\mu$m, [OIII] 88 $\mu$m, and [NII] 122 $\mu$m line maps, the emission is enhanced in clumps along the NE part of the ring. We observe evidence of rapid rotation in the circumnuclear ring, with a rotation velocity of ~220$km s$^{-1}$(inclination uncorrected) measured in all lines. The [OI] 63$\mu$m/[CII] 158$\mu$m ratio varies smoothly throughout the central region, and is enhanced on the northeastern part of the ring, which may indicate a stronger radiation field. This enhancement coincides with peaks in the [OI] 63$\mu$m and [OIII] 88$\mu$m maps. Variations of the [NII] 122$\mu$m/[NII] 205$\mu$m ratio correspond to a range in the ionized gas density between 150 and 400 cm$^{-3}$.Comment: Accepted for publication on the A&A Herschel Special Issu