TRPM4/5\u27s Role in Inspiratory Calcium-Activated Nonspecific Cation Current

In mammals, the breathing behavior originates in brainstem networks. Neurons of the mammalian respiratory rhythmogenerator, the PreBotzinger complex (preBotC), augment periodic synaptic input to generate robust envelopes of depolarization called inspiratory drive potentials, Calcium-activated non-specific cationic current (I-CAN) has been implicated in drive potential generation via an inositol 1,4,5-trisphosphate (IP3) dependent mechanism. The protein or proteins underlying this current, however, remain unknown. Because of their unique biophysical properties, two homologs of the transient receptor potential (TRP) channel family, TRPM4/5, make attractive candidates for I-CAN. Earlier RT-PCR experiments demonstrated expression of TRPM4/5 mRNAs within the preBotC. Additionally, using anatomical landmarks, earlier immunohistochemistry data demonstrate expression of TRPM4/5 protein in neurons of the inspiratory network. Here, we provide the first functional evidence for TRPM4/5 in the preBotC. Pharmacological inhibition of TRPM4 by a selective inhibitor, 9-phenanthrol, progressively attenuated drive potentials, consistent with a functional role for TRPM4 in inspiratory burst generation. Additionally, we propose a protocol that will facilitate single-channel recordings from preBotC neurons. We conclude that, while not definitive, many lines of evidence now suggest TRPM4/5 channels as the molecular identity of I-CAN

Methane emissions of beef cattle grazing tall fescue pastures

Methane (CH4;) produced by fermentation in cattle rumens is of interest because it represents an energetic inefficiency of fermentation and because of the role CH4; is suspected of playing in global warming scenarios. Tall fescue {Festuca arundinacea Schreb.) is an important forage in the eastern United States. The toxic syndrome associated with infection by the endophytic fungus Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin comb. nov. (E+), can be mitigated with management strategies which improve the forage quality of E+ tall fescue pastures. The sulfur hexafluoride (SF6;) tracer technique was used to determine the effects of tall fescue pasture management on consequential CH4; production in spring and summer 1997 and winter and spring 1998. Two steers on each of two pastures of E+ tall fescue, endophyte free (E-) tall fescue, E+/E- strips, and E+/clover, and four steers and four cows grazing an unimproved pasture (UP) and a best management practices (BMP) pasture were used to collect eructated CH4; samples. Average daily gains for the summer 1997 season were lower for steers grazing the E+, E-, and E+/E- tall fescue pastures (0.49 - 0.54 kg*d-1;) than for those grazing the E+ tall fescue/clover pastures (0.75 kg*d-1;). Daily CH4; emissions were between about 100 - 200 g*d-1; for steers and between about 150 - 240 g*d-1; for cows. When data from both years were combined, steers grazing the E+ tall fescue/clover pastures emitted 18 to 20 percent less CH4; as a function of ADG (252 g*kg-1;*d-1;) than steers grazing the other three pasture systems (309 - 326 g*kg-1;*d-1;) in the summer. Cows emitted more CH4; as a function of ADG (413 - 702 g*kg-1;*d-1;) than steers grazing the UP and BMP pastures (231 - 342 g*kg-1;*d-1;). This study represents the first estimation of CH4; emissions from cattle grazing tall fescue pastures in Tennessee. The improved management practices pastures were considered to be more efficient, since less CH4; was emitted per unit of animal performance

EFFECTS OF WEATHER, PARENTAL BEHAVIORAL PLASTICITY, AND LIFE HISTORY TRAITS ON OFFSPRING GROWTH, DEVELOPMENT, AND ENERGY EXPENDITURE IN SONGBIRDS

Weather creates energetic and survival challenges for organisms that can influence demography. Harsh weather often causes increased energy expenditure in adults, but how weather affects other life stages is less well understood. Juveniles are especially vulnerable because they must use energy to survive weather effects and maintain growth and development while having poorly developed thermoregulatory capabilities. Juveniles that spend energy overcoming harsh weather can have delayed growth and maturation, which can negatively affect competitive abilities, survival, and lifetime fitness. Understanding weather effects on offspring is particularly challenging in altricial species because parents have evolved strategies to ameliorate such effects. However, the degree to which parents ameliorate harmful effects of weather on offspring varies within and across species due to environmental and evolutionary constraints. Our ability to predict accurate ecological ramifications of climate change are currently limited by a paucity of studies of weather effects on developing offspring, and how parents are able and willing to mitigate these effects. This dissertation aims to fill such gaps in knowledge using empirical data within and across species of songbirds on 3 continents. In chapter 1, I tested whether slower growth and development of organisms living at high elevations is caused by harsh weather. At a study site at ca. 3200 m asl in Malaysian Borneo, I found that Mountain Blackeye (Chlorocharis emiliae) parents in experimentally heated and covered nests warmed their young less and provisioned more often. This behavioral plasticity resulted in faster mass gain and wing growth, and earlier fledging of young. Thus, slower growth and development of montane organisms partially reflects proximate responses to harsh weather. In chapter 2, I used samples from 664 nestlings across 54 species on 3 continents to test for proximate and evolutionary sources of offspring daily energy expenditure (DEE). Within species, heavier rain, colder Ta, and fewer siblings were each correlated with higher nestling DEE, highlighting the importance of weather and huddling with siblings on offspring energy use. Across species, DEE was positively correlated with adult and juvenile mortality, illustrating the evolved component of DEE that can be shaped by selection from age-specific mortality. In chapter 3, I simulated rain above nests of 5 species of songbirds in Malaysian Borneo to test the direct effects of rain on offspring DEE and parental behavior, and how these responses varied across nest type. Parents in enclosed nests did not change their behavior in response to rain, while parents in open nests brooded their young more, leading to no difference in nestling DEE in either nest type. These results suggest that parents using exposed nest types can ameliorate costs of short-term rain on young through behavioral plasticity. These results also suggest that parents using open nests may need to modify their behavior in locations where rain is predicted to increase from climate change

Binding and Detection of Anions Using Tripodal Hosts

The aim of this project was to investigate the anion-binding properties of a range of different receptor compounds. For the most part, the receptors reported here were tripodal in nature, wherein three hydrogen-bonding receptor groups, including amines, amides and ureas, are linked around a common structural core. In this study, a range of different cores were chosen, such as simple and flexible organic frameworks based on the tris(2-aminoethyl)amine (tren) precursor, conformationally-restricted and brightly coloured aromatic species based on the dye pararosaniline, and triply-ligated metal complexes of ruthenium(II). In order to assess the anion binding abilities of these receptors, a range of different techniques were employed, with 1H-NMR and UV/Visible spectroscopic titrations being the most common. Additionally, the incorporation of fluorescent pyrene moieties as a reporter group to some of the receptors allowed for the probing of anion binding via fluorimetric titrations in these cases. During the course of the experiments, a number of interesting, and in some cases, unexpected, binding conformations were found – in particular, the interactions between many of the organic receptor compounds with the planar 1,3,5-benzenetricarboxylate (trimesylate) trianion, and the pH dependency of the colour of the pararosaniline-based receptors. Additionally, the range of cyclic thioether-capped ruthenium(II) receptor compounds reported here showed an unusually high resistance to degradation by solvent and guest when compared to similar receptors with aromatic-capped ruthenium, and successfully gave tripodal ML3 complexes instead of the traditionally more stable ML2X dipodal complexes

An Underappreciated Radiation Hazard from High Voltage Electrodes in Vacuum

The use of high voltage (HV) electrodes in vacuum is commonplace in physics laboratories. In such systems, it has long been known that electron emission from an HV cathode can lead to bremsstrahlung X-rays; indeed, this is the basic principle behind the operation of standard X-ray sources. However, in laboratory setups where X-ray production is not the goal and no electron source is deliberately introduced, field-emitted electrons accelerated by HV can produce X-rays as an unintended hazardous byproduct. Both the level of hazard and the safe operating regimes for HV vacuum electrode systems are not widely appreciated, at least in university laboratories. A reinforced awareness of the radiation hazards associated with vacuum HV setups would be beneficial. We present a case study of a HV vacuum electrode device operated in a university atomic physics laboratory. We describe the characterisation of the observed X-ray radiation, its relation to the observed leakage current in the device, the steps taken to contain and mitigate the radiation hazard, and suggest safety guidelines.Comment: Submitted to Health Physic

Site U1334

Integrated Ocean Drilling Program (IODP) Site U1334 (7°59.998?N, 131°58.408?W; 4799 meters below sea level [mbsl]) (Fig. F1; Table T1) is located ~380 km southeast of previously drilled Ocean Drilling Program (ODP) Site 1218 (~42 Ma crust) in the central area drilled during the Pacific Equatorial Age Transect (PEAT) program (IODP Expedition 320/321). Site U1334 (~38 Ma crust) is situated ~100 km north of the Clipperton Fracture Zone on abyssal hill topography draped with ~280 m sediment (Fig. F2). The fabric of the abyssal hills within the sites is oriented either due north or slightly east of due north.Water depth in the vicinity of Site U1334 ranges between 5.0 and 5.1 km for the depressions between the abyssal hills. The abyssal hills range between 4.70 and 4.85 km water depth and generally show a thicker and more consistent sediment cover than the basins. In fact, a significant amount of the bathymetric difference between hills and basins is controlled by the amount of sediment cover. The comparison of sediment thickness and clarity of seismic sections led us to select a location on the middle elevation of one of the abyssal plateaus.Site U1334 sediments were estimated to have been deposited on top of late middle Eocene crust with an age of ~38 Ma and target the events bracketing the Eocene–Oligocene transition with the specific aim of recovering carbonate-bearing sediments of latest Eocene age prior to a large deepening of the calcium carbonate compensation depth (CCD) that occurred during this greenhouse to icehouse transition (Kennett and Shackleton, 1976; Miller et al., 1991; Zachos et al., 1996; Coxall et al., 2005). The Eocene–Oligocene transition experienced the most dramatic deepening of the Pacific CCD during the Paleogene (van Andel, 1975), which has now been shown by Coxall et al. (2005) to coincide with a rapid stepwise increase in benthic oxygen stable isotope ratios, interpreted to reflect a combination of growth of the Antarctic ice sheet and decrease in deepwater temperatures (DeConto et al., 2008; Liu et al., 2009).<br/