No description available.

The epithelial sodium channel (ENaC) is a key regulator of salt homeostasis. The classic ENaC consists of three subunits: α, β and γ, which are highly expressed in the kidney and colon where they mediate electrogenic Na⁺ influx into cells under the tight hormonal regulation of aldosterone. A fourth ENaC subunit named [delta]ENaC also generates Na⁺ influx with the β- and γENaC subunits in Xenopus oocytes. However [delta]ENaC differs to the other subunits in its channel properties and tissue distribution, suggesting that [delta]ENaC may possess a physiological role other than salt regulation. A copper-toxicosis related protein called COMMD1/Murr1 was previously identified to directly interact with [delta]ENaC and downregulate [delta]ENaC activity. COMMD1 is linked with multiple ubiquitination pathways, therefore we hypothesised that COMMD1 directly interacts with [delta]ENaC through novel protein-protein interaction motifs and promotes internalisation of [delta]ENaC from the cell surface through enhanced ubiquitination. With the use of GST pulldown assays and coimmunoprecipitation, it was found that the binding of COMMD1 to [delta]ENaC is mediated by the COMM domain of COMMD1, primarily through amino acids 120-150 of COMMD1. Immunocytochemical studies showed that the intracellular interaction between [delta]ENaC and COMMD1 predominantly occurred in the early and recycling endosomes, suggesting that COMMD1 may promote the retrieval of [delta]ENaC from the cell surface to the intracellular pool. COMMD1 mediated a decrease in the [delta]ENaC cell surface population, as shown by a biotinylation surface labelling assay. This may be driven by an ubiquitin-regulated endocytosis, as COMMD1 increased ubiquitination, but not proteasomal/lysosomal degradation, of [delta]ENaC. COMMD1 may promote [delta]ENaC ubiquitination through the action of the ubiquitin ligase Nedd4-2 as coexpression with Nedd4-2 enhanced the COMMD1-mediated decrease in surface [delta]ENaC expression. This is abolished by the addition of the Nedd4-2 downregulator kinase sgk1, suggesting that COMMD1 may downregulate [delta]ENaC through the Nedd4-2/sgk1 pathway. Surface levels of [delta]ENaC may also be affected by XIAP, a RING domain ubiquitin ligase which is able to decrease the levels of COMMD1. Coimmunoprecipitation of endogenous [delta]ENaC and COMMD1 proteins, and the enhanced colocalisation of endogenous [delta]ENaC in the recycling endosomes with transfected COMMD1, indicate that interaction between transfected [delta]ENaC and COMMD1 reflect the intracellular interactions of the endogenous proteins. Taken together, these findings suggest that COMMD1 downregulates [delta]ENaC activity by promoting the internalisation of surface [delta]ENaC into early and recycling endosomes and this may be mediated by enhanced [delta]ENaC ubiquitination via the ubiquitin ligase Nedd4-2.

Thesis (M.S.)--University of Wisconsin -- La Crosse, 1984. / Includes bibliographical references (leaves 54-59).

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Robert A. Sikes, Dept. of Biological Sciences. Includes bibliographical references.

25 years after the first sodium images of the human brain were created, sodium MRI remains on the periphery of MR research, despite intimate sodium involvement in cellular metabolism and implicated abnormal concentrations in numerous disorders. The difficulties of sodium MRI include not only tissue concentration, ~1750x less than proton, but also rapid biexponential signal decay. The purpose of this work was to optimize human brain sodium MRI and facilitate a study of sodium increase following onset of acute human stroke, with potential timing application for those patients who present with unknown time-of-onset, as effective treatment is currently bound by a 4.5 hour time-window. Optimization begins with radial center-out k-space acquisition, which minimizes echo time (TE) and signal loss, and in particular concerns the twisted projection imaging (TPI) technique, which has not found wide use. This thesis first considers a new application of TPI, i.e. k-space filtering by sampling density design to minimize detrimental ringing artifact associated with cerebral spinal fluid. Image noise correlation is addressed next, and a method for measuring volumes of statistical noise independence presented, as this correlation together with signal-to-noise ratio (SNR) defines the confidence of signal-averaging measurements. Radial acquisition is then considered with respect to a new imaging metric, i.e. the minimum object volume that can be precisely (with respect to noise) and accurately (with respect to image intensity modulation with object volume) quantified. It is suggested that TPI is a highly beneficial radial acquisition technique when implemented with long readout duration (countering common thought), reduced SNR (i.e. small voxel volumes), and in particular small TPI parameter p. Sequence optimization for bulk-tissue sodium analysis demonstrates a large SNR/voxel-volume advantage for TPI implementation in a steady-state approach, even though excitation pulse length and TE must be increased to mitigate power deposition. Finally, an inversion-recovery based fluid-nulling method that facilitates sodium environment separation based on rapid relaxation during soft inversion pulses is presented, with possible application for intracellular weighted imaging. On high quality sodium images a clear trend of lesion intensity increase with time-after-onset is demonstrated for the first time in acute stroke patients, as expected from animal models.

No description available.

ABSTRACT A purge and trap concentrator coupled to gas chromatography-pulsed flame photometric detector(GC-PFPD) after in situ ethylation with sodium tetraethylborate(NaBEt4) was used to analyze organotin compounds in water samples. The sample glassware with 5.5 ml water sample, 1.5 ml derivatizing reagent as well as 2 ml buffer solution was installed to purge and trap system, and then all steps were performed automatically, including ethylation, purge and trap, concentration, chromatography seperation and detection. Parameters including NaBEt4 concentration, purge flow rate, purge time, desorb time, the pH of buffer solution, H2 flow rate and the voltage of photomultiplier tube(PMT) of PFPD , which influence the speciation of organotin compounds were optimized. Method detection limits for dibutyltin and tributyltin were 0.50 and 0.46 ng as Sn/L, respectively. The calibration graphs were linear up to 2 orders of magnitude. Surface water samples collected from fourteen different locations of Kaohsiung harbor were analyzed. The concentration of dibutyltin ranged from nondetected(ND) to 272.2 ng as Sn/L and tributyltin ranged from nondetected to 105.4 ng as Sn/L. Recovery percentage for dibutyltin and tributyltin ranged from 88.9-95.3 %.

In this study, an electrolytic micro-machining tester is employed to investigate the effects of supply voltage and initial machining position on the geometry of the tungsten needle using the single-point and the reciprocating methods. The tungsten needle to be electrolyzed is dipped in an aqueous electrolyte of 2wt % sodium hydroxide as the anode, and the stainless steel needle with a diameter of 100 £gm as the cathode, and the electrode gap is set to be 10 £gm. Experimental results show that it is difficult to control the diameter of the tungsten needle because the reduction rate of its diameter is quite fast and the bubbles are generated violently to cause the breakage of the tungsten needle at the higher supply voltage. At the lower supply voltage, the tungsten needle can be machined to a finer scale, but it takes a long machining time. Under the single-point machining condition, it can be used to manufacture a short, uniform, and smooth tungsten needle with the diameter of 9 £gm at the supply voltage of 12V and the initial machining position of 75 £gm. Under the reciprocating machining condition, a long uniform micro-cylinder tungsten needle can be manufactured, but its surface becomes rough slightly at the supply voltage of 4V and the initial machining position in the range between -50 and 0 £gm. A tungsten needle with the aspect ratio of 30 and the diameter of 9 £gm can be manufactured using the following process: the machining time of 24 min at the supply voltage of 4V, and then the machining time of 28 min at the supply voltage of 2V. Key words¡Gtungsten needle, sodium hydroxide

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 128-138). Available also in a digital version from Dissertation Abstracts.

The scope of this master thesis was to investigate how a reconstruction at Skoghall Mill had changed the Na/S balance as well as evaluating how a new chemical plant manufacturing the mill’s chlorine dioxide would affect the balance. This was done by analyzing ingoing and outgoing process streams at the mill for sodium and sulfur and using obtained flow data for the period after the reconstruction. A balance was made to simulate how the system behaved at the time as well as balances simulating different shares of bleached pulp being manufactured. Balances with three possible types of chemical plants were also made, as well as calculations of the operating cost for each type of plant. From the balances and the operating costs it was concluded that the HPA process was the most beneficial for the Na/S balance as well as having the lowest operating cost.