In several tissues ammonium ions are able to use the transport pathways of other ions, particularly of K+. We investigated this possibility in the C11 clone of MDCK cells, thought to represent intercalated cells, in control and 0 Cl- conditions. Cell pH was measured by ratiometric fluorescence microscopy using the pH indicator BCECF. After preincubating the cells for 10 min in control or 0 Cl- (substituted by gluconate) Ringer, an ammonium pulse was applied to induce cell acidification. The magnitude of the initial alkalinization (DeltapH) was 0.24+/-0.03 ( n=28) pH units in controls, which fell to 0.023+/-0.01 ( n=12) in 0 Cl-, suggesting uptake of NH4+ balancing the alkalinization by NH3. Addition of 10(-3) M bumetanide or furosemide to the 0 Cl- medium, or 10(-4 )M hexamethylene amiloride, did not alter DeltapH. However, with 5 mM Ba+, DeltapH increased to 38% of control. When 2.5x10(-4) M ouabain, an inhibitor of Na+-K+ ATPase, was used, DeltapH increased to 46% of control. Inhibition of H+-K+ ATPase by SCH28080 or by omeprazol caused significant increase in DeltapH. In 0 Cl- solution, these cells underwent a mean volume reduction (-d V) of -10.24+/-1.96% per 10 min as measured by confocal microscopy. To investigate if NH4+ influx was regulated by cell volume or by cell Cl-, volume reduction was avoided by two procedures. When preincubating with NPPB, a Cl- channel blocker, in 0 Cl-, volume reduction was inhibited (d V=-2.12% per 10 min), and DeltapH was 0.24+/-0.04 ( n=5). When the cells were preincubated in hypotonic 0 Cl- (260 mosmol/l), cell volume reduction was abolished (d V=+2.6% per 10 min) and DeltapH was 0.52+/-0.07 ( n=7). Thus, activation of NH4+ influx by several transporters was due to volume reduction rather than to [Cl-] alteration.
5Exposure to damaging levels of noise is the most common cause of hearing loss and 1 6impairs high frequency hearing in more than 15 % of adult Americans. Using mice exposed 1 7to increasing levels of noise in combination with quantitative proteomics, we tested how 1 8 noise insults remodel the cochlear proteome both acutely and after a two-week recovery
<p></p><p>Novel
methyl and methoxy tri, tetra, penta ring-substituted isobutyl
phenylcyanoacrylates, RPhCH=C(CN)CO<sub>2</sub>CH<sub>2</sub>CH(CH<sub>3</sub>)<sub>2</sub><sub> </sub>, where R is 2,4,5-trimethyl, 2,4,6-trimethyl, 2,3,5,6-tetramethyl, pentamethyl,
2,3-dimethyl-4-methoxy, 2,5-dimethyl-4-methoxy, 2,4-dimethoxy-3-methyl, 2,4-dimethoxy-6-methyl
were synthesized by the piperidine catalyzed Knoevenagel condensation of
ring-substituted benzaldehydes and isobutyl cyanoacetate and characterized by
CHN analysis, IR, <sup>1</sup>H and <sup>13</sup>C NMR. The acrylates were
copolymerized with styrene in solution with radical initiation (ABCN) at 70°C. The compositions of the copolymers were calculated
from nitrogen analysis. </p><br><p></p>
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