Hasil untuk "physics.atom-ph"

D. Perrin, B. Dempsey

B. Poole, S. Ohkuma

The spectral characteristics of dextran, labeled with fluorescein, depend upon pH. We have loaded the lysosomes of mouse peritoneal macrophages with this fluorescence probe and used it to measure the intralysosomal pH under various conditions. The pH of the medium has no effect on the intralysosomal pH. Weakly basic substances in the medium cause a concentration-dependent increase in the intralysosomal pH. However, the concentration of base necessary to produce a significant change in the intralysosomal pH varies over a wide range for different bases. The active form of the base is the neutral, unprotonated form. Although most of these weak bases cause an increase in the volume of the lysosomes, increase in lysosomal volume itself causes only a minor perturbation of the intralysosomal pH. This was demonstrated in cells whose lysosomes were loaded with sucrose, and in cells vacuolated as a demonstrated in cells whose lysosomes were loaded with sucrose, and in cells vacuolated as a consequence of exposure to concanavalin A. The results of these studies are interpreted in terms of energy-dependent lysosomal acidification and leakage of protons out of the lysosomes in the form of protonated weak bases.

J. Skehel, P. Bayley, E. Brown et al.

J. Raven, F. A. Smith

W. Busa, R. Nuccitelli

W. Moolenaar, R. Tsien, P. Saag et al.

B. S. Stein, B. S. Stein, S. D. Gowda et al.

K. J. Ellis, J. Morrison

R. Naidu, N. Bolan, R. Kookana et al.

M. Chesler, K. Kaila

J. Jamieson, H. Stein, T. Demeester et al.

J. Elliott, Mara L Macdonald, J. Nie et al.

B. Zaid, D. Saidi, A. Benzaid et al.

Yi Liu, Vyacheslav S. Bryantsev, M. S. Diallo et al.

Yuping Li, Amran K. Asadi, M. Monroe et al.

S. Baruah, J. Dutta

A. Dhaka, V. Uzzell, A. Dubin et al.

Maintaining physiological pH is required for survival, and exposure to alkaline chemicals such as ammonia (smelling salts) elicits severe pain and inflammation through unknown mechanisms. TRPV1, the capsaicin receptor, is an integrator of noxious stimuli including heat and extracellular acidic pH. Here, we report that ammonia activates TRPV1, TRPA1 (another polymodal nocisensor), and other unknown receptor(s) expressed in sensory neurons. Ammonia and intracellular alkalization activate TRPV1 through a mechanism that involves a cytoplasmic histidine residue, not used by other TRPV1 agonists such as heat, capsaicin or low pH. Our studies show that TRPV1 detects both acidic and basic deviations from homeostatic pH.

A. Hoštacká, I. Čižnár, M. Štefkovičová

C. Wagner, N. Mohebbi

The formation of various types of kidney stones is strongly influenced by urinary pH. An alkaline pH favors the crystallization of calcium- and phosphate-containing stones, whereas and acidic urine pH promotes uric acid or cystine stones. The activity of many transport processes involved in calcium, citrate and phosphate handling are sensitive to changes in systemic or local pH as shown for several phosphate transporters, the citrate transporter NaDC1 and the TRPV5 calcium channel. Defects in urinary acidification (excretion of inappropriately alkaline or acidic urines, respectively) contribute to kidney stone disease. The low excretion of ammonium in patients with metabolic syndrome has been linked to more acidic urine and a higher incidence of uric acid stones. In this state, insulin resistance may reduce ammonium excretion by the proximal tubule. On the other hand, defensive mechanisms may protect from kidney stone formation in conditions such as hypercalciuria where high luminal calcium concentrations stimulate urinary acidification and reduce urinary concentration via a calcium-sensing receptor, resulting in the excretion of acidic and diluted urine. This review will discuss a few aspects that relate to the capacity of the kidney to regulate pH and its impact on the excretion of solutes that participate in the formation or prevention of stones.

D. Himmel, Sascha K. Goll, I. Leito et al.