Potassium chloride: absorption and excretion

The absorption of potassium chloride in liquid form has been studied, using urinary excretion as an index of absorption. The excretion of potassium chloride was observed after inducing a water diuresis and administering a single dose in liquid form. There is evidence that potassium chloride in liquid form is absorbed rapidly, probably from the stomach, and hence there is a good rationale for its use where rapid absorption is needed, as in digitalis intoxication.     

Thiocyanate inhibition of active chloride absorption in Aplysia intestine

This investigation was principally undertaken to examine the mechanism of active chloride absorption across the Aplysia californica intestine by using various inhibitors of ion transport. Isolated intestine, mounted between identical oxygenated sodium-free seawater solutions, maintained stable transmural potential differences (serosa negative) and short-circuit currents for several hours at 25 degrees C. The metabolic inhibitors, 2,4-dinitrophenol and fluoride, reduced both transmural potential difference and short-circuit current; however, the electrical characteristics were predominantly dependent upon glycolytic energy. The addition of thiocyanate to the mucosal solution inhibited both electrical characteristics in parallel, and this inhibition could be titrated according to the thiocyanate concentration. The short-circuit current was carried wholly by a net active chloride transfer from mucosa to serosa as determined by flux measurements. These results suggest that active chloride absorption may be mediated by a primary active transport process.     

Intracellular chloride activities and active chloride absorption in the intestinal epithelium of the winter flounder

Summary Intracellular chloride activities, (Cl) _c , and the electrical potential difference across the mucosal membrane, _mc, were determined in the isolated small intestine of the winter flounder, using Cl-selective and conventional (KCl-filled) microelectrodes. In the presence of a Na-containing buffer _mc averages –69mV and (Cl) _c averages 24mM, a value that is 3.4 times that predicted for an equilibrium distribution across the mucosal membrane. On the other hand, when the tissue is then perfused with Na-free buffer, (Cl) _c slowly falls to a value that does not differ significantly from that predicted for an equilibrium distribution, and _mc depolarizes significantly. Finally, when the tissue is again bathed in the Na-containing buffer, (Cl) _c rapidly returns to a value well above equilibrium.These results, together with those of Frizzellet al. (J. Membrane Biol. 46:27, 1979), provide direct evidence that: (1) Cl is accumulated against its electrochemical potential difference (32mV) by this tissue, and (2) this accumulation is coupled to and energized by the entry of Na down its steep electrochemical potential difference.     

The induction of cyanide-resistant respiration in Hansenula anomala

Cyanide-resistant respiration was induced in the yeast, Hansenula anomala in the presence of cyanide or antimycin A, which blocks the electron transport after ubiquinone. The de novo protein synthesis in cytosol and oxygen were deduced to be involved in this induction process. The period required for the induction varied during the growth stage, suggesting that involvement of additional physiological factor(s) in this induction process. The organism could multiply in the presence of antimycin A by developing cyanide-resistant respiration despite a decreased growth rate.     

GABA responses in rat dentate granule neurons are mediated by chloride

The dendrites of granule cells in hippocampal slices responded to gamma-aminobutyric acid (GABA) with a depolarization. The response was blocked by picrotoxin in a noncompetitive manner. Reductions in the extracellular chloride ion concentration changed the reversal potential of the response by an amount predicted from the Nernst equation for chloride ion. Chloride-dependent hyperpolarizing responses were sometimes also found in the cell body of the granule cells. Since the reversal potential followed that predicted from the Nernst equation for chloride, we conclude that the response was mediated by chloride ions alone with no contribution from other ions. This has not previously been shown for the depolarizing response to GABA in central neurons.     

Stress situations induce cyanide-resistant respiration in spoilage yeasts

AIMS: To investigate the conditions that promote the expression of cyanide-resistant respiration (CRR) in the spoilage yeasts Pichia membranifaciens and Debaryomyces hansenii. METHODS AND RESULTS: CRR was detected by sensitivity of oxygen consumption to salicylhydroxamic acid. It was absent in both yeasts in the early exponential phase, but was triggered by several stress situations. Starvation under aerobic conditions, decreasing pH or incubation of the culture in a narrow temperature range below the maximum temperature for growth promoted the emergence of CRR in both yeasts. In D. hansenii, CRR was also induced by 1.5-2 mol l(-1) NaCl. Although the presence of H2O2 and menadione induced CRR, radical scavengers had no effect on the emergence of CRR. Also, the level of reactive oxygen species did not vary with the CRR activity. CONCLUSIONS: Under aerobic conditions, a respiratory pathway alternative to the cytochrome chain is triggered by stress conditions in P. membranifaciens and D. hansenii. SIGNIFICANCE AND IMPACT OF THE STUDY: The relationship between stress situations and CRR must be taken into account in studies on the performance of spoilage yeasts in the food processing environments where several forms of stress are common.     

D-Erythroascorbic acid activates cyanide-resistant respiration in Candida albicans

Higher plants, protists and fungi possess cyanide-resistant respiratory pathway, which is mediated by alternative oxidase (AOX). The activity of AOX has been found to be dependent on several regulatory mechanisms including gene expression and posttranslational regulation. In the present study, we report that the presence of cyanide in culture medium remarkably retarded the growth of alo1/alo1 mutant of Candida albicans, which lacks d-arabinono-1,4-lactone oxidase (ALO) that catalyzes the final step of d-erythroascorbic acid (EASC) biosynthesis. Measurement of respiratory activity and Western blot analysis revealed that increase in the intracellular EASC level induces the expression of AOX in C. albicans. AOX could still be induced by antimycin A, a respiratory inhibitor, in the absence of EASC, suggesting that several factors may act in parallel pathways to induce the expression of AOX. Taken together, our results suggest that EASC plays important roles in activation of cyanide-resistant respiration in C. albicans.     

Increased template activity in chromatin from cadmium chloride treated pea tissues

Increases in the synthesis of the isoflavonoid, pisatin, and the activity of phenylalanine ammonia lyase (PAL) are induced in excised pea pods by low concentrations (5×10^?4M) of CdCL₂. The induction of pisatin synthesis and PAL are suppressed if RNA-synthesis-inhibiting concentrations of 6-methyl purine, actinomycin D or ∝-amanitin are applied within 1 h of inducer application. Cycloheximide (0.1 mg/ml) blocks the induction of these responses if applied to tissues within 6 h after inducer application. Within 1 h after CdCl₂ (5×10^?4M) is applied to pods there is an increase in the rate of synthesis of all sizes of RNA as well as an increase in the template activity and dye binding capacity of pea chromatin. The results support the hypothesis that conformational changes in DNA are associated with the induction process.     

The general fluid circuit theory of active chloride absorption

The original fluid circuit theory used to explain active intestinal absorption of chloride is modified to include diffusion and secretion of chloride and osmosis. The general differential equation developed is integrated in a particular case. The definition, “effective concentration of chloride in the fluid passing into the intestinal lumen,” leads to simplified general expressions.     

Response-velocity of chloride absorption by barley roots to oligomycin

Chloride absorption by excised barley roots is significantlyinhibited within the first 2 min of incubation in oligomycin.A steady inhibited absorption rate is attained in the presenceof oligomycin after 10 min (Received February 18, 1970; )     

Salicylic Acid induces cyanide-resistant respiration in tobacco cell-suspension cultures

Cyanide-resistant, alternative respiration in Nicotiana tabacum L. cv Xanthi-nc was analyzed in liquid suspension cultures using O₂ uptake and calorimetric measurements. In young cultures (4-8 d after transfer), cyanide inhibited O₂ uptake by up to 40% as compared to controls. Application of 20 μm salicylic acid (SA) to young cells increased cyanide-resistant O₂ uptake within 2 h. Development of KCN resistance did not affect total O₂ uptake, but was accompanied by a 60% increase in the rate of heat evolution from cells as measured by calorimetry. This stimulation of heat evolution by SA was not significantly affected by 1 mm cyanide, but was reduced by 10 mm salicylhydroxamic acid (SHAM), an inhibitor of cyanide-resistant respiration. Treatment of SA-induced or uninduced cells with a combination of cyanide and SHAM blocked most of the O₂ consumption and heat evolution. Fifty percent of the applied SA was taken up within 10 min, with most of the intracellular SA metabolized in 2 h. 2,6-Dihydroxybenzoic and 4-hydroxybenzoic acids also induced cyanide-resistant respiration. These data indicate that in tobacco cell-suspension culture, SA induces the activity and the capacity of cyanide-resistant respiration without affecting the capacity of the cytochrome c respiration pathway.     

Quantitative viability of seaweed tissues assessed with 2,3,5-triphenyltetrazolium chloride

A spectrophotometric quantification method was optimized to evaluate its utility in seaweed tissue viability tests using the enzymatic reduction of colorless 2,3,5-triphenyltetrazolium chloride (TTC) to a colored triphenylformazan (TPF). To allow accurate determination of TPF in the seaweed Porphyra thallus and conchocelis, 0.2 g of tissues are incubated with 4 mL of 0.8% TTC reagent in the dark at 20°C for 1 h under a mineral oil layer. The TPF formed in tissues was extracted for 15 min at 60°C with 2 mL of 0.2 N KOH in 25% ethanol. Then TPF is partitioned away by prompt addition of hexane and vortexing. By this procedure, we have observed nearly complete separation of TPF, and observed good spectrophotometric discrimination between TPF and other hexane-soluble pigments at 545 nm. This procedure has proved applicable to a wide range of seaweed taxa; 1 species of Chlorophyta, 4 species of Phaeophyta and 7 species of Rhodophyta tested. This revised version was published online in June 2006 with corrections to the Cover Date.