scholarly journals Effect of sodium humate on membrane potential in internodal cells of Nitellopsis obtusa

2014 ◽  
Vol 52 (3-4) ◽  
pp. 271-277 ◽  
Author(s):  
Maria Zientara
Keyword(s):  
Membrane Potential ◽  
Low Ph ◽  
Nitellopsis Obtusa ◽  
Sodium Humate ◽  
Ph Range ◽  
Electrophysiological Effects ◽  
External Ph

Membrane potential and resistance changes in <em>Nitellopsis obtusa</em> induced by Na-humate as a function of external pH were investigated. The administration of Na-humate at concentrations of 12.5, 25, 50 and 100 mg dm<sup>-3</sup> brought about a hyperpolarization of the membrane potential and a drop of d.c. resistance in the pH range between 4.0 and 9.0. Depolarization of the membrane potential induced by low pH was counteracted by Na-humate. The electrophysiological effects of Na-humate are compared with those of IAA.

Proton-sulfate cotransport: external proton activation of sulfate influx into human red blood cells

1984 ◽  
Vol 247 (3) ◽  
pp. C247-C259 ◽  
Author(s):  
M. A. Milanick ◽  
R. B. Gunn
Keyword(s):  
Membrane Potential ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Half Cycle ◽  
Ph Values ◽  
Human Red Blood Cells ◽  
Internal Ph ◽  
Ph Range ◽  
External Ph ◽  
Chloride Concentrations

Sulfate influx into human red blood cells was measured at 0 and 22 degrees C at several fixed external pH values between 3 and 10. These cells had normal internal pH and chloride concentrations so that sulfate influx was not limited by the efflux half-cycle reactions. The flux was a Michaelis-Menten function of sulfate concentration at each pH with K1/2SO4 = 4-10 mM. External protons activated influx 100-fold at a single site with a pK = 5.9 at 22 degrees C and 5.5 at 0 degrees C. This pK is similar to the value 5.99 +/- 0.3 for external proton binding to the sulfate-loaded transporter at 0 degrees C (J. Gen. Physiol. 79: 87-114, 1982). The flux was stilbene sensitive even in valinomycin-treated cells and was independent of membrane potential. This proton-activated influx appears to be proton-sulfate cotransport. At high pH there was a proton-independent flux that was membrane potential and stilbene sensitive. This proton-insensitive flux appears to be SO4(2-)/Cl- exchange or net sulfate influx. The sulfate influx over the entire pH range may be described in terms of an equation for the sum of the influxes through these two pathways on band 3.

Acid–base and electrolyte responses to low pH maintained by phosphate–citrate buffers in the bathing medium of the larval salamander Ambystoma tigrinum

1988 ◽  
Vol 66 (11) ◽  
pp. 2383-2389 ◽  
Author(s):  
Marie L. DeRuyter ◽  
Daniel F. Stiffler
Keyword(s):  
Low Ph ◽  
Blood Analysis ◽  
Ambystoma Tigrinum ◽  
Initial Increase ◽  
Bathing Medium ◽  
Arterial Ph ◽  
Ph Range ◽  
External Ph ◽  
Critical Ph ◽  
Pulmonary Excretion

Larval Ambystoma tigrinum were exposed to an external pH of 3.5 to 7.5 using phosphate – citrate buffers in the bathing medium. Blood analysis of cannulated Ambystoma tigrinum at pH 5.5, 4.5, and 3.5 indicated their ability to maintain relatively stable arterial pH at the two higher values; however, at pH 3.5, the blood pH diminished over the 12-h period before death. The greater stability of arterial pH at higher external pH is partially due to a reversal of an initial increase in arterial [Formula: see text]. This may not be due entirely to pulmonary excretion of CO2 as it also occurred in animals that were forced to exchange gases solely across the skin – gill unit by being deprived of access to an air space. This result suggests increased skin – gill perfusion and (or) ventilation as a mechanism for lowering arterial [Formula: see text]. Sodium transport across the skin of A. tigrinum was measured over a buffered pH range of 3.5 to 7.5. Na+ influx decreased from 1.0 ± 0.1 μequiv. 10 g−1 h−1 (mean ± SEM) at pH 7.0 to 0.1 ± 0.1 μequiv. 10 g−1 h−1 at pH 3.5. Na+ efflux increased to 38.1 ± 8.7 μequiv. 10 g−1 h−1 from 4.1 ± 0.9 μequiv. 10 g−1 h−1 as pH declined from 7.0 to 3.5. Calcium added to the buffer at pH 4.5 decreased Na+ efflux at that pH. Na+ fluxes measured in nonbuffered, low-pH solutions revealed qualitatively similar patterns with lower efflux rates and lower critical pH values.

scholarly journals Common Loon, Gavia immer, Breeding Success in Relation to Lake pH and Lake Size Over 25 Years

2009 ◽  
Vol 123 (2) ◽  
pp. 146 ◽  
Author(s):  
Robert Alvo
Keyword(s):  
Breeding Success ◽  
Low Ph ◽  
Single Pair ◽  
Gavia Immer ◽  
Common Loon ◽  
Sulphur Deposition ◽  
Acidic Lakes ◽  
Ph Range ◽  
Lake Size ◽  
Critical Ph

I monitored Common Loon (Gavia immer) breeding success in relation to lake pH (range 4.0–8.5) between 1982 and 2007 on 38 single-pair lakes (5–88 ha) in the Sudbury, Ontario, area. No chicks fledged on lakes with pH < 4.4. Chicks fledged on lakes with slightly higher pH only if the lakes were relatively large. Acidic lakes became less acidic as sulphur dioxide emissions from the Sudbury smelters and sulphur deposition from other long-range sources decreased. Two lakes initially too acidic to support successful loon reproduction eventually had successful reproduction. One loon pair used two large acidic lakes (combined area 140 ha) connected by shallow rapids, and one of the adults made extremely long dives (average = 99 s) while foraging for the chicks. One chick died on that lake after apparently ingesting a very large food item; the lack of smaller items was attributed to the lake’s acidity. My results suggest that a shortage of food for chicks is the main reason why low pH reduces breeding success. I suggest that, for lakes without high levels of dissolved organic carbon (DOC), the critical pH for loon breeding success is approximately 4.3, and the suboptimal pH is approximately 4.4–6.0.

The resting membrane potential of white muscle from brown trout (Salmo trutta) exposed to copper in soft, acidic water

2000 ◽  
Vol 203 (14) ◽  
pp. 2229-2236 ◽  
Author(s):  
M.W. Beaumont ◽  
E.W. Taylor ◽  
P.J. Butler
Keyword(s):  
Membrane Potential ◽  
Brown Trout ◽  
Salmo Trutta ◽  
White Muscle ◽  
Low Ph ◽  
Ammonium Ion ◽  
Muscle Membrane ◽  
Resting Membrane Potential ◽  
Muscle Fibres ◽  
Brown Trout Salmo Trutta

Previously, the distribution of ammonia between the intracellular and extracellular compartments has been used to predict a significant depolarisation of the resting membrane potential (E(M)) of white muscle from brown trout (Salmo trutta) exposed to a sub-lethal combination of copper and low pH. However, this prediction is based upon two assumptions (i) a relatively high membrane permeability for the ammonium ion with respect to that for ammonia gas and (ii) that this is unaltered by exposure to copper and low pH. Since there is conflicting evidence in the literature of the validity of these assumptions, in the present study E(M) was directly measured in white muscle fibres of trout exposed to copper and low pH (E(M)=−52.2+/−4.9 mV) and compared with that of unexposed, control animals (E(M)=−86.5+/−2.9 mV) (means +/− s.e.m., N=6). In confirming the predicted depolarisation, these data support the hypothesis of electrophysiological impairment as a factor in the reduction in the swimming performance of trout exposed to these pollutants. In addition, the results of this study support the role of a significant permeability of the muscle membrane to NH(4)(+) in determining the distribution of ammonia in fish.

pH dependence of kinetics and steady-state block of cardiac sodium channels by lidocaine

1993 ◽  
Vol 264 (5) ◽  
pp. H1588-H1598 ◽  
Author(s):  
D. J. Wendt ◽  
C. F. Starmer ◽  
A. O. Grant
Keyword(s):  
Steady State ◽  
Sodium Channel ◽  
Local Anesthetic ◽  
Ph Dependence ◽  
Membrane Depolarization ◽  
Low Ph ◽  
Proton Exchange ◽  
Phasic Block ◽  
Cardiac Sodium Channels ◽  
External Ph

The local anesthetic-class antiarrhythmic drugs produce greater depression of conduction in ischemic compared with normal myocardium. The basis for this relatively selective action is uncertain. A model of the pH-dependent interaction of tertiary amine drugs with the sodium channel suggests that the low pH occurring during ischemia slows drug dissociation from the channel by changing the drug's protonation. The importance of the proton exchange reaction and the effect of overall slowing of drug dissociation on steady-state sodium channel blockade is uncertain. We have measured whole cell sodium channel current in rabbit atrial myocytes during control and exposure to lidocaine while external pH was varied between 6.8 and 7.8 at membrane potentials of -140, -120, and -100 mV. Tonic blockade was little influenced by external pH. Decreasing the external pH from 7.8 to 6.8 slowed both the rate of development of phasic block and recovery from the block. Decreasing the membrane potential from -140 to -100 mV increased the degree of phasic block attained in the steady state. Block was further enhanced when low pH was combined with membrane depolarization. Experiments in which deuterium ions were substituted for protons suggest that the kinetics of proton exchange is not rate limiting in the dissociation of drugs from the sodium channel. We conclude that it is the combined effect of low pH and membrane depolarization that may be critical in the enhanced blocking action of local anesthetic-class drugs during ischemia.

scholarly journals THE ABSORPTION SPECTRUM OF VISUAL PURPLE

1938 ◽  
Vol 21 (4) ◽  
pp. 411-430 ◽  
Author(s):  
Aurin M. Chase ◽  
Charles Haig
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Light Transmission ◽  
Low Ph ◽  
The Other ◽  
Distilled Water ◽  
Color Purity ◽  
Chemical Combination ◽  
Ph Range ◽  
Sensitive Group

The absorption spectra of visual purple solutions extracted by various means were measured with a sensitive photoelectric spectrophotometer and compared with the classical visual purple absorption spectrum. Hardening the retinas in alum before extraction yielded visual purple solutions of much higher light transmission in the blue and violet, probably because of the removal of light-dispersing substances. Re-extraction indicated that visual purple is more soluble in the extractive than are the other colored retinal components. However, the concentration of the extractive did not affect the color purity of the extraction but did influence the keeping power. This suggests a chemical combination between the extractive and visual purple. The pH of the extractive affected the color purity of the resulting solution. Over the pH range from 5.5 to 10.0, the visual purple color purity was greatest at the low pH. Temperature during extraction was also effective, the color purity being greater the higher the temperature, up to 40°C. Drying and subsequent re-dissolving of visual purple solutions extracted with digitalin freed the solution of some protein impurities and increased its keeping power. Dialysis against distilled water seemed to precipitate visual purple from solution irreversibly. None of the treatments described improved the symmetry of the unbleached visual purple absorption spectrum sufficiently for it to resemble the classical absorption spectrum. Therefore it is very likely that the classical absorption spectrum is that of the light-sensitive group only and that the absorption spectra of our purest unbleached visual purple solutions represent the molecule as a whole.

Electrophysiological effects of GABA on cat pancreatic neurons

2001 ◽  
Vol 280 (3) ◽  
pp. G324-G331 ◽  
Author(s):  
L. Sha ◽  
S. M. Miller ◽  
J. H. Szurszewski
Keyword(s):  
Membrane Potential ◽  
Glial Cells ◽  
Channel Blocker ◽  
Islet Cells ◽  
Sympathetic Ganglia ◽  
Acid Decarboxylase ◽  
Protein Gene Product ◽  
Endogenous Gaba ◽  
Ganglion Neurons ◽  
Electrophysiological Effects

In mammalian peripheral sympathetic ganglia GABA acts presynaptically to facilitate cholinergic transmission and postsynaptically to depolarize membrane potential. The GABA effect on parasympathetic pancreatic ganglia is unknown. We aimed to determine the effect of locally applied GABA on cat pancreatic ganglion neurons. Ganglia with attached nerve trunks were isolated from cat pancreata. Conventional intracellular recording techniques were used to record electrical responses from ganglion neurons. GABA pressure microejection depolarized membrane potential with an amplitude of 17.4 ± 0.7 mV. Electrically evoked fast excitatory postsynaptic potentials were significantly inhibited (5.4 ± 0.3 to 2.9 ± 0.2 mV) after GABA application. GABA-evoked depolarizations were mimicked by the GABAA receptor agonist muscimol and abolished by the GABAA receptor antagonist bicuculline and the Cl− channel blocker picrotoxin. GABA was taken up and stored in ganglia during preincubation with 1 mM GABA; β-aminobutyric acid application after GABA loading significantly ( P < 0.05) increased depolarizing response to GABA (15.6 ± 1.0 vs. 7.8 ± 0.8 mV without GABA preincubation). Immunolabeling with antibodies to GABA, glial cell fibrillary acidic protein, protein gene product 9.5, and glutamic acid decarboxylase (GAD) immunoreactivity showed that GABA was present in glial cells, but not in neurons, and that glial cells did not contain GAD, whereas islet cells did. The data suggest that endogenous GABA released from ganglionic glial cells acts on pancreatic ganglion neurons through GABAA receptors.

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