The hyperpolarizing effect of hydrogen ions on transmembrane potential in frog skeletal muscle

1968 ◽  
Vol 46 (2) ◽  
pp. 151-157 ◽  
Author(s):  
G. W. Mainwood ◽  
S. L. Lee
Keyword(s):  
Transmembrane Potential ◽  
Ph Effect ◽  
Cell Activity ◽  
Ringer Solution ◽  
Buffer System ◽  
Hydrogen Ions ◽  
Transmembrane Conductance ◽  
Metabolic Conditions ◽  
External Potassium ◽  
Hyperpolarizing Response

The transmembrane potential of frog sartorius fibers in normal Ringer's solution is increased by a few millivolts following a fall in pH of the external medium. The same result is observed in either a bicarbonate–CO2 or a phosphate buffer system. The hyperpolarizing response is still observed when sodium in the Ringer solution is replaced by choline. Immediately after increasing the external potassium from 2.5 to 10 meq/l this effect is reversed. On changing the external potassium back to 2.5 meq/l the effect returns and is considerably enhanced. Chloride loading by presoaking muscles in isotonic KCl and transferring to sucrose causes a reversal of membrane potential and leads to an exaggerated pH effect. These observations, together with the fact that transmembrane conductance falls at a lower pH, suggest that hydrogen ions act mainly by lowering PCl. When ECl > Em, hydrogen ions will increase transmembrane potential. This effect may form the basis of a local control mechanism by which cell activity and local metabolic conditions regulate transmembrane potential.

scholarly journals Physiological roles of nicotinamide nucleotide transhydrogenase

1988 ◽  
Vol 254 (1) ◽  
pp. 1-10 ◽  
Author(s):  
J B Hoek ◽  
J Rydström
Keyword(s):  
Redox Potential ◽  
Buffer System ◽  
Emergency Protection ◽  
High Demand ◽  
Energy Depletion ◽  
Flexible Element ◽  
Metabolic Conditions ◽  
Effective Buffer ◽  
Kinetic Features ◽  
Reducing Equivalents

From the foregoing considerations, the energy-linked transhydrogenase reaction emerges as a powerful and flexible element in the network of redox and energy interrelationships that integrate mitochondrial and cytosolic metabolism. Its thermodynamic features make it possible for the reaction to respond readily to challenges, either on the side of NADPH utilization or on the side of energy depletion. Yet, the kinetic features are designed to prevent a wasteful input of energy when other sources of reducing equivalents to NADP are available, or to deplete the redox potential of NADPH in other than emergency conditions. By virtue of these characteristics, the energy-linked transhydrogenase can act as an effective buffer system, guarding against an excessive depletion of NADPH, preventing uncontrolled changes in key metabolites associated with NADP-dependent enzymes and calling on the supply of reducing equivalents from NAD-linked substrates only under conditions of high demand for NADPH. At the same time, it can provide an emergency protection against a depletion of energy, especially in situations of anoxia where a supply of reducing equivalents through NADP-linked substrates can be maintained. The flexibility of this design makes it possible that the functions of the energy-linked transhydrogenase vary from one tissue to another and are readily adjustable to different metabolic conditions.

Radiolysis of aqueous chloroform solutions

1970 ◽  
Vol 48 (2) ◽  
pp. 271-276 ◽  
Author(s):  
B. J. Rezansoff ◽  
K. J. McCallum ◽  
R. J. Woods
Keyword(s):  
Oxalic Acid ◽  
Formic Acid ◽  
Hydroxyl Radicals ◽  
Ph Effect ◽  
Hydrogen Ions ◽  
Γ Radiation ◽  
High Ph ◽  
Hydrated Electrons ◽  
Presence And Absence ◽  
Ph Range

Saturated aqueous chloroform solutions (0.07 M) with pH ranging from 0.8 to 12.6 have been irradiated with 60Co γ-radiation in the presence and absence of air. G(Cl− + ClO−) increases with increasing pH in the pH range 1–3 (aerated solutions) or 3–6 (deaerated solutions) and again at pH greater than 10.5. The variation in yield from aerated solutions in the region pH 1–3 is attributed to competition between chloroform and hydrogen ions for hydrated electrons. However, such competition cannot account for the pH effect observed in deaerated solutions between pH 3 and 6. Increased yields from both aerated and deaerated solutions at high pH are attributed to the formation of O− by reaction of hydroxyl radicals and hydroxide ions. Formic acid and oxalic acid have been identified as minor products when aerated chloroform solutions are irradiated.

scholarly journals Using Choline Chloride-Based DESs as Co-Solvent for 3,5-Bis(trifluoromethyl) Acetophenone Bioreduction with Rhodococcus erythropolis XS1012

Catalysts ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 30 ◽  
Author(s):  
Chen ◽  
Qian ◽  
Lin ◽  
Chen ◽  
Wang
Keyword(s):  
Substrate Concentration ◽  
Choline Chloride ◽  
Cell Activity ◽  
Great Influence ◽  
Rhodococcus Erythropolis ◽  
Deep Eutectic Solvents ◽  
Cell Membrane Permeability ◽  
Buffer System ◽  
High Substrate Concentration ◽  
Reaction Conditions

(S)-3,5-Bistrifluoromethylphenyl ethanol((S)-BTPE) is a key pharmaceutical intermediate of the NK-1 receptor antagonist. The asymmetric bioreduction of 3,5-bis(trifluoromethyl) acetophenone (BTAP) to (S)-BTPE using Rhodococcus erythropolis XS1012 has been established in a phosphate buffer system. To overcome the problem of unsatisfactory yields at high substrate concentration, deep eutectic solvents (DESs) have been introduced to the buffer system. After screening 13 kinds of choline chloride-based DESs, [choline chloride][urea] ([ChCl][U]) showed great influence on the cell activity and significantly increased the cell membrane permeability. Subsequently, some major parameters for this reaction were determined. A remarkable (S)-BTPE yield of 91.9% was gained at 150 mM substrate concentration under optimized reaction conditions with >99.9% product enantioselectivity. Compared to reduction in a buffer system, the developed [ChCl][U]-containing system increased the yield from 82.6% to 91.9%. It maintains a yield of 80.7% with the substrate concentration up to 300 mM, compared to only 63.0% in buffer system. This study demonstrated that [ChCl][U] is a feasible co-solvent to improve the bioreduction process.

Effects of CO-2 and extracellular H+ iontophoresis on single cell activity in the cat brainstem

1975 ◽  
Vol 38 (4) ◽  
pp. 688-695 ◽  
Author(s):  
P. L. Marino ◽  
T. W. Lamb
Keyword(s):  
Single Cell ◽  
Medulla Oblongata ◽  
Single Cells ◽  
Cell Activity ◽  
Hydrogen Ion ◽  
Hydrogen Ions ◽  
Peripheral Chemoreceptor ◽  
Single Cell Activity ◽  
Medullary Neurons

The activity of single cells in deep regions of the medulla oblongata was observed both during CO2 inhalation and during the extracellular iontophoresis of hydrogen ions in peripheral chemoreceptor-denervated cats. All 53 neurons that fired in synchrony with some part of the ventilatory cycle showed increased firing during CO2 inhalation; yet none responded in a graded fashion to the extracellular application of hydrogen ions. Seventy-one of the 74 nonperiodic cells studied showed no response to CO2 inhalation. Of the 3 nonperiodic cells that did respond to CO2, 2 also responded in a graded fashion to the extracellular iontophoresis of hydrogen ions. It is concluded that the cell bodies of medullary neurons with respiratory periodicity are relatively insensitive to hydrogen ions. Further the paucity of hydrogen ion-sensitive cells found in deep areas of the medulla does not support the notion that medullary hydrogen ion chemoreception is largely achieved by structures located deep in the lower brainstem.

scholarly journals Effect of Hydrogen Ion Presence in Adsorbent and Solution to Enhance Phosphate Adsorption

2021 ◽  
Vol 11 (6) ◽  
pp. 2777
Author(s):  
Taehoon Kim ◽  
Byungryul An
Keyword(s):  
Hydrochloric Acid ◽  
Adsorption Mechanism ◽  
Ph Effect ◽  
Total Surface Area ◽  
Point Of Zero Charge ◽  
Phosphate Adsorption ◽  
Hydrogen Ions ◽  
Solution Ph ◽  
Initial Ph ◽  
Ph Range

In this paper, the effect of hydrogen ions on the adsorption onto granular activated carbon (GAC) with the inorganic contaminant phosphate, which exists as a form of four species depending on the solution pH, is investigated. Various batch isotherm and kinetic experiments were conducted in an initial pH 4 as an acid, a pH 7 as neutral, and a pH 9 solution as a base for the GAC conditioned with deionized water and hydrochloric acid, referred to as GAC and GACA, respectively. The physical properties, such as the total surface area, pore volume, pore size distribution, and weight of the element, obtained from Brunauer–Emmett–Teller (BET) and scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM–EDX) represent no significant differences. However, the hydrochloric acid (HCl) condition results in an alteration of the pH of the point of zero charge from 4.5 to 6.0. The optimized initial pH was determined as being acid for the GAC and as being neutral for the GACA. According to the Langmuir isotherm, the relatively high Qm was obtained as being acid for the GAC and clearly distinguishes the pH effect as being the base for the GACA. An attempt was made to assess the adsorption mechanism using the pseudo-first-order (PFO), the pseudo-second-order (PSO), and the intraparticle diffusion models. The higher R2 for the PSO in the entire pH range indicated that chemisorption was predominant for phosphate adsorption, and the pH did not change the adsorption mechanism. A prolonged Bed Volume (BV) for the GACA demonstrated that the hydrogen ions on the surface of the GAC enhanced phosphate adsorption.

scholarly journals Biochemistry in the context of Beer Science

2019 ◽  
Vol 17 ◽  
pp. 110
Author(s):  
Gabriel Gerber Hornink
Keyword(s):  
Group Work ◽  
Ph Effect ◽  
Buffer System ◽  
Buffer Effect ◽  
Practical Applications ◽  
Fermentative Metabolism ◽  
Ph Buffer ◽  
Beer Production ◽  
Structure And Metabolism

Biochemistry contents are essentials to understanding brewing and students often fail to connect theory with practical applications, in this context, the discipline Beer Science was created, complimenting students` formation. The objective was to integrate the knowledge of biochemistry in beer production and evaluate the students' perception of importance of these. The discipline was given in 2017 and 2018, 24 students per class, with the prerequisite being Biochemistry approval. A didactic sequence was created, starting from the historical aspects and ending with a real beer production. Mains concepts: ph and buffer system; carbohydrates, proteins and lipids in the malt; hops oils/composition; malt and yeast enzymes; fermentative metabolism etc. A questionnaire was applied at the end of the course, evaluating students' perceptions about it, in addition, they delivered a group work simulating a production. Besides the lectures and exercises, 7 practical classes were created, involving the supplies characteristics, mashing buffer effect, temperature and pH effect on the mashing enzymes. There were 31 responses and the students felt very motivated and all considered the biochemical knowledges vital for brewing understanding, attributing greater importance to enzymes and fermentations knowledges, sequentially, to pH, buffer and carbohydrates structure and metabolism. The students emphasized the role of practical classes in order to establish the connections between biochemistry theory and beer production, highlighting the mashing comparison from a matrix of two pH and three temperatures, evaluating the starch hydrolysis with lugol, the amount of fermentable substrate by benedict reaction, and the density by light refractometer. The simulations evaluation indicated that practically all groups were able to apply theoretical knowledge. It is noteworthy that most students felt capable of brewing beer. Disciplines like this are fundamental for the connection between biochemical knowledge and practical applications, such as brewing, especially when developing practices that make this integration possible.

Effects of synthetic buffers on reflexes in the isolated frog spinal cord

1975 ◽  
Vol 229 (3) ◽  
pp. 831-837 ◽  
Author(s):  
RA Davidoff ◽  
ES Sears
Keyword(s):  
Spinal Cord ◽  
Dorsal Root ◽  
Ringer Solution ◽  
Membrane Properties ◽  
Buffer System ◽  
Bicarbonate Buffer ◽  
Frog Spinal Cord ◽  
Dorsal Root Reflex ◽  
Dorsal Root Potentials

Substitution of synthetic buffers (Tris, TES, HEPES, or 3,3-dimethylglutarate) for CO2-bicarbonate buffer in Ringer solution perfusing the isolated in vitro frog spinal cord preparation altered membrane properties and reflex activity. Perfusion with Ringer solution gassed with O2 and containing synthetic bu,fers consistently produced a depolarization of motoneurons and dorsal root fibers, decreased the amplitude (and usually the duration) of ventral and dorsal root potentials, and had variable effects on motoneuron and dorsal root reflex discharges. With Tris-Ringer these discharges decreased in amplitude; with Ringer containing one of the other synthetic buffers, these discharges were augmented. All changes were reversible when the cord was returned to bicarbonate-buffered Ringer aerated with 95% O2/5% CO2. The use of a combined buffer system-one containing a synthetic buffer and bicarbonate-induced smaller or minimal changes in bioelectric activity. At present the data are insufficient to allow firm conclusions concerning the mechanisms underlying these results; but it is evident 1) that changes in PCO2 and bicarbonate concentration and 2) that the pharmacological properties of synthetic buffers are important variables.

scholarly journals THE EFFECT OF HYDROGEN ION CONCENTRATION UPON THE INDUCTION OF POLARITY IN FUCUS EGGS

1938 ◽  
Vol 21 (6) ◽  
pp. 833-845 ◽  
Author(s):  
D. M. Whitaker
Keyword(s):  
Sea Water ◽  
Co2 Concentration ◽  
Growth Substance ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Buffer System ◽  
Hydrogen Ions ◽  
Morphological Response ◽  
Hydrogen Ion Concentration ◽  
Chemical Action

1. Gradients of hydrogen ion concentration across Fucus eggs growing in sea water determine the developmental polarity of the embryo. 2. Gradients may determine polarity even if removed before the morphological response begins. 3. The rhizoid forms on the acid side of the egg unless this is too acid, in which case it develops on the basic side of the egg. 4. Since gradients of hydrogen ion concentration in sea water produce gradients of CO2 tension, as a result of chemical action on the carbonate buffer system, it is not proven whether the physiological effects are due to the hydrogen ions, or to the CO2 which they produce in the medium. 5. The developmental response of the eggs to gradients of hydrogen ion (or CO2) concentration provides an adequate but not an exclusive explanation of the group effect in Fucus. 6. Hydrogen ions may exert their effect by activating growth substance. Hydrogen ions or CO2 probably also affect the underlying rhizoid forming processes in other ways as well.

THE INTERCONNECTION BETWEEN ACTIVE TRANSPORT AND CONTRACTURE IN UTERINE TISSUES

1964 ◽  
Vol 42 (4) ◽  
pp. 453-495 ◽  
Author(s):  
E. E. Daniel
Keyword(s):  
Active Transport ◽  
Energy Supply ◽  
Calcium Influx ◽  
Rhythmic Activity ◽  
Ringer Solution ◽  
Potassium Depletion ◽  
Glycogen Depletion ◽  
Potassium Loss ◽  
Uterine Muscle ◽  
External Potassium

A study of the effects of several procedures known to interfere with active transport in rat, rabbit, and cat uterine muscle has revealed certain differences between muscles and between inhibitory procedures. Ouabain, fluoride, and sudden cooling caused an initial contracture followed by subsequent loss of contractility in circumstances in which they inhibit active transport. Removal of external potassium increased and subsequently decreased isometric contractions at 37 °C of rat and cat uterine segments, and in most of rat uterine horns caused contracture at 24 °C followed by relaxation and loss of contractility. The parallelism between the initial contracture and inhibition of active transport extends to the necessity for a concentration of 10−4 M to 10−3 M ouabain for initiation of both in rat uteri in contrast to the effectiveness of 10−7 M to 10−5 M in rabbit and cat uteri. The contracture induced by ouabain in rat uteri was potentiated by a decrease in external potassium and prevented by an increase. Removal of the glucose from the medium for 1 to 2 minutes potentiated both ouabain and potassium depletion contractures, but did not significantly increase potassium loss. Lower concentrations of NaF caused contracture in the absence of glucose. The contractures induced by NaF and by cold were obtained in uteri depolarized by K2SO4 Ringer solution and none were prevented by selective antagonists to acetylcholine, adrenaline, histamine, or serotonin. All the procedures producing contracture were ineffective in uteri depleted of calcium. All are known to interfere with the activity of the Mg- and Na + K-activated membrane ATPase believed to be involved in active transport. Therefore, it is proposed that inhibition of this enzyme in uteri causes contracture. In view of other work, this is presumed to occur by failure of active extrusion or failure of binding of calcium at the cell surface leading to a net calcium influx. The potentiation of contractures by removal of glucose occurs too rapidly to derive from glucose or glycogen depletion and is attributed to interaction between glucose transport and cation transport mechanisms.In contrast to ouabain, fluoride, potassium depletion, and cold, iodoacetate and dinitrophenol inhibit active transport and contractility in uterine muscle without causing an initial contracture. It is proposed that these substances act either by decreasing energy supply or by acting at a non-membrane site different from that at which substances causing contracture act. Cyanide was less effective as an inhibitor of either process, and oxidative metabolism is presumed not to be essential for energy supply in these tissues. In general, the loss of ability of uterine muscle to contract on chemical stimulation was directly related to the extent of potassium depletion. Both potassium depletion and loss of contractility were attributed to decreased energy supply.Ouabain in concentrations insufficient to cause contracture or potassium loss in rat uteri prevented rhythmic activity.

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