Changes In Surface pH Research Articles

A method of producing calibrated microtubules for air embolism studies.

Utilizing the differential absorption techniques in conjunction with gas injection methods has enabled the production of calibrated microtubules with diameters ranging from 14 to 300 micron. Nitrogen was blended with CO2, the "diluent" gas, to produce the initial bubbles, while tris(hydroxymethyl)-aminomethane hydrochloride (THAM) was used as an absorbent to remove the diluent gas from the bubbles. Hence, the diameters of the initial bubbles were significantly reduced with only the inert gas remaining. The Coulter counter was used for immediate size monitoring of the microtubules. To verify the inertness of the absorbent medium, nine anesthetized dogs were infused with increasing amounts of the solution. In five of the animals plasma surface tension and pH (arterial) were measured, while in the remaining four arterial blood pressure, heart rate, breathing frequency, and pulmonary artery pressure was measured before, during, and after the injections. Changes in plasma surface tension and pH were minimal while acceptable physiological values were recorded, all of which were in agreement with previous investigations. Differential absorption techniques provided a reliable means for producing calibrated micro-bubbles for air embolism studies.

Cathodic reduction of glucose

The cathodic reduction of D-glucose was studied on Pb, Ni, Zn and Cd cathodes at three pH values in aqueous solution. The effect of cathode geometry and flow rate were also examined. Partial reduction current densities were obtained by g.l.c. analysis of the derivatised products. Current interruption and resumption, as well as runs using pretreated and untreated cathodes, all tend to suggest the presence of a surface film formed on the cathode during reductions. From these results and a re-interpretation of the data of other workers, a mechanism is proposed involving the near-electrode surface pH change, with the Tafel slope and reaction rate further altered by the solid formed at the cathode surface.

Salt-induced pH changes in spinach chloroplast suspension. Changes in surface potential and surface pH of thylakoid membranes

A pH decrease in chloroplast suspension in media of low salt concentration was observed when a salt was added at pH values higher than 4.4, while at lower pH values a pH increase was observed. The salt-induced pH changes depended on the valence and concentration of cations of added salts at neutral pH values (higher than 4.4) and on those of anions at acidic pH values (lower than 4.4). The order of effectiveness was trivalent > divalent > monovalent. The pH value change by salt addition was affected by the presence of ionic detergents depending on the sign of their charges. These characteristics agreed with those expected from the Gouy-Chapman theory on diffuse electrical double layers. The results were interpreted in terms of the changes in surface potential, surface pH and the ionization of surface groups which result in the release (or binding) of H + to (or from) the outer medium. The analysis of the data of KCl-induced pH change suggests that the change in the surface charge density of thylakoid membranes depends mainly on the ionization of carboxyl groups, which is determined by the surface pH. When the carboxyl groups are fully dissociated, the surface charge density reaches −1.0 ± 0.1 · 10 −3 elementary charge/square Å. Dependence of the estimated surface potential on the bulk pH was similar to that of electrophoretic mobility of thylakoid membrane vesicles.

Cerebral surface pH changes during asphyxia, hypotension, and circulatory arrest in the dog.

A technic is described for the measurement of cerebral surface pH in acute experiments in anesthetized dogs. During asphyxia and circulatory arrest, cerebral surface pH fell promptly and more profoundly than arterial blood or muscle surface pH; during hypovolemic hypotension (30 to 50 torr) cerebral surface pH declined later and less than muscle surface pH. The cerebral surface pH reflects the pH of the cortical interstitial fluid. Since the blood brain barrier is effectively impermeable to lactate, the changes recorded in the cerebral surface pH are a useful index of cortical intracellular metabolism.

The effects of extracellular pH and buffer concentration on the efflux of lactate from frog sartorius muscle

1. The rate of efflux of lactate from isolated frog sartorius muscles is measured with a superfusion technique. Efflux curves are followed after raising the internal lactate level of the muscles by repetitive electrical stimulation over a 200 sec period.2. With an external pH of 7.0 or below the measured efflux rates following stimulation reach 100-150 n-mole/g.min. Increasing the pH of the superfusion fluid to 8.0 results in a two or threefold increase in the peak efflux rate. The effect is independent of the buffer system used and occurs fairly rapidly when the pH of the superfusion fluid is changed. This suggests that the effect of pH on lactate efflux is extracellular.3. The increase in efflux rate due to an increase in pH is dependent on buffer concentration. This fact together with measurements of surface pH changes in muscles following arrest of superfusion indicates that a pH gradient exists through the muscle thickness during lactate efflux.4. The low lactate efflux rate seen at a low buffer concentration (1 mM) is reduced to an even lower level by depolarization with potassium sulphate suggesting a membrane potential dependent component. At pH 8.0 with a high buffer concentration (25 mM) potassium sulphate only reduces efflux rate slightly.The observations are interpreted as indicating that a fraction of lactate lost is in the form of undissociated acid and that this fraction increases with increasing external pH.5. Conditions which favour loss of hydrogen ions and lactate from muscle are also associated with improved recovery of twitch tension.

The Phosphorus Status of Eutrophic Lake Sediments as Related to Changes in Limnological Conditions—Total, Inorganic, and Organic Phosphorus

AbstractTo aid in the assessment of the role of sediments as a source of P to lake waters and to provide insight into the factors which may influence sediment P release, changes with time in the P status of noncalcareous sediments of a eutrophic lake were related to changes in sediment C and N, surface water composition, pH, temperature, and phytoplankton growth.The nature and extent of changes in sediment P status and the relationship of these changes to limnological conditions differed with location in the lake. Changes in sediment composition were greatest in a bay which received agricultural runoff in the early spring. This additional supply of nutrients apparently provided the initial impetus for increased surface water biological activity in the spring relative to other locations as reflected in increased surface water organic C and N, turbidity, and phytoplankton growth. At this location, total sediment P, C, and N decreased during the late spring and early summer. These changes corresponded to the period of exponential growth of the lake phytoplankton population. During the late summer and early fall when plankton growth entered the stationary and declination phases, sediment organic C, total N and P increased, evidently as a result of the deposition of detritus containing these elements.Changes in inorganic P accounted for most of the changes in total sediment P. Combining data from all sampling locations in the lake, sediment inorganic P was not correlated with changes in surface water temperature or pH, but was inversely correlated with surface water organic C. The results thus indicate that sediment inorganic P was directly related to the biological productivity of the surface waters, and in at least one location, sediments served as a significant source of P to these waters supporting increased biological growth.

Surface pH changes during and after myocardial ischemia in primates

Surface pH was measured in primate myocardium before and during periods of coronary ligation varying from 15 minutes to 4 hours. pH fell (7.43 to 6.95) after ligation, and release of the ligature produced a prompt return to preligation pH values. Return to normal pH occurred even in infarcted muscle and was thought to represent return of blood flow in spite of muscle infarction.

Changes in Blood-Brain Permeability during Pharmacologically induced Convulsions

Disturbances of the normal functions of the “blood–brain barrier” are well known following a large variety of pathological stresses. Relatively less attention has been directed toward the transient alterations in solute exchange between blood and brain that may accompany less destructive stimuli. Such alterations may be significant in the pathogenesis of certain disorders of central nervous system function. In this chapter, experiments on temporary alterations in the entry of sulfate into brain were found to accompany pharmacologically-induced convulsions. Marked concomitant changes in brain surface pH, oxygen and carbon dioxide tensions were recorded by direct measurement during the convulsion. As a result of these observations, the influence of hypercapnia and acidosis on brain vascular permeability was studied in some detail. Sulfate and albumin were employed as indicators. The chapter mainly deals with: The effects of pharmacologically induced convulsions on the penetration of sulfate into cat brain, the effect of Metrazol on the penetration of albumin into cat brain and the effect of hypercapnia on the penetration of sulfate and albumin into the brain. As a conclusion, the chapter states that hypercarbia had a profound effect on vascular permeability in some regions of the brain while sparing others.