Alkaline Shift In pH Research Articles

Ca2+/H+ antiport as a possible mechanism of the Ca2+-translocating ATPase functioning in vesicles of bean root nodule’s symbiosome membrane

Using vesicles of symbiosome membrane (SM), it was shown that the Ca2+-ATPase can function as an ATP-energized Ca2+/H+ antiporter. The initial rate of the acidic shift inside the vesicles, as well as the rate of the ITP-dependent alkalization of the medium inside them markedly increased in the presence of valinomycin. This process was rapidly stopped by eosin Y, a known inhibitor of the type IIB Ca2+-ATPase. ITP-dependent uptake of Ca2+ was blocked after the addition to the reaction mixture of nigericin in the presence of K+. Under these conditions, the alkaline shift of pH inside the vesicles occurred, leading to the inhibition of operation of the calcium pump in SM. Evaluation of the pH shifts inside the vesicles by using pH-indicator pyranine confirmed the ion-exchange mechanism of the Ca2+-ATPase functioning in the SM.

Intracellular alkalosis during hypoxia in newborn mouse brain in the presence of systemic acidosis: a phosphorus magnetic resonance spectroscopic study

We investigated the in vivo changes in cerebral energy metabolism and pH i in newborn mice noninvasively during 8 h of hypoxia with FiO 2 = 5%, using phosphorus magnetic resonance spectroscopy continuously. The intracellular brain pH (pH i) increased from 7.20 ± 0.03 to 7.36 ± 0.03 ( P < 0.05) at 1 h of hypoxia and then decreased gradually. On the other hand, the mixed arterial and venous blood pH decreased gradually during hypoxia, reaching a minimum value of 7.16 ± 0.01 at the end of the hypoxia. There was no significant difference in P CO 2 between control (47.4 ± 0.8 mm Hg) and 1-h hypoxic (49.0 ± 1.1 mm Hg) mice. The blood glucose concentration was significantly increased at 1 h of hypoxia. These results indicate that the alkaline shift in pH i during hypoxia was caused neither by systemic alkalosis due to hypocapnia nor hypoglycemia.

Guanidinoethane sulfate: brain pH alkaline shifter.

A new category of agents, brain pH alkaline shifters, is described. Using the prototype agent, guanidinoethane sulfate (GES), the actual alkaline shift in pH was demonstrated in adult mice brain by 31-phosphorus (31P) nuclear magnetic resonance (NMR) in vivo spectroscopy. This alkaline shift was also shown to effectively reduce the extent of brain intracellular lactic acidosis brought about by anoxic insult. These findings support the notion that a pH alkaline shift may protect the brain against the deleterious effects of lactic acidosis. Since higher pH has been shown to significantly reduce beta-amyloid deposition, alkaline shifters may also have therapeutic potential in Alzheimer's disease.

PH regulation of an egg cortex tyrosine kinase

Fertilization of the echinoderm egg is known to result in the phosphorylation, on tyrosine, of a high-molecular-weight cortical protein (HMWCP) localized in the egg cortex. Studies using various parthenogenic agents indicate that this phosphorylation event occurs in response to the alkaline shift in cytoplasmic pH 1 which normally occurs 1 to 2 min after fertilization. In the present study, the purified egg cell surface complex was used as an in vitro system to determine whether a small alkaline shift in pH, such as occurs upon fertilization, could stimulate the activity of theegg cortex-associated tyrosine kinase toward endogenous protein substrates. The results demonstrated thatthe cell surface complex is highly enriched in a tyrosine kinase activity which accounts for the majority of the protein kinase activity in this preparation. The activity of this tyrosine kinase toward the HMWCP and other cortical proteins was highly dependent on pH over the range pH 6.8 to 7.3. This indicates that the fertilization-associatedchange in cytoplasmic pH would be sufficient to trigger increased tyrosine phosphorylation of the high-molecular-weight cortical protein in vivo. The regulation of tyrosine phosphorylation by small changes in pH represents a novel control mechanism in which a tyrosine protein kinase may act as a pH-sensitive transducer.

The pH Dependence of the Binding of Pro-Urokinase to Fibrin/Celite

A re-examination of the affinity of pro-urokinase (pro-UK), HMW and LMW-urokinase (UK) to fibrin/Celite was undertaken in order to explain how the chance purification of pro-UK from freshly voided urine by fibrin/Celite affinity chromatography may be reconciled with the subsequent observations that pro-UK failed to bind significantly to fibrin clots in plasma. A significant pH dependence of pro-UK binding to fibrin/Celite was found. Substantial binding of pro-UK (native or recombinant from E. coli), but not of the two-chains forms, was seen at about pH 6.5, which is in the normal pH range of pooled, freshly voided urine. By contrast, at pH 7.4 fibrin binding of pro-UK was much reduced, though it was still significantly greater than that of HMW or LMW-UK. This finding helps to explain the fibrin-binding of pro-UK in freshly voided urine but not in blood. In order to determine if this pH dependence was the sole explanation for why pro-UK could not be isolated by this method from stored urine, the stability of pro-UK in urine was evaluated by incubating 125I-labeled pro-UK in urine. Incubation for up to 4 days (37 degrees C) was not accompanied by any degradation of the single-chain pro-UK as evidenced by autoradiography under reducing conditions. It was concluded that the alkaline shift in pH which occurs in urine left standing, rather than the degradation of pro-UK, explained why freshly voided urine was found to be essential. Clot lysis studies at pH 6.5 and 7.4 showed no promotion of fibrinolysis at the pH which favored fibrin/Celite binding. Therefore, while the present study defines the conditions under which pro-UK may be purified from urine by fibrin/Celite chromatography, it provides no evidence that this binding phenomenon plays any role in fibrinolysis.

Arterial acid-base changes in unanaesthetized rats in acute hypoxia

Arterial P O 2 , P CO 2 and pH, as well as lactate and pyruvate concentrations, were measured in unanaesthetized rats exposed to air or to gas mixtures containing from 15.30 to 5.07% O 2 for 5 to 30 min. In air-breathing controls the Pa O 2 was 91 mm Hg, Pa CO 2 41 mm Hg and pH 7.43. With reduction in inspired O 2 the Pa O 2 decreased to minimal values of 21 mm Hg (5% O 2), the Pa CO 2 tell to minimal values of 13 to 14 mm Hg (5% O 2) and the pH increased to maximal values of 7.661 (7% O 2). The decrease in Pa CO 2 and increase in pH occurred already at 15.3% O 2. With 5% O 2 there was a marked but variable nonrespiratory acidosis that either limited the alkaline shift in pH, or caused a net acid shift in pH. Accumulation of lactate occurred with 13% O 2, and with 11% O 2 there was an increase in lactate/pyruvate ratio. However, a significant pyruvate accumulation occurred only when the inspired O 2 was decreased to less than 7%.

Isolation and characterization of Mycoplasma arginini: spec. nov.

Ten strains of Mycoplasma were isolated from brain tissues of a scrapie infected sheep and mouse, joint exudate of an arthritic goat, and cell cultures established from human, chimpanzee, and dog tissues. These strains were related to each other, but were unrelated to known species of Mycoplasma. The present report characterizes the new strains, proposes that they be classified as Mycoplasma ariginini and discusses their ecological significance. Materials and Methods. Media for isolation. Hayflick (1), BYE (2), and BBL (3) broth and agar media were used under aerobic and anaerobic (5% CO2 in nitrogen) conditions (2). See Table I for media used for isolation of individual strains. Media for metabolic reactions. Arginine utilization reaction: Hayflick and BYE broth media were supplemented with 10 mM arginine, 10 mM glutamine, vitamins (4), 0.002% phenol red, and adjusted to pH 7.1. Glucose fermentation reaction: Hayflick broth medium was supplemented with 0.5% glucose, 10 mM glutamine, vitamins, 0.004% cresol red, and adjusted to pH 7.5. Urea metabolic reaction: Hayflick broth medium was supplemented with 0.5% urea, 0.002% phenol red, and adjusted to pH 6.0. Utilization of arginine and urea was indicated by an alkaline shift in pH while fermentation was indicated by an acid shift in pH. Isolation of strains. Source and origin of specimens from which 10 strains were isolated are given in Table I. Two strains were isolated from brain tissues of two animals infected with scrapie, 1 from a sheep (C506) with naturally acquired scrapie and the other from a mouse (G230) with scrapie experimentally induced by the intracerebral injection of a brain suspension from another sheep with naturally acquired scrapie. The latter suspension was not available for direct culturing for Mycoplasma. These 2 Mycoplasma strains were isolated by direct culture in both BYE and Hayflick broth and agar media aerobically and anaerobically.