Search results for "Bicarbonates"

Thermomineral waters of Greece: geochemical characterization

2020

Dependence of plasma pH on oxygen saturation

1969

Abstract The influence of haemoglobin oxygenation on the pH value of the blood plasma of healthy adolescents was investigated at 38°C by varying the parameters CO2 pressure, Hb concentration and buffer bases. A total of 5000 measurements gave the following results: 1. 1. The pHs difference between oxygenated and deoxygenated blood increases with diminishing CO2 pressure and with increasing Hb concentration. There is a linear relation between the pHs changes and the O2 saturation of the haemoglobin. 2. 2. Quantitatively these relationships can be expressed by the following equation: δpHs = (8 − pH ox − log 0.03 Pco 2 ) · [Hb] 225 · (100 − So 2 100 where ΔpHs is the pHs difference between par…

Unstimulated salivary flow rate, pH and buffer capacity of saliva in healthy volunteers

2004

Objectives: To assess the salivary flow rate, pH, and buffer capacity of healthy volunteers, and their relationships with age, gender, obesity, smoking, and alcohol consumption, and to establish the lower-end value of normal salivary flow (oligosialia). Methods: A prospective study was conducted in 159 healthy volunteers (age > 18 years, absence of medical conditions that could decrease salivary flow). Unstimulated whole saliva was collected during ten minutes, and salivary flow rate (ml/min), pH, and bicarbonate concentration (mmol/l) were measured using a Radiometer ABL 520. The 5 percentile of salivary flow rate and bicarbonate concentration was considered the lower limit of normality. R…

Dietary acid load and renal function have varying effects on blood acid-base status and exercise performance across age and sex

2017

Diet composition influences acid-base status of the body. This may become more relevant as renal functional capacity declines with aging. We examined the effects of low (LD) versus high dietary acid load (HD) on blood acid-base status and exercise performance. Participants included 22 adolescents, 33 young adults (YA), and 33 elderly (EL), who followed a 7-day LD and HD in a randomized order. At the end of both diet periods the subjects performed a cycle ergometer test (3 × 10 min at 35%, 55%, 75%, and (except EL) until exhaustion at 100% of maximal oxygen uptake). At the beginning of and after the diet periods, blood samples were collected at rest and after all workloads. Oxygen uptake, r…

Effect of alkalosis on plasma epinephrine responses to high intensity cycle exercise in humans

2002

The purpose of this study was to determine the effects of alkalosis on epinephrine concentrations in response to a 90 s maximal exercise test. A group of ten healthy men ingested either a bicarbonate (BS) supplement (0.3 g x kg(-1) of body mass of sodium bicarbonate) or placebo mixture (P) prior to performing a 90 s maximal cycle ergometer test. An indwelling Teflon cannula was placed in the antecubital vein and blood samples were drawn at three times at rest separated by 10 min, immediately following the protocol, and at 2.5, 5, and 10 min post exercise to determine plasma epinephrine concentrations. Sodium bicarbonate ingestion significantly ( P0.05) induced alkalosis both at rest [mean (…

Minireview: pH and synaptic transmission

2013

AbstractAs a general rule a rise in pH increases neuronal activity, whereas it is dampened by a fall of pH. Neuronal activity per se also challenges pH homeostasis by the increase of metabolic acid equivalents. Moreover, the negative membrane potential of neurons promotes the intracellular accumulation of protons. Synaptic key players such as glutamate receptors or voltage-gated calcium channels show strong pH dependence and effects of pH gradients on synaptic processes are well known. However, the processes and mechanisms that allow controlling the pH in synaptic structures and how these mechanisms contribute to normal synaptic function are only beginning to be resolved.

Nonenzymatic Transformation of Amorphous CaCO3 into Calcium Phosphate Mineral after Exposure to Sodium Phosphate in Vitro: Implications for in Vivo H…

2015

Studies indicate that mammalian bone formation is initiated at calcium carbonate bioseeds, a process that is driven enzymatically by carbonic anhydrase (CA). We show that amorphous calcium carbonate (ACC) and bicarbonate (HCO3 (-) ) cause induction of expression of the CA in human osteogenic SaOS-2 cells. The mineral deposits formed on the surface of the cells are rich in C, Ca and P. FTIR analysis revealed that ACC, vaterite, and aragonite, after exposure to phosphate, undergo transformation into calcium phosphate. This exchange was not seen for calcite. The changes to ACC, vaterite, and aragonite depended on the concentration of phosphate. The rate of incorporation of phosphate into ACC, …

Induction of carbonic anhydrase in SaOS-2 cells, exposed to bicarbonate and consequences for calcium phosphate crystal formation.

2013

Ca-phosphate/hydroxyapatite crystals constitute the mineralic matrix of vertebrate bones, while Ca-carbonate dominates the inorganic matrix of otoliths. In addition, Ca-carbonate has been identified in lower percentage in apatite crystals. By using the human osteogenic SaOS-2 cells it could be shown that after exposure of the cells to Ca-bicarbonate in vitro, at concentrations between 1 and 10 mm, a significant increase of Ca-deposit formation results. The crystallite nodules formed on the surfaces of SaOS-2 cells become denser and larger in the presence of bicarbonate if simultaneously added together with the mineralization activation cocktail (β-glycerophosphate/ascorbic acid/dexamethason…

In vitro prediction of in vivo absorption of ibuprofen from suspensions through rational choice of dissolution conditions

2020

Two ibuprofen suspension formulations were investigated for their dissolution in various bicarbonate, phosphate and acetate buffers. Phosphate and acetate gave faster release than bicarbonate at comparable molarities. Nevertheless, mass transport modelling using the reversible non-equilibrium (RNE) approach enabled the calculation of phosphate molarities that gave good matches to physiological bicarbonate in terms of ibuprofen dissolution. This shows that developing surrogate buffers for bicarbonate that are devoid of the technical difficulties associated with the bicarbonate-CO2 systems is possible. In addition, the intestinal dissolution kinetics of the tested suspensions were determined …

Toward Biopredictive Dissolution for Enteric Coated Dosage Forms

2016

The aim of this work was to develop a phosphate buffer based dissolution method for enteric-coated formulations with improved biopredictivity for fasted conditions. Two commercially available enteric-coated aspirin products were used as model formulations (Aspirin Protect 300 mg, and Walgreens Aspirin 325 mg). The disintegration performance of these products in a physiological 8 mM pH 6.5 bicarbonate buffer (representing the conditions in the proximal small intestine) was used as a standard to optimize the employed phosphate buffer molarity. To account for the fact that a pH and buffer molarity gradient exists along the small intestine, the introduction of such a gradient was proposed for p…