Fall In pH Research Articles

Ventilatory control in humans: constraints and limitations

Below the lactate threshold ((thetaL)), ventilation (V(E))responds in close proportion to CO(2) output to regulate arterial partial pressure of CO(2) (PaCO2). While ventilatory control models have traditionally included proportional feedback (central and carotid chemosensory) and feedforward (central and peripheral neurogenic) elements, the mechanisms involved remain unclear. Regardless, putative control schemes have to accommodate the close dynamic 'coupling' between and V(E) and V(CO2). Above (thetaL), PaCO2 is driven down to constrain the fall of arterial pH by a compensatory hyperventilation, probably of carotid body origin. When V(E) requirements are high (as in highly fit endurance athletes), V(E) can attain limiting proportions. Not only does this impair gas exchange at these work rates, but there may be an associated high metabolic cost for generation of respiratory muscle power, which may be sufficient to divert a fraction of the cardiac output away from the muscles of locomotion to the respiratory muscles, further compromising exercise tolerance.

Haemodynamic, electrolyte and metabolic changes during percutaneous nephrolithotomy

The objectives were to evaluate haemodynamic, electrolyte and metabolic changes in patients undergoing percutaneous nephrolithotomy when normal saline was used for irrigation; and to correlate these changes with irrigation time, volume of irrigation fluid absorbed and number of percutaneous interventions. Twenty adults undergoing percutaneous nephrolithotomy were studied. Heart rate, systolic and diastolic blood pressure, arterial blood gases, electrolytes and temperature were monitored before, during and after irrigation. Haemoglobin, urea and creatinine values were recorded before and 24 h after the procedure. Durations of anaesthesia and irrigation; volumes of irrigation fluid used and effluent fluid; and number of percutaneous interventions during the procedure were also recorded. No significant changes occurred in mean heart rate, systolic and diastolic blood pressure, electrolytes, haemoglobin, urea and creatinine. There was a significant fall in mean pH in postoperative period (P = 0.003) and bicarbonate values showed a negative correlation with duration of irrigation. Number of percutaneous interventions had positive correlations with duration of irrigation and volume of irrigant fluid absorbed. No significant changes occurred in haemodynamics and electrolytes, but there was a trend towards metabolic acidosis. Arterial blood gases should be monitored during and after PCNL in cases with prolonged irrigation time, repeated percutaneous interventions and patients having compromised renal function and metabolic status.

The aggregation of nonionic surfactants in the presence of poly(methacrylic acid)

The solution properties of homogeneous hexaethylene and octaethylene glycol mono(n-dodecyl) ethers, C12E6 and C12E8, respectively, and octaethylene glycol mono(n-decyl) ether, C10E8, with poly(methacrylic acid) (PMA) were investigated by dye solubilization, surface tension, fluorescence, viscosity, and pH measurements. The data were discussed regarding non-cooperative and cooperative binding of surfactant to polymer. Whereas in the interaction with poly(acrylic acid) (PAA), the critical aggregation concentrations (cac or T 1) of these surfactants were lower than the respective critical micelle concentration (cmc), in that with the more hydrophobic PMA, T 1’s of C12E6 and C12E8 were higher than the respective cmc, but that of C10E8 was lower than its cmc. These may be ascribed to the hydrophobic microdomains (HMD) of the PMA coil in water, probably in its inside. It is considered that some surfactants are bound first to the HMD non-cooperatively and then they are abruptly bound cooperatively at T 1. This raises T 1 higher than cmc when the cmc is low, and the amount bound by the HMD is relatively large and vice versa. T 1 of C12E6 or C12E8 is the former case, and that of C10E8 is the latter. Thus, different from PAA, T 1 for PMA + nonionic surfactant system consists of the amount of non-cooperative binding and the cac of the cooperative binding in equilibrium. Therefore, this T 1 has a different meaning from that for PAA and should be called apparent T 1. As the binding to the HMD is dependent on PMA concentration and cac is not, which is like in the PAA system, separation of apparent T 1 from the HMD binding was achieved by extrapolating T 1’s to zero PMA concentration (denoted intrinsic T 1). This value for C12E8 was found to be lower than the respective cmc and also lower than the respective T 1 for PAA. With increase in surfactant concentration, the pH of PMA solution rose and demonstrated a peak. This pH rise and fall may be induced by loosening of the HMD coil due to binding increase and by rearrangement of PMA + surfactant complex in high surfactant concentrations region. By raising the initial pH, the HMD were loosened; consequently, T 1 rose a little, and at higher pH, no surfactant binding took place.

Meat Quality and Storage Characteristics Depending on PSE Status of Broiler Breast Meat

The pale, soft, exudative (PSE) syndrome lowers storage quality and consumers acceptability in the particular meat. With the increase in the consumption of parted chickens in Korean meat consumption trade, a parallel increase in the concern over the PSE status of chickens have been noticed. The present study focused on the PSE status of broiler's breast to investigate the effects of different degrees of PSE on its quality and storage characteristics. A total of 46 broiler chickens of 35 days old averaging 1,251-1,350 g were selected for the study. Breast separated and skin was removed. The breast meat was stored at 4°C for 3 days and were analysed for pH, lightness, yellowness, redness, shear force, water-holding capacity (WHC), cooking loss, Thiobarbituric acid reactive substances (TBARS) and Volatile basic nitrogen (VBN) on day 1 and 3 during the storage. Increase in the degree of broilers breast PSE during storage caused fall in pH and shear force and increase in lightness, cooking loss, TBARS, VBN. Broilers breast PSE status confirms the actual pale soft and exudative nature of meat.

Effects of Nitrogen Deposition on Bryophyte Species Composition of Calcareous Grasslands

Regular additions of NH4NO3 (35–140 kg N ha−1 yr−1) and (NH4)2SO4 (140 kg N ha−1 yr−1) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure and composition of this calcareous bryophyte community. The lowest NH4NO3 additions of 35 kg N ha−1 yr−1 produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH4NO3 application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH4NO3 and (NH4)2SO4 additions provided conditions conducive for the establishment of two typical calcifuges — Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH4NO3 deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of >1 pH unit, between the NH4NO3 and (NH4)2SO4 treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of 35 kg N ha−1 yr−1 or less. These effects are of particular concern for rare or endangered species of low frequency.

Sorption of Cd(II) and Se(IV) from aqueous solution using modified rice husk

A carbonaceous sorbent was prepared from rice husk via sulfuric acid treatment. Removal of Cd(II) and Se(IV) from aqueous solution was studied varying time, pH, metal concentration, temperature and sorbent status (wet and dry). Cd(II) sorption was found fast reaching equilibrium within ∼2 h while Se(IV) sorption was slow reaching equilibrium within ∼200 h with better performance for the wet sorbent than for the dry. Kinetics data for both metals were found to follow pseudo-second order model. Cd(II) sorption was low at low pH values and increased with pH increase, however, Se(IV) sorption was high at low pH values, and decreased with the rise in initial pH until pH 7. A fall in the final pH was noticed with Cd(II) sorption due to the release of protons indicating an ion exchange mechanism. However, for Se(IV) sorption, a rise in the final pH was observed due to protons consumption in the process. For both metals, sorption fit well the Langmuir equation with higher uptake by rising the temperature. Analysis by scanning electron microscope and X-ray powder diffraction for the sorbent after the reaction with acidified Se(IV) confirmed the availability of elemental selenium, Se(0), as particles on the sorbent surface. The reduction process of acidified Se(IV) to Se(0) is accompanied by surface oxidation. Physicochemical tests showed an increase in sorbent acidity, cation exchange capacity and surface functionality after the reaction with acidified Se(IV) indicating that oxidation processes took place on the sorbent surface. On the other hand, no changes in physicochemical tests were found after Cd(II) sorption indicating the absence of redox processes between Cd(II) and the sorbent.

Effect of soft drinks on proximal plaque pH at normal and low salivary secretion rates

Objective. The aim of this study was to investigate the effect of different types of drinks on plaque pH during normal and drug-induced low salivary secretion rates. Material and methods. Three drinks were tested in 10 healthy adult subjects: 1) Coca-Cola regular, 2) Coca-Cola light, and 3) fresh orange juice. pH was measured in the maxillary incisor and premolar region with the microtouch method. The area under the pH curve (AUC) was calculated. Results. During normal salivary condition, mouth-rinsing with Coca-Cola regular resulted in a slightly more pronounced drop in pH during the first few minutes than it did with orange juice. After this initial phase, both products showed similar and relatively slow pH recovery. Coca-Cola light also resulted in low pH values during the very first minutes, but thereafter in a rapid recovery back to baseline. During dry mouth conditions, the regular Cola drink showed a large initial drop in pH, and slightly more pronounced than for orange juice. After the initial phase, both products had a similar and slow recovery back to baseline. At most time-points, AUC was significantly greater in dry conditions compared to normal conditions for Coca-Cola regular and orange juice, but not for Coca-Cola light. Coca-Cola light generally showed a significantly smaller AUC than Coca-Cola regular and orange juice. Conclusions. The main conclusion from this study is that a low salivary secretion rate may accentuate the fall in pH in dental plaque after gentle mouth-rinsing with soft drinks.

Studies on phosphoryl oligosaccharides

Some phosphate ester groups are known to link to glucosidic residues in starch molecule. We have prepared phosphoryl oligosaccharides (POs) from potato starch hydrolysates. POs were composed of two fractions, PO-1 and PO-2. The PO-1 fraction was the main fraction, and it was composed of maltotriose, maltotetraose, and maltopentaose to which one phosphoryl group was attached. The PO-2 fraction was predominantly composed of maltopentaose and maltohexaose to which at least two phosphoryl groups were attached. POs had the ability to form a soluble complex with calcium. Based on the function of the POs, we developed the POs of calcium (POs-Ca) for a food ingredient. POs-Ca was an advantageous food ingredient as a soluble calcium source and relatively high absorption in the intestinal tract. Relating to prevent of dental caries, POs cannot be fermented by cariogenic microorganisms, mutans streptococci, and reduces the plaque pH fall in vitro by mutans streptococci. Moreover, POs-Ca was effectively enhanced remineralization of early caries lesion. Although relatively higher pH in stimulated saliva is not suitable for Ca and phosphate (P) to be solubilized, POs-Ca would aid to maintain their solubility in oral environment. In results, the salivary Ca/P ratio can increase nearly up to the rate of hydroxyapatite (1.67) and enhanced enamel remineralization. Thereby, POs-Ca could be a beneficial material for oral health.Abbreviations :POs, phosphoryl oligosaccharides; POs-Ca, phosphoryl oligosaccharides of calcium; Ca, calcium; P, phosphate; 63-phosphoryl maltotriose, O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 62-phosphoryl maltotriose, O-α-D-glucopyranosyl-(1→4)-O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 63-phosphoryl maltotetraose, O-α-D-glucopyranosyl-(1→4)-O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 64-phosphoryl maltopentaose, O-α-D-glucopyranosyl-(1→4)-O-6-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 33-phosphoryl maltotetraose, O-α-D-glucopyranosyl-(1→4)-O-3-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose; 34-phosphoryl maltopentaose, O-α-D-glucopyranosyl-(1→4)-O-3-phosphoryl-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-O-α-D-glucopyranosyl-(1→4)-D-glucopyranose.

Aging time effect on quality meat from buffaloes fed on two different diets

The aim was to investigate the effect of two different diets on buffalo meat aging. The trial was carried out on 14 male buffaloes subdivided in two groups. During the finishing period the first group was fed mainly on alfalfa hay (AH), while the second group on maize silage (MS).The animals were slaughtered at 16 months of age and at 3 hours from slaughter the longissimus thoracis muscle was removed and stored at 2+1 °C until 14 days, to evaluate the effect of aging times on meat quality. The animals fed on maize silage, because of thicker fat layer, showed slower temperature fall and faster pH fall (5.53 vs 5.56 respectively for MS vs AH on 48 hours). Shear force value was higher for the animals fed on alfalfa hay during whole aging period (from 5.78 kg to 3.32 kg for AH and from 4.70 kg to 2.63 kg for MS) and their meat showed lower lightness particularly at 48 hours from slaughter (39.0 vs 41.2) and higher percentage of oxymyoglobin. Diet affect on aging performances, particularly for tenderness and also if the MS meat showed lower shear force it appeared more degraded and not very bright.

Achieving pH and Qr oscillations in a palladium-catalysed phenylacetylene oxidative carbonylation reaction using an automated reactor system

This Letter reports an experimental study which achieves reproducible oscillations in both pH and heat output (Qr) during a palladium-catalysed phenylacetylene oxidative carbonylation reaction in an homogeneous catalytic system (PdI 2–KI–Air–NaOAc in methanol solution). Experiments were performed in an HEL SIMULAR™ reaction calorimeter with precise control of temperature and gas flow rates. Under certain experimental conditions a second set of oscillations was observed. Oscillations in Qr were exothermic with no corresponding endotherm. Total energy released during oscillations followed a staircase function with a maximum of 600 J/oscillation. Heat release was in phase with pH fall, and decreased as pH increased.

The effect of O2 tension on pH homeostasis in equine articular chondrocytes

To determine the effects of varying O(2) on pH homeostasis, based on the hypothesis that the function of articular chondrocytes is best understood at realistic O(2) tensions. Cartilage from equine metacarpophalangeal/tarsophalangeal joints was digested with collagenase to isolate chondrocytes, and then loaded with the pH-sensitive fluorophore 2',7'-bis-2-(carboxyethyl)-5(6)-carboxylfluorescein. The radioisotope(22)Na(+) was used to determine the kinetics of Na(+)/H(+) exchange (NHE) and the activity of the Na(+)/K(+) pump, and ATP levels were assessed with luciferin assays. Levels of reactive oxygen species (ROS) were determined using 2',7'-dichlorofluorescein diacetate. The pH homeostasis was unaffected when comparing tissue maintained at 20% O(2) (the level in water-saturated air at 37 degrees C) with that at 5% O(2) (which approximates the normal level in healthy cartilage); however, an O(2) tension of <5% caused a fall in intracellular pH (pH(i)) and slowed pH(i) recovery following acidification, an effect mediated via inhibition of NHE activity (likely through acid extrusion by NHE isoform 1). The Na(+)/K(+) pump activity and intracellular ATP concentration were unaffected by hypoxia, but the levels of ROS were reduced. Hypoxic inhibition of NHE activity and the reduction in ROS levels were reversed by treatment with H(2)O(2), Co(2+), or antimycin A. Treatment with calyculin A also prevented hypoxic inhibition of NHE activity. The ability of articular chondrocytes to carry out pH homeostasis is compromised when O(2) tensions fall below those normally experienced, via inhibition of NHE. The putative signal is a reduction in levels of ROS derived from mitochondria, acting via altered protein phosphorylation. This effect is relevant to both physiologic and pathologic states of lowered O(2), such as in chronic inflammation.

Acidosis Augments Myogenic Constriction in Rat Coronary Arteries

The myogenic response is a process by which blood vessels autoregulate vascular smooth muscle tone in response to changes in transmural pressure. It is characterized by vessel contraction or dilation with increased or decreased pressure, respectively. We sought to identify whether acidosis impacts the myogenic response in rat coronary resistance arteries. Ventricular septal arteries were isolated from male Sprague-Dawley rats and mounted on a pressure myograph. The myogenic response was assessed by measuring the arterial diameter at pressures of 10-120 mm Hg. The fluorescence indicators 2',7'-bis-(carboxyethyl)-5(and-6)-carboxyfluorescein and Fura-2 were utilized to measure intracellular pH (pH(i)) and intracellular free calcium concentration ([Ca(2+)](i)), respectively. A decrease in the extracellular pH (pH(o)) from 7.4 to 6.9 produced a fall in pH(i) and an increase in the myogenic response. Under nominally HCO (3) (-) /CO(2)-free conditions at a constant pH(o), blockade of the sodium-hydrogen exchanger with HOE694 also resulted in a fall in pH(i) and a similar enhancement of myogenic activity. Concentration response curves were constructed to measure the potencies of the HOE694 effects: the EC(50) was 34 microM for the pH(i) change and 19 microM for vessel constriction. Apparent [Ca(2+)](i) remained unchanged during HOE694-induced intracellular acidification. Furthermore, in the presence of HCO (3) (-) , HOE694 did not markedly affect pH(i) and vascular tone remained unaltered. Our data demonstrate that acidosis augments myogenic constriction of rat coronary arteries. These effects are due to a fall in pH(i) consequent upon the reduction in pH(o) and may reflect an increased myofilament [Ca(2+)](i) sensitivity within vascular smooth muscle cells.

Effect of common packing materials on keeping quality of sugarcane jaggery during monsoon season

In experiments conducted in the Research Laboratory of Palli Siksha Bhavana (Institute of Agriculture), Visva-Bharati during 2002 and 2003, it was revealed that the best packing material for storinggur during monsoon season was heat-sealed LDPE (Low Density Polyethylene) packet of 150 gauge followed by glass jars. LDPE packets prevented moisture ingress, fall in pH and inversion of sucrose in the storedgur to the maximum extent. However, colour ofgur in LDPE packets was darker as compared togur stored in glass jars. PET (Poly Ethylene Terephthalate) jars were as good as glass jars but the storedgur darkened more in PET jars. Canisters were better in comparison to painted earthen pots provided those were with airtight lid.

Buffering effect of a prophylactic gel on dental plaque

The aim of this study was to evaluate the effect of a new prophylactic gel on plaque pH and plaque fluoride concentration. Twelve participants with normal (n=6, >or=0.7 ml/min) and low (n=6, <0.7 ml/min) stimulated whole salivary secretion rate were included. After 3 days of plaque accumulation, at random the participants were (1) treated with Profylin fluoride gel with buffering components (active gel), (2) treated with Profylin fluoride gel without buffering components (placebo gel), (3) asked to rinse with water, and (4) given no treatment. All test series were followed by rinsing with a nutrition solution; after which registration of plaque pH was performed during 60 min. There were two drop outs with low salivary secretion rate in the water session. The overall least pronounced pH fall was found after the use of the prophylactic gel. Significant differences between the prophylactic gel and the placebo gel were found for the participants with normal secretion rate. Fluoride plaque concentrations evaluated in 12 individuals after (1) application of the active gel, (2) rinsing with 0.2% NaF, and (3) rinsing with water showed significantly higher values after rinsing with the NaF solution. It can be concluded that application of the active gel, particularly in subjects with normal salivary secretion rate, in general, buffered plaque pH to higher levels. Factors like concentration of buffering agent and solubility of the gel need to be further evaluated to improve the effect.

Sequential injection analysis with second-order treatment for the determination of dyes in the exhaustion process of tanning effluents

A sequential injection (SI)-DAD spectrophotometric method to control the exhaustion of dyes in a mixture of three dyes from a tanning industry process has been developed. It is based on an interdiffusion process of the sample and reagents which leads to a gradual fall in pH through the channel to the detector recording a data matrix. The aim of this paper is to develop a second-order calibration model that is unaffected by interferents by applying multivariate curve resolution with alternating least squares (MCR-ALS). We obtained a linear calibration in the 5–30 mg l −1 range with a correlation coefficient of 0.999 for each dye with detection limits of 2.6, 3.9 and 2.1 mg l −1 for Acid Red, Acid Brown and Acid Orange, respectively. The simultaneous determination of the three dyes from tanning samples showed a satisfactory precision for the three analytes. The method has been validated comparing the concentration of some spiked samples with the expected concentration using a t-paired test. When we used this method to study the exhaustion of dyes, we found that there were several stages in this process. These data may be the key to optimising the exhaustion process.

Azaspiracids modulate intracellular pH levels in human lymphocytes

The azaspiracids (AZAs) are a group of marine toxins implicated in several intoxications whose mechanism of action is unknown. These phycotoxins include the five compounds shown in Fig. 1: AZA-1 ( 1), AZA-2 ( 2), AZA-3 ( 3), AZA-4 ( 4), and AZA-5 ( 5). The aim of this work was to study the effects of the five naturally occurring azaspiracids (AZA-1 to -5, Fig. 1) and four synthetic analogues ( 6– 9, Fig. 2) on intracellular pH, and the influence of Ca 2+ upon this effect. The AZAs ( 1– 5) were found to modulate cytosolic Ca 2+ levels in human lymphocytes, while some of them, but not all, had effects on the intracellular pH. AZA-1 ( 1) and AZA-2 ( 2) did not modify intracellular pH in a Ca 2+-containing or a Ca 2+-free medium. AZA-3 ( 3) increased intracellular pH by 0.16 units in the presence of extracellular Ca 2+, an effect that was blocked when a 1 mM solution of Ni 2+ was added. In a Ca 2+-free medium, the increase in pH induced by AZA-3 ( 3) was reduced to 0.08 pH units. AZA-4 ( 4) inhibited the basal pH increase even in the presence of a 1 mM solution of Ni 2+. In a Ca 2+-free medium, the inhibition caused by AZA-4 ( 4) was small, but when Ca 2+ was added back to the medium, the pH basal increase was again significantly inhibited. The alkalinization was also inhibited when AZA-4 ( 4) was added simultaneously, 10 min before or 10 min after thapsigargin (Tg), and also when the Ca 2+-influx induced by Tg was inhibited by Ni 2+. AZA-5 ( 5), on the other hand, did not modulate the intracellular pH profile in either a Ca 2+-containing or a Ca 2+-free medium. Finally, we investigated four synthetic analogues ( 6– 9, Fig. 2) whose structures were based on the four originally proposed structures of azaspiracid-1, with an opened E-ring. Compound 6 induced a small cytosolic Ca 2+ increase, but did not modify intracellular pH in saline solution. In a Ca 2+-free medium, compound 6 blocked the pH fall when Ca 2+ was added back to the medium. Compound 7 also did not modify intracellular pH in saline solutions, however it significantly blocked basal pH increases in a Ca 2+-free medium. Compound 8 did not alter intracellular pH, however compound 9 induced a small acidification when Ca 2+ was present in the extracellular medium. These results point to a structure–activity relationship in AZAs pH effect that affects the modulation and the coupling of intracellular pH and Ca 2+.

Analysis of Cardiovascular, Acid-Base Status, Electrolyte, and Coagulation Changes During Small Bowel Transplantation

The analysis of intraoperative hemodynamic, metabolic, and coagulation disorders of the recipients in relation to the newly reperfused organ during intestinal transplantation is necessary for an optimal patient management during small bowel transplantation (SBT). The interaction may be minor or may lead to postreperfusion syndrome, producing intense hemodynamic instability, important metabolic changes, and coagulation disorders. This research is based upon experience with 27 patients who underwent SBT. We observed significant decreases in PAM and IRVS after reperfusion in accordance with minor changes of mean pulmonary artery pressure, central venous pressure, and pulmonary capillary wedge pressure. The fall in pH upon revascularization was associated with a concomitant rise in partial carbon dioxide pressure probably due to the increased metabolic activity of the new organ. We found a significant increase in K levels, a rise that may be due to the output of metabolic products by the donor intestine. Patients displayed an hypocoagulative pattern, a derangement that did not seem to depend on ischemia time. It is possible that the same factors supporting the initial TEG pattern endure throughout the surgical procedure. The important and significant maximum amplitude indicator variation between the initial value and that after reperfusion may relate to the release of hypocoagulative factors superimposed on background abnormalities. These interesting metabolic disorders presumably reflected graft function and may provide predictive indices for a good outcome.

S-nitrosothiols regulate cell-surface pH buffering by airway epithelial cells during the human immune response to rhinovirus

Human rhinovirus infection is a common trigger for asthma exacerbations. Asthma exacerbations and rhinovirus infections are both associated with markedly decreased pH and ammonium levels in exhaled breath condensates. This observation is thought to be related, in part, to decreased activity of airway epithelial glutaminase. We studied whether direct rhinovirus infection and/or the host immune response to the infection decreased airway epithelial cell surface pH in vitro. Interferon-gamma and tumor necrosis factor-alpha, but not direct rhinovirus infection, decreased pH, an effect partly associated with decreased ammonium concentrations. This effect was 1) prevented by nitric oxide synthase inhibition; 2) independent of cyclic GMP; 3) associated with an increase in endogenous airway epithelial cell S-nitrosothiol concentration; 4) mimicked by the exogenous S-nitrosothiol, S-nitroso-N-acetyl cysteine; and 5) independent of glutaminase expression and activity. We then confirmed that decreased epithelial pH inhibits human rhinovirus replication in airway epithelial cells. These data suggest that a nitric oxide synthase-dependent host response to viral infection mediated by S-nitrosothiols, rather than direct infection itself, plays a role in decreased airway surface pH during human rhinovirus infection. This host immune response may serve to protect the lower airways from direct infection in the normal host. In patients with asthma, however, this fall in pH could be associated with the increased mucus production, augmented inflammatory cell degranulation, bronchoconstriction, and cough characteristic of an asthma exacerbation.

Inhibition of Acid Production in Dental Plaque Bacteria by Green Tea Catechins

The inhibition of acid production from dental plaque and mutans streptococci by epigallocatechin gallate (EGCg), one of the green tea catechins, was examined. The effect of EGCg solution on dental plaque pH was investigated.Subjects rinsed their mouths with 2 mg/ml EGCg solution and then, after 30-min interval, rinsed their mouths with 10% sucrose. Plaque samples were collected at appropriate times and the pH was measured. The pH values of plaque samples from 15 volunteers were significantly higher after treatment with catechin than after treatment with water. EGCg inhibited pH fall when cariogenic bacteria grown in medium with or without sucrose were incubated with sugar. In medium without sucrose, cultured cells were killed time-dependently by EGCg treatment. However, EGCg did not kill cells cultured in medium containing sucrose. Also, EGCg did not kill oral streptococci adhering to a saliva-coated hydroxyapatite disk. EGCg and epicatechin gallate inhibited lactate dehydrogenase activity much more efficiently than epigallocatechin, epicatechin, catechin or gallocatechin. These results suggest that EGCg is effective in reducing acid production in dental plaque and mutans streptococci.

Bovine muscle 20S proteasome: I. Simple purification procedure and enzymatic characterization in relation with postmortem conditions

Over the last decade, several sets of evidence support a possible contribution of the 20S proteasome to the meat tenderizing process. This assumption was emphasized by recent investigations demonstrating that the 20S proteasome was active in the absence of activators and exhibited endo- and exoproteolytic activities, a status often strongly debated before. In the present work, we developed a new rapid and simple purification procedure for muscle 20S proteasome and revisited the physicochemical properties of this complex in relation with the postmortem muscle environmental conditions, i.e. temperature, pH, osmolarity, etc. From a crude extract obtained from freshly excised muscle tissue, reasonable amounts of highly pure proteasome were prepared within a maximum of 4 days using only three chromatography steps. This purified proteasome was used to investigate the effect of pH, temperature, ionic strength and sodium dodecyl sulphate (SDS) on the major hydrolytic activities of this complex, i.e. trypsin-like (TL), chymotrypsin-like (CL) and peptidylglutamyl peptide hydrolase (PGPH) activities. Taken together, the data obtained suggest that the 20S proteasome constitutes a high hydrolytic potential in postmortem muscle conditions. To attest this finding, the 20S proteasome was further quantified by ELISA in at death and postmortem muscles including Longissimus, Rectus abdominis, Diaphragma pedialis and Tensor fascia latae bovine muscles. The primary conclusion was that time course changes in proteasome concentrations were not dependent on the kinetics of the pH fall. Secondly, the proteasome concentration in conditioned meat was in good agreement with previously reported proteolytic activity. Furthermore, the decrease in the muscle proteasome concentration can be considered as slow and this is particularly true in type 1 muscles for which the decrease in the amount of this complex did not exceed 7% during the first three days postmortem. This would suggest that the 20S proteasome was relatively stable during meat conditioning, a feature supporting a potential role in the meat tenderizing process.