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At least 1,585 records · Page 88Linked to original sources
PubMed1979

The pancreatic duct mucosal barrier.

The main pancreatic duct in cats possesses a relatively strong barrier to the diffusion of bicarbonate ions (HCO3-). We studied some of the characteristics of this barrier by perfusing the duct with a solution similar in composition to pancreatic juice before and after exposing the duct mucosa to various test agents. The difference in net flux of HCO3- across the duct before and after exposure to the test agent reflected damage to the barrier. The barrier was damaged by infected bile, aspirin (pH 2.3), hydrochloric acid (pH 2.3), ethanol (5 to 10 per cent), and secondary bile acids. It was not damged by sterile bile, aspirin (pH 6.5), and primary bile acids. These data indicate that the barrier to back diffusion in the pancreatic duct has unique properties, different in some respects from the properties of the gastric mucosal barrier. Furthermore, the barrier is vulnerable to some agents thought possibly to have a role in the pathogenesis of pancreatitis and pancreatic cancer.

Animals↗
PubMed1982

Role of acidosis in the protein wasting of fasting in the rat and the rabbit.

The purpose of these experiments was to determine if augmented renal ammoniagenesis in chronic metabolic acidosis could increase the negative nitrogen balance during prolonged fasting. To explore this question, rats and rabbits were fasted for up to 10 days because acidosis would markedly augment ammonium excretion in the rat but not in the rabbit. Since the ketoacidosis of fasting was mild in both species (less than 2 mM) and ketonuria virtually absent, a hydrochloric acid load was given to stimulate renal ammoniagenesis. Under these conditions, nitrogen balance was significantly more negative during acidosis in the rat but not in the rabbit. This increment in nitrogen excretion appeared as ammonium with no detectable difference in urea nitrogen excretion. Therefore, it appears that if more nitrogen is excreted as ammonium, net protein breakdown increases to furnish the substrate for ammoniagenesis rather than reducing the excretion of the other nitrogenous waste component urea. The implications of these findings will be discussed.

Acid-Base Equilibrium↗
PubMed1989

Neural reflex of the canine pylorus to intraduodenal acid infusion.

In 29 chloralose-urethane anesthetized dogs, a manometric assembly was inserted through a gastrostomy to monitor pressure of the pyloric region with a sleeve sensor. Antral and duodenal contractions were monitored with both manometric sideholes and serosal strain gauges. An additional tube channel allowed intraduodenal infusions 1-2 cm aborad from the pylorus. Intraluminal infusion of hydrochloric acid (0.1 N, 0.92 ml/min, for 2 min) reproducibly caused activation of motor activity in the pyloric region and peristaltic duodenal activity. Proximal duodenal activity probably contributed to the total phasic response recorded in the pylorus region. Excitatory responses could also be elicited by infusion of phenyl-biguanide (stimulant of sensory nerve endings), but not by control infusions with diluent (Krebs' buffer or saline). The motor response of the pyloric region to intraduodenal acid was blocked by intraduodenal application of 2% xylocaine. Atropine (30 micrograms/kg i.v. and 100 micrograms i.a.) or hexamethonium (10 mg/kg and 1 mg i.a.) markedly reduced or blocked the acid-induced pyloric motor response of this region but propranolol (1.0 mg/kg i.v. and 100 micrograms i.a.), phentolamine (1.5 mg/kg i.v. and 100 micrograms i.a.), or naloxone (200 micrograms/kg and 20 micrograms i.a.) had no effect. We believe these observations show the existence of a reflex from the duodenum to the pylorus in response to intraluminal stimuli mediated by a chain of cholinergic nerves. In the dog, endogenous opioid peptides do not contribute to the excitatory reflex pathway activated by intraduodenal acid or phenyl-biguanide. As intraluminal acid in the duodenum activates this reflex, it may play a role in the physiologic and pathophysiologic role of gastric emptying in this species.

Anesthesia, Local↗
PubMed2002

Adhesion/decalcification mechanisms of acid interactions with human hard tissues.

In order to study adhesion/decalcification mechanisms of acid interactions with human hard tissues such as bones and teeth, the chemical interaction of five carboxylic acids (acetic, citric, lactic, maleic, and oxalic) and two inorganic acids (hydrochloric and nitric) with enamel and two synthetic hydroxyapatite (HAp) powders with, respectively, a high and a low crystallinity were analyzed using X-ray photoelectron spectroscopy (XPS), atomic absorption spectrophotometry (AAS), and spectrophotometry (S). X-ray diffraction revealed that the crystallinity of the highly crystallized HAp was considerably higher than that of enamel while the crystallinity of the poorly crystallized HAp was similar to that of dentin and bone. XPS of acid-treated enamel demonstrated for all carboxylic acids ionic bonding to calcium of HAp. AAS and S showed for both HAps that all carboxylic and inorganic acids except oxalic acid extracted Ca significantly more than P, leading to a Ca/P ratio close to that of synthetic HAp (2.16 w/w). Oxalic acid extracted hardly any Ca, but substantially more P, leading to a significantly smaller Ca/P ratio than that of HAp. AAS showed that the calcium salt of oxalic acid hardly could be dissolved, whereas the calcium salts of all the other acids were very soluble in their respective acid solution. These results confirm the adhesion/decalcification concept (AD-concept) previously advanced. Depending on the dissolution rate of the respective calcium salts, acids either adhere to or decalcify apatitic substrates. It is concluded that the AD-concept that originally dictated the interaction of carboxylic acids with human hard tissues can be extended to inorganic acids, such as hydrochloric and nitric acid. Furthermore, HAp crystallinity was found not to affect the adhesion/decalcification behavior of acids when interacting with apatitic substrates, so that the AD-concept can be applied to all human hard tissues with varying HAp crystallinity.

Acids↗
PubMed2004

Sensitization of mechanosensitive gastric vagal afferent fibers in the rat by thermal and chemical stimuli and gastric ulcers.

In the present study we examined the effects of acute thermal and chemical stimuli and gastric ulceration on mechanosensitive gastric vagal afferent fibers. Single-fiber recordings were made from the cervical vagus nerve. Mechanosensitive afferent fibers were identified by response to gastric distension (GD). Intragastric pressure was maintained below 3 mmHg during intragastric instillation of saline, heated saline, HCl, or glycocholic acid. Responses to graded GD (5-60 mmHg, 20 s, 4-min interval) were determined before and after 30-min exposure to thermal or chemical stimuli. All mechanosensitive fibers studied were C-fibers (mean CV: 1.07 +/- 0.07 m/s). Saline (37 degrees C) did not affect resting activity or alter responses to GD, but exposure to heated saline (46 degrees C) significantly increased resting activity and sensitized responses to GD. The decrease in resting activity was hydrochloric acid concentration dependent (0.025-0.2 N), but responses to GD were sensitized after 30-min exposure to 0.1 N HCl (n = 7). The bile acid glycocholic acid significantly increased resting activity and desensitized responses to GD at an intragastric pH of 7, and similarly increased resting activity but sensitized responses to GD (n = 6) at an intragastric pH of 1.2. Vagal afferents recorded in rats with gastric ulcers had significantly greater resting activity and responses to GD than sham ulcer rats; intragastric instillation of glycocholic acid (pH 1.2) further increased afferent fiber excitability. These findings indicate that acute gastric thermal and chemical stimuli alter the response characteristics of mechanosensitive vagal afferents in the absence of inflammation or structural damage. Accordingly, acute sensitization of gastric afferents through different stimulus modalities may contribute to the development of dyspeptic symptoms. In the presence of gastric inflammation, mechanosensitive vagal afferents exhibit a further increase in excitability.

Animals↗
PubMed2002

Pulmonary responses to tracheal or esophageal acidification in guinea pigs with airway inflammation.

The association between asthma and gastroesophageal reflux has been attributed to microaspiration of gastric contents and/or vagally mediated reflex bronchoconstriction. In previous experimental studies concerning the pulmonary effects of tracheal or esophageal acid infusion, only animals without airway inflammation have been studied. We assessed the effects of esophageal and tracheal administration of hydrochloric acid (HCl) on normal guinea pigs (GP) and GP with airway inflammation induced by repeated ovalbumin exposures. These GP were anesthetized (pentobarbital sodium) and received 1) 20 microl of either 0.2 N HCl or saline into the trachea, or 2) 1 ml of either 1 N HCl or saline into the esophagus. Intratracheal HCl resulted in a significant increase in both respiratory system elastance and resistance (P < 0.001). There were no significant changes in respiratory mechanics when HCl was infused into the esophagus. In conclusion, we observed that infusion of large volumes of HCl into the esophagus did not change pulmonary mechanics significantly, even in guinea pigs with chronic allergen-induced airway inflammation. In contrast, intratracheal administration of small amounts of acid had substantial effects in normal GP and GP with airway inflammation.

Airway Resistance↗
PubMed1991

Location and identification of substituents with free amino group in lipopolysaccharides of gram-negative bacteria with the use of chromophore labelling.

Interaction of ten different lipopolysaccharides (LPS) with 2,4-dinitrofluorobenzene yielded quantitatively yellow dinitrophenyl derivatives (DNP-LPS) to show the presence of substituents with free amino group. The DNP-LPS samples were degraded with 1% acetic acid, and after removal of lipid A precipitates the supernatants were separated on a Sephadex G-25 column to give coloured polysaccharide, oligosaccharide and monomeric fractions monitored at lambda DNP = 365 nm. The coloured materials, including DNP-derivative of lipid A, were dephosphorylated with hydrofluoric acid followed by identification of the released DNP-amines by thin layer chromatography (TLC) on silica gel. Subsequently, the dephosphorylated materials were hydrolysed with hydrochloric acid followed by TLC analysis. The approach allowed to detect, locate and identify the substituents with free amino group within the LPS molecules. Moreover, two types of core structures within LPS preparation from one strain were discovered for five microorganisms.

Amino Acids↗
PubMed1984

Sodium sulfite as an antioxidant in the acid hydrolysis of bovine pancreatic ribonuclease A.

Treatment of hydrochloric acid with sodium sulfite prior to the acid hydrolysis of bovine pancreatic ribonuclease A has been found to suppress the oxidation of cystine, methionine, and tyrosine without adversely affecting the recoveries of other amino acids. Statistical analysis of the results indicated that the assumption of the independence of the mean and the variance, an assumption commonly used in the evaluation of the effects of various treatments, may not be valid in evaluating antioxidants used in the acid hydrolysis of proteins.

Amino Acids↗
PubMed1985

Isoproterenol or aminophylline attenuate pulmonary edema after acid lung injury.

We tested the hypothesis that isoproterenol and aminophylline would reduce both the pulmonary hypertension and increased pulmonary vascular permeability caused by the intratracheal instillation of hydrochloric acid. The lungs of New Zealand white rabbits were studied using a blood-perfused isolated lung preparation. Changes in pulmonary artery pressure and lung weight were measured for 30 min after acid injury (2 ml/kg 0.1 N HCl). In a control group without acid injury, pulmonary artery pressure and lung weight did not change throughout 1 h of perfusion. In an acid control group, pulmonary artery pressure increased 11 +/- 3 mmHg (p less than 0.01), and lung weight increased 19.2 +/- 5.1 g during the 30 min after acid injury (p less than 0.001). Pretreatment with aminophylline (p less than 0.01) or isoproterenol (p less than 0.001) completely prevented the increase in pulmonary artery pressure after acid instillation. Pretreatment with aminophylline strikingly reduced the increase in lung weight caused by acid injury to 3.6 +/- 1.0 g over 30 min (p less than 0.01). Pretreatment with isoproterenol prevented any increase in lung weight (0.5 +/- 0.5 g over 30 min, p less than 0.01). Post-treatment with isoproterenol beginning 3 min after acid instillation also prevented the increase in pulmonary artery pressure (p less than 0.01) and markedly reduced the increase in lung weight to 5.8 +/- 2.4 g over 30 min (p less than 0.01). The beneficial effect of isoproterenol is mediated through activation of beta-adrenergic receptors because propranolol reverses its effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminophylline↗
PubMed1991

Synthesis and purification of radioactive fatty acylcarnitines of high specific activity.

Micromole quantities of radiolabeled fatty acylcarnitines of high specific activity were synthesized by a simple one-step, one-pot acylation of [3H]carnitine in the presence of the respective fatty acid and acid chloride. The acylated product was isolated in high yield and high purity using liquid-liquid partitioning with isopropanol:hydrochloric acid:heptane (4:1:12 v/v) followed by butanol extraction. Product recovery was 91% for octanoyl[3H]carnitine and 90% for palmitoyl[3H]carnitine and contamination of both products with carnitine was less than 1%. The method is simple and fast, and results in high yields of pure fatty acylcarnitine in micromole scale.

1-Propanol↗
PubMed1992

Effect of DS-4574, a novel peptidoleukotriene antagonist with mast cell stabilizing action, on acute gastric lesions and gastric secretion in rats.

DS-4574 is a peptidoleukotriene antagonist with mast cell stabilizing activity. In the present study, we studied the effects of this compound on gastric secretion and various acute gastric lesions in rats. Intraduodenal administration of DS-4574 at doses of 5 to 10 mg/kg significantly and dose-dependently inhibited gastric acid secretion in pylorus-ligated rats, but a further increase in the dose up to 50 mg/kg did not cause any further inhibition. Shay ulceration in response to pylorus ligation was dose-dependently prevented by DS-4574 (10-25 mg/kg, i.d.). Water-immersion restraint stress- and aspirin-induced gastric ulcers were also significantly prevented in a dose-related manner by oral pretreatment with DS-4574 (10-50 mg/kg). The lower doses of DS-4574 (1-10 mg/kg, p.o.) significantly and dose-dependently protected the gastric mucosa against the necrotizing action of either absolute ethanol or concentrated hydrochloric acid, indicating that this compound possesses a potent gastroprotective activity. These antiulcer and gastric protective effects of DS-4574 were more potent than those of cimetidine used as a reference drug. These findings suggest that DS-4574 is useful for peptic ulcer therapy, as well as for the therapy of various allergic diseases, including asthma.

Animals↗
PubMed2005

Activated protein C attenuates acid-aspiration lung injury in rats.

Acid aspiration causes direct lung damage and secondary inflammatory response involving several cytokines and accumulation of neutrophils. Activated protein C (APC) exhibits antithrombotic and anti-inflammatory properties. We examined the effect and mechanism of pre-treatment APC on acid-aspirated lung injury in rats. Anesthetized rats were instilled intratracheally with normal saline (NS, 2 ml kg(-1)) or hydrochloric acid (HCl, 0.1 N, 2 ml kg(-1)). Thirty minutes before HCl instillation, APC (200 U kg(-1) h(-1)) was infused continuously into the right jugular vein. Animals were ventilated during the experiments. Five hours after HCl or NS instillation, bronchoalveolar lavage fluid (BALF) and lung tissue samples were obtained. Total and differential cell count, absorbance, albumin concentration, concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 and cytokine-induced neutrophil chemoattractant (CINC) in BALF, wet and dry weight (W/D) ratio were measured. Platelet count and fibrin degradation product (FDP) in peripheral blood were also measured. HCl instillation markedly increased these values in BALF as well as W/D ratio. APC attenuated the parameters increased by HCl-induced lung injury in rats. However, HCl instillation and APC treatment did not cause significant changes in platelet count and FDP compared with the control. We conclude that APC treatment protected the rats against HCl-induced lung injury and that this action seemed to be due to the anti-inflammatory properties of this protein rather than its anti-coagulant effects.

Albumins↗
PubMed1978

Erythrocyte acetylcholinesterase activity changes in the early stages of anemic and hypobaric hypoxia or after CoCl2 treatment in rabbits.

The authors studied the changes of erythrocyte acetylcholinesterase (AChE) activity in rabbits respectively subjected to bleeding, hypobaric hypoxia and CoCl2 treatment; in such conditions a rise of the enzyme activity was observed. Similar increases take place also as a consequence of intravenous infusions carried out by using lactic or hydrochloric acid. The authors suggest that these increases in the erythrocyte AChE activity are connected with the decrease of the pCO2 that occurs in the various experimental conditions achieved.

Acetylcholinesterase↗
PubMed2004

Ginsenoside Rh2 reduces ischemic brain injury in rats.

Ginseng was incubated under mildly acidic conditions and its inhibitory effect on a rat ischemia-reperfusion model was investigated. When ginseng was treated with 0.1% hydrochloric acid at 60 degrees C, its protopanaxadiol saponins were transformed to diasteromeric ginsenoside Rg3 and Delta20-ginsenoside Rg3. When the transformed ginseng extract, of which the main component was ginsenosides Rg3, was treated with human intestinal microflora, the main metabolite was ginsenoside Rh2. Orally administered acid-treated ginseng (AG) extract and ginsenoside Rh2 potently protect ischemia-reperfusion brain injury. The ginsenoside Rh2 also inhibited prostaglandin-E2 synthesis in lipopolysaccharide-stimulated RAW264.7 cells, but showed no in vitro antioxidant activity. These results suggest that AG and ginsenoside Rh2 can improve ischemic brain injury.

Administration, Oral↗
PubMed2004

An integrity assay for a meningococcal type B conjugate vaccine.

The development of an analytical procedure for the evaluation of a conjugate vaccine's structural wholeness or integrity is described. The principle component of the vaccine was the N-propionylated group B meningococcal polysaccharide (NPr-GBMP) covalently attached to a carrier protein. The goal of the procedure was to determine whether any whole polysaccharide, oligosaccharide, or monosaccharide, from minute to moderate levels, became detached off the conjugate. Free saccharide was isolated from the formulation, which included an aluminum hydroxide adjuvant for analysis. Due to its linkage, the NPr-GBMP did not release sialic acid efficiently with acid hydrolysis to the extent necessary for accurate quantitation. To accomplish depolymerization, the NPr-GBMP was subjected to methanolysis, 3N hydrochloric acid in methanol for 16h at 80 degrees C. The main product of the methanolysis reaction was a de-N-acylated methyl glycoside of sialic acid. N-acetylneuraminic acid oligomers and colominic acid were used to confirm the methanolysis depolymerization efficiency of the alpha(2 --> 8) saccharides; with the treatment all oligomers produced a common methyl glycoside. For this determination anion exchange chromatography and size exclusion chromatography were both interfaced to an integrated pulsed amperometric detector. Sensitivity and linearity were demonstrated to be sufficient for the application with vaccine dose formulations with low total saccharide concentrations.

Bacterial Capsules↗
PubMed1997

Gastric anti-ulcer and cytoprotective effect of l-serine in rats.

Effect of l-serine has been studied for its ability to inhibit gastric secretion and to protect the gastric mucosa against stress and chemically induced ulcers. Acid secretion studies were undertaken in pylorus-ligated rats with and without l-serine treatment. Experimental gastric lesions were induced by hypothermic-restraint stress, indomethacin and necrotizing agents including 80% ethanol, 0.2 M sodium hydroxide and 0.6 M hydrochloric acid in rats. The level of nonprotein sulfhydryl compounds and gastric wall mucus were also measured in the glandular stomach of the rats following ethanol-induced gastric lesions. The results of this study demonstrate that l-serine produces a dose-dependent inhibition of gastric acid secretions in rats. Pretreatment with l-serine also attenuated the formation of stress-, indomethacin- and necrotizing agents-induced gastric lesions. The antiulcer activity of l-serine was associated with significant inhibition of ethanol-induced depletion of nonprotein sulfhydryls and gastric wall mucus. In conclusion, this study demonstrates that l-serine possesses significant antiulcer and cytoprotective activity against various experimentally induced gastric lesions. Although the mechanism of action of l-serine requires further evaluation, the experimental observations derived from this study may have future clinical relevance and therefore deserve to be investigated thoroughly.

Animals↗
PubMed1979

[Behaviour of p-nitrophenol-glucuronide in hydrolysis with mineral acids (author's transl)].

The behaviour of p-nitrophenol and synthetic p-nitrophenol-glucuronide with mineral acids has been investigated. With sulfuric acid (33%) about 93% of the glucuronide derivative have been hydrolysed; the solution was heated in open vessel for 15 sec. With hydrochloric acid (6%) only about 65% of the conjugated p-nitrophenol have been converted to the free form. No losses were detected, when free p-nitrophenol was treated under the same conditions. Three other methods of hydrolysis have been applied.

Glucuronates↗
PubMedDate not supplied

Extraction of fipronil and thiobencarb from anaerobic water samples using solid-phase extraction.

Anaerobic water samples containing levels of soluble Fe(II) may form insoluble Fe(III) particulates that could hinder subsequent extraction and analysis. Solid-phase extraction (SPE) cartridges could become blocked by this material, reducing the volume that can be processed. The ability of ascorbic acid to reduce these Fe(III) colloids and/or to prevent further oxidation of Fe(II) by dissolved oxygen during sampling was investigated and compared to sample stabilization with hydrochloric acid. Ascorbic acid (5%, w/v) proved the most effective treatment because it prevented 95% of the dissolved iron in the sample from precipitating during processing, compared to 40% in untreated samples. The effect of ascorbic acid addition on degradation of 2 rice pesticides, fipronil and thiobencarb, was investigated and compared to degradation rates in water. Pesticide reduction by ascorbic acid over a 3 h period was insignificant compared to the natural degradation occurring in deionized water. While this method was shown to increase sample processing time, it also allowed the processing of large-volume anaerobic water samples (150 mL) that were previously not extractable due to rapid obstruction of the SPE cartridge.

Ascorbic Acid↗