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PubMed1991

Separation of rare earth elements by high-speed counter-current chromatography.

Besides being widely used in electronic and glass industries, rare earth elements have recently been found to have important biological effects including the ability to stabilize and enhance interferon activity [J.J. Sedmak and S.E. Grossberg, J. Gen. Virol, 52 (1981) 195]. In this paper, the rare earth elements have been separated using a high-speed counter-current chromatography (HSCCC) centrifuge equipped with three multilayer coils connected in series. Two-phase solvent systems were composed of n-heptane containing di-(2-ethylhexyl)phosphoric acid (stationary phase) and dilute hydrochloric acid (mobile phase) where the partition coefficient of each can be optimized by selecting the proper hydrochloric acid concentration. The mobile phase was eluted through the column at a flow-rate of 5 ml/min, while the apparatus was rotated at 900 rpm. Continuous detection of the rare earth elements was effected by means of a post-column reaction with arsenazo III and the elution curve was obtained by on-line monitoring at 650 nm. Excellent isocratic separations of closely related rare earth elements were achieved at high partition efficiencies up to several thousand theoretical plates. Versatility of the present method was demonstrated in an exponential gradient elution of hydrochloric acid concentration where fourteen rare earth elements were all resolved in about 4.5 h.

Centrifugation↗
PubMedDate not supplied

Gas chromatographic determination of oxalic acid in foods.

A new quantitative gas chromatographic (GC) method has been developed for the determination of oxalic acid in foods. Solid sample is extracted with water (soluble oxalic acid) or 2N hydrochloric acid (total oxalic acid) at room temperature. An aliquot of sample extract is evaporated to dryness, and the oxalic acid in the residue is methylated with 7% hydrochloric acid-methanol. The reaction mixture is extracted with chloroform, and dimethyl oxalate is quantitated by GC. Recovery of oxalic acid added to liquid samples averaged 100.6%; recoveries from extracts of solid samples were 96.2-99.5 and 97.2-100.1% for water and hydrochloric acid extractions, respectively. Results are shown for determination of oxalic acid in spinach and beverages. The technique is simple, rapid, and accurate, and small samples may be used. The limit of determination is 20 micrograms.

Beverages↗
PubMed1993

The effects of etching, micro-abrasion, and bleaching on surface enamel.

Conservative techniques for improving the appearance of discolored teeth have become popular in the past decade. These include: in-office bleaching with 30% hydrogen peroxide, which is applied on etched enamel with a gauze pad and then exposed to a bleaching light; home bleaching with a mild form of peroxide, such as 10% carbamide peroxide, which is applied on the tooth surface with custom-made mouthguards; and enamel micro-abrasion with 18% hydrochloric acid, which is applied in a pumice slurry. In this study, the in-office bleaching and enamel micro-abrasion techniques were performed on extracted teeth for investigation of their microscopic effects on the surface enamel. Specimens treated only with 37% phosphoric acid showed an enamel loss of 5.7 +/- 1.8 microns. The specimens treated with 37% phosphoric acid followed by 30% hydrogen peroxide showed enamel loss of 5.3 +/- 1.6 microns; this loss was probably not caused by the hydrogen peroxide, but rather by the etching with 37% phosphoric acid which preceded the hydrogen peroxide application. A direct application of 18% hydrochloric acid for 100 s resulted in a loss of 100 +/- 47 microns. The extent of enamel loss was much greater when the 18% hydrochloric acid was applied in a pumice slurry for the same period of time (360 +/- 130 microns), and the effect was time-dependent. Thus, the pumice and rotary prophy cup used in conjunction with the 18% hydrochloric acid contributed markedly to the loss of surface enamel, enhancing the non-selective stain-removing action of the hydrochloric acid. Therefore, the hydrochloric acid-pumice technique must be used clinically with caution.

Acid Etching, Dental↗
PubMed2004

Effect of acid on duodenal blood flow and mucus secretion measured by reflectance spectrophotometry: a prospective, randomized-controlled study.

BACKGROUND: In animals, hydrochloric acid increases blood flow and mucus secretion in the duodenal mucosa. A significant correlation between index of haemoglobin oxygen saturation and mucosal blood flow, and between change in index of haemoglobin concentration and mucus thickness, respectively, has been demonstrated by reflectance spectrophotometry. AIM: To examine the effect of topical hydrochloric acid upon mucosal blood flow and mucus secretion in the human duodenum. METHODS: This prospective study of 120 patients undergoing routine upper endoscopy, examined the effect of topical 0.1 n hydrochloric acid or 0.9% saline on the duodenal bulb in a randomized, double-blind fashion. Duodenal mucosal index of haemoglobin oxygen saturation and index of haemoglobin concentration were measured by endoscopic reflectance spectrophotometry before and after hydrochloric acid or saline. RESULTS: Baseline index of haemoglobin oxygen saturation, calculated blood flow and index of haemoglobin concentration measurements were comparable between hydrochloric acid (n = 60) and saline (n = 60) treated groups. A history of current use of non-steroidal anti-inflammatory drug was associated with a significantly lower baseline index of haemoglobin oxygen saturation and calculated blood flow. Hydrochloric acid resulted in a significant increase in index of haemoglobin oxygen saturation and calculated blood flow, but a decrease in index of haemoglobin concentration, reflecting an increase in mucus thickness compared with saline. CONCLUSIONS: Our observations in humans confirm data in animal studies that topical exposure to hydrochloric acid induces an increase in duodenal mucosal blood flow and mucus secretion. Post hoc analysis of the data also revealed that attenuation of basal duodenal mucosal blood flow is associated with a history of current non-steroidal anti-inflammatory drug use. Endoscopic reflectance spectrophotometry appears to be adequate to assess factors that influence duodenal defence mechanisms of blood flow and mucus secretion in humans.

Duodenum↗
PubMed1985

Effect of secretin on stress-induced gastric bleeding in rats.

The effect of secretin on gastric bleeding induced by water (20 degrees C) immersion stress was studied by means of either perfusion of hydrochloric acid (0.13 N) or instillation of hydrochloric acid solution (0.4 N) into the rat stomach. When the stomach was perfused with acid solution, gastric bleeding occurred 20 min after the stress of water immersion and the amount of bleeding increased with time. It was found that integrated amounts of gastric bleeding after stress were more significantly decreased in the secretin-treated group (7.5 clinical units/kg/hr) than the saline control. On the other hand, intraduodenal administration of cimetidine (100 mg/kg) or propantheline (30 mg/kg) did not affect gastric bleeding. It was also revealed that the total amount of glycoprotein in the 4-hr perfusate was decreased 30% by the water immersion, but that secretin treatment prevented the 30% decrease in glycoprotein in the perfusate. In experiments on intragastric instillation of hydrochloric acid solution, it was found that gastric bleeding was seen only when the concentration of hydrochloric acid solution was higher than 0.4 N. However, the bleeding was also significantly prevented by treatment with secretin (2.5 and 7.5 clinical units/kg/hr). In conclusion, secretin prevents stress-induced gastric bleeding at least in part by increasing glycoprotein secretion in the gastric mucosa in the rat.

Animals↗
PubMed1995

Inhibition of endogenous nitric oxide reduces basal mesenteric vascular tone but does not alter intraduodenal hydrochloric acid-induced intestinal hyperemia in rats.

There are conflicting reports on the role of endogenous nitric oxide (NO) in the regulation of basal intestinal blood flow. The effect of inhibition of NO in intraduodenal hydrochloric acid (HCl) induced intestinal hyperemia remains to be confirmed. We investigated the effect of inhibition of endogenous NO on basal intestinal blood flow, HCl-induced intestinal hyperemia, and duodenal villous injury. Superior mesenteric artery blood flow in rats was measured by pulsed Doppler flowmetry and duodenal villous injury evaluated by histology. Intravenous NG-nitro-L-arginine methyl ester (L-NAME), or L-arginine or D-arginine followed by L-NAME, was given to show inhibition, reversal of inhibition of endogenous NO synthase, and stereospecificity, respectively. An intraduodenal 2 ml/kg bolus or perfusion for 30 min of 0.1 N HCl was given 15 min after L-NAME or vehicle. Mean arterial blood pressure was increased by L-NAME, which also significantly reduced intestinal blood flow under basal condition and after intraduodenal HCl. Basal mesenteric blood flow was not altered by L- or D- arginine. The L-NAME-induced increase in blood pressure and decrease in basal blood flow was attenuated by L- but not D-arginine. The villous damage and the magnitude of the peak hyperemia was unchanged by L-NAME, L- or D-arginine. Inhibition of endogenous NO by L-NAME is suggested by the significant rise in blood pressure. The rise in blood pressure and reduction in blood flow are attenuated by L- but not D-arginine, indicating stereospecificity. Inhibition of endogenous NO reduces basal mesenteric vascular tone but does not alter intraduodenal HCl-induced intestinal hyperemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Fluorometric analysis of 2-thiobarbituric acid reactive substances in turkey.

Three experiments were conducted to develop a sensitive and reliable fluorometric thiobarbituric acid (TBA) reactive substances (TBARS) method to determine lipid oxidation products in meat. The first study was conducted to find the optimum sample preparation conditions for meat in the fluorometric method. The second study was to compare the original and the modified methods by using meat and blood samples. The modified fluorometric method was compared with a conventional spectrophotometric method in a third study. Four different extraction solutions (2.5 M acetic acid, 0.5 M hydrochloric acid, 0.8 M perchloric acid, and 1.4 M trichloroacetic acid) and two ratios of extraction solution to TBA (20 mM) solutions (2:1 and 1:1) were examined in the first study. Hydrochloric acid was the optimum among the four extraction solutions tested, and the ratio of extraction solution to TBA solution at 1:1 was the best for the fluorometric TBARS method in raw ground turkey. The modified fluorometric method had high recovery rates (91%, average), and the regression coefficient of the standard curve prepared with spikes was also high (r2 = 0.99). The analysis of raw meat and plasma samples indicated that the modified fluorometric method had greater sensitivity than the original method. The pH of the reaction mixture played an important role in extraction TBARS from samples, and low pH conditions were preferable to high pH conditions. The amount of lipid oxidation products in raw turkey breast meat indicated that the fluorometric method had much greater sensitivity than the spectrophotometric method. The results from the three studies showed that the modified fluorometric TBARS method was useful for the samples with low lipid oxidation products, such as fresh raw meat. The sensitivity of the modified fluorometric method also facilitates the determination of oxidation products in small quantities of samples.

Animals↗
PubMed1994

Duodenal acidification and secretin, but not intraduodenal fat, inhibit human gastric acid secretion via prostaglandins.

BACKGROUND/AIMS: Acid and fat in the duodenum inhibit gastric acid secretion and increase plasma secretin. The role of prostaglandins and secretin in the inhibition of gastric acid secretion by duodenal infusion of hydrochloric acid and fat in healthy human volunteers was studied. METHODS: Gastric acid secretion was submaximally stimulated with intravenous pentagastrin followed by duodenal infusion of 0.1N hydrochloric acid, oleic acid, or intravenous secretin. To inhibit endogenous prostaglandins, the protocol was then repeated after indomethacin treatment. RESULTS: Duodenal fat infusion inhibited acid secretion 80% +/- 5% and was unaffected by indomethacin treatment. Intraduodenal acidification inhibited acid secretion by 43% +/- 8% and was reduced by indomethacin treatment to 15% +/- 4% (P < 0.01). Similarly, intravenous secretin inhibited acid secretion by 34% +/- 3%, which was decreased to 13% +/- 6% by indomethacin treatment (P < 0.01). The increase in plasma secretin levels after intraduodenal hydrochloric acid treatment was significantly greater than that observed with intravenous secretin or introduodenal oleic acid treatment; all were within the physiological range. Acid in the duodenum releases secretin, which inhibits gastric acid secretion at least in part via prostaglandins. In contrast, fat in the duodenum strongly inhibits gastric acid secretion via a nonprostaglandin pathway. CONCLUSIONS: Secretin is the predominant mediator for the inhibition of human gastric acid secretion induced by the presence of acid, but not fat, in the duodenum.

Adolescent↗
PubMed2003

Modification of di- and tetrasaccharides from shark cartilage keratan sulphate by refined anhydromethanolic hydrochloric acid-treatments and evaluation of their specific desulphation.

Highly sulphated keratan di- and tetrasaccharides were prepared from keratan sulphate (KS) of shark cartilage by enzymatic digestion with keratanase II and subsequent chromatography. The tetrasaccharide fraction carrying four sulphate groups was completely desulphated by 100 mM anhydromethanolic hydrochloric acid (MeOH-HCl) treatment at room temperature for 16 h. The conditions for the desulphation reaction by MeOH-HCl treatment were examined using sulphated keratan di- and tetrasaccharides as substrates by means of reversed phase high performance liquid chromatography (HPLC) and/or capillary electrophoresis, followed by the preparation of partially desulphated keratan oligosaccharides. Sulphate substitution patterns of monosulphated keratan disaccharide and trisulphated keratan tetrasaccharide were evaluated by methylation analysis. The results suggested that 6-O-sulphate groups of Gal moieties are cleaved faster than those of GlcNAc moieties under the present conditions adopted for the MeOH-HCl treatment of KS-derived oligosaccharides.

Acetylglucosaminidase↗
PubMed1965

METABOLIC AND CHEMICAL PROPERTIES OF BASIC PROTEINS ISOLATED FROM NUCLEI OF RAT LIVER AND THYMUS GLAND.

1. The effects of alkylating agents and disulphides on the thiol-containing proteins of nuclei from rat thymus and liver were studied. Three protein fractions were examined: histones extracted with 50mm- and 250mm-hydrochloric acid and the residual protein. None of the reagents selectively reacted with any one of the protein fractions. 2. Amino acid uptake in vitro into the histones of nuclei from rat thymus was analysed by preparative electrophoresis of the proteins extracted with 50mm- and 250mm-hydrochloric acid. After 1hr. at 37 degrees the greater incorporation was into the proteins extracted with 50mm-hydrochloric acid. 3. Preparative electrophoresis was used to study the relative thiol contents of the proteins of the 50mm-hydrochloric acid extract from thymus nuclei by labelling the histones in vitro with (14)C-labelled N-ethylmaleimide. 4. The capacity of the proteins extracted from rat thymus with 50mm- and 250mm-hydrochloric acid, and of the components from these extracts separated by preparative electrophoresis, to combine with DNA and to depress DNA-dependent RNA synthesis was studied. The histones extracted with 50mm-hydrochloric acid were more lysine-rich than those extracted with 250mm-hydrochloric acid. Wide variations were found in the abilities of the separated components to depress RNA synthesis.

Alkylating Agents↗
PubMed2004

Hydrochloric acid-induced lung injury: effects of early partial liquid ventilation on survival rate, gas exchange, and pulmonary neutrophil accumulation.

OBJECTIVE: Partial liquid ventilation can improve respiratory functions in acid-induced lung injury. We studied the effects of the interval between induction of injury and initiation of partial liquid ventilation on survival, gas exchange, and pulmonary neutrophil accumulation. MATERIAL AND METHODS: Anesthetized rats were randomly assigned to one of five groups ( n = 6 per group). Group 1 served as the control group, in the other groups an extended lung injury was induced by intratracheal instillation of hydrochloric acid. Whereas lungs of group 2 were gas-ventilated, group 3 received an early partial liquid ventilation (5 min after acid instillation) and group 4 a delayed partial liquid ventilation (30 min after acid instillation, 5 ml/kg perfluorocarbon). Group 5 received an additional continuous perfluorocarbon application of 5 ml x kg(-1) x h(-1) (30 min after acid instillation). Blood gases were measured with an intravascular blood gas sensor. RESULTS: Acid instillation resulted in a marked decrease in PO(2)-values within 30 min (from 481+/-37 mmHg to 128+/-71 mmHg, FiO(2) 1.0). Survival rate of the study period (12 h) was higher with early partial liquid ventilation. We observed no differences between groups in peak PO(2)-values during treatment. Histopathological examination, however, showed less pulmonary neutrophil accumulation in lungs of the early partial liquid ventilation group when compared to the delayed partial liquid ventilation group. CONCLUSIONS: Our results suggest that early partial liquid ventilation increases survival after extended acid-induced lung injury. While effects on arterial oxygenation appear not to predict acute survival we observed less intrapulmonary neutrophil accumulation with early partial liquid ventilation.

Animals↗
PubMed1979

Release of gastric inhibitory polypeptide (GIP) by intraduodenal acidification in rats and humans and abolishment of the incretin effect of acid by GIP-antiserum in rats.

Intraduodenal infusion of 0.05-0.5 N hydrochloric acid dose-dependently increases serum levels of immunoreactive gastric inhibitory polypeptide (GIP) in rats. Immunoreactive GIP released by duodenal acidification is biologically active because it augments the glucose-induced release of immunoreactive insulin (IRI). This augmentation of glucose-induced IRI release by intraduodenal acid can be abolished for 30 min by simultaneous intravenous infusion of GIP-antiserum. From this it is concluded that the initial capacity to augment the glucose-induced insulin release (incretin activity) of hydrochloric acid is due to its ability to release GIP. Later on, other gut factors with incretin activity might be released by hydrochloric acid. Also, in humans, intraduodenal infusion of 0.1 N hydrochloric acid releases GIP without changing serum levels of glucose or insulin. The GIP release is a direct effect of intraduodenal acid and is not mediated via secretin release. Injection of secretin in supraphysiologic doses does not change serum levels of immunoreactive GIP. However, such secretin injections induce a short-term insulin release and a decrease in serum glucose concentration.

Animals↗
PubMed2001

Studies of the structure of insulin fibrils by Fourier transform infrared (FTIR) spectroscopy and electron microscopy.

Fibril formation (aggregation) of insulin was investigated in acid media by visual inspection, transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. Insulin fibrillated faster in hydrochloric acid than in acetic acid at elevated temperatures, whereas the fibrillation tendencies were reversed at ambient temperatures. Electron micrographs showed that bovine insulin fibrils consisted of long fibers with a diameter of 5 to 10 nm and lengths of several microns. The fibrils appeared either as helical filaments (in hydrochloric acid) or arranged laterally in bundles (in acetic acid, NaCl). Freeze-thawing cycles broke the fibrils into shorter segments. FTIR spectroscopy showed that the native secondary structure of insulin was identical in hydrochloric acid and acetic acid, whereas the secondary structure of fibrils formed in hydrochloric acid was different from that formed in acetic acid. Fibrils of bovine insulin prepared by heating or agitating an acid solution of insulin showed an increased content of beta-sheet (mostly intermolecular) and a decrease in the intensity of the alpha-helix band. In hydrochloric acid, the frequencies of the beta-sheet bands depended on whether the fibrillation was induced by heating or agitation. This difference was not seen in acetic acid. Freeze-thawing cycles of the fibrils in hydrochloric acid caused an increase in the intensity of the band at 1635 cm(-1) concomitant with reduction of the band at 1622 cm(-1). The results showed that the structure of insulin fibrils is highly dependent on the composition of the acid media and on the treatment.

Animals↗
PubMed1980

Factors influencing the fluorescence spectra of the formaldehyde-induced reaction product of 5-hydroxytryptamine.

Fluorescence excitation and emission spectra of the formaldehyde-induced fluorophore of 5-hydroxytryptamine in a Sephadex model have been examined following exposure to hydrochloric acid or ammonia vapour. Exposure to hydrochloric acid vapour produced excitation spectra with broad maxima centred around 400 nm, whilst exposure to ammonia vapour intensified the maximum normally seen at approximately 450 nm relative to that seen at 400 nm. The emission maximum was generally broad and poorly defined following exposure to hydrochloric acid vapour; exposure to ammonia vapour had little effect on its location. Exposure of the formaldehyde-induced fluorophore in models containing 5-hydroxytryptamine to 300 nm irradiation caused a substantial shift in the position of the emission maximum; a concomitant increase in the fluorescence intensity was also observed. When the fluorescence present in duodenal enterochromaffin cells was examined after similar treatment, a number of differences in the response of the fluorophore were noted.

Ammonia↗
PubMed1986

Development of a high-performance liquid chromatographic assay for digoxin using post-column fluorogenic derivatization.

An efficient high-performance liquid chromatographic (HPLC) separation for digoxin and its metabolites has been developed. Quantitation of digoxin at plasma levels was possible after the column effluent was passed through a fluorogenic post-column reactor. A study of the optimum post-column conditions was undertaken using a combination of ascorbic acid, hydrogen peroxide and hydrochloric acid, which was known to induce fluorescence in the digoxin molecule. Digoxin and its metabolites were separated on a 15 cm X 4.6 mm I.D., 3-microns reversed-phase (C18) HPLC column using methanol--ethanol--isopropanol--water (52:3:1:45) as the mobile phase at a flow-rate of 0.3 ml/min. A solution of 1.1 X 10(-3) M hydrogen peroxide in a 0.1% ascorbic acid solution and concentrated hydrochloric acid were added into the post-column reactor through a peristaltic pump at a combined flow with a flow-rate of 0.23 ml/min. The mixture was passed into the 20-m reaction coil maintained at 79 +/- 1 degrees C. The resulting digoxin fluorophore was monitored with a fluorescence detector. Detector responses were linear from 1.5 to 10 ng injected on-column. The overall performance demonstrated that this system has the sensitivity, linearity and stability desired in a digoxin plasma level determination. The total chromatographic time including the postcolumn derivatization step was about 40 min.

Chromatography, High Pressure Liquid↗
PubMed1988

Interaction of neurotensin, secretin and cholecystokinin on pancreatic exocrine secretion in conscious dogs.

The results of previous studies from our laboratory have shown that neurotensin can stimulate pancreatic secretion of bicarbonate and protein. This study was done to compare the stimulatory action of neurotensin on pancreatic exocrine secretion in conscious dogs to those of secretin and cholecystokinin (CCK). Six dogs with chronic pancreatic and gastric fistulas were given hydrochloric acid intraduodenally or CCK-8 intravenously to produce maximal bicarbonate or protein secretion. Neurotensin was then given intravenously in combination with intraduodenal hydrochloric acid or intravenous CCK-8. Incremental bicarbonate outputs in response to intraduodenal hydrochloric acid alone were measured and compared with intraduodenal hydrochloric acid plus intravenous neurotensin. Intravenous administration of neurotensin augmented pancreatic bicarbonate and protein secretory responses to a maximal dose of intraduodenal hydrochloric acid. Incremental protein responses to intravenous CCK-8 alone were measured and compared to intravenous CCK-8 plus intravenous neurotensin. Incremental bicarbonate responses to intravenous CCK-8 alone were compared with intravenous CCK-8 plus intravenous neurotensin. Similarly, intravenous neurotensin augmented pancreatic protein and bicarbonate secretory responses to a maximal dose of intravenous CCK-8. The results of this study indicate that neurotensin may stimulate pancreatic secretion of protein and bicarbonate by mechanisms which are different from those of CCK and secretin. Neurotensin apparently exerts its action through specific neurotensin receptors.

Animals↗
PubMed2003

Augmenting effect of acetic acid for acidification on bactericidal activity of hypochlorite solution.

AIMS: Bactericidal activity of chlorine solution is enhanced by weak acidification. We compared the effects of various acids on the bactericidal activity of hypochlorite solution to establish a method for safe and effective use of an acidic hypochlorite solution. METHODS AND RESULTS: The bactericidal activities of acidic hypochlorite solutions that had been adjusted to pH 5.0 with hydrochloric acid, acetic acid, citric acid, lactic acid, formic acid, phosphoric acid or sulphuric acid against Bacillus subtilis spores were compared. The acidic solutions prepared with hydrochloric acid and acetic acid showed the highest bactericidal activity, and all of the spores (5 x 106 cfu ml(-1)) were killed within 10 min. On the other hand, the solutions prepared with citric acid and lactic acid showed no bactericidal activity against any bacterial strains tested in this study despite the low pH. The amount of chlorine gas produced by the preparation using acetic acid was sixfold less than that produced from the preparation using hydrochloric acid. CONCLUSIONS: Acetic acid is the most suitable and safe acid for the preparation of an acidic hypochlorite solution. SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study provide useful information for establishing a method for safe and effective use of an acidic hypochlorite solution.

Acetic Acid↗