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At least 865 records · Page 48Linked to original sources
PubMed2000

Acid and base-catalyzed hydrolysis of bisphenol A-related compounds.

In order to ascertain whether an estrogenic bisphenol A is produced from bisphenol A-related monomers by chemical-induced hydrolysis and to clarify their hydrolytic mechanisms, bisphenol A dimethacrylate (Bis-DMA) and bisphenol A bis(glycidyl methacrylate) (Bis-GMA) were reacted with phosphoric acid, hydrochloric acid, and sodium hydroxide in methanol or methanol/water mixed media at 37 degrees C. Amounts of monomethacrylate intermediates as well as bisphenol A (BPA) were determined by the use of high-performance liquid chromatography (HPLC), and time-conversion curves of hydrolytic products were prepared. BPA and bisphenol A monomethacrylate were produced by acid-catalyzed hydrolysis of Bis-DMA. Bis-GMA was partly converted into monomethacrylate by phosphoric acid and into monomethacrylate and 2,2-bis[4-(2,3-dihydroxypropoxy) phenyl]propane (BHP) by hydrochloric acid. Hydrolytic reactions by sodium hydroxide were completed almost within 1 day, resulting in the production of BPA from Bis-DMA, and BHP from Bis-GMA. No BPA was formed from Bis-GMA by chemical-induced hydrolysis. The hydrolytic behaviors of these monomers were discussed.

Benzhydryl Compounds↗
PubMed1992

Study of unscheduled DNA synthesis following exposure of human cells to arecoline and extracts of betel nut in vitro.

Aqueous, acetic acid, hydrochloric acid and ethanol extracts of betel nut (Areca catechu L.) have been found to induce unscheduled DNA synthesis in Hep 2 cells obtained from human larynx carcinoma, in vitro. Different concentrations of extracts of betel nut induced dose-dependent unscheduled DNA synthesis in Hep 2 cells. Together with the viability of the Hep 2 cells, our results indicate that the aqueous and acetic acid extracts of betel nut induce relatively more unscheduled DNA synthesis than the hydrochloric acid and ethanol extracts and arecoline. The carcinogenic potency of raw and unprocessed betel nut of North-East India used in this study is discussed.

Arecoline↗
PubMed1980

Solubility and dissolution rate studies of ergotamine tartrate.

The solubility of ergotamine tartrate in aqueous solutions of tartaric acid, citric acid, hydrochloric acid, and caffeine and the dissolution rate of ergotamine tartrate in aqueous mixtures containing hydrochloric acid, caffeine, citric acid, or sodium acetate were studied. The Noyes-Whitney model of dissolution is useful for predicting the dissolution rate of ergotamine tartrate in most of the dissolution media. The relative slowness with which ergotamine chloride (a substance with low water solubility) precipitated when ergotamine tartrate was dissolved in 0.1 M HCl resulted in the solid dissolving faster in this medium than was predicted using the Noyes-Whitney equation.

Caffeine↗
PubMed2001

Tetracycline residues in meat and bone meals. Part 1: methodology and examination of field samples.

The incidence of tetracycline residues in commercially available samples of meat meals and meat and bone meals was investigated. Four different methods were used on each of the 87 samples from nine different rendering plants in Germany: examination using a screening fluorescence test; examination by high performance liquid chromatography analysis using three different extraction procedures (succinate buffer, hydrochloric acid, hydrochloric acid after sedimentation of bone particles). Tetracyclines were found in 100% of the samples by one or more of the extraction procedures. The highest concentrations found in meat meals were 2048 microgkg(-1), 1393 microgkg(-1) and 608 microgkg(-1) for oxytetracycline, tetracycline and chlortetracycline, respectively. In meat and bone meals the highest concentrations were 2295 microg oxytetracycline kg(-1) 848 microg tetracycline kg(-1) and 1274 microg chlortetracycline kg(-1). The extraction after sedimentation was the most effective of the applied extraction procedures and exposed the highest total tetracycline concentrations. The results of this investigation showed that considerable amounts of tetracyclines have to be expected in field samples. Further research has to be done on the heat stability of bound tetracycline residues.

Animal Feed↗
PubMed2000

Characterization of an encapsulation device for the production of monodisperse alginate beads for cell immobilization.

An encapsulation device, designed on the basis of the laminar jet break-up technique, is characterized for cell immobilization with different types of alginate. The principle of operation of the completely sterilizable encapsulator, together with techniques for the continuous production of beads from 250 microm to 1 mm in diameter, with a size distribution below 5%, at a flow rate of 1-15 mL/min, is described. A modification of the device, to incorporate an electrostatic potential between the alginate droplets and an internal electrode, results in enhanced monodispersity with no adverse effects on cell viability. The maximum cell loading capacity of the beads strongly depends on the nozzle diameter as well as the cells used. For the yeast Phaffia rhodozyma, it is possible to generate 700 microm alginate beads with an initial cell concentration of 1 x 10(8) cells/mL of alginate whereas only 1 x 10(6) cells/ml could be entrapped within 400 microm beads. The alginate beads have been characterized with respect to mechanical resistance and size distribution immediately after production and as a function of storage conditions. The beads remain stable in the presence of acetic acid, hydrochloric acid, water, basic water, and sodium ions. The latter stability applies when the ratio of sodium: calcium ions is less than 1/5. Complexing agents such as sodium citrate result in the rapid solubilization of the beads due to calcium removal. The presence of cells does not affect the mechanical resistance of the beads. Finally, the mechanical resistance of alginate beads can be doubled by treatment with 5-10 kDa chitosan, resulting in reduced leaching of cells.

Acetic Acid↗
PubMed2003

A study of air pollutants and acute asthma exacerbations in urban areas: status report.

A study to try to better understand the interactions between various air contaminants and acute asthma exacerbations is described. The study evaluates temporal associations between a panel of air contaminants and acute asthmatic exacerbations as measured by emergency room visits for asthma in communities in the Bronx and Manhattan in New York City (NYC). In addition, ambient levels of various air pollutants in two NYC communities are being compared. Almost 2 years of daily data have been collected for most of the air contaminants to be investigated. The air contaminants measured include gaseous compounds (ozone, sulfur dioxide, nitrogen oxides, aldehydes, nitrous acid, nitric acid, hydrochloric acid and ammonia), particulate matter components (metals, elemental and organic carbon, sulfate, hydrogen ion, pollen, mold spores and particle mass and number).

Acute Disease↗
PubMed2002

Outcome of acid ingestion related aspiration pneumonia.

BACKGROUND: The objective of this study is to assess the incidence and long-term results of a rarely discussed medical problem -- aspiration pneumonia resulting from the intentional ingestion of acid. MATERIALS AND METHODS: The medical records of 370 patients treated at one tertiary care institution for corrosive acid injury during a 12-year period were reviewed retrospectively. The study subjects included any patients who were found to have acid ingestion related aspiration pneumonia confirmed by chest film within 24h of injury. All available data of these patients with or without aspiration pneumonia were analyzed. RESULTS: Of the 370 patients with corrosive acid injury, 15 (4.2%) had acid-aspiration pneumonia which was related to their intentional ingestion of a strong acid, hydrochloric acid (pH<1). The data for 14 patients with aspiration pneumonia and 268 without aspiration pneumonia was complete and available for analysis. Patients with aspiration pneumonia were found to be significantly older (52.2+/-6.2 to 41.7+/-0.9 years old, P=0.017), had a higher incidence of nasogastric tube irrigation (35.7-6.0%, P=0.000), had more conscious disturbance (50.0-17.5%, P=0.016), and required more endotracheal tube intubation (50.0-3.0%, P=0.000). Aspiration pneumonia was found to significantly increase the mortality rate in acid injured patients who required emergency abdominal surgery (87.5-32.0%, P=0.000) and in those who did not (28.5-5.1%, P=0.05). Two of the six survivors of aspiration pneumonia later developed laryngeal sequelae. CONCLUSIONS: Aspiration pneumonia rarely occurs as a consequence of acid ingestion. When it does occur, it greatly increases the mortality rate of those involved. For those who survive, physicians can expect some laryngotracheal sequel in long-term follow-up.

Adolescent↗
PubMed1988

Increases in airway responsiveness following acute exposure to respiratory irritants. Reactive airway dysfunction syndrome or occupational asthma?

We describe a persistent increase in nonspecific bronchial responsiveness following acute exposure to strong respiratory irritants in four subjects with no past history of asthma or atopy and in a subject with mild asthma. They were exposed either to a bleaching agent, sulfuric acid, hydrochloric acid, perchloroethylene, or toluene diisocyanate fumes. In all cases the inhalation of high concentrations of irritant fumes was brief (less than one hour) and induced acute symptoms of cough and dyspnea. The asthmatic subject developed a severe bronchospasm which required mechanical ventilation. In all subjects the exposure led to prolonged (more than one year) symptoms of variable airflow obstruction induced on contact with common respiratory irritants. In the previously normal subjects, a mild hyperresponsiveness to methacholine could be observed. The asthmatic subject became dependent on steroids. No change in the forced expiratory volume in one second was observed when the subject exposed to sulfuric acid was rechallenged in the laboratory, but her nonspecific bronchial responsiveness was then back to normal at this time. When those exposed to perchloroethylene or toluene diisocyanate fumes were reexposed to these agents, a late asthmatic response occurred, suggesting that the subjects developed occupational asthma after an intense short-term exposure to perchloroethylene or toluene diisocyanate. We conclude that airway hyperresponsiveness can develop or increase after the inhalation of high concentrations of irritants and that these changes may be prolonged. Occupational asthma following intense short-term exposure to sensitizing agents should be differentiated from airway hyperresponsiveness which results from a nonsensitizing mechanism, as in the reactive airway dysfunction syndrome.

Adolescent↗
PubMed2001

Partial liquid ventilation reduces fluid filtration of isolated rabbit lungs with acute hydrochloric acid-induced edema.

BACKGROUND: Hydrochloric acid aspiration increases pulmonary microvascular permeability. The authors tested the hypothesis that partial liquid ventilation has a beneficial effect on filtration coefficients in acute acid-induced lung injury. METHODS: Isolated blood-perfused rabbit lungs were assigned randomly to one of four groups. Group 1 (n = 6) served as a control group without edema. In group 2 (n = 6), group 3 (n = 6), and group 4 (n = 6), pulmonary edema was induced by intratracheal instillation of hydrochloric acid (0.1 N, 2 ml/kg body weight). Filtration coefficients were determined 30 min after this injury (by measuring loss of perfusate after increase of left atrial pressure). Group 2 lungs were gas ventilated, and group 3 lungs received partial liquid ventilation (15 ml perfluorocarbon/kg body weight). In group 4 lungs, the authors studied the immediate effects of bronchial perfluorocarbon instillation on ongoing filtration. RESULTS: Intratracheal instillation of hydrochloric acid markedly increased filtration coefficients when compared with non-injured control lungs (2.3 +/- 0.7 vs. 0.31 +/- 0.08 ml.min(-1). mmHg(-1).100 g(-1) wet lung weight, P < 0.01). Partial liquid ventilation reduced filtration coefficients of the injured lungs (to 0.9 +/- 0.3 ml.min(-1).mmHg(-1).100 g(-1) wet lung weight, P = 0.022). Neither pulmonary artery nor capillary pressures (determined by simultaneous occlusion of inflow and outflow of the pulmonary circulation) were changed by hydrochloric acid instillation or by partial liquid ventilation. During ongoing filtration, bronchial perfluorocarbon instillation (5 ml/kg body weight) immediately reduced the amount of filtered fluid by approximately 50% (P = 0.027). CONCLUSIONS: In the acute phase after acid injury, partial liquid ventilation reduced pathologic fluid filtration. This effect started immediately after bronchial perfluorocarbon instillation and was not associated with changes in mean pulmonary artery, capillary, or airway pressures. The authors suggest that in the early phase of acid injury, reduction of fluid filtration contributes to the beneficial effects of partial liquid ventilation on gas exchange and lung mechanics.

Animals↗
PubMed2002

Kinetic-spectrophotometric determination of ascorbic acid by inhibition of the hydrochloric acid-bromate reaction.

A new analytical method was developed for the determination of ascorbic acid in fruit juice and pharmaceuticals. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolourisation of Methyl Orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The linearity range of the calibration graph depends on bromate concentration. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.6 x 10(-6) M and calibration rang is 8 x 10(-6)-1.2 x 10(-3) M ascorbic acid. The relative standard deviation of seven replication determinations of 8 x 10(-6) and 2 x 10(-5) M ascorbic acid was 2.8 and 1.7%, respectively. The influence of potential interfering substance was studied. The method was successfully applied for the determination of ascorbic acid in pharmaceuticals.

Ascorbic Acid↗
PubMed2003

Spectrophotometric reaction rate method for determination of barbituric acid by inhibition of the hydrochloric acid-bromate reaction.

A new kinetic-spectrophotometric method was developed for the determination of barbituric acid. The method is based on its inhibition effect on the reaction between hydrochloric acid and bromate. The decolorization of methyl orange by the reaction products was used to monitor the reaction spectrophotometrically at 510 nm. The variable affecting the rate of the reaction was investigated. The method is simple, rapid, relatively sensitive and precise. The limit of detection is 7.9x10(-7) M and calibration rang is 1x10(-6)-6.0x10(-4) M barbituric acid. The linearity range of the calibration graph is depends on bromate concentration. The relative standard deviation of seven replication determination of 5.6x10(-6) M barbituric acid was 1.8%. The influence of potential interfering substance was studied.

Barbiturates↗
PubMed1981

Development of chorda tympani taste responses in rat.

To learn whether neurophysiological taste responses change during structural development of the gustatory system, we recorded from the chorda tympani nerve in rats aged 7 to 92 days after birth. Chemical stimuli applied to the anterior tongue included four monochloride salts, two acids, sucrose, and urea. Responses to all chemicals were obtained as early as 7 days postnatally. Developmental changes in salt, acid, and sucrose responses were observed. Relative to NaCl and LiCl, NH4Cl and KCl gradually decrease in effectiveness as taste stimuli; or, relative to NH4Cl and KCl, NaCl and LiCl become more effective stimuli. These changes are similar to those observed prenatally and postnatally in sheep. Also, relative to NaCl, citric acid, hydrochloric acid, and sucrose become less effective stimuli; or, NaC1 becomes more effective as a stimulus, relative to these acids and sucrose. The period of most rapid functional change overlaps a period of rapid structural change. It seems most reasonable to hypothesize that the altering taste responses reflect developmental changes in receptor membrane composition. Since the taste system is not programmed to respond in a mature manner from the moment function begins, there is ample opportunity for changing taste experience to influence the developing taste system.

Aging↗