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At least 1,045 records · Page 58Linked to original sources
PubMed2005

[Safety destruction of tetramethylene disulfotetramine and its medical waste].

OBJECTIVE: To develop suitable methods for safety destruction of tetramethylene disulfotetramine (TETS) and the medical wastes polluted by TETS. METHODS: The chemical stability of TETS was evaluated under the conditions of acid, alkali and high temperature. TETS was treated with sodium hydroxide, hydrochloric acid, sulfuric acid and nitric acid under various treatment conditions, i.e. concentration, temperature and time, followed by determining remaining TETS using gas chromatograms to estimating the degradation efficiency of TETS. TETS was put into ampoule and heated under the different conditions of temperature and time. After heat treatment, TETS residue was determined. For evaluating the absorption factor of active carbon to TETS in water and blood, active carbon was added into the water and blood with content of TETS, incubated at room temperature for 24 hours, and then determined the remaining TETS in water and blood. RESULTS: The complete degradation of TETS was achieved by one of the following treatments: heating with 6.0 mol/L hydrochloric acid at 100 degrees C for half an hour, heating with 3.0 mol/L hydrochloric acid or 6.0 mol/L sodium hydroxide at 100 degrees C for 3 hours, mixing with concentrated sulfuric acid or nitric acid at room temperature for 24 hours, and dry heating at 300 degrees C for 4.5 hours. Active carbon showed a marked effectiveness in absorbing the TETS in blood and water, with the mean absorption efficiency of over 90%. CONCLUSIONS: The results of this study suggest that TETS powder should be degraded by acid or alkali, and that the solid medical wastes polluted by TETS should be destroyed at high temperature. For the blood and water having contents of TETS, the active carbon should be used as to absorbing the TETS and then be destroyed at high temperature.

Bridged-Ring Compounds↗
PubMed2006

Mucosal acid causes gastric mucosal microcirculatory disturbance in nonsteroidal anti-inflammatory drug-treated rats.

The mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) suppress gastric mucosal blood flow is not fully understood, although the depletion of mucosal prostaglandin E2 has been proposed as one possible explanation. We investigated the role of gastric acid on gastric mucosal blood flow in NSAID-treated rats. A rat stomach was mounted in an ex vivo chamber, and gastric mucosal blood flow was measured sequentially in a 5-mm2 area of the gastric corpus using a scanning laser Doppler perfusion image system. Results showed that diclofenac (5 mg/kg s.c.) and indomethacin (10 mg/kg s.c.) did not affect gastric mucosal blood flow, although both strongly decreased mucosal prostaglandin E2 when saline was instilled into the gastric chamber. On replacement of the saline in the chamber with 100 mM hydrochloric acid, these drugs caused a decrease in gastric mucosal blood flow levels within 30 min. The specific cyclooxygenase (COX)-2 inhibitors celecoxib (50 mg/kg s.c.) and rofecoxib (25 mg/kg s.c.) did not affect mucosal prostaglandin E2 level, nor did they decrease gastric mucosal blood flow, even when hydrochloric acid was added to the chamber. Furthermore, measurement of vasoconstrictive factors present in the mucosa showed that endothelin-1 levels increased after administration of diclofenac s.c. in the presence of intragastric hydrochloric acid. This indicates that the presence of mucosal hydrochloric acid plays an important role in the NSAID-induced decrease in gastric mucosal blood flow, while the COX-1-derived basal prostaglandin E2, which is unlikely to control gastric mucosal blood flow itself, protects microcirculatory systems from mucosal hydrochloric acid.

Animals↗
PubMed1980

Vasoactive intestinal peptide inhibition of stimulated gastric secretion. I. Inhibition of meat-stimulated gastric secretion.

In an effort to demonstrate a physiologic role of vasoactive intestinal peptide, awake dogs with either Heidenhain pouches or Thiry-Vella loops and duodenal cannulas with duodenoduodenostomies to prevent obstruction were stimulated with meat meals given by mouth and infusions of various substances given intraduodenally, including hypertonic saline solution or 0.16 normal hydrochloric acid. Stimulated Heidenhain pouch secretion was significantly inhibited by concomitant intraduodenal administration of hydrochloric acid. Plasma vasoactive intestinal polypeptide was highest in the animals who received hydrochloric acid intraduodenally among all the intraduodenal stimuli. These findings support a role for vasoactive intestinal polypeptide as a physiologic inhibitor of gastric secretion, at least in dogs.

Animals↗
PubMed1981

[Contribution to biotransformation and analysis of the psychopharmacon mefexamide (author's transl)].

After oral administration of a therapeutic dosage (400 mg) Mefexamide (I), six excretion products were detected in human urine and subsequently identified by GC/MS and TLC: in addition to the unchanged drug (I) in the acidic extracted urine without hydrolysis p-methoxiphenoxiaceticacid-methylester (II) and p-methoxiphenoxiaceticacid (III) were detected; the latter two and p-hydroxyanisole (IV) were also found in the acidic extract after hydrolysis (with hydrochloric acid or enzymatic). In the alkaline urine extract besides the unchanged drug (I) and the main metabolite V (partially described previously by Forist et al. [8]1), metabolite VI, which occurred only in very small amounts, could be detected. Additionally, 2-diethylaminoethylamine (VII) was identified as an artifact in the alkaline extract after acidic hydrolysis. Hydrolysis of mefexamide with hydrochloric acid led to substances II, III, IV, and VII. For the main metabolite V, a synthesis route is described. Approximately 15% of the administered drug was recovered in the 24-h urine; substances I and V could be detected a least 72h after application.

Administration, Oral↗
PubMed1989

Relationship between gastric acid and elevated plasma somatostatinlike immunoreactivity after a mixed meal.

The aim of this study was to examine whether hydrochloric acid plays a role mediating the post-prandial increase in plasma somatostatinlike immunoreactivity in normal subjects. Intravenous infusion of cimetidine was found to reduce by 45% the postprandial increment in plasma somatostatin-like immunoreactivity. This effect was reversed by concomitant intragastric administration of 0.1 N hydrochloric acid, which in previous studies in fasted subjects had not affected plasma somatostatinlike immunoreactivity. The effects of cimetidine on postprandial plasma gastrin were the inverse of those observed on postprandial somatostatin. There was a greatly enhanced increment in postprandial plasma gastrin during cimetidine infusion, which was reduced significantly toward control levels by concomitant intragastric infusion of hydrochloric acid. To exclude direct inhibition by cimetidine of nutrient-stimulated plasma somatostatinlike immunoreactivity we studied the effect of cimetidine on plasma somatostatinlike immunoreactivity stimulated by an intraduodenal infusion of fat. Cimetidine did not alter the incremental response of somatostatinlike immunoreactivity to intraduodenal fat infusion. These data show that cimetidine does not invariably reduce nutrient-stimulated plasma somatostatinlike immunoreactivity and are consistent with the hypothesis that the action of cimetidine in reducing the plasma somatostatin response to ingestion of a meal is a consequence of reduction of postprandial acid secretion. These data suggest that the postprandial elevation in plasma somatostatin observed in humans is mediated in part through postprandial secretion of gastric acid, which in turn acts to elevate plasma somatostatin.

Adult↗
PubMed1975

Evaluation of ventilatory therapy for acid aspiration.

Aspiration of hydrochloric acid in experimental animals results in severe, progressive hypoxia which is due to intrapulmonary shunting and depressed cardiac output. This preparation is useful therefore in studying the therapy of hypoxia. Mongrel dogs were subjected to acid aspiration and the effects of several ventilatory patterns on intrapulmonary shunt fractions and lung water accumulation observed. The combination of large tidal volumes (30 c.c. per kilogram) with positive end-expiratory pressure was effective in preventing intrapulmonary shunting and other ventilatory patterns were ineffective. Pulmonary edema uniformly followed acid aspiration and was not affected by ventilatory therapy. When ventilatory therapy was delayed for 4 hours, the progression of shunting apparently was limited, but the existing shunt was not reduced.

Animals↗
PubMed1989

Chemical sterilization of bacterially contaminated bone without destruction of osteogenic potential.

A method to sterilize bone that has been contaminated or to assure sterility of allografts would be quite useful in the practice of orthopedics. The literature documents the osteogenic potential of demineralized bone matrix, prepared by treatment with hydrochloric acid and ethanol. We became interested in whether these potent antibacterial agents could render contaminated bone sterile and thus usable. Thus, we tested immersion in 70% ethanol or 0.6 N hydrochloric acid as sterilization methods for contaminated bone specimens. Bone fragments were (heavily) surface contaminated for 30-60 s by immersion in a suspension of either Escherichia coli, Staphylococcus aureus, or Bacillus subtilis and then placed in either the ethanol or hydrochloric acid solutions for 15 min, 30 min, 1 h, 2 h, 4 h, or 8 h. Subsequently, they were incubated in broth culture for 14 days. Using 70% ethanol, 80-90% of contaminated bone specimens were sterile in 4 h and all were sterile in 8 h. Using 0.6 N hydrochloric acid, only 10% of bone specimens contaminated with Staphylococcus aureus, 60% with Escherichia coli, and 90% with Bacillus subtilis were sterile in 8 h. Consequently, 70% ethanol could possibly by used as an antiseptic or sterilizing agent for contaminated bone, although we feel that such bone should also be demineralized. Ethanol should not be used for routine treatment of mineralized cortical bone as it has been shown to diminish the already poor osteogenic potential of cortical bone.

Administration, Topical↗
PubMed1984

Determination of trialkyltin, dialkyltin, and triphenyltin compounds in environmental water and sediments.

An analytical procedure for the determination of trialkyltin (tributyltin, tripropyltin), triphenyltin and dialkyltin (dibutyltin) compounds in environmental water and sediment was studied. Water samples were extracted into benzene with hydrochloric acid and sodium chloride. Sediment samples were extracted into methanolic hydrochloric acid and converted into benzene. Silica gel, which was impregnated with hydrochloric acid and activated, was used for clean-up of these compounds. These extracts of organotin chlorides were hydrogenated with an ethanol solution of sodium borohydride. Organotin hydrides were measured by gas chromatography with electron-capture detection. Recoveries of these compounds were ca. 70-95% from river water and sediment samples. The detection limits were 0.4-0.8 micrograms/l in water and 0.02-0.04 micrograms/g in sediment samples.

Chromatography, Gas↗
PubMed1997

DNA denaturation sensitivity may invalidate bromodeoxyuridine--DNA flow cytometric analysis of potential doubling times in colorectal tumours.

BACKGROUND: Flow cytometric analysis of 5-bromo-2'-deoxyuridine (BrdU)-substituted DNA has been used to calculate tumour cell proliferation rate. In this methodology, DNA denaturation, commonly by hydrochloric acid, is essential to expose incorporated BrdU for quantification with monoclonal antibodies. This study was designed to establish the validity of this technique by examining the change in flow cytometric DNA profiles introduced by DNA denaturation procedures. METHODS: Four experiments were performed using suspensions of nuclei derived from human colorectal tumours exposed in vivo to 150 mg/m2 BrdU 8-11 h before sampling. RESULTS: After denaturation with hydrochloric acid 2 mol/l a significant decrease was observed in the DNA aneuploid G1 population (P < 0.001) with a concurrent increase in the DNA aneuploid S phase fraction (P < 0.05). These changes were independent of the washing-centrifugation step and were maximal at different hydrochloric acid concentrations for different tumours. CONCLUSION: Hydrochloric acid denaturation introduces a tumour-specific non-linear variation in the analysis of BrdU.

Aged↗
PubMed1996

Chemical and morphological analysis of explanted polyurethane vascular prostheses: the challenge of removing fixed adhering tissue.

During in vivo experiments to evaluate the biocompatibility and biostability of alternative biomaterials, the ideal protocol for the handling and preservation of the explanted material is often compromised in order to meet the needs of both the pathologist and the materials scientist. Explants surrounded by tissue are often fixed in formalin or glutaraldehyde to facilitate later pathological and histological analysis, but the subsequent removal of such fixed tissue from thermally sensitive and less chemically stable polymers, such as polyurethanes, poses major problems for the materials scientist, who does not wish to modify the chemical, physical or morphological characteristics of the underlying biomaterial. The present study has attempted to find a solution to this problem by exposing virgin specimens of the microporous polyurethane Vascugraft vascular prosthesis to six different cleaning conditions, all known to be effective in removing fixed tissue. These conditions included the use of 20% aqueous potassium hydroxide solution for 48 h at room temperature, 5% sodium bicarbonate solution for 5 min at the boil, and 9, 10, 11 and 12N hydrochloric acid for 48 h at room temperature. The appearance and chemical properties of the virgin and treated specimens were compared using electron spectroscopy for chemical analysis, Fourier transform infrared spectroscopy, gel permeation chromatography for molecular weight and differential scanning calorimetry techniques. The use of temperatures close to the boil resulted in the formation of a translucent, rubbery material with gross changes in the microporous and microfibrous structure. The strongly acidic and alkaline conditions caused a loss in the surface carbonate group content. In addition, 12N hydrochloric acid reduced the molecular weight and urethane content. Consequently, 9N hydrochloric acid is recommended as the cleaning agent of choice for removing fixed tissue from this type of microporous polyurethane. Control experiments on virgin material should also be included in any cleaning protocol.

Adhesiveness↗
PubMed1983

Drug interactions I: detection of inorganic nitrite in organic nitrate esters under acidic conditions simulating the human stomach.

Both unformulated (bulk) and formulated (drugs) organic nitrate esters (isosorbide dinitrate, nitroglycerin, and pentaerythritol tetranitrate) were studied in the presence and absence of hydrochloric acid to determine if they could be sources of nitrite (and therefore lead to nitrosamine formation) under acidic conditions similar to those found in the stomach. The presence and generation of nitrite ion was detected by a modification of the Griess reaction. Bulk isosorbide dinitrate and nitroglycerin were found to be contaminated with 13.8-121.4 mumoles of inorganic nitrite per mole of nitrate ester. In addition, in the presence of hydrochloric acid, these preparations generated 0.52-1.18 mumoles of inorganic nitrite/mole of nitrate ester/min. Unformulated nitroglycerin generated nitrite at a rate roughly twice that of isosorbide dinitrate. In contrast, no evidence for nitrite contamination or generation by pentaerythritol tetranitrate was found. Tablets and capsules of isosorbide dinitrate contained approximately 27-216 mumoles of nitrite/mole of nitrate ester and, in the presence of hydrochloric acid, generated an average of 0.55 mumole nitrite/min. For isosorbide dinitrate, this rate was similar for bulk and formulated drug. In comparison to isosorbide dinitrate, the amount of nitrite initially present in tablets and capsules of nitroglycerin varied more widely (approximately 25-2290 mumoles nitrite/mole of nitrate ester), and in this case nitrite was generated at higher rates than unformulated drug averaging approximately 4.7 mumoles nitrite/mole of nitrate ester/min. Contrary to a literature report, we found that nitrate ion is not reduced to nitrite by hydrochloric acid (pH 1-3).(ABSTRACT TRUNCATED AT 250 WORDS)

Chemistry, Pharmaceutical↗
PubMed1993

Improved method to extract and concentrate porphyrins from liver tissue for analysis by high-performance liquid chromatography.

A new method to extract and concentrate porphyrins from liver tissue for analysis by high-performance liquid chromatography is described. Porphyrins were extracted with acetonitrile-hydrochloric acid, concentrated on disposable octadecylsilyl columns, brought to dryness, and reconstituted in 1.2 M hydrochloric acid. Dried porphyrins were stable at -80 degrees C for at least three weeks, and porphyrins reconstituted in hydrochloric acid were stable for at least 20 h. Yields of uro-, heptacarboxyl-, hexacarboxyl-, pentacarboxyl- and coproporphyrin were > or = 90%. The method allows determination of porphyrin concentrations in small (10-100 mg) samples of liver tissue.

Acetonitriles↗
PubMed1990

Hydrochloric acid-pumice treatment of fluorosis-stained enamel.

The management of dark staining of teeth caused by dental fluorosis is discussed. The results of treatment of 20 patients with dental fluorosis by a hydrochloric acid-pumice technique are described. All patients showed considerable improvement in colour which was maintained for review periods of (up to) two years.

Fluorosis, Dental↗
PubMed1993

The hydrochloric acid-pumice microabrasion technique in the treatment of post-orthodontic decalcification.

A significant number of patients exhibit white spots of enamel decalcification after orthodontic treatment, despite the use of preventive regimes. The hydrochloric acid-pumice micro-abrasion technique offers a method for improving the appearance of these lesions where they are cosmetically unacceptable. The clinical procedure is described and the effects of the technique upon the dental structures are discussed.

Humans↗
PubMed2001

The effect of pH on the erosion of dentine and enamel by dietary acids in vitro.

The reported incidence of tooth erosion caused by acidic soft drinks has been increasingly documented. Citric and phosphoric acids are the two main dietary acids present in these soft drinks. Many variables need to be determined in order to assess risk factors for dental erosion caused by beverage consumption including pH, titratable acidity, pKa, buffering capacity, hence the aim of these in vitro investigations. Methodologies included profiling flat enamel and dentine samples (< +/- 0.3 microm profile) from unerupted human third molars. Groups of five specimens were placed in acidic solutions adjusted with alkali over the available pH range; citric, phosphoric and hydrochloric acid were adjusted with sodium hydroxide and citric acid with trisodium citrate. Tissue loss was calculated by profilometry. Results showed that under these conditions citric acid caused far more erosion over the pH range employed than phosphoric acid for both tissue types. Citric acid compared with hydrochloric acid highlighted dissolution and chelation effects. Phosphoric acid caused minimal erosion over pH 3 for enamel and pH 4 for dentine. These factors could be considered in order to reduce the erosivity of acidic soft drinks.

Adult↗
PubMed1970

The preparation of alpha-oxo acid derivatives suitable for specific-radioactivity determination.

1. Conditions favouring the condensation of o-phenylenediamine with alpha-oxo acids to form substituted quinoxalines have been investigated. The best yields (85-100%) are obtained by incubation of the reagents in 2m-hydrochloric acid. Substitution of acetic acid for hydrochloric acid, or of halogen-substituted 1,2-diaminobenzenes for phenylenediamine, increases the initial rate of reaction, but not the yield of quinoxalines. 2. The quinoxaline derivatives are insoluble in water and can be readily purified. They are very suitable for determination of the specific radioactivities of radioactively labelled alpha-oxo acids because they are colourless, soluble in dioxan-based scintillators, and their strong absorption of u.v. light facilitates their chemical determination. As little as 1 nmol can be accurately determined by means of the blue fluorescence produced by absorption of light at 340-360nm. 3. Optimum conditions for preparation, purification and separation by paper and thin-layer chromatography are described.

Acetates↗
PubMed2006

pKa value and buffering capacity of acidic monomers commonly used in self-etching primers.

PURPOSE: The aim of this investigation was to characterize acidic monomers used in self-etching primers/adhesives by determination of their pKa values and by calculation of their calcium dissolving capacity in comparison with phosphoric and hydrochloric acid. MATERIALS AND METHODS: The following acidic monomers were included in this study: 4-methacryloyloxyethyl trimellitate anhydride (4-META), 10-methacryloyloxydecyl dihydrogen phosphate (MDP), dimethacryloyloxyethyl hydrogen phosphate (di-HEMA-phosphate), ethyl 2-[4-(dihydroxyphosphoryl)-2-oxabutyl]acrylate (EAEPA), 2-[4-(dihydroxyphosphoryl)-2-ox-abutyl]acrylic acid (HAEPA), and 2,4,6 trimethylphenyl 2-[4-(dihydroxyphosphoryl)-2-oxabutyl]acrylate (MAEPA). The pKa values were obtained by titration with 0.1 mol/l NaOH in aqueous solution. The inflection points of the resulting potentiometric titration curve were determined as pKa values. In the case of the sparingly water-soluble acidic monomers MAEPA and 4-META, the co-solvent method using different water/ethanol ratios for MAEPA or water/acetone ratios for 4-META was used. The dissolving capacity of each acidic monomer is defined as the amount of hydroxyapatite (HA) dissolved by 1 g of acid. For each monomer, the HA dissolving capacity was calculated bythe corresponding pKa value and the molecular weight. To confirm the calculated dissolving capacities, increasing amounts of HA powder (100 mg portions) were slowly added to 15 mmol/l aqueous solutions of the monomers to determine how much HA could be dissolved in the acidic solutions. RESULTS: For all the investigated acidic monomers, pKal values between 1.7 to 2.5 were observed. The pKa2 values for the phosphate/phosphonate derivatives are between 7.0 and 7.3, and are comparable to phosphoric acid. For dicarboxylic acid derivatives, the pKa2 values are in the range of 4.2 to 4.5. Due to their comparable molecular weights and pKal values, the three tested acids di-HEMA phosphate, MDP and 4-META all possess comparable dissolving capacities for HA (ie, 0.26 to 0.28 g/g monomer). The same amount by weight of acidic monomer EAEPA dissolved more HA (ie, 0.35 g/g monomer). Due to their different molecular weights, phosphoric acid and hydrochloric acid dissolved three and ten times as much HA, respectively, as the first three acidic monomers. As a result, the ability of these acids to dissolve HA increases as their molecular weight decreases. CONCLUSION: There are no significant differences among the investigated acidic monomers in terms of their pKa values and HA dissolving capacities. Monomer selection criteria for new self-etching adhesives must include properties such as calcium salt stability, wetting of the substrate, and copolymerization behavior.

Acetone↗