Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PERCHLORIC ACID”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,171 records · Page 65Linked to original sources
PubMed1985

Endogenous acetaldehyde in rats. Effects of exogenous ethanol, pyrazole, cyanamide and disulfiram.

Male Long-Evans rats consumed the alcohol and aldehyde dehydrogenase inhibitors pyrazole, cyanamide or disulfiram, for 6 days. No endogenous blood acetaldehyde could be detected in controls and pyrazole treated rats, endogenous blood concentrations up to 2-5 nmoles/ml were, however, measured in the cyanamide and disulfiram-treated animals. Other rats received daily ethanol gastric intubations in addition to the consumption of the inhibitors. Little or no acetaldehyde was detected in the controls and pyrazole treated animals during acute ethanol intoxication or on the subsequent days. High blood levels (200-500 nmoles/ml) were observed in the rats consuming cyanamide and disulfiram, and concentrations up to 10-12 nmoles/ml were still found on the following day after all the ethanol had been eliminated. This acetaldehyde and the endogenous acetaldehyde could only be observed with the hemolyzation method in which blood hemolyzates were directly heated prior to headspace GC analysis; none was detected if blood proteins were first precipitated and removed with perchloric acid. It is suggested that aldehyde dehydrogenase inhibitors elevate endogenous concentrations of bound acetaldehyde and that exogenous ethanol increases this form of acetaldehyde.

Acetaldehyde↗
PubMed1985

Metabolism and action of neplanocin A in Chinese hamster ovary cells.

Neplanocin A is a naturally occurring carbocyclic analog of adenosine which contains a cyclopentene moiety in place of ribose and has demonstrated antitumor and antimicrobial activity. This compound was highly toxic to Chinese hamster ovary (CHO) cells; the approximate minimum inhibitory concentration of neplanocin A for inhibition of clone formation was 0.1 microM. The toxicity of the agent was greatly reduced by prior treatment with adenosine deaminase. [3H]Uridine incorporation into perchloric acid insoluble material in growing cells was inhibited by neplanocin A more dramatically than that of [3H]thymidine or [3H]leucine. Treatment with the drug resulted in a marked depression of ATP pool levels. High pressure liquid chromatographic analysis of cellular nucleotide pools from cells treated with neplanocin A revealed the formation of an apparent drug metabolite (NpcTP) that eluted in the triphosphate region of the chromatographic profile. Treatment of NpcTP with alkaline phosphatase produced a nucleoside with properties similar to neplanocin A. An adenosine-kinase-deficient cell line formed little, if any, NpcTP but demonstrated only slight resistance to the agent. These observations suggest that neplanocin A was efficiently metabolized to the triphosphate level but that this metabolite was responsible for only a fraction of the observed toxicity.

Adenosine↗
PubMed1988

Covalent protein binding of a metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to mouse and monkey brain in vitro and in vivo.

We have recently reported that a reactive metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is formed in rat brain in vitro by type B monoamine oxidase (MAO). In the present study, we further characterize the irreversible binding in vitro using tissues from mice and monkeys, two species more sensitive than rats to MPTP neurotoxicity. We also report the occurrence of irreversible binding of radioactivity after administration of tritiated MPTP in the same species in vivo. Tissue homogenates were incubated at 37 degrees with 1-[methyl-3H]MPTP in in vitro experiments. Animals were injected with labeled MPTP and sacrificed at different times in in vivo experiments. The perchloric acid precipitates of tissue homogenates from either procedure were washed exhaustively with organic solvents and counted for radioactivity. The amount of recovered radioactivity in in vitro experiments was similar using brain homogenates from mice and monkeys, whereas a considerably lower amount was found in mouse liver. MAO-B inhibitors decreased the covalent binding. However, the combined MAO-B/MAO-A inhibitor pargyline had no effect if added after 2 hr of incubation. Sulfhydryl-containing compounds decreased the covalent binding in a concentration-related manner. GSH reduced the rate of the reaction throughout the incubation. The covalent binding slowly increased in time in vivo in mouse brain, not in liver. There was a two-fold variation of covalently bound radioactivity in different brain areas of 3H2-MPTP-treated monkey. This reactive metabolite may play a role in MPTP neurotoxicity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Cytotoxicity of dichloromethane diphosphonate and of 1-hydroxyethane-1,1-diphosphonate in the amoebae of the slime mould Dictyostelium discoideum. A 31P NMR study.

Two pyrophosphate analogues, dichloromethane diphosphonate (Cl2MDP), and 1-hydroxyethane-1,1-diphosphonate (EHDP), at concentrations of 0.5-1 mM, efficiently inhibited the growth of amoebae of the slime mould Dictyostelium discoideum. Cell viability decreased markedly upon incubation with the diphosphonates. The mechanism of toxicity was investigated by in vivo 31P NMR spectroscopy and the formation of analogues of ATP [adenosine 5'-(beta, gamma-dichloromethane triphosphate) and adenosine 5'-(beta, gamma-1-hydroxyethane triphosphate)] was demonstrated. These two compounds were identified from their 31P NMR spectra in perchloric acid extracts prepared from amoebae poisoned with Cl2MDP or EHDP and may have been synthesized by reversible pyrophosphate exchange catalysed by cytosolic aminoacyl-tRNA synthetases.

Animals↗
PubMed1979

Involvement of catecholamines in eliciting LH peaks in 15-day-old female rats: effects of treatment with prolactin.

In the serum of 15-day-old female rats, treated either with alpha-methyl-p-tyrosine (alpha-MPT) or saline, serum LH levels were determined. From the brains of all animals the medial preoptic areas (MPO) and the anterior and posterior mediobasal hypothalami (AMBH and PMBH) were punched out and stored frozen in perchloric acid. In the punches of those animals with very high or basal LH levels catecholamine concentrations were measured radioenzymatically and on the basis of the degree of catecholamine depletion after alpha-MPT the turnover rates of dopamine (DA) and norepinephrine (NE) were calculated. NE turnover in the MPO was significantly higher in the animals with high LH levels as compared to those with low LH values. In the PMBH an inverse correlation between LH levels and NE turnover rates could be demonstrated. NE turnover in the AMBH, and DA turnover in all 3 structures did not correlate with serum LH levels. Serum FSH and prolactin levels were higher in the animals with high LH levels. These changes are similar to those observed in adult proestrous rats and it is concluded that the LH peaks in 15-day-old animals reflect a positive feedback action of estradiol. In a second experiment prolactin was administered to determine if it could prevent the occurrence of these LH peaks. Ovine prolactin (2 X 0.5 micrograms/g body weight) injected from day 8--15 suppressed serum LH levels to almost undetectable values. Catecholamine turnover measurements in these animals revealed increased DA turnover in the MPO, AMBH and PMBH, whereas NE turnover was not affected. These results indicate that DA turnover of the incertohypothalamic and of the tuberoinfundibular DA neurons is accelerated by prolactin and that an increased DA turnover in one of these systems is responsible for inhibition of LH release.

Animals↗
PubMed1990

Selective cross-activation/inhibition of second messenger systems and the reduction of age-related deficits in the muscarinic control of dopamine release from perifused rat striata.

Possible alterations in muscarinic cholinergic (mACh) signal transduction in senescence were studied in rat neostriata. Acetylcholine (ACh) activation of striatal muscarinic heteroreceptors by carbachol or oxotremorine enhances K(+)-evoked release of dopamine from perifused striata of 6- but not 24-month-old rats. Present experiments determined the effects of simultaneous activation or activation/inhibition of more than one second messenger on K(+)-evoked release of DA from perifused striatal slices from these age groups. Combinations of carbachol (500 microns), which stimulates inositol-1,4,5-bisphosphate (IP3) production and inhibits cyclic AMP production, with oxotremorine (500 microns), which inhibits cyclic AMP production, in the presence of 30 mM KCl (in a modified Krebs-Ringer medium) reduced the age-related reduction in mAChR enhancement of DA release (analyzed by HPLC coupled to electrochemical detection; 5 min fractions were collected on ice in perchloric acid; flow rate 120 microliters/min). Combinations of these agonists with the putative second messenger arachidonic acid (10 microM), also enhanced K(+)-evoked release of DA in the striatal tissue from the 24-month group. IP3 activation was lower in the striatal tissue from old animals than those from young under all conditions, but cross-activation/inhibition actually may have lowered the IP3 threshold necessary for enhanced DA release to occur. In a subsequent experiment, pre-loading striatal tissue from young animals with either carbachol or oxotremorine under basal release conditions reduced the responding when the basal release medium was switched to one containing 30 mM KCl and combinations of the agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Estradiol-induced prolactinomas: differential effects on dopamine in posterior pituitary and median eminence.

Prolactin release is inhibited by dopamine and stimulated by estradiol. Dopamine is released from nerve terminals in the median eminence and posterior pituitary. Estradiol may act directly on the anterior pituitary or by modulating the two dopaminergic systems. Estradiol treatment induces the formation of prolactinomas in Fischer 334 rats. Therefore, this strain was chosen as the experimental model. The first objective was to determine whether estradiol differentially regulates the two dopaminergic systems. The second objective was to explore whether the anterior pituitary in estradiol-treated rats acquires the capability for de novo synthesis of dopamine. Rats were ovariectomized and implanted with estradiol capsules (OVEX + E2). Controls were untreated ovariectomized rats (OVEX). Three weeks thereafter, rats were killed. Anterior and posterior pituitaries and medial basal hypothalami (MBH) were removed and individually incubated for 60 min in Hank's balanced salt solution containing 10 microCi [3H-]tyrosine. The median eminence was then dissected from the MBH. Tissues were homogenized in perchloric acid and the supernatant fluids were extracted with alumina. Both endogenous and tritiated dopamine were simultaneously quantitated by HPLC. Prolactinoma formation in OVEX + E2 rats was confirmed by dramatic rise (50-fold) in plasma prolactin levels and marked enlargement (3-fold) of the anterior pituitary. Estradiol treatment caused a significant 60% reduction in both dopamine content and synthesis in the median eminence. In contrast, estradiol treatment affected neither dopamine content nor synthesis in the posterior pituitary. There was no evidence for de novo synthesis of dopamine in anterior pituitaries from either OVEX or OVEX + E2 rats. We conclude that the two dopaminergic systems which regulate prolactin secretion, exhibit a differential response to estradiol.

Animals↗
PubMed1986

Activated human lymphocytes secrete a soluble factor that aggregates leukocytes.

Human polymorphonuclear leukocytes can be activated by various inflammatory stimuli to display increased cell aggregation which is potentially an important pathogenetic mechanism. This study describes a soluble factor produced by concanavalian A-stimulated lymphocytes that causes human leukocytes to aggregate. This factor could be assayed quantitatively by measuring the light absorbance of polynuclear leukocyte suspension using a spectrophotometer. The lymphokine involved, namely the leukocyte aggregating factor (LAgF) was released by non pulse exposure to the mitogen for up to 72 hr with a maximum at 48 hr. LAgF was characterized by Sephadex gel filtration, chromatofocusing, enzymatic and chemical treatment. Sephadex G 100 gel filtration showed LAgF activity in a molecular range of 40,000-65,000. Chromatofocusing of culture supernatant showed LAgF in a single broad peak (4.8-5.4) with a maximum activity at pI 5.2. Human LAgF was heat sensitive, inactivated by treatment with chymotrypsin, and not affected by neuraminidase. Activity was partially recovered from the supernatant after protein precipitation with 1 M perchloric acid and not destroyed by 0.02 M sodium periodate. These findings characterize LAgF as a protein. These data suggest that LAgF is not different from leukocyte inhibiting factor by virtue of its size and physiological properties.

Cell Adhesion Molecules↗
PubMed1980

Chemical reactivity and metabolism of norethindrone-4 beta,5 beta-epoxide by rat liver microsomes in vitro.

A method has been developed to separate norethindrone and norethindrone-4 beta,5 beta-epoxide by high performance liquid chromatography using isocratic solvent systems with either ODS-reverse phase or conventional silica gel columns. Using these techniques it was found that norethindrone epoxide, prepared chemically, was stable in aqueous buffer (pH 7.4) at 37 degrees C for at least 1 h. Under similar conditions, in the presence of a 10-fold molar excess of cysteine or glutathione, the half life for norethindrone epoxide was 15 and 32 min respectively. In 0.01 M perchloric acid at 37 degrees C the t 1/2 of norethindrone epoxide was 17 min. Norethindrone epoxide was rapidly degraded by rat liver microsomal epoxide hydratase to give a metabolite having properties consistant with it being norethindrone-4,5-dihydrodiol. Epoxide hydratase activities were stimulated about three fold by pretreating rats with phenobarbitone. The pH optimum for this reaction was pH 7.4. Conversion of norethindrone epoxide to norethindrone-dihydrodiol was inhibited by the epoxide hydratase inhibitor 1,2-epoxytrichloropropane. Although norethindrone was extensively metabolised in the presence of NADPH and rat liver microsomes, no conversion to norethindrone-4 beta,5 beta-epoxide could be demonstrated, either in the presence or absence of epoxytrichloropropane in the reaction mixture. If norethindrone epoxide was produced under these conditions it was suggested that it either reacted with microsomal proteins at or close to the site or production or was further metabolised. Norethindrone-4 beta,5 beta-epoxide did not cause any loss of cytochrome P-450 when incubated with rat liver microsomes in the absence of NADPH. Only in the presence of NADPH did further metabolism of norethindrone epoxide occur leading to the formation of active metabolites capable of breaking down cytochrome P-450. The initial rate of loss of cytochrome P-450 under these conditions was greater with norethindrone than with norethindrone epoxide as the substrate.

Animals↗
PubMed1981

The isolation and characterization of 3-(2-carboxyethyl)cytosine following in vitro reaction of beta-propiolactone with calf thymus DNA.

The new adduct 3-(2-carboxyethyl)cytosine (3-CEC) was isolated following in vitro reaction of the carcinogen beta-propiolactone (BPL) with calf thymus DNA. The structure of 3-CEC was confirmed by synthesis from BPL and dCyd. Reaction of BPL with cCyd (pH 7.0-7.5, 37 degrees C) gave 3-(2-carboxyethyl)deoxycytidine (3-CEdCyd) (9% yield) and 3,N4-bis(2-carboxyethyl)deoxycytidine (3,N4-BCEdCyd) (0.6% yield). 3-CEdCyd and 3,N4-BCEdCyd were hydrolyzed (1.5 N HCl, 100 degrees C, 2 h) to 3-CEC and 3,N4-bis(2-carboxyethyl)cytosine (3,N4-BCEC), respectively. The structure of 3-CEC was assigned on the basis of UV and NMR spectra and the electron impact (EI) mass spectra of 3-CEC and a tri-trimethylsilyl (TMS) derivative of 3 CEC as well as deuterated (d27) tri-TMS derivative of 3-CEC. The structure of 3,N4-BCEC was assigned on the basis of UV spectra and the EI mass spectra of a tri-TMS derivative. Ei and isobutane chemical ionization mass spectra of 3-methylcytosine (3-MeCyt) and a di-TMs derivative of 3-MeCyt were obtained and were helpful in deducing the structures of 3-CEC and 3,N4-BCEC. This is the first report of the alkylation by BPL of an exocyclic atom on a base in DNA. Compound 3,N4-BCEC was not detected in BPL-reacted calf thymus DNA. The relative amounts of 1-(2-carboxyethyl)-adenine (1-CEA), 7-(2-carboxyethyl)guanine (7-CEG), 3-(2-carboxyethyl)-thymine (3-CET) and 3-CEC isolated from BPL-reacted DNA following perchloric acid hydrolysis were 0.23, 1.00, 0.39 and 0.41 respectively, when the alkylation reaction was conducted in phosphate buffer at 0-5 degrees C and pH 7.5 and 0.10, 1.00, 0.29 and 0.28 respectively when the reaction was conducted in H2O at 37b degrees C and pH 7.0-7.5.

Animals↗
PubMed1986

A simplified procedure for lipid phosphorus analysis shows that digestion rates vary with phospholipid structure.

A simplified procedure for lipid digestion, well suited for handling a large number of samples, was used to analyze a variety of common phospholipids. This procedure involves digestion of phospholipids in perchloric acid at 130 degrees C with minimal sample manipulation. For all lipids tested, complete destruction, needed for quantitation of phosphate, was achieved after a few hours of digestion under these conditions. Rates of phospholipid destruction, monitored by the spectrophotometric quantitation of released phosphate, varied with lipid structure. Phosphatidic acid (PA), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylinositol (PI) were found to release phosphate faster than phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylcholine (PC). Although these differences may vary depending on the digestion conditions, they suggest that care should be exercised in lipid phosphate analyses to insure complete digestion.

Animals↗
PubMed1975

The fluorimetric determination of ammonia in protein-free filtrates of human blood plasma.

Ammonia has been determined in filtrates of human plasma after precipitation of the proteins by perchloric acid. After restoration of the pH to around 7.5, addition of 2-oxoglutarate, NADH and glutamate dehydrogenase (GDH) convers the ammonia to L-glutamate with oxidation of the NADH to NAD. This latter reaction was utilised in two ways. In the first, reduction of native NADH fluorescence under the conditions of the GDH reaction provided a measure of ammonia concentration. In the second, residual NADH was destroyed by acid treatment, and the fluorescent product generated from NAD under strongly alkaline conditions was assayed. The optimal requirements for both methods were defined, their linearity and precision ascertained, and their relative merits compared. The first method was convenient for "one-off" estimations, and the second for larger batches. Ammonia concentration increased in plasma and in acid protein-free filtrates of plasma irrespective of the conditions of storage; however when the latter were neutralised, storage at -20 degrees C was effective. The distribution of plasma ammonia concentration in healthy subjects was log-normal. The range for males was 21-58 mumol/1 and for females 17-51 mumol/1; this difference was statistically significant (P less than 0.01).

Ammonia↗
PubMed1976

Detection of circulating carcinoembryonic antigen (CEA) by counter-immunoelectrophoresis.

A sensitive method is described for detecting circulating carcinoembryonic antigen (CEA) by combined use of counter-immunoelectrophoresis and intensifiers. Perchloric acid extraction of serum was followed by counter-immunoelectrophoresis against monospecific antiserum to CEA. A precipitin line formed was intensified further by electrophoretic binding of anti-gammaG gamma-globulin and Amido Black staining. Less than 10 ng CEA/ml was detectable. Using this method, a total of 84 sera from patients with or without malignancy was examined. The results obtained were in general agreement with those reported by radioimmunoassay. The method appears to be useful as a diagnostic aid, since it requires neither labeled preparations of purified CEA nor special equipment for assay.

Antigens, Neoplasm↗
PubMed1983

Sensitive and simplified method for the differential determination of serum levels of ketone bodies.

A highly sensitive and simplified method for the differential determination of serum ketone bodies has been developed. Serum was deproteinized with perchloric acid, and acetoacetate contained in the supernate was reacted with newly synthesized p-nitrobenzene diazonium fluoroborate at 37 degrees C for 10 min. The formed hydrazo compound was converted by alkali to the more stable azo compound which has a peak absorbance at 645 nm. For the determination of 3-hydroxybutyrate, this was enzymatically converted to acetoacetate using 3-hydroxybutyrate dehydrogenase, LDH, NAD and pyruvate. Using 0.2 ml serum, acetoacetate and 3-hydroxybutyrate could be quantitated in 30 min. The described method is five times more sensitive than the enzymatic photometric method and can detect individual ketone bodies at concentrations as low as 20 mumol/l. Differential determination of serum levels of ketone bodies is clinically useful for the diagnosis of type 1 diabetes and in monitoring diabetic control.

3-Hydroxybutyric Acid↗
PubMed1993

A salt-free isocratic high-pressure liquid chromatographic method for the quantitation of benzodiazepines in serum.

A simple, rapid high-pressure liquid chromatography (HPLC) method was developed for detecting and quantifying benzodiazepines in serum. Seven major benzodiazepines were extracted from spiked serum samples using solid-phase extraction with prazepam as the internal standard. The eluted drugs were then resolved isocratically by HPLC within 11 min using a reversed-phase C8 column with a mobile phase consisting of acetonitrile, methanol, water, and perchloric acid. All drugs gave responses that varied linearly with concentration over the ranges studied. Within-day imprecision (CV) varied from 3.9 to 14.9%, day-to-day CV from 4.8 to 17.0%, absolute recoveries from 67% to 114%, and detection limits from 10 to 110 ng/mL. Tricyclic antidepressants did not interfere, and clinical results were in good agreement with those obtained by a gas chromatographic method. The advantage of this method is that it uses a salt-free isocratic mobile phase that can be easily manipulated to effect difficult benzodiazepine separations.

Anti-Anxiety Agents↗
PubMed1994

A method for determination of xylose utilizing glucose dehydrogenase.

A method is described for xylose determination on the Ciba-Corning 550 Express that utilizes the slower enzymatic action of glucose dehydrogenase (GDH) on D-xylose, after prior removal of glucose. Glucose oxidase is added to serum or urine and incubated for 120 min at 37 degrees C. After incubation, a perchloric acid filtrate of the specimen is added to the GDH reagent in the presence of NAD, the amount of NADH produced being proportional to the amount of xylose present. Absorbances at 340/380 nm are read at 180 s and 600 s after the reagent is added. The standard curve is linear to 7.50 mmol/L and the method showed day-to-day imprecision (CV%) of 2.7 (n = 18), 1.8 (n = 17), and 2.2 (n = 17) at concentrations of 0.62, 1.18, and 2.60 mmol/L, respectively. Recoveries ranged from 99 to 106% for sera and 96 to 100% for urines. Good correlation was obtained when tested against established automated ferricyanide and p-bromoaniline methods.

Glucose 1-Dehydrogenase↗
PubMed1984

Diffusible factors are responsible for differences in nuclease sensitivity among chromatins originating from different cell types.

We have examined the kinetics of nuclease digestion of chromatin from committed and uncommitted cells in experiments where the nuclei are mixed and co-digested. Cultures of the sea urchin, Arbacia punctulata, were grown to the 16-cell stage in either [3H]thymidine or [14C]thymidine and the macromere, mesomere, and micromere cell types separated. After isolation, sets of nuclei with two different blastomere types (each having different radionucleotide tagging) were mixed and co-digested with micrococcal nuclease or DNase. I. The extent of digestion was monitored by solubility in 5% perchloric acid (PCA). We find no significant differences in initial digestion rates or limit digests among the different cell types when co-digested with either nuclease. Differences in nuclease sensitivity observed when nuclei are digested separately are abolished when nuclei are probed in a mixing experiment. The results support the hypothesis that phenotypic differences in digestibility among different cell types in vitro reflect differences in chromatin-condensing factors which can diffuse between nuclei.

Animals↗
PubMed1990

31P NMR study of intracellular pH during the respiratory burst of macrophages.

The metabolic events occurring during the respiratory burst of macrophages previously primed in vivo with lipopolysaccharide were studied by 31P nuclear magnetic resonance, using the P388D1 cell line as a model of the mature macrophages. Using perchloric acid extracts, the presence of phosphocreatine was shown in the primed cells, indicating that in control P388 D1 macrophages, in which no phosphocreatine was seen, in vivo maturation was incomplete. The cells primed in vivo exhibited greater maturation than the control cells, as well as greater creatine kinase activity. Perfusion of gel-embedded macrophages allowed the monitoring of phosphorylated metabolite peak intensities and of the intracellular pH. After the respiratory burst of the primed macrophages had been triggered by concanavalin A, these intensities did not alter significantly, but the intracellular pH decreased. 31P NMR spectra reflected transient acidification in the primed cells, possibly due to the formation of endocytic vesicles and their fusion with lysosomes.

Animals↗