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PubMed1978

Kinetic studies on the formation of nitrosamines I. Formation of dimethylnitrosamine in aqeous solution of perchloric acid.

The kinetics of nitrosation of dimethylamine (DMA) in aqueous perchloric acid solution have been studied using a differential spectrophotometric technique. The rate law is Initial rate = e[DMA]0 [nitrite]2 0 [H+]/(f + [H+])2 where [DMA]0 and [nitrite]0 represent initial stoichiometric concentrations. At 310.0 K and mu = 2.0 M, e = (2.2 +/- 0.2) X 10(-5) M-1 s-1 and f = (1.28 +/- 0.02) X 10(-3) M. The associated activation energy is 56 +/- 3 kJ mol-1. A clear inhibition of the nitrosation rate by ionic strength has been observed in which only the kinetic parameter (f) has an effective change. It is concluded that under the experimental conditions of this work only the dinitrogen trioxid is the effective carrier for the nitrosation.

Dimethylnitrosamine↗
PubMed1995

Thyroid scintigraphy and perchlorate discharge test in the diagnosis of congenital hypothyroidism.

Quantitative thyroid scanning using low doses of technetium-99m sodium pertechnetate was performed on 147 infants (55 males and 92 females) with congenital hypothyroidism detected through the national neonatal screening programme. Thirty-two (21.8%) were athyrotic, while 62 (42.2%) had an ectopic thyroid and 53 (36%) had a eutopic gland with increased 99mTc uptake (mean 17%; range, 5%-38%). The perchlorate discharge test (PDT) was performed in nine of the infants with ectopic glands and 15 with eutopic glands; the findings were consistent with an organification defect in 22 cases (seven ectopic and 15 eutopic). Thyroid scintigraphy and PDT can add useful aetiological, genetic and prognostic information in the clinical evaluation of infants with congenital hypothyroidism detected by neonatal screening.

Choristoma↗
PubMed2004

Ki-ras mutational analysis in rat follicular-cell proliferative lesions of the thyroid gland induced by radioactive iodine and potassium perchlorate.

Although in both human and experimental pathology ras mutations have been related to the origin and progression of follicular-cell tumours, reports differ considerably with respect to the frequency of such mutations. The present paper reports, using direct sequencing, the incidence of Ki-ras mutations (codons 12 and 13) in follicular-cell carcinomas of the thyroid gland in Wistar rats induced by administration of radioactive iodine and potassium perchlorate. Direct sequencing revealed no mutations in the amplified gene segment of any of the 72 carcinoma samples studied. This absence of mutations agrees with some and is in sharp contrast with other previous reports in the literature, both for experimental animals and in studies of human thyroid follicular-cell carcinoma. Our results suggest that Ki-ras activation via mutations at codons 12 and 13 is neither a constant event nor an early event in the development of rat thyroid follicular-cell carcinoma.

Adenocarcinoma, Follicular↗
PubMed2001

Perchlorate stimulates insulin secretion by shifting the gating of L-type Ca2+ currents in mouse pancreatic B-cells towards negative potentials.

The effects of the chaotrophic anion perchlorate (ClO4-) on glucose-induced electrical activity, exocytosis and ion channel activity in mouse pancreatic B-cells were investigated by patch-clamp recordings and capacitance measurements. ClO4- stimulated glucose-induced electrical activity and increased the action potential frequency by 70% whilst not affecting the membrane potential when applied in the presence of a subthreshold concentration of the sugar. ClO4- did not influence ATP-dependent K (KATP) channel activity and voltage-gated delayed K+ current. Similarly, ClO4- had no effect on Ca2+-dependent exocytosis. The stimulation of electrical activity and insulin secretion was instead attributable to an enhancement of the whole-cell Ca2+ current. This effect was particularly pronounced at voltages around the threshold for action potential initiation and a doubling of the current amplitude was observed at -30 mV. This was due to a 7-mV shift in the gating of the Ca2+ current towards negative voltages. The action of ClO4- was more pronounced when added in the presence of 0.1 mM BAY K8644, whereas no stimulation was observed when applied at a maximal concentration of the agonist (1 mM). Single-channel recordings revealed that the effect of ClO4- on whole-cell currents was principally due to a 60% increase in the mean duration of the long openings and the number of active channels. We propose that ClO4- stimulates insulin secretion and electrical activity by exerting a BAY K8644-like action on Ca2+ channel gating.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2005

Effects of geometric isomerism in dinuclear platinum antitumor complexes on aquation reactions in the presence of perchlorate, acetate and phosphate.

The aquation and subsequent reactions of the dinuclear Pt antitumor complexes [{trans-PtCl(NH(3))(2)}(2)(mu-NH(2)(CH(2))(6)NH(2))](2+) (1,1/t,t) and [{cis-PtCl(NH(3))(2)}(2)(mu-NH(2)(CH(2))(6)NH(2))](2+) (1,1/c,c) in 15 mM perchlorate, acetate or phosphate solutions were followed at 298 K by [(1)H,(15)N] HSQC 2D NMR spectroscopy. Rate and equilibrium constants for the initial reversible aquation and the subsequent reversible reaction with phosphate or acetate are reported. The rate constant for the first aquation step is two-fold lower for 1,1/c,c than 1,1/t,t but the anation rate constants are similar so that the equilibrium lies further towards the chloro form for the 1,1/c,c compound. A pK (a) value of 6.01+/-0.03 was determined for the diaquated species [{cis-Pt(NH(3))(2)(H(2)O)}(2)(mu-NH(2)(CH(2))(6)NH(2))](4+) (1,1/c,c-3) which is 0.4 units higher than that of the 1,1/t,t compound. The rate constants for the binding of acetate and phosphate to 1,1/t,t are similar, but the rate constant for the reverse reaction is close to ten-fold higher in the case of phosphate so that equilibrium conditions are attained more rapidly (12 h compared with 64 h). On the other hand, for 1,1/c,c the rate constants for the forward and reverse reactions with acetate and phosphate are quite similar so that equilibrium conditions are reached very slowly (80-100 h) and a greater proportion of phosphate-bound species are present. The reduced lability of the bound phosphate for 1,1/c,c is attributed to the formation of a macrochelate phosphate-bridged species which was characterized by (31)P NMR and ESI-MS. The speciation profiles of 1,1/t,t and 1,1/c,c under physiological conditions are explored.

Acetates↗
PubMed1987

A direct determination of taurine in perchloric acid-deproteinized biological samples.

A high-performance liquid chromatographic method was developed to estimate the amount of taurine in tissue extracts and body fluids. Shodex Ionpak C-811, an adsorption-distribution type column, was chosen and combined with 3 mM perchloric acid as the mobile phase. The eluted taurine was derivatized with o-phthaladehyde-2-mercaptoethanol reagent and measured at an absorbance of 350 nm instead of fluorescent intensity. Using this method, it was possible to isolate and estimate the amount of taurine from other coexisting substances or structural analogs such as hypotaurine, cysteamine, or cysteinesulfinic acid. For rapid routine assays of taurine in many biological samples, it is advisable that the tissue extracts be pretreated with cation-exchange resin to exclude other interfering substances including O-phosphoserine. The linear relationship between the concentration of taurine and absorbance achieved over the concentration range 0.1-10.0 nmol and the recoveries obtained were 98-101% by the internal standard method. The specificity, reproducibility, and sensitivity of this method for taurine were good enough to be used for biological applications. Examples of the tissue levels of taurine in various organs of the rat, as determined by this new method, are also presented.

Animals↗
PubMed1989

Purification of human genomic DNA from whole blood using sodium perchlorate in place of phenol.

We have developed a new, rapid method for the extraction of human genomic DNA from whole blood samples. Traditionally, genomic DNA has been extracted from blood by overnight proteinase K digestion of lysed peripheral lymphocytes followed by phenol/chloroform extraction. In addition to being time consuming, the use of phenol involves inherent risks due to the toxic nature of the reagent. Our method for the extraction of DNA from whole blood uses sodium perchlorate and chloroform instead of phenol with a significant time savings realized as well as fewer hazards to the technician. Furthermore, DNA prepared by this new method is an excellent substrate for restriction endonuclease digestion and Southern hybridization analysis.

Blotting, Southern↗
PubMed1990

Formation of hydrogen peroxide during precipitation of red cells with perchloric acid. A cautionary note for precise determination of pyruvate, GSH, and NAD(P)H.

The instability of pyruvate in neutralized perchloric acid extracts of erythrocytes is well-known from the literature. As shown in this study, the main reason for this phenomenon is a reaction of pyruvate with hydrogen peroxide, which is formed from oxyhemoglobin during acid precipitation. Thereby, pyruvate is oxidized to carbon dioxide and acetate. This decomposition is easily prevented by addition of catalase to the neutralized extracts, whereby authentic pyruvate can be determined precisely. Similarly, GSH and NAD(P)H oxidation in the extracts is prevented by addition of catalase.

Chemical Precipitation↗
PubMed1977

Comparison of whole plasma and perchloric acid-extracted plasma assays for carcinoembryonic antigen.

A direct, paired, comparison was made of two plasma radioimmunoassays for carcinoembryonic antigen (CEA), between a perchloric acid-extracted, ammonium sulphate precipitation method; and a whole-plasma, double-antibody method. For both assays the same preparations of standard CEA, 125I-labelled CEA, and anti-CEA serum were used. Plasma samples were taken from young healthy subjects (24), cancer-free hospital inpatients (44) and cancer-proven untreated patients (94). Within-batch and between-batch variation were both greater for the extracted-plasma method. Cancer discriminatory ability was assessed by probabilistic means. With cancer-free inpatients as the reference group, no difference between the assay methods was revealed. With young healthy subjects as the reference group the whole-plasma assay was superior.

Adult↗
PubMed1993

Glutathione, but not glutamine, is detected in 13C-NMR spectra of perchloric acid extracts from C6 glioma cells.

Glutamine, which is expected to be produced by C6 glioma cells, is not detected in both amino-acid analyses and 13C-NMR spectra of perchloric acid extracts of cells incubated for 4 h with [1-13C]glucose in the absence of extracellular glutamine. However, the resonances of a glutamate-linked product are observed in these spectra. The analysis of the pH dependence of chemical shifts from various glutamate-derived compounds shows that the observed resonances came from glutathione. Glutamine and glutathione signals are in close proximity on the frequency scale, leading to possible misinterpretation of the spectra.

Brain Neoplasms↗
PubMed1982

Perchloric acid treatment of human blood for quantitative endotoxin assay using synthetic chromogenic substrate for horseshoe crab clotting enzyme.

A new reliable human blood treatment was established for quantitative endotoxin assay using synthetic chromogenic substrate [Boc-Leu-Gly-Arg-rho-nitroanilide]. Addition of perchloric acid in a final concentration of 1.25% to platelet-rich plasma or serum in a 2:1 volume ratio completely eliminated nonspecific amidase activities as well as inhibitors. By this method, the recovery of added endotoxin was nearly 100%, and was almost independent of sample dilutions and anticoagulants.

Amidohydrolases↗
PubMed1995

A critical assessment of brain metabolites: analysis of perchloric acid extracts using proton nuclear magnetic resonance.

A critical assessment of perchloric acid (PCA) brain tissue extracts for precise identification and quantitation of brain metabolites using in vitro proton nuclear magnetic resonance (1H NMR) spectroscopy was studied. One pulse with a presaturation NMR experiment was used. The chemical shifts and coupling networks of the major brain metabolites as a function of pH were characterized by using individual model compounds and a model mixture solution. We found that the conditions of the PCA solution are essential for accurate interpretation of NMR spectra of brain metabolites. The maximum spectral resolution was obtained at pH 4.92. Caution is necessary when using high resolution 1H NMR spectroscopy to identify and quantify brain metabolites.

Animals↗
PubMed1984

Perchloric acid treatment and use of chromogenic substrate in the Limulus test: application to veterinary diagnosis.

The Limulus test was carried out for endotoxin determination using a synthetic chromogenic substrate after perchloric acid(PCA) treatment to remove inhibiting substances in the blood. PCA treatment completely removed non-specific amidolytic activity and other factors which interfered with the Limulus test. The recovery of added endotoxin was about 100% irrespective of animal species. Endotoxin levels in PCA-treated blood plasma of healthy domestic animals were invariably below 1 pg ml-1. Many of the cows with gangrenous mastitis, from which Gram-negative rods were isolated, showed high endotoxin levels ranging from 22.8 to 138.0 pg ml-1. Endotoxin was also detected in the blood of cows affected with salmonellosis, colibacillosis, Haemophilus somnus infection and urethritis associated with Proteus.

Animals↗
PubMed1991

Purification of apyrase from yellow lupin cotyledons after extraction with perchloric acid.

Neutralized 1 M perchloric acid (PCA) extracts of yellow lupin (Lupinus luteus) seedling cotyledons contain considerable amounts of apyrase (EC 3.6.1.5). Investigators who use PCA extraction for the estimation of nucleotide levels, particularly in plant tissues, should be aware of this danger. Only when the material is treated with 1.8-2 M PCA are the extracts obtained free of apyrase activity. Chromatography of neutralized 1 M extracts obtained from 7-day-old seedling cotyledons on DEAE-Sephacel and Sephadex G-100 yields almost homogeneous apyrase that shows a band of M(r) 51,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels. The molecular weight of the native enzyme is also about 51,000. The apyrase preparation is free of nonspecific phosphatases, nucleotidases, and adenosine nucleosidase, as well as dinucleoside polyphosphate-degrading enzymes. The apyrase exhibits a broad pH optimum between 6 and 8. Mg2+ and Ca2+ are required for maximum activity; Zn2+ and Mn2+ are less effective and Co2+, Ni2+, and Cd2+ are without effect. The Km values for ATP and ADP are about 20 microM. All common 5'-nucleoside tri- and diphosphates as well as adenosine 5'-tetraphosphate are substrates.

Adenine Nucleotides↗
PubMed2005

Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of D-glucose and D-fructose by N-bromoacetamide in the presence of perchloric acid: a kinetic and mechanistic study.

The kinetics of Pd(II)-catalysed and Hg(II)-co-catalysed oxidation of D-glucose (Glc) and D-fructose (Fru) by N-bromoacetamide (NBA) in the presence of perchloric acid using mercury(II) acetate as a scavenger for Br- ions have been studied. The results show first-order kinetics with respect to NBA at low concentrations, tending to zero order at high concentrations. First-order kinetics with respect to Pd(II) and inverse fractional order in Cl- ions throughout their variation have also been noted. The observed direct proportionality between the first-order rate constant (k1) and the reducing sugar concentration shows departure from the straight line only at very higher concentration of sugar. Addition of acetamide (NHA) decreases the first-order rate constant while the oxidation rate is not influenced by the change in the ionic strength (mu) of the medium. Variation of [Hg(OAc)2] shows a positive effect on the rate of reaction. The observed negative effect in H+ at lower concentrations tends to an insignificant effect at its higher concentrations. The first-order rate constant decreases with an increase in the dielectric constant of the medium. The various activation parameters have also been evaluated. The products of the reactions were identified as arabinonic acid and formic acid for both the hexoses. A plausible mechanism involving HOBr as the reactive oxidising species, Hg(II) as co-catalyst, and [PdCl3.S]-1 as the reactive Pd(II)-sugar complex in the rate-controlling step is proposed.

Acetamides↗
PubMed2005

Spectrophotometric determination of uranium with arsenazo-III in perchloric acid.

A short, sensitive and reliable spectrophotometric method, which has advantages over all known "wet chemistry" methods for uranium determination with regard to tolerance to common interferences, has been developed for the determination of uranium. Selectivity, molar absorptivity and the determination range of uranium have been enhanced by using 0.07% arsenazo-III as a chromogenic reagent. The use of 3 mol dm(-3) perchloric acid as a medium of determination was found to be excellent in terms of good solvent compatibility on dilution, destruction of organic contamination and simplicity of operation. The uranium-arsenazo-III complex formed instantly, and was found to be stable for more than 3 weeks with constant absorbance. Beer's law was obeyed up to a uranium concentration of 16 microg g(-1), with a molar absorptivity at 651 nm of 1.45x10(5) mol(-1) dm(3) cm(-1) at 24+/-2 degrees C. Only phosphate and citrate at 70-fold excess over uranium interfere seriously, whereas other anions studied could be tolerated up to a 70-fold excess over uranium. Of the cations studied, only Mn(II), Co(II), Ni(II), Cu(II) and Cr(III) decreased the normal absorbance of the complex. Iron(III), Ce(III) and Y(III) enhanced the absorbance. Other cations studied did not affect the absorbance up to a 50-fold excess. The accuracy was checked by determining uranium from standard solutions in the range 10-50 microg g(-1). It was found to be accurate with a 96.0-98.6% recovery rate. The method has been successfully applied to standard reference materials and ore samples at microg g(-1) levels.

Absorption↗