Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Perchlorates”

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 253 records · Page 14Linked to original sources
PubMed2006

Determination of low levels of perchlorate in lettuce and spinach using ion chromatography-electrospray ionization mass spectrometry (IC-ESI-MS).

A sample preparation method was developed to quantify environmentally relevant (low micrograms per liter) concentrations of perchlorate (ClO4(-)) in leafy vegetables using IC-ESI-MS. Lettuce and spinach were macerated, centrifuged, and filtered, and the aqueous extracts were rendered water-clear using a one-step solid-phase extraction method. Total time for extraction and sample preparation was 6 h. Ion suppression was demonstrated and was likely due to unknown organics still present in the extract solution after cleanup. However, this interference was readily eliminated using a Cl(18)O4(-) internal standard at 1 microg/L in all standards and samples. Hydroponically grown perchlorate-free butterhead lettuce was spiked to either 10.3 or 37.7 microg/kg of fresh weight (FW), and recoveries were between 91 and 98% and between 93 and 101%, respectively. Five types of lettuce and spinach from a local grocery store were then analyzed; they contained from 0.6 to 6.4 microg/kg of FW. Spike recoveries using the store-bought samples ranged from 89 to 100%. The method detection limit for perchlorate in plant extracts is 40 ng/L, and the corresponding minimum reporting limit is 200 ng/L or 0.8 microg/kg of FW.

Chromatography↗
PubMed2001

Comparison and evaluation of laboratory performance on a method for the determination of perchlorate in fertilizers.

This report details the interlaboratory validation of a method for the determination of perchlorate in fertilizers. In this method (EPA/600/R-01/026), a solid sample of fertilizer is ground. Subsequently, the ground material is either leached with deionized water to dissolve any perchlorate salt in the case of minimally soluble fertilizers (e.g. supertriplephosphate or timed-release products), or simply dissolved in the case of highly soluble fertilizers (e.g. urea, NaNO3 or KCl). The resulting aqueous solution is then subjected to ion chromatography with suppressed conductivity detection. Four laboratories applied the method to field samples of 48 different products (commodity chemicals) and to seven quality control samples prepared by the Environmental Protection Agency (EPA). Additional tests were conducted by three other laboratories on specific materials. Recovery (81-111%) was demonstrated on spikes of known concentration, and a preliminary assured reporting level was determined for each fertilizer matrix by each laboratory. Injection-to-injection precision was satisfactory: generally less than 15% difference, and always less than 25%. All of the laboratories used Dionex IonPac AG16 guard and AS16 separation columns with NaOH or KOH as eluent. Detection was by suppressed conductivity. The method was shown to be sufficiently robust for the screening of fertilizers for perchlorate, but performance was low on a mixture of siliceous minerals (kaolinite and bentonite). Both laboratory performance and method performance are validated.

Calibration↗
PubMed1993

Rapid purification and direct microassay of calbindin9kDa utilizing its solubility in perchloric acid.

The 9 kDa calcium-binding protein, calbindin9kDa, was found to be soluble in 7% (v/v) perchloric acid. Calbindin9kDa was easily purified from rat duodenum in 1 day with perchloric acid precipitation followed by reverse-phase h.p.l.c. The yield was 21.4 +/- 2.3 nmol/g wet weight of tissue (mean +/- S.E.M.; n = 3) from normally fed 7-8-week-old rats (approx. 70% recovery). The purification was also effective with rabbit duodenum calbindin9kDa, but not with various other EF-hand calcium-binding proteins tested in the rat. Several criteria (h.p.l.c., u.v. spectrum, denaturing two-dimensional PAGE, N-terminal sequencing) indicated that the rat calbindin9kDa was purified to homogeneity and was not affected by proteolysis. High-affinity calcium-binding properties were retained and no evidence of isoforms or charge modification was observed. Residue 59, identified as Asn (not Asp as previously reported), was fully amidated. When adopted as a microassay with isocratic h.p.l.c., the perchloric acid procedure enabled rapid (less than 6 min) and direct (peptide bond absorbance) quantification of less than 1 pmol of calbindin9kDa. This new approach to purification and assay will be of particular utility for investigations of calbindin9kDa in previously intractable low-abundance sources (e.g. cultured cells).

Amino Acid Sequence↗
PubMed1995

Isolation and characterization of a novel perchloric acid-soluble protein inhibiting cell-free protein synthesis.

We found a novel protein in the postmitochondria supernatant fraction of rat liver, which is soluble in 5% perchloric acid and strongly inhibits protein synthesis in a rabbit reticulocyte lysate system. The protein extracted from the supernatant fraction with 5% perchloric acid was purified by ammonium sulfate fractionation and CM-Sephadex chromatography. The protein was shown to consist of two identical subunits with a molecular mass of 14 kDa. By immunoscreening with the rabbit antisera against the protein, a cDNA encoding the protein was cloned and sequenced. The cDNA contained an open reading frame of 411 base pairs encoding a 136-amino acid protein with a molecular mass of 14,149 Da. The deduced amino acid sequence was completely identical with that constructed from all of the above peptides. Interestingly, the perchloric acid-soluble protein inhibited cell-free protein synthesis in the rabbit reticulocyte lysate system in a different manner from RNase A. The protein is likely to inhibit an initiation stage of cell-free protein synthesis. Among the rat tissues tested, the protein was located only in liver and kidney. These findings are the first report on a new inhibitor that may be involved in the regulation of protein synthesis in those tissues.

Amino Acid Sequence↗
PubMed1999

Returning perchlorate-contaminated fume hood systems to service. Part II. Disassembly, decontamination, disposal, and analytical procedures.

Part I presented work leading up to and including a pilot study for remediation of laboratory fume hood systems contaminated with residues from processes that used fuming perchloric acid. Since publication of Part I, three incidents involving explosions and fires related to perchlorates have come to the attention of the authors. Experience has been gained through decontamination/remediation of 41 additional systems. This article expands on previous one and includes (1) administrative details that need to be addressed before and during the execution of the decontamination itself, (2) a seven-step procedure for decontamination-remediation/disposal, (3) some precautions associated with the use of methylene blue as a diagnostic tool for perchlorates, and-specific electrode to augment or replace the methylene blue test.

Air Pollutants, Occupational↗
PubMed1994

Perchlorate-induced formation of the alpha-helical structure of mastoparan.

Mastoparan, a basic tetradecapeptide from wasp venom, has been considered to be unfolded under aqueous conditions. On the basis of the far-UV circular dichroism spectrum, we found that sodium perchlorate at molar concentrations stabilizes an alpha-helical structure of mastoparan. To understand the mechanism of the perchlorate-induced stabilization of the alpha-helical structure, we synthesized a dimeric form of mastoparan derivative, which was linked at the C terminal by a disulfide bond. The linkage decreased the concentration of perchlorate required to stabilize the alpha-helical structure by 30-fold. With the dimeric mastoparan derivative, we measured the effects of several salts such as sodium trichloroacetate, sodium trifluoroacetate, and sodium chloride. The concentration of salts required to induce the conformational transition varied and the order of effectiveness of different salts was consistent with the electroselectivity series of anions toward anion-exchange resins, indicating that the anion binding to the positively charged amino groups is responsible for the transition. These results suggest that the salt-induced formation of the alpha-helical state of mastoparan can be explained by a mechanism similar to that proposed for the salt-induced conformational transition of melittin.

Amino Acid Sequence↗
PubMed1987

'Off' tails of intramembrane charge movements in frog skeletal muscle in perchlorate-containing solutions.

1. Charge movements in response to hyperpolarizing ('off') voltage-clamp steps were examined in frog skeletal muscle fibres in the presence of 8 mM-perchlorate. 2. The appearance of prolonged 'off' decays, of duration 50-100 ms coincided with those of slow 'q gamma' charge transfers in preceding 'on' transients. 3. Charge was conserved in the presence of perchlorate whether testing or pre-pulse voltages were varied. Additionally, steady-state charge as a function of voltage was independent of the direction from which the voltage was reached. 4. 'Off' recoveries were most prolonged at voltages around -90 to -100 mV and became less marked with depolarization. 5. Charging currents in response to hyperpolarizing steps that intercepted prolonged ('q gamma') 'on' decays showed reduced slow 'off' tails but intact 'off' decays at early times. 6. Transients elicited by depolarizing steps that intercepted 'off' tail currents showed decreased slow 'on' components. By varying the time at which 'off' responses were so intercepted, it was shown that 'off' tails can require well over 100 ms to attain a steady state in perchlorate. 7. Prolonged depolarization to a holding potential of -30 mV inactivated delayed ('q gamma') components in both 'on' and 'off' responses but left the more rapid ('q beta') decays intact. 8. These observations are easier to reconcile with parallel systems responsible for independent early ('q beta') and delayed ('q gamma') transients in both 'on' and 'off' steps than with the existence of 'q beta' and 'q gamma' transitions in a causal sequence.

Action Potentials↗
PubMed2003

Microbial isotopic fractionation of perchlorate chlorine.

Perchlorate contamination can be microbially respired to innocuous chloride and thus can be treated effectively. However, monitoring a bioremediative strategy is often difficult due to the complexities of environmental samples. Here we demonstrate that microbial respiration of perchlorate results in a significant fractionation ( approximately -15 per thousand ) of the chlorine stable isotope composition of perchlorate. This can be used to quantify the extent of biotic degradation and to separate biotic from abiotic attenuation of this contaminant.

Betaproteobacteria↗
PubMed1975

Immunization against experimental Chagas' disease by using culture forms of Trypanosoma cruzi killed with a solution of sodium perchlorate.

Protection against infection with virulent blood (trypomastigote) forms of Trypanosoma cruzi was accomplished in mice by immunization with culture (mainly epimastigote) forms killed by treatment with sodium perchlorate. Sodium chloride, used instead of sodium perchlorate, with all other conditions kept the same, failed to kill all the organisms, indicating that the effects of the perchlorate anion were not simply ionic or osmotic, suggesting that they might be chaotropic. A single dose of the immunogen, without adjuvants, was sufficient to significantly protect against the infection. Protection was achieved by either intraperitoneal, intramuscular, or subcutaneous immunization, though the first two routes appeared to be more effective. After challenge, parasitemias were negative in 25, 29, and 17% of the animals immunized intraperitoneally, intramuscularly, and subcutaneously, respectively.

Animals↗
PubMed1989

Treatment of amiodarone induced hyperthyroidism with potassium perchlorate and methimazole during amiodarone treatment.

To exploit the antiarrhythmic effect of amiodarone when patients develop the side effect of thyrotoxicosis three patients with hyperthyroidism induced by amiodarone were given simultaneously 1 g potassium perchlorate a day for 40 days and a starting dose of 40 mg methimazole a day while they continued to take amiodarone. As hyperthyroidism might have recurred after potassium perchlorate treatment was stopped the dose of methimazole was not reduced until biochemical hypothyroidism (raised thyroid stimulating hormone concentrations) was achieved. The patients became euthyroid (free triiodothyronine concentration returned to normal values) in two to five weeks and hypothyroid in 10 to 14 weeks. One patient became euthyroid while taking 5 mg methimazole a day and 600 mg amiodarone weekly; the two others required substitution treatment with thyroxine sodium while taking 5 mg methimazole or 50 mg propylthiouracil (because of an allergic reaction to methimazole) and 2100 or 1400 mg amiodarone weekly. Hyperthyroidism induced by amiodarone may be treated with potassium perchlorate and methimazole given simultaneously while treatment with amiodarone is continued.

Aged↗
PubMed1981

Paradoxical effect of perchlorate on thyroidal weight, glucose 6-phosphate dehydrogenase and polyamines in methylthiouracil-treated rats.

The effect of sodium perchlorate (NaClO4) on the methylthiouracil-induced increase in the activity of thyroid glucose 6-phosphate dehydrogenase (G6PDH), ornithine decarboxylase (ODC) and polyamine contents was studied in the rat. The G6PDH activity was increased nearly three-fold by methylthiouracil (MTU) but not by ClO4- at 7 days of treatment. Perchlorate lowered the MTU-induced enzyme activity to nearly the control level, without changing circulating thyrotrophin (TSH). The anion had no inhibitory effect on G6PDH activity in vitro. The possibility that an inhibitor specific for G6PDH was generated in ClO4- - treated rat thyroids was excluded. The activity of ODC was greatly increased by both ClO4- and MTU, the increase being significant as early as on the second day of treatment. Perchlorate had no inhibitory effect on MTU-induced ODC activity in vivo but decreased total contents of spermidine and spermine in the thyroid, without affecting the concentration (nmoles/g wet weight) of the polyamines. These results suggest that ClO4- acts directly on the thyroid to suppress specifically the stimulatory effect of TSH on G6PDH activity and possibly on polyamine accumulation.

Animals↗
PubMed1988

Effects of a selenium deficient diet on thyroid function of normal and perchlorate treated rats.

Pregnant rats were submitted to a selenium-deficient diet immediately after mating; it was continued for 4 weeks after delivery. The pups were sacrificed at 3 and 4 weeks of age. Perchlorate, an antithyroid agent inhibiting iodide trapping in the thyroid, was administered via the drinking water to half of the rats. Rats submitted to a normal laboratory diet and to the experimental diet supplemented with selenium were used as controls. The effects of selenium deficiency were an increase in the number of growth abnormalities, growth retardation, and decreased seleno-dependent glutathione peroxidase (GSH-Px) activity in plasma and in various organs. These effects were relieved by selenium supplementation in the diet. Perchlorate treatment induced the classic picture of primary hypothyroidism. Selenium deficiency increased thyroid hormone levels in perchlorate-treated rats and in controls drinking tap water. In the latter group, it also decreased TSH plasma concentration and thyroid weight. These effects were partially reversed by Se supplementation. In vitro experiments, performed on adult rats, revealed increased radioiodide uptake and organification in glands from the rats submitted to the selenium-free diet. Plasma T3 half-life was similar in control and Se-deficient rats. These data suggest a higher efficiency of thyroid hormone synthesis in the thyroids of selenium-deficient rats, despite a lower thyroid stimulation as evaluated by serum TSH. They are compatible with the hypothesis that decreased selenium supply, leading to a decreased GSH-Px in the thyroid, increases hydrogen peroxide steady state level and thus thyroid peroxidase activity and thyroid hormone synthesis.

Animals↗
PubMed1978

[Effect of potassium iodide and perchlorate on the process of thyroid hormone secretion].

The influence of potassium iodide and perchlorate on the parameters characterizing the thypoid hormones secretion, such as the cAMP level in the gland tissue and the number of intracellular colloid droplets under condition of stimulation by thyrotropic hormone was studied. It was shown that the abovementioned parameters were depressed by an excess of iodide, but perchlorate administration prevented the inhibitory effect of iodide. The results obtained favour the conception on the sensitivity of the thyroid adenylate cyclase system to the organic iodine concentration. Apparently and excess of iodide depressed the capacity of perchlorate to influence its concentration in the gland, and thereby the process of iodine organification and of the thyroid hormone secretion maintained at the optimal leve.

Animals↗
PubMed1990

Evaluation of determination of lactate dehydrogenase isoenzyme 1 by chemical inhibition with perchlorate or with 1,6-hexanediol.

We have evaluated the determination of lactate dehydrogenase (EC 1.1.1.27) isoenzyme 1 activity by chemical inhibition of the other isoenzymes with perchlorate and with 1,6-hexanediol. In the hexanediol method, we studied the effect of the duration of incubation with the inhibitor; a 5-min incubation yielded results closest to those of an immunochemical technique (Isomune-LD). The perchlorate method was the most precise, and the hexanediol method the least, although for none of the techniques did the coefficient of variation exceed the medically acceptable limit prescribed by the College of American Pathologists. Pairwise correlation among the immunoprecipitation, electrophoretic, and chemical inhibition methods was good (r greater than 0.991), although the differences between means were statistically significant (except for the comparison of the two chemical inhibition methods). Because of its ease, low cost, and precision, we recommend the perchlorate method for routine use.

Adult↗
PubMedDate not supplied

[Determination of perchlorate in drug preparations].

For quantitative analysis of perchlorate in capsules and solutions it has been proposed acidometric determination of perchloric acid in eluate after the use of cation exchangers. The comparison was made with colorimetric method of perchlorate determination after ion pairing with methylen blue which is extracted with chlorophorm and shows the maximum absorption at 655 nm. As an alternative method it has been used flame photometry of cations of these salts. The worked-out method with ion exchangers is recommended as a very suitable due to speed and simplicity of work and accurate and reproducible results.

Capsules↗
PubMed1984

Effect of perchlorate treatment on mitochondrial MAO-A and -B activities.

Rat liver mitochondrial monoamine oxidase-A (MAO-A) and -B (MAO-B) were solubilized and isolated by procedures that included two cycles of treatment with a non-ionic detergent, Triton X-100, and then treatment with sodium perchlorate. After the treatment cycles with Triton X-100 about 23 and 36% of the original mitochondrial MAO-A and MAO-B activity, respectively, towards 0.1 mM serotonin and benzylamine remained in the residue. Of those activities, virtually no (2%) MAO-A activity, but appreciable (28%) MAO-B activity survived in the soluble state after the subsequent perchlorate treatment. The Km value and molecular turnover number of the soluble MAO-B, for benzylamine, were similar to those of the original activity in mitochondria, suggesting that this form of MAO has not undergone any qualitative change. After selective labelling of either form of MAO in mitochondria with 3H-pargyline and application of the isolation procedures, similar amounts of labelled MAO-A and -B were found in a soluble state, indicating that both forms of the enzyme were solubilized by the perchlorate treatment but that MAO-A was present in an inactivated state.

Animals↗
PubMed2005

Perchlorate-selective membrane electrode based on a new complex of uranil.

A potentiometric ion-selective electrode based on new compound, as a carrier, has been successfully developed for detection of perchlorate anion in aqueous solution. Within the perchlorate ion concentration range 1.0x10(-6) to 1.0 mol L(-1) the electrode had a linear response with a Nernstian slope of 60.6+/-1.0 mV per decade . The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot was 8.0x10(-7) mol L(-1). The proposed electrode has fairly a good discriminating ability towards ClO(4) (-) ion in comparison to other anions. The sensor has a response time of < or =10 s and can be used for at least 2 months without substantial divergence in potential. It was successfully applied to direct determination of perchlorate in urine and water.

Journal Article↗