SEARCH · PubMed Health

Results for “POLAROGRAPHY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 739 records · Page 41Linked to original sources

PubMed1982

Workplace air sampling and polarographic determination of formaldehyde.

A polarographic method has been developed for the determination of formaldehyde in workplace air. Samples are collected in midget fritted glass bubblers containing an aqueous solution of 10% methanol. The collected formaldehyde in the absorbent solution is derivatized with hydrazine reagent to form a formaldehyde hydrazone compound. An aliquot of the resulting solution is analyzed by differential pulse polarography at a dropping mercury electrode. The sample generation system, impinger collection, polarographic analysis, and precision and accuracy data are described. The method was validated over the range of 5.8 to 17.7 mg/cu m, which corresponds to 0.5 to 2 times the (peak) OSHA-PEL for a 30-liter sample at a flow rate of 1 Lpm. The average recovery was 103%. The pooled coefficient of variation or relative standard deviation was 0.08.

Air Pollutants↗

PubMed1987

Development of a sampling and analytical method for measuring the epoxy content of aerosols: I. Development of the analytical method.

A method has been developed for determining the quantity of the epoxide functional group in pure epoxy resins, resins in partially-cured mixtures with amine curing agents, and commercial epoxy surface coatings. The method is based upon the reaction of the epoxide group with bromide in the presence of acid, with measurement of excess bromide in the reaction mixture by normal pulse polarography. The method extends the range of previously reported methods for epoxy analysis to samples containing 1 to 100 microequivalents (microeq) of epoxide functionality, while maintaining good precision and accuracy (coefficient of variation less than 0.06; accuracy within 2% of expected). The method has been developed for application to analysis of the epoxy content of environmental aerosols such as those of epoxy paint sprays.

Aerosols↗

PubMed1987

Development of a sampling and analytical method for measuring the epoxy content of aerosols: II. Application of the method to epoxy-containing aerosols.

Aerosols generated by epoxy spray painting consist of droplets containing partially-cured mixtures of epoxy resins and curing agents, as well as pigments, solvents and diluents. A sampling and analytical method has been developed to measure the epoxy content of these aerosols. The method collects the aerosol in a midget impinger containing dimethyl formamide, which inhibits the curing reaction between the epoxy and curing agent, preserving the unreacted epoxy functional groups present in the aerosol. The impinger contents are analyzed by reacting the epoxy with an excess of bromide generated in situ from tetraethylammonium bromide, and measuring the unreacted bromide in the reaction mixture by normal pulse polarography. The precision and accuracy of the method have been evaluated using a pure epoxy resin as a model compound. The method was applied to aerosols containing mixtures of epoxy resin and amine curing agents in various degrees of cure, to aerosols containing large quantities of nonepoxy compounds, and to aerosols of epoxy surface coatings. The method is capable of precise and accurate measurement of epoxide functionality, and it applicable to the measurement of epoxy-containing aerosols in spray finishing operations.

Aerosols↗

PubMed1980

On-line PO2 and PN2O analysis with an in vivo catheter electrode.

A technique was developed for the in vivo determination of PO2 and PN2O with a catheter electrode using double-pulse polarography. The method was evaluated in dog studies comparing readings from the electrode with those from a mass spectrometer employing an in vivo probe. The oxygen readings obtained from the catheter electrode were also compared with values obtained by conventional blood-gas analysis. Good agreement was observed between the electrode and the mass spectrometer for both PO2 and PN2O. Similar agreement was found between the electrode readings and blood-gas analysis for PO2. In the presence of halothane, the electrode over-read for both PO2 and PN2O; a remedy is suggested. The in vivo electrode provides an effective, less expensive, alternative to the mass spectrometer for the on-line measurement of PO2 and PN2O in vivo.

Animals↗

PubMed1974

Structural transitions of polyadenylic acid due to protonation: the influence of the length of single strands on the polarographic behaviour of the double-helical form.

Transition of single-stranded poly(A) into its double-helical protonated form was followed by means of derivative pulse polarography, spectrophotometry, and other methods. It was found that properties of protonated poly(A) depended on the length of single strands from which the protonated double helix was formed. In contrary to longer poly(A) transition of short single-stranded molecules (s(20),w lower than about 3) caused practically no decrease in the pulse-polarographic current. It was concluded that the formation of the protonated double helix of poly(A) did not result in the inaccesibility of the reduction sites (located in the vicinity of the surface of the molecule) for the electrode process, as it was in DNA-like double-helical polynucleotides. The current changes observed in the course of transition of longer poly(A) were explained as due to slower transport of long double-stranded molecules to the electrode.

Nucleic Acid Conformation↗

PubMed2000

Effects of moxonidine on corticocerebral blood flow under normal and ischemic conditions in conscious rabbits.

Hypertension associated with excessive liberation of circulating and tissue catecholamines is an independent risk factor for further cardiovascular complications and an important predictor of stroke. Moxonidine is a centrally acting anti-hypertensive drug with potent action on I1-imidazoline receptors. It inhibits catecholamine release and is therefore expected to exert an antiadrenergic effect at various levels in the regulation of the cardiovascular system. The aim of this study was to investigate the effect of moxonidine (0.025-0.1 mg/kg, i.v.) on the normal and unilateral carotid occlusion-induced impaired corticocerebral blood flow (cCBF) determined by hydrogen polarography, on mean arterial blood pressure (MABP) and heart rate (HR) in conscious rabbits. Moxonidine produced a reduction of MABP and HR. On the other hand, after administration of the drug, a significant increase in the normal and impaired cCBF was observed. Because the improvement in cCBF was conspicuous in both normal and ischemic conditions, moxonidine might be beneficial not only in the treatment of hypertension but also in the management of cerebral ischemia.

Analysis of Variance↗

PubMed2003

Effect of systemic administration of L-kynurenine on corticocerebral blood flow under normal and ischemic conditions of the brain in conscious rabbits.

Kynurenic acid, the only known endogenous antagonist of the excitatory amino acid receptors, exerts neuroprotective effect in focal cerebral ischemia. Kynurenic acid poorly while its bioprecursor, l-kynurenine (L-KYN) completely crosses the blood-brain barrier. The aim of our study was to investigate the effect of intravenous l-KYN (0.3, 1, and 3 mg/kg) on the normal and the unilateral carotid artery occlusion induced ischemic corticocerebral blood flow (cCBF) measured by hydrogen polarography in conscious rabbits. Administration of l-KYN produced a significant increase in the normal cCBF; the peak values were recorded at the dose of 1 mg/kg (187% at 120 and 150 mins. respectively). The cCBF-improving effect of l-KYN was immediate and highly pronounced also in rabbits with carotid occlusion (peak value was 192% at 120 mins. at the dose of 1 mg/kg). Pretreatment with either atropine or Nomega-nitro-L-arginine-methyl-ester (L-NAME) prevented the l-KYN induced enhancement of the normal and the ischemic cCBF alike. It is suggested that the cCBF-increasing effect of l-KYN might be mediated by activation of cholinergic and nitric oxide pathways.

Animals↗

PubMed1984

Equivalent oxygen percentage (EOP) technique: a standard calibration curve.

Between different oxygen concentrations (mixed with nitrogen) ranging from 0 to 21% were passed over the corneas of six subjects for 5 min. The resulting corneal oxygen responses were measured by polarography. The averages of these responses were used to calculate a "relative oxygen uptake response" (ROUR) value for each oxygen percentage. Analysis of these ordered pairs revealed a curvilinear relation which was best described by a third order equation; marked linearity was demonstrated in the middle of the oxygen range. The use of this third order equation as a "standard" or "average" equivalent oxygen percentage (EOP) calibration equation is suggested.

Adult↗

PubMed1999

Extracellular metal-binding activity of the sulphate-reducing bacterium Desulfococcus multivorans.

Polarography was used to measure the copper-binding ability of culture filtrates from a range of sulphate-reducing bacteria (SRB), including pure cultures and environmental isolates. Of those tested, Desulfococcus multivorans was shown to have the greatest copper-binding capacity and this organism was used for further experiments. Extracellular copper- and zinc-binding activities of Dc. multivorans culture filtrates from batch cultures increased over time and reached a maximum after 10 d growth. The culture filtrate was shown to bind copper reversibly and zinc irreversibly. Twelve-day-old Dc. multivorans culture filtrates were shown to have a copper-binding capacity of 3.64 +/- 0.33 micromol ml(-1) with a stability constant, log10K, of 5.68 +/- 0.64 (n=4). The metal-binding compound was partially purified from culture growth media by dichloromethane extraction followed by HPLC using an acetonitrile gradient.

Carrier Proteins↗

PubMed1987

Drug assays--the role of modern voltammetric techniques.

Modern voltammetric techniques, e.g. differential pulse polarography and voltammetry, anodic/cathodic stripping voltammetry and electrochemical detection for high performance liquid chromatography or flow injection analysis, are reviewed with respect to their basic theory, design and usage of available instrumentation and applications to drug assays in formulation and body fluid matrices.

Electrochemistry↗

PubMed1996

Allergic contact dermatitis and mercury exanthem due to mercury chloride in plastic boots.

We report a 5-year-old child with previous skin intolerance from Mercurochrome (merbromin), who developed a severe allergic contact dermatitis of both feet when wearing new polyvinyl chloride (PVC) boots. Within a few days, he developed a mercury exanthem involving both legs, groins and lateral parts of the trunk. Patch tests showed strong reactions to organic and inorganic mercury compounds, in particular to mercury chloride (mercury chloride; HgCl2), 0.01% pet., which was identified by atomic absorption spectrometry and polarography in the boots worn. New hidden sources of mercury in consumer goods may represent a potential source of danger for the future, if its use is not more strictly regulated.

Anti-Infective Agents, Local↗

PubMed1970

Hormonal interactions in Mucor mucedo and Blakeslea trispora.

Evidence is presented that progametangia in both the plus and the minus mating types of Mucor mucedo can be induced by one substance, namely (-)-trisporic acid B. A method is described for the determination of the concentration of the sex factors (trisporone, trisporic acid B, trisporic acid C) in mated cultures of Mucorales by polarography. It can be demonstrated that the amount of plus mycelium is limiting for the production of the sex factors in Blakeslea trispora. It is shown that the minus type of this organism is able to synthesize the sex factors when incubated in the filtered medium of a mated culture. Cycloheximide and 5-fluorouracil inhibit strongly the sex factor production in a mated culture of B. trispora at any time. This result suggests that sexual activity comprises the synthesis of proteins which are involved in the production of the sex factors.

Acids↗

PubMed1997

Increased sciatic nerve blood flow in diabetic rats: assessment by "molecular" vs. particulate microspheres.

Sciatic nerve blood flow in diabetic rats in typically increased or unchanged when assessed by the reference sample microsphere method in our laboratory. In contrast, blood flow is generally reported to be decreased approximately 50% when assessed with laser Doppler flowmetry or hydrogen clearance polarography. To address concerns that increased blood flow observed with microspheres might be anomalous because of their particulate nature and/or because insufficient numbers of microspheres are captured in the nerve, a plasma-soluble "molecular microsphere" ([3H]desmethylimipramine, mol wt = 266) and 11.3-micron 153Gd-labeled microspheres were injected sequentially to assess blood flow in rats with streptozotocin diabetes of 2-4 wk duration. Nerve blood flows in diabetic rats were increased 1.5- to 2-fold (vs. control rats) with both tracers; these increases were prevented by tolrestat, an inhibitor of aldose reductase. These observations indicate that blood flow in sciatic nerve (like that in retina and kidney) is increased early after the onset of diabetes and is 1) demonstrable with a plasma-soluble tracer as well as with particulate microspheres and 2) linked to increased metabolism of glucose via the sorbitol pathway.

Aldehyde Reductase↗

PubMed1997

Diabetes impairs sciatic nerve hyperemia induced by surgical trauma: implications for diabetic neuropathy.

The most widely used methods to assess nerve blood flow in diabetics rats are hydrogen clearance polarography and laser Doppler flowmetry, techniques requiring surgical exposure of the nerve. In these experiments, we examined the hypothesis that the trauma of surgical exposure introduces an important and hitherto largely unrecognized variable that could account for discordant reports on nerve blood flow changes induced by diabetes. We used the noninvasive (for sciatic nerve) reference sample microsphere method to quantify sciatic nerve blood flow in unexposed va. surgically exposed nerves in rats with streptozotocin-induced diabetes (at different temperatures and after curarization) and in unexposed vs. surgically exposed nerves in galactose-fed rats. Baseline resting blood flow in unexposed nerves in both animal models of diabetes was either normal or increased (but was decreased in diabetic rats given d-tubocurarine). Furthermore, the normal brisk hyperemic nerve blood flow response to the minimal trauma associated with surgical exposure of the nerve was markedly impaired in diabetic and in galactose-fed rats. Normalization of the blood flow response to trauma in galactose-fed rats by an aldose reductase inhibitor suggests that the impairment is linked to increased polyol pathway metabolism. These findings 1) confirm our previous findings that sciatic nerve blood flow in diabetic rats is increased or unchanged in unexposed nerves, while also confirming reports that in surgically exposed nerves blood flow is higher in control than in diabetic rats, and 2) indicate that blood flows in surgically exposed nerves are largely a measure of vascular responses to injury rather than (patho)physiological blood flow in undisturbed nerves.

Aldehyde Reductase↗

PubMed1991

Measurement of blood flow in rat eyes by hydrogen clearance.

Intraocular measurements of blood flow have been made in the rat eye using hydrogen-clearance polarography. Hydrogen was delivered by a bolus injection of hydrogen-saturated saline via a cannula in the lingual artery of the anesthetized rat. An intraocularly placed hydrogen-sensitive microelectrode monitored the arrival and clearance of hydrogen preretinally adjacent to retinal arteries, veins, and intervascular areas. The effect of stepwise penetration through the retina and into the choroid was also determined, and a map of hydrogen distribution in the retina during hydrogen delivery and clearance was produced. Intraocular measurements, which have the advantage that the electrode location can be clearly visualized, together with computer control of the bolus injection and data collection, have allowed highly repeatable measurements of local blood flow to be made. The mean blood flow in retinal tissue was 373 +/- 51 ml.min-1.100 g-1 (values are means +/- SD, n = 32). The correlation between the nature of the hydrogen clearance curve and the location of the electrode helps explain data from other studies in which the position of the electrode with respect to the vasculature was unknown.

Animals↗

PubMed2001

Defective mitochondrial ATP synthesis in oxyphilic thyroid tumors.

Oxyphilic tumors (oncocytomas or Hürthle cell tumors) form a rare subgroup of thyroid tumors characterized by cells containing abundant mitochondria. The relationship between the mitochondrial proliferation and the pathogenesis of these tumors is unknown. We have assessed the expression of the mitochondrial ND2 and ND5 (subunits of the nicotinamide adenine dinucleotide dehydrogenase complex) genes and the nuclear UCP2 (uncoupling protein 2) gene in 22 oxyphilic thyroid tumors and matched controls. The consumption of oxygen in mitochondria from tumors was determined by polarography. ATP assays were used to explore the mitochondrial respiratory chain activity and the oxidative phosphorylation coupling in seven fresh thyroid tumors and controls. Adenosine triphosphate synthesis was significantly lower in all the tumors, compared with controls, suggesting that a coupling defect in oxidative phosphorylation may be a cause of mitochondrial hyperplasia in oxyphilic thyroid tumors.

Adenoma, Oxyphilic↗

PubMed2004

Comparison of the synaptosomal uptake inhibition of serotonin by St John's wort products.

Although the number of prescriptions for psychotropic drugs has decreased in recent years, prescriptions for antidepressants are still increasing (Fritze 2002). Hypericum perforatum (St John's wort) is the main psychotherapeutic herbal medicinal product used for treatment of mild-to-moderate depression. The lipophilic constituent hyperforin (2-5% of the extract) demonstrated, similarly to chemical antidepressants, a significant effect on the synaptosomal uptake inhibition of several neurotransmitters in in-vitro assays. In Germany, St John's wort products are distributed via two different markets: products that are pharmacy restricted are only allowed to be distributed in pharmacies; traditionally used products, which do not claim to have a curative character, are allowed to be sold in supermarkets. Depending on the market wherein a St John's wort product is offered, it needs to fulfill the legal requirements regarding pharmaceutical quality, safety and efficacy. Our goal was to compare the quality of St John's wort products distributed in pharmacies with that of those available from supermarkets. Therefore, the quantity of the pharmaceutical active ingredients (the phloroglucinol derivate hyperforin, the flavonoids rutin, hyperoside, isoquercitrin, quercitrin and the biflavonoid biapigenin) was determined by high-performance liquid chromatography (HPLC). The naphthodianthrones hypericines and pseudohypericines were quantified by differential pulse polarography (DPP). The efficacy of the products was investigated by measuring their activity to inhibit serotonin (5-HT) uptake in-vitro using a radio ligand uptake assay. It could be demonstrated that the products were different not only in the concentration of pharmaceutically relevant ingredients but also in showing individual IC50 values (concentration producing half-maximal inhibition) in the serotonin reuptake assay (IC50 values between 3.07 and 17.9 microg extract mL(-1)). The results of our study confirm the assumption that the potency of St John's wort products in inhibiting the uptake of serotonin depends on the amount of hyperforin in their dosage forms. St John's wort products having greater hyperforin content and potency on synaptosomal serotonin uptake inhibition are restricted to be sold only in pharmacies.

Animals↗

PubMed1986

Transition metal-binding proteins from three Chesapeake Bay fish species.

Three species of Chesapeake Bay fish were collected, and endogenous levels of metal binding protein (MBP) were determined. In addition, the induction of metal-binding proteins by cadmium was studied. Livers from freshly caught fish were extracted and chromatographed on Sephadex G-75 to resolve MBP in the 5 to 20 kdalton range. All species studied exhibit measurable but varied levels of endogenous MBPs in the molecular weight range investigated, mostly as a copper protein complex. Upon induction with cadmium, the total MBP content increased in both catfish (Ictalurus punctatus) and striped bass (Morone saxatilis), with significant amounts of cadmium bound to the protein. In white perch (Morone americana), induction of MBPs with cadmium could not be demonstrated due to the large amount of constitutive Cu-BP present, although significant quantities of cadmium were bound to MBP. Electrophoresis in polyacrylamide gel was used to further identify these MBPs. Electrochemical analysis of the MBPs by polarography indicated that the wave properties of the fish MBPs resemble that of rat metallothionein. In conclusion, these studies indicate that: MBPs are present in estuarine fish from the Chesapeake Bay; concentrations of MBPs and their inducibility by exogenous cadmium vary with species, and fish MBPs may be related to mammalian metallothionein.

Animals↗