Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biological samples”

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 1,009 records · Page 56Linked to original sources
PubMed2004

The levels of kerosene components in biological samples after repeated dermal exposure to kerosene in rats.

The current study was experimentally investigated using rats whether or not kerosene components are accumulated from daily repeated dermal exposure. Rats received daily 1h-exposure to kerosene for 5 days (5K), daily 1h-exposure for 4 days and left for 1 day (4KL), a single 1h-exposure (1K), a single 1h-exposure and left for 1 day (1KL), or a single 1h-exposure, sacrificed and left dead for 1 day (1KLD). Kerosene components, trimethylbenzenes (TMBs) and aliphatic hydrocarbons (AHCs) in blood and tissues were determined by GC-MS. In blood, almost the same concentrations of TMBs were detected in the rats sacrificed immediately after exposure (5K, 1K and 1KLD), and only trace levels were detected in the rats sacrificed 1 day after exposure (4 and 1KL). Almost the same levels of AHCs in blood were detected among groups except for the rats sacrificed 1 day after a single exposure (1KL), in which AHCs were slightly lower. These results suggest that (1) AHCs tend to be accumulated from daily exposure, while TMBs do not, (2) the proportions of detected kerosene components in blood can be an indicator of whether the last exposure occurred just before death or not, (3) the kerosene levels last at least 1 day without blood circulation.

Adipose Tissue↗
PubMed2005

Catalytic kinetic spectrophotometry for the determination of trace amount of oxalic acid in biological samples with oxalic acid-rhodamine B-potassium dichromate system.

A new catalytic kinetic spectrophotometric method was proposed for determining trace oxalic acid based on the catalytic effect of oxalate on the oxidation of potassium dichromate with rhodamin B in 0.10 M of sulfuric acid. Good linearity is obtained over the concentration range 0.40-6.0 microg/mL of oxalic acid. After the reactions of the catalytic and non-catalytic systems were terminated by using 2.00 mL of 4 M sodium hydroxide solution, they can be stable for 3 h at room temperature. The apparent activation energy of the catalytic reaction is 12.44 kJ/mol. The effect of 50 coexisting substances was observed. The method was used to determine trace oxalic acid in tea, spinach and urine samples with satisfactory results.

Catalysis↗
PubMed1996

Vertical dimension of hydrated biological samples in tapping mode scanning force microscopy.

The vertical dimensions of the well-characterized test samples tobacco mosaic virus, T4 bacteriophage polyhead, purple membrane, and hexagonally packed intermediate (HPI) layer were investigated by tapping mode scanning force microscopy (SFM) in solution. Purple membrane and HPI layer were imaged in both contact mode and tapping mode SFM for direct comparison. All vertical dimensions match the known heights. The practical implications of the absence of frictional forces in tapping mode are discussed.

Bacteriophage T4↗
PubMed2001

Sources of interference in the use of 2,3-diaminonaphthalene for the fluorimetric determination of nitric oxide synthase activity in biological samples.

The use of 2,3-diaminonaphthalene (DAN) for the fluorimetric determination of nitric oxide synthase (NOS) activity in rat brain extracts has been re-examined. Two types of interference were observed, due either to components of the reaction mixture or to the enzymatic sample itself. One of the substrates (NADPH) and some cofactors (FADH(2), FMNH(2)) required for the enzyme activity interfere in the assay by quenching the fluorescence produced. Interference was minimized by using lower FADH(2), FMNH(2) and NADPH concentrations (1 micromol/l) and a NADPH recycling system in the reaction mixture. The addition of bovine serum albumin or hemoglobin to the sample quenched fluorescence intensity, but these protein interferences could be reduced by filtering the samples after reaction. We conclude that the DAN fluorimetric assay as originally described is not suitable for the determination of NOS activity in crude extracts such as rat brain cytosolic fraction, due to the presence of interfering substances. Nevertheless, DAN could be used for the determination of enzyme activity after reducing protein interference by filtering, or in less complex samples such as cell cultures (e.g. activated macrophages), or in chromatographic fractions obtained during the purification of the enzyme. A careful use of the commercial kits based on the use of DAN for the determination of NOS activity is recommended.

2-Naphthylamine↗
PubMed2002

An enzymatic method for the measurement of glycated albumin in biological samples.

BACKGROUND: In order to determine glycated albumin more easily and rapidly, we developed a new enzymatic method for glycated albumin in blood samples. METHODS: The method involves use of albumin-specific proteinase, ketoamine oxidase and serum albumin assay reagent. In the assay, glycated albumin is hydrolyzed to glycated amino acids by proteinase digestion, and ketoamine oxidase oxidizes the glycated amino acids to produce hydrogen peroxide, which is quantitatively measured. Glycated albumin is calculated as the percentage of glycated albumin in total albumin. RESULTS: The calibration curve for glycated albumin concentration was linear (r(p)=0.999) between 0.0 and 50.0 g/l and that for albumin concentration was linear (r(p)=0.999) between 0.0 and 60.0 g/l. The analytical recoveries of exogenous glycated albumin added to serum were 100-102.5%. The within-run and between-run CVs were 0.45-0.67% and 1.09-1.26%, respectively. This method was free from interference by bilirubin, chyle, glucose, globulins and labile intermediate. Weak interference by hemoglobin and ascorbic acid was observed. Glycated albumin detected by the present method was significantly correlated with glycated albumin detected by high-performance liquid-chromatographic (HPLC) method (serum: r(s)=0.989, plasma: r(p)=0.992). CONCLUSIONS: This new enzymatic method is simple, rapid, allows multiple determinations and enables quantitative analysis of glycated albumin.

Amino Acids↗
PubMed2003

Determination of a novel angiotensin-AT1 antagonist CR 3210 in biological samples by HPLC.

A simple and sensitive method for the determination of a new angiotensin-AT(1) antagonist i.e. CR 3210, 4-[4-[(2-ethyl-5,7-dimethylimidazo[4,5-b]pyridin-3-yl)methyl]phenyl]-3-(2H-tetrazol-5-yl)quinoline, is described. The assay was utilised to describe the pharmacokinetic profile of the title compound after intravenous and intraperitoneal administration to Sprague Dawley rats. CR 3210 and the internal standard CR 1505 (loxiglumide, 4-[(3,4-dichlorobenzoyl)amino-5-[(3-methoxypropyl)pentylamino]-5-oxopentanoic acid) were isolated from rat plasma by solid-phase extraction. The sorbent extraction material along with the pH in the conditioning solution and the washing volume were considered pivotal parameters for the optimisation of the procedure. The separations were performed by reversed-phase high-performance liquid chromatography with ultraviolet detection. The samples were injected onto the analytical column (Tracer Extrasil ODS1) and detected at 238 nm, giving a retention time of 6.19 min for CR 3210 and 4.39 min for the internal standard, respectively. The selectivity of the method showed to be satisfactory. The mean recovery of CR 3210 from spiked rat plasma was 80.3 at 1 microg/ml and 79.9 at 2 microg/ml. The lower limit of detection (LOD) was taken as 0.014 microg/ml in plasma samples. The lower limit of quantification (LOQ) was taken as 0.02 microg/ml, the lowest calibration standard using 500 microg rat plasma. The procedures were validated according to international standards with a good reproducibility and linear response from 0.02 to 2 microg/ml. The sensitivity of the method allowed for its application to pharmacokinetic studies. The maximal concentration was detected 5' after the IV administration, whereas no significant absorption was evident after IP administration of CR 3210 to Sprague-Dawley rats. Our study suggests the absence of extensive bio-transformation of the drug in vivo, supported by the evidence that no metabolites were detected in plasma samples.

Angiotensin II Type 1 Receptor Blockers↗
PubMed1983

Determination of drugs in biological samples by thin-layer chromatography-tandem mass spectrometry.

In this work thin-layer chromatography-tandem mass spectrometry (TLC-MS-MS) allowed detection and confirmation of caffeine and nicotine in human urine and of butorphanol, betamethasone, and clenbuterol in equine urine. In most cases of trace analysis of labile compounds the drugs could not be identified unless they were developed on a TLC plate, scraped from the plate and the TLC scrape eluted with a suitable organic solvent prior to MS-MS. Usually a sample prepared in this way still had several components in it, but was sufficiently cleaned up to allow collision-induced dissociation (CID) experiments to unequivocally identify the drug. In contrast, trace levels of labile drugs could not be identified by CID experiments either directly from the raw urine extracts or by thermally desorbing them from the TLC scrape.

Animals↗