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 631 records · Page 35Linked to original sources
PubMed2005

The identification of mivacurium and metabolites in biological samples.

Mivacurium is a muscle relaxant that is used in hospitals and has been implicated in a number of homicides. A validated, sensitive method for the analysis of mivacurium and metabolites from biological specimens is presented here. Sample cleanup involves the precipitation of proteins with acetonitrile followed by analyte isolation using a commercially available solid-phase extraction column. Screening is performed by liquid chromatography with fluorescence detection, and confirmation is performed by liquid chromatography with tandem mass spectrometric detection. This method has been used to analyze dozens of forensic samples, including clinical specimens from living patients, as well as autopsy specimens from exhumed bodies.

Body Fluids↗
PubMed2004

Atomic force microscopy contact, tapping, and jumping modes for imaging biological samples in liquids.

The capabilities of the atomic force microscope for imaging biomolecules under physiological conditions has been systematically investigated. Contact, dynamic, and jumping modes have been applied to four different biological systems: DNA, purple membrane, Alzheimer paired helical filaments, and the bacteriophage phi29. These samples have been selected to cover a wide variety of biological systems in terms of sizes and substrate contact area, which make them very appropriate for the type of comparative studies carried out in the present work. Although dynamic mode atomic force microscopy is clearly the best choice for imaging soft samples in air, in liquids there is not a leading technique. In liquids, the most appropriate imaging mode depends on the sample characteristics and preparation methods. Contact or dynamic modes are the best choices for imaging molecular assemblies arranged as crystals such as the purple membrane. In this case, the advantage of image acquisition speed predominates over the disadvantage of high lateral or normal force. For imaging individual macromolecules, which are weakly bonded to the substrate, lateral and normal forces are the relevant factors, and hence the jumping mode, an imaging mode which minimizes lateral and normal forces, is preferable to other imaging modes.

Bacillus Phages↗
PubMed2003

High-performance liquid chromatographic method for determination of amodiaquine, chloroquine and their monodesethyl metabolites in biological samples.

A high-performance liquid chromatographic method for determination of amodiaquine (AQ), desethylamodiaquine (DAQ), chloroquine (CQ) and desethylchloroquine (DCQ) in human whole blood, plasma and urine is reported. 4-(4-Dimethylamino-1-methylbutylamino)-7-chloroquinoline was used as internal standard. The drugs and the internal standard were extracted into di-isopropyl ether as bases and then re-extracted into an acidic aqueous phase with 0.1 M phosphate buffer at pH 4.0 for AQ samples and at pH 2.5 for CQ filter paper samples. A C(18) column was used and the mobile phase consisted of methanol-phosphate buffer (0.1 M, pH 3)-perchloric acid (250: 747.5:2.5, v/v). The absorbance of the drugs was monitored at 333 nm and no endogenous compound interfered at this wavelength. The limit of quantification in whole blood, plasma and urine was 100 nM for AQ and DAQ (sample size 100 microliter) as well as for CQ and DCQ in blood samples dried on filter paper. For 1000 microliter AQ and DAQ samples, the limit of quantification was 10 nM in all three biological fluids. The within-assay and between-assay coefficients of variations were always <10% at the limits of quantification. Plasma should be preferred for the determination of AQ and DAQ since use of whole blood may be associated with stability problems.

Amodiaquine↗
PubMed1980

Millimeter wave absorption spectra of biological samples.

A solid-state computer-controlled system has been used to make swept-frequency measurements of absorption of biological specimens from 26.5 to 90.0 GHz. A wide range of samples was used, including solutions of DNA and RNA, and suspensions of BHK-21/C13 cells, Candida albicans, C krusei, and Escherichia coli. Sharp spectra reported by other workers were not observed. The strong absorbance of water (10--30 dB/mm) caused the absorbance of all aqueous preparations that we examined to have a water-like dependence on frequency. Reduction of incident power (to below 1.0 microW), elimination of modulation, and control of temperature to assure cell viability were not found to significantly alter the water-dominated absorbance. Frozen samples of BHK-21/C13 cells tested at dry ice and liquid nitrogen temperatures were found to have average insertion loss reduced to 0.2 dB/cm but still showed no reproducible peaks that could be attributed to absorption spectra. It is concluded that the special resonances reported by others are likely to be in error.

Absorption↗
PubMed1989

Rapid isolation of DNA from complex biological samples using a novel capture reagent--methidium-spermine-sepharose.

We have synthesized and analyzed the functional properties of a novel DNA capture reagent containing a methidium moiety attached to a sepharose bead by a spermine linker. DNA present in a biological fluid or other complex sample binds to the reagent. The DNA-capture reagent complex is then separated from the sample by centrifugation and the DNA is released from the reagent by brief incubation in 0.1 to 0.5 N NaOH or KOH. Capture of DNA from complex samples is independent of the salt concentration of the sample, and occurs in the presence of high concentrations of EDTA, proteinase K and detergents. Many samples can be processed simultaneously. The following specific applications, in which denatured DNA is quantitated or characterized, are demonstrated: 1). Isolation of hepatitis B virus DNA from serum and quantitation by dot-blot hybridization, 2). Isolation and quantitation of DNA from urine, 3). Isolation of human genomic DNA from one microliter of blood or 100 HeLa cells followed by amplification of a specific gene sequence using the Polymerase Chain Reaction, 4). Isolation of single stranded phage M13 sequencing templates from bacterial cultures. These investigations suggest that a capture reagent containing an intercalating moiety bound to a solid support may be useful for many applications in molecular biology and molecular diagnostics.

Bacteriophages↗
PubMed1994

Application of the image analysis system and Imago program to biological samples.

Recent developments in computer systems and new stereological tools have made estimation of quantitative data in biological material simple, easy and fast. The purpose of the present study is to show the advantages and disadvantages of a new program developed by the University of Córdoba for the determination of stereological measurements. As an example, endometrial material was used for demonstrating the technical characteristics. Thus, the nuclear area and volume-weighted mean nuclear volume-Vv(nucl)-of 30 routinely processed, paraffin-embedded endometrial specimens from 12 atypical hyperplasias (AH) and 18 well-differentiated adenocarcinomas (WDA) were investigated. We show the excellent visualization of the material and rapid measurement of these quantitative parameters using the Imago program. In addition, the mean values of Vv(nucl) are more efficient and useful in separating AH and WDA than the mean nuclear area. It is concluded that Vv(nucl) is a superior and sensitive estimator for discrimination.

Adenocarcinoma↗
PubMed2006

Focused ion beam milling of vitreous water: prospects for an alternative to cryo-ultramicrotomy of frozen-hydrated biological samples.

The feasibility of using a focused ion beam (FIB) for the purpose of thinning vitreously frozen biological specimens for transmission electron microscopy (TEM) was explored. A concern was whether heat transfer beyond the direct ion interaction layer might devitrify the ice. To test this possibility, we milled vitreously frozen water on a standard TEM grid with a 30-keV Ga(+) beam, and cryo-transferred the grid to a TEM for examination. Following FIB milling of the vitreous ice from a thickness of approximately 1200 nm to 200-150 nm, changes characteristic of heat-induced devitrification were not observed by TEM, in either images or diffraction patterns. Although numerous technical challenges remain, it is anticipated that 'cryo-FIB thinning' of bulk frozen-hydratred material will be capable of producing specimens for TEM cryo-tomography with much greater efficiency than cryo-ultramicrotomy, and without the specimen distortions and handling difficulties of the latter.

Cryoultramicrotomy↗
PubMed1985

Chromatographic analysis of antituberculosis drugs in biological samples.

Numerous chromatographic and non-chromatographic methods of analysis for anti-tuberculosis drugs and metabolites in biological tissues have been discussed in this review. Depending upon the analytical methodology selected, limits of detection range from microgram to picogram levels. A number of examples have been given of the correlation between different types of assay procedures. The metabolism and pharmacokinetics have been described along with some of the commonly associated problems of sample collection and storage.

Aminosalicylic Acids↗
PubMed1994

Vapour-phase acid digestion of micro samples of biological material in a high-temperature, high-pressure asher for inductively coupled plasma atomic emission spectrometry.

This vapour-phase acid decomposition of small biological samples (50-165 mg) and concurrent purification of the reagent acid were achieved in a mini-quartz sample holder inserted in a commercial high-pressure digestion vessel. A 3.1 ml volume sample contained was developed to hold the sample and to maximize the successful decomposition of a variety of biological samples. When biological standard reference materials were digested at 230 degrees C and 122 bar (1770 psi), the residual carbon content in the digested samples was less than 1.8 +/- 0.1%. Inductively coupled plasma atomic emission spectrometric analysis of the digested materials for C, Ca, Cu, Cd, Fe, Mg, Mn and Zn provided good recoveries and low reagent blank values and demonstrated complete matrix decomposition.

Animals↗
PubMed1996

Aspects of cryofixation and cryosectioning for the observation of bulk biological samples in the hydrated state by cryoelectron microscopy.

Cryoelectron microscopy allows the observation of hydrated samples at high spatial resolution, and it would be of great interest in biology to apply this method to cells and tissues. However, because of technical problems, the cryo-observation of frozen hydrated ultrathin sections of bulk material has not become an established method. The major limitations are due to the difficulty of achieving the vitrification of such material, and the structural deformation caused by ultrathin sectioning: 1. The vitrification of cells in a physiological environment requires high-pressure freezing. However, new results suggest that the pressure may alter the ultrastructure of the sample. 2. Cryosectioning compresses structures in the cutting direction about 40%. This deformation does not necessarily destroy the character of macromolecular assemblies, but since it depends on the properties of the material, internal standards cannot be used to correct for the deformation of all the structures in a cell.

Animals↗
PubMed1990

Application of scanning electrochemical microscopy to biological samples.

The scanning electrochemical microscope can be used in the feedback mode in two-dimensional scans over biological substrates to obtain topographic information at the micrometer level. In this mode, the effect of distance between a substrate (either conductive or insulating) and a scanning ultramicroelectrode tip on the electrolytic current flowing at the tip is recorded as a function of the tip x-y position. Scans of the upper surface of a grass leaf and the lower surface of a Ligustrum sinensis leaf (which show open stomata structures) immersed in aqueous solution are shown. Scans of the upper surface of an elodea leaf in the dark and under irradiation, where the tip reaction is the reduction of oxygen produced by photosynthesis, demonstrate the possibility of obtaining information about the distribution of reaction sites on the substrate surface.

Electrochemistry↗
PubMed2000

A study of energy and effective atomic number dependence of the exposure build-up factors in biological samples.

A theoretical method is presented to determine the gamma-radiation build-up factors in various biological materials. The gamma energy range is 0.015-15.0 MeV, with penetration depths up to 40 mean free paths considered. The dependence of the exposure build-up factor on incident photon energy and the effective atomic number (Zeff) has also been assessed. In a practical analysis of dose burden to gamma-irradiated biological materials, the sophistication of Monte Carlo computer techniques would be applied, with associated detailed modelling. However, a feature of the theoretical method presented is its ability to make the consequences of the physics of the scattering process in biological materials more transparent. In addition, it can be quickly employed to give a first-pass dose estimate prior to a more detailed computer study.

Models, Biological↗
PubMed1981

Some aspects of analysis of single fibers in environmental and biological samples.

Nuclepore filters were used for sampling and evaluation of fibrous particles in ambient air, in liquids and in biological materials. The fiber counting and fiber size measurements were done by means of SEM-methods. The number of fibers and the distributions of fiber lengths and diameters were plotted. The specific identifications of asbestos, glass and other mineral fibrous particles were made by electron microprobe analysis. Certain elements proved to be approximative identification factors for different fibrous minerals in ambient air, in liquids, on material surfaces, or in biological materials. For ambient air, asbestos, glass, and many other inorganic fibrous particles were found in the urban atmosphere as well as in the atmosphere of remote regions. Fibrous gypsum, fibrous ammonium sulfates, fibrous silicates, fibrous mica, and quartz were identified among these particles. Even in remote ambient air, relatively high concentrations of inorganic fibrous particles could be measured.

Air Pollutants↗