SEARCH · Search PubMed
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.
The SFM setup has been used to image the three-dimensional surface structures of various biological specimens in air and in liquid cell. The samples like red blood cell (RBC), lymphocytes, aggregates of pronase, and surface of bone measured in air, and macrophage surface measured in PBS solution are presented.
A brief summary of current cryo-electron microscopy methods for processing and imaging biological tissues is provided. The main emphasis is given to two preparation procedures: frozen-hydrated samples because of the remarkable success of cryo-electron crystallography in obtaining near atomic resolution of integral membrane proteins, and high-pressure freezing because of the wide applicability for vitrification of large samples of normal and diseased tissues for ultrastructural and immunolabeling analysis. Methods for examining certain samples with a TEM cryo-stage are summarized. This includes an introduction to the relatively new area of cryo-electron tomography, which offers the possibility to observe the three-dimensional structure of subcellular components using only their natural variations in composition to generate contrast.
A colorimetric assay for the determination of alditols in complex extracts from biological sources, showing negligible interferences by other carbohydrates, has been worked out. The method involves mild oxidation of alditols by sodium periodate under acidic conditions, followed by reaction of the resulting formaldehyde with ammonia and acetylacetone (Hantzsch reaction) to yield a colored heterocycle amenable to spectrophotometric measurement. The assay is completed within a few minutes, and mannitol and other alditols can be detected down to the nanomolar range. The method is convenient in that it uses inexpensive chemicals of low potential hazard and requires only few minutes to complete. The method has been used for the determination of mannitol in aqueous extracts from olive leaves and fruits and has been validated by parallel determinations carried out by HPLC and enzymatic analysis with mannitol dehydrogenase.
A preirradiation separation procedure has been developed to separate Al, Cu, Mn, and V from biological materials. Chelex-100 resin is used as the separation medium, and the resin is irradiated directly. Three NIST biological Standard Reference Materials and five samples of human blood serum, obtained under carefully controlled conditions, have been analyzed by NAA following this separation.
The continuing development of the Nuclear Microprobe (NMP) has opened up new fields of applications in biology and medicine. Quantitative multielemental analysis in small sections of samples can be performed routinely. The use of techniques such as scanning transmission ion microscopy makes imaging as well as mass normalization possible at submicron resolution. Recent medical applications include studies on thin cryosections prepared from autopsies and biopsies, as well as single cells grown directly on the backing foil used in the NMP analyses. The purpose of the single cell analysis is often pharmacological, e.g., testing of new drugs, their uptake and distribution. New applications, for instance, in food chemistry, ecology and evolutionary genetics, are also taking advantage of the high analytical sensitivity of the NMP in combination with its imaging capability.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
An alternative method for the determination of [15N]ammonia enrichment in biological fluids was developed. It is based on the use of glutamate dehydrogenase of bovine liver (EC 1.4.1.2.) with 2-oxopentanoic acid as substrate, to convert the ammonia present in the sample into norvaline, the enrichment of which can be measured by gas chromatography/mass spectrometry as its tertiary butyldimethylsilyl (TBDMS) derivative under electron impact selective ion recording (SIR) conditions. The principal advantage of the present approach is that it is simpler and quicker than the previously described methods, because the synthetic product, norvaline, is not present in biological fluids and pre-processing of the sample is unnecessary. The procedure includes a pre-incubation stage which allows removal of contaminant ammonia present in the reagents used for the enzyme reaction. The contributions of other sources of nitrogen to norvaline production have been checked and quantified: these may provide limitations of the technique when samples for analysis are low in ammonia (e.g. arterial or hepatic venous blood). To reduce these contributions, short times of incubation are proposed. The results from two experiments in vivo in which two sheep were infused with [15N]ammonium chloride in the mesenteric vein are presented and the biological implications which arise from the results are discussed. The validity of the procedures was demonstrated by the quantitative recovery from the mesenteric and portal veins of [15N]ammonia infused.
The discovery of specific polypeptides of diagnostic relevance from a biological liquid is complicated by the overall vast number and the large concentration range of all polypeptides/proteins in the sample. Depletion or fractionation methodologies have been used for selectively removing abundant proteins; however, they failed to significantly enrich trace proteins. Here we expand upon a new method that allows the reduction of the protein concentration range within a complex mixture, like neat serum, through the simultaneous dilution of high abundance proteins and the concentration of low abundance ones in a single, simple step. This methodology utilizes solid-phase ligand libraries of large diversity. With a controlled sample-to-ligand ratio it is possible to modulate the relative concentration of proteins such that a large number of peptides or proteins that are normally not detectable by classical analytical methods become, easily detectable. Application of this method for reducing the dynamic range of unfractionated serum is specifically described along with treatment of other biological extracts. Analytical surface enhanced laser desorption/ionization mass spectrometry (SELDI-MS) technology and mono- and two-dimensional electrophoresis (1-DE and 2-DE) demonstrate the increase in the number of proteins detected. Examples linking this approach with additional fractionation methods demonstrate a further increase in the number of detectable species using either the so-called "top down" or "bottom up" approaches for proteomics analysis. By enabling the detection of a greater proportion of polypeptides/proteins within a sample, this method may contribute significantly towards the discovery of new biomarkers of diagnostic relevance.
A sensitive and specific method for the determination of chlorambucil and its metabolite in biological fluids is reported. The method is based on selected-ion monitoring detection following simple extraction of the parent compound, its metabolite, and an internal standard (chlorambucil-d8) from plasma and urine samples. The precision (reproducibility) of the method was 94.3 +/- 1.3% with 200 ng of chlorambucil added to 1 ml of plasma. Chlorambucil degradation or alkylation of plasma proteins was minimal with plasma incubated at 24 degrees for 4 hr. However, chlorambucil recovery decreased to 56% after plasma incubation at 37 degrees for 4 hr. Three chlorambucil degradation products in ethyl acetate solution were found, and their structures were studied by mass spectrometry.
A new method for the analysis of tetrahydroisoquinolines (TIQ) from biological materials is described. The method combines extraction and acylation of the TIQs from urine in a one-step procedure followed by analysis by gas chromatography/mass spectrometry. By this extractive derivatization method, a decrease of the extraction time, to speed up sample preparation in order to minimize oxidative side reaction, has been achieved. The detection limits for the analysis of salsolinol and salsolin in urine were 10 fmol/ml sample volume. Tetrahydropapaveroline could only be detected in spiked urine samples with a detection limit of 1 pmol/ml urine. The method is not only restricted to urine samples, but can also be applied to a variety of tissue types, including blood components.
A microbiopsy system for fast excision and transfer of biological specimens from donor to high-pressure freezer was developed. With a modified, commercially available, Promag 1.2 biopsy gun, tissue samples can be excised with a size small enough (0.6 mm x 1.2 mm x 0.3 mm) to be easily transferred into a newly designed specimen platelet. A self-made transfer unit allows fast transfer of the specimen from the needle into the specimen platelet. The platelet is then fixed in a commercially available specimen holder of a high-pressure freezing machine (EM PACT, Leica Microsystems, Vienna, Austria) and frozen therein. The time required by a well-instructed (but not experienced) person to execute all steps is in the range of half a minute. This period is considered short enough to maintain the excised tissue pieces close to their native state. We show that a range of animal tissues (liver, brain, kidney and muscle) are well preserved. To prove the quality of freezing achieved with the system, we show vitrified ivy leaves high-pressure frozen in the new specimen platelet.
Methylglyoxal was allowed to react with 4,5-dichloro-1,2-phenylenediamine, and the 6,7-dichloro-2-methylquinoxaline formed was determined by gas chromatography with electron-capture detection. The standard curve of the quinoxaline was linear up to 160 pmol/ml. The recoveries of methylglyoxal from coffee and rat liver homogenate were 84.1 and 77.6%, respectively. This procedure was very selective and so sensitive that as little as 9 fmol of the quinoxaline could be measured in biological and food samples.
Temperature excursions of short duration are useful in exploring the effects of stress on biological systems. Stress will affect the conformation of biological molecules such as proteins, which will lead to an effect on their function. The feasibility of generating such temperature excursions is demonstrated by solving the heat diffusion equation for an aqueous layer on a silicon wafer. The silicon is rapidly heated by a laser pulse and also acts as a heat sink to quench the temperature rise. An oxide layer was used to limit the maximum temperature attained by the sample. We show that exposures above a 50 degrees C benchmark can be confined to times less than 5 micros.
The concentration of glucose was determined by a combination of flow injection analysis (FIA) with amperometric enzyme sensor detection. The enzyme sensor was prepared by immobilizing glucose oxidase on an electrode coated with a polyion complex layer consisting of poly-L-lysine and poly(4-styrenesulfonate). The inner, polyion complex layer was useful for preventing electrochemical interferents (e.g., L-ascorbic acid, uric acid and acetaminophen) from reaching the electrode surface, which was effective for reducing the interferential responses upon the injections of biological and food samples. The sensor-based system could be used for the determination of glucose from 10 microM to 3 mM with the sampling rate of 180 h-1, and was stable for more than 2 months. An FIA system for determining L-glutamic acid (3 microM-0.5 mM) was also prepared by using an enzyme electrode based on a glutamate oxidase/polyion complex-bilayer as the detector.
An on-line flow injection preconcentration-ETAAS method is developed for trace determination of cobalt in biological materials and natural samples by ion-pair sorption on the inner walls of a PTFE knotted reactor. The ion-pair is formed between the negatively charged cobalt-nitroso-R-salt complex and the tetrabutylammonium counter-ion. An enhancement factor of 15, a sampling frequency of 17 and a concentration efficiency of 4 are obtained for a preconcentration time of 60 s and a sample loading flow rate of 5 mL min(-1). The detection limit (3sigma) is 5 ng L(-1). The relative standard deviation at the 0.2 microg L(-1) level is 2.3%. The analytical results obtained for standard reference materials are in good agreement with the certified or indicated values and satisfactory recoveries of spiked cobalt in tap water are obtained.
Described here is a computationally automated method for translating complex accurate mass spectra into biologically relevant and meaningful data. Rapid profiling of detailed high resolution mass spectra resulting from direct analysis of whole cells and tissues by matrix-assisted laser desorption/ionization (MALDI) Fourier transform mass spectrometry (FTMS) is discussed. Lipid and phospholipid ions create complex spectra containing multiple m/z values corresponding to the same fundamental chemical species. A computational approach is employed to sort ions, with mass to charge ratios lower than m/z 1000, into groups of similar lipid and phospholipid compositions for comprehensive and rapid analysis. By sorting or binning ions in this manner, variations in the degree of cation exchange can be avoided, thus increasing the comparability of the data. The result is displayed as a histogram that is easily interpretable and comparable with similar analyses and is particularly useful for direct comparison of similar tissues. Spectra of leaves from a healthy Prunus persica (peach) tree are compared with those from leaves infected by the fungus Taphrina deformans. Although the infection can be seen as a difference in leaf structure and by visual inspection of the mass spectra, the method described here details the chemical difference in phospholipid compositions and their relative abundances.
A rapid and simple liquid chromatographic method for the automated determination of amphetamines in biological fluids was developed. The proposed procedure is based on the injection of 250 microL of sample into a 20 x 2.1 mm id precolumn (packed with a 30 microns Hypersil C18 stationary phase) for enrichment and purification of the analytes. Next, the analytes are transferred to a 5 microns LiChrospher 100 RP18, 125 x 4 mm id analytical column for their separation under reversed-phase conditions. Water was used to eliminate the matrix components from the precolumn and a 0.2 M phosphate buffer (pH 3) containing 2% triethylamine was the mobile phase for the resolution of the amphetamines. The UV detector was set at 210 nm. The method was applied to the determination of different primary, secondary and tertiary amphetamines in plasma and urine: beta-phenylethylamine, norephedrine, ephedrine, N-methylpseudoephedrine, pseudoephedrine, N-methylephedrine, amphetamine, 3-phenylpropylamine and methamphetamine. The method provides satisfactory linearity and reproducibility within the tested concentration range (1.0-10.0 micrograms mL-1) and limits of detection of 50-500 ng/mL-1.