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At least 955 records · Page 53Linked to original sources
PubMed1982

Competitive rate nephelometric immunoassay for determination of theophylline, phenobarbital, and dilantin in serum.

The theophylline, phenobarbital and dilantin were measured in serum by rate nephelometric immunoassay with the Beckman Immunochemistry System (ICS, Beckman Inc. Brea., CA 92621). The procedures required less than three minutes after proper calibration and dilution, and only 42 microliters of serum theophylline and 100 microliters of serum for phenobarbital and dilantin per determination. It is simple and needs only pipetting and dilution with automatic dispenser and diluter. Day to day variation was determined by analyzing on 30 days two control sera containing theophylline level I (12 micrograms/ml 18-micrograms/ml) and level II (30 micrograms-38 micrograms/ml). The average theophylline level I concentration was 14.5 micrograms/ml, with a standard deviation of 0.70 micrograms/ml, and a coefficient of variation of 4.8%. The average theophylline level II concentration was 32.2 micrograms/ml, with a standard deviation of 1.89 micrograms/ml, and a coefficient of variation of 5.9%. Results attained in patients were compared with results of enzyme immunoassay procedure (EMIT, Syva Corp.). For theophylline, r-0.957, for phenobarbital, r=0.936, and for dilantin, r=0.972.

Humans↗
PubMed1982

Immunoturbidimetry of albumin and immunoglobulin G in urine.

I describe a rapid, sensitive immunoturbidimetric assay for measuring urinary albumin and immunoglobulin G with use of an automated spectrophotometer. Diluted urine samples and polyethylene glycol in phosphate-buffered saline are pipetted into the cuvettes of the spectrophotometer. The initial absorbances of the samples are measured at 340 nm; antiserum to albumin or to immunoglobulin G is added to each tube, and after 2 min at 37 degrees C the absorbance of the mixtures is read at 340 nm. The initial blank absorbances of the samples are subtracted from the final absorbances automatically. The change in absorbance is linear with concentration in the range of 5-400 mg/L for albumin and 3-1000 mg/L for IgG. The lower limit of the determination is 5 mg/L for albumin, 3 mg/L for IgG. Linear correlations were observed between the concentrations of albumin and immunoglobulin G determined by this method (x) and those determined by radial immunodiffusion (y). The regression equation for albumin was y = 0.84x + 0.03 (r = 0.99, n = 87), and for IgG y = 0.94x + 0.02 (r = 0.98, n = 87).

Albuminuria↗
PubMedDate not supplied

Measurement of plasma heparin levels using a fluorometric assay.

The performance of a fluorometric heparin assay system was evaluated. The system indirectly measures heparin by its inhibition of thrombin protease action on a synthetic substrate. Our results confirm that within the range of heparin concentrations recommended by the manufacturer, i.e., 0.1-0.8 units/ml, there is an excellent correlation between expected and observed values. Within-day coefficients of variation range from 1% to 2.6%; the between-day coefficient of variation is 6.5. The accuracy of the assay diminishes under 0.1 units/ml. The assay is not influenced by bilirubin, hemolysis, fibrin split products, or lipemia. Results can be generated in less than 5 min. Possible drawbacks are the wide range of acceptability for the supplied heparin standard, and the frequency of pipetting involved.

Fluorometry↗
PubMed1978

Determination of aluminum in biological samples by atomic absorption spectrophotometry with a graphite furnace.

Aluminum, generally considered non-essential and non-toxic, may accumulate in toxic amounts in the brain in cases of chronic renal failure. We describe a procedure for its analysis in biological fluids by atomic absorption spectrophotometry with a graphite furnace. No sample preparation is required and the procedure is sensitive at the appropriate concentrations. A sample of serum or urine is pipetted into the interior of the graphite tube, where it is sequentially dried, charred, and atomized. Precautions for sample handling are discussed and instrument settings are defined. Precision and accuracy of the method are evaluated, as are the effects of salts, protein content of serum, and specific gravity of urine. Serum of 23 persons who were not consuming aluminum-containing antacids contained 28 +/- 9 (SD) microgram of Al per liter (1.02 +/- 0.33 mumol/liter).

Aluminum↗
PubMed1980

A colourimetric screening test for evaluation of the buffer capacity of saliva.

A colourimetric method for screening buffer capacity of mixed paraffin stimulated saliva in general practice is described. Mixed paraffin stimulated saliva (1.00 ml) is pipetted into a standard tube belonging to a commercial "saliva kit" (Dentobuff, Orion Diagnostics Ltd). The tube is sealed with a plastic stopper and vigorously shaken for 10 seconds. The stopper is then removed and carbon dioxide is allowed to evaporate for 2--5 minutes. The colour is compared with a scale graded from pH 3 to pH 6. The method was evaluated using 136 dental patients and dental students, and a number of dentists and nurses, and the results were compared with the generally accepted clinical method developed by Ericsson (1959). Several different nurses, dentists and dental students took part in registering the results. In four cases the results differed by more than +/- 2.0 pH units between the two methods and in another 18 by more than +/- 1.0 units. Of the 80 tests performed on no occasion was a person with a "low" salivary buffer capacity evaluated as "normal" or "good". There was no obvious systematic deviation between the two methods, provided carbon dioxide was allowed to evaporate for 2--5 minutes before reading the colour. A thorough examination revealed that at a final pH over 5.5 the method gives lower values than Ericsson's method because of retained carbonic acid, a fact which was considered to be of minor importance, clinically. The method was found to be easy to handle and rapid and the accuracy was considered adequate. It is advisable, however, to repeat the test once or twice because of biological variation and in doubtful cases if "intermediate" results are repeatedly found to send the patient to a clinic with facilities for a complete test.

Adult↗
PubMed1980

Enzyme-linked immunoassay for placental lactogen in human serum.

We describe an enzyme-linked immunoassay for measuring human placental lactogen (HPL) in serum. After suitable dilution, sera are pipetted into the wells of polyvinyl microtitre plates previously coated with anti-HPL. After incubation the sera are decanted, and replaced by a conjugate of horseradish peroxidase and anti-HPL. An amount of enzyme proportional to the concentration of HPL in the serum is bound to the wells via an antibody--HPL--antibody bridge. Peroxidase activity is measured by oxidation of o-phenylenediamine, the resulting color being related to the concentration of HPL. Results correlate well with those by radioimmunoassay (r = 0.96). Our between-assay coefficient of variation was 13%; no discernible effect of protein was observed. This 4-h assay can be used to monitor placental function in pregnancy.

Evaluation Studies as Topic↗
PubMed1980

Quantitation of serum gentamicin concentration by a solid-phase immunofluorescence method.

We describe the use of a solid-phase immunofluorescence method (FIAX system) for measuring drug concentrations, specifically gentamicin, in serum or plasma. Antibody to gentamicin is immobilized on a polymeric surface. This Sampler is immersed in a mixture of serum standard or unknown and a buffered solution of fluorescent-labeled gentamicin. After 30 min, the fluorescence of the specifically bound labeled gentamicin is measured with a fluorometer. The assay detects gentamicin in concentrations as low as 50 mug/L. It is specific for gentamicin, cross reactivity to some other therapeutic drugs, except netilmicin and sisomicin, being low. Results by this assay compare well with those by a radioimmunoassay (r = 0.94) and a radioenzymic assay (r = 0.95). The assay is specific, economical, simply performed, requires little pipetting, and does not involve the use of radioisotopes.

Fluorescent Antibody Technique↗
PubMed1980

Application of x-ray microanalysis in reproductive physiology.

Sperm, testis, prostate, epididymis and uterus have all beeen examined by X-ray microanalysis in the electron microscope. Specimen preparation has included air drying of whole cells, fixation, histochemical treatment, cryoultramicrotomy and freeze substitution of soft tissues, and micropuncture and pipetting of microdroplets from tissue fluids. Early analyses involved the study of thick samples using the electron probe microanalyser (EPMA) with wavelength dispersive spectrometry (WDS). More recently energy dispersive spectrometers (EDS) have been coupled to EMMA, TEM, SEM and STEM instruments to study these tissues. Although spatial resolution and sensitivity of analysis have greatly improved recently, specimen preparation remains a major limitation to the successful analysis of physiological levels of elements in reproductive tissues. A review of comparative methods of analysis and specimen preparation procedures is given for tissues of male and female species.

Animals↗
PubMed1982

Versatile semiautomated sample processor and gamma counter to increase radioimmunoassay efficiency.

We describe a semiautomated batch-assay system designed to increase the speed and ease of performing radioimmunoassays while maintaining good accuracy and precision. The main components are a programmable pipetting unit (sample processor) and a gamma counter capable of simultaneously counting radioactivity in 12 samples. The processor uses prearranged sets of as many as 24 disposable pipette tips, which eliminates carryover between samples, and features a horizontal shaker and magnetic stirrer; 50 different assay protocols can be selected. Batches of tubes are easily transferred from the sample processor to the incubator and centrifuge. The gamma counter is controlled by a microprocessor, which is also used for data processing. Because the system is based on discrete rather than continuous-flow analysis and because of the ease with which consecutive samples can be processed, more than one operation and several different assays can be accommodated simultaneously, which saves time considerably.

Estriol↗
PubMed1982

[Consecutive spectrophotometric determinations in one cuvette: a new approach for checking the accuracy of single, profile and emergency determination (author's transl)].

A cost effective method for emergency and single assays is presented. By this method, a serial (consecutive) determination of reagent blank, sample, standard, and control serum is performed in one single cuvette and with only one pipetting of reagent. Compared to a sequential determination of sample, standard, and control serum, this is specially economical with regard to reagents and cuvettes. A particular application is seen in the field of prefilled cuvette tests, where the consecutive method allows analysis in the sample and in the control serum, and determination of the required standard absorption in a single test. The results found in the determination of glucose and of aspartate aminotransferase show that the consecutive measuring principle is feasible and even results in a more expressive control of accuracy. If the value found in the assay exceeds the measuring range due to too high a substance concentration or activity, or for photometry reasons, it is immediately seen from the incorrect value for the control serum. The same is not possible in the conventional technique, as it uses two separate tests for the sample and for the control serum.

Aspartate Aminotransferases↗
PubMed1982

High performance liquid chromatographic determination of vitamin D in fortified milks, margarine, and infant formulas.

Fortified milks were saponified overnight at room temperature with 1% ethanolic pyrogallol and KOH. The digest was extracted with hexane after adding water and ethanol, and the extract was washed consecutively with 5% KOH, water, and 55% aqueous ethanol to remove polar lipids. After evaporation, the residue was first chromatographed on a column of 5 micrometer silica. A fraction containing vitamin D was collected, evaporated, and rechromatographed on a reverse phase column for the separation and quantitation of vitamins D2 and D3. Recovery was 96-99% and the coefficient of variation was 3% (8 replicates). Infant formula was diluted and then saponified and extracted as in the analysis of milk. Margarine was saponified by shaking overnight with 1% ethanolic pyrogallol and 80% KOH. Water and ethanol were added to the digest before extraction. Extracts from formula and margarine were chromatographed as milk except, before HPLC, the extract was dissolved in isopropanol-hexane (1 + 99) and passed through 5 cm alumina in a Pasteur pipet, and the concentration of isopropanol in the first high performance liquid chromatographic (HPLC) solvent system was halved to improve the separation of vitamin D from other absorbing lipids. Usually several peaks were obtained during the final HPLC analysis, and the identification of vitamins D2 and D3 was less certain than in the analysis of milk. The coefficients of variation for formula and margarine were 6% (5 replicates) and 9% (6 replicates), respectively.

Animals↗
PubMed1982

Food analysis for lead using furnace atomic absorption and a L'vov platform.

Furnace atomic absorption is a very sensitive method for determination of lead and other trace metals in a variety of samples, but it is prone to matrix interferences. A major improvement in the method is achieved by the use of a L'vov platform, a small piece of graphite placed inside the furnace tube, onto which the sample solution is pipetted. The temperature of the platform rises more slowly than that of the tube wall during the atomization cycle, and sample vaporization is delayed until the furnace atmosphere is at a high and nearly constant temperature. The resulting atomization behavior is more consistent and less matrix-dependent for numerous analyte elements, including lead. Results are further improved by addition of ammonium phosphate to all samples and standards as a matrix modifier. For example, in comparing analyte sensitivity (slope of the absorbance vs concentration curve) in a variety of food sample types to the sensitivity in dilute HNO3, the average lead response showed 60 +/- 15% suppression due to the sample matrices. Use of the L'vov platform and matrix modifier virtually eliminated the suppression and improved the precision.

Food Analysis↗
PubMed1982

Titrimetric and gravimetric calibration of pipettors: a survey.

Methods for gravimetric and titrimetric calibration of pipets are described. Both methods of calibration gave good reproducibility from 5-500 microliters. The titrimetric method gave the lowest coefficient of variation for pipettors from 1-10 microliters and was the better method for these smaller volumes. In addition, the titrimetric method took one-third the time of the gravimetric method. Pipettors of various types were obtained from 38 different laboratories and used to survey performance. The titrimetric method was used to calibrate 572 pipettors of different types. A significant percentage of the pipettors were greater than 3% from their nominal value.

Calibration↗
PubMed1980

Comparison of lymphocyte transformation responses to fresh or frozen phytohemagglutinin.

Peripheral blood lymphocytes were cultured in microtiter plates with phytohemagglutinin which was added on the day of testing or had been previously pipetted and frozen. There was good correlation of transformation results using PHA concentrations from 0.25 to 10 microgram/ml (r = 0.772) to 0.828) PHA could be prepipetted and frozen for up to four weeks maintaining good correlation.

Adult↗
PubMed1981

Column affinity chromatography for bound/free separation in ligand assays. I. Radioimmunoassay of choriomammotropin (human placental lactogen).

A method is described for separating antibody-bound from free fractions in ligand assays by column affinity chromatography, and its application to radioimmunoassay of choriomammotropin. In the method, 70 x 10 mm (i.d.) polypropylene columns containing about 150 mg of immunosorbent (goat anti-rabbit gamma-globulins covalently linked to Sepharose CL-4B) are used. Standards or unknowns, tracer and antiserum, pipetted into bottom-capped columns, are kept separated from the immunosorbent bed by a porous polyethylene disc and allowed to react for 15 min at room temperature. The reaction mixture is then allowed to pass through the columns by removing the bottom caps. Free antigen is eluted by washing the column, and discarded; antibody-bound fractions remain bound to the immunosorbent. The radioactivity in the columns is counted. The major advantages of the present technique, arising from the liquid-phase reaction combined with the solid-phase separation by column affinity chromatography, are the very low nonspecific binding (less than 1%), good sensitivity (0.02 mg/L), good precision (CV 3.4%), and simple and fast (30-min) assay. For 50 clinical samples so assayed (gamma) and compared with a polyethylene glycol precipitation technique (x), the regression equation was: y - 0.14 + 0.98x (r = 0.994). The assay method was clinical validated by 3493 determinations.

Chromatography, Affinity↗
PubMed1980

Preparation and characterization of single cells from the avian salt gland.

In preparation for pulse-chase autoradiography experiments and studies of cell surface changes of relevance to plasma membrane biogenesis, we have prepared a cell suspension from the salt gland of ducklings. The method used was a modification of previous methods used for pancreas and salivary gland and included digestions with collagenase and hyaluronidase, divalent cation chelation, and dispersion by gentle pipetting. Yields were 1.13 X 10(7) cells/g gland, and cell recovery was 45% by DNA assay. Recovery of Na,K-ATPase, a marker for salt gland secretory cells was 40--47%. Cell viability was strongly indicated by trypan blue exclusion and 3H-leucine incorporation. Transmission and scanning electron microscopy revealed that most cells retained ultrastructural features characteristic of the intact gland. Smaller cells (3--8 micrometers in diameter), exhibiting few surface microvilli and relatively few cytoplasmic organelles, likely represented the undifferentiated, peripheral cells from the tips of secretory tubules. Larger cells (5--10 micrometers in diameter), exhibiting prominent surface membrane folds enclosing numerous mitochondria, likely represented the functional, secretory cells of the salt gland tubules in various stages of differentiation. The surface folds presented as microvilli and microplicae in scanning electron micrographs.

Animals↗
PubMed1981

Zinc determined in 10-microL serum or urine samples by flameless atomic absorption spectrometry.

We describe a precise flameless atomic absorption spectrometric method requiring only 10 microL of sample, which thus permits repeated measurements in the neonate. Standard curves covering the range of 0 to 30 mg of zinc per liter, with standards in various matrixes (albumin, glycerol, serum, or nitric acid) had slopes ranging from 0.49 to 1.17, relative to that for aqueous standards. We prepared low-zinc matrixes, which had slopes similar to that of serum, by dialyzing serum or a 50 g/L solution of albumin vs a buffered zinc-free dialysis fluid containing appropriate inorganic constituents. Use of thoroughly de-ionized water, reagent-grade chemicals, "ultrapure" nitric acid, specified disposable plastic ware, and appropriate pipet tip-rinsing techniques minimized extraneous contamination with zinc. Concentrations of zinc in serum calculated from a "rational-method" calibration algorithm fit to the standard curve agreed well with independent determinations by flame atomic absorption spectrometry.

Humans↗
PubMed1995

Cobas Integra: clinical laboratory instrument with continuous and random-access capabilities.

The Cobas Integra from Roche Diagnostic Systems is a new clinical laboratory analyzer with continuous and random-access features for routine chemistries, specific proteins, electrolytes, hormones, therapeutic drugs, and drugs of abuse. The system maintains 68 test-specific reagent cassettes on board, along with multiple ion-selective electrodes (ISEs) for electrolyte determinations. This gives the Cobas Integra the capability of analyzing as many as 72 analytes without having to load additional reagents. We describe the basic analyzer configuration and the subsystems for absorbance, fluorescence polarization, and ISE measurements. Performance characteristics for precision, methods comparison, and on-board stability are given for assays representative of the various test groups. The 29 Cobas Integra tests evaluated in the present study show good agreement (r > or = 0.98 and slopes generally 0.90 to 1.12) with the respective methods available on either the Olympus AU5000, Hitachi 911 or 717, Behring BNA, or Abbott TDx systems. Total assay precision (CV) ranged from 0.8% to 8.5%, and calibration curves were stable for as long as 20 weeks. Test throughput, which is dependent on pipetting sequence, was determined to be up to 600 tests per hour without ISE and up to 750 tests per hour with ISE; the time to first result was 2.0-10.0 min.

Calibration↗