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Biomedical subjects

S C Jacobson

Publications and source records attributed to S C Jacobson.

10 recordsLinked to original sources

Degenerate oligonucleotide primed-polymerase chain reaction and capillary electrophoretic analysis of human DNA on microchip-based devices.

Random amplification of the human genome using the degenerate oligonucleotide primed-polymerase chain reaction (DOP-PCR) was performed in a silicon-glass chip. An aliquot of the DOP-PCR amplified genomic DNA was then introduced into another silicon-glass chip for a locus-specific, multiplex PCR of the dystrophin gene exons in order to detect deletions causing Duchenne/Becker muscular dystrophy. Amplicons were analyzed by both conventional capillary electrophoresis and microchip electrophoresis and results were compared to those obtained using standard non-chip-based PCR assays. Results from microchip electrophoresis were consistent with those from conventional capillary electrophoresis. Whole genome amplification products obtained by DOP-PCR proved to be a suitable template for multiplex PCR as long as amplicon size was < 250 bp. Successful detection and resolution of all PCR products from the multiplex PCR clearly shows the feasibility of performing complex PCR assays using microfabricated devices.

DNA

Microchip device for cell lysis, multiplex PCR amplification, and electrophoretic sizing.

The steps of cell lysis, multiplex PCR amplification, and electrophoretic analysis are executed sequentially on a monolithic microchip device. The entire microchip is thermally cycled to lyse cells and to amplify DNA, and the products are then analyzed using a sieving medium for size separation and an intercalating dye for fluorescence detection. Using a standard PCR protocol, a 500-base pair (bp) region of bacteriophage lambda DNA and 154-, 264-, 346-, 410-, and 550-bp regions of E. coli genomic and plasmid DNAs are amplified. The electrophoretic analysis of the products is executed in <3 min following amplification using hydroxyethyl cellulose or poly(dimethylacrylamide) sieving gels. Product sizing is demonstrated by proportioning the amplified product with a DNA sizing ladder.

DNA, Bacterial

Microchip device for performing enzyme assays.

An automated enzyme assay was performed within a microfabricated channel network. Precise concentrations of substrate, enzyme, and inhibitor were mixed in nanoliter volumes using electrokinetic flow. Reagent dilution and mixing were controlled by regulating the applied potential at the terminus of each channel, using voltages derived from an equivalent circuit model of the microchip. The enzyme beta-galactosidase (beta-Gal) was assayed using resorufin beta-D-galactopyranoside (RBG), a substrate that is hydrolyzed to resorufin, a fluorescent product. Reaction kinetics were obtained by varying the concentration of substrate on-chip and monitoring the production of resorufin using laser-induced fluorescence. Derived Michaelis--Menten constants compared well between an on-chip and a conventional enzyme assay. Bias in the derived K(m) and kcat was primarily due to the limited solubility of RBG and the associated lack of measurements at substrate concentrations exceeding the K(m). A Ki of 8 microM for the inhibitor phenylethyl beta-D-thiogalactoside (PETG) was determined from plots of initial rate versus substrate concentration obtained at three concentrations of PETG. The relative inhibition of beta-Gal by lactose, p-hydroxymercuribenzoic acid, and PETG was determined by varying the inhibitor concentration with constant enzyme and substrate concentration. An enzyme assay performed on the microchip within a 20-min period required only 120 pg of enzyme and 7.5 ng of substrate, reducing the amount of reagent consumed by 4 orders of magnitude over a conventional assay.

Autoanalysis

Microchip electrophoresis with sample stacking.

A fused quartz microchip with a serpentine column geometry is fabricated to perform rapid microchip electrophoresis of dansylated amino acids. A 67 mm separation column is constructed in a 7 x 10 mm area on a quartz substrate using standard photolithographic, etching and deposition techniques. Buffer and sample flows within the channel manifold are precisely controlled through potentials applied to the reservoirs. To enhance the detection limits, a stacking injection technique is used to concentrate the sample at the inlet of the separation column. The stacked injections exhibit high reproducibility (2.1% relative standard deviation in peak area). Using a separation length of 67 mm and a separation field strength of 1100 V/cm, separations are performed in < or = 15 s generating approximately 40,000 theoretical plates.

Amino Acids

Estimation of the number of enantioselective sites of bovine serum albumin using frontal chromatography.

On a column with bovine serum albumin (BSA) immobilized covalently to silica, the adsorption isotherms of the enantiomers of mandelic acid, tryptophan, 2-phenylbutyric acid, and N-benzoylalanine are measured using a buffered mobile phase. Knowing the amount of BSA immobilized on the column (36 mg), the ratio of the number of enantiomer molecules needed to saturate the enantioselective retention mechanism to the number of BSA molecules is determined. The mean of the set of eight enantiomers is 0.28. These data confirm that at most one enantioselective site exists for each BSA molecule for the kind of enantiomers studied.

Adsorption

Enantiomeric separations using bovine serum albumin immobilized on ion-exchange stationary phases.

Bovine serum albumin (BSA) can be readily immobilized on ion-exchange stationary phases by frontal analysis of a proper solution. This provides a simple means of adjusting the amount of BSA contained in the column and of measuring it accurately. Although the immobilization is ionic and not covalent, the columns are stable for extensive periods of time. If needed, they can be easily regenerated by the same frontal analysis procedure.

Animals

Contribution of ionically immobilized bovine serum albumin to the retention of enantiomers.

The retention of the enantiomers of mandelic acid and N-benzoylalanine was studied on columns prepared by immobilizing bovine serum albumin (BSA) on an anion exchanger. The amount of BSA fixed on the column is easy to adjust and measure. The adsorption isotherms were determined. For each enantiomer, the isotherm is well accounted for by a bi-Langmuir equation. One term of the isotherm (which is the same for both enantiomers) corresponds to non-selective interactions and the other term to the chiral selective interactions. The column saturation capacity of this second term is 8% larger for the less strongly retained enantiomer. This saturation capacity corresponds approximately to one enantiomer molecule adsorbed for five BSA molecules immobilized. This result is in agreement with the assumption of the hydrophobic cavity of BSA being the chiral selective site.

Alanine

The quantity and distribution of radiolabeled dexamethasone delivered to tissue by iontophoresis.

A pilot study was conducted in the first of two monkeys using either radiolabeled Dm-Na-P or radiolabeled hydrocortisone sodium succinate, together with lidocaine HCl. This study indicated an approximately tenfold increase in the quantity of Dm-Na-P delivered to the test electrodes (4 mA; 20 minutes) whereas the quantity of hydrocortisone delivered from the test electrodes was only marginally (approximately 10%) increased as compared with that from the controls. In terms of an anti-inflammatory activity, the effective dose of Dm-Na-P in all tissue layers underlying the test electrodes was at least tenfold that of the hydrocortisone. Therefore, further trials with hydrocortisone were abandoned. In the second animal, positive test electrodes (5 mA; 20 minutes, were sited over five joints on the right side of the body and matching control electrodes (0 mA; 20 minutes) were placed over corresponding joints on the left side of the body. The control and test electrodes each contained 1.0 ml tritium-labeled Dm-Na-P (approximately 4.0 mg) and 2.0 ml 4% lidocaine HCl (80 mg). Local tissue concentrations of Dm-Na-P were higher than those that would be obtained by systematic therapy and lower than would be obtained by local injection.

Animals

An evaluation of computerized documentation of resident experiences in training.

This paper describes an evaluation of the University of Washington family practice project to document resident experiences in training. The production of aggregate reports using clustering techniques and peer group comparisons were well received by residents and faculty. A questionnaire survey and personal interview with a sample of faculty and residents analyzed attitudes toward the usefulness of such a documentation system as well as the actual uses of the reports produced. Documentation of inpatient and outpatient procedures was the most highly regarded application, but an overview of the scope and content of a resident ambulatory practice experience was also considered useful. Physician behavior was altered in subtle ways as a result of the feedback.

Ambulatory Care