PubMed Health⌕ Search

Biomedical subjects

H A O'Brien

Publications and source records attributed to H A O'Brien.

30 records · Page 2Linked to original sources
PubMed1979

Evaluation and application of alumina-based Rb-82 generators charged with high levels of Sr-82/85.

Generator-produced Rb-82, a 75-sec positron emitter with potential for myocardial blood-flow imaging, was studied with various ion-exchange columns to evaluate the characteristics of alumina as an adsorber for the 25-day Sr-82 parent. Test columns of alumina, Bio Rex 70, and Chelex 100 were loaded with multimillicurie amounts of no-carrier-added Sr-82/Sr-85 (Sr-85 is a production contaminant). The breakthrough of Sr-82/Sr-85, and the yield of Rb-82, were determined for long-term elutions from each column with up to 4 liter of 2% NaCl solution at pH 8 to 9. The breakthrough of Sr-82/85 was 10(-6)-10(-5) from aluminal 10(-6)-10(-4) from Chelex 100 and Bio Rex 70. The effects of eluent flow rate and concentration, and of alumina volume, on the breakthrough and yield were also studied. An improved and automated Rb-82 generator was used for myocardial and brain blood-flow studies in experimental animals and in man; it was equipped with solenoid flow-control valves and five in. of lead shielding for the alumina columns, which were charged with 25-50 mCi Sr-82 (100-150 mCi Sr-85). The Rb-82 generator with alumina column provided up to 20-40 mCi of Rb-82 as often as every 5-10 min with less than 10(-5) breakthrough of Sr-82/85 over the 2- to 3-mo, useful life of the generator.

Aluminum Oxide↗
PubMed1978

Rapid radioiodination of rose bengal at room temperature.

Published methods for radioiodination of rose bengal require reaction times of 1 hr or more at temperature from 50 to 120 degrees C. Through the use of an acidified ethanol solvent and potassium iodate oxidant, purified rose bengal is radioiodinated at room temperature within 15 min with chemical yields ranging between 93 and 97%. Radiochemical impurities are sufficiently minimized to permit preparation in a single 10-ml serum vial, requiring no additional purification steps. The method reported here is readily adaptable to cold-kit preparation.

Iodine Radioisotopes↗
PubMed1977

A radioisotope dilution assay for unlabelled vitamin B12-intrinsic factor complex employing the binding intrinsic factor antibody: probable evidence for two types of binding antibody.

A new radioisotope dilution assay for vitamin B12-intrinsic factor complex is described. The method is based on the use of the binding type intrinsic factor antibody (the binding reagent), which when combined with the intrinsic factor-vitamin B12 complex (labelled ligand), is quantitatively adsorbed onto zirconium phosphate gel at pH 6.25. The new assay has been shown to provide a measure of intrinsic factor comparable with other intrinsic factor assays, but it has the important advantage of being able to measure the unlabelled vitamin B12-intrinsic factor complex (unlabelled ligand), and will, therefore, be valuable in the study of physiological events in the gastrointestinal tract. During the study, it was found that there is some evidence for a least two types of binding intrinsic factor antibody: One which combines preferentially with the intrinsic factor-vitamin B12 complex and one which combines equally well with this complex or with free intrinsic factor.

Antibodies↗
PubMed1977

Rubidium-82 generators for imaging studies.

Strontium-82, produced by spallation reaction with medium-energy proton beams, was used to evaluate Bio-Rex 70 and Chelex-100 ion-exchange resins for use in a compact Rb-82 generator. Adsorption of Sr-82 to the resin column, Rb-82 elution yields, Sr breakthrough, and 82Rb-Sr separation factors were determined for newly prepared columns and for longterm elution conditions. Separation factors of 10(7) to 10(8) were obtained with 2% NaCl elutions from Bio-Rex 70 resin columns while the separation factors was about 5 X 10(4) with the Chelex-100 resin column.

Evaluation Studies as Topic↗
PubMed1975

A 82Sr-82Rb isotope generator for use in nuclear medicine.

An improved 82Sr-82Rb generator system, based on the complexing ion-exchange resin Chelex-100, has been developed. Columns of this material can be easily and rapidly milked, and the rubidium-strontium separation factor for a fresh generator under the experimental conditions studied was found to be greater than 10-7. Approximately 80% of the 82Rb present can be delivered in a 15-ml volume of aqueous 0.2 M NH4Cl solution. After more than 6 liters of eluant had passed through the generator, the rubidium-strontium separation factor was still observed to greater than 10-5 and no unusual strontium breakthrough behavior was seen in the system over nearly three 82Sr half-lives.

Ion Exchange Resins↗
PubMed1972

A simple assay of intrinsic factor-vitamin B12 complex employing the binding intrinsic factor antibody.

The reaction between binding intrinsic factor antibody and intrinsic factor-vitamin B(12) complex has been studied. Initially in the zone of antibody excess, the relationship between the amount of antigen present and the amount of antigen-antibody complex adsorbed onto zirconium phosphate gel was linear. With increasing amounts of antigen, the curve departed from linearity and reached a plateau. The linear portion of the reaction forms the basis of a simple and reproducible assay for quantitating intrinsic factor to which vitamin B(12) has already been bound. The assay provides a method for studying the fate of intrinsic factor-vitamin B(12) complex during digestion and absorption. In two normal subjects given radioactive vitamin B(12) orally, aspiration of ileal contents showed that only 50 to 70% of the radioactivity was bound to intrinsic factor at that level.

Adsorption↗
PubMedDate not supplied

Transport and intracellular distribution of copper in a human hepatoblastoma cell line, HepG2.

The uptake of radiocopper by HepG2 cells is a saturable, temperature-dependent and cellular energy-independent process with a Vmax of 7.1 +/- 0.2 pmoles min-1 mg protein-1 and an estimated Km of 3.3 +/- 0.5 microM. The rate of copper uptake is reduced at an equimolar concentration of albumin and is unaffected by zinc at a 10-fold molar excess. Approximately 70% of the newly incorporated radiocopper binds to membranes and organelles, while 30% is recovered in the cytosol. The soluble fraction can be resolved into two copper-binding protein peaks. Incubation of HepG2 with nonisotopic copper results in displacement of radiocopper associated with the proteins contained in the lower molecular weight peak. Exposure of the cells to cycloheximide inhibits the incorporation of the isotope into this fraction.

Biological Transport↗