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Biomedical subjects

M A Davis

Publications and source records attributed to M A Davis.

At least 217 records · Page 12Linked to original sources
PubMed1979

Evaluation of hepatobiliary imaging by radionuclide scintigraphy, ultrasonography, and contrast cholangiography.

Cholescintigraphy, ultrasonography, and contrast cholangiography were compared in 60 patients. Among those having abdominal pain but no biliary disease or jaundice, cholescintigraphy was normal in 14/14, ultrasound in 10/13, and cholangiography in 13/14. Jaundice due to hepatocellular disease was correctly distinguished from complete biliary obstruction by cholescintigraphy in 17/17 patients and by ultrasound in 14/17. In cholelithiasis, ultrasound was abnormal in 10/12 and cholangiography in 7/9. Cholescintigraphy appeared most sensitive to active cholecystitis; only cholangiography and ultrasound visualized gallstones.

Biliary Tract Diseases↗
PubMed1979

Potential column chromatography generators for ionic Ga-68. I. Inorganic substrates.

Chemical separations for Ga-68 from Ge-68 using adsorption chromatography on inorganic materials are described. The adsorbents used were TiO2, ZrO2, and SiO2. Distribution coefficients for Ge and Ga on these absorbents were determined as a function of reagent concentration and duration of equilibration. The distribution coefficient (w/w) for Ge on SiO2 reached 250 in 6 N HNO3, whereas Ga was no significantly adsorbed. Therefore, Ga-68 can be collected with a mall volume of 6 N HNO3 eluent. By contrast, large volumes of 1 N HNO3 were necessary to collect Ga-68 from ZrO2, since the KD of Ga under these circumstances was about 50. The Ga-68 eluted from TiO2 was chemically contaminated with titanates and would require additional chemical manipulation in order to make it injectable. All the adsorbents could lead to chromatographic systems that would allow acceptable chemical separations. However, the specific requirements for a radionuclide generator, usable in a hospital environment, make the SiO2-based system the most attractive.

Chromatography↗
PubMed1979

Tantalum-178-labeled agents for lung and liver imaging.

Despite its 9.3-min half-life, Ta-178 can be used to produce radiopharmaceuticals for lung and liver imaging. A variety of human serum albumin microspheres and other particulate radiopharmaceuticals were labeled with Ta-178. A period of approximately 10 min was required for their preparation and administration to rats. Extrapolation to the clinical situation suggests that imaging could take place after one half-life of the nuclide has elapsed. We found that satisfactory imaging is possible using Ta-178 radiopharmaceuticals with the Anger camera and a pinhole collimator. Since short imaging times, high spatial resolution, and low patient doses are reasonable objectives in pediatric scintigraphy, these new radiotracers may prove useful for lung and liver imaging in children.

Animals↗
PubMed1979

A comparison of two technetium-99m-labeled radiopharmaceuticals for lymphoscintigraphy: concise communication.

A comparison of stannous phytate and antimony sulfide colloid, both labeled with Tc-99m, was conducted during the performance of internal mammary lymphoscintigraphy in 46 patients. Thirteen of these patients were randomized to receive both radiotracers in two consecutive studies. The results indicated a statistical difference between agents; Tc-99m antimony sulfide allowed visualization of a greater number of more intense nodes, better delineation of the total length of the internal mammary lymph-node chain, and a more consistent visualization of supraclavicular nodes. Although previously published animal data suggest utility of Tc-99m stannous phytate for lymph-node imaging, Tc-99m antimony sulfide was shown in this clinical comparison to provide a more reliable representation of lymph-node anatomy.

Antimony↗
PubMed1978

Selenium-sulfur analogues. 1. Synthesis and biochemical evaluation of selenotetramisole.

(+/-)-2,3,5,6-Tetrahydro-6-phenylimidazo[2,1-b]selenazole (1-selenotetramisole) was prepared from 2-aminoselenazoline in a three-step synthetic sequence. Resolution with d-10-camphorsulfonic acid yielded the optical isomers which were compared with (+)- and (-)-tetramisole as inhibitors of alkaline phosphatase isoenzymes. At 8.7 X 10(-5) M the (-) isomer of both tetramisole and 1-selenotetramisole produced significant inhibition of bovine liver and placental isoenzymes but not of calf intestinal or human placental isoenzymes. The (+) isomers demonstrated no inhibition at these concentrations. The similarity in inhibitory activity of the (-) isomers indicates the virtual interchangeability of selenium for sulfur in the thiazolidine ring of the parent drug and the likelihood that 75Se-radiolabeled selenotetramisole can provide an in vivo tracer to tetramisole biodistribution.

Alkaline Phosphatase↗
PubMed1978

Synthesis and biologic distribution of radioiodinated beta-adrenergic antagonists.

Iodinated analogues 2, 7, and 8 were prepared from propranolol, practolol, and acebutolol in 30--50% yields. Radioisotopic exchange between carrier-free Na125I and the molten iodinated beta-adrenergic antagonist yielded the corresponding 125I-labeled product. The biodistribution in rats, determined at 15 and 60 min postinjection, indicated that the radioiodinated analogues of the cardioselective drugs practolol and acebutolol localized to a greater degree in the liver and heart than the analogue of propranolol. Conversely, [125I]iodopropranolol (2) was concentrated to a greater extent in the lungs than [125I]iodopractolol (7) or [125I]iodoacebutolol (8). Therefore, 123I- or 131I-labeled cardioselective beta-adrenergic antagonists, such as 7 or 8, may prove useful as radiodiagnostic agents for the external imaging of the myocardium.

Acebutolol↗
PubMed1978

A method for demonstrating the efficacy of interventions designed to limit infarct size following coronary occlusion: beneficial effect of hyaluronidase.

In order to measure the protective effect of interventions following coronary artery occlusions in dogs, the creatine kinase activity of myocardial tissue was assayed after 24 h and related to the myocardial blood flow of that tissue measured with 85Sr labelled microspheres injected 15 min after occlusion. This assay showed normal levels when flow exceeded 50 cm3.min-1.100 g-1. In myocardium with flow reduced to 0 to 15 cm3. min-1.100g-1, creatine kinase activity was 7.6 +/- 0.6 IU.mg-1 protein in control dogs and 13.1 +/- 1.8 IU.mg-1 protein (P less than 0.01) in dogs given 500 NF units.kg-1 of hyaluronidase 20 min after occlusion. Where myocardial blood flow was reduced to 16 to 50 cm3. min-1. 100g-1, creatine kinase activity was increased from 14.1 +/- 1.1 to 20.5 +/- 1.4 IU.mg-1 protein by hyaluronidase. This method therefore assesses ischaemic damage independent of electrophysiological measurements and confirms myocardial preservation by hyaluronidase.

Animals↗
PubMed1978

Radionuclide emission computed tomography of the body of laboratory animals.

Selective studies in the monkey and baboon demonstrate the normal physiologic distribution of 99mTc radiopharmaceuticals using single-photon emission computed tomography. The cases demonstrated the ability of the Cleon Transverse Section Brain Imager TM to do emission computed tomography of various organs. This experience shows what can be expected when equipment for emission computed tomography of the body becomes available for patient studies.

Animals↗
PubMed1978

Indium and iron as tracers for erythroid precursors.

External visualization and delineation of functional bone marrow is important for diagnostic, prognostic and therapeutic purposes. Because of difficulties in using the isotopes of iron for bone-marrow imaging, indium-111 chloride has been used extensively for this purpose. In this investigation we attempted to solve the problem of cellular localization of indium chloride by employing a rat model with erythropoietic precursors selectively damaged by lethal intracellular radiation from the Auger electrons of Fe-55. In the rat, we have shown that the absolute marrow uptakes of indium and iron are different, whereas the absolute uptakes of indium and sulfur colloid are the same. However, in animals whose erythroid activity was partially destroyed with Fe-55, the fractional depressions of iron and indium uptakes were the same and corresponded to the extent of the remaining erythroid activity. In addition, following an in vitro separation of the cellular elements of marrow with iron carbonyl, both iron and indium were found in the erythroid-rich supernatant, whereas sulfur colloid was in the precipitate. These results indicate that, in the rat, In-111 chloride is an effective in vivo marker for the early phases of iron uptake by the bone marrow.

Animals↗
PubMed1978

Tantalum-178--a short-lived nuclide for nuclear medicine: development of a potential generator system.

We describe a chemical separation that may form the basis of a generator system for the short-lived radionuclide Ta-178 (T 1/2 = 9 min). The parent nuclide W-178 (T 1/2 = 21.7 days) is loaded on an anion-exchange column and the daughter eluted with a mixture of dilute hydrochloric acid and hydrogen peroxide. The yields of tantalum and the breakthrough of the tungsten parent as a function of the eluting conditions are discussed, and preliminary animal distribution data are presented for various treatments of the eluant solution.

Animals↗
PubMed1978

A model for the radionuclide measurement of ascitic fluid volumes.

Technetium-99m phytate colloids formed in vitro and in vivo were examined as radioindicators for estimation of the volume of third-space fluid in an ovarian ascites model using C3HeB/FeJ mice. In double-label experiments, the accuracy of the colloids for dilution analysis was found to be equal or superior to that of I-125 HSA. Sampling times 3--5 min after intraperitoneal administration were found to produce the best volume estimates. Four needle-stopcock assemblies inserted sequentially into the quadrants of the peritoneal cavity were used for administration and sampling of the radioindicators. The stopcocks could be closed to prevent leakage of ascitic fluid during the procedure. In contrast to radiolabeled albumin, Tc-99m phytate colloids have clinical use for simultaneous imaging of radiotracer migration to assess potential occlusion of diaphragmatic lymphatics by neoplastic cells, and for dilution analysis to estimate volume of ascitic fluid.

Animals↗
PubMed1977

Myocardial infarct imaging with technetium-labeled complexes.

Detection of acute myocardial infarction as an area of increased activity has intrigued investigators for some time. Initial attempts with 203Hg-chlormerodrin and 203Hg-fluorescein analogues were successful in man. More recently, however, successful imaging of the acute myocardial infarct has been achieved with several 99mTc complexes. A large group of radiotracers localize in acutely damaged tissue in various models of experimental infarction. From these data, a number of specific structural properties associated with infarct avidity have been identified; these include the presence of mercury and the structural configuration of the organic carrier.

Animals↗
PubMed1977

Health status, socioeconomic status and utilization of outpatient services for members of a prepaid group practice.

When evaluating the effectiveness of medical care programs, one concern is whether receipt of care is based upon health care needs or upon socioeconomic status. This study describes the relation between health status and socioeconomic status and attempts to determine which has the greater effect on ambulatory care utilization. The study setting was an operating HMO serving a cross-sectional membership of nearly 200,000 persons. Outpatient utilization data were derived from the medical records of a five per cent sample of health plan members for 1969 and 1970. Social, economic, situational, and attitudinal data were provided by 2,603 respondents in a household interview survey. Since a population's perceived health status may reflect health need, information from the survey provided measures of health status that ranged from specific symptoms and complaints to a general measure of perceived health status. Although the findings varied somewhat according to which variables were considered, they generally showed health status to correlate more highly than socioeconomic factors with the utilization of services in this medical care system. An exception was the use of preventive services, which was not significantly related to health status measures but rather, for women, to education and, to a lesser extent, income.

Absenteeism↗