Biomedical subjects

Alan B Packard

Publications and source records attributed to Alan B Packard.

5 recordsLinked to original sources

PubMed2005

On the strong field dependence and nonlinear response to gadolinium contrast agent of proton transverse relaxation rates in dairy cream.

Dairy cream, as a suspension of lipid droplets in water, is a potentially useful magnetic resonance imaging (MRI) phantom material and an interesting material for studying fundamental relaxation mechanisms. Here we report a strong increase in the transverse relaxation rates with field strength for both the water and lipid protons in dairy cream. Also, studies at 4.7 T reveal a nonlinear response of transverse relaxation rates with increasing concentration of a common gadolinium (Gd)-based contrast agent, including an initial decrease of water relaxation rates as measured with Hahn spin echoes at the lower Gd concentrations. The results are treated within the framework of a model in which the magnetic susceptibility difference between the lipid droplets and the aqueous phase plays the prominent role for transverse relaxation. Second-order polynomial fits of the water proton transverse relaxation rate dependence on field strength and on Gd concentration at 4.7 T provided experimental parameters from which model parameters are extracted and compared with expectations available from the literature.

Contrast Media↗

PubMed2004

Fat fractions and spectral T2 values in vertebral bone marrow in HIV- and non-HIV-infected men: a 1H spectroscopic imaging study.

Fat fractions and spectral T2 values of fat and water within the vertebral marrow of non-HIV- and HIV-infected men were measured with the use of a Carr-Purcell-Meiboom-Gill (CPMG) line scan spectroscopic imaging sequence. The fat fraction for the HIV-infected men (0.29 +/- 0.08) was significantly lower (P < 0.05, Student's unpaired t-test) than the fat fraction found in non-HIV-infected men (0.40 +/- 0.12). The mean water and fat T2 values did not differ between the two groups, and did not show any systematic dependence on fat fraction over the wide range of fat fractions encountered in this study. The marrow water and fat T2 values measured with the CPMG approach were markedly longer than the spectral T2 values reported by other groups using the more common point-resolved spectroscopy (PRESS) and stimulated-echo acquisition mode (STEAM) acquisitions. Proton spectroscopic studies of vertebral marrow revealed differences between non-HIV- and HIV-infected men that may prove useful for studying the effects of this disease and/or antiretroviral agents on body composition.

Adult↗

PubMed2004

Assessment of rapid changes in renal blood flow with (191m)Ir, an ultra-short-lived radionuclide.

UNLABELLED: We investigated the feasibility of using (191m)Ir (half-life, 5 s) to measure rapid dynamic alterations in differential renal blood flow. METHODS: A nonobstructive constant renal pelvic pressure model was used. The renal pelves of 6 New Zealand White rabbits were drained by use of bilateral catheters, and increased hydrostatic pressure was achieved by raising 1 catheter to 16, 25, 30, or 35 cm above the level of the renal pelvis. The contralateral kidney served as the control. (191m)Ir first-pass angiograms were obtained at baseline, after the induction of elevated pressure in the renal pelvis, and after the pressure was returned to normal. A minimum of 3 sequential angiograms were obtained at each point. RESULTS: The differential blood flow values (mean +/- SD) were 47.5% +/- 7.3% at baseline, decreased to 42.3% +/- 2.6% when the renal pelvic pressure was elevated (P = 0.001), and returned to 51.1% +/- 4.0% after the pressure was returned to normal (P = 0.0017). There was no significant difference between baseline and postcompression values (P = 0.4807). CONCLUSION: It is possible to use (191m)Ir first-pass angiography to evaluate rapid dynamic changes in differential renal blood flow in an experimental animal model.

Animals↗

PubMed2002

A lariat-functionalized copper(II) diimine-dioxime complex.

The dimeric title copper(II) complex, diaqua-1kappaO,2kappaO-bis[3,9-dimethyl-6-(2-pyridylmethyl)-4,8-diazaundeca-3,8-diene-2,10-dione dioximato(1-)]-1k(4)N(2),N(4),N(8),N(10);1:2kappa(5)O(2):N(2),N(4),N(8),N(10)-dicopper(II) diperchlorate, [Cu(2)(C(17)H(24)N(5)O(2))(2)](ClO(4))(2), crystallizes with one Cu atom in a square-pyramidal environment and the other Cu atom displaying a distorted octahedral coordination. In each case, the four N atoms in the core of the ligand (two imine and two oxime N atoms) form the base of the pyramid, with a water molecule at an apex. The two parts of the dimer are linked by an interaction [2.869 (2) A] between one of the Cu atoms and one of the oxime O atoms coordinated to the second Cu atom, and also by a hydrogen bond between the apical water molecule on the second Cu atom and the pyridyl N atom from the coordination sphere of the first Cu atom. The pyridyl N atoms of the lariat arms are not coordinated to either of the Cu atoms. Thus, this potentially pentadentate ligand is only tetradentate when coordinated to Cu(II).

Copper↗

PubMed2002

Synthesis and biodistribution of a Lipophilic 64Cu-labeled monocationic Copper(II) complex.

The lipophilic, monocationic copper(II) complex of the diiminedioxime ligand 2,10-di-n-butyl-3,9-dimethyl-1,4,8,11-tetraazaundeca-1,3,8,10-tetraen-1,11-dione dioxime was synthesized and labeled with 64Cu. The biological properties of the 64Cu-labeled complex were measured in vivo and in vitro. In vivo, the complex shows uptake by the heart similar to that of 99mTc-tetrofosmin. In vitro, its uptake by multidrug resistant and non-resistant MES-SA tumor cells parallels that of 99mTc-MIBI, a well-characterized marker of multidrug resistance. These results suggest that this class of copper complexes may form the basis for the development of a 64Cu PET radiopharmaceutical for the functional imaging of multidrug resistance and/or myocardial perfusion.

ATP Binding Cassette Transporter, Subfamily B, Mem↗