To determine the feasibility of MR imaging of magnetically labeled cells, different cell lines were labeled with monocrystalline iron oxide (MION) particles. Phantoms containing MION labeled cells were then assembled and imaged by MR at 1.5 T using T1-weighted and T2-weighted pulse sequences. MION uptake ranged from 8.5 x 10(4) to 2.9 x 10(5) particles/cell for tumor cells (9L and LX1, respectively) to 1.5 x 10(6) to 4.8 x 10(8) particles/cell for "professional phagocytes" (J774 and peritoneal macrophages, respectively). On the T1-weighted images, cell-internalized MION appeared hyperintense relative to agar and similar to MION in aqueous solution. On T2-weighted images, signal intensity varied according to concentration of MION within cells. Cell-internalized MION caused similar MR signal changes of cells as did free MION; however, at a dose that was an order of magnitude lower, depending on the pulse sequence used. The detectability of MION within cells was approximately 2 ng Fe, which corresponded to 10(5) tumor cells/well or 5 x 10(3) macrophages/well. We conclude that a variety of cells can be efficiently labeled with MION by simple incubation. Intracellular labeling may be used for MR imaging of in vivo cell tracking.

Contrast Media↗

PubMedDate not supplied

Dynamic MR imaging of hepatolithiasis.

BACKGROUND: To report the dynamic magnetic resonance (MR) imaging findings of hepatolithiasis. METHODS: Dynamic MR images (fast spoiled gradient echo sequence with intravenous injection of gadopentate dimeglumine) and computed tomography, cholangiography, or angiography of nine patients with hepatolithiasis are analyzed. RESULTS: All affected hepatic segments showed atrophic changes and contained dilated intrahepatic ducts. These segments showed either iso- or hypointensity on T1-weighted imaging and hyperintensity on T2-weighted imaging. Preferential enhancement was noted throughout all phases of the dynamic study and persisted to delayed T1-weighted imaging in seven patients. In the last two patients, severe atrophic changes made evaluating signal intensity differences and enhancement patterns difficult. CONCLUSION: In addition to intrahepatic stones and biliary dilatation, segmental atrophy, signal intensity differences, and preferential and persistent enhancement are important MR findings of hepatolithiasis.

Adult↗

PubMedDate not supplied

Dopaminergic nature of amphetamine-induced pecking in pigeons.

d-Amphetamine was found to induce a pecking response in pigeons. The pecking response induced by d-amphetamine was antagonized by chlorpromazine, haloperidol or bulbocapnine indicating that this pecking response was caused by dopaminergic receptor stimulation. Pretreatment of pigeons with alpha-methyltyrosine (alpha-MT) reduced d-amphetamine-induced pecking, while the combined treatment of pigeons with alpha-MT and L-dihydroxyphenylalanine (L-DOPA, 100 mg/kg) partially restored the pecking response. d-Amphetamine-induced pecking was not reduced by a dopamine-beta-hydroxylase inhibitor, 1-phenyl-3-(2-thiazolyl)-2-thiourea (U-14,624). Alpha-MT reduced brain dopamine but not norepinephrine level, whereas U-14,624 decreased brain norepinephrine but not dopamine. Thus there is a correlation between brain dopamine level and d-amphetamine-induced pecking response. It is concluded that d-amphetamine-induced pecking is mediated indirectly by the release of dopamine.

Animals↗

PubMedDate not supplied

Antihypertensive and adrenergic receptor blocking properties of the enantiomers of medroxalol.

Explore the source record for details and available documents.

Adrenergic alpha-Antagonists↗

PubMedDate not supplied

Fat-suppressed three-dimensional fast spoiled gradient-recalled echo imaging: a modified FS 3D SPGR technique for assessment of patellofemoral joint chondromalacia.

Fast fat-suppressed (FS) three-dimensional (3D) spoiled gradient-recalled echo (SPGR) imaging of 64 articular cartilage regions in 16 patellofemoral joints was evaluated to assess its feasibility in diagnosing patellofemoral chondromalacia. It demonstrated good correlation with arthroscopic reports and took about half of the examination time that FS 3D SPGR did. This modified, faster technique has the potential to diagnose patellofemoral chondromalacia with shorter examination time than FS 3D SPGR did.

Adult↗

PubMedDate not supplied

The power issue: determination of KB or Ki from IC50. A closer look at the Cheng-Prusoff equation, the Schild plot and related power equations.

INTRODUCTION: The Cheng-Prusoff equation (1973) is often applied to the determination of equilibrium dissociation constant (KB) of a competitive antagonist when the IC50 value is available. The purpose of this study is to illustrate that the slope function (K) of an agonist concentration-response curve is critical to the determination of KB values. METHODS: The article describes new equations, which incorporate the slope function, consequently yielding more accurate estimation of KB values for antagonists, and tests them using simulated data. The value of KB was calculated according to the following new power equation: KB = IC50/(l + A(K)/Kp) = IC50/[l + (A/EC50)(K)], where IC50 is the concentration of the antagonist producing 50% inhibition, A is the concentration of the agonist against which the IC50 is being determined and KP is the apparent equilibrium dissociation constant of the agonist. RESULTS: The new equation is the same as the Cheng-Prusoff equation when the slope function K is exactly unity. Application of the equation avoids errors inherent in the use of the Cheng-Prusoff equation when the slope function of the agonist concentration-response curve deviates from unity. The new equation was applicable to slope functions less than, equal to or greater than unity. All inhibition curves have a negative slope function of 1, indicating that there is only one single receptor population even though different slope functions of agonist concentration-response curves are involved. The importance of the power function in the Schild plot is illustrated by using the equation: log (x(K) - 1) = log B - log KB, where x is the concentration ratio and B is the concentration of the antagonist. DISCUSSION: This investigation illustrates the application of six power equations for accurate estimation of KB values covering situations with different slope functions of the agonist concentration-response curves.

Binding, Competitive↗