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Biomedical subjects

S F Akber

Publications and source records attributed to S F Akber.

36 records · Page 2Linked to original sources
PubMed1991

N-isopropyl-123I-p-iodoamphetamine uptake mechanism in the lung--is it dependent on pH, lipophilicity or pKa?

The uptake and binding mechanism of biogenic amines in the lungs has been studied extensively with no conclusive results. The competition between N-isopropyl-123I-p-iodo amphetamines (123I-IMP) and propranolol and 123I-IMP and ketamine, in the lungs suggest that the pKa value of the biogenic amines has a significant role to play in the mechanism of uptake and retention of biogenic amines in the lungs.

Amphetamines↗
PubMed1989

Correlation between oxygen tension and spin-lattice relaxation rate in tumors.

The role of oxygen in influencing the spin-lattice and spin-spin relaxation mechanism in liquids has been known for decades. However, no concerted effort has been made to find a correlation between relaxation rates and oxygen dissolved in cell water. A procedure has been developed that allows both in vitro and in vivo measurement of oxygen tension in tumors and helps to calculate spin-lattice relaxation rate.

Animals↗
PubMed1988

The quagmire of relaxation times.

NMR researchers continue to be puzzled by the quagmire of relaxation times of normal and malignant cells. Here a simple theory points out that the dissimilarities of relaxation behavior are not due to macromolecule alterations or phase transition in the water but to the consumption of dissolved oxygen in the cell associated water. The percentage of hypoxic and anoxic cells and growth rate of a tumor will determine the oxygen consumption in the absence of reduced blood flow, which is indeed a reflection of relaxation behavior.

Humans↗
PubMed1988

The conundrum of relaxation times.

The current theories of proton relaxation times fall short of explaining satisfactorily the physical and biological mechanisms responsible for the dissimilarities of relaxation behavior in normal and pathological tissues. An alternative approach to understand these mechanisms is needed. This paper advances the possibility that the dissimilarities of relaxation behavior in normal and pathological tissues is due to the consumption of paramagnetic molecular O2 dissolved in cell-associated water.

Body Water↗
PubMed1987

A noninvasive assessment of pharmacological interaction of amines in the lung.

Lung endothelial binding sites of N-isopropyl-123I-p-iodoamphetamine (123I-IMP) were assessed employing the principle of competitive binding assay adapted for in vivo measurement using a computer-scintillation camera technique. A noninvasive modification of the Chinard-Crone technique was applied to the study of pulmonary extraction. 123I-IMP, the test cellular tracer and 99Tcm-dextran the vascular reference tracer were used in dogs to determine the first pass pulmonary extraction of 123I-IMP. The lung extraction of 123I-IMP decreases progressively from 90 to 62% as the amount of propranolol (administered 10 min prior to the injection of 99Tcm-dextran) gradually increased from 0 to 20 mg. The dissociation constant of 123I-IMP lung binding sites reaction in the presence of propranolol was calculated by Scatchard plot and found to be 10 mg. The in vivo procedure described in this paper will enable us to develop a model for the assay of the binding sites in the lungs for amine and its influence in both health and disease.

Amphetamines↗
PubMed1987

On the theory of the measurement of the first-pass pulmonary extraction using the indicator dilution technique.

Theory and concept of extraction involving invasive as well as non-invasive procedures to assess the first-pass extraction of tracers based on the indicator dilution technique are discussed. The experimental result of a non-invasive method using a gamma scintillation camera-computer system of first-pass pulmonary extraction of N-Isopropyl-123I-p-Iodoamphetamine (123I-IMP) are also discussed.

Amphetamines↗
PubMed1986

The physics of NMR tomography.

The nuclear magnetic resonance properties of the nuclei of atoms is a convenient means for elucidating the morphology and pathophysiology of the human body. The fundamental principles of Larmor precession are discussed from the classical as well as from the quantum mechanical point of view. In this paper, principles of NMR medical imaging and its clinical applications are discussed.

Humans↗
PubMed1984

Measurement of metabolic extraction of tracers in the lung using a multiple indicator dilution technique.

Selective pulmonary uptake of many natural and synthetic substances has been demonstrated by physiologists and pharmacologists using isolated perfused lung preparations or invasive techniques. It is difficult, however, to relate these laboratory studies to disease processes and to the study of problems encountered in a clinical environment. Our goal was to develop a noninvasive method for studying the pulmonary uptake of tracer substances using available radiotracers, gamma cameras, and computers that would give information similar, if not identical, to that from the invasive laboratory methods, and that could be applied in a clinical setting. The multiple-indicator dilution technique, modified for external counting, is well suited for such studies of pulmonary uptake of tracer substances. In this study, Tc-99m micro sulfur colloid (Tc-99m micro SC) was used as an intravascular reference tracer, N-isopropyl-p-[123I]iodoamphetamine (I-123 IMP) as a cellular test tracer amine, and In-111 DTPA as an extracellular tracer. Calculated first-pass lung uptakes of I-123 IMP and In-111 DTPA were 0.92 +/- 0.04 and 0.17 +/- 0.04, respectively, relative to the reference tracer. Using this approach, the first-pass pulmonary extraction of a variety of radiolabeled test tracers can be measured in a clinical environment in a variety of physiologic settings.

Amphetamines↗