Biomedical subjects
Publications and source records attributed to S F Akber.
The dissimilarities in spin-lattice relaxation time (T1) of water proton from one tumor to the other is due to the yield of hypoxic fraction in the tumor. The yield of higher relaxation time (T1) in the KHT tumor compared to the RIF-1 tumor as a function of growth is due to the hypoxic fraction of the tumor. The hypoxic fraction in the tumor is also responsible for the P-31 spectral parameter changes.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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.
The sensitivity for cell death induced by ionizing radiation and the spin-lattice relaxation time of water protons varies with the concentration of paramagnetic molecular oxygen. These two effects are complementary.
Explore the source record for details and available documents.
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.
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.
Explore the source record for details and available documents.
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.
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.
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.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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.
Explore the source record for details and available documents.