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Biomedical subjects

G Subramanian

Publications and source records attributed to G Subramanian.

At least 73 records · Page 4Linked to original sources
PubMed1977

An evaluation of 99mTc-labeled hepatobiliary agents.

Scintigraphic imaging of the hepatobiliary system has been significantly improved with the development of 99mTc-labeled compounds. Two of the most promising agents, pyridoxylideneglutamate and HIDA, each formed the basis for the development of a group of structural analogs. Condensation of pyridoxal with leucine and arginine (in place of glutamate) produced pyridoxylideneleucine and pyridoxylidenearginine. Since increasing the molecular weight and the lipid solubility of compounds tends to enhance their biliary excretion, several new IDA derivatives were synthesized by altering the lipophilic substituents on the ring of HIDA. The substitutions included ethyl and ethoxy groups as well as iodine. All compounds were compared with 131I-rose bengal using a baboon model that allowed blood, bile, and urine collection.

Acetanilides↗
PubMed1976

99mTc-Sn-acetylcysteine: a new renal scanning agent.

A new radiopharmaceutical, 99mTc-Sn-acetylcysteine, for renal scanning is reported. The preparation is simple and quick. It can also be adopted in the kit form. The complex has the advantage of great stability and fast clearance over earlier reported renal scanning radioagnostic agents.

Acetylcysteine↗
PubMed1975

Indium-113m-labeled polyfunctional phosphonates as bone-imaging agents.

Indium-113m complexed with polyfunctional phosphonates EDTMP (an analog of EDTA with carboxylic groups replaced by phosphate groups) and DTPMP (an analog of DTPA) showed preferential skeletal localization in experimental animals. Excellent images of the rabbit skeleton were obtained with both 113mIn and 111In complexes using the scintillation camera. In tissue radioassay using 85Sr as a simultaneous biologic standard, 113mIn-EDTMP compound showed higher concentration in the skeleton than the DTPMP complex and its bone uptake was comparable to that of 85Sr. Renal excretion was greater for the DTPMP complex (70% vs. 50% for EDTMP at 4 hr) and its blood clearance was faster than EDTMP. EDTMP was found to be the superior agent also to two other polyfunctional phosphonates, NTMP and HMDTMP. Because of the excellent skeletal localization with minimal soft-tissue levels, 113mIn-EDTMP may find use in bone scanning in humans wherever 99mTc bone-imaging agents are not available. These compounds may prove useful also in demonstrating acute myocardial infarcts, particularly for repeat studies after 99mTc bone agents have already been administered.

Animals↗
PubMed1975

Technetium-99m-labeled stannous imidodiphosphate, a new radiodiagnostic agent for bone scanning: comparison with other 99mTc complexes.

Imidodiphosphate (IDP) is an analog of pyrophosphate and diphosphonate, with a P-N-P bond instead of P-O-P or P-C-P. We have labeled IDP with 99mTc quantitatively (98%) using stannous ions as the reducing/complexing agent in a freeze-dried kit form. Radiobioassay of this compound was carried out in rabbits and the results were compared with those of eight other Tc-labeled bone-imaging agents, using the performance of simultaneously administered 85Sr as a reference standard. The 99mTc-IDP concentrated 20% higher in the bone, and its soft-tissue and blood levels were lower than with 85Sr. By comparison, the concentrations in the bone of the other 99mTc agents were 20% less than that of 85Sr. Regarding blood levels, Tc-IDP performed worse than the Tc-diphosphonate but better than the pyrophosphate and the other technetium complexes. Scintillation camera images of 99mTc-IDP in both rabbits and dogs showed excellent details of the skeleton. In a preliminary human study, images with 99mTc-IDP were somewhat inferior to those comparably procured with 99Tc-methylene diphosphonate, but count rates with the IDP complex were about twice those with the MDP compound. Because of its better bone uptake, however, it is suggested that 99mTc-IDP may be clinically useful in spite of its relatively slow blood clearance.

Adult↗
PubMed1975

Comparison of 99mTc complexes for renal imaging.

The distribution of 17 different agents for renal imaging was compared in the rabbit by organ radioassay at 1 hr. Similarly, 99mTc complexes of iron-ascorbate, glucoheptonate (GHA) and 2,3-dimercaptosuccinic acid (DMS), and 203Hg-chlormerodrin were compared in the dog. The distribution of 99mTc-GHA and DMS was assessed in the human by blood and urinary clearance, external renal measurements, and scintillation camera imaging, and compared with older renal radiopharmaceuticals. Radiation dose estimates, based chiefly on human data, were calculated. Technetium-99m-DMS reaches a high concentration in the renal cortex and its urinary excretion rate and blood clearance are slow. It is excellent for imaging the renal parenchyma without activity in pelvocalyceal collecting system. However, it readily oxidizes and must be used within 30 min of preparation. The biologic distribution of 99mTc-GHA is similar to gluconate and iron-ascorbate complex. Its renal concentration is not as great as that of DMS but its blood and urinary clearances are much faster, resulting in lower radiation doses to most organs. Early camera images with this agent usually demonstrate both the renal parenchyma and collecting system. In later images, ther is excellent demonstration of the parenchyma alone, superior to that obtained with 99mTc-Sn-DTPA. It is a very stable complex and may be used for at least 5 hr after preparation. All radioactive renal agents examined to date have a significant concentration in the liver, making an accurate quantitative comparison between the two kidneys difficult.

Albumins↗
PubMed1975

Technetium-99m-methylene diphosphonate--a superior agent for skeletal imaging: comparison with other technetium complexes.

Methylene diphosphonate (MDP) was formulated as a complex of 99mTc for skeletal imaging. This agent was compared with three other bone-seeking technetium agents: ethane-1-hydroxy-1, 1-diphosphonate (EHDP), pyrophosphate, and polyphosphate. In tissue radioassay experiments in rodents, the technetium complexes of MDP and EHDP were similar, but skeletal concentration with both of these agents was higher than that with pyrophosphate or polyphosphate. The total-body retention of MDP and EHDP complexed with 95mTc was studied in beagle dogs for 35 days by excretion measurements and total-body counting and compared with polyphosphate and pertechnetate. The long-term retention was greater for MDP. The 5-day cumulative fecal excretion of 95mTc was low when administered as EHDP or polyphosphate complexes and negligible when administered as MDP complex. In six human volunteers the blood clearance of 99mTc-mdp was similar to that of 18F and significantly faster than that of 99mTc-EHDP. Pyrophosphate cleared from the blood much faster than polyphosphate but slower than the diphosphonates. The urinary excretion of the MDP complex was greater than for EHDP within the first 2-3 hr after injection. The 24-hr urinary excretion of pyrophosphate and polyphosphate complexes was not as complete as for the diphosphonates. All four 99mTc complexes proved satisfactory for clinical imaging studies. The MDP complex produced images of superior quality as early as 2 hr after administration, attributable to its more rapid clearance from the blood and soft tissues. On the contrary, a longer interval of 3-4 hr after injection was usually needed for 99mTc-EHDP; pyrophosphate and polyphosphate complexes regularly required a waiting period of 4 hr. Comparitive radiation dose estimates were made based on the available biologic distribution data for these 99mTc skeletal-localizing agents.

Animals↗