PubMed Health⌕ Search

Biomedical subjects

M K Dewanjee

Publications and source records attributed to M K Dewanjee.

At least 91 records · Page 5Linked to original sources
PubMed1980

Noninvasive radioisotopic technique for detection of platelet deposition in mitral valve prosthesis and renal microembolism in dogs.

At 24 hrs after implantation of Björk-Shiley mitral prosthesis in 5 dogs, in vivo images were obtained with a gamma camera after intravenous administration (0.5-0.6 mCi) one hour postoperatively of autologous Indium-111-labeled platelets. The site of platelet deposition in the teflon ring and perivascular damaged cardiac tissue is clearly delineated in the scintiphoto. In vitro biodistribution (mean % +/- SD of injected dose) at 24 hrs after injection of the 5 implanted and 7 normal dogs performed with a gamma counter demonstrated that (45.1 +/- 10.6)% and (0.7 +/- 0.4)% were in blood and kidneys in normal dogs and (28.5 +/- 6.8)%, (1.6 +/- 0.6)%, (0.3 +/- 0.1)%, and (0.2 +/- 0.1)% were in blood, kidneys, teflon rings, and perivascular damaged cardiac tissue, respectively. The strut and pyrolytic carbon-coated disc retained only (0.0033 +/- 0.0004)% and (0.0031 +/- 0.0003)%, respectively. There was a 2.3-fold increase of labeled platelets in kidneys of implanted dogs due to renal trapping of microembolism. Also, three- to fivefold increase in ratios of lung, brain, cardiac, and skeletal muscle to blood indicates that internal organs and whole body work as filter for microembolism generated by cardiovascular surgery and mitral prosthesis. Twenty percent of the administered platelets are consumed in surgical repair of damaged tissue. Indium-111-labeled platelets thus provide a sensitive marker for noninvasive imaging of Björk-Shiley mitral prosthesis, thromboembolism after implantation of prosthetic device, and in vitro quantitation of surgical consumption.

Animals↗
PubMed1979

Pharmacodynamics of stannous chelates administered with 99mTc-labeled chelates.

The pharmacodynamics of several tin compounds were studied in healthy rabbits, rabbits with myocardial infarcts, and isolated myocardial tissue. The results showed that tin chelates of pyrophosphate, HEDP, DTPA, and glucoheptonate are very unstable in vivo, giving rise to free stannous ions. These ions localize mainly in bone, with the rest being primarily excreted in the urine. They also concentrate more in infarcted than in normal myocardium; there they enter the mitochondria. The supernatant of homogenates contains bound and free fractions, demonstrating a subcellular distribution pattern similar to that of calcium ions. Tin chelates have different pharmacodynamics from the corresponding 99mTc chelates.

Animals↗
PubMed1979

Noninvasive radioisotopic technique for detection of platelet deposition in coronary artery bypass grafts in dogs and its reduction with platelet inhibitors.

At 8 and 32 hours after saphenous vein bypass graft surgery in six dogs, in vivo images of the graft were obtained with a gamma camera after intravenous injection, 2 hours postoperatively of autologous platelets labeled with indium-111. Platelet deposition in the grafts could be imaged in vivo from the scintiphotos. In vitro images of the excised heart showed saphenous vein graft uptake confirming the in vivo image. In vitro determination of radioactivity in the graft averaged 17 +/- 14 times greater than in blood and 33 +/- 26 times greater than in the lung. Under identical conditions, in eight dogs treated with dipyridamole (55 mg/day) plus aspirin (325 mg/day), the grafts appeared to have considerably less platelet deposition as estimated by imaging. In vitro determination of radioactivity in the graft averaged 5 +/- 2 times greater than in blood and 8 +/- 4 times greater than in the lung (p less than 0.01). This noninvasive technique may be a promising tool for a better understanding of the role played by platelets in the process of occlusion of saphenous vein bypass grafts in man and its prevention with platelet inhibotors.

Animals↗
PubMed1979

Emission-computed tomography and its application to imaging of acute myocardial infarction in intact dogs using Tc-99m pyrophosphate.

The techniques of emission-computed tomography have been used to obtain in vivo quantitative estimates of the three-dimensional distribution of gamma-emitting radionuclides in dog hearts. Conjugate views, obtained for 60 equiangular projections around 360 degrees by rotating the object in front of a gamma camera, were used to reconstruct multiple-level emission transaxial images for various test objects, and for dogs with surgically induced acute myocardial infarcts. Corrections for attenuation were performed in the backprojection step of the convolution algorithm used for reconstruction. Quantitative estimates of the spatial extent and concentration of activity were obtained to within 10--15% rms error. Correlations were obtained between the radionuclide and histopathologic estimates of the extent and location of infarction.

Animals↗
PubMed1979

Heterotopic splenic autotransplantation in prevention of overwhelming postsplenectomy infection.

An experimental study was undertaken to evaluate the protective effect of heterotopic splenic autotransplantation in weanling rats. Rats were divided into three experimental groups: splenectomy, control, and splenic autotransplantation. Rats were challenged with i.v. type I pneumococcus. Bacterial bloodstream clearance and survival were determined. Splenic bacterial uptake was measured by determining the isotopic activity of technetium-99m-labeled pneumococci. Autoradiographs and material stained with hematoxylin and eosin and Gram strains were examined for histologic features. All autografts survived and were histologically compatible with normal splenic tissue. Bloodstream clearance of pneumococci was significantly greater in rats with splenic autotransplantation. Splenic autografts had 10 to 30 times greater uptake of pneumocci than did the liver. Rats with autotransplantation had a prolonged survival time. Heterotopic splenic autotransplantation may prove to be an important adjunctive surgical measure in the treatment of children undergoing splenectomy.

Animals↗
PubMed1979

Relative merits of partial splenectomy, splenic reimplantation, and immunization in preventing postsplenectomy infection.

Partial splenectomy, splenic autotransplantation, and immunization with pneumococcal vaccine have been reported to protect patients against overwhelming postsplenectomy infection, and this study was undertaken to evaluate these therapeutic alternatives. For this purpose 136 rats were divided into experimental groups: 34 controls, 34 splenectomy, 34 partial splenectomy, and 34 splenic autotransplantation animals. Five weeks after operation, two-thirds of the animals were immunized with killed pneumococci. The effects of operation and immunization were studied by challenging the animals intravenously with pneumococci. Pneumococcal antibody titers were determined, and phagocytic uptake of pneumococci by the spleen and liver was measured. Immunization impressively increased the survival rate in all groups. At low-challenge doses autotransplantation prolonged survival. At higher-challenge doses only partial splenectomy increased survival. Partial splenectomy and control animals had higher antibody titers than did splenectomy and autotransplantation rats. Animals with the highest antibody titers had the greatest splenic and hepatic phagocytic uptake of pneumococci. Partial splenectomy was more efficient in removing pneumococci than was autotransplantation. Thus immunization is one of the most important factors contributing to survival after splenectomy. Partial splenectomy is preferable to splenic autotransplantation because it is associated with higher antibody titers after immunization, better pneumococcal splenic uptake, and improved survival rates.

Animals↗
PubMed1978

Computed transaxial imaging using single gamma emitters.

Emission computed tomography (ECT) studies were performed on test objects and dogs. Conjugate views were obtained for 60 to 120 projections equispaced around 360 degrees by rotation of the subjects in front of a gamma camera. A convolution reconstruction algorithm in which gamma ray attenuation corrections are included in the backprojection step were used to reconstruct the emission images. Reconstructions of x-ray transmission data provided data for gamma ray attenuation corrections of the emission images of 99mTc-pyrophosphate uptake in dogs. Reconstructed images of test objects show spatial resolution uniformity, and attenuation corrections enable estimation of relative activity densities to within 10--15% rms errors, thus demonstrating quantitative imaging capabilities of emission CT.

Animals↗
PubMed1978

Imaging platelet deposition with 111In-labeled platelets in coronary artery bypass grafts in dogs.

At 8 and 32 hours after saphenous vein aortocoronary artery bypass graft surgery in four dogs, images of the grafts were obtained with a gamma camera after intravenous injection, 2 hours postoperatively, of autologous platelets labeled with indium-111. The location of platelet deposition could be accurately estimated from the scintiphotos. In vitro radioactivity counting of the segments of the isolated grafts showed 4 to 15 times greater activity in the grafts than in blood and 25 to 100 times greater activity than in normal myocardium. This was sufficient for delineating accurately the area of platelet deposition. This noninvasive technique may be a promising tool for a better understanding of the role played by platelets in the process of occlusion of saphenous vein bypass grafts in man.

Animals↗
PubMed1977

The place of 57Co-bleomycin scanning in the evaluation of tumors.

The clinical records and imaging studies of 140 patients who had 57Co-bleomycin scans were reviewed. In 53% of the patients with known tumor at the time of examination, all clinically demonstrable lesions picked up cobalt. The success rate was particularly high in carcinoma of the lung (15 of 17) and gastrointestinal tract (12 of 17). The major role of cobalt bleomycin seems to be as an early screening test for metastases in patients with carcinoma of the lung, gastrointestinal tract, and uterus. The scan is most useful in demonstrating spread to the brain, liver, and adrenals.

Adolescent↗
PubMed1976

Electrophoretic separation of radioisotopically labeled mouse lymphocytes.

A new preparative method is described for the separation and direct electrophoretic comparison of the distribution profile of radioisotopically labeled cells. The cell populations to be compared are labeled separately with different radioisotopes (e.g., 51Cr and 99mTc) and mixed. The cell mixture is subjected to density gradient electrophoresis and the distribution of each radioisotope in the collected fractions is ascertained by differential gamma counting. In the case of uniform label uptake by the cells in each distribution, the radioactivity counts represent cell frequency. Nonuniform labeling allows useful comparisons only in terms of relative mobility distribution. Model experiments performed with 51Cr- and 99mTc-labeled mouse thymocytes and spleen cells are in general agreement with mobility distribution results obtained previously by free flow electrophoresis.

Animals↗
PubMed1976

Mechanism of localization of 99mTc-labeled pyrophosphate and tetracycline in infarcted myocardium.

The gross and subcellular localizations of 99mTc-labeled pyrophosphate and tetracycline in myocardial infarcts were studied in a rabbit model. Experiments utilizing double-nuclide labeling were carried out using a useful mapping technique. Concentration of the various chelates decreases in an expected manner from the center of the infarcted area toward its periphery, but it is higher near the epicardial surface than toward the endocardium. Technetium-99m-pyrophosphate is concentrated in the same infarcted areas as 45Ca ion or 32P-pyrophosphate, but to a much greater degree. The uptake is dependent on both the degree of necrosis and residual blood flow. Gel filtration experiments with rabbit serum indicate that 99mTc-tagged pyrophosphate, tetracycline, and diphosphonate are mainly protein-bound, whereas 32P-pyrophosphate is not. Subcellular localization studies show that 99mTc-tetracycline and 99mTc-pyrophosphate are bound primarily to soluble protein, and only a small fraction is associated with nuclei, mitochondria, and microsomes. The uptake of technetium chelates in myocardial infarcts may be due to the formation of polynuclear complexes with denatured macromolecules rather than to the deposition of calcium in mitochrondria.

Animals↗
PubMed1976

Routine renal imaging after 99mTc-glucoheptonate brain scans.

Immediately after brain scanning with 99mTc-glucoheptonate, the kidneys were imaged in 200 prospectively studied cases. Abnormalities were found in 22 cases (11%); they included renal metastases, renal cysts, and kidney displacement or obstruction by masses. In five instances, significant previously unknown abnormalities were found. The renal contours were usually better seen than on intravenous urograms or bone scans. Most kidney studies could be completed in less than 2 min, making renal imaging worthwhile as a low-cost high-yield routine addition to brain scanning.

Adolescent↗
PubMed1976

New 68Ga-labeled skeletal-imaging agents for positron scintigraphy.

The present skeletal-imaging agents labeled with radiogallium rely upon carrier gallium to augment bone uptake; no gallium-labeled bone-imaging agent free of this disadvantage is available. In attempts to develop such agents, we prepared 68Ga-ethylenediaminetetramethylene phosphonate (68Gs-EDTMP) and 68Ga-diethylenetriaminepentamethylene phosphonate (68Ga-DTPMP) and determined their biologic distributions in rats and dogs. These compounds combine the bone-seeking characteristics of phosphonic acid and the complexing ability of EDTA and DTPA analogs. The chelates are administered without gallium carrier. In rats, 50-60% of the carrier-free dose accumulates in bone at 1 hr after intravenous injection, while 25--30% is excreted through the urine. In dogs, at 3 hr after intravenous injection 35% is found in bone. Although the general patterns of organ distribution of the two 68Ga chelates are similar, 68Ga-EDTMP appears superior because of its faster blood clearance. Bone images obtained with this compound in dogs, using a multidetector positron camera, are presented. The optimum time for imaging was found to be 2.5--3 hr after injection.

Animals↗
PubMed1976

Localization of skeletal-imaging 99mTc chelates in dead cells in tissue culture: concise communication.

Screening new agents for imaging myocardial infarcts and investigating the mechanism of cellular uptake and subcellular localization of these agents prompted us to develop a necrosis model in tissue culture. Live cells obtained from exponentially growing cultures and dead cells obtained from nutritionally depleted plateau-phase cultures were incubated with 99mTc-pyrophosphate, 99mTc-hydroxyethylene diphosphonate (99mTc-HEDP), 67Ga-citrate, and 45Ca-HEDP. For the bone-seeking 99mTc chelates, the ratio of dead to live cell radioactivity was 15--20 after 1 hr of incubation. On the other hand, no preferential binding of 67Ga-citrate was observed, indicating that the mechanism of 67Ga localization in infarcts is different from that of the 99mTc chelates. The death cells accumulated only twice as much 45Ca-HEDP or 45Ca-pyrophosphate as did live cells, possibly due to the carrier effect of calcium in the medium. The receptors for 99mTc chelates could be partially blocked by preincubating the dead cells with microgram amounts of Na-HEDP. Heat-denaturation of live cells also increased the localization of 99mTc-HEDP in the cells, and this uptake was proportional to the duration of heating. Bone-seeking 99mTc chelates could be used for marking dead cells instead of conventional staining methods.

Calcium Radioisotopes↗
PubMed1975

Myocardial mapping techniques and the evaluation of new 113mIn-labeled polymethylenephosphonates for imaging myocardial infarct.

The localization of 113mIn-ethylenediamine tetraethylenephosphonate and 113mIn-diethylenetriamine pentamethylenephosphonate in myocardial infarct induced in rabbits by coronary artery ligation was investigated. Double labeling of the same tissue with 45Ca ion was used as an index of tissue degeneration. The radioactivity ratio (40-50:1) of infarcted to normal myocardium was obtained 1.5 hours after injection and 2.5 hours after infarct. For the 45Ca-labeled phosphonate derivatives, a ratio of 7-6:1 was obtained at the same time. These agents will thus be useful for the detection and localization of acute infarct.

Animals↗