Technetium: The first artificially produced element and a radioactive fission product of URANIUM. Technetium has the atomic symbol Tc, atomic number 43, and atomic weight 98.91. All technetium isotopes are radioactive. Technetium 99m (m=metastable) which is the decay product of Molybdenum 99, has a half-life of about 6 hours and is used diagnostically as a radioactive imaging agent. Technetium 99 which is a decay product of technetium 99m, has a half-life of 210,000 years.Technetium Tc 99m Sulfur Colloid: A gamma-emitting radionuclide imaging agent used for the diagnosis of diseases in many tissues, particularly in the gastrointestinal system, liver, and spleen.Technetium Compounds: Inorganic compounds that contain TECHNETIUM as an integral part of the molecule. Technetium 99m (m=metastable) is an isotope of technetium that has a half-life of about 6 hours. Technetium 99, which has a half-life of 210,000 years, is a decay product of technetium 99m.Organotechnetium Compounds: Organic compounds that contain technetium as an integral part of the molecule. These compounds are often used as radionuclide imaging agents.Tin: A trace element that is required in bone formation. It has the atomic symbol Sn, atomic number 50, and atomic weight 118.71.Technetium Tc 99m Medronate: A gamma-emitting radionuclide imaging agent used primarily in skeletal scintigraphy. Because of its absorption by a variety of tumors, it is useful for the detection of neoplasms.Technetium Tc 99m Sestamibi: A technetium imaging agent used to reveal blood-starved cardiac tissue during a heart attack.Technetium Tc 99m Exametazime: A gamma-emitting RADIONUCLIDE IMAGING agent used in the evaluation of regional cerebral blood flow and in non-invasive dynamic biodistribution studies and MYOCARDIAL PERFUSION IMAGING. It has also been used to label leukocytes in the investigation of INFLAMMATORY BOWEL DISEASES.Technetium Tc 99m Aggregated Albumin: A gamma-emitting radionuclide imaging agent used for the diagnosis of diseases in many tissues, particularly in cardiovascular and cerebral circulation.Technetium Tc 99m Pentetate: A technetium imaging agent used in renal scintigraphy, computed tomography, lung ventilation imaging, gastrointestinal scintigraphy, and many other procedures which employ radionuclide imaging agents.Radionuclide Imaging: The production of an image obtained by cameras that detect the radioactive emissions of an injected radionuclide as it has distributed differentially throughout tissues in the body. The image obtained from a moving detector is called a scan, while the image obtained from a stationary camera device is called a scintiphotograph.Sodium Pertechnetate Tc 99m: A gamma-emitting radionuclide imaging agent used for the diagnosis of diseases in many tissues, particularly in the gastrointestinal system, cardiovascular and cerebral circulation, brain, thyroid, and joints.Radiopharmaceuticals: Compounds that are used in medicine as sources of radiation for radiotherapy and for diagnostic purposes. They have numerous uses in research and industry. (Martindale, The Extra Pharmacopoeia, 30th ed, p1161)Technetium Tc 99m Dimercaptosuccinic Acid: A nontoxic radiopharmaceutical that is used in the diagnostic imaging of the renal cortex.Oximes: Compounds that contain the radical R2C=N.OH derived from condensation of ALDEHYDES or KETONES with HYDROXYLAMINE. Members of this group are CHOLINESTERASE REACTIVATORS.Erythrocyte Inclusions: Pathologic inclusions occurring in erythrocytes.Tin Polyphosphates: Poly or pyrophosphates of tin. In conjunction with radioactive technetium these compounds are used as bone-scanning agents and in scintigraphy to diagnose myocardial and cerebral infarction.Technetium Tc 99m Diethyl-iminodiacetic Acid: A nontoxic radiopharmaceutical that is used in the clinical evaluation of hepatobiliary disorders in humans.Diphosphates: Inorganic salts of phosphoric acid that contain two phosphate groups.Soil Pollutants, Radioactive: Pollutants, present in soil, which exhibit radioactivity.Tin Compounds: Inorganic compounds that contain tin as an integral part of the molecule.Rosaniline Dyes: Compounds that contain the triphenylmethane aniline structure found in rosaniline. Many of them have a characteristic magenta color and are used as COLORING AGENTS.Technetium Tc 99m Lidofenin: A nontoxic radiopharmaceutical that is used in RADIONUCLIDE IMAGING for the clinical evaluation of hepatobiliary disorders in humans.Tomography, Emission-Computed, Single-Photon: A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image.Isotope Labeling: Techniques for labeling a substance with a stable or radioactive isotope. It is not used for articles involving labeled substances unless the methods of labeling are substantively discussed. Tracers that may be labeled include chemical substances, cells, or microorganisms.Etidronic Acid: A diphosphonate which affects calcium metabolism. It inhibits ectopic calcification and slows down bone resorption and bone turnover.Sugar AcidsPhosphines: Inorganic or organic compounds derived from phosphine (PH3) by the replacement of H atoms. (From Grant & Hackh's Chemical Dictionary, 5th ed)Technetium Tc 99m Disofenin: A radiopharmaceutical used extensively in cholescintigraphy for the evaluation of hepatobiliary diseases. (From Int Jrnl Rad Appl Inst 1992;43(9):1061-4)Technetium Tc 99m Pyrophosphate: A radionuclide imaging agent used primarily in scintigraphy or tomography of the heart to evaluate the extent of the necrotic myocardial process. It has also been used in noninvasive tests for the distribution of organ involvement in different types of amyloidosis and for the evaluation of muscle necrosis in the extremities.Rhenium: Rhenium. A metal, atomic number 75, atomic weight 186.2, symbol Re. (Dorland, 28th ed)Tissue Distribution: Accumulation of a drug or chemical substance in various organs (including those not relevant to its pharmacologic or therapeutic action). This distribution depends on the blood flow or perfusion rate of the organ, the ability of the drug to penetrate organ membranes, tissue specificity, protein binding. The distribution is usually expressed as tissue to plasma ratios.Radioimmunodetection: Use of radiolabeled antibodies for diagnostic imaging of neoplasms. Antitumor antibodies are labeled with diverse radionuclides including iodine-131, iodine-123, indium-111, or technetium-99m and injected into the patient. Images are obtained by a scintillation camera.Nitriles: Organic compounds containing the -CN radical. The concept is distinguished from CYANIDES, which denotes inorganic salts of HYDROGEN CYANIDE.Radioisotopes: Isotopes that exhibit radioactivity and undergo radioactive decay. (From Grant & Hackh's Chemical Dictionary, 5th ed & McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Xenon Radioisotopes: Unstable isotopes of xenon that decay or disintegrate emitting radiation. Xe atoms with atomic weights 121-123, 125, 127, 133, 135, 137-145 are radioactive xenon isotopes.Organometallic Compounds: A class of compounds of the type R-M, where a C atom is joined directly to any other element except H, C, N, O, F, Cl, Br, I, or At. (Grant & Hackh's Chemical Dictionary, 5th ed)Sentinel Lymph Node Biopsy: A diagnostic procedure used to determine whether LYMPHATIC METASTASIS has occurred. The sentinel lymph node is the first lymph node to receive drainage from a neoplasm.Gastric Emptying: The evacuation of food from the stomach into the duodenum.Organophosphorus Compounds: Organic compounds that contain phosphorus as an integral part of the molecule. Included under this heading is broad array of synthetic compounds that are used as PESTICIDES and DRUGS.Heart: The hollow, muscular organ that maintains the circulation of the blood.Technetium Tc 99m Mertiatide: A technetium diagnostic aid used in renal function determination.Aerosols: Colloids with a gaseous dispersing phase and either liquid (fog) or solid (smoke) dispersed phase; used in fumigation or in inhalation therapy; may contain propellant agents.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Evaluation Studies as Topic: Studies determining the effectiveness or value of processes, personnel, and equipment, or the material on conducting such studies. For drugs and devices, CLINICAL TRIALS AS TOPIC; DRUG EVALUATION; and DRUG EVALUATION, PRECLINICAL are available.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Bone Neoplasms: Tumors or cancer located in bone tissue or specific BONES.Predictive Value of Tests: In screening and diagnostic tests, the probability that a person with a positive test is a true positive (i.e., has the disease), is referred to as the predictive value of a positive test; whereas, the predictive value of a negative test is the probability that the person with a negative test does not have the disease. Predictive value is related to the sensitivity and specificity of the test.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Time Factors: Elements of limited time intervals, contributing to particular results or situations.
Technetium(IV) chlorideBectumomabTechnetium (99mTc) tetrofosminYunnan Tin: Yunnan Tin Group (Holding) Company Limited (YTC) is the largest tin producer and exporter in China and the world. It is headquartered in Kunming, Yunnan.Technetium (99mTc) sestamibiSingle-photon emission computed tomographySodium pertechnetateAvid Radiopharmaceuticals: Avid Radiopharmaceuticals is an American company, founded by Dr. Daniel Skovronsky, and based at the University City Science Center research campus in Philadelphia, Pennsylvania.DMSA scan: A DMSA scan is a radionuclide scan that uses dimercaptosuccinic acid (as a radioactive tracer) in assessing renal morphology, structure (static scan), and function. It is sometimes used as a test for the diagnosis of acute pyelonephritis.AcetaldoximeTetrasodium pyrophosphateTransparent conducting film: Transparent conducting films (TCFs) are optically transparent and electrically conductive in thin layers. They are an important component of a number of electronic devices including liquid-crystal displays, OLEDs, touchscreens and photovoltaics.FuchsineIctal-Interictal SPECT Analysis by SPM: ISAS (Ictal-Interictal SPECT Analysis by SPM) is an objective tool for analyzing ictal vs. interictal SPECT scans.Isotope-coded affinity tag: An Isotope-coded affinity tag (ICAT) is an isotopic labeling method used for quantitative proteomics by mass spectrometry that uses chemical labeling reagents. "Rapid quantitative analysis of proteins or protein function in complex mixtures," Rudolf Hans Aebersold et al.Risedronic acidSaccharolipidAluminium phosphide poisoning: Acute aluminium phosphide poisoning (AAlPP) is a large, though under-reported, problem in the Indian subcontinent. Aluminium phosphide (AlP), which is readily available as a fumigant for stored cereal grains, sold under various brand names such as QuickPhos and Celphos, is highly toxic, especially when consumed from a freshly opened container.Larry Henley: Lawrence Joel "Larry" Henley (June 30, 1937 – December 18, 2014) was an American singer and songwriter, best known for co-writing (with Jeff Silbar) the 1989 hit record "Wind Beneath My Wings."Rhenium pentachlorideRadioimmunodetection: Radioimmunodetection is an imaging technique using radiolabeled antibodies.FulvestrantList of radioactive isotopes by half-life: This is a list of radioactive isotopes ordered by half-life from shortest to longest.Metallocene: A metallocene is a compound typically consisting of two cyclopentadienyl anions (Cp, which is C5H5−) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C5H5)2M. Closely related to the metallocenes are the metallocene derivatives, e.Male breast cancerList of puddings: This list includes both sweet and savoury puddings that conform to one of two definitions:Chloro(cyclopentadienyl)bis(triphenylphosphine)rutheniumAchy Breaky HeartAerosolization: Aerosolization is the process or act of converting some physical substance into the form of particles small and light enough to be carried on the air i.e.Assay sensitivity: Assay sensitivity is a property of a clinical trial defined as the ability of a trial to distinguish an effective treatment from a less effective or ineffective intervention. Without assay sensitivity, a trial is not internally valid and is not capable of comparing the efficacy of two interventions.Lung receptor: Lung receptors sense irritation or inflammation in the bronchi and alveoli.Kennel clubErythrocrine: Erythrocrine describes red blood cell or erythrocyte for production and release of signaling molecules. The term “erythrocrine“ was coined by Song et al.Bone tumorTable of standard reduction potentials for half-reactions important in biochemistry: The values below are standard reduction potentials for half-reactions measured at 25°C, 1 atmosphere and a pH of 7 in aqueous solution.Temporal analysis of products: Temporal Analysis of Products (TAP), (TAP-2), (TAP-3) is an experimental technique for studying
(1/1995) 99mTc-labeled vasoactive intestinal peptide receptor agonist: functional studies.
Vasoactive intestinal peptide (VIP) is a naturally occurring 28-amino acid peptide with a wide range of biological activities. Recent reports suggest that VIP receptors are expressed on a variety of malignant tumor cells and that the receptor density is higher than for somatostatin. Our aims were to label VIP with 99mTc--a generator-produced, inexpensive radionuclide that possesses ideal characteristics for scintigraphic imaging--and to evaluate 99mTc-VIP for bioactivity and its ability to detect experimental tumors. METHODS: VIP28 was modified at the carboxy terminus by the addition of four amino acids that provided an N4 configuration for a strong chelation of 99mTc. To eliminate steric hindrance, 4-aminobutyric acid (Aba) was used as a spacer. VIP28 was labeled with 1251, which served as a control. Biological activity of the modified VIP28 agonist (TP3654) was examined in vitro using a cell-binding assay and an opossum internal anal sphincter (IAS) smooth muscle relaxivity assay. Tissue distribution studies were performed at 4 and 24 h after injection, and receptor-blocking assays were also performed in nude mice bearing human colorectal cancer LS174T. Blood clearance was examined in normal Sprague-Dawley rats. RESULTS: The yield of 99mTc-TP3654 was quantitative, and the yields of 125I-VIP and 1251-TP3654 were >90%. All in vitro data strongly suggested that the biological activity of 99mTc-TP3654 agonist was equivalent to that of VIP28. As the time after injection increased, radioactivity in all tissues decreased, except in the receptor-enriched tumor (P = 0.84) and in the lungs (P = 0.78). The tumor uptake (0.23 percentage injected dose per gram of tissue [%ID/g]) was several-fold higher than 125I-VIP (0.06 %ID/g) at 24 h after injection in the similar system. In mice treated with unlabeled VIP or TP3654, the uptake of 99mTc-TP3654 decreased in all VIP receptor-rich tissues except the kidneys. The blood clearance was biphasic; the alpha half-time was 5 min and the beta half-time was approximately 120 min. CONCLUSION: VIP28 was modified and successfully labeled with 99mTc. The results of all in vitro examinations indicated that the biological activity of TP3654 was equivalent to that of native VIP28 and tumor binding was receptor specific. (+info)
(2/1995) Sentinel lymph node biopsy and axillary dissection in breast cancer: results in a large series.
BACKGROUND: Axillary lymph node dissection is an established component of the surgical treatment of breast cancer, and is an important procedure in cancer staging; however, it is associated with unpleasant side effects. We have investigated a radioactive tracer-guided procedure that facilitates identification, removal, and pathologic examination of the sentinel lymph node (i.e., the lymph node first receiving lymphatic fluid from the area of the breast containing the tumor) to predict the status of the axilla and to assess the safety of foregoing axillary dissection if the sentinel lymph node shows no involvement. METHODS: We injected 5-10 MBq of 99mTc-labeled colloidal particles of human albumin peritumorally in 376 consecutive patients with breast cancer who were enrolled at the European Institute of Oncology during the period from March 1996 through March 1998. The sentinel lymph node in each case was visualized by lymphoscintigraphy, and its general location was marked on the overlying skin. During breast surgery, the sentinel lymph node was identified for removal by monitoring the acoustic signal from a hand-held gamma ray-detecting probe. Total axillary dissection was then carried out. The pathologic status of the sentinel lymph node was compared with that of the whole axilla. RESULTS: The sentinel lymph node was identified in 371 (98.7%) of the 376 patients and accurately predicted the state of the axilla in 359 (95.5%) of the patients, with 12 false-negative findings (6.7%; 95% confidence interval = 3.5%-11.4%) among a total of 180 patients with positive axillary lymph nodes. CONCLUSIONS: Sentinel lymph node biopsy using a gamma ray-detecting probe allows staging of the axilla with high accuracy in patients with primary breast cancer. A randomized trial is necessary to determine whether axillary dissection may be avoided in those patients with an uninvolved sentinel lymph node. (+info)
(3/1995) Bone marrow scintigraphy using technetium-99m antigranulocyte antibody in malignant lymphomas.
BACKGROUND: The purpose of this study was to elucidate the clinical reliability of immunoscintigraphy (IS) to detect infiltration of the bone marrow in patients with malignant lymphoma. PATIENTS AND METHODS: Whole body IS was performed in 103 patients with Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL) using Tc-99m labelled anti-NCA-95 which allows visualization of the granulopoietic bone marrow. Of these, 52% were studied prior to any therapy. Findings were compared to posterior iliac crest biopsy as well as MRI and/or follow-up examination. Criteria of marrow infiltration were a positive biopsy, positive follow-up, or positive results of MRI. RESULTS: Comparison of IS and biospy revealed concordant findings in 69 and discordant findings in 34 of 103 patients. Of the 34 patients with discordant results, IS showed lesions suspicious of bone marrow infiltration in 29 patients despite normal biopsy findings. When follow-up and additional examinations were taken into consideration, 10 patients remained with probably false positive and five with false negative IS findings. IS proved to be highly sensitive and specific in patients with HD (100% and 84%, respectively) and high-grade NHL (93% and 84%, respectively). Moderate sensitivity (60%) was found in low-grade NHL. This was possibly due to false negative IS in three to five patients with chemotherapy in contrast to one of five false negative results in patients without chemotherapy. CONCLUSION: Bone marrow scintigraphy using antigranulocyte antibodies is highly sensitive in HD and high-grade NHL. Positive findings in IS subsequent to a negative biopsy should be followed by guided re-biopsy or MRI. (+info)
(4/1995) Determination of intrapenial blood volume using 99mTc-labeled autologous red blood cells.
In 17 impotent patients, radioisotope penography was performed using 99mTc-red blood cells (the patient's own red blood cells labeled with 99mTc) for the quantitative analysis of intrapenial blood volume. A visual sexual stimulation (VSS) was given to the patient after injecting the 99mTc-red blood cells. Patients showing a complete erection had their intrapenial blood volumes 4.2-11.2 times greater than before VSS (mean increase, 8.0 times). In cases of incomplete erection after VSS the intrapenial blood volumes were 3.3-7.0 times greater than before VSS (mean increase, 4.9 times). In cases showing a gentle rise in their penogram curves without evidence of an erection, intrapenial blood volumes after VSS were 2.0-3.3 times those before VSS (mean increaae, 2.9 times). By contrast, in cases showing no response to the VSS or no rise in penogram curve, post-VSS increases in intrapenial pool of blood were very slight, slight, only 1.4-1.7 times the original volume of blood. (+info)
(5/1995) Specific targeting of activated endothelium in rat adjuvant arthritis with a 99mTc-radiolabeled E-selectin-binding peptide.
OBJECTIVE: To determine the potential of an E-selectin-binding peptide (ESbp) to specifically bind activated endothelium in rheumatoid arthritis (RA) animal models. METHODS: ESbp (KYDGDITWDQLWDLMK; 2,027 daltons) was labeled with biotin and 99mTc. The affinity of ESbp derivatives for E-selectin was measured by enzyme-linked immunosorbent assay. The binding of biotin-ESbp was compared with that of an anti-E-selectin antibody, by immunohistochemical analyses of human synovial sections and sections from the Mycoplasma pulmonis MRL-lpr/lpr mouse arthritis model. 99mTc-ESbp was sequentially imaged in vivo with a gamma camera in the rat adjuvant-induced arthritis model. RESULTS: E-selectin expression was detected in human RA synovium and mouse arthritic synovium using biotin-ESbp. Both biotin-ESbp and 99mTc-labeled ESbp had high affinity for E-selectin (dissociation constant 2-5 nM). In vivo imaging showed specific binding of 99mTc-ESbp to the rat ankle joint prior to clinical manifestations of inflammation. CONCLUSION: These results demonstrate that activated endothelium can be targeted with 99mTc-ESbp. The specificity of targeting can be used to evaluate up-regulation of E-selectin in RA models, and to follow changes in this up-regulation during treatment trials. (+info)
(6/1995) Washing plastic spacers in household detergent reduces electrostatic charge and greatly improves delivery.
Ionic detergents reduce electrostatic charge on plastic spacers, thereby improving in vitro drug delivery. The aim of this study was to gain practical information on the use of detergents and to evaluate the relevance of this information on in vivo drug deposition. Measurement of electrostatic charge and salbutamol particle size distribution was carried out on detergent-coated and noncoated plastic spacers. The efficiency of four household detergents was compared, and the influence of dilution and the duration of the antistatic effect were studied. In addition, the level of radiolabelled salbutamol deposition in the lungs of eight healthy adults was compared after inhalation through a new versus a detergent-coated spacer. In vitro, all tested detergents reduced the electrostatic charge on the spacer surface. This resulted in a mean increase of 37.4% (range 33.5-41.2) in small particle (<6.8 microm) salbutamol output compared with water-rinsed/drip-dried spacers. Dilution had no influence on the results and the effect lasted for at least four weeks. In vivo, the mean lung deposition of radiolabelled salbutamol in healthy subjects was 45.6% (range 43.4-49.5) through a detergent-coated spacer compared to 11.5% (range 7.6-17.9) through a static spacer (p<0.001). In conclusion, household detergents offer a simple and practical solution to the problem of static on plastic spacers and significantly improve both in vitro and in vivo delivery of salbutamol. (+info)
(7/1995) Optimization of a new scintillation gas detector used to localize electrons emitted by 99mTc.
We have developed a scintillation gas detector to localize electrons emitted by 99mTc. This type of detector allows direct quantification of images and so provides a clear advantage over autoradiographic film. We have optimized the device to give an image spatial resolution that closely approximates that of typical autoradiographic film. To improve this resolution, it was necessary to select only low-energy electrons (2 and 15 keV) and to devise novel detection and localization techniques for the ionizing particles. METHODS: A parallel-plate proportional avalanche chamber is subject to a uniform electrical field and amplifies the number of released electrons through collisions of ionizing particles in the gas mixture. Light emitted by the gas scintillator during the avalanche process is collected by a highly intensified charge coupled device camera. The centroid of each resulting light distribution is calculated, resulting in a quantitative mapping of the sample's activity. Insertion of the sample within the gas volume improves the efficiency and so provides a method that is both very sensitive and linear. RESULTS: We have shown that in a parallel-plate structure, the application of a high electrical field to the surface of the sample and the selection of appropriate light spots, according to their morphology, can overcome localization errors due to the particles' trajectories. We have obtained a resolution of the order of 30 microm, using electrons from 99mTc. CONCLUSION: This detection technique allows considerable improvement in image resolution. This "electron camera" is a serious rival to existing autoradiographic techniques, because it provides certain other advantages, including direct quantification, linearity, high dynamic range and low noise levels. Thus, new perspectives are made available in quantitative double tracer autoradiography, because electrons can be selected for imaging as a function of their energy. (+info)
(8/1995) Reduction of technetium by Desulfovibrio desulfuricans: biocatalyst characterization and use in a flowthrough bioreactor.
Resting cells of Desulfovibrio desulfuricans coupled the oxidation of a range of electron donors to Tc(VII) reduction. The reduced technetium was precipitated as an insoluble low-valence oxide. The optimum electron donor for the biotransformation was hydrogen, although rapid rates of reduction were also supported when formate or pyruvate was supplied to the cells. Technetium reduction was less efficient when the growth substrates lactate and ethanol were supplied as electron donors, while glycerol, succinate, acetate, and methanol supported negligible reduction. Enzyme activity was stable for several weeks and was insensitive to oxygen. Transmission electron microscopy showed that the radionuclide was precipitated at the periphery of the cell. Cells poisoned with Cu(II), which is selective for periplasmic but not cytoplasmic hydrogenases, were unable to reduce Tc(VII), a result consistent with the involvement of a periplasmic hydrogenase in Tc(VII) reduction. Resting cells, immobilized in a flowthrough membrane bioreactor and supplied with Tc(VII)-supplemented solution, accumulated substantial quantities of the radionuclide when formate was supplied as the electron donor, indicating the potential of this organism as a biocatalyst to treat Tc-contaminated wastewaters. (+info)