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
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
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
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
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
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
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
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