Gastric retention of zinc-based pennies: radiographic appearance and hazards.

PURPOSE: To determine the radiographic appearance and features of corrosion in U.S. coins exposed to gastric acid. MATERIALS AND METHODS: Six U.S. copper-based pre-1982 pennies, 12 zinc-based post-1982 pennies, a quarter, a nickel, and a dime were exposed to postprandial concentrations of gastric acid (0.15N HCl) for 7 days, and radiographs were obtained daily. Half the zinc-based coins were scraped to disrupt their copper coating. Coins were weighed at the start and completion of the study. RESULTS: Post-1982 zinc-based pennies developed radiolucent corrosive changes within 24 hours. Erosions on the coins became more apparent over time. Frank holes were present on day 2. The weights of these coins decreased 5%-8% during the study. Pre-1982 copper pennies and "silver-colored" coins showed no change on radiographs over 7 days. CONCLUSION: Unexpected radiolucent corrosions may develop in post-1982 zinc alloy pennies when retained in the stomach. Coins have long been considered innocuous foreign bodies in the gastrointestinal tracts of children. However, because of the potential for ulceration and zinc-related morbidity, closer clinical and radiographic observation is warranted. Coins with scalloped edges or holes should be endoscopically removed, as they have likely been retained longer than 1 or 2 days.

Clinical PET scanning. A "short-lived" orphan.

Positron emission tomography (PET) is a method of nuclear medicine imaging that uses short-lived radiopharmaceuticals to detect and quantify the metabolic abnormalities of disease processes. PET initially was developed in a research environment as a research tool; data from these research studies resulted in the gradual recognition that PET studies would be useful for various routine clinical applications. The diffusion of PET into clinical practice has been slow in comparison with other new imaging methods (e.g., magnetic resonance imaging). This slow diffusion is attributable to several factors, including the complexity and high cost of PET, the uncertain role of the U.S. Food and Drug Administration in regulating the radiopharmaceuticals that are produced and used on-site for PET studies, and the apparent slow pace at which the Health Care Financing Administration and other third-party payers are developing policies for reimbursing for PET.

Effects of characteristic x-rays on assay of I-123 by dose calibrator.

Large differences in dose-calibrator readings are obtained if "high-purity" I-123 is assayed in different containers. Large correction factors are necessary for assaying another isotope of iodine, I-125, in a dose calibrator, because of absorption of the low-energy (28.4-keV, weighted mean) emissions. We found that up to 70% of the dose-calibrator response to I-123 can be due to characteristic x-rays with energies exactly the same as those emitted by I-125, and that dose-calibrator response to I-123 is also strongly affected by the absorption properties of the vial. An appropriate method to define I-123 activity uses a gamma camera with a medium-energy collimator to establish correction factors for dose-calibrator assay of I-123 in different containers. Correction factors for a plastic syringe and a thick-wall glass vial, were determined using this method. Measurement of I-123 activity in a copper absorber will eliminate the response to x-rays, and the gamma camera is useful in establishing the necessary correction factors.

Monoclonal antibodies to different epitopes on a prostate tumor-associated antigen. Implications for immunotherapy.

Mouse monoclonal antibodies alpha Pro3 and alpha Pro5 bind to different epitopes on an antigen (p54) of 54 kD reduced and 175 kD nonreduced MW. p54 antigen has been characterized previously with regard to tissue distribution using alpha Pro3 monoclonal antibody; the p54 antigen is present in substantially greater quantities in malignant prostatic tissue extracts than in benign prostatic and nonmalignant nonurogenital tissue extracts. In this report, we have established that alpha Pro5 and alpha Pro3 monoclonal antibodies exhibit same molecule-different epitope recognition. That both antibodies recognize the same molecular entity has been established by partial physiochemical characterization of the antigen recognized by the two antibodies and by sequential immunoprecipitation experiments. Different determinant recognition was established by lack of competitive surface binding between alpha Pro3 and alpha Pro5 to a prostatic carcinoma cell line. The p54 antigen can be labeled with glucosamine and immunoprecipitated from urea-solubilized membrane proteins; however, p54 cannot be detected by immunoprecipitation in a glycosylated form in spent culture medium removed from glucosamine-labeled cells. Experiments using indirect cellular immunoassays and directly radioiodinated monoclonal antibody have shown that both alpha Pro3 and alpha Pro5 form stable complexes with p54 antigen on the prostatic carcinoma cell surface. To the extent that modulation occurs upon interaction of p54 with alpha Pro3 and alpha Pro5; endocytosis of the immune complex appears to be the primary route of modulation. Furthermore, modulation by endocytosis is more intense when alpha Pro3 and alpha Pro5 are used in combination than when either monoclonal antibody is used alone. Although in vivo biologic behavior does not invariably correlate with in vitro behavior, careful in vitro analysis of monoclonal antibodies with respect to cell surface behavior, nevertheless, should precede in vivo evaluation. The data presented in this report indicate that preliminary in vitro analyses will expedite the effectiveness of in vivo immunotherapeutic trials; preliminary in vitro evaluations are absolutely essential if monoclonal-toxic agent (e.g., ricin A) conjugates, which must be internalized by the tumor cell to achieve cytotoxicity, are employed as immunotherapeutic agents.

Localization of I-131-labeled goat and primate anti-carcinoembryonic antigen(CEA) antibodies in patients with cancer.

Thirty patients with anti-carcinoembryonic antigen (CEA)-producing cancers of the colon, breast, or thyroid were injected with 1 to 2 mCi of Iodine-131 (131I)-labeled, affinity-purified, goat or baboon anti-CEA antibodies. Images were obtained daily for four days. Computerized background subtraction using technetium 99m (99mTC)-labeled compounds was used. Images obtained with and without background subtraction were correlated with other evidence of disease. Activity levels in plasma, urine, and thyroid gland were monitored. Significant deiodination of antibody occurred within the first 24 hours. The mean plasma half-disappearance-time of baboon antibody was significantly longer than the mean half-disappearance-time of goat antibody. With exogenous blockade, total thyroid uptake was less than 0.1% of the injected dose. Without background subtraction, scintigraphic localization of known tumor was possible in one of two patients with colon carcinoma, in three of 20 patients with breast cancer, and in one of five patients with medullary carcinoma of the thyroid. With background subtraction, potential false-positive results could be generated for every patients, depending on the normalization site chosen and the degree of subtraction used. In contrast to results of previous reports, CEA-producing tumor was found to be infrequently localized using highly purified goat or primate radiolabeled anti-CEA. Furthermore, the subtraction technique described by previous investigators may lead to a high false-positive rate.

Radioiodination of biologically active compounds: a simplified solid-state enzymatic procedure.

A simplified solid-state enzymatic iodination procedure for routine labeling of unstable pure protein or complex amino acid-containing molecules is presented. The procedure was designed using agarose-bound lactoperoxidase to iodinate human IgG with iodine-125. This method consistently resulted in a labeling efficiency greater than 90% with high stability and undetectable gross structural alterations of the substrate as evaluated by immunodiffusion and electrophoresis. The technique presented is simple, efficient, and may be employed to yield a sterile, pyrogen-free labeled species.