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Biomedical subjects

A I Kassis

Publications and source records attributed to A I Kassis.

At least 109 records · Page 6Linked to original sources
PubMed1983

Transient toxicity of 2-deoxy-2-[18F]fluoro-D-glucose in mammalian cells: concise communication.

The kinetics of uptake and toxicity of the positron emitter F-18 have been examined in a cultured cell line. 2-Deoxy-2[18F]fluoro-D-glucose (18FDG) concentrated rapidly within Chinese hamster V79 cells, and the uptake was linear with the extracellular radioactive concentrations. Whereas 18FDG synthesized 2 hr before the incubation did not appear to be toxic, that synthesized 5 hr previously was highly toxic. Toxicity was transient and independent of both the extracellular/intracellular radioactive concentration and the energy released from the decay of fluorine-18. Similarly synthesized nonradioactive FDG and Na 18F were not toxic under comparable experimental conditions. We conclude that this transient toxicity is due to an unidentified chemical species that is cytocidal following intracellular localization. These toxic levels are not likely to be achieved in the clinical use of 18FDG due to dilution factors that are orders of magnitude greater than those used in these in vitro studies.

Animals↗
PubMed1983

Thallium-201: an experimental and a theoretical radiobiological approach to dosimetry.

The kinetics of uptake and retention of Tl-201, Rb-86, and K-42 and -43 have been studied in cultured mammalian cells and related to their radiotoxicities. Among the four radionuclides, the intracellular localization of Tl-201, the only emitter of Auger electrons, was important for the manifestation of its cytocidal effects. The results have been found consistent with the short-range nature of Auger electrons and are substantiated by our theoretical dosimetric calculations. The possible implications of this in vitro system for applications of Tl-201 in nuclear medicine are indicated.

Animals↗
PubMed1980

A rapid and reproducible method for the separation of cells from radioactive media.

A simple method is described for the rapid separation of cells, containing radioactive material, from their suspending medium. Cells, in aqueous medium, are layered on fetal bovine serum in microfuge tubes. The tubes are immediately spun for 1 min, frozen in ethanol-dry-ice, and their tips sliced and assayed. This method is both faster and more convenient than currently employed techniques.

Animals↗
PubMed1979

Mouse antibody-dependent eosinophil and macrophage adherence and damage to schistosomula of Schistosoma mansoni.

The effects of sera from S. mansoni-infected mice together with eosinophil- and macrophage-rich peritoneal exudate cells (PEC) on the schistosomula were examined in vitro. Adherence to and killing of the parasite by PEC is mediated through a complement-independent opsonizing IgG. Destruction of schistosomula was assessed morphologically and by evaluating their infectivity to normal mice. By using ferritin-labeled anti-mouse immunoglobulin, the antibody was localized on the surface of the schistosomula and at the cell-organism areas of contact. The serum antibody activity appears with the onset of egg production, does not correlate well with the duration of infection, and is relatively specific among schistosome species. Eosinophils and macrophages were demonstrated by electron microscopy to adhere firmly to the surface of the organisms; the latter cells were shown invading the schistosomula. Furthermore, depletion of eosinophils by prior incubation of PEC with monospecific anti-eosinophil serum blocked the early adherence phase, but a substantial part of PEC ability to kill the schistosomula was retained.

Animals↗
PubMed1977

Host serum proteins in Echinococcus multilocularis: complement activation via the classical pathway.

The presence of host serum proteins, including IgG and IgM, within the cyst membranes and on the surface of protoscoleces of Echinococcus multilocularis was demonstrated by the use of HRPO-conjugated purified antisera. Viable protoscoleces incubated either in EDTA- or EGTA-fresh human sera were not lysed; the addition of calcium restored the protoscolecidal activity of the EGTA serum. It is concluded that the complement-mediated lysis of this metazoan organism proceeds via the classical pathway of complement activation. The results are discussed in relation to the ability of this parasite to survive in the immunologically hostile environment of the host.

Animals↗
PubMedDate not supplied

Labeling of immunoglobulins with bifunctional, sulfhydryl-selective, and photoreactive coumarins.

4-(Bromomethyl)-6,7-dimethoxy-2-oxo-2H-benzopyran (1a) and 4-(bromomethyl)-7-methoxy-2-oxo-2H-benzopyran (1b) and their iodo analogs (2) reacted selectively with the sulfhydryl groups generated in a limited reduction of the hinge disulfide bonds of an immunoglobulin G (IgG) giving proteins labeled with a fluorescent and/or radioactive moiety. Quantitative alkylation of free thiol groups was obtained with 1 and 125/127I-2. Photodimerization of these adducts produced IgG with covalently joined heavy chains.

Adsorption↗
PubMedDate not supplied

Labeling of sulfhydryl groups in intact mammalian cells with coumarins.

4-(Bromomethyl)-6,7-dimethoxy-2-oxo-2H-benzopyran (1) and its 3-[125I]iodo derivative (2) were reacted with sulfhydryl groups of proteins in viable Chinese hamster V79 lung fibroblasts. Pretreatment of cells with dithiothreitol (DTT) as the reducing agent was necessary to give detectable levels of fluorescence. In the absence of DTT, V79 cells incorporated about 1 x 10(-3) pCi/cell of the radioiodinated, no-carrier-added derivative; following incubation of cells with 320 microM DTT the uptake was nearly doubled (1.87 x 10(-3) pCi/cell).

Animals↗
PubMedDate not supplied

Radiotoxicity of 5-[125I]iodo-2'-deoxyuridine in mammalian cells following treatment with 5-fluoro-2'-deoxyuridine.

We have enhanced the uptake of 5-[125I]iodo-2'-deoxyuridine (125IUdR) in Chinese hamster V79 cells with 5-fluoro-2'-deoxyuridine (FUdR) and have examined the combined toxicity of these agents. Although the uptake of 125IUdR increases approximately 3.2 +/- 0.5-fold in the presence of 1 microM FUdR, when cell survival fraction is plotted as a function of intranuclear 125IUdR content, the biphasic curve obtained reaches a plateau at a higher survival fraction than with control cells not exposed to FUdR. The results suggest that a greater number of cells were prevented from entering the S phase and consequently from incorporating 125IUdR. An FUdR- 125IUdR combination, therefore, does not seem to enhance the therapeutic potential of 125IUdR. Such observations are also of importance when FUdR and other inhibitors are used to enhance cold IUdR uptake in an effort to obtain an increase in radiosensitization effects.

Animals↗
PubMedDate not supplied

Detection of focal infection by 111In-human polyclonal IgG.

Eleven patients with suspected foci of inflammation and/or infection were scanned with 111In-labeled polyclonal human IgG. Seven patients were suspected of having the source of their infection in the abdomen, three in the musculoskeletal system and one in the thoracic aorta. The test was truly positive in seven patients, truly negative in three and falsely negative in one. All the true positive cases showed abnormally increased radiopharmaceutical uptake at the site of infection by six hours, suggesting the diagnosis, although the intensity of uptake increased progressively 24 hours later. There were no untoward effects noted in this series. This examination is potentially useful in the early depiction of focal sources of infection/inflammation.

Abscess↗
PubMedDate not supplied

Capping and internalization of a monoclonal antibody-surface antigen complex: a possible mode of interaction of monoclonal antibodies and tumor cells.

Our results demonstrate that upon incubation of 125I-3G5 (a monoclonal IgM against a membrane ganglioside antigen on RINm5F cells) with rat insulinoma RINm5F cell monolayers at 37 degrees C, the IgM is rapidly internalized. Cell-bound radioactivity, detectable within 10 to 15 minutes, reaches a peak at 4 hours. By 24 hours the intracellular radioactivity has decreased to about 37.5% of the 4-hour value, accompanied by an increase in free 125I in the incubation medium. The incubation of 125I-3G5 with RINm5F cell monolayers at 4 degrees C shows that this series of events is inhibited by low temperature. Microautoradiography confirms these events indicating the presence of radiolabeled antibody on the plasma membrane as well as distinct capping processes and diffuse radioactive deposits within the cells as early as 5 to 10 minutes after initiating incubation at 37 degrees C. Electron microscopy autoradiography provides a detailed demonstration of the capping phenomenon and of endocytic vacuoles, followed at later times by the distribution of radioactive deposits throughout the cell. This model constituted by the capping of the 125I-3G5-ganglioside complex on rat insulinoma RINm5F cells may be useful in elucidating a possible mode of interaction of monoclonal antibodies and tumor cells.

Animals↗