Autoradiographic studies on distribution of radiocobalt chloride in pregnant mice

Single Photon Emission Computed Tomography Tracer

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., ^99mTc, ¹²³I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

Single photon emission computed tomography tracer

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years. Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g. peptide, antibody fragment) and a γ-radiation emitting radionuclide (e.g. (99m)Tc, (123)I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases. Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

The biokinetics of inorganic cobalt in the human body

This paper reviews information on the biological behavior of inorganic cobalt in humans and laboratory animals and proposes a model of the systemic biokinetics of inorganic cobalt in adult humans. The model was developed as part of an effort to update the models of the International Commission on Radiological Protection (ICRP) for addressing intakes of radionuclides by workers but is also applicable to environmental or medical exposures to inorganic forms of radiocobalt. The model can be used in conjunction with any respiratory, gastrointestinal, or wound model that provides predictions of the time-dependent feed of cobalt to blood. In contrast to the ICRP's current systemic model for cobalt, which is a simple open catenary system, the proposed model is constructed within a physiologically realistic framework that depicts recycling of cobalt between blood and tissues and transfer from blood to excretion pathways. Compared with the ICRP's current model, the proposed model yields similar predictions of whole-body retention but substantially different predictions of the systemic distribution of cobalt as a function of time after uptake to blood.

In vitro comparative effect of Cd2+, Ni2+, and Co2+ on mouse postblastocyst development

Postblastocyst development of mouse preembryos was studied in vitro in order to determine direct effect of Cd2+, Ni2+, and Co2+ ions on embryogenesis during the peri-implantation stage. Uterine horns were flushed on Day 4 of pregnancy and expanded blastocysts were cultured for 4 days in the presence of micromolar Cd2+ (1.1-26.4), Ni2+ (0. 1-500) or Co2+ (1-200). Area of trophoblast outgrowth was measured and used as a quantitative toxicological endpoint. Hatching, attachment, outgrowth, and formation of inner cells mass were also registered. Significant adverse effect on the development stages were observed at 2.2 microM (Cd2+), at 10 microM (Ni2+), and at 100 microM (Co2+). Cd2+ and Co2+ decreased the area of trophoblast markedly at concentrations of 1.1 and 10 microM, respectively. Ni2+ exposure resulted in a slight increase at 10 microM followed by a marked reduction in the trophoblast area at 250 microM. Reduced proliferative ability of trophoblast cells may point to compromised invasiveness of the embryo. The lowest Cd2+ concentration (1.1 microM=0.25 microg/ml) significantly deteriorating trophoblast development was found to be lower than Cd levels ranging up to 0.512 microg/g, reported in clinical ovarian samples of occupationally nonexposed women. The morphological alteration and loss of cellular contacts in blastocysts induced by exposure to Cd2+, Ni2+, or Co2+ may adversely influence adhesion and recognition events and may disturb aggregation of mononuclear trophoblastic cells to multinucleated cells in the course of peri-implantation in vivo as well.

Distribution of 58Co from the oral cavity of mice

Whole body retention and tissue distribution of 58Co in mice having had an oral cavity depot of 58CoCl2 was studied at 1, 5 and 24 h after administration by means of gamma scintillation measurements and autoradiography. The whole body 58Co retention at 5 h after administration was 93.3% of the whole body 58Co content at 1 h. Corresponding 58Co-retention at 24 h after administration was 9.2%. Tissues analyzed by gamma scintillation measurements at 1, 5 and 24 h post administration were: serum, kidney, pancreas, spleen, liver, heart, lung, tongue and palatal mucosa. At all survival times after administration palatal mucosa showed the highest 58Co median content followed by tongue. The very high 58Co median content of palatal mucosa and tongue at 1 h after administration showed a strongly decrease at 5 and 24 h after administration. For the other tissues the highest 58Co median content was found in the liver and the lowest in the spleen with the highest 58Co median value for each tissue at 5 h after administration. The autoradiograms revealed a high 58Co uptake in oral, nasal, pharyngeal and esophageal mucosa, intestines and stomach. In liver, pancreas and kidney no uptake was observed at 1 h and a weak uptake was detected at 5 and 24 h.