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[en] The foot-and-mouth disease virus RNA-polymerase gene was mutagenised in its active site. Pst I digestion of the polymerase gene (cDNA) generated a 790 bp fragment containing the critical sequence. This fragment was subcloned in M13mp8 for mutagenesis method. The polymerase gene was then reconstructed and subcloned in pUC19. These mutants will be used to study the enzyme structure and activity and to develop intracellular immunization assays in eukaryotic cells. (author)

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[en] Technetium-99m (^99mTc) is a radionuclide widely used for nuclear medical examination. Called the workhorse of nuclear medicine, ^99mTc is the favoured choice because it has the appropriate physical and chemical characteristics for imaging. The gamma radiation emitted by ^99mTc has the appropriate energy (140 keV) to provide high efficiency detection with the advantage of reduced radiation burden for the patient and environmental (half-life of 6 h). Crotalus venom (CV) has been tested in a very few human cases and it has been shown to reduce tumours. Our group has shown that CV has antitumoural effects against some brain tumours in vitro. Pharmacokinetics and tissue distribution studies are very important for clinical use. The aim of the present study was to obtain an analogue of CV labelled with ^99mTc which preserves its biological activity for use in biodistribution and binding studies. A direct method for ^99mTc-labelling venom has been evaluated according to Pauwels, et al. The method employs stannous chloride and sodium borohydride as reducing agents. By altering the reaction conditions high yield of labelled venom was achieved. Labeling yield was estimated using chromatographic systems. Biological activity was assessed by haemolytic activity study. Comparing haemolytic activities of labelled and unlabeled venom we observed that neither ^99mTc-CV nor CV caused direct lysis on washed erythrocytes. However, both of them caused indirect hemolysis provided that the incubation medium contained an exogenous source of lecithin. So, the biological activity of CV was preserved after labeling. Biodistribution of ^99mTc-CV was evaluated in mice. Male swiss mice were injected i.p. with ^99mTc-CV, vital organs were isolated and their respective radioactivities were measured. High radioactivity was found in the kidneys suggesting renal excretion. On the other hand, this radioactivity was displaced in animals pre-treated with excess of non labelled CV (not shown). These data show that the uptake of ^99mTc-CV is specific. In this paper we reported the radiolabelling of CV with ^99mTc and showed that ^99mTc-CV kept its biological activity. Our results showed that ^99mTc-CV can be a useful tool for biodistribution and binding studies

[en] Crotoxin (Crtx) is the main toxin of South American rattlesnake (Crotalus durissus terrificus) venom. Research on antitumoral drugs has demonstrated the potential use of Crtx as tumour reducing agent. Tissue distribution studies are very important for clinical use and ^99mTc-labeling is a very convenient method for studies related to biodistribution. The aim of the present study was to label Crtx with ^99mTc keeping its biological activity for use in biodistribution and binding studies. High labeling yield was obtained using stannous chloride and sodium borohydride. Results demonstrated that biological activity of ^99mTc-Crtx was preserved and confirmed kidneys as the target organ. Biological activities of unlabeled and ^99mTc-labeled Crtx were evaluated after labeling. ^99mTc-Crtx can be a useful tool for imaging and binding studies. (author)

[en] Integrins are family of heterodimeric cell surface adhesion receptors able to recognize and bind to proteins in the extracellular matrix (ECM). This recognition is mainly through the RGD domain present in both the cell surface as the protein in the ECM. Various integrins have been identified as regulators of tumor progression. The RGD domain is also found in some snake venoms named disintegrins. Disintegrins inhibit cell-matrix and a cell-cell interaction mediated by integrin and has been shown that these proteins are able to inhibit metastasis in processes dependent on integrin. The disintegrin-like (ECD), as well as RGD-disintegrin are also able to bind to cell surface integrins and inhibit their adherence to the natural ligands. Leucurolysin-B (Leuc-B) is a metalloproteinase class P-III isolated from Bothrops leucurus (BLV) and possesses a disintegrin-like domain (ECD). The goals of this work were to synthesize a radioactive probe analog to Leuc-B using radioiodine ¹²⁵I and evaluate the interaction of ¹²⁵I-Leuc-B in tumor cells through the study of biodistribution in animals bearing Ehrlich tumor.125I-Leuc-B was synthesized using lactoperoxidase with high yield (90%) and specific activity of 1.2x10-7Bq/mmol. It was observed that ¹²⁵I-Leuc-B had very fast clearance from the blood stream (T1/2= 0.01 h). Tumor uptake of 125I-Leuc-B gradually increased up to (2 min) and remained for a quite long period. The tumor/normal tissue uptake ratios of ¹²⁵I-Leuc-B were 1.77 (tumor/normal paw) and 8.44 tumor/skeletal muscle. The results suggest that ¹²⁵I-Leuc- B may constitute a good template for development of a tool for detection of solid tumors. (author)

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