Dendrimers are branched nanomolecules, with a three dimensional structure, very low polydispersity and high functionality. Poly(amidoamine) (PAMAM) dendrimers are the most investigated class of dendrimers. In this study, PAMAM G4 dendrimer conjugated with HYNIC (hydrazinonicotinamide), an efficient bifunctional chelator, was characterized. Structure of the derivatized dendrimer was confirmed by (1)H-NMR and (13)C-NMR spectra and MALDI-TOF mass spectrometry. HYNIC-dendrimer was labeled with technetium-99m testing three different co-ligands (tricine, nicotinic acid and ethylenediaminodiacetic acid). The radiolabeled complexes were characterized by reverse phase HPLC, as well as their stabilities. Radiolabeling yield was about 99% with all co-ligands and complexes were found stable for 24 h. Biodistribution studies were performed administrating tricine-(99m)Tc-HYNIC-dendrimer, nicotinic acid-(99m)Tc-HYNICdendrimer and EDDA-(99m)Tc-HYNIC-dendrimer to normal mice; results showed blood clearance with hepatic and renal depuration in all cases. In this sense, labeling of PAMAM G4 dendrimer with technetium-99m using HYNIC could be obtained in high yield in a simple method and with high specific activity.
Owing to the rapid expansion of agriculture in South America in recent decades, soil erosion and fine 26 sediment supply to river networks, which lead to deleterious on-site and off-site environmental 27 impacts, are exacerbated in intensively cultivated catchments. Measuring soil inventories of bomb-28 derived fallout radiocesium ( 137 Cs) bound to fine particles is one of the few techniques available to reconstruct soil redistribution rates and evaluate the sustainability of farming practices over the recent 30 phase of agricultural intensification (1960s-2020). However, information about the spatial distribution 31 of 137 Cs fallout across the soils of South America remains scarce, and the published data has not been 32 synthesized at the scale of this subcontinent so far. The objective of the current research is therefore 33 to quantify and map the initial 137 Cs fallout at the scale of South America, based on the compilation of 34 published 137 Cs inventories, additional measurements conducted on undisturbed soil profiles and 35 digital soil mapping as this baseline information may be useful for a wide range of Earth Science 36 applications. A database of 137 Cs inventories at 96 reference sites (i.e. areas without soil erosion nor 37 accumulation) has been compiled for a variety of soil profiles (Argentina = 10, Brazil = 34, Chile = 46, 38 Uruguay = 5, French Guiana = 1) located between 5.3° North latitude and 53° South latitude. The spatial 39 distribution of 137 Cs fallout was shown to be highly latitude-dependent, with a maximum in the 30-50° 40 South latitude band. There were higher fallout levels than expected between 20 to 60° South latitude 41 compared to the previous estimations made by UNSCEAR. A partial least square regression approach 42 based on rainfall data and geographical information as covariates was used to create a baseline map 43 of 137 Cs fallout in soils of continental South America. This baseline map provides a powerful reference 44 dataset to anticipate the order of magnitude of 137 Cs inventories in undisturbed soil profiles collected 45 in Brazil and Southern Chile and for numerous other applications in Earth Sciences. The potential 46 application of the 137 Cs inventory technique in countries of South America in general, and in regions 47 investigate soil redistribution rates in most of South American countries where detectable levels of 52 137 Cs can be expected to be found in sites exposed to erosion.
Dendrimers are synthetic nanomolecules with well-defined chemical structures. Different strategies have been used for radiolabeling dendrimers with different radioisotopes. In this study, the aim was to conjugate dendrimers with (177)Lu, to observe the in vivo behavior of the labeled compound and to measure the elementary changes in tumor tissue that could be caused by ionizing radiation. PAMAM G4 dendrimers conjugated with DOTA were labeled with (177)Lu. The radiolabeled compound was characterized and its stability was evaluated by reverse phase high performance liquid chromatography. Radiolabeling yield was >98% and stable for 24 hours. Biodistribution studies of (177)Lu-DOTA-dendrimers in C57BL/6 melanoma-bearing mice showed blood clearance with hepatic and renal depuration and tumor uptake. The concentrations of Br, Ca, Cl, Fe, K, Mg, Na, Rb, S, and Zn were determined in tumor tissues of C57BL/6 mice treated with (177)Lu-DOTA-dendrimers and in untreated mice. The results showed decreased concentrations of Br (62%), Ca (24%), Cl (51%), K (12%) and Na (60%) and increased concentrations of Fe (8%), Mg (28%), Rb (100%), S (6%) and Zn (4%) in tumor tissues of mice treated with (177)Lu-DOTA-dendrimers. These data may be useful to evaluate changes in tumor tissues as indicators of damage that could be caused by ionizing radiation.
From 1985 onwards, South America has undergone a major expansion of agriculture at the expense of native vegetation (e.g. native Pampa grassland). As an emblematic crop, the surface area cultivated with soybeans has increased by 1000% between 1990 and 2020 in Uruguay. The environmental consequences of this massive land use conversion on soil degradation remain poorly documented although the agriculture expansion is projected to continue to increase in the coming years in South America. In this study, sediment cores were collected in reservoirs located downstream of two contrasted agricultural catchments draining the Rio Negro River (Uruguay) for reconstructing the sediment dynamics and the sources of erosion associated with this expansion.Results demonstrated the occurrence of two periods of acceleration of sediment delivery since the 1980s. The first period of acceleration was recorded in the mid-1990s and was related to afforestation programs. The second and larger acceleration phase was recorded after 2000 during the soybean crop expansion. This period has been marked by a greater supply of sediment from the native grassland source highlighting the impact of agriculture expansion at the expense of native vegetation. Conservation measures should therefore be urgently taken to preserve biodiversity and soil functions in this region.
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