The use of theranostic gadolinium-based nanoprobes to improve radiotherapy efficacy

A new efficient type of gadolinium-based theranostic agent (AGuIX®) has recently been developed for MRI-guided radiotherapy (RT). These new particles consist of a polysiloxane network surrounded by a number of gadolinium chelates, usually 10. Owing to their small size (<5 nm), AGuIX typically exhibit biodistributions that are almost ideal for diagnostic and therapeutic purposes. For example, although a significant proportion of these particles accumulate in tumours, the remainder is rapidly eliminated by the renal route. In addition, in the absence of irradiation, the nanoparticles are well tolerated even at very high dose (10 times more than the dose used for mouse treatment). AGuIX particles have been proven to act as efficient radiosensitizers in a large variety of experimental in vitro scenarios, including different radioresistant cell lines, irradiation energies and radiation sources (sensitizing enhancement ratio ranging from 1.1 to 2.5). Pre-clinical studies have also demonstrated the impact of these particles on different heterotopic and orthotopic tumours, with both intratumoural or intravenous injection routes. A significant therapeutical effect has been observed in all contexts. Furthermore, MRI monitoring was proven to efficiently aid in determining a RT protocol and assessing tumour evolution following treatment. The usual theoretical models, based on energy attenuation and macroscopic dose enhancement, cannot account for all the results that have been obtained. Only theoretical models, which take into account the Auger electron cascades that occur between the different atoms constituting the particle and the related high radical concentrations in the vicinity of the particle, provide an explanation for the complex cell damage and death observed.

[Composition of the Araneae (Arachnida) fauna of the provincial Iberá Reserve, Corrientes, Argentina]

A survey of the spider community composition and diversity was carried out in grasslands and woods in three localities: Colonia Pellegrini, Paraje Galarza and Estancia Rinc6n (Iberá province Reserve). Pit fall traps, leaf litter sifting, foliage beating, hand collecting and sweep nets were used. Shannon's diversity index, evenness, Berger-Parker's dominance index, beta and gamma diversity were calculated, and a checklist of spider fauna was compiled. Species richness was estimated by Chao 1, Chao 2, first and second order Jack-knife. A total of 4,138 spiders grouped into 150 species from 33 families of Araneomorphae and two species from two families of Mygalomorphae were collected. Five species are new records for Argentina and eleven for Corrientes province. Araneidae was the most abundant family (39.8%), followed by Salticidae (10.9%), Anyphaenidae (7.9%), Tetragnathidae (7.4%), and Lycosidae (5.5%). The other families represented less than 5% of the total catch. The web-builder guild had the highest number of specimens and the highest richness index. The abundance, observed richness, Shannon diversity and evenness indexes were highest in Colonia Pellegrini woodland and Paraje Galarza grassland. Alpha diversity represented 89% of the gamma; the remaining 11% corresponded to beta diversity. According to the indexes, between 67% and 97% of the existing spider fauna was represented in the collected specimens from Iberá.

[Domestic infestation by Triatoma infestans and prevalence of Trypanosoma cruzi seropositives in a rural area of the Argentinian northeast]

An epidemiological study was carried out from April 1991 to December 1993 to obtain a general view of T. cruzi domestic transmission in rural areas of San Miguei Department, Corrientes. From 100 analyzed households, 50.0% was infested by T infestans (Klug, 1834) and 1.0% by T. sordida (Stal, 1859). Domiciliary colonization by T. sordida is reported for first time in Corrientes province. T. cruzi infection of T. infestans was 23.1%. Indirect hemagglutination and indirect immunofluorescence antibody tests were used for detection of anti T. cruzi antibodies in 388 human sera, 23.4% showed serological reactivity. An important high rate (12.9%) was observed in the age group of higher transmission risk. Seropositives percentages increased with age and reached 50.0% in 31-40 years old group. Domestic infestation by T. infestans, seropositive human prevalence to T. cruzi and householders precarious life conditions prove that this endemic disease is still a problem in the studied area.

[Population statistics of Triatoma sordida Stäl 1859 (Hemiptera:Reduviidae) in experimental conditions]

Four cohorts of 100 Triatoma sordida eggs were reared under standard laboratory conditions (28 degrees C, 63% R.H.) and fed weekly on hens during 40 minutes. The numbers of dead insects, moults and eggs laid were recorded weekly. A constant survival value was observed without any important peaks in the four cohorts. Life expectancy was 37.4 weeks for males and 36.8 weeks for females. The average generation time was 61.7 weeks. The average net reproduction rate suggests that this population would increase 143.2 times during each generation. The average intrinsic rate of natural increase was 0.082 per individual per week. The highest reproductive value was observed 3 weeks after entering the adult stage. The age structure, assuming stable age distribution, would be 32% eggs, 26% of first instar nymphs, 19% of second instar nymphs, 13% of third instar nymphs, 6% of fourth instar nymphs, 3% of fifth instar nymphs and 1% of adults. Our results suggest that this species behaves as a k-strategist under experimental conditions.