Revision of Potamotrygonocotyle Mayes, Brooks & Thorson, 1981 (Platyhelminthes: Monogenoidea: Monocotylidae), with descriptions of four new species from the gills of the freshwater stingrays Potamotrygon spp. (Rajiformes: Potamotrygonidae) from the La Plata river basin

The only known monocotylid genus to parasitise Neotropical freshwater stingrays (Potamotrygonidae) is Potamotrygonocotyle Mayes, Brooks & Thorson, 1981, a monotypic genus erected to accommodate P. tsalickisi Mayes, Brooks & Thorson, 1981. For more than 20 years, no other species has been recognised in this genus, but new efforts to survey the diversity of parasites inhabiting potamotrygonids have revealed the existence of new species and the need to redefine the genus. Here, the generic diagnosis of Potamotrygonocotyle is amended, P. tsalickisi is redescribed and four new species are recognised and described based on samples collected from the gills of freshwater potamotrygonids from the La Plata river basin: Potamotrygonocotyle chisholmae n. sp. and P. dromedarius n. sp. from Potamotrygon motoro; Potamotrygonocotyle eurypotamoxenus n. sp. from Potamotrygon cf. motoro (type-host), P. castexi, P. falkneri and P. histrix; and Potamotrygonocotyle uruguayensis n. sp. from Potamotrygon brachyura. Potamotrygonocotyle is characterised by species possessing: (1) slightly sinuous sclerotised ridges on all septa; (2) two pairs of the dorsal haptoral accessory structures associated with the four posterior peripheral loculi and with anterior dorsal haptoral accessory structure bilobate or semicircular; and (3) male copulatory organ without an accessory piece.     

α-Glucosidase inhibition by flavonoids: an in vitro and in silico structure–activity relationship study

α-Glucosidase inhibitors are described as the most effective in reducing post-prandial hyperglycaemia (PPHG) from all available anti-diabetic drugs used in the management of type 2 diabetes mellitus. As flavonoids are promising modulators of this enzyme’s activity, a panel of 44 flavonoids, organised in five groups, was screened for their inhibitory activity of α-glucosidase, based on in vitro structure–activity relationship studies. Inhibitory kinetic analysis and molecular docking calculations were also applied for selected compounds. A flavonoid with two catechol groups in A- and B-rings, together with a 3-OH group at C-ring, was the most active, presenting an IC₅₀ much lower than the one found for the most widely prescribed α-glucosidase inhibitor, acarbose. The present work suggests that several of the studied flavonoids have the potential to be used as alternatives for the regulation of PPHG.     

Potential of the luminol reaction in the sensitive detection of pesticide residues by flow injection analysis.

This study presents the first analytical application of the luminol chemiluminescence (CL) reaction for the sensitive detection of carbamate residues. Some experiments have been carried out to check the influence of the presence of traces of a N-methylcarbamate (carbaryl) on the CL emission produced from the oxidation of luminol using different oxidants, showing a significant enhancing effect on the CL emission when the oxidation of luminol is produced by potassium permanganate in alkaline medium, this enhancement being proportional to the carbaryl concentration. This fact has permitted the establishment of a sensitive chemiluminescence flow-injection (CL-FIA) method for the direct determination of carbaryl. The optimization of instrumental and chemical variables influencing the CL response has been carried out by applying experimental designs. Under the optimal conditions, the CL intensity was linear for a carbaryl concentration over the range 5-100 ng/mL with a detection limit of 4.9 ng/mL. This luminol-KMnO4-based FIA-CL system in basic medium shows an easy, fast and cheap alternative detection mode for the analysis of carbaryl residues in environmental water samples.     

DNA vaccination can break immunological tolerance to PrP in wild-type mice and attenuates prion disease after intracerebral challenge

Transmissible spongiform encephalopathies (TSEs) can be ameliorated by prion protein (PrP)-specific antibodies, but active immunization is complicated by immune tolerance to the normal cellular host protein (PrP(C)). Here, we show that DNA immunization of wild-type mice can break immune tolerance against the prion protein, resulting in the induction of PrP-specific antibody and T-cell responses. PrP immunogenicity was increased by fusion to the lysosomal targeting signal from LIMPII (lysosomal integral membrane protein type II). Although mice immunized with a PrP-LIMPII DNA vaccine showed a dramatic delay in the onset of early disease signs after intracerebral challenge, immunization against PrP also had some deleterious effects. These results clearly confirm the feasibility of using active immunization to protect against TSEs and, in the absence of effective treatments, indicate a suitable alternative for combating the spread of these diseases.     

Land Reform and Land-Use Changes in the Lower Amazon: Implications for Agricultural Intensification

Land tenure has been considered one of the key factors that define patterns and change in land-use systems. This paper examines the implications of land reform for household decisions regarding patterns of land use, agricultural intensification, and forest conservation. We look at an Amazonian caboclo settlement in the Lower Amazon that had experienced land reform by the end of the 1980s. Results show that defined land tenure is not enough to guarantee agricultural intensification and forest conservation. In fact, several factors working at different scales are affecting land-use change in the region. At the settlement level, privatization of upland forest has led to an overall increase in cultivated land—pasture and annual crops—and increasing deforestation rates. However, at the farm-property level, different systems of agricultural production—intensive, extensive, or abandonment of land—occur according to availability of labor, and capital, and access to different natural resources.     

Boron deficiency causes accumulation of chlorogenic acid and caffeoyl polyamine conjugates in tobacco leaves

The effects of boron (B) deficiency on carbohydrate concentrations and the pattern of phenolic compounds were studied in leaves of tobacco plants (Nicotiana tabacum L.). Plants grown under B deficiency showed a notable increase in leaf carbohydrates and total phenolic compounds when compared to controls. The qualitative composition of phenolics was analyzed by HPLC-mass spectrometry. The level of caffeate conjugates (i.e., chlorogenic acid) increased in B-deficient plants. In addition, the accumulation of two caffeic acid amides (N-caffeoylputrescine and putative dicaffeoylspermidine) was observed.