Aglomerularism in Harpagifer bispinis: a subantarctic notothenioid fish living at reduced salinity

We investigated the renal morphology, histology and ultrastructure of Harpagifer bispinis, as a first step toward understanding the morpho-functional basis of its adaptation to potentially freezing brackish seawater. Fish were separated into two groups of ten individuals each, and acclimated to 2 and 38 salinity. A study of complete serial sections of the kidney revealed that the nephrons were aglomerular. At the highly convoluted proximal segment two different regions were evident, a feature that has not been previously reported for other aglomerular species. In electron photomicrographs we distinguished light and dark cells in the proximal tubule epithelium, with highly infolded basolateral membranes and closely associated mitochondria. The dark cells also had a large number of mitochondria in the apical region. The intercellular spaces at the epithelium of the proximal tubule were larger in fish acclimated at 2 salinity, a modification that might facilitate urine secretion, thus contributing to the survival of an aglomerular fish in a hyposmotic medium.     

Mitochondrial dysfunction due to in vitro exposure to atrazine and its metabolite in striatum

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) has been described as a potential toxic for dopaminergic metabolism both in vivo and in vitro. Its main metabolite diamino-chloro triazine (DACT) has been shown to achieve higher levels in brain tissue than atrazine. The aim of this study was to evaluate the in vitro effects of atrazine and DACT on striatal mitochondrial function, active oxygen species generation, and nitric oxide (NO) content. Incubation of mitochondria with atrazine (10 µM) was not able to modify oxygen consumption. However, a 50% increase in malate-glutamate state 4 respiratory rates was observed after DACT treatment (100 µM) without changes in respiratory state 3. Atrazine was able to inhibit complex I–III activity by 30% and DACT induced a tendency to decrease by 17% in the striatum. Regarding reactive oxygen species (ROS), DACT increased H₂O₂ production by 43%. Also, superoxide anion levels were higher (14%) after atrazine exposure than in control mitochondria. Incubation of striatal mitochondria with atrazine and DACT induced membrane depolarization by 15% and 19%, respectively. Also, atrazine increased NO content by 10% but no significant changes were observed after exposure of mitochondria to DACT. Glutathione peroxidase activity was inhibited (56%) by DACT and atrazine inhibited superoxide dismutase activity by 60%. Also, cardiolipin oxidation (15%) was observed after atrazine treatment. Summing up, the obtained results suggest that in vitro atrazine and DACT induce ROS production affecting striatal mitochondrial function. The atrazine effects would be attributed to a direct effect on the mitochondrial respiratory chain and superoxide dismutase activity while DACT appears to disturb glutathione-related enzyme system.     

Acidosis improves uptake of antigens and MHC class I-restricted presentation by dendritic cells

It is widely appreciated that inflammatory responses in peripheral tissues are usually associated to the development of acidic microenvironments. Despite this, there are few studies aimed to analyze the effect of extracellular pH on immune cell functions. We analyzed the impact of acidosis on the behavior of dendritic cells (DCs) derived from murine bone marrow. We found that extracellular acidosis (pH 6.5) markedly stimulated the uptake of FITC-OVA, FITC-dextran, and HRP by DCs. In fact, to reach similar levels of endocytosis, DCs cultured at pH 7.3 required concentrations of Ag in the extracellular medium almost 10-fold higher compared with DCs cultured at pH 6.5. Not only the endocytic capacity of DCs was up-regulated by extracellular acidosis, but also the expression of CD11c, MHC class II, CD40, and CD86 as well as the acquisition of extracellular Ags by DCs for MHC class I-restricted presentation. Importantly, DCs pulsed with Ag under acidosis showed an improved efficacy to induce both specific CD8(+) CTLs and specific Ab responses in vivo. Our results suggest that extracellular acidosis improves the Ag-presenting capacity of DCs.     

Osmotic and specific ion effects on the germination of Prosopis strombulifera

BACKGROUND AND AIMS: Salinity can affect germination of seeds either by creating osmotic potentials that prevent water uptake or by toxic effects of specific ions. Most studies have only used monosaline solutions, although these limit the extent to which one can interpret the results or relate them to field conditions. The aim of this work was to evaluate the germination of Prosopis strombulifera seeds under increasing salinity by using the most abundant salts in central Argentina in monosaline or bisaline iso-osmotic solutions, or in solutions of mannitol and polyethylene glycol. METHODS: Seeds were allowed to germinate under controlled conditions in a germination chamber at 30 +/- 1 degrees C and at 80 % r.h. Salinizing agents were KCl, NaCl, Na(2)SO(4), K(2)SO(4), NaCl + Na(2)SO(4) and KCl + K(2)SO(4) and osmotic agents were polyethylene glycol 6000 and mannitol. Treatments for all osmotica consisted of 0.0, -0.4, -0.8, -1.2, -1.5, -1.9 and -2.2 MPa solutions. KEY RESULTS: The percentage of germination decreased as salinity increased. SO(4)(2-) in monosaline solutions, with osmotic potentials -1.2 MPa and lower, was more inhibitory than Cl(-) at iso-osmotic concentrations. This SO(4)(2-) toxicity was alleviated in salt mixtures and was more noticeable in higher concentrations. K(+) was more inhibitory than Na(+) independently of the accompanying anion. CONCLUSIONS: Different responses to different compositions of iso-osmotic salt solutions and to both osmotic agents indicate specific ionic effects. This study demonstrates that the germination of P. strombulifera is strongly influenced by the nature of the ions in the salt solutions and their interactions. Comparative studies of Cl(-) and SO(4)(2-) effects and the interaction between SO(4)(2-) and Cl(-) in salt mixtures indicate that extrapolation of results obtained with monosaline solutions in the laboratory to field conditions can be speculative.     

The sex ratio distortion in the human head louse is conserved over time

Background

At the turn of the 19^th century the first observations of a female-biased sex ratio in broods and populations of the head louse, Pediculus humanus capitis, had been reported. A study by Buxton in 1940 on the sex ratio of lice on prisoners in Ceylon is still today the subject of reanalyses. This sex ratio distortion had been detected in ten different countries. In the last sixty years no new data have been collected, especially on scalp infestations under economically and socially more developed conditions.

Results

Here we report a female bias of head lice in a survey of 480 school children in Argentina. This bias is independent of the intensity of the pediculosis, which makes local mate competition highly unlikely as the source of the aberrant sex ratio; however, other possible adaptive mechanisms cannot be discounted. These lice as well as lice from pupils in Britain were carrying several strains of the endosymbiotic bacterium Wolbachia pipientis, one of the most wide spread intracellular sex ratio distorters. Similar Wolbachia strains are also present in the pig louse, Haematopinus suis, suggesting that this endosymbiont might have a marked influence on the biology of the whole order. The presence of a related obligate nutritional bacterium in lice prevents the investigation of a causal link between sex ratio and endosymbionts.

Conclusions

Regardless of its origin, this sex ratio distortion in head lice that has been reported world wide, is stable over time and is a remarkable deviation from the stability of frequency-dependent selection of Fisher's sex ratio. A female bias first reported in 1898 is still present over a hundred years and a thousand generations later.

     

Cytogenetic comparison of Podocnemis expansa and Podocnemis unifilis: A case of inversion and duplication involving constitutive heterochromatin

Podocnemis expansa and P. unifilis present 2n = 28 chromosomes, a diploid number similar to those observed in other species of the genus. The aim of this study was to characterize these two species using conventional staining and differential CBG-, GTG and Ag-NOR banding. We analyzed specimens of P. expansa and P. unifilis from the state of Tocantins (Brazil), in which we found a 2n = 28 and karyotypes differing in the morphology of the 13^th pair, which was submetacentric in P. expansa and telocentric in P. unifilis. The CBG-banding patterns revealed a heterochromatic block in the short arm of pair 13 of P. expansa and an interstitial one in pair 13 of P. unifilis, suggesting a pericentric inversion. Pair 14 of P. unifilis showed an insterstitial band in the long arm that was absent in P. expansa, suggesting a duplication in this region. Ag-NORs were observed in the first chromosome pair of both species and was associated to a secondary constriction and heterochromatic blocks.     

Sheep grazing differentially affects the canopy attributes and functional diversity of shrubs and perennial grasses in arid rangelands

Plant Ecology - We analysed how changes in community attributes promoted by domestic grazing are reflected on functional traits in canopies of shrubs and perennial grasses in rangelands of the...     

Isolation of a Aspergillus niger lipase from a solid culture medium with aqueous two-phase systems

The aim of this work is to find the best conditions to isolate lipase from a solid culture medium of Aspergillus niger NRRL3 strains using aqueous two-phase systems formed with polyethylene glycol and potassium phosphate or polyethylene glycol and sodium citrate. We studied the partitioning of a commercial lyophilizate from A. niger. Also, the lipase enzymatic activity was studied in all the phases of the systems and the results indicate that citrate anion increases lipase activity. An analysis by fluorescence spectroscopy of the interaction between lipase and the bottom and top phases of the systems shows that the protein tryptophan-environments are modified by the presence of PEG and salts. Separation of the enzyme from the rest of the proteins that make up the lyophilized was achieved with good yield and separation factor by ATPS formed by PEG 1000/Pi at pH 7, PEG 2000/Ci at pH 5.2 and PEG 4000/Ci at pH 5.2. The above mentioned systems were used in order to isolate extracellular lipase from a strain of A. niger in submerged culture and solid culture. The best system for solid culture, with high purification factor (30.50), is the PEG 4000/Ci at pH 5.2. The enzyme was produced in a solid culture medium whose production is simple and recovered in a phase poor in polymer, bottom phase. An additional advantage is that the citrate produces less pollution than the phosphate. This methodology could be used as a first step for the isolation of the extracellular lipase from A. niger.     

Track analysis of the North and Central American species of the Pantomorus–Naupactus complex (Coleoptera: Curculionidae)

We undertook a panbiogeographic analysis of the broad‐nosed weevils of the genera Naupactus Dejean, 1821, Pantomorus Schönherr, 1840 and Phacepholis Horn, 1876 (Coleoptera: Curculionidae) from North and Central America to propose a biogeographic scenario to explain their biotic diversification. Based on individual tracks of 30 species, we obtained six generalized tracks: Mesoamerican, Chiapas, Sierra Madre del Sur, Mexican Pacific Coast, Southern Great Plains and Northern Great Plains tracks. The Sierra Madre del Sur generalized track is the best supported, based on 10 species of the three genera. We found two nodes, one at the intersection of the Mesoamerican and Chiapas tracks, and another at the intersection of the Chiapas and Sierra Madre del Sur tracks. Species of Naupactus are primarily distributed in lowlands, associated mostly with dry forests and xeric environments. Species of Pantomorus and Phacepholis would have diversified from South American Naupactus‐like ancestors, mainly in montane habitats and lowlands of North and Central America, between sea level to about 2500 m of altitude.     

Evidence of the coevolution of antigenicity and host cell tropism of foot-and-mouth disease virus in vivo

In this work we analyze the antigenic properties and the stability in cell culture of virus mutants recovered upon challenge of peptide-vaccinated cattle with foot-and-mouth disease virus (FMDV) C3 Arg85. Previously, we showed that a significant proportion of 29 lesions analyzed (41%) contained viruses with single amino acid replacements (R141G, L144P, or L147P) within a major antigenic site located at the G-H loop of VP1, known to participate also in interactions with integrin receptors. Here we document that no replacements at this site were found in viruses from 12 lesions developed in six control animals upon challenge with FMDV C3 Arg85. Sera from unprotected, vaccinated animals exhibited poor neutralization titers against mutants recovered from them. Sequence analyses of the viruses recovered upon 10 serial passages in BHK-21 and FBK-2 cells in the presence of preimmune (nonneutralizing) sera revealed that mutants reverted to the parental sequence, suggesting an effect of the amino acid replacements in the interaction of the viruses with cells. Parallel passages in the presence of subneutralizing concentrations of immune homologous sera resulted in the maintenance of mutations R141G and L147P, while mutation L144P reverted to the C3 Arg85 sequence. Reactivity with a panel of FMDV type C-specific monoclonal antibodies indicated that mutant viruses showed altered antigenicity. These results suggest that the selective pressure exerted by host humoral immune response can play a role in both the selection and stability of antigenic FMDV variants and that such variants can manifest alterations in cell tropism.