Trypanosoma cruzi: attachment to perimicrovillar membrane glycoproteins of Rhodnius prolixus

Studies were carried out to identify proteins involved in the interface of Trypanosoma cruzi with the perimicrovillar membranes (PMM) of Rhodnius prolixus. Video microscopy experiments demonstrated high level of adhesion of T. cruzi Dm 28c epimastigotes to the surface of posterior midgut cells of non-treated R. prolixus. The parasites however were unable to attach to gut cells obtained from decapitated or azadirachtin-treated insects. The influence of carbohydrates on the adhesion to insect midgut was confirmed by inhibition of parasite attachment after midgut incubation with N-acetylgalactosamine, N-acetylmannosamine, N-acetylglucosamine, D-galactose, D-mannose or sialic acid. We observed that hydrophobic proteins in the surface of epimastigotes bind to polypeptides with 47.7, 45.5, 44, 43, 40.5, 36, 31 and 13kDa from R. prolixus PMM and that pre-incubation of lectins specifically inhibited binding to 31, 40.5, 44 and 45.5kDa proteins. We suggest that glycoproteins from PMM and hydrophobic proteins from epimastigotes are important for the adhesion of the parasite to the posterior midgut cells of the vector.     

Colocalization of synaptic GABAC-receptors with GABAA-receptors and glycine-receptors in the rodent central nervous system

Fast inhibition in the nervous system is preferentially mediated by GABA- and glycine-receptors. Two types of ionotropic GABA-receptor, the GABA_A-receptor and GABA_C-receptor, have been identified; they have specific molecular compositions, different sensitivities to GABA, different kinetics, and distinct pharmacological profiles. We have studied, by immunocytochemistry, the synaptic localization of glycine-, GABA_A-, and GABA_C-receptors in rodent retina, spinal cord, midbrain, and brain-stem. Antibodies specific for the α1 subunit of the glycine-receptor, the γ2 subunit of the GABA_A-receptor, and the ρ subunits of the GABA_C-receptor have been applied. Using double-immunolabeling, we have determined whether these receptors are expressed at the same postsynaptic sites. In the retina, no such colocalization was observed. However, in the spinal cord, we found the colocalization of glycine-receptors with GABA_A- or GABA_C-receptors and the colocalization of GABA_A- and GABA_C-receptors in approximately 25% of the synapses. In the midbrain and brain-stem, GABA_A- and GABA_C-receptors were colocalized in 10%–15% of the postsynaptic sites. We discuss the possible expression of heteromeric (hybrid) receptors assembled from GABA_A- and GABA_C-receptor subunits. Our results suggest that GABA_A- and GABA_C-receptors are colocalized in a minority of synapses of the central nervous system.     

Sporulation and diversity of arbuscular mycorrhizal fungi in Brazil Pine in the field and in the greenhouse

The aim of this work was to assess the sporulation and diversity of arbuscular mycorrhizal fungi (AMF) at different forest sites with Araucaria angustifolia (Bert.) O. Ktze. (Brazil Pine). In addition, a greenhouse experiment was carried out to test the use of traditional trap plants (maize + peanut) or A. angustifolia to estimate the diversity of AMF at each site. Soil samples were taken in two State Parks at southwestern Brazil: Campos do Jordão (Parque Estadual de Campos do Jordão [PECJ]) and Apiaí (Parque Estadual Turístico do Alto Ribeira [PETAR]), São Paulo State, in sites of either native or replanted forest. In PECJ, an extra site of replanted forest that was impacted by accidental fire and is now in a state of recuperation was also sampled. The spore densities and their morphological identification were compiled at each site. In the greenhouse, soil samples from each site were used as inoculum to promote spore multiplication on maize + peanut or A. angustifolia grown on a sandy, low-fertility substrate. Plants were harvested, respectively, after 4 months or 1 year of growth and assessed for mycorrhizal root colonization. Spore counts and identification were also performed in the substrate, after the harvest of plants. Twenty-five taxa were identified considering all sites. Species richness and diversity were greater in native forest areas, being Acaulospora, the genus with the most species. Differences in number of spores, diversity, and richness were found at the different sites of each State Park. Differences were also found when maize + peanut or A. angustifolia were used as trap plants. The traditional methodology using trap plants seems to underestimate the diversity of the AMF. The use of A. angustifolia as trap plant showed similar species richness to the field in PECJ, but the identified species were not necessarily the same. Nevertheless, for PETAR, both A. angustifolia and maize + peanut underestimated the species richness. Because the AMF sporulation can be affected by many conditions, it is impossible to draw detailed conclusions from this kind of survey. More precise experiments have to be set up to isolate the different factors that modulate the ecophysiological interactions between host plant and endophyte.     

Seasonal variation of suicide in Brazil

Most of what is known about the seasonal variation in suicide rate originates from studies conducted in the northern hemisphere; very few studies have been done in the southern hemisphere. The purpose of the present study was to explore the possibility that in Brazil, the seasonal variation of suicides is a function of photoperiod. This was accomplished by analyzing monthly suicide data for a 12 yr period (1979 to 1990), within latitudes ranging from 2°N to 33°S. Single cosinor analyses with periods of 12 or 6 months were applied to time series of monthly total and suicidal deaths, separated by gender and state. Significant spring or early summer peaks of suicide were found only in the south of Brazil for both men and women, except for the latter in one state. These peaks did not coincide with those found for total deaths, which occurred in the autumn or winter in all areas. No significant six-month period was found. In the present study, the chance of a suicide was typically 10-17% higher during the peak period than during the other months of the year. Although this moderate seasonal effect might not be sufficient to justify planning large scale prophylactic interventions, those dealing with patients who have suicide ideation should be aware of this high risk time.     

Omega-3 effects on electrocorticographic patterns of adult Wistar rats exposed to ionizing radiation

This study aimed to assess the effect of supplementation with omega-3 in Wistar rats exposed to ionizing radiation in a dose of 18 Gy on the cortical electrical activity, using mathematical methods such as the power spectrum (PS) and the detrended fluctuation analysis (DFA) in the evaluation of the electrocorticogram (ECoG) record. The PS analysis showed that in non-irradiated animals but supplemented with omega-3 there was a decrease in the power of the beta rhythm, while the DFA applied to different frequency ranges of the ECoG showed a significant increase in the long-range correlation only for the theta wave when compared with non-supplemented animals. In the evaluation of the radiation effect through the PS, an increase in the power of the theta rhythm was observed in both groups (non-supplemented and supplemented animals) only when they were evaluated one week after irradiation. The DFA method also showed difference in this wave. The PS and DFA methods applied to the ECoG record allowed a quantitative analysis of the cortical electrical activity in rats in response to the omega-3 effects, ionizing radiation, or both.     

Using predator feces as a repellent for free-ranging urban capybaras (Hydrochoerus hydrochaeris)

acta ethologica - Biological repellents have been used as a control method to mitigate human-wildlife conflict worldwide. We aimed to evaluate the effect of jaguar (Panthera onca) feces as a...     

Essential Oil from Bark of Aniba parviflora (Meisn.) Mez (Lauraceae) Reduces HepG2 Cell Proliferation and Inhibits Tumor Development in a Xenograft Model

Aniba parviflora (Meisn .) Mez (Lauraceae) is an aromatic plant of the Amazon rainforest, which has a tremendous commercial value in the perfumery industry; it is popularly used as flavoring sachets and aromatic baths. In Brazilian folk medicine, A. parviflora is used to treat victims of snakebites. Herein, we analyzed the chemical composition of A. parviflora bark essential oil (EO) and its effect on the growth of human hepatocellular carcinoma HepG2 cells in vitro and in vivo. EO was obtained by hydrodistillation and characterized by GC-MS and GC-FID. The main constituents of EO were linalool (16.3±3.15), α-humulene (14.5±2.41 %), δ-cadinene (10.2±1.09 %), α-copaene (9.51±1.12 %) and germacrene B (7.58±2.15 %). Initially, EO's cytotoxic effect was evaluated against five cancer cell lines (HepG2, MCF-7, HCT116, HL-60 and B16-F10) and one non-cancerous one (MRC-5), using the Alamar blue method after 72 h of treatment. The calculated IC₅₀ values were 9.05, 22.04, >50, 15.36, 17.57, and 30.46 μg/mL, respectively. The best selectivity was for HepG2 cells with a selective index of 3.4. DNA Fragmentation and cell cycle distribution were quantified in HepG2 cells by flow cytometry after a treatment period of 24 and 48 h. The effect of EO on tumor development in vivo was evaluated in a xenograft model using C.B-17 SCID mice engrafted with HepG2 cells. In vivo tumor growth inhibition of HepG2 xenograft at the doses of 40 and 80 mg/kg were 12.1 and 62.4 %, respectively.     

Extremely low-frequency magnetic fields can impair spermatogenesis recovery after reversible testicular damage induced by heat

Male infertility is often related to reproductive age couples experiencing fertility-related issues. Men may have fertility problems associated with reversible testicular damage. Considering that men have been increasingly exposed to extremely low-frequency magnetic fields generated by the production, distribution and use of electricity, this study analyzed whether 60?Hz and 1?mT magnetic field exposure may impair spermatogenesis recovery after reversible testicular damage induced by heat shock using rats as an experimental model. Adult male rats were subjected to a single testicular heat shock (HS, 43?°C for 12?min) and then exposed to the magnetic field for 15, 30 and 60?d after HS. Magnetic field exposure during the spermatogenesis recovery induced changes in testis components volume, cell ultrastructure and histomorphometrical parameters. Control animals had a reestablished and active spermatogenesis at 60?d after heat shock, while animals exposed to magnetic field still showed extensive testicular degeneration. Magnetic field exposure did not change the plasma testosterone. In conclusion, extremely low-frequency magnetic field may be harmful to fertility recovery in males affected by reversible testicular damage.