Experimental Evidence that 3-Methylglutaric Acid Disturbs Mitochondrial Function and Induced Oxidative Stress in Rat Brain Synaptosomes: New Converging Mechanisms

3-Methylglutaric acid (3MGA) is an organic acid that accumulates in various organic acidemias whose patients present neurodegeneration events in children coursing with metabolic acidurias. Limited evidence describes the toxic mechanisms elicited by 3MGA in the brain. Herein, we explored the effects of 3MGA on different toxic endpoints in synaptosomal and mitochondrial-enriched fractions of adult rat brains to provide novel information on early mechanisms evoked by this metabolite. At 1 and 5 mM concentration, 3MGA increased lipid peroxidation, but decreased mitochondrial function only at 5 mM concentration. Despite less intense effects were obtained at 1 mM concentration, its co-administration with the kynurenine pathway (KP) metabolite and N-methyl-d-aspartate receptor (NMDAr) agonist, quinolinic acid (QUIN, 50 and 100 µM), produced toxic synergism on markers of oxidative stress and mitochondrial function. The toxicity of 3MGA per se (5 mM) was prevented by the cannabinoid receptor agonist WIN55,212-2 and the NMDAr antagonist kynurenic acid (KYNA), suggesting cannabinoid and glutamatergic components in the 3MGA pattern of toxicity. The synergic model (3MGA?+?QUIN) was also sensitive to KYNA and the antioxidant S-allylcysteine, but not to the nitric oxide synthase inhibitor l-nitroarginine methyl ester. These findings suggest various underlying mechanisms involved in the neurotoxicity of 3MGA that may possibly contribute to the neurodegeneration observed in acidemias.     

A resurrection experiment finds evidence of both reduced genetic diversity and potential adaptive evolution in the agricultural weed Ipomoea purpurea

Despite the negative economic and ecological impact of weeds, relatively little is known about the evolutionary mechanisms that influence their persistence in agricultural fields. Here, we use a resurrection approach to examine the potential for genotypic and phenotypic evolution in Ipomoea purpurea, an agricultural weed that is resistant to glyphosate, the most widely used herbicide in current‐day agriculture. We found striking reductions in allelic diversity between cohorts sampled nine years apart (2003 vs. 2012), suggesting that populations of this species sampled from agricultural fields have experienced genetic bottleneck events that have led to lower neutral genetic diversity. Heterozygosity excess tests indicate that these bottlenecks may have occurred prior to 2003. A greenhouse assay of individuals sampled from the field as seed found that populations of this species, on average, exhibited modest increases in herbicide resistance over time. However, populations differed significantly between sampling years for resistance: some populations maintained high resistance between the sampling years whereas others exhibited increased or decreased resistance. Our results show that populations of this noxious weed, capable of adapting to strong selection imparted by herbicide application, may lose genetic variation as a result of this or other environmental factors. We probably uncovered only modest increases in resistance on average between sampling cohorts due to a strong and previously identified fitness cost of resistance in this species, along with the potential that nonresistant migrants germinate from the seed bank.     

Feeding habits of the swordfish (<Emphasis Type="Italic">Xiphias gladius</Emphasis> Linnaeus, 1758) in the subtropical northeast Pacific

Most of the studies carried out in the past on economically important fish species rely on single species approach. Ecosystem dynamics are characterized by complex interaction among species, sharing common habitat needs and thus forming characteristic assemblages. The analysis of spatio-temporal variability of fish community, coupled to the analysis of spatial indices, provides a synthetic view of the fish community status evidencing, if any, the way a community changes. Such considerations drive also to the development of ecosystem-based fishery management paradigm. In the present study changes in pelagic fish community structure in an upwelling ecosystem of the central Mediterranean Sea during the last 10 years was analysed, by focusing the attention on the five most abundant small pelagic species: Engraulis encrasicolus, Sardina pilchardus, Sardinella aurita, Trachurus trachurus and Boops boops. Our results evidenced a quite stable community structure, characterized by spatial occupation strongly driven by ecosystem characteristics and modulated according to specie-specific behaviour. Obtained results lead us to hypothesize that the observed stability of community could be linked to the presence of different environments leading to efficient space partitioning and resources utilization among species.     

Changes in the levels of human tropomyosins IEF 52,55, and 56 do not correlate with the loss of actin cables observed in SV 40 transformed MRC-5 fibroblasts

Summary A mouse monoclonal antibody (mAb 1D122G9) raised against human tropomyosin IEF 52 (HeLa protein catalogue number, Mr=35 kd) has been characterized both in terms of specificity and patterns of immunofluorescence staining in Triton extracted cultured cells. As determined by two dimensional gel immunoblotting of HeLa cell proteins the antibody recognized IEF 52 and two other acidic proteins (IEF 55, Mr=31.8 kd; IEF 56, Mr=31 kd) previously identified as putative tropomyosin-like proteins. Immunofluorescence staining of Triton extracted cultured cells revealed the striated or interrupted pattern on the actin cables characteristic of tropomyosin staining. Quantitation of the three tropomyosins in Triton cytoskeletons from normal and SV 40 transformed human MRC-5 fibroblasts showed that the latter contained significantly less of tropomyosin IEF's 52 (52%) and 56 (72%) as compared to their normal counterparts. The ratios of these two tropomyosins to actin however was very similar for both types of cytoskeletons. This was not the case for tropomyosin IEF 55, which was present in nearly twice the amount in the cytoskeletons from the SV 40 transformed cells. The ratio of actin to total tropomyosin for whole cells was found to be unchanged on transformation. This ratio however was 31% lower in the cytoskeletons from the transformed cells. These and other results presented here suggest that changes in the levels of these three tropomyosins are not enough to account for the magnitude of the loss of actin cables observed in the transformed cells.Abbreviations IEF isoelectric focusing - mAb monoclonal antibody - NEPHGE non equilibrium pH gradient electrophoresis     

Patterns of oviposition by Sandia xami (Lepidoptera, Lycaenidae) in relation to food plant apparency

ABSTRACT.

• 1 The butterfly Sandia xami (Reakirt) has a very clumped yearly pattern of oviposition on its food plant Echeveria gibbiflora D.C., and the mean number of eggs per plant is always very low.
• 2 Three features of host plants are highly associated with the probability of being oviposited upon: height of plant; degree of conspicuousness; and degree of isolation from conspecific plants.
• 3 The relative importance of these factors as predictors of the probability of oviposition change according to the time scale considered: height and conspicuousness are more important over short (weekly) time intervals whilst isolation takes precedence over longer (yearly) periods.
• 4 It is hypothesized that the clumped pattern of oviposition is responsible for the low numbers of the butterflies relative to their very abundant food plant.

     

Contrasting responses of cluster roots formation induced by phosphorus and nitrogen supply in Embothrium coccineum populations from different geographical origin

Plant and Soil - Embothrium coccineum is a pioneer tree that produces cluster roots (CR) induced by phosphorus (P) or nitrogen (N) deficiency, but the role which both N and P play in CR formation...     

Riparian Conservation Facilitated Expansion of Gray Hawks

Desert riparian ecosystems are among the most threatened biodiversity hotspots in the United States, and efforts to conserve them have been increasing. In 2010–2011 and 2014–2016, we examined shifts in the distribution, habitat characteristics, diet, nest success, and productivity of the gray hawk (Buteo plagiatus), 25 years after a Riparian National Conservation Area was established along the San Pedro River in Arizona, USA, to determine how the removal of grazing and agriculture may have affected the ecosystem. The gray hawk population increased and expanded from mesquite (Prosopis spp.)-dominated areas that they historically occupied into areas that were dominated by grassland. In contrast with the 1990s, percent of mesquite cover in pairs' territories did not correlate with their productivity. Gray hawk diets also included more mammals in our study period, particularly in territories with more grassland. We propose that conservation measures created habitat for gray hawks in areas that were previously unsuitable by allowing grasslands to regenerate and become habitat for their prey, and that management strategies in the San Pedro Riparian National Conservation Area could serve as a model for conservation of other desert riparian ecosystems. © 2020 The Wildlife Society.     

Deep evolutionary diversification of semicircular canals in archosaurs

Download : Download video (66MB)     

Protective effects of diphenyl diselenide in a mouse model of brain toxicity

Interest in organoselenide chemistry and biochemistry has increased in the past three decades, mainly due to their chemical and biological activities. Here, we investigated the protective effect of the organic selenium compound diphenyl diselenide (PhSe)₂ (5 μmol/kg), in a mouse model of methylmercury (MeHg)-induced brain toxicity. Our group has previously demonstrated that the oral and repeated administration (21 days) of MeHg (40 mg/L) induced MeHg brain accumulation at toxic concentrations, and a pattern of severe cortical and cerebellar biochemical and behavioral. In order to assess neurotoxicity, the neurochemical parameters, namely, mitochondrial complexes I, II, II–III and IV, glutathione peroxidase (GPx) and glutathione reductase (GR) activities, the content of thiobarbituric acid-reactive substances (TBA-RS), 8-hydroxy-2′-deoxyguanosine (8-OHdG), and brain-derived neurotrophic factor (BDNF), as well as, metal deposition were investigated in mouse cerebral cortex. Cortical neurotoxicity induced by brain MeHg deposition was characterized by the reduction of complexes I, II, and IV activities, reduction of GPx and increased GR activities, increased TBA-RS and 8-OHdG content, and reduced BDNF levels. The daily treatment with (PhSe)₂ was able to counteract the inhibitory effect of MeHg on mitochondrial activities, the increased oxidative stress parameters, TBA-RS and 8-OHdG levels, and the reduction of BDNF content. The observed protective (PhSe)₂ effect could be linked to its antioxidant properties and/or its ability to reduce MeHg deposition in brain, which was here histochemically corroborated. Altogether, these data indicate that (PhSe)₂ could be consider as a neuroprotectant compound to be tested under neurotoxicity.