The effects of food quantity,light, and temperature on clearance rates in freshwater bivalves (Cyrenidae and Unionidae)

Hydrobiologia - Assessing the environmental variables that influence freshwater bivalve filtration activity is key to better understand the functioning of stream ecosystems. In the present study,...     

Distribution and Chemical Composition of Lignin in Secondary Xylem of Cactaceae

Cactaceae family has heterogeneity in the accumulation of lignocellulose due to the diversity of shapes and anatomy of the wood. Most studies focus on fibrous and dimorphic species; but the non-fibrous species are poorly studied. The aims of this work were to analyze the syringyl/guaiacyl ratio of lignin and its distribution in secondary xylem, especially in non-fibrous species. The syringyl/guaiacyl (S/G) ratio was quantified from 34 species of cacti by nitrobenzene oxidation of free-extractive wood. The distribution of lignocellulose in wood sections stained with safranin O/fast green was determined with epifluorescence microscopy. The S/G ratio was heterogeneous; most of the non-fibrous species had a higher percentage of syringyl, while the fibrous ones accumulate guaiacyl. Fluorescence emission showed that vessel elements and wide-band tracheids had similar tonalities. It is hypothesized that the presence of a higher percentage of syringyl in most cacti is part of the defense mechanism against pathogens, which together with the succulence of the stem represent adaptations that contribute to survival in their hostile environments.     

Extracellular ferritin contributes to neuronal injury in an in vitro model of ischemic stroke

Journal of Physiology and Biochemistry - Previous clinical and experimental studies have shown that neurological decline and poor functional outcome after acute ischemic stroke in humans are...     

The citrus plant pathogen Xanthomonas citri has a dual polyamine-binding protein

ATP-Binding Cassette transporters (ABC transporters) are protein complexes involved in the import and export of different molecules, including ions, sugars, peptides, drugs, and others. Due to the diversity of substrates, they have large relevance in physiological processes such as virulence, pathogenesis, and antimicrobial resistance. In Xanthomonas citri subsp. citri, the phytopathogen responsible for the citrus canker disease, 20% of ABC transporters components are expressed under infection conditions, including the putative putrescine/polyamine ABC transporter, PotFGHI. Polyamines are ubiquitous molecules that mediate cell growth and proliferation and play important role in bacterial infections. In this work, we characterized the X. citri periplasmic-binding protein PotF (XAC2476) using bioinformatics, biophysical and structural methods. PotF is highly conserved in Xanthomonas sp. genus, and we showed it is part of a set of proteins related to the import and assimilation of polyamines in X. citri. The interaction of PotF with putrescine and spermidine was direct and indirectly shown through fluorescence spectroscopy analyses, and experiments of circular dichroism (CD) and small-angle X-ray scattering (SAXS), respectively. The protein showed higher affinity for spermidine than putrescine, but both ligands induced structural changes that coincided with the closing of the domains and increasing of thermal stability.     

Sumoylation of AMPKβ2 subunit enhances AMP-activated protein kinase activity

AMP-activated protein kinase (AMPK) is a sensor of cellular energy status. It is a heterotrimer composed of a catalytic α and two regulatory subunits (β and γ). AMPK activity is regulated allosterically by AMP and by the phosphorylation of residue Thr-172 within the catalytic domain of the AMPKα subunit by upstream kinases. We present evidence that the AMPKβ2 subunit may be posttranslationally modified by sumoylation. This process is carried out by the E3-small ubiquitin-like modifier (SUMO) ligase protein inhibitor of activated STAT PIASy, which modifies the AMPKβ2 subunit by the attachment of SUMO2 but not SUMO1 moieties. Of interest, AMPKβ1 is not a substrate for this modification. We also demonstrate that sumoylation of AMPKβ2 enhances the activity of the trimeric α2β2γ1 AMPK complex. In addition, our results indicate that sumoylation is antagonist and competes with the ubiquitination of the AMPKβ2 subunit. This adds a new layer of complexity to the regulation of the activity of the AMPK complex, since conditions that promote ubiquitination result in inactivation, whereas those that promote sumoylation result in the activation of the AMPK complex.     

The ovaries of aphids (Hemiptera,Sternorrhyncha, Aphidoidea): morphology and phylogenetic implications

The ovaries of aphids belonging to the families Eriosomatidae, Anoeciidae, Drepanosiphidae, Thelaxidae, Aphididae, and Lachnidae were examined at the ultrastructural level. The ovaries of these aphids are composed of several telotrophic ovarioles. The individual ovariole is differentiated into a terminal filament, tropharium, vitellarium, and pedicel (ovariolar stalk). Terminal filaments of all ovarioles join together into the suspensory ligament, which attaches the ovary to the lobe of the fat body. The tropharium houses individual trophocytes and early previtellogenic oocytes termed arrested oocytes. Trophocytes are connected with the central part of the tropharium, the trophic core, by means of broad cytoplasmic processes. One or more oocytes develop in the vitellarium. Oocytes are surrounded by a single layer of follicular cells, which do not diversify into distinct subpopulations. The general organization of the ovaries in oviparous females is similar to that of the ovaries in viviparous females, but there are significant differences in their functioning: (1) in viviparous females, all ovarioles develop, whereas in oviparous females, some of them degenerate; (2) the number of germ cells per ovariole is usually greater in females of the oviparous generation than in females of viviparous generations; (3) in oviparous females, oocytes in the vitellarium develop through three stages (previtellogenesis, vitellogenesis, and choriogenesis), whereas in viviparous females, the development of oocytes stops after previtellogenesis; and (4) in the oocyte cytoplasm of oviparous females, lipid droplets and yolk granules accumulate, whereas in viviparous females, oocytes accrue only lipid droplets. Our results indicate that a large number of germ cells per ovariole represent the ancestral state within aphids. This trait may be helpful in inferring the phylogeny of Aphidoidea.     

Absolute Quantification of E1, Ubiquitin-Like Proteins and Nedd8–MLN4924 Adduct by Mass Spectrometry

Ubiquitin (Ub) and ubiquitin-like (Ubl) proteins regulate a variety of important cellular processes by forming covalent conjugates with target proteins or lipids. Ubl conjugation is catalyzed by a cascade of proteins including activating enzymes (E1), conjugating enzymes (E2), and in many cases ligation enzymes (E3). The discovery of MLN4924 (Brownell et al., Mol Cell 37: 102–111, 1), an investigational small molecule that is a mechanism-based inhibitor of NEDD8-activating enzyme (NAE), reveals a promising strategy of targeting E1/Ubl pathway for therapeutic purposes. In order to better understand, the biochemical dynamics of Ubl conjugation in cells and tissues, we have developed a mass spectrometry-based method to quantify E1 and Ubls using isotope-labeled proteins as internal standards. Furthermore, we have used the described method to quantify levels of the covalent Nedd8-inhibitor adduct formed in MLN4924 treated cells and tissues. The Nedd8–MLN4924 adduct is a tight-binding inhibitor of NAE, and its cellular concentration represents an indirect pharmacodynamic readout of NAE/Nedd8 pathway inhibition.     

Molecular phylogenetic diversity in the widespread lizard Cercosaura ocellata (Reptilia: Gymnophthalmidae) in South America

For a long time, Cercosaura ocellata was considered polytypic, with three subspecies: C. ocellata ocellata, C. ocellata petersi and C. ocellata bassleri. Recently, C. ocellata bassleri was elevated to full species, based on analysis of a few molecular samples from Peru. This species complex is widely distributed in South America, occurring in Amazonia, Cerrado, Atlantic forest and Pampa biomes. The monophyly and species diversity of C. ocellata are still unstudied. Here, we infer phylogenetic relationships and species diversity of this group analysing 2326 base pairs of three mitochondrial (12S, 16S, and ND4) and one nuclear (c-mos) genes. Our taxon sampling of 115 specimens includes 72 samples of C. ocellata and sequences of other Cercosaura species and closely related Cercosaurinae. Maximum likelihood phylogenetic analysis recovered the monophyly of Cercosaura and that of C. ocellata with strong support. Our analyses suggest that C. ocellata is a complex of cryptic species, which possibly started diversifying in Amazonia.     

Prolonged lifespan with enhanced exploratory behavior in mice overexpressing the oxidized nucleoside triphosphatase hMTH1

The contribution that oxidative damage to DNA and/or RNA makes to the aging process remains undefined. In this study, we used the hMTH1‐Tg mouse model to investigate how oxidative damage to nucleic acids affects aging. hMTH1‐Tg mice express high levels of the hMTH1 hydrolase that degrades 8‐oxodGTP and 8‐oxoGTP and excludes 8‐oxoguanine from both DNA and RNA. Compared to wild‐type animals, hMTH1‐overexpressing mice have significantly lower steady‐state levels of 8‐oxoguanine in both nuclear and mitochondrial DNA of several organs, including the brain. hMTH1 overexpression prevents the age‐dependent accumulation of DNA 8‐oxoguanine that occurs in wild‐type mice. These lower levels of oxidized guanines are associated with increased longevity and hMTH1‐Tg animals live significantly longer than their wild‐type littermates. Neither lipid oxidation nor overall antioxidant status is significantly affected by hMTH1 overexpression. At the cellular level, neurospheres derived from adult hMTH1‐Tg neural progenitor cells display increased proliferative capacity and primary fibroblasts from hMTH1‐Tg embryos do not undergo overt senescence in vitro. The significantly lower levels of oxidized DNA/RNA in transgenic animals are associated with behavioral changes. These mice show reduced anxiety and enhanced investigation of environmental and social cues. Longevity conferred by overexpression of a single nucleotide hydrolase in hMTH1‐Tg animals is an example of lifespan extension associated with healthy aging. It provides a link between aging and oxidative damage to nucleic acids.