Thermal biology and locomotor performance of the Andean lizard Liolaemus fitzgeraldi (Liolaemidae) in Argentina

Ectotherms thermoregulate to maintain their body temperature within the optimal range needed for performing vital functions. The effect of climate change on lizards has been studied as regards the sensitivity of locomotor performance to environmental temperatures. We studied thermoregulatory efficiency and locomotor performance for Liolaemus fitzgeraldi in the Central Andes of Argentina. We determined body temperature, micro-environmental temperatures and operative temperatures in the field. In the laboratory, we measured preferred temperatures and calculated the index of thermoregulatory efficiency. We estimated the thermal sensitivity of locomotion by measuring sprint speed (initial velocity and long sprint) and endurance at five different body temperatures. Body temperature was not associated with either micro-environmental temperature, nor did it show differences with preferred temperatures. Thermoregulatory efficiency was moderate (0.61). Initial velocity and long sprint trials showed differences at different temperatures; however, endurance did not. Moreover, the optimal temperatures for the performance trials showed no significant differences among themselves. We conclude that Liolaemus fitzgeraldi has thermal sensitivity in locomotor performance with respect to body temperature and that it is an eurythermic lizard that experiences a large variation in body temperature and that has thermal flexibility in the cold.     

Ionotropic Receptors as a Driving Force behind Human Synapse Establishment

The origin of nervous systems is a main theme in biology and its mechanisms are largely underlied by synaptic neurotransmission. One problem to explain synapse establishment is that synaptic orthologs are present in multiple aneural organisms. We questioned how the interactions among these elements evolved and to what extent it relates to our understanding of the nervous systems complexity. We identified the human neurotransmission gene network based on genes present in GABAergic, glutamatergic, serotonergic, dopaminergic, and cholinergic systems. The network comprises 321 human genes, 83 of which act exclusively in the nervous system. We reconstructed the evolutionary scenario of synapse emergence by looking for synaptic orthologs in 476 eukaryotes. The Human–Cnidaria common ancestor displayed a massive emergence of neuroexclusive genes, mainly ionotropic receptors, which might have been crucial to the evolution of synapses. Very few synaptic genes had their origin after the Human–Cnidaria common ancestor. We also identified a higher abundance of synaptic proteins in vertebrates, which suggests an increase in the synaptic network complexity of those organisms.     

Differential proliferative response of the ventral prostate and seminal vesicle to testosterone replacement

We have investigated epithelial cell proliferation and the rate of glandular recovery of the ventral prostate (VP) and seminal vesicle (SV) promoted by testosterone replacement (TR) in castration-induced regressed glands. Adult male Wistar rats were castrated and, after 21 days, they were treated with testosterone propionate (4 mg/kg/day). Intact (CT) and castrated rats without TR (CS) were also analysed. VP and SV were processed for histochemistry, morphometric-stereological analysis and immunocytochemistry to determine the PCNA index (PI). After 10 days of TR, the VP weight reached approximately 72% of the CT values, while the SV weight exceeded approximately 17% of the CT values. By the third day of TR, VP and SV presented a mean PI of 34% and 94% for distal region and 14% and 22% for proximal region, respectively. SV also had more luminal cells PCNA-positive than VP, mainly in the distal region. The PI values fell on days 5, 7 and 10, but were still higher than CT. These findings indicate that epithelial cells from involuted SV are more responsive to TR than those from VP when stimulated to proliferate and replace the luminal cell population, suggesting a different mechanism regulating cell proliferation in response to androgenic stimuli.     

Symptoms induced by transgenic expression of p23 from Citrus tristeza virus in phloem‐associated cells of Mexican lime mimic virus infection without the aberrations accompanying constitutive expression

Citrus tristeza virus (CTV) is phloem restricted in natural citrus hosts. The 23‐kDa protein (p23) encoded by the virus is an RNA silencing suppressor and a pathogenicity determinant. The expression of p23, or its N‐terminal 157‐amino‐acid fragment comprising the zinc finger and flanking basic motifs, driven by the constitutive 35S promoter of cauliflower mosaic virus, induces CTV‐like symptoms and other aberrations in transgenic citrus. To better define the role of p23 in CTV pathogenesis, we compared the phenotypes of Mexican lime transformed with p23‐derived transgenes from the severe T36 and mild T317 CTV isolates under the control of the phloem‐specific promoter from Commelina yellow mottle virus (CoYMV) or the 35S promoter. Expression of the constructs restricted to the phloem induced a phenotype resembling CTV‐specific symptoms (vein clearing and necrosis, and stem pitting), but not the non‐specific aberrations (such as mature leaf epinasty and yellow pinpoints, growth cessation and apical necrosis) observed when p23 was ectopically expressed. Furthermore, vein necrosis and stem pitting in Mexican lime appeared to be specifically associated with p23 from T36. Phloem‐specific accumulation of the p23Δ158–209(T36) fragment was sufficient to induce the same anomalies, indicating that the region comprising the N‐terminal 157 amino acids of p23 is responsible (at least in part) for the vein clearing, stem pitting and, possibly, vein corking in this host.     

Stoichiometric modeling of oxidation of reduced inorganic sulfur compounds (Riscs) in Acidithiobacillus thiooxidans

The prokaryotic oxidation of reduced inorganic sulfur compounds (RISCs) is a topic of utmost importance from a biogeochemical and industrial perspective. Despite sulfur oxidizing bacterial activity is largely known, no quantitative approaches to biological RISCs oxidation have been made, gathering all the complex abiotic and enzymatic stoichiometry involved. Even though in the case of neutrophilic bacteria such as Paracoccus and Beggiatoa species the RISCs oxidation systems are well described, there is a lack of knowledge for acidophilic microorganisms. Here, we present the first experimentally validated stoichiometric model able to assess RISCs oxidation quantitatively in Acidithiobacillus thiooxidans (strain DSM 17318), the archetype of the sulfur oxidizing acidophilic chemolithoautotrophs. This model was built based on literature and genomic analysis, considering a widespread mix of formerly proposed RISCs oxidation models combined and evaluated experimentally. Thiosulfate partial oxidation by the Sox system (SoxABXYZ) was placed as central step of sulfur oxidation model, along with abiotic reactions. This model was coupled with a detailed stoichiometry of biomass production, providing accurate bacterial growth predictions. In silico deletion/inactivation highlights the role of sulfur dioxygenase as the main catalyzer and a moderate function of tetrathionate hydrolase in elemental sulfur catabolism, demonstrating that this model constitutes an advanced instrument for the optimization of At. thiooxidans biomass production with potential use in biohydrometallurgical and environmental applications. Biotechnol. Bioeng. 2013; 110: 2242–2251. © 2013 Wiley Periodicals, Inc.     

A food web analysis of the Río de la Plata estuary and adjacent shelf ecosystem: trophic structure,biomass flows,and the role of fisheries

This article performed a comprehensive assessment of the structure and functioning of the Río de la Plata estuary and adjacent shelf ecosystem, including the effect of fishing. A formerly implemented 37 trophic groups’ mass-balance model (Ecopath) was used to (1) evaluate the particular role of individual biotic components on the ecosystem; (2) characterize the ecosystem in terms of aquatic food web theory; and (3) assess the role of diverse fishing fleets on the ecosystem. Our results indicate a trophic structure and functioning common to other estuaries, where outstanding primary production exceeds consumption, and detritus accumulates in the system. Moreover, our analysis revealed an elevated total system throughput, herbivory outweighing detritivory, and an intermediate state in terms of ecosystem growth and development. Fisheries analyses showed widespread impacts produced by industrial bottom trawl fleets, and specific impacts produced by artisanal fisheries over several groups. Unexpectedly, the evaluation of the effects of fishing showed minor ecosystem consequences by the loss of secondary production and suggests exploitation rates at sustainable levels. This study sets up the basis for temporal ecosystem-level monitoring of the state of the Río de la Plata estuary and adjacent shelf ecosystem.