Physiological flexibility and climate change: The case of digestive function regulation in lizards

Our planet is undergoing fast environmental changes, which are referred as global change. In this new scenario, it is of paramount relevance to understand the mechanistic basis of animal responses to environmental change. Here we analyze to what extent seasonal changes in the digestive function of the lizard Liolaemus moradoensis is under endogenous (i.e., hard wired) or exogenous (i.e., environmentally determined) control. For this purpose we compared animals collected in the field during autumn, winter and summer, against (experimental) specimens collected in the field at the beginning of autumn and reared in the laboratory under simulated summer conditions until winter. We found that different aspects of the digestive function are under different types of control: small intestine length appears to be under endogenous control (i.e., experimental animals were similar to winter animals), small intestine mass appears to be under exogenous control (i.e., experimental animals were similar to summer animals), and specific enzyme activities did not change throughout the year. Thus, we suspect that processes related with gut length, such as cell division, may be under endogenous control, while others related with gut mass, such as enterocyte size and content, may be determined by exogenous factors, such as the presence of food in the intestinal lumen. Faced with accelerated changing conditions, the ability of vertebrates to cope will be closely related with their plasticity in fitness-associated traits. More studies aimed at determining the levels and limits of physiological flexibility will be necessary to understand this phenomenon.     

Electron Transport Activities of Isolated Thylakoids from Wheat Plants Grown in Salicylic Acid

Abstract: Wheat ( Triticum aestivum cv. Sonalika) plants were grown with three different concentrations of salicylic acid (SA; 50/500/1000 μM) for 7 days and the effects on the level of thylakoid photochemical activities were examined. SA treatment stimulated photosystem II-catalyzed electron flow in all concentrations tested. Photosystem I-associated electron transport activity was stimulated at low concentrations of SA (50 μM) but at higher concentrations (500 and 1000 μM) the electron transport activity was drastically attenuated. Thylakoids isolated from the leaves of seedlings grown with high concentrations of SA (500 and 1000 μM) showed a substantial reduction in uncoupler (NH₄Cl)-mediated stimulation in electron flow. In addition, they failed to support ADP-dependent stimulation of electron transport activity and induced a significant reduction in ATPase activity. Incubation of isolated thylakoids with SA, however, had no effect on thylakoid photofunction, indicating no direct effect of SA on photoelectron transport activity. Furthermore, high concentrations of SA specifically reduce the thylakoid cytochrome f₅₅₄ level. The results suggest that SA, depending on its concentration, imparts differential effects on the photofunction of thylakoids. A low concentration of SA favours photosynthetic activity while the high concentration induces drastic attenuation of photosynthetic activity because of the decline in cytochrome f₅₅₄.     

Environmental signaling and evolutionary change: can exposure of pregnant mammals to environmental estrogens lead to epigenetically induced evolutionary changes in embryos?

DNA methylation is one of the epigenetic and hereditary mechanisms regulating genetic expression in mammalian cells. In this review, we propose how certain natural agents, through their dietary consumption, could induce changes in physiological aspects in mammalian mothers, leading to alterations in DNA methylation patterns of the developing fetus and to the emergence of new phenotypes and evolutionary change. Nevertheless, we hypothesize that this process would require (i) certain key periods in the ontogeny of the organism where the environmental stimuli could produce effects, (ii) particular environmental agents as such stimuli, and (iii) that a genomic persistent change be consequently produced in a population. Depending on the persistence of the environmental stimuli and on whether the affected genes are imprinted genes, induced changes in DNA methylation patterns could become persistent. Moreover, some fragments could be more frequently methylated than others over several generations, leading to biased base change and evolutionary consequences.     

In silico modeling and hydrogen peroxide binding study of rice catalase

Homology modeling of the catalase, CatC cloned and sequenced from rice (Oryza sativa L., cv Ratna an Indica cultivar) has been performed based on the crystal structure of the catalase CatF (PDB code 1m7s) by using the software MODELLER. With the aid of molecular mechanics and molecular dynamics methods, the final model is obtained and is further assessed by PROCHECK and VERIFY - 3D graph, which show that the final refined model is reliable. With this model, a flexible docking study with the hydrogen peroxide, the substrate for catalase, is performed and the results indicate that Arg310, Asp343 and Arg346 in catalase are three important determinant residues in binding as they have strong hydrogen bonding contacts with the substrate. These hydrogen-bonding interactions play an important role for the stability of the complex. Our results may be helpful for further experimental investigations.     

Gastrointestinal and renal responses to water intake in the green-backed firecrown (Sephanoides sephanoides), a South American hummingbird

To maintain water balance, nectar-feeding vertebrates oscillate between meeting the challenges of avoiding overhydration and preventing dehydration. To understand how green-backed firecrowns (Sephanoides sephanoides) accomplish this, we examined the response of water-handling processes in the gastrointestinal tract (GIT) and kidney to different rates of water intake during the evening, night, and morning. Fractional water absorption in the GIT was independent of water intake rate (evening: 0.91 +/- 0.08; morning: 0.88 +/- 0.04). Consistent with this nonregulated water absorption, we found linear increases in water flux, fractional turnover of body water, and the rate of renal water loading as water intake rate increased during both the evening and morning. Despite these relationships, glomerular filtration rate (GFR) was insensitive to water loading (evening: 2.08 +/- 0.56 ml/h; morning: 1.84 +/- 0.68 ml/h) and less than the allometric expectation (2.92 ml/h). During the evening, fractional renal water reabsorption decreased linearly as the rate of water intake increased. At night, a period of natural fasting for hummingbirds, mean GFR was not different from zero (0.00 +/- 0.05 ml/h). These findings indicate that green-backed firecrowns eliminate excess ingested water by decreasing water reabsorption in the kidney; to conserve water, it appears that hummingbirds arrest whole kidney GFR, effectively preventing urinary water losses. After discounting evaporative water losses, our results show that hummingbirds rely principally on their renal system to resolve the osmoregulatory quandary posed by nectarivory.     

Computational analysis of the Phanerochaete chrysosporium v2.0 genome database and mass spectrometry identification of peptides in ligninolytic cultures reveal complex mixtures of secreted proteins

The white-rot basidiomycete Phanerochaete chrysosporium employs extracellular enzymes to completely degrade the major polymers of wood: cellulose, hemicellulose, and lignin. Analysis of a total of 10,048 v2.1 gene models predicts 769 secreted proteins, a substantial increase over the 268 models identified in the earlier database (v1.0). Within the v2.1 'computational secretome,' 43% showed no significant similarity to known proteins, but were structurally related to other hypothetical protein sequences. In contrast, 53% showed significant similarity to known protein sequences including 87 models assigned to 33 glycoside hydrolase families and 52 sequences distributed among 13 peptidase families. When grown under standard ligninolytic conditions, peptides corresponding to 11 peptidase genes were identified in culture filtrates by mass spectrometry (LS-MS/MS). Five peptidases were members of a large family of aspartyl proteases, many of which were localized to gene clusters. Consistent with a role in dephosphorylation of lignin peroxidase, a mannose-6-phosphatase (M6Pase) was also identified in carbon-starved cultures. Beyond proteases and M6Pase, 28 specific gene products were identified including several representatives of gene families. These included 4 lignin peroxidases, 3 lipases, 2 carboxylesterases, and 8 glycosyl hydrolases. The results underscore the rich genetic diversity and complexity of P. chrysosporium's extracellular enzyme systems.     

Cytokine gene polymorphisms and atopic disease in two European cohorts. (ECRHS-Basel and SAPALDIA)

Background

Avoidance of allergens is still recommended as the first and best way to prevent allergic illnesses and their comorbid diseases. Despite a variety of attempts there has been very limited success in the area of environmental control of allergic disease. Our objective was to identify a non-invasive, non-pharmacological method to reduce indoor allergen loads in atopic persons' homes and public environments. We employed a novel in vivo approach to examine the possibility of using aluminum sulfate to control environmental allergens.

Methods

Fifty skin test reactive patients were simultaneously skin tested with conventional test materials and the actions of the protein/glycoprotein modifier, aluminum sulfate. Common allergens, dog, cat, dust mite, Alternaria, and cockroach were used in the study.

Results

Skin test reactivity was significantly reduced by the modifier aluminum sulfate. Our studies demonstrate that the effects of histamine were not affected by the presence of aluminum sulfate. In fact, skin test reactivity was reduced independent of whether aluminum sulfate was present in the allergen test material or removed prior to testing, indicating that the allergens had in some way been inactivated.

Conclusion

Aluminum sulfate was found to reduce the in vivo allergic reaction cascade induced by skin testing with common allergens. The exact mechanism is not clear but appears to involve the alteration of IgE-binding epitopes on the allergen. Our results indicate that it may be possible to diminish the allergenicity of an environment by application of the active agent aluminum sulfate, thus producing environmental control without complete removal of the allergen.     

Digestive plasticity in tadpoles of the Chilean giant frog (Caudiverbera caudiverbera): factorial effects of diet and temperature

Anuran metamorphosis is one of the most spectacular processes in nature. Metamorphosis entails morphological transformations and extensive changes in feeding habits, such as transforming from an herbivore to a carnivore. This phenomenon is especially sensitive to environmental cues. We studied the phenotypic plasticity of intestinal morphology and enzyme activity in tadpoles of the Chilean giant frog Caudiverbera caudiverbera. We tested the effects of diet and temperature using a factorial design, which included a control of nontreated individuals. There was no significant effect of diet treatment (i.e., low- vs. high-quality diet) on any of the measured variables, including external morphology. We found significant effects of temperature on morphological traits. Temperature treatment also had significant effects on aminopeptidase-N and maltase activity. Both enzymes exhibited complex interactions with temperature along the intestine. Gut size varied significantly among temperatures, with intestines from warm-treated individuals smaller than the intestines from control and cold-treated tadpoles. Our findings suggest that phenotypic plasticity of intestinal morphology and physiology exists in larvae of this species, at least in response to temperature. However, we did not detect clear effects of diet or temperature on the timing of metamorphosis.     

The effect of amyloidogenic peptides on bacterial aging correlates with their intrinsic aggregation propensity

The formation of aggregates by misfolded proteins is thought to be inherently toxic, affecting cell fitness. This observation has led to the suggestion that selection against protein aggregation might be a major constraint on protein evolution. The precise fitness cost associated with protein aggregation has been traditionally difficult to evaluate. Moreover, it is not known if the detrimental effect of aggregates on cell physiology is generic or depends on the specific structural features of the protein deposit. In bacteria, the accumulation of intracellular protein aggregates reduces cell reproductive ability, promoting cellular aging. Here, we exploit the cell division defects promoted by the intracellular aggregation of Alzheimer's-disease-related amyloid β peptide in bacteria to demonstrate that the fitness cost associated with protein misfolding and aggregation is connected to the protein sequence, which controls both the in vivo aggregation rates and the conformational properties of the aggregates. We also show that the deleterious impact of protein aggregation on bacterial division can be buffered by molecular chaperones, likely broadening the sequential space on which natural selection can act. Overall, the results in the present work have potential implications for the evolution of proteins and provide a robust system to experimentally model and quantify the impact of protein aggregation on cell fitness.     

Synergistic effect of surfactin from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> C4 and <Emphasis Type="Italic">Achyrocline satureioides</Emphasis> extracts on the viability of <Emphasis Type="Italic">Paenibacillus larvae</Emphasis>

The aim of this work was to determine the in vitro effect of the mixture between the lipopeptide surfactin, synthesized by Bacillus subtilis C4 (strain isolated from honey) and the most active vegetal extract from Achyrocline satureioides, a traditional medicinal plant, on local strains of Paenibacillus larvae, the agent of American Foulbrood in honeybees. Five P. larvae strains isolated in Córdoba, Argentina, were phenotypically characterized. These and 12 other P. larvae strains from different regions of Argentina were analysed. The antimicrobial activities of the essential oil, hexane (HE) and benzene extracts from A. satureioides were assessed against P. larvae and the HE showed the highest anti-P. larvae activity. A combination of the biosurfactant surfactin, produced by B. subtilis C4, and the HE of A. satureioides revealed a synergistic action on P. larvae. The effective surfactin concentration in the mixture decreased from 32 to 1 μg ml⁻¹ and the HE concentration from 32 to 4 μg ml⁻¹, values similar or equal to minimal inhibitory concentrations observed for oxytetracycline. The fractional inhibitory concentration index confirmed synergism in 4 strains and partial synergism in one strain. The combination of surfactin synthesized by B. subtilis C4 and the HE from A. satureioides could be a natural alternative to help beekeepers to combat the American foulbrood agent P. larvae.