Days Of Exposition Research Articles

Unravelling the role of abscisic acid in chilling tolerance of zucchini during postharvest cold storage

Abscisic acid (ABA) is a key phytohormone in the regulation of most stress responses, which especially involve dehydration such as drought, high salinity, and low temperature. Under these stress conditions, plants accumulate ABA that triggers a response to cope with the adverse environment. In this study, we investigated the implication of ABA in the acquisition of chilling tolerance in zucchini during fruit postharvest. For that, we have analyzed ABA biosynthesis and response in fruit of two varieties with different chilling tolerance, ‘Natura’ (cold tolerant) and ‘Sinatra’ (cold sensitive). The results have showed that the biosynthesis of ABA was induced in ‘Natura’ fruit, with an increase of the abscisic aldehyde oxidase activity (AAO), and consequently an accumulation of ABA during the first day of exposition to cold. The levels of ABA showed a significant negative correlation with weight loss and chilling damage, and a positive correlation with firmness. Transcriptional analysis of some genes involved in ABA signaling and response, such as the ABA receptors PYL1 and PYL4, the transcription factors AI5L2/ABF3, NAC072/RD26, ATHB7, bHLH112, and the enzymes KAT2 as well as HDA6, a deacetylase involved in histone modification, presented different expression levels between varieties, showing ‘Natura’ the highest expression in most cases at least at short-term storage. Finally, to corroborate the role of ABA in cold tolerance, 5mM of sodium tungstate (an inhibitor of ABA biosynthesis) was applied to ‘Natura’ fruit and 0.5mM of ABA was applied to ‘Sinatra’ fruit and their postharvest behaviour at low temperature was followed. The treatment with tungstate induced cold-sensitivity in ‘Natura’ fruit, whereas ABA-treated ‘Sinatra’ fruit improved their quality during the storage at 4°C. The results obtained point to ABA as a phytohormone responsible for the acquisition of postharvest cold tolerance.

Survival, physical and physiological changes of Taenia hydatigena eggs under different conditions of water stress

Taenia hydatigena eggs were investigated for morphological and physiological changes under water stress conditions. Fresh eggs were exposed at 31%, 47% and 89% of relative humidity (RH), and survival, size and ultrastructural changes were accounted up to 365 days of exposition. The article shows how each RH environment affects the vitality of the eggs. Results of this study suggest that T. hydatigena eggs have mechanisms to withstand water stress, indicating that the eggs clustering improves protection against desiccation, and that endogenous metabolism using triacylglycerols play an important role in the maintenance of embryo vitality under low, medium and high relative humidity conditions. This contributes to understanding the water stress resistance mechanism in eggs belonging to Taeniidae family. The findings shown herein have provided a basis to better comprehend basic biology and epidemiology of the cysticercosis caused by T. hydatigena.

The influence of TSA and VPA on the in vitro differentiation of bone marrow mesenchymal stem cells into neuronal lineage cells: Gene expression studies.

Epigenetic mechanisms regulate the transcription of genes, which can affect the differentiation of MSCs. The aim of the current work is to determine how the histone deacetylase inhibitors TSA and VPA affect the expression of neuronal lineage genes in a culture of rat MSCs (rMSCs). We analyzed the expression of early neuron marker gene (Tubb3), mature neuron markers genes (Vacht, Th, Htr2a) and the oligodendrocyte progenitor marker gene (GalC). Moreover, changes in the gene expression after three different periods of exposure to TSA and VPA were investigated for the first time. After six days of exposition to TSA and VPA, the expression of Tubb3 and GalC decreased, while the expression of Th increased. The highest increase of VAChT expression was observed after three days of TSA and VPA treatment. A decrease in Htr2a gene expression was observed after TSA treatment and an increase was observed after VPA treatment. We also observed that TSA and VPA inhibited cell proliferation and the formation of neurospheres in the rMSCs culture. The central findings of our study are that TSA and VPA affect the expression of neuronal lineage genes in an rMSCs culture. After exposure to TSA or VPA, the expression of early neuronal gene decreases but equally the expression of mature neuron genes increases. After TSA and VPA treatment ER of the oligodendrocyte progenitor marker decreased. TSA and VPA inhibit cell proliferation and the formation of neurospheres in rMSCs culture.

Edge effect on bird nest predation in the fragmented caldén (Prosopis caldenia) forest of central Argentina: an experimental analysis

AbstractClearing of caldén (Prosopis caldenia) forests for agriculture and cattle raising in east‐central La Pampa Province, central Argentina, has created a highly fragmented landscape, a condition that has resulted in adverse effects on birds in other forests, mainly through increased predation rates near forest edges. We evaluated bird nest predation rates using artificial nests, assessing the effects of forest fragment size, distance to the edge and nest height. We measured survival rate of 570 artificial nests located in trees, in bushes and on the ground, at different distances from the edge, in six forest fragments ranging in size from 2.1 to 117.6 ha, during two consecutive breeding seasons. Nest predation rates were significantly related with the number of days of exposition of the nest, nest height and distance to the edge, whereas fragment size and year of the experiment were not associated with predation rates. Ground nests were less likely to be predated than those located in bushes and trees. Predation rates decreased with the distance to the edge, showing a pattern consistent with the existence of an edge effect.

Iron excess in rice: from phenotypic changes to functional genomics of WRKY transcription factors.

Iron (Fe) is an essential microelement for all living organisms playing important roles in several metabolic reactions. Rice (Oryza sativa L.) is commonly cultivated in paddy fields, where Fe goes through a reduction reaction from Fe3+ to Fe2+. Since Fe2+ is more soluble, it can reach toxic levels inside plant cells, constituting an important target for studies. Here we aimed to verify morphological changes of different rice genotypes focusing on deciphering the underlying molecular network induced upon Fe excess treatments with special emphasis on the role of four WRKY transcription factors. The transcriptional response peak of these WRKY transcription factors in rice seedlings occurs at 4 days of exposition to iron excess. OsWRKY55-like, OsWRKY46, OsWRKY64, and OsWRKY113 are up-regulated in BR IRGA 409, an iron-sensitive genotype, while in cultivars Nipponbare (moderately resistant) and EPAGRI 108 (resistant) the expression profiles of these transcription factors show similar behaviors. Here is also shown that some cis-regulatory elements known to be involved in other different stress responses can be linked to conditions of iron excess. Overall, here we support the role of WRKY transcription factors in iron stress tolerance with other important steps toward finding why some rice genotypes are more tolerant than others.

Thermal and photo-stability of the antioxidant potential of Spirulina platensis powder.

This work aimed to evaluate the thermal and photo stability of the antioxidant potential (AP) of the Spirulina platensis biomass. Thermal stability was established at 25ºC, 40ºC and 50ºC for 60 days, in the dark, protected from light. Photo stability was evaluated using UV (15 W, λ = 265 nm) and fluorescent (20 W, 0.16 A, power factor FP > 0.5, 50/60 Hz, 60 lm/w, 1200 lm) light for 90 days in capsules, glass and Petri dishes, at room temperature. The AP of the biomass in these conditions was determined at intervals (every 7 and 30 days in the studies of thermal and photo stability, respectively) using the induction of the oxidation of a lipid system by heat and aeration. In this lipid system, the biomass submitted to degradation was used as an antioxidant. The kinetics of the reaction was determined by the Arrhenius method. Thermal degradation was found to follow zero order kinetics, whereas photo degradation followed first order kinetics. The AP decreased 50% after 50 days at 25°C. At 40°C and 50°C, the AP decreased more than 50% after 35 and 21 days of exposition, respectively. The decrease of the AP of Spirulina was more sensible to UV and fluorescence light. After 30 days of exposition, the AP decreased more than 50% in all storage conditions tested. The antioxidant potential of Spirulina platensis is easily degraded when the biomass is exposed to heat and light, indicating the need for care to be taken in its storage.

Electrochemical Evaluation of Reinforcement Concrete Exposed to Soil Type SP Contaminated with Sulphates

The present research evaluates the electrochemical behaviour of concrete exposed to SP soil type, sand from marine environment and contaminated with 1, 2 and 3 % de MgSO4, this experimental setup simulates what happens on the foundations of civil infrastructure as bridges, docks, highways, etc., when they are built on contaminated soils with this aggressive agent due to discharges of wastewater, marine waters or areas polluted by agrochemicals. The concrete used in making specimens of study was designed according to the ACI method 211.1, it was considered to design the concrete mixture a ratio w/c=0.65 (f´c=250 kg/cm2), two types of cement, ordinary portland cement (CPC 30R) and sulphate-resisting cement (CPC 30R RS), in the specimens were embedded as reinforcement bars of steel AISI 1018 and Galvanized steel. Ecorr was evaluated according to the standard ASTM C-876-09 and the corrosion kinetics Icorr it was monitored by the technique of Linear Polarization Resistance (LPR), according to standard ASTM G-59-97(2009). The results of Ecorr and Icorr correspond to 266 days of exposition in specimens to SP soil type contaminated with MgSO4 indicating with increasing concentration of aggressive agent to 3% it is considerably decreased the corrosion resistance of the concrete specimens produced with sulphate resisting cement and reinforced with galvanized steel.

Suppositional measures for harmful microalga <i>Pseudo-nitzschia calliantha</i> control in aquaculture farms

Growth of potentially toxic diatom microalga Pseudo-nitzschia calliantha is investigated in laboratory culture under different conditions of cultivation. In the conditions without stirring, the highest abundance of algae was moderate (16131 cells/ml) and observed after 3 days of exposition; many chains of 5-8 cells were formed. Further exposition showed cyclic dynamics of the culture, the chains of 5-12 cells were numerous, chloroplasts looked healthy, their color was olive-green. After stirring, a short lag-phase preceded to the phase of active cells dividing with exponential growth of their number to the peaks of 59828-70566 cells/ml, chains of 2-8 cells were formed but rapidly settled to the vessel bottom, chloroplasts were discrete and bleached that indicated dying of the culture. P. calliantha is potentially toxic species, so the sites with active water circulation or constrained water mixing are recommended for aquaculture farming that protects the environments from its phycotoxins accumulation.

In situ analysis of soybeans and nuts by probe electrospray ionization mass spectrometry.

The probe electrospray ionization (PESI) is an ESI-based ionization technique that generates electrospray from the tip of a solid metal needle. In the present work, we describe the PESI mass spectra obtained by in situ measurement of soybeans and several nuts (peanuts, walnuts, cashew nuts, macadamia nuts and almonds) using different solid needles as sampling probes. It was found that PESI-MS is a valuable approach for in situ lipid analysis of these seeds. The phospholipid and triacylglycerol PESI spectra of different nuts and soybean were compared by principal component analysis (PCA). PCA shows significant differences among the data of each family of seeds. Methanolic extracts of nuts and soybean were exposed to air and sunlight for several days. PESI mass spectra were recorded before and after the treatment. Along the aging of the oil (rancidification), the formation of oxidated species with variable number of hydroperoxide groups could be observed in the PESI spectra. The relative intensity of oxidated triacylglycerols signals increased with days of exposition. Monitoring sensitivity of PESI-MS was high. This method provides a fast, simple and sensitive technique for the analysis (detection and characterization) of lipids in seed tissue and degree of oxidation of the oil samples.

The Selective Serotonin Reuptake Inhibitor-Sertraline Diminishes Conspecific Aggression in Male Fighting <i>Betta splendens</i> Fish

In conspecific type of aggression the modulation of 5-hydroxytryptamine (5-HT) plays a main role. A decrease of 5-HT in the brain intensifies this type of aggression and in contrast, the increase of 5-HT reduces it. The aim of this study was to examine the effects of different concentrations of sertraline HCl on aggressive behavior of Betta splendens male fish. It was concluded that sertraline added to aquarium water in the dose of 0.4, 4.0 and/or 100.0 μg·L-1 BW during 14 days of exposition increased synaptic levels of 5-HT which in turn resulted in reduction of specific aggressive behavior in the environmental concentrations (0.4 μg) and then times higher. Sertraline caused a periodic, and sometimes even total weakening of the male-male type fight, which was a standard trial applied in ethological research on the Siamese fighting fish. In the current study, the most effective one is proved to be the dose of 4.0 μg·L-1 BW (parallel to earlier investigated fluoxetine in the same dose).

Immunotoxicological effects of inorganic arsenic on gilthead seabream (Sparus aurata L.)

Arsenic (As) has been associated with multitude of animal and human health problems; however, its impact on host immune system has not been extensively investigated. In fish, there are very few works on the potential risks or problems associated to the presence of arsenic. In the present study we have evaluated the effects of exposure (30 days) to sub-lethal concentrations of arsenic (5μM As2O3) in the teleost fish gilthead seabream (Sparus aurata), with special emphasis in the innate immune response. The arsenic concentration was determined using atomic fluorescence spectrometry (AFS) in liver and muscle of exposed fish showing As accumulation in the liver after 30 days of exposure. The hepatosomatic index was increased at significant extent after 10 days but returned to control values after 30 days of exposure. Histological alterations in the liver were observed including hypertrophy, vacuolization and cell-death processes. Focusing on the immunological response, the humoral immune parameters (seric IgM, complement and peroxidase activities) were no affected to a statistically significant extent. Regarding the cellular innate parameters, head-kidney leucocyte peroxidase, respiratory burst and phagocytic activities were significantly increased after 10 days of exposition compared to the control fish. Overall, As-exposure in the seabream affects the immune system. How this might interfere with fish biology, aquaculture management or human consumers warrants further investigations. This paper describes, for the first time, the immunotoxicological effects of arsenic exposure in the gilthead seabream, which is a species with the largest production in Mediterranean aquaculture.

Biodistribution and In Vivo Anticancer Effects of Taxol Loaded Magnetic Nanospheres

Taxol (anticancer drug) loaded magnetic nanospheres were prepared and tested in vitro and in vivo in mice. Poly(D,L-lactide-co-glycolide) (PLGA) as polymer matrix for the encapsulation of the drug and magnetic (Fe3O4) particles was used. Pluronic F68 served as a stabilising agent of the polymeric nanospheres. The cytotoxicity of taxol loaded magnetic NPs suspensions towards B16 melanoma cells was investigated. Growth inhibitions of around 90% were reached in three days of exposition. Biodistribution of taxol administered in Cremophor-based injection formula as well as taxol loaded nanosphere compositions was determined in the plasma, selected organs and target tissue. The drug-loaded magnetically labeled nanospheres caused a reduction in tumor weight. A better result was achieved using the composition with higher magnetite/drug weight ratio than in the sample with the smaller ratio which is due to fact that the samples with higher magnetite content were trapped more effectively in target site (tumor) by the external field.

Periphytic algae colonization driven by variable environmental components in a temperate floodplain lake

The colonization of periphytic algae in a temperate floodplain was studied in Lake Sakadas, a part of a fluvial floodplain along the Danube River. An in situ investigation, using artificial substrata, was started after extremely high spring flooding and was carried out during long-lasting summer floods (July–August 2010). The physical and chemical environment was variable and large stands of metaphyton, submersed and floating macrophytes were spread along the lake. The periphyton development was initiated on the first day of exposition and algal abundance increased exponentially till day 27. Directional changes in the relative abundance of algal species, shown by the results of the non-metric multidimensional scaling, indicate a pattern of short-term sequences in algal colonization. The initial attachment of planktonic cyanobacteria and unicellular diatoms (initial phase, days 1–3) to the biofilm matrix was followed by the development of the filamentous chlorophytes, Cladophora glomerata and Oedogonium spp. (intermediate phase, days 6–15) and then by stalk-forming diatoms particularly Gomphonema spp . (late phase, days 18–33). According to the redundancy analyses, water temperature and oscillations of Danube water level that define the flooding pattern had the most significant influence on algal colonization. Flood-induced spreading of metaphyton firstly supported the rapid progress of algal colonization towards a climax community, while later, metaphyton together with macrophytes disrupted algal community by increasing the mechanical injuries, shading and grazing pressure. Consequently, algal abundance and community structure were returned to the intermediate phase of colonization.

Corrosion evaluation of orthodontic wires in artificial saliva solutions by using response surface methodology

In the present work, stainless steel and Ni-Ti commercial orthodontic wires were immersed in artificial saliva solutions, containing or not F- ions, in different pH values, during 30 days. The weight loss and the Ni2+ content in the solutions at 15 and 30 days of exposition were evaluated using a composite design 23 and response surface methodology. The open circuit potential (OCP) was measured over the same period of time. Polarization curves and morpHological analysis of the wires before and after the corrosion experiments were also carried out. The results showed that corrosion of the studied metal alloys depended on a combination among saliva pH, the exposition time, and the concentration of F- ions in the solution. The critical condition was observed for Ni-Ti wires at pH = 3.0, and high concentration of F- ions, causing a decrease in the OCP values and an increase in Ni dissolution and corrosion current density.

Acute and chronic effects of copper and cadmium on oxidative stress biomarkers in Gambusia holbrooki

In this study, the chronic effect of the insecticides carbofuran and deltamethrin on acetylcholinesterase (AChE) activity and malondialdehyde (MDA) and reduced glutathione (GSH) levels were examined in the brain of tench. Both pesticides were evaluated in two separate experiments, and animals were exposed in a continuous flow-system to three different concentrations of carbofuran (0, 10 and 100 μg/L) and deltamethrin (0, 0.0039 and 0.039 μg/L) for 60 days. After that period, animals were kept into pesticide-free water for other 30 days. In all cases, animals were sampled every 10 days all along the experience. AChE activity was significantly inhibited in fish exposed to 100 μg/L of carbofuran, during the first 30 days of exposition, returning to basal levels after this initial period. With respect to deltamethrin exposure, AChE activity was not significantly affected. When considering MDA levels, significant changes could only be detected during the recovery period for both pesticides, with a maximum of induction at 70 and 80 days, respectively associated to the highest dose of carbofuran and deltamethrin. Similarly, GSH levels varied all along the experience, with a maximum of significant increase at day 80 of exposition to the highest dose of both pesticides. This study shows that changes in AChE brain activity in tench can be used as a biomarker of early pesticide exposition in environmental monitoring programs, whereas MDA and GSH levels could be more associated to long-term expositions. The above results confirm and broaden former observations, suggesting that more investigations are needed before these biochemical parameters can be used as biomarkers.

Brain acetylcholinesterase, malondialdehyde and reduced glutathione as biomarkers of continuous exposure of tench, Tinca tinca, to carbofuran or deltamethrin

In this study, the chronic effect of the insecticides carbofuran and deltamethrin on acetylcholinesterase (AChE) activity and malondialdehyde (MDA) and reduced glutathione (GSH) levels were examined in the brain of tench. Both pesticides were evaluated in two separate experiments, and animals were exposed in a continuous flow-system to three different concentrations of carbofuran (0, 10 and 100 μg/L) and deltamethrin (0, 0.0039 and 0.039 μg/L) for 60 days. After that period, animals were kept into pesticide-free water for other 30 days. In all cases, animals were sampled every 10 days all along the experience. AChE activity was significantly inhibited in fish exposed to 100 μg/L of carbofuran, during the first 30 days of exposition, returning to basal levels after this initial period. With respect to deltamethrin exposure, AChE activity was not significantly affected. When considering MDA levels, significant changes could only be detected during the recovery period for both pesticides, with a maximum of induction at 70 and 80 days, respectively associated to the highest dose of carbofuran and deltamethrin. Similarly, GSH levels varied all along the experience, with a maximum of significant increase at day 80 of exposition to the highest dose of both pesticides. This study shows that changes in AChE brain activity in tench can be used as a biomarker of early pesticide exposition in environmental monitoring programs, whereas MDA and GSH levels could be more associated to long-term expositions. The above results confirm and broaden former observations, suggesting that more investigations are needed before these biochemical parameters can be used as biomarkers.

Effect of copper ions on spatial density of NO synthase-positive cells in intestine of the mussel Crenomytilus grayanus (mollusca: bivalvia: mytilidae). A histochemical study

By the histochemical method of detection of NADPH-diaphorase (NADPH-d) (EC 1.6.99.1) the state of nitroxidergic enteric nervous system of the mussel Crenomytilus grayanus was studied under conditions of an increased copper concentration in water. Under the action of copper ions the density of distribution of NADPH-d-positive cells has been established to be changed as compared with control throughout 28 days. A sharp rise of proportion of the labeled cells and their enzyme activity was noted after one day of the experiment. The labeled bipolar cells were of dark blue color and were located within the epithelium. There were revealed numerous nerve fibers penetrating the intestinal epithelium throughout its entire length as well as bipolar nerve cells in epithelium of the minor typhlosole and of crystalline style sac; in control molluscs the NADPH-d-positive cells in these parts were absent. After 7 days the difference between control and experimental decreased and remained at this level after 14 days, while after 21 days of exposition the proportion of labeled cells in the experimental mussels was lower than in control, but increased again after 28 days. It is suggested that nitric oxide is an important protective factor of the intestinal epithelium of the mussel C. grayanus and participates in adaptation of this mollusc to action of the elevated concentration of copper ions in water.

Association between As and Cu renal cortex accumulation and physiological and histological alterations after chronic arsenic intake

Arsenic (As) is one of the most abundant hazards in the environment and it is a human carcinogen. Related to excretory functions, the kidneys in humans, animal models or naturally exposed fauna, are target organs for As accumulation and deleterious effects. Previous studies carried out using X-ray fluorescence spectrometry by synchrotron radiation (SR-microXRF) showed a high concentration of As in the renal cortex of chronically exposed rats, suggesting that this is a suitable model for studies on renal As accumulation. This accumulation was accompanied by a significant increase in copper (Cu) concentration. The present study focused on the localization of these elements in the renal cortex and their correlation with physiological and histological As-related renal effects. Experiments were performed on nine male Wistar rats, divided into three experimental groups. Two groups received 100 microg/ml sodium arsenite in drinking water for 60 and 120 consecutive days, respectively. The control group received water without sodium arsenite (< 50 ppb As). For histological analysis, 5-mum-thick sections of kidneys were stained with hematoxylin and eosin. Biochemical analyses were used to determine concentrations of plasma urea and creatinine. The As and Cu mapping were carried out by SR-microXRF using a collimated white synchrotron spectrum (300 microm x 300 microm) on kidney slices (2 mm thick) showing As and Cu co-distribution in the renal cortex. Then, renal cortical slices (100 microm thick) were scanned with a focused white synchrotron spectrum (30 microm x 30 microm). Peri-glomerular accumulation of As and Cu at 60 and 120 days was found. The effects of 60 days of arsenic consumption were seen in a decreased Bowman's space as well as a decreased plasma blood urea nitrogen (BUN)/creatinine ratio. Major deleterious effects; however, were seen on tubules at 120 days of exposition. This study supports the hypothesis that tubular accumulation of As-Cu may have some bearing on the arsenic-associated nephrotoxicological process.

Responses of Antioxidant Systems After Exposition to Rare Earths and Their Role in Chilling Stress in Common Duckweed (Lemna minor L.): A Defensive Weapon or a Boomerang?

Extensive agriculture application of rare earth elements (REEs) in Far East countries might cause spreading of these metals in aquatic and terrestrial ecosystems, thus inducing a growing concern about their environmental impact. In this work the effects of a mix of different REE nitrate (RE) and of lanthanum nitrate (LA) on catalase and antioxidant systems involved in the ascorbate-glutathione cycle were investigated in common duckweed Lemna minor L. The results indicated that L. minor shows an overall good tolerance to the presence of REEs in the media. Treatments at concentrations up to 5 mM RE and 5 mM LA did not cause either visible symptoms on plants or significant effects on reactive oxygen species (ROS) production, chlorophyll content, and lipid peroxidation. Toxic effects were observed after 5 days of exposition to 10 mM RE and 10 mM LA. A remarkable increase in glutathione content as well as in enzymatic antioxidants was observed before the appearance of the stress symptoms in treated plants. Duckweed plants pretreated with RE and LA were also exposed to chilling stress to verify whether antioxidants variations induced by RE and LA improve plant resistance to the chilling stress. In pretreated plants, a decrease in ascorbate and glutathione redox state and in chlorophyll content and an increase in lipid peroxidation and ROS production levels were observed. The use of antioxidant levels as a stress marker for monitoring REE toxicity in aquatic ecosystems by means of common duckweed is discussed.

Morphological investigation of respiratory tract in rats affected by nitrogen dioxide

The study was performed in 120 Wistar male rats. Animals were exposed to nitrogen dioxide for 15, 30, 60 or 90 days. Ten intact rats were as controls for each exposed group. Histological examination was performed using immunohistochemistry and morphometry. Pathological changes developed simultaneously in all lung structures. After 15-day exposition with nitrogen dioxide, acute changes have been observed, such as oedema, mucosal thickening and inflammation, enhanced bronchial secretion. In 30 days, morphological features reflected a subacute stage. In 60 days of exposition, inflammation became chronic with sclerosis of bronchial wall followed by worsening of the pathology and occurrence of panacinar emphysema if exposition was prolonged to 90 days.