Toxic effects of the cylindrospermopsin and chlorpyrifos combination on the differentiated SH-SY5Y human neuroblastoma cell line

Due to climate change and anthropogenic activities, the levels of pollution of aquatic and terrestrial environments have increased in the last decades. In this sense, the rise of cyanobacterial blooms, which release secondary metabolites with toxic properties, and the global use of pesticides for agricultural purposes have a negative impact on ecosystems. Thus, it would be interesting to study the concomitance of both types of toxicants in the same sample, since it is possible that they appear together. The aim of the present work was to state the effects of the interaction between the cyanotoxin cylindrospermopsin and the pesticide chlorpyrifos in differentiated SH-SY5Y neuronal cells to assess how they could affect the nervous system. To this end, cytotoxicity, morphological, and acetylcholinesterase activity studies were performed during 24 and 48 h. The results revealed a concentration-dependent decrease in viability and interaction between both toxicants, together with clear signs of apoptosis and necrosis induction. In this sense, different stages on the differentiation process would lead to differences in the toxicity exerted by the compounds both isolated as in combination, which it is not observed in non-differentiated cells. Additionally, the acetylcholinesterase activity appeared not to be affected, which is a clear difference compared to non-differentiated cells. These results show the importance of studying not only the toxicants themselves, but also in combination, to assess their possible effects in a more realistic scenario.

Human Motor Noise Assessed by Electromagnetic Sensors and Its Relationship with the Degrees of Freedom Involved in Movement Control

Motor variability is a prominent feature of the human movement that, nowadays, can be easily measured through different sensors and analyzed using different types of variables, and it seems to be related to functional and adaptative motor behavior. It has been stated that motor variability is related to the system's flexibility needed to choose the right degrees of freedom (DoFs) to adapt to constant environmental changes. However, the potential relationship between motor variability and DoFs is unknown. The aim of this study was to analyze how motor variability, both the amount and structure, changes depending on the mechanical DoFs involved in the movement control. For this purpose, movement variability was assessed by a tracking sensor in five tasks with different DoFs, and the amount, using standard deviation, and the structure of variability, through fuzzy entropy and detrended fluctuation analysis, were also assessed. The results showed a higher amount of variability and a less predictable and more auto-correlated variability structure in the long-term when more mechanical DoFs are implied. The studies that analyze motor variability should consider the type of movement and the DoFs involved in the analyzed task since, as the findings have shown, both factors have a noticeable influence on the amount and the structure of motor variability.

Variations induced by the use of unstable surface do not facilitate motor adaptation to a throwing skill

Induced variability by the use of unstable surfaces has been proposed to enhance proprioceptive control to deal with perturbations in the support base better. However, there is a lack of evidence about its benefits facilitating motor adaptions in upper body skills. In this experiment, practice on an unstable surface was applied to analyze the adaptations in an upper limb precision throwing skill. After a pretest, twenty-one participants were randomly allocated into two groups: one group practiced the throwing task on a stable surface and the other group practiced the same task on an unstable support base. Differences in throwing performance between pre- and post-practice were analyzed in accuracy, hand movement kinematics and variability of the throw in both surface conditions. Fuzzy entropy of the horizontal force was calculated to assess the complexity dynamics of postural sway. Participants improved their performance on the stable and the unstable surface. Induced variability using an unstable surface reduced participants' variability and the complexity of postural sway, but it did not facilitate a superior adaptation of the throwing task. The results suggest that the variations induced by unstable surfaces would fall far from the family of specific motor solutions and would not facilitate additional motor performance of the throwing task.

The use of non-linear tools to analyze the variability of force production as an index of fatigue: A systematic review

Background: Fatigue is a process that results in a decreased ability to produce force, and which could eventually affect performance and increase the risk of injury. Force variability analysis has been proposed to describe the level of fatigue with the purpose of detecting the development of fatigue. Variability is credited to play a functional and adaptive role through which the components of a system self-organize to solve a motor problem. Non-linear tools have been applied to analyze the variability of physiological signals, revealing that the structure of motor fluctuations provides relevant information about the functional role of variability. It has been suggested that the presence of lower complexity in the variability structure could reveal a less functional and adaptative state (e.g., ageing or illness). In the last years, an increased number of studies have applied these techniques to force variability analysis in relation to fatigue. Objective: To provide an overview of the current knowledge on the use of non-linear tools on force variability as a fatigue index. Methods: Following PRISMA guidelines, a systematic search of SPORTDiscus, Scopus, Web of Science and PubMed was carried out. Studies included were: a) original studies that analyzed the effect of fatigue on humans during an action focused on force production; b) published studies with their title and abstract in English; c) studies that applied non-linear tools on a signal directly related to force production. Results: Twenty-five studies were included in this review. The relationship between fatigue and the complexity of force variability, the type of action and relative intensity, the nature of the signal and the non-linear tools used, and the methods of data acquisition and processing were identified. Conclusion: The articles reviewed suggest that fatigue leads to a decrease in complexity mostly in isometric contractions, but this is not as clear in dynamic contractions. This fatigue-induced loss of complexity seems to be a result of changes in the nervous system at the central level, albeit triggered by peripheral mechanisms. It should be noted that non-linear tools are affected by the relative intensity of contraction, non-stationarity, and the acquisition and treatment of the signal.

The effect of enhanced variability after performance stabilization through constant practice

There is a controversy about the benefits of variable practice on motor learning. This study aimed to analyze the effect of variable practice after the learner stabilized their performance. Thirty-two healthy adults performed a computer-simulated discrete accuracy task in which they had to release a virtual ball to try to hit a target. After a pre-test, the participants were distributed into three training groups: constant practice, variable practice and a group that started practicing in constant conditions, and when their performance stabilized, changed to variable practice. The participants performed 44 sets of 10 repetitions of the task. A post-test and two retention tests were carried out. Variable practice did not show a significant improvement compared to constant practice. Variable practice did not show higher benefits even when performance was stabilized through constant practice, but its effects seem to be modulated by the initial variability of the learners.

Postural control strategies are revealed by the complexity of fractional components of COP

The complexity of the center of pressure (COP) provides important information regarding the underlying mechanisms of postural control. The relationships between COP complexity and balance performance are not fully established and might depend on the task constraints and the filtering decomposition of the COP signal. This study assessed COP complexity under different task constraints and it was assessed if emergent dynamics of COP fluctuations differ according to fractional components of COP related to peripheral or central adjustments. One hundred and sixty-two participants performed two sitting balance tasks. Accuracy was required by following a target that moved in the mediolateral (ML) or in the anteroposterior (AP) axis. Complexity dynamics of COP were addressed through Detrended Fluctuation Analysis (DFA) in the axis constrained by accuracy requirements and in the one non-constrained. Decomposition of COP components was applied by low-pass, band-pass and high-pass filters. DFA of low-pass and band-pass components of COP in the constrained axis were small-to-moderately related (r = .190 to .237) to balance performance. DFA of the high-pass component of the COP exhibited the opposite relationship (r = -.283 to -.453) in both axes (constrained and non-constrained). This study evidences that COP complexity is linked to better performance. This positive relationship complexity/performance is observed in the low- and mid-frequency components of the COP. These components might be related to central mechanisms of postural control. The lack of relationships between the different frequencies analyzed in the study suggests that they are capturing different components of postural control.

Motor Synergies Measurement Reveals the Relevant Role of Variability in Reward-Based Learning

Currently, it is not fully understood how motor variability is regulated to ease of motor learning processes during reward-based tasks. This study aimed to assess the potential relationship between different dimensions of motor variability (i.e., the motor variability structure and the motor synergies variability) and the learning rate in a reward-based task developed using a two-axis force sensor in a computer environment. Forty-four participants performed a pretest, a training period, a posttest, and three retests. They had to release a virtual ball to hit a target using a vertical handle attached to a dynamometer in a computer-simulated reward-based task. The participants' throwing performance, learning ratio, force applied, variability structure (detrended fluctuation analysis, DFA), and motor synergy variability (good and bad variability ratio, GV/BV) were calculated. Participants with higher initial GV/BV displayed greater performance improvements than those with lower GV/BV. DFA did not show any relationship with the learning ratio. These results suggest that exploring a broader range of successful motor synergy combinations to achieve the task goal can facilitate further learning during reward-based tasks. The evolution of the motor variability synergies as an index of the individuals' learning stages seems to be supported by our study.

Balance dynamics are related to age and levels of expertise. Application in young and adult tennis players

In tennis, coaches consider balance fundamental for the acquisition of skilled motor performance. However, the potential relationship between balance and tennis expertise and performance has not been explored yet. Therefore, this study assessed the relationship between balance and tennis performance using linear and non-linear parameters through 1) the comparison of tennis players of different ages and levels of expertise, and 2) analyzing the relationship between balance and tennis serving speed and accuracy. One hundred and six recreational and expert male tennis players took part in the study (age range 10-35 years old). Temporal dynamics of postural control during a balance task on an unstable surface were analyzed through the mean velocity and the detrended fluctuation analysis (DFAV) of center of pressure (COP). Tennis serve performance was quantified by measuring accuracy and speed. Traditional variables measuring balance performance only showed differences according to age but not to sport performance. COP showed a reduction of auto-correlated variability (reflected by DFAV) with age but mainly in expert players. COP dynamics was the only balance parameter discriminating sport expertise and it was related to age. Balance dynamics exhibited by expert tennis players DFAV results support the idea that, along the years, sport experience induces balance adaptations characterized by a higher ability to perform postural adjustments. These results also reinforce the use of non-linear analysis to reveal subtle balance adaptations produced by sport practice. Finally, the lack of correlations suggests that balance, measured with scattering variables, in a non-specific task is not a main determinant of sport performance in tennis serve.

Adequacy and sufficiency evaluation of existing EFSA guidelines for the molecular characterisation, environmental risk assessment and post-market environmental monitoring of genetically modified insects containing engineered gene drives

Advances in molecular and synthetic biology are enabling the engineering of gene drives in insects for disease vector/pest control. Engineered gene drives (that bias their own inheritance) can be designed either to suppress interbreeding target populations or modify them with a new genotype. Depending on the engineered gene drive system, theoretically, a genetic modification of interest could spread through target populations and persist indefinitely, or be restricted in its spread or persistence. While research on engineered gene drives and their applications in insects is advancing at a fast pace, it will take several years for technological developments to move to practical applications for deliberate release into the environment. Some gene drive modified insects (GDMIs) have been tested experimentally in the laboratory, but none has been assessed in small-scale confined field trials or in open release trials as yet. There is concern that the deliberate release of GDMIs in the environment may have possible irreversible and unintended consequences. As a proactive measure, the European Food Safety Authority (EFSA) has been requested by the European Commission to review whether its previously published guidelines for the risk assessment of genetically modified animals (EFSA, 2012 and 2013), including insects (GMIs), are adequate and sufficient for GDMIs, primarily disease vectors, agricultural pests and invasive species, for deliberate release into the environment. Under this mandate, EFSA was not requested to develop risk assessment guidelines for GDMIs. In this Scientific Opinion, the Panel on Genetically Modified Organisms (GMO) concludes that EFSA's guidelines are adequate, but insufficient for the molecular characterisation (MC), environmental risk assessment (ERA) and post-market environmental monitoring (PMEM) of GDMIs. While the MC,ERA and PMEM of GDMIs can build on the existing risk assessment framework for GMIs that do not contain engineered gene drives, there are specific areas where further guidance is needed for GDMIs.

Functional Variability in Team-Handball Players during Balance Is Revealed by Non-Linear Measures and Is Related to Age and Expertise Level

Postural control is considered a key variable in team sports, such as handball, which require abilities strongly related to balance. However, postural control and its relationship to the performance of handball skills according to the players’ skill level and age has not been evaluated to date. This study analyzes the relationship between balance ability and team-handball performance according to age and expertise, applying a non-linear approach to balance assessment. Postural control from 114 male team-handball players was analyzed through the center of pressure (COP) during a balance task. Sport performance was measured by the accuracy and speed in throwing. Expert players threw faster, but not more accurately than recreational players. Balance performance was better for 18+ players (older than 18 years old) than those U12 (under 12 years old), but no differences were found according to their skill level. Players who threw with less accuracy showed slower COP velocity during the balance task and their moves were less irregular. Players who threw faster displayed more irregular and less auto-correlated COP movements. In conclusion, experienced team-handball players exhibited better balance performance, and this seems to be related to the maturation of the motor system more than to sport performance level. Nevertheless, non-linear measures of COP excursion revealed an exploratory behavior during balance in expert players, exhibiting more motion adjustments to reduce motor output error. Traditional variables measuring balance performance did not show sensitivity to this motor control process. A non-linear approach to balance assessment revealed functional variability during balance as an intrinsic characteristic of individuals’ motor control according to age and skill level.

In vitro assessment of the combination of cylindrospermopsin and the organophosphate chlorpyrifos on the human neuroblastoma SH-SY5Y cell line

Cylindrospermopsin (CYN) is a cyanotoxicant which occurrence is increasing due to climate change. Cylindrospermopsin is able to exert damage in the organism at several levels, among them, in the nervous system. Moreover, it is important to take into account that it is not usually present isolated in nature, but in combination with some other pollutants, being the case of the pesticide chlorpyrifos (CPF). Thus, the aim of the present work was to assess the effects of the interaction of CYN in combination with CPF in the human neuroblastoma cell line SH-SY5Y by evaluating cytotoxicity and mechanistic endpoints. The mixtures 0.25 + 21, 0.5 + 42, 1 + 84 μg/mL of CYN + CPF based on cytotoxicity results, were evaluated, and the isobologram method detected an antagonistic effect after 24 and 48 h of exposure. Moreover, although no alterations of reactive oxygen species were detected, a significant decrease of glutathione levels was observed after exposure to both, CPF alone and the combination, at all the concentrations and times of exposure assayed. In addition, CYN + CPF caused a marked decrease in the acetylcholinesterase activity, providing similar values to CPF alone. However, these effects were less severe than expected. All these findings, together with the morphological study results, point out that it is important to take into account the interaction of CYN with other pollutants. Further research is required to contribute to the risk assessment of CYN and other contaminants considering more realistic exposure scenarios.

Neurotoxic assessment of Microcystin-LR, cylindrospermopsin and their combination on the human neuroblastoma SH-SY5Y cell line

Microcystin-LR (MC-LR) and Cylindrospermopsin (CYN) are produced by cyanobacteria. Although being considered as a hepatotoxin and a cytotoxin, respectively, different studies have revealed neurotoxic properties for both of them. The aim of the present work was to study their cytotoxic effects, alone and in combination, in the SH-SY5Y cell line. In addition, toxicity mechanisms such as oxidative stress and acetylcholinesterase (AChE) activity, and morphological studies were carried out. Results showed a cytotoxic response of the cells after their exposure to 0-100 μg/mL of MC-LR or 0-10 μg/mL CYN in both differentiated and undifferentiated cells. Thus, CYN resulted to be more toxic than MC-LR. Respect to their combination, a higher cytotoxic effect than the toxins alone in the case of undifferentiated cells, and almost a similar response to the presented by MC-LR in differentiated cells were observed. However, after analyzing this data with the isobolograms method, an antagonistic effect was mainly obtained. The oxidative stress study only showed an affectation of glutathione levels at the highest concentrations assayed of MC-LR and the combination in the undifferentiated cells. A significant increase in the AChE activity was observed after exposure to MC-LR in undifferentiated cells, and after exposure to the combination of both cyanotoxins on differentiated cells. However, CYN decreased the AChE activity only on differentiated cultures. Finally, the morphological study revealed different signs of cellular affectation, with apoptotic processes at all the concentrations assayed. Therefore, both cyanotoxins isolated and in combination, have demonstrated to cause neurotoxic effects in the SH-SY5Y cell line.

Movement variability emerges in gait as adaptation to task constraints in dynamic environments

BACKGROUND

Motor variability has been related to motor control playing a functional role in human adaptive behaviours. However, the direction of the relationship between variability and motor control can be unclear. The specific relations that exist between task constraints and movement (re)organization could explain some of this controversy.

RESEARCH QUESTION

This study sought to understand whether manipulation of task constraints result in changes in the magnitude or structure of motor system variability observed in a basic walking task. We also investigated the relationship between performance in achieving task goals and the structure of motor variability.

METHODS

Twenty volunteers walked around a circular track with binary combinations of 3 task constraints, providing 8 conditions. The manipulated task constraints were: 1) track width; 2) surface stiffness; and 3), walking direction. Performance was analysed using standard deviation (SD) of sacral displacement and its mean velocity (MV). Fuzzy Entropy (FE) and Detrended Fluctuation Analysis (DFA) were used to assess the kinematic variability structure.

RESULTS

Individuals showed lower SD and MV walking on the narrower track. These changes were also followed by higher DFA values, indicating a more auto-correlated structure of variability. The foam surface was also associated with an increase in amplitude, velocity and irregularity (FE) of movement.

SIGNIFICANCE

Results of this study describe how specific task constraints, such as the width of the walking track and the surface stiffness, shape emergent movement coordination patterns as participants search for functional information from the environment to regulate performance behaviors. Changes in variability structure could reveal the search for adaptive strategies during walking. Smaller movement fluctuations and higher velocity in gait patterns are related to greater irregularity and lower autocorrelation in the kinematic variability structure, demonstrating that a specific relationship emerges between system variability and movement performance, which is driven by task constraints.

A Galacto-Oligosaccharides Preparation Derived From Lactulose Protects Against Colorectal Cancer Development in an Animal Model

Colorectal cancer (CRC) is one of the most common neoplasias worldwide, and its incidence is increasing. Consumption of prebiotics is a useful strategy in order to prevent this important disease. These nutraceutical compounds might exert protective biological functions as antitumors. In order to test the chemopreventive effect of GOS-Lu (galacto-oligosaccharides derived from lactulose) prebiotic preparation against this cancer, an animal model (Rattus norvegicus F344) was used. In this model, two doses of azoxymethane (10 mg/kg) and two treatments with dextran sodium sulfate (DSS) were administered to the animals. Animals were fed for 20 weeks, and either control drinking water or drinking water containing 10% (w/w) GOS-Lu prebiotic preparation was provided to them. Animals were sacrificed after those 20 weeks, and their digestive tract tissues were analyzed. The results revealed a statistically significant reduction in the number of colon tumors in the GOS-Lu cohort with respect to control animals. Metagenomics sequencing was used for studying colon microbiota populations, revealing significant reductions in populations of pro-inflammatory bacteria families and species, and significant increases in interesting beneficial populations, such as Bifidobacterium. Therefore, oral administration of the prebiotic GOS-Lu preparation may be an effective strategy for preventing CRC.

Assessment of endogenous allergenicity of genetically modified plants exemplified by soybean - Where do we stand?

According to EU regulation, genetically modified (GM) plants considered to be allergenic have to be assessed concerning their endogenous allergens before placement on the EU market, in line with the international standards described in Codex Alimentarius. Under such premises, a quantitative relevant increase in allergens might occur in GM plants as an unintended effect compared with conventionally produced crops, which could pose a risk to consumers. Currently, data showing a connection between dose and allergic sensitisation are scarce since the pathophysiological mechanisms of sensitisation are insufficiently understood. In contrast, data on population dose-distribution relationships acquired by oral food challenge are available showing a connection between quantity of allergenic protein consumed and the population of allergic individuals experiencing reactions. Soybean is currently the only recognised allergenic GM food by law for which EFSA has received applications and was therefore taken as an example for defining an assessment strategy. Identification of potential allergens, methodology for quantification as well as risk assessment considerations, are discussed. A strategy is proposed for the identification, assessment and evaluation of potential hazards/risks concerning endogenous allergenicity in food derived from plants developed by biotechnology. This approach could be expanded to other allergenic foods in the future, whenever required.

Can the structure of motor variability predict learning rate?

Recent studies show that motor variability is actively regulated as an exploration tool to promote learning in reward-based tasks. However, its role in learning processes during error-based tasks, when a reduction of the motor variability is required to achieve good performance, is still unclear. In this study, we hypothesized that error-based learning not only depends on exploration but also on the individuals' ability to measure and predict the motor error. Previous studies identified a less auto-correlated motor variability as a higher ability to perform motion adjustments. Two experiments investigated the relationship between motor learning and variability, analyzing the long-range autocorrelation of the center of pressure fluctuations through the α score of a Detrended Fluctuation Analysis in balance tasks. In Experiment 1, we assessed the relationship between variability and learning rate using a standing balance task. Based on the results of this experiment, and to maximize learning, we performed a second experiment with a more difficult sitting balance task and increased practice. The learning rate of the 2 groups with similar balance performances but different α scores was compared. Individuals with a lower α score showed a higher learning rate. Because the α scores reveal how the motor output changes over time, instead of the magnitude of those changes, the higher learning rate is mainly linked to the higher error sensitivity rather than the exploration strategies. The results of this study highlight the relevance of the structure of output motor variability as a predictor of learning rate in error-based tasks. (PsycINFO Database Record

Visual Search Strategies of Experienced and Nonexperienced Swimming Coaches

The aim of this study consists of the application of an experimental protocol that allows information to be obtained about the visual search strategies elaborated by swimming coaches. 16 swimming coaches participated. The Experienced group ( n = 8) had 16.1 yr. ( SD = 8.2) of coaching experience and at least five years of experience in underwater vision. The Nonexperienced group in underwater vision ( n = 8) had 4.2 yr. ( SD = 4.0) of coaching experience. Participants were tested in a laboratory environment using a video-projected sample of the crawl stroke of an elite swimmer. This work discusses the main areas of the swimmer's body used by coaches to identify and analyse errors in technique from overhead and underwater perspectives. In front-underwater videos, body roll and mid-water were the locations of the display with higher percentages of fixation time. In the side-underwater slow videos, the upper body was the location with higher percentages of visual fixation time and was used to detect the low elbow fault. Side-overhead takes were not the best perspectives to pick up information directly about performance of the arms; coaches attended to the head as a reference for their visual search. The observation and technical analysis of the hands and arms were facilitated by an underwater perspective. Visual fixation on the elbow served as a reference to identify errors in the upper body. The side-underwater perspective may be an adequate way to identify correct knee angles in leg kicking and the alignment of a swimmer's body and leg actions.

Contextual Interference in Learning Precision Skills

This research studied the effect of different organisations of practice (blocked and random) on the learning of three different types of throwing. 35 male students practiced three precise throws for 3 wk. Initially the subjects were separated into two groups who trained under different conditions of practice (blocked and random). All subjects improved significantly from initial performance, with both blocked practice and random practice. At the end of acquisition no differences were found between the groups. No significant differences were found on retention tests carried out 48 hr., 4 wk., and 8 wk. after the training period.

Effects of Unstable Conditions on Kinematics and Performance Variables in Young Handball Players

The execution variability and outcomes found in throwing actions have received special attention in numerous studies in recent years. The aim of this study was to analyze the effect of an unstable condition on velocity, accuracy and kinematics of movement in the seven metres throw in handball. Twenty-five young handball players took part in an experiment, throwing towards a target on a stable and an unstable surface. Each participant performed 32 throws, 16 for each situation. Linear variability of the dominant hand was assessed by 3D Motion Tracking. A radar sports gun was used to record the velocity of the ball and the throws were video recorded to establish their accuracy. Results showed significant decreases in throwing velocity in unstable conditions, but these did not significantly affect the accuracy achieved in performance. Differences were also found in movement kinematics between the two throwing conditions and relationships were found between kinematics, velocity and accuracy.

Effect of Performance Speed on Trunk Movement Control During the Curl-Up Exercise

Trunk exercise speed has significant effects on neuro-mechanical demands; however, the influence of a variety of exercise speeds on motor control of the trunk displacement remains unknown. The aim of this study was to assess the effect of performance speed on trunk motion control during the curl-up exercise by analyzing the kinematic variance about the sagittal trajectory. Seventeen subjects volunteered to perform curl-ups at different cadences controlled by a metronome. Standard deviation (SD) and range (RG) of shoulder girdle medial-lateral displacement (SGML) and detrended fluctuation analysis (DFA) of SGML were calculated to examine linear variability and long range autocorrelation of medial-lateral upper trunk displacements, respectively. In addition, SD, RG and DFA of centre of pressure medial-lateral displacement (COPML) were performed to analyze the behavior of the motor system while controlling trunk displacement. Although SD and RG of COPML increased as speed increased, the curl-up cadence did not have significant effects on SD and RG of SGML. These results suggest that although high speed curl-ups challenged participants' ability to carry out medial-lateral adjustments, an increase of performance speed did not modify the linear variability about the sagittal trajectory. Regarding DFA, the scaling exponent α of SGML and COPML was higher for the fastest movements, mainly in long term fluctuations. Therefore, to maintain the target trajectory, participants used different strategies depending on performance speed. This is to say, there were less trajectory changes when participants performed the fastest exercises.

Ecotypic variations in phosphoenolpyruvate carboxylase activity of the cordgrass Spartina densiflora throughout its latitudinal distribution range

This study compared the specific activity of phosphoenolpyruvate carboxylase (PEPC) of Spartina densiflora Brongn., collected from four populations along its latitudinal distribution range. Spartina densiflora is a halophyte with C(4) photosynthesis that has a very wide latitudinal distribution, from Patagonia to the southwest Iberian Peninsula. The basis of intraspecific differences in PEPC activity were analysed by recording the phosphorylation state and amount of the enzyme, comparing leaf anatomy and evaluating leaf gas exchange. S. densiflora individuals from Patagonia had 60% higher PEPC specific activity than plants from the other three populations due to higher levels of PEPC protein that coincided with lower activation mediated by phosphorylation, yielding similar net photosynthesis rate (c. 29 micromol CO(2)xm(-2)xs(-1)). Patagonian plants had a higher area of photosynthetic mesophyll relative to total chlorophyll than plants from north Argentina and the southwest Iberian Peninsula. Ecotypic differentiation in PEPC activity and leaf anatomy were found, distinguishing a higher-latitude ecotype from lower-latitude populations. The higher PEPC protein levels of the Patagonian ecotype seemed to be a response to lower light activation level of the enzyme, as judged by the low PEPC phosphorylation state.

Binding of tau protein to the ends of ex vivo paired helical filaments

Human recombinant tau can bind to the end of isolated human paired helical filaments (PHF). The sequential binding of tau protein to PHF could result in an elongation of the previously polymerized PHF. However, we have observed that the elongation takes place in a different way on different types of PHF. We have found that there are at least three populations of PHF. For one population, tau protein is able to bind to the ends of the filament and to elongate that filament. In the second PHF population, tau protein binds but does not elongates the filament. In the third, neither tau binding nor elongation was observed.

The role of the VQIVYK peptide in tau protein phosphorylation

Although it remains unclear whether they are related to one another, tau aggregation and phosphorylation are the main pathological hallmarks of the neuronal disorders known as tauopathies. The capacity to aggregate is impaired in a variant of the tau 3R isoform that lacks residues 306-311 (nomenclature for the largest CNS tau isoform) and hence, we have taken advantage of this feature to study how phosphorylation and aggregation may be related as well as the role of this six amino acid peptide (VQIVYK). Through these analyses, we found that the phosphorylation of the tau variant was higher than that of the complete tau protein and that not only the deletion of these residues, but also the interaction of these residues, in tau 3R, with thioflavin-S augmented tau phosphorylation by glycogen synthase kinase 3. In addition, the binding of the peptide containing the residues 306-311 to the whole tau protein provoked an increase in tau phosphorylation. This observation could be physiologically relevant as may suggest that tau-tau interactions, through those residues, facilitate tau phosphorylation. In summary, our data indicate that deletion of residues VQIVYK, in tau protein produces an increase in tau phosphorylation, without tau aggregation, because the VQIVYK peptide, that favors aggregation, is missing. On the other hand, when the whole tau protein interacts with thioflavin-S or the peptide VQIVYK, an increase in both aggregation and phosphorylation occurs.

Non-ATP competitive glycogen synthase kinase 3beta (GSK-3beta) inhibitors: study of structural requirements for thiadiazolidinone derivatives

The 2,4-disubstituted thiadiazolidinones (TDZD) were described as the first non-ATP competitive GSK-3beta inhibitors. New modifications in this heterocyclic ring are here reported to study the influence on the biological activity. The basic skeleton of 1,2,4-thiadiazole and also one of the carbonyl groups are kept, while different modifications are introduced in positions 3 and 5, respectively. The GSK-3beta activity of the new thiadiazole derivatives here synthesized showed IC(50) values for some of the compounds in the micromolar range. Additionally, ATP competition studies have been carried out, showing that as well as the first generation of TDZD, these new compounds act in a non-competitive manner. With this study, additional requirements for the biological activity of the TDZD family have been delineated.

Tramiprosate, a drug of potential interest for the treatment of Alzheimer's disease, promotes an abnormal aggregation of tau

Alzheimer's disease (AD) is characterized by the presence of two histopathological hallmarks; the senile plaques, or extracellular deposits mainly composed of amyloid-β peptide (Aβ), and the neurofibrillary tangles, or intraneuronal inclusions composed of hyperphosphorylated tau protein.

Since Aβ aggregates are found in the pathological cases, several strategies are under way to develop drugs that interact with Aβ to reduce its assembly. One of them is 3-amino-1-propane sulfonic acid (Tramiprosate, 3-APS, Alzhemed™), that was developed as a sulfated glycosaminoglycan mimetic, that could interact with Aβ peptide, preventing its aggregation.

However, little is known about the action of 3-APS on tau protein aggregation. In this work, we have tested the action of 3-APS on cell viability, microtubule network, actin organization and tau aggregation. Our results indicate that 3-APS favours tau aggregation, in tau transfected non-neuronal cells, and in neuronal cells. We also found that 3-APS does not affect the binding of tau to microtubules but may prevent the formation of tau-actin aggregates. We like to emphasize the importance of testing on both types of pathology (amyloid and tau) the potential drugs to be used for AD treatment.

Characteristics of the binding of thioflavin S to tau paired helical filaments

Binding of histological benzothiazole dye thioflavin S (ThS) to protein aggregates has been related with the presence of amyloid beta sheet structure in those protein aggregates. Paired helical filaments (PHF) from Alzheimer's disease (AD) patients, (whose main component is the microtubule associated protein, tau) bind to thioflavins. By using a novel immunofluorescence method, the binding of ThS to isolated tau filaments was tested. Also, the characteristics of this binding of ThS to PHF or to the in vitro assembled tau filaments, have been analyzed. Our results suggests that ThS binds to PHF with a higher affinity than to the straight filaments (SF), also found in AD.

In vitro tau fibrillization: mapping protein regions

We have investigated the propensity to form fibrillar aggregates of a variety of fragments and variants of the tau protein under the influence of a tau fibrillization inducer: coenzyme Q(0). To better identify fibrillization hotspots, we compare the polymerization propensity of tau fragments containing the sequence of putative hotspots with that of tau variants with that same sequence deleted. We also investigate the effects of biologically occurring modifications such as phosphorylation and deamidation. We found that residues 305 to 335 are essential for in vitro tau fibrillization. Residues 306 to 311 facilitate in vitro assembly, but are not sufficient to mimic the in vivo fibrillization of tau. Furthermore, the propensity of the 306-311 sequence to form fibrils is highly decreased by chemical modifications of tyrosine 310 that are commonly found in vivo.

Use of Chitosan for Selective Removal of β-Lactoglobulin from Whey

A method is described for selective removal of undenatured beta-lactoglobulin from cheese whey based on interactions between whey proteins and chitosan. Whey was previously clarified at pH 4.5 with addition of chitosan (25 mg/100 mL), and selective removal of beta-lactoglobulin was studied in the pH interval 4.6 to 6.5. Addition of chitosan caused selective precipitation of beta-lactoglobulin that increased with pH. The content of beta-lactoglobulin in whey decreased as the amount of chitosan added was increased. At pH 6.2, addition of 1.9 to 3.0 mg/mL of chitosan led to complete removal of beta-lactoglobulin, whereas at least 80% of the rest of whey proteins remained in solution. The production of cheese whey without beta-lactoglobulin could help to expand the applications of dairy by-products in food processing, and to isolate hypoallergenic whey protein concentrates.

SAR and 3D-QSAR studies on thiadiazolidinone derivatives: exploration of structural requirements for glycogen synthase kinase 3 inhibitors

The 2,4-disubstituted thiadiazolidinones (TDZD) are described as the first ATP-noncompetitive GSK-3 inhibitors. Following an SAR study about TDZD, different structural modifications in the heterocyclic ring aimed to test the influence of each heteroatom on the biological study are here reported here. Various compounds such as hydantoins, dithiazolidindiones, rhodanines, maleimides, and triazoles were synthesized and screened as GSK-3 inhibitors. After an extensive SAR study among these different heterocyclic families, TDZDs have been revealed as a privileged scaffold for the selective inhibition of GSK-3. A CoMFA analysis was also performed highlighting the molecular electrostatic field interaction in the interaction of TDZDs with GSK-3. Moreover, first mapping studies indicate two binding modes which in turn might imply relevant differences in the mechanism that underly the inhibitory activity of TDZDs.

Visual behavior and perception of trajectories of moving objects with visual occlusion

Experienced athletes in sports with moving objects have shown greater skill when using visual information to anticipate the direction of a moving object than nonexperienced athletes of those sports. Studies have shown that expert athletes are more effective than novices in occlusion situations in the first stages of the sports sequence. In this study, 12 athletes with different competitive experience in sports with moving objects viewed a sequence of tennis ball launches with and without visual occlusion, launched by a ball-shooting machine toward different areas with respect to the participant's position. The relation among visual behavior, occlusion time, and the precision of the task is reviewed. The spot where the balls bounced was analysed by a digital camera and visual behavior by an Eye Tracking System. Analysis showed that the nonexperienced athletes made significantly more errors and were more variable in visual occlusion conditions. Participants had a stable visual search strategy.

Neurotoxic dopamine quinone facilitates the assembly of tau into fibrillar polymers

Aberrant aggregation of microtubule associated protein tau is the main characteristic of different disorders known as tauopathies. Different compounds have been described to facilitate tau aberrant aggregation. In this work, we demonstrate that oxidized products of dopamine (neurotoxic dopamine quinone), a neurotransmitter involved in Parkinson's disease, promote tau polymerization. Curiously, neurons expressing dopamine (substantia nigra) show a low content of tau protein and seldom have tau aggregation in tauopathies. In non-dopaminergic neurons, quinone oxidation products may be involved in tau polymerization. These results support a link between oxidative damage and the onset of tauopathies.

Effect of quinones on microtubule polymerization: a link between oxidative stress and cytoskeletal alterations in Alzheimer's disease

Increases in the concentration of quinones, such as benzoquinone, in pathological processes mediated by oxidative imbalance play a role in the disorganization and disassembly of the microtubule network in both non-neural and neural cells. In this study, we show that the effects on microtubules appear to be a direct result of the action of the quinones on tubulin, the main component of microtubules, since tubulin modification by quinones, including benzoquinone and juglone, leads to aggregation into dimers and other oligomers. Therefore, quinones and quinone-mediated effects provide a mechanistic link between oxidative stress, microtubule disruption, neuronal dysfunction and death, i.e., key salient feature of Alzheimer's disease.

Selective recovery of glycosylated caseinmacropeptide with chitosan

The use of chitosan, a partially deacetylated chitin, to fractionate aqueous solutions of caseinmacropeptides (CMPs) was studied. The polycationic character of chitosan at acidic pH values allows the formation of complexes with negatively charged CMP molecules, inducing their flocculation. Glycosylated CMP (GMP) has higher affinity for chitosan than nonglycosylated forms (NGMP). The carboxylic groups in the carbohydrate moiety of the GMP increase the negative charge of the molecule and may play a role in the selective precipitation. At pH 5.0, 0.08 mg/mL of chitosan completely removed the GMP whereas 70% of NGMP remained in solution. As the pH increased, the amount of chitosan to ensure complete removal of GMP increased up to 0.19 and 0.34 mg/mL for pH 6.0 and 6.6, respectively.

Phosphorylation modulates the alpha-helical structure and polymerization of a peptide from the third tau microtubule-binding repeat

Paired helical filaments (PHFs) isolated from patients with Alzheimer's disease (AD) mainly consist of the microtubule-associated protein tau in a hyperphosphorylated form. It has been found that PHFs are the first example of pathological protein aggregation associated with formation of alpha-helices [Biochemistry (2002) 41, 7150-5]. In an effort to investigate the interplay between phosphorylation and the putative role of short regions of alpha-helix in the polymerization of tau, we have focused on the region of tau encompassing residues 317 to 335. This region is able to form protein fibrils in vitro and has two serines that are often found phosphorylated in PHFs. Using trifluoroethanol as an indicator of the alpha-helix, we find that the stability of the alpha-helix conformation is enhanced by phosphorylation. Circular dichroism data show that the phosphorylated peptide in water presents a content in alpha-helix similar to the unphosphorylated peptide at 40% of trifluoroethanol. Phosphorylation also stimulates the effect of juglone in promoting the in vitro polymerization. Furthermore, Fourier transformed infrared spectroscopy of samples of phosphorylated peptide polymerized with juglone renders a spectrum with maxima at approximately 1665 and approximately 1675 cm(-1), which are suggestive of a mixture of turns and alpha-helix conformations. Our results provide a direct mechanistic connection between phosphorylation and polymerization in tau. The connection between phosphorylation and polymerization appears to involve formation of alpha-helix structure.

Quinones facilitate the self-assembly of the phosphorylated tubulin binding region of tau into fibrillar polymers

The fragment of tau containing the first and third tubulin-binding motifs, involved in self-assembly of tau, was phosphorylated by protein kinase A (PKA). In the presence of hydroxynonenal (HNE) or in the presence of quinones such as juglone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone (coenzyme Q(0) or DMM), or menadione, the polymerization of this phosphorylated tau fragment is catalyzed, whereas polymerization of the unmodified fragment takes place in a lesser extent. The quinones coenzyme Q(0) and menadione are found in every cell, including neural cells, and may interact with tau protein to facilitate its assembly into filamentous structures. These tau filaments, assembled in the presence of quinones, have a fibrillar morphology very similar to that of paired helical filaments present in the brains of patients with Alzheimer's disease.

The comet assay differentiates efficiently and rapidly between genotoxins and cytotoxins in quiescent cells

Our main aim was to establish the efficiency of the single cell electrophoresis technique for differentiating between drugs that bind DNA and those that do not. The alkaline comet assay was used to test the responses of human leukocytes (quiescent cells) to damage induced by reportedly genotoxic and reportedly cytotoxic agents. Incubation of G0 leukocytes for 1 h with the genotoxic agents camptothecin and actinomycin C provoked DNA migration, observed as comet figures. On the other hand, when cells were treated with the cytotoxic agents cordycepin, fluorodeoxyuridine and puromycin, the leukocyte nuclei were indistinguishable from those of untreated cells. In addition, we have developed a rapid method using non-proliferating cells that requires neither culture nor lymphocyte isolation. This method promises to be useful as a rapid in vitro screening assay.

Thienyl and phenyl alpha-halomethyl ketones: new inhibitors of glycogen synthase kinase (GSK-3beta) from a library of compound searching

Glycogen synthase kinase (GSK-3beta) plays a crucial role in Alzheimer's disease (AD). Its inhibition is a valid approach to the treatment of AD. In this initial letter, some thienyl and phenyl alpha-halomethyl ketones are described as new non-ATP competitive inhibitors of GSK-3beta. They are considered as lead compounds for designing and synthesizing new series, to carry out SAR studies, clear up the mechanism of action, and, in general, evaluate their therapeutical usefulness.

DNA strand-breaks induced by the topoisomerase I inhibitor camptothecin in unstimulated human white blood cells

Camptothecin (CPT) and actinomicyn-induced strand-breaks, repair and apoptosis in unstimulated human blood cells were studied using the DNA comet assay, and electrophoresis of low molecular weight DNA extracts. On the one hand, incubation of G0 leukocytes for 1 h with CPT induced DNA strand-breaks that were observed using the single cell gel electrophoresis technique. On the other hand, internucleosomal DNA fragments were not observed, suggesting that apoptosis had not occurred. DNA-strand-breaks caused by CPT were repaired 24 h after treatment; the migration of DNA fragments was assessed by a reduction in the number of comets. These data strongly suggest that the unexpected clastogenic effect of this topoisomerase I inhibitor is not due to the collision of the cleavage complex with the replication fork, since replication does not occur in G0. In our opinion, this effect could be due instead to the topoisomerase I enzyme being able to bind DNA in the absence of replication, probably in a way that is not strictly related to the progression of the cell cycle. Thus, CPT does not provoke apoptosis in quiescent leukocytes.

Visual search strategies in experienced and inexperienced gymnastic coaches

The visual search strategies employed by gymnastic coaches with different levels of expertise were investigated. Expert (n=3) and novice coaches (n=3) watched 9 video sequences of 3 gymnastic techniques and were required to highlight errors in performance. Visual search patterns were monitored by an ASL-5000SE eye-tracking system during observation. Expert participants showed longer and fewer visual fixations than the novice group.

Mechanisms involved in the attenuation of intestinal toxicity induced by (S)-(+)-ketoprofen in re-fed rats

In addition to suppression of prostaglandins synthesis a number of factors have been implicated in nonsteroidal antiinflammatory drugs (NSAIDs) enteropathy, including oxygen radical-dependent microvascular injuries, depletion of glutathione, and food. Inflammatory cytokines such as tumor necrosis factor-alpha regulate endothelial adhesion molecules expression and promote vascular neutrophil adherence. Racemic ketoprofen is a potent NSAID with a chiral structure existing in two enantiomeric forms. Its therapeutic effects reside almost exclusively in the (S)-(+) isomer nevertheless the potential contribution to side effects of the (R)-(-) isomer cannot be ignored. The aims of this study were to explore the role of prostaglandins depletion, tumor necrosis factor-alpha production, and glutathione homeostasis in the comparative pathogenesis of intestinal injury induced by racemic-ketoprofen and its enantiomers in re-fed rats. Racemic ketoprofen and (R)-(-)-ketoprofen dose-dependently caused similar and multiple lesions in the mid-jejunum significantly higher than those observed with (S)-(+)-ketoprofen. All the treatments significantly decreased prostaglandins content. A significant increase of tumor necrosis factor-alpha production and decreases in glutathione levels and glutathione reductase activity after treatment of the racemate and (R)-(-)-ketoprofen, were observed whereas the (S)-(+)-isomer did not change these parameters. In conclusion, (S)-(+)-ketoprofen possesses a better intestinal toxicity profile than the racemate and its (R)-(-)-isomer. Despite inhibiting cyclooxygenase activity, the attenuation of (S)-(+)-ketoprofen-induced intestinal toxicity could be correlated with a reduced oxidative damage characterized not only by a lack of changes in glutathione reductase activity and glutathione levels but also by an absence of up-regulation of tumor necrosis factor-alpha production in intestinal mucosa.

First non-ATP competitive glycogen synthase kinase 3 beta (GSK-3beta) inhibitors: thiadiazolidinones (TDZD) as potential drugs for the treatment of Alzheimer's disease

Glycogen synthase kinase 3 beta (GSK-3beta) has a central role in Alzheimer's disease (AD). Selective inhibitors which avoid tau hyperphosphorylation may represent an effective therapeutical approach to the AD pharmacotherapy and other neurodegenerative disorders. Here, we describe the synthesis, biological evaluation, and SAR of the small heterocyclic thiadiazolidinones (TDZD) as the first non-ATP competitive inhibitor of GSK-3beta. Their synthesis is based on the reactivity of sulfenyl chlorides. In GSK-3beta assays, TDZD derivatives showed IC(50) values in the micromolar range, whereas in other protein kinases assays they were devoid of any inhibitory activity. SAR studies allowed the identification of the key structural features. Finally, a possible enzymatic binding mode is proposed.

P24, a glycogen synthase kinase 3 (GSK 3) inhibitor

A heat resistant glycogen synthase kinase 3 (GSK 3) binding protein, p24, that inhibits its kinase activity at a low magnesium concentration (in a way similar to that of lithium) was found in microtubules from adult rat brains. This protein associates with GSK 3 in microtubules and corresponds to one previously described in the literature as p25, although it has a relative molecular weight of 23472. p24 is a poor substrate for GSK 3 but it could be phosphorylated by other protein kinases such as cAMP dependent protein kinase and cdk 5. Since p24 could form complexes with GSK 3, it may not only regulate GSK 3 activity but also it might act as an anchoring protein for the kinase.

Heterogeneity of caprine kappa-casein macropeptide

The heterogeneity of caprine caseinmacropeptide (CMP) was determined by means of treatments with neuraminidase and acid phosphatase and analyses by anion exchange FPLC and reversed-phase (RP)-HPLC, with on-line and off-line electrospray ionization mass spectrometry. The main CMP components were two non-glycosylated and di-phosphorylated forms, as well as two other mono-phosphorylated species, each corresponding to a genetic variant of caprine kappa-casein due to the silent substitution Ile/Val at position 119. Asialo-aglyco mono- and di-phosphorylated forms were found in the ratios 8-14% and 86-92%, respectively. Approximately 36% of caprine CMP was glycosylated. Based on the obtained molecular masses, the occurrence of tri-, di- and monosaccharide-containing di-phosphorylated CMP are reported, assuming that N-acetylgalactosamine, galactose, N-acetyl and N-glycolylneuraminic acids would constitute the main monosaccharides of caprine CMP. CMP microheterogeneity due to the genetic polymorphism was also observed in the glycosylated forms.