Translational and rotational non-Gaussianities in homogeneous freely evolving granular gases

The importance of roughness in the modeling of granular gases has been increasingly considered in recent years. In this paper, a freely evolving homogeneous granular gas of inelastic and rough hard disks or spheres is studied under the assumptions of the Boltzmann kinetic equation. The homogeneous cooling state is studied from a theoretical point of view using a Sonine approximation, in contrast to a previous Maxwellian approach. A general theoretical description is done in terms of d_{t} translational and d_{r} rotational degrees of freedom, which accounts for the cases of spheres (d_{t}=d_{r}=3) and disks (d_{t}=2, d_{r}=1) within a unified framework. The non-Gaussianities of the velocity distribution function of this state are determined by means of the first nontrivial cumulants and by the derivation of non-Maxwellian high-velocity tails. The results are validated by computer simulations using direct simulation Monte Carlo and event-driven molecular dynamics algorithms.

Kinetic Theory and Memory Effects of Homogeneous Inelastic Granular Gases under Nonlinear Drag

We study a dilute granular gas immersed in a thermal bath made of smaller particles with masses not much smaller than the granular ones in this work. Granular particles are assumed to have inelastic and hard interactions, losing energy in collisions as accounted by a constant coefficient of normal restitution. The interaction with the thermal bath is modeled by a nonlinear drag force plus a white-noise stochastic force. The kinetic theory for this system is described by an Enskog–Fokker–Planck equation for the one-particle velocity distribution function. To get explicit results of the temperature aging and steady states, Maxwellian and first Sonine approximations are developed. The latter takes into account the coupling of the excess kurtosis with the temperature. Theoretical predictions are compared with direct simulation Monte Carlo and event-driven molecular dynamics simulations. While good results for the granular temperature are obtained from the Maxwellian approximation, a much better agreement, especially as inelasticity and drag nonlinearity increase, is found when using the first Sonine approximation. The latter approximation is, additionally, crucial to account for memory effects such as Mpemba and Kovacs-like ones.

Thermal versus entropic Mpemba effect in molecular gases with nonlinear drag

Loosely speaking, the Mpemba effect appears when hotter systems cool sooner or, in a more abstract way, when systems further from equilibrium relax faster. In this paper, we investigate the Mpemba effect in a molecular gas with nonlinear drag, both analytically (by employing the tools of kinetic theory) and numerically (direct simulation Monte Carlo of the kinetic equation and event-driven molecular dynamics). The analysis is carried out via two alternative routes, recently considered in the literature: first, the kinetic or thermal route, in which the Mpemba effect is characterized by the crossing of the evolution curves of the kinetic temperature (average kinetic energy), and, second, the stochastic thermodynamics or entropic route, in which the Mpemba effect is characterized by the crossing of the distance to equilibrium in probability space. In general, a nonmutual correspondence between the thermal and entropic Mpemba effects is found, i.e., there may appear the thermal effect without its entropic counterpart or vice versa. Furthermore, a nontrivial overshoot with respect to equilibrium of the thermal relaxation makes it necessary to revise the usual definition of the thermal Mpemba effect, which is shown to be better described in terms of the relaxation of the local equilibrium distribution. Our theoretical framework, which involves an extended Sonine approximation in which not only the excess kurtosis but also the sixth cumulant is retained, gives an excellent account of the behavior observed in simulations.

Hydrodynamics of granular gases of inelastic and rough hard disks or spheres. II. Stability analysis

Conditions for the stability under linear perturbations around the homogeneous cooling state are studied for dilute granular gases of inelastic and rough hard disks or spheres with constant coefficients of normal (α) and tangential (β) restitution. After a formally exact linear stability analysis of the Navier-Stokes-Fourier hydrodynamic equations in terms of the translational (d_{t}) and rotational (d_{r}) degrees of freedom, the transport coefficients derived in the companion paper [A. Megías and A. Santos, "Hydrodynamics of granular gases of inelastic and rough hard disks or spheres. I. Transport coefficients" Phys. Rev. E 104, 034901 (2021)10.1103/PhysRevE.104.034901] are employed. Known results for hard spheres [Garzó, Santos, and Kremer, Phys. Rev. E 97, 052901 (2018)10.1103/PhysRevE.97.052901] are recovered by setting d_{t}=d_{r}=3, while novel results for hard disks (d_{t}=2, d_{r}=1) are obtained. In the latter case, a high-inelasticity peculiar region in the (α,β) parameter space is found, inside which the critical wave number associated with the longitudinal modes diverges. Comparison with event-driven molecular dynamics simulations for dilute systems of hard disks at α=0.2 shows that this theoretical region of absolute instability may be an artifact of the extrapolation to high inelasticity of the approximations made in the derivation of the transport coefficients, although it signals a shrinking of the conditions for stability. In the case of moderate inelasticity (α=0.7), however, a good agreement between the theoretical predictions and the simulation results is found.

Hydrodynamics of granular gases of inelastic and rough hard disks or spheres. I. Transport coefficients

The transport coefficients for dilute granular gases of inelastic and rough hard disks or spheres with constant coefficients of normal (α) and tangential (β) restitution are obtained in a unified framework as functions of the number of translational (d_{t}) and rotational (d_{r}) degrees of freedom. The derivation is carried out by means of the Chapman-Enskog method with a Sonine-like approximation in which, in contrast to previous approaches, the reference distribution function for angular velocities does not need to be specified. The well-known case of purely smooth d-dimensional particles is recovered by setting d_{t}=d and formally taking the limit d_{r}→0. In addition, previous results [G. M. Kremer, A. Santos, and V. Garzó, Phys. Rev. E 90, 022205 (2014)10.1103/PhysRevE.90.022205] for hard spheres are reobtained by taking d_{t}=d_{r}=3, while novel results for hard-disk gases are derived with the choice d_{t}=2, d_{r}=1. The singular quasismooth limit (β→-1) and the conservative Pidduck's gas (α=β=1) are also obtained and discussed.

Relative entropy of freely cooling granular gases. A molecular dynamics study

Whereas the original Boltzmann’s H-theorem applies to elastic collisions, its rigorous generalization to the inelastic case is still lacking. Nonetheless, it has been conjectured in the literature that the relative entropy of the velocity distribution function with respect to the homogeneous cooling state (HCS) represents an adequate nonequilibrium entropy-like functional for an isolated freely cooling granular gas. In this work, we present molecular dynamics results reinforcing this conjecture and rejecting the choice of the Maxwellian over the HCS as a reference distribution. These results are qualitatively predicted by a simplified theoretical toy model. Additionally, a Maxwell-demon-like velocity-inversion simulation experiment highlights the microscopic irreversibility of the granular gas dynamics, monitored by the relative entropy, where a short “anti-kinetic” transient regime appears for nearly elastic collisions only.

Kullback-Leibler Divergence of a Freely Cooling Granular Gas

Finding the proper entropy-like Lyapunov functional associated with the inelastic Boltzmann equation for an isolated freely cooling granular gas is a still unsolved challenge. The original H-theorem hypotheses do not fit here and the H-functional presents some additional measure problems that are solved by the Kullback–Leibler divergence (KLD) of a reference velocity distribution function from the actual distribution. The right choice of the reference distribution in the KLD is crucial for the latter to qualify or not as a Lyapunov functional, the asymptotic “homogeneous cooling state” (HCS) distribution being a potential candidate. Due to the lack of a formal proof far from the quasielastic limit, the aim of this work is to support this conjecture aided by molecular dynamics simulations of inelastic hard disks and spheres in a wide range of values for the coefficient of restitution (α) and for different initial conditions. Our results reject the Maxwellian distribution as a possible reference, whereas they reinforce the HCS one. Moreover, the KLD is used to measure the amount of information lost on using the former rather than the latter, revealing a non-monotonic dependence with α.

Clinical and Neurophysiological Correlates of Emotion and Food Craving Regulation in Patients with Anorexia Nervosa

Background: Difficulties in emotion regulation and craving regulation have been linked to eating symptomatology in patients with anorexia nervosa (AN), contributing to the maintenance of their eating disorder. Methods: To investigate clinical and electrophysiological correlates of these processes, 20 patients with AN and 20 healthy controls (HC) completed a computerized task during EEG recording, where they were instructed to down-regulate negative emotions or food craving. Participants also completed self-report measures of emotional regulation and food addiction. The P300 and Late Positive Potential (LPP) ERPs were analysed. Results: LPP amplitudes were significantly smaller during down-regulation of food craving among both groups. Independent of task condition, individuals with AN showed smaller P300 amplitudes compared to HC. Among HC, the self-reported use of re-appraisal strategies positively correlated with LPP amplitudes during emotional regulation task, while suppressive strategies negatively correlated with LPP amplitudes. The AN group, in comparison to the HC group, exhibited greater food addiction, greater use of maladaptive strategies, and emotional dysregulation. Conclusions: Despite the enhanced self-reported psychopathology among AN, both groups indicated neurophysiological evidence of food craving regulation as evidenced by blunted LPP amplitudes in the relevant task condition. Further research is required to delineate the mechanisms associated with reduced overall P300 amplitudes among individuals with AN.

Risk proneness modulates the impact of impulsivity on brain functional connectivity

Impulsivity and sensation seeking are considered to be among the most important personality traits involved in risk-taking behavior. This study is focused on whether the association of these personality traits and brain functional connectivity depends on individuals' risk proneness. Risk proneness was assessed with the DOSPERT-30 scale and corroborated with performance in a motorcycle simulator. The associations of impulsivity- and sensation seeking-related traits with the between and within coupling of seven major brain functional networks, estimated from electroencefalograma (EEG) recordings, differ according to whether an individual is risk prone or not. In risk-prone individuals, (lack of) premeditation enhanced the coupling of the ventral attention and limbic networks. At the same time, emotion seeking increased the coupling of the frontoparietal network and the default mode networks (DMNs). Finally, (lack of) perseverance had a positive impact on the coupling of anterior temporal nodes of the limbic network whilst having a negative impact on some frontal nodes of the frontoparietal network and the DMNs. In general, the results suggest that the predisposition to behave riskily modulates the way in which impulsivity traits are linked to brain functionality, seemingly making the brain networks prepare for an immediate, automatic, and maladaptive response.

Sex differences in the association between impulsivity and driving under the influence of alcohol in young adults: The specific role of sensation seeking

INTRODUCTION

There is an outstanding need to identify predictors of driving under the influence of alcohol (DUI) among young adults, particularly women. Impulsivity, or the tendency to act without thinking, is a predictor of DUI, but the specific facets of impulsivity that predict DUI and their interaction with sex differences remain unclear. We aimed to investigate sex differences in the link between impulsivity facets and DUI. Moreover, we sought to replicate previous findings regarding sex differences on impulsivity, and associations between impulsivity facets and DUI.

METHOD

A total of 506 university students participated in the study (males, n = 128; females, n = 378). Participants completed measures of impulsivity (UPPS-P short version), alcohol use (AUDIT-C), frequency of DUI episodes and related perception of risk. The UPPS-P assesses five facets of impulsivity: sensation seeking, (lack of) premeditation and perseverance and positive and negative urgency.

RESULTS

Men showed higher sensation seeking and lack of perseverance, alcohol use and DUI frequency and lower risk perception than women. DUI frequency was negatively associated with perception of risk and positively associated with alcohol use and the five impulsivity facets. After controlling for alcohol use and risk perception, only lack of premeditation was associated with DUI frequency in the whole sample. Sensation seeking was positively associated with DUI frequency only in women.

DISCUSSION

The link between lack of premeditation and DUI suggest that pre-drinking planning strategies can contribute to prevent risky driving. In women, specific links between sensation seeking and DUI suggest the need for personality-tailored prevention strategies.

The relationship between aggression and ability emotional intelligence: The role of negative affect

This study aimed to contribute to the understanding of the mechanisms underlying the relationship between aggressive behaviour and individual levels of ability emotional intelligence (EI). Three hundred and ninety-five participants took part in this study. Participants were assessed on ability EI, negative affect (NA), and aggression by the Mayer-Salovey-Caruso Emotional Intelligence Test, the Positive and Negative Affect Schedule, and the Buss-Perry Aggression questionnaires, respectively. The results revealed a negative relationship between aggression and ability EI, but this relationship depended on multiple factors: the type of EI branches and aggression dimensions, the influence of NA, and gender. Emotional management ability showed a direct relationship with aggression, while emotional perception ability presented an indirect relationship with aggression through the effect of NA. These EI abilities were related to different aggression dimensions, highlighting the direct relationship with physical aggression. Moreover, gender differences showed that women possess greater EI abilities, higher levels of NA, less aggressive behaviour, and a lower relationship between NA and aggression compared with men. This research offers a better understanding of the psychological processes explaining aggression. The inclusion of our findings in the design of prevention and treatment programs could be of great help in the control of aggressive behaviour.

The role of emotional intelligence and negative affect as protective and risk factors of aggressive behavior: A moderated mediation model

The General Aggression Model (GAM) offers an integrative explanation of the aggressive behavior based on three stages: 1) inputs: personal and situational factors; 2) routes or individual internal states: affect, cognition, and arousal; and 3) outcomes: decision processes with a (non) aggressive result. Researchers are interested in looking for protective factors within the GAM to diminish aggression. Previous studies have found two relevant variables acting independently as risk and protective factors: emotional intelligence (EI) and negative affect (NA). The aim of the present study is to analyze a moderated mediation model including these variables as an explanation of aggressive behavior and integrate it within the GAM. Four hundred and six participants were assessed on EI, NA, and aggression. The moderated mediation analysis showed a significant negative indirect effect of the perceiving EI branch on total aggression mediated through NA levels, which, in turn, was moderated by the managing EI branch. Moreover, this relationship was also observed for the physical, anger, and hostility sub-scales of aggression. Our study demonstrates the importance of having a high ability to perceive emotions as a protective factor in the first stage of the GAM. These individuals will present lower NA in the second stage of the model, resulting in a reduction in aggression. Moreover, having a high ability to perceive emotions is particularly relevant for individuals that are less able to manage emotions, given that those participants with higher scores on the managing EI branch can reduce their aggressive behavior by mitigating the effect of NA on aggression in the third stage of the GAM.

The Relationship Between the Three Models of Emotional Intelligence and Psychopathy: A Systematic Review

Given the many instances of violence and crime that occur as a consequence of psychopathy, it is vital to find those variables that can reduce the expression of such behaviors. In this regard, one potentially useful variable is that known as Emotional Intelligence (EI) or the ability to perceive, use, understand, and regulate emotions. EI has been categorized according to three main approaches: performance-based ability, self-report ability, and self-report mixed models. Given the emotional deficits of the psychopathic population, EI could be a protective factor. Several studies have analyzed the relationship between EI and psychopathy, but the results are unclear. This disparity may be due to the EI model employed to measure EI. The aim of our research is to systematically review the relationship between the different models of EI and psychopathy, both in the total and clinical/inmate sample. We searched Scopus, Pubmed, and PsicINFO to find relevant articles. Twenty-nine eligible studies were found. They were divided according to the model of EI and the sample used. The results for the total sample differ according to the measure of EI: when the performance-based ability model is used, the majority of studies find a negative relationship between EI and psychopathy. When using self-reports, the results are inconsistent. The findings with the clinical/inmate sample are in the same direction as the total sample. In conclusion, the results suggest that higher EI abilities measured through performance-based ability models-but not through self-reports-are related to lower psychopathy deficits. Limitations and clinical implications are discussed.

The relationship between trait psychopathy and emotional intelligence: A meta-analytic review

Psychopathy is a personality construct that has been related to important emotional deficits. These findings have led to a growing interest in exploring if psychopathic traits are associated with emotional intelligence (EI). However, the literature exploring this association has revealed conflicting results. The aim of the present study was to provide a reliable estimate of the relationship between psychopathy traits and EI (measured as performance-based ability) through meta-analysis. A quantitative and systematic review of the literature using Scopus, Medline, Pubmed, and PsicINFO showed a total of 13 studies meeting inclusion criteria with a combined sample of 2401 participants. The meta-analysis revealed a significant negative relationship between both constructs, showing that higher psychopathic trait scores are related to lower EI levels. We propose several future research lines to clarify possible gaps and ambiguities in the current literature and a set of interesting clinical implications for the prevention, evaluation, and treatment of psychopathic traits by including EI factors in traditional models of psychopathy.

Performance on emotional tasks engaging cognitive control depends on emotional intelligence abilities: an ERP study

Cognitive control is a key process in decision making and adequately adapting our behavior to the environment. Previous studies have provided evidence of a lower capacity for cognitive control in emotion-laden contexts in comparison with neutral contexts. The aim of the present research was to study changes in cognitive control performance as a function of emotional intelligence (EI) level in contexts involving emotional information. The study sample was composed of 2 groups of 22 participants each: the high and low EI group. Participants carried out an emotional go/no-go task while brain activity was recorded by EEG. N2 and P3 ERPs were used as indices of cognitive control processing. Participants with higher EI showed a larger N2, reflecting a greater capacity for cognitive control related to changes in conflict monitoring, and to a better detection and evaluation of the emotional stimuli. Moreover, in general, response inhibition accuracy was reduced when emotional information was involved in this process. Our findings reveal that neural mechanisms underlying tasks that engage cognitive control depend on emotional content and EI level. This study indicates the important role played by EI in the relationship between emotion and cognition. EI training may be a very useful tool for improving performance in emotion-laden contexts.

Using negative emotional feedback to modify risky behavior of young moped riders

OBJECTIVE

The aim of this research was to investigate whether the use of messages with negative emotional content is effective in promoting safe behavior of moped riders and how exactly these messages modulate rider behavior.

METHODS

Participants received negative feedback when performing risky behaviors using a computer task. The effectiveness of this treatment was subsequently tested in a riding simulator.

RESULTS

The results demonstrated how riders receiving negative feedback had a lower number of traffic accidents than a control group. The reduction in accidents was accompanied by a set of changes in the riding behavior. We observed a lower average speed and greater respect for speed limits. Furthermore, analysis of the steering wheel variance, throttle variance, and average braking force provided evidence for a more even and homogenous riding style. This greater abidance of traffic regulations and friendlier riding style could explain some of the causes behind the reduction in accidents.

CONCLUSIONS

The use of negative emotional feedback in driving schools or advanced rider assistance systems could enhance riding performance, making riders aware of unsafe practices and helping them to establish more accurate riding habits. Moreover, the combination of riding simulators and feedback-for example, in the training of novice riders and traffic offenders-could be an efficient tool to improve their hazard perception skills and promote safer behaviors.

Spanish validation of the Domain-Specific Risk-Taking (DOSPERT-30) Scale

BACKGROUND

The aim of the present study was to develop and validate a Spanish version of the short Domain-Specific Risk-Taking (DOSPERT-30) scale, measuring risk-taking behavior, risk perception, and expected beneficial consequences (from taking risks) in five life domains: ethics, finance, health/security, recreational, and social decisions.

METHOD

The scale was back-translated, and administered online to 826 participants. Validity evidence was tested using correlations with construct-related instruments (UPPS-P and SSS-V), as well as using factor analysis. Internal consistency reliability was calculated with the ordinal Alpha coefficient, and gender differences were considered.

RESULTS

Internal consistency was good, and factor analysis confirmed the five factors proposed by the authors. With respect to the external validity, high correlations with the positive urgency and the sensation seeking subscales of the UPPS-P, as well as with the thrill and adventure seeking and disinhibition subscales of the SSS-V were found. Finally, gender differences were found in all subscales and domains, with men tending to take more risks, perceive less risk and expect more beneficial consequences, except for the social domain where an inverse pattern was found.

CONCLUSIONS

As these findings are in line with the original version, they indicate the scale was successfully adapted.

Seeing red on the road

Human and animal research has found that red perception is associated with specific behavioral reactions, generally characterized by intense responses. Here, we explored whether red cars are perceived as more dangerous than other colored cars. One hundred Spanish drivers examined several road scenarios which involved hazardous cars with different colors: red, green, yellow, black, gray, and white. Driver's behavior (response time and probability of braking) and the perceived level of risk for each scenario were analyzed. Although car color affected participants' response times, contrary to expectations, red cars did not elicit faster responses or higher perceived levels of risk.

Neural mechanisms underlying urgent and evaluative behaviors: An fMRI study on the interaction of automatic and controlled processes

Dual-process theories have dominated the study of risk perception and risk-taking over the last two decades. However, there is a lack of objective brain-level evidence supporting the two systems of processing in every-day risky behavior. To address this issue, we propose the dissociation between evaluative and urgent behaviors as evidence of dual processing in risky driving situations. Our findings show a dissociation of evaluative and urgent behavior both at the behavioral and neural level. fMRI data showed an increase of activation in areas implicated in motor programming, emotional processing, and visuomotor integration in urgent behavior compared to evaluative behavior. These results support a more automatic processing of risk in urgent tasks, relying mainly on heuristics and experiential appraisal. The urgent task, which is characterized by strong time pressure and the possibility for negative consequences among others factors, creates a suitable context for the experiential-affective system to guide the decision-making process. Moreover, we observed greater frontal activation in the urgent task, suggesting the participation of cognitive control in safe behaviors. The findings of this research are relevant for the study of the neural mechanisms underlying dual process models in risky perception and decision-making, especially because of their proximity to everyday activities.

Cocaine Dependent Individuals and Gamblers Present Different Associative Learning Anomalies in Feedback-Driven Decision Making: A Behavioral and ERP Study

Several recent studies have demonstrated that addicts behave less flexibly than healthy controls in the probabilistic reversal learning task (PRLT), in which participants must gradually learn to choose between a probably rewarded option and an improbably rewarded one, on the basis of corrective feedback, and in which preferences must adjust to abrupt reward contingency changes (reversals). In the present study, pathological gamblers (PG) and cocaine dependent individuals (CDI) showed different learning curves in the PRLT. PG also showed a reduced electroencephalographic response to feedback (Feedback-Related Negativity, FRN) when compared to controls. CDI's FRN was not significantly different either from PG or from healthy controls. Additionally, according to Standardized Low-Resolution Electromagnetic Tomography analysis, cortical activity in regions of interest (previously selected by virtue of their involvement in FRN generation in controls) strongly differed between CDI and PG. However, the nature of such anomalies varied within-groups across individuals. Cocaine use severity had a strong deleterious impact on the learning asymptote, whereas gambling intensity significantly increased reversal cost. These two effects have remained confounded in most previous studies, which can be hiding important associative learning differences between different populations of addicts.

Emotional and non-emotional pathways to impulsive behavior and addiction

Impulsivity is tightly linked to addiction. However, there are several pathways by means of which impulsive individuals are more prone to become addicts, or to suffer an addiction more intensely and for a longer period. One of those pathways involves an inadequate appraisal or regulation of positive and negative emotions, leading to lack of control over hazardous behaviors, and inappropriate decisions. In the present work, we assessed cocaine-dependent individuals (CDI; n = 20), pathological gamblers (PG; n = 21), and healthy controls (HC; n = 23) in trait impulsivity measures (UPPS-P model's dimensions), and decision-making tasks (Go/No-go; delay-discounting task). During the Go/No-go task, electroencephalographic (EEG) activity was recorded, and Go/No-go stimuli-evoked potentials (ERP) were extracted. Theory-driven ERP analyses focused on the No-go > Go difference in the N2 ERP. Our results show that negative urgency is one of the several psychological features that distinguish addicts from HC. Nevertheless, among the dimensions of trait impulsivity, negative urgency is unique at independently covarying with gambling over-pathologization in the PG sample. Cocaine-dependent individuals performed more poorly than gamblers in the Go/No-go task, and showed abnormal Go/No-go stimuli-evoked potentials. The difference between the No-go stimulus-evoked N2, and the Go one was attenuated by severity and intensity of chronic cocaine use. Emotional dimensions of impulsivity, however, did not influence Go/No-go performance.

Emotional and non-emotional pathways to impulsive behavior and addiction

Impulsivity is tightly linked to addiction. However, there are several pathways by means of which impulsive individuals are more prone to become addicts, or to suffer an addiction more intensely and for a longer period. One of those pathways involves an inadequate appraisal or regulation of positive and negative emotions, leading to lack of control over hazardous behaviors, and inappropriate decisions. In the present work, we assessed cocaine-dependent individuals (CDI; n = 20), pathological gamblers (PG; n = 21), and healthy controls (HC; n = 23) in trait impulsivity measures (UPPS-P model's dimensions), and decision-making tasks (Go/No-go; delay-discounting task). During the Go/No-go task, electroencephalographic (EEG) activity was recorded, and Go/No-go stimuli-evoked potentials (ERP) were extracted. Theory-driven ERP analyses focused on the No-go > Go difference in the N2 ERP. Our results show that negative urgency is one of the several psychological features that distinguish addicts from HC. Nevertheless, among the dimensions of trait impulsivity, negative urgency is unique at independently covarying with gambling over-pathologization in the PG sample. Cocaine-dependent individuals performed more poorly than gamblers in the Go/No-go task, and showed abnormal Go/No-go stimuli-evoked potentials. The difference between the No-go stimulus-evoked N2, and the Go one was attenuated by severity and intensity of chronic cocaine use. Emotional dimensions of impulsivity, however, did not influence Go/No-go performance.

The brain network of expectancy and uncertainty processing

BACKGROUND

The Stimulus Preceding Negativity (SPN) is a non-motor slow cortical potential elicited by temporally predictable stimuli, customarily interpreted as a physiological index of expectancy. Its origin would be the brain activity responsible for generating the anticipatory mental representation of an expected upcoming event. The SPN manifests itself as a slow cortical potential with negative slope, growing in amplitude as the stimulus approximates. The uncertainty hypothesis we present here postulates that the SPN is linked to control-related areas in the prefrontal cortex that become more active before the occurrence of an upcoming outcome perceived as uncertain.

METHODS/FINDINGS

We tested the uncertainty hypothesis by using a repeated measures design in a Human Contingency Learning task with two levels of uncertainty. In the high uncertainty condition, the outcome is unpredictable. In the mid uncertainty condition, the outcome can be learnt to be predicted in 75% of the trials. Our experiment shows that the Stimulus Preceding Negativity is larger for probabilistically unpredictable (uncertain) outcomes than for probabilistically predictable ones. sLoreta estimations of the brain activity preceding the outcome suggest that prefrontal and parietal areas can be involved in its generation. Prefrontal sites activation (Anterior Cingulate and Dorsolateral Prefrontal Cortex) seems to be related to the degree of uncertainty. Activation in posterior parietal areas, however, does not correlates with uncertainty.

CONCLUSIONS/SIGNIFICANCE

We suggest that the Stimulus Preceding Negativity reflects the attempt to predict the outcome, when posterior brain areas fail to generate a stable expectancy. Uncertainty is thus conceptualized, not just as the absence of learned expectancy, but as a state with psychological and physiological entity.

Effect of directional speech warnings on road hazard detection

BACKGROUND

In the last 2 decades, cognitive science and the transportation psychology field have dedicated a lot of effort to designing advanced driver support systems. Verbal warning systems are increasingly being implemented in modern automobiles in an effort to increase road safety.

OBJECTIVE

The study presented here investigated the impact of directional speech alert messages on the participants' speed to judge whether or not naturalistic road scenes depicted a situation of impending danger.

METHOD

Thirty-eight volunteers performed a computer-based key-press reaction time task.

RESULTS

Findings indicated that semantic content of verbal warning signals can be used for increasing driving safety and improving hazard detection. Furthermore, the classical result regarding signal accuracy is confirmed: directional informative speech messages lead to faster hazard detection compared to drivers who received a high rate of false alarms.

CONCLUSION

Notwithstanding some study limitations (lack of driver experience and low ecological validity), this evidence could provide important information for the specification of future Human-Machine-interaction (HMI) design guidelines.

Emotional modulation of urgent and evaluative behaviors in risky driving scenarios

This study demonstrated that task features are important factors for the understanding of risk behavior under emotional conditions in driving scenarios. We introduce a distinction between urgent and evaluative behaviors. Urgent behaviors are performed under high time-pressure and, when successful, they will help to avoid high negative outcomes. According to some social psychologists, evaluation is considered a type of value categorization (for example, risk or no risk). Emotional cues in the urgency task make participants slower and less able to discriminate risk from no risk, and prone to positive responses. However, negative emotional pictures speed up the evaluation of risk without affecting the ability to discriminate risk from no risk in a driving scenario.

[Role of peritoneal drainage in very low birth weight with enterocolitis]

Peritoneal drainage (PD) has been proposed as a temporizing procedure for perforated necrotizing enterocolitis (NEC) in very low birth weight neonates. This operation was designed for patients considered too unstable to undergo laparotomy (LAP). Since the introduction of PD some investigators have suggested that it may serve as a definitive therapy. The aim of our study is to determine the efficacy of PD for the stabilization of patients with complicated NEC and its utility as a definitive surgical treatment.

METHODS

We review the clinical records from all the patients treated in our unit because of NEC that required surgical therapy. We analyze the mean blood pressure, cardiac and respiratory rate, inspired oxygen concentration, mean airway pressure, diuresis, and arterial blood gases measured 6 and 12 hours after the initial surgical treatment. We divide patients in two different groups according to the initial surgical procedure, peritoneal drainage (PD) or laparotomy group (LAP). Data is shown as media +/- standard deviation, statistical analyses were performed using analysis of variance (ANOVA) for repeated measures and Mann-Withney test.

RESULTS

From January 1997 to January 2001 we treated 13 patients with necrotizing enterocolitis that required surgical treatment. Among this group 6 patients were managed initially with PD and 7 with LAP. The gestational age media was 29.07 +/- 3.81 weeks and the birth weight mean 1199.76 +/- 521 gr., without any significant differences between the two groups DP and LAP. All patients improved haemodynamically and respiratory 6 and 12 hours after the surgical treatment. Nevertheless, the mean blood pressure improved even more in the DP group (p<0.005). The DP group showed an improvement in all parameters 6 hours after the drainage was placed, but this effect wasn't maintained for the next 12 hours onwards. From the 12 hours after PD all patients suffered a steady worsening that required further surgical procedures. The overall mortality was 3 patients (23%), without differences between the two groups. The surgical techniques performed (bowel resection, diversion) were similar for both groups.

DISCUSSION

DP allows the stabilization for very critically ill patients with complicated NEC. However, this stabilization is temporary. This improvement lasts for a few hours providing a better status for the definitive surgical treatment for the perforated NEC. In our experience DP could not be considered as a definitive surgical treatment.

Disturbances of the sarcoplasmic reticulum and transverse tubular system in 24-h electrostimulated fast-twitch skeletal muscle

Chronic low-frequency stimulation of rabbit tibialis anterior muscle over a 24-h period induces a conspicuous loss of isometric tension that is unrelated to muscle energy metabolism (J.A. Cadefau, J. Parra, R. Cusso, G. Heine, D. Pette, Responses of fatigable and fatigue-resistant fibres of rabbit muscle to low-frequency stimulation, Pflugers Arch. 424 (1993) 529-537). To assess the involvement of sarcoplasmic reticulum and transverse tubular system in this force impairment, we isolated microsomal fractions from stimulated and control (contralateral, unstimulated) muscles on discontinuous sucrose gradients (27-32-34-38-45%, wt/wt). All the fractions were characterized in terms of calcium content, Ca2+/Mg2+-ATPase activity, and radioligand binding of [3H]-PN 200-110 and [3H]ryanodine, specific to dihydropyridine-sensitive calcium channels and ryanodine receptors, respectively. Gradient fractions of muscles stimulated for 24 h underwent acute changes in the pattern of protein bands. First, light fractions from longitudinal sarcoplasmic reticulum, enriched in Ca2+-ATPase activity, R1 and R2, were greatly reduced (67% and 51%, respectively); this reduction was reflected in protein yield of crude microsomal fractions prior to gradient loading (25%). Second, heavy fractions from the sarcoplasmic reticulum were modified, and part (52%) of the R3 fraction was shifted to the R4 fraction, which appeared as a thick, clotted band. Quantification of [3H]-PN 200-110 and [3H]-ryanodine binding revealed co-migration of terminal cisternae and t-tubules from R3 to R4, indicating the presence of triads. This density change may be associated with calcium overload of the sarcoplasmic reticulum, since total calcium rose three- to fourfold in stimulated muscle homogenates. These changes correlate well with ultrastructural damage to longitudinal sarcoplasmic reticulum and swelling of t-tubules revealed by electron microscopy. The ultrastructural changes observed here reflect exercise-induced damage of membrane systems that might severely compromise muscle function. Since this process is reversible, we suggest that it may be part of a physiological response to fatigue.

Responses of rat myocardial antioxidant defences and heat shock protein HSP72 induced by 12 and 24-week treadmill training

AIM

The purpose of this study was to determine the effects of both a short (12 weeks) and a long-term (24 weeks) endurance treadmill-training programme on the levels of oxidative stress markers, the activity of the enzymatic antioxidants, and the content of the 72 kDa heat shock protein (HSP72) in rat myocardium.

METHODS

Thirty male Wistar rats were randomly assigned to exercise trained (n = 16) and sedentary (n = 14) groups. After 12 week of training, eight rats were killed while the remaining eight continued the training programme until 24 week.

RESULTS

Seven sedentary controls were killed together with each trained group. Levels of thiobarbituric acid-reactive substances (TBARS), protein carbonyls, and total and oxidized glutathione (tGSH and GSSG) in myocardial homogenates were unchanged by training irrespective of the protocol duration. However, an increased content of the oxidative stress biomarkers was detected in hearts from both the 24-week trained rats and their sedentary controls when compared with their corresponding 12-week groups. The antioxidant enzymatic activities total and mitochondrial superoxide dismutase (tSOD and mtSOD, respectively), glutathione peroxidase (GPX) and glutathione reductase (GR), remained unchanged after the 12-week training period whereas a significant increase in tSOD and mtSOD activities (18%, P < 0.05) was observed in heart homogenates of 24-week trained animals as compared with their sedentary controls. HSP72 expression levels were not significantly modified after 12 week of training but a threefold increase was detected after 24 week (P < 0.05).

CONCLUSION

These results demonstrate that a long-term endurance training (24 weeks) induced discrete increases in antioxidant enzyme activities in rat myocardium and elicited a marked enhancement in HSP72 expression levels. However, a shorter training programme (12 weeks), was not effective in increasing heart antioxidant defences.

Regulation of transverse tubule ecto-ATPase activity in chicken skeletal muscle

Transverse tubule (T-tubule) ecto-ATPase from chicken skeletal muscle is an integral membrane glycoprotein that seems to exist as a homodimer and exhibits unusual properties. Treatment of T-tubule membranes with concanavalin A (Con A) did not significantly affect the thermal variation of the fluorescence anisotropy of vesicles labelled with 1,6-diphenyl-1,3,5-hexatriene or trimethylammonium-1,6-diphenyl-1,3,5-hexatriene. Cross-linking of membrane components with glutaraldehyde elicited effects on ecto-ATPase activity very similar to those of Con A treatment: a severalfold increase in activity, a decrease in Triton X-100 sensitivity and a requirement to be present before ATP to exert its action. In addition, glutaraldehyde and Con A normalized the temperature dependence and the kinetic behaviour of the enzyme. Membrane-perturbing agents (detergents, alcohols and cholesterol oxidase), with the sole exception of digitonin, caused a marked decrease in ecto-ATPase activity; the prior presence of Con A prevented this inhibition, whereas when the lectin was added after the membrane perturbing agent, recovery of the activity was not always possible. The addition of nucleotides before Con A led to a suppression of ecto-ATPase stimulation; it occurred when the nucleotide was hydrolysed (ATP or UTP) and when it was not (adenosine 5'-[beta,gamma-imido]triphosphate) and even in the presence of 3 mM P(i). A model is proposed for the complex regulatory mechanisms of chicken T-tubule ecto-ATPase that involves the occurrence of two different catalytic states in an equilibrium modulated by lectins and cross-linking agents, by the structure of the membrane and by the presence of ligands for a regulatory site.

[Yield of transthoracic echocardiography with high frequency transducer in the study of the anterior descending coronary artery]

INTRODUCTION AND OBJECTIVES

This study was performed to evaluate the feasibility and utility of a transthoracic high frequency transducer to detect and measure the left anterior descending coronary artery flow in patients with lesions in this artery or anterior myocardial infarction.

MATERIALS AND METHODS

We studied 11 subjects with lesions greater than 75% and another 10 with anterior myocardial infarction. We compared the results with a control group of 18 subjects. An ATL HDI 5000 ultrasound unit with a 5-8 MHz transducer was used to identify the left anterior descending in the anterior interventricular sulcus from an apical four chamber window. We considered that left anterior descending was detected when a diastolic predominant flow pattern was obtained with pulse Doppler.

RESULTS

Left anterior descending was detected in 37/39 of cases (94.4%). Patients with coronary lesions showed a decrease in the limit of significance in the diastolic/systolic peak velocity ratios: 2.5 (SD 0.7) vs 1.8 (SD 0.3) with a p = 0.024. Patients with anterior myocardial infarction obtained lower diastolic/systolic peak velocity ratios than controls: 2.5 (SD 0.7) vs 1.4 (SD 0.3) with a p = 0.001.

CONCLUSIONS

Left anterior descending coronary artery flow can be assessed by transthoracic high frequency echocardiography in greater than 90% of the cases. Patients with coronary lesions and those with anterior myocardial infarction have a decreased diastolic/systolic peak velocity ratio.

[Early assessment in perinatal hypoxia. Prognostic markers]

INTRODUCTION

Perinatal asphyxia and its neurological signs are the most important cause of brain damage and neurological sequelae in full term newborn babies. Neuroprotection treatments currently being investigated promise to reduce such sequelae, but these treatments are not without risk and the patients involved should be selected.

OBJECTIVE

To analyze a scale composed of variables recorded from the start of delivery until the fourth hour of life, comparing the neurological evolution of the patients. By means of this scale we aim to establish a criterion for the selection of neonates with acute perinatal asphyxia, who would benefit from neuroprotector treatment.

PATIENTS AND METHODS

A retrospective study was made of 50 patients with the diagnosis of perinatal asphyxia. Our scale was formed of the following variables: intrauterine meconiorrhexis, pathological cardiotocographic recordings, resuscitation at birth, Apgar score at five minutes, pH of the umbilical artery blood, neurological examination, multisystemic involvement, seizures, persistent metabolic acidosis and need for mechanical ventilation during the first hours of life. The patients were followed up for at least one year by means of periodical studies (neurological examination and evaluation of psychomotor development according to the Brunnet Lezinne test). For statistical analysis we used the chi squared test, Fisher's exact test, Kruskal-Wallis test and the area beneath the ROC curve.

RESULTS AND CONCLUSIONS

The scale presented constitutes a rapid, easy method which is statistically significant for the selection of perinatal asphyxia of high neurological risk which would benefit from neuroprotector treatment after the event.

Short-term effects of marathon running in master runners: no evidence of myocardial injury

The purpose of this investigation was to analyze the short-term effects of marathon running on serum levels of cardiac markers in a group of master runners (> 60 yrs). Ten marathoners (9 male and 1 female; 63+/-4 yrs) were enrolled in the study. All of them completed the Madrid Marathon (1998). Venous blood was drawn from each subject three times during the study (48 h before the race, immediately after the race, and 24 h post-competition) for the determination of the several biochemical markers, such as total creatine kinase catalytic activity (total CK), mass concentration of creatine kinase isoenzyme MB (CK-MB mass), and cardiac troponin I (Tnl-c). The most important finding was that in each sample (pre- or post-race) serum Tnl-c was below the commonly accepted level of 0.1 ng x m(-1) indicative of myocardial injury. Although further research is needed using more complete methodology, our results suggest that marathon running does not have an acute deleterious effect on the hearts of the elderly.

Short-term effects of marathon running: no evidence of cardiac dysfunction

PURPOSE

The purpose of this study was to analyze the short-term effects of a marathon race (Madrid Marathon) on both markers of cardiac damage and echocardiographic parameters in a group of 22 runners (17 male and 5 female; 34 +/- 5 yr; VO2max: 55.7 +/- 9.1 mL x kg(-1) x min(-1) with a wide range of fitness levels.

METHODS

Venous blood samples were collected from each subject 48 h before the race, at race finish, and 6, 24, and 48 h postexercise for the determination of myoglobin, total creatine kinase catalytic activity (total CK), mass concentration of creatine kinase isoenzyme MB (CK-MB mass), and cardiac isoforms of troponin T and I (TnT-c and TnI-c, respectively). In addition, echocardiographic parameters (M-mode two-dimensional and Doppler analysis) indicative of both left ventricular (LV) systolic and diastolic function were obtained three times from each runner: 2-5 d before the race, at race finish, and 24-36 h after exercise.

RESULTS

Except in one subject, levels of TnT-c and TnI-c were within normal limits (<0.1 ng x mL(-1)) in all the samples collected before or after the race. Overall LV systolic function was not altered by marathon running. Finally, LV diastolic function was transiently altered after the race since the ratio between peak early and late transmitral filling velocities (E/A) was significantly reduced at race finish (P < 0.01) and returned to resting levels after 24-36 h.

CONCLUSIONS

Our findings suggest that marathon running does not adversely affect the hearts of healthy individuals independently from their training status.

Chronic and acute exercise do not alter Ca2+ regulatory systems and ectonucleotidase activities in rat heart

The purpose of this investigation was to examine the effects of chronic and acute exercise on the main components involved in excitation-contraction coupling and relaxation in rat heart. Sixty male Wistar rats were divided into a sedentary (S) and three 12-wk treadmill-trained groups (T-1, moderate intensity; T-2, high intensity; T-3, interval running). After 12-wk, 15 rats from the S group and 15 rats from the T-2 group were subjected to a single treadmill-exercise session until exhaustion before being killed at 0, 24, or 48 h (acute exercise). The remaining animals were killed 48 h after the last standard exercise session (chronic exercise). The efficacy of the training programs was confirmed by an increase in treadmill endurance time and in skeletal muscle citrate synthase activity. None of the exercise programs modified heart weight or cardiac oxidative capacity. [(3)H]PN200-110 and [(3)H]ryanodine binding to cardiac homogenates indicated that the density of L-type and sarcoplasmic reticulum (SR) Ca(2+) channels was the same in S and trained rats. The SR Ca(2+)-ATPase activity was also unmodified. Finally, the activities of the ectoenzymes Mg(2+)-ATPase and 5'-nucleotidase, which are involved in degradation of extracellular nucleotides, were not affected by either of the running programs. After the acute exercise session, no changes were detected in either of the tested parameters in heart homogenates of S and T-2 animals. We conclude that neither treadmill-exercise training for 12 wk nor exhaustive exercise alters the density of Ca(2+) channels involved in excitation-contraction coupling or the SR Ca(2+)-ATPase and the ectonucleotidase activities in rat heart.

Measurement of sarcoplasmic reticulum Ca2+-ATPase activity and E-type Mg2+-ATPase activity in rat heart homogenates

The presence of a high and nonlinear Ca2+-independent (or basal) ATPase activity in rat heart preparations makes difficult the reliable measurement of sarcoplasmic reticulum (SR) Ca2+-ATPase activity by usual methods. A spectrophotometric assay for the accurate determination of SR Ca2+-ATPase activity in unfractionated homogenates from rat heart is described. The procedure is based on that reported by Simonides and van Hardeveld (1990, Anal. Biochem. 191, 321-331) for skeletal muscle homogenates. To avoid overestimation of the Ca2+-ATPase activity of cardiac homogenates that occurs when sequential measurements of total and basal ATPase activities are performed, two parallel and independent assays are required: one with low (micromolar) and other high (millimolar) calcium concentration. Addition of thapsigargin (0.2 microM) blocked totally the activity considered as Ca2+-ATPase activity. Using this method, the rat heart homogenate Ca2+-ATPase activity was 10.5 +/- 2.0 micromol. min-1 x g-1 tissue wet weight (n = 8). Likewise, a spectrophotometric assay for measuring E-type Mg2+-ATPase activity in cardiac total homogenates has been developed, comparing the following characteristics of the enzymatic activity in homogenate and a membrane-enriched fraction: first-order rate constant for ATP-dependent inactivation, Km for ATP, and effects of concanavalin A, Triton X-100, and specific inhibitors.

Rat liver lysosomal and mitochondrial activities are modified by anabolic-androgenic steroids

PURPOSE

The aim of this study was to examine the separate and combined effects of an 8-wk treatment with high doses of 17alpha-alkylated anabolic-androgenic steroids (AAS) and exercise training on selected lysosomal and mitochondrial enzyme activities in rat liver.

METHODS

Sedentary and treadmill-trained (25 m x min(-1), 45 min x d(-1), 5 d x wk(-1)) male rats were treated with fluoxymesterone, methylandrostanolone, or stanozolol (2 mg x kg body weight(-1), 5 d x wk(-1)) for 8 wk.

RESULTS

Acid phosphatase, arylsulfatase, beta-glucuronidase, and beta-galactosidase activities were increased in liver homogenates of sedentary and trained AAS-treated rats. The mitochondrial respiratory chain activities rotenone-sensitive NADH-cytochrome c reductase (NCCR), succinate cytochrome c reductase (SCCR), and cytochrome oxidase (COX) showed a significant decrease in steroid-administered rats, whereas citrate synthase (CS), a matrix enzyme, exhibited no changes in activity, pointing to a selective effect of AAS on mitochondrial membrane complexes. In vitro studies in mitochondrial fractions isolated from the liver of control rats showed that COX and CS activities were insensitive to the AAS, whereas NCCR and SCCR activities were partly inhibited. On the other hand, the mean values of serum parameters related to hepatic function were within normal ranges in all the experimental groups of animals.

CONCLUSIONS

The present data show that 8-wk ingestion of three different anabolic-androgenic steroids, either with or without concurrent exercise training, affects lysosomal hydrolases and mitochondrial respiratory chain electron transport in rat liver without modifying classical serum indicators of hepatic function.

T-tubule membranes from chicken skeletal muscle possess an enzymic cascade for degradation of extracellular ATP

The chicken T-tubule Mg2+-ATPase is an integral membrane glycoprotein that presents properties different from those of other ATPases located in skeletal muscle cells and exhibits ATP-hydrolysing activity on the extracellular side of the transverse tubule (TT) membranes. In this study we demonstrate that TT vesicles purified from chicken skeletal muscle possess ecto-ADPase and ecto-5'-nucleotidase activities that, along with ecto-ATPase, are able to sequentially degrade extracellular ATP to ADP, AMP and adenosine. Characterization studies of these TT ectonucleotidases revealed remarkable differences between ecto-ATPase and ecto-ADPase activities with respect to thermal stability, temperature dependence of the hydrolytic activity, effect of ionic strength, kinetic behaviour, divalent cation preference and responses to azide, N-ethylmaleimide, NaSCN, Triton X-100 and concanavalin A. Ecto-ATPase, but not ecto-ADPase, was inhibited by a polyclonal antibody against the chicken TT ecto-ATPase. On the basis of these results we propose that ATP and ADP hydrolysis are accomplished by two distinct enzymes and therefore the TT ecto-ATPase is not an apyrase. 5'-Nucleotidase activity was inhibited by adenosine 5'-[alpha,beta-methylene]diphosphate and concanavalin A, followed simple Michaelis-Menten kinetics and was released from the membranes by treatment with phosphatidylinositol-specific phospholipase C, indicating that AMP hydrolysis in T-tubules is catalysed by a typical ecto-5'-nucleotidase. Results obtained from electrophoresis experiments under native conditions suggest that ecto-ATPase, ecto-ADPase and 5'-nucleotidase might be associated, forming functional complexes in the T-tubule membranes. The TT ectonucleotidases constitute an enzymic cascade for the degradation of extracellular ATP that might be involved in the regulation of purinergic signalling in the muscle fibre.

Regulation of dihydropyridine receptor levels in skeletal and cardiac muscle by exercise training

To examine the influence of exercise training on the expression of dihydropyridine (DHP)-sensitive Ca2+ channels in skeletal and cardiac muscle, we have determined DHP receptor levels by [3H]PN200-110-binding and immunoblot analysis in homogenates and microsomal fractions of slow- and fast-twitch muscles and heart from rats subjected to a 12-week programme of moderate endurance training. We found that exercise increases the amount of DHP receptor in homogenates of the slow-twitch soleus (42%) and the fast-twitch extensor digitorum longus (60%). Comparable increases in DHP receptor density with training were also observed in the microsomal fractions isolated from both skeletal muscles; these increases were not due to differences in the membrane composition of the microsomal fractions, since the relative proportion of specific enzyme markers was not affected by exercise training. Levels of DHP receptor were not modified in cardiac muscle as a result of the exercise programme. These data suggest an up-regulation of the DHP receptor in the skeletal muscle as a consequence of exercise training, which may play a role in the adaptation of skeletal muscle to increased contractile activity.

Ultrastructural changes induced by anabolic steroids in liver of trained rats

The effects of anabolic steroid treatment in association with endurance training on biochemical serum parameters and liver ultrastructure have been investigated in male rats. Values of serum alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase were not significantly affected by administration of high doses of fluoxymesterone or methylandrostanolone. Electron microscopic examination of hepatic tissue from treated animals revealed ultrastructural alterations of hepatocytes. The most prominent changes were swelling of mitochondria, which presented electron-lucent matrix and slightly defined cristae, and a marked increase in the number of lysosomes. These changes were evident in both sedentary and trained treated rats, indicating that liver cell damage is produced by anabolic-androgenic steroids despite the simultaneous realization of physical exercise. The alterations observed were not detected by means of conventional biochemical liver tests.

Effect of training and anabolic-androgenic steroids on drug metabolism in rat liver

The effects of anabolic-androgenic steroid administration and exercise training on various aspects of hepatic function were investigated in sedentary and trained (treadmill for 12 wk) male and female rats treated orally with fluoxymesterone or methylandrostanolone (2 mg.kg-1 body weight, 5 d.wk-1 for 8 wk). The mean values of serum alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total and direct bilirubin, and total- and high-density lipoprotein-cholesterol remained within normal range in all groups of male animals. The same is true for female rats, except for an increase in alkaline phosphatase activity in the steroid-treated groups. Hepatic microsomal aniline p-hydroxylase activity was reduced in male and increased in female rats by either steroid, whereas no significant effect was detected on 7-ethoxycoumarin deethylase activity. The levels of cytochrome P-450 and cytochrome b5 were markedly decreased by the anabolic-androgenic steroid treatment in male rat microsomes, but neither the steroid administration nor exercise training induced significant changes in the cytochrome levels of female rat livers. Taking into account the significant increase in microsomal protein yield elicited by fluoxymesterone or methylandrostanolone treatment both in males and females, it is noteworthy that the total monooxygenase activities and cytochrome P-450 content, expressed on a per gram liver basis, were significantly increased in female whereas they were apparently unchanged in male rats. In conclusion, the present data show that the prolonged ingestion of high doses of anabolic-androgenic steroids, either with or without concurrent exercise training, can modify in a sex-dependent manner the capacity of rat liver to metabolize drugs without affecting classical serum indicators of hepatic function.

Transverse tubule Mg(2+)-ATPase of skeletal muscle. Evidence for extracellular orientation of the chicken and rabbit enzymes

The orientation of the enzyme Mg(2+)-ATPase (EC 3.6.1.3) in the transverse tubule (TT) membranes of skeletal muscle was investigated using highly purified chicken and rabbit TT vesicles. The percentage of sealed vesicles present in these preparations averaged 88 and 78%, respectively, as calculated from the detergent-induced increase in ouabain-sensitive (Na+, K+)-ATPase activity, ATP-dependent ouabain binding, and lactate dehydrogenase activity (sarcoplasmic enzyme trapped in the TT vesicles). Sidedness of the sealed vesicles, estimated from latency of 5'-nucleotidase, acetylcholinesterase, and adenylate cyclase, was predominantly right-side out (69-76%, chicken TT and 62-70%, rabbit TT). In both chicken and rabbit native vesicles, high Mg(2+)-ATPase activity was detected by addition of ATP to the extravesicular medium; this activity was increased 14-12% by alamethicin pointing to the external localization of the active site. Furthermore, the enzymatic activity resulted partially inhibited by treatment of the chicken TT vesicles with proteinase K or p-hydroxymercuribenzoate. Concanavalin A stimulated 4-fold the chicken TT Mg(2+)-ATPase activity, an effect not potentiated by detergent permeabilization of the intact vesicles, indicating that lectin-binding sites were also solvent accessible. This stimulatory effect was not observed in native or permeabilized rabbit TT vesicles. From these results we conclude that the TT Mg(2+)-ATPase is an ectoenzyme with its nucleotide-hydrolyzing site and glycosylated regions facing the extracellular space. Inhibitors of ion-motive ATPases did not modify the enzyme activity, suggesting a different physiological role for the TT Mg(2+)-ATPase which may be involved in the regulation of muscle fiber functions affected by extracellular ATP levels.

Effect of anabolic steroids on mitochondria and sarcotubular system of skeletal muscle

Soleus and extensor digitorum longus (EDL) mitochondria and sarcotubular system were examined in sedentary and trained (treadmill for 12 wk) male rats that were treated with fluoxymesterone or methandrostanolone (2 mg/kg, 5 days/wk, for 8 wk). Neither physical exercise nor anabolic/androgenic steroid administration resulted in a significant change in muscle wet weight. Treatment with the anabolizing androgens increased succinate dehydrogenase activity in fast-twitch muscle mitochondria; this effect was not enhanced by training and was not observed in soleus mitochondria. On the other hand, the content of the slow-twitch muscle in sarcotubular fraction was increased in sedentary rats by fluoxymesterone or methandrostanolone treatment, whereas no significant changes were found in EDL. The training program affected adenosinetriphosphatase (ATPase) activities in the sarcotubular fraction; Mg2(+)-ATPase was increased in both soleus and EDL, but Ca2(+)-ATPase was decreased only in soleus. However, in sedentary animals only the Mg2(+)-dependent activity of EDL was increased by anabolizing androgen treatment, and this change was not potentiated by additional training. The present data indicate that anabolic/androgenic steroids can affect mitochondrial and sarcotubular enzymes in skeletal muscle. The effects are muscle-type specific.

Abnormal properties of Mg2(+)-ATPase in transverse tubule membranes from dystrophic chicken

Purified transverse tubule membranes from normal and dystrophic chicken skeletal muscle were isolated by a calcium-loading procedure. Normal and dystrophic T-tubules were similar in cholesterol content and (Na+,K+)-ATPase and 5'-nucleotidase activities but a significant decrease of Mg2(+)-ATPase activity was observed in dystrophic membranes. A comparative analysis of the enzyme properties revealed that the kinetic parameters were altered in dystrophic T-tubules and the ATP-hydrolyzing activity was differently affected by the ionic strength. However, the influence of temperature and the regulatory effect of concanavalin A were the same as in normal T-tubules. Membrane fluidity was similar in both preparations as estimated by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene and trimethylammonium diphenylhexatriene. These results point to an impairment in the function of Mg2(+)-ATPase due to structural alterations of the enzyme.