Stochastic reaction-diffusion modeling of calcium dynamics in 3D dendritic spines of Purkinje cells.

Calcium (Ca2+) is a second messenger assumed to control changes in synaptic strength in the form of both long-term depression and long-term potentiation at Purkinje cell dendritic spine synapses via inositol trisphosphate (IP3)-induced Ca2+ release. These Ca2+ transients happen in response to stimuli from parallel fibers (PFs) from granule cells and climbing fibers (CFs) from the inferior olivary nucleus. These events occur at low numbers of free Ca2+, requiring stochastic single-particle methods when modeling them. We use the stochastic particle simulation program MCell to simulate Ca2+ transients within a three-dimensional Purkinje cell dendritic spine. The model spine includes the endoplasmic reticulum, several Ca2+ transporters, and endogenous buffer molecules. Our simulations successfully reproduce properties of Ca2+ transients in different dynamical situations. We test two different models of the IP3 receptor (IP3R). The model with nonlinear concentration response of binding of activating Ca2+ reproduces experimental results better than the model with linear response because of the filtering of noise. Our results also suggest that Ca2+-dependent inhibition of the IP3R needs to be slow to reproduce experimental results. Simulations suggest the experimentally observed optimal timing window of CF stimuli arises from the relative timing of CF influx of Ca2+ and IP3 production sensitizing IP3R for Ca2+-induced Ca2+ release. We also model ataxia, a loss of fine motor control assumed to be the result of malfunctioning information transmission at the granule to Purkinje cell synapse, resulting in a decrease or loss of Ca2+ transients. Finally, we propose possible ways of recovering Ca2+ transients under ataxia.

A stochastic signaling network mediates the probabilistic induction of cerebellar long-term depression.

Many cellular processes involve a small number of molecules and undergo stochastic fluctuations in their levels of activity. Cerebellar long-term depression (LTD) is a form of synaptic plasticity expressed as a reduction in the number of synaptic AMPA receptors (AMPARs) in Purkinje cells. We developed a stochastic model of the LTD signaling network, including a PKC-ERK-cPLA(2) positive feedback loop and mechanisms of AMPAR trafficking, and tuned the model to replicate calcium uncaging experiments. The signaling network activity in single synapses switches between two discrete stable states (LTD and non-LTD) in a probabilistic manner. The stochasticity of the signaling network causes threshold dithering and allows at the macroscopic level for many different and stable mean magnitudes of depression. The probability of LTD occurrence in a single spine is only modulated by the concentration and duration of the signal used to trigger it, and inputs with the same magnitude can give rise to two different responses; there is no threshold for the input signal. The stochasticity is intrinsic to the signaling network and not mostly dependent on noise in the calcium input signal, as has been suggested previously. The activities of the ultrasensitive ERK and of cPLA(2) undergo strong stochastic fluctuations. Conversely, PKC, which acts as a noise filter, is more constantly activated. Systematic variation of the biochemical population size demonstrates that threshold dithering and the absence of spontaneous LTD depend critically on the number of molecules in a spine, indicating constraints on spine size in Purkinje cells.

3D Modeling of Dendritic Spines with Synaptic Plasticity.

Computational modeling of diffusion and reaction of chemical species in a three-dimensional (3D) geometry is a fundamental method to understand the mechanisms of synaptic plasticity in dendritic spines. In this protocol, the detailed 3D structure of the dendrites and dendritic spines is modeled with meshes on the software Blender with CellBlender. The synaptic and extrasynaptic regions are defined on the mesh. Next, the synaptic receptor and synaptic anchor molecules are defined with their diffusion constants. Finally, the chemical reactions between synaptic receptors and synaptic anchors are included and the computational model is solved numerically with the software MCell. This method describes the spatiotemporal path of every single molecule in a 3D geometrical structure. Thus, it is very useful to study the trafficking of synaptic receptors in and out of the dendritic spines during the occurrence of synaptic plasticity. A limitation of this method is that the high number of molecules slows the speed of the simulations. Modeling of dendritic spines with this method allows the study of homosynaptic potentiation and depression within single spines and heterosynaptic plasticity between neighbor dendritic spines.

Mirror Neurons Modeled Through Spike-Timing-Dependent Plasticity are Affected by Channelopathies Associated with Autism Spectrum Disorder.

Mirror neurons fire action potentials both when the agent performs a certain behavior and watches someone performing a similar action. Here, we present an original mirror neuron model based on the spike-timing-dependent plasticity (STDP) between two morpho-electrical models of neocortical pyramidal neurons. Both neurons fired spontaneously with basal firing rate that follows a Poisson distribution, and the STDP between them was modeled by the triplet algorithm. Our simulation results demonstrated that STDP is sufficient for the rise of mirror neuron function between the pairs of neocortical neurons. This is a proof of concept that pairs of neocortical neurons associating sensory inputs to motor outputs could operate like mirror neurons. In addition, we used the mirror neuron model to investigate whether channelopathies associated with autism spectrum disorder could impair the modeled mirror function. Our simulation results showed that impaired hyperpolarization-activated cationic currents (Ih) affected the mirror function between the pairs of neocortical neurons coupled by STDP.

Effects of lidocaine and the inclusion complex with 2-hydroxypropyl-ß-cyclodextrin on cell viability and proliferation of oral squamous cell carcinoma.

OBJECTIVES: Squamous cell carcinoma (SCC) is a malignant disease that affects the oral cavity. Lidocaine has shown antiproliferative and cytotoxic activity on several cell types. The rapid dispersion is a limitation issue; however, the complexation in cyclodextrin improved pharmacological features and modified the drug release. This study investigated the effects of lidocaine (lido) complexed with 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD-lido) on cell viability and proliferation of human tongue squamous cell carcinoma SCC9 and SCC25. METHODS: The complex formation was confirmed by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Cells SCC9 and SCC25 were exposed to lido and HP-ß-CD-lido (40-4000 µm), and the effects on cell viability (MTT) and antiproliferative activity (SRB) were tested. KEY FINDINGS: Differential scanning calorimetry and SEM results demonstrated the occurrence of host-guest interaction. Lido and HP-ß-CD-lido (4000 µm) significantly reduced the viability of SCC9 cells to 83% and 63%, respectively. The viability of SCC25 treated with lido, and HP-ß-CD-lido (4000 µm) was 71% and 44%, respectively. Lido (4000 µm) reduced the proliferation of SCC9 and SCC25 to 39.5% and 23.7%, respectively. HP-ß-CD-lido (4000 µm) was cytotoxic for both cell lines. CONCLUSIONS: HP-ß-CD was able to potentiate the in vitro cytotoxic effects of lidocaine on human squamous cell carcinoma.

Bioactive coating of sodium alginate and agar added with essential oils of thyme (thymus vulgaris l.) and sweet orange (citrus aurantium var. dulcis) with antimicrobial properties applied over strawberries

Minimally processed strawberries have high acceptability but a short shelf life. The application of edible coatings with essential oils may be an alternative to preserve these fruits. Our objective was to develop, apply and characterize the effect of bioactive edible coatings based on agar or sodium alginate with thyme and/or sweet orange essential oils with antimicrobial properties, mainly against Listeria monocytogenes, for strawberries. The effect of the coatings on the physicochemical, microbiological, and sensory properties that determine the shelf life of strawberries was verified at 1, 8, and 15 days. The effect against Listeria monocytogenes bacteria in strawberries artificially contaminated with this microorganism was also evaluated. Thyme and sweet orange essential oils had thymol and D-limonene, respectively, as main components. Alginate coating with sweet orange and thyme essential oil showed the best results. For Listeria monocytogenes, the coating applied after fruit contamination had an antimicrobial effect.

Las fresas mínimamente procesadas tienen una alta aceptación, pero una vida útil corta. La aplicación de recubrimientos comestibles con aceites esenciales puede ser una alternativa para conservar estos frutos. El objetivo fue desarrollar, aplicar y caracterizar el efecto del uso de recubrimientos comestibles bioactivos, a base de agar agar o alginato de sodio, adicionados con aceites esenciales de tomillo y/o naranja dulce, con propiedades antimicrobianas, principalmente anti-Listeria monocytogenes sobre la fresa. Se verificó el efecto de los recubrimientos sobre las características fisicoquímicas, microbiológicas y sensoriales que determinan la vida útil de las fresas a 1, 8 y 15 días. También se evaluó el efecto contra la bacteria Listeria monocytogenes en fresas contaminadas artificialmente con este microorganismo. Los aceites esenciales de tomillo y naranja dulce presentaron timol y D-limoneno como compuestos mayoritarios, respectivamente. El recubrimiento de alginato con aceite esencial de naranja dulce y tomillo mostró los mejores resultados. Para Listeria monocytogenes, el recubrimiento aplicado después de la contaminación de la fruta tuvo un efecto antimicrobiano.

Olfactory receptor signaling.

The guanine nucleotide protein (G protein)-coupled receptors (GPCRs) superfamily represents the largest class of membrane protein in the human genome. More than a half of all GPCRs are dedicated to interact with odorants and are termed odorant-receptors (ORs). Linda Buck and Richard Axel, the Nobel Prize laureates in physiology or medicine in 2004, first cloned and characterized the gene family that encode ORs, establishing the foundations to the understanding of the molecular basis for odor recognition. In the last decades, a lot of progress has been done to unravel the functioning of the sense of smell. This chapter gives a general overview of the topic of olfactory receptor signaling and reviews recent advances in this field.

Modelling intracellular competition for calcium: kinetic and thermodynamic control of different molecular modes of signal decoding.

Frequently, a common chemical entity triggers opposite cellular processes, which implies that the components of signalling networks must detect signals not only through their chemical natures, but also through their dynamic properties. To gain insights on the mechanisms of discrimination of the dynamic properties of cellular signals, we developed a computational stochastic model and investigated how three calcium ion (Ca(2+))-dependent enzymes (adenylyl cyclase (AC), phosphodiesterase 1 (PDE1), and calcineurin (CaN)) differentially detect Ca(2+) transients in a hippocampal dendritic spine. The balance among AC, PDE1 and CaN might determine the occurrence of opposite Ca(2+)-induced forms of synaptic plasticity, long-term potentiation (LTP) and long-term depression (LTD). CaN is essential for LTD. AC and PDE1 regulate, indirectly, protein kinase A, which counteracts CaN during LTP. Stimulations of AC, PDE1 and CaN with artificial and physiological Ca(2+) signals demonstrated that AC and CaN have Ca(2+) requirements modulated dynamically by different properties of the signals used to stimulate them, because their interactions with Ca(2+) often occur under kinetic control. Contrarily, PDE1 responds to the immediate amplitude of different Ca(2+) transients and usually with the same Ca(2+) requirements observed under steady state. Therefore, AC, PDE1 and CaN decode different dynamic properties of Ca(2+) signals.

Influence of the estrous cycle on the behavior of rats in the elevated T-maze.

The elevated T-maze is an animal anxiety model which can discriminate between anxiety-like and fear-like behaviors. The estrous cycle is an important variable of the response in animal anxiety tests and is known to affect other models. The aim of the present study was to investigate the influence of the estrous cycle on behavior displayed in the elevated T-maze test. Seventeen male and 60 female rats were submitted to one session in this test, with the females being screened for the estrous cycle and divided into groups according to the various phases. The elevated T-maze had three arms of equal dimensions ( 50 cm x 10 cm), one enclosed by 40-cm high walls and perpendicular to the others, the apparatus being elevated 50 cm above the floor. Each rat was placed in the end of the enclosed arm and the latency for it to leave this arm was recorded. These measurements were repeated three times separated by 30-s intervals (passive avoidance). After trial 3, each rat was placed at the distal end of the right open arm and the latency to exit this arm was recorded. Whenever latencies were greater than 300 s the trial was finished. The results demonstrated females in diestrus exhibited anxiety-like behaviors while females in metaestrus behaved in a similar way as the males. There were no differences between groups in fear-like behaviors. The results also indicate the elevated T-maze to be a sensitive test to measure anxiety.

Mechanisms of regulation of olfactory transduction and adaptation in the olfactory cilium.

Olfactory adaptation is a fundamental process for the functioning of the olfactory system, but the underlying mechanisms regulating its occurrence in intact olfactory sensory neurons (OSNs) are not fully understood. In this work, we have combined stochastic computational modeling and a systematic pharmacological study of different signaling pathways to investigate their impact during short-term adaptation (STA). We used odorant stimulation and electroolfactogram (EOG) recordings of the olfactory epithelium treated with pharmacological blockers to study the molecular mechanisms regulating the occurrence of adaptation in OSNs. EOG responses to paired-pulses of odorants showed that inhibition of phosphodiesterases (PDEs) and phosphatases enhanced the levels of STA in the olfactory epithelium, and this effect was mimicked by blocking vesicle exocytosis and reduced by blocking cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) and vesicle endocytosis. These results suggest that G-coupled receptors (GPCRs) cycling is involved with the occurrence of STA. To gain insights on the dynamical aspects of this process, we developed a stochastic computational model. The model consists of the olfactory transduction currents mediated by the cyclic nucleotide gated (CNG) channels and calcium ion (Ca(2+))-activated chloride (CAC) channels, and the dynamics of their respective ligands, cAMP and Ca(2+), and it simulates the EOG results obtained under different experimental conditions through changes in the amplitude and duration of cAMP and Ca(2+) response, two second messengers implicated with STA occurrence. The model reproduced the experimental data for each pharmacological treatment and provided a mechanistic explanation for the action of GPCR cycling in the levels of second messengers modulating the levels of STA. All together, these experimental and theoretical results indicate the existence of a mechanism of regulation of STA by signaling pathways that control GPCR cycling and tune the levels of second messengers in OSNs, and not only by CNG channel desensitization as previously thought.

Electrical responses of three classes of granule cells of the olfactory bulb to synaptic inputs in different dendritic locations.

This work consists of a computational study of the electrical responses of three classes of granule cells of the olfactory bulb to synaptic activation in different dendritic locations. The constructed models were based on morphologically detailed compartmental reconstructions of three granule cell classes of the olfactory bulb with active dendrites described by Bhalla and Bower (1993, pp. 1948-1965) and dendritic spine distributions described by Woolf et al. (1991, pp. 1837-1854). The computational studies with the model neurons showed that different quantities of spines have to be activated in each dendritic region to induce an action potential, which always was originated in the active terminal dendrites, independently of the location of the stimuli, and the morphology of the dendritic tree. These model predictions might have important computational implications in the context of olfactory bulb circuits.

Prática esportiva do idoso: autoimagem, autoestima e qualidade de vida / Elderly's sports practice: self-image, self-esteem and quality of life

Objetivou-se comparar qualidade de vida, autoestima e autoimagem referidas por idosos praticantes de esportes individuais ou grupais e idosos não praticantes de atividades físicas. Participaram 36 idosos, do gênero masculino, de 60 a 74 anos, selecionados por conveniência. Foram utilizados o Questionário Sociodemográfico, WHOQOL-Bref, WHOQOL-Old e o Questionário de Autoimagem e Autoestima. Os dados coletados foram analisados quantitativamente, com uso de estatística descritiva e inferencial. A comparação entre os grupos revelou resultados significantes referentes à autoimagem e autoestima, em que os praticantes de esportes coletivos apresentaram valores superiores ao de esportes individuais. Em relação à qualidade de vida, o mesmo grupo se revelou superior ao grupo sedentário. Como limitações do estudo destacam-se o uso de questionários de autoavaliação/autorrelato, que podem ter a interferência da desejabilidade social e não terem sido controladas as atividades de vida diária, em especial do grupo sedentário. Sugerem-se novas pesquisas com ampliação da amostra e maior controle de variáveis.

This study aimed to compare quality of life, self-image and self-esteem reported by elderly individuals or group practice athletes, and seniors who do not practice physical activities. Participants were 36 elderly, male, 60 to 74 years old, selected by convenience. A sociodemographic questionnaire, the WHOQOL-Bref, the WHOQOL-Old and the Self Concept and Self-Esteem Questionnaire were used. The collected data were analyzed quantitatively using descriptive and inferential statistics. The comparison between groups showed significant differences regarding self-image and self-esteem, in which the practitioners of team sports had higher values than the individual sports practitioners. Regarding quality of life, the same group made superior evaluations compared to the sedentary group. The limitations of the study include the use of self-assessment questionnaires / self-report, which are prone to have the interference of social desirability and not have controlled activities of daily life, especially of the sedentary group. Further research with larger sample and greater control of variables is suggested.

The effects of diazepam on the elevated T-maze are dependent on the estrous cycle of rats

In order to determine the modulation of anxiolytic and panicolytic-like effects of diazepam by the hormonal cycle of female rats, male and female rats - the latter divided per estrous cycle phase (estrus, diestrus, metaestrus and proestrus) - were tested in the elevated T-maze, a behavioral model of panic and anxiety. Diazepam (0.5, 1.0 and 2.0 mg/kg) or saline solution was injected in individual animals that were submitted to one session in the elevated T-maze 25 min after drug/saline administration. The test consisted of three avoidance trials and one escape trial, separated by a 30 s interval, during which the animals were isolated in individual cages. The avoidance trials began with the animal being placed at the end of the maze's enclosed arm. The time necessary for the animal to leave the central square was considered as the response's latency. The trials that exceeded 300 s were considered as failures. Results demonstrate a decrease in the effects of diazepam in inhibitory avoidance (anxiety) trials in females in diestrus and proestrus, but no relation of gender or estrous cycle on diazepam effects on escape trials (fear). The results support the hypothesis that down-regulation of GABA A receptors by activation of nuclear estrogen receptors and induction of PKC-mediated GABA A receptor phosphorylation by activation of surface estrogen receptors in raphe neurons underlie the modulation of diazepam sensitivity by estrogen.

Variações da ansiedade relatada em função do ciclo menstrual e do uso de pílulas anticoncepcionais / Changes of mood and anxiety during the menstrual cycle with use of oral contraceptives

A ação hormonal é uma das principais fontes de influência sobre o comportamento, sendo notada, em mulheres, ao longo do ciclo menstrual, especialmente no período pré-menstrual, onde muitas delas relatam uma variação de humor e ansiedade. O objetivo desse trabalho foi verificar os índices de ansiedade relatados ao longo do ciclo menstrual, de forma a mapear sua variação e as possíveis influências do uso de anticoncepcionais na ansiedade. Para tanto, 32 mulheres, divididas em dois grupos de acordo com o uso (B) ou não uso(A) de pílula anticoncepcional, auto-aplicaram o IDATE (Inventário de Ansiedade Traço-Estado) em três períodos diferentes: antes, durante e após a menstruação. Os dados foram tabulados e analisados estatísticamente, apontando significância para a variação entre as fases, mas não para o tipo de ansiedade (traço ou estado) ou para a ingestão de anticoncepcional. Para a ansiedade-traço o pós-teste (Teste T de Boferroni) da variação entre as fases indicou diferença significativa entre a fase pós-menstrual e as demais, no grupo A, e entre as fases pré e menstrual, no grupo B. Para a ansiedade-estado, os dados indicam diferenças significativas entre as fases pré e menstrual, no grupo A, e entre as fases pré e menstrual e pré e pós-menstrual no grupo B. Os resultados indicam que: 1) o ciclo menstrual é uma fonte de variação de ansiedade relatada; 2) o uso de anticoncepcionais não altera esta flutuação; e 3) a diminuição correlata da ansiedade-traço pode indicar alteração na auto-percepção das mulheres ao longo do ciclo menstrual(AU)