Neurotoxicity of hexaconazole on rat brain: The aspect of biological rhythm.

Hexaconazole is a widely used and frequently detected fungicide which is also reported to be persistent in environment. The toxicity of Hex to non-organisms such as reproductive toxicity, endocrine disrupting toxicity, and carcinogenic toxicity had been reported. However, study on the Hex-induced neurotoxicity is rare and the mechanism is still unclear. Therefore, in this study, environmental related concentrations of Hex were chosen to investigate the effects of Hex on nervous system from the aspect of biological rhythm under 90 d sub-chronic exposure. The results showed that Hex significantly affected the cognitive function of rats resulting in the deterioration of learning and memory ability and induced oxidative stress in rat brain. Moreover, the notable changes of neurotransmitters in rat brain suggested the disorder of nerve signaling conduction induced by Hex. The influence of Hex on biological rhythm was further detected which showed that levels of rhythm regulatory genes and proteins significantly disturbed at four monitored time periods. Based on these results, it was supposed that the underlying mechanism of Hex-induced cognitive dysfunction might through oxidative stress pathway. Our findings could systematically and comprehensively clarify the effects of Hex on nervous system and were helpful for prevention neurological diseases induced by triazole pesticides.

Evidence accumulation for value computation in the prefrontal cortex during decision making.

A key step of decision making is to determine the value associated with each option. The evaluation process often depends on the accumulation of evidence from multiple sources, which may arrive at different times. How evidence is accumulated for value computation in the brain during decision making has not been well studied. To address this problem, we trained rhesus monkeys to perform a decision-making task in which they had to make eye movement choices between two targets, whose reward probabilities had to be determined with the combined evidence from four sequentially presented visual stimuli. We studied the encoding of the reward probabilities associated with the stimuli and the eye movements in the orbitofrontal (OFC) and the dorsolateral prefrontal (DLPFC) cortices during the decision process. We found that the OFC neurons encoded the reward probability associated with individual pieces of evidence in the stimulus domain. Importantly, the representation of the reward probability in the OFC was transient, and the OFC did not encode the reward probability associated with the combined evidence from multiple stimuli. The computation of the combined reward probabilities was observed only in the DLPFC and only in the action domain. Furthermore, the reward probability encoding in the DLPFC exhibited an asymmetric pattern of mixed selectivity that supported the computation of the stimulus-to-action transition of reward information. Our results reveal that the OFC and the DLPFC play distinct roles in the value computation during evidence accumulation.

Sub-chronic exposure to hexaconazole affects the lipid metabolism of rats through mTOR-PPAR-γ/SREBP1 signaling pathway mediated by oxidative stress.

Hexaconazole (Hex) is a widely used and high frequency detected triazole fungicide in agricultural products and environment which may pose potential toxicity to the nontargeted organisms. Hex had been reported to affect lipid homeostasis while the mechanism was undefined. This study aims to explore the characteristic lipidomic profiles and clarify the underlying signaling pathways of Hex-induced lipid metabolism disorder in rat liver. The results showed that sub-chronic exposure to environmental related concentrations of Hex caused histopathological changes, oxidative stress, fat accumulation, lipid biochemical parameter increase in rats. Moreover, the untargeted lipidomic analysis showed that the levels of TAG, PC, and PE and the pathway of glycerophospholipid metabolism were heavily altered by Hex. We further analyzed the lipid metabolism related genes and proteins which revealed that Hex exposure increased amount of lipogenesis by activating oxidative stress-mediated mTOR-PPAR-γ/SREBP1 signaling pathways. The imbalance of lipid homeostasis induced by Hex exposure might further lead to obesity, cardiovascular diseases (CVDs), and hyperlipidemia. Our results provided systematic and comprehensive evidence for the mechanism of Hex-induced lipid metabolism disorder at environmental concentrations and supplied a certain basis for its health risks assessment.

Effect of Processing on Reduction in Chiral Pesticide Hexaconazole for Kiwifruit Juice.

In this study, the residue levels of chiral pesticide hexaconazole during kiwifruit juice processing (peeling, homogenization, and sterilization) were investigated by using high-performance liquid chromatography (HPLC), and the dietary risk during these processes was also assessed. Hexaconazole was applied at dosages of 173.33 and 346.66 mg/L (recommended and double recommended dosage) in kiwifruit. In the peeling process, 87.7% to 89.2% of the residues were decreased after peeling. Levels of hexaconazole residues in homogenization and sterilization processes further increased from 0.49% to 24.3% and from 0.2% to 3.0%, respectively. Processing factors (PFs) for (+)- and (-)-hexaconazole after peeling, homogenization, and sterilization were 0.12, 0.88, 0.99 for low-dose treatment and 0.12, 0.87, 0.99 for high-dose treatment, respectively. The enantioselectivity of hexaconazole during these procedures was evaluated by enantiomeric fractions (EFs) values, which were around 0.5 throughout all the procedures, indicating that hexaconazole enantiomers had similar dissipation behaviors during kiwifruit juice processing. The RQc of hexaconazole in pre-peeling samples was significantly greater than 100% under two dosages, while the peeling process can notably decrease the values to an acceptable level. The results of this study could provide guidance for agriculture applications and kiwi commodity production to decrease the risk of hexaconazole residue.

A general strategy exploiting m5C duplex-remodelling effect for selective detection of RNA and DNA m5C methyltransferase activity in cells.

RNA:5-methylcytosine (m5C) methyltransferases are currently the focus of intense research following a series of high-profile reports documenting their physiological links to several diseases. However, no methods exist which permit the specific analysis of RNA:m5C methyltransferases in cells. Herein, we described how a combination of biophysical studies led us to identify distinct duplex-remodelling effects of m5C on RNA and DNA duplexes. Specifically, m5C induces a C3'-endo to C2'-endo sugar-pucker switch in CpG RNA duplex but triggers a B-to-Z transformation in CpG DNA duplex. Inspired by these different 'structural signatures', we developed a m5C-sensitive probe which fluoresces spontaneously in response to m5C-induced sugar-pucker switch, hence useful for sensing RNA:m5C methyltransferase activity. Through the use of this probe, we achieved real-time imaging and flow cytometry analysis of NOP2/Sun RNA methyltransferase 2 (NSUN2) activity in HeLa cells. We further applied the probe to the cell-based screening of NSUN2 inhibitors. The developed strategy could also be adapted for the detection of DNA:m5C methyltransferases. This was demonstrated by the development of DNA m5C-probe which permits the screening of DNA methyltransferase 3A inhibitors. To our knowledge, this study represents not only the first examples of m5C-responsive probes, but also a new strategy for discriminating RNA and DNA m5C methyltransferase activity in cells.

Linking oxidative DNA lesion 8-OxoG to tumor development and progression.

Cells of the aerobic metabolic organism are inevitably subjected to the damage from reactive oxygen species (ROS). ROS cause multiple forms of DNA damage, among which the oxidation product of guanine G 8-hydroxyguanine (8-oxoG) is the most frequent DNA oxidative damage, recognized by the specific glycosidase OGG1 that initiates the base excision repair pathway. If left unrepaired, 8-oxoG may pair with A instead of C, leading to a mutation of G: C to T: A during replication. Thus, the accumulation of 8-oxoG or the abnormal OGG1 repair is thought to affect gene function, which in turn leads to the development of tumor or aging-related diseases. However, a series of recent studies have shown that 8-oxoG tends to be produced in regulatory regions of the genome. 8-oxoG can be regarded as an epigenetic modification, while OGG1 is a specific reader of this information. Substrate recognition, binding or resection by OGG1 can cause DNA conformation changes or affect histone modifications, causing up-regulation or down-regulation of genes with different properties. Thus, in addition to the potential genotoxicity, the association of guanine oxidative damage with development of tumors is closely related to its aberrant initiation of gene expression through epigenetic mechanisms. In this review, we summarize the underlying mechanism of 8-oxoG and repair enzyme OGG1 in tumor development and progression, with aims to interpret the relationship between DNA oxidative damage and tumor from a new perspective, and provide new ideas and targets for tumor treatment.

A recurrent neural network framework for flexible and adaptive decision making based on sequence learning.

The brain makes flexible and adaptive responses in a complicated and ever-changing environment for an organism's survival. To achieve this, the brain needs to understand the contingencies between its sensory inputs, actions, and rewards. This is analogous to the statistical inference that has been extensively studied in the natural language processing field, where recent developments of recurrent neural networks have found many successes. We wonder whether these neural networks, the gated recurrent unit (GRU) networks in particular, reflect how the brain solves the contingency problem. Therefore, we build a GRU network framework inspired by the statistical learning approach of NLP and test it with four exemplar behavior tasks previously used in empirical studies. The network models are trained to predict future events based on past events, both comprising sensory, action, and reward events. We show the networks can successfully reproduce animal and human behavior. The networks generalize the training, perform Bayesian inference in novel conditions, and adapt their choices when event contingencies vary. Importantly, units in the network encode task variables and exhibit activity patterns that match previous neurophysiology findings. Our results suggest that the neural network approach based on statistical sequence learning may reflect the brain's computational principle underlying flexible and adaptive behaviors and serve as a useful approach to understand the brain.

Rapid detection of five pesticide residues using complexes of gold nanoparticle and porphyrin combined with ultraviolet visible spectrum.

BACKGROUD: Pesticides are widely used to control insect infestation and weeds in agriculture. However, concerns about the pesticide residues in agricultural products have been raised in recent years because of public interest in health and food quality and safety. Thus, rapid, convenient, and accurate analytical methods for the detection and quantification of pesticides are urgently required. RESULTS: A nanohybrid system composed of gold nanoparticles (AuNPs) and tetrakis(N-methyl-4-pyridiniumyl) porphyrin (TMPyP) was used as an optical probe for the detection and quantification of five pesticides (Paraquat, Dipterex, Dursban, methyl thiophanate and Cartap). The method is based on the aggregation effect of pesticides on the carboxyl group modified by AuNPs. Subsequently, with the help of particle swarm optimization-optimized sample weighted least squares-support vector machine (PSO-OSWLS-SVM), all the pesticides could be successfully quantified. In addition, partial least squares discriminant analysis (PLS-DA) was applied and the five pesticides were satisfactorily recognized based on data array obtained from the ultraviolet visible (UV-visible) spectra of AuNP-TMPyP complex. Furthermore, the quantitative and qualitative analysis of the five pesticides could be also achieved in the complex real samples, in which all the relative standard deviations (RSDs) were less than 0.3‰ and all the linear absolute correlation coefficients were more than 0.9990. Furthermore, recognition rate of the training set and the prediction set based on multiplicative scatter correction (MSC), or second-order derivative (2nd derivative) UV-visible spectra in PLS-DA model could reach 100%. CONCLUSION: This method was successfully applied for the rapid and accurate determination of multicomponent pesticide residues in real food samples. © 2020 Society of Chemical Industry.

A neural network model for the orbitofrontal cortex and task space acquisition during reinforcement learning.

Reinforcement learning has been widely used in explaining animal behavior. In reinforcement learning, the agent learns the value of the states in the task, collectively constituting the task state space, and uses the knowledge to choose actions and acquire desired outcomes. It has been proposed that the orbitofrontal cortex (OFC) encodes the task state space during reinforcement learning. However, it is not well understood how the OFC acquires and stores task state information. Here, we propose a neural network model based on reservoir computing. Reservoir networks exhibit heterogeneous and dynamic activity patterns that are suitable to encode task states. The information can be extracted by a linear readout trained with reinforcement learning. We demonstrate how the network acquires and stores task structures. The network exhibits reinforcement learning behavior and its aspects resemble experimental findings of the OFC. Our study provides a theoretical explanation of how the OFC may contribute to reinforcement learning and a new approach to understanding the neural mechanism underlying reinforcement learning.

A role for primate subgenual cingulate cortex in sustaining autonomic arousal.

The subgenual anterior cingulate cortex (subgenual ACC) plays an important role in regulating emotion, and degeneration in this area correlates with depressed mood and anhedonia. Despite this understanding, it remains unknown how this part of the prefrontal cortex causally contributes to emotion, especially positive emotions. Using Pavlovian conditioning procedures in macaque monkeys, we examined the contribution of the subgenual ACC to autonomic arousal associated with positive emotional events. After such conditioning, autonomic arousal increases in response to cues that predict rewards, and monkeys maintain this heightened state of arousal during an interval before reward delivery. Here we show that although monkeys with lesions of the subgenual ACC show the initial, cue-evoked arousal, they fail to sustain a high level of arousal until the anticipated reward is delivered. Control procedures showed that this impairment did not result from differences in autonomic responses to reward delivery alone, an inability to learn the association between cues and rewards, or to alterations in the light reflex. Our data indicate that the subgenual ACC may contribute to positive affect by sustaining arousal in anticipation of positive emotional events. A failure to maintain positive affect for expected pleasurable events could provide insight into the pathophysiology of psychological disorders in which negative emotions dominate a patient's affective experience.

[Development of the Intracranial Pressure and Intracranial Temperature Monitor and Experimental Research on Trauma].

OBJECTIVES: A set of intracranial pressure and intracranial temperature monitor was developed. Moreover, it was verified to be effective in the monitoring of intracranial parameters by designed experiments. METHODS: The intracranial pressure and intracranial temperature monitor was tested in the water bath comparing with the Codman intracranial pressure monitor and mercury thermometers. As well, the monitor was applied in the monitoring of rat brain edema in vivo. RESULTS: The maximum error is less than 266.64 Pa in the intracranial pressure measurement compared to the Codman intracranial pressure monitor, and the maximum error is less than 0.3 oC in the temperature measurement according to mercury thermometers. Furthermore, the monitor could real-time obtain the intracranial pressure and intracranial temperature in the brain edema in vivo. CONCLUSIONS: The intracranial pressure and intracranial temperature monitor realizes the real-time in vivo monitoring of intracranial pressure and intracranial temperature. The measurement accuracy meets the acquirement of doctors. The instrument has potential for clinical use.

The strength of gradually accruing probabilistic evidence modulates brain activity during a categorical decision.

The evolution of neural activity during a perceptual decision is well characterized by the evidence parameter in sequential sampling models. However, it is not known whether accumulating signals in human neuroimaging are related to the integration of evidence. Our aim was to determine whether activity accumulates in a nonperceptual task by identifying brain regions tracking the strength of probabilistic evidence. fMRI was used to measure whole-brain activity as choices were informed by integrating a series of learned prior probabilities. Participants first learned the predictive relationship between a set of shape stimuli and one of two choices. During scanned testing, they made binary choices informed by the sum of the predictive strengths of individual shapes. Sequences of shapes adhered to three distinct rates of evidence (RoEs): rapid, gradual, and switch. We predicted that activity in regions informing the decision would modulate as a function of RoE prior to the choice. Activity in some regions, including premotor areas, changed as a function of RoE and response hand, indicating a role in forming an intention to respond. Regions in occipital, temporal, and parietal lobes modulated as a function of RoE only, suggesting a preresponse stage of evidence processing. In all of these regions, activity was greatest on rapid trials and least on switch trials, which is consistent with an accumulation-to-boundary account. In contrast, activity in a set of frontal and parietal regions was greatest on switch and least on rapid trials, which is consistent with an effort or time-on-task account.

Efficient reinforcement learning of a reservoir network model of parametric working memory achieved with a cluster population winner-take-all readout mechanism.

The brain often has to make decisions based on information stored in working memory, but the neural circuitry underlying working memory is not fully understood. Many theoretical efforts have been focused on modeling the persistent delay period activity in the prefrontal areas that is believed to represent working memory. Recent experiments reveal that the delay period activity in the prefrontal cortex is neither static nor homogeneous as previously assumed. Models based on reservoir networks have been proposed to model such a dynamical activity pattern. The connections between neurons within a reservoir are random and do not require explicit tuning. Information storage does not depend on the stable states of the network. However, it is not clear how the encoded information can be retrieved for decision making with a biologically realistic algorithm. We therefore built a reservoir-based neural network to model the neuronal responses of the prefrontal cortex in a somatosensory delayed discrimination task. We first illustrate that the neurons in the reservoir exhibit a heterogeneous and dynamical delay period activity observed in previous experiments. Then we show that a cluster population circuit decodes the information from the reservoir with a winner-take-all mechanism and contributes to the decision making. Finally, we show that the model achieves a good performance rapidly by shaping only the readout with reinforcement learning. Our model reproduces important features of previous behavior and neurophysiology data. We illustrate for the first time how task-specific information stored in a reservoir network can be retrieved with a biologically plausible reinforcement learning training scheme.

Identification of 3,5,6-substituted indolin-2-one's inhibitors of Aurora B by development of a luminescent kinase assay.

Aurora B kinase plays an important role in the cell normal mitosis and overexpresses in a variety of tumors. Inhibition of Aurora B kinase resulted in an apoptosis of cancer cells, which prevented tumor growth in xenograft models. In this Letter, we developed a luminescent kinase assay to perform high-throughput screening for identification of small molecule Aurora B inhibitors. Two 3,5,6-substituted indolin-2-one derivatives were identified within an in-house compound library. Their new derivatives were then designed and synthesized that resulting two new inhibitors of Aurora B kinase with improved potency. Docking simulation further demonstrated the proposed binding modes between indolin-2-one inhibitor and Aurora B.

Contributions of the hippocampus and entorhinal cortex to rapid visuomotor learning in rhesus monkeys.

The hippocampus and adjacent structures in the medial temporal lobe are essential for establishing new associative memories. Despite this knowledge, it is not known whether the hippocampus proper is essential for establishing such memories, nor is it known whether adjacent regions like the entorhinal cortex might contribute. To test the contributions of these regions to the formation of new associative memories, we trained rhesus monkeys to rapidly acquire arbitrary visuomotor associations, i.e., associations between visual stimuli and spatially directed actions. We then assessed the effects of reversible inactivations of either the hippocampus (Experiment 1) or entorhinal cortex (Experiment 2) on the within-session rate of learning. For comparison, we also evaluated the effects of the inactivations on performance of problems of the same type that had been well learned prior to any inactivations. We found that inactivation of the entorhinal cortex but not hippocampus produced impairments in acquiring novel arbitrary associations. The impairment did not extend to the familiar, previously established associations. These data indicate that the entorhinal cortex is causally involved in establishing new associations, as opposed to retrieving previously learned associations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Functionalized acridin-9-yl phenylamines protected neuronal HT22 cells from glutamate-induced cell death by reducing intracellular levels of free radical species.

The in vitro neuronal cell death model based on the HT22 mouse hippocampal cell model is a convenient means of identifying compounds that protect against oxidative glutamate toxicity which plays a role in the development of certain neurodegenerative diseases. Functionalized acridin-9-yl-phenylamines were found to protect HT22 cells from glutamate challenge at submicromolar concentrations. The Aryl(1)-NH-Aryl(2) scaffold that is embedded in these compounds was the minimal pharmacophore for activity. Mechanistically, protection against the endogenous oxidative stress generated by glutamate did not involve up-regulation of glutathione levels but attenuation of the late stage increases in mitochondrial ROS and intracellular calcium levels. The NH residue in the pharmacophore played a crucial role in this regard as seen from the loss of neuroprotection when it was structurally modified or replaced. That the same NH was essential for radical scavenging in cell-free and cell-based systems pointed to an antioxidant basis for the neuroprotective activities of these compounds.

Spectroscopic analysis on the interaction of ferulic acid and tetramethylpyrazine with trypsin.

The interaction of trypsin with tetramethylpyrazine (TMP) and ferulic acid (FA) was studied using fluorescence, synchronous fluorescence, UV-vis absorption, circular dichroism (CD) and three-dimensional (3D) fluorescence spectra techniques. Using fluorescence quenching calculations, the bimolecular quenching constant (kq), apparent quenching constant (KSV), effective binding constant (Ka) and binding site number (n) were obtained. The distance r between donor and acceptor was found to be 2.049 and 1.281 nm for TMP-trypsin and FA-trypsin complexes. TMP and FA can quench the fluorescence intensity of trypsin by a static quenching procedure. Thermodynamic parameters calculated on the basis of different temperatures revealed that the binding of trypsin to TMP/FA mainly depended on van der Waals' forces and hydrogen bonds. The effect of TMP and FA on the conformation of trypsin was analyzed using synchronous fluorescence, CD, 3D fluorescence spectra and molecular docking studies.

MTH1 inhibition synergizes with ROS-inducing agents to trigger cervical cancer cells undergoing parthanatos.

Cervical cancer cells possess high levels of reactive oxygen species (ROS); thus, increasing oxidative stress above the toxicity threshold to induce cell death is a promising chemotherapeutic strategy. However, the underlying mechanisms of cell death are elusive, and efficacy and toxicity issues remain. Within DNA, 8-oxo-7,8-dihydroguanine (8-oxoG) is the most frequent base lesion repaired by 8-oxoguanine glycosylase 1 (OGG1)-initiated base excision repair. Cancer cells also express high levels of MutT homolog 1 (MTH1), which prevents DNA replication-induced incorporation of 8-oxoG into the genome by hydrolyzing 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP). Here, we revealed that ROS-inducing agents triggered cervical cancer to undergo parthanatos, which was mainly induced by massive DNA strand breaks resulting from overwhelming 8-oxoG excision by OGG1. Furthermore, the MTH1 inhibitor synergized with a relatively low dose of ROS-inducing agents by enhancing 8-oxoG loading in the DNA. In vivo, this drug combination suppressed the growth of tumor xenografts, and this inhibitory effect was significantly decreased in the absence of OGG1. Hence, the present study highlights the roles of base repair enzymes in cell death induction and suggests that the combination of lower doses of ROS-inducing agents with MTH1 inhibitors may be a more selective and safer strategy for cervical cancer chemotherapy.

Gastrodin stimulates anticancer immune response and represses transplanted H22 hepatic ascitic tumor cell growth: Involvement of NF-κB signaling activation in CD4+ T cells.

Gastrodia elata Blume (G. elata) is a famous restorative food in East Asia. It can be used as an auxiliary reagent in hepatocellular carcinoma (HCC) treatment. Previous studies unveiled that G. elata exhibited immunomodulatory activities. To explore the active ingredients contributing to its immunomodulatory activities, gastrodin, vanillin, and parishin B were purified from G. elata and their anti-HCC effects were assessed in vivo. Among these compounds, only gastrodin was capable of repressing transplanted H22 ascitic hepatic tumor cell growth in vivo with low toxicity. Further investigations were designed to explore the effects of gastrodin on the immune system of tumor-bearing mice and potential molecular mechanisms underlying these effects. Our data showed that gastrodin ameliorated tumor cell transplantation-induced activation of endogenous pro-apoptotic pathway in CD4+ T cells and abnormalities in serum cytokine profiles in host animals. These events enhanced cytotoxic activities of natural killer and CD8+ T cells against H22 hepatic cancer cells. Gastrodin administration specifically upregulated mRNA levels of several nuclear factor κB (NF-κB) responsive genes in CD4+ T cells but not in CD8+ T cells. Chromatin immunoprecipitation assay showed that gastrodin increased the association of NF-κB p65 subunit to the promoter regions of IL-2 and Bcl-2 encoding genes in CD4+ T cells. Our investigations demonstrated that gastrodin is the main active ingredient contributing to the anticancer immunomodulatory properties of G. elata. Promoting NF-κB-mediated gene transcription in CD4+ T cells is implicated in its immunomodulatory activity.

Probabilistic reasoning by neurons.

Our brains allow us to reason about alternatives and to make choices that are likely to pay off. Often there is no one correct answer, but instead one that is favoured simply because it is more likely to lead to reward. A variety of probabilistic classification tasks probe the covert strategies that humans use to decide among alternatives based on evidence that bears only probabilistically on outcome. Here we show that rhesus monkeys can also achieve such reasoning. We have trained two monkeys to choose between a pair of coloured targets after viewing four shapes, shown sequentially, that governed the probability that one of the targets would furnish reward. Monkeys learned to combine probabilistic information from the shape combinations. Moreover, neurons in the parietal cortex reveal the addition and subtraction of probabilistic quantities that underlie decision-making on this task.