Muscarinic receptor activation promotes destabilization and updating of object location memories in mice

The storage of long-term memories is a dynamic process. Reminder cues can destabilize previously consolidated memories, rendering them labile and modifiable. However, memories that are strongly encoded or relatively remote at the time of reactivation can resist destabilization only being rendered labile under conditions that favour memory updating. Using the object location recognition task, here we show in male C57BL/6 mice that novelty-induced destabilization of strongly-encoded memories requires muscarinic acetylcholine receptor (mAChR) activation. Furthermore, we use the objects-in-updated locations task to show that updating of object location memories is mAChR-dependent. Thus, mAChR stimulation appears to be critical for spatial memory destabilization and related memory updating. Enhancing our understanding of the role of ACh in memory updating should inform future research into the underlying causes of behavioural disorders that are characterized by persistent maladaptive memories, such as age-related cognitive inflexibility and post-traumatic stress disorder.

Activating M1 muscarinic cholinergic receptors induces destabilization of resistant contextual fear memories in rats

Destabilization of previously consolidated memories places them in a labile state in which they are open to modification. However, strongly encoded fear memories tend to be destabilization-resistant and the conditions required to destabilize such memories remain poorly understood. Our lab has previously shown that exposure to salient novel contextual cues during memory reactivation can destabilize strongly encoded object location memories and that activity at muscarinic cholinergic receptors is critical for this effect. In the current study, we similarly targeted destabilization-resistant fear memories, hypothesizing that exposure to salient novelty at the time of reactivation would induce destabilization of strongly encoded fear memories in a muscarinic receptor-dependent manner. First, we show that contextual fear memories induced by 3 context-shock pairings readily destabilize upon memory reactivation, and that this destabilization is blocked by systemic (ip) administration of the muscarinic receptor antagonist scopolamine (0.3 mg/kg) in male rats. Following that, we confirm that this effect is dorsal hippocampus (dHPC)-dependent by targeting M1 receptors in the CA1 region with pirenzepine. Next, we show that more strongly encoded fear memories (induced with 5 context-shock pairings) resist destabilization. Consistent with our previous work, however, we report that salient novelty (a change in floor texture) presented during the reactivation session promotes destabilization of resistant contextual fear memories in a muscarinic receptor-dependent manner. Finally, the effect of salient novelty on memory destabilization was mimicked by stimulating muscarinic receptors with the selective M1 agonist CDD-0102A (ip, 0.3 mg/kg). These findings reveal further generalizability of our previous results implicating novel cues and M1 muscarinic signaling in promoting destabilization of resistant memories and suggest possible therapeutic options for disorders characterized by persistent, maladaptive fear memories such as PTSD and phobias.

E3 ubiquitin ligase APC/CCdh1 regulates SLC35F2 protein turnover and inhibits cancer progression in HeLa cells

BACKGROUND

The solute carrier family 35 F2 (SLC35F2), belongs to membrane-bound carrier proteins that control various physiological functions and are activated in several cancers. However, the molecular mechanism regulating SLC35F2 protein turnover and its implication in cancer progression remains unexplored. Therefore, screening for E3 ligases that promote SLC35F2 protein degradation is essential during cancer progression.

METHODS

The immunoprecipitation and Duolink proximity ligation assays (PLA) were used to determine the interaction between APC/CCdh1 and SLC35F2 proteins. A CRISPR/Cas9-mediated knockdown and rescue experiment were used to validate the functional significance of APC/CCdh1 on SLC35F2 protein stabilization. The ubiquitination function of APC/CCdh1 on SLC35F2 protein was validated using in vitro ubiquitination assay and half-life analysis. The role of APC/CCdh1 regulating SLC35F2-mediated tumorigenesis was confirmed by in vitro oncogenic experiments in HeLa cells.

RESULTS

Based on the E3 ligase screen and in vitro biochemical experiments, we identified that APC/CCdh1 interacts with and reduces SLC35F2 protein level. APC/CCdh1 promotes SLC35F2 ubiquitination and decreases the half-life of SLC35F2 protein. On the other hand, the CRISPR/Cas9-mediated depletion of APC/CCdh1 increased SLC35F2 protein levels. The mRNA expression analysis revealed a negative correlation between APC/CCdh1 and SLC35F2 across a panel of cancer cell lines tested. Additionally, we demonstrated that depletion in APC/CCdh1 promotes SLC35F2-mediated cell proliferation, colony formation, migration, and invasion in HeLa cells.

CONCLUSION

Our study highlights that APC/CCdh1 is a critical regulator of SLC35F2 protein turnover and depletion of APC/CCdh1 promotes SLC35F2-mediated tumorigenesis. Thus, we envision that APC/CCdh1-SLC35F2 axis might be a therapeutic target in cancer.

SARS-CoV-2: analysis of the effects of mutations in non-structural proteins

A worldwide pandemic that started in China in late 2019 was caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a single-stranded RNA virus belonging to the family Coronaviridae. Due to its structural variability and mutability, this virus continues to evolve and pose a major health threat around the world. Its characteristics, such as transmissibility, antigenicity, and resistance to drugs and vaccines, are continually altered through mutations. Examining mutational hotspots and their structural repercussions can thus aid in the development of more-effective vaccinations and treatment plans. In this study, we used full genome sequences of SARS-CoV-2 variants to predict structural changes in viral proteins. These sequences were obtained from the Global Initiative on Sharing Avian Influenza Data (GISAID), and a set of significant mutations were identified in each of the non-structural proteins (NSP1-16) and structural proteins, including the envelope, nucleocapsid, membrane, and spike proteins. The mutations were characterized as stabilizing or destabilizing based on their effect on protein dynamics and stability, and their impact on structure and function was evaluated. Among all of the proteins, NSP6 stands out as especially variable. The results of this study augment our understanding of how mutational events influence virus pathogenicity and evolution.

Lycopene destabilizes preformed Aβ fibrils: Mechanistic insights from all-atom molecular dynamics simulation

The therapeutic strategy employing destabilization of the preformed Aβ fibril by various natural compounds, as studied by experimental and computational methods, has been reported significant in curing Alzheimer's disease (AD). However, lycopene (a carotenoid), from terpenes family, needs investigation for its destabilization potential of Aβ fibril. The highest antioxidant potential and ability to cross blood brain barrier makes lycopene a preferred choice as drug lead for treating AD. The current study focuses on investigating the destabilization potential and underpinning mechanism of lycopene on different polymorphic forms of Aβ fibril via Molecular Dynamics (MD) simulation. The key findings highlight binding of lycopene to the outer surface of the chain F of the fibril (2NAO). Herein G9, K16 and V18 residues were found to be involved in van der Waals with the methyl groups of the lycopene. Additionally, Y10 and F20 residues were observed to interact via π-π interactions with CC bonds of the lycopene. The surface mediated binding of lycopene to the fibril is attributed to the large size and structural rigidity of lycopene along with the bulky size of 2NAO and narrow space of fibrillar cavity. The destabilization of the fibril is evident by breakage of inherent H-bonds and hydrophobic interactions in the presence of one lycopene molecule. The lesser β-sheet content explains disorganization of the fibril and bars the higher order aggregation curbing neurotoxicity of the fibril. The higher concentration of the lycopene is not found to be linearly correlated with the extent of destabilization of the fibril. Lycopene is also observed to destabilize the other polymorphic form of Aβ fibril (2BEG), by accessing the fibrillar cavity and lowering the β-sheet content. The destabilization observed by lycopene on two major polymorphs of Aβ fibril explains its potency towards developing an effective therapeutic approach in treating AD.

Destabilization of polystyrene nanoplastics with different surface charge and particle size by Fe electrocoagulation

Nanoplastics (NPs) discharged from wastewater could pose a major threat to organisms in aquatic environments. Effective removal of NPs by the current conventional coagulation-sedimentation process is not yet satisfactory. This study aimed to investigate the destabilization mechanism of polystyrene NPs (PS-NPs) with different surface properties and sizes (i.e., 90 nm, 200 nm, and 500 nm) by Fe electrocoagulation (EC). Two types of PS-NPs were prepared by a nanoprecipitation method using sodium dodecyl sulfate and cetrimonium bromide solutions to produce negatively-charged SDS-NPs and positively-charged CTAB-NPs. For both NPs, obvious floc aggregation from 7 μm to 14 μm was observed only at pH 7 with particulate Fe accounted for >90 %. At pH 7, Fe EC removed 85.3 %, 82.8 %, and 74.7 % of the negatively-charged SDS-NPs at small-, mid-, and large-sizes from 90 nm, 200 nm, to 500 nm, respectively. Small-size SDS-NPs_{(90 nm)} were destabilized through physical adsorption on the surface of Fe flocs, while the main removal mechanism of mid- and large-SDS-NPs_{(200 nm and 500 nm)} involved the enmeshment of large Fe flocs. Compared to SDS-NPs_{(200 nm and 500 nm)}, Fe EC performed similar destabilization behavior to two CTAB-NPs_{(200 nm and 500 nm)}, but it resulted in much lower removal rates of 54.8 % - 77.9 %. The Fe EC also exhibited no removal (<1 %) ability toward the small-size and positively-charged CTAB-NPs_{(90 nm)} due to insufficient formation of effective Fe flocs. Our results provide insight into the destabilization of PS in nano-scale with different sizes and surface properties, which clarifies the behavior of complex NPs in a Fe EC-system.

Enhanced stability of a disaggregated Aβ fibril on removal of ligand inhibits refibrillation: An all atom Molecular Dynamics simulation study

The extraneuronally deposited senile plaques, composed of neurotoxic aggregates of Aβ fibril, define Alzheimer's disease (AD). Natural compounds have been tested for their destabilization potential on Aβ fibril, thereby curing AD. However, the resultant destabilized Aβ fibril, needs to be checked for its irreversibility to the native organized state after removal of the ligand. Herein, we assessed the stability of a destabilized fibril after the ligand (ellagic acid represented as REF) is removed from the complex. The study has been conducted via Molecular Dynamics (MD) simulation of 1 μs for both Aβ-Water (control) and Aβ-REF″ (test or REF removed) system. The increased value of RMSD, R_g, SASA, lower β-sheet content and reduced number of H-bonds explains enhanced destabilization observed in Aβ-REF″ system. The increased inter-chain distance demonstrates breaking of the residual contacts, testifying the drift of terminal chains from the pentamer. The increased SASA along with the ∆G_ps(polar solvation energy) accounts for the reduced interaction amongst residues, and more with solvent molecules, governing irreversibility to native state. The higher Gibb's free energy of the misaligned structure of Aβ-REF″ ensures irreversibility to the organized structure due to its inability to cross such high energy barrier. The observed stability of the disaggregated structure, despite ligand elimination, establishes the effectiveness of the destabilization technique as a promising therapeutic approach towards treating AD.

Demulsification of water-in-oil emulsions stabilized with glycerol monostearate crystals

HYPOTHESIS

Colloidal particles can be used to generate water-in-oil (W/O) emulsions resistant against coalescence. Demulsification is possible with addition of low molecular weight surfactants to the emulsion continuous oil phase. Whether surfactants demulsify particle-stabilized W/O emulsions depends on their ability to modify the wettability of interfacially-bound particles.

EXPERIMENTAL

Crystals of glycerol monostearate (GMS) were prepared followed by water addition to generate GMS-stabilized W/O emulsions. The surfactants sorbitan monooleate (SMO), sorbitan monolaurate (SML), citric acid esters of monoglycerides (CITREM), sorbitan trioleate (STO), propylene glycol monolaurate (PgML), and polyglycerol polyricinoleate (PGPR) were added to the emulsion oil phase. Emulsion microstructure was characterized by light microscopy and cryo-scanning electron microscopy. Surfactant activity and crystal wetting were characterized by interfacial tension and three-phase contact angle measurements. Salt release from within the emulsions was used to assess demulsifier efficacy.

FINDINGS

Emulsions stabilized by platelet-like GMS crystals were generated. Of the six surfactants, SMO, SML, and CITREM were effective demulsifiers whereas STO, PgML, and PGPR were ineffective. The former three sufficiently modified the wettability of GMS crystals on the droplet surface, as they adsorbed to both the oil-water interface and GMS crystal surface. Emulsion destabilization was associated with faster NaCl release from the emulsion internal phase.

[Muscle activation times facing to a perturbation in patients with early-stage Parkinson's disease]

OBJECTIVES

Parkinson's disease (PD) generates a high incidence of falls, however, there is little evidence of instabilities in the initial stages. This investigation sought to compare the muscle activation times in patients with initial PD against a postural disturbance vs. a control group.

MATERIALS AND METHODS

The electromyographic activity (EMG) of 10 patients with PD in early stages (61.3 ±3.8 years) and a control group of 10 adults (62.2 ±3.0 year) was evaluated. The participants were subjected to a surface disturbance, which generated a stabilization response. The test was performed under 2conditions: eyes open (OA) v/s eyes closed (OC). Trunk (spinal erector) and lower extremity (soleus, tibialis anterior, femoral biceps, femoral rectus, adductor magnus, gluteus medius) muscle activation time was analyzed using surface EMG.

RESULTS

The PD group showed faster response times compared to the control group in the soleus muscle in OC (P=.04). This same muscle showed differences when comparing OA vs. OC only in the PD group (P=.04), showing a shorter response time in the OC condition. When comparing the spinal erector muscle, the PD group showed slower response times in the OA (P=.02) and OC (P=.04) conditions compared to the control group.

CONCLUSIONS

Muscle activation times show that people with PD respond slower in the trunk muscles, while activation times decrease at the distal level. In the early stages, the slower responses at the trunk level could explain the onset of instability postural in these patients.

Identification and characterization of a flexile G-quadruplex in the distal promoter region of stemness gene REX1

We have identified a parallel G-quadruplex (R1WT) in the distal promoter region (-821 base-pairs upstream of the TSS) of the pluripotent gene REX1. Through biophysical and biochemical approach, we have characterized the G-quadruplex (GQ) as a potential molecular switch that may control REX1 promoter activity to determine the transcriptional fate. Small- molecule interactive study of the monomeric form of R1WT (characterized as R1mut2) with TMPyP4 and BRACO-19 revealed GQ destabilization upon interaction with TMPyP4 and stabilization upon interaction with BRACO-19. This distinctive drug interactivity suggests the in cellulo R1WT to be a promising drug target. The endogenous existence of R1WT was confirmed by BG4 antibody derived chromatin immunoprecipitation experiment. Here in, we also report the endogenous interaction of GQ specific transcription factors (TFs) with R1WT region in the human chromatin of cancer cell. The wild-type G-quadruplex was found to interact with four important transcription factors, (i) specificity protein (Sp1) (ii) non-metastatic cell 2 (NM23-H2): a diphosphatase (iii) cellular nucleic acid binding protein (CNBP) and (iv) heterogenous nuclear ribonucleoprotein K (hnRNPK) in the REX1 promoter. In contrast, nucleolin protein (NCL) binding was found to be low to the said G-quadruplex. The flexibility of R1WT between folded and unfolded states, obtained from experimental and computational analysis strongly suggests R1WT to be an important gene regulatory element in the genome. It controls promoter DNA relaxation with the coordinated interaction of transcription factors, the deregulation of which seeds stemness characteristic in cancer cells for further metastatic progression.

Dissociating the involvement of muscarinic and nicotinic cholinergic receptors in object memory destabilization and reconsolidation

The content of long-term memory is neither fixed nor permanent. Reminder cues can destabilize consolidated memories, rendering them amenable to change before being reconsolidated. However, not all memories destabilize following reactivation. Characteristics of a memory, such as its age or strength, impose boundaries on destabilization. Previously, we demonstrated that presentation of salient novel information at the time of reactivation can readily destabilize resistant object memories in rats and this form of novelty-induced destabilization is dependent upon acetylcholine (ACh) activity at muscarinic receptors (mAChRs). In the present study, we sought to determine if this same mechanism for initiating destabilization of resistant object memories is present in mice and further expand our understanding of the mechanisms through which ACh modulates object memory destabilization by investigating the role of nicotinic receptors (nAChRs). We provide evidence that in mice mAChRs are necessary for destabilizing object memories that are readily destabilized and those that are resistant to destabilization. Conversely, nAChRs were found to be necessary only when memories are readily destabilized. We then investigated the role of both receptors in the reconsolidation of destabilized object memory traces and determined that nAChRs, but not mAChRs, are necessary for object memory reconsolidation. Together, these results suggest that nAChRs may play a more selective role in the re-storage of object memories following destabilization and that ACh acts through mAChRs to act as an override signal to initiate destabilization of resistant object memories following reactivation with novelty. These findings expand our current understanding of the role of ACh in the dynamic storage of long-term memory.

The evidence for and against reactivation-induced memory updating in humans and nonhuman animals

Systematic investigation of reactivation-induced memory updating began in the 1960s, and a wave of research in this area followed the seminal articulation of "reconsolidation" theory in the early 2000s. Myriad studies indicate that memory reactivation can cause previously consolidated memories to become labile and sensitive to weakening, strengthening, or other forms of modification. However, from its nascent period to the present, the field has been beset by inconsistencies in researchers' abilities to replicate seemingly established effects. Here we review these many studies, synthesizing the human and nonhuman animal literature, and suggest that these failures-to-replicate reflect a highly complex and delicately balanced memory modification system, the substrates of which must be finely tuned to enable adaptive memory updating while limiting maladaptive, inaccurate modifications. A systematic approach to the entire body of evidence, integrating positive and null findings, will yield a comprehensive understanding of the complex and dynamic nature of long-term memory storage and the potential for harnessing modification processes to treat mental disorders driven by pervasive maladaptive memories.

Differential involvement of nucleus tractus solitarius projections and locus coeruleus projections to the basolateral amygdala in morphine-associated memory destabilization

Drug-related memory can be transiently destabilized by memory retrieval, after which memories are reconsolidated. Neurons in the basolateral amygdala (BLA) that are activated by emotional information may be one of the key mechanisms underlying this destabilization. However, the specific neural circuits underlying this destabilization process remain unknown. Because BLA receives noradrenergic inputs from the nucleus tractus solitarius (NTS) and locus coeruleus (LC), we studied the role of afferent projections into the BLA in the destabilization of morphine self-administration memory in rats. We first showed that morphine (unconditioned stimulus, US) + morphine-associated conditioned stimuli (CS) exposure, rather than CS exposure alone, destabilized morphine self-administration memory. Then, we measured projection-specific activation after the US + CS or CS retrieval test using c-fos (activity marker)-labeling in projection areas. Compared with CS exposure, we found that US + CS exposure induced more neuronal activation in the BLA and NTS but not in the LC. Next, we determined the effects of chemogenetic inactivation or activation of NTS or LC projections to BLA (NTS → BLA or LC → BLA) on this destabilization. We found that NTS → BLA, but not LC → BLA inactivation during memory retrieval, prevented memory destabilization induced by US + CS exposure. Furthermore, NTS → BLA, but not LC → BLA activation during CS retrieval induced destabilization. Thus, our results identify a specific neural circuit underlying the transformation of a stable opiate-associated memory into an unstable memory and subsequently guide reconsolidation.

Activation of CB1 pathway in the perirhinal cortex is necessary but not sufficient for destabilization of contextual fear memory in rats

According to the reconsolidation theory, memories can be modified through the destabilization-reconsolidation process. The rodent perirhinal cortex (PER; Brodmann areas 35 and 36) critically participates in the process of fear conditioning. Previous studies showed that some of the parahippocampal regions are critical for contextual fear memory reconsolidation. In our research, through a three-day paradigm of CFC, we showed that protein synthesis in PER of rats is required for memory reconsolidation, and activation of CB1 pathway is necessary but not sufficient in inducing memory destabilization. This result underlines parahippocampal regions in destabilization and reconsolidation process of fear memory besides amygdala and hippocampus.

Electron microscopy study of carbides precipitated during destabilization and tempering heat treatments of 25 wt.%Cr-0.7 wt.%Mo high chromium cast irons

The effect of a 0.7 wt.%Mo addition on the microstructure and hardness of a heat treated 25 wt.%Cr-2.4 wt.%C cast iron has been studied via comparison with a Mo free reference 25 wt.%Cr-2.4 wt.%C iron. Destabilization led to precipitation of M₇C₃ and M₂₃C₆ secondary carbides in the reference iron, whereas M₂₃C₆ secondary carbide was found in the iron with 0.7 wt.%Mo. Tempering resulted in additional secondary carbide precipitation and formation of ferrite. Secondary hardening was found in the iron with 0.7 wt.%Mo. For the destabilized + tempered condition the macro-hardness of the iron with 0.7 wt.%Mo addition was higher than the reference iron due to a finer and denser distribution of secondary-carbides.

Displacement of interfacially-bound monoglyceride crystals in water-in-oil emulsions by a non-ionic surfactant

HYPOTHESIS

Micron and nano-scale particles are increasingly used to stabilize water-in-oil (W/O) emulsions. Though remarkably stable, the resulting emulsions can be broken by adding low molecular weight surfactants that modify the wettability of the interfacially-adsorbed particles.

EXPERIMENTS

W/O emulsions were prepared using lipophilic crystals of the monoglyceride glycerol monostearate (GMS), followed by addition of sorbitan monooleate (SMO) at concentrations below and above its critical micelle concentration (CMC). Systematic measurements of interfacial tension and three-phase contact angles, as well as characterization of emulsion sedimentation and microstructure, were used to assess GMS crystal wettability and emulsion destabilization.

FINDINGS

GMS crystals formed shells around the dispersed droplets, resulting in emulsions stable against breakdown under quiescent conditions. With SMO concentrations added below CMC, emulsion stability was not significantly affected. At SMO concentrations above CMC, the integrity of the crystalline shell was markedly affected. Notably, the GMS crystals transitioned from preferential oil-wet to water-wet behavior, eventually leading to their diffusion into the droplets. Therefore, in-situ modification of particle wettability at the oil-water interface was responsible for emulsion breakdown. Findings from this study may provide a pathway for the design of particle-stabilized W/O emulsions with controllable breakdown properties for applications such as tailored release of aqueous bioactive compounds.

Memory reconsolidation impairments in sign-tracking to an audiovisual compound stimulus

Studies of memory reconsolidation of pavlovian memories have typically employed unimodal conditioned stimuli, despite the use of multimodal compound stimuli in other settings. Here we studied sign-tracking behaviour to a compound audiovisual stimulus. First, we observed not unexpectedly that sign-tracking was poorer to the audiovisual compound than to unimodal visual stimuli. Then, we showed that, depending on the parameters of compound stimulus re-exposure at memory reactivation, systemic MK-801 treatment either impaired extinction to improve sign-tracking at test, or disrupted reconsolidation to impair test behaviour. When memory reactivation consisted of re-exposure to only the auditory component of the compound stimulus, we observed sign-tracking impairments following MK-801 treatment, but only under certain test conditions. This was in contrast to the consistent impairment following reactivation with the full audiovisual compound. Moreover, the parameters of auditory stimulus presentation to enable MK-801-induced impairment at test varied depending on whether the stimulus was presented within or outside the training context. These findings suggest that behaviour under the control of appetitive pavlovian compound stimuli can be modulated by targeting both extinction and reconsolidation, and that it is not necessary to re-expose to the full compound stimulus in order to achieve a degree of modulation of behaviour.

A methodology for analyzing and forecasting sociopolitical destabilization

The article presents a methodology for the analysis of political crises meant to assess the current situation of sociopolitical (in)stability of the developing and developed societies in question, provide an inertial forecast of the developing situation in a given period, analyse threats to stability threats, and examine possible measures to counteract such threats and their likely influence on the situation. The methodology is based on modeling sociopolitical stability in the country in question with the help of an elaborate logical-mathematical model.

Small molecule-induced simultaneous destabilization of β-catenin and RAS is an effective molecular strategy to suppress stemness of colorectal cancer cells

BACKGROUND

Cancer stem cells (CSCs), the major driver of tumorigenesis, is a sub-population of tumor cells responsible for poor clinical outcomes. However, molecular mechanism to identify targets for controlling CSCs is poorly understood.

METHODS

Gene Set Enrichment Analyses (GSEA) of Wnt/β-catenin and RAS signaling pathways in stem-like subtype of colorectal cancer (CRC) patients were performed using two gene expression data set. The therapeutic effects of destabilization of β-catenin and RAS were tested by treatment of small molecule KYA1797K using CRC patient derived cells.

RESULTS

Treatment with KYA1797K, a small molecule that destabilizes both β-catenin and RAS via Axin binding, effectively suppresses the stemness of CSCs as shown in CRC spheroids and small intestinal tumors of Apc^Min/+/K-Ras^G12DLA2 mice. Moreover, KYA1797K also suppresses the stemness of cells in CRC patient avatar model systems, such as patient-derived tumor organoids (PDTOs) and patient-derived tumor xenograft (PDTX).

CONCLUSION

Our results suggest that destabilization of both β-catenin and RAS is a potential therapeutic strategy for controlling stemness of CRC cells. Video abstract.

The dorsal hippocampus mediates synaptic destabilization and memory lability in the amygdala in the absence of contextual novelty

The recall of a previously formed fear memory triggers a process through which synapses in the amygdala become "destabilized". This labile state at retrieval may be critical for the plasticity required to modify, update, or disrupt long-term memories. One component of this process involves the rapid internalization of calcium impermeable AMPA receptors (CI-AMPAR). While some recent work has focused on the details of modifying amygdala synapses, much less is known about the environmental factors that control memory updating and the important circuit level processes. Synchrony between the hippocampus and amygdala increases during memory retrieval and stable memories can sometimes be made labile with hippocampal manipulations. Recent work shows that memory lability at retrieval is influenced by the novelty of the retrieval environment, and detection of this novelty likely relies on the dorsal hippocampus (DH). Our goal was to determine how local activity in the DH contributes to memory lability and synaptic destabilization in the amygdala during retrieval when contextual novelty is introduced. We found that contextual novelty during retrieval is necessary for alterations in amygdala activity and CI-AMPAR internalization. In the absence of novelty, suppression of local activity in the DH prior to learning allowed for retrieval-dependent CI-AMPAR internalization in the amygdala. We next tested whether the changes in AMPAR internalization were accompanied by differences in memory lability. We found that a memory was made labile when activity within the DH was disrupted in the absence of contextual novelty. These results suggest that the DH is important for encoding contextual information during learning that regulates retrieval-dependent memory modification in the amygdala.

Stability of collagen in ionic liquids: Ion specific Hofmeister series effect

In protein-ionic liquids (ILs) interactions, anions play an important role. In this work, imidazolium-based ILs (IILs) with varying anions namely dicyanamide (DCA), hydrogen sulfate (HS), dimethyl phosphate (DP), acetate (A), sulfate (S) and dihydrogen phosphate (DHP) have been chosen with the aim of understanding the role of anions in bringing about the destabilization effect on collagen based on the kosmotropicity and chaotropicity of ions. Imidazolium-based ILs destabilized the triple helical structure of collagen, thereby proving as strong denaturants for collagen and this was confirmed by various spectroscopic techniques viz., CD, FT-IR, viscosity and impedance measurements. The solution studies were in accordance to the changes in the dimensional stability of RTT collagen fibres at the fibrillar level. Imidazolium cations with varied anions have exhibited destabilizing effect on collagen in order of ions in Hofmeister series; IDP < IDHP < IA < IDCA < IS < IHS. Presumably, these notable effect and changes were facilitated by electrostatic interactions between the anions and amine functional groups of collagen.

Reaction dynamics of bentonite clay, FeCl3, Al2(SO4)3 and Na2CO3 dosage in AMD using varying dispersion techniques

200 mL solution of acid mine drainage (AMD) sample was collected from Krugerdorp gold mine in South Africa. The samples were poured into five 500 mL glass beakers, and varying volumes of 0.043 M of FeCl₃, Al₂(SO₄)₃, Na₂CO₃, and 2.0 g of bentonite clay were added respectively. The samples settled for 1 h, after which the pH and turbidity were measured. Second and third similar sets of experiments were conducted using five 500 mL glass beakers and Erlenmeyer flasks respectively, treated in a jar test or a shaker; at 250 rpm for 2 min respectively, similar settling and measurements were conducted. A fourth similar set of experiments was conducted dosing the samples with a combination of 2.0 g bentonite clay and Na₂CO₃ (flocculent) using 250 rpm rapid mixing between 20 and 60 s, 1 h settling and measurements. Turbidity removal of the samples dosed with a flocculent is lower than that of the samples with dosage of other reagents. The turbidity/heavy metals removal of the samples treated with mixing, shaking and without mixing is relatively identical. Turbidity of the samples without mixing of pH adjustment was also low. The SEM micrographs show that turbidity removal is a physico-chemical phenomenon.

Reconsolidation/destabilization, extinction and forgetting of fear memory as therapeutic targets for PTSD

Post-traumatic stress disorder (PTSD) is a psychiatric disorder associated with memories of traumatic experiences. Conditioned fear memory, a representative model of traumatic memories, is observed across species from lower to higher animals, including humans. Numerous studies have investigated the mechanisms of conditioned fear memory and have led to the identification of the underlying processes involved in fear memory regulation, including cellular and systems consolidation of fear conditioning, destabilization/reconsolidation and extinction after fear memory retrieval, and forgetting of fear memory. These studies suggested that mechanisms for fear memory regulation are shared by humans and other higher animals. Additionally, rodent studies have identified the mechanisms of fear memory at the molecular, cellular, and circuit levels. Findings from these studies in rodents have been applied to facilitate the development and improvement of PTSD intervention. For instance, reconsolidation and extinction of fear memories have been applied for PTSD treatment to improve prolonged exposure (PE) therapy, an effective psychotherapy for PTSD. Combination of medications weakening retrieved traumatic memory (e.g., by facilitating both destabilization and extinction) with PE therapy may contribute to improvement of PTSD. Interestingly, a recent study in mice identified forgetting of fear memory as another potential therapeutic target for PTSD. A better understanding of the mechanisms involved in fear memory processes is likely to facilitate the development of better treatments for PTSD. This review describes fear memory processes and their mechanisms and discusses the pros and cons of applying how this knowledge can be applied in the development of interventions for PTSD.

Electromyographic analysis of balance exercises in single-leg stance using different instability modalities of the forefoot and rearfoot

PURPOSE

To investigate the activity of lower extremity muscles in response to single-leg stance on a training device, destabilizing the forefoot while the rearfoot stands on a fixed plate and vice versa compared with a balance pad and the floor.

DESIGN

Cross-sectional study.

SETTING

University's laboratory.

PARTICIPANTS

Twenty-seven healthy adults.

METHODS

Surface electromyography and 2D video analysis were used to record the activity of lower extremity muscles and to control sagittal knee joint angle during single-leg stance trials under one stable control condition and five unstable conditions.

RESULTS

The majority of lower extremity muscles were significantly more active when the forefoot was destabilized while the rearfoot remained stable compared with the stable condition and the conditions where the forefoot was stable and the rearfoot unstable (p <0 .001). Mean change of knee joint angle was significantly increased under the conditions rearfoot stable/forefoot unstable (p = 0.001). The soleus muscle activation was significantly increased when balancing on the balance pad (p < 0.001).

CONCLUSIONS

Increased activity in the majority of lower extremity muscles and sagittal knee joint angles indicate that destabilizing the forefoot while the rearfoot remains stable is the most challenging balance task. Soleus muscle activation increased when performing ankle plantarflexion on the soft balance pad.

Quantitative contributions of processes by which polyanion drugs reduce intracellular bioavailability and transfection efficiency of cationic siRNA lipoplex

RNA Interference (RNAi) is a potentially useful tool to correct the detrimental effects of faulty genes; several RNAi are undergoing clinical evaluation in various diseases. The present study identified the relative contributions of three mechanisms by which polyanion drugs reduced the gene silencing activity of Lipoplex, a complex of small interfering RNA (siRNA) and cationic liposomes. The study used a siRNA against the chemoresistance gene survivin and two model polyanion drugs (suramin, heparin). Products of Lipoplex destabilization were separated, identified, and/or quantified using ultrafiltration, gel electrophoresis, and RT-qPCR (quantitative reverse transcription polymerase chain reaction). Cell binding and endocytosis of fluorescence-labeled Lipoplex and the amount of siRNA at its site of action RISC (RNA-induced silencing complex) were evaluated using endocytosis markers, confocal microscopy, quantitative image analysis, immunoprecipitation, and RT-qPCR. The results show suramin and heparin exerted multiple concentration-dependent effects. First, these agents altered several Lipoplex properties (i.e., reduced particle size, changed surface charge, modified composition of protein biocorona). Second, both caused Lipoplex destabilization to release double- and single-strand siRNA and/or smaller siRNA-lipid complexes with reduced siRNA cargo. Third, both prevented the cell surface binding and internalization of Lipoplex, diminished the siRNA concentration in RISC, and retarded the mRNA knockdown. Suramin and heparin yielded qualitatively and quantitatively different results. Analysis of the experimental results of suramin using quantitative pharmacology (QP) modeling indicated the major cause of gene silencing activity loss depended on drug concentration, changing from inhibition of endocytosis at lower concentration (accounting for 60% loss at ~9μM) to inhibition of cell surface binding and loss of siRNA cargo at higher concentrations (accounting for 64% and 27%, respectively, at 70μM). In summary, the present study demonstrates the complex and dynamic interactions between polyanions and Lipoplex, and the use of QP modeling to delineate the contributions of three mechanisms to the eventual loss of gene silencing activity.

Potential impacts of changing supply-water quality on drinking water distribution: A review

Driven by the development of water purification technologies and water quality regulations, the use of better source water and/or upgraded water treatment processes to improve drinking water quality have become common practices worldwide. However, even though these elements lead to improved water quality, the water quality may be impacted during its distribution through piped networks due to the processes such as pipe material release, biofilm formation and detachment, accumulation and resuspension of loose deposits. Irregular changes in supply-water quality may cause physiochemical and microbiological de-stabilization of pipe material, biofilms and loose deposits in the distribution system that have been established over decades and may harbor components that cause health or esthetical issues (brown water). Even though it is clearly relevant to customers' health (e.g., recent Flint water crisis), until now, switching of supply-water quality is done without any systematic evaluation. This article reviews the contaminants that develop in the water distribution system and their characteristics, as well as the possible transition effects during the switching of treated water quality by destabilization and the release of pipe material and contaminants into the water and the subsequent risks. At the end of this article, a framework is proposed for the evaluation of potential transition effects.

Toward a better understanding on the role of prediction error on memory processes: From bench to clinic

Experimental psychology defines Prediction Error (PE) as a mismatch between expected and current events. It represents a unifier concept within the memory field, as it is the driving force of memory acquisition and updating. Prediction error induces updating of consolidated memories in strength or content by memory reconsolidation. This process has two different neurobiological phases, which involves the destabilization (labilization) of a consolidated memory followed by its restabilization. The aim of this work is to emphasize the functional role of PE on the neurobiology of learning and memory, integrating and discussing different research areas: behavioral, neurobiological, computational and clinical psychiatry.

Protein Destabilization as a Common Factor in Diverse Inherited Disorders

Protein destabilization by amino acid substitutions is proposed to play a prominent role in widespread inherited human disorders, not just those known to involve protein misfolding and aggregation. To test this hypothesis, we computationally evaluate the effects on protein stability of all possible amino acid substitutions in 20 disease-associated proteins with multiple identified pathogenic missense mutations. For 18 of the 20 proteins studied, substitutions at known positions of pathogenic mutations are significantly more likely to destabilize the native protein fold (as indicated by more positive values of ∆∆G). Thus, positions identified as sites of disease-associated mutations, as opposed to non-disease-associated sites, are predicted to be more vulnerable to protein destabilization upon amino acid substitution. This finding supports the notion that destabilization of native protein structure underlies the pathogenicity of broad set of missense mutations, even in cases where reduced protein stability and/or aggregation are not characteristic of the disease state.

Oxidized low-density lipoprotein accelerates the destabilization of extracellular-superoxide dismutase mRNA during foam cell formation

Extracellular-superoxide dismutase (EC-SOD) is one of the main anti-oxidative enzymes that protect cells against the damaging effects of superoxide. In the present study, we investigated the regulation of EC-SOD expression during the oxidized low density lipoprotein (oxLDL)-induced foam cell formation of THP-1-derived macrophages. The uptake of oxLDL into THP-1-derived macrophages was increased and EC-SOD expression was decreased in a time-dependent manner by oxLDL. Furthermore, EC-SOD suppression by oxLDL was mediated by the binding to scavenger receptors, especially CD36, from the results with siRNA experience. EC-SOD expression is known to be regulated by histone acetylation and binding of the transcription factor Sp1/3 to the EC-SOD promoter region in human cell lines. However, oxLDL did not affect these processes. On the other hand, the stability of EC-SOD mRNA was decreased by oxLDL. Moreover, oxLDL promoted destabilization of ectopically expressed mRNA from EC-SOD or chimeric Cu,Zn-SOD gene with the sequence corresponding to 3'UTR of EC-SOD mRNA, whereas oxLDL had no effect on ectopic mRNA produced from EC-SOD gene lacking the sequence. These results suggested that oxLDL decreased the expression of EC-SOD, which, in turn, accelerated the destabilization of EC-SOD mRNA, leading to weaker protection against oxidative stress and atherosclerosis.

Memory labilization in reconsolidation and extinction--evidence for a common plasticity system?

Reconsolidation and extinction are two processes occurring upon memory retrieval that have received great attention in memory research over the last decade, partly due to their purported potential in the treatment of anxiety disorders. Due to their opposite behavioral effects, the two phenomena have usually been considered as separate entities, with few attempts to build a unified view of how both could be produced by similar mechanisms. Based on computational modeling, we have previously proposed that reconsolidation and extinction are behavioral outcomes of the same set of plasticity systems, albeit working at different synapses. One of these systems seems to be pharmacologically similar to the one involved in initial memory consolidation, and likely involves traditional Hebbian plasticity, while the second seems to be more involved with the labilization of existing memories and/or synaptic changes. In this article, we review the evidence for the existence of a plasticity system specifically involved in memory labilization, as well as its possible molecular requirements, anatomical substrates, synaptic mechanisms and physiological roles. Based on these data, we propose that the field of memory updating might ultimately benefit from a paradigm shift in which reconsolidation and extinction are viewed not as separate processes but as different instantiations of plasticity systems responsible for reinforcement and labilization of synaptic changes.

A small point regarding DLVO coagulation conditions

Criteria for colloidal destabilization that we had imposed in earlier studies (Yeung et al., 2003 [1] and Esmaeili et al., 2012 [2]) are re-examined. Those conditions are shown here to be incorrect, but with only negligible error. We also note a minor issue with the widely-accepted condition of coagulation that is seen in almost all colloids literature.