The mammalian endocytic cytoskeleton

Clathrin-mediated endocytosis (CME) is the major route through which cells internalise various substances and recycle membrane components. Via the coordinated action of many proteins, the membrane bends and in-vaginates to form a vesicle that buds off-along with its contents-into the cell. The contribution of the actin cytoskeleton to this highly dynamic process in mammalian cells is not well understood. Unlike in yeast, where there is a strict requirement for actin in CME, the significance of the actin cytoskeleton to mammalian CME is variable. However, a growing number of studies have established the actin cytoskeleton as a core component of mammalian CME, and our understanding of its contribution has been increasing at a rapid pace. In this review, we summarise the state-of-the-art regarding our understanding of the endocytic cytoskeleton, its physiological significance, and the questions that remain to be answered.Peer reviewe

Mercury levels in tar mat contaminated beaches and its marine organisms living along the Qatari coasts

One of the pollutants that affects the coastal environment of Qatar is the vast expanse of oil residue ‘tarmats’ deposited on its beaches. The current study is aimed at gauging the concentration levels of total mercury (THg) in tarmat contaminated sediments and test their presence in selected coastal species. Three biota classes (Gastropoda, Bivalvia, and Crustacea) have been found on the tarmat of Ras Rakan and Umm Tais islands. Layers of hard asphalt-like tarmats and sediments samples were collected from 34 sites, along the coast of Qatar. Moreover, the Biota Sediment Accumulation Factor (BSAF) was calculated for THg through sentinel species. The mean concentrations of THg is 0.089 ± 0.02 μg.g-1. Compared to earlier studies, a relatively higher concentration of THg (0.463 μg.g-1) had been observed

ASD-Associated De Novo Mutations in Five Actin Regulators Show Both Shared and Distinct Defects in Dendritic Spines and Inhibitory Synapses in Cultured Hippocampal Neurons

Many actin cytoskeleton-regulating proteins control dendritic spine morphology and density, which are cellular features often altered in autism spectrum disorder (ASD). Recent studies using animal models show that autism-related behavior can be rescued by either manipulating actin regulators or by reversing dendritic spine density or morphology. Based on these studies, the actin cytoskeleton is a potential target pathway for developing new ASD treatments. Thus, it is important to understand how different ASD-associated actin regulators contribute to the regulation of dendritic spines and how ASD-associated mutations modulate this regulation. For this study, we selected five genes encoding different actin-regulating proteins and induced ASD-associated de novo missense mutations in these proteins. We assessed the functionality of the wild-type and mutated proteins by analyzing their subcellular localization, and by analyzing the dendritic spine phenotypes induced by the expression of these proteins. As the imbalance between excitation and inhibition has been suggested to have a central role in ASD, we additionally evaluated the density, size and subcellular localization of inhibitory synapses. Common for all the proteins studied was the enrichment in dendritic spines. ASD-associated mutations induced changes in the localization of alpha-actinin-4, which localized less to dendritic spines, and for SWAP-70 and SrGAP3, which localized more to dendritic spines. Among the wild-type proteins studied, only alpha-actinin-4 expression caused a significant change in dendritic spine morphology by increasing the mushroom spine density and decreasing thin spine density. We hypothesized that mutations associated with ASD shift dendritic spine morphology from mushroom to thin spines. An M554V mutation in alpha-actinin-4 (ACTN4) resulted in the expected shift in dendritic spine morphology by increasing the density of thin spines. In addition, we observed a trend toward higher thin spine density withmutations inmyosin IXb and SWAP-70. Myosin IIb and myosin IXb expression increased the proportion of inhibitory synapses in spines. The expression of mutated myosin IIb (Y265C), SrGAP3 (E469K), and SWAP-70 (L544F) induced variable changes in inhibitory synapses.Peer reviewe

Factors Behind the Higher COVID-19 Risk in Diabetes: A Critical Review

Diabetes mellitus (DM) and coronavirus disease 2019 (COVID-19) are public health issues worldwide, and their comorbidities trigger the progress to severe disease and even death in such patients. Globally, DM has affected an estimated 9.3% adults, and as of April 18, 2021, the World Health Organization (WHO) has confirmed 141,727,940 COVID-19 confirmed cases. The virus is spread via droplets, aerosols, and direct touch with others. Numerous predictive factors have been linked to COVID-19 severity, including impaired immune response and increased inflammatory response, among others. Angiotensin receptor blockers and angiotensin converting enzyme 2 have also been identified as playing a boosting role in both susceptibility and severity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Specifically, in DM patients, both their control and management during this pandemic is herculean as the restriction periods have markedly hampered the maintenance of means to control glycemia, hypertension, and neuroendocrine and kidney diseases. In addition, as a result of the underlyin cardio-metabolic and immunological disorders, DM patients are at a higher risk of developing the severe form of COVID-19 despite other comorbidities, such as hypertension, also potentially boosting the development of higher COVID-19 severity. However, even in non-DM patients, SARS-CoV-2 may also cause transient hyperglycemia through induction of insulin resistance and/or pancreatic ß-cell injury. Therefore, a strict glucose monitoring of DM patients with COVID-19 is mandatory to prevent life-threatening complications.NC-M acknowledges the Portuguese Foundation for Science and Technology under the Horizon 2020 Program (PTDC/PSI-GER/28076/2017)

Tropomyosin Tpm3.1 is required to maintain the structure and function of the axon initial segment

The axon initial segment (AIS) is the site of action potential initiation and serves as a cargo transport filter and diffusion barrier that helps maintain neuronal polarity. The AIS actin cytoskeleton comprises actin patches and periodic sub-membranous actin rings. We demonstrate that tropomyosin isoform Tpm3.1 co-localizes with actin patches and that the inhibition of Tpm3.1 led to a reduction in the density of actin patches. Furthermore, Tpm3.1 showed a periodic distribution similar to sub-membranous actin rings but Tpm3.1 was only partially congruent with sub-membranous actin rings. Nevertheless, the inhibition of Tpm3.1 affected the uniformity of the periodicity of actin rings. Furthermore, Tpm3.1 inhibition led to reduced accumulation of AIS structural and functional proteins, disruption in sorting somatodendritic and axonal proteins, and a reduction in firing frequency. These results show that Tpm3.1 is necessary for the structural and functional maintenance of the AIS.Peer reviewe

The Structure and Dynamics of the Actin Cytoskeleton in the Axon Initial Segment

The axon initial segment (AIS) is the site of action potential initiation and plays an important role in maintaining neuronal polarity. Recent advances in super-resolution microscopy revealed the presence of an intricate membrane-associated periodic lattice in the AIS that contains sub-membranous actin rings periodically spaced ~190 nm and connected to a spectrin-ankyrin lattice. The precise function of these actin rings in unclear, as well as details of their structure and dynamics. The insensitivity of the AIS to actin-disrupting drugs led to the long-held view that actin is not a critical component of AIS structure. Here I show that the AIS contains a population of relatively stable, latrunculin-resistant actin filaments that are decorated by the tropomyosin isoform Tpm3.1. Disrupting these filaments through the perturbation of Tpm3.1 function led to the loss of accumulation of ankyrin G and other AIS markers, disruption of neuronal polarity, the loss of the clustering of voltage-gated sodium channels, and a rapid reduction in firing frequency. The findings I present in this thesis suggest that actin plays an important role in maintaining AIS structure and function, more important than previously appreciated.Hermosolut ovat pitkälle erikoistuneita soluja ja niiden eri haarakkeilla on erilaiset tehtävät. Tuojahaarakkeet tuovat signaalin muista hermosoluista hermosolun keskukseen, soomaan. Soomasta lähtee viejähaarake, joka vie signaalin taas eteenpäin. Viejähaarakkeen alussa, heti soomasta lähtiessä, on erityinen alue, jota suomeksi kutsutaan viejähaarakkeen alkuosaksi (englanniksi axon initial segment). Viejähaarakkeen alkuosa on tärkeä, sillä siinä päätetään, lähteekö signaali eteenpäin seuraaville hermosoluille. Viejähaarakkeen alkuosa myös säätelee mitkä solun rakennusaineet kuljetetaan viejähaarakkeisiin ja mitkä pidetään soomassa tai tuojahaarakkeissa. Näin solu pystyy erilaistamaan solun eri osat eri tehtäviä varten, tuoja- ja viejähaarakkeet on rakennettu eri rakennuskomponenteista. Viejähaarakkeen rakenne ja proteiinien järjestys on ensiarvoisen tärkeää viejähaarakkeen alkuosan tehokkaalle toiminnalle. Mikroskopiatekniikoiden kehittyminen viime vuosina on mahdollistanut viejähaarakkeen aktiinitukirangan rakenteen tarkemman tarkastelun. Aktiinitukiranka on solujen luusto ja lihakset, aktiinimolekyylit järjestäytyvät aktiinisäikeiksi, joista voi rakentaa soluun erilaisia rakenteita. Säätelystä riippuu miten pysyviä tai dynaamisia nämä rakenteet ovat. Väitöskirjassani selvitin viejähaarakkeen aktiinitukirangan rakennetta ja aktiinisäikeiden dynamiikkaa. Havaitsin että viejähaarakkeen alkuosan aktiinisäikeet ovat hyvin stabiileja. Tutkin myös miten aktiinisäikeisiin sitoutuva tropomyosiini 3.1 proteiini säätelee viejähaarakkeen alkuosan aktiinitukirankaa. Yllätyksekseni tämä tropomyosiini oli hyvin keskeinen koko viejähaarakkeen alkuosan rakenteen ylläpidolle. Kun poistin tropomyosiini 3.1 proteiinin, tai estin sen toimintaa hermosoluissa, tuhosin samalla viejähaarakkeen rakenteen ja toimivuuden, sekä rakennuskomponenttien kuljetuksen säätelyn, että signaalin eteenpäin viemisen. Aiemmin luultiin että aktiinitukiranka ei ole tärkeä viejähaarakkeen alkuosan rakenteelle tai toiminnalle. Tulokseni kuitenkin osoittavat, että aktiinitukirangan normaali rakenne on edellytys koko viejähaarakkeen rakenteen ja toiminnan ylläpidolle

Measuring Properties of the Membrane Periodic Skeleton of the Axon Initial Segment using 3D-Structured Illumination Microscopy (3D-SIM)

Funding Information: Dr. Pirta Hotulainen is acknowledged for her critical comments, invaluable for preparing this manuscript. Dr. Rimante Minkeviciene is acknowledged for her help in preparing the neuronal cultures used for the original experiments. All imaging was performed in the Biomedicum Imaging Unit. This work was supported by the Academy of Finland (D.M., SA 266351) and Doctoral Programme Brain & Mind (A.A.) Funding Information: Dr. Pirta Hotulainen is acknowledged for her critical comments, invaluable for preparing this manuscript. Dr. Rimante Minkeviciene is acknowledged for her help in preparing the neuronal cultures used for the original experiments. All imaging was performed in the Biomedicum Imaging Unit. This work was supported by the Academy of Finland (D.M., SA 266351) and Doctoral Programme Brain & Mind (A.A.). Publisher Copyright: © 2022, Journal of Visualized Experiments. All rights reserved.The axon initial segment (AIS) is the site at which action potentials initiate and constitutes a transport filter and diffusion barrier that contribute to the maintenance of neuronal polarity by sorting somato-dendritic cargo. A membrane periodic skeleton (MPS) comprising periodic actin rings provides a scaffold for anchoring various AIS proteins, including structural proteins and different ion channels. Although recent proteomic approaches have identified a considerable number of novel AIS components, details of the structure of the MPS and the roles of its individual components are lacking. The distance between individual actin rings in the MPS (~190 nm) necessitates the employment of super-resolution microscopy techniques to resolve the structural details of the MPS. This protocol describes a method for using cultured rat hippocampal neurons to examine the precise localization of an AIS protein in the MPS relative to sub-membranous actin rings using 3D-structured illumination microscopy (3D-SIM). In addition, an analytical approach to quantitively assess the periodicity of individual components and their position relative to actin rings is also described.Peer reviewe

The efficacy of two household cleaning and disinfecting agents on Lentil (Lens culinaris Medik) and Faba bean (Vicia faba) seed germination

A germination test of Vicia faba and Lens culinaris seeds under the effect of bleach and vinegar was conducted for seven days, and the observations were recorded daily. The completely randomized design (CRD) was used to examine the germination with three replicates at the lab conditions. Six germination parameters were measured, including germination percentage (GP), germination index (GI), mean germination time (MGT), mean germination rate (MGR), vigour index (VI), plus the fresh weight (FW) and dry weight (DW) of Vicia faba and Lens culinaris seeds. As a legume crop seeds model, the efficacy of four treatment levels from 0.005% to 0.5% of bleach and vinegar on the germination was tested. A chemical analysis was performed using the ion chromatography (IC) to evaluate the effect of chloride and acetate anions up-take on the seedling germination in addition to other essential nutrients. A significant inhibition in seedling growth was observed with increasing the treatment concentration. The maximum inhibition was recorded for both seeds at 0.5%, followed by 0.1% levels, while a positive effect was represented with the lower concentrations. The chemical analysis of the up-taking active ingredients was corroborated by the germination outputs

An integrated risk management model for recovery projects in the construction sector : a proposal after the Canterbury earthquakes, New Zealand.

The increase of the world's population located near areas prone to natural disasters has given rise to new ‘mega risks’; the rebuild after disasters will test the governments’ capabilities to provide appropriate responses to protect the people and businesses. During the aftermath of the Christchurch earthquakes (2010-2012) that destroyed much of the inner city, the government of New Zealand set up a new partnership between the public and private sector to rebuild the city’s infrastructure. The new alliance, called SCIRT, used traditional risk management methods in the many construction projects. And, in hindsight, this was seen as one of the causes for some of the unanticipated problems. This study investigated the risk management practices in the post-disaster recovery to produce a specific risk management model that can be used effectively during future post-disaster situations. The aim was to develop a risk management guideline for more integrated risk management and fill the gap that arises when the traditional risk management framework is used in post-disaster situations. The study used the SCIRT alliance as a case study. The findings of the study are based on time and financial data from 100 rebuild projects, and from surveying and interviewing risk management professionals connected to the infrastructure recovery programme. The study focussed on post-disaster risk management in construction as a whole. It took into consideration the changes that happened to the people, the work and the environment due to the disaster. System thinking, and system dynamics techniques have been used due to the complexity of the recovery and to minimise the effect of unforeseen consequences. Based on an extensive literature review, the following methods were used to produce the model. The analytical hierarchical process and the relative importance index have been used to identify the critical risks inside the recovery project. System theory methods and quantitative graph theory have been used to investigate the dynamics of risks between the different management levels. Qualitative comparative analysis has been used to explore the critical success factors. And finally, causal loop diagrams combined with the grounded theory approach has been used to develop the model itself. The study identified that inexperienced staff, low management competency, poor communication, scope uncertainty, and non-alignment of the timing of strategic decisions with schedule demands, were the key risk factors in recovery projects. Among the critical risk groups, it was found that at a strategic management level, financial risks attracted the highest level of interest, as the client needs to secure funding. At both alliance-management and alliance-execution levels, the safety and environmental risks were given top priority due to a combination of high levels of emotional, reputational and media stresses. Risks arising from a lack of resources combined with the high volume of work and the concern that the cost could go out of control, alongside the aforementioned funding issues encouraged the client to create the recovery alliance model with large reputable construction organisations to lock in the recovery cost, at a time when the scope was still uncertain. This study found that building trust between all parties, clearer communication and a constant interactive flow of information, established a more working environment. Competent and clear allocation of risk management responsibilities, cultural shift, risk prioritisation, and staff training were crucial factors. Finally, the post-disaster risk management (PDRM) model can be described as an integrated risk management model that considers how the changes which happened to the environment, the people and their work, caused them to think differently to ease the complexity of the recovery projects. The model should be used as a guideline for recovery systems, especially after an earthquake, looking in detail at all the attributes and the concepts, which influence the risk management for more effective PDRM. The PDRM model is represented in Causal Loops Diagrams (CLD) in Figure 8.31 and based on 10 principles (Figure 8.32) and 26 concepts (Table 8.1) with its attributes