Hypothesis Relating the Structure, Biochemistry and Function of Active Zone Material Macromolecules at a Neuromuscular Junction

This report integrates knowledge of in situ macromolecular structures and synaptic protein biochemistry to propose a unified hypothesis for the regulation of certain vesicle trafficking events (i.e., docking, priming, Ca2+-triggering, and membrane fusion) that lead to neurotransmitter secretion from specialized “active zones” of presynaptic axon terminals. Advancements in electron tomography, to image tissue sections in 3D at nanometer scale resolution, have led to structural characterizations of a network of different classes of macromolecules at the active zone, called “Active Zone Material’. At frog neuromuscular junctions, the classes of Active Zone Material macromolecules “top-masts”, “booms”, “spars”, “ribs” and “pins” direct synaptic vesicle docking while “pins”, “ribs” and “pegs” regulate priming to influence Ca2+-triggering and membrane fusion. Other classes, “beams”, “steps”, “masts”, and “synaptic vesicle luminal filaments’ likely help organize and maintain the structural integrity of active zones. Extensive studies on the biochemistry that regulates secretion have led to comprehensive characterizations of the many conserved proteins universally involved in these trafficking events. Here, a hypothesis including a partial proteomic atlas of Active Zone Material is presented which considers the common roles, binding partners, physical features/structure, and relative positioning in the axon terminal of both the proteins and classes of macromolecules involved in the vesicle trafficking events. The hypothesis designates voltage-gated Ca2+ channels and Ca2+-gated K+ channels to ribs and pegs that are connected to macromolecules that span the presynaptic membrane at the active zone. SNARE proteins (Syntaxin, SNAP25, and Synaptobrevin), SNARE-interacting proteins Synaptotagmin, Munc13, Munc18, Complexin, and NSF are designated to ribs and/or pins. Rab3A and Rabphillin-3A are designated to top-masts and/or booms and/or spars. RIM, Bassoon, and Piccolo are designated to beams, steps, masts, ribs, spars, booms, and top-masts. Spectrin is designated to beams. Lastly, the luminal portions of SV2 are thought to form the bulk of the observed synaptic vesicle luminal filaments. The goal here is to help direct future studies that aim to bridge Active Zone Material structure, biochemistry, and function to ultimately determine how it regulates the trafficking events in vivo that lead to neurotransmitter secretion.

(M)Unc13s in Active Zone Diversity: A Drosophila Perspective

The so-called active zones at pre-synaptic terminals are the ultimate filtering devices, which couple between action potential frequency and shape, and the information transferred to the post-synaptic neurons, finally tuning behaviors. Within active zones, the release of the synaptic vesicle operates from specialized “release sites.” The (M)Unc13 class of proteins is meant to define release sites topologically and biochemically, and diversity between Unc13-type release factor isoforms is suspected to steer diversity at active zones. The two major Unc13-type isoforms, namely, Unc13A and Unc13B, have recently been described from the molecular to the behavioral level, exploiting Drosophila being uniquely suited to causally link between these levels. The exact nanoscale distribution of voltage-gated Ca2+ channels relative to release sites (“coupling”) at pre-synaptic active zones fundamentally steers the release of the synaptic vesicle. Unc13A and B were found to be either tightly or loosely coupled across Drosophila synapses. In this review, we reported recent findings on diverse aspects of Drosophila Unc13A and B, importantly, their nano-topological distribution at active zones and their roles in release site generation, active zone assembly, and pre-synaptic homeostatic plasticity. We compared their stoichiometric composition at different synapse types, reviewing the correlation between nanoscale distribution of these two isoforms and release physiology and, finally, discuss how isoform-specific release components might drive the functional heterogeneity of synapses and encode discrete behavior.

Nano-Organization at the Synapse: Segregation of Distinct Forms of Neurotransmission

Synapses maintain synchronous, asynchronous, and spontaneous modes of neurotransmission through distinct molecular and biochemical pathways. Traditionally a single synapse was assumed to have a homogeneous organization of molecular components both at the active zone and post-synaptically. However, recent advancements in experimental tools and the further elucidation of the physiological significance of distinct forms of release have challenged this notion. In comparison to rapid evoked release, the physiological significance of both spontaneous and asynchronous neurotransmission has only recently been considered in parallel with synaptic structural organization. Active zone nanostructure aligns with postsynaptic nanostructure creating a precise trans-synaptic alignment of release sites and receptors shaping synaptic efficacy, determining neurotransmission reliability, and tuning plasticity. This review will discuss how studies delineating synaptic nanostructure create a picture of a molecularly heterogeneous active zone tuned to distinct forms of release that may dictate diverse synaptic functional outputs.

Development of an Automatic Solar-driven Hand Sanitizing System (AHSS) using Proximity Sensors

Inception of COVID ’19 has brought new normal globally. Contagious nature of various infectious diseases necessitated frequent hand washing in order to reduce rate of contamination and community transmission. The need to contain the spread of COVID-19 necessitated the development of an Automatic Hand Sanitizing System (AHSS). The AHSS employed proximity sensor (IR) to sense the hand and actuate the 5V DC submersible pumps in charge of both water and sanitizer units of the AHSS. The DC voltage that powered the system was harvested from the Sun with the help of 5v Photovoltaic cell connected to a controlled charging circuit. The system responded to presence of user object within the active zone of the IR proximity sensors. This presence sends signal to the pumps to release either the Sanitizer/water. Evaluation based on Delay Time (DT), Average DT (ADT), True Positive (TP), False Positive (FP), Unable to Detect (UTD) and Accuracy (A) was conducted. The system was tested 180 times among students of School of Engineering, Federal Polytechnic, Ile-Oluji (FEDPOLEL). Results of evaluation indicate 12s, 180, 0.00, 0.00 and 100% for ADT, TP, FP, UTD and Accuracy, respectively. Accuracy of the designed AHSS was encouraging. An AHSS that can notify user about level of water and sanitizer, also test for presence of COVID-19 infection can also be designed and constructed.

CALCULATION OF ELECTROTHERMAL PROCESSES IN THE INDUCTION CHANNEL FURNACE IN THE STEADY-STATE OPERATION BASED ON THE THEORY OF THERMAL CIRCUITS

Based on the theory of thermal circuits, a computer model of an induction channel furnace has been developed, which is used to obtain industrial copper wire rods in the mode of continuous casting. The model allows calculating the established electrothermal processes considering the flows of cold and molten metal in its core. In the developed thermal model, it is proposed to consider the convection fluxes of heat in the metal using controlled current sources. The temperature distribution in the active zone of the channel furnace is calculated, and the influence of the mass flow of metal at the inlet and outlet of the furnace on the non-uniformity of temperature distribution in the active zone is shown. The obtained results allow determining the required electric power of the furnace at different values ​​of the flow rate of the metal that moves continuously through its core while heating to a given temperature. The developed model is relatively easy to implement, using the Matlab/Simulink package, and allows online to estimate the melt temperature in different zones depending on the electric power consumed by the furnace and the metal consumption at the outlet of the furnace, as well as to determine rational modes of its operation. Ref. 7, fig. 4.

GAS TEMPERATURE MEASUREMENT IN THE ACTIVE ZONE OF STREAMER DISCHARGE UNDER DIFFERENT APPLIED VOLTAGES

The experimental results on the gas temperature measurement in the active zone of streamer discharge in air at the atmospheric pressure are presented. The gas temperature value was obtained by the optical method for measur-ing the relative intensity of the rotational lines for the radiation of the second positive (II+) system of molecular ni-trogen, transition bands (С3Пu(0)→B3Пg(0)). It was found that in discharge gap d = 8 mm, depending on the ap-plied voltage (in the range of 6.1…7.8 kV with a step of 0.2 kV), the gas temperature varied from 609 to739 K. The unevenness of the gas temperature change in the active zone of discharge with the increase in the applied voltage is shown. This may be related to the possible changes in the rotational state of nitrogen molecules upon excitation of their electronic state by electrons.

Homeostatic active zone remodeling consolidates memories in the Drosophila mushroom body

Establishing a detailed understanding of how the distinct forms of synaptic plasticity spatio-temporally engage into the initial storage and subsequent consolidation of memories remains a fundamental challenge of neuroscience. In addition to the better understood postsynaptic plasticity, different forms of presynaptic plasticity are widely expressed in mammalian brains and apparently operate along Hebbian or homeostatic rules. Their behavioral relevance remains enigmatic, however. Lately, acute upregulation of active zone (AZ) scaffold protein BRP and release factor Unc13A via specific axonal transport factors were shown to mediate stable expression of presynaptic homeostatic plasticity (PHP) at Drosophila neuromuscular junctions (NMJs). We here demonstrate that AZ scaling processes are specifically needed for stable expression of both, NMJ PHP as well as aversive olfactory mid-term memory within intrinsic neurons of the Drosophila mushroom body (MB). We first demonstrate that AZ upscaling via BRP is specifically needed for expression but not induction of NMJ homeostatic plasticity, thus establishing a direct temporal plasticity sequence of molecularly distinct AZ remodeling steps. Notably, when we reduced BRP and associated transport factors in MB intrinsic neurons, short-term memory persisted but robust deficits in stable memory expression for a few hours after conditioning were observed. In contrast, AZ release site protein RIM-BP affecting PHP induction was additionally needed for successful formation of short-term memory. Taken together, our data establish a specific role of homeostatic presynaptic long-term plasticity for memory consolidation. Such homeostatic refinement processes might well be needed to successfully integrate and display synaptic engrams constituting intermediary term memories.

Seismicity and development of Romashkino hydrocarbon field’s Almetyevskaya area

The relationship between the various human activities and seismic activity has become more evident in the last several decades. One of the important domains where such a relationship manifests itself is hydrocarbon fields’ development. South East Tatarstan (Russia) is a region where the link between seismicity and the development of the giant Romashkino hydrocarbon field has been established. The goal of the current study is to conduct the causative analysis between the seismic activity and the development of the Romashkino hydrocarbon field’s Almetyevskaya area which is located in the most seismically active zone of the south-eastern Tatarstan.

Synuclein Regulates Synaptic Vesicle Clustering and Docking at a Vertebrate Synapse

Neurotransmission relies critically on the exocytotic release of neurotransmitters from small synaptic vesicles (SVs) at the active zone. Therefore, it is essential for neurons to maintain an adequate pool of SVs clustered at synapses in order to sustain efficient neurotransmission. It is well established that the phosphoprotein synapsin 1 regulates SV clustering at synapses. Here, we demonstrate that synuclein, another SV-associated protein and synapsin binding partner, also modulates SV clustering at a vertebrate synapse. When acutely introduced to unstimulated lamprey reticulospinal synapses, a pan-synuclein antibody raised against the N-terminal domain of α-synuclein induced a significant loss of SVs at the synapse. Both docked SVs and the distal reserve pool of SVs were depleted, resulting in a loss of total membrane at synapses. In contrast, antibodies against two other abundant SV-associated proteins, synaptic vesicle glycoprotein 2 (SV2) and vesicle-associated membrane protein (VAMP/synaptobrevin), had no effect on the size or distribution of SV clusters. Synuclein perturbation caused a dose-dependent reduction in the number of SVs at synapses. Interestingly, the large SV clusters appeared to disperse into smaller SV clusters, as well as individual SVs. Thus, synuclein regulates clustering of SVs at resting synapses, as well as docking of SVs at the active zone. These findings reveal new roles for synuclein at the synapse and provide critical insights into diseases associated with α-synuclein dysfunction, such as Parkinson’s disease.