Complexity Of Nervous System Research Articles

Brief freezing steps lead to robust immunofluorescence in the Drosophila nervous system.

Drosophila melanogaster possesses a complex nervous system, regulating sophisticated behavioral outputs, that serves as a powerful model for dissecting molecular mechanisms underlying neuronal function and neurodegenerative disease. Immunofluorescence techniques provide a way to visualize the spatiotemporal organization of these networks, permitting observation of their development, functional location, remodeling and, eventually, degradation. However, basic immunostaining techniques do not always result in efficient antibody penetration through the brain, and supplemental techniques to enhance permeability can compromise structural integrity, altering spatial organization. Here, slow freezing of brains is shown to facilitate antibody permeability without loss of antibody specificity or brain integrity. To demonstrate the advantages of this freezing technique, the results of two commonly used permeation methods – detergent-based and partial proteolytic digestion – are compared.

Transition from Acute to Chronic Pain: Evaluating Risk for Chronic Postsurgical Pain

Background: The pathophysiology of pain involves complex nervous system interactions after initial noxious stimuli. When stimuli persist, biochemical and structural changes occur in the nociceptive pathways of the central and peripheral nervous systems, leading to pain sensitization. Peripheral and central sensitization are key in the transition from acute to chronic pain. This development of chronic pain is particularly common following various surgical procedures, with many postsurgical patients experiencing persistent pain for significant periods. Chronic pain is a common and severe complication of surgery, and preventing its development is tantamount in improving patient outcomes. Objectives: To understand underlying pathophysiology of chronic postsurgical pain (CPSP) and the underlying risk factors predisposing the transition from acute to CPSP. To review our ability to identify patients at highest risk for the development CPSP. To identify evidence-based multimodal approaches that can aid in the prevention of CPSP. Study Design: Narrative review of peer-reviewed literature. Setting: Inpatient surgical centers. Methods: Medline and Cochrane databases were reviewed to identify publications relevant to CPSP pathophysiology, risk factors, predictive models, and prevention. Publications were selected based on author expertise to summarize our current understanding of CPSP. Results: This review presents our current understanding of CPSP in the following domains: underlying pathophysiology, predisposing risk factors, predictive models of CPSP, and preventative strategies. Each section provides a structured review of key evidence base to understand the complex topic of CPSP. Limitations: This narrative review is a nonsystematic review of relevant publications aimed at presenting succinct overview of CPSP. Conclusions: The incidence of CPSP can potentially be reduced through early identification of perioperative, genetic, physiologic, and psychologic factors. Models predicting the development of CPSP continue to improve and may help focus preventative efforts in patients at highest risk. There is a growing body of evidence supporting the use of multimodal analgesia and anesthetic techniques in the reducing rates of CPSP development. Key words: Acute pain, chronic postsurgical pain, pain sensitization, chronic pain prevention, regional anesthesia, pain adjuncts, neuraxial anesthesia, chronic pain risk factors

The neural basis of consciousness

Consciousness has evolved and is a feature of all animals with sufficiently complex nervous systems. It is, therefore, primarily a problem for biology, rather than physics. In this review, I will consider three aspects of consciousness: level of consciousness, whether we are awake or in a coma; the contents of consciousness, what determines how a small amount of sensory information is associated with subjective experience, while the rest is not; and meta-consciousness, the ability to reflect upon our subjective experiences and, importantly, to share them with others. I will discuss and compare current theories of the neural and cognitive mechanisms involved in producing these three aspects of consciousness and conclude that the research in this area is flourishing and has already succeeded to delineate these mechanisms in surprising detail.

Development of a contrast-enhanced micro computed tomography protocol for the oval squid (Sepioteuthis lessoniana) brain.

Coleoid cephalopods (squid, cuttlefish, and octopus) have a well-developed and complex central nervous system. Its absolute size is the largest among invertebrates, and the brain-to-body mass ratio is larger than that of fish and reptiles and equivalent to that of birds and mammals. Although a number of histological studies have been conducted on the brains of cephalopods, most of them used a light microscope or an electron microscope, which show the microstructure of the brain, but often cannot image the whole brain instantaneously. Of late, micro computed tomography (CT) has gained popularity for imaging animal brains because it allows for noninvasive three-dimensional (3D) reconstruction and preprocessing that are not cumbersome. To perform micro-CT on cephalopod brains, we first tested conditions suitable for preprocessing, paying special attention to staining conditions that would provide high contrast images. Four agents, iodine in 99.5% ethanol, iodine potassium iodide in water (IKI), phosphotungstic acid in 70% ethanol, and nonionic iodinated contrast agent in water, were tested at various concentrations and durations on brain of juvenile oval squid. To evaluate the quality of staining, we calculated the contrast ratio of the two-dimensional (2D) images and compared 3D segmentation of the best and worst 2D images. We concluded that 3% IKI staining for 7 days was the best combination to enhance the images contrast of the oval squid brain, in which each brain lobe was clearly detected and 3D segmentation of the whole brain was possible. The wider applicability of this preprocessing method for micro-CT of the brains of other cephalopods is discussed.

Chemical Responses to the Biotic and Abiotic Environment by Early Diverging Metazoans Revealed in the Post-Genomic Age.

For many years methodological constraints limited insights on the molecular biology of non-model organisms. However, the development of various sequencing platforms has led to an explosion of transcriptomic and genomic data on non-model systems. As a consequence the molecular drivers of organismal phenotypes are becoming clearer and the chemicals that animals use to detect and respond to their environments are increasingly being revealed-this latter area inspired our symposium theme. The papers in this volume broadly address this theme by their more specific focus in one of the following general areas: 1) sensory biology and the molecular basis of perception, 2) chemicals deployed to deal with the biotic and abiotic environment, and 3) chemical interactions along the parasite-mutualist continuum. Here we outline and synthesize the content of these papers-an exercise which demonstrates that sophisticated gene repertoires enable early diverging metazoans to encode many of the signaling, sensory, defensive, and offensive capacities typically associated with animals that have complex nervous systems. We then consider opportunities and associated challenges that may delay progress in comparative functional biochemistry, a reinvigorated field that can be expected to rapidly expand with new 'omics data. Future knowledge of chemical adaptations should afford new perspectives on the comparative evolution of chemical mediators.

The Use of Myelinating Cultures as a Screen of Glycomolecules for CNS Repair.

In vitro cell-based assays have been fundamental in modern drug discovery and have led to the identification of novel therapeutics. We have developed complex mixed central nervous system (CNS) cultures, which recapitulate the normal process of myelination over time and allow the study of several parameters associated with CNS damage, both during development and after injury or disease. In particular, they have been used as a reliable screen to identify drug candidates that may promote (re)myelination and/or neurite outgrowth. Previously, using these cultures, we demonstrated that a panel of low sulphated heparin mimetics, with structures similar to heparan sulphates (HSs), can reduce astrogliosis, and promote myelination and neurite outgrowth. HSs reside in either the extracellular matrix or on the surface of cells and are thought to modulate cell signaling by both sequestering ligands, and acting as co-factors in the formation of ligand-receptor complexes. In this study, we have used these cultures as a screen to address the repair potential of numerous other commercially available sulphated glycomolecules, namely heparosans, ulvans, and fucoidans. These compounds are all known to have certain characteristics that mimic cellular glycosaminoglycans, similar to heparin mimetics. We show that the N-sulphated heparosans promoted myelination. However, O-sulphated heparosans did not affect myelination but promoted neurite outgrowth, indicating the importance of structure in HS function. Moreover, neither highly sulphated ulvans nor fucoidans had any effect on remyelination but CX-01, a low sulphated porcine intestinal heparin, promoted remyelination in vitro. These data illustrate the use of myelinating cultures as a screen and demonstrate the potential of heparin mimetics as CNS therapeutics.

Substance P appears to affect growth via growth hormone-releasing hormone (GHRH) neurons in the human hypothalamus.

Substance P is an eleven-amino acid neuropeptide (undecapeptide) with multiple effects on the gastrointestinal, cardiovascular, and urinary systems as well as complex central nervous system functions such as pain, learning, memory, and sexual homeostasis. Previous studies also revealed that substance P exhibits regulatory effects on growth possibly via influencing hypothalamic GHRH release in human. However, the morphological substrate of this phenomenon has not been elucidated yet. In the present study, we examined the putative presence of juxtapositions between the substance P- and GHRH-immunoreactive (IR) systems using double-label immunocytochemistry. High-magnification light microscopy with oil immersion was used to identify putative juxtapositions between these systems. Our studies revealed substance P-IR fiber network abutting on the surface of the majority of GHRH-immunoreactive neurons in the human hypothalamus. These fiber varicosities often cover a significant surface area on the GHRH-IR neurons, forming basket-like encasements with multiple en passant type contacts. The majority of these densely innervated GHRH-IR neurons were found in the infundibular nucleus/median eminence, while substance P-IR fibers often abut on the GHRH-IR neurons in the periventricular zone and basal perifornical area of the tuberal region and in the dorsomedial subdivision of the ventromedial nucleus. The posterior hypothalamus did not contain observable substance P-GHRH associations. The density and the morphology of these intimate associations suggest that substance P influences growth by regulating hypothalamic GHRH release by direct synaptic contacts.

Family of neural wiring receptors in bilaterians defined by phylogenetic, biochemical, and structural evidence

The evolution of complex nervous systems was accompanied by the expansion of numerous protein families, including cell-adhesion molecules, surface receptors, and their ligands. These proteins mediate axonal guidance, synapse targeting, and other neuronal wiring-related functions. Recently, 32 interacting cell surface proteins belonging to two newly defined families of the Ig superfamily (IgSF) in fruit flies were discovered to label different subsets of neurons in the brain and ventral nerve cord. They have been shown to be involved in synaptic targeting and morphogenesis, retrograde signaling, and neuronal survival. Here, we show that these proteins, Dprs and DIPs, are members of a widely distributed family of two- and three-Ig domain molecules with neuronal wiring functions, which we refer to as Wirins. Beginning from a single ancestral Wirin gene in the last common ancestor of Bilateria, numerous gene duplications produced the heterophilic Dprs and DIPs in protostomes, along with two other subfamilies that diversified independently across protostome phyla. In deuterostomes, the ancestral Wirin evolved into the IgLON subfamily of neuronal receptors. We show that IgLONs interact with each other and that their complexes can be broken by mutations designed using homology models based on Dpr and DIP structures. The nematode orthologs ZIG-8 and RIG-5 also form heterophilic and homophilic complexes, and crystal structures reveal numerous apparently ancestral features shared with Dpr-DIP complexes. The evolutionary, biochemical, and structural relationships we demonstrate here provide insights into neural development and the rise of the metazoan nervous system.

Genomic signatures of G-protein-coupled receptor expansions reveal functional transitions in the evolution of cephalopod signal transduction.

Coleoid cephalopods show unique morphological and neural novelties, such as arms with tactile and chemosensory suckers and a large complex nervous system. The evolution of such cephalopod novelties has been attributed at a genomic level to independent gene family expansions, yet the exact association and the evolutionary timing remain unclear. In the octopus genome, one such expansion occurred in the G-protein-coupled receptors (GPCRs) repertoire, a superfamily of proteins that mediate signal transduction. Here, we assessed the evolutionary history of this expansion and its relationship with cephalopod novelties. Using phylogenetic analyses, at least two cephalopod- and two octopus-specific GPCR expansions were identified. Signatures of positive selection were analysed within the four groups, and the locations of these sequences in the Octopus bimaculoides genome were inspected. Additionally, the expression profiles of cephalopod GPCRs across various tissues were extracted from available transcriptomic data. Our results reveal the evolutionary history of cephalopod GPCRs. Unexpanded cephalopod GPCRs shared with other bilaterians were found to be mainly nervous tissue specific. By contrast, duplications that are shared between octopus and the bobtail squid or specific to the octopus' lineage generated copies with divergent expression patterns devoted to tissues outside of the brain. The acquisition of novel expression domains was accompanied by gene order rearrangement through either translocation or duplication and gene loss. Lastly, expansions showed signs of positive selection and some were found to form tandem clusters with shared conserved expression profiles in cephalopod innovations such as the axial nerve cord. Altogether, our results contribute to the understanding of the molecular and evolutionary history of signal transduction and provide insights into the role of this expansion during the emergence of cephalopod novelties and/or adaptations.

GEOFFREY HARRIS PRIZE LECTURE 2018: Novel pathways regulating neuroendocrine function, energy homeostasis and metabolism in humans.

The discovery of leptin, an adipocyte-secreted hormone, set the stage for unraveling the mechanisms dictating energy homeostasis, revealing adipose tissue as an endocrine system that regulates appetite and body weight. Fluctuating leptin levels provide molecular signals to the brain regarding available energy reserves modulating energy homeostasis and neuroendocrine response in states of leptin deficiency and to a lesser extent in hyperleptinemic states. While leptin replacement therapy fails to provide substantial benefit in common obesity, it is an effective treatment for congenital leptin deficiency and states of acquired leptin deficiency such as lipodystrophy. Current evidence suggests that regulation of eating behavior in humans is not limited to homeostatic mechanisms and that the reward, attention, memory and emotion systems are involved, participating in a complex central nervous system network. It is critical to study these systems for the treatment of typical obesity. Although progress has been made, further studies are required to unravel the physiology, pathophysiology and neurobehavioral mechanisms underlying potential treatments for weight-related problems in humans.

Who needs a brain? Slime moulds, behavioural ecology and minimal cognition

Although human decision making seems complex, there is evidence that many decisions are grounded in simple heuristics. Such heuristic models of decision making are widespread in nature. To understand how and why different forms of information processing evolve, it is insightful to study the minimal requirements for cognition. Here, we explore the minimally cognitive behaviour of the acellular slime mould, Physarum polycephalum, in order to discuss the ecological pressures that lead to the development of information processing mechanisms. We discuss evidence for memory, basic forms of learning and economically irrational choice in P. polycephalum. We compare P. polycephalum’s behaviour with a number of other non-neuronal organisms in order to question the evolutionary need for complex nervous systems to develop cognitive traits. By highlighting a few examples of common mechanisms, we conclude that all organisms contain the building blocks for more complex information processing. Returning the debate about cognition to the biological basics demystifies some of the confusion around the term ‘cognition’.

Measurement of Sleep and Arousal in Drosophila.

Sleep is a conserved neurobehavioral state observed in animals with sufficiently complex nervous systems and is critical for survival. While the exact function of sleep remains unknown, the lack of sleep can have a range of physiological and behavioral effects. Studies in invertebrates and vertebrates have identified conserved neural mechanisms and cellular pathways in control of sleep, wakefulness and arousal. Methodologies to measure sleep have ranged from EEG recordings in humans and rodents to in-depth analysis of locomotor patterns in flies, fish and worms. Here we focus on sleep measurements using activity monitoring in the highly versatile experimental model system, Drosophila melanogaster, which is amenable to a number of genetic, physiological and behavioral manipulations. Further, we also describe methods used to manipulate sleep and wakefulness to understand the neural regulation of sleep and how organisms balance sleep, wakefulness and behavioral arousal. Sleep as a behavioral state is regulated by a number of factors including food, environmental conditions, and genetic background. The methodologies described here provide, a high-throughput approach to study neural regulation of sleep and factors that affect this complex behavior.

Xenacoelomorph Neuropeptidomes Reveal a Major Expansion of Neuropeptide Systems during Early Bilaterian Evolution

Neuropeptides are neurosecretory signaling molecules in protostomes and deuterostomes (together Nephrozoa). Little, however, is known about the neuropeptide complement of the sister group of Nephrozoa, the Xenacoelomorpha, which together form the Bilateria. Because members of the xenacoelomorph clades Xenoturbella, Nemertodermatida, and Acoela differ extensively in their central nervous system anatomy, the reconstruction of the xenacoelomorph and bilaterian neuropeptide complements may provide insights into the relationship between nervous system evolution and peptidergic signaling. Here, we analyzed transcriptomes of seven acoels, four nemertodermatids, and two Xenoturbella species using motif searches, similarity searches, mass spectrometry and phylogenetic analyses to characterize neuropeptide precursors and neuropeptide receptors. Our comparison of these repertoires with previously reported nephrozoan and cnidarian sequences shows that the majority of annotated neuropeptide GPCRs in cnidarians are not orthologs of specific bilaterian neuropeptide receptors, which suggests that most of the bilaterian neuropeptide systems evolved after the cnidarian–bilaterian evolutionary split. This expansion of more than 20 peptidergic systems in the stem leading to the Bilateria predates the evolution of complex nephrozoan organs and nervous system architectures. From this ancient set of neuropeptides, acoels show frequent losses that correlate with their divergent central nervous system anatomy. We furthermore detected the emergence of novel neuropeptides in xenacoelomorphs and their expansion along the nemertodermatid and acoel lineages, the two clades that evolved nervous system condensations. Together, our study provides fundamental insights into the early evolution of the bilaterian peptidergic systems, which will guide future functional and comparative studies of bilaterian nervous systems.

The Cephalopod Large Brain Enigma: Are Conserved Mechanisms of Stem Cell Expansion the Key?

Within the clade of mollusks, cephalopods have developed an unusually large and complex nervous system. The increased complexity of the cephalopod centralized “brain” parallels an amazing amount of complex behaviors that culminate in one order, the octopods. The mechanisms that enable evolution of expanded brains in invertebrates remain enigmatic. While expression mapping of known molecular pathways demonstrated the conservation of major neurogenesis pathways and revealed neurogenic territories, it did not explain why cephalopods could massively increase their brain size compared to other mollusks. Such an increase is reminiscent of the expansion of the cerebral cortex in mammalians, which have enlarged their number and variety of neurogenic stem cells. We hypothesize that similar mechanisms might be at play in cephalopods and that focusing on the stem cell biology of cephalopod neurogenesis and genetic innovations might be smarter strategies to uncover the mechanism that has driven cephalopod brain expansion.

PrismPlus: a mouse line expressing distinct fluorophores in four different brain cell types

To screen the complex central nervous system (CNS) injury responses, we created a quadruple-labelled ‘PrismPlus’ mouse line with a genetically encoded distinct fluorescent tag in oligodendrocytes, microglia, neurons, and astrocytes. Cx3cr1-gfp and Prism mice originally developed by Jung et al., 2000 and Dougherty et al., 2012, respectively, were cross-bred. First, we confirmed the presence of fluorophores in appropriate cell types in PrismPlus mice. PrismPlus mice were then used to examine the cellular responses to brain implanted micro-devices. We observed an increase in microglial response at earlier time points as compared to 4 weeks, a progressive astrocytic response, and fewer neurons at the vicinity of an implanted device. These results are similar to what has been described in literature using other rodent strains, previously attainable only through time-consuming and variable immunohistochemistry methods. Finally, we demonstrate the compatibility of PrismPlus brain tissue with CLARITY, an advanced tissue clearing technique, opening the door to future thick tissue imaging studies. This report confirms PrismPlus transgenic fluorescence and highlights the utility of these mice to study CNS injuries. The work herein seeks to establish a novel transgenic mouse line to improve experimental scope, consistency, and efficiency for CNS researchers.

Octopus vulgaris: An Alternative in Evolution.

Octopus vulgaris underwent a radical modification to cope with the benthic lifestyle. It diverged from other cephalopods in terms of body plan, anatomy, behavior, and intelligence. It independently evolved the largest and most complex nervous system and sophisticated behaviors among invertebrates in a separate evolutionary lineage. It is equipped with unusual traits that confer it an incredible evolutionary success: arms capable of a wide range of movements with no skeletal support; developed eyes with a complex visual behavior; vestibular system; primitive "hearing" system; chemoreceptors located in epidermis, suckers, and mouth; and a discrete olfactory organ. As if these were not enough, the occurrence of recently discovered adult neurogenesis and the high level of RNA editing give it a master key to face environmental challenges. Here we provide an overview of some of the winning evolutionary inventions that octopus puts in place such as the capacity to see color, smell by touch, edit own genes, and rejuvenate own brain.

Presence and persistence of the amnesic shellfish poisoning toxin, domoic acid, in octopus and cuttlefish brains

Domoic acid (DA) is a neurotoxin that causes degenerative damage to brain cells and induces permanent short-term memory loss in mammals. In cephalopod mollusks, although DA is known to accumulate primarily in the digestive gland, there is no knowledge whether DA reaches their central nervous system. Here we report, for the first time, the presence of DA in brain tissue of the common octopus (Octopus vulgaris) and the European cuttlefish (Sepia officinalis), and its absence in the brains of several squid species (Loligo vulgaris, L. forbesi and Todarodes sagittatus). We argue that such species-specific differences are related to their different life strategies (benthic/nektobenthic vs pelagic) and feeding ecologies, as squids mainly feed on pelagic fish, which are less prone to accumulate phycotoxins. Additionally, the temporal persistence of DA in octopus’ brain reinforces the notion that these invertebrates can selectively retain this phycotoxin. This study shows that two highly-developed invertebrate species, with a complex central nervous system, where glutamatergic transmission is involved in vertebrate-like long-term potentiation (LTP), have the ability of retaining and possibly tolerating chronic exposure to DA, a potent neurotoxin usually acting at AMPA/kainate-like receptors. Here, we filled a gap of information on whether cephalopods accumulated this neurotoxin in brain tissue, however, further studies are needed to determine if these organisms are neurally or behaviourally impaired by DA.

Fish perform like mammals and birds in inhibitory motor control tasks

Inhibitory control is an executive function that positively predicts performance in several cognitive tasks and has been considered typical of vertebrates with large and complex nervous systems such as primates. However, evidence is growing that some fish species have evolved complex cognitive abilities in spite of their relatively small brain size. We tested whether fish might also show enhanced inhibitory control by subjecting guppies, Poecilia reticulata, to the motor task used to test warm-blooded vertebrates. Guppies were trained to enter a horizontal opaque cylinder to reach a food reward; then, the cylinder was replaced by a transparent one, and subjects needed to inhibit the response to pass thought the transparency to reach the food. Guppies performed correctly in 58% trials, a performance fully comparable to that observed in most birds and mammals. In experiment 2, we tested guppies in a task with a different type of reward, a group of conspecifics. Guppies rapidly learned to detour a transparent barrier to reach the social reward with a performance close to that of experiment 1. Our study suggests that efficient inhibitory control is shown also by fish, and that its variation between-species is only partially explained by variation in brain size.

A Chemical Reaction Network to Generate Random, Power-Law-Distributed Time Intervals.

In Lévy walks (LWs), particles move with a fixed speed along straight line segments and turn in new directions after random time intervals that are distributed according to a power law. Such LWs are thought to be an advantageous foraging and search strategy for organisms. While complex nervous systems are certainly capable of producing such behavior, it is not clear at present how single-cell organisms can generate the long-term correlated control signals required for a LW. Here, we construct a biochemical reaction system that generates long-time correlated concentration fluctuations of a signaling substance, with a tunable fractional exponent of the autocorrelation function. The network is based on well-known modules, and its basic function is highly robust with respect to the parameter settings.

Parkinson's Disease Subtypes Identified from Cluster Analysis of Motor and Non-motor Symptoms.

Parkinson's disease is now considered a complex, multi-peptide, central, and peripheral nervous system disorder with considerable clinical heterogeneity. Non-motor symptoms play a key role in the trajectory of Parkinson's disease, from prodromal premotor to end stages. To understand the clinical heterogeneity of Parkinson's disease, this study used cluster analysis to search for subtypes from a large, multi-center, international, and well-characterized cohort of Parkinson's disease patients across all motor stages, using a combination of cardinal motor features (bradykinesia, rigidity, tremor, axial signs) and, for the first time, specific validated rater-based non-motor symptom scales. Two independent international cohort studies were used: (a) the validation study of the Non-Motor Symptoms Scale (n = 411) and (b) baseline data from the global Non-Motor International Longitudinal Study (n = 540). k-means cluster analyses were performed on the non-motor and motor domains (domains clustering) and the 30 individual non-motor symptoms alone (symptoms clustering), and hierarchical agglomerative clustering was performed to group symptoms together. Four clusters are identified from the domains clustering supporting previous studies: mild, non-motor dominant, motor-dominant, and severe. In addition, six new smaller clusters are identified from the symptoms clustering, each characterized by clinically-relevant non-motor symptoms. The clusters identified in this study present statistical confirmation of the increasingly important role of non-motor symptoms (NMS) in Parkinson's disease heterogeneity and take steps toward subtype-specific treatment packages.