Branch architecture of the fly larval abdominal serotonergic neurons

In the metazoan central nervous system (CNS), serotonergic neurons send projections throughout the synaptic neuropil. Little is known about the rules that govern these widespread neuromodulatory branching patterns. In this study, we utilize the Drosophila as a model to examine serotonergic branching. Using single cell GFP labeling we show that within each segment of the Drosophila ventral nerve cord (VNC), each of two serotonergic neurons tiles distinct innervation patterns in the contralateral neuropil. In addition, branches extend only a short distance from the target segment. Through ablation-mediated isolation of serotonergic cells, we demonstrate that the distinct areas of innervation are not maintained through competition between neighboring like-serotonergic neurites. Furthermore, the basic branching pattern of serotonergic neurons within the neuropil remains unchanged despite alterations of initial axonal trajectories.     

CNS midline cells influence the division and survival of lateral glia in the Drosophila nervous system

Central nervous system (CNS) midline cells are essential for identity determination and differentiation of neurons in the Drosophila nervous system. It is not clear, however, whether CNS midline cells are also involved in the development of lateral glial cells. The roles of CNS midline cells in lateral glia development were elucidated using general markers for lateral glia, such as glial cell missing and reverse polarity, and specific enhancer trap lines labeling the longitudinal, A, B, medial cell body, peripheral, and exit glia. We found that CNS midline cells were necessary for the proper expression of glial cell missing, reverse polarity, and other lateral glia markers only during the later stages of development, suggesting that they are not required for initial identity determination. Instead, CNS midline cells appear to be necessary for proper division and survival of lateral glia. CNS midline cells were also required for proper positioning of three exit glia at the junction of segmental and intersegmental nerves, as well as some peripheral glia along motor and sensory axon pathways. This study demonstrated that CNS midline cells are extrinsically required for the proper division, migration, and survival of various classes of lateral glia from the ventral neuroectoderm.     

Identification of N-glycosylated proteins from the central nervous system of Drosophila melanogaster

Although the function of many glycoproteins in the nervous system of fruit flies is well understood, information about the glycosylation profile and glycan attachment sites for such proteins is scarce. In order to fill this gap and to facilitate the analysis of N-linked glycosylation in the nervous system, we have performed an extensive survey of membrane-associated glycoproteins and their N-glycosylation sites isolated from the adult Drosophila brain. Following subcellular fractionation and trypsin digestion, we used different lectin affinity chromatography steps to isolate N-glycosylated glycopeptides. We identified a total of 205 glycoproteins carrying N-linked glycans and revealed their 307 N-glycan attachment sites. The size of the resulting dataset furthermore allowed the statistical characterization of amino acid distribution around the N-linked glycosylation sites. Glycan profiles were analyzed separately for glycopeptides that were strongly and weakly bound to Concanavalin A (Con A), or that failed to bind Concanavalin A, but did bind to wheat germ agglutinin (WGA). High- or paucimannosidic glycans dominated each of the profiles, although the wheat germ agglutinin-bound glycan population was enriched in more extensively processed structures. A sialylated glycan structure was unambiguously detected in the wheat germ agglutinin-bound fraction. Despite the large amount of starting material, insufficient amount of glycopeptides was retained by the Wisteria floribunda (WFA) and Sambucus nigra columns to allow glycan or glycoprotein identification, providing further evidence that the vast majority of glycoproteins in the adult Drosophila brain carry primarily high-mannose, paucimannose, and hybrid glycans. The obtained results should facilitate future genetic and molecular approaches addressing the role of N-glycosylation in the central nervous system (CNS) of Drosophila.     

Enchancer detector analysis of the extent of genomic involvement in nervous system development in Drosophila melanogaster

We conducted a survey of the patterns of gene expression in the central nervous system (CNS) of larvae of the fruitfly Drosophila melanogaster to identify genes that may be important in the development of the CNS, aid in the recognition of basic organizing features that might underlie CNS development, and estimate the extent of the use of information encoded in the genome in the construction of the nervous system. A so-called enhancer detector strategy was used to generate many thousands of lines containing a β-galactosidase reporter gene. These lines were screened as third-instar larvae for patterns of expression in the developing optic lobes and other portions of the CNS. Most of the lines recovered which evidence staining within the CNS could be included in one of a relatively small number of patterns. A random sample of 594 lines from the larger population screened was selected to quantify the relative frequencies of these patterns, and a more careful analysis of the changes in the patterns of expression with developmental time was done for representative lines of nine of the patterns. These studies demonstrated great variability in the patterns of gene expression as a function of developmental stage. Few, if any, lines showed β-galactosidase activity limited to the optic lobes; similarly, few lines were identified in which staining was limited to only a small number of cells. Together with the limited number of patterns of gene expression seen, this suggests that in the larval CNS developmental pathways may be controlled by a combinatorial process of gene activity that involves the majority of the genome rather than by having a specific gene specify the fate of only a few neuronal precursors. © 1993 John Wiley & Sons, Inc.     

Pyridine alkaloids with activity in the central nervous system

This review discusses all pyridine alkaloids with CNS activity, their therapeutic potential, and the interesting array of sources whence they originate.     

Motor effects of serotonin in the central nervous system

Serotoneric pathways in the CNS affect posture and movement, as well as behavioral responses to arousing stimuli. Pharmacologic analysis of these effects has led to an increasingly complex and confusing literature. Increased availability of serotonin (5-HT) by administration of precursors, or by its direct intracranial infusion can induce inhibitory or excitatory behavioral effects depending on the conditions of the experiment, although generally motor inhibition has been found. Availability of 5-HT has been decreased by electrolytic lesions of the raphe nuclei, inhibition of tryptophan hydroxylase, or use of selective neurotoxins. These treatments have generally increased motor activity, especially spontaneous locomotion in a familiar environment, as well as sexual or aggressive behaviors; other behaviors, such as responses in a novel environment, presumably associated with curiosity or fear, have been paradoxically decreased after loss of 5-HT. This differentiation may occur to an important extent through 5-HT projections to hippocampus and limbic structures, notably from the median raphe. Increases or decreases of brain 5-HT, respectively, generally tend to decrease and increase responses to catecholamine agonists such as amphetamines, and some effects of 5-HT may be mediated through catecholaminergic systems. Increased availability of 5-HT in the presence of MAO inhibitors, or challenge with 5-HT-agonists after selective 5-HT-denervation in the CNS has led to a behavioral syndrome marked by hyperactivity, autonomic arousal and myoclonic seizures. The mechanisms underlying this complex response may be mediated by descending 5-HT systems that result in motor excitation at the spinal cord level, in contrast to rostral projections to forebrain that may mediate many behaviorally inhibitory responses.     

Physiological and pathological roles of interleukin-6 in the central nervous system

The cytokine interleukin-6 (IL-6) is an important mediator of inflammatory and immune responses in the periphery. IL-6 is produced in the periphery and acts systemically to induce growth and differentiation of cells in the immune and hematopoietic systems and to induce and coordinate the different elements of the acute-phase response. In addition to these peripheral actions, recent studies indicate that IL-6 is also produced within the central nervous system (CNS) and may play an important role in a variety of CNS functions such as cell-to-cell signaling, coordination of neuroimmune responses, protection of neurons from insult, as well as neuronal differentiation, growth, and survival. IL-6 may also contribute to the etiology of neuropathological disorders. Elevated levels of IL-6 in the CNS are found in several neurological disorders including AIDS dementia complex, Alzheimer's disease, multiple sclerosis, systemic lupus erythematosus, CNS trauma, and viral and bacterial meningitis. Moreover, several studies have shown that chronic overexpression of IL-6 in transgenic mice can lead to significant neuroanatomical and neurophysiological changes in the CNS similar to that commonly observed in various neurological diseases. Thus, it appears that IL-6 may play a role in both physiological and pathophysiological processes in the CNS.     

Adenosine in the central nervous system: release mechanisms and extracellular concentrations

Adenosine has several functions within the CNS that involve an inhibitory tone of neurotransmission and neuroprotective actions in pathological conditions. The understanding of adenosine production and release in the brain is therefore of fundamental importance and has been extensively studied. Conflicting results are often obtained regarding the cellular source of adenosine, the stimulus that induces release and the mechanism for release, in relation to different experimental approaches used to study adenosine production and release. A neuronal origin of adenosine has been demonstrated through electrophysiological approaches showing that neurones can release significant quantities of adenosine, sufficient to activate adenosine receptors and to modulate synaptic functions. Specific actions of adenosine are mediated by different receptor subtypes (A(1), A(2A), A(2B) and A(3)), which are activated by various ranges of adenosine concentrations. Another important issue is the measurement of adenosine concentrations in the extracellular fluid under different conditions in order to know the degree of receptor stimulation and understand adenosine central actions. For this purpose, several experimental approaches have been used both in vivo and in vitro, which provide an estimation of basal adenosine levels in the range of 50-200 nM. The purpose of this review is to describe pathways of adenosine production and metabolism, and to summarize characteristics of adenosine release in the brain in response to different stimuli. Finally, studies performed to evaluate adenosine concentrations under physiological and hypoxic/ischemic conditions will be described to evaluate the degree of adenosine receptor activation.     

Gut microbiome and the risk factors in central nervous system autoimmunity

Humans are colonized after birth by microbial organisms that form a heterogeneous community, collectively termed microbiota. The genomic pool of this macro-community is named microbiome. The gut microbiota is essential for the complete development of the immune system, representing a binary network in which the microbiota interact with the host providing important immune and physiologic function and conversely the bacteria protect themselves from host immune defense. Alterations in the balance of the gut microbiome due to a combination of environmental and genetic factors can now be associated with detrimental or protective effects in experimental autoimmune diseases. These gut microbiome alterations can unbalance the gastrointestinal immune responses and influence distal effector sites leading to CNS disease including both demyelination and affective disorders. The current range of risk factors for MS includes genetic makeup and environmental elements. Of interest to this review is the consistency between this range of MS risk factors and the gut microbiome. We postulate that the gut microbiome serves as the niche where different MS risk factors merge, thereby influencing the disease process.     

Lysophospholipids and their receptors in the central nervous system

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), two of the best-studied lysophospholipids, are known to influence diverse biological events, including organismal development as well as function and pathogenesis within multiple organ systems. These functional roles are due to a family of at least 11 G protein-coupled receptors (GPCRs), named LPA_1–6 and S1P_1–5, which are widely distributed throughout the body and that activate multiple effector pathways initiated by a range of heterotrimeric G proteins including G_i/o, G_12/13, G_q and G_s, with actual activation dependent on receptor subtypes. In the central nervous system (CNS), a major locus for these signaling pathways, LPA and S1P have been shown to influence myriad responses in neurons and glial cell types through their cognate receptors. These receptor-mediated activities can contribute to disease pathogenesis and have therapeutic relevance to human CNS disorders as demonstrated for multiple sclerosis (MS) and possibly others that include congenital hydrocephalus, ischemic stroke, neurotrauma, neuropsychiatric disorders, developmental disorders, seizures, hearing loss, and Sandhoff disease, based upon the experimental literature. In particular, FTY720 (fingolimod, Gilenya, Novartis Pharma, AG) that becomes an analog of S1P upon phosphorylation, was approved by the FDA in 2010 as a first oral treatment for MS, validating this class of receptors as medicinal targets. This review will provide an overview and update on the biological functions of LPA and S1P signaling in the CNS, with a focus on results from studies using genetic null mutants for LPA and S1P receptors. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.     

Thioredoxin and glutaredoxin system proteins—immunolocalization in the rat central nervous system

Background

The oxidoreductases of the thioredoxin (Trx) family of proteins play a major role in the cellular response to oxidative stress. Redox imbalance is a major feature of brain damage. For instance, neuronal damage and glial reaction induced by a hypoxic–ischemic episode is highly related to glutamate excitotoxicity, oxidative stress and mitochondrial dysfunction. Most animal models of hypoxia–ischemia in the central nervous system (CNS) use rats to study the mechanisms involved in neuronal cell death, however, no comprehensive study on the localization of the redox proteins in the rat CNS was available.

Methods

The aim of this work was to study the distribution of the following proteins of the thioredoxin and glutathione/glutaredoxin (Grx) systems in the rat CNS by immunohistochemistry: Trx1, Trx2, TrxR1, TrxR2, Txnip, Grx1, Grx2, Grx3, Grx5, and γ-GCS, peroxiredoxin 1 (Prx1), Prx2, Prx3, Prx4, Prx5, and Prx6. We have focused on areas most sensitive to a hypoxia–ischemic insult: Cerebellum, striatum, hippocampus, spinal cord, substantia nigra, cortex and retina.

Results and conclusions

Previous studies implied that these redox proteins may be distributed in most cell types and regions of the CNS. Here, we have observed several remarkable differences in both abundance and regional distribution that point to a complex interplay and crosstalk between the proteins of this family.

General significance

We think that these data might be helpful to reveal new insights into the role of thiol redox pathways in the pathogenesis of hypoxia–ischemia insults and other disorders of the CNS.This article is part of a Special Issue entitled Human and Murine Redox Protein Atlases.     

Regeneration in the central nervous system of a pulmonate mollusc,Melampus

Summary The left cerebral ganglion was ablated from 72 anesthetized, adult Melampus bidentatus (Mollusca: Pulmonata). Skin incisions were well healed and normal feeding and locomotion observed four days after surgery. Dissections of animals sacrificed weekly showed that most nerves and connectives regrew within 30 days, attaching to the swollen end of the major labial nerve. The enlarged end of this nerve later developed into a distinctive bud; some of these buds contained cell bodies as soon as 42 days after surgery. As the first known report of central nervous tissue regeneration in molluscs, this study points to the need for controls in experiments involving section or ablation of nervous tissue in molluscs.I am grateful to Dr. W.D. Russell-Hunter for his guidance in the course of this work. Support was principally provided by a grant from the National Science Foundation to Dr. Russell-Hunter (Research Grant No. GB-36757 continued as BMS-72-02511-A01)and by two successive grants to the author from the Theodore Roosevelt Memorial Fund of the American Museum of Natural History, New York     

Acute differential sensitivity and role of the central nervous system in the feeding behavior of Drosophila melanogaster

Feeding behavior of the fruitfly, Drosophila melanogaster, isexamined quantitatively by determining the amount of fool intakecolorimetrically. The obtained differential sensitivity (Weberfraction l/l = 0.025) by the two-choice test is surprisinglyacute, compared with the previously reported values for insects.Besides, files also choose only the most stimulative prey inthree-choice tests and even a single fly, free from ‘gangingup’ exhibits a clear intake choice. Adaptation in thetest organ was experimentally proved not to play a leading rolein ingestion choice. The present experimental results supportan important role of the central nervous system in choice behavior.Although deprivation significantly enhances the amount of ingestion,it does not affect the choice itself under the present conditions,suggesting that the choice centre exists separately from theingestion center. Discrimination sensitivity depends considerablyon the food distribution and taste intensities paired.     

Metamorphosis of the central nervous system of Drosophila

The study of the metamorphosis of the central nervous system of Drosophila focused on the ventral CNS. Many larval neurons are conserved through metamorphosis but they show pronounced remodeling of both central and peripheral processes. In general, transmitter expression appears to be conserved through metamorphosis but there are some examples of possible changes. Large numbers of new, adult-specific neurons are added to this basic complement of persisting larval cells. These cells are produced during larval life by embryonic neuroblasts that had persisted into the larval stage. These new neurons arrest their development soon after their birth but then mature into functional neurons during metamorphosis. Programmed cell death is also important for sculpting the adult CNS. One round of cell death occurs shortly after pupariation and a second one after the emergence of the adult fly.     

Genetic depletion of histamine from the nervous system of Drosophila eliminates specific visual and mechanosensory behavior

The role of histamine as a fast neuro-transmitter of imaginai insect photoreceptors is firmly established. In adult Drosophila, histamine is also found in mechanosensory receptors of cuticular hair sensilla and in a small number of nonreceptor neurons in head and body ganglia. Here we investigate the function of histamine by immunohistochemical and behavioral analysis of mutants deficient in the hdc gene that codes for histidine decarboxylase. The allele hdc ^JK910 appears to be a null mutation, as histamine immunoreactivity is almost entirely eliminated. Homozygous flies are blind in various behavioral paradigms. Mutant larvae, on the other hand, show normal photokinetic responses. Thus, adult Drosophila photoreceptors most likely utilize only a single substance, histamine, as a neurotransmitter, whereas larval photoreceptors apparently employ a different transmitter. With the alleles hdc ^p211 , hdc ^p217 , and hdc ^p218 , variable amounts of histamine are found in photoreceptors and mechanoreceptors, but no histamine could be detected in any of the nonreceptor neurons. These mutants show various degrees of visual and mechanosensory impairment, as determined by quantitative behavioral assays. We conclude that histamine is required for normal function of cuticular hair sensilla and for efficient grooming of the body surface. Thus, in Drosophila, histamine represents a major functional neurotransmitter for mechanosensory receptors.Abbreviations ERG electroretinogram - WT wild type     

Glycomics of pediatric and adulthood diseases of the central nervous system

Glycosylation consists in the covalent linkage of a carbohydrate structure to membrane bound and secreted glycoconjugates. It is a common post-translational modification that serves multiple functions in cell differentiation, signaling and intercellular communication. Unlike DNA/RNA/protein, the addition of complex carbohydrates is not-template driven and it is conceivable that both genetics and environmental factors might interact to influence glycosylation machinery in several pathological processes. Over the last few decades, the recognition of Congenital Disorders of Glycosylation (CDG) as an increasing number of genetic diseases of glycosylation with almost constant nervous system involvement, dramatically illustrated the consequences of abnormal glycosylation as improper CNS development and function. In addition, CDG recognition contributed to postulate that aberrant glycosylation processes might play a role in multifactorial, complex CNS diseases. On this context, CNS glycomics explores the effects of possible aberrant glycosylation to identify potential glyco-biomarkers useful for the diagnosis and ultimately for potential intervention strategies in neurological diseases. Up to date, CNS glycomics is an emerging, still uncharted area because of the specificity of CNS glycosylation, the complexity of the neurological disorders and for the inaccessibility and invasiveness of disease relevant samples. Here we review current knowledge on clinical glycomics of nervous system diseases, starting with CDG to include those pediatric and adulthood neuropsychiatric diseases where some evidences suggest that multifactor determinants converge to dysregulate glycosylation. Conventional and mass spectrometry-based high throughput technology for glyco-biomarker detection in CNS diseases is reported.