Higher Invertebrates Research Articles

Neuraminidases-Key Players in the Inflammatory Response after Pathophysiological Cardiac Stress and Potential New Therapeutic Targets in Cardiac Disease.

Glycoproteins and glycolipids on the cell surfaces of vertebrates and higher invertebrates contain α-keto acid sugars called sialic acids, terminally attached to their glycan structures. The actual level of sialylation, regulated through enzymatic removal of the latter ones by NEU enzymes, highly affects protein-protein, cell-matrix and cell-cell interactions. Thus, their regulatory features affect a large number of different cell types, including those of the immune system. Research regarding NEUs within heart and vessels provides new insights of their involvement in the development of cardiovascular pathologies and identifies mechanisms on how inhibiting NEU enzymes can have a beneficial effect on cardiac remodelling and on a number of different cardiac diseases including CMs and atherosclerosis. In this regard, a multitude of clinical studies demonstrated the potential of N-acetylneuraminic acid (Neu5Ac) to serve as a biomarker following cardiac diseases. Anti-influenza drugs i.e., zanamivir and oseltamivir are viral NEU inhibitors, thus, they block the enzymatic activity of NEUs. When considering the improvement in cardiac function in several different cardiac disease animal models, which results from NEU reduction, the inhibition of NEU enzymes provides a new potential therapeutic treatment strategy to treat cardiac inflammatory pathologies, and thus, administrate cardioprotection.

NEUROTOXIC EFFECT OF ACETYLCHOLINESTERASE INHIBITORS ON THE ORGANISM OF THE FREE-LIVING SOIL NEMATODE CAENORHABDITIS ELEGANS MAUPAS

The investigation of the influence of acetylcholinesterase inhibitors aldicarb and neostigmine on soil nematode Caenorhabditis elegans swimming as induced by mechanical stimulus was performed. Short-term (30 minutes) to aldicarb (10–40 µM) or neostigmine (4–8 mM) caused disturbances of C. elegans motor program of swimming in dose-dependent manner by the retention of swimming ability of all nematodes. These results indicate that partial acetylcholinesterase inhibition in C. elegans organism disturbs the balance of muscle excitation and inhibition necessary for sinusoidal body movements during swimming, but cholinergic synaptic transmission in neuro-muscular junctions is retained. Octopamine and dopamine increased the sensitivity of C. elegans behavior to toxic aldicarb action. Octopamine and dopamine in C. elegans organism don't influence directly on locomotor muscles. Therefore their influence on behavior sensitivity to aldicarb may be a consequence of modulation of neuron-neuron synapses, but not neuromuscular junctions by octopamine and dopamine. Disturbances of motor program of C. elegans swimming revealed in this work are the consequence of anomalous rise of acetylcholine level in the nervous system, but not in neuromuscular junctions. The most likely mechanism of disturbances of functions of C. elegans nervous system by partial acetylcholinesterase inhibition is hyperactivation of neuronal nicotinic cholinoreceptors. Results of this work show that reasons of toxic action of anomalous high acetylcholine level are highly conservative in evolution, and the most sensitive target of exceeding of optimal level of endogenous acetylcholine not only in human organisms, organisms of vertebrates and higher invertebrates, but also in simple organisms of nematodes is the nervous system.

Beauvericin potentiates the activity of pesticides by neutralizing the ATP-binding cassette transporters in arthropods

Multi-drug resistance is posing major challenges in suppressing the population of pests. Many herbivores develop resistance, causing a prolonged survival after exposure to a previously effective pesticide. Consequently, resistant pests reduce the yield of agricultural production, causing significant economic losses and reducing food security. Therefore, overpowering resistance acquisition of crop pests is a must. The ATP binding cassette transporters (ABC transporters) are considered as the main participants to the pesticide efflux and their neutralization will greatly contribute to potentiate failed treatments. Real-Time PCR analysis of 19 ABC transporter genes belonging to the ABCB, ABCC, ABCG, and ABCH revealed that a broad range of efflux pumps is activated in response to the exposure to pesticides. In this study, we used beauvericin (BEA), a known ABC transporters modulator, to resensitize different strains of Tetranychus urticae after artificial selection for resistance to cyflumetofen, bifenazate, and abamectin. Our results showed that the combinatorial treatment of pesticide (manufacturer’s recommended doses) + BEA (sublethal doses: 0.15 mg/L) significantly suppressed the resistant populations of T. urticae when compared to single-drug treatments. Moreover, after selective pressure for 40 generations, the LC50 values were significantly reduced from 36.5, 44.7, and 94.5 (pesticide) to 8.3, 12.5, and 23.4 (pesticide + BEA) for cyflumetofen, bifenazate, and abamectin, respectively. While the downstream targets for BEA are still elusive, we demonstrated hereby that it synergizes with sub-lethal doses of different pesticides and increases their effect by inhibiting ABC transporters. This is the first report to document such combinatorial activity of BEA against higher invertebrates paving the way for its usage in treating refractory cases of resistance to pesticides. Moreover, we demonstrated, for the first time, using in silico techniques, the higher affinity of BEA to ABC transformers subfamilies when compared to xenobiotics; thus, elucidating the pathway of the mycotoxin.

Numerous peptidoglycan recognition protein genes expressed in the bacteriome of the green rice leafhopper Nephotettix cincticeps (Hemiptera, Cicadellidae)

Peptidoglycan recognition proteins (PGRPs) contribute to the immune response of vertebrates and higher invertebrates. Animals have a varying number of PGRP genes: 4 in human and mouse, 13 in Drosophila, and 0 in an aphid. Transcriptome analyses revealed that numerous PGRP genes (> 300 in an RNA-Seq analysis) were expressed in the green rice leafhopper Nephotettix cincticeps (Uhler) (Hemiptera, Cicadellidae). PGRP genes were mostly expressed in the bacteriomes, in which two bacterial endosymbionts, Sulcia and Nasuia, are harbored. E. coli inoculation upregulated antimicrobial peptide gene expression in the leafhopper, whereas PGRP gene expression was not affected by the bacterial challenge. High and constant expression of PGRP genes in the bacteriomes and the lack of an immune response against invading bacteria suggest that these PGRPs play a hitherto unknown role in the bacteriomes, implicating a relationship with symbiotic association in N. cincticeps.

Lysosomal enzymes and their receptors in invertebrates: an evolutionary perspective.

Lysosomal biogenesis is an important process in eukaryotic cells to maintain cellular homeostasis. The key components that are involved in the biogenesis such as the lysosomal enzymes, their modifications and the mannose 6-phosphate receptors have been well studied and their evolutionary conservation across mammalian and non-mammalian vertebrates is clearly established. Invertebrate lysosomal biogenesis pathway on the other hand is not well studied. Although, details on mannose 6-phosphate receptors and enzymes involved in lysosomal enzyme modifications were reported earlier, a clear cut pathway has not been established. Recent research on the invertebrate species involving biogenesis of lysosomal enzymes suggests a possible conserved pathway in invertebrates. This review presents certain observations based on these processes that include biochemical, immunological and functional studies. Major conclusions include conservation of MPR-dependent pathway in higher invertebrates and recent evidence suggests that MPR-independent pathway might have been more prominent among lower invertebrates. The possible components of MPR-independent pathway that may play a role in lysosomal enzyme targeting are also discussed here.

Live imaging of nervous system development and function using light‐sheet microscopy

In vivo imaging applications typically require carefully balancing conflicting parameters. Often it is necessary to achieve high imaging speed, low photo-bleaching, and photo-toxicity, good three-dimensional resolution, high signal-to-noise ratio, and excellent physical coverage at the same time. Light-sheet microscopy provides good performance in all of these categories, and is thus emerging as a particularly powerful live imaging method for the life sciences. We see an outstanding potential for applying light-sheet microscopy to the study of development and function of the early nervous system in vertebrates and higher invertebrates. Here, we review state-of-the-art approaches to live imaging of early development, and show how the unique capabilities of light-sheet microscopy can further advance our understanding of the development and function of the nervous system. We discuss key considerations in the design of light-sheet microscopy experiments, including sample preparation and fluorescent marker strategies, and provide an outlook for future directions in the field.

Erythrocyte membrane bound and plasma sialic acid during aging

Sialic acid, a nine-carbon sugar, is an acetylated derivative of neuraminic acid predominantly found in vertebrates, a few higher invertebrates, and certain types of bacteria. Red blood cells (RBCs) have a net negative surface charge and this bulk charge is due to ionized sialic acid. Decreased surface charge and sialic acid content have been reported in older erythrocytes, and it is postulated that the decreased electro-negativity may be related to cell senescence. In the present study we report the RBC and plasma sialic acid content during aging in rats. Our results show a significant decrease in RBC sialic acid content and increase in plasma sialic acid as a function of rat aging. The decreased sialic acid in erythrocyte membrane with increasing rat age presents a good biomarker of the aging process. The elevated plasma sialic acid may be a manifestation of several factors including increased expression of acute phase proteins and increased damage to various organs.

The location of the soma in higher invertebrates - bug or feature?

Event Abstract Back to Event The location of the soma in higher invertebrates - bug or feature? Janina Hesse1, 2 and Susanne Schreiber1, 2* 1 Bernstein Center for Computational Neuroscience Berlin, Germany 2 Humboldt Universitaet zu Berlin, Institute for Theoretical Biology, Germany The morphology of neurons in the central nervous system of higher invertebrates considerably differs from that of a typical mammalian neuron. Whereas in mammals dendrites and axon arise directly from the soma - often placing the soma into a central position of the space covered by the neuron - in insects the soma is "externalized": The soma connects to the axon and dendrites only via a thin process of several tens or hundreds of micrometers (the primary neurite) and is hence in a relatively peripheral position. Neurons with this morphological shape are unipolar. Their typical arrangement in ganglia allows the processes to meet in the center; somata are placed close to the surface of the ganglion. Whether the particular position of the soma - central or peripheral with respect to dendrites and axon - fulfills a functional role and provides mammals or invertebrates (or both) with specific advantages is unknown. Here, we explore several hypotheses how evolutionary constraints may have shaped neuronal morphology in insects and mammals. To this end, we use simple multicompartmental models which locate the soma either between axon and dendrites or at the end of a primary neurite, and analyze fundamental aspects of neuronal signaling, including the efficiency of orthodromic and antidromic action-potential propagation and metabolic cost. Acknowledgements This work was funded by grants from the Federal Ministry of Education and Research, Germany (01GQ1001A, 01GQ0901) and the Deutsche Forschungsgemeinschaft (SFB618, GK1589/1). Keywords: compartmental modelling, morphology, neuronal shape, unipolar Conference: Bernstein Conference 2012, Munich, Germany, 12 Sep - 14 Sep, 2012. Presentation Type: Poster Topic: Other Citation: Hesse J and Schreiber S (2012). The location of the soma in higher invertebrates - bug or feature?. Front. Comput. Neurosci. Conference Abstract: Bernstein Conference 2012. doi: 10.3389/conf.fncom.2012.55.00204 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 11 May 2012; Published Online: 12 Sep 2012. * Correspondence: Prof. Susanne Schreiber, Bernstein Center for Computational Neuroscience Berlin, Berlin, 10115, Germany, s.schreiber@hu-berlin.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Janina Hesse Susanne Schreiber Google Janina Hesse Susanne Schreiber Google Scholar Janina Hesse Susanne Schreiber PubMed Janina Hesse Susanne Schreiber Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

In situ Monitoring of In vitro Sialylation by Inclusion Bodies

Sialic acids usually terminate oligosaccharide chains expressed on the cell surfaces and glycoproteins of vertebrates, higher invertebrates and some microorganisms. They have various important biological roles. Two of these roles, determination of anti-inflammatory activity of IgG antibodies and increasing the circulating half-life of glycoproteins and blood cells, can find application in pharmaceutical industry and medicine. For this reason, there is a need for efficient in vitro protein sialylation processes. To evaluate the efficiency of in vitro sialylation, a method for in situ monitoring in high throughput screens has been developed. It is represented by hemagglutination caused by inclusion bodies of SabA lectin. SabA lectins are proteins expressed on the cell surface of bacteria Helicobacter pylori and bind to sialic acids on the host cell surfaces. They are responsible for H. pylori mediated agglutination of erythrocytes in vitro. This presented method is fast, simple and one can avoid time-consuming purification of analyzed glycoprotein. In addition, it could provide a basic diagnostic method for determination of sialylation level of erythrocytes.

Digital Scanned Laser Light-Sheet Fluorescence Microscopy (DSLM) of Zebrafish and Drosophila Embryonic Development

Embryonic development is one of the most complex processes encountered in biology. In vertebrates and higher invertebrates, a single cell transforms into a fully functional organism comprising several tens of thousands of cells, arranged in tissues and organs that perform impressive tasks. In vivo observation of this biological process at high spatiotemporal resolution and over long periods of time is crucial for quantitative developmental biology. Importantly, such recordings must be realized without compromising the physiological development of the specimen. In digital scanned laser light-sheet fluorescence microscopy (DSLM), a specimen is rapidly scanned with a thin sheet of light while fluorescence is recorded perpendicular to the axis of illumination with a camera. Combining light-sheet technology and fast laser scanning, DSLM delivers quantitative data for entire embryos at high spatiotemporal resolution. Compared with confocal and two-photon fluorescence microscopy, DSLM exposes the embryo to at least three orders of magnitude less light energy, but still provides up to 50 times faster imaging speeds and a 10-100-fold higher signal-to-noise ratio. By using automated image processing algorithms, DSLM images of embryogenesis can be converted into a digital representation. These digital embryos permit following cells as a function of time, revealing cell fate as well as cell origin. By means of such analyses, developmental building plans of tissues and organs can be determined in a whole-embryo context. This article presents a sample preparation and imaging protocol for studying the development of whole zebrafish and Drosophila embryos using DSLM.

Roles of glial cells in neural circuit formation: Insights from research in insects

Investigators over the years have noted many striking similarities in the structural organization and function of neural circuits in higher invertebrates and vertebrates. In more recent years, the discovery of similarities in the cellular and molecular mechanisms that guide development of these circuits has driven a revolution in our understanding of neural development. Cellular mechanisms discovered to underlie axon pathfinding in grasshoppers have guided productive studies in mammals. Genes discovered to play key roles in the patterning of the fruitfly's central nervous system have subsequently been found to play key roles in mice. The diversity of invertebrate species offers to investigators numerous opportunities to conduct experiments that are harder or impossible to do in vertebrate species, but that are likely to shed light on mechanisms at play in developing vertebrate nervous systems. These experiments elucidate the broad suite of cellular and molecular interactions that have the potential to influence neural circuit formation across species. Here we focus on what is known about roles for glial cells in some of the important steps in neural circuit formation in experimentally advantageous insect species. These steps include axon pathfinding and matching to targets, dendritic patterning, and the sculpting of synaptic neuropils. A consistent theme is that glial cells interact with neurons in two-way, reciprocal interactions. We emphasize the impact of studies performed in insects and explore how insect nervous systems might best be exploited next as scientists seek to understand in yet deeper detail the full repertory of functions of glia in development.

Phagocytosis of sperm by follicle cells of the carnivorous sponge Asbestopluma occidentalis (Porifera, Demospongiae)

During spermatogenesis of the carnivorous sponge Asbestopluma occidentalis, follicle cells that lined the spermatocysts phagocytosed unreleased mature sperm. Such follicle cells are part of the complex envelope that limits spermatocysts of A. occidentalis, which is also comprised of a collagen layer, a thick layer of intertwined cells, and spicules. Follicle cells showed vesicles containing single phagocytosed spermatozoa within their cytoplasm. Additionally, lipids and other inclusions were observed within the cytoplasm of follicle cells. It is likely that follicle cells recapture nutrients by phagocytosing spermatozoa and use them to form lipids and other inclusions. Such sperm phagocytosis is usually performed in higher invertebrates and vertebrates by Sertoli cells that are located in the testis wall. While Sertoli cells develop a wide range of functions such as creating a blood-testis barrier, providing crucial factors to ensure correct progression of spermatogenesis, and phagocytosis of aberrant, degenerating, and unreleased sperm cells, sponge follicle cells may only display phagocytotic activity on spermatogenic cells.

Identification of the key amino acid residues in Sabellastarte arginine kinase for distinguishing chiral guanidino substrates ( d- and l-arginine)

Arginine kinase (AK, EC 2.7.3.3) is a phosphagen kinase widely distributed in lower and higher invertebrates. Sabellastarte indica AKs (AK1 and AK2) are the only AKs that use d-arginine in addition to l-arginine as a substrate. S. indica AKs are therefore clearly unrelated to typical AK. The purpose of this work was to identify the amino acid residues responsible for distinguishing the chirality of d- and l-arginine. The three-dimensional structure of Sabellastarte AK2 was predicted using the SWISS-MODEL automated modeling server. Two amino acids, L64 in the N-terminal flexible loop and N320 in the C-terminal flexible loop, were found to be closest to the substrate arginine. We introduced several mutations around the predicted binding site of the substrate arginine. In the L64I mutant, the affinity for l-arginine was greatly increased (9.5-fold that of the wild-type), whereas its affinity for d-arginine was increased 2.9-fold, indicating that the L64I mutant enzyme was more specific for l-arginine. On the other hand, the L64V mutant showed a 1.7-fold decrease in affinity for l-arginine, but unchanged affinity for d-arginine. Thus the L64V mutant enzyme was more specific for d-arginine. Since the replacement of amino acid residue L64 by I or V significantly affected the affinity for l-arginine or d-arginine, it can be concluded that amino acid 64 is a key residue for distinguishing d- and l-arginine. Seven mutants at position 320 (N320H, Q, D, E, R, K and A) had considerably reduced enzymatic activity (0.05–52% of the wild-type). The reduction in enzyme activity was more significant when d-arginine was the substrate rather than l-arginine, except for N320D, suggesting that the carbonyl oxygen of the Asn320 side chain forms a hydrogen bond with the α-amino nitrogen attached to the asymmetric carbon of the d-arginine substrate. In addition, we found that even a residue remote from the guanidino substrate-binding site, such as G54 and Y89 in Sabellastarte AK2, significantly affected guanidino substrate specificity.

Biological origins of protective mechanisms activated by the disruption of higher nervous activity

Unexpected changes in experimental conditions are shown to cause similar responses and effects of nootropic drugs in higher and lower vertebrates and higher invertebrates. The basis of this universal reaction is the nonspecific activation of protective abilities of the body in response to unexpected environmental changes, which is evolutionally related with a threat to the physical integrity of the body, and the nonspecific effects of neurotropic substances.

Habituation of caddies Chaetopteryx villosa Fabr. Larvae to vibrational stimulus and effect of piracetam on it

Habituation to a vibrational stimulus was studied in intact caddies Chaetopteryx villosa Fabr. of the last age before pupation and of the larvae placed for 72 h into pyracetam solution (100 mg/l). The vibrational stimulus was shown to produce a passive-defensive reaction: the caddies were pulled into the house and stood still. In the course of the experiment the time of stay in the house decreased statistically significantly in both groups. Pyracetam did not affect the defensive reaction at the initial moment of the first vibrational stimulus, so both in the experimental and in the control groups the number of contracted larvae was equal and all of them remained in the house for the first seconds of vibration. However, the compound increased the number of larvae that did not respond to the next vibrational stimulus and decreased the number of larvae that remain in the house throughout all 10 s of action by accelerating on the whole the habituation. Hence, on this model, the mnemotropic effect of the standard nootrope has been realized, which earlier was established by other methods in mammals, the lower vertebrates, and the higher invertebrates. This indicates that this model also is perspective for comparative studies of effect of nootropic substances on the higher nervous activity.

Highly Conserved Caspase and Bcl-2 Homologues from the Sea Anemone Aiptasia pallida: Lower Metazoans as Models for the Study of Apoptosis Evolution

Key insight into the complexities of apoptosis may be gained from the study of its evolution in lower metazoans. In this study we describe two genes from a cnidarian, Aiptasia pallida, that are homologous to key genes in the apoptotic pathway from vertebrates. The first is a novel ancient caspase, acasp, that displays attributes of both initiator and executioner caspases and includes a caspase recruitment domain (CARD). The second, a Bcl-2 family member, abhp, contains a BH1 and BH2 domain and shares structural characteristics and phylogenetic affinity with a group of antiapoptotic Bcl-2s including A1 and Bcl-2L10. The breadth of occurrence of other invertebrate homologues across the phylogenetic trees of both genes suggests that the complexity of apoptotic pathways is an ancient trait that predates the evolution of vertebrates and higher invertebrates such as nematodes and flies. This paves the way for establishing new lower metazoan model systems for the study of apoptosis.

Biological Bulletin Virtual Symposium: Marine Invertebrate Models of Learning and Memory.

Plato’s Symposium emphasized a two-tiered view of reality—the world of Being and the world of Becoming. While the world of Being is absolute and transcendent, the world of Becoming is always in movement, always changing. As reviewed in this Virtual Symposium, our present understanding of the neurobiological bases of learning and memory in marine invertebrate models reflects such a dichotomy. While common principles have emerged from the collective study of the models represented here, and many more that could not be included due to space limitations, the field retains a vital level of flux. An appreciation for the extraordinary learning capabilities of invertebrates has a long history (Romanes, 1895; Jennings, 1906; Young, 1961; see Corning et al., 1973). About 40 years ago, neurobiologists began to exploit the advantageous properties of the nervous systems of certain higher invertebrates toward disclosing cellular mechanisms of behavioral plasticity (Kandel, 1970; Alkon, 1974; Davis and Gillette, 1978). These investigations established that several forms of learning could be explained in terms of neuronal, and specifically synaptic, plasticity. Thus, they paved the way for the intense study of synaptic mechanisms of learning and memory in the mammalian central nervous system that followed. Despite the extraordinary advances that have emerged from the study of long-term synaptic plasticity in the mammalian CNS, the invertebrate systems, with their relatively simple circuits and large identifiable neurons, still present superior opportunities to relate physiological mechanisms to the behavioral phenomena of learning (Krasne and Glanzman, 1995; Kandel, 2001). We are pleased to have 14 contributions to this Virtual Symposium covering a variety of topics in learning and memory and encompassing a range of marine model systems. The articles reflect the latitude of the guidelines that were provided to participants. Contributors were asked to imagine a real symposium at a conference, organized with the purpose of encapsulating the current state of the field and stimulating further investigation. Such a symposium would consist of several keynote addresses reviewing entire research programs, as well as shorter presentations describing specific studies or even single experiments that could add to the overall objective. Throughout the symposium, individuals would have the opportunity to provide observations and commentary. Finally, participants were encouraged to consider their contributions in the overall historical context of the field and to suggest future directions. The symposium begins with a comprehensive review of the temporal phases of memory in Aplysia by Hawkins, Kandel, and Bailey. This article highlights the complex signaling pathways that support these memory stages. It is followed by six primary reports that cover topics ranging from behavioral and electrophysiological substrates to molecular studies of signaling systems that produce learningspecific modifications. Adamo et al. examine a form of context-dependent learning in cuttlefish that occurs during an ecologically relevant task. They detail how the modification of body pattern by control of the chromatophore organs may be useful for studying cephalopod cognitive abilities. Kuzirian et al. contribute a paper on the enhancement of memory in Hermissenda by the protein kinase C (PKC) agonist bryostatin. Bryostatin is found to influence consolidation of memory in a dose-dependent manner, further supporting the importance of PKC in the Hermissenda learning model. A study of activity-dependent synaptic plasticity and metaplasticity in the Aplysia feeding central Received 27 April 2006; accepted 27 April 2006. * To whom correspondence should be addressed. E-mail: mcphie@helix. mgh.harvard.edu Reference: Biol. Bull. 210: 171–173. (June 2006) A contribution to The Biological Bulletin Virtual Symposium © 2006 Marine Biological Laboratory on Marine Invertebrate Models of Learning and Memory.

Are dendrites in Drosophila homologous to vertebrate dendrites?

Dendrites represent arborising neurites in both vertebrates and invertebrates. However, in vertebrates, dendrites develop on neuronal cell bodies, whereas in higher invertebrates, they arise from very different neuronal structures, the primary neurites, which also form the axons. Is this anatomical difference paralleled by principal developmental and/or physiological differences? We address this question by focussing on one cellular model, motorneurons of Drosophila and characterise the compartmentalisation of these cells. We find that motorneuronal dendrites of Drosophila share with typical vertebrate dendrites that they lack presynaptic but harbour postsynaptic proteins, display calcium elevation upon excitation, have distinct cytoskeletal features, develop later than axons and are preceded by restricted localisation of Par6-complex proteins. Furthermore, we demonstrate in situ and culture that Drosophila dendrites can be shifted from the primary neurite to their soma, i.e. into vertebrate-like positions. Integrating these different lines of argumentation, we propose that dendrites in vertebrates and higher invertebrates have a common origin, and differences in dendrite location can be explained through translocation of neuronal cell bodies introduced during the evolutionary process by which arthropods and vertebrates diverged from a common urbilaterian ancestor. Implications of these findings for studies of dendrite development, neuronal polarity, transport and evolution are discussed.

Descending neurons of the suprapharyngeal ganglion of a dragonfly Aeschna larvae

Opioid peptides have been revealed in representatives of practically all large taxonomic groups of invertebrates, and the opiate receptors are found even in unicellulars. The opioid system seems to belong to the evolutionary ancient signal systems. The comparative data indicate that the most conservative and ancient function of opioids is control of the adequate level of protective reactions. In the infusorian Stentor the opiate ligands suppress a contractile response to mechanical stimulation, i.e., the protective behavior. In all studies multicellular invertebrates, agonists also suppress protective behavior, whereas antagonists produce opposite effects. This initially signal meaning of opioids might have become a basis for divergent development of their functions in evolution. Already in higher invertebrates, molluscs and arthropods, many functions of opioids, for example, stress-induced analgesia, regulation of feeding and mating behavior, of social aggression, are similar to those in vertebrates. It is suggested that the main events in formation of functions of the endogenous opioid system have occurred in the lower invertebrates that have remained so far the least studied.

Nitric oxide in invertebrates.

Nitric oxide (NO) is considered an important signaling molecule implied in different physiological processes, including nervous transmission, vascular regulation, immune defense, and in the pathogenesis of several diseases. The presence of NO is well demonstrated in all vertebrates. The recent data on the presence and roles of NO in the main invertebrate groups are reviewed here, showing the widespread diffusion of this signaling molecule throughout the animal kingdom, from higher invertebrates down to coelenterates and even to prokaryotic cells. In invertebrates, the main functional roles described for mammals have been demonstrated, whereas experimental evidence suggests the presence of new NOS isoforms different from those known for higher organisms. Noteworthy is the early appearance of NO throughout evolution and striking is the role played by the nitrergic pathway in the sensorial functions, from coelenterates up to mammals, mainly in olfactory-like systems. All literature data here reported suggest that future research on the biological roles of early signaling molecules in lower living forms could be important for the understanding of the nervous-system evolution.