Invertebrate Neuroscience最新文献

Over the past decade, many new peptide families have been identified via in silico analyses of genomic and transcriptomic datasets. While various molecular and biochemical methods have confirmed the existence of some of these new groups, others remain in silico discoveries of computationally assembled sequences only. An example of the latter are the CCRFamides, named for the predicted presence of two pairs of disulfide bonded cysteine residues and an amidated arginine-phenylalanine carboxyl-terminus in family members, which have been identified from annelid, molluscan, and arthropod genomes/transcriptomes, but for which no precursor protein-encoding cDNAs have been cloned. Using routine transcriptome mining methods, we identified four Homarus americanus (American lobster) CCRFamide transcripts that share high sequence identity across the predicted open reading frames but more limited conservation in their 5' terminal ends, suggesting the Homarus gene undergoes alternative splicing. RT-PCR profiling using primers designed to amplify an internal fragment common to all of the transcripts revealed expression in the supraoesophageal ganglion (brain), eyestalk ganglia, and cardiac ganglion. Variant specific profiling revealed a similar profile for variant 1, eyestalk ganglia specific expression of variant 2, and an absence of variant 3 expression in the cDNAs examined. The broad distribution of CCRFamide transcript expression in the H. americanus nervous system suggests a potential role as a locally released and/or circulating neuropeptide. This is the first report of the cloning of a CCRFamide-encoding cDNA from any species, and as such, provides the first non-in silico support for the existence of this invertebrate peptide family.

Neonicotinoids are the most widely used synthetic insecticides in the world. These insecticides are widely distributed in the ecosystem, indicating that more attention should be paid to the potential risks regarding their use in agriculture. Due their intensive use, non-target species in the environment are also exposed to their putative effects. Within acute exposure trials, the time related effect of sublethal dose of the neonicotinoid preparation APACS 50 WG was investigated on swimming behaviour and the multi-xenobiotic resistance system (MXR) activity, as a first line defence pathway of adult Dikerogammarus villosus. Results showed that treated animals manifested an increased swimming activity. Exposed animals were monitored by the rhodamine B accumulation assay, and APACS 50 WG exerted distinct changes in the MXR activity as well. Our results suggested that application of neonicotinoid at a low concentration (3.9 ng/l) contributed to the activation of locomotor activity and at the same concentration range the transmembrane transport mechanisms was altered too.

Each pedal ganglion of the pteropod mollusc Clione limacina contains a cluster of serotonin-immunoreactive neurons that have been shown to modulate contractions of the slow-twitch musculature of the wing-like parapodia, and contribute to swim accelerations. Each cluster has a variable number of neurons, between 5 and 9, but there is no significant difference between right and left ganglia. In experiments with electrophysiological recordings followed by dye-injection (carboxyfluorescein), the clusters were found to contain two subsets of neurons. The majority innervate the ipsilateral wing via nerve n4. Two of the neurons in each cluster send processes out of the pedal ganglion in nerves n3 and n8. The processes in nerve n3 innervate the body wall of the neck region, while those in nerve n8 innervate the body wall of the tail. The baseline electrophysiological activity of the two subsets of neurons was different as "wing" neurons had constant barrages of small synaptic activity, while the "body wall" neurons had few synaptic inputs. The potential roles of the Pd-SW cluster in swim acceleration (wing neurons) and control of fluid pressure in the body and wing hemocoelic compartments (body wall neurons) are discussed.

The forced swim test is commonly used as a preclinical screen of antidepressant medication efficacy in rats and mice. Neckameyer and Nieto-Romero (Stress 18:254-66, 2015) adopted the forced swim test for use with the fruit fly Drosophila melanogaster and showed that behavior in this test is sensitive to several physiologically relevant stressors. However, whether this test might be sensitive to the effects of antidepressant medications or other compounds is unknown. In the current studies, we fed drugs to male and female flies that we expected to either decrease or increase the duration of immobility in the forced swim test, including fluoxetine, desipramine, picrotoxin, reserpine, 3-iodo-tyrosine, and ethanol. Fluoxetine was the only drug tested that affected behavior in this test, and surprisingly, the direction of the effect depended on the duration of feeding. Short-term (30 min) feeding of the drug prior to test resulted in the expected increase in latency to immobility, while a longer feeding duration (20-24 h) decreased this measure. These results suggest that the pharmacological profile of the fly FST is more restricted than that of the rat or mouse FST, and that the duration of drug exposure is an important consideration in pharmacological research using flies.

Sensory and motor systems in insects with hemimetabolous development must be ready to mediate adaptive behavior directly on hatching from the egg. For the desert locust S. gregaria, cholinergic transmission from antennal sensillae to olfactory or mechanosensory centers in the brain requires that choline acetyltransferase (ChAT) and the vesicular acetylcholine transporter (vAChT) already be present in sensory cells in the first instar. In this study, we used immunolabeling to demonstrate that ChAT and vAChT are both expressed in sensory cells from identifiable sensilla types in the immature antennal nervous system. We observed ChAT expression in dendrites, neurites and somata of putative basiconic-type sensillae at the first instar stage. We also detected vAChT in the sensory axons of these sensillae in a major antennal nerve tract. We then examined whether evidence for cholinergic transmission is present during embryogenesis. Immunolabeling confirms that vAChT is expressed in somata typical of campaniform sensillae, as well as in small sensory cell clusters typically associated with either a large basiconic or coeloconic sensilla, at 99% of embryogenesis. The vAChT is also expressed in the somata of these sensilla types in multiple antennal regions at 90% of embryogenesis, but not at earlier (70%) embryonic stages. Neuromodulators are known to appear late in embryogenesis in neurons of the locust central complex, and the cholinergic system of the antenna may also only reach maturity shortly before hatching.

Fenoxycarb 0-ethyl N-(2-(4-pheoxyphenoxy)-ethyl) carbamate is the most potent juvenile hormone analogue against a variety of insect species including the silkworm Bombyx mori. In this study, the effects of fenoxycarb on silkworm Bombyx mori brain neurosecretory cells in 5th instar were investigated. Fenoxycarb (1 ng/10 µl) was applied topically along the dorsa-medial line to the animals in the spinning behavior on day 1 of the experimental group. Brains removed by dissection were histologically examined by hematoxylin eosin (hem&eosin) and paraldehyde fuchsin staining. Three types of neurosecretory cells (NSCs) were identified, NSC-1, NSC-2 and NSC-3. It was determined that cell secretions were in different density on different days. It was shown that the secretion density of cells on different days was not the same as the experimental and control groups. The fenoxycarb was found to suppress the bombyxin (insulin-like peptides) secretion of cells in the spinning behavior on day 2. Also, it stimulated the division of NSCs on the spinning behavior on day 5.

Natural light is regarded as a key regulator of biological systems and typically serves as a Zeitgeber for biological rhythms. As a natural abiotic factor, it is recognized to regulate multiple behavioral and physiological processes in animals. Disruption of the natural light regime due to light pollution may result in significant effects on animal learning and memory development. Here, we investigated whether sensitivity to various photoperiods or light intensities had an impact on intermediate-term memory (ITM) and long-term memory (LTM) formation in the pond snail Lymnaea stagnalis. We also investigated the change in the gene expression level of molluscan insulin-related peptide II (MIP II) is response to the given light treatments. The results show that the best light condition for proper LTM formation is exposure to a short day (8 h light) and low light intensity (1 and 10 lx). Moreover, the more extreme light conditions (16 h and 24 h light) prevent the formation of both ITM and LTM. We found no change in MIP II expression in any of the light treatments, which may indicate that MIP II is not directly involved in the operant conditioning used here, even though it is known to be involved in learning. The finding that snails did not learn in complete darkness indicates that light is a necessary factor for proper learning and memory formation. Furthermore, dim light enhances both ITM and LTM formation, which suggests that there is an optimum since both no light and too bright light prevented learning and memory. Our findings suggest that the upsurge of artificial day length and/or night light intensity may also negatively impact memory consolidation in the wild.

Cestodes are common gastrointestinal parasites of humans and livestock. They attach to the host gut and, without a mouth or intestinal system, absorb nutrients through their epidermis. Here we show that despite this simplified anatomy and sessile lifestyle, they maintain a complex neuromuscular system. We used fluorescently labelled phalloidin as a specific probe for filamentous actin to define the overall organisation of several distinct muscle systems in the cyclophyllidean Moniezia expansa. Like all flatworms, the body wall musculature below the neodermis of this intestinal parasite of sheep is characterised by outer circular and inner longitudinal muscle fibres. Diagonal fibres, typically found in free-living and trematode platyhelminths, on the other hand, are notably absent. Prominent longitudinal sheaths dominate the parenchyma and provide retractor muscles to the four acetabula in the scolex; they attach at the bottom of each cup-shaped holdfast. Within sexually mature proglottids, circular fibres dominate the duct walls of the male and female reproductive systems. Nerve cells and fibres that express serotonin or neuropeptide F supply well-developed innervation to several of the described muscle systems: emanating from the central nervous system, fibres in the periphery develop pervasive nerve nets that anastomose within body wall musculature as well as the parenchymal longitudinal and oblique muscle fibres, and innervate the sexual organs and gonopore in mature proglottids. Using homology searches, we provide evidence for 20 neuropeptide precursors together with four prepropeptide processing enzymes as well as several 5-HT signalling components to be represented in the Moniezia transcriptome.

Electron microscopy revealed that glial cells in the posterior sub-esophageal mass of the brain in Sepia officinalis had a well-developed rough endoplasmic reticulum formed by long coverslips with rectilinear or curvilinear arrangements. The coverslips appeared dilated and have a large amount of adhered polysomes. Vesicular lamellae coexisted with the elongated lamellae of RER and dictyosomes of Golgi apparatus. Endocytosis was evidenced through the pale vesicles which were appeared next to the apical border of microvilli in some glial cells. Sub-cellular features of endocytosis, predominantly the fluid phase, were observed in the apical glial cell cytoplasm. Glial cells were related to phagocytosis of apoptotic neurons, endocytosis, pinocytosis and adsorption. These functions were proposed based on their ultrastructure characteristics and a significant number of vesicles with different shapes (oval to polygonal), sizes 0.052-0.67 µm and contents. Glycogen, MPS and lipid were detected in the glial cells. Alkaline phosphatase was not observed, while an activity of acid phosphatase was bound to lysosomes. ATPases were present in the glial cells along the lateral and basal plasma lemma as well as on the membranes of cell organelles. Unspecific esterase was clearly recognizable by electron microscopy. The monoamine and cytochrome oxidase activities were demonstrated, while the succinate dehydrogenase showed a weak enzyme activity.

In previous works, we identified a RNA-binding protein in presynaptic terminal of squid neurons, which is likely involved in local mRNA processing. Evidences indicate this strongly basic protein, called p65, is an SDS-stable dimer protein composed of ~ 37 kDa hnRNPA/B-like subunits. The function of p65 in presynaptic regions is not well understood. In this work, we showed p65 and its subunit p37 are concentrated in RNA-enriched regions in synaptosomes. We performed in vitro binding studies with a recombinant protein and showed its propensity to selectively bind actin mRNA at the squid presynaptic terminal. Biochemical analysis using lysed synaptosomes suggested RNA integrity may affect p65 and p37 functions. Mass spectrometry analysis of oligo(dT) pull down indicated squid hnRNPA1, hnRNPA1-like 2, hnRNPA3 and ELAV-like proteins as candidates to interact with p65 and p37 forming a ribonucleoprotein complex, suggesting a role of squid hnRNPA/B-like proteins in site-specific RNA processing.