Neural regulation of immunity: Role of NPR-1 in pathogen avoidance and regulation of innate immunity

The nervous and immune systems consist of complex networks that have been known to be closely interrelated. However, given the complexity of the nervous and immune systems of mammals, including humans, the precise mechanisms by which the two systems influence each other remain understudied. To cut through this complexity, we used the nematode Caenorhabditis elegans as a simple system to study the relationship between the immune and nervous systems using sophisticated genetic manipulations. We found that C. elegans mutants in G-protein coupled receptors (GPCRs) expressed in the nervous system exhibit aberrant responses to pathogen infection. The use of different pathogens, different modes of infection, and genome-wide microarrays highlighted the importance of the GPCR NPR-1 in avoidance to certain pathogens and in the regulation of innate immunity. The regulation of innate immunity was found to take place at least in part through a mitogen-activated protein kinase signaling pathway similar to the mammalian p38 MAPK pathway. Here, the results that support the different roles of the NPR-1 neural circuit in the regulation of C. elegans responses to pathogen infection are discussed.     

Two chemically and immunologically distinct forms of luteinizing hormone-releasing hormone are differentially expressed in frog neural tissues

Immunoreactive luteinizing hormone-releasing hormone (IR-LRF) has been measured in several neural tissues of the frog Rana catesbeiana and characterized by bioassay, chromatography and immunological analysis. Frog brain contains the mammalian form of LRF (mLRF), whereas, sympathetic ganglia and adrenal glands contain a form of LRF (pLRF) chromatographically and immunologically similar to the IR-LRF found in the central nervous systems of several piscine species. Frog retina contains both mLRF and pLRF, in a ratio of about 1:2. The two forms of LRF are apparently equipotent in their ability to release LH from rat gonadotrophs in vitro. Immunological analysis of the pLRF found in the frog nervous system suggests that it is a decapeptide, like mLRF, with one or more amino acid substitutions in the mLRF molecule.     

Localization of leech excitatory peptide, a member of the GGNG peptides, in the central nervous system of a leech (Whitmania pigra) by immunohistochemistry and in situ hybridization

We have recently isolated a myoactive peptide, called leech excitatory peptide, belonging to the GGNG peptide family from two species of leeches, Hirudo nipponia and Whitmania pigra. Immunohistochemistry and in situ hybridization were employed to localize leech excitatory peptide-like peptide(s) and its gene expression in the central nervous system of W. pigra. A pair of neuronal somata were stained by both immunohistochemistry and in situ hybridization in the supraesophageal, subesophageal, and segmental ganglia. In addition, several other neurons showed positive signals by either immunohistochemistry or in situ hybridization in these ganglia. An immunoreactive fiber was observed to run in the anterior root of segmental ganglion 6, which is known to send axons to the sexual organs, though we failed to detect immunoreactivity in possible target tissues. Antiserum specificity was established by enzyme-linked immunosorbent assay using different leech excitatory peptide-related peptides. Leech excitatory peptide elicited muscular contraction of isolated preparations of penis and intestine at concentrations of 10(-8 )M. These results suggest that leech excitatory peptide is a neuropeptide modulating neuromuscular transmission in multiple systems, including regulation of reproductive behavior.     

A comparative ultrastructural and physiological study on melanophores of wild-type and periodic albino mutants of Xenopus laevis

Summary The central and visceral nervous systems of the cockroach Periplaneta americana were studied by means of the peroxidase-antiperoxidase immunocytochemical method, with the use of antibody to bovine pancreatic polypeptide (PP). PP-like immunoreactive neuron somata are most numerous in the brain; at least 6 pairs of cell groups occur in clearly defined regions. Three pairs of cells each are also present in the suboesophageal ganglion and the thoracic ganglia, one pair of a single cell each in the first abdominal and the frontal ganglia, and 4 to 6 pairs of single cells in the terminal ganglion. No reactive cells were found in the retrocerebral complex and the second to the fifth abdominal ganglia. The axons containing PP-like immunoreactivity issue many branches that are distributed in the entire brain-retrocerebral complex, ventral cord, and visceral nervous system. PP-like immunoreactive material produced in the brain seems to be transported by three routes: protocerebrum to corpora cardiaca (-allata) through the nervi corporis cardiaci, tritocerebrum to visceral nervous system through frontal commissures, and to ventral cord through circumoesophageal connectives.A possible homology between the mammalian brain-GEP (gastro-enteropancreatic) system and the brain-midgut system of this insect is discussed.     

Dopamine in a molluscan nervous system: Synthesis and fluorescence histochemistry

The nervous system of the pond snail, Helisoma trivolvis, was investigated for its ability to synthesize and accumulate ³H-catecholamines from ³H-tyrosine. ³H-Dopamine, but not ³H-norepinephrine, was synthesized by several ganglia. The highest accumulations were found in the cerebral, pedal, and buccal ganglia. The Falck-Hillarp and glyoxylic acid fluorescence histochemical techniques were applied to the buccal ganglia to visualize dopamine-containing cells. Fluorescing cells were found on both dorsal and ventral sides of the ganglion. Peripheral nerves of the buccal ganglia also displayed catecholamine fluorescence and accumulated ³H-dopamine. However, no ³H-dopamine synthesis occurred in the cerebral-buccal connectives, which connect the buccal ganglia with the rest of the central nervous system. Therefore, we conclude that there is a dopaminergic system intrinsic to the buccal ganglia and their peripheral targets.     

Further studies on the morphology of the Triviidae (Gastropoda: Prosobranchia) with emphasis on species from southern Africa

Aspects of the morphology of II species of Triviidae are described, including the living animal, shell, radula, mantle complex, central nervous system and reproductive system. Interspecific differences in radular morphology are important in distinguishing closely allied species. Trivia aperta, T. costata and T. verhoeft are protandric hermaphrodites while T. caluariola, T. neglccta, T. pellucidula, T. rubra, T. solandri and T. suavis are gonochoric. The elaboration of the receptaculum seminis varies between species. In T. aperta, T. calvariola, T. neglecta and T. who& the receptaculum is undivided while in T. costafa, T. pellucidula, T. solandri and T. suavis there are two or more lobes of the receptaculum.     

Cytochemical demonstration of cholinergic, serotoninergic and peptidergic nerve elements in Gorgoderina vitelliloba (Trematoda: Digenea)

Standard enzyme cytochemical and indirect immunocytochemical techniques have been used in conjunction with light and confocal scanning laser microscopy (CSLM) to visualize cholinergic, serotoninergic and peptidergic nerve elements in whole-mount preparations of the amphibian urinary-bladder fluke, Gorgoderina vitelliloba. Cholinesterase (ChE) activity was localized in paired anterior ganglia, a connecting dorsal commissure and in the origins of the ventral nerve cords. Cholinergic ganglia were also evident in shelled embryos in the uterus. Serotonin-immunoreactivity (IR) was more extensive than ChE activity and was identified in both the central and peripheral nervous systems. Serotoninergic nerve fibres were associated with the somatic musculature and female reproductive ducts. Antisera to nine mammalian peptides and one invertebrate (FMRFamide) peptide have been used to investigate the peptidergic nervous system in the parasite. Immunoreactivity was obtained to five peptides, namely pancreatic polypeptide (PP), peptide YY (PYY), neuropeptide Y (NPY), substance P (SP) and FMRFamide. Peptidergic nerve fibres were found to be more abundant than demonstrable cholinergic or serotoninergic nerve fibres. NPY-IR was identified only in the main components of the central nervous system. However, PP- and PYY-IR occurred in the anterior ganglia, dorsal commissure, main nerve cords and in numerous small varicose fibres that ramified throughout the worm. Additionally, PP-immunoreactive nerve fibres were found to innervate the musculature of the female reproductive tracts. Six sites of IR were found in the acetabulum, using antisera directed towards the C-terminal end of PP and PYY, and these matched with the distribution of six non-ciliated rosette-like papillae observed by scanning electron microscopy. SP- and FMRFamide-IR were identified in the CNS, and FMRFamide-immunopositive nerve fibres were also evident in association with the gonopore cirrus region and with the terminal excretory pore. Results are discussed with respect to possible roles for each of the neurochemical types.     

Life History Studies on the Genus Trillium (Liliaceae) I. Reproductive Biology of Four Japanese Species

Abstract Four Japanese Trillium (Liliaceae) species which are representative perennial herbs of the temperate deciduous forests— Trillium kamtschaticum (2x), T. apetalon (4x), T. tschonoskii (4x) and T. smallii (6x)—were studied for their reproductive characteristics, e.g., patterns of reproductive resource allocation and reproductive output.
In spite of the differences in ploidy levels (from 2x to 6x), all four species showed very similar reproductive traits. It became evident that in response to the increase in reproductive allocation to total reproductive organs (RA), the number of seeds produced per plant (P_N) clearly increased. This trend is well in accord with the relationship found in four North American species and also several temperate woodland perennial herbs which occur in closed, stable and predictable environments, and possess typical xenogamous breeding systems. Although there is no conspicuous trend between ploidy levels and P_N, one of the significant differences noted in this study was in seed weight, which ranged from 2.93 mg in diploids, to 3.42–3.45 mg in tetraploids, and to 4.47 mg in hexaploids.     

Localization of a substance P-like material in the central and peripheral nervous system of the snail Helix aspersa

Summary A monoclonal antibody against substance P was used for immunocytochemical staining of the central ganglia of the snail Helix aspersa and several peripheral tissues including the gut, reproductive system, cardiovascular system, tentacle and other muscles.Within the central ganglia many neurones, and many fibres in the neuropile and the nerves entering the ganglia, were stained for the SP-like material. The largest numbers of reactive cell bodies were in the pleural ganglia and on the dorsal surfaces of the pedal ganglia. A group of cells was also found, surrounding the right pedal-cerebral connective, that did not fluoresce, but were enveloped by reactive processes terminating directly onto the neurone somata.Specific staining was observed in all peripheral tissues examined and always appeared to be concentrated in nerve terminals. Most particularly these occurred in the heart and aorta, the pharyngeal retractor muscle and the tentacle. Although mostly present in muscular tissues, some fluorescence was also observed in the nervous layer surrounding the retina. The tentacular ganglion also contained immunoreactive cell bodies.     

BIOLOGICAL AND HISTORICAL FACTORS INFLUENCING GENETIC DIVERSITY IN THE SCUTELLARIA ANGUSTIFOLIA COMPLEX (LABIATAE)

Studies of genetic diversity at isozyme loci were used to examine the phylogenetic distribution of several frequently reported population-genetic parameters in a putatively monophyletic group of plant species, the Scutellaria angustifolia complex. The influence of taxon-specific differences in habitat preference, breeding system, degree of endemism, and phylogenetic relatedness was examined. Many characters of reproductive morphology traditionally used in phylogenetic inference vary with breeding system. To the extent that reproductive systems are conservative markers of phylogenetic relationships, one would expect the distribution of genetic variation to be similar in closely related taxa. Results showed that closely related taxa may exhibit very different genetic-diversity statistics and that distantly related taxa may exhibit very similar genetic-diversity statistics. This suggests that complex patterns of evolution of breeding systems and morphological characters have occurred in the ten taxa included in the Scutellaria angustifolia complex. Similarity in habitat is not associated with similarity in genetic diversity in this group of species.     

Localization of a substance P-like material in the central and peripheral nervous system of the snail Helix aspersa

A monoclonal antibody against substance P was used for immunocytochemical staining of the central ganglia of the snail Helix aspersa and several peripheral tissues including the gut, reproductive system, cardiovascular system, tentacle and other muscles. Within the central ganglia many neurons, and many fibres in the neuropile and the nerves entering the ganglia, were stained for the SP-like material. The largest numbers of reactive cell bodies were in the pleural ganglia and on the dorsal surfaces of the pedal ganglia. A group of cells was also found, surrounding the right pedal-cerebral connective, that did not fluoresce, but were enveloped by reactive processes terminating directly onto the neurone somata. Specific staining was observed in all peripheral tissues examined and always appeared to be concentrated in nerve terminals. Most particularly these occurred in the heart and aorta, the pharyngeal retractor muscle and the tentacle. Although mostly present in muscular tissues, some fluorescence was also observed in the nervous layer surrounding the retina. The tentacular ganglion also contained immunoreactive cell bodies.     

Comparative distribution of urocortin- and CRF-like immunoreactivities in the nervous system of the earthworm Lumbricus terrestris

Corticotropin-releasing factor (CRF) and urocortin (Ucn) are both members of the CRF neuropeptide family. The distribution of Ucn- and CRF-like immunoreactive (ir) structures in the central nervous system of several vertebrate species has been studied, but little is known about that in non-vertebrates. We used a highly specific polyclonal antibody against rat Ucn and CRF to determine and compare the distribution of Ucn- and CRF-like immunoreactivity in the earthworm nervous system. Several Ucn- and CRF-like ir perikarya were described in the cerebral ganglion, subesophageal and ventral cord ganglia. The majority of Ucn-like ir cells were found in the ventral ganglia, whereas CRF-like ir cells were most abundant in the cerebral ganglion. Scattered Ucn- and CRF-like ir varicose fiber terminals were seen in all areas of the earthworm central nervous system. Ucn-like ir cell bodies and fiber terminals were also demonstrated in the pharyngeal wall. No co-localization of Ucn- and CRF-like ir nervous structures were observed. This study provided morphological evidence that Ucn- and CRF-like neurosecretory products exist in the earthworm central nervous system. Furthermore, both the distribution and morphology of Ucn- and CRF-like ir structures were distinct, therefore, it can be hypothesized that these neuropeptides exert different neurendocrine functions in the earthworm nervous system.     

Serotonin-like immunoreactivity in the stomatogastric nervous systems of crayfishes from four genera

We used whole-mount immunocytochemistry to characterize the distribution of serotonin in the stomatogastric nervous systems of seven species of crayfish representing three genera from the family Cambaridae (Orconectes, Cambarus, and Procambarus) and one from the family Astacidae (Pacifastacus). In all species, we observed serotonin-like immunoreactivity in four gastropyloric receptor (GPR) neurons located in the lateral ventricular nerves, with one pair of neurons in each nerve. As in other crustaceans, the GPR axons project to the stomatogastric ganglion and to the bilateral commissural ganglia. In three crayfishes, we observed the GPR axons crossing the commissural ganglia, and extending toward the thoracic nervous system. This feature was most clearly and consistently seen in Pacifastacus leniusculus. The number of stained somata in the commissural ganglia varied among crayfish species from two (in Procambarus clarkii) to five (in Pacifastacus leniusculus). The largest soma (the L cell) displayed both serotonin- and tyrosine hydroxylase-like immunoreactivity in all species, suggesting that serotonin and dopamine are cotransmitters in this cell. The inferior esophageal nerve and a branch of this nerve (the inner labral nerve) contained several axons with serotonin-like immunoreactivity. These axons were clearly present in only one species (Procambarus clarkii). Serotonin acts as a neuromodulator of rhythms produced by circuits in the crab and lobster stomatogastric ganglion, and is likely to play a similar role in crayfish. Differences are apparent in the distribution of serotonin among crayfish species and between crayfish and other crustaceans, and could result in differences in the physiological action of this modulator.     

Observations of serotonin and FMRFamide-like immunoreactivity in palp sensory structures and the anterior nervous system of spionid polychaetes

Evidence suggests that ciliated sensory structures on the feeding palps of spionid polychaetes may function as chemoreceptors to modulate deposit-feeding activity. To investigate the probable sensory nature of these ciliated cells, we used immunohistochemistry, epi-fluorescence, and confocal laser scanning microscopy to label and image sensory cells, nerves, and their organization relative to the anterior central nervous system in several spionid polychaete species. Antibodies directed against acetylated alphatubulin were used to label the nervous system and detail the innervation of palp sensory cells in all species. In addition, the distribution of serotonin (5-HT) and FMRFamide-like immunoreactivity was compared in the spionid polychaetes Dipolydora quadrilobata and Pygospio elegans. The distribution of serotonin immunoreactivity was also examined in the palps of Polydora cornuta and Streblospio benedicti. Serotonin immunoreactivity was concentrated in cells underlying the food groove of the palps, in the palp nerves, and in the cerebral ganglion. FMRFamide-like immunoreactivity was associated with the cerebral ganglia, nuchal organs and palp nerves, and also with the perikarya of ciliated sensory cells on the palps.     

Distinct patterns of genetic variation in Pristionchus pacificus and Caenorhabditis elegans, two partially selfing nematodes with cosmopolitan distribution

Hermaphroditism has evolved several times independently in nematodes. The model organism Caenorhabditis elegans and Pristionchus pacificus are self-fertile hermaphrodites with rare facultative males. Both species are members of different families: C. elegans belongs to the Rhabditidae and P. pacificus to the Diplogastridae. Also, both species differ in their ecology: C. elegans is a soil-dwelling nematode that is often found in compost heaps. In contrast, field studies in Europe and North America indicate that Pristionchus nematodes are closely associated with scarab beetles. In C. elegans, several recent studies have found low genetic diversity and rare out-crossing events. Little is known about diversity levels and population structure in free-living hermaphroditic nematodes outside the genus Caenorhabditis. Taking a comparative approach, we analyse patterns of molecular diversity and linkage disequilibrium in 18 strains of P. pacificus from eight countries and four continents. Mitochondrial sequence data of P. pacificus isolates reveal a substantially higher genetic diversity on a global scale when compared to C. elegans. A mitochondrial-derived hermaphrodite phylogeny shows little geographic structuring, indicating several worldwide dispersal events. Amplified fragment length polymorphism and single strand conformation polymorphism analyses demonstrate a high degree of genome-wide linkage disequilibrium, which also extends to the mitochondrial genome. Together, these findings indicate distinct patterns of genetic variation of the two species. The low level of genetic diversity observed in C. elegans might reflect a recent human-associated dispersal, whereas the P. pacificus diversity might reflect a long-lasting and ongoing insect association. Thus, despite similar lifestyle characteristics in the laboratory, the reproductive mode of hermaphroditism with rare facultative males can result in distinct genetic variability patterns in different ecological settings.     

Tissue distribution of PACAP27 and -38 in oligochaeta: PACAP27 is the predominant form in the nervous system of Lumbricus polyphemus

The levels of pituitary adenylate cyclase-activating polypeptide (PACAP)27 and -38 were measured in the nervous, intestinal, excretory, and reproductive systems of Lumbricus polyphemus by radioimmunoassay. Although both PACAP27 and -38 were significantly detectable in all of the examined tissues, the distribution of the peptides was very heterogeneous. Their highest concentrations were found in the cerebral ganglia and the ventral cord, followed by the alimentary tract and the nephridial system, respectively. Moreover, the reproductive system also contained a substantial amount of PACAP. The dominant form of the peptide discovered in the majority of tissues was PACAP27. Interestingly, about 10 times more PACAP27 than PACAP38 was found, with the latter representing only a fraction of PACAP-like immunoreactivity in the tissues of Lumbricus polyphemus.