Neuropeptides in platyhelminths.
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Amino Acid Sequence↗
Biomedical subjects
D W Halton
Publications and source records attributed to D W Halton.
The complete primary structure of pancreatic polypeptide from the European common frog, Rana temporaria.
Using an antiserum directed against the highly-conserved C-terminal hexapeptide amide of mammalian pancreatic polypeptide (PP), numerous immunoreactive endocrine cells were identified within the pancreas of the European common frog, R. temporaria. An acidified ethanolic extract of pancreatic tissue (0.859 g, n = 35) contained 26.2 nmol equivalents/g of tissue. Gel permeation chromatography of the extract resolved a single peak of immunoreactivity co-eluting with synthetic bovine PP standard. Reverse phase HPLC of this material resolved a single peak of immunoreactivity which was purified to homogeneity following chromatography on a semipreparative C-18 column and an analytical C-8 column. Plasma desorption mass spectrometry (PDMS) of the purified peptide resolved a single component with a molecular mass of 4240.9 Da. Direct gas phase sequencing established the sequence of the first 26 residues. Following incubation of the peptide with endopeptidase Asp-N and direct application of the digest to the sequencer, the entire primary structure of the peptide was established as: APSEPHHPGDQATQDQLAQYYSDLYQYITFVTRPRF. The derived molecular mass of this peptide, incorporating a C-terminal amide, was 4240.6 Da which is entirely consistent with that obtained by PDMS.
Amino Acid Sequence↗
Immunoreactivity to the pancreatic polypeptide family in the nervous system of the adult human blood fluke, Schistosoma mansoni.
The presence and distribution of neuropeptides belonging to the pancreatic polypeptide family have been demonstrated by an indirect immunofluorescence technique in the nervous systems of adult male and female Schistosoma mansoni. Seven antisera of differing regional specificity to pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) were employed on both whole-mount and cryostat-sectioned material. Positive immunoreactivity (IR) was obtained with all antisera except an N-terminally-directed antiserum to NPY. In the CNS, immunoreactivity was restricted to cell bodies and nerve fibres in the anterior ganglia, central commissure and dorsal and ventral nerve cords of both sexes, whereas, in the PNS, positive-IR was present in the plexuses innervating the subtegumental musculature and the oral and ventral suckers. Intense immunoreactivity was observed in a plexus of nerve fibres and cell bodies in the lining of the gynaecophoric canal and in fine nerve fibres innervating the dorsal tubercles of the male. In contrast, in the female, strong immunoreactivity was evident in nerve plexuses innervating the lining of the ovovitelline duct and in the wall of the ootype, but most notably in a cluster of cells in the region of Mehlis' gland. Results suggest that molecules with C-terminal homology to the PP-family are present in S. mansoni. These peptides would appear to be important regulatory molecules in the parasite's nervous system and may play a role in the control of egg production.
Animals↗
An ontogenetic study of the cholinergic and serotoninergic nervous systems in Trilocularia acanthiaevulgaris (Cestoda, Tetraphyllidea).
The localisation and distribution of the cholinergic and serotoninergic components of the nervous system in the plerocercoid, adult and free proglottis stages of the tetraphyllidean tapeworm Trilocularia acanthiavulgaris were determined by enzyme histochemical and immunocytochemical techniques. The central nerve ring (CNR) in the scolex contains two lateral ganglia and gives rise to five pairs of longitudinal nerve cords (LNC's; three lateral, two median). The nerve cords run posteriorly throughout the bodies of the plerocercoid and adult worms and the free proglottis. Nerves from the CNR and accessory lateral LNC's pass to the bothridia, where they give rise to extensive nerve plexuses. As the individual proglottides develop along the strobila, a small nerve ring forms at the anterior end of each proglottis; within the nerve ring, distinct bilateral ganglia develop prior to the release of the proglottis. All ten LNC's are present in the free proglottis. The genital atrium and cirrus sac are innervated by cholinergic and serotoninergic elements. The cholinergic nervous system predominates in the CNS within the scolex, whereas there is a larger population of 5-HT-immunoreactive nerve cells associated with the LNC's and segmental ganglia along the strobila and within the free proglottis.
Animals↗
Peptidergic nerve elements in three developmental stages of the tetraphyllidean tapeworm Trilocularia acanthiaevulgaris. An immunocytochemical study.
The localization and distribution of seven neuropeptides in the nervous system of the plerocercoid, adult and free proglottis stages of the tetraphyllidean tapeworm Trilocularia acanthiaevulgaris have been determined by an indirect immunofluorescence technique. Six of the peptides are vertebrate-derived, namely, pancreatic polypeptide (PP), peptide tyrosine tyrosine (PYY), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), substance P (SP) and somatostatin (SRIF); the seventh is the invertebrate neuropeptide, FMR Famide. This is the first demonstration of VIP and SP immunoreactivity in a cestode parasite, and for SRIF this is its first description in any parasitic platyhelminth. Cell bodies and nerve fibres immunoreactive to PP, PYY, VIP, SP and FMRFamide are present throughout the CNS; the distributions of PHI and SRIF were more restricted. In the PNS, nerve fibres immunoreactive to PP occur in the bothridia, whilst in the free proglottis nerve fibres immunoreactive to PYY and VIP innervate the gonads; VIP-immunoreactive nerve elements also supply the reproductive ducts. Extra-neuronal sitings of peptide immunoreactivities were evident for PHI, in association with the excretory system, and for SRIF, in presumed tegumental cell bodies in the free proglottis. The results are discussed in relation to the possible roles of the peptides in the neurophysiology and developmental biology of the worm.
Animals↗
Occurrence and distribution of putative neurotransmitters in the frog-lung parasite Haplometra cylindracea (Trematoda: Digenea).
The localisation and distribution of the cholinergic, serotoninergic and peptidergic components of the nervous system of the frog-lung fluke Haplometra cylindracea have been determined by the application of standard enzyme cytochemical and immunocytochemical techniques to cryostat sections and whole-mount preparations. Cholinesterase activity (ChE), as indicative of acetylcholine, has been demonstrated cytochemically in the CNS and PNS; however, the anterior ganglia were notably unreactive. The occurrence of serotonin was examined by an indirect immunofluorescence technique, and immunoreactivity (IR) was demonstrable in small, paired anterior ganglia and in fine nerve fibres associated with the somatic muscle, cirrus and gonopore. The peptidergic portion of the nervous system was investigated using antisera to 17 mammalian regulatory peptides and the invertebrate peptide FMRFamide, and was visualised by both indirect immunofluorescence and confocal scanning laser microscopy. Positive immunostaining occurred with antisera raised against pancreatic polypeptide (PP), peptide tyrosine tyrosine (PYY), substance P (SP), peptide histidine isoleucine (PHI) and FMRFamide. Immunoreactivity to PP, PYY and FMRFamide was widespread throughout the nervous system and was evident in large, paired anterior ganglia, the dorsal commissure, main nerve tracts and the extensive array of small fibres that constitute the PNS. In contrast, the distribution of nerves immunoreactive to SP and PHI was less apparent, with PHI-IR occurring exclusively within the fibrous neuropile of the ganglia and in fibres of the ventral nerve cord. Results are discussed with respect to the distribution of the various neurochemical elements and their roles as putative neurotransmitters and/or regulatory molecules.
Animals↗
Oogenesis in the free proglottis of Trilocularia acanthiaevulgaris (Cestoda, Tetraphyllidea).
The early (ovarian) stages of oogenesis in Trilocularia acanthiaevulgaris have been studied by light microscope histochemistry and transmission electron microscopy. The process proceeds as far as meiotic prophase in the primary oocyte. The oogonia and early immature primary oocytes occupy the anterior and outer edges of the ovary and are typically undifferentiated cells, showing a high nucleo-cytoplasmic ratio. The scant cytoplasm is packed with free ribosomes and contains a small number of mitochondria and a few short strands of granular endoplasmic reticulum (GER). The oogonia undergo a number of mitotic divisions, marked by the presence of centrioles. The immature primary oocytes enter meiotic prophase, as evidenced by the appearance of nuclear synaptonemal complexes. The maturing primary oocytes, which occupy the inner, central region of the ovary, undergo a growth phase that is accompanied by an increased nucleolar volume and export of RNA to the cytoplasm via nuclear pores, and by an increase in the number of mitochondria. A GER network develops and, together with the Golgi complexes, is involved in the production of a small number of cortical granules. The GER often takes the form of concentric cisternae. Numerous lipid droplets are also present in the cytoplasm. The mature primary oocytes predominate in the posterior region of the ovary, near the oviduct. They represent a resting phase in development, in which cellular activity is minimal. Lipid droplets are abundant and the cortical granules remain in more central regions of the cell and do not migrate to the periphery of the cell. The ovary contains a second, non-germinal type of cell, the follicle cell. The cell body is smaller in size than the oogonia, and cytoplasmic processes from it ramify around the periphery of the ovary. The different cell types within the ovary are embedded in a cytoplasmic matrix that contains a number of organelles.
Animals↗
A cytochemical study of the serotoninergic, cholinergic and peptidergic components of the reproductive system in the monogenean parasite, Diclidophora merlangi.
The reproductive system of the monogenean gill parasite, Diclidophora merlangi, was examined for the presence of cholinergic, serotoninergic and peptidergic innervation using cytochemical and immunocytochemical techniques. Cholinesterase activity and 5-hydroxytryptamine immunoreactivity (5-HT-IR) were confined to neural elements of the male reproductive system, being evident in the innervation of the cirrus, whereas only 5-HT was present in nerves and somata of the elongate seminal vesicle. Peptidergic innervation was localised to both the male and female reproductive systems of the worm. Within the female reproductive apparatus pancreatic polypeptide, peptide tyrosine tyrosine, neuropeptide Y, substance P, neurokinin A, eledoisin, FMRFamide and gastrin/cholecystokinin immunoreactive fibres and somata were observed in the oviduct, vitelline reservoir and ovovitelline duct. Intense peptide immunoreactivity was identified in fibres in the wall of the ootype and in a surrounding population (greater than 100) of somata that were situated beyond Mehlis' gland cells and all of which were connected to the ootype wall by fine cytoplasmic connectives. The strategic location of this peptidergic cell population infers its involvement in the egg-forming sequence in this platyhelminth parasite.
Animals↗
Hymenolepis diminuta: intestinal goblet cell response to infection in male C57 mice.
Intestinal goblet cell numbers in two regions of the small intestine (20-30% and 60-70% distance form the pylorus) of male, 6- to 8-week-old C57 mice have been monitored following a 5-cysticercoid infection of the rat tapeworm, Hymenolepis diminuta. Test and sham-infected control mice were autopsied 0, 4, 8, 10, 14, and 28 days postprimary infection (p-1 degree-i) and 2, 4, 5, 7, and 14 days postsecondary infection (p-2 degree-i), administered 28 days p-1 degree-i. Results show a statistically significant increase in the number of mucus-containing goblet cells in both regions of the intestine during primary and secondary infections. Peak goblet cell numbers occurred on Day 8 p-1 degree-i and Day 5 p-2 degree-i in the 20-30% region and on Day 10 p-1 degree-i and Day 5 p-2 degree-i in the 60-70% region. In both regions, cell numbers declined to control levels by Day 14 p-1 degree-i, but remained significantly above control values 14 days p-2 degree-i. The increase in cell numbers correlated with an increase in goblet cell theca size and observable amounts of luminal mucus. The same infection regime in mice treated with cortisone elicited no goblet cell response. Male Wistar rats given a 10-cysticercoid infection and autopsied on Day 0, Day 10, and 15 months p-i showed a statistically significant increase in mucus-containing goblet cells only in the 60-70% region of intestine 10 days p-i; however, the worm burden was not eliminated. The functional significance of these results is discussed in relation to host immunity and murine cestode rejection.
Animals↗
Regulatory peptides in parasitic platyhelminths.
Regulatory peptides are short chains of amino acids that regulate cell-to-cell interactions in widely divergent animal groups. Evidence is accumulating to suggest that they mediate many aspects of physiology and behaviour, serving as neurotransmitters, neuromodulators and hormones. While most data in this field derive from studies on the mammalian nervous and endocrine systems, the last decade has witnessed an upsurge of interest in invertebrate peptide biology, not least because it is likely that many regulatory peptides originated in the nervous system of invertebrates. Platyhelminths, like other invertebrate groups investigated, contain numerous neuropeptides, and here David Halton and colleagues review the evidence that these putative signalling agents serve key roles in parasite motility, reproduction and morphogenesis. The physicochemical differences between host and parasite peptides raise the possibility that selective disruption of peptidergic control systems in parasites could be an exploitable target in future chemotherapeutic strategies.
Journal Article↗
Confocal scanning laser microscopy and helminth neuroanatomy.
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Journal Article↗
Mammalian regulatory peptide immunoreactivity in the trematode parasite Haplometra cylindracea and the lung of its frog host, Rana temporaria: comparative chromatographic characterisation using reverse-phase high-performance liquid chromatography.
1. Extracts of Haplometra cylindracea and lung tissues of its host, Rana temporaria, were subjected to radioimmunoassay using antisera to nine mammalian regulatory peptides. 2. In these extracts, immunoreactivity was measured to pancreatic polypeptide, substance P, neurokinin A, gastrin-releasing peptide and glucagon. The levels of each peptide varied considerably with some marked differences between those demonstrable in parasite and host (notably pancreatic polypeptide). 3. Reverse-phase HPLC fractionation of extracts revealed general chemical differences between parasite and host peptides, with some peptides present in more than one molecular form.
Animals↗
Tachykinin immunoreactivity in the European common frog, Rana temporaria: localization, quantification and chromatographic characterization.
1. Tachykinin immunoreactivity has been localized, quantified and chromatographically-characterized in the brain, stomach, intestine and skin of Rana temporaria. 2. Antisera to mammalian substance P (SP) and neurokinin A (NKA) immunostained nerve fibres in all tissues except skin, and a population of mucosal endocrine cells in the intestinal epithelium. 3. Radioimmunoassay of tissue extracts identified SP immunoreactivity in all tissues but NKA immunoreactivity was restricted to the brain. 4. Chromatographic analysis of both frog tachykinins revealed that they possessed different physico-chemical properties than their mammalian counterparts.
Amino Acid Sequence↗
The serotoninergic, cholinergic and peptidergic components of the nervous system in the monogenean parasite, Diclidophora merlangi: a cytochemical study.
Confocal scanning laser microscopy has been employed with immunocytochemical techniques to map the distribution of serotoninergic and peptidergic components in the nervous system of the monogenean gill-parasite, Diclidophora merlangi; results are compared with the distribution of cholinergic components, following histochemical staining for cholinesterase activity. While all three neurochemical elements are present in the central and peripheral nervous systems, the cholinergic and peptidergic systems dominate the CNS, whereas the PNS has a majority of serotoninergic nerve fibres. The cholinergic and peptidergic neuronal pathways overlap extensively in staining patterns, suggesting possible co-localization of acetylcholine and neuropeptides. Within the peptidergic nervous system, immunoreactivity to the pancreatic polypeptide family of peptides and FMRFamide were the most prevalent. Gastrin/cholecystokinin (CCK)-, neuropeptide Y-, substance P-, neurokinin A- and eledoisin-like immunoreactivities have been demonstrated for the first time in a monogenean parasite. The gastrin/CCK- and tachykinin-like immunoreactivities had an apparently restricted distribution in the worm.
Acetylcholinesterase↗
A confocal scanning laser microscope study of the peptidergic and serotoninergic components of the nervous system in larval Schistosoma mansoni.
The localization and distribution of the serotoninergic and peptidergic elements of the nervous system of larval Schistosoma mansoni have been investigated using an indirect immunofluorescence technique in conjunction with confocal scanning laser microscopy (CSLM). A range of antisera was used, raised to the biogenic amine, 5-hydroxytryptamine (5-HT, or serotonin), the vertebrate peptides pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) and to the native invertebrate peptide, FMRFamide; all these antisera were shown previously to be immunopositive in the adult worm. No immunoreactivity to 5-HT was detected in any of the larval stages, but both miracidia and cercariae were consistently immunoreactive to all 4 peptides. The peptidergic nervous system of the miracidium is relatively simple, taking the form of a central neural mass with associated paired anterior and posterior nerve tracts. The cercarial peptidergic nervous system comprises a central commissure joining paired anterior ganglia, from which emanate paired dorsal and ventral nerve tracts, which terminate at the body/tail junction. The excretory bladder region of the tail is also immunoreactive for the 4 peptides, and a fine pair of nerve tracts extends the length of the tail shaft. Immunoreactive nerve cell bodies are also evident in the midbody region of the intrasprocystic cercariae, these same structures being immunoreactive for the neuronal marker, neurone-specific enolase (NSE). The organization of the larval peptidergic nervous system is compared to that of the cholinergic nervous system and contrasted with the peptidergic system in the adult worm. The absence of immunoreactivity to 5-HT is discussed in relation to the proposed development of the aminergic nervous system upon establishment in the definitive host.
Animals↗
Hymenolepis diminuta: changes in intestinal morphology and the enterochromaffin cell population associated with infection in male C57 mice.
Mean villus height, crypt depth and the number of 5-HT-positive enterochromaffin (EC) cells have been examined in two regions of the small intestine (20-30% and 60-70% distance from the pylorus) of male, 6 to 8-week-old, C57 mice following a 5-cysticercoid infection of the rat tapeworm, Hymenolepis diminuta. Test mice and sham-infected controls were autopsied 0, 4, 8, 10, 14 and 28 days post-primary infection (p-1 degree-i) and 2, 4, 5, 7 and 14 days post-secondary infection (p-2 degrees-i), administered 28 days p-1 degree-i. Morphometric analysis revealed a statistically significant increase in crypt depth in the 60-70% intestine region in infected mice during both primary and secondary infections; no significant deviation from the control was observed for villus height in infected mice. Statistical analysis showed a significant increase in the number of 5-HT-positive EC cells in infected mice. This response occurred in the lower portion of the intestine on days 10-p-1 degree-i and 5-p-2 degrees-i, and was not due to increased mucosal surface area in this region. Results are discussed with reference to murine cestode rejection and the possible involvement therein of the neuroendocrine system.
Animals↗
Spermatogenesis and the fine structure of the mature spermatozoon in the free proglottis of Trilocularia acanthiaevulgaris (Cestoda, Tetraphyllidea).
Spermatogenesis and the structure of the mature spermatozoon of Trilocularia acanthiaevulgaris have been studied by light microscopic histochemistry and transmission and scanning electron microscopy. The primary spermatogonia occupy the periphery of the testis and undergo four mitotic divisions; incomplete cytokinesis results in two secondary, four tertiary and eight quaternary spermatogonia and sixteen primary spermatocytes. The quaternary spermatogonia and successive stages develop in a plasmodial rosette with their nuclei at the periphery and connected to the cytophore by cytoplasmic bridges. The primary spermatocytes undergo two meiotic divisions, resulting in 64 spermatids that develop into spermatozoa. Intranuclear synaptonemal complexes in primary spermatocytes confirm the first meiotic division. The onset of spermiogenesis is marked by an elongation of the spermatid nucleus and the appearance of "arching membrane-bound clefts" (after Rosario 1964) that delimit the differentiation zone. The latter contains a pair of axonemes with their associated basal bodies and rootlets and, as it extends, the nucleus migrates into it. At first, the axonemes grow at right angles to the extension, but during development they rotate through 90 degrees and come to fuse with the cytoplasmic extension. The mature spermatozoon has a broad head region, a middle piece and a narrow tail region. It consists of a highly coiled nucleus, paired axonemes of the 9 + 1 pattern typical of platyhelminths, one of which extends the full length of the tail and the other ends part-way along the tail, particles of beta-glycogen and peripheral microtubules. A crested body spirals around the outside of the sperm body in the tail region. T. acanthiaevulgaris is placed in context within the phylogenetic schemes for cestodes based on sperm ultrastructure.
Animals↗