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  • 1
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Reproductive stress is apparent inAbra alba as a result of infection with the sporocysts ofBucephaloides gracilescens, culminating in castration in heavily infected specimens. The bivalve is also subject to mechanical stress from actively growing sporocyst tubules and nutritional stress due to the nutrient requirement of large numbers of germ balls within the sporocysts. Using the digestive cell lysosomal system ofAbra as a monitor, it was possible to demonstrate quantitatively a parasite-induced cellular stress response by applying a sensitive cytochemical test for lysosomal stability. Lysosomal stability was determined as the labilisation period for latent Nacetyl-β-hexosaminidase (NAH), measured by microdensitometry. In uninfectedAbra, digestive cell lysosomal NAH expressed structure-linked latency. Hence a significantly longer labilisation period was required compared with infectedAbra, where the parasitic burden with its associated stress effects resulted in a destabilisation of the lysosomal membrane. This reduced the latency of the enzyme, so that a much shorter labilisation period was required for the stressed tissue to express maximum lysosomal enzyme activity. It is suggested that the lysosomal system of the digestive cells inAbra can be used as a sensitive monitor of the stress induced by the sporocysts and developing cercariae ofBucephaloides.
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  • 2
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 3
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Excystment in vitro ofCotylurus variegatus metacercariae requires a trypsin-bile salt medium for digesting the cyst wall, and events are triggered by a rise in environmental temperature of up to 41°C. Pepsin pretreatment, while effective in removing extraneous host tissues, is not a prerequisite for excystment in vitro. The metacercaria plays an active role in its release, contractile movements being stimulated by bile salts over a temperature range of 30–41° C. Synthetic sodium taurocholate was only one third effective in excystment compared with sodium taurocholate from ox bile. Excystment was maximal at pH 7.5, but conditions of osmolarity, redox potential or gas phase were not of apparent importance.
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  • 4
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The development in vitro of a strigeoid trematode,Cotylurus erraticus from the sexually undifferentiated metacercaria to ovigerous adult has been examined at 24-h intervals, using section autoradiography. Nuclear accumulation of trace-labelled3H-thymidine showed that DNA synthesis was triggered in the genital anlagen within 4 h of excystment and that spermatogonia and oogonia were evident within 3 days of culture. Germ cells were fully differentiated by day 4, and by day 5 vitellogenesis was complete and eggs were present in the uterus. The pattern of reproductive development was identical to that of worms grown in the natural definitive host (Larus ridibundus), although the slightly slower triggering of events in vitro culminated in a 24-h delay in egg production. The eggs produced in vitro failed to embryonate fully or to hatch.
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  • 5
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The localisation and distribution of 5-hydroxytryptamine (5-HT or serotonin) in the nervous system ofFasciola hepatica has been determined by an indirect immunofluorescence technique. Cell bodies and nerve fibres immunoreactive to 5-HT are present in the anterior ganglia, and the longitudinal nerve cords and their commissures in the central nervous system. In the peripheral nervous system, similar immunoreactivity occurs in the nerve plexuses supplying the sub-tegumental muscle layers and the muscular lining of various reproductive ducts, including the ootype, uterus and cirrus pouch. The significance of these results in the light of previous studies on the role of 5-HT inF. hepatica is discussed.
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  • 6
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 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 (〉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.
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  • 7
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The early (ovarian) stages of oogenesis inTrilocularia 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.
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  • 8
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Antisera to a highly conserved region of chromogranin A (sequence KELTAE) and to a hexapeptide (sequence KGQELE) adjacent to the putative C-terminus of pancreastatin, a peptide whose sequence is found within the chromogranin A molecule, have been used to examine the localisation of immunoreactivity (IR) to these peptides inAscaris suum. IR to both peptides was found in the nerve rings and nerve cords. In addition, KGQELE-IR was also observed in the pharyngeal neurones and in a network of fibres on the surface of the female gonoduct. The staining was specific in that it could be abolished by preincubation of the antisera with the appropriate antigen. The two antisera appeared to be staining different subsets of neurones, suggesting that (at least) two peptides were being recognised. The widespread distribution of IR to both peptides throughout the nervous system of the parasite suggests that the peptides carrying the epitopes recognised by the antisera are of fundamental importance to the functioning of the parasite's nervous system.
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  • 9
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using an indirect immunofluorescence technique interfaced with confocal scanning laser microscopy, whole-mount preparations of three general of marine trematode larvae,Cryptocotyle lingua, Cercaria emasculans andHimasthla leptosoma, were screened for 5-hydroxytryptamine (5-HT) and selected neuropeptide immunoreactivities (IRs). IRs for pancreatic polypeptide (PP), peptide YY (PYY) and FMRFamide were found in the central nervous systems of the three species of cercariae, immunostaining the paired ganglia and central commissure and the longitudinal nerve cords, with slight differences in both distribution and intensity of IRs being observed for the different antisera used. PP, PYY and FMRFamide IRs were evident in both central and peripheral components of the nervous system in the rediae ofC. lingua. 5-HT IR was confined to the peripheral nervous systems of the cercariae ofC. emasculans and the rediae ofC. lingua, appearing in the form of a network of immunoreactive fibres and associated large cell bodies. A moderate substance P IR was observed in the nervous system of the cercariae ofC. lingua. The patterns of immunostaining described were compared with those obtained using antiserum directed to the C-terminal decapeptide amide of neuropeptide F (NPF), a native parasitic peptide from the cestodeMoniezia expansa. Results demonstrated that serotoninergic and peptidergic components were present in the nervous systems of all of the trematode larvae studied and that some, if not all, of the IR for PP, PYY and FMRFamide was due to the presence of a trematode NPF homologue.
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  • 10
    ISSN: 1573-5117
    Keywords: Plathelminthes ; Platyhelminthes ; nervous system ; immunocytochemistry ; neuropeptide F ; FMRF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The first ‘native’ flatworm regulatory peptide, neuropeptide F (NPF) has recently been isolated and sequenced from the cestode Moniezia expansa (see Maule et al., 1991) and the turbellarian Artioposthia triangulata, (see Curry et al., 1992). NPF belongs to the neuropeptide Y (NPY) superfamily and the antiserum is known to show cross-reactivity to the vertebrate neuropeptides of the NPY superfamily. It terminates in RFamide, like the invertebrate neuropeptides FMRFamide and RFamide, and may cross-react with neuropeptides of the FMRFamide family. Strong immunoreactivity (IR) to FMRF- and RF-amide has been demonstrated in members of most flatworm groups. In the present study, IR to NPF (diluted 1:1000) is demonstrated in Stenostomum leucops (Catenulida) and Microstomum lineare (Macrostomida). The controls included: omitting primary antibody, using non-immune serum and liquid-phase absorption with the homologous antigen (1000 ng ml−1). The NPF IR pattern was compared to the FMRF and RF-amide IR patterns in order to reveal differences or co-localization. In addition, the sequential appearance of NPF-positive cells in developing zooids was followed and double staining with a-5-HT made to complete the study.
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