Molecular cytogenetic analysis of a triploid population of the human broad tapeworm, Dibothriocephalus latus (Diphyllobothriidea).

The large-sized tapeworm Dibothriocephalus latus is known as the broad or fish-borne cestode of mammals that is capable to infect humans and cause diphyllobothriosis. Recently, molecular data on D. latus has been accumulating in the literature and a complete genome sequence has been published; however, little is known about the karyotype and chromosome architecture. In this study, an in-depth karyological analysis of 2 D. latus specimens was carried out. The plerocercoids originated from a perch caught in subalpine Lake Iseo (Italy) and the tapeworms were reared in hamsters. Both specimens contained cells with a highly variable number of chromosomes ranging from18 to 27. Nevertheless, the largest portion of mitotic figures (47%) showed a number corresponding to the triploid set, 3n = 27. Accordingly, the karyotype of the analyzed specimens consisted of 9 triplets of metacentric chromosomes. Fluorescence in situ hybridization (FISH) with the 18S rDNA probe clearly demonstrated the presence of 3 clusters of hybridization signals on the triplet of chromosome 7, thus confirming the triploid status of the specimens. FISH with a telomeric (TTAGGG)n probe confined hybridization signals exclusively to the terminal chromosomal regions, supporting the earlier findings that this repetitive motif is a conserved feature of tapeworm telomeres.

Prostaglandins E2 and D2-regulators of host immunity in the model parasite Diphyllobothrium dendriticum: An immunocytochemical and biochemical study.

The spectrum of immunomodulating molecules produced by tapeworms is not yet well understood. The aims of this study, on the tapeworm Diphyllobothrium dendriticum, were: 1) detection and quantification of prostaglandins (PGs) E2 and D2 by high performance liquid chromatography; 2) visualization of PGE2 and PGD2 in specific cells, using methods of immunocytochemistry and confocal laser scanning microscopy; and 3) investigation of the ultrastructure of the cells potentially producing PGE2 and PGD2. The PGE2 immunoreaction (IR) was found in the apical terminals of the frontal glands and sensory organs in the tegument and in small neurons belonging to the main cords and commissures. PGE2-IR partly coincided with α-tubulin-IR. PGD2-IR occurred in the muscle fibers of longitudinal and transverse body muscles and coincided with phalloidin TRITC staining. Both PGE2 and PGD2 were found in the flame cells of the excretory system. Ultrastructural study of the tegument revealed two types of structures that potentially produce PGE2: ciliated and unciliated free nerve endings and frontal gland terminals reinforced with neurotubules. In the main nerve cords, small neurons were identified as potentially exhibiting PGE2-immunoreactivity. In homogenates of the plerocercoids, the measured content of PGE2 and PGD2 was 33.15ngmg-1 and 1.94ngmg-1 of fresh tissue weight, respectively. We found evidence of PGE2 and PGD2 in D. dendriticum parasitizing Coregonus autumnalis (fish) and proved excretion of PGE2 and PGD2 in response to C. autumnalis blood serum. Prostaglandins produced by D. dendriticum probably play a dual role: 1) PGE2 and PGD2 potentially modulate the fish antiparasitic immune response; 2) PGE2 is presumably necessary for proper development and function of the nervous system, and PGD2 can act as an antagonist against mediators causing muscle contraction.

[Localization of prostaglandin E2, γ-aminobutyric acid, and other potential immunomodulators in the plerocercoid Diphyllobothrium dendriticum (Cestoda)].

For the first time, the potential immunomodulators prostaglandin E2 and γ-aminobutyric acid (GABA) have been revealed in the plerocercoid Diphyllobothrium dendriticum, which is a parasite in the tissues and abdominal cavity of the Baikal omul Coregonus migratorius. The localization of immunomodulators in parasite tissues was compared with the location of typical markers of the nervous system (serotonin (5-HT) and FMRF-amide) and a marker of microtubules (α-tubulin). Prostaglandin E2 was revealed in the cells that are immunoreactive to α-tubulin and are situated in the cortical parenchyma outside the central nervous system (CNS). It is supposed that prostaglandin E2 is produced by the frontal glands and is carried out onto the tegument surface through specialized ducts. Immunoreaction to GABA was revealed in the central and peripheral nervous systems. GABA-ergic neurosomes, the neurites of which form a net on the surface of muscle layers and in the subtegument, were revealed in the cerebral ganglion and main nerve cords. The morphological characteristics for the identification of serotoninergic neurons in the CNS were described.

[Hematological and immunological properties of herring gull (Larus argentatus) nestlings experimentally infected with Diphyllobothrium dendriticum (Cestoda: Pseudophyllidae)].

The morphological structure of the blood in herring gull nestlings and their immune system response to experimental infection with tapeworm Diphyllobothrium dendriticum have been studied. The leukocyte reaction pattern and the dynamics of immunoglobulin synthesis and populations of immunocompetent cells in the blood of nestlings during early invasion indicated a short duration of the cellular immune response and an insignificant humoral immune response. A pronounced trend to decrease in the hemoglobin level in the blood of infected nestlings has been revealed and this reduction was in part compensated by intensified erythropoiesis. It is shown, that the changes in hematologic and immune responses of the obligate definitive host provide for the mutual host-parasite adaptation.

Never ending growth and a growth factor. I. Immunocytochemical evidence for the presence of basic fibroblast growth factor in a tapeworm.

Basic fibroblast growth factor immunoreactivity (bFGF-IR) was detected in a specific set of nerve cells in the central nervous system of the gull-tapeworm Diphyllobothrium dendriticum (Cestoda)--an obligatory endoparasite. The long varicose processes of the bFGF-IR neurons extend along the two main nerve cords, which contain an actively growing population of nerve cells. A neurotrophic function for the bFGF-like material is proposed. The adult tapeworm lives in the intestine of a homeothermic host and has a pattern of very active and never ending growth. The larval stages live in poikilothermic hosts and grow very slowly. The bFGF-IR nerve cells occur both in II stage larvae and in adult worms. Thus, no correlation between the presence of bFGF-IR and the general growth rate of the worm was found. Western blot analysis revealed the presence of an anti-bFGF immunoreactive peptide with a molecular mass of 47 kDa in both larval and adult worms.

Immunocytochemical demonstration of neuropeptides and serotonin in the tapeworm Diphyllobothrium dendriticum.

The present immunocytochemical study concerns the distribution of four neuropeptides, FMRF-amide, vasotocin, leu-enkephalin and neurotensin, and of the bioamine serotonin in the plerocercoid larva of Diphyllobothrium dendriticum. Anti-FMRF-amide and vasotocin-reactivity occurs in perikarya and nerve fibres in the CNS and PNS of this worm. The peptide-containing fibres surround and seem to innervate the musculature and to terminate beneath the basal lamina of the tegument at the inner surface of the bothridia, suggesting a neurotransmitter function. Anti-leu-enkephalin reaction occurs in perikarya and fibres in the main nerve cords and in the PNS. Anti-neurotensin reactive fibres were observed in the neuropile of the nerve cords. Serotonin immunoreactivity was found in neurons in the ganglionic commissure of the brain and along the main nerve cords. This study is the first immunocytochemical identification of neuropeptides and serotonin in a parasitic flatworm and the information gained may be of importance for the development of new antihelminthics.

[Cytochemical characteristics of the labrocyte-like cells in the capsule of the plerocercoids of Triaenophorus nodulosus (Pallas, 1781) and Diphyllobothrium dendriticum (Nitzsch, 1824) cestodes]. / Tsitokhimicheskaia kharakteristika labrotsitopodobnykh kletok v kapsule plerotserkoidov tsestod Triaenophrus nodelosus (Pallas, 1781), i Diphyllobothrium dendriticum (Nitzsch, 1824).

Out of six fish species examined (Esox lucius, Paracottus kessleri, Perca fluviatilis, Leuciscus leuciscus baicalensis, Coregonus autumnalis migratorius, Thymallus arcticus baicalensis) labrocyte-like cells were detected in Esox lucius, Leuciscus leuciscus baicalensis, Coregonus autumnalis migratotius. The cells contain large metachromatic granules. Histochemical methods revealed in them sulfated and carboxylic acid mucopolysacharides. The amount of labrocyte-like cells in the capsules around plerocercoids of Triaenophrus nodulosis from Esox lucits liver depends on the age of the capsule and that of the plerocercoid. It increases when the connective tissue papsule is forming and decreases again under aging and degeneration of the capsule containing plerocercoid. The amount of labrocyte-like cells in the cestodes capsules of Raillietina increases sharply when they locate in an accidental organ (liver). This demonstrates the acuteness of organ reactivity to a nonspecific helminth.