Promotion of hyphal growth in Ustilago violacea by host factors from Silene alba

Ustilago violacea specifically parasitizes susceptible members of the Caryophyllaceae. We isolated water-soluble compounds from leaves of Silene alba which promoted hyphal development in the dimorphic pathogen. We also isolated hyphal growth promoting -tocopherol from S. alba. The water-soluble activity, which we term hyphal growth factor, or HGF, separated into four bands with gel filtration chromatography and represented over 40% of the total hyphal growth promoting activity isolated from S. alba. The water-soluble HGF activity may be host-specific and may function as a determinant of the host-parasite specificity between U. violacea and caryophyllaceous host plants.Abbreviations HGF Hyphal growth factor - BHT butylated hydroxytoluene     

Effects of the parasitic botfly Philornis carinatus on nestling house wrens,Troglodytes aedon,in Costa Rica

I studied the life cycle of a botfly (Diptera: Muscidae: Philornis carinatus) and examined the effects of botfly ectoparasitism on nestling house wrens (Passeriformes: Troglodytidae: Troglodytes aedon) during three years in Costa Rica. At three study sites, I found that nestlings were relatively unaffected by botflies, in contrast to all other studies of birds infected with philornid botflies. At Monteverde, the main study site, infected chicks grew slightly slower and had slightly shorter tarsi and wing chords than uninfected chicks, but both groups fledged at similar weights. Since weight at fledging is the only growth character associated with post-fledging survivorship, botfly infections likely cost wrens little in terms of fitness. At all sites, fledging success did not differ between infected and uninfected nests. Botfly infections were more prevalent at two lower elevation sites than at the high elevation Monteverde side. Infection prevalence increased during the nesting season at all study sites, which suggests a botfly life cycle in which adult population levels increase during the wren breeding season and then decline during a dormant period when wrens are not nesting. Finally, botflies may attack chicks throughout the period before fledging, but there is no indication they locate nests before hatching. In sum, botfly parasitism on wrens appears to be benign, perhaps because the study sites are at the edge of the botfly's range or because wrens are not a preferred host.     

Leishmania donovani Attachment Stimulates PKC-Mediated Oxidative Events in Bone Marrow-Derived Macrophages

We investigated activation signaling events in bone marrow-derived macrophages after infection with Leishmania donovani, an intracellular parasite of macrophages. Leishmania donovani infection caused a general suppression of activation parameters like O₂^- and NO production. However, conditions which allow parasite attachment and prevent entry resulted in triggering of O₂^- and NO production and stimulation of O₂ consumption. Optimal NO and O₂^- production occurred when bone marrow-derived macrophages and Leishmania ratio was 1:100. The activation signal for O₂^- production was initiated 15 min after parasite attachment, whereas augmentation of NO production started 6 h after attachment. Activation of O₂^- and NO generation by L. donovani attachment was inhibited by staurosporine as well as by prolonged treatment of phorbol myristate acetate suggesting a protein kinase C-dependent mechanism. Translocation studies showed that protein kinase C activity in cell membrane fraction rapidly and transiently increased following parasite attachment. No such protein kinase C translocation event occurred in L. donovani infected bone marrow-derived macrophages. Phorbol myristate acetate was found to stimulate membrane translocation of protein kinase C in parasite attached cells whereas it was impaired in infected cells. However, both attachment and infection induced a similar shift of phorbol receptors from cytosolic to membrane fraction indicating that in infected cells the translocation of protein kinase C protein was not impaired but the activity of the membrane associated enzyme was somehow inhibited. These results suggest that although internalization of intracellular parasites like L. donovani caused inhibition of nitrite and superoxide release, mere attachment on macrophage surface resulted in an activation of protein kinase C-mediated downstream oxidative events.     

Ultrastructure of cuticular exudations in parasitic juvenileHeterodera schachtii,as related to cuticle structure

Summary The development ofHeterodera schachtii inside roots of a cruciferous host plant grown under monoxenic conditions in an agar medium was observed with video-enhanced contrast light microscopy. One to 6 days after inoculation, roots were excised and processed for electron microscopic observations. Exudates were present on the cuticle surfaces of J 2 and early J 3 juveniles located at feeding sites. Fibrillar exudations were correlated with similar fibrillar patterns in the epicuticle, exocuticle, intermediate zone, and the striated endocuticle. Secretion vesicles assembled at many Golgi sites in the hypodermis, appeared to coalesce and form large electron translucent vesicles in the cytoplasm. We propose that secretion vesicles migrate toward the cuticle, contact the plasmalemma and transfer their contents by exocytosis or a similar mechanism to a secretion accumulation site. These contents are associated with cuticle structure and emerge as surface exudations.     

The fine structure and cytology of the association between the parasitic red algaHolmsella australis and its red algal hostGracilaria furcellata

Summary Holmsella australis Noble andKraft ms. is a colourless red algal parasite, forming whitish pustules on its photosynthetic red algal host,Gracilaria furcellata Harvey. In the infected region, host cortical tissue continues to grow and enclose the expanding pustule. Filaments of both host and parasite grow apically, the cells being connected by primary pit connections (PCs). Secondary PCs form between cells of the same species, and in addition,H. australis initiates the formation of secondary PCs with cells ofG. furcellata. All three types of secondary PC are morphologically distinct. In hostparasite PCs the surface adjoining the host cell is similar in structure to a host-host PC, while that adjoining the parasite cell has the structure of a parasite-parasite PC. The plasma membrane is continuous between the cells of the unrelated host and parasite. In addition, a cap membrane is typically produced only on the host surface, though occasionally the parasite side is enclosed by a cap membrane as well. Cap membranes are absent from parasite-parasite PCs (making them intracellular), while host-host PCs are typically extracellular, both cells producing cap membranes. The presence or absence of a cap membrane in certain positions appears to vary, and suggests that cells may be able to regulate its presence. Since transport of nutrients would be expected to occur from host to parasite cells, and between parasite cells, the morphological evidence presented here suggests the PCs may be the pathway.     

Ethylene formation by germinating,Drechslera graminea — Infected barley (Hordeum sativum) grains: A simple test for fungicides

Grains of barley (Hordeum sativum L.); infected with the parasitic, systemic fungus Drechslera graminea, produce more ethylen than uninfected controls. Treatment of infected grains with mercury-free fungicides yields a differentiated suppression of the ethylene evolution 7 d after the beginning of germination. Suppression of visible symptoms (chlorotic stripes on leaves) appearing six to eight weeks after germination of infected, untreated seeds correlates with the decrease in ethylene formation after treatment with fungicides. The gaschromatographic ethylene determination thus allows for an early and reliable (significance higher than 99.9%) differentiation of fungicidal activities against the barley stripe disease.Abbreviations ACC I-aminocyclopropane-1-carbonic acid - CD critical difference     

Ornithodiplostomum ptychocheilus: migration to the brain of the fish intermediate host, Pimephales promelas.

Migration of cercariae of the diplostomatid trematode, Ornithodiplostomum ptychocheilus, to the brain of the fathead minnow, Pimephales promelas, takes place via directed, nonrandom movement. Penetration of the fish epidermis is rapid and is essentially complete by 2 hr postinfection. Migration to the central nervous system occurs almost exclusively via the general body musculature and connective tissue, although a few cercariae gain direct access to the nervous system via the eyes. Cercariae enter either the neural canal and spinal cord, or the brain via the spinal or cranial nerves and their associated foramina, although cercariae appear to remain in (on) these peripheral nerves for only a short time. Cercariae associated with cranial nerves continue to the brain. Those becoming associated with spinal nerves travel up the neural canal and (or) spinal cord to the brain. Data suggest that most arrive at the brain via the neural canal and spinal cord. Within the brain, most developing metacercariae (neascus-type) occur in the optic lobes and cerebellum. Whether this is “selective localization” or merely the result of the larger space afforded by these brain regions could not be determined.     

Schistosomatium douthitti: effects of Lymnaea catascopium age on susceptibility to infection

Laboratory-reared Lymnaea catascopium snails (1–269 days old) were exposed individually to different numbers of Schistosomatium douthitti miracidia. Increasing the exposure dosage from 3 to 10 miracidia generally increased infection rates, in some age classes up to 100%. Successful re-exposure of snails not infected after a primary exposure was possible. Neonatal snails were least likely to become infected, primarily because miracidia were not attracted to them. Snails 12–55 days old were most susceptible to infection. Miracidia were readily attracted to these snails, and many were ingested and subsequently penetrated the host esophageal wall. Miracidial penetration of external snail surfaces was rare. Susceptibility of older snails (65–269 days) progressively declined with age. Many miracidia were entangled and immobilized in mucus produced by these snails, and fewer were ingested. No conspicuous host cellular responses to mother sporocysts were observed in any of the snails sectioned. A comparison of susceptibility of deliberately stunted snails and comparably aged controls of normal size indicated that the former were more susceptible.     

Mesocestoides corti (syn. vogae, cestoda): characterization of genes encoding cysteine-rich secreted proteins (CRISP)

With the aim of identifying genes involved in development and parasite adaptation in cestodes, four coding sequences were isolated from the cyclophyllidean Mesocestoides corti larval stage (tetrathyridium). Genes showed significant similarity to the cysteine-rich secreted protein (CRISP) encoding genes, a large family that includes stage and tissue-specific genes from diverse organisms, many associated with crucial biological processes. The full-length McCrisp2 cDNA encodes a predicted protein of 202 residues in length, containing 10 cysteines and a putative signal peptide. The expression level of McCrisp2 was estimated by Real-time PCR, relative to GAPDH, showing an increase of 75% in segmented worms compared to tetrathyridia. By in situ hybridization, McCrisp2 expression was localized mainly at the larvae apical region of tetrathyridia and in the proglottids of segmented worms. Taken together our results suggest a possible role for M. corti CRISP proteins as ES products, potentially involved in differentiation processes as proposed for homologs in other organisms.     

Glycomics-driven discoveries in schistosome research

Schistosome glycans and glycoconjugates play a prominent role in the parasite's biology, in particular in the interaction with the human host. A large amount of structural data regarding glycosylation of different schistosome life stages and glycoconjugate subsets has been collected in the last decade, but many significant gaps in our knowledge of the schistosomal glycome remain. Here we will present a concise review of the already available data guided by a selection of recently generated stage-specific glycan profiles, and discuss implications and prospects of glycomics studies of schistosomes.