Vincent A. Connors

In vitro effect of larval Schistosoma mansoni excretory-secretory products on phagocytosis-stimulated superoxide production in hemocytes from Biomphalaria glabrata.

The in vitro production of the reactive oxygen metabolite superoxide (O2-) was confirmed in hemocytes from the schistosome intermediate host Biomphalaria glabrata. Active forms of the enzyme superoxide dismutase (SOD) inhibited reduction of nitroblue tetrazolium (NBT) to formazan in cells that had phagocytozed zymosan particles, whereas an inactivated form of SOD did not. Moreover, based on the prevalence of O2(-)-positive hemocytes and the relative intensity of NBT staining reactions, hemocytes from the Schistosoma mansoni-resistant 10-R2 strain of B. glabrata possessed an overall greater capacity for generating superoxide than did those from S. mansoni-susceptible M-line snails. Schistosoma mansoni excretory-secretory (E-S) products, released during in vitro transformation of miracidia to sporocysts, inhibited phagocytosis of zymosan particles and superoxide activity in hemocytes from both snail strains, but 10-R2 hemocytes maintained higher levels of phagocytosis and superoxide production than did M-line hemocytes. The dose-dependent decreases in phagocytosis observed in both snail strains in the presence of E-S products could not account fully for the concomitant decrease in superoxide levels detected, indicating that either a single E-S factor differentially affects phagocytosis and superoxide production, or that different E-S factors are involved in the specific interference of each of these hemocyte functions.

Recombinant human interleukin-1-mediated killing of Schistosoma mansoni primary sporocysts in Biomphalaria glabrata.

Previous work has indicated that injection of recombinant-human interleukin (rhIL)-1beta in Schistosoma mansoni-infected M-line Biomphalaria glabrata resulted in a significant reduction in the number of cercariae shed. The purpose of the present work was to determine if primary sporocysts were killed following rhIL-1beta injection in susceptible snails and, if so, to determine if killing was the direct result of hemocyte activity. Counting of primary sporocysts indicated a 50% reduction in the number surviving at 3 days PE in snails from 2 susceptible strains following injection. Histological analysis indicated that killing occurred with little-to-no observable hemocyte/parasite contact, whereas short-term culture of primary sporocysts with cell-free plasma (hemolymph) from injected snails rapidly initiated killing in vitro. Because levels of a snail IL-1-like molecule (SnaIL-1) drop significantly following schistosome exposure in M-line snails, because resistant snails maintain higher SnaIL-1 levels following infection, and because rhIL-1beta upregulates hemocyte cytotoxic mechanisms, these data support the contention that SnaIL-1 plays a role in determining resistance in B. glabrata. These data also indicate that schistosome death may be separated from parasite encapsulation by hemocytes and that an as yet unidentified humoral killing mechanism/factor may exist in B. glabrata. Lastly, these data further support the hypothesis that cytokine-like molecules are important, functionally conserved immunodefense mediators in both vertebrates and invertebrates.

PHILOMETRIDS OF THE SOUTHERN FLOUNDER PARALICHTHYS LETHOSTIGMA: A MULTIDIMENSIONAL APPROACH TO DETERMINE THEIR DIVERSITY

Abstract Two species of philometrid nematode, Philometra overstreeti and Philometroides paralichthydis, infect the southern flounder, Paralichthys lethostigma. Individuals of P. overstreeti are located between the teeth and inside the bony part of the branchial arches of the fish. Individuals of P. paralichthydis are associated with the bones of the buccal cavity and among muscles that control the dorsal and anal fins. Sequencing of part of the cytochrome oxidase I gene revealed 4 distinct genetic clades, each corresponding exactly to the 4 respective locations of the parasites in the host, suggesting the need for taxonomic revision. We hypothesized that each clade represented a separate species and, because the worms are morphologically indistinguishable, compared population level parameters of the clades comprising each currently recognized species. For each currently recognized species, the presence of worms from 1 clade was negatively correlated with the presence of worms from the other. Results also indicated significant differences between the clades in prevalences relative to both biotic and abiotic factors. Results clearly indicated major differences in the ecology of the philometrids constituting each clade. Taken as a whole, molecular and ecological data support the contention that the 4 genetic clades are likely 4 distinct species.

Chemokinetic Effect of Interleukin-1β on Cultured Biomphalaria glabrata Embryonic Cells

Abstract Previous studies have indicated that a molecule with cytokine activity, possibly an interleukin-1-like (IL-1) molecule, plays a role in the killing of larval stages of the blood fluke Schistosoma mansoni in the snail host Biomphalaria glabrata. The purpose of the present experiment was to test the effects of recombinant-human IL-1β (rhIL-1β) on embryonic B. glabrata (Bge) cell motility to determine whether the cells respond to the cytokine. Response was measured using a variation of a chemokinetic assay in which cells in culture were separated from variable concentrations of rhIL-1β by a semi-permeable membrane containing pores to allow migration. A double staining technique was developed to ascertain cell movement across the membrane. The number of cells moving across the membrane significantly increased in a concentration-dependent manner relative to the presence of increasing amounts of rhIL-1β below the membrane. The number of cells that moved across the membrane increased until a threshold was reached, after which migration decreased. Further, the rhIL-1β-mediated increase in Bge cell migration across the membrane was abrogated by the addition of IL-1 receptor antagonist protein. These data indicate that Bge cells respond specifically to rhIL-1β. As such, these data also indicate that Bge cells may serve as a useful model for elucidation of the role of cytokines or cytokine-like molecules in the snail/schistosome relationship.

Distribution of Kudoa inornata Plasmodia in the Musculature of its Host, the Spotted Seatrout Cynoscion nebulosus

ABSTRACT: The myxozoan Kudoa inornata is a common parasite of the skeletal muscles of spotted seatrout, Cynoscion nebulosus. This study was conducted to determine the distribution of plasmodia of K. inornata within individual C. nebulosus in order to identify muscle areas of least variation where future sampling would result in easily obtainable, repeatable, and dependable measurement of infection status. Fish were captured in the wild during June 2011. Muscle samples from 9 body areas were collected, in replicate, from each of 15 specimens of C. nebulosus of various ages and lengths infected by K. inornata. Body areas sampled included 6 locations from the fish epaxial and hypaxial muscles and 1 from each of the adductor mandibulae (cheek muscle), the cranial epaxial muscle, and the muscle of the caudal peduncle. Replicate samples were weighed and the number of plasmodia in each was recorded to determine the average density of plasmodia per gram of muscle in each area. The average density of plasmodia amo...

Striped Bass, Morone saxatilis, a New Intermediate Host for the Heterophyid Ascocotyle nana

ABSTRACT: Striped bass, Morone saxatilis (Moronidae), collected from several rivers in South Carolina, U.S.A., were found to be infected with heterophyid metacercariae whose morphology was consistent with Ascocotyle (Phagicola) nana on the basis of descriptions from the literature and via comparison with reference specimens of metacercariae from largemouth bass, Micropterus salmoides (Centrarchidae), a known intermediate host for A. nana. Morphology of metacercariae from both fish species was similar and partial sequencing of their 18S ribosomal DNA gene confirmed that metacercariae from both fish belonged to the same heterophyid species. Young-of-the-year striped bass were not infected and over 65% of the population sampled (N = 39) age 1 yr and older were infected with up to 49 metacercariae per gram of somatic muscle. Mid-line red muscle (lateralis superficialis) had a significantly higher density of metacercariae than epaxial and hypaxial white muscle. Some metacercariae showed signs of degradation...