Spatial and temporal patterns in the occurrence of peritrich ciliates as epibionts on calanoid copepods in the Chesapeake Bay, USA

We investigated temporal and spatial patterns of distribution in two peritrich ciliates (i.e. Zoothamnium intermedium and Epistylis sp.) living as epibionts on calanoid copepods (i.e. Acartia tonsa and Eurytemora affinis) in Chesapeake Bay. Net tow samples collected along the main axis of the Bay were analyzed to estimate the occurrence of epibionts on copepods and to explore relationships among infestation prevalence, host abundance, and environmental variables. Zoothamnium intermedium and Epistylis sp. colonized populations of A. tonsa during spring and summer months, while only Z. intermedium colonized E. affinis during spring. Occurrence of epibionts on copepods showed high interannual variation, marked seasonality, and geographic heterogeneity. Extensive statistical analyses rejected simple scenarios of interactions between epibiosis, environmental variables, and host density, suggesting a more complex dynamics for the system. Analyses of epibiont colonies and zooids per host area (i.e. the sum of width and length of the body including antennae and swimming legs calculated assuming a cylindrical shape) were also performed. Overall, epibiont infestation prevalence (i.e. colonies/host area) and load (i.e. zooids/host area) were higher on copepodites than on adults for both host species, suggesting a preferential attachment to juveniles, or a higher predation pressure on adult stages. Infestation density and loads of both epibiont species were higher on the cephalothorax and abdomen of A. tonsa and E. affinis in comparison to the antennae and swimming legs, suggesting that ciliates can more easily colonize less active parts of the host.     

Phytoremediation of pesticide wastes in soil

Soils at agrochemical dealer sites often are contaminated with pesticide residues from decades of accidental and incidental spillage. We have determined that prairie grasses native to the Midwestern U.S. are suitable for phytoremediation because they are tolerant of most herbicides and of climatic extremes, such as heat, cold, drought, and flooding. A mixed stand of big bluestem, switch grass, and yellow indiangrass develops a rhizosphere with microflora that can readily detoxify pesticide residues. Specific atrazine-degrading bacteria or the free enzyme atrazine chlorohydrolase also can enhance the rate of biotransformation of atrazine in soil. Metolachlor degradation can be accelerated significantly by the prairie grass/rhizosphere effect. Several grasses used in filter strips have also been evaluated for their pesticide-degradation capabilities. The prairie grasses also have been demonstrated to reduce the rates of leaching of pesticides through intact soil columns, since less water leaches out of vegetated soil columns compared to non-vegetated soil columns. The evaluation of the degree of success of remediation has relied heavily on chemical residue analysis, but recent studies on biological endpoints have shown promise for providing more ecologically relevant indications of the potential exposure of organisms to pesticides in the soil. Earthworm 8-day bioaccumulation assays and root growth assays have shown the value of assessing the bioavailability of the residues. Mass balance experiments have utilized radiolabeled atrazine and metolachlor to ascertain the complete metabolism and binding profile of those two pesticides in phytoremediation studies.     

Differential resistance among host and non-host species underlies the variable success of the hemi-parasitic plant Rhinanthus minor

BACKGROUND AND AIMS: Rhinanthus minor is a root hemiparasitic plant that attacks a wide range of host species which are severely damaged by the parasite. Rhinanthus minor also attempts unsuccessfully to form connections to a range of non-hosts which in contrast are not damaged by the parasite; however, the underlying physiological basis of these differences is not fully understood. METHODS: Biomass of host-parasite combinations was studied, and histology, electron microscopy and FT-IR microspectroscopy were used to determine the cellular-level interactions between Rhinanthus haustoria (the parasite's connective structure) and the roots of a range of potential host species. RESULTS: Two distinct defence responses were observed in the non-host forbs Plantago lanceolata and Leucanthemum vulgare. Firstly, L. vulgare was able to encapsulate the parasite's invading structures preventing it from gaining access to the stele. This was supported by FT-IR microspectroscopy, used to monitor lignification in response to Rhinanthus haustoria. Secondly, host cell fragmentation was observed at the interface between the parasite and P. lanceolata. Growth data confirmed the non-host status of the two forbs whilst, in contrast, grasses and a legume which were good hosts showed no evidence of defence at the host/parasite interface. CONCLUSIONS: Variable resistance to Rhinanthus is shown for the first time to be controlled by cellular-level resistance to haustoria by either cell fragmentation or lignification at the host/parasite interface.     

Reaching a Better Understanding of the Control of Bimanual Movements in Older Adults

The ability to interact skilfully with the environment is essential for independent living and therefore a critical factor for the aging population. Here we investigate the differences between young and older adults in a bimanual reaching task where the goal is to bring two objects together to the same location with a synchronous placement. Older (mean age 74) and young (mean age 20) adults were asked to pick up two spatially disparate objects, one in each hand, and bring them together to place them in one of three trays laid out in front of them from left to right. The results showed that the older adults were no more detrimentally affected than the young by asymmetric bimanual movements compared to symmetric ones, and both groups completed their movements in the same time. Nevertheless, compared to the young, the older adult group produced reaches characterised by higher peak velocities (although this effect was marginal), shorter hover times, and where the movement distance varied for each hand the scaling of the kinematic profile across the two limbs diverged from that found with younger participants. They then spent longer than the young in the final adjustment phase and during this phase they made more adjustments than the young, and as a result were more synchronous in terms of the final placement of the objects. It seems that the older adults produced reach movements that were designed to reach the vicinity of the tray quite rapidly, after which time they made discreet adjustments to their initial trajectories in order to exercise the precision necessary to place the objects in the tray. These findings are consistent with the idea that older adults have problems using online control (as they wait until they can fixate both objects before making adjustments).     

101 Effect of Karlodinium Micrum Toxin on Success of the Parasitic Dinoflagellate Amoebophyra SP.

Parasitic dinoflagellates of the genus Amoebophrya infect and kill bloom‐forming dinoflagellates, including the toxic species Karlodinium micrum. Unlike non‐toxic hosts, K. micrum is partially resistant to infection, a trait that may be related to toxin production. Here we tested the hypothesis that parasitism of K. micrum is inversely related to toxin concentration in the culture medium. Time‐course studies were conducted to determine the influence of extracted toxin and toxin carrier (methanol) on host growth, parasite prevalence, and parasite load. Results indicate that methanol concentrations below 0.1% have no effect on these variables. When methanol concentration was maintained below 0.1%, extracted toxin equivalent to 100 to 10,000 K. micrum per ml had no effect on host abundance. We are currently analyzing sample to assess the fate of Amoebophrya dinospores when exposed to K. micrum toxin. We will also consider the effect of intracellular host toxin on parasite success, by examining the fate of Amoebophrya dinospores when inoculated to K. micrum cultures that express different levels of toxin production. Understanding the effect of toxins on parasite success will contribute to our knowledge of host‐parasite biology and provide insight into the role of dinoflagellate toxins as a defense against parasitism.     

PARASITISM OF PHOTOSYNTHETIC DINOFLAGELLATES BY THREE STRAINS OF AMOEBOPHRYA (DINOPHYTA): PARASITE SURVIVAL,INFECTIVITY, GENERATION TIME,AND HOST SPECIFICITY1

Amoebophrya ceratii (Koeppen) Cachon is an obligate parasite of dinoflagellates and may represent a species complex. However, little is known about the biology and host range of different strains of Amoebophrya Cachon. Here, we determined parasite generation time and dinospore infectivity, survival, and ability to infect nonprimary hosts for strains of Amoebophrya from Akashiwo sanguinea (Hirasaka) G. Hansen et Moestrup, Gymnodinium instriatum (Freudenthal et Lee) Coats comb. nov., and Karlodinium micrum (Leadbeater et Dodge) J. Larsen. Akashiwo sanguinea was readily infected, with parasite prevalence reaching 100% in dinospore:host inoculations above a 10:1 ratio. Parasitism also approached 100% in G. instriatum, but only when inoculations exceeded a 40:1 ratio. Karlodinium micrum appeared partially resistant to infection, as parasite prevalence saturated at 92%. Parasite generation time differed markedly among Amoebophrya strains. Survival and infectivity of dinospores decreased over time, with strains from G. instriatum and A. sanguinea unable to initiate infections after 2 and 5 days, respectively. By contrast, dinospores from Amoebophrya parasitizing K. micrum remained infective for up to 11 days. Akashiwo sanguinea and G. instriatum were not infected when exposed to dinospores from nonprimary Amoebophrya strains. Karlodinium micrum, however, was attacked by dinospores of Amoebophrya from the other two host species, but infections failed to reach maturity. Observed differences in host–parasite biology support the hypothesis that Amoebophrya ceratii represents a complex of host‐specific species. Results also suggest that Amoebophrya strains have evolved somewhat divergent survival strategies that may encompass sexuality, heterotrophy during the “free‐living” dinospore stage, and dormancy.     

ENCYSTMENT OF THE DINOFLAGELLATE GYRODINIUM UNCATENUM: TEMPERATURE AND NUTRIENT EFFECTS1

Sexual reproduction and encystment of the marine dinoflagellate Gyrodinium uncatenum Hulburt were induced in nitrogen and phosphorus-limited batch cultures. Sexuality did not occur under nutrient-replete conditions even when growth rate was reduced by non-optimal temperatures. Growth was optimal over a broader temperature range than encystment and virtually no cysts were produced at some low and high temperatures where growth occurred. Most cells initiated sexuality as intracellular pools of each limiting nutrient reached minimum or subsistence levels as much as four days after extracellular nutrients were exhausted. High nitrogen cell quotas during the phosphorus experiment indicate that sexuality was induced by a shortage of phosphorus and not by an indirect effect on nitrogen uptake. Total cyst yield corresponded to successful encystment of 9–13% of the motile populations, yet 60–85% of the plateau-phase motile cells were planozygotes (swimming zygotes formed from fusing gametes). Batch culture studies monitoring total cyst yield may thus seriously underestimate the extent of sexuality. More importantly, the number of cysts produced in a dinoflagellate population may be significantly reduced by environmental factors acting on the cells after sexual induction and fusion.     

PHYLOGENY OF FOUR DINOPHYSIACEAN GENERA (DINOPHYCEAE,DINOPHYSIALES) BASED ON rDNA SEQUENCES FROM SINGLE CELLS AND ENVIRONMENTAL SAMPLES1

Dinoflagellates are a highly diverse and environmentally important group of protists with relatively poor resolution of phylogenetic relationships, particularly among heterotrophic species. We examined the phylogeny of several dinophysiacean dinoflagellates using samples collected from four Atlantic sites. As a rule, 3.5 kb of sequence including the nuclear ribosomal genes SSU, 5.8S, LSU, plus their internal transcribed spacer (ITS) 1 and 2 regions were determined for 26 individuals, including representatives of two genera for which molecular data were previously unavailable, Ornithocercus F. Stein and Histioneis F. Stein. In addition, a clone library targeting the dinophysiacean ITS2 and LSU sequences was constructed from bulk environmental DNA from three sites. Three phylogenetic trees were inferred from the data, one using data from this study for cells identified to genus or species (3.5 kb, 28 taxa); another containing dinoflagellate SSU submissions from GenBank and the 12 new dinophysiacean sequences (1.9 kb, 56 taxa) from this study; and the third tree combing data from identified taxa, dinophysiacean GenBank submissions, and the clone libraries from this study (2.1 kb, 136 taxa). All trees were congruent and indicated a distinct division between the genera Phalacroma F. Stein and Dinophysis Ehrenb. The cyanobionts containing genera Histioneis and Ornithocercus were also monophyletic. This was the largest molecular phylogeny of dinophysoid taxa performed to date and was consistent with the view that the genus Phalacroma may not be synonymous with Dinophysis.     

The discovery of benzoxazine sulfonamide inhibitors of NaV1.7: Tools that bridge efficacy and target engagement

The voltage-gated sodium channel Na_V1.7 has received much attention from the scientific community due to compelling human genetic data linking gain- and loss-of-function mutations to pain phenotypes. Despite this genetic validation of Na_V1.7 as a target for pain, high quality pharmacological tools facilitate further understanding of target biology, establishment of target coverage requirements and subsequent progression into the clinic. Within the sulfonamide class of inhibitors, reduced potency on rat Na_V1.7 versus human Na_V1.7 was observed, rendering in vivo rat pharmacology studies challenging. Herein, we report the discovery and optimization of novel benzoxazine sulfonamide inhibitors of human, rat and mouse Na_V1.7 which enabled pharmacological assessment in traditional behavioral rodent models of pain and in turn, established a connection between formalin-induced pain and histamine-induced pruritus in mice. The latter represents a simple and efficient means of measuring target engagement.