Determinants of parasite distribution in Arctic charr populations: catchment structure versus dispersal potential.

Parasite distribution patterns in lotic catchments are driven by the combined influences of unidirectional water flow and the mobility of the most mobile host. However, the importance of such drivers in catchments dominated by lentic habitats are poorly understood. We examined parasite populations of Arctic charr Salvelinus alpinus from a series of linear-connected lakes in northern Norway to assess the generality of lotic-derived catchment-scale parasite assemblage patterns. Our results demonstrated that the abundance of most parasite taxa increased from the upper to lower catchment. Allogenic taxa (piscivorous birds as final host) were present throughout the entire catchment, whereas their autogenic counterparts (charr as final hosts) demonstrated restricted distributions, thus supporting the theory that the mobility of the most mobile host determines taxa-specific parasite distribution patterns. Overall, catchment-wide parasite abundance and distribution patterns in this lentic-dominated system were in accordance with those reported for lotic systems. Additionally, our study highlighted that upper catchment regions may be inadequate reservoirs to facilitate recolonization of parasite communities in the event of downstream environmental perturbations.

Baseline histopathological survey of a recently invading island population of 'killer shrimp', Dikerogammarus villosus.

Dikerogammarus villosus, an invasive amphipod, has recently been detected in UK freshwaters. To assess the potential for pathogen introduction with the invader, a year-long histopathology survey of the D. villosus population inhabiting the initial site of detection (Grafham Water, Cambridgeshire, UK) was conducted. Additional samples were collected from 2 other subsequently identified populations within the UK (Cardiff Bay and Norfolk Broads), and from established populations in France (River Rhine) and Poland (River Vistula). The data revealed a range of pathogens and commensals. Several pathogens occurring within continental populations were not present within the UK populations. Microsporidian parasites and a novel viral pathogen were amongst those not observed in the UK. The absence of these pathogens at UK sites may therefore impart significant survival advantages to D. villosus over native fauna, thereby increasing its success as an invader. The contrast in pathogen profile between UK and continental-invasive populations of D. villosus provides preliminary evidence for so-called 'enemy release' in UK populations of D. villosus and is suggestive of single-point introductions, rather than continual incursion events as previously observed throughout its continental invasive range. This baseline survey provides important data on the pathogen and commensal profile of a high-impact, invasive species early in its invasion history of the UK. It can be utilised to assess potential for temporal pathogen acquisition by non-native invasive aquatic species and to investigate competitive advantages placed upon this invader due to absence of important pathogens experienced within its native range.

Branchiobdellidan infestation on endangered white-clawed crayfish (Austropotamobius pallipes) in the UK.

Branchiobdellidans or crayfish worms are clitellate annelids and ectosymbionts of freshwater crayfish. An investigation of branchiobdellidan infestation was undertaken in a population of endangered white-clawed crayfish (Austropotamobius pallipes) in the river Aire, UK. Thirty two percent of animals were infested either by the adult parasite or their cocoons (n=107). Parasite burden increased with host size, but did not differ with sex. Observations of crayfish gill tissue revealed a strong positive relationship between melanization of filaments and parasite prevalence and burden. Taxonomic identification revealed that 1 species of branchiobdellidan was present, Branchiobdella astaci. The first sequences were generated for this species and phylogenetically analysed alongside published sequences for 5 other branchiobdellidan species in Europe. The position of B. astaci within the genus Branchiobdella was confirmed, and it was found to cluster as a sister group to B. parasita.

Host choice and penetration by Schistosoma haematobium miracidia.

Schistosome parasites commonly show specificity to their intermediate mollusc hosts and the degree of specificity can vary between parasite strains and geographical location. Here the role of miracidial behaviour in host specificity of Schistosoma haematobium on the islands of Zanzibar is investigated. In choice-chamber experiments, S. haematobium miracidia moved towards Bulinus globosus snail hosts in preference to empty chambers. In addition, miracidia preferred uninfected over patent B. globosus. This preference should benefit the parasite as patent snails are likely to have mounted an immune response to S. haematobium as well as providing poorer resources than uninfected snails. Miracidia also discriminated between the host B. globosus and the sympatric, non-host species Cleopatra ferruginea. In contrast, S. haematobium did not discriminate against the allopatric Bulinus nasutus. Penetration of the host by miracidia was investigated by screening snails 24 h after exposure using polymerase chain reaction (PCR) with S. haematobium specific DraI repeat primers. There was no difference in the frequency of penetration of B. globosus versus B. nasutus. These responses to different snail species may reflect selection pressure to avoid sympatric non-hosts which represent a transmission dead end. The distribution of B. nasutus on Unguja is outside the endemic zone and so there is less chance of exposure to S. haematobium, hence there will be little selection pressure to avoid this non-host snail.

Size matters: predation of fish eggs and larvae by native and invasive amphipods.

Invasive predators can have dramatic impacts on invaded communities. Extreme declines in macroinvertebrate populations often follow killer shrimp (Dikerogammarus villosus) invasions. There are concerns over similar impacts on fish through predation of eggs and larvae, but these remain poorly quantified. We compare the predatory impact of invasive and native amphipods (D. villosus and Gammarus pulex) on fish eggs and larvae (ghost carp Cyprinus carpio and brown trout Salmo trutta) in the laboratory. We use size-matched amphipods, as well as larger D. villosus reflecting natural sizes. We quantify functional responses, and electivity amongst eggs or larvae and alternative food items (invertebrate, plant and decaying leaf). D. villosus, especially large individuals, were more likely than G. pulex to kill trout larvae. However, the magnitude of predation was low (seldom more than one larva killed over 48 h). Trout eggs were very rarely killed. In contrast, carp eggs and larvae were readily killed and consumed by all amphipod groups. Large D. villosus had maximum feeding rates 1.6-2.0 times higher than the smaller amphipods, whose functional responses did not differ. In electivity experiments with carp eggs, large D. villosus consumed the most eggs and the most food in total. However, in experiments with larvae, consumption did not differ between amphipod groups. Overall, our data suggest D. villosus will have a greater predatory impact on fish populations than G. pulex, primarily due to its larger size. Higher invader abundance could amplify this difference. The additional predatory pressure could reduce recruitment into fish populations.

The Novel Small Molecule Inhibitor, OSU-T315, Suppresses Vestibular Schwannoma and Meningioma Growth by Inhibiting PDK2 Function in the AKT Pathway Activation.

Activation of PKB/AKT signaling, which requires PDK1 and PDK2 function, drives Vestibular Schwannoma (VS) and meningioma growth. PDK2 function is defined as a molecule that phosphorylates AKT-Ser473. Integrin-Linked Kinase (ILK) functions as PDK2 in PKB/AKT activation in many cancers; therefore, we hypothesized that OSU-T315, a small molecule ILK inhibitor, will inhibit the ILK-PDK2 function in PKB/AKT signaling activation in VS and meningioma cell growth. OSU-T315 decreased cell viability at IC50 < 2µM in VS (HEI193) and meningioma (Ben-Men-1) cell lines, in primary cells at < 3.5µM, while in normal primary Schwann cells at 7.1µM. OSU-T315 inhibits AKT signaling by decreasing phosphorylation at AKT-Ser473, AKT-Thr308, ILK-Ser246 and ILK-Thr173. In addition, OSU-T315 affected the phosphorylation or expression levels of AKT downstream proliferation effectors as well as autophagy markers. Flow cytometry shows that OSU-T315 increased the percentage of cells arrested at G2/M for both, HEI193 (39.99%) and Ben-Men-1 (26.96%) cells, compared to controls (21.54%, 8.47%). Two hours of OSU-T315 treatment increased cell death in both cell lines (34.3%, 9.1%) versus untreated (12.1%, 8.1%). Though longer exposure increased cell death in Ben-Men-1, TUNEL assays showed that OSU-T315 does not induce apoptosis. OSU-T315 was primarily cytotoxic for HEI193 and Ben-Men-1 inducing a dysregulated autophagy. Our studies suggest that OSU-T315 has translational potential as a chemotherapeutic agent against VS and meningioma.

Inherited microorganisms, sex-specific virulence and reproductive parasitism.

Parasites show an amazing repertoire of adaptations, highlighted by complex life cycles that allow both survival in the host and transmission among hosts. However, there is one heterogeneous group of microorganisms whose adaptations are perhaps even more surprising: parthenogenesis induction, feminization of genetic males, killing of male hosts and sperm-mediated sterilization of uninfected eggs. The common feature of these microorganisms is their mode of transmission: inheritance from mother to offspring. Here, we present an introduction to hereditary symbiosis, focusing on microsporidia and bacteria that manipulate host reproduction in arthropods (reproductive parasites). We also discuss the implications of one of these microorganisms, Wolbachia, for the control of arthropod pests and vectors and for the therapy of filarial diseases. Finally, we discuss whether some parasites of vertebrates might show sex-specific virulence.

Microsporidian life cycles and diversity: the relationship between virulence and transmission.

The microsporidia are obligate intracellular parasites which have diverse life cycles involving both horizontal and vertical transmission and parasitise a wide range of vertebrate and invertebrate hosts. In this paper we consider the life cycles and diversity of the microsporidia. We focus in particular on the relationship between parasite transmission and virulence and its implications for host-parasite coevolution. The use of horizontal and vertical routes of transmission varies between species and there is a strong link between transmission and virulence. Horizontal transmission is characterised by a high parasite burden and associated pathogenicity. In contrast, vertical transmission is characterised by low virulence, which has led to under-reporting of this important transmission route. Vertically transmitted microsporidia may also cause male killing or feminisation of their host, with implications for host population sex ratio and stability. Phylogenetic analysis shows that vertical transmission occurs in diverse branches of the Microspora. We find that there is evidence for vertical transmission in both vertebrate and invertebrate hosts and conclude that it is a common or possibly even ubiquitous transmission route within this phylum.

Transovarial transmission in the microsporidia.

The microsporidia are an ancient and diverse group of protists which have many unusual characteristics. These include prokaryotic-like 70s ribosomes, enclosed nuclear division, a lack of mitochondria and complex life cycles which frequently involve vertical transmission. This use of vertical transmission is unparalleled by other protists and is seen only among bacterial endosymbionts and sex ratio distorters and in host cell organelles. Transovarially transmitted microsporidia can have unusual and profound effects on host population sex ratios. We here consider the mechanisms of transovarial transmission and its implications for parasite evolution. We review parasite/host relationships and the evolution of virulence under transovarial transmission and consider the implications of these parasites for host ecology and evolution.

Incomplete feminisation by the microsporidian sex ratio distorter, Nosema granulosis, and reduced transmission and feminisation efficiency at low temperatures.

We investigated the effects of temperature on transovarial transmission and feminisation by Nosema granulosis, a microsporidian sex ratio distorter of the brackish water amphipod Gammarus duebeni. There was no difference in parasite transmission efficiency to the F(1) eggs of infected females maintained under two temperature conditions, 5 and 10 degrees C (89 and 86%, respectively). When F(1) individuals were screened as adults, the proportion infected was also similar at both temperatures (74 and 75%, respectively). However, transmission to the eggs of the F(2) generation was significantly reduced at low temperatures (61% at 5 degrees C and 91% at 10 degrees C). In addition, feminisation efficiency was reduced substantially at low temperatures; at 10 degrees C, a calculated 85% of infected males were feminised, but at 5 degrees C only 49% were feminised. This is the first evidence for incomplete feminisation and temperature-dependent transmission and feminisation by this sex ratio distorter. We examine the consequences for parasite spread and maintenance in natural populations using a model to predict parasite prevalence in large populations. Reduced feminisation at low temperatures impedes the spread of the parasite so that it attains a substantially lower frequency, or may even be excluded, from host populations.

Immunoglobulin E anaphylaxis in rabbits: mechanisms of pulmonary resistance and compliance changes.

Factors causing changes in pulmonary resistance and dynamic compliance with immunoglobulin (Ig) E anaphylaxis in spontaneously breathing rabbits were assessed in ventilated rabbits using tantalum bronchography and wet-to-dry wt ratios. Ventilated rabbits demonstrated changes in resistance and compliance similar to spontaneously breathing rabbits. Chlorpheniramine pretreatment prevented increases in resistance but not decreases in compliance. Anaphylaxis constricted small (less than 1 mm) airways 20.9 +/- 16.0% (mean +/- SD) and intermediate (between 1 and 3 mm) airways 21.8 +/- 19.8%. Chlorpheniramine (10 mg/kg) prevented small airway changes and attenuated those in intermediate airways. Chlorpheniramine prevented histamine-induced constriction of small (23.6 +/- 15.7%) and intermediate (17.6 +/- 15.0%) airways. Lung wet-to-dry wt ratios were unchanged. Changes in resistance and compliance during rabbit IgE anaphylaxis are not due to changes in tidal volume or frequency. Histamine, via H1 receptors, is the principal mediator of pulmonary resistance increases but not dynamic compliance reductions. Chlorpheniramine-sensitive increases in resistance are caused by constrictions of intermediate and small airways, whereas the chlorpheniramine-resistant decrease in compliance is not caused directly by constriction of the smallest measurable airways (0.25 mm) or changes in lung water.

Chronic lateral ventricle infusion of a pineal gland-derived decapeptide alters pulsatile secretion of LH in rats.

The object of this investigation was to determine whether chronic lateral ventricle infusion of a pineal gland-derived antigonadotropic decapeptide (AGD) would affect pulsatile luteinizing hormone (LH) release in conscious, unrestrained male rats. Adult male Harlan SD rats were bilaterally orchiectomized and maintained under conditions of controlled photoperiods and temperature. After three (Experiment one) or four (Experiment two) weeks each was fitted stereotaxically with a stainless steel cannula for infusion into the right lateral ventricle. Each cannula was attached to a subcutaneous osmotic minipump filled either with artificial cerebrospinal fluid (CSF) or AGD in CSF (0.5 microgram/microliter). CSF (1.0 microliter/hr) or the AGD (0.5 microgram/microliter hr) was infused over a period of four days. Blood samples for determined of LH by radioimmunoassay were obtained at five minute intervals from a Tygon microbore cannula inserted via a femoral artery into the abdominal aorta. LH pulses were defined and identified with a computerized deconvolution algorithm designed to determine spontaneous LH secretory events. Although mean LH levels were not significantly reduced, LH secretory pulse frequency and nadirs were significantly decreased by ADG infusion (p<0.01). Additionally, LH secretory pulse amplitude and LH secretory response to LHRL administration were significantly increased (p<0.01) by AGD treatment. These results confirm initial reports of depressive effects of the AGD on LH secretion and support its hypothesized central site of action.

Direct effects of luteal regression on anterior pituitary response to GNRH.

The preovulatory period of the ewe is marked by a dramatic decrease in concentrations of progesterone in serum during the late luteal phase, followed by elevated luteinizing hormone (LH) secretion, final follicular maturation and ovulation. This experiment was designed to ascertain the extent to which removal of endogenous progesterone negative feedback at the anterior pituitary gland, independent of effects at the hypothalamus, promotes increased secretion of LH in the hours immediately after induction of luteolysis. Estrus was synchronized in ovary-intact ewes with two injections of prostaglandin F2 alpha (PGF2 alpha) analog given 10 d apart (Day 0 = second day after the second PGF2 alpha injection). Ewes were subjected to hypothalamic-pituitary disconnection (HPD; n = 6) on Day 3 and were pulsed with gonadotropin-releasing hormone (GnRH). Ewes were used during the estrous cycle or received approximately 400 IU pregnant mare serum gonadotropin (PMSG) on Day 2 to stimulate ovulation; there was no difference (P < 0.10) in ovulation rate or progesterone production between these two groups. Luteal regression was induced by injection of PGF2 alpha analog on approximately Day 10 of the estrous cycle. Blood samples were collected around exogenous GnRH pulses before and at 2- or 4-hr intervals after PGF2 alpha administration and concentrations of LH and progesterone determined. At 4, 12, and 24 hr after PGF2 alpha administration, mean serum progesterone levels in all ewes had decreased by 54.7%, 66.2% and 89.4%, respectively (P < 0.05) from pre-injection levels. The decrease in progesterone was associated with an increase (P < 0.01) in LH pulse amplitude with means at 4-hr post-PGF2 alpha ranging from 190% to 288% of pre PGF2 alpha values. Mean serum LH levels were also increased (P < 0.01) within 4 hr of PGF2 alpha administration and remained elevated at all but the 24-hr time point. The timing of this increase (within 4 hr) indicates that it is independent of changes in serum estradiol concentrations, which do not increase for at least 16 hr after induction of luteolysis. Thus, removal of endogenous progesterone negative feedback at the anterior pituitary gland in the hours immediately after induction of luteolysis seems to play a role in facilitating LH release independently of hypothalamic action.

Field study on the epidemiology and pathogenicity of different isolates of bovine Ostertagia spp.

The epidemiological features of three different isolates of bovine Ostertagia spp under similar initial levels of larval challenge were compared in the field. Two of the isolates, consisting mainly of Ostertagia ostertagi, and a low proportion of Skrjabinagia lyrata conformed in epidemiological behaviour with those investigated by previous workers, though the worm burdens which established did not give rise to the expected clinical signs. The third isolate behaved in a different way, yielding very high faecal egg counts which were followed by high pasture larval counts, heavy worm burdens and severe clinical disease. This isolate, while consisting mainly of O ostertagi and a few S lyrata, also contained a proportion of O leptospicularis, and it is suggested that this species may influence the dynamics of the host-parasite relationship in bovine ostertagiasis.

Observations on the infectivity and pathogenicity of three isolates of Ostertagia spp sensu lato in calves.

After experimental infection of three groups of calves with three different defined isolates of Ostertagia spp sensu lato a marked variation in the infectivity and degree of pathological change was noted. The most highly infective and pathogenic isolate contained approximately 30 per cent O leptospicularis in addition to O ostertagi (70 per cent) and a negligible number of Skrjabinagia lyrata. The other two isolates consisted solely of O ostertagi (approximately 90 per cent) and S lyrata (approximately 10 per cent) and showed comparable infectivity and pathogenicity to that commonly recorded. The greater pathogenicity of the isolate containing O leptospicularis was attributed to the higher infectivity and the greater damage caused to the gastric mucosa by individual parasites when compared with O ostertagi.

1992 NAPNAP membership survey: part II. Practice characteristics of pediatric nurse practitioners indicate greater autonomy for PNPs.

The 1992 membership survey, authorized by the Executive Board of NAPNAP as part of an ongoing plan to survey members every 4 years, had three foci: (a) demographic characteristics of NAPNAP members, (b) practice characteristics of NAPNAP members, and (c) opinions of NAPNAP members related to health care issues. Information gathered from this membership survey will be used to assist in planning NAPNAP programs and direction, to advocate for pediatric nurse practitioners and for NAPNAP, and to inform health professionals, policy makers, and the general public about characteristics of a pediatric nurse practitioner and the work pediatric nurse practitioners do. NAPNAP members received the survey during the summer 1992, and 65% of the random sample of 800 were returned, a clear indication of strong interest on the part of NAPNAP members to be heard. This article, the second of two describing survey results, presents data describing characteristics of members' practice and the clients they serve.

1992 NAPNAP membership survey. Part I: Member characteristics, issues, and opinions. National Association of Pediatric Nurse Associates and Practitioners.

Significant changes have occurred in the 4 years since the last NAPNAP membership survey was conducted. Membership in NAPNAP has shown strong, sustained growth; the role of nurses in advanced practice has expanded greatly, and an increasing possibility exists for national health care reform. In response to these changes and as a part of its long-range strategic planning, the NAPNAP Executive Board, in 1991, authorized an ongoing plan to conduct a membership survey every 4 years. The 1992 membership survey was mailed to a random sample of 800 NAPNAP members. Sixty-five percent were returned. The survey collected information on (a) demographic characteristics of NAPNAP members, (b) practice characteristics of NAPNAP members, and (c) opinions of NAPNAP members related to health care issues. This article presents summary data on demographic characteristics, issues, and opinions of NAPNAP members.

1997 NAPNAP membership survey.

The 1997 NAPNAP membership survey examined demographic and practice characteristics of NAPNAP members. Surveys were mailed to a random sample of 800 NAPNAP members in spring 1997. Five hundred seventy-three surveys (70%) were returned. Two hundred eighty-eight respondents (50.8%) stated that they worked full time as a nurse practitioner (NP); 158 (27.9%) worked part time as an NP; and 121 (21.3%) were not employed as an NP. Data relating to the nature and scope of pediatric nurse practitioner practice were compiled from the responses of those who worked either full time or part time. Characteristics of pediatric nurse practitioners, their practice, and the clients they serve are described. Comparisons are made with data from previous NAPNAP membership surveys.

Evaluation of buffer zone effectiveness in mitigating the risks associated with agricultural runoff in Prince Edward Island.

To minimize the risk posed by runoff from row crops, Prince Edward Island introduced buffer legislation in 2000. The legislation mandates 10-m and 20-m buffers, respectively, for moderate sloped (i.e. <5%) and steep sloped (i.e. >5%) agricultural fields that border streams. Since 2001, Environment Canada has been evaluating the effectiveness of various buffer widths on operational farms in reducing toxicity and contaminant concentrations in runoff. Sample collectors, placed in 44 fields at the field edge (0m), 10m and at distances out to 30m, collected overland flow following rainfall-induced runoff events. Samples were collected within 24 hours of an event and analysed for seven pesticides (endosulfan, chlorothalonil, carbofuran, linuron, metribuzin, metalaxyl, mancozeb), water quality parameters and Daphnia magna toxicity. The 10-m buffer required for moderate sloped fields was effective at reducing contaminant concentrations but not always to less than lethal concentrations to Daphnia magna. Limited data beyond 10m for fields of both slope types precluded making recommendations on a suitable buffer width for shallow sloped fields and evaluating the effectiveness of 20-m buffers for steep sloped fields. When paired data were combined and statistically tested for all fields, the studied pesticides underwent a 52-98% and 68-100% reduction in aqueous and particulate concentrations within 10m and 30m, respectively. In addition, by 10m, soluble phosphorus, nitrate-nitrogen and total suspended solids were reduced by 34%, 38% and 64%, respectively. Results suggest buffer zones on operational farms are capable of achieving contaminant reductions comparable to those reported for controlled experiments. Inconsistent siting of sample collectors beyond 10m limited the evaluation of the effects of field slope and buffer width on buffer effectiveness on working farms. Future studies on buffer efficiency on operational farms should focus on building the data set beyond 10m and evaluating load reductions.