Kinetic resonances and stratification of the positive column of a discharge.

Resonance formation of the electron velocity distribution function (EDF) in an inert gas dc discharge at low pressures and small currents is analyzed on the basis of an accurate numerical solution of the Boltzmann kinetic equation in spatially periodic sinusoidally modulated striation-like fields. Calculations are performed for neon at pressures around 1 Torr . The dependences of the EDF, electron density and mean energy, and excitation rate on the electric field spatial period length are investigated.

Anisotropy of the electron component in a cylindrical magnetron discharge. II. Application to real magnetron discharge.

The physical processes occurring in electrode regions and the positive column of a cylindrical magnetron discharge in crossed electric and magnetic fields are investigated based on the solution of the Boltzmann kinetic equation by a multiterm decomposition of the electron phase space distribution function in terms of spherical tensors. The influence of the distribution function anisotropy on the absolute values and radial profiles of the electron density and rates of various transport and collision processes is analyzed. The spiral lines for the directed particle and energy transport are obtained to illustrate the anisotropy effects in dependence on the magnetic field.

Anisotropy of the electron component in a cylindrical magnetron discharge. I. Theory of the multiterm analysis.

A general multiterm representation of the phase space electron distribution function in terms of spherical tensors is used to solve the Boltzmann kinetic equation in crossed electric and magnetic fields. The problem is formulated for an axisymmetric cylindrical magnetron discharge with the homogeneous magnetic field being directed axially and the electric field between the coaxial cathode and anode varying in radius only. A spherical harmonic representation of the velocity distribution function in Cartesian coordinates becomes especially cumbersome in the presence of the magnetic field.

Allergen-specific IgE and IgG4 are markers of resistance and susceptibility in a human intestinal nematode infection.

IgG4 has been proposed to act as a 'blocking antibody' due to its ability to compete for the same epitopes as IgE thus preventing IgE-dependent allergic responses. IgG4 and IgE are both elevated in helminth infections and strong anti-parasite IgE responses are associated with resistance to infection. We wished to determine the relationship between anti-parasite IgG4 and IgE and Ascaris lumbricoides infection status.

Parasite populations in the brown rat Rattus norvegicus from Doha, Qatar between years: the effect of host age, sex and density.

A total of 179 urban rats were sampled in the city of Doha in Qatar across the winter seasons (February-April) of 2002 and 2003. Only two parasites were identified, with overall prevalences of 35.8% and 41.

Isolates of Trichuris muris elicit different adaptive immune responses in their murine host.

The J and S isolates of Trichuris muris have different infection profiles in C57BL/6 mice; J worms are expelled, S worms survive to chronicity. Building on this, the ability of the J and S isolates to survive, and the quality of the immune response induced was explored in three different strains of mouse. The resistant BALB/c mouse mounted a strong Th2 response against both isolates, which were quickly expelled.

Apicomplexan parasites: environmental contamination and transmission.

The Apicomplexa are a diverse group of intracellular parasitic protists. The majority of species from the classes Coccidea, Haemosporea and Piroplasmea are responsible for widespread diseases of humans and domestic animals. Oocysts of these parasites can persist for long periods of time in the environment (i.

Medium-term temporal stability of the helminth component community structure in bank voles (Clethrionomys glareolus) from the Mazury Lake District region of Poland.

The structure of helminth communities in wild rodents is subject to seasonal variation, and is dependent on host age within years. Although between-year variation has been monitored, seldom has it been assessed rigorously by appropriate multifactorial analysis with potentially confounding factors taken into account. In this study we tested the null hypothesis that despite seasonal, host age and sex effects, helminth communities should show relative stability between years.

Assessment of the anthelmintic effect of natural plant cysteine proteinases against the gastrointestinal nematode, Heligmosomoides polygyrus, in vitro.

We examined the mechanism of action and compared the anthelmintic efficacy of cysteine proteinases from papaya, pineapple, fig, kiwi fruit and Egyptian milkweed in vitro using the rodent gastrointestinal nematode Heligmosomoides polygyrus. Within a 2 h incubation period, all the cysteine proteinases, with the exception of the kiwi fruit extract, caused marked damage to the cuticle of H. polygyrus adult male and female worms, reflected in the loss of surface cuticular layers.

The modulatory influence of Trypanosoma brucei on challenge infection with Haemonchus contortus in Nigerian West African Dwarf goats segregated into weak and strong responders to the nematode.

Although Nigerian West African Dwarf (WAD) goats are relatively resistant to infection with Haemonchus contortus and are also trypanotolerant, natural outbreaks of both infections are known to occur. Despite their relative resistance to H. contortus WAD goats nevertheless show variability in response phenotype and it was of interest to examine the effect of this variability on the outcome of concurrent trypanosome infection.

Associations between filarial and gastrointestinal nematodes.

The possibility that positive or negative associations occur between the filarial nematode Onchocerca volvulus and the gastrointestinal nematodes Ascaris lumbricoides and Trichuris trichiura was investigated in 205 children attending three schools in central Cameroon. Despite the closeness of their locations, marked differences between the schools were detected with respect to the number of species carried, the prevalence of O. volvulus and T.

Remote site production of sterile purified water from available surface water.

A water purification and sterilization device was tested for its functional capabilities. Challenge water consisting of potable water augmented with bacteria, endotoxin, virus, suspended solids, and dissociable ions (sodium chloride, lead or arsenic salts) was passed through the device. The product water quality attributes were analyzed.

An in vitro larval motility assay to determine anthelmintic sensitivity for human hookworm and Strongyloides species.

With the implementation of programs to control lymphatic filariasis and soil-transmitted helminths using broad spectrum anthelmintics, including albendazole and ivermectin, there is a need to develop an in vitro assay for detection of drug resistance. This report describes an in vitro assay for measuring the effects of ivermectin and benzimidazoles on the motility of larvae of the hookworm species Ancylostoma ceylanicum, A. caninum, and Necator americanus, and Strongyloides species including Strongyloides stercoralis, and S.

T helper cell type 2 responsiveness predicts future susceptibility to gastrointestinal nematodes in humans.

Some humans are persistently more susceptible to gastrointestinal nematodes than others. Here, for the first time, susceptibility to reinfection has been linked to host cytokine responses. Ascaris lumbricoides and Trichuris trichiura abundance was assessed immediately before and 8-9 months after deworming in a Cameroonian population (starting n=191).

Cytokine response profiles predict species-specific infection patterns in human GI nematodes.

This study investigated associations between pre-treatment cytokine expression and infection patterns, before and after de-worming, in humans exposed to two gastrointestinal nematode species. Quantitative measures of Ascaris lumbricoides and Trichuris trichiura infection (based on faecal egg counts) were estimated immediately before and 8-9 months after treatment in a Cameroonian population. Whole blood cytokine responses to parasite-derived antigens were assayed immediately pre-treatment.

Variation in the helminth community structure in spiny mice (Acomys dimidiatus) from four montane wadis in the St Katherine region of the Sinai Peninsula in Egypt.

We compared helminth communities in spiny mice (Acomys dimidiatus) from 4 wadis in the arid montane region of the southern Sinai in Egypt, in a 4-week period in late summer. Total helminth species richness was 14 (8 nematodes, 5 cestodes and 1 acanthocephalan) with 94% of mice carrying at least 1 species and an overall mean species richness of 1.85.

Copro-antigen capture ELISA for the detection of Teladorsagia (Ostertagia) circumcincta in sheep: improvement of specificity by heat treatment.

A copro-antigen capture ELISA for the detection of Teladorsagia circumcincta infection in sheep was developed and evaluated. Experiments with faeces from worm-free sheep, that had been spiked with known concentrations of excretory-secretory (E-S) antigen indicated that a positive signal was generated with 180 ng of E-S/ml. A nested design, based on 8 infected and 8 worm-free sheep, was employed to assess the stages during sample preparation contributing to variation in signal from the assay.

Variability in the resistance of the Nigerian West African Dwarf goat to abbreviated escalating trickle and challenge infections with Haemonchus contortus.

The West African Dwarf (WAD) goat is known to be relatively resistant to infection with Haemonchus contortus. An experiment was carried out to assess variability in resistance under escalating trickle and single pulse challenge infection protocols. Thirty two 7-8 month old goats were subjected to trickle infection beginning with a thrice weekly dose of 100 L3 and increasing to 500 L3 by week 5, the last dose being administered on D30.

Density-dependent effects on the survival and growth of the rodent stomach worm Protospirura muricola in laboratory mice.

The spirurid nematode, Protospirura muricola, is of intrinsic interest as a rodent model of gastric nematode infections. Since worm burdens can be very heavy in nature, density dependent processes may constrain parasite growth. Laboratory mice (BKW) were exposed to varying doses of infective larvae of P.

Factors affecting the component community structure of haemoparasites in common voles ( Microtus arvalis) from the Mazury Lake District region of Poland.

The prevalence and abundance of infections with haemoparasites were studied over a 4-year period in Microtus arvalis (common vole, n =321) sampled from fallow grassland sites in north-eastern Poland. Total species richness was five (prevalence= Haemobartonella sp. 63.

Th2 cytokines are associated with reduced worm burdens in a human intestinal helminth infection.

Although T helper 2 (Th2) cytokines are known to be critical in the generation of protective immunity against intestinal helminths in mouse models, it is unclear whether they are important in natural immunity against gut helminthiases in humans. Therefore, we investigated cytokine production in ex vivo whole-blood cultures in response to Ascaris lumbricoides antigen and mitogen in a cross-section of a community where the parasite is hyperendemic. The intensity of A.

Polyparasitism with Schistosoma haematobium and soil-transmitted helminth infections among school children in Loum, Cameroon.

Prevalence and abundance of Schistosoma haematobium and soil-transmitted helminths (STH) were assessed among a total of 1600 pupils (urine, n = 1190; faecal samples, n = 1454) attending five schools in Loum, Littoral Province, Cameroon, with the specific aim of assessing the extent of polyparasitism and the extent to which infections were focused in particular subsets of the study group. Prevalence of S. haematobium was 62.

Preliminary molecular characterization of Cryptosporidium parvum isolates of wildlife rodents from Poland.

Isolates of Cryptosporidium were collected from 3 species of woodland and field rodents (Clethrionomys glareolus, Microtus arvalis, and Apodemus flavicollis) and were characterized by polymerase chain reaction amplification and sequencing of fragments of the oocyst wall protein (COWP) gene and of the 18S ribosomal RNA gene. Sequence analysis of these markers revealed that the animals were infected with C. parvum, and that the genotype involved was almost identical to the mouse genotype previously described from Mus musculus.

Resonance effects in the electron distribution function formation in spatially periodic fields in inert gases.

The calculations of the electron distribution function (EDF) in striationlike, sinusoidally modulated electric fields were performed to determine the dependence on spatial period length. The calculations were done for a discharge in neon at pR=2 Torr cm, i/R=5 mA/cm, and electric field E/p=1.9 V cm(-1) Torr(-1).