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E R James

Publications and source records attributed to E R James.

At least 37 records · Page 2Linked to original sources
PubMed1990

Hydrogen peroxide is the most toxic oxygen species for Onchocerca cervicalis microfilariae.

The toxicity of the active oxygen species hydrogen peroxide, superoxide radical, hydroxyl radical and singlet oxygen to microfilariae (mf) has been studied in vitro, using active oxygen-generating systems and scavengers/inhibitors. Mf viability was monitored by uptake of the radiolabel, [3H]2-deoxy-D-glucose. Hydrogen peroxide and singlet oxygen, but not superoxide radical or hydroxyl radical, are toxic for mf. Hydrogen peroxide was toxic for mf within 2 h at concentrations as low as 5 microM, an amount eosinophils have been shown to release in vitro (Weiss et al. 1986). Catalase and thiourea, but not inactivated catalase, superoxide dismutase (SOD), singlet oxygen scavengers, or hydroxyl radical scavengers, protected mf. Mf have relatively high levels of endogenous SOD but no measurable glutathione peroxidase and low levels of catalase when compared with other parasites (Callahan, Crouch & James, 1988). The low levels of hydrogen peroxide-scavenging enzymes correlate well with mf sensitivity to hydrogen peroxide and the protective effect of exogenous catalase.

Animals↗
PubMed1990

Antigenic and dynamic properties of the surface of Onchocerca microfilariae.

We analyzed the antigenicity and stability of the surface of skin microfilariae (mf) of Onchocerca cervicalis, a horse parasite. These mf express antigens on their surface that are cross-reactive with the cattle parasite O. lienalis and with the human parasite O. volvulus. The surface of living O. cervicalis mf was radioiodinated using Iodogen and the labeled components were solubilized in buffers containing sodium dodecyl sulphate (SDS), or extracted with the milder detergent octyl-beta-D-glucopyranoside (OGP). Electrophoresis of this material showed seven prominent bands, one of which (14 kDa) was specifically precipitated by antisera from rabbits immunized with mf from either O. cervicalis, O. lienalis, or O. volvulus, and by human sera obtained from infected individuals in Chiapas, Mexico. Other components were precipitated by either the rabbit or the human sera. In addition, antisera from mice immunized with O. cervicalis mf bound specifically to the surface of freeze-thawed uterine O. lienalis and O. volvulus mf as detected by immunofluorescence. This fluorescence was lost from the surface of O. cervicalis mf in a temperature-dependent fashion. Live mf incubated on ice with mouse anti-mf antisera and secondary FITC-GAM, showed uniform surface fluorescence. When these mf were incubated at 37 degrees C, but not at 0 degrees C, the fluorescent pattern changed with time. First, small non-fluorescent patches arose, followed by an increasingly wide belt devoid of fluorescence, and finally, no visible fluorescence. These changes in the mf surface suggest potential mechanisms for immune evasion by filarial parasites.

Animals↗
PubMed1989

Extracellular proteases of Onchocerca.

Two important events in infection by Onchocerca parasites involve cutaneous tissue migration by larval stages. L3 larvae migrate from the blackfly bite site to subcutaneous locations for adult development, and microfilariae from subcutaneous nodules to distant regions of the skin and sometimes the eye. By analogy to other tissue-invasive helminth larvae, it has been proposed that migration of Onchocerca larvae through cutaneous tissue is facilitated by secretion of proteolytic enzymes. To test this hypothesis, neutral protease activity capable of degrading a model of cutaneous extracellular matrix was assayed using live L3 larvae of O. lienalis and microfilariae of O. cervicalis and O. cervipedis. Five hundred L3 larvae degraded most of the matrix within 24 hr of incubation. Substrate gel electrophoresis and other protease assays showed a 43-kDa serine elastase was secreted by O. lienalis L3 larvae. Larvae and adults of the free-living nematode, Caenorhobditis elegans, by contrast, did not secrete neutral proteases and large numbers of motile C. elegans juveniles and adults produced no degradation of the extracellular matrix. Expression of Onchocerca neutral protease activity was stage specific. No protease activity corresponding to that seen in L3 larvae was found in adult worms. Microfilariae of O. cervicalis and O. cervipedis produced both a serine and a metalloprotease, but the level of protease activity of these microfilariae was substantially lower than that of L3 larvae, and no significant protease activity was detected in extracts of O. lienalis microfilariae. Uterine microfilariae of O. cervicalis had different protease species than skin microfilariae, suggesting that changes in protease expression parallel other morphologic and biochemical changes in the development of skin microfilariae. The serine protease of L3 larvae probably plays an important parasitic function, facilitating L3 migration from the blackfly bite site to distant regions of the body where adults will develop and form nodules. The protease activity of microfilariae, while individually considerably less than that of L3 larvae, may still contribute to the tissue destruction seen with heavy skin densities of microfilariae.

Animals↗
PubMed1989

An in vitro radiolabel uptake viability assay for Onchocerca microfilariae.

A radiolabel uptake viability assay for Onchocerca cervicalis using [3H]2-deoxy-D-glucose in Hanks' balanced salt solution, pH 7.5, at 30 C is described and compared to the traditional visual motility assay. A correlation of r = 0.92 between the assays was found, with the radiolabel uptake method apparently a more sensitive indicator of microfilarial viability.

Animals↗
PubMed1988

Helminth anti-oxidant enzymes: a protective mechanism against host oxidants?

Highly reactive oxygen species potentially represent a powerful effector mechanism against parasites. They are produced during normal cellular metabolism, especially by activated phagocytes, and also by some anti parasitic drugs. From studies to date, all protozoan and helminth parasites appear to have one or more anti-oxidant enzymes able to scavenge or quench the reactive oxygen species, and there is strong evidence that such enzymes play a crucial role in protecting against the host response. This detailed review, which summarizes studies on the major anti-oxidant enzymes of helminths, clearly illustrates that methods to block or overcome anti-oxidant protection may be a fertile field in the search for improved ways to inhibit parasite survival.

Journal Article↗
PubMed1988

Cryopreservation of Trichinella spiralis muscle stage larvae.

A cryopreservation protocol for Trichinella spiralis muscle stage larvae is described. Larvae are pretreated in 10% bile at 37 degrees C for 1 hr to induce an increase in surface permeability, than incubated in 20% v/v ethanediol at 37 degrees C for 10 min, transferred to 0 degrees C for a second incubation step of 15 min in a v/v mixture of 33% ethanediol: 33% methanol: 34% saline at 0 degrees C followed by rapid cooling (approximately 5,100 degrees C min-1) of aliquots distributed onto glass coverslips. The larvae are thawed by dropping the coverslips into 2 ml saline at room temperature (20 degrees C) and immediately agitating, which simultaneously dilutes (1:100) the cryoprotectants. Groups of 6 mice were infected with muscle stage larvae by gastric intubation. Five days post-infection 14.5 +/- 3.2% of control untreated unfrozen MSL and 16.5 +/- 4.1% of unfrozen bile and cryoprotectant treated controls were recovered as adult worms from the small intestine. Of the cryopreserved larvae, 1.1 +/- 0.4% were recovered as adults, which represents 7.6% compared to the untreated unfrozen controls. When the bile pretreatment step was omitted fewer adult worms (0.09 +/- 0.04%) were recovered and no second generation muscle stage larvae were produced. Modifying this technique by omitting the first incubation step in 20% ethanediol and extending the second incubation step to 25 min yielded 72.3% recovery of T. nativa adult worms 5 days post-infection compared to unfrozen controls. The reproductive capacity index of bile treated cryopreserved T. spiralis was 2.5 +/- 0.6 compared to 51.8 +/- 18.8 for normal muscle stage controls.

Animals↗
PubMed1987

Equine ocular pathology ascribed to Onchocerca cervicalis infection: a re-examination.

Eyes from 292 old (15-20 years) horses originating in the eastern, southeastern and midwestern United States were examined for the presence of Onchocerca cervicalis microfilariae (mf) and concurrently for anterior and posterior segment ocular pathological changes. One-hundred-fifty-three animals (52.4%) were positive for dermal mf (range 0.03-5,364/mg). Of these, 60 animals had anterior segment changes. An additional 58 animals with pathological changes had no dermal mf. Mf were recovered from the ocular tissues of 18% of animals (range 0.07-29/mg). All animals with ocular mf were positive for dermal mf. Lesions most frequently encountered were punctate scleral opacities (in 14.0% of horses--7.2% with mf), temporal scleral viteligo (in 11.6%--6.8% with mf) and uveitis (11.0% of horses--6.2% with mf). Few significant posterior segment changes were seen. These data suggest that no ocular pathological changes represent reliable indicators for the presence of O. cervicalis infection.

Animals↗
PubMed1986

Partial protection of baboons against Schistosoma mansoni using radiation-attenuated cryopreserved schistosomula.

Three groups of five baboons were vaccinated in Kenya using three doses of 10,000 viable cryopreserved schistosomula attenuated with either 10, 20 or 60 krad 60Co-irradiation prepared in England. Animals were vaccinated at four-week intervals, challenged after a further six weeks with 2,000 cercariae and perfused at 10 weeks after challenge. High antibody titres to schistosomula mediating in vitro cytoadherence with P 388D1 macrophage-like cells were demonstrated in all vaccinated animals but not in controls. Significant titres to soluble egg antigen (SEA) were also demonstrated by ELISA in the 10 and 20 krad vaccinated groups following the first vaccination. The subsequent vaccinations and the challenge boosted this response considerably. Mean anti-SEA titres were only elevated above background in the 60-krad group six weeks after the third vaccination and in the challenge controls six weeks after challenge. Peripheral eosinophil counts were slightly reduced and neutrophil counts slightly elevated before challenge while eosinophil and erythrocyte counts were elevated and neutrophil counts depressed after challenge. PCV values were erratic in all groups. Eggs appeared in the faeces from six weeks after challenge and excretion rates were higher in all three vaccinated groups than in the challenge controls by necropsy 10 weeks after challenge. Body-weights were depressed in all groups after challenge but subsequently rose in the 10 and 20 krad groups. The 60 krad and challenge control groups lost 12.4% and 7.9% of body-weight respectively after challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Studies on the cryopreservation of Dictyocaulus viviparus (Nematoda) third-stage larvae.

Various cooling (0.1-5,100 degrees C min-1) and warming (20-6,800 degrees C min-1) rates, stepped cooling schedules and four cryoprotective additives (dimethyl sulphoxide, methanol, ethanediol and glycerol) were investigated in cryopreservation studies with Dictyocaulus viviparus third-stage larvae. Exsheathment with sodium hypochlorite was essential to achieve significant survival. With uninterrupted cooling, highest survival (30% normally motile) was achieved with rates of 10-70 degrees C min-1. Survival was higher (50-75%) using 1 degree C min-1 to -10 degrees C followed by plunging into liquid nitrogen. The optimum warming rate was 6,800 degrees C min-1. The use of cryoprotectants led to marginally lower survival while varying the suspending media had no significant effect on survival. X-irradiated, exsheathed third-stage larvae cryopreserved by the optimum protocol yielded 38.3 +/- 4.2% survival. Two calves each infected with 45,000 (15,000 viable) exsheathed, unirradiated, cryopreserved third-stage larvae harboured 494 worms (1.1% infectivity) and 355 worms (0.8%) at necropsy. Numbers of first-stage larvae in the faeces reached 420/g and 105/g respectively 27 days after infection.

Animals↗
PubMed1986

Leishmania donovani: immunization against infection as a function of parasite growth phase.

C57BL/6 mice were immunized against Leishmania donovani infection with a subcutaneous vaccination protocol. Groups received 3 injections at 4-day intervals combining glucan and killed promastigotes harvested from either logarithmic or stationary phase cultures. Controls were immunized with glucan alone, stationary or log phase promastigotes alone, or were untreated. All groups were challenged intravenously with stationary phase promastigotes at day 45 post-immunization. Results revealed that animals immunized with the glucan-killed parasite vaccine, utilizing promastigotes derived from either log (GPL) or stationary phase cultures (GPS), demonstrated significant resistance against infection as compared to controls or untreated mice. Additionally, the reduction in hepatic amastigote proliferation in mice immunized with GPS was significantly greater than in mice immunized with GPL.

Animals↗
PubMed1986

Invasion of the mouse eye by Onchocerca microfilariae.

Onchocerca cervicalis microfilariae (mf) were injected s.c. into the scalp between the eyes of CBA/H mice. Invasion was followed by slit-lamp biomicroscopy and H & E stained serial sections at varying times post infection. The first mf observed were found 24 hr p.i. on the corneal surface in tear fluid. At 48 hr mf were observed actively swimming in the anterior chamber and by 3 d in the corneal stroma. Histologically mf appeared in orbital muscle connective tissue, subcutaneously in the eyebrows at the eyelid/conjunctiva junction from 6 hr p.i. By 12 hr some mf had moved into the suprascleral muscle junctions, the sclera and into the superior corneal stroma. By 24 hr mf were present in larger numbers in all these sites. Mf were found in all eyes up to 42 d p.i. No mf were seen in any sections of the retina or optic nerve. Rabbit antiserum raised to mf, used in an avidin-biotin immunostain to check whether mf might have been hidden within the retinal nuclear layers, revealed no mf although they were plainly seen in other ocular tissues. Retinal invasion was induced by injection of mf into the lateral tail vein: serial sections revealed mf associated with blood vessels in the sclera, suprascleral muscle blocks and inner plexiform layer of the retina from 5 min p.i.

Animals↗
PubMed1985

Prevalence of equine onchocerciasis in southeastern and midwestern United States.

Of 664 horses reported to have originated in southeastern and midwestern United States, 341 (51.4%) were positive for Onchocerca cervicalis cutaneous microfilariasis. The highest prevalence of 68.8% was recorded for horses from Virginia. Horses with the highest concentrations of microfilariae (as high as 19,770 microfilariae/mg in 1 horse) were from the Southeast (Georgia, Florida, Tennessee, and Alabama). For horses from South Carolina, the prevalence of infection was 57.1%; from the Midwest (Kentucky, Illinois, Ohio, and Indiana), 54.4%; from North Carolina, 45.5%; from Pennsylvania, 7.7%; and from Minnesota, 5%. Histories and ages of the horses were not known, but most horses were approximately 15 years old. Compared with horses from other states, horses from Pennsylvania were younger, which may have accounted for their lower prevalence of infection.

Abattoirs↗
PubMed1985

A note on the efficacy of a new class of compounds, 9-acridanone-hydrazones, against Schistosoma mansoni in a primate--the baboon.

Five 9-acridanone-hydrazone compounds were tested against moderately heavy Schistosoma mansoni infections in baboons. They were administered as a single oral dose at a rate of 50 mg/kg body-weight. Compared with results from an untreated control baboon, four of the compounds showed high levels of activity judged by the reduction or elimination of faecal egg production, adult worms and tissue eggs.

Animals↗
PubMed1985

Comparison of the protective resistance induced by 60Co-irradiated cercariae and schistosomula of the WFFS and NMRI strains of Schistosoma mansoni.

Mice, CBA/HT6T6 and C57BL/10, were vaccinated with 1 X 350 or 1 X 500 Schistosoma mansoni cercariae or schistosomula attenuated with 20 or 56 krad 60Co irradiation and challenged with 200 cercariae. Protective resistance against homologous strain challenge was compared using the Winches Farm Field Station (WFFS) and Naval Medical Research Institute (NMRI) strains of S. mansoni. Maximal resistance to challenge was obtained in both strains of mice with cercariae or schistosomula of either WFFS or NMRI strain attenuated with 20 krad. Protection using organisms attenuated with 56 krad was significantly lower. Since previous studies with the two parasite strains have shown that the biological effects of irradiation are similar, the difference in the immunogenicity of the 56 krad-irradiated NMRI strain in this study from earlier studies must be due either to different local conditions for irradiation or to adaptation of the NMRI strain to a new laboratory environment. This finding may have important implications for vaccination studies and investigations of the mechanisms of immunity where radiation-attenuated parasites are used.

Animals↗
PubMed1985

Protection of sheep against Schistosoma bovis using cryopreserved radiation-attenuated schistosomula.

Three sheep were vaccinated with two doses of 3 krad-irradiated cryopreserved Schistosoma bovis schistosomula containing 20,000 and 17,000 organisms respectively, injected intramuscularly 23 days apart after storage in liquid nitrogen for between 9 and 46 days. A challenge of 5360 S. bovis cercariae was administered percutaneously approximately four weeks after the last vaccine dose to these animals and to three controls. Post-challenge the vaccinated animals gained significantly more weight (27% v. 9%), produced fewer eggs in their faeces, showed a smaller reduction in PCV values (-18% v. -27%) and were over-all in better condition than control animals. At perfusion 49.1% fewer adult worms were found in the vaccinated sheep than in controls. The tissue egg burdens were similar in both groups. Histopathologically both groups were similar except that fewer and smaller egg lesions were observed in the livers of vaccinated animals.

Animals↗