Biomedical subjects

J F Ryley

Publications and source records attributed to J F Ryley.

At least 37 records · Page 2Linked to original sources

PubMed1978

Effects of saturated sodium chloride solution on coccidial oocysts.

Using the ability to sporulate as a measure of viability, the effects of exposure of unsporulated oocysts of 10 species of coccidia of chickens, rabbits and cattle to saturated NaCl solution has been studied. Although appreciable deformation and collapse of the oocyst occurred after 1-2 days contact, the effect was reversible after washing free from salt and incubating. Some reduction in ability to sporulate following several days contact with saturated salt was noted in most species, although no effect was seen with Eimeria stiedai following 7 days exposure, Eimeria tenella was one of the more sensitive species studied. Culture titration experiments in chickens with E. tenella indicated that oocysts which had sporulated following prolonged exposure to salt were in no way inferior in virulence or ability to retain virulence on prolonged storage to oocysts prepared with minimal contact with salt. No evidence was obtained to contra-indicate the use of salt-flotation methods for the separation of oocysts from faeces.

Animals↗

PubMed1978

Tricyclic aryl-substituted anticoccidial azauracils.

Syntheses of tricyclic aryl-substituted 6-azauracils are described. These compounds showed anticoccidial activity when tested against Eimeria tenella and E. necatrix. Compound activity was correlated with the chemical shift of the azauracil ring proton. No correlation existed between activity and compound lipophilicity. One of the compounds, 2-(11-oxo-6,11-dihydrodibenzo[b,e]thiepin-3yl)-as-triazine-3,5(2H,4H)-dione (23), was tested extensively against E. tenella and E. brunetti both in vivo and in vitro. Compound 23 controlled mortality due to E. tenella at 62 ppm, and it afforded protection as measured by weight gain at 31 ppm. Compound 23 afforded little protection against E. brunetti. In vitro experiments with 23 showed that it exerted a coccidiostatic effect.

Animals↗

PubMed1978

Speciation studies with Eimeria acervulina and Eimeria mivati.

Eimeria mivati was described as a new species of chicken coccidia in 1964 by Edgar and Seibold, but recently some British workers have relegated its status to that of a variety of Eimeria acervulina. Using strains supplied by Dr. Edgar, we have prepared lines of E. acervulina resistant to methyl benzoquate, sulfaquinoxaline and robenidine and a line of E. mivati resistant to methyl benzoquate. Genetic transfer of resistance between the various lines of E. acervulina to produce doubly-resistant coccidia has been demonstrated, but no such transfer could be obtained between E. mivati resistant to methyl benzoquate and the resistant lines of E. acervulina. Although some immunological relationship between E. acervulina and E. mivati has been demonstrated, we conclude that this failure of the 2 organisms to interbreed lends support to the status of E. mivati as a distinct species.

Animals↗

PubMed1976

Life cycle studies with Eimeria magna Pérard, 1925.

Excystation of Eimeria magna required exposure to CO2 at body temperature followed by trypsin and bile. Incubation in the presence of CO2 produced marked effects on the inner layer of the oocyst wall. The evidence suggests that CO2 stimulates enzymic activity from within the oocyst rather than exerting a physico-chemical effect on the oocyst wall from the outside. Released sporozoites measured 19.65 X 3.33 mum. In the rabbit, E. magna undergoes at least 5 cycles of asexual schizogony before gametogony takes place. First-generation schizonts were observed at 30 hr, measured 15 X 11 mum and contained 4, 6, 8 or occasionally 12 merozoites; the merozoites were characterised by two very large and prominent refractile granules. As the infection progressed, schizont size and merozoite numbers became more variable; some schizonts contained 2-8 fat merozoites, many probably multinuclear, while other schizonts contained 12-100 thinner merozoites. First generation schizogony took place in the glands; all subsequent stages developed in the upper parts of the villi of the small intestine. Sexual forms have been seen as early as 96 hr, but maximum sexual activity was noted at 120-192 hr. Oocysts measured 35.87 X 24.05 mum. The first oocysts were passed 6-7 days after inoculation, with peak production at 8-9 days. Sporulation was optimal at 30 degrees C; higher temperatures inhibited sporulation, and were in time lethal, while sporulation would take place normally after suppression by cold for at least 11 months. Single oocyst inoculations indicated a maximum reproductive potential of 26.15 million. Pathogenic effects were mostly mild, amounting to growth depression over days 4-7 and softening of the faeces; occasionally diarrhoea and/or death occurred.

Animals↗

PubMed1976

Drug screening in cell culture for the detection of anticoccidial activity.

Methods for screening compounds against Eimeria tenella in cell culture and in the chicken are described. An analysis for incidence of anticoccidial activity and host cell toxicity has been made of 11550 compounds screened in vitro, and some correlation of activity in vitro and in vivo has been attempted. The results show that screening compounds in tissue (cell) culture is not a satisfactory or reliable alternative to screening in chickens, although in vitro studies undoubtedly have a part to play in the evaluation of an active drug.

Animals↗

PubMed1976

Laboratory studies with some older anticoccidials.

Features of the anticoccidial activity of nicarbazin, amprolium, zoalene, sulphadimidine, diaveridine, Darvisul, spiramycin, chloramphenicol and oxytetracycline have been re-investigated both in vivo and in cell culture using Eimeria tenella. Of the drugs studied, only spiramycin was appreciably coccidiocidal, although nicarbazin and amprolium showed possibly slower coccidiocidal activity. In order to show activity against a particular stage in the life-cycle, higher concentrations of drug than those usually recommended for field usage had in most cases to be used. Under these conditions, parasites were usually inhibited as multinucleate 1st generation schizonts. With delayed medication, effects against 2nd generation parasites were in most cases found, and in many cases, although the parasites never matured to give viable merozoites, the large degenerating forms produced were able to cause extensive tissue destruction and haemorrhage. Methodology in this type of study is discussed in relation to more active and more recent anticoccidials, and some further experiments with robenidine reported.

Amprolium↗

PubMed1976

Methods in coccidiosis research: separation of oocysts from faeces.

Factors which may be important in the large-scale extraction of coccidial oocysts from faeces ha.ve been investigated with Eimeria tenella. Age of bird, inoculum, feeding status at the time of inoculation, period of collection, feeding status during collection, collection medium, homogenization and sieving, flotation, washing, sporulation and further purification have all been considered. The aim has been to establish a method to produce the maximum number of oocysts of a required degree of purity and viability, with the expenditure of the minimum amount of physical effort, time, animals and chemicals. In our method, groups of chickens 3-4 weeks of age are inoculated with 5000 oocysts of E. tenella and food is supplied ad lib. Over the period 5-8 days after inoculation, faeces are collected in trays containing 2% (w/v) potassium dichromate solution, while food intake is restricted. The faecal material is homogenized, passed once through 40 and 100 mesh sieves, centrifuged and the oocysts recovered from the sediment by 3 flotations in saturated salt solution. Following washing, oocysts are sporulated by forced aeration at 30 degrees C and may be further purified by hypochlorite treatment, or passage in 5% Tween 80 solution through a glass bead column followed by sucrose density gradient centrifugation. Routine passages along these lines over a 5 year period have given a recovery of 46% of the oocysts excreted by over 7000 birds.

Animals↗

PubMed1975

Pathogenic mechanisms not operating in Eimeria necatrix infections.

Having investigated certain aspects of Eimeria necatrix coccidiosis in chickens, workers of the Hannover Veterinary School postulated "that death following a single inoculation of a large number of oocysts is due to an alarm reaction and not a specific pathogenic action of the parasites". Because this hypothesis is somewhat revolutionary in its consept, several pieces of evidence on which it is based and several logical deductions which can be made from it have been examined. It has been confirmed that injection of chichens with cysteamine or 5-hydroxytryptamine 30 min before inoculation of the birds with a lethal dose of E. necatrix oocysts reduces subsequent mortality; the reason for this, however, appears not to be the neutralisation of the proposed shock reaction, but rather an inhibition of the excystation process, brought about indirectly through the host. Inoculation of chickens with a non-lethal dose of E. necatrix oocysts 30 min before inoculation with a lethal dose of oocysts was followed by increased mortality rather than the decreased mortality which the hypothesis would predict. Treatment of chickens with sulphadimidine starting 48 h after inoculation resulted in survival of the birds rather than death which would ensue if in fact mortality was due to a shock reaction irreversibly initiated at the time of inoculation. A direct effect of sulphadimidine on the parasite has been shown both in vivo and in vitro.

Adrenocorticotropic Hormone↗

PubMed1975

Laboratory studies with some recent anticoccidials.

The activities of monensin, lasalocid and halofuginone against Eimeria tenella, E. brunetti and E. necatrix have been studied under laboratory conditions. Complete control of experimental infections in the chick, separable from toxicity, was not obtained with monensin, but was achieved with the other two compounds at levels of 150 and 6 ppm in the food respectively. All three compounds appear to inhibit coccidial development very early in the life-cycle, and to have a fairly rapid lethal effect, monensin and lasalocid more so than the febrifugine derivative. In vivo observations have been supplemented with in vitro studies. Some discussion of the difficulties of relating laboratory experiments to field performance is given.

Administration, Oral↗

PubMed1975

Lerbek, a synergistic mixture of methyl benzoquate and clopidol for the prevention of chicken coccidiosis.

Methyl benzoquate at 20 ppm or clopidol at 250 ppm in the diet show true coccidiostatic activity in infections with Eimeria tenella in the chick. Lerbek, a synergistic mixture yielding 8-35 ppm methyl benzoquate and 100 ppm clopidol, produced a partially coccidiocidal effect; relapses following restricted periods of medication were less severe, and suppression of parasite development following delayed medication was quicker and more effective with either component of the mixture used alone.

Animals↗

PubMed1974