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Biomedical subjects

B J Millard

Publications and source records attributed to B J Millard.

At least 19 recordsLinked to original sources
PubMed1992

Variation in susceptibility of inbred lines of chickens to seven species of Eimeria.

The pattern of oocyst production of 8 inbred lines of chickens was compared for each of the 7 species of Eimeria which infect this host. Both the overall numbers and the pattern of oocyst production differed in the inbred lines, but there was no evidence of prolonged cycling of schizogenic developmental stages. Comparison of the numbers of oocysts produced by the different lines indicates that there may be common genetic factors affecting susceptibility to 6 of the 7 species. Surprisingly there appears to be an inverse relationship between susceptibility to E. tenella and susceptibility to the other species: lines which produced most oocysts of E. tenella produced least oocysts of the other species and vice-versa.

Analysis of Variance↗
PubMed1992

Intestinal changes associated with expression of immunity to challenge with Eimeria vermiformis.

To provide more information on the mechanisms involved in the immune inhibition of eimeria infections, NIH mice were adoptively immunized against infection with Eimeria vermiformis by the transfer of mesenteric lymph node cells from primed animals and homologously challenged. Subsequent changes in the architecture and cellular composition of the intestine were compared with those observed in similarly challenged susceptible control mice and correlated with the development of the parasite in the two groups. Actively immunized mice were also examined. In adoptively immunized mice, the development of E. vermiformis was inhibited within 3 days of administering the challenge inoculum. Concurrent changes in the intestine included lymphocytic infiltration, crypt hyperplasia, flattening of the crypt epithelium, and a reduction in the number of Paneth cells. Hyperplasia of goblet and pyroninophilic cells in response to challenge, although accelerated and enhanced in adoptively immunized hosts, occurred after the inhibition of the parasites, and mastocytosis was not observed in these animals, findings which suggest that the activities of goblet, pyroninophilic, and mast cells were not instrumental in reducing the numbers of parasites. The intestines of immunized mice contained fewer intraepithelial lymphocytes at the time of inhibition of the parasites than did those of the controls. The protective effects and intestinal changes described above did not differ appreciably from those seen after challenge of mice that had been immunized by infection.

Animals↗
PubMed1987

Eimeria spp. of domestic fowl: the migration of sporozoites intra- and extra-enterically.

Chickens were dosed orally with sporulated oocysts of Eimeria acervulina, E. brunetti, E. maxima, or E. praecox and the subsequent presence, in various tissues, of parasites capable of inducing patent infections was detected by transferring the tissues to coccidia-free recipients. Similar results were obtained with each of the 4 species studied, irrespective of whether initial development occurs in the superficial (E. praecox, E. brunetti) or crypt (E. acervulina, E. maxima) epithelium. Infection was transferable by gut scrapings and liver homogenates at all time intervals (3, 6, 12, 18, 24, and 36 hr postinoculation) studied. Infection was also transferable with blood and with splenic homogenates but not consistently. Transfers made within a short time of the inoculation of donors were more successful in producing patent infections in the recipients. In all transfers the prepatent period was normal for the species. These findings suggest that sporozoites enter the mucosa very shortly after inoculation, and some of them pass to the liver and spleen and then leave these tissues at a somewhat slower rate, possibly to reenter the mucosa. Sporozoites in the lamina propria of the gut were found within host mononuclear cells in all 4 species studied. Most of the cells harbouring E. maxima and some of those with E. praecox were identified as intraepithelial lymphocytes while all others could only be identified as agranular mononuclear cells that were not characteristically macrophages.

Animals↗
PubMed1985

Eimeria vermiformis: host strains and the developmental cycle.

After confirmatory studies of the endogenous development of Eimeria vermiformis in hybrid mice, a comparison, both qualitative and quantitative, was made of the developmental cycle of the parasite in two strains of host of contrasting susceptibility. No differences were apparent between the resistant, BALB/c, and susceptible, C57BL/6, during the first 5 days of the cycle. Thereafter, more parasites were seen in the C57BL/6, they were more widely distributed along the intestine, and they persisted in the tissues for a considerably greater time. Schizogony continued for longer in the C57BL/6 mice, concurrently with gametogony, and there were probably up to four additional generations of schizonts, which resembled those of the accepted third generation. The kinetics of oocyst production, measured in the feces, reflected events in the intestinal epithelium. The findings are discussed in relation to eimerian life cycles and the immune response.

Animals↗
PubMed1985

Host specificity in eimerian coccidia: development of Eimeria vermiformis of the mouse, Mus musculus, in Rattus norvegicus.

The ability of Eimeria vermiformis, a coccidium which normally parasitizes the mouse, to develop in rats was investigated. The Rowett strain (Lac: RNU) rats were euthymic (rnu/+), treated or untreated with cortisone acetate, and athymic (rnu/rnu). E. vermiformis completed its development only in rnu/rnu rats, which passed small numbers of oocysts capable of sporulating and infecting C57BL/6 mice. In the rnu/+ rats, irrespective of cortisone treatment, development appeared to terminate with the completion of the asexual (schizogonic) stages since no gametocytes were recognized in the tissues and no oocysts were detected in the faeces. The findings are discussed with reference to the factors which govern host specificity.

Animals↗
PubMed1979

Studies on Eimeria dispersa Tyzzer 1929 in turkeys.

Eimeria dispersa was isolated from young, intensively housed turkeys in Britain. The parasite has morphological features in common with those of the original description. At least two generations of schizonts occur before gametogony and one or two more schizont generations are concurrent with gametogony. Four generations of schizonts are needed to account for the observed reproduction index of 2.08 x 10(6)/oocyst inoculated. The first oocysts were discharged by 105 h and these sporulated within 30 h at 30 degree C. A single dose of between 1 x 10(2) and 1 x 10(6) oocysts depressed body weight gain of 3-week-old poults and 2 poults died 6 and 12 days after receiving 1 x 10(4) or 1 x 10(6) oocysts. A single dose of oocysts protected against a challenge inoculation given 14 days later. Poults immunized against E. dispersa were resistant to challenge with a strain of E. dispera obtained from the United States. Electrophoretic examination of 2 enzymes from both strains of E. dispersa showed that they had similar mobilities. Attempts to infect chickens, guinea-fowl and Japanese quail with E. dispersa were unsuccessful. The strain of E. dispersa isolated here is best referred to as E. dispersa (Briston).

Animals↗
PubMed1979

Rejection of Eimeria by foreign hosts.

Oocysts of Eimeria maxima inoculated into guinea fowl do not develop. Infection occurs when intestinal mucosa or liver tissue from guinea fowl given E. maxima is transferred to susceptible chickens. By transferring material at different times after inoculation, it was shown that most of the stages are lost between 6 and 12 h and few, if any, survive to 48 h. Sporozoites of E. tenella had low infectivity after 48 h contact in vitro with peritoneal macrophages from guinea fowls and turkeys. Sporozoites of E. grenieri from the guinea fowl appeared to be destroyed within macrophages taken from chickens.

Animals↗
PubMed1979

Immunological differences in Eimeria maxima: effect of a mixed immunizing inoculum on heterologous challenge.

The immunological differences known to exist between laboratory strains of Eimeria maxima was confirmed. Protection against challenge with different strains or field isolates of the species could be achieved by including small numbers (25 oocysts) of each in the immunizing inoculum. Similar protection was obtained when 4 distinct populations which were allowed to interbreed were used in the immunizing inoculum. This hybrid mixture of E. maxima was used to immunize chickens against challenge with 7 new isolates of E. maxima from poultry houses in different parts of England. The results show that although immunological differences exist within E. maxima good protection against many strains of this species may be achieved by initial infection with the hybrid mixture of E. maxima.

Animals↗
PubMed1979

An isolator for avian disease research.

An isolator is described, fabricated in glass-reinforced plastic, suitable for housing 25-30 chicks to 6 weeks of age, or for fewer older birds, for use in experiments involving infectious agents.

Animals↗
PubMed1978

Fine structural aspects of an embryo-adapted strain of Eimeria tanella in the epithelial cells of the chorio-allantoic membrane.

The fine structure and development of the endogenous stages of an embryo-adapted strain of Eimeria tenella in chicken embryos is described. First-generation merozoites were formed by endodyogeny in uninucleate developmental stages as well as schizogony and the endoplasmic reticulum of merozoites of the second-generation schizonts appeared as a circular structure, often enclosing other organelles. In contrast to the parent strain, development of the second-generation schizonts was restricted to cells of epithelial origin. These observations confirm that the complete endogenous cycle of the embryo-adapted strain of E. tenella is restricted to epithelial cells of the chorio-allantoic membrane (CAM) and that no major ultrastructural changes have occurred as a result of repeated embryo passage.

Animals↗
PubMed1977

Evidence for the lack of a carrier effect in the solvent extraction and determination of octopamine by gas chromatography mass spectrometry.

It has been shown that there is no significant carrier effect when low levels of [3H]octopamine (100 pg) are extracted by ethyl acetate from aqueous solutions containing a 10(3) or 10(6) times excess of unlabelled octopamine. It is also shown that there is no carrier effect when low levels of octopamine as the tetrakis-TMS derivative are injected with 100 times the amount of the [2H3] analogue on an SE 30 column.

Chromatography, Gas↗
PubMed1977

Studies on the growth, chemotherapy and enzyme variation of Eimeria acervulina var. diminuta and E. acervulina var. mivati.

Eimeria acervulina var. diminuta was serially passaged 12 times in chicken embryos, but growth in cultured chick kidney cells was limited to 2 generations of schizonts. After 7 embryo passages the sensitivities of E. acervulina var. diminuta and an embryo-adapted strain of E. acervulina var. mivati to the anticoccidial drugs amprolium, methyl benzyquate, robenidine and sulphaquinoxaline were compared. Both parasites were sensitive to all the anticoccidials but E. acervulina var. diminuta was more sensitive to sulphaquinoxaline and amprolium. The chicken-maintained strain of E. acervulina var. diminuta was extremely sensitive to clopidol, sulphaquinoxaline and decoquinate. Electrophoretic analyses of several enzymes from E. acervulina var. diminuta revealed enzyme profiles with similarities and differences to the embryo-adapted strain of E. acervulina var. mivati.

Animals↗
PubMed1977

Strain variations within Eimeria meleagrimitis from the turkey.

During the course of a field study of coccidiosis in turkeys, Eimeria oocysts were found which had much smaller dimensions that any previously recorded isolate from the turkey. These oocysts were purified by single oocyst infection of a turkey. The first oocysts (mean dimensions 16-15 X 14-75 micrometer) were recovered 103 h later. Inoculation of between 0-5 and 2-5 X 10(5) oocysts of this isolate caused severe effects on body weight gain. Cross-immunity studies showed the parasite to be a strain of E. meleagrimitis. Electrophoretic analyses of two enzymes showed that the strain could be differentiated from another strain of E. meleagrimitis (Weybridge strain B). The results show that strain variation occurs within the species E. meleagrimitis and extreme caution should be used in identifying species of Eimeria from the turkey by the oocyst characters.

Animals↗