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Biomedical subjects

S C Bishop

Publications and source records attributed to S C Bishop.

47 records · Page 3Linked to original sources
PubMed1996

An ovine lymphocyte antigen is associated with reduced faecal egg counts in four-month-old lambs following natural, predominantly Ostertagia circumcincta infection.

Ovine lymphocyte antigen is associated with reduced faecal egg counts in 4-month-old lambs following natural, predominantly Ostertagia circumcincta infection. International Journal for Parasitology 26: 423-428. Ten lymphocyte antigens were defined in a flock of Scottish Blackface sheep known to be naturally exposed to infection with Ostertagia circumcincta. Population and family studies suggested that the 10 antigens were products of class I loci. Antigen G13br was in linkage disequilibrium with allele g2 at the DRB1 locus. The g2 allele has previously been associated with reduced faecal egg counts in a different crop of lambs from the same farm. In this study antigen G13br was also associated with a reduction in faecal egg counts. The results provide partial confirmation of the role of the major histocompatibility complex in resistance to natural, predominantly O. circumcincta infection.

Alleles↗
PubMed1996

The key components of resistance to Ostertagia circumcincta in lambs.

One of the most remarkable features of parasitic infections in general, and Ostertagia circumcincta infection of sheep in particular, is the extensive variation among hosts in resistance to infection, as assessed by parasite burdens and production of eggs or infective larvae. Here Mike Stear, Michael Park and Stephen Bishop describe the factors that account for the variation among animals within a flock, including dam, sire, sex, date of birth and history of exposure to infection. There are no detectable genetic effects in lambs less than three months old. Genetic control of an acquired response develops in two stages: first, a reduction in the average egg production per worm, which is associated with the development of a parasite-specific local IgA response; and second, control of worm burden, which is associated with the production of globule leukocytes in the abomasal mucosa.

Journal Article↗
PubMed1995

The repeatability of faecal egg counts, peripheral eosinophil counts, and plasma pepsinogen concentrations during deliberate infections with Ostertagia circumcincta.

Faecal egg counts, peripheral blood eosinophil counts and plasma pepsinogen concentrations were monitored during 2 successive, deliberate infections in 24 Scottish Blackface sheep. For all 3 techniques, the repeatability of replicate counts or of measurements made at short intervals were high which suggests that all 3 assays were reliable. Within an infection the repeatability of different samples from the same animal decreased as the interval between samples increased. The repeatability between infections was only moderate for faecal egg counts but high for peripheral eosinophil counts and plasma pepsinogen concentrations. Of the 3 variables, faecal egg count was the most strongly associated with the worm burden. Together, the three variables accounted for, in a statistical sense, one half of the variation in worm burden. The three variables, if measured concurrently, should provide a more effective identification of resistant and susceptible lambs.

Animals↗
PubMed1995

Different patterns of faecal egg output following infection of Scottish blackface lambs with Ostertagia circumcincta.

Faecal nematode egg counts were monitored in 184 Scottish Blackface lambs during natural exposure to a mixed, predominantly Ostertagia circumcincta infection and 12 lambs were selected which showed consistently zero (low count group; nine lambs) or consistently positive faecal egg counts (high count group; three lambs). These lambs were then treated with anthelmintic and challenged with 50,000 infective larvae of O. circumcincta and monitored thrice-weekly for 38 weeks; they were then re-challenged with another 50,000 infective larvae of O. circumcincta and monitored for a further 8 weeks. All sheep gave positive egg counts following deliberate infection. However, there was considerable variation among sheep in the size and timing of the peak in egg production. In particular, the pattern of mean values for faecal egg counts was different in the two groups. Egg counts were lower in the later periods of the extended infection in both groups of sheep. During the first half of the extended infection, egg counts were lower in sheep from the low count group, but during the second half of the infection the pattern was reversed and egg counts were lower in sheep from the high count group. There was a weak positive correlation between egg counts following anthelmintic treatment and 28 days exposure to natural infection and egg counts 28 days after a deliberate infection. Egg counts in the later stages of the deliberate infection were strongly but negatively correlated with egg counts following natural infection. The results of these studies show that differences in egg count following natural infection can be reproduced in experimental infections and that there is substantial variation in the pattern of egg production over time in different sheep. They also suggest that naturally resistant lambs are better able to delay worm development than naturally susceptible lambs.

Abomasum↗
PubMed1995

Regulation of egg production, worm burden, worm length and worm fecundity by host responses in sheep infected with Ostertagia circumcincta.

Following infection with Ostertagia circumcincta there was considerable variation in worm burdens, worm size and number of inhibited larvae even among sheep matched for age, sex, breed, farm of origin and history of parasite exposure. There was also substantial variation among sheep in the concentration of mast cells, globule leucocytes, eosinophils, IgA-positive plasma cells and parasite-specific IgA in the abomasal mucosa. With the exception of faecal egg counts over time, the parasitological and immunological traits were all continually distributed among animals and sheep did not fall into discrete high and low-responder categories. The responses were correlated. Sheep with more mast cells also had more globule leucocytes, more eosinophils, more IgA plasma cells and greater amounts of parasite-specific IgA in the abomasal mucosa. Female worm length was strongly and positively correlated with the number of eggs in utero. Faecal egg counts were associated with variation in worm number and with variation in the number of eggs in utero. The worm burden was negatively correlated with the number of globule leucocytes in the abomasal mucosa, suggesting that worm numbers are regulated by immediate hypersensitivity reactions. Decreased female worm length was associated with an increased local IgA response to fourth stage larvae. The number of inhibited larvae was positively associated with the size of the local IgA response and positively associated with the size of the worm burden. The results suggest that variation among mature sheep in faecal egg counts is due, at least in part, to variation in local IgA responses which regulate worm fecundity and to variation in local immediate hypersensitivity reactions which regulate worm burdens.

Animals↗
PubMed1995

Relationships between cleft severity and attractiveness of newborns with unrepaired clefts.

Perceptions of attractiveness of newborns with unrepaired clefts were investigated by using a range of photographs with clefts of differing severity as ordered by a rule of thumb system commonly adopted by surgeons. The investigation involved a combination of factors such as completeness, unilaterality or bilaterality, and palate involvement. Orderings of attractiveness by surgeons, nursing staff, and adult groups unfamiliar with clefts were remarkably consistent. In addition, the responses reflected the rule of thumb system with ranked preferences of the raters being significantly related to the severity of cleft impairment. The scale devised could be used for comparative treatment outcome studies requiring assessments of initial infant attractiveness.

Adult↗
PubMed1985

DNA repair elicited by UVB during PUVA therapy for psoriasis.

The skin of patients receiving psoralen and UVA (PUVA) therapy for psoriasis is exposed to trace amounts of UVB radiation emitted by PUVA irradiators in addition to UVA. DNA repair activity was measured using autoradiography in the uninvolved skin of PUVA-treated patients in order to determine whether 8-methoxypsoralen (8-MOP) plus UVA elicits repair, inhibits the skin repair response to UVB, or protects epidermal-cell DNA from UVB damage by promoting a tan. Epidermal-DNA repair activity was observed in 27 out of 37 patients following the first PUVA treatment. Phototesting with multiples of the initial UV dose elicited a linear increase in repair activity. Glass-filtered radiation failed to stimulate repair, indicating that the reaction was due to UVB, not to 8-MOP plus UVA. The same amount of repair activity was observed in the skin of patients irradiated either before or after 8-MOP ingestion, demonstrating that the drug did not interfere with the response of the skin to UVB. At clearing, however, the repair activity was never greater than that elicited at the initial treatment and was often undetectable despite a tenfold increase in UV exposure. It is proposed that DNA damage should be measured to determine whether epidermal cells are entirely protected from UVB radiation at the completion of therapy.

DNA Repair↗
PubMed1979

DNA repair synthesis in human skin exposed to ultraviolet radiation used in PUVA (psoralen and UV-A) therapy for psoriasis.

The ultraviolet radiation used for PUVA therapy stimulated DNA repair activity in normal human skin and in the uninvolved skin from psoriatic patients. The activity detected by autoradiography increased linearly with exposure time. No stimulation was observed when the UV-B component was removed from the incident radiation by filtration through glass. Therefore UV-B damage to DNA was found responsible for the activity detected following exposure to the unfiltered PUVA light source.

Autoradiography↗