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Biomedical subjects

F Jackson

Publications and source records attributed to F Jackson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Comparison of saline incubation and pepsin digestion as methods for recovering Ostertagia circumcincta larvae from the abomasum of sheep.

Incubation in saline at 37 degrees C was compared with pepsin digestion as a quantitative method for recovering larval stages of Ostertagia circumcincta from the abomasal mucosa of sheep. Experiments showed that the techniques were of roughly similar efficiency even when the larvae were arrested but that the saline method was preferable because worm searching was easier and quicker.

Abomasum↗
PubMed1984

Further observations on faecal egg output in lambs dosed continuously with Ostertagia circumcincta.

The relationship between size of intake of infective larvae of Ostertagia circumcincta and faecal egg output by lambs was examined in two experiments in four-month-old Suffolk cross lambs dosed five times per week for 10 weeks. The first experiment compared two strains, Weybridge and Moredun, at two levels, 400 and 4000 per dose. The second experiment compared two levels, 40 and 400 per dose, of Moredun larvae. The group mean output of worm eggs was almost unaffected by the 10-fold reduction in intake from 4000 to 400. The further reduction from 400 to 40 reduced egg output by a factor of 2.5.

Animals↗
PubMed1984

Resistance to Haemonchus contortus transferred between genetically histocompatible sheep by immune lymphocytes.

The pattern of faecal egg counts after infection with 10,000 Haemonchus contortus larvae was similar within but not between, four pairs of monozygous twin sheep. Transfer of whole lymph or washed lymph cells from three immune donor sheep to their identical co-twin recipients reduced the susceptibility of the recipients to challenge with 10,000 larvae as measured by faecal egg counts. Cells from a nonimmune donor did not have this effect. In a final experiment, washed cells from an immune triplet sheep, which was actively responding to a repeated challenge infection, transferred a secondary local IgA response to a second recipient triplet and resulted in a marked reduction in worm count when compared with that of a third infectivity control triplet.

Animals↗
PubMed1983

False start.

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Education, Nursing↗
PubMed1983

Studies on the local immune response of the lactating ewe infected with Ostertagia circumcincta.

Changes in the flow and composition of gastric lymph were monitored in groups of lactating and non-lactating ewes which were repeatedly infected with Ostertagia circumcincta. As judged by faecal egg counts and worm burdens the lactating group was more susceptible than the non-lactating controls to the challenge infection. Increased amounts of pepsinogen as well as larger numbers of eosinophils and neutrophils entering the gastric lymph indicated considerable abomasal damage and inflammation in the lactating ewes. However, measurement of the flow of lymphocytes as well as the amount of IgA and IgA antibody in the lymph did not indicate that these aspects of the local immune response were impaired during lactation; in fact the output of IgA-containing lymphocytes as well as IgA itself was usually raised in the lactating sheep. Lymph flow was increased and lymph globulin concentrations proportionally decreased in lactating ewes, irrespectively of whether they were infected with worms. It is suggested that these changes were caused by the increase in voluntary food intake which occurs during lactation.

Animals↗
PubMed1983

Local immunity and Ostertagia circumcincta: changes in the gastric lymph of sheep after a primary infection.

Some aspects of the kinetics of the primary local immune response to O. circumcincta were studied by monitoring the flow and composition of gastric lymph from 4 sheep for 3 weeks after infection with 50 000 larvae. A significant increase in the frequency of lymphoblasts in the lymph showed that all the sheep were responding immunologically to the parasites from day 8 onwards. However, considerable individual variation in degree and timing was evident in other aspects of the immune response; 2 animals responded with large increases in lymphocyte output which reached a peak on day 5 or day 10, whereas the main response in the other 2 sheep appeared to be inflammatory in nature, with large increases in lymph flow and eosinophil output which occurred during the third week of infection. No significant changes in the content of IgA or IgA anti-worm antibody were detected in the lymph, but pepsinogen concentrations were significantly raised from day 12 onwards.

Animals↗
PubMed1983

Local immunity and Ostertagia circumcincta: changes in the gastric lymph of immune sheep after a challenge infection.

Immunity to Ostertagia circumcincta was demonstrated in 5 previously infected sheep which were killed 10 days after challenge with 50 000 larvae. This immunity was expressed as a reduction in the number as well as the degree of development of the surviving parasites compared with those found in 6 control sheep. Gastric lymph was sampled from the immune group from 2 days before till 10 days after challenge and a secondary local immune response was detected. The main features of this response were a large increase in cell output in the lymph, especially in lymphoblasts and IgA-containing cells, which reached a peak on day 4 or 5, followed by a ten-fold increase in IgA immunoglobulin and IgA anti-worm antibody which reached a peak 7 or 8 days after challenge. The timing of these events suggested that the cellular, but not the IgA, response could have been involved in a putative mechanism which caused arrested development, although both components could have been implicated in mechanisms which may have caused expulsion of developing larvae.

Animals↗
PubMed1983

Immune exclusion, a mechanism of protection against the ovine nematode Haemonchus contortus.

The fate of exsheathed Haemonchus contortus larvae injected directly into the abomasal lumen was studied in groups of naive and hyperimmune sheep. Within 48 hours of challenge, more than 90 per cent of the larvae were lost from hyperimmune sheep. The larvae had a propensity to associate with the superficial mucus in both groups and, in naive sheep, approximately 50 per cent of the larvae entered glandular tissue within four hours of challenge. By contrast, although initially associated with the mucosal surface, larvae in immune sheep were excluded from the glandular tissues. It is postulated that the rapid loss of worms from the hyperimmune abomasum is a consequence of 'immune exclusion' and the possible mechanisms underlying this process are discussed.

Abomasum↗
PubMed1983

Development of morphological changes in the small intestine of lambs continuously infected with Trichostrongylus vitrinus.

Groups of three-month-old worm-free Suffolk cross lambs were given 2500 Trichostrongylus vitrinus larvae on five days each week for four, six, eight and 13 weeks and killed one week later. Severe villous atrophy, epithelial erosion and cellular infiltration were common features in the duodenum and the following 2 to 3 m of intestine of lambs killed at weeks 5 and 7. There was evidence of intestinal recovery in the lambs killed at weeks 9 and 14; five of the seven lambs had large areas of intestine which appeared relatively normal and worm activity appeared to be confined largely within focal areas ("fingerprint lesions'). There was no change in the linear distribution of the worms in the intestine over the course of the experiment. The highest percentage of the larval challenge was recovered from lambs killed at week 5 and worm burdens were not cumulative. Lambs killed at week 14 were resistant to larval reinfection.

Animals↗
PubMed1982

Changes in the flow and composition of gastric lymph in sheep given a primary infection of 10,000 Haemonchus contortus.

Some aspects of the local immune response to a primary infection with 10,000 Haemonchus contortus were studied in five sheep by monitoring changes in the flow and composition of gastric lymph continuously sampled for up to 34 days from the start of infection. Increases in lymph flow rates were recorded in four animals at varying times after the start of infection. These were usually associated with an increase in the protein content of the lymph and were considered to be a consequence of inflammatory reactions in the abomasum. Apart from a small increase in lymphocyte traffic no changes which could be attributed to a local immune responses were observed in the lymph. It is suggested that the chronic nature of infections like haemonchosis is possibly because the worms can parasitise the gut without stimulating a vigorous local immune response.

Albumins↗
PubMed1982

Attempts to immunise sheep against Ostertagia circumcincta with irradiated larvae.

Mature sheep immunised with two doses of 10,000 irradiated Ostertagia circumcincta larvae were only slightly resistant to challenge with a single dose of 10,000 larvae. This slight resistance was abolished if the 'vaccine' worm population was removed one week before challenge. In contrast, seven of eight sheep immunised with irradiated Haemonchus contortus larvae were highly resistant to homologous challenge. Evidence of some cross protection against challenge with O circumcinta was observed in five of six sheep immunised with irradiated H contortus in that egg counts were lower and more worms were retarded as fourth stage larvae.

Animals↗
PubMed1982

Specific identification of strongyle eggs in small samples of sheep faeces.

A method for the specific identification of strongyle eggs in small samples of sheep faeces based on dimensional and biological characteristics is described. More than 90 per cent of the eggs of Ostertagia spp and of Trichostrongylus vitrinus can be positively identified. For other species supporting information from larval cultures may be needed but this need will vary according to the composition of the sample.

Animals↗
PubMed1981

Explant culture of rat esophagus in a chemically defined medium.

Esophagus from adult male CDF rats was cultured for a period of 28 d in CMRL-1066 medium supplemented with pyruvic acid, HEPES buffer, beta-retinyl acetate, and antibiotics. Morphological, radioautographic, and biochemical studies indicated that the survival of the tissue in serum-free medium was equivalent to that in medium containing 5% heat-inactivated fetal bovine serum. There was a relatively constant uptake of [3H]thymidine into DNA and [3H]leucine into protein of the esophageal explants during the incubation. Only the basal cells of the epithelium incorporated [3H]thymidine into their nuclei. The normal morphology of the tissue was preserved when the explants were maintained at both 37 and 30 degrees C, and in either 50 or 20 % 02. Ninety-five percent O2 was highly toxic to the cells of the explants. This culture system should be suitable for a variety of investigations in esophageal cell differentiation and carcinogenesis.

Animals↗