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Biomedical subjects

J M Finch

Publications and source records attributed to J M Finch.

12 recordsLinked to original sources
PubMed1996

Effects of in vitro supplementation with alpha-tocopherol and selenium on bovine neutrophil functions: implications for resistance to mastitis.

A low vitamin E/selenium status has been associated with increased vulnerability of dairy cattle to mastitis. Since polymorphonuclear leucocytes (PMN) provide the major cellular defence mechanism within the mammary gland, the effect of in vitro supplementation with vitamin E and selenium on the function of these cells was investigated. Both vitamin E and selenium enhanced the chemotactic and random migration of PMN and increased the production of superoxide following stimulation with phorbol myristate acetate. Vitamin E, but not sodium selenite, was also found to enhance the phagocytosis of opsonised Staphylococcus aureus by PMN. No synergistic effects of the two nutrients were observed. These results obtained in vitro may indicate the potential benefits of in vivo supplementation of dairy cows with vitamin E and selenium in terms of enhancing their natural resistance to mastitis.

Animals↗
PubMed1996

Effects of selenium and vitamin E on the immune responses of domestic animals.

The gross effects of selenium and vitamin E deficiency on animal production and the potential benefits of supplementation are recognised, and the influence of these micronutrients on the resistance of animals to a variety of infections has also been reported. As a result, deficiencies could compromise the immune system and result in a decline in production and performance before gross effects become apparent. Data obtained by laboratories studying different animal species indicate that the responses of domestic animals, particularly ruminants, differ from those of human beings and laboratory animals as well as differing among themselves. This paper provides a comprehensive review of the effects of selenium and vitamin E on the immune responses of domestic animals and discusses their effects with respect to the differences in the basal nutritional status of the animals concerned, the type of supplements used, the route and timing of their administration and the different agents which have been used to stimulate an immune response.

Animals↗
PubMed1995

Effects of in vitro supplementation of bovine mammary gland macrophages and peripheral blood lymphocytes with alpha-tocopherol and sodium selenite: implications for udder defences.

vitamin E and selenium have been observed to enhance the functions of bovine mammary gland macrophages and peripheral blood lymphocytes. In vitro supplementation with these compounds enhanced the production of neutrophil chemotaxins by macrophages stimulated with opsonised Staphylococcus aureus. Supplementation also enhanced the proliferation of peripheral blood lymphocytes in response to stimulation with concanavalin A but not to phytohaemagglutinin or pokeweed mitogen. There was no evidence of additive or synergistic effects of vitamin E and selenium. Results suggest that supplementation of cattle may optimise resistance to mastitis by enhancing the functions of resident macrophage and lymphocyte populations.

Animals↗
PubMed1994

Immune modification of the pathogenesis of Streptococcus uberis mastitis in the dairy cow.

Two groups of 4 cows were vaccinated subcutaneously with live Streptococcus uberis strain 0140J or a surface extract derived from the same strain, at 14 days prior to the cessation of lactation (drying off) and at calving. Both groups also received an intramammary administration of the surface extract 7 days after drying off. A third group of unvaccinated animals acted as controls. Following intramammary challenge of two quarters per cow with the vaccine strain, all quarters on control cows and those vaccinated only with surface extract developed clinical mastitis. However, only 12.5% of challenged quarters on cows which were vaccinated with live bacteria developed clinical mastitis. In addition, the numbers of bacteria in the milk following challenge were 10(5) times higher from the control and extract vaccinated cows than those which received live vaccine. Serum levels of S. uberis specific IgG2 were elevated in the animals vaccinated with the live organism when compared to that of either extract-vaccinates or controls, whilst S. uberis specific levels of IgG1 and IgM were similar in all groups throughout the experiment. Specific antibody levels in milk were unaffected by vaccination. Despite increased levels of IgG2, no increase in opsonic activity was detected in any serum or milk samples. Peripheral blood lymphocytes from animals vaccinated with live organisms showed a considerable increase in proliferative response to S. uberis antigen in vitro when compared with lymphocytes from control and extract-vaccinated animals. These results suggest that neutrophils and specific opsonising antibody may not form the major defence against infection with S. uberis.

Animals↗
PubMed1994

Local vaccination with killed Streptococcus uberis protects the bovine mammary gland against experimental intramammary challenge with the homologous strain.

The ability of killed streptococcus uberis to induce protection against mastitis when administered either into the cistern of the dry mammary gland (intramammary vaccination) without adjuvant or subcutaneously with adjuvant was investigated. Bacteria were never reisolated from vaccinated quarters following challenge with the same strain during the subsequent lactation, and no inflammatory response was detected. In contrast, following subcutaneous vaccination, milk from challenged quarters contained very small numbers of bacteria, but these quarters did exhibit clinical disease, whereas quarters on nonvaccinated control animals produced discolored, clotted secretion with large numbers of bacteria and somatic cells and required antibiotic therapy by 60 h postchallenge. There was a significant increase in the levels of S. uberis-specific immunoglobulin G1 (IgG1), IgG2, and IgM in milk following intramammary vaccination and in the levels of specific IgG1 and IgG2 in milk following subcutaneous vaccination. Levels of specific antibody in serum were also elevated following vaccination by either route. However, despite this, there was no increase in the opsonic activity of serum or milk. Both peripheral blood lymphocytes and dry-period mammary gland lymphocytes showed strong proliferative responses to S. uberis in vitro following subcutaneous vaccination, but only mammary gland lymphocytes responded following intramammary vaccination. It was concluded that the protection seen in vaccinated quarters did not appear to be related to levels of specific antibody or neutrophil function and was possibly brought about by the inhibition of bacterial growth.

Animals↗
PubMed1991

Studies on the incidence of clinical mastitis and blood levels of vitamin E and selenium in dairy herds in England.

In a trial conducted in the south of England in January to February 1989, blood samples were obtained from nine dairy herds with more than 30 cases of clinical mastitis/100 cows and from nine herds with less than 30 cases/100 cows during the previous 12 months. Whole blood glutathione peroxidase (GSHPx) activity and plasma vitamin E concentration were determined for 12 cows in each herd. The mean (+/-sd) values for the herds with the lower incidence of mastitis were 7.57 +/- 1.86 micrograms/ml plasma vitamin E and 23.8 +/- 22.8 U/ml rbc GSHPx activity, compared with 7.74 +/- 1.69 micrograms/ml plasma vitamin E and 20.61 +/- 8.8 U/ml rbc GSHPx activity for the herds with the higher incidence of the disease. These values indicate that the vitamin E levels were generally adequate but that some animals and herds had low GSHPx activities, suggesting that their diets may have contained inadequate selenium. The activities of GSHPx and the vitamin E levels in plasma were not significantly different in the two groups of herds, and no relationship was found between the two nutrients and the incidence of clinical mastitis. However, there was a significant negative correlation between the activity of GSHPx and the bulk milk cell counts in the herds with a low incidence of mastitis suggesting that there was an association between the incidence of subclinical mastitis or inflammation and the selenium status of these herds.

Animals↗
PubMed1990

Immunological malfunctions associated with low selenium-vitamin E diets in lambs.

Lymphoproliferative responses to phytohaemagglutinin and other phytolectins declined following prolonged exposure of lambs to a diet deficient in both selenium and vitamin E, coinciding with the development of nutritional myopathy. Supplementation restored lymphocyte responses within a week and led to a rapid decline in circulating activity of the muscle enzyme creatine kinase in serum. Lymphocyte responses of the dams remained largely unaltered throughout the experiment. There was no evidence of erythrocyte damage in myopathic lambs, concentrations of serum IgG, IgM and lysozyme were similar to those in healthy lambs, and chemiluminescence tests on whole blood samples failed to reveal a phagocytic defect in response to particulate and non-particulate stimuli. However, serum from myopathic lambs did show a reduced opsonic capacity.

Aging↗
PubMed1989

Enhancement of ovine lymphocyte responses: a comparison of selenium and vitamin E supplementation.

Lymphocytes of lambs on a low selenium/vitamin E diet were isolated from peripheral blood, and mitogenic responses to phytohaemagglutinin (PHA) tested in the presence of different doses of sodium selenite and emulsified vitamin E added in vitro. An enhancing effect of selenium was observed at doses of 1 ng/ml or less, and reached a plateau at about 10 ng/ml. Toxic effects were evident beyond 1 micrograms/ml. The stimulatory potential of selenium among lambs was inversely related to their ability to respond to PHA in control cultures but was not related to the blood glutathione peroxidase activity of the animals concerned. Optimal doses of vitamin E added to culture (0.15-1.5 micrograms/ml) elevated responses beyond those seen with selenium, but synergistic effects were not apparent. Similar results were obtained when lymphocytes from deficient, myopathic lambs were cultured with serum from lambs supplemented in vivo, and when PHA responses of untreated and treated lambs were compared. Tests with other phytolectins (concanavalin A and pokeweed mitogen) suggested that the two micronutrients exert a differential influence on lymphocyte sub-populations. It was also concluded that the poor lymphocyte responses seen in myopathic lambs can be readily and rapidly reversed by injection of these nutrients, and that prophylaxis is most effective during the first 6 weeks of life.

Animals↗
PubMed1986

Selenium supplementation in lambs: effects on antibody responses to a salmonella vaccine.

In trials conducted in 1984 and 1985, the effects of selenium injections on the antibody responses of lambs marginally deficient in selenium to Salmonella dublin were assessed. Control lambs (mean glutathione peroxidase [GSHPx] less than 20 iu/ml) responded well to the vaccine. No difference was observed in the antibody titres of animals treated twice with 5 mg selenium as sodium selenate. During the following season animals given 50 mg selenium as barium selenate showed slightly higher titres than controls. The results show that marginally selenium deficient lambs are able to elicit strong antibody titres to a bacterial antigen and that supplementation with selenium produces, at best, a marginal enhancement of the responses observed.

Animals↗
PubMedDate not supplied

Phagocytosis of Streptococcus uberis by bovine mammary gland macrophages.

The ability of macrophages isolated from the bovine mammary gland to phagocytose and kill Streptococcus uberis was investigated. The strains of S uberis used were selected on the basis of their known resistance (C197C) or sensitivity (EF20) to phagocytosis by bovine peripheral blood neutrophils in the same assay system. Macrophages isolated from mammary secretions collected during the mid-dry period were capable of phagocytosing both strains of S uberis in the presence of serum and skimmed milk. The removal of complement from serum by heat-inactivation did not influence the opsonization of S uberis for phagocytosis by mammary macrophages and both IgG1 and IgG2 isotypes were found to opsonise both strains. The uptake of S uberis into the cells was confirmed by electron microscopy. Potential mechanisms by which S uberis could resist phagocytosis by neutrophils but not by macrophages are discussed.

Animals↗