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Biomedical subjects

R M Cook

Publications and source records attributed to R M Cook.

At least 55 records · Page 3Linked to original sources
PubMed1987

Activity of rat peritoneal eosinophils following induction by different methods.

The numbers and proportions of eosinophils in peritoneal washings taken from rats were increased by giving one or three injections of Sephadex G200 intravenously or physiological saline intraperitoneally or by infection with Mesocestoides corti. Purified eosinophils were morphologically similar and contained similar levels of lactate dehydrogenase and peroxidase. They were equally efficient at releasing peroxidase when stimulated with complement-coated particles. Eosinophils from infected rats and from animals given repeated injections of Sephadex showed enhanced chemiluminescent and cytotoxic responses to phorbol myristate acetate compared with cells obtained from rats given a single injection of Sephadex or saline. Sephadex-induced cells displayed more activity in antibody-dependent cell cytotoxic assays and formed a greater proportion of rosettes with antibody-treated sheep erythrocytes than did eosinophils from saline-treated or M. corti-infected rats. Only eosinophils from parasitized rats were stimulated with f-Met-Leu-Phe to lyse chick red blood cells. It is concluded that the method used to recruit eosinophils in the rat can have a marked effect on their responses in vitro and this needs to be considered in studies of functional activity.

Animals↗
PubMed1987

Eosinophil- and neutrophil-mediated injury of human lung fibroblast cells.

The effect of culturing purified rat peritoneal neutrophils and eosinophils with the human foetal lung fibroblast cell line, MRC-5, was studied. Target cell damage was measured by the failure of the MRC-5 cells to form confluent monolayers during a 6-day incubation period. Neutrophils were more effective at inhibiting cell growth than were eosinophils with greater than 50% inhibition being recorded at initial effector: target cell ratios of 5:1 using neutrophils and 40:1 using eosinophils. Following stimulation with phorbol myristate acetate (PMA), one quarter the number of eosinophils was required to give 50% inhibition of cell growth. The addition of either catalase or superoxide dismutase partly reduced the activity of PMA-stimulated eosinophils, although only with catalase did this reach significance. PMA-stimulated neutrophils did not show any enhanced activity against the MRC-5 cells. Addition of the bacterial analogue f-Met-Leu-Phe (10(-7)M) was unable to increase the cytotoxic activity of eosinophils. Disrupted eosinophil suspensions were as effective as intact cells at inhibiting the growth of target cells whereas some loss in effectiveness was seen with disrupted neutrophils. Membrane-free supernatants from both eosinophils and neutrophils were inactive. The results suggest that although eosinophils and neutrophils are both capable of damaging lung fibroblast cells in culture, the latter is more effective, eosinophils appearing to require an additional stimulation in vitro. Possible mechanisms of cytotoxicity are discussed.

Animals↗
PubMed1987

T cell reactivity of conjugates of N-formyl-methionyl-leucyl-phenylalanine and rye-grass pollen allergens.

Conjugates of rye-grass pollen extract and N-formyl-methionyl-leucyl-phenylalanine were prepared using an activated form of the tripeptide. Introduction of the peptide into the extract brought about an extensive reduction of reactivity with grass-pollen-specific IgE, as measured by RAST inhibition. Despite this loss, guinea pig alveolar macrophages and murine splenic macrophages readily presented the conjugates to T lymphocytes specific for grass pollen allergens and caused their proliferation in vitro.

Animals↗
PubMed1986

Suppression of murine IgE responses with amino acid polymer/allergen conjugates. III. Activity in vitro.

Conjugates of poly-N-methylglycine (polysarcosine) and grass pollen allergen extracts, which have been previously shown to suppress murine IgE responses, were examined for their ability to modify lymphocyte activity in vitro. Allergen-specific T lymphocytes obtained from Balb/c mice gave a reduced response to syngeneic accessory cells pulsed with conjugates of polysarcosine-allergen compared with the response found using equivalent concentrations of native extract. Pretreatment of accessory cells with either polysarcosine or polysarcosine-allergen conjugates did not impair their subsequent ability to present grass pollen extract to immune T cells. Incubation of allergen-specific spleen cells with polysarcosine-allergen conjugates, but not with polysarcosine or allergen alone, resulted in specific cell-mediated suppression which significantly reduced proliferation in vitro. This activity was sensitive to treatment of cells with anti-T-lymphocyte antisera plus complement. Spleen cells obtained from animals immunised with allergen and taken 21 days after intravenous treatment with polysarcosine-allergen conjugates, a regimen that suppressed IgE antibody production, did not proliferate in the presence of grass pollen extract and failed to suppress a secondary lymphoproliferative response in vitro. Spleen cells obtained from similarly treated animals 3 days after the final polysarcosine-allergen injection responded to pollen extract in culture and, additionally, impaired a secondary response. The results suggest that the reduced IgE response found in animals treated with polysarcosine-allergen conjugates may be due, in part, to the generation of a short-lived antigen-specific T cell suppression.

Allergens↗
PubMed1985

In vitro production of IgE and IgG protein by blood mononuclear cells from non-atopic and atopic donors.

The production of IgE and IgG protein by human peripheral blood mononuclear cells in culture has been examined. Cells obtained from 18 grass-sensitive donors during the grass pollen season and from 11 atopic dermatitis patients (total serum IgE levels greater than 960 ng/ml), spontaneously produced significant amounts of IgE but not IgG with time. Similar results were obtained using B-cell enriched preparations from both groups. Cells from 16 non-atopic donors had mean levels of pre-formed IgE similar to those of grass pollen-sensitive donors, but there was no increase in culture IgE with time. Treatment of mononuclear cells with pokeweed mitogen did not influence the production of IgE but markedly increased the amount of IgG synthesized by non-atopic and atopic donor cells. Slight, but significant increases in culture IgE, but not IgG, were seen following a 7-day mixed lymphocyte reaction involving both unrelated non-atopic donor cells and the lymphoblastoid B-cell line, Raji. Treatment of cells with 50 HA units of influenza A/Hong Kong/1/68 (H3N2) virus or with 0.02% v/v (240 IU/ml) of a purified beta-interferon preparation did not alter IgE or IgG produced.

Dermatitis, Atopic↗
PubMed1985

Murine lymphocyte responses to purified components of rye grass pollen extract.

The ability of lymphocytes obtained from mice treated with whole rye grass pollen extract or purified major allergen components (R7--apparent molecular weight 31,000; R14a-apparent molecular weight 11,000) to proliferate in culture on challenge with these allergens has been studied. Whole rye grass pollen extract was found to stimulate responses with lymphocytes from all treated but not non-treated animals, whereas the purified allergens failed to effect proliferation except with cells obtained from animals treated with the homologous allergen. These results accord with previous observations that, of the antigen present in the whole rye grass pollen extract, the components showing greatest immunogenicity in murine systems are not those commonly regarded as being the major allergens in man. The mouse may not thus provide a relevant model of human immune responses to rye grass pollen extracts.

Animals↗
PubMed1984

Accessory cell response to rye grass pollen extract in mice, guinea pigs and man.

The ability of murine, guinea-pig and human accessory cells to function in antigen presentation has been assayed by a T-cell proliferative response to adherent cells pulsed with rye grass pollen extract. A population of phagocytic, esterase-positive, plastic-adherent splenocytes from non-immune Balb/c mice briefly incubated with solubilized rye antigen were capable of stimulating syngeneic T lymphocytes from immune mice in an antigen-specific manner. Accessory cell function was H-2 restricted and required Ia-positive cells. Treatment with a monoclonal anti-Ia antibody impaired proliferation, whereas the presence of polyclonal rabbit anti-rye antibody increased activity. Guinea-pig peritoneal and alveolar adherent cells pulsed with up to 1 mg/ml antigen increased the response of rye-immune lymph node T cells in vitro. Proliferation was dose-dependent, despite less than 0.1% of the available antigen being cell-associated, and could be inhibited by treating the accessory cells with trypsin, sodium iodoacetate and chloroquine. Adherent human peripheral blood cells treated with rye antigen supported the proliferation of non-adherent and nylon wool-enriched mononuclear cells obtained from both grass pollen-sensitive donors and from individuals lacking either detectable serum IgE antibody or a positive skin test to rye antigen.

Adult↗
PubMed1984

Proliferation of mouse lymphocytes to rye grass pollen extract: effect of inflammatory exudate cells.

The ability of inflammatory peritoneal exudate cells to modify a murine lymphoproliferative response to rye grass pollen extract was investigated. Popliteal and mesenteric lymph node cells from Balb/c mice immunised with either aqueous rye or rye grass emulsified in complete Freund's adjuvant were co-cultured with 2 X 10(3)-10(5) macrophage or polymorphonuclear neutrophil (PMN)-enriched exudate cells. There was a dose-dependent increase in the response to rye grass antigen with increasing numbers of PMN. A similar enhancement was seen with up to 10(4) macrophages per culture; higher numbers were inhibitory. Lymph node cells from rye grass or ovalbumin-immune mice that had been challenged with a combination of sensitising antigen plus 10(7) PMN gave an increased antigen-specific response in vitro. Neither antigen alone, PMN nor a mixture of PMN plus heterologous antigen was active. Adoptive transfer of a similar number of peritoneal macrophages plus antigen was also without effect. These results are in accord with the suggestion that cells obtained from acute inflammatory lesions can directly influence the activity of immunocompetent lymphocytes.

Animals↗
PubMed1984

Production responses of dairy cows fed diets supplemented with ammonium salts of iso C-4 and C-5 acids.

A three-university study examined effects of ammonium salts of volatile fatty acids on dairy cows for a full lactation cycle. Objectives were a) to determine the most efficacious amount and ratio of two components, ammonium salts of C-5 acids and ammonium isobutyrate, and b) to compare responses of this optimum blend with the control in a response surface design. This design tested six blends of the two components defined by the center point and the five points of an equilateral pentagon from which response surfaces would be computed and a control. Each treatment consisted of 23 cows for a total of 161 multiparous Holstein cows. All cows were fed corn silage for ad libitum consumption, 1.8 kg of urea-mineral-vitamin-premix plus supplement based on corn grain and corn gluten meal according to milk production. Response surfaces, based on milk yield, defined an optimum blend composed of 61 g ammonium salts of C-5 acids plus 28 g ammonium isobutyrate per cow per day equivalent to 120 g aqueous blend (74% solids). The optimum blend was similar to the center point blend. Cows receiving the center point blend peaked higher and produced more milk, 4% fat-corrected milk, milk protein, and total solids than control cows. For the first trimester of lactation, milk yields for control and center point blend were 28.6 and 31.8 kg. The 305-day milk, 4% fat-corrected milk yields, and dry matter intakes (kg) were: control 20.5, 19.7, 17.3; center point blend 23.2, 21.6, 17.5. Increased milk production was associated with improved feed utilization. No effect on health or reproduction was observed.

Animal Feed↗
PubMed1983

Activity of cyclosporin A in experimental influenza virus infection in mice.

Oral administration of the immunosuppressive fungal metabolite cyclosporin A increased the mortality of Balb/c mice infected intranasally with influenza A/Hong Kong/1/68 (H3N2) virus. Cyclosporin A also increased the amount of virus that could be recovered from the lungs of infected mice and delayed the rate at which it was eliminated. Treatment with cyclosporin A did not, however, prevent the appearance of haemagglutination inhibiting antibody in the sera of animals that had been infected with a sub-lethal concentration of virus.

Animals↗
PubMed1981

Regulation of volatile fatty acid uptake by mitochondrial acyl CoA synthetases of bovine liver.

Mitochondria of bovine liver contain acyl CoA synthetases necessary for the uptake of propionate, butyrate, and valerate whereas acetate is bound only weakly. Purification of these enzymes separated a distinct propionyl CoA synthetase highly specific for propionate and acrylate and a butyrate-activating fraction with broad substrate specificity for short and medium chain fatty acids. Evidence from kinetic studies and sucrose density centrifugation suggested that this latter fraction was composed of two enzymes, a butyryl CoA synthetase and a valeryl CoA synthetase. The apparent molecular weights of the propionyl, butyryl, and valeryl CoA synthetases were 72,000, 67,000, and 65,000. The Michaelis-Menten constants of propionyl CoA synthetase for propionate, adenosine 5'-triphosphate, and coenzyme A were 1.3 x 10(-3)M, 1.3 x 10(-3)M, and 6.3 x 10(-4)M. Enzyme activity is regulated by the concentration of propionate in portal blood. Relative to propionyl, butyryl, or valeryl CoA synthetases little acetyl CoA synthetase could be demonstrated. In ruminants hepatic metabolism is such that use of acetate as an energy source is minimum. This ensures that an alternative energy source to glucose, as acetate units, will reach the extrahepatic tissues. Separation of a distinct propionyl CoA synthetase regulated by the concentration of propionate in portal blood is significant because a primary role of ruminant liver is to synthesize glucose from ruminally derived propionate.

Animals↗
PubMed1981

Regulation of volatile fatty acid uptake by mitochondrial acyl CoA synthetases of bovine heart.

Purification of components of heart mitochondria activating short chain fatty acids prepared from tissue of lactating Holstein cows demonstrated predominantly one acyl CoA synthetase, acetyl CoA synthetase activating acetate, and propionate. Activity of butyryl CoA synthetase was low. Propionyl CoA synthetase characteristically in bovine liver and kidney tissue could not be demonstrated in heart mitochondria. Thus, of the ruminally derived volatile fatty acids only acetate can be used by heart mitochondria as a primary energy source because of small quantities of propionate in peripheral blood. Acetyl CoA synthetase was a glycoprotein composed of a single polypeptide chain of apparent molecular weight 67,500. The Michaelis-Menten constant for acetate was 1.8 x 10(-4)M. By comparison with literature for blood acetate concentration we concluded that enzyme is saturated with substrate at all physiological concentrations of acetate. These kinetic properties ensure a constant supply of acetate as an energy source for maintaining heart function in ruminants.

Acetate-CoA Ligase↗
PubMed1981

Partial purification of enzymes of bovine kidney mitochondria activating volatile fatty acids.

Mitochondria were prepared from kidney cortex tissue of lactating Holstein cows, and enzymes activating volatile fatty acids partially purified. Two fractions activating volatile fatty acids were obtained; one was similar to components isolated from bovine heart mitochondria activating acetate and propionate (acetyl CoA synthetase). The other was similar to components of bovine liver mitochondria and activated propionate, butyrate, and valerate but not acetate. On calcium phosphate gel chromatography this latter fraction could be separated into a distinct propionyl CoA synthetase (Michaelis-Menten constant for propionate 2.54 x 10(-3)M) and a fraction activating butyrate and valerate. The role of a distinct propionyl CoA synthetase in kidney mitochondria remains to be elucidated because propionate is not a major substrate in peripheral blood of ruminants. We concluded that volatile fatty acid activation by bovine kidney mitochondria is due to an acetyl CoA synthetase, a propionyl CoA synthetase, and a butyrate and valerate-activating fraction probably composed of separate butyryl and valeryl CoA synthetases.

Acetate-CoA Ligase↗