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Biomedical subjects

M I Stiff

Publications and source records attributed to M I Stiff.

12 recordsLinked to original sources
PubMed1992

Fibrinogen-degrading proteins from Haemonchus contortus used to vaccinate sheep.

Sixteen nonsibling sheep, approximately 12 months old, that were raised in a helminth-free environment, were used for 2 protection studies 6 months apart. Sheep were vaccinated weekly for 5 weeks by IM injection of fibrinogen-degrading proteins derived from the intestinal tract of adult Haemonchus contortus. Ten days after the last vaccination, sheep were given 2,500 infective H contortus larvae by intraruminal injection. Vaccinated sheep produced specific antibodies, and were protected from the worm challenge. Significant differences in mean fecal worm egg counts for 56 days after worm challenge, in mean numbers of H contortus worms, and female fecundity ratios at necropsy were detected in vaccinated sheep, compared with those in control sheep. These data suggest that the fibrinogen-degrading proteins have a protective role in vaccination of sheep against H contortus.

Abomasum↗
PubMed1991

Protective studies in sheep immunized with cuticular collagen proteins and peptides of Haemonchus contortus.

Twenty-eight nonsibling sheep aged approximately 12 months and raised in a helminth-free environment were used in two protection studies. Immunizations were conducted by two intramuscular injections 30 days apart with a synthetic 18AA cuticle collagen peptide and native cuticle collagens derived from the third- and fourth-stage larvae of Haemonchus contortus. Ten days following the last immunization, the sheep were each given 500 infective H. contortus larvae per day for five consecutive days by intraruminal injection. Both collagen materials induced antibodies reactive with cuticle collagens; however, neither induced reproducible protection to H. contortus infections in vaccinated/infected sheep. In the most extensive test, there were no statistical differences in mean faecal worm egg count for 56 days post worm challenge, in mean numbers of H. contortus and female fecundity ratios at necropsy of immunized and unimmunized sheep. Failure to reproducibly immunize sheep with cuticle collagens may be due to the inability of antibodies or host immune cells to reach the collagen epitopes in the nematode cuticle without prior surface coat removal as postulated in human nematode studies.

Adjuvants, Immunologic↗
PubMed1990

Effect of in vivo T-cell depletion on the effector T-cell function of immunity to Eimeria falciformis.

BALB/c mice were exposed to the enteric parasite Eimeria falciformis to produce a natural acquired immunity. The mice were then depleted of their effector T-cell function by in vivo administration of a cytotoxic Thy-1.2 mouse monoclonal antibody. T-cell depletion was demonstrated by a reduction in concanavalin A-induced proliferation of splenic lymphocytes in treated mice compared with that in controls. Twenty-four hours following T-cell depletion, the mice were challenged with 5,000 oocysts of E. falciformis. Daily total oocyst counts were done for each mouse from days 6 to 21 following challenge. Our studies demonstrated that depleting mice of their effector T-cell function following establishment of immunity caused an abrogation of protective immunity to this parasite.

Animals↗
PubMed1986

Polymorphonuclear leukocyte dysfunction associated with feline leukaemia virus infection.

The chemiluminescent characteristics of enriched (greater than 95%) peripheral blood polymorphonuclear leukocyte populations (PMN) from normal and feline leukaemia virus (FeLV)-infected cats were investigated. FeLV-infected cats demonstrated a significantly lower (P less than 0.001) PMN chemiluminescent response when compared to the response of normal age-matched controls. Normal PMN treated with FeLV-infected cat serum exhibited a depressed response in comparison to control cells. A titration of serum from infected cats supplemented with normal serum revealed a titratable suppression of chemiluminescence with increasing concentration of serum from the infected cats. However, PMN from FeLV-infected cats treated with normal serum displayed a slight increase in chemiluminescence over the same cells in autologous serum. The addition of inactivated FeLV to normal PMN caused a titratable decrease in chemiluminescence.

Animals↗
PubMed1986

Density-gradient sedimentation of feline bone marrow cells with polyvinyl-pyrrolidone-coated silica gel.

Feline bone marrow cells were separated based on their density distribution in a continuous polyvinyl-pyrrolidone-coated silica gel density gradient. Morphologic identification of cytocentrifuged preparations at specific densities revealed a progressive increase in density with maturation of the cells within the granulocytic and erythroid series. Segmented eosinophils peaked at 1.084 g/ml, monocytes at 1.07 g/ml, and lymphocytes spanned the density of 1.068 to 1.084 g/ml. Bone marrow samples from 6 healthy specific-pathogen-free cats were separated by the continuous polyvinyl-pyrrolidone-coated silica gel gradient and were studied for progenitor colony formation in methylcellulose. Erythroid colony formation was greatest at a density of 1.084 g/ml and also appeared in cells from 4 cats at a lighter density of 1.016 to 1.05 g/ml. Colony formation in the granulocytic series revealed progenitors throughout the gradient with enrichment at 1.055 g/ml.

Animals↗
PubMed1985

Retroviral-associated eosinophilic leukemia in the cat.

Fourteen specific-pathogen-free cats were inoculated with a putative env gene recombinant feline retrovirus, PR8. An isolate of the Rickard strain of feline leukemia virus (FeLV-R), PR8, has the properties of both an exogenous (FeLV-R) and an endogenous (xenotropic) feline retrovirus (RD-114). Twelve of the PR8-inoculated cats developed viremia; 2 of the 12 cats developed eosinophilia, with 1 being diagnosed with eosinophilic leukemia and the other with extreme eosinophilic hyperplasia. Eosinophilic leukemia is rare in cats and has not previously been associated with retroviral infection. Changes in the viral envelope properties may have altered the pathogenicity of the exogenous virus to cause this rare form of leukemia.

Animals↗
PubMed1984

Feline one-way mixed leukocyte reaction.

The feline one-way mixed leukocyte reaction (MLR) was accomplished by a microtechnique assay using gradient purified mononuclear leukocytes from the peripheral blood of specific-pathogen-free (SPF) cats. An eight day assay was required with an appropriate serum supplement of rabbit or cat serum and obtainable cell concentrations of 1 X 10(5) mononuclear cells per well of each responder and stimulator population. This assay was devised as an in vitro correlate of cell-mediated immunity and to demonstrate that feline histocompatibility differences can be detected in culture.

Animals↗
PubMed1983

Effects of retrovirus protein on the feline one-way mixed leukocyte reaction.

The objective of this study was to evaluate the effects of feline retrovirus protein on cat lymphocyte recognition of allogeneic cells in the mixed leukocyte reaction (MLR), using u.v.-inactivated feline leukaemia virus (FeLV) and a non-disease-producing endogenous cat virus (RD-114). Twenty micrograms of u.v.-inactivated virus protein from each virus were added to mixed leukocyte cultures. FeLV induced significant suppression of the MLR (P less than 0.005) whereas no significant suppression was found using RD-114. Since feline leukaemia infection is associated with immunosuppression, the retrovirus proteins may be interfering with the response of immunocompetent cells when they are confronted with an altered host cell.

Leukemia Virus, Feline↗
PubMed1982

Loss of the short-lived suppressive function of peripheral leukocytes in feline retrovirus-infected cats.

Normal feline peripheral blood mononuclear cells demonstrated increased phytomitogen blast transformation after a 24 hr delay in mitogen addition as compared to 0 hr mitogenesis. Increased stimulation after 24 hr which is not due to enhancing factors accumulating in the culture medium has been attributed to a short-lived suppressor cell which loses its effect after 24 hr in culture. This short-lived suppressive phenomenon was studied in normal specific-pathogen-free cats and compared to experimental animals infected with retrovirus (FeLV). Experimental cats demonstrated a subsequent loss of this function following acquisition of a persistent viremia.

Animals↗
PubMedDate not supplied

Development of immunity in broilers continuously exposed to Eimeria sp.

A series of experiments was conducted to determine the time required to induce absolute immunity to three species of Eimeria in young broiler chickens continuously exposed to the parasite. Acquisition of immunity was measured by cessation of oocyst production in each bird. Initial experiments were performed in broilers beginning at age 7 days with continuous oocyst administration for 28 days with E. tenella, E. maxima, or E. acervulina. Evaluation of oocyst production demonstrated a major decline in oocyst output of E. maxima and E. tenella by 2 weeks, with cessation by 25 days. Exposure to E. acervulina caused cessation of oocyst production by day 16. To study whether chickens of different ages varied in their capacity to immunize within this time frame, 1-day-old birds also were studied. For E. tenella, exposures also were initiated in 14- and 21-day-old birds. This study demonstrated that regardless of the age of the broiler, all were capable of establishing complete protective immunity to E. tenella, E. maxima, and E. acervulina under continuous exposure within 25, 24, and 16 days, respectively.

Age Factors↗