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Biomedical subjects

M Ristic

Publications and source records attributed to M Ristic.

At least 73 records · Page 4Linked to original sources
PubMed1982

Isolation of an in vitro-produced soluble Anaplasma-albumin complex.

A soluble Anaplasma-albumin complex was isolated from supernatants of A marginale cultures by affinity chromatography. Holstein calves inoculated with this fraction produced anti-A marginale antibodies detected in the indirect fluorescent antibody test at titers similar to those found in cattle immunized with unfractionated culture supernatant. Titers of both groups peaked slightly above 1:2,000 on postinoculation day 46.

Anaplasma↗
PubMed1981

Bovine babesiosis: protection of cattle with culture-derived soluble Babesia bovis antigen.

Adult Hereford (Bos taurus) cattle were protected from severe reactions and death caused by the tick-borne protozoan hemoparasite Babesia bovis, 3 months after vaccination with a cell culture--derived immunogen. The immunogen consisted of filtered, freeze-dried supernatant fluid collected from long-term cultures of Babesia bovis in vitro. It was reconstituted with saponin adjuvant and injected twice subcutaneously at 2-week intervals. Serum collected from vaccinated cattle caused thickening of the merozoite surface coat, aggregation, and lysis of merozoites in vitro. This reaction was identical to that caused by serum from immune carrier cattle suggesting that the protective antigen present in culture fluids is merozoite surface coat antigen. No mortality occurred among vaccinated cattle, whereas mortality among unvaccinated cattle and Babesia bigemina--immune cattle was 62.5 percent indicating that immunity to bovine babesiosis is species-specific.

Animals↗
PubMed1981

Isolation and partial characterization of culture-derived soluble Babesia bovis antigens.

Immunochemical analyses of soluble antigens derived from microaerophilous stationary phase cultures of Babesia bovis demonstrated that at least three parasite antigens were released in vitro. These antigens have molecular weights within the range of 37,000 to 40,000, fast electrophoretic mobility in the albumin and alpha 1 regions, and are proteinaceous in nature as determined by the sensitivity to proteolytic enzymes trypsin and papain. Purification of these antigens should allow complete characterization of their respective physiochemical and immunogenic properties.

Animals↗
PubMed1981

Evidence of a serologic relationship between Ehrlichia canis and Rickettsia sennetsu.

A serologic relationship between Rickettsia sennetsu, the etiologic agent of human sennetsu rickettsiosis in western Japan, and Ehrlichia canis, the agent of canine ehrlichiosis, has been demonstrated. Using the indirect fluorescent antibody test, convalescent sera from patients with sennetsu fever reacted with Ehrlichia canis antigen. In the direct fluorescent antibody test, immunoglobulins from four patients with sennetsu rickettsiosis stained E. canis morulae in canine monocytes. This finding is significant in view of the morphologic uniqueness of the two agents and a lack of serologic relatedness with other major rickettsial agents.

Adolescent↗
PubMed1981

Antibody kinetics in response to vaccination against Babesia bovis.

The kinetics of specific indirect fluorescent antibody (IFA) test titers and total serum immunoglobulin (Ig) G and IgM values were determined in cattle vaccinated with culture-derived soluble Babesia organisms. Nineteen days after challenge exposure (postinoculation day 67), vaccinated cattle had a strong anamnestic response and mean IFA titers reached 1:48,710. Serum IgG and IgM concentrations were increased after vaccination and after challenge exposure. A nonspecific suppression of total IgG (controls) and IgM (vaccinated animals and controls) values also was observed, the depression coinciding with the period of peak parasitemia.

Animals↗
PubMed1980

Babesia bovis: continuous cultivation in a microaerophilous stationary phase culture.

The protozoan parasite Babesia bovis, a causative agent of bovine babesiosis, has been continuously cultivated in a settled layer of bovine erythrocytes. Lowered oxygen tension within the layer of host erythrocytes results in a darkening of infected cultures and provides a rapid means of evaluating parasite growth. Deprivation of carbon dioxide causes the merozoites to accumulate in the medium rather than involving new erythrocytes. When separated from the culture, these extraerythrocytic parasites retain their infectivity. Parasites produced in vitro are morphologically identical to parasites from the blood of infected cattle and are susceptible to antibabesial drugs.

Animals↗
PubMed1980

Cell-mediated and humoral immune responses of German Shepherd Dogs and Beagles to experimental infection with Ehrlichia canis.

The cell-mediated and the humoral immune responses of 12 German Shepherd Dogs and 5 Beagles inoculated with Ehrlichia canis were evaluated. Results indicated that specific and nonspecific immunosuppression due to E canis occurred in the German Shepherd Dogs. Canine leukocyte migration-inhibition factor was successfully isolated and shown to be physically and functionally similar to human and guinea pig migration inhibition factor. Of the German Shepherd Dogs, 58% developed positive cell-mediated responses; 80% of the Beagles became positive. German Shepherd Dogs that developed severe chronic ehrlichiosis did not respond to as great a degree as did the German Shepherd Dogs and Beagles with mild chronic disease. The cell-mediated responses decreased with time and disappeared by 147 days after inoculation. Humoral antibody titers in all inoculated dogs increased with time and remained at increased concentrations. Treatment of four inoculated dogs with antilymphocyte serum did not modify the course of the disease. The findings indicated that cell-mediated immunity may have a significant role in determining the course of disease in dogs infected with E canis.

Animals↗
PubMed1980

Bovine babesiosis: pathogenicity and heterologous species immunity of tick-borne Babesia bovis and B bigemina infections.

A total of 22 nonsplenectomized Hereford, Holstein-Friesian, and cross-bred 18-month-old cattle were used to assess the degree of protection conferred by previous infection with Babesia bovis or B bigemina against infection and disease from tick-borne challenge exposure with the heterologous species. Prior infection with B bigemina or B bovis did not significantly (P less than 0.05) reduce the susceptibility of cattle to tick-borne infection and disease caused by the heterologous species. Carrier infections were not activated during heterologous species challenge exposure, nor was the severity of the challenge-exposure infection aggravated. Immunologic cross reactivity in the indirect fluorescent antibody test was restricted to the period during and shortly after recovery. Homologous indirect fluorescent antibody titers persisted long after primary infections with B bovis, but gradually declined in B bigemina-immune cattle. Babesia bovis infections caused severe reactions characterized by high fever, pancytopenia, and death of 9 of 15 infected cattle. Total serum bilirubin and urea nitrogen values increased markedly within 24 hours preceding death and were often accompanied by clinical signs of CNS involvement (incoordination, opisthotonos, and paddling). Microscopic lesions were restricted largely to kidney, CNS, and liver parenchyma and were characterized by vascular congestion and aggregation of infected erythrocytes in small vessels. Babesia bigemina, in contrast, caused only mild fever and anemia despite prolonged parasitemia and marked thrombocytopenia. The absence of significant (P less than 0.05) heterologous species immunity indicated that protection of cattle from these 2 babesial parasites will require specific immunization against each species.

Animals↗
PubMed1980

Optimization of the suspension culture method for in vitro cultivation of Babesia bovis.

An evaluation of some system variables for the suspension-culture method of in vitro Babesia bovis cultivation has identified some variables as critical and suggested optimum values for others. Growth of Babesia was not affected by siliconizing the culture vessels or including HEPES buffer in the culture medium. THe culture pH, however, markedly influenced the growth rate. When supplemented with a large amount of serum, even Hanks's balanced salt solution was an adequate medium to support growth of B bovis, but growth improved with increasing medium complexity. A comparison of growth in the complex mammalian tissue culture mediums RPMI-1640, medium 199, and NCTC-135 showed no significant differences. Heparinized plasma (plasma with added heparin ) could not be substituted for serum. While serum could be stored by either freezing or refrigeration at 4 C for up to a week RBC rapidly lost their ability to support growth of B bovis when stored at 4 C. Preliminary experiments with the gaseous environment indicated that CO2 is required and that the optimum oxygen tension was near the normal atmospheric level of about 20%.

Animals↗
PubMed1980

Comparison of three methods of immunization against bovine anaplasmosis: an examination of postvaccinal effects.

Normandy calves ranging in age from 7 to 11 months were immunized against bovine anaplasmosis, using a diluted virulent Anaplasma marginale stabilate of Colombian origin, diluted bovine blood containing an apparently mild strain of A marginale isolated in Colombia, or an attenuated A marginale vaccine of ovine origin from the United States. Calves given the stabilate generally showed a moderate degree of parasitemia and reduction in packed cell volume (PCV). Calves given the apparently mild Colombian isolate of A marginale developed a moderate parasitemia, a reduction in PCV, and in some instances, required treatment to moderate the premunization procedure. Calves given the attenuated vaccine showed minimal evidence of parasitemia and PCV reduction. Most of the immunized calves became seropositive in the complement-fixation test for anaplasmosis and all calves sampled showed evidence of a cell-mediated response, using the leukocyte migration-inhibition test.

Anaplasma↗
PubMed1980

Comparison of three methods of immunization against bovine anaplasmosis: evaluation of protection afforded against field challenge exposure.

The efficacy of three immunization methods for bovine anaplasmosis was tested on 88 yearling Normandy cattle which were challenge-exposed under field conditions in an enzootic zone in Colombia, South American. A total of 30 cattle were immunized (premunized) with a presumed mild Colombian isolate of Anaplasma marginale; 29 calves were vaccinated with an attenuated A marginale of ovine origin; and 29 were exposed to a virulent A marginale stabilate of Colombian origin. Twenty-nine nonvaccinated cattle served as controls. Parasitemia, packed cell volume, body weight, and complement-fixation antibody response were monitored to determine host response to challenge exposure. The calves experienced a Babesia challenge exposure following arrival in the enzootic zone, after which a transient increase in Anaplasma parasitemia, accompanied by a decrease in packed cell volume, occurred in most of the vaccinated calves. However, neither clinical anaplasmosis nor mortality due to the disease occurred in the immunized cattle. Twenty-seven of the nonvaccinated calves had signs of clinical anaplasmosis and five (17%) died of the disease.

Anaplasmosis↗
PubMed1980

Continuous in vitro cultivation of Babesia bovis.

Babesia bovis was isolated from an experimentally infected calf (No. 1) and was maintained in vitro for 32 days by subculturing 14 times, using a total dilution of 192,000. A splenectomized calf was inoculated with subculture Babesia (isolate B). The agent (isolate C) was isolated and maintained in vitro for 17 days prior to inoculation of a third splenectomized calf. Babesia organisms (isolate D) were isolated and retained in vitro for 270 days. After 85 days in vitro, organisms from this third isolation (isolate D) were injected into a fourth splenectomized calf to test for infectivity. Responses of the three calves to cultural inoculation were similar to those responses that occurred from inoculation of infected bovine blood (calf 1). There was no observed change in the microscopic appearance of the Babesia in vitro with time.

Animals↗
PubMed1979

Mortality, weight loss and anaemia in Bos taurus calves exposed to Boophilus microplus ticks in the tropics of Colombia.

One hundred and sixteen pure-bred Normandy calves previously immunised against babesiosis and anaplasmosis were transported to the Caribbean Coast of Colombia where they divided into 2 equal groups and placed in separate pastures. One group sustained heavy infestation with Boophilus microplus ticks. The second group became lightly infested. The heavily infested calves suffered average losses in body weight of 38 kg and a 48% decrease in mean packed cell volume. Twenty-three (40%) died 16 to 39 days following arrival from severe ixodiasis and babesiosis. Mortality did not occur nor were significant weight losses observed in the group of lightly infested calves.

Anemia↗