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Biomedical subjects

M Ristic

Publications and source records attributed to M Ristic.

At least 109 records · Page 6Linked to original sources
PubMed1977

Cell-mediated immune response to virulent and attenuated Anaplasma marginale administered to cattle in live and inactivated forms.

The leukocyte migration-inhibition test (LMIT) and lymphocyte transformation of blood leukocytes from cattle exposed to virulent, attenuated, and inactivated preparations of Anaplasma marginale served as indices of cell-mediated immunity in bovine anaplasmosis. The LMIT response increased markedly in cattle vaccinated with attenuated A marginale or injected with virulent A marginale. Cattle inoculated with inactivated anaplasma developed a transient, low-level LMIT response. The response to antigenic stimulation recorded in the lymphocyte transformation test of leukocytes collected from cattle which were given live anaplasma was less than the response elicited from leukocytes collected from cattle vaccinated with inactivated anaplasma in adjuvant.

Anaplasma↗
PubMed1977

Cell-mediated immunity related to challenge exposure of cattle inoculated with virulent and attenuated strains of Anaplasma marginale.

Cattle which were given virulent Anaplasma marginale as a premunization procedure or were vaccinated with live attenuated or killed anaplasma preparations were challenge inoculated with virulent A marginale. Exposure of cattle to virulent or attenuated A marginale, which induced a strong and lasting cell-mediated response as measured by the leukocyte migration-inhibition test, protected against the development of high parasitemia, anemia, and clinical signs of disease after challenge inoculation with virulent A marginale. Cattle which were vaccinated with killed anaplasma preparations that induced transient and low-level cell-mediated responses were not protected against the development of severe anemia after challenge inoculation, although postchallenge parasitemia seemed to be controlled.

Anaplasma↗
PubMed1977

Autologous lymphocyte-mediated cytotoxicity against monocytes in canine ehrlichiosis.

The 51Cr-release technique for detecting cytotoxicity had been adapted to immunologic studies of canine ehrlichiosis. Lymphocytes from dogs infected with Ehrlichia canis, cause of canine ehrlichiosis, were shown to be cytotoxic for autologous monocytes. The effect was dependent on the concentraton of lymphocytes, being optimal at 100:1 lymphocyte:monocyte ratio. Neither immune serum and complement, nor anti-canine globulin had any observable effect on cytotoxicity. The monocytotoxicity bore a temporal relationship to the thrombocytopenia. It is suggested that T lymphocyte activation accompanying ehrlichiosis contributes to pathogenesis of the disease and that the specific immune elimination of parasitized monocytes is antibody independent.

Animals↗
PubMed1976

Ultrastructural observations on Ehrlichia equi organisms in equine granulocytes.

The ultrastructure of the etiological agent of equine ehrlichiosis, Ehrlichia equi, was studied in equine peripheral leukocytes. The organisms occurred within membrane-lined cytoplasmic vacuoles of neutrophils and eosinophils. Ovoid, round, and rod-shaped profiles were observed. From 1 to 33 organisms were present in a thin-section profile of a cytoplasmic vacuole. Many cells contained multiple organism-containing vacuoles. The organisms had a cell wall and plasma membrane, and internally they consisted of electron-dense and lucid areas. A great variation in size was observed. The morphological features were most consistent with agents of the genus Ehrlichia.

Animals↗
PubMed1976

Neutralization of a transmissible gastroenteritis virus of swine by colostral antibodies elicited by intestine and cell culture-propagated virus.

Cross-protection studies of gilts exposed to 4 transmissible gastroenteritis viruses--Ilinois (field strain), Miller-3, Miller low passage (M-LP), and Miller high passage (M-HP) tissue culture-adapted--indicated that only the gilt vaccinated with Illinois strain was protected, along with its newborn pigs, against challenge exposure with field virus. Similar results were obtained when the 4 viruses were incubated in vitro with colostrum from each of the 4 vaccinated gilts and subsequently used to orally inoculate newborn pigs. However, when the colostrums were used to neutralize M-HP virus in cell cultures, the neutralization titers were similar, indicating that a close antigenic relationship existed among the viruses. Neutralization studies in cell cultures, using immunoglobulin (Ig) fractions derived from colostrums of sows exposed to Illinois and M-HP virus, indicated that Illinois virus elicited more neutralizing activity in IgA than in the IgG fraction and that M-HP virus elicited more IgG than IgA antibody activity. In another study, Illinois virus was treated with these Ig-enriched fractions and then inoculated into the lumen of the jejunum of 3-day-old pigs. Anti-Illinois IgA was the only class of antibody which prevented replication of the Illinois virus in the intestine. Similar intraintestinal inoculations were used to test invasiveness of untreated Illinois and M-HP viruses. It was demonstrated that Illinois virus caused marked effect on the intestine: shortening of the villi, intestinal distension, edema, and presence of accumulated intestinal fluid within 60 hours after inoculation. The M-HP virus grew in the intestinal cells without affecting the length of the villi. The degree of invasiveness of Illinois or M-HP virus may account for the difference in the antibody class elicited in the colostrums.

Animals↗
PubMed1976

Intestinal immune response of feeder pigs to infection with transmissible gastroenteritis virus.

Five feeder pigs 4 to 6 months old were orally inoculated with transmissible gastroenteritis virus. Diagnosis of transmissible gastroenteritis was made on the basis of clinical signs and examination of intestinal mucosa by the fluorescent antibody technique. Immunoglobulins were extracted from intestinal fluid of infected feeder pigs. Virus-binding and neutralizing antibodies were detected in intestinal extracts between 7 and 56 days after infection. The concentration of binding antibodies reached a peak at 21 days after infection and was on the decline at the end of the experiment on the 56th postinfection day. In contrast, neutralizing intestinal antibody concentration was increasing on day 56. In both systems, the predominant immunoglobulin was of the IgA class. Examination of blood serums of the pigs by the plaque-reduction technique showed progressive antibody increases ranging in titer from 1:8 on day 7 to 1:256 on day 56 after infection. An analysis of the protein profiles from these serums showed a significant increase in the concentration of gamma-globulins and a decrease in the albumin fraction.

Animals↗
PubMed1976

Cutaneous hypersensitivity and isoantibody production in cattle injected with live or inactivated Anaplasma marginale in bovine and ovine erythrocytes.

Delayed cutaneous hypersensitivity and the production of isoagglutinins against normal bovine erythrocytes were measured in cattle inoculated with erythrocytic preparations containing live or inactivated Anaplasma marginale. The effect of blood group substances versus parasitic components on induction of delayed cutaneous hypersensitivity and isoimmunity was examined by using test antigens derived from normal and parasitized erythrocytes, virulent A marginale in bovine erythrocytes, and attenuated A marginale in ovine erythrocytes. The use of inactivated vaccine of bovine origin induced production of isoantibodies and cutaneous hypersensitivity to both bovine and ovine blood group factors, whereas a similar vaccine preparation of ovine origin stimulated antibodies and cutaneous reactivity only against ovine blood group factors.

Anaplasma↗
PubMed1975

Isolation in Illinois of a foreign strain of Ehrlichia canis, the causative agent of canine ehrlichiosis (tropical canine pancytopenia).

Ehrlichiosis (tropical canine pancytopenia) was diagnosed in Illinois in a 4 1/2-year-old mixed breed dog that had spent the previous 2 years in India. The dog had periodic epistaxis, anemia, leukopenia, hypoalbuminemia, and hypergammaglobulinemia. A titer of 1:160 for Ehrlichia canis was detected by the indirect fluorescent antibody test (IFAT). Subinoculation of blood into a clinically normal dgo resulted in typical signs of canine ehrlichiosis, and E canis was identified in circulating mononuclear cells. The recipient died 23 days after inoculation, and typical gross and microscopic lesions of ehrlichiosis were found at necropsy. Ecchymoses and petechiae were found on the gallbladder, kidneys, small intestinal mucosa, cerebrum, and cerebellum. Plasmacytosis and perivascular cuffing was evident in various organs, especially the cerebrum, cerebellum, and meninges.

Animals↗
PubMed1975

Platelet kinetics in canine ehrlichiosis: evidence for increased platelet destruction as the cause of thrombocytopenia.

A significant (P < 0.025) increase in the mean platelet diameter occurred in five Ehrlichia canis-infected dogs when platelet numbers decreased to 100,000/mul or less. Maximal incorporation of [(75)Se]selenomethionine into platelets of six uninfected dogs was 0.080 +/- 0.019% (mean +/- standard error) and occurred 5 to 6 days after dosage, whereas maximal incorporation was 0.036 +/- 0.004% within 2 to 3 days after dosage in seven chronically infected dogs that had thrombocytopenia. Analysis of the [(75)Se]selenomethionine curves yielded a platelet lifespan of 9 days in uninfected dogs versus 4 days in chronically infected dogs. Thus, megakaryocyte maturation and/or platelet release occurred at an accelerated rate in infected dogs, whereas increased destruction of newly produced labeled platelets diminished their number of peripheral blood. [(51)Cr]sodium chromate-labeled platelet survival was exponential, with a half-life of approximately 1 day in two dogs at 2 to 4 days postinfection and three chronically infected dogs. Platelet survival time was 8 days and rectilinear in four uninfected dogs. Platelet recovery was 39.43 +/- 2.86% in infected dogs as compared with 68.2 +/- 10.72% in uninfected dogs. Whole-body scans of one dog prior to and 7 days after infection showed that labeled platelets were destroyed primarily in the spleen. It is concluded that the thrombocytopenia in E. canis-infected dogs is the result of increased platelet destruction which begins within a few days after infection.

Animals↗
PubMed1975

Protective effect of immunoglobulins in serum and milk of sows exposed to transmissible gastroenteritis virus.

Experimental exposure of susceptible pregnant sows by various routes to the gut-origin transmissible gastroenteritis virus stimulated production of milk and serum antibodies. These antibodies neutralized the cytopathic effect of transmissible gastroenteritis virus propagated in cell culture. This in vitro neutralizing antibody resided in the IgG and IgA immunoglobulin classes. On the other hand, protection for baby pigs resided in the IgA class of milk immunoglobulin of sows exposed orally or intramammarily but not of sows exposed intramuscularly to the virus.

Animals↗
PubMed1975

Experimentally induced infection of dogs, cats, and nonhuman primates with Ehrlichia equi, etiologic agent of equine ehrlichiosis.

Dogs (German Shepherd Dogs and Beagles), cates, rhesus macaques (Macaca mulatta), and baboons (Papio anubis) were inoculated with Whrlichia equi, the etiologic agent of equine ehrlichiosis. Within 3 to 7 days after inoculation, morulae were observed in the eosinophils of cats, neurtrophils of macaques and baboons, and in both neutrophils and eosinophils of dogs. The severe disease produced in horses by this agent was not a feature of E equi infection in dogs, cats, macaques, and baboons. However, a susceptible horse, inoculated with the pooled blood of 2 infected macaques, developed severe clinical signs of equine ehrlichiosis. Infection with E equi did not alter the susceptibiltiy of dogs to infection with Ehrlichia canis and did not prevent development of signs of disease resulting from this infection. The broad experimental host range from this infection. The broad experimental host range of E equi distinguishes it from other ehrlichial agents which are characterized by a rather narrow host range. The susceptibiltiy of nonhuman primates to infection with E equi provides a basis for consideration of the potential transmission of ehrlichial agents to man.

Animals↗
PubMed1975

A method for separation of bovine blood leukocytes for in vitro studies.

Various methods have been developed for separation of the cellular components of blood. Size and density differences in cellular blood elements of various animal species necessitate the use of specific separative procedures. This study describes a method which combines isopycnic density-gradient centrifugation with erythrocyte aggregation as a means of isolating leukocytes from bovine blood. The procedure yields a viable population of mixed leukocytes which has proven useful for cell culture and in vitro tests of cell-mediated immunity.

Animals↗
PubMed1975

Canine ehrlichiosis (tropical canine pancytopenia) in Thailand.

An epizootic of canine ehrlichiosis has occurred in military working dogs in Thailand. During the epizootic, 161 cases of ehrlichiosis were identified serologically in a population of 316 dogs, and 54 dogs exhibited clinical signs of disease. The epizootic is being controlled by elimination of ticks, by serologic identification and treatment of carriers with 30 mg/lb body weight/day of tetracycline for 14 days, and by continuous daily prophylactic administration of 3 mg/lb body weight/day of tetracycline. Clinical and serologic recognition of ehrlichiosis among pet dogs in widely separated regions of Thailand suggest that the disease has been endemic in Thailand for an extended time. Under such circumstances it is possible that pet and stray dogs have served as a source of infection for the epizootic in military working dogs.

Animals↗
PubMed1975

Kinetics of antibody response to Ehrlichia canis assayed by the indirect fluorescent antibody method.

The kinetics of antibody production response to experimentally induced infection of dogs with Ehrlichia canis was determined by ion-exchange and molecularsieve chromatography and by indirect fluorescent antibody (IFA) test. The first IFA antibody at 7 days after inoculation resided in immunoglobulin M (IgM) and immunoglobulin A (IgA) classes. At approximately 21 days after inoculation, the antibody was in IgM, IgA, and immunoglobulin G (IgG) classes. Thereafter, antibody concentrations continued to increase in the IgG class; those in the other 2 immunoglobulin classes had a variable pattern. In 2 dogs which died 60 and 114 days after inoculation, a decrease of antibody concentration in the 3 immunoglobulin classes was evident at the time of death. In the carrier dog, however, which was killed 147 days after inoculation, antibody concentrations sustained increasing titers in the 3 immunoglobulin classes.

Animals↗