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Biomedical subjects

D W Johnson

Publications and source records attributed to D W Johnson.

At least 325 records · Page 18Linked to original sources

Screening tests for new teat dips.

Increased use of after-milking teat dips has resulted in the appearance of many new teat dips and a need for methods of evaluation of efficacy. A method was developed for determining the ability of a disinfectant to kill bacteria on the teat ends. Results from several known efficacious products indicated an approximate 95% reduction in bacterial flora. Additional data are presented on some experimental products. This method will provide a measure of effectiveness of a producton teat-skin disinfection. The effect of some changes in the testing procedure on bacterial reduction is demonstrated: 1) Increased times between inoculation and dipping and between dipping and swabbing tended to decrease recoveries on control teats. 2) Saline dips on controls teats provided increased recoveries of test organisms.

Animals↗

Experimentally induced Mycobacterium avium serotype 8 infection in swine.

Five of 6 swine experimentally inoculated with Mycobacterium avium serotype 8 had microgranulomas in the cervical or mesenteric lymph nodes at necropsy 92 days later. In vivo tuberculin skin reactivity and in vitro lymphocyte immunostimulation responses were evaluated at 10 and 12 weeks after the pigs were inoculated. Positive responses were obtained on both tests in inoculated pigs, whereas test results in noninoculated pigs and pigs given killed bacterial cells were negative. Mycobacterium avium serotype 8 was isolated at necropsy from the cervical or mesenteric lymph nodes of each of the pigs inoculated with viable microorganisms and from the 2 pigs kept in the pen with inoculated swine. Mycobacteria were not isolated from tissues of the noninoculated swine or those given killed cells.

Animals↗

Mechanism of protection from primary bovine viral diarrhea virus infection. I. The effects of dexamethasone.

A series of investigations was designed to study the role of cellular immunity and passive antibody in protecting neonatal calves from primary bovine viral diarrhea virus infection. Administration of corticosteroids (dexamethasone) in doses capable of suppressing cellular immunity markedly potentiated systemic bovine viral diarrhea virus infection in calves which lacked bovine viral diarrhea passive neutralizing antibody. Immunosuppressed calves did not form neutralizing antibody to bovine viral diarrhea virus and developed a fatal viremia. Calves with high levels of passive bovine viral diarrhea neutralizing antibodies were protected from the effect of corticosteroids. The results suggest an essential role for humoral passive antibody, but not for cellular immunity, in protection from primary systemic bovine viral diarrhea virus infection in calves.

Animals↗

Externship program for large animal clinical education at the University of Minnesota: description and evaluation.

In 1970, the College of Veterinary Medicine at the University of Minnesota started an externship program as part of their large animal clinical education program. The basic idea was to work in cooperation with practitioners, using their practice world as a teaching resource. During the 1973-1974 school year, this program was evaluated by the University of Minnesota Measurement Services Center. In this externship program, senior year students spend 1 or 2 weeks in practice that closely matches each student's career interest, eg, cow-calf, dairy, swine, or zoo. The participating veterinarians are charged with the responsibility of performing as teachers during the field experience and of assisting the student in preparing a seminar topic. This seminar topic is presented in a discussion format during the spring quarter to other externship students, faculty, and attending practitioners. Since 1970, a total of 176 students have taken externships, and every year 15 to 20 group practices have participated. The principal evaluation results were based on questionnaire responses from 36 students and 20 practices during the 1973-1974 academic year. Students and practitioners indicated that the externship had been a beneficial experience for them. Many felt that the period of externship should have been longer. In general, practitioners agreed that students were able to manage most diagnostic situations and manipulative procedures that occurred during the externship. The seminar was judged by students and practitioners to be a valuable part of the program, and faculty who participated in the seminar believed that it made them more aware of field situations facing practicing veterinarians.

Animals↗

Effect of ambient temperature on heat production and heat loss in burn patients.

Four controls and eight burned patients with thermal injury ranging from 7 to 84% total body surface were studied in an environmental chamber at 25 and 33 degrees C ambient temperature and a constant vapor pressure during two consecutive 24-h periods. Hypermetabolism was present in the burn patients in both ambient temperatures and core and skin temperatures were consistently higher than in the normal men despite increased evaporative water loss. The higher environmental temperature decreased metabolic rate in patients with large thermal injuries in whom the decrement in dry heat loss produced by higher ambient temperature exceeded the increase of wet heat loss. In patients with burns smaller than 60%, these changes equaled one another and higher environmental temperature exerted no effect on metabolic rate. Core-skin heat conductivity increased with burn size; patients with large burns were characterized by inadequate core-skin insulation when exposed to the cooler environment, necessitating the compensatory increase of metabolic rate. This increase, however, was small and of the order of 5-8 kcal times m-2 times h-1.

Adolescent↗

Development of specific in vitro lymphocyte responses in cattle infected with Mycobacterium bovis and with Mycobacterium avium.

Two calves infected with Mycobacterium avium and another 2 with Mycobacterium bovis were studied for development and specificity of lymphocyte activation responses and skin reactivity to purified protein derivatives (PPD). Lymphocytes cultured in vitro from infected calves manifested significant uptake of tritiated thymidine in response to the PPD prepared from the homologous organisms, whereas heterologous PPD produced little or no stimulation. The time of appearance of specifically sensitized lymphocytes was studied, as was the specificity of skin reactivity.

Animals↗

Development of specific lymphocyte immunostimulation and tuberculin skin reactivity in swine infected with Mycobacterium bovis and Mycobacterium avium.

Swine infected with Mycobacterium bovis and Mycobacterium avium were studied for development and specificity of lymphocyte immunostimulation and tuberculin skin reactivity to purified protein derivatives (PPD) of tuberculins. Lymphocytes from infected animals had maximal blastogenic responses to PPD prepared from the homologous organisms. The time of appearance of specifically sensitized lymphocytes was studied, as was the specificity of skin reactivity. In vitro lymphocyte responses of M avium serotype 1-infected swine to M avium serotype 1 PPD were greater than were the responses of M avium serotype 2-infected swine to the same antigen. Results indicate that the specific stimulation of sensitized lymphocytes might prove useful in the diagnosis of tuberculosis in swine and in differentiating infections due to different serotypes of M avium.

Administration, Oral↗

Effects of corticosteroids on responses of bovine peripheral blood lymphocytes cultured with phytohemagglutinin.

Corticosteroids given in vivo altered the response of lymphocytes in the peripheral blood of calves. Lymphocytes were cultured and stimulated in vitro with phytohemagglutinin (PHA). After an initial suppression of lymphocyte responses to PHA, there was a rapid return to normal. It is concluded that, in calves, short-term, high-dose immunosuppressive therapy with corticosteroids produces a population of lymphocytes resistant to corticosteroids, possibly by destruction of corticosteroid-sensitive lymphocytes.

Animals↗

Comparison of lymphocyte stimulation and tuberculin skin reactivity in Mycobacterium bovis-infected Macaca mulatta.

Lymphocyte immunostimulation tests were conducted on Mycobacterium bovis-infected and tuberculin-negative rhesus macaques (Macaca mulatta), using purified protein derivative (PPD) tuberculins prepared from strains of Mycobacterium tuberculosis and Mycobacterium avium. The stimulation of lymphocytes with M tuberculosis PPD was significantly greater for the M bovis-infected macaques than for the noninfected controls (P smaller than 0.05). The response of lymphocytes from M bovis-infected macaques to stimulation with M tuberculosis PPD was greater than the responses to stimulation with M avium PPD (P smaller than 0.01). The results of in vitro lymphocyte stimulation and tuberculin skinreactivity were similar.

Animals↗

Macrophage-dependent lymphocyte immunostimulation in cattle infected with Mycobacterium bovis and with Mycobacterium avium.

Cultures of bovine peripheral blood leukocytes were prepared from calves inoculated with Mycobacterium bovis and with M. avium. Suitable lymphocyte stimulation was obtained with specific and nonspecific mycobacterial mitogens. Leukocyte cultures depleted of adherent, macrophage-type cells did not respond to stimulation with purified protein derivative, although they were responsive to phytohemagglutinin.

Animals↗

CAMP factor of group B streptococci: production, assay, and neutralization by sera from immunized rabbits and experimentally infected cows.

Quantitative assay methods for CAMP factor activity of group B streptococci and for neutralization of this activity by animal sera are described. The course of the CAMP reaction is influenced by preincubation of red cells with staphylococcal beta-hemolysin and the rate of the reaction by the concentration of CAMP factor. The production of CAMP factor is enhanced by substitution of maltose for glucose in culture broth. Rising inhibitory titers to CAMP activity in sera of rabbits injected with sterile culture supernates of group B streptococci suggest that CAMP factor is an antigen in the rabbit. Cows with experimentally induced group B streptococcal mastitis also demonstrated significant rises in neutralizing titers for CAMP activity.

Animals↗