PubMed Health⌕ Search

Biomedical subjects

P Fiset

Publications and source records attributed to P Fiset.

51 records · Page 3Linked to original sources
PubMed1978

Mechanisms of immunity in typhus infection: some characteristics of Rickettsia mooseri infection of guinea pigs.

Rickettsia mooseri infection has been studied in syngeneic guinea pigs inoculated intradermally with the objective of developing a model for the study of immune mechanisms. Characterization of infection included the following: a study of replication, dissemination, and clearance of rickettsiae; measurement of the antibody response with different rickettsial antigens and tests; and attempts to measure the cell-mediated immune response using the correlate of delayed-type hypersensitivity skin reactions. Following intradermal inoculation, rickettsiae replicate locally and then spread to the draining lymph nodes and subsequently cause systemic infection. Spread to draining lymph nodes occurred before the appearance of circulating antibody, whereas systemic infection occurred afterwards. Two distinct patterns of acquired resistance developed. The first was marked by a cessation of rickettsial growth within a given organ and the second by a clearance of rickettsiae. The duration of each of these phases differed markedly from one organ to another. Delayed-type hypersensitivity was not demonstrated by skin testing.

Animals↗
PubMed1978

Role of nonagglutinating antibody in the protracted immunity of vaccinated mice to Pseudomonas aeruginosa infection.

Effective immunization against infection with Pseudomonas aeruginosa is difficult to evaluate because agglutinin levels decline rapidly. Because fractionation of hyperimmune sera often yields more specific antibody than can be accounted for by direct agglutination tests, an immunoglobulin-specific assay based on antiglobulin augmentation was used to characterize antibody responses of C3H/HeJ mice vaccinated with P. aeruginosa type 2 lipopolysaccharide. Nonagglutinating antibodies, initially detected at 2 weeks post-primary vaccination, were predominantly immunoglobulin G after 5 weeks, and they remained elevated at levels usually 32-fold higher than the direct titer throughout the 4-month study period. The sequential production of immunoglobulin M, then immunoglobulin G, followed that found in orthodox immunological responses. Sera that contained nonagglutinating antibodies but not direct agglutinins (14 to 16 weeks) enhanced phagocytosis of P. aeruginosa type 2 by macrophages from unimmunized mice and passively immunized mice against lethal challenge doses; bactericidal activity of these sera was not demonstrated in the presence or absence of complement. When challenged with 1, 10, and 100 50% lethal doses at 16 weeks, survival rates of actively immunized mice were significantly higher than those of unvaccinated mice (P < 0.001). Thus, at a time when no direct agglutinins were detectable, the augmented system detected nonagglutinating antibodies that could confer protracted resistance in vaccinated mice to pseudomonas infection.

Agglutinins↗
PubMed1978

Mechanisms of immunity in typhus infection: some characteristics of intradermal Rickettsia mooseri infection in normal and immune guinea pigs.

Rickettsia mooseri infection in skin at sites of intradermal inoculation was studied in nonimmune and immune guinea pigs with respect to dynamics of infection, localization of rickettsiae within tissues, and gross and microscopic pathology. Intradermal inoculation of R. mooseri into nonimmune guinea pigs resulted in gross lesions which, in magnitude, were directly related to the number of rickettsiae inoculated. The lesions progressively enlarged through 3 or 4 days and remained enlarged through at least 7 days. Histological examination revealed an early acute inflammation which progressed to a predominantly monocyte-macrophage inflammation and subsequently condensed into lymphocyte-containing granulomatous foci. Rickettsiae in the skin at sites of inoculation increased in numbers from 6 h through 3 days, in parallel with the increasing diffuse monocyte-macrophage inflammatory response, and then declined markedly on days 4 or 5 as ganulomatous foci appeared. Some rickettsiae, however, persisted through at least day 7. Fluorescent-antibody studies suggested that R. mooseri infected only a subset of cells available, i.e., cells associated with the microvascular system. Dissemination of infection was demonstrated by the presence of rickettsiae in the skin at sites distant from the point of inoculation. Immune guinea pigs, made immune by intradermal infection with R. mooseri 12 days before intradermal challenge, displayed an accelerated response. The lesions were maximal by 24 to 48 h and subsequently regressed. The inflammatory response of immune guinea pigs was a greater magnitude than the response of similarly challenged nonimmune guinea pigs, and the respose from acute inflammation through the formation of granulomatous lesions was accelerated. The number of rickettsiae in the skin of immune guinea pigs declined steadily from the time of inoculation, until no rickettsiae were recovered on or after day 3. Furthermore, dissemination of rickettsiae to sites in skin distant from the site of inoculation was not demonstrable. The results are discussed in terms of pathogenesis and of immunity to typhus.

Animals↗
PubMed1976

Factors influencing results for thyroxine concentration in blood, as measured in paper filter spots in a screening program for neonatal hypothyroidism.

To reduce the number of false-positives in our screening program for neonatal hypothyroidism, we investigated the effect of age, body weight, and interval between sampling and analysis on results for filter paper spot thyroxine determination. The statistical analysis included an analysis of covariance. The age of the infant did not influence the results, the interval influenced them minimally, but weight did require a correction factor of about 0.16 ng/kg below the mean weight. This correction factor should reduce our false-positives from 0.75% to 0.60%. Furthermore, because all hypothyroid infants had results that fell more than 2.8 SD below the geometric mean, we intend to measure thyrotropin concentrations in the blood eluate of all the spots with a thyroxine concentration below that cut-off point.

Body Weight↗
PubMed1975

Immunologic evidence of human fetal infection with Coxiella burneti.

Immunologic evidence of human fetal infection with Coxiella burneti is presented. Cord sera obtained from normal newborns in an area of high Q fever endemicity, the United Arab Republic, were shown to have high antibody titers against C. burneti and elevated IgM levels. Absorption of the sera with C. burneti antigen removed all detectable specific antibody activity and reduced the IgM level to accepted normal limits.

Agglutination Tests↗
PubMedDate not supplied

A comparison of some biologic characteristics of isolates of the Legionnaires' disease bacterium.

The ability of three isolates of serogroup 1 and one isolate of serogroup 4 of Legionnaires' disease bacterium (LDB) to infect and cause fever and death in guinea pigs was studied, as well as their ability to produce plaques in cultured primary chick embryo cells. The serogroup 4 isolate originally was recovered from cord clot and placental tissue from a healthy mother following delivery of a normal child. The effects on LDB of prolonged cultivation on supplemented Mueller-Hinton (MH) agar medium and of subsequent cultivation in yolk sacs of chick embryos were examined. Prolonged cultivation of LDB on MH medium resulted in great loss of ability to produce plaques and to cause fever and death in guinea pigs. Subsequent passage in embryonated eggs of MH-adapted LDB tended to restore ability to produce plaques and to cause infection and illness in guinea pigs. Fatty acid composition profiles of the four strains were similar to each other.

Animals↗