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Biomedical subjects

H Bauer

Publications and source records attributed to H Bauer.

At least 523 records · Page 29Linked to original sources
PubMed1966

The enhancing effect of the microbial flora on macrophage function and the immune response. A study in germfree mice.

The immune response to bacteria and to a soluble protein was compared in germfree and conventionalized mice. Sixty germfree and 59 conventionalized mice received a suspension of killed Serratia marcescens into one front foot-pad and sterile horse ferritin into the other and were sacrificed in groups from 2 hr to 14 days after inoculation. All mice had no pre-existing antibody to either antigen and the flora of the conventionalized mice never contained Serratia. Lymphatic tissue changes and the fate of the antigens were followed in axillary lymph nodes and the spleens by histologic, fluorescent antibody, and autoradiographic techniques after tritiated thymidine injection. Individual serum antibody titers for both antigens were determined at each time period. The cellular and serologic responses were slightly delayed in the germfree mice but later equaled and sometimes exceeded those of the conventional animals. In all animals, lymph nodes draining the site of Serratia injection showed a more vigorous response than those on the ferritin-injected side but the reaction was qualitatively the same for both antigens. All lymph nodes contained the antigens by 2 hr after foot-pad injection. With time, both antigens lost their particulate nature sooner in conventionalized than in germfree macrophages. In the latter, both antigens persisted throughout the study while no longer demonstrable with fluoresceinated antiserum in conventional macrophages after the first week. While phagocytosis is equal in germfree and conventional mice, a greater digestive capacity of macrophages for antigens seems to result from the continuous exposure of conventional animals to the immunologic effects of the microbial flora. Conversely, the lack of substantial antigenic stimulation of lymphatic tissue in germfree animals fails to develop these macrophage functions beyond their basic ability to degrade foreign substances. Although the onset of the immune response is delayed in germfree mice, the relatively prolonged antigen digestion and the presumably slower release of immunogenic antigen fragments result in a more sustained and sometimes greater response than in conventional animals. This modifying effect of the microflora on the function of macrophages during the immune response is independent of previous experience with, or the nature of, the antigen.

Animals↗
PubMed1966

The role of the microbial flora in uremia. II. Uremic colitis, cardiovascular lesions, and biochemical observations.

Uremic colitis of varying severity occurred in the majority of conventionalized rats dying after removal of both kidneys, but was not found in uremic conventionalized and germfree rats sacrificed preterminally, or in germfree and limited-flora rats dying from uremia, or in any of the controls. The lesions were restricted to the cecum and their incidence and severity paralleled a shorter duration of survival. Cardiovascular damage including focal myocardial necrosis and calcification and patchy aortic and coronary calcification were observed in uremic rats regardless of their microbial status. These lesions had a higher incidence, developed more rapidly, and were more severe in the germfree and limited-flora rats than in the conventionalized animals. The presence or severity of the lesions, however, did not correlate with survival time of rats dying from uremia or with total plasma calcium and inorganic phosphorus levels of individual animals. Generalized necrotizing arteritis was not observed. Wound healing was poor in all uremic rats regardless of microbial status. Focal infection was noted in a few conventionalized rats dying from uremia, did not correlate with survival time, and was absent in all other groups. Comparison of biochemical findings between uremic germfree and conventionalized rats show a higher blood urea nitrogen and elevated plasma indoxyl sulfate in the presence of a microbial flora and a greater amount of plasma inorganic phosphorus in its absence. Uremia resulted in a decrease in hematocrit and increase in plasma and muscle potassium that were similar for germfree and conventionalized rats. Plasma and muscle sodium, total plasma calcium, glucose, and total protein were essentially unchanged by microbial status or uremia. Because the foregoing differences in the metabolic and histopathologic changes of uremia are linked to the known difference in microbial status of the fasting bilaterally-nephrectomized rats that were studied, they are a tangible indication of ways by which the indigenous microbial flora and its composition may affect the course of acute uremia.

Animals↗