Postirradiation changes in small intestine mucosa of piglets selectively decontaminated by peroral antibiotics.

There was performed light microscopic and morphometric comparison of changes in the intestinal mucosa structure after the irradiation of the lower part of body by radiation 60Co in a dose of 12 Gy, observed the third day after irradiation in piglets kept under conventional conditions and the fifth, the fifteenth and the twentieth days after irradiation in piglets kept under the conditions of selective decontamination by peroral antibiotics. The non-irradiated animals kept conventionally as well as under the conditions of decontamination served as controls. The estimation was performed on transverse slices of the cranial part of jejunum and of the caudal part of ileum. The slices were stained by the method hematoxylin-eosin. The drawings prepared with the help of the projective microscope Pictoval were used for measuring on the apparatus for the quantitative analysis of image MOP AM 03. A markedly lower damage of the intestinal mucosa was evidenced in piglets selectively decontaminated by peroral antibiotics. In the studied time intervals after irradiation in a dose of 12 Gy, the epithelial cover of mucosa, the crypt epithelium and the general outline of mucosa are much better maintained. The favourable effect of the selective decontamination on the maintenance and regeneration of the mucosa of jejunum and ileum is confirmed by a range of morphometric parameters.

Stimulating effect of Streptococcus faecalis on phagocytosis in gnotobiotic piglets.

The concentration of active phagocytes in peripheral blood remained in germfree pigs up to the age of one year approximately at the same level as found at the age of 7 d and did not exceed 0.3 X 10(9)/L of blood, whereas a steady increase was established in conventional pigs. Monoassociation of gnotobiotic piglets with Streptococcus faecalis increased during 24 h the concentration of circulating granulocytes and the concentration of active phagocytes. An even more pronounced effect was obtained when formolized S. faecalis cells were applied intraperitoneally to germfree piglets. This treatment elevated the phagocytosis index also in conventional piglets, as well as in germfree piglets previously given cyclophosphamide. Escherichia coli O 83 or a mixture of anaerobic bacteria did not cause any serious changes in the activity of phagocytosis in gnotobiotic piglets. S. faecalis seems to be a natural factor stimulating both the release of granulocytes from their depots as well as their phagocytic activity.

Immunological state of adult germfree miniature Minnesota pigs.

Fundamental hematological and immunological data were obtained on sexually mature germfree miniature pigs fed, after the milk diet period, with cereal-type diet sterilized by gamma-radiation, and were compared with data of control conventional animals. Germfree adult pigs had a lower count of peripheral blood leukocytes with a lower percentage of neutrophil granulocytes and without any younger forms, a lower total serum protein level with a negligible amount of gamma and alpha 2 globulin fractions and a higher serum albumin and beta globulin level. In the mesenteric lymph nodes and in spleen, surface IgA-bearing cells predominated over surface IgG-bearing cells. Also a large amount of IgA-containing cells was found in the intestinal lamina propria, where the IgG cells were present in a negligible amount. IgM cells were the most frequent surface isotype in peripheral blood. The count of blood T lymphocytes was more than doubled.

Toxicity of staphylococcal toxic shock syndrome toxin 1 for germ-free and conventional piglets.

The susceptibilities of conventional and germ-free miniature pigs to staphylococcal toxic shock syndrome toxin 1 (TSST-1) were studied and compared. TSST-1 at doses of 100 micrograms/kg evoked reactions similar to those observed in rabbits, i.e., hyperthermia, diarrhea, apathy, conjunctival hyperemia, and various changes indicating toxic damage of different organs, but it was never lethal at this dose. Germ-free piglets were less susceptible than were corresponding conventional animals, a finding that may support the concept that endogenous endotoxin is involved in the pathogenesis of toxic shock syndrome.

The adherence of Escherichia coli to the intestinal epithelium of piglets.

The ability of some pathogenic strains of E. coli to adhere to the intestinal epithelium significantly enhances their effectivity. This adhesion of particular pigs' strains is mediated by specific pili possessing the K 88 antigen found on the outer membrane of the bacterial cell. In in vitro experiments with isolated piglets' enterocytes, a considerable adherence of the E. coli K 88+ strain was found when compared with the same bacterial strain but lacking this plasmid-directed antigen. Comparable results were obtained in in vivo experiments with ligated intestinal loops as well as with monoassociated piglets. Furthermore, the adherence ability is most pronounced at the early postnatal period and is negligible in adult pigs.

Protective activity of Streptococcus faecalis against pathogenic action of Escherichia coli O55 in gnotobiotic pigs.

Peroral administration of Streptococcus faecalis suppresses the lethal effect of simultaneous or subsequent infection with pathogenic Escherichia coli O55 in gnotobiotic colostrum-free piglets. The presence of S. faecalis in the intestine and mesenteric lymph nodes in artificially diassociated colostrum-free piglets influences neither multiplication of E. coli in the intestine nor its penetration into the organism.

Selective decontamination, induced colonization resistance and connected immunological changes in piglets.

14-d-old conventional piglets were picked from normal piggery, washed with disinfectants, placed into isolators suitable for germfree work, fed a sterile diet and treated with peroral antibiotics (nalidixic acid, kanamycin, and nystatin). Beginning with day 5 or 7, Enterobacteriaceae were not found in feces. The absence of these bacteria was proved by inoculation of germfree newborn piglets with caecal content. In selectively decontaminated piglets, the white blood cell count in blood had fallen to 6 X 10(9)/L; this decrease was due to an extremely low number of granulocytes (to 0.8 X 10(9)/L). On day 35, IgG-positive cells almost disappeared from the spleen, whereas IgA cells were found in an unusually great amount. Corresponding changes in serum levels were established. The colonization resistance effect in Enterobacteriaceae-deprived piglets was confirmed; settling of introduced various E. coli strains did not occur or was delayed.

Opsonic, cytotoxic, precipitating, blocking of bacterial adherence, and other activities of monoclonal IgE antibody compared with IgA and IgM.

Monoclonal IgE anti-TNP antibodies were compared with monoclonal anti-TNP, IgM and IgA isotypes in different biological reactions. The reaginic activity of IgE antibodies demonstrated in passive cutaneous anaphylaxis reactions and degranulation of mast cells was accompanied by a number of activities known to be associated with other isotypes. The occurrence of relatively high numbers of lymphoid cells and macrophages bearing Fc epsilon receptors suggests a possible role of IgE antibodies in host defence mechanisms acting systematically and/or locally on mucosal surfaces.

Absorption and metabolism of fructose in the small intestine of conventional and germ-free piglets in vitro.

The aerobic uptake and metabolism of D-fructose in the rings of the small intestine of conventional and germ-free piglets during development was studied. No accumulation of fructose in the intracellular water against its concentration gradient was found. In both groups of animals the intracellular concentration of fructose decreases with increasing age, being highest in the newborn intestine and the sharptest decrease being observed on the first two days of post-natal life. Lactic acid was found to be the main metabolic product of fructose; a considerable amount of it was formed also from endogenous sources of the small intestine. In the newborn piglet fructose does not affect the formation of lactic acid, on the first two days after birth this effect of fructose is already apparent and more pronounced in germ-free piglets than in conventional ones. Conventional and germ-free animals differ markedly in endogenous lactic acid production. While in the former with increasing age endogenous lactate formation decreases, in the latter it rises after a sharp drop on the first post-natal day.