Germfree animal

It has recently been shown (14) that nitrate from food can be detected in the feces of germfree animals but not in the feces of conventional animals. This result and the results of Witter et al. (18-20) suggest that nitrate is available in the lower gastrointestinal tract and is metabolized by the microbial flora. The intestine may thus be a site for the endogenous formation of N-nitroso compounds. 

The importance of the gut microflora in the metabolism of isoflavones has been demonstrated. Antibiotic administration blocks isoflavone metabolism and germfree animals do not excrete metabolites. Moreover, only germfree rats colonized with microflora from a good equol producer excrete equol when fed soy. ... 

Thorbecke, G.J. (1959). Some histological and functional aspects of lymphoid tissue in germfree animals. I. Morphological studies. Ann. N.Y. Acad. Sci. 78, 237-246. 

The presence of regulatory cells is necessary to maintain systemic homeostasis. It has been observed that their contact with commensal flora of mucous membranes in the first days of life is the condition for their development. In germfree animals it is impossible to induce food tolerance mediated by Th2 lymphocytes. Perhaps this is the answer to the question Why is the number of allergic diseases on the increase, although the exposure to allergens is decreasing ... 

Eight- to ten-week-old male germfree mice, which experience colonization for 14 days, showed 57% increase in total body fat with 61% increase in epididymal fat and 7% decrease in lean mass with no difference in body weight. Lipid profile did not change after colonization. A similar change was determined by colonization of germfree animals at birth or for different amount of time however, increasing colonization time did not amplify the effect on adipose tissue (Backhed et al., 2004). 

Germfree animal a gnotobiote that is free from all demonstrable associated forms of life, including bacteria, viruses, fungi, protozoa, and other saprophytic or parasitic forms. 

II. STUDIES OF CHOLESTEROL CATABOLISM TO BILE ACIDS IN GERMFREE ANIMALS... 

Conventional animals excrete more bile acids, both qualitatively and quantitatively, than do germfree animals. It appears that the qualitative modification of bile acids in vitro is the result of many different microorganisms of widely varying taxonomic types. The studies reported here have characterized the differences in the bile acid metabolism between the two types of animal but have not explained the factor(s) responsible for these differences. 

The conventional animal may be thought of as a middle state in a continuum bounded at one end by the germfree animal and at the other by the animal in a state of severe steatorrhea. Thus one could conclude that the conventional animal is in a state of mild malabsorption, which, since it is the common condition, we define as normal. ... 

The oral administration of antibiotics resulted in the production of germfree characteristics with respect to propachlor metabolism in rats ( ) and pigs (31), i.e. no 2-methylsulfonyl acetanilides were formed and only MAP metabolites were excreted. This observation may have economic implications. It is possible that the growth stimulation observed upon incorporation of antibiotics into animal feed could be effected by the suppression of such mechanisms. This could be accomplished either by the prevention of the metabolic formation of new xenobiotics of unknown biological activities or by the conservation of detoxication energy or both. 

Gnotobiote an animal, stock, or strain, derived by aseptic caesarean section or sterile hatching of eggs, which is reared and continuously maintained with germfree techniques under isolator conditions in which the composition of any associated fauna and flora, if present, is fully defined by accepted current methodology. 

C. Cholesterol Feeding and Liver and Serum Cholesterol Levels of Germfree and Conventional Animals... 

PHYSIOLOGICAL OBSERVATIONS IN GERMFREE VERSUS CONVENTIONAL ANIMALS... 

Portman and Murphy (24) reported that the type of diet had an influence on turnover of cholic acid in conventional rats. Gustafsson and Norman (25) have investigated whether this effect is seen in germfree rats. In their study, they concluded that no significant difference existed in the percent of bile acid in the cecum of their rats among different groups of animals kept on different diets or between germfree and conventional ani-... 

Kellogg and Wostmann (14) studied the fecal bile acid excretion of germfree and conventional rats by direct chromatographic procedures. The germfree rats average 11.3 2.4 mg and the conventional rats 21.4 9.9 mg of bile acid/kg body wt/day p < 0.005) (Table III and Fig. 1). The coefficients of variation were 21 and 46%, respectively, suggesting that at least half of the quantitative variation seen in fecal bile acid excretion in the conventional animal was derived from effects of the intestinal microflora. 

Reyniers, J. P., (1979). Renal toxicity of lysinoalanine and its potential catabolites in germfree and conventional animals. Piss. Abstr. Int. B. 39(10), 1820. 

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