Review article: bifidobacteria as probiotic agents -- physiological effects and clinical benefits

Bifidobacteria, naturally present in the dominant colonic microbiota, represent up to 25% of the cultivable faecal bacteria in adults and 80% in infants. As probiotic agents, bifidobacteria have been studied for their efficacy in the prevention and treatment of a broad spectrum of animal and/or human gastrointestinal disorders, such as colonic transit disorders, intestinal infections, and colonic adenomas and cancer. The aim of this review is to focus on the gastrointestinal effects of bifidobacteria as probiotic agents in animal models and man. The traditional use of bifidobacteria in fermented dairy products and the GRAS ('Generally Recognised As Safe') status of certain strains attest to their safety. Some strains, especially Bifidobacterium animalis strain DN-173 010 which has long been used in fermented dairy products, show high gastrointestinal survival capacity and exhibit probiotic properties in the colon. Bifidobacteria are able to prevent or alleviate infectious diarrhoea through their effects on the immune system and resistance to colonization by pathogens. There is some experimental evidence that certain bifidobacteria may actually protect the host from carcinogenic activity of intestinal flora. Bifidobacteria may exert protective intestinal actions through various mechanisms, and represent promising advances in the fields of prophylaxis and therapy.

Review article: bifidobacteria as probiotic agents -- physiological effects and clinical benefits

Bifidobacteria, naturally present in the dominant colonic microbiota, represent up to 25% of the cultivable faecal bacteria in adults and 80% in infants. As probiotic agents, bifidobacteria have been studied for their efficacy in the prevention and treatment of a broad spectrum of animal and/or human gastrointestinal disorders, such as colonic transit disorders, intestinal infections, and colonic adenomas and cancer. The aim of this review is to focus on the gastrointestinal effects of bifidobacteria as probiotic agents in animal models and man. The traditional use of bifidobacteria in fermented dairy products and the GRAS ('Generally Recognised As Safe') status of certain strains attest to their safety. Some strains, especially Bifidobacterium animalis strain DN-173 010 which has long been used in fermented dairy products, show high gastrointestinal survival capacity and exhibit probiotic properties in the colon. Bifidobacteria are able to prevent or alleviate infectious diarrhoea through their effects on the immune system and resistance to colonization by pathogens. There is some experimental evidence that certain bifidobacteria may actually protect the host from carcinogenic activity of intestinal flora. Bifidobacteria may exert protective intestinal actions through various mechanisms, and represent promising advances in the fields of prophylaxis and therapy.

Luminal and intracellular cGMP inhibit the mTAL reabsorptive capacity through different pathways

Since, in the presence of ANF, urinary cGMP was shown to be of glomerular origin, a possible paracrine effect of luminal cGMP on the medullary thick ascending limb (mTAL) function was investigated. Net chloride reabsorption (JCl) was determined on isolated microperfused tubules from mouse kidney. Addition of 10(-6) M cGMP to the lumen significantly decreased JCl by 46.5 +/- 4.6%. A concentration-dependent decrease of the transepithelial voltage was observed, with a 10(-8) M threshold. Added to the bath, ANF (10(-7) M) as well as urodilatin (6 x 10(-8) M) decreased JCl by 29.8 +/- 3.9% and 36.9 +/- 5.1%, respectively, an effect reproduced by 8-bromo cGMP and associated with a significant increase in tubular cGMP content. The inhibitory effect of ANF was similar whether or not cGMP was present in the lumen. Furthermore, increasing intracellular cGMP content by 8-bromo cGMP did not prevent a further effect of luminal cGMP. Finally, H-8, which blocked the effect of ANF, urodilatin, and 8-bromo cGMP, failed to abolish the luminal cGMP-induced decrease of JCl, suggesting that this effect did not require a cGMP-dependent protein kinase activation. It is concluded that luminal cGMP inhibits the reabsorptive function of the mTAL through a pathway different from the intracellular cGMP production.