The administration of bovine lactoferrin (LF) with 1 mg/g body weight before the murine cytomegalovirus (MCMV) infection completely protected the BALB/c mice from death due to the infection. In these LF-treated mice, a significant increase in the activity was found in the NK cells but not in the cytolytic T lymphocytes which recognized an MCMV-derived peptide. Moreover, the elimination of the NK cell activity by an injection with anti-asialo GM1 antibody abrogated such augmented resistance, thus supporting the hypothesis that the LF-mediated antiviral effect in vivo is performed through the augmentation of NK cell activity. No such LF-mediated antiviral effect in vivo with the increased NK cell activity was found in athymic nude mice, whereas it was restored completely by the transfer of splenic T cells from LF-treated donors. These findings therefore suggest that T lymphocytes induce both the augmentation of NK cell activity and the resultant antiviral effect in the LF-treated hosts.

No abstract

In the intestinal flora of patients with diarrhea, a close correlation exists between a decrease in numbers of anaerobes and a reduction in levels of short-chain fatty acids. The drastic reduction of intestinal volatile fatty acids (VFAs) accompanying decreased counts of anaerobes during the diarrheal state and the increase in pH thought to arise from these changes result in increased fecal water content. Our data suggest that free bile acids and VFAs may be factors controlling intestinal bacterial populations in vivo, especially in enteric infections. Thus the role of nonspecific factors such as VFAs, which are among the bile acid metabolites produced by anaerobic intestinal bacteria, deserves emphasis in the evaluation of protective mechanisms provided by the intestinal flora against enteric infections.

The capacity for reproduction in germfree mice remain inferior to their conventional counterparts even after improvement of feed and other such rearing conditions. The authors provide evidence of increased reproductive capacity in germfree mice following association with bacteria. Estrous cycles were normalized in female mice accidentally contaminated with bacteria, and in mice given fecal suspensions of the accidentally contaminated mice per os. Significant rises were seen in their copulation and implantation rates, reaching levels comparable to values in conventional mice. In male mice, bacterial contamination induced significant increase in sperm motility. Bacteria were identified in the feces of the contaminated mice, and reproductive capacity was examined in mice associated with the identified bacteria. As a result, normalization of the estrous cycle, and rises in copulation and implantation rates were noted in B. distasonis and C. perfringens di-associated mice. Values from B. subtilis mono-associated mice were comparable to those in germfree mice. These results from our accidental contamination indicate that B. distasonis and C. perfringens are capable of normalizing estrous cycles in female germfree mice, and in increasing their reproductive capacity by raising their rates of copulation and implantation.

An investigation was undertaken to study the effects of germfree (GF) status and mild food restriction on life span in GF and specific pathogen-free (SPF) male ICR mice either full-fed (ad libitum) or on a restricted diet of 4.5 grams per day (equivalent to approximately 80% of full-fed intake) from five-week-old. The mean life span of the full-fed SPF and GF mice was 75.9 and 88.9 weeks respectively, whie the mean life span of the food-restricted SPF and GF mice was 117.5 and 109.6 weeks, respectively. Mice in both GF and SPF food-restricted groups were characterized by lower body weight and increased survival. These findings suggest that the cessation of growth may be importantly and perhaps causally related to longevity. The GF mice survived longer than the SPF mice, but the combination of GF status with food restriction did not seem to extend life span more than food restriction alone.