Environmental enrichment during rearing alters corticosterone levels, thymocyte numbers, and aggression in female BALB/c mice.

The goal of environmental enrichment for laboratory animals is to improve welfare, but some enrichment practices may affect research in unintended ways or even be harmful to the animals themselves. We previously found that mice raised at a commercial vendor then given multiple enrichment devices upon arrival at our facilities experienced thymic atrophy and greater variation in measured parameters than did their unenriched counterparts, suggesting that enrichment conditions affected corticosteroid expression in mice. The current study verified and expanded these results, examining 120 female BALB/c mice raised with or without nesting material at a commercial vendor (n = 60 per group) and allocated (n = 20 per group) to receive no enrichment, nesting material, or 'superenrichment' on arrival at our facilities. Nesting material provided prior to weaning was associated with higher levels of urinary corticosteroid, whereas superenrichment and nesting material during the adult period both led to increased thymic atrophy. Paradoxically, mice that never received enrichment, despite having the lowest corticosterone levels and least thymic atrophy, had increased tail wounds resulting from aggressive interactions. Therefore, enrichment devices that are as seemingly innocuous as nesting material, even if only provided in the preweaning period, may lead to significant, lasting changes in behavioral, physical, or immunologic measures with the potential to alter research outcomes.

Effects of housing density and cage floor space on three strains of young adult inbred mice.

Some recommendations in the Guide for the Care and Use of Laboratory Animals (the Guide) are based on best professional judgment. Our current efforts are directed toward replacement with data-driven standards. We demonstrated earlier that young adult C57BL/6J mice could be housed with half the floor space recommended in the Guide without discernable negative effects. This report extends that work by examining optimal housing densities for young adult male and female BALB/cJ, NOD/LtJ, and FVB/NJ mice. These 8-week studies were initiated with 3-week-old BALB/cJ and NOD/LtJ mice and 3- to 5-week-old FVB/NJ mice housed in three cage types. We adjusted the number of mice per cage to house them with the floor space recommended in the Guide (approximately 12 in2 [ca. 77 cm2] per mouse) down to 5.6 in2 [ca. 36 cm2] per mouse. Early-onset aggression occurred among FVB/NJ male mice housed at all densities in cages having 51.7 in2 (ca. 333 cm2) or 112.9 in2 (ca. 728 cm2) of space. FVB/NJ male mice housed in shoebox (67.6 in2 [ca. 436 cm2]) cages did not exhibit aggression until the fifth week. Urinary testosterone output was density-dependent only for BALB/cJ male mice in shoebox cages (output decreased with increasing density) and FVB/NJ male mice. We conclude that all but FVB/NJ male mice can be housed with half the floor space specified in the Guide. The aggression noted for male FVB/NJ mice may have been due to their age span, although this did not impact negatively on the female FVB/NJ mice.

Urinary glycolipids of YC8 lymphoma bearing mice: effectors of glycosylation process.

Glycolipids from YC8 lymphoma bearing mice urines have peen obtained by the method of Folch and fractionated on silicic column and on silica gel plates. One fraction, among the five obtained, may be used by sera galactosyltransferase as an acceptor for galactose, to form a new glycolipid compound. Furthermore this fraction has shown an inhibitory effect on phosphatase activity, in agreement with hypothesis which relates relates glycosyltransferase and phosphatase activities during tumorous process.