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.

Molecular heterogeneity in the Major Urinary Proteins of the house mouse Mus musculus.

Major Urinary Proteins (MUPs) from different inbred strains of mouse have been analysed by high-resolution ion-exchange chromatography and mass spectrometry. MUPs from six strains were resolved chromatographically into four major protein peaks which characterized two distinct phenotypes, typified by the profiles obtained from the Balb/c and C57BL/6 inbred strains. A combination of ion-exchange chromatography and electrospray ionization mass spectrometry analysis of the MUPs from each strain identified five proteins, only one of which was common to both strains. The charge and mass data, together with N-terminal sequence analyses, were correlated with the masses of the proteins inferred from published cDNA sequences. Several members of the family of MUP sequences differ in only four positions, and in some circumstances the substitutions elicit a minimal change in protein mass (Lys/Gln; Lys/Glu). Peptide mapping with endopeptidase Lys-C, followed by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry permitted identification of new MUPs that were correlated with partial cDNA sequence data. In the two strains there are at least 13 different MUPs, either observed or predicted, indicating the heterogeneity of expression of this group of proteins.

Upg-2: a urinary pepsinogen variant located on chromosome 1 of the mouse.

Acrylamide gel electrophoresis of mouse urine distinguishes two groups of pepsinogens, the fast-migrating group A and the slow-migrating group B. Inbred mouse strains fall into two categories with respect to group B pepsinogens, one expressing a single-banded and the other a double-banded phenotype. This variation is controlled by a single locus, urinary pepsinogen-2 or Upg-2, which has at least two alleles, Upg-2s and Upg-2d. Typing of recombinant inbred strains suggests that the location of the Upg-2 locus is on chromosome 1, in the vicinity of loci coding for other peptidases, namely, Pep-2 and Rnr, and of the Acf-1 locus.

False negative hyperglucosuria test-strip reactions in laboratory mice.

Inhibition of a variety of commercial test strips for hyperglucosuria was experienced in laboratory mice. All mouse strains tested were found to have sufficiently high levels of ascorbic acid to cause inhibition, and male levels were higher than those of females. A regime to obtain optimum detection of positive results is discussed.

Single-mouse urine collection and pH monitoring system.

A glass cage with minimal surface area was designed and used to house mice for 24-hour urine collections. An experiment was performed with a radio-labeled compound excreted in the urine to assess the collection efficiency of the cage. In this experiment 74.2 +/- 6.5% of the excreted radioactivity was recovered in the urine, with 25.8 +/- 6.5% found adhering to the cage surfaces. When a flow-through pH electrode, meter, and recorder were attached, the system provided a continuous pH versus time urination record.

Genetic and endocrine studies of the pregnancy-blocking pheromone of mice.

Secretion of the pregnancy-blocking pheromone was stimulated by injection of depo-testosterone cypionate into females and males of inbred strains of mice which do not normally secrete the pheromone. Testosterone treatment of SJL males altered pheromone secretion so that pregnancies were blocked when the stud male was of the same inbred strain; an event that does not normally occur. Injection of epiandrosterone, androstenedione, androsterone or testosterone significantly increased pheromone secretion in SJL females, but progesterone and dehydroepiandrosterone were ineffective. Kidney weights were significantly increased by administration of androgen metabolites and the possibility of the kidney being the site of pheromone synthesis is discussed. The preputial gland can be excluded as the site of pheromone synthesis since males which are hemizygous for the Tabby-J gene and have no preputial glands blocked pregnancies as effectively as their normal littermates. Preliminary results are also presented concerning the isolation of the pregnancy-blocking pheromone from urine. Urine was analysed by gas chromatography and a peak was observed whose concentration could be correlated with secretion of the pheromone, although the compound(s) has not been identified or tested for biological activity.