Physiological effects of housing density on C57BL/6J mice over a 9-month period

The NRC has consistently recommended floor space for animals used in science and agriculture. For mice, the recommended floor space is 77.4 cm(2) (12 in(2)) for a 15- to 25-g mouse. The NRC noted that its recommendations were based on "best professional judgment" and encouraged alternatives that were data driven. As part of a continual effort of The Jackson Laboratory to ensure the health and well-being of production and research mice, while promoting cost-effective, state-of-the-art research, several density-driven studies have been conducted by lab researchers. The objectives of this study were to determine the effect of housing density on variables related to mouse physiology and air quality in cages and assess the value of specific measured variables in such studies. In the present study, we monitored C57BL/6J mice in individually ventilated cages from weaning until 9 mo of age. Housing densities were equivalent to 66.4 or 36.8 cm(2) per mouse (10.3 or 5.7 in(2)). Clinical physiological variables representing general health and well-being were measured. Hematological traits, plasma lipids, and glucose, growth, bone mineral density, and percent body fat did not differ between housing densities. In the more densely housed mice, however, adrenal glands were significantly smaller, heart rates were significantly less, and food consumption was less. Cage air microenvironment was evaluated for ammonia, carbon dioxide, temperature, and humidity in cages changed weekly or every 2 wk. The cage microenvironment remained within acceptable limits at the higher density of mice at both cage-changing frequencies. The results suggest that mice housed for as long as 9 mo at up to twice the density currently recommended by NRC show no measurable adverse effects. Continued re-evaluation of the recommendation by measuring additional relevant variables of health and general well-being, and studying additional strains of mice is warranted.

Gender- and compartment-specific bone loss in C57BL/6J mice: correlation to season?

Seasonal variation in bone mineral density (BMD) has been documented in humans, and has been attributed to changes in 25-hydroxyvitamin D [25(OH)D] synthesis. To test the hypothesis that seasonal changes in bone mass occur in laboratory mice, we measured body composition, femoral bone phenotypes, and serum bone markers in 16-wk-old male and female C57BL/6 (B6) mice during the summer (June-August) and winter (December-February) months at The Jackson Laboratory in Bar Harbor, Maine. Both male and female B6 mice had higher volumetric BMD in the summer than winter. Females showed reduced trabecular bone, whereas males showed changes in bone volume. Males, but not females, had higher insulin-like growth factor 1 in summer than in winter, and only males showed an increase in body weight during the winter. No seasonal differences in serum TRAP5b, osteocalcin, or 25(OH)D were noted for either sex. We conclude that seasonal variation in skeletal and body composition parameters in B6 mice is significant and must be considered when performing longitudinal phenotyping of the skeleton. Further studies are needed to determine the environmental factors that cue seasonal changes in body composition and the mechanisms that produce these changes.

Biliary scanning with Tc-99m pyridoxylideneglutamate--the effect of food in normal subjects: concise communication

Technetium-99m pyridoxylideneglutamate biliary scans were performed in 19 normal subjects in both the fasted and nonfasted state. The effect of eating was to reduce visualization of the gallbladder from 100% (fasted) to 47% (nonfasted). The common bile duct was seen in 84% on both occasions but intrahepatic and cystic ducts were seen less frequently in the nonfasted group. Preparation of patients by fasting is essential if information concerning gallbladder function is sought.

The role of biliary scanning in the investigation of the surgically jaundiced patient

The diagnostic accuracy of biliary scanning using 99mTc-pyridoxylideneglutamate has been determined in a series of 51 surgically jaundiced patients. This noninvasive technique was found to be safe, reliable and universally applicable in all instances of jaundice, regardless of the serum bilirubin value or prothrombin time. The results were found to compare favorably with those of other investigative procedures. It is suggested that the 99mTc-pyridoxylideneglutamate biliary scan is most advantageously carried out after clinical assessment and full biochemical evaluation of the patient. The scan result will indicate the next logical step in the management of the patient whether it be endoscopic retrograde cholangiopancreatography, percutaneous transhepatic cholangiography, biopsy of the liver or laparotomy.