Fighting was recorded 1.3 ± 0.5 times during the one-hour observation periods preceding mechanical loading in grouped male mice and never observed in females. This difference selleck chemical in the number of fights between groups was statistically significant (p < 0.05). Fighting in grouped males consisted of brief flurries of activity, usually involving two or three individuals at any one time. All males were seen to be involved in fights at least once during the observation period. No injuries were observed as a result of these episodes. There

were no significant differences between left control tibiae from grouped or individual females for any parameter measured in trabecular or cortical bone (Table 1). In trabecular bone, loading significantly increased trabecular BV/TV, primarily due to an increase in Tb.Th. In cortical bone, Ct.Ar was significantly higher in right limbs after loading primarily due to an increase in Tt.Ar with no significant difference in Ma.Ar. click here There were no significant differences in the response to mechanical loading between grouped and individual female mice (Fig. 1). Serum corticosterone concentration was not different between grouped and individual females (Table 1). In contrast to females, the left non-loaded tibiae of grouped male mice had

significantly higher trabecular BV/TV (28.6% higher than individual male mice, O-methylated flavonoid p < 0.001, Table 1) due primarily to greater Tb.Th (19.0%, p < 0.01) and a smaller, but still significant difference in Tb.N (7.9%, p < 0.05). The left non-loaded tibiae of grouped males also had higher Ct.Ar (11.5%, p < 0.01) and Tt.Ar (12.5%, p < 0.05, Table 1). No difference in serum testosterone concentration was detected between grouped and individual males. However, somewhat surprisingly, grouped

males had a significantly lower serum corticosterone concentration (− 59.4%, p < 0.05). When loaded and non-loaded tibiae were compared in individual male mice, there was a highly significant difference in trabecular BV/TV (28.7%, p < 0.001) and Tb.Th (21.8%, p < 0.001). This difference was much less in grouped males (0.8%, p = 0.85 and 4.9%, p < 0.05 respectively, Fig. 1). In cortical bone, loading was associated with a significantly increased Ct.Ar in individual males (8.7%, p < 0.01), again associated with increased Tt.Ar (5.5%, p < 0.01). However, grouped males showed a smaller difference in Ct.Ar (5.4%, p < 0.05) and no difference in Tt.Ar (1.8%, p = 0.13) between loaded and non-loaded bones. Data from our pilot experiment suggested that male C57BL/6 mice showed a lower osteogenic response to artificial loading than females, contradicting the results from previous studies demonstrating no such sex-related difference [7] and [11].