We examined the mechanical properties of rat bones treated with etidronate intermittent cyclic treatment (etidronate-ICT). Fifty Fisher rats, 7 months of age, underwent ovariectomy (OVX; n = 40) or sham operation (n = 10). The OVX rats were assigned to 4 groups injected with etidronate at the respective dose of 0, 2, 4, or 8 mg/kg of body weight (bw) 5 days each week for 2 weeks, followed by a 10-week period of no treatment. This regimen was repeated for 48 weeks. At the end of the treatment period, the ultimate bending strength and structural stiffness of the femoral midshaft in the OVX-alone group were not reduced compared with the values of the sham group, while those in the etidronate-treated groups were significantly larger than the values of the OVX group. The compressive stiffness and strength of the vertebral bodies specimens prepared from L3 and L5 vertebrae were markedly decreased in the OVX group compared with those in the sham group, but the values in the etidronate-treated groups were maintained at the same levels as those in the sham group. Mechanical properties at the tissue level, such as elastic modulus and material strength of the femoral cortex, were increased in etidronate-treated groups compared with the OVX group. The flexural modulus was also increased. The compressive elastic modulus of vertebral body in treated groups was preserved at the same level as that in the sham group. These results clearly demonstrate that in ovariectomized rats long-term etidronate intermittent cyclic treatment preserves the mechanical properties both at the whole bone and the tissue level.

Background and Purpose The capacity of an intravenous infusion of double-stranded tissue-type plasminogen activator to salvage neurological functions in a rat model of thromboembolic stroke was studied.Methods The model of thromboembolic stroke was induced by the intracarotid injection of 2-hour-old homologous blood clots to rats. Neurological functions were scored on a 5-point scale 48 hours after the injection of the clots. Infarction size was determined by triphenyltetrazolium chloride staining, and cerebral hemorrhage was examined macroscopicalry.Results Intravenous infusion of tissue-type plasminogen activator (1 or 5X1O 3 IU/kg) within 3 hours after embolization significantly improved neurological functions (P<.01) and reduced infarction size (P<.05). Tissue-type plasminogen activator treatment 6 hours after embolization failed to attenuate the neurological status score. Treatment with tissue-type

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