An evaluation of the effect of pulsed wave low-level laser therapy on the biomechanical properties of the vertebral body in two experimental osteoporosis rat models.

Osteoporosis (OP) increases vertebral fragility as a result of the biomechanical effects of diminished bone structure and composition. This study has aimed to assess the effects of pulsed wave low-level laser therapy (PW LLLT) on cancellous bone strength of an ovariectomized (OVX-d) experimental rat model and a glucocorticoid-induced OP (GIOP) experimental rat model. There were four OVX-d groups and four dexamethasone-treated groups. A group of healthy rats was used for baseline evaluations. The OVX-d rats were further subdivided into the following groups: control rats with OP, OVX-d rats that received alendronate, OVX-d rats treated with PW LLLT, and OVX-d rats treated with alendronate and PW LLLT. The remaining rats received dexamethasone and were divided into four groups: control, alendronate-treated rats, laser-treated rats, and laser-treated rats with concomitant administration of alendronate. PW LLLT (890 nm, 80 Hz, 0.972 J/cm(2)) was performed on the spinal processes of the T12, L1, L2, and L3 vertebras. We extracted the L1 vertebrae and submitted them to a mechanical compression test. Biomechanical test findings showed positive effects of the PW LLLT and alendronate administration on increasing bending stiffness and maximum force of the osteoporotic bones compared to the healthy group. However, laser treatment of OVA-d rats significantly increased stress high load compared to OVA-d control rats. PW LLLT preserved the cancellous (trabecular) bone of vertebra against the detrimental effects of OV-induced OP on bone strength in rats compared to control OV rats.

Supraphysiologic glucocorticoid administration increased biomechanical bone strength of rats' vertebral body.

The aim of this study is to assess the effects of different glucocorticoid administration protocols on biomechanical properties of the first lumbar vertebral body in rats. We divided 40 male rats into the following groups: control, dexamethasone (7 mg/week), dexamethasone (0.7 mg/week), methylprednisolone (7 mg/kg/week), methylprednisolone (5 mg/kg twice weekly), dexamethasone (7 mg/kg three times per week), dexamethasone (0.7 mg/kg three times per week, and low-level laser treated rats. Lumbar vertebrae in rats were exposed to the pulsed laser. We conducted a biomechanical test to examine the mechanical properties of vertebral body in rats' lumbar bone. Supraphysiologic glucocorticoid administration protocols did not impair the biomechanical properties of rats' vertebral bodies compared to control and laser-treated rats. Supraphysiologic glucocorticoid administration caused an anabolic effect on the vertebral bodies.

Effect of low-level laser therapy on mast cells in second-degree burns in rats.

OBJECTIVE: This study sought to investigate whether low-level laser therapy (LLLT) with a helium-neon (He-Ne) laser would affect mast cell number and degranulation in second-degree burns in rats. BACKGROUND DATA: LLLT has been recently applied to stimulate the wound healing process. MATERIALS AND METHODS: Sixty-five rats were randomly allocated to one of five groups. A deep second-degree burn was inflicted on all rats except those in the control group. In the sham-exposed group burns remained untreated. In the two laser-treated groups, the burns were irradiated every day by LLLT, with energy densities of 1.2 and 2.4 J/cm(2). In the fifth group the burns were treated topically with 0.2% nitrofurazone cream every day. The unburned skin of the rats in the control group were used for baseline study. The effects on mast cell number and degranulation were assessed by counting the number of intact and degranulated mast cells in sections fixed in formalin and stained with toluidine blue. RESULTS: On the seventh and 16th days post-burn, the type 1 mast cell count in the 2.4-J/cm(2) laser-treated group was significantly higher than that of the control group. On the 30th day, the total numbers of mast cells in the laser-treated groups were lower than those in the control and sham-exposed groups. CONCLUSION: LLLT of deep second-degree cutaneous burns in rats significantly increased the number of intact mast cells during the inflammatory and proliferative phases of healing, and decreased the total number of mast cells during the remodeling phase.