Vibrational bone characteristics versus bone density for the assessment of osteoporosis in ovariectomized rats.

Our previous research findings suggested this integrated study in order to monitor changes of bone properties and assess bone integrity using vibrational characteristics in osteoporosis. The method is based on measurement of the bone dynamic characteristic modal damping factor (MDF). The experimental animal model is ovariectomized rat followed by alendronate treatment. According to the experimental design, adult female Wistar rats are ovariectomized and 60 days later, with confirmed osteoporosis, the population is divided into two groups. One is administered alendronate and the second is given no treatment. Furthermore, established techniques such as pQCT and histomorphometry are applied at all time points, in order to compare and correlate to MDF. The results indicate induction of osteoporosis due to ovariectomy and render MDF capable of monitoring changes in bone material properties and architecture, with high sensitivity and repeatability.

Evaluation of modal damping factor as a diagnostic tool for osteoporosis and its relation with serum osteocalcin and collagen I N-telopeptide for monitoring the efficacy of alendronate in ovariectomized rats.

Osteoporosis is a metabolic bone disease characterized by reduced bone mass and deterioration of bone microarchitecture. It results from the shift of the osteoblast-osteoclast activity equilibrium in favor of the later. Although, a number of biochemical markers, such as collagen I N-telopeptide (NTx) and osteocalcin (OC), have been used for monitoring bone remodeling, a new, monitoring, non-invasive method, which is based on the measurement of the dynamic characteristic of bone and is known as modal damping factor (MDF), has not been evaluated as a diagnostic tool for osteoporosis. Bisphosphonates, such as alendronate, have an established role in the treatment of osteoporosis. The aim of the present study was, therefore, to evaluate the effects of alendronate on the levels of MDF, serum NTx and OC on osteoporosis induced by ovariectomy in rats. Furthermore, the effects of alendronate on osteoporosis have been histologically evaluated. Fifteen adult female Wistar rats were bilaterally ovariectomized and osteoporosis was histologically confirmed and by the use of peripheral quantitative computerized tomography (pQCT). MDF was applied to assess the bone structural integrity. The serum levels of NTx (37.4+/-0.5 nM bone collagen equivalents, BCE) and OC (111.0+/-8.2 ng/mL) were found to significantly increase following ovariectomy (72.0+/-2.9 nM BCE and 213.5+/-12.1 ng/mL, respectively, p<0.001). As assessed by histology and the levels of NTx and OC in sera, animals treated with alendronate presented a statistically significant deceleration in the progression of the disease in comparison to the no-therapy control group (alendronate group NTx levels: 146.3+/-8.9 nM BCE versus no-therapy control group NTx levels: 265.3+/-14.0 nM BCE, p<0.001, alendronate group OC levels: 205.6+/-18.2 ng/mL versus no-therapy group OC levels: 353.9+/-26.1 ng/mL, p<0.001). Data obtained from the vibration analysis performed illustrated that the change in damping was equal or greater to the change in total and trabecular density, respectively. Damping increased with decreasing bone density, as expected, given that damping accounts for the structural integrity of bone (MDF value before ovariectomy: 0.058+/-0.003 versus MDF value after ovariectomy: 0.098+/-0.003, p<0.001). The higher damping values correspond to more deteriorated structures. In particular, both total and trabecular density were significantly decreased following ovariectomy (total density before ovariectomy: 702.4+/-19.0 versus total density after ovariectomy: 542.2+/-12.8, p<0.001, trabecular density before ovariectomy: 445.3+/-13.0 versus trabecular density after ovariectomy: 396.7+/-8.4, p<0.05). MDF value of the alendronate group (0.07+/-0.002) was significantly lower (p<0.001) as compared to MDF value after ovariectomy (0.098+/-0.003) and that of the no-therapy group (0.1+/-0.004, p<0.001). The administration of alendronate seemed to have no effect on either total or trabecular density, since both parameters continued to decrease (alendronate group total density: 549.4+/-12.3, alendronate group trabecular density: 368.4+/-14.7). However, when this was compared to the no-therapy group, a statistically significant difference of total density at the 0.05 level was observed (no-therapy total density: 464.8+/-9.1). The results of this study suggest that combined measurements of MDF, NTx and OC may be a potential diagnostic tool for osteoporosis and monitoring bone integrity during treatment with bisphosphonates. Furthermore, administration of alendronate showed to offer a critical deceleration in the progression of osteoporosis.

Protective role of the glans penis during coitus.

To examine the hypothesis that the glans penis acts protectively, absorbing forces, during coitus. Five potent patients (mean age 46.8+/-9.7 y), who had indication for surgical excision of the glans for penile carcinoma were included in the present study. Intraoperatively, intracavernosal pressure (ICP) was adjusted by saline infusion and maintained by a pressure feedback infusion pump to a pressure value of 70 mmHg. Using a dynamometer, an external compressive force of 0.5 kg was applied at the glans penis and the changes in ICP were monitored. Measurements were repeated after surgical excision of the glans. Significant ICP changes were noticed in all patients after excision of the glans. Mean preoperative ICP was 161+/-11.5 mmHg, while after glansectomy it reached 206.6+/-13 mmHg. DeltaICP was 45.8+/-10.57 mmHg. Two of the patients' partners reported pain during intercourse postoperatively, possibly due to the impact of the force applied by the rigid corpora cavernosa on the anterior vaginal wall without any absorption by the glans. The glans penis restricts the increase in ICP during sexual intercourse, playing a protective role for both the corpora cavernosa and the female genitalia.

Low-frequency acoustic sweep monitoring of bone integrity and osteoporosis.

We developed a noninvasive method to evaluate bone structural integrity. It is based on the measurement of the dynamic characteristics of the bone using sweeping sound excitation in the range of acoustic frequencies. The Quality Factor (a measure of material damping) has been used as an indicator of the tendency of the bone to fracture. Results of animal studies have supported this hypothesis since linear correlations were observed between bone density, quality factor, and impact strength. A vibration excitation in the form of an acoustic sweep signal is applied to a bone to measure the quality factor. Rat bones were tested, obtained from animals with osteoporosis age-dependent (tested in vitro) or ovariectomy-induced (tested in vivo), and compared with bones of healthy (control) rats. The change in damping was, on average, equal or greater to the change in density. Moreover, excellent correlation of the quality factor was obtained with bone fracture energy measured with an impact test. During a vibration cycle, the changing strain results in temperature changes due to the reciprocity of temperature and strain. Nonreversible conduction of heat due to the unequal temperature change results in entropy production that is enhanced due to the stress concentration about the voids associated with bone porosity. Damping is a measure of the production of entropy. Its measure, the quality factor, represents a potentially useful tool for monitoring bone integrity, which is deteriorating in diseases characterized by disruption of the trabecular architecture, such as osteoporosis. A computational model yielded results that are in good correlation with the experimental results.