Age-related disk degeneration: preliminary report of a naturally occurring baboon model.

Anteroposterior and lateral radiographs of 126 adult baboons were reviewed. The mean age was 15.7 years (range 6-30 years). Evidence of disk degeneration, to include disk-space narrowing, osteophyte formation, endplate changes, and facet joint arthropathy, was noted, and a grading scale, grades 0-3, was used to assign each animal an overall grade for degree of disk degeneration. Lateral radiographs were measured in the area of maximal sagittal plane curvatures. Radiographic review demonstrated a strongly positive correlation between the age of the baboons and the degree of degenerative change (p less than 0.0001), between the degree of kyphosis and the degree of degenerative change (p less than 0.0001), and between the age of the animal and the degree of kyphosis (p less than 0.001). This pilot study demonstrates plain radiographic confirmation of a naturally occurring primate model of disk degeneration, the first such model described, and is the basis for further investigation into magnetic resonance imaging and histopathologic confirmation of this model.     

Methods underpinning national clinical guidelines for hypertension: describing the evidence shortfall

Background  

To be useful, clinical practice guidelines need to be evidence based; otherwise they will not achieve the validity, reliability and credibility required for implementation.     

Templated microwave synthesis of luminescent carbon nanofibers

Carbon based nanomaterials offer the potential to provide solutions to key technological challenges. This work describes the preparation of luminescent carbon nanofibers by template-assisted microwave pyrolysis of environmentally friendly precursors, citric acid and polyethyleneimine, in aqueous solution. SEM reveals a dense forest of vertically aligned cylindrical carbon nanofibers with an average diameter of ca. 200 nm, which are shown by TEM to be amorphous. Compositional analysis indicated the incorporation of amino and pyrrolic nitrogen, and carbon–oxygen moieties. These species contribute to UV light absorption with an absorption shoulder and tail towards visible wavelengths. UV excitation gave visible (blue) emission at ca. 450 nm with a quantum yield of ca. 5%; emission decay under pulsed excitation was predominantly mono-exponential with a lifetime of ca. 1 ns. The emission maximum is largely excitation wavelength independent suggesting the involvement of citrazinic acid-type functionalities in the fiber photophysics. Reversible pH-dependent excitation and emission behaviour was observed, with maximum emission at ca. pH 7. Nanofiber emission was also quenched in aqueous solutions of metal cations, in a concentration-dependent manner. Single nanofiber emission intensity was quite stable under continuous excitation permitting single fiber quenching-based metal ion detection whereby a significant (>90%) and prompt (sub-10 s) quenching was observed upon exposure to sub-millimolar Fe(iii) solutions. The introduction of these new 1D luminescent carbon nanofibers offers the potential for exciting developments across a range of applications.

This work describes the preparation of luminescent carbon nanofibers by template-assisted microwave pyrolysis of environmentally friendly precursors in aqueous solution.     

Considerations in sagittal evaluation of the scoliotic spine

Purpose

To predict the sagittal spinal parameters as measured in a 3D model of the spine using the 2D radiographic measurements.

Methods

Bi-planar low-dose stereoradiography images of 73 right thoracic AIS patients were processed to generate 3D models of the spine and pelvis. T1–T12 kyphosis, L1–S1 lordosis, and pelvic rotation were calculated using these 3D models. With the same X-rays, T1–T12 kyphosis, L1–S1 lordosis, thoracic and lumbar frontal curves, and pelvic rotation (calculated from the frontal and sagittal distances between the femoral heads) were manually measured on the X-rays by two independent observers. 3D sagittal parameters were predicted from only 2D sagittal parameters (simple regression) and from 2D sagittal parameters, 2D frontal parameters, and pelvic rotation (multiple regression). The simple and multiple regression models were compared for efficiency and accuracy of prediction.

Results

Comparing single and multiple regression models, multiple regression improved the prediction of the 3D sagittal parameters for kyphosis (R²?=?0.78–0.86) and lordosis (R²?=?0.88–0.92) measurements when compared to simple regression. The impact of pelvic rotation was significant when 2D kyphosis was higher than 40° and thoracic curve was less than 60° or 2D kyphosis was less than 40° and thoracic curve was higher than 60°, p?<?0.05. Lordosis of 60° and higher were more prone to measurement error when pelvic rotation was present, p?<?0.05.

Conclusions

Both pelvic rotation and frontal deformity affect the accuracy of the 2D sagittal measurements of the scoliotic spine. We suggest the importance of the 3D considerations in sagittal evaluation of AIS.