Circadian rhythmicity, variability and correlation of interleukin-6 levels in plasma and cerebrospinal fluid of healthy men.

BACKGROUND: Interleukin-6 (IL-6) is a cytokine with pleiotropic actions in both the periphery of the body and the central nervous system (CNS). Altered IL-6 secretion has been associated with inflammatory dysregulation and several adverse health consequences. However, little is known about the physiological circadian characteristics and dynamic inter-correlation between circulating and CNS IL-6 levels in humans, or their significance. METHODS: Simultaneous assessment of plasma and cerebrospinal fluid (CSF) IL-6 levels was performed hourly in 11 healthy male volunteers over 24h, to characterize physiological IL-6 secretion levels in both compartments. RESULTS: IL-6 levels showed considerable within- and between-subject variability in both plasma and CSF, with plasma/CSF ratios revealing consistently higher levels in the CSF. Both CSF and plasma IL-6 levels showed a distinctive circadian variation, with CSF IL-6 levels exhibiting a main 24h, and plasma a biphasic 12h, circadian component. Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was at around 7 p.m. There was no correlation between coincident CSF and plasma IL-6 values, but evidence for significant correlations at a negative 7-8h time lag. CONCLUSIONS: This study provides evidence in humans for a circadian IL-6 rhythm in CSF and confirms prior observations reporting a plasma biphasic circadian pattern. Our results indicate differential IL-6 regulation across the two compartments and are consistent with local production of IL-6 in the CNS. Possible physiological significance is discussed and implications for further research are highlighted.

Magnetic resonance discography in cadavers: tears of the annulus fibrosus.

The purpose of this study was to investigate the diagnostic capabilities of magnetic resonance discography in the detection of tears of the annulus fibrosus, and to compare the findings with those derived from conventional magnetic resonance imaging. Twenty-four intervertebral discs from cadavers were examined with magnetic resonance imaging and magnetic resonance discography, and anatomic correlation was done. Forty-six annular tears were documented on anatomic inspection of the specimens. Magnetic resonance discography allowed significantly better observation of radial than transverse annular tears, and identification of radial tears was significantly better than that of concentric tears. With magnetic resonance discography, detectability of concentric tears was not significantly better than that of the transverse tears. No significant differences in the detection of different types of annular tears were appreciated on the magnetic resonance images obtained before discography. Magnetic resonance discography allowed direct diagnosis of radial, transverse, and concentric tears in 100%, 57%, and 21% of specimens, respectively. With magnetic resonance imaging, the diagnosis of radial, transverse, and concentric tears was possible in 67%, 71%, and 21% of specimens, respectively. Magnetic resonance discography does well in the evaluation of the clinically important radial tears of the annulus fibrosus, although not uniformly well in the identification of other types of annular tears.

Cartilaginous endplates of the spine: MRI with anatomic correlation in cadavers.

PURPOSE: The purpose of this work was to describe the MR appearance of cartilaginous endplates (CEPs) with close anatomic correlation in cadavers derived from elderly subjects. METHOD: High-resolution MRI was performed on five cadaveric lumbar spines, and a total of 48 CEPs were studied with T1-weighted spin echo, T2-weighted fast spin echo, and fat-suppressed 3D spoiled GRASS gradient echo (SPGR) MR images. All specimens underwent anatomic sectioning, and gross anatomic findings were correlated with those of MRI. RESULTS: Conventional MR images allowed gross morphologic evaluation of the integrity of the CEPs and demonstrated cartilaginous nodes. In all specimens, fat-suppressed 3D-SPGR images invariably improved visualization of the fine anatomic structures at the diskovertebral junction (p < 0.01). Various morphologic abnormalities of the CEPs demonstrated on MR images, including thinning, irregularity, erosions, cartilaginous defects, and Schmorl nodes, were confirmed on anatomic inspection. CONCLUSION: Results in our study indicate that MRI may delineate the normal anatomy of CEPs and demonstrate morphologic changes occurring at the diskovertebral junction. Dedicated high-resolution technique and fat-suppressed 3D-SPGR images may significantly improve the diagnostic capabilities of MRI of this particular anatomic region.