The use of tetrahydrofuran (THF) as mobile phase in size exclusion chromatography (SEC) has been found to lead to partial loss of sample and to give anomalous results in the characterization of a liquefaction extract and its hydrocracking products. The problem has been resolved by using NMP (1-methyl-2-pyrrolidinone) as mobile phase in SEC, showing significant fractions of sample eluting at the exclusion limit of an identical SEC column. This fraction has not previously been observed in SEC chromatograms obtained in THF. Comparison of SEC chromatograms obtained by UV-absorption and UV-fluorescence detection (in NMP) suggests that the material observed at the exclusion limit of the column corresponds to larger, more complex polynuclear aromatic ring systems than those present in material separated by the column. In NMP, samples produced during progressively higher temperature hydrocracking experiments eluted, as expected, at longer times, indicating progressive molecular size reduction with increasing intensity of the reaction. These data are consistent with the UV-fluorescence spectra and TGA-derived boiling point distributions of the set of samples. A twofold mechanism for loss of material in THF-based SEC may be proposed: (i) not all the sample dissolves in THF and (ii) some of the larger/more polar molecules apparently soluble in THF tend to deposit on column packings and do not elute through the column. Considerable caution therefore appears necessary in using THF as mobile phase in SEC work for the characterization of complex coal-derived liquids.

Calcitonin-gene-related peptide (CGRP) is a neuropeptide, which is widely distributed throughout the central and peripheral nervous systems. Numerous mechanisms underlying the action of CGRP in osteoblast-associated cells have been suggested for bone growth and metabolism. The present study was designed to closely investigate the osteoblast‑ and osteoclast-associated mechanisms of the effect of CGRP administration on bone metabolism in primary osteoblasts. Primary osteoblasts were obtained from newborn rabbit calvaria and incubated with different concentrations of human CGRP (hCGRP), hCGRP and hCGRP (8‑37), or without treatment as a control. Intracellular calcium (Ca2+) and cyclic adenosine monophosphate (cAMP) were detected following treatment, as well as the expression levels of osteoblast differentiation markers, including activating transcription factor‑4 (ATF4) and osteocalcin (OC), and receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG). The isolated primary osteoblasts were found to stain positively for ALP. hCGRP treatment had no significant effect on transient intracellular Ca2+ in the osteoblasts. Treatment of the osteoblasts with hCGRP led to elevations in the expression levels of cAMP, ATF4 and OPG, and downregulation in the expression of RANKL, in a dose‑dependent manner. These effects were markedly reversed by the addition of hCGRP (8‑37). The results of the present study demonstrated that CGRP administration not only stimulated osteoblast differentiation, as demonstrated by upregulated expression levels of ATF4 and OC in the hCGRP‑treated osteoblasts, but also inhibited OPG/RANKL‑regulated osteoclastogenesis. CGRP may act as a modulator of bone metabolism through osteoblast and osteoclast-associated mechanisms, which result in osteoblast formation with subsequent activation of bone formation.

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