[Bone density of spongiosa and cortical bone of the lumbar spine. Relations to sex, age and spinal deformities in a regional collective of the European Study of Vertebral Osteoporosis (EVOS)]

BACKGROUND AND METHOD

In an additional bone density measurement protocol to the European Vertebral Osteoporosis Study (EVOS) separate spongious and cortical density measurements (sQCT) were carried out at the first 3 lumbar vertebrae in 293 volunteers (92 men and 201 women) in 3 Berlin regional centers.

RESULTS

The spongious mineral density decreases from proximal to distal (L1 to L3), the cortical density increases from proximal to distal, mainly in men. Men showed no significant decrease of cortical density and a lower decrease of spongious density with age compared to women. A comparison of bone mineral density with vertebral height indices of McCloskey/Kanis, Eastell/Melton and Felsenberg showed significant differences of spongious density between a group with normal vertebral height and a group with at least one pathologically degraded vertebra. Individuals with osteoporosis according to the WHO-definition showed a higher prevalence of vertebral deformities. No significant loss of cortical density was observed in these people.

Inhibition of the biosynthesis of N-acetylneuraminic acid by metal ions and selenium in vitro

In liver homogenate the biosynthesis of N-acetylneuraminic acid using N-acetylglucosamine as precursor can be followed stepwise by applying different chromatographic procedures. In this cell-free system 16 metal ions (Zn2+, Mn2+, La3+, Co2+, Cu2+, Hg2+, VO3-, Pb2+, Ce3+, Cd2+, Fe2+, Fe3+, Al3+, Sn2+, Cs+ and Li+) and the selenium compounds, selenium(IV) oxide and sodium selenite, have been checked with respect to their ability to influence a single or possibly several steps of the biosynthesis of N-acetylneuraminic acid. It could be shown that the following enzymes are sensitive to these metal ions (usually applied at a concentration of 1 mmol l-1): N-acetylglucosamine kinase (inhibited by Zn2+ and vandate), UDP-N-acetylglucosamine-2'-epimerase (inhibited by Zn2+, Co2+, Cu2+, Hg2+, VO3-, Pb2+, Cd2+, Fe3+, Cs+, Li+, selenium(IV) oxide and selenite), and N-acetylmannosamine kinase (inhibited by Zn2+, Cu2+, Cd2+ and Co2+). Dose dependent measurements have shown that Zn2+, Cu2+ and selenite are more efficient inhibitors of UDP-N-acetylglucosamine-2'-epimerase than vanadate. As for the N-acetylmannosamine kinase inhibition, a decreasing inhibitory effect exists in the following order Zn2+, Cd2+, Co2+ and Cu2+. In contrast, La3+, Al3+ and Mn2+ (1 mmol l-1) did not interfere with the biosynthesis of N-acetylneuraminic acid. Thus, the conclusion that the inhibitory effect of the metal ions investigated cannot be regarded as simply unspecific is justified.