Rheological properties of cross-linked hyaluronan-gelatin hydrogels for tissue engineering

Hydrogels that mimic the natural extracellular matrix (ECM) are used in three-dimensional cell culture, cell therapy, and tissue engineering. A semi-synthetic ECM based on cross-linked hyaluronana offers experimental control of both composition and gel stiffness. The mechanical properties of the ECM in part determine the ultimate cell phenotype. We now describe a rheological study of synthetic ECM hydrogels with storage shear moduli that span three orders of magnitude, from 11 to 3 500 Pa, a range important for engineering of soft tissues. The concentration of the chemically modified HA and the cross-linking density were the main determinants of gel stiffness. Increase in the ratio of thiol-modified gelatin reduced gel stiffness by diluting the effective concentration of the HA component.     

Nutritional regulation of serum osteocalcin: study in kwashiorkor

The serum levels of osteocalcin (bone gla protein) in two groups of Senegalese children, healthy controls and severely malnourished (kwashiorkor) children during nutritional rehabilitation, were measured. The serum osteocalcin of all kwashiorkor children was dramatically decreased on admission to hospital, but increased fourfold during rehabilitation. Serum osteocalcin was low in the control group. In both groups these low levels seemed to be independent of those of 1,25-dihydroxyvitamine D3 which were in the normal range. The results suggest that serum osteocalcin levels might be related to protein-energy status.