Packing of human erythrocytes in a centrifugal field

The rate of packing of human erythrocytes in whole blood and washed ones in aqueous suspension was investigated in a centrifugal field of 250 g. The Voigt-Kelvin rheological model was found to be well suited to describe the packing process. The ratio of the elastic modulus to viscosity was evaluated from this model. Its value suggests that the flexibility of the cell plays a minor role compared to other viscosity factors. Also the model suggests that the rate of packing is a complicated function of various viscoelastic factors. Empirical parameters describing the rate of packing are sensitive to drastic changes in cell flexibility, such as caused by formaldehyde treatment, whereas no fluidizing effect of procaine on cell membrane was detected. The rate of packing is not affected by decreasing the pH from 7.4 to 6.5. The method of mild centrifugation could be of some use for rapid evaluation of substantial flexibility changes in washed blood cells.     

Role of the α1β1 integrin complex in collagen gel contraction in vitro by fibroblasts

Matrix remodeling, critical to embryonic morphogenesis and wound healing, is dependent on the expression of matrix components, their receptors, and matrix proteases. The collagen gel assay has provided an effective model for the examination of the functional role(s) of each of these groups of molecules in matrix remodeling. Previous investigations have indicated that collagen gel contraction involves the β1 integrin family of matrix receptors and is stimulated by several growth factors, including TGF-β, PDGF, and angiotensin II. In particular, collagen gel remodeling by human cells involves the α2β1 and, to a lesser extent the α1β1 integrin complexes. The present studies were undertaken to determine the role of the α1 integrin chain, a collagen/laminin receptor, in collagen gel contration by rodent and avian fibroblasts. A high degree of correlation was found between the expression of the α1β1 integrin complex and the relative ability of cells to contract collagen gels. Further studies using antibodies and antisense oligonucleotides against the α1 integrin indicated a significant role for this integrin chain in contraction of collagen gels by rat cardiac fibroblasts. In addition, antibodies to the α1 integrin chain inhibited migration of these fibroblasts on a collagen substratum, suggesting that at least one role of this integrin is in migration of cells in collagen gels. These results indicate that the α1β integrin complex plays a significant role in cellular interactions with interstital collagen that are involved in matrix remodeling such as is seen during morphogenesis and wound healing. © 1995 Wiley-Liss, Inc.     

An automated fluorescence method for determination of K+-dependent phosphatase

An automated fluorescence method for the determination of K⁺-dependent umbelliferone phosphatase activity is described. This activity is associated with a (Na⁺ + K⁺)-dependent ATPase in brain and kidney microsomal preparations. The ratio of phosphatase activity/ATPase activity is greater in kindney.