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Objective. To investigate the effect of isolated hydrostatic pressure on proteoglycan metabolism in chondrocytes.Methods. Bovine articular chondrocytes cultured in agarose gels were subjected to 5 MPa hydrostatic pressure for 4 hours in either a static or a pulsatile (1 Hz) mode, and changes in glycosaminoglycan (GAG) synthesis, hydrodynamic size, and aggregation properties of proteoglycans and aggrecan messenger RNA (mRNA) levels were determined.Results. The application of 5 MPa static pressure caused a significant increase in GAG synthesis of 11% (P < 0.05). Column chromatography showed that this increase in GAG synthesis was associated with large proteoglycans. In addition, semiquantitative reverse transcriptase-polymerase chain reaction showed a 4-fold increase in levels of aggrecan mRNA (P < 0.01).Conclusion. Hydrostatic pressure in isolation, which does not cause cell deformation, can affect proteoglycan metabolism in chondrocytes cultured in agarose gels, indicating an important role of hydrostatic pressure in the regulation of extracellular matrix turnover in articular cartilage.It is generally recognized that mechanical loading is essential in maintaining homeostasis of articular cartilage. However, the physical response of the cartilage matrix to mechanical load is complex and involves many factors, including tissue and cell deformation, change in hydrostatic pressure, and fluid flow (1). This fluid flow not only causes changes in the concentration of extracellular components, but also carries positive counterions and induces streaming potentials and currents (2).Recent reports have described the effects of mechanical compression or hydrostatic pressure applied either directly to cartilaginous tissue or to isolated chondrocytes in culture systems (3-13). Some of these studies have shown that hydrostatic pressure is an important element of mechanical load in the regulation of proteoglycan metabolism in chondrocytes (5,7,9,10,13). It is considered that the interaction of cells with extracellular matrix should be eliminated by isolating chondrocytes from the matrix surrounding them, in order to investigate the effect of a single factor (e.g., hydrostatic pressure) among the various events that occur during the application of mechanical load. However, in all the previous studies regarding the effect of hydrostatic pressure on the metabolism of isolated chondrocytes (not cartilage specimens), pressures were applied to chondrocytes in monolayer culture systems, which could cause dedifferentiation of cells into fibroblastic phenotype (14) and make interpretation of data somewhat difficult.The aim of the current study was to investigate the effect of hydrostatic pressure alone on chondrocyte metabolism in an attempt to dissect the effects of the individual processes affecting physiologic responses of chondrocytes to changes in the mechanical environment. A novel experimental system was developed to apply hydrostatic pressure to chondrocytes cultured in 3-dimensional agarose gels. It thus maintained phenotypic ...

A copper(I)-catalyzed stereospecific reaction for the preparation of cis- and trans-1-silyl-2-borylcyclobutanes as well as 1-phenyl-2-borylcyclobutanes is reported. (Z)- and (E)-Homoallylic methanesulfonates were converted to the corresponding trans- and cis-cyclobutane derivatives, respectively, in the presence of a CuCl/dppp catalyst, bis(pinacolato)diboron, and K(O-t-Bu)/THF. Stereospecific derivatizations of the cis- and trans-borylcyclobutanes were carried out to demonstrate the utility of the borylcyclobutanes.

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