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ObjectiveCCN family protein 2/connective tissue growth factor (CCN2/CTGF) promotes cartilage regeneration in experimental osteoarthritis (OA) models. However, CCN2 production is very low in articular cartilage. The aim of this study was to investigate whether or not CCN2 was promoted by cultured chondrocytes treated with low-intensity pulsed ultrasound (LIPUS) and to clarify its mechanism.MethodsHuman chondrocytic cell line (HCS)-2/8, rat primary epiphyseal and articular cartilage cells, and Ccn2-deficient chondrocytes that impaired chondrocyte differentiation, were treated with LIPUS for 20 min at 3.0 MHz frequency and 60 mW/cm2 power. Expressions of chondrocyte differentiation marker mRNAs were examined by real-time PCR (RT-PCR) analysis from HCS-2/8 cells and Ccn2-deficient chondrocytes at 30 min and 1 h after LIPUS treatment, respectively. CCN2 production was examined by Western blotting after 5 h of LIPUS treatment. Moreover, Ca2+ influx was measured by using a Fluo-4 probe.ResultsThe gene expression of chondrocyte differentiation markers and CCN2 production were increased in cultured chondrocytes treated with LIPUS. In addition, Ca2+ influx and phosphorylation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK)1/2 were increased by LIPUS treatment, and the stability of TRPV4 and BKca channel mRNAs was decreased by siRNA against CCN2. Consistent with those findings, the LIPUS-induced the gene expressions of type II collagen (COL2a1) and Aggrecan (ACAN) observed in wild-type cells were not observed in the Ccn2-deficient chondrocytes.ConclusionThese data indicate that chondrocyte differentiation represented by CCN2 production was mediated via MAPK pathways activated by LIPUS-stimulated Ca2+ influx, which in turn was supported by the induced CCN2 molecules in articular chondrocytes.

The microscopic magnetic properties of the CuO2 planes in YBa2Cu3O6.63 (Tc=62 K) have been investigated in Cu and O NMR experiments. Unlike the fully oxygenated Y-Ba-Cu-O7 (Tc 90 K), the various components of the Cu and O Knight-shift tensors show strong but identical temperature dependences in the normal state. This supports the picture that there is only one spin component in the CuO2 planes. The spin susceptibility deduced from Knight-shift results shows significant reduction with decreasing temperature in the normal state. The temperature dependences of the nuclear-spin-relaxation rates (1/T1) are very different for the Cu and the O sites. 1/(T1T) at the O sites is nearly proportional to the spin susceptibility. 1/(T1T) at the Cu sites shows a broad peak around 150 K. We discuss these relaxation behaviors based on a model of the dynamical spin susceptibility proposed by Millis, Monien, and Pines. © 1991 The American Physical Society.

We report a study of single-crystal La2CuO4+, a 38-K superconductor produced by high-pressure oxygenation. We employ La139 NMR to probe the behavior of copper spins in the CuO2 planes. At low temperatures we observe two signals, one originating from regions of the crystal rich in oxygen and a second having no excess oxygen (0). Upon warming through 265 5 K, the volume fraction of the crystal poor in oxygen goes to zero. The magnetic shift of the peak intensity of the line originating in the oxygen-rich portion of the crystal does not change in the vicinity of 265 K. These observations provide direct microscopic evidence for phase separation in the crystal. © 1990 The American Physical Society.

We report a study of single-crystal La2CuO4+, a 38-K superconductor produced by high-pressure oxygenation. We employ La139 NMR to probe the behavior of copper spins in the CuO2 planes. At low temperatures we observe two signals, one originating from regions of the crystal rich in oxygen and a second having no excess oxygen (0). Upon warming through 265 5 K, the volume fraction of the crystal poor in oxygen goes to zero. The magnetic shift of the peak intensity of the line originating in the oxygen-rich portion of the crystal does not change in the vicinity of 265 K. These observations provide direct microscopic evidence for phase separation in the crystal. © 1990 The American Physical Society.

We report NMR measurements of the nuclear relaxation rate at all copper and oxygen sites in magnetically aligned powder samples of YBa2Cu3O7. Comparison of the oxygen and copper relaxation reveals a characteristic temperature greater than Tc. The copper relaxation rate is enhanced by antiferromagnetic copper spin fluctuations which are undiminished in the superconducting state. The absence of a coherence peak indicates that the superconductive pairing is not of the conventional BCS type. © 1989 The American Physical Society.

We have measured the copper nuclear relaxation rate in GdBa2Cu3O7 in zero applied field using nuclear quadrupole resonance. Fluctuations in the 4f moment associated with the gadolinium contribute strongly to the copper relaxation rate, and this contribution will depend strongly on the copper-gadolinium separation. This separation differs considerably for the two copper sites. Comparison of the relaxation rates shows that the copper signal at the higher frequency (32 MHz) originates from the Cu(2) site, which is located closer to the gadolinium than is the Cu(1) site. © 1988 The American Physical Society.

Precise measurements of the Knight shift at Cu(1) (chain) and Cu(2) (plane) sites have been made in the normal state of a YBa2Cu3O7 powder sample, for which the c axis of each grain has been aligned in a magnetic field. By combining these data with the Knight shift data in the superconducting state and the anisotropic magnetic susceptibility, it is shown that (1) the anisotropy of the magnetic susceptibility is mainly due to the orbital moment of the 3d electrons, (2) the magnitude of the spin contribution to the Knight shift is similar at both sites, and (3) the isotropic part of the Cu hyperfine field is large and positive (112 kOe/B). © 1989 The American Physical Society.

The Cu63 Knight shift in YBa2Cu3O7 has been measured at both Cu(1) (chain) and Cu(2) (plane) sites, using a uniaxially aligned powder. The isotropic part of the spin Knight shift (Ks) was found to be positive for both sites, suggesting large transferred hyperfine fields from oxygen p states. The Knight shifts at both sites show significant change below Tc, indicating important roles of both the planes and chains in the superconductivity. Despite the uncertainty in the diamagnetic screening, the axial part of Ks at Cu(2) sites is found to show linear-T behavior at low temperatures. © 1989 The American Physical Society.

We present our 17O NMR experimental results in a magnetically aligned powder sample of YBa2Cu3O7-δ (Tc = 93 K). The sign of the anisotropic Knight shift shows that the spin density resides mainly on the pσ orbitals at the planar O(2,3) and bridging O(4) sites. About 30 % of the total spin susceptibility is attributed to the oxygen 2pσ states. The Knight shift at the O(2,3) sites decrease more rapidly than that at the chain O(1) sites, indicating a larger gap in the planes. The nuclear relaxation rate at the O(2,3) sites shows linear-T (Korriga) behavior above Tc, in contrast to the much weaker temperature dependence at the planar Cu(2) sites. However, these two rates show identical temperature dependence below about 110 K, indicating that an important change in the spin dynamics takes place above Tc. © 1989.

We report an anomalous temperature dependence of the magnetization and the NMR line width at the planar Cu(2) and oxygen sites in the mixed state of aligned YBa2Cu3O7-δ powder at relatively high field (≥ 30 kOe), where hysteresis of the magnetization due to flux pinning is not important. Both the magnetization and the NMR line width at all sites show a steep increase at low temperature. We found a much larger line width at Cu(2) sites than at oxygen sites when the magnetic field is applied perpendicular to the c-axis, indicating a very microscopic local field modulation. © 1989.

We report NMR measurements of the nuclear relaxation rate at all copper and oxygen sites in magnetically aligned powder samples of YBa2Cu3O7. There is no peak in the oxygen relaxation rate below Tc at any oxygen site supporting the possibility that d-wave pairs are formed in the superconducting state. Comparison of the oxygen and copper rates in the planes reveals a characteristic temperature greater than Tc. © 1989.

O17 nuclear-magnetic-resonance spectra are obtained, using uniaxially aligned powder of YBa2Cu3O7, and resonance lines from the four inequivalent oxygen sites are clearly distinguished. Principal components of the electric field gradient (EFG) and the shift tensors are obtained in the normal state. Assigning the direction of the largest EFG components of Cu-O bond axes, the anisotropy of the shift suggests that the spin density at the plane O(2,3) and the bridging O(4) sites resides on the p orbitals. The domonant contribution to the spin susceptibility comes from Cu d states. © 1989 The American Physical Society.

The Cu63 Knight shift in YBa2Cu3O7 has been measured at both Cu(1) (chain) and Cu(2) (plane) sites, using a uniaxially aligned powder. The isotropic part of the spin Knight shift (Ks) was found to be positive for both sites, suggesting large transferred hyperfine fields from oxygen p states. The Knight shifts at both sites show significant change below Tc, indicating important roles of both the planes and chains in the superconductivity. Despite the uncertainty in the diamagnetic screening, the axial part of Ks at Cu(2) sites is found to show linear-T behavior at low temperatures. © 1989 The American Physical Society.

O17 nuclear-magnetic-resonance spectra are obtained, using uniaxially aligned powder of YBa2Cu3O7, and resonance lines from the four inequivalent oxygen sites are clearly distinguished. Principal components of the electric field gradient (EFG) and the shift tensors are obtained in the normal state. Assigning the direction of the largest EFG components of Cu-O bond axes, the anisotropy of the shift suggests that the spin density at the plane O(2,3) and the bridging O(4) sites resides on the p orbitals. The domonant contribution to the spin susceptibility comes from Cu d states. © 1989 The American Physical Society.

We present our 17O NMR experimental results in a magnetically aligned powder sample of YBa2Cu3O7-δ (Tc = 93 K). The sign of the anisotropic Knight shift shows that the spin density resides mainly on the pσ orbitals at the planar O(2,3) and bridging O(4) sites. About 30 % of the total spin susceptibility is attributed to the oxygen 2pσ states. The Knight shift at the O(2,3) sites decrease more rapidly than that at the chain O(1) sites, indicating a larger gap in the planes. The nuclear relaxation rate at the O(2,3) sites shows linear-T (Korriga) behavior above Tc, in contrast to the much weaker temperature dependence at the planar Cu(2) sites. However, these two rates show identical temperature dependence below about 110 K, indicating that an important change in the spin dynamics takes place above Tc. © 1989.