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Objective: The vascularization of subchondral bone plays a significant role in the progression of knee osteoarthritis (OA). Treatment with platelet-rich plasma (PRP) has positive effects on cartilage lesions. However, PRP's efficacy for subchondral bone marrow lesions and the relationship of these lesions to cartilage are still undiscovered. Therefore, our aims were first to longitudinally investigate the change in subchondral flow by dynamic contrast enhanced MRI and degeneration of cartilage by MRI T2∗ in an anterior cruciate transection rodent (ACLT) model, and second to examine changes in parameters after intra-articular PRP injection.Design: A 32-week investigation in 18 rats allocated to sham-control, ACLT with normal saline injection (ACLT + NS), and ACLT with PRP injection groups ended with histological evaluation. Another rat was used as a donor of allogenic PRP.Results: Compared to the sham-control group, the ACLT + NS group had higher subchondral blood volume A (0.051, 95% confidence interval: 0.009, 0.092) and lower venous washout kel (-0.030: -0.055, -0.005) from week 4; lower permeability kep from week 18 (-0.954: -1.339, -0.569); higher cartilage T2∗ values (1.803: 1.504, 2.102) reflecting collagen loss beginning at week 10. For the PRP treatment group, subchondral bone marrow A and cartilage T2∗ decreased from week 10. Histological results confirmed and were correlated with the MRI findings.Conclusion: Subchondral hyper-perfusion plays a vital role in the pathogenesis of OA and was associated with cartilage degeneration. The efficacy of PRP can be observed from reduced perfusion and MRI T2∗ values. [ABSTRACT FROM AUTHOR]

Investigates the photodissociation dynamics of water at 121.6 nm through the B[sup 1]A[sub 1] state using the high-resolution hydrogen atom Rydberg tagging technique. Different dissociation pathways to form the ground OH products; Enhancement of the dissociation through the B-A Coriolis coupling by preparing the water molecules at higher rotational temperatures.

Presents a study on the dynamical interference of photodissociation pathways in water. Investigation of the photodissociation of water by using the H-atom Rydberg tagging technique; Observation of an even-odd intensity oscillation in the OH(X) product rotational distribution; Chemical analog of Young's double-slit experiment; Inference.

Photodissociation of H[sub 2]O, D[sub 2]O, and HOD on the A˜ [sup 1]B[sub 1][sup ′] surface through 157.6 nm excitation has been studied using the H(D) atom Rydberg tagging time-of-flight technique. Vibrational state distribution has been measured for the OH/OD product from the photodissociation of the H[sub 2]O, D[sub 2]O, and HOD molecules. Comparisons of our results with previous theoretical calculations and experimental results obtained using the laser induced fluorescence (LIF) technique have been made. Experimental results in this work indicate that the relative populations for vibrationally excited OH(v>=2) products measured using LIF are significantly underestimated, suggesting that LIF as a technique to quantitatively measure vibrational distributions of reaction product OH is seriously flawed. The experimental results presented here are in rather good agreement with previous theoretical calculations. However, our results indicate that the calculated vibrational populations for the higher vibrational states of OH are still somewhat overestimated. Relative branching ratio of H and D productions from HOD has also been estimated. This complete set of data for the photodissociation of H[sub 2]O should provide an excellent testing ground for improving the theoretical potential energy surface of the first electronically excited state of the water molecule. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]