Mesenchymal Stromal Cells and Platelet-Rich Plasma Promote Tendon Allograft Healing in Ovine Anterior Cruciate Ligament Reconstruction

Purpose The effect of bone marrow mesenchymal stromal cells (BMSCs) and platelet-rich plasma (PRP) on tendon allograft maturation in a large animal anterior cruciate ligament (ACL) reconstruction model was reported for the first time. It was hypothesised that compared with non-augmented ACL reconstruction, BMSCs and PRP would enhance graft maturation after 12 weeks and this would be detected using magnetic resonance imaging (MRI). Methods Fifteen sheep underwent unilateral tendon allograft ACL reconstruction using aperture fixation and were randomised into three groups (n = 5). Group 1 received 10 million allogeneic BMSCs in 2 ml fibrin sealant; Group 2 received 12 ml PRP in a plasma clot injected into the graft and bone tunnels; and Group 3 (control) received no adjunctive treatment. At autopsy at 12 weeks, a graft maturation score was determined by the sum for graft integrity, synovial coverage and vascularisation, graft thickness and apparent tension, and synovial sealing at tunnel apertures. MRI analysis (n = 2 animals per group) of the signal–noise quotient (SNQ) and fibrous interzone (FIZ) was used to evaluate intra-articular graft maturation and tendon–bone healing, respectively. Spearman’s rank correlation coefficient (r) of SNQ, autopsy graft maturation score and bone tunnel diameter were analysed. Results The BMSC group (p = 0.01) and PRP group (p = 0.03) had a significantly higher graft maturation score compared with the control group. The BMSC group scored significantly higher for synovial sealing at tunnel apertures (p = 0.03) compared with the control group. The graft maturation score at autopsy significantly correlated with the SNQ (r = − 0.83, p < 0.01). The tunnel diameter of the femoral tunnel at the aperture (r = 0.883, p = 0.03) and mid-portion (r = 0.941, p = 0.02) positively correlated with the SNQ. Conclusions BMSCs and PRP significantly enhanced graft maturation, which indicates that orthobiologics can accelerate the biologic events in tendon allograft incorporation. Femoral tunnel expansion significantly correlated with inferior maturation of the intra-articular graft. The clinical relevance of this study is that BMSCs and PRP enhance allograft healing in a translational model, and biological modulation of graft healing can be evaluated non-invasively using MRI

Research strategies for organizational history:a dialogue between historical theory and organization theory

If history matters for organization theory, then we need greater reflexivity regarding the epistemological problem of representing the past; otherwise, history might be seen as merely a repository of ready-made data. To facilitate this reflexivity, we set out three epistemological dualisms derived from historical theory to explain the relationship between history and organization theory: (1) in the dualism of explanation, historians are preoccupied with narrative construction, whereas organization theorists subordinate narrative to analysis; (2) in the dualism of evidence, historians use verifiable documentary sources, whereas organization theorists prefer constructed data; and (3) in the dualism of temporality, historians construct their own periodization, whereas organization theorists treat time as constant for chronology. These three dualisms underpin our explication of four alternative research strategies for organizational history: corporate history, consisting of a holistic, objectivist narrative of a corporate entity; analytically structured history, narrating theoretically conceptualized structures and events; serial history, using replicable techniques to analyze repeatable facts; and ethnographic history, reading documentary sources "against the grain." Ultimately, we argue that our epistemological dualisms will enable organization theorists to justify their theoretical stance in relation to a range of strategies in organizational history, including narratives constructed from documentary sources found in organizational archives. Copyright of the Academy of Management, all rights reserved

SHAPE EFFECT IN THE SPECTRUM OF MOLECULAR CRYSTALS

Author Institution: Mellon Institute; Department of Physics, State University of New York at Stony Brook“The algebraic diagonalization of the secular determinant for a doubly degenerate molecular state in a cubic crystal is straight-forward and yields (in the K = O approximation) two triply degenerate states and one doubly degenerate stale. Transitions to the triply degenerate slates are allowed. These stales are separated, according to the first order perturbation treatment used, by matrix elements for mining the sense of the angular momentum characteristic of the unperturbed doubly degenerate molecular states, upon different molecules. When the wavelength of the light is greater than the size of crystallite studied, such matrix elements are shown to be strongly dependent upon the surface energy and, thus, the shape of the crystallite. Several examples of the effect will he presented and the experimental importance will he discussed.

INFRARED SPECTRA OF QUINOL CLATHRATE COMPOUNDS

$^{1}$ D. E. Palin and H. M. Powell, J. Chem. Soc. (1947), 208.""Author Institution: Baker Laboratories, Cornell UniversityThe case of synthesis of ""inclusion compounds"" of hydroquinone with small molecules, such as HCl, $H_{2}S, SO_{2}$ and $CO_{2}$, affords an unique opportunity to study restricted rotational and translational motion of such molecules, as well as to elucidate the nature of the binding of the lattices of such compounds. Spectra, both absorption and differential, of such compounds, when suspended in KBr pellets, covering the range $0.8-15 \mu$, are reported, which demonstrate the $proposed^{1}$ difference in crystal structure between a-hydroquinone and its $\beta$ allomorph. In addition, some results are presented which indicate the extent of freedom of rotational motion of the small molecules included in the clathrate, and the extent of the binding of the small molecules to the clathrate lattice