James Saunders

BACKGROUND: Insufficient techniques exist for rapid and reliable phenotype characterization of genetically manipulated mouse models of cardiac dysfunction. We developed a new, robust, 3-dimensional echocardiography (3D-echo) technique and hypothesized that this 3D-echo technique is as accurate as magnetic resonance imaging (MRI) and histology for assessment of left ventricular (LV) volume, ejection fraction, mass, and infarct size in normal and chronically infarcted mice. METHODS AND RESULTS: Using a high-frequency, 7/15-MHz, linear-array ultrasound transducer, we acquired ECG and respiratory-gated, 500-microm consecutive short-axis slices of the murine heart within 4 minutes. The short-axis movies were reassembled off-line in a 3D matrix by using the measured platform locations to position each slice in 3D. Epicardial and endocardial heart contours were manually traced, and a B-spline surface was fitted to the delineated image curves to reconstruct the heart volumes. Excellent correlations were obtained between 3D-echo and MRI for LV end-systolic volumes (r=0.99, P<0.0001), LV end-diastolic volumes (r=0.99, P<0.0001), ejection fraction (r=0.99, P<0.0001), LV mass (r=0.94, P<0.0019), and infarct size (r=0.98, P<0.0001). Also, excellent correlations were found between the 3D-echo-derived LV mass and necropsy LV mass in normal mice (r=0.99, P<0.0001), as well as for 3D-echo-derived infarct size and histologically determined infarct size (r=0.99, P<0.0001) in mice with chronic heart failure. Bland-Altman analysis showed excellent limits of agreement between techniques for all measured parameters. CONCLUSIONS: This new, fast, and highly reproducible 3D-echo technique should be of widespread applicability for high-throughput murine cardiac phenotyping studies.

CD31 is a member of the immunoglobulin superfamily consisting of six Ig-related domains. It is constitutively expressed by platelets, monocytes, and some lymphocytes, but at tenfold higher levels on vascular endothelial cells. CD31 has both homotypic and heterotypic adhesive properties. We have mapped the homotypic binding sites using a deletion series of CD31-Fc chimeras and a panel of anti-CD31 monoclonal antibodies. An extensive surface of CD31 is involved in homotypic binding with domains 2 and 3 and domains 5 and 6 playing key roles. A model consistent with the experimental data is that CD31 on one cell binds to CD31 on an apposing cell in an antiparallel interdigitating mode requiring full alignment of the six domains of each molecule. In addition to establishing intercellular homotypic contacts. CD31 binding leads to augmented adhesion via beta 1 integrins. The positive cooperation between CD31 and beta 1 integrins can occur in heterologous primate cells (COS cells). The interaction is specific to both CD31 and beta 1 integrins. Neither intercellular adhesion molecule-1 (ICAM-1)/leukocyte function-associated antigen-1 (LCAM-1) nor neural cell adhesion molecule (NCAM)/NCAM adhesion leads to recruitment of beta 1 integrin adhesion pathways. Establishment of CD31 contacts have effects on the growth and morphology of endothelial cells. CD31(D1-D6)Fc inhibits the growth of endothelial cells in culture. In addition, papain fragments of anti-CD31 antibodies (Fab fragments) disrupt interendothelial contact formation and monolayer integrity when intercellular contacts are being formed. The same reagents are without effect once these contacts have been established, suggesting that CD31-CD31 interactions are critically important only in the initial phases of intercellular adhesion.

Though a significant body of literature exists on the safety performance and effectiveness of various types of front seat occupant restraint systems, there is a paucity of data on the performance of rear seat occupant restraint systems. A research program was initiated to better understand rear seat restraint performance. Research included examining real world data using National Automotive Sampling System/Crashworthiness Data System (NASS/CDS) and Fatality Analysis Reporting System (FARS) as well as conducting full frontal vehicle crashes into rigid barriers with dummies restrained in rear seats. Child dummies (Hybrid III 6 year-old) and adult dummies (Hybrid III 5th percentile female and 50th percentile male) were used for this purpose. The dummies were placed in rear outboard seats with lap/shoulder belts as well as in the center seating position where the lap/shoulder belts were integrated to the seat. A double-paired comparison study using FARS data files suggested that while occupants younger than 50 years of age benefit from sitting in rear seats in frontal crashes, restrained adult occupants older than 50 years are significantly better off in the front seats than the rear seats. The most injured body region for restrained children in rear seats is the head while that for restrained adults is the thorax. The major injury source for restrained occupants, not in child safety seats, is the seat belts while that for unrestrained occupants is the front seat back. The injury measures of restrained adult dummies in rear seats in frontal crash tests were generally higher than those of dummies of the same size in the driver and front passenger seat. The seat backs of integrated rear seats experienced excessive forward rotation in frontal crash tests, thereby causing the dummy’s head to hit the console or front seatback, resulting in high head and neck injury measures. The field and vehicle crash test data indicate that rear seat restraints could be further optimized to mitigate injury in frontal crashes for older rear seat occupants.

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;In September 2009 the National Highway Traffic Safety Administration (NHTSA) published a report that investigated the incidence of fatalities to belted non-ejected occupants in frontal crashes involving late-model vehicles. The report concluded that after exceedingly severe crashes, the largest number of fatalities occurred in crashes involving poor structural engagement between the vehicle and its collision partner, present in crashes characterized as corner impacts, oblique crashes, impacts with narrow objects, and heavy vehicle underrides. By contrast, few if any of these 122 fatal crashes were full-frontal or offset-frontal impacts with good structural engagement, excepting crashes that were of extreme severity or the occupants that were exceptionally vulnerable.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;The intent of this research program is to develop a test protocol that replicates real-world injury potential in small overlap impacts (SOI) and oblique offset impacts (Oblique) in motor vehicle crashes. Previous work towards this goal has led to the development of a Research Moving Deformable Barrier-to-Vehicle (RMDBtV) test protocol, which is further evaluated in this paper. While there were some inherent differences in the Vehicle-to-Vehicle (VtV) and RMDBtV test results, the overall agreement of vehicle and occupant responses proved promising enough to perform another VtV to RMDBtV comparison. As in the previous study, the first step is to compare the RMDBtV to VtV test for the same vehicle. This comparison focuses on the target vehicle crash metrics (pulse shape, average deceleration, slope of the velocity time-history, total change in velocity, exterior crush profile, and interior intrusion) as well as occupant kinematics and injury assessment values.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;The second step of this research program is to assess the performance of new vehicles in the SOI RMDBtV and the Oblique RMDBtV test procedures. This research will provide insight on the ability of these two test procedures to replicate vehicle and occupant response as seen in the field. This paper presents the results of 7 different 2010-2011 model year vehicles tested in both the SOI and the Oblique test procedures. In these tests the overlap and RMDB closing speed was held constant for both procedures. The vehicle response demonstrated a decreasing trend of delta-V and longitudinal acceleration with increasing vehicle mass, but the trend did not hold for lateral acceleration. Aside from the lightest vehicle showing the largest magnitude of intrusion, there was no apparent trend of vehicle mass with intrusion. The occupant kinematics demonstrated head contact locations that are common in the field, torso loading of the restraint system and steering wheel, and a distribution of injury assessment values that is representative of the field injury risk.&lt;/div&gt;&lt;/div&gt;