Exercise capacity and cardiac hemodynamic response in female ApoE/LDLR^{-/-} mice : a paradox of preserved V'O_{2max} and exercise capacity despite coronary atherosclerosis

We assessed exercise performance, coronary blood flow and cardiac reserve of female ApoE/LDLR-/- mice with advanced atherosclerosis compared with age-matched, wild-type C57BL6/J mice. Exercise capacity was assessed as whole body maximal oxygen consumption (V'O2max), maximum running velocity (vmax) and maximum distance (DISTmax) during treadmill exercise. Cardiac systolic and diastolic function in basal conditions and in response to dobutamine (mimicking exercise-induced cardiac stress) were assessed by Magnetic Resonance Imaging (MRI) in vivo. Function of coronary circulation was assessed in isolated perfused hearts. In female ApoE/LDLR-/- mice V'O2max, vmax and DISTmax were not impaired as compared with C57BL6/J mice. Cardiac function at rest and systolic and diastolic cardiac reserve were also preserved in female ApoE/LDLR-/- mice as evidenced by preserved fractional area change and similar fall in systolic and end diastolic area after dobutamine. Moreover, endothelium-dependent responses of coronary circulation induced by bradykinin (Bk) and acetylcholine (ACh) were preserved, while endothelium-independent responses induced by NO-donors were augmented in female ApoE/LDLR-/- mice. Basal COX-2-dependent production of 6-keto-PGF1α was increased. Concluding, we suggest that robust compensatory mechanisms in coronary circulation involving PGI2- and NO-pathways may efficiently counterbalance coronary atherosclerosis-induced impairment in V'O2max and exercise capacity

A Simple Sperm DNA Toroid Integrity Test and Risk of Miscarriage

Current methods of analyzing sperm chromatin competency overlook the inner sperm compartment which is inaccessible to probes and reagents. By breaking the molecular protamine disulfide bridges, the DNA toroids are exposed to integrity analysis. The aim was to develop a simple nuclear toroid test and determine its association with fertilization, pregnancy, and miscarriage. The approach involved treating washed sperm remaining after ICSI procedures (N=35 cases) with acidified Triton X-100 and dithiothreitol (DTT) before Diff-Quik staining. Percentages of sperm with normal chromatin indicated by light-colored nuclei were assessed. The toroid integrity test showed more sperm with normal chromatin in the pregnant group (73.6 ± 1.7%, mean ± SEM) when compared with the miscarriage (51.2 ± 6.6%) or nonpregnant groups (60.9 ± 4.8%). Furthermore, the toroid results were correlated with ICSI fertilization (R=0.32, P=0.04) and pregnancy outcome (pregnant cases 73.6 ± 1.7% versus nonpregnant 58.0 ± 3.9%, P=0.001). ROC calculated cut-off was >70.0% for normal toroid integrity (sensitivity 0.98, specificity 0.33, and diagnostic accuracy 78.3%). An association between normal sperm toroid integrity and miscarriage was evident when the staining procedure included acidified detergent DTT pretreatment

Comprehensive MRI for the detection of subtle alterations in diastolic cardiac function in apoE/LDLR^{-/-} mice with advanced atherosclerosis

ApoE/LDLR-/- mice represent a reliable model of atherosclerosis. However, it is not clear whether cardiac performance is impaired in this murine model of atherosclerosis. Here, we used MRI to characterize cardiac performance in vivo in apoE/LDLR-/- mice with advanced atherosclerosis. Six-month-old apoE/LDLR-/- mice and age-matched C57BL/6J mice (control) were examined using highly time-resolved cine-MRI [whole-chamber left ventricle (LV) imaging] and MR tagging (three slices: basal, mid-cavity and apical). Global and regional measures of cardiac function included LV volumes, kinetics, time-dependent parameters, strains and rotations. Histological analysis was performed using OMSB (orceine with Martius, Scarlet and Blue) and ORO (oil red-O) staining to demonstrate the presence of advanced coronary atherosclerosis. MR-tagging-based strain analysis in apoE/LDLR-/- mice revealed an increased frequency of radial and circumferential systolic stretch (25% and 50% of segments, respectively, p≤0.012), increased radial post-systolic strain index (45% of segments, p=0.009) and decreased LV untwisting rate (-30.3° (11.6°)/cycle, p=0.004) when compared with control mice. Maximal strains and LV twist were unchanged. Most of the cine-MRI-based LV functional and anatomical parameters also remained unchanged in apoE/LDLR-/-mice, with only a lower filling rate, longer filling time, shorter isovolumetric contraction time and slower heart rate observed in comparison with control mice. The coronary arteries displayed severe atherosclerosis, as evidenced by histological analysis. Using comprehensive MRI methods, we have demonstrated that, despite severe coronary atherosclerosis in six-month-old apoE/LDLR-/- mice, cardiac performance including global parameters, twist and strains, was well preserved. Only subtle diastolic alterations, possibly of ischemic background, were uncovered