Changing Views of the Biomechanics of Vulnerable Plaque Rupture: A Review

This review examines changing perspectives on the biomechanics of vulnerable plaque rupture over the past 25 years from the first finite element analyses (FEA) showing that the presence of a lipid pool significantly increases the local tissue stress in the atheroma cap to the latest imaging and 3D FEA studies revealing numerous microcalcifications in the cap proper and a new paradigm for cap rupture. The first part of the review summarizes studies describing the role of the fibrous cap thickness, tissue properties, and lesion geometry as main determinants of the risk of rupture. Advantages and limitations of current imaging technologies for assessment of vulnerable plaques are also discussed. However, the basic paradoxes as to why ruptures frequently did not coincide with location of PCS and why caps >65 μm thickness could rupture at tissue stresses significantly below the 300 kPa critical threshold still remained unresolved. The second part of the review describes recent studies in the role of microcalcifications, their origin, shape, and clustering in explaining these unresolved issues including the actual mechanism of rupture due to the explosive growth of tiny voids (cavitation) in local regions of high stress concentration between closely spaced microinclusions oriented along their tensile axis.     

ST-segment elevation after abdominal aortic aneurysm repair

We describe a case of post-operative inferior myocardial infarction after abdominal aortic aneurysm repair due to compromise of a gastroepiploic coronary arterial graft.     

The conventional versus automated measurement of blood pressure in the office (CAMBO) trial: masked hypertension sub-study

OBJECTIVES:: To determine the prevalence of masked hypertension [normal office blood pressure (BP) with high awake ambulatory BP] using automated office BP (AOBP) or conventional manual office BP (MOBP) measurement in routine clinical practice. METHODS:: The prevalence of masked hypertension was evaluated on three consecutive visits during a median 6 months period in patients with systolic hypertension randomized to management with AOBP (n?=?140) or continued conventional MOBP (n?=?112) in routine primary care practice. AOBP was recorded using the automated BpTRU device with the patient resting alone in a quiet examining room. All patients underwent 24-h ambulatory BP monitoring. RESULTS:: The prevalence of masked hypertension on any one of three visits calculated using only SBP varied between 12 and 17% in the AOBP group compared with 19 and 22 % in the MOBP group. Masked hypertension was present on both of the first two visits in 7 and 12% and on all three visits in 6 and 7% of AOBP and MOBP patients, respectively. The prevalence for masked hypertension based upon both SBP and DBP was similar being 11-15% for AOBP and 19-20% for MOBP patients on single visits, but decreased to 6 and 10% when readings from the first two visits were used and to 4 and 6% when all three visits were used for the AOBP and MOBP groups, respectively. CONCLUSION:: The prevalence of masked hypertension is lower with AOBP compared with MOBP. The number of patients with masked hypertension decreases if the criteria for having this condition need to be met on multiple visits.     

Local vanadium release from a calcium sulfate carrier accelerates fracture healing

This study evaluated the efficacy of using calcium sulfate (CaSO₄) as a carrier for intramedullary delivery of an organic vanadium salt, vanadyl acetylacetonate (VAC) after femoral fracture. VAC can act as an insulin‐mimetic and can be used to accelerate fracture healing in rats. A heterogenous mixture of VAC and CaSO₄ was delivered to the fracture site of BB Wistar rats, and mechanical testing, histomorphometry, micro‐computed tomography (micro‐CT) were performed to measure healing. At 4 weeks after fracture, maximum torque to failure, effective shear modulus, and effective shear stress were all significantly higher (p < 0.05) in rats treated with 0.25 mg/kg VAC–CaSO₄ as compared to carrier control rats. Histomorphometry found a 71% increase in percent cartilage matrix (p < 0.05) and a 64% decrease in percent mineralized tissue (p < 0.05) at 2 weeks after fracture in rats treated with 0.25 mg/kg of VAC–CaSO₄. Micro‐CT analyses at 4 weeks found a more organized callus structure and higher trending maximum connected z‐ray. fraction for VAC–CaSO₄ groups. Evaluation of radiographs and serial histological sections at 12 weeks did not show any evidence of ectopic bone formation. As compared to previous studies, CaSO₄ was an effective carrier for reducing the dose of VAC required to accelerate femoral fracture healing in rats. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:727–734, 2014.     

The Interaction Between Radiation and Complexes of Cis-Pt(II) and Rh(II): Studies at the Molecular and Cellular Level

Summary

A range of Rh(II) carboxylates and cis-Pt(II) complexes have been examined for their ability to increase the radiation sensitivity of aerobic and hypoxic V79 cells in vitro. The transition metal complexes sensitize in both air and nitrogen, with the greater effect generally occurring in nitrogen. The cis-Pt(II) complexes only show small levels of sensitization with dose modification factors (DMFs) of no more than 1·2. In contrast, the Rh(II) complexes can give DMFs of 2·0. Radiation chemical experiments show the transition metal complexes to have substantially lower redox potentials than metronidazole and, in addition, neither type of complex undergoes electron transfer reaction or adduct formation on interaction with radicals derived from DNA bases. Thus, the inorganic complexes do not operate by mechanisms similar to those occurring with electron affinic or stable free radical sensitizers. The increase in radiation sensitivity for cells treated with the Rh(II) carboxylates, but not the cis-Pt(II) complexes, is attributed to the ability of the Rh compounds to deplete intracellular thiols. Further, the efficiency of sensitization by the Rh(II) complexes and their ability to interact with cellular thiols depends upon the nature of the carboxylate ligand and follows the order butyrate > propionate > acetate > methoxyacetate. The differences between the carboxylates may be due to differences in drug uptake. A combination of the Rh(II) complexes with misonidazole given to hypoxic cells irradiated in vitro gives an additive response. However, it was not possible to demonstrate a similar effect in tumours in mice given the combination of Rh(II) methoxyacetate and the misonidazole analogue RSU 1070.     

Label-free histological imaging of tissues using Brillouin light scattering contrast

Brillouin light scattering offers a unique label-free approach to measure biomechanical properties non-invasively. While this technique is used in biomechanical analysis of cells and tissues, its potential for visualizing structural features of tissues based on the biomechanical contrast has not been much exploited. Here, we present high-resolution Brillouin microscopy images of four basic tissue types: muscular, connective, epithelial, and nervous tissues. The Brillouin contrast distinguishes between muscle fiber cells and endomysium in skeletal muscle and reveals chondrocytes along with spatially varying stiffness of the extracellular matrix in articular cartilage. The hydration-sensitive contrast can visualize the stratum corneum, epidermis, and dermis in the skin epithelium. In brain tissues, the Brillouin images show the mechanical heterogeneity across the cortex and deeper regions. This work demonstrates the versatility of using the Brillouin shift as histological contrast for examining intact tissue substructures via longitudinal modulus without the need for laborious tissue processing steps.     

Openness to experience predicts intrinsic value shifts after deliberating one’s own death

Individual differences that might moderate processes of value shifting during and after deliberating one’s own death remain largely unexplored. Two studies measured participants’ openness and relative intrinsic-to-extrinsic value orientation (RIEVO) before randomly assigning them to conditions in which they wrote about their own death or dental pain for 6 days, after which RIEVO was assessed again up to 12 days later. When participants confronted thoughts about their own death over a sustained period, high openness to experience helped them shift toward intrinsic values. Implications for understanding openness’ role in value reorientation from existential deliberation processes are discussed.