Effect of tafamidis on left atrial function of patients with transthyretin amyloid cardiomyopathy.

Transthyretin amyloid cardiomyopathy (ATTR-CM) is characterized by the functional and structural effects of amyloid infiltration, predominantly within the ventricles, causing biventricular wall thickening. Amyloid infiltration can be observed in the left atrium in ATTR-CM patients, but the association of left atrial (LA) myocardial function with cardiovascular events and of changes in LA myocardial function with tafamidis administration have not yet been clarified. Our aim was, therefore, to use speckle-tracking strain for investigating LA myocardial function in patients with ATTR-CM treated with tafamidis. We studied 55 patients with biopsy-proven ATTR-CM who had been treated with tafamidis (age: 76 ± 2 years, male: 93%). For speckle-tracking analysis of LA myocardial function, the systolic LA strain (LA reservoir function) was defined for this study as LA myocardial function from the apical 4-chamber view. The primary endpoint was defined as a composite comprising cardiovascular death and/or heart failure hospitalization after tafamidis administration over a median follow-up period of 28 ± 4 months. Patients with baseline LA strain < 8.6% (median value) experienced significantly more cardiovascular events than those without (log-rank P = 0.002). Moreover, LA strain in 26 patients worsened after tafamidis administration, and multivariate logistic regression analysis showed age, global longitudinal strain and relative apical longitudinal strain index were identified as independent determinants of deterioration of LA strain after tafamidis administration. In conclusion, baseline LA reservoir function is closely associated with cardiovascular events after tafamidis administration, and could be an additional parameter for the management of patients with ATTR-CM.

Left ventricular reverse remodeling following initiation of sacubitril/valsartan for heart failure with reduced ejection fraction and low blood pressure.

Sacubitril/valsartan has become an important first-line drug for symptomatic heart failure (HF) patients, especially with left ventricular (LV) ejection fraction (LVEF) < 50%. However, the impact of sacubitril/valsartan on cardiovascular outcomes, especially LV reverse remodeling for such patients with low blood pressure, remains uncertain. We retrospectively studied 164 HF patients with LVEF < 50% who were treated with sacubitril/valsartan from two institutions. Echocardiography was performed before and 9.5 ± 5.1 months after initiation of maximum tolerated dose of sacubitril/valsartan. The maximum tolerated dose of sacubitril/valsartan was lower for the low blood pressure group (≤ 100 mmHg in systole) than for the non-low blood pressure group (> 100 mmHg in systole) (165 ± 106 mg vs. 238 ± 124 mg, P = 0.017). As expected, significant LV reverse remodeling was observed in the non-low blood pressure group after initiation of sacubitril/valsartan. It was noteworthy that significant LV reverse remodeling was also observed in the low blood pressure group after initiation of sacubitril/valsartan (LV end-diastolic volume: 177.3 ± 66.0 mL vs. 137.7 ± 56.1 mL, P < 0.001, LV end-systolic volume: 131.6 ± 60.3 mL vs. 94.6 ± 55.7 mL, P < 0.001, LVEF: 26.8 ± 10.3% vs. 33.8 ± 13.6%, P = 0.015). Relative changes in LV volumes and LVEF after initiation of sacubitril/valsartan were similar for the two groups. In conclusion, significant LV reverse remodeling occurred after initiation of sacubitril/valsartan, even in HF patients with LVEF < 50% and systolic blood pressure ≤ 100 mmHg.

Identification of factors associated with progression of left atrial enlargement in patients with atrial fibrillation.

Left atrial (LA) enlargement frequently occurs in atrial fibrillation (AF) patients, and this enlargement is associated with the development of heart failure, thromboembolism, or atrial functional mitral regurgitation (AFMR). AF patients can develop LA enlargement over time, but its progression depends on the individual. So far, the factors that cause progressive LA enlargement in AF patients have thus not been elucidated, so that the aim of this study was to identify the factors associated with the progression of LA enlargement in AF patients. We studied 100 patients with persistent or permanent AF (aged: 67 ± 2 years, 40 females). Echocardiography was performed at baseline and 12 (5-30) months after follow-up. LA size was evaluated as the LA volume index which was calculated with the biplane modified Simpson's method from apical four-and two-chamber views, and then normalized to the body surface area (LAVI). The deterioration of AFMR after follow-up was defined as a deterioration in severity of mitral regurgitation (MR) by a grade of 1 or more. Multivariate regression analysis demonstrated that hypertension (p = .03) was an independently associated parameter of progressive LA enlargement, as was baseline LAVI. In addition, the Kaplan-Meier curve indicated that patients with hypertension tended to show greater deterioration of AFMR after follow-up than those without hypertension (log-rank p = .08). Hypertension proved to be strongly associated with progression of LA enlargement over time in patients with AF. Our findings provide new insights for better management of patients with AF to prevent the development of AFMR.

Synthesis and Evaluation of MGB Polyamide-Oligonucleotide Conjugates as Gene Expression Control Compounds.

MGB polyamide-oligonucleotide conjugates ON 1-4 with linked MGB polyamides at the 2-exocyclic amino group of a guanine base using aminoalkyl linkers were synthesized and evaluated in terms of binding affinity for complementary DNA containing the MGB polyamide binding sequence using T m and CD analyses. The MGB polyamides comprised pyrrole polyamides (Py4- and Py3-), which possess binding affinity for A-T base pairs, and imidazole (Im3-) and pyrrole-γ-imidazole (Py3-γ-Im3-) polyamide hairpin motifs, which possess binding affinity for C-G base pairs. It was found that the stability of modified dsDNA was greatly influenced by the linker length. Py4- and Py3-oligonucleotide conjugates (ON 1 (n = 4) and ON 2 (n = 4)) containing the 4-aminobutyl linker formed stable dsDNA with complementary DNA. Although Im3-oligonucleotide conjugate ON 3 (n = 4) containing the 4-aminobutyl linker formed stable dsDNA with complementary DNA, stabilization of dsDNA by the imidazole amide moiety of ON 3 (n = 4) was lower compared with the pyrrole amide moiety of ON 2 (n = 4). The Py3-γ-Im3-oligonucleotide conjugate ON 4 (n = 2), which possesses binding affinity for C-G base pairs via a pyrrole/imidazole combination and contains a 2-aminoethyl linker, showed high binding ability for complementary DNA. Furthermore, the DNA sequence recognition of MGB polyamide-oligonucleotide conjugates was investigated using single-base mismatch DNAs, which possess a mismatch base in the MGB polyamide binding sequence. The Py3-γ-Im3-oligonucleotide conjugate ON 4 (n = 2) showed high sequence recognition ability for complementary DNA.

Viscosity of bridgmanite determined by in situ stress and strain measurements in uniaxial deformation experiments.

To understand mantle dynamics, it is important to determine the rheological properties of bridgmanite, the dominant mineral in Earth's mantle. Nevertheless, experimental data on the viscosity of bridgmanite are quite limited due to experimental difficulties. Here, we report viscosity and deformation mechanism maps of bridgmanite at the uppermost lower mantle conditions obtained through in situ stress-strain measurements of bridgmanite using deformation apparatuses with the Kawai-type cell. Bridgmanite would be the hardest among mantle constituent minerals even under nominally dry conditions in the dislocation creep region, consistent with the observation that the lower mantle is the hardest layer. Deformation mechanism maps of bridgmanite indicate that grain size of bridgmanite and stress conditions at top of the lower mantle would be several millimeters and ~105 Pa to realize viscosity of 1021-22 Pa·s, respectively. This grain size of bridgmanite suggests that the main part of the lower mantle is isolated from the convecting mantle as primordial reservoirs.

Low-spin ferric iron in primordial bridgmanite crystallized from a deep magma ocean.

The crystallization of the magma ocean resulted in the present layered structure of the Earth's mantle. An open question is the electronic spin state of iron in bridgmanite (the most abundant mineral on Earth) crystallized from a deep magma ocean, which has been neglected in the crystallization history of the entire magma ocean. Here, we performed energy-domain synchrotron Mössbauer spectroscopy measurements on two bridgmanite samples synthesized at different pressures using the same starting material (Mg0.78Fe0.13Al0.11Si0.94O3). The obtained Mössbauer spectra showed no evidence of low-spin ferric iron (Fe3+) from the bridgmanite sample synthesized at relatively low pressure of 25 gigapascals, while that directly synthesized at a higher pressure of 80 gigapascals contained a relatively large amount. This difference ought to derive from the large kinetic barrier of Fe3+ rearranging from pseudo-dodecahedral to octahedral sites with the high-spin to low-spin transition in experiments. Our results indicate a certain amount of low-spin Fe3+ in the lower mantle bridgmanite crystallized from an ancient magma ocean. We therefore conclude that primordial bridgmanite with low-spin Fe3+ dominated the deeper part of an ancient lower mantle, which would contribute to lower mantle heterogeneity preservation and call for modification of the terrestrial mantle thermal evolution scenarios.

Mantle dynamics inferred from the crystallographic preferred orientation of bridgmanite.

Seismic shear wave anisotropy is observed in Earth's uppermost lower mantle around several subducted slabs. The anisotropy caused by the deformation-induced crystallographic preferred orientation (CPO) of bridgmanite (perovskite-structured (Mg,Fe)SiO3) is the most plausible explanation for these seismic observations. However, the rheological properties of bridgmanite are largely unknown. Uniaxial deformation experiments have been carried out to determine the deformation texture of bridgmanite, but the dominant slip system (the slip direction and plane) has not been determined. Here we report the CPO pattern and dominant slip system of bridgmanite under conditions that correspond to the uppermost lower mantle (25 gigapascals and 1,873 kelvin) obtained through simple shear deformation experiments using the Kawai-type deformation-DIA apparatus. The fabrics obtained are characterized by [100] perpendicular to the shear plane and [001] parallel to the shear direction, implying that the dominant slip system of bridgmanite is [001](100). The observed seismic shear- wave anisotropies near several subducted slabs (Tonga-Kermadec, Kurile, Peru and Java) can be explained in terms of the CPO of bridgmanite as induced by mantle flow parallel to the direction of subduction.

Stress measurement under high pressure using Kawai-type multi-anvil apparatus combined with synchrotron radiation.

A system for stress measurement under high pressure has been developed at beamline BL04B1, SPring-8, Japan. A Kawai-type multi-anvil apparatus, SPEED-1500, was used to pressurize polycrystalline KCl to 9.9 GPa in a mechanically anisotropic cell assembly with the KCl sample sandwiched between dense Al(2)O(3) pistons. The variation of deviatoric stress was determined from the lattice distortion measured using two-dimensional X-ray diffraction with monochromatic synchrotron X-rays. The low-pressure B1 phase transformed to the high-pressure polymorph B2 during compression. The deviatoric stress increased with increasing pressure in both the B1 and B2 phases except for the two-phase-coexisting region at a pressure of 2-3 GPa. This new system provides one of the technical foundations for conducting precise rheological measurements at conditions of the Earth's lower mantle.