CaMKII-mediated phosphorylation of RyR2 plays a crucial role in aberrant Ca2+ release as an arrhythmogenic substrate in cardiac troponin T-related familial hypertrophic cardiomyopathy

AIMS

Cardiac Troponin T (TnT) mutation-linked familial hypertrophic cardiomyopathy (FHC) is known to cause sudden cardiac death at a young age. Here, we investigated the role of the Ca²⁺ release channel of the cardiac sarcoplasmic reticulum (SR), ryanodine receptor (RyR2), in the pathogenic mechanism of lethal arrhythmia in FHC-related TnT-mutated transgenic mice (TG; TnT-delta160E).

METHODS AND RESULTS

In TG cardiomyocytes, the Ca²⁺ spark frequency (SpF) was much higher than that in non-TG cardiomyocytes. These differences were more pronounced in the presence of isoproterenol (ISO; 10 nM). This increase in SpF was largely reversed by a CaMKII inhibitor (KN-93), but not by a protein kinase A inhibitor (H89). CaMKII phosphorylation at Ser2814 in RyR2 was increased significantly in TG. Spontaneous Ca²⁺ transients (sCaTs) after cessation of a 1-5 Hz pacing, frequently observed in ISO-treated TG cardiomyocytes, were also attenuated by KN-93, but not by H89. The RyR2 stabilizer dantrolene attenuated Ca²⁺ sparks and sCaTs in ISO-treated TG cardiomyocytes, indicating that the mutation-linked aberrant Ca²⁺ release is mediated by destabilized RyR2.

CONCLUSIONS

In FHC-linked TnT-mutated hearts, RyR2 is susceptible to CaMKII-mediated phosphorylation, presumably because of a mutation-linked increase in diastolic [Ca²⁺]_i, causing aberrant Ca²⁺ release leading to lethal arrhythmia.

Ischemic or Nonischemic Functional Mitral Regurgitation and Outcomes in Patients With Acute Decompensated Heart Failure With Preserved or Reduced Ejection Fraction

The aim of this study was to evaluate the association of functional mitral regurgitation (FMR), preserved or reduced ejection fraction (EF), and ischemic or nonischemic origin with outcomes in patients discharged alive after hospitalization for acute decompensated heart failure (HF). Of the 4,842 patients enrolled in the Acute Decompensated Heart Failure Syndromes (ATTEND) registry, 3,357 patients were evaluated to assess the association of FMR, preserved or reduced EF, and ischemic or nonischemic origin with the primary end point (all-cause death and readmission for HF after discharge). At the time of discharge, FMR was assessed semiquantitatively (classified as none, mild, or moderate to severe) by color Doppler analysis of the regurgitant jet area. According to multivariable analysis, in the ischemic group, either mild or moderate to severe FMR in patients with a preserved EF had a significantly higher risk of the primary end point than patients without FMR (hazard ratio [HR] 1.60; 95% confidence interval [CI] 1.12 to 2.29; p = 0.010 and HR 1.98; 95% CI 1.30 to 3.01; p = 0.001, respectively). In patients with reduced EF with an ischemic origin, only moderate to severe FMR was associated with a significantly higher risk of the primary end point (HR 1.67; 95% CI 1.11 to 2.50; p = 0.014). In the nonischemic group, there was no significant association between FMR and the primary end point in patients with either a preserved or reduced EF. In conclusion, among patients with acute decompensated HF with a preserved or reduced EF, the association of FMR with adverse outcomes may differ between patients who had an ischemic or nonischemic origin of HF.

Mitochondrial deformity confined to a single cardiomyocyte in human endomyocardial biopsy specimens: Report of 4 cases

During electron microscopic examination of 156 consecutive human endomyocardial biopsy specimens, we found marked mitochondrial deformity within a single cardiomyocyte in each of 4 specimens. The deformed mitochondria were unevenly distributed, but the deformities were confined to the one cardiomyocyte. Those affected cardiomyocytes were accompanied by nonspecific degenerative changes such as nuclear hypertrophy and/or rarefaction of the myofibrils. Mitochondria in all other cells within the specimens appeared normal. Such an abnormality has never been reported to date. Each of the four cases was diagnosed with a different ailment: post-myocarditis, dilated cardiomyopathy, amyloidosis, and tachycardia-induced heart failure. However, all four cases were accompanied by left ventricular systolic dysfunction at biopsy. The very limited mitochondrial deformation may thus reflect a type of degenerative change that accompanies heart failure. <Learning objective: A marked mitochondrial deformity must have been overlooked to date, which is confined to a single cardiomyocyte in an endomyocardial biopsy specimen. Its etiology is still unknown but may reflect a type of degenerative change that accompanies heart failure.>.

The question of whether or not to perform therapeutic hypothermia: A case of neonatal spinal cord injury

Neonatal spinal cord injury is an extremely rare perinatal complication that often occurs concurrently with hypoxic ischemic encephalopathy (HIE), further complicating diagnosis of spinal cord injury. Although therapeutic hypothermia for moderate to severe HIE is widely recommended in Japan, it is difficult to determine whether it satisfies the neurological findings-related entry criteria in some patients.We describe a female infant with neonatal spinal cord injury after forceps delivery, who underwent therapeutic hypothermia upon diagnosis of HIE. The Apgar scores were 5 at 1 min, 6 at 5 min, and not recorded at 10 min. Blood gas analysis of her umbilical artery was not performed. Since respiratory failure, hypotonia and the absence of primitive reflexes were found at 2 hours after birth, she was initially diagnosed with moderate HIE and underwent a therapeutic hypothermia. Magnetic resonance imaging after therapeutic hypothermia revealed the spinal cord was narrowed from the lower medulla oblongata to the upper cervical cord. Thus she was diagnosed with an upper spinal cord injury at that time.Some patients with neonatal spinal cord injuries satisfy the criteria for therapeutic hypothermia. When neonates with asphyxia present with prolonged respiratory failure and hypotonia, spinal cord injury should be considered in the differential diagnosis. Thus, an early MRI is vital for the diagnosis of spinal cord injury.

Faraday-cup-type lost fast ion detector on Heliotron J

A Faraday-cup type lost-fast ion probe (FLIP) has been designed and installed in Heliotron J for the purpose of the studies of interaction between fast ions and MHD instabilities. The FLIP can measure the co-going fast ions whose energy is in the range of 1.7-42.5 keV (proton) and pitch angle of 90^∘-140^∘, especially for fast ions having the injection energy of neutral beam injection (NBI). The FLIP successfully measured the re-entering passing ions and trapped lost-fast ions caused by fast-ion-driven energetic particle modes in NBI heated plasmas.

Development of beam emission spectroscopy for turbulence transport study in Heliotron J

This paper describes the development study of the beam emission spectroscopy (BES) for the turbulent transport study in Heliotron J. Modification of the sightlines (10 × 4 for edge and 10 × 2 for edge) enables us to obtain 2-dimensional BES imaging. The cooling effect on the reduction in the electrical noise of avalanche photodiode (APD) assembly has been investigated using a refrigerant cooling system. When the temperature of the APD element has set to be -20 °C, the electrical noise can be reduced more than 50%. The measurement error of the phase difference in the case of low signal level has been tested by two light-emitting diode lamps. The APD cooling has an effect to improve the measurement error at the low signal level of APD.

18F-FDG uptake in the stomach on screening PET/CT: value for predicting Helicobacter pylori infection and chronic atrophic gastritis

Background

The aim of this study was to determine the value of ¹⁸F-FDG uptake on screening PET/CT images for the prediction of Helicobacter pylori (H. pylori) infection and chronic atrophic gastritis.

Methods

Among subjects who underwent ¹⁸F-FDG PET/CT for cancer screening from April 2005 to November 2015, PET/CT images were analyzed in 88 subjects who had gastrointestinal fiberscopy within 6 months. The volumes of interest (VOIs) were placed in the fornix, corpus and antrum of the stomach to determine maximal standardized uptake value (SUVmax) and mean SUV (SUVmean). Receiver operating characteristic curve (ROC) analysis was performed to determine the diagnostic performance of SUV indicators in predicting H. pylori infection and chronic atrophic gastritis.

Results

SUV indicators of the stomach were significantly higher in subjects with H. pylori infection than those without (from P < 0.001 to P < 0.05). ROC analysis revealed that SUVmean had the highest performance in predicting H. pylori infection (AUC 0.807) and chronic atrophic gastritis (AUC 0.784). SUVmean exhibited the sensitivity of 86.5 % and the specificity of 70.6 % in predicting H. pylori infection, and the sensitivity of 75.0 % and 78.6 % in predicting chronic atrophic gastritis.

Conclusion

Assessment of ¹⁸F-FDG uptake in the stomach reflecting active inflammation is useful in predicting patients with H. pylori infection and subsequent chronic atrophic gastritis which is closely associated with the risk of gastric neoplasms.

Logarithmic discretization and systematic derivation of shell models in two-dimensional turbulence

A detailed systematic derivation of a logarithmically discretized model for two-dimensional turbulence is given, starting from the basic fluid equations and proceeding with a particular form of discretization of the wave-number space. We show that it is possible to keep all or a subset of the interactions, either local or disparate scale, and recover various limiting forms of shell models used in plasma and geophysical turbulence studies. The method makes no use of the conservation laws even though it respects the underlying conservation properties of the fluid equations. It gives a family of models ranging from shell models with nonlocal interactions to anisotropic shell models depending on the way the shells are constructed. Numerical integration of the model shows that energy and enstrophy equipartition seem to dominate over the dual cascade, which is a common problem of two-dimensional shell models.

Injection barrel with a tapered structure for a low speed and small size cryogenic hydrogen pellet in medium-sized plasma fusion devices

An injection barrel was designed and fabricated for a small size 0.8 mm cryogenic pellet with a low speed of 200-300 m/s in medium-sized plasma fusion devices. Pellet injection with pneumatic acceleration was examined using a conventional in situ technique. A tapered structure was applied in the downstream side of the injection barrel to satisfy the requirement of pellet speed reduction by expansion of the propellant gas. Shadowgraph and light gate measurements show that the intact pellets have speeds of 260 ± 30 m/s and a typical size of 1.1-1.2 mm. The pellet ablation code based on a neutral gas shielding model shows that the penetration depth of the measured pellet parameters does not cross the plasma center, even in medium-sized plasma devices such as the Heliotron J helical device. The injection barrel with a tapered structure developed in this study is feasible for low speed pellet injection.