Immunological responses following the third dose of the BNT162b2 SARS-CoV-2 vaccine among Japanese healthcare workers.

INTRODUCTION: A limited number of studies have shown a decline in antibody titers in healthcare workers beyond six months after the second dose of the BNT162b2 vaccine, and has been insufficiently investigated yet in the respective Asian ethnic groups. METHODS: We conducted a longitudinal observational study on 187 healthcare workers and other personnel and healthy adults at least eight months after vaccination at the International University of Health and Welfare. RESULTS: The baseline (before the third dose of BNT162b2) anti-receptor binding domain (RBD) IgG level was 569[377-943] AU/mL 245[240-250] days after the second dose. The mean antibody titer of participants aged 20-29 years was 4.6 times higher than that of participants aged 70-79 years. After booster vaccination, serum anti-RBD antibody levels were elevated in all participants with a median titer of 23,250[14,612-33,401] AU/mL 21[19-23] days after the third dose. The median post-booster antibody titers in the 20-29, 30-39, 40-49, 50-59, 60-69, and 70-79 years age groups were 30.6, 33.0, 33.8, 27.4, 50.1, and 90.3 times, respectively, higher than the pre-booster ones. Antibody levels were 15% lower in daily drinkers compared to nondrinkers, suggesting that daily alcohol consumption can prevent antibody levels from increasing after vaccination. Our results show decreased antibody titers after two doses of the vaccine, especially in the elderly; however, the third dose of the vaccine resulted in a significant increase in antibody titers in all age groups. CONCLUSIONS: We provided information on antibody responses following primary and booster doses of the BNT162b2 mRNA COVID-19 vaccine in Japan.

Cardioprotective Effect against Ischemia-Reperfusion Injury of PAK-200, a Dihydropyridine Analog with an Inhibitory Effect on Cl- but Not Ca2+ Current.

We examined the effects of a dihydropyridine analog, PAK-200, on guinea pig myocardium during experimental ischemia and reperfusion. In isolated ventricular cardiomyocytes, PAK-200 (1 µM) had no effect on the basal peak inward and steady-state currents but inhibited the isoprenaline-induced time-independent Cl- current. In the right atria, PAK-200 had no effect on the beating rate and the chronotropic response to isoprenaline. In an ischemia-reperfusion model with coronary-perfused right ventricular tissue, a decrease in contractile force and a rise in tension were observed during a period of 30-min no-flow ischemia. Upon reperfusion, contractile force returned to less than 50% of preischemic values. PAK-200 had no effect on the decline in contractile force during the no-flow ischemia but reduced the rise in resting tension. PAK-200 significantly improved the recovery of contractile force after reperfusion to about 70% of the preischemic value. PAK-200 was also shown to attenuate the decrease in tissue ATP during ischemia. Treatment of ventricular myocytes with an ischemia-mimetic solution resulted in depolarization of the mitochondrial membrane potential and an increase in cytoplasmic and mitochondrial Ca2+ concentrations. PAK-200 significantly delayed these changes. Thus, PAK-200 inhibits the cAMP-activated chloride current in cardiac muscle and may have protective effects against ischemia-reperfusion injury through novel mechanisms.

Postpartum infective endocarditis with Enterococcus faecalis in Japan: a case report.

BACKGROUND: The clinical characteristics of infective endocarditis include the presence of predisposing cardiac disease, a history of illegal drug use, and high morbidity in the elderly. Only a few cases of the disease after delivery have been reported in the literature. We describe here a first case of enterococcal postpartum infective endocarditis without underlying disease in Japan. CASE PRESENTATION: We report the case of a 31-year-old Japanese woman with postpartum infective endocarditis by Enterococcus faecalis. She had no significant medical history or any unusual social history. After emergency surgery for severe mitral regurgitation and antimicrobial treatment for 6 weeks, she was discharged from our hospital and is now being monitored at an out-patient clinic. CONCLUSIONS: We encountered a case of Enterococcus faecalis infective endocarditis that occurred in the native valve of a postpartum healthy woman. Although the pathogenesis of this case remains unclear, it could be due to bacteremia arising from the administration of prophylactic broad-spectrum antibiotics used for cesarean section. Previous use of cefotiam and urinary catheter insertion may be risk factors for nosocomial enterococcal bacteremia in this case.

Membrane-labeled MDCK cells and confocal microscopy for the analyses of cellular volume and morphology.

A clone of Madin-Darby canine kidney (MDCK) cells whose cell membrane was stably labeled with expressed cyan fluorescent protein (CFP) was established, and changes in their volume and shape induced by hyposmotic stress were analyzed with confocal microscopy. The membrane-targeted CFP was present not only on the cell membrane but also in the endoplasmic reticulum and Golgi apparatus, but was excluded from the mitochondria and cell nucleus. During hyposmosis, the initial swelling and the following regulatory volume decrease could be accurately measured by summation of the cellular volume in every confocal slice crossing the cell at different heights. Changes in the cellular height roughly paralleled the changes in cellular volume when the mean value was compared, but dissociation as much as 30% was observed for individual cells due to changes in cell shape. The present experimental system, which enables direct measurement of cell volume and simultaneous observation of various intracellular phenomena, would be useful for further investigation of cellular volume regulation.

Involvement of intracellular Ca(2+) in the regulatory volume decrease after hyposmotic swelling in MDCK cells.

We examined the source of Ca(2+) involved in the volume regulation of Madin-Darby canine kidney (MDCK) cells with confocal microscopy and fluoroprobes. Hyposmosis induced a transient increase in cell volume, as well as cytoplasmic Ca(2+), which peaked at 3 to 5 min and gradually decreased to reach the initial value within about 30 min. This late decrease in cell volume, as well as the transient rise in cytoplasmic Ca(2+), was reduced in Ca(2+)-free solution and was abolished by pretreatment with thapsigargin. In conclusion, Ca(2+) released from the intracellular store contributes to the regulatory volume decrease following hyposmotic swelling in MDCK cells.

Analysis of arrhythmogenic profile in a canine model of chronic atrioventricular block by comparing in vitro effects of the class III antiarrhythmic drug nifekalant on the ventricular action potential indices between normal heart and atrioventricular block heart.

The chronic atrioventricular block dog is a useful model for predicting the future onset of drug-induced long QT syndrome in clinical practice. To better understand the arrhythmogenic profile of this model, we recorded the action potentials of the isolated ventricular tissues in the presence and absence of the class III antiarrhythmic drug nifekalant. The action potential durations of the Purkinje fiber and free wall of the right ventricle were longer in the chronic atrioventricular block dogs than in the dogs with normal sinus rhythm. Nifekalant in concentrations of 1 and 10 microM prolonged the action potential durations of Purkinje fiber and the free wall in a concentration-dependent manner. The extent of prolongation was greater in the chronic atrioventricular block dogs than in the normal dogs. However, increase of temporal dispersion of ventricular repolarization including early afterdepolarization was not detected by nifekalant in either group of dogs, indicating lack of potential to trigger arrhythmias in vitro. These results suggest that the ventricular repolarization delay in the chronic atrioventricular block model by nifekalant may largely depend on the decreased myocardial repolarization reserve, whereas the trigger for lethal arrhythmia was not generated in the in vitro condition in contrast to the in vivo experiment.

Atria selective prolongation by NIP-142, an antiarrhythmic agent, of refractory period and action potential duration in guinea pig myocardium.

NIP-142 is a novel benzopyran compound that was shown to prolong the atrial effective refractory period and terminate experimental atrial fibrillation in the dog. In the present study, we examined the effects of NIP-142 on isolated guinea pig myocardium and on the G-protein-coupled inwardly rectifying potassium channel current (acetylcholine-activated potassium current; I(KACh)) expressed in Xenopus oocytes. NIP-142 (10 and 100 microM) concentration-dependently prolonged the refractory period and action potential duration in the atrium but not in the ventricle. E-4031 and 4-aminopyridine prolonged action potential duration in both left atrium and right ventricle. Prolongation by NIP-142 of the atrial action potential duration was observed at stimulation frequencies between 0.5 and 5 Hz. In contrast, the prolongation by E-4031 was not observed at higher frequencies. Tertiapin, a blocker of I(KACh), prolonged action potential duration in the atrium but not in the ventricle. NIP-142 completely reversed the carbachol-induced shortening of atrial action potential duration. NIP-142 (1 to 100 microM), as well as tertiapin (0.1 to 100 nM), concentration-dependently blocked I(KACh) expressed in Xenopus oocytes; the blockade by NIP-142 was not affected by membrane voltage. In conclusion, NIP-142 was shown to prolong atrial refractory period and action potential duration through blockade of I(KACh) which may possibly explain its previously described antiarrhythmic activity. NIP-142 has pharmacological properties that are different from classical class III antiarrhythmic agents such as atria specificity and lack of reverse frequency dependence, and thus appears promising for the treatment of supraventricular arrhythmia.