Diazoxide-induced cardioprotection via ΔΨm loss depending on timing of application

Although the role of mitochondrial ATP-sensitive potassium (mitoKATP) channels in cardioprotection is widely accepted, it remains unclear when their opening is critical for protection. We tested the hypothesis that the mitoKATP channel acts as a trigger or mediator of protection against apoptosis through loss of mitochondrial inner membrane potential (DeltaPsim). Exposure of neonatal rat cardiomyocytes to H2O2 (0.5 mmol/L) resulted in apoptosis associated with severe DeltaPsim loss. Pretreatment with diazoxide (20 to 100 micromol/L) prevented H2O2-induced apoptosis and DeltaPsim loss at 2 but not 18 h after exposure, while the latter was prevented by cotreatment with diazoxide. Lack of protection by pretreatment with diazoxide was observed in cardiomyocytes cultured in a medium containing H2O2 for 2 h and then not containing for 16 h. The slopes of the regression lines of the relationship between the proportion of apoptotic cells and DeltaPsim loss (y = -0.89 vs. -0.42) and the proportion of cells with high side scatter signal differed between cardiomyocytes exposed H2O2 for 2 and 18 h. Diazoxide per se caused a transient DeltaPsim loss (within 30 min) with a recovery followed by persistent DeltaPsim loss (after 6 h). Inhibition of the former by 5-hydroxydecanoate (5-HD, 0.5 mmol/L) abolished protection of pretreatment with diazoxide (trigger phase), while that of the latter prevented the protection of cotreatment with diazoxide (mediator phase). Our results suggest that mitoKATP channels act as a trigger and mediator of cardioprotection through a transient or persistent DeltaPsim loss depending on phenotypic consequence in response to oxidants.

A case of giant cell tumor of the parotid gland

In this study, we report a recent patient with a giant cell tumor located in the parotid gland. This condition appears to be very rare; there have been only a few reports of similar patients. The origin of the tumor has remained unclear in previous patients, as well as in our present patient, and awaits further investigation.

[Significance of magnetic resonance imaging in diffuse axonal injury]

Advantages of magnetic resonance imaging (MRI) to computed tomography (CT) on a diagnosis of diffuse axonal injury (DAI) were discussed. Sixteen patients diagnosed as DAI defined by the criteria of Gennarelli were studied with CT and MRI. Lesions were demonstrated as high intensity areas on MRI of T2 weighted imaging (SE 2000/111) in all of the patients. These lesions were located only in a cerebral white matter in the cases of mild DAI, whereas in the cases of severe DAI located in a basal ganglia, corpus callosum, dorsal part of the brain stem as well as in the cerebral white matter. As for the findings of CT, these parenchymal lesions were not visualized in nine cases including six cases without any pathological findings. Our series suggest that MRI is superior to CT on the diagnosis of DAI and provides some information to evaluate the severity of DAI.