Two similar cases of encephalopathy, possibly a reversible posterior leukoencephalopathy syndrome: serial findings of magnetic resonance imaging, SPECT and angiography.

Two young women who had encephalopathy that resembled reversible posterior leukoencephalopathy syndrome are presented. The brain magnetic resonance imaging (MRI) of these patients exhibited similar T2-high signal lesions, mostly in the white matter of the posterior hemispheres. Xe-SPECT during the patients' symptomatic period showed hypoperfusion in the corresponding areas, and angiography demonstrated irregular narrowing of the posterior cerebral artery. Clinical manifestations subsided soon after treatment, and the abnormal radiological findings also were almost completely resolved. Thus, we concluded that transient hypoperfusion followed by ischemia and cytotoxic edema might have had a pivotal role in these cases.

[Serial MRI, SPECT and 1H-MRS findings in a case of herpes simplex encephalitis].

We report herein a case of herpes simplex encephalitis (HSE) in which magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and proton magnetic resonance spectroscopy (1H-MRS) were performed sequentially. Both MRI and SPECT demonstrated a lesion on the left temporal lobe in its early stage. However, SPECT seemed more sensitive because it could detect subtle alterations of the blood flow. Hyperperfusion identified by SPECT had returned to normal levels while the abnormal MRI findings still remained. This may indicate that normalization of the blood perfusion precedes the tissue recovery. Contrast enhancement using Gd-DTPA was observed along the surface of the cerebral cortex on MRI, but that involved only part of the hyperperfusion areas depicted with SPECT. In the affected left temporal lobe, 1H-MRS exhibited reduction of N-acetyl-asparate (NAA), and an elevated lactate level. The former represented the neuronal loss, and the latter indicated impairment of oxidative metabolism. Furthermore, alterations of NAA/creatine (Cr) and choline (Cho)/Cr ratios were also observed in the seemingly normal right temporal lobe. Those ratios returned to nearly normal levels in accordance with the patient's clinical recovery. Subsequently, our results indicate that 1H-MRS might be a very useful tool in qualifying the tissue damage and possibly estimating the prognosis.

[Proton MR spectroscopy in patients with unilateral temporal lobe epilepsy].

The authors assessed proton magnetic resonance spectroscopy (1H-MRS) in patients with unilateral refractory temporal bole epilepsy. The subjects consisted of 20 patients (those with brain tumors, trauma, malformations or definite organic lesions were excluded) and 10 normal volunteers. 1H-MRS and MRI were performed using a 1.5 tesla machine. 1H-MRS was achieved using point-resolved spectroscopy (PRESS) or the stimulated echo acquisition mode (STEAM), and a 3 x 3 x 3 cm volume of interest was positioned at the hippocampus. N-Acetyl-aspartate (NAA) and choline-containing substance (Cho) signals were evaluated. The results showed decreased NAA and elevated Cho or asymmetry of both NAA and Cho in the epileptogenic focus in 19/20 cases. The reductions in NAA presumably reflect neuronal loss, while the elevation of Cho probably represents membrane break down within the lesion. These abnormalities were observed in 19/20 cases (95%), whereas abnormal magnetic resonance imaging was detected in only 6/20 (30%) of the patients. Thus, 1H-MRS appears to be a useful, non-invasive modality for evaluating metabolic changes in epileptogenic foci, and these metabolic changes can serve as a more sensitive indicator than magnetic resonance imaging.

Inhibition of acto-myosin subfragment-1 ATPase activity by peptides corresponding to various segments of the 20-kDa domain of myosin heavy chain.

As reported previously, the synthetic heptapeptide having the amino acid sequence around the reactive Cys (SH1) of myosin heavy chain, IRICRKG-NH2, inhibited acto-myosin subfragment-1 (S-1) ATPase activity and half inhibition (K1/2) was observed at a peptide concentration of 0.06 mM. The inhibitory ability of the peptide was found to be decreased to one-fifth by acetylation of its N-terminal alpha-amino group. A similar effect of N-acetylation was observed with a nonapeptide, EGIRICRKG-NH2, and an undecapeptide, VLEGIRICRKG-NH2. These results indicate that N-terminal-free synthetic peptides do not act as proper analogs of the corresponding segment of S-1 heavy chain against F-actin. We isolated a longer peptide extending from Thr682 to Lys709 in S-1 heavy chain, with two Cys residues corresponding to SH1 and SH2. This peptide, having 28 residues (28peptide), inhibited acto-S-1 ATPase activity with a K1/2 of 0.23 mM. A cosedimentation binding assay indicated that the 28peptide completely dissociated acto-S-1 in the presence of ATP. This behavior is different from that observed with the N-terminal-free synthetic heptapeptide, and thus the 28peptide might be an analog of the corresponding segment. There is a possibility that the region corresponding to the 28peptide in S-1 heavy chain may bind directly with F-actin and may be involved in determining the acto-S-1 link during the steady state of the acto-S-1 ATPase reaction.