The progress of myelination in the cerebrum was evaluated by visual inspection, and magnetic resonance (MR) imaging and the transverse relaxation time (T2) was calculated from double echo images. Twenty-three pediatric cases, who did not show intracranial organic changes on MR examination, were included. The T2 values in the corpus callosum (CC), frontal deep white matter (FWM), occipital deep white matter (OWM) and centrum semiovale (CS) were calculated, and the changes in these values with age were followed. During the first year of life, a rapid decrease in the T2 value was seen, followed by a more gradual decrease. The T2 value seemed to reach the adult level between 2 and 3 years of life in all areas examined. The T2 values between 2 and 16 years in CC, FWM, OWM and CS were 59.7 +/- 3.6, 64.5 +/- 5.2, 69.8 +/- 4.8 and 66.3 +/- 3.3 ms (mean +/- S.D.), respectively. The T2 values in patients with clinically diagnosed Pelizaeus-Merzbacher disease (PMD) and late onset Krabbe disease were also calculated. In PMD, non-progressive prolongation of the T2 value was observed in all areas. In late onset Krabbe disease, on the other hand, progressive prolongation of the T2 values was mainly demonstrated in OWM and the posterior part of CS. These results suggest that the T2 value in the cerebral white matter allows more objective judgement than visual inspection, and makes it possible to clarify the mechanism underlying abnormal myelination, i.e. progressive or not.

Adolescent↗

PubMedDate not supplied

MR diffusion imaging in Pelizaeus-Merzbacher disease.

A case of classical type Pelizaeus-Merzbacher disease was reported. This patient exhibited marked motor and mental developmental delay, and nystagmus, with a positive familial history. Electrophysiological studies, such as on brainstem auditory evoked potentials, blink reflex and somatosensory evoked potentials, suggested marked disturbance of nerve conduction in CNS. T2-weighted magnetic resonance (MR) images revealed non-progressive diffuse T2 prolongation of cerebral white matter after a 2-year interval, indicating congenital hypomyelination in CNS. A newly developed magnetic resonance diffusion imaging method demonstrated the existence of diffusional anisotropy in the corpus callosum, internal capsule, and white matter of the frontal lobe. Although the diffusional anisotropy was considered to depend on the well-developed multiple layers of myelin around the axons, the imaging data of this patient demonstrated that the diffusional anisotropy did not necessarily depend on those multiple layers. These results may indicate the potential usefulness of MR diffusion imaging, combined with electrophysiological studies and conventional MR imaging, for analyzing the lesions of the cerebral white matter.

Anisotropy↗

PubMedDate not supplied

Hemin (Fe(3+))-- and heme (Fe(2+))--smectite conjugates as a model of hemoprotein based on spectrophotometry.

Hemin (Fe(3+)) was adsorbed onto synthetic smectite (clay mineral) in acetone to form a hemin-smectite conjugate. The hemin-smectite conjugate became soluble in water to form a transparent colloidal solution with a dark brown color. Its absorption spectrum in water showed a sharp Soret band at 398 nm with the molar extinction coefficient as epsilon(398nm) = 11.6 x 10(4) M(-1) cm(-1), which is in good agreement with epsilon(398nm) = (12.2 +/- 3) x 10(4) M(-1) cm(-1) of monomeric hematin (1). Hemin (Fe(3+))-smectite conjugate had a peroxidase-like activity in the presence of hydrogen peroxide (a hydrogen acceptor) and guaiacol (a hydrogen donor) in aqueous solution and its activity was higher than that of hematin. Hemin (Fe(3+))-smectite conjugate in water was reduced by adding sodium dithionite to form a heme (Fe(2+))-smectite conjugate which is also a transparent colloidal solution in water. Its absorption spectrum in aqueous solution was surprisingly in close agreement with that of oxyhemoglobin. Its peak positions of alpha, beta, and Soret bands were located in only a 9--3 nm shift to shorter wavelengths in comparison with those of oxyhemoglobin. Therefore, heme (Fe(2+))-smectite conjugate was bound to O(2) to form O(2)-heme (Fe(2+))-smectite conjugate. The addition of carbon monoxide, CO, to O(2)-heme (Fe(2+))-smectite conjugate caused the formation of CO-heme (Fe(2+))-smectite conjugate with a similar absorption spectrum of carboxyhemoglobin (HbCO) accompanied by shifting 8--10 nm to shorter wavelength. Therefore, the transformation of O(2)-heme (Fe(2+))-smectite conjugate to CO-heme (Fe(2+))-smectite conjugate was accompanied by shifting of 7, 4, and 3 nm to shorter wavelengths in the alpha, beta, and Soret bands respectively, which are similar to the spectral change from oxyhemoglobin to carboxyhemoglobin. Also the ratio (1:1.6) of the molar extinction coefficient of Soret band of O(2)-heme (Fe(2+))-smectite conjugate and CO-heme (Fe(2+))-smectite conjugate was surprisingly agreement with ratio (1:1.5) of oxyhemoglobin and carboxyhemoglobin. The phenomenon shown above was unexpectedly found during the course of study of bioconjugate of a bioactive substance, hemin (Fe(3+)) or heme (Fe(2+)), and a clay mineral, smectite, in place of the protein of globin in hemoglobin.

Gastrointestinal Agents↗

PubMedDate not supplied

Serial assessment of left ventricular function during dobutamine stress by means of electrocardiography-gated myocardial SPECT: combination with dual-isotope myocardial perfusion SPECT for detection of ischemic heart disease.

BACKGROUND: Technetium-labeled myocardial perfusion tracers allow simultaneous assessment of myocardial perfusion and left ventricular function by electrocardiography (ECG)-gated myocardial single photon emission computed tomography (SPECT). The purpose of this study was to evaluate left ventricular performance during dobutamine stress by means of ECG-gated myocardial perfusion SPECT with short-time data collection. METHODS AND RESULTS: After administration of Tc-99m sestamibi or tetrofosmin (600-740 MBq), 67 patients with ischemic heart disease, including 35 with prior myocardial infarction, were examined by ECG-gated myocardial perfusion SPECT at rest and during dobutamine stress (at dosages of 4, 8, 12, 16, and 20 microg/kg/min, with increments every 8 minutes). The ECG-gated data collection time was 5 minutes for each dobutamine dosage. After acquisition of gated SPECT data at the highest dose, thallium 201 chloride (111 MBq) was injected, and dual-isotope SPECT was also performed to assess the myocardial ischemia. In 32 patients without prior myocardial infarction, the sensitivity of individual stenosed-vessel detection with dual-isotope perfusion SPECT, with wall motion abnormality obtained from gated SPECT, and with the combined method was 55.9%, 52.9%, and 73.5%, respectively, based on coronary angiography. ECG-gated SPECT during dobutamine infusion revealed regional wall motion abnormalities (worsening or biphasic response) in 19 (57.6%) of 33 infarcted areas with culprit coronary arterial stenosis. The prevalence of reversible perfusion defects on dual-isotope SPECT was higher in segments with wall motion abnormalities than in segments with normal wall motion response (89.5% vs 42.9%, P <.02). CONCLUSIONS: Myocardial perfusion and left ventricular function during dobutamine infusion were analyzed in a single examination by means of the combined method. This procedure has the potential to provide comprehensive information with which to evaluate patients with ischemic heart disease.

Blood Pressure↗