Izumi Anno

Early phase adaptations of muscle use and strength to isokinetic training

The purpose of this study was to investigate the effect of short periods of isokinetic resistance training on muscle use and strength. Seven men trained the right quadriceps femoris muscles (QF) 9 d for 2 wk using 10 sets of 5 knee extensions each day. Isometric and isokinetic torques of QF were measured at six angular velocities. Cross-sectional areas (CSA) of QF were determined from axial images using magnetic resonance imaging (MRI). Transverse relaxation time (T2) and activated area of QF, which represented the area greater than the mean resting T2 + ISD in MR[pixels, were calculated at rest and immediately after repetitive isokinetic knee extensions based on T2-weighted MR images. Muscle fiber types, fiber area, and phosphofructokinase (PFK) activities were determined from biopsies of the vastus lateralis muscle. No changes were found in CSA of QF, muscle fiber types, fiber area, and PFK activities after the training. Isometric and isokinetic peak torques at 60-240 degrees x s(-1) and relative area of QF activated by knee extensions increased significantly after the training. These results suggest that muscle strength increases after short periods of isokinetic resistance training without muscle hypertrophy would be due to increased muscle contractile activity.

Quantification of cerebral metabolites in glioma patients with proton MR spectroscopy using T2 relaxation time correction.

This study was aimed to investigate the significance of absolute concentration of metabolites in glioma patients using proton MR spectroscopy (MRS) with T2 relaxation time correction using three different echo times. The absolute concentrations of metabolites in 7 normal subjects and in 23 gliomas (10 low-grade, 13 high-grade) were obtained by proton MRS using a tissue water signal as an internal standard. The signal intensities of metabolites and tissue water were corrected by T2 relaxation time. In low-grade glioma, the T2 relaxation time of NAA was shorter, and T2 relaxation time of water was prolonged as compared to normal subjects (p < 0.001). In high-grade glioma, the T2 relaxation time of NAA (p < 0.001) and T2 relaxation time of Cr (p < 0.01) were shorter, and T2 relaxation time of water (p < 0.001) was prolonged as compared to normal subjects. Moreover, high-grade gliomas revealed a shorter T2 relaxation time of Cr than low-grade gliomas (p < 0.05). In glioma, NAA and Cr concentration were decreased, and Cho were increased as compared to normal subjects. Moreover, high-grade glioma revealed a significant lower Cr (p < 0.001) and Cho (p < 0.01) concentration compared to low-grade gliomas. Low Cr concentration is the most reliable indicator of malignancy in glioma. Cho concentration did not correlate with malignancy in gliomas.

Control of the rate of phosphocreatine resynthesis after exercise in trained and untrained human quadriceps muscles.

We examined the effect of differences in exercise intensity on the time constant (tc) of phosphocreatine (PCr) resynthesis after exercise and the relationships betweentc and maximal oxygen uptake (VO2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO2max = 66.2 and 52.0 ml · min−1 · kg−1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr + inorganic phosphate (Pi)] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). Thec remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lowertc at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation betweentc and [ADP] in light exercise and betweentc and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH andtc was a PCr: (PCr + Pi) ratio of 0.5. There was a significant negative correlation between the VO2max andtc after all levels of exercise (P<0.05).However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use oftc at an end-exercise PCr:(PCr + Pi) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.

Changes in magnetic resonance images in human skeletal muscle after eccentric exercise

To investigate the time-course of changes in transverse relaxation time (T2) and cross-sectional area (CSA) of the quadriceps muscle after a single session of eccentric exercise, magnetic resonance imaging was performed on six healthy male volunteers before and at 0, 7, 15, 20, 30 and 60 min and 12, 24, 36, 48, 72 and 168 h after exercise. Although there was almost no muscle soreness immediately after exercise, it started to increase 1 day after, peaking 1–2 days after the exercise (P<0.01). Immediately after exercise, T2 increased significantly in the rectus femoris, vastus lateralis and intermedius muscles (P<0.05) and decreased quickly continuing until 60 min after exercise. At and after the 12th h, a significant increase was perceived again in the T2 values of the vastus lateralis and intermedius muscles (P<0.01) [maximum 9.3 (SEM 2.8)% and 10.9 (SEM 2.2)%, respectively]. The maximal values were exhibited at 24–36 h after exercise. In contrast, the rectus femoris muscle showed no delayed-stage increase. Also, in CSA, an increase after 12 h was observed in addition to the one immediately after exercise in the vastus lateralis, intermedius and medialis and quadriceps muscles as a whole (P < 0.01), reaching the maximal values at 12–24 h after exercise. The plasma creative kinase activity remained unchanged up to 24 h after and then increased significantly 48 h after exercise (P < 0.05). Beginning 12 h after exercise, the subjects whose T2 and CSA increased less than the others displayed a faster decrease in muscle soreness. These results suggested that T2 and CSA displayed bimodal responses after eccentric exercise and the time-courses of changes in them were similar to those in muscle soreness.

Super‐parallel MR microscope

A super‐parallel MR microscope in which multiple (up to 100) samples can be imaged simultaneously at high spatial resolution is described. The system consists of a multichannel transmitter–receiver system and a gradient probe array housed in a large‐bore magnet. An eight‐channel MR microscope was constructed for verification of the system concept, and a four‐channel MR microscope was constructed for a practical application. Eight chemically fixed mouse fetuses were simultaneously imaged at the 200 μm3 voxel resolution in a 1.5 T superconducting magnet of a whole‐body MRI, and four chemically fixed human embryos were simultaneously imaged at 120 μm3 voxel resolution in a 2.35 T superconducting magnet. Although the spatial resolutions achieved were not strictly those of MR microscopy, the system design proposed here can be used to attain a much higher spatial resolution imaging of multiple samples, because higher magnetic field gradients can be generated at multiple positions in a homogeneous magnetic field. Magn Reson Med 50:183–189, 2003.

Intracranial dural arteriovenous fistula showing diffuse MR enhancement of the spinal cord: case report and review of the literature.

BACKGROUND Cervical myelopathy resulting from intracranial dural arteriovenous fistula (AVF) is uncommon. Knowledge of the magnetic resonance imaging (MRI) appearance of such lesions is important because many patients with myelopathy are initially examined by MRI, and an incorrect diagnosis could result in delayed or improper treatment. We describe a rare case of myelopathy due to an intracranial dural AVF showing diffuse enhancement of the cervical spinal cord. CASE DESCRIPTION A 64-year-old male presented with progressive myelopathy and respiratory insufficiency. Cerebral angiography disclosed an AVF at the craniocervical junction draining intrathecally into the spinal medullary veins. MRI revealed dilated perimedullary vessels around the craniocervical junction, as well as spinal cord swelling with high signal intensity changes. Diffuse intense enhancement of the cervical spinal cord was also seen on postcontrast images. Embolization via the afferent artery was successfully performed, and the fistula was then microsurgically obliterated via a lateral suboccipital approach. This procedure arrested a rapidly progressive myelopathy. CONCLUSION Intracranial dural AVF showing diffuse enhancement of the spinal cord is extremely rare, and this enhancement effect may indicate pathologic changes of the spinal cord. MRI only is not useful for diagnosis, but also for demonstrating pathologic changes and predicting the outcomes of patients with intracranial dural AVF.

Mitochondrial encephalomyopathy (MELAS) with mental disorder

SummaryA case of mitochondrial encephalomyopathy (MELAS) with mental disorder is reported. The SPECT study using123I-iodoamphetamine (IMP) and MRI study revealed abnormality in the left parieto-occipital areas without abnormality in the brain CT or brain scintigram. These findings suggest a localized dysfunction of the brain capillary endothelium in association with the cerebral involvement of mitochondrial encephalomyopathy.

Knee extension and flexion: MR delineation of normal and torn anterior cruciate ligaments

OBJECTIVE Our goal was to assess the effect of joint position of semiflexed and extended knees in MR delineation of the anterior cruciate ligament (ACL). METHODS With a mobile knee brace and a flexible surface coil, the knee joint was either fully extended or bent to a semiflexed position (average 45 degrees of flexion) within the magnet bore. Sets of oblique sagittal MR images were obtained for both extended and flexed knee positions. Thirty-two knees with intact ACLs and 43 knees with arthroscopically proven ACL tears were evaluated. Two observers compared paired MR images of both extended and flexed positions and rated them by a relative three point scale. Anatomic correlation in MR images was obtained by a cadaveric knee with incremental flexion. RESULTS The MR images of flexed knees were more useful than of extended knees in 53% of the case reviews of femoral attachments and 36% of reviews of midportions of normal ACLs. Compared with knee extensions, the MR images for knee flexion provided better clarity in 48% of reviews of disrupted sites and 52% of residual bundles of torn ACLs. Normal ACL appeared taut in the knee extension and lax in semiflexion. CONCLUSION Compared with MR images of knees in extension, MR images of knees in flexion more clearly delineate the femoral side of the ligament with wider space under the intercondylar roof and with decreased volume-averaging artifacts, providing superior visualization of normal and torn ACLs.

Relationships between Fiber Composition and NMR Measurements in Human Skeletal Muscle

The purpose of this study was to examine the relationships between the relative contents of phosphocreatine (PCr), inorganic phosphate (Pi), β‐adenosine triphosphate (ATP), and transverse relaxation time (T2) with fiber composition, which determined histochemically in the human skeletal muscle. The vastus lateralis muscles of 28 volunteers were subjected to phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, magnetic resonance imaging (MRI) and muscle biopsy. Muscle fibers were divided into type I and type II fibers using myosin ATPase stain. A wide range of fiber composition levels were observed in the subjects (27.3–74.6% type I fibers). The PCr/ATP, Pi/ATP and (PCr+Pi)/ATP ratios were positively related to the percentage of type II fibers (r=0.695, p<0.001, r=0.429, p<0.05 and r=0.773, p<0.001, respectively). There was no correlation between fiber composition and the PCr/Pi ratio (r 0.127, n.s.) or intracellular pH (r=0.305, n.s.). Moreover, no correlation was found between T2 and fiber type (r=0.144, n.s.). These results suggest that 31P NMR can detect the differences in relative content of phosphates between type I and type II fibers, thereby noninvasively evaluating fiber composition in human skeletal muscle.

Correlation between choline and MIB-1 index in human gliomas. A quantitative in proton MR spectroscopy study

BACKGROUND Choline (Cho) containing compounds are usually evaluated using magnetic resonance spectroscopy (MRS) by relative ratios such as Cho/N-acetylaspartate (NAA) and Cho/creatine (Cre) ratios. To clarify the significance of Cho level in gliomas, we evaluated the quantified Cho level using MRS and compared it with the proliferation activity as determined by MIB-1 immunoreactivity in the histological specimen. METHODS There were seven benign and seven malignant gliomas. MRS was obtained using a single-voxel proton regional imaging of metabolites (PRIME) sequence with three different TE for T2 compensation. Quantified Cho level was compared with the number of MIB-1 immunopositive positive cells and cell density in surgical specimens. RESULT A positive correlation was observed between Cho and MIB-1 in benign gliomas, whereas there was a trend to an inverse correlation in malignant gliomas. This inverse correlation became a positive correlation when the necrotic area of the tumor (on the T1-weighted gadolinium enhanced images) was excluded from the voxel of interest (VOI) for MRS, but this correlation did not reach statistical significance. CONCLUSIONS The quantification data clarified the behavior of Cho in malignant gliomas. The quantification method has the advantage of limiting the influence of other metabolites on Cho determination. In particular, the levels of other commonly measured metabolites, including Cre, may also be altered in glioma, making ratios between metabolites misleading. Heterogeneity in the MRS VOI should be considered when evaluating the proliferative activity of malignant glioma by MRS.