Takao Satoh

Regional cerebral blood flow, blood volume, oxygen extraction fraction, and oxygen utilization rate in normal volunteers measured by the autoradiographic technique and the single breath inhalation method

By means of a high resolution PET scanner, the regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rCMRO2) for major cerebral gyri and deep brain structures were studied in eleven normal volunteers during an eye-covered and ear-unplugged resting condition. Regional CBF was measured by the auto-radiographic method after intravenous administration of H215O. Regional OEF and rCMRO2 were measured by the single inhalation of15O2. With MR T1-weighted images as an anatomical reference, thirteen major cerebral gyri, caudate nucleus, lentiform nucleus, thalamus, midbrain, pons, cerebellum and vermis were defined on the CMRO2 images. Values were read by using circular regions of interest 16 mm in diameter. The posterior part of the cingulate gyri had the highest rCBF and rCMRO2 values among brain structures, followed by the lentiform nucleus, the cerebellum, the caudate nucleus, and the thalamus. Parahippocampal gyri had the lowest rCBF and rCMRO2 values amongthe cortical gyri.RegionalOEFforthepontinenuclei (0.34 ± 0.04), the midbrain (0.35 ± 0.05), the parahippocampal gyri (0.35 ± 0.04 for the right and 0.37 ± 0.05 for the left), and the thalami (0.37 ± 0.05 for the right and 0.36 ± 0.04 for the left) were significantly lower than the mean OEF for the cerebral cortices (0.42 ± 0.04) (p < 0.05 or less). The global CBF and CMRO2 were consistent with those obtained by the Kety-Schmidt method. Although several limitations to the quantification derived from an inadequate spacial resolution remain unsolved, the performance of the present PET scanner and the method for the quantification employed provide regional estimates of brain circulation and oxygen metabolism more acurately than the PET system and the steady state method previously used.

Subcortical Hypoperfusion Associated With Asymptomatic White Matter Lesions on Magnetic Resonance Imaging

BACKGROUND AND PURPOSE We examined whether hemodynamic and metabolic abnormalities in the cerebral white matter, basal ganglia, and thalamus are associated with asymptomatic white matter lesions (WML) depicted on MR images. METHODS A positron emission tomographic study with H2(15)O, C15O, and 15O2 was performed in eight normal control subjects without any WML (mean +/- 1 SD age, 68.5 +/- 10.2 years) and in 15 asymptomatic subjects with WML (71.3 +/- 8.5 years) to measure regional cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and oxygen metabolic rate. RESULTS In the cerebral white matter in the asymptomatic subjects with WML, significantly lower CBF (20.3 +/- 3.9 mL/100 mL per minute; P < .05) and significantly higher OEF (0.43 +/- 0.08; P < .05) were found compared with those for control subjects (23.5 +/- 2.6 mL/100 mL per minute and 0.37 +/- 0.06, respectively). The severity of WML was not related to the magnitude of hypoperfusion. In the basal ganglia, significantly lower CBF (44.9 +/- 6.9 mL/100 mL per minute; P < .01) and significantly higher OEF (0.54 +/- 0.08; P < .01) were found in the WML group than in control subjects (70.1 +/- 12.0 mL/100 mL/min and 0.39 +/- 0.03, respectively). In the thalamus, there was no significant difference in CBF and OEF between the control and WML groups. CONCLUSIONS Hypoperfusion of the cerebral white matter and basal ganglia in asymptomatic WML subjects may be induced by the arteriosclerosis of long penetrating medullary arteries and lenticulostriate arteries but may not be directly related to the production of WML. The role of hypoperfusion in the production of WML and acceleration of its development remains to be elucidated.

Central Benzodiazepine Receptor Distribution After Subcortical Hemorrhage Evaluated by Means of [123I]Iomazenil and SPECT

BACKGROUND AND PURPOSE [123I]Iomazenil is a single-photon emission computed tomography (SPECT) tracer that selectively binds to central benzodiazepine receptor in the neuron membrane. With this ligand, we studied the central benzodiazepine receptor distribution in the cortex remote from subcortical hematoma in intracerebral hemorrhage patients. METHODS Four patients with unilateral putaminal hemorrhage and one patient with right thalamic hemorrhage were studied (mean +/- 1 SD age, 50.0 +/- 8.8 years). The initial volume of hematoma ranged from 4.3 to 31.0 mL (mean +/- 1 SD, 17.5 +/- 12.3 mL). SPECT images obtained 3 hours after intravenous administration of [123I]iomazenil (167 MBq/750 ng) were analyzed. In three patients, perfusion was evaluated with [123I]IMP. On SPECT images, the radioactivity ratio of the ipsilateral to the contralateral cerebral cortex (I/C ratio) or of the contralateral to the ipsilateral cerebellar hemisphere (C/I ratio) was measured. RESULTS The I/C ratio for iomazenil was significantly decreased compared with unity in the temporal lobe (0.84 +/- 0.08, P < .01) and the parietal lobe (0.87 +/- 0.10, P < .05), but the C/I ratio in the cerebellum (1.00 +/- 0.03) was not. The C/I ratio for perfusion in the cerebellar cortex (0.83 +/- 0.04, P < .01) was significantly decreased compared with that in normal subjects. CONCLUSIONS Central benzodiazepine receptor-[123I]iomazenil binding was decreased in the ipsilateral cerebral cortex remote from the subcortical hematoma. This preliminary result may facilitate further study of the potential damage of the cortical neurons remote from subcortical hematoma.

New obstructions for the surjectivity of the Johnson homomorphism of the automorphism group of a free group

In this paper we construct new obstructions for the surjectivity of the Johnson homomorphism of the automorphism group of a free group. We also determine the structure of the cokernel of the Johnson homomorphism for degrees 2 and 3.

The cokernel of the Johnson homomorphisms of the automorphism group of a free metabelian group

In this paper, we determine the cokernel of the k-th Johnson homomorphisms of the automorphism group of a free metabelian group for k > 2 and n > 4. As a corollary, we obtain a lower bound on the rank of the graded quotient of the Johnson filtration of the automorphism group of a free group. Furthermore, by using the second Johnson homomorphism, we determine the image of the cup product map in the rational second cohomology group of the IA-automorphism group of a free metabelian group, and show that it is isomorphic to that of the IA-automorphism group of a free group which is already determined by Pettet. Finally, by considering the kernel of the Magnus representations of the automorphism group of a free group and a free metabelian group, we show that there are non-trivial rational second cohomology classes of the IA-automorphism group of a free metabelian group which are not in the image of the cup product map.

The abelianization of the congruence IA-automorphism group of a free group

We fill a gap in the construction of the extended Johnson homomorphism, stated in Section 2 of the paper The abelianization of the congruence IA-automorphism group of a free group

On the derivation algebra of the free Lie algebra and trace maps

We mainly study the derivation algebra of the free Lie algebra and the Chen Lie algebra generated by the abelianization H of a free group, and trace maps. To begin with, we give the irreducible decomposition of the derivation algebra as a GL.n; Q/‐ module via the Schur‐Weyl duality and some tensor product theorems for GL.n; Q/. Using them, we calculate the irreducible decomposition of the images of the Johnson homomorphisms of the automorphism group of a free group and a free metabelian group. Next, we consider some applications of trace maps: Morita’s trace map and the trace map for the exterior product of H . First, we determine the abelianization of the derivation algebra of the Chen Lie algebra as a Lie algebra, and show that the abelianization is given by the degree one part and Morita’s trace maps. Second, we consider twisted cohomology groups of the automorphism group of a free nilpotent group. In particular, we show that the trace map for the exterior product of H defines a nontrivial twisted second cohomology class of it. 17B40, 20C15; 20F28

On the rings of Fricke characters of free abelian groups

In this paper, we study the structure of the rings of Fricke characters of free abelian groups. More precisely, we consider a descending filtration of ideals in the ring, and give a basis of its graded quotients. Then by using this fact, we show that the ring of Fricke characters of a free aberian group is an integral domain.

On the basis-conjugating automorphism groups of free groups and free metabelian groups

In this paper we study the images of the Johnson homomorphisms of the basis-conjugating automorphism groups of free groups and free metabelian groups. In particular, we show that the Johnson image is contained in a certain proper Lie subalgebra

The kernel of the Magnus representation of the automorphism group of a free group is not finitely generated

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