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Biomedical subjects

Akiko Mizuno

Publications and source records attributed to Akiko Mizuno.

8 recordsLinked to original sources
PubMed2006

Partially enhanced thalamocortical functional connectivity in autism.

Based on evidence for thalamic abnormalities in autism, impairments of thalamocortical pathways have been suspected. We examined the functional connectivity between thalamus and cerebral cortex in terms of blood oxygen level dependent (BOLD) signal cross-correlation in 8 male participants with high-functioning autism and matched normal controls, using functional MRI during simple visuomotor coordination. Both groups exhibited widespread connectivity, consistent with known extensive thalamocortical connectivity. In a direct group comparison, overall more extensive connectivity was observed in the autism group, especially in the left insula and in right postcentral and middle frontal regions. Our findings are inconsistent with the hypothesis of general underconnectivity in autism and instead suggest that subcortico-cortical connectivity may be hyperfunctional, potentially compensating for reduced cortico-cortical connectivity.

Adolescent↗
PubMed2006

[A case of Behçet disease with multiple nodular shadows and aneurysm of the brachiocephalic trunk caused by necrotizing vasculitis].

A 36-year-old man was admitted to our hospital in 1994 because of fever, and abdominal CT showed multiple low-density areas in the liver. Although granulomas were found in a liver biopsy specimen, a definitive diagnosis could not be established. With complaints of oral and genital ulcerations and erythema nodosum, Behçet disease was diagnosed in 1995 and he was treated with colchicine and cyclosporin. In May 1997 he had fever, leg edema, and proteinuria, and a renal biopsy revealed secondary amyloidosis. Cavitary lesions were found on a chest X-ray for the first time, but these later disappeared spontaneously. In October 2002, nodular shadows, cavitary lesions, and a mediastinal tumor appeared on a chest X-ray film. The nodular shadows in the lung fields had transformed into cavity lesions, resulting in the disappearance of the shadows. Specimens obtained from an open lung biopsy showed necrotizing granulomas and destructive vasculitis of the lung, and aneurysm of the brachiocephalic trunk caused by destructive vasculitis. Because multiple nodular shadows with cavitary lesions in Behçet disease, as in this case, have never been reported, we think this is a rare case.

Aneurysm↗
PubMed2005

Reduced functional connectivity between V1 and inferior frontal cortex associated with visuomotor performance in autism.

Some recent evidence has suggested abnormalities of the dorsal stream and possibly the mirror neuron system in autism, which may be responsible for impairments of joint attention, imitation, and secondarily for language delays. The current study investigates functional connectivity along the dorsal stream in autism, examining interregional blood oxygenation level dependent (BOLD) signal cross-correlation during visuomotor coordination. Eight high-functioning autistic men and eight handedness and age-matched controls were included. Visually prompted button presses were performed with the preferred hand. For each subject, functional connectivity was computed in terms of BOLD signal correlation with the mean time series in bilateral visual area 17. Our hypothesis of reduced dorsal stream connectivity in autism was only in part confirmed. Functional connectivity with superior parietal areas was not significantly reduced. However, the autism group showed significantly reduced connectivity with bilateral inferior frontal area 44, which is compatible with the hypothesis of mirror neuron defects in autism. More generally, our findings suggest that dorsal stream connectivity in autism may not be fully functional.

Adolescent↗
PubMed2004

Abnormal activity patterns in premotor cortex during sequence learning in autistic patients.

BACKGROUND: Evidence for frontal abnormality in autism has accumulated in recent years. Our own studies have shown abnormal activation in prefrontal cortex during finger tapping and visuomotor coordination. Studies in healthy adults suggest reduced premotor and increased prefrontal activity during advanced learning stages. We examined hemodynamic changes during visuomotor learning in autistic patients. METHODS: We studied eight high-functioning autistic patients and eight control subjects during learning of an 8-digit sequence over a period of 8 min, using functional magnetic resonance imaging. RESULTS: Autistic patients showed overall less prefrontal activation during late visuomotor learning; however, the main finding was a complementary one of enhanced activation in right pericentral and premotor cortex. In the autism group, Brodmann areas 3, 4, and 6 of the right hemisphere became more involved during late learning stages (trials 25-48), compared with early stages (trials 1-24). This effect was not seen in the control group. CONCLUSIONS: Our findings suggests that in autistic patients 1) primary sensorimotor and premotor cortex, which is normally predominant in early stages of visuomotor learning, plays an atypical role in later stages, even when learning is evident; and 2) handedness and side of execution interact with asymmetry of visuomotor learning activations, contrary to what is seen in normal adults.

Adult↗
PubMed2004

Stereo- and biochemical profiles of the 5-6- and 6-6-junction isomers of alpha-D-mannopyranosyl [60]fullerenes.

The 5-6- and 6-6-junction isomers of alpha-D-mannopyranosyl [60]fullerene were studied by means of circular dichroism (CD), deuterium labeling, 1H-NMR, molecular-dynamics (MD) calculations, and a lectin-binding assay. The CD spectra of the O-acetylated derivatives allowed clear discrimination of the isomers, while the 1H-NMR spectra, with assistance from deuterium labeling and MD calculations, served to disclose the unique conformation and molecular geometry of each acetylated isomer in chloroform solution. The deprotected 5-6- and 6-6-isomers, which gave colloidal suspensions in aqueous mixtures, displayed marked activity in blocking lectin-induced hemagglutination by concanavalin A.

Carbohydrate Conformation↗
PubMed2002

Plasmodium falciparum cysteine protease falcipain-2 cleaves erythrocyte membrane skeletal proteins at late stages of parasite development.

Plasmodium falciparum-derived cysteine protease falcipain-2 cleaves host erythrocyte hemoglobin at acidic pH and specific components of the membrane skeleton at neutral pH. Analysis of stage-specific expression of these 2 proteolytic activities of falcipain-2 shows that hemoglobin-hydrolyzing activity is maximum in early trophozoites and declines rapidly at late stages, whereas the membrane skeletal protein hydrolyzing activity is markedly increased at the late trophozoite and schizont stages. Among the erythrocyte membrane skeletal proteins, ankyrin and protein 4.1 are cleaved by native and recombinant falcipain-2 near their C-termini. To identify the precise peptide sequence at the hydrolysis site of protein 4.1, we used a recombinant construct of protein 4.1 as substrate followed by MALDI-MS analysis of the cleaved product. We show that falcipain-2-mediated cleavage of protein 4.1 occurs immediately after lysine 437, which lies within a region of the spectrin-actin-binding domain critical for erythrocyte membrane stability. A 16-mer peptide containing the cleavage site completely inhibited the enzyme activity and blocked falcipain-2-induced fragmentation of erythrocyte ghosts. Based on these results, we propose that falcipain-2 cleaves hemoglobin in the acidic food vacuole at the early trophozoite stage, whereas it cleaves specific components of the red cell skeleton at the late trophozoite and schizont stages. It is the proteolysis of skeletal proteins that causes membrane instability, which, in turn, facilitates parasite release in vivo.

Animals↗
PubMed2002

Physiological significance of the structure and components of the apoplast canal system for water absorption in plants.

The non-linear differential equation that describes the coupling between water transport and solute transport in the apoplast canal system in plants was proposed by Katou and Furumoto in 1986. In the present paper, we analytically solved the equation in order to find the law describing the canal system. In the canal system, water transport is regulated linearly by solute transport under physiological conditions. The approximate solution of the differential equations defines the conditions of the structure and components of the apoplast canal for optimal water absorption. Water absorption during cell elongation in plants requires that the apoplast canal be composed of a cell wall with an appropriate diffusion coefficient for solute.

Algorithms↗