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Biomedical subjects

Akira Yoshii

Publications and source records attributed to Akira Yoshii.

9 recordsLinked to original sources
PubMed2005

Focal status epilepticus as atypical presentation of pyridoxine-dependent epilepsy.

Pyridoxine-dependent epilepsy usually presents in the neonatal period or even in utero, is refractory to antiepileptic medications, and is treatable with lifelong administration of pyridoxine. The seizures are typically generalized tonic-clonic, although myoclonic seizures or infantile spasms have been described. We report an infant who presented at 5 months of age with a right-sided clonic seizure with fever. Subsequently, she had recurrent right focal or generalized seizures despite sequential treatment with various antiepileptic medications. At 7 months, she was hospitalized with status epilepticus, which was finally controlled with pyridoxine. After she became seizure free, she continued to have a strong left arm preference with mild weakness of the right arm and delayed language skill. Eventually, she outgrew these symptoms. This case illustrates that pyridoxine-dependent epilepsy, although rare, must be included in the differential diagnosis of focal seizures, especially when the seizures are refractory to traditional antiepileptic drugs.

Diagnosis, Differential↗
PubMed2004

Microarray analysis of microRNA expression in the developing mammalian brain.

BACKGROUND: MicroRNAs are a large new class of tiny regulatory RNAs found in nematodes, plants, insects and mammals. MicroRNAs are thought to act as post-transcriptional modulators of gene expression. In invertebrates microRNAs have been implicated as regulators of developmental timing, neuronal differentiation, cell proliferation, programmed cell death and fat metabolism. Little is known about the roles of microRNAs in mammals. RESULTS: We isolated 18-26 nucleotide RNAs from developing rat and monkey brains. From the sequences of these RNAs and the sequences of the rat and human genomes we determined which of these small RNAs are likely to have derived from stem-loop precursors typical of microRNAs. Next, we developed a microarray technology suitable for detecting microRNAs and printed a microRNA microarray representing 138 mammalian microRNAs corresponding to the sequences of the microRNAs we cloned as well as to other known microRNAs. We used this microarray to determine the profile of microRNAs expressed in the developing mouse brain. We observed a temporal wave of expression of microRNAs, suggesting that microRNAs play important roles in the development of the mammalian brain. CONCLUSION: We describe a microarray technology that can be used to analyze the expression of microRNAs and of other small RNAs. MicroRNA microarrays offer a new tool that should facilitate studies of the biological roles of microRNAs. We used this method to determine the microRNA expression profile during mouse brain development and observed a temporal wave of gene expression of sequential classes of microRNAs.

Animals↗
PubMed2004

Genitourinary anomaly in congenital varicella syndrome: case report and review.

We describe a 1-year-old boy with congenital varicella syndrome who had vesicoureteral reflux (VUR) and neurogenic bladder. His mother had varicella during the 3rd month of pregnancy. At birth the patient presented with right microphthalmia, right microcornea, and persistent hyperplastic primary vitreous of the right eye. He had chronic constipation from 3 months of age. He had urinary tract infection at 1 year of age. Urological investigation revealed left grade V VUR and neurogenic bladder. His varicella zoster virus IgG titer measured by ELISA was 39.4 antibody index (normal <0.1). He had repeated episodes of urinary tract infection despite antibiotic prophylaxis and clean intermittent catheterization, and underwent a uretero-vesiconeostomy at 2 years of age. Maternal infection during early pregnancy and the serological evidence of varicella zoster IgG antibodies without a history of varicella after birth led to the diagnosis of congenital varicella syndrome. Urogenital anomalies have previously been described in 14 cases of congenital varicella syndrome. Most of these patients had neurogenic bladder, the pathophysiology of which could be explained by the known neurotropic nature of the virus.

Abnormalities, Multiple↗
PubMed2004

Receptor compartmentalization and trafficking at glutamate synapses: a developmental proposal.

This article focuses on NMDA receptor subunit changes that occur in the forebrain and midbrain during development, namely the switch from predominance of NMDA receptors rich in NR2B subunits to that of NMDA receptors rich in NR2A subunits. We review the potential roles in brain plasticity of two membrane-associated guanylate kinases (MAGUKs), SAP102 and PSD95, which form a scaffold for the ion-passing glutamate receptors at the postsynaptic density, and we consider the known functional significance of these molecules in subunit switching. In addition, based on recent analyses of the synaptic location of glutamate receptors, activity-dependent changes in developing visual neurons, and extensive data on MAGUKs, we propose a model of glutamatergic synaptic differentiation. In this model, different NMDA receptor scaffolding and signaling complexes effect the trafficking and synaptic localization of NR2A-rich and NR2B-rich receptors, leading to tangential compartmentalization of these receptors and their movement between synaptic and extrasynaptic compartments.

Animals↗
PubMed2003

Eye opening induces a rapid dendritic localization of PSD-95 in central visual neurons.

The membrane-associated guanylate kinase PSD-95 scaffolds N-methyl-d-aspartate receptors to cytoplasmic signaling molecules, and associates with other glutamate receptors at central synapses. However, regulation of PSD-95 in vivo is poorly understood. We provide evidence of an activity-dependent redistribution of PSD-95 to dendrites in central visual neurons that is tied to eye opening. Six hours after eye opening, increased dendritic PSD-95 coimmunoprecipitates with the same proportions of stargazin, increased proportions of the N-methyl-d-aspartate receptor subunit NR2A, and decreased proportions of NR2B. Sustained high levels of PSD-95 in dendrites are dependent on continued pattern vision in juvenile but not mature animals, suggesting that the stabilization of PSD-95 at synapses may be involved in the control of developmental plasticity.

Animals↗
PubMed2003

Developmental loss of miniature N-methyl-D-aspartate receptor currents in NR2A knockout mice.

The N-methyl-d-aspartate (NMDA) glutamate receptor (NMDAR), long implicated in developmental plasticity, shows decay time kinetics that shorten postnatally as NR2A subunits are added to the receptor. Neither the mechanism nor immediate effect of this change is known. We studied developing NMDAR currents by using visual neurons in slices from NR2A knockout (NR2AKO) and WT mice. Both strains show increased dendritic levels of synaptic density scaffolding protein PSD-95 with age. Dendritic levels of NR2A increased at the same time in WT and immunoprecipitated with PSD-95. PSD-95NMDAR binding was significantly decreased in the NR2AKO. Moreover, NMDAR miniature currents (minis) were lost and rise times of NMDAR evoked currents increased in mutant mice. Age-matched WT cells showed NR2A-rich receptors predominating in minis, yet slow NR2B mediated currents persisted in evoked currents. Disrupting photoreceptor activation of retinal ganglion cells eliminated increases in PSD-95 and NR2A in superior collicular dendrites of WT mice and slowed the loss of miniature NMDAR currents in NR2AKOs. These data demonstrate that NMDARs that respond to single quantal events mature faster during development by expressing the NR2A subunit earlier than NMDARs that respond to evoked release. We hypothesize that NR2A-rich NMDARs may be localized to the center of developing synapses by an activity-dependent process that involves the targeting of PSD-95 to the postsynaptic density. Neonatal receptors become restricted to perisynpatic or extrasynaptic sites, where they participate primarily in evoked currents.

Animals↗
PubMed2002

Diffusion-weighted images in neonatal cerebral hypoxic-ischemic injury.

Diffusion-weighted images of magnetic resonance imaging, obtained by mapping apparent diffusion coefficients, are more sensitive than other magnetic resonance imaging sequences in the earliest detection of acute cytotoxic injury. The usefulness of diffusion-weighted images in focal ischemic brain injury has been documented in children and adults. We report eight full-term neonates with global cerebral hypoxic-ischemic injury and abnormalities on diffusion-weighted images. Distribution of diffusion-weighted imaging abnormalities in the eight neonates was consistent with global hypoxic-ischemic injury in full-term neonates, with diffuse cortical necrosis, border-zone infarcts, or basal ganglia/thalamic injury. Magnetic resonance imaging scans with diffusion-weighted images were obtained within the first 4 days of age in all eight neonates. In each patient, standard magnetic resonance imaging sequences substantially underestimated the extent of injury when compared with diffusion-weighted images in unmyelinated neonatal brains. Extensive injury bilaterally with basal ganglia and thalamic and widespread multifocal cortical injury correlated with a severe neurologic outcome. Lesser degrees of injury, limited to smaller sectors of cortical or border zone involvement, were associated with better neurologic outcome. The high sensitivity of diffusion-weighted images to map the extent of hypoxic-ischemic injury in neonates makes it a potentially useful tool for assessing future neuroprotective strategies for neonatal hypoxic-ischemic injury.

Brain↗
PubMed2002

Fas-Fas ligand system as a possible mediator of spermatogenic cell apoptosis in human maturation-arrested testes.

To elucidate the mechanism of maturation arrest, known as one of the male infertility, we addressed whether germ cell apoptosis occurs during maturation arrest, and if so, whether Fas and Fas ligand expressions are involved in the apoptosis. By electron microscopy and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL), typical apoptotic features were frequently found around the spermatocytic stage in maturation arrest, compared to that in normal testes. When paraffin-embedded sections reacted with anti-Fas antiserum, staining for Fas was found in the plasma membranes of spermatocytes in the maturation-arrested testes, while no positive spermatogenic cells were seen in the normal testes. On the other hand, positive immunostaining for Fas ligand was restricted to Sertoli cells in the maturation-arrested testes as well as in the normal testes, although the intensity of staining for Fas ligand in normal testicular Sertoli cells was much weaker than that of maturation-arrested ones. Thus, these findings demonstrate that "maturation arrest" is characterized by frequent apoptosis of spermatocytes, and that Fas and Fas ligand staining are associated with a high frequency of apoptosis.

Adult↗