Biomedical subjects

Takuma Mori

Publications and source records attributed to Takuma Mori.

8 recordsLinked to original sources

PubMed2006

The efficiency of interference of Potato virus X infection depends on the target gene.

RNA silencing is a natural defense response against viral infection. This phenomenon has been used to interfere with viral infections by exploiting fragments of viral genomes as sources of RNA silencing. Agrobacterium-mediated transient expression of a hairpin RNA derived from the TGBp1 gene of Potato virus X (PVX) induced RNA silencing of the TGBp1 gene and resulted in interference of PVX infection. The interference was induced in the infiltrated leaves but not in the upper non-infiltrated leaves. Transient expression of a CP hairpin RNA also induced interference of PVX. The TGBp1 hairpin RNA showed more efficient interference of PVX infection than the CP hairpin RNA.

Agrobacterium tumefaciens↗

PubMed2005

Heterogeneity of the developmental patterns of neurotrophin protein levels among neocortical areas of macaque monkeys.

Based on morphological and physiological characteristics, the mammalian neocortex is divided into various neocortical areas and its diversity is prominent in the primates including humans. These neocortical areas are constructed during development, but the details of the developmental events remain unclear, especially at the molecular level. We measured the mRNA and protein levels of neurotrophins in various neocortical areas of developing rhesus monkeys. The expression patterns of both the neurotrophin-3 (NT-3) mRNA and the protein showed area differences. In the sensory and motor areas, NT-3 mRNA and protein levels had started to decline by a week after birth. In contrast, the levels declined after the third postnatal week in the association neocortical areas. The level of brain-derived neurotrophic factor (BDNF) protein changed in an area-dependent manner during development, but that of mRNA did not. The decline of the BDNF protein level started earlier in the sensory and motor neocortical areas than in the association neocortical areas, suggesting that sensory and motor neocortical areas develop earlier than the association areas in terms of the developmental changes in neurotrophins.

Animals↗

PubMed2005

Developmental changes in concentrations and distributions of neurotrophins in the monkey cerebellar cortex.

Neurotrophins are involved in the survival, differentiation, migration and neurite outgrowth of various neuronal populations. Neurotrophins and their receptors are widely expressed in the developing cerebellum of various experimental animals. To gain some insight into the possible roles played by these molecules in monkey cerebellum, we examined the protein levels of BDNF, NT-4/5 and NT-3 and distributions of those neurotrophins and TrkC, a high affinity receptor for NT-3, in the cerebellum of developing macaque monkeys using ELISAs and immunohistochemical methods. We found that the level of BDNF increased during development, while the level of NT-3 was higher during embryonic stages and decreased toward adulthood. The level of NT-4/5 increased from embryonic stages to infant stages and gradually declined with age. Among the three neurotrophins, BDNF immunoreactivity was found in all kinds of cerebellar neurons, including all inhibitory interneurons, throughout the postnatal periods examined, indicating that BDNF may be an essential factor for the maintenance of cerebellar neural functions. The Bergmann glial fibers and the internal part of the external granule cell layer were strongly NT-3 immunopositive at the early postnatal stages, and more weakly immunoreactive toward adulthood. In addition, we found that the premigratory precursors of the granule cells were TrkC immunopositive at early postnatal stages. These findings suggest that NT-3 in Bergmann glial fibers may be involved in the migration of the premigratory granule cells.

Animals↗

PubMed2005

Phylogenetic characteristics, genomic heterogeneity and symptomatic variation of five closely related Japanese strains of Potato virus X.

To elucidate the genomic determinants of Potato virus X (PVX) strains, which cause diverse responses in host plants, we determined the complete genomic RNA sequences of four Japanese PVX strains: PVX-BS, -BH, -OG, and -TO. These four strains, plus the previously sequenced PVX-OS strain, differ in their pathogenicity in wild potato (Solanum demissum) and tobacco (Nicotiana tabacum cv. Samsun NN). The genomic sequences of these five PVX strains were highly homologous (i.e., the nucleotide sequence identity ranged from 95.4 to 98.5%). Phylogenetic analysis indicated that the Japanese PVX strains originated from an ancestral PVX strain in the European group, and that the virulence of these strains in both S. demissum and tobacco is not correlated with their phylogenetic relationships, suggesting that the pathogenicity of each strain in these host plants is determined by a relatively small number of nucleotides and can easily be altered independent of phylogenetic relationships. Particularly, OS, BH, and BS, which respectively produce markedly contrasting ringspot, mosaic, and asymptomatic infections in tobacco leaves, were the most closely related, suggesting that these three strains are an attractive model for analyzing the genetic determinants causing these symptoms. A possible correlation between the genomic and biological differences of these strains is discussed.

Amino Acid Sequence↗

PubMed2005

A single amino acid residue of RNA-dependent RNA polymerase in the Potato virus X genome determines the symptoms in Nicotiana plants.

A Potato virus X (PVX) strain, PVX-OS, causes a necrotic mosaic in Nicotiana benthamiana and ring spot mosaic in N. tabacum cv. SamsunNN. By contrast, strain PVX-BS causes a mild mosaic in N. benthamiana and systemic asymptomatic infection in N. tabacum cv. SamsunNN. To investigate the viral determinant of this difference, we produced various infectious cDNA clones chimeric between these PVX genomes and clones with point mutations introduced by site-directed mutagenesis. Inoculation tests with these clones mapped the symptom determinant in Nicotiana plants to the 1422 amino acid residue in the region of the C-terminus of RNA-dependent RNA polymerase (RdRp). Western blot analysis and local lesion assay indicated that virus accumulation in the infected leaves was similar for these PVX strains, suggesting that the symptom difference was not due to virus accumulation.

Amino Acid Substitution↗

PubMed2004

Differential expression patterns of TrkB ligands in the macaque monkey brain.

We measured the concentrations of brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) in the brains of mature and developing macaque monkeys. In the adult macaque brain, the highest level of BDNF was found in the hippocampus. Comparisons between cortical regions showed higher levels of BDNF in the prefrontal, temporal, and parietal association cortices than elsewhere. In contrast, NT-4 levels were 3-30 times lower than those of BDNF. During development, the contents of BDNF and NT-4 protein in cerebral cortices were highest at the postnatal second month and at embryonic day 140, respectively. These results suggest that the two TrkB ligands, BDNF and NT-4, may be differently regulated and might play separate roles in monkey cortical development.

Animals↗

PubMed2003

Levels of serum brain-derived neurotrophic factor in primates.

Brain-derived neurotrophic factor (BDNF) has been reported to exist not only in nervous tissue but also in serum. In contrast to the wealth of knowledge regarding the various physiological functions of BDNF in the nervous system, information about possible roles in other systems is limited. To elucidate the physiological function of serum BDNF in primates, it is first necessary to establish a method to determine the levels of BDNF in serum of primates. In the present study, we established an enzyme-linked immunosorbent assay (ELISA) method which we used to measure levels of serum BDNF in non-human primates. We found that serum BDNF levels were similar among several species of primates. The present results suggest that our BDNF ELISA may be useful in measuring serum BDNF concentration as a physiological marker, and that levels of serum BDNF may be similar among primates including humans.

Animals↗

PubMed2002

Changes in NT-3 and TrkC in the primary visual cortex of developing macaques.

In the present study, we measured the levels of neurotrophin-3 (NT-3) protein and mRNA by ELISA and quantitative RT-PCR, and examined TrkC-immunoreactive structures using immunohistochemical method. In the nervous system of the adult monkey, higher levels of NT-3 were found in the hippocampus and cerebellum. During the development of the primary visual cortex, detected amounts of NT-3 protein peaked at embryonic day 140 and then gradually decreased. TrkC imunoreactivity was observed in the neurons in layer VI of the primary visual cortex of an embryonic monkey. These results support the hypothesis that NT-3 is involved in the specification of axon targeting from layer VI to layer IV during the late embryonic stages.

Aging↗