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Masao Ito

Publications and source records attributed to Masao Ito.

At least 19 recordsLinked to original sources
PubMed2006

Dose-dependent effects of hypergravity on body mass in mature rats.

INTRODUCTION: Previous reports have shown that exposure to hypergravity decreases rat body mass during the initial phase, with this decrease and level of gravity showing a dose-response relationship. The present study examined whether rate of body mass gain after the initial phase of exposure is attenuated by hypergravity in a dose-dependent manner and sought to identify any threshold. METHODS: Male 10-wk-old rats (n = 64) were used, with 16 rats serving as 1.0-G controls, and 48 rats exposed to hypergravity for 14 d in 4 groups (1.5, 2.0, 2.5, and 3.5 G; n = 12 each). Body mass gain was evaluated according to slope of change in body mass from day 7 of exposure to hypergravity, as both absolute and relative values. RESULTS: Slopes of body mass gain did not differ between the 1.0- and 1.5-G groups (6.09 and 5.75 g x d(-1), respectively), but were significantly less for the 2.0-, 2.5-, and 3.5-G groups (4.91, 3.03 and 1.99 g x d(-1), respectively) than for the 1.0- and 1.5-G groups. Body mass gain as a relative value did not differ between the 1.0-, 1.5-, and 2.0-G groups (1.5 +/- 0.2, 1.6 +/- 0.6 and 1.4 +/- 0.3 g x d(-1) x 100 g(-1) body mass, respectively), but was significantly less for the 2.5- and 3.5-G groups (1.1 +/- 0.6 and 0.8 +/- 0.3 g x d(-1) x 100 g(-1) body mass, respectively) than for the 1.0-, 1.5-, and 2.0-G groups. Absolute values and rate of body mass gain were reduced with increases in gravity. CONCLUSION: Exposure to hypergravity attenuates body mass gain in a dose-dependent manner, with a threshold possibly existing between 1.5- and 2.5-G for 10-wk-old male rats.

Animals↗
PubMed2005

Bases and implications of learning in the cerebellum--adaptive control and internal model mechanism.

The cerebellum has a fine compartment structure, which represents various discrete functions. Evolutionarily old, medial parts of the cerebellum are involved in the adaptive control of various brainstem and spinal cord functions, and long-term depression (LTD) plays a key role in this adaptive control. To extend these views to evolutionarily newer, lateral parts of the cerebellum involved in cerebral cortical functions such as voluntary movement, perception and language, the internal model hypothesis is instrumental. This hypothesis explains not only the characteristic cerebellar symptom, dysmetria, but also a number of otherwise unexplainable phenomena displayed in movements and mental actions.

Adaptation, Physiological↗
PubMed2005

Buffalo rat liver cells produce factors that support preimplantation development of mouse embryos cultured in vitro.

To examine the effects of buffalo rat liver (BRL) cells on the preimplantation development of mouse embryos in vitro, we first cultured two-cell mouse embryos alone in serum-free Dulbecco modified Eagle medium. As expected, the embryos did not develop to subsequent stages. However, when cocultured with BRL cells, the embryos developed to the blastocyst stage efficiently. Direct contact of embryos with BRL cells was not necessary for development: the medium conditioned by BRL cells contained soluble factors that supported the preimplantation development of mouse embryos. Embryos cultured with BRL-conditioned medium that was replaced at various intervals had a further increased rate of development to the blastocyst stage. This finding indicated that the activities of the factors were maintained only briefly. Seven proteins between 35 and 44 kDa that were detected in the medium were highly beneficial to the development of the embryos. Follistatin-related protein and pigment epithelium-derived factor are believed to be the factors supporting embryo development. The other five proteins also may improve the environment for the development of mouse embryos cultured in vitro.

Amino Acid Sequence↗
PubMed2004

Frequent inactivation of RASSF1A, BLU, and SEMA3B on 3p21.3 by promoter hypermethylation and allele loss in non-small cell lung cancer.

Non-small cell lung cancer frequently shows loss of heterozygosity of the chromosome 3p21.3 region and several genes such as RASSF1A, BLU, and SEMA3B have been identified as candidate tumor suppressor genes at this region since their downregulation and hypermethylation at their promoter regions were frequently detected in lung cancer. To determine whether these three genes are simultaneously inactivated during lung cancer development, we studied 138 primary non-small cell lung cancers for the promoter methylation status of these genes and allelic loss of the chromosome 3p21.3 region. We found promoter hypermethylation at 32% in RASSF1A, 30% in BLU, and 47% in SEMA3B. Allelic loss of 3p21.3 was detected in 54 (58%) of 93 informative tumors. Despite the weak association of methylation status among these three genes, there was no correlation between the methylation status of each gene and loss of heterozygosity. We also studied possible genes downstream of RASSF1A in 16 primary non-small cell lung cancers and found that the expressions of SM22 and SPARC were significantly downregulated in RASSF1A-hypermethylated tumors. Our results showed that, while candidate tumor suppressor genes at this locus can be simultaneously inactivated by epigenetic alterations, loss of heterozygosity without any hypermethylation of the three genes can also occur in some cases, suggesting that just one allelic loss might also be sufficient for the inactivation of any of these genes for lung cancer development.

Aged↗
PubMed2004

'Nurturing the brain' as an emerging research field involving child neurology.

'Nurturing the brain' is an emerging research field integrating brain science, child care and education, which also involves child neurology. It has emerged from the recent remarkable progress in brain science and strong social demands for improvements in child care and education. This article reviews the current status of three major research themes in this field. First, developmental disorders represented by attention deficit/hyperactivity disorder, autism and Asperger syndrome often introduce difficulties in child care and education, which are to be addressed by appropriate assessment and treatment of affected children based on new knowledge of the pathogenesis of these disorders. Second, recent progress in research on the critical/sensitive periods of development of brain structures and functions promises useful advice for teachers and parents regarding optimal timing and ways of teaching various subjects. Third, the development of the brain throughout infancy, childhood and adolescence is paralleled by the growth and maturation of the mind. Neuronal mechanisms underlying the theory of mind, mirror neurons, internal model, cognitive control, and cognitive emotion regulation are important themes that bridge our understandings of the brain and the mind.

Attention Deficit Disorder with Hyperactivity↗
PubMed2004

Purkinje cell functions in the in vitro cerebellum isolated from neonatal rats in a block with the pons and medulla.

The cerebellum dissected from neonatal rats in a block including the pons and medulla and maintained in a modified Krebs solution provides a unique preparation of brain tissue with preserved major fiber connections. Electrophysiological and optical recordings revealed that, at postnatal days 4-8 (P4-P8), Purkinje cells in the lateral portion of the cerebellum responded to the stimulation of climbing fiber afferents at the inferior olive and of parallel fibers at the posterior vermis, and that the combination of these inputs induced long-term depression. These observations and pharmacological testings indicate that certain functional features of Purkinje cells mature around P5 in the lateral portion of the cerebellum.

Animals↗
PubMed2004

Specific differential expression of phospholipase A2 subtypes in rat cerebellum.

Phospholipase A2 (PLA2) is a family of enzymes playing diverse roles in lipid signaling in neurons and glia cells. In this study, we examined the expression of subtypes of PLA2 in the cerebellum using immunolabeling and in situ hybridization methods. Two Ca2+-dependent cytosolic subtypes (cPLA2alpha and cPLA2beta), one Ca2+-independent cytosolic subtype (iPLA2), and two secretory subtypes (sPLA2IIA and sPLA2V) were detected in the cerebellum. cPLA2alpha is present in somata and dendrites of Purkinje cells, while sPLA2IIA is associated with the endoplasmic reticulum in perinuclear regions of Purkinje cell somata. iPLA2 is present in granule cells, stellate cells and also in the nucleus of Purkinje cells. In addition, cPLA2beta is localized in granule cells, and sPLA2V in Bergmann glia cells. These results provide an important basis for identifying functional roles of PLA2s in the cerebellum.

Animals↗
PubMed2004

Sphingomonas oligophenolica sp. nov., a halo- and organo-sensitive oligotrophic bacterium from paddy soil that degrades phenolic acids at low concentrations.

The taxonomic position of a halo- and organo-sensitive, oligotrophic soil bacterium, strain S213(T), was investigated. Cells were Gram-negative, non-motile, strictly aerobic, yellow-pigmented rods of short to medium length on diluted nutrient broth. When 0.1-0.4 % (w/v) NaCl was added to diluted media composed of peptone and meat extract, growth was inhibited with increasing NaCl concentration and the cells became long aberrant forms. When 6 mM CaCl(2) was added, the cells grew quite normally and aberrant cells were no longer found at 0.1-0.5 % (w/v) NaCl. Chemotaxonomically, strain S213(T) contains chemical markers that indicate its assignment to the Sphingomonadaceae: the presence of ubiquinone Q-10 as the predominant respiratory quinone, C(18 : 1) and C(16 : 0) as major fatty acids, C(14 : 0) 2-OH as the major 2-hydroxy fatty acid and sphingoglycolipids. 16S rRNA gene sequence analysis indicated that strain S213(T) belongs to the genus Sphingomonas, exhibiting high sequence similarity to the 16S rRNA gene sequences of Sphingomonas mali IFO 15500(T) (98.3 %), Sphingomonas pruni IFO 15498(T) (98.0 %), Sphingomonas asaccharolytica IFO 15499(T) (97.9 %) and Sphingomonas echinoides DSM 1805(T) (97.8 %). The results of DNA-DNA hybridization experiments and its phenotypic characteristics clearly distinguished the strain from its nearest neighbours and demonstrate that strain S213(T) represents a novel Sphingomonas species, for which the name Sphingomonas oligophenolica sp. nov. is proposed. The type strain is S213(T) (=JCM 12082(T)=CIP 107926(T)).

Aerobiosis↗
PubMed2004

Zona-float method for separating mouse eggs from other cells.

We have developed a new method for separating mouse eggs from other cells, such as cumulus cells, using centrifugation with Percoll. Solutions of 45, 22.5, 11.3, and 5.6% Percoll were tested. With the 22.5% solution, 99% of whole eggs obtained by in vitro fertilization were collected from the upper part of the Percoll solution, and 98% of 2-cell embryos collected from these eggs developed to the blastocyst stage. Offspring were obtained after transfer of collected embryos to female mice. The greatest advantage of this method is that undamaged eggs are separated from other cells in one simple operation, regardless of the number of eggs.

Animals↗
PubMed2004

Morphometric changes in vagal nerves of fourth generation mice passage-bred in a 2-G environment.

INTRODUCTION: Previous studies have shown that microgravity induces both functional and structural adaptations in the autonomic nerves. Functional adaptation to hypergravity has also been reported, but structural change has not yet been isolated. The purpose of this study was to evaluate structural adaptation to hypergravity in the parasympathetic nerve. METHOD: We selected fourth generation mice which were passage-bred in a 2-G environment by cycles of coupling, delivery, and growth. Complete left cervical vagal nerves of these mice were studied in transverse sections by electron microscopy. The number of small (diameter < 5 microm, thin and light-stained myelin sheath) and large (diameter > 5 microm, thick and dark-stained myelin sheath) myelinated fibers was counted. RESULTS: The total number of all myelinated fibers (2 G: 795 +/- 103, 1 G: 644 +/- 60) and the number of small myelinated fibers (2 G: 657 +/- 95, 1 G: 522 +/- 66) were significantly greater in the 2-G mice than those in the 1-G mice (p < 0.05). The number of large myelinated fibers in the 2-G mice was greater than that in the 1-G mice, although it was not statistically significant (2 G: 138 +/- 15, 1-G: 122 +/- 16; p = 0.091). DISCUSSION: The results show that the autonomic nerves can adapt structurally to hypergravity. We contend that the present results are due to the fact that the mice were passage-bred. As far as we know, this is the first report to show an increase in myelinated fibers in autonomic nerves under prolonged exposure to an increased G environment.

Adaptation, Physiological↗
PubMed2003

Loss of heterozygosity of chromosome 12p does not correlate with KRAS mutation in non-small cell lung cancer.

Activating mutations of RAS gene families have been found in a variety of human malignancies, including lung cancer, suggesting their dominant role in tumorigenesis. However, several studies have shown a frequent loss of the wild-type KRAS allele in the tumors of murine models and an inhibition of oncogenic phenotype in tumor cell lines by transfection of wild-type RAS, indicating that wild-type RAS may have oncosuppressive properties. To determine whether loss of wild-type KRAS is involved in the development of human lung cancer, we investigated the mutations of KRAS, NRAS and BRAF in 154 primary non-small cell lung cancers (NSCLCs) as well as 10 NSCLC cell lines that have been shown to have KRAS mutations. We also determined the loss of heterozygosity status of KRAS alleles in these tumors. We detected point mutations of KRAS in 11 (7%) of 154 NSCLCs, with 10 cases at codon 12 and 1 at codon 61, but no mutations of NRAS or BRAF were found. Using the laser capture microdissection technique, we confirmed that 9 of the 11 tumors and 7 of the 10 NSCLC cell lines retained the wild-type KRAS allele. Among the cell lines with heterozygosity of mutant and wild-type KRAS, all of the cell lines tested for expression were shown to express more mutated KRAS than wild-type mRNA, with higher amounts of KRAS protein also being expressed compared to the cell lines with a loss of wild-type KRAS allele. In addition, among 148 specimens available for immunohistochemical analysis, 113 (76%) showed positive staining of KRAS, indicating that the vast majority of NSCLCs continue to express wild-type KRAS. Our findings indicate that the wild-type KRAS allele is occasionally lost in human lung cancer, and that the oncogenic activation of mutant KRAS is more frequently associated with an overexpression of the mutant allele than with a loss of the wild-type allele in human NSCLC development.

Base Sequence↗
PubMed2003

Thr123 of rat G-substrate contributes to its action as a protein phosphatase inhibitor.

Rat G-substrate cDNA was isolated from a cerebellar library and characterized. The deduced amino acid sequence of rat G-substrate contained two putative phosphorylation sites for PKG at Thr72 and Thr123; the amino acid sequences (KPRRKDT(p)PA) around these sites are conserved in human, mouse and rabbit. G-substrate phosphorylated by PKG inhibited the catalytic subunits of both protein phosphatase-1 (IC(50) 14.1 nM) and -2A (IC(50) 5.9 nM). Mutation of Thr123 (site 2) to Ala significantly reduced the inhibition of both PP-1 and PP-2A, while mutation of Thr72 (site 1) to Ala had little effect on inhibitory activity. In situ hybridization analysis revealed that G-substrate mRNA was localized exclusively in cerebellar Purkinje cells. Immunoperoxidase staining showed that in Purkinje cells, G-substrate was present in somata, dendrites and axons. In rat cerebellar slices, activation of PKG with a nitric oxide (NO) donor, NOR3, or 8-Br-cGMP, increased phosphorylation of G-substrate, as demonstrated with a phosphorylation-specific antibody. These results characterize further the inhibition of PP-1 and PP-2A by phospho-G-substrate, and demonstrate its physiological phosphorylation in rat Purkinje cells.

Amino Acid Sequence↗
PubMed2003

Evolution and phylogenetic utility of alignment gaps within intron sequences of three nuclear genes in bumble bees (Bombus).

To test whether gaps resulting from sequence alignment contain phylogenetic signal concordant with those of base substitutions, we analyzed the occurrence of indel mutations upon a well-resolved, substitution-based tree for three nuclear genes in bumble bees (Bombus, Apidae: Bombini). The regions analyzed were exon and intron sequences of long-wavelength rhodopsin (LW Rh), arginine kinase (ArgK), and elongation factor-1alpha (EF-1alpha) F2 copy genes. LW Rh intron had only a few uninformative gaps, ArgK intron had relatively long gaps that were easily aligned, and EF-1alpha intron had many short gaps, resulting in multiple optimal alignments. The unambiguously aligned gaps within ArgK intron sequences showed no homoplasy upon the substitution-based tree, and phylogenetic signals within ambiguously aligned regions of EF-1alpha intron were highly congruent with those of base substitutions. We further analyzed the contribution of gap characters to phylogenetic reconstruction by incorporating them in parsimony analysis. Inclusion of gap characters consistently improved support for nodes recovered by substitutions, and inclusion of ambiguously aligned regions of EF-1alpha intron resolved several additional nodes, most of which were apical on the phylogeny. We conclude that gaps are an exceptionally reliable source of phylogenetic information that can be used to corroborate and refine phylogenies hypothesized by base substitutions, at least at lower taxonomic levels. At present, full use of gaps in phylogenetic reconstruction is best achieved in parsimony analysis, pending development of well-justified and generally applicable methods for incorporating indels in explicitly model-based methods.

Animals↗
PubMed2003

Aspiration method to collect epithelial cells from mouse, rat, and monkey oviducts.

When oviduct epithelial cells are collected by using enzymatic methods that involve protease such as trypsin, other cells unintentionally are collected as well, especially from small laboratory animals such as mice and rats, thus contaminating the collected sample. We therefore developed a simple nonenzymatic method that involves using a glass micropipette to aspirate the oviduct epithelial cells from the oviduct. This aspiration method easily removed oviduct epithelial cells from mice, rats, and cynomolgus monkeys. Culture of the collected oviduct epithelial cells confirmed that the cells could adhere and grow on a petri dish. Although this aspiration technique was developed for use in small animals, our results show that it can be applied to cynomolgus monkeys. The advantages of this technique are its simplicity and its success in collecting oviduct epithelial cells from oviducts.

Animals↗
PubMed2003

[Why "nurturing the brain" now?].

"Nurturing the Brain" is a new research field aiming at facilitating development and maintenance of healthy brains and keeping their learning capabilities at full display throughout life. It is based on recent remarkable progress in developmental neuroscience and non-invasive technologies for visualizing brain activities in humans, even infants and children. "Nurturing the Brain" research will help us to cure or prevent various types of developmental disorders such as ADHD and autism. It will also help us in choosing an appropriate timing for child care and education on the basis of new knowledge of the critical period of development for various brain functions.

Brain↗