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Biomedical subjects

Naoto Yamada

Publications and source records attributed to Naoto Yamada.

7 recordsLinked to original sources
PubMed2003

Development of a high-throughput bioassay to screen melatonin receptor agonists using human melatonin receptor expressing CHO cells.

Melatonin receptors belong to the superfamily of G-protein-coupled receptors and appear to couple with Gi type of G protein, which has an inhibitory effect on the adenylate cyclase. Normally, melatonin dose not induce transient elevation of intracellular calcium concentration in CHO cells stably expressing melatonin receptors. Accordingly, the cells are unable to be used for fluorescent imaging plate reader (FLIPR), which is the device used to measure the cellular signal as a calcium elevation. To overcome this issue we tried to transfect chimeric G protein, Gqi5, into CHO cells expressing melatonin receptors. The Gqi5 is a chimeric Gq protein containing the five carboxyl-terminal amino acids from Gi, which interact with Gi-coupled receptor and possess the function of evaluating calcium concentration through the Gq pathway. The transfected cells result in a calcium elevation in a concentration-response manner. The specificity of this assay was similar to that of radioreceptor binding assay. Therefore, this FLIPR assay, using melatonin receptor and Gqi5 expressing CHO cells, is available for clinical bioassay of melatonin and for the screening of specific ligands of melatonin.

Animals↗
PubMed2003

Mutation screening of the human period 2 gene in bipolar disorder.

We tested whether the human period 2 gene (hper2), one of the essential components of the circadian oscillator, might have influence on bipolar disorder. We screened 88 bipolar disorder patients and 127 controls, all of Japanese origin. Screening in the casein kinase I epsilon (CKIepsilon) binding region of hper2, which was previously reported in familial advanced sleep-phase syndrome patients, with polymerase chain reaction amplification revealed four polymorphisms. One of the four polymorphisms had an amino acid substitution of a serine at 662 with a glycine (S662G). The frequencies of the S662G allele and genotypes on patients with bipolar disorder were very low and had no difference from those in controls. Polymorphism on the CKIepsilon binding region of hper2 gene which was previously reported, is unlikely to play an important role in the development of bipolar disorder.

Adolescent↗
PubMed2002

Disrupted-in-Schizophrenia-1 (DISC-1): mutant truncation prevents binding to NudE-like (NUDEL) and inhibits neurite outgrowth.

Disrupted-in-Schizophrenia-1 (DISC-1) is a gene whose mutant truncation is associated with major psychiatric illness with a predominance of schizophrenic symptomatology. We have cloned and characterized rodent DISC-1. DISC-1 expression displays pronounced developmental regulation with the highest levels in late embryonic life when the cerebral cortex develops. In yeast two-hybrid analyses, DISC-1 interacts with a variety of cytoskeletal proteins. One of these, NudE-like (NUDEL), is associated with cortical development and is linked to LIS-1, the disease gene for a form of lissencephaly, a disorder of cortical development. The disease mutant form of DISC-1 fails to bind NUDEL. Expression of mutant, but not wild-type, DISC-1 in PC12 cells reduces neurite extension. As schizophrenia is thought to reflect defects in cortical development that are determined by cytoskeletal protein activities, the cellular disturbances we observe with mutant DISC-1 may be relevant to psychopathologic mechanisms.

Animals↗
PubMed2002

Mutation screening of the human Clock gene in circadian rhythm sleep disorders.

We tested whether the human Clock (hClock) gene, one of the essential components of the circadian oscillator, is implicated in the vulnerability to delayed sleep phase syndrome (DSPS) and non-24-hour sleep-wake syndrome (N-24). Screening in the entire coding region of the hClock gene with PCR amplification revealed three polymorphisms, of which two predicted the amino acid substitutions R533Q and H542R. The frequencies of the R533Q and H542R alleles in patients with DSPS or N-24 were very low and not significantly different from those in control subjects. A T3111C polymorphism in the 3'-untranslated region of hClock, which had been reportedly associated with morning or evening preference for activity, was also investigated; the results showed that the 3111C allele frequency decreased in DSPS. Polymorphisms in the coding region of the hClock gene are unlikely to play an important role in the development of DSPS or N-24. The possible contribution of the T3111C polymorphism to DSPS susceptibility should be studied further.

Adult↗