Biomedical subjects

M Yamao

Publications and source records attributed to M Yamao.

17 recordsLinked to original sources

PubMed2001

Multiphotoreceptor and multioscillator system in avian circadian organization.

Photoperiodism and circadian rhythms have been studied intensively in birds because Aves are typical seasonal breeders and diurnal animals. Light is the most important environmental factor involved in entrainment of circadian rhythms and photoperiodism. The eyes and the extraocular photoreceptors, such as the pineal organ and hypothalamus, are reported to have an important function not only for photoreception but also for circadian organization in nonmammalian vertebrates, including birds. In this report, we review the roles of the eyes, pineal organ, and deep brain as the components of the multiphotoreceptor and multioscillator system in avian circadian organization.

Animals↗

PubMed1999

Gene targeting in the silkworm by use of a baculovirus.

The Bombyx mori fibroin light (L)-chain gene was cloned and the green fluorescent protein (GFP) gene inserted into exon 7. The chimeric L-chain-GFP gene was used to replace the polyhedrin gene of Autographa californica nucleopolyhedrovirus (AcNPV). This recombinant virus was used to target the L-chain-GFP gene to the L-chain region of the silkworm genome. Female moths were infected with the recombinant virus and then mated with normal male moths. Genomic DNA from their progenies was screened for the desired targeting event. This analysis showed that the chimeric gene had integrated into the L-chain gene on the genome by homologous recombination and was stably transmitted through generations. The chimeric gene was expressed in the posterior silk gland, and the gene product was spun into the cocoon layer.

Animals↗

PubMed1999

Differentiation of pinopsin-immunoreactive cells in the developing quail pineal organ: an in-vivo and in-vitro immunohistochemical study.

The avian pineal organ contains several types of photoreceptors with different photopigments: rhodopsin, iodopsin, and pinopsin. We have previously examined the differentiation of both rhodopsin-like and iodopsin-like immunoreactive cells during pineal development in quail embryos to determine the onset of synthesis of specific proteins and their cellular localization. In the present study, we have performed pinopsin immunohistochemistry on in-vivo developing and in-vitro cultured pineal organs of quail embryos. The results were compared with those obtained with rhodopsin and iodopsin immunohistochemistry. In the developing pineal organs, pinopsin immunoreactivity was detected at embryonic day 8, i.e. five days earlier than rhodopsin-like and iodopsin-like immunoreactivities. It was localized exclusively in the protrusions extending into the lumen throughout development, whereas rhodopsin-like and iodopsin-like immunoreactivities were usually found both in cell bodies and processes. These differences were also observed under two different types of culture conditions (dissociated cell culture and organ culture) indicating that, in the avian pineal organ, the expression pattern of the pinopsin gene is basically different from those of the other two pineal photopigments. The present study suggests that pineal cells have a mechanism for the polarized transport of pinopsin molecules.

Animals↗

PubMed1998

Early embryonic interaction of retinal pigment epithelium and mesenchymal tissue induces conversion of pigment epithelium to neural retinal fate in the silver mutation of the Japanese quail.

The neural retina and retinal pigment epithelium (RPE) diverge from the optic vesicle during early embryonic development. They originate from different portions of the optic vesicle, the more distal part developing as the neural retina and the proximal part as RPE. As the distal part appears to make contact with the epidermis and the proximal part faces mesenchymal tissues, these two portions would encounter different environmental signals. In the present study, an attempt has been made to investigate the significance of interactions between the RPE and mesenchymal tissues that derive from neural crest cells, using a unique quail mutant silver (B/B) as the experimental model. The silver mutation is considered to affect neural crest-derived tissues, including the epidermal melanocytes. The homozygotes of the silver mutation have abnormal eyes, with double neural retinal layers, as a result of aberrant differentiation of RPE to form a new neural retina. Retinal pigment epithelium was removed from early embryonic eyes (before the process began) and cultured to see whether it expressed any phenotype characteristic of neural retinal cells. When RPE of the B/B mutant was cultured with surrounding mesenchymal tissue, neural retinal cells were differentiated that expressed markers of amacrine, cone or rod cells. When isolated RPE of the B/B mutant was cultured alone, it acquired pigmentation and did not show any property characteristic of neural retinal cells. The RPE of wild type quail always differentiated to pigment epithelial cells. In the presence of either acidic fibroblast growth factor (aFGF) or basic FGF (bFGF), the RPE of the B/B mutant differentiated to neural retinal cells in the absence of mesenchymal tissue, but the RPE of wild type embryos only did so in the presence of 10-40 times as much aFGF or bFGF These observations indicate that genes responsible for the B/B mutation are expressed in the RPE as well as in those cells that have a role in the differentiation of neural crest cells. They further suggest that development of the neural retina and RPE is regulated by some soluble factor(s) that is derived from or localized in the surrounding embryonic mesenchyme and other ocular tissues, and that FGF may be among possible candidates.

Animals↗

PubMed1995

Transovarian transmission of a foreign gene in the silkworm, Bombyx mori, by Autographa californica nuclear polyhedrosis virus.

We introduced a firefly luciferase gene, expressed under control of Drosophila heat shock protein gene promoter, into Autographa californica nuclear polyhedrosis virus (AcNPV). When the 5th instar larvae of the silkworm, Bombyx mori, were inoculated with the recombinant virus, luciferase activities were detected in the virus-infected larvae and pupae, and in the newly hatched larvae of the next generation. PCR amplification and Southern blot hybridization analysis demonstrated that the luciferase gene was transmitted through at least the F2 generation. In addition, the V-cathepsin gene, encoding a cysteine protease of AcNPV, was also detected in the DNA of all individuals of the F2 generation. These results show that AcNPV can be utilized as vector for the transovarian transmission of foreign genes in the silkworm.

Animals↗

PubMed1988