Kazutoshi Yamamoto - Academia.edu (original) (raw)

Papers by Kazutoshi Yamamoto

Endocrinologia Japonica, 1981

Biology of Reproduction, 1998

In this study, the measurement both of peripheral gonadotropins (FSH and LH) and of sex steroids ... more In this study, the measurement both of peripheral gonadotropins (FSH and LH) and of sex steroids in male and female wild anuran, Rana esculenta, was performed during the annual reproductive cycle; moreover, the role of gonadotropins in the vitellogenic process and in ovarian steroidogenesis was investigated through in vitro experiments. LH plasma changes in males showed high values during autumn-winter months and during the mating period, when high androgen levels were found. Conversely, for the first time in male vertebrates, a clear correspondence between plasma FSH and estradiol-1710 (E 2) was shown. In females, FSH peak values were found at the beginning of the mating period in parallel with those of plasma vitellogenin (VTG) and E 2 ; in contrast, high LH levels went together with ovarian weight (gonadosomatic index), which is considered a good marker for the plasma sequestration of VTG by growing oocytes. The in vivo results are corroborated by in vitro studies showing the direct effects of both FSH and LH in inducing hepatic VTG synthesis and release in the culture media. Lastly, although it is not yet known whether or not FSH and LH have separate functions in amphibians, it was clearly shown that they induce ovarian steroid production. These results are discussed in terms of the high seasonality previously demonstrated in this wild frog.

ACTA HISTOCHEMICA ET CYTOCHEMICA, 1993

Hormones and Behavior, 2003

Effects of arginine vasotocin (AVT) on reproductive events such as courtship behavior, pheromone ... more Effects of arginine vasotocin (AVT) on reproductive events such as courtship behavior, pheromone release, and spermatophore discharge were investigated in the male newt Cynops pyrrhogaster. AVT enhanced the incidence and frequency of androgen-induced courtship behavior. In this case, AVT was likely to act centrally because the behavior was evoked with a much smaller amount of AVT when the hormone was administered intracerebroventricularly than when given intraperitoneally. Involvement of endogenous AVT in spontaneously occurring courtship behavior was also evidenced by the fact that administration of a V1 (vasopressor) receptor antagonist, [d(CH 2) 5 1 , Tyr(Me) 2 , Arg 8-vasopressin] suppressed the expression of the courtship behavior. The water in which AVT-treated males had been kept showed considerable female-attracting activity as compared with the water in which saline-injected males had been kept. Moreover, the content of sodefrin, a female-attracting pheromone in the abdominal gland, was decreased by the intraperitoneal injection of AVT, suggesting that the neurohypophyseal hormone stimulated the release of sodefrin from the abdominal gland into the water. AVT induced contraction of the excised abdominal gland concentration-dependently, and, again, the V1 receptor antagonist suppressed the AVT-induced contraction. Thus, we concluded that AVT induces the pheromone discharge, acting peripherally on a contractile structure of the abdominal gland. AVT was also found to induce spermatophore deposition in the male kept in the absence of the female. Administration of the V1 receptor blocker to the sexually developed males suppressed the spermatophore deposition. All these results indicate the involvement of AVT in reproductive events acting centrally and peripherally.

Endocrinologia Japonica, 1982

Sexual Reproduction in Animals and Plants, 2014

Previous studies have shown that brief treatment of follicle cells from ovaries of the starfi sh ... more Previous studies have shown that brief treatment of follicle cells from ovaries of the starfi sh Asterina pectinifera with Ca 2+-free seawater (CaFSW) deprived the follicle cells of their capacity to respond to gonad-stimulating substance (GSS). To elucidate the failure of GSS, this study examined the hormonal action of GSS on CaFSW-treated follicle cells of A. pectinifera , particularly the mode of signal transduction. GSS failed to stimulate the production of 1-methyladenine (1-MeAde) and cyclic AMP (cAMP) in CaFSW-treated follicle cells and the incapacity was irreversible. According to competitive experiments using radioiodinated and radioinert GSS, highly specifi c binding was observed in follicle cells, although their affi nities and binding sites in CaFSW-treated follicle cells were absolutely inferior to those in intact cells. Furthermore, GSS did not stimulate adenylyl cyclase in membrane preparations of CaFSW-treated follicle cells. Both Gsα and Giα were detected immunologically in membranes of CaFSW-treated follicle cells as well as those of nontreated cells. These results suggest that signal transduction for GSS in CaFSW-treated follicle cells does not fl ow readily from GSS receptors to G proteins.

Zoological Science, 1995

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access t... more BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Proceedings of the Japan Academy. Ser. B: Physical and Biological Sciences, 1998

The nucleus intercollicularis (ICo) is a critical region for avian vocalization. Implantation of ... more The nucleus intercollicularis (ICo) is a critical region for avian vocalization. Implantation of a testosterone pellet into a specific area in the midbrain of Japanese quail chicks rapidly alters their vocal behavior to crowing from distress calling. The speed with which this change occurs cannot be accounted for by the genomic action of testosterone. We found and purified testosterone binding proteins in the membrane of neurons within the ICo. We suggest that this protein mediates the action of testosterone on vocal behavior. This is the direct evidence that neural membrane protein mediates the action of steroid hormones.

Peptides, 2004

This article reviews the current state of understanding of reproductive pheromones in amphibians,... more This article reviews the current state of understanding of reproductive pheromones in amphibians, focusing mainly on the purification and characterization of peptide pheromones in newts of the genus Cynops, molecular cloning of cDNAs encoding the pheromone molecules, and hormonal control of secretion of these pheromones. Pheromones that attract sexually developed female Cynops pyrrhogaster and C. ensicauda newts were isolated from the male abdominal glands. The C. pyrrhogaster and C. ensicauda pheromones are peptides, designated sodefrin and silefrin, with the amino acid sequences SIPSKDALLK and SILSKDAQLK, respectively. Each pheromone attracts only conspecific females. Molecular cloning of cDNAs encoding sodefrin and silefrin revealed the presence of precursor proteins that are considered to generate these pheromone peptides. Pheromone precursor mRNA levels and radioimmunoassayable pheromone concentrations in the abdominal glands were elevated by prolactin and androgen. Sexual dimorphism and hormone dependency of the responsiveness of vomeronasal epithelium to sodefrin were noted. Significance of pheromones in the form of peptide for those performing reproductive behavior in an aquatic environment was also discussed.

Journal of Reproduction and Development, 1997

The effects of coffee cherry (CC), the residue left after the removal of coffee beans from the fr... more The effects of coffee cherry (CC), the residue left after the removal of coffee beans from the fruit, on the lactation of SHN mice were examined. Free access to drinking water with 0.01 % and 0.025 % solutions of the water extract of CC between days 1 and 12 of lactation improved the pup growth rate used as an index of lactational performance. The treatments affected little any of mother weight, mammary gland contents of DNA, RNA and lactose, serum levels of prolactin, growth hormone and non-esterified free fatty acid and major endocrine organ weights. The period of time spent by the mother mice in the nest was significantly elongated in the experimental mice given CC compared to the control. The results strongly suggest that CC can stimulate the growth of pups through its improvement of the nesting behavior of mother mice.

Advances in Chemical Signals in Vertebrates, 1999

An attempt has been made to isolate and characterize the female-attracting pheromone in the abdom... more An attempt has been made to isolate and characterize the female-attracting pheromone in the abdominal glands of male red-bellied newts, Cynops pyrrhogaster. The active substance was isolated by two steps of purification using reverse-phase high-performance liquid chromatography. Direct sequencing of the final product revealed that it is a novel decapeptide. Its minimum effective concentration was estimated to be between 0.1 pM and 1.0 pM. The synthetic peptide showed a female-attracting activity similar to that of the native peptide. It acts through the olfactory organ of female newts. An immunoelectron microscopic study using the antiserum against sodefrin revealed that sodefrin exists predominantly within secretory granules in the epithelial cells of the abdominal glands. The immunoassayable sodefrin content in C. pyrrhogaster males was diminished by castration and hypophysectomy. The sodefrin level was increased markedly in the castrated and hypophysectomized newts after treatment with both testosterone and prolactin. Se-Advances in Chemical Signals in Vertebrates, edited by Johnston et al.

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, Jan 29, 2016

Gonadotropin-inhibitory hormone (GnIH) acts as a negative regulator of reproduction by acting on ... more Gonadotropin-inhibitory hormone (GnIH) acts as a negative regulator of reproduction by acting on gonadotropes and gonadotropin-releasing hormone (GnRH) neurons. Despite its functional significance, the molecular mechanism of GnIH action in the target cells has not been fully elucidated. To expand our previous study on GnIH actions in gonadotropes, we investigated the potential signal transduction pathway that conveys the inhibitory action of GnIH in GnRH neurons by using the GnRH neuronal cell line, GT1-7. We examined whether GnIH inhibits the action of kisspeptin and vasoactive intestinal polypeptide (VIP), positive regulators of GnRH neurons. Although GnIH significantly suppressed the stimulatory effect of kisspeptin on GnRH release in hypothalamic culture, GnIH had no inhibitory effect on kisspeptin stimulation of serum response element and nuclear factor of activated T-cells response element activities and ERK phosphorylation, indicating that GnIH may not directly inhibit kisspe...

Frontiers in endocrinology, 2011

We have identified cDNA encoding a functional growth hormone secretagogue-receptor 1a (GHS-R1a, g... more We have identified cDNA encoding a functional growth hormone secretagogue-receptor 1a (GHS-R1a, ghrelin receptor) in two species of anuran amphibian, the bullfrog (Rana catesbeiana), and the Japanese tree frog (Hyla japonica). Deduced receptor protein for bullfrog and Japanese tree frog (tree frog) was comprised of 374- and 371-amino acids, respectively. The two receptors shared 86% identity, and are grouped to the clade of the tetrapod homologs by phylogenetic analysis. In functional analyses, ghrelin and GHS-R1a agonists increased intracellular Ca(2+) concentration in GHS-R1a-transfected-HEK293 cell, but ligand selectivity of ghrelin with Ser(3) and Thr(3) was not observed between the two receptors. Bullfrog GHS-R1a mRNA was mainly expressed in the brain, stomach, and testis. In the brain, the gene expression was detected in the diencephalon and mesencephalon, but not in the pituitary. Tree frog GHS-R1a mRNA was predominantly expressed in the gastrointestinal tract and ovary, but ...

Journal of toxicologic pathology, 2009

Congenitally primary hypothyroid growth-retarded (grt) mice exhibit a characteristic growth pause... more Congenitally primary hypothyroid growth-retarded (grt) mice exhibit a characteristic growth pause followed by delayed onset of pubertal growth. We characterized the developmental pattern of somatotropes, lactotropes and thyrotropes in the anterior pituitary, as well as plasma levels of their secretory hormones, in grt mice. Compared with normal mice, the weight of grt pituitary gland was similar at 8 weeks of age but significantly heavier after 12 weeks of age. Compared with normal mice, there were significantly fewer somatotropes in the grt pituitary until 8 weeks of age, but the number gradually increased up to 48 weeks. The number of lactotropes in grt mice was consistently lower than that in normal mice from 2 through 48 weeks, whereas the number of thyrotropes in the grt pituitary was consistently higher than in the normal pituitary. Thyrotropes in the grt pituitary exhibited hypertrophy and hyperplasia with less intensive thyroid-stimulating hormone (TSH) immunoreactivity than...

Zoological Science, 2000

$Research paper thumbnail of Effect of growth hormone-containing fraction obtained from bullfrog hypophyses on growth of Xenopus juveniles$

Proceedings of the Japan Academy, Series B, 1984

Nature Communications, 2013

Sexual differentiation leads to structural and behavioural differences between males and females.... more Sexual differentiation leads to structural and behavioural differences between males and females. Here we investigate the intrinsic sex identity of the brain by constructing chicken chimeras in which the brain primordium is switched between male and female identities before gonadal development. We find that the female chimeras with male brains display delayed sexual maturation and irregular oviposition cycles, although their behaviour, plasma concentrations of sex steroids and luteinizing hormone levels are normal. The male chimeras with female brains show phenotypes similar to typical cocks. In the perinatal period, oestrogen concentrations in the genetically male brain are higher than those in the genetically female brain. Our study demonstrates that male brain cells retain male sex identity and do not differentiate into female cells to drive the normal oestrous cycle, even when situated in the female hormonal milieu. This is clear evidence for a sex-specific feature that develops independent of gonadal steroids.

Journal of Reproduction and Development, 1998

To understand the relationship between transforming growth factor α (TGFα) and mammary gland invo... more To understand the relationship between transforming growth factor α (TGFα) and mammary gland involution, changes in the growth of normal and preneoplastic mammary glands, the expression of TGFα and epidermal growth factor receptor (EGFR) mRNAs in the mammary gland, and serum prolactin (PRL) level were examined in 3-month-old virgin SHN mice 4 to 108 days after ovariectomy (OVX). The formation of normal end-buds and preneoplastic hyperplastic alveolar nodules was significantly reduced after 9 days of OVX, associated with the decreased serum PRL level. Both TGFα and EGFR mRNA expression in the mammary glands declined 18 days after OVX. Thereafter, TGFα mRNA tended to increase, while EGFR mRNA continued to decrease. These observations suggest that the decline of both estrogen and PRL play major roles in the mammary gland involution after OVX, and that the decline of EGFR, through which TGFα manifests its effects, play a secondary role in this process.