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Takashi YAMAMURA Yoshihiro WAKABAYASHI Satoshi OHKURA Victor M. NAVARRO Hiroaki OKAMURA 《The Journal of reproduction and development》2015,61(1):20-29
Recent evidence suggests that neurokinin B (NKB), a member of the neurokinin (tachykinin) peptide family, plays a pivotal role in gonadotropin-releasing hormone (GnRH) pulse generation. Three types of neurokinin receptors (NKRs), NK1R, NK2R and NK3R, are found in the brain. Although NKB preferentially binds to NK3R, other NKRs are possibly also involved in NKB action. The present study examined the effects of intravenous administration of the NKR subtype-selective agonists GR73632 (NK1R), GR64349 (NK2R), and senktide (NK3R) on GnRH pulse generator activity and luteinizing hormone (LH) secretion. Multiple-unit activity (MUA) was monitored in ovariectomized goats (n = 5) implanted with recording electrodes. Characteristic increases in MUA (MUA volleys) were considered GnRH pulse generator activity. Although three NKR agonists dose-dependently induced an MUA volley and an accompanying increase in LH secretion, the efficacy in inducing the volley markedly differed. As
little as 10 nmol of senktide induced an MUA volley in all goats, whereas a dose of 1000 nmol was only effective for the NK1R and NK2R agonists in two and four goats, respectively. When the treatment failed to evoke an MUA volley, no apparent change was observed in the MUA or LH secretion. Similar effects of the NK2R and NK3R agonists were observed in the presence of estradiol. The results demonstrated that NK3R plays a predominant role in GnRH pulse generation and suggested that the contributions of NK1R and NK2R to this mechanism may be few, if any, in goats. 相似文献
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Overexpression of the LASAP2 gene for secretory acid phosphatase in white lupin improves the phosphorus uptake and growth of tobacco plants 总被引：1，自引：0，他引：1
Jun WASAKI Hayato MARUYAMA Miho TANAKA Takuya YAMAMURA Hiraki DATEKI Takuro SHINANO Susumu ITO Mitsuru OSAKI 《Soil Science and Plant Nutrition》2009,55(1):107-113
Secretion of acid phosphatase (APase) from the roots to take up phosphorus (P) is a well-known strategy of plants under P-deficient conditions. White lupin, which shows vigorous growth in low-P soils, is noted for its ability to secrete APase under P-deficient conditions. The APase secreted by white lupin roots is stable in soil solution and shows low substrate specificity, suggesting that genetic modification of plants using the APase gene LASAP2 might improve their ability to use organic P. The objective of the present study was to evaluate the potential of LASAP2 transgenic plants to increase organic P utilization. Dry matter production and P accumulation were higher in LASAP2 transgenic tobacco plants grown in gel media containing soluble phytate as the sole P source than in wild-type tobacco plants. Phosphorus uptake by the transgenic plants also increased in soil culture conditions. LASAP2 was apparently more effective in the liberation of organic P, including phytate, in the soil than the native tobacco APase. Thus, the enzymatic stability of LASAP2 in the soil appears to be an important factor for P acquisition. 相似文献
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Mirai WATANABE Shigeki YAMAMURA Takejiro TAKAMATSU Masami K. KOSHIKAWA Seiji HAYASHI Tomoyoshi MURATA Shoko S. SAITO Kazuyuki INUBUSHI Kazunori SAKAMOTO 《Soil Science and Plant Nutrition》2010,56(1):123-132
Volcanic acidification has created unique ecosystems that have had to adapt to the acidic environments in volcanic regions. To characterize the primary microbial properties of strongly acidified soils in such environments, we investigated microbial biomass, nitrogen transformations and other relevant chemical properties in the surface soils of solfatara and forests from Osorezan, a typical volcanic region in Japan, and compared the results to common Japanese forest soils. Soil microbial biomass C (MBC) and N (MBN) were determined using the chloroform fumigation–extraction method. Potential net N mineralization and net nitrification were measured in aerobic laboratory incubations. Long-term acidification in the Osorezan soils by volcanic hydrogen sulfide deposition caused low soil pH (3.0–3.8), base cation deficiency and increased concentrations of toxic ions such as Al3+ . The proportions of MBC to total carbon (MBC/TC ratio) and MBN to total nitrogen (MBN/TN ratio) were lower than those in common Japanese forest soils. The extreme acidic conditions may have inhibited microbial survival in the Osorezan acid soils. Net N mineralization occurred at rates comparable to those in common Cryptomeria japonica forest soils, probably because of the presence of acid-tolerant soil microorganisms. Net nitrification was completely inhibited and autotrophic ammonia oxidizers were not detected by the MPN method. The inhibition of nitrification prevents nitrogen leaching from the soils, thus maintaining a nitrogen cycle in the volcanic acid region in which (and NH3 ) is recycled among microorganisms and plants. 相似文献
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KAZUHISA UCHIKAWA ORIO YAMAMURA DAIJI KITAGAWA YASUNORI SAKURAI 《Fisheries Science》2002,68(5):1034-1040
The diet of Notoscopelus japonicus , one of the dominant mesopelagic fishes in the transitional waters of the western North Pacific, was examined in 106 specimens collected over the continental slope off the Pacific coast of northern Japan during April and October 1996. The prey comprised mainly crustaceans, such as copepods, ostracods, euphausiids and amphipods. Euphausia pacifica was the dominant prey, representing 83.1% by number and 72.4% by wet weight of the total diet. Between April and October, there was no shift in prey species consumed, but prey size decreased significantly and prey number per fish stomach increased in October. These results indicate that, in October, N. japonicus consumed larger numbers of smaller E. pacifica , rather than shifting to other prey taxa. The pronounced importance of E. pacifica in the diet was ascribed to its co-occurrence with N. japonicus at night in the surface layer and during the daytime in the near-bottom layer. 相似文献
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Ken-ichiro TATEMATSU Mitsumi IKEDA Yoshihiro WAKABAYASHI Takashi YAMAMURA Kazuhiro KIKUCHI Junko NOGUCHI Hideki SEZUTSU 《The Journal of reproduction and development》2021,67(6):402
Porcine zona pellucida proteins (ZPs) have been utilized as female immunocontraceptive antigens. The purpose of this study was to explore the potential use of silkworm recombinant bovine ZP4 as an alternative. When the protein was injected with monophosphoryl lipid A (MPL) – an immuno-stimulative agent – into two female goats, marked elevation of the anti-ZP4 titer was detected. Application of the purified specific IgG to a porcine in vitro fertilization system reduced the sperm penetration rate. In one goat, the cyclic profile of serum progesterone disappeared as the anti-ZP4 titer increased. Histological examination of the ovaries revealed degeneration of antral follicles with sparse infiltration of inflammatory cells in the theca, indicating that autoimmune oophoritis had been induced. Together, the present results suggest that recombinant ZP4 disturbs fertilization and exerts a pathogenic effect on follicle development in goats, thus indicating its potential as a female immunocontraceptive antigen. 相似文献
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Yoshihiro WAKABAYASHI Takashi YAMAMURA Kohei SAKAMOTO Yuji MORI Hiroaki OKAMURA 《The Journal of reproduction and development》2013,59(1):40-48
Neurons in the arcuate nucleus (ARC) that concomitantly express kisspeptin, neurokinin B
(NKB) and dynorphin A are termed KNDy neurons and are likely candidates for the intrinsic
gonadotropin-releasing hormone (GnRH) pulse generator. Our hypothesis is that KNDy neurons
are functionally and anatomically interconnected to generate discrete neural signals that
govern pulsatile GnRH secretion. Our goal was to address this hypothesis using
electrophysiological and anatomical experiments in goats. Bilateral electrodes targeting
KNDy neurons were implanted into ovariectomized goats, and GnRH pulse generator activity,
represented by characteristic increases in multiple-unit activity (MUA volleys), was
measured. Spontaneous and pheromone- or senktide (an NKB receptor agonist)-induced MUA
volleys were simultaneously recorded from both sides of the ARC. An anterograde tracer,
biotinylated dextran amine (BDA), was also injected unilaterally into the ARC of castrated
male goats, and the distribution of fibers containing both BDA and NKB was examined using
dual-labeling histochemistry. The results showed that MUA volleys, regardless of origin
(spontaneous or experimentally induced), occur simultaneously between the right and left
sides of the ARC. Tract tracing indicated that axons projecting from NKB neurons in the
ARC were directly apposed to other NKB neuronal cells located bilaterally in the ARC.
These results demonstrate that GnRH pulse generator activity occurs synchronously between
both sides of the ARC in goats and that KNDy neurons are bilaterally interconnected in the
ARC via NKB-containing fibers. Taken together, the results suggest that KNDy neurons form
a neuronal circuit to synchronize burst activity among KNDy neurons and thereby generate
discrete neural signals that govern pulsatile GnRH secretion. 相似文献
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ABSTRACT: The species composition of demersal fish was studied in nearshore waters (33–116 m depth) of south-eastern Hokkaido, the coldest area around the Japan Archipelago due to the influence of the cold Oyashio Current, using bottom gillnet samples collected during October 1996, August 1997, May 1998 and September 1999. The water temperature just above the sea bottom in the study area was lowest (< 2°C) during May and then rose through autumn (> 14°C). Cottids were the most abundant family in terms of both overall biomass and number, but their gravimetric dominance decreased from May (84%) through October (14%), whereas pleuronectids and stichaeids increased. Of the 57 fish species sampled, plain sculpin Myoxocephalus jaok was the dominant species in terms of overall biomass, accounting for 29.0% of the total biomass, followed by horned sculpin Enophrys diceraus (19.5%), Kamchatka flounder Atheresthes evermanni (6.5%) and blackline prickleback Acantholumpenus mackayi (4.9%). Plain sculpin dominated during May and September, but its predominance was low during October (9.6%), when witch flounder Glyptocephalus stelleri (22.7%) and blackline prickleback (10.8%) became important. This seasonal change appears to reflect the annual life cycle events of the fish, such as spawning. 相似文献