Publications by authors named "Masami Shibaya"

Autotaxin, also known as ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2), is a secreted enzyme that has lysophospholipase D activity, which converts lysophosphatidylcholine to bioactive lysophosphatidic acid. Lysophosphatidic acid activates at least six G-protein coupled recpetors, which promote cell proliferation, survival, migration and muscle contraction. These physiological effects become dysfunctional in the pathology of cancer, fibrosis, and pain.

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Vascular endothelial growth factor (VEGF) is a well known angiogenic factor that has been suggested to play some physiological roles in reproductive organs. To clarify whether VEGF is involved in regulating bovine endometrial function locally, in experiment 1, we determined the expression of VEGF, VEGF receptor (VEGFR) 1 and VEGFR2 throughout the estrous cycle in endometrial tissues. Endometrial tissue was collected at estrus (Day 0), the early I (Days 2-3), early II (Days 5-6), mid (Days 8-12) and late luteal stages (Days 15-17) and the follicular stage (Days 19-21).

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In order to enable monitoring of the reproductive status of the female giant panda after observation of estrus behavior, we developed an enzyme immunoassay (EIA) system for urinary pregnanediol-3-glucuronide (PdG), a progesterone metabolite, using commercial reagents and examined the changes in the urinary concentration of PdG in a female giant panda that showed pseudopregnancy and suspicious pseudopregnancy in 6 consecutive years. The developed EIA system had good reproducibility (intra- and interassay CVs 6.1% and 16.

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Estrogen (E) exerts its function by binding to two intracellular estrogen receptors, ERalpha and ERbeta. Although ERs have been reported to be expressed in the bovine corpus luteum (CL), the mechanisms that control ER expression in the bovine CL are not fully understood. To determine the possible regulatory mechanisms of ERalpha and ERbeta that meditate distinct E functions, we examined 1) the changes in the protein expressions of ERs in the CL throughout the luteal phase and 2) the effects of prostaglandin (PG) F2alpha, tumor necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma) on the expressions of ERs in cultured bovine luteal cells.

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Calf serum (CS) is a common supplement used in cell culture. It has been suggested that CS contains substances protecting cells against apoptosis. To examine whether a culture system including CS is appropriate for studying apoptosis in bovine luteal cells, we examined the influence of CS on the expression of Fas, bcl-2 and bax gene.

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Prolactin (PRL) is known to be synthesized not only in the anterior pituitary, but also in other organs including the ovary. Among its various functions, PRL is regarded as the most important constituent of the luteotropic complex in rodents and pigs. The purpose of the present study was to determine whether PRL is produced locally in bovine corpus luteum (CL) and to determine its possible roles in CL.

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Prostaglandins (PGs) are known to modulate the proper cyclicity of bovine reproductive organs. The main luteolytic agent in ruminants is PGF2alpha, whereas PGE2 has luteotropic actions. Estradiol 17beta (E2) regulates uterus function by influencing PG synthesis.

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A number of substances have been implicated in the regulation of oxytocin (OT) secretion from bovine corpus luteum in vivo. However, isolated bovine luteal cells cultured in a monolayer lose the ability to secrete OT in response to stimulatory substances. The present study investigated how cell-to-cell contact and the cytoskeleton affect OT secretion by isolated bovine luteal cells.

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Progesterone is suggested to be a suppressor of apoptosis in bovine luteal cells. Fas antigen (Fas) is a cell surface receptor that triggers apoptosis in sensitive cells. Furthermore, apoptosis is known to be controlled by the bcl-2 gene/protein family and caspases.

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Luteinizing hormone (LH)-stimulated steroidogenesis in luteal cells is known to be mediated through the activation of cyclic AMP (cAMP)-dependent protein kinase, and to be also modulated by calcium-dependent mechanisms. In the present study, we tested the hypothesis that LH stimulates progesterone (P4) production in bovine luteal cells through activation of phospholipase (PL) C by using a cell culture system. Bovine mid-luteal cells (Days 8-12 of the estrous cycle) were cultured for 24 h and then exposed to a PLC inhibitor (U-73122; 10 microM) with or without LH (10 ng/ml) for 4 h.

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To establish a storage system for isolated endometrial cells, we investigated the basal, oxytocin (OT)- and tumor necrosis factor (TNF) alpha-stimulated production of prostaglandin (PG) F(2alpha) in bovine-passaged and frozen-thawed endometrial cells. Stromal and epithelial cells obtained from cows in the early stage of the estrous cycle (Days 2-5) were frozen at -80 C or further cultured and/or passaged until passage 4 in DMEM/Ham's F-12 supplemented with 10% calf serum. A fresh-unfrozen primary culture and one-time passaged fresh-unfrozen cells were used as the control.

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The aim of this study was to investigate whether functional tumor necrosis factor-alpha (TNFalpha) receptors are present in the granulosa cells and the cells of theca interna (theca cells), obtained from bovine follicles classified into one of three groups. Each group was defined as either small vesicular ovarian follicles (small follicles; 3-5 mm in diameter), preovulatory mature ovarian follicles (preovulatory follicles) or atretic follicles (12-18 mm) according to gross examination of the corpus luteum in the epsilateral or contralateral ovary and the uterus (size, color, consistency and mucus), and the ratio of progesterone (P(4)) and estradiol-17beta (E(2)) concentrations in follicular fluid. A Scatchard analysis showed the presence of a high-affinity binding site on both granulosa and theca cells from all follicles examined (dissociation constant: 4.

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We have suggested in a previous in vitro study that tumor necrosis factor-alpha (TNFalpha) plays a role in the initiation of luteolysis in cattle. The aim of the present study was to examine the influence of different doses of TNFalpha on the estrous cycle in cattle by observing the standing behavior and measuring peripheral concentrations of progesterone (P4) during the estrous cycle. Moreover, we evaluated the secretion of P4, oxytocin (OT), nitric oxide (NO), and luteolytic (prostaglandin F2alpha [PGF2alpha] and leukotriene C4 [LTC4]) and luteotropic (PGE2) metabolites of arachidonic acid in peripheral blood plasma as parameters of TNFalpha actions.

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