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排序方式: 共有145条查询结果,搜索用时 46 毫秒
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Michiru Akamatsu Ryosuke Hirozumi Yuko Cho Yuta Kudo Keiichi Konoki Yasukatsu Oshima Mari Yotsu-Yamashita 《Marine drugs》2022,20(3)
Saxitoxin and its analogues, paralytic shellfish toxins (PSTs), are potent and specific voltage-gated sodium channel blockers. These toxins are produced by some species of freshwater cyanobacteria and marine dinoflagellates. We previously identified several biosynthetic intermediates of PSTs, as well as new analogues, from such organisms and proposed the biosynthetic and metabolic pathways of PSTs. In this study, 12β-deoxygonyautoxin 5 (12α-gonyautoxinol 5 = gonyautoxin 5-12(R)-ol) was identified in the freshwater cyanobacterium, Dolichospermum circinale (TA04), and 12β-deoxysaxitoxin (12α-saxitoxinol = saxitoxin-12(R)-ol) was identified in the same cyanobacterium and in the marine dinoflagellate Alexandrium pacificum (Group IV) (120518KureAC) for the first time from natural sources. The authentic standards of these compounds and 12α-deoxygonyautoxin 5 (12β-gonyautoxinol 5 = gonyautoxin 5-12(S)-ol) were prepared by chemical derivatization from the major PSTs, C1/C2, produced in D. circinale (TA04). These standards were used to identify the deoxy analogues by comparing the retention times and MS/MS spectra using high-resolution LC-MS/MS. Biosynthetic or metabolic pathways for these analogues have also been proposed based on their structures. The identification of these compounds supports the α-oriented stereoselective oxidation at C12 in the biosynthetic pathway towards PSTs. 相似文献
3.
Hoshi K Tanaka R Shibazaki A Nagashima Y Hirao H Namiki R Takashima K Noishiki Y Yamane Y 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2003,65(3):357-361
The goal of the current study was to compare the efficiency of gas exchange and platelet conservation of a new extracapillary blood flow oxygenator versus an endocapillary blood flow oxygenator during open heart surgery with extracorporeal circulation in dogs. Dilation and remodeling of the right ventricular outflow tract of dogs was performed using a patch graft technique to simulate pulmonary stenosis. Sequential pre- and post-operative blood analysis revealed that gas exchange efficiency and platelet conservation was significantly greater with the extracapillary blood flow oxygenator than with the endocapillary blood flow oxygenator. However, the priming volume of the extracapillary blood flow oxygenator was significantly greater, leading to hemodilution. We conclude that while the extracapillary blood flow oxygenator provided benefits in terms of gas exchange and platelet conservation, development of a smaller extracapillary blood flow type oxygenator to reduce hemodilution effects would be beneficial. 相似文献
4.
When animals do not become pregnant, regression of the corpus luteum (CL) is essential for normal cyclicity because it allows the development of a new ovulatory follicle. Luteal regression is caused by a pulsatile release of prostaglandin (PG) F2α from the uterus in the late luteal phase in most mammals including cattle. Although it has been proposed in ruminants that pulsatile PGF2α secretion is generated by a positive feedback loop between luteal and/or hypophyseal oxytocin and uterine PGF2α, the bovine endometrium may possess other mechanisms for initiation of luteolytic PGF2α secretion. There is increasing evidence that several cytokines mainly produced by immune cells modulate CL and uterine function in many species. Tumor necrosis factor‐α (TNF‐α) stimulates PGF2α output from bovine endometrium not only at the follicular phase but also at the late luteal phase. Administration of TNF‐α at a high concentration prolongs luteal lifespan, whereas administration of a low concentration of TNF‐α accelerates luteal regression in cows. The data obtained from the authors’ previous in vitro and in vivo studies strongly suggest that TNF‐α is a crucial factor in regulating luteolysis in cows. The authors’ recent study has shown that interleukin‐1α mediates PG secretion from bovine endometrium as a local regulator. Furthermore, interferon‐τ (IFN‐τ) suppresses the action of TNF‐α on PGF2α synthesis by the bovine endometrium in vitro, suggesting that IFN‐τ plays a luteoprotective role by inhibiting TNF‐α‐induced PGF2α production in early pregnancy. The purpose of the present review is to summarize current understanding of the endocrine mechanisms that regulate uterine function by cytokines during the estrous cycle and early pregnancy in cows. 相似文献
5.
Dielectric properties in three main directions for hinoki wood (Chamaecyparis obtusa) specimens conditioned at various levels of relative humidity were measured in the frequency range from 20 Hz to 10 MHz over
the temperature range from −150°C to 20°C. Three relaxations were observed in the specimens conditioned at high levels of
relative humidity. The relaxation in the highest frequency range was ascribed to the motions of adsorbed water molecules.
The relaxation in the middle frequency range remained unchanged by the ethanol–benzene extraction of specimens. The relaxation
location was independent of measuring directions. The relaxation in the lowest frequency range was not detected in the specimens
impregnated with methyl methacrylate (MMA). This result suggested that the relaxation was due to electrode polarization. The
Cole-Cole circular arc law applied well to two relaxations recognized in the specimens impregnated with MMA. The relaxation
magnitude in the middle frequency range was extremely large, and the distribution of relaxation times was very narrow. These
characteristics suggested relaxation of the Maxwell-Wagner type resulting from the interfacial polarization in the heterogeneous
structure, which included adsorbed water with large electrical conductivity within the insulating cell walls. 相似文献
6.
Fumie MAGATA Yoshikazu ISHIDA Akio MIYAMOTO Hidefumi FURUOKA Hisashi INOKUMA Takashi SHIMIZU 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(1):81-84
We investigated the
concentration of the bacterial endotoxin lipopolysaccharide (LPS) in the blood, ovarian
follicular fluid and uterine fluid of a clinical case of bovine metritis. A 2-year-old
lactating Holstein cow exhibited continuous fever >39.5°C for more than 2 weeks after
normal calving. The cow produced a fetid, watery, red-brown uterine discharge from the
vagina and was diagnosed with metritis. The LPS concentrations in plasma and uterine fluid
were 0.94 and 6.34 endotoxin units (EU)/ml, respectively. One of seven
follicles showed an extremely high level of LPS (12.40 EU/ml) compared to
the other follicles (0.62–0.97 EU/ml). These results might suggest the
presence of high concentration of LPS in follicles in cows with postpartum metritis. 相似文献
7.
Hironori ABE Ryosuke SAKUMOTO Kiyoshi OKUDA 《The Journal of reproduction and development》2015,61(4):277-286
We recently demonstrated that luteal cells flow out from the ovary via lymphatic vessels during luteolysis. However, the regulatory mechanisms of the outflow of luteal cells are not known. Matrix metalloproteinases (MMPs) can degrade the extracellular matrix and basal membrane, and tissue inhibitors of matrix metalloproteinases (TIMPs) inhibit the activity of MMPs. To test the hypothesis that MMP expression in luteal cells is regulated by luteolytic factors, we investigated the effects of prostaglandin F2α (PGF), interferon γ (IFNG) and tumor necrosis factor α (TNF) on the mRNA expression of MMPs and TIMPs in cultured luteal cells. Luteal cells obtained from the CL at the mid-luteal stage (days 8–12 after ovulation) were cultured with PGF (0.01, 0.1, 1 μM), IFNG (0.05, 0.5, 5 nM) and TNF (0.05, 0.5, 0.5 nM) alone or in combination for 24 h. PGF and IFNG significantly increased the expression of MMP-1 mRNA. In addition, 1 μM PGF in combination with 5 nM IFNG
stimulated MMP-1 and MMP-9 mRNA expression significantly more than either treatment alone. In contrast, IFNG significantly decreased the level of MMP-14 mRNA. The mRNA expression of TIMP-1, which preferentially inhibits MMP-1, was suppressed by 5 nM INFG. One μM PGF and 5 nM IFNG suppressed TIMP-2 mRNA expression. These results suggest a new role of MMPs: luteal MMPs stimulated by PGF and IFNG break down the extracellular matrix surrounding luteal cells, which accelerates detachment from the CL during luteolysis, providing an essential prerequisite for outflow of luteal cells from the CL to lymphatic vessels. 相似文献
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