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61.
Although the acyl groups of phosphatidylserine in brain are uniquely enriched in docosahexaenoic acid (22:6n3), the mechanism for this enrichment is not well understood. When rat brain homogenates and microsomes were incubated in the presence of lysophosphatidylserine (LPS) together with [14C]22:6n3 and cofactors for activation to its acylCoA, very little radioactivity was incorporated into phosphatidylserine (PS). On the other hand, [14C]20:4n6 was more actively incorporated into PS. Addition of LPS (1-10 uM), however, resulted in a 2-5 fold enhancement of the transfer of labeled 22:6n3 and 20:4n6 to phosphatidic acid (PA). Kinetic analysis indicated the ability of LPS to lower the Km and increase the Vmax of the lysophosphatidic acid (LPA) acyltransferase reaction. Among other lysophospholipids tested, lysophosphatidylserine was most effective in enhancing PA biosynthesis. Since PA is an important intermediate for de novo biosynthesis of phospholipids, these results reveal a novel mechanism for promoting synthesis of PA enriched in polyunsaturated fatty acids in brain. 相似文献
62.
M Cannon L Hu J Ye D Lawson 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1991,197(4):465-470
The objective of this study was to determine the effects of thyrotropin-releasing hormone (TRH) and bromocriptine on plasma levels of biologically active prolactin in ovariectomized, diethylstilbestrol (DES)-treated rats. Female Long-Evans and Holtzman rats were ovariectomized and each was given a subcutaneous implant of diethylstilbestrol (DES). One week later, groups of DES-treated rats were fitted with indwelling intra-atrial catheters, and 2 days later blood samples were withdrawn before and at 1, 2, 5, 10, and 20 min after intravenous administration of TRH (250, 500, or 1000 ng/rat). Blood samples were obtained from other groups at 4 weeks of DES treatment by orbital sinus puncture under ether anesthesia before and at 30, 60, and 120 min after bromocriptine administration (2.5 mg/rat sc). Plasma was assayed for prolactin by conventional radioimmunoassay (RIA) and by Nb2 lymphoma bioassay (BA). Holtzman rats released significantly more prolactin following TRH than did Long-Evans rats when the RIA was used to measure prolactin. However, when the BA was used to assay prolactin in the same samples, the Long-Evans rats released more prolactin than did the Holtzman rats. In addition, the ratio of the BA to RIA values was significantly increased in both strains following TRH, but the greatest increase was observed in the Long-Evans rats, in which the ratio was 4.5 at the peak of the TRH-induced rise in plasma prolactin. Gel filtration chromatography of plasma obtained at 5 min after TRH treatment in Long-Evans rats revealed large molecular forms of prolactin with BA to RIA ratios of 4-5. In addition, monomeric prolactin had a BA to RIA ratio of 2. Bromocriptine treatment reduced prolactin levels in both strains, but the effect was more rapid in Holtzman than in Long-Evans rats. In addition, bromocriptine treatment of Holtzman, but not Long-Evans, rats significantly reduced the BA to RIA ratio of plasma prolactin. The results indicate that TRH and bromocriptine affect the release of biologically active prolactin to a greater extent than prolactin detected by antibody in the RIA, and that Long-Evans and Holtzman rats respond to these secretagogues differently with regard to BA to RIA comparisons. 相似文献
63.
M Cannon L Hu J Ye D Lawson 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1991,197(4):471-476
This study was conducted to determine the plasma levels of prolactin in prepubertal and young, postpubertal, proestrus rats of mammary tumor-susceptible (Sprague-Dawley) and tumor-resistant (Long-Evans) strains using a sensitive bioassay-Nb2 lymphoma cell replication. Prepubertal Long-Evans rats had significantly higher levels of prolactin than did Holtzman Sprague-Dawley rats of the same age. Likewise, Long-Evans rats secreted significantly more prolactin into the blood on the afternoon and evening of proestrus than did Holtzman rats. Finally, ovariectomized Long-Evans rats released more prolactin into the blood at 1 day, but not at 8 or 15 days, of treatment with diethylstilbestrol. Prolactin levels determined by conventional radioimmunoassay and by bioassay were similar except on the afternoon of proestrus, when, in both strains of rats, the bioassay to radioimmunoassay ratio increased significantly above 1.0 during the late evening. In addition, the ratio was significantly less than 1.0 in the early and late afternoon in the Holtzman rats, but not Long-Evans rats. These data indicate that a strain of rats that is resistant to experimentally induced mammary cancer has higher prolactin levels in the blood than does a strain that is susceptible to mammary cancer at a time when mammary gland growth is rapid. Furthermore, there are times during the proestrus prolactin surge when the bioassay yielded higher and lower values of prolactin than radioimmunoassay of the same samples, suggesting functional heterogeneity of prolactin that may impact on mammary gland or other target tissue function. 相似文献
64.
W L Hu C E Goldring N R Rao C Rice-Evans R H Burdon A T Diplock 《BioFactors (Oxford, England)》1992,4(1):47-49
Studies on glutathione (GSH) metabolism in an established baby hamster kidney fibroblast cell line (BHK-21/C13) and in its polyoma virus-transformed counterpart (BHK-21/PyY) have revealed a significant stimulation of intracellular GSH peroxidase (GSHpx) activity (selenium-independent plus selenium-dependent) by alpha-tocopherol supplementation (14 microM). This stimulation was found to be much greater in the transformed cells. Other GSH-requiring enzyme activities (i.e. GSH reductase and GSH S-transferase) were unaltered by alpha-tocopherol treatment, suggesting a degree of specificity in its action on GSHpx. In unsupplemented growth media, the GSHpx activity in both cell lines was significantly decreased by oxidative stress. However, the same stress applied to the alpha-tocopherol-supplemented cells had no effect on the stimulated GSHpx activity, suggesting that some protection was afforded by the alpha-tocopherol. 相似文献
65.
66.
神农架金丝猴的生态学观察 总被引:3,自引:0,他引:3
金丝猴(Rhinopithecus roxellanae)仅产于我国,属国家Ⅰ级保护动物,自然分布于四川、陕西、甘肃的部分地区和湖北省神农架自然保护区。1983年以来,笔者对神农架金丝猴生存环境生态习性等作了长期观察研究,结果报道如下。 相似文献
67.
真菌种类多,分布广,对人类的生产和生活关系非常密切,因此近来对真菌特别是丝状真菌的研究日益引起高度重视。1981—1990年我们对桂北龙胜县里骆林区、桂中宜山县庆远林区、桂南岑溪县七坪林区和桂西田林县老山林区森林土壤微生物区系进行了分析,其中丝状真菌是我们重点研究的内容之一。在上述森林土壤中共分离出丝状真菌2084株,经鉴定归属于25属。现将广西森林土壤丝状真菌生态分布的研究结果报道如下。 相似文献
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