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151.
An assay method based on thin layer chromatography to study the arachidonic acid (AA) metabolism in gill tissues was optimized and the effect of osmotically different incubation mediums on AA metabolism was evaluated. Rainbow trout gill tissues metabolize AA into PGE2 in highest concentration followed by PGD2, PGF2 and 6-keto-PGF1 (the stable metabolite of PGI2) among the prostanoids tested. Approximately 40% of PGE2 is synthesized within the first minute of incubation and is directly dependent on the substrate concentration (AA). As in mammalian tissues, PGE2 synthesis in fish gills is inhibited by the cyclooxygenase inhibitor indomethacin. PGE2 synthesis in gill homogenate and isolated gill cells incubated in trout Ringer was 0.45 and 1.9 ng/mg protein, respectively, and increased to 8.9 and 4.3 ng/mg protein, respectively, when incubated in KPO4 buffer, due to a ten-fold increase in the free AA. The hydroxy acid synthesis of the gill homogenate was higher (13%), and that of the isolated gill cells incubated in KPO4 buffer was lower (44%) compared to gill homogenate and cells incubated in trout Ringer. Gill homogenate incubated in 50 mM phosphate buffer with increasing sodium or potassium concentrations (up to 250 mM) exhibited a concentration-dependent increase in PGE2 synthesis (220% and 72%, respectively). Prolactin stimulated the PGE2 synthesis up to 30% while PGD2, PGF2 and 6-keto-PGF1 synthesis was not affected. This effect of prolactin was maximal when PGE2 synthesis was estimated 30 minutes after prolactin addition and diminished after two hours. These results suggest that rainbow trout gills possess the ability to metabolize AA through the cyclooxygenase and lipoxygenase pathways. PGE2 synthesis may be under the influence of ion balance and prolactin availability, indicating the probable involvement of AA metabolites in the regulation of ion balances across the gill membrane. 相似文献
152.
Tariq Mahmood Muhammad H. Rahman Gary R. Stringam Francis Yeh Allen Good 《Euphytica》2005,144(1-2):157-167
A population of 112 F1-derived doubled haploid lines was produced from a reciprocal cross of Brassica juncea. The parents differed for seed quality, seed color and many agronomic traits. A detailed RFLP linkage map of this population,
comprising 316 loci, had been constructed, and was used to map quantitative trait loci (QTL) for seed yield and yield components,
viz. siliqua length, number of seeds per siliqua, number of siliques per main raceme and 1000-seed weight. Stable and significant
QTLs were identified for all these yield components except seed yield. For yield components, a selection index based on combined
phenotypic and molecular data (QTL effects) could double up the efficiency of selection compared to the expected genetic advance
by phenotypic selection. Selection indices for high seed yield, based on the phenotypic data of yield and yield components,
could only improve the efficiency of selection by 4% of the genetic advance that can be expected from direct phenotypic selection
for yield alone. Inclusion of molecular data together with the phenotypic data of yield components in the selection indices
did not improve the efficiency of selection for higher seed yield. This is probably due to often negative relationships among
the yield components. Most of the QTLs for yield components were compensating each other, probably due to linkage, pleiotropy
or developmentally induced relationships among them. The breeding strategy for B. juncea and challenges to marker assisted selection are discussed. 相似文献
153.
154.
Muhammad Nadeem ASHRAF Cheng HU Xiangru XU Tariq AZIZ Lei WU Muhammad Ahmed WAQAS Muhammad FAROOQ Xu HU Wenju ZHANG Minggang XU 《土壤圈》2023,33(2):343-354
Soil organic carbon(SOC) and nitrogen(N) mineralization are important biogeochemical processes associated with soil fertility. These processes are influenced by physically, chemically, and biologically stabilized SOC fractions, the mechanisms of which are not well known. The present study was conducted to evaluate the combined effect of manure and mineral fertilizers on the contents of SOC fractions to promote the mineralization of SOC and N.Treatments included: i) no fertilizer control(CK); ii)... 相似文献