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Nitric oxide synthesis in the CNS endothelium and macrophages differs in its sensitivity to inhibition by arginine analogues. 总被引:9,自引:0,他引:9
L E Lambert J P Whitten B M Baron H C Cheng N S Doherty I A McDonald 《Life sciences》1991,48(1):69-75
Inhibition of nitric oxide production by arginine analogues was examined in three cell systems; macrophages, CNS tissue and endothelial cells. Nitric oxide production was assessed indirectly using in vitro assays measuring nitrite production (macrophages), cGMP elevation (CNS) and acetylcholine-induced relaxation of aortic ring segments (endothelium). NG-monomethyl-L-arginine and NG-amino-L-arginine possessed similar inhibitory activity in all three assays, while NG-nitro-L-arginine displayed a striking selectivity for inhibition of brain and endothelial cell nitric oxide synthesis, with IC50 values of 0.05 microM in the CNS versus 200 microM in macrophages. These results suggest that distinct enzymes are responsible for nitric oxide synthesis in different cell types, and indicate that it may be possible to selectively modulate nitric oxide production in vivo. 相似文献
3.
When carrot cell cultures, after growth in semicontinuous culture, were transferred to media containing excess nutrients, they grew at different rates. The growth rates were generally higher after semicontinuous culture at higher dilution rates. There appears to be a limit on dilution rate above which growth rate does not increase. These changes were also displayed by clones from the parental culture. The possibility that these changes in growth rate reflect a need for the cultures to adapt to their new conditions is discussed. The growth rates of the cultures is markedly increased at 25 degrees C compared with 22 degrees C with little further increase at 28 degrees C. Growth rate is altered by less than 20% when pH is changed from 4.5 to either 5.5 or 4.2. The rates of anthocyanin accumulation by the cultures were similar under all conditions tested except at 22 degrees C. They were larger than the rates of dry weight accumulation. In contrast, the amounts of anthocyanin accumulated in the clones and in the parental cultures grown at pH 5.5 instead of pH 4.5 were very different. The observations were interpreted as showing that the clones differ in the rate of metabolism but not in the rate of synthesis of anthocyanins and that at pH 5.5 the rate of metabolism of anthocyanins but not the rate of synthesis is higher than it is at pH 4.5. The use of semicontinuous cultures as a source of inoculum for batch cultures rather than as a source of biomass for extraction of chemicals is discussed. 相似文献
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A reevaluation of floral and vegetative morphology together with data from analysis of floral fragrance and flavonoid co-pigment
chemistry suggest that specific status is warranted for the two kinds ofPhalaenopsis violacea Witte known informally as the “Bornean type” and the “Malayan type.”Phalaenopsis violacea var.bellina Rchb.f. is elevated to specific rank, providing a name for the “Bornean type” plants. 相似文献
6.
The accumulation of anthocyanin by clones and subclones from a cell suspension culture of wild carrot (Daucus carota L.) has been measured under standard conditions. Clones which accumulate low amounts of anthocyanin were shown, by recloning after maintenance by serial passage, to have become heterogenous and to contain cells with increased accumulation of anthocyanin. There appears to be a maximum amount of anthocyanin that clones can accumulate. Clones which accumulate the maximum amount of anthocyanin were shown by recloning after maintenance by serial passaging, to have become heterogenous and to contain many cells which accumulate less than the maximum possible amount of anthocyanin. When clones which accumulate the maximum amount of anthocyanin are maintained by serial passage, the decline in anthocyanin accumulation is different in different media. The results indicate that the changes in the ability of cells to accumulate anthocyanin involve no qualitative change in the genetic information of the cells, i.e., the changes are not the consequence of mutations. 相似文献
7.
W. Mark Whitten 《American journal of botany》1981,68(3):435-442
Monarda didyma L. and M. clinopodia L. occasionally form introgressive populations in the mountains of eastern Tennessee and western North Carolina. Monarda didyma produces large red scentless nectar-rich flowers and is pollinated primarily by the Ruby-throated Hummingbird (Archilochus colubris [Linnaeus]). The smaller, white, scented flowers of Monarda clinopodia produce small amounts of nectar and are pollinated mainly by bumblebees (Bombus spp.). The two species are highly interfertile and have strongly overlapping flowering periods. Differences in pollinator sets and pollinator constancy appear to be only partial barriers to hybridization. Lack of suitable habitats for the establishment of hybrid progeny might be the most important isolating mechanism between the two species. 相似文献
8.
G. HOLSBEEK J. MERGEAY H. HOTZ J. PLÖTNER F. A. M. VOLCKAERT L. DE MEESTER 《Molecular ecology》2008,17(23):5023-5035
In Western Europe, many pond owners introduce amphibians for ornamental purposes. Although indigenous amphibians are legally protected in most European countries, retailers are circumventing national and international legislation by selling exotic nonprotected sibling species. We investigated to what extent non‐native species of the European water frog complex (genus Pelophylax) have become established in Belgium, using morphological, mitochondrial and nuclear genetic markers. A survey of 87 sampling sites showed the presence of non‐native water frogs at 47 locations, mostly Marsh frogs (Pelophylax ridibundus). Surprisingly, at least 19% of all these locations also harboured individuals with mitochondrial haplotypes characteristic of Anatolian water frogs (Pelophylax cf. bedriagae). Nuclear genotyping indicated widespread hybridization and introgression between P. ridibundus and P. cf. bedriagae. In addition, water frogs of Turkish origin obtained through a licensed retailer, also contained P. ridibundus and P. cf. bedriagae, with identical haplotypes to the wild Belgian populations. Although P. ridibundus might have invaded Belgium by natural range expansion from neighbouring countries, our results suggest that its invasion was at least partly enhanced by commercial trade, with origins as far as the Middle East. Also the invasion and rapid spread of Anatolian lineages, masked by their high morphological similarity to P. ridibundus, is likely the result of unregulated commercial trade. We expect that Anatolian frogs will further invade the exotic as well as the native range of P. ridibundus and other Pelophylax species elsewhere in Western and Central Europe, with risks of large‐scale hybridization and introgression. 相似文献
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