Exogenously applied

Antagonist. A drug that blocks the biologic effects of an endogenous substance or exogenously applied drug. 

Figure 1.9 Comparison of the effects of an endogenously released and exogenously applied neurotransmitter on neuronal activity (identity of action). Recordings are made either of neuronal firing (extracellularly, A) or of membrane potential (intracellularly, B). The proposed transmitter is applied by iontophoresis, although in a brain slice preparation it can be added to the bathing medium. In this instance the applied neurotransmitter produces an inhibition, like that of nerve stimulation, as monitored by both recordings and both are affected similarly by the antagonist. The applied neurotransmitter thus behaves like and is probably identical to that released from the nerve...

Exogenously applied SIP binds to specific GPCRs to activate multiple signal transduction pathways. Additionally, some SIP could be taken up... 

The use of allelochemicals may overcome one of many long-term drawbacks of synthetic agrochemicals, namely the unnatural excessive application of these chemicals. Such an application can be counterproductive at times, in that the process of exogenously applying a high selection pressure of chemicals can cause rapid selection for organisms resistant to these agrochemicals, and thereby defeat the objective. However, such interim measures are, at times, necessary. 

Because selective detoxication by a crop plant would be important if allelochemlcals are to be useful as natural herbicides, the first objective of these studies was to determine if the cereal oats can metabolize exogenously applied salicylic acid, a known allelopathio agent. The second objective was to identify and partially purify any enzyme responsible for such metabolism of salicylic acid in oat roots. 

Translation arrest or nuclease digestion by exogenously applied antisense oligonucleotides or by antisense mRNA produced from DNA delivered by a plasmid. Heterogeneous nuclear RNA is hnRNA. 

In TPM, fluorescence emission of a fluorophore (either intrinsic to the sample or an exogenously applied chromophore) is detected. A fluorophore is used to obtain specific chemical information in the skin, as discussed in more detail below. To excite the fluorophore, two-photon excitation is used, which is achieved by the simultaneous... 

Interestingly, the conversion of 3-dehydro-24-e/ i-teasterone to 24-epi-teasterone follows the opposite direction of the proposed biosynthesis pathway. Feeding experiments support this observation Exogenously applied 3-dehydro-24-e/ /-teasterone was converted to 24-epj-teasterone as the major metabolite (95%), and to only traces (5%) of 24-epi-typhasterol [23]. Thus, it is very likely that there is a different pathway in tomato cell cultures. In addition, preliminary studies with protein extracts of Arabidopsis cell cultures also reveal differences in enzyme distribution and specificity depending on the origin of the culture [Winter, unpublished]. 

Nevertheless, there are many questions still open because of problems to detect enzyme activities corresponding to each step of the pathway. The model of biosynthesis pathway was put together by studying the metabolism of exogenously applied intermediates in cell cultures of various origins and combining these results with data of native brassinosteroid patterns. It is more or less accepted that there are three pathways in parallel, the early and the late C6 oxidation pathway, as well as the 24/ -epimers follow ing the same route. Some observations in the analysis of native brassinosteroid patterns suggest a possible connection between the pathways. It was shown that seeds of Arabidopsis contain castasterone and 24-epi-brassinolide [34]. Also members of both 24-epimers, brassinolide and 24-epi-brassinolide were detected in tomato seeds [Winter, unpublished]. 

A number of exogenously applied chemicals, including polyacrylic acid, acetylsalicylic acid, salicylic acid and isonicotinic acid (NA) derivatives, have also been shown to induce resistance. Usually the resistance is localised to the treated parts of the plants (Gianinazzi Kassanis, 1974 White, 1979), but in the IN A compounds the resistance can be systemic (Metraux et al., 1991). These observations led to the suggestion that SAR might provide a new strategy for crop protection, either by discovering... 

Swaaij, van A.C., Jacobsen, E. Feenstra, W.J. (1985). Effect of cold hardening, wilting and exogenously applied proline on leaf proline content and frost tolerance of several genotypes of Solanum. Physio-logia Plantarum 64, 230-6. 

Tamogami, S., Rakwal, R., Kodama, O. Phytoalexin production elidted by exogenously applied jasmonic add in rice leaves (Oryza sativa L.) is under the control of cytokinins and ascorbic add. FEBS Lett 1997b 412 61-64. 

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