In an investigation conducted over 5 years, tests of samples from the Scottish Seed Potato Classification Scheme showed that when monoclonal antibodies (McABs) were used with the enzyme‐linked immunosorbent assay (ELISA), they reliably detected the tobacco veinal necrosis strain of potato virus Y (PVYN). Polyclonal antibodies used in the first 3 years of the investigation were unreliable in differentiating PVYN from the ordinary strain (PVYN). It is suggested that ELISA and McABs be routinely used to diagnose PVYN and that all samples which give negative results be further assayed biologically to identify the virus or to indicate strains of PVYN not detectable by the McAB. Problems encountered with both assay systems are discussed.
The protein product of the early response gene, Egr-1, is required for macrophage differentiation. Egr-1 mRNA is induced by lipopolysaccharide within minutes in murine peritoneal macrophages through an effect on the rate of transcription of Egr-1. Therefore, we undertook a series of studies to characterize Egr-1 protein induced by LPS and to define enhancer elements in the Egr-1 promoter which mediate the effect of LPS in murine macrophages. Salmonella minnesota Re 595 LPS (10 ng/ml or higher) induced Egr-1 protein of 80 kDa within 45 min in thioglycollate-elicited peritoneal macrophages. The promoter region of Egr-1 contains six serum response elements (SRE) which each contain a core CArG box. CAT activity in LPStreated macrophages transfected with Egr-1-CAT constructs containing the two most upstream 5' SREs was increased 4.7-fold whereas CAT activity in macrophages transfected with constructs lacking these two most upstream SREs was not affected by LPS. LPS induced CAT activity in macrophages transfected with constructs containing tetramers of each of the two most 5' SREs upstream of a heterologous promoter linked to CAT. Mutation of the CArG box abolished the effect of LPS. These findings suggest that the CArG box elements within the two most upstream SREs may mediate the effect of LPS on transcription of Egr-1.
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