MRNA levels, changes

Maximal levels of IL-1 /3 mRNA are detected within 1 h exposure to GM-CSF levels then decline to about 50% of maximal by 2 h and then fall to near base-line levels by 8 h (Fig. 7.10). Similarly, levels of IL-1 j8 protein are transiently expressed, broadly following the changes in mRNA levels. Thus, levels of antigenically-detectable protein are maximal by 2-4 h (in cell extracts) and are detected extracellularly in the culture medium by 4 h. Whilst IL-1 (IL-1 a and IL-1/) at 1 ng/ml) and TNF (at 5 ng/ml) are capable of stimulating an increase in IL-1/) mRNA levels, they can synergise with... 

Pauly JR, Stitzel JA, Marks MJ, Collins AC (1989) An autoradiographic analysis of cholinergic receptors in mouse brain. Brain Res BuU 22 453 59 Pauly JR, Marks MJ, Robinson SF, van de Kamp JL, Collins AC (1996) Chronic nicotine and mecamylamine treatment increase brain nicotinic receptor binding without changing alpha 4 or beta 2 mRNA levels. J Pharmacol Exp Ther 278 361-369 Perkins K, Sayette M, Conklin C, Caggiula A (2003) Placebo effects of tobacco smoking and other nicotine intake. Nicotine Tob Res 5 695-709... 

Toxicogenomics tries to assess the toxicity and safety of chemical compounds by analyzing gene expression changes detected by measuring mRNA levels using DNA microarrays (1,2). 

The time- and concentration-dependent inhibitory and stimulatory effects of IL-1 on insulin secretion by islets are paralleled by similar changes in preproinsulin mRNA levels. Treatment of rat islets with concentrations of IL-1 that inhibit insulin sectetion reduce preproinsulin mRNA content. Conditions of IL-1 treatment which stimulate insulin secretion increase preproinsulin mRNA content of islets (Spinas et al., 1987 Eizirilc, et al., 1990). Islet-cell replication is also inhibited by exposure to IL-1. The importance of these findings are unknown, although increases in preproinsulin mRNA levels have been suggested to participate in lL-1-induced stimulation of glucose-induced insulin secretion (Spinas et al., 1987). The reduction of preproinsulin mRNA levels by lL-1 treatment on the other hand does not appear to participate in IL-1-induced inhibition of glucose-stimulated insulin secretion (see below). 

Another important issue is what can be used to predict change in protein levels. In a review of the literature, it is apparent from the measurements in yeast and mouse liver that there is yet no strong correlation between mRNA level and that of proteins, especially in the case of poorly expressed genes. Therefore, conducting gene expression measurements may not be sufficient to infer protein expression. Thus, the analytical methods used in proteomics must provide detection of proteomes present in multiple-modified forms at relatively low levels. 

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