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Publisher Summary To cover fully the system for effective cell-free translations of elastin mRNAs, the methodology is divided into four sections dealing with (1) isolation of RNA and preparation of mRNA, (2) preparation of the mRNA-dependent reticulocyte lysate and optimal conditions for the cell-free translation of elastin mRNAs, (3) identification of tropoelastins in a cell-free translation assay, and (4) quantitation of tropoelastins in the cell-free translation system. It is important to note that the discussion of the cell-free synthesis of elastin involves the synthesis of two proteins designated tropoelastins a and b. All the evidence to date suggests strongly that these two tropoelastins are separate gene products. Consequently, the methodologies described are geared not only for the production of soluble elastin, but also for the separate identification of tropoelastins a and b.

Pancreas-specific messenger RNAs, in particular that for amylase, have been measured during the course of development. In addition the modulation of specific gene expression during differentiation in vitro by bromodeoxyuridine and the glucocorticoid, dexamethasone, has been examined. BrdU depresses the accumulation of all of the tissue-specific mRNAs. Dexamethasone selectively increases the concentration of amylase mRNA. Changes in the levels of mRNAs correlate directly with changes in the levels of pancreas-specific proteins. Pancreatic rudiments release into the incubation medium a characteristic subset of cellular proteins. Some of these, including amylase, represent the secretory digestive (pro)enzymes. Another group of proteins are also released by immature rudiments which have not yet accumulated the digestive enzymes. Some of these proteins persist throughout development and may be diagnostic of and functionally associated with pancreatic differentiation.