Indicators of delayed maturation of rat heart treated prenatally with dexamethasone.

We investigated the effects of prenatal dexamethasone treatment on indicators of cardiac maturation: heart weight/body weight ratios, myosin heavy chain (MHC) expression, cell proliferation, and extracellular matrix. We administered dexamethasone, a synthetic glucocorticoid (approximately 48 microg/d, 3-wk slow release pellets), to pregnant rats (n = 8) beginning at 17 d postconception. Control dams were unmanipulated (n = 8).

Cloning and characterization of a pectate lyase gene from Erwinia carotovora EC153.

A pel gene cloned from strain EC153 of Erwinia carotovora encoded a pectate lyase that macerated plant tissue with moderate efficiency. This gene, called pel153, was sequenced and found to possess considerable homology with a pectate lyase gene from Yersinia pseudotuberculosis. The Yersinia protein, however, was truncated at the carboxyl terminal end relative to the Erwinia gene product and had a lower isoelectric point.

Molecular cloning of pectate lyase genes from Erwinia chrysanthemi and their expression in Escherichia coli.

A genomic library of Erwinia chrysanthemi EC16 was constructed in plasmid pHC79, and seven putative pectate lyase (PL) clones in Escherichia coli were selected on pectate agar. Six of the recombinant cosmids contained a common PstI fragment of ca. 8.

A standardized procedure for quantification of the Ames Salmonella/mammalian-microsome mutagenicity test.

Factors determining the precision and variability of the Ames Salmonella test for mutagenicity were investigated. The most important source of variability in the agar-overlay method was nonuniformity in the soft-agar layer thickness. Solution of this problem resulted from application of an agar-leveling table described in this paper.