Increased endothelial cell selectivity of triazole-bridged dihalogenated A-ring analogues of combretastatin A-1

The antiproliferative activity on ovarian cancer (SK-OV-3) cells of a series of triazole-bridged combretastatin analogues (37, 38, 40-43) containing dihalogenation of the A-ring is reported, and compared with their trimethoxy analogues (5, 15, 39). It was found that dihalogenation with either bromine or iodine was a tolerated modification when compared to the parent compound combretastatin (CA-4, 1) and had less effect than B-ring modification on potency. These compounds exhibited G(2)/M arrest, and maintained antitubulin activity. Further assays on human umbilical vein endothelial cells (HUVECs) demonstrated the potential antivascular effects of these triazoles. Of particular note was a 3,5-diiodo-4-methoxyaryl triazole (43) which had promising 7-fold selectivity for HUVECs over ovarian cancer cells.     

Identification and cardiotropic actions of brain/gut-derived tachykinin-related peptides (TRPs) from the American lobster Homarus americanus

Two tachykinin-related peptides (TRPs) are known in decapods, APSGFLGMRamide and TPSGFLGMRamide. The former peptide appears to be ubiquitously conserved in members of this taxon, while the latter has been suggested to be a genus (Cancer)- or infraorder (Brachyura)-specific isoform. Here, we characterized a cDNA from the American lobster Homarus americanus (infraorder Astacidea) that encodes both TRPs: six copies of APSGFLGMRamide and one of TPSGFLGMRamide. Mass spectral analyses of the H. americanus supraoesophageal ganglion (brain) and commissural ganglia confirmed the presence of both peptides in these neural tissues; both isoforms were also detected in the midgut. Physiological experiments showed that both APSGFLGMRamide and TPSGFLGMRamide are cardioactive in H. americanus, eliciting identical increases in both heart contraction frequency and amplitude. Collectively, our data represent the first genetic confirmation of TRPs in H. americanus and of TPSGFLGMRamide in any species, demonstrate that TPSGFLGMRamide is not restricted to brachyurans, and show that both this peptide and APSGFLGMRamide are brain-gut isoforms, the first peptides thus far confirmed to possess this dual tissue distribution in H. americanus. Our data also suggest a possible role for TRPs in modulating the output of the lobster heart.     

Future directions in plant hormone research

Future directions in plant hormone research are discussed, with particular reference to the regulation of hormone biosynthesis, hormone perception, and signal transduction.