A lot of anticancer agents have been isolated from natural sources, especially from microorganisms and plants. However, there is no special type of compounds for cancer therapy. Various types of substances are effective for various types of cancers and tumors : for instance, alka1oids, lignans, terpenes and steroids, etc. In this report, the authors will describe especially about higher plants.
This review summarizes the regulatory mechanisms and physiological functions of the novel sub-pS Cl-channel (0.3 pS) that is present abundantly in the basolateral membrane of rabbit gastric parietal cells. The sub-pS Cl- channel is voltage-independent and inhibited by NPPB, a Cl- channel blocker. We found that this gastric Cl- channel is linked to three important physiological roles. First, the sub-pS Cl- channel has a housekeeping role through dominating the cell membrane potential. Although several types of cation channels are present, they do not significantly contribute to the membrane potential in the parietal cells. Second, the Cl- channel is activated by prostaglandin E2 via the EP3 receptor/Ca2+/nitric oxide (NO)/cGMP pathway. A vasodilator ecabapide also activates the channel by increasing the intracellular cGMP content. The NO/cGMP pathway-mediated opening of the sub-pS Cl- channel is essential for cytoprotection against ethanol-induced damage in the gastric parietal cells. The NO/cGMP-elicited cytoprotection is abolished by NPPB. To our knowledge, this Cl- channel is the first identified target for the cytoprotective NO/cGMP pathway. Third, the sub-pS Cl- channel is inhibited by the GTP-binding protein-mediated intracellular production of superoxide anion. Hydrogen peroxide and hydroxyl radicals have no effect on the channel activity. The intracellular superoxide anion acts as a messenger in the negative regulatory mechanism of the sub-pS Cl- channel. The similar sub-pS Cl- channel is also found in rat gastric parietal cells.
Analytical ultracentrifuges, XL-A and XL-I, developed by Beckman Company now find a broad application not only in universities but also in industries. Especially they are utilized conveniently in industries aiming at the development of proteins as a therapeutic drug or in those targeting drugs composed of small molecules developed on the basis of the structures of proteins. Sedimentation techniques can be used 1) to determine the molecular weight of proteins in solution, 2) to examine protein aggregation, 3) to evaluate the molecular shape of proteins, 4) to study the interaction of proteins, e.g. between ligands and receptors, and 5) to obtain insight into biological functions of homologous proteins. Application of this technique to molecular biology and pharmaceutical science will be reviewed with ample examples.
Synthetic phenylurea derivatives such as N-phenyl-N'-(4-pyridyl)urea (4PU) and N-(2-chloro-4-pyridyl)-N'-phenylurea (4PU30) have strong cytokinin activities. Using tritiated 4PU30 as a probe, we found the presence of a cytokinin-specific binding protein (CSBP) with high affinity for 4PU30 (Ka for 4PU30=4×1010M-1) in the soluble fraction of etiolated mung bean seedlings. We purified CSBP by the use of 4PU-Sepharose 4B, an affinity gel ligated with 4PU. Analysis of its cDNA revealed that CSBP was a novel member of a major pollen allergen/pathogenesis-related protein family with a calculated molecular weight of 17 kDa. Recombinant CSBP was expressed in Escherichia coli was confirmed to bind specifically to cytokinins.