Biochemical characteristics of a preneoplastic marker enzyme glutathione S-transferase P-form(7-7)

Investigation of biochemical characteristics of the glutathione S-transferase P-form (GST 7-7), a specific marker enzyme for preneoplastic cells arising during chemical hepatocarcinogenesis in the rat, revealed distinct functional differential from six other major GST forms. While the GST 7-7 substrate specificity was generally broader, binding ability for diverse organic anions such as bilirubin, hematin, and sulfobromophthalein was as high as in any of the other six forms. Furthermore, the enzymatic activity of GST 7-7 was found to be highly insensitive to the inhibitory actions of a wide range of organic anions at physiological pH in contrast to the other forms which proved more susceptible. The functional characteristics of GST 7-7 may in part account for its overproduction in the preneoplastic cells.     

Clinical significance of gene amplification studied in human neuroblastoma xenografts: relationship with tumor growth rate, chemotherapeutic sensitivities and levels of neuron-specific enolase

Tumor doubling time, sensitivity to chemotherapeutic agents and concentrations of neuron-specific enolase were studied in nine human neuroblastoma xenografts, in which amplifications of N-myc, clones 8 and G21 were known; N-myc was amplified in eight, clone 8 in five and clone G21 in four of these nine xenografts. Tumor doubling time was longest in one xenograft, TNB10, which lacks the amplification of either N-myc or clone 8 or G21, and shortest in TNB1 in which all three DNA sequences are amplified with a DNA rearrangement in clone 8. No correlations were found between genomic amplification of N-myc, clones 8 and G21 and effectiveness of five chemotherapeutic drugs tested, except for cis-platinum. cis-Platinum was found to be effective on all but the one xenograft, TNB10, with the longest tumor doubling time. Concentration of neuron-specific enolase in tumor extract was lowest in TNB1 and correlated with the length of the tumor doubling time.     

Nonlethal G0-ts mutant tsJT60 becomes lethal at the nonpermissive temperature after transformation: a hint for new cancer chemotherapeutics

tsJT60 is a nonlethal temperature-sensitive (ts) mutant of a Fischer rat cell line (3Y1) classified as a G0 mutant; i.e., the ts defect is not expressed within the cell growth cycle but is expressed only between the G0 and S phase. tsJT60 clones transformed with oncogenes such as adenovirus E1A, polyoma large T, polyoma middle T, v-Ki-ras, and LTR activated c-myc, or with a chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine, grew well at 34 degrees C. However, most of these clones grew slowly at 40 degrees C, producing many floating dead cells, and some clones were killed at 40 degrees C. When they were cultured under conditions inadequate for growth of untransformed cells, such as high cell density or serum restriction, they were killed at 40 degrees C. These and previous results from SV40- and adenovirus-transformed tsJT60 clones favour the idea that transformed tsJT60 cells occasionally enter the G0 phase and are metabolically imbalanced at 40 degrees C during self-stimulation from the G0 to S phase. We propose that a drug which exclusively block, G0-G1 transition would be cytocidal to transformed cells but cytostatic to normal cells.     

Prodigiosin-25 C

A water-insoluble red antibiotic pigment was isolated from mycelia of a strain of Streptomyces. It was found that the pigment is a new C₂₅-prodigiosin-analogue and the authors propose to designate it prodigiosin-25 C. The chemical structure (XI) has been deduced from visible absorption spectra, NMR spectra, mass spectra and analysis of degradation products of the pigment.     

Oxygenation of cobalt(II) protoporphyrin IX dimethyl ester bound to copolymer of 4-vinylpyridine and styrene

The polymeric cobalt(II) porphyrin complexes were prepared from cobalt(II) protoporphyrin IX dimethyl ester(Co(II)P) and copolymers of 4-vinylpyridine and styrene(PSP), and their binding ability of molecular oxygen was studied in toluene solution. The five- and six-coordinate structure of CoP-PSP complexes were confirmed by esr spectra. The esr parameters for the CoP-PSP complexes were not affected by the molecular weight and the vinylpyridine-unit content of PSP-ligand. The 1:1 dioxygen-Co complex was reversibly formed when the solution of CoP-PSP was exposed to oxygen atmosphere at low temperature. While the visible spectra and esr parameters for the dioxygen complexes of CoP-PSP were the same as those of the CoP-pyridine complex, the equilibrium constant for the oxygen binding increased with the vinylpyridine-unit content of the PSP-ligand. The larger entropy change was observed for the oxygenation in the CoP-PSP system especially, of which the vinylpyridine-unit content was large.     

Novel Zn2+ Modulated GPR39 Receptor Agonists Do Not Drive Acute Insulin Secretion in Rodents

Type 2 diabetes (T2D) occurs when there is insufficient insulin release to control blood glucose, due to insulin resistance and impaired β-cell function. The GPR39 receptor is expressed in metabolic tissues including pancreatic β-cells and has been proposed as a T2D target. Specifically, GPR39 agonists might improve β-cell function leading to more adequate and sustained insulin release and glucose control. The present study aimed to test the hypothesis that GPR39 agonism would improve glucose stimulated insulin secretion in vivo. A high throughput screen, followed by a medicinal chemistry program, identified three novel potent Zn²⁺ modulated GPR39 agonists. These agonists were evaluated in acute rodent glucose tolerance tests. The results showed a lack of glucose lowering and insulinotropic effects not only in lean mice, but also in diet-induced obese (DIO) mice and Zucker fatty rats. It is concluded that Zn²⁺ modulated GPR39 agonists do not acutely stimulate insulin release in rodents.     

Cooperative reactions of poly-L-lysine-heme complex with molecular oxygen, carbon monoxide, or cyanide ion.

The interaction of the alpha-helical poly-L-lysine-heme complex with molecular oxygen, carbon monoxide, or cyanide ion was studied. Binding equilibrium curve and activation parameters for the reactions were determined. Sigmoid responses were observed for the absorption of molecular oxygen or carbon monoxide by the complex and the cooperative parameter was found to be 2.1. This indicated a cooperative interaction between hemes situated on a cylindrical alpha-helix of poly-L-lysine. But those of other polymer-ligand-heme complexes were 1.0. The cooperative reaction mechanism, in which an alpha-helical poly-L-lysine plays an important role, was suggested.