The synthesis of amino-acid functionalized beta-carbolines as topoisomerase II inhibitors

The synthesis and biological activity of amino acid functionalized beta-carboline derivatives, which are structurally related to azatoxin and the tryprostatins, are reported. These compounds were assayed for their growth inhibition properties in H520 and PC3 cell lines and were examined for their abilities to inhibit topoisomerase II-mediated DNA relaxation.     

A lead-gill binding model to predict acute lead toxicity to rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss, approximately 2 g) were exposed to 0.6-1.0 microM Pb (125-200 microgl(-1)) for 3 h in ion-poor water. Complexing ligands (citrate, ethylenediamine, organic matter (OM)) or competing cations (Ca, Mg, Na) were added to the water. After exposure, trout gills were removed and analyzed for accumulated Pb. From these exposures, a conditional equilibrium binding constant (K) for Pb-gill binding was calculated (log K(Pb-gillPb)=6.0), plus conditional binding constants for cationic competition at the Pb binding sites and for Pb binding to OM in the water. These log K values were entered into the MINEQL+ aquatic chemistry equilibrium program, to calculate binding of Pb by trout gills. Two versions of the Pb-gill binding model were generated, one of which took into account OM quality as indicated by a simple measure of OM aromaticity, the specific absorption coefficient. The two model versions were tested against acute Pb toxicity (as the time to reach 50% fish mortality; LT50) during 1-week exposures of trout to 3.9 microM Pb in water collected from across southern Ontario. Both versions of the model generated highly significant correlations between the LT50 values and gill Pb concentrations calculated from measured exposure water chemistry, with the OM quality version correlating slightly better. Water pH also correlated well with the LT50 values, because the Pb exposures were in the pH range (7-8) where there is a nearly linear relationship between water pH and inorganic complexation of Pb. Advantages of the Pb-gill binding model include its completeness and the flexibility inherent in its conceptual framework, for example the inclusion of competition by Ca and H(+) for Pb binding sites on gills, and inclusion of complexation of Pb in the water column by natural OM and by carbonate.     

A difference in optomotor behaviour of two Antarctic nototheniid fishes is correlated with the presence of a choroid<Emphasis Type="Italic"> rete mirabile</Emphasis> and Root effect

The hypothesis that fish vision is influenced by the presence of a choroid rete mirabile (an oxygen-concentrating apparatus in the eye) and the Root effect was tested using the optomotor response in two nototheniid species from Antarctica. Pagothenia borchgrevinki, an active cryopelagic zooplanktivore, does not exhibit a major Root effect and the rete is absent. In contrast, the sluggish, benthic nototheniid, Trematomus bernacchii, possesses both a rete and a significant Root effect. Whole-eye ocular PO2 was higher in T. bernacchii (18.6 kPa) than in P. borchgrevinki (18.1 kPa) and the optomotor response of T. bernacchii was positively influenced by subtended angle on a moving background whereas P. borchgrevinki did not respond to any subtended angle (0–600 min of arc). The optomotor response of T. bernacchii may therefore have been facilitated by elevated ocular PO2 due to the presence of the choroid rete and the Root effect.     

Patch-clamp experiments with porins extracted from a marine bacterium (Photobacterium profundum strain SS9) and reconstituted in liposomes

The reconstitution of bacterial porins in liposome bilayers for patch-clamp recording is well established. However, the solutions used in the dehydration, rehydration, and osmotic swelling of the liposomes have been developed for porins from enteric bacteria. Porins from marine bacteria normally function in contact with seawater whose ionic composition and osmotic pressure would appear to be incompatible with the established methods. Here, we show that, contrary to expectation, an established reconstitution and patch-clamp method works well with porins, mainly OmpH and OmpL, extracted from the deep-sea marine bacterium Photobacterium profundum strain SS9 and that seawater can be introduced at a supplementary stage.     

Increased levels of cytosolic phospholipase A2 in dyslexics

Research findings are increasingly reporting evidence of physiological abnormalities in dyslexia and sites for dyslexia have been identified on three chromosomes. It has been suggested that genetic inheritance may cause phospholipid abnormalities in dyslexia somewhat similar to those found in schizophrenia. A key enzyme in phospholipid metabolism, Type IV, or cytosolic, phospholipase A2 (cPLA2), releases arachidonic acid (AA), a 20-carbon fatty acid, which is the major source of production of prostaglandins and leukotrienes. An entirely new assay, which for the first time has enabled determination of the amount of the enzyme rather than its activity, was used to measure cPLA2 in dyslexic-type adults and controls and the two groups were found to differ significantly, the dyslexic-types having more of the enzyme. A report elsewhere of schizophrenics having even greater amounts of the enzyme suggests that dyslexia may be on a continuum with schizophrenia, as may be other neurodevelopmental disorders - which have also been described as phospholipid spectrum disorders.     

Nucleotide chain length and the morphology of complexes with cationic amphiphiles: (31)P-NMR observations

31P-NMR and UV spectroscopies were used to study the interactions between cationic amphiphile-containing lipid bilayers and either a phosphorothioate oligonucleotide (OligoS) (n=21) or polyadenylic acid (PolyA) (n approximately 18,000). Multilamellar vesicles (MLVs) were composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) in binary mixture with either of the cationic lipids, N-[1-(2, 3-dioleoyloxy)propyl]-N',N',N'-trimethylammonium chloride (DOTAP) or cetyltrimethylammonium bromide (CTAB). A UV-difference assay showed that OligoS binding ceased above a 1:1 anion/cation ratio, while PolyA binding continued until a 2:1 ratio was reached, indicating a 'flat' conformation for bound OligoS, but not necessarily for PolyA. Cross-polarization (31)P-NMR of the nucleotide chains bound to 100% DOTAP MLVs produced spectra virtually identical to those of dry powders of OligoS or PolyA, indicating effective immobilization of the surface-bound nucleotide chains. Hahn echo (31)P-NMR showed that MLVs composed of binary mixtures of POPC with DOTAP or CTAB retained a lamellar bilayer architecture upon adding nucleotide chains. At less than stoichiometric anion/cation ratios little or no signal attributable to free nucleotide chains was visible. A narrow signal at the chemical shift expected for phosphorothiodiesters or phosphodiesters became visible at greater levels of added OligoS or PolyA, respectively, indicating the presence of mobile nucleotide chains. Salt addition caused complete desorption of the nucleotide chains. When POPC was replaced with DOPE, binding of OligoS or PolyA produced non-bilayer lipid phases in the presence of DOTAP, but not in the presence of CTAB.