Frequent Occurrence of HIV-Inhibitory Sulphated Polysaccharides in Marine Invertebrates

Aqueous extracts of many marine invertebrates have exhibited some activity in the National Cancer Institute's primary screen for anti-HIV cytopathicity. Using a variety of techniques, including gel permeation, size exclusion and ion exchange chromatography, toluidine blue metachromicity, 13C-NMR spectroscopy and combustion analyses, we have determined that this activity is largely due to sulphated polysaccharides. Because of the wide occurrence of this class of compounds in these organisms we sought a method for the rapid dereplication of sulphated polysaccharides. It was critical that the method selected for dereplication allow differentiation of anionic polysaccharides from other AIDS-antiviral chemotypes. After evaluating a variety of methods, we found that the most efficient strategy appeared to be precipitation of the polysaccharide fraction from aqueous ethanolic solutions of the crude aqueous extracts.

Can animal performance be predicted from short-term grazing processes?

Despite all the biotic and abiotic factors affecting foraging by ruminants, there is a common and fundamental process, which is bite gathering. We hypothesised that because the mechanics of bite formation dominate the foraging process, changes in short-term bite mass are reflected in longer-term animal performance across a wide range of sward conditions. We focus at the meal level of foraging, using experiments in which the effect of abiotic factors and digestive constrains are minimised, making intake rate the main currency. We estimated bite mass across a wide range of structural challenges to large-herbivore foraging in a long-term experiment with heterogeneous native grasslands. A conceptual model was developed for average daily gain, where energy gain and energy costs were proximate causal variables. Energy gain was a function of diet quality and components of daily intake rate, where bite mass was the main component estimated. In turn, components of intake rate were determined by sward structure and bodyweight. Energy costs were a function of bodyweight and abiotic conditions. Finally, sward structure, bodyweight and abiotic conditions were determined by experimental treatments, seasons and years. Then, the conceptual model was translated into statistical models that included variables measured or estimated, and coefficients representing all links in the conceptual model. Weight gain was a function of bite mass, forage characteristics, and animal and abiotic conditions. Models were set up to test whether forage and stocking conditions affected monthly gain beyond the effects through bite mass, after correcting for abiotic factors. Forage mass, height and disappearance did help predict monthly gain after bite mass was included in the model, which supported our hypothesis. However, stocking treatments and season had significant effects not incorporated in bite mass. Although the model explained 77.9% of liveweight gain variation, only 35.2% was due to fixed effects, with 10.8% accounted by bite mass and its interactions. Concomitant experiments showed that sward structure (first with sward height and the second with tussock cover) does determine bite mass and short-term intake rate in the complex native grasslands we studied. Yet, other temporal varying components of monthly gain not correlated with bite mass, temperature or wind, added most of the observed variation in monthly animal performance. Part of the model failure to account for variation in performance may be related to a significant and temporally variable grazing of tussocks. We used a bite mass model that assumed no tussock grazing. In light of these results and a parallel experiment, we conclude that tussock grazing must be incorporated in future versions of the model.

Optimization of 4-phenylamino-3-quinolinecarbonitriles as potent inhibitors of Src kinase activity

Subsequent to the discovery of 4-[(2,4-dichlorophenyl)amino]-6,7-dimethoxy-3-quinolinecarbonitrile (1a) as an inhibitor of Src kinase activity (IC(50) = 30 nM), several additional analogues were prepared. Optimization of the C-4 anilino group of 1a led to 1c, which contains a 2,4-dichloro-5-methoxy-substituted aniline. Replacement of the methoxy group at C-7 of 1c with a 3-(morpholin-4-yl)propoxy group provided 2c, resulting in increased inhibition of both Src kinase activity and Src-mediated cell proliferation. Analogues of 2c with other trisubstituted anilines at C-4 were also potent Src inhibitors, and the propoxy group of 2c was preferred over ethoxy, butoxy, or pentoxy. Replacement of the morpholine group of 2c with a 4-methylpiperazine group provided 31a, which had an IC(50) of 1.2 nM in the Src enzymatic assay, an IC(50) of 100 nM for the inhibition of Src-dependent cell proliferation and was selective for Src over non-Src family kinases. Compound 31a, which had higher 1 and 4 h plasma levels than 2c, effectively inhibited tumor growth in xenograft models.

Effect of iron supplementation on oxidative stress and intestinal inflammation in rats with acute colitis

In this study, we investigated the effect of intraperitoneal iron dextran (100 mg/100 g body weight) on oxidative stress and intestinal inflammation in rats with acute colitis induced by 5% dextran sulfate sodium. In both colitis and healthy animals, disease activity index, crypt and inflammatory scores, colon length, plasma and colonic lipid peroxides, and plasma vitamins E, C, and retinol were assessed. The results showed that iron-supplemented groups had moderate iron deposition in the colonic submucosa and lamina propria. In the colitis group supplemented with iron, colon length was significantly shorter; disease activity index, crypt, and inflammatory scores and colonic lipid peroxides were significantly higher; and plasma alpha-tocopherol was significantly lower compared to the colitis group without iron supplementation. There was no intestinal inflammation and no significant increase in colonic lipid peroxides in healthy rats supplemented with iron. In conclusion, iron injection resulted in an increased oxidative stress and intestinal inflammation in rats with colitis but not in healthy rats.

Immobilized artificial membrane chromatography with mass spectrometric detection: a rapid method for screening drug-membrane interactions

A high-performance liquid chromatography (HPLC)/electrospray ionization mass spectrometry method for measuring drug-membrane interactions was developed using immobilized artificial membrane (IAM) fast-screening mini-columns. The HPLC mobile phase consisted of phosphate-buffered saline (i.e., 5.0 mM phosphate buffer at pH 7.4, 1.35 mM KCl, and 68.5 mM NaCl) and acetonitrile. This method facilitated the measurement of IAM retention time of over ten compounds in one experiment, significantly reducing analysis time compared with the earlier IAM-HPLC method. The particular electrospray source used demonstrated the ability to tolerate the high salt-containing nonvolatile buffer used for retention time measurement.

Base-catalyzed isomerism in elfamycin antibiotics. Structures of ganefromycins epsilon and epsilon 1

The structures of ganefromycins epsilon (2a) and epsilon 1 (2b) have been determined by spectroscopic techniques. The compounds are isomeric deoxygenated precursors of the parent antibiotics ganefromycins alpha and beta. The nature of the isomerism was determined by chemical interconversion experiments and spectroscope analysis to be a change in configuration at C-21. Evidence is provided for other cases of this type of isomerism in the elfamycin class of antibiotics.

A reinvestigation of Maprounea triterpenes

Anti-HIV activity and the inhibition of phorbol ester receptor binding activity in two species of Maprounea were traced to small amounts of highly potent phorbol esters of the daphnane type. The triterpenes previously isolated from this genus were found to be devoid of biological activity when scrupulously purified. Four new triterpene esters were elucidated; two [3,4] were found in M. africana, while three [4,6,7] were found in M. membranacea. Nmr assignments have also been made for two previously known compounds [2,5] in this group.

Koumbalones A and B, new casbane diterpenes from Maprounea africana

The organic extract of Maprounea africana yielded koumbalones A [1] and B [2], defined by spectral methods as new variations on the casbane ring system. The gross structures, relative configurations, and solution conformations were determined by a combination of spectral analyses and molecular modeling. Because koumbalone A spontaneously converts to koumbalone B at room temperature, koumbalone B may be an artifact of isolation.

A chemical screening strategy for the dereplication and prioritization of HIV-inhibitory aqueous natural products extracts

A relatively high percentage (ca. 15%) of aqueous extracts from terrestrial plants, cyanobacteria, and marine invertebrates and algae has exhibited activity in the National Cancer Institute's primary AIDS-antiviral screen. By removal of anionic polysaccharides in a first stage of dereplication, we have eliminated from further consideration a considerable number of these extracts. However, a still substantial proportion of the active extracts remained, from which we wished to select and prioritize a small percentage for our detailed bioassay-directed fractionation studies. Therefore, a chemical screening protocol, utilizing various solid-phase extraction cartridges, has been developed for a second-stage dereplication and to assist in prioritization of these extracts for our further investigations.

Benzylated 1,2,3-triazoles as anticoccidiostats

Substituted 5-amino-4-carbamoyl-1,2,3-triazoles 3a-w were prepared by two synthetic schemes and evaluated in vivo for anticoccidial activity. Both schemes proceeded by brominating appropriately substituted toluenes 4a-s,v to 5a-s,v. In Scheme I, the brominated benzyl analogues 5 were converted to the corresponding benzyl azides 6, which were treated with cyanoacetamide to yield 1-substituted-5-amino-4-carbamoyl-1,2,3-triazoles 3. In Scheme II, the benzyl halides 5 were employed to alkylate the sodium salt of 5-amino-4-carbamoyl-1,2,3-triazole (7). Preliminary screening data against Eimeria acervulina and E. tenella in chickens suggested structural requirements for maximizing activity. Further evaluation against a relatively resistant series of eight Eimeria field isolates revealed L-651,582 (3a) to be a highly effective coccidiostat. However, unacceptable tissue residues precluded further development. Mechanistic studies on this series of 5-amino-4-carbamoyl-1,2,3-triazoles and, in particular, on L-651,582 (3a) revealed that its mode of action does not involve inhibition of IMP dehydrogenase, but probably interferes with host cell calcium entry. In addition, L-651,582 has been found to have antiproliferative activity in several disease models and was recently reported to possess antimetastatic activity in a model of ovarian cancer progression.

Habituation and sensitization of startle reflexes elicited electrically from the brainstem

Repetitive elicitation of startle-like responses by electrical stimulation of the cochlear nucleus led to sensitization followed by habituation. In contrast, repetitive elicitation of startle-like responses by electrical stimulation of the reticular formation led only to sensitization. Since these different locations represent different points along the acoustic startle circuit, the data suggest that sensitization may be related to the motor side of reflex arcs, whereas habituation may be related to the sensory side.

Improvements in tests of long-range charge independence

The procedure used to determine the pionnucleon coupling constant g(2) from multi-energy fits to nucleon-nucleon (N-N) scattering data has been shortened without a material loss of accuracy. The g(2) presetting effect is discussed in connection with the limited accuracy of g(2) determinations in general and the possibilities of the "optimized polynomial expansions". The desirability of the Yale graded introduction of one-pion exchange (OPE)-to-"searched" transition energies (E(tr)) is brought out. Corrections for virtual discontinuities in phase-shift-energy dependence at the E(tr) decreased the violation of long-range charge independence (LRCI). The effect of two-pion exchange (TPE) has been calculated on the ps theory as approximately 1 for go(2)(p-p) - go(2)(n-p), go(2) = g(2)/[unk]c; a result consistent with LRCI. Searching all phase parameters including g(2) for both isospin values I in g(2) determinations from n-p data, but with fixed I = 1 non-OPE phases as deduced from p-p data in the base search with frozen g(2), the OPE effect of the neutral pion, pi degrees , was separated from that of the charged pion, pi(c). The g(2) for pi(c) in n-p scattering is determined with much better statistical accuracy than that for pi degrees . The overall n-p value of g(2) is nearly equal to that for pi(c). The results suggest that the distinction between p-p and n-p values of g(2), if present, is in first approximation that arising from the difference between pi degrees -N and pi(c)-N couplings. Some limitations on the validity of the conclusions are mentioned.