Cyclization of natural allene oxide in aprotic solvent: formation of the novel oxylipin methyl cis-12-oxo-10-phytoenoate

Allene oxide, (9Z,11E)-12,13-epoxy-9,11-octadecadienoic acid (12,13-EOD), was prepared by incubation of linoleic acid (13S)-hydroperoxide with flaxseed allene oxide synthase (AOS) and purified (as methyl ester) by low temperature HPLC. Identification of pure 12,13-EOD was substantiated by its UV and (1)H NMR spectra and by GC-MS data for its methanol trapping product. The methyl ester of 12,13-EOD (but not the free carboxylic acid) is slowly cyclized in hexane solution, affording a novel cyclopentenone cis-12-oxo-10-phytoenoic acid. Free carboxylic form of 12,13-EOD does not cyclize due to the exceeding formation of macrolactone (9Z)-12-oxo-9-octadecen-11-olide. The spontaneous cyclization of pure natural allene oxide (12,13-EOD) into cis-cyclopentenone have been observed first time.     

Collimonas fungivorans, an unpredicted in vitro but efficient in vivo biocontrol agent for the suppression of tomato foot and root rot

Although bacteria from the genus Collimonas have demonstrated in vitro antifungal activity against many different fungi, they appeared inactive against the plant-pathogenic fungus Fusarium oxysporum f.sp. radicis-lycopersici (Forl), the causal agent of tomato foot and root rot (TFRR). Visualization studies using fluorescently labelled organisms showed that bacterial cells attached extensively to the fungal hyphae under nutrient-poor conditions but not in glucose-rich Armstrong medium. Collimonas fungivorans was shown to be as efficient in colonizing tomato root tips as the excellent colonizer Pseudomonas fluorescens strain WCS365. Furthermore, it appeared to colonize the same sites on the root as did the phytopathogenic fungus. Under greenhouse conditions in potting soil, C. fungivorans performed as well in biocontrol of TFRR as the well-established biocontrol strains P. fluorescens WCS365 and Pseudomonas chlororaphis PCL1391. Moreover, under biocontrol conditions, C. fungivorans did not attach to Forl hyphae colonizing plant roots. Based on these observations, we hypothesize that C. fungivorans mainly controls TFRR through a mechanism of competition for nutrients and niches rather than through its reported mycophagous properties, for which attachment of the bacteria to the fungal hyphae is assumed to be important.     

Effects of inducible overexpression of DNp73alpha on cancer cell growth and response to treatment in vitro and in vivo

The p73 gene has a complex regulation, which leads to the expression of different isoforms, often with opposite biological effects. We have generated in the human colocarcinoma cell line HCT116, expressing a wild-type p53, an inducible DNp73alpha expressing system. Two clones (HCT116/DN3 and HCT116/DN14), upon doxycycline addition, show a strong expression of DNp73alpha. In vitro the two DNp73alpha overexpressing clones grow at similar rate of the control transfected clone (HCT116/8a) and similarly respond to DNA damage. When injected in mice, HCT116/DN3, HCT116/DN14, and HCT116/8a cells grew similarly in the absence or presence of tetracycline. In HCT116/DN3 and HCT116/DN14 tumors, tetracycline induced a strong expression of DNp73alpha both as mRNA and protein. These results indicate that in this system the overexpression of the DNp73alpha does not induce a more aggressive phenotype and does not seem to be associated with a reduced response of the cells to treatment with anticancer agents.     

Mathematical modeling of tumor therapy with oncolytic viruses: Regimes with complete tumor elimination within the framework of deterministic models

Background  

Oncolytic viruses that specifically target tumor cells are promising anti-cancer therapeutic agents. The interaction between an oncolytic virus and tumor cells is amenable to mathematical modeling using adaptations of techniques employed previously for modeling other types of virus-cell interaction.     

Birth and death of protein domains: A simple model of evolution explains power law behavior

Background  

Power distributions appear in numerous biological, physical and other contexts, which appear to be fundamentally different. In biology, power laws have been claimed to describe the distributions of the connections of enzymes and metabolites in metabolic networks, the number of interactions partners of a given protein, the number of members in paralogous families, and other quantities. In network analysis, power laws imply evolution of the network with preferential attachment, i.e. a greater likelihood of nodes being added to pre-existing hubs. Exploration of different types of evolutionary models in an attempt to determine which of them lead to power law distributions has the potential of revealing non-trivial aspects of genome evolution.     

Anaerobic contribution to the time to exhaustion at the minimal exercise intensity at which maximal oxygen uptake occurs in elite cyclists, kayakists and swimmers

Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to the time to exhaustion (t _lim) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (V˙O_{2 max}) occurs (I _{V˙O2 max}) was assessed by analysing the relationship between the t _lim and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of V˙O_{2 max}, the exercise intensity was increased so that each subject reached his I _V˙O2max in 30 s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2 min steps for determining the I _V˙O2max and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure at I _V˙O2max . The AOD for the t _lim exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9–24.1] with significant differences between swimmers and kayakists (16.8% vs 11.5%, P≤0.05) and cyclists and kayakists (16.4% vs 11.5%, P≤0.05). Absolute AOD values ranged from 26.4 ml · kg⁻¹ to 83.6 ml · kg⁻¹ with a mean value of 45.9 (SD 18) ml · kg⁻¹. Considering all the subjects, the t _lim was found to have a positive and significant correlation with AOD (r = 0.62, P≤0.05), and a negative and significant correlation with V˙O_{2 max} (r = −0.46, P≤0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at I _V˙O2max should not be ignored when t _lim is used as a supplementary parameter to evaluate specific adaptation of athletes. Accepted: 17 December 1996