Indomethacin antagonizes the ethanol-induced suppression of breathing activity but not the suppression of brain activity in the near-term fetal sheep

The effect of indomethacin on the ethanol-induced suppression of fetal breathing movements, low-voltage electrocortical (ECoG) activity, and electro-ocular (EOG) activity was studied in the near-term fetal sheep. Ten conscious instrumented pregnant ewes (between 129 and 131 days of gestation; term, 147 days) received 1-h maternal intravenous infusion of 1 g ethanol/kg total body weight and simultaneous fetal treatment with either indomethacin (2 mg/kg fetal body weight/h) (n = 5) or an equivalent volume of phosphate buffer (n = 5) intravenously for 9 h. Fetal ECoG activity, EOG activity, and fetal breathing movements were monitored continuously over the experimental periods. In animals treated with ethanol and buffer (n = 5), fetal breathing movements were suppressed for 8 h and low-voltage ECoG and EOG activity was suppressed for 2 h below preinfusion levels. In animals treated with ethanol and indomethacin (n = 5), fetal breathing movements were elevated for 13 h but low-voltage ECoG and EOG activity remained suppressed for 3 h below preinfusion levels. The data suggests that indomethacin can antagonize the ethanol-induced suppression of fetal breathing movements, but does not alter the ethanol-induced suppression of ECoG or EOG activity.     

Sphingomyelin synthase as a potential target for D609-induced apoptosis in U937 human monocytic leukemia cells

Tricyclodecan-9-yl-xanthogenate (D609) is a selective tumor cytotoxic agent. However, the mechanisms of action of D609 against tumor cells have not been well established. Using U937 human monocytic leukemia cells, we examined the ability of D609 to inhibit sphingomyelin synthase (SMS), since inhibition of SMS may contribute to D609-induced tumor cell cytotoxicity via modulating the cellular levels of ceramide and diacylglycerol (DAG). The results showed that D609 is capable of inducing U937 cell death by apoptosis in a dose- and time-dependent manner. The induction of U937 cell apoptosis was associated with an inhibition of SMS activity and a significant increase in the intracellular level of ceramide and decrease in that of sphingomyelin (SM) and DAG, which resulted in an elevation of the ratio between ceramide and DAG favoring the induction of apoptosis. In addition, incubation of U937 cells with C(6)-ceramide and/or H7 (a selective PKC inhibitor) reduced U937 cell viability; whereas pretreatment of the cells with a PKC activator, PMA or 1-oleoyl-2-acetylglycerol (OAG), attenuated D609-induced U937 cell apoptosis. These results suggest that SMS is a potential target of D609 and inhibition of SMS may contribute to D609-induced tumor cell death via modulation of the cellular levels of ceramide and DAG.     

The composition and timing of flower odour emission by wild <Emphasis Type="Italic">Petunia axillaris</Emphasis> coincide with the antennal perception and nocturnal activity of the pollinator <Emphasis Type="Italic">Manduca sexta</Emphasis>

In the genus Petunia, distinct pollination syndromes may have evolved in association with bee-visitation (P. integrifolia spp.) or hawk moth-visitation (P. axillaris spp). We investigated the extent of congruence between floral fragrance and olfactory perception of the hawk moth Manduca sexta. Hawk moth pollinated P. axillaris releases high levels of several compounds compared to the bee-pollinated P. integrifolia that releases benzaldehyde almost exclusively. The three dominating compounds in P. axillaris were benzaldehyde, benzyl alcohol and methyl benzoate. In P. axillaris, benzenoids showed a circadian rhythm with an emission peak at night, which was absent from P. integrifolia. These characters were highly conserved among different P. axillaris subspecies and P. axillaris accessions, with some differences in fragrance composition. Electroantennogram (EAG) recordings using flower-blends of different wild Petunia species on female M. sexta antennae showed that P. axillaris odours elicited stronger responses than P. integrifolia odours. EAG responses were highest to the three dominating compounds in the P. axillaris flower odours. Further, EAG responses to odour-samples collected from P. axillaris flowers confirmed that odours collected at night evoked stronger responses from M. sexta than odours collected during the day. These results show that timing of odour emissions by P. axillaris is in tune with nocturnal hawk moth activity and that flower-volatile composition is adapted to the antennal perception of these pollinators.     

Human Cytochrome P450 2E1 Structures with Fatty Acid Analogs Reveal a Previously Unobserved Binding Mode

Human microsomal cytochrome P450 (CYP) 2E1 is widely known for its ability to oxidize >70 different, mostly compact, low molecular weight drugs and other xenobiotic compounds. In addition CYP2E1 oxidizes much larger C9–C20 fatty acids that can serve as endogenous signaling molecules. Previously structures of CYP2E1 with small molecules revealed a small, compact CYP2E1 active site, which would be insufficient to accommodate medium and long chain fatty acids without conformational changes in the protein. In the current work we have determined how CYP2E1 can accommodate a series of fatty acid analogs by cocrystallizing CYP2E1 with ω-imidazolyl-octanoic fatty acid, ω-imidazolyl-decanoic fatty acid, and ω-imidazolyl-dodecanoic fatty acid. In each structure direct coordination of the imidazole nitrogen to the heme iron mimics the position required for native fatty acid substrates to yield the ω-1 hydroxylated metabolites that predominate experimentally. In each case rotation of a single Phe²⁹⁸ side chain merges the active site with an adjacent void, significantly altering the active site size and topology to accommodate fatty acids. The binding of these fatty acid ligands is directly opposite the channel to the protein surface and the binding observed for fatty acids in the bacterial cytochrome P450 BM3 (CYP102A1) from Bacillus megaterium. Instead of the BM3-like binding mode in the CYP2E1 channel, these structures reveal interactions between the fatty acid carboxylates and several residues in the F, G, and B′ helices at successive distances from the active site.     

Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake,Alaska

Long-term fertilization of acidic tussock tundra has led to changes in plant species composition, increases in aboveground production and biomass and substantial losses of soil organic carbon (SOC). Root litter is an important input to SOC pools, although little is known about fine root demography in tussock tundra. In this study, we examined the response of fine root production and live standing fine root biomass to short- and long-term fertilization, as changes in fine root demography may contribute to observed declines in SOC. Live standing fine root biomass increased with long-term fertilization, while fine root production declined, reflecting replacement of the annual fine root system of Eriophorum vaginatum, with the long-lived fine roots of Betula nana. Fine root production increased in fertilized plots during an unusually warm growing season, but remained unchanged in control plots, consistent with observations that B. nana shows a positive response to climate warming. Calculations based on a few simple assumptions suggest changes in fine root demography with long-term fertilization and species replacement could account for between 20 and 39% of the observed declines in SOC stocks.     

Impact of urban fragmentation on the genetic structure of the eastern red-backed salamander

Urban development is a major cause of habitat loss and fragmentation. Few studies, however, have dealt with fragmentation in an urban landscape. In this paper, we examine the genetic structure of isolated populations of the eastern red-backed salamander (Plethodon cinereus) in a metropolitan area. We sampled four populations located on a mountain in the heart of Montréal (Québec, Canada), which presents a mosaic of forested patches isolated by roads, graveyards and buildings. We assessed the genetic structure of these populations using microsatellite loci and compared it to the genetic structure of four populations located in a continuous habitat in southern Québec. Our results indicate that allelic richness and heterozygosity are lower in the urban populations. Exact differentiation tests and pairwise F _ST also show that the populations found in the fragmented habitat are genetically differentiated, whereas populations located in the continuous habitat are genetically homogeneous. These results raise conservation concerns for these populations as well as for rare or threatened species inhabiting urban landscapes.     

Theoretical investigation of the formation of a new series of antioxidant depsides from the radiolysis of flavonoid compounds

This paper deals with the formation of a series of antioxidant depsides obtained from flavonoid solutions irradiated with gamma rays. These reactions take place in radiolyzed alcohol solutions, a medium that is very rich in many different highly reactive species and that hosts specific reactions. We focus on the first step of those reactions, i.e., reactivity of the solute (flavonoid) with the alkoxy radicals CH(3)O(*) and CH(3)CH(2)O(*) formed in methanol and ethanol, respectively, and their carbon-centered isomers: the 1-hydroxy-methyl ((*)CH(2)OH) and the 1-hydroxy-ethyl (CH(3)(*)CHOH) radicals. Among the different flavonoid groups of molecules, only flavonols are transformed. To establish the structure-reactivity relationship that explains why the radiolytic transformation occurs only for those compounds, the process is rationalized theoretically, with Density Functional Theory calculations, taking into account the solvent effects by a Polarizable Continuum Model and a microhydrated environment (one or two water molecules surrounding the active center). The first redox reaction, occurring between the flavonol and the reactive species formed upon irradiation of the solvent, is studied in terms of (1) the O-H bond dissociation enthalpy of each OH group of the flavonoids and (2) electron abstraction from the molecule. We conclude that the reaction, initiated preferentially by the alkoxy radicals, first occurs at the 3-OH group of the flavonol. It is then followed by the formation of a peroxyl radical (after molecular oxygen or superoxide addition). The different cascades of reactions, which lead to the formation of depsides via C-ring opening, are discussed on the basis of the corresponding calculated energetic schemes.