Conversion of Cellulose to Methane and Carbon Dioxide by Triculture of Acetivibrio cellulolyticus, Desulfovibrio sp., and Methanosarcina barkeri

The fermentation of cellulose by monocultures of Acetivibrio cellulolyticus and cocultures of A. cellulolyticus-Methanosarcina barkeri, A. cellulolyticus-Desulfovibrio sp., and A. cellulolyticus-M. barkeri-Desulfovibrio sp. was studied. The monoculture produced ethanol, acetate, H₂, and CO₂. More acetate and less ethanol was formed by the cocultures than by the monoculture. Acetate was utilized by M. barkeri in coculture with A. cellulolyticus after a lag period, whereas ethanol was metabolized by the sulfate reducer only under conditions of low H₂ partial pressure, i.e., when cocultured with A. celluloyticus-M. barkeri or when grown together with the methanogen. Only the three-component culture carried out the rapid conversion of cellulose to CO₂ and methane. Furthermore, this culture hydrolyzed the most cellulose—85% of that initially present. This amount was increased to 90% by increasing the population of M. barkeri in the triculture. Methane production was also increased, and a quicker fermentation rate was achieved.     

Toxoplasma gondii: lymphocyte function during acute infection in mice

T-cell function during acute Toxoplasma gondii infection was evaluated in murine models. Blastogenic response to the T-cell mitogen concanavalin A (Con A) was not depressed during infection with either the C37 or the C56 strain of T. gondii in either $\text{BALB}\text{c}$ or $\text{C}\text{57}\text{BL}\text{6}\text{J}$ mice that were inoculated either intravenously or intraperitoneally with varying doses of tachyzoites 7, 14, or 30 days earlier. In evaluation of lymphocytes from individual mice, utilization of a range of concentrations of Con A was found to be important for correct interpretation of results. There was variability in the magnitude of response of individual mice and in the concentration of mitogen that produced an optimal response among the inbred mice. The T-cell-dependent, primary antibody response to sheep red blood cells (SRBC) was not depressed in $\text{BALB}\text{c}$ mice infected with the C37 strain of Toxoplasma 1 and 8 days prior to inoculation with SRBC. A lower blastogenic reponse to Con A of lymphocytes from $\text{C}\text{57}\text{BL}\text{6}\text{J}$ mice compared with that of $\text{BALB}\text{c}$ mice appeared to correlate with increased susceptibility of $\text{C}\text{57}\text{BL}\text{6}\text{J}$ mice to low-challenge inocula of T. gondii.     

A lectin-like receptor on mammalian macrophages

Rat Kupffer cells in vitro strongly bind neuraminidase-treated rat erythrocytes but not untreated erythrocytes. Binding between cells is inhibited by preincubation of macrophages with D-galactose and related sugars, but not with unrelated saccharides. We therefore suggest that cell adherence is mediated by a galactose-specific receptor on the Kupffer cell membrane.     

Simultaneous tissue profiling of eicosanoid and endocannabinoid lipid families in a rat model of osteoarthritis

We describe a novel LC method for the simultaneous and quantitative profiling of 43 oxylipins including eicosanoids, endocannabinoids, and structurally related bioactive lipids with modified acyl groups. The LC-MS/MS method uses switching at a defined time between negative and positive electrospray ionization modes to achieve optimal detection sensitivity for all the lipids. The validated method is linear over a range of 0.01–5 nmol/g (0.1–50 nmol/g for 2-arachidonoyl glycerol) with intra- and interday precision and accuracy between 1.38 and 26.76% and 85.22 and 114.3%, respectively. The method successfully quantified bioactive lipids in different tissue types in the rat, including spinal cord, dorsal root ganglia (DRGs), knee joint, brain, and plasma. Distinct regional differences in the pattern of lipid measured between tissue types were observed using principle component analysis. The method was applied to analyze tissue samples from an established preclinical rat model of osteoarthritis (OA) pain and showed that levels of 12-hydroxyeicosatetraenoic acid were significantly increased in the OA rat knee joint compared with controls, and that 15-hydroxyeicosatetraenoic acid was significantly increased in the DRGs in the model of OA compared with controls. The developed LC-MS/MS method has the potential to provide detailed pathway profiling in tissues and biofluids where the disruption of bioactive oxylipins may be involved in disease states.     

Structure of a conserved retroviral RNA packaging element by NMR spectroscopy and cryo-electron tomography

The 5′-untranslated regions of all gammaretroviruses contain a conserved “double-hairpin motif” (Ψ^CD) that is required for genome packaging. Both hairpins (SL-C and SL-D) contain GACG tetraloops that, in isolated RNAs, are capable of forming “kissing” interactions stabilized by two intermolecular G-C base pairs. We have determined the three-dimensional structure of the double hairpin from the Moloney murine leukemia virus ([Ψ^CD]₂, 132 nt, 42.8 kDa) using a ²H-edited NMR-spectroscopy-based approach. This approach enabled the detection of ¹H-¹H dipolar interactions that were not observed in previous studies of isolated SL-C and SL-D hairpin RNAs using traditional ¹H-¹H correlated and ¹H-¹³C-edited NMR methods. The hairpins participate in intermolecular cross-kissing interactions (SL-C to SL-D′ and SLC′ to SL-D) and stack in an end-to-end manner (SL-C to SL-D and SL-C′ to SL-D′) that gives rise to an elongated overall shape (ca 95 Å × 45 Å ×  25 Å). The global structure was confirmed by cryo-electron tomography (cryo-ET), making [Ψ^CD]₂ simultaneously the smallest RNA to be structurally characterized to date by cryo-ET and among the largest to be determined by NMR. Our findings suggest that, in addition to promoting dimerization, [Ψ^CD]₂ functions as a scaffold that helps initiate virus assembly by exposing a cluster of conserved UCUG elements for binding to the cognate nucleocapsid domains of assembling viral Gag proteins.     

A global analysis of the determinants of alien geographical range size in birds

Aim Determining the causes of range size variation in the distributions of alien species is important for understanding the spread of invasive species. Factors influencing alien range size have been explored for some species at a regional level, but to date there has been no global analysis of an entire class. Here, we present such an analysis for birds, testing for the effects of introduction event, location and species‐level variables on alien range sizes. Location Global. Methods We used a novel dataset on the global distributions of alien bird species to test for relationships between alien range size and colonization pressure, residence time, extent of the global climatic niche, native range size, body mass and specialization, using a statistical approach based on phylogenetic generalized least squares models. We performed this analysis globally, and for separate biogeographical realms. Results Approximately half of the variation in alien bird range size is explained by colonization pressure in univariate analysis. We identified consistent effects of higher colonization pressure at global and realm levels, as well as support for effects of native range size and residence time. We found less support for effects of body mass, specialization or extent of the global climatic niche on alien range size. Main conclusions Alien bird range sizes are generally small relative to their native range sizes, and many are continuing to expand. Nevertheless, current variation is predictable, most strongly by the event‐level factor of colonization pressure. Whether a species is widespread is a better predictor of alien range size than whether a species could be widespread (estimated by global climatic niche extent), while we also find effects of residence time on alien range size. These relationships may help to identify those alien species that are more likely to spread and hence have greater environmental and economic impacts where they have been introduced.