Geographic variation in forest composition and precipitation predict the synchrony of forest insect outbreaks

Evaluating the causes of spatial synchrony in population dynamics in nature is notoriously difficult due to a lack of data and appropriate statistical methods. Here, we use a recently developed method, a multivariate extension of the local indicators of spatial autocorrelation statistic, to map geographic variation in the synchrony of gypsy moth outbreaks. Regression analyses indicated that local synchrony of gypsy moth defoliation increased with the local synchrony of precipitation and the proportion of host tree density composed of oaks, especially those in the Lobatae (red oak) section. This may be the first study that demonstrates a relationship between defoliator population synchrony and host tree composition. More broadly, this study contributes to a small body of recent work that illustrates how mapping hotspots of unusually high or low synchrony facilitates an improved understanding of factors influencing spatially synchronous population dynamics generally, and triggers of pest insect outbreaks, more specifically.     

Evidence for bidirectional transverse diffusion of spin-labeled phospholipids in the plasma membrane of guinea pig blood cells

The distribution and transverse diffusion kinetics of four spin-labeled phospholipid analogues (two with choline heads: phosphatidylcholine (PC) and sphingomyelin (SM); two with amino heads: phosphatidylserine (PS) and phosphatidylethanolamine (PE) were studied in the plasma membrane of guinea pig blood cells: erythrocytes, reticulocytes, and leukemic lymphocytes. Nitroxide reduction by the internal content of the cells was used as an indicator to determine the phospholipids that penetrated the cells. The reduction rates were in the order, PS greater than PE greater than PC greater than SM in all cells. Reoxidation of phospholipids extracted by serum albumin revealed the distribution of the phospholipids at a given time. In all cells, the distribution equilibrium was reached in less than 2 h and the amounts left in the external leaflet were in the following proportional order: PS less than PE less than PC less than SM. In the erythrocytes and especially in the reticulocytes, the shape change induced by adding phospholipids relaxed partially or completely at a lower speed but kept the same proportional order as at equilibrium. All the results were analyzed quantitatively with a simple kinetic model including the rates of transverse diffusion (flip and flop), the exchange between plasma membrane and internal membranes, and the reduction rate of free radicals (determined in either the internal or external membrane leaflet). The calculated rate constants of transverse diffusion varied from 2 x 10(-3) to 1.2 x 10(-1) min-1 for the flip and from 4 x 10(-3) to 1.2 x 10(-1) for the flop, depending on the polar head and the cell type. Possible interpretations of the external phospholipid reduction mechanism and cell deformation are discussed.     

Microbial polysaccharides with actual potential industrial applications

The microbial polysaccharides reviewed include xanthan gum, scleroglucan, PS-10, PS-21 and PS-53 gums, polysaccharides from Alcaligenes sp., PS-7 gum, gellan gum, curdlan, bacterial alginate, dextran, pullulan, Baker's Yeast Glycan, 6-deoxy-hexose-containing polysaccharides and bacterial cellulose. Factors limiting the commercial potential of certain microbial polysaccharides such as availability, rheological properties, and polyvalency are outlined. The polysaccharides are classified according to their uses as viscosity-increasing agents and as gelling agents. A third category includes polysaccharides with specific applications such as tailor-made dextran and pullulan and polysaccharides used as substrates for the preparation of rare sugars. The difficulties encountered in development of a polysaccharide at the industrial level are pointed out.     

Novel MicroRNA Reporter Uncovers Repression of Let-7 by GSK-3β

Several members of the let-7 microRNA family are downregulated in ovarian and other cancers. They are thought to act as tumor suppressors by lowering growth-promoting and anti-apoptotic proteins. In order to measure cellular let-7 levels systematically, we have developed a highly sensitive let-7 reporter assay system based on the expression of a chimeric mRNA that contains the luciferase coding region and a 3′-untranslated region (UTR) bearing two let-7-binding sites. In cells expressing the reporter construct, termed pmirGLO-let7, luciferase activity was high when let-7 was absent, while luciferase activity was low when let-7 levels were elevated. The ovarian cancer cell lines BG-1 and UCI-101 were transfected with the let-7 reporter and surveyed with a library of kinase inhibitors in order to identify pathways affecting let-7 activity. Among the inhibitors causing changes in endogenous let-7 abundance, the lowering of glycogen synthase kinase 3 (GSK-3)β function specifically increased let-7 levels and lowered luciferase activity. Similarly, silencing GSK-3β increased both mature and primary-let-7 levels in BG-1 cells, and decreased BG-1 cell survival. Further studies identified p53 as a downstream effector of the GSK-3β-mediated repression of let-7 biosynthesis. Our studies highlight GSK-3β as a novel therapeutic target in ovarian tumorigenesis.     

Asymmetrical intraguild interactions with coyotes,red foxes,and domestic dogs may contribute to competitive exclusion of declining gray foxes

Species coexistence is governed by availability of resources and intraguild interactions including strategies to reduce ecological overlap. Gray foxes are dietary generalist mesopredators expected to benefit from anthropogenic disturbance, but populations have declined across the midwestern USA, including severe local extirpation rates coinciding with high coyote and domestic dog occurrence and low red fox occurrence. We used data from a large‐scale camera trap survey in southern Illinois, USA to quantify intraguild spatial and temporal interactions among the canid guild including domestic dogs. We used a two‐species co‐occurrence model to make pairwise assessments of conditional occupancy and detection rates. We also estimated temporal activity overlap among species and fit a fixed‐effects hierarchical community occupancy model with the four canid species. We partitioned the posterior distributions to compare gray fox occupancy probabilities conditional on estimated state of combinations of other species to assess support for hypothesized interactions. We found no evidence of broadscale avoidance among native canids and conclude that spatial and temporal segregation were limited by ubiquitous human disturbance. Mean guild richness was two canid species at a site and gray fox occupancy was greater when any combination of sympatric canids was also present, setting the stage for competitive exclusion over time. Domestic dogs may amplify competitive interactions by increasing canid guild size to the detriment of gray foxes. Our results suggest that while human activities can benefit some mesopredators, other species such as gray foxes may serve as bellwethers for habitat degradation with trophic downgrading and continued anthropogenic homogenization.     

Phorbol diester-induced alterations in the expression of protein kinase C isozymes and their mRNAs. Analysis in wild-type and phorbol diester-resistant HL-60 cell clones.

In an HL-60 cell subline (PR-17) which was greater than 100-fold resistant to the differentiating and cytostatic activities of phorbol 12-myristate 13-acetate (PMA), the protein kinase C phenotype was found to be nearly identical to that of wild-type HL-60 cells. A measurable decrease (30%) in the specific activities of crude preparations of PR-17 cell protein kinase C was observed when the enzyme was measured with histone as the phosphate acceptor substrate, but other aspects of the protein kinase C phenotype (intracellular concentrations and binding affinities of phorbol diester receptors, translocation of activated enzyme from cytosolic to particulate subcellular fractions, relative expression of the alpha and beta isozyme proteins) were equivalent in both PMA-resistant PR-17 cells and in wild-type HL-60 cells. Direct analysis of the behavior of the alpha and beta isozymes after the exposure of each cell type to 100 nM PMA for 12 h revealed that the activities and intracellular concentrations of both isozymes were downregulated to an equivalent extent in both wild-type and PMA-resistant cells. These results suggest that the cellular basis for the resistance to the effects of PMA was present "down-stream" from the activation and down-regulation of protein kinase C and was perhaps a nuclear component. Among the genes which were likely to be differentially regulated when each of the two cell lines were treated with PMA were those for the protein kinase C isozymes themselves. In wild-type HL-60 cells, the intracellular concentrations of type HL-60 cells, the intracellular concentrations of mRNA for each of the beta isozymes were increased (up to 5-fold) 48 h after the initiation of PMA treatment; further studies indicate that an activator of protein kinase C could influence the expression of HL-60 cell protein kinase C genes in an isozyme-specific manner. Comparable PMA-induced alterations in mRNA levels were not observed in PMA-resistant cells, even under conditions of significant activation and subsequent down-regulation of protein kinase C protein. Taken together, these data suggest that activation and down-regulation of the isozymes of protein kinase C may not represent absolute determinants of the PMA-induced differentiation of HL-60 cells, but that specific alterations in the levels of the mRNA for the beta isozymes of protein kinase C, or of other genes which may be regulated by the activated kinase isozymes, are important to the induction of leukemia cell differentiation by PMA.     

Methylobacterium extorquens AM1 produces a novel type of acyl-homoserine lactone with a double unsaturated side chain under methylotrophic growth conditions

Acyl-homoserine lactones (acyl-HSLs) have emerged as important regulatory molecules for many gram-negative bacteria. We have found that Methylobacterium extorquens AM1, a member of the pink-pigmented facultative methylotrophs commonly present on plant surfaces, produces several acyl-HSLs depending upon the carbon source. A novel HSL was discovered with a double unsaturated carbon chain (N-(tetradecenoyl)) (C14:2) and characterized by MS and proton NMR. This long-chain acyl-HSL is synthesized by MlaI that also directs synthesis of C14:1-HSL. The Alphaproteobacterium also produces N-hexanoyl-HSL (C6-HSL) and N-octanoyl-HSL (C8-HSL) via MsaI.