Strong influences of a dominant,ground‐nesting ant on recruitment,and establishment of ant colonies and communities

Many factors drive the organization of communities including environmental factors, dispersal abilities, and competition. In particular, ant communities have high levels of interspecific competition and dominance that may affect community assembly processes. We used a combination of surveys and nest supplementation experiments to examine effects of a dominant ground‐nesting ant (Pheidole synanthropica) on (1) arboreal twig‐nesting, (2) ground‐foraging, and (3) coffee‐foraging ant communities in coffee agroecosystems. We surveyed these communities in high‐ and low‐density areas of P. synanthropica over 2 years. To test for effects on twig ant recruitment, we placed artificial nesting resources on coffee plants in areas with and without P. synanthropica. The first sampling period revealed differences in ant species composition on the ground, in coffee plants, and artificial nests between high‐ and low‐density sites of P. synanthropica. High‐density sites also had significantly lower recruitment of twig ants and had species‐specific effects on twig ant species. Prior to the second survey period, abundance of P. synanthropica declined in the high‐density sites, such that P. synanthropica densities no longer differed. Subsequent sampling revealed no difference in total recruitment of twig ants to artificial nests between treatments. Likewise, surveys of ground and coffee ants no longer showed significant differences in community composition. The results from the first experimental period, followed by survey results after the decline in P. synanthropica densities suggest that dominant ants can drive community assembly via both recruitment and establishment of colonies within the community.     

Determination of Oxidative Glucose Metabolism In Vivo in the Young Rat Brain Using Localized Direct-Detected <Superscript>13</Superscript>C NMR Spectroscopy

Determination of oxidative metabolism in the brain using in vivo ¹³C NMR spectroscopy (¹³C MRS) typically requires repeated blood sampling throughout the study to measure blood glucose concentration and fractional enrichment (input function). However, drawing blood from small animals, such as young rats, placed deep inside the magnet is technically difficult due to their small total blood volume. In the present study, a custom-built animal holder enabled temporary removal of the animal from the magnet for blood collection, followed by accurate repositioning in the exact presampling position without degradation of B₀ shimming. ¹³C label incorporation into glutamate C4 and C3 positions during a 120 min [1,6-¹³C₂] glucose infusion was determined in 28-day-old rats (n = 4) under α-chloralose sedation using localized, direct-detected in vivo ¹³C MRS at 9.4T. The tricarboxylic acid cycle activity rate (V _TCA) determined using a one-compartment metabolic modeling was 0.67 ± 0.13 μmol/g/min, a value comparable to previous ex vivo studies. This methodology opens the avenue for in vivo measurements of brain metabolic rates using ¹³C MRS in small animals.     

Megalencephaly Syndromes: Exome Pipeline Strategies for Detecting Low-Level Mosaic Mutations

Two megalencephaly (MEG) syndromes, megalencephaly-capillary malformation (MCAP) and megalencephaly-polymicrogyriapolydactyly-hydrocephalus (MPPH), have recently been defined on the basis of physical and neuroimaging features. Subsequently, exome sequencing of ten MEG cases identified de-novo postzygotic mutations in PIK3CA which cause MCAP and de-novo mutations in AKT and PIK3R2 which cause MPPH. Here we present findings from exome sequencing three unrelated megalencephaly patients which identified a causal PIK3CA mutation in two cases and a causal PIK3R2 mutation in the third case. However, our patient with the PIK3R2 mutation which is considered to cause MPPH has a marked bifrontal band heterotopia which is a feature of MCAP. Furthermore, one of our patients with a PIK3CA mutation lacks syndactyly/polydactyly which is a characteristic of MCAP. These findings suggest that the overlap between MCAP and MPPH may be greater than the available studies suggest. In addition, the PIK3CA mutation in one of our patients could not be detected using standard exome analysis because the mutation was observed at a low frequency consistent with somatic mosaicism. We have therefore investigated several alternative methods of exome analysis and demonstrate that alteration of the initial allele frequency spectrum (AFS), used as a prior for variant calling in samtools, had the greatest power to detect variants with low mutant allele frequencies in our 3 MEG exomes and in simulated data. We therefore recommend non-default settings of the AFS in combination with stringent quality control when searching for causal mutation(s) that could have low levels of mutant reads due to post-zygotic mutation.     

Use ofClostridium acetobutylicum P262 for production of solvents from whey permeate

Summary The production of solvents from whey permeate in batch fermentation usingClostridium acetobutylicum P262 was examined. An overall reactor productivity of 0.24 g/l.h was observed, representing a marked improvement over reports using other strains of clostridia. Using a semi-synthetic medium galactose was shown to be as effective a substrate as glucose. When whey permeate was used in which the lactose was hydrolysed prior to fermentation, preferential uptake of glucose over galactose was observed, and such hydrolysis provided no advantage to the fermentation process.     

Novel structural determinants of mu-conotoxin (GIIIB) block in rat skeletal muscle (mu1) Na+ channels

mu-Conotoxin (mu-CTX) specifically occludes the pore of voltage-dependent Na(+) channels. In the rat skeletal muscle Na(+) channel (mu1), we examined the contribution of charged residues between the P loops and S6 in all four domains to mu-CTX block. Conversion of the negatively charged domain II (DII) residues Asp-762 and Glu-765 to cysteine increased the IC(50) for mu-CTX block by approximately 100-fold (wild-type = 22.3 +/- 7.0 nm; D762C = 2558 +/- 250 nm; E765C = 2020 +/- 379 nm). Restoration or reversal of charge by external modification of the cysteine-substituted channels with methanethiosulfonate reagents (methanethiosulfonate ethylsulfonate (MTSES) and methanethiosulfonate ethylammonium (MTSEA)) did not affect mu-CTX block (D762C: IC(50, MTSEA+) = 2165.1 +/- 250 nm; IC(50, MTSES-) = 2753.5 +/- 456.9 nm; E765C: IC(50, MTSEA+) = 2200.1 +/- 550.3 nm; IC(50, MTSES-) = 3248.1 +/- 2011.9 nm) compared with their unmodified counterparts. In contrast, the charge-conserving mutations D762E (IC(50) = 21.9 +/- 4.3 nm) and E765D (IC(50) = 22.0 +/- 7.0 nm) preserved wild-type blocking behavior, whereas the charge reversal mutants D762K (IC(50) = 4139.9 +/- 687.9 nm) and E765K (IC(50) = 4202.7 +/- 1088.0 nm) destabilized mu-CTX block even further, suggesting a prominent electrostatic component of the interactions between these DII residues and mu-CTX. Kinetic analysis of mu-CTX block reveals that the changes in toxin sensitivity are largely due to accelerated toxin dissociation (k(off)) rates with little changes in association (k(on)) rates. We conclude that the acidic residues at positions 762 and 765 are key determinants of mu-CTX block, primarily by virtue of their negative charge. The inability of the bulky MTSES or MTSEA side chain to modify mu-CTX sensitivity places steric constraints on the sites of toxin interaction.     

Metabolomic Analysis of Cerebrospinal Fluid Indicates Iron Deficiency Compromises Cerebral Energy Metabolism in the Infant Monkey

Iron deficiency anemia affects many pregnant women and young infants worldwide. The health impact is significant, given iron’s known role in many body functions, including oxidative and lipid metabolism, protein synthesis and brain neurochemistry. The following research determined if ¹H NMR spectroscopy-based metabolomic analysis of cerebrospinal fluid (CSF) could detect the adverse influence of early life iron deficiency on the central nervous system. Using a controlled dietary model in 43 infant primates, distinct differences were found in spectra acquired at 600 MHz from the CSF of anemic monkeys. Three metabolite ratios, citrate/pyruvate, citrate/lactate and pyruvate/glutamine ratios, differed significantly in the iron deficient infant and then normalized following the consumption of dietary iron and improvement of clinical indices of anemia in the heme compartment. This distinctive metabolomic profile associated with anemia in the young infant indicates that CSF can be employed to track the neurological effects of iron deficiency and benefits of iron supplementation.     

Toxicity and effects of epidermal growth factor on glucose metabolism of MDA-468 human breast cancer cells

Epidermal growth factor (EGF) has an in vitro inhibitory effect on tumor cells which exhibit a high number of EGF receptors (EGFR). Studies were performed in order to delineate the effects of EGF on glucose metabolism of MDA-468 human breast cancer cells, which have a large number of EGFR. Glucose consumption and lactate production were found to be substantially increased in MDA-468 cells following EGF exposure, while no such effects were detected in MCF-7 breast cancer cells, which have a very low number of EGFR. When glucose levels in the growth medium were increased, the toxicity of EGF was diminished. The energetic status of MDA-468 cells perfused with growth medium containing EGF was monitored by 31P magnetic resonance spectroscopy, and no signs of compromised metabolic state or viability were noted for up to 36 h. The rate of glucose transport and phosphorylation was quantitated by 13C magnetic resonance spectroscopy, utilizing [6-13C]2-deoxyglucose, and a 97% increase was found in MDA-468 cells following EGF administration. The profound effects of EGF on glucose metabolism in cells with very high numbers of EGFR and the lack of toxicity in the perfused system may indicate that the growth-inhibitory effect is confined to the in vitro cultured cells.     

Multiple specificities in the murine CD4+ and CD8+ T-cell response to dengue virus.

The target epitopes, serotype specificity, and cytolytic function of dengue virus-specific T cells may influence their theoretical roles in protection against secondary infection as well as the immunopathogenesis of dengue hemorrhagic fever. To study these factors in an experimental system, we isolated dengue virus-specific CD4+ and CD8+ T-cell clones from dengue-2 virus-immunized BALB/c mice. The T-cell response to dengue virus in this mouse strain was heterogeneous; we identified at least five different CD4+ phenotypes and six different CD8+ phenotypes. Individual T-cell clones recognized epitopes on the dengue virus pre-M, E, NSl/NS2A, and NS3 proteins and were restricted by the I-Ad, I-Ed, Ld, and Kd antigens. Both serotype-specific and serotype-cross-reactive clones were isolated in the CD4+ and CD8+ subsets; among CD8+ clones, those that recognized the dengue virus structural proteins were serotype specific whereas those that recognized the nonstructural proteins were serotype cross-reactive. All of the CD8+ and one of five CD4+ clones lysed dengue virus-infected target cells. Using synthetic peptides, we identified an Ld-restricted epitope on the E protein (residues 331 to 339, SPCKIPFEI) and a Kd-restricted epitope on the NS3 protein (residues 296 to 310, ARGYISTRVEM GEAA). These data parallel previous findings of studies using human dengue virus-specific T-cell clones. This experimental mouse system may be useful for studying the role of the virus serotype and HLA haplotype on T-cell responses after primary dengue virus infection.     

Ability of laboratory methods to predict in-use efficacy of antimicrobial preservatives in an experimental cosmetic

Volume 60, no. 12, p. 4553: a present address for S. J. Wells should be given, as follows: (dag) Present address: Cadbury Beverages North America, Trumbull, CT 06611. [This corrects the article on p. 4553 in vol. 60.].