Endogenous Stochastic Decoding of the CUG Codon by Competing Ser- and Leu-tRNAs in Ascoidea asiatica

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CEP128 Localizes to the Subdistal Appendages of the Mother Centriole and Regulates TGF-β/BMP Signaling at the Primary Cilium

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Optimal control for micro‐algae on a raceway model

We apply numerical optimal control methods to an existing algae growth model with the aim to determine the best performance of the model under known conditions using a variety of decision variables. We transform the system of differential algebraic equations in the existing model to a system of ordinary differential equations which introduces dynamics for average light intensity and chlorophyll. In addition, we allow for variable nitrogen concentration of the inflow as well as variable initial nitrogen concentration of the raceway. Our main focus is on optimizing of the production of lipids. We calculate both open and closed loop optimal controllers and test their robustness. Finally, we also consider raceway depth as a decision variable. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:107–119, 2018     

Comparative phylogeography of Aedes mosquitoes and the role of past climatic change for evolution within Africa

The study of demographic processes involved in species diversification and evolution ultimately provides explanations for the complex distribution of biodiversity on earth, indicates regions important for the maintenance and generation of biodiversity, and identifies biological units important for conservation or medical consequence. African and forest biota have both received relatively little attention with regard to understanding their diversification, although one possible mechanism is that this has been driven by historical climate change. To investigate this, we implemented a standard population genetics approach along with Approximate Bayesian Computation, using sequence data from two exon‐primed intron‐crossing (EPIC) nuclear loci and mitochondrial cytochrome oxidase subunit I, to investigate the evolutionary history of five medically important and inherently forest dependent mosquito species of the genus Aedes. By testing different demographic hypotheses, we show that Aedes bromeliae and Aedes lilii fit the same model of lineage diversification, admixture, expansion, and recent population structure previously inferred for Aedes aegypti. In addition, analyses of population structure show that Aedes africanus has undergone lineage diversification and expansion while Aedes hansfordi has been impacted by population expansion within Uganda. This congruence in evolutionary history is likely to relate to historical climate‐driven habitat change within Africa during the late Pleistocene and Holocene epoch. We find differences in the population structure of mosquitoes from Tanzania and Uganda compared to Benin and Uganda which could relate to differences in the historical connectivity of forests across the continent. Our findings emphasize the importance of recent climate change in the evolution of African forest biota.     

Activation of Maxi-K Channels by Parathyroid Hormone and Prostaglandin E2 in Human Osteoblast Bone Cells

Patch clamp experiments were performed on two human osteosarcoma cell lines (MG-63 and SaOS-2 cells) that show an osteoblasticlike phenotype to identify and characterize the specific K channels present in these cells. In case of MG-63 cells, in the cell-attached patch configuration (CAP) no channel activity was observed in 2 mm Ca Ringer (control condition) at resting potential. In contrast, a maxi-K channel was observed in previously silent CAP upon addition of 50 nm parathyroid hormone (PTH), 5 nm prostaglandin E₂ (PGE₂) or 0.1 mm dibutyryl cAMP + 1 μm forskolin to the bath solution. However, maxi-K channels were present in excised patches from both stimulated and nonstimulated cells in 50% of total patches tested. A similar K channel was also observed in SaOS-2 cells. Characterization of this maxi-K channel showed that in symmetrical solutions (140 mm K) the channel has a conductance of 246 ± 4.5 pS (n = 7 patches) and, when Na was added to the bath solution, the permeability ratio (P_K/P_Na) was 10 and 11 for MG-63 and SaOS-2 cells respectively. In excised patches from MG-63 cells, the channel open probability (P _o ) is both voltage- (channel opening with depolarization) and Ca-dependent; the presence of Ca shifts the P _o vs. voltage curve toward negative membrane potential. Direct modulation of this maxi-K channel via protein kinase A (PKA) is very unlikely since in excised patches the activity of this channel is not sensitive to the addition of 1 mm ATP + 20 U/ml catalytic subunit of PKA. We next evaluated the possibility that PGE₂ or PTH stimulated the channel through a rise in intracellular calcium. First, calcium uptake (⁴⁵Ca⁺⁺) by MG-63 cells was stimulated in the presence of PTH and PGE₂, an effect inhibited by Nitrendipine (10 μm). Second, whereas PGE₂ stimulated the calcium-activated maxi-K channel in 2 mm Ca Ringer in 60% of patches studied, in Ca-free Ringer bath solution, PGE₂ did not open any channels (n = 10 patches) nor did cAMP + forskolin (n = 3 patches), although K channels were present under the patch upon excision. In addition, in the presence of 2 mm Ca Ringer and 10 μm Nitrendipine in CAP configuration, PGE₂ (n = 5 patches) and cAMP + forskolin (n = 2 patches) failed to open K channels present under the patch. As channel activation by phosphorylation with the catalytic subunit of PKA was not observed, and Nitrendipine addition to the bath or the absence of calcium prevented the opening of this channel, it is concluded that activation of this channel by PTH, PGE₂ or dibutyryl cAMP + forskolin is due to an increase in intracellular calcium concentration via Ca influx. Received: 17 September 1995/Revised: 7 December 1995     

Short-chain saturated fatty acids in the regulation of pollination-induced ethylene sensitivity of Phalaenopsis flowers

Pollination greatly accelerates petal senescence. The first observed event after pollination is an increase in the flower's sensitivity to ethylene, followed by an increase in ethylene biosynthesis. Our objectives were to study the mode of action of the increase in ethylene sensitivity and the possible involvement of short-chain saturated fatty acids (SCSFAs) in this process. Application of SCSFAs, ranging in chain length from 7 to 10 carbons onto stigmas of Phalaenopsis (Phalaenopsis hybrid, cv. Herbert Hager) flowers increased their sensitivity to ethylene in the same way as pollination. Following pollination, there was a significant increase in the endogenous content of these fatty acids in the flower's column and perianth, with octanoic acid (C₈) being the main SCSFA observed. The increase in SCSFA content was observed as early as 6 h after pollination and began to decline 6 h later. Incorporation of octanoic acid into liposomes or microsomal membranes isolated from Phalaenopsis petals resulted in a decrease in lipid order that was detected by fluorescence polarization of dansyl pyrrolidine (DNSP) but not of 1,6-diphenyl-1,3,5-hexatriene (DPH). At peak ethylene sensitivity, 10 h after pollination, there was a significant decrease in the lipid order of microsomal membranes isolated from Phalaenopsis columns and perianths, again as detected by DNSP but not by DPH. Stigmatic application of octanoic acid mimicked the effect of pollination on membrane lipid order. We suggest that SCSFAs may be the ethylene 'sensitivity factors' produced following pollination, and that their mode of action involves a decrease in the order of specific regions in the membrane lipid bilayer, consequently altering ethylene action.     

Metals (Fe, Mn, Zn) in the root plaque of submerged aquatic plants collected in situ: Relations with metal concentrations in the adjacent sediments and in the root tissue

We have investigated the extent of iron oxyhydroxide deposition on the roots of two common freshwater species, Vallisneria americana Michx. and Heteranthera dubia (Jacq.) MacM., collected from different sites in the St. Lawrence River, Québec, Canada, and have related metal concentrations in the root plaques both to the geochemical conditions prevailing in the host sediments (pH; metal partitioning) and to the metal concentrations within the plant root tissue. Possible effects of root plaque on sediment geochemistry are also discussed.At those sites where the two submerged plants co-existed, the amounts of Fe deposited on their respective root surfaces were positively correlated, indicating that sediment geochemistry (pH; concentration of labile metal) exerted a more important influence on plaque formation than did inter-species differences (root physiology, morphology). Iron and Mn concentrations in the root plaque were positively correlated with each other, and with the readily extractable fractions (F1, 172) of these metals in the adjacent sediments. In contrast, Zn concentrations in the root plaque of V. americana were not related to Zn concentrations in the sediments — the dominant geochemical process at the root surface is Fe deposition, such that the quantities of Zn deposited on the roots are determined not by Zn geochemistry per se but rather by the amount of Fe deposition. Indeed the Zn/Fe ratios in the root plaque were related to the Zn/Fe ratios in the surrounding sediments (NH₂OHHCl extract).On a concentration basis (g/g), more Fe, Mn and Zn was found outside the root, in the iron plaque, than inside the root tissues. For all 3 metals, significant relationships were observed between the metal concentrations in the plaque and those inside the roots. For Zn, however, the best statistical relationship was not with [Zn]_plaque, but rather with the [Zn]/[Fe] ratio in the plaque. It is hypothesized that the Zn/Fe ratio in the root plaque reflects the free Zn²⁺ concentration adjacent to the root surface, and that this in turn affects Zn uptake by the plant root. For a given value of Zn in the sediments or in the root plaque, the Zn content of the root is inversely related to the concentration of Fe oxyhydroxides, implying that Fe plays a protective role in regulating Zn bioavailability.     

Recent advances in understanding of the evolution and maintenance of sex

The evolution of sex has been the focus of considerable attention during recent years. There is some consensus that the solution to the mystery is that sex either enables the creation and spread of advantageous traits (possibly parasite resistance) or helps to purge the genome of deleterious mutations. Recent experimental work has allowed testing of some of the assumptions underlying the theoretical models, most particularly whether interactions between genes are synergistic and whether the mutation rate is adequately high. However, although a variety of theories point out advantages to sex, most of them predict that a little sex and recombination can go a long way towards improving the fitness of a population, and it remains unclear why obligate sex is so common.     

Evolution of the response patterns to dietary carbohydrates and the developmental differentiation of gene expression of α-amylase in Drosophila

Intraspecific variation of -amylase activity in D. melanogaster and D. immigrans, which is distantly related to D. melanogaster, and interspecific variation of -amylase activity in 18 Drosophila species were examined. The amount of intraspecific variation of -amylase activities measured in terms of coefficient of variation in D. melanogaster and D. immigrans was one-half and one-tenth or less, respectively, of the interspecific variation in 18 Drosophila species. We also surveyed the response patterns of -amylase activity to dietary carbohydrates at the larval and adult stages. The levels of -amylase activity depended on both repression by dietary glucose (glucose repression) and induction by dietary starch (starch induction). In general, our data suggest that glucose repression was conserved among species at both stages while starch induction was mainly observed in larvae, although the degree of the response depended on species. In D. lebanonensis lebanonensis and D. serrata, larvae expressed electrophoretically different -amylase variants (isozymes) from those of adult flies. These results may suggest that the regulatory systems responsible both for the response to environment and developmental expression are different among species in Drosophila. Correspondence to: T. Yamazaki