Aedes aegypti Piwi4 Structural Features Are Necessary for RNA Binding and Nuclear Localization

The PIWI-interacting RNA (piRNA) pathway provides an RNA interference (RNAi) mechanism known from Drosophila studies to maintain the integrity of the germline genome by silencing transposable elements (TE). Aedes aegypti mosquitoes, which are the key vectors of several arthropod-borne viruses, exhibit an expanded repertoire of Piwi proteins involved in the piRNA pathway, suggesting functional divergence. Here, we investigate RNA-binding dynamics and subcellular localization of A. aegypti Piwi4 (AePiwi4), a Piwi protein involved in antiviral immunity and embryonic development, to better understand its function. We found that AePiwi4 PAZ (Piwi/Argonaute/Zwille), the domain that binds the 3′ ends of piRNAs, bound to mature (3′ 2′ O-methylated) and unmethylated RNAs with similar micromolar affinities (K_D = 1.7 ± 0.8 μM and K_D of 5.0 ± 2.2 μM, respectively; p = 0.05) in a sequence independent manner. Through site-directed mutagenesis studies, we identified highly conserved residues involved in RNA binding and found that subtle changes in the amino acids flanking the binding pocket across PAZ proteins have significant impacts on binding behaviors, likely by impacting the protein secondary structure. We also analyzed AePiwi4 subcellular localization in mosquito tissues. We found that the protein is both cytoplasmic and nuclear, and we identified an AePiwi4 nuclear localization signal (NLS) in the N-terminal region of the protein. Taken together, these studies provide insights on the dynamic role of AePiwi4 in RNAi and pave the way for future studies aimed at understanding Piwi interactions with diverse RNA populations.     

Surface chemical characterization of 2.5-microm particulates (PM2.5) from air pollution in Salt Lake City using TOF-SIMS, XPS, and FTIR

Particulate matter with a diameter of 2.5 microm collected in Salt Lake City (SLC PM2.5) was studied using TOF-SIMS (time-of-flight secondary-ion mass spectrometry), XPS (X-ray photoelectron spectroscopy), and FTIR (Fourier transform infrared spectroscopy). The high spatial resolution and high surface sensitivity of TOF-SIMS allow the surfaces of individual particulates to be analyzed. The high mass-resolution of TOF-SIMS provides good separation of signals from different chemical species at the same nominal mass, and the extremely high detection sensitivity of TOF-SIMS makes the detection of trace elements possible. Metallic elements such as Li, Na, Mg, Al, K, Ca, Cr, Mn, Fe, Cu, Zn, Cs, and Bi were detected by TOF-SIMS on the surface of SLC PM25. The uranium ion U+ together with its oxide ions UO+ and UO2+ were also found. Inorganic compounds detected include oxides, hydroxides, nitrates, sulfates, silicates, borates, chlorides, etc. Organic compounds detected include hydrocarbons, alcohols, aldehydes, ethers, carboxylic acids, amines, amides, nitriles, etc. A number of polycyclic aromatic hydrocarbons (PAH) and nitrated polycyclic aromatic hydrocarbons were detected by TOF-SIMS. High-resolution XPS Cls spectrum shows functional groups such as C-O, CO2, C-CO2, C-C, and C-H and aromatic pi-pi* shake-up transitions. High-resolution XPS O 1s spectrum indicates the coexistence of different oxygen compounds on the surface of PM2.5. FTIR results confirm the presence of various organic compounds in SLC PM2.5 detected by TOF-SIMS and XPS.     

The Effects of Irradiation, High Hydrostatic Pressure, and Temperature during Pressurization on the Characteristics of Cooked-reheated Salmon and Catfish Fillets

ABSTRACT: Fully‐cooked salmon and catfish fillets were treated by ionizing radiation (0, 3, or 6 kGy), high hydrostatic pressure (HHP) (0, 414, or 690 MPa), 2 different temperatures during pressurization (ambient‐HHP approximately equal to 21 °C, or heated‐HHP = 70 °C), and combinations of the treatments. Kramer shear values increased for salmon and catfish fillets treated by HHP, heated‐HHP, and a combination treatment. Tenderness and juiciness scores of salmon and catfish fillets were lower with HHP, heated‐HHP, and a combination treatment. Irradiation decreased CIE a* values of salmon, and CIE b* values of salmon and catfish. Irradiation increased tenderness and juiciness scores of salmon and increased flavor intensity of catfish.     

A diverse set of nuclear RNAs transfer between nuclei of yeast heterokaryons

Small nuclear RNAs and small nucleolar RNAs function in the nucleus of eukaryotic cells during pre-mRNA splicing and ribosomal RNA processing, respectively. In metazoan cells, the small nuclear RNAs shuttle between the nucleus and the cytoplasm during ribonucleoprotein particle assembly. Nuclear export of these small RNAs in yeast, however, has not been demonstrated. Therefore, we have attempted to visualize internuclear RNA movements by in situ hybridization in heterokaryon yeast cells. Using the kar1Delta15 mutation to block karyogamy, we mated two strains, each expressing a unique allele of U1 snRNA. In these heterokaryons, we observed a time-dependent transfer of U1 snRNA from one nucleus to the other. This transfer was reduced two-fold by the addition of the Crm1p-inhibitor leptomycin B. Interestingly, however, we observed identical transfer of the U2 and U6 snRNAs and SNR4, SNR8, SNR9 and SNR11 snoRNAs. Remarkably, when the U2, U6 or SNR4 RNAs were observed in the same heterokaryon as the U1 snRNA, both RNAs always transferred simultaneously. These data suggest a global leaking or transport of material between nuclei of yeast heterokaryons. Our results suggest that caution must be taken when testing nuclear envelope shuttling in yeast heterokaryons.     

Dystocia, stillbirth, gestation length, and birth weight in Holstein, Jersey, and reciprocal crosses from a planned experiment

Holstein and Jersey cows were mated to 4 Holstein (H) bulls and 4 Jersey (J) bulls to create HH, HJ, JH, and JJ genetic groups (sire breed listed first) in a diallele crossbreeding scheme. Calvings (n = 756) occurred in research herds in Virginia, Kentucky, and North Carolina with 243, 166, 194, and 153 calvings in the HH, HJ, JH, and JJ groups, respectively. Birth weights (BW), dystocia scores (0 for unassisted and 1 for assisted), and stillbirth (0 for alive or 1 for dead within 48 h) were recorded at calving. Gestation lengths (GL) were determined from breeding dates. An animal model was used to analyze BW and GL, and an animal model with logistic regression was used for dystocia and stillbirth. Fixed effects considered for model inclusion were genetic group, herd-year-season, sex, parity (primiparous or multiparous), twin status, and gestation length. Genetic group and effects significant in the model building process were kept in the final model for each trait. Heifer calves had lower BW, shorter GL, and had a lower odds ratio (0.53) for dystocia than bull calves. Twins had lower BW, shorter GL, were 3.86 times more likely to experience dystocia, and 7.80 times more likely to be stillborn than single births. Primiparous cows had calves with lower BW, shorter GL, were 2.50 times more likely to require assistance at birth, and were 2.35 times more likely to produce stillborns than calves from multiparous cows. Genetic group did not affect GL. Least squares means (kg) for BW were 37.7 ± 1.1, 29.1 ± 1.1, 30.3 ± 1.0, and 22.5 ± 1.3 for HH, HJ, JH, and JJ, respectively. Animals in HH weighed more than animals of other genetic groups; the JJ group had the smallest BW, with no differences for BW between HJ and JH. Probability of dystocia in JJ and JH were 5.73% and 18.98% of HH. Calves in HJ and HH were not different for dystocia. Calves in HJ were 3.38 times more likely to be stillborn than calves in JH, but no other genetic group differences were significant for probability of stillbirth. Groups HJ and JH differed for calving traits, with JH crosses experiencing less dystocia than HJ; JJ showed no indication of dystocia. No differences were observed between HH and JJ for stillbirths. Additional investigation of stillbirths in Jerseys is justified.     

Flame spread over thin fuels in actual and simulated microgravity conditions

Most previous research on flame spread over solid surfaces has involved flames in open areas. In this study, the flame spreads in a narrow gap, as occurs in fires behind walls or inside electronic equipment. This geometry leads to interesting flame behaviors not typically seen in open flame spread, and also reproduces some of the conditions experienced by microgravity flames.Two sets of experiments are described, one involving flame spread in a Narrow Channel Apparatus (NCA) in normal gravity, and the others taking place in actual microgravity. Three primary variables are considered: flow velocity, oxygen concentration, and gap size (or effect of heat loss). When the oxidizer flow is reduced at either gravity level, the initially uniform flame front becomes corrugated and breaks into separate flamelets. This breakup behavior allows the flame to keep propagating below standard extinction limits by increasing the oxidizer transport to the flame, but has not been observed in other microgravity experiments due to the narrow samples employed. Breakup cannot be studied in typical (i.e., “open”) normal gravity test facilities due to buoyancy-induced opposed flow velocities that are larger than the forced velocities in the flamelet regime.Flammability maps are constructed that delineate the uniform regime, the flamelet regime, and extinction limits for thin cellulose samples. Good agreement is found between flame and flamelet spread rate and flamelet size between the two facilities. Supporting calculations using FLUENT suggest that for small gaps buoyancy is suppressed and exerts a negligible influence on the flow pattern for inlet velocities ?5 cm/s. The experiments show that in normal gravity the flamelets are a fire hazard since they can persist in small gaps where they are hard to detect. The results also indicate that the NCA quantitatively captures the essential features of the microgravity tests for thin fuels in opposed flow.     

BGA评估中使用的分析方法

球珊阵列（BGAs）在印刷电路板（PCB）组件上已经相当常见,进而带来了新的故障模式,要求新的分析工具或方法,以便正确评估这些元件。传统式SMT元件,如SOICs或OFPs,允许以可视方式检测焊点,查找异常情况;而BGAs则做不到这一点,因为大多数焊点隐藏在元件下面,人眼是看不到的。本文讨论了STI实验室遇到的部分故障模式,以及进行调查使用的工具和方法。     

Effect of Crystallization on Thermal Conductivity and Specific Heat of Two Corning Glass-Ceramics

A magnesium aluminosilicate glass-ceramic (Corning Code 9606) has been heat-treated at 900°, 1010°, 1200°, and 1260°C for up to 90 min., and the effect on the thermal conductivity between 30 and 300 K has been studied. It has been shown that the large increase of the thermal conductivity which results from the ceramming occurs predominantly when crystalline cordierite forms. At 1260°C, heat treatment for only 20 min leads to a thermal conductivity identical to that measured for commercial 9606, which has been cerammed for 8 h at the same temperature. This observation provides further evidence for the usefulness of commercial 9606 as a thermal conductivity standard. Measurements of the specific heats of Code 9606 before and after ceramming have been reviewed and have been found to be close to that of crystalline SiO₂ above ∼ 30 K, regardless of the state of ceramming. A review has also been made of thermal conductivity and specific heat of several ZrTiO₄ nucleated lithium aluminosilicate glass-ceramics at various states of ceramming. The thermal conductivity of these glass-ceramics seems to be sufficiently independent of chemical composition as well as of the degree of crystallization to warrant a recommended curve for this class of glass-ceramics.     

Biodesulfurization of dibenzothiophene sulfone by Arthrobacter sp. and studies with oxidized Illinois No. 6 coal

A bacterium identified as Arthrobacter sp. was grown on dibenzothiophene (DBT) sulfone as a sole source of sulfur, producing sulfite and sulfate. Sulfur in DBT sulfone (1.0 mM) was nearly quantitatively converted to sulfate by the organism. The organism could also use DBT sulfone as a sole source of carbon and energy. There was evidence for transient accumulation of benzoic acid in the culture medium after growth of the cells slowed. The DBT sulfoxide analogue 9-fluorenone was converted by resting cells to a product identified as 1,10-dihydroxy-1,10-dihydrofluoren-9-one, suggesting that DBT sulfone may be metabolized via an angular hydroxylation resulting in carbon- sulfur bond cleavage. This strain of Arthrobacter showed no ability to desulfurize oxidized Illinois No. 6 coal.     

Kinetics of hydantoin formation

The reaction of lignite in a slagging gasifier produces reactants which in turn form 5,5-dimethylhydantoin (DMH) as a major constituent in the condensate water. Variations in plant operating conditions made it impossible to accurately study the kinetics of formation of DMH in the actual gasifier water, and thus a model system was chosen. The reaction of acetone cyanohydrin in the presence of excess ammonium carbonate at concentrations approaching those obtained in the condensate water were studied at 50,70, and 90 °C. Secondorder kinetics were obeyed, and the pseudo second-order rate constants at the respective temperatures were 1.86, 3.6, and 4.62 dm³ mol^{? 1} h^{? 1}. Independent variation of the concentration of either acetone, cyanide, ammonia or carbonate gave results consistent with the interpretation that the formation of DMH is first order in all reactants: rate of formation of DMH = k[acetone][HCN][NH₃][CO₂]. The pseudo second-order rate constant is a complex rate constant including several rapid equilibria. A mechanism consistent with the kinetic data is presented.