Effects of ribosomes on the kinetics of Qβ replication

Bacteriophage Qβ utilizes some host cell translation factors during replication. Previously, we constructed a kinetic model that explains replication of long RNA molecules by Qβ replicase. Here, we expanded the previous kinetic model to include the effects of ribosome concentration on RNA replication. The expanded model quantitatively explained single- and double-strand formation kinetics during replication with various ribosome concentrations for two artificial long RNAs. This expanded model and the knowledge obtained in this study provide useful frameworks to understand the precise replication mechanism of Qβ replicase with ribosomes and to design amplifiable RNA genomes in translation-coupling systems.     

Diatom assemblages promote ice formation in large lakes

We present evidence for the directed formation of ice by planktonic communities dominated by filamentous diatoms sampled from the ice-covered Laurentian Great Lakes. We hypothesize that ice formation promotes attachment of these non-motile phytoplankton to overlying ice, thereby maintaining a favorable position for the diatoms in the photic zone. However, it is unclear whether the diatoms themselves are responsible for ice nucleation. Scanning electron microscopy revealed associations of bacterial epiphytes with the dominant diatoms of the phytoplankton assemblage, and bacteria isolated from the phytoplankton showed elevated temperatures of crystallization (T_c) as high as −3 °C. Ice nucleation-active bacteria were identified as belonging to the genus Pseudomonas, but we could not demonstrate that they were sufficiently abundant to incite the observed freezing. Regardless of the source of ice nucleation activity, the resulting production of frazil ice may provide a means for the diatoms to be recruited to the overlying lake ice, thereby increasing their fitness. Bacterial epiphytes are likewise expected to benefit from their association with the diatoms as recipients of organic carbon excreted by their hosts. This novel mechanism illuminates a previously undescribed stage of the life cycle of the meroplanktonic diatoms that bloom in Lake Erie and other Great Lakes during winter and offers a model relevant to aquatic ecosystems having seasonal ice cover around the world.     

LGR4 is required for sequential molar development

Tooth development requires proliferation, differentiation, and specific migration of dental epithelial cells, through well-organized signaling interactions with mesenchymal cells. Recently, it has been reported that leucine-rich repeat-containing G protein coupled receptor 4 (LGR4), the receptor of R-spondins, is expressed in many epithelial cells in various organs and tissues and is essential for organ development and stem cell maintenance. Here, we report that LGR4 contributes to the sequential development of molars in mice. LGR4 expression in dental epithelium was detected in SOX2⁺ cells in the posterior end of the second molar (M2) and the early tooth germ of the third molar (M3). In keratinocyte-specific Lgr4-deficient mice (Lgr4^{K5 KO}), the developmental defect became obvious by postnatal day 14 (P14) in M3. Lgr4^{K5 KO} adult mice showed complete absence or the dwarfed form of M3. In M3 development in Lgr4^{K5 KO} mice, at Wnt/β-catenin signal activity was down-regulated in the dental epithelium at P3, as indicated by lymphoid enhancer-binding factor-1 (LEF1) expression. We also confirmed the decrease, in dental epithelium of Lgr4^{K5 KO} mice, of the number of SOX2⁺ cells and the arrest of cell proliferation at P7, and observed abnormal differentiation at P14. Our data demonstrated that LGR4 controls the sequential development of molars by maintaining SOX2⁺ cells in the dental epithelium, which have the ability to form normal molars.     

Effect of light-adaptation on the photoreaction of bacteriorhodopsin from Halobacterium halobium

Light-induced formation of the 410 nm intermediate was investigated on dark-and light-adapted bacteriorhodopsin. The amplitude of the light-induced absorption increase at 410 nm of the light-adapted bacteriorhodopsin was twice as large as that of the dark-adapted bacteriorhodopsin. The amount of protons released from bacteriorhodopsin in response to illumination was also enhanced by light-adaptation. The degree of the enhancement was independent of the temperature in the dark-adaptation. The relation between these photochemical events and the isomeric configurations of retinal is discussed.     

Two aquaporins,SIP1;1 and PIP1;2, mediate water transport for pollen hydration in the Arabidopsis pistil

Pollination is the crucial initial step that brings together the male and female gametophytes, and occurs at the surface of the stigmatic papilla cell in Arabidopsis thaliana. After pollen recognition, pollen hydration is initiated as a second critical step to activate desiccated mature pollen grains for germination, and thus water transport from pistil to pollen is essential for this process. In this study, we report a novel aquaporin-mediated water transport process in the papilla cell as a control mechanism for pollen hydration. Coupled with a time-series imaging analysis of pollination and a reverse genetic analysis using T-DNA insertion Arabidopsis mutants, we found that two aquaporins, the ER-bound SIP1;1 and the plasma membrane-bound PIP1;2, are key players in water transport from papilla cell to pollen during pollination. In wild type plant, hydration speed reached its maximal value within 5 min after pollination, remained high until 10–15 min. In contrast, sip1;1 and pip1;2 mutants showed no rapid increase of hydration speed, but instead a moderate increase during ∼25 min after pollination. Pollen of sip1;1 and pip1;2 mutants had normal viability without any functional defects for pollination, indicating that decelerated pollen hydration is due to a functional defect on the female side in sip1;1 and pip1;2 mutants. In addition, sip1;1 pip1;2 double knockout mutant showed a similar impairment of pollen hydration to individual single mutants, suggesting that their coordinated regulation is critical for proper water transport, in terms of speed and amount, in the pistil to accomplish successful pollen hydration.     

Wet hibernacula promote inoculative freezing and limit the potential for cryoprotective dehydration in the Antarctic midge,Belgica antarctica

The terrestrial midge, Belgica antarctica, occupies a diverse range of microhabitats along the Antarctic Peninsula. Although overwintering larvae have the physiological potential to survive by freezing or cryoprotective dehydration, use of the latter strategy may be constrained by inoculative freezing within hibernacula. To investigate the influence of microhabitat type on larval overwintering, we selected four substrate types that differed markedly in their composition and hydric characteristics. Organic content of these substrates ranged from 14 to 89 %. High organic content was associated with higher values for saturation moisture content (up to 2.0 H₂O g^?1 dry mass) as well as elevated levels of field moisture content. Seasonal values of field moisture content remained near or above the saturation moisture value for each microhabitat type, and when larvae were cooled in substrates rehydrated to field-based levels, they were unable to avoid inoculation by environmental ice, regardless of substrate type. Consequently, our data suggest that wet hibernacula would force most larvae to overwinter in a frozen state. Yet, dehydrated larvae were collected in April during the seasonal transition to winter suggesting that spatial and temporal variations in precipitation and microhabitat conditions may expose larvae to dehydration and promote larval overwintering in a cryoprotectively dehydrated state.     

Graphite Furnace Atomic Absorption Spectrometric Evaluation of Iron Excretion in Mouse Urine Caused by Whole-Body Gamma Irradiation

Biological Trace Element Research - A procedure for the determination of iron in mice urine using graphite furnace atomic absorption spectrometry was developed. The mice urinary samples contain...     

Development of neuraminidase detection using gold nanoparticles boron-doped diamond electrodes

Gold nanoparticles-modified boron-doped diamond (AuNPs–BDD) electrodes, which were prepared with a self-assembly deposition of AuNPs at amine-terminated boron-doped diamond, were examined for voltammetric detection of neuraminidase (NA). The detection method was performed based on the difference of electrochemical responses of zanamivir at gold surface before and after the reaction with NA in phosphate buffer solution (PBS, pH 5.5). A linear calibration curve for zanamivir in 0.1 M PBS in the absence of NA was achieved in the concentration range of 1 × 10⁻⁶ to 1 × 10⁻⁵ M (R² = 0.99) with an estimated limit of detection (LOD) of 2.29 × 10⁻⁶ M. Furthermore, using its reaction with 1.00 × 10⁻⁵ M zanamivir, a linear calibration curve of NA can be obtained in the concentration range of 0–12 mU (R² = 0.99) with an estimated LOD of 0.12 mU. High reproducibility was shown with a relative standard deviation (RSD) of 1.14% (n = 30). These performances could be maintained when the detection was performed in mucin matrix. Comparison performed using gold-modified BDD (Au–BDD) electrodes suggested that the good performance of the detection method is due to the stability of the gold particles position at the BDD surface.