Effect of Oil Overlay on Inhibition Potential of Roscovitine in Sheep Cumulus‐Oocyte Complexes

Inhibitors of cyclin‐dependent kinases, as roscovitine, have been used to prevent the spontaneous resumption of meiosis in vitro and to improve the oocyte developmental competence. In this study, the interference of oil overlay on the reversible arrest capacity of roscovitine in sheep oocytes as well as its effects on cumulus expansion was evaluated. For this, cumulus‐oocyte complexes (COCs) were cultured for 20 h in TCM 199 with 10% foetal bovine serum (Control) containing 75 μm roscovitine (Rosco). Subsequently, they were in vitro matured (IVM) for further 18 h in inhibitor‐free medium with LH and FSH. The culture was performed in Petri dishes under mineral oil (+) or in 96 well plates without oil overlay (?) at 38.5°C and 5% CO₂. At 20 and 38 h, the cumulus expansion and nuclear maturation were evaluated under stereomicroscope and by Hoechst 33342 staining, respectively. No group presented cumulus expansion at 20 h. After additional culture with gonadotrophins, a significant rate of COCs from both Control groups (+/?) exhibited total expansion while in both Rosco groups (+/?) the partial expansion prevailed. Among the oocytes treated with roscovitine, 65.2% were kept at GV in the absence of oil overlay while 40.6% of them reached MII under oil cover (p < 0.05). This meiotic arrest was reversible, and proper meiosis progression also occurred in the Control groups (+/?). So, the culture system without oil overlay improved the meiotic inhibition promoted by roscovitine without affecting the cumulus expansion rate or the subsequent meiosis progression.     

Determination of microbial mineralization activity in soil by modified Wright and Hobbie method

Summary The Wright and Hobbie (1966) procedure, originally proposed for measurements of microbial activity in water, was adapted for soil studies. It was critically assessed, both for technical details and for the theoretical background of the isotope dilution principle. The heterogeneity of the soil microbial community was taken into account by introducing a double Michaelis-Menten equation instead of the simple Michaelis-Menten form. More complicated models were unsuitable because the kinetic parameters were not sufficiently stable in view of fluctuations of the experimental data within the measurement error. An integrated form of kinetic equation was preferable to a differential one, and a non-linear regression was better than a linear analysis of transformed data. In grey forest soil the heterotrophic potential of microorganisms was estimated to be 1.31 and 4.26 mg C h^–1 kg^–1 of soil for oligotrophic and copiotrophic components, respectively. The turnover time of indigenous, readily available, soil organic matter was 2.82 h.     

Antagonism of detomidine with tolazoline in isoflurane-anaesthetised ponies

The effects of tolazoline (4.0 mg/kg iv) antagonism of detomidine (0.02 mg/kg iv) were evaluated in isoflurane-anaesthetised, ventilated ponies. Each of 6 ponies received both tolazoline and saline treatment during separate anaesthetic episodes only (no surgery was performed). Detomidine administration produced an increase in blood pressure, decrease in heart rate and decrease in P_aO₂ Tolazoline treatment transiently increased heart rate while blood pressure returned to baseline after both treatments. Arterial oxygenation decreased further after tolazoline treatment while oxgenation recovered towards baseline with saline treatment. No other cardiopulmonary effects were detected. Recovery from anaesthesia tended to be more rapid when detomidine was antagonized. The potential benefit of antagonizing detomidine-induced bradycardia with tolazoline, during isoflurane anaesthesia should be weighed against the potential to produce a decrease in arterial oxygenation. The mechanism for this effect is not clear.     

Effect of pH on rheotaxis of bull sperm using microfluidics

The aim of the present research is to study the effect of pH values on the sperm rheotaxis properties. Semen collected from bulls was diluted with SOF medium (1:10). pH of the medium was adjusted using a digital pH meter to the following pH values: 6.0, 6.2, 6.4, 6.4, 6.8, 7.0. All kinetic parameters of sperm (n = 3,385) were determined through a computer‐assisted sperm analysis (CASA) system using microfluidic devices with controlled flow velocity. The following parameters were determined: total motility (TM%), positive rheotaxis (PR%), straightline velocity (VSL, μm/s), average path velocity (VAP, μm/s), linearity (LIN, as VSL/VCL, %), beat cross‐frequency (BCF, Hz) and curvilinear velocity (VCL, μm/s). Nitric oxide, calcium and potassium were estimated in semen at different pH values. To confirm the effect of nitric oxide and K⁺, we used sodium nitroprusside (an NO donor) and KCL as (a K⁺ donor) to see their effect on sperm PR%. The results showed no difference in TM% at pH (6–7). The PR% was the lowest at pH 6 and 7. The best parameters for the PR% were at pH 6.4–6.6. The concentration of Ca⁺² did not change at different pH values. The mean NO values decreased with the increase of pH; however, the mean values of K⁺ increased with the increase of pH. Addition of high concentration of NO and K⁺ to the semen media at fixed pH level had a negative effect on TM% and PR%. In conclusion, the bull sperm had the best rheotaxis properties at pH 6.4–6.6 and sensitive to the change of seminal NO and K⁺.     

Simrank: Rapid and sensitive general-purpose k-mer search tool

Background  

Terabyte-scale collections of string-encoded data are expected from consortia efforts such as the Human Microbiome Project . Intra- and inter-project data similarity searches are enabled by rapid k-mer matching strategies. Software applications for sequence database partitioning, guide tree estimation, molecular classification and alignment acceleration have benefited from embedded k-mer searches as sub-routines. However, a rapid, general-purpose, open-source, flexible, stand-alone k-mer tool has not been available.     

Tunneling into a single magnetic atom: spectroscopic evidence of the kondo resonance

The Kondo effect arises from the quantum mechanical interplay between the electrons of a host metal and a magnetic impurity and is predicted to result in local charge and spin variations around the magnetic impurity. A cryogenic scanning tunneling microscope was used to spatially resolve the electronic properties of individual magnetic atoms displaying the Kondo effect. Spectroscopic measurements performed on individual cobalt atoms on the surface of gold show an energetically narrow feature that is identified as the Kondo resonance-the predicted response of a Kondo impurity. Unexpected structure in the Kondo resonance is shown to arise from quantum mechanical interference between the d orbital and conduction electron channels for an electron tunneling into a magnetic atom in a metallic host.     

Membrane probe array: Technique development and observation of CO2 and CH4 diurnal oscillations in peat profile

The purpose of this study was to monitor the dynamics of gases such as CO₂ and CH₄ in a soil profile with sufficient temporal resolution to observe possible diurnal variations. A computer-controlled device called a membrane probes array (MPA) was developed that consisted of 9-12 individual membrane probes installed at various soil depths. Each probe was made of a stainless steel pipe with a 1 mm orifice covered with a silicone membrane. Soil gases diffuse through the membrane at a rate proportional to the ambient soil gas concentration. To measure diffusion rates, the probes are flushed with N₂ one-by-one at regular time intervals and accumulated gas is detected as a spike with IR and FID analyzers. The longer the period between flushings the higher the gas accumulation and the lower the detection limit for a particular soil gas. The developed MPA agreed well with conventional manual gas sampling in West-Siberian mesotrophic fen. In peat cores with intact Carex-Sphagnum vegetation incubated under constant temperature, water level and artificial light:dark (14:10) cycles, regular diurnal oscillations of soil CO₂ and CH₄ occurred in the upper part of the peat core down to 19 cm. Gas content in the top layer (3 cm) grew during the light phase, and returned back during the dark phase. In layers further down in the soil, the same events were observed but with progressively increased time delay and lower amplitude. The obtained data agreed with the hypothesis that diurnal variations in soil CO₂ and CH₄ content are caused by periodic changes in intensity of root exudation that provide a major C- and energy source for soil microorganisms including methanogens. At a soil depth of 23 cm, where the peak of gas bubbles occurred, the signal for both gases became chaotic and not related to the light:dark cycle.     

Microbial activity in soils frozen to below −39 °C

Recent research on life in extreme environments has shown that some microorganisms metabolize at extremely low temperatures in Arctic and Antarctic ice and permafrost. Here, we present kinetic data on CO₂ and ¹⁴CO₂ release from intact and ¹⁴C-glucose amended tundra soils (Barrow, Alaska) incubated for up to a year at 0 to −39°C. The rate of CO₂ production declined exponentially with temperature but it remained positive and measurable, e.g. 2-7 ng CO₂-C cm⁻³ soil d⁻¹, at −39 °C. The variation of CO₂ release rate (v) was adequately explained by the double exponential dependence on temperature (T) and unfrozen water content (W) (r²>0.98): v=A exp(λT+kW) and where A, λ and k are constants. The rate of ¹⁴CO₂ release from added glucose declined more steeply with cooling as compared with the release of total CO₂, indicating that (a) there could be some abiotic component in the measured flux of CO₂ or (b) endogenous respiration is more cold-resistant than substrate-induced respiration. The respiration activity was completely eliminated by soil sterilization (1 h, 121 °C), stimulated by the addition of oxidizable substrate (glucose, yeast extract), and reduced by the addition of acetate, which inhibits microbial processes in acidic soils (pH 3-5). The tundra soil from Barrow displayed higher below-zero activity than boreal soils from West Siberia and Sweden. The permafrost soils (20-30 cm) were more active than the samples from seasonally frozen topsoil (0-10 cm, Barrow). Finding measurable respiration to −39 °C is significant for determining, understanding, and predicting current and future CO₂ emission to the atmosphere and for understanding the low temperature limits of microbial activity on the Earth and on other planets.     

Size fractions of organic matter pools influence their stability: Application of the Rock-Eval® analysis to beech forest soils

Soil organic matter (SOM) is a complex heterogeneous mixture formed through decomposition and organo-mineral interactions, and characterization of its composition and biogeochemical stability is challenging. From this perspective, Rock-Eval^® is a rapid and efficient thermal analytical method that combines the quantitative and qualitative information of SOM, including several parameters related to thermal stability. This approach has already been used to monitor changes in organic matter (OM) properties at the landscape, cropland, and soil profile scales. This study was aimed to assess the stability of SOM pools by characterizing the grain size fractions from forest litters and topsoils using Rock-Eval^® thermal analysis. Litter (organic) and topsoil samples were collected from a beech forest in Normandy (France), whose management in the last 200 years has been documented. Fractionation by wet sieving was used to separate large debris (> 2 000 μm) and coarse (200-2 000 μm) and fine particulate OM (POM) (50-200 μm) in the organic samples as well as coarse (200-2 000 μm), medium (50-200 μm), and fine (< 50 μm) fractions of the topsoil samples. Rock-Eval^® was able to provide thermal parameters sensitive enough to study fine-scale soil processes. In the organic layers, quantitative and qualitative changes were explained by the progressive decomposition of labile organic compounds from plant debris to the finest organic particles. Meanwhile, the grain size fractions of topsoils presented different characteristics. The coarse organo-mineral fractions showed higher C contents, albeit with a different composition, higher thermal stability, and greater decomposition degree than the plant debris forming the organic layer. These results are consistent with those of previous studies that microbial activity is more effective in this fraction. The finest fractions of topsoils showed low C contents, the highest thermal stability, and low decomposition degree, which can be explained by the stronger interactions with the mineral matrix. Therefore, it is suggested that the dynamics of OM in the different size fractions be interpreted in the light of a plant-microbe-soil continuum. Finally, three distinct thermostable C pools were highlighted through the grain size heterogeneity of SOM:free coarse OM (large debris and coarse and fine particles), weakly protected OM in (bio)aggregates (coarse fraction of topsoil), and stabilized OM in the fine fractions of topsoil, which resulted from the interactions within organo-mineral complexes. Therefore, Rock-Eval^® thermal parameters can be used to empirically illustrate the conceptual models emphasizing the roles of drivers played by the gradual decomposition and protection of the most thermally labile organic constituents.