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.     

The Earth's Mantle: Evidence of Non-Newtonian Flow

Recent information from experimentally deformed dunite coupled with a reanalysis of data on the Fennoscandian postglacial rebound suggest that the rheological behavior of the upper mantle is distinctly non-Newtonian, and that the shear strain rate is proportional to the shear stress raised to about the third power.     

An approximately 15,000-year record of El Nino-driven alluviation in southwestern ecuador

Debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the Pacific Ocean, in Ecuador. These storm-induced events were dated by radiocarbon, and the age of laminae that are less than 200 years old matches the historic record of El Nino events. From about 15,000 to about 7000 calendar years before the present, the periodicity of clastic deposition is greater than or equal to 15 years; thereafter, there is a progressive increase in frequency to periodicities of 2 to 8.5 years. This is the modern El Nino periodicity, which was established about 5000 calendar years before the present. This may reflect the onset of a steeper zonal sea surface temperature gradient, which was driven by enhanced trade winds.     

Species composition and abundance of aphids in Australian hop gardens and their impact on spatiotemporal patterns of Carlavirus epidemics

The species composition and abundance of aphids in commercial cv. Agate and cv. Super Pride hop gardens in Tasmania, Australia, were characterized over three seasons (1999–2001). Gunns Plains recorded 14 aphid species and Bushy Park 11 species, with nine of these common to both sites. The majority of aphids were trapped in the first 2 months (October and November) of active hop growth in all three seasons. Cultivar and geographical location had significant effects on the abundance of total aphids (species pooled) trapped and several individual aphid species in the three seasons. In general, significantly more aphids (total and individual species) were trapped in cv. Agate than cv. Super Pride gardens, and higher numbers were trapped at Bushy Park than at Gunns Plains. This coincided with a higher incidence of plants infected by carlaviruses in cv. Agate gardens at both locations. Differences in the spatiotemporal dynamics of Carlavirus epidemics were described by fitting a stochastic model to the data, with parameters for local spread within the garden (contagion) and background infection (disease increase unrelated to infected plants within the gardens). Local spread of Hop latent virus (HpLV) and Hop mosaic virus (HpMV) was indicated within all gardens. For HpMV in cv. Agate at Gunns Plains, however, infections caused by immigrant viruliferous aphids were also apparent. Using join-count statistics, spatial aggregation of both virus diseases was found for all years, except for the initial year (1999) when incidence was low. Clusters of diseased plants extended to greater distances for HpLV than for HpMV. Based on spatial and spatiotemporal analyses, local spread (mechanical transmission and/or aphid movement within the garden) appears to be the dominant factor in the epidemics of HpLV. Aphid immigration from outside the crop over time may play a more significant role for HpMV epidemics, at least for one location.