Atomic force spectroscopy-based essay to evaluate oocyte postovulatory aging

Postovulatory aging is a process occurring in the mature (MII) oocyte leading the unfertilized ones to apoptosis. The optimal time window of fertility for different mammalian species after oocytes maturation depends on its timeliness: the higher the time elapsed from the accomplishment of the MII stage, the lower are the chances of fertilization and of development of a viable embryo. In the in vitro fertilization, the selection of competent oocytes for intracytoplasmic sperm injection (ICSI) is mostly made by the visual inspection of the MII oocyte morphology, which does not allow to determine the oocyte postovulatory age. On the other hand, more specific tests usually involve some kind of staining, thus compromising the viability of the oocyte for reproductive purposes. Hence, the need of a noninvasive analysis of oocyte aging to improve the success rate of in vitro fertilization procedures. Here, we exploit atomic force microscopy to examine the evolution of the mechanical properties of mouse oocytes during in vitro postovulatory aging. Three hours before the occurrence of any visual morphological feature related to degradation, we observe a sudden change of the mechanical parameters: the elastic modulus doubles its initial value, while the viscosity decreases significantly. These mechanical variations are temporally correlated with the release of the cortical granules, investigated by fluorescence microscopy. Interestingly, the oocyte mechanics correlates as well with the yield of embryo formation, evaluated up to the blastocyst formation stage. These results demonstrate that minimally invasive mechanical measurements are very sensitive to the aging of the oocyte and can be used as a label-free method to detect the age of the postovulatory oocytes.

Morphology and Light-Dependent Spatial Distribution of Spin Defects in Carbon Nitride

Carbon nitride (CN) is a heterogeneous photocatalyst that combines good structural properties and a broad scope. The photocatalytic efficiency of CN is associated with the presence of defective and radical species. An accurate description of defective states-both at a local and extended level-is key to develop a thorough mechanistic understanding of the photophysics of CN. In turn, this will maximise the generation and usage of photogenerated charge carriers and minimise wasteful charge recombination. Here the influence of morphology and light-excitation on the number and chemical nature of radical defects is assessed. By exploiting the magnetic dipole-dipole coupling, the spatial distribution of native radicals in CN is derived with high precision. From the analysis an average distance in the range 1.99-2.34 nm is determined, which corresponds to pairs of radicals located approximately four tri-s-triazine units apart.

In vitro application of Eruca vesicaria subsp. sativa leaf extracts and associated metabolites reduces the growth of Oomycota species involved in Kiwifruit Vine Decline Syndrome

This study aimed to determine whether leaf extracts from seven Eruca vesicaria subsp. sativa cultivars and their biochemically active compounds (glucosinolates and downstream-derived products) inhibit mycelia growth of three well-known pathogenic oomycetes, Phytopythium chamaehyphon, Phytopythium vexans and Phytophthora citrophthora; being the most significant in the development of Kiwifruit Vine Decline Syndrome (KVDS). Leaf extract quantity of 10, 20 and 30 mg were inoculated in Petri dish (90 mm Ø, each 22 mL of liquid medium - Potato Dextrose Agar), for in vitro bioassays. A pathogen plug was placed in the centre of each plate and the Oomycota colony perimeter was marked 5 days after inoculation. Radial colony growth was measured from 4 marks per plate 5, 10, and 15 days after inoculation, further elaborated with Image J software image analysis. Growth rates for all strains were inhibited by around 67% after 15 days. This was most pronounced when applying the highest concentration of leaf extract. By using Liquid Chromatography Mass Spectrometry (LC-MS) and Gas Chromatography Mass Spectrometry (GC-MS), fifteen glucosinolate compounds, of which glucosativin was found in the highest quantity, were identified. Concentrations of hydrolysis products produced by leaves (erucin and sativin) were also investigated, and were significantly associated with colony radial growth, especially towards Pp. chamaehyphon and Pp. vexans. Three downstream products of glucosinolates (two pure isothiocyanates, AITC and PEITC; and one indole I3C; all commonly present in Brassicaceae) were also tested, and a statistically significant inhibition of growth was observed at the highest concentration (0.6 µL).