The reprogramming of parental methylomes is essential for embryonic development. In mammals, paternal 5-methylcytosines (5mCs) have been proposed to be actively converted to oxidized bases. These paternal oxidized bases and maternal 5mCs are believed to be passively diluted by cell divisions. By generating single-base resolution, allele-specific DNA methylomes from mouse gametes, early embryos and primordial germ cell (PGC), as well as single-base resolution maps of oxidized cytosine bases for early embryos, we report the existence of 5hmC and 5fC in both maternal and paternal genomes and find that 5mC or its oxidized derivatives, at the majority of demethylated CpGs, are converted to unmodified cytosines independent of passive dilution from gametes to 4-cell embryos. Therefore, we conclude that paternal methylome and at least a significant proportion of maternal methylome go through active demethylation during embryonic development. Additionally, all the known imprinting control regions (ICRs) were classified into germ-line or somatic ICRs.

Ultraviolet (UV) weathering performance of unpigmented and rutile titanium dioxide pigmented rigid polyvinyl chloride (PVC)/wood-fiber composites has been studied. The composite samples were manufactured by dry-blending PVC, wood fibers, and other processing additives in a high-intensity mixer. The dry-blended compounds were extruded and compression molded into panel samples. The manufactured samples were artificially weathered using laboratory accelerated UV tests. Composite samples were exposed to 340-nm fluorescent UV lamps and assessed every 200 h, for a total of 1200 h of accelerated weathering. Each assessment consisted of a visual examination of surface roughness or erosion, a contact angle measurement, a FTIR collection, and a color measurement. The experimental results indicated that wood fibers are effective sensitizers and that their incorporation into a rigid PVC matrix has a deleterious effect on the ability of the matrix to resist degradation caused ultraviolet irradiation. The light stability of these composites could be improved quite efficiently with the addition of rutile titanium dioxide photoactive pigment during formulation.

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