Ocular syphilis - a case series of four patients.

Ocular manifestations of syphilis with visual impairment symptoms may occur already at the stage of secondary syphilis. They may also be the only manifestation of syphilis and mimic other diseases of the eye. Therefore, in all patients with uveitis, optic neuritis, optic atrophy, acute ocular muscle paresis, or loss of visual acuity, syphilis infection should be ruled out, even if the medical history does not initially raise suspicion. Ocular involvement should be treated as neurosyphilis. Delayed diagnosis and inadequate therapy are often associated with irreversible consequences for the affected patient. As with any syphilis infection, HIV infection should be considered and excluded, especially in the case of ocular manifestations.

Heterosis in early seed development: a comparative study of F1 embryo and endosperm tissues 6 days after fertilization.

Heterosis specifies the superior performance of heterozygous individuals and although used in plant breeding the underlying molecular mechanisms still remain largely elusive. In this study, we demonstrate the manifestation of heterosis in hybrid maize embryo and endosperm tissue 6 days after fertilization in crosses of several inbred lines. We provide a comparative analysis of heterosis-associated gene expression in these tissues by a combined approach of suppression subtractive hybridization and microarray hybridizations. Non-additive expression pattern indicated a trans-regulatory mechanism to act early after fertilization in hybrid embryo and endosperm although the majority of genes showed mid-parental expression levels in embryo and dosage dependent expression levels in endosperm. The consistent expression pattern within both tissues and both inbred line genotype combinations of genes coding for chromatin related proteins pointed to heterosis-related epigenetic processes. These and genes involved in other biological processes, identified in this study, might provide entry points for the investigation of regulatory networks associated with the specification of heterosis.

Epigenetic resetting of a gene imprinted in plant embryos.

Genomic imprinting resulting in the differential expression of maternal and paternal alleles in the fertilization products has evolved independently in placental mammals and flowering plants. In most cases, silenced alleles carry DNA methylation. Whereas these methylation marks of imprinted genes are generally erased and reestablished in each generation in mammals, imprinting marks persist in endosperms, the sole tissue of reported imprinted gene expression in plants. Here we show that the maternally expressed in embryo 1 (mee1) gene of maize is imprinted in both the embryo and endosperm and that parent-of-origin-specific expression correlates with differential allelic methylation. This epigenetic asymmetry is maintained in the endosperm, whereas the embryonic maternal allele is demethylated on fertilization and remethylated later in embryogenesis. This report of imprinting in the plant embryo confirms that, as in mammals, epigenetic mechanisms operate to regulate allelic gene expression in both embryonic and extraembryonic structures. The embryonic methylation profile demonstrates that plants evolved a mechanism for resetting parent-specific imprinting marks, a necessary prerequisite for parent-of-origin-dependent gene expression in consecutive generations. The striking difference between the regulation of imprinting in the embryo and endosperm suggests that imprinting mechanisms might have evolved independently in both fertilization products of flowering plants.