ABSTRACT
Vertigo is a common presenting symptom, but rarely may be caused by a malignancy. We present a case of a 44-year-old man who presented with nystagmus and vertigo precipitated by movement, with accompanying nausea and weight loss. Diagnostic workup revealed a right testicular mass that was resected and found to be a seminoma. The patient's symptoms resolved after surgical resection and treatment with corticosteroids.
Subject(s)
Paraneoplastic Syndromes/etiology , Seminoma/diagnosis , Testicular Neoplasms/diagnosis , Vertigo/etiology , Adult , Humans , Male , Nystagmus, Pathologic/etiology , Paraneoplastic Syndromes/diagnosisABSTRACT
The mechanism by which homologous chromosomes pair during meiosis, as a prelude to recombination, has long been mysterious. At meiosis, the telomeres in many organisms attach to the nuclear envelope and move together to form the telomere bouquet, perhaps to facilitate the homologous search. It is believed that diffusion alone is not sufficient to account for the formation of the bouquet, and that some directed movement is also required. Here we consider the formation of the telomere bouquet in a wheat-rye hybrid both experimentally and using mathematical modelling. The large size of the wheat nucleus and wheat's commercial importance make chromosomal pairing in wheat a particularly interesting and important process, which may well shed light on pairing in other organisms. We show that, prior to bouquet formation, sister chromatid telomeres are always attached to a hemisphere of the nuclear membrane and tend to associate in pairs. We study a mutant lacking the Ph1 locus, a locus ensuring correct homologous chromosome pairing, and discover that bouquet formation is delayed in the wild type compared to the mutant. Further, we develop a mathematical model of bouquet formation involving diffusion and directed movement, where we show that directed movement alone is sufficient to explain bouquet formation dynamics.
Subject(s)
Secale/genetics , Telomere , Triticum/genetics , Chromosomes, Plant , Genes, Plant , Hybridization, Genetic , Models, TheoreticalABSTRACT
Despite possessing multiple sets of related (homoeologous) chromosomes, hexaploid wheat (Triticum aestivum) restricts pairing to just true homologs at meiosis. Deletion of a single major locus, Pairing homoeologous1 (Ph1), allows pairing of homoeologs. How can the same chromosomes be processed as homologs instead of being treated as nonhomologs? Ph1 was recently defined to a cluster of defective cyclin-dependent kinase (Cdk)-like genes showing some similarity to mammalian Cdk2. We reasoned that the cluster might suppress Cdk2-type activity and therefore affect replication and histone H1 phosphorylation. Our study does indeed reveal such effects, suggesting that Cdk2-type phosphorylation has a major role in determining chromosome specificity during meiosis.
Subject(s)
Cyclin-Dependent Kinase 2/metabolism , Meiosis/physiology , Plant Proteins/metabolism , Triticum/metabolism , Cyclin-Dependent Kinase 2/genetics , Gene Expression Regulation, Plant/genetics , Gene Expression Regulation, Plant/physiology , Meiosis/genetics , Molecular Sequence Data , Plant Proteins/genetics , Triticum/geneticsABSTRACT
At the onset of meiosis, chromosomes first decondense and then condense as the process of recognition and intimate pairing occurs between homologous chromosomes. We show here that okadaic acid, a drug known to induce chromosome condensation, can be introduced into wheat interspecific hybrids prior to meiosis to induce chromosome pairing. This pairing occurs in the presence of the Ph1 locus, which usually suppresses pairing of related chromosomes and which we show here delays condensation. Thus the timing of chromosome condensation during the onset of meiosis is an important factor in controlling chromosome pairing.
