Inhibition of RNA Synthesis and the Relationship between Nucleolar and Mitotic Cycles in Zea mays Root Meristems

The relationship between nucleolar and mitotic cycles has beendetermined after treatment of root apices of Zea mays with ethidiumbromide. In the meristematic regions of the stele the two cyclesare not much displaced in relation to each other except fora delay in the onset of the disorganization phase. A few nucleolipersist into metaphase and a few nuclei undergo an amitoticdivision. In the cap initials the drug greatly delays the onsetof disorganization of the nucleolus, which normally occurs beforeprophase in this region. It also delays the completion of reorganizationso that fully organized nucleoli are no longer available duringthe last half of telophase. In the quiescent centre the onsetof disorganization and the end of reorganization of the nucleoliare also delayed in relation to mitosis. There is no evidencefor a delay in the onset of reorganization in any region ofthe meristem. Some cells form multiple micronucleoli and this aberrant behaviouroccurs more often in the cap initials than elsewhere as doesamitotic division.     

Remodeling of angiogenesis and lymphangiogenesis in cervical cancer development

The ability to stimulate angiogenesis/lymphangiogenesis is an intrinsic property of cancer cells, providing them necessary conditions for growth and metastasis. The “angiogenic switch” is one of the earliest consequences of malignant transformation; it involves altered expression of numerous genes and triggers a complex set of signaling pathways in endothelial cells. Processes of tumor microvascular network formation are closely associated with the stages of carcinogenesis (from appearance of benign lesions to invasive forms) and occur with numerous deviations from the norm. Analysis of expression of proangiogenic factors during sequential steps of cervical cancer development (intraepithelial neoplasia, cancer in situ, microinvasive, and invasive cancer) provides opportunity to reconstruct the regulatory mechanisms of angiogenesis/lymphangiogenesis with emphasis on the most important components. This review summarizes literature data on expression of key regulators of angiogenesis in cervical intraepithelial neoplasia and cervical cancer and analyses their possible involvement in molecular mechanisms of neoplastic transformation of epithelial cells, as well as invasion and tumor metastasis. Correlation between expression of proangiogenic molecular factors and various clinicopathological parameters is considered in the context of their possible use in molecular diagnostics and targeted therapy of cervical cancer. Special attention is paid to rather poorly studied regulators of lymphangiogenesis and “non-VEGF dependent,” or alternative, angiogenic pathways that constitute the prospect of future research in the field.     

Stromule-like protrusions of plastid membrane envelope in root cells

The work presents the results of the electron-microscopy visualization of stromule-like protrusions of plastid membrane envelope in root cells. Cases of the appearance of a long, narrow protrusion of the outer membrane, in which the shorter protrusion of the plastid envelope inner membrane was located, are discussed. The possible role of cytoskeleton and plastoskeleton in formation of outer and inner protrusions, respectively, is considered. It is concluded that items of the structure and functions of stromules in plant cells are to be considered to be the same as the structure and functions of the intracavity space of endoplasmic reticulum.     

Identification of the ORC Complex Subunits That Can Interact with the ENY2 Protein of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The interaction of the Drosophila ENY2 protein with the ORC complex subunits was investigated. It is found that ORC4 and ORC6 subunits directly interact with ENY2.     

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.