Localization of satellite DNA and associated proteins in respect to nucleolar precursor bodies in one- and two-cell mouse embryos

Nucleolar precursor bodies (NPB) are discrete entities in zygotic pronuclei and in the nuclei of two-cell mouse embryos. Centromeric (CEN) and pericentromeric (periCEN) chromosome regions are associated with the chromatin layer surrounding NPB. Four types of satellite DNA (satDNA) are currently known in Mus musculus, including mouse minor satellite 4 (MiSat), mouse satellite 3 (MS3) in the CEN region, mouse major satellite (MaSat), and mouse satellite (MS4) in the periCEN region. We determined the localization of these four types of mouse satDNA and associated proteins (RNA-helicase p68, SMC3, Rad21 subunits of the cohesin complex and SYCP3 subunit of the synaptonemal complex) in respect to NPB. Partially flattened nuclei of the one- and two-cell intact embryos and embryos treated with okadaic acid (OA) were used. It was found that different satDNA are localized in different regions at the NPB surface: periCEN MaSat occupied almost the whole NPB surface; CEN MiSat, MS3 and periCEN MS4 were located more peripherally. All four satDNA did not cover the entire NPB area, which indicates the presence of other DNA sequences involved in the association with NPB periphery. Among the proteins probed, RNA-helicase p68 and components of multiprotein cohesin and synaptonemal complexes (SCs) showed the most prominent colocolization with NPB. Our results support the idea that NPB are chromocenter precursors.     

Generation of rat-induced pluripotent stem cells: Reprogramming and culture medium

The rat represents an animal model highly attractive for studying pharmacology, physiology, aging, cardiovascular diseases, etc., that in many aspects is more adequate than the mouse model. Derivation of induced pluripotent stem cells from rats (riPS) opens the opportunity for gene targeting in specific rat strains, as well as for the development of new protocols for the treatment of different degenerative diseases. Here we report an improved protocol for riPS cell generation, which is based on lentivirus delivery of reprogramming factors with their subsequent excision from the genome, application of serum-free media and chemical inhibitors MEK and GSK. We compared various conditions for riPS cell derivation, analyzed the cell karyotype, and assessed the pluripotency of the established cells. These data may prompt further iPS cell-based gene targeting in rat, as well as the development of iPS-based cell therapy, using this animal model.     

Understanding the basic biology underlying the flavor world of children

Health organizations worldwide recommend that adults and children minimize intakes of excess energy and salty, sweet, and fatty foods (all of which are highly preferred tastes) and eat diets richer in whole grains, low- and non- fat dairy products, legumes, fish, lean meat, fruits, and vegetables (many of which taste bitter). Despite such recommendations and the well-established benefits of these foods to human health, adults are not complying, nor are their children. A primary reason for this difficulty is...     

Theoretical and applied aspects of epigenetic reprogramming in mammalian development

Epigenetic reprogramming implies changes in germ and somatic cells of an embryo, which are the consequences of gene activity regulation by means of DNA methylation, histone modification, and altered chromatin compaction. This suggests that epigenetic changes in mammalian cell nucleus occur during gametogenesis and toti-potent zygote formation. Epigenetic changes proceed during morphological and inductive interactions between cleaving blastomeres and subsequent interactions between the inner cell contents and trophoectoderm, as well as when the germinal layers (blastophyllums) and their derivatives appear, i.e., during the embryonic histogenesis. Some authors assume that in vitro fertilization and consequent human zygote cultivation lead to defects of genomic imprinting. This leads to abnormal embryonic and fetal development and increased incidence of hereditary diseases-Beckwith-Wiederman or Angelman syndromes. The present review, critically considers the facts on which the above hypothesis is based.     

Morphogenesis of neural derivates after transplantation of the rat embryo telencephalon to the testis of sexually mature animals

Some aspects of proliferation (the number of DNA synthesizing cells) and differentiation of forebrain (telencephalon) isolated from a 14.5 day old rat embryo and then transplanted into the testis of syngenetic animals were studied for 90 days. The embryonic cells proliferated for 12 days then their differentiation started and many types of differentiated neuronal and glial cells of the definitive brain were found in the transplant. Histological structure of the transplant was without cytoarchitecture of cerebral cortex. The comparison of the obtained data and literature allows us to make a conclusion that realization of morphogenetic potencies of the rat forebrain anlage are the same not only after transplantation into definitive brain, but after being transplanted into different ectopic places; including testis.     

Renewal time, proliferative pool and duration of the mitotic cycle of the epithelial cells of the common bile duct]

Using cholchicine and H3-thymidine the following parameters of the mitotic cycle (in hours) were calculated: T=56.6; tm=0.9; tg2=1.2; ts=6; tg1=48.5 The proliferative pool was 7.5% and the time of epithelium renewal--754.5 hours. The common bile duct epithelium should be referred to the tissue systems with slow renewal.     

Reference concentrations of cholecalciferol in animals: a basis for establishing non-target exposure

Abstract

Cholecalciferol (vitamin D₃) is widely used as a vertebrate pesticide in New Zealand. However, cholecalciferol also occurs naturally in animals. Therefore, when trying to determine whether a non-target animal has been exposed to cholecalciferol baits, knowledge of the baseline cholecalciferol concentrations in the animal's plasma and tissue is required. We analysed cattle, sheep, pig, deer, dog and cat plasma and liver samples for the vitamin D₃ metabolite 25-hydroxycholecalciferol (25-OHD), a sensitive biomarker for cholecalciferol. Based on these data and a literature search we present 25-OHD reference ranges. We also examined the literature for 25-OHD concentrations in poisoned animals and compared these to the reference ranges. Where plasma and liver samples have 25-OHD concentrations at least four times higher than our reference ranges it is likely that the animal has been exposed to cholecalciferol baits. 25-OHD concentrations 10 times higher than the reference range indicate ingestion of abnormally high amounts of cholecalciferol.