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Contents Transcription of the ribosomal RNA (rRNA) genes occurs in the nucleolus resulting in ribosome synthesis. The rRNA gene activation and the associated nucleolus formation may be used as a marker for the activation of the embryonic genome in mammalian embryos and, thus, serve to evaluate the developmental potential of embryos originating from different embryo technological procedures. In bovine in-vitro-produced embryos, functional ribosome-synthesizing nucleoli become structurally recognizable towards the end of the fourth post-fertilization cell cycle. A range of important nucleolar proteins (e.g. fibrillarin, nucleophosmin, nucleolin, topoisomerase I, upstream binding factor and RNA polymerase I) become localized to the nucleolar anlage over several cell cycles and this localization is completed towards the end of the fourth cell cycle. In nuclear transfer embryos originating from day 5–6 in-vitro-produced bovine embryos, fully developed nucleoli are apparently detected one cell cycle later, and a substantial proportion of the nuclear transfer embryos display aberrations in protein localization in one or more blastomeres. This information may help to explain the abnormalities observed in a proportion of fetuses and offspring derived from nuclear transfer embryos. [ABSTRACT FROM AUTHOR]

The body condition score (BCS) of cows affects their reproductive efficiency, but the underlying mechanism is unclear. We examined the effect of BCS on the basic ovarian cell functions and their responses to gonadotropic and metabolic hormones. We isolated ovarian cells from cows with a tendency toward emaciation (BCS2) and those with an average body condition (BCS3), and we compared their hormonal release and responses to FSH, leptin, ghrelin, and neuropeptide Y (NPY) added at doses of 0, 1, 10, or 100 ng/mL. Progesterone, testosterone, estradiol, and insulin-like growth factor I (IGF-I) release were evaluated by RIA. No differences were found in progesterone or testosterone release between BCS2 and BCS3 cells; however, ovarian cells from BCS2 cows released more estradiol and IGF-I than cells from BCS3 cows. FSH, ghrelin, and NPY promoted progesterone release in BCS2 cells but had no stimulatory or inhibitory effect on BCS3 cells. In contrast, leptin promoted progesterone release in BCS3 cells and inhibited progesterone release in BCS2 cells. FSH also promoted testosterone release in both BCS2 and BCS3 cells but inhibited progesterone at a low dose in BCS3 cells. Leptin inhibited testosterone release in BCS3 cells but not in BCS2 cells. Estradiol release was promoted by leptin and ghrelin in BCS3 cells; however, it was unaffected by leptin and inhibited by ghrelin in BCS2 cells. IGF-I production was promoted by FSH and inhibited by leptin in both groups. Ghrelin suppressed IGF-I release in BCS2 cells and increased IGF-I release in BCS3 cells. NPY promoted IGF-I release in BCS2 cells but not in BCS3 cells. Our results demonstrate the effects of BCS on ovarian cell estradiol and IGF-I (but not progesterone or testosterone) release, as well as on the responses of ovarian cells to FSH, leptin, ghrelin, and NPY. [ABSTRACT FROM AUTHOR]

Abstract: The nucleolus is the site of ribosomal RNA (rRNA) and ribosome production. In the bovine primordial follicle oocyte, this organelle is inactive, but in the secondary follicle an active fibrillo-granular nucleolus develops and proteins involved in rDNA transcription (topoisomerase I, RNA polymerase I and upstream binding factor) and early (fibrillarin) or late rRNA processing (nucleolin and nucleophosmin) localize to it. At the end of the oocyte growth phase, the nucleolus is inactivated again and transforms into a solid remnant. The nucleolar remnant is dissolved when meiosis is resumed. Upon fertilization, structures resembling the nucleolar remnant, now referred to as nucleolus precursor bodies (NPBs), are established in the pronuclei. These entities are engaged in the re-establishment of fibrillo-granular nucleoli at the major activation of the embryonic genome. This nucleolar formation can be classified into two different modes: one where nucleolus development occurs inside NPBs (internal; e.g. cattle) and the other where it occurs on the surface of NPBs (external; e.g. pig). Oocyte derived proteins engaged in late rRNA processing (nucleolin and nucleophosmin) may to some degree be re-used for nucleolar formation in the embryo, while the other nucleolar proteins require de novo embryonic transcription in order to be allocated to the developing nucleoli. Moreover, unprocessed rRNA inherited from the oocyte targets to the developing embryonic nucleoli. In conclusion, the nucleolus is important for the development of oocytes and embryos and may serve as a marker for the completion of oocyte growth and the normality of activation of the embryonic genome. [Copyright &y& Elsevier]

Abstract: Pre-implantation embryos derived by in vitro fertilization differ in their developmental potential from embryos obtained in vivo. In order to characterize changes in gene expression profiles caused by in vitro culture environment, we employed microarray constructed from bovine oocyte and preimplantation embryo-specific cDNAs (BlueChip, Université Laval, Québec). The analysis revealed changes in the level of 134 transcripts between in vitro derived (cultured in COOK BVC/BVB media) and in vivo derived 4-cell stage embryos and 97 transcripts were differentially expressed between 8-cell stage in vitro and in vivo embryos. The expression profiles of 7 selected transcripts (BUB3, CUL1, FBL, NOLC1, PCAF, GABPA and CNOT4) were studied in detail. We have identified a switch from Cullin 1-like transcript variant 1 to Cullin 1 transcript variant 3 (UniGene IDs BT.36789 and BT.6490, respectively) expressions around the time of bovine major gene activation (8-cell stage). New fibrillarin protein was detected by immunofluorescence already in early 8-cell stage and this detection correlated with increased level of fibrillarin mRNA. The qRT-PCR analysis revealed significant differences in the level of BUB3, NOLC1, PCAF, GABPA and CNOT4 gene transcripts between in vivo derived (IVD) and in vitro produced (IVP) embryos in late 8-cell stage. The combination of these genes represents a suitable tool for addressing questions concerning normal IVD embryo development and can be potentially useful as a marker of embryo quality in future attempts to optimize in vitro culture conditions. [Copyright &y& Elsevier]

An abstract of the study "Expression Pattern of DNMT1 and DNMT3a Genes During Intergeneric Somatic Cell Nuclear Transfer Embryo Development," by M. Morovic et al, is presented.

An abstract of the study "Limitations of Porcine Ooplasm to Reprogram Bovine Somatic Cells," by F. Strejcek et al is presented.

Ooplasm posses several, undefined factors allowing for reprogramming of somatic genome into pluripotent state. However, it is presently unknown if and to what extent the ooplasm is able to interact with a transferred somatic cell from another species in the context of interspecies somatic cell nuclear transfer (SCNT). The 1-cell stage embryos were processed at different time points (2, 4, 8, and 12h post-activation) for detailed nuclear and nucleolar analysis by TEM, and immunofluorescence for visualisation of nucleolar proteins related to transcription (UBF) and processing (fibrillarin). The embryos produced by SCNT of porcine fibroblast into non-activated bovine ooplasm were compared to bovine parthenogenetic counterparts. In the absence of morphological remodelling features (premature chromatin condensation, nuclear envelope break-down), intergeneric embryos showed bovine nuclear and nucleolar precursor body (NPB) morphology. The somatic cell introduced into the bovine ooplasm displayed intranuclear activity at the post-translational level signalling a universal function of ooplasmic factors. The lack of distinct UBF localization in intergeneric embryos, however, suggests failures in sequence-specific interactions between the ooplasm and transferred cell from another genus. We conclude that sperm or a somatic cell of the same species is required for successful embryonic development. Clonet MRTN-CT-2006-035468; MedRat LSHG-CT-2006-518240; PluriSys FP7-HEALTH-2007-223485; DFG, Alexander von Humboldt fellowship, VEGA 1/0057/08; VEGA 1/0012/10. [ABSTRACT FROM AUTHOR]