Publications

Export 32 results:
Sort by: Author Title Type [ Year  (Desc)]
2012
a. Gad, K. Schellander, M. Hoelker, and D. Tesfaye, "Transcriptome profile of early mammalian embryos in response to culture environment", Animal Reproduction Science, vol. 134, issue 2010: Elsevier B.V., pp. 76-83, 2012. Abstract

n/a

a Abdoon, S., N. Ghanem, O. M. Kandil, A. Gad, K. Schellander, and D. Tesfye, "cDNA microarray analysis of gene expression in parthenotes and in vitro produced buffalo embryos.", Theriogenology, vol. 77, pp. 1240-1251, 2012. Abstract

The retarded development of parthenote embryo could be due to aberrant epigenetic imprinting, which may disrupt many aspects and lead to conceptus demise. The present work was conducted to: 1) compare the development of in vitro produced (IVP) and parthenogenetically developed (P) buffalo embryos from the 2-cell to blastocyst stage; 2) investigate the global gene expression profile and search for new candidate transcripts differing between IVP and P buffalo blastocyst using cDNA microarray analysis (validated by Real Time PCR); 3) follow the particular expression patterns of PLAC8 and OCT4 genes at five different stages of preimplantation development by Real Time PCR; and 4) study the expression of CDX2 at the blastcocyst stage. Cleavage rate was higher (P < 0.05) in P than IVP buffalo embryos, while, progression to blastocyst and number of cells per blastocyst were lower (P < 0.05) in P than IVP blastocysts. Microarray analysis indicate that 56 differentially expressed genes between the two groups, of which 51 genes (91.07%) were up-regulated, and five genes were downregulated in IVP blastocyst, using 1.4 fold-changes as a cutoff. Differentially expressed genes are related to translation, nucleic acid synthesis, cell adhesion and placentation. Validation of candidate genes revealed that the transcript abundance of PTGS2, RPS27A, TM2D3, PPA1, AlOX15, RPLO and PLAC8 were downregulated (7/8) in parthenote blastocyst compared to the IVP blastocyst. PLAC8 gene expression was higher (P < 0.05) at 2-cell, morula and blastocyst stages in IVP embryos compared with parthenote embryos. The OCT4 gene expression was higher (P < 0.05) in 2-cell, 4-cell, 8-cell and blastocysts produced in vitro. In conclusion, the retarded development of parthenogenetic buffalo embryos could be due to downregulation of genes related to translation, nucleic acid synthesis, cell adhesion, and placental development. The low expression of PLAC8 and OCT4 during the different stages of development may be responsible, in part, to the failure of development of parthenote buffalo embryos.

Forde, N., F. Carter, S. di Francesco, J. P. Mehta, M. Garcia-Herreros, A. Gad, D. Tesfaye, M. Hoelker, K. Schellander, and P. Lonergan, "Endometrial response of beef heifers on day 7 following insemination to supraphysiological concentrations of progesterone associated with superovulation.", Physiological genomics, vol. 44, issue 22, pp. 1107-15, 2012. Abstract

Ovarian stimulation is a routine procedure in assisted reproduction to stimulate the growth of multiple follicles in naturally single-ovulating species including cattle and humans. The aim of this study was to analyze the changes induced in the endometrial transcriptome associated with superovulation in cattle and place these observations in the context of our previous data on changes in the endometrial transcriptome associated with elevated progesterone (P4) concentrations within the physiological range and those changes induced in the embryo due to superovulation. Mean serum P4 concentrations were significantly higher from day 4 to day 7 in superovulated compared with unstimulated control heifers (P < 0.05). Between-group analysis revealed a clear separation in the overall transcriptional profile of endometria from unstimulated control heifers (n = 5) compared with superovulated heifers (n = 5). This was reflected in the number of differentially expressed genes (DEGs) identified between the two groups with 795 up- and 440 downregulated in superovulated endometria. Ten times more genes were altered by superovulation (n = 1,234) compared with the number altered due to elevated P4 within physiological ranges by insertion of a P4-releasing intravaginal device (n = 124) with only 22 DEGs common to both models of P4 manipulation. Fewer genes were affected by superovulation in the embryo compared with the endometrium, (443 vs. 1,234 DEGs, respectively), and the manner in which genes were altered was different with 64.5% of genes up- and 35.5% of genes downregulated in the endometrium, compared with the 98.9% of DEGs upregulated in the embryo. In conclusion, superovulation induces significant changes in the transcriptome of the endometrium which are distinct from those in the embryo.

2011
Ghanem, N., D. Salilew-Wondim, A. Gad, D. Tesfaye, C. Phatsara, E. Tholen, C. Looft, K. Schellander, and M. Hoelker, "Bovine blastocysts with developmental competence to term share similar expression of developmentally important genes although", Reproduction, vol. 142, issue 4, pp. 551-64, 2011. Abstract

n/a

Gad, A., U. Besenfelder, F. Rings, N. Ghanem, D. Salilew-Wondim, M. M. Hossain, D. Tesfaye, P. Lonergan, a Becker, U. Cinar, et al., "Effect of reproductive tract environment following controlled ovarian hyperstimulation treatment on embryo development and global transcriptome profile of blastocysts: implications for animal breeding and human assisted reproduction.", Human reproduction (Oxford, England), vol. 26, issue 7, pp. 1693-707, 2011. Abstract

In mammals, the reproductive tract plays a crucial role in the success of early reproductive events and provides an optimal microenvironment for early embryonic development. However, changes in the reproductive tract environment associated with controlled ovarian hyperstimulation and the influence on the embryo transcriptome profile have not been investigated. Therefore, we investigated differences in the development rate and the transcriptome profile of bovine blastocysts developing in the reproductive tract of unstimulated or superovulated heifers.

Abd El Naby, W. S., T. H. Hagos, M. M. Hossain, D. Salilew-Wondim, Y. a Gad, F. Rings, M. U. Cinar, E. Tholen, C. Looft, K. Schellander, et al., "Expression analysis of regulatory microRNAs in bovine cumulus oocyte complex and preimplantation embryos.", Zygote (Cambridge, England), pp. 1-21, 2011. Abstract

SummaryMicroRNAs (miRNAs) are small endogenous molecules that are involved in a diverse of cellular process. However, little is known about their abundance in bovine oocytes and their surrounding cumulus cells during oocyte development. To elucidate this situation, we investigated the relative expression pattern of sets of miRNAs between bovine oocyte and the surrounding cumulus cells during in vitro maturation using miRNA polymerase chain reaction (PCR) array. Results revealed that a total of 47 and 51 miRNAs were highly abundant in immature and matured oocytes, respectively, compared with their surrounding cumulus cells. Furthermore, expression analysis of six miRNAs enriched in oocyte miR-205, miR-150, miR-122, miR-96, miR-146a and miR-146b-5p at different maturation times showed a dramatic decrease in abundance from 0 h to 22 h of maturation. The expression of the same miRNAs in preimplantation stage embryos was found to be highly abundant in early stages of embryo development and decreased after the 8-cell stage to the blastocyst stage following a typical maternal transcript profile. Similar results were obtained by localization of miR-205 in preimplantation stage embryos, in which signals were higher up to the 4-cell stage and reduced thereafter. miR-205 and miR-210 were localized in situ in ovarian follicles and revealed a spatio-temporal expression during follicular development. Interestingly, the presence or absence of oocytes or cumulus cells during maturation was found to affect the expression of miRNAs in each of the two cell types. Hence, our results showed the presence of distinct sets of miRNAs in oocytes or cumulus cells and the presence of their dynamic degradation during bovine oocyte maturation.

2007
El-Gendy, E. A., A. Y. Gad, and A. Mostageer, "Sperm-mediated gene transfer in poultry 1. The relationship with cock sperm viability", Arab Journal of Biotechnology, vol. 10, issue 1, pp. 1-12, 2007. Abstract

n/a

Tourism