RESUMO
In this paper, we provide solid evidence to show that among an overwhelming structural diversity, alkaline earth metals (Ca, Sr, Ba) have the ability to form inverted sandwich compounds with C6H6, C7H7(+), and C8H8(2+) of Dnh symmetry and general formula [E-(CnHn)-E](n-6) (n = 6-8) with planar 10-π-electron aromatic cores by virtue of transferring two electrons per metal atom to the ring. However, the origin of the orbital interaction between the metals and the carbon ring is quite different; while [E-(C6H6)-E] complexes are dominated by δ-interactions, both π- and δ-interactions are important in [E-(C7H7)-E](+) and [E-(C8H8)-E](2+) complexes.
RESUMO
The degenerate rearrangement in the 21-homododecahedryl cation (1) has been studied via density functional theory computations and Born-Oppenheimer Molecular Dynamics simulations. Compound 1 can be described as a highly fluxional hyperconjugated carbocation. Complete scrambling of 1 can be achieved by the combination of two unveiled barrierless processes. The first one is a "rotation" of one of the six-membered rings via a 0.8 kcal·mol(-1) barrier, and the second one is a slower interconvertion between two hyperconjomers via an out-of-plane methine bending (ΔG(⧧) = 4.0 kcal·mol(-1)).
RESUMO
ABSTRACT Early embryonic mortality is one of the main sources of reproductive wastages and major constraints for full exploitation of the production potential of livestock. The survivality of embryo during early embryonic life is mostly dependent on the efficiency with which the maternal recognition of pregnancy (MRP) is established. Maternal recognition of pregnancy involves molecular dialogue between the trophoblast of conceptus and uterine endometrium. Embryonic development to the blastocyst stage and uterine differentiation to the receptive environment are crucial for successful establishment of the embryo-uterine cross-talk that leads to the initiation and progression of successful implantation. Unravelling the complex intricate molecular and cellular dialogues between the conceptus and uterine environment will facilitate development of strategies to augment early embryo survivality.
RESUMO
The present study evaluated the effect of fibroblast growth factor 2 (FGF2) and insulin-transferrin-selenium (ITS) to the in vitro maturation and embryo culture media on ovine oocyte maturation, cleavage and embryo development. Oocytes having more than five layers of unexpanded cumulus cells and granular homogenous ooplasm were cultured into 50 μL droplets of eight different culture systems: (i) TCM-199 (Tissue Culture Medium-199); (ii) TCM-199+10 ng/mL FGF2; (iii) TCM-199+20 ng/mL FGF2; (iv) TCM-199+30 ng/mL FGF2; (v) TCM-199+10 ng/mL ITS; (vi) TCM-199+20 ng/mL ITS; (vii) TCM-199+30 ng/mL ITS and (viii) TCM-199+20 ng/mL ITS+20 ng/mL FGF2 in a CO2 incubator at 38.50C for 24 h. All the oocyte culture media were supplemented with 10% FBS, FSH (10 μg/mL) and gentamicin (50 µg/mL). The maturation rate was assessed based on the degree of expansion of cumulus cells and identifying first polar body extrusion into perivitelline space. The matured oocytes were inseminated with 1 to 2 million spermatozoa/mL in Brackett and Oliphant medium and the cleavage rate was checked after 42-48 h post insemination and further cultured for 6-7 days. Maturation and cleavage rates were significantly higher (P<0.05) in the oocytes cultured in TCM-199 +10% FBS+FSH (10 μg/mL) supplemented with both 20 ng/mL ITS and 20 ng/mL FGF2 as compared to the control. It was concluded that the supplementation of ITS and FGF2 in maturation medium was beneficial for improving maturation and cleavage rates of sheep oocytes. The addition of ITS and FGF2 in embryo culture medium did not improve the development of sheep embryos.