Egg yolk-based diluents provide adequate cryoprotection for the sperm of several mammalian species. Traditionally, chicken egg yolk has been used as additive for the freeze preservation of spermatozoa because of its w...
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Egg yolk-based diluents provide adequate cryoprotection for the sperm of several mammalian species. Traditionally, chicken egg yolk has been used as additive for the freeze preservation of spermatozoa because of its wide availability. Variations in the chemical composition of the egg yolk of different avian species appear to influence the protection afforded during cooling, freezing, and thawing. The aim of the present study was to assess the use of quail egg yolk as a novel additive for the epididymal spermatozoa of a threatened wild ruminant species-the Spanish ibex-and to compare its efficacy with chicken egg yolk. Epididymal spermatozoa were diluted using a Tris-citric acid-glucose medium (TCG) composed of 3.8% Tris (w v(-1)), 2.2% citric acid (w v(-1)), 0.6% glucose (w v(-1)), 5% glycerol (v v(-1)), and 6% egg yolk (v v(-1)). Sperm masses from the right epididymes were diluted with TCG-6% chicken egg yolk medium, while those from the left were diluted with TCG-6% quail egg yolk. The thawed spermatozoa preserved with TCG-6% quail egg yolk extender exhibited lower motility (P < 0.001), membrane integrity (P < 0.001), and viability (P < 0.01) than those diluted with the TCG-6% chicken egg yolk extender. The fertility of spermatozoa frozen in TCG-6% chicken egg yolk tended to be higher than in those frozen with TCG-6% quail egg yolk (63.3% vs 36.4%, P = 0.19). These results show that quail egg yolk offers no advantages over chicken egg yolk in the cryopreservation of Spanish ibex epididymal spermatozoa. (C) 2008 Elsevier Inc. All rights reserved.
A novel, highly stable photochromic dyad 3 based on a perylene bisimide (PBI) fluorophore and a diarylethene (DAE) photochrome was synthesized and the optical and photophysical properties of this dyad were studied in ...
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A novel, highly stable photochromic dyad 3 based on a perylene bisimide (PBI) fluorophore and a diarylethene (DAE) photochrome was synthesized and the optical and photophysical properties of this dyad were studied in detail by steady-state and time-resolved ultrafast spectroscopy. This photochromic dyad can be switched reversibly by UV-light irradiation of its ring-open form 3?o leading to the ring-closed form 3?c, and back reaction of 3?c to 3?o by irradiation with visible light. Solvent-dependent fluorescence studies revealed that the emission of ring-closed form 3?c is drastically quenched in solvents of medium (e.g., chloroform) to high (e.g., acetone) polarities, while the emission of the ring-open form 3?o is appreciably quenched only in highly polar solvents like DMF. The strong fluorescence quenching of 3?c is attributed to a photoinduced electron-transfer (PET) process from the excited PBI unit to ring-closed DAE moiety, as this process is thermodynamically highly favorable with a Gibbs free energy value of -0.34 eV in dichloromethane. The electron-transfer mechanism for the fluorescence quenching of ring-closed 3?c is substantiated by ultrafast transient measurements in dichloromethane and acetone, revealing stabilization of charge-separated states of 3?c in these solvents. Our results reported here show that the new photochromic dyad 3 has potential for nondestructive read-out in write/read/erase fluorescent memory systems.
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