Oocyte morphology and estrogen concentrations following a reduction in progesterone in beef cattle

Low dosages of progestogens promote persistent follicles, high systemic estrogen and low fertility. The objectives of this study were to determine effects of a reduction in progesterone on (1) morphology of oocytes and intrafollicular concentrations of estradiol. Cows on low progesterone (n = 12) received used intravaginal progesterone inserts on d 4 after estrus and prostaglandin (PG) F2alpha (25 mg, i.m.) on d 6. Control animals (n = 12) received saline on d 6. The oocyte and follicular fluid were recovered from the largest follicle on d 8 or d 10.;Serum estradiol was lower during d 4--6 but greater (P \u3c .01) during d 7--10 in cows treated with progesterone inserts and PGF 2alpha while the largest follicle was larger in treated cows on day 10 only (14 vs. 12 mm; P \u3c .05). Intrafollicular concentrations of estrogen were greater in treated than in control cows (990 +/- 87 vs 191 +/- 106; P \u3c .01). Progesterone in follicular fluid (mean = 42 ng/ml) did not differ. Oocytes were observed in oocyte nuclear stage I in the control group on d 8. All other oocytes were in nuclear stage II. In addition, the degree of clumping of mitochondria, the percentage of intact cumulus cell processes and percentage of normally shaped mitochondria was greater in oocytes from d 8 control cows than in all other groups.;Changes in concentrations of estradiol and oocyte morphology typically associated with the preovulatory period had occurred within 2 d after a reduction in progesterone, even when low peripheral concentrations of progesterone were maintained. These earliest stages of oocyte maturation occurred in response to a reduction in progesterone. Similar changes in oocyte morphology were observed in control animals by d 10 of the estrous cycle, probably representing the onset of atresia

Mapping the Evolution of Optically-Generated Rotational Wavepackets in a Room Temperature Ensemble of D2_2

A coherent superposition of rotational states in D$_2$ has been excited by nonresonant ultrafast (12 femtosecond) intense (2 $\times$ 10$^{14}$ Wcm$^{-2}$) 800 nm laser pulses leading to impulsive dynamic alignment. Field-free evolution of this rotational wavepacket has been mapped to high temporal resolution by a time-delayed pulse, initiating rapid double ionization, which is highly sensitive to the angle of orientation of the molecular axis with respect to the polarization direction, $\theta$. The detailed fractional revivals of the neutral D$_2$ wavepacket as a function of $\theta$ and evolution time have been observed and modelled theoretically.Comment: 4 pages, 3 figures. Accepted for publication in Phys. Rev. A. Full reference to follow.