Effect of photoperiod on ovarian morphology, reproductive hormone secretion, and hormone receptor mRNA expression in layer ducks during the pullet phase.

We evaluated the effect of photoperiod on ovarian morphology, reproductive hormone secretion, and hormone receptor mRNA expression in layer ducks during the pullet phase. A total of 480 71-d-old Jinding layer ducks were randomly divided into 5 groups that received 6L (hours of light):18D (hours of darkness), 8L:16D, 10L:14D, 12L:12D, or 14L:10D, respectively. Each group had 6 replicates with 16 birds each. The photoperiod feeding trial lasted 80 d until 150 d of age. The age at first egg (AFE), the total number, and weight of eggs increased linearly with increasing photoperiods (P < 0.05); lower values of AFE occurred with photoperiods ≥8 h, whereas a higher total number and weight of eggs occurred with photoperiods ≥10 h, compared with 6L:18D (P > 0.05). Oviduct weight, ovary percentage, and initial and bare stroma (weight and percentage) increased quadratically with increasing photoperiods (P < 0.05), and 10.24, 10.01, and 10.10 h were the optimal photoperiods for oviduct weight, bare stroma (follicles ≥2 mm in diameter removed) weight, and bare stroma percentage, respectively, as calculated from reliable regression equations (R2 ≥ 0.5791). Compared with 6L:18D, 10L:14D had a higher total large white follicle weight, small yellow follicle number, and weight (P < 0.05). In addition, higher serum levels of follicle-stimulating hormone, luteinizing hormone, and progesterone were observed with ≥10-h photoperiods (P < 0.05), as were levels of hormone receptor mRNA expression in ovarian follicles (P < 0.05), with the highest values for both measures at 10L:14D. In the hypothalamus, mRNA expression of gonadotropin-releasing hormone increased in ≥8-h photoperiods, with the highest value at 10L:14D. In contrast, gonadotropin-inhibitory hormone increased in photoperiods ≥12 h (P < 0.05). In conclusion, an appropriate photoperiod led to early sexual maturity and improved the development of reproductive organs and ovarian follicles through effects on reproductive hormones and their receptors; 10 to 10.24 h is an adequate photoperiod for layer ducks during the pullet phase.

Establishment of soft-tissue-injury model of high-voltage electrical burn and observation of its pathological changes.

A realistic model is very useful in laying the foundation for clinical treatment and further study of high-voltage electrical burns. We therefore established a soft-tissue-injury model of high-voltage electrical burn in rabbits using the highest voltage alternating current reported. Twenty-five healthy big-ear white rabbits were randomly divided into five groups (five in each group): control group (C group) before injury and 0.5-h, 24-h, 48-h and 72-h groups after injury. Except for the control group, the rabbits in the other four groups were anaesthetised with ketamine and the electrodes were placed in their left limbs. Electric shock was administered from a distance of 7 cm at 3000 V output voltage for 0.1s to observe the skin temperature, electric resistance, wound morphology, histological change and to measure the level of muscle viability and serum myocardial enzymes, among others. Instant current application reached 3-5A (mean: 4.1+/-0.8A), and electric shock voltage was fixed at 3000 V. The resistance between the two electrodes in the left limb decreased from between 1500 and 3600 Omega (mean: 2590.3+/-812.9 Omega) to 921.5+/-528.7 Omega after the electric shock. The skin temperature of the control group was 30.1+/-2.5 degrees C, which elevated to 50.3+/-4.5 degrees C after the electric shock. Muscle necrosis occurred progressively 24-72 h after the injury with obvious acute inflammation. Electron microscopic examination revealed a bilaminar sarolemma membrane structure, multiple mitochondria between muscle bundles and disappearance of shortened mitochondrial crista 48 h after injury. Additionally, the muscle viability index decreased gradually to 0.376+/-0.071 72 h after the injury, while in the control group it was 1.354+/-0.117. The skin, arterial walls, and peripheral nerves showed obvious degeneration and necrosis. Moreover, pathological changes were found in vital organs distal to the electric shock sites, such as the heart, liver, lung and kidney, indicating systemic injuries. The level of serum myocardial enzymes was significantly elevated, especially 24h after injury. Thus, electric shock at 3000 V output electric voltage for 0.1s can cause severe, focal, soft-tissue injury and pathological changes in the vital organs such as heart, liver, kidney and lung with the characteristics similar to those of high-voltage-electrical-burn patients.