Age-related changes of yolk precursor formation in the liver of laying hens.

A rapid decline in egg production of laying hens begins after 480 d of age. Such a rapid decrease results predominantly from the ovarian aging, accompanied by endocrine changes, decreased yolk synthesis and accumulation, and the reduction in follicles selected into the preovulatory hierarchy. In this study, hens at 90, 150, 280, and 580 d old (D90, D150, D280, and D580, respectively) were compared for yolk precursor formation in the liver to elucidate effects of aging on laying performance. The results showed that liver lipid synthesis increased remarkably in hens from D90 to D150, but decreased sharply at D580 as indicated by the changes in triglyceride (TG) levels. This result was consistent with the age-related changes of the laying performance. The levels of liver antioxidants and total antioxidant capacity decreased significantly in D580 hens and the methane dicarboxylic aldehyde in D580 hens was much higher than that at other stages. The serum 17ß-estradiol level increased from D90 to D280, but decreased at D580 (P<0.05). The expression of estrogen receptor α and ß mRNAs in the liver displayed similar changes to the serum 17ß-estradiol in D580 hens. Expressions of the genes related to yolk precursor formation and enzymes responsible for fat acid synthesis were all decreased in D580 hens. These results indicated that decreased yolk precursor formation in the liver of the aged hens resulted from concomitant decreases of serum 17ß-estradiol level, transcription levels of estrogen receptors and critical genes involved in yolk precursor synthesis, and liver antioxidant status.

[Dexamethasone acetate microemulsions: formulation and effect on skin permeability].

The present project was designed to optimize the microemulsion (ME) formulation of oil in water (O/W) for dexamethasone acetate (DA), and examine its impact on DA percutaneous permeation. The saturated solubility of DA in different oils, surfactants and co-surfactants was tested. The ratio of surfactant to co-surfactant was selected by constructing pseudo three phase diagrams to investigate the maximal microemulsion area. In vitro permeation studies of DA from microemulsion and suspension were performed to optimize the formulation further. Differential scanning calorimetry(DSC) and attenuated total reflection flourier transformed infrared spectroscopy (ATR-FTIR) were performed to investigate the mechanism of microemulsion action on skin. The optimized formulation was composed of oleic acid/Labrasol/propylene glycol/water with 8/45/15/32 (w/w), and the DA loading was 0.75% (w/w). The permeation enhancement of microemusion was 6.00-fold as that of suspension, and the DA from microemulsion retained in the skin was 4.79-fold as that of suspension. DSC and ATR-FTIR results suggested that microemulsion could affect the intercellular lipid lamellae and keratin of the stratum corneum. The barrier function of stratum corneum was disordered by the microemulsion so that the dermal drug delivery was enhanced. Therefore, the optimized microemulsion enhanced DA percutaneous permeation significantly through the interaction of microemulsion with skin, microemulsion is a promising approach for DA percutaneous delivery.

Follicle-stimulating hormone promotes proliferation of cultured chicken ovarian germ cells through protein kinases A and C activation.

The study was conducted to investigate the effects of follicle-stimulating hormone (FSH) on embryonic chicken ovarian germ cell proliferation and its possible involvements of protein kinases A (PKA) and C (PKC) pathways. Ovarian cells were treated with FSH alone or in the presence of forskolin (FRSK), PKA inhibitor (H(89)), PKC activator (PMA) or inhibitor (H(7)). The germ cell number was counted from micropictures. The immunocytochemistry of proliferating cell nuclear antigen (PCNA) was applied to identify the proliferating cells. The germ cell labeling index (LI) was determined for cell proliferation. The FSH treatment increased the germ cell number, and this stimulating effect was enhanced by FRSK or PMA, but inhibited by H(89) or H(7) in a dose-dependent manner. Moreover, the PCNA-LI showed parallel changes with germ cell numbers. This study suggests that FSH may stimulate proliferation of cultured chicken ovarian germ cells by activation of both the PKA and PKC signaling pathways.

Attenuating effect of daidzein on polychlorinated biphenyls-induced oxidative toxicity in mouse testicular cells.

The attenuating effect of daidzein (DAI) on oxidative toxicity induced by Aroclor 1254 (A1254) was investigated in mouse testicular cells. Cells were exposed to A1254 alone or with DAI. The oxidative damage was estimated by measuring malondialdehyde (MDA) formation, superoxide dismutase (SOD) activity and glutathione (GSH) content. Results show that A1254 induced a decrease of germ cell number, an elevation in thiobarbituric acid reactive substances (TBARS) but a decrease in SOD activity and GSH content. However, simultaneous supplementation with DAI decreased TBARS level and increased SOD activity and GSH content. Consequently, dietary DAI may restore the intracellular antioxidant system to attenuate the oxidative toxicity of A1254 in testicular cells.