西红花酸对动脉粥样硬化鹌鹑血清一氧化氮含量的影响及其机制

目的：观察西红花酸（CCT）对动脉粥样硬化（AS）鹌鹑血清一氧化氮（NO）含量的影响并探讨其可能的作用机制.方法：用高脂饲料复制鹌鹑AS模型并灌胃给予CCT,9周后做主动脉HE染色观察AS病理变化、酶法测定血清中NO含量;培养牛主动脉内皮细胞（BAECs）,用氧化低密度脂蛋白（OX-LDL）作用后测定培养液中NO含量和细胞中内皮源性NOS（eNOS）、诱导型NOS（iNOS）活性,RT-PCR方法测定eNOS基因表达水平,观察CCT对上述指标的影响.结果：CCT（25,50,100 mg/kg）能够明显改善鹌鹑AS病变,显著升高AS鹌鹑血清中NO含量;OX-LDL能显著减少BAECs培养液中NO含量,降低细胞内eNOS活性,下调eNOS mRNA表达水平.CCT（1,10 μmol/L）能显著增加OX-LDL作用后细胞培养液中NO含量,提高细胞内eNOS活性、上调eNOS mRNA表达水平.OX-LDL和CCT对细胞内iNOS活性没有明显影响.结论：CCT能显著增加AS鹌鹑血清NO含量,提高OX-LDL作用后牛主动脉内皮细胞NO含量和eNOS活性,其机制与CCT上调eNOS mRNA表达水平有关.     

茶多酚预防鹌鹑高脂血症的实验研究

用高脂饲料诱发鹌鹑造成高脂血症，同时预防性给予三种剂量茶多酚，并设立空白对照组，模型组及烟酸组，观察茶多酚对鹌鹑高脂血症形成和发展的影响。结果表明：茶多酚抑制鹌鹑血清总胆固醇，甘油三酯及低密度脂蛋白胆固醇水平的升高，茶多酚大剂量组抑制ＴＣ水平升高的作用强于烟酸组，抑制ＴＧ和ＬＤＬ－Ｃ水平升高的作用与烟酸组相仿。     

Avian neurosteroids. I. Pregnenolone biosynthesis in the quail brain

The present study was carried out to determine steroid biosynthesis from cholesterol in the brain of adult male Japanese quails. As an initial step of the experiments, the concentrations of pregnenolone, dehydroepiandrosterone and their sulfate esters in the brain and plasma extracts were measured by specific radioimmunoassays (RIAs). To exclude the possibility that these steroids in the brain are derived from peripheral steroidogenic glands, hypophysectomized and sham-operated birds were used in this experiment. The pregnenolone concentration was much larger in the brain than in the plasma in these two groups. Hypophysectomy led to decreases in the plasma and brain pregnenolone concentrations, but the change in the brain was less pronounced than that in the plasma. Although pregnenolone sulfate ester, dehydroepiandrosterone and its sulfate ester were also detected in brain extracts, those levels were low in both hypophysectomized and sham-operated birds. The biochemical demonstration of cholesterol metabolism was further conducted in intact mitochondria. When mitochondrial fractions obtained from the whole brain were incubated with cholesterol at 37°C, the pregnenolone level in mitochondria increased as a function of incubation time. Finally, Western immunoblot analysis using a purified IgG with polyclonal antibodies against the purified bovine adrenal cytochrome P450scc was performed after SDS-gel electrophoresis of homogenates of the hypothalamus and preoptic area. A protein recognized the antibody as a band of electrophoretic mobility in the proximity of reference bovine P450scc. These results suggest that the brain produces pregnenolone from cholesterol in adult male Japanese quails. Most accumulation of pregnenolone in the brain may be independent of the peripheral endocrine gland system.     

The effects of estradiol and 1,25 (OH)2D3 on skeletal metabolism in female japanese quail

Two experiments were performed comparing the effects of 17β-estradiol implants or a series of intramuscular injections of either 1,25 dihydroxycholecalciferol (1,25 (OH)₂D₃) (.5 μg/injection) and 17 β-estradiol (13 μg/injection) on bone turnover, calcium content (Ca) and breaking strength. Plasma was analyzed for 1,25 (OH)₂D₃ and Ca. Bone resorption was determined by labelling the bones with tritiated tetracycline and measuring the relative decline in radioactivity over the 3 week treatment period. When 16 to 28 month old quail were given estradiol implants, significantly reduced bone turnover was observed in these ovulating quail. In experiment 2, both estradiol and 1,25-(OH)₂D₃ administration served to decrease bone turnover. Estradiol, however, had a more pronounced effect and significantly increased bone Ca and breaking strength. Both hormone treatments raised plasma Ca and 1,25 (OH)₂D₃ levels. Estradiol was more effective in increasing the bone strength and mass than 1,25-(OH)₂D₃. It appears that estradiol plays a multifaceted role in the control of bone metabolism. Part of this effect is through increased 1,25-(OH)₂D₃ levels circulating in the blood.     

The circadian nature of melatonin secretion in Japanese quail (Coturnix coturnix japonica)

Abstract: Plasma melatonin concentrations were measured in Japanese quail held under different photoperiods and constant darkness (<1 lux). When subjected to LD6:18 (6 hr light: 18 hr darkness), levels rose ～2 hr after lights-off, attained a peak level 8 hr after lights off, and subsequently declined to low daytime levels before the next lights-on signal. This generated a distinct daily rhythm in melatonin secretion with a duration of ～13 h. On exposing quail to a range of photoperiods, containing 6, 9, 11, 12, 13, 15, 18, or 20 hr of light per day, the onset of melatonin secretion remained essentially similar with the rise occurring soon after lights-off. However, the offset of melatonin secretion was suppressed by the light of the next day and thus a much truncated rhythm was produced under long (> 12 hr) photoperiods. Importantly, between night lengths of 4 to 18 hr (i.e., LD 20:4 to LD 6:18) a linear relationship existed between the duration of night-length and secretion of melatonin with the duration increasing by about 0.8 hr for each additional hour of darkness. If quail were released into darkness following a short (LD 6:18) or long (LD 20:4) day schedule, the rhythm persisted for at least two cycles with peaks occurring at about 24 hr intervals. In those quail coming into darkness from long days (LD 20:4), the rhythm of melatonin secretion decompressed rapidly on both sides of the peak, indicating that both the onset and offset of melatonin secretion were suppressed under long days. The endogenous nature of melatonin secretion was tested further by exposing birds to LD 6:30 for 4 cycles and then releasing into darkness. The rhythm in melatonin secretion persisted for at least three cycles before beginning to damp-out. The circadian nature of the rhythm in melatonin secretion was also examined by subjecting quail to T-cycles and then releasing into darkness. Both under the T-cycles and darkness following T-cycle treatments, the phase of the melatonin rhythm was advanced by > 3 hr under T = 27 hr cycles (LD 3:24) compared with T = 24 hr cycles (LD 3:21). This property is consistent with the melatonin oscillator being a circadian rhythm.     

HERG- and IRK-like Inward Rectifier Currents are Sequentially Expressed During Neuronal Development of Neural Crest Cells and their Derivatives

Quail neural crest cells were cultured in a differentiative medium to study the inward K⁺ channel profile in neuronal precursors at various stages of maturation. Between 12 and 24 h of culture, neural crest-derived neurons displayed, in addition to the previously described outward depolarization-activated K⁺ currents, an inward current enhanced in high K⁺ medium. A biophysical and pharmacological analysis led us to conclude that this inward K⁺ current is identical to that previously demonstrated in mouse and human neuroblastoma cell lines (I_IR). This current (quail I_IR or ql_lR), which is active at membrane potentials positive to -35 mV, was blocked by Cs⁺ and by class Ill antiarrhythmic drugs, thus resembling the K⁺ current encoded by the human ether-a-go-go-related gene (HERG). At later stages of incubation (>48 h), neural crest-derived neurons underwent morphological and biochemical differentiation and expressed fast Na⁺ currents. At this stage the cells lost qll_R, displaying instead a classical inward rectifier K⁺ (IRK) current (quail I_IRK= qI_IRK). This substitution was reflected in the resting potential (V_REST), which became hyperpolarized by >20 mV compared with the 24 h cells. Neurons were also harvested from peripheral ganglia and other derivatives originating from the migration of neural crest cells, viz. ciliary ganglia, dorsal root ganglia, adrenal medulla and sympathetic chain ganglia. After brief culture following harvesting from young embryos, ganglionic neurons always expressed qi_lR. On the other hand, when ganglia were explanted from older embryos (7–12 days), briefly cultured neurons displayed the IRK-like current. Again, in all the above derivatives the ql_lR substitution by ql_lRK was accompanied by a 20 mV hyperpolarization of V_REST. Together, these data indicate that the V_REST of normal neuronal precursors is sequentially regulated by HERG- and IRK-like currents, suggesting that HERG-like channels mark an immature and transient stage of neuronal differentiation, probably the same stage frozen in neuroblastomas by neoplastic transformation.     

Smaller axon and unaltered numbers of microtubules per axon in relation to number of myelin lamellae of myelinated fibers in the mutant quail deficient in neurofilaments

To characterize the morphological features of the myelinated fibers in the mutant quails deficient in neurofilaments (NF), caused by a nonsense mutation in the NF-L gene, the morphological parameters of the axon and myelin sheath, and their relationships in the peroneal nerve were evaluated. In the mutant, the axonal area was smaller than in the control (P>0.01), reflecting the lack of large diameter axons. There was no significant difference in the mean number of myelin lamellae and of their spacings between controls and mutants. Therefore, it was decided to analyze the alteration of axonal parameters in relation to the number of myelin lamellae. In the regression analysis, the number of microtubules (MT) per square micrometer of the axonal area was greater in the mutant than in the control (P<0.05); however, the number of MT per axon was similar in controls and mutants with the same given number of myelin lamellae. The number of MT+NF per axon was smaller in the mutant than in the control only for myelinated fibers with more than 25 myelin lamellae (P>0.05). These findings indicate that there was a less significant effect of NF deficiency on the smaller than on the larger myelinated fibers. There was no compensatory increase in the numbers of MT per axon of the myelinated fibers in the mutant as found previously in the unmyelinated fibers of the mutant.     

The effects of testosterone and its metabolites on sexual behavior and morphology in male and female Japanese quail

Adult Japanese quail are sexually dimorphic. Even when implanted with testosterone (T), ovariectomized females fail to copulate and their cloacal glands are smaller than those of males. This may be due to a reduced capacity of the females to transform testosterone into active metabolites (estradiol-17β and 5α-dihydrotestosterone). Indeed, in the male quail, estradiol-17β (E₂) activates copulation whereas 5α-dihydrotestosterone (5α-DHT) activates crowing, strutting and the development of the cloacal gland. To test this hypothesis, we studied the effects of in vivo treatments of male and female quail with the different T-metabolites. Forty-one castrated male and female quail were implanted with subcutaneous silastic implants of T, 5α-DHT, E₂ and E₂ in combination with 5α-DHT. When implanted with these metabolites, females failed to copulate and their cloacal glands remained less developed than those of males. Sexual differences in behavior and morphology thus cannot be entirely explained by sexual dimorphism of the metabolism.     

Vagal neural crest cell migratory behavior: a transition between the cranial and trunk crest

Migration and differentiation of cranial neural crest cells are largely controlled by environmental cues, whereas pathfinding at the trunk level is dictated by cell-autonomous molecular changes owing to early specification of the premigratory crest. Here, we investigated the migration and patterning of vagal neural crest cells. We show that (1) vagal neural crest cells exhibit some developmental bias, and (2) they take separate pathways to the heart and to the gut. Together these observations suggest that prior specification dictates initial pathway choice. However, when we challenged the vagal neural crest cells with different migratory environments, we observed that the behavior of the anterior vagal neural crest cells (somite-level 1-3) exhibit considerable migratory plasticity, whereas the posterior vagal neural crest cells (somite-level 5-7) are more restricted in their behavior. We conclude that the vagal neural crest is a transitional population that has evolved between the head and the trunk.