中麻黄(Ephedra intermedia)胚胎发育及双受精作用在进化上的意义

本文对中麻黄(Ephedra intermedia)的双受精作用进行了较为详细的研究。其主要结果如下： 1．中麻黄约5月中旬传粉，5月下旬受精。中央细胞分裂形成卵核及腹沟核。卵核沿合点端方向移至卵细胞质富含细胞器区，被富含细胞器的细胞质所包围。卵核的受精发生在浓厚卵细胞质区内。精子向卵核靠近，穿过浓厚细胞质区，与卵核建立联系，二核逐渐靠拢。卵核核膜出现凹陷，并逐渐包围精子，最后完成受精。刚受精后的精核卵核的核质并不立即融合，各自保持独立。之后不久，二核完成融合，形成合子。 2．腹沟核刚形成后， 并不退化而是继续发育，并象卵核一样沿合点端方向从其顶端位置向卵细胞基部移动至卵细胞质富含细胞器区。第二个精子向腹沟核移动，靠近，并建立联系，最后完成融合，形成第二个合子。 3．双受精是中麻黄的正常生殖特征。中麻黄的双受精及第二次受精产物的命运具有重要的进化上的意义。 4．两个合子连续二次分裂形成八个游离核，或者叫次生合子。八个游离核进一步发育并细胞化形成具胚性功能的单细胞原胚．或者次生合子进一步分裂增殖形成多余游离核后再进一步发育并细胞化形成具胚性功能的单细原胚或在胚的发育中解体退化，以提供营养．一个胚珠可观察到一至七个发育时期不同的胚成熟胚珠中只有一个成熟胚，双子叶。 5．由游离核发育而来的单细胞原胚在进一步的发育中沿合点端方向向配子体内上移并形成单细胞球形胚。单细胞球形胚分裂形成二细胞胚，即胚原始细胞及胚柄细胞。胚原始细胞先进行一次平周分裂而后进行一次垂周分裂形成四细胞胚。之后胚体进一步分裂发育形成多细胞球形胚。发育至一定时期后，胚柄细胞及次生胚柄分裂、膨大、伸长形成胚柄，胚柄细胞逐渐增多、增长、弯曲疏松，成熟的胚中胚柄系统消失。胚体发育至圆柱状后，中央一层弧行排列的细胞形成根冠原始细胞，之后这些根冠原始细胞不断分裂、发育分化形成成熟胚的各种组织包括胚皮层、髓、原形成层及根冠等等。

Extract of Ginkgo biloba leaves reverses yohimbine-induced spatial working memory deficit in rats

Extract of Ginkgo biloba is used to alleviate age-related decline in cognitive function, which may be associated with the loss of catecholamines in the prefrontal cortex. The purpose of this study was to verify whether alpha-2 adrenergic activity is involved in the facilitative effects of extract of Ginkgo biloba on prefrontal cognitive function. Male Wistar rats were trained to reach criterion in the delayed alternation task (0, 25, and 50-s delay intervals). A pilot study found that 3 or 4 mg/kg of yohimbine (intraperitoneal) reduced the choice accuracy of the delayed alternation task in a dose and delay-dependent manner, without influencing motor ability or perseverative behaviour. Acute oral pre-treatment with doses of 50, 100, or 200 mg/kg (but not 25 mg/kg) of extract of Ginkgo biloba prevented the reduction in choice accuracy induced by 4 mg/kg yohimbine. These data suggest that the prefrontal cognition-enhancing effects of extract of Ginkgo biloba are related to its actions on alpha-2-adrenoceptors.

Effects of ginkgo biloba extract on cation currents in rat ventricular myocytes

Ginkgo biloba extract (GBE), a valuable natural product for cerebral and cardiovascular diseases, is mainly composed of two classes of constituents: terpene lactones (e.g., ginkgolide A and B, bilobalide) and flavone glycosides (e.g., quercetin and kaempferol). Its electrophysiological action in heart is yet unclear. In the present study, using whole-cell patch clamp technique, we investigated electrophysiological effects of GBE on cation channel currents in ventricular myocytes isolated from rat hearts. We found that GBE 0.01-0.1% inhibited significantly the sodium current (I-Na), L-type calcium current (I-Ca) and transient outward potassium current (IKto) in a concentration-dependent manner. Surprisingly, its main ingredients, ginkgolide A (GB A), ginkgolide B (GB B) and bilobalide (GB BA) at 0.1 mM did not exhibit any significant effect on these cation channel currents. These results suggested that GBE is a potent non-selective cation channel modulator in cardiaomyocytes. Other constituents (rather than GB A, GB B and GB BA) might be responsible for the observed inhibitory effects of GBE on cation channels. (C) 2004 Elsevier Inc. All rights reserved.

The effect of cyanobacterial crude extract on the transcription of GST mu, GST kappa and GST rho in different organs of goldfish (Carassius auratus)

The glutathione S-transferases play important roles in the detoxification of microcystin. Core-sequences of three classes of GST (mu, kappa and rho) were cloned from goldfish (Carassius auratus L) i.p. injected with cyanobacterial crude extract at two doses (50 and 200 mu g MC-LReq kg(-1) BW). The relative changes of the mRNA abundance in liver, kidney and intestine were analyzed by real-time PCR. The transcription of GST mu was inhibited in intestine at both doses and the transcription of GST kappa was inhibited from 12 to 48 h in kidney at both doses. The decreased transcription of GST rho was detected in all three organs at the high dose. It is suggested that transcription inhibition of GST rho might be significant in MCs toxicity at higher toxin concentration in omnivorous freshwater fish. Alteration in transcription of GSTs stimulated by MCs implicates an increased health risk to fish. (C) 2008 Published by Elsevier B.V.

Free radical scavenging and antioxidant enzymes activation of polysaccharide extract from Nostoc sphaeroides

Nostoc sphaeroides Kuetzing has been used as a traditional medicine in China to treat a variety of ailments. This research identified the antioxidant activities of polysaccharide extract from Nostoc sphaeroides. The extract, which contains 46.2% carbohydrates, exhibited an effective scavenging capability on superoxide radical, hydroxyl radicals in non site-specific as well as site-specific assays, and also performed lipid peroxidation inhibition in a dose-dependent manner. Polysaccharide extract had no 1,1-diphenyl-2-picrylhydrazyl radical scavenging potential at all test concentrations. Activities of superoxide dismutase, catalase, and glutathione peroxidase in human embryo kidney 293 cells were increased effectively when Nostoc sphaeroides extract was applied. These results suggested that the use of N. sphaeroides in treating ailments may be based on the antioxidant capacities of polysaccharide composition.

Influence of Hypericum perforatum Extract on Piglet Infected with Porcine Respiratory and Reproductive Syndrome Virus

To study the influence of Hypericum perforatum extract (HPE) on piglets infected with porcine respiratory and reproductive syndrome virus (PRRSV), enzyme-labeled immunosorbent assay (ELISA) and cytopathic effect (CPE) were used to determine in vitro whether HPE could induce swine pulmonary alveolar macrophages (PAMs) to secrete IFN-gamma, and whether PRRSV titers in PAMs were affected by the levels of HPE-induced IFN-gamma. HPE (200 mg kg(-1)) was administrated by oral gavage to piglets infected with the PRRSV in vivo to observe whether HPE affected the viremia, lung viral titers, and weight gain of piglets infected with PRRSV. The results showed that HPE was capable of inducing PAMs to produce IFN-gamma in a dose dependent manner and HPE pretreatment was capable of significantly reducing PRRSV viral titers in PAMs (P<0.01). Administration of HPE to the PRRSV-infected animals significantly (P<0.05) reduced viremia over time as compared with the PRRSV-infected animals. But there was not significant decrease in lung viral titers at day 21 post-infection between the HPE-treated animals and the PRRSV-infected control piglets. There were no significant differences in weight gain over time among the HPE-treatment animals, the normal control, and the HPE control animals. The PRRSV-infected animals caused significant (P<0.01) growth retardation as compared with the HPE controls and the normal piglets. It suggested that HPE might be an effective novel therapeutic approach to diminish the PRRSV-induced disease in swine.

Direct characterization of bitter acids in a crude hop extract by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

The applicability of on-line coupling of reversed-phase high-performance liquid chromatography to atmospheric pressure ionization tandem mass spectrometry for the separation and characterization of hop acids mixture from the crude extract of Humulus lupulus was investigated. The solvent system consisting of acetonitrile-aqueous formic acid was used to give proper separation of the six main hop bitter acids within 30 min. Further structural information about the components was acquired by collision-induced dissociation (CID). On the basis of analyses of the fragmentation patterns of the major alpha- and beta-bitter acids respectively, identification of the minor ones was performed using selected reaction monitoring (SRM) with a group of qualitatively relevant selected precursor-product ion transitions for each bitter acid in a single high performance liquid chromatography (HPLC) run. Using this technique, six minor hop acids, including "adprelupulone" observed for the first time in natural resources, were detected along with the six major acids. This hyphenated techniques provides potency for rapid qualitative determination of analogs and homologs in mixtures. (C) 2004 American Society for Mass Spectrometry.