维甲酸纳米颗粒混悬剂的制备及表征

采用溶剂分散法制备了不同药物质量浓度的维甲酸纳米颗粒混悬剂,并对其进行了冷冻干燥;采用光子相关谱(PCS)测定了冷冻干燥前后混悬剂中纳米粒子的平均粒径;透射电镜(TEM)观察其微观形貌;高效液相色谱法(HPLC)对不同时间混悬剂中全反式维甲酸的质量浓度进行定量测定．结果表明,混悬剂中维甲酸纳米粒子(RA-NP)的粒径保持在200～400nm之间,大都为完整的球形;与维甲酸硅油10～15mg／L的药物质量浓度相比,纳米颗粒混悬剂中有效药物的质量浓度可显著提高至35mg／L;药物降解速度得到明显降低,4周之内能维持抑制细胞增殖的有效药物质量浓度．维甲酸纳米颗粒混悬剂有望成为一种新型的增殖性玻璃体视网膜病变(PVR)治疗用药物载体．     

A human retinoic acid receptor which belongs to the family of nuclear receptors

A cDNA encoding a protein that binds retinoic acid with high affinity has been cloned. The protein is homologous to the receptors for steroid hormones, thyroid hormones and vitamin D3, and appears to be a retinoic acid-inducible trans-acting enhancer factor, suggesting that the molecular mechanisms of the effect of retinoids (vitamin A) on embryonic development, differentiation and tumour cell growth are similar to those described for other members of this nuclear receptor family.     

人参皂甙Rh2和桦木酸协同诱导A549细胞凋亡的研究

我们已经发现,天然成分人参皂甙Rh2(G-Rh2)和桦木酸(Bet A)能够协同作用诱导人源肺癌A549细胞死亡.通过细胞形态观察、流式细胞检测分析、酶活性测定、免疫印记分析等实验技术,从细胞和分子水平提供证据,证明了G-Rh2和Bet A协同诱导A549细胞死亡的过程为细胞凋亡作用,且涉及线粒体途径.     

Noggin and retinoic acid transform the identity of avian facial prominences.

The signals that determine body part identity in vertebrate embryos are largely unknown, with some exceptions such as those for teeth and digits. The vertebrate face is derived from small buds of tissue, facial prominences, that surround the embryonic oral cavity. In chicken embryos, the skeleton of the upper beak is derived from the frontonasal mass and maxillary prominences. Here we show that bone morphogenetic proteins (Bmps) and the vitamin A derivative, retinoic acid (RA), are used to specify the identity of the frontonasal mass and maxillary prominences. Implanting two beads adjacent to the stage-15 presumptive maxillary field, one soaked in the Bmp antagonist Noggin and one soaked in RA, induces a duplicate set of frontonasal mass skeletal elements in place of maxillary bones. We also show that the duplicated beak is due to transformation of the maxillary prominence into a second frontonasal mass and not due to ectopic migration of cells or splitting of the normal frontonasal mass. Thus the levels of Bmp and RA determine whether specific regions of the face form maxillary or frontonasal mass derivatives.     

Selective inhibition of the anchorage-independent growth of myc-transfected fibroblasts by retinoic acid

Fischer rat 3T3 (FR3T3) fibroblasts transfected with a cellular myc gene can be induced to grow and form colonies in soft agar by treatment either with epidermal growth factor (EGF) alone or with the combination of platelet-derived growth factor (PDGF) and type-beta transforming growth factor (TGF-beta). We now show that induction of anchorage-independent growth by each of these sets of growth factors involves different cellular pathways which can be distinguished by their sensitivity to retinoic acid. Colony formation induced by the combined action of PDGF and TGF-beta is 100-fold more sensitive to inhibition by retinoic acid than is colony formation induced by treatment of the myc-transfected cells with EGF. Moreover, retinoic acid (10(-8) M) is inhibitory for colony growth whenever TGF-beta is present, regardless of whether the effects of TGF-beta are stimulatory, as occurs in the presence of PDGF, or inhibitory, as found in the presence of EGF.     

Spatial and temporal expression of the retinoic acid receptor in the regenerating amphibian limb

Retinoic acid is known to have dramatic effects on vertebrate limb pattern in development and regeneration, supporting a model in which a gradient of retinoic acid serves as a morphogen to differentially supply positional information to a developing limb. The discovery of a retinoic acid receptor (RAR) and its homology to the steroid and thyroid hormone receptors provided a potential molecular mechanism for limb morphogenesis. One prediction of this model is that the receptor must be expressed in the developing and regenerating limb anlage. We investigated the expression of the RAR in the adult newt, Notophthalmus viridescens, whose amputated limbs are capable of regenerating and upon which retinoic acid can act to alter pattern. We report the cloning of cDNAs encoding a functional newt RAR and the localization of high and uniform levels of RAR mRNA specifically in the regenerating cells that control limb pattern. These results indicate that the morphogenic field is established through differential activation of pre-existing retinoic acid receptors rather than differential expression of the RAR gene.     

Evidence that Hensen's node is a site of retinoic acid synthesis.

Hensen's node of amniotes, like the Spemann organizer of amphibians, can induce a second body axis when grafted into a host embryo. The avian node, as well as several midline structures originating from it (notochord, floor plate), can also induce digit pattern duplications when grafted into the chick wing bud. We report here that the equivalent of Hensen's node from mouse is an effective inducer of digits in the chick wing bud. Tissues anterior and posterior to the node also evoke pattern duplications, but with a significantly lower efficiency. The finding that the murine node operates in an avian wing bud suggests that the same inducing agent(s) function in both primary and secondary embryonic fields and have been conserved during vertebrate evolution. Digit pattern duplications are also evoked by local administration of all-trans-retinoic acid. This similarity raises the possibility that Hensen's node is a source of retinoic acid. The mouse node is capable of synthesizing retinoic acid from its biosynthetic precursor all-trans-retinol at a substantially higher rate than either anterior or posterior tissues.     

体液免疫中IL-2/IL-2R整合CD4+T细胞信号形成Tfh

总结了参与Th细胞各种亚型分化的主要信号途径,并对IL-2/IL-2R信号影响Th亚型分化的分子机制进行了深入探讨.IL-2/IL-2R信号可能作为一种调节分子可以整合CD4+T细胞在免疫应答中的多种信号,从而将T细胞打造成一种更为成熟的形式,然后迁移至B淋巴滤泡和生发中心处辅助B细胞产生抗体和形成记忆B细胞.据此,推测这种成熟形式的Th就是Tfh,并提出了Tfh细胞产生及功能发挥的新模型,以正确认识Tfh在体液免疫中的关键作用.     

Identification of a novel retinoic acid receptor in regenerative tissues of the newt

In urodele amphibians, the progenitor cells that regenerate amputated limbs (known as the blastema) normally replace only the missing structures. After systemic delivery of retinoic acid (RA), more proximal structures are also formed, indicating that RA can control position specification in the proximal-distal axis of the regenerating limb. According to dose and experimental context, retinoids can also re-specify the anteroposterior axis of the limb, induce deletions of skeletal elements, or block re-growth completely. To study the molecular basis of these morphogenetic effects, we screened complementary DNA libraries of newt regenerative tissues (limbs and tails) for hormone nuclear receptors activated by RA. Two functional retinoic acid receptors (RARs) were identified, one of which is the newt homologue of the human alpha-receptor (RAR alpha). The second receptor, called RAR delta, is novel. Sequence analysis suggests that the composite newt RAR previously reported is chimaeric, consisting of 5'RAR-beta-like and 3' RAR delta clones. We conclude that multiple RARs are expressed during limb regeneration in amphibians and suggest that receptor heterogeneity may underlie the different effects of retinoids on limb morphogenesis.     

9-cis retinoic acid stereoisomer binds and activates the nuclear receptor RXR alpha.

Vitamin A (retinol) and its natural derivatives are required for many physiological processes. The activity of retinoids is thought to be mediated by interactions with two subfamilies of nuclear retinoic acid receptors, RAR and RXR. The RARs bind all-trans retinoic acid (t-RA) with high affinity and alter gene expression as a consequence of this direct ligand interaction. RXR alpha is activated by t-RA, yet has little binding affinity for this ligand. t-RA may be converted to a more proximate ligand that directly binds and activates RXR alpha, and we have developed a method of nuclear receptor-dependent ligand trapping to test this hypothesis. Here we report the identification of a stereoisomer of retinoic acid, 9-cis retinoic acid, which directly binds and activates RXR alpha. These results suggest a new role for isomerization in the physiology of natural retinoids.     

Homodimer formation of retinoid X receptor induced by 9-cis retinoic acid.

Retinoid response pathways are mediated by two classes of receptors, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs). A central question is whether distinct response pathways are regulated by these two classes of receptors. The observation that the stereoisomer 9-cis-retinoic acid binds with high affinity to RXRs suggested that this retinoid has a distinct role in controlling RXR activity, but it was almost simultaneously discovered that RXRs function as auxiliary receptors for RARs and related receptors, and are essential for DNA binding and function of those receptors. Hence, although RARs seem to operate effectively only as heterodimeric RAR/RXR complexes, RXRs themselves apparently function predominantly, if not exclusively, as auxiliary receptors. Here we report that 9-cis-retinoic acid induces RXR homodimer formation. Our results demonstrate a new mechanism for retinoid action by which a ligand-induced homodimer mediates a distinct retinoid response pathway.     

饮食限制58d对小鼠学习记忆及抗氧化能力的影响

采用行为观察和生化检测方法,研究了饮食限制58 d对小鼠学习记忆的影响及其各组织中超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量的变化.结果显示:限食小鼠在新环境中更显得不安,66.7%饮食限制组小鼠记忆能力最弱而空间识别能力最强4,0%饮食限制组小鼠学习能力最强;限食小鼠各器官的脏器系数相比自由饮食组都有所升高;各组小鼠所测器官的SOD活性没有明显的区别,但心、肾和脑中MDA含量随饮食限制水平的升高而增高.提示饮食限制对机体器官有一定的损伤作用,适当饮食限制能提高学习能力,但对抗氧化能力的影响不明显.     

全反式维甲酸对HL-60细胞hTERT基因表达和端粒酶活性的影响

目的：探讨全反式维甲酸（ATRA）诱导HL－60细胞分化过程中人类端粒酶逆转录酶（hTERT)蛋白表达和端粒酶活性的改变,方法：应用间接免疫荧光标记法通过流式细胞仪检测hTERT蛋白含量的变化;采用多聚酶链反应－酶联免疫反应（PCR－ELISA）方法检测ATRA处理HL－60细胞前后端粒酶活性的改变,用碘化丙锭染色经流式细胞仪检测细胞周期的变化,结果：ATRA作用于HL－60细胞后,细胞内hTERT蛋白含量逐渐降低,细胞的端粒酶活性相应受到抑制。结论：在IL－60细胞分化过程中,可以通过hTERT基因的表达下调而抑制端粒酶的活性。