丙线照射所致大鼠胃粘膜易损性及其与内源性PGs和血栓素A_2的关系

本文观察了丙线照射大鼠胃粘膜的易损性及其与由源性PG_s和血检素A_2的关系。结果表明:丙线1500rad局部照射后28天,大鼠对牛磺胆酸所致胃粘膜坏死易损性明显加重,预先给予外源性PGE_2则可抑制这一现象;进一步采用放射免疫方法测定胃粘膜PG_s等的含量发现,照射后组织PGE和PGI_2含量明显降低,而血栓素A_2含量则明显升高,PGI_2/血栓素A_2,比值下降。这些结果说明,丙线照射可使大鼠胃粘膜的易损性明显加重,而内源性PGE和PGI_2含量的降低以及血栓素A_2含量的升高是照射造成易损性的主要原因之一。     

6-Keto-PGF_(1α)和TXB_2在胃粘膜适应性细胞保护中的作用

PGI_2和TXA_2均系前列腺酸的衍生物,胃粘膜细胞可不断合成和释放,具有很强的细胞保护作用。然而,关于它们与胃蛋白酶的适应性细胞保护作用的关系,尚未见报道。本文则采用放射免疫方法,测定了胃粘膜组织 PGI_2和TXA_2的代谢物 6-Keto-PGF_(1α)和TXB_2含量在不同情况下的变化。结果表明,单纯胃蛋白酶225U或胃蛋白酶150U溶于0.1NHCl或75U溶于0.2NHCl中,提前15min灌胃,均可防止由25％NaCl高渗溶液和沸水所致的胃粘膜坏死的发生,这种保护作用呈明显的量效关系。在上述三种配方灌胃后15min,胃粘膜组织PGI_2和TXA_2含量明显升高,约为对照组的2.0—2.15和1.7—2.0倍;且以PGI_2含量的增加占优势;胃蛋白酶浓度与两者含量呈现明显的量效关系。说明胃蛋白酶作为弱刺激对高渗和物理性烫伤所致的胃粘膜损伤均有保护作用,其作用机制是通过诱发内源性PG_s 的合成和释放而实现的,这一现象对解释胃粘膜的自身耐受机制,具有重要的生理意义。     

胃内PGE和PGF_(2α)介导胃蛋白酶的适应性细胞保护作用的观察

胃粘膜细胞不断合成和释放的前列腺素(PGs),具有很强的细胞保护作用。我们的前一工作表明,预先用胃蛋白酶灌胃,可防止牛磺胆酸所致的胃粘膜坏死的发生,这一保护作用可被消炎痛所阻断;间接提示这种适应性细胞保护的发生机制可能与内源性PGs有关。本文则用放射免疫方法,直接测定了胃粘膜组织PGE和PGF_(2α)含量在不同情况下的变化。结果表明,单纯胃蛋白酶225U,胃蛋白酶150U溶于 0.1N HCl或75单位溶于 0.2N HCl中,提前 15min灌胃,均可防止由0.2N NaOH、0.6N HCl 和无水乙醇所致的胃粘膜坏死的发生,这种保护作用呈明显的量效关系。上述三种配方的胃蛋白酶溶液灌胃后15min,胃粘膜组织PGE和PGF_(2α)含量明显升高,分别为对照组的2.7—2.9倍和1.9—2.5倍;且以PGE含量的上升占优势。进一步观察不同浓度胃蛋白酶溶于生理浓度盐酸中对胃粘膜PG含量的影响发现,胃蛋白酶与胃粘膜组织PGE和PGF_(2α)含量的增加呈现明显的量效关系。这些结果说明,胃蛋白酶作为弱刺激对强酸、强碱和无水乙醇所致的胃粘膜损伤均有保护作用,其作用机制则是通过诱发内源性PGs的合成和释放而实现的。     

胃蛋白酶的适应性细胞保护作用及其机制

胃蛋白酶是否具有适应性细胞保护作用,尚不清楚。本工作观察了胃蛋白酶对牛磺胆酸所致的胃粘膜损伤的影响。酸性牛磺胆酸80mM 给禁食大鼠灌胃,90min 后可引起严重的胃粘膜损伤。胃蛋白酶225单位(U)溶于水、150U 溶于0.1N HCl 或75U 溶于0.2N HGl,三者分别作为“弱刺激”提前15min 灌胃,均可防止由牛磺胆酸所致胃粘膜的损伤;这种保护作用呈明显的量效关系,并可持续约90min 之久。消炎痛(一种前列腺素合成酶的抑制剂) 提前60min 皮下注射,可阻断胃蛋白酶的适应性细胞保护作用,如果皮下给予外源性前列腺素 E_2(PGE_2),则能使这一作用重新恢复。这些结果说明,弱的胃蛋白酶刺激具有对胃粘膜的适应性细胞保护作用,其产生机制可能是通过诱发内源性 PG 的合成和释放而实现的。     

胃粘膜适应性细胞保护作用及其可能机制

预先给以弱刺激,可防止发生随后给予坏死性物质所引致的胃粘膜损伤,这就是适应性细胞保护作用,它具有极重要的生理意义。这种现象是由于弱刺激可诱发内源性前列腺素合成以及其释放增加的结果。前列腺素具有促进胃粘液和HCO_3~-分泌、加强粘膜屏障、刺激胃粘膜细胞更新和改善粘膜血流量等功能,从而阻止了胃粘膜损伤     

细胞更新对慢性饮酒大鼠胃黏膜适应性细胞保护的影响

目的: 以低浓度酒精作为弱刺激,通过慢性饮酒的大鼠动物模型,探讨慢性饮酒和大鼠胃粘膜适应性细胞保护作用之间的关系,以及胃粘膜细胞更新的作用.方法: 分别在饮酒不同时程的大鼠胃内灌注2 ml 100%酒精,分析胃粘膜的损伤情况.以流式细胞术、免疫组化和计算机图像处理技术观察大鼠胃粘膜的细胞增殖和凋亡,探讨胃粘膜的细胞更新情况.结果: ①纯酒精可使大鼠的胃体和胃窦出现溃疡和出血,饮用6%(v/v)酒精3～14 d的大鼠这种现象明显减轻,饮用6%(v/v)酒精1 d和28 d的大鼠则无改变.②饮用6%(v/v)酒精3～14 d的大鼠胃粘膜细胞更新加快,而饮酒28 d大鼠胃粘膜细胞凋亡增加,细胞增殖减少.结论: 细胞更新加快是适度低浓度酒精刺激引起的胃粘膜适应性细胞保护作用的重要原因,低浓度酒精刺激超过一定时限可引起胃粘膜萎缩性病变的趋势,使胃粘膜抵抗能力降低.     

适应性细胞保护作用与胃粘液-碳酸氢盐屏障的关系

本文观察了由天然或外源性弱刺激引起的适应性细胞保护作用与胃粘液-HCO_3~-屏障的关系,并分析了它的可能机制。结果表明,胃蛋白酶150单位(溶于0.1 mol/L 盐酸)或20%酒精灌胃,均可引起胃壁结合粘液分泌明显增加,并呈现明显的量效关系,一次处理后,作用可持续60min。这一作用可被消炎痛所阻断;给予外源性 PGE_2又可重新恢复。用醋唑酰胺阻断胃粘膜 HCO_3~-分泌,则上述两种弱刺激的保护作用均明显减弱。说明天然或外源性弱刺激通过诱发内源性 PGs 的合成和释放,使胃粘膜-HCO_3~-屏障的机能加强。这可能是它产生适应性细胞保护作用的机制之一。     

花生四烯酸与动脉粥样硬化和血栓形成的关系

花生四烯酸 (AA) 对机体有类似前列腺素(PG)的广泛作用,尤其是对血液和心血管有重要的影响。AA有降低血胆固醇、舒张血管平滑肌、降低血压、增加窦房结频率和心肌收缩力、舒张冠状动脉、增加冠状动脉血流量以及抗心率不齐等作用。AA有很强的使血小板聚集的作用,主要是通过其生物合成血栓素(thromboxane A_2,TXA_2) 而起作用;而它的另一种生物合成产物前列环素 (PGI_2) 的作用恰相反。动脉粥样硬化和血栓形成,主要是由于血管壁AA生物合成PGI_2减少,而血小板生物合成TXA_2增多所致。动脉粥样硬化症与花生四烯酸代谢有一定关系,利用影响AA生物合成TXA_2和PGI_2的药物,可能对防治动脉粥样硬化和血栓形成有重要意义。     

花生四烯酸与动脉粥样硬化和血栓形成的关系

花生四烯酸(AA)对机体有类似前列腺素(PG)的广泛作用,尤其是对血液和心血管有重要的影响。AA有降低血胆固醇、舒张血管平滑肌、降低血压、增加窦房结频率和心肌收缩力、舒张冠状动脉、增加冠状动脉血流量以及抗心率不齐等作用。AA有很强的使血小板聚集的作用,主要是通过其生物合成血栓素(thromboxane A_2,TXA_2)而起作用;而它的另一种生物合成产物前列环素(PGI_2)的作用恰相反。动脉粥样硬化和血栓形成,主要是由于血管壁AA生物合成PGI_2减少,而血小板生物合成TXA_2增多所致。动脉粥样硬化症与花生四烯酸代谢有一定关系、利用影响AA生物合成TXA_2和PGI_2的药物,可能对防治动脉粥样硬化和血栓形成有重要意义。     

胃肠道的细胞保护

胃肠道粘膜经常遭受食物、饮料和消化液的物理性和化学性冲击。胃粘膜上皮细胞不断合成和释放前列腺素(PG),它们具有强烈的细胞保护作用。PG的这一作用是一个特有的独立的活性,不是由于其抗胃液分泌所致。PG还对肠上皮、胰、肝细胞具有保护作用。给予弱的损伤性刺激后,还可阻止随后给予的强刺激所造成的损伤,这称为“适应性细胞保护”,具有极为重要的生理意义。一些脑肠肽如生长柳素、胰多肽、神经降压素、脑啡肽等也有细胞保护作用。本文还对细胞保护作用的产生机制作了简述。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.