细胞外钠离子浓度对羊浦肯野纤维膜钠泵活动的影响

采用离子选择电极测量羊浦肯野纤维细胞膜内钠离子活度(~(ai)N_a),细胞间钾离子活度(a~ok)及细胞膜电位(v_m),观察不同浓度低钠,无钙液对其影响,在无钙低钠液中,细胞内Na~+逐出,α~iNa 降低,其变化速率,幅值与[Na]_o 相关,同时也受细胞 a~iNa 初始水平(aiNa(o))的影响。aiNa 下降6min 时的稳态水平与[Na]_o 呈直线正相关,这些结果表明,[Na]_o 降低时,细胞膜钠泵活动加强,细胞内 Na~+逐出增加,其最终结果是使 Na+跨膜梯度维持相对稳定,因而可以认为是 Na~+跨膜梯度而不是单纯的细胞内 Na~+控制膜钠泵活动。在低 Na~+液引起细胞内 Na~+主动逐出增加的同时,细胞膜出现超极化,[Na]_o 愈低,膜超极化程度愈高,从低钠液引起的 a~i_(Na),V_m,α~o_k 变化之间的时程关系看,膜超极化主要由加大的外向泵电流引起,同时发生的细胞间 K~+浓度变化对其也有一定影响。     

胰岛素对蟾蜍卵母细胞膜电位及电解质的影响

应用普通玻璃微电极和离子选择性微电极,对正常及经过胰岛素处理的中华大蟾蜍卵母细胞膜电位、细胞内Na~+、K~+、Cl~-、H~+等活度及膜对Na~+、K~+的转运系数进行了测定。结果表明,胰岛素在促进蟾蜍卵母细胞发育成熟同时,具有使膜电位降低、细胞内Na~+、Cl~-活度增加、K~+、H~+活度减少及K~+转运系数降低等作用。胰岛素的上述作用可能与膜的通透性改变及膜上钠泵活性和Na~+/H~+交换的改变有关。     

“缺血”引起的绵羊浦肯野纤维跨膜电位与离子流变化

以低氧、高钾、低pH、无能量供应的模拟缺血溶液灌流离体绵羊心脏浦肯野纤维,观察“缺血”对心肌跨膜电位和离子流的影响。实验共24例。跨膜电位的变化过程如下:模拟缺血液灌流后2-3min,首先出现最大舒张电位(MDP)轻度除极,4期舒张除极速率减慢,随后动作电位时程(APD)缩短(n=13)或先缩短、后延长、再缩短的变化(n=11),平台逐渐消失,最后MDP进一步除极,动作电位波幅(APA)减小,兴奋性逐渐降低,以致不能引出动作电位(AP)。其中6例即使MDP高于-60mV时AP已不能引出。以上变化过程历时长短不等,在不同标本为30-160min。跨膜离子流方面,当APD缩短时,在所有膜电位水平即时外向电流都明显增加。稳态电流-电压关系曲线由正常的S形变成直线,内向整流现象消失。慢内向离子流由“缺血”前的6.74±4.48nA减少到0.86±1.39nA,(M±SD,P<0.01,n=8),在多数测试电位水平都有显著减少,其电流-电压关系曲线向较负电位方向移位。以上结果提示:心肌“缺血”时浦肯野细胞起搏功能受抑制,细胞内大量K~+外流,Ca~(2+)内流减少,心肌细胞除极,以上多种变化可能为心肌缺血时心律失常发生的原因。     

Ni^2＋对心肌细胞Na^＋,K^＋活度及膜钠泵活动的影响

本实验应用离子选择性微电极方法,动态监测了Ｎｉ２＋对心肌细胞Ｎａ＋、Ｋ＋活度的影响,并以细胞内Ｎａ＋逐出速率［ｄ（ａｉＮａ）／ｄｔ］作为膜钠泵活动度的指标,观察了Ｎｉ２＋对膜钠泵活动的影响。结果显示：（１）在本实验浓度下Ｎｉ２＋对静息及活动（自律或电刺激）的细胞内Ｎａ＋、Ｋ＋活度无明显影响;（２）可使细胞外Ｋ＋活度升高;（３）便刺激停止即刻细胞内Ｎａ＋逐出速率下降;（４）减小无钠无钙液引起的细胞外Ｋ＋活度下降幅度。结果提示：Ｎｉ２＋对处于高水平活动的心肌细胞膜钠泵具有明显的抑制作用,而对处于一般活动状态的膜钠泵则未见有明显影响;在Ｎｉ２＋存在下心肌细胞膜对Ｋ＋的通透性有不同程度的提高。     

利用~3H-哇巴因测定人红细胞钠泵数量的方法

红细胞钠泵对于维持红细胞形态及功能具有重要的意义。用~(86)Rb测定钠泵活性,受细胞内代谢物及各底物浓度的影响,用Na~ -K~ -ATP酶活性表示钠泵活性也受[Na~ ]、[K~ ]、[ATP]等的影响。因此上述方法难以作为膜上钠泵数量的确切指标。     

细胞膜钠钾泵生理学

动物机体的细胞内外液中,Na~+、K~+浓度有显著差别。以神经细胞为例,静息状态下,膜内K~+浓度高于膜外约30倍,膜外Na~+浓度高于膜内约12倍。这个浓度差是产生静息电位的基础。采用微电极技术可测到各种细胞的静息电位,一般在—10———100毫伏之间。细胞靠什么机制产生并维持着如此巨大的电化学梯度呢?人们早就设想:这些细胞膜上普遍存在一种能逆着浓度差主动地将细胞外液的K~+移入膜内,同时把进入细胞内的Na~+移至膜外的机构,并称之为钠钾泵或简称钠泵。     

高血压病红／白细胞变形性的研究

本文观察了52例原发性高血压和24例正常人的红细胞、白细胞变形性,红细胞膜钙泵、钠泵活性,血粘度及血浆粘度,结果发现:原发性高血压组高、中切变率血粘度和钠泵活性显著高于正常组,红细胞变形性和钙泵活性显著高于正常组;红细胞变形性和钙泵活性显著低于正常组.白细胞变形性、低切变率血粘度及血浆粘度与正常组比较无显著差别.原发性高血压组红细胞变形性与年龄、平均动脉压、钙泵活性,高、中切变率血粘度相关.心痛定和川芎嗪治疗后,红细胞变形性显著改善,川芎嗪还能降低高切变率血粘度.结果提示:在高血压病中红细胞变形性降低、血粘度增高的分子水平机制主要是红细胞膜钙泵活性降低。基于微循环的改善,在扩大治疗例数后,心痛定和川芎嗪可能作为降压治疗的优选药与辅助药。     

心脏钙矛盾现象的研究

钙矛盾现象的形态学变化特点是细胞在闺盘处分离,细胞内肌节聚集为单一收缩带;心肌代谢的改变以高能磷酸键迅速减少、离子平衡失调为主。产生的机制是细胞膜钠泵、钙泵功能减弱,造成细胞排钙能力下降,细胞内 Na~+浓度升高,使恢复正常钙灌注时 Na~—Ca~(2+)迅速交换,造成 Ca~(2+)大量内流而导致一系列心肌细胞损伤。     

异丙肾上腺素和氨甲酰胆碱对心肌延迟后除极的影响

用乙酰毒毛旋花子甙元2.0×10~(-7)mol/L,在绵羊心室浦肯野纤维产生延迟后除极(DAD)为实验模型,观察异丙肾上腺素与氨甲酰胆碱对DAD的影响。异丙肾上腺素1.0—3.0×10~(-8)mol/L能增加DAD幅值,为剂量依赖性,并可诱发出触发型心律失常。氨甲酰胆碱2.0×10~(-6)mol/L单独作用对DAD幅值无影响,然而在异丙肾上腺素增强DAD幅值或产生触发型心律失常后,同样浓度的氨甲酰胆碱能显著地减小DAD幅值以及消除触发型心律失常。但氨甲酰胆碱对由高钙、氨茶碱和组胺等所增加的DAD幅值却无抑制作用。以上结果表明,氨甲酰胆碱能拮抗异丙肾上腺素引起的DAD增强作用,可能与M受体的激活,并继而降低膜上β受体激活时所提高的腺苷酸环化酶活性有关。     

新生大鼠脊髓切片运动神经元的电生理参数测定

用微电极技术对新生大鼠脊髓横切薄片运动神经元(MN)进行细胞内记录,测得静息电位为-62±4mV(n=26),膜电阻为67±31MΩ,时间常数3.8±1.6ms,动作电位幅度68±7mV(n=26),阈电位-50±8mV,超射值6±4mV。灌流谷氨酸(1～30mmol/L)诱导伴膜电阻降低的缓慢去极化反应,5-羟色胺(50μmol/L)介导伴膜电导降低的电压依赖性内向电流。结果表明新生大鼠脊髓切片MN的细胞内生物电记录是一种稳定可靠的电生理学和药理学研究方法。     

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.     

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.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.