低氧对高原鼠兔肝细胞内质网和心肌肌浆网Ca^2＋泵的影响

模拟高原低氧条件研究高原鼠兔肝细胞内质网（Ｅｎｄｏｐｌａｓｍｉｃｒｅｔｉｃｕｌｕｍ,ＥＲ）和心肌肌浆网（Ｓａｒｃｏｐｌａｓｍｉｃｒｅｔｉｃｕｌｕｍ,ＳＲ）钙泵功能变化。实验设对照组（海拔２３００ｍ）和两个低氧实验组（模拟海拔５０００ｍ和７０００ｍ）。２４ｈ急性低氧时,海拔５０００ｍ组高原鼠兔ＥＲ的Ｃａ２＋泵活性无变化,海拔７０００ｍ组高原鼠兔ＥＲＣａ２＋泵活性下降２９．０２％。７ｄ亚急性低氧时高原鼠兔ＳＲ的Ｃａ２＋泵活性无显著变化。高原鼠兔ＥＲ的Ｃａ２＋泵活性在海拔５０００ｍ组和７０００ｍ组分别升高３２．５０％和３３．３３％。２５ｄ慢性低氧时高原鼠兔ＥＲ,ＳＲ的Ｃａ２＋泵活性均无显著变化．表明：急性低氧对Ｃａ２＋泵功能有抑制作用,低氧７ｄ后抑制缓解,至２５ｄ低氧时趋于恢复。     

骨骼肌内质网Ca2+泵转运Ca2+的结构基础

Ca2 泵(Ca2 -ATPase)是调节细胞内Ca2 浓度的重要蛋白质之一.Ca2 泵在转运Ca2 的过程中经历一系列构象变化.其中,E1状态为外向的Ca2 高亲和状态,E2状态则为内向的Ca2 低亲和状态.目前,骨骼肌内质网Ca2 泵转运Ca2 过程中的几个中间状态,包括E1-2Ca2 ,E1-ATP,E1-P-ADP,E2-Pi和E2状态的三维晶体结构已经解析.介绍这几种状态的晶体结构,并分析Ca2 泵在执行功能过程中结构与功能的关系.     

CoCl2预处理对大鼠海马神经元急性低氧后Na+、K+电流的影响

目的：观察氯化钴(COCl2)预处理对急性低氧后海马神经元电压门控性Na^ 、K^ 电流的影响。方法：原代培养大鼠海马神经元,分为COCl2预处理和非处理组,采用膜片钳全细胞记录技术,检测急性低氧后海马神经元钠电流(INa)、钾电流(Ik)的变化。结果：急性低氧后,海马神经元INa、Ik电流幅度明显降低,INa阈值右移,而经CoCl2预处理的海马神经元INa、Ik电流的降低幅度明显减轻。结论：COCl2预处理减轻急性低氧所致的INa、Ik电流变化,对神经元有明显的保护作用。     

Ca2+对钠通道作用新发现

钠通道是参与心肌兴奋传导和维持心脏节律的重要物质。ca2+在心肌细胞的兴奋-收缩偶联中起重要     

植物中解密Ca2+信号转导特异性的机制

Ca^2＋信号介导植物对外界信号的刺激反应,并调节多种生理过程。CBL是一种在植物中发现的Ca^2＋结合蛋白,其靶蛋白为CIPK,现对CBL-CIPK信号转导系统及其如何解密Ca^2＋信号转导特异性进行综述。     

Na+和Ca2+对拟南芥根原生质体质膜内向K+通道电流的影响

以拟南芥(Arabidopsis thaliana Columbia)根为材料,利用膜片钳技术测定其根细胞原生质体质膜内向K^ 电流,并对Na^ 对其K^ 电流的影响进行了初步研究,发现Na^2 可明显抑制拟南芥根细胞原生质体的内向K^ 电流,外施Ca^2 可缓解Na^ 对内向K^ 电流的抑制．说明Ca^2 参与了质膜上K^ 通道对K^ ／Na^ 的选择性吸收的调节,从而使植物适应盐胁迫．     

Ca2+对低氧胁迫下黄瓜幼苗生长和根系无氧呼吸酶的影响

采用营养液水培,以抗低氧能力不同的2个黄瓜品种为试材,研究了Ca2+对黄瓜幼苗植株生长和根系无氧呼吸酶活性的影响.结果表明,在低氧胁迫下,LDH、PDC和ADH活性提高程度与幼苗的抗低氧性和Ca2+浓度密切相关.与抗低氧性较弱的"中农8号"相比,抗低氧性强的"绿霸春4号"幼苗根系LDH活性增加缓慢,而PDC和ADH活性增加幅度较大,因此增强了植株对低氧胁迫的抗性.低氧胁迫下,营养液中8 mmol·L-1 Ca2+处理能显著提高根系ADH活性,降低LDH和PDC活性,0 mmol·L-1 Ca2+处理表现出相反的规律.由此可以说明,低氧胁迫下,Ca2+能够提高ADH活性,降低LDH和PDC活性,可增强黄瓜植株对低氧胁迫的抗性.     

钙肥对富士苹果品质及Ca2+-ATPase活性影响的研究

以盛果期的矮化富士为材料,研究了不同钙肥对富士苹果品质和Ca2+-ATPase活性的影响.结果表明,喷钙后单果重增加,Vc含量提高,可溶性固形物和花青苷含量增大,而成熟果实的叶绿素和可滴定酸含量下降.不同钙肥效果顺序为巨金钙>氨基酸钙>翠康钙宝>钙宝2000.钙肥对Ca2+-ATPase活性影响极为显著,其活性明显高于对照,不同钙肥间Ca2+-ATPase活性的变化趋势与果实品质的变化趋势相同.     

大鼠心肌线粒体L-Arg/ NO系统对线粒体Ca2+转运功能的影响

目的和方法采用大鼠心肌线粒体体外孵育的方法,观察线粒体L-精氨酸/一氧化氮系统对线粒体Ca2+转运功能的影响.结果NO生成的底物L-Arg (10-4 mol/L)、外源性NO供体硝普纳(5×10-7 mol/L)孵育的线粒体NO-2的生成量分别高于对照组66%、89% (P<0.01);钙含量较对照组分别低40%、54% (P<0.01); 线粒体Ca2+的摄入量较对照组分别减少67%、85%(P<0.01), 线粒体Ca2+释放率(11%、8%)降低与对照组(14%)相比差异显著(P<0.05、P<0.01).NO合酶抑制剂左旋硝基精氨酸甲酯(L-NAME, 10-4 mol/L)与相同浓度的L-Arg共同孵育的线粒体,明显抑制了L-Arg对线粒体的效应,与单纯L-Arg组比较,NO2生成减少,线粒体钙含量和反映线粒体45 Ca2+的摄入与释放能力都接近对照组水平.结论心肌线粒体L-精氨酸/一氧化氮系统参与了线粒体对心肌细胞Ca2+浓度的调节,其生理和病理生理意义值得进一步探讨.     

白细胞介素-2对大鼠心肌Ca2+ATPase和Na+ /K+ATPase的影响

为了探讨IL－2对心肌细胞内钙影响的可能机制,用光学法检测心肌肌浆网Ca^2 ATPase的活性,以及细胞膜Ca^2 ATPase和Na^ /K^ ATPase的活性。结果：（1）用IL－2（10、40、200、800U/ml）灌流心脏后,其肌浆网Ca^2 ATPase的活性随IL－2浓度的升高而增强;（2）在ATP浓度为0.1-4mmol/L时,Ca^2 ATPase的活性随ATP浓度的升庙则增强,由IL－2（200U／ml）灌流后的心脏获得肌浆网（SR）,其Ca^2 ATPase的活性对ATP的反应强于对照组;（3）在[Ca^2 ]为1－40μmol/L时,心脏SR Ca^2 ATPase的活性随[Ca^2 ]增加而增强,而IL－2灌流心脏后分离的SR,其Ca^2 ATPase活性在[Ca^2 ]升高时没有明显改变;（4）用nor-BNI(10nmol/L）预处理5min后,IL－2（200U／ml）灌流后不再使SR Ca^2 ATPase的活性增强;（5）用PTX（5mg/L）预处理后,IL－2对SR Ca^2 ATPase的影响减弱;（6）用磷脂酶C（PLC）抑制剂U73122（5μmol/L）处理后,IL－2不再使SR Ca^2 ATPase活性增高;（7）用IL－2直接处理从正常大鼠分离的SR后,对SR Ca^2 ATPase活性无明显影响;（8）IL－2灌流后,对心肌细胞膜Ca^2 ATPase和Na^ /K^ ATPase活性没有显著。上述结果表明,IL－2灌流心脏后使心肌肌浆网Ca^2 ATPase的活性增加,心肌细胞膜上的κ－阿片受体及其下游的G蛋白和PLC介导了IL－2的作用。尽管IL－2提高SR Ca^2 ATPase对ATP的反应性,但却抑制SR Ca^2 ATPase对钙离子的敏感性。IL－2对心肌细胞膜Ca^2 ATPase和Na^ /K^ ATPase的活性无明显影响。     

ENZYME-STRUCTURE RELATIONSHIPS IN THE ENDOPLASMIC RETICULUM OF RAT LIVER : A Morphological and Biochemical Study

Subfractionation of preparations of rat liver microsomes with a suitable concentration of sodium deoxycholate has resulted in the isolation of a membrane fraction consisting of smooth surfaced vesicles virtually free of ribonucleoprotein particles. The membrane fraction is rich in phospholipids, and contains the microsomal NADH-cytochrome c reductase, NADH diaphorase, glucose-6-phosphatase, and ATPase in a concentrated form. The NADPH-cytochrome c reductase, a NADPH (or pyridine nucleotide unspecific) diaphorase, and cytochrome b₅ are recovered in the clear supernatant fraction. The ribonucleoprotein particles are devoid of, or relatively poor in, the enzyme activities mentioned. Those enzymes which are bound to the membranes vary in activity according to the structural state of the microsomes, whereas those which appear in the soluble fraction are stable. From these findings the conclusion is reached that certain enzymes of the endoplasmic reticulum are tightly bound to the membranes, whereas others either are loosely bound or are present in a soluble form within the lumina of the system. Some implications of these results as to the enzymic organization of the endoplasmic reticulum are discussed.     

大鼠粒细胞内质网的电镜细胞化学反应

本实验用电镜细胞化学方法观察了大鼠骨髓粒细胞发育过程中内质网的髓过氧化物酶(MPO)反应和葡萄糖-6-磷酸酶(G-6-P)反??应。结果表明:MPO除定位于内质网、核膜,还出现在高尔基体和颗粒,它是粒细胞内质网的合成产物。G-6-P只在内质网、核膜中出现,它是内质网膜的结构成分。MPO反应的超微结构定位随粒细胞发育而变,利用这种变化作标志可以划分不同发育阶段的粒细胞;G-6-P反应定位不随发育而变,但反应强度与内质网的多寡、功能状态相对应。实验还表明核膜与内质网在结构、功能上的一致性;尤其在成熟粒细胞内质网很少的情况下,核膜可能代替了内质网的功能。     

EFFECTS OF CORTISONE ON RAT LIVER MITOCHONDRIA

Experiments were designed to determine the effects of parenteral administration of cortisone on mitochondrial numbers of rat liver cells. Observations were made in three ways: (1) after osmic acid fixation and appropriate stain, (2) by phase microscopy on intact cells, (3) by actual enumeration of mitochondria and nuclei to provide data on mitochondria per cell. The results of the experiments indicate that the mitochondria per cell are significantly reduced under the conditions used. Each experimental approach provided similar data, and each tended to support the results obtained from the others.     

REVERSAL BY ADENINE OF THE ETHIONINE-INDUCED LIPID ACCUMULATION IN THE ENDOPLASMIC RETICULUM OF THE RAT LIVER : A Preliminary Report

Within 3.5 to 4 hours after thionine administration, numerous small osmiophilic bodies, liposomes, appear in the endoplasmic reticulum of the liver cells. By fusion, the liposomes lead to the formation of larger collections of fat, giant liposomes. Adenine administration to ethionine-treated rats removes the liposomes from the hepatocytes and causes the transitory appearance of osmiophilic droplets in the sinusoidal space of Disse. The characteristic disaggregation of hepatic polysomes seen in the liver after ethionine administration is corrected by the injection of adenine.     

慢性缺氧大鼠心肌肌浆网功能及其钙泵基因表达的动态变化

将实验大鼠放置模拟５０００ｍ海拔高度低压舱内１、２和４周。结果表明：与对照组比较,１,２和４周组动物的心肌重量分别增加１５％,１８％和５７％;心肌ＳＲＣａ２＋摄取分别降低３３％,３８％和５３％;心肌ＳＲＣａ２＋ＡＴＰａｓｅ活性分别降低５４％,６０％和７４％;钙泵ｍＲＮＡ含量（基因表达分别降低１４％,４６％和６８％。这些结果提示,缺氧导致的ＳＲ钙泵功能降低可能是心肌功能受损的重要生化基础之一,而钙泵数目减少可能是钙泵功能降低的分子生物学机制。     

OSMIUM STAINING OF ENDOPLASMIC RETICULUM AND MITOCHONDRIA IN THE RAT ADRENAL CORTEX

The zona fasciculata of the rat adrenal cortex synthesizes and secretes glucocorticoids. As observed after aldehyde fixation, the cells in this zone contain an extensive endoplasmic reticulum (ER), a small Golgi apparatus, a moderate number of lipid droplets, and abundant mitochondria with tubulovesicular cristae. Numerous areas within the endoplasmic reticulum and mitochondrial cristae appear clear. In addition, a small percentage of mitochondria encompasses large, clear areas. After immersion of finely minced adrenal cortex in unbuffered 2% OsO₄ (40–48 hr at 40°C), deposits of osmium are seen within the Golgi apparatus, the entirety of the ER, and occasionally within mitochondria. In some mitochondria, the deposits are within cristae; in others, within vacuoles; in still others, in both cristae and vacuoles. These localizations correspond best to the clear areas found in aldehyde-fixed tissue. Osmium is not deposited in lipid droplets, in bar-containing inclusions, in mitochondrial matrix inclusions, or in the peripheral, outer mitochondrial spaces. Addition of zinc-iodide to OsO₄ increases the amount of Golgi apparatus and mitochondrial staining. Adrenocorticotropin (ACTH) does not affect the localization of deposits; hypophysectomy decreases mitochondrial staining. This study (a) emphasizes the necessity for electron microscopic confirmation of osmium localization when this technique is used as a Golgi apparatus stain; and (b) suggests that the ER-staining pattern may be consistent in cells actively synthesizing steroids or steroid-like compounds.     

ON THE RELATIONSHIP OF LIVER GLUCOSE-6-PHOSPHATASE TO THE PROLIFERATION OF ENDOPLASMIC RETICULUM IN PHENOBARBITAL INDUCTION

The differentiated effects of phenobarbital treatment on liver microsomal enzymes have been further studied. The relationship between the resulting decrease in the specific glucose-6-phosphatase activity and the enhancement of formation of endoplasmic reticulum membranes with high drug-hydroxylating activity has been investigated with biochemical and histochemical methods. Biochemically and histochemically demonstrable glucose-6-phosphatase activity was found to be present in all endoplasmic reticulum membranes, including the phenobarbital-induced smooth-surfaced proliferates, even though there was an over-all decrease in activity. Actinomycin D did not inhibit the decrease in glucose-6-phosphatase activity. The findings are discussed with reference to the enzyme-membrane relationship in phenobarbital induction.     

慢性高原低氧对高原鼠兔和大鼠肝脏的作用

我们曾经发现,移入高原的实验大鼠子一代和高原鼠兔(Ochotona curzoniae)对高原低气压低氧有完全不同的适应能力和适应机理(杜继曾等,1982)。我们还观察到,在24小时急性高原低氧时,由低地移入2300米高原的大鼠后裔在5000米和8000米的高度上,出现了以转氨酶、肝溶酶体酸性磷酸酶活力升高、肝糖原和蛋白质含量下降的肝脏代谢异常和肝脏病理变化,而高原鼠兔只是在8000米高度时,才始出现部分指标的轻度变异(杜继曾等,1982),从而揭示了高原鼠兔的肝细胞代谢在细胞水平上对低氧的适应机制优越于移入高原的实验大鼠后代。慢性低氧又如何作用于大鼠和高原鼠兔的肝脏代谢?迄今尚无人研究。因此对这一作用规律的认识和阐明,在环境适应生理学领域、人类高原活动和畜牧业生产上都是十分重要的。     

ONTOGENETIC CHANGES OF PROTEINS OF ENDOPLASMIC RETICULUM

The proteins of the smooth and rough endoplasmic reticulum from fetal, immature, and adult male rats were compared after incorporation of two radioactively labeled precursors, ¹⁴C-labeled amino acids and δ-aminolevulinic acid-³H by means of gel electrophoresis. The labeling patterns indicated that protein components present in two major electrophoretic bands underwent significant synthesis in fetal tissue while three actively incorporating protein bands were noted in adult tissue. Although the uptake of the amino acids-¹⁴C decreased for the smooth and rough elements of the endoplasmic reticulum as a whole during liver development, the qualitative patterns were not significantly different in adult and fetal livers. The over-all incorporation (disintegrations per minute per milligram protein) of the heme precursor into the smooth and rough elements also did not change with development. However, a change was noted in the distributional electrophoretic patterns with development. The estimation of molecular weight (by disc electrophoresis) and the incorporation of the heme precursor suggested the similarity of the two major protein bands to cytochrome P-450 and cytochrome b₅, components of the endoplasmic reticulum, thought to be involved in the mixed-function oxidase system. The evidence indicated that in fetal liver, at a time when the oxidase capability was low, the amino acid incorporation into these two protein groups was the same as in the adult. The incorporation of the heme moiety, however, was different, decreasing in the cytochrome b₅ region and increasing in the cytochrome P-450 region during development. These results correlate with the increase in oxidase activity associated with liver development.