染色体辐射效应的微机检测 Ⅱ断片率 微核率与细胞畸变率间的相关性检测

本文继前文后,按照设计的线性回归程序在“IBM—PC/XT”微型计算机上,进一步检测了断片率、微核率与细胞畸变率之间的相关性,肯定了微核测定法,断片测定法可以替代染色体畸变分析法。     

The binding of anionic and nonionic surfactants to collagen through the hydrophobic effect

The adsorption of nonionic surfactants on hide powder previously treated with anionic surfactants has been studied. The adsorption of nonionic surfactants takes place through hydrophobic interactions. A mechanism has been proposed for this interaction, assuming that the nonionic surfactant has been fixed by means of secondary adsorption (hydrophobic interaction) after the primary adsorption of the anionic surfactant (ionic and hydrophobic interaction) which makes it possible.     

Cooperativity in the calcium ion-induced quenching of the intrinsic fluorescence of a series of normal and GLA-deficient bovine prothrombin fragment 1 molecules

Ca²⁺ titrations of the intrinsic fluorescence of a series of -carboxyglutamic acid (GLA)-deficient bovine prothrombin fragments 1 yield response Hill plot parameters useful for characterization of the metal ion-binding process. 11-, 10-, and 9-GLA fragments 1 exhibitT _m (the (Ca²⁺)_total concentration at which ln (B/F)=0 in the response Hill plot) values between 0.2 and 0.3 mM. A 22-fold increase inT _m to 5.4 mM is observed for 8-GLA fragment 1.T _m decreases to 3.8 mM for the 7- and 6-GLA proteins. The value ofh, about 2.8±0.2 for 11-, 10-, and 9-GLA fragments 1, abruptly decreases to 1.2–1.3 for 8-, 7-, and 6-GLA fragments 1. The observed degree of quenching induced by saturating levels of calcium ions is affected by both changes in the intrinsic fluorescence of the metal ion-free proteins and in the maximum possible degree of quenching in the presence of calcium. The kinetic characteristics of the calcium ion-induced quenching of the intrinsic fluorescence of 6-GLA fragment 1 are identical to those observed in 10-GLA fragment 1, suggesting that the fluorescence quenching observed in the 6- and 10-GLA fragments 1, while different in magnitude, involves similar processes. Observation of an abrupt change in the relative electrophoretic mobilities of 11- to 9-GLA fragments 1 compared to 8- to 6-GLA fragments 1, in the absence or presence of Ca²⁺, suggests the existence of a major protein conformation change which occurs concomitantly with the noted changes inT _m andh response Hill plot parameters. Molecular mechanics calculations suggest a structural hypothesis unifying these observations. Central to this model is the presumption of the existence of hydrogen bond-mediated interactions between metal ion-binding sites.     

Activation of the inositol trisphosphate second messenger system by cAMP in a mouse fibroblast cell line

Intracellular Ca²⁺ mobilization events were assessed in mouse L cells, which contain native prostaglandin E₁ receptors and transfected human ₂ adrenergic receptors. Both Fura2 (single cell measurements) and Quin 2, (cuvette assays) were used to determine [Ca²⁺]_i levels. Our results demonstrate that in the transfected cells there is a dose-dependent increase in [Ca²⁺]_i in response to isoproterenol (0.1 nM–100 nM), which is inhibited by the -adrenergic antagonist, propranolol, and is a result of intracellular Ca²⁺ release. [Ca²⁺]₁ in these cells was also increased by prostaglandin E₁, 8 bromo cyclic AMP, and aluminum fluoride. Both 8 bromo cAMP and isoproterenol induced a rapid increase in the levels of IP₁, IP₂, and IP₃. The data presented demonstrate that the elevation of intracellular cyclic AMP induces an increase in IP₃ production which leads to an elevation in [Ca²⁺];. We propose that this cyclic AMP dependent activation of the IP₃ generating system occurs at a post-receptor site.Abbreviations cAMP Adenosine Cyclic 3-5-Monophosphate - [Ca²⁺]_i intracellular [Ca²⁺]_i - 8 Br cAMP 8 Bromo Adenosine Cyclic 3-5-Monophosphate - DAG Diacylglycerol - EGTA] [Ethylene Bis (oxyethylenenitrilo)] Tetracetic acid - BSA Bovine Serum Albumin - HBSS-H Hanks' Balanced Salt Solution buffered with HEPES to pH 7.4 - HEPES 4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid - PIP₂ Phosphatidylinositol 4,5-bisphosphate - IP₂ Inositol 4 Phosphate - IP₂ Inositol 4,5 Bisphosphate - IP₃ Inositol Trisphosphate - PGE₁ Prostaglandin E₁ - PBS Phosphate Buffered Saline Solution     

Role of Ca2+ ion on Leishmania-macrophage attachment

Summary Leishmania donovani, the etiological agent for the disease visceral leishmaniasis, attach themselves to the macrophages for initiation of the disease. The attachment process has been found to be regulated by Ca²⁺ ions. Verapamil, a Ca²⁺-channel blocker inhibits Leishmania-macrophage attachment. The inhibitory effect is increased with time. Nifedipine, another Ca²⁺-channel blocker exhibits the same effect. The attachment process is stimulated by Ca²⁺-ionophore alone. The inhibitory effects of the calcium channel blockers are reversed by the ionophore.     

Cell signalling through phospholipid breakdown

There is much evidence that G-proteins transduce the signal from receptors for Ca²⁺-mobilizing agonists to the phospholipase C that catalyzes the hydrolysis of phosphoinositides. However, the specific G-proteins involved have not been identified. We have recently purified a 42 kDa protein from liver that activates phosphoinositide phospholipase C and cross-reacts with antisera to a peptide common to G-protein -subunits. It is proposed that this protein is the a-subunit of the G-protein that regulates the phospholipase in this tissue.Ca²⁺-mobilizing agonists and certain growth factors also promote the hydrolysis of phosphatidylcholine through the activation of phospholipases C and D in many cell types. This yields a larger amount of diacylglycerol for a longer time than does the hydrolysis of inositol phospholipids. Consequently phosphatidylcholine breakdown is probably a major factor in long-term regulation of protein kinase C. The functions of phosphatidic acid produced by phospholipase D are speculative, but there is evidence that it is a major source of diacylglycerol in many cell types. The regulation of phosphatidylcholine phospholipases is multiple and involves direct activation by G-proteins, and regulation by Ca²⁺ protein kinase C and perhaps growth factor receptor tyrosine kinases.     

Ca2+ transport activities of inside-out vesicles prepared from density-separated erythrocytes from rat and human

The plasma membrane Ca²⁺ ATPase in erythrocytes is vital for the maintenance of intracellular Ca²⁺ levels. Since the cytoplasmic Ca²⁺ concentration is elevated in older erythrocytes, the properties of the Ca²⁺ transport ATPase were examined during cell aging using inside-out vesicles (IOVs) prepared from density-separated, young (less dense, Ey) and old (more dense, Eo) rat and human erythrocytes. The transport of Ca²⁺ and the coupled hydrolysis of ATP were measured using radiolabeled substrates. The calmodulin-independent Ca²⁺ transport activity (Ey, 38.8 vs. Eo, 23.3 nmols/min/mg IOV protein) and the Ca²⁺ dependent ATP phosphohydrolase activity (Ey, 53.5 vs. Eo, 48.8 nmols/min/mg protein) were greater in IOVs prepared from younger (less dense) rat erythrocytes. The calmodulin-independent Ca²⁺ transport activity in IOVs from human erythrocytes was 12.9 nmols/min/mg IOV protein for Ey and 10.7 nmols/min/mg IOV protein for Eo. Inside-out vesicles from older (more dense) cells exhibited a lower pumping efficiency as determined by the calculated stoichiometry, molecule of Ca²⁺ transported per molecule of ATP hydrolyzed (rat: Ey, 0.74 vs. Eo, 0.49; human: Ey, 1.22 vs. Eo, 0.77). The enzymatic activity of rat and human Ey IOVs was labile. The Ca²⁺ transport activity in Ey but not Eo IOVs rapidly declined during cold storage (4°C). The decrease in Ca²⁺ transport activity during aging may accentuate the age-related decline in several erythrocytic properties.Abbreviations IOV Inside-Out Vesicles - Ey Erythrocytes enriched with young (less dense) cells - Eo Erythrocytes enriched with old (more dense) cells - ACEase Acetylcholinesterase     

钙通道阻断剂异搏定对缺氧性肺动脉高压形成的影响

为考察Ca~( )在缺氧性肺动脉高压形成中的作用,我们观察了钙通道阻断剂异搏定对慢性连续性缺氧大鼠肺动脉压及左右心功能的影响。将动物置于模拟海拔5000m高原的低压舱内,腹腔注射异搏定,剂量为4mg/kg BW,每日两次。实验结果表明:异搏定可以减弱缺氧15天所引起的肺动脉压升高和右心功能加强的程度,对颈动脉压及左心功能无明显影响,提示Ca~( )的跨膜内流是构成缺氧性肺动脉高压形成的重要基础之一。我们还比较了异搏定对缺氧持续时间不同(15天、10天、5天)的大鼠肺循环的影响,并讨论了异搏定发生作用的机制。     

Enhanced formation of mouse hybridomas without hat treatment in a serum-free medium

Summary A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without the need for hypoxanthine-aminopterinthymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in serum- and HAT-containing medium or are masked by serum.     

Cationic probes: Specificity of distribution of metal-binding sites in bovine sperm

Salts of transition elements that alter the rate of sperm cell movement act at or near calcium-binding sites. After living bull sperm cells had been preincubated in VO₄^3?, Ni²⁺, Zn²⁺, Mn²⁺, and also La³⁺, they were then fixed. Crisply defined organelles and the absence of particulate deposits in the morphological controls contrasted sharply with the treated specimens; the latter contained regions of increased electron density, the nature and distribution of which depended on the test substance, reflecting the differential affinities of the specific ions. La³⁺ formed fine dense areas, mainly at the exocytic surface of the plasma membrane. VO₄^3? marks the cell surface but also left particulate densities within the cell. Ni²⁺ caused a nearly uniformly dense deposit at the surface and on the satellite fibers and axonemal microtubules. Zn²⁺ formed less uniform but coarser deposits, while in Mn²⁺ the distribution was similar to that in Zn²⁺ but much denser in the axonemal matrix and on the satellite fibers. Verapamil restricted the size and number of the opacities, while procaine permitted a similar distribution of slightly larger size reaction product. The differences in size and distribution of the enhanced densities were consistent and replicable for the individual assay substances. Vanadate, which specifically inhibits Na, K-ATPase, bound to ouabain-sensitive enzyme loci, however, completely disrupting the axonemal complex. This suggests that an important role of dynein in flagellar motion may relate to intracellular transport of Ca²⁺.