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961.
BCL-2-Related Protein Expression in Apoptosis: Oxidative Stress Versus Serum Deprivation in PC12 Cells 总被引:5,自引:0,他引:5
Abstract: Expression of the BCL-2 protein family members, BAX, BAK, BAD, BCL-xL, BCL-xS, and BCL-2, was measured (by western blotting using specific antibodies) in PC12 cells before and during apoptosis induced by either H2 O2 treatment or by serum deprivation and during rescue from apoptosis by nerve growth factor (NGF). H2 O2 -induced apoptosis, as measured by DNA fragmentation, caused: (a) a dose-dependent increase in BAX, (b) a dose-independent increase in BAK, and (c) a dose-dependent inhibition of BAD expression. By comparison, apoptosis induced by serum deprivation resulted in a time-dependent decrease in both BAX and BAK, along with a dramatic and sudden decrease in BAD expression. However, when PC12 cells were incubated in an apoptosis-sparing medium (i.e., NGF-supplemented serum-free medium), both BAX and BAK were increased significantly, whereas BAD expression remained inhibited. BCL-xL expression was increased by H2 O2 but unaffected by serum deprivation or long-term NGF treatment. Neither BCL-2 nor BCL-xS expression could be detected in PC12 cells under the experimental conditions tested. Our results show that the expression of BAX, BAK, BAD, and BCL-xL is altered in a stimulus-dependent manner but cannot be used to define whether a cell will undergo or survive apoptosis. The similarity between changes in expression of BCL-2-related proteins induced by H2 O2 exposure and NGF rescue could reflect activation in part of a common antioxidant pathway. 相似文献
962.
963.
TANG Liang LIN ZhengjiongZHOU Yuancong 《中国科学:生命科学英文版》1997,40(5):481-487
Agkistrodotoxin, a neutral phospholipase A2 with high presynaptic neurotoxicity from the venom of Agkistrodon halys Pallas, has been crystallized by hanging drop vapor diffusion method. The crystal belongs to P21 space group with the cell dimensions a = 10.836 nm, b=8.486nm, c = 7.082nm, β=109.87$ showing C2 pseu-do-symmetry. Diffraction data to 0. 26 nm resolution have been collected on a Siemens X-200B area detector. C2 pseu-do-symmetry suggests that there exists a non-crystallographic two-fold axis parallel to crystallographic b axis. Self-rotation function calculation with different integrated radius and resolution ranges using the program POLARRFN yields four stable high peaks corresponding to three more non-crystallographic two-fold axis and one special non-crystal-lographic symmetry. The molecules in the asymmetric unit are suggested to be arranged in a manner of "dimer of dimers" by inference. 相似文献
964.
位于突触体质膜的外向型(ecto)Mg^2-ATP酶具有水解ATP活性,能量偶联的AC-MA荧光淬灭实验表明Mg^2+-ATP酶水解ATP时向膜内转移质子,建立跨膜质子梯度,跨膜质子梯度可以被电中性K^+/H^+离子载体Nigericin消除,利用H^+敏感的BCECF荧光分子测定突触的pHi变化,结果表明水解ATP产生的质子转移突触体pHi下降了光分子测定突触的pHi变化,结果表示水解ATP产生 相似文献
965.
NADH specific glutamate dehydrogenase (GDH) activity was examined in roots and shoots of maize seedlings grown in half-strength
Hoagland’s solution containing NH4NO3 as sole nitrogen source under irradiance of 60 W m−2 and temperature of 25±2°C. When 5,5′-dithio-bis (2-nitrobenzoic acid) (DTNB) was supplied to the assay mixture, it inhibited
NADH-GDH activity in both roots and shoots, irrespective of whether the enzymes were extracted from light- or dark-treated
roots and shoots. In each case the inhibition increased with the increase in DTNB concentration. At the maximum concentration
of DTNB used (20 μM) the inhibition of shoot NADH-GDH was more pronounced than inhibition of root enzyme. This indicated differences
in shoot and root NADH-GDH. 相似文献
966.
Comparative study of seed albumins in the Old-WorldLupinus species (Fabaceae) by reversed-phase HPLC
B. P. Salmanowicz 《Plant Systematics and Evolution》1995,195(1-2):77-86
Seed albumins and 2S proteins isolated from the albumin fraction of 36 accessions representing 10 Old-WorldLupinus species (5 smooth- and 5 rough-seeded) were studied using reversed-phase high-performance liquid chromatography. In addition, the globulin fraction was analyzed to determine its 2S protein content. The performed separations showed the suitability of RP-HPLC technique in the analysis of variation of the seed albumin composition in lupins. In the group of rough-seeded lupins, 3 types of RP-HPLC elution profiles of albumins were distinguished: (1)L. atlanticus, (2)L. cosentinii andL. digitatus, (3)L. palaestinus andL. pilosus. All the species of this group were found to have proteins not observed in smooth-seeded species. Smooth-seeded species exhibited more abundant protein spectra, each species distinguishing by its specific RP-HPLC elution profile. It was found that 2S proteins classified as 2S albumins were responsible for the observed variation. Depending onLupinus species, the 2S albumin class consists of two to six proteins. 相似文献
967.
We determined the 240-nueleotide sequences of the E/NS1 gene junction of four dengue-2 viruses by the primer extension dideoxy chain termination method. These viruses were isolated from dengue patients with different clinical severities in Nakhon Phanom, Northeastern Thailand in 1993. The results were compared with the 52 published dengue-2 sequences of the same gene region. Sequence divergence of four new isolates varied from 4.17% to 5.42% compared with dengue-2 prototype New Guinea C strain whereas it varied from 5.42% to 6.67% and from 6.67% to 7.09% when compared with Jamaica 1409 strain and PR159/S1 strain, respectively. All nucleotide substitutions were found at the 3rd position of the codons which were silent mutations. All 56 isolates studied were classified into five genotypic groups by constructing the dendrogram. The results indicated that four new isolates from Northeastern Thailand belong to genotype II of dengue virus serotype 2, and were most closely related to prototype New Guinea C strain. We also observed the variation in nucleotide and amino acid sequences among clusters of isolates (Thailand-1980, Malaysia-1989 and Thailand-1993) which were obtained from the dengue patients with different clinical severities. The significance of these genetic differences have been discussed in terms of the possible correlation between genetic variability and virulence. 相似文献
968.
Omar Benzakour Chryso Kanthou Florea Lupu Ulla Dennehy Chris Goodwin Michael F. Scully Vijay V. Kakkar David N. Cooper 《Journal of cellular biochemistry》1995,59(4):514-528
Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS-PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R155-S156. Cleavage at R271-T272 generated fragment 1.2 and prethrombin 2 whilst cleavage at R284-T285 yielded truncated prothrombin 2 (prethrombin 2′). However, cleavage at R320-I321 which, during prothrombin activation produces two-chain α-thrombin, was not detectable. Studies on HVSMC-conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell-secreted factor(s). Amidolytic activity analysis indicated that 1–3% catalytically active thrombin-like activity was generated upon incubation of prothrombin with HVSMC-conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell-derived serine proteinase-like factor(s) at R271-S272 and by α-thrombin at R155-S156 and R284-T285. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30–40 kDa. © 1995 Wiley-Liss, Inc. 相似文献
969.
Rabindranath Chakrabarti Joseph Y. Chang Kent L. Erickson 《Journal of cellular biochemistry》1995,58(3):344-359
In this study, we showed that cross-linking CD3 molecules on the T cell surface resulted in Ca2+ release from the intracellular stores followed by a sustained Ca2+ influx. Inhibition of release with TMB-8 did not block the influx. However, inhibition of phospholipase C activity suppressed both Ca2+ release and influx. Once activated, the influx pathway remained open in the absence of further hydrolysis of PIP2. Thapsigargin, a microsomal Ca2+ -ATPase inhibitor, stimulated Ca2+ entry into the cells by a mechanism other than emptying Ca2+ stores. In addition, Ca2+ entry into the Ca2+ -depleted cells was stimulated by low basal level of cytosolic Ca2+, not by the emptying of intracellular Ca2+ stores. Both the Ca2+ release and influx were dependent on high and low concentrations of extracellular Ca2+. At low concentrations, Mn2+ entered the cell through the Ca2+ influx pathway and quenched the sustained phase of fluorescence; whereas, at higher Mn2+ concentration both the transient and the sustained phases of fluorescence were quenched. Moreover, Ca2+ release was inhibited by low concentrations of Ni2+, La3+, and EGTA, while Ca2+ influx was inhibited by high concentrations. Thus, in T cells Ca2+ influx occurs independently of IP3-dependent Ca2+ release. However, some other PIP2 hydrolysis-dependent event was involved in prolonged activation of Ca2+ influx. Extracellular Ca2+ influenced Ca2+ release and influx through the action of two plasma membrane Ca2+ entry pathways with different pharmacological and biochemical properties. 相似文献
970.