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91.
国产硅藻土经氢氧化铵处理后可用于从发酰液中直接取青霉素G酰化酶,平均吸附量为90U/g。吸附的酶可用22%硫酸铵-0.3mol/LPBS(pH8.0)溶液洗脱。平均比18U/18Umg蛋白(NIPAB法)。硅藻土可反复使用。苯乙酰胺-Sepharose4B树脂可对酶作进一步的纯化。 相似文献
92.
Casein Kinase II Activity in the Postischemic Rat Brain Increases in Brain Regions Resistant to Ischemia and Decreases in Vulnerable Areas 总被引:1,自引:1,他引:0
Abstract: Casein kinase II (CKII) is a protein kinase acting in the intracellular cascade of reactions activated by growth factor receptors, and that has a profound influence on cell proliferation and survival. In this investigation, we studied the changes in the activity and levels of CKII in the rat brain exposed to 10. 15 and 20 min of transient forebrain ischemia followed by variable periods of reperfusion. The cytosolic CKII activity decreased during reperfusion by ∼ 30 and ∼ 50% in the selectively vulnerable areas, striatum and the CA1 region of the hippocampus, respectively. In the resistant CA3 region of hippocampus and neocortex, the activity increased by ∼ 20 and ∼ 60%, respectively. The postischemic changes in CKII activity were dependent on the duration of the ischemic insult. The levels of CKII did not change after ischemia, suggesting that the enzyme is modulated by covalent modification or is interacting with an endogenous inhibitor/activator. Treatment of the cytosolic fraction from cortex of rats exposed to ischemia and 1 h of reperfusion with agarose-bound phosphatase decreased the activity of CKII to control levels, suggesting that CKII activation after ischemia involves a phosphorylation of the enzyme. The correlation between postischemic CKII activity and neuronal survival implies that preservation or activation of CKII activity may be important for neuronal survival after cerebral ischemia. 相似文献
93.
Depression of Neuronal Protein Synthesis Initiation by Protein Tyrosine Kinase Inhibitors 总被引:2,自引:1,他引:1
Abstract— Growth factors stimulate cellular protein synthesis, but the intracellular signaling mechanisms that regulate initiation of mRNA translation in neurons have not been clarified. A rate-limiting step in the initiation of protein synthesis is the formation of the ternary complex among GTP, eukaryotic initiation factor 2 (elF-2), and the initiator tRNA. Here we report that genistein, a specific tyrosine kinase inhibitor, decreases tyrosine kinase activity and the content of phosphotyrosine proteins in cultured primary cortical neurons. Genistein inhibits protein synthesis by >80% in a dose-dependent manner (10–80 μg/ml) and concurrently decreases ternary complex formation by 60%. At the doses investigated, genistein depresses tyrosine kinase activity and concomitantly stimulates PKC activity. We propose that a protein tyrosine kinase participates in the initiation of protein synthesis in neurons, by affecting the activity of elF-2 directly or through a protein kinase cascade. 相似文献
94.
As above,not so below: Long-term dynamics of net primary production across a dryland transition zone
Drylands are key contributors to interannual variation in the terrestrial carbon sink, which has been attributed primarily to broad-scale climatic anomalies that disproportionately affect net primary production (NPP) in these ecosystems. Current knowledge around the patterns and controls of NPP is based largely on measurements of aboveground net primary production (ANPP), particularly in the context of altered precipitation regimes. Limited evidence suggests belowground net primary production (BNPP), a major input to the terrestrial carbon pool, may respond differently than ANPP to precipitation, as well as other drivers of environmental change, such as nitrogen deposition and fire. Yet long-term measurements of BNPP are rare, contributing to uncertainty in carbon cycle assessments. Here, we used 16 years of annual NPP measurements to investigate responses of ANPP and BNPP to several environmental change drivers across a grassland–shrubland transition zone in the northern Chihuahuan Desert. ANPP was positively correlated with annual precipitation across this landscape; however, this relationship was weaker within sites. BNPP, on the other hand, was weakly correlated with precipitation only in Chihuahuan Desert shrubland. Although NPP generally exhibited similar trends among sites, temporal correlations between ANPP and BNPP within sites were weak. We found chronic nitrogen enrichment stimulated ANPP, whereas a one-time prescribed burn reduced ANPP for nearly a decade. Surprisingly, BNPP was largely unaffected by these factors. Together, our results suggest that BNPP is driven by a different set of controls than ANPP. Furthermore, our findings imply belowground production cannot be inferred from aboveground measurements in dryland ecosystems. Improving understanding around the patterns and controls of dryland NPP at interannual to decadal scales is fundamentally important because of their measurable impact on the global carbon cycle. This study underscores the need for more long-term measurements of BNPP to improve assessments of the terrestrial carbon sink, particularly in the context of ongoing environmental change. 相似文献
95.
Eszter Szász Fanni Sarkadi Eszter Szöllősi Renáta Kopena János Török Balázs Rosivall 《Journal of evolutionary biology》2023,36(1):156-168
Brood sex ratios (BSRs) have often been found to be nonrandom in respect of parental and environmental quality, and many hypotheses suggest that nonrandom sex ratios can be adaptive. To specifically test the adaptive value of biased BSRs, it is crucial to disentangle the consequences of BSR and maternal effects. In multiparous species, this requires cross-fostering experiments where foster parents rear offspring originating from multiple broods, and where the interactive effect of original and manipulated BSR on fitness components is tested. To our knowledge, our study on collared flycatchers (Ficedula albicollis) is the first that meets these requirements. In this species, where BSRs had previously been shown to be related to parental characteristics, we altered the original BSR of the parents shortly after hatching by cross-fostering nestlings among trios of broods and examined the effects on growth, mortality and recruitment of the nestlings. We found that original and experimental BSR, as well as the interaction of the two, were unrelated to the fitness components considered. Nestling growth was related only to background variables, namely brood size and hatching rank. Nestling mortality was related only to hatching asynchrony. Our results therefore do not support that the observed BSRs are adaptive in our study population. However, we cannot exclude the possibility of direct effects of experimentally altered BSRs on parental fitness, which should be evaluated in the future. In addition, studies similar to ours are required on various species to get a clearer picture of the adaptive value of nonrandom BSRs. 相似文献
96.
Wei Dai Yong gang Dai Dong feng Ren Da wei Zhu 《Journal of biochemical and molecular toxicology》2023,37(5):e23313
This study investigated that dieckol (DKL), a natural drug, inhibits colon cancer cell proliferation and migration by inhibiting phosphoinositide-3-kinase (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR) phosphorylation in HCT-116 cells. The cells were treated with DKL in various concentrations (32 and 50 μM) for 24 h and then analyzed for various experiments. MTT (tetrazolium bromide) and crystal violet assay investigated DKL-mediated cytotoxicity. Dichlorodihydrofluorescein diacetate staining was used to assess the reactive oxygen species (ROS) measurement, and apoptotic changes were studied by dual acridine orange and ethidium bromide staining. Protein expression of cell survival, cell cycle, proliferation, and apoptosis protein was evaluated by western blot analysis. Results indicated that DKL produces significant cytotoxicity in HCT-116, and the half-maximal inhibitory concentration was found to be 32 μM for 24-h incubation. Moreover, effective production of ROS and enhanced apoptotic signs were observed upon DKL treatment in HCT-116. DKL induces the expression of phosphorylated PI3K, AKT, and mToR-associated enhanced expression of cyclin-D1, proliferating cell nuclear antigen, cyclin-dependent kinase (CDK)-4, CDK-6, and Bcl-2 in HCT-116. In addition, proapoptotic proteins such as Bax, caspase-9, and caspase-3 were significantly enhanced by DKL treatment in HCT-116. Hence, DKL has been considered a chemotherapeutic drug by impeding the expression of PI3K-, AKT-, and mTOR-mediated inhibition of proliferation and cell cycle-regulating proteins. 相似文献
97.
98.
N6-methyladenosine (m6A) is a dynamic and reversible RNA modification that has emerged as a crucial player in the life cycle of RNA, thus playing a pivotal role in various biological processes. In recent years, the potential involvement of RNA m6A modification in aging and age-related diseases has gained increasing attention, making it a promising target for understanding the molecular mechanisms underlying aging and developing new therapeutic strategies. This Perspective article will summarize the current advances in aging-related m6A regulation, highlighting the most significant findings and their implications for our understanding of cellular senescence and aging, and the potential for targeting RNA m6A regulation as a therapeutic strategy. We will also discuss the limitations and challenges in this field and provide insights into future research directions. By providing a comprehensive overview of the current state of the field, this Perspective article aims to facilitate further advances in our understanding of the molecular mechanisms underlying aging and to identify new therapeutic targets for aging-related diseases. 相似文献
99.
Marie-Dominique Rhoda-Hardy-Dessources René-Serge de Neef Guy Mérault Françoise Giraud 《生物化学与生物物理学报:疾病的分子基础》1993,1181(1):90-96
PtdIns and PtdInsP kinases from normal erythrocyte (AA) membranes and sickle cell anaemia erythrocyte (SS) membranes have been characterized. PtdIns kinase was studied in native membranes under conditions in which PtdInsP kinase and PtdInsP phosphatase do not express any activity. Kinetic analysis of the AA and SS PtdIns kinases indicate similar Km values for PtdIns and ATP but higher Vmax values for SS PtdIns kinase. PtdInsP kinase was partially purified from erythrocyte ghosts by NaCl extraction. The kinetic parameters of PtdInsP kinase determined under these conditions were similar in AA and SS NaCl extracts. These data suggest the presence of some effector of PtdIns kinase in SS cell membranes, resulting in a greater activity of the enzyme. This leads consequently, to increase the PtdInsP pool and to activate PtdInsP kinase, in agreement with our previous observations of a greater [32P]Pi incorporation in both polyphosphoinositides in SS cells relatively to AA cells. 相似文献
100.
Xuebin Yu Qiufeng Teng Kaimin Bao Maryam Chudhary Hui Qi Wenying Zhou Hongxin Che Junli Liu Xiang Ren Li Kong 《Journal of cellular biochemistry》2023,124(3):421-433
As one of the common and serious chronic complications of diabetes mellitus (DM), the related mechanism of diabetic retinopathy (DR) has not been fully understood. Müller cell reactive gliosis is one of the early pathophysiological features of DR. Therefore, exploring the manner to reduce diabetes-induced Müller cell damage is essential to delay DR. Thioredoxin 1 (Trx1), one of the ubiquitous redox enzymes, plays a vital role in redox homeostasis via protein–protein interactions, including apoptosis signal-regulating kinase 1 (ASK1). Previous studies have shown that upregulation of Trx by some drugs can attenuate endoplasmic reticulum stress (ERS) in DR, but the related mechanism was unclear. In this study, we used DM mouse and high glucose (HG)-cultured human Müller cells as models to clarify the effect of Trx1 on ERS and the underlying mechanism. The data showed that the diabetes-induced Müller cell damage was increased significantly. Moreover, the expression of ERS and reactive gliosis was also upregulated in diabetes in vivo and in vitro. However, it was reversed after Trx1 overexpression. Besides, ERS-related protein expression, reactive gliosis, and apoptosis were decreased after transfection with ASK1 small-interfering RNA in stable Trx1 overexpression Müller cells after HG treatment. Taken together, Trx1 could protect Müller cells from diabetes-induced damage, and the underlying mechanism was related to inhibited ERS via ASK1. 相似文献