Stress and Depression Among the Oldest-Old: A Longitudinal Analysis

Stress and psychosocial resources play a crucial role in late-life depression. While most studies focus on predominantly those who are young-old, this study used a sample aged 85 and older. The authors' study aims to examine three research questions: (1) What are the trajectories of depression and its associated factors such as types of stress and psychosocial resources among the oldest-old? (2) What are the longitudinal relationships among the changes in stress, psychosocial resources, and depressive symptoms? (3) Are the effects of the changes in stress on depression trajectory mediated by changes in psychosocial resources? The study used a convenience sample of 193 community-dwelling elders aged 85 and older with four interviews every six months from 1986 to 1988. Using multilevel modeling analyses, longitudinal results showed that changes in positive life events, daily hassles (worries), and mastery were significantly associated with changes in late-life depression among the oldest-old.     

A Meta-Analysis of Oxidative Stress Markers in Depression

ObjectStudies have suggested that depression was accompanied by oxidative stress dysregulation, including abnormal total antioxidant capacity (TAC), antioxidants, free radicals, oxidative damage and autoimmune response products. This meta-analysis aims to analyse the clinical data quantitatively by comparing the oxidative stress markers between depressed patients and healthy controls.MethodsA search was conducted to collect the studies that measured the oxidative stress markers in depressed patients. Studies were searched in Embase, Medline, PsychINFO, Science direct, CBMDisc, CNKI and VIP from 1990 to May 2015. Data were subjected to meta-analysis by using a random effects model for examining the effect sizes of the results. Bias assessments, heterogeneity assessments and sensitivity analyses were also conducted.Results115 articles met the inclusion criteria. Lower TAC was noted in acute episodes (AEs) of depressed patients (p<0.05). Antioxidants, including serum paraoxonase, uric acid, albumin, high-density lipoprotein cholesterol and zinc levels were lower than controls (p<0.05); the serum uric acid, albumin and vitamin C levels were increased after antidepressant therapy (p<0.05). Oxidative damage products, including red blood cell (RBC) malondialdehyde (MDA), serum MDA and 8-F₂-isoprostanes levels were higher than controls (p<0.05). After antidepressant medication, RBC and serum MDA levels were decreased (p<0.05). Moreover, serum peroxide in free radicals levels were higher than controls (p<0.05). There were no differences between the depressed patients and controls for other oxidative stress markers.ConclusionThis meta-analysis supports the facts that the serum TAC, paraoxonase and antioxidant levels are lower, and the serum free radical and oxidative damage product levels are higher than controls in depressed patients. Meanwhile, the antioxidant levels are increased and the oxidative damage product levels are decreased after antidepressant medication. The pathophysiological relationships between oxidative stress and depression, and the potential benefits of antioxidant supplementation deserve further research.     

Cortisol Response to Repeated Psychosocial Stress

Psychosocial stress plays a major role in the etiology and the course of mental disorders that often show an altered activation of the hypothalamus–pituitary–adrenal (HPA) axis. The Trier Social Stress Test (TSST) reliably activates the HPA axis and reflects real life stress exposure. However, habituation may confound the results of clinical trials that apply TSST. The present study investigates the cortisol response after repeated psychosocial stress induction with short-term and long-term intervals between repeated testing sessions. Forty-one healthy subjects were exposed to the TSST four times with an interval of 24 h between the first and the second testing session (t1 and t2). The 3rd and the 4th testing session (t3 and t4) were also separated by a 24-hour interval whereas there were 10 weeks between t2 and t3. A significant decrease in the salivary cortisol responses was noticed from testing session t1 to t2 as well as from testing session t3 to t4. By contrast, there were no differences in the HPA axis reactivity between testing session t2 and t3. Our results demonstrated the habituation of the HPA axis to a standardized psychosocial stress test when testing was repeated after 24 h. By contrast, a renewed challenge with a ten-week-interval in-between activated the HPA axis in a similar manner as before. It is suggested that studies designed to investigate the HPA axis activity under repeated psychosocial stress conditions should apply the TSST three times in order to separate habituation from intervention effects.     

Response of Tea Plants to Water Stress

Two-year-old potted plants of six Camellia sinensis cultivars (TV-18, TV-26, UPASI-3, UPASI-26, T-78 and HV-39) were subjected to water stress for 4, 8 and 12 d. Relative water content (RWC) of leaves of all cultivars declined with water stress, but in the two drought tolerant cultivars (UPASI-3 and UPASI-26), higher RWC were maintained in comparison to the others. Phenol content and activities of phenylalanineammonialyase, polyphenoloxidase and peroxidase initially increased, but decreased during extended drought. Chlorophyll contents decreased, whereas proline contents increased during water stress. SDS-PAGE analysis of proteins revealed increased accumulation of proteins of intermediate molecular masses (42 – 44 kDa) and low molecular masses (14 – 26 kDa). After 12 d of water stress, most of these proteins disappeared in T-78 and HV-39, but in the other cultivars they were still detectable.     

嫁接茄子对NaCl胁迫的反应

NaCl处理自根茄子苗的半致死浓度为6.267 g·L-1.嫁接苗株高抑制率和茎粗抑制率均低于自根苗,自根苗受NaCl伤害明显重于嫁接苗.在NaCl胁迫下,嫁接苗的电导率和丙二醛(MDA)含量均低于自根苗,但其脯氨酸含量则明显高于自根苗.     

Molecular Aspects of MicroRNAs and Phytohormonal Signaling in Response to Drought Stress: A Review

Phytohormones play an essential role in plant growth and development in response to environmental stresses. However, plant hormones require a complex signaling network combined with other signaling pathways to perform their proper functions. Thus, multiple phytohormonal signaling pathways are a prerequisite for understanding plant defense mechanism against stressful conditions. MicroRNAs (miRNAs) are master regulators of eukaryotic gene expression and are also influenced by a wide range of plant development events by suppressing their target genes. In recent decades, the mechanisms of phytohormone biosynthesis, signaling, pathways of miRNA biosynthesis and regulation were profoundly characterized. Recent findings have shown that miRNAs and plant hormones are integrated with the regulation of environmental stress. miRNAs target several components of phytohormone pathways, and plant hormones also regulate the expression of miRNAs or their target genes inversely. In this article, recent developments related to molecular linkages between miRNAs and phytohormones were reviewed, focusing on drought stress.     

Dunaliella salina: A model System for Studying the Response of Plant Cells to Stress

This review focuses on the biochemical and physiological responseof the halotolerant green alga, Dunaliella salina, to conditionsof stress. It is now well established that in response to stress,cells of Dunaliella salina var. bardawil show increased glycerolproduction, massive ßcarotene accumulation and enhancedabscisic acid metabolism. In this respect, cellular responsesare regulatory and seem to depend on a diversity of mechanismswhich may be linked to a modification of the abscisic acid balance.Dunaliella lacks a rigid cell wall and the cellular contentsare enclosed by an elastic plasma membrane that permits rapidcell volume changes in response to extracellular changes inosmolarity. Based on the ‘stretch activated ion channelsmodel’ reviewed recently by Kirst (1990) we propose thefollowing cascade of responses: volume change/distortion ofplasmalemma     

木质部液流的碱化：一个综合的干旱胁迫响应信号

土壤干旱会改变植物木质部液流的离子组成,引起木质部碱化,提高液流的pH值。因而认为木质部液流碱化是诱使叶上气孔关闭的最可能的根源土壤干旱信号。本文章介绍了这一领域的研究进展。     

Prion Switching in Response to Environmental Stress

Evolution depends on the manner in which genetic variation is translated into new phenotypes. There has been much debate about whether organisms might have specific mechanisms for “evolvability,” which would generate heritable phenotypic variation with adaptive value and could act to enhance the rate of evolution. Capacitor systems, which allow the accumulation of cryptic genetic variation and release it under stressful conditions, might provide such a mechanism. In yeast, the prion [PSI⁺] exposes a large array of previously hidden genetic variation, and the phenotypes it thereby produces are advantageous roughly 25% of the time. The notion that [PSI⁺] is a mechanism for evolvability would be strengthened if the frequency of its appearance increased with stress. That is, a system that mediates even the haphazard appearance of new phenotypes, which have a reasonable chance of adaptive value would be beneficial if it were deployed at times when the organism is not well adapted to its environment. In an unbiased, high-throughput, genome-wide screen for factors that modify the frequency of [PSI⁺] induction, signal transducers and stress response genes were particularly prominent. Furthermore, prion induction increased by as much as 60-fold when cells were exposed to various stressful conditions, such as oxidative stress (H₂O₂) or high salt concentrations. The severity of stress and the frequency of [PSI⁺] induction were highly correlated. These findings support the hypothesis that [PSI⁺] is a mechanism to increase survival in fluctuating environments and might function as a capacitor to promote evolvability.     

植物铁蛋白与氧化胁迫应激

植物铁蛋白是植物体重要的铁调节蛋白。许多研究表明植物铁蛋白与氧化胁迫抗性之间具有较强关联。植物铁蛋白不仅能抵御高铁产生的氧化毒性,在很多氧化胁迫及环境胁迫抗性中也发挥作用。对植物铁蛋白在氧化及逆境胁迫中的应激加以综述,为铁蛋白在生物工程领域的应用提供理论依据。     

长穗薄冰草（Thinopyrum ponticum）对盐碱胁迫的生理响应

实验采用不同浓度（以干土重0.3%、0.5%、0.7%和0.9%计）Na2SO4、NaCl、NaHCO3、Na2CO3,Na2SO4：NaCl=1：1、NaHCO3：Na2CO3=1：1和Na2SO4：NaCl：NaHCO3：Na2CO3=1：1：1：1对长穗薄冰草进行胁迫,研究长穗薄冰草对盐碱胁迫的生理响应.结果表明：根系活力、SOD活性随盐碱浓度的增加逐渐下降,脯氨酸含量呈上升趋势,叶绿素含量除Na2SO4处理组外,呈先上升后下降的趋势.其中碱性盐（NaHCO3、Na2CO3、NaHCO3：Na2CO3=1：1、Na2SO4：NaCl：NaHCO3：Na2CO3=1：1：1：1）对长穗薄冰草的胁变效应较中性盐（Na2SO4、NaCl、Na2SO4：NaCl=1：1）大,以Na2SO4处理组对长穗薄冰草的影响最小,0.7% Na2CO3是长穗薄冰草正常生长的临界浓度.