Stress induces the assembly of RNA granules in the chloroplast of Chlamydomonas reinhardtii

Eukaryotic cells under stress repress translation and localize these messenger RNAs (mRNAs) to cytoplasmic RNA granules. We show that specific stress stimuli induce the assembly of RNA granules in an organelle with bacterial ancestry, the chloroplast of Chlamydomonas reinhardtii. These chloroplast stress granules (cpSGs) form during oxidative stress and disassemble during recovery from stress. Like mammalian stress granules, cpSGs contain poly(A)-binding protein and the small, but not the large, ribosomal subunit. In addition, mRNAs are in continuous flux between polysomes and cpSGs during stress. Localization of cpSGs within the pyrenoid reveals that this chloroplast compartment functions in this stress response. The large subunit of ribulosebisphosphate carboxylase/oxygenase also assembles into cpSGs and is known to bind mRNAs during oxidative stress, raising the possibility that it plays a role in cpSG assembly. This discovery within such an organelle suggests that mRNA localization to granules during stress is a more general phenomenon than currently realized.     

Decrease in the stress reaction and the ulcerative lesions of the stomach under the influence of gamma-hydroxybutyric acid

The effect of preliminary Na gamma-hydroxybutyric acid (GHBA) injection on the activation of adrenergic and hypophyseal-adrenal systems during emotional-painful stress and ulcerous affection of the stomach after the stress cessation was studied in experiments on rats. It was established that the preliminary GHBA administration inhibits stimulation of stress causing systems and thereby prevents ulcerous affection of the stomach mucosa. It is suggested that the activation of GHBA-ergic inhibiting system, which accompanies the stress, is a natural mechanism of limitation of the stress reaction and prevention of the stress affections.     

Emerging trends in the functional genomics of the abiotic stress response in crop plants

Plants are exposed to different abiotic stresses, such as water deficit, high temperature, salinity, cold, heavy metals and mechanical wounding, under field conditions. It is estimated that such stress conditions can potentially reduce the yield of crop plants by more than 50%. Investigations of the physiological, biochemical and molecular aspects of stress tolerance have been conducted to unravel the intrinsic mechanisms developed during evolution to mitigate against stress by plants. Before the advent of the genomics era, researchers primarily used a gene-by-gene approach to decipher the function of the genes involved in the abiotic stress response. However, abiotic stress tolerance is a complex trait and, although large numbers of genes have been identified to be involved in the abiotic stress response, there remain large gaps in our understanding of the trait. The availability of the genome sequences of certain important plant species has enabled the use of strategies, such as genome-wide expression profiling, to identify the genes associated with the stress response, followed by the verification of gene function by the analysis of mutants and transgenics. Certain components of both abscisic acid-dependent and -independent cascades involved in the stress response have already been identified. Information originating from the genome-wide analysis of abiotic stress tolerance will help to provide an insight into the stress-responsive network(s), and may allow the modification of this network to reduce the loss caused by stress and to increase agricultural productivity.     

Tensile Tissue Stress Affects the Orientation of Cortical Microtubules in the Epidermis of Sunflower Hypocotyl

Abstract In turgid multicellular organs, it is convenient to differentiate between the two kinds of tensile forces acting in cell walls as a result of turgor pressure. The primary forces occur both in situ and in cells isolated from the organ, whereas the secondary forces occur only in situ. The latter are an unavoidable physical consequence of the variation in mechanical parameters of tissues forming layers or strands. The most rigid tissue is under maximal tensile force, whereas the least rigid is under maximal compressive force. These forces cause tissue stresses (that is, certain tissues are under tensile stress, whereas others are under compressive stress in the organ). The primary and secondary forces result in primary and secondary stress in cell walls, respectively. The anisotropy of the primary stress is a function of cell shape. For instance, in cylindric cells the anisotropy expressed as the ratio of longitudinal to transverse stresses is 0.5. The anisotropy of the secondary stress is a function of the compound structure of the organ. For example, in the epidermis of sunflower hypocotyl, the longitudinal secondary stress is much higher than the transverse stress. The primary and secondary stresses are superimposed, and, as a consequence, the stress anisotropy in the outer thick walls of epidermal cells is greater than 1. These outer epidermal walls transmit most of the tissue stress. When the epidermis is peeled but remains turgid, only primary stress remains, but loading of the peel can reestablish the original stress anisotropy. We studied the effect of stress anisotropy changes on the orientation of cortical microtubules (CMTs) in the sunflower hypocotyl epidermis. We showed that changes in stress anisotropy cause the CMT orientation to change in the direction of maximal wall stress. In situ, the relatively high tensile tissue stress in the epidermis causes maximal stress in the longitudinal direction and relatively steep CMT orientation. When the tissue stress is removed from the epidermis by peeling, the CMTs tend to reorient toward the transverse direction, which is the direction of maximal stress in the primary component. On application of external longitudinal stress, to substitute for tissue stress, CMTs tend to reorient in the longitudinal direction. However, a relatively high rate of plastic strain is caused by the stress applied to the peel in an acid medium. This produces a less steep orientation of CMTs. It appears that the change in stress anisotropy orients the CMT in the direction in which the stress is maximal after the change, but there is also some effect of the growth rate on the orientation. Received 4 January 2000; accepted 10 February, 2000     

Interaction of genetic and environmental components in the determination of tryptophan hydroxylase activity in the mouse brain in stress

The interaction between genetic and environmental components of phenotype variety in the response to cold and emotional stress of the brain serotonin system was studied in 11 inbred strains of mice. It was shown that the variety in the degree of tryptophan hydroxylase activity's changes under stress are mainly due to the genotypic differences. The presence of different genotypic systems controlling the activity of tryptophan hydroxylase under basal conditions and under stress was revealed. Differences in hereditary mechanisms determining the tryptophan hydroxylase reactions to different kinds of stress were noted.     

Role of the GABAergic system in the mechanism of the stress-regulating action of phenibut

Disturbances in GABA-ergic inhibitory system were noted upon the exposure of thalamus and hypothalamus of experimental animals to stress of 18 hours and longer duration but not of 3 hours duration. Phenibut (I mg/kg) eliminates the symptoms of GABA-system disturbances revealed upon exposure to stress, decreases the tension of stress reaction and hyperglucocorticoidemia which causes hyperglycemia. In the bodies of intact rats phenibut causes "switching on" of adaptive GABA-system function, which is more physiological than the one appearing on short-term stress.     

Conserved features of chronic stress across phyla: the effects of long-term stress on behavior and the concentration of the neurohormone octopamine in the cricket, Gryllus texensis

Many of the deleterious effects of chronic stress in vertebrates are caused by the long-term elevation of stress hormones. These negative effects are thought to be unavoidable by-products of sustained activation of the stress response, but the details remain unclear. A comparative perspective may help in understanding chronic stress. We exposed crickets (Gryllus texensis) to a mock predator. A single exposure to a mock predator induced a transient increase in the hemolymph (blood) concentration of the insect stress neurohormone, octopamine. Repeated exposure to the mock predator increased basal levels of octopamine, similar to the effects of chronic stress on the basal levels of vertebrate stress hormones. This study is the first to report an increase in the basal levels of an invertebrate stress hormone in response to repeated flight-or-fight stress. Chronic stress reduced weight gain, and decreased feeding and enhanced weight loss after food deprivation in adult female crickets. However, chronic stress also increased the tendency of crickets to produce sustained flight. Therefore, this study supports the hypothesis that increasing basal levels of stress hormones may be a phylogenetically common response to chronically stressful conditions. It also demonstrates that chronic stress has both positive and negative effects in insects.     

Dependence of the circadian changes in stressor response of the rat hypophyseal-adrenocortical system on the stress intensity

Circadian responses of the hypophyseal-adrenal axis to stress were greater is the PM as compared with AM after small stress intensity, but it were similar after high stress intensity. Was shown to depend on the intensity of the stress factor. The circadian variations of the adrenal glands response to the ACTH seem to play a major role in determining the character of the hypophyseal-adrenal axis response to stress.     

Ontogeny of the response of the hypothalamo-pituitary-adrenal axis to maternal immobilization stress in rats.

In this study we investigated the response of the rat fetal hypothalamo-pituitary-adrenal (HPA) axis to an acute maternal stress in late gestation. On day 20 of gestation, pregnant rats were exposed to forced immobilization stress for up to 60 min. In mothers, a significant increase in plasma ACTH and corticosterone(B) was observed at 20 and 60 min. The ACTH content in the maternal pituitary decreased significantly at 60 min. Fetal blood pH was decreased by the maternal stress, showing a hypoxic condition of the fetus. Fetal plasma ACTH increased transiently at 20 min. Fetal plasma B increased at 20 and 60 min. ACTH in the fetal pituitary and the placenta did not show marked changes due to the maternal stress. Pregnant rats on day 18-21 of gestation were subjected to a 20 min maternal stress. In the basal condition without stress, fetal plasma ACTH and B showed parallel ontogenic patterns, having a peak value on day 19 of gestation. Fetal plasma ACTH as well as plasma B were increased significantly by the maternal stress at all points evaluated. These results indicate that fetal hypoxia is important in stress transmission to the fetal HPA axis in this type of maternal stress, and the fetal HPA axis responds to the stress as early as day 18 of gestation.     

Effect of stress exposure on the activation pattern of enkephalin-containing perikarya in the rat ventral medulla

We examined the effects of acute and chronic psychogenic stress on the activation pattern of enkephalin-containing perikarya in the rat ventrolateral medulla. Rats allocated to the chronic stress groups were subjected to 90 min of immobilization for 10 days. On the 11th day, the chronically stressed rats were exposed to homotypic (90-min immobilization) or to heterotypic but still psychogenic (90-min immobilization coupled to air jet stress) stress. The acute stress group was subjected once to an acute 90-min immobilization. For each group, the rats were anesthetized either before stress (time 0) or 90, 180, and 270 min after the onset of stress. Brain sections were then processed using immunocytochemistry (Fos protein) followed by radioactive in situ hybridization histochemistry (enkephalin mRNA). Following immobilization, the acute group displayed a marked increase in the number of activated enkephalin-containing perikarya within the paragigantocellularis and lateral reticular nuclei. This level of activation was sustained up to 180 min following the onset of the immobilization stress and had returned to baseline levels by 270 min from the initiation of the stress. However, this stress-induced activation of enkephalin-containing perikarya of the ventrolateral medulla was not seen following either homotypic or heterotypic stress in the chronically stressed group. These results provide evidence that enkephalin-containing perikarya of the ventrolateral medulla may constitute a potential circuit through which they regulate some aspect of the stress responses. Conversely, this enkephalinergic influence from the ventrolateral medulla was shown to be absent following chronic stress exposure. This would suggest a decrease in enkephalin inhibitory input originating from the ventrolateral medulla, thereby allowing a neuroendocrine and/or autonomic response to chronic stress.     

Involvement of corticotropin-releasing factor in restraint stress-induced anorexia and reversion of the anorexia by somatostatin in the rat

The mechanism by which restraint stress induces suppression of food intake and the influence of intracerebroventricular (icv) administration of somatostatin on the anorexia induced by restraint stress were examined in the rat. Ninety minutes of restraint stress reduced food intake of rats to approximately 60% that of control. Anorexia induced by 90 min restraint stress was partially reversed by icv administration of alpha-helical CRF (9-41), a corticotropin-releasing factor (CRF) antagonist, and completely reversed by anti-CRF gamma-globulin. These results provide further evidence in support of the theory that CRF is involved in the inhibitory mechanism of food intake in restraint stress. ICV administration of somatostatin 14 and SMS 201-995, an analog of somatostatin, also reversed restraint stress-induced anorexia. It is, therefore, suggested that somatostatin may counteract the suppressive action of CRF on food intake in stress.     

逆境胁迫下作物基因表达更替的研究进展

本文综述了高等植物在厌氧、热激,盐分胁迫,养分胁迫,紫外辐射等各种逆境条件下,基因表达更替的一系列过程,提出基因表达变化对作物适应逆境条件的意义,并对今后的研究作了展望。     

Effects of zinc on the induction of metallothionein isoforms in hippocampus in stress rats

Metallothioneins (MTs) are involved in the cellular metabolism of zinc and in cytoprotection against stress factors. Hippocampus plays a specific role in the body's response to stressors. The present study was conducted to evaluate the effects of zinc on the expression of metallothionein isoforms in the hippocampus of stress rats. The animal model of psychologic stress was developed by restraint for 4 weeks. Wistar rats were randomly assigned to 6 groups: control group, zinc-deficient group, zinc-supplemented group, and the corresponding 3 stress groups. Three separate diets of different zinc contents (1.73 ppm, 17.7 ppm, and 41.4 ppm, respectively) were used in this study. Compared with the control group, the stress groups had higher inductions of MTs and MT-1 and MT-3 mRNA in hippocampus. On the one hand, the expressions of MTs and their mRNAs in hippocampus were downregulated in the zinc-deficient group; however, their expressions were evidently enhanced in the stress zinc-deficient group. MT induction in the zinc-supplemented group was increased. Furthermore, the stress zinc-supplemented group had a more significant yield of MTs and their mRNAs. In addition, the levels of plasma cortisol, interleukin-6 (IL-6), IL-1, and nitric oxide (NO) were increased clearly in the zinc-deficient group and the stress groups. The results suggest that zinc deficiency may decrease and zinc supplementation may increase the expressions of MTs and their mRNAs in hippocampus; moreover, stress can increase their expressions dramatically. The impairment of stress on the body may be involved with the nutrition status of zinc, and zinc deficiency can lower the body's adaptability to stress.     

Study of the information stress problem in operators

On the basis of analysis of the special features of operator performance under extreme conditions, a special form of occupational and psychological stress was determined, i.e., information stress in the operator. The relations between workload and stress are determined, and basic information stressors are indicated. The results of the use of information stress models and the data on personality-related determination of this condition are analyzed. The assumptions on the mental control mechanisms of stress resistance in the operator are suggested.     

The adaptive reactions in hemopoietic system of the irradiated mice of two lines, differing in the level of emotionally-stress reactions on the emotional stress

On lines of the mice genetically differing on the sensitivity on emotional stress (steady--of the mouse of the line C57BL/6 or sensitive--of the mouse of the line BALB/c), the research of the development of the adaptive reactions in the system of the blood on the emotional stress influencing animals on the background of the preliminary irradiation in a low dose (0.9 Gy) is carried out. The unirradiated mice of the line C57BL/6 adequately reacted on the stress, that was shown in a moderate behavioural reaction during the period of stress, and the development of high-grade adaptive reactions in the hemopoietic system. Among the mice of the line C57BL/6 in conditions of the combined influence of ionizing radiation and of the emotional stress was not revealed of the infringements of the adaptive reactions of the hemogenesis. As opposed to these data, among unirradiated mice of the line BALB/c the sharply expressed behavioural reactions during the stress were marked, that was accompanied by incomplete development of the adaptive reactions in the system of a blood on the stress. Under the influence of stress on the previously irradiated animal line BALB/c was observed the inhibition of the medullar hemopoiesis.     

Analysis of the strain and stress distribution in the wall of the developing and mature rat aorta

The variation of wall stress distribution with age in the thoracic and abdominal aortas of normotensive rats was studied. Dimensions of the zero-stress configurations were measured at the ages of 4, 8, 12, 20, and 52 weeks. Using data from previously published inflation tests, the circumferential stress-strain relationship was obtained in each age group. The calculated stress distribution showed that the average circumferential stress remained practically constant after the age of 20 weeks. The circumferential stress at the innermost part of the arterial wall was greater than the stress at the outermost part, but the difference was maintained at a moderate level with adjustments in the zero-stress configuration. It is speculated that, after the age of 20 weeks, changes in arterial geometry and rheological properties tend to maintain a constant stress distribution under varying conditions of loading. This distribution was achieved by enhanced growth at the inner part of the media in comparison with the growth at its outer margins and suggests that during development and maturity, the growth of the aorta is modulated by circumferential stress.