The effect of irrigation regimes on plum (Prunus cerasifera) root system development dynamics

Prunus genus species are widely spread in semi-arid regions due to their ability to adjust to the limited water supply. Former research described the effect of water deficit on their aboveground development. However, less is known about the effects of water stress on the development of the root system. In order to investigate the effects of the irrigation regime on the root system development, young plum (Prunus cerasifera) trees were grown under three irrigation regimes for a period of five months. The effects of the irrigation regime on different root order and total root system elongation, biomass growth and tip numbers were analyzed. The results indicate that the responses vary according to the stress level. Under moderate stress, the total root system biomass decreases relative to the full irrigation treatment. However, low-order root formation remains similar to that found under no stress conditions. Under severe stress, the formation of low-order roots is also inhibited. Our results suggest that plum trees’ response to water deficit stress escalates according to the stress level. Namely, moderate stress affects the growth rate of the root system but does not alter the relative contribution of different orders, while severe stress both inhibits the total growth and changes the relative contribution of the different root orders. The combined measurements of the total root system and the different orders enable the identification of a stepwise response to water stress.     

Construction of collagen gel scaffolds for mechanical stress analysis

We designed a cyclic compression system using readily available six-well culture plates to investigate the influence of mechanical stress on skin-like structures. The effects of cyclic mechanical stress on protein expression by cells were easily examined, and hence, this system should be useful for further analysis of skin responses to mechanical stress.     

Disruptions in the blood system upon exposure to low-dose ionizing radiation depending on duration of emotional stress

In experiments on rats, disturbances in the development of blood system adaptive reactions on emotional stress were found. Under the combined effect of preliminary (before stress) exposure to 0.8 Gy of gamma-radiation and the emotional stress of various duration (2, 4 and 8 days), a compensatory capability of the blood system decreased. The degree of the disturbances directly depended on the duration of the emotional stress.     

Influence of stress on the maturity of T-cells

Stress is known to influence the immune function via an effect on the central nervous system. We previously presented data showing that stress alters the population of T-cell subsets in mice. The variations of T-cell subsets in the thymus, peripheral blood, and spleen in mice similarly stressed by immobilization or by unavoidable and opioid-dependent stress were measured by flow cytometry using the monoclonal antibodies anti-L3T4, anti-Lyt 1, anti-Lyt 2 and anti-Thy 1, 2. Immobilization stress was applied for three days and T-cell subsets were measured on the days 1, 2 and 3, as well as on day 7 after release from immobilization. Lyt 2-positive cells in the thymus were the most sensitive to stress, showing significant variations. The proportion of immature T-cells increased in the thymus, blood and spleen of the stressed mice. When diazepam or naloxone were administered 30 min before the initiation of stress, these variations tended to decrease. Thus, the ratio of T-cell subsets varied with the duration of immobilization stress. This appeared to be partly mediated by the opioid system and the central nervous system.     

Radiotelemetry-based study of occupational heat stress in a steel factory

Heat stress conditions prevailing in a steel factory were evaluated using a newly developed radiotelemetry system. This system was used as a station monitor for determining environmental temperature conditions and as a personal monitor to obtain data of worker physiological responses. Environmental information was used in calculating wet-bulb globe temperature heat stress index values. Physiological data were used in confirming safety limits. The study demonstrated the effectiveness of radiotelemetry in assessing occupational exposures to heat stress.     

Dopaminergic modulation of the septo-hippocampal cholinergic system activity under stress

The effects of the dopaminergic agonist apomorphine or the antagonist sulpiride on high affinity choline uptake and newly synthesized acetylcholine release by hippocampal synaptosomal preparations, were examined in rats subjected to immobilization stress. Increased dopamine uptake by septal synaptosomal preparations was taken as evidence for increased mesoseptal dopaminergic activity in response to stress. While apomorphine treatment failed to alter choline uptake or acetylcholine release in unhandled rats, it did however prevent the stress-induced increase in these cholinergic parameters. In contrast, after treatment with sulpiride both choline uptake and acetylcholine release were increased in unhandled rats, as they were after acute stress. Acute stress of sulpiride treated rats however resulted in changes similar to those produced by administration of either sulpiride or stress separately. We conclude that the mesoseptal dopaminergic system plays an important role in modulating the activity of the septo-hippocampal cholinergic system under stress.     

捕食应激过程中大鼠脑边缘系统一氧化氮合酶神经元的变化

探讨应激状态下大鼠脑边缘系统内一氧化氮合酶 (Nitricoxidesynthase,NOS )阳性神经元的变化及这种变化与脑神经元损伤发生的关系。采用捕食应激动物模型 ,将 80只雄性SD大鼠随机分为 3组 :对照组 (n =2 0 )、单纯捕食应激组 (n =30 )、加强捕食应激组 (n =30 )。采用还原型尼克酰胺腺嘌呤二核苷酸黄递酶(NADPH d)组织化学方法 ,研究应激后 1、 3、 6、 12、 2 1、 30dNOS阳性神经元的分布规律。结果表明 :对照组NOS活性平稳 ,但应激后NOS活性变化明显。与对照组比较 ,应激 1- 3d ,单纯应激组和加强应激组NOS阳性神经元数目在皮质、纹状体、海马、下丘脑等部位增多 ,即NOS活性升高 ;第 4 - 12d ,NOS活性进一步升高 ,除皮质外与对照组相比具显著性差异 (P <0 0 1) ;其中 ,应激单纯组和加强组海马和下丘脑室旁核分别在第 6d、第 12dNOS活性最高。从第 13d起NOS阳性神经元的活性开始逐渐降低 ;到第 30dNOS活性下降明显 ,但其活性仍高于对照组 (P <0 0 5 )。对于同一时间点而言 ,与对照组相比 ,加强应激组的NOS活性变化大于相应的单纯应激组。结果提示 :NOS活性程度与心理应激程度密切相关 ;应激过程中大鼠脑边缘系统过量增多的NO产生的神经毒性可能是应激导致大鼠脑边缘系统神经元受损的原因之一     

Identical Hik-Rre systems are involved in perception and transduction of salt signals and hyperosmotic signals but regulate the expression of individual genes to different extents in synechocystis

In previous studies, we characterized five histidine kinases (Hiks) and the cognate response regulators (Rres) that control the expression of approximately 70% of the hyperosmotic stress-inducible genes in the cyanobacterium Synechocystis sp. PCC 6803. In the present study, we screened a gene knock-out library of Rres by RNA slot-blot hybridization and with a genome-wide DNA microarray and identified three Hik-Rre systems, namely, Hik33-Rre31, Hik10-Rre3, and Hik16-Hik41-Rre17, as well as another system that included Rre1, that were involved in perception of salt stress and transduction of the signal. We found that these Hik-Rre systems were identical to those that were involved in perception and transduction of the hyperosmotic stress signal. We compared the induction factors of the salt stress- and hyperosmotic stress-inducible genes that are located downstream of each system and found that these genes responded to the two kinds of stress to different respective extents. In addition, the Hik33-Rre31 system regulated the expression of genes that were specifically induced by hyperosmotic stress, whereas the system that included Rre1 regulated the expression of one or two genes that were specifically induced either by salt stress or by hyperosmotic stress. Our observations suggest that the perception of salt and hyperosmotic stress by the Hik-Rre systems is complex and that salt stress and hyperosmotic stress are perceived as distinct signals by the Hik-Rre systems.     

Bone marrow hemopoiesis at emotional stress reactions of various intensity upon a background of exposure to low dose ionizing radiation

Rats preliminary exposed to 0.9 Gy of ionizing radiation showed disturbances in the development of adaptive reactions of blood system to emotional stress, compensatory capacity of the blood system being decreased. A degree of the disturbances directly depended on the duration and intensity of the emotional stress: at the prolonged intensive emotional stress a sharp decrease in the adaptive and compensatory capacity of blood system was found; at short intensive or moderate stress the changes in the adaptive and compensatory capacity of hemopoiesis were less pronounced. A combined action of low-dose ionizing radiation and short weak emotional stress did non affect the adaptive and compensatory capacity of hemopoietic system.     

多倍体植物抗逆性研究进展

许多逆境能诱导多倍体植物发生,并可能作为筛选压力推动多倍体的形成。多倍体植物具有细胞、器官巨大化的特点,但株型不一定巨大化。在几种主要逆境条件下(如低温、高温、干旱、盐碱、病害等),多倍体植物抗逆性往往增强。多倍体植物主要通过调整细胞大小和结构、调节生物膜系统、提高渗透调节物质含量、增强抗氧化系统活性、增加基因表达和通过表观遗传变化来增强抗逆性,但也有研究显示多倍体植物的抗逆性降低。多倍体植物的抗逆性还需要更深入和细致研究,才能阐明抗逆机理。该文对近年来国内外有关多倍体植物的形成、特征、抗逆性表现及其调控机制等方面的研究进展进行综述。     

The glutathione-glutaredoxin system in Rhodobacter capsulatus: part of a complex regulatory network controlling defense against oxidative stress

Mutants with defects in components of the glutathione-glutaredoxin (GSH/Grx) system of Rhodobacter capsulatus were constructed to study its role in defense against oxidative stress and the redox-dependent formation of photosynthetic complexes. The lack of the glutaredoxin 3 gene (grxC) or the glutathione synthetase B gene (gshB) resulted in lower growth rates under aerobic conditions and higher sensitivity to oxidative stress, confirming the role of the GSH/Grx system in oxidative stress defense. Both mutants are highly sensitive to disulfide stress, indicating a major contribution of the GSH/Grx system to the thiol-disulfide redox buffer in the cytoplasm. Like mutations in the thioredoxin system, mutations in the GSH/Grx system affected the formation of photosynthetic complexes, which is redox dependent in R. capsulatus. Expression of the genes grxC, gshB, grxA for glutaredoxin 1, and gorA for glutathione reductase, all encoding components of the GSH/Grx system, was not induced by oxidative stress. Other genes, for which a role in oxidative stress was established in Escherichia coli, acnA, fpr, fur, and katG, were strongly induced by oxidative stress in R. capsulatus. Mutations in the grxC, and/or gshB, and/or trxC (thioredoxin 2) genes affected expression of these genes, indicating an interplay of the different defense systems against oxidative stress. The OxyR and the SoxRS regulons control the expression of many genes involved in oxidative stress defense in E. coli in response to H2O2 and superoxide, respectively. Our data and the available genome sequence of R. capsulatus suggest that a SoxRS system is lacking but an alternative superoxide specific regulator exists in R. capsulatus. While the expression of gorA and grxA is regulated by H2O2 in E. coli this is not the case in R. capsulatus, indicating that the OxyR regulons of these two species are significantly different.     

Flow in the well: computational fluid dynamics is essential in flow chamber construction

A perfusion system was developed to generate well defined flow conditions within a well of a standard multidish. Human vein endothelial cells were cultured under flow conditions and cell response was analyzed by microscopy. Endothelial cells became elongated and spindle shaped. As demonstrated by computational fluid dynamics (CFD), cells were cultured under well defined but time varying shear stress conditions. A damper system was introduced which reduced pulsatile flow when using volumetric pumps. The flow and the wall shear stress distribution were analyzed by CFD for the steady and unsteady flow field. Usage of the volumetric pump caused variations of the wall shear stresses despite the controlled fluid environment and introduction of a damper system. Therefore the use of CFD analysis and experimental validation is critical in developing flow chambers and studying cell response to shear stress. The system presented gives an effortless flow chamber setup within a 6-well standard multidish.     

<Emphasis Type="SmallCaps">l</Emphasis>-Proline is a sedative regulator of acute stress in the brain of neonatal chicks

The purpose of the present study was to clarify the central nervous system function of amino acids during acute stress. In Experiment 1, changes in free amino acid pattern were investigated in the brain of neonatal chicks exposed to either restraint with isolation-induced or fasting stress. l-Proline and l-arginine were decreased in the telencephalon and diencephalon under any stress. Since the central nervous system functions of l-arginine during the stress response has recently been reported, in Experiment 2, the effect of intracerebroventricular injection of l-proline (0.5, 1.0, 2.0 μmol) during isolation-induced stress was investigated. l-Proline induced sedative and hypnotic effects in a dose-dependent manner. It is suggested that l-proline may have an important role to attenuate the stress response in the central nervous system of chicks.     

The glutathione system as a stress marker in plant ecophysiology: is a stress-response concept valid?

Environmental stress impacts cause an increased formation of reactive oxygen species (ROS) in the chloroplasts (photo-oxidative stress). The role of glutathione in the antioxidative defence system provides a rationale for its use as a stress marker. However, responses of glutathione concentrations and redox states are not consistent among the large number of available publications. In the present review the hypothesis that stress responses of the glutathione system follow a general ecophysiological stress-response concept is investigated. In this view, an initial response phase would be followed by an acclimation phase where a new steady-state is established. Alternatively, if successful acclimation is not achieved, degradation of the system will follow. Recent publications dealing with responses to photochilling, salinity, and drought are analysed as to whether the results fit the concept. In general, an initial stress response was related to changes in the glutathione redox state, whereas acclimation was marked by increased glutathione concentrations, increased related enzyme activities, and/or a more reduced redox state of glutathione. The latter was interpreted as overcompensation leading to enhanced regeneration of glutathione. Deterioration effects upon strong stress impacts were related to progressive degradation and oxidation of the glutathione pool. A time-course analysis, which has rarely been done in the published literature, showed this sequence of events. When apple trees were subjected to progressing drought, the initial response was a slight oxidation of the glutathione pool, followed by increased glutathione concentrations. When the stress increased, glutathione concentrations dropped and redox state became more oxidized, which marked the degradation of the system. In spite of the general congruency of these results with the suggested stress-response concept, several limitations have to be highlighted: The importance of the glutathione system relative to other components of the photoprotective and antioxidative defence system, as well as relative to stress avoidance strategies, has to be established. It is suggested that a variety of parameters taking into account alternative protection pathways (e.g. photorespiration, light dissipation) and other components of the antioxidative systems should be measured. Within such response patterns the glutathione system is a valuable stress marker in ecophysiological studies.     

Plasma hormone levels in human subject during stress loads in microgravity and at readaptation to Earth's gravity

In great part of the investigations of endocrine system functions in astronauts during space flights the plasma levels of hormones and metabolites were determined only in resting conditions, usually from one blood sample collection. Such levels reflected the psychical and physical state and new hormonal homeostasis of organism at the time of blood collection, however, the functional capacity of neuroendocrine system to respond to various stress stimuli during space flight remained unknown. The aim of present investigations was to study dynamic changes of hormone levels during the stress and metabolic loads (insulin induced hypoglycemia, physical exercise and oral glucose tolerance test) at the exposure of human subject to microgravity on the space station MIR. The responses of sympatico-adrenomedullary system to these stress and workloads were presented by Kvetnansky et al.     

Total leukocytes, T cell subpopulation and natural killer (NK) cell activity in rats exposed to restraint stress

Rats were stressed by immobilization for 3 hrs daily for 11 days and either sacrificed immediately after the last stress session (chronic stress group) or allowed to recover for 12 days and then sacrificed (recovery group). After 11 days of stress, leukocytes and lymphocytes were significantly decreased and neutrophils and large granular lymphocytes were markedly increased. The number of total, helper and suppressor T cells was significantly decreased but the percentage of T cells remained unchanged. Natural Killer (NK) cell activity was unaffected. After a 12 day recovery period from stress, the number of leukocytes returned to normal but the percentage of neutrophils was now below baseline whereas the percentages of lymphocytes and large granular lymphocytes had increased significantly. The number and percentage of total T cells and helper T cells was enhanced and NK cell activity tended to be increased. Thus, chronic stress as well as recovery from stress can affect individual components of the cellular immune system quite selectively and differently. In addition, a comparison of the effects of stress seen in this study with healthy rats with those seen under identical conditions in tumor bearing rats shows that stress or recovery from stress can affect the immune system differently in healthy or tumor bearing animals.     

Effect of isolation stress on ethanol pharmacokinetics in the blood of rats developing a taste for alcohol and in the stage of physical dependence on alcohol

Head space chromatography was used to study the rate of ethanol excretion as a criterion of the activity of ethanol-oxidizing enzymatic system in rats. Isolation stress was shown to be one of the factors determining inclination to voluntary ethanol intake. The level of alcohol motivation directly correlated with the degree of stress. At the stage of physical dependence on ethanol the activity of ethanol-oxidizing enzymatic system and ethanol consumption were independent of the isolation stress, but related to profound biochemical and neurochemical variations.     

The formation of mixed culture biofilms of oral species along a gradient of shear stress

A chemostat mixed culture system was used to produce two distinct ecological states, state-1 (caries-like microcosm) and state-2 (periodontal-like microcosm). Eleven bacterial species (Streptococcus gordonii, Strep. mitis I, Strep. mutans, Strep. oralis, Actinomyces naeslundii, Lactobacillus casei, Neisseria subflava, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella nigrescens, Veillonella dispar) were used to inoculate the planktonic system. A flow cell, designed to produce convergent flow with increasing shear stress, was attached to the chemostat system, and the resultant biofilms developed from the state-1 and state-2 microcosms along the shear stress gradient were examined and compared using image analysis and viable counts. The biofilm produced from state-1 showed a lower shear stress tolerance (0.146 Pa) than the state-2 biofilm (0.236 Pa). The biofilm compositions did not vary along the gradient of shear stress and were dependent on the initial inoculum conditions. Gram-positive species were predominant in the state-1 biofilm, while Gram-negative species were predominant in state-2.     

Oxidative Stress Tolerance Mechanism in Rice under Salinity

The research was conducted to investigate comparative oxidative damage including probable protective roles of antioxidant and glyoxalase systems in rice (Oryza sativa L.) seedlings under salinity stress. Seedlings of two rice genotypes: Pokkali (tolerant) and BRRI dhan28 (sensitive) were subjected to 8 dSm⁻¹ salinity stress for seven days in a hydroponic system. We observed significant variation between Pokkali and BRRI dhan28 in phenotypic, biochemical and molecular level under salinity stress. Carotenoid content, ion homeostasis, antioxidant enzymes, ascorbate and glutathione redox system and proline accumulation may help Pokkali to develop defense system during salinity stress. However, the activity antioxidant enzymes particularly superoxide dismutase (SOD), catalase (CAT) and non-chloroplastic peroxidase (POD) were observed significantly higher in Pokkali compared to salt-sensitive BRRI dhan28. Higher glyoxalase (Gly-I) and glyoxalase (Gly-II) activity might have also accompanied Pokkali genotype to reduce potential cytotoxic MG through non-toxic hydroxy acids conversion. However, the efficient antioxidants and glyoxalase system together increased adaptability in Pokkali during salinity stress.     

Stress-induced somatic embryogenesis in vegetative tissues of Arabidopsis thaliana

Somatic embryogenesis is an obvious experimental evidence of totipotency, and is used as a model system for studying the mechanisms of de-differentiation and re-differentiation of plant cells. Although Arabidopsis is widely used as a model plant for genetic and molecular biological studies, there is no available tissue culture system for inducing somatic embryogenesis from somatic cells in this plant. We established a new tissue culture system using stress treatment to induce somatic embryogenesis in Arabidopsis. In this system, stress treatment induced formation of somatic embryos from shoot-apical-tip and floral-bud explants. The somatic embryos grew into young plantlets with normal morphology, including cotyledons, hypocotyls, and roots, and some embryo-specific genes (ABI3 and FUS3) were expressed in these embryos. Several stresses (osmotic, heavy metal ion, and dehydration stress) induced somatic embryogenesis, but the optimum stress treatment differed between different stressors. When we used mannitol to cause osmotic stress, the optimal conditions for somatic embryogenesis were 6-9 h of culture on solid B5 medium containing 0.7 m mannitol, after which the explants were transferred to B5 medium containing 2,4-dichlorophenoxyacetic acid (2,4-D, 4.5 microm), but no mannitol. Using this tissue culture system, we induced somatic embryogenesis in three major ecotypes of Arabidopsis thaliana-Ws, Col, and Ler.