Senescence constitutes the final stage of a plant organ and tissue development and is a subject to gene control and strict regulation. By the late growing season, when Alhagi sparsifolia entered the natural senescence period, a girdling treatment was carried out on the phloem to increase the sugar content in leaves and to investigate carbohydrate-induced leaf senescence. After the semi-girdling and full-girdling treatment, organic matter could not leave leaves due to the destruction of sieve tubes. This led to constantly increasing sugar contents in leaves. Girdling was shown to greatly accelerate the senescence of plants. In girdled leaves, chlorophyll (Chl) a, Chl b, carotenoids (Car), and both ratios of Chl a/b and Chl/Car were significantly reduced. On the donor side of PSII, the oxygen-evolving complex was inhibited under high concentrations of carbohydrates, which was manifested as the emergence of the K phase in fluorescence kinetic curves. On the acceptor side of PSII, the high carbohydrate content also led to the disruption of electron transport and reduced light-use efficiency, which was manifested as a reduction in numerous fluorescence parameters. We believe that the emergence and development of plant senescence was not necessarily induced by the high content of carbohydrates, because even a decrease in the carbohydrate concentration could not stop the senescence process. Although the high content of carbohydrates in plants could induce plant senescence, this kind of senescence was likely a pathological process, including degradations of physiological functions., G.-L. Tang, X.-Y. Li, L.-S. Lin, F.-J. Zeng, Z.-Y. Gu., and Obsahuje seznam literatury
Our aim was to investigate the influence of microgravity on the sensitivity of the skin to mechanical stimulation, epidermal thickness, peripheral nerve density in the upper dermis, and serum levels of a stress marker in a rat hindlimb suspension (HS) model. Thirty 8-week-old male Wistar rats were randomly divided into 3 groups: HS, n=10; sham HS, n=10; control, n=10. The suspension system was attached to rat tails in both the HS and sham-HS groups, but the hindlimbs were suspended only in the HS group. The HS and sham-HS groups were treated for 4 weeks. In behavioral tests using von-Frey filaments (n=5 in each group), mechanical hypersensitivity developed in the HS and sham HS groups. Serum corticosterone levels increased significantly in the HS and sham HS groups compared to the control group, and no changes in epidermal thickness or peripheral nerve density were observed immediately after the removal of HS (n=5 in each group). These data indicated that the mechanical hypersensitivity observed in the HS group was not caused by microgravity or inactivity, but rather by restraint stress. We suggest that microgravity does not affect skin sensitivity and histology in these animals., Y. Tanaka, ... [et al.]., and Obsahuje seznam literatury
Ultrastructural changes in chloroplasts of primary leaves of 15-d-old bean plants (Phaseolus vulgaris L. cv. Cheren Starozagorski) in response to a single stress (increasing water deficit, WD) as well as to combined stress (WD plus high temperature, WD+HT) were investigated under the possible protective or reparatory effects of the carbamide cytokinin 4-PU-30 [N-(2-chloro-4-pyridyl)-N-phenylurea] applied before or after the stress. Essential structural changes in chloroplast ultrastructure occurred mainly in plants that had experienced WD+HT: the thylakoids were swollen, the envelope was destroyed, and the spatial orientation of inner membrane system was not typical. Changed starch accumulation was also observed. 4-PU-30 protected chloroplast ultrastructure under WD+HT. and D. Stoyanova. I. Yordanov.
Dynorphin A (1-13) and its analog dynorphin A (1-10) amide were applied intracerebroventricularly in male ICR mice. Both dynorphins did not reveal any analgesic activity in tail-flick test under normal (non-stressed) conditions. However, in combination with stress (forced swimming or whole body vibration) both dynorphins prolonged tail- flick latencies when compared with stressed saline controls. Naloxone inhibited the effect of dynorphins in forced swimming test. Neither dynorphin A (1-13) nor dynorphin A (1-10) amide increased tail-flick latencies when combined with weak immobilization stress. Our results suggest that the analgesic effects of dynorphins are potentiated by strong stressors.
The paper presents analysis of the stress changes due to creep in statically determinate reinforced wood beams. Each beam consists of glue-laminated timber []-section, acting compositely with steel rods, or steel-plate; U-profile, symmetrical or unsymmetrical attached to the upper or lower surface of the beams. The mathematical formulation of this problem involves the equation of equilibrium, compatibility and constitutive relationship, i.e. an elastic law for the steel part and an integral-type creep law for the wooden part. For determining the redistribution of stresses in beam section between wood beam and steel part with respect no time ‘t‘, Volterra integral equations of the second kind have been derived, on the basis of the theory of the viscoelastic body of Boltzmann - Volterra. Analytical method, which makes use of Laplace transformation and numerical method, which makes quadrature formulae for solving these equations, are proposed. The computer programs are realized in environment of a high-performance language for technical computing MATLAB®, Some relevant examples with the model proposed are investigated and discussed. In this mathematical model, different creep function are assumed and compared by describing of the time depended behavior of the wood. Finally, this analysis shows the way how to be integrated the advantages of the highly perfect model of visco-elastic body, describing the creep of wood, and availability of powerful software productts. The proposed methods give us the possibilities for realistic estimates of the behaviour of the reinforced glue-laminated wood beams, subjected to sustained service. and Obsahuje seznam literatury
The review sums up research conducted at CIAT within a multidiscipline effort revolving around a strategy for developing improved technologies to increase and sustain cassava productivity, as well as conserving natural resources in the various eco-edaphic zones where the crop is grown, with emphasis on stressful environments. Field research has elucidated several physiological plant mechanisms underlying potentially high productivity under favourable hot-humid environments in the tropics. Most notable is cassava inherent high capacity to assimilate carbon in near optimum environments that correlates with both biological productivity and root yield across a wide range of germplasm grown in diverse environments. Cassava leaves possess elevated activities of the C4 phosphoenolpyruvate carboxylase (PEPC) that also correlate with leaf net photosynthetic rate (PN) in field-grown plants, indicating the importance of selection for high PN. Under certain conditions such leaves exhibit an interesting photosynthetic C3-C4 intermediate behaviour which may have important implications in future selection efforts. In addition to leaf PN, yield is correlated with seasonal mean leaf area index (i.e. leaf area duration, LAD). Under prolonged water shortages in seasonally dry and semiarid zones, the crop, once established, tolerates stress and produces reasonably well compared to other food crops (e.g. in semiarid environments with less than 700 mm of annual rain, improved cultivars can yield over 3 t ha-1 oven-dried storage roots). The underlying mechanisms for such tolerance include stomatal sensitivity to atmospheric and edaphic water deficits, coupled with deep rooting capacities that prevent severe leaf dehydration, i.e. stress avoidance mechanisms, and reduced leaf canopy with reasonable photosynthesis over the leaf life span. Another stress-mitigating plant trait is the capacity to recover from stress, once water is available, by forming new leaves with even higher PN, compared to those in nonstressed crops. Under extended stress, reductions are larger in shoot biomass than in storage root, resulting in higher harvest indices. Cassava conserves water by slowly depleting available water from deep soil layers, leading to higher seasonal crop water-use and nutrient-use efficiencies. In dry environments LAD and resistance to pests and diseases are critical for sustainable yields. In semiarid zones the crop survives but requires a second wet cycle to achieve high yields and high dry matter contents in storage roots. Selection and breeding for early bulking and for medium/short-stemmed cultivars is advantageous under semiarid conditions. When grown in cooler zones such and as in tropical high altitudes and in low-land sub-tropics, leaf PN is greatly reduced and growth is slower. Thus, the crop requires longer period for a reasonable productivity. There is a need to select and breed for more cold-tolerant genotypes. Selection of parental materials for tolerance to water stress and infertile soils has resulted in breeding improved germplasm adapted to both favourable and stressful environments.
Dodržování protiepidemických opatření určuje, jak se společnost vypořádá s pandemií nového koronaviru. K objasnění, proč někteří lidé opatření nedodržují, využíváme teorii osobních konstruktů. Ta předpokládá, že stresující události v pandemii invalidizují do té doby smysluplný obraz světa (konzistentní konstruování). Pokud se jedinec snaží invalidizované konstruování zachovat místo jeho změny, uplatňuje strategii hostility – například devalvuje informace a názory, které jsou s jeho/jejím konstruováním nekompatibilní. Tím dochází k upevňování nedůvěřivých postojů vůči institucím a k nerespektování opatření, která vyhlašují. Tento model konfrontujeme s informacemi z rozhovorů s 20 respondenty. Analýza dospěla k pěti kategoriím, které odráží, jak respondenti pandemické situaci rozumí: zodpovědnost, kritika, odstup, produktivní dialog, neproduktivní dialog. Respondentky z kategorie „kritika“ čelily výrazným stresujícím/invalidizujícím změnám. Své kritické postoje k protiepidemickým opatřením udržovaly prostřednictvím hostilního pohledu na osoby s jiným názorem a prostřednictvím nedůvěry v instituce a média. Většina ostatních respondentů opatření dodržovala. Ve svém pohledu na pandemickou situaci brali v potaz různé perspektivy, neuplatňovali hostilní pohled a vyjadřovali určité porozumění lidem s jinými názory. Hostilita tedy může být základním neadaptivním mechanizmem k udržení smysluplného obrazu světa v nepřehledné pandemické době, která však vede k nedůvěře, společenské polarizaci a nedodržování opatření. and Non-adherence to public health measures determines how society copes with the new coronavirus pandemic. In this study, we apply the personal construct theory to answer why some people comply with anti-epidemic measures. The theory assumes that stressful events in the pandemic situation invalidate an individual’s worldview (individual’s construing). If the individual attempts to maintain this construing instead of its reconstruction, s/he may apply the hostility strategy. For example, s/he dismisses information or opinions that are incompatible with his/her original construing. This leads to an elaboration of distrust and critical attitudes towards institutions and to non-compliance with measures they order. We investigate this model by an interview analysis with 20 respondents. The analysis yielded five categories showing how respondents construe the pandemic situation: responsibility, criticism, distance from the subject, productive dialogue, and unproductive dialogue. Respondents from the category “criticism” were facing substantial stressful/invalidating changes. They maintained their critical attitude towards anti-epidemic measures through a hostile view of those with differing opinions and a strong distrust in institutions and media. The other respondents mostly complied with the measures. In their construing of the pandemic situation, they took different perspectives into the account, did not experience hostility, and expressed some degree of understanding to people with different opinions. Thus, hostility could be a fundamental psychological principle to preserve a meaningful worldview in times of the pandemic. Hostility, however, leads to distrust, opinion polarization, and non-compliance with anti-epidemic measures.
The ultrastructure and dimensions of chloroplasts in leaf mesophyll cells were quantitatively examined in three parental inbred lines of maize (Zea mays L.) and their four hybrids subjected to two types of four-week low-temperature (LT) treatment: the abrupt onset of chilling temperatures ("severe chilling", SC) and the gradual, more moderate one ("moderate chilling", MC). The relationship between the response of individual genotypes to one or the other type of chilling was analyzed as well as the possibility to predict the behaviour of chloroplasts in hybrids from that of their parents. Although selected parameters of chloroplast ultrastructure (e.g. volume densities of granal and intergranal thylakoids, plastoglobuli, and peripheral reticulum) and dimensions changed due to the exposure of maize plants to LT, no general pattern of such changes was found for this species due to the observed intraspecific variability. The response of some genotype to SC could not be predicted from its behaviour under MC (and vice versa) and no clear rules could be applied for the inheritance of chloroplast response to chilling in the general sense. Thus, great caution should be always taken when interpreting the results of studies aimed at the dissection of chloroplast ultrastructure as affected by LT, particularly in case such studies are made with one genotype or under one type of chilling only. and D. Holá ... [et al.].
A sense of purpose in life is inextricably linked with a firm conviction of exercising control over it, and having one’s priorities set straight. Health in turn, is affected by stress, by salutogenetic factors, as presented by A. Antonovsky. Disturbances of sense of purpose in life result in psychosomatic disorders. Hypothesis: there is a relevant statistical correlation between the level of sense of purpose in life and noopsychosomatic disorders. Methods: 1) Crumbaugh-Maholick Purpose-in-Life Test, 2) K. Mausch Questionnaire of Psychosomatic Ailments. Test group: 683 pedagogy students from the University of Szczecin. There is a relevant statistical correlation between the level of sense of purpose in life and psychosomatic disorders. The research results require comparison with other post-soviet countries, as well as democratic ones.
Negativní vliv tíživé prosociální aktivity, byl předmětem řady psychologických výzkumů. Péče o staré lidi, nevyléčitelně nemocné, umírající se za určitých okolností může stát značně zatěžující činností, jejíž důsledky se mohou projevit v oblasti zdraví poskytovatele této péče. Péče o umírajícího člověka nebo člověka starého, imobilního, často s postupující demencí, je pro pečujícího velmi náročná. Péče o chronicky nemocné, nevyléčitelně nemocné, se může stát dlouhodobě zatěžující aktivitou. Péče o umírajícího pacienta, práce s rodinnými příslušníky, kterým umírá jejich bližní, je situací extrémní zátěže. Vypjaté emoční reakce, zvláště hněv, různé formy agrese, jsou situace, které se zvládají velmi obtížně.
Obecně lidé, kteří se angažují v pomáhajících profesích, jsou díky tomuto faktu ohroženi ve všech oblastech zdraví – fyzické, psychické i sociální. Poskytování péče nevyléčitelně nemocným je situací značné dlouhodobé zátěže – říkáme jí chronický stres. Působení chronického stresu jakékoli kvality může mít na člověka poměrně negativní vliv. Výzkumy naznačují, že v pozadí mnoha nemocí je přítomen faktor chronické, dlouhodobé zátěže – kardiovaskulární onemocnění, narušená funkce imunitního systému, nespecifické bolesti zad, onemocnění trávícího traktu. Samostatnou speciální problematikou je syndrom vyhoření. and The negative impact of the onerous prosocial activity has been examined in a great bulk of psychological research studies. Under certain conditions, taking care of the elderly, terminally ill, and the death ward might be quite a demanding activity. Its consequences may be reflected in the health condition of the care provider. Caring for a dying or an immobile elderly person, often with a progressive dementia, is very challenging for the provider. Servicing a chronically ill or terminally ill people might become a long-term burden. Servicing a dying person and working with his or her family relatives is an extremely burdening situation. The extreme emotional reactions, primarily anger and various kinds of rage, are unusually thorny to manage.
Consequently, people that are engaged in helping these people are generally endangered in all spheres of their health, i.e. physical, mental and social. Providing care to terminally ill is burdensome in the long run. It is known as chronic stress. Any kind of chronic stress has a potentially negative impact on human beings. Previous research indicates that long-term chronic burden might cause cardiovascular diseases, disorders of immunity, non-specific backaches, and digestive disorders. The special issue is a burnout syndrome.