The effect of temperature and water stress on the timing of leaf death in Vicia faba

The timing and pattern of leaf death was studied in three field experiments from observations of the area and dates of death of individual leaves. Two linear regression lines adequately described the pattern of leaf death on the plant in all experiments and treatments. These represented an initial phase with a slow rate of leaf death changing to a second phase with a more rapid rate of leaf death. The change from the first to second phase of leaf death occurred when the maximum seed dry weight was reached. The rates of both the first and second phases of leaf death increased with temperature. This was confirmed in an experiment in growth rooms. The rate of leaf death in both phases of plants grown at three constant temperatures increased linearly with temperature from 14 °C to 22 °C. The rate of leaf death in phase 2 increased with increasing solar irradiance and vapour pressure deficit. The rate of leaf death in both phases increased with increasing water stress in three irrigation treatments in the field.     

Heat tolerance in cowpea: effect of timing and duration of heat stress

Reproductive processes and pod yield in cowpea (Vigna unguiculata (L.) Walp), an important crop grown in semi-arid sub-Saharan Africa, are adversely affected by high temperature. Genotypic differences in heat tolerance have been identified under hot, long-days, but it was not known if this tolerance is also exhibited in hot, short-day environments typical of sub-Saharan Africa. The objectives of the work reported here were to determine whether heat tolerance identified under hot, long-days was expressed at the same stages of development under hot, short-days, and whether responsiveness to temperature was additive and quantitative. A heat-tolerant (Prima) and heat-susceptible (IT84S-2246) cultivar of cowpea were grown in controlled environments under short-days (12 h day^-1), initially at 30°C/24°C (Mod-T), and then transferred at 0, 10, 20, 30 and 40 days after emergence (DAE) to 36°C/27°C (High-T), where they remained for 5, 10 or 20 days duration before returning to Mod-T. Control plants remained at Mod-T or High-T for 50 days, when the first pods were mature and the experiment was terminated. There were significant effects of duration (D) and timing (T) (P < 0.001), and interactions between D × T (P < 0.001), T × genotype (G) (P < 0.01) and D × T × G (P < 0.05) on pod weight plant^-1. Prima was significantly (P < 0.001) more tolerant to high temperature during flowering than IT84S-2246, confirming that heat tolerance was expressed under hot, short days. The greater heat tolerance of Prima was associated with an ability to maintain peduncle and flower production at High-T, and with greater podset. The sensitive period in IT84S-2246 started at floral bud initiation (15–20 DAE), and effects of High-T thereafter were additive and quantitative.     

The antitumor natural compound falcarindiol promotes cancer cell death by inducing endoplasmic reticulum stress

Falcarindiol (FAD) is a natural polyyne with various beneficial biological activities. We show here that FAD preferentially kills colon cancer cells but not normal colon epithelial cells. Furthermore, FAD inhibits tumor growth in a xenograft tumor model and exhibits strong synergistic killing of cancer cells with 5-fluorouracil, an approved cancer chemotherapeutic drug. We demonstrate that FAD-induced cell death is mediated by induction of endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR). Decreasing the level of ER stress, either by overexpressing the ER chaperone protein glucose-regulated protein 78 (GRP78) or by knockout of components of the UPR pathway, reduces FAD-induced apoptosis. In contrast, increasing the level of ER stress by knocking down GRP78 potentiates FAD-induced apoptosis. Finally, FAD-induced ER stress and apoptosis is correlated with the accumulation of ubiquitinated proteins, suggesting that FAD functions at least in part by interfering with proteasome function, leading to the accumulation of unfolded protein and induction of ER stress. Consistent with this, inhibition of protein synthesis by cycloheximide significantly decreases the accumulation of ubiquitinated proteins and blocks FAD-induced ER stress and cell death. Taken together, our study shows that FAD is a potential new anticancer agent that exerts its activity through inducing ER stress and apoptosis.     

The physiological effects of psychological stress

The study of behavior is a powerful tool in the captive management of wild animals. It can, if properly applied, provide insight into a wide variety of problems. The interpretation of behavioral observations requires a firm understanding and characterization of the environmental parameters that can induce the physiological state of stress through neurological means in the study subjects. These factors include, but are not limited to, territorial factors, including social and physical accommodations, photo factors, and acoustical factors. Proper interpretation of behavioral observations also requires a basic understanding of the biochemical and physiological impacts of neuroendocrine-mediated stress. These include alterations in an individual's ability to metabolize toxic substances, resist infections, and reproduce. Confounding effects of these alterations must be considered in the examination of behavioral data. The most powerful experimental designs in comparative behavior are those that concurrently examine environmental stressors, physiological status, and behavior.     

MicroRNA pathways in flies and worms: growth,death, fat,stress, and timing

Drosophila geneticists have uncovered roles for microRNAs in the coordination of cell proliferation and cell death during development, and in stress resistance and fat metabolism. In C. elegans, a homolog of the well-known fly developmental regulator hunchback acts downstream of the microRNAs lin-4 and let-7 in a pathway controlling developmental timing.     

The influence of climate on the timing and rate of spring bird migration

Ecological processes are changing in response to climatic warming. Birds, in particular, have been documented to arrive and breed earlier in spring and this has been attributed to elevated spring temperatures. It is not clear, however, how long-distance migratory birds that overwinter thousands of kilometers to the south in the tropics cue into changes in temperature or plant phenology on northern breeding areas. We explored the relationships between the timing and rate of spring migration of long-distance migratory birds, and variables such as temperature, the North Atlantic Oscillation (NAO) and plant phenology, using mist net capture data from three ringing stations in North America over a 40-year period. Mean April/May temperatures in eastern North America varied over a 5°C range, but with no significant trend during this period. Similarly, we found few significant trends toward earlier median capture dates of birds. Median capture dates were not related to the NAO, but were inversely correlated to spring temperatures for almost all species. For every 1°C increase in spring temperature, median capture dates of migratory birds averaged, across species, one day earlier. Lilac (Syringa vulgaris) budburst, however, averaged 3 days earlier for every 1°C increase in spring temperature, suggesting that the impact of temperature on plant phenology is three times greater than on bird phenology. To address whether migratory birds adjust their rate of northward migration to changes in temperature, we compared median capture dates for 15 species between a ringing station on the Gulf Coast of Louisiana in the southern USA with two stations approximately 2,500 km to the north. The interval between median capture dates in Louisiana and at the other two ringing stations was inversely correlated with temperature, with an average interval of 22 days, that decreased by 0.8 days per 1°C increase in temperature. Our results suggest that, although the onset of migration may be determined endogenously, the timing of migration is flexible and can be adjusted in response to variation in weather and/or phenology along migration routes.     

The effect of traumatic brain injury on the timing of sleep

While there have been single case reports of the development of circadian rhythm sleep disorders, most commonly delayed sleep phase syndrome following traumatic brain injury (TBI), to our knowledge there have been no group investigations of changes to sleep timing in this population. The aim of the present study was to investigate sleep timing following TBI using the dim light melatonin onset (DLMO) as a marker of circadian phase and the Morningness-Eveningness Questionnaire (MEQ) as a measure of sleep-wake behavior. A sleep-wake diary was also completed. It was hypothesized that the timing of DLMO would be delayed and that there would be a greater tendency toward eveningness on the MEQ in a post-acute TBI group (n=10) compared to a gender and age matched control group. Participants were recruited at routine outpatient review appointments (TBI) and from the general population (control) as part of a larger study. They attended the sleep laboratory where questionnaires were completed, some retrospectively, and saliva melatonin samples were collected half-hourly according to a standard protocol. The results show that the TBI and control groups reported similar habitual sleep times and this was reflected on the MEQ. There was, however, significant variability in the TBI group's change from the pre-injury to the current MEQ score. The timing of melatonin onset was not different between the groups. While subtle changes (advances or delays) in this small sample may have cancelled each other out,. the present study does not provide conclusive objective evidence of shift in circadian timing of sleep following TBI. Furthermore, although participants did report sleep timing changes, it is concluded that the MEQ may not be suitable for use with this cognitively impaired clinical group.     

水分胁迫对植物与植食性昆虫互作的影响

水分作为一种重要的环境因子,对陆地生物生长发育有着至关重要的作用。随着全球气候变暖,异常天气频发,水分胁迫也成为了影响农作物及其害虫生长发育的重要逆境胁迫。本文从水分胁迫对植食性昆虫的直接和间接影响进行阐述:从湿度、降雨量和土壤含水量角度讨论了水分胁迫对昆虫的直接影响;从水分影响植物和天敌角度,讨论了水分胁迫对植物-植食者性昆虫-天敌三营养阶层互作的间接影响,以期为理解农业害虫发生机制及其可持续治理决策提供研究信息和理论参考。     

The evolution of developmental timing in natural enemy systems

A population of [PSI⁺] Saccharomyces cerevisiae cells can be cured of the [PSI⁺] prion by the addition of guanidine hydrochloride (GdnHCl). In this paper we extend existing nucleated polymerisation simulation models to investigate the mechanisms that might underlie curing. Our results are consistent with the belief that prions are dispersed through the cells at division following GdnHCl addition. A key feature of the simulation model is that the probability that a polymer is transmitted from mother to daughter during cell division is dependent upon the length of the polymer. The model is able to reproduce the essential features of data from several different experimental protocols involving addition and removal of GdnHCl.     

The influence of natural surface microtopographies on fouling

Multiple antifouling strategies of marine organisms may consist of combinations of physical, chemical and mechanical mechanisms. In this study, the role of surface microtopography (< 500 microns) of different marine organisms, such as Cancer pagurus, Mytilus edulis, Ophiura texturata and the eggcase of Scyliorhinus canicula, has been investigated as a possible component of their defence systems. High resolution resin replicates of these natural surface structures were exposed to natural fouling in field experiments. Abundances of recruits were determined and compared to those on untextured, but otherwise identical, control surfaces to quantify the influence of the different microtopographies on fouling rates. Antifouling effects of microtopographies varied with type of microtopography and coloniser species. The surface microtopography of C. pagurus significantly rejected macrofoulers. The surface structures of the eggcase and O. texturata had repellent effects on microfoulers. Barnacle settlement was temporarily reduced on surface microtopographies of M. edulis and the eggcase. These results emphasise the promising nontoxic antifouling properties of microtextured surfaces.     

The evolutionary ecology of seed germination of Arabidopsis thaliana: variable natural selection on germination timing

Germination timing of Arabidopsis thaliana displays strong plasticity to geographic location and seasonal conditions experienced by seeds. We identified which plastic responses were adaptive using recombinant inbred lines in a field manipulation of geographic location (Kentucky, KY; Rhode Island, RI), maternal photoperiod (14-h and 10-h days), and season of dispersal (June and November). Transgressive segregation created novel genotypes that had either higher fitness or lower fitness in certain environments than either parent. Natural selection on germination timing and its variation explained 72% of the variance in fitness among genotypes in KY, 30% in June-dispersed seeds in RI, but only 4% in November-dispersed seeds in RI. Therefore, natural selection on germination timing is an extremely efficient sieve that can determine which genotypes can persist in some locations, and its efficiency is geographically variable and depends on other aspects of life history. We found no evidence for adaptive responses to maternal photoperiod during seed maturation. We did find adaptive plasticity to season of seed dispersal in RI. Seeds dispersed in June postponed germination, which was adaptive, while seeds dispersed in November accelerated germination, which was also adaptive. We also found maladaptive plasticity to geographic location for seeds dispersed in June, such that seeds dispersed in KY germinated much sooner than the optimum time. Consequently, bet hedging in germination timing was favorable in KY; genotypes with more variation in germination timing had higher fitness because greater variation was associated with postponed germination. Selection on germination timing varied across geographic location, indicating that germination timing can be a critical stage in the establishment of genotypes in new locations. The rate of evolution of germination timing may therefore strongly influence the rate at which species can expand their range.     

Assessing the effectiveness of mandatory outdoor mask policy: The natural experiment of Campania

Face masks are possibly the main symbol of the COVID-19 pandemic. Once rarely used in Western countries, in the last two years they have become an object it is impossible to leave one’s home without. Italy made their use a legal requirement, even outdoors, from late 2020 to early 2022. The effectiveness of this policy in reducing COVID-19 cases has been widely debated. The recent cancellation of their mandatory use in Italy offers an interesting setting in which to test its impact, since one Italian region (Campania) extended the restriction for a further three weeks. We aim to shed some light on the real-world impact of mandatory use of face masks outdoors, identifying the effect of this policy on the spread of COVID-19. By means of a quantitative analysis, employing a synthetic control method approach, we find that Campania had statistically the same number of cases as its synthetic counterfactual, built from a donor pool formed from the other Italian provinces. Hence, results suggest that while it imposes a burden on the public, the use of face masks outdoors is not correlated with a decrease in the number of COVID-19 cases.     

The effects of physical and psychological stress on the gastro-intestinal tract: lessons from animal models

Physical and psychological stresses are widely accepted as triggers and / or modifiers of the clinical course of diverse gastrointestinal disorders such as peptic ulcer, irritable bowel syndrome or inflammatory bowel disease. Growing experimental evidence from a variety of models such as immobilization, thermal injury or early maternal deprivation in laboratory animals uniformly supports the ability of stress to induce the development of gastric ulcers, altered gastrointestinal motility and ion secretion, and increased intestinal permeability leading to the passage of antigens to the lamina propria and bacterial translocation. Stress can also synergize with other pathogenic factors such as Helicobacter pylori, non-steroidal anti-inflammatory drugs or colitis-inducing chemicals to produce gastrointestinal disease. The brain-gut axis provides the anatomical basis through emotions and environmental influences modulate the gastrointestinal function through the regulation of gastrointestinal immune system and mucosal inflammation; in this sense, mucosal mast cells - at cellular level - and corticotropin releasing factor (CRF) - at molecular level - seem to play a crucial role. On the other hand, an array of adaptive responses have been evolved in order to maintain the homeostasis and to ensure the survival of the individual. In the gut mucosa anti-inflammatory pathways counteract the deleterious effect of the stressful stimuli on the gastrointestinal homeostasis. In the present review we discuss the several experimental approaches used to mimic human stressful events or chronic stress in laboratory animals, the evidence of stress-induced gastrointestinal inflammation and dysfunction derived from them, and the involved cellular and molecular mechanisms that are being discovered during the last years.     

Sexual conflict in viscous populations: The effect of the timing of dispersal

In recent years, there has been increasing theoretical and empirical examination of how sexual conflict can arise between males and females. However, much this work has implicitly assumed that interactions take place in panmictic populations with complete dispersal, where interactions are between unrelated individuals. Here, we examine the consequences of limited dispersal and population structure for the evolution of a male phenotype that is associated with the males pre- and post-copulatory reproductive success, using an inclusive-fitness based analysis applied to group-structured populations. We show that: (i) the sex-specific timing of the dispersal phase of the life cycle can drive the evolution of sexual conflict; (ii) the inclusive fitness of a female in this conflict is determined solely by direct (i.e. personal) effects on its own competitive ability. Our analysis is supported by results from individual-based simulations of multi-level selection. Our results support the suggestion that kin selection can influence the evolution of sexual conflict, but reveal that such a role might be more complex than previously appreciated when sex-specific life histories are taken into consideration. We discuss the implications of our results for sexual conflict in various species of insects, but focus primarily on dipteran flies of the family Sepsidae.     

The effect of an intruded event on peak-interval timing in rats: isolation of a postcue effect

The present experiment employed the peak-interval (PI) procedure to study the effect of an intruded cue on timing behavior. Rats were trained on a 30-s PI procedure with a tone cue. Subsequently, a 6-s flashing light was paired off-baseline with foot shock (Experiment 1) or presented alone (Experiment 2). Then, in test trials, the light cue was presented 9s prior to (before) or 3s after (during) the onset of the timing cue, or the light was omitted (probe). Results showed rightward shifts in peak time occurring on both before and during trials in both experiments. Peak shifts on during trials exceeded the reset prediction in Experiment 1. When PI functions for before and probe trials were normalized in peak rate and peak time, they superimposed better than when functions were adjusted additively along the time axis, suggesting that the light cue may engender a decrease in functional clock rate. The findings suggested that the intruded cue produced both intracue and postcue interference with timing that was enhanced by fear conditioning.     

The effectiveness of the Uchida-Kraepelin test for psychological stress: an analysis of plasma and salivary stress substances

Background  

The hypothalamic-pituitary-adrenocortical (HPA) axis and sympathetic adrenomedullary (SAM) system are the major stress-response pathways. Plasma adrenocorticotropic hormone (ACTH) represents HPA axis activity, while plasma catecholamines are used as markers of the SAM system. Salivary alpha amylase (AA), chromogranin A (CgA), and immunoglobulin A (IgA) are candidate markers of stress activation, although their role has not been established. The Uchida-Kraepelin (U-K) test is a questionnaire that requires intense concentration and effort, and has been used as a tool to induce mental stress. However, it is not clear whether or not the test is effective as a psychological/mental stressor.     

The influence of anoxia and ethanol on barley seed death

Survival of deteriorated barley seeds in wet soil was improved by exposure to 70% oxygen compared with that in air and decreased by the imposition of anoxia. Deteriorated seeds were more sensitive to anoxia than non-deteriorated seeds, the former died within 4 days, while the latter survived more than 7 days. Ethanol accumulated in non-deteriorated seeds in wet soil conditions during the first 24 h and thereafter declined, while it increased to higher concentrations over 3–4 days in deteriorated seeds. High concentrations of ethanol were recorded in seeds in anaerobic conditions regardless of the level of deterioration. It was concluded that oxygen diffusion to the seeds was severely restricted in wet soil resulting in a switch to anaerobic respiration, the products of which, indicated by ethanol content, accumulated within the tissues. Non-deteriorated seeds tolerated higher concentrations of ethanol than deteriorated seeds and the coleorhiza extruded through the covering layers more rapidly facilitating gaseous exchange, while in the latter, anaerobic products accumulated to toxic levels.