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| 2. |
- Gustavsson, Anna-Karin, 1986, et al.
(author)
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Allosteric regulation of phosphofructokinase controls the emergence of glycolytic oscillations in isolated yeast cells
- 2014
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In: The FEBS Journal. - : Wiley. - 1742-464X .- 1742-4658. ; 281:12, s. 2784-2793
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Journal article (peer-reviewed)abstract
- Oscillations are widely distributed in nature and synchronization of oscillators has been described at the cellular level (e.g. heart cells) and at the population level (e.g. fireflies). Yeast glycolysis is the best known oscillatory system, although it has been studied almost exclusively at the population level (i.e. limited to observations of average behaviour in synchronized cultures). We studied individual yeast cells that were positioned with optical tweezers in a microfluidic chamber to determine the precise conditions for autonomous glycolytic oscillations. Hopf bifurcation points were determined experimentally in individual cells as a function of glucose and cyanide concentrations. The experiments were analyzed in a detailed mathematical model and could be interpreted in terms of an oscillatory manifold in a three-dimensional state-space; crossing the boundaries of the manifold coincides with the onset of oscillations and positioning along the longitudinal axis of the volume sets the period. The oscillatory manifold could be approximated by allosteric control values of phosphofructokinase for ATP and AMP.
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| 3. |
- Tan, Hung, et al.
(author)
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Widespread psychoactive pollutant augments daytime restfulness and disrupts diurnal activity rhythms in fish
- 2023
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In: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 326
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Journal article (peer-reviewed)abstract
- Pharmaceutical pollution is a major driver of global change, with the capacity to alter key behavioural and physiological traits in exposed animals. Antidepressants are among the most commonly detected pharmaceuticals in the environment. Despite well-documented pharmacological effects of antidepressants on sleep in humans and other vertebrates, very little is known about their ecologically relevant impacts as pollutants on non-target wildlife. Accordingly, we investigated the effects of acute 3-day exposure of eastern mosquitofish (Gambusia holbrooki) to field-realistic levels (nominal concentrations: 30 and 300 ng/L) of the widespread psychoactive pollutant, fluoxetine, on diurnal activity patterns and restfulness, as indicators of disruptions to sleep. We show that exposure to fluoxetine disrupted diel activity patterns, which was driven by augmentation of daytime inactivity. Specifically, unexposed control fish were markedly diurnal, swimming farther during the day and exhibiting longer periods and more bouts of inactivity at night. However, in fluoxetine-exposed fish, this natural diel rhythm was eroded, with no differences in activity or restfulness observed between the day and night. As a misalignment in the circadian rhythm has been shown to adversely affect fecundity and lifespan in animals, our findings reveal a potentially serious threat to the survival and reproductive success of pollutant-exposed wildlife.
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| 4. |
- Adyari, Bob, et al.
(author)
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Strong impact of micropollutants on prokaryotic communities at the horizontal but not vertical scales in a subtropical reservoir, China
- 2020
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In: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 721
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Journal article (peer-reviewed)abstract
- Micropollutants have become of great concern, because of their disrupting effects on the structure and function of microbial communities. However, little is known about the relative importance of trace micropollutants on the aquatic prokaryotic communities as compared to the traditional physico-chemical characteristics, especially at different spatial dimensions. Here, we investigated free-living (FL) and particle-associated (PA) prokaryotic communities in a subtropical water reservoir, China, across seasons at horizontal (surface water) and vertical (depth-profile) scales by using 16S rRNA gene amplicon sequencing. Our results showed that the shared variances of physico-chemicals and micropollutants explained majority of the spatial variations in prokaryotic communities, suggesting a strong joint effect of the two abiotic categories on reservoir prokaryotic communities. Micropollutants appeared to exert strong independent influence on the core sub-communities (i.e., abundant and wide-spread taxa) than on the satellite (i.e., less abundant and narrow-range taxa) counterparts. The pure effect of micropollutants on both core and satellite sub-communities from FL and PA fractions was similar to 1.5 folds greater than that of physico-chemical factors at the horizontal scale, whereas an opposite effect was observed at the vertical scale. Moreover, eight micropollutants including anti-fungal agents, antibiotics, bisphenol analogues, stimulant and UV-filter were identified as the major disrupting compounds with strong associations with core taxa of typical freshwater prokaryotes. Altogether, we concluded that the ecological disrupting effects of micropollutants on prokaryotic communities may vary along horizontal and vertical dimensions in freshwater ecosystems.
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| 5. |
- Briscoe, Bob, et al.
(author)
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Reducing Internet Latency : A Survey of Techniques and Their Merits
- 2016
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In: IEEE Communications Surveys and Tutorials. - : IEEE. - 1553-877X. ; 18:3, s. 2149-2196
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Journal article (peer-reviewed)abstract
- Latency is increasingly becoming a performance bottleneck for Internet Protocol (IP) networks, but historically, networks have been designed with aims of maximizing throughput and utilization. This paper offers a broad survey of techniques aimed at tackling latency in the literature up to August 2014, as well as their merits. A goal of this work is to be able to quantify and compare the merits of the different Internet latency reducing techniques, contrasting their gains in delay reduction versus the pain required to implement and deploy them. We found that classifying techniques according to the sources of delay they alleviate provided the best insight into the following issues: 1) The structural arrangement of a network, such as placement of servers and suboptimal routes, can contribute significantly to latency; 2) each interaction between communicating endpoints adds a Round Trip Time (RTT) to latency, particularly significant for short flows; 3) in addition to base propagation delay, several sources of delay accumulate along transmission paths, today intermittently dominated by queuing delays; 4) it takes time to sense and use available capacity, with overuse inflicting latency on other flows sharing the capacity; and 5) within end systems, delay sources include operating system buffering, head-of-line blocking, and hardware interaction. No single source of delay dominates in all cases, and many of these sources are spasmodic and highly variable. Solutions addressing these sources often both reduce the overall latency and make it more predictable.
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| 6. |
- Melander, Bob, et al.
(author)
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Trace-Driven Network Path Emulation
- 2002
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Reports (other academic/artistic)abstract
- This paper reports on on-going work where a trace-driven approach to network path emulation is investigated. Time stamped probe packets are sent along a network path whereby a probe packet trace can be generated. It basically contains the send times and the one-way delays/loss indications of the probe packets. Inside the emulator, the probe packet trace is used by a loss model and a delay model. These determine if a packet should be dropped or what the delay of the packet should be. Three loss models and three delay models are evaluated. For non-responsive UDP-based flows, the trace-driven loss and delay models that determine loss and delay based on loss-rates and delay distribution parameters calculated across the probe packet trace using a small gliding window are found to perform best. For adaptive TCP flows, none of the evaluated trace-driven models performs well. Instead, the Bernoulli loss model and an independent average delay model performs best.
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| 7. |
- Wong, Bob, et al.
(author)
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Environmental deterioration compromises socially enforced signals of male quality in three-spined sticklebacks
- 2007
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In: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 170:2, s. 184-189
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Journal article (peer-reviewed)abstract
- Social costs are often important in promoting the honesty of sexually selected traits. What happens, then, when social costs are relaxed? In species that breed in shallow coastal waters, increases in the frequency and severity of phytoplankton blooms may undermine the value of visual signals by reducing visibility and, in so doing, lead to dishonest signaling by relaxing the social consequences of high signaling effort for poor-quality individuals. Here, we experimentally test the effects of algally induced water turbidity on the role of male-male competition in facilitating reliable sexual displays in three-spined sticklebacks. We found that males in poor condition reduced their courtship effort in the presence of competition in turbid water. This reduction, however, was to a much lesser extent than that observed in clear water. Thus, courtship under conditions of algal turbidity did not reflect male condition as honestly as courtship in clear water. Algal turbidity also influenced breeding coloration, with males in poor condition reducing their area of red nuptial coloration in turbid conditions. Our findings suggest that anthropogenic disturbance to the signaling environment can potentially reduce the evolutionary potential of sexual selection by diminishing the efficacy of visual displays and weakening socially enforced signals of male quality.
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| 8. |
- Brand, Jack A., et al.
(author)
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Temperature change exerts sex-specific effects on behavioural variation
- 2023
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In: Proceedings of the Royal Society of London. Biological Sciences. - 0962-8452 .- 1471-2954. ; 290:2002
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Journal article (peer-reviewed)abstract
- Temperature is a key factor mediating organismal fitness and has important consequences for species' ecology. While the mean effects of temperature on behaviour have been well-documented in ectotherms, how temperature alters behavioural variation among and within individuals, and whether this differs between the sexes, remains unclear. Such effects likely have ecological and evolutionary consequences, given that selection acts at the individual level. We investigated the effect of temperature on individual-level behavioural variation and metabolism in adult male and female Drosophila melanogaster (n = 129), by taking repeated measures of locomotor activity and metabolic rate at both a standard temperature (25°C) and a high temperature (28°C). Males were moderately more responsive in their mean activity levels to temperature change when compared to females. However, this was not true for either standard or active metabolic rate, where no sex differences in thermal metabolic plasticity were found. Furthermore, higher temperatures increased both among- and within-individual variation in male, but not female, locomotor activity. Given that behavioural variation can be critical to population persistence, we suggest that future studies test whether sex differences in the amount of behavioural variation expressed in response to temperature change may result in sex-specific vulnerabilities to a warming climate.
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| 9. |
- Lehtonen, Topi K., et al.
(author)
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Adjustment of brood care behaviour in the absence of a mate in two species of Nicaraguan crater lake cichlids
- 2011
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In: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 65:4, s. 613-619
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Journal article (peer-reviewed)abstract
- In many taxa, parental strategies can vary among individuals. This is especially true in species with biparental care, with males, more often than females, deserting their mates. While there is an abundance of theoretical predictions and empirical data on factors inducing mate abandonment by males, much less is known about what consequences this may have on female behaviour, particularly in the field and in non-avian systems. Here, we compared brood defence rate, behavioural defence types, and brood success of solitary and paired females in two species of Neotropical cichlid fish in their natural habitat. In terms of the rate of territorial aggression towards potential brood predators, solitary females were able to fully compensate in the absence of a male but, in so doing, ended up maintaining smaller territories, which appeared to compromise offspring fitness in at least one of the two species. Hence, our results suggest that even extensive quantitative compensation in parental effort by solitary females may not be enough to ensure adequate qualitative compensation for the lack of male participation, highlighting the importance of distinguishing between these two aspects of compensatory parental care.
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| 10. |
- Tan, Hung, et al.
(author)
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No evidence that the widespread environmental contaminant caffeine alters energy balance or stress responses in fish
- 2023
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In: Ethology. - 0179-1613 .- 1439-0310. ; 129:12, s. 666-678
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Journal article (peer-reviewed)abstract
- Anthropogenic sources of environmental pollution are ever-increasing as urban areas expand and more chemical compounds are used in daily life. The stimulant caffeine is one of the most consumed chemical compounds worldwide, and as a result, has been detected as an environmental contaminant in all types of major water sources on all continents. Exposure of wildlife to environmental pollutants can disrupt the energy balance of these organisms, as restoration of homeostasis is prioritised. In turn, energy allocated to other key biological processes such as growth or reproduction may be affected, consequently reducing the overall fitness of an individual. Therefore, we aimed to investigate if long-term exposure to environmentally relevant concentrations of caffeine had any energetic consequences on wildlife. Specifically, we exposed wild eastern mosquitofish (Gambusia holbrooki) to one of three nominal concentrations of caffeine (0, 100 and 10,000 ng/L) and assayed individuals for metabolic rate, general activity, antipredator and foraging behaviour and body size as measures of energy expenditure or energy intake. We found no differences in any measured traits between any of the given exposure treatments, indicating that exposure to caffeine at current environmental levels may not adversely affect the energy balance and fitness of vulnerable freshwater fish.
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