Ultrafast spectroscopy is capable of monitoring electronic and vibrational states. For electronic states a few eV apart, an X-ray laser source is required. We propose an alternative method based on the time-domain high-order harmonic spectroscopy where a coherent superposition of the electronic states is first prepared by the strong optical...

Although pain is a prevalent nonmotor symptom in Parkinson’s disease (PD), it is undertreated, in part because of our limited understanding of the underlying mechanisms. Considering that the basal ganglia are implicated in pain sensation, and that their synaptic outputs are controlled by the subthalamic nucleus (STN), we hypothesized that...

Genetic polymorphisms in the region of the trimeric serine hydrolase high-temperature requirement 1 (HTRA1) are associated with increased risk of age-related macular degeneration (AMD) and disease progression, but the precise biological function of HtrA1 in the eye and its contribution to disease etiologies remain undefined. In this study, we have...

Genetic variants within complement factor H (CFH), a major alternative complement pathway regulator, are associated with the development of age-related macular degeneration (AMD) and other complementopathies. This is explained with the reduced binding of CFH or its splice variant factor H-like protein 1 (FHL-1) to self-ligands or altered self-ligands (e.g.,...

Triple-negative breast cancer (TNBC) accounts for 10 to 20% of breast cancer, with chemotherapy as its mainstay of treatment due to lack of well-defined targets, and recent genomic sequencing studies have revealed a paucity of TNBC-specific mutations. Recurrent gene fusions comprise a class of viable genetic targets in solid tumors;...

Recent epidemics demonstrate the global threat of Zika virus (ZIKV), a flavivirus transmitted by mosquitoes. Although infection is usually asymptomatic or mild, newborns of infected mothers can display severe symptoms, including neurodevelopmental abnormalities and microcephaly. Given the large-scale spread, symptom severity, and lack of treatment or prophylaxis, a safe and...

Toward the goal of increasing the throughput of high-resolution mass characterization of intact antibodies, we developed a RapidFire–mass spectrometry (MS) assay using electrospray ionization. We achieved unprecedented screening throughput as fast as 15 s/sample, which is an order of magnitude improvement over conventional liquid chromatography (LC)-MS approaches. The screening enabled...

Does infant temperament predict adult personality and life-course patterns? To date, there is scant evidence examining relations between child temperament and adult outcomes, and extant research has relied on limited methods for measuring temperament such as maternal report. This prospective longitudinal study followed a cohort of infants (n = 165)...

Legumes tend to be nodulated by competitive rhizobia that do not maximize nitrogen (N2) fixation, resulting in suboptimal yields. Rhizobial nodulation competitiveness and effectiveness at N2 fixation are independent traits, making their measurement extremely time-consuming with low experimental throughput. To transform the experimental assessment of rhizobial competitiveness and effectiveness, we...

Synaptic activity in neurons leads to the rapid activation of genes involved in mammalian behavior. ATP-dependent chromatin remodelers such as the BAF complex contribute to these responses and are generally thought to activate transcription. However, the mechanisms keeping such “early activation” genes silent have been a mystery. In the course...

Our study in PNAS (1) applies a mathematically based framework to the study of reported emotional experience evoked by music in the United States and China. Germane to theoretical debate, our methods reveal how specific emotions such as “triumph” are more primary across cultures than valence and arousal, a finding...

A growing literature at the intersection of personality psychology and behavioral economics investigates the interplay between personality and decision making in social dilemmas (1, 2). Engelmann et al. (3) extend prior research in this area by investigating the role of antisocial personality in the context of a trust game with...

Engelmann et al. ask whether “personality traits [can] help us better understand economic behavior across strategic contexts” (ref. 1, p. 12781), and, as an answer to this, identify “an antisocial personality profile” (APP) (ref. 1, p. 12785). There is much to like about this investigation; in particular, it illustrates “that...

Proteasomes are essential protease complexes that maintain cellular homeostasis, and aberrant proteasomal activity supports cancer development. The regulatory mechanisms and biological function of the ubiquitin-26S proteasome have been studied extensively, while those of the ubiquitin-independent 20S proteasome system remain obscure. Here, we show that the cap ’n’ collar (CNC) family transcription factor NRF3 specifically enhances 20S proteasome assembly in cancer cells and that 20S proteasomes contribute to colorectal cancer development through ubiquitin-independent proteolysis of the tumor suppressor p53 and retinoblastoma (Rb) proteins. The NRF3 gene is highly expressed in many cancer tissues and cell lines and is important for cancer cell growth. In cancer cells, NRF3 upregulates the assembly of the 20S proteasome by directly inducing the gene expression of the 20S proteasome maturation protein POMP. Interestingly, NRF3 knockdown not only increases p53 and Rb protein levels but also increases p53 activities for tumor suppression, including cell cycle arrest and induction of apoptosis. Furthermore, protein stability and cell viability assays using two distinct proteasome inhibitor anticancer drugs, the 20S proteasome inhibitor bortezomib and the ubiquitin-activating enzyme E1 inhibitor TAK-243, show that the upregulation of the NRF3-POMP axis leads to ubiquitin-independent proteolysis of p53 and Rb and to impaired sensitivity to bortezomib but not TAK-243. More importantly, the NRF3-POMP axis supports tumorigenesis and metastasis, with higher NRF3/POMP expression levels correlating with poor prognoses in patients with colorectal or rectal adenocarcinoma. These results suggest that the NRF3-POMP-20S proteasome assembly axis is significant for cancer development via ubiquitin-independent proteolysis of tumor suppressor proteins.

Cep57 has been characterized as a component of a pericentriolar complex containing Cep63 and Cep152. Interestingly, Cep63 and Cep152 self-assemble into a pericentriolar cylindrical architecture, and this event is critical for the orderly recruitment of Plk4, a key regulator of centriole duplication. However, the way in which Cep57 interacts with the Cep63-Cep152 complex and contributes to the structure and function of Cep63-Cep152 self-assembly remains unknown. We demonstrate that Cep57 interacts with Cep63 through N-terminal motifs and associates with Cep152 via Cep63. Three-dimensional structured illumination microscopy (3D-SIM) analyses suggested that the Cep57-Cep63-Cep152 complex is concentrically arranged around a centriole in a Cep57-in and Cep152-out manner. Cep57 mutant cells defective in Cep63 binding exhibited improper Cep63 and Cep152 localization and impaired Sas6 recruitment for procentriole assembly, proving the significance of the Cep57-Cep63 interaction. Intriguingly, Cep63 fused to a microtubule (MT)-binding domain of Cep57 functioned in concert with Cep152 to assemble around stabilized MTs in vitro. Thus, Cep57 plays a key role in architecting the Cep63-Cep152 assembly around centriolar MTs and promoting centriole biogenesis. This study may offer a platform to investigate how the organization and function of the pericentriolar architecture are altered by disease-associated mutations found in the Cep57-Cep63-Cep152 complex.

ABSTRACT

Insights into the interaction between phages and their bacterial hosts are crucial for the development of phage therapy. However, only one study has investigated global gene expression of Clostridioides (formerly Clostridium) difficile carrying prophage, and transcriptional reprogramming during lytic infection has not been studied. Here, we presented the isolation, propagation, and characterization of a newly discovered 35,109-bp phage, JD032, and investigated the global transcriptomes of both JD032 and C. difficile ribotype 078 (RT078) strain TW11 during JD032 infection. Transcriptome sequencing (RNA-seq) revealed the progressive replacement of bacterial host mRNA with phage transcripts. The expressed genes of JD032 were clustered into early, middle, and late temporal categories that were functionally similar. Specifically, a gene (JD032_orf016) involved in the lysis-lysogeny decision was identified as an early expression gene. Only 17.7% (668/3,781) of the host genes were differentially expressed, and more genes were downregulated than upregulated. The expression of genes involved in host macromolecular synthesis (DNA/RNA/proteins) was altered by JD032 at the level of transcription. In particular, the expression of the ropA operon was downregulated. Most noteworthy is that the gene expression of some antiphage systems, including CRISPR-Cas, restriction-modification, and toxin-antitoxin systems, was suppressed by JD032 during infection. In addition, bacterial sporulation, adhesion, and virulence factor genes were significantly downregulated. This study provides the first description of the interaction between anaerobic spore-forming bacteria and phages during lytic infection and highlights new aspects of C. difficile phage-host interactions.

IMPORTANCE C. difficile is one of the most clinically significant intestinal pathogens. Although phages have been shown to effectively control C. difficile infection, the host responses to phage predation have not been fully studied. In this study, we reported the isolation and characterization of a new phage, JD032, and analyzed the global transcriptomic changes in the hypervirulent RT078 C. difficile strain, TW11, during phage JD032 infection. We found that bacterial host mRNA was progressively replaced with phage transcripts, three temporal categories of JD032 gene expression, the extensive interplay between phage-bacterium, antiphage-like responses of the host and phage evasion, and decreased expression of sporulation- and virulence-related genes of the host after phage infection. These findings confirmed the complexity of interactions between C. difficile and phages and suggest that phages undergoing a lytic cycle may also cause different phenotypes in hosts, similar to prophages, which may inspire phage therapy for the control of C. difficile.

Introduction:

Understanding patients’ perspectives about their diabetes and what causes those perspectives to shift is critical to building a treatment strategy with the patient and facilitating patient self-management behavior. Key "turning points" can provide crucial opportunities to enact a change in perspective. The goal of this study is to identify "turning points" that have significance to diabetes-related health.

Lucy A. Winder, Stewart A. White, Andreas Nord, Barbara Helm, and Dominic J. McCafferty

During winter at temperate and high latitudes, the low ambient temperatures, limited food supplies and short foraging periods mean small passerines show behavioural, morphological and physiological adaptations to reduce the risk of facing energy shortages. Peripheral tissues vasoconstrict in low ambient temperatures to reduce heat loss and cold injury. Peripheral vasoconstriction has been observed with food restriction in captivity but has yet to be explored in free-ranging animals. We experimentally food restricted both wild and captive great tits (Parus major) during winter months and measured surface temperatures of the bill and eye region using thermal imaging, to investigate whether birds show rapid local heterothermic responses, which may reduce their thermoregulatory costs when facing a perceived imminent food shortage. Our results of a continuously filmed wild population showed that bill temperature was immediately reduced in response to food restriction compared with when food was available ad libitum, an apparent autonomic response. Such immediacy implies a ‘pre-emptive’ response before the bird experiences any shortfalls in energy reserves. We also demonstrate temporal variation in vasoconstriction of the bill, with bill temperature gradually rising throughout the food restriction after the initial drop. Eye-region temperature in the wild birds remained at similar levels throughout food restriction compared with unrestricted birds, possibly reflecting the need to maintain steady circulation to the central nervous and visual systems. Our findings provide evidence that birds selectively allow the bill to cool when a predictable food supply is suddenly disrupted, probably as a means of minimising depletion of body reserves for a perceived future shortage in energy.

Fredrik Andreasson, Arne Hegemann, Andreas Nord, and Jan-Ake Nilsson

The capacity to get rid of excess heat produced during hard work is a possible constraint on parental effort during reproduction [heat dissipation limit (HDL) theory]. We released hard-working blue tits (Cyanistes caeruleus) from this constraint by experimentally removing ventral plumage. We then assessed whether this changed their reproductive effort (feeding rate and nestling size) and levels of self-maintenance (change in body mass and innate immune function). Feather-clipped females reduced the number of feeding visits and increased levels of constitutive innate immunity compared with unclipped females but did not fledge smaller nestlings. Thus, they increased self-maintenance without compromising current reproductive output. In contrast, feather clipping did not affect the number of feeding visits or innate immune function in males, despite increased heat loss rate. Our results show that analyses of physiological parameters, such as constitutive innate immune function, can be important when trying to understand sources of variation in investment in self-maintenance versus reproductive effort and that risk of overheating can influence innate immune function during reproduction.

Ana Gabriela Jimenez, Emily Cornelius Ruhs, Kailey J. Tobin, Katie N. Anderson, Audrey Le Pogam, Lyette Regimbald, and Francois Vezina

Seasonal changes in maximal thermogenic capacity (M_sum) in wild black-capped chickadees suggests that adjustments in metabolic performance are slow and begin to take place before winter peaks. However, when mean minimal ambient temperature (T_a) reaches –10°C, the chickadee phenotype appears to provide enough spare capacity to endure days with colder T_a, down to –20°C or below. This suggests that birds could also maintain a higher antioxidant capacity as part of their cold-acclimated phenotype to deal with sudden decreases in temperature. Here, we tested how environmental mismatch affected oxidative stress by comparing cold-acclimated (–5°C) and transition (20°C) phenotypes in chickadees exposed to an acute 15°C drop in temperature with that of control individuals. We measured superoxide dismutase, catalase and glutathione peroxidase activities, as well as lipid peroxidation damage and antioxidant scavenging capacity in pectoralis muscle, brain, intestine and liver. We generally found differences between seasonal phenotypes and across tissues, but no differences with respect to an acute cold drop treatment. Our data suggest oxidative stress is closely matched to whole-animal physiology in cold-acclimated birds compared with transition birds, implying that changes to the oxidative stress system happen slowly.

Irene Verhagen, Barbara M. Tomotani, Phillip Gienapp, and Marcel E. Visser

Phenotypic plasticity is an important mechanism by which an individual can adapt its seasonal timing to predictable, short-term environmental changes by using predictive cues. Identification of these cues is crucial to forecast the response of species to long-term environmental change and to study their potential to adapt. Individual great tits (Parus major) start reproduction early under warmer conditions in the wild, but whether this effect is causal is not well known. We housed 36 pairs of great tits in climate-controlled aviaries and 40 pairs in outdoor aviaries, where they bred under artificial contrasting temperature treatments or in semi-natural conditions, respectively, for two consecutive years, using birds from lines selected for early and late egg laying. We thus obtained laying dates in two different thermal environments for each female. Females bred earlier under warmer conditions in climate-controlled aviaries, but not in outdoor aviaries. The latter was inconsistent with laying dates from our wild population. Further, early selection line females initiated egg laying consistently ~9 days earlier than late selection line females in outdoor aviaries, but we found no difference in the degree of plasticity (i.e. the sensitivity to temperature) in laying date between selection lines. Because we found that temperature causally affects laying date, climate change will lead to earlier laying. This advancement is, however, unlikely to be sufficient, thereby leading to selection for earlier laying. Our results suggest that natural selection may lead to a change in mean phenotype, but not to a change in the sensitivity of laying dates to temperature.

Peter J. Edmunds and Scott C. Burgess

Experiments with coral fragments (i.e. nubbins) have shown that net calcification is depressed by elevated P_CO2. Evaluating the implications of this finding requires scaling of results from nubbins to colonies, yet the experiments to codify this process have not been carried out. Building from our previous research demonstrating that net calcification of Pocillopora verrucosa (2–13 cm diameter) was unaffected by P_CO2 (400 and 1000 µatm) and temperature (26.5 and 29.7°C), we sought generality to this outcome by testing how colony size modulates P_CO2 and temperature sensitivity in a branching acroporid. Together, these taxa represent two of the dominant lineages of branching corals on Indo-Pacific coral reefs. Two trials conducted over 2 years tested the hypothesis that the seasonal range in seawater temperature (26.5 and 29.2°C) and a future P_CO2 (1062 µatm versus an ambient level of 461 µatm) affect net calcification of an ecologically relevant size range (5–20 cm diameter) of colonies of Acropora hyacinthus. As for P. verrucosa, the effects of temperature and P_CO2 on net calcification (mg day^–1) of A. verrucosa were not statistically detectable. These results support the generality of a null outcome on net calcification of exposing intact colonies of branching corals to environmental conditions contrasting seasonal variation in temperature and predicted future variation in P_CO2. While there is a need to expand beyond an experimental culture relying on coral nubbins as tractable replicates, rigorously responding to this need poses substantial ethical and logistical challenges.

Daniel P. Small, Piero Calosi, Samuel P. S. Rastrick, Lucy M. Turner, Stephen Widdicombe, and John I. Spicer

Regulation of extracellular acid–base balance, while maintaining energy metabolism, is recognised as an important aspect when defining an organism's sensitivity to environmental changes. This study investigated the haemolymph buffering capacity and energy metabolism (oxygen consumption, haemolymph [l-lactate] and [protein]) in early benthic juveniles (carapace length <40 mm) of the European lobster, Homarus gammarus, exposed to elevated temperature and P_CO2. At 13°C, H. gammarus juveniles were able to fully compensate for acid–base disturbances caused by the exposure to elevated seawater P_CO2 at levels associated with ocean acidification and carbon dioxide capture and storage (CCS) leakage scenarios, via haemolymph [HCO₃^–] regulation. However, metabolic rate remained constant and food consumption decreased under elevated P_CO2, indicating reduced energy availability. Juveniles at 17°C showed no ability to actively compensate haemolymph pH, resulting in decreased haemolymph pH particularly under CCS conditions. Early benthic juvenile lobsters at 17°C were not able to increase energy intake to offset increased energy demand and therefore appear to be unable to respond to acid–base disturbances due to increased P_CO2 at elevated temperature. Analysis of haemolymph metabolites suggests that, even under control conditions, juveniles were energetically limited. They exhibited high haemolymph [l-lactate], indicating recourse to anaerobic metabolism. Low haemolymph [protein] was linked to minimal non-bicarbonate buffering and reduced oxygen transport capacity. We discuss these results in the context of potential impacts of ongoing ocean change and CCS leakage scenarios on the development of juvenile H. gammarus and future lobster populations and stocks.

Zhi-Jun Zhao, Davina Derous, Abby Gerrard, Jing Wen, Xue Liu, Song Tan, Catherine Hambly, and John R. Speakman

Lactating mice increase food intake 4- to 5-fold, reaching an asymptote in late lactation. A key question is whether this asymptote reflects a physiological constraint, or a maternal investment strategy (a ‘restraint’). We exposed lactating mice to periods of food restriction, hypothesizing that if the limit reflected restraint, they would compensate by breaching the asymptote when refeeding. In contrast, if it was a constraint, they would by definition be unable to increase their intake on refeeding days. Using isotope methods, we found that during food restriction, the females shut down milk production, impacting offspring growth. During refeeding, food intake and milk production rose again, but not significantly above unrestricted controls. These data provide strong evidence that asymptotic intake in lactation reflects a physiological/physical constraint, rather than restraint. Because hypothalamic neuropeptide Y (Npy) was upregulated under both states of restriction, this suggests the constraint is not imposed by limits in the capacity to upregulate hunger signalling (the saturated neural capacity hypothesis). Understanding the genetic basis of the constraint will be a key future goal and will provide us additional information on the nature of the constraining factors on reproductive output, and their potential links to life history strategies.

Karen L. Carleton, Daniel Escobar-Camacho, Sara M. Stieb, Fabio Cortesi, and N. Justin Marshall

Among vertebrates, teleost eye diversity exceeds that found in all other groups. Their spectral sensitivities range from ultraviolet to red, and the number of visual pigments varies from 1 to over 40. This variation is correlated with the different ecologies and life histories of fish species, including their variable aquatic habitats: murky lakes, clear oceans, deep seas and turbulent rivers. These ecotopes often change with the season, but fish may also migrate between ecotopes diurnally, seasonally or ontogenetically. To survive in these variable light habitats, fish visual systems have evolved a suite of mechanisms that modulate spectral sensitivities on a range of timescales. These mechanisms include: (1) optical media that filter light, (2) variations in photoreceptor type and size to vary absorbance and sensitivity, and (3) changes in photoreceptor visual pigments to optimize peak sensitivity. The visual pigment changes can result from changes in chromophore or changes to the opsin. Opsin variation results from changes in opsin sequence, opsin expression or co-expression, and opsin gene duplications and losses. Here, we review visual diversity in a number of teleost groups where the structural and molecular mechanisms underlying their spectral sensitivities have been relatively well determined. Although we document considerable variability, this alone does not imply functional difference per se. We therefore highlight the need for more studies that examine species with known sensitivity differences, emphasizing behavioral experiments to test whether such differences actually matter in the execution of visual tasks that are relevant to the fish.

Samantha M. Logan, Kama E. Szereszewski, Nigel C. Bennett, Daniel W. Hart, Barry van Jaarsveld, Matthew E. Pamenter, and Kenneth B. Storey

Mole-rats are champions of self-preservation, with increased longevity compared to other rodents their size, strong antioxidant capabilities, and specialized defenses against endogenous oxidative stress. However, how the brains of these subterranean mammals handle acute in vivo hypoxia is poorly understood. This study is the first to examine the molecular response to low oxygen in six different species of hypoxia-tolerant mole-rats from sub-Saharan Africa. Protein carbonylation, a known marker of DNA damage (hydroxy-2’-deoxyguanosine), and antioxidant capacity did not change following hypoxia but HIF-1 protein levels increased significantly in the brains of two species. Nearly 30 miRNAs known to play roles in hypoxia-tolerance were differentially regulated in a species-specific manner. The miRNAs exhibiting the strongest response to low oxygen stress inhibit apoptosis and regulate neuroinflammation, likely providing neuroprotection. A principal component analysis using a subset of the molecular targets assessed herein revealed differences between control and hypoxic groups for two solitary species (Georychus capensis and Bathyergus suillus), which are ecologically adapted to a normoxic environment, suggesting a heightened sensitivity to hypoxia relative to species that may experience hypoxia more regularly in nature. By contrast, all molecular data were included in the PCA to detect a difference between control and hypoxic populations of eusocial Heterocephalus glaber, indicating they may require many lower-fold changes in signaling pathways to adapt to low oxygen settings. Finally, none of the Cryptomys hottentotus subspecies showed a statistical difference between control and hypoxic groups, presumably due to hypoxia-tolerance derived from environmental pressures associated with a subterranean and social lifestyle.

Yi Huang, Jazmin Osorio Mendoza, Catherine Hambly, Baoguo Li, Zengguang Jin, Li Li, Moshen Madizi, Sumei Hu, and John R. Speakman

The heat dissipation limit theory predicts lactating female mice consuming diets with lower specific dynamic action (SDA) should have enhanced lactation performance. Dietary fat has lower SDA than other macronutrients. Here we tested the effects of graded dietary fat levels on lactating Swiss mice. We fed females five diets varying in fat content from 8.3 to 66.6%. Offspring of mothers fed diets of 41.7% fat and above were heavier and fatter at weaning compared to those of 8.3% and 25% fat diets. Mice on dietary fat contents of 41.7% and above had greater metabolizable energy intake at peak lactation (8.3%: 229.4±39.6, 25%: 278.8±25.8, 41.7%: 359.6±51.5, 58.3%: 353.7±43.6, 66.6%: 346±44.7 kJ day^–1), lower daily energy expenditure (8.3%: 128.5±16, 25%: 131.6±8.4, 41.7%: 124.4±10.8, 58.3%: 115.1±10.5, 66.6%: 111.2±11.5 kJ day^–1) and thus delivered more milk energy to their offspring (8.3%: 100.8±27.3, 25%: 147.2±25.1, 41.7%: 225.1±49.6, 58.3%: 238.6±40.1, 66.6%: 234.8±41.1 kJ day^–1). Milk fat content (%) was unrelated to dietary fat content, indicating females on higher fat diets (> 41.7%) produced more rather than richer milk. Mothers consuming diets with 41.7% fat or above enhanced their lactation performance compared to those on 25% or less, probably by diverting dietary fat directly into the milk, thereby avoiding the costs of lipogenesis. At dietary fat contents above 41.7% they were either unable to transfer more dietary fat to the milk, or they chose not to do so, potentially because of a lack of benefit to the offspring that were increasingly fatter as maternal dietary fat increased.

Lakshman Abhilash, Arshad Kalliyil, and Vasu Sheeba

Even though the rhythm in adult emergence and rhythm in locomotor activity are two different rhythmic phenomena that occur at distinct life-stages of the fly life cycle, previous studies have hinted at similarities in certain aspects of the organisation of the circadian clock driving these two rhythms. For instance, the period gene plays an important regulatory role in both rhythms. In an earlier study, we have shown that selection on timing of adult emergence behaviour in populations of Drosophila melanogaster leads to the co-evolution of temperature sensitivity of circadian clocks driving eclosion. In this study, we were interested in asking if temperature sensitivity of the locomotor activity rhythm has evolved in our populations with divergent timing of adult emergence rhythm, with the goal of understanding the extent of similarity (or lack of it) in circadian organisation between the two rhythms. We found that in response to simulated jetlag with temperature cycles, late chronotypes (populations selected for predominant emergence during dusk) indeed re-entrain faster than early chronotypes (populations selected for predominant emergence during dawn) to 6-h phase-delays, thereby indicating enhanced sensitivity of the activity/rest clock to temperature cues in these stocks (entrainment is the synchronisation of internal rhythms to cyclic environmental time-cues). Additionally, we found that late chronotypes show higher plasticity of phases across regimes, day-to-day stability in phases and amplitude of entrainment, all indicative of enhanced temperature sensitive activity/rest rhythms. Our results highlight remarkably similar organisation principles between emergence and activity/rest rhythms.

Daniel J. Tobiansky, Meredith C. Miles, Franz Goller, and Matthew J. Fuxjager

Performance trade-offs can dramatically alter an organism's evolutionary trajectory by making certain phenotypic outcomes unattainable. Understanding how these trade-offs arise from an animal's design is therefore an important goal of biology. To explore this topic, we study how androgenic hormones, which regulate skeletal muscle function, influence performance trade-offs relevant to different components of complex reproductive behaviour. We conduct this work in golden-collared manakins (Manacus vitellinus), a Neotropical bird in which males court females by rapidly snapping their wings together above their back. Androgens help mediate the snap displays by radically increasing the twitch speed of a dorsal wing muscle [scapulohumeralis caudalis (SH)], which actuates the bird's wing-snap. Through hormone manipulations and in situ muscle recordings, we test how these positive effects on SH speed influence trade-offs with endurance. Indeed, this trait impacts the display by shaping signal length. We find that androgen-dependent increases in SH speed incur a cost to endurance, particularly when this muscle performs at its functional limits. Moreover, when behavioural data are overlaid on our muscle recordings, displaying animals appear to balance display speed with fatigue-induced muscle fusion (physiological tetanus) to generate the fastest possible signal while maintaining an appropriate signal duration. Our results point to androgenic hormone action as a functional trigger of trade-offs in sexual performance—they enhance one element of a courtship display, but in doing so, impede another.

Noemie Liesch and Friedrich Ladich

In vocal fish species, males possess larger sound-generating organs and signal acoustically with pronounced sex-specific differences. Sound production is known in two out of three species of croaking gouramis (Trichopsis vittata and T. schalleri). The present study investigates sex-specific differences in sonic organs, vocalizing behaviour and sounds emitted in the third species, the pygmy gourami T. pumila, in order to test the hypothesis that females are able to vocalize despite their less-developed sonic organs, and despite contradictory reports. Croaking gouramis stretch and pluck two enhanced (sonic) pectoral fin tendons during alternate fin beating, resulting in a series of double-pulsed bursts termed croaking sound. We measured the diameter of the first and second sonic tendon and showed that male tendons were twice as large as in same-sized females. We also determined the duration of dyadic contests, visual displays, number of sounds and buttings. Sexes differ in all sound characteristics but in no behavioural variable. Male sounds consisted of twice as many bursts, a higher percentage of double-pulsed bursts and a higher burst period. Additionally, male sounds had a lower dominant frequency and a higher sound level. In summary, female pygmy gouramis possessed sonic organs and vocalized in most dyadic contests. The sexual dimorphism in sonic tendons is clearly reflected in sex-specific differences in sound characteristics, but not in agonistic behaviour, supporting the hypothesis that females are vocal.

Simon Tapper, Joseph J. Nocera, and Gary Burness

Climatic warming is predicted to increase the frequency of extreme weather events, which may reduce an individual's capacity for sustained activity due to thermal limits. We tested whether the risk of overheating may limit parental provisioning of an aerial insectivorous bird in population decline. For many seasonally breeding birds, parents are thought to operate close to an energetic ceiling during the 2-3 week chick-rearing period. The factors determining the ceiling remain unknown, although it may be set by an individual's capacity to dissipate body heat (the heat dissipation limitation hypothesis). Over two breeding seasons we experimentally trimmed the ventral feathers of female tree swallows (Tachycineta bicolor, Vieillot, 1808) to provide a thermal window. We then monitored maternal and paternal provisioning rates, nestling growth rates, and fledging success. We found the effect of our experimental treatment was context-dependent. Females with an enhanced capacity to dissipate heat fed their nestlings at higher rates than controls when conditions were hot, but the reverse was true under cool conditions. Control females and their mates both reduced foraging under hot conditions. In contrast, male partners of trimmed females maintained a constant feeding rate across temperatures, suggesting attempts to match the feeding rate of their partners. On average, nestlings of trimmed females were heavier than controls, but did not have a higher probability of fledging. We suggest that removal of a thermal constraint allowed females to increase provisioning rates, but additionally provided nestlings with a thermal advantage via increased heat transfer during maternal brooding. Our data provide support for the heat dissipation limitation hypothesis and suggest that depending on temperature, heat dissipation capacity can influence reproductive success in aerial insectivores.

Jing Wen, Tingbei Bo, Xueying Zhang, Zuoxin Wang, and Dehua Wang

Ambient temperature and food composition can affect energy metabolism of the host. Thermal transient receptor potential (thermo-TRPs) ion channels can detect temperature signals and are involved in the regulation of thermogenesis and energy homeostasis. Further, the gut microbiota has also been implicated in thermogenesis and obesity. In the present study, we tested the hypothesis that thermo-TRPs and gut microbiota are involved in reducing diet-induced obesity (DIO) during low temperature exposure. C57BL/6J mice in obese (body mass gain >45%), lean (body mass gain <15%), and control (body mass gain<1%) groups were exposed to high (23±1°C) or low (4±1°C) ambient temperature for 28 days. Our data showed that low temperature exposure attenuated DIO, but enhanced brown adipose tissue (BAT) thermogenesis. Low temperature exposure also resulted in increased norepinephrine (NE) concentrations in the hypothalamus, decreased TRP melastatin 8 (TRPM8) expression in the small intestine, and altered composition and diversity of gut microbiota. In DIO mice, there was a decrease in overall energy intake along with a reduction in TRP ankyrin 1 (TRPA1) expression and an increase in NE concentration in the small intestine. DIO mice also showed increases in Oscillospira, [Ruminococcus], Lactococcus, and Christensenella and decreases in Prevotella, Odoribacter, and Lactobacillus at the genus level in fecal samples. Together, our data suggest that thermos-TRPs and gut microbiota are involved in thermogenesis and energy metabolism during low temperature exposure in DIO mice.

Kelsey L. Jones, Rahmatollah Rajabzadeh, Guncha Ishangulyyeva, Nadir Erbilgin, and Maya L. Evenden

Flight polyphenisms naturally occur as discrete or continuous traits in insects. Discrete flight polyphenisms include winged and wingless morphs, whereas continuous flight polyphenisms can take the form of short- or long-distance fliers. The mountain pine beetle (Dendroctonus ponderosae) exhibits polyphenic variation in flight distance but the consequences of this flight variation on life history strategies of beetles is unknown. This study assessed the effect of flight on two particular aspects of beetle biology: (1) an energetic trade-off between flight distance and host colonisation capacity; and (2) the relationship between flight distance and pheromone production. A 23-h flight treatment was applied to a subset of beetles using computer. After flight treatment, both flown and unflown (control) beetles were given the opportunity to colonise bolts of host trees, and beetles that entered hosts were aerated to collect pheromone. A trade-off occurred between initiation of host colonisation and percent body weight lost during flight, which indicates energy-use during flight affects host acceptance in female mountain pine beetles. Furthermore, production of the aggregation pheromone trans-verbenol by female beetles was influenced by both percent weight lost during flight and flight distance. Male production of exo-brevicomin was affected by beetle condition following flight but not by the energy used during flight. These novel results give new insight into the polyphenic flight behaviour of mountain pine beetles. Flight variation is adaptive by acting to maintain population levels through safe and risky host colonisation strategies. These findings suggest mechanisms that facilitate the extremities of the continuous flight polyphenism spectrum. These opposing mechanisms appear to maintain the high variation in flight exhibited by this species.

Joachim Ostheim, Julia A. M. Delius, and Juan D. Delius

The visual control of pecking by pigeons (Columba livia) has latterly been thought to be restricted to the fixation stops interrupting their downward head movements because these stops prevent interference by motion blur. Pigeons were also assumed to close their eyes during the final head thrust of the peck. Here we re-examine their pecking motions using high-speed video recordings and supplementary provisions that permitted a three-dimensional spatial analysis of the movement, including measurements of their pupil diameters and eyelid slit width. The results confirm that pigeons do not close their eyes completely during the presumed optically ballistic phase of pecking. Instead their eyelids are narrowed to a slit. The width of this slit is sensitive to both the ambient illumination levels and the visual backgrounds against which seed targets have to be detected and grasped. There is also evidence of some interaction between pupil diameter and eyelid slit width. We surmise that besides being an eye-protecting reflex, the partial covering of the pupil with the eyelids may increase the depth of focus, enabling pigeons to obtain sharp retinal images of peck target items at very close range and during the beak-gape ‘handling’ of food items and occasional grit particles.

Emily J. Lombardi, Candice L. Bywater, and Craig R. White

The Oxygen and Capacity-Limited Thermal Tolerance (OCLTT) hypothesis proposes that the thermal tolerance of an animal is shaped by its capacity to deliver oxygen in relation to oxygen demand. Studies testing this hypothesis have largely focused on measuring short-term performance responses in animals under acute exposure to critical thermal maximums. The OCLTT hypothesis, however, emphasises the importance of sustained animal performance over acute tolerance. The present study tested the effect of chronic hypoxia and hyperoxia during development on medium to long-term performance indicators at temperatures spanning the optimal temperature for growth in the speckled cockroach, Nauphoeta cinerea. In contrast to the predictions of the OCLTT hypothesis, development under hypoxia did not significantly reduce growth rate or running performance, and development under hyperoxia did not significantly increase growth rate or running performance. The effect of developmental temperature and oxygen on tracheal morphology and metabolic rate were also not consistent with OCLTT predictions, suggesting that oxygen delivery capacity is not the primary driver shaping thermal tolerance in this species. Collectively, these findings suggest that the OCLTT hypothesis does not explain moderate-to-long-term thermal performance in Nauphoeta cinerea, which raises further questions about the generality of the hypothesis.

Itsumi Nakamura, Rui Matsumoto, and Katsufumi Sato

It is generally assumed that the body temperature of large animals is less likely to change due to their large body size, resulting in a high thermal inertia and a smaller surface area to volume ratio. The goal of this study was to investigate the stability of body temperature in large fish using data from field experiments. We measured the muscle temperatures of free-ranging whale sharks (Rhincodon typus), the largest extant fish globally, and investigated their ectothermic physiology and the stability of their body temperatures. The measured muscle temperature of the whale sharks changed substantially more slowly than the water temperature fluctuations associated with vertical movements, and the whole-body heat-transfer coefficients (HTC) of whale sharks estimated using heat-budget models were lower than those of any other fish species measured to date. The heat-budget models also showed that internal heat production does not contribute to changes in muscle temperature. A comparative analysis showed that the HTC at cooling in various fish species including both ectothermic and endothermic species ranging from 10^–4 to 10³ kg was proportional to body mass^–0.63. This allometry was present regardless of whether the fish were ectothermic or endothermic, and was an extension of the relationship observed in previous studies on small fish. Thus, large fish have the advantage of body temperature stability while moving in environments with large temperature variations. Our results suggest that the large body size of whale sharks aids in preventing a decrease in body temperature during deep excursions to more than 1000 m depths without high metabolic costs of producing heat.

Nadia Vicenzi, Alejandro Laspiur, Paola L. Sassi, Ruben Massarelli, John Krenz, and Nora R. Ibargüengoytia

In ectotherms, temperature exerts a strong influence on the performance of physiological and ecological traits. One approach to understand the impact of rising temperatures on animals and their ability to cope with climate change is to quantify variation in thermal-sensitive traits. Here, we examined the thermal biology, the temperature dependence and the thermal plasticity of bite force (endurance and magnitude) in Diplolaemus leopardinus, an aggressive and territorial lizard, endemic to Mendoza province, Argentina. Our results indicated that this lizard behaves like a moderate thermoregulator which uses the rocks of its environment as the main heat source. Bite endurance was not influenced by head morphometry and body temperature, whereas bite force was influenced by head length and jaw length, and exhibited thermal dependence. Before thermal acclimation treatments, the maximum bite force for D. leopardinus occured at the lowest body temperature and fell sharply with increasing body temperature. After acclimation treatments, lizards acclimated at higher temperatures exhibited greater bite force. Bite force showed phenotypic plasticity, which reveals that leopard iguanas are able to maintain (and even improve) their bite force under a rising-temperature scenario.

Jorge de Costa, Gustavo Barja, and Pedro F. Almaida-Pagan

Lipid composition of cell membranes is linked to metabolic rate and lifespan in mammals and birds but very little information is available for fishes. In this study, three fish species of the short-lived annual genus Nothobranchius with different maximum lifespan potentials (MLSP) and the longer-lived outgroup species Aphyosemion australe were studied to test whether they conform to the predictions of the longevity-homeoviscous adaptation (LHA) theory of aging. Lipid analyses were performed in whole fish samples and peroxidation indexes (PIn) for every PL class and for the whole membrane, were calculated. Total PL content was significantly lower in A. australe and N. korthausae, the two species with the highest MLSP, and a negative correlation between membrane total PIn and fish MLSP was found, this meaning that the longer-lived fish species have more saturated membranes and therefore, a lower susceptibility to oxidative damage, as the LHA theory posits.

David E. Cade, J. Jacob Levenson, Robert Cooper, Rafael de la Parra, D. Harry Webb, and Alistair D. M. Dove

Whale sharks (Rhincodon typus Smith 1828) – the largest extant fish species – reside in tropical environments, making them an exception to the general rule that animal size increases with latitude. How this largest fish thrives in tropical environments that promote high metabolism but support less robust zooplankton communities has not been sufficiently explained. We used open-source inertial measurement units (IMU) to log 397 hours of whale shark behavior in Yucatan, Mexico, at a site of both active feeding and intense wildlife tourism. Here we show that the strategies employed by whale sharks to compensate for the increased drag of an open mouth are similar to ram-feeders five orders of magnitude smaller and one order of magnitude larger. Presumed feeding constituted 20% of the total time budget of four sharks, with individual feeding bouts lasting up to 11 consecutive hrs. Compared to normal, sub-surface swimming, three sharks increased their stroke rate and amplitude while surface feeding, while one shark that fed at depth did not demonstrate a greatly increased energetic cost. Additionally, based on time-depth budgets, we estimate that aerial surveys of shark populations should consider including a correction factor of 3 to account for the proportion of daylight hours that sharks are not visible at the surface. With foraging bouts generally lasting several hours, interruptions to foraging during critical feeding periods may represent substantial energetic costs to these endangered species, and this study presents baseline data from which management decisions affecting tourist interactions with whale sharks may be made.

Shih-Jung Hsu and Bo Cheng

In the presence of wind or background image motion, flies are able to maintain a constant retinal slip velocity via regulating flight speed to the extent permitted by their locomotor capacity. Here we investigated the retinal slip compensation of tethered blue-bottle flies (Calliphora vomitoria) flying semi-freely along an annular corridor in a magnetically levitated flight mill enclosed by two motorized cylindrical walls. We perturbed the flies’ retinal slip via spinning the cylindrical walls, generating bilaterally averaged retinal slip perturbations from -0.3 to 0.3 m·s^–1 (or -116.4 to 116.4 deg.·s^–1) When the perturbation was less than ~0.1 m·s^–1 (38.4 deg.·s^–1), the flies successfully compensated the perturbations and maintained a retinal slip velocity by adjusting their airspeed up to 20%. However, with greater retinal slip perturbation, the flies’ compensation became saturated, as the flies’ airspeed plateaued, indicating that they were unable to further maintain a constant retinal slip velocity. The compensation gain, i.e., the ratio of airspeed compensation and retinal slip perturbation, depended on the spatial frequency of the grating patterns, being the largest at 12 m^–1 (0.04 deg.^–1).

Annette E. Allen, Joshua W. Mouland, Jessica Rodgers, Beatriz Bano-Otalora, Ronald H. Douglas, Glen Jeffery, Anthony A. Vugler, Timothy M. Brown, and Robert J. Lucas

An animal's temporal niche – the time of day at which it is active – is known to drive a variety of adaptations in the visual system. This includes variations in the topography, spectral sensitivity and density of retinal photoreceptors, and changes in the eye's gross anatomy and spectral transmission characteristics. We have characterised visual spectral sensitivity in the murid rodent Rhabdomys pumilio (‘the four-striped grass mouse’), which is the same family as (nocturnal) mice and rats, but exhibits a strong diurnal niche. As is common in diurnal species, the Rhabdomys lens acts as a long-pass spectral filter, providing limited transmission of light <400nm. Conversely, we found strong sequence homologies with the Rhabdomys SWS and MWS opsins and those of related nocturnal species (mice and rats) whose SWS opsins are maximally sensitive in the near UV. We continued to assess in vivo spectral sensitivity of cone vision using electroretinography and multi-channel recordings from the visual thalamus. These revealed that responses across the human visible range could be adequately described by those of a single pigment (assumed to be MWS opsin) maximally sensitive ~500nm, but that sensitivity in the near UV required inclusion of a second pigment whose peak sensitivity lay well into the UV range (_max <400nm, likely ~360nm). We therefore conclude that, despite the UV-filtering effects of the lens, the Rhabdomys retains an SWS pigment with a UV-A _max. In effect, this somewhat paradoxical combination of long-pass lens and UV-A _max results in narrow-band sensitivity for SWS cone pathways in the UV-A range.

Brad A. Seibel and Curtis Deutsch

The capacity to extract oxygen from the environment and transport it to respiring tissues in support of metabolic demand reportedly has implications for species’ thermal tolerance, body-size, diversity and biogeography. Here we derive a quantifiable linkage between maximum and basal metabolic rate and their oxygen, temperature and size dependencies. We show that, regardless of size or temperature, the physiological capacity for oxygen supply precisely matches the maximum evolved demand at the highest persistently available oxygen pressure and this is the critical PO₂ for the maximum metabolic rate. For most terrestrial and shallow-living marine species, this "P_crit-max" is the current atmospheric pressure, 21 kPa. Any reduction in oxygen partial pressure from current values will result in a calculable decrement in maximum metabolic performance. However, oxygen supply capacity has evolved to match demand across temperatures and body sizes and so does not constrain thermal tolerance or cause the well-known reduction in mass-specific metabolic rate with increasing body mass. The critical oxygen pressure for resting metabolic rate, typically viewed as an indicator of hypoxia tolerance, is, instead, simply a rate-specific reflection of the oxygen supply capacity. A compensatory reduction in maintenance metabolic costs in warm-adapted species constrains factorial aerobic scope and the critical PO₂ to a similar range, between ~2 and 6, across each species’ natural temperature range. The simple new relationship described here redefines many important physiological concepts and alters their ecological interpretation.

Maria Stager, Nathan R. Senner, Bret W. Tobalske, and Zachary A. Cheviron

Flexibility in heat generation and dissipation mechanisms provides endotherms the ability to match their thermoregulatory strategy with external demands. However, the degree to which these two mechanisms account for seasonal changes in body temperature regulation is little explored. Here we present novel data on the regulation of avian body temperature to investigate how birds alter mechanisms of heat production and heat conservation to deal with variation in ambient conditions. We subjected Dark-eyed Juncos (Junco hyemalis) to chronic cold acclimations of varying duration and subsequently quantified their metabolic rates, thermal conductance, and ability to maintain normothermia. Cold-acclimated birds adjusted traits related to both heat generation (increased summit metabolic rate) and heat conservation (decreased conductance) to improve their body temperature regulation. Increases in summit metabolic rate occurred rapidly, but plateaued after one week of cold exposure. In contrast, changes to conductance occurred only after nine weeks of cold exposure. Thus, the ability to maintain body temperature continued to improve throughout the experiment, but the mechanisms underlying this improvement changed through time. Our results demonstrate the ability of birds to adjust thermoregulatory strategies in response to thermal cues and reveal that birds may combine multiple responses to meet the specific demands of their environments.

Background

Experimental and observational studies have raised concerns that giving intravenous (IV) iron to patients, such as individuals receiving maintenance hemodialysis, might increase the risk of infections. The Proactive IV Iron Therapy in Haemodialysis Patients (PIVOTAL) trial randomized 2141 patients undergoing maintenance hemodialysis for ESKD to a high-dose or a low-dose IV iron regimen, with a primary composite outcome of all-cause death, heart attack, stroke, or hospitalization for heart failure. Comparison of infection rates between the two groups was a prespecified secondary analysis.

Background

Nephropathic cystinosis, a hereditary lysosomal storage disorder caused by dysfunction of the lysosomal cotransporter cystinosin, leads to cystine accumulation and cellular damage in various organs, particularly in the kidney. Close therapeutic monitoring of cysteamine, the only available disease-modifying treatment, is recommended. White blood cell cystine concentration is the current gold standard for therapeutic monitoring, but the assay is technically demanding and is available only on a limited basis. Because macrophage-mediated inflammation plays an important role in the pathogenesis of cystinosis, biomarkers of macrophage activation could have potential for the therapeutic monitoring of cystinosis.

Background

Water and solute transport across epithelia can occur via the transcellular or paracellular pathways. Tight junctions play a key role in mediating paracellular ion reabsorption in the kidney. In the renal collecting duct, which is a typical absorptive tight epithelium, coordination between transcellular sodium reabsorption and paracellular permeability may prevent the backflow of reabsorbed sodium to the tubular lumen along a steep electrochemical gradient.

Background

The serine/threonine kinases MST1 and MST2 are core components of the Hippo pathway, which has been found to be critically involved in embryonic kidney development. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are the pathway’s main effectors. However, the biologic functions of the Hippo/YAP pathway in adult kidneys are not well understood, and the functional role of MST1 and MST2 in the kidney has not been studied.