Journal of Experimental Biology最新文献

Cardiac phenotypic plasticity, the remodelling of heart structure and function, is a response to any sustained (or repeated) stimulus or stressor that results in a change in heart performance. Cardiac plasticity can be either adaptive (beneficial) or maladaptive (pathological), depending on the nature and intensity of the stimulus. Here, we draw on articles published in this Special Issue of Journal of Experimental Biology, and from the broader comparative physiology literature, to highlight the core components that enable cardiac plasticity, including structural remodelling, excitation-contraction coupling remodelling and metabolic rewiring. We discuss when and how these changes occur, with a focus on the underlying molecular mechanisms, from the regulation of gene transcription by epigenetic processes to post-translational modifications of cardiac proteins. Looking to the future, we anticipate that the growing use of -omics technologies in integration with traditional comparative physiology approaches will allow researchers to continue to uncover the vast scope for plasticity in cardiac function across animals.

Leptin is a hormone that secreted by adipocytes and may promote energy expenditure by increasing thermogenesis. Our previous studies have shown that thermo-transient receptor potentials (thermo-TRPs) and gut microbiota are associated with thermoregulation in Mongolian gerbils, which are characterized by relative high serum leptin concentrations. Here, we test whether leptin can stimulate non-shivering thermogenesis (NST) in Mongolian gerbils, and whether thermo-TRPs and gut microbiota are involved in leptin-induced thermogenesis. First, gerbils were given acute leptin treatment (ALT) with different doses. Results showed that ALT significantly increased the body temperature of gerbils and change the composition of gut microbiota. Moreover, ALT groups showed a trend towards increased expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT). Then, we investigated the effect of chronic leptin treatment (CLT) on gerbils. Surprisingly, CLT did not affect gerbils' food intake and body weight, but it significantly increased the body temperature at the end. Besides, CLT did not affect the expression of thermogenic markers in BAT, white adipose tissue (WAT) and skeletal muscle. However, CLT increased the expression of leptin receptors and TRPV2 in the small intestine and affected the composition of gut microbiota. Together, our data suggest leptin may increase body temperature by regulating gut microbiota. In conclusion, the Mongolian gerbils with serum hyperleptin is beneficial for adapting the cold living environments, and TRPV2 and gut microbiota are involved.

To assess the relationship among various measures of thermal tolerance and performance suggested for use in fish, we determined the critical thermal maximum (CTmax), Ucrit, maximum thermal tolerance while swimming [CTSmax] and realistic aerobic scope (ASR) of juvenile schoolmaster snapper (Lutjanus apodus). Their CTSmax (37.5±0.1°C) was only slightly lower than their CTmax (38.9±0.1°C), and this is likely because their maximum metabolic rate (MMR) and ASR during the former test were∼42 and 65% higher, respectively. Further, we did not observe a transition to unsteady (i.e., anaerobically fueled) swimming in the CTSmax test as we did in the Ucrit protocol. These data strongly suggest that thermal tolerance tests on fishes whose lifestyle involves schooling or sustained activity should be performed at ecologically-relevant swimming speeds. Further, they do not support the hypothesis that failure during a CTSmax test is due to a fish's inability to meet its tissue oxygen demands.

Whiskers (vibrissae) are important tactile sensors for most mammals. We introduce a novel approach to quantitatively compare 3D geometry of whisker arrays across species with different whisker numbers and arrangements, focusing on harbor seals (Phoca vitulina), house mice (Mus musculus) and Norway rats (Rattus norvegicus). Whiskers of all three species decrease in arclength and increase in curvature from caudal to rostral. They emerge from the face with elevation angles that vary linearly with dorsoventral position, and with curvature orientations that vary diagonally as linear combinations of dorsoventral and rostrocaudal positions. In seals, this diagonal varies linearly with horizontal emergence angles, and is orthogonal to the diagonal for rats and mice. This work provides the first evidence for common elements of whisker arrangements across species in different mammalian orders. Placing the equation-based whisker array on a CAD model of a seal head enables future mechanical studies of whisker-based sensing, including wake-tracking.

Evolutionary and functional adaptations of morphology and postural tone of the spine and trunk are intrinsically shaped by the field of gravity in which humans move. Gravity also significantly impacts the timing and levels of neuromuscular activation, particularly in foot-support interactions. During step-to-step transitions, the centre of mass velocity must be redirected from downwards to upwards. When walking upright, this redirection is initiated by the trailing leg, propelling the body forward and upward before foot contact of the leading leg, defined as an anticipated transition. In this study, we investigated the neuromechanical adjustments when walking with a bent posture. Twenty adults walked on an instrumented treadmill at 4 km h-1 under normal (upright) conditions and with varying degrees of anterior trunk flexion (10, 20, 30 and 40 deg). We recorded lower-limb kinematics, ground reaction forces under each foot, and the electromyography activity of five lower-limb muscles. Our findings indicate that with increasing trunk flexion, there is a lack of these anticipatory step-to-step transitions, and the leading limb performs the redirection after the ground collision. Surprisingly, attenuating distal extensor muscle activity at the end of stance is one of the main impacts of trunk flexion. Our observations may help us to understand the physiological mechanisms and biomechanical regulations underlying our tendency towards an upright posture, as well as possible motor control disturbances in some diseases associated with trunk orientation problems.

Researchers in the Global South (GS, developing countries) make valuable contributions to the field of comparative physiology, but face economic and scientific disparities and several unique challenges compared with colleagues in the Global North (developed countries). This Perspective highlights some of the challenges, knowledge gaps and disparities in opportunity faced by GS researchers, especially those at early-career stages. We propose collaborative solutions to help address these issues, and advocate for promoting investment and cultural and societal change for a more inclusive research community. Additionally, we highlight the role of GS researchers in contributing expert knowledge on local biodiversity and the environment; this knowledge can help to shape the future of comparative physiology, allowing us to achieve a better understanding of the evolution of physiological mechanisms and to develop innovative solutions to environmental and biomedical challenges. With this Perspective, we hope to highlight the need to foster a more diverse, equitable and inclusive research landscape in comparative physiology; one that empowers GS scientists to address the global challenges associated with biodiversity loss, climate change and environmental pollution.

Insect guts house a complex community of microbes that affect host physiology, performance and behavior. Gut microbiome research has largely focused on bacteria-host symbioses and paid less attention to other taxa, such as yeasts. We found that axenic Drosophila melanogaster (reared free of microbes) develops from egg to adult more slowly (ca. 13 days) than those with a natural microbiota (ca. 11.5 days). Here, we showed that live yeasts are present and reproducing in the guts of flies and that the fast development time can be restored by inoculating larvae with a single yeast species (either Saccharomyces cerevisiae or Lachancea kluyveri). Nutritional supplements (either heat-killed yeasts, or a mix of essential vitamins and amino acids) slightly sped the development of axenic flies (to ca. 12.5 days), but not to the same extent as live yeasts. During the first two instars, this acceleration appears to result from additional macronutrient availability, but during the third instar, when most growth occurs, live yeasts increased feeding rate, implying an effect mediated by the gut-brain axis. Thus, the fly-yeast interaction extends beyond yeasts-as-food to yeasts as beneficial interactive symbionts.

The gait characteristics associated with arboreal locomotion have been frequently discussed in the context of primate evolution, wherein they present as a trio of distinctive features: a diagonal-sequence, diagonal-couplet gait pattern; a protracted arm at forelimb touchdown; and a hindlimb-biased weight support pattern. The same locomotor characteristics have been found in the woolly opossum, a fine-branch arborealist similar in ecology to some small-bodied primates. To further our understanding of the functional link between arboreality and primate-like locomotion, we present comparative data collected in the laboratory for three musteloid taxa. Musteloidea represents an ecologically diverse superfamily spanning numerous locomotor specializations that includes the highly arboreal kinkajou (Potos flavus), mixed arboreal/terrestrial red pandas (Ailurus fulgens) and primarily terrestrial coatis (Nasua narica). This study applies a combined kinetic and kinematic approach to compare the locomotor behaviors of these three musteloid taxa, representing varying degrees of arboreal specialization. We observed highly arboreal kinkajous to share many locomotor traits with primates. In contrast, red pandas (mixed terrestrial/arborealist) showed gait characteristics found in most non-primate mammals. Coatis, however, demonstrated a unique combination of locomotor traits, combining a lateral-sequence, lateral-couplet gait pattern typical of long-legged, highly terrestrial mammals, varying degrees of arm protraction, and a hindlimb-biased weight support pattern typical of most primates and woolly opossums. We conclude that the three gait characteristics traditionally used to describe arboreal walking in primates can occur independently from one another and not necessarily as a suite of interdependent characteristics, a phenomenon that has been reported for some primates.

Flying snakes (genus Chrysopelea) glide without the use of wings. Instead, they splay their ribs and undulate through the air. A snake's ability to glide depends on how well its morphing wing-body produces lift and drag forces. However, previous kinematics experiments under-resolved the body, making it impossible to estimate the aerodynamic load on the animal or to quantify the different wing configurations throughout the glide. Here, we present new kinematic analyses of a previous glide experiment, and use the results to test a theoretical model of flying snake aerodynamics using previously measured lift and drag coefficients to estimate the aerodynamic forces. This analysis is enabled by new measurements of the center of mass motion based on experimental data. We found that quasi-steady aerodynamic theory under-predicts lift by 35% and over-predicts drag by 40%. We also quantified the relative spacing of the body as the snake translates through the air. In steep glides, the body is generally not positioned to experience tandem effects from wake interaction during the glide. These results suggest that unsteady 3D effects, with appreciable force enhancement, are important for snake flight. Future work can use the kinematics data presented herein to form test conditions for physical modeling, as well as computational studies to understand unsteady fluid dynamics effects on snake flight.

This study investigates how hibernation affects the surface activity of pulmonary surfactant with respect to temperature and breathing pattern. Surfactant was isolated from a hibernating species, the 13-lined ground squirrel, and a homeotherm, the rabbit, and analysed for biophysical properties on a constrained sessile drop surfactometer. The results showed that surfactant from ground squirrels reduced surface tension better at low temperatures, including when mimicking episodic breathing, as compared with rabbit surfactant. In addition, low temperature adaptation was also observed using only the hydrophobic components of surfactant from ground squirrels. Overall, the data support the conclusion that ground squirrel surfactant has adapted to maintain surface activity during low temperature episodic breathing patterns, and that temperature adaptation is maintained with the hydrophobic components of the surfactant.