nils-herrmann/clean_scirepeval huggingface dataset:
Molecular characterization and distribution of the voltage-gated sodium channel, Para, in the brain of the grasshopper and vinegar fly
Venue: Journal of Comparative Physiology A

Voltage-gated sodium (NaV) channels, encoded by the gene para , play a critical role in the rapid processing and propagation of visual information related to collision avoidance behaviors. We investigated their localization by immunostaining the optic lobes and central brain of the grasshopper Schistocerca americana and the vinegar fly Drosophila melanogaster with an antibody that recognizes the channel peptide domain responsible for fast inactivation gating. NaV channels were detected at high density at all stages of development. In the optic lobe, they revealed stereotypically repeating fascicles consistent with the regular structure of the eye. In the central brain, major axonal tracts were strongly labeled, particularly in the grasshopper olfactory system. We used the NaV channel sequence of Drosophila to identify an ortholog in the transcriptome of Schistocerca . The grasshopper, vinegar fly, and human NaV channels exhibit a high degree of conservation at gating and ion selectivity domains. Comparison with three species evolutionarily close to Schistocerca identified splice variants of Para and their relation to those of Drosophila . The anatomical distribution of NaV channels molecularly analogous to those of humans in grasshoppers and vinegar flies provides a substrate for rapid signal propagation and visual processing in the context of visually-guided collision avoidance.
Calcium homeostasis during hibernation and in mechanical environments disrupting calcium homeostasis
Venue: Journal of Comparative Physiology B

To maintain calcium homeostasis during physical inactivity, precise coordination is necessary between different organs of the body. There are a number of factors which alter an organism’s calcium balance, such as growth, aging, physical inactivity and acquired or inherited disorders which ultimately lead to bone loss. In non-hibernating mammals, physical inactivity causes bone loss which may not be completely recoverable during the lifespan of an individual despite a resumption of activity. Extreme physical inactivity and nutritional deprivation are two other important factors that lead to bone loss in non-hibernating mammals. The mechanism of bone loss is still poorly understood, however, there is some evidence which shows that during hibernation, smaller mammals (ground squirrels, bats, and hamsters) undergo bone loss. While on the other hand, hibernating bears do not show any sign of bone loss and retain their bone structure and strength. This may be due to differences in their hibernation patterns, as smaller mammals may excrete calcium throughout the hibernation period, which ultimately leads to bone loss, whereas bears seem to have a more developed and advanced mechanism to prevent calcium loss and maintain their bone structure. In this review, we summarize calcium homeostasis and its adaptive mechanisms with reference to bone loss in hibernating as compared to non-hibernating mammals. We also review the effect of microgravity and simulated microgravity on bone physiology and subsequent adaptation.
Osmoregulation and electrolyte balance in a fully marine mammal, the dugong (Dugong dugon)
Venue: Journal of Comparative Physiology B

Dugongs ( Dugong dugon ) are fully marine mammals that live independently of fresh water so must balance water and electrolytes in a hyperosmotic environment. To investigate osmoregulation, matched plasma and urine from 51 live wild dugongs were analysed for osmolality, major electrolytes (Na + , Cl − , K + ), urea, creatinine, and glucose. Maximum urine osmolality (1468 mOsm kg –1 ) and Na + , K + , and Cl – concentrations (757, 131.3, 677 mmol L –1 , respectively) indicate that dugongs are capable of concentrating urine above seawater and could potentially realise a net gain of free water from drinking seawater. However, mean urine osmolality of 925.4 (± 46.6) mOsm kg –1 suggests that mariposia is unlikely to be an important osmoregulatory mechanism. Dugongs may obtain enough preformed water from their seagrass diet and metabolic oxidation to maintain homeostasis. Mean plasma osmolality of 339.6 (± 1.8) mOsm kg –1 is higher than in the related manatees but within the range for fully marine cetaceans. Relatively high mean plasma Na + (175.5 ± 1.7 mmol L –1 ) and K + (6.9 ± 0.1 mmol L –1 ), as well as mean urinary Na + (469.6 ± 22.5 mmol L –1 ) and K + levels (32.5 ± 4.5 mmol L –1 ) may reflect a salt-rich seagrass diet. Pregnant females had higher mean plasma osmolality (355.3 ± 4.9 mmol L –1 ) than non-pregnant females and males (337.9 ± 1.7 mOsm kg –1 ), suggesting that fluid retention was not a feature of pregnancy. Further research on water intake and endocrinology will enhance our understanding of osmoregulation in dugongs.
Functional and structural changes in aorta of mice divergently selected for basal metabolic rate
Venue: Journal of Comparative Physiology B

Cardiovascular diseases (CVD) are one of the most common causes of mortality likely genetically linked to the variation in basal metabolic rate (BMR). A robust test of the significance of such association may be provided by artificial selection experiments on animals selected for diversification of BMR. Here we asked whether genetically determined differences in BMR correlate with anatomical shift in endothelium structure and if so, the relaxation and contraction responses of the aorta in mice from two lines of Swiss-Webster laboratory mice ( Mus musculus ) divergently selected for high or low BMR (HBMR and LBMR lines, respectively). Functional and structural study of aorta showed that a selection for divergent BMR resulted in the between-line difference in diastolic aortic capacity. The relaxation was stronger in aorta of the HBMR mice, which may stem from greater flexibility of aorta mediated by higher activity of Ca 2+ -activated K + channels. Structural examination also indicated that HBMR mice had significantly thicker aorta's middle layer compared to LBMR animals. Such changes may promote arterial stiffness predisposing to cardiovascular diseases. BMR-related differences in the structure and relaxation ability of aortas in studied animals may be reminiscent of potential risk factors in the development of CVD in humans.
A comparison of uterine contractile responsiveness to arginine vasopressin in oviparous and viviparous lizards
Venue: Journal of Comparative Physiology B

Nonapeptides and their receptors regulate a diverse range of physiological processes. We assessed the contractile responsiveness of uteri from the squamate viviparous-oviparous species pair, Pseudemoia entrecasteauxii and Lampropholis guichenoti , as well as the bimodally reproductive species, Saiphos equalis , to arginine vasopressin (AVP). We assessed the resulting uterine contractility as a function of pregnancy status, species and parity mode. We also measured mRNA abundance for the nonapeptide receptor, oxytocin receptor ( oxtr ), in uteri from P. entrecasteauxii and L. guichenoti and compared expression across pregnancy status and parity mode. We found that pregnant uteri exhibited a significantly greater contractile response to AVP than non-pregnant uteri in all three lizard species studied. Cross-species comparisons revealed that uteri from viviparous P. entrecasteauxii were significantly more responsive to AVP than uteri from oviparous L. guichenoti during both pregnant and non-pregnant states. Conversely, for non-pregnant S. equalis , uteri from viviparous individuals were significantly less responsive to AVP than uteri from oviparous individuals, while during pregnancy, there was no difference in AVP contractile responsiveness. There was no difference in expression of oxtr between L. guichenoti and P. entrecasteauxii , or between pregnant and non-pregnant individuals within each species. We found no significant correlation between oxtr expression and AVP contractile responsiveness. These findings indicate that there are differences in nonapeptide signalling across parity mode and suggest that in these lizards, labour may be triggered either by an increase in plasma nonapeptide concentration, or by an increase in expression of a different nonapeptide receptor from the vasopressin-like receptor family.
Lipid and protein catabolism contribute to aerobic metabolic responses to exhaustive exercise during the protracted spawning run of the lamprey Geotria australis
Venue: Journal of Comparative Physiology B

This paper has integrated new and past data to elucidate how lipid, protein and glycogen metabolism contribute to generating the ATP required by the southern hemisphere lamprey Geotria australis during its ~ 13–15 months, non-trophic upstream spawning migration. Energy is required for maintenance, swimming, the development of gonads and secondary sexual characters and spawning and post-spawning activities. Plasma and muscle metabolites were measured in animals subjected to an exercise-recovery regime at the commencement and completion of the spawning run. The present study demonstrated the following. At all stages of the migration, plasma glucose and glycerol concentrations increased during exercise and then declined, whereas plasma FFAs exhibited the reverse trend. During exercise and recovery, alanine declined and ammonia increased in the plasma of early migrants, while the opposite occurred in mature males. Following exercise, muscle alanine rose and then declined in early migrants, but declined and then rose in mature males. The composite data emphasise that, while the same catabolic processes are employed by both sexes early in the migration, when animals are immature, they differ markedly between the sexes as they mature and then spawn, reflecting their different demands. Energy is supplied predominantly via anaerobic metabolism in early migrants, but by anaerobic and aerobic metabolism in prespawning females and by aerobic metabolism in mature males and spent females. Although proteolysis is limited early in the migration, it is employed extensively during maturation and particularly by females, which undergo a substantial reduction in length in the lead-up to spawning.
Electrophysiological adaptations of insect photoreceptors and their elementary responses to diurnal and nocturnal lifestyles
Venue: Journal of Comparative Physiology A

Nocturnal vision in insects depends on the ability to reliably detect scarce photons. Nocturnal insects tend to have intrinsically more sensitive and larger rhabdomeres than diurnal species. However, large rhabdomeres have relatively high membrane capacitance ( C m ), which can strongly low-pass filter the voltage bumps, widening and attenuating them. To investigate the evolution of photoreceptor signaling under near dark, we recorded elementary current and voltage responses from a number of species in six insect orders. We found that the gain of phototransduction increased with C m , so that nocturnal species had relatively large and prolonged current bumps. Consequently, although the voltage bump amplitude correlated negatively with C m , the strength of the total voltage signal increased. Importantly, the background voltage noise decreased strongly with increasing C m , yielding a notable increase in signal-to-noise ratio for voltage bumps. A similar decrease in the background noise with increasing C m was found in intracellular recordings in vivo. Morphological measurements of rhabdomeres were consistent with our C m estimates. Our results indicate that the increased photoreceptor C m in nocturnal insects is a major sensitivity-boosting and noise-suppressing adaptation. However, by requiring a compensatory increase in the gain of phototransduction, this adaptation comes at the expense of the signaling bandwidth.
Auditory brainstem responses in the bat Carollia perspicillata: threshold calculation and relation to audiograms based on otoacoustic emission measurement
Venue: Journal of Comparative Physiology A

An objective method to evaluate auditory brainstem-evoked responses (ABR) based on the root-mean-square (rms) amplitude of the measured signal and bootstrapping procedures was used to determine threshold curves (see Lv et al.  Eng Phys 29:191–198, 2007; Linnenschmidt and Wiegrebe  2019). The rms values and their significance for threshold determination depended strongly on the filtering of the signal. Using the minimum threshold values obtained at three different low-frequency filter corner frequencies (30, 100, 300 Hz), ABR threshold curves were calculated. The course of the ABR thresholds was comparable to that of published DPOAE (distortion-product otoacoustic emission) thresholds based on a − 10 dB SPL threshold criterion for the 2f1–f2 emission (Schlenther et al.  2014, frequency range 10–90 kHz). For frequencies between 20 and 80 kHz, which is the most sensitive part of the bat’s audiogram, median thresholds ranged between 10 and 28 dB SPL, and the DPOAE thresholds ranged between 10 and 23 dB SPL. At frequencies below 20 kHz (5–20 kHz) and above 80 kHz (80–120 kHz), ABR thresholds increased by 20 dB/octave and 45 dB/octave, respectively. We conclude that the combination of objective threshold determination and multiple filtering of the signal gives reliable ABR thresholds comparable to cochlear threshold curves.
A characterization of the electrophysiological properties of the cardiomyocytes from ventricle, atrium and sinus venosus of the snake heart
Venue: Journal of Comparative Physiology B

A detailed description of the electrophysiological features of cardiomyocytes in the various contractile chambers of the vertebrate heart is essential to understand the evolution of cardiac electrical activity, yet very little is known about reptiles. The present study characterizes major ionic currents (I Na , I CaL , I Kr , I K1 and I KACh ) and action potential (AP) configuration in cardiomyocytes from the ventricle, the right atrium and the sinus venosus (SV) of Burmese pythons ( Python molurus ) using sharp microelectrode and patch clamp recordings. Special attention was given to SV, since it consists of myocardial cells and appears to contribute to right atrial filling in snakes. We demonstrate that most of the SV in pythons has a stable resting potential of − 82.3 ± 2.6 mV ( n  = 9) and lacks pacemaker activity. AP duration at 50% repolarization was similar in cells from SV and atria (350.2 ± 8.7 and 330.4 ± 17.2 ms, respectively; n  = 7), but shorter than ventricular APs (557.6 ± 19.2 ms, n  = 5) at 30 °C. The densities of ionic currents, however, differed substantially between atrial and SV cells, where the latter had much lower densities of I Na , I CaL and I Kr than atrial and ventricular myocytes. I K1 in ventricle was ninefold greater than in atrial cells and 23-fold greater than in myocytes from SV. However, I KACh was absent in ventricular cells, while it was equally large in atrial and SV myocytes. Consistent with this observation, APs of atrium and SV, but not ventricle, were greatly shortened upon addition of acetylcholine (10 −6  M). Thus, snake SV, right atrium and ventricle have distinct patterns of ionic currents, but the resulting electrical activity is similar in atrium and SV.
Chromatic information processing in the first optic ganglion of the butterfly Papilio xuthus
Venue: Journal of Comparative Physiology A

The butterfly Papilio xuthus has acute tetrachromatic color vision. Its eyes are furnished with eight spectral classes of photoreceptors, situated in three types of ommatidia, randomly distributed in the retinal mosaic. Here, we investigated early chromatic information processing by recording spectral, angular, and polarization sensitivities of photoreceptors and lamina monopolar cells (LMCs). We identified three spectral classes of LMCs whose spectral sensitivities corresponded to weighted linear sums of the spectral sensitivities of the photoreceptors present in the three ommatidial types. In ~ 25% of the photoreceptor axons, the spectral sensitivities differed from those recorded at the photoreceptor cell bodies. These axons showed spectral opponency, most likely mediated by chloride ion currents through histaminergic interphotoreceptor synapses. The opponency was most prominent in the processes of the long visual fibers in the medulla. We recalculated the wavelength discrimination function using the noise-limited opponency model to reflect the new spectral sensitivity data and found that it matched well with the behaviorally determined function. Our results reveal opponency at the first stage of Papilio’s visual system, indicating that spectral information is preprocessed with signals from photoreceptors within each ommatidium in the lamina, before being conveyed downstream by the long visual fibers and the LMCs.
Ultradian oscillations in brain temperature in sheep: implications for thermoregulatory control?
Venue: Journal of Comparative Physiology B

We compared body temperature patterns and selective brain cooling (SBC) in eight adult female sheep in an indoor (22–25 °C) and outdoor (mean ~ 21 °C) environment, by measuring brain, carotid arterial, and jugular venous blood temperatures at 5-min intervals using implanted data loggers. To investigate whether ultradian oscillations in brain temperature had thermoregulatory consequences for the sheep, we determined the cranial arterio-venous (AV) temperature difference as an indicator of respiratory evaporative heat loss (REHL). The 24-h pattern of SBC was similar in both environments, despite carotid blood temperature fluctuating 0.4 °C more outdoors compared to indoors. The sheep employed SBC more often during the night than during the day, but SBC was abolished at intervals of 1–3 h throughout the 24-h period. The suppression of SBC appeared to be associated with events that increased sympathetic nervous system activity, including shifts between stages of sleep. Short-term changes (over 5-min) in brain temperature were positively correlated with changes in the AV temperature difference 5 min later, and negatively correlated with changes in carotid temperature 10 min later. These data support the idea that increases in brain temperature modulate thermoregulation by increasing REHL, which leads to a decrease in carotid blood temperature. Ultradian oscillations in core temperature of sheep, therefore, appear to arise as a consequence of frequent brain temperature changes invoked by non-thermal inputs, in animals housed both in indoor and outdoor environments.
Spectral response properties of higher visual neurons in Drosophila melanogaster
Venue: Journal of Comparative Physiology A

The fruit fly Drosophila melanogaster can process chromatic information for true color vision and spectral preference. Spectral information is initially detected by a few distinct photoreceptor channels with different spectral sensitivities and is processed through the visual circuit. The neuroanatomical bases of the circuit are emerging. However, only little information is available in chromatic response properties of higher visual neurons from this important model organism. We used in vivo whole-cell patch-clamp recordings in response to monochromatic light stimuli ranging from 300 to 650 nm with 25-nm steps. We characterized the chromatic response of 33 higher visual neurons, including their general response type and their wavelength tuning. Color-opponent-type responses that had been typically observed in primates and bees were not identified. Instead, the majority of neurons showed excitatory responses to broadband wavelengths. The UV (300–375 nm) and middle wavelength (425–575 nm) ranges could be separated at the population level owing to neurons that preferentially responded to a specific wavelength range. Our results provide a first mapping of chromatic information processing in higher visual neurons of D. melanogaster that is a suitable model for exploring how color-opponent neural mechanisms are implemented in the visual circuits.
Distinct expression of potassium channels regulates visual response properties of lamina neurons in Drosophila melanogaster
Venue: Journal of Comparative Physiology A

The computational organization of sensory systems depends on the diversification of individual cell types with distinct signal-processing capabilities. The Drosophila visual system, for instance, splits information into channels with different temporal properties directly downstream of photoreceptors in the first-order interneurons of the OFF pathway, L2 and L3. However, the biophysical mechanisms that determine this specialization are largely unknown. Here, we show that the voltage-gated Ka channels Shaker and Shal contribute to the response properties of the major OFF pathway input L2. L3 calcium response kinetics postsynaptic to photoreceptors resemble the sustained calcium signals of photoreceptors, whereas L2 neurons decay transiently. Based on a cell-type-specific RNA-seq data set and endogenous protein tagging, we identified Shaker and Shal as the primary candidates to shape L2 responses. Using in vivo two-photon imaging of L2 calcium signals in combination with pharmacological and genetic perturbations of these Ka channels, we show that the wild-type Shaker and Shal function is to enhance L2 responses and cell-autonomously sharpen L2 kinetics. Our results reveal a role for Ka channels in determining the signal-processing characteristics of a specific cell type in the visual system.
The effect of biological and anthropogenic sound on the auditory sensitivity of oyster toadfish, Opsanus tau
Venue: Journal of Comparative Physiology A

Many aquatic organisms use vocalizations for reproductive behavior; therefore, disruption of their soundscape could adversely affect their life history. Male oyster toadfish (Opsanus tau) establish nests in shallow waters during spring and attract female fish with boatwhistle vocalizations. Males exhibit high nest fidelity, making them susceptible to anthropogenic sound in coastal waters, which could mask their vocalizations and/or reduce auditory sensitivity levels. Additionally, the effect of self-generated boatwhistles on toadfish auditory sensitivity has yet to be addressed. To investigate the effect of sound exposure on toadfish auditory sensitivity, sound pressure and particle acceleration sensitivity curves were determined using auditory evoked potentials before and after (0-, 1-, 3-, 6- and 9-day) exposure to 1- or 12-h of continuous playbacks to ship engine sound or conspecific vocalization. Exposure to boatwhistles had no effect on auditory sensitivity. However, exposure to anthropogenic sound caused significant decreases in auditory sensitivity for at least 3 days, with shifts up to 8 dB SPL and 20 dB SPL immediately following 1- and 12-h anthropogenic exposure, respectively. Understanding the effect of self-generated and anthropogenic sound exposure on auditory sensitivity provides an insight into how soundscapes affect acoustic communication.