nils-herrmann/clean_scirepeval huggingface dataset:
Effects of acetylcholinesterase inhibitor paraoxon denote the possibility of non-quantal acetylcholine release in myocardium of different vertebrates
Venue: Journal of Comparative Physiology B

Effects of organophosphorous acetylcholinesterase inhibitor paraoxon were studied in the isolated atrial and ventricular myocardium preparations of a fish (cod), an amphibian (frog) and a mammal (rat) using the microelectrode technique. Incubation of isolated atrium with paraoxon (5 × 10−6–5 × 10−5 M) caused significant reduction of action potential duration and marked slowing of sinus rhythm. These effects were abolished by muscarinic blocker atropine and therefore are caused by acetylcholine, which accumulates in the myocardium due to acetylcholinesterase inhibition even in the absence of vagal input. Hemicholinium III is a blocker of high affinity choline-uptake transporters, which are believed to mediate non-quantal release of acetylcholine from cholinergic terminals in different tissues. In the atrial myocardium of all the three studied species, hemicholinium III (10−5 M) significantly suppressed all the effects of paraoxon. Blocker of parasympathetic ganglionic transmission hexamethonium bromide (10−4 M) and inhibitor of vesicular acetylcholine transporters vesamicol (10−5 M) failed to attenuate paraoxon effects. Among ventricular myocardium preparations of three species paraoxon provoked marked cholinergic effects only in frog, hemicholinium III abolished these effects effectively. We conclude that paraoxon stops degradation of acetylcholine in the myocardium and helps to reveal the effects of acetylcholine, which is continuously secreted from the cholinergic nerves in non-quantal manner. Thus, non-quantal release of acetylcholine in the heart is not specific only for mammals, but is also present in the hearts of different vertebrates.
A radical approach to beating hypoxia: depressed free radical release from heart fibres of the hypoxia-tolerant epaulette shark (Hemiscyllum ocellatum)
Venue: Journal of Comparative Physiology B

Hypoxia and warm ischemia are primary concerns in ischemic heart disease and transplant and trauma. Hypoxia impacts tissue ATP supply and can induce mitochondrial dysfunction that elevates reactive species release. The epaulette shark, Hemiscyllum ocellatum, is remarkably tolerant of severe hypoxia at temperatures up to 34°C, and therefore provides a valuable model to study warm hypoxia tolerance. Mitochondrial function was tested in saponin permeabilised ventricle fibres using high-resolution respirometry coupled with purpose-built fluorospectrometers. Ventricular mitochondrial function, stability and reactive species production of the epaulette shark was compared with that of the hypoxia-sensitive shovelnose ray, Aptychotrema rostrata. Fibres were prepared from each species acclimated to normoxic water conditions, or following a 2 h, acute hypoxic exposure at levels representing 40% of each species’ critical oxygen tension. Although mitochondrial respiratory fluxes for normoxia-acclimated animals were similar for both species, reactive species production in the epaulette shark was approximately half that of the shovelnose ray under normoxic conditions, even when normalised to tissue oxidative phosphorylation flux. The hypoxia-sensitive shovelnose ray halved oxidative phosphorylation flux and cytochrome c oxidase flux was depressed by 34% following hypoxic stress. In contrast, oxidative phosphorylation flux of the epaulette shark ventricular fibres isolated from acute hypoxia exposed the animals remained similar to those from normoxia-acclimated animals. However, uncoupling of respiration revealed depressed electron transport systems in both species following hypoxia exposure. Overall, the epaulette shark ventricular mitochondria showed greater oxidative phosphorylation stability and lower reactive species outputs with hypoxic exposure, and this may protect cardiac bioenergetic function in hypoxic tropical waters.
Large odorous frogs (Odorrana graminea) produce ultrasonic calls
Venue: Journal of Comparative Physiology A

We present the first data on the vocalizations of large odorous frogs (Odorranagraminea, previously Odorrana livida), from southern China. The males produce diverse broadband signals most of which contain ultrasonic harmonics. Six basic call-types were identified based on the number of call notes, fundamental frequency, call/note duration, frequency modulation patterns and spectral composition. O. graminea is one of only a few non-mammalian vertebrates able to detect ultrasound, but its tympanic membranes are not recessed. These results should stimulate further studies to provide new insights into the mechanisms underlying high-frequency communication in anurans.
Spatial reflection patterns of iridescent wings of male pierid butterflies: curved scales reflect at a wider angle than flat scales
Venue: Journal of Comparative Physiology A

The males of many pierid butterflies have iridescent wings, which presumably function in intraspecific communication. The iridescence is due to nanostructured ridges of the cover scales. We have studied the iridescence in the males of a few members of Coliadinae, Gonepteryx aspasia, G. cleopatra, G. rhamni, and Colias croceus, and in two members of the Colotis group, Hebomoia glaucippe and Colotis regina. Imaging scatterometry demonstrated that the pigmentary colouration is diffuse whereas the structural colouration creates a directional, line-shaped far-field radiation pattern. Angle-dependent reflectance measurements demonstrated that the directional iridescence distinctly varies among closely related species. The species-dependent scale curvature determines the spatial properties of the wing iridescence. Narrow beam illumination of flat scales results in a narrow far-field iridescence pattern, but curved scales produce broadened patterns. The restricted spatial visibility of iridescence presumably plays a role in intraspecific signalling.
The scotopic electroretinogram of the sugar glider related to histological features of its retina
Venue: Journal of Comparative Physiology A

The flash electroretinogram (ERG) was used to characterize the scotopic retinal function in a marsupial. Key parameter values of the a- and b-waves of adult male sugar gliders, Petaurus breviceps breviceps, elicited with ganzfeld flashes were determined under dark- and light-adapted conditions. Using standard histological methods, the thicknesses of the major layers of the retina were assessed to provide insight into the nature of the ERG responses. The ERG and histological results were compared to corresponding data for placental C57Bl/6 mice to establish whether the functional retinal specialization that underlies scotopic visual function in a marsupial parallels that of a placental mouse. The sensitivity of the a-wave assessed with the Lamb and Pugh (Invest Ophthalmol Vis Sci 47:5138–5152, 2006) “model” and that of the b-wave assessed with standard methods were lower in the sugar glider compared to the mouse. The thickness of the sugar glider retina was two-third of that of the mouse. The high-intensity flash ERG of the sugar glider substantially differed in shape from that of the mouse reflecting perhaps structural and functional differences between the two species at the level of the inner retina.
Responses of round goby (Neogobius melanostomus) olfactory epithelium to steroids released by reproductive males
Venue: Journal of Comparative Physiology A

The wild perciform teleost Neogobius melanostomus (the round goby) originated from the Ponto-Caspian region and is now a highly successful invasive species in the Laurentian Great Lakes. Males may attract females into their nests for spawning by releasing reproductive pheromones, and it has been previously shown that reproductive males synthesize and release the 5β-reduced and 3α-hydroxyl steroids 3α-hydroxy-5β-androstane-11,17-dione (11-oxo-etiocholanolone; 11-O-ETIO) and 3α-hydroxy-5β-androstane-11,17-dione 3-sulfate (11-oxo-etiocholanolone-3-sulfate; 11-O-ETIO-3-s) and 3α,17β-dihydroxy-5β-androstan-11-one 17-sulfate. In this study, we investigated properties of these released steroids by recording field potential responses from the olfactory epithelium (electro-olfactogram, EOG). The steroid 3α,17β-dihydroxy-5β-androstan-11-one 17-sulfate did not elicit olfactory responses while both 11-O-ETIO and 11-O-ETIO-3-s stimulated olfactory field potentials in the round goby, but not in the goldfish. Cross-adaptation analysis demonstrated that round gobies discriminated between11-O-ETIO and 11-O-ETIO-3-s (as well as etiocholanolone, ETIO) at the sensory level. Second messenger cascades depending on both cAMP and IP3 were inferred for steroids from pharmacological inhibition studies, while the canonical teleost odors taurocholic acid (a bile acid) and l-alanine (an amino acid) used only cAMP and IP3, respectively. The round goby presents itself as an excellent species for the study of olfactory function of fish in the wild, given its possible use of these released steroids as pheromones.
Body condition, hormonal correlates and consequences for survival in common tern chicks
Venue: Journal of Comparative Physiology A

Although sibling competition in avian species has been extensively studied, the proximate mechanisms remain largely unknown. Recent research proposed that steroid hormones, in particular testosterone (T) and corticosterone (CORT), might play a role either in promoting competitive behavioral displays or in response to chronic nutritional stress accompanied by a sustained competitive situation. Here, we examine body condition, endogenous T levels and fecal glucocorticoid metabolites (FGM) as non-invasive measures of CORT in sibling broods of wild common tern chicks (Sterna hirundo) during three post-natal developmental stages. In this species, distinct within-brood size asymmetries are imposed by an asynchronous hatching interval, and sexes show slightly different growth patterns. First-hatched (a-)chicks were in better condition than their later-hatched sibling (b-chick). FGM levels inversely covaried with condition and were elevated at the end of pre-fledging development. T levels of a- and b-chicks changed with age, although the direction of the changes differed, with b-chicks eventually having higher levels than their older siblings. Survival to fledging was not associated with FGM but with T levels, which tended to be higher in surviving chicks. Our results are discussed with regard to how plasticity in steroid hormones could be involved in mediating sibling competition in common terns.
From optics to attention: visual perception in barn owls
Venue: Journal of Comparative Physiology A

Barn owls are nocturnal predators which have evolved specific sensory and morphological adaptations to a life in dim light. Here, some of the most fundamental properties of spatial vision in barn owls are reviewed. The eye with its tubular shape is rigidly integrated in the skull so that eye movements are very much restricted. The eyes are oriented frontally, allowing for a large binocular overlap. Accommodation, but not pupil dilation, is coupled between the two eyes. The retina is rod dominated and lacks a visible fovea. Retinal ganglion cells form a marked region of highest density that extends to a horizontally oriented visual streak. Behavioural visual acuity and contrast sensitivity are poor, although the optical quality of the ocular media is excellent. A low f-number allows high image quality at low light levels. Vernier acuity was found to be a hyperacute percept. Owls have global stereopsis with hyperacute stereo acuity thresholds. Neurons of the visual Wulst are sensitive to binocular disparities. Orientation based saliency was demonstrated in a visual-search experiment, and higher cognitive abilities were shown when the owl’s were able to use illusory contours for object discrimination.
Physiological and molecular endocrine changes in maturing wild sockeye salmon, Oncorhynchus nerka, during ocean and river migration
Venue: Journal of Comparative Physiology B

Maturing adult sockeye salmon Oncorhynchus nerka were intercepted while migrating in the ocean and upstream in freshwater over a combined distance of more than 1,300 km to determine physiological and endocrine changes associated with ionoregulation. Sockeye migrating through seawater and freshwater showed consistent declines in gill Na+/K+-ATPase (NKA) activity, plasma osmolality and plasma chloride concentration. In contrast, plasma sodium concentration became elevated in seawater as fish approached the river mouth and was then restored after sockeye entered the river. Accompanying the movement from seawater to freshwater was a significant increase in mRNA for the NKA α1a subunit in the gill, with little change in the α1b subunit. Potential endocrine signals stimulating the physiological changes during migration were assessed by measuring plasma cortisol and prolactin (Prl) concentrations and quantifying mRNA extracted from the gill for glucocorticoid receptors 1 and 2 (GR1 and GR2), mineralocorticoid receptor (MR), growth hormone 1 receptor (GH1R), and prolactin receptor (PrlR). Plasma cortisol and prolactin concentrations were high in seawater suggesting a preparatory endocrine signal before freshwater entry. Generally, the mRNA expression for GR1, GR2 and MR declined during migration, most notably after fish entered freshwater. In contrast, PrlR mRNA increased throughout migration, particularly as sockeye approached the spawning grounds. A highly significant association existed between gill PrlR mRNA and gill NKA α1a mRNA. GH1R mRNA also increased significantly, but only after sockeye had migrated beyond tidal influence in the river and then again just before the fish reached the spawning grounds. These findings suggest that cortisol and prolactin stimulate ionoregulation in the gill as sockeye salmon adapt to freshwater.
Osmoregulation and epithelial water transport: lessons from the intestine of marine teleost fish
Venue: Journal of Comparative Physiology B

For teleost fish living in seawater, drinking the surrounding medium is necessary to avoid dehydration. This is a key component of their osmoregulatory strategy presenting the challenge of excreting excess salts while achieving a net retention of water. The intestine has an established role in osmoregulation, and its ability to effectively absorb fluid is crucial to compensating for water losses to the hyperosmotic environment. Despite this, the potential for the teleost intestine to serve as a comparative model for detailed, integrative experimental studies on epithelial water transport has so far gone largely untapped. The following review aims to present an assessment of the teleost intestine as a fluid-transporting epithelium. Beginning with a brief overview of marine teleost osmoregulation, emphasis shifts to the processing of ingested seawater by the gastrointestinal tract and the characteristics of intestinal ion and fluid transport. Particular attention is given to acid–base transfers by the intestine, specifically bicarbonate secretion, which creates the distinctly alkaline gut fluids responsible for the formation of solid calcium carbonate precipitates. The respective contributions of these unique features to intestinal fluid absorption, alongside other recognised ion transport processes, are then subsequently considered within the wider context of the classic physiological problem of epithelial water transport.
Responses to magnetic stimuli recorded in peripheral nerves in the marine nudibranch mollusk Tritonia diomedea
Venue: Journal of Comparative Physiology A

Prior behavioral and neurophysiological studies provide evidence that the nudibranch mollusk Tritonia orients to the earth’s magnetic field. Earlier studies of electrophysiological responses in certain neurons of the brain to changing ambient magnetic fields suggest that although certain identified brain cells fire impulses when the ambient field is changed, these neuron somata and their central dentritic and axonal processes are themselves not primary magnetic receptors. Here, using semi-intact animal preparations from which the brain was removed, we recorded from peripheral nerve trunks. Using techniques to count spikes in individual nerves and separately also to identify, then count individual axonal spikes in extracellular records, we found both excitatory and inhibitory axonal responses elicited by changes in the direction of ambient earth strength magnetic fields. We found responses in nerves from many locations throughout the body and in axons innervating the body wall and rhinophores. Our results indicate that primary receptors for geomagnetism in Tritonia are not focally concentrated in any particular organ, but appear to be widely dispersed in the peripheral body tissues.
Comparative patterns of adrenal activity in captive and wild Canada lynx (Lynx canadensis)
Venue: Journal of Comparative Physiology B

Stress and animal well-being are often assessed using concentrations of glucocorticoids (GCs), a product of the hypothalamic–pituitary–adrenal axis. However, GC concentrations can also be modulated by predictable events, such as changes in season or life history stage. Understanding normative patterns of adrenal activity is critical for making valid conclusions about changes in GC concentrations. In this study, we validated an assay for monitoring fecal glucocorticoid metabolites (FGM) in Canada lynx. We then used this technique to assess patterns of adrenal activity in Canada lynx across several contexts. Our results show that captive lynx have higher FGM concentrations than wild lynx, which may be related to differences in stress levels, metabolic rate, diet, or body condition. We also found that FGM concentrations are correlated with reproductive status in females, but not in males. For males, seasonal increases in FGM expression coincide with the onset of the breeding season, whereas in females, FGM increase toward the end of the breeding season. This information provides a valuable foundation for making inferences about normative versus stress-induced changes in adrenal activity in Canada lynx.
Does habitat fragmentation cause stress in the agile antechinus? A haematological approach
Venue: Journal of Comparative Physiology B

Although the vertebrate stress response is essential for survival, frequent or prolonged stress responses can result in chronic physiological stress, which is associated with a suite of conditions that can impair survivorship and reproductive output. Anthropogenic habitat fragmentation and degradation are potential stressors of free-living vertebrates, and in theory could result in chronic stress. To address this issue, we compared haematological indicators of stress and condition in agile antechinus (Antechinus agilis) populations in 30 forest fragments and 30 undisturbed, continuous forest sites (pseudofragments) in south-eastern Australia over 2 years. In peripheral blood, the total leucocyte count was lower and the neutrophil/lymphocyte ratio and percentage of eosinophils in the total leucocyte population was higher in fragment than pseudofragment populations, indicating that fragment populations were probably experiencing higher levels of stress hormone-mediated and/or parasite infection-related chronic physiological stress. The total erythrocyte count and haematocrit were higher and mean erythrocyte haemoglobin content was lower in fragment than pseudofragment populations. This suggests that fragment populations showed possible signs of regenerative anaemia, a syndrome associated with elevated hypothalamus–pituitary–adrenal axis mediated stress. However, mean erythrocyte volume was also lower in fragments, and red blood cell distribution width did not differ between the study populations, findings which were not consistent with this diagnosis. Whole blood and mean cell haemoglobin concentrations were similar in fragment and pseudofragment populations. We suggest that where anthropogenic activity results in habitat fragmentation and degradation, chronic stress could contribute to a decline in agile antechinus populations. The broader implication is that chronic stress could be both symptomatic of, and contributing to, decline of some vertebrate populations in anthropogenically fragmented and degraded habitats.
Factors affecting plasticity in whole-organism thermal tolerance in common killifish (Fundulus heteroclitus)
Venue: Journal of Comparative Physiology B

We characterized the degree of plasticity in thermal tolerance (assessed as critical thermal maxima; CTMax) and the relationship between thermal tolerance and underlying physiological and biochemical factors in two subspecies of a teleost fish, Fundulus heteroclitus. CTMax was not affected by repeated daily heat shock, but increased within a few days in response to warm acclimation. Loss of tolerance with acclimation to lowered temperatures occurred more slowly. Exposure to hypoxia decreased CTMax, and hyperoxia had no effect. CTMax showed a daily rhythm in both subspecies. Thermal acclimation changed the value of CTMax but did not affect the amplitude of the rhythm. Exposure to altered photoperiod had complex effects with a summer photoperiod producing a daily rhythm at higher CTMax than a spring photoperiod, and a winter photoperiod removing the rhythm. There was no daily rhythm in routine metabolic rate in either subspecies. There was no relationship between CTMax and the protein levels of the constitutive 70 and 90 kDa heat shock proteins (HSC70, HSP90β) in gill, or with mRNA levels of hsc70 in liver. There was a daily rhythm in the basal levels of the inducible hsp70-2 mRNA. Induction of hsp70-2 mRNA with mild heat shock occurred only in the evening and at night, and not during the day. These results demonstrate that there is substantial plasticity of thermal tolerance in killifish, and that this plasticity does not differ between subspecies. CTMax has a complex relationship with physiological and biochemical mechanisms that have been hypothesized to affect thermal tolerance.
The metabolic effects of prolonged starvation and refeeding in sturgeon and rainbow trout
Venue: Journal of Comparative Physiology B

The present study examines the particular metabolic strategies of the sturgeon Acipenser naccarii in facing a period of prolonged starvation (72 days) and subsequent refeeding (60 days) compared to the trout Oncorhynchus mykiss response under similar conditions. Plasma metabolites, endogenous reserves, and the activity of intermediate enzymes in liver and white muscle were evaluated. This study shows the mobilization of tissue reserves during a starvation period in both species with an associated enzymatic response. The sturgeon displayed an early increase in hepatic glycolysis during starvation. The trout preferentially used lactate for gluconeogenesis in liver and white muscle. The sturgeon had higher lipid-degradation capacity and greater synthesis of hepatic ketone bodies than the trout, although this latter species also showed strong synthesis of ketone bodies during starvation. During refeeding, the metabolic activity present before starvation was recovered in both fish, with a reestablishment of tissue reserves, plasmatic parameters (glucemia and cholesterol), and enzymatic activities in the liver and muscle. A compensatory effect in enzymes regarding lipids, ketone bodies, and oxidative metabolism was displayed in the liver of both species. There are metabolic differences between sturgeon and trout that support the contention that the sturgeon has common characteristics with elasmobranchs and teleosts.