nils-herrmann/clean_scirepeval huggingface dataset:
Osmoregulatory bicarbonate secretion exploits H+-sensitive haemoglobins to autoregulate intestinal O2 delivery in euryhaline teleosts
Venue: Journal of Comparative Physiology B

AbstractMarine teleost fish secrete bicarbonate (HCO3−) into the intestine to aid osmoregulation and limit Ca2+ uptake by carbonate precipitation. Intestinal HCO3− secretion is associated with an equimolar transport of protons (H+) into the blood, both being proportional to environmental salinity. We hypothesized that the H+-sensitive haemoglobin (Hb) system of seawater teleosts could be exploited via the Bohr and/or Root effects (reduced Hb-O2 affinity and/or capacity with decreasing pH) to improve O2 delivery to intestinal cells during high metabolic demand associated with osmoregulation. To test this, we characterized H+ equilibria and gas exchange properties of European flounder (Platichthys flesus)
haemoglobin and constructed a model incorporating these values, intestinal blood flow rates and arterial–venous acidification at three different environmental salinities (33, 60 and 90). The model suggested red blood cell pH (pHi) during passage through intestinal capillaries could be reduced by 0.14–0.33 units (depending on external salinity) which is sufficient to activate the Bohr effect (Bohr coefficient of −0.63), and perhaps even the Root effect, and enhance tissue O2 delivery by up to 42 % without changing blood flow. In vivo measurements of intestinal venous blood pH were not possible in flounder but were in seawater-acclimated rainbow trout which confirmed a blood acidification of no less than 0.2 units (equivalent to −0.12 for pHi). When using trout-specific values for the model variables, predicted values were consistent with measured in vivo values, further supporting the
model. Thus this system is an elegant example of autoregulation: as the need for costly osmoregulatory processes (including HCO3− secretion) increases at higher environmental salinity, so does the enhancement of O2 delivery to the intestine via a localized acidosis and the Bohr (and possibly Root) effect.
Effects of reproductive status and high ambient temperatures on the body temperature of a free-ranging basoendotherm
Venue: Journal of Comparative Physiology B

Tenrecs (Order Afrosoricida) exhibit some of the lowest body temperatures (Tb) of any eutherian mammal. They also have a high level of variability in both active and resting Tbs and, at least in cool temperatures in captivity, frequently employ both short- and long-term torpor. The use of heterothermy by captive animals is, however, generally reduced during gestation and lactation. We present data long-term Tb recordings collected from free-ranging S. setosus over the course of two reproductive seasons. In general, reproductive females had slightly higher (~32 °C) and less variable Tb, whereas non-reproductive females and males showed both a higher propensity for torpor as well as lower (~30.5 °C) and more variable rest-phase Tbs. Torpor expression defined using traditional means (using a threshold or cut-off Tb) was much lower than predicted based on the high degree of heterothermy in captive tenrecs. However, torpor defined in this manner is likely to be underestimated in habitats where ambient temperature is close to Tb. Our results caution against inferring metabolic states from Tb alone and lend support to the recent call to define torpor in free-ranging animals based on mechanistic and not descriptive variables. In addition, lower variability in Tb observed during gestation and lactation confirms that homeothermy is essential for reproduction in this species and probably for basoendothermic mammals in general. The relatively low costs of maintaining homeothermy in a sub-tropical environment might help shed light on how homeothermy could have evolved incrementally from an ancestral heterothermic condition.
Behavioral and ecological factors account for variation in the mass-independent energy expenditures of endotherms
Venue: Journal of Comparative Physiology B

A persistent controversy has concerned the identification of the factors that influence the quantitative variation in the physiological characters of species, an example of which is the basal rate of metabolism of endotherms. The most important factor accounting for its variation is body mass as long as the range in mass is appreciable. But mass never accounts for all of the variation and none if species have the same mass. Most of the residual variation around the mass curve is associated with behavioral characters, ecological factors, and phylogeny, i.e., history. These agents influence energy expenditure by different means and at different stages in the life history of species. Phylogeny describes the historic origin, evolution, and distribution of character states in contemporary species. However, the level of energy expenditure is quantitatively determined by the collective of realized states in combination with conditions in the environment. Therefore, two stages determine energy expenditure: (1) the evolution of character states and (2) their impact in conjunction with conditions on the environment. Behavioral characters and ecological factors, when coupled with log10 mass, usually account for >94 % of the variation in the log10 basal rates of birds and mammals, a capacity not found in phylogenetic analyses. The difficulty of determining a direct impact of phylogeny on physiological characters results from its correlation with behavioral characters. When appropriate, the passerine/non-passerine dichotomy in birds and the sub/infraclass dichotomy in mammals combine with behavioral characters, ecological factors, and log10 mass to increase r2 to account for 96–99 % of the variation in log10 basal rate. This occurs because dichotomies incorporate factors other than those already in the analyses. The clearest demonstration of the direct impact of character states is the equality of energy expenditure in species convergent with species from other clades without any evidence of the clade to which the species belong. A multifactorial approach depends on the inclusion of life history characteristics of species, but this analysis applies only to continuous, quantitative relationships, which are often modified by discontinuous agents. Distinctive character states distinguish species and therefore must be included in any attempt to account for differences in their level of energy expenditure. No analysis that ignores life history characteristics can account for the quantitative variation in energy expenditure beyond that associated with body mass.
Which way is up? Asymmetric spectral input along the dorsal–ventral axis influences postural responses in an amphibious annelid
Venue: Journal of Comparative Physiology A

Medicinal leeches are predatory annelids that exhibit countershading and reside in aquatic environments where light levels might be variable. They also leave the water and must contend with terrestrial environments. Yet, leeches generally maintain a dorsal upward position despite lacking statocysts. Leeches respond visually to both green and near-ultraviolet (UV) light. I used LEDs to test the hypothesis that ventral, but not dorsal UV would evoke compensatory movements to orient the body. Untethered leeches were tested using LEDs emitting at red (632 nm), green (513 nm), blue (455 nm) and UV (372 nm). UV light evoked responses in 100 % of trials and the leeches often rotated the ventral surface away from it. Visible light evoked no or modest responses (12–15 % of trials) and no body rotation. Electrophysiological recordings showed that ventral sensilla responded best to UV, dorsal sensilla to green. Additionally, a higher order interneuron that is engaged in a variety of parallel networks responded vigorously to UV presented ventrally, and both the visible and UV responses exhibited pronounced light adaptation. These results strongly support the suggestion that a dorsal light reflex in the leech uses spectral comparisons across the dorsal–ventral axis rather than, or in addition to, luminance.
Cross-modal interaction between visual and olfactory learning in Apis cerana
Venue: Journal of Comparative Physiology A

The power of the small honeybee brain carrying out behavioral and cognitive tasks has been shown repeatedly to be highly impressive. The present study investigates, for the first time, the cross-modal interaction between visual and olfactory learning in Apis cerana. To explore the role and molecular mechanisms of cross-modal learning in A. cerana, the honeybees were trained and tested in a modified Y-maze with seven visual and five olfactory stimulus, where a robust visual threshold for black/white grating (period of 2.8°–3.8°) and relatively olfactory threshold (concentration of 50–25 %) was obtained. Meanwhile, the expression levels of five genes (AcCREB, Acdop1, Acdop2, Acdop3, Actyr1) related to learning and memory were analyzed under different training conditions by real-time RT-PCR. The experimental results indicate that A. cerana could exhibit cross-modal interactions between visual and olfactory learning by reducing the threshold level of the conditioning stimuli, and that these genes may play important roles in the learning process of honeybees.
Aging alters contractile properties and fiber morphology in pigeon skeletal muscle
Venue: Journal of Comparative Physiology B

In this study, we tested the hypothesis that skeletal muscle from pigeons would display age-related alterations in isometric force and contractile parameters as well as a shift of the single muscle fiber cross-sectional area (CSA) distribution toward smaller fiber sizes. Maximal force output, twitch contraction durations and the force–frequency relationship were determined in tensor propatagialis pars biceps muscle from young 3-year-old pigeons, middle-aged 18-year-old pigeons, and aged 30-year-old pigeons. The fiber CSA distribution was determined by planimetry from muscle sections stained with hematoxylin and eosin. Maximal force output of twitch and tetanic contractions was greatest in muscles from young pigeons, while the time to peak force of twitch contractions was longest in muscles from aged pigeons. There were no changes in the force–frequency relationship between the age groups. Interestingly, the fiber CSA distribution in aged muscles revealed a greater number of larger sized muscle fibers, which was verified visually in histological images. Middle-aged and aged muscles also displayed a greater amount of slow myosin containing muscle fibers. These data demonstrate that muscles from middle-aged and aged pigeons are susceptible to alterations in contractile properties that are consistent with aging, including lower force production and longer contraction durations. These functional changes were supported by the appearance of slow myosin containing muscle fibers in muscles from middle-aged and aged pigeons. Therefore, the pigeon may represent an appropriate animal model for the study of aging-related alterations in skeletal muscle function and structure.
Living in the fast lane: rapid development of the locomotor muscle in immature harbor porpoises (Phocoena phocoena)
Venue: Journal of Comparative Physiology B

Cetaceans (dolphins and whales) are born into the aquatic environment and are immediately challenged by the demands of hypoxia and exercise. This should promote rapid development of the muscle biochemistry that supports diving, but previous research on two odontocete (toothed whales and dolphins) species showed protracted postnatal development for myoglobin content and buffering capacity. A minimum of 1 and 1.5 years were required for Fraser’s (Lagenodelphis hosei) and bottlenose (Tursiops truncatus) dolphins to obtain mature myoglobin contents, respectively; this corresponded to their lengthy 2 and 2.5-year calving intervals (a proxy for the dependency period of cetacean calves). To further examine the correlation between the durations for muscle maturation and maternal dependency, we measured myoglobin content and buffering capacity in the main locomotor muscle (longissimus dorsi) of harbor porpoises (Phocoenaphocoena), a species with a comparatively short calving interval (1.5 years). We found that at birth, porpoises had 51 and 69 % of adult levels for myoglobin and buffering capacity, respectively, demonstrating greater muscle maturity at birth than that found previously for neonatal bottlenose dolphins (10 and 65 %, respectively). Porpoises achieved adult levels for myoglobin and buffering capacity by 9–10 months and 2–3 years postpartum, respectively. This muscle maturation occurred at an earlier age than that found previously for the dolphin species. These results support the observation that variability in the duration for muscular development is associated with disparate life history patterns across odontocetes, suggesting that the pace of muscle maturation is not solely influenced by exposure to hypoxia and exercise. Though the mechanism that drives this variability remains unknown, nonetheless, these results highlight the importance of documenting the species-specific physiological development that limits diving capabilities and ultimately defines habitat utilization patterns across age classes.
Toxins induce ‘malaise’ behaviour in the honeybee (Apis mellifera)
Venue: Journal of Comparative Physiology A

To avoid poisoning and death when toxins are ingested, the body responds with a suite of physiological detoxification mechanisms accompanied by behaviours that in mammals often include vomiting, nausea, and lethargy. Few studies have characterised whether insects exhibit characteristic ‘malaise-like’ behaviours in response to intoxication. Here, we used the honeybee to investigate how intoxication produced by injection or ingestion with three toxins with different pharmacological modes of action quinine, amygdalin, and lithium chloride affected behaviour. We found that toxin-induced changes in behaviour were best characterised by more time spent grooming. Bees also had difficulty performing the righting reflex and exhibited specific toxin-induced behaviours such as abdomen dragging and curling up. The expression of these behaviours also depended on whether a toxin had been injected or ingested. When toxins were ingested, they were least 10 times less concentrated in the haemolymph than in the ingested food, suggesting that their absorption through the gut is strongly regulated. Our data show that bees exhibit changes in behaviour that are characteristic of ‘malaise’ and suggest that physiological signalling of toxicosis is accomplished by multiple post-ingestive pathways in animals.
Characterisation of whisker control in the California sea lion (Zalophus californianus) during a complex, dynamic sensorimotor task
Venue: Journal of Comparative Physiology A

Studies in pinniped whisker use have shown that their whiskers are extremely sensitive to tactile and hydrodynamic signals. While pinnipeds position their whiskers on to objects and have some control over their whisker protractions, it has always been thought that head movements are more responsible for whisker positioning than the movement of the whiskers themselves. This study uses ball balancing, a dynamic sensorimotor skill that is often used in human and robotic coordination studies, to promote sea lion whisker movements during the task. For the first time, using tracked video footage, we show that sea lion whisker movements respond quickly (26.70 ms) and mirror the movement of the ball, much more so than the head. We show that whisker asymmetry and spread are both altered to help sense and control the ball during balancing. We believe that by designing more dynamic sensorimotor tasks we can start to characterise the active nature of this specialised sensory system in pinnipeds.
Dietary effect on immunological energetics in mice
Venue: Journal of Comparative Physiology B

Defense against natural aggressors, such as bacterial infections, requires both energy and an immune-cellular response. However, the question as to how these two components are interconnected in small endotherms by means of the host diet remains only poorly understood. Here, we tested in laboratory mice whether dietary proteins and carbohydrates can modulate the interplay between energy expenditure, food intake and the innate and adaptive immune response when confronting a bacterial challenge (Bacillus Calmette-Guérin, BCG). We observed that mice fed with a high protein diet (HP) developed a better immune response associated to increased numbers of circulating monocytes. In addition, HP diet directly influenced the peripheral blood proportions of both T and B lymphocytes even before the BCG challenge. Interestingly, animals that developed this type of immune response after BCG challenge showed an increased rate of metabolism and food consumption before being challenged. Thus, HP diet induced in non-challenged animals a similar energy expenditure and food intake described by BCG-treated mice. These data suggest that a high amount of proteins in diet can modify the energetic and nutrient dynamic in the host causing a better immune reaction against a microbial challenge.
Adjustments in cholinergic, adrenergic and purinergic control of cardiovascular function in snapping turtle embryos (Chelydra serpentina) incubated in chronic hypoxia
Venue: Journal of Comparative Physiology B

Adenosine is an endogenous nucleoside that acts via G-protein coupled receptors. In vertebrates, arterial or venous adenosine injection causes a rapid and large bradycardia through atrioventricular node block, a response mediated by adenosine receptors that inhibit adenylate cyclase and decrease cyclic AMP concentration. Chronic developmental hypoxia has been shown to alter cardioregulatory mechanisms in reptile embryos, but adenosine’s role in mediating these responses is not known. We incubated snapping turtle embryos under chronic normoxic (N21; 21 % O2) or chronic hypoxic conditions (H10; 10 % O2) beginning at 20 % of embryonic incubation. H10 embryos at 90 % of incubation were hypotensive relative to N21 embryos in both normoxic and hypoxic conditions. Hypoxia caused a hypotensive bradycardia in both N21 and H10 embryos during the initial 30 min of exposure; however, fH and Pm both trended towards increasing during the subsequent 30 min, and H10 embryos were tachycardic relative to N21 embryos in hypoxia. Following serial ≥1 h exposure to normoxic and hypoxic conditions, a single injection of adenosine (1 mg kg−1) was given. N21 and H10 embryos responded to adenosine injection with a rapid and large hypotensive bradycardia in both normoxia and hypoxia. Gene expression for adenosine receptors were quantified in cardiac tissue, and Adora1 mRNA was the predominant receptor subtype with transcript levels 30–82-fold higher than Adora2A or Adora2B. At 70 % of incubation, H10 embryos had lower Adora1 and Adora2B expression compared to N21 embryos. Expression of Adora1 and Adora2B decreased in N21 embryos during development and did not differ from H10 embryos at 90 % of incubation. Similar to previous results in normoxia, H10 embryos in hypoxia were chronically tachycardic compared to N21 embryos before and after complete cholinergic and adrenergic blockade. Chronic hypoxia altered the development of normal cholinergic and adrenergic tone, as well as adenosine receptor mRNA levels. This study demonstrates that adenosine may be a major regulator of heart rate in developing snapping turtle embryos, and that chronic hypoxic incubation alters the response to hypoxic exposure.
Mechanisms of Na+ uptake, ammonia excretion, and their potential linkage in native Rio Negro tetras (Paracheirodon axelrodi, Hemigrammus rhodostomus, and Moenkhausia diktyota)
Venue: Journal of Comparative Physiology B

Mechanisms of Na+ uptake, ammonia excretion, and their potential linkage were investigated in three characids (cardinal, hemigrammus, moenkhausia tetras), using radiotracer flux techniques to study the unidirectional influx (Jin), efflux (Jout), and net flux rates (Jnet) of Na+ and Cl−, and the net excretion rate of ammonia (JAmm). The fish were collected directly from the Rio Negro, and studied in their native “blackwater” which is acidic (pH 4.5), ion-poor (Na+, Cl− ~20 µM), and rich in dissolved organic matter (DOM 11.5 mg C l−1). JinNa, JinCl, and JAmm were higher than in previous reports on tetras obtained from the North America aquarium trade and/or studied in low DOM water. In all three species, JinNa was unaffected by amiloride (10−4 M, NHE and Na+ channel blocker), but both JinNa and JinCl were virtually eliminated (85–99 % blockade) by AgNO3 (10−7 M). A time course study on cardinal tetras demonstrated that JinNa blockade by AgNO3 was very rapid (<5 min), suggesting inhibition of branchial carbonic anhydrase (CA), and exposure to the CA-blocker acetazolamide (10−4 M) caused a 50 % reduction in JinNa.. Additionally, JinNa was unaffected by phenamil (10−5 M, Na+ channel blocker), bumetanide (10−4 M, NKCC blocker), hydrochlorothiazide (5 × 10−3 M, NCC blocker), and exposure to an acute 3 unit increase in water pH. None of these treatments, including partial or complete elimination of JinNa (by acetazolamide and AgNO3 respectively), had any inhibitory effect on JAmm. Therefore, Na+ uptake in Rio Negro tetras depends on an internal supply of H+ from CA, but does not fit any of the currently accepted H+-dependent models (NHE, Na+ channel/V-type H+-ATPase), or co-transport schemes (NCC, NKCC), and ammonia excretion does not fit the current “Na+/NH4+ exchange metabolon” paradigm. Na+, K+-ATPase and V-type H+-ATPase activities were present at similar levels in gill homogenates, Acute exposure to high environmental ammonia (NH4Cl, 10−3 M) significantly increased JinNa, and NH4+ was equally or more effective than K+ in activating branchial Na+,(K+) ATPase activity in vitro. We propose that ammonia excretion does not depend on Na+ uptake, but that Na+ uptake (by an as yet unknown H+-dependent apical mechanism) depends on ammonia excretion, driven by active NH4+ entry via basolateral Na+,(K+)-ATPase.
Modulation of aquaporin 2 expression in the kidney of young goats by changes in nitrogen intake
Venue: Journal of Comparative Physiology B

In ruminants, a decrease of dietary nitrogen (N) is an appropriate feeding concept to reduce environmental pollution and costs. In our previous study, when goats were kept on an N-reduced diet, a decrease of plasma urea concentration and an increase of renal urea transporters were demonstrated. Renal urea absorption plays a crucial role for renal water absorption and urine concentration. Renal collecting duct water absorption is mainly mediated by the water channel aquaporin 1 and 2 (AQP1 and AQP2). Therefore, the aim of the present study was to investigate the effects of a dietary N reduction on expression of renal AQP1 and AQP2 in young goats. Twenty male White Saanen goats, 3 months old, were divided equally into two feeding groups, receiving either a diet with an adequate or a reduced-N supply. Goats fed a reduced-N diet showed significantly higher amounts of AQP1 mRNA in cortical tissue, and the expression of AQP2 mRNA and protein were highly elevated in renal outer medulla. An increase of vasopressin concentrations in plasma were detected for the N-reduced fed goats. Therefore, a stimulation of renal water absorption can be assumed. This might be an advantage for ruminants in times of N reduction due to higher urea concentrations in the tubular fluid and which might result in higher absorption of urea by renal urea transporters. Therefore, interplay of aquaporin water channels and urea transporters in the kidney may occur to maintain urea metabolism in times of N scarcity in young goats.