bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Monovalent Cation/Proton Antiporters in Na+-Resistance and pH Homeostasis in Bacillus: An Alkaliphile Versus A Neutralophile
Authors: Krulwich Terry Ann , Cheng Jianbo , Guffanti Arthur A. 
Published: April 2021

ABSTRACT
Both neutralophilic Bacillus subtilis and alkaliphilic Bacillus firmus OF4 depend upon electrogenic Na+/H+ antiporters, which are energized by the gradients established by respiration-coupled proton extrusion, to achieve Na+-resistance and pH homeostasis when the external pH is very alkaline. The interplay of proton and sodium cycles is discussed. In B. subtilis, pH homeostasis, up to pH 9, can be achieved using K+ when Na+ is unavailable or when the gene encoding the Na+/H+ antiporter that is involved in Na+-dependent pH homeostasis is disrupted. That gene is a member of the tetracycline efflux family of genes. A second gene, encoding a Na+/H+ antiporter that functions in Na+-resistance, has been identified, and candidates for the K+/H+ antiporter genes are under investigation. Aggregate Na+/H+ antiport activity in B. subtilis is as much as 10 times lower than in the alkaliphile, and the neutralophile cannot regulate its internal pH upon a shift to pH 10.5. Upon such a shift, there is a pronounced reduction in the generation of a primary electrochemical proton gradient. The alkaliphile, by contrast, maintains substantial driving forces and regulates its internal pH in an exclusively Na+-coupled manner upon shifts to either pH 8.7 or 10.5. One gene locus has been identified and a second locus has been inferred as encoding relevant antiporter activities.
Uniporters, Symporters and Antiporters
Authors: Wolfersberger Michael G. 
Published: April 2021

ABSTRACT
Transporters are a diverse group of membrane proteins that facilitate the movement of water-soluble solutes through the lipid bilayer of biological membranes. The least complex transporters are the uniporters (Kakuda and MacLeod, 1994). They simply facilitate the diffusion of their substrates across membranes and dissipate substrate gradients that arise as the result of other processes. Uniporters fall into two classes, channels and carriers, which mediate transmembrane solute movement by fundamentally different mechanisms. Channel proteins contain hydrophilic pores that span the lipid bilayer. Water-soluble solutes move across the membrane by diffusion through these pores. The lumen of a channel is accessible from either side of the membrane simultaneously. Carriers may also span the lipid bilayer, but their substrate binding sites are never accessible from both sides of the membrane simultaneously. Because of this difference in mechanism, carriers but not channels are able to mediate countertransport (Harold, 1986). Since carriers are much more closely related, at least mechanistically, to symporters and antiporters than to channels, they are the type of uniporter emphasized in this volume.
Gene-Product Designations for Amino Acid Transporters
Authors: Christensen Halvor N. , Albritton Lorraine M. , Kakuda Donald K. , Macleod Carol L. 
Published: April 2021

ABSTRACT
The molecular cloning of genes that encode amino acid transporters presents the scientific community with the opportunity to name their gene products using a scheme that could usefully recall the well-defined transport system most similar in properties to the newly identified cloned gene product. To avoid the problem of rising confusion, we propose to take advantage of established designation methods that indicate the types of amino acids transported and the co-substrate ion requirement of their transport. The economy obligated by the necessity to keep the number of symbols in a gene name to a minimum will rarely permit a listing of the full range of substrates, since amino acid transport systems have broad substrate specificities with co-substrate requirements that can differ in a substrate-specific manner. Hence, the use of established systems to codify groups of amino acid transport systems, which allow identification of the substrate range by using 1–3 letters, e.g. A, L or even ASC, could be integrated with a system used to indicate the ion-dependence of transport. The discoverers of transporters are mainly proceeding with commendable reserve and are inviting discussion, a desire which this essay urges be facilitated by more formal arrangements for further planning. These discoverers have also shown, along with an expressed desire for guidance, well-advised spontaneity in making reference to the substrate range, two trends that together suggest that a good set of designations can evolve that will be highly descriptive. We propose that this can be accomplished without a struggle to accommodate awkwardly to the requirements of the huge human genome data base cataloging system, nor to any single comprehensive systematic scheme. Instead, a combined scheme that takes into account the biological and biochemical characteristics, as well as the historical designations, of amino acid transport systems, is offered here for evaluation.
Is Walking Costly For Anurans? the Energetic Cost of Walking in the Northern Toad Bufo Boreas Halophilus
Authors: Walton B. Michael , Peterson Charles C. , Bennett Albert F. 
Published: April 2021

ABSTRACT
Locomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. Species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. We tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of Bufo boreas halophilus, a toad that walks, but does not hop. Rates of oxygen consumption during locomotion were measured in an enclosed variable-speed treadmill. The steady-state rate of oxygen consumption increased linearly within a range of sustainable speeds [ (ml O2 g−1 h−1) = 0.93 X speed (km h−1) + 0.28]. The minimum cost of transport, Cmin (the slope of this relationship), varied significantly among individual toads. When expressed in units of oxygen consumed per distance travelled (ml O2 km−1), Cmin scaled isometrically with body mass: Cmin = 0.69mass1.07. Consequently, mass-specific Cmin (ml O2 g−1 km−1) was uncorrelated with body mass. Variation in Cmin was also unrelated to experimental temperature. Mass-specific Cmin estimates were similar to previous allometric predictions for terrestrial animals of similar size, which contrasts with previous findings for another toad species. Maximum rates of oxygen consumption measured in closed, rotating respirometers were significantly higher than the maximum rates achieved on the treadmill, but lower than those measured previously in other Bufo species. Our results indicate that walking is not necessarily a costly gait for toads and that high maximum rates of oxygen consumption are not associated with reliance on walking within the genus Bufo.
Graviresponses in Paramecium Caudatum and Didinium Nasutum Examined Under Varied Hypergravity Conditions
Authors: Bräucker Richard , Machemer-Röhnisch Sigrun , Machemer Hans 
Published: April 2021

ABSTRACT
The swimming behaviours of two species of ciliates characterized by different mechanosensory and ciliary motor properties were investigated under hypergravity up to 5.4 g. The experiments were designed to examine large numbers of cells using video recording, digital data processing and statistics for the documentation of the rates and orientations of swimming. The gravikinetic responses (change in active swimming rates) were calculated from (1) the velocities of vertical swimming in the gravity field, (2) sedimentation of Ni2+ -immobilized cells and (3) the intrinsic rate of propulsion, independent of gravity. Propulsion was determined from the intersection of regression lines of the gravity-dependent upward and downward swimming velocities. The rates of swimming and sedimentation, and consequently the gravikineses, were linear functions of gravitational acceleration. Comparisons of cell populations from different cultures suggest that there is an age-dependent change in gravikinesis. In starved Paramecium caudatum (7-day cultures), the kinetic responses antagonizing sedimentation (negative gravikinesis) increased with acceleration. In Didinium nasutum, negative gravikinesis was documented at 1 g in downward-swimming specimens only, which agrees with the mechanosensory organization of this cell. Hypergravity induced the gravikinesis of Didinium to change sign. In both species, and at all accelerations tested, a neutral gravitaxis was documented. Such behaviour incorporates distinct acceleration-dependent orientational and velocity responses, keeping populations of cells stationary in the gravity field (taxis coefficients close to zero).
Heterothermy, Torpor, Respiratory Gas Exchange, Water Balance and the Effect of Feeding in Gould’s Long-Eared Bat Nyctophilus Gouldi
Authors: Morris Steve , Curtin Alison L. , Thompson Michael B. 
Published: April 2021

ABSTRACT
The effects of temperature and nutritional status on the metabolic rate of Nyctophilus gouldi were examined. Bats fed marked meals first defecated approximately 1.34 h after feeding and were calculated to have a mean retention time of 5.38±0.57 h but to be truly post-absorptive after 9 h. Over the temperature range 1–35°C, the metabolic rate and body temperature (Tb) of fasted bats were extremely labile. Below 30°C, the bats all entered torpor and between 10 and 15°C showed a mean 84% reduction over the maximal . Body temperature was also minimal over this range (Tb=12.5°C, Ta=10–15°C). Both total and dry thermal conductance increased in a curvilinear manner with temperature, total conductance from 3.38±0.65 J g−1 h−1°C−1 at 1°C to 24.25±1.99 J g−1 h−1°C−1 at 35°C (mean ± S.E.M.), while the rate of evaporative water loss increased with Ta by a maximum of 10-fold from 0.21 mg g−1 h−1 at 5°C to 2.69 mg g−1 h−1 at 35°C. Between 10 and 25°C, intermittent respiration characterised by episodic bouts of breathing/gas exchange and periods of apnoea with no measurable occurred. Although the duration of apnoea decreased when temperature was increased, the volume of oxygen taken up in each episode did not change. Mean respiratory exchange ratio (RER) was low (0.64–0.77) in post-absorptive bats, typical of fat utilisation, but during torpor ranged from near 0 to near 2, indicating discontinuous and disproportional gas exchange. Feeding produced a condition of relatively sustained homeothermy and high RER in the bats which persisted for 9 h, after which the N. gouldi became torpid. Immediately after feeding, the of the bats increased fivefold above the post-absorptive level, while the increased by more than eightfold. Similarly, body temperature also increased, declining to torpid values after 9 h. The RER in immediately post-feeding bats was near 1.0 but subsequently declined to near 0.7, indicating a switch from carbohydrate to fat utilisation. Therefore, the N. gouldi were heterothermic, exhibited a highly labile metabolic rate, and rates of heat and water loss, and a Tb which were influenced both by ambient temperature and by nutritional status.
Modulating a Modulator: Biogenic Amines at Subthreshold Levels Potentiate Peptide-Mediated Cardioexcitation of the Heart of the Tobacco Hawkmoth Manduca Sexta
Authors: Prier K. R. , Beckman O. H. , Tublitz N. J. 
Published: April 2021

ABSTRACT
The central nervous system of the moth Manduca sexta contains a group of myoregulatory neuropeptides, the CAPs (Cardioacceleratory Peptides), which cause a physiologically important, dose-dependent increase in heart rate during wing inflation and flight in adult moths. We report here that the response of the adult heart to a subset of the CAPs, the CAP2s, is potentiated nearly twofold in the chronic presence of subthreshold levels of the biogenic amine octopamine or near-threshold levels of the biogenic amine serotonin. Subthreshold levels of the CAP2s fail to alter the response of the heart to octopamine.
We have begun to investigate the molecular mechanisms underlying this potentiation. Previous work on the adult heart has shown that the CAP2s act through an inositol-1,4,5-trisphosphate second-messenger system. Here, we demonstrate that the cardioexcitatory effects of the two amines, in contrast to those of the CAP2s, are both mediated by cyclic AMP. Application to the heart of either 10−5 mol l−1 octopamine or 10−6 mol l−1 serotonin elicits a threefold increase in intracellular cyclic AMP levels. The CAP2s have no effect on cyclic AMP levels in the heart. These results illustrate a mechanism by which the effectiveness of a neurohormone can be increased with minimal cost to the animal. In Manduca sexta, subthreshold levels of octopamine are found in the haemolymph during wing inflation and flight. Thus, it is possible that octopamine up-regulates the effects of CAP2 via a cyclic-AMP-dependent mechanism during these activities.
The Dorsal Giant Interneurons Mediate Evasive Behavior in Flying Cockroaches
Authors: Libersat Frederic 
Published: April 2021

ABSTRACT
Cockroaches escape from terrestrial predators by making an evasive turn and running away (Camhi, 1984). The air displacement produced by the predator’s strike is sensed by wind-sensitive receptors on the cerci, two posterior antenna-like organs. These receptors excite two distinct populations of giant interneurons, the ventral giant interneurons (vGIs) and the dorsal giant interneurons (dGIs), in the last abdominal ganglion of the nerve cord (Camhi, 1984). The vGIs are known to control the direction of the escape turn when the animal is on the ground (Camhi, 1988; Ritzmann, 1993; Comer and Dowd, 1993; Liebenthal et al. 1994), while the dGIs are known to initiate and maintain flight (Ritzmann et al. 1982; Libersat et al. 1989; Libersat, 1992). Since cockroaches are not equipped with an ultrasonic hearing sense (Yager and Scaffidi, 1993) and consequently do not respond to ultrasound with escape maneuvers, as many other insects do (Hoy et al. 1989; Libersat and Hoy, 1991), it is reasonable to envisage that, while flying, cockroaches may recruit their wind escape circuit to evade aerial predators such as bats. Indeed, recently Ganihar et al. (1994) have shown that flying cockroaches produce various flight maneuvers that should cause an evasive turn away from a wind stimulus. Such flight maneuvers are not produced after cercal ablation. The most likely candidates to mediate these evasive flying maneuvers are the dGIs, because the wind sensitivity of the vGIs is greatly reduced during flight (Libersat et al. 1989; Libersat, 1992). In contrast, the dGIs retain their wind sensitivity during flight (Libersat, 1992) and also they respond in a directionally sensitive manner to a wind puff delivered from the side (Ganihar et al. 1994). In this study, the possibility that the dGIs mediate evasive flying maneuvers was investigated by stimulating individual identified dGIs during flight and measuring the asymmetrical responses in a pair of left and right flight depressor muscles, the subalars of the metathoracic wings.
Spiking Induced By Cooling In The Myocardium Of The Lobster Panulirus Japonicus
Authors: Kuramoto T. 
Published: April 2021

ABSTRACT
The heart rate of crustaceans changes with variations in ambient temperature within the normal environmental range (Maynard, 1960). The temperature coefficient (Q10) of the heart rate of crabs over the range 4–19°C is about 2 (Florey and Kriebel, 1974). There are few studies of the heart response to a rapid change in temperature, although aquatic crustaceans often meet with warm or cold water masses (Spaargaren and Achituv, 1977). Electromechanical coupling of muscle fibres becomes less effective with decreasing temperature (Dudel and Ruedel, 1968), but a mechanism has been described that compensates for the tonus effect during leg muscle activity (Fischer and Florey, 1981). Compensatory mechanisms may also exist for heart muscle, and I have recently found that myocardial cells of a marine lobster begin to produce large action potentials in response to cooling. Lobster myocardial fibres develop tension in response to excitatory junction potentials (EJPs) generated by impulse activity of motor neurones in the cardiac ganglion (Van der Kloot, 1970; Anderson and Cooke, 1971; Kuramoto and Kuwasawa, 1980; Kuramoto and Ebara, 1984a). The heart tension produced is fed back to the cardiac ganglion because the cardiac neurones are sensitive to filling pressure (Maynard, 1960; Kuramoto and Ebara, 1984a, 1985, 1988, 1991). Thus, the responses of the isolated heart to cooling will result from the combined activities of the cardiac ganglion and the muscle cells. This report focuses on the development of a spiking response by the myocardial cells when the heart is cooled. The spikes produced correspond to enhanced contractions of the myocardium, suggesting that the myocardial cells may use this as a mechanism to compensate for the reduced efficacy of excitation–contraction coupling that occurs with falling temperature.
The MalpighianC Tubules Of Drosophila Melanogaster: A Novel Phenotype For Studies Of Fluid Secretion And Its Control
Authors: Dow Julian A. T. , Maddrell Simon H. P. , Görtz Andreas , Skaer Nick J. V. , Brogan Scott , Kaiser Kim 
Published: April 2021

ABSTRACT
The insect renal (Malpighian) tubule has long been a model system for the study of fluid secretion and its neurohormonal control (Maddrell, 1981; Maddrell and O’Donnell, 1992). Classical physiology suggests a model for tubular secretion of iso-osmotic fluid in most insects, in which ions are thought to enter basally either through a series of ion channels (Na+, K+ and Cl−) or through a bumetanide-sensitive Na+/K+/2Cl− cotransport. Apical fluxes are energised by a plasma-membrane H+-pumping V-ATPase, driving secretion of Na+ or K+ through one or more exchangers, at least one of which is amiloride-sensitive and appears to be closely similar to the Na+/H+ exchanger of vertebrates (Maddrell and O’Donnell, 1992). Cl− follows passively, perhaps through apical Cl− channels. Water follows the major ions, and haemolymph solutes diffuse across the tubule wall passively via a paracellular route. There are also transcellular active transport processes for certain metabolites or toxins, such as acylamides (Maddrell et al. 1974) and plant alkaloids (Maddrell, 1976; O’Donnell et al. 1983).
Periodic Air-Breathing Behaviour In A Primitive Fish Revealed By Spectral Analysis
Authors: Hedrick Michael S. , Katz Stephen L. , Jones David R. 
Published: April 2021

ABSTRACT
The ventilatory patterns of air-breathing fish are commonly described as ‘arrhythmic’ or ‘irregular’ because the variable periods of breath-holding are punctuated by seemingly unpredictable air-breathing events (see Shelton et al. 1986). This apparent arrhythmicity contrasts with the perceived periodism or regularity in the gill ventilation patterns of some fish and with lung ventilation in birds and mammals. In this sense, periodism refers to behaviour that occurs with a definite, recurring interval (Bendat and Piersol, 1986). The characterisation of aerial ventilation patterns in fish as ‘aperiodic’ has been generally accepted on the basis of qualitative examination and it remains to be validated with rigorous testing.
The Effects of Branchial Chloride Cell Proliferation on Respiratory Function in the Rainbow Trout Oncorhynchus Mykiss
Authors: Bindon Shawn D. , Gilmour Kathleen M. , Fenwick James C. , Perry Steve F. 
Published: April 2021

ABSTRACT
The objectives of this study were to induce chloride cell (CC) proliferation on the gill lamellae of rainbow trout Oncorhynchus mykiss and to evaluate the consequences for respiratory function. Chronic elevation of hormone levels was used to induce CC proliferation; fish were injected with a combination of cortisol (8 mg kg−1 intramuscularly every day for 10 days) and ovine growth hormone (2 mg kg−1 intraperitoneally every second day for 10 days). The extent of CC proliferation was quantified using scanning electron microscopy and a two-dimensional analysis. An extracorporeal preparation in combination with environmental hypoxia was used to assess the effects of CC proliferation on respiratory function. Arterial blood was routed from the coeliac artery through an external circuit in which pH (pHa), partial pressure of oxygen and partial pressure of carbon dioxide were monitored continuously. Environmental hypoxia was imposed by gassing a water equilibration column supplying the experimental chamber with N2.
The hormone treatment increased the average CC surface area by 2.7-fold and CC density by 2.2-fold; the combined effect was a fivefold increase in CC fractional area. While the values of hormone-treated and control fish were similar at &gt;12.0 kPa, the arterial O2 tensions of treated fish were significantly lower than those of the control group for ⩽12.0 kPa. In comparison with control fish at all environmental O2 tensions, the hormone-treated fish exhibited elevated values and a significant acidosis. The effects of CC proliferation on blood gas variables in hormone-treated fish were accompanied by a significantly elevated ventilation amplitude and a lowered ventilation frequency.
The results of this study demonstrated (i) that impairment of respiratory gas transfer coincides with CC proliferation, (ii) that O2 and CO2 transfer are influenced differently and (iii) that partial compensation is achieved through physiological adjustments.
The Neural Control of Egg-Laying Behaviour in the Pond Snail Lymnaea Stagnalis: Motor Control of Shell Turning
Authors: Hermann P. M. , Maat A. Ter , Jansen R. F. 
Published: April 2021

ABSTRACT
Behavioural and neurophysiological techniques were used to study the neuronal control of shell turning during egg-laying in the pond snail Lymnaea stagnalis. Egg-laying consists of three phases: resting, turning and oviposition, and is triggered by an electrical discharge in a group of neuroendocrine cells, the caudodorsal cells. During the discharge, several peptides encoded on two CDCH genes are known to be released. Behavioural experiments in which different combinations of nerves were lesioned indicated that the inferior cervical nerves are necessary for turning behaviour to occur. The right inferior cervical nerve innervates the right dorsal longitudinal muscle and contains axons of neurones that are active just prior to, and during, shell movements in freely behaving animals. These axons are probably the axons of motor neurones. The motor neurones of the dorsal longitudinal muscle were identified in the cerebral A and pedal N clusters. We have demonstrated that there is a correlation between the state of excitability of the caudodorsal cells and the electrical activity of the pedal N motor neurones. Our results indicate that the pedal N motor neurones are involved in executing the turning phase during egg-laying.