bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular Physiology of Norepinephrine and Serotonin Transporters
Authors: Blakely Randy D. , De Felice Louis J. , Hartzell H. Criss 
Published: April 2021

ABSTRACTCocaine- and antidepressant-sensitive norepinephrine and serotonin transporters (NETs and SERTs) are closely related members of the Na+/Cl− transporter gene family, whose other members include transporters for inhibitory amino acid transmitters, neuromodulators, osmolytes and nutrients. Availability of cloned NET and SERT cDNAs has permitted rapid progress in the definition of cellular sites of gene expression, the generation of transporter-specific antibodies suitable for biosynthetic and localization studies, the examination of structure–function relationships in heterologous expression systems and a biophysical analysis of transporter function. In situ hybridization and immunocytochemical studies indicate a primary expression of NET and SERT genes in brain by noradrenergic and serotonergic neurons, respectively. Both NET and SERT are synthesized as glycoproteins, with multiple glycosylation states apparent for SERT proteins in the brain and periphery. N-glycosylation of NET and SERT appears to be essential for transporter assembly and surface expression, but not for antagonist binding affinity. Homology cloning efforts have revealed novel NET and SERT homologs in non-mammalian species that are of potential value in the delineation of the precise sites for substrate and antagonist recognition, including a Drosophila melanogaster SERT with NET-like pharmacology. Electrophysiological recording of human NETs and SERTs stably expressed in HEK-293 cells reveals that both transporters move charge across the plasma membrane following the addition of substrates; these currents can be blocked by NET- and SERT-selective antagonists as well as by cocaine.
Energizing Porters by Proton-Motive Force
Authors: Nelson Nathan 
Published: April 2021

ABSTRACT
It is generally accepted that the chemistry of water was the most crucial determinant in shaping life on earth. Among the more important chemical features of water is its dissociation into protons and hydroxyl ions. The presence of relatively high proton concentrations in the ambient solution resulted in the evolution of proton pumps during the dawn of life on earth. These proton pumps maintained neutral pH inside the cells and generated electrochemical gradients of protons (proton-motive force) across their membranes. The existence of proton-motive force enabled the evolution of porters driven by it that are most probably among the more primitive porters in the world. The directionality of the substrate transport by the porters could be to both sides of the membranes because they can serve as proton symporters or antiporters. One of the most important subjects of this meeting is the mechanism by which proton-motive and other ion-motive forces drive the transport processes through porters. Is there a common mechanism of action for all proton-driven porters? Is there some common partial reaction by which we can identify the way that porters are energized by proton-motive force? Is there a common coupling between proton movement and uptake or secretion of certain molecules? Even a partial answer to one of these questions would advance our knowledge… or confusion. As my mentor Efraim Racker used to say: ‘If you are not totally confused you do not understand the issue’.
Locomotory Energetics and Metabolic Fuel Reserves of the Virginia Opossum
Authors: Fournier Randy A. , Weber Jean-Michel 
Published: April 2021

ABSTRACT
Marsupials have lower resting metabolic rates than placental mammals, but it is not clear whether particular species can extend this energetic advantage to locomotion. Some active marsupials have a low cost of locomotion, but other more sedentary species, such as the Virginia opossum, appear to run very inefficiently. Steady-state rates of O2 consumption and CO2 production were measured at rest and during horizontal treadmill exercise in wild-caught, trained opossums. Average daily in undisturbed animals was 7.73±0.40 ml O2 kg−1 min−1 (5.67±0.20 ml O2 kg−1 min−1 during light and 9.84±0.81 ml O2 kg−1 min−1 during dark hours, mean ± S.E.M., N=6). Net cost of locomotion ranged between 6.16 and 8.99 J kg−1 s−1 as speed increased and was always higher than for an average mammal of equivalent mass. Net cost of transport decreased as speed increased and was 15–80% higher than for an average mammal. During aerobic locomotion, most of the energy was provided by carbohydrate oxidation, which accounted for 60–95% of as speed increased. Glycogen and triglyceride reserves were quantified in the major storage depots to estimate potential survival time and travelling distance. Enough metabolic fuel was stored to survive for at least 1 week without eating, and 95% of this energy was in adipose tissue triglycerides. However, maximal travelling distance was less than 2 km because opossum locomotion is mainly supported by carbohydrate reserves, which represented only 4% of the available energy. We conclude that aerobic, ground locomotion of Virginia opossums is associated with two major energetic handicaps because their particularly high cost of transport and the nature of the main oxidative fuel they consume are both incompatible with prolonged locomotion.
Oxygen Transport in Egg Masses of the Amphibians Rana Sylvatica and Ambystoma Maculatum: Convection, Diffusion and Oxygen Production by Algae
Authors: Pinder Alan W. , Friet Stephen C. 
Published: April 2021

ABSTRACT
Many amphibians lay their eggs in gelatinous masses up to 10–20 cm in diameter, posing problems for diffusive oxygen delivery. Oxygen may also be provided by water convection between eggs or by oxygen production by endogenous algae. We studied egg masses of two local amphibians, Rana sylvatica and Ambystoma maculatum, to estimate the importance of each of these processes. We injected dye to check for water channels, measured oxygen partial pressures within egg masses to determine the influence of external water convection and lighting, measured oxygen consumption and production in darkness and light and calculated expected gradients through egg masses with a cylindrical, homogeneous egg mass model.
Rana sylvatica had relatively loose egg masses with water channels between the eggs; water convection was important for oxygen delivery. Ambystoma maculatum had firm egg masses with no spaces in the jelly between eggs; thus, there was no opportunity for convective oxygen delivery. The egg masses were cohabited by Oophila ambystomatis, a green alga found specifically in association with amphibian egg masses. Oxygen delivery in A. maculatum was by diffusion and by local production by the algal symbiont. Analysis of a cylindrical egg mass model and measurement of oxygen gradients through egg masses indicated that diffusion alone was not adequate to deliver sufficient O2 to the innermost embryos at late developmental stages. In the light, however, egg masses had a net oxygen production and became hyperoxic. Over the course of a day with a 14 h:10 h light:dark cycle, the innermost embryos were alternately exposed to hyperoxia and near anoxia.
K+ Channel Permeation and Block in the Midgut Epithelium of the Tobacco HornwormManduca Sexta
Authors: Schirmanns K. , Zeiske W. 
Published: April 2021

ABSTRACTThe K+-secreting larval midgut of Manduca sexta in vitro was voltage-or current-clamped. In contrast to Tl+, NH4+and Na+, both Rb+and K+generated a short-circuit current, although with different saturation kinetics. The dependence of the short-circuit current on Rb+ /K+ mole fraction gave no evidence for multi-ion occupation of the basolateral K+ channels. After ‘functionally’ eliminating the apical membranes using the ionophore amphotericin B and the ‘apical K+pump’ blockers trimethyltin chloride or Tl+, the K+channels could be more closely investigated. By measuring zero-current potentials, permeability ratios PX/PK were estimated using an adapted version of the Goldman–Hodgkin–Katz voltage equation. Their sequence was K+ (1) = Tl+ &gt; Rb+ (0.38) &gt; NH4+ (≈0.3) &gt; Cs+(0.03) &gt; Na+(≈0). The K+channels could not be blocked by basally applied Cs+, Na+ or tetraethylammonium. Blockade of K+ current by Ba2+ was typically voltage-dependent, but only at moderate transbasal voltages. The relative electrical distance δ of the Ba2+ binding site from the basal channel opening was determined to be 0.2. At zero transbasal voltage, the apparent inhibition constant for barium KB* a was 1.7 mmol l−1.
The Effects of Altering Extracellular Potassium Ion Concentration on the Membrane Potential and Circadian Clock of Paramecium Bursaria
Authors: Johnson Carl Hirschie , Nakaoka Yasuo , Miwa Isoji 
Published: April 2021

ABSTRACT
In some neural models of circadian rhythmicity, membrane potential and transmembrane flux of potassium and calcium ions appear to play important roles in the entrainment and central mechanisms of the biological clock. We wondered whether these cellular variables might be generally involved in circadian clocks, even non-neural clocks. Therefore, we tested the impact of changing extracellular potassium level on the circadian rhythm of photoaccumulation of Paramecium cells, whose membrane potential responds to changes of extracellular potassium in a manner similar to that of neurones. We found that pulse or step changes of extracellular potassium concentration did not phase-shift the circadian clock of P. bursaria cells in a phase-specific manner. Furthermore, modifying the extracellular concentration of calcium did not affect the magnitude of light-induced phase resetting. Therefore, while membrane potential and calcium fluxes may be crucial components of the circadian clock system in some organisms, especially in neural systems that involve intercellular communication, the P. bursaria data indicate that membrane potential changes are not necessarily an intrinsic component of circadian organization at the cellular level.
Embryonic and Larval Respiration In the Arboreal foam Nests of the African Frog Chiromantis Xerampelina
Authors: Seymour Roger S. , Loveridge John P. 
Published: April 2021

ABSTRACT
In Zimbabwe, female Chiromantis xerampelina construct spherical foam nests that are suspended above temporary water. The nests average 624 ml in volume and contain 854 eggs. The 1.7 mm ova have exceptionally thin jelly capsules and are dispersed in the foamy core of the nest, which is surrounded by a layer of eggless foam. At 25°C, each embryo requires 3.5 days to reach hatching at developmental stage 22, during which it consumes 30 μl of oxygen. After hatching, each larva remains in the nest for 2 more days and consumes a further 123 μl of oxygen. The fresh foam contains 77% air, which is sufficient to supply all of the oxygen requirements of the embryos until well after they hatch. Therefore, the size of the egg mass is not limited by oxygen availability as it is in many other anurans. Oxygen also diffuses into the nest from the atmosphere, but the rate is severely restricted by the wet foam, despite the presence of bubbles. Drying of the outer layer of foam greatly increases its oxygen conductance, but the larvae remain in the inner core of wet foam, where they compete for oxygen at the periphery. With further drying of the nest, the wet foam diminishes in volume and concentrates the larvae at a time when their oxygen demands are approaching the maximum. Oxygen pressures within the wet foam drop below 10 kPa and oxygen uptake by the larvae becomes progressively limited, possibly stimulating their emergence from the nest. The delay between hatching and escape from the nest permits the larvae to grow and mature to a stage at which all of the clutch can emerge simultaneously.
Odor Plumes and How Blue Crabs Use Them in Finding Prey
Authors: Weissburg Marc J. , Zimmer-Faust Richard K. 
Published: April 2021

ABSTRACT
Orientation of animals using chemical cues often takes place in flows, where the stimulus properties of odorants are affected by the characteristics of fluid motion. Kinematic analysis of movement patterns by animals responding to odor plumes has been used to provide insight into the behavioral and physiological aspects of olfactory-mediated orientation, particularly in terrestrial insects. We have used this approach in analyzing predatory searching by blue crabs in response to plumes of attractant metabolites released from the siphons of live clams in controlled hydrodynamic environments. Crabs proceed directly upstream towards clams in smooth-turbulent flows and show high locomotory velocities and few periods of motionlessness. Crabs assume more indirect trajectories and display slower locomotion and more stopping in rough-turbulent flows. This degradation of foraging performance is most pronounced as flow shifts from a smooth-to a rough-turbulent regime, where the change in hydraulic properties is associated with contraction of the viscous sublayer region of the boundary layer. Because flow in this region is quasi-laminar, the viscous sublayer may be a particularly effective vehicle for chemical stimulus transmission, such that orientation is severely compromised when it is reduced or removed. Our results also suggest that rheotactic and chemical information are both necessary for successful orientation. Perception of chemical cues acts to bias locomotion upcurrent, and feedback from odorant stimulus distributions appears directly to regulate subsequent stopping and turning en route to prey. Although the mechanisms of orientation to odorant plumes displayed by insects and blue crabs are largely similar, blue crabs appear to rely more heavily on spatial and/or temporal aspects of chemical stimulus distributions than has been suggested for insect systems.
Quantitative Flow Analysis Around Aquatic Animals Using Laser Sheet Particle Image Velocimetry
Authors: Stamhuis Eize J. , Videler John J. 
Published: April 2021

ABSTRACT
Two alternative particle image velocimetry (PIV) methods have been developed, applying laser light sheet illumination of particle-seeded flows around marine organisms. Successive video images, recorded perpendicular to a light sheet parallel to the main stream, were digitized and processed to map the flow velocity in two-dimensional planes. In particle tracking velocimetry (PTV), displacements of single particles in two subsequent images were determined semi-automatically, resulting in flow diagrams consisting of non-uniformly distributed velocity vectors. Application of grid-cell averaging resulted in flow field diagrams with uniform vector distribution. In sub-image correlation PIV (SCPIV), repetitive convolution filtering of small sub-areas of two subsequent images resulted in automatic determination of cross-correlation peaks, yielding flow field diagrams with regularly spaced velocity vectors. In both PTV and SCPIV, missing values, caused by incomplete particle displacement information in some areas of the images or due to rejection of some erroneous vectors by the vector validation procedure, were interpolated using a two-dimensional spline interpolation technique.
The resultant vector flow fields were used to study the spatial distribution of velocity, spatial acceleration, vorticity, strain and shear. These flow fields could also be used to test for flow in the third dimension by studying the divergence, and to detect the presence and location of vortices. The results offer detailed quantitative descriptions of the flow morphology and can be used to assess dissipated energy. The versatile character of the technique makes it applicable to a wide range of fluid mechanical subjects within biological research. So far it has been successfully applied to map the flow around swimming copepods, fish larvae and juvenile fish and the ventilation current of a tube-living shrimp.
Effects of Hypoxia on Rainbow Trout (Oncorhynchus Mykiss): Intraerythrocytic Phosphates
Authors: Val Adalberto L. , Lessard Joanne , Randall David J. 
Published: April 2021

ABSTRACT
Intraerythrocytic levels of guanosine and adenosine phosphates were estimated in normoxic and hypoxic rainbow trout after intra-arterial injection with either saline or carbonic anhydrase. A significant reduction of the total pool of adenosine and guanosine was observed in hypoxic animals. Similarly, a decrease in both ATP and GTP levels occurred in hypoxic animals injected either with saline or with carbonic anhydrase. Interestingly, there was a highly significant relationship between ATP and GTP levels, indicating that they are under similar control. In addition, a significant positive relationship between nucleoside triphosphate (NTP) and Mg2+ levels was observed. It is possible that the availability of ATP and GTP to hemoglobin (Hb) may be proportionally smaller than their intraerythrocytic absolute levels. No clear relationship between intraerythrocytic NTP levels and plasma carbonic anhydrase infusion was observed, despite the significant effect of carbonic anhydrase on acid–base balance. There was a significant relationship between red blood cell pH and [NTP]:[Hb] in fish exposed to hypoxia for 48 h. No such relationship existed during the first 6 h of hypoxic exposure. Possible mechanisms accounting for the reduction in NTP levels during the initial phases of hypoxia are discussed.
Postnatal Development of Synchronous Stepping in the Gerbil (Gerbillus Dasyurus)
Authors: Blumberg-Feldman Hagit , Eilam David 
Published: April 2021

ABSTRACT
During the first two postnatal weeks, Wagner’s gerbil (Gerbillus dasyurus) pups employed stepping sequences considered to be more basic than in the later stages of development and displayed alternate stepping of the legs in each girdle. In the third postnatal week, the adult mode of locomotion, the bound, became prominent and synchronous stepping dominated locomotion, gradually replacing alternate stepping. Motor performance of the gerbil pups corroborates previous studies in following a developmental motor gestalt termed ‘warm-up’, which involves an ordered incorporation of movements along three distinct spatial dimensions. In the present results, the validity of warm-up has been extended to a quantitative perspective: the order in which movement types reached their peak performance was identical to the order of their emergence in ontogeny. Transient modes of locomotion were also employed by gerbil pups during postnatal development, in accordance with changes in body morphology, indicating that there exists a causal link between body design and specific modes of locomotion.
Feeding Kinematics of Phyllomedusine Tree Frogs
Authors: Gray Lucie A. , Nishikawa Kiisa C. 
Published: April 2021

ABSTRACT
Previous studies have demonstrated that the phyllomedusine hylids possess highly protrusible tongues, a derived characteristic within the family Hylidae. In the present study, the kinematics of the feeding behavior of a phyllomedusine species, Pachymedusa dacnicolor, was analyzed using high-speed video (180 frames s-1). Its behavior was compared with that of Hyla cinerea, a species with a weakly protrusible tongue. P. dacnicolor exhibits a faster rate of tongue protraction, a longer gape cycle and more variable feeding kinematics than H. cinerea. In addition, the tongue is used in a unique ‘fly-swatter’ fashion, to pin the prey to the substratum as the frog completes the lunge. The rapid tongue protraction, extended gape cycle and fly-swatter action may have evolved in response to a diet of large, rapidly moving insects. In addition, several duration variables of the feeding cycle were greater for misses than for captures and drops, which suggests that sensory feedback rather than biomechanics controls gape cycle duration.
The Mechanical Properties of fast and Slow Skeletal Muscles of the Mouse in Relation to their Locomotory Function
Authors: James Rob S. , Altringham John D. , Goldspink David F. 
Published: April 2021

ABSTRACT
The mechanical properties of soleus and extensor digitorum longus (EDL) muscles from the mouse were studied using the work loop technique. Under optimum conditions, the EDL produced a maximum mean power output of 107 W kg-1 at a cycle frequency of 10 Hz. In comparison, the maximum mean power output of the soleus was 34 W kg-1 at 5 Hz cycle frequency. Video analysis of mice determined the stride frequency range to be from 2.87 Hz at a walk to 8.23 Hz at a flat-out gallop, with the trot-to-gallop transition occurring at 5.89 Hz. In vivo EDL electromyogram (EMG) activity is recorded primarily during shortening and the muscle operates in a power-generating mode. The soleus is close to isometric when EMG activity is recorded, but mechanical activity persists into the shortening phase. Both muscles are likely to operate over cycle frequency ranges just below, or at, those yielding maximal power. Soleus and EDL produced maximal power output in vitro when operating at mean sarcomere lengths of 2.58 μm and 2.71 μm respectively. These lengths are slightly above the plateau of the length–force curve predicted for rat leg muscle (2.3–2.5 μm). The sarcomere length ranges used in vivo by the soleus and EDL were determined, by fixing muscles in the extreme active positions predicted from video and cine analysis, to be 2.28–2.57 μm and 2.49–2.88 μm respectively. These ranges are both close to those shown to yield maximum power output in vitro and to the plateau of the sarcomere length–force curve.
Motor Innervation of the Oviducts and Central Generation of the Oviductal Contractions in two Orthopteran Species (Calliptamus SP. and Decticus Albifrons)
Authors: Kalogianni E. , Theophilidis G. 
Published: April 2021

ABSTRACT
The oviducts of the female Decticus albifrons (Orthoptera: Tettigonidae) are innervated by six bilaterally paired neurones, while those of the female Calliptamus sp. (Orthoptera: Catantopidae) are innervated by three bilaterally paired neurones, located in the seventh abdominal ganglion. Using intracellular recording and staining, five of the six oviductal neurones of D. albifrons and the three oviductal neurones of Calliptamus sp. were physiologically and morphologically identified. All three oviductal neurones of Calliptamus sp. have a motor function. In D. albifrons, however, there is evidence for motor function in only three of the five identified oviductal neurones that appear to participate in the generation of the oviductal contractions. The remaining two identified neurones of D. albifrons have a branching pattern similar to that of motor neurones, but their physiological characteristics, large overshooting soma action potentials (30–40 mV) with a long afterhyperpolarising phase, are similar to those of the oviductal unpaired median neurones, which are known to modulate the oviductal contractions. The oviductal muscle exhibits two different modes of contractions: (a) fast and slow myogenic contractions, the fast contractions being produced by spontaneous potentials (30–40 mV) generated by some oviductal muscle fibres; and (b) neurogenic contractions caused by the rhythmic spiking of the oviductal motor neurones. This motor pattern is produced by the oviductal central pattern generator, a neural network residing in the last two abdominal ganglia (seventh and terminal abdominal ganglia) of the species examined here. When isolated both anteriorly and posteriorly, the seventh abdominal ganglion generates rhythmic oviductal contractions of lower frequency and amplitude than those recorded when the connectives between the genital ganglia are intact. The oviductal pattern generator is activated through release from descending inhibition, which originates, in Calliptamus sp., from the compound metathoracic ganglion (fused metathoracic and first three abdominal neuromeres) and in, D. albifrons, from the first free abdominal ganglion (fused second and third abdominal neuromeres).