bluuebunny/crossref_metadata_2025_split huggingface dataset:
Is the High Cost of Body/Caudal Fin Undulatory Swimming Due to Increased Friction Drag or Inertial Recoil?
Authors: Webb Paul W. 
Published: April 2021

ABSTRACT
Deep-bodied fish, such as the bluegill sunfish (Lepomis macrochirus), are considered to have relatively larger wetted surface areas for their size than fusiform fish. On the basis of the boundary layer thinning hypothesis attributing high power requirements of undulatory swimming to enhanced friction drag, power (=drag) coefficients should be higher for such fish. Areas are typically normalized with total length, L, as L2 for comparison among species. Bluegill had a wetted surface area of 0.65 L2, compared with areas of about 0.41 L2 for trout of similar mass. However, absolute areas and volume2/3 of bluegill and trout were similar. Power requirements and power coefficients calculated from kinematics during steady swimming were lower for bluegill sunfish than for cruisers, such as trout, and power coefficients were also lower than those of accelerators, such as tiger musky. Large body depth also damps inertial recoil arising from the side force generated largely by the tail. Inertial energy losses appear to be more important contributors than friction to mechanical power requirements.
A Time-Dependent Excitability Change in the Soma of an Identified Insect Motoneurone
Authors: Hancox Jules C. , Pitman Robert M. 
Published: April 2021

ABSTRACT
Long-term, current-clamp recordings were made from the cell body of the fast coxal depressor motoneurone (Df) of the third thoracic ganglion of the cockroach Periplaneta americana. In freshly dissected preparations the response to short-duration, suprathreshold, depolarising current pulses was a graded series of damped membrane oscillations similar to those reported previously in this neurone. The response to current injection changed, however, with increasing time after setting up the preparation: cells developed the ability to exhibit all-or-none action potentials. Their amplitude, however, was usually insufficient to overshoot 0mV. Our observations suggest that the enhancement in excitability is dependent on time following dissection rather than on time following impalement.
Recordings taken from neurone somata mechanically divided from their processes indicated that the time-dependent changes in excitability were not attributable to changes in synaptic input to the neurone and, moreover, that the cell body was involved in action potential genesis. The action potentials were resistant to treatment with the sodium channel blocker tetrodotoxin (up to 10−5moll-1), but were reversibly abolished when preparations were bathed in saline containing cadmium ions (1 mmol l-1) or manganese ions (20 or 40mmoll-1) and, therefore, the inward current underlying these events was largely, if not entirely, carried by calcium ions.
These time-dependent action potentials can co-exist with plateau potentials. In neurones giving both plateau potentials and time-dependent action potentials, plateau potentials can drive action potentials in bursts.
Temperature Dependency of Wing-Beat Frequency in Intact and Deafferented Locusts
Authors: Foster Jane A. , Robertson R. Meldrum 
Published: April 2021

ABSTRACT
Locusts do not regulate thoracic temperature during flight and as a result the thoracic temperature of a flying locust generally exceeds ambient temperature by 5-8 °C. Elevated thoracic temperatures were shown to affect wing-beat frequency in intact and deafferented Locusta migratoria. Tethered locusts were flown in a wind tunnel. Temperature was elevated by increasing the ambient temperature of the apparatus and by exposing flying animals to heat pulses. Electromyographic (EMG) recordings were made in deafferented locusts perfused with salines at different temperatures. Wing-beat frequency was shown to vary with thoracic temperature in both the intact and the deafferented situation. The slope of the rise in wing-beat frequency with experimental increases in thoracic temperature was similar in intact and deafferented animals. These experiments demonstrate an effect of temperature on the central flight circuitry. Further intracellular investigations are needed to determine the neural basis of these effects.
Muscle Firing Patterns in two Arachnids Using Different Methods of Propulsive Leg Extension
Authors: Shultz Jeffrey W. 
Published: April 2021

ABSTRACT
Activity patterns of six morphologically similar, homologous muscles were recorded from the fourth leg pair in two species of arachnids that use different mechanisms to extend the femur-patella (knee) joint during locomotion. The giant whipscorpion Mastigoproctus giganteus (Uropygi) lacks femur-patella extensor muscles but extends this joint with hydraulic pressure, a mechanism that appears to be phylogenetically primitive in arachnids. The black emperor scorpion Pandinus imperator (Scorpiones) has an unusual muscle that promotes simultaneous extension at the femur-patella joint and distally adjacent patella-tibia joint. Comparison of electromyograms from freely walking animals revealed similarities in muscle firing patterns of the two species, including asymmetrical alternation of trochanter-femur levator and depressor muscles, transfemoral muscle activation during protraction and abrupt termination just prior to levator activation, and persistence of flexor activity during retraction (extension). These results indicate that the apparent evolutionary transition from hydraulic to muscular extension occurred without substantial alteration of several components of the primitive motor programme. It is suggested that the patterns of extension force generated by hydraulic pressure and by bifunctional extensors are similar and that this similarity is associated with conservation of the motor programme.
A Simple Method for Construction of Flexible, Subminiature Ion-Selective Electrodes
Authors: O’donnell M. J. 
Published: April 2021

ABSTRACT
Liquid membrane electrodes have greatly facilitated the measurement of pH and ion activities in intra- and extracellular fluids. Ion-selective microelectrodes (ISMEs) can be constructed by introducing a short column of a neutral carrier or ion-exchanger cocktail into the tip of a glass micropipette. The inner surface of the glass is first made hydrophobic by exposure to compounds containing silane (Thomas, 1978; Amman, 1986). This process, termed silanization, prevents subsequent displacement of the hydrophobic cocktail, either by entry of aqueous biological fluids through the tip of the micropipette or by migration of the backfilling solution. Macroscopic electrodes (5–10 mm diameter) can be produced by first incorporating appropriate neutral carriers into solvent polymeric membranes of polyvinyl chloride (PVC) or silicone rubber. Membranes can then be stamped out with a cork borer and glued or fused onto PVC tubing or commercially available electrode bodies (Meier et al. 1980). Electrodes with outer diameters of 1.5–1.7 mm have been formed by dipping tubing into a cocktail containing the ionophore, PVC and solvents. Solvent evaporation forms a membrane about 25 μm thick on the tip of the tubing (Oesch et al. 1987). A technique for the construction of miniature double-barrelled K+ electrodes with a total o.d. of 600 μm and a shank 1.3 cm long has been described by Hill et al. (1978).
Maternal and Paternal Nitrogen Investment in Blattella Germanica (L.) (Dictyoptera; Blattellidae)
Authors: Mullins Donald E. , Keil Clifford B. , White Robert H. 
Published: April 2021

ABSTRACT
The investment of nitrogenous materials by female and male German cockroaches Blattella germanica (L.) into their progeny was examined. Adult females maintained on dog food invested 34 % of their dry mass and 26 % of their nitrogen into an ootheca during their first gonadotrophic cycle. Females maintained on a low-(5%) protein diet and injected simultaneously with [3H]leucine and [14C]hypoxanthine incorporated less [3H]leucine-derived radiolabel in their oothecae than those on a dog food diet (25% crude protein). Females on the lowprotein diet incorporated more [14C]hypoxanthine-derived material (primarily as [14C]urates) into their oothecae than they retained in their bodies. Stored [L4C]urates were metabolized more readily by females on the low-protein diet. Oothecae obtained from females provided with an [15N]urate-amended diet contained at least four 15N-enriched amino acids, which supports the hypothesis that urates are utilized as a nitrogen resource in these insects.
Dietary effects on paternal investment were also found to be significant. Females fed a low-protein diet and their oothecae contained 63 % of the radiolabel made available to them at mating when paired with males injected simultaneously with [3H]leucine and [14C]hypoxanthine, whereas dog-food-fed females and their oothecae contained only 17 % of the total radiolabel made available to them at mating.
Degenerative Changes in the Structure of Neuromuscular Junctions of Manduca Sexta During Metamorphosis
Authors: Rheuben Mary B. 
Published: April 2021

ABSTRACT
During the degenerative processes that precede and accompany metamorphosis of the larval mesothoracic dorsal longitudinal muscles of Manduca sexta, the motor nerves and neuromuscular junctions undergo a variety of structural changes that are largely secondary to the changing morphologies of their respective glia. In the central region of the main motor nerve, the multiple layers of glial processes surrounding each of the large axons withdraw, leaving them apposed. In the peripheral region of the main motor nerve and in the secondary and tertiary nerve branches supplying the muscle, the outer glial processes of the nerve sheath and those that loosely wrap accompanying small neurosecretory axons all swell. Phagocytic cells and cells of unknown function invade the outer region of the nerve. In the neuromuscular junctions, the glial cells withdraw their processes from a complicated interdigitation with processes from the muscle fiber and from their relationship with the nerve terminal. As degeneration proceeds, this allows a greater area of contact between each nerve terminal and the muscle fiber. Within each junction there is a mixture of both functional and non-functional regions and active zones, as determined by both thin-section and freeze-fracture observations. No correlation was found between the degree of degeneration of a neuromuscular junction and its association with a particular muscle fiber or its position on the fiber relative to the origin or insertion.
Degenerative Changes in the Muscle Fibers of Manduca Sexta During Metamorphosis
Authors: Rheuben Mary B. 
Published: April 2021

ABSTRACT
The ultrastructural changes associated with the early stages of degeneration of the larval mesothoracic muscle fibers of Manduca sexta were examined during the prepupal period and on the first day after ecdysis. Over this 5 day period, the muscle fibers decrease in cross-sectional area but increase in apparent surface area compared to the dimensions of early fifth-instar fibers. Large numbers of electrondense granules or droplets are formed and extruded from the muscle cytoplasm into the hemolymph; this process may account for some of the decrease in muscle fiber mass and may represent a developmental mechanism for recycling nutrients. As the fibers shrink, the thick basal lamina is thrown into folds. Phagocytic hemocytes (granulocytes) congregate in clusters over the surface of the degenerating fibers and appear to remove specifically the basal lamina. The timely removal of the thick larval basal lamina may be essential for subsequent fusion of myoblasts to the residual larval myofibers. The contractile elements within the degenerating muscle fibers become disorganized but are not dysfunctional at the end of the first 12 h after the pupal ecdysis. Tracheoles withdraw from intimate contact with each muscle fiber in its clefts and T-tubules and associate in groups adjacent to it. Mitochondria appear to be degenerating. These structural changes are concurrent with a previously observed decline in resting potential and suggest that a significant change in the electrical properties of the muscle fibers should be expected as well.
Sodium-Extruding and Calcium-Extruding Sodium/Calcium Exchangers Display Similar Calcium Affinities
Authors: Schoenmakers TH. J. M. , Flik G. 
Published: April 2021

ABSTRACT
Na+/Ca2+ exchange activities in purely inside-out and mixed inside-out and right-side-out fish enterocyte basolateral plasma membrane vesicle preparations display equal affinities for Ca2+, showing that only the intracellular Ca2+ transport site of the Na+/Ca2+ exchanger is detected in experiments on vesicle preparations with mixed orientation. Therefore, Ca2+ pump and Na+/Ca2+ exchange activity may be compared directly without correction for vesicle orientation. The Na+/Ca2+ exchange activity in fish enterocyte vesicles is compared to the activity found in dog erythrocyte vesicles. The calcium-extruding exchanger in fish basolateral plasma membranes shows values of Km and Vmax for calcium similar to those found for the sodium-extruding exchanger in dog erythrocyte membranes, indicating that differences in electrochemical gradients underlie the difference in cellular function of the two exchangers.
The Effect of Catecholamines, Substance P and Vasoactive Intestinal Polypeptide on Blood Flow to the Gut In the Dogfish Squalus Acanthias
Authors: Holmgren Susanne , Axelsson Michael , Farrell Anthony P. 
Published: April 2021

ABSTRACT
The effects of adrenaline, noradrenaline, substance P and vasoactive intestinal polypeptide (VIP) on dorsal aortic blood pressure, coeliac artery blood flow and heart rate were studied in unrestrained dogfish, Squalus acanthias. Changes in the coeliac vascular bed were calculated from these variables. Perfused tail preparations were used to study the effects of the various drugs on the somatic vascular bed. Corrosion casts were made to study the gross architecture of the coeliac vascular bed.
Adrenaline and noradrenaline increased dorsal aortic pressure and reduced the coeliac artery blood flow. Adrenaline caused a small increase in heart rate while noradrenaline caused a small decrease. Both drugs increased the resistance in the coeliac vascular bed. VIP increased dorsal aortic pressure, heart rate and resistance in the coeliac vascular bed. Substance P caused an increase in heart rate, cardiac output and, in particular, in coeliac artery blood flow; dorsal aortic pressure was simultaneously reduced. Voluntary swimming or fright immediately caused a pronounced reduction in blood flow in the coeliac artery, even though cardiac output and dorsal aortic pressure increased.
It is concluded that adrenergic mechanisms and possibly VIP are involved in reducing the blood flow to the gut, while substance P increases the flow to the gut.
A Mechanosensory Mechanism for Evoking Cellular Contraction in Vorticella
Authors: Katoh Kaoru , Naitoh Yutaka 
Published: April 2021

ABSTRACT
Vorticella contracted (i.e. shrinkage of the cell body and coiling of the stalk) in response to being touched with a microneedle. The threshold excursion of the microneedle required to evoke a contraction was smallest on the cell body. On the stalk, it was larger in regions farther from the cell body. Hitting the stalk did not evoke a contraction if the stalk was mechanically clamped in a region between the site of the hit and the cell body. Rapidly drawing a small portion of the cell body into a micropipette by suction evoked a contraction, whereas a similar stimulus applied to the stalk did not. The threshold depression of the surface membrane of the cell body required to evoke a contraction was inversely proportional to the rate of depression. Tilting the stalk of a specimen detached from its substratum evoked a contraction. The threshold degree of tilting was inversely proportional to the angular velocity of tilting. Tilting the stalk is assumed to cause a localized depression of the surface membrane of the cell body around the stalk. We concluded (1) that the cell body is mechanosensitive and is the site where contractions are initiated; (2) that hitting the stalk evokes a contraction because the hit exerts a mechanical effect on the cell body; and (3) that the rate of expansion of the membrane of the cell body is responsible for activation of a hypothetical mechanoreceptor mechanism which initiates a contraction.
‘Facilitation’ of Melanophore Responses in Winter Flounder Pseudopleuronectes Americanus
Authors: Burton D. , O’driscoll M. P. 
Published: April 2021

ABSTRACT
Melanophores of winter flounder (Pseudopleuronectes americanus) subjected to repeated transfers between black and white backgrounds display pronounced enhancement of the rates of melanosome aggregation and dispersion. Melano-some aggregation in response to repeated injection of noradrenaline displays a similar enhancement. In vitro preparations of microscopic skin samples on scales removed during successive cycles of background changes also display increasing melanophore response rates to K+ stimulation. It is concluded that a physiological ‘priming’ mechanism is involved peripherally at the melanophore level and it is proposed that this represents a form of facilitation. Also, it is deduced from these experiments that a modulation of the microtubular channels associated with melanosome translocation is probably the basis of the facilitation process.
The Photic Environment of a Salmonid Nursery Lake
Authors: Novales-Flamarique Iñigo , Hendry Andrew , Hawryshyn Craig W. 
Published: April 2021

ABSTRACT
The spectral characteristics of Lake Cowichan (Vancouver Island) were examined using a LiCor underwater spectroradiometer. The results were analyzed in terms of salmonid vision with special emphasis placed on the ultraviolet part of the spectrum. Irradiance measurements were taken by SCUBA divers every 3 m from 18m to the surface at each of seven locations. The measurements at each depth consisted of four scans from 300 to 850 nm of downwelling, upwelling and horizontal light in the sun and antisun directions. The study covered different times of day and variable atmospheric conditions. According to predictions from the absorptive properties of water molecules and scattering by these and suspended particulates, it was found that the ultraviolet part of the spectrum was the least transmitted. The light field varied in intensity and dominant wavelengths depending on direction and time of day. The relative proportion of ultraviolet, short and middle wavelengths with respect to the entire spectrum peaked during crepuscular periods; the opposite was true for long wavelengths. An analysis of the irradiance values with respect to salmonid vision showed that there was enough light to stimulate all the photoreceptor mechanisms found in juvenile salmonid retinae (sensitive to ultraviolet, short, middle and long wavelengths) at all depths studied. Nevertheless, 18 m was found to be the limiting depth for stimulation of the ultraviolet cone mechanism, which is required for perception of ultraviolet polarized fight. This depth restriction may be linked to the observed salmonid movements close to the surface during crepuscular periods.
Compartmental Distributions of Carbon Dioxide and Ammonia in Rainbow Trout at Rest and Following Exercise, and the Effect of Bicarbonate Infusion
Authors: Tang Y. , Lin H. , Randall D. J. 
Published: April 2021

ABSTRACT
The carbon dioxide content of the intracellular compartment of fish muscle was determined by direct measurements of CO2 and pH in tissue homogenates of rainbow trout, Oncorhynchus mykiss. The results agree with the concept that compartmental distribution of CO2 is pH-dependent and that muscle membranes are not very permeable to bicarbonate. The interaction between CO2 and ammonia excreted from fish muscle was also investigated by altering plasma CO2 content using bicarbonate infusion following exhaustive exercise. Removal of the acid boundary layer in white muscle by bicarbonate infusion resulted in retention of ammonia in the muscle, indicating that ammonia excretion across the muscle membrane might be enhanced by the hydration of excreted CO2 in the extracellular fluid. Passive diffusion of NH3, rather than NH4+ transfer, is probably the dominant pathway of ammonia excretion through fish muscle membranes.
Uptake and Metabolism of L-Alanine by Freshly Isolated Trout (Salmo Trutta) Hepatocytes: The Effect of Fasting
Authors: Canals P. , Gallardo M. A. , Blasco J. , Sánchez J. 
Published: April 2021

ABSTRACT
Uptake and metabolism of L-alanine by freshly isolated trout hepatocytes has been analyzed. This amino acid is incorporated ‘uphill’ by different carriers, either Na+-dependent or Na+-independent. Na+-dependent uptake shows the characteristics of an ASC system on the basis of cation dependence and substrate preferences. The Na+-independent uptake is split between an L-cysteine-sensitive system and a non-saturable component. No uptake through system A has been found, suggesting that this carrier is lacking in trout hepatocytes. On the basis of inhibition by several preferred amino acids, L-alanine is not taken up through either the L or N systems.
Fasting induced changes in both the uptake of L-alanine and its metabolism to CO2 and glucose. There was an increase in uptake that showed an inverse relationship with L-alanine plasma levels. Glucose production from L-alanine rose during food deprivation, while CO2 production showed an initial increase, similar to that of glucose. At the end of the fasting time considered, however, there was a drop in CO2 production, indicating a different kind of regulation for alanine oxidation and gluconeogenesis.
Activation by Membrane Stretch and Depolarization of an Epithelial Monovalent Cation Channel From Teleost Intestine
Authors: Chang Wenhan , Loretz Christopher A. 
Published: April 2021

ABSTRACT
The intestine of euryhaline teleosts is an important osmoregulatory organ which actively absorbs Na+, Cl− and water from the lumen. This ion-transporting epithelium experiences a variety of physical stimuli resulting from variations in luminal osmolality and distension and from peristaltic contractions. Using patchclamp techniques in the inside-out configuration, single stretch-activated channels (SA channels) were identified and characterized. These SA channels had a conductance of about 67 pS in symmetrical solutions containing 140 mmol l−1 NaCl and were permeable to both Na+ and K+ (PNa/PK≈0.83) but not to anions. In excised, inside-out membrane patches, channel activity could be enhanced in the absence of membrane tension by strong depolarization of the membrane potential (Vm) to between 0 mV and +90 mV, with Vo [Vm at which the single-channel open probability (Po)=0.5] at +25.7mV. In the presence of membrane tension, the voltage-dependence of channel activity was shifted into the physiological range of Vm. Each kPa (10cmH2O) of applied pressure (ΔP) generated the same effect on Po as a membrane depolarization of 49 mV. Membrane tension also increased the single-channel current and single-channel conductance in a dose-dependent manner. The kinetic data suggest that this channel has two open states and three closed states. Both stretch- and depolarization-induced increases in Po were attributed to prolongation of the lifetime of the longer open state. Possible physiological roles for this channel include the cellular uptake of Na+ from the lumen as part of the salt and water absorptive process or a yet undefined involvement in cell volume regulation.