bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium and chloride transport in the isolated intestine of the earthworm,Lumbricus terrestris(L.)
Authors: Cornell John C. 
Published: April 2021

ABSTRACTMeasurements of electrical potential difference (PD), short-circuit current (SCC) and unidirectional fluxes of sodium and chloride were made across portions of the intestine. Based on the results, the intestine can be divided into at least four physiologically distinct regions. These four physiological regions, designated from anterior to posterior as R I–fl, R III A, R III B and R IV, do not completely correspond to the four anatomically distinct regions of the intestine. The PD (serosal side positive) in R I–II, R III A, R III B and R IV is 1·08, 12·4, 5·61 and 31·7 mV, respectively. The SCC in these same regions is 9·9, 50·4, 49·7, and 16·4μA cm2, respectively. When short-circuited, net sodium and net chloride fluxes in the above regions are –0·36 and –0·27, 1·46*** and –0·92*, 1·74*** and –0·06 and 0·01*** and 0·07 μmol cm-2 h-1, respectively. Positive fluxes indicate net mucosal to serosal movements and asterisks indicate significant net fluxes (* P &lt; 0·05, *** P &lt; 0·001). There is good agreement between the SCC and net sodium transport in R III B. In the other regions of the intestine the ionic basis of the SCC has not been completely explained. The properties of the intestine in vitro appear to make the intestine well suited for the task of conserving sodium, a function which the intestine performs in vivo.
Saccadic eye movements are coordinated with head movements in walking chickens
Authors: Pratt David W. 
Published: April 2021

ABSTRACT
Saccadic eye movements during walking were studied in chickens using cinematography. Saccades were made during about 80% of the thrust phases of head bobbing, and not made in the hold phases. The coordination of saccades with head movements maintains clear vision for the largest possible proportion of the time. The absence of saccades in hold phases and in some thrusts is probably not the result of insufficient time to organize a saccade.
Energetics and mechanics of terrestrial locomotion. II. Kinetic energy changes of the limbs and body as a function of speed and body size in birds and mammals
Authors: Fedak M. A. , Heglund N.C. , Taylor C.R. 
Published: April 2021

ABSTRACT
This is the second paper in a series examining the link between energetics and mechanics of terrestrial locomotion. In this paper, the changes in the kinetic energy of the limbs and body relative to the centre of mass of an animal (EKE, tot) are measured as functions of speed and body size. High-speed films (light or X-ray) of four species of quadrupeds and four species of bipeds running on a treadmill were analysed to determine EKE, tot . A mass-specific power term, ĖKE, tot/Mb was calculated by adding all of the increments in EKE. during an integral number of strides and dividing by the time interval for the strides and body mass. The equations relating ĖKE, tot /M6 and speed were similar for all bipeds and quadrupeds regardless of size. One general equation for the rate at which muscle and tendons must supply energy to accelerate the limbs and body relative to the centre of mass seems to apply for all of the animals :
where Ė′KE, tot/Mb has the units W kg-1 and vg is ground speed in m s-1. Therefore, Ė′KE, tot/Mb does not change in parallel with the mass-specific rate at which animals consume energy (Ėmetab/Mb), either as a function of speed or as a function of body size.
Water loss and nitrogen excretion in sharp-nosed reed frogs (Hyperolius nasutus:anura, Hyperoliidae)
Authors: Withers Philip C. , Hillman Stanley S. , Drewes Robert C. , Sokol Otto M. 
Published: April 2021

ABSTRACTSharp-nosed African reed frogs, Hyperolius nasutus Gunther, are small (0·4 g) hyperoliids which have minimal rates of evaporative water loss (4·5 mg g−1 h−1; 0·3 mg cm−2 h−1) that are only 1/10 to 1/20 that of a typical frog, Hyla regilla, of comparable size ( 171 mg g−1 h−1,4·8 mg cm−2 h−1). The surface-area-specific resistance to water flux of H. nasutus dorsal skin (96–257 sec cm−1) is similar to that of other ‘waterproof’ frogs (300–400), of cocooned frogs (40–500), and of desert reptiles (200–1400). However, H. nasutus can greatly increase the rate of evaporative water loss during radiative heat stress by mucous gland discharge, and by exposing the ventral skin.Urea is the principal nitrogenous waste product of H. nasutus and uric acid comprises less than 1 % of the total nitrogen excretion for both H. nasutus and H. regilla. Other ‘waterproof’ frogs, in contrast, are uricotelic.Lethal dehydration requires less than two weeks in H. nasutus, despite its low surface-area-specific rate of water loss, because of its small size and concomitantly high surface-to-volume ratio. The rate of urea accumulation during dehydration was 23 mM g−1 day−1, which is sufficiently low that urea accumulation would not be lethal before the frog had succumbed to dehydrational death. Consequently, there appears to be little or no selective advantage for uricotely in small ‘waterproof’ frogs, such as H. nasutus.
The respiratory metabolism of temperature-adapted flatfish at rest and during swimming activity and the use of anaerobic metabolism at moderate swimming speeds
Authors: Duthie Garry G. 
Published: April 2021

ABSTRACTThe standard oxygen consumption and the oxygen consumption during measured swimming activity have been determined in three flatfish species at 5, 10 and 15 °C. The relationship between weight and standard oxygen consumption for flatfish conform to the general relationship Y = aWb. On an interspecies basis, standard oxygen consumption of flatfish is significantly lower than that of roundfish. A semilogarithmic model describes the relationship between oxygen consumption and swimming speed for the three species. Values for maximum oxygen consumption, metabolic scopes and critical swimming speeds are low in comparison to salmonids. The optimum swimming speeds and critical swimming speeds of flatfish are similar. It is suggested that, over long distances, flatfish adopt a strategy of swimming at supercritical speeds with periods of intermittent rest to repay the accrued oxygen debt. Elevated lactic acid levels in flounder white muscle after moderate swimming indicate an additional 15 % anaerobic contribution to the cost of locomotion as calculated from aerobic considerations.
Water-electrolyte balance in goldfishCarassius auratus, under constant and diurnally cycling temperature conditions
Authors: Houston A. H. , Koss T. F. 
Published: April 2021

ABSTRACTThe effects of acclimation to constant and diurnally cycling temperatures upon water-electrolyte regulation were examined in goldfish held at 20, 25, 30 and 25 ± 5 °C, and sampled at 03.00, 09.00, 15.00 and 21.00 h. Plasma and epaxial muscle levels of Na, K, Ca, Mg, Cl and water were determined. Using Cl space as an indicator of extracellular phase volume, mean cellular cation concentrations were estimated. Fish held at constant temperature exhibited significant diurnal variations in all ions except plasma magnesium and muscle potassium. With the exception of muscle choride, however, the occurrence of peak and/or minimum concentrations tended to be inconsistent in relation to specific sampling times. Somewhat more regularity was apparent in terms of dark or light periods. Under constant temperature conditions plasma Cl increased with increasing temperature, while Na declined. Plasma magnesium was consistently higher at 25 °C than at either 20 or 30 °C. This was true of muscle Mg as well and, generally, also of Na, K and CL Water content tended to rise at higher temperatures in these animals, as did cellular phase volume, while extracellular phase volume was reduced. Exposure to cycling temperatures was associated with a number of significant departures from the pattern seen at constant temperature. Ionic concentrations tended to be lower. By comparison with animals sampled at constant temperature and comparable times, diurnal stability was greater. In several instances (e.g. muscle Cl− and K+, cellular and extracellular phase volumes) variations with temperature were significantly different. This was also the case with ion pairs such as K and Na, and Ca and Mg. These observations raise obvious questions regarding the validity of earlier descriptions of water-electrolyte status in species normally exposed to fluctuating temperatures. The variations seen under cycling temperature conditions, however, appeared to be adaptively appropriate. Reductions in plasma ion levels, for example, would tend to reduce costs of ionic regulation. The stability of plasma: cellular K concentrations should desensitize muscular excitability in relation to changing temperature conditions. This was also true of cellular levels of generally stimulating (Mg, K) and generally inhibitory ions (Ca, Na) known to influence metabolic processes.
Energetics and mechanics of terrestrial locomotion. IV. Total mechanical energy changes as a function of speed and body size in birds and mammals
Authors: Heglund N. C. , Fedak M. A. , Taylor C. R. , Cavagna G. A. 
Published: April 2021

ABSTRACTThis is the nal paper in our series examining the link between the energetics and mechanics of terrestrial locomotion. In this paper the kinetic energy of the limbs and body relative to the centre of mass (EKE,tot of paper two) is combined with the potential plus kinetic energy of the centre of mass (ECM,tot of paper three) to obtain the total mechanical energy (excluding elastic energy) of an animal during constant average-speed locomotion. The minimum mass-specific power required of the muscles and tendons to maintain the observed oscillations in total energy, Ėtot/Mb, can be described by one equation : where Ėtot/Mb is in W kg−1 and vg is in m s−1. This equation is independent of body size, applying equally as well to a chipmunk or a quail as to a horse or an ostrich. In marked contrast, the metabolic energy consumed by each gram of an animal as it moves along the ground at a constant speed increases linearly with speed and is proportional to Mb−0·3. Thus, we have found that each gram of tissue of a 30 g quail or chipmunk running at 3 m s−1 consumes metabolic energy at a rate about 15 times that of a 100 kg ostrich, horse or human running at the same speed while their muscles are performing work at the same rate. Our measurements demonstrate the importance of storage and recovery of elastic energy in larger animals, but they cannot confirm or exclude the possibility of elastic storage of energy in small animals. It seems clear that the rate at which animals consume energy during locomotion cannot be explained by assuming a constant efficiency between the energy consumed and the mechanical work performed by the muscles. It is suggested that the intrinsic velocity of shortening of the active muscle motor units (which is related to the rate of cycling of the cross bridges between actin and myosin) and the rate at which the muscles are turned on and off are the most important factors in determining the metabolic cost of constantspeed locomotion. Faster motor units are recruited as animals increase speed, and equivalent muscles of small animals have faster fibres than those of larger animals. Also, the muscles are turned on and off more quickly as an animal increases speed, and at the same speed a small animal will be turning muscles on and off at a much higher rate. These suggestions are testable, and future studies should determine if they are correct.
Long-term submergence at 3 degrees C of the turtle Chrysemys picta bellii in normoxic and severely hypoxic water. III. Effects of changes in ambient and subsequent air breathing
Authors: Ultsch Gordon R. , Jackson Donald C. 
Published: April 2021

ABSTRACT
Western Painted Turtles, Chrysemys picta bellii (N = 5), were maintained submerged and apneic for 90 days: days 0–21 in severely hypoxic water ( = 0–5 mmHg), days 22–43 aerated water ( ∼ 160 mmHg), and days 44–90 again in hypoxic water. From day 90 onward, the water was aerated and the turtles were allowed access to the air ; water and air temperatures were maintained at 3 °C.
Arterial blood samples were taken periodically and analysed for , pH, [Na+], [K+], [Cl−], [lactate−], [glucose] and haematocrit. Plasma [HCO3−] was calculated for all samples and total plasma calcium was measured on samples from two animals.
Each exposure to low water caused progressive lactic acidosis and a transient respiratory acidosis with an accompanying fall in plasma [Cl−] and rise in plasma [K+] and [calcium]. During the intervening period in aerated water, blood pH recovered significantly (from 7·33 to 7·74 in 7 days), due primarily to a fall in , (from 233 to 10·6 mmHg), while [lactate−] remained unchanged (at about 50 mM), and [HCO3−] rose slightly. Plasma [K+] promptly returned to nearly normal values.
When permitted to breathe on day 90, the three surviving turtles rapidly restored pH to normal by pronounced hyperventilation ( &lt; 5 mmHg). Metabolic acidosis, however, disappeared slowly with a for [lactate−] and [HCO3−] restoration of about 2 weeks.
We conclude that a wintering turtle can stabilize or even slightly improve its acid-base and ionic status by moving from an anoxic environment to well-oxygenated water. Further improvement can be gained by breathing air, but recovery proceeds at a very slow rate if the animal remains at 3 °C.
On Peripheral Control Mechanisms Acting on the Central Pattern Generators for Swimming in the Dogfish
Authors: Grillner Sten , Wallén Peter 
Published: April 2021

ABSTRACT
When sinusoidal movements were artificially imposed on the tail region of the curarized spinal dogfish during ‘fictive locomotion’ the coordinated burst pattern recorded in the ventral roots was effectively entrained to follow movement frequencies above as well as below the resting rate. The entrainment was characterized by: (1) a broad range of effective movement frequencies and amplitudes (down to a few degrees) ; (2) frequency-dependent timing of entrained bursts to the movement; (3) constant burst durations at low and moderate frequencies; (4) incomplete entrainment in response to high or low movement frequencies combined with a low amplitude; (5) entrainment was still present when mean position of movement was displaced laterally; (6) effects persisted when the tail region was devoid of skin and muscle tissue.
Entrainment effects may be explained by the activation of stretch receptors on either side of the vertebral column-spinal cord, exciting the presumed central pattern generators (CPGs) in the hemisegments ipsilateral to the stretch, while inhibiting the contralateral CPGs.
Effect of Maintained Hypoxic Exposure on the CrayfishOrconectes Rusticus: II. Modulation of Haemocyanin Oxygen Affinity
Authors: Wilkes P. R. H. , McMahon B. R. 
Published: April 2021

ABSTRACTHaemolymph Na+, Cl−, K+, Mg2+, Ca2+, Cu2+ and protein levels, in vivo postbranchial acid-base status (total CO4, pH and ), in vitro haemolymph buffer value, Bohr value and oxygen affinity were measured before and after a -week period in which control crayfish were maintained at normoxia and experimental crayfish were maintained at an ambient oxygen tension of 50–55 torr. Analysis of haemolymph Cu2+ and protein levels in control and experimental crayfish indicated no increase in haemocyanin and therefore oxygen carrying capacity of the haemolymph. Although the Bohr value was not significantly different between control and experimental crayfish, the haemocyanin oxygen affinity was elevated in the hypoxic crayfish by two mechanisms. The first was dependent upon the haemolymph H+ concentration, i.e. a Bohr shift resulting from a respiratory alkalosis. The second mechanism was independent of haemolymph H+ concentration in that at a given pH haemolymph from experimental crayfish had a significantly higher oxygen affinity. The decrease in P50 probably cannot be attributed to a specific cation effect.
Re-Examination of Presumed Feeding Motor Activity in the Isolated Nervous System of Pleurobranchaea
Authors: McClellan Andrew D. 
Published: April 2021

ABSTRACT
In most isolated gastropod nervous systems, presumed feeding motor patterns are thought to be represented by the alternating motor activity in buccal roots, which underlies rhythmic radula movement. Since this movement accompanies several types of behaviour in the gastropod Pleurobranchaea (McClellan, 1979, 1980, 1982), the presumed feeding motor activity in the isolated nervous system of this animal was re-examined in more detail. Alternating buccal root activity was shown here to be associated with other types of behaviour besides feeding, and is, therefore, not sufficiently unique to serve as a ‘neural correlate’ for feeding in Pleurobranchaea and presumably other gastropods. Unlike the isolated nervous systems of most gastropods, which generate only one buccal rhythm, that of Pleurobranchaea generates two different buccal motor patterns which alternate: (1) a slow ‘primary’ rhythm whose behavioural identity is unclear, and (2) brief periods of a relatively fast rhythm which underlie bouts of vomiting. In general, a buccal rhythm generated by an isolated gastropod nervous system can only be assigned a function if there are features of the rhythm that are unique to only one of the several behavioural responses involving the buccal mass.
The Contribution of the Branchial Heart to the Accessory Branchial Pump in the Octopoda
Authors: Smith P. J. S. 
Published: April 2021

ABSTRACT
Experimental and anatomical observations upon the Octopoda suggest that the branchial hearts are not the sole contributors to the increase in venous blood pressure between the anterior vena cava and the afferent branchial vessel.
The lateral venae cavae are proposed as an additional source of pressure generation, thus contributing to the octopod accessory branchial pump.
Bone Strength in Small Mammals and Bipedal Birds: Do Safety Factors Change With Body Size?
Authors: Biewener Andrew A. 
Published: April 2021

ABSTRACTMeasurements of the cross-sectional geometry and length of bones from animals of different sizes suggest that peak locomotory stresses might be as much as nine times greater in the limb bones of a 300 kg horse than those of a 0·10 kg chipmunk. To determine if the bones of larger animals are stronger than those of small animals, the bending strength of whole bone specimens from the limbs of small mammals and bipedal birds was measured and compared with published data for large mammalian cortical bone (horses and bovids). No significant difference (P &gt; 0·2) was found in the failure stress of bone over a range in size from 0·05–700 kg (233 ± 53 MN/m1 for small animals compared to 200 ± 28 MN/m2 for large animals). This finding suggests that either the limb bones of small animals are much stronger than they need to be, or that other aspects of locomotion (e.g. duty factor and limb orientation relative to the direction of the ground force) act to decrease peak locomotory stresses in larger animals.
A Dual Effect of Cobalt Ions on the Spontaneous Release of Transmitter At Insect Motor Nerve Terminals
Authors: Washio Hiroshi 
Published: April 2021

ABSTRACT
The effect of extracellular cobalt on the frequency of miniature excitatory post-synaptic potentials (MEPSPs) was studied in cockroach leg muscle fibres that had been depolarized with 20·8 mm-K saline. Cobalt ions had a dual effect on the spontaneous release of transmitter, an inhibitory action being followed by an acceleratory. A reciprocal relationship between Ca2+ and Co2+ was found for both the inhibitory and acceleratory effects. The equilibrium dissociation constant for Co2+ as a competitive antagonist of spontaneous release ranged from 0·4 to 0·65 mm. It is concluded that Co2+ is much more potent than Mg2+ in suppressing spontaneous transmitter release at the insect neuromuscular junction. The antagonism by extracellular Co2+ appears to occur only at the external surface site on the terminal membrane.
The Distribution and Molecular Characteristics of the Tanning Hormone, Bursicon, in the Tobacco Hornworm Manduca Sexta
Authors: Taghert Paul H. , Truman James W. 
Published: April 2021

ABSTRACT
The distribution and molecular properties of the tanning hormone bursicon were studied using an isolated wing biological assay. Wing cuticle tanning activity was measured in saline homogenates of the central nervous system and selected muscles. Activity was detected in all ganglia of the nervous system in both the prepupal and pharate adult developmental stages. In both stages, this activity was predominantly located in the abdominal portion of the nervous system. The titres in all ganglia, except the suboesophageal, increased during metamorphosis. Of the various non-neural tissues examined, only the closer muscle of the spiracle contained detectable levels of activity.
All activity in the nervous tissue was sensitive to proteolytic digestion; it could not be mimicked by any of the 17 putative transmitter and/or hormonal substances tested. Partial purification of the tanning activity indicated an apparent molecular weight of 20–30 K.
The partially purified material (from gel filtration) resembled the hormone bursicon in the following three ways : its titre in the tissue declined following normal bursicon release ; it could be recovered from the haemolymph during normal bursicon release; it could be released from isolated nervous tissue following high potassium stimulation in a calcium-dependent manner.
It was concluded that the hormone bursicon represents most if not all the tanning activity present in the central nervous system, that it is widely distributed in that tissue and that it is present as a peptide (or class of peptides) with homogeneous size and charge.
Thermal Acclimation in A Crustacean Neuromuscular System
Authors: Stephens Philip J. , Atwood Harold L. 
Published: April 2021

ABSTRACTEffects of temperature on the muscle fibre membrane and synapses of stretcher muscle preparations made from autotomized limbs of the Pacific shore crab (Pachygrapsus crassipes) were investigated. Acclimation of the crabs to different temperatures modified properties of both muscle fibre membrane and synapses. Increased temperature produced an increase in membrane potential of the muscle fibres. A semi-log plot of these data revealed two linear phases of the membrane potential-temperature relationship, with a change in slope near the acclimation temperature. Maximum values for excitatory junction potential (EJP) amplitude and time constant of EJP decay, and minimum values for facilitation were obtained at temperatures close to the acclimation temperature. It is suggested that the decline in EJP amplitude and time constant of decay produced by deviations in temperature from the acclimation temperature is compensated for by an increase in the amount of facilitation. In this way, maximum tension can be produced by the stretcher muscle in a range of at least 8 °C around the acclimation temperature.
Effects of Temperature on the Endogenous Activity and Synaptic Interactions of the Salivary Burster Neurones in the Terrestrial SlugLimax Maximus
Authors: Prior David J. , Grega Debra S. 
Published: April 2021

ABSTRACTThe activity of the endogenously active salivary burster neurones (SBs) shows temperature acclimation and has characteristic cold and warm Blockade temperatures. Temperature acclimation affects the upper and lower limits of the temperature range over which SBs are active. The absolute range, in centigrade degrees, during warming, is unaffected by acclimation. Acclimatization of burster activity is a slow response to the mean ambient temperature. There is increased synchrony of activity between the right and left salivary bursters at low temperature which is correlated with an increased electrical coupling between the SBs and protractor motoneurones (B7s). There is a corresponding increase in the input resistance of B7 at low temperatures.