bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Acid-Base Status of Prenatal Pups of the Dogfish, Squalus Acanthias, in the Uterine Environment
Authors: Kormanik Gregg A. , Evans David H. 
Published: April 2021

ABSTRACT
The acid-base status of late-term Squalus acanthias L. pups in the uterine seawater environment was examined. Blood values for pH, total CO2, partial pressure of CO2, urea and sodium concentrations in late-term pups were not significantly different from those of the mothers. Haematocrit was slightly lower, while total plasma lipid and ammonia concentrations were several times higher.
The uterine environment in which these pups reside and maintain normal acidbase status is nevertheless quite remarkable. In the later months of gestation, up to six pups (approx. 60 g each) reside in each horn of the uterus, in about 100 ml of seawater, in which they ventilate. While the major ion concentrations of the uterine fluid resemble normal seawater, the pH may be as low as 5·9, and the ammonia concentration as high as 22 mmol 1−1.
This system provides a unique opportunity to study acid-base balance, respiration and nitrogenous waste excretion in developing elasmobranchs under quite unusual conditions.
Fracture Toughness Design In Horse Hoof Keratin
Authors: Bertram J. E. A. , Gosline J. M. 
Published: April 2021

ABSTRACT
An engineering fracture mechanics approach was applied to the analysis of the fracture resistance of equine hoof-wall. The relationship between fracture toughness and the morphological organization of the keratin hoof tissue was investigated. Fracture toughness was evaluated using the J-integral analysis method which employs the compact tension test geometry. Tensile tests were also conducted to evaluate the effect of the morphological organization on the stress-strain behaviour. Hoof-wall has greatest fracture resistance for cracks running proximally, parallel to the tubular component of the wall keratin. For fully hydrated material tested in this direction the mean critical J-integral value at failure was 1·19× 104 J m−2. This was nearly three times greater than the value determined for the weakest orientation, in which the crack ran parallel to the material between the tubules. The lower fracture toughness of the intertubular material dominates the fracture behaviour of this tissue. The tubular components of the wall appear to reinforce against fracture along the weak plane and the entire wall organization provides the mechanical capability for limiting and controlling fracture in this tissue.
Intrinsic Mechanical Properties of the Perfused Rainbow Trout Heart and the Effects of Catecholamines and Extracellular Calcium Under Control and Acidotic Conditions
Authors: Farrell A. P. , MACLEOD K. R. , Chancey B. 
Published: April 2021

ABSTRACT
A perfused rainbow trout heart was developed which generated its own intrinsic heart rate and a physiological power output. This preparation wàs used to examine the intrinsic mechanical properties of the trout heart, the dose-response effects of catecholamines and extracellular calcium on these properties, and the effects of catecholamines and extracellular calcium during exposure to acidotic conditions. The trout heart was relatively pressure-insensitive to a physiological range of ventral aortic pressures. Preload exerted an important control over cardiac output through the Starling response. Heart rate was independent of both these intrinsic mechanisms. The intrinsic mechanical capabilities of the trout heart were greater than those observed previously in less active, benthic teleosts. Physiological concentrations of catecholamines significantly improved cardiac contractility through positive inotropy and chronotropy. Adrenaline was more potent than noradrenaline, indicating that these effects were mediated by β2-adrenoceptors. Elevated extracellular calcium produced only a modest improvement of cardiac contractility compared to that produced by adrenaline. Positive inotropy and negative chronotropy were observed with elevated extracellular calcium. Extracellular acidosis always reduced cardiac contractility through negative chronotropy and inotropy. Extracellular calcium improved the inotropic state of the acidotic heart and restored contractility, but the overall improvement of cardiac performance was compromised by an accompanying negative chronotropy. Physiological levels of adrenaline improved cardiac performance during extracellular acidosis. The roles of catecholamines and extracellular calcium are discussed with respect to post-exercise cardiac performance in trout.
An Approach to the Mechanics of Pleating in Dragonfly Wings
Authors: Newman D. J. S. , Wootton R. J. 
Published: April 2021

ABSTRACT
A structural engineering approach to the pleated wings of Odonata has been developed during a functional study of wing morphology in the group. The wing can be regarded as a folded plate structure within which each pleat-side acts as a deep plate-girder. Small cross-veins act as stiffeners within the girders, allowing the membrane to carry web shearing forces as pure tension, through a stressed-skin effect. Bending experiments confirm that the membrane significantly increases the rigidity of wing components. The properties of the membrane are unknown. It lacks birefringence, is very thin, and may be pure epicuticle. The advantages of stressed-skin construction are discussed, and possible modes of structural failure considered. The wing seems adapted to yield reversibly to unpredictable heavy loads.
Neural Correlates of Colour Change in Cuttlefish
Authors: Messenger J. B. , Miyan J. A. 
Published: April 2021

ABSTRACT
This paper presents the first direct demonstration in a living cephalopod of neural activity associated with chromatic behaviour. It has long been known that colour change in these molluscs is unique in that it is brought about by chromatophores controlled neurally rather than hormonally (e.g. Hofmann, 1907). The chromato-phore muscles are innervated directly by nerves whose cell bodies lie in the brain itself (Sereni & Young, 1932; Boycott, 1953); the muscles respond tetanically when these motoneurones are stimulated above 10-15 Hz (Florey, 1966) ; electrical stimulation in the chromatophore lobes of the brain causes darkening of the skin (Boycott, 1961) ; stimulation in the optic lobes can elicit patterning (the expansion of some sets of chromatophores and the simultaneous retraction of others) (Boycott, 1961; Chichery & Chanelet, 1976). Darkening, paling and patterning can also be elicited by introducing specific neurotransmitters into the blood supplying the brain (Andrews, Messenger & Tansey, 1983). But until now no-one has successfully recorded from the nerves supplying a specific set of chromatophores in the living animal and shown changes in activity as the display is switched on and off.
Classification of Ocellar Interneurones in the Cockroach Brain
Authors: Mizunami Makoto , Tateda Hideki 
Published: April 2021

ABSTRACT
Nine types of ocellar interneurones with arborizations in the ocellar tract have been identified in the cockroach, Periplaneta americana. These neurones are classified into (1) five types of ‘PS-neurone’, which project into the posterior slope, (2) two types of ‘OL-neurone’, which project into the lobula and medulla of the optic lobe, and (3) two types of ‘D-neurone’, which descend to the thoracic ganglia. When recordings were made in the ocellar tract, all types of neurones exhibited similar responses: a tonic hyperpolarization during illumination and one or a few transient depolarizations at the end of illumination. However, these neurones are classified into several physiological types from the responses recorded in their axons or terminal regions.
Phase-Dependent Modulation of Auxiliary Swimmeret Muscle Activity in the Equilibrium Reactions of the Norway Lobster, Nephrops Norvegicus L.
Authors: Neil Douglas M. , Miyan Jaleel A. 
Published: April 2021

ABSTRACT
The activity of swimmeret muscles of the lobster Nephrops norvegius during beating in the upright and tilted animal has been examined. The responses to tilt are produced primarily by stimulation of the statocysts. The anatomy of the swimmeret muscles is described. Although essentially similar to previous descriptions, important new aspects are presented. The arrangement of the main powerstroke and retumstroke muscle groups in relation to the peg-and-hook articulation of the swimmeret produces a segregation of action, with different muscles contributing progressively to force production. The auxiliary muscles of the basipodite, M9, M10 and M13 act to twist the swimmeret laterally. The auxiliary muscle Ml 1-12-14—15 acts to maintain a rearward powerstroke. The innervation of swimmeret muscles and the location of their motoneurone cell bodies in the abdominal ganglia have been revealed by cobalt staining. There is a clear segregation of powerstroke and returnstroke motoneurones. Intraganglionic fibre tracts as well as four interganglionic fibres are identified. Intracellular studies on the twister muscles show that M9 receives at least three excitatory units, and M10 at least six. No inhibitory activity was ever recorded in these muscles. M9 and the medial bundle of M10 receive tonic excitatory inputs, while the lateral bundle of M10 receives phasic inputs and is normally silent in the absence of lateral beating. In the absence of swimmeret beating, body roll about the long axis induces tonic motor activation of the lateral twister muscles (M9 and M10) and the return-stroke muscles in the swimmerets on the side tilted upwards. When beating occurs it is predominantly in the swimmerets tilted upwards, and there is an entrainment of phasic activity in M9, M10 and M13 to the powerstroke phase of the beats. Tonic units to the retumstroke muscle remain unaffected. The results are discussed with particular reference to the interaction of descending statocyst information with the central pattern generator for swimmeret beating.
Swimmeret Proprioceptors in the Lobsters Nephrops Norvegicus L. and Homarus Gammarus L.
Authors: Miyan Jaleel A. , Neil Douglas M. 
Published: April 2021

ABSTRACT
The morphology, sensory responses and reflex effects of two proprioceptive systems in the swimmerets of the Norway lobster Nephrops norvegieus are described. Two bipolar cells embedded in an elastic strand (strand B) which spans from the sternal rib to the proximal edge of the basipodite respond to stretch of the strand, applied directly or through swimmeret protraction. Powerstroke motoneurones are excited by a negative feedback reflex, and the transition from retumstroke to powerstroke movement is thereby sharpened. When protraction movements of the swimmeret are blocked, the intensity of beating is reduced both in the blocked swimmeret, and in neighbouring (particularly posterior) swimmerets. A second receptor strand, the twisting muscle receptor (TMR), stretches from the sternal rib wall to the proximal end of the twisting muscle M10 in both the lobsters Nephrops norvegieus and Homarus gammarus. It contains the sensory endings of two cells which have somata in the abdominal ganglion. The axons of these cells convey conventional spikes in response to strand stretch, which occurs on release of M10 from imposed extension or following active M10 contraction. They produce a specific activation of M10 motoneurones, which represents a positive feedback reflex. This reinforces the twist of the swimmeret blade, so that the beat is directed laterally to its greatest extent throughout the powerstroke. It is suggested that the TMR is homologous with the crayfish non-spiking swimmeret receptors, which also have central cell bodies. However, the receptors differ in their location, mode of afferent transmission and reflex actions. The discovery of these differences resolves anomalies between previous studies on lobsters and crayfish. The results are discussed in terms of the homologies of all limb proprioceptors with central cell bodies in decapod crustaceans, and of the proprioceptive control of swimmeret beating.
Monitoring the Metabolic Rate and Activity of Free-Swimming squid With Telemetered Jet Pressure
Authors: Webber D. M. , O’Dor R. K. 
Published: April 2021

ABSTRACT
Measurements of oxygen consumption and mantle cavity pressure (P, kPa) of squid, Illex illecebrosus, of various masses (M,kg), swimming at various speeds (U, ms−1) in a tunnel respirometer yielded two relationships: Both jet frequency and peak pressures increase with increasing speed. Patterns varied considerably between individuals, but total area under the pressure curve (P) was well correlated with oxygen consumption and speed. A differential pressure transducer linked to an ultrasonic transmitter carrying average pressure data encoded on impulse frequency was designed to be carried inside the mantle cavity. It was tested in both the swim-tunnel and in video-taped free-swimming animals. The relationships above held over a range of speeds from 0 to 1·4ms−1, the maximum speed observed, indicating that such transducers could provide direct estimates of both the metabolic rates and activities of these pelagic carnivores in nature; their use to test hypotheses about several energy-saving strategies is discussed. Average thrusts, calculated from pressure data, are consistent with rigid body drag predictions and with overall locomotor efficiencies of 5 %, which are also consistent with the relative costs of transport and efficiency estimates for fish.
Blood pressure control during exercise in the Atlantic cod, Gadus morhua
Authors: Axelsson M. , Nilsson S. 
Published: April 2021

ABSTRACT
Atlantic cod were subjected to 12–15 min swimming exercise at 2/3 body lengths s−1 in a Blazka-type swim tunnel. Pre-and postbranchial blood pressures, cardiac output (ventral aortic blood flow) and heart rate were continuously recorded, and blood samples for measurement of arterial and mixed venous oxygen tension were taken before and at the end of the exercise period. In a second group of fish, subjected to similar exercise regimes, blood samples were taken for analysis of the plasma concentrations of catecholamines.
Pre-and postbranchial blood pressures and cardiac output increase during exercise, while the mixed venous oxygen tension decreases. The effect on cardiac output is due to an increase of both heart rate and stroke volume. There are no significant changes in either systemic or branchial vascular resistances, or in the plasma concentrations of catecholamines.
Injection of the adrenergic neurone-blocking drug bretylium produces a decrease in postbranchial blood pressure in resting cod, due to a decrease in the systemic vascular resistance. Exercising cod treated with bretylium have a significantly lower pre-and postbranchial blood pressure than exercising control cod. This is due mainly to a dramatic reduction in the systemic vascular resistance. The α-adrenoceptor antagonist phentolamine does not further affect the blood pressure in cod treated with bretylium.
It is concluded that the exercise hypertension observed in cod depends on the effect of adrenergic vasomotor fibres maintaining the systemic vascular resistance, and also on the increase in cardiac output. An adrenergic innervation of the heart may play some role in the control of cardiac performance both at rest and during exercise, but the main cardioregulatory mechanism is likely to be non-adrenergic, most probably including cardiac control via variation of the cholinergic vagal cardio-inhibitory tonus.
Motor correlates of learning behaviour: feeding on novel prey by pumpkinseed sunfish (Lepomis gibbosus)
Authors: Wainwright P. C. 
Published: April 2021

ABSTRACT
The functional basis of learning in prey capture was investigated in the pumpkin-seed sunfish (Lepomis gibbosus). Feeding performance of sunfishes was assessed when the fish were first fed a novel, elusive prey (guppies) and compared with their performance after several weeks of experience with capturing guppies. During these feedings electromyographic recordings were made to document the pattern of activity in four jaw muscles at the strike. With experience, the L. gibbosus improved their ability to capture guppies, and several changes in the pattern of muscle activity were associated with this improved performance. Average duration and maximum amplitude of activity in all muscles increased between trials. Previous studies of muscle activity modulation in fishes indicate that these changes could improve feeding performance on an elusive prey. Thus, specific modifications of muscle activity appear to be one functional determinant of feeding success in fishes.
Heat loss from deer mice (Peromyscus): evaluation of seasonal limits to thermoregulation
Authors: Conley K. E. , Porter W. P. 
Published: April 2021

ABSTRACT
This paper investigates the influence of seasonal adaptations to thermoregulatory heat loss for deer mice (Peromyscus) during summer and winter. A general, mechanistic model of heat transfer through fur was evaluated for the structural properties of the fur of deer mice. The model was validated against heat production determined from mice exposed to a range of radiative (wall) temperatures (tr) at air temperatures (ta) of 15, 27 and 34°C. Calculated heat loss from the appendages was subtracted from the measured heat production to yield heat loss from the furred torso. This calculated torso heat loss agreed closely with the predicted fur heat loss for all conditions, as shown by a regression slope near 1 (0·99). Simulations using models of fur and appendage heat loss reveal that the winter increase in thermogenic (heat production) capacity has a greater effect than changes in fur properties in expanding the limits to thermoregulation. Both wind and a clear night sky increase heat loss and can limit thermoregulation to air temperatures above those found in deer mice habitats during winter (—25°C). Thus, despite seasonal adaptations, these simulations indicate that thermoregulation is not possible under certain winter conditions, thereby restricting deer mice to within the protected environment of the leaf litter or snow tunnels.
The Physiology of Dehydration Stress in the Land Crab, Cardisoma Carnifex: Respiration, Ionoregulation, Acid-Base Balance and Nitrogenous Waste Excretion
Authors: Wood Chris M. , Boutilier R. G. , Randall D. J. 
Published: April 2021

ABSTRACT
Air-breathing Cardisoma carnifex, collected in Moorea, French Polynesia, were held in fresh water similar in chemical composition to that in their burrows. Under control conditions, which allowed branchial chamber flushing but not ventilation of the medium, crabs demonstrated net Na+ and Cl− uptake, and ammonia, urea and base excretion (= acidic equivalent uptake). Throughout 192 h of water deprivation, crabs dehydrated slowly at a rate of 0·55 gH2Okg−1 h−1, eventually reaching a near lethal 18% loss of total body water. Increases in haemolymph osmolytes were quite variable (0–29%); electrolyte excretion was negligible. and both decreased by approximately 55%, maintaining an unusually low gas exchange ratio (R = 0·53), and suggesting general metabolic depression. There was no evidence of internal hypoxia as haemolymph lactate remained at hydrated levels and actually increased. The dominant acid-base response was a progressive metabolic alkalosis accompanied by a partially compensating rise in . Alkalosis was probably caused by blockage of the normal aquatic excretion of base produced by the metabolism of this herbivore. Other possible causes were eliminated: i.e. alkalaemia due to contraction of the ECFV; entrainment via strong ion shifts; CaCO3 mobilization; and ammonia accumulation in the haemolymph. In the absence of water, net ammonia production and excretion both appeared to cease, and alternate end products (urea, uric acid) did not generally accumulate. Within 2h of rehydration, crabs regained more than half the lost water, and increased above control levels, and ammonia excretion and haemolymph concentration both exhibited a prolonged (56 h) 4- to 6-fold rise. At the same time, metabolic alkalosis was reversed in association with elevated net base excretion into the water; the latter was correlated with an increase in the strong ion difference (SID) flux ([Na+ + K+4-Ca2++Mg2+-Cl−]).
Effects of flow rate, duration of stimulation and mineralocorticoids on the electrolyte concentrations of mandibular saliva from the red kangaroo (Macropus rufus)
Authors: Beal A. M. 
Published: April 2021

ABSTRACT
Mandibular saliva was collected at eight flow rates ranging between 0·052 ± 0·0059 (S.E. of mean) and 4·294 ± 0·0717 ml min−1 from anaesthetized red kangaroos receiving ipsilateral intracarotid infusions of acetylcholine. The concentrations of sodium (4·04 ± 0·759 to 75·9 ± 4·64 mmol 1−1) and chloride (51·2±2·46 to 85·0 ± 6·90 mmol 1−1) and the osmolality (99·7±4·88 to 178·9 ± 13·50 mosmol kg ‘) were positively correlated with salivary flow rate over most or all of the flow range, whereas the concentrations of potassium (50·3 ±2·03 to 19-7 ±3·16mmol 1−1), calcium (5·43 ± 1·696 to 1·26 ± 0·055 mmol 1−1), magnesium (259·8 ±49·3 to 19·0 ± 1·88 μmoll−1), hydrogen ions (457·7 ± 107·3 to 69·3 ± 5·64 nmol 1−1) and phosphate (2·22 ± 0·171 to 0·27 ± 0·040 mmol 1−1) were negatively correlated with flow rate. Salivary bicarbonate concentration (15·6 ± 1·76 to 2·19 ± l·83mmoll−1) showed little flow dependency except possibly at high levels of stimulation. Spontaneous secretion was not observed during anaesthesia.
During continuous stimulation of flow at two rates (0·5 and 2·0 ml min−1) for periods of 90 min, rest transients were observed for sodium, potassium, calcium, chloride and phosphate in the initial sample and the sodium concentration rose by 17·56 % during the first 60 min of steady-state flow and stimulation.
Indications that the gland was capable of responding rapidly to changes in endogenous mineralocorticoid levels were confirmed by intracarotid infusion of aldosterone at 80μgh−1. With the mean salivary flow rate lying between 1·3 and 1·4 ml min−1, the salivary Na+/K+ ratio began to fall at 45-60 min of aldosterone infusion and after 4h of infusion had fallen to 0·62 ±0·116. Administration of deoxycorticosterone acetate (DOCA) for 21 days at 0·25 or 0·3mgkg−112h−1 caused a further lowering of the Na+/K+ ratio to 0·09 ± 0·013 at similar flow rates. Biopsy showed this increase to be associated with a moderate level of hypertrophy of the intralobular ducts of the gland. Two types of intralobular duct were identified on the basis of glycogen granulation after DOCA administration.
It was concluded that the mandibular gland of the red kangaroo, with its high secretory capacity, its responsiveness to low levels of mineralocorticoids and its saliva being essentially a markedly hypotonic sodium/potassium chloride solution, is functionally better adapted to act as the primary source of saliva used as an external coolant than is the parotid gland.
Calcium-dependent action potentials in the prothoracic gland of Manduca sexta
Authors: Eusebio EJ , Moody WJ 
Published: April 2021

ABSTRACT
The physiological changes which occur during insect moulting are brought about by the steroid hormone 20-hydroxyecdysone (Riddiford & Truman, 1978). The prohormone ecdysone is secreted by the bilaterally paired prothoracic glands (PGs) in response to prothoracicotropic hormone (PTTH) released from the brain (Bollenbacher, Agui, Granger & Gilbert, 1979). Recently, Smith, Gilbert & Bollenbacher (1985) demonstrated that Ca2+ is required for PTTH-stimulated ecdysone synthesis and, consequently, proposed the existence of a hormone-dependent calcium channel associated with the PTTH receptor. In the present study, we show for the first time the existence of voltage-dependent calcium channels in PG cells. Furthermore, we have observed electrical coupling between the cells which appears sufficiently strong to permit the propagation of an action potential throughout the gland in response to stimulation at a single location.