bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Interrelationship Between Pulmonary Mechanics and The Spontaneous Breathing Pattern in the Tokay Lizard, Gekko Gecko
Authors: Milsom William K. 
Published: April 2021

ABSTRACT
The normal breathing pattern of the Tokay gecko (Gekko gecko) consists of single breaths or bursts of a few breaths separated by periods of breath holding. Increases in pulmonary ventilation that accompany rises in body temperature are caused by increases in respiratory frequency due to shortening of the periods of breath holding. Tidal volume and breath duration remain relatively constant. Measurements of the mechanical work associated with spontaneous breathing yielded values that were similar to those calculated for breaths of the same size and duration based on work curves generated during pump ventilation of anaesthetized animals. In this species, the pattern of periodic breathing and the ventilatory responses to changes in respiratory drive correspond with predictions of optimal breathing patterns based on calculations of the mechanical cost of ventilation. Bilateral vagotomy drastically alters the breathing pattern producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of the breath duration. These alterations greatly increase the mechanical cost of ventilation. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal afferent control and which serves to minimize the cost of breathing.
Calcium-Dependent Action Potentials in Leech Giant Salivary Cells
Authors: Marshall Cameron G. , Lent Charles M. 
Published: April 2021

ABSTRACT
Two pairs of discrete salivary glands are located at the base of the muscular proboscis of the sanguivorous Glossiphoniid leechesHaementeria ghilianii and Haementeria officinalis. Each anterior gland is 0·8 cm to 2cm in length, and comprises over 200 giant salivary cell bodies ranging from 150 μm to over 1000 μm in diameter, depending on the size of the animal. The salivary cells are neither electrically nor dye coupled, and there is no acinar structure or common duct, but instead each cell extends an individual ductule.
The cells fire action potentials of 100–200 ms duration and 70–100 mV amplitude in response to depolarizing pulses, or at the cessation of a hyperpolarizing pulse. The impulse is abolished by procedures known to antagonize calcium currents, and persists in sodium-free solution, or when calcium is replaced with strontium or barium. Our results support the hypothesis of a purely calcium-dependent impulse.
Mechanical Synchronization of Ciliary Beating Within Comb Plates of Ctenophores
Authors: Tamm Sidney L. 
Published: April 2021

ABSTRACT
The mechanism which synchronizes the beating of the hundreds of thousands of long cilia making up a ctenophore comb plate was investigated by microsurgical experiments on single comb plates of Mnemiopsis and Pleurobrachia. Comb plates of lobate ctenophores (e.g. Mnemiopsis) are triggered to beat by ciliated grooves which run between the centres of adjacent plates. By creating gaps or introducing mechanical barriers between two parts of a plate, or by severing the cells at the base of a plate, it was shown that physical proximity of cilia, not tissue continuity, is required for synchronization of beating. In Pleurobrachia only the first comb plate of each row is activated by a ciliated groove, and similar experiments to those done on Mnemiopsis gave identical results. Although adjacent comb plates in Pleurobrachia are triggered mechanically by movements of the preceding plates without the need for an intraplate synchronizing mechanism, unilateral amputation of a plate showed that cilia within these plates may also be synchronized by mechanical coupling. Therefore, in cases where the beating of a comb plate is triggered by a ciliated groove — either at the head of a comb row (in all ctenophores) or along the row (lobates only) - the cilia within the plate are synchronized by hydrodynamic coupling forces between them, not by electrical coupling between their cells as assumed previously.
Antidiuretic Action of a Corpus Cardiacum Factor (Ctsh) on Long-Term Fluid Absorption Across Locust Recta in vitro
Authors: Proux B. , Proux J. , Phillips J. E. 
Published: April 2021

ABSTRACT
Long-term fluid absorption (Jv) by everted rectal sacs from locusts is stimulated by both corpus cardiacum (CC) extracts and cAMP in a dosedependent manner. This hormonal antidiuretic activity (ADH) is present in both nervous and glandular lobes of CC. This distribution is similar to that of chloride transport stimulating hormone (CTSH) but not to that of other factors previously reported from this gland. As expected if ADH were due to CTSH acting on electrogenic Cl- transport, CC extracts also increased the electropotential across rectal sacs, and the stimulation of fluid absorption ceased in Cl-free salines. CC extracts also caused recta to absorb fluid against larger osmotic gradients, suggesting that the antidiuretic factor acts on the ion-dependent active transport of fluid rather than on the osmotic permeability of the rectal wall.
Functional Roles and Circuitry in an Inhibitory Pathway to Feeding Command Neurones in Pleurobranchaea
Authors: London J. A. , Gillette R. 
Published: April 2021

ABSTRACT
The paracerebral neurones (PCNs) of the brain of Pleurobranchaea californica serve a command role in the initiation of feeding behaviour (Gillette, Kovac & Davis, 1978). The PCNs are synaptically excited by food stimuli applied to the oral veil of hungry, naive animals. In food avoidance-conditioned animals, the PCNs are inhibited by a barrage of inhibitory postsynaptic potentials concomitant with the suppression of feeding (Davis & Gillette, 1978). In this paper, an interneuronal pathway is described which causes inhibition of the PCNs and potentially mediates the effects of learning. The inhibitory pathway consists of three serially connected interneurones. One population, designated the Interneurone Is (Int-ls), mono-synaptically inhibits the PCNs. A second population, the Interneurone 2s (Int-2s), excites the Int-1 population. They also excite other neurones of the brain including the metacerebral giant neurones. A third population, the Interneurone 3s (Int-3s), monosynaptically excites the Interneurone 2 population. Dual intracellular recordings and current injection show that ipsilateral members of the Int-2 population are electrically coupled via a nonrectifying connection. Contralateral members of the Int-2 population are excitatorily coupled via a polysynaptic pathway. The Int-1 population is phasically active during the rhythmic motor activity that underlies feeding. In the isolated nervous system Int-1 activity is phase-locked with rhythmic PCN activity; Int-1 activity occurs maximally at the end of a PCN burst, during the retraction phase of the cycle. Int-2 activity also occurs during the retraction phase. During actual feeding in the whole animal preparation, the Int-2s are also phasically active; maximal excitation occurs during buccal mass retraction and maximal inhibition during protraction and the bite. Stimulated activity in a single Int-2 can entirely suppress the rhythmic motor activity of the feeding network evoked by electrical stimulation of the stomatogastric nerve. The suppressant effects of Int-2 activity must be mediated widely within the feeding network because the rhythmic motor output so driven is not dependent on PCN spiking. Application of an appetitive chemosensory stimulus to whole and semiintact animal preparations initiated feeding and elicited excitation of the Int-1 and Int-2 populations. Noxious chemosensory stimuli, such as a dilute soap solution or ethanol, elicited oral veil withdrawal and inhibition of the Int-2s by multiple inhibitory postsynaptic potentials. When divalent ion concentration was raised in the saline surrounding the brain, to suppress polysynaptic activity, the Int-2s but not the PCNs were excited by appetitive chemosensory stimuli. This suggests that the Int-2s receive monosynaptic sensory input from the oral veil while the PCNs do not.
The Haemolymph as A Storage Site for Cuticular Ions During Premoult in the Freshwater/Land Crab Holthuisana Transversa
Authors: Sparkes Stephen , Greenaway Peter 
Published: April 2021

ABSTRACT
Holthuisana transversa (von Martens) utilizes the haemolymph as a storage site for ions reabsorbed from the cuticle in premoult. 66 % of the total body calcium, magnesium and phosphate from the preceding intermoult stage was stored in the haemolymph in premoult. Almost all of the calcium and phosphate and 73 % of the magnesium in the haemolymph was located in microspherules of average diameter 0·25μm. The concentration of total calcium in the haemolymph in premoult was 150 times the normal intermoult value (13·2 mmol 1-1) but the activity of calcium in the haemolymph decreased from an intermoult value of 4*52 mmol 1-1 to 3·37 mmol 1-1 in premoult. Postmoult crabs absorbed calcium from the water at a high rate and showed a high affinity for calcium ions; Km = 0·105 ±0·013 mmol 1-1 Ca.
Identification of Neurones in the Leech Through Local Ionic Manipulations
Authors: Friesen W. Otto , Brodfuehrer Peter D. 
Published: April 2021

ABSTRACT
The identification of neurones which generate and control specific animal movements can typically be made with conventional intracellular recording techniques during the expression of the movement pattern. Neurones whose membrane potentials are highly correlated to the patterns under investigation are potentially part of the pattern-controlling system. Further searches may then be made to find the pre-synaptic and postsynaptic cells. Such neuronal circuits are now known for several invertebrates (Friesen & Stent, 1978; Delcomyn, 1980; Kristan, 1980). However, a serious drawback to these search procedures is that many time-consuming trial and error experiments are required, in which hundreds, or even thousands of candidate cells must be impaled with microelectrodes.
Patterns in mammalian muscle energetics
Authors: Kushmerick M. J. 
Published: April 2021

ABSTRACT
A description of cellular energetics of muscular contraction is given in terms of the rates and extents of high-energy phosphate splitting during contractile activity, in terms of high-energy phosphate resynthesis by respiration and net anaerobic glycolysis, and in terms of the associated uptake and/or release of H+. These chemical changes have been studied quantitatively by rapid freeze-clamping methods and by 31P-NMR methods. The pattern of chemical changes in a fast-twitch glycolytic muscle is rapid depletion of phosphocreatine and later ATP levels, cellular acidification, and a much slower rate of resynthesis of high-energy phosphate compounds during the recovery period afterwards than occurs in the slow-twitch oxidative muscles. In steady-state contractile activity below the maximal, graded levels of high-energy phosphates and of cellular respiration are achieved in both fast-twitch and slow-twitch muscles. Within the metabolic range up to the maximal aerobic capacity, which differs several-fold for different fibre types, this gradation is mediated by the creatine kinase reaction and phosphocreatine stores. Thus while the amount of enzyme present and the content of phosphocreatine differs among muscles of different types, the same general energetic function is seen to occur in all muscle cells. The creatine kinase reaction is both an energy reservoir and a buffer preventing large swings in the ATP/ADP ratios.
Development and adaptability of microvasculature in skeletal muscle
Authors: Hudlická O. 
Published: April 2021

ABSTRACT
In skeletal muscle, the size of the capillary bed is adapted to the type of muscle metabolism and can be altered by adaptation to different environments or increased activity. Muscle fibres with high aerobic metabolism have more capillaries, and an increase in aerobic metabolism is usually followed by capillary growth. It is assumed that local hypoxia -created by increased demand for oxygen during growth, cold exposure or increased activity -can stimulate proliferation of capillaries. Capillary density is reduced in parallel with enhanced glycolytic metabolism.
The size of the capillary bed can also increase without any apparent change in the oxidative metabolism (e.g. in the early stages of chronic electrical muscle stimulation or as a result of long-term administration of vasodilating drugs), and it is argued that the growth of capillaries in these cases may be due to various mechanical factors connected with increased blood flow.
Force development during sustained locomotion: a determinant of gait, speed and metabolic power
Authors: Taylor C. R. 
Published: April 2021

ABSTRACT
This paper develops three simple ideas about force development during sustained locomotion which provide some insights into the mechanisms that determine why animals change gait, how fast they can run, and how much metabolic energy they consume. The first idea is that the alternate stretch-shorten pattern of activity of the muscles involved in locomotion allows muscle-tendon units to function as springs, affecting the amount of force a given cross-sectional area of muscle develops, and the metabolic requirements of the muscles for force development. Animals select speeds and stride frequencies which optimize the performance of these springs. The second idea is that muscle stress (force/cross-sectional area) determines when animals change gait, how fast they run and their peak accelerations and decelerations. It is proposed that terrestrial birds and mammals develop similar muscle stresses under equivalent conditions (i.e. preferred speed within a gait) and that animals change gaits in order to reduce peak stresses as they increase speed. Finally, evidence is presented to support the idea that it is the time course of force development during locomotion, rather than the mechanical work that the muscles perform, that determines the metabolic cost of locomotion.
Efficiency of vertebrate locomotory muscles
Authors: Heglund N. C. , Cavagna G. A. 
Published: April 2021

ABSTRACT
We have examined the efficiency of vertebrate striated muscle at two different organizational levels: whole animals and isolated muscles. Terrestrial locomotion is used as a model of ‘normal’ muscular contraction; animal size and running speed are used as independent variables in order to change either the metabolic requirements of the muscles or the mechanical power production by the muscles over a wide range of values. The weight-specific metabolic power input to an animal increases nearly linearly with speed and increases with decreasing body size, while the weight-specific mechanical power output increases curvilinearly with speed and is independent of size. Consequently, the efficiency of the muscles in producing positive work increases with speed and the peak efficiency increases with increasing body size, attaining values of over 70 % in large animals, but only 7 % in small ones. The isolated muscle experiments were performed on frog muscle, and rat ‘fast’ and ‘slow’ muscles. We measured the work done, the oxygen consumed during recovery from the stimulation, and calculated the efficiency and the ‘economy’ (the cost of maintaining tension). The muscles were made to: (i) emulate the contractions seen during locomotion, i.e. shorten after a pre-stretch; or (ii) shorten at the same velocity and from the same muscle length as in (i), but without the pre-stretch. It was found that in mammalian muscles the peak efficiency with a pre-stretch attained high values, approaching the peak efficiencies in large animals. The maximum efficiency (attained at 1 length s−1 in fast muscle and at 0 · 5 lengths s−1 in slow muscle) did not differ much in the two muscles, whereas economy was greater in the slow muscle than in the fast muscle.
Design and performance of muscular systems: an overview
Authors: Weibel ER 
Published: April 2021

ABSTRACT
For a general physiologist, A.V. Hill’s definition that ‘muscle is a machine that converts chemical to mechanical energy at constant temperature’ is still a valid concept. But it is clearly not sufficient to tell us how muscles are used to perform a variety of different functions, such as locomotion, pumping blood through the circulation or air into the lung, or even catching prey and ingesting food. Muscles must be organized in a proper way, they must be operated in a well controlled fashion, and they need fuel which must be supplied according to needs. The ‘muscular system’ (Fig. 1) can thus be defined as the concerted action of molecular events permitting the generation of mechanical force, with the biochemical and physiological functions of energy supply under the control of the nervous system. Because of the dependence of all parts of the system on all others, any part can in principle limit the performance of the entire system. One important question is therefore to see how the various parts react when the demands on the system are altered, in other words, to see how malleable the system is.
Storage and release of mechanical energy by active muscle: a non-elastic mechanism?
Authors: Cavagna G. A. , Mazzanti M. , Heglund N. C. , Citterio G. 
Published: April 2021

ABSTRACT
In frog muscle fibres, tetanically stimulated at a sarcomere length of about 2 pm, stretched at a velocity of 1 length s-1 and released against a force equal to the maximum isometric, P0, a phase of rapid isotonic shortening takes place after release. As the amplitude of the stretch is increased from 1 · 5 to 9 % of the initial length: (1) the amount of rapid isotonic shortening increases up to 9–10 nm per half sarcomere and (2) the stiffness of the fibre (an indication of the number of bridges attached) decreases to a value about equal to that measured during an isometric contraction. If a 5-10 ms delay is left between the end of stretch and release, the amount of rapid isotonic shortening increases to about 12nmhs-1. A 300-500 ms delay, however, results in a decrease in rapid isotonic shortening to about 5nmhs-1 and also results in velocity transients against P0 that are similar to those described during release from a state of isometric contraction. It is concluded that the force attained after large, fast stretches is due to a greater force developed by each bridge and not to a greater number of bridges. After the elastic recoil (when the force is suddenly reduced to P0), these strained bridges are able to shorten by about 12nmhs-1, suggesting that, during and immediately after stretching, they are charged to levels of potential energy greater than those attained in an isometric contraction.
The influence of inactivity on membrane resting conductances of rat skeletal muscle fibres undergoing reinnervation
Authors: Conte-Camerino Diana , Bryant S. H. , Lograno M. D. , Mambrini M. 
Published: April 2021

ABSTRACT
The role of activity in the maintenance of the normal component resting conductances of skeletal muscle fibres has been evaluated in vitro in rat extensor digitorum longus muscle during reinnervation from 2 to 40 days (a) after crushing of the peroneus nerve and (b) after local application of tetrodotoxin (TTX) to the crushed nerve. Whereas membrane conductances were regained after crushing alone, they were not completely restored when impulse propagation was blocked faith TTX. It is concluded that nerve trophic factors are of primary importance in the control of muscular membrane conductances, and that transmission at the endplate and the muscle usage triggered by it have a minor but significant effect.
Gill and Body Surface Areas of the Carp in Relation to Body Mass, With Special Reference to the Metabolism-Size Relationship
Authors: Oikawa Shin , Itazawa Yasuo 
Published: April 2021

ABSTRACT
The relationships of resting metabolism per unit mass of body to gill and body surface areas were examined by measuring gill, body surface and fin areas of carp ranging from 0·0016 to 2250g. There was a triphasic allometry for the relationship between gill area and body mass : during the prelarval (0·0016-0·003g) and postlarval (0·003-0·2g) stages there was a positive allometry (slopes of 7·066 and 1·222, respectively), during the juvenile and later stages (0·2-2250 g) there was a negative allometry with a slope of 0·794. There was a diphasic negative allometry for the relationship between surface area of the body or the fins and body mass, with a slope of 0·596 or 0·523 during the larval stage and 0·664 or 0·724 during the juvenile and later stages, respectively. Except for the 3rd phase (juvenile to adult) of gill area, these slopes were significantly different (P&lt;0·01) from the slope for the relationship between resting metabolism and body mass of intact carp (0·84; value from Winberg, 1956). It is considered, therefore, that gill, body surface and fin areas do not directly regulate the resting metabolism of the fish, in the larval stage at least.
Sensory Control of Respiratory Pumping in Aplysia Californica
Authors: Croll Roger P. 
Published: April 2021

ABSTRACT
The frequency of respiratory pumping in Aplysia increases when CO2 is bubbled through the bathing sea water. Air, O2 and N2 do not have this effect. The sensitivity to CO2 may be mediated by receptors which are sensitive to pH changes within the range encountered during hypercapnia. In addition to the frequency change during hypercapnia, increases in the rate of pumping occur after titration to low pH with hydrochloric, acetic, nitric and sulphuric acids, thus indicating sensitivity to changes in the concentration of hydrogen ions and not to any specific anions. High pH and large deviations from normal in the tonicity of the sea water are ineffective in influencing the rate of pumping. The locus of pH sensitivity resides primarily within the mantle cavity. Lesions of the osphradium indicate that this chemosensory organ mediates a large degree of sensory control over respiratory pumping.
Oculomotor Function at Low Temperature: Antarctic Versus Temperate Fish
Authors: Montgomery J. C. , Macdonald J.A. 
Published: April 2021

ABSTRACT
The peripheral oculomotor system can be modelled as a first order linear system (Montgomery, 1983), and hence specified by its characteristic frequency and ‘d. c.’ gain. These parameters can be determined by recording eye movements produced by stimulation of the abducens nerve with sinusoidally modulated pulse trains, and compare well with those independently derived from the relationship between motoneurone firing and spontaneous eye movement. Characteristic frequency and gain of the peripheral oculomotor system were determined for two species of antarctic teleost and one temperate species, to examine temperature compensation within a complete motor output pathway. Compared with low temperature function in temperate fish, the characteristic frequency is clearly temperature compensated in antarctic fish, which explains in part the observed temperature compensation of their rapid eye movement. The ‘d.c.’ gain of the peripheral oculomotor system is inversely related to temperature, providing an automatic compensation for possible reductions in central nervous system output and sensory gain at low temperature.
Comparison of Running Energetics in Male and Female Domestic Fowl
Authors: Brackenbury J. H. , El-Sayed M. S. 
Published: April 2021

ABSTRACT
Carbon dioxide production and end-exercise venous lactate concentration were compared in intensively-trained, mature male and female domestic fowl running on a treadmill for 10-min periods at maximal and sub-maximal work loads. The relationship between and running speed was linear and had the same slope in male and female birds. However the maximum sustainable running speed of the males was. approximately twice that in the females and the maximum weight-specific was 60 % higher in males. End-exercise venous lactate concentration rose significantly above resting at work loads above 75 % maximum in females, but only at work loads above 95 % maximum in fully-trained males. The results indicate a greater work capability in male than in female birds in the conditions of the experiments.