bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Possible Role for Catecholamines in the Ventilatory Responses Associated with Internal Aciosis or External Hypoxia in Rainbow TroutOncorhynchus Mykiss
Authors: Aota S. , Holmgren K. D. , Gallaugher P. , Randall D. J. 
Published: April 2021

ABSTRACTPlasma catecholamine levels and gill ventilation were measured in rainbow trout (Oncorhynchus mykiss) during acidosis and hypoxia. There was an increase in both plasma catecholamines and ventilation correlated with the acidosis. Fish exposed to hyperoxia prior to acid infusion did not show significant changes in catecholamines or ventilation. Those treated with the β-adrenergic antagonist propranolol before acidosis showed increases in catecholamines but not ventilation. Hypoxia was also associated with increases in endogenous catecholamines and ventilation, and the increase in ventilation could be partially blocked with propranolol. This increase in ventilation during hypoxia was not inhibited by a saline injection alone. It is proposed that catecholamines act to modulate ventilatory responses in fish under both acidotic and hypoxic conditions. If a central H+ chemoreceptor exists in fish to control breathing, it can be inhibited by hyperoxia or by β-receptor blockade.
Characteristics of neurones projecting from the supraoesophageal ganglion in the shadow reflex pathway of the barnacle
Authors: Gwilliam G. F. , Stuart A. E. 
Published: April 2021

ABSTRACTBarnacles respond to decreases in light intensity (shadows). Previous evidence indicates that the first stages of the visual pathway within the supraoesophageal ganglion comprise a limited number of neurones: a single pair of second-order neurones (I-cells), a pair of third-order projection neurones (A-cells), and at least five other projection neurones (four A-like shadow-excited cells and one shadow-inhibited cell) whose spikes may be recorded extracellularly from the circumoesophageal connective nerve. Here we present evidence that information in this pathway diverges at the A-cell stage. Destruction of both A-cells by intense illumination of cells injected with carboxyfluorescein abolishes all shadow-evoked activity in the connectives and also the ability of shadows to influence motor neurones in the ventral ganglion.In addition, we have located the somata of these previously unidentified projection neurones, injected them with carboxyfluorescein, and observed that they have distinct branching patterns different from that of the A-cell. We name these cells ‘alpha’ (α), ‘beta’ (β) and ‘gamma’ (γ) cells. Simultaneous impalements show that A-cells drive at least one of the β-cells but not vice versa. The same observation has not yet been made with regard to α- or γ-cells. Depolarizing an I-cell does not readily drive a β-cell impaled simultaneously. These observations support our conclusion that information diverges from the A-cells and not from the second-order I-cells to the other projection neurones in this ganglion.
Activity-dependent and age-dependent recruitment and regulation of synapses in identified Crustacean Neurones1
Authors: Atwood H. L. , Govind C. K. 
Published: April 2021

ABSTRACT
Adaptation of neural systems to altered activity and age often involves recruitment, inactivation or modification of synapses. Crustacean motor systems are amenable to experimental investigation of these processes. They possess large identifiable neurones that can be observed over long periods during development, adulthood, regeneration and degeneration. Numerous small individual synapses are present on the transmitting terminals of the motor neurones; their ultrastructural features are non-uniform, indicating different degrees of functional potency. Ultrastructural studies show many more individual synapses than required for maximal quantal output; probably some are ineffective, but can be brought into a transmitting state in a short time by neural activity. During development, progressive reorganization and relocation of synapses take place. As the size of a postsynaptic target changes, synapses are added, and functionally adaptive alterations in quantal content and quantal effectiveness occur. Sectioning an axon results in slow degeneration of distal processes, but transmission is sustained for months. Short-term adjustments in number of effective synapses occur in response to altered activity. If activity of a neurone is chronically increased or decreased, characteristic semi-permanent adaptations in physiology and ultrastructure are seen. Synaptic transmission at low frequencies is down-regulated, while resistance to synaptic depression increases. These effects require protein synthesis, and at least two different changes - one related to down-regulation of synapses, the other related to fatigue resistance - can be selectively demonstrated through critically timed interruption of axoplasmic transport or imposition of different patterns of neural activity. In older animals, the ability to adapt to activity is reduced in some neurones, but may be restored during regeneration of neural processes. Selective changes in activity in one of several neurones innervating a common postsynaptic target lead to adaptive changes in synaptic transmission of non-active neurones, indicating activity-mediated interaction and adjustment. Mechanisms of adaptation similar to those outlined here probably occur in nervous systems of other species.
Cell recognition and pattern formation in the developing nervous system
Authors: Trisler David 
Published: April 2021

ABSTRACT
Laboratory of Biochemical Genetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
The topographic map of cell position in the avian retina is conserved and inverted when retinal ganglion neurons synapse with neurons in the optic tectum. Developmental mechanisms based on molecular gradients that specify positional information and pattern formation have been postulated in the establishment of these topographic maps of cells in retina and optic tectum. Two cell surface proteins in retina, TOPDV and TOPAP, are distributed in dorsoventral and anteroposterior topographic gradients, respectively. Corresponding gradients of TOP molecules present in the tectum are inverted with respect to the retinal gradients. These orthogonal gradients of TOPDV and TOPAP molecules provide a possible Cartesian coordinate system for designation of cell position at all points in the retinotectal map.
The role of afferent activity in the maintenance of primate neocortical function
Authors: Jones E. G. 
Published: April 2021

ABSTRACT
The major neuronal populations of the primate cerebral cortex can be classified immunocytochemically according to their transmitters and in terms of the differential expression of certain other molecules such as neuropeptides, calcium-binding proteins and protein kinases. We have been able to chart the time course of developmental expression of these molecules and to show that gene expression for many of them is regulated in adult and infant animals by afferent activity entering the cortex.
In the visual cortex of adult monkeys, levels of immunocytochemically detectable gamma aminobutyric acid (GABA), of its synthesizing enzyme glutamic acid decarboxylase (GAD) and of the tachykinins are greatly reduced in deprived ocular dominance columns within 24 h of blocking impulse activity in the optic nerve by intraocular injection of tetrodotoxin (TTX). Conversely, levels of immunocytochemically detectable calcium-calmodulin-dependent protein kinase (CAM II kinase) are increased in deprived eye dominance columns. These effects are quickly reversible on restoration of binocular vision, and experiments involving in situ hybridization and S1 nuclease protection assays show that the changes are associated with parallel changes in mRNA levels for preprotachykinin and CAM II kinase, but not for GAD, which appears to be regulated by post-transcriptional mechanisms. Experiments in the primate somatic sensory cortex suggest comparable activity-dependent effects on gene expression there also.
It is proposed that effects of this type underlie the establishment of cortical maps during development and their activity-dependent mutability in adulthood.
Morphological plasticity of postsynaptic neurones in reactive synaptogenesis
Authors: Hamori J. 
Published: April 2021

ABSTRACT
Partial deafferentation of certain brain regions (septal nuclei, hippocampus, etc.) in adult animals results (1) in the disappearance of degenerating axon terminals and (2) in the short-term persistence of vacant postsynaptic sites. These postsynaptic sites have been shown to be re-supplied by sprouted axon terminals of intact axons. This paper will demonstrate that, in brain regions (e.g. cerebellar cortex, lateral geniculate nucleus) where axonal sprouting of local elements or of persisting afferent axons is negligible or absent, synaptic reorganization involves the active participation of postsynaptic dendritic and somatic elements of surviving local nerve cells. Synaptic regeneration can be demonstrated by morphological means both in developing and in adult central nervous system. The dendrites may show two types of response to deafferentation: (1) the formation of presynaptic specializations along their otherwise ‘classical’ postsynaptic membrane (the axonization of dendrites) resulting in the formation of new, dendro-dendritic synapses, and (2) the ‘adaptive’ (structural) reduction in size (‘atrophy’) of the denervated nerve cell dendritic arborization, leading to a relative increase in density of the surviving (though non-sprouting) afferent axon terminals. In both cases a partial functional recovery can be demonstrated.
Development of the mammalian retinogeniculate pathway: target finding, transient synapses and binocular segregation
Authors: So K. F. , Campbell G. , Lieberman A. R. 
Published: April 2021

ABSTRACT
This review is concerned with the development of the mammalian retinogeniculate projection from the perspective of our studies on the hamster and to a lesser extent on the cat. In these, and other mammalian species, axons from the two eyes initially spread throughout the dorsal lateral geniculate nucleus (dLGN) and thus completely overlap. Later they segregate, the axons from each eye coming to occupy discrete, non-overlapping territories within the dLGN. The process of segregation to establish the adult pattern coincides with the death of retinal ganglion cells projecting to inappropriate areas of the dLGN and with the loss, by degeneration or retraction, of the axons and/or axonal branches initially located within inappropriate territory of the dLGN. These events occur in the early postnatal period in hamsters, before the eyes have opened, and in cats and monkeys they occur entirely during embryonic life: thus, they do not depend on the onset of normal visual function. If one eye is removed before segregation has begun, the terminal fields of the crossed and uncrossed axons from the remaining eye do not segregate, suggesting that segregation in normal development may depend on some form of interaction between retinal ganglion cells from the two eyes. Attractive and/or repulsive influences exerted by the dLGN on retinogeniculate axons may also be involved in the formation of eye-specific territories.
Experimental ultrastructural studies in hamster and cat show that the overlap phase is associated with the formation, by inappropriately located axons, of transient synapses similar to those made by retinogeniculate axons in appropriate parts of the dLGN. In the cat, the transient synapses are made by the axon trunk and by side branches of retinogeniculate axons with terminal arbors in appropriate parts of the nucleus; the transient synapses disappear as the side branches are shed or retracted during the segregation period.
Because of good evidence that electrical activity of the retinogeniculate axons may be involved in binocular segregation of inputs, we suggest that the formation and elimination of transient synapses play a significant role in the development of the orderly retinogeniculate projections.
The Role of Series Elastic Structures in Prestretch-Induced Work Enhancement During Isotonic and Isokinetic Contractions
Authors: Ettema G. J. C. , Soest A. J. Van , Huijing P. A. 
Published: April 2021

ABSTRACT
The influence of series elastic structures on the dynamics of the contractile machinery was examined in the gastrocnemius medialis (GM) of five male Wistar rats, with respect to enhancement of work of a muscle-tendon complex after active stretch. Imposed isotonic and isokinetic contractions were preceded by either an isometric phase (PI) or an active stretch (PS). The effects of fibre length differences at the onset of shortening, due to differences of extension of tendinous structures, were studied. For the isotonic experiments fibre length and shortening velocity were estimated 30 ms after release and compared with the PI length velocity curve determined at the same force level. For shortening above the optimum length, about half of the enhanced shortening found after prestretch could be explained by PS—PI fibre length differences. Below the optimum length, PS shortening velocity was somewhat lower than expected on the basis of length-velocity characteristics. Enhancement of work output due to stretch was different for isokinetic and isotonic shortening. In isokinetic shortening, following prestretch, fibre work was limited because of enhanced shortening of the tendinous structures.
In stretch-shortening cycles imposed on a muscle-tendon complex, the length of the complex affected all prestretch effects, i.e. potentiation of the contractile element, contractile element interaction with the tendinous structures, and elastic energy release.
It is concluded that, besides potentiation effects and enhanced elastic energy release, the influence of series elastic structures on fibre dynamics determines active stretch-induced work enhancement. The contribution by these mechanisms to this work enhancement depends largely on the type of stretch-shortening cycle.
The Work and Energetic Cost of Locomotion: I. The Effects of Limb Mass Distribution in Quadrupeds
Authors: Steudel Karen 
Published: April 2021

ABSTRACT
Does limb design influence the cost of locomotion in quadrupedal mammals? If not, morphologists must dismiss the economy of locomotion from consideration when assessing the adaptive factors shaping limb structure. Several studies have recently used externally applied loads to demonstrate a relationship between limb mass distribution and energy costs in human subjects. It is not clear whether a similar correlation would hold for quadrupeds, given their very different gaits. The present study addresses this question by measuring the rate of oxygen consumption in domestic dogs running on a treadmill with mass added either to the limbs or to the back. Trials with no additional mass were used as a control. The use of externally applied loads has the advantage of allowing limb mass to be altered in a system in which other aspects of physiology that might influence cost of locomotion are held constant. The cost of adding mass to the limbs in dogs was found to be significantly greater than that of adding it at the center of mass. Limb mass distribution does affect the cost of locomotion in quadrupeds. A comparison of the results from a variety of studies in which the energetic cost of adding external loads has been measured in animals across a wide size range suggests a qualitative difference in the factors determining the cost of locomotion in large and small animals.
The Work and Energetic Cost of Locomotion: II. Partitioning the Cost of Internal and External Work within a Species
Authors: Steudel Karen 
Published: April 2021

ABSTRACT
Previous studies have shown that large animals have systematically lower mass specific costs of locomotion than do smaller animals, in spite of there being no demonstrable difference between them in the mass-specific mechanical work of locomotion. Larger animals are somehow much more efficient at converting metabolic energy to mechanical work. The present study analyzes how this decoupling of work and cost might occur. The experimental design employs limb-loaded and back-loaded dogs and allows the energetic cost of locomotion to be partitioned between that used to move the center of mass (external work) and that used to move the limbs relative to the center of mass (internal work). These costs were measured in three dogs moving at four speeds.
Increases in the cost of external work with speed parallel increases in the amount of external work based on data from previous studies. However, increases in the cost of internal work with speed are much less (&lt;50 %) than the increase in internal work itself over the speeds examined. Furthermore, the cost of internal work increases linearly with speed, whereas internal work itself increases as a power function of speed. It is suggested that this decoupling results from an increase with speed in the extent to which the internal work of locomotion is powered by non-metabolic means, such as elastic strain energy and transfer of energy within and between body segments.
Speed, Jet Pressure and Oxygen Consumption Relationships in Free-Swimming Nautilus
Authors: O’dor R. K. , Wells J. , Wells M. J. 
Published: April 2021

ABSTRACT
Neutrally buoyant, ultrasonically telemetering, differential pressure transducers were attached to Nautilus pompilius L. to record mantle cavity pressures while the animals were induced to swim in a flume in response to food. Synchronized videotapes and computer data files showed that jet pressures (p, Pa) increased linearly with swimming speed (u, ms−1), p=1565 u – 8. Because of their stereotyped responses to food, Nautilus could be induced to produce similar pressures in 51 respirometers, where oxygen consumption () increased as a power function of pressure, . Combining these equations gave an oxygen consumption-speed relationship, . We used this equation to show that the cost of transport for Nautilus is dramatically lower than that for squid and, at speeds below 0.05 m s−1, even lower than that of an undulatory swimmer, the salmon. Calculated power inputs and outputs suggest that squid have increased their power density (W kg−1) 100-fold over their ectocochleate ancestors, and that Nautilus is very efficient in its low-speed, low-energy environment. These laboratory ‘calibrations’ are a basis for field studies using telemetered pressure data to develop energy budgets for this unique living fossil as a reference for comparing the energetic requirements of ancient and modern seas.
Effects of Cold Exposure on Oxygen Consumption, Ventilation and Interclavicular Air-Sac Gases in the Little Penguin (Eudyptula Minor)
Authors: Johannesen Hege , Nicol Stewart C. 
Published: April 2021

ABSTRACT
Oxygen consumption , tidal volume, respiratory frequency and the composition of the gas in the interclavicular air sac were measured in the little penguin Eudyptula minor (Forster) at ambient temperatures (Ta) of 5 and 20 °C.
increased from 14.60 ml 02 kg−1 min−1 at 20°C to 18.29 ml 02 kg−1 min−1 at 5 °C. However, the elevated at the low Ta was not matched by a similar rise in total inspiratory ventilation . The ventilatory requirement thus decreased from 0.5751 mmol−1 at 20°C to 0.4401 mmol−1 at 5°C. An increased gas exchange efficiency during cold exposure was also shown by the composition of the gas in the interclavicular air sac. decreased from 11.95 kPa at 20°C to 10.24kPa at 5°C, while the corresponding increase in was from 6.61 to 7.50 kPa.
Oxygen extraction, calculated from and O2 content of the inspired air, increased from 24.60% at 20°C to 31.04% at 5°C. Oxygen extraction calculated from the O2 contents of inspired air and interclavicular air-sac gas was 38.73 % at 20°C and 47.18% at 5 °C.
The results confirm previous findings for the little penguin which showed a decrease in the ventilatory requirement with increasing oxygen uptake. However, the improved gas exchange efficiency during cold exposure and the strong correlation found between oxygen extraction and oxygen consumption have not been demonstrated previously for this species.
Characterization of Red Blood Cell Metabolism in Rainbow Trout
Authors: Walsh Patrick J. , Wood Chris M. , Thomast Serge , Perry Steve F. 
Published: April 2021

ABSTRACT
Red blood cell metabolism was studied in vitro using whole blood obtained by catheter from resting rainbow trout (Oncorhynchus mykiss). Preparations were viable as shown by stable NTP, metabolite and catecholamine levels and acid-base status, all of which remained at in vivo levels over the 2h incubation period. Enzymes diagnostic of glycolysis, the tricarboxylic acid (TCA) cycle and phosphagen metabolism were all present-in significant amounts in red blood cells. In direct comparisons of 14C-labelled substrates at normal resting plasma concentrations, rates of CO2 production were in the order: glucose&gt;lactate&gt;ala-nine&gt;oleate. Total CO2 production rates from these four oxidative substrates did not equal directly measured O2 consumption rates, indicating that other substrates may also be important in vivo. Oxidative pathway Km values for glucose (8.4mmoll−1), lactate (3.3mmoll−1) and alanine (0.8mmoll−1) were well within the normal physiological ranges of plasma concentrations. Glucose concentration did not affect lactate oxidation rates, but there was some inhibition (27%) of glucose oxidation by high lactate concentrations (20mmol l−1). The observed Km values and competitive interactions suggest that changes in plasma concentrations associated with environmental stresses can considerably alter the relative rates of oxidation of glucose and lactate in vivo. Considerable pentose-phosphate shunt activity was detected in red cells, as indicated by high activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase and high CO2 production rates from (l-14C)-labelled glucose. Even in the presence of normal O2 levels, a significant percentage (28%) of glucose metabolism was directed to lactate production. Taken together, these results demonstrate that rainbow trout whole blood incubated in vitro constitutes a dynamic and viable system for metabolic studies at the pathway level.
Breathing in Rana Pipiens: the Mechanism of Ventilation
Authors: Vitalis Timothy Zoltan , Shelton Graham 
Published: April 2021

ABSTRACT
The mechanism and pattern of ventilation in unrestrained Rana pipiens were investigated by simultaneous measurements of pulmonary pressure, buccal pressure and air flow at the nostrils. The buccal cavity was ventilated continuously at a rate of 90±3.2 oscillations min−1 by low-amplitude pressure swings above and below atmospheric. The lungs were ventilated intermittently by the buccal pump at a rate of 6.3±0.8 breaths min−1. Expiration of gas from the nostrils occurred on two occasions during a lung ventilation. Ventilation of the lungs was achieved by precise timing of two valves, the nostrils and glottis. The timing of the valves determined the volume of expiratory flow on these two occasions and its relationship to inspiratory flow. Thus, the breathing movements could cause inflation, deflation, or no change in the lung volume. Periodically the lung was inflated by a sequence of successive breaths. During inflations the nostrils closed simultaneously with glottal opening and almost no gas was expired during the first expiratory phase. This caused a complete mixing of buccal contents and pulmonary gas and this mixture was pumped back into the lung. Deflations were characterized by a delay in nostril closing that resulted in a large outflow of gas from the lung and buccal cavity during the first phase of expiration. More gas left the system than was pumped into the lungs. The results suggest that coherent air flow from glottis to nostrils, as required by the ‘jet stream’ hypothesis of Gans et al. (1969), is not likely to occur.