bluuebunny/crossref_metadata_2025_split huggingface dataset:
Respiratory Function in Exercising Fowl Following Occlusion of the Thoracic Air Sacs
Authors: Brackenbury John H. , Darby Carl , El-Sayed Mahmoud S. 
Published: April 2021

ABSTRACT
Oxygen consumption, respiratory evaporative water loss, respiratory rate and gas tensions in the clavicular and abdominal air sacs and in arterial blood were monitored after occluding either the cranial thoracic air sac only (CRT group) or the cranial and caudal thoracic air sacs together (CRT-CT group). Respiratory water loss was used to estimate minute ventilation. Both experimental groups were able to maintain control levels of ventilation at rest and during treadmill exercise at approximately three times the resting metabolic rate. The CRT group regulated blood and intrapulmonary and normally, but there was a slight hypoxaemia/hypercapnaemia in the CRT-CT group, apparently as a result of parabronchial hypoventilation. The differential distribution of gas tensions between the cranial and caudal groups of air sacs was the same in control and experimental birds, suggesting that a normal intrapulmonary airflow pattern was preserved in the absence of the thoracic air sacs. The findings are discussed in the light of current models of the control of intrapulmonary airflow in birds.
Influence of Hormones, Second Messengers and pH on the Expression of Metabolic Responses to Anoxia in a Marine Whelk
Authors: Brooks Stephen P. J. , Storey Kenneth B. 
Published: April 2021

ABSTRACT
The roles of hormones, second messengers and pH in triggering or potentiating biochemical responses to anaerobiosis were evaluated using in vitro incubations of isolated muscle tissues (foot, radular retractor, ventricle) from the marine whelk Busycon canaliculatum (L.). Incubating tissues in vitro under anoxic conditions stimulated changes in muscle fructose-2,6-bisphosphate levels and pyruvate kinase kinetics (Km values for phosphoenolpyruvate, values for L-alanine) that were virtually equivalent to those that occur in vivo. Additions of hormones (epinephrine, norepinephrine, octopamine, serotonin, glucagon, insulin) or inhibitors of prostaglandin synthesis (dexamethasone, aspirin) had no effect on these metabolic responses to anoxia. The second messenger compounds, dibutyryl cyclic AMP and Ca2+ + ionophore A23187 + phorbol myristate acetate, produced isolated and tissue-specific responses in muscles incubated under aerobic conditions, but the magnitude and pattern of these responses differed from those seen in anoxia. Second messengers also had no effect on the development of biochemical responses in anoxic muscles. Tissue pH was artificially altered in order to evaluate the role of pH change (acidification occurs during anoxia in vivo) in the control of metabolic responses to anoxia. In all cases, the changes in the kinetic properties of pyruvate kinase (PK) correlated with the state of oxygenation of the tissue and not with the measured tissue pH value; higher tissue pH did not prevent anoxia-induced phosphorylation of PK and lower tissue pH did not alter the kinetic patterns of the aerobic enzyme. Overall, the study indicates that cells and tissues of the whelk respond individually to anoxia and that coordination of the action of protein kinases during anoxia is not mediated by pH or by common second-messenger mechanisms.
Relationship of Wing Beat Frequency and Temperature During Take-Off Flight in Temperate-Zone Beetles
Authors: Oertli J. J. 
Published: April 2021

ABSTRACT
In 24 species of temperate-zone beetles thoracic temperatures (Tth), and wing beat frequency (n) were measured over a range of ambient temperatures (Ta) during take-off flight. The sensitivity of wing beat frequency to thoracic temperature varied greatly in different species: Q10 values ranged from 0·8 to 1·3. The wing beat frequency of beetles with higher average n was more sensitive to thoracic temperature. It is suggested that the temperature sensitivity of wing beat frequency results from temperature-dependent changes in the resonant properties of the beetle flight system rather than from changes in the temperature sensitivity of the muscle or nervous system.
There was large variability in thermoregulatory precision. Beetles with higher n tended to thermoregulate more precisely than beetles with lower n. Measurements of thoracic temperature before and after flight indicated endothermic heat production during pre-flight activity, but not during the brief take-off flights.
Energetically Defining the Thermal Limits of the Snow Crab
Authors: Foyle Timothy P. , O’Dor Ronald K. , Elner Robert W. 
Published: April 2021

ABSTRACT
The snow crab, Chionoecetes opilio, is a cold-water species found naturally at temperatures below 5 °C. Its physiology and energetics were examined to understand the metabolic limitations that restrict the snow crab to these temperatures. The species is not confined to cold water because of a limited respiratory system. Routine oxygen demand can be met even at lethal temperatures of 18°C (56mgO2kg−1h−1, with a Q10 of 2·2). Blood lactate levels remain below 1·5 mmol 1−1 and actually decline slightly with temperature.
Energy budgets, which were constructed from an examination of oxygen uptake, activity and food consumption in morphometrically mature male animals between 0 and 18 °C, indicate that the snow crab is energetically restricted to cold water. Rising metabolic costs overtake caloric intake around 7 °C. This is probably due to digestive metabolism which is temperature-sensitive. Food consumption increases up to 6°C but then falls. Crabs stop feeding above 12°C. Although the growth equation is positive between 1 and 7°C, it becomes slightly negative below 1°C. This observation is unexpected since snow crabs are commonly found between 0 and 1 °C. Slight temperature changes in the natural environment may, therefore, regulate growth and reproduction in this species.
Sodium- and Calcium-Dependent Mechanisms in the Action Potential of the Secretory Epithelium of a Clam Mantle
Authors: Beirão Paulo S. , Nascimento José Hamilton M. 
Published: April 2021

ABSTRACT
The secretory epithelium of the mantle of the clam Anomalocardia brasiliana is excitable. The ionic dependence of its action potentials was investigated. Two distinct phases could be recognized by their ionic dependences. The early spike phase, that appeared in all action potentials, was dependent on the Na+ concentration of the solution in the interstitial space and was insensitive to tetrodotoxin (TTX) at concentrations as high as 36μmoll−1. It was inhibited by local anesthetics, and its repolarization was inhibited by veratrine. The data show this electrogenesis is caused by TTX-insensitive sodium channels located at the basolateral membrane of this epithelium. Cardiac-like action potentials were recorded in several specimens: the rapid Na+-dependent spike was followed by a slower repolarization phase that formed a plateau and increased the action potential duration. The plateau amplitude was markedly increased when the external Ca2+ concentration was increased to 60 mmol I−1 and it was inhibited by the addition of inorganic calcium channel blockers such as Mn2+ and Cd2+. These observations suggest that inward Ca2+ currents cause the sustained depolarization during the plateau.
Second-messenger systems underlying amine and peptide actions on cardiac muscle in the horseshoe crab Limulus polyphemus
Authors: Groome J. R. , Watson W. H. 
Published: April 2021

ABSTRACT
The biochemical mechanisms by which octopamine, catecholamines and the peptide proctolin exert their actions on Limulus cardiac muscle were investigated. Amines produced long-lasting increases in the amplitude of contractions evoked by electrical stimulation. At 10−5moll−1, the apparent order of potency for amine-induced increases in evoked contraction amplitude was dopamine≈ octopamine &gt; norepinephrine ≈ epinephrine. At this dose, amines produced long-lasting increases in the levels of cyclic AMP (octopamine &gt; dopamine ≈ norepinephrine ≈ epinephrine), but not of cyclic GMP, in Limulus cardiac muscle.
Like the amines, the adenylate cyclase activator forskolin enhanced cardiac muscle contractility and increased levels of cyclic AMP, but not of cyclic GMP. The phosphodiesterase inhibitor IBMX produced a transient increase in cardiac muscle contractility, but typically produced long-lasting negative inotropy. This agent increased levels of both cyclic AMP and cyclic GMP in Limulus cardiac muscle.
Proctolin and the protein kinase C activator phorbol dB increased the contraction amplitude of the intact heart and the electrically stimulated myocardium. These compounds, as well as dopamine, elicited sustained contractures and rhythmic contractions when applied to deganglionated Limulus cardiac muscle rings. Unlike the amines, proctolin and phorbol dB did not increase cardiac muscle cyclic AMP levels.
These results suggest that several second-messenger systems may be utilized by amines and peptides to produce excitatory actions on cardiac muscle fibers of the Limulus heart. Cyclic AMP appears to be an important second messenger underlying the effects of amines to enhance cardiac muscle contractility. Pharmacological data suggest that proctolin may alter cardiac muscle contractility and excitability by a mechanism which involves the phosphatidylinositol pathway. Dopamine, unlike the other amines, produces a number of proctolin-like effects and may activate both the cyclic AMP and the phosphatidylinositol systems in Limulus cardiac muscle.
The Effect of Seasonal Acclimatization on the Buffering Capacity and Lactate Dehydrogenase Activity in Tissues of the Freshwater Turtle Chrysemys Picta Marginata
Authors: Olson John M. , Crawford Kenneth M. 
Published: April 2021

ABSTRACT
Freshwater turtles are remarkably tolerant of anoxic conditions, a tolerance essential for animals that spend much of their time submerged (Belkin, 1963). Many metabolic adaptations for efficient anaerobiosis have been elucidated in turtles, and are essential for allowing these animals not only to dive over a wide range of water temperatures (Gatten, 1981) but also to survive the long hibernation during winter in the higher latitudes (see Penney, 1987, for a review).
Dependence of Blood Viscosity on Haematocrit and Shear Rate in a Primitive Vertebrate
Authors: G. Wells R. M. , Forster M. E. 
Published: April 2021

ABSTRACT
Hagfish have an unusual circulation with intravascular pressures that are lower than those in other vertebrates (Davie et al. 1987; Forster, 1989) and since peripheral resistances appear similar to those of teleost fishes (Flood, 1979; Eiger, 1987), it follows that blood flow rates will also be lower. One might therefore predict that the relatively low haematocrits in hagfish (Johansen et al. 1962; Forster et al. 1989) and lack of plasma albumins (Manwell, 1963) would maintain a relatively low blood viscosity at low flow rates when blood tends to become more viscous by virtue of its non-Newtonian behaviour (McDonald, 1974; Fletcher & Haedrich, 1987).
Honeybees can be Trained to Respond to very Small Changes in Geomagnetic Field Intensity
Authors: Walker Michael M. , Bitterman M. E. 
Published: April 2021

ABSTRACT
It has been demonstrated repeatedly (Kirschvink & Kirschvink, 1989; Walker et al. 1989; Walker & Bitterman, 1985, 1989) that free-flying honeybees can be trained to respond to local anomalies in the geomagnetic field, but none of the training methods previously available has been sensitive enough for threshold studies. Here we report some determinations of intensity thresholds with a new and more powerful technique that permits objective measurement of response.
A Malpighian Tubule Lime Gland in an Insect Inhabiting Alkaline Salt Lakes
Authors: Herbst David B. , Bradley Timothy J. 
Published: April 2021

ABSTRACT
The alkali fly, Ephydra hians Say, inhabits alkaline salt lakes which can contain concentrations of dissolved carbonate and bicarbonate as high as 500 mmol l−1. Larvae of the alkali fly possess two pairs of Malpighian tubules. The posterior pair has a morphology similar to that of the tubules of most other insects, but the anterior pair is modified into an enlarged gland containing white microsphere concretions. We describe the ultrastructure of all cell types in both pairs of tubules. Using scanning electron microscope (SEM) X-ray microanalysis and chemical CO2 quantification, we demonstrate that the concretions in the lime glands are composed of nearly pure calcium carbonate. Isolated preparations of lime gland tubules accumulate 45Ca significantly more rapidly than do normal tubules. Although similar to the lime concretions found in the Malpighian tubules of other Diptera, the lime glands of this insect may function to regulate the high concentrations of carbonate and bicarbonate encountered in their aquatic environment. It is proposed that the mechanism of this regulation may be chemical precipitation of carbonate/bicarbonate with calcium in the lumen of these specialized lime gland tubules.
Long-Term Adaptation of a Phasic Extensor Motoneurone in Crayfish
Authors: Mercier A. Joffre , Atwood Harold L. 
Published: April 2021

ABSTRACT
Long-term adaptation (LTA), a phenomenon previously studied in the crayfish claw, was examined in one of the motoneurones innervating the phasic abdominal extensor muscles. The motoneurone was conditioned by electrically stimulating the second root of the third abdominal ganglion in situ for 4 h per day, using trains of stimuli with an average impulse frequency of 2·5 Hz. In juvenile crayfish, 3 days of conditioning produced a marked (81%) reduction in EPSP amplitude, which recovered only slightly during the succeeding 7 days. The quantal content of synaptic currents also decreased (by an average of 65 %). Estimated values of the binomial parameter p were lower for conditioned neurones than for controls, suggesting that the observed decrease in transmitter release involves a decrease in release probability. Conditioned neurones also displayed less synaptic depression than controls during repetitive stimulation at 5 Hz.
In adult crayfish, conditioning for 7 days also produced a marked (74%) reduction in EPSP amplitude and resistance to synaptic depression. These results differ from those of previous work with the phasic axon of the claw closer muscle, which shows virtually no synaptic changes in adults after conditioning for 2 weeks. The ability to exhibit LTA, therefore, is not lost with age in all neurones.
Visual pigments and the acquisition of visual information
Authors: Lythgoe J. N. , Partridge J. C. 
Published: April 2021

ABSTRACT
All the information available to the brain for the interpretation of the visual scene comes from the number of photons absorbed by a very limited number of photoreceptor types which are characterized by their spectral sensitivity. In vertebrates there are considerable differences in the spectral absorption of the rods and cones making up the retinal mosaic of different animals and, in some cases, including fish and primates, there are considerable differences between the cone sets of individuals within a species.
Broadly speaking, the spectral sensitivity of the photoreceptors is related to the spectral distribution of the ambient light and this is particularly true of the colour-biased light under water. When an animal migrates from one visual environment to another, its cone complement may change to that suited to the new conditions. However, significant differences between the cone sets of animals living within the same environment and colour vision polymorphism within a species suggest that visual tasks critical to survival or breeding success require particular visual pigment sets. A start has been made in trying to understand what tasks are best served by different pigment sets.
Descending Interneurones of the Locust Reporting Deviation from Flight Course: What is their role in Steering
Authors: Rowell C. H. F. 
Published: April 2021

ABSTRACT
Some descending intemeurones (DNs) in insects encode deviation from flight course. Intracellular recording reveals their inputs (from eyes, wind hairs, proprioceptive information from the neck and in some cases ocelli). Intracellular stimulation during flight reveals their motor effects. All components of steering (modification of wing stroke, ruddering with the hind legs, ruddering with the abdomen and head rotation) can be initiated by single DNs. Steering in flight involves the concerted action of at least 10 pairs of DNs synapsing with motor neurones and premotor intemeurones. The whole system forms an autopilot, well suited for corrective steering. It is modulated principally by head movements, which have both optical and proprioceptive effects: compensatory head move-ments increase the accuracy of correctional steering by reducing overshoot, and disable the autopilot during turns evoked by directional pulsed ultrasound for purposes of bat-evasion. DNs responding specifically to visual flow fields are also known, but appear to be related to control of velocity rather than to steering.
Processing of mechanosensory signals in local reflex pathways of the locust
Authors: Burrows M. 
Published: April 2021

ABSTRACT
The processing of mechanosensory signals responsible for the reflex adjustment of the posture or movement of the legs of the locust is described in terms of the actions and connections of identified neurones. Signals can be followed from the major classes of exteroceptors of a leg, through their various integrative stages in the central nervous system to their emergence as specific patterns in known motor neurones. Particular emphasis is placed on the integrative roles of two classes of local interneurones. The spiking local interneurones map the leg as a series of overlapping receptive fields and reverse the sign of the afferent input. The nonspiking local interneurones control the output of the motor neurones by the graded release of chemical transmitter and can adjust the gain of a local reflex depending on the position and movements of the joints of that leg.
The reflex movements of one leg must not impair the stability of the animal and must therefore be influenced by events at the other legs. Populations of intersegmental interneurones convey sensory information from one segment to another to ensure such coordination. These interneurones do not produce stereotyped intersegmental reflexes but, instead, alter the performance of a local reflex in a distant leg by making synaptic connections with nonspiking local interneurones. These connections change the effectiveness of the outputs to the motor neurones and consequently the local reflex. The local interneurones therefore play a crucial role both in the production of local reflexes and in the integration of these actions with the movements of the other legs.
Principles of auditory information-processing derived from neuroethology
Authors: Suga N. 
Published: April 2021

ABSTRACT
For auditory imaging, a bat emits orientation sounds (pulses) and listens to echoes. The parameters characterizing a pulse-echo pair each convey particular types of biosonar information. For example, a Doppler shift (a difference in frequency between an emitted pulse and its echo) carries velocity information. For a 61-kHz sound, a 1·0-kHz Doppler shift corresponds to 2·8ms-1 velocity. The delay of the echo from the pulse conveys distance (range) information. A 1·0-ms echo delay corresponds to a target distance of 17 cm. The auditory system of the mustached bat, Pteronotus parnellii, from Central America solves the computational problems in analyzing these parameters by creating maps in the cerebral cortex.
The pulse of the mustached bat is complex. It consists of four harmonics, each of which contains a long constant-frequency (CF) component and a short frequency-modulated (FM) component. Therefore, there are eight components in the emitted pulse (CF1-4 and FM1-4). The CF signal is particularly suited for target velocity measurement, whereas the FM signal is suited for target distance measurement. Since the eight components differ from each other in frequency, they are analyzed in parallel at different regions of the basilar membrane in the inner ear. Then, they are separately coded by primary auditory neurons and are sent up to the auditory cortex through several auditory nuclei. During the ascent of the signals through these auditory nuclei, neurons responding to the FM components process range information, while other neurons responding to the CF components process velocity information.
A comparison of the data obtained from the mustached bat with those obtained from other species illustrates both the specialized neural mechanisms specific to the bat’s auditory system, and the general neural mechanisms which are probably shared with many different types of animals.
The neural coding of auditory space
Authors: Takahashi T. T. 
Published: April 2021

ABSTRACT
The barn owl’s auditory system computes interaural differences in time and amplitude and derives from them the horizontal and vertical coordinates of the sound source, respectively. Within the external nucleus of its inferior colliculus are auditory neurones, called ‘space-specific neurones’, that have spatial receptive fields. To activate a space-specific neurone, a sound must originate from a circumscribed region of space, or, if the sounds are delivered to each ear separately, using earphones, the stimuli must have the combination of interaural time and amplitude difference that simulates a sound broadcast from their receptive field. The sound-localization cues are processed in parallel, nonoverlapping pathways extending from the cochlear nuclei to the subdivision of the inferior colliculus that innervates the space-specific neurones. Processing in the time pathway involves the coding of monaural phase angle, the derivation of sensitivity for interaural phase difference, and the calculation of interaural time difference (1TD) from interaural phase difference. The last process involves groups of neurones in the inferior colliculus whose collective firing signals a unique 1’1 L), even though the activity of each constituent neurone signals multiple ITDs. The projections of these ensembles to the space-specific neurone endow the latter with a selectivity for IHD. Processing in the amplitude channel, about which less is known, initially involves an inhibitory process that sharpens the directional sensitivity of neurones in a lateral lemniscal nucleus. The inhibition is mediated by a commissural projection from the same lemniscal nucleus of the opposite side. At higher levels of the auditory system, neurones that are tuned to a limited range of interaural amplitude differences are found. It is proposed that at these higher stages, interaural amplitude difference, like ITD, is coded amidst an ensemble of neurones.