bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Dietary Protein Levels and Haemolymph Composition on the Sensitivity of the Maxillary Palp Chemoreceptors of Locusts
Authors: Abisgold J. D. , Simpson S. J. 
Published: April 2021

ABSTRACT
Previous work has shown that fifth-instar nymphs of Locusta migratoria (L.) compensate for a dilution of their dietary protein by reducing intermeal interval (Simpson & Abisgold, 1985). The effect of dietary protein on intermeal interval is regulated, either directly or indirectly, by the osmolality and free amino acid content of the haemolymph (Abisgold & Simpson, 1987). The possibility that levels of dietary protein and haemolymph composition affect the response of the maxillary palp gustatory receptors is investigated. Insects fed a low-protein diet had a significantly greater receptor response (measured as the total number of spikes in the first second of stimulation of a sensillum) to stimulation with 0·0125 moll-1 leucine in 0·05 moll-1 NaCl, 0·05 mol 1-1 NaCl alone or 0·025 mol 1-1 sucrose in 0·05 mol 1-1 NaCl than did insects fed a high-protein diet, although for both diets the response to sucrose was significantly lower than the response to the other two solutions. Increasing the free amino acid profile of the haemolymph of a low-protein-fed locust up to that of a high-protein-fed locust by injection markedly reduced the response of the receptors to subsequent stimulation with a 0·0125 mol 1-1 mix of eight of the 10 amino acids injected, but did not reduce the response to stimulation with 0·025 mol 1-1 sucrose in 0·05 mol 1-1 NaCl. This reduction was independent of the effect of injection on blood osmolality and was sustained for 50 min after the injection. The response to 0·05 mol 1-1 NaCl alone was influenced both by increases in blood amino acid levels and by osmolality, but the effect was less marked than the specific reduction in response to amino acid stimulation. The possible significance of a reduction in receptor sensitivity on feeding behaviour and the relative roles of blood osmolality and free amino acid content are discussed.
Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae I. The Transbasal Electrochemical Gradient
Authors: Moffett David F. , Koch Alan R. 
Published: April 2021

ABSTRACT
Basal membrane potential (Vb) and intracellular K+ activity [(K+)i] were recorded, using microelectrodes, in isolated, superfused, short-circuited midgut of fifth instar larvae of Manduca sexta. The electrochemical gradient across the basal membrane was favourable for K+ entry as long as [K+]b was 32mequivl-1 or greater. In 20mequivl-1 K+ Vb rose so that in some cells the basal electrochemical gradient was unfavourable for K+ entry. In 10mequivl-1 K+, the basal electro-chemical gradient of all cells was unfavourable for K+ entry. This result suggests that an active K+ pump may augment passive basal K+ entry.
Addition of 2 mmol 1-1 Ba2+ to midgut resulted in substantial hyperpolarization of Vb accompanied by relatively small changes in (K+)i; the net effect was to move (K+)i farther away from electrochemical equilibrium with external K+.
Identification of recorded cells by ionophoretic injection of Lucifer Yellow showed that both major cell types of the epithelium (goblet and columnar cells) had similar control values of Vb and (K+)i and responded similarly to Ba2+, suggesting the presence of effective chemical or electrical coupling between the transporting goblet cells and the non-transporting columnar cells.
Hypoxia reduced transepithelial K+ transport, both in the absence and in the presence of Ba2+. In the absence of Ba2+, (K+)i was within a few millivolts of equilibrium and the effect of hypoxia was small. In the presence of Ba2+, when (K+)i was far from equilibrium with extracellular K+, hypoxia markedly depolarized the basal membrane.
The results are compatible with the suggestion that Ba2+ partially blocks basal K+ entry, but does not directly affect the apical pump. Hypoxia inhibits the apical pump. Since the active transepithelial transport of K+ was reduced after Ba2+ treatment even though (K+)i was unchanged, it appears that the activity of the apical pump is primarily controlled by the voltage step across the apical membrane.
Wind Tunnel Experiments to Assess the Effect of Back-Mounted Radio Transmitters on Bird Body Drag
Authors: Obrecht Holliday H. , Pennycuick C. J. , Fuller Mark R. 
Published: April 2021

ABSTRACT
The aerodynamic drag of bird bodies was measured in a wind tunnel, with and without back-mounted dummy radio transmitters. Flight performance estimates indicate that the drag of a large transmitter can cause a substantial reduction of a migrant’s range, that is, the distance it can cover in non-stop flight. The drag of the transmitter can be reduced by arranging the components in an elongated shape, so minimizing the frontal area. The addition of a rounded fairing to the front end, and a pointed fairing behind, was found to reduce the drag of the transmitter by about one-third, as compared with an unfaired rectangular box.
Metabolic Control of Spontaneous Glowing in Isolated Photophores of Porichthys
Authors: Rees J. F. , Baguet F. 
Published: April 2021

ABSTRACT
Isolated photophores of the epipelagic fish Porichthys notatus become spontaneously luminescent after a few hours in saline at 20°C. This luminescence is not significantly affected by the adrenergic antagonists propranolol and phentolamine. The addition of glucose, mannose, fructose or galactose in saline inhibits glowing according to their respective rates of metabolism in fishes. Glycolytic metabolites, such as phosphoenolpyruvate and pyruvate, prevent or abolish the spontaneous glowing. Monoiodoacetate (IAA), the classical inhibitor of glycolysis, reverses the inhibitory effect of glucose but not of pyruvate. We suggested that glycolysis provides an energy supply to an inhibitory mechanism that keeps the Porichthys photophore in a non-luminescent state.
Connections of Hindwing Tegulae with Flight Neurones in the Locust, Locusta Migratoria
Authors: Pearson K. G. , Wolf H. 
Published: April 2021

ABSTRACT
The connections of afferents from the hindwing tegulae to flight motoneurones and interneurones in the locust, Locusta migratoria, have been determined by selectively stimulating the tegula afferents while recording intracellularly from identified neurones in the meso- and metathoracic ganglia. Electrical stimulation of the hindwing tegula nerve (nerve ICla) revealed two groups of afferents distinguished by a difference in their conduction velocities. Both groups of afferents made excitatory connections to hindwing elevator motoneurones in the ipsilateral half of the metathoracic ganglion. Latency measurements indicated that these connections were monosynaptic. Stimulation of the hindwing tegula nerve also evoked excitatory postsynaptic potentials (EPSPs) in elevator motoneurones in the mesothoracic ganglion and in the contralateral half of the metathoracic ganglion, and inhibitory postsynaptic potentials (IPSPs) in forewing and hindwing depressor motoneurones. The latencies of these evoked EPSPs and IPSPs indicated that the initial responses were produced via interneuronal pathways. None of the recordings revealed EPSPs in depressor motoneurones or IPSPs in elevator motoneurones in response to hindwing tegula stimulation. This observation differs from that in Schistocerca gregaria where it has been reported that the large tegula afferents produce EPSPs in depressors and IPSPs in elevators (Kien & Altman, 1979). Some of the interneurones in disynaptic excitatory and inhibitory pathways to motoneurones were identified. These interneurones received input from both hindwing tegulae and were readily excited beyond threshold by mechanical stimulation of the tegulae or by electrical stimulation of the tegula afferents. The contribution of one excitatory interneurone to the electrically evoked EPSPs was assessed by blocking spike initiation in the interneurone while recording simultaneously from a flight motoneurone. Based on our observations of the central connections of tegula afferents to flight motoneurones and the previously reported discharge patterns of these afferents during tethered flight (Neumann, 1985), we propose that a major function of the hindwing tegulae in L. migratoria is to generate the initial depolarizations in forewing and hindwing elevator motoneurones during flight. Consistent with this proposal was our finding that ablation of the hindwing tegulae delayed the onset of elevator activity relative to the onset of the preceding depressor activity.
Learning by the Aplysia Model System: Lack of Correlation Between Gill and Gill Motor Neurone Responses
Authors: Colebrook Elaine , Lukowiak Ken 
Published: April 2021

ABSTRACT
A semi-intact preparation of Aplysia californica was used to monitor simultaneously behavioural and motor neurone responses during classical conditioning of the gill withdrawal reflex. Gill motor neurone responses and gill withdrawal responses were both capable of enhancement in response to the conditioned stimulus after associative training. The neuronal and behavioural responses did not, however, correlate. In 32% of the conditioned (paired) preparations and 27% of the control (unpaired) preparations, the neuronal response was facilitated whereas the gill withdrawal response did not change, or decreased. In addition, amongst those preparations that showed behavioural enhancement, the acquisition of learning of gill withdrawal followed a different pattern from that displayed by the central neurones. This suggests that facilitation of the central sensory-motor neurone synapses is not primarily responsible for conditioning of the gill withdrawal reflex. The gill withdrawal response elicited by direct depolarization of the central motor neurones decreased following the unpaired (control) presentations of the conditioned and unconditioned stimuli, and remained unchanged following paired presentations, suggesting that there is a site of neuronal plasticity in the gill.
Induced Drag Savings From Ground Effect and Formation Flight in Brown Pelicans
Authors: Hainsworth F. Reed 
Published: April 2021

ABSTRACT
Ciné films of brown pelicans flying in formation were used to measure altitudes and wing tip spacing (WTS, distance perpendicular to the flight path between wing tips of adjacent birds at maximum span) for birds flying in ground effect, and vertical displacements and WTS for birds flying out of ground effect. Views were near coplanar with the plane of flight paths, and maximum wing span was used for scale. Induced drag savings in ground effect averaged 49% for gliding. Average WTS varied considerably with no evidence for systematic positioning near an optimum. There were also no differences in average WTS between flapping and gliding in or out of ground effect. Vertical displacements out of ground effect varied less than WTS but more than vertical displacements in ground effect. Few birds had wing beat frequencies similar to the bird ahead as would be needed to track vertical variation in trailing wing tip vortex positions. Imprecision in WTS may be due to unpredictable flow fields in ground effect, and difficulty in maintaining position under windy conditions out of ground effect.
The Aerobic Capacity of Locomotory Muscles in the Tufted Duck, Aythya Fuligula
Authors: Turner D. L. , Butler P. J. 
Published: April 2021

ABSTRACT
The locomotory muscles of the tufted duck, Aythya fuligula (L.), were analysed for mass, aerobic and anaerobic enzyme activities, fibre-type proportions, capillarity, mitochondrial and myoglobin content. The estimated aerobic capacity of the muscles correlated well with the muscles’ maximal oxygen uptake both when measured during swimming and when predicted for steady-state flight. The results suggest that exercise performance in birds cannot be predicted purely on the basis of muscle mass (see Butler & Woakes, 1985); the specific enzyme complement of each muscle must also be taken into account.
The delivery of oxygen to mitochondria is facilitated by the dense capillarity and high myoglobin content of the muscles.
Regional Distribution of Blood Flow During Swimming in the Tufted Duck (Aythya Fuligula)
Authors: Butler P. J. , Turner D. L. , Al-Wassia A. , Bevan R. M. 
Published: April 2021

ABSTRACT
The distribution of blood flow to a number of organs and tissues of the tufted duck was determined (by the microsphere technique) before and while the birds were swimming at close to their maximum sustainable velocity (i.e. at 0·69 ± 0·01 ms−1).
During swimming, oxygen uptake was twice the pre-exercise value. Cardiac output increased by 70%, there was no significant change in arterial blood pressure and total systemic conductance increased by 44 %. There were no significant changes in blood flow to the brain, liver, adrenal glands, spleen and respiratory muscles. Not surprisingly, there were increases in blood flow to the heart (30 % increase) and to the muscles of the hindlimbs (to 3·1 times the pre-exercise value). Significant reductions in flow occurred to various parts of the gastrointestinal tract (although not to the gastrointestinal tract as a whole), to the pancreas and to the pectoralis muscles. In the case of the flight musculature as a whole, the reduction was to approximately 40% of the values in the ducks before exercise.
Thus, despite the fact that cardiac output was some three times lower than it would have been during flight, there was a clear redistribution of blood away from some visceral organs and inactive muscles during surface swimming in the tufted duck. This lends support to the suggestion that blood is selectively directed to the legs, as well as to the brain and central nervous system (CNS) and away from the visceral organs and inactive muscles during voluntary diving in these birds.
Anomalous Behaviour of 86Rb as a Tracer for Transintestinal Potassium Transport in the Fowl, Gallus Domesticus
Authors: Grubb Barbara R. , Brown Helen V. , Bentley P. J. 
Published: April 2021

ABSTRACT
Fluxes of potassium ions across biological membranes can be measured using 42K as a tracer. This isotope, however, has a half-life of only 12-4 h and it is expensive. Rubidium belongs to the alkali metal series of elements and rubidium ions behave in many respects, physicochemically and biologically, like K+. Furthermore, 86Rb has a half-life of 18-7 days and is less expensive than 42K. Thus 86Rb has been used quite widely as a tracer for estimating K+ transport. In mammals this usage has included erythrocytes (Beauge & Adragna, 1971), the crystalline lens (Becker, 1962), renal tubules (Ellison, Velazquez & Wright, 1986) and large intestine (Tannen, Marino & Dawson, 1986; Freel, 1987). In these instances, the ratios of the measured fluxes, JK/JRb were not found to differ significantly from unity. In non-mammals, 86Rb has been shown to be a useful substitute for K+ in transport studies using flounder intestine (Frizzell et al. 1984), salmon erythrocytes (Bourne & Cossins, 1984) and frog skin (Zerahn, 1983). In fish gills, the ratio JK/JRB was consistently found to be about 1·3 (Sanders & Kirschner, 1983), thus allowing for correction of estimates of K+ flux based on the use of 86Rb as a tracer. In the American silkworm (Hyalophora cecropia) gut, this ratio was 1·1 in a flat-sheet preparation (Wood & Harvery, 1979), but in a spherical preparation it was rather unpredictable with a mean of 1 -7 (Zerahn, 1980). None of these authors considered 86Rb to be a reliable substitute for 42K. Eddy (1985) has drawn attention to such possible disparities of K+ metabolism estimated by the use of 86Rb in fish. We have also found differences in estimates of K+ transport using 42K and 86Rb as tracers in the avian intestine.
A Simple Analyser for Gases In Mixed Samples
Authors: Kozacik John J. 
Published: April 2021

ABSTRACT
It is often necessary to measure the concentration of a single gas in a sample of mixed gases. Dalton’s Law of Partial Pressures indicates that this may be done by measuring the volume of a sample before and after absorption of the gas of interest; the ratio of the difference between the two volumes to the original volume stating exactly the concentration of the absorbed gas.
Central Coordination of Buccal and Pedal Neuronal Activity in the Pond Snail Lymnaea Stagnalis
Authors: Kyriakides M. A. , McCROHAN C. R. 
Published: April 2021

ABSTRACT
Cyclical synaptic inputs were recorded from identified giant neurones and neuronal cluster cells in the pedal ganglia of Lymnaea stagnalis. They occurred in phase with rhythmical inputs to buccal ganglion motoneurones, which have been shown to originate from interneurones of the buccal central pattern generator for feeding. In pedal neurones, the cyclical inputs were mainly inhibitory, and occurred predominantly during the radula retraction phase of the feeding cycle.
Tonic depolarization of higher-order interneurones in the feeding system, to activate the buccal central pattern generator, led to the onset of cyclical inputs to pedal neurones. These inputs were abolished after cutting the cerebrobuccal connectives, supporting the hypothesis that they originate from the buccal ganglia. The possible role of these inputs in coordinating foot and body wall movements with the buccal feeding rhythm is discussed.
Induction of Potential for Sperm Motility by Bicarbonate and pH In Rainbow Trout and Chum Salmon
Authors: Morisawa Sachiko , Morisawa Masaaki 
Published: April 2021

ABSTRACT
Spermatozoa of rainbow trout and chum salmon, which have no potential for motility in the testis, acquire that potential in the sperm duct. This paper demonstrates that there is little difference between the levels of sodium, potassium, calcium, magnesium, chloride and osmolality of the seminal plasma in the testis and in the sperm duct. However, the bicarbonate concentration of the seminal plasma and the pH value of semen were higher in the sperm duct than in the testis. When immotile spermatozoa obtained from the testis were incubated in artificial seminal plasma with a high pH and containing HCO3−, spermatozoa became motile within 1 h. These results suggest that spermatozoa of salmonid fish acquire the potential for motility as a result of the increase in seminal bicarbonate concentration and pH that occurs as spermatozoa pass from the testis to the sperm duct.
Unpaired Median Neurones in a Lepidopteran Larva (Antheraea Pernyi): II. Peripheral Effects and Pharmacology
Authors: Brookes S. J. H. 
Published: April 2021

ABSTRACT
Two unpaired median cells (MCI and MC2) had a temporal pattern of firing that correlated with phasic muscular activity in preparations of larval Antheraea pernyi, and previous work has indicated that the axons of median cells are associated with nerve trunks innervating blocks of muscle. In spite of this, action potentials in median cells were not found to have any one-for-one effects on either the tension or the electrical activity of somatic muscle fibres. However, bursts of action potentials in MC2 were shown to modulate both tension production and electrophysiological activity of a number of motor units. These effects consisted of an increase in twitch tension, a relaxation of basal resting tension, an increase in relaxation rate following contractions, a hyperpolarization of some muscle fibres and an increase in amplitude of excitatory junction potentials. The relative potency of these different effects varied between fast and slow muscles. All of these effects were mimicked by the application of octopamine and synephrine, and in higher concentrations by a number of other biogenic amines and adrenergic agonists. The possibility that the effects of median cell activity were mediated by the release of endogenous octopamine was supported by the observation that phentolamine (10−5moll-1) blocked the effects of both MC2 impulses and the application of exogenous octopamine, whereas propanolol affected neither set of responses. This observation also indicated a pharmacological similarity with a number of other octopamine-sensitive insect tissue preparations. MCI had similar effects to MC2 on the electrical activity of a number of muscles, suggesting that these two cells play a similar role. These observations provide strong evidence for the presence of an identifiable octopaminergic system of neurones, similar to the dorsal unpaired median (DUM) neurones that have been extensively studied in the locust.
Spectral Sensitivity of Photoreceptors and Colour Vision in the Solitary Bee, Osmia Rufa
Authors: Menzel R. , Steinmann E. , De Souza J. , Backhaus W. 
Published: April 2021

ABSTRACT
The spectral sensitivity of single photoreceptors of Osmia rufa was determined by a fast voltage-clamp technique. Three receptor types were found whose spectral sensitivity functions followed a rhodopsin-like photopigment absorption function with λmax values at 348nm (ultraviolet receptor), 436nm (blue receptor) and 572nm (green receptor). The λmax of the green receptor in Osmia rufa is shifted to much longer wavelengths compared with other insect species. Discrimination of colour signals was tested after training a bee at the entrance to its nest. The colour signals were filter discs (70 mm in diameter) with a hole (10 mm in diameter) in the centre and the bees quickly learned to use the coloured disc as a marker of the nest entrance. Tests were dual forced-choice tests with two coloured discs closely positioned next to each other. 94 different tests were each repeated 5–15 times and were performed after training to 12 different colour signals.
A photoreceptor model was used to calculate the loci of the colour signals in a three-dimensional colour space and in a chromaticity diagram. The perceptual distance between the colour loci was calculated as line elements (minimum number of just noticeable difference, jnd-steps), which were based on the noise properties of the photoreceptors. The discrimination determined by the behavioural tests correlated very well with the jnd-steps. The correlation was better for the line elements in the colour plane than in the colour space. Osmia rufa was compared with the honeybee Apis mellifera and the stingless bee Melipona quadrifasciata. There is no difference in colour selection between Osmia and Apis, whereas Melipona discriminates less well in the violet-blue region. The model calculation was used to compare the chromaticity diagrams and the spectral discrimination functions of the three species. It is concluded that the receptor model used in this study predicts the discrimination behaviour of the three bee species very well. Therefore, comparative studies on colour vision in flower visiting insects may be based on spectral measurements of the photoreceptors, and in many cases this reduces the extent of laborious behavioural studies.