bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo Lactate Kinetics at Rest and During Recovery From Exhaustive Exercise in Coho Salmon (Oncorhynchus Kisutch) and Starry Flounder (Platichthys Stellatus)
Authors: Milligan C. Louise , Mcdonald D. Gordon 
Published: April 2021

ABSTRACT
A bolus injection of [14C] lactate was used to measure lactate turnover rates at rest and during recovery from exhaustive exercise in coho salmon (Oncorhynchus kisutch) and starry flounder (Platichthys stellatus). At rest, lactate turnover rate in salmon was almost double that in flounder (1·33 versus 0·76 μmol min−1 kg−1), which reflected the higher blood lactate level in salmon (1·00 versus 0·12mmol l−1). From 2 to 4h after exercise, when blood lactate levels were at their peak and constant, turnover rates were elevated in both species, though to a greater extent in salmon than in flounder (11·88 versus 2·27 μmol min−1 kg−1). Lactate concentration and turnover rate were linearly correlated in both species. The higher turnover rate in salmon was solely a consequence of the higher blood lactate levels since, at similar blood lactate concentrations, turnover rates in flounder and salmon were the same. Therefore, the lower blood lactate levels in flounder after exercise were not a consequence of higher turnover. In neither species was the turnover rate adequate to account for the rate of lactate clearance from the muscle, suggesting a large portion was retained within the muscle and metabolized in situ. Furthermore, following injection of [14C] lactate, &gt;80% of the total blood activity was recovered as lactate, indicating that little label was incorporated into other products (e.g. glucose). These data suggest that the Cori cycle plays a minimal role in the metabolism of lactate in salmon and flounder. Furthermore, at least in flounder, there was no correlation between the kinetics of lactate clearance and O2 consumption, suggesting that the classical concept of ‘O2 debt’ is not applicable in this species.
A Neuronal Role for A Crustacean Red Pigment Concentrating Hormone-Like Peptide: Neuromodulation of the Pyloric Rhythm in the Crab, Cancer Borealis
Authors: Nusbaum Michael P. , Marder Eve 
Published: April 2021

ABSTRACT
The distribution of red pigment concentrating hormone (RPCH)-like immuno-reactivity (RPLI) in the stomatogastric nervous system of the crab, Cancer borealis, was studied using whole-mount immunocytochemistry. RPLI was seen in neuropilar processes in the stomatogastric ganglion (STG), and in somata in the oesophageal ganglion and commissural ganglia. Staining was blocked by preincubating the antiserum with RPCH, as well as with a number of adipokinetic hormones (AKHs) and related peptides.
Synthetic RPCH had strong actions on the pyloric rhythm of the isolated STG. Bath applications of RPCH (10−9-10−6moll−1) increased the cycle frequency in preparations displaying slow pyloric rhythms, and initiated rhythmic pyloric activity in silent preparations. In the presence of tetrodotoxin (TTX), RPCH evoked rhythmic non-impulse-mediated alternations in membrane potential in the lateral pyloric and pyloric dilator motor neurones. The effects of RPCH were compared to those of a series of AKHs which resemble RPCH structurally.
The immunocytochemical and physiological data together suggest that RPCH or a similar molecule is a neurally released modulator of the STG.
Influx and Transepithelial Flux of Amino Acids in the Mussel, Mytilus Edulis
Authors: Rice Michael A. , Stephens Grover C. 
Published: April 2021

ABSTRACT
The uptake of amino acids by the non-gill epithelia of the mantle cavity of Mytilus edulis L. was studied and compared with uptake by the gills. Amino acid entry rates and the subsequent distribution of amino acids to the other tissues of the animals were studied using high-performance liquid chromatography and radiochemical techniques. Uptake via the non-gill epithelia lining the mantle cavity was separated from uptake via the gill by employing a preparation in which the gills were surgically removed. Amino acid uptake by such animals was compared with that of suitably sham-operated controls.
In short-term experiments (up to 2h), transfer of substrate from the gills to other tissues of the animal is extremely limited. Amino acids taken up by the non-gill epithelia of the mantle cavity are rapidly transferred to deeper tissues. Roughly 25 % of alpha-amino acids enter the animal via the non-gill epithelia. Estimates of total epithelial surface area for the gills and non-gill mantle epithelium are compared with entry rates of amino acid substrates via the two routes. The apparent densities of carriers for alanine and cycloleucine per unit area of surface are approximately equal for these two substrates. The density of taurine carriers per unit area of non-gill epithelium is apparently significantly higher than their density per unit area of gill epithelium. Finally, evidence is presented for differential sensitivity of taurine transporters in the non-gill epithelium to inhibition by alpha-amino acids.
Retinoid Changes in the in vitro Regeneration of Frog Visual Pigments
Authors: Azuma Masami , Azuma Katsu 
Published: April 2021

ABSTRACT
To investigate the regeneration of visual pigment, the changes in composition and quantity of retinoids were measured by high-performance liquid chromatography (HPLC). Eye cups or eye cup sections of dark-adapted frogs were exposed to light (&gt;500 nm) and incubated in the dark for several hours (pH 7·4, 27 ± 1°C). Retinoids extracted by the oxime method before and after illumination were analysed by HPLC.
In the dark, every eye cup or eye cup section contained 11-cis and all-trans isomers of retinyl palmitate (the proportion of 11-CIS was nearly 40 %). The amount of retinyl palmitate was 1–1·-5 molequiv of visual pigment. After 80% of the visual pigment had been bleached by illumination, eye cups or eye cup sections were incubated in the dark for 10 h. During the incubation, 70% of the bleached pigment was regenerated, and the proportion of 11-cis retinyl ester decreased from 40% to 13 %. These results indicate that stored 11-cis retinyl ester is used for the regeneration. The regeneration rate of A2-pigment (half time = 75 min) was faster than that of A1-pigment (half time = 90min), consistent with the result of Tsin & Flores’ (1986) in vivo experiment with goldfish.
Isolated Giant Smooth Muscle Fibres in Beroe Ovata: Ionic Dependence of Action Potentials Reveals two Distinct Types of Fibre
Authors: Bilbaut André , Meech Robert W. , Hernandez-Nicaise Mari-Luz 
Published: April 2021

ABSTRACT
The ionic dependence of action potentials evoked in giant smooth muscle fibres isolated by enzymatic digestion from the body wall of the marine invertebrate Beroe ovata (Ctenophora) has been investigated using conventional electrophysiological techniques. Differences were observed in the two fibre types studied. The resting membrane potential was –60 ± 1·35 mV (N = 25) in longitudinal muscle fibres and –66 ± 1·37 mV (N =32) in radial fibres. Action potentials had a short plateau in longitudinal fibres but not in radial fibres. The action potential overshoot of both fibre types was decreased in Ca2+-free artificial sea water (ASW). In Na+-deficient ASW, action potentials could not be generated in radial fibres and showed a reduced overshoot in longitudinal fibres. Tetrodotoxin (10−smoll−1) added to ASW or Ca2+-free ASW did not affect the action potentials of either type of fibre. Action potentials of both fibres were partially blocked by Co2+ (20-50 mmol 1−1) or Cd2+ (1-2 mmol 1−1). Action potentials of longitudinal fibres in Na+-deficient ASW were abolished by Co2+ (20 mmol 1−1). In Ca2+-free ASW, the action potential overshoots of both sets of fibres were restored following the addition of Sr2+ or Ba2+. In longitudinal fibres, Sr2+ increased the duration of the action potential plateau. In both longitudinal and radial muscle fibres, Ba2+ prolonged the action potential. In longitudinal fibres exposed to tetraethylammonium chloride (TEACI) or 4-aminopyridine (4AP), the action potential was slightly prolonged. In these fibres, TEA+ or 4AP added to Ca2+-free ASW induced only a long-lasting depolarizing plateau. In radial fibres, the action potential duration was slightly increased in the presence of TEA+; it was unaffected by 4AP. In Ca2+-free ASW, TEA+ and 4AP induced an oscillating membrane response which appeared to be dependent on the intensity of the injected current pulse. It is concluded that (a) there are significant differences between the action potentials of longitudinal and radial muscle fibres but that both are dependent on Na+ and Ca2+, (b) in longitudinal fibres, a Ca2+-activated K+ conductance and a TEA+-sensitive voltage-activated K+ conductance contribute to the repolarizing phase of the action potential, the former being predominant, (c) in radial fibres, the repolarizing phase of action potentials probably involves different membrane K+ conductances among which is a TEA+-sensitive K+ conductance.
Octopamine in a Neurohaemal Area Within the Antennal Heart of the American Cockroach
Authors: Pass Günther , Sperk Günther , Agricola Hans , Baumann Eckehard , Penzlin Heinz 
Published: April 2021

ABSTRACT
A great deal of research suggests that octopamine functions as a neuromodulator, neurotransmitter and neurohormone in insects (Orchard, 1982; Evans, 1985; Hoyle, 1985). Especially high concentrations of this biogenic amine have been reported for neurohaemal tissue such as the corpora cardiaca and the neurohaemal organs of the medial nervous system (Evans, 1985). In the presented paper, octopamine is shown to occur in another neurohaemal area located within the antennal heart of the cockroach, Periplaneta americana.
Relationship Between Wing Loading, Wingbeat Frequency and Body Mass in Homopterous Insects
Authors: Byrne David N. , Buchmann Stephen L. , Spangler Hayward G. 
Published: April 2021

ABSTRACT
Several biophysical properties of members of Aleyrodidae and Aphididae were examined in order to explore how homopterous insects fly. Five species of aphids were found to weigh significantly more than five whitefly species (range 1 · 14-7·02×10–4g for aphids vs 3·3-8·0x 10–5g for whiteflies) and to have significantly larger wing surface areas (range 0·0103–0·1106 cm2vs 0·0096-0·0264cm2). As a consequence whiteflies and aphids can be partitioned into two groups with respect to wing loading (range 0·00633-0·01412 g cm–2 for aphids, 1·74-5·23X 10–3gcm–2 for whiteflies). Members of the two families are also separated in terms of wingbeat frequency (range 81·1-123·4Hz for aphids, 165·6–224·2 Hz for whiteflies). Since our animals were much smaller than any insects examined previously for these parameters, values were compared with the same parameters for 149 insect species recorded in the literature. Using these data, we found wingbeat frequency to be significantly correlated with wing loading only in insects weighing more than 0·03 g. Larger insects seem to employ a strategy similar to other flying animals, by compensating for high wing loading with higher wingbeat frequencies. The lack of correlation for these two parameters in insects weighing less than ·03 g probably results from the use of different flying strategies. These include employment of a clap and fling mechanism and the possession by some of exceedingly low wing loading. Also, small insects may have reduced settling velocities because they possess high drag coefficients. Previous studies which failed to establish a relationship between wing loading and wingbeat frequency in larger insects may have considered too few subjects or too great a range of body masses. The mass range is important because smaller insects which employ increased wingbeat frequency must use rates exponentially higher than those of larger insects utilizing the same strategy.
Functional Principles of Pattern Generation for Walking Movements of Stick Insect Forelegs: the Role of the Femoral Chordotonal Organ Afferences
Authors: Bässler Ulrich 
Published: April 2021

ABSTRACT
A rampwise stretch of the femoral chordotonal organ is known often to elicit a response in the active decerebrate stick insect that is termed an ‘active reaction’, and which can be considered to represent part of the step cycle. During the first part of the response, the flexor motor neurones are excited and the excitatory extensor motor neurones are inhibited, forming a positive feedback loop. When the chordotonal organ reaches a position corresponding to a flexed femur-tibia joint, the flexor motor neurones are inhibited and the extensor motor neurones are excited.
In this study, extracellular and intracellular recordings showed that, during an active reaction, the excitation of the retractor unguis motor neurones usually paralleled that of the flexor motor neurones, whereas the protractor coxae motor neurones were less strongly coupled to this system.
The first part of the active reaction occurred only at low stimulus velocities. At high stimulus velocities negative feedback was present. The first part therefore represents some kind of velocity-control-system for active flexions.
ElecTr1cal stimulation of the nerve containing the axons of trochanteral campaniform sensilla and of the hairfield trHP decreased the likelihood that concurrent chordotonal organ stimulation would elicit an active reaction. Further-more, most of the active reactions that occurred under these stimulus conditions involved only the flexor tibiae muscle.
The results indicate that: the walking pattern generator is composed of subunits that are only loosely coupled centrally; it probably does not include a central pattern generator; and generation of an active reaction is a two-step process.
The Organs of Adhesion in the Aphid Megoura Viciae
Authors: Lees A. D. , Hardie Jim 
Published: April 2021

ABSTRACT
The anatomy of the adhesive organs is described in Megoura viciae Buckton. The claws serve as grappling hooks which are locked in position by the retractor unguis tendon. The pulvilli, pliable cuticular sacs, are everted from the tibiotarsal articulation. They bear a surface adhesive, a non-volatile oil, which is secreted through the cuticle. The pulvilli are everted by blood pressure and are withdrawn inside the tibia by contraction of the tibial muscles. The adhesion of these organs to various types of surface was tested by covering over the pulvilli or by claw amputation. Pulling forces were applied by progressively loading the aphid with weights. The pulvilli perform best on relatively smooth surfaces. Aphids are dislodged from the underside of polished glass by a mass of approx. 9-14 mg (a pulling force of 8·8-13·7xl0-5N). The claws cannot engage a completely smooth surface but are highly effective on rough ones, withstanding a load of approx. 57 mg on dry filter paper. Adhesion of the pulvilli to waxy surfaces is only slightly less than on glass but is greatly reduced on surfaces with still lower free energies, such as Teflon. On a glass surface the pulvilli sometimes leave ‘footprints’ consisting of oily droplets of variable size. Nevertheless, in many instances such deposits are small or absent, indicating that the bond sometimes breaks between the adhesive and the substratum. In a selected series of footprints with large deposits, their volume was found to be sufficient to form a layer at least 17·7xl0-9m in thickness over the area of pulvillar contact. This is consistent with the view that surface tension forces would adequately account for adhesion, an additional limiting factor being the physical properties (wettability) of the substratum. Viscous forces would impede the very rapid (less than 0-02 s) removal of the pulvilli, were it not for the retraction mechanism which peels off the pulvillus from the distal edge, like a piece of adhesive tape. The ultrastructure of the pulvillar gland is described. The epidermal cells discharge into a cavity which is confluent with a further reservoir within the spongy endocuticle, itself a meshwork of dissociated cuticular microfibrils. The points of exit of the secretion appear to be the epicuticular filaments. The product of the gland, which can be collected by pricking the pulvilli, is water soluble and proteinaceous, differing entirely from the hydrophobic lipid-soluble end-product on the pulvillar surface. We presume that the lipoprotein precursor is dissociated enzymatically at the level of the inner epicuticle.
Further Observations on Dipteran Flight: Details of the Mechanism
Authors: Miyan Jaleel A. , Ewing Arthur W. 
Published: April 2021

ABSTRACT
We took high-intensity flash photographs of the wing base during tethered flight of Lucilia sericata. These show that the radial stop and the pleural wing process separate during the upper part of the wing beat and then mate together on the downstroke. Using tungsten needle probes attached to wire strain gauges, we measured the movements of the parascutal shelf (PSS), of the lateral and dorsal scutum, and of the scutellum during tethered flight. We made a detailed study of the wing base sclerites and associated muscles in order to answer criticisms of our original model (Miyan & Ewing, 1985a,b). The PSS rotates upwards about its hinge with the lateral scutum at the start of the downstroke. 4. The dorsal scutum and medial edge (at the hinge) of the PSS are held down, presumably as a result of dorsoventral muscle activity. As the downstroke progresses, the whole of the PSS and dorsal scutum are lifted together suggesting the action of a locking mechanism. At the bottom of the downstroke there is an opposite, downward rotation of the shelf about its hinge that follows the start of downward scutal movement at the beginning of the upstroke. This is followed by downward movement of the whole PSS and scutum. Movements of the lateral scutum exactly follow scuteliar and lateral PSS movements and are probably dictated by the articulation. Scanning electron micrographs illustrate the probable components of the wing base-PSS locking mechanism. Rotation of the first axillary sclerite, brought about by the rising scutellar lever arm, results in mating of its medial arm with a recess in the PSS. This prevents further rotation of the PSS which is now held at two points by the sclerite and is lifted by further movement of the lever. There is no evidence that the third axillary muscles act as wing pronators. Scanning electron micrographs show a mechanism that maintains the line of action of the muscles on the posterior edge of the wing.
The Role of Fast Extensor Motor Activity in the Locust Kick Reconsidered
Authors: Heitler W. J. , Bräunig P. 
Published: April 2021

ABSTRACT
Fast extensor tibiae (FETi) activity has been implicated as a crucial element underlying the locust kick motor programme with regard to four circuits, (i) A positive feedback reflex from extensor tibiae (ETi) muscle tension helps maintain FETi spiking during co-contraction. (ii) A central connection from FETi to flexor tibiae (FITi) motor neurones helps initiate FITi spiking at the start of co-contraction. (iii) Reflex feedback from ETi tension to FITi motor neurones helps maintain the latter spiking during co-contraction after the central connection has decremented, (iv) A proprioceptive gate controlled by ETi tension ensures that FITi trigger activity does not occur until sufficient ETi tension has developed to allow an effective kick.
The hypotheses concerning these circuits have been tested in two ways. First, FETi was phasically inhibited for varying periods during co-contraction, abolishing its spikes and hence its central output, and reducing ETi tension. Second, the nerve containing the FETi axon was cut in the femur, thus partially denervating the ETi muscle, and reducing its tension without directly affecting FETi activity. In both cases, kicks were analysed to see whether the motor programme changed in accordance with the circuit model. The overall conclusion is that the model is not correct, since considerable experimentally induced changes in FETi activity and ETi tension had no obvious effects on the motor programme. The circuits may play a supplementary role in generating the programme, but they are not crucial to it.
Quantitative Analysis of Resting Membrane Electrogenesis in Insect (Diptera) Skeletal Muscle : II. Testing of A Model Involving Contributions from Potassium and Sodium Ions, and the Anomalous Effect of Reducing Extracellular Sodium
Authors: Djamgoz M. B. A. , Dawson Jill 
Published: April 2021

ABSTRACT
A model of resting membrane electrogenesis in skeletal muscles of prepupal Calliphora erythrocephala was formulated. From experiments in which reversible effects of changing extracellular K+ and Na+ activities on the membrane potential (EM) were measured, three different values of a (the ratio of the partial permeabilities of the membrane to Na+ and K+) were derived, each from a different range of extracellular Na+ and K+ activities. Two independent tests were carried out to determine the most realistic value of a. Intracellular K+ and Na+ activities and EM values were measured in a population of cells, and the EM values predicted using the Goldman-Hodgkin-Katz equation for different values of a. The best fit for the data was obtained for α= 0·036. In ionic substitution experiments, in which passive movements of Cl− were prevented or minimized, the changes in EM around the resting level could be explained with a high degree of accuracy by assuming again that α = 0·036. However, tests of the model by investigation of direct effects of reducing extracellular Na+ concentration over a wide range of EM values gave an anomalous result. In low-Na+ Ringer, EM values became more positive than the respective resting levels. The anomalous effect of low-Na+ Ringer on EM did not involve a change in the K+ equilibrium potential. Instead, it was probably due to a reduction in the K+ permeability of the membrane. Possible mechanisms underlying this effect are discussed.
Cephalic Neuroendocrine Regulation of Integumentary Water Loss in the Cockroach Periplaneta Americana L
Authors: Noble-Nesbitt John , Al-Shukur Marwan 
Published: April 2021

ABSTRACT
Our experiments show that the brain of cockroaches produces, stores (tempor-arily or otherwise) and releases a water-loss promoting factor (BHP) and a water-loss restricting factor (BHR), depending on the physiological state of the cockroach and environmental conditions.
Fully hydrated cockroaches produce, temporarily store and release the BHP factor, and store but do not release the BHR factor: this leads to high rates of integumentary water loss.
Desiccation arrests the production and storage of BHP factor and stimulates the release of BHR factor, resulting in rapid restriction of integumentary water loss.
Brain homogenates prepared from fully hydrated cockroaches (HBH) contain some BHP factor and much BHR factor, whereas brain homogenates prepared from predesiccated cockroaches (DBH) contain only BHR factor.
Control saline-only injections produce only slight elevations in water loss of either fully hydrated or predesiccated intact cockroaches.
Lowering of integumentary water loss of intact fully hydrated cockroaches (HI) in response to desiccation is little affected by either HBH or DBH injection.
Conversely, injection of HBH into intact predesiccated cockroaches (DI) causes a highly significant increase in water loss during continued desiccation, confirming the presence of BHP factor in HBH.
DBH injection into DI cockroaches has little or no effect, presumably since it adds only BHR factor which is already present and active in the host.
Injected restricting factor (BHR) seems to be more effective than injected promoting factor (BHP) in decapitated cockroaches. Thus, considerably lower losses are found in decapitated fully hydrated cockroaches (HD) following HBH injection (Treherne & Willmer, 1975 and confirmed by us) or DBH injection (present results). Slightly elevated losses are found in decapitated predesiccated cockroaches (DD) following HBH injection, whereas DBH injection has little effect.