bluuebunny/crossref_metadata_2025_split huggingface dataset:
Blood Flow Distribution in Submerged and Surface-Swimming Ducks
Authors: Stephenson Richard , Jones David R. 
Published: April 2021

ABSTRACT
Observations that the response of the avian heart rate to submergence varies under different circumstances have led to speculation about variability of blood flow distribution during voluntary dives. We used a radiological imaging technique to examine the patterns of circulating blood flow in captive redhead ducks (Aythya americana) during rest, swimming, escape dives, forced dives and trapped escape dives and have shown that blood flow distribution in escape dives was the same as that in ducks swimming at the water surface. The response during trapped escape dives, however, was highly variable. Blood pressure was unchanged from the resting value during all activities. Predictions made about blood flow distribution during unrestrained dives on the basis of heart rate and other indirect data were confirmed in this study. However, the trapped escape dive responses indicated that heart rate alone is not always a reliable indicator of tissue blood flow in exercising ducks.
Mechanisms Controlling Modulation by Haemolymph Amino Acids of Gustatory Responsiveness in The Locust
Authors: Simpson S. J. , Simpson C. L. 
Published: April 2021

ABSTRACT
Previous work has shown that fifth-instar nymphs of Locusta migratoria (L.) adjust their feeding behaviour to compensate for variation in dietary protein and carbohydrate levels. These changes in behaviour are accompanied by nutrient-specific changes in the responsiveness of taste receptors on the mouthparts. Levels of free amino acids in the haemolymph affect the responsiveness of maxillary gustatory receptors to stimulation by amino acids. The mechanisms mediating this response are investigated. Sectioning the maxillary nerve does not prevent an injection of amino acids into the haemolymph from causing reduced chemo-responsiveness, indicating that centrifugal neural feedbacks are not involved. Isolating the distal two segments of the palp by ligature and then micro-injecting amino acids into the palp tip also causes modulation of responsiveness, showing that the effect is mediated at, or close to, the sensory receptors. Radio-labelling studies indicate that amino acids injected into the abdomen are found in the haemolymph of the palp within the time necessary to cause a peripheral change in gustatory responsiveness. Possible mechanisms enabling amino acids in the blood of the palp to influence sensory responsiveness are discussed. The simplest mechanism consists of amino acids in the haemolymph reaching the sensillum liquor and adapting the receptors to further stimulation from the food.
Utilization and Digestion of Carbohydrates by the Adult Blowfly
Authors: Fraenkel Gottfried 
Published: April 2021

ABSTRACT
It has been frequently stated that many species of flies, including houseflies and blowflies, can be kept alive and healthy on a diet consisting only of cane sugar and water; on this they are able to live for the maximum length of time, which, in the case of the blowfly Calliphora erythrocephala, is about 2 months at 27° C. Addition of protein is essential only for the development of the eggs, as it does not increase the duration of life and there is, indeed, evidence that it may have the contrary effect. Flies thus represent an excellent medium for studying problems of carbohydrate metabolism, and the present investigation deals particularly with two questions: what effect have substances other than cane sugar on the length of life of the fly, and to what extent does the presence and absence of enzymes in the gut account for the utilization or non-utilization of these various substances?
Studies on Amphibian Metamorphosis
Authors: Helff O. M. 
Published: April 2021

ABSTRACT
Previous work by the writer has shown that normal development of the tympanic membrane in R. pipiens is due to inductive influences of the annular tympanic cartilage. The present work concerns the nature of the developmental influences, specifically as regards whether or not non-living cartilage still possesses inductive properties. The experiments performed and results obtained were as follows:
Controls consisted of autoplastic transplantation of annular tympanic cartilage beneath back integument of metamorphosed and involuting R. palustris larvae. In general, integumentary thinning, coupled with partial to total glandular degeneration, occurred. This is typical of partial membrane formation.
Similar transplantations were made involving cartilage killed in ethyl alcohol, saturated chloretone solution, and boiling water, or by desiccation in strong sunlight. The results differed considerably depending on the type of killing treatment employed and the degree of subsequent transplant degeneration. Partial membrane formation was usually induced, however, in the overlying back integument. Similar series were run with half-metamorphosed larvae. In general, membrane induction was even more pronounced.
The same experiments were performed on R. catesbeiana larvae. Transplantation, however, was made beneath the skin of the upper jaw, posterior-ventral to the external nares. Wide variations in results were observed. No membrane changes occurred in some cases, while in others considerable transformation was induced.
It is concluded that dead annular tympanic cartilage still retains inductive influences capable of initiating varying degrees of tympanic membrane formation in integument. In general, the greater the degree of cartilage degeneration, the less the extent of membrane formation.
The results are discussed in general and the conclusion reached that the inductive influences arising in the developing annular tympanic cartilage of the anuran are quite probably chemical secretions or excretions. These, when transmitted to the integument of the ear region during metamorphosis, serve to induce a dedifferentiation of the larval skin into that type characteristic of adult tympanic membrane.
Feeding Performance And Muscular Constraints In Fish
Authors: Aerts Peter , Vree Frits De 
Published: April 2021

ABSTRACT
Analysis of the feeding kinematics of Astatotilapia (a small cichlid fish) suggests the presence of peripheral feedback modulation of the motor pattern, allowing the act of suction to be abbreviated. In this way, the effort spent in suction is minimized. The biological significance of the development of such a modulating feedback system is not immediately obvious from a ‘classical ecological’ point of view. It is postulated that the muscular metabolism itself might constrain the short, transient and strenuous motor output typical of suction feeding. Thus, reducing the suction effort makes sense when successive strenuous head-part movements are immediately required for additional suction, buccal transport or spitting. This hypothesis was tested by in vivo electrical stimulation of muscles important in feeding: the epaxials, which lift the skull and expand the buccal cavity. Reliable stimulation variables for the epaxial muscles were determined from preliminary stimulation experiments and from electromyographic recordings of these muscles in a specimen feeding on crickets. Stimulation trains of variable duration (&lt;150ms) were applied in series of five trains. The intervals between trains were variable as well (&lt;1s). The mechanical output was measured by means of an accelerometer, a force transducer or a magnetoresistive displacement transducer. In the latter case, the time course of the mechanical output could be recorded and analysed. The hypothesis predicts a decrease in the muscular output with increasing effort (long trains) and fast repetition (short intervals). The experimental results show the expected decline in mechanical output from one stimulation train to the next when longer stimulation bursts are imposed in quick succession. Statistical analyses (multiple regression) showed that train length, train rate and train number contribute significantly to the observed variation in mechanical output, supporting the hypothesis. Explanations for the phenomena are discussed.
The Energetic Costs of Calling in the Bushcricket Requena Verticalis (Orthoptera: Tettigoniidae: Listroscelidinae)
Authors: Bailey W. J. , Withers P. C. , Endersby M. , Gaull K. 
Published: April 2021

ABSTRACT
The metabolic costs of calling for male Requena verticalis Walker (Tettigoniidae: Listroscelidinae) were measured by direct recordings of oxygen consumption. The acoustic power output was measured by sound pressure levels around the calling bushcricket. The average metabolic cost of calling was 0.143ml g−1 h-1 but depended on calling rate. The net metabolic cost of calling per unit call, the syllable, was calculated to be 4.34×10−6±8.3X10−7 ml O2 syllable−1 g−1 bodymass (S.E.) from the slope of the relationship between total and rate of syllable production. The resting , calculated as the intercept of the relationship, was 0.248ml O2 g−1 bodymass h−1. The energetic cost of calling for R. verticalis (average mass 0.37g) was estimated at 31.85×10−6 J syllable−1. Sound pressure levels were measured around calling insects. The surface area of a sphere of uniform sound pressure level [83dB SPL root mean square (RMS) acoustic power] obtained by these measurements was used to calculate acoustic power. This was 0.20mW. The metabolic efficiency of calling, based on total metabolic energy utilisation, was 6.4%. However, we propose that the mechanical efficiency for acoustic transmission is closer to 57%, since only about 10% of muscle metabolic energy is apparently available for sound production. R. verticalis emits chirps formed of several syllables within which are discrete sound pulses. Wing stroke rates, when the insect is calling at its maximal rate, were approximately 583min−1. This is slow compared to the rates observed in conehead tettigoniids, the only other group of bushcrickets where metabolic costs have been measured. The thoracic temperatures of males that had been calling for 5min were not significantly different from those of non-calling males. For R. verticalis, calling with relatively slow syllable rates may reduce the total cost of calling, and this may be a compensatory mechanism for their other high energetic cost of mating (a large spermatophylax).
Active Na+-, Cl−-and Hco3−-Dependent Acid Extrusion in Atlantic Cod Red Blood Cells in Winter Activated by Hypercapnia
Authors: Berenbrink M. , Bridges C. R. 
Published: April 2021

ABSTRACT
The relationship between intracellular pH (pHi) and extracellular pH (pHe) was investigated in red blood cells from the Atlantic cod (Gadus morhua) in carbon dioxide/bicarbonate-buffered salines. In summer animals (August/September), similar transmembrane distribution ratios of chloride ([Cl−]i/[Cl−]e=rCl−) and protons ([H+]e/[H+]i=rH+) suggested a passive Donnan distribution of these ions across the red blood cell membrane at pHe 6.7–8.4. In winter animals (February/March), a marked discrepancy occurred between rH+ and rCl− at low pHe values. The pronounced increase in rH+ resulted in significantly higher pHi values compared with those of red blood cells from summer animals and at pHe 6.7 pHi exceeded pHe by 0.3 units. The increases in rH+ values were completely abolished by cyanide and 2,4-dinitrophenol. The high disequilibrium rH+ values were sodium-, chloride-and bicarbonate-dependent. During hypercapnic acidosis, proton equivalents were extruded from the red blood cell. The resulting high rH+ values were accompanied by a reduced chloride shift into the red blood cell and a ouabain-insensitive net sodium influx. The net sodium influx into red blood cells from winter animals was significantly reduced in the presence of DIDS (4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid). The results suggest the activation of a Na+-dependent Cl−/HCO3−exchanger at low pHe in the red blood cells of the Atlantic cod in winter.
Glycolytic Function in Goldfish Hepatocytes at Different Temperatures: Relevance for Na+ Pump Activity and Protein Synthesis
Authors: Krumschnabel Gerhard , Malle Sabine , Schwarzbaum Pablo J. , Wieser Wolfgang 
Published: April 2021

ABSTRACT
Cellular metabolism of ectotherms may respond to temperature changes with a shift in the choice of substrate preferentially catabolized for ATP production (Johnston and Dunn, 1987). This has been shown in acclimated fish, in which a temperature-dependent switch from carbohydrates as the main fuel for energy metabolism to other fuels, or vice versa, can occur. Such shifts help to indicate the relative importance of aerobic glycolysis as an ATP-supplying process. The preferred energy source at a given temperature depends upon the temperature range investigated, as well as on the species, on the tissue and upon nutritional factors. The adaptive significance of shifts between energy sources is not always clear. While in some cases ecological arguments may provide plausible explanations (e.g. seasonal adaptation to migration and reproductive requirements; Stone and Sidell, 1981; Moerland and Sidell, 1981), evidence is accumulating that structural or functional features inherent in the metabolic organisation of the cell may also play a role in determining the nature of such responses (Sidell, 1983; Sidell and Hazel, 1987). Of particular relevance in this respect is the interaction between diffusional flux and the rate of enzymatic activity in shaping specific temperature effects on cellular metabolism.
On The Respiratory Flow in the Cuttlefish Sepia Officinalis
Authors: Bone Q. , Brown E. R. , Travers G. 
Published: April 2021

ABSTRACT
The respiratory flow of water over the gills of the cuttlefish Sepia officinalis at rest is produced by the alternate activity of the radial muscles of the mantle and the musculature of the collar flaps; mantle circular muscle fibres are not involved. Inspiration takes place as the radial fibres contract, thinning the mantle and expanding the mantle cavity. The rise in mantle cavity pressure (up to 0.15 kPa), expelling water via the siphon during expiration, is brought about by inward movement of the collar flaps and (probably) mainly by elastic recoil of the mantle connective tissue network ‘wound up’ by radial fibre contraction during inspiration. Sepia also shows a second respiratory pattern, in which mantle cavity pressures during expiration are greater (up to 0.25 kPa). Here, the mantle circular fibres are involved, as they are during the large pressure transients (up to 10 kPa) seen during escape jetting. Active contraction of the muscles of the collar flaps is seen in all three patterns of expulsion of water from the mantle cavity, electrical activity increasing with increasing mantle cavity pressures. Respiratory expiration in the resting squid Loligo vulgaris is probably driven as in Sepia, whereas in the resting octopus Eledone cirrhosa, the mantle circular musculature is active during expiration. The significance of these observations is discussed.
Swimming Metabolism of Wild-Type and Cloned Zebrafish Brachydanio Rerio
Authors: Plaut Itai , Gordon Malcolm S. 
Published: April 2021

ABSTRACT
The availability of a gynogenetic isogenic homozygous diploid clonal strain (C) of the zebrafish (Brachydanio rerio), combined with the small adult body size of the species, made possible a study of the following two questions. (1) Is the genetic uniformity of a group of fish reflected in decreased variability of features of organismic performance physiology? (2) Is the metabolic cost of subcarangiform swimming significantly different in small fishes compared with large ones?
Wild-type (WT) and C strain zebrafish maintained at 28°C can all swim very rapidly [up to relative swimming speeds of 13 body lengths s −1 (BL s −1)] for extended periods (at least 2 h) without visibly tiring. Oxygen consumption rates were measured for both types at swimming speeds of 1.5–13 BL s −1. Whole-body lactate concentrations were also measured during routine activity and after prolonged exercise for both fish types. The slopes of the linear regressions between the logarithm of mass-specific oxygen consumption rates and relative swimming speeds for WT zebrafish were low (0.010–0.024) and were not significantly different from zero. Regression slopes were also low (0.009–0.026), but different from zero, for C zebrafish. Standard metabolic rates were 0.60–1.54 and 0.40–0.85 ml O2 g−1 h−1 for WT and C zebrafish respectively. Variances of slopes were significantly larger for WT than for C fish. Whole-body lactate concentrations and their variances were not significantly different between types and between rested and exercised fishes. The results demonstrate unusual swimming performance capacities, a remarkably low cost of swimming and some reductions in variability of C fish. Several possible explanations for the results are discussed.
Capillary Blood Transit Time in Muscles in Relation to Body Size and Aerobic Capacity
Authors: Kayar S. R. , Hoppeler H. , Jones J. H. , Longworth K. , Armstrong R. B. , Laughlin M. H. , Lindstedt S. L. , Bicudo J. E. P. W. , Groebe K. , Taylor C. R. , Weibel E. R. 
Published: April 2021

ABSTRACT
The mean minimal transit time for blood in muscle capillaries (tc) was estimated in six species, spanning two orders of magnitude in body mass and aerobic capacity: horse, steer, dog, goat, fox and agouti. Arterial and mixed venous blood O2 concentrations, blood hemoglobin concentrations ([Hb]) and oxygen uptake rates were measured while the animals ran on a treadmill at a speed that elicited the maximal oxygen consumption rate from each animal. Blood flow to the muscles (Q̇m) was assumed to be 85% of cardiac output, which was calculated using the Fick relationship. Total muscle capillary blood volume (Vc) and total muscle mitochondrial volume were estimated by morphometry, using a whole-body muscle sampling scheme. The tc was computed as Vc/Q̇m. The tc was 0.3–0.5 s in the 4 kg foxes and agoutis, 0.7–0.8 s in the 25 kg dogs and goats, and 0.8–1.0 s in the 400 kg horses and steers. The tc was positively correlated with body mass and negatively correlated with transcapillary O2 release rate per unit capillary length. Mitochondrial content was positively correlated with and with the product of Q̇m and [Hb]. These data suggested that Q̇m, Vc, maximal hemoglobin flux, and consequently tc, are co-adjusted to result in muscle O2 supply conditions that are matched to the O2 demands of the muscles at
Mechanisms of K+ Uptake Across the Basal Membrane of Malpighian Tubules of Formica Polyctena: The Effect of Ions and Inhibitors
Authors: Leyssens A. , Dijkstra S. , Van Kerkhove E. , Steels P. 
Published: April 2021

ABSTRACT
In the presence of 6 mmol l−1 Ba2+, known to block the K+ channels in the basal membrane, a rise in bath [K+] ([K+]bl) induced an increase in intracellular K+ concentration ([K+]i) similar in amount and in time course to that obtained in the absence of Ba2+. The presence of active and passive (other than through K+ channels) K+ uptake mechanisms across the basal membrane was investigated in different bath K+ concentrations. Dihydro-ouabain (10−3 mol l−1), a blocker of the Na+/K+-ATPase, tested in low bath [K+], and Sch28080 (10−4 mol l−1), a K+/H+-ATPase inhibitor, were without effect on fluid secretion. Dihydro-ouabain was also without effect on electrical potential differences either in the absence or in the presence of Ba2+. Vanadate (10−3 mol l−1), in contrast, strongly reduced fluid secretion not only in control solution but also in high-K+, Na+-free medium and reduced the transepithelial and the apical membrane potential differences but not the basal membrane potential difference or [K+]i. Omitting Na+ from the bathing medium, replacing Cl-by Br− or applying bumetanide (10−5 mol l−1) inhibited fluid secretion only in a low-K+ (10 mmol l−1) medium. In 51 mmol l−1 [K+]bl, omitting Na+ was without effect and 10-4 mol l−1 bumetanide was needed to inhibit secretion. Replacing Cl−by Br−stimulated fluid secretion at this K+ concentration. Bumetanide (10−4 mol l−1) had no effect in 113 mmol l−1 [K+]bl. Bumetanide (10−4 mol l−1) in 51 mmol l−1 [K+]bl did not affect membrane potentials, did not lower [K+]i and did not affect the rise in [K+]i observed on an increase in [K+]bl. The results were summarized in a model proposing that K+ channels play a dominant role in high-K+ (113 mmol l−1) bathing medium. A K+/Cl−cotransporter may become more important in 51 mmol l−1 [K+]bl and a K+/Na+/2Cl− cotransporter may gain in importance in 10 mmol l−1 [K+]bl. Active mechanisms for K+ uptake across the basal membrane seem to play no detectable role in sustaining fluid secretion. The response to vanadate might be due to an effect on the apical electrogenic H+ pump.
The Shift in Visual Pigment Dominance in the Retinae of Juvenile Coho Salmon (Oncorhynchus Kisutch): an Indicator of Smolt Status
Authors: Alexander G. , Sweeting R. , McKeown B. 
Published: April 2021

ABSTRACT
Smolting juvenile coho salmon were sampled to determine (1) whether a correlation between hypo-osmoregulatory ability and visual pigment composition existed and (2) whether the hormone 3,5,3′-tri-iodothyronine (T3) was playing a role in the visual pigment conversion process. Plasma sodium levels of seawater-challenged fish (30 ‰) indicated that there was a 5 week period of optimal ability to excrete excess plasma sodium ions (hypo-osmoregulation) in the late spring/early summer that represented the ‘window of opportunity’ for the entry or introduction to sea water of the salmon. Early in the smoltification process, the vitamin-A2-based visual pigment porphyropsin increased its dominance in the retinae, and radioimmunoassay of plasma indicated that T3 levels were at a maximum prior to this increase in porphyropsin. As the parr–smolt transformation continued, there was a steady decrease in the relative amounts of porphyropsin, indicating that the retinae were favouring the acquisition of rhodopsin. Rhodopsin dominance virtually coincided with the period of best hypo-osmoregulatory ability. Subsequently, the salmon showed a loss of hypo-osmoregulatory ability and concomitant increases in the amount of porphyropsin in the retina were observed. The relationship between the visual pigment shift and the smoltification process is discussed in terms of preparation for migration and thyroid hormone involvement, and the use of retinal visual pigment composition as an index of smolt status is proposed.