bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Haemoglobin Concentration on the Oxygen Affinity of Intact Lamprey Erythrocytes
Authors: Airaksinen S. , Nikinmaa M. 
Published: April 2021

ABSTRACT
We investigated whether the oxygen affinity of lamprey haemoglobin decreases with increasing oxygen concentration at the high (10–25 mmol l-1 monomeric) haemoglobin concentrations prevailing within the erythrocytes. The intracellular concentration of haemoglobin was experimentally adjusted by shrinking the cells osmotically: the osmolality of the equilibration medium was increased from approximately 250 mosmol kg-1 by 90 mosmol kg-1 to 340 mosmol kg-1 or by 180 mosmol kg-1 to 430 mosmol kg-1 by adding sucrose in the medium. This increased the mean cellular haemoglobin concentration from 16.9±0.23 mmol l-1 (monomeric haemoglobin) to 20.0±0.20 mmol l-1 (monomeric haemoglobin) and to 23.0±0.36 mmol l-1 (monomeric haemoglobin), respectively (means ± S.E.M., N=35–40; all the samples from 7–8 different pools of blood at each osmolality combined). The oxygen equilibrium curves at each osmolality were determined by Tucker’s method. An increase in haemoglobin concentration shifted the oxygen equilibrium curve to the right as indicated by the P50 values, which were 4.26±0.07 kPa at the lowest, 4.64±0.13 kPa at the intermediate and 5.64±0.40 kPa (means ± S.E.M., N=7–8) at the highest haemoglobin concentrations. The decrease in haemoglobin oxygen-affinity was attributed to the volume changes, since the intracellular pH did not decrease with increasing mean cellular haemoglobin concentration. Thus, the variations in red blood cell volume commonly observed during hypoxia may play a role in the regulation of haemoglobin function.
Uptake and Metabolism of Glucose, Alanine and Lactate by Red Blood Cells of the American Eel Anguilla Rostrata
Authors: Soengas José L. , Moon Thomas W. 
Published: April 2021

ABSTRACT
The uptake and metabolism of glucose, alanine and lactate were assessed in red blood cells (RBCs) of the American eel Anguilla rostrata. L-Lactate was metabolized at the highest rates as assessed by O2 consumption and CO2 production, followed by glucose and alanine (rates were approximately half of those observed for lactate). A saturable (Km 10.36±0.60 mmol l−1, Jmax 27.42±2.16 µmol 3-OMG l−1 cell water min−1), sodium-independent but cytochalasin-B-sensitive carrier for D-glucose was observed, which was stereospecific and inhibited by other hexoses. These characteristics are in agreement with those reported for the GLUT-1 glucose carrier of human and Japanese eel erythrocytes. These cells also contained a saturable carrier for L-lactate in the concentration range 0–10 mmol l−1 (Km 6.74±0.36 mmol l−1, Jmax 2.29±0.09 mmol lactate l−1 cell water min−1) whereas, at higher concentrations (10–40 mmol l−1), transport occurred by simple diffusion. The carrier was stereospecific, sodium-independent, fully inhibited by α-cyano-4-hydroxycinnamate, DIDS and pyruvate, but less sensitive to SITS, IBCLA and pCMBS. We suggest that this carrier is similar to the H+/monocarboxylate carrier found in mammalian RBCs. Despite the fact that L-alanine transport did not saturate, transport was stereospecific because it was inhibited by D-alanine. These experiments do not, therefore, exclude the existence of an alanine carrier in the eel RBC. The rates of substrate uptake exceeded the ability of the RBC to metabolize the substrate (using 1 mmol l−1 extracellular concentration), with uptake rate/metabolic rate ratios being 2 for alanine, 5 for glucose and 151 for lactate. These experiments indicate that uptake does not limit the ability of the American eel RBC to utilize glucose, alanine or lactate, but that the mechanism(s) of substrate uptake is species-specific.
Axial Kinematics and Muscle Activity During Terrestrial Locomotion of the Centipede Scolopendra Heros
Authors: Anderson Bruce D. , Shultz Jeffrey W. , Jayne Bruce C. 
Published: April 2021

ABSTRACT
For centipedes moving steadily on a treadmill at speeds of 0.5, 1.0 and 1.5 L s−1, where L is body length, we obtained video tapes of movement that were synchronized with electromyograms (EMGs) from lateral flexor muscles at six standardized longitudinal positions. Field-by-field analysis of video tapes revealed posteriorly propagated waves of bending at all speeds. Muscle activity was also propagated posteriorly at the same speed as the kinematic wave, and EMGs of the lateral flexors were generally unilateral and alternating (between the left and right sides). The timing of EMG activity relative to lateral bending was consistent with electrical activity during the shortening of muscle fibers; therefore, activity of the axial musculature appears to cause lateral bending. Analysis of variance revealed widespread effects of speed on both kinematic and electromyographic variables, whereas longitudinal position within the centipede (between body segments 8 and 18) generally did not have significant effects on the same variables. For example, as speed increased from 0.5 to 1.5 L s−1, the amplitude of lateral displacement approximately doubled and the amplitude of lateral bending increased approximately threefold. Lag times (in seconds) indicating the propagation of kinematic and EMG events along the length of the centipede decreased significantly with speed. Phase lags among longitudinal sites decreased significantly with increased speed, indicating that the kinematic and EMG wavelengths increased with increased speed. EMG duration approximated 50 % of cycle duration and was unaffected by speed, and the phase of the EMG activity relative to lateral bending was also unaffected by locomotor speed. Hence, all results from all speeds are consistent with active bending of the axial segments during centipede locomotion, conflicting with the widely accepted hypothesis that lateral bending is imposed on the body by the metachronal stepping pattern of the legs and that bending is resisted by axial muscles.
Age-Dependent and Task-Related Morphological Changes in the Brain and The Mushroom Bodies of The Ant Camponotus Floridanus
Authors: Gronenberg Wulfila , Heeren Silke , Hölldobler Bert 
Published: April 2021

ABSTRACT
Based on a brief description of the general brain morphology of Camponotus floridanus, development of the brain is examined in ants of different ages (pupa to 10 months). During this period, brain volume increases by approximately 20 % while the antennal lobes and the mushroom body neuropile show a more substantial growth, almost doubling their volume. In addition to the age-dependent changes, the volume of the mushroom body neuropile also increases as a consequence of behavioural activity associated with brood care and foraging. Foraging activity may lead to a more than 50 % additional increase in mushroom body neuropile volume. It is unlikely that the growth of mushroom body neuropile results from cell proliferation because no neurogenesis could be observed in adult ant brains.
Octopaminergic Innervation and Modulation of a Locust Flight Steering Muscle
Authors: Stevenson Paul A. , Meuser Susanne 
Published: April 2021

ABSTRACT
We demonstrate that the meso- and metathoracic pleuroaxillary flight steering muscle (M85 mesothorax, M114 metathorax) of the migratory locust are each innervated by a single dorsal unpaired median neurone (DUM3,4,5a). The soma of this neurone can be localized by retrograde staining of the motor nerve with Neurobiotin, but not with cobalt salts. The primary neurite projects in the superficial DUM cell tract, and the axons run in nerve roots 3, 4 and 5 and in all their secondary branches. Other muscle targets include the second tergal remotor coxa (M120) and the posterior rotator coxae (M122, M123, M124), but not the first tergal remotor coxa (M119) and subalar (M129) flight muscles.
Octopamine-like immunoreactive varicosities occur on the pleuroaxillary muscles. Stimulation of DUM3,4,5a and octopamine (10-6 mol l-1) superfusion increased the amplitude and the relaxation velocity of neurally evoked twitch contractions of this muscle. Octopamine also significantly reduced the tonic tension that this muscle develops when stimulated at flight frequency (20 Hz), while increasing the amplitude of each phasic twitch. A catch-like tension is also reduced in the presence of octopamine. Simulations of the motor pattern experienced by the pleuroaxillary muscles during roll manoeuvres suggest that transient changes in tension underlying corrective steering could be doubled in the presence of octopamine.
Freezing Survival by Isolated Malpighian Tubules of the New Zealand Alpine Weta Hemideina Maori
Authors: Neufeld Douglas S. , Leader John P. 
Published: April 2021

ABSTRACT
The ability of isolated Malpighian tubules from a freeze-tolerant insect, the New Zealand alpine weta (Hemideina maori), to withstand freezing was assessed by measuring post-freeze membrane potentials and rates of fluid secretion. The hemolymph of cold-acclimated Hemideina maori was found to contain relatively high concentrations of the cryoprotectants trehalose (&gt;300 mmol l−1) and proline (41 mmol l−1). Survival of isolated Malpighian tubules was correspondingly high when a high concentration of trehalose was present in the bathing saline. Tubules allowed to recover for 20 min from a 1 h freeze to −5°C in saline containing 400 mmol l−1 trehalose had a basolateral membrane potential of −53 mV compared with a potential of −63 mV in tubules not exposed to a freeze/thaw cycle. Fluid secretion in tubules that had experienced a freeze/thaw cycle in saline containing 400 mmol l−1 trehalose was 9.9±2.6 nl h−1 compared with 18.7±5.0 nl h−1 (means ± S.E.M., N=18) in tubules that had not been frozen. Tubules frozen in saline containing a lower concentration of trehalose (200 mmol l−1) or in glucose (400 mmol l−1) showed a similar ability to survive freezing to −5°C. In contrast, freezing for 1 h at −5°C in saline containing 400 mmol l−1 sucrose produced a 57% decrease in membrane potential and an 88% decrease in secretion rate. Tubules held in saline lacking high concentrations of sugars showed no survival after freezing to −5°C for 1 h. When frozen to −15°C, tubules appeared to survive best in saline with the highest trehalose concentration (400 mmol l−1). Freezing damage was not simply the result of exposure to cold, since tubules chilled (unfrozen) to −5°C for 1 h were not compromised even when the bathing saline lacked a high sugar concentration. Exposure of tubules to a combination of low temperature and high osmolality mimicked damage caused by actual freezing: the membrane potential showed a 60% recovery when the test was performed in saline containing trehalose, but showed no recovery in saline containing sucrose.
Postprandial exercise: prioritization or additivity of the metabolic responses?
Authors: Bennett Albert F. , Hicks James W. 
Published: April 2021

SUMMARY
Monitor lizards (Varanus exanthematicus) were used to examine the prioritization or additivity of the metabolic responses associated with exercise and digestion, either of which can elevate metabolic rate independently. Rates of oxygen consumption (V̇.O2) and ventilation (V̇.E) were measured in lizards during fasting exercise, postprandial rest and postprandial exercise. In fasting animals, V̇.O2 increased with walking speed to a maximal value of 15.9mlO2kg−1min−1 at 1.25kmh−1. Postprandial resting metabolic rate was elevated significantly above fasting levels (4.1 versus 2.0mlO2kg−1min−1). During postprandial exercise, V̇.O2 increased to a maximal value of 18.8mlO2kg−1min−1 at 1.25kmh−1. At every level of exercise, V̇.O2 was significantly higher in postprandial animals by a similar increment; the maximal rate of oxygen consumption was significantly increased by 18% in postprandial individuals. Maximal V̇.E did not differ in fasting and postprandial animals and, therefore, the greater V̇.O2max of postprandial animals cannot be attributed to a higher ventilation rate. Air convection requirement (V̇.E/V̇.O2) is significantly lower in postprandial animals at rest and at all levels of exercise, indicating a relative hypoventilation and increased pulmonary oxygen extraction efficiency. We suggest that this increased oxygen extraction may be due to decreased cardiopulmonary shunts and/or to lower mixed venous oxygen content. The data unequivocally support an additivity model rather than prioritization models for the allocation of elevated metabolic rate: the postprandial metabolic increment is not suspended during exercise, but rather is added onto the cost of exercise. It is clear that fasting exercise did not elicit truly maximal levels of cardiopulmonary oxygen transport in these animals, indicating problems for design models that make this assumption.
Impact of movement and movement-related feedback on the lamprey central pattern generator for locomotion
Authors: Guan Li , Kiemel Tim , Cohen Avis H. 
Published: April 2021

SUMMARY
A semi-reduced, minimally restrained lamprey preparation was used to investigate the impact of movement and movement-related feedback during d-glutamate-induced locomotion. The preparation consisted of the trunk alone with the spinal cord exposed to the bathing solution. Two conditions were compared using electromyography or nerve recording: (i) muscle and spinal cord, (ii) spinal cord alone supported by the notochord. Compared with the isolated spinal cord, movement in the presence of muscle consistently and significantly increased the frequency of the motor output and reduced the phase delay among the segments. In moving preparations, coupling among the segments was reduced by two staggered hemisections to permit the strength and direction of intersegmental coupling to be estimated. The estimates revealed that movement increased the total intersegmental coupling strength and increased the proportion of the coupling that was descending over those of the isolated spinal cord.
The effects on the phase and frequency of bursting can be explained in the light of the excitation evoked by bending that we have reported previously. Thus, we demonstrate that movement and movement-related feedback that arise from spinally induced motor patterns can alter the form of the movement and the functional coupling strength among the segments of the lamprey spinal cord.
Limits to the salience of ultraviolet: lessons from colour vision in bees and birds
Authors: Kevan Peter G. , Chittka Lars , Dyer Adrian G. 
Published: April 2021

SUMMARYUltraviolet is an important component of the photic environment. It is used by a wide variety of animals and plants in mutualistic communication, especially in insect and flower inter-relationships. Ultraviolet reflections and sensitivity are also becoming well considered in the relationships between vertebrates and their environment. The relative importance of ultraviolet vis à vis other primary colours in trichromatic or tetrachromatic colour spaces is discussed, and it is concluded that ultraviolet is, in most cases, no more important that blue, green or red reflections. Some animals may use specific wavebands of light for specific reactions, such as ultraviolet in escape or in the detection of polarised light, and other wavebands in stimulating feeding, oviposition or mating. When colour vision and, thus, the input from more than a single spectral receptor type are concerned, we point out that even basic predictions of signal conspicuousness require knowledge of the neuronal wiring used to evaluate the signals from all receptor types, including the ultraviolet. Evolutionary analyses suggest that, at least in arthropods, ultraviolet sensitivity is phylogenetically ancient and undergoes comparatively little evolutionary fine-tuning. Increasing amounts of ultraviolet in the photic environment, as caused by the decline of ozone in the atmosphere, are not likely to affect colour vision. However, a case for which ultraviolet is possibly unique is in the colour constancy of bees. Theoretical models predict that bees will perform poorly at identifying pure ultraviolet signals under conditions of changing illumination, which may explain the near absence of pure ultraviolet-reflecting flowers in nature.
The control of flight force by a flapping wing: lift and drag production
Authors: Sane Sanjay P. , Dickinson Michael H. 
Published: April 2021

SUMMARYWe used a dynamically scaled mechanical model of the fruit fly Drosophila melanogaster to study how changes in wing kinematics influence the production of unsteady aerodynamic forces in insect flight. We examined 191 separate sets of kinematic patterns that differed with respect to stroke amplitude, angle of attack, flip timing, flip duration and the shape and magnitude of stroke deviation. Instantaneous aerodynamic forces were measured using a two-dimensional force sensor mounted at the base of the wing. The influence of unsteady rotational effects was assessed by comparing the time course of measured forces with that of corresponding translational quasi-steady estimates. For each pattern, we also calculated mean stroke-averaged values of the force coefficients and an estimate of profile power. The results of this analysis may be divided into four main points.(i) For a short, symmetrical wing flip, mean lift was optimized by a stroke amplitude of 180° and an angle of attack of 50°. At all stroke amplitudes, mean drag increased monotonically with increasing angle of attack. Translational quasi-steady predictions better matched the measured values at high stroke amplitude than at low stroke amplitude. This discrepancy was due to the increasing importance of rotational mechanisms in kinematic patterns with low stroke amplitude.(ii) For a 180° stroke amplitude and a 45° angle of attack, lift was maximized by short-duration flips occurring just slightly in advance of stroke reversal. Symmetrical rotations produced similarly high performance. Wing rotation that occurred after stroke reversal, however, produced very low mean lift.(iii) The production of aerodynamic forces was sensitive to changes in the magnitude of the wing’s deviation from the mean stroke plane (stroke deviation) as well as to the actual shape of the wing tip trajectory. However, in all examples, stroke deviation lowered aerodynamic performance relative to the no deviation case. This attenuation was due, in part, to a trade-off between lift and a radially directed component of total aerodynamic force. Thus, while we found no evidence that stroke deviation can augment lift, it nevertheless may be used to modulate forces on the two wings. Thus, insects might use such changes in wing kinematics during steering maneuvers to generate appropriate force moments.(iv) While quasi-steady estimates failed to capture the time course of measured lift for nearly all kinematic patterns, they did predict with reasonable accuracy stroke-averaged values for the mean lift coefficient. However, quasi-steady estimates grossly underestimated the magnitude of the mean drag coefficient under all conditions. This discrepancy was due to the contribution of rotational effects that steady-state estimates do not capture. This result suggests that many prior estimates of mechanical power based on wing kinematics may have been grossly underestimated.
HOW THE BODY CONTRIBUTES TO THE WAKE IN UNDULATORY FISH SWIMMING
Authors: MÜLLER ULRIKE K. , SMIT JORIS , STAMHUIS EIZE J. , VIDELER JOHN J. 
Published: April 2021

SUMMARY
Undulatory swimmers generate thrust by passing a transverse wave down their body. Thrust is generated not just at the tail, but also to a varying degree by the body, depending on the fish's morphology and swimming movements. To examine the mechanisms by which the body in particular contributes to thrust production, we chose eels, which have no pronounced tail fin and hence are thought to generate all their thrust with their body. We investigated the interaction between body movements and the flow around swimming eels using two-dimensional particle image velocimetry. Maximum flow velocities adjacent to the eel's body increase almost linearly from head to tail, suggesting that eels generate thrust continuously along their body. The wake behind eels swimming at 1.5Ls-1, where L is body length,consisted of a double row of double vortices with little backward momentum. The eel sheds two vortices per half tail-beat, which can be identified by their shedding dynamics as a start—stop vortex of the tail and a vortex shed when the body-generated flows reach the `trailing edge' and cause separation. Two consecutively shed ipsilateral body and tail vortices combine to form a vortex pair that moves away from the mean path of motion. This wake shape resembles flow patterns described previously for a propulsive mode in which neither swimming efficiency nor thrust is maximised but sideways forces are high. This swimming mode is suited to high manoeuvrability. Earlier recordings show that eels also generate a wake reflective of maximum swimming efficiency. The combined findings suggest that eels can modify their body wave to generate wakes that reflect their propulsive mode.
MALARIA-INDUCED APOPTOSIS IN MOSQUITO OVARIES
Authors: HOPWOOD JANE A. , AHMED ASHRAF M. , POLWART ANTHONY , WILLIAMS GWYN T. , HURD HILARY 
Published: April 2021

SUMMARYMany insects are able to adjust their egg production according to physiological conditions such as nutrient supply and mating success. One way in which this is achieved is by resorption of some, or all, of the ovarian follicles at some stage during oogenesis. We have shown that the mosquito Anopheles stephensi responds in this manner when ookinetes of the malaria parasite Plasmodium yoelii nigeriensis first begin to invade the midgut. Little is known about the initiation and regulation of follicle resorption in any insect. Here, we demonstrate that there is a significant positive correlation between follicle resorption and the presence of follicular epithelial cells that are undergoing apoptosis. The parasite causes significantly more follicles to contain apoptotic cells from 16 h post-infection onwards. Injection of a caspase inhibitor immediately after feeding on an infective blood meal prevents parasite-induced resorption of follicles and thus demonstrates that apoptosis precedes resorption. Ultrastructural studies show that patches of follicular epithelial cells contain condensed nuclear chromatin, a characteristic of apoptosis, and that no patency develops in these cells. Our work suggests that apoptosis plays a role in malaria-initiated inhibition of mosquito oogenesis and that caspase is central to this process. Follicle resorption is one of the main factors contributing to malaria-induced fecundity reduction in mosquitoes.