bluuebunny/crossref_metadata_2025 huggingface dataset:
Branchial Chloride Cells in Larvae and Juveniles of Freshwater Tilapia Oreochromis Mossambicus
Authors: Li Jie , Eygensteyn Jelle , Lock Robert A. C. , Verbost Pieter M. , Heijden Angelique J. H. Van Der , Bonga Sjoerd E. Wendelaar , Flik Gert
Published: April 2021

Branchial chloride cells in the developing larvae and juveniles of freshwater tilapia, Oreochromis mossambicus, were identified and the membrane Na+/K+-ATPase was localized in situ through binding of the fluorescent dye anthroylouabain. After co-labelling of the cells with the fluorescent probes DASPMI and Con-A-FITC, the mitochondria and apical crypt in the same chloride cells were visualized using confocal laser scanning microscopy. The high density of apical crypts indicated that many chloride cells were functional. The density of branchial chloride cells in larvae 10 days after hatching was approximately 6000 mm−2. An extremely high Na+/K+-ATPase specific activity of approximately 1500μmol Pi h−1 mg−1 was measured in the gills 10 days after hatching. With the development of secondary lamellae and hence an increase in the amount of branchial epithelial protein, a concomitant decrease in the specific activity of the enzyme in the gill tissues was observed. Total Na+/K+-ATPase activity increased markedly in the early life stages. Our data indicate that in larval stages of fish the gills form a functional ionoregulatory organ before they start functioning as a gas-exchange organ.
Effect of Haemoglobin Concentration on the Oxygen Affinity of Intact Lamprey Erythrocytes
Authors: Airaksinen S. , Nikinmaa M.
Published: April 2021

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

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

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

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

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

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 (>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

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

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

Ultraviolet 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

We 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

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

Many 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.
Molecular cloning and sequence ofSparus aurataskeletal myosin light chains expressed in white muscle: developmental expression and thyroid regulation
Authors: Moutou Katerina A. , Canario Adelino V. M. , Mamuris Zissis , Power Deborah M.
Published: April 2021

Two full-length cDNA clones encoding the skeletal myosin light chain 2 (MLC2; 1452bp) and myosin light chain 3 (MLC3; 972bp) were isolated from a cDNA library prepared from gilthead sea bream Sparus aurata larvae. The MLC2 cDNA encoded a predicted protein of 170 residues that was 79% identical to rabbit MLC2 over the entire length and 87% identical within the Ca2+-binding region. The deduced amino acid sequence of MLC3 was 153 residues in length and was 91% and 69% identical to the zebrafish and rabbit MLC3, respectively. Northern blot analysis revealed that in adults both transcripts were expressed in fast white muscle only. MLC2 appeared earlier in development: MLC2 transcripts were detectable from the beginning of segmentation, whereas MLC3 transcripts did not appear until 27h post-fertilisation. At this developmental stage, a second MLC2 transcript of 0.89 kilobase-pairs was present. MLCs exhibited a different age-related pattern of response to varied thyroidal states, which were experimentally induced by the administration of 1μgg−1bodymass of thyroxine (T4) or triiodothyronine (T3), or 5ngg−1bodymass of the hypothyroidal compound thiourea; MLC3 expression was not significantly affected, whereas levels of MLC2 transcripts were significantly elevated in the white muscle only of juvenile sea bream after administration of T4. Although the mechanism of thyroidal regulation of MLC expression remains unknown, the present results suggest that different regulatory mechanisms exist for different MLCs.
Recovery periods restore mechanosensitivity to dynamically loaded bone
Authors: Robling Alexander G. , Burr David B. , Turner Charles H.
Published: April 2021

Bone cells are capable of sensing and responding to mechanical forces, but mechanosensitivity begins to decline soon after the stimulus is initiated. Under continued stimulation, bone is desensitized to mechanical stimuli. We sought to determine the amount of time required to restore mechanosensitivity to desensitized bone cells in vivo by manipulating the recovery time (0, 0.5, 1, 2, 4 or 8 h) allowed between four identical daily loading bouts. We also investigated the osteogenic effectiveness of shorter-term recovery periods, lasting several seconds (0.5, 3.5, 7 or 14 s), introduced between each of 36 identical daily loading cycles. Using the rat tibia four-point bending model, the right tibia of 144 adult female Sprague-Dawley rats was subjected to bending, sham bending or no loading. In the rats receiving recovery periods between loading bouts, histomorphometric measurements from the endocortical surface of the loaded and nonloaded control (left) tibiae revealed more than 100 % higher relative bone formation rates in the 8 h recovery group than in the 0 and 0.5 h recovery groups. Approximately 8 h of recovery was sufficient to restore full mechanosensitivity to the cells. In the rats allowed time to recover between load cycles, 14 s of recovery resulted in significantly higher (66–190 %) relative bone formation rates compared to any of the three shorter recovery periods. In both experiments, bone formation in the sham-bending animals was similar to that in the nonloaded control group. The results demonstrate the importance of recovery periods for (i) restoring mechanosensitivity to bone cells and (ii) maximizing the osteogenic effects of mechanical loading (exercise) regimens.
Effects of longitudinal body position and swimming speed on mechanical power of deep red muscle from skipjack tuna (Katsuwonus pelamis)
Authors: Syme Douglas A. , Shadwick Robert E.
Published: April 2021

The mechanical power output of deep, red muscle from skipjack tuna (Katsuwonus pelamis) was studied to investigate (i) whether this muscle generates maximum power during cruise swimming, (ii) how the differences in strain experienced by red muscle at different axial body locations affect its performance and (iii) how swimming speed affects muscle work and power output. Red muscle was isolated from approximately mid-way through the deep wedge that lies next to the backbone; anterior (0.44 fork lengths, ANT) and posterior (0.70 fork lengths, POST) samples were studied. Work and power were measured at 25°C using the work loop technique. Stimulus phases and durations and muscle strains (±5.5 % in ANT and ±8 % in POST locations) experienced during cruise swimming at different speeds were obtained from previous studies and used during work loop recordings. In addition, stimulus conditions that maximized work were determined. The stimulus durations and phases yielding maximum work decreased with increasing cycle frequency (analogous to tail-beat frequency), were the same at both axial locations and were almost identical to those used by the fish during swimming, indicating that the muscle produces near-maximal work under most conditions in swimming fish. While muscle in the posterior region undergoes larger strain and thus produces more mass-specific power than muscle in the anterior region, when the longitudinal distribution of red muscle mass is considered, the anterior muscles appear to contribute approximately 40 % more total power. Mechanical work per length cycle was maximal at a cycle frequency of 2–3 Hz, dropping to near zero at 15 Hz and by 20–50 % at 1 Hz. Mechanical power was maximal at a cycle frequency of 5 Hz, dropping to near zero at 15 Hz. These fish typically cruise with tail-beat frequencies of 2.8–5.2 Hz, frequencies at which power from cyclic contractions of deep red muscles was 75–100 % maximal. At any given frequency over this range, power using stimulation conditions recorded from swimming fish averaged 93.4±1.65 % at ANT locations and 88.6±2.08 % at POST locations (means ± s.e.m., N=3–6) of the maximum using optimized conditions. When cycle frequency was held constant (4 Hz) and strain amplitude was increased, work and power increased similarly in muscles from both sample sites; work and power increased 2.5-fold when strain was elevated from ±2 to ±5.5 %, but increased by only approximately 12 % when strain was raised further from ±5.5 to ±8 %. Taken together, these data suggest that red muscle fibres along the entire body are used in a similar fashion to produce near-maximal mechanical power for propulsion during normal cruise swimming. Modelling suggests that the tail-beat frequency at which power is maximal (5 Hz) is very close to that used at the predicted maximum aerobic swimming speed (5.8 Hz) in these fish.
The Effect of Lesions to the Vertical and Optic Lobes on Tactile Discrimination in Octopus
Authors: Wells M. J. , Wells J.
Published: April 2021

Blind octopuses were trained to make tactile discriminations between the members of pairs of objects and their performance was compared with that of other blind animals having. parts of the brain removed. It was found that removal of the optic lobes, together constituting more than half of the total mass of the brain, did not affect the performance of animals in these discrimination Removal of the vertical lode, on the other hand, produced deficiencies proportiante to the amount d tissue removed; these deficiencies were mat marked in the cose of the more difIicult of the two discrimination problems used in the tests. It was possible to compensate for loss of the vertical lobe to a considerable extent by arranging trials at more frequent intervals. Animals unable to learn a tactile discrimination when trained at rate of 8 trials per day did so when trained at 40 trials per day. When animals trained at the latter rate were subjected to reversed training, thoselacking the vertical lobe re-learned in fewer trials than controls, indicating shorter persistence of the effects of pre-reversal training. It is concluded that the vertical lobe is concerned with the persistence of conditions set up in the nervous system as a result of sensory experience. It is not known whether the vertical lobe serves to increase the initial intensity of these conditions, or to delay their decay.
The Site of Impulse Initiation in Bipolar Receptor Neurons of Callinectes Sapidus L.*
Authors: Mendelson Martin
Published: April 2021

In bipolar neurons of the P.D. organ of Callinectes sapidus the initiation of impulses at the soma requires depolarization of at least 4-5 mV. Impulses produced by mechanical stimulation of the organ arise abruptly from the resting (potential) level without prepotential, and it is impossible to demonstrate the occurrence of generator potentials of the magnitude required for spike triggering at or near the soma. Anti- and orthodromic invasion of the soma may be differentially blocked by hyperpolarization; orthodromic block often reveals a small potential that appears to result from impulse activity in the distal process of the cell. Blockade of the soma spike to leave only the electrotonic potential of the distal process results in interruption of axonal transmission in the impaled cell. It is concluded that P.D. bipolar cells originate impulses in their distal processes with subsequent conduction through the soma into the axon.
The Mechanism of Orientation of Roach, Rutilus Rutilus L. In an Odour Gradient
Authors: Hemmings C. C.
Published: April 2021

The behaviour of individual roach was tested in a horizontal linear gradient of roach odour. Tests with a chemical model suggested that the gradient was logarithmic. The swimming speed of the fish was not directly related to odour concentration but was low when fish swam into decreasing concentration and much higher in the opposite direction. This does not support an ortho-kinesis. Turning was more frequent at the high concentration end of the gradient which the fish ‘preferred’. This is the reverse of klino-kinesis. It is suggested that orientation is by spatial and temporal comparison of intensities, that speed is related to change in stimulation and that variation in turning serves to maintain fish at high odour concentrations.
The Repetitive Responses of Isolated Axons from the Crab, Carcinus Maenas
Authors: Chapman R. A.
Published: April 2021

A method is described that enables the electrical responses of motor axons isolated from the leg nerve of the crab Carcinus to be studied close to or at the site of imposed electrical currents, while this area is continuously bathed by physiological solution. The three classes of repetitive responses originally described by Hodgkin (1948) have occurred during the present work and additional features of these responses have been described. The results support Hodgkin’s original thesis that the development of the spike generating mechanisms determine the response frequency during a repetitive response, but a progressive lengthening of the relative refractory period occurs during this response and is considered to be the agency that causes the gradual slowing down of the response frequency, i.e. the adaption. The processes of membrane restoration (repolarization and recovery) have been shown to be sensitive to applied currents; anodal current hastening and cathodal current slowing it. These phenomena provide a basis for interpreting the change in the duration of the relative refractory period observed during the repetitive response. The differences between the form of the repetitive response in the crab axon and the predictions of the Hodgkin-Huxley equations is discussed and it seems likely that the rapid recovery of the membrane resistance during the repolarization phase of the crab axon action potential underlies this difference.
The functional significance of the haemoglobin in a marine nematode, Enoplus brevis (Bastian)
Authors: Atkinson H.J.
Published: April 2021

An animal chamber and a simple microspectrophotometer for investigating the in vivo oxygenation of the haemoglobin of E. brevis are described.

The in vivo absorption peaks of this haemoglobin occur at similar wavelengths to those of other nematodes. Mean values, given with their corresponding standard errors, occur at 577·6 ±0·6nm, 543·6 ± 0·5 nm and 421·7 ± 1·9 nm for oxyhaemoglobin, and 555·2 ± 0·9 nm and 432·2 ± 1·3 nm for the deoxygenated pigment.

The percentage of oxyhaemoglobin in the pharynx of E. brevis decreased at external oxygen tensions of less than 20 Torr, and the pigment was completely deoxygenated at 5 Torr. Stimulation of individuals in aerated sea water for 1–2 min caused a partial deoxygenation of the haemoglobin; the pigment reloaded soon after this period of increased activity had ended. The functional significance of the haemoglobin of E. brevis is discussed.
Evaluation of C-reactive protein and hematological parameters in smokeless tobacco users: A comparative cross-sectional study
Authors: Memon Sikander Munir , Kumar Naresh , Rahman Aneela Atta Ur , Syed Binafsha Manzoor
Published: April 2021

Objective: To investigate the changes in levels of C-reactive protein (CRP) and hematological parameters among smokeless tobacco (SLT) users.

Methods: A comparative cross-sectional study was conducted at the community level in the coastal districts of Sindh province namely Badin, Thatta, and Sujawal from January 2017 to December 2019. The CRP and hematological parameters were evaluated by well-established methods among SLT and non-SLT users.

Results: There was a statistically significant difference between SLT users (mean CRP = 0.77) versus non-users (mean CRP = 0.18), p = <0.001. Among hematological parameters, white blood cells (SLT users median = 7.85 versus non-SLT users median = 8.50, p = 0.004), monocytes (SLT users median = 6.00 versus non-SLT users median = 6.00, p = 0.001) and erythrocyte sedimentation rate (SLT users median = 15.00 versus non-SLT users median = 10.00, p = 0.006) showed statistically significant difference.

Conclusions: Significantly elevated CRP was observed in SLT users similarly hematological parameters also showed changes. WBCs, monocytes and ESR were significantly deranged among SLT users. Further studies looking into long term effects of these changes would be helpful.

doi: https://doi.org/10.12669/pjms.37.4.3841

How to cite this:Memon SM, Kumar N, Atta-Ur-Rahman A, Syed BM. Evaluation of C-reactive protein and hematological parameters in smokeless tobacco users: A comparative cross-sectional study. Pak J Med Sci. 2021;37(4):983-987.    doi: https://doi.org/10.12669/pjms.37.4.3841

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Η αλληλεπίδραση των ενδογενών ρετροϊών και της μεταγωγικής οδού των ιντερφερονών με την υπομεθυλιωτική θεραπεία στα Μυελοδυσπλαστικά Σύνδρομα
Authors: Κορδελλά Χρυσούλα
Published: April 2021

Τα μυελοδυσπλαστικά σύνδρομα (ΜΔΣ) και η οξεία μυελογενής λευχαιμία (ΟΜΛ) χαρακτηρίζονται από μη φυσιολογικά πρότυπα μεθυλίωσης του DNA, τα οποία συμβάλλουν στη παθοφυσιολογία της νόσου, με αποτέλεσμα τη μη φυσιολογική επιγενετική καταστολή και διαφοροποίηση των αιμοποιητικών βλαστικών κυττάρων του μυελού των οστών (HSCs). Οι υπομεθυλιωτικοί παράγοντες (ΥΜΠ), οι οποία αντιστρέφουν αυτή την επιγενετική καταστολή, όπως είναι η 5-αζακυτιδίνη (AZA) και η 5-αζα-2'-δεοξυκυτιδίνη (DAC), παραμένουν η κύρια θεραπεία επιλογής για τους ασθενείς με ΜΔΣ υψηλού κινδύνου και ΟΜΛ. Παρόλο αυτά, ο ακριβής μηχανισμός δράσης των ΥΜΠ παραμένει αδιευκρίνιστος, ενώ απουσιάσουν και προγνωστικοί παράγοντες απόκρισης στους ΥΜΠ. Πρόσφατα δεδομένα σε καρκινικές κυτταρικές σειρές δείχνουν ότι η επανενεργοποίηση ενδογενών ρετροϊικών στοιχείων και η επακόλουθη επαγωγή κυτταρικής ενδογενούς αντιϊικής απόκρισης ενδέχεται να αποτελούν το υπόβαθρο της αντικαρκινικής δραστηριότητας των ΥΜΠ. Χρησιμοποιώντας την τεχνική RNA sequencing (RNA-seq), πραγματοποιήθηκε σύγκριση των επιπέδων μεταγραφής των ενδογενών ρετροϊικών στοιχείων σε HSC απομονωμένα από το μυελό των οστών ασθενών με ΜΔΣ και χρόνιας μυελομονοκυτταρική λευχαιμία (CMML) πριν και μετά τη θεραπεία με AZA και σε HSC μυελού των οστών προερχόμενα από υγιείς δότες και ασθενείς με πρωτοπαθή ΟΜΛ. Σε συμφωνία και με προηγούμενες βιβλιογραφικές αναφορές, διαπιστώθηκε ότι η θεραπεία με ΑZA αύξησε τη μεταγραφή των ενδογενών ρετροϊικών στοιχείων. Ωστόσο, η αύξηση αυτή δε συσχετίστηκε με το αποτέλεσμα της θεραπείας με ΑΖΑ, καθώς παρατηρήθηκε τόσο στους αποκρινόμενους όσο καις τους μη αποκρινόμενους ασθενείς. Η παρατήρηση αυτή επιβεβαιώθηκε και με τη τεχνική της de novo συναρμολόγησης του μεταγραφώματος, αποκαλύπτοντας ότι οι, αποκρινόμενοι στην ΑΖΑ, ενδογενείς ρετροϊοί δεν αποτελούν καθοριστικό παράγοντα για το αποτέλεσμα της θεραπείας με ΥΜΠ. Επίσης, παρατηρήθηκε έλλειψη επαγωγής μίας αντιϊικής απόκρισης των ιντερφερονών η οποία να σχετίζεται με την απόκριση στη θεραπεία με ΑΖΑ. Αντίθετα, αποκαλύφθηκε ότι η προθεραπευτική έκφραση και η διαδικασία του εναλλακτικού ματίσματος συγκεκριμένων, αναπτυξιακά ρυθμιζόμενων, γονιδίων μπορεί να αποτελούν προγνωστικούς παράγοντες για την ανταπόκριση των ασθενών με ΜΔΣ και CMML-ΙΙ στη θεραπεία με AZA. Συμπερασματικά, η παρούσα διδακτορική διατριβή αναδεικνύει τη μη συμμετοχή των ενδογενών ρετροϊικών στοιχείων στην αποτελεσματικότητα δράσης των ΥΜΠ. Προσδιορίζει ταυτόχρονα τις αναπτυξιακά ρυθμιζόμενες μεταγραφικές υπογραφές συγκεκριμένων γονιδίων, που είτε κωδικοποιούν την αντίστοιχη πρωτεΐνη είτε όχι, ως συσχετίζομενα με μια ευνοϊκή ανταπόκριση των ασθενών με ΜΔΣ και CMML-ΙΙ στη θεραπεία με AZA, προσφέροντας νέους υποψηφίους δείκτες για περαιτέρω αξιολόγηση.
Essential oils as alternatives to chemical feed additives for maximizing livestock production
Authors: AKRAM MZ , ASGHAR MU , JALAL H
Published: April 2021

This review is aimed at providing basic and current knowledge about possible mechanisms and nutritional applications of essential oils (EOs) for food animals. Public concern on the excessive use of antibiotics in livestock production has started extensive research to find safe and efficient options. EOs extracted from aromatic plants are known to have a range of biologically active properties that can be applied to modern animal production. Primarily, EOs possess anti-inflammatory, anti-microbial, and digestion enhancing effects as they improve digestive enzymes, improve feed conversion ratio, modulate ruminal fermentation, add antioxidant properties, and underpin animal immunity. The dietary supplementation of EOs demonstrated as a simple and proficient approach to enhance the performance of livestock. However, mechanisms involved in enhancing animal performance, modulating ruminal fermentation, and microflora are still unclear. Moreover, limited information is available regarding interactions among feed, EOs, and gut ecosystem of animals. EOs could be used as nutraceuticals with possible commercial applications in modern animal nutrition such as antimicrobials, antioxidants, growth promoters, and immunomodulators, alternatives to chemical feed additives. This knowledge encourages further investigations about EOs to realize their full potential and build up their standard use in livestock production.
The effect of morning versus evening administration of empagliflozin on its pharmacokinetics and pharmacodynamics characteristics in healthy adults: a two-way crossover, non-randomised trial
Authors: ElDash Rana M. , Raslan Mohamed A. , Shaheen Sara M. , Sabri Nagwa Ali
Published: April 2021

Background: Empagliflozin is an SGLT2 inhibitor approved for use in patients with diabetes mellitus type 2 (DMT2) with or without other cardiovascular disease. Empagliflozin is taken once daily without rationale on the optimal timing for administration. This study aimed to determine the chronopharmacological effects of morning vs evening administration of empagliflozin (10 mg) in healthy Egyptian adults, by investigating the pharmacokinetics and pharmacodynamics parameters of empagliflozin depending on the intake time.

Methods: An open label, sequential, two‐way crossover trial comprised of two periods with a washout period of 7 days. All participants received a single oral dose of empagliflozin (JARDIANCE ®; 10 mg film coated tablet) in the evening, and after a seven-day washout period, the morning. Pharmacokinetics parameters (primary endpoints: tmax (h), Cmax (ng/ml), AUC 0-t (ng.h/ml); secondary endpoints: AUC 0 to ∞(ng.h/ml)) were assessed. Method validation was done prior to injection in LC/MS/MS and samples were processed by Liquid-Liquid extraction. The pharmacodynamic profile (UGE 0-24) was determined after method validation (glucose hexokinase method).

Results: Tmax increased by 35% in the evening phase compared to the morning phase, while Cmax decreased by -6.5% in the evening dose compared to the morning dose. Additionally, AUC0 to ∞ increased in the evening phase by 8.25% compared to the morning phase. The mean cumulative amount of glucose excreted (UGE (0-24)) increased by 43% in the evening dose compared to the morning dose

Conclusion: Despite the difference in pharmacokinetics parameters between evening and morning doses, Cmax, AUC0-t, AUC 0-∞, didn’t differ on the bioequivalence level. In addition, as UGE (0-24) didn’t statistically differ, thus, we can conclude that there is no statistical significance between the morning and evening doses.

Trial registration: Clinal Trials.gov, ID: NCT03895229 (registered on 29th March 2019).
Site «MLESYS – multilevel education Internet-system for teachers and students»
Authors: Gaponenko Artiom , Sergeev Denis
Published: April 2021

Site MLESYS (Multilevel education system) - multilevel educational Internet-system for the teachers (heads of scientific and educational groups) and the students (participants of groups) which allows teachers to create remote groups and also to form the storehouse of materials on their disciplines (lectures, manuals, presentations, tasks for independent work, etc.) with an opportunity of access to corresponding kinds of these materials by means of special links. Site MLESYS is developed on platform WordPress and on hosting Hostland. Site MLESYS allows: 1) for teachers: to create educational and scientific groups for remote communication of the participants of educational process, to include students in these groups; to place all necessary materials for the group (manuals, lectures, presentations, etc.); to form the storehouse of materials on each discipline (tests, tasks, cases, etc.), access to these materials can be carried out only by means of the link to the specific page; to communicate with participants of the group; 2) for the students: on condition of inclusion into remote group to have an opportunity to enter the group, to open and download the materials placed by the teacher; to get access to the materials by means of links (publications, tests, tasks, cases, etc.) of the corresponding teacher of a discipline from the storehouse of materials; to communicate with the teacher and participants of the group.
The Challenge of Rival Versions of Moral Enquiry Within Leadership-As-Practice
Authors: Mensch Kirk
Published: April 2021

Herein, I clarify my concern regarding Raelin’s Leadership-as-Practice (L-A-P) and argue that inconsistent moral philosophies undermine the veracity of leadership theory, especially more recent democratic, shared, collective, and practice oriented theories; that this problem seems to be proliferating in the social sciences, and that this is especially concerning in socio-psychologically oriented theories. I contend that the moral foundations of L-A-P remain philosophically disquieting, unless it is understood as excluding moral agents other than those of a genealogical tradition, and that such exclusionary consequences in practice may lead to moral disengagement, which might then lead to cognitive dissonance and even self-harm.
REVIEWS
Authors: Faux Karen
Published: April 2021

This month's recommendations are perfect for reading during quiet, one-to-one time, sharing a theme that it is always important to be yourself. Reviews by Claire Hewson and Karen Hart.