bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acid–Base Regulation, Metabolism and Energetics in Sipunculus Nudus As a Function of Ambient Carbon Dioxide Level
Authors: Pörtner H. O. , Reipschläger A. , Heisler N. 
Published: April 2021

ABSTRACT
Changes in the rates of oxygen consumption and ammonium excretion, in intra- and extracellular acid–base status and in the rate of H+-equivalent ion transfer between animals and ambient water were measured during environmental hypercapnia in the peanut worm Sipunculus nudus. During exposure to 1% CO2 in air, intracellular and coelomic plasma values rose to levels above those expected from the increase in ambient CO2 tension. Simultaneously, coelomic plasma was reduced below control values. The rise in also induced a fall in intra- and extracellular pH, but intracellular pH was rapidly and completely restored. This was achieved during the early period of hypercapnia at the expense of a non-respiratory increase in the extracellular acidosis. The pH of the extracellular space was only partially compensated (by 37%) during long-term hypercapnia. The net release of basic equivalents under control conditions turned to a net release of protons to the ambient water before a net, albeit reduced, rate of base release was re-established after a new steady state had been achieved with respect to acid–base parameters.
Hypercapnia also affected the mode and rate of metabolism. It caused the rate of oxygen consumption to fall, whereas the rate of ammonium excretion remained constant or even increased, reflecting a reduction of the O/N ratio in both cases. The transient intracellular acidosis preceded a depletion of the phosphagen phospho-L-arginine, an accumulation of free ADP and a decrease in the level of Gibbs free energy change of ATP hydrolysis, before replenishment of phosphagen and restoration of pHi and energy status occurred in parallel.
In conclusion, long-term hypercapnia in vivo causes metabolic depression, a parallel shift in acid–base status and increased gas partial pressure gradients, which are related to a reduction in ventilatory activity. The steady-state rise in H+-equivalent ion transfer to the environment reflects an increased rate of production of protons by metabolism. This observation and the reduction of the O/N ratio suggest that a shift to protein/amino acid catabolism has taken place. Metabolic depression prevails, with completely compensated intracellular acidosis during long-term hypercapnia eliminating intracellular pH as a significant factor in the regulation of metabolic rate in vivo. Fluctuating levels of the phosphagen, of free ADP and in the ATP free energy change values independent of pH are interpreted as being correlated with oscillating ATP turnover rates during early hypercapnia and as reflecting a tight coupling of ATP turnover and energy status via the level of free ADP.
Kinematic Models Of The Buccal Mass Of Aplysia Californica
Authors: Drushel Richard F. , Neustadter David M. , Hurwitz Itay , Crago Patrick E. , Chiel Hillel J. 
Published: April 2021

ABSTRACT
The feeding behavior of the marine mollusc Aplysia californica is an intensively studied model system for understanding the neural control of behavior. Feeding movements are generated by contractions of the muscles of the buccal mass. These muscles are internal and cannot be visualized during behavior. In order to infer the movements of the muscles of the buccal mass, two kinematic models were constructed. The first kinematic model assumed that the complex consisting of the pincer-like radula and the underlying odontophore was spherical in shape. In this model, the radula/odontophore was moved anteriorly or posteriorly and the more superficial buccal muscles (11/13 and 12) were fitted around it. Although the overall buccal mass shapes predicted by this model were similar to those observed in vivo during protraction, the shapes predicted during retraction were very different. We therefore constructed a second kinematic model in which the shape of the radula/odontophore was based on the shapes assumed by those structures in vitro when they were passively forced into protraction, rest or retraction positions. As each of these shapes was rotated, the second kinematic model generated overall shapes of the buccal mass that were similar to those observed in vivo during swallowing and tearing, and made predictions about the antero-posterior length of the buccal mass and the relative location of the lateral groove. These predictions were consistent with observations made in vivo and in vitro. The kinematic patterns of intrinsic buccal muscles 11 and 12 in vivo were estimated using the second model. Both models make testable predictions with regard to the functions and neural control of intrinsic buccal muscles 12 and 13.
Cry1Ac, a bacillus thuringiensis toxin, triggers extracellular Ca2+ influx and Ca2+ release from intracellular stores in Cf1 cells (Choristoneura fumiferana, lepidoptera)
Authors: Potvin L. , Laprade R. , Schwartz J. L. 
Published: April 2021

ABSTRACT
Intracellular Ca2+ concentration was measured in single Cf1 cells (Choristoneura fumiferana, spruce budworm) loaded with Fura-2, a Ca2+-sensitive fluorescent probe. Cf1 cells displayed Ca2+ surges in response to Cry1Ac and Cry1C proteins, two Cf1-toxic Bacillus thuringiensis products, but not to Cry1Aa and Cry3A, which are not toxic to Cf1 cells. In the presence of extracellular Ca2+, the toxin-induced Ca2+ response was insensitive to methoxyverapamil, a voltage-dependent Ca2+ channel blocker, but was abolished by lanthanum, a general inhibitor of Ca2+ transport. In the absence of external Ca2+, Cry1Ac induced a small intracellular Ca2+ transient which was inhibited by TMB-8, a blocker of Ca2+ release from inositol-1,4,5-trisphosphate-sensitive pools. Under these conditions, thapsigargin, which inhibits intracellular Ca2+-ATPases, elicited a Ca2+ surge when applied alone. However, subsequent addition of Cry1Ac failed to induce a Ca2+ signal, indicating a depletion of intracellular Ca2+ pools. In Cf1 cells, therefore, bioactive B. thuringiensis toxins triggered intracellular Ca2+ surges which were mainly due to the influx of extracellular Ca2+ through toxin-made pores, as confirmed by planar lipid bilayer experiments. Furthermore, TMB-8- and thapsigargin-sensitive Ca2+ stores contributed to the Cry1Ac-induced Ca2+ signal.
Orientation Of Snow Buntings (Plectrophenax Nivalis) Close To The Magnetic North Pole
Authors: Sandberg Roland , Bäckman Johan , Ottosson Ulf 
Published: April 2021

ABSTRACT
Orientation experiments were performed with first-year snow buntings (Plectrophenax nivalis) during their autumn migration in a natural near-vertical geomagnetic field approximately 400 km away from the magnetic north pole. Migratory orientation of snow buntings was recorded using two different techniques: orientation cage tests and free-flight release experiments. Experiments were performed under clear skies, as well as under natural and simulated complete overcast. Several experimental manipulations were performed including an artificial shift of the E-vector direction of polarized light, depolarization of incoming light and a 4 h slow clock-shift experiment. The amount of stored fat proved to be decisive for the directional selections of the buntings. Fat individuals generally chose southerly mean directions, whereas lean birds selected northerly headings. These directional selections seemed to be independent of experimental manipulations of the buntings’ access to visual cues even in the local near-vertical magnetic field. Under clear skies, the buntings failed to respond to either a deflection of the E-vector direction of polarized light or an experimental depolarization of incoming skylight. When tested under natural as well as simulated overcast, the buntings were still able to select a meaningful mean direction according to their fat status. Similarly, the free-flight release test under complete overcast resulted in a well-defined southsoutheast direction, possibly influenced by the prevailing light northwest wind. Clock-shift experiments did not yield a conclusive result, but the failure of these birds to take off during the subsequent free-flight release test may indicate some unspecified confusion effect of the treatment.
Swimming Kinematics And Respiratory Behaviour Of Xenopus Laevis Larvae Raised In Altered Gravity
Authors: Fejtek Monika , Souza Kenneth , Neff Anton , Wassersug Richard 
Published: April 2021

ABSTRACT
We examined the respiratory behaviours and swimming kinematics of Xenopus laevis tadpoles hatched in microgravity (Space Shuttle), simulated microgravity (clinostat) and hypergravity (3 g centrifuge). All observations were made in the normal 1 g environment. Previous research has shown that X. laevis raised in microgravity exhibit abnormalities in their lungs and vestibular system upon return to 1 g.
The tadpoles raised in true microgravity exhibited a significantly lower tailbeat frequency than onboard 1 g centrifuge controls on the day of landing (day0), but this behaviour normalized within 9 days. The two groups did not differ significantly in buccal pumping rates. Altered buoyancy in the space-flight microgravity tadpoles was indicated by an increased swimming angle on the day after landing (day1). Tadpoles raised in simulated microgravity differed to a greater extent in swimming behaviours from their 1 g controls. The tadpoles raised in hypergravity showed no substantive effects on the development of swimming or respiratory behaviours, except swimming angle. Together, these results show that microgravity has a transient effect on the development of locomotion in X. laevis tadpoles, most notably on swimming angle, indicative of stunted lung development. On the basis of the behaviours we studied, there is no indication of neuromuscular retardation in amphibians associated with embryogenesis in microgravity.
Hypertrehalosaemic Neuropeptides Decrease Levels Of The Glycolytic Signal Fructose 2,6-Bisphosphate In Cockroach Fat Body
Authors: Becker Andreas , Wegener Gerhard 
Published: April 2021

ABSTRACT
In cockroach fat body, trehalogenesis and glycolysis compete for glucose phosphates as common substrates. During trehalogenesis, glycolysis is inhibited, although the mechanism responsible for this is not known. Incubation of the isolated fat body from the Argentine cockroach Blaptica dubia with an extract of the corpora cardiaca containing as little as 0.005 gland equivalents ml−1 of incubation medium increased the release of trehalose (anthrone-positive material) from the tissue by more than 100 %. The content of the glycolytic activator fructose 2,6-bisphosphate was decreased by up to 50 %. A decapeptide was isolated from the corpora cardiaca of B. dubia and shown to be identical to the naturally occurring Blaberus discoidalis hypertrehalosaemic peptide (Bld HrTH), which was also found in the corpora cardiaca. Synthetic Bld HrTH at 2 nmol l−1 and above increased trehalose production and decreased the content of fructose 2,6-bisphosphate to the same extent as did corpus cardiacum extract. The octapeptides Periplaneta americana cardioacceleratory hormones I and II (Pea CAH-I and Pea CAH-II) also had a significant effect on both parameters. Fructose 2,6-bisphosphate is a potent activator of phosphofructokinase from cockroach fat body if the enzyme is assayed at near-physiological concentrations of substrates and effectors. It is suggested that, because of the decrease in fructose 2,6-bisphosphate levels in the fat body, the activity of the key glycolytic enzyme phosphofructokinase is diminished. This can explain the inhibition of glycolytic flux by hypertrehalosaemic peptides which alters the balance of glucose metabolism in favour of trehalose formation.
The Effects of Increased Protein Intake on Kidney Size and Function
Authors: Hammond Kimberly A. , Janes Donald N. 
Published: April 2021

ABSTRACT
In endothermic vertebrates, long-term increases in metabolic energy demand are often associated with increases in food intake and accompanied by increases in organ mass. Wide-scale increases in organ mass have often been attributed to a metabolic response to increased energy intake and utilization. On a constant diet, however, increased food intake is also associated with increased protein intake. We hypothesized that, while increased food intake itself may be responsible for increases in digestive tract mass, the consequent increased protein intake would be the factor responsible for increased kidney mass and function. Thus, we exposed male and female mice to diets differing in protein level (7 %, 15 % or 46 % casein by mass) at different acclimation temperatures (5 °C or 23 °C). Within an acclimation temperature, food intake rate remained constant over the entire range of dietary protein level, and protein intake rate increased as dietary content increased. The mice in the cold-acclimation group increased food intake rate by 48–120 % over those in the warm-acclimation group. Liver, kidney and stomach mass increased with protein intake rate, while digestive tract and other vital organ masses increased only in response to increased energy intake rate. Blood urea nitrogen levels increased with protein intake rate. Glomerular filtration rates increased with increases in dietary protein level in male mice but not female mice. Finally nitrogen filtration rate increased with protein intake rate for mice on the high-protein diet. We suggest that it is primarily the increased protein intake rate rather than the increased food intake rate that results in the changes in kidney and liver mass and kidney function observed to occur in situations of high energy demand.
Augmented Respiration in a Flying Insect
Authors: Komai Yutaka 
Published: April 2021

ABSTRACT
The properties of the gas transport system in a tethered flying insect were investigated by directly measuring the oxygen partial pressure in a wing muscle of the sweet potato hawkmoth Agrius convolvuli using a needle electrode.
At rest, a distribution of corresponding to levels in the muscle and tracheal structures was observed. At the onset of tethered flight, in the muscle decreased. However, during a long stable flight, increased and reached a plateau approximately 2 min after the onset of flight. During stable tethered flight, in the centre of the second layer of the dorsal longitudinal muscle was locally higher than that during rest. As wing amplitude increased, increased in spite of the concurrent increase in metabolic rate. During tethered flight at a constant wing amplitude, was proportional to the mean wing positional angle.
The results suggest that this insect effectively uses muscle movement, which increases the frequency and stroke volume of ventilation, to augment gas exchange during flight.
Variation in Kinematics and Dynamics of the Landing Flights of Pigeons on a Novel Perch
Authors: Green Patrick R. , Cheng Peter 
Published: April 2021

ABSTRACT
Pigeons made 10 flights to a novel perch. Kinematic measurements of these flights were obtained from video recordings, and the forces exerted on the perch on each landing were measured. There was wide variation (20-fold range) in the kinetic energy of the pigeons just before landing, arising almost entirely from variation in horizontal velocity. The maximum force exerted on the perch varied in magnitude from approximately twice to eight times the pigeons’ body weight, and in direction from 40 to 90 ° below the horizontal. In landings with high final kinetic energy, the maximum force exerted on the perch was larger and was applied at a shallower angle than in those with low final kinetic energy. Landing flights with high final kinetic energy showed straighter trajectories and a larger peak deceleration during the last 300 ms of approach flight than those with low final kinetic energy, which had downward-curving trajectories and a more prolonged and steady pattern of deceleration. Mean final kinetic energy was lower in the first two landings made on the perch than in subsequent landings, indicating that pigeons are more likely to adopt a slow, downward-curving approach to a novel perch and a fast, straight approach to a familiar one.
Interactive Effects of Salinity On Metabolic Rate, Activity, Growth and Osmoregulation in the Euryhaline Milkfish (Chanos Chanos)
Authors: Swanson Christina 
Published: April 2021

ABSTRACT
The euryhaline milkfish (Chanos chanos) is an excellent subject for studies of the physiological and behavioral processes involved in salinity adaptation. In this study, energy partitioning for metabolism, activity and growth, maximal activity performance and blood osmotic concentrations were assessed at two activity levels in juvenile milkfish fed equal rations and maintained at a relatively constant temperature (26±2 °C) and at salinities (15, 35 and 55 ‰) that represented a wide range of osmoregulatory challenges. Changes in the measured parameters were not consistently related to the magnitude of the trans-integumentary osmotic gradients. Routine oxygen consumption rates were high in 35 ‰ salinity (mean ±1 S.E.M. 167±8 mg O2 kg−1 h−1) and comparably low in 15 and 55 ‰ salinity (133±6 and 127±3 mg O2 kg−1 h−1, respectively). Routine activity levels (relative swimming velocity) were highest in 35 ‰ salinity (0.96±0.04 L s−1), where L is standard length, intermediate in 15 ‰ salinity (0.77±0.03 L s−1) and lowest in 55 ‰ salinity (0.67±0.03 L s−1). Growth was significantly higher in 55 ‰ salinity (3.4±0.2 % increase in wet body mass per day) than in 35 ‰ salinity (2.4±0.2 % increase per day) and intermediate in 15 ‰ salinity (2.9±0.5 % increase per day). Maximum swimming velocities decreased with increases in salinity, from 9.9±0.7 L s−1 in 15 ‰ salinity to 6.6±0.5 L s−1 in 55 ‰ salinity. Sustained swimming activity above routine levels for 2 h resulted in an increase in blood osmotic concentrations in milkfish in 55 ‰ salinity, but osmoregulation was re-established during the second 2 h of activity. Thus, patterns of variation in metabolic rate and growth were largely parallel to variations in routine activity although, comparing 15 and 55 ‰ salinity, elevated maintenance costs for osmoregulation at the high salinity were detectable. Reduced osmoregulatory abilities and reductions in maximal swimming performance suggest that high salinity may constrain activity. The results demonstrate that investigations of salinity adaptation in euryhaline fishes should take into account the interactive effects of salinity on physiology and behavior.
Inter-Tissue Differences In Mitochondrial Enzyme Activity, Rna And Dna In Rainbow Trout (Oncorhynchus Mykiss)
Authors: Leary S. C. , Battersby B. J. , Moyes C. D. 
Published: April 2021

ABSTRACT
We examined whether the relationships between mitochondrial enzyme activity, mitochondrial DNA (mtDNA) and mitochondrial RNA (mtRNA) were conserved in rainbow trout (Oncorhynchus mykiss) tissues that differ widely in their metabolic and molecular organization. The activity of citrate synthase (CS), expressed either per gram of tissue or per milligram of total DNA, indicated that these tissues (blood, brain, kidney, liver, cardiac, red and white muscles) varied more than 100-fold in mitochondrial content. Several-fold differences in the levels of CS mRNA per milligram of DNA and CS activity per CS mRNA were also observed, suggesting that fundamental differences exist in the regulation of CS levels across tissues. Although tissues varied 14-fold in RNA g−1, poly(A+) RNA (mRNA) was approximately 2 % of total RNA in all tissues. DNA g−1 also varied 14-fold across tissues, but RNA:DNA ratios varied only 2.5-fold. The relationship between two mitochondrial mRNA species (COX I, ATPase VI) and one mitochondrial rRNA (16S) species was constant across tissues. The ratio of mtRNA to mtDNA was also preserved across most tissues; red and white muscle had 10-to 20-fold lower levels of mtDNA g−1 but 7-to 10-fold higher mtRNA:mtDNA ratios, respectively. Collectively, these data suggest that the relationship between mitochondrial parameters is highly conserved across most tissues, but that skeletal muscles differ in a number of important aspects of respiratory gene expression (‘respiratory genes’ include genes located on mtDNA and genes located in the nucleus that encode mitochondrial protein) and mtDNA transcriptional regulation.
Stimulation Of Fluid Secretion Of Malpighian Tubules Of Drosophila Melanogaster Meig. By Cyclic Nucleotides Of Inosine, Cytidine, Thymidine And Uridine
Authors: Riegel J. A. , Maddrell S. H. P. , Farndale R. W. , Caldwell F. M. 
Published: April 2021

ABSTRACT
External application of the 3′,5′-cyclic monophosphates of inosine, cytidine, uridine and thymidine stimulated the fluid secretion rate (FSR) of Malpighian tubules isolated from Drosophila melanogaster. The evidence suggested that the cyclic nucleotides acted intracellularly in some capacity. Receptors of the ‘purinergic’ type appeared not to be major contributors to fluid secretion; of three purinergic agonists tried, adenosine, adenosine 5′-monophosphate (AMP) and adenosine 5′-triphosphate (ATP), only adenosine had an effect, but this was not observed consistently. None of the purinergic agonists interfered with the stimulation of the FSR by adenosine 3′,5′-cyclic monophosphate (cAMP). The maximum stimulation of the fluid-secretion rate by any cyclic nucleotide was approximately double the unstimulated (control) rate. Tubules stimulated to less than maximal FSR by one cyclic nucleotide could be stimulated maximally by an appropriate concentration of another cyclic nucleotide. Malpighian tubules bathed in solutions that contained either [3H]cAMP or [3H]cGMP accumulated radioactivity to a level many times that in the medium. Accumulation of radioactivity by tubules bathed in 430 nmol l−1 [3H]cAMP was suppressed by 1 mmol l−1 non-radioactive cyclic nucleotides in the order cAMP⪢cGMP&gt;cIMP&gt;cCMP; neither cTMP nor cUMP suppressed the accumulation of [3H]cAMP. Approximately 35 % of the [3H]cAMP and 80 % of the [3H]cGMP that entered the Malpighian tubule cells was metabolised to compounds that were not identified. It was concluded that cyclic nucleotides enter the Malpighian tubule cells by at least one transport mechanism which is particularly sensitive to purine-based nucleotides.
Sarcomere Number Adaptation After Retinaculum Transection In Adult Mice
Authors: Burkholder Thomas J. , Lieber Richard L. 
Published: April 2021

ABSTRACT
Skeletal muscle has been shown to adjust serial sarcomere number in response to chronic static length changes. However, the adaptive responses to alterations in the dynamic environment are less well defined. The adaptations of the adult mouse tibialis anterior (TA) muscle to altered length and excursion were investigated by surgical transection of the flexor retinaculum. TA moment arm and muscle excursion increased by 38±7 % (mean ± S.E.M.) and fully extended (plantarflexed) muscle length was decreased by 8 % after flexor retinaculum transection. In spite of the significant shortening of the muscle in full plantar- and dorsiflexion, serial sarcomere number decreased by 10±1 % after 2 weeks of recovery. Gait analysis of these transected animals revealed a 14±3 % decrease in dorsiflexion angular velocity after transection. The decrease in angular velocity was less than the increase in moment arm and, as a result, muscle velocity was calculated to increase by 20±4 %. These data suggested that the muscle adapted in response to the underlying change in length, irrespective of the altered excursion or velocity.