bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vitro Differentiation Of Isolated Stem Cells From The Midgut Of Manduca Sexta Larvae
Authors: Sadrud-Din Sakeena , Loeb Marcia J. , Hakim Raziel S. 
Published: April 2021

ABSTRACT
Isolated spherical stem cells from midguts of pharate fourth-instar larvae of Manduca sexta proliferated in vitro in the presence of 1 ng ml-1 20-hydroxyecdysone and co-cultured fat body tissue or cell-free fat body extract from M. sexta, Lymantria dispar or Heliothis virescens. In this environment, the stem cells were able to undergo mitosis and increase in number. However, stem cells were only able to differentiate to mature goblet and columnar cells when cell-free conditioned medium, taken from midgut cell cultures containing mature cells as well as stem cells and differentiating forms, was introduced into the culture medium. The presence of early and mature goblet cells, lying randomly on their sides, suggested that cell polarity developed in vitro as an intrinsic property of individual cells rather than with reference to an external inductive material. The differentiation factor (or factors) from the conditioned medium appears to include a heat-stable, peptide-like molecule of 10 kDa or less.
Structural Correlates of Speed and Endurance in Skeletal Muscle: The Rattlesnake Tailshaker Muscle
Authors: Schaeffer Paul J. , Conley Kevin E. , Lindstedt Stan L. 
Published: April 2021

ABSTRACT
The western diamondback rattlesnake Crotalus atrox can rattle its tail continuously for hours at frequencies approaching 90 Hz. We examined the basis of these fast sustainable contractions using electromyography, data on oxygen uptake and the quantitative ultrastructure of the tailshaker muscle complex. The tailshaker muscle has no apparent unique structures; rather, the relative proportions of the structures common to all skeletal muscles appear to be present (1) to minimize activation, contraction and relaxation times via an extremely high volume density of sarcoplasmic reticulum (26 %) as well as, (2) to maximize ATP resysnthesis via a high volume density of mitochondria (26 %). The high rate of ATP supply is reflected in the in vivo muscle mass-specific oxygen uptake of this group of muscles which, at 585 ml O2 kg−1 min−1 during rattling at 30 °C body temperature, exceeds that reported for other ectotherm and many endotherm muscles. Since the change in oxygen uptake paralleled that of the rattling frequency over the range of measured body temperatures, there was a nearly constant O2 cost per muscle contraction (0.139±0.016 μl O2 g−1). Electromyo-graphic analysis suggests that each of the six muscles that make up the shaker complex may be a single motor unit. Finally, the maximum rate of mitochondrial oxygen uptake is similar to that of various mammals, a hummingbird, a lizard, an anuran amphibian and of isolated mitochondria (at 10 000–40 000 molecules O2 s−1 μm2 of cristae surface area, when normalized to 30 °C), suggesting a shared principle of design of the inner mitochondrial membrane among the vertebrates.
Localization Of Bursicon In Ccap-Immunoreactive Cells In The Thoracic Ganglia Of The Cricket Gryllus Bimaculatus
Authors: Kostron Barbara , Kaltenhauser Ulrike , Seibel Birgit , Bräunig Peter , Honegger H. Willi 
Published: April 2021

ABSTRACT
Bursicon is a neuropeptide that induces tanning of the cuticle in freshly moulted insects. In an earlier investigation, we demonstrated that bursicon activity can be detected throughout the ventral nerve cord of the cricket Gryllus bimaculatus. This study aims at identifying the neurosecretory cells within the thoracic ganglia that produce bursicon. When homogenates of anterior pieces of thoracic ganglia were separated using SDS gel electrophoresis, proteins with bursicon activity could be eluted only from a slice of the gel spanning the 28–33 kDa region. In the anterior lateral cortex of the thoracic ganglia, there are two bilaterally paired neurosecretory cells with large vacuoles that project contralaterally to neurohaemal release sites associated with segmental nerves N5 and N6. These cells and their processes in N5 and N6 were labelled using antisera against crustacean cardioactive peptide (CCAP). The cell projecting into N6 showed a Tyndall effect (i.e. appeared opaque under oblique illumination) in older adults, and single isolated somata contained bursicon activity. Homogenates of nerves N5 and N6 also showed bursicon activity, but neither bursicon activity nor CCAP-immunoreactive processes were found in segmental nerve N4. The thoracic connectives, which contain three major CCAP-immunoreactive processes, also showed bursicon activity. Homogenates of posterior pieces of the thoracic ganglia did not contain bursicon activity. Western blots demonstrated that the anti-CCAP serum does not recognize the 30 kDa bursicon-active protein fraction. These results suggest that a CCAP-like neuropeptide and a protein with bursicon activity are co-localized in the anterior lateral neurosecretory cells of the thoracic ganglia and in their segmental homologues in the other ganglia. Additionally, we have shown using western blots that a monoclonal antibody raised against a 56 kDa protein from the housefly Musca domestica, a protein thought to be bursicon, does not label the 30 kDa bursicon-active protein of crickets. However, this antibody does label an unidentified 56 kDa protein isolated from anterior as well as posterior pieces of thoracic ganglia.
Adjustment of K′ for the Creatine Kinase, Adenylate Kinase and Atp Hydrolysis Equilibria to Varying Temperature and Ionic Strength
Authors: Teague Walter E. , Golding Elke M. , Dobson Geoffrey P. 
Published: April 2021

ABSTRACT
Comparative physiologists and biochemists working with tissues at varying temperatures and ionic strength are required to adjust apparent equilibrium constants (K′) of biochemical reactions to the experimental conditions prior to calculating cytosolic bioenergetic parameters (transformed Gibbs free energy of formation, fΔG′ATP; cytosolic phosphorylation ratio, [ATP]/[ADP][Pi]; [phosphocreatine]:[orthophosphate] ratio [PCr]/[Pi]) and kinetic parameters (free [ADP], [Pi] and [AMP]). The present study shows how to adjust both K′ and the equilibrium constants of reference reactions (Kref) of creatine kinase (ATP: creatine N-phosphotransferase; EC 2.7.3.2), adenylate kinase (ATP:AMP phosphotransferase; EC 2.7.4.3) and adenosinetriphosphatase (ATP phosphohydrolase; EC 3.6.1.3) to temperature and ionic strength. This information, together with our previous study showing how to adjust equilibria to varying pH and pMg, is vital for the quantification of organ and tissue bioenergetics of ectotherms and endotherms under physiological conditions.
Roles of Gastric Gata DNA-Binding Proteins
Authors: Maeda Masatomo , Kubo Kentaro , Nishi Tsuyoshi , Futai Masamitsu 
Published: April 2021

ABSTRACT
The gastric H+/K+-ATPase is a P-type ATPase that is specifically expressed in gastric parietal cells and is responsible for acid secretion into the stomach. We have found one or more gastric mucosal nuclear proteins that recognize a sequence motif in the 5’-upstream regions of the H+/K+-ATPase α-and β-subunit genes. This gastric motif, (G/C)PuPu(G/C)NGAT(A/T)PuPy, may be a binding site for a positive transcriptional regulator that functions specifically in parietal cells. We further demonstrated using cDNA cloning and in situ hybridization that novel zinc-finger proteins (GATA-GT1 and GATA-GT2) are present in the gastric parietal cells and bind to this motif. The proteins activate the transcription of the reporter gene with the 5’-upstream region of the H+/K+-ATPase β-subunit gene. These results suggest that gastric GATA DNA-binding proteins have important roles in transcriptional activation of H+/K+-ATPase genes in the parietal cells.
Age-Related Variation in Body Temperature, Thermoregulation and Activity in A Thermally Polymorphic Dragonfly
Authors: Marden James H. , Kramer Melissa G. , Frisch John 
Published: April 2021

ABSTRACT
Thoracic temperatures (Tth) of Libellula pulchella dragonflies during activity in the field were compared between age classes and with laboratory measures of optimal thoracic temperature for flight performance (Tth,opt; a trait that varies during adult maturation in this species). Newly emerged adults (tenerals) had mean Tth values during flight (34.5 °C; range 29–40 °C) that did not differ from their mean Tth,opt (34.6 °C; range 28.5–43.8 °C). Mature adults had higher and more precisely regulated thoracic temperatures (mean Tth 41.7 °C; range 37.5–45.2 °C), which were somewhat lower than their mean Tth,opt (43.6 °C; range 38.7–49.9 °C). Among matures, behaviors requiring the highest levels of flight exertion (aerial copulation; mate guarding; escalated territorial contests) caused an elevation of Tth above that of concurrently sampled individuals engaged in routine flight (mean Tth difference 1.3 °C), which raised mean Tth to a level that was not significantly different from Tth,opt (42.5 versus 43.5 °C). Compared with tenerals, matures spent more time flying, made longer-duration flights and showed a more restricted pattern of daily activity. Sympatric Anax junius dragonflies that regulate Tth endothermically had a uniform pattern of activity across the entire day, i.e. occupied a broader ecological niche than that of L. pulchella. These results support the hypotheses that optimal body temperature evolves to match the elevated body temperatures that occur during exercise and that the ecological benefits of an expanded niche are a secondary benefit rather than a primary selective force during the evolution of homeothermy and high body temperatures.
Modulation of Membrane Currents by Cyclic Amp in Cleavage-Arrested Drosophila Neurons
Authors: Alshuaib Waleed B. , Byerly Lou 
Published: April 2021

ABSTRACT
A number of Drosophila learning mutants have defective intracellular second-messenger systems. In an effort to develop techniques that will allow direct measurement of the effects of these mutations on whole-cell neuronal membrane currents, the perforated-patch whole-cell (PPWC) technique has been applied to cleavage-arrested cultured embryonic Drosophila neurons. This technique permits the measurement of membrane currents without disturbing the intracellular environment. As a result of the maintenance of the intracellular environment, Drosophila neuron currents are found to be much more stable than when measured using the conventional whole-cell (CWC) patch-clamp technique. Ca2+ channel currents, which typically ‘wash out’ within a few minutes of the beginning of CWC recording, are stable for the duration of the seal (tens of minutes) when measured using the PPWC technique. Since the learning mutations dunce and rutabaga disrupt cyclic AMP signalling, the actions of externally applied dibutyryl cyclic AMP (db-cAMP) and theophylline on Ca2+ and K+ channel currents were studied. db-cAMP and theophylline enhanced the Ba2+ current, carried by Ca2+ channels, but had no effect on the K+ current in the cleavage-arrested neurons. However, the large variability and reduction in density of Ba2+ and K+ currents raise questions about the suitability of using these cleavage-arrested cells as models for Drosophila neurons.
Short-Term Emersion Affects Cardiac Function and Regional Haemolymph Distribution in the Crab Cancer Magister
Authors: Airriess Chris N. , Mcmahon Brian R. 
Published: April 2021

ABSTRACT
Changes in cardiac function and arterial haemolymph flow associated with 6 h of emersion were investigated in the crab Cancer magister using an ultrasonic flowmeter. This species is usually found sublittorally but, owing to the large-scale horizontal water movements associated with extreme tides, C. magister may occasionally become stranded on the beach. Laboratory experiments were designed such that the emersion period was typical of those that might be experienced by this crab in its natural environment.
The frequency of the heart beat began to decline sharply almost immediately after the start of the experimental emersion period. Cardiac stroke volume fell more gradually. The combined reduction in these two variables led to a maximum decrease in cardiac output of more than 70 % from the control rate. Haemolymph flow through all the arteries originating at the heart, with the exception of the anterior aorta, also declined markedly during emersion. As the water level in the experimental chamber fell below the inhalant branchial openings, a stereotypical, dramatic increase in haemolymph flow through the anterior aorta began and this continued for the duration of the emersion period.
The rapid time course of the decline in heart-beat frequency and the increase in haemolymph flow through the anterior aorta suggest a neural mechanism responding to the absence of ventilatory water in the branchial chambers. These responses may be adaptations, respectively, to conserve energy by reducing the minute volume of haemolymph pumped by the heart and to protect the supply of haemolymph to cephalic elements of the central nervous system. The decline in cardiac stroke volume, which occurs more slowly over the emersion period, may be a passive result of the failure to supply sufficient O2 to meet the aerobic demands of the cardiac ganglion.
In Vivo Muscle Protein Synthesis Rates in the American Lobster Homarus Americanus During the Moult Cycle and in Response to 20-Hydroxyecdysone
Authors: Haj Alicia J. El , Clarke Susan R. , Harrison Paul , Chang Ernest S. 
Published: April 2021

ABSTRACT
Simultaneous measurements of in vivo rates of protein synthesis (Ks) in claw, leg and abdominal muscles were made in the American lobster Homarus americanus at three stages of the moult cycle. Ks values are significantly elevated during the premoult (stage D2–D3) and fall during the intermoult (stage C4) periods in all three muscles. Postmoult (stage A/B) levels are not significantly elevated above intermoult levels. Intermoult levels are between 0.3 and 0.4 % protein synthesized per day. In the premoult animals, the ribosomal activity (milligrams protein synthesized per microgram RNA per day) of the claw, abdominal and leg muscles is elevated three-to fivefold. The claw muscle maintains an elevated ribosomal activity into the postmoult stage whereas, by this stage, that of the other muscle tissues has fallen to intermoult levels. The RNA/protein ratios of the three muscle groups from intermoult, premoult and postmoult animals do not show any significant differences. 18S ribosomal RNA levels fluctuate slightly, with no consistent pattern over the moult cycle. In vivo injection of premoult concentrations of 20-hydroxyecdysone (20-HE) into intermoult lobsters results in elevated Ks values and ribosomal activity for the muscles after 3 days. RNA/protein ratios remain constant in the muscles in response to injections of 20-HE in vivo. In vitro preparations of leg muscle treated with 20-HE did not show similar elevated rates of protein synthesis.
Power at the Expense of Efficiency in Contraction of White Muscle Fibres From Dogfish Scyliorhinus Canicula
Authors: Curtin N. A. , Woledge R. C. 
Published: April 2021

ABSTRACT
Work and heat production of white myotomal muscle fibres from dogfish were measured during sinusoidal movement (0.71–5.0 Hz) at 12 ˚C. Stimulus phase (stimulus timing relative to movement) and duty cycle (stimulus duration as a fraction of movement cycle duration) were varied to determine the parameters optimal for power output and for efficiency (work/total energy output). Movements of 0.067 and 0.120L0 were used, where L0 is the muscle fibre length giving maximum force in an isometric tetanus. At each frequency of movement and duty cycle, the stimulus phase giving the highest power was the same as that giving the highest efficiency. In contrast, at each frequency and optimal stimulus phase, the dependence of power on duty cycle was very different from the dependence of efficiency on duty cycle. Power generally increased with increasing duty cycle, whereas efficiency decreased. Thus, high power can be achieved at the expense of efficiency by adjusting stimulus duty cycle. When stimulus phase and duty cycle were optimized, efficiency was always higher for the larger distance of movement. The efficiency of energy conversion can be maintained at a high level as the frequency of movement increases from 1.25 to 5.0 Hz.
Dipeptide Transport by Crustacean Hepatopancreatic Brush-Border Membrane Vesicles
Authors: Thamotharan M. , Ahearn G. A. 
Published: April 2021

ABSTRACT
Epithelial brush-border membrane vesicles (BBMVs) of lobster (Homarus americanus) hepatopancreas were formed by a Mg2+ precipitation technique. In these BBMVs, [14C]glycylsarcosine ([14C]Gly-Sar) uptake was stimulated by a transmembrane proton gradient. transmembrane K+ diffusion potential (inside negative) stimulated [14C]Gly-Sar uptake above that observed with short-circuited vesicles, while an inwardly directed Na+ gradient had no stimulatory effect on peptide uptake. [14C]Gly-Sar influx (over 10 s) occurred by a low-affinity, saturable, proton-gradient-dependent carrier system (Kt=5.90±0.13 mmol l−1, Jmax=4662±487 pmol mg−1 protein 10 s−1; mean ± S.E.M., N=3). This carrier exhibited a high-affinity proton binding site (KH=235±25 nmol l−1; pK=6.6) and an apparent 1H+:1Gly-Sar transport stoichiometry. Influx of 0.1 mmol l−1 [14C]Gly-Sar into lobster hepatopancreatic BBMVs was significantly (P&lt;0.01) cis-inhibited by 10 mmol l−1 diethylpyrocarbonate and by a variety of other dipeptides (10 mmol l−1), suggesting a broad transport specificity. These observations strongly suggest that transport of peptides into crustacean hepatopancreas is proton-gradient-dependent and electrogenic, qualitatively resembling the peptide transport paradigm proposed for fish and mammals.
Intestinal Na+ and Cl− Levels Control Drinking Behavior in the Seawater-Adapted Eel Anguilla Japonica
Authors: Ando Masaaki , Nagashima Kei 
Published: April 2021

ABSTRACT
To analyze drinking mechanisms in seawater teleosts, seawater-adapted eels were used as a model system. When the intestine of the eel was perfused with iso-osmotic mannitol, the eels drank sea water. However, when the perfusion medium was switched to iso-osmotic NaCl, seawater drinking was depressed. This depression was observed even after blocking NaCl absorption across the intestine by replacement of the perfusate with choline chloride or by treatment with furosemide, an inhibitor of NaCl and water absorption across the eel intestine. Furthermore, depression of drinking rate preceded an increase in urine flow by over 1 h. These results indicate that this depression is not due to a recovery of blood volume and suggest that intestinal Cl− itself inhibits drinking. Direct action of luminal Cl− on drinking behavior was further supported by the observation that perfusion with iso-osmotic NMDG–HCl, Tris–HCl, choline chloride and RbCl all inhibited seawater drinking. When NaCl in the perfusion medium was replaced with sodium acetate, sodium butyrate, sodium methylsulfate or NaSCN, the drinking rate was enhanced threefold, suggesting that Na+ itself stimulates drinking in the absence of Cl−. In the present study, concentrations of Na+ and Cl− in the swallowed fluid were also measured simultaneously. As the drinking rate was enhanced, the Na+ and Cl− concentrations in the gastrointestinal fluid were increased. On the basis of these results, it seems possible that high concentrations of Cl− in the intestine reduce the drinking rate, thus lowering esophageal Cl− concentration due to desalination of the ingested sea water. When Cl− concentration in the intestine falls below a certain level, Na+ will stimulate seawater drinking again.
Shape oscillations of human neutrophil leukocytes: characterization and relationship to cell motility
Authors: Ehrengruber Markus U. , Deranleau David A. , Coates Thomas D. 
Published: April 2021

ABSTRACT
When neutrophil leukocytes are stimulated by chemotactic factors or by substratum contact, they change their shape. Shape changes are a prerequisite for cellular migration and typically involve the extrusion of thin, veil-like lamellipods and the development of morphological polarity. Stimulation also leads to changes in the neutrophil content of filamentous actin (F-actin), which is the major cytoskeletal component. Suspensions of human neutrophils stimulated with chemoattractants exhibit sinusoidal light-scattering oscillations with a period of approximately 8 s at 37 °C. These oscillations arise from periodic fluctuations in the cell body size caused by lamellipod extension and retraction cycles. The light-scattering oscillations are paralleled by corresponding oscillations in F-actin content. This raises the interesting possibility that cyclic actin polymerization constitutes the driving force for shape oscillations of suspended neutrophils. Similar periodic shape changes are present in neutrophils crawling on a surface, suggesting that shape oscillations are important for neutrophil motion. This review summarizes our present knowledge about shape oscillations in suspended and crawling neutrophils and discusses a possible role for these oscillations in neutrophil motility.
Local Differences in Myotendinous Junctions in Axial Muscle Fibres of Carp (Cyprinus Carpio L.)
Authors: Spierts Igor L. Y. , Akster H. A. , Vos I. H. C. , Osse J. W. M. 
Published: April 2021

ABSTRACT
We studied the myotendinous junctions of anterior and posterior red and white axial muscle fibres of carp using stereology. In posterior axial muscle fibres of swimming fish, stress (load on the myotendinous junction) must be higher than in anterior fibres as posterior fibres have a longer phase of eccentric activity. As we expected the magnitude of the load on the junction to be reflected in its structure, we compared the interfacial ratio, the ratio between the area of the junctional sarcolemma and the cross-sectional fibre area, of these muscle fibres. This ratio differed significantly between the investigated groups, with red fibres and posterior fibres having the larger ratios. The higher interfacial ratio of posterior myotendinous junctions is in accordance with the proposition mentioned above. The difference between myotendinous junctions of red and white fibres is probably related to a difference in the duration of the load on the junction.