bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are Integrins Involved in the Aggregatory and Phagocytic Behaviour of Fish Haemostatic Cells?
Authors: Hill Darryl J. , Rowley Andrew F. 
Published: April 2021

ABSTRACT
The involvement of a putative integrin-like fibrinogen receptor in the aggregatory and phagocytic behaviour of thrombocytes (platelet equivalents of fish) from the rainbow trout Oncorhynchus mykiss was studied. Aggregation of trout thrombocytes was induced by the thromboxane mimetic U-46619 in the presence of trout fibrinogen. Thrombocyte aggregation was inhibited by the tetrapeptide RGDS, but not by RGES or fibrinogen binding inhibitor peptide (HHLGGAKQAGDV). A range of monoclonal antibodies against the human platelet integrin α IIbα 3 (anti-CD41a, anti-α 3 and LK7r) showed no reactivity with trout thrombocytes. Subsequently, a panel of monoclonal antibodies was raised against thrombocyte membrane preparations in an attempt to obtain an antibody against the putative integrin fibrinogen receptor. Of these monoclonal antibodies, four were found to inhibit thrombocyte aggregation, namely 12G2, 30D8, 32F8 and 32H10. The antibody 32H10 was shown significantly to inhibit the attachment of thrombocytes to immobilised trout fibrinogen, suggesting that it and the other antibodies recognise the putative fibrinogen receptor on trout thrombocytes. FITC-labelled Bacillus cereus were employed as test particles to prove that thrombocytes internalise bacteria via an active process and not simply by passive sequestration into the open canalicular system. Preincubation of bacteria with trout fibrinogen resulted in a significant increase in the number of thrombocytes exhibiting phagocytosis. This enhancement of phagocytosis by preincubation of B. cereus with trout fibrinogen could be inhibited by the tetrapeptide RGDS, but not by RGES, hence implicating the putative fibrinogen receptor in the internalisation of microorganisms. The relevance of these findings to the possible existence of an integrin-like receptor on trout thrombocytes is discussed.
Sound Radiation by the Bladder Cicada Cystosoma Saundersii
Authors: Bennet-Clark H. C. , Young D. 
Published: April 2021

ABSTRACT
Male Cystosoma saundersii have a distended thin-walled abdomen which is driven by the paired tymbals during sound production. The insect extends the abdomen from a rest length of 32–34 mm to a length of 39–42 mm while singing. This is accomplished through specialised apodemes at the anterior ends of abdominal segments 4–7, which cause each of these intersegmental membranes to unfold by approximately 2 mm.
The calling song frequency is approximately 850 Hz. The song pulses have a bimodal envelope and a duration of approximately 25 ms; they are produced by the asynchronous but overlapping action of the paired tymbals. The quality factor Q of the decay of the song pulses is approximately 17.
The abdomen was driven experimentally by an internal sound source attached to a hole in the front of the abdomen. This allowed the sound-radiating regions to be mapped. The loudest sound-radiating areas are on both sides of tergites 3–5, approximately 10 mm from the ventral surface. A subsidiary sound-radiating region is found mid-ventrally on sternites 4–6. Sound is radiated in the same phase from all these regions. As the abdomen was extended experimentally from its resting length to its maximum length, the amplitude of the radiated sound doubled and the Q of the resonance increased from 4 to 9. This resonance and effect are similar at both tergite 4 and sternite 5.
Increasing the effective volume of the abdominal air sac reduced its resonant frequency. The resonant frequency was proportional to 1/√(total volume), suggesting that the air sac volume was the major compliant element in the resonant system. Increasing the mass of tergite 4 and sternites 4–6 also reduced the resonant frequency of the abdomen. By extrapolation, it was shown that the effective mass of tergites 3–5 was between 13 and 30 mg and that the resonant frequency was proportional to 1/√(total mass), suggesting that the masses of the tergal sound-radiating areas were major elements in the resonant system.
The tymbal ribs buckle in sequence from posterior (rib 1) to anterior, producing a series of sound pulses. The frequency of the pulse decreases with the buckling of successive ribs: rib 1 produces approximately 1050 Hz, rib 2 approximately 870 Hz and rib 3 approximately 830 Hz. The sound pulse produced as the tymbal buckles outwards is between 1.6 and 1.9 kHz. Simultaneous recordings from close to the tymbal and from tergite 4 suggest that the song pulse is initiated by the pulses produced by ribs 2 and 3 of the leading tymbal and sustained by the pulses from ribs 2 and 3 of the second tymbal.
An earlier model suggested that the reactive elements of the abdominal resonance were the compliance of the abdominal air sac volume and the mass of the abdomen undergoing lengthwise telescoping. The present work confirms these suggestions for the role of the air sac but ascribes the mass element to the in–out vibrations of the lateral regions of tergites 3–5 and the central part of sternites 4–6.
Responses of the Na+/H+ exchanger of european flounder red blood cells to hypertonic, β-adrenergic and acidotic stimuli
Authors: Weaver Y. R. , Kiessling K. , Cossins A. R. 
Published: April 2021

ABSTRACT
The transport pathways mediating regulatory volume increase (RVI) and β-adrenergic responses in red cells of the European flounder Platichthys flesus have been investigated. Hypertonic treatment under a low-atmosphere led to a complete RVI and to a three-to fourfold increase in Na+ influx. The RVI and the activated Na+ influx were blocked by the transport inhibitors amiloride and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS), both at a concentration of 10−4 mol l−1, and the RVI was abolished in a Na+-free saline, indicating the involvement of a hypertonically induced Na+/H+ exchanger and an accompanying Cl−/HCO3− exchanger. Both the hypertonically induced Na+ influx and the RVI were blocked by oxygenation of shrunk cells. The β-adrenergic agonist isoproterenol also strongly activated a Na+ influx and caused cell swelling. This response was also inhibited by amiloride and DIDS but was unaffected by oxygenation. Simultaneous application of isoproterenol and hypertonic shrinkage did not lead to additive Na+ influxes, suggesting that both responses were mediated by the same pool of exchangers. Mild cell acidification activated a Na+ influx under iso-osmotic conditions; amiloride caused partial inhibition of this influx, but oxygenation had no effect. Acid-induced and isoproterenol-induced Na+ fluxes were again non-additive. Thus, the Na+/H+ exchanger of flounder red cells is strongly activated by three physiological stimuli: hypertonic shrinkage, β-adrenergic hormones and cell acidification. Of these responses, only the first is affected by oxygenation, indicating some differentiation of their respective transduction mechanisms. These characteristics contrast with those of the corresponding exchangers from rainbow trout and eel red cells.
Control of gill ventilation and air-breathing in the bowfin Amia calva
Authors: Hedrick Michael S. , Jones David R. 
Published: April 2021

ABSTRACT
The purpose of this study was to investigate the roles of branchial and gas bladder reflex pathways in the control of gill ventilation and air-breathing in the bowfin Amia calva. We have previously determined that bowfin use two distinct air-breathing mechanisms to ventilate the gas bladder: type I air breaths are characterized by exhalation followed by inhalation, are stimulated by aquatic or aerial hypoxia and appear to regulate O2 gas exchange; type II air breaths are characterized by inhalation alone and possibly regulate gas bladder volume and buoyancy. In the present study, we test the hypotheses (1) that gill ventilation and type I air breaths are controlled by O2-sensitive chemoreceptors located in the branchial region, and (2) that type II air breaths are controlled by gas bladder mechanosensitive stretch receptors. Hypothesis 1 was tested by examining the effects of partial or complete branchial denervation of cranial nerves IX and X to the gill arches on gill ventilation frequency (fG) and the proportion of type I air breaths during normoxia and hypoxia; hypothesis II was tested by gas bladder inflation and deflation. Following complete bilateral branchial denervation, fG did not differ from that of sham-operated control fish; in addition, fG was not significantly affected by aquatic hypoxia in sham-operated or denervated fish. In sham-operated fish, aquatic hypoxia significantly increased overall air-breathing frequency (fAB) and the percentage of type I breaths. In fish with complete IX–X branchial denervation, fAB was also significantly increased during aquatic hypoxia, but there were equal percentages of type I and type II air breaths. Branchial denervation did not affect the frequency of type I air breaths during aquatic hypoxia. Gas bladder deflation via an indwelling catheter resulted in type II breaths almost exclusively; furthermore, fAB was significantly correlated with the volume removed from the gas bladder, suggesting a volume-regulating function for type II air breaths. These results indicate that chronic (3–4 weeks) branchial denervation does not significantly affect fG or type I air-breathing responses to aquatic hypoxia. Because type I air-breathing responses to aquatic hypoxia persist after IX–X cranial nerve denervation, O2-sensitive chemoreceptors that regulate air-breathing may be carried in other afferent pathways, such as the pseudobranch. Gas bladder deflation reflexly stimulates type II breaths, suggesting that gas bladder volume-sensitive stretch receptors control this particular air-breathing mechanism. It is likely that type II air breaths function to regulate buoyancy when gas bladder volume declines during the inter-breath interval.
Does Membrane Fluidity Contribute to Thermal Compensation of β-Adrenergic Signal Transduction in Isolated Trout Hepatocytes?
Authors: Mckinley Susan J. , Hazel Jeffrey R. 
Published: April 2021

ABSTRACT
The potential role of compensatory adjustments to membrane components in determining the function of the β-adrenergic receptor/adenylyl cyclase (β-AR/AC) signal-transduction system was studied in isolated hepatocytes of 5 °C- and 20 °C-acclimated rainbow trout Oncorhynchus mykiss. Rates of epinephrine-stimulated cyclic AMP (cAMP) production, although slowed (by a factor of 1.6-to 2.4-fold) by an acute drop in assay temperature from 20 to 5 °C, were significantly temperature-compensated, being approximately twofold higher in hepatocytes of 5 °C-than of 20 °C-acclimated trout. Membrane order in the bilayer interior of hepatocyte plasma membranes (as assessed by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene) was consistently lower in cold-than in warm-acclimated trout, reflecting an efficacy of homeoviscous adaptation of approximately 50 %. Temperature-induced changes in plasma membrane fatty acid composition (i.e. an increase in the proportions of polyunsaturated fatty acids with acclimation to 5 °C) were consistent with both the observed changes in the order of the bilayer interior and the extent of homeoviscous adaptation. However, isothermal fluidization of the bilayer interior by the addition of benzyl alcohol (30 mmol l−1) decreased rather than increased the rate of cAMP production. Significantly more (1.81-fold) β-adrenergic receptors were present in plasma membranes of hepatocytes from 5 °C-acclimated (6.23×104±4206 receptors per cell; mean ± S.E.M., N=3) than 20 °C-acclimated fish (3.44×104±4360 receptors per cell; N=3) when assayed at the acclimation temperature, whereas the equilibrium dissociation constants (Kd) (13.73±4.33 nmol l−1 at 5 °C; 9.75±3.29 nmol l−1 at 20 °C; N=3) were similar. On the basis of a strong correlation between β-adrenoceptor number and the rate of cAMP production (r2=0.956), regardless of assay or acclimation temperature, we conclude that modulation of receptor number is the primary acclimatory response of this signal-transduction pathway to temperature change in trout liver.
Thermal Thresholds of Lipid Restructuring and Δ9-Desaturase Expression in the Liver of Carp (Cyprinus Carpio L.)
Authors: Trueman R. J. , Tiku P. E. , Caddick M. X. , Cossins A. R. 
Published: April 2021

ABSTRACT
Cold acclimation induces a transient enzymatic activation of the acyl CoA-Δ9-desaturase in carp liver. We have determined thresholds for two underlying mechanisms; namely, the activation of latent enzyme and the induced synthesis of new desaturase. Carp were progressively cooled from 30 °C to 23, 17 and 10 °C, where they were held for up to 5 days. Endoplasmic reticulum phospholipids showed substantial changes in fatty acid composition, with linear decreases in the proportion of saturates with temperature over the full range of cooling (11.3 % in phosphatidylcholine and 15.8 % in phosphatidylethanolamine). In the phosphatidyl-ethanolamine fraction, this was linked to increased proportions of monoenes, particularly 20:1(n-9).
Modest cooling to 23 °C on day 1 induced a 2.5-fold transient increase in Δ9-desaturase activity without any change in the amount of desaturase protein or transcript. Further cooling to 17 °C induced a greater and more sustained increase in desaturase activity, reaching sevenfold on day 5, with a 10- to 20-fold increase in the amount of desaturase transcript. Extreme cooling to 10 °C led to a very large, but transient, 40- to 50-fold increase in desaturase transcript amounts, a modest 40–50 % increase in desaturase protein but no further increase in activity over that observed at 17 °C.
These results distinguish at least three mechanisms involved in cold-induced lipid restructuring; the activation of latent desaturase observed with gentle cooling, the induction of desaturase gene transcription and, finally, a third unidentified lipid compensatory mechanism that occurs with extreme cooling. The complex nature of cold-induced lipid restructuring also involves changes in the activity of other biosynthetic enzymes, including elongase and positional- and phospholipid-specific acyltransferases.
The Interplay Among Cardiac Ultrastructure, Metabolism and The Expression of Oxygen-Binding Proteins in Antarctic Fishes
Authors: O’Brien Kristin M. , Sidell Bruce D. 
Published: April 2021

ABSTRACT
We examined heart ventricle from three species of Antarctic fishes that vary in their expression of oxygen-binding proteins to investigate how some of these fishes maintain cardiac function despite the loss of hemoglobin (Hb) and/or myoglobin (Mb). We quantified ultrastructural features and enzymatic indices of metabolic capacity in cardiac muscle from Gobionotothen gibberifrons, which expresses both Hb and Mb, Chionodraco rastrospinosus, which lacks Hb but expresses Mb, and Chaenocephalus aceratus, which lacks both Hb and Mb. The most striking difference in cellular architecture of the heart among these species is the percentage of cell volume occupied by mitochondria, Vv(mit,f), which is greatest in Chaenocephalus aceratus (36.53±2.07), intermediate in Chionodraco rastrospinosus (20.10±0.74) and lowest in G. gibberifrons (15.87±0.74). There are also differences in mitochondrial morphologies among the three species. The surface area of inner mitochondrial membrane per volume of mitochondria, Sv(imm,mit), varies inversely with mitochondrial volume density so that Sv(imm,mit) is greatest in G. gibberifrons (29.63±1.62 μm−1), lower in Chionodraco rastrospinosus (21.52±0.69 μm−1) and smallest in Chaenocephalus aceratus (20.04±0.79 μm−1). The surface area of mitochondrial cristae per gram of tissue, however, is greater in Chaenocephalus aceratus than in G. gibberifrons and Chionodraco rastrospinosus, whose surface areas are similar. Despite significant ultrastructural differences, oxidative capacities, estimated from measurements of maximal activities per gram of tissue of enzymes from aerobic metabolic pathways, are similar among the three species. The combination of ultrastructural and enzymatic data indicates that there are differences in the density of electron transport chain proteins within the inner mitochondrial membrane; proteins are less densely packed within the cristae of hearts from Chaenocephalus aceratus than in the other two species. High mitochondrial densities within hearts from species that lack oxygen-binding proteins may help maintain oxygen flux by decreasing the diffusion distance between the ventricular lumen and mitochondrial membrane. Also, high mitochondrial densities result in a high intracellular lipid content, which may enhance oxygen diffusion because of the higher solubility of oxygen in lipid compared with cytoplasm. These results indicate that features of cardiac myocyte architecture in species lacking oxygen-binding proteins may maintain oxygen flux, ensuring that aerobic metabolic capacity is not diminished and that cardiac function is maintained.
Sensory Preconditioning in Honeybees
Authors: Müller Dirk , Gerber Bertram , Hellstern Frank , Hammer Martin , Menzel Randolf 
Published: April 2021

ABSTRACT
Sensory preconditioning means that reinforcement of stimulus A after unreinforced exposure to a compound AB also leads to responses to stimulus B. Here, we describe and analyze sensory preconditioning in an insect, the honeybee Apis mellifera. Using two-element odorant compounds in classical conditioning of the proboscis extension reflex, we found (i) that sensory preconditioning is not due to stimulus generalization, (ii) that paired, but not unpaired, presentation of elements supports sensory preconditioning, (iii) that simultaneous, but not sequential, exposure to the elements of the compound supports sensory preconditioning and (iv) that a single presentation of the compound yields maximal sensory preconditioning. The results are discussed with respect to configural and chain-like associative explanations for sensory preconditioning. We suggest an experience-dependent step of compound processing, establishing configural units, as an additional explanation for sensory preconditioning.
The Oxalate/Sulfate Antiporter in Lobster Hepatopancreas: Internal and External Binding Constants
Authors: A. Gerencser George , Burgin Charles , Robbins Frank , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
Utilizing a purified basolateral plasma membrane vesicle (BLMV) preparation containing a sulfate/oxalate antiporter, it was demonstrated that sulfate exhibited similar binding characteristics to the transporter whether bound internally or externally. It was also demonstrated that oxalate had similar binding characteristics to the antiporter whether it was bound internally or externally. Oxalate had a greater affinity to the transporter than did sulfate. Several organic anions affected binding and, therefore, overall transport by the antiporter. Most notably, sulfate was the only anion that stimulated oxalate uptake into BLMVs, which suggests a conservative binding specificity for the antiporter. 4-Acetamido-4′-isothiocyanostilbene-2,2′-disulfonic acid (SITS) and/or 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) inhibited the transport rate, confirming the existence of oxalate/sulfate exchange by the transporter. These results suggest that oxalate, not sulfate, regulates the transport rate because of its greater affinity to the transporter.
Dynamics of Mallard (Anas Platyrhynchos) Gastrocnemius Function During Swimming Versus Terrestrial Locomotion
Authors: Biewener Andrew A. , Corning William R. 
Published: April 2021

ABSTRACT
This study investigates how the contractile function of a muscle may be modulated to accommodate changes in locomotor mode and differences in the physical environment. In vivo recordings of lateral gastrocnemius (LG) activation, force development (measured using tendon buckle transducers) and length change (measured using sonomicrometry) were obtained from mallard ducks (Anas platyrhynchos) as they swam at steady speeds in a water tank and walked or ran on land. LG force recordings were compared with combined lateral and medial gastrocnemius (MG) muscle–tendon force recordings obtained from the contralateral limb, allowing force development by the MG to be estimated relative to that of the LG. Although similar stresses were calculated to act in the LG and MG muscles during terrestrial locomotion (126 and 115 kPa, respectively), stresses were considerably greater in the LG compared with the MG during swimming (62 versus 34 kPa, respectively). During both steady swimming and terrestrial locomotion, the LG developed force while shortening over a considerable range of its length (swimming 23.6 % versus terrestrial 37.4 %). Activation of the muscle occurred near the end of passive lengthening during the recovery stroke, just prior to muscle shortening. As a result, the muscle generated broad positive work loops during both locomotor modes. LG work during swimming (4.8 J kg− 1) averaged 37 % of the work performed during terrestrial locomotion (13.1 J kg− 1), consistent with the twofold greater force and 58 % greater strain of the muscle during walking and running. Because limb cycle frequency was similar for the two locomotor modes (swimming 2.65 versus terrestrial 2.61 Hz), differences in power output (swimming 12.6 W kg− 1 versus terrestrial 32.4 W kg− 1) largely reflected difference in work per cycle. Tendon elastic energy savings was a small fraction (&lt;5 %) of the work performed by the muscle, consistent with a fiber–tendon design of these two muscles that favors muscle work to produce limb movement with little tendon strain. These results are consistent with a higher cost of terrestrial locomotion in ducks compared with other, more cursorial birds that may operate their muscles more economically and achieve greater tendon elastic savings.
The Vortex Wake of the Free-swimming Larva and Pupa of CULEX PIPIENS (Diptera)
Authors: Brackenbury John 
Published: April 2021

SUMMARY
The kinematics and hydrodynamics of free-swimming pupal and larval (final-instar) culicids were investigated using videography and a simple wake-visualisation technique (dyes). In both cases, swimming is based on a technique of high-amplitude, side-to-side (larva) or up-and-down (pupa) bending of the body. The pupa possesses a pair of plate-like abdominal paddles; the larval abdominal paddle consists of a fan of closely spaced bristles which, at the Reynolds numbers involved, behaves like a continuous surface. Wake visualisation showed that each half-stroke of the swimming cycle produces a discrete ring vortex that is convected away from the body.
Consecutive vortices are produced first to one side then to the other of the mean swimming path, the convection axis being inclined at approximately 25° away from dead aft. Pupal and larval culicids therefore resemble fish in using the momentum injected into the water to generate thrust. Preliminary calculations for the pupa suggest that each vortex contains sufficient momentum to account for that added to the body with each half-stroke. The possibility is discussed that the side-to-side flexural technique may allow an interaction between body and tail flows in the production of vorticity.