bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulmonary Mechanics and the Work of Breathing in the Semi-Aquatic Turtle, Pseudemys Scripta
Authors: Vitalis Timothy Z. , Milsom William K.
Published: April 2021

Measurements of pulmonary mechanics on anaesthetized specimens of the aquatic turtle Pseudemys scripta (Schoepff) indicate that the static pulmonary mechanics of the total respiratory system are determined primarily by the mechanics of the body wall rather than those of the lungs. This is also true under the dynamic conditions of pump ventilation at low pump frequencies. As pump frequency increases, the work required to inflate the multicameral lungs of the turtle begins to contribute an increasing portion to the total mechanical work required to produce each breath as measured from pressure volume loops. The rise in the work performed on the lungs results from an increase in the non-elastic, flow-resistive forces which must be overcome during ventilation. The primary bronchus to each lung is the most likely site of flow resistance. There is also a small elastic component to the work required to ventilate the lungs associated with movement of the intrapulmonary septa and the striated muscle surrounding the lungs. The contribution of the work required to distend the body cavity as a percentage of the total mechanical work required to generate each breath remains relatively unchanged with increasing ventilation frequency, indicating that the majority of the forces to be overcome in the body wall are elastic in nature. For a constant rate of minute pump ventilation, as frequency increases, the work done per minute to overcome elastic forces decreases, while that done to overcome non-elastic forces begins to rise. These opposing trends produce an optimum combination of pump volume and frequency at which the rate of mechanical work is minimum.
Kinetics of Oxygen Uptake and Release by Red Blood Cells of Chicken and Duck
Authors: Phu D. Nguyen , Yamaguchi K. , Scheid P. , Piiper J.
Published: April 2021

The specific conductance (G) for O2 transfer by red blood cells (RBCs) of chicken and muscovy duck was measured using the experimental (stopped-flow) and analytical techniques (RBC model) previously applied to human RBC (Yamaguchi, Nguyen Phu, Scheid & Piiper, 1985). Avian RBCs behaved similarly to human RBCs: G values were of similar magnitude; G for O2 uptake decreased with time and increasing O2 saturation; G for O2 release at high levels of dithionite decreased slightly with decreasing O2 saturation; G for O2 release was higher than G for O2 uptake. The deoxygenation kinetics of oxyhaemoglobin in solution was similar for both avian species.

The G measured for O2 release at high dithionite concentration, considered to represent a good approximation to intra-erythrocyte O2 diffusion conductance, averaged (in mmol min-1 Torr-1 ml-1 RBC) 0·33 for chicken and 0·25 for duck (at 41°C, pH of the suspension = 7·5, O2 saturation range 0·4-0·8). These species differences can be explained by differences in cell size, the RBC volume averaging 104, μm3 in the chicken and 155 μm3 in the duck. Compared with human RBCs, the G estimates for avian RBCs are somewhat smaller than would be predicted from size differences, which can be explained by the discoid shape of mammalian RBCs which constitutes an advantage compared with the ovoid avian RBC.
Chemoreception In Sea Anemones: Betaine Stimulates The Pre-Feeding Response In Urticina Eques and u. Felina
Authors: Boothby Kate M. , Mcfarlane Ian D.
Published: April 2021

Chemical stimulation can evoke complex behaviour patterns in sea anemones. In pre-feeding behaviour a diffusible component of food causes the oral disc to expand and the column to extend and bend from side to side. These movements may increase the chance of catching nearby food (Pollock, 1883). The response is coordinated by the ectodermal slow conduction system (SSI). In Urticina eques, food extracts that excite the pre-feeding response evoke a low-frequency series of SSI pulses; and electrical stimulation of the SSI, in the absence of food, causes pre-feeding movements (McFarlane, 1970). The SSI, the SS2 (an endodermal slow system) and a through-conducting nerve net (TCNN) are the three known conducting systems that appear to coordinate sea anemone behaviour (McFarlane, 1982). Other conducting systems have been proposed (e.g. Lawn & Ross, 1982) but not confirmed.
The Effect of Screening Pigment Migration on Spectral Sensitivity in a Crayfish Reflecting Superposition Eye
Authors: Bryceson Kim P.
Published: April 2021

In crayfish, there is some evidence that visual pigments in the eye affect the spectral sensitivity, both at the receptor level (Goldsmith & Fernandez, 1968; Kong & Goldsmith, 1977) and in the optic fibres (Woodcock & Goldsmith, 1970). However, there is a discrepancy between the absorption spectrum of rhodopsin as measured by microspectrophotometry (λmax is 530–550 nm, Goldsmith, 1978) and published measurements of spectral sensitivity [e.g. electroretinogram (ERG) peaks of 565–570 nm (Kennedy & Bruno, 1961) and intracellular recordings of 556 nm and 600–620 nm (Nosaki, 1969) and 538–634 nm (Waterman & Fernandez, 1970)]. Woodcock & Goldsmith (1970) suggested that sensitivity maxima in the orange and red were due to the non-alignment of the stimulating beam with the optical axis of the cell, thereby allowing light to filter obliquely through red and brown proximal screening pigment surrounding the rhabdom. Goldsmith (1978) showed (theoretically) that the red-brown proximal screening pigments of crayfish and lobster are indeed capable of shifting the effective absorption of the rhabdoms enough to account for the discrepancy between the absorption peak of the visual pigment and the published measurements of spectral sensitivity. However, the effect on spectral sensitivity of the migration of the proximal screening pigment has not been documented.
Short Communication Aquatic Prey Capture in Fishes: Experimental and Theoretical Approaches
Authors: Lauder George V.
Published: April 2021

In our attempts to understand how animals work, the diversity of animal design and the physiological basis of animal behaviour it is common to make theoretical models of animal function and to conduct experiments to test these models. Experimental analyses often provide a direct test of competing models, evaluate the accuracy of assumptions of models and, at a more descriptive level, simply provide increased observational precision. On the other hand, theoretical models may play an important heuristic role in suggesting new experiments and may provide a general predictive framework within which research can progress.
Changes in Membrane Potential during Adaptation to External Potassium Ions in Paramecium Caudatum
Authors: Oka Takashi , Nakaoka Yasuo , Oosawa Fumio
Published: April 2021

When Paramecium are transferred from the solution to which they have been adapted to a solution of a different K+ concentration, they initially change their swimming behaviour and then gradually recover normal swimming. This adaptation to the new solution takes 2–3 h. We found that in the process of adaptation there was a change in membrane potential: transfer of the cells to a lower K+ concentration caused depolarization of the potential, whereas transfer to a higher concentration produced a hyperpolarization. In both cases, the change in potential was followed by a gradual repolarization to the original value in the control solution. During adaptation, the intracellular concentration of K+ did not change much. It is probable that the cells change their membrane potential towards a constant level by controlling the membrane conductance for K+.
Formation of Specific Connections in Culture by Identified Leech Neurones Containing Serotonin, Acetylcholine and Peptide Transmitters
Authors: Arechiga H. , Chiquet M. , Kuffler D. P. , Nicholls J. G.
Published: April 2021

Connections made in culture by identified leech neurones have been studied using pairs of cells that contain various transmitters. These cells were: motoneurones innervating the heart; the anterior pagoda neurones (which contain both acetyl-choline and an FMRFamide-like peptide); the Retzius cells (which contain serotonin) ; and the pressure sensory neurones, which contain an unidentified transmitter. Heart motoneurones (HE) and anterior pagoda (AP) cells in culture reacted with antiserum against the peptide FMRFamide. The immunoreactive peptide was found in dense-core vesicles at presumptive sites of transmitter release. In culture the HE, AP and Retzius cells formed non-rectifying electrical synapses with one another within 2 days. Some pairs of cells made connections resembling those seen in normal leech ganglia; others formed novel connections seen only in culture. Electrical connections made by sensory P cells with HE and AP cells showed rectification. Confirming earlier results, P cells never established electrical connections with Retzius cells. In certain pairs of neurones, chemically mediated synaptic interactions developed. Thus, stimulation of AP cells evoked hyperpolarizing synaptic potentials that arose after a delay in Retzius cells and in P cells. Similarly, stimulation of HE cells gave rise to delayed, slow synaptic potentials in AP cells and in isolated heart muscle fibres in culture. P cells, which in culture are never presynaptic to Retzius cells, made chemical connections with AP cells. These results support the conclusion that identified leech neurones in culture make synaptic connections with certain specific target cells while ignoring others.
Oxygen Consumption and Luminescence of Maurolicus Photophores Stimulated by Potassium Cyanide
Authors: Mallefet J. , Baguet F.
Published: April 2021

Isolated photophores of Maurolicus muelleri, maintained in saline at 20 °C, consume oxygen at a mean rate of 1·25 ± 0·07 nmol O2 min-1(N = 50). In the presence of 5 × 10−6 mol l−1 KCN, seven preparations did not luminesce while two showed only dim luminescence. In all nine preparations, the resting oxygen consumption decreased by about 50%. In the presence of 5× 10−s mol l−1 KCN, all of the photophores produced a slow, low luminescence and their oxygen consumption decreased by about 75%. In the presence of 5× 10−4mol l−1 KCN, all of the photophores produced a slow, high luminescence and their oxygen consumption decreased rapidly by about 92%. It is suggested that the oxygen needs for light production by the isolated photophores of the mesopelagic fish, Maurolicus, differ from those of the epipelagic fish, Porichthys.
Short Communications: The Spectral Sensitivity of Nautilus Pompilius
Authors: Muntz W. R. A.
Published: April 2021

Recent studies (Muntz & Raj, 1984; Muntz, 1986) have measured the visual acuity and sensitivity of Nautilus pompilius, using two behavioural responses (the optomotor response and the positive phototactic response) which are well developed in this species. In both cases, as might be expected for an animal that has a pin-hole camera eye, vision was poor compared to that of animals that have camera eyes with lenses. Thus for visual acuity it was found that the minimum separable angle lay between 1·25° and 5·5°, compared with values between 4·9′ and 10·8′ for various species of fish (Muntz, 1974), and a value of 17′ or better for Octopus vulgaris (Sutherland, 1963), and the absolute sensitivity was estimated to be around 2 log units worse than for a typical deep-sea fish.
Short Communications: Interneurones Sensitive to Water Vibrations in the Second Abdominal Ganglion of the Crayfish
Authors: Tautz Jürgen , Hamm Iris
Published: April 2021

The body and appendages of crayfish are covered with mechanoreceptive sensory hairs which are highly sensitive to slight water movements (e.g. Wiese, 1976; Tautz & Sandeman, 1980). The central processing of this sensory input has been studied primarily in the abdominal ganglia and especially in the last (sixth) ganglion which innervates the tailfan of the crayfish (Wine, 1984). Plummer, Tautz & Wine (1986) describe the frequency selectivity of three types of mechanosensory interneurones in the sixth ganglion. The work presented here was undertaken to find out if these classes are represented in other abdominal ganglia as well.
Warm-Up and Stridulation in the Buschcricket, Hexacentrus Unicolor Serville (Orthoptera, Conocephalidae, Listroscelidinae)
Authors: Heller Klaus-Gerhard
Published: April 2021

The morphology of the stridulatory organ of the tropical bushcricket Hexacentrus unicolor is described and an investigation is made of stridulatory movements and muscle activities.

The song is produced by extremely fast stridulatory movements (320-415 Hz), during which, while closing the wings, a highly specialized file is brought into contact with the plectrum to produce sound. The muscles are activated with the same frequency, i.e. they work synchronously (neurogenic). A few minutes before the stridulation starts, the muscles are activated in a similar rhythm to that pertaining during singing (pattern of spike trains and pauses). As a result, the thorax temperature increases considerably (up to approximately 37°C, 13-15°C higher than the ambient temperature). The frequency of the muscle potentials within the spike trains rises during warm-up. There are, however, indications that no phase displacement of antagonistically working muscles takes place.
Modulation of Output from an Isolated Gastropod Heart: Effects of Acetylcholine and FMRFamide
Authors: Smith P. J. S. , Hill R. B.
Published: April 2021

In this study, two cardioactive drugs, acetylcholine (ACh) and the tetrapeptide FMRFamide, are perfused through the isolated systemic heart of the gastropod, Busycon canaliculatum. Their effect is examined in terms of the regulation of output, and is then related to the in vivo regulation of stroke volume.

ACh decreases cardiac output by reducing both stroke volume and heart rate. End-diastolic volume and cardiac reserve increase with drug concentration. These effects are accompanied by a slowing in the rise time of the electromyogram prepotential and an increase in the duration of the plateau phase. Low concentrations of FMRFamide increase output by accelerating the heart rate. Stroke volume is only affected at higher concentrations (5× 10−7moll−1), and then negatively. End-diastolic volume is reduced. Between 10−9 and 10−8moll−1, FMRFamide increases the rise time of the prepotential and the amplitude of the plateau; the duration of the plateau is markedly shortened. At 5× 10−7mol l−1 and above, the plateau is extended and the cardiac reserve is reduced to zero. The two drugs have opposite effects on the characteristics of the aortic pressure pulse: ACh reduces the amplitude of the pulse, but increases its duration.
The Electrical Constants of the Fibres from Two Leg Muscles of the Locust Schistocerca Gregaria*
Authors: Kornhuber M. E. , Walther C.
Published: April 2021

The passive electrical properties of the fibres from the M. extensor tibiae and the M. retractor unguis in the hindleg of the locust Schistocerca gregaria were investigated using short cable theory. The dependence on various physicochemical parameters was determined. The sarcoplasmic resistivity (R,) was the same in the extensor and in the retractor muscle. R, was ≈175 Ωcm at 20°C. The specific membrane resistance (Rm) was considerably lower in the retractor muscle (≈5100 Ωcm2) than in the extensor muscle (≈13 000 Ωcm2; [K+]o = 10mmoll−1; temperature = 20°C). Rm increased by more than 100% if the external potassium concentration was lowered from 10 to 5 mmol l−1 and it decreased by approximately 75 % if the calcium concentration was lowered from 2 to 0·2 mmol l−1. The specific membrane capacity (Cm) increased with fibre diameter. The different mean values for Cm in the extensor (8·5μFcm−2) and retractor muscle (6·3 μF cm−2) can be accounted for by the different mean fibre diameters. The temperature coefficients (Q10) of the electrical constants were 0·74 for Ri, 0·48 for Rm, 1·01 for Cm and 1·21 for the resting membrane potential (temperature, 16– 27 °C). There was close agreement between the membrane time constant (rm) derived from the decay of the excitatory junction potential (EJP) and that derived from injection of current pulses. Thus Rm and the length constant (λ) can be derived from the EJP and the fibre diameter if the sarcoplasmic resistivity and the specific membrane capacity are known. The temporospatial dependence of miniature EJPs in a fibre can be predicted satisfactorily from the electrical constants as is demonstrated by an example given in the Appendix.
Stretch Activation of a K+ Channel in Molluscan Heart Cells
Authors: Sigurdson Wade J. , Morris Catherine E. , Brezden Borys L. , Gardner David R.
Published: April 2021

Heart ventricle cells of Lymnaea stagnalis contain a stretch-activated K+ channel which exhibits two open states and three closed states. Over the range 0 to –25 mmHg (1 mmHg = 133·3 Pa), the probability that the channel is open is a steeply non-linear function of negative pressure. Pressure-dependent decreases in the mean times of the longest component of the closed-time distribution are observed in the same range and (because other mean times show no consistent or sufficiently large changes with pressure) are assumed to account for increases in the probability of being open. Channel activity characteristically occurs as bursts with a mean time of 3·6ms. These bursts contain, on average, 1·7 closings; 78% of the burst time is spent in the open state. It is concluded that the stretch-sensitive kinetic component is an interburst closed state.
Potassium Activity Measurements in the Microenvironment of the Central Nervous System of an Insect
Authors: Hendy C. H. , Djamgoz M. B. A.
Published: April 2021

The activity of K+ and the control of influx of K+ into the extracellular space (micro-environment) of the central nervous system of the cockroach, Periplaneta americana, were measured directly with K+-sensitive microelectrodes. Using an in vivo preparation, it was possible to follow the effects of changes in K+ concentration in the medium bathing the nervous system on extracellular K+ and spontaneous and evoked neuronal activity. For bath K+ levels less than 31 mmol I−1, roughly corresponding to maximal haemolymph level in natural physiological conditions, the blood-brain barrier was found to be suitably efficient in restricting the influx of K+ and thereby allowing normal neural activity. At an external K+ concentration of 100 mmol I−1, however, the system was unable to maintain a sufficiently low extracellular K+ concentration and neuronal activity was suppressed. Influx of K+ from the external medium into the micro-environment occurred mainly in two phases. The early phase had a fast time course and probably reflects the physical aspects of the blood-brain barrier. The later, second phase was a slower process possibly corresponding to activation of metabolic ion pumps. The time courses of the functioning of these two systems and their control of the extra-axonal K+ activity are also discussed.
Surface and Subsurface Swimming of the Sea Snake Pelamis Platurus
Authors: Graham Jeffrey B. , Lowell William R. , Rubinoff Ira , Motta Jorge
Published: April 2021

During anguilliform swimming at the surface, four half waves are present along the body of the yellow-bellied sea snake Pelamis platurus (Hydrophiidae). As in other anguilliform swimmers, wave amplitude increases towards the tail; however, the relative caudal amplitude of P. platurus is less than that of the aquatic snakes Natrix and Nerodia and the eel Anguilla. Kinematic analyses of near-surface swimming at 15 and 32cms−1 were made from high-speed ciné films, and Lighthill’s bulk momentum hydromechanical model was used to calculate swimming thrust power at these two velocities. The total thrust power generated by a 51 cm snake is 3·641 × 10−4 J s−1 at 15 cms−1 and 29·877× 10−4 J s−1 at 32 cm s−1, with respective Froude efficiencies of 79% and 81%. Subsurface swimming velocities are low (2–4 cm s−1), and snakes usually assume a posture in which the tail is elevated and the posterior part of the body assumes a nearly vertical orientation. Undulatory movements by snakes swimming in this posture involve torsional and rolling motions of the body which, through changes in the camber of the keel and body, may contribute to thrust.
The Telson Flexor Neuromuscular System of the Crayfish: II. Segment-Specific Differences in Connectivity Between Premotor Neurones and the Motor Giants
Authors: Dumont J. P. C. , Wine J. J.
Published: April 2021

The telson and sixth ganglion of the crayfish contain a fast flexor system that is homologous to that found in anterior segments, but doubled (Dumont & Wine, 1986a). In this paper we document differences in connections to the motor giants (MoGs) in the telson as compared to the MoGs in the anterior five abdominal segments. Unlike their homologues in anterior segments, the telson MoGs receive excitatory input via a trisynaptic pathway that is activated by the escape command axons, the lateral and medial giants (LGs and MGs), and includes the identified corollary discharge interneurones 12 and 13. For 13, at least, the connection to the MoGs is monosynaptic, electrical and rectifying, and is sufficiently strong that simultaneous activation of the two I3s alone fires the telson MoGs. The trisynaptic pathway from the LGs to the telson MoGs is inhibited by central, command-derived, postsynaptic inhibition of the telson MoGs, which typically arrives earlier than the excitation. In experimental preparations, this inhibition can be partially circumvented by stimulating the LGs anywhere anterior to the third abdominal ganglion. This is possible because the polysynaptic excitatory pathway is recruited in the third ganglion, while inhibition is recruited by the LGs locally in the sixth ganglion. Hence the site of impulse initiation in the LG affects the relative timing of excitation and inhibition of the telson MoGs. This arrangement makes it possible, in principle, for the site of impulse initiation in the LG to affect the form of the resulting tailflip. In dissected preparations, LG impulses initiated anterior to the third ganglion fired the telson MoGs in 16 out of 25 experiments, while impulses initiated posteriorly never fired the telson MoGs (nine experiments). Behavioural studies indicate that anterior stimuli which evoke LG activity do not cause activation of the telson MoGs. We suggest that in intact animals inhibition of the telson MoGs is more effective than in physiological preparations. As far as we can tell from available evidence, the 13 input to the telson MoG is never expressed, and therefore cannot be explained in functional terms. We suggest that the differences between the inputs to the MoGs of the telson and of the fourth and fifth ganglia is the incidental result of developmental constraints during evolution.
The Relationship Between Dive and Pre-Dive Heart Rates in Restrained and Free Dives by Diving Ducks
Authors: Furilla R. A. , Jones David R.
Published: April 2021

Dive heart rate was plotted against pre-dive heart rate in forced and voluntary dives and dabbles by restrained and free ducks. The relationship between pre-dive heart rate and the cardiac interval occurring just before or coincident with submersion (first cardiac interval) and the heart rate after 2–5 s submergence (stabilized heart rate) was emphasized. Stabilized heart rate in forced dives by restrained ducks at rest and at the end of a bout of exercise, and heart rate in voluntary dives and dabbles were linearly related on a plot of dive heart rate against the logarithm of predive heart rate. Even the heart rate occurring 2–5 s after ducks were ‘trapped’ under water, compared with the rate immediately before ‘trapping’, fitted on this line. The line was described by the equation y = – 451+2461ogx where y is dive (or trapped) and x is pre-dive (or pre-trap) heart rate (r2 = 0-98). The relationship was unaltered by β-blockade with propranolol. Furthermore, nasal blockade with Xylocaine, O2 breathing before submersion, and arterial baroreceptor denervation had no marked effect on the relationship in voluntary and trapped dives. Implantation of stimulating electrodes bilaterally on the cut distal ends of vagal and cardiac sympathetic nerves suggested that in all these dives there is a similar increase in the level of efferent vagal activity during submersion. However, the first cardiac interval in voluntary dives represents a much lower heart rate and therefore higher level of vagal activity. The present data suggest that there is considerable psychogenic modulation of cardiac responses in voluntary diving and only in forced dives, by restrained animals, is cardiac control largely reflexogenic.
Membrane-Potential-Sensitive, Na+ -Independent Lysine Transport by Lobster Hepatopancreatic Brush Border Membrane Vesicles
Authors: Ahearn Gregory A. , Clay Laurel P.
Published: April 2021

Transport of L-[3H]lysine by epithelial brush border membrane vesicles (BBMV) of lobster hepatopancreas, formed by a magnesium precipitation technique, was insensitive to transmembrane gradients of Na+, K+, TMA+ or H +. Apparent initial lysine entry rates (15 s uptake) and extent of amino acid accumulation against a concentration gradient (overshoot) were both stimulated by transmembrane anion gradients according to the following sequence: SCN−> Cl−> gluconate−. The magnitude of this anion-gradient-dependent transport was significantly increased by bilateral acidic pH. Lysine transport at acidic pH strongly responded to transmembrane potential developed by addition of valinomycin to K+-loaded vesicles, or was markedly reduced if K+-equilibrated vesicles were incubated with the ionophore in the presence of an inwardly directed SCN− gradient. Lysine influx occurred by the combination of at least one carrier process and ‘apparent diffusion’. L-Arginine, L-alanine and L-leucine, added to the external medium, were all strong inhibitors of lysine influx. The first two were competitive inhibitors of lysine entry, while the latter was non-competitive in effect. These results suggest that lysine, arginine and alanine may share a common, Na+-independent, membrane-potential-sensitive transport mechanism in lobster BBMV. Leucine transport may occur in these membranes by a separate agency.
Instantaneous Oxygen Consumption and Muscle Stroke Work in Malacosoma Americanum During Pre-Flight Warm-Up
Authors: Casey Timothy M. , Hegel-Little Jeri R.
Published: April 2021

Instantaneous rates of oxygen consumption , thoracic temperature (Tth) and wing stroke frequency (n) were continuously measured at several ambient temperatures (T2) during pre-flight warm-up and subsequent cooling in a small volume (30 ml), open flow (240–300 ml min−1) respirometer. Heat production (HP) was tightly coupled to Tth and independent of T2. The rate of change of HP (mWmin−1) was directly related to T2. Total cost of warm-up was strongly, inversely related to Ta. The energetic cost of cooling was a small fraction of the total cost of warm-up. Increased energy expenditure occurred as a result of increases in both n and stroke work input. The latter increased from 0·58 to 1·1 mJ stroke−1 at low Tth (13–25°C) and was essentially constant at higher Tth (25–40°C). Wing stroke frequency increased continuously and linearly with Tth. In contrast to previous estimates based on heat exchange analyses, stroke work during warm-up was equivalent to values measured during free hovering flight. These data are consistent with the hypothesis that energy expenditure is maximized during warm-up.
Ionic Mechanism of Thermoreception in Paramecium
Authors: Nakaoka Yasuo , Kurotani Tohru , Itoh Hirokazu
Published: April 2021

The localization of thermoreceptors in Paramecium, and the ionic basis of thermoreception, was investigated in posterior and anterior fragments of cells. Transverse section of the animals was used to obtain these fragments, which sealed up and swam actively. In the anterior fragment, an increase in the frequency of directional changes in swimming and depolarization of the membrane was produced by cooling below the temperature of the culture. In the posterior fragment, these effects were produced by wanning above culture temperature. Reversal potentials of these effects were found by injection of constant current to change membrane potential. In the anterior fragment, the reversal potential of the response to cooling was more negative than the resting potential and was potassium-dependent (52 mV/ log[K+]0). In the posterior fragment, the reversal potential of the warming response was above resting potential and was primarily calcium-dependent (28 mV/ log[Ca2+]0). It is concluded that cooling results in changes in the frequency of directional changes in swimming of Paramecium by causing a transient change in the membrane conductance for potassium, whereas warming produces its effects by a transient change in calcium conductance.
Regulation of ecdysone biosynthesis in the tobacco hornworm, Manduca sexta: titre of the haemolymph stimulatory factor during the last larval instar
Authors: Watson R. D. , Williams T. K. , Bollenbacher W. E.
Published: April 2021

A recently isolated haemolymph protein appears to be an important regulator of ecdysone biosynthesis by prothoracic glands in Manduca sexta. Using a dose-response titration protocol, the haemolymph titre of this stimulatory factor was determined during the last larval instar. The titre was high (>2·0UmU1) on days0 and 1, then dropped significantly to 0·55 U ml-1 on day 2, and remained depressed until day 4. The titre of the stimulatory factor then increased to a peak of 1·62U ml-1 on day 7, and remained elevated (approx. 1·1 U ml-1) until the end of the instar. A set of physical and biochemical criteria was used to confirm that the stimulatory activity present in haemolymph on different days of the instar rep-resented the presence of the factor. The data are consistent with the hypothesis that fluctuations in the titre of the haemolymph stimulatory factor play a critical role in regulating ecdysone biosynthesis during larval-pupal development.
Cuticular mechanics during larval development of the tobacco hornworm, Manduca sexta
Authors: Wolfgang W. J. , Riddiford L. M.
Published: April 2021

Tensile properties of the larval cuticle of Manduca sexta were measured during the fifth instar. It was found that as the larvae grew and the cuticle thickened, the tangent modulus (intrinsic stiffness) for the cuticle declined rapidly. The extensibility of the cuticle during the growth period remained relatively high and fairly constant, while the flexural stiffness remained low. Subsequently, during the wandering and burrowing stage the extensibility decreased dramatically. Finally, in the prepupal stage extensibility remained low while flexural stiffness was highest. Using the cuticle deposition inhibitor diflubenzuron we demonstrated that the increase in larval cuticular flexural stiffness was required for normal pupation to proceed. Thus, during larval growth the cuticle remains flexible and extensible. Once growth is completed, the cuticle becomes much less extensible and more rigid, converting the previously hydrostatic skeleton into a self-supporting skeleton. This conversion was associated with changes in cuticular structure, hydration and protein composition.
Flight of Auks (Alcidae) and Other Northern Seabirds Compared with Southern Procellarhformes: Ornithodolite Observations
Authors: Pennycuick C. J.
Published: April 2021

Airspeeds in flapping and flap-gliding flight were measured at Foula, Shetland for three species of auks (Alcidae), three gulls (Landae), two skuas (Stercorariidae), the fulmar (Procellariidae), the gannet (Sulidae) and the shag (Phalacrocoracidae). The airspeed distributions were consistent with calculated speeds for minimum power and maximum range, except that observed speeds in the shag were unexpectedly low in relation to the calculated speeds. This is attributed to scale effects that cause the shag to have insufficient muscle power to fly much faster than its minimum power speed. The wing adaptations seen in different species are considered as deviations from a ‘procellariiform standard’, which produce separate effects on flapping and gliding speeds. Procellariiformes and the gannet flap-glide in cruising flight, but birds that swim with their wings do not, because their gliding speeds are too high in relation to their flapping speeds. Other species in the sample also do not flap-glide, but the reason is that their gliding speeds are too low in relation to their flapping speeds.
The effects of forced activity on circulating catecholamines and pH and water content of erythrocytes in the toad
Authors: Tufts B. L. , Mense D. C. , Randall D. J.
Published: April 2021

In vivo experiments were carried out to determine the effect of forced activity on circulating catecholamine levels, haematocrit, and the pH and water content of erythrocytes in the toad, Bufo marinus. In addition, the effect of the beta-adrenergic agonist isoproterenol on erythrocte pH and water content was examined in vitro.

Forced activity caused a significant decrease in both whole blood and erythrocyte pH, while haematocrit and circulating adrenaline and noradrenaline levels increased. Erythrocyte water content did not change following forced activity. Addition of isoproterenol to toad blood in vitro had no effect on either erythrocyte pH or water content. The apparent absence of beta-adrenergic effects on erythrocyte pH and water content in the toad is in sharp contrast to the response of teleost fish erythrocytes to beta-adrenergic stimulation. The significance of these differences is discussed.
Evidence that myoglobin does not support heart performance at maximal levels of oxygen demand
Authors: Canty AA , Driedzic WR
Published: April 2021

Myoglobin binds reversibly with oxygen and can facilitate oxygen diffusion across artificial membranes in vitro (Wittenberg, 1970). Myoglobin-enhanced oxygen consumption in heart is particularly important under conditions of hypoxia. This has been established directly with fish heart models (Bailey & Driedzic, 1986; Driedzic, Stewart & Scott, 1982) and indirectly by following discharge of high-energy phosphates in rat heart (Taylor, Matthews & Radda, 1986). Simple mathematical models are consistent with the importance of myoglobin during hypoxia and, in addition, predict that the protein should play a role in the support of oxygen consumption at maximal rates of respiration (Meyer, Sweeney & Kushmerick, 1984). In this study, the hypothesis that myoglobin-enhanced oxygen consumption is vital in meeting the demands of elevated levels of respiration by a teleost heart is tested indirectly. Myoglobin’s importance was assessed by monitoring isometric force development of ventricle strips from sculpin bathed in media with a constant level of either 21 % or 1 % O2. Additions to the bathing media included 2,4-dinitrophenol (DNP) to uncouple mitochondria and induce maximal oxygen consumption, and hydroxylamine which effectively converts myoglobin into the iron III form incapable of binding oxygen (Driedzic, 1983; Wittenberg, Wittenberg & Caldwell, 1975). The major finding is that myoglobin does not play a critical role in the maintenance of performance under normoxia at maximal rates of oxygen consumption.
Energy Partitioning in Fish: The Activityrelated Cost of Osmoregulation in a Euryhaline Cichlid
Authors: Febry Ricardo , Lutz Peter
Published: April 2021

We have investigated how the maintenance, net cost of swimming and total (maintenance + net cost of swimming) metabolic rates of red, hybrid tilapia (Oreochromis mossambicus ♀ × O. homorum ♂) responded to different acclimation salinities, and if these responses correlated with changes in ion-osmoregulation (= osmoregulation) costs.

Three groups of fish were acclimated to either fresh water (FW, 0‰), isosmotic sea water (ISW, 12‰) or full strength sea water (SW, 35 ‰) and oxygen consumption was measured while they swam at 10, 20, 30 and 40cms−1. Maintenance oxygen consumption (estimated by extrapolation), for an average fish (63g), increased among groups in the following order: FW < ISW < SW. The net cost of swimming increased in the order ISW < SW < FW, and total oxygen consumption (maintenance + net cost of swimming) increased in the order ISW < FW < SW.

We assumed that the contribution of cardiac, branchial and swimming muscles to the net cost of swimming was proportional to swimming speed only, and therefore, at similar speeds, differences in the net cost of swimming among salinities were due to changes in the activity-related cost of osmoregulation. Consequently, the order in which the net cost of swimming increases from one group to another is the same as the order in which the cost of osmoregulation increases. Since the sequences for maintenance and total metabolic rates differed from that for the net cost of swimming, salinity-related increases in these rates cannot be attributed exclusively to changes in osmoregulation cost.

We conclude, based on the differences in the net cost of swimming, that osmoregulation in FW is more expensive than in SW, and that it is cheapest in ISW. Although we were not able to estimate the total cost of osmoregulation in FW and SW, we estimated the activity-related cost, relative to the cost in ISW, at different swimming speeds (net cost of swimming in FW or SW minus net cost of swimming in ISW at each speed). For a 63-g fish in FW, this cost increased from zero at rest, to 41 mgO2kg−1 h−1 (16% of the total metabolic rate, 24% of the net cost swimming) at 40 cm s−1. In SW the same cost increased only to 32 mg O2 kg−1 h−1 ( 12 % of the total metabolic rate, 20% of the net cost of swimming) at 40cms−1. The net cost of swimming in FW or SW increased with swimming speed at a rate 3-4 times faster than the rate of increase in osmoregulation costs, suggesting that the latter did not limit the delivery of oxygen to the swimming, and other supporting, muscles.
Coronary flow in a perfused rainbow trout heart
Authors: Farrell A. P.
Published: April 2021

A preparation was developed to perfuse the coronary circulation in working hearts from rainbow trout (Salmo gairdneri Richardson). The preparation was used to examine pressure–flow relationships for the coronary circulation as the heart generated physiological and subphysiological work loads. Coronary vascular resistance increased exponentially as coronary flow rate decreased. Coronary resistance was also influenced by cardiac metabolism and acclimation temperature. When heart rate was increased, extravascular compression increased in coronary resistance. Direct vasoconstriction of the coronary vessels, produced by injections of adrenaline into the coronary circulation, was temperature-dependent.
Apical Membrane Permeability of Mytilus Gill: Influence of Ultrastructure, Salinity and Competitive Inhibitors on Amino Acid Fluxes
Authors: Wright Stephen H. , Secomb Timothy W. , Bradley Timothy J.
Published: April 2021

The apical membrane of gill integumental cells from the mussels Mytilus edulis and M. californianus serves as a permeability barrier separating sea water from a cytoplasm rich in amino acids and other small organic molecules. Morphometric analysis of transmission electronmicrographs indicates that the membrane area of these cells is increased between 10-and 18-fold by the presence of a microvillous brush border. The microvilli do not appear to influence the kinetics of solute transport across the cell apex, as determined using a mathematical model of the relationship between membrane structure and the kinetics of transport. Rates of amino acid loss from the integument were low, and estimates of the upper limit of the passive permeability of the apical membrane to amino acids ranged from 0·5 to 10 × 10−10 cm s−1. Abrupt exposure of intact mussels or isolated gill tissue to 60 % sea water (19%o salinity) resulted in a transient, 40-to 80-fold increase in the rate of loss of all amino acids from integumental tissues. Upon exposure to full-strength sea water, efflux rates returned to near control values. Exposure to 60 % sea water also inhibited the carrier-mediated accumulation of amino acid: uptake of 0·5 μmol l−1 [l4C]alanine and [14C]taurine was reduced by 80% compared to control uptake in 100% sea water. This inhibition was not adequate to account for the increase in net efflux of taurine from gill tissue into 60% artificial sea water (ASW), though the inhibition of alanine uptake may have contributed significantly to the increased loss of this amino acid. Efflux of discrete structural classes of amino acid occurred when integumental tissues were exposed to 50 μmol l−1 concentrations of structurally related analogues. It is concluded that the apical membrane of gill cells has a very low passive permeability to amino acids, and that the overall permeability of the gill can be increased in a reversible fashion by exposure to reduced salinity or to high external concentrations of amino acid.
Phenyliminoimidazolidine Derivatives Activate Both Octopamine1 and Octopamine2 Receptor Subtypes in Locust Skeletal Muscle
Authors: Evans Peter D.
Published: April 2021

The actions of the phenyliminoimidazolidine derivatives, NC7 and NC5 on octopamine receptors in the extensor-tibiae neuromuscular preparation of the locust are described. The derivatives activate both OCTOPAMINE1 and OCTOPAMINE2 receptors in this preparation. They are not selective agonists of OCTOPAMINE2 receptors that activate adenylate cyclase. The relative potencies of NC5 and NC7 on OCTOPAMINE1 and OCTOP-AMINE2 receptors differ, suggesting that they may be useful in the development of selective agonists that can distinguish between the different pharmacological subclasses of octopamine receptor. The octopamine-mediated increases in cyclic AMP levels in this preparation can be separated into high-and low-affinity components. NC5 and NC7 appear to activate the high-affinity component of this response selectively.
Effects of Wing Campaniform Sensilla Lesions on Stridulation in Crickets
Authors: Schäffner Karl-Heinz , Koch Uwe T.
Published: April 2021

The degradations in the cricket’s calling song after lesions of the cubital campaniform sensilla (CCS) are investigated using extracellular recording and angular movement recording techniques. In the intact male, nerve potentials from the CCS during the closing stroke are demonstrated. In the lesioned male, syllable shortenings and missing syllables can be traced to abnormalities in the wing motion: irregular stops (‘sticking’), anomalously high closing speeds with sound emission (‘overspeed’), or high closing speeds without sound emission (‘slipping’) are observed. Despite these defects, the activation pattern of the main opener and closer muscles remains completely unaffected. The defects are interpreted as disturbance of a regulatory system normally maintaining proper engaging forces of the wings.
Do cardiorespiratory frequencies show entrainment with hopping in the tammar wallaby?
Authors: Baudinette R. V. , Gannon B. J. , Runciman W. B. , Wells S. , Love J. B.
Published: April 2021

Breathing, heart and gait frequencies, tidal volume, cardiac output, and rates of oxygen consumption were measured in tammar wallabies (Macropus eugenii Desmarest) hopping on a treadmill. At speeds greater than 1·6 ms−1 the rate of metabolic power consumption was independent of hopping speeds. Blood lactate levels within the speed range where was independent of speed showed a mean increase of 4·8 mmol l−1. During bipedal hopping, the frequencies of breathing and limb movement are phase-locked in the ratio of 1:1. Inspiration begins as the animal leaves the ground and may be a passive process driven by a visceral piston. A relatively large central tendon in the diaphragm may correlate this function. Unlike breathing frequencies, cardiac frequencies show no entrainment with hopping. The site of dissipation of the presumed large arterial pressure excursion is unknown.
Single nephron function of the lesser spotted dogfish, Scyliorhinus canicula, and the effects of adrenaline
Authors: Brown J. A. , Green C.
Published: April 2021

Function of the kidney and the nephron in the lesser spotted dogfish, Scyliorhinus canicula, was investigated by clearance, renal tubular micropuncture and ferrocyanide infusion techniques. 70% of the glomerular filtrate was reabsorbed within the renal tubule, producing slightly hypotonic urine. Glomeruli were: perfused and filtering (F); arterially perfused but not filtering (NF); or non-arterially perfused and hence not filtering (NP). Adrenaline reduced the proportion of filtering glomeruli from 94% to 70%. Despite this reduction, a marked overall glomerular diuresis occurred. Single nephron glomerular filtration rates (SNGFRs) ranged from 1·5 to 26 nl min−1 with a mean rate of 9·5 nl min−1 during control periods. Adrenaline elevated SNGFR to a mean value of 22·9 nl min−1 (range 2·4–64·6 nl min−1). Tubular fluid/plasma inulin concentration ratios (TF/Pin) indicated reabsorption of around 74% of the glomerular filtrate by the proximal segments. Comparison of TF/P and urine/plasma inulin concentrations (U/Pin) strongly suggests tubular secretion of water beyond the point of puncture. Adrenaline infusion appears to increase both proximal water reabsorption and distal tubular secretion.
The Physiology of Compensation by Locusts for Changes in Dietary Protein
Authors: Abisgold J. D. , Simpson S. J.
Published: April 2021

Previous work has demonstrated that fifth-instar nymphs of Locusta migratoria L. respond to differences in levels of dietary protein by altering intermeal interval but not meal size (Simpson & Abisgold, 1985): insects fed a diet with 14% protein (p) eat the same sized meals more frequently than those fed a diet with 28% protein (P). The physiological basis for this compensatory response is investigated. Insects fed the P-diet had a significantly larger increase in blood osmolality during and after a meal than did those fed the p-diet. Unexpectedly, this difference in blood osmolality did not result in a variation in the rate at which the fore-, mid- and hindgut emptied. Therefore a change in the rate of decline in negative feedback from gut stretch receptors does not underlie the alteration in interfeed interval. 40 % of the difference in blood osmolality between p- and P-fed insects was attributable to changes in the blood concentration of free amino acids. Of the 16 free amino acids found, 11 occurred in significantly higher concentrations in the blood of P-fed insects. There was no significant difference in the polypeptide and protein content of the blood of insects fed the p- or P-diet. Increasing either blood osmolality or free amino acid concentration by injection delayed the next meal:injections that increased both had the greatest effect. A mechanism is discussed whereby both blood osmolality and the concentration of various free amino acids regulate the time between meals, and thus compensatory feeding in response to changes in dietary protein.