bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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−&gt; Cl−&gt; 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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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 (&gt;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

ABSTRACT
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.