bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thoracic Connections Between Crayfish Giant Fibres and Motor Giant Neurones Reverse Abdominal Pattern
Authors: Heitler W. J. , Fraser K. 
Published: April 2021

ABSTRACT
The escape tail-flip of the crayfish is ‘commanded’ by two bilaterally paired sets of giant fibre (GF) interneurones, the lateral giant (LG) and medial giant (MG) (see e.g. Wine, 1984, for a review). The two classes of GF respond to different stimuli and initiate tail-flips with different kinematic forms. An arousal stimulus applied to the front of the animal initiates a spike in the MG system, and this causes a tail-flip that drives the animal directly backwards, away from the stimulus. An arousal stimulus applied to the rear of the animal initiates a spike in the LG system, and this causes a tail-flip that drives the animal upwards and forwards, again moving it away from the stimulus. The major motor output path from the GFs is through monosynaptic rectifying electrical connections to a class of powerful trunk flexor motor neurones called the motor giant (MoG) neurones (Furshpan and Potter, 1959a). There is one MoG neurone in each hemisegment of the thorax and abdomen.
Vision in the Ctenid Spider Cupiennius Salei: Spectral Range and Absolute Sensitivity
Authors: Barth Friedrich G. , Nakagawa Takanao , Eguchi Eisuke 
Published: April 2021

ABSTRACT
Electroretinograms were recorded from all eyes of the wandering spider Cupiennius salei (Ctenidae) and were found to be simple cornea-negative potential differences with amplitudes of up to 10mV. In both the principal eyes and all of the secondary eyes, the spectral response curves show a prominent green peak at 520 or 540nm and a shoulder in the ultraviolet between 340 and 380nm. The largest response in the ultraviolet measures between 65% and 80% of the green peak. Selective chromatic adaptation to either green or ultraviolet monochromatic light does not change these relative response levels and fails to indicate the presence of more than one spectral type of receptor. In the range 450–500nm, however, the Dartnall curve clearly deviates from the spectral sensitivity (SS) curve. Since the SS curves of all eyes have a small shoulder in the blue at 480nm, the existence of two or even three visual pigments is a possibility. Intensity curves were determined with white and monochromatic light. For white light, absolute corneal illuminance thresholds were clearly below 0.01lx. For monochromatic light stimuli, a corneal illuminance of approximately 3×1012 photonscm−2 s−1 is needed to elicit a half-maximal response. At threshold, the equivalent value is 3×109 photonscm−2 s−1, which corresponds to a retinal illuminance of 5.9×109 photonscm−2 s−1. Consequently, Cupiennius salei should be able to use its visual sense not only shortly after sundown but also under much poorer light conditions, such as those provided by moonlight. The log–linear response range of all eyes covers a stimulus intensity range of 4logunits. The sensitivity of the principal eyes increases by up to 0.81logunits at night as compared with daytime. The chromophore of the visual pigment of all eyes is 11-cis retinal.
The Effects of Altered Aquatic and Aerial Respiratory Gas Concentrations on Air-Breathing Patterns in a Primitive Fish (Amia Calva)
Authors: Hedrick Michael S. , Jones David R. 
Published: April 2021

ABSTRACT
The mechanisms and physiological control of air-breathing were investigated in an extant halecomorph fish, the bowfin (Amia calva). Air flow during aerial ventilation was recorded by pneumotachography in undisturbed Amia calva at 20–24°C while aquatic and aerial gas concentrations were independently varied. Separation of aquatic and aerial gases was used in an attempt to determine whether Amia calva monitor and respond to changes in the external medium per se or to changes in dissolved gases within the body. Air flow measurements revealed two different types of ventilatory patterns: type I air-breaths were characterized by exhalation followed by inhalation; type II air-breaths, which have not been described previously in Amia calva, consisted of single inhalations with no expiratory phase. Expired volume (Vexp) for type I breaths ranged from 11.6±1.1 to 26.7±2.9mlkg−1 (95% confidence interval; N=6) under normoxic conditions and was unaffected by changes in aquatic or aerial gases. Gas bladder volume (VB), determined in vitro, was 80mlkg−1; the percentage of gas exchanged for type I breaths ranged from 14 to 33% of VB in normoxia.
Fish exposed to aquatic and aerial normoxia , or aerial hypercapnia in normoxic water, used both breath types with equal frequency. Aquatic or aerial hypoxia significantly increased air-breathing frequency in four of eight fish and the ventilatory pattern changed to predominantly type I air-breaths (75–92% of total breaths). When fish were exposed to 100% O2 in the aerial phase while aquatic normoxia or hypoxia was maintained, air-breathing frequency either increased or did not change. Compared with normoxic controls, however, type II breaths were used almost exclusively (more than 98% of total breaths).
Type I breaths appear to be under feedback control from O2-sensitive chemoreceptors since they were stimulated by aquatic or aerial hypoxia and were nearly abolished by aerial hyperoxia. These results also indicate that Amia calva respond to changes in intravascular ; however, externally facing chemoreceptors that stimulate air-breathing in aquatic hypoxia cannot be discounted. Type II air-breaths, which occurred in aerial hyperoxia, despite aquatic hypoxia, appear to be stimulated by reductions of VB, suggesting that type II breaths are controlled by volume-sensitive gas bladder stretch receptors. Type II breaths are likely to have a buoyancy-regulating function.
Positive Coupling of β-Like Adrenergic Receptors With Adenylate Cyclase In The Cnidarian Renilla Koellikeri
Authors: Awad Edward W. , Anctil Michel 
Published: April 2021

ABSTRACT
Coupling of the previously characterized β1-and β2-like adrenoceptors in the sea pansy Renilla koellikeri with adenylate cyclase was examined in membrane preparations from this cnidarian. Adenylate cyclase activity was stimulated by several guanine nucleotides, such as GTP, Gpp(NH)p and GTPγS. Fluoride ions and cholera toxin greatly enhanced the enzyme activity, whereas forskolin had no effect on basal or isoproterenol-induced stimulation of the enzyme. The stimulation of adenylate cyclase activity by several β-adrenergic agonists in different parts of the animal reflected a positive coupling with the β2-and β1-like adrenoceptors in autozooid and peduncle tissues, respectively. In addition, isoproterenol-induced stimulation of adenylate cyclase activity was dependent on guanine nucleotides, suggesting coupling mediated by a G protein. The pharmacological profile of various antagonists on isoproterenol-sensitive adenylate cyclase in autozooid and peduncle tissues matched that of previous radioligand binding studies. Isoproterenol-induced stimulation of adenylate cyclase activity in rachidial tissues was partially inhibited by trifluoperazine or (±)CGP12177 and was completely blocked in the presence of both antagonists. This suggests that coupling of the enzyme occurs with β1-and β2-like adrenoceptors, both being present in the rachis. Serotonin and dopamine were also found to stimulate adenylate cyclase activity. Their stimulatory effect was additive to isoproterenol-induced activation, suggesting the presence of dopaminergic and serotonergic receptors in the tissues of the sea pansy. Along with the data presented previously on β-adrenergic binding, this study suggests that elements of receptor-dependent G protein signal transduction originated early in invertebrate evolution.
Myotomal Muscle Function at Different Locations in the Body of a Swimming Fish
Authors: Altringham J. D. , Wardle C. S. , Smith C. I. 
Published: April 2021

ABSTRACT
We describe experiments on isolated, live muscle fibres which simulate their in vivo activity in a swimming saithe (Pollachius virens). Superficial fast muscle fibres isolated from points 0.35, 0.5 and 0.65bodylengths (BL) from the anterior tip had different contractile properties. Twitch contraction time increased from rostral to caudal myotomes and power output (measured by the work loop technique) decreased. Power versus cycle frequency curves of rostral fibres were shifted to higher frequencies relative to those of caudal fibres. In the fish, phase differences between caudally travelling waves of muscle activation and fish bending suggest a change in muscle function along the body. In vitro experiments indicate that in vivo superficial fast fibres of rostral myotomes are operating under conditions that yield maximum power output. Caudal myotomes are active as they are lengthened in vivo and initially operate under conditions which maximise their stiffness, before entering a positive power-generating phase. A description is presented for the generation of thrust at the tail blade by the superficial, fast, lateral muscle. Power generated rostrally is transmitted to the tail by stiffened muscle placed more caudally. A transition zone between power generation and stiffening travels caudally, and all but the most caudal myotomes generate power at some phase of the tailbeat. Rostral power output, caudal force, bending moment and force at the tail blade are all maximal at essentially the same moment in the tailbeat cycle, as the tail blade crosses the swimming track.
Regulation of Body Fluid Compartments During Dehydration of the Tenebrionid Beetle Rhytinota Praelonga
Authors: Zachariassen Karl Erik , Einarson Sigrun 
Published: April 2021

ABSTRACT
Tenebrionid beetles are an important element of the fauna on the African dry savanna. In contrast to the majority of savanna insect groups, which spend the dry season as larvae, the tenebrionids pass the dry season as adults. The adult tenebrionids probably feed on dry plant material and detritus (Louw and Seely, 1982), and they may undergo severe dehydration during the dry season (authors’ observation), probably because of their limited access to water.
Taurine Transport Characteristics of the Embryonic Skate (Raja Eglanteria) Heart
Authors: Goldstein Leon , Luer Carl A. , Blum Patricia C. 
Published: April 2021

ABSTRACT
The hearts of elasmobranchs, like those of other vertebrates, accumulate high concentrations of the amino acid taurine (Boyd et al. 1977), which is used to maintain osmotic equilibrium with the extracellular fluid. We recently demonstrated that embryonic hearts of the clearnose skate (Raja eglanteria Bosc) were able to accumulate taurine equally as well as hearts of adult skates and, as in adults, the accumulation was the result of transport from extracellular taurine across the cell membrane against a steep concentration gradient (Goldstein et al. 1990). In adult skate hearts, the uptake of taurine is Na+-dependent and competitively inhibited by β-alanine (Forster and Hannafin, 1980a), indicating that transport occurs by the β-amino acid system found in many vertebrate hearts (Huxtable, 1992). During hypotonic stress, adult skate hearts release taurine and other amino acids. The Na+/taurine cotransport system permits the skate heart to maintain high concentrations of intracellular taurine, while the hypotonicity-activated taurine release aids in cell volume regulation following dilution of the extracellular fluid. The aims of the present study were to determine whether taurine uptake in the embryonic skate heart is Na+-dependent as in the adult and whether the skate heart has the capability of cell volume regulation (during hypotonic stress) before hatching.
Water Propulsion Speeds and Power Output by Comb Plates of the Ctenophore Pleurobrachia Pileus Under Different Conditions
Authors: Barlow David , Sleigh Michael A. 
Published: April 2021

ABSTRACT
Parameters of ciliary beating and water propulsion can be studied in a unique fashion in ctenophores because the beat frequency can be controlled. Pleurobrachia pileus comb plates were driven at frequencies between 2 and 25Hz and at temperatures between 10 and 25°C. As frequency is increased from 5 to 25Hz, the rest period between beats is first shortened and then disappears: the duration of the effective stroke is reduced because the angular velocity (which is directly proportional to the sliding velocity of the microtubules) and the tip speed of each plate increase whilst the amplitude of the beat remains unchanged. The recovery stroke is shortened because the recovery bend is propagated more quickly to the tip of the plate. The phase difference between adjacent plates in the metachronal wave (expressed as a percentage of the cycle) is increased in spite of a sharp decrease in the time delay between adjacent plates, a reduction in the number of plates per wave and an increase in the metachronal wave velocity. The water flow speed becomes more continuous and increases in approximate proportion to the tip speed whilst the estimated power output of a metachronal wave increases exponentially, from 10−10W at a tip speed of about 20 mm s−1 to 10−8 W at a tip speed of about 75 mms−1. When comb plates are driven to beat at 10 Hz and the temperature is raised from 10°C towards 20°C, the duration of the effective stroke is reduced and the comb plates have a somewhat higher angular velocity and tip speed; the duration of the recovery stroke is reduced with a faster propagation of the recovery bend; a rest phase first appears between successive beats and then becomes longer. The phase difference between adjacent plates in a metachronal wave (expressed as a percentage of the cycle time) is decreased, as is the time delay between successive plates in a metachronal wave, so that the number of plates per wave and the wave velocity are increased. The water flow speed and power output are increased by a modest amount (a rise in temperature from 10 to 20°C produces changes equivalent to those produced by a 5Hz increase in frequency at 20°C). The cooperation between adjacent plates in the antiplectic metachronal wave makes a major contribution to the dramatic increase in power output of each metachronal wave that is seen as the beat frequency is increased.
Load-Compensating Reactions in the Proximal Leg Joints of Stick Insects During Standing and Walking
Authors: Schmitz Josef 
Published: April 2021

ABSTRACT
The responses of retractor coxae and protractor coxae motoneurones and of the retractor coxae muscle to cuticular stress applied to the leg were investigated in standing and walking stick insects, Carausius morosus. The coxa of a middle or hind leg was restrained and the trochanterofemur was bent by moving the distal tip of the femur anteriorly or posteriorly, i.e. perpendicular to its normal plane of movement. The maximum amplitude used was 200 μm, which corresponds to a deflection of 0.95°, and the forces necessary to bend the trochanterofemur were between 0.29 and 2.91mN. Thus, cuticular stress could be applied in particular directions and with controlled amplitudes within the physiological range. This cuticular stress induced direction- and amplitude-dependent reflex responses in excitatory retractor coxae and protractor coxae motoneurones. The reflexes clearly constitute a negative feedback system which continuously compensates cuticular stress in the legs of standing and walking animals. Two groups of trochanteral campaniform sensilla, the posterior group and the anterior ventral group, were shown to underlie this feedback loop. These results prove directly for the first time the important function of single groups of trochanteral campaniform sensilla in the control of posture and locomotion in stick insects. I discuss the importance of these results for the interpretation of previous findings on stick insects subjected to increased load during walking.
Hindbrain Circuitry Mediating Common Mode Suppression of Ventilatory Reafference in the Electrosensory System of the Little Skate Raja Erinacea
Authors: Montgomery John C. , Bodznick David 
Published: April 2021

ABSTRACT
Elasmobranch fish have an electrosensory system which they use for prey detection and for orientation. Sensory inputs to this system are corrupted by a form of reafference generated by the animal’s own ventilation, but this noise is reduced by sensory processing within the medullary nucleus of the electrosensory system. This noise cancellation is achieved, at least in part, by a common mode rejection mechanism. In this study we have examined characteristics of neurones within the medullary nucleus in an attempt to understand the neural circuitry responsible for common mode suppression. Our results are in accord with previous indications that ascending efferent neurones of the medullary nucleus are monosynaptically activated from the ipsilateral electrosensory nerves and project to the midbrain. We demonstrate that in Raja erinacea, as has been previously shown in one other species (Cephaloscyllium isabella), ascending efferent neurones typically have a discrete focal excitatory receptive field and an inhibitory receptive field which may be discrete or diffuse and which often includes a contralateral component. We identify a group of interneurones within the medullary nucleus which are driven monosynaptically from the electrosensory nerves, have simple discrete excitatory receptive fields and respond vigorously to imposed common mode signals. The simplest model of the circuitry underlying common mode rejection that is consistent with the evidence is that direct afferent input impinges onto the basal dendrites of the ascending efferent neurones and onto interneurones within the nucleus, and the interneurones in turn inhibit the ascending efferents. The pattern of this projection, including commissural inputs, determines the nature and extent of ascending efferents’ inhibitory surrounds and mediates the suppression of common mode signals.
Investigation of Stimulus–Secretion Coupling in Equine Sweat Gland Epithelia Using Cell Culture Techniques
Authors: Wilson Stuart M. , Pediani John D. , Ko Wing Hung , Bovell Douglas L. , Kitson Susan , Montgomery Ian , Brown Ursilla M. O. , Smith Godfrey L. , Elder Hugh Y. , Jenkinson David McEwan 
Published: April 2021

ABSTRACT
When sweat glands isolated from samples of horse skin were explanted and cultured under favourable conditions, they could exhibit cellular outgrowth. This growth could be maintained for 2–4 weeks and these primary cultures were then disaggregated and the resultant cell suspensions used to initiate epithelial cell lines. Secretion from intact equine sweat glands is regulated by β 2-adrenoceptors and appears to be mediated by cyclic AMP, but there is evidence that calcium may also play a role. Adrenaline could increase the cyclic AMP content of the cultured cells and this response was mediated by 2-adrenoceptors. Adrenaline was also able to evoke a small increase in intracellular free calcium ([Ca2+]i) but the pharmacology of this response remains obscure. Adrenaline thus activates at least two potentially important second-messenger signalling pathways which have the capacity to interact, because adrenaline-evoked cyclic AMP formation was inhibited if [Ca2+]i was raised with ionomycin. The chloride permeability of mammalian epithelial cells characteristically rises during secretion, and adrenaline could increase chloride permeability in the cultured epithelia but the cells did not contain cyclic-AMP-dependent chloride channels and so this response was mediated by [Ca2+]i.
Locust Medial Neurosecretory Cells in vitro: Morphology, Electrophysiological Properties and Effects of Temperature
Authors: Rössler Wolfgang , Bickmeyer Ulf 
Published: April 2021

ABSTRACT
The medial neurosecretory cells of the pars intercerebralis in the protocerebrum of larval and adult locusts (Locusta migratoria) were cultured in a chemically defined serum-free culture medium. The morphology of the cells was investigated by light microscopy and the electrophysiological properties were studied using the patch-clamp technique in the whole-cell configuration. The dissociated neurosecretory cells grew new processes under these conditions and were maintained in culture for up to 2 months. The percentage of cells showing outgrowth was significantly higher in third-instar larvae than in instars 4 and 5 and adults. A primary axonal stump promoted a unipolar cell morphology; in other cases, most neurosecretory cells became multipolar. The presence of glial cells in undissociated groups of neurosecretory cells improved outgrowth and the formation of neurite bundles. A considerable number of the recorded cells showed spiking activity in response to depolarization. The influences of temperature on spike frequency, duration and amplitude as well as on membrane potential and ionic currents were investigated. The results suggest that temperature may directly affect the function of neurosecretory cells.
Toads Taste Sodium With Their Skin: Sensory Function in a Transporting Epithelium
Authors: Hoff Karin Von Seckendorff , Hillyard Stanley D. 
Published: April 2021

ABSTRACT
Amphibians do not normally ingest water orally. Rather, they obtain water by osmotic flow across their skin (Bentley and Yorio, 1979). Previous studies of the desert toad, Bufo punctatus, showed that dehydrated animals placed on a surface moistened with pure water adopted a particular type of behavior, termed the water absorption response (WR), in which toads splayed their hindlimbs and oscillated their body to maximize the area of skin in contact with the surface (Brekke et al. 1991). If the surface was moistened with a hyperosmotic urea solution, the animals moved over the surface as if to search for osmotically available water and soon jumped off the surface without initiating WR behavior. Since the skin was the only part of the animal in contact with the surface, it was concluded that receptors in the skin enabled the animals to avoid WR behavior on surfaces where water was not osmotically available. Similarly, toads did not initiate WR behavior when NaCl was used as the solute. These observations suggested that toads have either cutaneous receptors for detecting osmolality, per se, or cutaneous receptors for specific solutes.
HIGH pH IN THE ECTOPERITROPHIC SPACE OF THE LARVAL LEPIDOPTERAN MIDGUT
Authors: Gringorten J. L. , Crawford D. N. , Harvey W. R. 
Published: April 2021

ABSTRACT
The midgut lumen of lepidopteran larvae is highly alkaline (Waterhouse, 1949; Berenbaum, 1980), a condition maintained in the presence of a large and opposing transapical H + gradient from the midgut epithelial cells. Lumen pH values of approximately 11 may be common (Dow, 1984), whereas the cell cytoplasm itself is maintained at approximately neutral pH (Dow and O’Donnell, 1990; Chao et al. 1991), giving rise to cell/lumen H + concentration ratios of 10 4 or more. Dow (1984) reported a mean pH of 12.0 in the midgut of a sphingid larva, Acherontia atropos, and Schultz and Lechowicz (1986) recorded a maximum reading of pH12.4 in the European gypsy moth, Lymantria dispar. These values are among the highest recorded in any biological system.