bluuebunny/crossref_metadata_2025 huggingface dataset:
The Whole-Body Withdrawal Response of Lymnaea Stagnalis II. Activation of Central Motoneurones and Muscles by Sensory Input
Authors: Ferguson Graham P. , Benjamin Paul R.
Published: April 2021

The role of centrally located motoneurones in producing the whole-body withdrawal response of Lymnaea stagnalis (L.) was investigated. The motoneurones innervating the muscles used during whole-body withdrawal, the columellar muscle (CM) and the dorsal longitudinal muscle (DLM) were cells with a high resting potential (–60 to –70 mV) and thus a high threshold for spike initiation. In both semi-intact and isolated brain preparations these motoneurones showed very little spontaneous spike activity. When spontaneous firing was seen it could be correlated with the occurrence of two types of spontaneous excitatory postsynaptic potential (EPSP). One was a unitary EPSP that occasionally caused the initiation of single action potentials. The second was a larger-amplitude, long-duration (presumably compound) EPSP that caused the motoneurones to fire a burst of high-frequency action potentials. This second type of EPSP activity was associated with spontaneous longitudinal contractions of the body in semi-intact preparations. Tactile stimulation of the skin of Lymnaea evoked EPSPs in the CM and DLM motoneurones and in some other identified cells. These EPSPs summated and usually caused the motoneurone to fire action potentials, thus activating the withdrawal response muscles and causing longitudinal contraction of the semi-intact animal. Stimulating different areas of the body wall demonstrated that there was considerable sensory convergence on the side of the body ipsilateral to stimulation, but less on the contralateral side. Photic (light off) stimulation of the skin of Lymnaea also initiated EPSPs in CM and DLM motoneurones and in some other identified cells in the central nervous system (CNS). Cutting central nerves demonstrated that the reception of this sensory input was mediated by dermal photoreceptors distributed throughout the epidermis. The activation of the CM and DLM motoneurones by sensory input of the modalities that normally cause the whole-body withdrawal of the intact animal demonstrates that these motoneurones have the appropriate electrophysiological properties for the role of mediating whole-body withdrawal.
Adrenergic stimulation of substrate utilization by cardiac myocytes isolated from rainbow trout
Authors: Milligan C. L.
Published: April 2021

A method is described for the isolation of calcium-tolerant myocytes from adult rainbow trout. Isolated myocytes remain viable for at least 4 h in suspension as indicated by (1) maintenance of ATP, phosphocreatine (PCr) and glycogen levels; (2) maintenance of the integrity of cell membranes, shown by low rates of leakage of lactate dehydrogenase (LDH) to the medium and exclusion of Trypan Blue; (3) the ability to metabolize substrates; and (4) sensitivity to adrenergic agonists. CO2 production from both glucose and lactate was sensitive to adrenergic stimulation, with the following order of potency: isoproterenol greater than noradrenaline much greater than adrenaline greater than phenylephrine, which indicates the presence of beta 1-adrenoceptors. Myocytes isolated from trout acclimated to 20 degrees C in the summer were more sensitive to beta-adrenergic stimulation than myocytes isolated from trout acclimated to 9 degrees C in either summer or winter. In the absence of exogenous fuel, there was a net reduction in myocyte glycogen content and glycogenolysis was further stimulated by 10(−7) mmol l-1 noradrenaline. However, in the presence of exogenous fuel (either 5 mmol l-1 lactate or 5 mmol l-1 glucose), glycogen was ‘spared’ and noradrenaline-stimulated glycogenolysis was apparently inhibited.
The Mechanism of Tongue Protraction During Prey Capture in the Frog Discoglossus Pictus
Authors: NISHIKAWA KIISA C. , ROTH GERHARD
Published: April 2021

The mechanism of tongue protraction in the archaeobatrachian frog Discoglossus pictus was studied using high-speed video motion analysis before and after denervation of the submentalis and genioglossus muscles. The kinematics of prey capture were compared (1) between successful and unsuccessful feeding attempts before surgery; (2) before and after denervation of the m. submentalis; and (3) before and after denervation of the m. genioglossus. Prey capture by D. pictus is similar to that of Ascaphus truei, hypothesized to be the sister group of all other living frogs. These archaeobatrachians have tongues of limited protrusibility (maximum tongue reach=0.21-0.27cm) and lunge forward with the whole body to catch prey. In Discoglossus, unsuccessful attempts to capture prey differ from successful captures in having a longer duration of most kinematic variables. These results suggest that kinematic events are postponed in unsuccessful attempts at prey capture, owing to the absence of the somatosensory feedback that results from successful prey contact. Denervation of the m. submentalis prevents mandibular bending, but does not affect tongue protraction. Denervation of the m. genioglossus significantly decreases maximum tongue reach and maximum tongue height, but does not affect mandibular bending. The m. submentalis is necessary for mandibular bending, but neither mandibular bending nor m. submentalis activity are necessary or sufficient for tongue protraction. The m. genioglossus is necessary for normal tongue protraction. It does more than stiffen and support the tongue. These results are not consistent with the current model of tongue protraction developed for the neobatrachian toad Bufo marinus. If this model withstands the denervation test in Bufo marinus, then archaeobatrachians and neobatrachians must differ in their mechanisms of tongue protraction.

Note:

Present address: Brain Research Institute FB2, University of Bremen, D-2800 Bremen, Federal Republic of Germany.
Ventilation in Namib Desert Tenebrionid Beetles: Mass Scaling and Evidence of a Novel Quantized Flutter-Phase
Authors: LIGHTON JOHN R. B.
Published: April 2021

The mass scaling of discontinuous ventilation (DV) phenomena in adult motionless insects is currently unknown. I present DV phenomena from 10 species of Namib Desert tenebrionid beetles; four from the dune-sea habitat, five from the river-bed habitat and one from the gravel plain habitat, which is characterized by very low and patchy resource availability. This species differed from the others in many respects. However, all species exhibited a previously undescribed, convective and quantized F phase ventilation (ISP, or intermittent serial pulsation, phase). For dune-sea and river-bed habitat species, all DV characteristics except DV frequency (V phase CO2 emission volume and rate, total and per-burst ISP phase CO2 emission volume, and total rate) scaled tightly with body mass with a scaling exponent close to 1.0 (typical r2>0.95-0.98), as did overall rate of CO2 production and hence metabolic rate (MR). Consequently these parameters were independent of body mass when expressed on a mass-specific basis, explaining the independence of body mass and DV frequency. These findings are compatible with published DV data in other species and orders of insects, suggesting that these scaling phenomena may be widespread. The gravel plain species (Epiphysa arenicola) had an MR of 38%, V phase CO2 volume of 41% and V phase CO2 emission rate of 23% of those predicted on the basis of its body mass, and it emitted a greater proportion of CO2 during its ISP phase (47% vs 24% of total CO2 output per DV cycle in the other species). It is suggested that these discrepancies are respiratory and ventilatory adaptations to scarce and patchy energy and water availability.
K+ transport across the lamprey erythrocyte membrane: characteristics of a Ba(2+)- and amiloride-sensitive pathway
Authors: Kirk K.
Published: April 2021

The characteristics of K+ transport in erythrocytes from the river lamprey (Lampetra fluviatilis) were investigated using standard radioisotope flux techniques. The cells were shown to have a ouabain-sensitive transport pathway that carried 43K+ and 86Rb+ into the cell at similar rates. Most of the ouabain-resistant 43K+ and 86Rb+ influx was via a pathway that was insensitive to cotransport inhibitors and to the replacement of extracellular Cl- or Na+. This pathway showed a strong selectivity for 43K+ over 86Rb+. It was inhibited fully by Ba2+ (I50 approximately 2.8 mumol l-1), amiloride (I50 approximately 150 mumol l-1) and ethylisopropylamiloride (I50 approximately 3.3 mumol l-1) and less effectively by quinine and by the tetraethylammonium ion. Inhibition by Ba2+ took full effect within a few minutes whereas the full inhibitory effect of amiloride took more than 1 h to develop. Experiments with the membrane potential probe [14C]tetraphenylphosphonium ion gave results consistent with the lamprey erythrocyte membrane having a Ba(2+)-sensitive K+ conductance that was significantly greater than the membrane Na+ conductance and which gave rise to a marked dependence of the membrane potential on the extracellular K+ concentration. The rate constants for Ba(2+)-sensitive 43K+ and 86Rb+ influx decreased (proportionally) with increasing extracellular K+ concentration in a manner that was consistent with the transport being via a conductive pathway. The decrease was attributed to a depolarisation of the membrane (in response to the increasing extracellular K+ concentration) and a consequent decrease in the driving force for the conductive movement of 43K+ and 86Rb+ into the cells. Ba(2+)-sensitive 86Rb+ influx increased significantly with decreasing cell volume and with increasing intracellular pH (at a constant extracellular pH) but increased only slightly with increasing extracellular pH. The pathway operated normally in the complete absence of extracellular Ca2+ but its activity decreased in cells pretreated with ionomycin and EGTA; this suggests a role for intracellular Ca2+ in the operation of the pathway.
Force-Velocity Relationships of a Locust Flight Muscle at Different Times During a Twitch Contraction
Authors: MALAMUD JEAN G. , JOSEPHSON ROBERT K.
Published: April 2021

The force-velocity relationships during isotonic shortening were determined for the metathoracic second tergocoxal muscle of the locust Schistocerca americana (Drury). This muscle is a synchronous flight muscle. During the plateau of a tetanic contraction, the maximum shortening velocity (Vmax) determined from the force-velocity curve was 5.2 muscle lengths s−1 (25°C) and the curvature (a/Po) was 0.62. The maximum isometric force (P0) was 36.3 N cm−2.

Early in a twitch (at times shorter than the isometric twitch rise time) the values for Vmax and curvature were similar to those during the tetanic plateau, but the curves at different times during the twitch intercepted the force axis at values less than P0. Later in the twitch, Vmax declined.

A variable termed degree of activation (DA) is developed as a measure of the force-generating capacity of a muscle when this may be time-varying, as throughout most of a twitch. DA is determined from the shortening velocity at an intermediate load and is the predicted intercept of the force-velocity curve with the force axis relative to the tetanic intercept. In the locust muscle, DA rose to a maximum in 2–3 ms after the end of the latent period. DA reached 80° of the tetanic value during a single twitch; during the second twitch of a pair, the peak DA reached approximately the tetanic value. After a brief plateau, DA declined approximately exponentially. The time constant of DA decay was about 14 ms.

Note:

Present address: Department of Physiology, Emory University, Atlanta, GA30322, USA.
The Seasonal Variation in Biological Composition of Certain Plankton Samples from the North Sea in Relation to Their Content of Vitamin A, Carotenoids, Chlorophyll, and Total Fatty Matter
Authors: Gillam A. E. , El Ridi M. S. , Wimpenny R. S.
Published: April 2021

The occurrence of relatively large stores of vitamin A in the liver oils of many fish has naturally aroused considerable interest in the ultimate origin of this source of the vitamin. From the results obtained by a number of workers, there is no doubt that many constituent organisms of the plankton exhibit the biological activity associated with vitamin A (Jameson et al. 1922; Hjort, 1922; Ahmad, 1930; Drummond & Gunther, 1930), but, whilst it is probable that the carotenoids produced (presumably photochemically) by certain phytoplanktonic organisms are converted into vitamin A itself in vivo in some of the organisms constituting the zooplankton, precise information as to the exact locale of this conversion is lacking. Thus, whilst shrimps (Hjort, 1922) and molluscs (Jameson et al. 1922) have been shown to exhibit the biological activity of vitamin A, some samples of zooplankton have been found to possess no activity of this nature at all (Drummond & Gunther, 1930, 1934).
The Maintenance of Reproductive Activity in Xenopus Laevis for Pregnancy Diagnosis
Authors: Landgrebe F. W.
Published: April 2021

In 279 cases 97 % agreement was obtained between Zondek-Aschheim and Xenopus laevis pregnancy tests. Feeding once a week with either beef or liver is sufficient to maintain ovarian growth in Xenopus laevis but a diet of liver is more propitious if the frequency of feeding is less. The superiority of a liver diet is not due to its greater manganese or vitamin content. The effect of overcrowding upon the reproductive activity of Xenopus laevis is not due to pollution alone but also to some form of interaction between the animals themselves. The maximum density level compatible with ovarian growth is higher if the water is kept running than if it is only changed after feeding. Ovulation in Xenopus laevis as a response to injection of tissue extracts in doses up to 5 g. of tissue is specific to water extracts of the anterior lobe of the pituitary. Instructions for the technique of the Xenopus pregnancy test are outlined.
The Function of the Quintuple Innervation of A Crustacean Muscle
Authors: van Harreveld A. , Wiersma C. A. G.
Published: April 2021

The functions of the five fibres innervating the flexor muscle of the carpopodite was investigated in Panulirus interruptus. The four thicker fibres were found to be motor axons, each eliciting a contraction with different characteristics. These four contractions were accompanied by four different types of action currents.

The thinnest fibre when stimulated simultaneously with any of the four motor fibres caused inhibition of the contraction.

It is concluded that all four contractions take place in all the muscle fibres and that the conception of the mechanism of crustacean nerve muscle system developed before is enlarged to include the new results. The possible biological significance of the quintuple innervation is discussed.
The Action of Drugs, Especially Acetylcholine, on the Annelid Body Wall (Lumbricus, Arenicola)
Authors: Wu K. S.
Published: April 2021

In the course of a recently published investigation (Wu, 1939) it was found that the gut of the earthworm differed from the well-known preparation of the dorsal musculature of the leech (Fühner, 1918; Minz, 1932), as regards its reactions to acetylcholine, in the following respects: (1) in the absence of eserine the body wall of the leech is very much less sensitive to acetylcholine than is the gut (crop and gizzard) of the earthworm, the lowest effective concentration of the drug being 10−4 to 10−5 for the former and 10−5 to 10−10 for the latter; (2) treatment with eserine increases the sensitivity to acetylcholine of the leech dorsum enormously and that of the earthworm gut only slightly, so that the former (lowest effective concentration 10−8 to 10−10) is now nearly as sensitive as the latter (10−10 to 10−10); (3) adopting the classification of Dale (1914), the action of acetylcholine on the leech is a “nicotine-action” (abolished by large doses of nicotine) while that on the earthworm gut is a “muscarine-action’’ (abolished by small doses of atropine). The question therefore arises, are these differences due to the fact that we are dealing with two species, earthworm and leech, or with two organs, body wall and gut? To answer this question, the writer has studied the action of acetylcholine and certain other relevant drugs on the body wall of the earthworm (Lumbricus terrestris) and of the lugworm (Arenicola marina). By putting these results beside those already established for the leech, a comparison can be drawn between the reactions of the body wall in representatives of all of the three great divisions of the annelid phylum. As regards the gut, the data of Wu (1939) on the earthworm and of Wells (1937) on the lugworm are also available for comparison.
Studies on Living Protoplasm
Authors: Harris J. E.
Published: April 2021

A study has been made of the rate of fall of the nucleolus through the nuclear fluid of echinoderm oocytes. Analysis of the results obtained on the oocytes of Echinus esculentus leads to the following conclusions :

The absence of sudden velocity changes during the fall indicates the absence of gross heterogeneities in the nuclear fluid. The nuclear fluid is thixotropic. Complete reconstitution of its elastic structure takes place within 10 min. of its disruption by the moving nucleolus. In addition to the gravitational force producing the fall, there is acting on the nucleolus a much weaker force, constant in magnitude and direction for any one oocyte. The presence of this additional force is indicated by a constantly reproducible difference in the rate of nucleolar fall in two opposing directions, and also by horizontal motion of the nucleolus during its fall. The force does not arise from viscosity differences in different regions of the nucleus ; the nuclear fluid is apparently homogeneous and has an absolute viscosity of approximately 0·1, i.e. 10 times that of water. Neither nucleolar asymmetry nor streaming of the nuclear protoplasm can account for the phenomenon. The electrical nature of the force on the nucleolus is suggested by the elimination of these possible mechanical explanations and by the presence of a surface charge on the nucleolus. The order of magnitude of the potential field required by this hypothesis is consistent with the energy output of the respiring oocyte. The polarized force on the nucleolus is abolished in M/500 potassium cyanide, and also by heating above 30° C. The bearing of these results on the structure of the nucleus and on the origin of polarity in the unfertilized egg is discussed.
The Significance of the Relationship between Actinians and Zooxanthellae
Authors: Smith H. G.
Published: April 2021

Unicellular algae (zooxanthellae) occur in certain Actiniaria. The first important experimental work on the nature of the association was that of Brandt (1883 a, b), who starved anemones in Light and in darkness. From the results of these experi-ments he concluded that the animals obtained nutriment from the zooxanthellae when deprived of animal food. Later work by Boschma (1926) on Cribina xantho-grammica supports Brandt’s view. Brandt was unable to observe the digestion of the zooxanthellae and assumed that food material was passed in soluble form from algae to animal. By studying the mesenterial filaments of C. xanthogrammica Boschma brought forward evidence in favour of the view that zooxanthellae are actually digested by the anemone. In his opinion such actinians live partly on animal matter and partly on the zooxanthellae. During starvation they depend chiefly on the algae.
Response Properties and Adaptation of Neurones Sensitive to Image Motion in the Butterfly Papilio Aegeus
Authors: Maddess T. , Dubois R. A. , Ibbotson M. R.
Published: April 2021

Wide-field direction-selective neurones from the optic lobes of the butterfly Papilio aegeus show some properties similar to those displayed by the large neurones of the fly lobula plate. Temporal and spatial frequency threshold tuning curves show that butterfly optic lobe neurones sensitive to different directions of image motion are fed by presynaptic subunits similar to those of the fly. However, unlike fly lobula plate neurones, the butterfly optic lobe neurones show a steep low-spatial-frequency roll-off which persists even at high temporal frequencies. Also exceptional is the temporal resolution of rapid changes in image speed by the butterfly neurones. When the cells are adapted to continuous motion their responses indicate a further increase in temporal resolution. Evidence is provided that in any one state of adaptation the neurones may be thought of as piece-wise linear and, thus, their responses can be predicted by convolution with a velocity kernel measured for that adaptation state. Adaptation to continuous motion results in the cells responding to motion in proportion to the mean motion signal. Motion in the non-preferred direction also appears to adapt the cells. Velocity impulse responses of both butterfly and blowfly neurones were determined with one-dimensional gratings and two-dimensional textured patterns and the results for the two stimuli are shown to be very similar.
Architecture of Cerebral Neurosecretory Cell Systems in the Silkworm Bombyx Mori
Authors: Ichikawa Toshio
Published: April 2021

Anatomical and physiological characteristics of putative neurosecretory cells (NSCs) in the medial and lateral areas of the larval brain of Bombyx mori, identifiable by the opalescent appearance of their somata, were examined by means of intracellular recording and staining. Intracellular injection of Lucifer Yellow revealed that the medial cell group consisted of at least six subgroups of cells distinguishable by the geometry of their dendritic branches. Five subgroups of cells project axons to the contralateral corpus allatum (CA) or to the corpus cardiacum (CC). The remaining subgroup sends an axon to the ipsilateral ventral nerve cord. Three subgroups of cells were identified in the lateral group, projecting axons to the ipsilateral CC, to the CA or to the contralateral CA. Large and prolonged action potentials, similar to those recorded in some neurosecretory systems, were recorded from these medial and lateral cells. However, two pairs of medial cells containing paraldehyde-fuchsin-positive (neurosecretory) material and with axons extending to the contralateral nerve cord had action potentials of a short duration, more typical of non-NSCs such as tritocerebral cells innervating the stomodeal dilator muscles via the CC.
in Vitro Metabolic Depression of Tissues From the Aestivating Frog Neobatrachus Pelobatoides
Authors: Flanigan James E. , Withers Philip C. , Guppy Michael
Published: April 2021

The desert frog Neobatrachus pelobatoides reduced its resting metabolism in vivo by 60–70% during 5–7 weeks of aestivation (summer dormancy). The rate of oxygen consumption (V˙O2) of isolated and intact skeletal muscle, measured in vitro, was 70% lower for aestivating frogs compared with non-aestivating frogs. The cause of the reduced V˙O2 of aestivating frog muscle must lie in the tissue itself rather than being induced by external factors such as oxygen supply or bloodborne metabolites (because these were identical in the in vitro assay conditions), by any short-term effects produced by hormones (as these would have been washed out of the tissues during incubation) or by tissue dehydration (as the tissues from aestivating frogs had rehydrated to non-aestivating levels). The reduced in vitro muscle V˙O2 accounted for 60–77% of the frogs in vivo metabolic depression that accompanied aestivation. Other tissues of the aestivating frog, namely intestine, liver, skin and fat, did not have a reduced in vitroV˙O2. We suggest that metabolic depression is initiated by reduced energy demand in cells and this consequently leads to reduced energy production.
Simultaneous Measurements of Spiracular and Cuticular Water Losses in Periplaneta Americana: Implications for Whole-Animal Mass Loss Studies
Authors: Machin J. , Kestler P. , Lampert G. J.
Published: April 2021

Spiracular and cutaneous water loss through the cuticle and spiracles of Periplaneta americana was measured in animals of differing initial water contents under controlled temperature, humidity and airflow conditions, by continuous weighing (resolution ±10μg). Stable water loss rates (2.09×10−8 to 3.47 ×10−8 g h−1 cm−2 Pa−1) were as much as an order of magnitude less than those reported in earlier studies employing intermittent weighing techniques. We suggest that increased water loss caused by substantial increases in ventilatory water loss during the episodic disturbances required by intermittent weighing is the principal contributor to this discrepancy.

Water losses, as well as the interval between spiracular ventilations, decreased with water content. However, greater variation was primarily due to interruptions of the regular cyclic pattern of ventilation by highly variable, activity-related bouts of increased ventilatory loss. Variations in water loss appear to be too large and too rapid to be convincingly explained in terms of cuticular conductance. Our results suggest that previous experiments using 5% CO2 anaesthesia, linking changes in total water loss to the conducting properties of the cuticle, were not valid. There seems to be no adaptive value for the proposed voluntary increases in cuticular permeability in an animal where ventilatory water losses can be so high.
Kinematic and Electromyographic Analysis of the Functional Role of the Body Axis During Terrestrial and Aquatic Locomotion in the Salamander Ambystoma Tigrinum
Authors: Frolich Larry M. , Biewener Andrew A.
Published: April 2021

Aquatic neotenic and terrestrial metamorphosed salamanders (Ambystoma tigrinurn) were videotaped simultaneously with electromyographic (EMG) recording from five epaxial myotomes along the animal’s trunk during swimming in a flow tank and trotting on a treadmill to investigate axial function during aquatic and terrestrial locomotion. Neotenic and metamorphosed individuals swim using very similar axial wave patterns, despite significant differences in axial morphology. During swimming, both forms exhibit traveling waves of axial flexion and muscle activity, with an increasing EMG-mechanical delay as these waves travel down the trunk. In contrast to swimming, during trotting metamorphosed individuals exhibit a standing wave of axial flexion produced by synchronous activation of ipsilateral epaxial myotomes along the trunk. Thus, metamorphosed individuals employ two distinct axial motor programs -one used during swimming and one used during trotting. The transition from a traveling axial wave during swimming to a standing axial wave during trotting in A. tigrinurn may be an appropriate analogy for similar transitions in axial locomotor function during the original evolution of terrestriality in early tetrapods.
Abdominal Postural Motor Responses Initiated by The Muscle Receptor Organ in Lobster Depend Upon Centrally Generated Motor Activity
Authors: Sukhdeo Suzanne C. , Page Charles H.
Published: April 2021

Stretch stimulation of the abdominal muscle receptor organ of the lobster Homarus americanus initiated spike discharge of its tonic sensory neuron (SRI). This sensory response evoked a series of tonic postural reflex responses in the motor neurons that innervate the superficial extensor and flexor muscles of the abdominal postural system. The type of motor response depended on whether a flexion or extension pattern of spontaneous activity was being generated by the postural efferents. Spontaneous shifts between these centrally generated motor activities completely changed the SRl-evoked reflex responses. During spontaneous centrally initiated flexion activity, tonic SRI neuron discharge elicited an assistance response that included excitation of a medium-sized flexor excitor (f3) and the peripheral extensor inhibitor (e5), and inhibition of at least one extensor excitor. Neither the other flexor excitors nor the peripheral flexor inhibitor (f5) were affected by SRI excitation. During spontaneous centrally initiated extension activity, SRI activity elicited a response that included excitation of the extensor excitors and the flexor peripheral inhibitor (f5) only, f3 and e5 spontaneous activities were unchanged. This response was a resistance reflex, since SRI discharge normally resulted from an imposed abdominal flexion. The SRl-initiated control of postural motor activity in lobster differs from previously published results in the crayfish Procambarus clarkii.
Thermosensitivity of Different Parts of the Spinal Cord of the Pigeon (Columba Livia)
Authors: Østnes Jan E. , Bech Claus
Published: April 2021

In the present study we compared the metabolic responses to selective cooling of the cervical (C9–Th1) and the thoracic (Th1–Th5) parts of the spinal cord of pigeons. To obtain selective cooling of the two parts, two thermodes (4.5 cm) were inserted into the vertebral canal through an aperture in the first thoracic vertebra. During the experiments, one of the two thermodes was perfused with water at a constant temperature for periods of 15 min. The thermosensitivity was defined as the relationship between the amount of extra heat produced and the amount of heat extracted from the stimulated area. Cooling of the thoracic part resulted in a substantially higher increase in metabolic heat production and body temperature (Tb) than did cooling of the cervical part. It is concluded that the thoracic part of the spinal cord has a greater thermosensitivity than the cervical part. In addition, it was found that the difference in elevation of Tb during cooling of the two parts was not simply a result of differences in the amount of heat produced. When the changes in Tb were related to the difference between the extra heat produced and the amount of heat extracted, the increase in Tb during thoracic cooling was greater than that recorded during cervical cooling. This indicates that cooling of the two different parts of the spinal cord also had different effects on the thermoregulatory effector mechanisms that influence thermal conductance.

The study seems to provide evidence in favour of afferent transmission of cold signals in the spinal cord.
Influence of Ambient Calcium Levels on Stanniocalcin Secretion in the European EEL (Anguilla Anguilla)
Authors: Hanssen R. G. J. M. , Mayer-Gostan N. , Flik G. , Bonga S. E. Wendelaar
Published: April 2021

The cells of the corpuscles of Stannius appeared to be more active in eels acclimated to sea water than in eels acclimated to fresh water. In acclimated eels, however, total and ionic plasma calcium concentrations and stanniocalcin titers did not differ. This suggests that levels of stanniocalcin in freshwater-acclimated eels are sufficient to maintain normocalcemia in sea water. When freshwater-acclimated eels were transferred directly to sea water, total and ionic calcium concentrations in the plasma increased significantly within 24 h but there was no apparent effect on the corpuscles of Stannius within the same time. This suggests that changes in secretory activity of the corpuscles of Stannius do not occur rapidly when they are presented with a hypercalcemic challenge. Conversely, when seawater-acclimated eels were transferred to fresh or distilled water there appeared to be a very rapid reduction in secretory activity in the corpuscles of Stannius, as indicated by the rapid accumulation of secretory granules. These data suggest that stanniocalcin turnover is more rapid in seawater-acclimated eels and that the secretory activity of the corpuscles of Stannius is rapidly reduced when a hypercalcic challenge is removed.
Electrical Responses to Chemical Stimulation of Squid Olfactory Receptor Cells
Authors: Lucero Mary T. , Horrigan Frank T. , Gilly Wm F.
Published: April 2021

Electrical properties of isolated olfactory receptor cells were studied using voltage- and current-clamp techniques based on whole-cell patch-clamp methods. Squid olfactory receptor cells contain voltage-gated Na+ and K+ channels and are capable of generating action potentials. Chemicals that elicit escape-jetting responses in behavioral experiments affect the excitability of isolated receptor cells. One set of such chemicals, including quaternary ammonium ions and aminopyridines, blocks K+ channels and increases excitability. Squid ink and L-Dopa also elicit escape jetting, but these substances increase membrane conductance, hyperpolarize the receptor cell and decrease excitability. These experiments indicate that sensory neurons of the olfactory organ are capable of detecting chemical signals and that at least two different transduction mechanisms can lead to similar behavioral responses.
Integumental Taurine Transport in Mytilus Gill: Short-Term Adaptation to Reduced Salinity
Authors: Silva Arnold L. , Wright Stephen H.
Published: April 2021

Taurine, a principal osmolyte in molluscan integument, is actively transported from sea water by Mytilus gill by means of a Na+-dependent process. In this study we examined the response of this transport to reductions in external salinity, i.e. the response to reductions in osmotic concentration as well as Na+ concentration. Acute exposure of isolated gill tissue to 60 % artificial sea water (ASW) resulted in a greater than 85 % inhibition of taurine uptake, substantially more than the 45 % inhibition predicted on the basis of the acute reduction in external [Na+], Within 60min, however, taurine transport recovered to the level predicted by the Na+ concentration in dilute sea water. Isolated gills acutely exposed to 60% ASW made isosmotic to normal (100 %) ASW with mannitol had rates of taurine uptake comparable to gills acclimated for 60min. Taurine uptake by gill tissue exposed to 60% ASW for 60 min and then returned to 100% ASW for 90 min was not significantly different from that of control gills held in 100% ASW. Glucose uptake by the gill during acute exposure to reduced salinity responded in a pattern similar to that of taurine. Gill tissue increased by 20 % in wet mass within 2 min of exposure to 60% ASW, but returned to control mass within 30-60 min, presumably reflecting cell volume regulation. Long-term (12 days) exposure to reduced salinities was not accompanied by increases in taurine transport over that of gills observed following the 60min ‘short-term’ acclimation. These results suggest that Mytilus gill undergoes a rapid (albeit incomplete) recovery from the extreme inhibition of transport associated with abrupt changes in salinity, and the extent of recovery is defined by the availability of Na+ in the external medium. The extreme sensitivity of taurine uptake observed after acute exposure of gills to reduced salinity is related to the osmotic concentration of the medium, and is possibly linked to a change in cell volume.
Evidence for a Brain Factor That Stimulates Deposition of Puparial Hydrocarbons in Diapausing Flesh Flies
Authors: Yoder Jay A. , Denlinger David L.
Published: April 2021

Puparia from diapausing pupae of the flesh fly Sarcophaga crassipalpis are lined with twice as much hydrocarbon as puparia from nondiapausing pupae (J. A. Yoder, D. L. Denlinger, M, W. Dennis and P. E. Kolattukudy, unpublished observations). The additional hydrocarbon favors water conservation during diapause by reducing water loss, enhancing water vapor absorptivity and elevating the critical transition temperature (Yoder and Denlinger, 1991). In this study we seek to identify the source of a hormonal modulator that would account for this difference in hydrocarbons. Our results suggest that a factor unique to the brains of diapause-programmed larvae is responsible for increasing the quantity of hydrocarbon deposited on the puparium. Cyclic AMP elicits the same effect, suggesting that the factor is probably a neuropeptide or another modulator that uses cyclic AMP as a second messenger.
Adenosine Release in the Anoxic Turtle Brain: A Possible Mechanism for Anoxic Survival
Authors: Nilsson Göran E. , Lutz Peter L.
Published: April 2021

In the brain of most vertebrates, anoxia or ischaemia rapidly causes a fall in ATP levels and in the activity of the Na+/K+ pump, resulting in general depolarization followed by a cascade of catastrophic events (Hansen, 1985; Hochachka, 1986). By contrast, the brain of freshwater turtles survives many hours of complete anoxia at 25°C. Hence, the turtle brain has become the archetype of an anoxia-tolerant brain, and considerable efforts have been devoted to finding the mechanisms underlying its exceptional ability to survive without oxygen. The turtle brain’s main strategy for anoxic survival seems to be to decrease energy utilization, so that ATP consumption can be met by glycolytic ATP production alone (Sick et al. 1982; Lutz et al. 1985; Chih et al. 1989). However, the mechanisms mediating the lowered energy consumption have remained obscure.
Non-Catch Contraction in Paramyosin-Containing Muscle in an Echinothuriid Sea Urchin Asthenosoma Ijimai
Authors: Tsuchiya Teizo , Obinata Takasi , Sato Makoto , Mori Takao , Suzuki Emiko , Amemiya Shonan
Published: April 2021

It has long been known that certain molluscan smooth muscles become stretch resistant and can hold the shell closed for extended periods without fatigue and at low rates of oxygen consumption. This prolonged state of contraction is called catch, and the maintenance of catch force is at least 10 times more economical than the contraction that precedes catch. This mechanism has been extensively studied in the anterior byssus retractor muscle (ABRM) of Mytilus edulis (Rüegg, 1971, 1986).
Respiratory and Circulatory Adjustments During Aquatic Treadmill Exercise In The European Shore Crab Carcinus Maenas
Authors: Hamilton N. M. , Houlihan D. F.
Published: April 2021

Carcinus maenas (L.) were exercised using a novel design of aquatic treadmill respirometer. Tethered exercise was performed in sea water at 5.8mmin−1 for 5 min. The rate of oxygen consumption and the heart and scaphognathite beat rates increased at the onset of exercise, reaching a steady state within 180 s. The estimated haemolymph flow rate rose 2.6-fold during exercise, achieved by a 1.8-fold increase in heart rate and a 1.5-fold increase in the estimated cardiac stroke volume. The haemolymph total oxygen content difference increased significantly during exercise. Haemolymph total carbon dioxide content did not change significantly during exerise, but haemolymph pH deceased as a result of an L-lactate-induced metabolic acidosis. The acidosis may also have led to a reduced Bohr shift. It is concluded that O2 and CO2 exchange were not impaired during exercise and that C. maenas relied primarily upon O2 to fuel underwater running at 5.8 m min−1.
A Method for Controlling the Feeding Behaviour of Aquatic Birds: Heart Rate and Oxygen Consumption During Dives of Different Duration
Authors: Bevan R. M. , Keijer E. , Butler P. J.
Published: April 2021

Tufted ducks, Aythya fuligula, were trained to dive for different durations in shallow tanks using a computer-controlled system of lights. The birds were rewarded with food for a correct response, i.e. performing a dive of the required duration. When dive durations (td) elicited by the system were longer than the durations required, the extra time was spent feeding. As the required duration was increased, so the time spent feeding decreased, and the required and actual dive durations approached equality. This occurred at approximately 40 s, although some birds did perform dives of up to 45 s.

Heart rate (FH) and oxygen consumption () were measured from the birds during voluntary diving using an implanted radiotransmitter and respirometry, respectively. The oxygen consumption during submersion decreased with increasing mean td, and may reflect a reduction in aerobic metabolism as a dive progressed, possibly as a result of reduced buoyancy or through a gradual switch to anaerobic metabolism.

Over a total dive cycle (the time spent submerged plus that spent on the surface between dives), FH proved to be a very good predictor of , with an error of only +7.9%. This compares favourably with other methods used to determine the energy expenditures of animals, e.g. the doubly labelled water and the time energy budget methods, and shows that the electronic acquisition of fH could be a useful tool for estimating the energy usage of free-living, aquatic birds.
The Influence of Cerebellar Lesions on the Swimming Performance of the Trout
Authors: Roberts B. L. , Rossem A. Van , Jager S. De
Published: April 2021

The influence of partial cerebellar ablation on the performance of rainbow trout, Oncorhynchus mykiss, swimming in a water tunnel was studied. Before surgery, all fish maintained a steady position in the water tunnel at all speeds tested. A linear relationship was found between the specific velocity (body lengths−1) and the tail-beat frequency. After partial cerebellectomy, the fish swam well in the tunnel at low speeds, retaining the relationship between tail-beat frequency and specific velocity, but they were unable to maintain a steady position at water speeds requiring tail-beat frequencies above 3.5 s−1 and were swept backwards. Two sham-operated fish swam at all water speeds tested. Post mortem histological investigation showed that the lesions were restricted to the cerebellar corpus. We conclude that the cerebellum plays no role in the generation of motor programmes but may be essential for their selection and implementation.
Responses to Freezing Exposure of Hatchling Turtles Trachemys Scripta Elegans: Factors Influencing the Development of Freeze Tolerance by Reptiles
Authors: Churchill Thomas A. , Storey Kenneth B.
Published: April 2021

Hatchling red-eared turtles Trachemys (=Pseudemys) scripta elegans (Wied) from a Louisiana population display a significant ability to withstand the freezing of extracellular body fluids. All animals survived at least 2 h of freezing at –2.5 or –4°C. At –2.5°C, survival declined to 50% after 6h of freezing and no animals recovered after 24 h or longer, when mean ice content reached 54.7± 1.4% of total body water. At –4°C, all turtles recovered from 4h of freezing exposure with a mean ice content of 49.6±2.4%, but survival dropped sharply thereafter with no animals recovering after 8h, when ice content had reached 64.5±0.7%. Survival times were substantially shorter and percentage ice values greater than comparable values for hatchling painted turtles (Chrysemys picta (Schneider)) from northern populations subjected to identical freezing exposures. The ability to synthesize cryoprotectants in response to freezing was poorly developed in T. s. elegans; maximal accumulation of glucose was only 3.2 μmolg−1 wet mass in liver. Lactate content increased two-to threefold in oxygen-sensitive organs (heart and brain) during freezing, but levels of lactate and other putative cryoprotectants were unchanged in other organs. Total free amino acid content rose significantly in liver, muscle and blood during freezing; increased taurine concentration was primarily responsible for the changes in liver and blood. The capacity for freezing survival by T. s. elegans hatchlings from southern populations would be of limited use for hibernation in a cold climate, but the metabolic responses to freezing displayed by these animals might be enhanced by northern populations to increase their freeze tolerance.
The Relationship Between β-Adrenoceptors and Adrenergic Responsiveness in Trout (Oncorhynchus Mykiss) and Eel (Anguilla Rostrata) Erythrocytes
Authors: Perry Steve F. , Reid Scott D.
Published: April 2021

Experiments were performed invitro specifically to elucidate the underlying mechanism(s) of the attenuated adrenergic responses of eel (Anguillarostrata) erythrocytes. This was achieved by comparing β-adrenoceptor numbers and affinities in addition to (i) Na+/H+ exchange activity, (ii) cell swelling and (iii) cyclic AMP formation mediated by catecholamines in eel and trout (Oncorhynchusmykiss) erythrocytes under normoxic and hypoxic conditions.

Under normoxic conditions, eel erythrocytes displayed a total absence of Na+/H+ exchange activity (as determined from measurements of extracellular pH) after addition of noradrenaline (50–1000 nmol l− 1) in contrast to a pronounced dose-dependent response in trout. Incubation of the blood under hypoxic conditions, to achieve approximately 50% haemoglobin O2-saturation, further increased the extent of Na+/H+ exchange activation in trout and elicited a statistically significant, although physiologically small (10% of the response in trout), activation of H+ extrusion activity in eel. Catecholamine-mediated cell swelling, although obvious in trout, was absent in eel when estimated under hypoxic conditions.

Eel erythrocytes possessed approximately 50% fewer surface β-adrenoceptors than did trout erythrocytes, although the dissociation constants (KD) of these receptors did not differ between eel and trout. The numbers and affinities of the erythrocyte β-adrenoceptors were not significantly affected by the hypoxic incubation.

Both eel and trout erythrocytes displayed a dose-dependent elevation of cyclic AMP concentration in response to noradrenaline that was further increased by hypoxia. Surprisingly, eel erythrocytes produced larger quantities of cyclic AMP despite the lower numbers of surface ^adrenoceptors. Thus, the absence of adrenergic swelling and the attenuated H+ extrusion response in eel erythrocytes cannot be attributed to insufficient numbers of β-adrenoceptors or to functional uncoupling of these receptors from adenylate cyclase. Instead, the differences between trout and eel may reflect differing numbers of Na+/H+ exchangers or fundamental differences in the manner by which these exchangers are activated by cyclic AMP.
Actin Gene Expression During Muscle Growth in Carcinus Maenas
Authors: Whiteley N. M. , Taylor E. W. , Haj A. J. El
Published: April 2021

As in other crustaceans, growth in Carcinus maenas (L.) is closely associated with the moult cycle because of the restrictions imposed by the calcified exoskeleton. The greatest increase in body mass occurs after ecdysis when the old exoskeleton is shed and rates of water uptake are elevated with a consequent increase in body volume (Drach, 1939; Mykles, 1980; Hartnoll, 1982). Growth of the walking leg extensor muscles in crustaceans such as Homarus americanus and Carcinus maenas is achieved both by the addition of sarcomeres to lengthen the muscle fibres and by increasing the number of myofibrils to add to their diameter (Govind, 1982; El Haj et al. 1984; El Haj and Houlihan, 1987). Addition of sarcomeric proteins to the fibres is relatively rapid, being restricted to the few days when ecdysis and the immediate postecdysial stages occur, while increases in fibre diameter may occur over the longer intermoult periods (Houlihan and El Haj, 1985; El Haj and Houlihan, 1987). The factors regulating muscle growth in crustaceans have not been identified and the stages of the moult cycle where regulation occurs have not been defined.