bluuebunny/crossref_metadata_2025 huggingface dataset:
Saxitoxin differentiates between two types of Na+-dependent potentials in the retzius cell of hirudinid leeches
Authors: Johansen J. , Kleinhaus A. L.
Published: April 2021

The effects of tetrodotoxin (TTX) and saxitoxin (STX) on the action potentials recorded in Ca2+-free solution in the absence of Ca2+ and K+ currents were investigated in the Retzius cell of three hirudinid leech species (Hirudo medicinalis, Macrobdella decora and Poecilobdella granulosa) and in the glossiphoniid leech Haementeria ghilianii.

In the four leech species, stimulation of the Retzius cell in the presence of 25 mmol l-1 tetraethylammonium chloride (TEA), 3 mmol l−1 4-aminopyridine (4-AP) and 2 mmol l−1 Mn2+ evoked prolonged action potentials consisting of an initial fast-rising spike followed by a plateau lasting several hundreds of milliseconds. The amplitude and duration of both components of action potentials recorded under these conditions were dependent on [Na+]o.

In the hirudinid leeches the initial spike was unaffected by TTX and STX whereas the plateau was selectively blocked by micromolar concentration of STX. In Haementeria both the initial spike and the subsequent plateau were sensitive to nanomolar concentrations of STX and TTX with an estimated ED50 of approximately 20 nmol l−1 for inhibition of of the fast spike.

The results suggest that there are two types of ionic currents mediating the two distinct components of Na+-dependent action potentials in the Retzius cell: (1) a fast-inactivating one, presumably underlying the normal spike which is TTX-and STX-resistant in hirudinid leeches but sensitive to both agents in Haementeria and (2) a low-threshold, prolonged current which underlies the plateau recorded from these cells in the absence of Caz+ and K+ currents and which is selectively blocked by STX in hirudinid leeches but sensitive to both STX and TTX in Haementeria.

It is likely that the variable kinetic and pharmacological properties that characterize the various Na+ potentials in these identified homologous neurones may be of functional significance and result from differences in the molecular structure of their Na+ channels.
Gas Exchange in the Loggerhead Sea Turtle Caretta Caretta
Authors: Lutcavage M. E. , Lutz P. L. , Baier H.
Published: April 2021

Pulmonary CO diffusion capacity (DLCO), lung volume (VL), oxygen uptake and pulmonary blood flow (Q̇L) were measured simultaneously in the loggerhead sea turtle Caretta caretta (Linnaeus) (8-11 kg) using a gas rebreathing technique (syringe pump ventilation).

Calculated DLCO and values in the loggerhead turtle are approximately twice those of non-varanid reptiles and about 25 % of values for resting mammals. Evidence based on an estimated lung-capillary O2 gradient, , shows that only a small driving gradient is required for O2 conductance across the loggerhead turtle lung. Pulmonary blood flow values are high compared to those for other reptiles; on the basis of the Fick principle, this implies a substantial blood convection requirement.

Differences in oxygen transport mechanisms between the loggerhead sea turtle and other highly aerobic but terrestrial reptiles may result from divergent lung structures and breathing patterns. In sea turtles, the coupling of respiration with locomotory behaviour is one factor that may limit aerobic performance. Since sea turtles have only intermittent access to air, they are required to load both arterial and venous blood with O2 before submerging.
Localization of FMRFamide-like peptides in the snail Helix aspersa
Authors: Lehman H. K. , Price D. A.
Published: April 2021

The distribution of FMRFamide-like material in the gastropod mollusc, Helix aspersa, was studied by radioimmunoassay (RIA) and immunocytochemistry. Most of the RIA activity was concentrated in the central nervous system, the male reproductive tract, the tentacles and the posterior digestive system (Table 1). The density of FMRFamidergic perikarya, nerves and nerve varicosities in the muscle tissue of all these regions, as indicated immunocytochemically (Fig. 2), was well correlated with the distribution as determined by RIA.

Gel chromatography of each extract resolved two peaks of FMRFamide-like immunoreactivity (Fig. 3). The first of these was further analysed by high-pressure liquid chromatography (HPLC), and the components included two major immunoreactive peaks identifiable, both by their retention times and their effects on the radula protractor muscle of Busycon contrarium, as the known peptides FMRFamide and pQDPFLRFamide (Figs 4–6). The second peak from gel chromatography gave only a single peak, distinct from that of FMRFamide and pQDPFLRFamide, in two HPLC systems (Fig. 7), but it did not behave like a competitive ligand in the FMRFamide RIA. Moreover, its immunoreactivity, unlike any peptides we tested, was not affected by carboxypeptidase Y (Fig. 8), and it was not active on the radula protractor muscle. Thus, it is certainly not an FMRFamide-like peptide.

We conclude that Helix aspersa contains at least two FMRFamide-like peptides, FMRFamide and pQDPFLRFamide. These peptides appear to act both as neurohormones and as neurotransmitters or modulators in the central ganglia, reproductive, digestive, muscular and circulatory systems.
Habituation of the cardiac response to involuntary diving in diving and dabbling ducks
Authors: Gabbott G. R. , Jones D. R.
Published: April 2021

Bradycardia in response to forced submergence was habituated in dabbling (Anas platyrhynchos, Linnaeus) and diving (Aythya americana, Eyton) ducks by repetitively submerging the animals, each day for several days, for periods of 40 and 20 s, respectively. The onset of pronounced bradycardia was delayed with each successive trial, until little or no bradycardia occurred during submergence. Diving bradycardia is driven by chemoreceptors in the dabbler and caused by stimulation of narial receptors in the diver. Mean arterial blood pressure in dives was unchanged from pre-dive levels in both naive and trained dabbling ducks. and pHa at the end of a dive were similar before and after habituation training. Bradycardia occurred in dives by habituated dabbling ducks if the animal breathed 15 % O2 before submergence. The ventilator responses to breathing high and low levels of oxygen were unaffected by habituation training. The changes in blood gases during dives by naive and habituated dabbling ducks were the same: therefore, in the absence of a demonstrated decrement in receptor chemosensitivity or efferent potency, the locus of habituation must reside in the central nervous system.
Effect of burst swimming and adrenaline infusion on O2 consumption and CO2 excretion in rainbow trout, Salmo gairdneri
Authors: Steffensen J. F. , Tufts B. L. , Randall D. J.
Published: April 2021

Immediately following burst swimming, the oxygen consumption of rainbow trout increased by 71%, carbon dioxide excretion by 104% and the respiratory exchange ratio by 17%. 80 min after burst swimming all of these parameters had returned to levels which were not significantly different from control values. Infusion of adrenaline into resting fish had no significant effect on oxygen consumption or carbon dioxide excretion and therefore there was no significant change in the respiratory exchange ratio. This infusion of adrenaline caused a significant elevation in the red blood cell pH which was still present 80 min later. The present results contrast with those of van den Thillart, Randall & Lin (1983), who demonstrated carbon dioxide retention after burst swimming. While it is possible that catecholamines may inhibit bicarbonate flux through the red blood cell, our experiments indicate that this inhibition would not result in detectable changes in carbon dioxide excretion or, therefore, in the respiratory exchange ratio.
Anaerobic Metabolism and Changes in Acid-Base Status: Quantitative Interrelationships and pH Regulation in the Marine Worm Sipunculus Nudus
Authors: Pörtner Hans-Otto
Published: April 2021

The quantitative influence of anaerobic metabolism on acid-base status and on acid-base regulation is investigated in Sipunculus nudus L. Proton generation by metabolism is calculated from theoretical predictions. The quantitative comparison of metabolic protons with non-respiratory protons found in the acid-base status is performed assuming a simplified model of the total animal. Taking the protonequivalent ion exchange between animals and ambient water into account, changes in the anaerobic acid-base status can be explained exclusively by proton generation in metabolism. It is concluded that the classical concept of acid-base physiology is adequate and that the consideration of strong ions is not required for a quantitative treatment of the acid-base status.

The hypothesis that a quantitative correlation exists between metabolic and acid-base events is tested by comparing changes in acid-base status and in metabolism in animals exhibiting different metabolic rates. For this purpose, a method is developed for the calculation of intracellular pH from metabolite concentrations and extracellular acid–base parameters. Proton exchange between intra-and extracellular compartments, which is found to depend upon the total amount of accumulated non-respiratory protons, demonstrates that pHi is regulated even during anaerobiosis. The defended pH1 value, however, is lower during anaerobiosis than during subsequent recovery.
Identification of Agrin in Electric Organ Extracts and Localization of Agrin-Like Molecules in Muscle and Central Nervous System
Authors: Smith Martin A. , Yao Yung-Mae M. , Reist Noreen E. , Magill Catherine , Wallace Bruce G. , Mcmahan U. J.
Published: April 2021

The portion of the muscle fibre’s basal lamina that occupies the synaptic cleft at the neuromuscular junction contains molecules that cause the aggregation of acetylcholine receptors and acetylcholinesterase on regenerating muscle fibres. Agrin, which is extracted from basal lamina-containing fractions of the Torpedo electric organ and causes the formation of acetylcholine receptor and acetylcholine esterase aggregates on cultured myotubes, may be similar, if not identical, to the acetylcholine receptor- and acetylcholinesterase-aggregating molecules at the neuromuscular junction. Here we summarize experiments which led to the identification of agrjn and established that the basal lamina at the neuromuscular junction contains molecules antigenically similar to agrin. We also discuss results which raise the possibility that agrin-like molecules at the neuromuscular junction are produced by motor neurones.
Selective Innervation of Types of Fibres in Developing Rat Muscle
Authors: Thompson W. J. , Soileau L. C. , Balice-Gordon R. J. , Sutton L. A.
Published: April 2021

The technique of glycogen depletion has been used to identify the types of muscle fibres innervated by individual motor neurones in the neonatal rat. This analysis shows that neonatal motor units are highly biased in their fibre type composition, even at times when the fibres receive extensive polyneuronal innervation. This finding suggests that the innervation of muscle fibres is somehow sorted according to type during early development. This sorting does not appear to occur during the removal of the polyneuronal innervation because little, if any, increase in the bias of unit compositions occurs as the number of synapses present in the muscle is reduced 2-to 3-fold. To determine whether the sorted innervation might be explained by a selective synaptogenesis, a study was made of the type compositions of units formed by reinnervation of neonatal soleus muscle. Glycogen depletion of single units 2 weeks following crush of the soleus nerve at postnatal day 2 showed that most of them (10/12) had biased type compositions which could not be explained by a random reinnervation. The location of fibres in the reinnervated motor units suggests that the regenerating axons innervated a novel set of fibres. The differentiation of fibres into types was apparently not changed during their reinnervation. These results imply that regenerating motor neurones in the neonatal rat selectively reinnervate muscle fibre types. These and other studies further imply that the organization of fibres into motor units during normal development does not occur, as is widely believed, by a random innervation of naive fibres and their subsequent differentiation under the influence of innervation.
Mechanisms of Function of Neural Grafts In The Adult Mammalian Brain
Authors: Dunnett Stephen B. , Björklund Anders
Published: April 2021

Evidence for the survival, growth and function of grafted neural tissues in the adult mammalian brain is reviewed. In addition to considering the viability of grafts in the different model systems that have been investigated, consideration is given to alternative mechanisms by which the grafts might exert a functional influence over the host brain and the host animal′s behaviour: (a) acute influence over spontaneous recovery of function, (b) chronic but diffuse secretion of neurochemicals into the host neuropile, (c) tonic reinnervation of the host brain, (d) bridging grafts, and (e) reciprocal reinnervation and full incorporation of graft tissue into host circuitry. It is concluded that no one mechanism is primary, but that different levels of reorganization can take place in different graft paradigms and neural systems.
Immune Reactivity in the Nervous System: Modulation of T-lymphocyte Activation By Glial Cells
Authors: Wekerle H. , Sun D. , Oropeza-Wekerle R. L. , Meyermann R.
Published: April 2021

The vertebrate central nervous system (CNS) has been traditionally thought to be inaccessible for the passenger lymphocytes of the immune system. This does not seem to be the case: activated T-lymphocytes can readily cross the endothelial blood-brain barrier (BBB) and some glial cells, notably the astrocytes, seem to be programmed to act as most efficient and complex partners for antigen-specific T-lymphocytes.

We used myelin basic protein (MBP) specific permanent rat T-lymphocyte lines as probes to assess the immune status of the CNS. These cells, upon activation in vitro, are able to transfer lethal, experimentally induced autoimmune-encephalomyelitis (EAE) to normal syngeneic recipients. Activated T-lymphocytes, but not resting ones, can break through the BBB irrespective of their antigen specificity. Immune surveillance of the CNS thus seems to be executed by activated T-lymphocytes.

Having crossed the BBB, the activated T-cells interact with local glial cells by releasing factors, including interferon-y, which induce astrocytes to synthesize and express, on their membranes, class II major histocompatibility antigens (la determinants), which are critically required for immunogenic presentation of antigens to T-cells. Indeed, la-induced astrocytes of the CNS (and the Schwann cells of peripheral nerves) are efficient antigen presenter cells, which are able strongly to up-regulate antigen-reactive T-lymphocytes.

In addition, it has recently been shown that at least some astrocytes are able to down-regulate immune cells. Some, but not all, astrocytes are capable of suppressing activation of T-cells. This suppression can be modulated by interferon-y, and is sensitive to irradiation. The question of whether suppression is mediated by direct cell-to-cell contact or via soluble mediators (e.g. apolipoprotein E) is under investigation. Astrocytes have been found to be most subtle regulators of immunocompetent T-cells. Most probably they are centrally involved in physiological immune reactivity of the CNS, and it will be tempting to learn how far glial cells are involved in transmitting regulatory signals between the immune and nervous systems.
Functional Significance and Neural Basis of Larval Lamprey Startle Behaviour
Authors: Currie S. N. , Carlsen R. C.
Published: April 2021

The vibration-evoked startle response mediates rapid withdrawal in burrowed larval lampreys (ammocoetes). Ammocoetes withdraw in response to vibration by contracting pre-existing lateral bends in the trunk and tail, thus pulling their heads deeper into the burrow. The motor effects of an ammocoete startle response are dependent on preexisting posture. Areas of lateral body curvature contract more and exhibit larger electromyogram (EMG) amplitudes on their inner sides than on their outer sides. Both of the anterior Mth and posterior Mth′ (Mauthner) cells and both of the B1 and B2 (bulbar) Müller cells fired action potentials in response to vibration of the otic capsules. Both B3 and B4 Müller cells were inhibited by vibration, while M (mesencephalic) and I1 (isthmic) Müller cells were inhibited by ipsilateral vibration and excited by contralateral vibration. Simultaneous action potentials in both of the anterior Mth cells were appropriate and sufficient for initiating the startle response EMG in a semi-intact preparation. This study demonstrates a Mauthner-initiated startle response which activates musculature on both sides of the body to produce a rapid withdrawal movement and is thus adapted to the eel-like form and burrowed lifestyle of larval lampreys.
Compensation of Progressive Hypercapnia in Channel Catfish and Blue Crabs
Authors: Cameron James N. , Iwama George K.
Published: April 2021

Channel catfish (Ictalurus punctatus Rafinesque) were progressively acclimated to CO2 partial pressures of 7·5, 15, 30, 45 and 58mmHg (1, 2, 4, 6 and 8% CO2 in air) and blue crabs (Callinectes sapidus Rathbun) to 15, 30 and 45 mmHg, with 24 h at each partial pressure. Measurements of both conventional acid-base parameters (pH, total CO2) and ′strong′ ion concentrations (Na+, K+, Mg2+, Ca2+ and Cl−) were made at various times during each treatment. Intracellular [Na+], [K+] and [Cl−] were determined for red and white muscle in control and hypercapnic (8%) catfish. Extracellular [HCO3−] and strong ion difference (SID) both rose during hypercapnic compensation, with correlation coefficients (r) of 0·97 (P<0·01) for catfish and 0·41 (NS) for blue crabs. Since [HCO3−] is calculated from two rapid measurements, and SID from four separate procedures, the former appears to be the measurement of choice. The results also dispel the notion of a 30mequivl−1 upper limit to bicarbonate compensation: [HCO3−] values over 50mequivl−1 were achieved in both animals, and %pH regulation remained around 70% at the highest . Due to superior intracellular buffering, the large change in extracellular SID did not lead to a measurable change in the concentrations of the major intracellular ions. The primary gill filaments of hypercapnic catfish showed a 30% increase in numbers and a 75 % increase in area of apical crypts of chloride cells. The chloride cell ′patches′ in crab gills increased in staining density after hypercapnia but did not enlarge.
Selective and Reversible Blocking of the Lateral Line in Freshwater Fish
Authors: Karlsen Hans Erik , Sand Olav
Published: April 2021

Fish possess two separate systems for detection of low-level sound and water motions in the low-frequency range: the inner ear and the lateral line. The relative roles of these systems in normal fish behaviour is still not clear. There is, for instance, a lack of experimental evidence showing the involvement of the lateral line and the inner ear in detection of infrasound, in directional hearing in the near field, and in detection and attack of swimming prey below the surface. To provide a useful tool for such studies, we have developed a pharmacological method for selective and reversible blocking of the lateral line in the roach (Rutilas nitilus). By recording multi-unit activity from the lateral line nerve and microphonic potentials from the inner ear, we have shown that cobalt ions in the external water may completely block the mechanosensitivity of the lateral line without affecting the utricular microphonic activity. This inhibiting effect of Co2+ is antagonized by Ca2+, making the ratio between these ions the important blocking factor. For practical work, we recommend 12-24h exposure to 0·1mmoll−1 Co2+ at a Ca2+ concentration of less than 0-1 mmol l−1. The fish showed no sign of general behavioural disorders even after 1 week in this solution, and the microphonic sensitivity of the inner ear was not reduced. The blocking effect of Co2+ was clearly reversible, and the recovery was dependent upon both the duration of the Co2+ exposure and the Ca2+ concentration of the recovery solution.
The Effects of Salinity Acclimation on The Osmotic Properties of Mitochondria From The Gill of Crassostrea Virginica
Authors: Ballantyne James S. , Moyes Christopher D.
Published: April 2021

Glutamate oxidation in mitochondria from the gills of oysters (Crassostrea virginica Gmelin) acclimated to sea water (SW) is sensitive to assay medium osmolantv. Compared to a medium of the osmolarity of sea water, decreasing osmolarity stimulates glutamate oxidation and increasing osmolarity inhibits glutamate oxidation. Glutamate oxidation by mitochondria from oysters acclimated to dilute sea water (DSW) is 2·5-fold greater than in SW animals when each is assayed under isosmotic conditions. The maximal rates obtained in both acclimation groups are equal. Although the DSW animals were acclimated to an osmolarity approximately 660mosmol1−1 lower than SW animals, the osmotic optimum was only 100-200 mosmol 1−1 lower in the former group. Isolation medium osmolarity does not affect the osmolarity at which the maximum rate of glutamate oxidation is observed in either acclimation group. A low-osmolarity isolation medium reduces the oxidation rates and quality of the mitochondria, as assessed by the respiratory control ratio in both acclimation groups. These data suggest that an optimal matrix solute concentration or ionic strength is required for maximal rates of glutamate oxidation rather than an optimal mitochondrial volume. The optimal mitochondrial matrix milieu can be achieved both by acclimation to dilute sea water and by incubation in hypo-osmotic media.
Pigeon Homing: Familiarity With the Release Site Reduces the Release Site Bias
Authors: Kowalski Ute , Wiltschko Roswitha
Published: April 2021

When homing pigeons are released, they usually do not depart directly towards home, but deviate from the home direction: the so-called ′release site bias′ (Keeton, 1973 as a translation of the German Ortseffekt by Wallraff, 1959a). These deviations, which were first described by Kramer (1957), vary in size. At most sites, they are not very large, but occasionally may be as much as 180°. Releases at the same site normally produce very similar results, which are independent of weather conditions, age and general experience of the birds (Wallraff, 1959b) so that the bias is characteristic for any given location (Keeton, 1973). In view of the modern concepts of a learned navigational ′map′ (see Wallraff, 1974; Wiltschko & Wiltschko, 1978, 1982, 1987) it is interesting to know how local experience at the site itself could affect the pigeons′ behaviour.
Temperature Regulation in Bee- and Wasp-Mimicking Syrphid Flies
Authors: Morgan Kenneth R. , Heinrich Bernd
Published: April 2021

Thoracic temperatures were measured in 12 syrphid species. During field activity the flies maintained thoracic temperatures near 30°C by a combination of basking and endothermy. In the 10 species which were mimics of Hymenoptera, thoracic temperatures averaged a few degrees below those of their models. All of the syrphids tested demonstrated a marked capacity for endothermic warm-up in the laboratory. Warm-up rates ranged from 1·2–5·5°C min−1. The maximum rate of warm-up increased in a linear fashion with body mass, with a slope of 4-3. The flies sometimes sustained endothermy beyond the 2–5 min necessary for thoracic temperature to reach flight temperature. One individual maintained an average temperature excess of 13·4°C for more than 26 min. Cooling rates were highly dependent on body mass and did not differ significantly between pubescent Bombus mimics and glabrous species. Removal of pile from the thorax of Bombus mimics increased their cooling rates by about 30%. From the comparisons between wasp and bee mimics, we conclude that although the pubescence of Bombus-mimicking flies aids endothermy, it is not necessary to achieve it. Their pubescence has apparently evolved primarily to improve visual mimicry.
Indoor Flight Experiments With Trained Kestrels: I. Flight Strategies in Still Air With and Without Added Weight
Authors: Videler J. J. , Vossebelt G. , Gnodde M. , Groenewegen A.
Published: April 2021

Two kestrels, a male and a female, were trained to fly over 50 and 125 m in a windless corridor. Both distances were flown with or without dead weights attached to the feet during 13 flight sessions for each bird. Added weight was either 0·3 N (31 g lead) or 0·6 N (61 g). Each session was devoted to one distance and one flight weight category. Flight duration was automatically recorded at the landing points and at four positions along the track. Gliding bouts were hand-clocked and flight altitudes were estimated with the aid of sidewall markings.

An analysis was made of 1226 flights by the female over a total of 100 km, and 1017 flights by the male over 84·6 km.

Different flight strategies were observed under the different experimental situations, and were compared with model predictions for optimal speeds.

In the unloaded situations the birds flew at velocities close to the maximum range speed. Under load, speeds were lower and close to the predicted speeds for minimum power when 0·6 N was added to the weight.
Circulation in the Leech, Hirudo Medicinalis L.
Authors: Hildebrandt Jan-Peter
Published: April 2021

In the leech, the physiological significance of high-pressure phases (HIP) and low-pressure phases (LOP) of the lateral vessels was studied by intravascular pressure recordings and observation of blood flow in different parts of the circulatory system, and by measurements of the blood flow velocities in the dorsal vessel.

Different shapes of the pressure pulses were found in the anterior lateral vessel segments during HIP and LOP phases, according to the different modes of diastolic filling in both phases.

Pressure recordings in the lateral abdominal vessels showed the different action of the lateral abdominal sphincters in the HIP and LOP phases of the ipsilateral lateral vessel. The LOP contractions were responsible for the blood supply to the capillary networks of the organs and the body wall, with the possible exception of the intestine. The HIP contractions caused a forward bloodflow within the lateral vessel.

In the dorsal vessel, the blood pressure was about 0·9-l·9kPa in different animals. The blood flow was discontinuous with velocities of 0·5-10 mm s−1. Average blood flow in the dorsal vessel was 22·9μ1 min−1.

An improved model of the circulation in the leech is presented.
Vibration Sensitivity in the Statocyst of the Northern Octopus, Eledone Cirrosa
Authors: Williamson R.
Published: April 2021

The question of whether cephalopods have a sense of hearing has recently received renewed attention in the literature (Moynihan, 1985; Hanlon & Budelmann, 1987). However, the scarcity of physiological data (Maturana & Sperling, 1963; see also Budelmann, 1977) has meant that both those taking the view that cephalopods are deaf (Moynihan, 1985) and those of the opposing view (Hanlon & Budelmann, 1987) have relied almost entirely on morphological and behavioural evidence. Unfortunately, the morphological evidence cannot be conclusive and some behavioural experiments indicate no reaction to sound by cephalopods (Hubbard, 1960), although this is contradicted by other observations (Maniwa, 1976).
A New Technique to Monitor the Flight Paths of Birds
Authors: Bramanti M. , Dall’antonia L. , Papi F.
Published: April 2021

The study of the mechanisms which govern bird orientation and navigation is severely hindered by the difficulty of reconstructing the route taken by the bird. Several methods have been used to study bird flights: direct observation using binoculars; following the bird by aeroplane or helicopter (Griffin, 1943; Hitchcock, 1952; Fiaschi, Baldaccini, loalè & Papi, 1981); using a transmitter carried by the bird (Michener & Walcott, 1966; Schmidt-Koenig & Walcott, 1978); and location of the bird using radar techniques (Eastwood, 1967; Papi & Pardi, 1978). All these techniques require that the bird and the monitoring equipment always be within optical or electromagnetic ‘visibility’.
Eye/Photophore Coordination and Light-Following in Krill, Euphausia Superba
Authors: Grinnell A. D. , Narins P. M. , Awbrey F. T. , Hamner W. M. , Hamner P. P.
Published: April 2021

Eight of the 10 photophores of the Antarctic krill, Ettphausia superba, are located at the ends of muscular stalks and exhibit coordinated orientation responses to incident white light; light emitted from the photophores is directed away from the incident light. Moreover, eye rotation occurs synchronously with photophore movement. Immobilization of one or both eyes eliminated the photophore light-following response in 40% of the trials, but in the remaining 60%, photophores continued to exhibit oriented, but less stable responses. In the presence of a stationary light source the eyes could be passively rotated without affecting photophore position. Furthermore, eye removal or covering the head with an opaque hood eliminated coordinated photophore movement. We conclude that vision is necessary for light-following responses by the photophores. In addition, the control signal for that movement is CNS-derived, may occur spontaneously or may be light-induced, and appears to be accompanied by a parallel signal governing eye rotation. Subtle differences in photophore response when krill were oriented other than horizontally imply that krill may have a gravity sense that could help them orient in darkness.
In Vivo Lactate Kinetics at Rest and During Recovery From Exhaustive Exercise in Coho Salmon (Oncorhynchus Kisutch) and Starry Flounder (Platichthys Stellatus)
Authors: Milligan C. Louise , Mcdonald D. Gordon
Published: April 2021

A bolus injection of [14C] lactate was used to measure lactate turnover rates at rest and during recovery from exhaustive exercise in coho salmon (Oncorhynchus kisutch) and starry flounder (Platichthys stellatus). At rest, lactate turnover rate in salmon was almost double that in flounder (1·33 versus 0·76 μmol min−1 kg−1), which reflected the higher blood lactate level in salmon (1·00 versus 0·12mmol l−1). From 2 to 4h after exercise, when blood lactate levels were at their peak and constant, turnover rates were elevated in both species, though to a greater extent in salmon than in flounder (11·88 versus 2·27 μmol min−1 kg−1). Lactate concentration and turnover rate were linearly correlated in both species. The higher turnover rate in salmon was solely a consequence of the higher blood lactate levels since, at similar blood lactate concentrations, turnover rates in flounder and salmon were the same. Therefore, the lower blood lactate levels in flounder after exercise were not a consequence of higher turnover. In neither species was the turnover rate adequate to account for the rate of lactate clearance from the muscle, suggesting a large portion was retained within the muscle and metabolized in situ. Furthermore, following injection of [14C] lactate, >80% of the total blood activity was recovered as lactate, indicating that little label was incorporated into other products (e.g. glucose). These data suggest that the Cori cycle plays a minimal role in the metabolism of lactate in salmon and flounder. Furthermore, at least in flounder, there was no correlation between the kinetics of lactate clearance and O2 consumption, suggesting that the classical concept of ‘O2 debt’ is not applicable in this species.
A Neuronal Role for A Crustacean Red Pigment Concentrating Hormone-Like Peptide: Neuromodulation of the Pyloric Rhythm in the Crab, Cancer Borealis
Authors: Nusbaum Michael P. , Marder Eve
Published: April 2021

The distribution of red pigment concentrating hormone (RPCH)-like immuno-reactivity (RPLI) in the stomatogastric nervous system of the crab, Cancer borealis, was studied using whole-mount immunocytochemistry. RPLI was seen in neuropilar processes in the stomatogastric ganglion (STG), and in somata in the oesophageal ganglion and commissural ganglia. Staining was blocked by preincubating the antiserum with RPCH, as well as with a number of adipokinetic hormones (AKHs) and related peptides.

Synthetic RPCH had strong actions on the pyloric rhythm of the isolated STG. Bath applications of RPCH (10−9-10−6moll−1) increased the cycle frequency in preparations displaying slow pyloric rhythms, and initiated rhythmic pyloric activity in silent preparations. In the presence of tetrodotoxin (TTX), RPCH evoked rhythmic non-impulse-mediated alternations in membrane potential in the lateral pyloric and pyloric dilator motor neurones. The effects of RPCH were compared to those of a series of AKHs which resemble RPCH structurally.

The immunocytochemical and physiological data together suggest that RPCH or a similar molecule is a neurally released modulator of the STG.
Influx and Transepithelial Flux of Amino Acids in the Mussel, Mytilus Edulis
Authors: Rice Michael A. , Stephens Grover C.
Published: April 2021

The uptake of amino acids by the non-gill epithelia of the mantle cavity of Mytilus edulis L. was studied and compared with uptake by the gills. Amino acid entry rates and the subsequent distribution of amino acids to the other tissues of the animals were studied using high-performance liquid chromatography and radiochemical techniques. Uptake via the non-gill epithelia lining the mantle cavity was separated from uptake via the gill by employing a preparation in which the gills were surgically removed. Amino acid uptake by such animals was compared with that of suitably sham-operated controls.

In short-term experiments (up to 2h), transfer of substrate from the gills to other tissues of the animal is extremely limited. Amino acids taken up by the non-gill epithelia of the mantle cavity are rapidly transferred to deeper tissues. Roughly 25 % of alpha-amino acids enter the animal via the non-gill epithelia. Estimates of total epithelial surface area for the gills and non-gill mantle epithelium are compared with entry rates of amino acid substrates via the two routes. The apparent densities of carriers for alanine and cycloleucine per unit area of surface are approximately equal for these two substrates. The density of taurine carriers per unit area of non-gill epithelium is apparently significantly higher than their density per unit area of gill epithelium. Finally, evidence is presented for differential sensitivity of taurine transporters in the non-gill epithelium to inhibition by alpha-amino acids.
Retinoid Changes in the in vitro Regeneration of Frog Visual Pigments
Authors: Azuma Masami , Azuma Katsu
Published: April 2021

To investigate the regeneration of visual pigment, the changes in composition and quantity of retinoids were measured by high-performance liquid chromatography (HPLC). Eye cups or eye cup sections of dark-adapted frogs were exposed to light (>500 nm) and incubated in the dark for several hours (pH 7·4, 27 ± 1°C). Retinoids extracted by the oxime method before and after illumination were analysed by HPLC.

In the dark, every eye cup or eye cup section contained 11-cis and all-trans isomers of retinyl palmitate (the proportion of 11-CIS was nearly 40 %). The amount of retinyl palmitate was 1–1·-5 molequiv of visual pigment. After 80% of the visual pigment had been bleached by illumination, eye cups or eye cup sections were incubated in the dark for 10 h. During the incubation, 70% of the bleached pigment was regenerated, and the proportion of 11-cis retinyl ester decreased from 40% to 13 %. These results indicate that stored 11-cis retinyl ester is used for the regeneration. The regeneration rate of A2-pigment (half time = 75 min) was faster than that of A1-pigment (half time = 90min), consistent with the result of Tsin & Flores’ (1986) in vivo experiment with goldfish.
Isolated Giant Smooth Muscle Fibres in Beroe Ovata: Ionic Dependence of Action Potentials Reveals two Distinct Types of Fibre
Authors: Bilbaut André , Meech Robert W. , Hernandez-Nicaise Mari-Luz
Published: April 2021

The ionic dependence of action potentials evoked in giant smooth muscle fibres isolated by enzymatic digestion from the body wall of the marine invertebrate Beroe ovata (Ctenophora) has been investigated using conventional electrophysiological techniques. Differences were observed in the two fibre types studied. The resting membrane potential was –60 ± 1·35 mV (N = 25) in longitudinal muscle fibres and –66 ± 1·37 mV (N =32) in radial fibres. Action potentials had a short plateau in longitudinal fibres but not in radial fibres. The action potential overshoot of both fibre types was decreased in Ca2+-free artificial sea water (ASW). In Na+-deficient ASW, action potentials could not be generated in radial fibres and showed a reduced overshoot in longitudinal fibres. Tetrodotoxin (10−smoll−1) added to ASW or Ca2+-free ASW did not affect the action potentials of either type of fibre. Action potentials of both fibres were partially blocked by Co2+ (20-50 mmol 1−1) or Cd2+ (1-2 mmol 1−1). Action potentials of longitudinal fibres in Na+-deficient ASW were abolished by Co2+ (20 mmol 1−1). In Ca2+-free ASW, the action potential overshoots of both sets of fibres were restored following the addition of Sr2+ or Ba2+. In longitudinal fibres, Sr2+ increased the duration of the action potential plateau. In both longitudinal and radial muscle fibres, Ba2+ prolonged the action potential. In longitudinal fibres exposed to tetraethylammonium chloride (TEACI) or 4-aminopyridine (4AP), the action potential was slightly prolonged. In these fibres, TEA+ or 4AP added to Ca2+-free ASW induced only a long-lasting depolarizing plateau. In radial fibres, the action potential duration was slightly increased in the presence of TEA+; it was unaffected by 4AP. In Ca2+-free ASW, TEA+ and 4AP induced an oscillating membrane response which appeared to be dependent on the intensity of the injected current pulse. It is concluded that (a) there are significant differences between the action potentials of longitudinal and radial muscle fibres but that both are dependent on Na+ and Ca2+, (b) in longitudinal fibres, a Ca2+-activated K+ conductance and a TEA+-sensitive voltage-activated K+ conductance contribute to the repolarizing phase of the action potential, the former being predominant, (c) in radial fibres, the repolarizing phase of action potentials probably involves different membrane K+ conductances among which is a TEA+-sensitive K+ conductance.
The Landing Response of Tethered Flying Drosophila Is Induced at A Critical Object Angle
Authors: Wittekind W. C.
Published: April 2021

An investigation was made to find which simple parameters of a visual stimulus are critical to induce a landing response in tethered flying Drosophila melanogaster.
Octopamine in a Neurohaemal Area Within the Antennal Heart of the American Cockroach
Authors: Pass Günther , Sperk Günther , Agricola Hans , Baumann Eckehard , Penzlin Heinz
Published: April 2021

A great deal of research suggests that octopamine functions as a neuromodulator, neurotransmitter and neurohormone in insects (Orchard, 1982; Evans, 1985; Hoyle, 1985). Especially high concentrations of this biogenic amine have been reported for neurohaemal tissue such as the corpora cardiaca and the neurohaemal organs of the medial nervous system (Evans, 1985). In the presented paper, octopamine is shown to occur in another neurohaemal area located within the antennal heart of the cockroach, Periplaneta americana.
Relationship Between Wing Loading, Wingbeat Frequency and Body Mass in Homopterous Insects
Authors: Byrne David N. , Buchmann Stephen L. , Spangler Hayward G.
Published: April 2021

Several biophysical properties of members of Aleyrodidae and Aphididae were examined in order to explore how homopterous insects fly. Five species of aphids were found to weigh significantly more than five whitefly species (range 1 · 14-7·02×10–4g for aphids vs 3·3-8·0x 10–5g for whiteflies) and to have significantly larger wing surface areas (range 0·0103–0·1106 cm2vs 0·0096-0·0264cm2). As a consequence whiteflies and aphids can be partitioned into two groups with respect to wing loading (range 0·00633-0·01412 g cm–2 for aphids, 1·74-5·23X 10–3gcm–2 for whiteflies). Members of the two families are also separated in terms of wingbeat frequency (range 81·1-123·4Hz for aphids, 165·6–224·2 Hz for whiteflies). Since our animals were much smaller than any insects examined previously for these parameters, values were compared with the same parameters for 149 insect species recorded in the literature. Using these data, we found wingbeat frequency to be significantly correlated with wing loading only in insects weighing more than 0·03 g. Larger insects seem to employ a strategy similar to other flying animals, by compensating for high wing loading with higher wingbeat frequencies. The lack of correlation for these two parameters in insects weighing less than ·03 g probably results from the use of different flying strategies. These include employment of a clap and fling mechanism and the possession by some of exceedingly low wing loading. Also, small insects may have reduced settling velocities because they possess high drag coefficients. Previous studies which failed to establish a relationship between wing loading and wingbeat frequency in larger insects may have considered too few subjects or too great a range of body masses. The mass range is important because smaller insects which employ increased wingbeat frequency must use rates exponentially higher than those of larger insects utilizing the same strategy.
Functional Principles of Pattern Generation for Walking Movements of Stick Insect Forelegs: the Role of the Femoral Chordotonal Organ Afferences
Authors: Bässler Ulrich
Published: April 2021

A rampwise stretch of the femoral chordotonal organ is known often to elicit a response in the active decerebrate stick insect that is termed an ‘active reaction’, and which can be considered to represent part of the step cycle. During the first part of the response, the flexor motor neurones are excited and the excitatory extensor motor neurones are inhibited, forming a positive feedback loop. When the chordotonal organ reaches a position corresponding to a flexed femur-tibia joint, the flexor motor neurones are inhibited and the extensor motor neurones are excited.

In this study, extracellular and intracellular recordings showed that, during an active reaction, the excitation of the retractor unguis motor neurones usually paralleled that of the flexor motor neurones, whereas the protractor coxae motor neurones were less strongly coupled to this system.

The first part of the active reaction occurred only at low stimulus velocities. At high stimulus velocities negative feedback was present. The first part therefore represents some kind of velocity-control-system for active flexions.

ElecTr1cal stimulation of the nerve containing the axons of trochanteral campaniform sensilla and of the hairfield trHP decreased the likelihood that concurrent chordotonal organ stimulation would elicit an active reaction. Further-more, most of the active reactions that occurred under these stimulus conditions involved only the flexor tibiae muscle.

The results indicate that: the walking pattern generator is composed of subunits that are only loosely coupled centrally; it probably does not include a central pattern generator; and generation of an active reaction is a two-step process.
The Organs of Adhesion in the Aphid Megoura Viciae
Authors: Lees A. D. , Hardie Jim
Published: April 2021

The anatomy of the adhesive organs is described in Megoura viciae Buckton. The claws serve as grappling hooks which are locked in position by the retractor unguis tendon. The pulvilli, pliable cuticular sacs, are everted from the tibiotarsal articulation. They bear a surface adhesive, a non-volatile oil, which is secreted through the cuticle. The pulvilli are everted by blood pressure and are withdrawn inside the tibia by contraction of the tibial muscles. The adhesion of these organs to various types of surface was tested by covering over the pulvilli or by claw amputation. Pulling forces were applied by progressively loading the aphid with weights. The pulvilli perform best on relatively smooth surfaces. Aphids are dislodged from the underside of polished glass by a mass of approx. 9-14 mg (a pulling force of 8·8-13·7xl0-5N). The claws cannot engage a completely smooth surface but are highly effective on rough ones, withstanding a load of approx. 57 mg on dry filter paper. Adhesion of the pulvilli to waxy surfaces is only slightly less than on glass but is greatly reduced on surfaces with still lower free energies, such as Teflon. On a glass surface the pulvilli sometimes leave ‘footprints’ consisting of oily droplets of variable size. Nevertheless, in many instances such deposits are small or absent, indicating that the bond sometimes breaks between the adhesive and the substratum. In a selected series of footprints with large deposits, their volume was found to be sufficient to form a layer at least 17·7xl0-9m in thickness over the area of pulvillar contact. This is consistent with the view that surface tension forces would adequately account for adhesion, an additional limiting factor being the physical properties (wettability) of the substratum. Viscous forces would impede the very rapid (less than 0-02 s) removal of the pulvilli, were it not for the retraction mechanism which peels off the pulvillus from the distal edge, like a piece of adhesive tape. The ultrastructure of the pulvillar gland is described. The epidermal cells discharge into a cavity which is confluent with a further reservoir within the spongy endocuticle, itself a meshwork of dissociated cuticular microfibrils. The points of exit of the secretion appear to be the epicuticular filaments. The product of the gland, which can be collected by pricking the pulvilli, is water soluble and proteinaceous, differing entirely from the hydrophobic lipid-soluble end-product on the pulvillar surface. We presume that the lipoprotein precursor is dissociated enzymatically at the level of the inner epicuticle.
Further Observations on Dipteran Flight: Details of the Mechanism
Authors: Miyan Jaleel A. , Ewing Arthur W.
Published: April 2021

We took high-intensity flash photographs of the wing base during tethered flight of Lucilia sericata. These show that the radial stop and the pleural wing process separate during the upper part of the wing beat and then mate together on the downstroke. Using tungsten needle probes attached to wire strain gauges, we measured the movements of the parascutal shelf (PSS), of the lateral and dorsal scutum, and of the scutellum during tethered flight. We made a detailed study of the wing base sclerites and associated muscles in order to answer criticisms of our original model (Miyan & Ewing, 1985a,b). The PSS rotates upwards about its hinge with the lateral scutum at the start of the downstroke. 4. The dorsal scutum and medial edge (at the hinge) of the PSS are held down, presumably as a result of dorsoventral muscle activity. As the downstroke progresses, the whole of the PSS and dorsal scutum are lifted together suggesting the action of a locking mechanism. At the bottom of the downstroke there is an opposite, downward rotation of the shelf about its hinge that follows the start of downward scutal movement at the beginning of the upstroke. This is followed by downward movement of the whole PSS and scutum. Movements of the lateral scutum exactly follow scuteliar and lateral PSS movements and are probably dictated by the articulation. Scanning electron micrographs illustrate the probable components of the wing base-PSS locking mechanism. Rotation of the first axillary sclerite, brought about by the rising scutellar lever arm, results in mating of its medial arm with a recess in the PSS. This prevents further rotation of the PSS which is now held at two points by the sclerite and is lifted by further movement of the lever. There is no evidence that the third axillary muscles act as wing pronators. Scanning electron micrographs show a mechanism that maintains the line of action of the muscles on the posterior edge of the wing.