bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Phlorizin on the Metabolism of Cytolysing Sea-Urchin Eggs
Authors: Rothschild Lord
Published: April 2021

Unfertilized sea-urchin eggs produce acid when they are cytolysed or fertilized (Ashbel,, 1929; Runnstr öm, 1933 a, 1935). Neither the post-fertilization nor the post-cytolysis acid has been identified. The number of different acids which might be released is large, and it has not so far been considered expedient to attempt direct analysis of the sea water surrounding the activated eggs. One way of establishing the nature of the acid is by observing the effect of specific metabolic inhibitors on its production. Runnström (1933 b, 1935) used this technique, but the inhibitors used were all negative in their effect, i.e. they did not inhibit acid production. Runnströom investigated the effect of inhibitors which affect one type of glycolysis.1 This paper is also concerned with the effect of a glycogen breakdown inhibitor. If the acid production after cytolysis is associated with the formation of hexose phosphate from glycogen, it should be partly or wholly inhibited in the presence of phlorizin (Lundsgaard, 1933).
Colorimetric Method for Estimation of Dissolved Oxygen in the Field
Authors: Johnson M. L. , Whitney R. J.
Published: April 2021

The suitability of the Winkler method for the estimation of oxygen dissolved in water is well established (Standard Methods of Water Analysis, 1936; Fox & Wingfield, 1938). Its usefulness in the field, however, is limited by the fact that it is necessary either to titrate the iodine solutions in the field, or to carry back to the laboratory numerous samples of water. Moreover, the titration of iodine solutions necessitates the frequent standardization of the sodium thiosulphate solution. With the modification of the Winkler method described here, the oxygen content of water can be estimated quickly and easily in the field without bulky apparatus. As no standard solutions are required the method is particularly useful when estimations are made only occasionally.
Studies in Animal Locomotion
Authors: Gray J.
Published: April 2021

The locomotory movements of a typical polychaete worm, such as Nereis diversicolor, are of interest in that they are effected by two distinct mechanisms, (i) a series of parapodia which act as levers comparable to the appendages of terrestrial animals, (ii) the longitudinal muscles of the body. When Nereis is moving slowly over a solid surface, only the parapodia are active; during more rapid motion, or when the animal is swimming through water, the movements of the parapodia are co-ordinated with those of the longitudinal muscles and the two mechanisms combine to give a highly co-ordinated locomotory mechanism.
Studies on Amphibian Metamorphosis
Authors: Helff O. M.
Published: April 2021

The histolysis of the anuran operculum during forelimb perforation formation has been accredited to the action of autolysing gill tissue, to cutaneous gland secretions, and to self-degeneration of the integument by Helff, Weber, and Blacher et al. respectively. The writer has reinvestigated the problem as follows:

Opercular integument, homoplastically transplanted to the back and side of R. temporaria larvae, underwent a process of partial degeneration. The histolysis was not confined to any localized region of the transplant. Autoplastic transplantation of opercular integument to the back and side produced a variety of results. Normal histological structure was maintained in certain transplants, generalized degeneration was observed in others, while in several instances localized histolysis resulting in perforation formation occurred. Homoplastic and autoplastic transplantation of back and side skin to the opercular region resulted in histolysis and perforation formation in such transplants during larval involution. The right forelimbs (in early stages of development) with attached portions of the shoulder girdle were extirpated in R. temporaria and B. bufo. During subsequent metamorphosis, normal opercular histolysis followed by perforation formation in many cases was observed. In most instances, serial sections of the peribranchial cavity revealed the absence of cutaneous glands. Extirpation of the right forelimb only was made in the same two species. Opercular histolysis subsequently occurred in all instances, resulting in perforation formation in the great majority of cases during larval involution. In many of the B. bufo animals two separate perforations developed, one filled with limb stump and the other with gill tissue. It is concluded that in R. temporaria a particular area of the operculum may in some individuals possess self-degenerative potentialities conducive to histolysis and perforation formation during metamorphosis. In both R. temporaria and B. bufo histolytic influences emanating from the atrophying gill tissue and the cutaneous glands of the forelimb are probably also responsible for operêular histolysis and perforation formation. Limb pressure must be considered a supplemental factor. The results are discussed in general and attention called to the fact that opercular histolysis and perforation formation are “doubly assured” in some species and possibly even “triply assured” in others. Emphasis is placed on the evidently wide divergence between species as regards the particular combination of factors responsible for opercular histolysis and perforation formation. Apparently, no one explanation can serve to account for the phenomenon as it occurs in various species of anurans.
Potentials and Effective Ionic Mobilities in Frog Skin
Authors: Dean R. B.
Published: April 2021

Frog skin has been used by many workers in the study of bioelectric phenomena of living membranes. The isolated living skin mounted with Ringer’s solution on both sides maintains a potential of from 10 to 100 mV., the inside of the skin being positive. This potential can be modified by changing the chemical or physical conditions. Many workers have attempted to interpret the results of such changes in terms of simple membrane potentials but without much success. Dean & Gatty (1937) point out some of the difficulties of such interpretation and review the literature. There is evidence of at least two sources of potential in the skin which may at times be opposed (Steinbach, 1933), and also that the active surfaces are not uniform but present a mosaic structure (see also Dean, 1938).
Experiments on the Effect of Dyes on Induction and Respiration in the Amphibian Gastrula
Authors: Beatty R. A. , de Jong S. , Zieliński M. A.
Published: April 2021

It is shown that pieces of presumptive epidermis (ventral ectoderm of the gastrula), when isolated into weak solutions of several dyes, will undergo neural differentiation. Dyes such as Janus green and neutral red, which are not known to accelerate cell respiration, appear to have this effect, as well as methylene blue, the accelerating action of which on cell respiration is well known. Measurements of the oxygen consumption of isolated pieces of the gastrula by the Cartesian Diver method show that methylene blue, if in weak concentration, has an accelerating action of about 45 %. In stronger concentrations it is inhibitory.
The Micro-Estimation of Sodium, Potassium, Calcium, Magnesium, Chloride, and Sulphate in Sea Water and the Body Fluids of Marine Animals
Authors: Robertson J. D. , Webb D. A.
Published: April 2021

Methods are presented for the estimation of sodium, potassium, calcium, magnesium, chloride and sulphate in sea water and in other solutions, such as the blood and body fluids of marine animals, whose inorganic composition is similar to that of sea water.

The estimations may be performed on 1 ml. samples, and the limit of error is about 2 %.

Sodium is precipitated and weighed as sodium zinc uranyl acetate ; potassium is precipitated as potassium silver cobaltinitrite which is titrated with ceric sulphate ; calcium is titrated with ceric sulphate after two precipitations as oxalate ; magnesium is precipitated with hydroxyquinoline and the precipitate brominated and estimated iodometrically; chloride is treated with silver iodate and the released iodate estimated iodometrically; sulphate is titrated with barium chloride using sodium rhodizonate as indicator.
On The Physiology and Pharmacology of the Earthworm Gut
Authors: Wu K. S.
Published: April 2021

The physiology of the gut movements in invertebrates has been little studied. In the case of the earthworm, although numerous investigations have been published on the physiology of locomotion and of the neuro-muscular structures of the body wall, nothing has yet appeared on the gut movements. It was with the intention of throwing light on this problem that the present investigation was undertaken.
A Method for the Direct Study of Natural Selection
Authors: Gordon Cecil
Published: April 2021

Decisive experiments on selection of mutants of Drosophila melanogaster can be carried out under natural conditions in Britain where this species is not indigenous. This communication records an experiment in which a balanced population containing 25 % ebony mutants was released in South Devon. The frequency of the genotype among the descendants was estimated after a period equivalent to six discrete generations, by testing trapped flies, most of which were wild type in appearance, for heterozygosis. The frequency estimated was very close to what would be deduced on the assumption that elimination of the recessive type before maturity was complete.
Central Nervous Activity in the Earthworm
Authors: Collier H. O. J.
Published: April 2021

Regular rhythmic peristaltic movements of a preparation consisting of 20–40 complete segments of the earthworm may be initiated by longitudinal tension and by certain types of tactile stimulation. Peristaltic movements do not occur in such a preparation in the absence of stimulation, and cease within a finite period after the cessation of a stimulus. Peristaltic movements do not occur after excision of the nerve cord. The rhythmic responses to tension and touch are therefore together described as the peristaltic, reflexes, and the response to tension is individually described as the tension reflex. The preparation shows a variety of responses to touch. Tactile stimuli may evoke peristalsis; they may also elicit arhythmic contractions accompanied by immobilization of peristalsis. The peristaltic reflexes can be immobilized both by heavy vibration of the apparatus, and by certain tactile stimuli. The immobilization can occur without the accompaniment of any arhythmic contraction of the preparation. The immobilization can be referred to as an inhibitory process, since it exhibits features characteristic of inhibition: (i) lessening in the amplitude of beat in recovery from complete immobilization; (ii) reduction of the frequency of beat in the same circumstance. The inhibition of peristalsis is conducted through the central nervous system. The inhibitory effect persists for a considerable period after cessation of the stimulus. Inhibition may be followed by “rebound”. “Rebound” may be caused by the subsidiary exciting effect of the inhibitory stimulus.
Central Nervous Activity in the Earthworm
Authors: Collier H. O. J.
Published: April 2021

The tension reflex in a number of isolated intact segments of the earthworm exhibits a definite threshold to weight. The value of the threshold in the series of preparations tested, varies between 0·1 and 1·0 g., measured as direct tension applied to the preparation. There is also a threshold for the duration of application of the weight. In the figure shown this lies above 0·5 sec. After an applied stimulus has been removed the peristaltic response of a preparation may continue for a finite length of time which seldom exceeds 3 min. The period for which the movement persists after the stimulus has been removed depends on the magnitude of the stimulus applied but not on the height of the contractions occurring. This fact is taken to support the view that the continuation of the response after the stimulus has been removed is a true after-discharge, due to a persistence of excitement in some region of the reflex arc. The after-discharge consists of a co-ordinated movement of both muscle sets which may be perfectly rhythmic. The after-discharge may be inhibited by suitable stimuli. The frequency of the after-discharge may be increased by the application of a stimulus of a different type from that which elicited the original response. When the preparation is submitted to a continuous tension, the response dies away within a period which does not normally exceed 25 min. The rate of beat in these circumstances shows three phases : a phase of acceleration, a plateau phase and a phase of decline. After the disappearance of a reflex under continuous stimulation, the response can be elicited once more by the addition of further tension. The frequency of beat in any one preparation shows a well-defined upper limit which, over the series of experiments carried out, was never observed to exceed 1 beat in 2·0 sec. The maximum frequency of beat is obtained with tensions intermediate between those of threshold value and those near the upper limit of endurance of the preparation. Lower and higher tensions than that producing maximum frequency produce submaximal rates of beat. The range of variation between rates of beat produced by a series of different tensions is less than the range of tensions used. After a tension reflex has been evoked, an increase in the weight applied may accelerate a submaximal frequency of beat, but cannot force the rhythm above its maximum. Large increments in weight lower the rate of beat. The rate of beat of a tension reflex may be accelerated by the application of a tactile stimulus and the frequency of a response to tactile stimulation may be accelerated by the application of tension. By whatever stimulus the acceleration of beat of a reflex is carried out, it is not accompanied by any break in the rhythm.
Regulation of the Haemolymph in the Saline Water Mosquito Larva Aedes Detritus Edw
Authors: Beadle L. C.
Published: April 2021

The larvae of the mosquito Aedes detritus have been reported only from definitely saline waters. They have been found in water of salinity equivalent to c. 10 % NaCl. In the laboratory they were acclimatized with ease to distilled water, sea water (7 % NaCl), 3 ·5 % NaCl, and glycerol (3 ·5 % NaCl). They also show considerable resistance to N/20 NaOH, but less to N/20 KOH and N/50 HC1. They are unable to live permanently in solutions of the chlorides of potassium, calcium and magnesium of osmotic pressure equivalent to 3 ·5 % NaCl. In sea water of varying salinity they can regulate both the total osmotic pressure and chloride content of the haemolymph. A rise from nil to 6 ·0 % NaCl in the osmotic pressure of the medium is reflected in an increase of from c. 0 ·8 % to 1 ·4% NaCl in that of the haemolymph. In hypotonic solutions and distilled water much chloride is lost, but this is compensated by an increase in the non-chloride fraction. In hypertonic sea water the rise in osmotic pressure is due to increase in the chloride fraction, the nonchloride fraction remaining constant. From this and from experiments with non-electrolytes it is concluded that the larva is permeable to salts and to molecules as large as glycerol, and that the regulatory mechanism in hypertonic saline is concerned with compensation rather for penetration of salts than for loss of water by osmosis. Ligature experiments suggest that this mechanism is the excretion of salt by the Malpighian tubes, but further proof is required. Salt exchange with the environment takes place via the gut, the body surface being impermeable to salts and water. The larvae are able to concentrate chloride from hypotonic solutions but not as effectively as fresh-water species and only when the chloride content of the medium is a little below that of the haemolymph. The anal gills, as in all salt-water species, are very small and appear to be impermeable to salts and water. It is therefore concluded that they are not the seat of the chloride-absorbing mechanism. The osmotic pressure of the haemolymph is trebled by treatment with glycerol (3 ·5 % NaCl), which must be mainly the result of penetration of glycerol. The larva will however live normally in this, and an important factor in the resistance to abnormal media is therefore the adaptability of the tissues to changes in the concentration and composition of the haemolymph. The increase in the osmotic pressure of the haemolymph induced by hypertonic sea water and glycerol does not alter the amount of fluid in the tracheoles. This is discussed in relation to the possible mechanism for the absorption of the trecheóle fluid.
The Intact Central Nervous System of the Newborn Opossum in Long-Term Culture: Fine Structure and Gaba-Mediated Inhibition of Electrical Activity
Authors: Stewart R. R. , Zou D.-J. , Treherne J. M. , Møllgård K. , Saunders N. R. , Nicholls J. G.
Published: April 2021

The entire central nervous system (CNS) of the newly born, South American opossum (Monodelphis domestica) was isolated and maintained in basal medium, Eagle’s (BME) with 0.2% foetal calf serum and antibiotics. Isolated CNS preparations remained electrically excitable for up to 10 days. The fine structure of the spinal cord was normal after 5 days in culture: axons, synapses, dendrites and glia were virtually unchanged. Signs of degeneration were evident only in dorsal areas of the spinal cord, which had been denervated by removal of the dorsal root ganglia during dissection. Amino acid transmitters such as glycine, glutamate, N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acid (GABA), applied to the bathing fluid, rapidly and reversibly inhibited synaptic transmission in cervical segments of the spinal cord. GABA (10–100 μmoll−1) produced a dose-dependent reduction in the magnitude of ventral root responses evoked by dorsal root stimulation. GABA also inhibited synaptically activated compound action potentials produced by spinal cord stimulation. Dose-response curves for GABA obtained in different preparations were highly reproducible. Both GABAA and GABAB receptors were reversibly activated by selective agonists and inhibited by specific antagonists. The actions of GABA were potentiated by benzodiazepines, competitively antagonised by bicuculline (a selective GABAA antagonist) and mimicked by muscimol (a GABAA agonist). Baclofen (a specific GABAB agonist) also inhibited electrical activity and was competitively antagonised by the GABAB antagonist, CGP 35348. After 5 days of culture in BME or minimal essential medium (MEM), GABA dose-response curves were unchanged from those observed immediately after removal of the CNS. The inhibitory potency of baclofen was also unaffected by culture in BME. By contrast, after 5 days of culture in MEM, baclofen no longer inhibited electrical activity. This difference between BME and MEM could be attributed to the higher content of L-histidine in MEM. Thus, addition of 150 μmoll−1 L-histidine to BME produced similar results to culture in MEM: the inhibitory action of baclofen was virtually abolished after 3–5 days. L-Histidine had no effect on freshly dissected preparations. Chronic application of L-histidine did not affect glycine or glutamate responses after 5 days. Addition of D-histidine or other amino acids, such as arginine, to BME did not abolish the responses to baclofen. These results show that the isolated CNS of the newborn opossum survives well in long-term culture and that it provides a useful preparation to study receptor development and plasticity of an intact mammalian CNS in vitro. The rapid and reversible penetration of agonists and antagonists into the preparation also allows for pharmacological manipulation of the neuronal environment.
Addition of Artificial Loads to Long-Eared Bats Plecotus Auritus: Handicapping Flight Performance
Authors: Hughes Patsy M. , Rayner Jeremy M. V.
Published: April 2021

A series of experiments is described in which two brown long-eared bats Plecotus auritus Linnaeus (Chiroptera: Vespertilionidae) were flown in a 1 m ×1 m×4.5 m flight enclosure at a range of body masses (n=9 experiments for a female bat, and n=11 for a male bat). The highest three of these masses incorporated artificial loads. Stroboscopic stereophotogrammetry was used to make three-dimensional reconstructions (n=124) of the bats’ flight paths. Over the entire range of experiments, wing loading was increased by 44% for the female and 46% for the male bat. Effects arising from captivity were controlled for: experiments at certain wing loadings were repeated after a period in captivity and the response to load was found to be unaltered. Flight speed fell with total mass M or with wing loading, varying as M−0.49 in the female and M−0.42 in the male bat. Wingbeat frequency increased with total mass or wing loading, varying as M0.61 in the female and M0.44 in the male bat. Hence frequency, but not speed, changed with mass in the direction predicted by aerodynamic theory. These results were used in a mathematical model to predict wingbeat amplitude, flight power and cost of transport. The model was also used to estimate the optimal flight speeds Vmr and Vmp. The model predicted that amplitude increases with load. Measurements of wingbeat amplitude did not differ significantly from the predicted values. The observed flight speed was below the predicted minimum power speed Vmp (which increases with load), and diverged further from this with progressive loading. The increase in cost of flight calculated by the model over the range of wing loadings was approximately double that which it would have been had the bats adopted the optimal approach predicted by the model. The limitations inherent in the theoretical model, and the possible constraints acting on the animals, are discussed.
Voltage-Activated Ionic Currents in Myoepithelial Cells Isolated from the Sea Anemone Calliactis Tricolor
Authors: Holman Molly A. , Anderson Peter A. V.
Published: April 2021

Myoepithelial cells were isolated from the apical ends of mesenteries of the sea anemone Calliactis tricolor and examined using the whole-cell configuration of the patch-clamp technique. The isolation procedure produced cell fragments that were contractile and produced action potentials when depolarized. These action potentials are formed by a complex array of ionic currents consisting of at least one, and possibly two, inward calcium currents and four outward potassium currents. The ionic selectivity of the calcium currents was Ca2+>Sr2+>Ba2+. Outward currents consisted of a calcium-dependent outward current and three voltage-activated currents, including a 4-aminopyridine-sensitive current, a transient outward current and a steady-state current.
The Dopamine and 5-Hydroxytryptamine Content of Locust and Cockroach Salivary Neurones
Authors: Gifford A. N. , Nicholson R. A. , Pitman R. M.
Published: April 2021

The salivary glands of the cockroach and locust are innervated primarily from two pairs of motoneurones, designated SN1 and SN2, in the suboesophageal ganglion. Intracellular cobalt fills and subsequent silver intensification were used to reveal the morphology of these cells in both species.

Fluorescent microscopy, following treatment of the ganglion with glyoxylic acid, showed that in both species only the SN1 neurones contained catecholamines. A radioenzymatic assay for dopamine, performed on the locust SN1 neurones, confirmed that this catecholamine was present.

A radioenzymatic assay for 5-hydroxytryptamine (5-HT), performed on both pairs of salivary neurones in the locust, revealed small quantities of this amine in the SN2 neurones, but no significant amount in the SN1 neurones. In the cockroach, 5-HT was assayed in the SN2 neurones only. In contrast to the locust, however, the 5-HT content of these cells was not significantly above that of control cells taken from other ganglia.

These observations demonstrate that only the SN1 neurones are the source of the catecholaminergic fibres investing the locust and cockroach salivary glands. The difference in neurotransmitter content between the SN1 and SN2 neurones suggests that these neurones have separate functions in the control of salivary secretion.
Intracellular pH in the Toad Bufo Marinus Following Hypercapnia
Authors: Snyder Gregory K. , Nestler James R.
Published: April 2021

We investigated the effects of hypercapnia on intracellular acid-base regulation in brain and liver of the toad Bufo marinus L. After 1 h at 5% CO2, arterial PCO2 increased significantly, from 1.6±0.04 to 5.7±0.23kPa, while brain and liver intracellular pH (pHi) decreased significantly. Reductions in pHi of both tissues were partially compensated by increased levels of bicarbonate. Surprisingly, however, compensation was lower than expected in brain and higher than expected in liver. We suggest that compensation in brain may be limited by secondary effects of bicarbonate loading in this tissue.
The Role of Cyclic Amp in the Octopaminergic Modulation of Flight Muscle in the Locust
Authors: Whim Matthew D. , Evans Peter D.
Published: April 2021

The role of cyclic AMP in the octopaminergic modulation of the dorsal longitudinal flight muscles of the locust Schistocerca gregaria has been investigated. Several techniques have been used to elevate cyclic AMP levels in this tissue by mechanisms that bypass the receptor activation stage. These include the use of phosphodiesterase inhibitors to block the metabolism of cyclic nucleotides, the use of forskolin, the diterpene activator of adenylate cyclase, and the direct application of permeable and phosphodiesterase-resistant analogues of cyclic AMP. All these approaches can be shown to mimic the modulatory effects of octopamine on the flight muscle. Surprisingly, the phosphodiesterase inhibitors used were not able to potentiate the actions of octopamine on this preparation. Octopamine increases cyclic AMP levels in a similar fashion in all five motor units of this muscle, an effect that is selectively blocked by phentolamine, an α-adrenergic blocking agent that blocks octopamine receptors in other preparations. In addition, stimulation of the dorsal unpaired median neurone to the dorsal longitudinal flight muscles (DUMDL) results in a frequency-dependent increase in cyclic AMP levels in the muscle that is also blocked by phentolamine. The data presented suggest that the octopamine-mediated modulation of neurally evoked tension in this muscle is brought about by a mechanism that involves an increase in cyclic AMP levels in the tissue.
A Calcium-Activated Nonspecific Cation Channel From Olfactory Receptor Neurones of the Silkmoth Antheraea Polyphemus
Authors: Zufall F. , Hatt H. , Keil T. A.
Published: April 2021

Single-channel patch-clamp techniques were used to identify and characterize a Ca2+-activated nonspecific cation channel (CAN channel) on insect olfactory receptor neurones (ORNs) from antennae of male Antheraea polyphemus. The CAN channel was found both in acutely isolated ORNs from developing pupae and in membrane vesicles from mature ORNs that presumably originated from inner dendritic segments. Amplitude histograms of the CAN single-channel currents presented well-defined peaks corresponding to at least four channel substates each having a conductance of about 16 pS. Simultaneous gating of the substates was achieved by intracellular Ca2+ with an EC50 value of about 80 nmol 1−1. Activity of the CAN channel could be blocked by application of amiloride (IC50-<100nmoll−1). Moreover, in the presence of lμmoll−1 Ca2+, opening of the CAN channel was totally suppressed by 10μmoll−1 cyclic GMP, whereas ATP (1 mmol 1−1) was without effect. We suggest that the CAN channel plays a specific role in modulation of cell excitability and in shaping the voltage response of ORNs.
The Role of Blood Glucose in the Restoration of Muscle Glycogen During Recovery from Exhaustive Exercise in Rainbow Trout (Oncorhynchus Mykiss) and Winter Flounder (Pseudopleuronectes Americanus)
Authors: Pagnotta Antonella , Milligan C. Louise
Published: April 2021

The role of blood-borne glucose in the restoration of white muscle glycogen following exhaustive exercise in the active, pelagic rainbow trout (Oncorhynchus my kiss) and the more sluggish, benthic winter flounder (Pseudopleuronectes americanus) were examined. During recovery from exhaustive exercise, the animals were injected with a bolus of universally labelled [14C]glucose via dorsal aortic (trout) or caudal artery (flounder) catheters. The bulk of the injected label (50–70%) remained as glucose in the extracellular fluid in both species. The major metabolic fates of the injected glucose were oxidation to CO2 (6–8%) and production of lactate (6–8%), the latter indicative of continued anaerobic metabolism post-exercise. Oxidation of labelled glucose could account for up to 40% and 15% of the post-exercise in trout and flounder, respectively.

Exhaustive exercise resulted M˙O2 in a reduction of muscle glycogen stores and accumulation of muscle lactate. Glycogen restoration in trout began 2–4 h after exercise, whereas in flounder, glycogen restoration began within 2h. Despite a significant labelling of the intramuscular glucose pool, less than 1% of the infused labelled glucose was incorporated into muscle glycogen. This suggests that blood-borne glucose does not contribute significantly to the restoration of muscle glycogen following exhaustive exercise in either trout or flounder and provides further evidence against a prominent role for the Cori cycle in these species.
The Midgut as a Model System for Insect K+-Transporting Epithelia: Immunocytochemical Localization of a Vacuolar-Type H+ Pump
Authors: Klein Ulla , Löffelmann Günter , Wieczorek Helmut
Published: April 2021

In Manduca sexta midgut, a vacuolar-type H+-ATPase and a K+/nH+ antiport represent the functional elements of the electrogenic K+ pump. This vacuolar-type ATPase was localized by immunofluorescence and immunogold staining using monoclonal antibodies to defined subunits of the midgut ATPase. The antibodies labelled the membrane projections of the goblet cell apical plasma membrane, the site of active K+ transport. Furthermore, an immunologically related epitope was localized in the apical brush border of Manduca Malpighian tubules. In addition, cross-reactivity of protein bands corresponding to the major subunits of the midgut vacuolar-type ATPase was found in crude homogenates of Malpighian tubules and antennal sensory epithelium of Manduca by immunostaining with a polyclonal anti-holoenzyme serum to the midgut ATPase. This comparative immunological approach suggests that a vacuolar-type ATPase may be a common constituent of insect plasma membranes bearing the insect K+ pump. These results support the hypothesis that a vacuolar-type H+-ATPase provides an alternative to the Na+/K+-ATPase in energizing animal plasma membranes.
Behavioral and Neurophysiological Demonstration of a Lateralis Skin Photosensitivity in Larval Sea Lampreys
Authors: Ronan Mark , Bodznick David
Published: April 2021

Larval lampreys respond to skin illumination with a delayed burst of swimming in an attempt to escape the light. The photoresponse, which is independent of the lateral eyes and pineal organs, is most readily elicited by light shone on the tail. Behavioral studies in larval lampreys demonstrate that photosensory afferents innervating the tail are carried by a trunk lateral line nerve supplying regions caudal to the head. The present results confirm that bilateral transection of this nerve in larval sea lampreys markedly diminishes the photoresponse. The trunk lateral line nerve consists of the recurrent ramus of the anterior lateral line nerve and a ramus of the posterior lateral line nerve. Bilateral transection of the recurrent ramus does not affect the photoresponse, indicating that lateralis photosensory afferents enter the brain via the posterior lateral line nerve and terminate in the medial octavolateralis nucleus. Photosensory units were subsequently recorded in the trunk lateral line nerve, posterior lateral line nerve and the lateral line area of the medulla. Medullary photosensory units were localized to the medial nucleus, previously regarded as the primary mechanosensory nucleus. Photosensory units in lateral line nerves and the brain exhibited low, irregular spontaneous activity and, after latencies of 1–4 s, responded to tail illumination with repeated impulse bursts. Response thresholds were 0.1–0.9 mW cm−2. Responses to sustained illumination were slowly adapting. A skin photosense is thus an additional lateralis modality in lampreys.
The K+-Driven Amino Acid Cotransporter of the Larval Midgut of Lepidoptera: Is Na+ an Alternative Substrate?
Authors: Hanozet G. M. , Sacchi V. F. , Nedergaard S. , Bonfanti P. , Magagnin S. , Giordana B.
Published: April 2021

Amino acid accumulation within brush-border membrane vesicles (BBMV) from the larval midgut of Lepidoptera is driven by a K+ gradient. However, it can also be driven by a Na+ gradient, although with reduced efficiency. To examine the possibility that sodium and potassium ions are handled by the same amino acid transporter, glycine uptake into BBMV from Philosamia cynthia Drury was measured in the presence of a pH gradient and of a transmembrane electrical potential difference, i.e. in simulated ‘physiological’ conditions. The kinetics of glycine uptake at extravesicular saturating Na+ or K+ concentrations discloses a higher affinity of the cotransporter for the amino acid in the presence of Na+ but a maximum transport rate with K+. Glycine uptake at a fixed concentration as a function of external Na+ or K+ concentration yields curves that show saturation but do not fit a rectangular hyperbola, with Hill coefficients less than 1 with Na+ and greater than 1 with K+. These coefficients vary according to glycine concentration. Increasing the concentration of extravesicular Na+ at a saturating external K+ concentration reduced glycine uptake to 70% of the control value. This inhibition curve is compatible with competition between the two cations for the same cotransporter and with the presence of different kinetic constants with Na+ or K+. The data are consistent with a steady-state random two-substrate mechanism for glycine transport, with Na+ and K+ as alternative substrates.
Effect of Manduca Sexta Diuretic Hormone and Related Peptides on Isolated Malpighian Tubules of the House Cricket Acheta Domesticus (L.)
Authors: Coast Geoffrey M. , Hayes Timothy K. , Kay Iain , Chung Jum-Sook
Published: April 2021

Previously, a corticotropin releasing factor (CRF)-like diuretic peptide (Man-duca-DH) has been isolated from Manduca sexta and shown to stimulate fluid excretion in vivo in post-eclosion Pieris rapae adults and in pre-wandering postfeeding Manduca sexta larvae. However, Manduca-DH was reported to have no effect on Malpighian tubules in vitro.

Manduca-DH and [Nle2,11]-Manduca-DH were synthesized in Texas and assayed in London on isolated Malpighian tubules of Acheta domesticus. Man-duca-DH stimulated fluid secretion by about 60% of the maximum response achievable with extracts of corpora cardiaca and increased the production of cyclic AMP. In combination with 10−4moll−1 3-isobutyl-l-methyl xanthine (IBMX), Manduca-DH stimulated maximal secretion. A number of CRF-related peptides also stimulated fluid secretion and cyclic AMP production in cricket tubules, and the CRF antagonist α-helical-CRF[9–41] blocked the stimulation of fluid secretion by Manduca-DH. [Nle2,11]-Manduca-DH was more active than Manduca-DH in both assays, suggesting that methionine residues in the natural peptide may become oxidized.

Taken in conjunction with previous in vivo studies, the present findings suggest that a Manduca-DH-like diuretic peptide is the hormone controlling post-eclosion diuresis in butterflies, and Manduca-DH was shown to stimulate both fluid secretion and cyclic AMP production in Malpighian tubules from 1–12 h posteclosion Pieris rapae adults. The function of the peptide in Manduca sexta is discussed.
Influence of Substrate on Retraction of Neurites Following Electrical Activity of Leech Retzius Cells in Culture
Authors: Grumbacher-Reinert Simone , Nicholls John
Published: April 2021

The aim of these experiments was to determine how electrical stimulation of identified neurones in culture influences their growth on defined substrates. Single Retzius cells isolated from the central nervous system (CNS) of the leech were plated in culture dishes coated with the plant lectin Concanavalin A or with extracellular matrix extract containing leech laminin to promote neurite outgrowth. Stimuli were applied by a fine tungsten microelectrode placed close to the cell surface. The efficacy of electrical stimulation was checked occasionally by recording intracellularly with a microelectrode. After the period of stimulation had ended, there was a short delay before neurones plated on leech laminin retracted their neurites. Of 112 neurones, only 11 failed to respond to stimulation. Neurite retraction in each cell was nonuniform, some processes retracting while others did not. After having retracted, most neurites subsequently showed clear regrowth. The degree of retraction depended on the duration of the stimulus train: whereas a few minutes was sufficient to produce observable effects, prolonged periods of stimulation caused more extensive retraction. Trains of impulses at 4 s−1 were equally effective when they were delivered in intermittent bursts or continuously. The time in relation to growth at which stimuli were applied was of critical importance. Neurones stimulated during the phase of rapid outgrowth on leech laminin did not retract their neurites, which continued to elongate during and after stimulation. Neurones that had not retracted during the early phase were stimulated again later, when extension and outgrowth of neurites had ceased or slowed. At this stage stimulation was followed by retraction and subsequent regrowth. Retzius cells plated on a substrate of Concanavalin A instead of leech laminin failed to show any retraction after stimulation. To investigate the possible role of Ca2+, cells were grown with raised concentrations of Mg2+ in the bathing fluid. Raised [Mg2+] did not influence the rate or the extent of neurite outgrowth. It reduced, but did not block, the effects of electrical stimulation. Earlier experiments have shown that growth on Concanavalin A occurs without obvious Ca2+ entry following stimulation. Together with the present experiments, the results suggest that Ca2+ entry following impulses in cells grown on laminin is responsible for the massive retraction.
Gas Exchange, Metabolite Status and Excess Post-Exercise Oxygen Consumption After Repetitive Bouts of Exhaustive Exercise in Juvenile Rainbow Trout
Authors: Scarabello M. , Heigenhauser G. J. F. , Wood C. M.
Published: April 2021

Juvenile rainbow trout (approximately 6 g) were exercised to exhaustion in two 5 min bouts given 6h apart. Resting levels of whole-body lactate and glycogen were restored prior to the second bout. The rate of O2 consumption increased about threefold 5 min after each bout of exercise, while recovery time decreased from 4h after the first bout to 2–3h after the second. The excess post-exercise oxygen consumption, i.e. ‘oxygen debt’, was significantly reduced by 40% after the second exercise bout, despite almost identical rates of lactate clearance and glycogen resynthesis. The rates of CO2 and ammonia excretion increased sixfold and threefold, and recovery times decreased from 4–6 h to 3h and from 3h to 1.5 h, respectively. After the first bout, whole-body lactate levels peaked at 5 min post-exercise at about 8.5 times pre-exercise levels. After the second bout, lactate levels peaked at 0 min post-exercise and fell more rapidly during recovery. Whole-body glycogen levels decreased by 70% and 80% and ATP levels decreased by 75% and 65% after the first and second bouts, respectively, while glucose levels increased about 1.5-fold immediately after both bouts. Creatine phosphate levels decreased by 70% and 80% after the first and second bouts, respectively. After 6h of recovery, creatine phosphate levels were higher after the second bout than after the first. These findings suggest that exhaustive exercise may cause a ‘nonspecific’ increase in metabolic rate not directly related to the processing of metabolites, which is reduced upon a subsequent exercise bout. This is in contrast with the classical ‘oxygen debt hypothesis’, which states that the oxygen debt and lactate clearance are linked. Furthermore, it appears that two sequential exercise bouts are sufficient to induce a ‘training effect’, i.e. improved rates of metabolic recovery.
Effect of Season and Temperature Acclimation on the Function of Crucian Carp (Carassius Carassius) Heart
Authors: Matikainen Nina , Vornanen Matti
Published: April 2021

The temperature dependence of heart rate and isometric contractile properties of cardiac tissue was determined in thermally acclimated crucian carp (Carassius carassius L.). Fish were adapted for more than 3 weeks to 5 and 15°C during both summer and winter. At all but the lowest experimental temperatures, heart rate (FH), maximal isometric force (Fmax) and pumping capacity were higher in summer fish acclimated to 15°C than in winter fish acclimated to 5°C. Except for fH, similar acclimation effects were observed when comparing cold- and warm-acclimated crucian carp in both seasons. In contrast, the kinetics of isometric contraction was not modified either by seasonal acclimatization or by thermal acclimation within a given season: the temperature dependence of time to peak force (TPT) and time to half-relaxation (T1/2R) was independent of the previous thermal history of the fish. The hearts of winter fish were about 10% smaller than those of summer fish. These results show that acclimation to cold does not induce positive compensatory changes in function or size of crucian carp heart, as happens in many other teleost fishes. Instead, an inverse or noncompensatory acclimation was found. Owing to the inverse thermal acclimation, in winter (at 4°C) the contractile performance of the crucian carp heart is less than one-third of that in summer (at 20°C). The low cardiac activity in cold-acclimated crucian carp seems to be associated with its inactive life style, which is necessary during the winter months to minimize energy consumption in a severely hypoxic environment.
Calcium Transients In Identified Leech Glial Cells In Situ Evoked By High PotaSsium Concentrations And 5-Hydroxytryptamine
Authors: Munsch Thomas , Deitmer Joachim W.
Published: April 2021

We have recorded the fluorescence of Fura-2-loaded, identified glial cells in the neuropile of the central nervous system of the leech Hirudo medicinalis using the ratio of emission at 350 nm excitation to that at 380 nm excitation as an indicator of intracellular Ca2+ concentration ([Ca2+]i). The neuropile glial cells were exposed by mechanically removing the overlying ganglionic capsule and the neuronal cell bodies and were then impaled using a microelectrode under visual control to inject Fura-2 ionophoretically. The resting Ca2+ level was measured using digitonin or Triton to permeabilize the cell membrane at different external concentrations of Ca2+; it was found to vary between 5 and 79 nmol l−1 and averaged 32±23nmol l−1 (±S.D., N=7). Raising the external K+ concentration from 4 to 20mmol l−1 or adding 50 μmol l−1 5-hydroxytryptamine (5-HT) produced a rapid, reversible rise in [Ca2+]i During prolonged exposure to high [K+] or 5-HT, [Ca2+]i remained high. Upon restoring normal external [K+] or removing 5-HT, [Ca2+], returned to its initial resting value within 1–2 min. The responses of [Ca2+]i to high [K+] and 5-HT were greatly reduced in nominally Ca2+-free saline, suggesting that the [Ca2+], transients required an influx of Ca2+ into the cells. In the presence of 5-HT, the rise in [Ca2+]i was accompanied by a decrease in the resistance and an increase in the responsiveness to K+ of the glial cell membrane, indicating the existence of a Ca2+-dependent K+ conductance elicited by 5-HT.
Can we Determine When Marine Endotherms Feed? A Case Study With Seabirds
Authors: Wilson Rory P. , Cooper John , Plötz Joachim
Published: April 2021

The foraging ecology of marine endotherms was, until recently, obscure because most species spend the greater part of their life at sea where they are difficult to observe. However, advances in solid state technology have made it possible to develop units that can be attached to animals to give information on movements (e.g. Jouventin and Weimerskirch, 1990; Wilson et al. 1991) or activity (e.g. Ponganis et al. 1991; Thompson et al. 1991) while animals are at sea. Information on the prey consumed may be obtained by stomach lavage techniques (e.g. Wilson, 1984). Assessment of stomach contents allows researchers to determine prey types but not when prey were ingested. To build up a more comprehensive picture of foraging activity of marine endotherms a unit is needed to record information on prey ingestion.
Endogenous Rhythms in the Amounts of 11-cis Retinal in the Compound eye of Ligia Exotica (Crustacea, Isopoda)
Authors: Hariyama Takahiko , Tsukahara Yasuo
Published: April 2021

The volume of the rhabdom of Ligia exotica changes diurnally, with the rhythm persisting autogenically in continuous darkness. The morphological changes are accompanied by variations in the amounts of the different chromophores making up the visual pigment. The amount of 11-cis retinal was found to be high at night (26.2±3.5 pmol per eye) and low during the day (10.9±2.6pmol per eye) and to display an endogenous rhythm. At dawn and dusk, the amount was 19.1 ±1.2 pmol. This rhythmicity persisted in continuous darkness, although the average amount of 11-cis retinal present gradually increased. In the case of all-trans retinal, changes in the amount were rhythmic in light-dark conditions. The amount of all-trans retinal present in the eye increased shortly after the onset of light and decreased soon after the end of illumination. There was about twice as much 11-cis retinyl ester as 11-cis retinal in the compound eye of Ligia exotica. Rhythmicity in the amount of 11-cis retinyl ester present during the light-dark cycle was observed, but it was opposite in phase to that of 11-cis retinal. Under conditions of continuous darkness a clear rhythm was not apparent: the amount of 11-cis retinyl ester increased not only during the subjective day but also during the following subjective night. Thus, a clear correlation exists between changes in structural organization of the rhabdom and the amounts of 11-cis retinal present. Both show features of a circadian rhythm.