bluuebunny/crossref_metadata_2025 huggingface dataset:
Gas transport in the haemolymph of arachnids I. Oxygen transport and the physiological role of haemocyanin
Authors: Paul R. J. , Bergner B. , Pfeffer-Seidl A. , Decker H. , Efinger R. , Storz H.
Published: April 2021

Oxygen equilibrium curves and the relationships between the partial pressure of CO2 and pH were determined for the haemolymph of the arachnids Eurypelma californicum, Pandinus imperator and Cupiennius salei. A new type of experimental apparatus was constructed, tested and used to make these measurements on small undiluted cell-free haemolymph samples. Most of its components were made in our workshop and were inexpensive. The apparatus proved to be very reliable as demonstrated by control (oxygen concentration) experiments. In previous reports on O2 equilibrium curves of E. californicum haemocyanin, Tris–HCl buffer was used to set the pH, whereas in our experiments, pH was adjusted by altering the partial pressure of CO2. The O2 concentration measurements demonstrate an increase in oxygen affinity of E. californicum haemocyanin when using Tris–HCl buffer. The position and shape of the O2 equilibrium curves of E. californicum and P. imperator haemocyanin show a distinct dependency on pH. Oxygen affinity is lower in E. californicum and cooperativity changes with pH in E. californicum, but not in P. imperator. Oxygen transport in the haemolymph of E. californicum during rest, activity and recovery was calculated on the basis of the O2 equilibrium curves of undiluted haemolymph. Apart from oxygen transport, there are indications that haemocyanin is also involved in other physiological processes. For example, it may function as a storage protein.
Neurosecretion of crustacean hyperglycemic hormone evoked by axonal stimulation or elevation of saline K+ concentration quantified by a sensitive immunoassay method
Authors: Keller R. , Haylett B. , Cooke I.
Published: April 2021

A sandwich-type enzyme-linked immunosorbent assay (ELISA) was utilized to quantify crustacean hyperglycemic hormone (as Carcinus maenas equivalents) released by single X-organ–sinus gland systems of the crab Cardisoma carnifex during continuous perifusion. Basal rates of secretion (20–60 pg min−1) were stable for at least 4 h. Electrical stimulation (600 stimuli in 5 min) of the axon tract increased secretion two-to threefold, but only if it resulted in neural activity that was propagated to the terminals of the sinus gland. No difference was observable when stimuli were given repetitively or as a series of trains. Perifusion with saline having ten times the normal K+ concentration augmented secretion by as much as fivefold. Augmented secretion of crustacean hyperglycemic hormone evoked by either electrical or K+ stimulation appeared abruptly but declined slowly (over tens of minutes) after stimulation was stopped. K+-evoked secretion of crustacean hyperglycemic hormone was maintained without decrement for at least 1 h. Basal secretion increased in saline from which Ca2+ had been omitted, but decreased in saline containing Mn2+. Neither electrical stimulation nor high [K+] augmented secretion in Ca2+-deficient saline or if Mn2+ was present. Introduction of Mn2+ during K+-evoked secretion immediately reduced release to unstimulated levels; secretion resumed promptly upon removal of Mn2+. Tetrodotoxin reversibly blocked both electrical and secretory responses to axonal stimulation, but it did not block basal or K+-evoked secretion.

Release of crustacean hyperglycemic hormone by isolated axon terminals was augmented two-to threefold by perifusion with saline having ten times the normal K+ concentration. The responses were similar to those of the intact systems, having a rapid onset, well-maintained secretion and a long ‘tail’ of secretion after removal of the K+ stimulus.
Blind mexican cave fish (Astyanax Hubbsi) respond to moving visual stimuli
Authors: Teyke Thomas , Schaerer Stephanie
Published: April 2021

In apparatus for measuring optomotor behaviour, blind Mexican cave fish, Astyanax hubbsi, increase their swimming velocity upon rotation of a striped cylinder, i.e. in response to a solely visual stimulus. The fish follow the movements of the stripes at (i) rotation velocities between 60 degrees s−1 and 80 degrees s−1, (ii) light intensities of less than 20 lx and, (iii) stimulus widths subtending an angle of less than 1 °.

Extirpation of the vestigial eye structures does not affect the response to the moving visual stimulus, which indicates that the response is mediated by extra-ocular photoreceptors.

An optomotor response can be reliably evoked in a round test aquarium. Fish do not respond when the test aquarium contains environmental cues, such as bars on the wall or when a section of the round aquarium is divided off. This indicates that the fish obtain information about their environment from different sensory sources and that the visual stimulus is effective only when no other means of orientation are available. We suggest a modified theory of the optomotor response, which emphasizes the crucial role of the environment in eliciting the response and which permits behaviours more complex than just following the stimulus.
Oxidative capacity distribution in skeletal muscle fibers of the rat
Authors: Philippi Maria , Sillau A. H.
Published: April 2021

To study the distribution of oxidative capacity in muscle fibers, mitochondrial volume density and the oxidative capacity of isolated mitochondria were evaluated. Mitochondria were isolated from the subsarcolemmal and interfibrillar areas of the soleus (a muscle largely made up of slow oxidative fibers) and the gastrocnemius medial head (a muscle largely made up of fast glycolytic fibers) of the rat, and their oxidative capacities were evaluated using NADH- and FADH-generating substrates. In the soleus muscle, the subsarcolemmal mitochondria showed a lower oxidative capacity than interfibrillar mitochondria when NADH-generating substrates were used. This difference was not observed when FADH-generating substrates were used. In the gastrocnemius, there were no differences in the oxidative capacity of the subsarcolemmal and the interfibrillar mitochondria. Additionally, citrate synthase activity was found to be lower in mitochondria isolated from the subsarcolemmal area of the soleus than in the other mitochondrial preparations. These findings indicate that the difference in oxidative capacity of the isolated mitochondria is not related to differences in the inner mitochondrial membranes. Mitochondrial volume density was evaluated using electron micrographs of the subsarcolemmal and interfibrillar areas of slow oxidative fibers from the soleus and fast glycolytic fibers from the gastrocnemius. In the slow oxidative fibers, mitochondrial volume density in the subsarcolemmal area was four times higher than in the interfibrillar area. In the fast glycolytic fibers, mitochondrial volume densities in the subsarcolemmal and interfibrillar areas did not differ from that of the interfibrillar area of the slow oxidative fibers.

The oxidative capacity of the tissue, calculated by multiplying the mitochondrial oxidative capacities by the mitochondrial volume densities, was 2–4 times higher in the subsarcolemmal areas of the soleus fibers than in the other areas studied. This was true in spite of the fact that the oxidative capacity of the subsarcolemmal mitochondria of the slow oxidative fibers was lower than those of the other mitochondrial populations studied. These results indicate that the difference in oxidative capacity between slow oxidative fibers and fast glycolytic fibers is the result of the much greater mitochondrial volume density in the subsarcolemmal area of the slow oxidative fibers.
A Simple Colorimetric Micro-Method for Determining the Oxygen Content of Watery Solutions
Authors: Brinkman R. , Van Schreven A.
Published: April 2021

Gilcreas (1935) describes a method for the approximate colorimetric determination of dissolved oxygen with 2-4-diaminophenol dihydrochloride, using a concentrated solution of this substance and a mixture of cobalt chloride and potassium dichro-mate solutions for colour comparison. The colour formed is described as a combination of red and yellow, which varies with the concentration of oxygen, but is not directly proportional to the oxygen content. It is intended for field work and not for accurate determinations.
The Alternation Problem in Animal Psychology
Authors: Honigmann H.
Published: April 2021

The original aim of this paper was to give a contribution to the study of number conception in animals. It has been repeatedly maintained that birds can be trained to take every second and even every third from a row of identical grains. These experiments were carried out with rows of equidistant grains. Thus the bird’s achievement was possibly only a training to a certain distance. This eventuality has not previously been properly excluded, for we shall see that the apparently successful results after doubling or halving the usual distances between the grains are not convincing. Neither have attempts been made previously to train birds to select every second or third from a line of unequally spaced grains. Such an achievement, independent of any pecking rhythm and without the ‘figurai help’ of any pattern in the distribution of the grains, could be considered as a preliminary stage to counting. It was therefore intended to train birds first to select every second (or third) from a line of equidistant grains, and to extend this training later to rows with unequally spaced grains. Finally, the row of grains had to be covered by an opaque moving lid, so that it became visible to the bird not as a whole, but gradually. By modifying the speed of the lid any training to a temporal rhythm could be avoided, and by using a lid with a ‘window’ showing only one or two grains at a time a training to a figurai pattern could also be excluded.
The Fluctuation of pH and Organic Acids in the Rumen of the Sheep
Authors: Phillipson A. T.
Published: April 2021

It has long been known that bacterial fermentation of cellulose in the rumen is associated with the production of a mixture of lower fatty acids, methane and carbon dioxide. It was first shown by Pringsheim (1912) and later confirmed by Woodman & Stewart (1928) that the addition of toluene to thermophilic cultures of cellulose-splitting bacteria resulted in the accumulation of glucose, and Woodman (1930) suggested that glucose was the product that was of nutritional value to the animal. Broadly speaking, theories regarding digestion of cellulose fall into two categories; those that emphasize the importance of the chemical products of fermentation, glucose and the lower fatty acids, and those that regard the food eaten by the animal as a substrate upon which the organisms of the rumen thrive, the bacteria and Protozoa forming the end-product which is subsequently digested by the sheep. Pochon (1935, 1938) put forward an ingenious explanation which belongs to the first school of thought; he isolated a cellulose-splitting organism which he named Plectridium cellulolyticum from the rumen of the ox and found that if the pH of the medium in which active cellulose fermentation was proceeding was reduced to 4, glucose accumulated. This change is similar to that which occurs when ingesta pass from the rumen to the abomasum, and he suggests that glucose is formed in the abomasum of the animal and the lower fatty acids that are formed in the rumen are waste products. Baker (1939) supports the second theory. He studied the decomposition of plant tissue microscopically with the use of polarized light and was able to observe the breakdown of cellulose by the loss of double refraction in the cell walls. Bacteria were intimately related to the areas where erosion was occurring and these organisms were iodophilic. He considers that the bacteria besides exerting cytoclastic activity take up the sugars formed by hydrolysis of cellulose and so protect them from further degradation. These sugars are condensed to an amylodextrin type of polysaccharide and so produce the blue staining reaction with iodine. The bacteria are subsequently digested by the ruminant either before or after ingestion by the ciliates of the rumen..
The Excitation of Nematocysts
Authors: Pantin C. F. A.
Published: April 2021

Though an enormous amount of work has been done on nematocysts, the problem of how they are discharged remains unsolved. There are really two separate problems. First, what is the natural stimulus which excites the cnidoblast; second, what is the physical mechanism by which the nematocyst itself discharges? There is more work on the mechanics of discharge than on any other aspect of the problem, but it still awaits a satisfactory solution. As Graham (1938) points out, most of the work is remarkable for the chemical violence of the reagents used. Reactions to strong acids and alkalis, or to gross changes in osmotic or mechanical pressure can only throw an indirect light on the physical nature of the nematocysts’ diècharge. But it is not intended to discuss here the mechanics of discharge. Existing work has been reviewed by Weill (1934). This essay concerns the primary question of what is the effective stimulus to the cnidoblast, a problem to which much less work had been devoted.
Calcium magnesium phosphate granules: atomistic simulations explaining cell death
Authors: Simkiss K. , Taylor M. G.
Published: April 2021

A large number of invertebrates have cells that produce intracellular granules of amorphous calcium magnesium phosphates that are thought to act as ion stores or sites of metal detoxification. The interatomic potentials and force constants have been calculated for these ions, and computer simulations of the crystal lattices have been used to determine the effects of ion substitutions on these lattice energies. The results provide insights into the mechanisms of granule formation and the effects of ion substitutions on cell physiology.
Nitrogenous excretion in the terrestrial carnivorous crab Geograpsus grayi: site and mechanism of excretion
Authors: Varley D. G. , Greenaway Peter
Published: April 2021

The rate and mechanism of nitrogen excretion were examined in Geograpsus grayi. This species excretes waste nitrogen as gaseous NH3 in periodic bursts. The mean concentration of total ammonia ([NH3]+[NH4+]) in the primary urine during bursts of excretion (1.72 mmol l−1) was similar to that of haemolymph (2.07 mmol l−1) but was significantly lower (P<0.005) than that of branchial fluid (80.6 mmol l−1).

The effects of ion exchange inhibitors on the apical membrane of the gill epithelium in Geograpsus grayi were examined. The presence of an amiloride-sensitive Na+/NH4+ exchanger was confirmed and a SITS-sensitive Cl− influx suggested Cl−/HCO3− exchange.

Thus, the site of nitrogenous excretion in this species is the branchial chamber, which is also the site of reprocessing of urine for ion regulation in other terrestrial crabs. Gaseous ammonia excretion is achieved by volatilisation of NH3 from the branchial fluid. High partial pressures of ammonia in the branchial fluid are produced by apical Na+/NH4+ exchange and elevation of the pH.
Cardiovascular adaptations enhance tolerance of environmental hypoxia in the crab Cancer magister
Authors: Airriess C. N. , McMahon B. R.
Published: April 2021

Unrestrained crabs instrumented with probes for ultrasonic measurement of arterial haemolymph flow were subjected to 6 h of hypoxic exposure. During this interval, the inhalant O2 partial pressure was reduced in steps from 18 to 3 kPa. Measurement of haemolymph flow through all arteries leaving the heart allowed direct calculation of cardiac output, stroke volume and the distribution of cardiac output for both non-stressed and hypoxic animals.

Resting levels of cardiac output were low compared with previously reported values for this and other species of decapod crustaceans. During exposure to the most severe level of hypoxia tested, haemolymph flow through the anterior arteries decreased while flow through the posterior aorta and sternal artery increased by 55 % and 27 % respectively. Cardiac output increased from a control value of 9.8±1.6 to 11.9±1.2 ml kg−1 min−1 despite a decrease in heart-beat frequency. Scaphognathite beat frequency increased from 82.1±4.3 min−1 to more than 120 min−1 after 90 min of hypoxic exposure and remained at this level for the duration of the exposure period.

The decrease in haemolymph flow, via the anterior arteries, to the antero-dorsal region of the animal concurrent with an increase in flow to the posterior and antero-ventral regions, via the posterior aorta and sternal artery, implicates an active mechanism for redistribution of haemolymph flow during hypoxic exposure. The high rate of scaphognathite pumping, presumably to maximise O2 uptake during experimental hypoxia, was probably made possible by an increased blood supply to these organs, which are perfused by downstream branches of the sternal artery.
The effects of myomodulin and structurally related neuropeptides on skeletal neuromuscular transmission in the locust
Authors: Evans Peter D.
Published: April 2021

The modulatory actions of myomodulin A on tension generated in the extensor-tibiae muscle of the locust hindleg by stimulation of the slow excitatory motoneurone (SETi) depend upon the frequency of stimulation. Myomodulin A has no consistent effect on the tension induced by the fast extensor motoneurone (FETi) or upon the myogenic rhythm present in the extensor. The effects of a range of structurally related neuropeptides have also been assessed. At low frequencies of SETi stimulation (1 Hz and below), the predominant modulatory effects are increases in the amplitude, contraction rate and relaxation rate of twitch tension. At higher frequencies, where twitches summate but tetanus is incomplete (up to 20 Hz), these effects are superimposed upon an increase of maintained tension. The modulatory actions of myomodulin-like peptides show some similarities to and some differences from the modulatory actions of octopamine, proctolin and FMRFamide-like neuropeptides in this preparation, but are likely to be mediated via a distinct set of receptors. The results of the present study, taken together with the localization of myomodulin-like immunoreactivity in specific sets of neurones in the locust nervous system, suggest the presence of a novel modulatory system in insects that uses myomodulin-like neuropeptides. It also indicates that myomodulins, which were first identified in molluscs, may represent another interphyletic family of neuropeptides.
Tunas as small as 207mm fork length can elevate muscle temperatures significantly above ambient water temperature
Authors: Dickson Kathryn A.
Published: April 2021

Tunas (family Scombridae) maintain muscle temperatures (Tm) elevated significantly above ambient water temperature (Ta) by using vascular counter-current heat exchangers (retia mirabilia) to conserve metabolic heat generated by continuous contraction of red muscle fibers. Previous work has documented endothermy and both behavioral and physiological thermoregulation in tunas, but only individuals greater than approximately 1 kg body mass had been studied. The purpose of this study was to measure Tm and to examine heat exchanger morphology in smaller fish in order to determine the minimum size at which tunas can elevate Tm significantly above Ta. Measurements of Tm made immediately after capture in field-caught and laboratory-raised tunas (Euthynnus lineatus, Auxis thazard, A. rochei and Thunnus albacares) spanning a size range of 15.5–667mm fork length (FL) show that tunas 207mm FL (162.3g) and larger can elevate red muscle temperature by at least 3.0°C above Ta. E. lineatus, A. thazard and A. rochei of this size possess blood vessels serving the red muscle that are arranged as both lateral and central heat exchangers; the smallest tuna with evidence of a rete was a 108.5mm FL E. lineatus. In the ectothermic scombrid Scomberomorus sierra (108.7–132.0mm FL), Tm was elevated 0.2–0.5°C above Ta, and the greatest Tm elevation reported in any ectothermic species is only 2.7°C. Taken together, these data provide evidence that tunas greater than207mm FL are endothermic.
Circadian locomotor activity and its entrainment by food in the crayfish Procambarus clarki
Authors: De Miguel Francisco Fernández , Aréchiga Hugo
Published: April 2021

The aim of our experiments has been to study the effect of light and food in the locomotor activity rhythm of the crayfish Procambarus clarki. Experiments were carried out under light:dark (LD) cycles of 12 h:12 h, under continuous darkness (DD) and under continuous light (LL). Under LD cycles, two peaks of activity were observed during the night phase of the cycle, while resting was characteristic of the day phase. Under DD or LL, it was possible to follow a free-running rhythm with a periodicity of 22.3±0.84 h in DD and 24.8±0.27 h in LL, typical of circadian rhythms of nocturnal species.

A single delivery of food in the day phase of the LD cycle resulted in an outburst of locomotor activity that lasted for several hours. In the ensuing days, an activity peak appeared in phase with the time of food delivery. The food-related activity peak could be followed for up to 2 weeks without food reinforcement. Under DD and LL, food induced an activity rhythm in previously arrhythmic animals. Here the period was longer than 24 h in DD (26.2±0.12 h) and shorter in LL (22.5±0.46 h). Together, these results strongly suggest that light and food may play a role entraining a locomotor activity rhythm in crayfish.
The relationship between oxygen uptake and ion loss in fish from diverse habitats
Authors: Gonzalez Richard J. , McDonald D. G.
Published: April 2021

A recent examination of the relationship between O2 uptake and diffusive sodium loss in a freshwater fish showed that Na+ losses after exhaustive exercise exceeded those expected on the basis of , probably due to distortion of the paracellular tight junctions (the primary site of diffusive ion loss) and/or glomerular-type filtration caused by increased lamellar pressure. In the present study, an examination of this relationship in nine species of fish from diverse habitats supports this model. Under routine conditions, the rate of Na+ loss per unit of O2 consumed (termed the ion/gas ratio or IGR) was similar in all the species tested, averaging 61.6 pmol Na+ nmol−1 O2. After exhaustive exercise, the degree to which the IGR of each species increased relative to its routine levels (post-exercise IGR/routine IGR) was exponentially related to the relative rise in , i.e. greater rates of O2 uptake led to even greater ion losses. Further analysis revealed that, although naturally active species had the lowest proportionate increase in , by virtue of their high routine rates, they had the highest post-exercise rates of O2 uptake. In fact, there was an inverse correlation between post-exercise IGR and , i.e. species with low values lost more Na+ per mole of O2 taken up than did species with high ones. Thus, naturally active species, such as the common and golden shiner, were able to achieve higher rates of O2 uptake while avoiding high rates of ion loss. Surprisingly, species such as banded sunfish, yellow perch and smallmouth bass did not limit ion loss associated with exercise despite their apparent ability to do so. They demonstrated a strong ability to limit ion losses caused by a brief osmotic shock and by exposure to soft water (both of which distort tight junctions).
The Orientation of the E-Vector of Linearly Polarized Light Does not Affect the Behaviour of the Pigeon Columba Livia
Authors: Coemans M. A. J. M. , Vos Hzn J. J. , Nuboer J. F. W.
Published: April 2021

Orientation with reference to the time-compensated sun-azimuth compass has been established for the homing pigeon Columba livia. Previous qualitative studies claim that pigeons are sensitive to the orientation of a polarizer and it has been suggested that these animals are able to use sky-light polarization as an indirect reference to the sun’s position when the latter is shielded from view. We report experiments which were undertaken to quantify the sensitivity of the homing pigeon to the orientation of linearly polarized light. The results of our initial experiments suggested that the animals responded to secondary cues. Further experiments were carried out to avoid such artefacts. Under circumstances where secondary cues were rigorously avoided, we were, however, not able to demonstrate any directional response that was caused by the E-vector orientation of the illumination. These results throw doubt on the suggested polarization-sensitivity of birds in general.
Flight Physiology of Neotropical Butterflies: Allometry of Airspeeds During Natural Free Flight
Authors: Dudley Robert , Srygley Robert B.
Published: April 2021

Airspeed measurements during natural free flight were made on a total of 270 neotropical butterflies representing 62 species. Morphological data were obtained from the same individuals for which airspeeds had been determined. Flight speed was positively correlated with body mass, thoracic mass and wing loading. Controlling for body mass, higher wing loadings were correlated with increased flight speed. Flight speed and wing aspect ratio were negatively correlated. No consistent correlations were found between airspeed and wing length, wing area or body length. Released butterflies and butterflies encountered in natural free flight did not differ substantially in flight speed allometry. The observed scaling of flight speeds was similar to that derived for a much smaller sample of butterflies flying in an insectary, although absolute values of flight speed were approximately three times higher in natural flight and correlation coefficients of allometric regressions were typically lower. These results suggest that butterfly airspeeds under natural conditions can reasonably be predicted from morphological measurements, and that studying flight in enclosed spaces preserves the allometry of flight speeds.
Bicuculline/Baclofen-Insensitive Gaba Response in Crustacean Neurones in Culture
Authors: Jackel C. , Krenz W.-D. , Nagy F.
Published: April 2021

Neurones were dissociated from thoracic ganglia of embryonic and adult lobsters and kept in primary culture. When y-aminobutyric acid (GABA) was applied by pressure ejection, depolarizing or hyperpolarizing responses were produced, depending on the membrane potential. They were accompanied by an increase in membrane conductance. When they were present, action potential firing was inhibited.

The pharmacological profile and ionic mechanism of GABA-evoked current were investigated under voltage-clamp with the whole-cell patch-clamp technique. The reversal potential of GABA-evoked current depended on the intracellular and extracellular Cl− concentration but not on extracellular Na+ and K+. Blockade of Ca2+ channels by Mn2+ was also without effect. The GABA-evoked current was mimicked by application of the GABAA agonists muscimol and isoguvacine with an order of potency muscimol>GABA>isoguvacine. cis-4-aminocrotonic acid (CACA), a folded and conformationally restricted GABA analogue, supposed to be diagnostic for the vertebrate GABAC receptor, also induced a bicuculline-resistant chloride current, although with a potency about 10 times lower than that of GABA. The GABA-evoked current was largely blocked by picrotoxin, but was insensitive to the GABAA antagonists bicuculline, bicuculline methiodide and SR 95531 at concentrations of up to 100 μmol l−1. Diazepam and phenobarbital did not exert modulatory effects. The GABAB antagonist phaclophen did not affect the GABA-induced current, while the GABAB agonists baclophen and 3-aminopropylphosphonic acid (3-APA) never evoked any response.

Our results suggest that lobster thoracic neurones in culture express a chloride-conducting GABA-receptor channel which conforms to neither the GABAA nor the GABAB types of vertebrates but shows a pharmacology close to that of the novel GABAC receptor described in the vertebrate retina.
Detection of Airborne Sound by a Cockroach ‘Vibration Detector’: A Possible Missing Link in Insect Auditory Evolution
Authors: Shaw S. R.
Published: April 2021

Extracellular recordings from nerve 5 in metathoracic legs of Periplaneta americana disclose a sense organ that is extremely responsive to vibration but also detects sound (best response near 1.8 kHz) with a sensitivity similar to some insect auditory organs. The energy required from an auditory signal for a criterion response is similar or even smaller than for an optimal vibratory input. Responses originate in the subgenual organs (SGO) in the proximal tibiae, and cross-modal adaptation indicates that the same cells respond to both vibration and sound. Sound is picked up directly on some internal structure, not via sound-induced substratum vibration. Adaptation at different frequencies discloses no frequency-selectivity in the SGO. The nerve response is a burst of synchronized impulses at a frequency, fR, of approximately 300 Hz, that is practically invariant both with sound intensity and within the burst, suggesting that fR might represent some underlying resonance phenomenon, either of the SGO or of air in the tracheal system. The latter possibility is ruled out by observations made while the tracheae are perfused with He–O2. Similar responses can be recorded from the pro-and mesothoracic legs. Although Periplaneta is thought to be deaf and appears to ignore loud tones presented to the home colony, a more sensitive assay detects small leg movements in response to sound, confirming the presence of a functional auditory sense. The SGO is suspended from an expansion of the leg trachea, which may function to enhance sensitivity to vibration. This linkage preadapts the SGO to detect airborne sound transmitted in the tracheal system, and contact vibration may also stimulate the system in part by deforming the tracheae. It is proposed that auditory organs of crickets evolved from an ancestral SGO that already possessed dual responsiveness by subsequently developing effective vibration-isolating filters.
Hindlimb Kinematics During Terrestrial Locomotion In A Salamander (Dicamptodon Tenebrosus)
Authors: Ashley-Ross Miriam A.
Published: April 2021

A quantitative study of hindlimb kinematics during terrestrial locomotion in a non-specialized salamander was undertaken to allow comparisons with limb movements in other groups of tetrapods. Five Dicamptodon tenebrosus were videotaped at 200 fields s−1 walking on a treadmill. Coordinates of marker points on the salamander’s midline, pelvic girdle and left hindlimb were digitized through at least three strides at both a walk (0.77 SVL s−1, where SVL is snout–vent length) and a trot (2.90 SVL s−1). Marker coordinates were used to compute kinematic variables summarizing trunk flexion, pelvic girdle rotation, femoral protraction/retraction and knee flexion/extension. The stride is characterized by uninterrupted trunk and pelvic girdle oscillation, femoral retraction throughout stance phase, and knee flexion in early stance followed by extension. Mean angular excursions are: trunk, 66°; pelvic girdle, 38.5°; pelvic girdle–femur, 106°; and knee, 65°. The hindlimb and pelvic girdle also show a complicated pattern of lateral movement related to knee flexion/extension and periods of support by the contralateral hindlimb during the step cycle. Dicamptodon shares the following features of the hindlimb step cycle with other tetrapod taxa: rotation of the pelvic girdle through a 30–40° arc, femoral retraction beginning simultaneously with and persisting throughout stance phase, flexion of the knee in early stance, and extension of the knee in late stance.
Haemolymph and Tissue Titres of Achetakinins in the House Cricket Acheta Domesticus: Effect of Starvation and Dehydration
Authors: Chung Jum Sook , Goldsworthy Graham J. , Coast Geoffrey M.
Published: April 2021

Achetakinin-like immunoreactive material in tissues and haemolymph of adult male crickets was quantified by radioimmunoassay. Achetakinin-like material was found in the brain, suboesophageal ganglia and the thoracic and abdominal ganglia, but the largest amount was within the retrocerebral complex. A Ca2+-dependent release of achetakinin-like immunoreactive material was demonstrated from retrocerebral complexes incubated in vitro in saline containing a high concentration of K+. The concentration of achetakinin-like material in haemolymph from fed crickets was estimated to be 2.8 nmol l−1 and increased more than 10-fold in insects starved for 48 h without access to water. The presence of achetakinin-like material in haemolymph suggests that these peptides are released in vivo and function as circulating neurohormones.
Urea Transport By Hepatocytes And Red Blood Cells Of Selected Elasmobranch And Teleost Fishes
Authors: Walsh Patrick J. , Wood Chris M. , Perry Steve F. , Thomas Serge
Published: April 2021

Although urea transport is receiving increased attention in mammalian systems, very little is known about urea transport in fish tissues. This study examined mechanisms of urea transport in red blood cells and hepatocytes from the lesser spotted dogfish (Scyliorhinus canicula), Atlantic stingray (Dasyatis sabina), turbot (Scopthalmus maximus), redfish (Scianops ocellatus), gulf toadfish (Opsanus beta) and oyster toadfish (Opsanus tau). Urea appeared to be passively distributed in both tissues (i.e. there was no difference between plasma and tissue urea concentrations). Additionally, a number of in vitro experiments examining [14C]urea flux were performed. In red blood cells from all species except redfish, urea transport occurred via simple passive diffusion, but redfish red blood cells showed a small (25%) phloretin-sensitive uptake component. In hepatocytes of the two elasmobranch species (dogfish and stingray), urea efflux was also by simple passive diffusion. However, urea efflux in toadfish (both O. beta and O. tau) hepatocytes exhibited a marked phloretin-sensitivity, and O. beta hepatocytes were used in further experiments with other inhibitors and treatments. Urea transport in O. beta had a relatively high specificity for urea compared with the urea analogues acetamide, thiourea and N-methylurea, was unaffected by phloridzin and extracellular Na+ removal, and was not inhibited by physiological levels of glucose (0.5–10 mmol l−1). A phloretin-sensitive glucose transport, that was not inhibited by physiological levels of urea, was discovered in O. beta hepatocytes. The results are discussed in terms of patterns of species distribution and similarities between urea and glucose transport.
Buccalin-Like and Myomodulin-Like Peptides in the Stomatogastric Ganglion of the Crab Cancer Borealis
Authors: Christie Andrew E. , Hall Cassandra , Oshinsky Michael , Marder Eve
Published: April 2021

The buccalins and myomodulins are families of peptides originally isolated and purified from the accessory radula closer (ARC) nerve–muscle system of the marine mollusc Aplysia californica (Cropper et al. 1987a,b, 1988). In A. californica, the buccalin family consists of 19 related peptides (buccalins A–S), each of which exhibits a homologous carboxyl terminal sequence, Phe-X-Gly-Gly-X-NH2 (Cropper et al. 1988; Miller et al. 1993a). A cDNA clone encoding a buccalin precursor polypeptide has recently been isolated (Miller et al. 1993a). This buccalin gene appears to be present as a single copy in the A. californica genome. The precursor peptide predicted from this gene encodes all 19 buccalin-like molecules, several in multiple copies.
Ion Transport in the Intestine of Anguilla Anguilla: Gradients and Translocators
Authors: Marvão P. , Emílio M. G. , Ferreira K. Gil , Fernandes P. L. , Ferreira H. Gil
Published: April 2021

The transport of Na+, K+ and Cl− across the isolated epithelium of the eel intestine was studied using a combination of four experimental strategies: short-circuiting, measurements of intracellular potentials and ion concentrations, application of a variety of transport inhibitors and measurement of unidirectional fluxes with radioactive tracers. When short-circuited, the system performs a net transport of Cl− and Na+ towards the blood side, with a stoichiometry approaching 2, and a much smaller net transport of K+ towards the lumen. The system is totally driven by the sodium pump located in the basolateral barrier and the main coupling between the fluxes of the three ions is through the operation of a furosemide-sensitive transporter in the apical barrier, probably a 2Cl−/Na+/K+ symporter. The inhibitory effect of DIDS and picrylsulphonic acid on the short-circuit current, when added to the serosal side, suggests the presence of a sodium-dependent anionic shuttle located in the basolateral membrane. The short-circuit current is inhibited by H25, a non-specific inhibitor of the K+/Cl− symport, added to the serosal side. This effect occurs after a delay of at least 5 min and may result from the diffusion of the drug to the apical barrier, where it blocks the 2Cl−/Na+/K+ symport with much higher affinity.
Molecular Physiology of Norepinephrine and Serotonin Transporters
Authors: Blakely Randy D. , De Felice Louis J. , Hartzell H. Criss
Published: April 2021

Cocaine- and antidepressant-sensitive norepinephrine and serotonin transporters (NETs and SERTs) are closely related members of the Na+/Cl− transporter gene family, whose other members include transporters for inhibitory amino acid transmitters, neuromodulators, osmolytes and nutrients. Availability of cloned NET and SERT cDNAs has permitted rapid progress in the definition of cellular sites of gene expression, the generation of transporter-specific antibodies suitable for biosynthetic and localization studies, the examination of structure–function relationships in heterologous expression systems and a biophysical analysis of transporter function. In situ hybridization and immunocytochemical studies indicate a primary expression of NET and SERT genes in brain by noradrenergic and serotonergic neurons, respectively. Both NET and SERT are synthesized as glycoproteins, with multiple glycosylation states apparent for SERT proteins in the brain and periphery. N-glycosylation of NET and SERT appears to be essential for transporter assembly and surface expression, but not for antagonist binding affinity. Homology cloning efforts have revealed novel NET and SERT homologs in non-mammalian species that are of potential value in the delineation of the precise sites for substrate and antagonist recognition, including a Drosophila melanogaster SERT with NET-like pharmacology. Electrophysiological recording of human NETs and SERTs stably expressed in HEK-293 cells reveals that both transporters move charge across the plasma membrane following the addition of substrates; these currents can be blocked by NET- and SERT-selective antagonists as well as by cocaine.
Energizing Porters by Proton-Motive Force
Authors: Nelson Nathan
Published: April 2021

It is generally accepted that the chemistry of water was the most crucial determinant in shaping life on earth. Among the more important chemical features of water is its dissociation into protons and hydroxyl ions. The presence of relatively high proton concentrations in the ambient solution resulted in the evolution of proton pumps during the dawn of life on earth. These proton pumps maintained neutral pH inside the cells and generated electrochemical gradients of protons (proton-motive force) across their membranes. The existence of proton-motive force enabled the evolution of porters driven by it that are most probably among the more primitive porters in the world. The directionality of the substrate transport by the porters could be to both sides of the membranes because they can serve as proton symporters or antiporters. One of the most important subjects of this meeting is the mechanism by which proton-motive and other ion-motive forces drive the transport processes through porters. Is there a common mechanism of action for all proton-driven porters? Is there some common partial reaction by which we can identify the way that porters are energized by proton-motive force? Is there a common coupling between proton movement and uptake or secretion of certain molecules? Even a partial answer to one of these questions would advance our knowledge… or confusion. As my mentor Efraim Racker used to say: ‘If you are not totally confused you do not understand the issue’.
Locomotory Energetics and Metabolic Fuel Reserves of the Virginia Opossum
Authors: Fournier Randy A. , Weber Jean-Michel
Published: April 2021

Marsupials have lower resting metabolic rates than placental mammals, but it is not clear whether particular species can extend this energetic advantage to locomotion. Some active marsupials have a low cost of locomotion, but other more sedentary species, such as the Virginia opossum, appear to run very inefficiently. Steady-state rates of O2 consumption and CO2 production were measured at rest and during horizontal treadmill exercise in wild-caught, trained opossums. Average daily in undisturbed animals was 7.73±0.40 ml O2 kg−1 min−1 (5.67±0.20 ml O2 kg−1 min−1 during light and 9.84±0.81 ml O2 kg−1 min−1 during dark hours, mean ± S.E.M., N=6). Net cost of locomotion ranged between 6.16 and 8.99 J kg−1 s−1 as speed increased and was always higher than for an average mammal of equivalent mass. Net cost of transport decreased as speed increased and was 15–80% higher than for an average mammal. During aerobic locomotion, most of the energy was provided by carbohydrate oxidation, which accounted for 60–95% of as speed increased. Glycogen and triglyceride reserves were quantified in the major storage depots to estimate potential survival time and travelling distance. Enough metabolic fuel was stored to survive for at least 1 week without eating, and 95% of this energy was in adipose tissue triglycerides. However, maximal travelling distance was less than 2 km because opossum locomotion is mainly supported by carbohydrate reserves, which represented only 4% of the available energy. We conclude that aerobic, ground locomotion of Virginia opossums is associated with two major energetic handicaps because their particularly high cost of transport and the nature of the main oxidative fuel they consume are both incompatible with prolonged locomotion.
Oxygen Transport in Egg Masses of the Amphibians Rana Sylvatica and Ambystoma Maculatum: Convection, Diffusion and Oxygen Production by Algae
Authors: Pinder Alan W. , Friet Stephen C.
Published: April 2021

Many amphibians lay their eggs in gelatinous masses up to 10–20 cm in diameter, posing problems for diffusive oxygen delivery. Oxygen may also be provided by water convection between eggs or by oxygen production by endogenous algae. We studied egg masses of two local amphibians, Rana sylvatica and Ambystoma maculatum, to estimate the importance of each of these processes. We injected dye to check for water channels, measured oxygen partial pressures within egg masses to determine the influence of external water convection and lighting, measured oxygen consumption and production in darkness and light and calculated expected gradients through egg masses with a cylindrical, homogeneous egg mass model.

Rana sylvatica had relatively loose egg masses with water channels between the eggs; water convection was important for oxygen delivery. Ambystoma maculatum had firm egg masses with no spaces in the jelly between eggs; thus, there was no opportunity for convective oxygen delivery. The egg masses were cohabited by Oophila ambystomatis, a green alga found specifically in association with amphibian egg masses. Oxygen delivery in A. maculatum was by diffusion and by local production by the algal symbiont. Analysis of a cylindrical egg mass model and measurement of oxygen gradients through egg masses indicated that diffusion alone was not adequate to deliver sufficient O2 to the innermost embryos at late developmental stages. In the light, however, egg masses had a net oxygen production and became hyperoxic. Over the course of a day with a 14 h:10 h light:dark cycle, the innermost embryos were alternately exposed to hyperoxia and near anoxia.
K+ Channel Permeation and Block in the Midgut Epithelium of the Tobacco HornwormManduca Sexta
Authors: Schirmanns K. , Zeiske W.
Published: April 2021

The K+-secreting larval midgut of Manduca sexta in vitro was voltage-or current-clamped. In contrast to Tl+, NH4+and Na+, both Rb+and K+generated a short-circuit current, although with different saturation kinetics. The dependence of the short-circuit current on Rb+ /K+ mole fraction gave no evidence for multi-ion occupation of the basolateral K+ channels. After ‘functionally’ eliminating the apical membranes using the ionophore amphotericin B and the ‘apical K+pump’ blockers trimethyltin chloride or Tl+, the K+channels could be more closely investigated. By measuring zero-current potentials, permeability ratios PX/PK were estimated using an adapted version of the Goldman–Hodgkin–Katz voltage equation. Their sequence was K+ (1) = Tl+ > Rb+ (0.38) > NH4+ (≈0.3) > Cs+(0.03) > Na+(≈0). The K+channels could not be blocked by basally applied Cs+, Na+ or tetraethylammonium. Blockade of K+ current by Ba2+ was typically voltage-dependent, but only at moderate transbasal voltages. The relative electrical distance δ of the Ba2+ binding site from the basal channel opening was determined to be 0.2. At zero transbasal voltage, the apparent inhibition constant for barium KB* a was 1.7 mmol l−1.
The Effects of Altering Extracellular Potassium Ion Concentration on the Membrane Potential and Circadian Clock of Paramecium Bursaria
Authors: Johnson Carl Hirschie , Nakaoka Yasuo , Miwa Isoji
Published: April 2021

In some neural models of circadian rhythmicity, membrane potential and transmembrane flux of potassium and calcium ions appear to play important roles in the entrainment and central mechanisms of the biological clock. We wondered whether these cellular variables might be generally involved in circadian clocks, even non-neural clocks. Therefore, we tested the impact of changing extracellular potassium level on the circadian rhythm of photoaccumulation of Paramecium cells, whose membrane potential responds to changes of extracellular potassium in a manner similar to that of neurones. We found that pulse or step changes of extracellular potassium concentration did not phase-shift the circadian clock of P. bursaria cells in a phase-specific manner. Furthermore, modifying the extracellular concentration of calcium did not affect the magnitude of light-induced phase resetting. Therefore, while membrane potential and calcium fluxes may be crucial components of the circadian clock system in some organisms, especially in neural systems that involve intercellular communication, the P. bursaria data indicate that membrane potential changes are not necessarily an intrinsic component of circadian organization at the cellular level.