bluuebunny/crossref_metadata_2025 huggingface dataset:
Disk-Sphere Transformation in Mammalian Red Cells
Authors: Furchgott Robert F. , Ponder Eric
Published: April 2021

The transformation of red cells from disks to spheres in a drop of a saline suspension between slide and coverglass (Ponder, 1929, 1934) has recently been shown by one of us (Furchgott, 1939) to be the result of two changes. The first is a rise in the pH of the suspension above 9·2 because of the alkaline nature of the glass surfaces. The second is an adsorption out of the suspension by the glass surfaces of a substance which, if present, prevents the formation of spheres at the pH attained between slide and coverglass. The determination of the chemical nature of this substance, termed the “anti-sphering factor”, and experimental attempts to gain an insight into the physical mechanism of the phenomena of shape changes are the subject of this paper.
The Effect of Deafferentation Upon the Locomotory Activity of Amphibian Limbs
Authors: Gray J. , Lissmann H. W.
Published: April 2021

In 1912-13 Graham Brown and Sherrington showed, independently, that rhythmical activity could be maintained in a pair of deafferentated antagonistic mammalian muscles; since then it has been customary to regard locomotory rhythms as the expression of intrinsic activity within the nerve cord. On the other hand, a study of the responses of vertebrate limbs to suitable reflex stimulation makes it difficult to believe that impulses coming from peripheral sense organs do not play a very important role in the co-ordination of normal locomotory movements. The present paper constitutes an attempt to decide how far locomotion can occur in animals whose limbs have been completely desensitized by cutting the roots of their afferent nerves.
The Daily Rhythm of Activity of the Cockroach, Blatta Orientalis L
Authors: Mellanby Kenneth
Published: April 2021

Trapping experiments were made to investigate the activity of cockroaches in a naturally infested animal room. Under normal conditions of illumination (light by day and dark by night), activity only occurred at night, and most activity occurred during the period just before midnight. There was little activity during the later hours of darkness. Artificial illumination of the order of 6 m.c. almost entirely prevented the cockroaches from appearing. Even lower intensities of light greatly reduced the number which appeared. Darkening the room during the day did not cause the cockroaches to appear, unless the room had been artifically illuminated during the previous night. Mechanical vibration and air movements appear to have little effect on the rhythmic activity of the cockroach. The rhythmic activity of the cockroach appears to be controlled by some internal mechanism which we do not yet understand. External factors like light can modify the rhythm and may temporarily abolish it, but under normal conditions it is readily re-established.
The Humidity Behaviour of the Mealworm Beetle, Tenebrio Molitor L
Authors: Pielou D. P. , Gunn D. L.
Published: April 2021

Humidity is well known to be a factor of great importance in the lives of many insects and other terrestrial arthropods. Apart, however, from the pioneer work of Shelford (1913) and his school on the rather complex stimulus of “evaporating power of the air”, there has been, until recently, little detailed and exact study of the behaviour of animals towards humidity as a stimulus. The recently developed methods of Gunn & Kennedy (1936) now make such study possible. By means of these methods, humidity behaviour has been examined in the wood-louse, Porcellio scaber, by Gunn (1937); in the locust, Locusta migratoria, by Kennedy (1937); in the mosquitoes, Anopheles gambiae and A.funestus, by De Meillon (1937); in the mosquito, Culex fatigans, by Thomson (1938) and in the cockroach, Blatta orientalis, by Gunn & Cosway (1938). The work described below deals with the reactions of the adult mealworm beetle, Tenebrio molitor L., towards humidity. This beetle lives in flour, bran and similar products and is moderately resistant to desiccation. It loses about 4% of its weight per day in dry air at 25° C. and dies in 8–9 days. Its resistance to desiccation is therefore less than that of its. larva, which was investigated by Buxton (1930).
Physiological Effects of a Hypotonic Environment
Authors: Wells G. P. , Ledingham Isabel C.
Published: April 2021

Numerous studies have been published on the extent to which aquatic animals can maintain internal environments differing in osmotic pressure from their surroundings. In the case of polychaete worms, it has been shown that some species, especially Nereis diversicolor, can maintain a considerable degree of hypertonicity, even in very dilute brackish water, while in others, such as Arenicola marina, the internal and external fluids are always isotonic (Schlieper, 1929; Beadle, 1937; Zenkewitch, 1938). These facts have been correlated with the extent to which the various species can invade brackish water. In one respect, however, our knowledge is at present very deficient. Remarkably little—in the case of polychaete worms, nothing—is known about the extent to which the tissues of animals can tolerate dilution of their bathing media. Information on this question is evidently necessary if the significance of the body-fluid data is to be properly understood.
Second-Order Olfactory and Visual Learning in the Optic Tectum of the Goldfish
Authors: Sanders F. K.
Published: April 2021

The goldfish (Carassius auratus) learns to swim to concealed food when an illuminated disk is presented. The presentation of an olfactory stimulus at the same time as the optic stimulus, during reinforcement of this visual learning, results in the addition of the olfactory stimulus to the stimulus complex necessary to call forth the learned reaction. Five animals learned to react to a situation in which—after preliminary training with an optic stimulus with food as reward—amyl acetate was given as olfactory stimulus and the optic stimulus as reward. This effect is termed second-order learning. It is comparable to second-order conditioned reflexes. In four animals trained in this way operations involving removal of large areas of the optic tectum, or cuts made at its anterior border, caused disturbances in the second-order learning. There exists, therefore, in the Teleostean optic tectum a mechanism capable of second-order olfactory-optic learning. The connexion between the telencephalic primary olfactory centre and the tectum involved in this learning passes into the tectum at its anterior border, since cuts made in this region interfered with the learning while leaving a great deal of the tectum intact.
The Effect of Certain Environmental Factors on the Growth of Brown Trout (Salmo Trutta L.)
Authors: Wingfield C. A.
Published: April 2021

The factors responsible for seasonal variations in the growth of brown trout in any one environment are examined. The probable basic importance of the water temperature is established. A critical temperature of 6° C. below which no growth takes place is deduced. It is shown that the seasonal variations in growth observed do not result in corresponding variations in the width of the scale rings: such variations appear to be the direct result of fluctuations in available food supply. Under natural conditions both water temperature and available food supply apparently act as limiting factors during the winter: during the summer, provided that the water temperature does not rise to a lethal level, only the available food supply is limiting. The possible importance of light intensity as a limiting factor is indicated. Differences in the growth rate of trout from different environments are also considered. The role of dissolved calcium is investigated. It appears unlikely that the amount of dissolved calcium is responsible for the differences in trout growth in “hard” and “soft” waters. It is suggested that such differences may be effected not by differences in the concentration of any one specific ion, but by departures from the optimum ionic balance brought about by variations in the relative concentration of any of the ions present.
Effects of Diet on Responses to Hypoxia in Sturgeon (Acipenser Naccarii)
Authors: Randall D. J. , McKenzie D. J. , Abrami G. , Bondiolotti G. P. , Natiello F. , Bronzi P. , Bolis L. , Agradi E.
Published: April 2021

We investigated the effects of a diet enriched in omega-3 (ω3) polyunsaturated fatty acids (PUFA) and vitamin E on responses of sturgeon (Acipenser naccarii) to hypoxia. After 3 months of feeding, there were significant increases in ω3 PUFA in liver and muscle, and of vitamin E in muscle, of fish fed the enriched diet (ED) compared with fish on a standard diet (SD), indicating that tissue composition is influenced by diet. Acute exposure to hypoxia (10 min at 10.8 kPa water O2 tension, ) had no effect on oxygen consumption , increased gill ventilation frequency (fg) and reduced arterial blood O2 content in both dietary groups, but ED sturgeon exhibited a significantly smaller decrease in than did SD animals. Progressive hypoxic exposure ( decreasing gradually from 20.5 to 3.6kPa within 45–60min) led to a significant increase in at intermediate levels of in SD sturgeon that was not seen in ED animals. Furthermore, ED sturgeon showed no significant reduction in arterial plasma pH (pHa) and at levels that caused significant reductions in these variables in SD sturgeon. ED sturgeon exhibited a smaller increase in plasma lactate level than did SD fish. We suggest that PUFA and/or vitamin E contribute significantly to regulation of metabolism in hypoxia.
The Effect of Temperature on the Burst Swimming Performance of Fish Larvae
Authors: Batty R. S. , Blaxter J. H. S.
Published: April 2021

Newly hatched herring and plaice larvae were stimulated by probes to make C-start escape responses at temperatures between 5 and 15°C. The responses and the subsequent burst-speed swimming were recorded and analysed using highspeed video at 400 frames s−1. The muscle contraction time of the initial C-start was temperature-dependent, ranging from 22–33 ms at 5°C to 17–21 ms at 15°C. Immediately following the C-start, tail-beat frequency ranged from 18s−1 at 5°C to 35 s−1 at 15°C. Tail-beat amplitude, equivalent to 0.4–0.6 of a body length (L), and stride length, about 0.5 L, were not temperature-dependent. The escape speed ranged from 8Ls−1 at 5°C to 15 Ls−1 at 15°C. These results and those of other workers can be described by the equation: where f is tail-beat frequency, t is temperature and L is length.
Electrophysiological Pharmacology of the Nicotinic and Muscarinic Cholinergic Responses of Isolated Neuronal Somata From Locust Thoracic Ganglia
Authors: Benson Jack A.
Published: April 2021

Mechanically isolated neuronal somata from the thoracic ganglia of the locust Locusta migratoria remain electrophysiologically viable under current-or voltage-clamp in vitro for many hours. Nicotine and muscarine evoke different responses when pressure-microapplied to these somata. The response to acetylcholine is mainly nicotinic but contains a small muscarinic component. The nicotinic (AChl) response is a rapid depolarisation accompanied by a decrease in membrane resistance. In voltage-clamped somata, the current mediating the AChl response is inward over the membrane potential range −30 to − 110 mV, decreasing with depolarisation and with a projected reversal potential of about +20 mV. The muscarinic (ACh2) response is a slow depolarisation accompanied by a decrease in membrane resistance. In voltage-clamped somata, the current mediating the ACh2 response is inward, decreasing to zero at potentials of −80 to −90 mV. The AChl response is evoked by nicotine, anabasine, tetramethylammonium, DMPP and relatively high concentrations of the nitromethylene heterocycle insecticide, PMNI. Suberyldicholine or decamethonium evoke the response only when acetylcholine is present in the bathing saline. Nicotinic antagonists of the AChl response, in descending order of potency, are PMN1 > α-bungarotoxin⩾lobeline⩾mecamylamine>trimethaphan camsylate>chlorisondamine⩾d-tubo-curarine⩾hexamethomium⩾gallamine triethiodide⩾tetracthylammonium. This response is also potently blocked by strychnine and more weakly blocked by δ-philanthotoxin, bicuculline and picrotoxin. The ACh2 response is evoked by muscarine, oxotremorine, arecoline, pilocarpine and, very weakly, by the Mj-selective agonist McN-A-343. Muscarinic antagonists of the ACh2 response, in descending order of potency, are QNB> scopolamine>atropine>4-DAMP (M3) ⩾benactyzine⩾HHSiD (M1/M3) ⩾ pirenzepine (M1). QNX (M1), AF-DX116 (M2), gallamine triethiodide (M2) and methoctramine (M2) are almost or completely inactive. With the exception of pirenzepine and QNX, all of the muscarinic antagonists used in this study also block the nicotinic AChl response with EC50 values in the range 5 to 50μmol l−1, similar to those for δ-philanthotoxin, bicuculline and picrotoxin. Pirenzepine is inactive (10μmol l−1), but QNX is potently active, with an EC50 value of approximately 20 nmol l−1, similar to that of α-bungarotoxin. The extrasynaptic nicotinic and muscarinic receptors of Locusta migratoria neurones are pharmacologically distinct from the corresponding mammalian receptors studied so far.
Suppression of Ventilatory Reafference in the Elasmobranch Electrosensory System: Medullary Neuron Receptive Fields Support A Common Mode Rejection Mechanism
Authors: Bodznick David , Montgomery John C.
Published: April 2021

Elasmobranch fishes have an electroreceptive system which they use for prey detection and orientation. Sensory inputs in this system are corrupted by a form of reafference generated by the animal’s own ventilation. However, we show here that in the carpet shark, Cephaloscylium Isabella, as in two previously studied batoid species, this ventilatory ‘noise’ is reduced by sensory processing within the medullary nucleus of the electrosensory system. It has been proposed that the noise cancellation is achieved by a common mode rejection mechanism. One prediction of this hypothesis is that secondary neurons within the medullary nucleus should have both excitatory and inhibitory components to their receptive fields. This prediction is experimentally verified here. Projection neurons of the medullary nucleus in the carpet shark typically have a focal excitatory, and a diffuse inhibitory, receptive field organization including a component of contralateral inhibition. This result provides strong support for the hypothesis that ventilatory suppression in the elasmobranch electrosensory system is achieved by a common mode mechanism.
Calcium and Potassium Currents in leg Motoneurons During Postembryonic Development in the Hawkmoth Manduca Sexta
Authors: Hayashi Jon H. , Levine Richard B.
Published: April 2021

During insect metamorphosis the nervous system is reorganized to accommodate changes in behavior. In the hawkmoth, Manduca sexta, many identified larval motoneurons persist to innervate new adult muscles, while undergoing changes in dendritic morphology and synaptic connections. The thoracic leg motoneurons, for example, innervate different sets of muscles in the larva and adult and participate in distinct types of locomotor behavior in the two stages of life. To determine whether changes in the biophysical properties of these motoneurons accompany the structural and functional modifications that have been described, we used the whole-cell voltage-clamp technique to compare the Ca2+ and K+ currents expressed by leg motoneurons isolated from the larval, pupal and adult stages of Manduca. After 24h in culture, the somata of leg motoneurons isolated from all three stages expressed voltage-sensitive Ca2+ currents that could be blocked by Cd2+, Co2+ or Ni2+. The currents were larger with Ba2+ as the charge carrier. The Ca2+ current density was significantly lower in these motoneurons during the early pupal stage than in either the larva or adult. Similar experiments revealed both transient and sustained K+ currents in the leg motoneurons that could be blocked with Cs+. There was a significant decrease in the density of the transient, inactivating outward current in leg motoneurons isolated from the early pupal stage. Thus, the levels of some types of ionic currents are modulated during metamorphosis. These changes may be important for the developmental or behavioral changes that accompany metamorphosis.
Infrasound Sensitivity in the Plaice (Pleuronectes Platessa)
Authors: Karlsen Hans Erik
Published: April 2021

The sensitivity of plaice (Pleuronectes platessa) to infrasound has been examined using a seawater-filled test chamber suspended by steel wires like a swing and driven by a vibrator. The sensitivity to low-frequency vibrations was determined using the cardiac conditioning technique. All plaice readily responded to infrasound down to 0.1 Hz, which was the lowest frequency tested, with threshold values of approximately 4×10−5ms−2 rms. This sensitivity is comparable to infrasound thresholds found in other fish species and it agrees with the acceleration thresholds for plaice in the frequency range 30–100 Hz. The water movements relative to the fish surface produced during stimulation were below lateral-line thresholds. The inner ear otolith organs are thus probably responsible for the observed responses to infrasound. The hearing capabilities of plaice may be explained by these organs functioning as slightly underdamped harmonic oscillators with a resonant frequency close to 100Hz.
Postmoult Uptake of Calcium by the Blue Crab (Callinectes Sapidus) in Water of Low Salinity
Authors: Neufeld Douglas S. , Cameron James N.
Published: April 2021

After moulting, blue crabs (Callinectes sapidus) acclimated to a salinity of 2 ‰ were able to calcify as rapidly and accumulate as much calcium as crabs in sea water. Immediately after moult, the total masses of calcium, magnesium and strontium present in the whole body were 4.6, 15.6 and 3.0%, respectively, of their intermoult values. During the time of most rapid calcification, calcium uptake was 5.4±1.4mmol l−1, which is comparable to the maximum rate found in seawater-acclimated crabs. The concentrations of bound and free calcium in the blood changed very little with acclimation salinity, remaining at approximately 3 and 8 mmol l−1. respectively, both during intermoult and 1 day postmoult. Free calcium changed relatively little through the moult cycle, varying between 6.9 and 8.1 mmol l−1, but bound calcium rose to a peak of 6.4 mmol l−1 prior to moult then dropped to 2.6 mmol l−1 after moult, concurrent with a decrease of approximately 80% in the protein concentration of the blood. The concentration of total magnesium in the blood increased from a premoult low of 9.0 mmol l−1 to a postmoult high of 11.7 mmol l−1 and remained elevated throughout the period of rapid mineralization. During the postmoult period of rapid calcium uptake, the internal-to-external concentration ratio for total calcium was 6.6 to 1. The activity ratio, however, was only 2.5 to 1 because 28% of the calcium in the blood was bound to protein, and because the lower ionic strength of the medium resulted in a 2.5-fold higher activity coefficient for the water compared to blood. The transepithelial potential at postmoult (–5.4±0.7mV) was significantly more negative than at intermoult (–3.1±0.6mV). In artificial 2‰ sea water, the transepithelial potential (–9.3±0.7 mV) was higher than the equilibrium potential for calcium (–12.0±0.5 mV), implicating active transport in the uptake of calcium.
Evidence That Acetylcholine Is An Inhibitory Transmitter Of Heart Interneurons In The Leech
Authors: Schmidt Joachim , Calabrese Ronald L.
Published: April 2021

In the leech, synaptic transmission between heart interneurons (HN cells) and between HN cells and heart motor neurons (HE cells) is blocked by bicuculline methiodide. Gamma-aminobutyric acid, when applied focally onto the somata of HN cells or when added to the superfusate, has no effect on the membrane potential of HN cells. Both acetylcholine (ACh) and the ACh agonist carbachol hyperpolarize HN cells and HE cells when applied focally onto their somata or into the neuropil or when added to the superfusate. Inhibitory postsynaptic-potential-like responses elicited by focal application of carbachol onto the somata of HN cells and HE cells are blocked by bicuculline methiodide and are reversed when Cl− is injected into the cells. Focal application of carbachol onto the somata of HN cells and HE cells increases membrane conductance. The results indicate that HN cells use ACh as an inhibitory transmitter, that the postsynaptic receptors for ACh are blocked by bicuculline methiodide and that inhibition of HN cells and HE cells is mediated by an increased Cl− conductance.
Exercise-Generated Heat Contributes to Thermoregulation by Gambel’s Quail in the Cold
Authors: Zerba Eileen , Walsberg Glenn E.
Published: April 2021

The purpose of this study was to investigate the relationship between the allocation of exercise-generated heat and resting metabolic heat production during cold exposure. We tested the hypothesis that, during cold exposure, exercise-generated heat contributes to the fulfillment of the thermostatic requirement. Our assumption was that the thermostatic requirement is higher for exercising than for resting birds in still air because of the disruption of boundary and plumage insulation layers. We predicted that, during moderate exercise, the metabolic heat production of exercising birds would be higher than that for resting birds in still air but would not differ significantly from the metabolic heat generated by resting birds exposed to similar convective conditions. To test our hypothesis we measured whole-animal oxygen consumption of Gambel’s quail (Callipepla gambelii Gambel) running in a circular metabolic chamber and at rest in still air at ambient temperatures below the animal’s lower critical temperature. We compared these data to previous data for Gambel’s quail at rest exposed to wind at a speed equal to the running speed used in our experiments. In addition to oxygen consumption measurements, we measured body temperatures of exercising and resting birds. The data supported our assumption and predictions. (1) Whole-body thermal resistance for exercising birds was lower than that for resting birds in still air, indicating that the thermostatic requirement was higher for exercising birds because of the disruption of boundary and plumage insulation layers. (2) Heat productions of exercising birds were significantly higher than those of resting birds in still air but were not significantly different from the heat productions of resting birds exposed to similar convective conditions. (3) Body temperatures were not significantly different between resting birds in still air and exercising birds. The mean body temperature of exercising birds, however, was 2°C higher than that of resting birds exposed to wind. We concluded that an exercising animal probably does not incur an energetic cost associated with locomotor activity at low ambient temperatures in comparison to an inactive animal exposed to a similar convective regime.
Evidence that fin whales respond to the geomagnetic field during migration
Authors: Walker M. M. , Kirschvink J. L. , Ahmed G. , Dizon A. E.
Published: April 2021

We challenge the hypothesis that fin whales use a magnetic sense to guide migration by testing for associations between geophysical parameters and the positions where fin whales were observed over the continental shelf off the northeastern United States. Monte Carlo simulations estimated the probability that the distribution of fin whale sighting was random with respect to bottom depth, bottom slope and the intensity and gradient of the geomagnetic field. The simulations demonstrated no overall association of sighting positions with any of these four geophysical parameters. Analysis of the data by season, however, demonstrated statistically reliable associations of sighting positions with areas of low geomagnetic intensity and gradient in winter and fall, respectively, but no association of sighting positions with bathymetric parameters in any season. An attempt to focus on migrating animals by excluding those observed feeding confirmed the associations of sighting positions with low geomagnetic intensity and gradient in winter and fall, respectively, and revealed additional associations with low geomagnetic gradients in winter and spring. These results are consistent with the hypothesis that fin whales, and perhaps other mysticete species, possess a magnetic sense that they use to guide migration.
Chloride channels of intracellular organelles and their potential role in cystic fibrosis
Authors: Al-Awqati Qais , Barasch Jonathan , Landry Donald
Published: April 2021

Chloride channels were previously purified from bovine kidney cortex membranes using a drug affinity column. Reconstitution of the purified proteins into artificial liposomes and planar bilayers yielded chloride channels. A 64× 10Mr protein, p64, identified as a component of this chloride channel, was used to generate antibodies which depleted solubilized kidney membranes of all chloride channel activity. This antibody has now been used to identify a clone, H2B, from a kidney cDNA library. Antibodies, affinity-purified against the fusion protein of H2B, also depleted solubilized kidney cortex from all chloride channel activity. The predicted amino acid sequence of p64 shows that it contains two and possibly four putative transmembrane domains and potential phosphorylation sites by protein kinases A and C. There was no significant homology to other protein (or DNA) sequences in the data base including other anion channels or the cystic fibrosis transmembrane conductance regulator. The protein is expressed in all cells tested and probably represents the chloride channel of intracellular organelles.

Cystic fibrosis (CF) is associated with a defect in a cyclic-AMP-activated chloride channel in secretory epithelia which leads to decreased fluid secretion. In addition, many mucus glycoproteins show decreased sialylation but increased sulfation. We have recently shown that the pH of intracellular organelles is more alkaline in CF cells, an abnormality that is due to defective chloride conductance in the vesicle membranes. We postulate that the defect in the intracellular chloride channel, and hence the alkalization, could explain the glycosylation abnormalities since the pH optimum of Golgi sialyltransferase is acid while that of focusyl-and sulfotransferases is alkaline. Defects in sialyation of glycolipids might also generate receptors for Pseudomonas, which is known to colonize the respiratory tract of CF patients.
Insect ion homeostasis
Authors: Zeiske Wolfgang
Published: April 2021

The constant composition of body fluids in insects is maintained by the cooperative interaction of gastrointestinal and urinary tissues. Water follows ionic movements, which are driven by the basolateral Na+/K+-ATPase and/or the apical ‘K+(or Na+) pump’. The latter now is thought to be the functional expression of a parallel arrangement of a protonmotive V-ATPase and a K+(or Na+)/nH+ antiport. This review focuses on the pathways for the movement of monovalent inorganic ions through epithelia involved in ion homeostasis. A graphical summary compares the principal findings with respect to cation secretion in lepidopteran caterpillar midgut goblet cells (K+) and in brush-border cells of Malpighian tubules (K+, Na+).
The F0 complex of the proton-translocating F-type ATPase of Escherichia coli
Authors: Deckers-Hebestreit Gabriele , Altendorf Karlheinz
Published: April 2021

The ATP synthase (F1F0 ) of Escherichia coli consists of two structurally and functionally distinct entities. The F1 part is composed of five subunits α, β, γ, δ and ϵ (3:3:1:1:1) and carries the catalytic centres of the enzyme. The membrane-bound F0complex functions as a proton channel and consists of the three subunits a, b and c (l:2:10±l).

Subunit c (8288 Mr) exhibits a hairpin-like structure within the membrane. A conserved acidic residue (Asp-61) in the C-terminal hydrophobic segment is absolutely required for proton translocation through F0, whereas the hydrophilic loop region is necessary for F, binding. Expression of the chloroplast proteolipid together with subunits a and b of E. coli did not produce an active F0 hybrid complex. Therefore, the construction of hybrid c subunits consisting of parts of the proteolipid from both organisms is in progress to determine those parts of subunit c that are essential for a functional interplay with subunits a and b.

Subunit a (30276 Mr), which is also involved in proton translocation, is an extremely hydrophobic protein with 5–8 membrane-spanning helices. Studies with alkaline phosphatase fusion proteins resulted in controversial conclusions about the localization of the N and C termini of the protein. A foreign epitope (13 amino acids) has been inserted into the N-or C-terminal region of subunit a without affecting the function of Fo. Binding studies with a monoclonal antibody against this epitope are now under investigation to determine the orientation of subunit a.

Subunit b (17265 Mr) is anchored in the membrane by its apolar N-terminal region, whereas the hydrophilic part protrudes into the cytoplasm. Studies with proteases and truncated b′ subunits revealed that the C-terminal part of subunit b is involved in binding of F1 to F0 and is necessary for correct assembly of F0.
Biogenesis of the yeast vacuolar H+-ATPase
Authors: Kane Patricia M.
Published: April 2021

Achieving an understanding of the biosynthesis, assembly and intracellular targeting of the vacuolar H+-ATPase is critical for understanding the distribution of acidic compartments and the regulation of organelle acidification. The assembly of the yeast vacuolar H+-ATPase requires the attachment of several cytoplasmically oriented, peripheral subunits (the V1 sector) to a complex of integral membrane subunits (the Vo sector) and thus is not easily described by the established mechanisms for transport of soluble or vacuolar membrane proteins to the vacuole. In order to examine the assembly of the enzyme complex, yeast mutants lacking one of the subunit genes have been constructed and the synthesis and assembly of the other subunits have been examined. In mutants lacking one subunit, the remaining ATPase subunits seem to be synthesized, but in many cases are either not assembled or not targeted to the vacuole. Immunofluorescence and subcellular fractionation experiments have revealed that deletion of one peripheral subunit prevents the other peripheral subunits, but not the integral membrane subunits, from reaching the vacuole. In contrast, the absence of one of the integral membrane subunits appears to prevent both the peripheral subunits and another integral subunit from reaching the vacuole and also results in reduced cellular levels of the other integral membrane subunit. These data suggest that transport of integral and peripheral membrane subunits to the vacuole may employ somewhat independent mechanisms and that some assembly of the V1 and Vo sectors may occur before the two sectors are joined. Current models for the assembly process and the implications for organelle acidification are discussed.
The Ionic Basis of the Receptor Potential of Frog Taste Cells Induced by Water Stimuli
Authors: Okada Yukio , Miyamoto Takenori , Sato Toshihide
Published: April 2021

The ionic mechanism underlying the receptor potential induced by a deionized water stimulus was studied in frog taste cells with conventional microelectrodes. The taste cells located in the proximal portion of the tongue generated a depolarizing receptor potential which averaged 10mV in response to stimulation with deionized water. The cell membrane of the water-sensitive taste cell could be divided into the taste-receptive (apical) and basolateral membranes and the cells were classified into two types: Cl−-dependent and Cl−-independent. In Cl−-dependent cells whose input resistance was decreased or unchanged by deionized water, the magnitude of the water-induced depolarization decreased with an increase in concentration of superficial Cl− in contact with the receptive membrane and with addition of blockers of anion channels (0.1mmol l−1 SITS and 0.1mmol l−1 DIDS) to deionized water. The reversal potential for the depolarization in this type shifted according to the concentration of superficial Cl−. These properties of the responses were consistent with those of the glossopharyngeal nerve which innervates the taste disc. In Cl−-independent cells whose input resistance was increased by deionized water, the reversal potential was approximately equal to the equilibrium potential for K+ at the basolateral membrane. The water-induced response of the glossopharyngeal nerve was decreased to about 60% of the control value by addition of interstitial 2mmol l−1 Ba2+. It is concluded that the water-induced receptor potential is produced by Cl− secretion through the taste-receptive membrane in about 70% of water-sensitive frog taste cells, while it is generated by an inhibition of the resting K+ conductance of the basolateral membrane in the remaining 30% of the cells.
Centrally Generated Rhythmic Activity and Modulatory Function of the Oviductal Dorsal Unpaired Median (Dum) Neurones in Two Orthopteran Species (Calliptamus SP. and Decticus Albifrons)
Authors: Kalogianni E. , Theophilidis G.
Published: April 2021

The rhythmic firing pattern of the putatively octopaminergic dorsal unpaired median (DUM) neurones supplying the oviductal system of female orthopterans, Calliptamus sp. and Decticus albifrons, was examined. Our data provide evidence that the oviductal DUM neurones in the seventh abdominal ganglion modulate the oviductal motor pattern, both peripherally and centrally, during the inhibition of egg-laying behaviour.

In a minimally dissected animal, rhythmic activation of the oviductal DUM and motor neurones can be readily elicited by isolation of the seventh abdominal ganglion from the anterior part of the nerve cord. The bursting activity of the DUM neurones is temporally correlated with the oviductal motor rhythm. Both populations of oviductal neurones retain their rhythmic firing pattern after total isolation of the genital ganglia, indicating the presence of an oviductal central pattern generator.

The effects of stimulation of oviductal DUM neurones on the oviductal motor activity were monitored by recording intracellularly from oviductal muscle fibres and extracellularly from motor axons. These effects consist of a reduction in the amplitude and frequency of excitatory postsynaptic potentials (EPSPs) in the muscle fibre and in the firing rate in oviductal motor neurones. We suggest that the change in EPSP amplitude results from peripheral release of octopamine by DUM neurones. The decreased firing rate of motor neurones, however, appears to be a central effect, possibly caused by central release of octopamine by DUM neurones.
Cardiac Responses of Grey Seals During Diving at Sea
Authors: Thompson David , Fedak Michael A.
Published: April 2021

Heart rate, swimming speed and diving depth data were collected from free-ranging grey seals, Halichoerus grypus, as they foraged and travelled in the sea around the Hebrides Islands off western Scotland. Information was collected on a tracking yacht using a combination of sonic and radio telemetry. Diving heart rate declined as a function of dive duration. In long dives, grey seals employed extreme bradycardia, with heart rates falling to 4beatsmin−1 for extended periods, despite the animal being free to breathe at will. This extreme dive response is part of the normal foraging behaviour. Seals spent 89% of the time submerged during bouts of long dives; swimming was restricted to ascent and descent. Dive durations exceeded estimated aerobic dive limit, even assuming resting metabolic rates. These results indicate that behavioural, and possibly cellular, energy-sparing mechanisms play an important role in diving behaviour of grey seals. This has implications not only for studies of mammalian energetics but also for our understanding of the foraging tactics and prey selection of marine mammals. If some seals are using energy-sparing mechanisms to reduce metabolic costs while at depth, they may be forced to wait for and ambush prey rather than to search for and chase it.
ATPase Activity in the Midgut of the Mosquito, Anopheles Stephensi: Biochemical Characterisation of Ouabain-Sensitive and Ouabain-Insensitive Activities
Authors: Macvicker J. A. K. , Billingsley P. F. , Djamgoz M. B. A.
Published: April 2021

Na+/K+-ATPase activity was demonstrated in the midgut of Anopheles stephensi. More than 80% of the total ATPase activity was sensitive to inhibition by ouabain with an IC50 of 4.5×10−7±0.3×10−7 mol l−1 and with maximal inhibition occurring at 10−4 moll−1. This ouabain-sensitive Na+/K+-ATPase was maximally activated at a Mg2+:ATP ratio of 1:1.3, with a Km of 0.3mmol l−1 and a Vmax of 2.4 µmol Pi mg−1 proteinmin−1 for ATP. Maximal activation was reached at 15mmol l−1 K+ with a Km of 0.72mmol l−1. Activation with Na+ showed an increase up to 120mmol l−1 with a Km of 6.47mmol l−1, and the optimal K+:Na+ ratio was 1:5.5. The ouabain-sensitive enzyme was inhibited by Ca2+ with an IC50 of 1.11±0.07mmol l−1. The pH optima were 7.2 for the ouabain-sensitive enzyme and 8.9 for the ouabain-insensitive fraction. The minor ouabain-insensitive fraction was unaffected by Na+, K+ or Ca2+, but was dependent to some extent on Mg2+. The demonstration of a ouabain-sensitive Na+/K+-ATPase being a major ATPase in the mosquito midgut is consistent with the hypothesis that this region is actively involved in post-feeding ion and water regulation.
Bulk Flow of the Medium and Cutaneous Sodium Uptake in Frogs: Potential Significance of Sodium and Oxygen Boundary Layers
Authors: Feder Martin E. , Gonzalez Richard J. , Robbins Tzvi , Talbot Colleen R.
Published: April 2021

To examine the potential impact of fluid dynamic boundary layers on cutaneous ion exchange, we investigated how bulk flow of dilute Na+ solutions (≤1.0mmol l− 1) over the skin of intact frogs (Rana catesbeiana and Rana pipiens) affects cutaneous Na+ uptake and transepithelial potential (TEP). Cessation of stirring resulted in a 14–35% decrease in TEP and a 14–65% decrease in . Two weeks’ acclimation to an unstirred bath increased to levels 70% greater than in frogs acclimated to a continuously stirred bath and to levels comparable to those of frogs acclimated to deionized water. These effects are consistent with depletion of Na+ in the boundary layer, but are also consistent with depletion of O2 in the boundary layer, which might limit generation of ATP consumed by ATPases responsible for cutaneous Na+ uptake. To investigate this latter possibility, we measured TEP and while manipulating the of well-stirred external media at constant [Na+]. Hyperoxia increased by 28% and had little or no effect on TEP. Hypoxia reduced by 48% and decreased TEP by 22%. These results suggest that ionic and gaseous boundary layers may interact to affect cutaneous ion transport.
Mammalian Spinal Biomechanics: I. Static and Dynamic Mechanical Properties of Intact Intervertebral Joints
Authors: Gál Julianna M.
Published: April 2021

Four-point bending was used to apply pure extension and flexion moments to the ligamentous lumbosacral spine and pelvic girdle of monkey (Macaca fascicularis), rabbit (domestic and wild, Oryctolagus cuniculus ), badger (Meles meles), wallaby (Wallabia rufogrisea frutica), sheep (Ovis aries), seal (Phoca vitulina) and tiger ( Panthera tigris). The absolute ranges of angular change in lumbar–lumbar joints (from X-radiographs) were considerable and similar in monkey and wallaby (greater in flexion) and in rabbit and badger (symmetrical in extension and flexion). Mass-specific bending comparisons showed that monkey and seal joints were the most and least resistant, respectively, to these moments. The patterns of mobility showed no clear scaling effects. Subsequently, additional ligamentous joint complexes (three vertebrae and two intervertebral discs) of monkey, wallaby, tiger, jaguar (Panthera onca) and seal (Halichoerus grypus) were subjected to cyclic extension and flexion moments. Changes in intervertebral angle (y, from X-radiographs) were modelled as functions of applied specific bending moments (x): y=A(1−e−Bx). A and B values represented bending capacities and joint compliances respectively. Homologous monkey and wallaby joints had considerable flexion capacities, with low compliances. Homologous jaguar and tiger joints had limited flexion capacities, but greater compliances. The data suggest that flexion resistance may be controlled by different mechanisms in different species.
Mammalian Spinal Biomechanics: II. Intervertebral Lesion Experiments and Mechanisms of Bending Resistance
Authors: Gál Julianna M.
Published: April 2021

Three-point cyclic bending was applied to intervertebral joint complexes (three vertebrae with two intervertebral discs) of monkey (Macaca fascicularis), wallaby (Wallabia rufogrisea frutica), tiger (Panthera tigris ), jaguar (Panthera onca) and seal (Halichoerus grypus). Force–displacement loops were recorded for intact specimens in both extension and flexion. Reductions in peak forces at given displacements were measured, following lesions of ventral ligaments, superspinous ligaments, interspinous ligaments and muscles, ligamenta flava and the articular capsules. Subsequently, the vertebral arches were removed from the specimens to test the bending resistance of the intervertebral discs alone. The results of these lesion experiments, coupled with details of intervertebral joint anatomy, suggest that extension resistance is ultimately due to articular joint impaction for all species tested. The prominent ligamenta flava of the monkey and wallaby contrast with the robust discs of jaguar and tiger and illustrate two distinct mechanisms for resisting flexion in mammalian intervertebral joints. The conspicuous absence of soft structural elements in seal intervertebral joints contributes to their low bending resistance. The implications of these findings for mammalian locomotion, behaviour and scaling are discussed.
Endothermy in the Solitary Bee Anthophora Plumipes: Independent Measures of Thermoregulatory Ability, Costs of Warm-Up and the Role of Body Size
Authors: Stone Graham N.
Published: April 2021

This study examines variation in thoracic temperatures, rates of pre-flight warm-up and heat loss in the solitary bee Anthophora plumipes (Hymenoptera; Anthophoridae). Thoracic temperatures were measured both during free flight in the field and during tethered flight in the laboratory, over a range of ambient temperatures. These two techniques give independent measures of thermoregulatory ability. In terms of the gradient of thoracic temperature on ambient temperature, thermoregulation by A. plumipes is more effective before flight than during flight. Warm-up rates and body temperatures correlate positively with body mass, while mass-specific rates of heat loss correlate negatively with body mass. Larger bees are significantly more likely to achieve flight temperatures at low ambient temperatures. Simultaneous measurement of thoracic and abdominal temperatures shows that A. plumipes is capable of regulating heat flow between thorax and abdomen. Accelerated thoracic cooling is only demonstrated at high ambient temperatures. Anthophora plumipes is able to fly at low ambient temperatures by tolerating thoracic temperatures as low as 25°C, reducing the metabolic expense of endothermic activity. Rates of heat generation and loss are used to calculate the thermal power generated by A. plumipes and the total energetic cost of warm-up under different thermal conditions. The power generated increases with thoracic temperature excess and ambient temperature. The total cost of warm-up correlates negatively with ambient temperature.
The Locust Ovipositor Opener Muscle: Properties of the Neuromuscular System
Authors: Belanger Jim H. , Orchard Ian
Published: April 2021

A new preparation for studying properties of neuromuscular transmission and neuromodulation in insects, the ventral opener muscle of the locust ovipositor, is described. It consists of the complete musculoskeletal apparatus of the ventral opener muscle and the associated abdominal ganglia containing the central pattern generator that drives oviposition digging. In this preparation it is possible to record simultaneously motoneurone activity, muscle electromyograms, intracellular muscle fibre activity and behaviourally relevant tension production. The muscle displays ultrastructural and physiological characteristics typical of insect intermediate-type fibres: abundant sarcoplasmic reticulum, active Ca2+-dependent membrane responses, phasic contractions when stimulated by high-potassium saline and a low twitch:tetanus ratio. Superfused glutamate (10−4 mol l−1) and proctolin (10−8 mol l−1) induce contractions of the muscle, while GABA (10−4 mol l−1) reduces potassium-induced depolarizations. HPLC, bioassay and immunological methods show that proctolin is associated with all of the ventral ovipositor muscles, and combined back-filling/immunohistochemistry suggests that at least one of the ventral opener motoneurones is proctolinergic.
The Locust Ovipositor Opener Muscle: Proctolinergic Central and Peripheral Neuromodulation in a Centrally Driven Motor System
Authors: Belanger Jim H. , Orchard Ian
Published: April 2021

The pentapeptide proctolin has multiple effects on the locust oviposition digging system. At the neuromuscular junction of the ventral opener muscle, it has a concentration-dependent range of modulatory effects. At low concentrations (10−10 mol l−1), proctolin causes an increase in the frequency of miniature excitatory junctional potentials, but has no apparent effects on the muscle membrane or contractile properties. In the middle range of concentrations (approximately 10−9 mol l−1) proctolin increases neurally evoked twitch tension three-to fourfold with little change in the basal tension. At high concentrations (>10−8 mol l−1), proctolin causes a large increase in basal tension, upon which is occasionally superimposed a slow (approximately 0.3–0.5Hz) myogenic rhythm. Stimulation of the ventral opener nerve at 30Hz for 5min releases approximately 8% of the proctolin store of the muscle. In vitro ganglion–muscle preparations which are expressing the oviposition digging rhythm produced in the terminal abdominal ganglion release about 25% of the store of endogenous proctolin during 5min of superfusion. This declines to below the level of detectability over about 20min of superfusion. Muscle contractions decline and then cease over the same period, although the patterned neural input and muscle electromyogram responses are still present. Superfusion of 10−9 mol l−1 proctolin restores the muscle contractions to their original magnitude. Superfusion of 10−8 mol l−1 proctolin over preparations in which the oviposition digging pattern has slowed results in the frequency of the rhythm being restored to its original levels. We suggest that, rather than having a facultative modulatory role in this neuromuscular system, proctolin is required for it to function normally. Furthermore, proctolin may maintain the functional integrity of the central systems driving oviposition digging.
Conopressin G Increases Bursting Activity in Command Neurons Mediating Respiratory Pumping in Aplysia Californica
Authors: Martinez-Padron Manuel , Lukowiak Ken
Published: April 2021

Periodic spontaneous gill movements (SGMs) are one of the most obvious of the 21 general action patterns described in the ethogram of Aplysia californica (Leonard and Lukowiak, 1986). SGMs are thought to be a prime component of Aplysia’s respiratory cycle (Koester et al. 1974; Byrne and Koester, 1978) and in the intact animal the frequency of SGMs can be modified by changes in the partial pressures of CO2 and O2 of the sea water (Croll, 1985; Levy et al. 1989).