bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mechanism Of Tongue Projection In Chameleons: I. Electromyographic Tests Of Functional Hypotheses
Authors: Wainwright Peter C. , Bennett Albert F.
Published: April 2021

In this paper we document the activity of key muscles of the tongue, hyobranchia! apparatus and head during prey capture in the lizard Chamaeleo jacksonii Boulenger and use these data to test current hypotheses of chameleon tongue function. Electromyographic recordings were made during 27 feedings from nine individuals and synchronized with high-speed video recordings (200fields s−1), permitting an assessment of the activity of muscles relative to the onset of tongue projection, contact between tongue and prey, and tongue retraction. Four major results were obtained. (1) The hyoglossi muscles exhibit a single burst of activity that begins between 10 ms before and 20 ms after the onset of tongue projection and continues throughout the period of tongue retraction. (2) The accelerator muscle exhibits a biphasic activity pattern, with the first burst lasting about 185 ms and ending an average of 10.6 ms prior to the onset of projection. (3) The accelerator muscle shows regional variation in morphology that corresponds with variation in motor pattern. The anterior region of the muscle, unlike the posterior portion, exhibits only a single burst of activity that begins 2.5 ms after the onset of tongue projection and is thus not involved in launching the tongue. (4) The geniohyoidei, sternohyoidei, sternothyroidei, depressor mandibulae, adductor mandibulae and pterygoideus all exhibit activity patterns consistent with previously reported kinematic patterns and their proposed roles. The major implications of these results for models of the chameleon feeding mechanism are (1) that the hyoglossi do not act to hold the tongue on the entoglossal process during a loading period prior to tongue projection, and (2) that the presence of 185 ms of intense activity in the accelerator muscle prior to tongue projection suggests the presence of a preloading mechanism, the nature of which is the subject of the companion paper.
Ontogenetic Scaling and Mechanical Behaviour of the Tibiae of the African Desert Locust (Schistocerca Gregaria)
Authors: Katz Stephen L. , Gosline John M.
Published: April 2021

Current models for scaling of skeletal morphology were examined to test their applicability to the ontogenetic growth of an exoskeletal animal, the African desert locust ( Schistocerca gregaria). It was found that the tibial leg segments of both the mesothoracic (i.e. non-jumping) and the metathoracic (jumping) legs scaled in a manner that produced relatively longer, more slender skeletal elements as the animal grew. Metathoracic tibial length scaled to tibial diameter raised to the power 1.21. This result deviates both from isometric (i.e. geometric similarity) and distortive (constant stress, elastic similarity) allometric models.

The mechanical properties of the metathoracic tibiae were measured using a dynamic, three-point bending technique. The flexural stiffness of metathoracic tibiae scaled to body mass raised to the power 1.53. This was intermediate to the predictions made by constant stress and elastic similarity models. Thus, the mechanical properties scaled as predicted by mechanical scaling expectations in spite of the morphological developmental programme.

It may be that the thin-walled skeleton developed in the exoskeletal body plan has allowed a finer control over the distribution of load-bearing material in the leg. Such a distribution may be responsible for the observed increase in mechanical stiffness of legs that exhibit an unexpectedly spindly morphology. The rationale for the observed morphological programme may be a design that takes advantage of the inherent deformability of long, slender beams. Thus, it may be that the tibiae, which have been treated as rigid levers, are in fact flexible springs. Calculations indicate that the energy stored in the substantial deflection of the adult, metathoracic tibiae during a jump may be as high as 10% of the total kinetic energy of the jump.
The Mechanism of Tongue Projection in Chameleons: II. Role of Shape Change in a Muscular Hydrostat
Authors: Wainwright Peter C. , Bennett Albert F.
Published: April 2021

In this paper we investigate the interaction between the accelerator muscle (the muscle that powers tongue projection) and the entoglossal process (the tongue’s skeletal support) that occurs during tongue projection in chamaeleonid lizards. Previous work has shown that there is a delay of about 185 ms between the onset of accelerator muscle activity and the onset of tongue projection. In conjunction with anatomical observations, in vitro preparations of the accelerator muscle mounted on isolated entoglossal and surrogate processes were stimulated tetanically, and the resulting movements were recorded on video at 200 fields s−1. Three results indicate that morphological features of the entoglossus and the accelerator muscle delay the onset of tongue projection following the onset of accelerator contrac-tion: ( 1) the entoglossus is parallel-sided along the posterior 90% of its shaft, only tapering at the very tip, (2) the sphincter-like portion of the accelerator muscle, which effects tongue projection, makes up the posterior 63% of the muscle and does not contact the tapered region of the entoglossus at rest, and (3) accelerator muscles mounted on the entoglossus undergo longitudinal extension and lateral constriction for 83 ms following the onset of electrical stimulation, before projecting off the entoglossus. It is proposed that, during elongation of the accelerator muscle, the sphincter-like region ultimately comes into contact with the tapered region of the entoglossus, causing the onset of projection. This conclusion is supported by the observation that the time between the onset of stimulation and the onset of projection was longer in preparations with surrogate entoglossal processes that had no tapered tip and shorter with surrogate processes that had a tapered tip about four times as long as the natural entoglossus.

Tetanically stimulated accelerator muscles reached 90% of peak force 110 ms after the onset of stimulation, indicating that the 185 ms delay between the onset of accelerator activity and the onset of projection seen in vivo allows the accelerator to achieve peak force prior to the onset of projection. Thus, the delay in projection may be crucial in maximizing the acceleration and velocity achieved by the projected chameleon tongue.
Mechanics and Protein Content of Insect Flight Muscles
Authors: Peckham Michelle , Cripps Richard , White David , Bullard Belinda
Published: April 2021

In asynchronous insect flight muscles, stretch activation may arise from a matching of the helix periodicities of actin target sites to myosin heads and/or a special form of troponin subunit called troponin-H (Tn-H, relative molecular mass 80×103), which has so far only been found in the asynchronous flight muscles of Drosophila (Diptera) and Lethocerus (Hemiptera). The sequence of Tn-H in Drosophila shows it to be a fusion protein of tropomyosin and a hydrophobic proline-rich sequence. Tn-H in Lethocerus is immunologically similar. From immunoblots of synchronous (non-stretch-activated) and asynchronous flight muscles from a wide range of insects, using antibodies against tropomyosin and the hydrophobic sequence of Tn-H, raised against Lethocerus proteins, we found two forms of Tn-H. One, found in most flight muscles, only reacted with antibodies to the hydrophobic sequence. The other, found in asynchronous flight muscles from Diptera and Hemiptera, reacted with antibodies to both the hydrophobic sequence and to tropomyosin, although in the Hemiptera the reaction of Tn-H with anti-tropomyosin was weak. When we compared the mechanics of most of the asynchronous flight muscles used in this study, we found that in the Diptera Ca2+-activated tension was much lower at rest length and stretch-activated tension was more highly dependent on muscle length than in other orders of insects. This suggests that, when Tn-H is in the form found in Diptera, it may be able to modulate Ca2+-activated and stretch-activated tension. We conclude that Tn-H is not sufficient for stretch-activation, but it may enhance stretch-activation, particularly when it is in the form found in the Diptera.
A Neural Mechanism for Processing Colour Information in Molluscan Extra-Ocular Photoreceptors
Authors: Nishi Takako , Gotow Tsukasa
Published: April 2021

This study was conducted to clarify the electrical and spectral properties of the combined photoresponses of two extra-ocular photoreceptor neurones, A-P-l and Es-1, in the abdominal ganglion of the marine mollusc Onchidium verruculatum. The depolarizing receptor potential or inward receptor current of Es-1 appeared to result from a decrease in K+ conductance, in the same way as in A-P-l. The direct photoresponse of Es-1 had a peak at 580 nm, while A-P-l had its peak at 490nm. Under normal conditions, Es-1 was hyperpolarized by blue-green light (490nm) and was depolarized by yellow light (580nm), indicating that its responses were wavelength-dependent. Slow inhibitory synaptic potentials in Es-1 occurred during a sustained depolarization of A-P-l, suggesting that Es-1 received some inhibitory synaptic input from A-P-l. The amplitude of these slow synaptic hyperpolarizations was dependent on graded changes in the depolarization of A-P-l. However, presynaptic spikes in A-P-l were not followed by discrete synaptic potentials in Es-1. These results suggest that graded photoresponses of A-P-l could produce the slow hyperpolarization of Es-1 and that the photore-sponse of A-P-l is thereby transmitted to Es-1 with reversed polarity. The differing responses of Es-1 to light of different wavelengths may have a role in colour discrimination.
In Vivo Analysis of Gas Transport in Arterial and Venous Blood of the Sea Lamprey Petromyzon Marinus
Authors: Tufts B. L. , Bagatto B. , Cameron B.
Published: April 2021

Exercise in sea lampreys resulted in a significant decrease in the extracellular pH (pHe) in both arterial and venous blood. At rest, the erythrocyte pH (pHi) of venous blood was significantly greater than the pHi of arterial blood. Despite the considerable extracellular acidosis after exercise, both arterial and venous pHi were maintained throughout the recovery period. In the venous blood, there was a reversal of the pH gradient (ΔpH) across the erythrocyte membrane immediately after exercise. Exercise also resulted in significant reductions in the partial pressure of oxygen and hemoglobin oxygen-carriage and a significant increase in the partial pressure of CO2 in arterial and venous blood. Although the total CO2 concentration of the plasma decreased after exercise, erythrocyte total CO2 concentrations increased. In venous blood, the immediately after exercise was double the resting value. At rest, partitioning of the total CO2 content between plasma and erythrocytes indicated that 16% and 22% of the total CO2 could be attributed to the erythrocytes in arterial and venous whole blood, respectively. After exercise, these percentages increased to 25% (arterial) and 38% (venous). Changes in accounted for 62% of the arteriovenous difference in whole-blood total CO2 at rest. This increased to 78% immediately after exercise. Thus, unlike other vertebrates, CO2 transport in the lamprey in vivo is largely dependent on erythrocyte CO2-carriage.
The Effects of Glutamate Agonists on Voltage-Clamped Motoneurons of the Lobster Cardiac Ganglion
Authors: Hashemzadeh-Gargari H. , Freschi J.
Published: April 2021

The effects of L-glutamate and its analogues were studied in voltage-clamped motoneurons of the lobster cardiac ganglion. These excitatory amino acids caused a dose-dependent increase in membrane conductance and an inward current at the resting membrane potential. The EC50 for L-glutamate was 150 μmoll−1. The rank order of potencies of the various agonists was quisqualate > L-glutamate= L-aspartate>kainate>cysteine. Kainate, unlike the other agonists, showed no desensitization. Of various antagonists studied, only the quinoxalinediones inhibited the response to glutamate. These antagonists also reduced the amplitude and duration of the pacemaker-driven burst potential, suggesting that glutamate may be released by some of the endogenous synapses within the ganglion. The reversal potential of the glutamate-induced current was −15 mV. When Na+ was replaced with K+, the glutamate-induced current still reversed between 0 and −20 mV. When Na+ was replaced with the impermeant ion N-methyl-D-glucamine, the current was inhibited. The amplitude of responses evoked by glutamate and its analogues was reduced in salines containing either high or low concentrations of Ca2+. These results of pharmacological and of reversal potential and ion substitution experiments indicate that glutamate acts on receptors of the non-NMDA (N-methyl-D-aspartate), quisqualate/kainate type to open a channel permeable to both Na+ and K+.
The Response of the Water-Regulating Mechanism of Developmental Stages of the Common Toad, Bufo Bufo Bufo (L.), to Treatment with Extracts of the Posterior Lobe of the Pituitary Body
Authors: Howes N. H.
Published: April 2021

Investigations made in recent years have demonstrated a connexion between the posterior lobe of the pituitary gland and water regulation in Amphibia. Injection of extracts causes a retention of water in the body of frogs (Brunn, 1921 ; Heller, 1930; Steggerda, 1931 ; Collin & Drouet, 1932; teggerda & Essex, 1934; Oldham, 1936 ; Boyd & Brown, 1938 ; Boyd & Whyte, 1939), toads (Steggerda, 1931 ; Novelli, 1933), Amblystoma (Bëlehràdek & Huxley, 1927), Necturus maculatus (Steggerda, 1937), and some reptiles (Boyd & Dingwall, 1939). In mammals the antidiuretic effect of the posterior lobe is now well established. On the other hand, freshwater fish show no such effect even when given doses of pituitrin up to 2·0 1.u. per 10 g. body weight. Nevertheless, the fish pituitary contains a substance causing a typical water retention in frogs (Boyd & Dingwall, 1939). It appears therefore that while the principle concerned is elaborated in the fish pituitary, either the appropriate effector is not developed or an alternative system which deals with the greater part of water regulation, is present. Thus, on the basis of the data available, it may be said that the regulation of the body water by agents of the posterior pituitary is characteristic of terrestrial but not of primarily aquatic vertebrates.
The Experimental Modification of the Oestrous Cycle in the Ferret by Different Intensities of Light Irradiation and other Methods
Authors: Marshall F. H. A.
Published: April 2021

The original discovery by Bissonette (1932) that the recurrence of oestrus in the ferret was greatly accelerated by light was corroborated and extended by Marshall & Bowden (1934, 1936), who found that ultra-violet light had a more long-continued effect than rays from the visible part of the spectrum, but that rays of long wave-lengths caused no acceleration. The experiments described in this paper were upon (1) the effects of different degrees of light intensity as obtained by placing the cages at different distances from the electric lamp, (2) the effect of ultra-violet light on the duration of oestrus, (3) the effect of feeding vitamin D to anoestrous animals, and (4) the effects of copulation as shown by the discontinuance of oestrus and the subsequently observed state of the ovaries and other reproductive organs. Under present circumstances it has not been possible to continue the experiments, but the results, although not so complete as originally hoped for, seem sufficiently conclusive to make their publication desirable.
A Note on the Biochemistry of Embryonic Determination in Echinoderms
Authors: Needham Joseph , Needham Dorothy M.
Published: April 2021

Apart from the Amphibia, the echinoderms are the class of animals about which our knowledge of embryonic determination and its biochemical basis has in recent times made the most important forward strides. This is largely due to the brilliant work of the Scandinavian school. The fundamental facts of echinoderm experimental embryology are now available in a review in the English language by Hörstadius (1939), while on the biochemical side there are general accounts by Runnström (1935 a) and particularly by Lindahl (1936).
A Note on the Osmotic Pressure of the Blood of Various Animals
Authors: Aldred Patricia
Published: April 2021

The experiments described below were undertaken originally in conjunction with Dr Dacie of King’s College Hospital in an attempt to determine whether a relation exists between the osmotic pressure and the “fragility” of blood corpuscles. It was found, however, that the osmotic pressure differences hardly accounted for the fragility differences, and the experiments were continued on the osmotic pressure alone.
The Choice of Drinking Water by the Honeybee
Authors: Butler C. G.
Published: April 2021

A brief review of the literature on this subject is given. By means of “training table” experiments in which use was made of the Latin square system in order to allow of rapid statistical analysis of the results obtained, it was shown that:

The honeybee prefers dilute sodium chloride and ammonium chloride solutions to distilled water. It does not prefer concentrations of these salts higher than N/20 solutions and solutions of various other salts to distilled water. The honeybee appears unable to distinguish between N/160 sodium chloride or N/160 ammonium chloride and distilled water. The honeybee is probably largely attracted to such sources of drinking water as rain water from gutters choked with decaying organic matter, sewage effluent, etc.: by a water perception sense coupled with an olfactory appreciation of various volatile substances contained in these sources of water. The volatile substances present in the distillates from the various naturally occuring solutions examined could be absorbed on to animal charcoal to a large extent, in which case the resulting supernatant fluid was found to have lost its great attraction for the honeybee and was no longer clearly distinguished from distilled water. The salts contained in these sources of drinking water do not appear to play an important part in attracting the bee thither. It was found possible to express the preference shown by the honeybee for various solutions by means of numerical factors based on distilled water having an arbitrary factor of 10. Forty different solutions have been arranged in order of preference by this means.
The Daily Rhythm of Activity of the Cockroach, Blatta Orientalis L
Authors: Gunn D. L.
Published: April 2021

In an aktograph at 25 ·5 ° C., at upwards of 75% relative humidity and with food present, the average locomotory activity of the cockroach per day does not depend on whether there is continuous light for weeks, or continuous darkness, or a daily alternation of light and darkness. When temperature and humidity do not vary during the day and other factors are kept as constant as possible, the cockroach’s activity can be largely concentrated into any desired half of the day, simply by suitably adjusting the time of onset of the half-day’s darkness. A rhythm can thus be set up, so that the main activity occurs at the same hours each day. This activity rhythm persists for some days in continuous light or continuous darkness, but eventually activity becomes much more evenly spread over the whole day, leaving only a slight residual rhythm which is unrelated to the previous conspicuous one. A new conspicuous rhythm can then be started at once by alternation of light and darkness. There are indications that animal responses to physical stimuli may depend to a considerable extent on whether the animal is in the active or the inactive phase of its daily cycle. A method is suggested for making it possible to study the nocturnal phase during the daytime.
The Humidity Behaviour of the Mealworm Beetle, Tenebrio Molitor L
Authors: Gunn D. L. , Pielou D. P.
Published: April 2021

It has previously been shown that, under suitable experimental conditions, Tenebrio molitor reacts clearly to humidity (Pielou & Gunn, 1940) and that the humidity receptors are probably the pit-peg organs and peg organs on the antennae (Pielou, 1940). The present work is an attempt to analyse the mechanism of this reaction both qualitatively and quantitatively, in terms of elementary animal behaviour.
The Effects on the Fat and Starch Metabolism of Gebia by the Parasite Gyge Branchialis
Authors: Hughes T. E.
Published: April 2021

Males of Upogebia Uttoralis parasitized by Gyge branchialis show a marked increase in fat content from 1·04 to 1·6%. Parasitized females have a fat content practically the same as that of ordinary non-ovigerous females, 1·2 %. Ovigerous females have a fat content considerably higher than that of parasitized males or non-ovigerous females, namely 2·2%. The parasite Gyge has a relatively high fat content, 4·4 %. There is a significant difference in glycogen content between normal males and females. There may be a slight increase in glycogen following parasitization. The results are essentially in agreement with the theory of metabolic stimuli put forward by Geoffrey Smith.
Studies on the Physiology of Arenicola Marina L.
Authors: Wells G. P. , Ledingham Isabel C.
Published: April 2021

Of the large number of published studies on the ion relations of invertebrate rhythmic muscles, the great majority concern preparations from Crustacea and molluscs—largely because the animals of these groups are provided with vigorous and experimentally convenient hearts. Data on members of other phyla are relatively few and, from the comparative point of view, their multiplication is evidently desirable. Recently, one of us published a description of the so-called “isolated extrovert” of the lugworm, Arenicola marina L., a preparation consisting of the proboscis and part of the oesophagus (Wells, 1937). Suspended in sea water, the isolated extrovert maintains for many hours a very regular and characteristic activity pattern, consisting of a series of outbursts of vigorous rhythmical contraction separated by periods of relative rest. That this is the normal activity pattern was shown in the paper already mentioned. Because of its vigour, its regularity, its long survival after excision and the ease with which that operation is performed, it is an excellent object for experiments on the action of chemical factors. The writers have undertaken a study of ion actions on this preparation. The results obtained by varying the Mg concentration form the subject of the present communication. Experiments with K and Ca have been begun and it is hoped to complete them shortly.
Relationship Between Heart Rate and Oxygen Consumption During Steady-State Swimming in California Sea Lions
Authors: Butler P. J. , Woakes A. J. , Boyd I. L. , Kanatous S.
Published: April 2021

Heart rate (fH) and rate of oxygen uptake were measured in six subadult California sea lions Zalophus californianus while they were at rest and while they were swimming for 15 min at controlled speeds of up to 1.4ms”1 and pulling loads of up to 3 kg.

There was a good linear relationship between fH and in all six sea lions. The slopes of the individual regression lines varied between 2.66 and 4.36 beats ml−lO2kg−1, the intercepts varied between 48.2 and 63.0 beats min”1 and r2 varied between 0.82 and 0.93. The mean relationship for all six sea lions is fh = (57.4 ± 2.0) + (3.58 ± 0.23) , r2=0.89±0.01. The mean of the lowest values was 5.1±0.4ml min−1 kg−1 and the mean of the highest values was 26.9±1.9 ml min−1 kg−1. The means of the lowest and highest values of fH were less extreme, being 72±3 beats min−1 and 155±5 beats min−1, respectively.

It is concluded that, by using data storage devices and grouped data, fH could be used in otariids as an indicator of aerobic metabolism under field conditions, in particular for breeding females during the period of lactation.
Resolution and Sensitivity in the Eye of the WinkleLittorina Littorea
Authors: Seyer Jan-Olof
Published: April 2021

The winkle Littorina littorea (L.) has camera-type (simple) eyes. Light and electron microscopy were used to generate an accurate geometrical model of the eye, and this was used to predict the eye’s visual performance. The lens is spherical with a diameter of 112μm, and examination of images formed by isolated lenses indicates a mean focal length in water of 126μm. These images are crisp and apparently aberration-free. This, in addition to a shorter than expected focal length, implicates the presence of a gradient of refractive index in the lens. The lens has a focal length to lens-radius ratio of 2.3, which is close to the ‘Matthiessen ratio’ of 2.5 found in the aplanatic lenses of many other marine animals. The lens is predicted to focus images within the retina only when the eye is submerged in water: in air, images are focused distal to the retina. In the central retina, the inter-receptor angle is 1.8° and the rhabdom diameter is 4μm (5.5 times larger than the diffraction blur-circle), indicating a retinal array coarser than that necessary to sample all the information contained in the image. In addition, a low F-number (1.2) and the large possible angles of incidence of rays striking the retina (up to 40°) mean that the eye is likely to suffer substantial spreading of light between rhabdoms (which are unshielded) and further degradation of resolution. Possible behavioural roles for the eyes are discussed.
The Inner Ear Is Responsible For Detection Of Infrasound In The Perch (Perca Fluviatilis)
Authors: Karlsen Hans Erik
Published: April 2021

In a previous study of infrasound detection in the cod, the inner ear was suggested to be the sensory organ responsible for the responses. However, a possible involvement of the lateral-line system in the observed low-frequency detection could not be ruled out. The infrasound sensitivity was therefore studied in perch (Perca fluviatilis) with normal and blocked lateral-line organs. The experiments were performed using a standing wave acoustic tube and the cardiac conditioning technique. All perch readily responded to infrasound frequencies down to 0.3Hz with threshold values of approximately 2×10−4ms−2. These thresholds were not affected by complete blocking of the lateral-line system with Co2+, which suggests that the inner ear is responsible for the observed infrasound detection by the perch.
Wind-Evoked Escape Running of the Cricket Gryllus Bimaculatus:I. Behavioural Analysis
Authors: Gras Heribert , Hörner Michael
Published: April 2021

Spontaneous walking and escape running in response to wind puffs directed to the abdominal cerci were quantitatively studied in tethered walking crickets.

An apparatus for optically recording rotations of an air-supported sphere was developed to measure the intended locomotion of insects with high linear and temporal resolution but without mechanically imposed bias. During spontaneous locomotion without sensory cues for orientation, alternate pauses of 0.35–2.2 s and walking phases of 0.5–6 s resulted in a highly variable pattern of locomotion on a meandering path. A single air puff to one or both of the wind-sensitive cerci evoked a short run, whereas a continuous sequence of puffs caused sustained escape running with a tendency to turn away from the stimulus source. Escape running was characterized by a series of stereotyped running bouts and pauses, both significantly shorter than those recorded during spontaneous locomotion. Forward speed and angular speed of escape running correlated linearly with the wind puff frequency between 5 and 10Hz. This was caused by a shortening of the standing phases, while the durations of the running bouts were constant. The reflex-like running bouts and the pattern of escape running were largely independent of the duty cycle of the wind puff series and the wind speed. Neither individual steps nor running bouts were synchronized with the stimulus pattern. The behavioural modes of spontaneous walking and escape running were maintained with a minor reduction in general activity in partly dissected specimens during intracellular recording in the prothoracic ganglion. Each impaled local interneurone with locomotion-related activity generated action potentials in the actual step rhythm of walking and running bouts, but did not show specific activity during escape running. Some of these local neurones, however, showed modulations of spike frequency before or during intended turns and may participate in the coordination of the prothoracic legs.
Control of Impulse Discharge of Visual Interneurones by the Receptive Field Surround in Butterfly Larvae
Authors: Ichikawa Toshio
Published: April 2021

The influence of interactions between the antagonistic centre and surround areas of receptive fields on the electrical activities of medulla neurones was examined in the larval swallowtail butterfly Papilio xuthus. Weak signals from the surround had a significant depressive effect on the maintained discharge, which increased for on-centre cells or decreased for off-centre cells in response to illumination of the centre. Moderation of the maintained discharge suppressed saturation of the response and extended the graded response range of the neurones. Surround illumination also reduced irregular fluctuations in the membrane potentials and variability in the discharge rate of impulses. The results indicate that the spatial inhibitory mechanism is important for the larval visual system in order to increase the efficiency of signal processing.
The role of V-ATPase in neuronal and endocrine systems
Authors: Moriyama Yoshinori , Maeda Masatomo , Futai Masamitsu
Published: April 2021

Synaptic vesicles have important roles in the neural transmission at nerve terminals: the storage and the controlled exocytosis of neurotransmitters. At least two different factors are responsible for the concentration process: the vacuolar-type H+-ATPase (V-ATPase), establishing an electrochemical gradient of protons, and specific transport systems for transmitters. We will discuss our recent progress on the energy-transducing systems in synaptic vesicles: (1) structural aspects of V-ATPase; (2) energy coupling of transport of transmitters; (3) reconstitution of transporters; (4) effects of neurotoxins and neuron blocking agents; (5) function of synaptic-vesicle-like microvesicles from endocrine tissues.
The osteoclast proton pump differs in its pharmacology and catalytic subunits from other vacuolar H+-ATPases
Authors: Chatterjee D. , Chakraborty M. , Leit M. , Neff L. , Jamsa-Kellokumpu S. , Fuchs R. , Bartkiewicz M. , Hernando N. , Baron R.
Published: April 2021

Osteoclasts are multinucleated cells derived from the mononuclear phagocyte system in the hematopoietic bone marrow. Their function is to resorb bone during skeletal growth and remodeling. They perform this function by acidifying an enclosed extracellular space, the bone resorbing compartment. Analysis of proton transport by inside-out vesicles derived from highly purified chicken osteoclast membranes has revealed the presence of a novel type of multisubunit vacuolar-like H+-ATPase. Unlike H+-ATPases derived from any other cell type or organelle, proton transport and ATPase activity in osteoclast vesicles are sensitive to two classes of inhibitors, namely V-ATPase inhibitors [N-ethyl-maleimide (NEM) and bafilomycin Ai] and vanadate (IC50 100 μmol l−1), an inhibitor previously found to affect only P-ATPases. The osteoclast V-ATPase morphologically resembles vacuolar proton pumps and contains several vacuolar-like subunits (115×103, 39×103 and l6×103Mr), demonstrated by Western blot analysis. Subunits A and B of the catalytic domain of the enzyme, however, differ from that of other V-ATPases. In osteoclasts, subunit A has an Mrof 63×103 instead of 67×103–70×I03; in contrast, monocytes, macrophages and kidney microsomes, which contain a vanadate-insensitive H+-ATPase, express the classical subunit A (70×103Mr). Moreover, two types of 57×103–60×103MrB subunits are also found: they are differentially recognized by antibodies and one is expressed predominantly in osteoclasts and the other in bone marrow cells and in kidney microsomes. Preliminary cloning data have indicated that the B subunit expressed in osteoclasts may be similar to the brain isoform. The osteoclast proton pump may, therefore, constitute a novel class of V-ATPase, with a unique pharmacology and specific isoforms of two subunits in the catalytic portion of the enzyme.
The role of the V-ATPase in renal epithelial H+ transport
Authors: Gluck Stephen , Nelson Raoul
Published: April 2021

This article provides a brief review of the history of the identification and characterization of the renal V-ATPase, and a review of the physiology of renal bicarbonate reabsorption and H+ transport.
Biochemistry of the renal V-ATPase
Authors: Gluck Stephen L. , Nelson Raoul D. , Lee Beth S. , Wang Zhi-Qiang , Guo Xiao-Li , Fu Ji-Yi , Zhang Kun
Published: April 2021

In most eukaryotic cells, vacuolar H+-ATPases (V-ATPases) are present primarily or exclusively in intracellular membrane compartments, functioning in the acidification of the endocytic and secretory vacuolar apparatus necessary for constitutive cell function. V-ATPases also participate in renal hydrogen ion secretion in both the proximal and distal nephron, residing at high concentrations on the plasma membrane, where they are regulated physiologically to maintain the acid-base balance of the organism. Recent experiments have begun to reveal how the kidney controls transcellular proton transport while still maintaining acidification of intracellular compartments. Control may occur by recruitment of proton pumps to or away from the plasma membrane. The protontransporting plasma membrane of intercalated cells is a specialized apparatus that translocates the enzyme between an intracellular membrane pool and the plasma membrane in response to physiological stimuli. Regulation may also occur by changes in the kinetics of the V-ATPase. V-ATPases are a family of structurally similar enzymes which differ in the composition of specific subunits. Cytosolic regulatory enzymes present in renal cells may preferentially affect V-ATPases in selective membrane compartments.
Complex modulation of cation channels in the tonoplast and plasma membrane of Saccharomyces cerevisiae: single-channel studies
Authors: Bertl A. , Slayman C. L.
Published: April 2021

Detailed patch-clamp studies have been made of ion channels in the plasma membrane and tonoplast of the yeast Saccharomyces cerevisiae. The predominant tonoplast channel is a high-conductance cation-selective inward rectifier (passing ions easily into the cytoplasm from the vacuole), with its open probability (Po) peaking at about −80mV (cytoplasm negative) and falling to near zero at +80mV. It has a maximal slope conductance of approximately 150pS in 100mmoll−1 KCl, and conducts Na+, K+ and Ca2+. Elevated cytoplasmic Ca2+ concentration, alkaline pH and reducing agents can activate the channel, its likely physiological function being to adjust cytoplasmic Ca2+ concentration from the vacuolar reservoir. The predominant plasma-membrane channel is a strongly outward rectifying K+ channel (passing K+ easily out of the cytoplasm to the extracellular medium), which is activated by positive-going membrane voltages as well as by elevated cytoplasmic Ca2+ concentration and alkaline pH. Interaction between membrane voltage and [Ca2+]cyt is complex and defines three parallel closed states for the channel: a Ca2+-independent brief closure (I), a calcium-inhibited long closure (G) and, at large positive voltages, a calcium-induced brief blockade (B). This channel is likely to function in steady-state turgor regulation and in charge balancing during proton-coupled substrate uptake.
Energization of sodium absorption by the H+-ATPase pump in mitochondria-rich cells of frog skin
Authors: Harvey Brian J.
Published: April 2021

The frog skin in vivo is capable of active transepithelial H+ secretion (JH) which is matched by Na+ absorption (JNA). Studies in vitro demonstrate that JH is generated by an H+-ATPase pump localized in apical membranes of mitochondria-rich (MR) cells, whereas JNa occurs through an amiloride-sensitive pathway in principal (P) cells. The H+ pump is sensitive to inhibitors of carbonic anhydrase (e.g. acetazolamide) and to specific inhibitors of mitochondrial F1F0 H+-ATPase (oligomycin) and vacuolar (V)-type H+-ATPase (N-ethylmaleimide) and to inhibitors of both these types of H+-ATPases (dicyclohexylcarbodiimide, DCCD). JH is independent of external K+, which differentiates it from gastric H+/K+-ATPase and is strictly dependent on aerobic metabolism. The proton pump is primarily implicated in whole-body acid–base regulation. Acute stimulation of JH in response (seconds–minutes) to an acid load involves insertion of H+ pumps (exocytosis) from a cytosolic pool into the apical membrane. The chronic response (days) to metabolic acid load involves morphological changes (increased apical membrane surface area and number of MR cells). Whole-cell patch-clamp recordings of membrane capacitance and current fluctuations from MR cells demonstrate that a respiratory acid load and aldosterone produce rapid exocytotic insertion of DCCD-sensitive conductive membrane.

A secondary role of the H+ pump is to energize sodium absorption (JNa ) via principal cells from dilute solutions in the absence of a permeant anion under open-circuit conditions. The apparent 1:1 stoichiometry between JH and JNa is a result of transepithelial electrical coupling between these electrogenic fluxes. The H+ pump in MR cells generates a transepithelial current (serosa to apical) which acts as a physiological voltage-clamp to hyperpolarize the apical membrane of P cells. This hyperpolarization can facilitate passive Na+ entry across the apical membrane against a threefold chemical gradient. Since both JH and JNa are sensitive to membrane potential, inhibition or activation of one will produce similar effects on the transport of the other ion. For example, inhibition of JH by ethoxzolamide will reduce JNa. Conversely, blocking JNa with amiloride also inhibits JH. These effects can be avoided or reversed if variations in membrane potential are prevented by voltage-clamping the epithelium. A paradoxical activation of JNa is observed when JH is stimulated by an acid load (CO2), despite inhibition of Na+ channel activity by H+ in P cells. Patch-clamp studies reveal the presence of Na+ channels in MR cells which may provide a route for Na+ absorption energized by the H+ pump when Na+ channels in P cells are closed by an acid load.
Ion transport in parasitic protozoa
Authors: Bakker-Grunwald Tilly
Published: April 2021

Many parasitic protozoa go through complex life cycles in the course of which they adapt to widely different environments; ion transport processes are expected to play a role both in pathogenicity and in adaptation. So far, studies on ion transport have been virtually limited to Leishmania, Plasmodium and Entamoeba. The distribution of ion pumps in the former two organisms generally appears to conform to the picture established for other protozoa, i.e. a proton-motive P-ATPase in the plasma membrane provides the driving force for H+-coupled secondary-active transport, a proton-motive V-ATPase in the digestive vacuoles is responsible for vacuolar acidification, and an F-ATPase (ATP synthase) is found in the mitochondria. The situation in Entamoeba, an archaic organism that lacks mitochondria, could be different from that in the two other parasites in that a V-ATPase may be present and active both in the plasma membrane and in the membranes of the endocytic vesicles.
V-ATPase-energized epithelia and biological insect control
Authors: Wolfersberger Michael G.
Published: April 2021

Background is provided for the experimentally detailed contributions concerning the structure, distribution and function of V-ATPase-based ion pumps in insect epithelia. The mode of action of an insecticidal bacterial protein, which is dependent upon the V-ATPase-energized state in larval lepidopteran midgut for activity, is discussed.
Circuit analysis of transmembrane voltage relationships in V-ATPase-coupled ion movements
Authors: Martin Francis G.
Published: April 2021

The concept of electrical circuit analysis is extended to include components found in membrane ionic transport systems. As in classical electrical equivalent circuits, resistors and capacitors are used to represent ion channels and the membrane capacitances, respectively; batteries represent energy sources driven by chemical reactions. In the extensions proposed, energy stored in various ionic concentrations is treated as charges on compartmental capacitors; symporters and antiporters are treated as energy-coupling devices analogous to transformers in alternating current electrical circuits. Pumps are shown to be special cases of porters in which the input circuit derives its energy from a chemical reaction. Using these components, circuit diagrams are drawn for several examples of membrane ion transport systems. By applying appropriate circuit analysis techniques, these diagrams facilitate the quantitative description of the energy distributions throughout the system.
The importance of being acid: the role of acidification in intracellular membrane traffic
Authors: Mellman Ira
Published: April 2021

Ever since the early work of Elie Metchnikoff at the turn of the century, it has been clear that the ability of vacuolar organelles to generate and maintain pH plays a crucial role in a variety of critical cellular functions. Using a variety of crude pH indicators such as neutral red or litmus particles, Metchnikoff observed that bacteria ingested by phagocytic cells of the immune system were transferred to acidic structures in the cytoplasm, killed and then digested. Without any understanding or knowledge of membranes, organelles or proton pumps, Metchnikoff drew accurate conclusions concerning the necessity of an acidic milieu for intracellular digestion, the role of cellular energy in maintaining the acidic pH, and the likelihood that the acidity was due to diffusible protons as opposed to the infusion of acidic substances such as DNA (which had, in fact, been offered as an explanation by some of Metchnikoff s contemporaries).
Insect malpighian tubules: V-ATPase action in ion and fluid transport
Authors: Maddrell S. H. P. , O’Donnell M. J.
Published: April 2021

Insect Malpighian tubules secrete fluid into the lumen as part of their function as excretory organs. The underlying ion transport is, when stimulated, faster than in any other known tissue. It is driven by the activity of an H+-transporting V-ATPase situated on the luminal cell membranes. This ATPase, together with cation/H+ antiporter(s), constitutes a common cation pump which can transport sodium ions, potassium ions or both. Treatments that selectively slow cation transport across the epithelium cause the secreted fluid to become alkaline, whereas those that selectively reduce the rate of anion passage lead to secretion of acid fluid.
Escherichia coli ATP synthase (F-ATPase): catalytic site and regulation of H+ translocation
Authors: Futai Masamitsu , Iwamoto Atsuko , Omote Hiroshi , orita Yuji , Shin Kouichirou , Nakamoto Robert K. , Maeda Masatomo
Published: April 2021

We discuss our recent results on the Escherichia coli F-ATPase, in particular its catalytic site in the β subunit and regulation of H+ transport by the γ subunit. Affinity labelling experiments suggest that βLys-155 in the glycine-rich sequence is near the γ-phosphate moiety of ATP bound at the catalytic site. The enzyme loses activity upon introduction of missense mutations in βLys-155 or βThr-156 and changes catalytic properties upon introduction of other mutations. By analysis of mutations and their pseudo revertants, residues β Ser-174, β Glu-192 and β Val-198 were found to be located near the glycine-rich sequence. The combined approaches of chemical labelling and genetics have been fruitful in visualizing the structure of the catalytic site. Analysis of mutations in the y subunit suggests that this subunit has an essential role in coupling catalysis with proton translocation.
The chloroplast H+-ATPase: partial reactions of the proton
Authors: Junge Wolfgang , Engelbrecht Siegfried , Griwatz Cord , Groth Georg
Published: April 2021

This article reviews proton intake, charge transfer and proton release by F-ATPases, based in part on flash spectrophotometric studies on the chloroplast ATPase in thylakoid membranes, CF1F0. The synthesis-coupled translocation of charges by CF1F0 (maximum rate < 1500 s−1) and the dissipative flow through its exposed channel portion, CF0 (rate >10000 s−1), are extremely proton-specific (selectivity H+:K+>107:1). The protonspecific filter is located in CF0. Proton flow through exposed CF0 can be throttled by adding subunit δ or subunit β of CF0. These subunits thus may provide energytransducing contacts between CF1 and CF0. Recently, we characterized two conditions where, in contrast to the above situation, proton intake by CF1F0 was decoupled from proton transfer across the main dielectric barrier: (a) CF1F0 structurally distorted by low ionic strength transiently trapped protons in a highly cooperative manner, but remained proton tight. This result has been interpreted in terms of Mitchell’s proton well, (b) In the absence of nucleotides there is a proton slip. Addition of nucleotides (100 nmol l−1 ADP) abolished proton conduction but not proton intake by CF|FO. These experiments functionally tag proton binding groups on CF1F0 that are located before the main dielectric barrier.
Mutations in the yeast vacuolar ATPase result in the mislocalization of vacuolar proteins
Authors: Klionsky Daniel J. , Nelson Hannah , Nelson Nathan , Yaver Debbie S.
Published: April 2021

The vacuolar ATPase of the yeast Saccharomyces cerevisiae acidifies the vacuolar lumen and generates an electrochemical gradient across the vacuole membrane. We have investigated the role of compartment acidification of the vacuolar system in the sorting of vacuolar proteins. Strains with chromosomal disruptions of genes (Δ vat) encoding the A (69×103Mr), B (57×103Mr) or c (16× 103Mr) subunits of the vacuolar ATPase accumulate and secrete precursor forms of the soluble vacuolar hydrolases carboxypeptidase Y and proteinase A. A kinetic analysis suggests that these precursor proteins accumulate in, and are secreted from, the Golgi complex or post-Golgi vesicles. In addition, subcellular fractionation shows that vacuolar hydrolase-invertase hybrid proteins are inefficiently localized to the vacuole in Avar strains. This result suggests that the vat mutations cause a steady-state defect in vacuolar protein sorting. The vat mutations also affect the sorting of vacuolar membrane proteins. Precursor forms of alkaline phosphatase are accumulated in vat mutant cells, but to a lesser extent than is seen for the soluble vacuolar hydrolases. This finding, coupled with the insensitivity of alkaline phosphatase to the ATPase inhibitor bafilomycin Ai, suggests that vacuolar membrane protein sorting is less sensitive to changes in lumenal pH when compared with the targeting of soluble vacuolar proteins. These results indicate that acidification of the vacuolar system is important for efficient sorting of soluble proteins to the vacuole.