bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chloroplast H+-ATPase: partial reactions of the proton
Authors: Junge Wolfgang , Engelbrecht Siegfried , Griwatz Cord , Groth Georg 
Published: April 2021

ABSTRACT
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 &lt; 1500 s−1) and the dissipative flow through its exposed channel portion, CF0 (rate &gt;10000 s−1), are extremely proton-specific (selectivity H+:K+&gt;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

ABSTRACT
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.
Correlations of the Position of Center of Body Mass With Butterfly Escape Tactics
Authors: Srygley Robert B. , Dudley Robert 
Published: April 2021

ABSTRACT
Using the evolution of neotropical butterflies as a natural experiment, we examine Ellington’s biomechanical hypothesis that the position of center of body mass affects insect maneuverability. We find that the position of center of body mass is correlated with the butterflies’ palatability, natural flight speeds and their ability to evade predators in a small cage. Relative to distasteful species, palatable butterflies fly faster and maneuver more successfully to evade attacks from aerial predators. The large thorax and short abdomen of palatable species position the center of body mass near to the wing base, whereas the mass allocation and body shape of distasteful butterflies position center of body mass further posteriorly. The position of center of body mass is an important indicator of flight performance, including both aerial maneuverability and flight speed, that warrants incorporation into future studies of invertebrate and vertebrate flight.
Body Size, Muscle Power Output and Limitations on Burst Locomotor Performance in the Lizard Dipsosaurus Dorsalis
Authors: Johnson Timothy P. , Swoap Steven J. , Bennett Albert F. , Josephson Robert K. 
Published: April 2021

ABSTRACT
The power output of fast-glycolytic (FG) muscle fibres isolated from the iliofibularis (IF) muscle of desert iguanas (Dipsosaurus dorsalis) was measured at 35°C using the oscillatory work-loop technique. To simulate cyclical muscle length changes during running, isolated fibre bundles were subjected to sinusoidal length changes and phasic stimulation during the strain cycle. At constant strain (12%), the duration and timing (phase) of stimulation were adjusted to maximise power output. Using both hatchlings (4–8g) and adults of varying sizes (15–70g), the intraspecific allometries of IF length and contractile properties were described by regression analysis. The muscle length at which isometric force was maximum ( L0, mm) increased geometrically with body mass (M, g) (L0=5.7M0.33). Maximum power output and the force produced during shortening showed no significant relationship to body size; work output per cycle (Wopt, Jkg−1) under conditions required to maximise power did increase with body size (Wopt=3.7M0.24). Twitch duration (Td, ms), measured from the onset of force generation to 50% relaxation, increased allometrically with body mass (Td=12.4M0.18). Limb cycling frequency during burst running (f, reported in the literature) and the frequency required to maximise power output in vitro (fopt) decreased with body size, both being proportional to body mass raised to the power 0.24. These findings suggest that limb cycling frequency may be limited by twitch contraction kinetics. However, despite corresponding proportionality to body size, limb cycling frequencies during burst running are about 20% lower than the cycling frequencies required to maximise power output. Differences in the contractile performance of the IF in vitro and in vivo are discussed in relation to constraints imposed by gravitational forces and the design of muscular, nervous and skeletal systems.
Odor Sensitivity of Cultured Lobster Olfactory Receptor Neurons is Not Dependent on Process Formation
Authors: Fadool D. A. , Michel W. C. , Ache B. W. 
Published: April 2021

ABSTRACT
Cultured lobster olfactory receptor neurons (ORNs) were surveyed for their odor sensitivity with whole-cell, voltage-clamp recording. The nature of the adequate stimuli, the degree of tuning (response spectra) of the cells, the threshold of sensitivity and the dual polarity of the odor-evoked currents are consistent with chemosensitivity in the cultured ORNs being olfactory. The ability of odors to evoke currents in cultured ORNs that lack processes suggests that lobster ORNs can be induced in vitro to insert all the elements of the transduction cascade in the soma, including those that might normally be confined to processes. This should greatly facilitate analysis of olfactory transduction in these cells.
The Modulatory Effects of Serotonin, Neuropeptide F1 and Proctolin on the Receptor Muscles of the Lobster Abdominal Stretch Receptor and Their Exoskeletal Muscle Homologues
Authors: Pasztor Valerie M. , Golas Lillian B. 
Published: April 2021

ABSTRACT
The muscle receptor organ (MRO) of the lobster is a complex proprioceptive system lying in parallel with the axial extensor musculature. Two peripherally located sensory neurones extend stretch-sensitive dendrites into individual receptor muscle strands one tonic (RM1) and one phasic (RM2). Previous studies have shown that the sensitivity of the sensory neurones to passive stretch could be enhanced by serotonin and proctolin. Here we show that the receptor muscles and their exoskeletal muscle homologues are also responsive to serotonin, proctolin and, in addition, to neuropeptide F1 (TNRNFLRF-NH2).
Two measures of motor performance were enhanced by all three neurohormones: EJP amplitude and nerve-evoked tension development. Serotonin was the most effective modulator of both tonic and phasic muscles. F1 had powerful effects on the phasic extensor muscle. A low incidence of tonic muscle fibres with synapses responding to the neurohormones suggests that there are distinct populations of synapses: those sensitive to specific modulators and others that are insensitive. These findings, taken together with the enhancing effects of modulation on the primary sensory afferents, suggest that circulating neurohormones may act at multiple loci in the MRO system in a concerted and hormone-specific manner to alter the flow of proprioceptive feedback.
The Role of the Spleen During Exercise in the Antarctic Teleost, Pagothenia Borchgrevinki
Authors: Franklin Craig E. , Davison William , Mckenzie Jan C. 
Published: April 2021

ABSTRACT
Physiological changes in fish associated with swimming are highly dependent on the intensity of exercise performed (Wood, 1991). Swimming at high speed requires large increases in the delivery of oxygen to the tissues and the circulatory system must be able to meet this demand. Exercise at a speed great enough to cause exhaustion results in an elevation in haematocrit (Hct), which can increase the oxygen content of the blood. The magnitude of the Hct increase varies among different species of fish, although generally the increase is about 50% (Milligan and Wood, 1987; Wells and Weber, 1990; Yamamoto et al. 1980; Yamamoto and Itazawa, 1989). The antarctic cryopelagic teleost Pagothenia borchgrevinki (Boulenger, 1902, see also Notothenia hodgsoni) appears to be an exception as exercise produces an increase in Hct of more than 110% (Davison et al. 1988), an increase approximately 2–4 times greater than that in other species of fish studied.
A Novel Pattern of Embryonic Nutrition in a Viviparous Reptile
Authors: Stewart James R. , Thompson Michael B. 
Published: April 2021

ABSTRACT
Vitellogenesis and placental transfer both contribute substantially to embryonic nutrition in the viviparous scincid lizard Pseudemoiaentrecasteauxii. Neonatal wet mass was 396% greater than egg wet mass and neonatal dry mass was 168% greater than egg dry mass. We estimate that 49% of the organic molecules for embryonic growth and metabolism were provided by placental nourishment. This pattern of embryonic nutrition, in which ovarian and uterine contributions are approximately equivalent, has not been reported previously for reptiles. Female Bassiana duperreyi, a closely related oviparous species, produced larger clutches of larger eggs. Although there was a great disparity in egg mass between these two species, differences in newborn composition were less pronounced. Mean dry mass, adjusted for female size, of B. duperreyi eggs was 135% greater than mean dry mass of P. entrecasteauxii eggs, yet mean dry mass of B. duperreyi offspring was only 21% greater than that of P. entrecasteauxii offspring. Embryonic gains in water and inorganic salts during gestation in P. entrecasteauxii were substantial and resulted in the production of neonates that contained greater quantities of these variables compared to offspring of B. duperreyi. These data confirm Weekes’ hypothesis that P. entrecasteauxii is matrotrophic and support her hypothesis that this species has undergone evolutionary reduction in yolk quantity.
Propranolol Impairs the Hyperventilatory Response to Acute Hypercapnia in Rainbow Trout
Authors: Kinkead R. , Aota S. , Perry S. F. , Randall D. J. 
Published: April 2021

ABSTRACT
This study investigated the possible role of catecholamines in the ventilatory response of rainbow trout (Oncorhynchus mykiss) to acute external hypercapnia. The ventilatory response to hypercapnia [partial pressure of CO2 in water of fish pre-treated with the selective β-adrenoceptor antagonist, D,L-propranolol, was compared with that of D-propranolol (an isomer with minimal β-antagonistic activity) and saline pre-treated fish (sham). A sustained 3.6-fold increase in gill ventilation volume was observed in the sham and D-propranolol-treated groups during the 30min interval of hypercapnia. Fish pre-treated with D,L-propranolol displayed a blunted hyperventilatory response to hypercapnia (1.9-fold increase at 30min). These results indicate that the β-component of an adrenergic response is involved in the usual hyperventilatory response to external hypercapnia. It is suggested that the impaired hyperventilatory response of the D,L-propranolol-treated group reflects an inhibition of central adrenergic mechanism(s) involved in the hyperventilatory reflex to respiratory acidosis.
Osmoregulation in the Parasitic Nematode Pseudoterranova Decipiens
Authors: Fusé M. , Davey K. G. , Sommerville R. I. 
Published: April 2021

ABSTRACT
When subjected to hyper-or hypo-osmotic stress at 5°C for 24h, third-stage larvae of the parasitic nematode Pseudoterranova decipiens do not exhibit changes in mass or in the osmotic pressure of the pseudocoelomic fluid. Immersion in solutions containing 3H2O demonstrates that exchange with the water in the pseudocoelomic fluid is substantially complete within 24h. Sacs composed of cylinders of body wall without the intestine and pseudocoelomic fluid do not gain weight when immersed for 24h in hypotonic medium. Metabolic poisons abolish the ability of whole worms and sacs to maintain their weight when immersed in hypotonic media. These observations support the conclusion that the nematode is capable of at least short-term osmoregulation and that the site of osmoregulation is the body wall. The observations that more fluid is passed from the anus in some hypo-osmotically stressed worms and that worms ligatured at the tail exhibit a small increase in mass when exposed to hypo-osmotic conditions may indicate that the intestine plays a minor and subsidiary role in osmoregulation.
Allosteric Control of Oxygen Binding by Haemoglobin During Embryonic Development in the Crocodile Crocodylus Porosus: The Role of Red Cell Organic Phosphates and Carbon Dioxide
Authors: Grigg G. C. , Wells R. M. G. , Beard L. A. 
Published: April 2021

ABSTRACT
The P50 of whole blood [30°C, (15.6mmHg)] decreases during embryonic development from approximately 6.7kPa (50mmHg) at 15 days to about half this value at hatching (86 days), paralleling a decrease in ATP from 100 to 5–10 μmol g−1 Hb. There is also a progressive changeover from embryonic to adult haemoglobin (HbA). A pulse of 2,3-diphosphoglycerate (2,3-DPG) (18μmol g−1 Hb) occurs late in embryonic life. It has no effect on whole-blood oxygen-affinity and falls rapidly at hatching to values typical of post-hatchling crocodilians in general (&lt;1.0 μmol g−1 Hb). ATP has a marked effect on the oxygen affinity of embryonic haemoglobin (HbE) but not on HbA. 2,3-DPG has only very small effects on the oxygen affinities of HbE and HbA. CO2 has a small effect on the oxygen affinity of HbE but a marked effect on that of HbA. Values of measured in the chorio-allantoic artery [2.9kPa (22mmHg)] and vein [5.9kPa (52mmHg)] imply an increase in saturation from approximately 30% to more than 80%. Neither whole-blood oxygen-affinity nor ATP level was altered in response to an experimental 7-day exposure to low ambient oxygen levels [10.7kPa (80mmHg)]. The results do not lend themselves easily to the pan-selectionist paradigm in which all physiological traits are viewed as being adaptive.
The Effect of Thermal Acclimation And Exercise Upon The Binding of Glycolytic Enzymes in Muscle of the Goldfish Carassius Auratus
Authors: Huber Maria , Guderley Helga 
Published: April 2021

ABSTRACT
To examine whether the changes in metabolic organization induced by thermal acclimation modify glycolytic enzyme-binding, we acclimated goldfish, Carassius auratus, to 8 and 25 °C and measured the binding of phosphofructokinase (PFK), aldolase, pyruvate kinase and lactate dehydrogenase to subcellular particles in red and white muscle. When fish were sampled at rest at their acclimation temperature, only the percentage binding of PFK in red muscle was altered by thermal acclimation. By contrast, exhausting exercise at 15 °C led to markedly higher levels of binding of PFK in muscle of warm-than of cold-acclimated fish. This pattern was apparent in both red and white muscle. The specific activity of PFK in red muscle declined with exhausting exercise in warm-but not in cold-acclimated fish. In contrast, the units of PFK bound per gram of muscle did not differ in exhausted warm- and cold-acclimated fish. Cold-and warm-acclimated fish did not differ in their accumulation of lactate in white muscle at exhaustion. Furthermore, the PFK from white muscle of warm- and cold-acclimated fish did not differ in the pH dependence of binding to subcellular particles. These changes in the dynamics of PFK binding with temperature acclimation suggest that soluble PFK may be more susceptible to exercise-induced inhibition in warm- than in cold-acclimated goldfish. While the percentage binding and the specific activity of the other glycolytic enzymes were little affected by exhausting exercise, the units of aldolase bound per gram of white muscle decreased with exercise in warm-acclimated fish.
Fluid Uptake And The Maintenance of Blood Volume in Octopus
Authors: Wells M. J. , Wells J. 
Published: April 2021

ABSTRACT
The replacement of fluid following withdrawal of up to 40% of the blood from Octopus vulgaris can be tracked over a period of days by measuring the dilution of haemocyanin, which is not simultaneously replaced. Haemocyanin concentration was measured from the copper content or the oxygen-carrying capacity of further small blood samples. Fluid lost was replaced within 1–2h, provided that the digestive gland ducts were left intact. If these were ligated, the haemocyanin concentration remained the same as before withdrawal of the initial large blood sample and the animals died within a few hours. Evidence presented elsewhere has indicated that the site of the fluid uptake is the digestive gland appendages. Urine production would be continued or increased during the restoration of blood volume. When urine volume is added to the volume of fluid replaced, it appears that this fluid transport system must be capable of moving at least its own volume of fluid from the gut into the blood every 5min. An immediate consequence of blood withdrawal is a fall in blood pressure and pulse amplitude, followed within minutes by a transient rise to high blood pressures, apparently as a result of an increase in peripheral resistance as circulation to the arms is restricted, conserving the blood for vital central organs. Following these transient swings, the diastolic blood pressure returns to normal values despite blood loss; pulse amplitude returns as blood volume is replaced. Duct-ligated animals continue to show a reduced pulse.
Beating of Cilia of Sea Urchin Embryos: A Critical Comparison of the Normal and Reversed Beating of Cilia of Isolated Cells
Authors: Mogami Yoshihiro , Sekiguchi Shima , Baba Shoji A. 
Published: April 2021

ABSTRACT
Two different types of ciliary beating, normal and reversed, were analyzed on the same cilia on cells isolated from echinoplutei. Bends on the cilium in reversed beating were observed to increase in curvature during propagation in the effective stroke of the beat, whereas in normal beating, bends propagate with a constant curvature in both effective and recovery strokes. The proximal region of the cilium showed an almost identical oscillation of shear angle in both normal and reversed beating with respect to the time normalized to the average beat period, which was determined by the rotational movement of the cell body. In reversed beating, a common temporal profile generated at the proximal region was preserved in the oscillation over the length of the cilium. The local oscillations in normal beating, however, changed in temporal profile as seen from base to tip. The conversion of the temporal oscillatory profile from normal to reversed beating occurred in association with changes in the centre of the oscillation (static bias), whose difference increased with the distance from the base. The data indicate that the changes in bending pattern between normal and reversed beating of sea urchin embryo cilia are not due to changes in the initiation of the oscillation at the base, but largely to temporal and static changes in the pattern of propagation of the oscillatory activity.
Characterization of insect sense organs and optical clearing of whole-mount preparations using diI in fixed tissues
Authors: Zill Sasha N. , Frazier S. Faith , Macfarland Dawn L. , Fish Stephen E. 
Published: April 2021

ABSTRACT
Studies of invertebrate sensory receptors have been greatly aided by the use of compounds, such as cobalt salts, which can diffuse or be transported in peripheral nerves, to characterize morphologically and to label identified exteroceptive and proprioceptive sense organs (Bräunig, et al. 1981). However, most of these methods require the maintenance of live preparations, which can be difficult when attempting to fill axons over long distances. We have mapped sense organs of the cockroach leg using the carbocyanine dye, diI. This lipid-soluble dye, recently developed for use in vertebrates (Honig and Hume, 1989), diffuses passively in neuronal membranes and can be used in fixed tissues. However, because of its lipid solubility, it has the disadvantage that it dissolves in standard organic clearing agents. We have developed methods of applying diI and clearing cockroach preparations that permit the visualization of both sensory neuron somata under fluorescent illumination and their associated cuticular specializations by conventional light microscopy. These experiments have confirmed the location of many receptors previously identified by serial sectioning and light microscopy (Dresden and Nijenhuis, 1958; Nijenhuis and Dresden, 1952, 1956). We have also mapped sense organs on the distal leg segments and demonstrated the widespread presence of multiply innervated, chemoreceptor-like sense organs on all segments of the cockroach mesothoracic and metathoracic legs.