bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.
Chloride channels of intracellular organelles and their potential role in cystic fibrosis
Authors: Al-Awqati Qais , Barasch Jonathan , Landry Donald 
Published: April 2021

ABSTRACTChloride 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

ABSTRACTThe 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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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

ABSTRACT
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.