bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crucial Role of the Membrane Potential for ATP Synthesis by F1Fo ATP Synthases
Authors: Dimroth Peter , Kaim Georg , Matthey Ulrich 
Published: April 2021

ABSTRACT
ATP, the universal carrier of cell energy, is manufactured from ADP and phosphate by the enzyme ATP synthase using the free energy of an electrochemical gradient of protons (or Na+). The proton-motive force consists of two components, the transmembrane proton concentration gradient (ΔpH) and the membrane potential. The two components were considered to be not only thermodynamically but also kinetically equivalent, since the chloroplast ATP synthase appeared to operate on ΔpH only. Recent experiments demonstrate, however, that the chloroplast ATP synthase, like those of mitochondria and bacteria, requires a membrane potential for ATP synthesis. Hence, the membrane potential and proton gradient are not equivalent under normal operating conditions far from equilibrium. These conclusions are corroborated by the finding that only the membrane potential induces a rotary torque that drives the counter-rotation of the a and c subunits in the Fo motor of Propionigenium modestum ATP synthase.
Structure, Mechanism and Regulation of the Clathrin-Coated Vesicle and Yeast Vacuolar H+-ATPases
Authors: Forgac Michael 
Published: April 2021

ABSTRACT
The vacuolar H+-ATPases (or V-ATPases) are a family of ATP-dependent proton pumps that carry out acidification of intracellular compartments in eukaryotic cells. This review is focused on our work on the V-ATPases of clathrin-coated vesicles and yeast vacuoles. The coated-vesicle V-ATPase undergoes trafficking to endosomes and synaptic vesicles, where it functions in receptor recycling and neurotransmitter uptake, respectively. The yeast V-ATPase functions to acidify the central vacuole and is necessary both for protein degradation and for coupled transport processes across the vacuolar membrane.
The V-ATPases are multisubunit complexes composed of two functional domains. The V1 domain is a 570 kDa peripheral complex composed of eight subunits of molecular mass 73–14 kDa (subunits A–H) that is responsible for ATP hydrolysis. The Vo domain is a 260 kDa integral complex composed of five subunits of molecular mass 100–17 kDa (subunits a, d, c, c′ and c′′) that is responsible for proton translocation. To explore the function of individual subunits in the V-ATPase complex as well as to identify residues important in proton transport and ATP hydrolysis, we have employed a combination of chemical modification, site-directed mutagenesis and in vitro reassembly.
A central question concerns the mechanism by which vacuolar acidification is controlled in eukaryotic cells. We have proposed that disulfide bond formation between conserved cysteine residues at the catalytic site of the V-ATPase plays an important role in regulating V-ATPase activity in vivo. Other regulatory mechanisms that are discussed include reversible dissociation and reassembly of the V-ATPase complex, changes in the tightness of coupling between proton transport and ATP hydrolysis, differential targeting of V-ATPases within the cell and control of the Cl− conductance that is necessary for vacuolar acidification.
Surface Oxidase and Oxidative Stress Propagation in Aging
Authors: Morré Dorothy M. , Lenaz Giorgio , Morré D. James 
Published: April 2021

ABSTRACT
This report summarizes new evidence for a plasma-membrane-associated hydroquinone oxidase designated as CNOX (constitutive plasma membrane NADH oxidase) that functions as a terminal oxidase for a plasma membrane oxidoreductase (PMOR) electron transport chain to link the accumulation of lesions in mitochondrial DNA to cell-surface accumulations of reactive oxygen species. Previous considerations of plasma membrane redox changes during aging have lacked evidence for a specific terminal oxidase to catalyze a flow of electrons from cytosolic NADH to molecular oxygen (or to protein disulfides). Cells with functionally deficient mitochondria become characterized by an anaerobic metabolism. As a result, NADH accumulates from the glycolytic production of ATP. Elevated PMOR activity has been shown to be necessary to maintain the NAD+/NADH homeostasis essential for survival. Our findings demonstrate that the hyperactivity of the PMOR system results in an NADH oxidase (NOX) activity capable of generating reactive oxygen species at the cell surface. This would serve to propagate the aging cascade both to adjacent cells and to circulating blood components. The generation of superoxide by NOX forms associated with aging is inhibited by coenzyme Q and provides a rational basis for the anti-aging activity of circulating coenzyme Q.
Dynamic Mechanical Characterization of a Mutable Collagenous Tissue: Response of Sea Cucumber Dermis to Cell Lysis and Dermal Extracts
Authors: Szulgit Greg K. , Shadwick Robert E. 
Published: April 2021

ABSTRACT
The dermis of the holothurian Cucumaria frondosa is a mutable collagenous tissue (MCT). In this study, the inner and outer regions of the dermis were separated and used to make two different tissue extracts. These extracts were applied to intact pieces of dermis, one invoking a stiff mechanical state and the other invoking a compliant state. The extracts were effective on tissues incubated in artificial sea water (ASW) and in those incubated in Ca2+-chelated ASW. Furthermore, the extracts were effective on both fresh tissues and tissues in which the cells had been lysed by freeze–thawing, indicating that the sites of action are in the extracellular matrix. Dynamic oscillatory shear tests and analyses were used to measure both the dynamic shear stiffness (G*) and the relative damping (tanδ) of the tissue. These two parameters proved to be inversely related to each other (i.e. when G* increased, tanδ decreased). A theoretical viscoelastic model is constructed to interpret the results of these tests. It is concluded that changes in the mechanical state of the tissue involve interactions between elastic elements within the tissue rather than an alteration of its viscous components.
Hagfish (Myxine Glutinosa) Red Cell Membrane Exhibits no Bicarbonate Permeability as Detected by 18O Exchange
Authors: Peters Thomas , Forster Robert E. , Gros Gerolf 
Published: April 2021

ABSTRACT
The bicarbonate permeability of the plasma membrane of intact hagfish (Myxine glutinosa) red blood cells and the intracellular carbonic anhydrase activity of these cells were determined by applying the 18O exchange reaction using a special mass spectrometric technique. When the macromolecular carbonic anhydrase inhibitor Prontosil–Dextran was used to suppress any extracellular carbonic anhydrase activity, the mean intracellular acceleration of the CO2 hydration/HCO3− dehydration reaction over the uncatalyzed reaction (referred to as intracellular carbonic anhydrase activity Ai) was 21 320±3000 at 10 °C (mean ± S.D., N=9). The mean bicarbonate permeability of the red blood cell membrane was indistinguishable from zero. It can be concluded that CO2 transport within hagfish blood does not follow the classical scheme of CO2 transport in vertebrate blood. It is suggested that the combination of considerable intraerythrocytic carbonic anhydrase activity and low may serve to enhance O2 delivery to the tissue in the exceptionally hypoxia-tolerant hagfish.
Comb-Wax Discrimination by Honeybees Tested with the Proboscis Extension Reflex
Authors: Fröhlich Birgit , Riederer Markus , Tautz Jürgen 
Published: April 2021

ABSTRACT
We used the proboscis extension reflex of honeybees to test their ability to discriminate between comb waxes of different ages (wax scales, 1-week-old wax, 2-to 3-year-old wax, 8-to 10-year-old wax). Such waxes differ in their chemical composition, and an ability to discriminate between them may aid the orientation of the bees in the nest.
To train the bees, we used whole extracts of waxes and four different fractions of the whole extract based on different elutions of solid-phase extractions (extract I, fraction A eluted with hexane and fraction B with diethylether; extract II, fraction B further subdivided into fraction C by elution with isopropylchloride and fraction D by elution with diethylether).
In a differential training regime (six learning and six test trials) with whole extracts or with the different fractions, we paired one type of wax with a reward and another with no reward. The bees learned to discriminate between all tested pairs of whole extracts. The two subfractions (fractions A and B) gave different results: the bees could discriminate between waxes of different ages when fraction B was used but not when fraction A was used. A further subdivision of fraction B into fractions C and D showed that only fraction D contained the elements that enabled bees to discriminate between old and new wax.
Fraction D makes up only 5–8 % of the total wax mass and contains hydroxy alkyl esters (5–6 % of the total wax mass), primary alcohols (0.3–0.5 % of the total wax mass) and acids (0.06–1.0 % of the total wax mass). Fractions A and C (together forming 62–64 % of the total wax mass), which consist of unbranched and branched aliphatic hydrocarbons and alkyl esters, could not be discriminated by the bees. The remaining wax mass (25–29 %) was eluted with a mixture of chloroform, methanol and water (13:5:1) as fraction E.
The Emetic Reflex in a Reptile (Crocodylus Porosus)
Authors: Andrews Paul L. R. , Axelsson Michael , Franklin Craig , Holmgren Susanne 
Published: April 2021

ABSTRACT
The emetic (vomiting) reflex in a crocodilian, Crocodylus porosus, was characterised for the first time using the plant alkaloid veratrine (5 mg kg−1i.v. or i.p.) as an emetic stimulus. The latency to the onset of vomiting was 8.0±0.9 min (mean ± S.E.M., N=5 animals). Vomiting was preceded by a clearly defined set of prodromal behaviours including, in temporal sequence, rhythmic contraction of the pharynx, sneezing and jaw snapping. Expulsion of vomitus was not particularly forceful and was accompanied by lateral shaking of the head. Physiological studies revealed that vomiting was accompanied by oscillatory (9.1±0.7 oscillations over 29.7±3.6 s, N=9 episodes in three animals) increases in intraperitoneal pressure (7.0±0.9 kPa, cf. 0.7±0.1 kPa during respiration). The significance of these results is discussed in the context of the role(s) of vomiting as a protective reflex and as a mechanism for removal of indigestible food residues (e.g. fur, claws) from the gut.
Digital Motion Analysis As A Tool For Analysing The Shape And Performance of The Circulatory System in Transparent Animals
Authors: Schwerte Thorsten , Pelster Bernd 
Published: April 2021

ABSTRACT
The analysis of perfusion parameters using the frame-to-frame technique and the observation of small blood vessels in transparent animals using video microscopy can be tedious and very difficult because of the poor contrast of the images. Injection of a fluorescent probe (fluorescein isothiocynate, FITC) bound to a high-molecular-mass dextran improved the visibility of blood vessels, but the gray-scale histogram showed blurring at the edges of the vessels. Furthermore, injection of the fluorescent probe into the ventricle of small zebrafish (Danio rerio) embryos (body mass approximately 1 mg) often resulted in reduced cardiac activity. Digital motion analysis, however, proved to be a very effective tool for analysing the shape and performance of the circulatory system in transparent animals and tissues. By subtracting the two fields of a video frame (the odd and the even frame), any movement that occurred within the 20 ms necessary for the acquisition of one field could be visualised. The length of the shifting vector generated by this subtraction, represented a direct measure of the velocity of a moving particle, i.e. an erythrocyte in the vascular system. By accumulating shifting vectors generated from several consecutive video frames, a complete trace of the routes over which erythrocytes moved could be obtained. Thus, a cast of the vascular system, except for those tiny vessels that are not entered by erythrocytes, could be obtained. Because the gray-scale value of any given pixel or any given group of pixels increased with the number of erythrocytes passing it, digital motion analysis could also be used to visualise the distribution of blood cells in transparent tissues. This method was used to describe the development of the peripheral vascular system in zebrafish larvae up to 8 days post-fertilisation. At this stage, food intake resulted in a clear redistribution of blood between muscle tissue and the gut, and α-adrenergic control of peripheral blood flow was established.
5-Hydroxytryptamine Modulates Pheromone-Evoked Local Field Potentials in The Macroglomerular Complex of The Sphinx Moth Manduca Sexta
Authors: Kloppenburg Peter , Heinbockel Thomas 
Published: April 2021

ABSTRACT
Extra- and intracellular recordings from an intact brain preparation were used to study the effects of 5-hydroxytryptamine (5-HT or serotonin) on projection neurons in the sexually dimorphic macroglomerular complex (MGC) in the antennal lobe of the male moth Manduca sexta. The MGC is a group of three identified glomeruli specialized for synaptic processing of primary afferent information about the multi-component sex pheromone of the female. We investigated the modulatory effects of 5-HT on pheromone-evoked local field potentials in the MGC. The magnitude and duration of these potentials, which are thought to be generated by a population of pheromone-sensitive projection neurons of the MGC, were increased by 5-HT. Using intracellular recordings from the neurites of individual MGC projection neurons, we found that 5-HT increased the number of action potentials in response to pheromonal stimulation. These findings correlate well with earlier experiments that used other recording techniques. Our results are further evidence that 5-HT modulates a population of pheromone-sensitive MGC projection neurons that relay information about the pheromonal stimulus from the MGC to higher-order centers in the protocerebrum and are therefore pivotal for mate-finding and odor-guided behavior.
Skin Darkening, A Potential Social Signal in Subordinate Arctic Charr (Salvelinus Alpinus): The Regulatory Role of Brain Monoamines and Pro-Opiomelanocortin-Derived Peptides
Authors: Höglund Erik , Balm Paul H. M. , winberg Svante 
Published: April 2021

ABSTRACT
Arctic charr were allowed to interact in groups of three for 5 days. Skin darkness was quantified by measuring the mean brightness of individual fish before and after social interaction. Brain levels of monoamines and monoamine metabolites and plasma concentrations of cortisol, adrenocorticotropic hormone (ACTH), N-acetyl-β-endorphin and α-melanocyte-stimulating hormone (α-MSH) were analysed. The results show that social subordination resulted in a significant skin darkening. Furthermore, plasma concentrations of α-MSH, ACTH and cortisol were elevated in subordinates, and these fish also displayed elevated levels of 5-hydroxyindoleacetic acid (5-HIAA) in the telencephalon. The ratio of [5-HIAA] to serotonin [5-HT] was increased in several brain areas. In addition, the ratio of 3-methoxy-4-hydroxyphenylglycol (MHPG) to norepinephrine (NE) concentrations was significantly increased in the optic tectum of subordinate fish. Skin darkness following social interaction showed a significant positive correlation with plasma levels of α-MSH. Plasma levels of ACTH and α-MSH were both positively correlated with that of cortisol. Brain [5-HIAA]/[5-HT] ratios were positively correlated with circulating plasma levels of ACTH, and a similar positive correlation was seen between [MHPG]/[NE] ratios in the optic tectum and plasma levels of ACTH, α-MSH and N-acetyl-β-endorphin. In contrast, hypothalamic [MHPG]/[NE] ratios displayed a negative correlation with plasma α-MSH concentrations. The present study demonstrates that social stress induces skin darkening in Arctic charr and that this effect could be mediated by a stress-induced increase in the levels of α-MSH in the circulation. Furthermore, the results suggest that 5-HT and NE in the central nervous system could be factors regulating the pituitary release of ACTH and α-MSH.
Physiological Variability in Neonatal Armadillo Quadruplets: Within- and Between-Litter Differences
Authors: Bagatto B. , Crossley D. A. , Burggren W. W. 
Published: April 2021

ABSTRACT
The role of genetics on neonatal physiological variability was examined in the nine-banded armadillo (Dasypus novemcinctus). Since armadillos give birth to only monozygous quadruplets, the genetic variation within litters is essentially zero. Quadruplets born in captivity were isolated a.nd weighed within 8 h of birth. Oxygen consumption was measured in resting neonates by flow-through respirometry, heart rate obtained from an electrocardiogram and ventilation was measured by impedance techniques. Following the measurements, neonates were returned to the mother. Measurements were repeated at 4 and 8 days after birth. Mean heart rate significantly increased from 132 beats min−1 on the day of birth to 169 beats min−1 on day 8. Mean ventilation rate significantly decreased from 81 breaths min−1 on the day of birth to 54 breaths min−1 on day 8. During this same developmental period, mean mass significantly increased from 100 g to 129 g, and mean mass-specific oxygen consumption significantly decreased from ml O2 kg−1 min−1 to 28.6 ml O2 kg−1 min−1. For all variables measured, within-litter variability was always significantly less than between-litter variability, confirming a ‘sibling effect’ that we attribute to the genetic components determining physiological characters.
Developmental Dimorphism And Expression of Chemosensory-Mediated Behavior: Habitat Selection By A Specialist Marine Herbivore
Authors: Krug Patrick J. , Zimmer Richard K. 
Published: April 2021

ABSTRACT
Developmental dimorphisms provide an opportunity to compare sensory systems and behavior patterns between different forms of a single species. Alternative morphs differing in dispersal ability often show behavioral differences that mediate life-history trade-offs. We measured the behavioral responses of both long-lived, feeding larvae and short-lived, non-feeding larvae of the specialist marine herbivore Alderia modesta during habitat selection. Larvae immediately responded to waterborne cues from the adult host algae by increasing their turning rate, by changing their swimming speed in the water and by moving in rapid hops or spiraling along the bottom. These behavior patterns retained larvae in areas where the dissolved cue was initially perceived, and prolonged exposure to the cue increased the percentage of larvae that initiated metamorphosis. Despite their differences in life span and trophic mode, both larval morphs displayed similar behavior patterns when stimulated by the waterborne cue. Long-lived larvae had a stronger response, however, suggesting that settlement behavior may offset the costs of a prolonged larval life. This is the first study to examine the effects of dimorphic development on chemosensory-mediated behavior.
The Functional Morphology of the Avian Flight Muscle M. Coracobrachialis Posterior
Authors: Woolley J. D. 
Published: April 2021

ABSTRACT
The extensive range of movement of the avian glenohumeral joint makes functional interpretation of any muscle that crosses the joint difficult. Multiple functional roles for the M. coracobrachialis posterior (CBP), an architecturally complex muscle that lies deep to the M. pectoralis, have been assigned on the basis of its anatomical position. The mechanical properties, neuromotor pattern during flight and the biochemical properties of the CBP in pigeons (Columba livia) were studied by in situ length/active tension and length/passive tension measurements, in vivo electromyography and muscle histochemistry. The action of the muscle was studied directly through in situ stimulation and measurement of humeral excursion in non-reduced preparations.
Cops and Robbers: Putative Evolution of Copper Oxygen-Binding Proteins
Authors: Decker Heinz , Terwilliger Nora 
Published: April 2021

ABSTRACT
Two closely related copper proteins, phenoloxidase and haemocyanin, are known to be involved in different physiological functions such as the primary immune response and oxygen transport. Although the proteins differ structurally, they have the same active site by which dioxygen is bound. Recent results reveal that haemocyanin also exhibits phenoloxidase activity. A scenario is proposed for the evolutionary relationships among copper oxygen-binding proteins (COPs).
Activity Before Exercise Influences Recovery Metabolism in the Lizard Dipsosaurus Dorsalis
Authors: Scholnick David A. , Gleeson Todd T. 
Published: April 2021

ABSTRACT
During recovery from even a brief period of exercise, metabolic rate remains elevated above resting levels for extended periods. The intensity and duration of exercise as well as body temperature and hormone levels can influence this excess post-exercise oxygen consumption (EPOC). We examined the influence of activity before exercise (ABE), commonly termed warm-up in endotherms, on EPOC in the desert iguana Dipsosaurus dorsalis. The rate of oxygen consumption and blood lactate levels were measured in 11 female D. dorsalis (mass 41.1±3.0 g; mean ± S.E.M.) during rest, after two types of ABE and after 5 min of exhaustive exercise followed by 60 min of recovery. ABE was either single (15 s of maximal activity followed by a 27 min pause) or intermittent (twelve 15 s periods of exercise separated by 2 min pauses). Our results indicate that both single and intermittent ABE reduced recovery metabolic rate. EPOC volumes decreased from 0.261 to 0.156 ml of oxygen consumed during 60 min of recovery when lizards were subjected to intermittent ABE. The average cost of activity (net during exercise and 60 min of recovery per distance traveled) was almost 40 % greater in lizards that exercised without any prior activity than in lizards that underwent ABE. Blood lactate levels and removal rates were greatest in animals that underwent ABE. These findings may be of particular importance for terrestrial ectotherms that typically use burst locomotion and have a small aerobic scope and a long recovery period.
TISSUE-SPECIFIC EXPRESSION OF ZEBRAFISH (DANIO RERIO) HEAT SHOCK FACTOR 1 mRNAS IN RESPONSE TO HEAT STRESS
Authors: Råbergh Christina M. I. , Airaksinen Susanna , Soitamo Arto , Björklund Harry V. , Johansson Tove , Nikinmaa Mikko , Sistonen Lea 
Published: April 2021

ABSTRACT
All organisms respond to environmental, chemical and physiological stresses by enhanced synthesis of an evolutionarily conserved family of proteins known as heat shock proteins (HSPs) or stress proteins. Certain HSPs are also expressed constitutively during cell growth and development, and they function as molecular chaperones. The transcriptional regulation of hsp genes is mediated by the heat shock transcription factor (HSF). The stress response has been studied mostly in mammalian cell lines or organisms normally maintained under constant laboratory conditions. There is much less information on the regulation of the stress response of animals, such as fish, that have to tolerate large fluctuations in environmental and internal conditions. To characterize the regulation of the heat shock response in fish, we have cloned the first heat shock transcription factor from fish, zebrafish Danio rerio. Phylogenetic analysis confirms that the isolated zebrafish HSF belongs to the HSF1 family and is therefore designated zHSF1. Analysis by reverse transcriptase polymerase chain reaction (RT-PCR) shows the presence of two zHSF1 mRNA forms that are expressed in a tissue-specific fashion upon exposure to heat stress. Both forms are expressed in gonads under all conditions; in liver and to a lesser extent in the gills, the longer splice form of zHSF1 disappears upon heat shock. We present evidence for a unique tissue-specific regulation of HSF1 upon exposure to elevated temperature.