bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biogenesis and Function of the Yeast Plasma-Membrane H+-ATPase
Authors: Ambesi Anthony , Miranda Manuel , Petrov Valery V. , Slayman Carolyn W. 
Published: April 2021

ABSTRACT
One of the most abundant proteins in the yeast plasma membrane is the P-type H+-ATPase that pumps protons out of the cell, supplying the driving force for a wide array of H+-dependent cotransporters. The ATPase is a 100 kDa polypeptide, anchored in the lipid bilayer by 10 transmembrane α-helices. It is structurally and functionally related to the P-type Na+,K+-, H+,K+- and Ca2+-ATPases of animal cells and the H+-ATPases of plant cells, and it shares with them a characteristic reaction mechanism in which ATP is split to ADP and inorganic phosphate (Pi) via a covalent β-aspartyl phosphate intermediate. Cryoelectron microscopic images of the H+-ATPase of Neurospora crassa and the sarcoplasmic reticulum Ca2+-ATPase of animal cells have recently been obtained at 8 nm resolution. The membrane-embedded portion of the molecule, which presumably houses the cation translocation pathway, is seen to be connected via a narrow stalk to a large, multidomained cytoplasmic portion, known to contain the ATP-binding and phosphorylation sites. In parallel with the structural studies, efforts are being made to dissect structure/function relationships in several P-type ATPases by means of site-directed mutagenesis. This paper reviews three phenotypically distinct classes of mutant that have resulted from work on the yeast PMA1 H+-ATPase: (1) mutant ATPases that are poorly folded and retained in the endoplasmic reticulum; (2) mutants in which the conformational equilibrium has been shifted from the E2 state, characterized by high affinity for vanadate, to the E1 state, characterized by high affinity for ATP; and (3) mutants with altered coupling between ATP hydrolysis and proton pumping. Although much remains to be learned before the transport mechanism can be fully understood, these mutants serve to identify critical parts of the polypeptide that are required for protein folding, conformational change and H+:ATP coupling.
Assembly and Regulation of the Yeast Vacuolar H+-ATPase
Authors: Kane Patricia M. , Parra Karlett J. 
Published: April 2021

ABSTRACT
The yeast vacuolar H+ -ATPase (V-ATPase) consists of a complex of peripheral subunits containing the ATP binding sites, termed the V1 sector, attached to a complex of membrane subunits containing the proton pore, termed the Vo sector. Interaction between the V1 and Vo sectors is essential for ATP-driven proton transport, and this interaction is manipulated in vivo as a means of regulating V-ATPase activity. When yeast (Saccharomyces cerevisiae) cells are deprived of glucose for as little as 5 min, up to 75 % of the assembled V-ATPase complexes are disassembled into cytoplasmic V1 sectors and membrane-bound Vo sectors. Remarkably, this disassembly is completely reversible. Restoration of glucose to the growth medium results in quantitative reassembly of the disassembled complexes in as little as 5 min, even in the absence of any new protein synthesis. Cells also appear to regulate the extent of V1 Vo assembly on a long-term basis. Yeast cells grown for extended periods in a poor carbon source contain a high proportion of free V1 and Vo sectors, and these sectors remain poised for reassembly when growth conditions improve. Parallel experiments on the Manduca sexta V-ATPase suggest that reversible disassembly may be a general regulatory mechanism for V-ATPases. These results imply that V-ATPases are surprisingly dynamic structures, and their unique ‘regulated instability’ raises a number of interesting physiological and structural questions. How are extracellular conditions such as carbon source communicated to V-ATPase complexes present on intracellular membranes? How are such major structural changes in the V-ATPase generated and how are V1 sectors ‘silenced’ in vivo to prevent unproductive hydrolysis of cytoplasmic ATP by the dissociated enzyme? We are addressing these questions using a combination of genetic and biochemical approaches.
The Cellular Biology of Proton-Motive Force Generation by V-ATPases
Authors: Nelson Nathan , Perzov Natalie , Cohen Adiel , Hagai Keren , Padler Vered , Nelson Hannah 
Published: April 2021

ABSTRACT
The vacuolar H+-ATPase (V-ATPase) is one of the most fundamental enzymes in nature. It functions in almost every eukaryotic cell and energizes a wide variety of organelles and membranes. In contrast to F-ATPases, whose primary function in eukaryotic cells is to form ATP at the expense of the proton-motive force, V-ATPases function exclusively as ATP-dependent proton pumps. The proton-motive force generated by V-ATPases in organelles and across plasma membranes of eukaryotic cells is utilized as a driving force for numerous secondary transport processes. The enzyme is also vital for the proper functioning of endosomes and the Golgi apparatus. In contrast to yeast vacuoles, which maintain an internal pH of approximately 5.5, it is believed that the vacuoles of lemon fruit may have a pH as low as 2. Similarly, some brown and red algae maintain an internal pH as low as 1 in their vacuoles. It was yeast genetics that allowed the identification of the special properties of individual subunits and the discovery of the factors that are involved in V-ATPase biogenesis and assembly.
Null mutations in genes encoding V-ATPase subunits of Saccharomyces cerevisiae result in a phenotype that is unable to grow at high pH and is sensitive to high and low metal-ion concentrations. Treatment of these null mutants with ethyl methanesulphonate causes mutations that suppress the V-ATPase null phenotype, and these cells are able to grow at pH 7.5. The suppressor mutants were denoted as svf (Suppressor of V-ATPase Function). The svf mutations are recessive: crossing the svf mutants with their corresponding V-ATPase null mutants resulted in diploid strains that were not able to grow at pH 7.5. A novel gene family in which null mutations cause pleiotropic effects on metal-ion resistance or on the sensitivity and distribution of membrane proteins in different targets was discovered. We termed this gene family VTC (Vacuolar Transporter Chaperon) and discovered four genes in S. cerevisiae that belong to the family. Inactivation of one of them, VTC1, in the background of V-ATPase null mutations resulted in an svf phenotype that was able to grow at pH 7.5. Apparently, Vtc1p is one of a few membrane organizers that determine the relative amounts of different membrane proteins in the various cellular membranes. We utilize the numerous yeast mutants generated in our laboratory to identify the specific organelle whose acidification is vital. The interaction between V-ATPase and the secretory pathway is investigated.
The Energetic Cost of Short Flights in Birds
Authors: Nudds Robert L. , Bryant David M. 
Published: April 2021

ABSTRACT
Many small birds perform short flights, for which take-offs, ascents and descents form a large component of the total flight time and which are characterised by low airspeeds. Using the doubly-labelled water technique, zebra finches Taeniopygia guttata engaging in repeated short flights were found to expend 13.65 kJ more than ‘non-flying’ controls, which equated to a flight expenditure of 27.8 times their basal metabolic rate. This is over three times the predicted flight expenditure derived from existing aerodynamic models. These data were used to determine a coefficient (0.11) for converting the mechanical power derived from aerodynamic models into metabolic power. An equation is presented, based on body mass, which can be used to predict the costs of short flights in ecological and behavioural studies of birds.
Behaviour-Locked Signal Analysis Reveals Weak 200–300 Hz Comb Vibrations During the Honeybee Waggle Dance
Authors: Nieh James C. , Tautz Jürgen 
Published: April 2021

ABSTRACT
Waggle-dancing honeybees produce vibratory movements that may facilitate communication by indicating the location of the waggle dancer. However, an important component of these vibrations has never been previously detected in the comb. We developed a method of fine-scale behavioural analysis that allowed us to analyze separately comb vibrations near a honeybee waggle dancer during the waggle and return phases of her dance. We simultaneously recorded honeybee waggle dances using digital video and laser-Doppler vibrometry, and performed a behaviour-locked Fast Fourier Transform analysis on the substratum vibrations. This analysis revealed significantly higher-amplitude 200–300 Hz vibrations during the waggle phase than during the return phase (P=0.012). We found no significant differences in the flanking frequency regions between 100–200 Hz (P=0.227) and 300–400 Hz (P=0.065). We recorded peak waggle phase vibrations from 206 to 292 Hz (244±28 Hz; mean ± S.D., N=11). The maximum measured signal − noise level was +12.4 dB during the waggle phase (mean μ5.8±2.7 dB). The maximum vibrational velocity, calculated from a filtered signal, was 128 µm s−1 peak-to-peak, corresponding to a displacement of 0.09 μm peak-to-peak at 223 Hz. On average, we measured a vibrational velocity of 79±28 μm s−1peak-to-peak from filtered signals. These signal amplitudes overlap with the detection threshold of the honeybee subgenual organ.
Ontogenetic Changes in Visual Sensitivity of The Parasitic Salmon Louse Lepeophtheirus Salmonis
Authors: Flamarique Iñigo Novales , Browman Howard I. , Bélanger Marise , Boxaspen Karin 
Published: April 2021

ABSTRACT
The salmon louse, Lepeophtheirus salmonis, is an ectoparasitic copepod of salmonid fishes whose life cycle involves two broadly defined, free-living larval stages, the nauplius and the copepodid. After settling on a host, the copepodid goes through various transformations to become a mobile adult. We recorded swimming responses of free-swimming salmon lice at the naupliar, copepodid and adult stages to the onset (ON) and offset (OFF) of lights of varying spectral irradiance and polarization. Nauplii showed a prominent swim-up OFF response across the spectrum 352–652 nm, but no ON response. Copepodids exhibited a swim-up ON response and a passive (sinking) OFF response across the same spectral range. Adults showed active swim-up responses to both ON and OFF stimuli, although the OFF response was proportionately stronger. The spectral range of the adult ON and OFF responses was the same as that of the copepodids and slightly greater than that of the nauplii, which did not exhibit responses at 652 nm. The absolute sensitivity of copepodids under white light (approx. 10−13 photons m2 s1) was higher than that of nauplii (approx. 10−17 photons−1 m2 s, OFF response) and that of adult female lice (approx. 10−14 photons−1 m2 s). This suggests that the naupliar visual system is best suited for detection of shadows (e.g. the host) under a bright light field (daylight hours), while copepodids and adults may be more specialized for host detection at crepuscular periods and during the night, when light levels are low. None of the developmental stages responded to the rotation of the plane of polarized light or exhibited any difference in directed response when polarized light was used in place of diffuse light.
Ventilation And Gas Exchange During Treadmill Locomotion in The American Alligator (Alligator Mississippiensis)
Authors: Farmer Colleen G. , Carrier David R. 
Published: April 2021

ABSTRACT
A number of anatomical characters of crocodilians appear to be inconsistent with their lifestyle as sit-and-wait predators. To address this paradoxical association of characters further, we measured lung ventilation and respiratory gas exchange during walking in American alligators (Alligator mississippiensis). During exercise, ventilation consisted of low-frequency, large-volume breaths. The alligators hyperventilated severely during walking with respect to their metabolic demands. Air convection requirements were among the highest and estimates of lung PCO2 were among the lowest known in air-breathing vertebrates. Air convection requirements dropped immediately with cessation of exercise. These observations indicate that the ventilation of alligators is not limited by their locomotor movements. We suggest that the highly specialized ventilatory system of modern crocodilians represents a legacy from cursorial ancestors rather than an adaptation to a lifestyle as amphibious sit- and-wait predators.
Octopamine Mimics the Effects of Parasitism on the Foregut of the Tobacco Hornworm Manduca Sexta
Authors: Miles Carol I. , Booker Ronald 
Published: April 2021

ABSTRACT
The parasitic braconid wasp Cotesia congregata lays its eggs inside the body of the larval stage of its host, the moth Manduca sexta. The Cotesia congregata larvae develop within the hemocoel of their host until their third instar, when they emerge and spin cocoons and pupate on the outer surface of the caterpillar. From this time until their death approximately 2 weeks later, the Manduca sexta larvae show striking behavioral changes that include dramatic declines in spontaneous activity and in the time spent feeding.
Coincident with these behavioral changes, it is known that octopamine titers in the hemolymph of the host become elevated by approximately 6.5-fold. Octopamine is an important modulator of neural function and behavior in insects, so we examined hosts for neural correlates to the behavioral changes that occur at parasite emergence. We found that, in addition to the changes reported earlier, after parasite emergence (post-emergence), Manduca sexta larvae also showed marked deficits in their ability to ingest food because of a disruption in the function of the frontal ganglion that results in a significant slowing or the absence of peristaltic activity in the foregut. This effect could be produced in unparasitized fifth-instar larvae by application of blood from post-emergence parasitized larvae or of 10−6 mol l−1 D,L-octopamine (approximately the level in the hemolymph of post-emergence larvae). In contrast, blood from parasitized larvae before their parasites emerge or from unparasitized fifth-instar larvae typically had no effect on foregut activity. The effects of either post-emergence parasitized blood or 10−6 mol l−1 octopamine could be blocked by the octopamine antagonists phentolamine (at 10−5 mol l−1) or mianserin (at 10−7 mol l−1).
Skin Temperatures During Free-Ranging Swimming And Diving In Antarctic Fur Seals
Authors: Boyd I. L. 
Published: April 2021

ABSTRACT
This study tests the hypothesis that an endothermic homeotherm should minimise heat flux in cold polar waters by minimising skin temperature. Temperature variability was measured at the surface of the skin of three Antarctic fur seals (Arctocephalus gazella) at intervals of 2 s over a total of 9.7 days while they were swimming and diving freely in polar waters at temperatures of 1.5–4 °C. The temperature difference (ΔT) between skin on the dorsal thorax and the water varied from more than 20 °C to close to equality over periods of less than 1 h. Shorter-term variations in ΔT of up to 5 °C occurred in association with diving, although these types of variations also occurred without diving. In general, ΔT began to decline during the descent phase of a dive and began to increase again during the ascent or at the end of the dive. One of the three individuals examined showed little variation in ΔT, which remained low (approximately 3 °C) throughout the experiment. In the other two fur seals, ΔT tended to decline during periods of sustained diving and usually increased during periods spent at the surface. Mean calculated heat flux varied from 95 to 236 W m−2 depending on the individual. Metabolic rates based on these calculated heat fluxes were towards the lower end of those measured in previous studies using different methodologies. The study has shown that Antarctic fur seal skin temperature is highly dynamic and suggests that the thoracic surface is an organ used for active thermoregulation.
Hydrodynamic Drag In Steller Sea Lions (Eumetopias Jubatus)
Authors: Stelle Lei Lani , Blake Robert W. , Trites Andrew W. 
Published: April 2021

ABSTRACT
Drag forces acting on Steller sea lions (Eumetopias jubatus) were investigated from ‘deceleration during glide’ measurements. A total of 66 glides from six juvenile sea lions yielded a mean drag coefficient (referenced to total wetted surface area) of 0.0056 at a mean Reynolds number of 5.5×106. The drag values indicate that the boundary layer is largely turbulent for Steller sea lions swimming at these Reynolds numbers, which are past the point of expected transition from laminar to turbulent flow. The position of maximum thickness (at 34 % of the body length measured from the tip of the nose) was more anterior than for a ‘laminar’ profile, supporting the idea that there is little laminar flow. The Steller sea lions in our study were characterized by a mean fineness ratio of 5.55. Their streamlined shape helps to delay flow separation, reducing total drag. In addition, turbulent boundary layers are more stable than laminar ones. Thus, separation should occur further back on the animal. Steller sea lions are the largest of the otariids and swam faster than the smaller California sea lions (Zalophus californianus). The mean glide velocity of the individual Steller sea lions ranged from 2.9 to 3.4 m s−1 or 1.2–1.5 body lengths s−1. These length-specific speeds are close to the optimum swim velocity of 1.4 body lengths s−1 based on the minimum cost of transport for California sea lions.
Vertebrate Ancient (Va) Opsin and Extraretinal Photoreception in the Atlantic Salmon (Salmo Salar)
Authors: Philp Alisdair R. , Garcia-Fernandez Jose M. , Soni Bobby G. , Lucas Robert J. , Bellingham James , Foster Russell G. 
Published: April 2021

ABSTRACT
A member of a new photopigment family first isolated from teleost fish, vertebrate ancient (VA) opsin, has recently been shown to form a functional photopigment and to be expressed within a subset of horizontal and amacrine cells of the inner retina. These sites of expression (and structural features) of VA opsin suggest that this photopigment might mediate non-image-forming light-detection tasks. We attempted to gain support for this hypothesis by examining the expression of VA opsin within the central nervous system (CNS) (pineal and deep brain) of the Atlantic salmon Salmo salar. In addition, we examined the sites of rod-opsin, cone-opsin and α-transducin expression within the salmon CNS to provide a more complete description of the extraretinal photoreceptors of a teleost vertebrate. We show that multiple populations of cells within the salmon CNS appear to contain photoreceptors: VA opsin was strongly expressed in the pineal organ and in bilateral columns of subependymal cells in the epithalamus; anti-cone-opsin antibodies labelled cells within the pineal and numerous cells in the anterior hypothalamus (suprachiasmatic nucleus, nucleus preopticus magnocellularis, nucleus preopticus parvocellularis); anti-rod-opsin antibodies labelled cells within the pineal but no other areas within the central brain; and anti-α-transducin antibodies labelled cells within the pineal and the ventral telencephalon. Collectively, our results suggest that VA opsin is a photopigment specialised for irradiance detection tasks within the eye, pineal and central brain, and that the salmon has multiple and varied populations of photoreceptors within the CNS. We review the significance of these findings within the broad context of vertebrate extraretinal photoreception.
Chromaticity as a Signal of Ripeness in Fruits Taken by Primates
Authors: Sumner Petroc , Mollon J. D. 
Published: April 2021

ABSTRACT
We have measured the reflectance spectra of many samples of fruit eaten by chimpanzees and three frugivorous monkey species. If the fruit are plotted in a colour space appropriate for catarrhine primates, several distinct ripening patterns are evident. The degree of ripeness of many species would be discernible by dichromatic primates, but for most fruit a trichromatic consumer would be at an advantage. However, by calculating which set of possible photopigments would maximise the chromatic distance between samples of each fruit species, we show that the spectral positions of the primate long-(L) and middle-wavelength (M) cone pigments are not optimised for this task.
Gaba and Responses to Gaba in the Stomatogastric Ganglion of the Crab Cancer Borealis
Authors: Swensen Andrew M. , Golowasch Jorge , Christie Andrew E. , Coleman Melissa J. , Nusbaum Michael P. , Marder Eve 
Published: April 2021

ABSTRACT
The multifunctional neural circuits in the crustacean stomatogastric ganglion (STG) are influenced by many small-molecule transmitters and neuropeptides that are co-localized in identified projection neurons to the STG. We describe the pattern of γ-aminobutyric acid (GABA) immunoreactivity in the stomatogastric nervous system of the crab Cancer borealis and demonstrate biochemically the presence of authentic GABA in C. borealis. No STG somata show GABA immunoreactivity but, within the stomatogastric nervous system, GABA immunoreactivity co-localizes with several neuropeptides in two identified projection neurons, the modulatory proctolin neuron (MPN) and modulatory commissural neuron 1 (MCN1). To determine which actions of these neurons are evoked by GABA, it is necessary to determine the physiological actions of GABA on STG neurons. We therefore characterized the response of each type of STG neuron to focally applied GABA. All STG neurons responded to GABA. In some neurons, GABA evoked a picrotoxin-sensitive depolarizing, excitatory response with a reversal potential of approximately −40 mV. This response was also activated by muscimol. In many STG neurons, GABA evoked inhibitory responses with both K+- and Cl−-dependent components. Muscimol and β-guanidinopropionic acid weakly activated the inhibitory responses, but many other drugs, including bicuculline and phaclofen, that act on vertebrate GABA receptors were not effective. In summary, GABA is found in projection neurons to the crab STG and can evoke both excitatory and inhibitory actions on STG neurons.
Three-Dimensional Loading and Growth of the Zygomatic Arch
Authors: Rafferty Katherine L. , Herring Susan W. , Artese Flavia 
Published: April 2021

ABSTRACT
Despite a number of previous biomechanical studies on the zygomatic arch, unanswered questions remain about its three-dimensional loading and growth. Using young miniature swine, we have for the first time recorded strains from both the medial and lateral aspects of the squamosal bone during mastication and masseter muscle stimulation. Strains from the zygomatic bone flange and zygomatic arch growth data were also obtained from the same animals. A second study on a younger group of animals examined the growth of the zygomatic flange following partial removal of the masseter. Strain data indicated that the squamosal bone is bent out-of-plane and that this pattern of loading is quite different from that of the adjacent zygomatic bone, which experiences much lower strains with little evidence of out-of-plane bending. Surprisingly, strains were higher in the zygomatic flange during contralateral chews and contralateral masseter stimulations than during ipsilateral chews/stimulations. These strains proved to arise from movement of the condyle, explaining why partial removal of the masseter had little effect on the growth of the flange. Other growth results indicated an approximately threefold greater rate of subperiosteal deposition on the lateral surface of the squamosal bone than on the zygomatic bone. This difference in growth rate is attributed to the presence of sutures that contribute to the lateral displacement of the zygomatic bone but not the squamosal bone. This explanation does not exclude the possibility that the rapid apposition on the lateral squamosal surface is regulated by the high surface strains that result from out-of-plane bending.