Articoli di riviste: "Vertebrates Physiology"

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Hedrick, Michael S., Stanley S. Hillman, Robert C. Drewes e Philip C. Withers. "Lymphatic regulation in nonmammalian vertebrates". Journal of Applied Physiology 115, n. 3 (1 agosto 2013): 297–308. http://dx.doi.org/10.1152/japplphysiol.00201.2013.

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All vertebrate animals share in common the production of lymph through net capillary filtration from their closed circulatory system into their tissues. The balance of forces responsible for net capillary filtration and lymph formation is described by the Starling equation, but additional factors such as vascular and interstitial compliance, which vary markedly among vertebrates, also have a significant impact on rates of lymph formation. Why vertebrates show extreme variability in rates of lymph formation and how nonmammalian vertebrates maintain plasma volume homeostasis is unclear. This gap hampers our understanding of the evolution of the lymphatic system and its interaction with the cardiovascular system. The evolutionary origin of the vertebrate lymphatic system is not clear, but recent advances suggest common developmental factors for lymphangiogenesis in teleost fishes, amphibians, and mammals with some significant changes in the water-land transition. The lymphatic system of anuran amphibians is characterized by large lymphatic sacs and two pairs of lymph hearts that return lymph into the venous circulation but no lymph vessels per se. The lymphatic systems of reptiles and some birds have lymph hearts, and both groups have extensive lymph vessels, but their functional role in both lymph movement and plasma volume homeostasis is almost completely unknown. The purpose of this review is to present an evolutionary perspective in how different vertebrates have solved the common problem of the inevitable formation of lymph from their closed circulatory systems and to point out the many gaps in our knowledge of this evolutionary progression.

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Esposito, Alfonso, Luca Ambrosino, Silvano Piazza, Salvatore D’Aniello, Maria Luisa Chiusano e Annamaria Locascio. "Evolutionary Adaptation of the Thyroid Hormone Signaling Toolkit in Chordates". Cells 10, n. 12 (2 dicembre 2021): 3391. http://dx.doi.org/10.3390/cells10123391.

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The specification of the endostyle in non-vertebrate chordates and of the thyroid gland in vertebrates are fundamental steps in the evolution of the thyroid hormone (TH) signaling to coordinate development and body physiology in response to a range of environmental signals. The physiology and biology of TH signaling in vertebrates have been studied in the past, but a complete understanding of such a complex system is still lacking. Non-model species from non-vertebrate chordates may greatly improve our understanding of the evolution of this complex endocrine pathway. Adaptation of already existing proteins in order to perform new roles is a common feature observed during the course of evolution. Through sequence similarity approaches, we investigated the presence of bona fide thyroid peroxidase (TPO), iodothyronine deiodinase (DIO), and thyroid hormone receptors (THRs) in non-vertebrate and vertebrate chordates. Additionally, we determined both the conservation and divergence degrees of functional domains at the protein level. This study supports the hypothesis that non-vertebrate chordates have a functional thyroid hormone signaling system and provides additional information about its possible evolutionary adaptation.

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Zang, Jingjing, e Stephan C. F. Neuhauss. "Biochemistry and physiology of zebrafish photoreceptors". Pflügers Archiv - European Journal of Physiology 473, n. 9 (17 febbraio 2021): 1569–85. http://dx.doi.org/10.1007/s00424-021-02528-z.

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AbstractAll vertebrates share a canonical retina with light-sensitive photoreceptors in the outer retina. These photoreceptors are of two kinds: rods and cones, adapted to low and bright light conditions, respectively. They both show a peculiar morphology, with long outer segments, comprised of ordered stacks of disc-shaped membranes. These discs host numerous proteins, many of which contribute to the visual transduction cascade. This pathway converts the light stimulus into a biological signal, ultimately modulating synaptic transmission. Recently, the zebrafish (Danio rerio) has gained popularity for studying the function of vertebrate photoreceptors. In this review, we introduce this model system and its contribution to our understanding of photoreception with a focus on the cone visual transduction cascade.

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Liang, Ping, Craig A. Jones, Brent W. Bisgrove, Lei Song, Sean T. Glenn, H. Joseph Yost e Kenneth W. Gross. "Genomic characterization and expression analysis of the first nonmammalian renin genes from zebrafish and pufferfish". Physiological Genomics 16, n. 3 (13 febbraio 2004): 314–22. http://dx.doi.org/10.1152/physiolgenomics.00012.2003.

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Liang, Ping, Craig A. Jones, Brent W. Bisgrove, Lei Song, Sean T. Glenn, H. Joseph Yost, and Kenneth W. Gross. Genomic characterization and expression analysis of the first nonmammalian renin genes from zebrafish and pufferfish. Physiol Genomics 16: 314–322, 2004. First published November 25, 2003; 10.1152/physiol-genomics. 00012.2003.—Renin is a key enzyme in the renin-angiotensin system (RAS), a pathway which plays an important physiological role in blood pressure and electrolyte homeostasis. The origin of the RAS is believed to have accompanied early evolution of vertebrates. However, renin genes have so far only been unequivocally identified in mammals. Whether or not a bona fide renin gene exists in nonmammalian vertebrates has been an intriguing question of physiological and evolutionary interest. Using a genomic analytical approach, we identified renin genes in two nonmammalian vertebrates, zebrafish ( Danio rerio) and pufferfish ( Takifugu rubripes). Phylogenetic analysis demonstrates that the predicted fish renins cluster together with mammalian renins to form a distinct subclass of vertebrate aspartyl proteases. RT-PCR results confirm generation of the predicted zebrafish mRNA and its expression in association with the opisthonephric kidney of adult zebrafish. Comparative in situ hybridization analysis of wild-type and developmental mutants indicates that renin expression is first detected bilaterally in cells of the interrenal primordia at 24 h postfertilization, which subsequently migrate to lie adjacent to, but distinct from, the glomerulus of the developing pronephric kidney. Our report provides the first molecular evidence for the existence of renin genes in lower vertebrates. The observation that the earliest renin-expressing cells, arising during ontogeny of this teleost vertebrate, are of adrenocortical lineage raises an interesting hypothesis as regards the origin of renin-expressing cells in the metanephric kidney of higher vertebrates.

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Wood, Philip G., Olga V. Lopatko, Sandra Orgeig, Jean M. P. Joss, Allan W. Smits e Christopher B. Daniels. "Control of pulmonary surfactant secretion: an evolutionary perspective". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 278, n. 3 (1 marzo 2000): R611—R619. http://dx.doi.org/10.1152/ajpregu.2000.278.3.r611.

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Pulmonary surfactant, a mixture consisting of phospholipids (PL) and proteins, is secreted by type II cells in the lungs of all air-breathing vertebrates. Virtually nothing is known about the factors that control the secretion of pulmonary surfactant in nonmammalian vertebrates. With the use of type II cell cultures from Australian lungfish, North American bullfrogs, and fat-tailed dunnarts, we describe the autonomic regulation of surfactant secretion among the vertebrates. ACh, but not epinephrine (Epi), stimulated total PL and disaturated PL (DSP) secretion from type II cells isolated from Australian lungfish. Both Epi and ACh stimulated PL and DSP secretion from type II cells of bullfrogs and fat-tailed dunnarts. Neither Epi nor ACh affected the secretion of cholesterol from type II cell cultures of bullfrogs or dunnarts. Pulmonary surfactant secretion may be predominantly controlled by the autonomic nervous system in nonmammalian vertebrates. The parasympathetic nervous system may predominate at lower body temperatures, stimulating surfactant secretion without elevating metabolic rate. Adrenergic influences on the surfactant system may have developed subsequent to the radiation of the tetrapods. Furthermore, ventilatory influences on the surfactant system may have arisen at the time of the evolution of the mammalian bronchoalveolar lung. Further studies using other carefully chosen species from each of the vertebrate groups are required to confirm this hypothesis.

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Wichmann, Lukas, e Mike Althaus. "Evolution of epithelial sodium channels: current concepts and hypotheses". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 319, n. 4 (1 ottobre 2020): R387—R400. http://dx.doi.org/10.1152/ajpregu.00144.2020.

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The conquest of freshwater and terrestrial habitats was a key event during vertebrate evolution. Occupation of low-salinity and dry environments required significant osmoregulatory adaptations enabling stable ion and water homeostasis. Sodium is one of the most important ions within the extracellular liquid of vertebrates, and molecular machinery for urinary reabsorption of this electrolyte is critical for the maintenance of body osmoregulation. Key ion channels involved in the fine-tuning of sodium homeostasis in tetrapod vertebrates are epithelial sodium channels (ENaCs), which allow the selective influx of sodium ions across the apical membrane of epithelial cells lining the distal nephron or the colon. Furthermore, ENaC-mediated sodium absorption across tetrapod lung epithelia is crucial for the control of liquid volumes lining the pulmonary surfaces. ENaCs are vertebrate-specific members of the degenerin/ENaC family of cation channels; however, there is limited knowledge on the evolution of ENaC within this ion channel family. This review outlines current concepts and hypotheses on ENaC phylogeny and discusses the emergence of regulation-defining sequence motifs in the context of osmoregulatory adaptations during tetrapod terrestrialization. In light of the distinct regulation and expression of ENaC isoforms in tetrapod vertebrates, we discuss the potential significance of ENaC orthologs in osmoregulation of fishes as well as the putative fates of atypical channel isoforms in mammals. We hypothesize that ancestral proton-sensitive ENaC orthologs might have aided the osmoregulatory adaptation to freshwater environments whereas channel regulation by proteases evolved as a molecular adaptation to lung liquid homeostasis in terrestrial tetrapods.

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Little, A. G., K. M. Kocha, S. C. Lougheed e C. D. Moyes. "Evolution of the nuclear-encoded cytochrome oxidase subunits in vertebrates". Physiological Genomics 42, n. 1 (giugno 2010): 76–84. http://dx.doi.org/10.1152/physiolgenomics.00015.2010.

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Vertebrate mitochondrial cytochrome c oxidase (COX) possesses 10 nuclear-encoded subunits. Six subunits have paralogs in mammals, but the origins and distribution of isoforms among vertebrates have not been analyzed. We used Bayesian phylogenetic analysis to interpret the origins of each subunit, inferring the roles of gene and genome duplications. The paralogous ancestries of five genes were identical throughout the major vertebrate taxa: no paralogs of COX6c and COX7c, two paralogs of COX4 and COX6a, and three paralogs of COX7a. Two genes had an extra copy in teleosts (COX5a, COX5b), and three genes had additional copies in mammals (COX6b, COX7b, COX8). Focusing on early vertebrates, we examined structural divergence and explored transcriptional profiles across zebrafish tissues. Quantitative transcript profiles revealed dramatic differences in transcript abundance for different subunits. COX7b and COX4 transcripts were typically present at very low levels, whereas COX5a and COX8 were in vast excess in all tissues. For genes with paralogs, two general patterns emerged. For COX5a and COX8, there was ubiquitous expression of one paralog, with the other paralog in lower abundance in all tissues. COX4 and COX6a shared a distinct expression pattern, with one paralog dominant in brain and gills and the other in muscles. The isoform profiles in combination with phylogenetic analyses show that vertebrate COX isoform patterns are consistent with the hypothesis that early whole genome duplications in basal vertebrates governed the isoform repertoire in modern fish and tetrapods, though more recent lineage-specific gene/genome duplications also play a role in select subunits.

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Storey, Kenneth B., e Janet M. Storey. "Molecular Physiology of Freeze Tolerance in Vertebrates". Physiological Reviews 97, n. 2 (aprile 2017): 623–65. http://dx.doi.org/10.1152/physrev.00016.2016.

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Freeze tolerance is an amazing winter survival strategy used by various amphibians and reptiles living in seasonally cold environments. These animals may spend weeks or months with up to ∼65% of their total body water frozen as extracellular ice and no physiological vital signs, and yet after thawing they return to normal life within a few hours. Two main principles of animal freeze tolerance have received much attention: the production of high concentrations of organic osmolytes (glucose, glycerol, urea among amphibians) that protect the intracellular environment, and the control of ice within the body (the first putative ice-binding protein in a frog was recently identified), but many other strategies of biochemical adaptation also contribute to freezing survival. Discussed herein are recent advances in our understanding of amphibian and reptile freeze tolerance with a focus on cell preservation strategies (chaperones, antioxidants, damage defense mechanisms), membrane transporters for water and cryoprotectants, energy metabolism, gene/protein adaptations, and the regulatory control of freeze-responsive hypometabolism at multiple levels (epigenetic regulation of DNA, microRNA action, cell signaling and transcription factor regulation, cell cycle control, and anti-apoptosis). All are providing a much more complete picture of life in the frozen state.

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Hoffmann, Else K., Ian H. Lambert e Stine F. Pedersen. "Physiology of Cell Volume Regulation in Vertebrates". Physiological Reviews 89, n. 1 (gennaio 2009): 193–277. http://dx.doi.org/10.1152/physrev.00037.2007.

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The ability to control cell volume is pivotal for cell function. Cell volume perturbation elicits a wide array of signaling events, leading to protective (e.g., cytoskeletal rearrangement) and adaptive (e.g., altered expression of osmolyte transporters and heat shock proteins) measures and, in most cases, activation of volume regulatory osmolyte transport. After acute swelling, cell volume is regulated by the process of regulatory volume decrease (RVD), which involves the activation of KCl cotransport and of channels mediating K+, Cl−, and taurine efflux. Conversely, after acute shrinkage, cell volume is regulated by the process of regulatory volume increase (RVI), which is mediated primarily by Na+/H+exchange, Na+-K+-2Cl−cotransport, and Na+channels. Here, we review in detail the current knowledge regarding the molecular identity of these transport pathways and their regulation by, e.g., membrane deformation, ionic strength, Ca2+, protein kinases and phosphatases, cytoskeletal elements, GTP binding proteins, lipid mediators, and reactive oxygen species, upon changes in cell volume. We also discuss the nature of the upstream elements in volume sensing in vertebrate organisms. Importantly, cell volume impacts on a wide array of physiological processes, including transepithelial transport; cell migration, proliferation, and death; and changes in cell volume function as specific signals regulating these processes. A discussion of this issue concludes the review.

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Barrick, Reese E. "Isotope Paleobiology of the Vertebrates: Ecology, Physiology, and Diagenesis". Paleontological Society Papers 4 (ottobre 1998): 101–37. http://dx.doi.org/10.1017/s1089332600000413.

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Isotopic studies of vertebrate material have a short history, while isotopic analyses of invertebrates originated in the 1940's. Interestingly, the driving force behind Harold Urey's desire to derive a carbonate paleotemperature scale in the 1940's and 1950's was the hope that it would solve the mystery of dinosaur extinction by demonstrating temperature changes at the K/T boundary. The most useful and commonly investigated stable isotopes for paleobiologic studies of vertebrates are carbon, nitrogen and oxygen. Oxygen is available from the inorganic bone or tooth apatite phase. Carbon is most often derived from tooth enamel carbonate or organic collagen, and nitrogen is derived from collagen. Each of these stable isotopes provides information on different aspects of an animal's biology and when combined, provide powerful analyses for ecological and evolutionary reconstructions. In the 1970's, much work was done describing the carbon and nitrogen variations in plants. This period was followed in the late 1970's and early 1980's by research on these isotopic variables in mammals (e.g., DeNiro and Epstein, 1978, 1981; Vogel, 1978; Van der Merwe, N.J., 1982). The utility of these isotopes for dietary recognition led to their extensive investigation in archeological studies. Not until the mid to late 1980's and 1990's have these isotopes been utilized in both the inorganic component of teeth and bones as well as the organic component of bones in Pleistocene and older paleobiologic studies. The 1980's also saw the emergence of research on the oxygen isotopic variations in mammals. However, the focus of isotopic studies on vertebrates was not for paleobiologic purposes, but rather, for attempts to derive paleohydrologic or paleoclimatic information from them (e.g., Longinelli, 1984; Luz et al., 1984).

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Parrizas, M., M. A. Maestro, N. Banos, I. Navarro, J. Planas e J. Gutierrez. "Insulin/IGF-I binding ratio in skeletal and cardiac muscles of vertebrates: a phylogenetic approach". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 269, n. 6 (1 dicembre 1995): R1370—R1377. http://dx.doi.org/10.1152/ajpregu.1995.269.6.r1370.

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Insulin and insulin-like growth factor (IGF-I) receptor binding and tyrosine kinase activity were characterized in cardiac and skeletal muscles of several vertebrates. Specific insulin binding per unit weight of skeletal muscle was clearly higher in pigeon and rat than in ectothermic vertebrates (32 +/- 5 and 25 +/- 2.7%/100 mg initial tissue in pigeon and rat, respectively, vs. 4.4 +/- 0.2%/100 mg in carp samples). Insulin binding clearly predominated over IGF-I binding in skeletal muscle of endotherms (IGF-I binding was 7.7 +/- 0.5%/100 mg in rat). In ectothermic vertebrates the situation was reversed, and IGF-I binding was higher than insulin binding. In cardiac muscle, specific binding of both insulin and especially IGF-I was higher than the values found in skeletal muscle of the same species (IGF-I binding was 60 +/- 4, 103 +/- 2, and 20 +/- 3%/100 mg in carp, turtle, and rat, respectively). The tyrosine kinase activity of insulin and IGF-I receptors of all species studied presented basal phosphotransferase rates (250-1,600 fmol P.micrograms protein-1.30 min-1) and percentage of stimulation (150-520%) with clear differences between species. The present data suggest that insulin and IGF-I binding to skeletal and cardiac muscles change through the vertebrate scale in both quantity and activity.

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Rayner, Jeremy M. V. "Mechanics and physiology of flight in fossil vertebrates". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 80, n. 3-4 (1989): 311–20. http://dx.doi.org/10.1017/s0263593300028753.

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ABSTRACTFlight—defined as the ability to produce useful aerodynamic forces by flapping wings—is one of the most demanding adaptations in vertebrates. The mechanical problems of flight ensure considerable external morphological homogeneity and behavioural similarity in extant fliers. Observations of the vortex wakes and wingbeat geometry of modern birds and bats confirm that the two groups are mechanically very similar, despite differences in phylogeny, anatomy and physiology. With this background it is possible to attack two problems: the evolution of flight in vertebrates, and the flight performance of extinct animals such as pterosaurs and Archaeopteryx.The origin of flight has been surrounded by considerable controversy, due in part to terminological inconsistencies, in part to phylogenetic uncertainty over the relationships of birds, bats and pterosaurs, in part to disagreement over the interpretation of the available fossil evidence, and in part to argument over the relative importance of morphological, mechanical and ecological specialisations. The mechanical changes needed in the course of the evolution of flight favour a gliding origin of tetrapod flight, and on mechanical and ecological grounds the alternative cursorial hypothesis may be discounted. This argument is particularly strong in bats, but has been thought to be weaker in birds owing to apparent inconsistencies with the fossil evidence. However, fossils of the Jurassic theropod dinosaur Archaeopteryx also support a gliding origin for flight, and suggest that this animal was adapted for flapping flight at moderately high speeds associated with gliding; it could fly less well at the slow speeds which would have been required for incipient flight in a running cursor, and at which the wingbeat is aerodynamically and kinematically considerably more complex. Slow flight in birds and bats is the more derived condition, and vertebrate flapping flight apparently evolved through a gliding stage.The pterosaurs have become the subject of much controversy over the nature of their stance, the wing surface, and the degree of involvement of the leg in the wing membrane. Reconstruction of their wings indicates proficient flying animals, and comparison with birds suggests that most pterosaurs probably occupied marine or coastal/estuarine habitat.

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Sobczak, Katja, Anne Willing, Kristina Kusche, Nadine Bangel e Wolf-Michael Weber. "Amiloride-sensitive sodium absorption is different in vertebrates and invertebrates". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 292, n. 6 (giugno 2007): R2318—R2327. http://dx.doi.org/10.1152/ajpregu.00549.2006.

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Amiloride-sensitive Na+ absorption is a well-described feature of numerous transporting epithelia in vertebrates. Yet, very little is known about this important physiological process regarding invertebrates. In the present paper, we compare vertebrate Na+ absorption mediated by the amiloride-sensitive epithelial Na+ channel (ENaC) and its invertebrate counterpart. We used the dorsal skin of the annelid Hirudo medicinalis as a model for the Na+ absorption of invertebrate epithelia. In applying electrophysiological, molecular, and biochemical techniques we found striking functional and structural differences between vertebrate and invertebrate amiloride-sensitive Na+ absorption. Using modified Ussing chambers, we analyzed the influence of different known blockers and effectors of vertebrate ENaC on leech epithelial Na+ absorption. We demonstrate that the serine protease trypsin had no effect on the Na+ transport across leech integument, while it strongly activates vertebrate ENaC. While protons, and the divalent cations Ni2+ and Zn2+ stimulate vertebrate ENaC, amiloride-sensitive Na+ currents in leech integument were substantially reduced. For molecular studies, we constructed a cDNA library of Hirudo medicinalis and screened it with specific ENaC antibodies. We performed numerous PCR approaches using a vast number of different degenerated and specific ENaC primers to identify ENaC-like structures. Yet, both strategies did not reveal any ENaC-like sequence in leech integument. From these data we conclude that amiloride-sensitive Na+ absorption in leech skin is not mediated by an ENaC-like Na+ channel but by a still unknown invertebrate member of the ENaC/DEG family that we termed lENaTP (leech epithelial Na+ transporting protein).

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Koldkjær, Pia, M. Danielle McDonald, Ian Prior e Michael Berenbrink. "Pronounced in vivo hemoglobin polymerization in red blood cells of Gulf toadfish: a general role for hemoglobin aggregation in vertebrate hemoparasite defense?" American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 305, n. 10 (15 novembre 2013): R1190—R1199. http://dx.doi.org/10.1152/ajpregu.00246.2013.

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Two human hemoglobin (Hb) variants, Hb C and Hb S, are known to protect against Plasmodium falciparum malaria and have evolved repeatedly in malaria endemic areas. Both aggregate to insoluble crystals (Hb C) or polymers (Hb S) under certain physiological conditions, impair parasite growth, and may facilitate retention of infected red blood cells (RBCs) in the spleen. Given the profound effects of parasites on host evolution in general, and that RBC Hb concentration is often close to its solubility limit throughout vertebrates, similar mechanisms may operate in nonhuman vertebrates. Here we show exercise-induced, profound in vivo Hb polymerization in RBCs of the Gulf toadfish. Hb aggregation was closely associated with the extent of plasma acidosis, fully reversible, and without any signs of hemolysis or anemia. Our literature analysis suggests that aggregation prone Hbs may be relatively old, evolved multiple times in nonhuman vertebrates, show enhanced aggregation during hemoparasite infections, and can be uncovered in vivo by splenectomy. We discuss the working hypothesis that widespread Hb aggregation within several vertebrate groups may be the result of ongoing or past selection pressure against RBC parasites. Further comparative studies of these evolutionary old systems may provide valuable insights into hemoparasite susceptibility and reservoir potential of livestock and companion animals but also into human malaria and sickle cell disease.

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Werner, Andreas, e Rolf K. H. Kinne. "Evolution of the Na-Picotransport systems". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 280, n. 2 (1 febbraio 2001): R301—R312. http://dx.doi.org/10.1152/ajpregu.2001.280.2.r301.

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Membrane transport systems for Pitransport are key elements in maintaining homeostasis of Piin organisms as diverse as bacteria and human. Two Na-Picotransporter families with well-described functional properties in vertebrates, namely NaPi-II and NaPi-III, show conserved structural features with prokaryotic origin. A clear vertical relationship can be established among the mammalian protein family NaPi-III, a homologous system in C. elegans, the yeast system Pho89, and the bacterial Pitransporter Pit. An alternative lineage connects the mammalian NaPi-II-related transporters with homologous proteins from Caenorhabditis elegans and Vibrio cholerae. The present review focuses on the molecular evolution of the NaPi-II protein family. Preliminary results indicate that the NaPi-II homologue cloned from V. cholerae is indeed a functional Pitransporter when expressed in Xenopus oocytes. The closely related NaPi-II isoforms NaPi-IIa and NaPi-IIb are responsible for regulated epithelial Na-dependent Pitransport in all vertebrates. Most species express two different NaPi-II proteins with the exception of the flounder and Xenopus laevis, which rely on only a single isoform. Using an RT-PCR-based approach with degenerate primers, we were able to identify NaPi-II-related mRNAs in a variety of vertebrates from different families. We hypothesize that the original NaPi-IIb-related gene was duplicated early in vertebrate development. The appearance of NaPi-IIa correlates with the development of the mammalian nephron.

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Shiels, Holly A., e Gina L. J. Galli. "The Sarcoplasmic Reticulum and the Evolution of the Vertebrate Heart". Physiology 29, n. 6 (novembre 2014): 456–69. http://dx.doi.org/10.1152/physiol.00015.2014.

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The sarcoplasmic reticulum (SR) is crucial for contraction and relaxation of the mammalian cardiomyocyte, but its role in other vertebrate classes is equivocal. Recent evidence suggests differences in SR function across species may have an underlying structural basis. Here, we discuss how SR recruitment relates to the structural organization of the cardiomyocyte to provide new insight into the evolution of cardiac design and function in vertebrates.

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Schwandt, Sara E., Sarath C. Peddu e Larry G. Riley. "Differential Roles for Octanoylated and Decanoylated Ghrelins in Regulating Appetite and Metabolism". International Journal of Peptides 2010 (17 marzo 2010): 1–6. http://dx.doi.org/10.1155/2010/275804.

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Since its identification in 1999, ghrelin has been identified in all vertebrate groups. The “active core” of ghrelin is highly conserved among vertebrates, suggesting its biological activity to be also conserved. In fish, both acylated forms of ghrelin have been identified; however, the ratio of the ghrelin-C8 to ghrelin-C10 is not as great as observed in mammals. In the tilapia (Oreochromis mossambicus), ghrelin-C10 is the major form of ghrelin. Since fish are known to inhabit every ecological niche on earth, studies on fish have provided valuable insight into vertebrate physiology in general; it is likely that understanding the role of both acylated forms of ghrelin, in more detail, in fish will result into novel insights in the biology of ghrelin within vertebrates. In this paper we discuss ghrelin's role in regulating appetite and metabolism in fish, in general, and provide evidence that the two tilapia ghrelins exhibit different biological roles.

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Shaffer, Justin F., e Todd E. Gillis. "Evolution of the regulatory control of vertebrate striated muscle: the roles of troponin I and myosin binding protein-C". Physiological Genomics 42, n. 3 (agosto 2010): 406–19. http://dx.doi.org/10.1152/physiolgenomics.00055.2010.

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Troponin I (TnI) and myosin binding protein-C (MyBP-C) are key regulatory proteins of contractile function in vertebrate muscle. TnI modulates the Ca2+ activation signal, while MyBP-C regulates cross-bridge cycling kinetics. In vertebrates, each protein is distributed as tissue-specific paralogs in fast skeletal (fs), slow skeletal (ss), and cardiac (c) muscles. The purpose of this study is to characterize how TnI and MyBP-C have changed during the evolution of vertebrate striated muscle and how tissue-specific paralogs have adapted to different physiological conditions. To accomplish this we have completed phylogenetic analyses using the amino acid sequences of all known TnI and MyBP-C isoforms. This includes 99 TnI sequences (fs, ss, and c) from 51 different species and 62 MyBP-C sequences from 26 species, with representatives from each vertebrate group. Results indicate that the role of protein kinase A (PKA) and protein kinase C (PKC) in regulating contractile function has changed during the evolution of vertebrate striated muscle. This is reflected in an increased number of phosphorylatable sites in cTnI and cMyBP-C in endothermic vertebrates and the loss of two PKC sites in fsTnI in a common ancestor of mammals, birds, and reptiles. In addition, we find that His132, Val134, and Asn141 in human ssTnI, previously identified as enabling contractile function during cellular acidosis, are present in all vertebrate cTnI isoforms except those from monotremes, marsupials, and eutherian mammals. This suggests that the replacement of these residues with alternative residues coincides with the evolution of endothermy in the mammalian lineage.

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Dzialowski, Edward M. "Comparative physiology of the ductus arteriosus among vertebrates". Seminars in Perinatology 42, n. 4 (giugno 2018): 203–11. http://dx.doi.org/10.1053/j.semperi.2018.05.002.

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Naftalin, R. "Comparative Physiology of the Digestive System of Vertebrates". Gut 39, n. 3 (1 settembre 1996): 498. http://dx.doi.org/10.1136/gut.39.3.498-a.

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Milsom, W. K. "Intermittent Breathing in Vertebrates". Annual Review of Physiology 53, n. 1 (ottobre 1991): 87–105. http://dx.doi.org/10.1146/annurev.ph.53.030191.000511.

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Stevens, B. R. "Vertebrate intestine apical membrane mechanisms of organic nutrient transport". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 263, n. 3 (1 settembre 1992): R458—R463. http://dx.doi.org/10.1152/ajpregu.1992.263.3.r458.

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This paper presents the current understanding of comparative vertebrate intestine basic mechanisms of brush-border membrane transport. Animals control the uptake of monosaccharides and amino acids at three levels: 1) mucosal hyperplasia increases uptake nonselectively, 2) individual enterocytes increase the transport capacity of specific transporter systems, and 3) the transporters themselves are modulated by solute and ion electrochemical gradients. In light of the current literature, This paper summarizes the kinetics, thermodynamics, and the physical arrangement of one mode of transport, the prototype Na(+)-solute cotransporter. The model presented is experimentally consistent with “preferred random” kinetics, with Na+ binding preferentially before solute at the extracellular face. In the case of glucose, the cotransporter system may be physically arranged in the membrane as a tetramer comprising 73,000 Da subunits. All vertebrates may have evolved with a similar mechanism, with particular variations reflecting selected arrangements from a pool of polypeptide sequence blocks. The same fundamental transport mechanisms may be observed in the intestines of animals ranging from lower vertebrates through humans.

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Dufour, Sylvie, Bruno Quérat, Hervé Tostivint, Catherine Pasqualini, Hubert Vaudry e Karine Rousseau. "Origin and Evolution of the Neuroendocrine Control of Reproduction in Vertebrates, With Special Focus on Genome and Gene Duplications". Physiological Reviews 100, n. 2 (1 aprile 2020): 869–943. http://dx.doi.org/10.1152/physrev.00009.2019.

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In humans, as in the other mammals, the neuroendocrine control of reproduction is ensured by the brain-pituitary gonadotropic axis. Multiple internal and environmental cues are integrated via brain neuronal networks, ultimately leading to the modulation of the activity of gonadotropin-releasing hormone (GnRH) neurons. The decapeptide GnRH is released into the hypothalamic-hypophysial portal blood system and stimulates the production of pituitary glycoprotein hormones, the two gonadotropins luteinizing hormone and follicle-stimulating hormone. A novel actor, the neuropeptide kisspeptin, acting upstream of GnRH, has attracted increasing attention in recent years. Other neuropeptides, such as gonadotropin-inhibiting hormone/RF-amide related peptide, and other members of the RF-amide peptide superfamily, as well as various nonpeptidic neuromediators such as dopamine and serotonin also provide a large panel of stimulatory or inhibitory regulators. This paper addresses the origin and evolution of the vertebrate gonadotropic axis. Brain-pituitary neuroendocrine axes are typical of vertebrates, the pituitary gland, mediator and amplifier of brain control on peripheral organs, being a vertebrate innovation. The paper reviews, from molecular and functional perspectives, the evolution across vertebrate radiation of some key actors of the vertebrate neuroendocrine control of reproduction and traces back their origin along the vertebrate lineage and in other metazoa before the emergence of vertebrates. A focus is given on how gene duplications, resulting from either local events or from whole genome duplication events, and followed by paralogous gene loss or conservation, might have shaped the evolutionary scenarios of current families of key actors of the gonadotropic axis.

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24

Morley, N. J., J. W. Lewis e D. Hoole. "Pollutant-induced effects on immunological and physiological interactions in aquatic host–trematode systems: implications for parasite transmission". Journal of Helminthology 80, n. 2 (giugno 2006): 137–49. http://dx.doi.org/10.1079/joh2006345.

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AbstractUnder conditions of pollution both host and parasite are susceptible to the pathogenic effects of toxicants, which in turn may result in detrimental changes to their immunological and physiological processes. Digenetic trematodes, which encompass species of both medical and economic importance, possess complex life cycles and are common parasites of both vertebrates and molluscs. The combined stress induced by pollution and parasitism influences the physiology of the host which can have implications not only on host survival but also on the functional biology of resident parasite populations. The present paper reviews the effects of pollutants on the immunology and physiology in both vertebrate and molluscan host–trematode systems and the implications for parasite transmission.

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25

Padian, Kevin, e Armand de Ricqlès. "Inferring the physiological regimes of extinct vertebrates: methods, limits and framework". Philosophical Transactions of the Royal Society B: Biological Sciences 375, n. 1793 (13 gennaio 2020): 20190147. http://dx.doi.org/10.1098/rstb.2019.0147.

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What can we know of the physiological regimes of ancient vertebrates? Essential to the exploration of this question are several epistemological tools: (i) a phylogenetic framework for interpreting whole animals and individual tissues, (ii) reliable knowledge of variation in populations and among climates and geographies, (iii) an understanding of phenotypic variation during ontogeny and between sexes, and (iv) a sense of the patterns of body size change, both phyletically and ontogenetically. Palaeobiologists are historically bound to a dichotomous set of terms developed long ago to describe the relatively depauperate living vertebrate fauna. This system sees only binary categories of five major groupings: the ‘cold-blooded’ fishes, amphibians, and reptiles, and the ‘warm-blooded’ birds and mammals. The integration of histoanatomical data with patterns of size, growth and phylogeny provides an opportunity to re-imagine not only vertebrate palaeophysiology, but vertebrate physiology in general. Here, we discuss how four ‘signals’ or ‘influences’ on bone tissues—phylogeny, ontogeny, mechanics and environment—can help to address these questions. This article is part of the theme issue ‘Vertebrate palaeophysiology’.

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Pugh, E. N., e W. H. Miller. "Special Topic: Phototransduction in Vertebrates". Annual Review of Physiology 49, n. 1 (marzo 1987): 711–14. http://dx.doi.org/10.1146/annurev.ph.49.030187.003431.

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27

CARROLL, ROBERT L., JASON IRWIN e DAVID M. GREEN. "Thermal physiology and the origin of terrestriality in vertebrates". Zoological Journal of the Linnean Society 143, n. 3 (marzo 2005): 345–58. http://dx.doi.org/10.1111/j.1096-3642.2005.00151.x.

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28

Burggren, W. W., e A. W. Pinder. "Ontogeny of Cardiovascular and Respiratory Physiology in Lower Vertebrates". Annual Review of Physiology 53, n. 1 (ottobre 1991): 107–35. http://dx.doi.org/10.1146/annurev.ph.53.030191.000543.

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29

Homyack, Jessica A. "Evaluating habitat quality of vertebrates using conservation physiology tools". Wildlife Research 37, n. 4 (2010): 332. http://dx.doi.org/10.1071/wr08093.

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Abstract (sommario):

Studies examining how wildlife populations perceive and respond to habitat are common, and many attempt to understand how the quality of available habitats influences population processes such as survival and recruitment. Traditional methods to estimate habitat quality (e.g. population density) have not led to great advancement in our understanding of relationships between habitat and fitness in recent years. Metrics from the discipline of conservation physiology could help researchers to address these difficulties and to meet the challenges that habitat alteration poses to biodiversity. Incorporating physiological metrics that relate energetics or environmental stress to habitats may be powerful measures of habitat quality. By quantifying field metabolic rates, body condition, or concentrations of stress hormones in individual organisms, researchers may identify mechanisms associated with habitat that underlie observed patterns in vital rates (survival and fecundity). Physiological metrics offer useful tools that may identify mechanisms of habitat quality and detect the causes of declines in biodiversity. However, integration among physiologists, ecologists and conservation biologists will require new partnerships and approaches to respond to complex ecological issues.

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30

Cabernard, Clemens, Marc Neumann e Markus Affolter. "Cellular and molecular mechanisms involved in branching morphogenesis of the Drosophila tracheal system". Journal of Applied Physiology 97, n. 6 (dicembre 2004): 2347–53. http://dx.doi.org/10.1152/japplphysiol.00435.2004.

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Recent comparative studies have shown that, in many instances, the genetic network underlying the development of distinct organ systems is similar in invertebrate and vertebrate organisms. Genetically well-characterized, simple invertebrate model systems, such as Caenorhabditis elegans and Drosophila melanogaster, can thus provide useful insight for understanding more complex organ systems in vertebrates. Here, we summarize recent progress in the genetic analysis of tracheal development in Drosophila and compare the results to studies aimed at a better understanding of lung development in mouse and man. Clearly, both striking similarities and important differences are apparent, but it might still be too early to conclude whether the former or the latter prevail.

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31

Gardner, Jacob D., Michel Laurin e Chris L. Organ. "The relationship between genome size and metabolic rate in extant vertebrates". Philosophical Transactions of the Royal Society B: Biological Sciences 375, n. 1793 (13 gennaio 2020): 20190146. http://dx.doi.org/10.1098/rstb.2019.0146.

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Genome size has long been hypothesized to affect the metabolic rate in various groups of animals. The mechanism behind this proposed association is the nucleotypic effect, in which large nucleus and cell sizes influence cellular metabolism through surface area-to-volume ratios. Here, we provide a review of the recent literature on the relationship between genome size and metabolic rate. We also conduct an analysis using phylogenetic comparative methods and a large sample of extant vertebrates. We find no evidence that the effect of genome size improves upon models in explaining metabolic rate variation. Not surprisingly, our results show a strong positive relationship between metabolic rate and body mass, as well as a substantial difference in metabolic rate between endothermic and ectothermic vertebrates, controlling for body mass. The presence of endothermy can also explain elevated rate shifts in metabolic rate whereas genome size cannot. We further find no evidence for a punctuated model of evolution for metabolic rate. Our results do not rule out the possibility that genome size affects cellular physiology in some tissues, but they are consistent with previous research suggesting little support for a direct functional connection between genome size and basal metabolic rate in extant vertebrates. This article is part of the theme issue ‘Vertebrate palaeophysiology’.

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32

Rotwein, Peter. "The insulin-like growth factor 2 gene and locus in nonmammalian vertebrates: Organizational simplicity with duplication but limited divergence in fish". Journal of Biological Chemistry 293, n. 41 (28 agosto 2018): 15912–32. http://dx.doi.org/10.1074/jbc.ra118.004861.

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The small, secreted peptide, insulin-like growth factor 2 (IGF2), is essential for fetal and prenatal growth in humans and other mammals. Human IGF2 and mouse Igf2 genes are located within a conserved linkage group and are regulated by parental imprinting, with IGF2/Igf2 being expressed from the paternally derived chromosome, and H19 from the maternal chromosome. Here, data retrieved from genomic and gene expression repositories were used to examine the Igf2 gene and locus in 8 terrestrial vertebrates, 11 ray-finned fish, and 1 lobe-finned fish representing >500 million years of evolutionary diversification. The analysis revealed that vertebrate Igf2 genes are simpler than their mammalian counterparts, having fewer exons and lacking multiple gene promoters. Igf2 genes are conserved among these species, especially in protein-coding regions, and IGF2 proteins also are conserved, although less so in fish than in terrestrial vertebrates. The Igf2 locus in terrestrial vertebrates shares additional genes with its mammalian counterparts, including tyrosine hydroxylase (Th), insulin (Ins), mitochondrial ribosomal protein L23 (Mrpl23), and troponin T3, fast skeletal type (Tnnt3), and both Th and Mrpl23 are present in the Igf2 locus in fish. Taken together, these observations support the idea that a recognizable Igf2 was present in the earliest vertebrate ancestors, but that other features developed and diversified in the gene and locus with speciation, especially in mammals. This study also highlights the need for correcting inaccuracies in genome databases to maximize our ability to accurately assess contributions of individual genes and multigene families toward evolution, physiology, and disease.

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33

Cai, Shi-Ying, Lin Wang, Nazzareno Ballatori e James L. Boyer. "Bile salt export pump is highly conserved during vertebrate evolution and its expression is inhibited by PFIC type II mutations". American Journal of Physiology-Gastrointestinal and Liver Physiology 281, n. 2 (1 agosto 2001): G316—G322. http://dx.doi.org/10.1152/ajpgi.2001.281.2.g316.

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Bile secretion is a fundamental function of the liver of all vertebrates and is generated by ATP-dependent transport proteins at the canalicular membrane of hepatocytes, particularly by the bile salt export pump BSEP. To determine the evolutionary origin and structure-function relationship of this transport mechanism, a liver cDNA library from the marine skate Raja erinacea, a 200 million-year-old vertebrate, was screened for BSEP orthologues. A full-length clone was isolated that encodes for 1,348 amino acids and shares 68.5% identity to human BSEP. Northern blot analysis revealed a 5-kb transcript only in skate liver. Expression of skate Bsep in Sf9 cells demonstrated a sixfold stimulation of ATP-dependent taurocholate transport compared with controls, with a Michaelis-Menten constant of 15 μM, which is comparable to rat Bsep. Sequences at the site of published mutations in human BSEP are also conserved in skate Bsep. When two of these mutations were introduced into the skate Bsep cDNA, this resulted in defective expression of the mutant proteins in Sf9 cells. These studies demonstrate that Bsep is a liver-specific ATP-dependent export pump that is highly conserved throughout evolution and provide insights into critical determinants for the function of this transporter in higher vertebrates.

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34

Morales, O. Y., J. M. Navarrete, I. Gracia, L. Macias, M. Rivera e F. Sanchez. "Effect of fulvic acids on the electrolytes physiology in vertebrates". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 652, n. 1 (ottobre 2011): 838–40. http://dx.doi.org/10.1016/j.nima.2010.09.055.

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35

Martinez-Conde, S., e S. L. Macknik. "Fixational eye movements across vertebrates: Comparative dynamics, physiology, and perception". Journal of Vision 8, n. 14 (1 dicembre 2008): 28. http://dx.doi.org/10.1167/8.14.28.

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36

Lomax, Jo E., Chelcie H. Eller e Ronald T. Raines. "Comparative functional analysis of ribonuclease 1 homologs: molecular insights into evolving vertebrate physiology". Biochemical Journal 474, n. 13 (21 giugno 2017): 2219–33. http://dx.doi.org/10.1042/bcj20170173.

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Pancreatic-type ribonucleases (ptRNases) comprise a class of highly conserved secretory endoribonucleases in vertebrates. The prototype of this enzyme family is ribonuclease 1 (RNase 1). Understanding the physiological roles of RNase 1 is becoming increasingly important, as engineered forms of the enzyme progress through clinical trials as chemotherapeutic agents for cancer. Here, we present an in-depth biochemical characterization of RNase 1 homologs from a broad range of mammals (human, bat, squirrel, horse, cat, mouse, and cow) and nonmammalian species (chicken, lizard, and frog). We discover that the human homolog of RNase 1 has a pH optimum for catalysis, ability to degrade double-stranded RNA, and affinity for cell-surface glycans that are distinctly higher than those of its homologs. These attributes have relevance for human health. Moreover, the functional diversification of the 10 RNase 1 homologs illuminates the regulation of extracellular RNA and other aspects of vertebrate evolution.

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37

Voitenko, L. P. "Vestibulospinal system organization in vertebrates". Neurophysiology 24, n. 2 (marzo 1992): 139–58. http://dx.doi.org/10.1007/bf01893034.

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38

WIESER, W. "Energetics of fish larvae, the smallest vertebrates". Acta Physiologica Scandinavica 154, n. 3 (luglio 1995): 279–90. http://dx.doi.org/10.1111/j.1748-1716.1995.tb09912.x.

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39

Catterall, W. A. "Genetic Analysis of Ion Channels in Vertebrates". Annual Review of Physiology 50, n. 1 (ottobre 1988): 395–406. http://dx.doi.org/10.1146/annurev.ph.50.030188.002143.

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40

Danks, JA, MK Trivett, DM Power, AVM Canario, TJ Martin e PM Ingleton. "PARATHYROID HORMONE-RELATED PROTEIN IN LOWER VERTEBRATES". Clinical and Experimental Pharmacology and Physiology 25, n. 9 (settembre 1998): 750–52. http://dx.doi.org/10.1111/j.1440-1681.1998.tb02290.x.

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41

Muller, M., e K. Heeck. "Why vertebrates have semicircular ducts". Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology 150, n. 3 (luglio 2008): S101. http://dx.doi.org/10.1016/j.cbpa.2008.04.205.

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42

Weber, Roy E., Wolfgang Voelter, Angela Fago, Hartmut Echner, Estela Campanella e Philip S. Low. "Modulation of red cell glycolysis: interactions between vertebrate hemoglobins and cytoplasmic domains of band 3 red cell membrane proteins". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 287, n. 2 (agosto 2004): R454—R464. http://dx.doi.org/10.1152/ajpregu.00060.2004.

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Several vital functions/physical characteristics of erythrocytes (including glycolysis, the pentose phosphate pathway, ion fluxes, and cellular deformability) display dependence on the state of hemoglobin oxygenation. The molecular mechanism proposed involves an interaction between deoxyhemoglobin and the cytoplasmic domain of the anion-exchange protein, band 3 (cdB3). Given that band 3 also binds to membrane proteins 4.1 and 4.2, several kinases, hemichromes, and integral membrane proteins, and at least three glycolytic enzymes, it has been suggested that the cdB3-deoxyhemoglobin interaction might modulate the pathways mediated by these associated proteins in an O2-dependent manner. We have investigated this mechanism by synthesizing 10-mer peptides corresponding to the NH2-terminal fragments of various vertebrate cdB3s, determining their effects on the oxygenation reactions of hemoglobins from the same and different species and examining binding of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase to the erythrocytic membrane of mouse erythrocytes. The cdB3 interaction is strongly dependent on pH and the number of negative and positive charges of the peptide and at the effector binding site, respectively. It lowers the O2association equilibrium constant of the deoxygenated (Tense) state of the hemoglobin and is inhibited by magnesium ions, which neutralize cdB3's charge and by 2,3-diphosphoglycerate, which competes for the cdB3-binding site. The interaction is stronger in humans (whose erythrocytes derive energy predominantly from glycolysis and exhibit higher buffering capacity) than in birds and ectothermic vertebrates (whose erythrocytes metabolize aerobically and are poorly buffered) and is insignificant in fish, suggesting that its role in the regulation of red cell glycolysis increased with phylogenetic development in vertebrates.

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43

Nieder, Andreas. "Interrelation of kinetic and stereoscopic depth: behavior and physiology in vertebrates". Behavioural Processes 64, n. 1 (agosto 2003): 13–16. http://dx.doi.org/10.1016/s0376-6357(03)00055-x.

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Stark, Heiko, e Stefan Schuster. "Comparison of various approaches to calculating the optimal hematocrit in vertebrates". Journal of Applied Physiology 113, n. 3 (1 agosto 2012): 355–67. http://dx.doi.org/10.1152/japplphysiol.00369.2012.

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Abstract (sommario):

An interesting problem in hemorheology is to calculate that volume fraction of erythrocytes (hematocrit) that is optimal for transporting a maximum amount of oxygen. If the hematocrit is too low, too few erythrocytes are present to transport oxygen. If it is too high, the blood is very viscous and cannot flow quickly, so that oxygen supply to the tissues is again reduced. These considerations are very important, since oxygen transport is an important factor for physical performance. Here, we derive theoretical optimal values of hematocrit in vertebrates and collect, from the literature, experimentally observed values for 57 animal species. It is an interesting question whether optimal hematocrit theory allows one to calculate hematocrit values that are in agreement with the observed values in various vertebrate species. For this, we first briefly review previous approaches in that theory. Then we check which empirical or theoretically derived formulas describing the dependence of viscosity on concentration in a suspension lead to the best agreement between the theoretical and observed values. We consider both spatially homogeneous and heterogeneous distributions of erythrocytes in the blood and also possible extensions, like the influence of defective erythrocytes and cases where some substances are transported in the plasma. By discussing the results, we critically assess the power and limitations of optimal hematocrit theory. One of our goals is to provide a systematic overview of different approaches in optimal hematocrit theory.

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45

Karasov, William H., Duong Phan, Jared M. Diamond e F. Lynn Carpenter. "Food Passage and Intestinal Nutrient Absorption in Hummingbirds". Auk 103, n. 3 (1 luglio 1986): 453–64. http://dx.doi.org/10.1093/auk/103.3.453.

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Abstract We studied adaptations of digestive physiology that permit Rufous (Selasphorus rufus) and Anna's hummingbirds (Calypte anna) to absorb sugar-water meals rapidly and efficiently. As measured with soluble markers, transit times (<15 min) and mean retention times (ca. 48 min) of meals in the hummingbird digestive tract are brief compared with values for most other vertebrates. Glucose is extracted with an efficiency of 97%. We describe a new method, employing double isotope dilution, for measuring crop-emptying kinetics. Based on this method, the crop empties half of a meal in ca. 4 min and all of the meal in 15-20 min. Rufous and Anna's hummingbirds may be energy maximizers limited by crop emptying times, rather than foraging-time minimizers. This would explain why hummingbirds spend a majority of each hour sitting rather than feeding. The intestine's passive permeability to glucose is the lowest of any vertebrate studied to date. This may be an adaptation to prevent solute loss from the blood in the face of high fluid transit rates through the intestine. Active transport accounts for essentially all intestinal glucose absorption. Compared with intestines of other vertebrates, the glucose absorption sites of hummingbird intestines have normal binding constants but are present at extremely high densities. Comparisons of hummingbirds, chickens, and shrikes suggest that intestinal absorption rates for amino acids are independent of trophic habits in birds as in other vertebrate classes, but that sugar absorption decreases in the sequence herbivore > omnivore > carnivore.

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Gillis, G., e G. Lauder. "Kinematics of feeding in bluegill sunfish: is there a general distinction between aquatic capture and transport behaviors?" Journal of Experimental Biology 198, n. 3 (1 marzo 1995): 709–20. http://dx.doi.org/10.1242/jeb.198.3.709.

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Despite numerous studies of food transport in terrestrial vertebrates, little is known about this aspect of the feeding repertoire in aquatic vertebrates. Previous work had predicted that the kinematics of aquatic prey capture by suction feeding should be similar to those of prey transport. However, recent analyses of aquatic prey capture and transport in the tiger salamander Ambystoma tigrinum have contradicted this hypothesis, and document numerous differences between these two behaviors. In this study, using high-speed video and statistical analyses, we compare prey capture and transport kinematics in a ray-finned fish (Lepomis macrochirus, the bluegill sunfish) to examine the generality of differences between capture and transport behaviors in aquatic vertebrates. Compared with prey capture, prey transport is significantly more rapid and tends to have reduced lower jaw excursions, while having similar hyoid movements. A nested analysis of variance was used to analyze six variables common to both this analysis of Lepomis macrochirus and a previous study of Ambystoma tigrinum; none of these six variables showed significant variation between taxa. These results indicate that aquatic prey transport is kinematically distinct from capture behavior and that the distinctions between these two behaviors are remarkably consistent in two phylogenetically divergent lower vertebrate taxa. Such consistent kinematic differences have not been found in amniote taxa studied to date, but may constitute a plesiomorphic feature of vertebrate feeding systems.

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Calder, W. A. "Scaling Energetics of Homeothermic Vertebrates: an Operational Allometry". Annual Review of Physiology 49, n. 1 (marzo 1987): 107–20. http://dx.doi.org/10.1146/annurev.ph.49.030187.000543.

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48

Gluck, S. "V-ATPases of the plasma membrane." Journal of Experimental Biology 172, n. 1 (1 novembre 1992): 29–37. http://dx.doi.org/10.1242/jeb.172.1.29.

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V-ATPases reside in high densities on the plasma membrane in specialized types of insect and vertebrate cells. They provide unique biochemical and electrophysiological properties that allow them to function in energizing the plasma membrane in insects, and in cellular acid excretion in vertebrates.

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Campbell, Scott S., Patricia J. Murphy e Andrea G. Suhner. "EXTRAOCULAR PHOTOTRANSDUCTION AND CIRCADIAN TIMING SYSTEMS IN VERTEBRATES". Chronobiology International 18, n. 2 (gennaio 2001): 137–72. http://dx.doi.org/10.1081/cbi-100103183.

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Bertolucci, Cristiano, e Augusto Foà. "Extraocular Photoreception and Circadian Entrainment in Nonmammalian Vertebrates". Chronobiology International 21, n. 4-5 (gennaio 2004): 501–19. http://dx.doi.org/10.1081/cbi-120039813.

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