Comparison of the respiratory transition at birth or hatching in viviparous and oviparous amniote vertebrates.

Regardless of the mode of reproduction, three things must occur at birth or hatching in amniote vertebrates: initiation of breathing, pulmonary fluid elimination and reabsorption, and adequate perfusion of pulmonary circulation. Although data on these events are few, there appears to be no fundamental difference in them that can be associated with the oviparity to viviparity transition. There are, however, differences in the timing of these events in oviparous and viviparous amniotes. The transition to neonatal respiration tends to be very quick in viviparous species because the vascular support for oxygen uptake provided by the mother is rapidly disassociated from the mechanism for uptake by the embryo. By contrast, hatching often is a slow process, taking 24 h or more in some species, as chorioallantoic blood flow slowly gives way to clearing of the lungs and pulmonary gas exchange. Little is known of the mechanisms of pulmonary fluid elimination and reabsorption or lung inflation in reptiles, but the cellular structures and surfactant systems are similar in all amniote vertebrates. Nevertheless, there are differences, particularly of timing and maturation of various systems, but there has been no exploration of the functional (or phylogenetic) bases of these differences. Perfusion of the neonatal pulmonary system to support respiration in reptiles remains to be investigated. In mammals and birds, closure of the ductus arteriosus is important, but the role played by the ductus arterioisus in reptilian hatching or birth is not known.     

Lipids of the eggs and neonates of oviparous and viviparous lizards

The purpose of this article is to collate the compositional data for the lipids of the eggs and neonates of ten species of lizards displaying a range of parity modes, to highlight emergent trends and to identify some of the physiological changes central to the evolution of viviparity. The eggs of oviparous species and of viviparous species with a simple (type I) placenta are characterised by very high proportions of triacylglycerol which forms over 80% (wt. /wt.) of the total yolk lipid. The eggs of viviparous species with complex (types II and III) placentae contain lower proportions of triacylglycerol (about 70% of total yolk lipid) and commensurately greater proportions of phospholipid, cholesteryl ester and free cholesterol. The fatty acid compositions of the yolk lipids are very similar for all the lizard species, irrespective of parity mode; in particular, the proportions of docosahexaenoic acid are consistently low. For all the species, the proportions of both docosahexaenoic and arachidonic acids are higher in the phospholipid of the neonate compared with the egg. The difference between the lipid contents of the eggs and the neonates indicates that, in species of Pseudemoia which have a complex (type III) placenta, more than 50% of the total lipid supplied to the embryo is derived from placental transport.     

Comparison of ovarian functions for keeping embryos by measurement of dissolved oxygen concentrations in ovaries of copulatory and non-copulatory oviparous fishes and viviparous fishes

To investigate causes of anomalous development of embryos facultatively fertilized in the ovary of a non-copulatory oviparous fish Hemilepidotus gilberti (Scorpaeniformes: Cottdae), dissolved oxygen (DO) concentrations were measured in ovaries of copulatory oviparous (Alcichthys alcicornis, Bero elegans), non-copulatory oviparous (H. gilberti, Hexagrammus otakii), and viviparous (Sebastes taczanowskii, Zoarces elongatus) fishes. DO concentrations changed during vitellogenesis and ovulation cycles, and also before and after ovulation. DO concentrations in the ovary of H. gilberti and H. otakii at ovulation were 0.27±0.03 and 0.15±0.03 mg O₂ l⁻¹, respectively, whereas in A. alcicornis and B. elegans, the concentrations were 0.47±0.08 and 0.20±0.06 mg O₂ l⁻¹, respectively. In the ovaries of intralumenal gestation viviparous fishes, S. taczanowskii and Z. elongatus, DO concentration was from 0.01 to 0.11 mg O₂ l⁻¹. The average DO concentration during the artificial pregnancy of A. alcicornis was 0.97±0.19 mg O₂ l⁻¹, but all embryos showed deformity. DO concentrations recorded in oviparous fishes in this study were lower than the oxygen level at which most oviparous fish embryos exhibit retardation or death, and it probably caused the anomalous embryonic development. In contrast, the normal development of viviparous fish embryos at low oxygen level was attributed to the specialized structure of ovary, e.g. the dual arterial system to supply the developing embryos with the respiratory demands in Sebastes.     

Microanatomy of the amniote femur and inference of lifestyle in limbed vertebrates

The femoral microanatomy of 155 species of extant amniotes (57 species of mammals, 15 species of turtles, 56 species of lepidosaurs, and 27 species of birds) of known lifestyle is studied to demonstrate a possible link between some basic parameters of bone structure and specific lifestyles, as well as phylogenetic relationships between taxa. Squared change parsimony with random taxon reshuffling and pairwise comparisons reveal that most compactness and size parameters exhibit both phylogenetic and ecological signals. A discriminant analysis produces several inference models, including a ternary model (aquatic, amphibious, terrestrial) that yield the correct lifestyle in 88% of the cases. These models are used to infer the lifestyle of three extinct Permian temnospondyls: Eryops megacephalus, Acheloma dunni, and Trimerorhachis insignis. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 644–655.     

Comparative ultrastructural investigations of the uterine epithelium in the viviparous Salamandra atra Laur. and the ovoviviparous Salamandra salamandra (L.) (Amphibia,Urodela)

The uterine epithelium of the viviparous Salamandra atra and the ovoviviparous Salamandra salamandra was studied in non pregnant and ovulating females and in females during different stages of pregnancy. The epithelium of both species is organized in a monolayer. The epithelial cells are characterized by a moderate secretory activity, a variable amount of apical granules which include PAS-positive material and by some apical and basal exo- or endocytotic vesicles. Adjacent cells are joined by junctional complexes. The lateral surfaces form a tortuous boundary with adjoining cells which suggest that the epithelium is involved in transport. Sporadic light cells possess highly variable cytoplasmic inclusions and are not joined with neighbouring cells. Possibly they represent migratory cells. The entire epithelium, except for a small cranial portion of the uterus in S. atra, undergoes no remarkable morphological changes during the different physiological stages examined except that flattened cells seem to be more numerous in pregnant females. The results are discussed with regard to the possible supply of the developing young by the mother.     

The effect of ambient temperature on the relationship between ventilation and metabolism in a small parrot (Agapornis roseicollis)

Summary Values for basal metabolism, standard tidal volume (V _T), standard minute volume ( ), and mean extraction efficiency (EO₂) in the thermal neutral zone (TNZ) inAgapornis roseicollis (1.84 ml·min^–1; 0.95 ml·br^–1, STPD; and 33.3 ml·min^–1, STPD; and 22.5%; respectively) were all very similar to values for these parameters previously measured inBolborhynchus lineola, a similarly sized, closely related species from a distinctly different habitat.Having both a lower critical temperature (T_lc) below and an upper critical temperature (T_uc) above those ofB. lineola, the TNZ ofA. roseicollis extended from 25° to at least 35°C. The thermal conductance below the TNZ ofA. roseicollis was 14% less than that ofB. lineola. Therefore, at 5°C the standard metabolic rate (SMR) of the former is 17% less than that of the latter, and at 35°C it is 20% less. At 5°CA. roseicollis has a lower EO₂ and at 35°C a higher EO₂ than that ofB. lineola. The patterns of resting energy metabolism and of ventilation ofA. roseicollis and ofB. lineola are consistent with the former species being better suited to living in a more variable thermal environment than the latter.MeanV _T has a weak positive correlation with the rate of oxygen consumption ( ) at a constant ambient temperature (T _a) but a much stronger correlation when resting increases in response to a decrease inT _a.V _t is the only ventilatory parameter which is linearly correlated toT _a from 35° to –25°C. The data suggest thatT _a may have a regulatory effect onV _T somewhat independent of or .     

Thermoregulatory and respiratory responses in asthmatic and nonasthmatic subjects breathing cold and warm air during exercise in the cold

1.

The effects of whole-body exposure to ambient temperature of −15 °C on thermoregulatory and respiratory responses in asthmatic and nonasthmatic subjects were investigated. The subjects were exposed to inhalation of cold dry and warm humid air during 30 min submaximal exercise.     

Development of the uterine shell glands during the preovulatory and early gestation periods in oviparous and viviparous Lacerta vivipara

The evolutionary process leading to the emergence of viviparity in Squamata consists of lengthening the period of egg retention in utero coupled with marked reduction in the thickness of the eggshell. We used light microscopy and scanning electron microscopy to study uterine structure during the reproductive cycle of oviparous and viviparous females of the reproductively bimodal Lacerta vivipara. We compared the structure of the uterine shell glands, which secrete components of the eggshell, during preovulatory and early gestation phases of the reproductive cycle and also compared histochemistry of the eggshells. The uterine glands of both reproductive forms undergo considerable growth within a period of a few weeks during folliculogenesis and vitellogenesis preceding ovulation. The majority of the proteinaceous fibers of the shell membrane are secreted early in embryonic development and the uterine glands regress shortly thereafter. This supports previous observations indicating that, in Squamata, secretion of the shell membrane occurs very rapidly after ovulation. The most striking differences between reproductive modes were larger uterine glands at late vitellogenesis in oviparous females, 101 microm compared to 60 microm in viviparous females, and greater thickness of the shell membrane during early gestation in oviparous females (52-73 microm) compared to viviparous females (4-8 microm). Our intraspecific comparison supports the conclusions of previous studies that, prior to ovulation, the uterine glandular layer is less developed in viviparous than in oviparous species, and that this is the main factor accounting for differences in the thickness of the shell membrane of the two reproductive forms of squamates.     

Reproductive isolation between oviparous and viviparous lineages of the Eurasian common lizard Zootoca vivipara in a contact zone

Contact zones between two evolutionary lineages are often useful for understanding the process of speciation because the observed genetic pattern reflects the history of differentiation. The Eurasian lacertid lizard Zootoca vivipara is a potentially interesting model for studying the role of reproductive mode in the speciation of squamate reptiles because it has both oviparous (Zootoca vivipara carniolica) and viviparous (Zootoca vivipara vivipara) populations that have recently been shown to be genetically distinct. We studied a newly‐discovered syntopic area of these two Zootoca subspecies in the central Italian Alps using genetic markers to investigate the level of introgression between them. Patterns of genetic differentiation in a fragment of the mitochondrial DNA cytb gene and a set of nuclear microsatellites show that the speciation process is complete in this area, with no evidence of recent introgression. Phylogenetic and genotypic divergence suggests that the two subspecies have experienced long independent evolutionary histories, during which genetic and phenotypic differences evolved. The possible roles of biogeography, reproductive mode, and cytogenetic differentiation in this speciation process are discussed. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 566–573.     

Hyperpnoea and CO2 sensitivity of the respiratory centres during exercise

The aim of this study was to specify whether exercise hyperpnoea was related to the CO2 sensitivity of the respiratory centres measured during steady-state exercise of mild intensity. Thus, ventilation (VE), breathing pattern [tidal volume (VT), respiratory frequency (f), inspiratory time (TI), total time of the respiratory cycle (TTOT), VT/TI, TI/TTOT] and CO2 sensitivity of the respiratory centres determined by the rebreathing method were measured at rest (SCO2re) and during steady-state exercise (SCO2ex) of mild intensity [CO2 output (VCO2) = 20 ml.kg-1.min-1] in 11 sedentary male subjects (aged 20-34 years). The results showed that SCO2re and SCO2ex were not significantly different. During exercise, there was no correlation between VE and SCO2ex and, for the same VCO2, all subjects had very close VE values normalized for body mass (bm), regardless of their SCO2ex (VEbm0.75 = 1.44 l.min-1.kg-1 SD 0.10). A highly significant positive correlation between SCO2ex and VT (normalised for bm) (r = 0.80, P less than 0.01), TI (r = 0.77, P less than 0.01) and TTOT (r = 0.77, P less than 0.01) existed, as well as a highly significant negative correlation between SCO2ex and (normalised for bm-0.25) (r = -0.73, P less than 0.01). We conclude that the hyperpnoea during steady-state exercise of mild intensity is not related to the SCO2ex. The relationship between breathing pattern and SCO2ex suggests that the breathing pattern could influence the determination of the SCO2ex. This finding needs further investigation.     

Respiratory and hematological responses of the bonnethead shark, Sphyrna tiburo, to acute changes in dissolved oxygen

Behavioral and physiological responses to acute changes in dissolved oxygen were examined in the bonnethead shark, Sphyrna tiburo. In two sets of respirometry experiments, sharks were randomly exposed to seawater in oxygen contents of 6.0, 5.0, 4.0 and 3.0 mg l⁻¹. During exposure, bonnetheads increased mouth gape from 0.8 cm at 6.0 mg l⁻¹ to 2.2 cm at 3.0 mg l⁻¹, while ventilation volume increased from 0.61 to 5.28 l min⁻¹ kg⁻¹. Standard oxygen consumption remained unchanged (163-181 mg O₂ kg⁻¹ h⁻¹) throughout all treatments and was not significantly different. Utilization (%) declined from 52.3% at 6.0 mg l⁻¹ to 21.3% when oxygen levels reached 3.0 mg l⁻¹. Changes in oxygen content of ambient water also caused no significant change in either blood oxygen content or hematocrit. Using cellulose acetate electrophoresis, a single hemoglobin profile was identified at seawater of 6.0 mg l⁻¹ and hypoxic conditions. Results suggest bonnetheads are physiologically able to tolerate moderate levels of hypoxia.     

Fundamentals of viviparity: comparison of seasonal changes in the uterine epithelium of oviparous and viviparous Lerista bougainvillii (Squamata: Scincidae)

Distinct differences in epithelial response between oviparous and viviparous species of skinks led us to investigate morphological differences in the uterus of a species that exhibits bi-modal reproduction and that may indicate specialities for the different requirements of viviparity and oviparity. The uteri of females from oviparous and viviparous populations of the Australian scincid lizard, Lerista bougainvillii, are described in detail to determine whether the occurrence of uterodomes and the plasma membrane transformation, found in other viviparous species but not oviparous species, are indeed features characteristic of viviparity. Oviductal tissue was dissected at three different stages of reproduction from lizards from both populations: 1) vitellogenic, 2) gravid or pregnant, and 3) non-reproductive or quiescent. Tissue was observed using both scanning and transmission electron microscopy. Lerista bougainvillii has a simple placental morphology with simple squamous epithelium. In contrast to mammals and other viviparous skinks, L. bougainvillii does not undergo a plasma membrane transformation, but early signs of placentation in viviparous individuals are indicated by changes in the uterine surface that occur largely after embryonic stage 30. There are no obvious cellular differences between the uteri of oviparous and viviparous L. bougainvillii at the non-reproductive and vitellogenic phase of the reproductive cycle but throughout gestation/gravidity, the cellular differences that could be related to the changing functional requirements with the retention of the viviparous embryo, became apparent. A plasma membrane transformation with ensuing uterodome formation does not occur, which suggests that these more sophisticated changes are a feature of advanced placental development in reptiles.     

Distribution and immunochemical character of neurotensin-like material in representative vertebrates and invertebrates: Apparent conservation of the COOH-terminal region during evolution

Using a radioimmunoassay for bovine neurotensin (NT) and various region specific antisera which react selectively with different portions of the molecule, the presence of immunoreactive NT (iNT) in a wide range of vertebrate and invertebrate species has been demonstrated. While antisera directed towards the N-terminal region of NT recognized only mammalian forms of NT, antisera directed towards the C-terminal region of NT recognized materials from all species examined, including representatives of all vertebrates and invertebrate classes. When extracts of the brain and gut of the vertebrates examined were chromatographed on Sephadex G-25 multiple NT-like substances were observed, and the patterns of iNT obtained seemed to fall into three groups: (a) mammals, (b) birds and reptiles and (c) amphibians and fish. Extracts of invertebrates also exhibited multiple peaks of iNT on Sephadex G-25 and the profiles observed resembled those for lower vertebrates. Partially purified iNT obtained from chicken, turtle, dogfish and lobster was shown to increase hematocrit and induce cyanosis in anesthetized rats. These findings indicate (a) that NT-like substances appear to be present throughout the animal kingdom, (b) that the C-terminal region of NT is highly conserved while the N-terminal region varies, and (c) that in any one animal multiple substances sharing C-terminal homologies with NT exist. These findings are consistent with the notion that NT and related peptides participate in important processes basic to animal life and that their functioning depends highly upon elements located in their C-terminal regions. They further suggest the existence of an entire family of NT-related peptides in each animal form, possibly distributed differently and functioning differently in the various organs of the animal.     

Bioinformatic analysis of the origin, sequence and diversification of mu opioid receptors in vertebrates

Opioid receptors are a class of G protein-coupled receptors that mediate the effects of the different families of endogenous opioid peptides and natural alkaloid drugs such as morphine and its synthetic derivatives. In particular, the μ opioid receptor (MOR) represents the principal molecular target for morphine and it plays key roles in opioid analgesia and addiction. In this work, new putative MORs from different vertebrate species were identified in silico and their gene organization and predicted protein products are compared with the previously characterized MORs. Also, for the first time a new genomic organization in euteleleostei teleosts has been identified. Moreover, we suggest that MORs may be specific to craniate lineage. The analysis of functional mapping of MORs we present is an important contribution to the identification of their evolutionarily conserved regions.     

Gene and genome duplications in vertebrates: the one-to-four (-to-eight in fish) rule and the evolution of novel gene functions

One important mechanism for functional innovation during evolution is the duplication of genes and entire genomes. Evidence is accumulating that during the evolution of vertebrates from early deuterostome ancestors entire genomes were duplicated through two rounds of duplications (the 'one-to-two-to-four' rule). The first genome duplication in chordate evolution might predate the Cambrian explosion. The second genome duplication possibly dates back to the early Devonian. Recent data suggest that later in the Devonian, the fish genome was duplicated for a third time to produce up to eight copies of the original deuterostome genome. This last duplication took place after the two major radiations of jawed vertebrate life, the ray-finned fish (Actinopterygia) and the sarcopterygian lineage, diverged. Therefore the sarcopterygian fish, which includes the coelacanth, lungfish and all land vertebrates such as amphibians, reptiles, birds and mammals, tend to have only half the number of genes compared with actinopterygian fish. Although many duplicated genes turned into pseudogenes, or even 'junk' DNA, many others evolved new functions particularly during development. The increased genetic complexity of fish might reflect their evolutionary success and diversity.     

Comparison of marker models for the analysis of the volume variation and thoracoabdominal motion pattern in untrained and trained participants

Respiratory assessment and the biomechanical analysis of chest and abdomen motion during breathing can be carried out using motion capture systems. An advantage of this methodology is that it allows analysis of compartmental breathing volumes, thoraco-abdominal patterns, percentage contribution of each compartment and the coordination between compartments. In the literature, mainly, two marker models are reported, a full marker model of 89 markers placed on the trunk and a reduced marker model with 32 markers. However, in practice, positioning and post-process a large number of markers on the trunk can be time-consuming. In this study, the full marker model was compared against the one that uses a reduced number of markers, in order to evaluate (i) their capability to obtain respiratory parameters (breath-by-breath tidal volumes) and thoracoabdominal motion pattern (compartmental percentage contributions, and coordination between compartments) during quiet breathing, and (ii) their response in different groups such as trained and untrained, male and female.Although tests revealed strong correlations of the tidal volume values in all the groups (R² > 0.93), the reduced model underestimated the trunk volume compared with the 89 marker model. The highest underestimation was found in trained males (bias of 0.43 L). The three-way ANOVA test showed that the model did not influence the evaluation of compartmental contributions and the 32 marker model was adequate to distinguish thoracoabdominal breathing pattern in the studied groups.Our findings showed that the reduced marker model could be used to analyse the thoracoabdominal motion in both trained and untrained populations but performs poorly in estimating tidal volume.     

Effects of atropine and propranolol on the respiratory, circulatory, and ECG responses to high altitude in man

In order to analyze the respiratory, cardiovascular, and ECG responses to acute hypoxic hypoxia, three experimental series were carried out in a randomized manner on 11 healthy, unacclimatized volunteers at rest during standardized stepwise exposure to 6000 m (PAO2 35.2 +/- 2.9 mmHg/4.7 +/- 0.4 kPa) in a low-pressure chamber a) without (control), b) with propranolol, and c) with atropine combined with propranolol. The results show that hypoxic hyperventilation and alveolar gases are not affected by activation of the sympatho-adrenal axis or by parasympathetic withdrawal. Sympathetic activity, however, increases heart rate, stroke volume (pulse pressure), estimated cardiac output and systolic blood pressure, whereas decreased parasympathetic activity increases heart rate and estimated cardiac output, but lowers stroke volume. The fall in peripheral resistance, observed during progressive hypoxia in all three groups, is thought to be due to hypoxia-induced depression of the vasomotor center. At altitude catecholamine secretion and vagal withdrawal synergistically account in the ECG for the R-R shortening, the relative Q-T lengthening, the elevation of the P wave and the ST-T flattening. Probable direct hypoxic effects on the heart are the increase in P-Q duration and the minor but still significant depression of the T wave. It is concluded that at altitude increased sympatho-adrenal and decreased parasympathetic activity is without effect on hypoxic hyperventilation, but accounts for most of the cardiovascular and ECG changes. Diminution of sympathetic activity and imminent vagotonia arising after acute ascent to 6000 m probably reflect hypoxia of the central nervous system.     

Delineation of the conserved functional properties of D1A, D1B and D1C dopamine receptor subtypes in vertebrates

The three main subtypes of dopamine D(1) receptor (D(1A), D(1B) and D(1C)) subtypes found in most vertebrate groups were generated by two major steps of gene duplications, early in evolution. To identify the functional characteristics contributing to conservation of these paralogous D(1) receptors in vertebrates, the pharmacological and functional properties of fish (Anguilla anguilla), amphibian (Xenopus laevis) and human receptors were systematically analysed in transfected cells. The ligand-binding parameters appeared essentially similar for orthologous receptors, but differed significantly among the subtypes. The D(1A) receptors from the three species displayed low intrinsic activity and a fast rate of agonist-induced desensitization. All the orthologous D(1B) receptors exhibited a similar desensitization time-course, but with smaller amplitude of decrease than D(1A) receptors, in agreement with their higher basal activity. In contrast, D(1C) receptors, which do not exist in mammals, have low intrinsic activity and exhibit only weak, but rapid, agonist-induced desensitization, without any changes upon longer treatment with agonist. Thus, each of the three D(1) receptor subtypes are characterized by activation and desensitization properties, in a sequence-specific manner, which has been probably acquired early after gene duplications, and constrained their conservation during vertebrate evolution. These properties have been instrumental to adapt dopamine system to the physiology of the numerous neuronal networks and functions they control in the large and complex brains of vertebrates.     

Deletion of STK40 Protein in Mice Causes Respiratory Failure and Death at Birth

STK40 is a putative serine/threonine kinase and was shown to induce extraembryonic endoderm differentiation from mouse embryonic stem cells. However, little is known about its physiological function in vivo. Here, we generate Stk40 knock-out mice and demonstrate that loss of the Stk40 gene causes neonatal lethality at birth. Further examination reveals that the respiratory distress and atelectasis occur in the homozygous mutants. The maturation of lung and alveolar epithelium is delayed in the mutant, as indicated by narrowed air spaces, thickened interstitial septa, and increased glycogen content in the lungs of Stk40^−/− mice. The reduction in levels of T1-α, SP-B, and SP-C indicates delayed maturation of both type I and type II respiratory epithelial cells in Stk40^−/− lungs. Moreover, Stk40 is found to be most highly expressed in lungs of both fetal and adult mice among all organs tested. Mechanistically, a genome-wide RNA microarray analysis reveals significantly altered expression of multiple genes known to participate in lung development. The expression of some genes involved in lipid metabolism, immune response, and glycogen metabolism is also disrupted in the lung of Stk40^−/− mice. Protein affinity purification identifies RCN2, an activator of ERK/MAPK signaling, as an STK40-associated protein. Consistently, Stk40 deficiency attenuates the ERK/MAPK activation, and inhibition of ERK/MAPK activities reduces surfactant protein gene expression in lung epithelial cells. Collectively, this study uncovers an important role of STK40 for lung maturation and neonatal survival. STK40 may associate with RCN2 to activate ERK/MAPK signaling and control the expression of multiple key regulators of lung development.     

Egg-cases and size at hatching of Sympterygia acuta in the south-western Atlantic

Ten egg-cases of Sympterygia acuta were collected from the surf line at Cassino Beach, Rio Grande do Sul, Brazil, and incubated in the laboratory. The egg-cases and neonates (77–84 mm total length) are described.