Microscopic anatomy of the pulmonary vascular bed in the cat lung

The pulmonary microcirculation of the cat was analyzed by light and electron microscopy. In order to establish the precise structure and ultrastructure of the components of the vascular wall of each segment, special efforts were made to identify positively the pulmonary arterioles and venules by tracing their connection to small pulmonary arteries and veins, respectively. Also, the pulmonary arterioles and venules were studied with respect to their relationship to the alveolar capillary network via the precapillary sphincter areas and the postcapillary venules. It was confirmed that the small pulmonary arteries, arterioles, and precapillary sphincter areas are provided with smooth muscle cells which are present up to the point where the pulmonary capillaries branch out, although the number of smooth muscle cells decreases gradually toward the capillary bed. Cholinergic and noradrenergic nerves accompany all arterial segments. The capillary network described by many investigators in several mammalian species was studied only to the extent that a three-dimensional conceptualization could be obtained. With respect to the postcapillary venules and pulmonary venules, it was discovered that, in the cat lung, true smooth muscle cells, albeit widely scattered, are present in these segments of the pulmonary microcirculation. These smooth muscle cells display extensive areas of myoendothelial junctions. That is, the cell membranes of the endothelial cells and the smooth muscle cells make contact without an intervening basal lamina. Some myoendothelial junctions were identified also in the arterioles and precapillary sphincter areas. However, they were few in number and had points of only limited membrane contact. The functional implications of these findings are discussed in terms of possible regulatory influence on the pulmonary microcirculation and hypothetical role in the development of pulmonary hypertension.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22645/1/0000196.pd

A global reptile assessment highlights shared conservation needs of tetrapods

Comprehensive assessments of species? extinction risks have documented the extinction crisis1 and underpinned strategies for reducing those risks2. Global assessments reveal that, among tetrapods, 40.7% of amphibians, 25.4% of mammals and 13.6% of birds are threatened with extinction3. Because global assessments have been lacking, reptiles have been omitted from conservation-prioritization analyses that encompass other tetrapods4,5,6,7. Reptiles are unusually diverse in arid regions, suggesting that they may have different conservation needs6. Here we provide a comprehensive extinction-risk assessment of reptiles and show that at least 1,829 out of 10,196 species (21.1%) are threatened?confirming a previous extrapolation8 and representing 15.6 billion years of phylogenetic diversity. Reptiles are threatened by the same major factors that threaten other tetrapods?agriculture, logging, urban development and invasive species?although the threat posed by climate change remains uncertain. Reptiles inhabiting forests, where these threats are strongest, are more threatened than those in arid habitats, contrary to our prediction. Birds, mammals and amphibians are unexpectedly good surrogates for the conservation of reptiles, although threatened reptiles with the smallest ranges tend to be isolated from other threatened tetrapods. Although some reptiles?including most species of crocodiles and turtles?require urgent, targeted action to prevent extinctions, efforts to protect other tetrapods, such as habitat preservation and control of trade and invasive species, will probably also benefit many reptiles.Fil: Cox, Neil. No especifíca;Fil: Young, Bruce E.. No especifíca;Fil: Bowles, Philip. No especifíca;Fil: Fernandez, Miguel. George Mason University; Estados Unidos. Universidad Mayor de San Andrés; BoliviaFil: Marin, Julie. Universite de Paris 13-Nord; FranciaFil: Rapacciuolo, Giovanni. California Academy of Sciences; Estados UnidosFil: Böhm, Monika. The Zoological Society of London; Reino UnidoFil: Brooks, Thomas M.. University of The Philippines; Filipinas. University of Tasmania; AustraliaFil: Hedges, S. Blair. Temple University; Estados UnidosFil: Hilton Taylor, Craig. Biodiversity Assessment & Knowledge Team; Reino UnidoFil: Hoffmann, Michael. The Zoological Society of London; Reino UnidoFil: Jenkins, Richard K. B.. Biodiversity Assessment & Knowledge Team; Reino UnidoFil: Tognelli, Marcelo F.. No especifíca;Fil: Alexander, Graham J.. University of the Witwatersrand; SudáfricaFil: Allison, Allen. Bishop Museum; Estados UnidosFil: Ananjeva, Natalia B.. Zoological Institute; RusiaFil: Auliya, Mark. Zoological Research Museum Alexander Koenig; AlemaniaFil: Avila, Luciano Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico para el Estudio de los Ecosistemas Continentales; ArgentinaFil: Chapple, David G.. Monash University; AustraliaFil: Cisneros Heredia, Diego F.. Universidad San Francisco de Quito; EcuadorFil: Cogger, Harold G.. Australian Museum Research Institute; AustraliaFil: Colli, Guarino Rinaldi. Universidade do Brasília; BrasilFil: de Silva, Anslem. No especifíca;Fil: Eisemberg, Carla C.. Charles Darwin University; AustraliaFil: Els, Johannes. Government of Sharjah; Emiratos Arabes UnidosFil: Fong G, Ansel. Centro Oriental de Biodiversidad y Ecosistemas; CubaFil: Grant, Tandora D.. No especifíca;Fil: Hitchmough, Rodney A.. No especifíca;Fil: Iskandar, Djoko T.. Institut Teknologi Bandung; IndonesiaFil: Kidera, Noriko. Okayama University of Science; Japón. National Institute for Environmental Studies; JapónFil: Martins Pimentel, Márcio. Universidade de Sao Paulo; BrasilFil: Meiri, Shai. Universitat Tel Aviv; IsraelFil: Mitchell, Nicola J.. University of Western Australia; AustraliaFil: Molur, Sanjay. No especifíca;Fil: Nogueira, Cristiano de C.. Universidade de Sao Paulo; BrasilFil: Ortiz, Juan Carlos. Universidad de Concepción; ChileFil: Penner, Johannes. Staatliches Museum fur Naturkunde Stuttgart; AlemaniaFil: Rhodin, Anders G. J.. Chelonian Research Foundation; Estados UnidosFil: Rivas, Gilson A.. Universidad del Zulia; VenezuelaFil: Rödel, Mark-Oliver. Staatliches Museum fur Naturkunde Stuttgart; AlemaniaFil: Roll, Uri. Ben Gurion University of the Negev; IsraelFil: Sanders, Kate L.. University of Adelaide; AustraliaFil: Santos Barrera, Georgina. Universidad Nacional Autónoma de México; MéxicoFil: Shea, Glenn M.. University of Western Sydney; AustraliaFil: Spawls, Stephen. No especifíca;Fil: Stuart, Bryan L.. North Carolina Museum of Natural Sciences; Estados UnidosFil: Tolley, Krystal A.. University of the Witwatersrand; SudáfricaFil: Trape, Jean-François. Institut de Recherche Pour Le Développement Dakar; SenegalFil: Vidal, Marcela A.. Universidad del Bio Bio; ChileFil: Wagner, Philipp. No especifíca;Fil: Wallace, Bryan P.. No especifíca;Fil: Xie, Yan. Chinese Academy of Sciences; República de Chin

Evaluating the Significance of Paleophylogeographic Species Distribution Models in Reconstructing Quaternary Range-Shifts of Nearctic Chelonians

<div><p>The climatic cycles of the Quaternary, during which global mean annual temperatures have regularly changed by 5–10°C, provide a special opportunity for studying the rate, magnitude, and effects of geographic responses to changing climates. During the Quaternary, high- and mid-latitude species were extirpated from regions that were covered by ice or otherwise became unsuitable, persisting in refugial retreats where the environment was compatible with their tolerances. In this study we combine modern geographic range data, phylogeny, Pleistocene paleoclimatic models, and isotopic records of changes in global mean annual temperature, to produce a temporally continuous model of geographic changes in potential habitat for 59 species of North American turtles over the past 320 Ka (three full glacial-interglacial cycles). These paleophylogeographic models indicate the areas where past climates were compatible with the modern ranges of the species and serve as hypotheses for how their geographic ranges would have changed in response to Quaternary climate cycles. We test these hypotheses against physiological, genetic, taxonomic and fossil evidence, and we then use them to measure the effects of Quaternary climate cycles on species distributions. Patterns of range expansion, contraction, and fragmentation in the models are strongly congruent with (i) phylogeographic differentiation; (ii) morphological variation; (iii) physiological tolerances; and (iv) intraspecific genetic variability. Modern species with significant interspecific differentiation have geographic ranges that strongly fluctuated and repeatedly fragmented throughout the Quaternary. Modern species with low genetic diversity have geographic distributions that were highly variable and at times exceedingly small in the past. Our results reveal the potential for paleophylogeographic models to (i) reconstruct past geographic range modifications, (ii) identify geographic processes that result in genetic bottlenecks; and (iii) predict threats due to anthropogenic climate change in the future.</p></div