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51.
Topographical distribution of pulmonary perfusion and ventilation, assessed by PET in supine and prone humans. 总被引:6,自引:0,他引:6
Guido Musch J Dominick H Layfield R Scott Harris Marcos F Vidal Melo Tilo Winkler Ronald J Callahan Alan J Fischman Jose G Venegas 《Journal of applied physiology》2002,93(5):1841-1851
Using positron emission tomography (PET) and intravenously injected (13)N(2), we assessed the topographical distribution of pulmonary perfusion (Q) and ventilation (V) in six healthy, spontaneously breathing subjects in the supine and prone position. In this technique, the intrapulmonary distribution of (13)N(2), measured during a short apnea, is proportional to regional Q. After resumption of breathing, regional specific alveolar V (sVA, ventilation per unit of alveolar gas volume) can be calculated from the tracer washout rate. The PET scanner imaged 15 contiguous, 6-mm-thick, slices of lung. Vertical gradients of Q and sVA were computed by linear regression, and spatial heterogeneity was assessed from the squared coefficient of variation (CV(2)). Both CV and CV were corrected for the estimated contribution of random imaging noise. We found that 1) both Q and V had vertical gradients favoring dependent lung regions, 2) vertical gradients were similar in the supine and prone position and explained, on average, 24% of Q heterogeneity and 8% of V heterogeneity, 3) CV was similar in the supine and prone position, and 4) CV was lower in the prone position. We conclude that, in recumbent, spontaneously breathing humans, 1) vertical gradients favoring dependent lung regions explain a significant fraction of heterogeneity, especially of Q, and 2) although Q does not seem to be systematically more homogeneous in the prone position, differences in individual behaviors may make the prone position advantageous, in terms of V-to-Q matching, in selected subjects. 相似文献
52.
David M. L. Lilburn Theodore Hughes-Riley Joseph S. Six Karl F. Stupic Dominick E. Shaw Galina E. Pavlovskaya Thomas Meersmann 《PloS one》2013,8(8)
Ex vivo rodent lung models are explored for physiological measurements of respiratory function with hyperpolarized (hp) 129Xe MRI. It is shown that excised lung models allow for simplification of the technical challenges involved and provide valuable physiological insights that are not feasible using in vivo MRI protocols. A custom designed breathing apparatus enables MR images of gas distribution on increasing ventilation volumes of actively inhaled hp 129Xe. Straightforward hp 129Xe MRI protocols provide residual lung volume (RV) data and permit for spatially resolved tracking of small hp 129Xe probe volumes during the inhalation cycle. Hp 129Xe MRI of lung function in the excised organ demonstrates the persistence of post mortem airway responsiveness to intravenous methacholine challenges. The presented methodology enables physiology of lung function in health and disease without additional regulatory approval requirements and reduces the technical and logistical challenges with hp gas MRI experiments. The post mortem lung functional data can augment histological measurements and should be of interest for drug development studies. 相似文献
53.
Philip M. Hansbro Matthew J. Hamilton Michael Fricker Shaan L. Gellatly Andrew G. Jarnicki Dominick Zheng Sandra M. Frei G. William Wong Sahar Hamadi Saijun Zhou Paul S. Foster Steven A. Krilis Richard L. Stevens 《The Journal of biological chemistry》2014,289(26):18214-18227
Protease serine member S31 (Prss31)/transmembrane tryptase/tryptase-γ is a mast cell (MC)-restricted protease of unknown function that is retained on the outer leaflet of the plasma membrane when MCs are activated. We determined the nucleotide sequences of the Prss31 gene in different mouse strains and then used a Cre/loxP homologous recombination approach to create a novel Prss31−/− C57BL/6 mouse line. The resulting animals exhibited no obvious developmental abnormality, contained normal numbers of granulated MCs in their tissues, and did not compensate for their loss of the membrane tryptase by increasing their expression of other granule proteases. When Prss31-null MCs were activated with a calcium ionophore or by their high affinity IgE receptors, they degranulated in a pattern similar to that of WT MCs. Prss31-null mice had increased baseline airway reactivity to methacholine but markedly reduced experimental chronic obstructive pulmonary disease and colitis, thereby indicating both beneficial and adverse functional roles for the tryptase. In a cigarette smoke-induced model of chronic obstructive pulmonary disease, WT mice had more pulmonary macrophages, higher histopathology scores, and more fibrosis in their small airways than similarly treated Prss31-null mice. In a dextran sodium sulfate-induced acute colitis model, WT mice lost more weight, had higher histopathology scores, and contained more Cxcl-2 and IL-6 mRNA in their colons than similarly treated Prss31-null mice. The accumulated data raise the possibility that inhibitors of this membrane tryptase may provide additional therapeutic benefit in the treatment of humans with these MC-dependent inflammatory diseases. 相似文献
54.
Sipkema D Yosef NA Adamczewski M Osinga R Mendola D Tramper J Wijffels RH 《Marine biotechnology (New York, N.Y.)》2006,8(1):40-51
The marine sponges Dysidea avara and Chondrosia reniformis (globular forms) were cultured in the laboratory on a diet of viable Phaeodactylum tricornutum cells and dissolved nutrients (algae and fish powders). Our growth data were combined with literature data for Pseudosuberites andrewsi (a globular sponge) and for the encrusting sponges Oscarella lobularis, Hemimycale columella, and Crambe crambe. The suitability of three growth models—linear, exponential, and radial accretive—for describing the growth of globular and
encrusting sponges was assessed. Radial accretive growth was determined to be the best model to describe growth of both encrusting
and globular sponges. Average growth rates of 0.051 ± 0.016 and 0.019 ± 0.003 mm/day (calculated as the increase of the radius
of the sponge per day) were obtained experimentally for D. avara and C. reniformis, respectively. 相似文献
55.
56.
Conrad JC Gibiansky ML Jin F Gordon VD Motto DA Mathewson MA Stopka WG Zelasko DC Shrout JD Wong GC 《Biophysical journal》2011,(7):1608-1616
Bacterial biofilms are structured multicellular communities that are responsible for a broad range of infections. Knowing how free-swimming bacteria adapt their motility mechanisms near a surface is crucial for understanding the transition from the planktonic to the biofilm phenotype. By translating microscopy movies into searchable databases of bacterial behavior and developing image-based search engines, we were able to identify fundamental appendage-specific mechanisms for the surface motility of Pseudomonas aeruginosa. Type IV pili mediate two surface motility mechanisms: horizontally oriented crawling, by which the bacterium moves lengthwise with high directional persistence, and vertically oriented walking, by which the bacterium moves with low directional persistence and high instantaneous velocity, allowing it to rapidly explore microenvironments. The flagellum mediates two additional motility mechanisms: near-surface swimming and surface-anchored spinning, which often precedes detachment from a surface. Flagella and pili interact cooperatively in a launch sequence whereby bacteria change orientation from horizontal to vertical and then detach. Vertical orientation facilitates detachment from surfaces and thereby influences biofilm morphology. 相似文献
57.
Lana Krol Robert P. Moore Adrian G. Mutlow Sean M. Brady Dominick Dorsa II 《Zoo biology》2020,39(6):405-410
Mortality data for Magellanic penguins (Spheniscus magellanicus) housed in zoos and aquariums in the United States has not previously been published. Necropsy and histopathology records were examined for Magellanic penguins housed at 12 Association of Zoos and Aquariums institutions from 2008 through 2018. If birds lived through the first year, the mean longevity was found to be 18.9 years of age (standard deviation: 7.9). Prefledge chicks and geriatric penguins experienced the highest mortality rates. Aspergillosis was a major cause of death in this species. There was no significant difference in mortality between males and females. Based on these data, recommendations for the husbandry and veterinary care of captive Magellanic penguins can be made. 相似文献
58.
59.
60.
Ultrastructure of pigmented adult eyes in errant polychaetes (Annelida): implications for annelid evolution 总被引:1,自引:1,他引:0
The evolution of photoreceptor cells and eyes in Metazoa is far from being resolved, although recent developmental and structural
studies have provided strong evidence for a common origin of photoreceptor cells and existence of sister cell types already
in early metazoans. These sister cell types are ciliary and rhabdomeric photoreceptor cells, depending on which part of each
cell is involved in photoreception proper. However, a crucial point in eye evolution is how the enormous structural diversity
of photoreceptor cells and visual systems developed, given the general molecular conservation of the photoreceptor cells.
One example of this diversity can be observed in Annelida. Within the polychaetes the errant forms, taxon Aciculata, constitute
the only group possessing true multicellular eyes in the adult stage. Thus far these organs have been investigated only in
taxa of Phyllodocida, a subgroup of Aciculata. Data on Eunicida and Amphinomida as well as certain phyllodocidan taxa had
been lacking. The ultrastructure of these adult eyes was investigated in various species of errant polychaetes, belonging
to Amphinomidae, Eunicidae and Hesionidae, to elucidate whether they provide any phylogenetic clues regarding either the evolution
of visual systems in Annelida or lophotrochozoan phylogeny in general. These eyes are composed of numerous supportive pigment
cells and rhabdomeric photoreceptor cells and sometimes additional cell types. As a rule the pigment and rhabdomeric cell
types form a continuous epithelium in which the two types intermingle. Presence of granules with shading pigment in sensory
cells is a common feature but is apparently restricted to a taxon comprising Phyllodocida and Eunicida s. str. Very likely
a lens-like structure does not belong to the ground pattern of annelid eyes, despite its presence in Phyllodocida. These lens-like
structures are formed by secretions or cellular processes of the pigment cells. In many species the eye cup communicates with
the exterior via a small cuticularized canal. This canal is interpreted as a rudiment due to the mode of formation in the
epidermis. With respect to current phylogenetic hypotheses, these multicellular eyes have either been developed in the stem
species of a taxon Aciculata nested within the polychaetes or have been evolved in the stem lineage of Annelida. Similarities
to gastropod eyes are interpreted as convergent and not as indication of common origin. Except for the photoreceptor cells
proper, the structure of the adult eyes in polychaetes most likely does not help to resolve lophotrochozoan phylogeny. 相似文献