The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform

Richard C Boucher - One of the best experts on this subject based on the ideXlab platform.

  • abnormal surface liquid ph regulation by cultured cystic fibrosis bronchial epithelium
    Proceedings of the National Academy of Sciences of the United States of America, 2003
    Co-Authors: Raymond D Coakley, Barbara R Grubb, Anthony M Paradiso, J T Gatzy, Larry G Johnson, Sylvia M Kreda, Wanda K Oneal, Richard C Boucher
    Abstract:

    Abstract Cystic fibrosis (CF) transmembrane conductance regulator (CFTR)-dependent airway epithelial bicarbonate transport is hypothesized to participate in airway surface liquid pH regulation and contribute to lung defense. We measured pH and ionic composition in apical surface liquid (ASL) on polarized normal (NL) and CF primary bronchial epithelial cell cultures under basal conditions, after cAMP stimulation, and after challenge with luminal acid loads. Under basal conditions, CF epithelia acidified ASL more rapidly than NL epithelia. Two ASL pH regulatory paths that contributed to basal pH were identified in the apical membrane of airway epithelia, and their activities were measured. We detected a ouabain-sensitive (nongastric) H+,K+-ATPase that acidified ASL, but its activity was not different in NL and CF cultures. We also detected the following evidence for a CFTR-dependent secretory pathway that was defective in CF: (i) ASL [] was higher in NL than CF ASL; (ii) activating CFTR with forskolin/3-isobutyl-1-methylxanthine alkalinized NL ASL but acidified CF ASL; and (iii) NL airway epithelia more rapidly and effectively alkalinized ASL in response to a luminal acid challenge than CF epithelia. We conclude that cultured human CF bronchial epithelial pHASL is abnormally regulated under basal conditions because of absent CFTR-dependent secretion and that this defect can lead to an impaired capacity to respond to airway conditions associated with acidification of ASL.

  • regulation of the epithelial sodium channel by serine proteases in human airways
    Journal of Biological Chemistry, 2002
    Co-Authors: Scott H Donaldson, Richard C Boucher, Andrew J Hirsh, Dong Chen Li, Ginger Holloway, Julie Chao, Sherif E Gabriel
    Abstract:

    Abstract The epithelial sodium channel (ENaC) constitutes the rate-limiting step for sodium absorption across airway epithelia, which in turn regulates airway surface liquid (ASL) volume and the efficiency of mucociliary clearance. This role in ASL volume regulation suggests that ENaC activity is influenced by local factors rather than systemic signals indicative of total body volume homeostasis. Based on reports that ENaC may be regulated by extracellular serine protease activity in Xenopus and mouse renal epithelia, we sought to identify proteases that serve similar functions in human airway epithelia. Homology screening of a human airway epithelial cDNA library identified two trypsin-like serine proteases (prostasin and TMPRSS2) that, as revealed by in situ hybridization, are expressed in airway epithelia. Functional studies in theXenopus oocyte expression system demonstrated that prostasin increased ENaC currents 60–80%, whereas TMPRSS2 markedly decreased ENaC currents and protein levels. Studies of primary nasal epithelial cultures in Ussing chambers revealed that inhibition of endogenous serine protease activity with aprotinin markedly decreased ENaC-mediated currents and sensitized the epithelia to subsequent channel activation by exogenous trypsin. These data, therefore, suggest that protease-mediated regulation of sodium absorption is a function of human airway epithelia, and prostasin is a likely candidate for this activity.

  • molecular insights into the physiology of the thin film of airway surface liquid
    The Journal of Physiology, 1999
    Co-Authors: Richard C Boucher
    Abstract:

    The epithelia that line the airways of the lung exhibit two general functions: (1) airway epithelia in all regions ‘defend’ the lung against infectious and noxious agents; and (2) airway epithelia in the proximal regions replenish water lost from airway surfaces, i.e. the ‘insensible water loss’, consequent to conditioning inspired air. How airway epithelia perform both functions, and co-ordinate them in health and disease, is the subject of this review.

Scott P Kelly - One of the best experts on this subject based on the ideXlab platform.

  • Occluding junctions of invertebrate epithelia
    Journal of Comparative Physiology B, 2016
    Co-Authors: Sima Jonusaite, Andrew Donini, Scott P Kelly
    Abstract:

    Invertebrate diversity and architecture is immense. This is achieved by the organization and function of four tissue types found in most metazoan phyla—epithelial, connective, muscle and nervous tissue. Epithelial tissue is found in all extant animals (parazoan and metazoan alike). Epithelial cells form cellular sheets that cover internal or external surfaces and regulate the passage of material between separated compartments. The transepithelial movement of biological material between compartments can occur across the transcellular pathway (i.e. across cells) or the paracellular pathway (i.e. between cells) and the latter is regulated by occluding junctions that typically link cells in a subapical domain. In this review, information on occluding junctions of invertebrate epithelia is consolidated and discussed in the context of morphology, ultrastructure and physiology. In addition, an overview of what is currently known about invertebrate occluding junction proteins and their role in maintaining the integrity of invertebrate epithelia and regulating the barrier properties of these tissues is presented.

  • tight junction protein gene expression patterns and changes in transcript abundance during development of model fish gill epithelia
    The Journal of Experimental Biology, 2014
    Co-Authors: Dennis Kolosov, Helen Chasiotis, Scott P Kelly
    Abstract:

    In vertebrates, tight junction (TJ) proteins play an important role in epithelium formation and development, the maintenance of tissue integrity and regulation of TJ permeability. In this study, primary cultured model gill epithelia composed of pavement cells (PVCs) were used to examine TJ protein transcript abundance during the development of epithelium confluence and epithelium resistive properties. Differences in TJ protein expression patterns and transcript abundance between gill models composed of PVCs and models composed of PVCs and mitochondrion-rich cells (MRCs) were also examined. Marked alterations in TJ protein transcript abundance were observed as cells developed to confluence in flask-cultured model gill epithelia. In contrast, during the formation of tissue resistance in insert-cultured epithelia (i.e. epithelia cultured on a permeable substrate), changes in TJ protein mRNA abundance were conservative, despite paracellular marker flux decreasing by orders of magnitude. In both cases significant changes in claudin-8b, -8d, -27b, -28b and -32a transcript abundance were observed, suggesting that temporal alterations in the abundance of these genes are important end points of model gill epithelium integrity. When MRCs were present in cultured gill models, the mRNA abundance of several TJ proteins significantly altered and claudin-10c, -10d and -33b were only detected in preparations that included MRCs. These data provide insight into the role of select TJ proteins in the formation and development of gill epithelia and the maintenance of gill barrier properties. In addition, observations reveal a heterogeneous distribution of claudin TJ proteins in the gill epithelial cells of rainbow trout.

  • cultured gill epithelia as models for the freshwater fish gill
    Biochimica et Biophysica Acta, 2002
    Co-Authors: Chris M Wood, Scott P Kelly, Mary Fletcher, Michael J Odonnell, Brighitta Eletti, B. Zhou, Peter Part
    Abstract:

    Abstract We review recent progress in the development of models for the freshwater teleost gill based on reconstructed flat epithelia grown on permeable filter supports in primary culture. Methods are available for single-seeded insert (SSI) preparations consisting of pavement cells (PVCs) only from trout and tilapia, and double-seeded insert (DSI) preparations from trout, containing both PVCs (85%) and mitochondria-rich cells (MRCs, 15%), as in the intact gill. While there are some quantitative differences, both SSI and DSI epithelia manifest electrical and passive permeability characteristics typical of intact gills and representative of very tight epithelia. Both preparations withstand apical freshwater exposure, exhibiting large increases in transepithelial resistance (TER), negative transepithelial potential (TEP), and low rates of ion loss, but there is only a small active apical-to-basolateral “influx” of Cl− (and not of Na+). Responses to various hormonal treatments are described (thyroid hormone T3, prolactin, and cortisol). Cortisol has the most marked effects, stimulating Na+,K+-ATPase activity and promoting active Na+ and Cl− influxes in DSI preparations, and raising TER and reducing passive ion effluxes in both epithelia via reductions in paracellular permeability. Experiments using DSI epithelia lacking Na+ uptake demonstrate that both NH3 and NH4+ diffusion occur, but are not large enough to account for normal rates of branchial ammonia excretion, suggesting that Na+-linked carrier-mediated processes are important for ammonia excretion in vivo. Future research goals are suggested.

  • cultured gill epithelia from freshwater tilapia oreochromis niloticus effect of cortisol and homologous serum supplements from stressed and unstressed fish
    The Journal of Membrane Biology, 2002
    Co-Authors: Scott P Kelly, Chris M Wood
    Abstract:

    : Procedures for the preparation and culture of branchial epithelia from dispersed gill cells of freshwater tilapia (Oreochromis niloticus) are described. Epithelia were cultured on permeable supports (terephthalate membranes, "filters") and bathed on both the apical and basolateral side with isotonic media containing 6% fetal bovine serum (FBS). When the apical medium was replaced with freshwater (pseudo in vivo asymmetrical culture conditions), transepithelial resistance (TER) increased markedly, transepithelial potential became negative, and paracellular permeability decreased. The physiological effects of cortisol and 10% homologous (tilapia) serum were investigated. Tilapia serum (TS) was prepared from unstressed and stressed fish and therefore allowed comparison between the effects of homologous serum derived from fish in differing physiological states. Under both symmetrical and asymmetrical culture conditions, cortisol significantly elevated TER across cultured tilapia gill epithelia, indicative of a significant increase in epithelial "tightness." Cortisol reduced transepithelial Na + and Cl? movement and paracellular permeability. The glucocorticoid agonist dexamethasone elicited a similar response, which was inhibited by the glucocorticoid antagonist (receptor blocker) RU486. Cortisol did not stimulate active ion transport across epithelia under either symmetrical or asymmetrical culture conditions. In epithelia supplemented with TS from stressed fish, physiological changes in cultured preparations were consistent with those observed in FBS + cortisol-supplemented epithelia. Differences between the physiological status of epithelia supplemented with TS from unstressed and stressed fish could be abolished with RU486. Using TS as a medium supplement did not stimulate active ion transport under asymmetrical culture conditions, although Na +-K +-ATPase activity increased in TS-supplemented epithelia relative to FBS-supplemented preparations.

Peter Part - One of the best experts on this subject based on the ideXlab platform.

  • 7-Ethoxyresorufin O-deethylase induction in rainbow trout gill epithelium cultured on permeable supports: asymmetrical distribution of substrate metabolites.
    Aquatic toxicology (Amsterdam Netherlands), 2020
    Co-Authors: C. Carlsson, Peter Part
    Abstract:

    The induction of 7-ethoxyresorufin O-deethylase (EROD) has been measured in cultured epithelia from rainbow trout gills. Epithelia incubated with water on the apical side and culture media at the basolateral side were exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), beta-naphthoflavone (betaNF), benzo[k]fluoranthene (B(k)F), and 3,3',4,4',5-pentachlorobiphenyl (PCB#126) from the water. EROD activity was measured as the formation of resorufin from 7-ethoxyresorufin over time in intact epithelia. The EC(50) values obtained after 24 h of exposure (mean+/-S.D.) were for TCDD (n=9) 4.1+/-3.2x10(-11) M, for betaNF (n=6) 1.6+/-3.8x10(-9) M, for B(k)F (n=4) 5.4+/-3.0x10(-9) M and for PCB#126 (n=4) 6.15+/-10.1x10(-9) M. When assaying for EROD activity, it was found that the resorufin concentrations differed between the apical and the basolateral compartments, indicating an asymmetrical distribution of the enzymatically formed resorufin molecules. Generally, the resorufin concentration was highest in the basolateral compartment, but there were differences between epithelia obtained from different fish individuals. Of a total of 13 preparations 10 had the highest resorufin concentration in the basolateral compartment, while in three preparations, the resorufin was uniformly distributed or slightly higher in the apical compartment. The reasons for this asymmetrical distribution of substrate metabolites are not known, and the addition of multidrug resistance inhibitors (verapamil and cyclosporin A) did not alter the asymmetrical pattern. The transepithelial electrical resistance (TER) was also measured to diagnose the tightness of the epithelia. The change from culture media to experimental water (containing TCDD, betaNF, or DMSO as control) in the apical compartment resulted in a large increase in TER, followed by a decline, measured after 24 h. The cytochrome P450 1A (CYP1A) inducers had no effect on the TER and were judged, therefore, not to affect the tightness of the epithelia.

  • cultured gill epithelia as models for the freshwater fish gill
    Biochimica et Biophysica Acta, 2002
    Co-Authors: Chris M Wood, Scott P Kelly, Mary Fletcher, Michael J Odonnell, Brighitta Eletti, B. Zhou, Peter Part
    Abstract:

    Abstract We review recent progress in the development of models for the freshwater teleost gill based on reconstructed flat epithelia grown on permeable filter supports in primary culture. Methods are available for single-seeded insert (SSI) preparations consisting of pavement cells (PVCs) only from trout and tilapia, and double-seeded insert (DSI) preparations from trout, containing both PVCs (85%) and mitochondria-rich cells (MRCs, 15%), as in the intact gill. While there are some quantitative differences, both SSI and DSI epithelia manifest electrical and passive permeability characteristics typical of intact gills and representative of very tight epithelia. Both preparations withstand apical freshwater exposure, exhibiting large increases in transepithelial resistance (TER), negative transepithelial potential (TEP), and low rates of ion loss, but there is only a small active apical-to-basolateral “influx” of Cl− (and not of Na+). Responses to various hormonal treatments are described (thyroid hormone T3, prolactin, and cortisol). Cortisol has the most marked effects, stimulating Na+,K+-ATPase activity and promoting active Na+ and Cl− influxes in DSI preparations, and raising TER and reducing passive ion effluxes in both epithelia via reductions in paracellular permeability. Experiments using DSI epithelia lacking Na+ uptake demonstrate that both NH3 and NH4+ diffusion occur, but are not large enough to account for normal rates of branchial ammonia excretion, suggesting that Na+-linked carrier-mediated processes are important for ammonia excretion in vivo. Future research goals are suggested.

  • 7 ethoxyresorufin o deethylase induction in rainbow trout gill epithelium cultured on permeable supports asymmetrical distribution of substrate metabolites
    Aquatic Toxicology, 2001
    Co-Authors: C. Carlsson, Peter Part
    Abstract:

    Abstract The induction of 7-ethoxyresorufin O-deethylase (EROD) has been measured in cultured epithelia from rainbow trout gills. Epithelia incubated with water on the apical side and culture media at the basolateral side were exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), β-naphthoflavone (βNF), benzo[k]fluoranthene (B(k)F), and 3,3′,4,4′,5-pentachlorobiphenyl (PCB#126) from the water. EROD activity was measured as the formation of resorufin from 7-ethoxyresorufin over time in intact epithelia. The EC 50 values obtained after 24 h of exposure (mean±S.D.) were for TCDD (n=9) 4.1±3.2×10−11 M, for βNF (n=6) 1.6±3.8×10−9 M, for B(k)F (n=4) 5.4±3.0×10−9 M and for PCB#126 (n=4) 6.15±10.1×10−9 M. When assaying for EROD activity, it was found that the resorufin concentrations differed between the apical and the basolateral compartments, indicating an asymmetrical distribution of the enzymatically formed resorufin molecules. Generally, the resorufin concentration was highest in the basolateral compartment, but there were differences between epithelia obtained from different fish individuals. Of a total of 13 preparations 10 had the highest resorufin concentration in the basolateral compartment, while in three preparations, the resorufin was uniformly distributed or slightly higher in the apical compartment. The reasons for this asymmetrical distribution of substrate metabolites are not known, and the addition of multidrug resistance inhibitors (verapamil and cyclosporin A) did not alter the asymmetrical pattern. The transepithelial electrical resistance (TER) was also measured to diagnose the tightness of the epithelia. The change from culture media to experimental water (containing TCDD, βNF, or DMSO as control) in the apical compartment resulted in a large increase in TER, followed by a decline, measured after 24 h. The cytochrome P450 1A (CYP1A) inducers had no effect on the TER and were judged, therefore, not to affect the tightness of the epithelia.

Regine Jahn - One of the best experts on this subject based on the ideXlab platform.

  • Epithemia hirudiniformis and related taxa within the subgenus rhopalodiella subg nov in comparison to Epithemia subg rhopalodia stat nov bacillariophyceae from east africa
    Cryptogamie Algologie, 2018
    Co-Authors: Christine Cocquyti, Wolfhenning Kusber, Regine Jahn
    Abstract:

    Epithemia hirudiniformis and three morphologically related taxa, described in Rhopalodia by O. Muller from material collected in East Africa at the end of the 19th and the beginning of the 20th century were re-evaluated and lectotypes designated. Rhopalodiella as a new subgenus is proposed which refines O. Muller's infrageneric classification and to which all these taxa belong. In addition, the type of Epithemia rhopala, described by Ehrenberg from Egypt, was studied to examine the assumed synonymy, introduced by Hustedt, with some of Muller's species. This study, using light and scanning electron microscopy, was not only based on historic material but also more recent material from Africa, including samples from the Island of Reunion from which the new species Epithemia vandevijveri is described. The distribution of Epithemia subg. Rhopalodiella, known to be restricted to tropical Africa, is discussed based on literature data and own observations. Corresponding to recent molecular-based studies, Rhopalodia is given a new status as subgenus.

  • Algae of the Ehrenberg collection — 3. Typification of seven diatom taxa described by C. G. Ehrenberg predominantly from Greece
    Willdenowia, 2006
    Co-Authors: Regine Jahn, Wolfhenning Kusber
    Abstract:

    Abstract Jahn, R. & Kusber, W.-H.: Algae of the Ehrenberg collection — 3. Typification of seven diatom taxa described by C. G. Ehrenberg predominantly from Greece. — Willdenowia 36 (Special Issue): 527–535. — ISSN 0511-9618; © 2006 BGBM Berlin-Dahlem. doi:10.3372/wi.36.36150 (available via http://dx.doi.org/) Lectotypes are selected and illustrated for seven names of diatom species described by Ehrenberg in 1840 from Greece: Amphitetras antediluviana, Epithemia hellenica (Eunotia hellenica), Lyrella praetexta (Navicula praetexta), Rhopalodia graeca (Cocconema graecum), Stictodiscus parallelus (Amphitetras? parallela), Triceratium favus and T. pileus. This includes the type of the genera Amphitetras and Triceratium. New combinations are validated for Epithemia hellenica and Rhopalodia graeca.

Mary E. Power - One of the best experts on this subject based on the ideXlab platform.

  • Nutrient induced changes in the species composition of epiphytes on Cladophora glomerata Kütz. (Chlorophyta)
    Hydrobiologia, 2001
    Co-Authors: Jane C. Marks, Mary E. Power
    Abstract:

    Cladophora glomerata is a widely distributed filamentous freshwater alga that hosts a complex microalgal epiphyte assemblage. We manipulated nutrients and epiphyte abundances to access their effects on epiphyte biomass, epiphyte species composition, and C. glomerata growth. C. glomerata did not grow in response to these manipulations. Similarly, nutrient and epiphyte removal treatments did not alter epiphyte biovolume. Epiphyte species composition, however, changed dramatically with nutrient enrichment. The epiphyte assemblage on unenriched C. glomerata was dominated by Epithemia sorex and Epithemia adnata, whereas the assemblage on enriched C. glomerata was dominated by Achnanthidium minutissimum, Nitzschia palea and Synedra spp. These results indicate that nutrients strongly structure epiphyte species composition. Interactions between C. glomerata and its epiphytes were not affected by epiphyte species composition in our experiment but may be when C. glomerata is actively growing.