Item	Title	Date	Author	Species	Bulletin	Report
11015	A System to Study the Teleost Chloride Cell with the Ussing Chamber	1972	Karl J. Karnaky, Jr. MDI Biological Laboratory	Hemitripterus americanus Sea raven	Volume 12 - 1972	28	A System to Study the Teleost Chloride Cell with the Ussing Chamber Item: 11015    Date: 1972 Author: Karl J. Karnaky, Jr. MDI Biological Laboratory Species: Hemitripterus americanus Sea raven Bulletin: Volume 12 - 1972 Type: Bulletin, Report Report: 28
11117	Accumulation of 3H-DDA by Flounder, Pseudopleuronectes americanus, Kidney Tubules In Vitro	1974	John B. Pritchard Medical University of South Carolina Karl J. Karnaky, Jr. MDI Biological Laboratory Harold H. Church MDI Biological Laboratory William B. Kinter MDI Biological Laboratory	Pseudopleuronectes americanus (was Pleuronectes americanus) Winter flounder	Volume 14 - 1974	30	Accumulation of 3H-DDA by Flounder, Pseudopleuronectes americanus, Kidney Tubules In Vitro Item: 11117    Date: 1974 Author: John B. Pritchard Medical University of South Carolina Karl J. Karnaky, Jr. MDI Biological Laboratory Harold H. Church MDI Biological Laboratory William B. Kinter MDI Biological Laboratory Species: Pseudopleuronectes americanus (was Pleuronectes americanus) Winter flounder Bulletin: Volume 14 - 1974 Type: Bulletin, Report Report: 30
12064	An Atrial Natriuretic Peptide-Like Factor Isolated from the Dogfish Shark (Squalus acanthias ) Rectal Gland: Initial Characterization	1991	Karl J. Karnaky, Jr. Medical University of South Carolina William F. Oehlenschlager Medical University of South Carolina James D. Stidham Presbyterian College David S. Nelson Presbyterian College Andrew S. McCraw Presbyterian College John D. Valentich University of Texas Michael P. Kennedy Medical University of South Carolina Mark G. Currie Monsanto Company	Squalus acanthias Spiny dogfish	Volume 31 - 1991	54	An Atrial Natriuretic Peptide-Like Factor Isolated from the Dogfish Shark (Squalus acanthias ) Rectal Gland: Initial Characterization Item: 12064    Date: 1991 Author: Karl J. Karnaky, Jr. Medical University of South Carolina William F. Oehlenschlager Medical University of South Carolina James D. Stidham Presbyterian College David S. Nelson Presbyterian College Andrew S. McCraw Presbyterian College John D. Valentich University of Texas Michael P. Kennedy Medical University of South Carolina Mark G. Currie Monsanto Company Species: Squalus acanthias Spiny dogfish Bulletin: Volume 31 - 1991 Type: Bulletin, Report Report: 54
11928	Atriopeptin Stimulates Chloride Secretion by Cultured Shark (Squalus acanthias) Rectal Gland Epithelium	1989	Karl J. Karnaky, Jr. Medical University of South Carolina John D. Valentich University of Texas Mark G. Currie Medical University of South Carolina William F. Oehlenschlager Medical University of South Carolina	Squalus acanthias Spiny dogfish	Volume 29 - 1989	38	Atriopeptin Stimulates Chloride Secretion by Cultured Shark (Squalus acanthias) Rectal Gland Epithelium Item: 11928    Date: 1989 Author: Karl J. Karnaky, Jr. Medical University of South Carolina John D. Valentich University of Texas Mark G. Currie Medical University of South Carolina William F. Oehlenschlager Medical University of South Carolina Species: Squalus acanthias Spiny dogfish Bulletin: Volume 29 - 1989 Type: Bulletin, Report Report: 38
11082	Autoradiographic Localization of 3H-Ouabain Binding by Na-K-ATPase in Perfused Gills of Fundulus heterclitus	1973	Charles Stirling University of Washington Karl J. Karnaky, Jr. MDI Biological Laboratory Lewis Kinter MDI Biological Laboratory William B. Kinter MDI Biological Laboratory	Fundulus heteroclitus Mummichog	Volume 13 - 1973	47	Autoradiographic Localization of 3H-Ouabain Binding by Na-K-ATPase in Perfused Gills of Fundulus heterclitus Item: 11082    Date: 1973 Author: Charles Stirling University of Washington Karl J. Karnaky, Jr. MDI Biological Laboratory Lewis Kinter MDI Biological Laboratory William B. Kinter MDI Biological Laboratory Species: Fundulus heteroclitus Mummichog Bulletin: Volume 13 - 1973 Type: Bulletin, Report Report: 47
11197	Autoradiographic Localization of 3H-Ouabain Binding in Dogfish (Squalus acanthias) Rectal Gland	1976	Karl J. Karnaky, Jr. MDI Biological Laboratory William B. Kinter MDI Biological Laboratory Patricio Silva Harvard University/Beth Israel Hospital	Squalus acanthias Spiny dogfish	Volume 16 - 1976	28	Autoradiographic Localization of 3H-Ouabain Binding in Dogfish (Squalus acanthias) Rectal Gland Item: 11197    Date: 1976 Author: Karl J. Karnaky, Jr. MDI Biological Laboratory William B. Kinter MDI Biological Laboratory Patricio Silva Harvard University/Beth Israel Hospital Species: Squalus acanthias Spiny dogfish Bulletin: Volume 16 - 1976 Type: Bulletin, Report Report: 28
12062	C-Type Natriuretic Peptide is a Potent Secretagogue for the Cultured Shark (Squalus acanthias) Rectal Gland	1991	Karl J. Karnaky, Jr. Medical University of South Carolina James D. Stidham Presbyterian College David S. Nelson Presbyterian College Andrew S. McCraw Presbyterian College John D. Valentich University of Texas Michael P. Kennedy Medical University of South Carolina Mark G. Currie Monsanto Company	Squalus acanthias Spiny dogfish	Volume 31 - 1991	52	C-Type Natriuretic Peptide is a Potent Secretagogue for the Cultured Shark (Squalus acanthias) Rectal Gland Item: 12062    Date: 1991 Author: Karl J. Karnaky, Jr. Medical University of South Carolina James D. Stidham Presbyterian College David S. Nelson Presbyterian College Andrew S. McCraw Presbyterian College John D. Valentich University of Texas Michael P. Kennedy Medical University of South Carolina Mark G. Currie Monsanto Company Species: Squalus acanthias Spiny dogfish Bulletin: Volume 31 - 1991 Type: Bulletin, Report Report: 52
11375	Correlation of Chloride Cell Number and Short-Circuit Current in Chloride Secretin Epithelia of Fundulus heteroclitus	1979	Karl J. Karnaky, Jr. Temple University Kevin J. Degnan New York University José A. Zadunaisky New York University	Fundulus heteroclitus Mummichog	Volume 19 - 1979	53	Correlation of Chloride Cell Number and Short-Circuit Current in Chloride Secretin Epithelia of Fundulus heteroclitus Item: 11375    Date: 1979 Author: Karl J. Karnaky, Jr. Temple University Kevin J. Degnan New York University José A. Zadunaisky New York University Species: Fundulus heteroclitus Mummichog Bulletin: Volume 19 - 1979 Type: Bulletin, Report Report: 53
11356	Effect of Changes in Salinity on Surface Ultrastructure of Gill Filaments of Fundulus heteroclitus	1979	Fred E. Hossler Louisiana State University Franklin H. Epstein Harvard University/Beth Israel Hospital Karl J. Karnaky, Jr. Temple University	Fundulus heteroclitus Mummichog	Volume 19 - 1979	34	Effect of Changes in Salinity on Surface Ultrastructure of Gill Filaments of Fundulus heteroclitus Item: 11356    Date: 1979 Author: Fred E. Hossler Louisiana State University Franklin H. Epstein Harvard University/Beth Israel Hospital Karl J. Karnaky, Jr. Temple University Species: Fundulus heteroclitus Mummichog Bulletin: Volume 19 - 1979 Type: Bulletin, Report Report: 34
12442	Effect of Rectal Gland Removal on Na+,K+-ATPase Expression in the Gills and Kidneys of Raja erinacea	1998	Peter M. Piermarini University of Florida Keith P. Choe Georgia Southern University Karl J. Karnaky, Jr. Medical University of South Carolina	Raja erinacea (now Leucoraja erinacea) Little skate Squalus acanthias Spiny dogfish	Volume 38 - 1998	20	Effect of Rectal Gland Removal on Na+,K+-ATPase Expression in the Gills and Kidneys of Raja erinacea Item: 12442    Date: 1998 Author: Peter M. Piermarini University of Florida Keith P. Choe Georgia Southern University Karl J. Karnaky, Jr. Medical University of South Carolina Species: Raja erinacea (now Leucoraja erinacea) Little skate Squalus acanthias Spiny dogfish Bulletin: Volume 38 - 1998 Type: Bulletin, Report Report: 20
12568	Evidence for a Guanylin/Guanylate Cyclase Signaling System in the Intestine, but not in Rectal Glands of the Dogfish Shark (Squalus acanthias)	2000	Karl J. Karnaky, Jr. Medical University of South Carolina Leonard R. Forte University of Missouri - Columbia Joshua T. Bridges Sumner Memorial High School Erin Brown MDI Biological Laboratory Suzanne J. Forrest Yale University John N. Forrest, Jr. Yale University Sarah E. Decker Middlebury College Andrea Pelletier MDI Biological Laboratory	Squalus acanthias Spiny dogfish	Volume 40 - 2000	24	Evidence for a Guanylin/Guanylate Cyclase Signaling System in the Intestine, but not in Rectal Glands of the Dogfish Shark (Squalus acanthias) Item: 12568    Date: 2000 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Leonard R. Forte University of Missouri - Columbia Joshua T. Bridges Sumner Memorial High School Erin Brown MDI Biological Laboratory Suzanne J. Forrest Yale University John N. Forrest, Jr. Yale University Sarah E. Decker Middlebury College Andrea Pelletier MDI Biological Laboratory Species: Squalus acanthias Spiny dogfish Bulletin: Volume 40 - 2000 Type: Bulletin, Report Report: 24
12108	Evidence for the Multidrug Transporter, P-Glycoprotein, in the Killifish, Fundulus heteroclitus	1992	Karl J. Karnaky, Jr. Medical University of South Carolina William Kyle Suggs Medical University of South Carolina Stacey French University of Maine at Farmington Mark C. Willingham Medical University of South Carolina	Fundulus heteroclitus Mummichog	Volume 32 - 1992	26	Evidence for the Multidrug Transporter, P-Glycoprotein, in the Killifish, Fundulus heteroclitus Item: 12108    Date: 1992 Author: Karl J. Karnaky, Jr. Medical University of South Carolina William Kyle Suggs Medical University of South Carolina Stacey French University of Maine at Farmington Mark C. Willingham Medical University of South Carolina Species: Fundulus heteroclitus Mummichog Bulletin: Volume 32 - 1992 Type: Bulletin, Report Report: 26
12405	Excretion of Multispecific Organic Anion Transporter (MOAT) Substrates by Dogfish Shark (Squalus acanthias) Rectal Gland Tubules	1997	Karl J. Karnaky, Jr. Medical University of South Carolina Rosalinde Masereeuw University Nijmegen John H. Henson Dickinson College Kate Sojka Medical University of South Carolina James D. Stidham Presbyterian College Catherine Clayton Presbyterian College Samantha J. Hawkins Deer Isle-Stonington High School David S. Miller National Institutes of Environmental Health Sciences	Squalus acanthias Spiny dogfish	Volume 37 - 1997	45	Excretion of Multispecific Organic Anion Transporter (MOAT) Substrates by Dogfish Shark (Squalus acanthias) Rectal Gland Tubules Item: 12405    Date: 1997 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Rosalinde Masereeuw University Nijmegen John H. Henson Dickinson College Kate Sojka Medical University of South Carolina James D. Stidham Presbyterian College Catherine Clayton Presbyterian College Samantha J. Hawkins Deer Isle-Stonington High School David S. Miller National Institutes of Environmental Health Sciences Species: Squalus acanthias Spiny dogfish Bulletin: Volume 37 - 1997 Type: Bulletin, Report Report: 45
11196	Fine Structure of Winter Flounder (Pseudopleuronectes americanus) Intestine	1976	Karl J. Karnaky, Jr. MDI Biological Laboratory William B. Kinter MDI Biological Laboratory Michael Field Harvard University/Beth Israel Hospital	Pseudopleuronectes americanus (was Pleuronectes americanus) Winter flounder	Volume 16 - 1976	27	Fine Structure of Winter Flounder (Pseudopleuronectes americanus) Intestine Item: 11196    Date: 1976 Author: Karl J. Karnaky, Jr. MDI Biological Laboratory William B. Kinter MDI Biological Laboratory Michael Field Harvard University/Beth Israel Hospital Species: Pseudopleuronectes americanus (was Pleuronectes americanus) Winter flounder Bulletin: Volume 16 - 1976 Type: Bulletin, Report Report: 27
12619	Guanylin/Guanylate Cyclase Signaling in the Intestine of Dogfish Shark (Squalus acanthias) and American Eel (Anguilla rostrata)	2001	Karl J. Karnaky, Jr. Medical University of South Carolina Emily Milner Presbyterian College John N. Forrest, Jr. Yale University Leonard R. Forte University of Missouri - Columbia	Anguilla rostrata American eel Squalus acanthias Spiny dogfish	Volume 41 - 2001	18	Guanylin/Guanylate Cyclase Signaling in the Intestine of Dogfish Shark (Squalus acanthias) and American Eel (Anguilla rostrata) Item: 12619    Date: 2001 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Emily Milner Presbyterian College John N. Forrest, Jr. Yale University Leonard R. Forte University of Missouri - Columbia Species: Anguilla rostrata American eel Squalus acanthias Spiny dogfish Bulletin: Volume 41 - 2001 Type: Bulletin, Report Report: 18
12461	Guanylin/Uroguanylin Regulation of Dogfish Shark (Squalus acanthias) Rectal Gland Chloride Secretion	1998	Karl J. Karnaky, Jr. Medical University of South Carolina Peter M. Piermarini University of Florida Leonard R. Forte University of Florida	Squalus acanthias Spiny dogfish	Volume 38 - 1998	39	Guanylin/Uroguanylin Regulation of Dogfish Shark (Squalus acanthias) Rectal Gland Chloride Secretion Item: 12461    Date: 1998 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Peter M. Piermarini University of Florida Leonard R. Forte University of Florida Species: Squalus acanthias Spiny dogfish Bulletin: Volume 38 - 1998 Type: Bulletin, Report Report: 39
12598	Human Uroguanylin, Opossum Guanylin and Heat Stable E. coli Enterotoxin Do Not Stimulate Chloride Secretion in the Perfused Rectal Gland of the Dogfish Shark (Squalus acanthias)	2000	Suzanne J. Forrest Yale University Andrea Pelletier Yale University Leonard R. Forte University of Missouri - Columbia John N. Forrest, Jr. Yale University Sarah E. Decker Middlebury College Karl J. Karnaky, Jr. University of South Carolina	Didelphis virginiana Virginia opossum Escherichia coli E. coli Homo sapiens Human Squalus acanthias Spiny dogfish	Volume 40 - 2000	54	Human Uroguanylin, Opossum Guanylin and Heat Stable E. coli Enterotoxin Do Not Stimulate Chloride Secretion in the Perfused Rectal Gland of the Dogfish Shark (Squalus acanthias) Item: 12598    Date: 2000 Author: Suzanne J. Forrest Yale University Andrea Pelletier Yale University Leonard R. Forte University of Missouri - Columbia John N. Forrest, Jr. Yale University Sarah E. Decker Middlebury College Karl J. Karnaky, Jr. University of South Carolina Species: Didelphis virginiana Virginia opossum Escherichia coli E. coli Homo sapiens Human Squalus acanthias Spiny dogfish Bulletin: Volume 40 - 2000 Type: Bulletin, Report Report: 54
12000	Intracellular Cyclic GMP in Cultured Squalus acanthias Rectal Gland Epithelium: Effects of Atrial Natriuretic Peptide (ANP) and Escherichia coli Heat Stable Enterotoxin (STa)	1990	Michael P. Kennedy Medical University of South Carolina John D. Valentich University of Texas Mark G. Currie Monsanto Company William F. Oehlenschlager Medical University of South Carolina Karl J. Karnaky, Jr. Medical University of South Carolina	Squalus acanthias Spiny dogfish	Volume 30 - 1990	43	Intracellular Cyclic GMP in Cultured Squalus acanthias Rectal Gland Epithelium: Effects of Atrial Natriuretic Peptide (ANP) and Escherichia coli Heat Stable Enterotoxin (STa) Item: 12000    Date: 1990 Author: Michael P. Kennedy Medical University of South Carolina John D. Valentich University of Texas Mark G. Currie Monsanto Company William F. Oehlenschlager Medical University of South Carolina Karl J. Karnaky, Jr. Medical University of South Carolina Species: Squalus acanthias Spiny dogfish Bulletin: Volume 30 - 1990 Type: Bulletin, Report Report: 43
12569	MRP2-Like Transport in the Malpighian Tubule of the Cricket, Acheta domesticus	2000	Karl J. Karnaky, Jr. Medical University of South Carolina Martina Sedmerova Medical University of South Carolina Joshua T. Bridges Sumner Memorial High School Sarah Wade Boatwright Mount Holyoke College David S. Miller National Institutes of Environmental Health Sciences David H. Petzel Creighton University	Acheta domesticus House cricket	Volume 40 - 2000	25	MRP2-Like Transport in the Malpighian Tubule of the Cricket, Acheta domesticus Item: 12569    Date: 2000 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Martina Sedmerova Medical University of South Carolina Joshua T. Bridges Sumner Memorial High School Sarah Wade Boatwright Mount Holyoke College David S. Miller National Institutes of Environmental Health Sciences David H. Petzel Creighton University Species: Acheta domesticus House cricket Bulletin: Volume 40 - 2000 Type: Bulletin, Report Report: 25
12893	Mrp2-Like Transport Model System from Cricket, Acheta domesticus, Malpighian Tubules	2005	Karl J. Karnaky, Jr. Medical University of South Carolina Jessica Daniels College of Charleston Monica Davis College of Charleston Stephanie Tully College of Charleston Linda Jones College of Charleston Kai E. Swenson National Institutes of Environmental Health Sciences David S. Miller National Institutes of Environmental Health Sciences	Acheta domesticus House cricket	Volume 45 - 2005	56	Mrp2-Like Transport Model System from Cricket, Acheta domesticus, Malpighian Tubules Item: 12893    Date: 2005 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Jessica Daniels College of Charleston Monica Davis College of Charleston Stephanie Tully College of Charleston Linda Jones College of Charleston Kai E. Swenson National Institutes of Environmental Health Sciences David S. Miller National Institutes of Environmental Health Sciences Species: Acheta domesticus House cricket Bulletin: Volume 45 - 2005 Type: Bulletin, Report Report: 56
12508	MRP2-Like Transport of Texas Red by Malphigian Tubules of the Common American Cockroach, Periplaneta americana	1999	Karl J. Karnaky, Jr. Medical University of South Carolina Martina Sedmerova Medical University of South Carolina Abby Gross Deer Isle-Stonington High School David S. Miller National Institutes of Environmental Health Sciences David H. Petzel Creighton University	Periplaneta americana American cockroach	Volume 39 - 1999	28	MRP2-Like Transport of Texas Red by Malphigian Tubules of the Common American Cockroach, Periplaneta americana Item: 12508    Date: 1999 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Martina Sedmerova Medical University of South Carolina Abby Gross Deer Isle-Stonington High School David S. Miller National Institutes of Environmental Health Sciences David H. Petzel Creighton University Species: Periplaneta americana American cockroach Bulletin: Volume 39 - 1999 Type: Bulletin, Report Report: 28
12059	Neuropeptide Inhibition of Active Transport in Cultured Rectal Gland Cells of Squalus acanthias	1991	Franklin H. Epstein Harvard University/Beth Israel Hospital Patricio Silva Harvard University/Beth Israel Hospital Richard J. Solomon New York Medical College James D. Stidham Medical University of South Carolina Andrew S. McCraw Medical University of South Carolina David S. Nelson Medical University of South Carolina Karl J. Karnaky, Jr. Medical University of South Carolina Sonya Hornung Harvard University/Beth Israel Hospital Katherine C. Spokes Harvard University/Beth Israel Hospital	Squalus acanthias Spiny dogfish	Volume 31 - 1991	49	Neuropeptide Inhibition of Active Transport in Cultured Rectal Gland Cells of Squalus acanthias Item: 12059    Date: 1991 Author: Franklin H. Epstein Harvard University/Beth Israel Hospital Patricio Silva Harvard University/Beth Israel Hospital Richard J. Solomon New York Medical College James D. Stidham Medical University of South Carolina Andrew S. McCraw Medical University of South Carolina David S. Nelson Medical University of South Carolina Karl J. Karnaky, Jr. Medical University of South Carolina Sonya Hornung Harvard University/Beth Israel Hospital Katherine C. Spokes Harvard University/Beth Israel Hospital Species: Squalus acanthias Spiny dogfish Bulletin: Volume 31 - 1991 Type: Bulletin, Report Report: 49
12491	Paracrine Regulation of Ion Transport Across the Opercular Epithelium of the Killifish Fundulus heteroclitus	1999	David H. Evans University of Florida Joseph E.C. Hagen University of Florida Brian Corrigan Deer Isle-Stonington High School Abby Gross Deer Isle-Stonington High School Karl J. Karnaky, Jr. Medical University of South Carolina	Fundulus heteroclitus Mummichog Squalus acanthias Spiny dogfish	Volume 39 - 1999	11	Paracrine Regulation of Ion Transport Across the Opercular Epithelium of the Killifish Fundulus heteroclitus Item: 12491    Date: 1999 Author: David H. Evans University of Florida Joseph E.C. Hagen University of Florida Brian Corrigan Deer Isle-Stonington High School Abby Gross Deer Isle-Stonington High School Karl J. Karnaky, Jr. Medical University of South Carolina Species: Fundulus heteroclitus Mummichog Squalus acanthias Spiny dogfish Bulletin: Volume 39 - 1999 Type: Bulletin, Report Report: 11
12520	Processing and Localization of the Cystic Fibrosis Transmembrane Conductance Regulator in Gill and Operculum from Fundulus heteroclitus	1999	John E. Mickle Johns Hopkins University Karl J. Karnaky, Jr. Medical University of South Carolina Timothy J. Jensen Mayo Clinic and Foundation David S. Miller National Institutes of Environmental Health Sciences Sylvie A. Terlouw University Nijmegen Abby Gross Deer Isle-Stonington High School Brian Corrigan Deer Isle-Stonington High School John R. Riordan Mayo Clinic and Foundation Garry R. Cutting Johns Hopkins University	Fundulus heteroclitus Mummichog	Volume 39 - 1999	40	Processing and Localization of the Cystic Fibrosis Transmembrane Conductance Regulator in Gill and Operculum from Fundulus heteroclitus Item: 12520    Date: 1999 Author: John E. Mickle Johns Hopkins University Karl J. Karnaky, Jr. Medical University of South Carolina Timothy J. Jensen Mayo Clinic and Foundation David S. Miller National Institutes of Environmental Health Sciences Sylvie A. Terlouw University Nijmegen Abby Gross Deer Isle-Stonington High School Brian Corrigan Deer Isle-Stonington High School John R. Riordan Mayo Clinic and Foundation Garry R. Cutting Johns Hopkins University Species: Fundulus heteroclitus Mummichog Bulletin: Volume 39 - 1999 Type: Bulletin, Report Report: 40
12675	Regulation of Intestinal Chloride Secretion and Cloning of Uroguanylin in the Killifish, Fundulus heteroclitus	2002	Karl J. Karnaky, Jr. Medical University of South Carolina Pearl Ryder Maine School of Science and Mathematics Leonard R. Forte University of Missouri - Columbia	Fundulus heteroclitus Mummichog	Volume 42 - 2002	16	Regulation of Intestinal Chloride Secretion and Cloning of Uroguanylin in the Killifish, Fundulus heteroclitus Item: 12675    Date: 2002 Author: Karl J. Karnaky, Jr. Medical University of South Carolina Pearl Ryder Maine School of Science and Mathematics Leonard R. Forte University of Missouri - Columbia Species: Fundulus heteroclitus Mummichog Bulletin: Volume 42 - 2002 Type: Bulletin, Report Report: 16

Save these search results as a PDF file