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Biomedical subjects

C Cannon

Publications and source records attributed to C Cannon.

31 records · Page 2Linked to original sources
PubMed1989

Isolation and culture of HCO3- -secreting intercalated cells.

Intercalated cells of the distal nephron secrete either H+ or HCO3-. We have succeeded in isolating HCO3- -secreting intercalated cells from the rabbit kidney. When seeded onto collagen-coated permeable supports, these cells form monolayers with a resistance of 595 +/- 75 omega.cm2. The monolayers maintain the characteristics of an epithelium, with apical microvillae and tight junctions. They display the same polarity as do HCO3- -secreting intercalated cells in vivo, namely apical peanut lectin binding and apical Cl- -HCO3- exchange. The monolayers are capable of transepithelial HCO3- transport via this exchanger. The rate of Cl- -dependent transepithelial HCO3- transport is 4 +/- 0.4 nmol.min-1.cm-2. Transepithelial HCO3- transport is completely abolished by 50 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid applied to the apical side of the monolayer. These cultured HCO3- -secreting intercalated cells should prove useful for defining the cellular regulation of HCO3- secretion.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1987

Chromosome aberrations and sister chromatid exchanges in Chinese hamster ovary cells: evaluations of 108 chemicals.

Results from the testing of 108 coded chemicals in Chinese hamster ovary (CHO) cells for the induction of chromosome aberrations and sister chromatid exchanges (SCEs) are presented. All chemicals were tested with and without exogenous metabolic activation, using protocols designed to allow testing up to toxic doses. Cell harvest times could also be extended if chemical-induced cell cycle delay was seen. Chromosome aberrations were induced by 43 of the chemicals, and 66 induced SCEs; 37 of the chemicals were positive for both endpoints.

Animals↗
PubMed1983

Regulation of proton transport in urinary epithelia.

In urinary epithelia, like the turtle bladder, protons are transported by a H+ translocating ATPase located in the luminal membrane. We have recently discovered that the H+ pump is stored in small vesicles that lie underneath the luminal membrane. CO2, a major regulator of H+ transport causes these vesicles to fuse with the membrane thereby inserting more H+ pumps. We have now isolated these vesicles from the turtle bladder and from beef kidney medulla. Based on inhibitor sensitivity and substrate specificity this proton translocating ATPase is different from the mitochondrial F0-F1 ATPase, yeast plasma membrane and the gastric H+,K+-ATPase. Solubilization and reconstitution of the enzyme into liposomes shows retention of transport activity and inhibitor sensitivity.

Acid-Base Equilibrium↗
PubMed1982

Exocytosis regulates urinary acidification in turtle bladder by rapid insertion of H+ pumps into the luminal membrane.

Urinary acidification by the turtle bladder is due to a H+-ATPase that is located in the luminal membrane. The rate of H+ transport is stimulated by an increase in the ambient CO2. Using the fluorescent dye acridine orange, we showed that the mitochondria-rich cell of this equilibrium contains vesicles whose internal pH is acidic. We measured the pH of these vesicles by using endocytosed fluorescein isothiocyanate-labeled dextran and found it to be near 5.0. The pH increased after treatment with protonophores or metabolic inhibitors, suggesting that it was due to a H+ pump rather than to a Donnan effect. In bladders preloaded with fluorescent dextran, CO2 stimulated exocytosis and H+ transport measured simultaneously in the same bladder. The increase in the H+ current correlated well with the extent of exocytosis, and both were inhibited by pretreatment with colchicine. We conclude that the turtle bladder contains an intracellular reserve of vesicles containing H+ pumps and CO2 stimulates rapid fusion of these vesicles with the luminal membrane with consequent insertion of H+ pumps, thereby stimulating H+ secretion across the whole epithelium.

Acid-Base Equilibrium↗
PubMedDate not supplied

Carbon-dioxide-induced exocytotic insertion of H+ pumps in turtle-bladder luminal membrane: role of cell pH and calcium.

The contents of endocytic vesicles and other intracellular organelles (such as Golgi and microsomes) are acidified by an electrogenic proton-translocating ATPase that is remarkably similar to that found in urinary epithelia. We recently found that the number of H+ ATPases in the apical plasma membrane of these epithelia is regulated by exocytotic insertion of endocytic vesicles whose membranes contain this H+ pump. Carbon dioxide, a major stimulus for urinary acidification, causes rapid fusion of these vesicles with the luminal membrane, thereby inserting these pumps there and increasing the rate of net transepithelial H+ secretion; CO2 also inhibits endocytic retrieval of the pumps from the luminal membrane. Such reciprocal regulation of endocytosis and exocytosis by a physiological modulator makes this system particularly attractive for studying the cellular events regulating membrane fusion. Here we present evidence that CO2 induces exocytosis by a cascade of events, the first step of which is cytoplasmic acidification. Cell acidification then increases calcium activity, which causes the fusion event.

Animals↗
PubMedDate not supplied

A pharmacology review for private duty nurses using computers and self learning concepts.

Computers, rather than instructors, patiently tutored the nurses, providing them with as much practice as necessary to master calculation skills. Instruction was consistent and readily available. Traditional printed material also was used because of its portability and accessibility. It was reassuring for the nurses to have something tangible to review. Program evaluations were positive. Comments such as the following were not uncommon: "The computer is a patient tutor; it never criticizes or tires"; "It was better than attending a workshop or lecture. I really learned the material because I was responsible for my learning." Currently, this group of nurses is using computer-assisted instructional programs for professional development. With the help and guidance of the PENZANCE staff, they overcame their fear of the technology and are now requesting that more programs be made available. It was a good experience for all.

Computer-Assisted Instruction↗