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J A Jarrell

Publications and source records attributed to J A Jarrell.

10 recordsLinked to original sources
PubMed1987

Development of intercellular communication during the epithelial reorganization of a renal cell line (LLC-PK1).

Junctional permeability determinations after microinjection of the fluorescent tracer, Lucifer Yellow CH, show that the cells in confluent monolayers of the renal epithelial cell lines LLC-PK1 and A6 are interconnected by intercellular junctions. This cell-to-cell communication network permits the fluorescent dye to diffuse from the microinjected cell into multiple adjacent neighboring cells. Cell-to-cell diffusion of the fluorescent dye was not observed at pH 6.0. Full recovery occurred, however, when the pH of the extracellular medium was adjusted to 7.4. To provide a sensitive index of the averaged efficacy of junctional communication, we measured the number of cells that survived ouabain treatment in a 50% mixture of wild and ouabain-resistant mutant LLC-PK1 cells. Electron probe microanalysis in uncoupled cells showed that ouabain treatment produced two populations of cells, with totally different intracellular Na+ and K+ content. Under this condition, only 50% of the population survived after 48 h of treatment. When ouabain treatment was initiated 24 h after plating, however, 100% survival was observed, and the cells contained uniform intracellular Na+ and K+ concentration. This finding is consistent with the theory that this protective effect is mediated through the presence of the functional communicating intercellular junctions. When ouabain was applied at different times after plating, full protection is reached by 2 h. The early development of cell-to-cell communication, which precedes the development of the occluding junctions and several transport systems by several hours, is consistent with the involvement of the intercellular junctions in the synchronization of the polarization process.

Cell Communication↗
PubMed1987

Gap junctions and synchronization of polarization process during epithelial reorganization.

The formation of intercellular communication during epithelial reorganization of LLC-PK1 cells was studied with a new, nondisruptive flow cytometric technique. The assembly of these junctions, as demonstrated by cell-to-cell transfer of the fluorescent dye carboxy dimethyl fluorescein, occurs very early during epithelial reorganization. Close cell-to-cell interaction is required for the assembly to occur. Low temperature, treatment with 10(-3) M ouabain, or treatment with the Ca2+ ionophore A23187 inhibits assembly of these junctions. Removal of Ca2+ from the incubation medium, on the other hand, has no effect. Cycloheximide (10(-6) M) is also without effect, suggesting that protein synthesis is not required during the assembly of the junctions and that either the trypsin used to disperse the cells does not affect the junctional components or the cells have a rather extensive reserve pool of junctional precursors. The concomitant delay in the development of intercellular communication and the reorganization of the epithelial membrane, as previously observed with cells in asynchronous growth [Am. J. Physiol. 251 (Renal Fluid Electrolyte Physiol. 20): F978-F987, 1986], is consistent with the theory that junctional intercellular communication coordinates cellular activity during epithelial reorganization.

Animals↗
PubMed1983

Reversible carbon dioxide-induced inhibition of dye coupling in Necturus gallbladder.

The cells of Necturus gallbladder epithelium are electrically coupled. This work used intracellular injection of the fluorescent dye Lucifer yellow to demonstrate that these cells are also dye coupled and that this coupling is rapidly and reversibly inhibited by high concentrations of carbon dioxide. Dye coupling is also inhibited by the calcium ionophore A23187.

Animals↗
PubMed1981

A scanning micropipette molecule microscope.

A movable quartz micropipette, whose tip is sealed with a polymer plug, is used as a liquid-vacuum interface to a mass spectrometer. A light microscope allows observation of, and positioning of, the micropipette tip on the surface of a sample mounted in a perfusion chamber. This forms the basis of an instrument which enables one to study, in vitro, the localization of transepithelial transport of water and other molecules. Some preliminary results from the use of this instrument are presented.

Animals↗
PubMed1981

Interaction of ouabain with the Na+ pump in intact epithelial cells.

To determine the specificity and efficacy of [(3)H]ouabain binding as a quantitative measure of the Na(+) pump (Na(+), K(+)-ATPase) and as a marker for the localization of pumps involved in transepithelial Na(+)-transport, we analyzed the interaction of [(3)H]ouabain with its receptor in pig kidney epithelial (LLC-PK(1)) cells. When these epithelial cells are depleted of Na(+) and exposed to 2 muM [(3)H]ouabain in a Na(+)-free medium, binding is reduced by 90 percent. When depleted of K(+) and incubated in a K(+)- free medium, the ouabain binding rate is increase compared with that measured at 5 mM. This increase is only demonstable when Na(+) is present. The increased rate could be attributed to the predominance of the Na(+)-stimulated phosphorylated form of the pump, as K(+) is not readily available to stimulate dephosphorylation. However, some binding in the K(+)-free medium is attributable to pump turnover (and therefore, recycling of K(+)), because analysis of K(+)-washout kinetics demonstrated that addition of 2 muM ouabain to K(+)-depleted cells increased the rate of K(+) loss. These results indicate that in intact epithelial cells, unlike isolated membrane preparations, the most favorable condition for supporting ouabain binding occurs when the Na(+), K(+)-ATPase is operating in the Na(+)-pump mode or is phosphorylated in the presence of Na(+). When LLC-PK(1) cells were exposed to ouabain at 4 degrees C, binding was reduced by 97 percent. Upon rewarming, the rate of binding was greater than that obtained on cells kept at a constant 37 degrees C. However, even at this accelerated rate, the time to reach equilibrium was beyond what is required for cells, swollen by exposure to cold, to recover normal volume. Thus, results from studies that have attempted to use ouabain to eliminate the contribution of the conventional Na(+) pump to volume recovery must be reevaluated if the exposure to ouabain was done in the cold or under conditions in which the Na(+) pump is not operating.

Animals↗
PubMed1981

A mass spectrometer to measure transepithelial unidirectional labeled water fluxes.

A sealed quartz micropipette forms a liquid-vacuum interface that together with a uranium reduction element and a mass spectrometer functions as an in vitro real-time labeled water-selective microelectrode. Its performance is demonstrated by monitoring unidirectional fluxes across toad urinary bladder. This instrument has direct applicability to studies of water flux across epithelial membranes and could also be useful in monitoring water fluxes across such preparations as isolated tubules or capillaries.

Animals↗
PubMed1980

Protection of cultured renal tubular epithelial cells from anoxic cell swelling and cell death.

In order to study the relationship between cell swelling and cell death due to ischemia, we have developed an in vitro model by using primary cultures of renal tubular epithelial cells. With this model, we have studied two components of ischemia--namely, anoxia along with substrate deprivation. After 2 hr of anoxia in the absence of substrate, the cultured cells swelled and blebbed. Cells similarly treated in the presence of 8% polyethylene glycol, an oncotic agent, did not swell and bleb, and when cells were counted 18 hr later, similar numbers of cells were seen as in the untreated cultures. However, tubule cells exposed to anoxia without 8% polyethylene glycol had 50% fewer cells 18 hr later. Therefore, if cell swelling is prevented during 2 hr of anoxia, cell viability is improved.

Animals↗
PubMed1976

Biochemical assay by immobilized enzymes and a mass spectrometer.

By counting the volatile molecules produced by an immobilized-enzyme catalyzed reaction which is interfaced to a mass spectrometer via a semi-permeable membrane, a general approach to biochemical measurement and detection is obtained which offers the potential of high sensitivity, specificity and speed. In combination with molecule microscopy, this method should allow, for example, a mapping of suitable enzyme distributions in non-stained and non-fixed tissue slices. Immobilized urease (urea amidohyrdrolase, EC 3.5.1.5) was used to assay urea using CO2 as the volatile product, and alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) was used to assay NADH using ethanol as the volatile product.

Alcohol Oxidoreductases↗