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Biomedical subjects

M J Stutts

Publications and source records attributed to M J Stutts.

At least 55 records · Page 3Linked to original sources
PubMed1988

3. Epithelial injury. Mechanisms and cell biology of airway epithelial injury.

Injury of airway epithelia involves selective interactions of toxins with the cellular and paracellular components of the epithelial barrier. Repair of epithelial injury appears to involve mitogenic and differentiating factors that function in autocrine and paracrine modes. Fruitful techniques for future study of airway epithelial injury and repair will include combinations of cell culture and modulation of gene expression.

Cell Division↗
PubMed1988

Cell calcium levels of normal and cystic fibrosis nasal epithelium.

To determine whether epithelial ion transport abnormalities in cystic fibrosis (CF) might reflect abnormal regulation of intracellular Ca2+ levels, cytosolic free calcium (Cai2+) was measured using fura-2 or quin2 in suspensions of normal or CF nasal epithelial cells derived from primary cell culture. The basal Cai2+ level measured with fura-2 in CF nasal epithelia was 155 +/- 9 nM (n = 5), a value not significantly different from normal nasal epithelia (143 +/- 16 nM, n = 5). Total cell calcium was measured by atomic absorption spectroscopy and no differences were observed between CF (6.3 +/- 0.5 nmol/mg protein; n = 3) and normal (6.2 +/- 1.2 nmol/mg protein; n = 3) nasal epithelial cells. Placing Na+ loaded cells in a low (10 mM) extracellular Na+ solution resulted in a rapid increase in Cai2+ consistent with Ca2+ uptake via a plasmalemmal Na+-Ca2+ exchanger. The level of Cai2+ achieved by this low Na+ maneuver was not significantly different in CF cells compared to normal cells. Neither isoproterenol (10(-5) M) nor forskolin (10(-6) M) had any effect on Cai2+ in normal or CF nasal epithelial cells. Thus, it appears that differences in cell Cai2+, as measured by fluorescent chelators in suspensions of cultured cells, do not account for the abnormalities in basal or isoproterenol stimulated ion transport in CF tissues.

Adolescent↗
PubMed1987

Abnormal apical cell membrane in cystic fibrosis respiratory epithelium. An in vitro electrophysiologic analysis.

The transepithelial chloride permeability of airway and sweat ductal epithelium has been reported to be decreased in patients with cystic fibrosis (CF). In the present study, we investigated whether the airway epithelial defect was in the cell path by characterizing the relative ion permeabilities of the apical membrane of respiratory epithelial cells from CF and normal subjects. Membrane electric potential difference (PD) and the responses to luminal Cl- replacement, isoproterenol, and amiloride were measured with intracellular microelectrodes. The PD across the apical barrier was smaller for CF (-11 mV) than normal (-29 mV) epithelia whereas the PD across the basolateral barrier was similar, (-26 and -34 mV respectively). In contrast to normal nasal epithelium, the apical membrane in CF epithelia was not Cl- permselective and was not responsive to isoproterenol. Amiloride, a selective Na+ channel blocker, induced a larger apical membrane hyperpolarization and a greater increase in transepithelial resistance in CF epithelia. Both reduced apical cell membrane Cl- conductance and increased Na+ conductance appear to contribute to the abnormal function of respiratory epithelia of CF patients.

Amiloride↗
PubMed1987

Effects of ozone on airway epithelial permeability and ion transport.

Hartley guinea pigs had a 3-h sham exposure or a 3-h exposure to 1.0 ppm ozone. Within 2 h tracheas were excised and mounted in conventional Ussing chambers. Potential difference (PD), short circuit current (Isc), conductance (G) and unidirectional fluxes of 22Na, 36Cl and [14C]mannitol were measured in blinded experiments. Compared to the tracheal epithelia of sham-exposed animals, those from exposed animals had a larger PD (45%), an increased Isc (41%) and no change in G. In both groups, the Isc was approximately equivalent to net sodium absorption. The higher current in the exposed animal's tissues was disproportionately more sensitive to inhibition by the specific sodium channel blocker amiloride (44% vs. 13%). These observations suggest that early consequences of exposure of airway epithelium to ozone include increases in the density or open time of sodium channels in the luminal cell membrane or a change in sodium pump activity that increases the gradient for sodium entry across the luminal cell membrane. By 24 h after exposure these changes had been obscured by an increase in epithelial permeability, perhaps as the result of an inflammatory response to the ozone exposure.

Animals↗
PubMed1987

Cell culture approaches to the investigation of human airway ion transport.

Several techniques for the study of human airway epithelial ion transport employing cultured cells were explored. Human nasal epithelial cells were cultured in serum-free, hormone supplemented media. For bioelectric characterization of ion transport functions of cultured cells, cells were inoculated into heterologous grafts, and implanted into immunocompromised mice, or onto collagen membranes maintained in vitro. Cells populating either preparation exhibited a pattern of Na+ and Cl- transport similar to that of freshly excised nasal specimens. Differences between preparations were observed for absolute transport rates, tissue resistance, and morphology. We conclude that (1) cell culture techniques will be useful in investigating ion transport activities of human pulmonary epithelia from normal and abnormal lungs; and (2) the selection of specific culture techniques should be guided by the nature of the epithelial functions tested.

Adolescent↗
PubMed1986

Effects of formaldehyde on bronchial ion transport.

The functions of the epithelium that lines mammalian airways are potential targets for the toxic effects of reactive chemicals such as formaldehyde. We examined the effects of formaldehyde on bioelectric properties and ion permeation of excised canine and human bronchial epithelium. Concentration-dependent reductions in short-circuit current were induced in both tissues. Sodium absorption and transcellular chloride fluxes across canine bronchial epithelium were inhibited by 65 and 35%, respectively, by 10(-3) M formaldehyde. The QO2 of isolated dog bronchial epithelial cells was reduced by 32% by 10(-3) M formaldehyde. These results are consistent with an action of formaldehyde on cellular ion permeability but effects secondary to metabolic inhibition cannot be dismissed.

Animals↗
PubMed1986

Effects of Pseudomonas aeruginosa on bronchial epithelial ion transport.

During chronic lung infections the effects of bacterial exoproducts on the function of the airways epithelium could play a role in the overall pathophysiology of infection. We measured the effects of Pseudomonas aeruginosa culture on ion transport and solute permeability of dog bronchial epithelium to determine if this organism produces toxins that affect these epithelial functions. Thirty-six-hour trypticase soy broth cultures of P. aeruginosa at 1:40 dilutions decreased short-circuit current and active sodium absorption and lowered conductance and chloride unidirectional fluxes. At 1:4 dilutions, P. aeruginosa increased conductance and the permeability coefficient of 14C-mannitol, suggesting that solute flow around cells was increased. These effects appear to be caused by a heat-stable glycolipid hemolysin produced by P. aeruginosa.

Animals↗
PubMed1986

Deposition, clearance, and effects of aerosolized amiloride in sheep airways.

Persistent Na+ absorption across a relatively Cl- impermeable epithelial barrier may contribute to the smaller water content of airway surface liquid (ASL) in cystic fibrosis. In this study, the feasibility and effectiveness of delivering an inhibitor of Na+ absorption, amiloride, by aerosol to the ASL of awake sheep was evaluated. Aerosolization of 6 X 10(-3) M amiloride, with [14C]amiloride, resulted in an estimated concentration of 7 X 10(-4) M in ASL. The transtracheal electric potential difference (PD), an index of the rate of Na+ absorption, was significantly inhibited (-29%) immediately after aerosolization of amiloride. The inhibition was short-lived and was correlated with rapid disappearance of the drug from ASL (half-time, 10.5 min between 0 and 30 min after aerosolization). Amiloride but not aerosol vehicle increased ASL volume significantly. The unidirectional flow of [14C]amiloride from the lumen to the submucosa across excised, short-circuited sheep airways exceeded flow from submucosa to lumen by a factor of at least 6. This finding suggests that amiloride is actively absorbed and is consistent with the rapid clearance from the airway surface and the short-lived effects of aerosolized amiloride in vivo. We conclude that sufficient concentrations of amiloride can be delivered to sheep airways by aerosol to inhibit PD and Na+ absorption for short periods.

Aerosols↗
PubMed1986

Na+ transport in cystic fibrosis respiratory epithelia. Abnormal basal rate and response to adenylate cyclase activation.

The transepithelial potential difference (PD) of cystic fibrosis (CF) airway epithelium is abnormally raised and the Cl- permeability is low. We studied the contribution of active Na+ absorption to the PD and attempted to increase the Cl- permeability of CF epithelia. Nasal epithelia from CF and control subjects were mounted in Ussing chambers and were short-circuited. The basal rate of Na+ absorption was raised in CF polyps compared with control tissues. Whereas beta agonists induced Cl- secretion in normal and atopic epithelia, beta agonists further increased the rate of Na+ absorption in CF epithelia without inducing Cl- secretion. This unusual effect is not due to an abnormal CF beta receptor because similar effects were induced by forskolin, and because cAMP production was similar in normal and CF epithelia. We conclude that CF airway epithelia absorb Na+ at an accelerated rate. The abnormal response to beta agonists may reflect a primary abnormality in a cAMP-modulated path, or a normal cAMP-modulated process in a Cl- impermeable epithelial cell.

Adenylyl Cyclases↗
PubMed1986

Oxygen consumption and ouabain binding sites in cystic fibrosis nasal epithelium.

Ion transport by the epithelium lining the airways of patients with cystic fibrosis (CF) is characterized by a raised transepithelial PD and an increased amiloride sensitivity (1). These properties could arise from normal sodium transport across an epithelium with decreased cell chloride permeability and limited chloride secretion. Alternatively, a higher than normal rate of sodium absorption could contribute to these abnormalities. We investigated the latter possibility by measuring oxygen consumption and specific ouabain binding of CF and atopic polyp epithelia and normal turbinate epithelium. Tissue from CF patients consumed oxygen at a rate that was two to three times that of non-CF tissues and had 60% more ouabain binding sites than non-CF epithelium. These results are not consistent with an isolated defect in chloride permeability but support recent findings that the sodium conductance of the apical cell membrane and net sodium absorption by CF nasal epithelium are greater than those of non-CF nasal epithelium.

Adolescent↗
PubMed1986

Abnormal respiratory epithelial ion transport in cystic fibrosis.

The respiratory epithelium of cystic fibrosis patients exhibits excessive sodium (and volume) absorption and an absence of chloride (and volume) secretion in response to usual stimuli. These abnormalities likely contribute to the pathophysiology of cystic fibrosis lung disease, and provide a rationale for a novel therapeutic approach to this problem.

Animals↗
PubMed1985

Chloride uptake into cultured airway epithelial cells from cystic fibrosis patients and normal individuals.

The chloride permeability of airway and sweat ductal epithelium of cystic fibrosis (CF) patients is decreased. This abnormality could represent an intrinsic characteristic of the epithelial cell or the response to a tonic extrinsic stimulus, in vivo. We cultured airway epithelial cells derived from CF and non-CF individuals under identical conditions that were free from donor-specific factors. Differences in the characteristics of cells that multiplied under these circumstances are unlikely to reflect the effects of extrinsic modulation present in the host. After 8-12 days in culture, the cells of CF and non-CF patients were similar in morphology and intracellular electrolyte content, but the CF cultures took up chloride at a reduced rate. The difference could not be attributed to a higher intracellular potential in CF cells or to the presence of a stilbene anion-sensitive chloride-chloride exchange in non-CF cells. We conclude that epithelial cells from CF patients grown in the absence of extracellular factors of the host express reduced cellular chloride permeability, a defect similar to that found in vivo and in freshly excised nasal epithelium.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1983

Abnormal ion permeation through cystic fibrosis respiratory epithelium.

The epithelium of nasal tissue excised from subjects with cystic fibrosis exhibited higher voltage and lower conductance than tissue from control subjects. Basal sodium ion absorption by cystic fibrosis and normal nasal epithelia equaled the short-circuit current and was amiloride-sensitive. Amiloride induced chloride ion secretion in normal but not cystic fibrosis tissue and consequently was more effective in inhibiting the short-circuit current in cystic fibrosis epithelia. Chloride ion-free solution induced a smaller hyperpolarization of cystic fibrosis tissue. The increased voltage and amiloride efficacy in cystic fibrosis reflect absorption of sodium ions across an epithelium that is relatively impermeable to chloride ions.

Absorption↗
PubMed1981

Regional differences in airway surface liquid composition.

Liquid from canine airway surfaces was absorbed onto filter paper strips and analyzed. In resting conditions, tracheal surface liquid was hyperosmolal (330 mosmol/kg H2O) compared to plasma with raised Na+ (158 meq/l), Cl- (134 meq/l), K+ (28 meq/l), and HCO3- (32 meq/l) concentrations. The volume collected was increased by repetitive sampling, a response blocked by atropine, or by methacholine injection. Compared to nose breathing, tracheal surface liquid osmolality was increased by 10 min of mouth breathing (410 mosmol/kg H2O). Surface liquid from 0.5-cm diameter bronchi was nearly isosmolal (304 mosmol/kg H2O) with plasma in resting conditions, with Na and Cl concentrations lower than plasma (120 and 106 meq/l, respectively), and K+ (52 meq/l), and HCO3- (50 meq/l) concentrations higher than those of plasma or tracheal liquid. Although the K+ in tracheal fluid approaches the value for electrochemical equilibrium, K+ in fluid from the bronchi and HCO3- in both regions cannot be accounted for by passive forces. The regional difference in osmolality supports the concept that the higher osmolality of tracheal liquid reflects evaporative water loss from this site. The transepithelial osmotic gradient generated by evaporative water loss may be a driving force for hydration of the tracheal surface.

Animals↗