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C W Davis

Publications and source records attributed to C W Davis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Mucin production by SPOC1 cells--an immortalized rat tracheal epithelial cell line.

An airway epithelial mucous goblet cell line would be useful towards understanding mechanisms underlying the common problem of respiratory mucus hypersecretion. SPOC1 is a novel rat tracheal epithelial (RTE) cell line that developed cytologic features suggestive of mucous goblet cells when grown in tracheal grafts in vivo (Am. J. Respir. Cell Mol. Biol. 1995; 12:385-395). Our aims were to determine whether SPOC1 cells were capable of mucin synthesis and to directly compare mucin production by SPOC1 cells and RTE cells. Towards this end, we validated the use of monoclonal antibody (mAb) RTE11 (Exp. Lung Res. 1992; 18:323-342) as an immunologic probe for rat airway secretory mucin. Our results strongly suggest that mAb RTE11 detects a carbohydrate antigen that is a sensitive and specific marker for rat tracheobronchial secretory mucin. SPOC1 cells in tracheal grafts in vivo contained granules with ultrastructural features similar to mucous granules in normal rat airway goblet cells and they were strongly stained by mAb RTE11. Retinoic acid (RA) and culture on porous supports are known to profoundly modify airway epithelial cell phenotype in vitro. Expression of several retinoid-responsive proteins was similar in cultured SPOC1 and primary RTE cells, but major differences in mucin production were noted. Primary RTE cells in vitro only made mucin when grown on porous supports in the presence of RA, whereas SPOC1 cells produced mucin when grown on plastic or glass surfaces and even in the absence of RA. Interestingly, RA enhanced mucin secretion by SPOC1 cells during the early plateau stage of culture but there were no differences due to RA late in the culture period. SPOC1 cells are capable of mucin production and will be a useful tool for studying select aspects of airway secretory cell differentiation and function.

Animals↗
PubMed1995

Invasive pneumococcal infection in children, 1981-92: a hospital-based study.

OBJECTIVE: To document the pattern and sequelae of invasive pneumococcal infection in hospitalized children. METHODOLOGY: Retrospective review of Streptococcus pneumoniae (Sp) isolates from normally sterile sites from 1981 to 1992 at three paediatric centres in Sydney for demographic data, spectrum of disease, predisposing conditions, mortality, and sequelae from meningitis. RESULTS: Four hundred and thirty-one episodes in 417 patients were identified. Foci of infection were: meningitis, 34%; pneumonia, 29%; bacteraemia without apparent focus, 30%; and other foci, 7%. Sixty-one per cent of all cases and 64% of cases with meningitis were less than 2 years old. Predisposing conditions were present in 37%, were significantly more common in patients over age 2 years and were more common with foci other than meningitis. Overall mortality was 6.6% whereas the mortality for those with meningitis was 8%. Neurological sequelae were identified in 34% of previously normal children, and severe hearing loss occurred in 11.5%. CONCLUSIONS: The high morbidity and mortality from invasive pneumococcal infection in children justifies further evaluation of preventive strategies.

Adolescent↗
PubMed1995

Role of CNP in human airways: cGMP-mediated stimulation of ciliary beat frequency.

Ciliated airway epithelial cells contribute to mucociliary transport systems via ciliary beating and electrolyte transport mechanisms. Both of these activities are regulated by agonists acting through intracellular calcium- and adenosine 3',5'-cyclic monophosphate (cAMP)-dependent processes (5, 15, 18, 27). This study examines the role of guanosine 3',5'-cyclic monophosphate (cGMP) in the regulation of both ciliary beat frequency (CBF) and electrolyte transport in human airway epithelia (HAE). In a previous report, cGMP production in HAE was observed after stimulation with either C-type natriuretic peptide (CNP) or sodium nitroprusside (SNP) (6). In this study, CNP was found to increase CBF by 30 +/- 6.9%, and this effect was mimicked by the cGMP analogue, 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP), but not by sodium nitroprusside. CNP-induced increases in CBF do not appear to be mediated by changes in either intracellular calcium or cAMP levels. Using modified Ussing chambers, we also investigated CNP's potential modulation of sodium and chloride transport rates. Neither CNP, nor SNP, nor 8-BrcGMP altered active ion transport rates. We conclude that CNP regulates ciliary beat via cGMP-dependent mechanisms, whereas no effect of CNP or cGMP on ion transport was detected.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1995

Phenotype and differentiation potential of a novel rat tracheal epithelial cell line.

In this report we described the establishment and characterization of a continuous rat tracheal epithelial (RTE) cell line spontaneously derived from secondary RTE cell cultures. Designated SPOC1, this cell line is nontumorigenic and maintains a diploid karyotype with specific, nonrandom chromosomal alterations involving chromosomes 1, 3, and 6. SPOC1 cells demonstrate decreased requirements for peptide growth factors, compared with primary RTE cells. Upon inoculation into denuded rat tracheas, which are then implanted into syngeneic hosts, SPOC1 cells initially form a stratified squamous epithelium, which becomes less stratified with time and forms glandlike invaginations into the surrounding lamina propria. No evidence of ciliated cell differentiation is detected. The epithelium formed by SPOC1 cells in tracheal grafts reacts with antibodies specific for keratin 14, 13, and 19 (but not keratin 18) at both early and late time points, although the localization of antibody staining changes as the epithelium becomes less stratified with time. The suprabasal epithelial cells become positive for alcian blue-periodic acid-Schiff staining at later time points. The near-normal karyotype and differentiation potential of SPOC1 cells make this cell line a unique window into early changes occurring during immortalization of airway epithelial cells and will allow studies of relationships between differentiation state and neoplastic transformation.

Animals↗
PubMed1994

Calcein accumulation as a fluorometric functional assay of the multidrug transporter.

Acetoxymethyl ester (AM) derivatives of various fluorescent indicators (fura-2, fluo-3, indo-1, BCECF, calcein) are actively extruded by the multidrug transporter (MDR1, P-glycoprotein-Homolya, L. et al. (1993) J. Biol. Chem. 268, 21493-21496). In the present paper we show that the measurement of the accumulation of a fluorescent cell viability marker, calcein, can be effectively used as a rapid and sensitive fluorometric and flow cytometric assay for studying P-glycoprotein function. The rate of calcein accumulation in human MDR1-expressing cells is significantly lower than in the control cells, while various drug-resistance reversing agents (verapamil, vinblastine, oligomycin, cyclosporin A and UIC2 monoclonal antibody) greatly increase calcein trapping only in the MDR1-expressing cells. Since calcein-AM is not fluorescent and free calcein is not a substrate of the multidrug transporter, the assay is readily applicable for rapid kinetic studies of the MDR1 function. Calcein has a high fluorescence intensity in the visible range, thus changes in calcein uptake can be easily visualised and MDR1-expressing and control cells separated by conventional flow cytometry.

3T3 Cells↗
PubMed1994

Selective response of human airway epithelia to luminal but not serosal solution hypertonicity. Possible role for proximal airway epithelia as an osmolality transducer.

The response of cultured human nasal epithelia to hypertonic bathing solutions was tested using ion-selective microelectrode and quantitative microscopy. Raised luminal, but not serosal, osmolality (+/- 150 mM mannitol) decreased Na+ absorption but did not induce Cl- secretion. Raised luminal osmolality increased cell Cl- activity, Na+ activity, and transepithelial resistance and decreased both apical and basolateral membrane potentials and the fractional resistance of the apical membrane; equivalent circuit analysis revealed increases in apical, basolateral, and shunt resistances. Prolonged exposure (10 min) to 430 mosM luminal solution elicited no regulation of any parameter. Optical measurements revealed a reduction in the thickness of preparations only in response to luminal hypertonic solutions. We conclude that (a) airway epithelial cells exhibit asymmetric water transport properties, with the apical membrane water permeability exceeding that of the basolateral membrane; (b) the cellular response to volume loss is a deactivation of the basolateral membrane K+ conductance and the apical membrane Cl- conductance; (c) luminal hypertonicity slows the rate of Na+ absorption but does not induce Cl- secretion; and (d) cell volume loss increases the resistance of the paracellular path. We speculate that these properties configure human nasal epithelium to behave as an osmotic sensor, transducing information about luminal solutions to the airway wall.

Adult↗
PubMed1993

Nucleotide regulation of goblet cells in human airway epithelial explants: normal exocytosis in cystic fibrosis.

The regulation of mucin secretion by airway goblet cells is poorly understood and the receptor-based regulatory mechanisms have not been described in human airways. In the present study, we report that extracellular triphosphate nucleotides regulate the rate of granule release from goblet cells in both normal and cystic fibrosis (CF) airway epithelial explants. Explants isolated from nasal and tracheobronchial tissues were mounted in perfusion chambers and the secretory activity was assessed by videomicroscopic determination of degranulation in single goblet cells and by ELISA determination of mucins secreted into the mucosal perfusate. Baseline degranulation was measured at 0.05 degranulation events (DE)/min. In normal goblet cells, mucosal ATP (10(-4) M, n = 17) induced a biphasic secretory response comprising 29.1 +/- 4.9 DE during the first 5 min, with an initial rate of 118.2 +/- 10.2 DE/min. Mucosal UTP (10(-4) M, n = 9) induced a similar response to ATP (initial rate: 89.2 +/- 23.9 DE/min, 17.9 +/- 5.1 DE in 5 min), but mucosal 2-MeSATP was not an effective agonist (initial rate: 1.5 +/- 1.4 DE/min, 2.3 +/- 0.5 DE in 5 min). Determination of mucins by ELISA confirmed that both ATP and UTP induced similar secretory responses but that 2-MeSATP was not effective. In CF explants, mucosal UTP (10(-4) M, n = 6) induced similar responses to those observed in normal tissues (initial rate: 82.5 +/- 27.5 DE/min, 18.8 +/- 4.1 DE in 5 min). We conclude that human nasal and tracheobronchial goblet cells are stimulated by mucosal nucleotides, probably via a 5'-nucleotide receptor, and that this response is unaffected by CF.

Bronchi↗
PubMed1992

Goblet cell degranulation in isolated canine tracheal epithelium: response to exogenous ATP, ADP, and adenosine.

Mucin secretion by goblet cells was determined by quantifying degranulation events (DE) in isolated, superficial epithelium from canine trachea. The epithelium was isolated and explanted to a novel transparent, permeable support, and the goblet cells were visualized by video microscopy. Baseline degranulation events were quantified at 0.05 DE/min. Luminal ATP (10(-4) M, n = 10) stimulated a biphasic secretory response; a burst, maximum rate = 87.9 +/- 25.3, was followed by a plateau, rate = 1.9 +/- 0.3 DE/min. Serosal ATP elicited a complex set of responses: 9 cells failed to respond, 13 exhibited a trivial response, and 31 responded vigorously but with highly variable patterns of degranulation. Nonhydrolyzable 5'-adenylylimidodiphosphate caused degranulation from both sides of the epithelium. Luminal ADP and adenosine were ineffective. Serosal ADP and adenosine elicited a range of responses that was similar in diversity and magnitude to the ATP response. Our conclusions were as follows: 1) goblet cells in the superficial epithelium of the airway can be studied at the single-cell level in explants; 2) nucleotides stimulate goblet cells to secrete mucin; and 3) the goblet cell expresses different nucleotide receptors on its apical and basolateral membranes.

Adenine Nucleotides↗
PubMed1991

Effects of cholinergic drugs on longitudinal contraction in levamisole-susceptible and -resistant Haemonchus contortus.

A novel force transducer was used to measure the effects of cholinergic agonists on longitudinal contraction in Haemonchus contortus. Drugs were applied to whole worms or injected via a cannula in the pseudocoelomic cavity. A number of agonists, including nicotine and the anthelmintics m-aminolevamisole, levamisole and morantel, caused contractions in whole worms. Four- to 25-fold increases in concentration of the active compounds were required to cause contractions in each of two levamisole-resistant strains of H. contortus. Of the other compounds tested, bephenium had equivalent activity against susceptible and resistant strains. Anticholinesterase compounds caused contractions after a slight delay in susceptible, but not resistant worms. Numerous cholinergic agonists and other compounds did not cause contraction when applied to whole worms. One of these, acetylcholine, caused contractions in cannulated worms. Compared with the susceptible strain, five- to six-fold higher concentrations of acetylcholine were required to cause equivalent contractions in the resistant strains. Levamisole resistance in adult H. contortus is likely to be due to a change in the characteristics of the cholinergic receptor(s).

Animals↗
PubMed1991

Axis II comorbidity in substance abusers.

OBJECTIVE: To assess the complex relationship between substance abuse and personality disorders, the authors determined the prevalence of personality disorders in a group of middle-class substance abusers and compared the subjects who had personality disorders with those who did not. METHOD: The subjects were drawn from patients consecutively admitted to an inpatient substance abuse program in a private psychiatric hospital; they were the first 100 who agreed to participate. Substance dependence was diagnosed according to DSM-III-R, and the patients were assessed with the Structured Clinical Interview for DSM-III-R Personality Disorders, Alcohol Use Inventory, MMPI, Health and Daily Living Form, Shipley Institute of Living Scale, and measures of chemical use and life satisfaction. RESULTS: Of the 100 substance abusers, 57 had personality disorders. These patients differed significantly from the 43 patients without personality disorders in several ways: they had greater involvement with illegal drugs, had different patterns of alcohol use, had greater psychopathology, were less satisfied with their lives, and were more impulsive, isolated, and depressed. CONCLUSIONS: Because of the marked differences between the substance abusers with and without personality disorders, a uniform approach to substance abuse treatment may be inadequate.

Adult↗
PubMed1991

The importance of street drug terms as diagnostic clues.

"Words are both better and worse than thoughts; they express them and add to them" [Tyrone Edwards]. Choice of street terms is a clinical expression of the mental state and the drug history of the individual which evolves from repetition and frequent use. Broadened experiences usually accompany continued use, including experimentation with esoteric and powerful drug combinations. Drug terms employed by the user may have diagnostic utility for the experienced clinician in determining severity of symptoms. Recommendations for relapse prevention become more credible through a familiar lexicon. Practitioner understanding of drug terms as a tool to elicit information may lead to a deeper understanding of the breadth and depth of patient use of drugs. The authors recognize that they have contributed to the homogeneity, understanding, and distribution of terms by this article.

Communication↗
PubMed1989

Na+ and Cl- transport across rabbit nonciliated bronchiolar epithelial (Clara) cells.

Radioisotopic flux measurements were performed on rabbit Clara cell epithelium cultured in serum-free hormone-supplemented medium to identify the major ion transport pathways in the cell type. Clara cells cultured in serum-free hormone-supplemented medium exhibit a large short-circuit current compared with cells maintained in serum-containing medium (45 microA/cm2 vs. 15 microA/cm2). The responses to amiloride and isoproterenol, however, are similar for cells grown in the two media. A net amiloride-sensitive movement of Na+ in the mucosal (M)-to-serosal (S) direction undershort- and open-circuit conditions is detected (1.48 and 0.67 mueq.h-1.cm-2, respectively). No statistically significant difference in the unidirectional fluxes of Cl- is apparent in the basal state, but a net flux of Cl- in the S-to-M direction is observed after exposure of the apical membrane to amiloride (0.93 mueq.h-1.cm-2). The partial ionic conductances for Na+ and Cl- estimated from the fluxes measured in the passive directions (JNaS----M, JClM----S) exceed the total tissue conductance by 20%. Ussing flux ratio analyses of Cl- movements at clamped potentials between -60 and +20 mV show that Cl- movements are not strictly through passive conductive pathways at negative potentials. The movement of Cl- can be modeled by passive diffusion combined with Cl- -Cl- exchange equal to 20% of total passive fluxes of Na+ and Cl-. These observations indicate that 1) Na+ absorption is the major active ion transport pathway across cultured Clara cells, 2) active Cl- secretion is minimal in the basal state, and 3) approximately 20% of the unidirectional Cl- fluxes occur via nonconductive pathways.

Amiloride↗
PubMed1989

Intracellular Cl- activity and cellular Cl- pathways in cultured human airway epithelium.

Cl- transport was studied in human nasal epithelium, a predominantly Na+-absorbing proximal airway epithelium. Intracellular Cl- activity (aClc) and the electrical potentials across the apical (Va) and basolateral (Vb) membranes were measured with double-barreled, Cl- -selective microelectrodes to characterize the driving forces for Cl- flow across each membrane. Under control conditions (bilateral Krebs-bicarbonate Ringer), Va was -26.1 +/- 1.2 mV, Vb was -36.2 +/- 1.2 mV, and aCL(c) was 42.7 +/- 2.0 mM (n = 34), indicating that Cl- is near electrochemical equilibrium across the apical membrane but significantly above equilibrium across the basolateral membrane. Reduction of luminal [Cl-] from 120 to 3 mM reduced aClc from 42.7 +/- 4.0 to 27.0 +/- 3.5 mM, depolarized Va, and increased fractional apical membrane resistance (fRa) and transepithelial resistance (Rt). Serosal bumetanide reduced aClc by 10 mM without affecting electrical parameters. Reduction of serosal [Cl-] from 120 to 3 mM resulted in a rapid decrease in Vb, a decrease in fRa and an increase in Rt. Also, serosal [Cl-] reduction led to a slow decrease in aClc rom 45.5 +/- 2.5 to 31.1 +/- 4.2 mM) that could be inhibited by bumetanide. The data are consistent with the following conclusions: 1) Cl- is transported across the apical membrane through a conductive pathway; and 2) Cl- is translocated across the basolateral membrane by an electrically silent bumetanide-sensitive cotransport system and by a minor conductive path.

Adolescent↗
PubMed1989

Cellular Cl- transport in cultured cystic fibrosis airway epithelium.

Cultured human nasal epithelia derived from cystic fibrosis (CF) patients were studied with double-barreled, Cl- -selective microelectrodes to measure membrane potentials and intracellular Cl- activity (aClc). The aClc of CF cultures was 46.5 +/- 2.5 mM (n = 28), a value not significantly different from aClc of normal human nasal cells. Reduction of the luminal [Cl-] from 120 to 3 mM failed to reveal any apical Cl- permeability (conductive or nonconductive) in CF cultures. Bumetanide (10(-4) M, serosal) led to a 10 mM decrease in aClc without affecting the electrical parameters of the cells. Reduction of serosal [Cl-] led to a marked decrease in aClc (from 58.0 +/- 6.7 to 26.8 +/- 2.9 mM) that could partly be blocked by bumetanide. Reduction of serosal [Cl-] led to a rapid depolarization (5.4 +/- 0.7 mV) of the basolateral membrane potential (Vb), a decrease of the fractional apical membrane resistance (0.03 +/- 0.01), and an increase (34 +/- omega.cm2) in the transepithelial resistance (Rt). We conclude that 1) the apical membrane of CF airway epithelia is impermeable to Cl-, and 2) Cl- transport across the basolateral membrane occurs mainly through a bumetanide-inhibitable cotransport system but also through a Cl- conductance, neither of which appears to be affected by CF.

Adolescent↗
PubMed1988

Potassium-induced cell swelling in Necturus gallbladder epithelium.

In Necturus gallbladder epithelium, elevation of mucosal K+ to 95 mM in the presence of 10 mM Na+ resulted in cell swelling at a rate of 3.2% original volume per minute, followed by volume-regulatory shrinking. When Na+ was completely removed from or when amiloride (10(-4) M) was added to the mucosal medium, K+-induced cell swelling was abolished. In the presence of 10 mM Na+, 1 mM Ba2+ abolished and substitution of mucosal Cl- by NO-3 had no effect on K+-induced swelling. Thus solute entry following elevation of mucosal K+ is effected by separate K+ and Cl- pathways. Furthermore, substitution of 95 mM K+ for Na+ in the mucosal bathing medium leads to the development of a Cl- conductance in the basolateral membrane as long as some Na+ remains in the medium. However, cell swelling induced by mucosal dilution does not lead to the appearance of a Cl- conductance. Thus the activation of this conductance requires both swelling and membrane depolarization. These results show that 1) high mucosal K+ leads to cell swelling due to the entry of Cl- along with K+ and the Cl- can enter across either membrane, 2) the Cl- pathways require the presence of mucosal Na+, and 3) cell volume regulation is activated by an increase in volume per se, i.e., a hyposmotic exposure is not required for volume regulation to occur.

Animals↗
PubMed1987

Interactions of sodium transport, cell volume, and calcium in frog urinary bladder.

The volume of individual cells in intact frog urinary bladders was determined by quantitative microscopy and changes in volume were used to monitor the movement of solute across the basolateral membrane. When exposed to a serosal hyposmotic solution, the cells swell as expected for an osmometer, but then regulate their volume back to near control in a process that involves the loss of KCl. We show here that volume regulation is abolished by Ba++, which suggests that KCl movements are mediated by conductive channels for both ions. Volume regulation is also inhibited by removing Ca++ from the serosal perfusate, which suggests that the channels are activated by this cation. Previously, amiloride was observed to inhibit volume regulation: in this study, amiloride-inhibited, hyposmotically swollen cells lost volume when the Ca++ ionophore A23187 was added to Ca++-replete media. We attempted to effect volume changes under isosmotic conditions by suddenly inhibiting Na+ entry across the apical membrane with amiloride, or Na+ exit across the basolateral membrane with ouabain. Neither of these Na+ transport inhibitors produced the expected results. Amiloride, instead of causing a decrease in cell volume, had no effect, and ouabain, instead of causing cell swelling, caused cell shrinkage. However, increasing cell Ca++ with A23187, in both the absence and presence of amiloride, caused cells to lose volume, and Ca++-free Ringer's solution (serosal perfusate only) caused ouabain-blocked cells to swell. Finally, again under isosmotic conditions, removal of Na+ from the serosal perfusate caused a loss of volume from cells exposed to amiloride. These results strongly suggest that intracellular Ca++ mediates cell volume regulation by exerting a negative control on apical membrane Na+ permeability and a positive control on basolateral membrane K+ permeability. They also are compatible with the existence of a basolateral Na+/Ca++ exchanger.

Animals↗
PubMed1985

Regulation of adenosine 3':5'-monophosphate-dependent protein kinase in cerebral cortex.

Alterations in the cyclic AMP-dependent protein kinase activity ratio in response to putative neurotransmitters and other cyclic AMP-elevating agents in intact cerebral cortical slices and Krebs-Ringer particulate preparations from cerebral cortex were examined. Both norepinephrine (30 microM) and forskolin (20 microM) produced a time-dependent increase in intracellular levels of cyclic AMP in cerebral cortical slices which was paralleled by an increase in both cyclic AMP and the protein kinase activity ratio. The increases were maximal at 5 min. and remained elevated for at least 15 min. Forskolin, norepinephrine, adenosine and isoproterenol produced a concentration-dependent increase in both cyclic AMP and the protein kinase activity ratio, however, the degree of increase observed was dissimilar. Thus, a 5-fold change in intracellular cyclic AMP resulted in only a 2-fold increase in the activity ratio. Of the agents examined, forskolin produced the most marked change in the activity ratio (from 0.23 to 0.78 at 100 microM) while isoproterenol at 100 microM produced only a 50% increase in the activity ratio. The half-time for the decline in forskolin elicited elevations of either the activity ratio or cyclic AMP was about 4-6 min. In the presence of the phosphodiesterase inhibitor, Ro 20-1724, both were significantly prolonged being 60-70% of the maximum observed immediately after forskolin stimulation, at 15 min. Potentiation of forskolin elicited increases in the activity ratio by Ro 20-1724 were also observed but the increase in the activity ratio was maximal at 7.5 min. while cyclic AMP accumulations continued to rise during the entire 15 min. incubation. Particulate preparations from cerebral cortex were found to contain a cyclic AMP-dependent protein kinase which could be activated 2 to 3-fold with either forskolin, norepinephrine, or adenosine. Unlike the intact brain slice the changes in protein kinase activity ratio and intracellular levels of cyclic AMP in cell-free particulate preparations were similar in both time and degree.

Adenosine↗