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Biomedical subjects

N Sen

Publications and source records attributed to N Sen.

33 records · Page 2Linked to original sources
PubMed1994

Stimulation of lung surfactant secretion by endothelin-1 from rat alveolar type II cells.

Endothelin-1 (ET-1), a potent vasoactive peptide released by endothelial cells, alters cytosolic Ca2+ and phosphoinositide metabolism in cells of myogenic and nonmyogenic origin. We evaluated the effect of ET-1 on surfactant phosphatidylcholine (PC) secretion from alveolar type II cells labeled with [methyl-3H]choline. ET-1 stimulated the secretion of PC in a time- and dose-dependent manner. Binding of 125I-labeled ET-1 to type II cell membranes was saturable at approximately 1 nM and suggested the presence of a single type of receptor. The secretagogue effect of ET-1 was independently inhibited by nifedipine and nitrendipine, both L-type calcium channel blockers, and removal of extracellular calcium. ET-1 also increased cellular diacylglycerol content by approximately 50% within 30 s, which could not be attenuated by pretreatment with nifedipine, suggesting an early activation of protein kinase C that was independent of Ca2+ influx. Further, ET-1-stimulated PC secretion was also blocked by inhibitors of protein kinase C. Collectively, these results indicate that the binding of ET-1 to type II cells is coupled to the activation of protein kinase C, which increases calcium influx through L-type calcium channels, and results in increased secretion of lung surfactant. Since ET-1 is released from pulmonary micro- and macrovasculature endothelial cells in close proximity to type II cells, our findings support the novel concept that endothelial cells interact with alveolar type II cells in a paracrine fashion to regulate surfactant secretion.

Adenosine Triphosphate↗
PubMed1993

Inhibition of phosphatidylcholine secretion by stilbene disulfonates in alveolar type II cells.

Various agents stimulate the secretion of lung surfactant from alveolar type II cells by increasing intracellular Ca2+, cyclic adenosine-3':5'-monophosphate (cAMP), or diacylglycerol. A few agents, including the purified surfactant protein A, are known to inhibit the secretion by an unknown mechanism. In the present study, we demonstrated that stilbene disulfonic acids, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), are potent but reversible inhibitors of lung surfactant secretion. The inhibition was concentration dependent, and the EC50 was 5 microM for DIDS and 50 microM for SITS. The inhibition was not specific to agonists for any one type of receptor, and was also observed for secretion stimulated by 8-bromo-cAMP, or tetradecanoyl phorbol acetate, suggesting that the site of inhibition was distal to the generation of intracellular second messengers. This was also supported by the failure of DIDS to block the stimulus-mediated increase in diacylglycerol content of type II cells. Further, DIDS and SITS were also inhibitory for basal secretion. Based on the reversibility of inhibition and the fact that inhibition was observed with both basal and stimulated secretion, we suggest that stilbene disulfonic acids affect a component of the exocytosis process that occurs at or near the plasma membrane.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1991

Enhancement of disaturated phosphatidylcholine synthesis by epidermal growth factor in cultured fetal lung cells involves a fibroblast-epithelial cell interaction.

Epidermal growth factor (EGF) increases the rate of choline incorporation into disaturated phosphatidylcholine in cultured fetal rat type II cells via an indirect mechanism. Whereas-EGF has no effect on the rate of disaturated phosphatidylcholine synthesis when added directly to type II pneumocytes, the growth factor is effective if it is present during preliminary conditioning of the media by lung fibroblasts. This effect is concentration dependent with a maximal effect at 20 ng/ml. When lung fibroblasts are incubated with both glucocorticoids and EGF, there is no significant effect of the growth factor over and above that seen with the steroid alone. This suggests that the two agents might act via a similar mechanism. This is supported by the observation that each inducer leads to the production by lung fibroblasts of a stimulatory factor that has a similar, if not identical, chromatographic elution profile. We conclude that EGF may contribute significantly to the normal onset of lung maturation by elaborating a fibroblast-derived factor that stimulates phosphatidylcholine synthesis in type II pneumocytes.

Animals↗
PubMed1987

Comparison of the effects of etomidate and thiopentone on intraocular pressure.

The effects of etomidate and thiopentone on intraocular pressure were studied in 50 patients of either sex undergoing routine non-ophthalmic surgery. Both drugs decreased intraocular pressure significantly. However, etomidate induced a significantly greater decrease in intraocular pressure than did thiopentone.

Adolescent↗
PubMedDate not supplied

Statistical optimization of transdermal drug delivery system of terbutaline sulfate by factorial analysis.

A matrix type of transdermal drug delivery system of terbutaline sulfate was designed and developed by full 3(2) factorial method using polyvinyl alcohol (PVA) of medium molecular weight and polyvinyl pyrrolidone (PVP K-30) as matrix forming polymer and propylene glycol as plasticizer. Patches were designed to deliver 62 micrograms/cm2/hr of the drug into the systemic circulation. These were evaluated for in vitro skin permeation study through excised guinea pig skin. The permeation followed Higuchi kinetics, as its coefficients of correlation (r = 0.965-0.978) predominates over other permeation kinetics. Various physico-chemical parameters of the patches were investigated. Statistical optimization of in vitro permeation rate of the drug from the films were evaluated using two way analysis of variance (ANOVA), regression analysis.

Administration, Cutaneous↗