Teaching computer searching to health care professionals: why does it take so long?
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Computer User Training↗
Biomedical subjects
B T Smith
Publications and source records attributed to B T Smith.
Characterization of proteoglycans synthesized by fetal rat lung type II pneumonocytes in vitro and the effects of cortisol.
The synthesis of proteoglycans by primary cultures of 19-day gestation fetal rat lung Type II pneumonocytes was studied. The cells were grown in the presence of [3H]-glucosamine and/or [35S]-Na2SO4 and the radioactive label incorporated into proteoglycans was analyzed. Proteoglycans of high molecular weight (approximately 200 Kd) were isolated by gel permeation chromatography and contained both [3H] and [35S]. The glycosaminoglycan composition of the proteoglycans was determined by electrophoresis and autoradiography. The medium contained 65-80% of the labeled proteoglycans and was enriched for hyaluronate, with lesser amounts of the sulfated glycosaminoglycans (dermatan sulfate greater than heparan sulfate greater than chondroitin sulfate). The cell layers retained 20-35% of the labeled proteoglycans and was enriched for heparan sulfate, with lesser amounts of chondroitan sulfate greater than dermatan sulfate greater than hyaluronate. The synthesis of proteoglycans was time-dependent and was stimulated by increasing concentrations of fetal bovine serum. Cortisol inhibited proteoglycan synthesis, apparently by decreasing the availability of proteoglycan core-protein.
Animals↗
Surfactant sufficiency for immature infants--prenatal induction vs. postnatal treatment.
The prenatal and postnatal therapeutic management of surfactant insufficiency are reviewed. Prenatal maternal glucocorticoid therapy promotes lung maturation and enhances lung surfactant levels in the neonate, but a minimum of 24 hr treatment is required and the therapy is of limited effectiveness even under optimal conditions. Relatively few women in premature labour are good candidates for glucocorticoid therapy. Research into combinations of glucocorticoids with hormones (e.g. thyroid), and adrenergic agents in progress. The authors are studying the effects of fibroblast-pneumonocyte factor (FPF) on the fetal lung surfactant system. Postnatal therapy with insufflated natural and artificial surfactants has been studied in several centres with varying degrees of success. Currently, the risk:benefit ratios favour attempts to reduce the risks of respiratory distress syndrome (RDS) by both prenatal surfactant induction and postnatal replacement therapy. Greater understanding of the underlying mechanisms should permit the establishment of more satisfactory treatment.
Female↗
The cellular mechanism of glucocorticoid acceleration of fetal lung maturation. Fibroblast-pneumonocyte factor stimulates choline-phosphate cytidylyltransferase activity.
The cellular mechanism by which glucocorticoids stimulate phosphatidylcholine biosynthesis has been studied in the fetal rat lung in vivo and in cultured fetal rat lung cells of varying levels of complexity. Administration of dexamethasone to pregnant rats at 18 days gestation resulted in a significant increase in saturated phosphatidylcholine content in fetal lung 24 h after injection. Dexamethasone administration increased the activity of fetal lung choline-phosphate cytidylyltransferase by 34%. It had no effect on the activities of fetal lung choline kinase and choline phosphotransferase. Exposure of fetal lung type II cells in organotypic cultures (which contain both type II cells and fibroblasts) to cortisol resulted in a 1.6-fold increase in the incorporation of [Me-3H]choline into saturated phosphatidylcholine. The activities of the enzymes in the choline pathway for the de novo biosynthesis of phosphatidylcholine were not significantly altered except for a 105% increase in choline-phosphate cytidylyltransferase activity. Treatment of monolayer cultures of fetal type II cells with cortisol-conditioned medium from fetal lung fibroblasts resulted in a 1.5-fold increase in saturated phosphatidylcholine production. This effect correlated with a doubling of choline-phosphate cytidylyltransferase activity. Additional evidence that this stimulatory action is mediated by fibroblast-pneumonocyte factor, produced by fetal lung fibroblasts in response to cortisol, was obtained. The factor was partially purified from cortisol-conditioned medium of fetal lung fibroblasts by gel filtration and affinity chromatography. Based on biological activity, a 3000-fold purification was obtained. Stimulation of saturated phosphatidylcholine synthesis in type II cells by fibroblast-pneumonocyte factor was maximal within 60 min of incubation. Pulse-chase experiments indicated that the stimulatory effect was correlated with an increased conversion of choline phosphate into CDP choline. Moreover, the enhanced phosphatidylcholine formation by fetal type II cells in response to fibroblast-pneumonocyte factor was accompanied by decreased levels of cellular choline phosphate. These findings further support the concept that glucocorticoid action on surfactant-associated phosphatidylcholine synthesis occurs ultimately at the level of the alveolar type II cell and involves fibroblast-pneumonocyte factor which stimulates the activity of choline-phosphate cytidylyltransferase.
Animals↗
Reciprocal autocrine and paracrine regulation of growth of mesenchymal and alveolar epithelial cells from fetal lung.
The regulation of DNA synthesis in 19 day rat fetal lung epithelial (alveolar type II) and mesenchymal (fibroblast) cells by protein growth factors has been studied. In each case a single growth factor is capable of stimulating 3H-thymidine incorporation into DNA: platelet-derived growth factor in the case of the alveolar type II cell and epidermal growth factor in the case of the fetal lung fibroblast. We hypothesize that these results indicate that the type II cell endogenously produces progression activities (i.e., epidermal growth factor-like and somatomedin-like activity) while the fibroblast produces competence (i.e., platelet-derived growth factor-like) and progression (i.e., somatomedin-like activity). The latter is in keeping with previous observations with skin fibroblasts. To test the above hypothesis, the effect of fetal lung fibroblast-derived conditioned media upon the growth of fetal alveolar type II cells has been determined. The results indicate that, indeed, such media contain competence activity for this cell type. The mitogenic activity was further characterized as heat-sensitive, trypsin-sensitive, and has an apparent molecular weight of 30,000 Daltons. It is not synthesized by 19 day fetal liver, kidney or skin fibroblasts and its synthesis is higher in lung fibroblasts isolated from 19 day fetuses as compared to those isolated on day 16 or day 22.
Animals↗
Hormonal/intercellular control of lung maturation.
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Animals↗
Molecular basis for a pulmonary mesenchymal-epithelial interaction.
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Cell Communication↗
Glucocorticoids affect the synthesis of pulmonary fibroblast-pneumonocyte factor at a pretranslational level.
Glucocorticoids accelerate fetal lung maturation by acting on the fetal lung fibroblast to induce the synthesis of fibroblast-pneumonocyte factor which in turn stimulates pulmonary surfactant synthesis by the alveolar type II cell. We have studied the site of glucocorticoid regulation of fibroblast-pneumonocyte factor synthesis in primary cultures of fetal rat lung fibroblasts. Conditioned media from fetal rat lung fibroblasts exposed to cortisol stimulate [Me-3H]choline incorporation into saturated phosphatidylcholine by primary cultures of fetal rat lung alveolar type II cells. This effect is blocked by the presence of actinomycin D during the first, but not the second, 24 h of incubation of the fibroblasts with cortisol. Cycloheximide blocks this effect if present during either the first or second 24 h of incubation. We fractionated mRNA from fetal rat lung fibroblasts incubated in the presence or absence of dexamethasone and observed that cell-free translation products from a fraction of approximately 500 bases possess biological activity in the bioassay. Such activity is only present in cell-free translation products of mRNA isolated from fibroblasts treated with dexamethasone. These results suggest that glucocorticoids act at a pretranslational level to induce production of fibroblast-pneumonocyte factor and that the primary translation products are biologically active.
Animals↗
Synthesis of surfactant lipids in developing rat lung: studies with isolated alveolar type-II cells.
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Animals↗
Cell culture of embryonic chick duodenal cells: preparation of epithelial-fibroblast bilayers and homotypic cultures of fibroblasts and epithelial cells.
A method for the primary cell culture of trypsin-dissociated embryonic chick duodenum is described. Both heterotypic (epithelial cells and fibroblasts together) and homotypic (highly enriched cultures of epithelial cells or fibroblasts alone) cell cultures were established. Dispersed duodenal epithelial cells and fibroblasts grown in 10% fetal bovine serum (FBS) spontaneously aggregated and proliferated as a bilayer of cells with the epithelial cells growing on top of the fibroblasts. Changing the serum supplement to 6% chicken serum (CS) and 4% FBS when the fibroblast monolayer reached confluence resulted in epithelial cell proliferation. Homotypic cultures of epithelial cells and fibroblasts were prepared and analyzed by scanning electron microscopy and transmission electron microscopy. Fibroblasts, isolated by differential adhesion and grown in 10% FBS, did not demonstrate measurable alkaline phosphatase activity. Homotypic epithelial cell cultures, isolated by floating them off the fibroblasts with collagenase, and maintained on collagen in 6% CS/4% FBS, demonstrated higher alkaline phosphatase-specific activity (16.1 +/- 2.3 U/mg protein) compared with epithelial-fibroblast bilayer cell cultures (12.1 +/- 1.3 U/mg protein).
Alkaline Phosphatase↗
Compartmentalization of 11-oxidoreductase within fetal lung alveolus.
The role of 11-oxidoreductase in the cellular process of fetal lung surfactant production and its localization within the alveolar domain have been investigated. In organotypic cultures of fetal rat lung, cortisol and cortisone markedly stimulate saturated phosphatidylcholine synthesis by the alveolar type II cell; a 10-fold excess of 11-ketoprogesterone blocks the bioactivity of cortisone. Both cortisol and cortisone also stimulate fibroblast-pneumonocyte factor production, whereas 11-ketoprogesterone blocks the effect of cortisone, but not of cortisol, suggesting that cortisone stimulation of fibroblast-pneumonocyte factor production depends on its conversion to cortisol by 11-oxidoreductase. A survey of the cells that are present in the alveolar domain revealed that 11-oxidoreductase activity is only present in the fibroblast. Localization of both 11-oxidoreductase and fibroblast-pneumonocyte factor production within the same cell emphasizes the significance of 11-oxidoreductase in the regulation of fetal lung surfactant production.
11-beta-Hydroxysteroid Dehydrogenases↗
Relation of kidney tissue somatomedin-C/insulin-like growth factor I to postnephrectomy renal growth in the rat.
In kidney tissue extracts, we observed elevated somatomedin-C (SmC) tissue concentrations in the kidney remaining after nephrectomy compared to those in the kidney removed at surgery or kidneys from sham-operated animals. In hypophysectomized animals, we observed a response of the same magnitude, but from significantly lowered basal SmC concentrations. In neither case did nephrectomy affect SmC levels in serum or other tissues studied (liver and lung). The increased tissue levels of SmC in the regenerating kidney, with a return to baseline levels within 30 days, along with the absence of elevated serum levels suggest a local role for this mitogen in organ growth.
Animals↗
Pool sizes of precursors for phosphatidylcholine formation in adult rat lung type II cells.
The pool sizes of the choline intermediates and cofactors involved in the CDPcholine pathway were studied in alveolar type II cells from adult rat lung. The choline phosphate pool was much larger than both the choline and CDPcholine pools. Kinetic analysis of the pool sizes revealed that cholinephosphate cytidylyltransferase catalyzes a non-equilibrium reaction. These results are consistent with the idea that cholinephosphate cytidylyltransferase regulates the choline flux into phosphatidylcholine in adult rat lung type II cells.
Animals↗
The rate-limiting reaction in phosphatidylcholine synthesis by alveolar type II cells isolated from fetal rat lung.
The rate-limiting reaction in the formation of phosphatidylcholine by type II cells isolated from fetal rat lung was examined. Studies on the uptake of [Me-3H]choline and its incorporation into its metabolites indicated that in these cells the choline phosphate pool was much larger than both the choline and CDPcholine pools. Chemical measurements of the pool sizes showed that the choline phosphate pool was indeed much larger than the intracellular choline and CDPcholine pools. Pulse-chase studies with [Me-3H]choline revealed that labelled choline taken up by the cells was rapidly phosphorylated to choline phosphate and that the radioactivity lost from choline phosphate during the chase period appeared in phosphatidylcholine. Little change was observed in the labelling of CDPcholine during the chase period. These results indicate that cholinephosphate cytidylyltransferase catalyzes a rate-limiting reaction in phosphatidylcholine formation by fetal rat lung type II cells.
Animals↗
Effect of fibroblast-pneumonocyte factor on the synthesis of surfactant phospholipids in type II cells from fetal rat lung.
The effect of fibroblast-pneumonocyte factor on the formation of surfactant-associated phospholipids was studied in fetal rat lung type II cells in primary culture. Exposure of the cells to fibroblast-pneumonocyte factor enhanced the incorporation of radioactively labelled choline, glycerol and palmitate into total and saturated phosphatidylcholine. Fibroblast-pneumonocyte factor also stimulated the formation of phosphatidylglycerol from labelled glycerol and palmitate but did not significantly affect the synthesis of the other phospholipids. This indicates that fibroblast-pneumonocyte factor specifically stimulates the production of surfactant lipids in fetal lung.
Animals↗
Concepts of epithelial-mesenchymal interactions during development: tooth and lung organogenesis.
One of the major problems in developmental biology concerns how differential gene activity is regionally controlled. One approach to this problem is the use of mesenchyme specification of epithelial-specific gene expression, such as, during tooth morphogenesis or lung morphogenesis. In the example of tooth morphogenesis, dental papilla ectomesenchyme induces de novo gene expression as assayed by detection of amelogenin transcripts, or immunodetection of amelogenin polypeptides within ameloblast cells. This process does not require serum supplementation or exogenous factors during epithelial-mesenchymal interactions in vitro. In contrast, lung morphogenesis requires hormones to mediate mesenchyme-derived influences upon type II epithelial cell differentiation and the production of pulmonary surfactant (eg, neutral and phospholipids, surfactant proteins). Glucocorticoids are required to stimulate the release of fetal pneumonocyte factor (FPF) from fibroblasts which, in turn, enhance the production of pulmonary surfactant. Thyroxin appears to regulate the relative responsiveness of progenitor type II cells to steroid-stimulated release of FPF. This review will highlight key concepts associated with these developing organ systems and emphasize the problem of regional controls which regulate epithelial cell-specific gene activity.
Ameloblasts↗
Localization of pulmonary surfactant protein during mouse lung development.
During lung development type II alveolar epithelial cells produce extracellular pulmonary surfactant. Polyclonal antibodies were produced against nonserum proteins associated with human surfactant. The present studies were designed (i) to determine if mouse surfactant proteins were antigenically cross-reactive with polyclonal antibodies directed against human surfactant proteins; and (ii) to determine surfactant protein localization during fetal, neonatal, and adult mouse lung development. Two-dimensional gel electrophoresis studies in conjunction with immunologic techniques provided evidence that mouse and human surfactant proteins shared antigenic determinants. The major monomeric form of mouse surfactant protein in a glycoprotein of approximately Mr 35,000 under reducing conditions. A less abundant form was identified as a Mr 45,000 polypeptide. Immunohistochemical localization showed that type II cells contain surfactant protein at Theiler stage 26. A gradient of immunostaining was localized within alveolar surfaces. The antigen was not detected in heart, blood vessels, or pulmonary interstitial cells. Surfactant protein was detected lining alveolar surfaces in mature adult lung. The distribution of this protein during fetal and neonatal lung morphogenesis suggests that this extracellular constituent of pulmonary surfactant may be extremely useful as a phenotypic marker with which to evaluate normal and abnormal lung development.
Animals↗
Insulin inhibition of tyrosine aminotransferase induction by dexamethasone is species-related.
Dexamethasone induces TAT in the embryonic chick liver, but this effect is not blocked by prior administration of insulin at a dose sufficient to increase the hepatic protein/DNA ratio. Similarly, insulin does not block dexamethasone induction of TAT in chick embryo hepatocytes in vitro. In contrast, insulin reduces TAT induction by dexamethasone in fetal rat hepatocytes by 35-40%. No significant differences in insulin binding were noted between chick and rat hepatocytes.
Animals↗