Biomedical subjects

R H Simon

Publications and source records attributed to R H Simon.

At least 55 records · Page 3Linked to original sources

PubMed1990

Arachidonate metabolism increases as rat alveolar type II cells differentiate in vitro.

Rat type II alveolar epithelial cells are known to undergo morphological and functional changes when maintained in culture for several days. Having previously demonstrated that these cells can deacylate free arachidonic acid (AA) and metabolize it to products of the cyclooxygenase pathway, the present study was undertaken to determine whether in vitro differentiation was accompanied by alterations in the availability and metabolism of AA. We assessed the constitutive and ionophore A23187-induced deacylation and metabolism of endogenous AA, as well as the metabolism of exogenously supplied AA, in primary cultures of rat type II cells at days 2, 4, and 7 after isolation. Levels of free endogenous AA were increased at day 4, whereas eicosanoid synthesis, predominantly prostaglandin E2 and prostacyclin, increased markedly only at day 7. A similar time course of augmentation of prostanoid release was seen in response to exogenous AA. Type II cells cultured on fibronectin, intended to hasten cell flattening and spreading, demonstrated accelerated increases in available free AA in response to A23187; cells cultured on basement membrane derived from Engelbreth-Holm-Swarm mouse sarcoma, known to maintain the type II phenotype, exhibited diminished levels of available free AA. From these findings, we conclude that alterations in arachidonate metabolism are linked to alterations in cellular phenotype. The potentiation of eicosanoid synthesis accompanying in vitro differentiation suggests a possible role for the alveolar epithelium in the modulation of inflammation and fibrosis in the distal lung.

Animals↗

PubMed1990

Expression of urokinase-type plasminogen activator by rat pulmonary alveolar epithelial cells.

Intra-alveolar fibrin deposition accompanies many forms of inflammatory lung injury. Appropriate clearance of this fibrin matrix is important for normal healing and remodeling. The local generation of plasmin by the action of plasminogen activators (PAs) represents a pivotal step in the fibrinolytic process. To investigate whether the alveolar epithelium plays a role in the modulation of intra-alveolar fibrinolysis, we have studied PA regulation by rat pulmonary alveolar epithelial cells. We have found large quantities of PA activity both in conditioned media and cell lysates from epithelial monolayers in culture. Casein-plasminogen zymography reveals that this PA activity migrates as a tight doublet with an apparent mol wt of 45 kD, clearly distinct from rat tissue-type PA (tPA, greater than 68 kD). Analysis of freshly isolated type II alveolar epithelial cells demonstrates readily measurable PA activity in cell lysates, as well as expression of urokinase-type PA (uPA) mRNA on Northern blot analysis. Upregulation of PA activity occurs progressively with time in culture as the alveolar epithelial cells lose type II cell characteristics and become more flattened. Stimulation of alveolar epithelial cell monolayers with lipopolysaccharide or tumor necrosis factor increases levels of secreted PA activity. The relative abundance of uPA mRNA was shown to change in parallel with PA activity during in vitro differentiation or after exposure to inflammatory mediators. Thus, alveolar epithelial cells are likely an important source of uPA in the lung, the expression of which is influenced by the state of cellular differentiation as well as the presence of inflammatory mediators.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Resistance of rat pulmonary alveolar epithelial cells to neutrophil- and oxidant-induced injury.

We have previously reported that rat pulmonary alveolar epithelial cells are resistant to neutrophil-generated oxidants in contrast to the situation described for endothelial cells. In the present study, we investigated the roles of intracellular catalase and glutathione-dependent reactions in providing protection against cytotoxic concentrations of H2O2 and stimulated neutrophils. Catalase was found to be instrumental in protecting epithelial cells because when inhibited by either azide or 3-amino-1,2,4-triazole, there was an increase in the cytotoxic effect of exogenous H2O2 and stimulated neutrophils. Associated with this potentiation of injury was a reduction in epithelial cell clearance of H2O2. Partial inhibition of glutathione-dependent reactions by depleting intracellular glutathione with buthionine sulfoximine or by inhibiting the enzyme glutathione reductase with 1,3-bis(2-chloroethyl)-1-nitrosourea also augmented the cytotoxic effect of both H2O2 and stimulated neutrophils. This increase in neutrophil-induced cytotoxicity was caused by the addition of an oxidant-dependent mechanism of killing on top of the previously described oxidant-independent pathway. Importantly, the increased susceptibility to injury caused by inhibition of glutathione-dependent reactions was not associated with a reduction in epithelial cell consumption of exogenous H2O2, contrary to the case with catalase. This suggests that there are glutathione-dependent reactions that protect epithelial cells in ways separate from reducing the total burden of exogenous H2O2 on the cells.

Amitrole↗

PubMed1989

Cholinephosphate cytidylyltransferase in fetal rat lung cells: activity and subcellular distribution in response to dexamethasone, triiodothyronine, and fibroblast-conditioned medium.

The initiation of pulmonary surfactant synthesis during fetal development has been shown to be under hormonal control. Using cultured lung cells isolated from 19-day-gestation fetal rats, we evaluated the effects of various hormones on the activity and subcellular distribution of cholinephosphate cytidylyltransferase, a rate-controlling enzyme in phosphatidylcholine synthesis. The cells were incubated in medium containing 10% carbon-stripped fetal bovine serum to which dexamethasone, triiodothyronine, and/or conditioned medium from dexamethasone-treated fetal rat lung fibroblasts were added for 48 h. Dexamethasone and fibroblast-conditioned medium increased microsomal enzyme activity 169% +/- 6% (mean +/- SE, p less than 0.01) and 150% +/- 2% (p less than 0.05) over control levels, respectively. Further, dexamethasone increased cytosolic specific activity 160% +/- 17% (p less than 0.05). Addition of T3 to the fibroblast-conditioned medium caused a further increase in microsomal activity, but T3 alone had no effect. Increased microsomal cytidylyltransferase activity correlated with an increased rate of [3H]choline incorporation into disaturated phosphatidylcholine. Hormonal induced increases in enzyme activity were not adequately explained by simple translocation of enzyme from cytosol to microsomes. Cycloheximide (5 micrograms/ml) inhibited enzyme stimulation by dexamethasone and fibroblast-conditioned medium, suggesting that protein synthesis of new enzyme or regulatory proteins is involved. We conclude that hormones modulate cytidylyltransferase activity of isolated fetal lung cells. Dexamethasone and fibroblast-conditioned medium exert their major effects by stimulating microsomal activity.

Animals↗

PubMed1989

Ultrastructural cytochemical analysis of oxygen radical-mediated immunoglobulin A immune complex induced lung injury in the rat.

Recent studies suggest that IgA immune complex induced lung injury in the rat is oxygen radical mediated. A cerium chloride (CeCl3) method was used to ultrastructurally analyze the in situ elaboration of H2O2 in IgA immune complex injured lungs. After induction of IgA immune complex lung injury, the lungs were instilled with a reaction buffer containing CeCl3 which forms an electron-dense precipitate when exposed to H2O2. Ultrastructural examination and x-ray microanalysis revealed electron-dense cerium deposits on the surfaces and in cytoplasmic vacuoles of alveolar macrophages located along damaged alveolar septae. Similar deposits were prominent on the luminal surfaces of injured pneumocytes, especially alveolar type II cells. No cerium-containing deposits were found in undamaged negative control lungs (IgA alone without antigen) or in lungs of rats that received IgA immune complexes in the presence of catalase. To further define the source of cerium-reactive products, monolayers of rat pulmonary alveolar epithelial cells were incubated with IgA complexes. Alveolar epithelial cells exposed to complexes produced no detectable H2O2 as measured by two spectrophotometric assays, and in the presence of CeCl3, exhibited negligible amounts of electron-dense material regardless of the presence or absence of catalase. The data corroborate indirect in vivo and in vitro studies which suggest that IgA immune complex induced lung injury is mediated by oxygen-derived metabolites produced by lung macrophages. Use of the CeCl3 method in intact rat lungs allows direct ultrastructural cytochemical analysis of H2O2 production in inflamed tissue.

Animals↗

PubMed1988

Brain tumors in pregnancy.

There seems to be no higher incidence of primary brain tumor in pregnancy. There are no extracranial tumors that are likely to metastasize that are uniquely related to the specific pregnancy. Choriocarcinoma during the index pregnancy is rare. Although pregnancy-related choriocarcinoma has a high propensity for brain metastasis, it is in the postpartum period or later that such tumors and their metastases present. The fetus seems to be spared from any complications resulting from maternal tumor, provided that it is safely delivered. There is a rich literature on the immunology and steroid receptor pharmacology of brain tumor but alterations in immunity or in receptor sites seem to have little impact on the incidence of tumors during pregnancy. There may be modification of the behavior of brain tumors by pregnancy and hence possibly by steroid hormones. The principle governing management of the mother is primarily common sense. As the ability to manage brain tumors in general improves, the necessity of interfering with either the pregnancy or mode of delivery evaporates.

Adenoma↗

PubMed1988

Hydrogen-peroxide-induced arachidonic acid metabolism in the rat alveolar macrophage.

Mounting evidence suggests that reactive oxygen metabolites can initiate the release and metabolism of arachidonic acid (AA). We therefore examined the effects of hydrogen peroxide (H2O2), a biologically relevant oxygen metabolite, on AA release and cyclooxygenase metabolism by the rat alveolar macrophage (AM). At concentrations between 10(-4) and 10(-3) M, which were largely noncytotoxic as assessed by chromium release, H2O2 exposure for 30 min caused a steep dose-dependent increase in AA release that peaked at approximately 5-fold stimulation at 10(-3) M H2O2. AA release induced by H2O2 was inhibited by the H2O2 scavenger catalase, but not by inactivated catalase or by scavengers of superoxide anion, hydroxyl radical, or ferric iron. An evaluation of cyclooxygenase metabolite formation by specific radioimmunoassays and high performance liquid chromatography demonstrated a greater than 2-fold increment in thromboxane (Tx)A2 (measured as TxB2) synthesis at 10(-4) M H2O2, but no increment in prostaglandin (PG) E2 synthesis. H2O2-induced TxB2 synthesis was cyclooxygenase-dependent, since it was inhibited by indomethacin (1 microM). There was no significant degradation of either PGE2 or TxB2 in AM cultures by H2O2 at concentrations to 10(-2) M. The effect of H2O2 on agonist-induced cyclooxygenase metabolism was also examined. H2O2 at 10(-4) M inhibited PGE2 synthesis induced by zymosan and A23187, whereas agonist-induced TxB2 synthesis was either unaffected (zymosan) or augmented (A23187) by H2O2. These findings suggest inhibition by H2O2 of PGE2 synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Rat alveolar macrophages synthesize leukotriene B4 and 12-hydroxyeicosatetraenoic acid from alveolar epithelial cell-derived arachidonic acid.

Although recent reports have described arachidonic acid metabolism of individual types of lung cells, the actual profile of eicosanoids that are produced in the lung may reflect interactions between different cell types. Because macrophages and epithelial cells are in close physical contact within the alveolus, we measured the eicosanoids produced by combined cultures of these cells. We found that the [14C]arachidonic acid that was released from previously labeled epithelial cells following A23187 stimulation was metabolized by alveolar macrophages to leukotriene B4 and 12-hydroxyeicosatetraenoic acid, which are products not normally produced by these epithelial cells. Simultaneously, there was a decrease in 6-keto-prostaglandin F1 alpha, the end product of prostacyclin metabolism and a major product of epithelial cell arachidonate metabolism but not macrophage arachidonate metabolism. A net increase in leukotriene B4 and a net decrease in 6-keto-prostaglandin F1 alpha were demonstrated by radioimmunoassay. Thus, the interaction of stimulated alveolar macrophages and epithelial cells alters the eicosanoid profile produced by each cell type alone in a manner that would tend to accentuate inflammatory processes within the alveolus.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1988

Arachidonic acid metabolism by rat alveolar epithelial cells.

Arachidonic acid release and metabolism by stimulated cultures of rat type II alveolar epithelial cells (94 +/- 2% pure) were studied. As compared with unstimulated cultures, a marked increase in the release of [14C]arachidonic acid from prelabeled cells was observed when the cells were incubated with the calcium ionophore A23187. Radioimmunoassay of unlabeled cultures demonstrated significant increases in the production of prostaglandin E2 greater than 6-Keto-prostaglandin F1 alpha greater than prostaglandin F2 alpha greater than thromboxane B2 with A23187 stimulation. Reverse-phase high performance liquid chromatography of media from cells prelabeled with [14C]arachidonic acid confirmed the identities and relative amounts of these metabolites. As expected, the production of these cyclooxygenase products was inhibited by indomethacin. Stimulation with A23187 led to no increment in immunoreactive leukotriene C4 production, but yielded a statistically significant but quantitatively small increment in leukotriene B4 production; its production by small numbers of contaminating macrophages cannot be ruled out. Analysis by high performance liquid chromatography of media from prelabeled cells after 30 minutes stimulation revealed no peaks of radioactivity coeluting with the lipoxygenase products leukotriene B4, leukotriene C4, or 5-, 12-, or 15-hydroxy-6,8,11,14-eicosatetraenoic acid. The results indicate that rat alveolar epithelial cells have the capacity to release arachidonic acid and metabolize it to an array of cyclooxygenase products. However, after stimulation, little or no lipoxygenase products accumulated in media. Thus, the alveolar epithelium may be a source of bioactive eicosanoids with potentially important roles in pulmonary physiology and pathophysiology.

Animals↗

PubMed1988

Effects of oxygen metabolites on rat alveolar type II cell viability and surfactant metabolism.

Neutrophil-derived reactive oxygen metabolites have been implicated as one mechanism for the cellular injury in the adult respiratory distress syndrome. Previous studies have demonstrated that alveolar lung fluid of patients with adult respiratory distress syndrome has abnormal composition and surface active properties. To examine the effects of oxygen metabolites on the viability and metabolism of type II alveolar pneumocytes, the cellular source of surfactant, isolated rat type II pneumocytes were exposed to reactive oxygen metabolites generated by the enzymatic action of xanthine oxidase upon hypoxanthine. Utilizing a 51Cr release assay to detect cellular death, we found that oxygen metabolites were lethal to type II cells in a dose-dependent manner. To demonstrate that oxygen metabolites were responsible for the toxicity, we assessed the protective effects of catalase and superoxide dismutase, scavengers of hydrogen peroxide and the superoxide anion, respectively. At a xanthine oxidase concentration of 50 mU/ml, catalase reduced the percentage of 51Cr release from 58.9 +/- 3.1% (SEM) to 7.2 +/- 2.3% (p less than 0.0001), whereas superoxide dismutase was without protection (58.9 +/- 3.1% versus 54.2 +/- 1.8% (p greater than 0.05). To determine whether oxygen metabolites also impair surfactant metabolism, we measured the incorporation of [3H]palmitate into the surfactant component disaturated phosphatidylcholine by type II pneumocytes. We found that sublethal amounts of generated oxygen metabolites caused a progressive decrease in the amount of [3H]palmitate incorporated into disaturated phosphatidylcholine. For example, using a xanthine oxidase concentration of 5 mU/ml (which causes no increased 51Cr release), we found that [3H]palmitate incorporation into disaturated phosphatidylcholine fell from a control level of 3.53 +/- 0.22 X 10(5) to 0.66 +/- 0.10 X 10(5) dpm/10(6) cells/4 hours (p less than 0.0001). Both catalase and superoxide dismutase protected the [3H]palmitate incorporation of oxygen metabolite-exposed type II cells. We conclude that reactive oxygen metabolites are injurious to type II pneumocytes and may result in impaired surfactant synthesis even at sublethal doses. Thus, oxygen metabolites generated by stimulated phagocytic cells may be responsible in part for the decreased surfactant that has been observed in adult respiratory distress syndrome.

Animals↗

PubMed1987

Lung injury in acute pancreatitis: primary inhibition of pulmonary phospholipid synthesis.

Alterations in the pulmonary surfactant system are partly responsible for the respiratory insufficiency seen with acute pancreatitis. In this model of cerulein-induced pancreatitis in rats, we utilized a new stable isotope metabolic tracer technique to examine one aspect of the pulmonary surfactant system and its relationship to associated lung injury. We have demonstrated primary, early depression of lung phospholipid synthesis reflected in both lung tissue and alveolar washings. We suggest that this quantitative change in pulmonary surfactant synthetic rate may partly explain the occurrence of respiratory failure with acute pancreatitis.

Acute Disease↗

PubMed1987

Plasma hypoxanthine and exercise.

During exercise, ATP is converted to ADP and AMP to supply energy for muscular contraction. It is then regenerated via various pathways of intermediary metabolism. However, with high levels of exercise, net ATP degradation in muscle occurs. In exercise and other clinical situations, adenine nucleotide degradation leads to an accumulation of degradative purine products including hypoxanthine. In an effort to monitor events of energy metabolism, we examined plasma hypoxanthine levels at various exercise intensities. Peak plasma hypoxanthine levels after maximal exercise (18.9 +/- 2.6 microM, mean +/- SEM) were significantly greater than resting levels (1.1 +/- 0.1 microM; p less than 0.001). Hypoxanthine levels after steady state exercise at 52, 76, and 97% of ventilatory threshold did not exceed resting levels. However, plasma hypoxanthine rose significantly after exercise at 124% of ventilatory threshold (6.3 +/- 1.0 microM; p less than 0.01) and at 152% of ventilatory threshold (17.0 +/- 3.6 microM; p less than 0.001). Exercise at subventilatory threshold intensity (74% of ventilatory threshold) for a prolonged time period, such that total work equaled that performed at 152% of ventilatory threshold, did not elevate hypoxanthine levels (0.46 +/- 0.1 microM) above resting values. We conclude that elevation of plasma hypoxanthine levels occur during exercise at intensities that exceed the ventilatory threshold and indicate that net adenine nucleotide degradation has occurred.

Adenosine Triphosphate↗

PubMed1987

Pulse oximetry for tapering supplemental oxygen in hospitalized patients. Evaluation of a protocol.

In a randomized study, we determined the clinical and financial effects of replacing arterial blood gas measurements with finger pulse oximeter readings during the process of tapering supplemental oxygen in hospitalized patients. The 16 patients in the control group, whose management followed conventional practice in our hospital, received a total of 57 arterial blood gas measurements during the 6.6 (mean) days it took for them to taper to their discharge supplemental oxygen level (usually room air). The 13 patients randomized to the oximeter study group had their arterial oxygen saturation monitored by pulse oximetry. The physicians of patients in the oximeter group were at liberty to obtain arterial blood gas determinations during the study if they desired. The oximeter study group had fewer (p less than 0.005) arterial punctures for blood gas measurements (total of 16 for the group) and fewer (p less than 0.001) days on supplemental oxygen (mean of 2.7 days per patient). We conclude that substituting noninvasive pulse oximetry for arterial blood gas measurements during reductions of supplemental oxygen shortened the days of oxygen use and decreased the number of arterial blood gas determinations in our patients. In addition to reducing the discomfort to patients, the use of oximetry was of financial benefit in that it reduced medical personnel time, blood gas analyzer use, and duration of oxygen administration.

Adult↗

PubMed1987

Source of iron in neutrophil-mediated killing of endothelial cells.

Recently we have shown that human neutrophils activated with phorbol ester are cytotoxic for cultured bovine pulmonary artery endothelial cells in an iron-dependent manner. By using the ferric iron chelator deferoxamine mesylate, we have now investigated the source of the iron. Pretreatment of neutrophils with deferoxamine mesylate affected neither their production of O2- nor their cytotoxicity for endothelial cells after addition of phorbol ester. However, similar pretreatment of endothelial cells with deferoxamine mesylate, followed by washing of the cells, resulted in a persistent presence of chelator associated with the endothelial cells and high degrees of protection of endothelial cells from cytotoxicity. The protection was dependent on the amount of chelator used and on the duration of exposure of the endothelial cells to the chelator. These data suggest that iron, which plays an important role in oxygen radical-mediated killing of endothelial cells by neutrophils, is derived from the target (endothelial) cells.

Animals↗

PubMed1986

Binding of Griffonia simplicifolia I lectin to rat pulmonary alveolar macrophages and its use in purifying type II alveolar epithelial cells.

We report that the isolectin Griffonia simplicifolia I-B4 isolated from G. simplicifolia seeds binds to rat alveolar macrophages present in frozen sections of lung tissue or bronchoalveolar lavage fluid. G. simplicifolia I-B4 does not bind to alveolar epithelial cells. We established that G. simplicifolia I-B4 binds to the macrophages via interaction with terminal alpha-D-galactopyranosyl residues present on these cells. This was substantiated by demonstrating that binding is inhibited either by the haptenic sugar alpha-D-galactopyranoside or by treating the cells with coffee bean alpha-galactosidase. Because murine laminin is known to contain terminal alpha-D-galactopyranosyl end-groups, and because we found that an anti-laminin antiserum binds to rat alveolar macrophages, we suspect that G. simplicifolia I-B4 may be binding to laminin present on the macrophages. To isolate alveolar type II epithelial cells from rat lungs, we developed a method that utilizes the lectin G. simplicifolia I. When proteinase-derived suspensions of pulmonary cells are incubated with G. simplicifolia I, the macrophages agglutinate and can be removed by filtration through nylon mesh. After incubating the resulting cellular suspension in tissue culture, the adherent cells are 94 +/- 2% (S.D.) type II cells. When compared to cells isolated by repeated differential adherence, the lectin-prepared type II cells have similar morphology and staining characteristics, form domes in monolayers and incorporate similar amounts of palmitate into disaturated phosphatidylcholine. We believe that the procedure outlined in this report provides a simple and effective method to isolate type II alveolar epithelial cells from rat lungs.

Animals↗

PubMed1986

Oxidant activity in expired breath of patients with adult respiratory distress syndrome.

Hydrogen peroxide levels were measured in the breath condensate of 43 patients receiving mechanical ventilation. In 16 patients the mean breath condensate peroxide level was 1.68 +/- 0.35 mumol/l on the day they met diagnostic criteria for adult respiratory distress syndrome (ARDS). The peak breath condensate peroxide level in the 27 patients in whom ARDS did not develop was significantly lower (0.34 +/- 0.08 mumol/l). Plasma lysozyme, a measure of in-vivo neutrophil turnover, was significantly higher in ARDS than in non-ARDS patients (9.2 +/- 2.2 U/ml v 3.4 +/- 1.1 U/ml). These findings support the hypothesis that neutrophil activation and oxidant production are involved in the pathogenesis of ARDS.

Breath Tests↗

PubMed1986

Adult respiratory distress syndrome in neutropenic patients.

The precise pathophysiologic mechanisms that cause the adult respiratory distress syndrome are unknown. Indirect evidence from human studies and extrapolations from animal models have suggested that phagocytic neutrophils are important in the pathogenesis of this disease. To further evaluate the role of neutrophils, the frequency of neutropenia in 18 bacteremic patients who had the adult respiratory distress syndrome was compared with that in a control group who had bacteremia alone. Three of 18 patients in the group with the adult respiratory distress syndrome were neutropenic as opposed to one of 18 in the control group (p greater than 0.6). Histologic examination of the lungs from two patients with the adult respiratory distress syndrome and neutropenia demonstrated the absence of neutrophils. It is likely that there are many pathways that lead to the adult respiratory distress syndrome. Although neutrophils may be involved in some of these processes, this study demonstrates that neutrophils are not required for the development of the syndrome. In the appropriate clinical setting, the diagnosis of the adult respiratory distress syndrome should not be excluded solely because of neutropenia.

Adult↗

PubMed1986

Morphine increases metastatic tumor growth.

Walker 256 carcinosarcoma cells produce subpleural pulmonary metastases when given intravenously to the Sprague-Dawley rat. The number of metastases increases when the rat is given morphine subsequent to the tumor load. The increase in the number of metastases can be blocked be pretreatment with the opiate antagonist naloxone. Naloxone itself does not influence the number of metastases. Pentazocine is an opiate that is agonistic to the endorphin kappa-type opiate receptor and partially antagonistic to the mu-type receptor, where morphine acts primarily. While pentazocine alone has no influence on metastases and may decrease the number when given early, pentazocine partially blocks the metastatic inducing effect of morphine.

Animals↗