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A Clement

Publications and source records attributed to A Clement.

At least 73 records · Page 4Linked to original sources
PubMed1991

SV40T-immortalized lung alveolar epithelial cells display post-transcriptional regulation of proliferation-related genes.

To study the regulation of proliferation of lung alveolar epithelial type 2 cells, we have established a cell line derived from neonatal type 2 cells by transfection with the SV40 large T antigen gene. We find that this cell line, designated SV40-T2, displays the same post-transcriptional control of expression of proliferation-related genes, including c-myc, ornithine decarboxylase, thymidine kinase, and histone, that we have previously described in primary isolates of type 2 cells (Clement et al., Proc. Natl. Acad. Sci. USA 87, 318-322, 1990). Both proliferating and nonproliferating SV40-T2 cells express these genes at high levels, but their translation products are only detected in proliferating cells. Using the histone gene as an example, we have found that regulation of expression occurs at the level of transcription and of mRNA turnover, as previously described in other mammalian systems. However, in addition, regulation of expression also occurs at the level of translation of the histone mRNA, because its protein product is not detectable in nonproliferating SV40-T2 cells. We have analyzed the steps which are potentially involved in this translational regulation of histone gene expression in SV40-T2 cells. In both proliferating and nonproliferating cells, histone mRNA was found to be efficiently transported from the nucleus to the cytoplasm and to associate with the translationally active heavy polysomal fractions. These results indicate that control of histone gene expression (and perhaps that of other proliferation-related genes) in lung epithelial cells may involve either rapid and selective degradation of histone protein or binding factor(s) which modulate translational efficiency of histone mRNA.

Animals↗
PubMed1990

Constitutive expression of growth-related mRNAs in proliferating and nonproliferating lung epithelial cells in primary culture: evidence for growth-dependent translational control.

We describe the control of proliferation and growth-related gene expression in primary cultures of epithelial cells derived from rat lung. Type 2 epithelial cells line the gas-exchange surface of the alveoli where they produce and secrete surfactant. When isolated from adult animals, type 2 cells do not proliferate in culture, although they have a limited ability to do so in vivo. We show that type 2 cells isolated from neonatal rats proliferate in culture and that growth can be reversibly arrested by withdrawing serum from the medium. We studied the expression of five genes whose mRNA levels fluctuate with the state of proliferation in several cell systems: the c-myc and c-Ha-ras protooncogenes and the genes encoding actin, ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17), and histone 3.2. All five mRNAs were constitutively expressed at identical levels in proliferating and nonproliferating (serum deprived) neonatal cells and in adult cells. Thus, at the level of mRNA abundance, the expression of these five genes was uncoupled from the growth state of the cells. By contrast, synthesis of the replication-dependent histones and the activity of ornithine decarboxylase were detectable only in proliferating neonatal cells and not in serum-deprived neonatal cells or in adult cells. The results suggest that, in type 2 cells, growth factors might regulate the translation, rather than the mRNA abundance, of at least some growth-related genes and that the ability to respond to this translational control may be developmentally regulated.

Aging↗
PubMed1990

Growth-related gene expression in type 2 alveolar epithelial cells.

Our laboratory is studying mechanisms of growth control in alveolar type 2 cells. This highly differentiated cell is induced to proliferate in lungs of animals of all ages during various forms of growth and during the repair process after lung injury. Using type 2 (T2) cells isolated from adult and neonatal rat lungs and an SV40-T transfected T2 cell line, we have shown tha growth-arrested T2 cells constitutively express genes associated with G1 and S phase of the cell cycle, yet they do not efficiently translate the proteins encoded by these genes. This block of growth-related gene expression is post-transcriptional and appears to involve mechanisms that control translation, perhaps at the level of initiation. Furthermore, growth-arrested T2 cells initiate DNA synthesis; however, the cells do not complete the cell cycle, suggesting that they are arrested in a late stage, perhaps the G1/S border. Differential screening of a cDNA library of growth-arrested T2 cells with DNA from growing and growth-arrested T2 cells has identified four families of genes preferentially expressed in the growth-arrested cells. These genes, which are in the process of being characterized, may be responsible for the unusual type of growth arrest demonstrated by T2 cells.

Animals↗
PubMed1990

[3H]thymidine incorporation does not correlate with growth state in cultured alveolar type II cells.

Quantitative measurement of [3H]thymidine [( 3H]TdR) incorporation into cultured cells is widely used as an indicator of cell proliferation. The observation that adult type II cells are able to incorporate large amounts of [3H]TdR despite the fact that they are not proliferating raised the question of the meaning of [3H]TdR incorporation in these cells. Comparing different systems of proliferating and nonproliferating type II cells and lung fibroblasts, we show that nonproliferating type II cells are able to synthesize some thymidine nucleotides used as immediate precursors for DNA synthesis and that most of the radioactivity incorporated into acid-insoluble material in these cells is actually in DNA. We found that hydroxyurea inhibited [3H]TdR incorporation into DNA, suggesting that nonreplicating type II cells use thymidine for scheduled, i.e., replicative, rather than unscheduled, or repair, DNA synthesis. However, newly synthesized DNA does not appear to be in a stable form, available for replication. These studies demonstrate that, in culture, adult type II cells initiate but are unable to complete scheduled DNA synthesis. They also establish that [3H]TdR incorporation cannot be used as an indicator of cell proliferation in cultured type II cells.

Animals↗
PubMed1990

Serum accelerates the loss of type II cell differentiation in vitro.

The differentiated phenotype of the alveolar type II cell is rapidly altered in vitro. To evaluate factors that might influence this process, we isolated and plated rat type II cells in serum-supplemented media to promote adherence and then maintained the cells in a simple nutrient medium in the absence (S- cells) or presence (S+ cells) of serum for 5 to 7 d. The type II S- cells remained metabolically active. Despite protein synthesis that was 50% that of S+ cells, S- cells continued to synthesize a broad spectrum of proteins and to express several features of type II cell differentiation. They synthesized an apical integral membrane glycoprotein, Maclura pomifera agglutinin (MPA)-gp200, and a cytokeratin, No. 19, while S+ cells did not. When supplemented with linoleic acid, S- cells contained lamellar and multivesicular bodies, incorporated cell surface MPA into these structures, and secreted their phosphatidylcholine (PC) in response to mastoparan. Despite the relative synthesis of higher levels of total and saturated PC in S- cells supplemented with linoleic acid, phosphatidylglycerol remained diminished. A surfactant protein (SP-A) was present in S- cells, but synthesis was not detected. These studies demonstrate that serum accelerates the loss of type II cell differentiation in vitro and that the expression of type II cell markers of differentiation is not inherently linked.

Animals↗
PubMed1988

Activation of alveolar macrophages from children with the acquired immunodeficiency syndrome-related complex.

The ability of alveolar macrophages (AM) to release hydrogen peroxide (H2O2), an indicator of AM function, was studied in five children with the acquired immunodeficiency syndrome (AIDS) related complex and, for comparison, in 11 children without disorders of the lung parenchyma. In the AIDS-related complex group, pulmonary manifestations were mild, and lung involvement was suspected by moderate clinical and/or radiological features. None had a past history of opportunistic infections; neither did any have lymphopenia. Cytologic study of the bronchoalveolar lavage (BAL) fluid revealed increased cellularity with increased percentage of lymphocytes. The study of H2O2 release was performed on unstimulated AM and on AM stimulated by phorbol myristate acetate (PMA). Under both experimental conditions, the amount of H2O2 accumulated in the medium was significantly increased in the group with AIDS-related complex (P less than 0.001). As no enhanced oxidative activity has been reported in AM from patients with full-blown AIDS, an increased ability of AM to release oxygen metabolites from children with AIDS-related complex may reflect an initial and temporary step in the course of the LAV/HTLV-III pulmonary disease. Determining AM activation might be a reliable method of assessing the evolution of lung disorder in AIDS.

AIDS-Related Complex↗
PubMed1988

Peripheral neuropathy with essential mixed cryoglobulinemia: biopsies from 5 cases.

Essential mixed cryoglobulinemia, which can cause hypersensitivity vasculitis, was observed in five patients with peripheral neuropathy. Three cases presented with multifocal neuropathies and two cases with symmetrical polyneuropathy. One had cryoglobulinemia with IgM monoclonal gammopathy IgG polyclonal gammopathy, and the other four had cryoglobulinemia with polyclonal gammopathy. Biopsies showed perivascular infiltration by mononuclear cells around medium, and mainly small-sized blood vessels. This was observed in the epineurium (five cases) and muscular fragments (three cases). At ultrastructural examination two cases showed severe damage of most myelinated fibers, which presented acute stages of Wallerian-like degeneration, and the three other cases showed a less widespread destruction of myelinated fibers. Most endoneurial capillaries showed swollen endoneurial cells. Myelino-axonal degeneration of myelinated fibers is probably due mainly to the vasculitis always present in the epineurium. This damage was probably worsened by the modifications of endoneurial capillaries. These lesions and their mechanisms are quite different from those observed in cases of cryoglobulinemia with an isolated monoclonal gammopathy.

Aged↗
PubMed1988

Alveolar macrophage status in bronchopulmonary dysplasia.

The predominant inflammatory cell type within the alveolar structure in bronchopulmonary dysplasia (BPD) is the alveolar macrophage (AM). AM ability to release hydrogen peroxide, a way to evaluate the cell status, was studied in nine infants who developed clinical and radiological evidence of BPD, and was compared to those from infants without lung parenchymal disorders (n = 6). AM were collected by bronchoalveolar lavage which was done after the mechanical ventilation stage in the BPD group. The experiments were performed on unstimulated AM and on AM stimulated by phorbol myristate acetate. Results revealed that the amount of hydrogen peroxide accumulated in the culture medium was significantly enhanced in the BPD group, in both experimental conditions (p less than 0.01 and less than 0.001, respectively). Furthermore, improvement of patients treated with glucocorticoids was closely related to a reduction of the alveolitis with a decrease of AM ability to generate hydrogen peroxide. These data indicate that AM activation is a central component of alveolitis in BPD and that extracellular production of oxidants by stimulated AM may play a critical role in the pathogenesis of the disease.

Bronchopulmonary Dysplasia↗
PubMed1987

Use of total inspiratory pressure-volume curves for determination of appropriate positive end-expiratory pressure in newborns with hyaline membrane disease.

Thirty newborns with hyaline membrane disease were treated by mechanical ventilation with individualized appropriate positive end-expiratory pressure (APEEP) from inspiratory pressure-volume curves of the total respiratory system. APEEP was started before H24 in group 1 (19 patients), and after H24 in group 2 (11 patients). Until APEEP, the 2 groups had classical PEEP levels (lower than 0.8 kPa) either without or with incomplete improvement in arterial hypoxia. The mean APEEP of each group was greater than classical PEEP (p less than 0.001). In group 1 the time of exposure to FiO2 greater than 0.4 was shorter (23.8 +/- 13.7 h) than in group 2 (88.6 +/- 56.9 h) (p less than 0.001) and rapid improvement in blood gas exchanges was seen in group 1 compared to group 2 that was independent of the severity of the disease. Tolerance was excellent. APEEP ventilation started before H24 is of special interest in the management of newborns with severe alveolar injury.

Hemodynamics↗
PubMed1987

A controlled study of oxygen metabolite release by alveolar macrophages from children with interstitial lung disease.

The ability of alveolar macrophages (AM) to release O2 metabolites was studied in 8 children with interstitial lung disease (ILD), and in 11 children without lung parenchyma disorder. AM were collected by bronchoalveolar lavage. The experiments were performed on unstimulated AM and on AM stimulated by phorbol myristate acetate (PMA) or zymosan. Our results indicated that, with or without triggering agent, the amount of O2 metabolites release was a linear function pattern with time. The accumulation of superoxide anion (O2-) and hydrogen peroxide (H2O2) into the extracellular medium differed depending on the triggering agent used: with PMA, the amount of O2- released was threefold the amount of H2O2 detected in the medium, whereas with zymosan the O2- accumulation was tenfold higher than the amount of H2O2 measured. In patients with ILD, a significant increase in the amount of H2O2 release was observed for both unstimulated and stimulated AM (p less than 0.001). In this group, the measurement was repeated after a 2-month steroid treatment: prednisone had markedly improved the clinical, radiologic, and functional status of the patients, and this improvement was in good correlation with the decrease of O2 metabolite production. The amount of H2O2 release in each case was within the range of control values. Evaluation of O2 metabolite release by AM could be a useful parameter in the assessment of the activity of ILD.

Adolescent↗
PubMed1984

Comparison of transcutaneous and alveolar partial pressure of carbon dioxide during carbon dioxide breathing in healthy children.

In 18 healthy children three to 13 years of age, the transcutaneous partial pressure of carbon dioxide (PtcCO2) (Radiometer electrode) and the alveolar partial pressure of carbon dioxide (PACO2) (Beckman analyzer) were measured simultaneously during the breathing of room air and 5 percent carbon dioxide. The PtcCO2 electrode was placed on the anterior thorax and heated to 42 degrees C. The PACO2 was calculated on the 4/5 part of the carbon dioxide expired trace. Minute ventilation (VE) was measured in 11 cases. There was a significant correlation between PtcCO2 (in millimeters of mercury) and PACO2 (in millimeters of mercury) while breathing room air (PtcCO2 = 0.82 PACO2 + 19.7; r = 0.55; p less than 0.02) and while breathing 5 percent carbon dioxide (PtcCO2 = 0.77 PACO2 + 22.5; r = 0.61; p less than 0.01); however, the ratio of PtcCO2 over PACO2 was significantly lower while breathing 5 percent carbon dioxide (p less than 0.01) than while breathing room air. When considering the relationship between the increase in VE (delta VE while breathing 5 percent carbon dioxide and the changes in PACO2 (delta PACO2) or in PtcCO2 (delta PtcCO2), a significant correlation was found only between delta VE and delta PACO2, ie, delta VE = 0.41 delta PACO2 + 0.44 (r = 0.63; p less than 0.01). These results suggest that breathing carbon dioxide modified the factors acting on PtcCO2, possibly by changes in the vasomotor tone of cutaneous blood vessels. These modifications appeared to be variable from subject to subject. Therefore, we conclude that PtcCO2 does not appear to be an accurate quantitative index to assess ventilatory response to carbon dioxide.

Adolescent↗
PubMedDate not supplied

Decreased phosphatidyl choline content in bronchoalveolar lavage fluids of children with bronchopulmonary dysplasia: a preliminary investigation.

Bronchoalveolar lavage (BAL) was performed on 12 infants who had recovered from neonatal acute respiratory failure and on 12 patients with bronchopulmonary dysplasia (BPD) in order to evaluate the concentration of phosphatidyl choline (PC) in BAL fluid. These two groups were similar at birth (mean birth weight: 1,980 and 1,750 g, respectively; mean gestational age: 33.4 and 32.1 weeks respectively). Mechanical ventilation based on oxygen requirement lasted longer in the group with BPD. BAL was performed at the end of the first year of life (at 8.5 and 10.3 months, respectively) and the results were compared to control values (from infants of the same age without neonatal disease). Whereas the protein concentration in BAL fluid was similar in the two groups, a dramatic decrease of the BAL PC was found in BPD: The mean values of BAL-PC over protein ratio were 0.9 in the group without pulmonary sequelae and 0.3 in the group with BPD. These preliminary results suggest an impairment of the pulmonary surfactant metabolism in this chronic lung disease following neonatal acute respiratory failure.

Bronchopulmonary Dysplasia↗