Biomedical subjects

J Lwebuga-Mukasa

Publications and source records attributed to J Lwebuga-Mukasa.

6 recordsLinked to original sources

PubMed1999

Does cartilage down-regulate growth factor expression in tracheal epithelium?

BACKGROUND: Maintaining tracheal integrity and restoring normal physiologic function after injury is complex. Some of the critical events in this process are deposition of a provisional extracellular matrix, tissue remodeling, and angiogenesis. These events are coordinated with epithelial migration and proliferation to restore the mucosal barrier. The ability of respiratory epithelial cells (REC) to migrate and proliferate and restore denuded areas of the large conducting airway after injury is poor. OBJECTIVE: To test the hypotheses that (1) the cartilaginous framework, underlying the extracellular matrix (submucosa) and epithelium, decreases the migratory ability of REC when compared with REC on the same provisional extracellular matrix (type I collagen) alone, and (2) this phenomenon is associated with a change in expression of transforming growth factor (TGF)-alpha and TGF-beta, both of which have been demonstrated in cutaneous models to be important in epithelial migration and proliferation. DESIGN: We developed a culture system that reconstitutes the tracheal lumen in vitro, consisting of dissociated chondrocytes cultured in a manner to form cartilage, submucosa (type I collagen), and REC (termed a "composite culture"). Control cultures consisted of epithelial cells grown on type I collagen alone. Control and composite cultures were evaluated morphologically using scanning electron and light microscopy. Expression of TGF-alpha and TGF-beta was determined in day 14 cultured epithelial cells from control and composite cultures by semiquantitative polymerase chain reaction. RESULTS: Epithelial cells from composite cultures did not spread and were less squamoid in morphological appearance than epithelial cells on type I collagen alone. Expression of both growth factors was reduced in epithelial cells from composite cultures compared with those on type I collagen. CONCLUSIONS: Cartilage modulates TGF-alpha and TGF-beta expression in REC, and may contribute to regulation of REC proliferation and differentiation.

Animals↗

PubMed1997

Isolation and characterization of basal cells from human upper respiratory epithelium.

Cellular pathways of normal and reparative differentiation of upper airway epithelium are not well understood. Of the three main cell types, basal and secretory cells are known to divide, while ciliated cells are considered terminally differentiated. Several investigations support the role of the basal cell as a progenitor cell type, but others suggest that the secretory cell can regenerate a complete mucocilliary epithelium. Thus, lineage relationships within renewing adult epithelia are still unclear. Understanding the pathways involved in upper airway epithelial cell differentiation is critical for studying injury and repair mechanisms and for developing clinical strategies for tracheal reconstruction. We undertook the current studies to determine the integrin profile of isolated human upper airway basal cells. Respiratory epithelial cells (REC) were isolated by elastase digestion, stained with FITC-labeled Griffonia simplicifolia isolectin B4 (GSI-B4), and sorted by flow cytometry. Approximately 80% of the lectin-positive cells were basal cells, as determined by morphology and cytokeratin staining. These cells expressed integrins alpha 1, alpha 2, alpha 3, alpha 5, alpha v beta 5, beta 1, beta 3, and alpha 6 beta 4, by immunohistochemistry. This is the first report to identify the integrin profile of isolated human upper airway basal cells. These basal cells could be maintained on type I collagen for at least 7 days, where they became partially confluent and retained expression of cytokeratins 5 and 14. Availability of pure populations of basal cells should permit investigations of their role in both normal and maladaptive repair of adult upper airway epithelium.

Adult↗

PubMed1991

Comparison of the Maclura pomifera lectin-binding glycoprotein in late fetal and adult rat lung.

The lectin, Maclura pomifera agglutinin (MPA), binds to alpha-galactose residues of glycoproteins on the apical surface of type II alveolar cells. It has recently been shown to bind to macrophages. We isolated the cell surface glycoprotein, which binds the MPA lectin, from fetal and adult rat whole lung to determine if changes in this glycoprotein occur during development from fetal to adult life. The glycoprotein was purified from whole lung cell membranes by lectin affinity chromatography that resulted in 10(5)-fold enrichment. The MPA binding glycoproteins from both fetal and adult lung had the same apparent molecular weight of 170 kD as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Amino acid analysis revealed similar composition of the fetal and adult proteins. Two-dimensional peptide maps of the 170 kD proteins isolated from fetal and adult lung were also similar. These data indicate that the glycoprotein that binds MPA to lung cell membranes does not change during this stage of development. Our method for the isolation of this glycoprotein can be used for the generation of antibodies or other molecular probes for further study of this protein.

Amino Acids↗

PubMed1988

Radiolabeled fibronectin for the scintigraphic detection of pulmonary emboli in dogs.

Plasma fibronectin, a glycoprotein that is a component of blood thrombi, was evaluated for the in vivo scintigraphic detection of pulmonary emboli in dogs. Fibronectin (canine or human) was labeled with either 131I or with 111In and diethylenetriaminepenta-acetic acid (DTPA) as the bifunctional chelating agent using a modification of the mixed anhydride method. The radiolabeled proteins were administered intravenously 20 to 30 minutes after the embolization of a 99mTc-labeled thrombus. The uptake of radioactivity by the embolus was monitored scintigraphically up to 24 hours. At the end of each experiment, the animal was killed and in vitro tissue counting of radioactivity was performed. Comparative study of the 131I- and 111In-labeled agent is presented with particular reference to their pharmacokinetics. The in vivo uptake of radioactivity by the emboli was limited, indicating that radiolabeled fibronectin is not a good scintigraphic agent for the detection of pulmonary emboli.

Animals↗

PubMed1986

Surfactant-anti-surfactant immune complexes in infants with respiratory distress syndrome.

The authors sought to determine whether treatment of respiratory distress syndrome (RDS) with human surfactant resulted in the formation of detectable circulating immune complexes. Preterm infants with severe RDS were divided into two groups: one group received human surfactant by intratracheal instillation and the other group did not. Both groups received ventilatory management involving intermittent mandatory ventilation. Plasma samples were drawn from these babies prior to treatment and at intervals thereafter. The authors developed an ELISA assay specific for surfactant-anti-surfactant immune complexes and analyzed the plasma samples for such immune complexes. Complement levels were also measured. They found that with time plasma from RDS infants in both groups showed evidence of surfactant-anti-surfactant immune complex formation. The concentrations of immune complexes generally peaked within the first week of life and then appeared to diminish over 1-4 weeks after birth in RDS infants. There was no evidence at any time in either group of immune-complex-mediated injury or of decreased serum complement levels. It is concluded that circulating immune complexes between surfactant and antibodies to surfactant are probably found in most neonates with respiratory distress syndrome, that they do not produce pulmonary damage detectable by clinical and serologic means, and that treatment of neonatal RDS with human surfactant similarly does not produce lung injury as determined with these techniques.

Antibody Specificity↗

PubMed1985

Characteristics of primary isolates of alveolar type II cells from neonatal rats.

Alveolar type II cells from 6-day-old rat pups were obtained at approximately 90% purity, as judged by light and electron microscopy. Within 48-72 h in culture, the cells formed a monolayer with tight junctions typical of epithelial cells. Type II cells aggregated into raised domelike areas, which when sectioned showed alveolarlike structures comprised of type II cells. After 3 days in culture these structures showed abundant lamellar body secretion. Phospholipid profiles were characteristic of type II cells, with disaturated phosphatidylcholine (DSPC) the predominant secreted phospholipid. The cells also released DSPC in response to beta-adrenergic stimulation. This release was inhibited by the specific beta-antagonist propranolol. The results show that morphologic differentiation and biochemical properties of neonatal type II cells can be studied using an isolated cell system in tissue culture.

Animals↗