Barking up the wrong tree? Use of polymerase chain reaction to diagnose syphilitic aortitis.

The presentation of syphilitic aortitis is often atypical and available serological tests are non-specific. The diagnostic gold standard remains direct identification of microorganisms in tissue. We present a case of syphilitic aortitis that presented as a mediastinal mass and report the use of polymerase chain reaction for Treponema pallidum to diagnose syphilitic aortic disease.

Ontogeny of pulmonary alveolar epithelial markers of differentiation.

We studied differentiation of the pulmonary epithelium in the periphery of fetal rat lung in vivo and in vitro by comparing the ontogeny of cell-surface glycoconjugates with that of surfactant phospholipids. Apical surface binding of the lectin Maclura pomifera agglutinin (MPA) and expression of a 200-kDa MPA-binding glycoprotein (MPA-gp200) was evident at 20 days gestation in type 2 cells, but did not correlate with ultrastructural features of type 2 cell differentiation. Epithelial cells isolated from peripheral lung of 18-day gestation fetal rats displayed hormone-sensitive surfactant synthesis prior to the hormone-insensitive expression of MPA-gp200. Expression of MPA-gp200 occurred in association with the appearance of many new apical surface proteins suggesting a hormone-independent process of polar membrane differentiation. Thus membrane and secretory differentiation are discordant and can be dissociated. In vivo binding of Ricinus communis 1 agglutinin (RCA1), an apical marker of the differentiated alveolar type 1 cell occurred in undifferentiated peripheral lung epithelial cells as early as 18 days gestation, disappeared from differentiating type 2 cells and appeared in differentiated type 1 cells. Both undifferentiated fetal epithelial cells at 18 days gestation and fully differentiated type 1 cells express multiple glycoproteins with terminal beta-linked galactose residues which bind RCA1. Some of these RCA1-binding glycoproteins appear to be similar. These observations suggest that alveolar epithelial type 1 cells may derive directly from undifferentiated peripheral lung epithelial cells as well as from fully differentiated type 2 cells. In addition, terminal differentiation of fetal lung peripheral epithelium into type 1 and type 2 cells may involve repression as well as induction of differentiation-related genes.

Human pulmonary alveolar type 2 cells contain an apical membrane glycoprotein common to malignant cells.

A monoclonal antibody, Ca1, raised against a detergent extract of Hep 2 cells derived from a human laryngeal carcinoma, was shown in these studies to bind to the apical surface of normal alveolar type 2 cells but not type 1 cells in the human lung. In lung specimens from patients with alveolitis, the antibody also bound to hyperplastic type 2 cells and to transition cells which were in the process of becoming alveolar type 1 cells. Ca1 binds to the apical plasma membrane and to internal membranes of cytoplasmic vesicles thought to be involved in the packaging of pulmonary surfactant. A surfactant-enriched fraction of human lung lavage did not bind the Ca1 antibody suggesting that the antigen was not an integral component of secreted surfactant. In normal human lung parenchyma, Ca1 binds only to type 2 cells, however it also binds to the apical surface of Clara cells in areas of cellular hyperplasia. Solubilized homogenates of whole lung, of a cell membrane fraction and of Hep 2 cells, immunoprecipitated with Ca2, separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and probed with iodinated lectins, revealed that terminal glycosylation of the type 2 cell antigen differed from that of Hep 2 cells. Ca1 and a 330 kilodalton type 2 cell glycoprotein bind the lectin Maclura pomifera agglutinin. These two glycoproteins represent the first defined membrane markers of the apical surface of the human type 2 cell.

Identification and characterization of the pulmonary alveolar type II cell Maclura pomifera agglutinin-binding membrane glycoprotein.

The lectin Maclura pomifera agglutinin (MPA) binds to the apical surface of pulmonary alveolar type II but not type I cells. We show that MPA binds to a single membrane glycoprotein in type II cells with a molecular mass of 230 kDa in the rabbit and 200 kDa in the rat. The glycoprotein has an abundance of terminal N-acetylgalactosamine residues. It is a hydrophilic integral membrane protein suggesting that it has an extensive extramembrane domain or is an ion channel. The glycoprotein is similar in rat and rabbit, with the exception that the rat glycoprotein is partially sialylated and is trypsin sensitive. The MPA-binding glycoprotein represents a new integral membrane marker of the apical domain of the pulmonary alveolar type II cell.