Alteration of alveolar macrophage chemotaxis,cell adhesion,and cell adhesion molecules following ozone exposure of rats

Ozone (O₃) exposure of humans and animals induces an inflammatory response in the lung, which is associated with macrophage stimulation, release of chemotactic agents, and recruitment of polymorphonuclear leukocytes (PMNs). This study was designed to investigate the functional aspects of the macrophages that impact inflammatory processes in the lung. Macrophages recovered by bronchoalveolar lavage (BAL) from rats exposed to purified air or 0.8 ppm O₃ were studied for their chemotactic activity, adhesive interactions with alveolar epithelial cells in culture, surface morphology, and surface expression of cell adhesion molecules. The macrophages isolated from O₃-exposed rats exhibited a greater motility in response to a chemotactic stimulus than the macrophages isolated from rats exposed to purified air. The macrophages from O₃-exposed animals also displayed greater adhesion when placed in culture with epithelial cells isolated from adult rat lung (ARL-14) than the macrophages from control rats. Both chemotactic motility and cell adhesion stimulated by O₃ exposure were attenuated when the macrophages were incubated in the presence of monoclonal antibodies to leukocyte adhesion molecules, CD11b, or epithelial cell adhesion molecules, ICAM-1. Flow cytometry revealed a modest increase in the surface expression of CD11b but no change in ICAM-1 expression in macrophages from O₃-exposed rats when compared to those from the air-exposed controls. The results demonstrate an alteration of macrophage functions following O₃ exposure and suggest the dependence of these functions on the biologic characteristics, rather than the absolute expression, of the cell adhesion molecules. © 1996 Wiley-Liss, Inc.     

Synaptotagmin VII is targeted to secretory organelles in PC12 cells, where it functions as a high-affinity calcium sensor

Synaptotagmin (syt) I is thought to act as a Ca2+ sensor that regulates neuronal exocytosis. Fifteen additional isoforms of syt have been identified, but their functions are less well understood. Here, we used PC12 cells to test the idea that different isoforms of syt impart cells with distinct metal (i.e., Ca2+, Ba2+, and Sr2+) requirements for secretion. These cells express syt's I and IX (syt IX sometimes referred to as syt V), which have low apparent metal affinities, at much higher levels than syt VII, which we show has a relatively high apparent affinity for metals. We found that syt I and VII partially colocalize on large dense core vesicles and that upregulation of syt VII produces a concomitant increase in the divalent cation sensitivity of catecholamine release from PC12 cells. Furthermore, RNA interference-mediated knockdown of endogenous syt VII reduced the metal sensitivity of release. These data support the hypothesis that the complement of syt's expressed by a cell, in conjunction with their metal affinity, determines the divalent cation sensitivity of exocytosis.     

Systems modeling: a pathway to drug discovery

Systems modeling is emerging as a valuable tool in therapeutics. This is seen by the increasing use of clinically relevant computational models and a rise in systems biology companies working with the pharmaceutical industry. Systems models have helped understand the effects of pharmacological intervention at receptor, intracellular and intercellular communication stages of cell signaling. For instance, angiogenesis models at the ligand-receptor interaction level have suggested explanations for the failure of therapies for cardiovascular disease. Intracellular models of myeloma signaling have been used to explore alternative drug targets and treatment schedules. Finally, modeling has suggested novel approaches to treating disorders of intercellular communication, such as diabetes. Systems modeling can thus fill an important niche in therapeutics by making drug discovery a faster and more systematic process.     

Metabolomics and its role in understanding cellular responses in plants

A natural shift is taking place in the approaches being adopted by plant scientists in response to the accessibility of systems-based technology platforms. Metabolomics is one such field, which involves a comprehensive non-biased analysis of metabolites in a given cell at a specific time. This review briefly introduces the emerging field and a range of analytical techniques that are most useful in metabolomics when combined with computational approaches in data analyses. Using cases from Arabidopsis and other selected plant systems, this review highlights how information can be integrated from metabolomics and other functional genomics platforms to obtain a global picture of plant cellular responses. We discuss how metabolomics is enabling large-scale and parallel interrogation of cell states under different stages of development and defined environmental conditions to uncover novel interactions among various pathways. Finally, we discuss selected applications of metabolomics. This special review article is dedicated to the commemoration of the retirement of Dr. Oluf L. Gamborg after 25 years of service as Founding Managing Editor of Plant Cell Reports. RB and KN have contributed equally to this review.     

Fine needle aspiration cytology of a dedifferentiated liposarcoma: report of a case with histologic and immunohistochemical follow-up

BACKGROUND: Dedifferentiation is a histologic progression of a neoplasm from low grade to high grade histology. It occurs in tumors of the retroperitoneum and in those undergoing treatment. This usually occurs in the setting of radiation or chemotherapy or as a spontaneous process over a long period. The features of dedifferentiation can be toward any mesenchymal element of the underlying neoplastic process. CASE: We report the cytologic features of a dedifferentiated liposarcoma arising in a 76-year-old man who had a history of well-differentiated liposarcoma. Papanicolaou- and Diff-Quik-stained smears from a radiologically guided fine needle aspiration biopsy showed a hypercellular sample. The smears showed a mixed population of cells. There were multinucleated, pleomorphic giant cells with abundant cytoplasm, smaller clusters of cells with a high nuclear/cytoplasmic ratio and cells with spindled and elongated nuclear features. The follow-up surgical resection specimen showed a dedifferentiated liposarcoma with strong and diffuse immunoreactivity to vimentin, desmin and CD68 in the large, pleomorphic cells; focal and weak immunoreactivity to smooth muscle actin and S-100 in these cells; and strong and focal immunoreactivity to desmin, smooth muscle actin and muscle-specific actin in the spindle cells. This supports the dedifferentiated components of this tumor to be of fibrohistiocytic and leiomyosarcomatous differentiation. CONCLUSION: Dedifferentiation of a well-differentiated liposarcoma should be entertained in the setting of a mass lesion in the retroperitoneum in patients with prior histories of well-differentiated liposarcoma. The radiologic features of a particular neoplastic process can be very helpful in determining the nature of this process.     

Control of human potassium channel inactivation by editing of a small mRNA hairpin

Genomic recoding by A-->I RNA editing plays an important role in diversifying the proteins involved in electrical excitability. Here, we describe editing of an intronless potassium channel gene. A small region of human K(V)1.1 mRNA sequence directs efficient modification of one adenosine by human adenosine deaminase acting on RNA 2 (hADAR2). Mutational analysis shows that this region adopts a hairpin structure. Electrophysiological characterization reveals that the editing event (I/V) profoundly affects channel inactivation conferred by accessory beta subunits. Drosophila melanogaster Shaker channels, mimicking this editing event through mutation, exhibit a similar effect. In addition, we demonstrate that mRNAs for the paralogous D. melanogaster Shab potassium channel are edited at the same position by fly ADAR-a clear example of convergent evolution driven by adenosine deamination. These results suggest an ancient and key regulatory role for this residue in K(V) channels.     

Adaptive stochastic-deterministic chemical kinetic simulations

MOTIVATION: Biochemical signaling pathways and genetic circuits often involve very small numbers of key signaling molecules. Computationally expensive stochastic methods are necessary to simulate such chemical situations. Single-molecule chemical events often co-exist with much larger numbers of signaling molecules where mass-action kinetics is a reasonable approximation. Here, we describe an adaptive stochastic method that dynamically chooses between deterministic and stochastic calculations depending on molecular count and propensity of forward reactions. The method is fixed timestep and has first order accuracy. We compare the efficiency of this method with exact stochastic methods. RESULTS: We have implemented an adaptive stochastic-deterministic approximate simulation method for chemical kinetics. With an error margin of 5%, the method solves typical biologically constrained reaction schemes more rapidly than exact stochastic methods for reaction volumes >1-10 micro m(3). We have developed a test suite of reaction cases to test the accuracy of mixed simulation methods. AVAILABILITY: Simulation software used in the paper is freely available from http://www.ncbs.res.in/kinetikit/download.html