Tryptophan 650 of human granulocyte colony-stimulating factor (G-CSF) receptor, implicated in the activation of JAK2, is also required for G- CSF-mediated activation of signaling complexes of the p21ras route

Granulocyte colony-stimulating factor (G-CSF) induces rapid phosphorylation of JAK kinases as well as activation of the p21ras route through interaction with its specific receptor (G-CSF-R). The cytoplasmic membrane-proximal region of G-CSF-R (amino acids 631 to 684) is necessary for proliferation induction and activation of JAK2. In contrast, activation of Shc and Syp, signaling molecules implicated in the p21ras signaling route, depends on the phosphorylation of tyrosine residues located in the membrane-distal region (amino acids 685 to 813) of G-CSF-R. We investigated whether G-CSF-induced activation of signaling complexes of the p21ras route depends on the function of the membrane-proximal cytoplasmic region of G-CSF-R. A G- CSF-R mutant was constructed in which tryptophan 650 was replaced by arginine and expressed in BAF3 cells (BAF/W650R). In contrast to BAF3 cell transfectants expressing wild-type G-CSF-R, BAF/W650-R cells did not proliferate and did not show activation of JAK2, STAT1, or STAT3 in response to G-CSF. Immunoprecipitations with anti-Shc and anti-Grb2 antisera showed that mutant W650R also failed to activate Syp and Shc. These data indicate that the membrane-proximal cytoplasmic domain of G- CSF-R is not only crucial for proliferative signaling and activation of JAK2 and STATs, but is also required for activation of the p21ras route, which occurs via the membrane-distal region of G-CSF-R.     

The CD11b promoter directs high-level expression of reporter genes in macrophages in transgenic mice [published erratum appears in Blood 1995 Apr 1;85(7):1983]

CD11b is the alpha chain of the Mac-1 integrin and is preferentially expressed in myeloid cells (neutrophils, monocytes, and macrophages). We have previously shown that the CD11b promoter directs cell-type- specific expression in myeloid lines using transient transfection assays. To confirm that these promoter sequences contain the proper regulatory elements for correct myeloid expression of CD11b in vivo, we have used the -1.7-kb human CD11b promoter to direct reporter gene expression in transgenic mice. Stable founder lines were generated with two different reporter genes, a Thy 1.1 surface marker and the Escherichia coli lacZ (beta-galactosidase) gene. Analysis of founders generated with each reporter demonstrated that the CD11b promoter was capable of driving high levels of transgene expression in murine macrophages for the lifetime of the animals. Similar to the endogenous gene, transgene expression was preferentially found in mature monocytes, macrophages, and neutrophils and not in myeloid precursors. These experiments indicate that the -1.7 CD11b promoter contains the regulatory elements sufficient for high-level macrophage expression. This promoter should be useful for targeting heterologous gene expression to mature myeloid cells.     

Natural bioburden levels detected on rigid lumened medical devices before and after cleaning

Controversy exists concerning the degree of microbial contamination associated with the us of rigid lumened medical devices, the efficacy of standard cleaning techniques used to remove pathogenic microorganisms from lumen channels, and whether patients are placed at risk of cross infection because of microbial contamination. In this study the level and types of microorganisms found on rigid lumened medical devices before and after cleaning in a hospital environment were investigated. The bioburden level after clinical use was found to be relatively low, ranging from 10¹ to 10⁴ colony forming units (CFU) per device. After the instruments were cleaned, none of the devices studied contained bioburden levels greater than 10⁴ CFU and 83% had bioburden levels less than or equal to 10² CFU. The bioburden present before cleaning was comprised of organisms derived from the handling of the device, from the hospital environment, and from the patient. The bioburden present after cleaning was comprised of organisms typically derived from the handling of the device and from the hospital environment. The level of bioburden per device was also related to the anatomic site where the device was used, with lower numbers of organisms found on devices exposed to sterile body sites and the respiratory tract.     

Autoimmunity and interstitial lung disease

PURPOSE OF REVIEW: The pathogenesis of idiopathic pulmonary fibrosis as well as that of several other interstitial lung diseases is poorly understood. The role of autoimmunity in interstitial lung diseases associated with connective tissue disorders such as systemic sclerosis, systemic lupus erythematosus, and rheumatoid arthritis as well as the vasculitides is well established. There is at least some evidence in the literature that supports the role of autoimmunity as one of the mechanisms of alveolar injury responsible for idiopathic pulmonary fibrosis. This review is an attempt to summarize the studies on this subject. RECENT FINDINGS: Repeated extraneous insults and exposures are considered to be responsible for recurrent alveolar injury, inflammation, dysregulated tissue repair, and fibroproliferation resulting in pulmonary fibrosis. The presence of autoantibodies in the sera of patients with idiopathic pulmonary fibrosis has been demonstrated in a few studies. Several autoantibodies, including anti-Sm antibodies, antibodies to U1 ribonucleoproteins, and antibodies to U3 ribonucleoproteins, have been demonstrated in connective tissue disorders, many of which are associated with interstitial lung involvement. Autoimmunity has been also suggested as a possible mechanism of rejection caused by bronchiolitis obliterans after lung transplantation. SUMMARY: It might seem that the role of autoimmunity in interstitial lung disease has been underestimated or even underinvestigated. The subject requires further investigation, especially with regard to the problems of lung allograft rejection due to bronchiolitis obliterans of nonalloimmunity origin and the failure of patients with idiopathic pulmonary fibrosis to respond to most forms of currently available therapy.     

Adult respiratory distress syndrome in the tropics

Today ARDS is more frequently recognized and managed in tropical countries, although published data from most locations is meager. The spectrum of disorders causing ARDS in tropical countries includes virtually all conditions encountered in the West. Additionally, tropical infections and other disorders are seen far more commonly. In particular, malaria and TB are important infections that predispose patients to ARDS in the tropics. Both of these illnesses give lead to severe forms of disease, such as falciparum malaria, acute miliary TB or TB bronchopneumonia, and may cause ARDS. Awareness of the complications helps in early recognition and differential diagnosis from several similar manifestations. Although earlier reports painted a gloomy picture of the outcome of these patients in general--mainly due to financial and logistic constraints--the scenario is improving quickly with better and wider availability of newer diagnostic and management tools.