PubMed Health⌕ Search

Biomedical subjects

P F Weller

Publications and source records attributed to P F Weller.

At least 19 recordsLinked to original sources
PubMed2001

Induction of endothelial cell cytoplasmic lipid bodies during hypoxia.

Lipid bodies (LBs), lipid-rich cytoplasmic inclusions found in many cell types, seem to act as nonmembrane sites of eicosanoid formation. Because alterations in eicosanoid products have been demonstrated in endothelial cells (ECs) during hypoxia, we investigated induction of LBs in systemic and pulmonary ECs exposed to acute and/or chronic hypoxia. LBs in ECs were O(2)-concentration dependent, increasing approximately fivefold during acute exposure to 0% O(2) in both cell types. During chronic exposure to 3% O(2), LBs were induced only in systemic ECs. LBs were not induced by other cellular stresses (heat shock or glucose deprivation). Subsequent studies suggested that protein kinase C-dependent and tyrosine kinase-dependent pathways are important in LB induction during hypoxia. PGH synthase was demonstrated in LBs in every case in which they were induced. These are the initial studies to demonstrate induction of LBs in ECs and to demonstrate LB induction during exposure to hypoxia in any cell type. These results imply that in ECs, LBs are structurally distinct inducible sites for synthesis of eicosanoid mediators.

Animals↗
PubMed2000

Benefits of negative penicillin skin test results persist during subsequent hospital admissions.

For an initial series of 38 patients with negative skin test results, we reviewed retrospectively all subsequent admissions over a 2-year period. For 38 patients with negative initial skin test results, there were 48 subsequent readmissions to our institution, of which 35 required antibiotics. beta-lactams were prescribed for 86% of admissions; a penicillin for 37%, and a cephalosporin for 51%. All infections were cured, and there were no allergic drug reactions during any of the admissions that were reviewed.

Anti-Bacterial Agents↗
PubMed2000

EliCell: a gel-phase dual antibody capture and detection assay to measure cytokine release from eosinophils.

Eosinophils contain many preformed cytokines and chemokines, which are stored in specific granules along with cationic granule proteins. Mobilization and release of these granule contents can be selective and mediated by vesicular transport. We have developed a sensitive method to detect and quantitate eosinophil vesicular transport-mediated release of specific eosinophil proteins. Our EliCell assay is based on microscopic observations of individual viable eosinophils embedded in an agarose matrix that contains immobilized antibody to the protein of interest. Following stimulation of eosinophils, released protein is bound by the capture antibody at its site of release and is detected by a fluorochrome-conjugated detection antibody. We have validated this assay by evaluating interferon-gamma-induced release of RANTES from eosinophils. Extracellularly released RANTES was visualized as focal immunoflourescent staining and was quantitated by scoring the numbers of eosinophils releasing RANTES and by measuring the fluorescent intensity over individual eosinophils. In comparison with ELISA assays of RANTES released into supernatant fluids by interferon-gamma-stimulated eosinophils, EliCell assays were more sensitive enabling detection of RANTES release at earlier times and at lower levels of interferon-gamma stimulation. The EliCell assay provides a sensitive method to study the regulated release of eosinophil-derived cytokines, chemokines and other granule proteins.

Antibodies↗
PubMed2000

Phosphatidylinositide 3-kinase localizes to cytoplasmic lipid bodies in human polymorphonuclear leukocytes and other myeloid-derived cells.

Phosphatidylinositide 3-kinase (PI3K) is a key enzyme implicated in intracellular signaling of diverse cellular responses including receptor-mediated responses and neutrophil activation. Several PI3K subunits have been cloned and shown to be localized to plasma membrane receptors, the cytosol, or intracellular vesicles or caveolae. We report the localization of PI3K to a distinct intracellular site, cytoplasmic lipid bodies, in leukocytes. In U937 monocyte cells, PI3K p85 regulatory and p110beta catalytic subunits were localized to lipid bodies by immunocytochemistry and/or immunoblotting and enzyme assays of subcellular fractions. In RAW murine macrophages, p55, p85alpha, and p85beta PI3K subunits were present at isolated lipid bodies. PI3K p85 was also shown to colocalize and, by co-immunoprecipitation, to be physically associated with phosphorylated Lyn kinase in lipid bodies induced to form in human polymorphonuclear leukocytes. These findings, therefore, indicate a novel site for PI3K compartmentalization and suggest that PI3K-mediated signaling is active within cytoplasmic lipid bodies in leukocytes.

Animals↗
PubMed2000

Eosinophilia and helminthic infections.

Among microbial agents, helminths are the most common cause of eosinophilia. An approach to the evaluation of a patient with eosinophilia is outlined, with particular emphasis on clues in the history, examination and routine laboratory data that can help with the diagnosis. Multiple helminthic infections have been associated with eosinophilia, and the characteristic modes of spread, clinical manifestations, diagnostic tests and therapeutic considerations of these infections are discussed.

Animals↗
PubMed2000

Lymph node trafficking and antigen presentation by endobronchial eosinophils.

Because eosinophils recruited into the airways in allergic diseases are exposed to inhaled allergens, we evaluated whether eosinophils within the endobronchial lumen can function in vivo as antigen-presenting cells for inhaled antigens. We recovered eosinophils from the airways after aerosol antigen challenge in sensitized mice or from the peritoneal cavities of IL-5 transgenic mice and fluorescently labeled these cells ex vivo. These labeled cells, instilled intratracheally into normal mice, migrated into draining paratracheal lymph nodes and localized to T cell-rich paracortical areas. The homing of airway eosinophils to lymph nodes was not governed by eotaxin, because CCR3(-/-) and CCR3(+/+) eosinophils migrated identically. Airway eosinophils, recovered after inhalational antigen challenge in sensitized mice, expressed MHC class II and costimulatory CD80 and CD86 proteins and functioned in vitro as CD80- and CD86-dependent, antigen-specific, antigen-presenting cells. Moreover, when instilled into the airways of antigen-sensitized recipient mice, airway eosinophils recovered after inhalational antigen challenge stimulated antigen-specific CD4(+) T cell proliferation within paratracheal lymph nodes. Thus, eosinophils within the lumina of airways can process inhaled antigens, traffic to regional lymph nodes, and function in vivo as antigen-presenting cells to stimulate responses of CD4(+) T cells.

Animals↗
PubMed2000

RNA is closely associated with human mast cell secretory granules, suggesting a role(s) for granules in synthetic processes.

The distribution of ribosomes in mature human mast cells, a major granulated secretory cell, does not resemble that in other secretory cells, such as pancreatic acinar cells and plasma cells. By routine ultrastructural analysis, ribosomes in human mast cells are often close to, attached to, or even appear to be within secretory granules. To document better these relationships, we used multiple electron microscopic imaging methods, based on different principles, to define RNA, ribosome, and granule relationships in mature human mast cells. These methods included EDTA regressive staining, RNase digestion, immunogold labeling of ribonucleoproteins or uridine, direct binding or binding after ultrastructural in situ hybridization of various polyuridine probes to polyadenine in mRNA, and ultrastructural autoradiographic localization of [3H]-uridine incorporated into cultured human mast cells. These different labeling methods demonstrated ribosomes, RNA, U1SnRNP (a small nuclear RNP specific for alternative splicing of mRNA), mRNA, and uridine to be associated with secretory granules in human mast cells, implicating granules in a larger synthetic role in mast cell biology.

Autoradiography↗
PubMed1999

Eosinophil ablation and tumor development.

Tissue eosinophilia in squamous cell carcinoma has long been recognized; however, the role of eosinophils in tumor development remains unclear. Studies have reported both favorable and unfavorable prognoses for patients with tumors exhibiting tumor-associated tissue eosinophilia (TATE). This study seeks to elucidate the potential role of the eosinophil in squamous cell carcinoma development and provide an experimental model for future studies. The carcinogen-induced hamster oral cancer model was found to fulfill these objectives. Eosinophils progressively infiltrate into this carcinogen-induced oral cancer model. We now demonstrate that TATE is completely abolished by the use of an anti-interleukin-5 monoclonal antibody (mAb) preparation, TRFK-5. Clinical observations revealed that TRFK-5-treated hamsters exhibited smaller tumor burden and delayed onset of tumor development. The results suggest that anti-interleukin-5 antibody treatment may delay and/or inhibit tumor development, and that eosinophils may have a tumor-promoting role.

Animals↗
PubMed1999

The American Society of Tropical Medicine and Hygiene initiative to stimulate educational programs to enhance medical expertise in tropical diseases.

More than a decade ago, at a time when current and emerging tropical diseases posed growing threats to the United States, expert panels convened by the Institute of Medicine of the U.S. National Academy of Sciences concluded that medical expertise within the United States competent to address diseases of the tropics had declined. Recognizing a national need to encourage and enhance such, The American Society of Tropical Medicine and Hygiene developed a program to stimulate new postgraduate medical education in diseases of the tropics. The Society formally requested academic institutions within the United States and Canada to propose new postgraduate programs. To assure the quality of these new curricular offerings, the Society developed an outline of key areas of competency and agreed to offer an examination that would grant physicians a Certificate of Knowledge in Clinical Tropical Medicine and Travelers Health. The certifying examination was to be an integral component of a program to stimulate academic institutions to provide instructional programs in tropical diseases and to encourage physicians to become trained, evaluated, and recognized for their knowledge of clinical tropical diseases and travelers' health. The Society's initiative to stimulate educational programs in tropical medicine is reviewed.

Canada↗
PubMed1998

IL-4-dependent regulation of TGF-alpha and TGF-beta1 expression in human eosinophils.

TGFs play important roles in wound healing and carcinogenesis. We have previously demonstrated that eosinophils infiltrating into different pathologic processes elaborate TGF-alpha and TGF-beta1. Eosinophils infiltrating hamster cutaneous wounds were found to express TGFs sequentially. In this study, we examined the biologic mediators that may regulate the expression of TGF-alpha and -beta1 by eosinophils. Eosinophils were isolated from the peripheral blood of healthy donors and cultured in the absence or presence of IL-3, IL-4, and IL-5. Cells were analyzed by in situ hybridization and immunohistochemistry. Supernatants from these cultures were assayed for secreted TGF-alpha and TGF-beta1 using TGF-specific ELISAs. IL-3, IL-4, and IL-5 independently up-regulated TGF-beta1 mRNA and product expression by eosinophils in all donors. Interestingly, TGF-alpha production by eosinophils was up-regulated by IL-3 and IL-5 but was down-regulated by IL-4. Consistent with the ability of IL-4 to regulate eosinophil responses, IL-4 signaling molecules are present in human eosinophils. The observation that IL-4 can differentially regulate the expression of TGF-alpha and TGF-beta1 suggests that IL-4 may serve as a physiologic molecular switch of TGF expression by the infiltrating eosinophils in wound healing and carcinogenesis.

Adult↗
PubMed1998

Pathways for eosinophil lipid body induction: differing signal transduction in cells from normal and hypereosinophilic subjects.

Although lipid bodies, inducible cytoplasmic inclusions active in arachidonic acid metabolism, are abundant in activated leukocytes, including eosinophils, mechanisms for eosinophil lipid body formation are not certain. Eosinophils from hypereosinophilic syndrome (HES) donors contained about twice (approximately 18/cell) as many lipid bodies as eosinophils froin normal donors (approximately 10/cell). By immunocytochemistry both 5- and 15-lipoxygenases were localized at lipid bodies in HES eosinophils. Platelet-activating factor (PAF) induced rapid, receptor-mediated increases in lipid bodies in normal and HES eosinophils. Protein kinase C (PKC) inhibitors, chelerythrine and calphostin C, inhibited PAF-induced lipid body formation partially in normal and HES eosinophils. In HES, but not normal, eosinophils, PAF-induced lipid body formation was completely blocked by two tyrosine kinase inhibitors, herbimycin A and genistein, which were not acting on 5-lipoxygenase because they also blocked 5-HETE-induced lipid body formation in HES, and not normal, eosinophils. After 24 h culture with eosinophil growth factor cytokines [interleukin (IL)-3, IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) or GM-CSF alone but not IL-5 or IL-3 alone], normal eosinophils were induced to exhibit an HES-like phenotype, including increased lipid body numbers and tyrosine kinase-dependent signaling for PAF-induced lipid body formation. Thus, signal transduction mechanisms involved in PAF-induced lipid body formation in eosinophils can be differentially recruited. Tyrosine kinase-dependent signaling is not involved in normal eosinophils, but is active in HES eosinophils and in normal eosinophils cultured with GM-CSF. PKC- and tyrosine kinase-dependent pathways are involved in the formation of eosinophil lipid bodies, which may facilitate enhanced synthesis of lipoxygenase-derived eicosanoids.

Adult↗
PubMed1998

Co-compartmentalization of MAP kinases and cytosolic phospholipase A2 at cytoplasmic arachidonate-rich lipid bodies.

Lipid bodies are inducible lipid domains abundantly present in leukocytes engaged in inflammation. They are rich in esterified arachidonate and are also potential sites for eicosanoid-forming enzyme localization. It is therefore of interest to know whether arachidonate-releasing cytosolic phospholipase A2 (cPLA2) localizes at lipid bodies. Here, we present evidence that cPLA2 and its activating protein kinases, mitogen-activated protein (MAP) kinases, co-localize at lipid bodies. U937 cells express high levels of cPLA2 and contain numerous cytoplasmic lipid bodies. Using double-labeling immunocytochemistry we demonstrated punctate cytoplasmic localizations of both cPLA2 and MAP kinases in U937 cells that were perfectly concordant with fluorescent fatty-acid-labeled lipid bodies. The co-localization of cPLA2 and MAP kinases at lipid bodies was confirmed by subcellular fractionation and immunoblot. Lipid body fractions free of cytosol and other organelles contained significant amounts of [14C]arachidonate-labeled phosphatidylcholine and cPLA2 enzymatic activities. Immunoblotting with specific antibodies identified cPLA2 as well as MAP kinases, including ERK1, ERK2, p85, and p38, in lipid bodies. The co-compartmentalization within arachidonate-rich lipid bodies of cPLA2 and its potentially activating protein kinases suggests that lipid bodies may be structurally distinct intracellular sites active in extracellular ligand-induced arachidonate release and eicosanoid formation.

Arachidonic Acid↗
PubMed1997

The cells of the allergic response: mast cells, basophils, and eosinophils.

Mast cells, basophils, and eosinophils have long been regarded as important effector cells in allergic disorders. Indeed, it is thought that the cells' cytoplasmic granule-associated or lipid mediators contribute to many of the signs and symptoms that are characteristic of these diseases. Mast cells, basophils, and eosinophils also probably contribute to protective host responses, especially to parasites. In addition, recent evidence shows that mast cells, basophils, and eosinophils can secrete a wide spectrum of cytokines and, in some cases, express functions that may permit them to regulate the development or perpetuation of allergic responses. Thus, mast cells, basophils, and eosinophils may express immunoregulatory activities, as well as serve as effector cells.

Basophils↗
PubMed1997

Eosinophil lipid bodies: specific, inducible intracellular sites for enhanced eicosanoid formation.

The specific intracellular sites at which enzymes act to generate arachidonate-derived eicosanoid mediators of inflammation are uncertain. We evaluated the formation and function of cytoplasmic lipid bodies. Lipid body formation in eosinophils was a rapidly (<1 h) inducible response which was platelet-activating factor (PAF) receptor-mediated, involved signaling through protein kinase C, and required new protein synthesis. In intact and enucleated eosinophils, the PAF-induced increases in lipid body numbers correlated with enhanced production of both lipoxygenase- and cyclooxygenase-derived eicosanoids. All principal eosinophil eicosanoid-forming enzymes, 5-lipoxygenase, leukotriene C4 synthase, and cyclooxygenase, were immunolocalized to native as well as newly induced lipid bodies in intact and enucleated eosinophils. Thus, lipid bodies are structurally distinct, inducible, nonnuclear sites for enhanced synthesis of paracrine eicosanoid mediators of inflammation.

Adult↗
PubMed1997

Structure and expression of a novel filarial gene for glia maturation factor.

Factors that influence neural growth and development in parasitic nematodes have not yet been identified. We have isolated and sequenced a Brugia malayi nematode 3.4-kb genomic DNA fragment and its corresponding cDNA, which encode a predicted protein of 138 amino acids with 52% identity and 75% similarity to the mammalian neuroglial growth factor, glia maturation factor-beta (GMF). GMF promotes the differentiation of mammalian glia and neurons and stimulates axonal regeneration. The filarial nematode gene Bmgmf for Brugia malayi glia maturation factor contains six predicted exons, with the first exon encoding only the initiation methionine. Brugia malayi GMF (BmGMF) is also related to a large family of eukaryotic actin depolymerizing factors (ADFs). Although BmGMF does not contain the consensus actin-depolymerizing motif of ADFs, it does share a similar intron exon structure, including the unusual first exon, with the unc-60 ADF gene of the nematode Caenorhabditis elegans. RT-PCR experiments reveal that BmGMF is trans-spliced with the nematode spliced leader sequence SL1 and is expressed in microfilariae but not in third-stage larvae or adult worms. We speculate that BmGMF may function as a stage-specific neuroglial growth factor.

Actin Depolymerizing Factors↗
PubMed1997

Ultrastructural localization of Charcot-Leyden crystal protein in human eosinophils and basophils.

The Charcot-Leyden crystal (CLC) protein with lysophospholipase activity and carbohydrate-binding properties is a characteristic constituent of eosinophils and basophils. We investigated its subcellular distribution using immunoelectron microscopy. Eosinophil progenitors, mature eosinophils and basophils all contained CLC protein in their cytosol and in the euchromatin of the nucleus. A minor population of granules in eosinophils, increasing in number with maturation, and a more abundant granule-population in basophils, were found to contain CLC protein. Double-labeling experiments showed, in eosinophils, that CLC protein-containing granules contain also eosinophil peroxidase, a characteristic specific granule protein. This suggests a relationship between the CLC protein-containing organelle and the specific granule. In basophils both the CLC protein positive and the negative granules showed the same characteristic particulate-like structure of the granular matrix and both share the same membrane marker CD63. In nasal polyps, macrophages were observed phagocytosing necrotic eosinophils. In these macrophages CLC protein-containing vesicles were observed, probably representing late endosomes. The dual (cytosolic/nuclear and granular) localization of CLC protein suggests that this protein enters both a secretory and a nonsecretory pathway during its biosynthesis, indicating functional roles for this protein both within the cell and extracellularly.

Basophils↗