Inhibitory receptors bind ANGPTLs and support blood stem cells and leukaemia development.

How environmental cues regulate adult stem cell and cancer cell activity through surface receptors is poorly understood. Angiopoietin-like proteins (ANGPTLs), a family of seven secreted glycoproteins, are known to support the activity of haematopoietic stem cells (HSCs) in vitro and in vivo. ANGPTLs also have important roles in lipid metabolism, angiogenesis and inflammation, but were considered 'orphan ligands' because no receptors were identified.

IGF binding protein 2 supports the survival and cycling of hematopoietic stem cells.

The role of IGF binding protein 2 (IGFBP2) in cell growth is intriguing and largely undefined. Previously we identified IGFBP2 as an extrinsic factor that supports ex vivo expansion of hematopoietic stem cells (HSCs). Here we showed that IGFBP2-null mice have fewer HSCs than wild-type mice.

Ex vivo expanded hematopoietic stem cells overcome the MHC barrier in allogeneic transplantation.

The lack of understanding of the interplay between hematopoietic stem cells (HSCs) and the immune system has severely hampered the stem cell research and practice of transplantation. Major problems for allogeneic transplantation include low levels of donor engraftment and high risks of graft-versus-host disease (GVHD). Transplantation of purified allogeneic HSCs diminishes the risk of GVHD but results in decreased engraftment.

Components of the hematopoietic compartments in tumor stroma and tumor-bearing mice.

Solid tumors are composed of cancerous cells and non-cancerous stroma. A better understanding of the tumor stroma could lead to new therapeutic applications. However, the exact compositions and functions of the tumor stroma are still largely unknown.

Angiopoietin-like protein 3 supports the activity of hematopoietic stem cells in the bone marrow niche.

The physiologic roles of angiopoietin-like proteins (Angptls) in the hematopoietic system remain unknown. Here we show that hematopoietic stem cells (HSCs) in Angptl3-null mice are decreased in number and quiescence. HSCs transplanted into Angptl3-null recipient mice exhibited impaired repopulation.

EphB receptors regulate stem/progenitor cell proliferation, migration, and polarity during hippocampal neurogenesis.

The adult brain maintains two regions of neurogenesis from which new neurons are born, migrate to their appropriate location, and become incorporated into the circuitry of the CNS. One of these, the subgranular zone of the hippocampal dentate gyrus, is of primary interest because of the role of this region in learning and memory. We show that mice lacking EphB1, and more profoundly EphB1 and EphB2, have significantly fewer neural progenitors in the hippocampus.

EphB receptors coordinate migration and proliferation in the intestinal stem cell niche.

More than 10(10) cells are generated every day in the human intestine. Wnt proteins are key regulators of proliferation and are known endogenous mitogens for intestinal progenitor cells. The positioning of cells within the stem cell niche in the intestinal epithelium is controlled by B subclass ephrins through their interaction with EphB receptors.

Bidirectional signaling mediated by ephrin-B2 and EphB2 controls urorectal development.

Incomplete urethral tubularization (hypospadias) and anorectal abnormalities are two common and poorly understood birth defects that affect the extreme caudal midline of the human embryo. We now show that cell surface molecules essential for proper axon pathfinding in the developing nervous system, namely ephrin-B2 and the ephrin receptors EphB2 and EphB3, also play major roles in cell adhesion events that tubularize the urethra and partition the urinary and alimentary tracts. Mice carrying mutations which disrupt the bidirectional signals that these molecules transduce develop with variably penetrant severe hypospadias and incomplete midline fusion of the primitive cloaca.

Ephrin-B2 reverse signaling is required for axon pathfinding and cardiac valve formation but not early vascular development.

Vascular development begins with the formation of a primary vascular plexus that is rapidly remodeled by angiogenesis into the interconnected branched patterns characteristic of mature vasculature. Several receptor tyrosine kinases and their ligands have been implicated to control early development of the vascular system. These include the vascular endothelial growth factor receptors (VEGFR-1 and VEGFR-2) that bind VEGF, the Tie-1 and Tie-2 receptors that bind the angiopoietins, and the EphB4 receptor that binds the membrane-anchored ligand ephrin-B2.

Interference with the constitutive activation of ERK1 and ERK2 impairs EWS/FLI-1-dependent transformation.

The chimeric gene EWS/FLI-1, the hallmark of the Ewing's sarcoma and primitive neuroectodermal tumor family, encodes a fusion protein with enhanced transcriptional activation properties and preserved recognition of canonical ETS binding sites. Although EWS/FLI-1 alters the expression of various genes, the precise mechanism by which EWS/FLI-1 acts as an oncogene remains to be defined. In this study we report that members of the mitogen-activated protein kinase (MAPK) signaling pathway, ERK1 and ERK2, are constitutively activated in NIH 3T3 cells expressing EWS/FLI-1.

Role of mucosal IgA in the resistance to Acanthamoeba keratitis.

Purpose: To determine whether oral immunization with Acanthamoeba castellanii antigens elicits mucosal antibodies of the IgA isotype and whether mucosal antibodies affect parasite adhesion to the corneal epithelium.

Methods: Chinese hamsters were immunized with 100 microg aqueous Acanthamoeba antigen mixed with cholera toxin (Ac-CT) and subsequently challenged with parasite-laden contact lenses that were applied to abraded corneal surfaces. Tears and stool samples were examined for the presence of Acanthamoeba-specific IgA antibodies by enzyme-linked immunosorbent assay (ELISA).

Mannose induces the release of cytopathic factors from Acanthamoeba castellanii.

Acanthamoeba keratitis is a chronic inflammatory disease of the cornea which is highly resistant to many antimicrobial agents. The pathogenic mechanisms of this disease are poorly understood. However, it is believed that the initial phases in the pathogenesis of Acanthamoeba keratitis involve parasite binding and lysis of the corneal epithelium.

In vitro amoebicidal activity of propamidine and pentamidine isethionate against Acanthamoeba species and toxicity to corneal tissues.

Effective chemotherapy for Acanthamoeba keratitis has been hampered because of the marked resistance of the parasites to a variety of antimicrobial agents. In view of the fact that topical Brolene (propamidine isethionate) and neosporin are currently considered to be the medical treatment of choice in Europe, we sought to determine whether pentamidine may be equally effective, because the drug is more readily available to ophthalmologists in the United States. In this study, we compared the amoebicidal activity of the Brolene (commercial product), propamidine isethionate and pentamidine isethionate (Pentam) in vitro against three different species of Acanthamoeba, and the drugs' corresponding biocompatibility with rabbit corneal epithelial and endothelial cell cultures.

Susceptibility of corneal and conjunctival pathogens to ciprofloxacin.

Ciprofloxacin 0.3% ophthalmic solution has been shown to be effective in the treatment of bacterial keratitis and conjunctivitis, and many physicians use ciprofloxacin as sole therapy in these conditions. In this retrospective study, we found seven of 84 isolates from corneal and conjunctival cultures that were resistant to ciprofloxacin.

Antibody-dependent neutrophil-mediated killing of Acanthamoeba castellanii.

Neutrophils from naive rats lysed low numbers of Acanthamoeba castellanii in the presence of normal rat serum and significantly higher numbers of the parasite in the presence of serum from immunized rats. With normal rat serum, neutrophils from rats immunized with crude parasite extract or from naive rats killed similar percentages of A. castellanii.

Relation of cholesterol-stimulated Staphylococcus aureus growth to chronic blepharitis.

Purpose: Many types of chronic blepharitis have been believed to be primarily microbial in origin; however, it was proposed that differences and changes in lipid composition of meibomian secretion may be the initiating factor in some of these. It was recently reported that there are two subgroups of normals, those whose meibomian secretions contain high levels of cholesterol esters and those whose secretions contain very low levels of these esters. Thus, these subgroups of normals were defined on the basis of detailed lipid analyses of meibomian secretions from individuals showing no clinical signs of chronic blepharitis.

The role of contact lenses, trauma, and Langerhans cells in a Chinese hamster model of Acanthamoeba keratitis.

Purpose: To determine the role of contact lenses, corneal trauma, and Langerhans cells in the development of keratitis caused by Acanthamoeba organisms in Chinese hamsters.

Methods: Various methods were used to induce corneal infections in Chinese hamsters, including application of parasite-laden contact lenses. The role of corneal epithelial defects in promoting parasite binding was examined in vitro in a microscopic binding assay.

Characterization and pathogenic potential of a soil isolate and an ocular isolate of Acanthamoeba castellanii in relation to Acanthamoeba keratitis.

Acanthamoeba castellanii, one isolate from the eye and one from the soil, were compared on the basis of: (a) pathogenic potential; (b) plasminogen activator activity; (c) chemotactic activity; (d) cytopathic effects; (e) collagenolytic activity; (f) binding ability to contact lenses; and (g) and binding ability to corneal buttons. The ocular isolate of A. castellanii was found to be pathogenic based on its ability to produce corneal infections in Chinese hamsters.

Chemotactic response of macrophages to Acanthamoeba castellanii antigen and antibody-dependent macrophage-mediated killing of the parasite.

The chemotactic potential of antigens of Acanthamoeba castellanii for macrophages and the ability of naive and immune rat peritoneal macrophages to kill A. castellanii in vitro were assessed. The amoebolytic capacity of immune rat serum and complement was also examined.

A pig model of Acanthamoeba keratitis: transmission via contaminated contact lenses.

A model of contact lens-induced Acanthamoeba keratitis was developed in Yucatan micropigs. Pigs fitted with parasite-laden soft contact lenses developed corneal infections that clinically and histopathologically mimicked the human counterpart. Three distinct stages of disease became apparent and were categorized as: acute, condensed infiltrate, and resolution stages.

Susceptibility of corneas from various animal species to in vitro binding and invasion by Acanthamoeba castellanii [corrected].

A crucial requirement for establishing corneal infection by the extracellular protozoal parasite, Acanthamoeba, is the ability of the parasite to bind to the corneal surface. In a series of in vitro studies, we examined the ability of Acanthamoeba castellanii [corrected] to adhere, invade, and damage normal, intact corneas of 11 mammalian and one avian species. A.

The role of tetracycline in chronic blepharitis. Inhibition of lipase production in staphylococci.

Tetracycline administered in low doses can be effective in the long-term management of patients with meibomian keratoconjunctivitis (MKC). However, the mechanism of action does not appear to be a reduction of bacteria. Seventy-five percent of the ocular staphylococci in such patients are resistant to tetracycline.

In vitro penetration of human corneal epithelium by Acanthamoeba castellanii: a scanning and transmission electron microscopy study.

Human corneal buttons were exposed to Acanthamoeba castellanii trophozoites and cysts for 12 hours at 35 degrees C. The buttons examined by light microscopy and scanning and transmission electron microscopy had severe epithelial ulceration and penetration by trophozoites. Observations on trophozoites below the surface suggest that penetration is accomplished by both secreted cytolytic enzymes and phagocytosis.

Effect of contact lens preservatives on Acanthamoeba.

Single preservatives used in contact lens solutions were evaluated for their effectiveness in killing Acanthamoeba castellanii and Acanthamoeba polyphaga trophozoites and cysts. Preservatives were tested against amoebae at intervals varying from 30 minutes to 24 hours. The preservatives were tested with axenically and nonaxenically grown organisms.