Stress reticulocytes lose transferrin receptors by an extrinsic process involving spleen and macrophages.

As they mature into erythrocytes during normal erythropoiesis, reticulocytes lose surface transferrin receptors before or concurrently with reticulin. Exosome release accounts for most of the loss of transferrin receptors from reticulocytes. During erythropoietic stress, reticulocytes are released early from hematopoietic tissues and have increased reticulin staining and transferrin receptors.

Current practices in determining return to play following head injury in professional football in the UK.

Objective: To investigate the awareness of English football team doctors of the 'Consensus in Sport' (CIS) guidelines for the assessment and management of concussion, and to identify adherence to these internationally accepted recommendations.

Method: A questionnaire was sent to Club Medical Officers of all the 92 English Football league teams.

Results: The majority (55.

Reducing the activity and secretion of microbial antioxidants enhances the immunogenicity of BCG.

Background: In early clinical studies, the live tuberculosis vaccine Mycobacterium bovis BCG exhibited 80% protective efficacy against pulmonary tuberculosis (TB). Although BCG still exhibits reliable protection against TB meningitis and miliary TB in early childhood it has become less reliable in protecting against pulmonary TB. During decades of in vitro cultivation BCG not only lost some genes due to deletions of regions of the chromosome but also underwent gene duplication and other mutations resulting in increased antioxidant production.

Involvement of ERK-1/2 in IL-21-induced cytokine production in leukemia cells and human monocytes.

Cytokines play an important role in the immune system, and abnormalities in their production have been found in many human diseases. Interleukin-21 (IL-21), a type I cytokine produced by activated T cells, has diverse effects on the immune system, but its ability to induce production of other cytokines is not well delineated. Furthermore, the signaling pathway underlying its action is poorly understood.

Adherence to macrophages in erythroblastic islands enhances erythroblast proliferation and increases erythrocyte production by a different mechanism than erythropoietin.

Erythroblasts adhere to central macrophages forming erythroblastic islands in hematopoietic tissues, but the function of these islands is not understood. Murine erythroblastic islands were reconstituted in vitro with macrophages and developmentally synchronous proerythroblasts. Erythroblasts cocultured with macrophages proliferated 3-fold greater than erythroblasts cultured alone.

Bcl-x(L) prevents apoptosis of late-stage erythroblasts but does not mediate the antiapoptotic effect of erythropoietin.

The long form of B-cell lymphoma-x (Bcl-x(L)), an outer mitochondrial membrane protein, has been proposed to mediate the antiapoptotic action of erythropoietin on erythroid progenitor cells and to be necessary for heme synthesis in erythroblasts. Mice with conditional knockout of Bcl-x(L) (conditional bcl-x(-/-) mice) develop severe anemia that has been attributed to hemolysis and is accompanied by splenomegaly. We characterized further the anemia of conditional bcl-x(-/-) mice and investigated the role of Bcl-x(L) in the action of erythropoietin and in heme synthesis.

Induction by transforming growth factor-beta1 of epithelial to mesenchymal transition is a rare event in vitro.

Introduction: Transforming growth factor (TGF)-beta1 is proposed to inhibit the growth of epithelial cells in early tumorigenesis, and to promote tumor cell motility and invasion in the later stages of carcinogenesis through the induction of an epithelial to mesenchymal transition (EMT). EMT is a multistep process that is characterized by changes in cell morphology and dissociation of cell-cell contacts. Although there is growing interest in TGF-beta1-mediated EMT, the phenotype is limited to only a few murine cell lines and mouse models.

Anti-CD20 treatment depletes B-cells in blood and lymphatic tissue of cynomolgus monkeys.

Introduction: Macaque species offer a valuable model for translational allo-transplantation and tolerance studies. Cardiac allograft vasculopathy in Macaca fascicularis is associated with elaboration of anti-donor antibodies. Since T-independent pathways of B cell activation have been described, and anti-B cell strategies have proven to be a fruitful tolerogenic adjunct in rodent and xenogenic models, here we investigate whether an anti-CD20 antibody (rituximab) would be useful to deplete B-cells in a pre-clinical allo-transplantation setting in macaques.

The role of chondrocyte senescence in osteoarthritis.

Replicative senescence occurs when normal somatic cells stop dividing. Senescent cells remain viable, but show alterations in phenotype, e.g.

Reduction of cell cycle progression in human erythroid progenitor cells treated with tumour necrosis factor alpha occurs with reduced CDK6 and is partially reversed by CDK6 transduction.

Tumor necrosis factor alpha (TNFalpha) potently inhibits the in vitro growth of highly purified human d-6 erythroid colony forming cells (ECFC). Unlike the inhibitory effect of TNFalpha on other cells, including more immature ECFC, this antiproliferative effect of TNFalpha is not related to apoptosis because the d-6 cell descendants were morphologically normal, without apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling assay and without caspase activation by Western blots after TNFalpha treatment. TNFalpha did not appear to affect the cell cycle distribution, but the cell cycle duration was significantly longer in TNFalpha-treated cells.

The novel taxane analogs, BMS-184476 and BMS-188797, potentiate the effects of radiation therapy in vitro and in vivo against human lung cancer cells.

Purpose: To evaluate the novel taxane analogs, BMS-184476 and BMS-188797, as potential radiosensitizers in vitro and in vivo.

Methods And Materials: Human H460 lung cancer cells were incubated with either paclitaxel or a taxane analog and irradiated at various times. Surviving fractions were then determined using a clonogenic assay.

Stimulation of mitogenic pathways through kinase-impaired mutants of the epidermal growth factor receptor.

Two residues have been shown to be critical for the kinase activity of the receptor for epidermal growth factor (EGF): lysine-721, which functions in the binding of ATP by correctly positioning the gamma-phosphate for phosphoryl transfer, and aspartate-813, which functions as the catalytic base of the kinase. Mutation of either of these two residues has been shown to disrupt kinase activity of the receptor. However, studies performed in different laboratories had suggested that while EGF receptors mutated at lysine-721 are unable to stimulate significant increases of [(3)H]thymidine incorporation into DNA in response to EGF treatment, cells expressing EGF receptors mutated at aspartate-813 do stimulate significant incorporation of [(3)H]thymidine into DNA in response to EGF.

Apoptosis in megaloblastic anemia occurs during DNA synthesis by a p53-independent, nucleoside-reversible mechanism.

Deficiency of folate or vitamin B(12) (cobalamin) causes megaloblastic anemia, a disease characterized by pancytopenia due to the excessive apoptosis of hematopoietic progenitor cells. Clinical and experimental studies of megaloblastic anemia have demonstrated an impairment of DNA synthesis and repair in hematopoietic cells that is manifested by an increased percentage of cells in the DNA synthesis phase (S phase) of the cell cycle, compared with normal hematopoietic cells. Both folate and cobalamin are required for normal de novo synthesis of thymidylate and purines.

Reversible G(1) arrest induced by inhibition of the epidermal growth factor receptor tyrosine kinase requires up-regulation of p27(KIP1) independent of MAPK activity.

We have used quinazoline inhibitors of the epidermal growth factor receptor (EGFR) tyrosine kinase to study the link between EGFR signaling and G(1) to S traverse. Treatment of A431 and MDA-468 human tumor cells with 0.1-10 microM AG-1478 inhibited basal and ligand-stimulated EGFR phosphorylation without a decrease in receptor content, EGF-binding sites, or binding affinity.

Distinct roles of JNKs/p38 MAP kinase and ERKs in apoptosis and survival of HCD-57 cells induced by withdrawal or addition of erythropoietin.

Erythropoietin (EPO), a major regulator of erythroid progenitor cells, is essential for the survival, proliferation, and differentiation of immature erythroid cells. To gain insight into the molecular mechanism by which EPO functions, we analyzed the activation of Jun N-terminal kinases (JNKs) and extracellular signal-regulated kinases (ERKs) in HCD-57 cells, a murine erythroid progenitor cell line that requires EPO for survival and proliferation. Withdrawal of EPO from the cell culture medium resulted in sustained activation of JNKs plus p38 MAP kinase, and inactivation of ERKs, preceding apoptosis of the cells.

Blockade of tumor cell transforming growth factor-betas enhances cell cycle progression and sensitizes human breast carcinoma cells to cytotoxic chemotherapy.

We have examined the effect of neutralizing TGF-beta antibodies on cisplatin-mediated cytotoxicity against MDA-231 human breast tumor cell spheroids. These tridimensional in vitro systems have been shown to recapitulate the drug sensitivity pattern of tumor cells in vivo. MDA-231 tumor cell spheroids exhibit higher protein levels of the cyclin-dependent kinase (Cdk) inhibitors p21 and p27 and >10-fold lower Cdk2 activity compared to adherent cell monolayers, as well as pRb hypophosphorylation, a predominant G1 population, and a cisplatin 1-h IC50 of approximately 100 microM.

Secondary excitotoxicity contributes to dopamine-induced apoptosis of dopaminergic neuronal cultures.

Dopamine (DA) and related catechols may contribute to selective degeneration of dopaminergic neurons in the substantia nigra in Parkinson's disease. To investigate whether DA induces apoptosis of dopaminergic neurons, we characterized the effects of various concentrations of exogenous DA on a substantia nigra/neuroblastoma hybrid cell line (MES 23.5 or MES).

Differential cell cycle checkpoint response in normal human keratinocytes and fibroblasts.

The incidence of DNA mutation and subsequent risk of transformation in different cell types may depend on cell type-specific variation in position and duration of cell cycle arrest after exposure to DNA-damaging agents. To determine whether cell type-specific checkpoints occur, normal human epidermal keratinocytes (HKs) and human dermal fibroblasts (HFs), isolated from the same tissue, were exposed to genotoxic agents. Following exposure, cell cycle arrest profiles, cell proliferation rates, and select protein levels and activities were analyzed and found to be cell type dependent.

Fas ligand is present in human erythroid colony-forming cells and interacts with Fas induced by interferon gamma to produce erythroid cell apoptosis.

Interferon gamma (IFNgamma) inhibits the growth and differentiation of highly purified human erythroid colony-forming cells (ECFCs) and induces erythroblast apoptosis. These effects are dose- and time-dependent. Because the cell surface receptor known as Fas (APO-1; CD95) triggers programmed cell death after activation by its ligand and because incubation of human ECFCs with IFNgamma produces apoptosis, we have investigated the expression and function of Fas and Fas ligand (FasL) in highly purified human ECFCs before and after incubation with IFNgamma in vitro.

Interferon gamma downregulates stem cell factor and erythropoietin receptors but not insulin-like growth factor-I receptors in human erythroid colony-forming cells.

Interferon gamma (IFNgamma) has been shown to inhibit proliferation and differentiation of erythroid progenitor cells and to produce apoptosis of erythroid cells, whereas stem cell factor (SCF), erythropoietin (EP), and insulin-like growth factor-I (IGF-I) have distinct roles in enhancing erythroid cell production and preventing apoptosis. The mechanism by which IFNgamma exerts an inhibitory effect on the positive roles of these growth factors is unknown. Although some inhibitory cytokines including IFNgamma have been shown to downregulate growth factor receptors, the effect of IFNgamma on SCF, EP, and IGF-I receptors of human erythroid progenitor cells has not been defined.

Abrogation of cisplatin-induced programmed cell death in human breast cancer cells by epidermal growth factor antisense RNA.

Background: Epidermal growth factor receptor (EGF-R) perturbation by receptor ligand(s), e.g., epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha), or receptor-specific antibodies accentuates cisplatin-induced toxicity in tumor cells.

Leukocyte low density lipoprotein receptor (LDL-R) does not contribute to LDL clearance in vivo: bone marrow transplantation studies in the mouse.

The targeted disruption of the low density lipoprotein (LDL) receptor gene in mice results in accumulation of plasma LDL cholesterol and in predisposition to diet-induced aortic atherosclerosis. Although the liver is the central organ for receptor mediated clearance of LDL, the in vivo role of other organs and tissues in LDL catabolism has not been directly studied. Since bone marrow-derived cells such as blood leukocytes and tissue macrophages express LDL receptors and contribute a large mass to the body, we designed bone marrow transplantation (BMT) experiments to reconstitute LDL receptor null mice [LDL-R(-/-)] with marrow obtained from LDL-R wild-type mice [LDL-R(+/+)] and evaluate the effects on parameters of plasma lipid metabolism.

Stem cell factor can overcome inhibition of highly purified human burst-forming units-erythroid by interferon gamma.

Highly purified human blood burst-forming units-erythroid (BFU-E) were used to study the effects of interferon gamma (IFN gamma). IFN gamma inhibited erythroid colony formation, cell proliferation, and differentiation of day 3 to day 6 mature BFU-E in a dose-dependent manner. The primitive BFU-E (day 1 and day 2 cells) and later day 7 cells were less affected.