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D Chappell

Publications and source records attributed to D Chappell.

16 recordsLinked to original sources
PubMed2003

Morphological assessment of reperfusion injury in a concordant xenogeneic primate model.

Ischemia and consecutive reperfusion injury of the graft cannot be avoided in organ transplantation. One principal characteristic of this process is the temporary and permanent adherence of leukocytes to endothelial cells of the graft as well as damage of the associated tissue. Polyclonal antithymocyte globulins (ATGs) are used to prevent acute rejection after transplantation and to overcome graft vs. host disease. ATGs induce apoptosis and complement-mediated cell death in peripheral T-lymphocytes having the potential to inhibit leukocyte adhesion by direct binding to adhesion molecules. The aim of the present study was to analyse in a non-human primate model (cynomolgus monkeys) morphological changes within the microvasculature and the different cell-subpopulations upon ischemia/reperfusion after immunosuppressive treatment. Our results show a decrease of the tissue damage and WBC infiltration in muscular structures as well as a lower number of mononuclear cells in peripheral blood in the ATG-treated group compared to a non-treated control group. We may conclude that pATGs have a beneficial effect on the early mechanisms of ischemia/reperfusion injury.

Animals↗
PubMed2001

Thyroid hormone receptor-interacting protein 1 modulates cytokine and nuclear hormone signaling in erythroid cells.

Erythropoietin (Epo) and thyroid hormone (T(3)) are key molecules in the development of red blood cells. We have shown previously that the tyrosine kinase Lyn is involved in differentiation signals emanating from an activated erythropoietin receptor. Here we demonstrate that Lyn interacts with thyroid hormone receptor-interacting protein 1 (Trip-1), a transcriptional regulator associated with the T(3) receptor, providing a link between the Epo and T(3) signaling pathways. Trip-1 co-localized with Lyn and the T(3) receptor alpha in the cytoplasm/plasma membrane of erythroid cells but translocated to discrete nuclear foci shortly after Epo-induced differentiation. Our data reveal that T(3) stimulated the proliferation of immature erythroid cells, and inhibited maturation promoted by erythropoietin. Removal of T(3) reduced cell division and enhanced terminal differentiation. This was accompanied by large increases in the cell cycle inhibitor p27(Kip1) and by increasing expression of erythroid transcription factors GATA-1, EKLF, and NF-E2. Strikingly, a truncated Trip-1 inhibited both erythropoietin-induced maturation and T(3)-initiated cell division. This mutant Trip-1 acted in a dominant negative fashion by eliminating endogenous Lyn, elevating p27(Kip1), and blocking T(3) response elements. These data demonstrate that Trip-1 can simultaneously modulate responses involving both cytokine and nuclear receptors.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2000

Dominant action of mutated erythropoietin receptors on differentiation in vitro and erythroleukemia development in vivo.

J2E cells produce rapid, fatal erythroleukemias in vivo but still respond to erythropoietin (epo) in vitro by differentiating, proliferating and remaining viable in the absence of serum. Mutant epo receptors were introduced into these cells to determine whether they could influence the different biological responses to epo in vitro and the development of erythroleukemias. Three mutant receptors were used as cytoplasmic truncation mutants Delta257 and Delta321 (above box 1 and below box 2 respectively), and the cytoplasmic point mutant W282R (defective for JAK2 activation). Strikingly, the Delta321 mutation produced a hyper-sensitive response in vitro to epo-induced differentiation and viability, but not to proliferation. In contrast with the Delta321 receptor, the Delta257 and W282R mutants inhibited all biological responses to epo due to impaired JAK2 phosphorylation. Significantly, erythroleukemias took almost twice as long to develop with cells containing the W282R mutation, indicating that JAK2 plays an important role in the emergence of these leukemias. These data demonstrate that mutant epo receptors dominantly altered responses of J2E cells to epo in culture and the development of erythroleukemias. Oncogene (2000) 19, 953 - 960.

Animals↗
PubMed1997

Haemoglobin synthesis in erythropoietin-stimulated J2E cells does not require increased numbers of transferrin receptors.

Changes in transferrin-receptor numbers and iron utilisation were monitored during erythropoietin-induced maturation of J2E erythroid cells. Uptake of transferrin and iron doubled 24 h after exposure to erythropoietin, due to a twofold rise in surface transferrin receptors. In addition, a tenfold increase in iron incorporation into haem was observed after erythropoietin stimulation, as iron taken up from transferrin was directed towards haem biosynthesis and away from storage in ferritin. The rise in iron chelation into haem correlated extremely well with haemoglobin synthesis. However, the increase in numbers of transferrin receptors was not essential for haemoglobin synthesis; rather, it was linked with a burst in proliferation stimulated by erythropoietin. We have shown previously that amiloride blocks erythropoietin-enhanced proliferation of J2E cells, but potentiates maturation [Callus, B. A., Tilbrook, P. A., Busfield, S. J. & Klinken, S. P. (1995) Exp. Cell Res. 219, 39-46]. Here we demonstrate that amiloride suppressed the hormone-induced increase in transferrin receptors, whereas the enhanced incorporation of iron into haem was not inhibited. Similarly, when sodium butyrate was used to induce differentiation of J2E cells, proliferation ceased and surface transferrin receptors remained unaltered, while haemoglobin production was accelerated. It was concluded from these experiments that the erythropoietin-stimulated rise in transferrin receptors during the final stages of J2E cell maturation is linked to cell division, and is not essential for haemoglobin synthesis.

Amiloride↗
PubMed1997

Prevention of apoptosis in J2E erythroid cells by erythropoietin: involvement of JAK2 but not MAP kinases.

The J2E erythroid cell line, transformed by retroviral v-raf/v-myc oncogenes, proliferates and differentiates in response to erythropoietin. Here we show that J2E cells undergo apoptosis rapidly after serum withdrawal and that only erythropoietin of seven growth factors tested, could protect the cells from death. The role of JAK2 and MAP kinases in transmitting viability signals initiated by erythropoietin was examined in these cells. Despite constitutive raf kinase activity, phosphorylation of MAP kinases fell after serum withdrawal. However, an antisense oligonucleotide strategy revealed that JAK2, but not the MAP kinases, was involved in transmitting signals to maintain the viability of J2E cells. Several cell cycle proteins and transcription factors were also studied; although c-jun rose sharply during apoptosis, erythropoietin could not suppress this increase. It was concluded that erythropoietin-induced protection from apoptosis involved JAK2, but not MAP kinases or c-jun.

Journal Article↗
PubMed1996

Disrupted signaling in a mutant J2E cell line that shows enhanced viability, but does not proliferate or differentiate, with erythropoietin.

The immature erythroid J2E cell line proliferates and terminally differentiates following erythropoietin stimulation. In contrast, the mutant J2E-NR clone does not respond to erythropoietin by either proliferating or differentiating. Here we show that erythropoietin can act as a viability factor for both the J2E and J2E-NR lines, indicating that erythropoietin-initiated maturation is separable from the prevention of cell death. The inability of J2E-NR cells to mature in response to erythropoietin was not due to a defect in the erythropoietin receptor sequence, although surface receptor numbers were reduced. Both the receptor and Janus kinase 2 were phosphorylated after erythropoietin stimulation of J2E-NR cells. However, protein interactions with the erythropoietin receptor and Grb2 were restricted in the mutant cells. Subsequent investigation of several other signaling molecules exposed numerous alterations in J2E-NR cells; phosphorylation changes to phosphatidylinositol 3-kinase, phospholipase Cgamma, p120 GAP, and mitogen-activated protein kinases (p42 and p44) observed in erythropoietin-stimulated J2E cells were not seen in the J2E-NR line. These data indicate that some pathways activated during erythropoietin-induced differentiation may not be essential for the prevention of apoptosis.

3T3 Cells↗
PubMed1994

Development of a braille training device.

This article discusses the development of a system to more easily train both sighted and blind individuals the braille code. The system consists of a braille cell touchpad, a computer, a screen reading program, a voice synthesizer, and software to drive each of these components. The system runs with minimal user input and can be customized to meet user needs.

Blindness↗
PubMed1986

Mechanical and biochemical properties of human articular cartilage in osteoarthritic femoral heads and in autopsy specimens.

We studied the mechanical and biochemical properties of articular cartilage from 22 osteoarthritic femoral heads obtained at operation and 97 femoral heads obtained at autopsy. Cartilage from the zenith and from the antero-inferior aspect of each head was tested both in tension and in compression. Water content, swelling ability and proteoglycan content were measured, the cartilage was examined histologically and the density of the underlying bone was assessed. Fifty-five of the autopsy specimens were defined as macroscopically normal because they exhibited no progressive fibrillation patterns on staining with Indian ink; but significant changes in water content, bone density and tensile strength related to age were seen in this group. In 20 pairs of femoral heads which were both macroscopically normal, we found, surprisingly, that cartilage from the left and right sides of the same patient was sometimes very different. Compared with the normal autopsy specimens the osteoarthritic specimens had a significantly increased swelling ability, a lower proteoglycan content and impaired mechanical properties, being both weaker in tension and softer in compression. Abnormal autopsy specimens had values intermediate between those of osteoarthritic and normal groups. Results from this abnormal group suggest that there is no primary loss of proteoglycan in early osteoarthritis.

Adolescent↗
PubMed1986

Mechanical and biochemical properties of human articular cartilage from the femoral head after subcapital fracture.

Articular cartilage from the femoral heads of 27 patients having an arthroplasty for subcapital fracture was studied, and its mechanical and chemical properties compared to those of a group of 33 age-matched macroscopically normal autopsy specimens. Water and proteoglycan contents were measured, as were swelling ability, compressive and tensile strength of the cartilage, and the density of the underlying bone. Cartilage from the fracture specimens had a significantly reduced proteoglycan content, as measured by fixed charge density, and increased swelling ability. These results indicate that this group differs from the "normal" population and care should be taken before they are accepted as control material for studies on osteoarthritic cartilage. Another finding was that bone density was much the same in the fracture and the normal group. This casts some doubt upon the concept that patients who sustain subcapital fractures are more osteoporotic than the average for the same age range.

Adolescent↗