Hagen Bræ: A Surging Glacier in North Greenland-35 Years of Observations

We use remotely sensed ice velocities in combination with observations of surface elevation and glacier area change to investigate the dynamics of Hagen Bræ, North Greenland in high detail over the last 35 years. From our data, we can establish for the first time that Hagen Bræ is a surge-type glacier with characteristics of both Alaskan- and Svalbard-type surging glaciers. We argue that the observed surge was preconditioned by the glacier geometry and triggered by englacially stored meltwater. At present, the glacier is in a transitional state between active and quiescence phases and is not building up to its pre-surge geometry. We suggest that the glacier is adjusting to the loss of its floating section, general thinning, and changes in fjord conditions that occurred over the study period which are unrelated to the surge behavior. The high temporal resolution of the ice velocity data gives insight to the sub-annual glacier flow.

Rapid expansion of Greenland's low-permeability ice slabs

In recent decades, meltwater runoff has accelerated to become the dominant mechanism for mass loss in the Greenland ice sheet^1-3. In Greenland's high-elevation interior, porous snow and firn accumulate; these can absorb surface meltwater and inhibit runoff⁴, but this buffering effect is limited if enough water refreezes near the surface to restrict percolation^5,6. However, the influence of refreezing on runoff from Greenland remains largely unquantified. Here we use firn cores, radar observations and regional climate models to show that recent increases in meltwater have resulted in the formation of metres-thick, low-permeability 'ice slabs' that have expanded the Greenland ice sheet's total runoff area by 26 ± 3 per cent since 2001. Although runoff from the top of ice slabs has added less than one millimetre to global sea-level rise so far, this contribution will grow substantially as ice slabs expand inland in a warming climate. Runoff over ice slabs is set to contribute 7 to 33 millimetres and 17 to 74 millimetres to global sea-level rise by 2100 under moderate- and high-emissions scenarios, respectively-approximately double the estimated runoff from Greenland's high-elevation interior, as predicted by surface mass balance models without ice slabs. Ice slabs will have an important role in enhancing surface meltwater feedback processes, fundamentally altering the ice sheet's present and future hydrology.

The rho-kinase inhibitors Y-27632 and fasudil act synergistically with imatinib to inhibit the expansion of ex vivo CD34(+) CML progenitor cells

Evidence from cell line-based studies indicates that rho-kinase may play a role in the leukaemic transformation of human cells mediated by the BCR/ABL tyrosine kinase, manifest clinically as chronic myeloid leukaemia (CML). We therefore employed two separate inhibitors, Y-27632 and fasudil, to inhibit the activity of rho-kinase against ex vivo CD34(+) cells collected from patients with CML. We compared the effects of rho-kinase inhibition in those cells with the effects of direct inhibition of BCR/ABL using the specific inhibitor imatinib. We found that inhibition of rho-kinase inhibited the effective proliferation, and reduced survival of CML progenitor cells. When combined with imatinib, rho-kinase inhibition added to the anti-proliferative and pro-apoptotic effects of the BCR/ABL inhibitor. Our studies may indicate therapeutic benefit in some cases for the combination of rho-kinase inhibitors with imatinib.

The effect of Bcr-Abl protein tyrosine kinase on maturation and proliferation of primitive haematopoietic cells

BACKGROUND

Chronic Myeloid Leukaemia (CML) is characterised by the chromosomal translocation resulting in expression of the Bcr-Abl protein tyrosine kinase (PTK) in early stem cells and their progeny. However the precise nature of Bcr-Abl effects in primitive CML stem cells remains a matter of active debate.

MATERIALS AND METHODS

Extremely primitive Bcr-Abl fusion positive cells were purified from patients with CML using multiparameter flow cytometric analysis of CD34, Thy, and lineage marker (Lin) expression, plus rhodamine-123 (Rh-123) brightness. Progenitor cells of increasing maturity were examined for cycling status by flow cytometry and their proliferative status directly correlated with cell phenotype. The activation status of a key transcription factor, signal transducers and activators of transcription (STAT-5), was also analyzed by immunocytochemistry.

RESULTS

The most primitive stem cells currently defined (CD34+Lin-Thy+ Rh-1231o) were present as a lower proportion of the stem cell compartment (CD34+Lin-) of CML patients at presentation than of normal individuals (2.3% +/- 0.4 compared with 5.1% +/- 0.6 respectively). Conversely there was a significantly higher proportion of the more mature cells (CD34+Lin-Thy-Rh-123 hi) in CML patients than in normal individuals (79.3 +/- 1.8 compared with 70.9 +/- 3.3). No primitive subpopulation of CML CD34+Lin- cells was cycling to a significantly greater degree than cells from normal donors, in fact, late progenitor cells (CD34+Lin+) were cycling significantly less in CML samples than normal samples. STAT5, however, was observed to be activated in CML cells.

CONCLUSIONS

We conclude that no subpopulation of CML stem cells displays significantly increased cell cycling. Thus, increased cycling cannot be a direct consequence of Bcr-Abl PTK acquisition in highly enriched stem cells from patients with CML. In vivo CML need not be considered a disease of unbridled stem cell proliferation, but a subtle defect in the balance between self renewal and maturation.

Macrophage-inflammatory protein-1alpha receptor expression on normal and chronic myeloid leukemia CD34+ cells

We have assessed expression of MIP-1alpha binding sites on the surface of CD34+ cells from normal bone marrow (NBM) and chronic myeloid leukemia (CML) peripheral blood. This study has highlighted a small subpopulation of CD34+ (15.7 +/- 6.2% in NBM and 9 +/- 4% in CML), which has specific macrophage-inflammatory protein-1alpha (MIP-1alpha) cell surface binding sites. Further phenotypic characterization of the receptor-bearing cells has shown that they do not express the Thy-1 Ag, suggesting that they are committed progenitor cells rather than CD34+ Thy+ stem cells. However, more than 80% of methanol-fixed CD34+ cells do bind MIP-1alpha, suggesting that these cells may possess a pool of internal receptors, although we were unable to induce cell surface expression by cytokine stimulation. The percentage of these CD34+, MIP-1alpha-R+ cells present in the CD34 compartment of NBM is significantly higher than in CML, implicating lack of binding sites as part of the mechanism for the loss of response to this chemokine seen in CML. Specific Ab to the MIP-1alpha receptor implicated in HIV infection, CCR5, revealed that very few CD34+ cells expressed these receptors and that expression was confined to the CD34+ Thy- progenitor population. Data presented in this work suggest that active binding sites for the stem cell growth inhibitor MIP-1alpha are not constitutively expressed on the surface of most resting primitive multipotent cells, and that these cells are not potential targets for HIV-1 infection through CCR5.

Flt3 ligand can promote survival and macrophage development without proliferation in myeloid progenitor cells

Flt3 ligand elicits a variety of effects on early hemopoietic progenitors by occupying its cognate receptor, Flt3, a member of the type III tyrosine kinase receptor family. The cytokines macrophage colony-stimulating factor (M-CSF) and stem cell factor (SCF) bind to related members of this tyrosine kinase receptors family, c-fms and c-kit, respectively. The relative effects of the cytokines M-CSF, SCF, and Flt3L on the proliferation and development of the late myeloid progenitors granulocyte-macrophage colony-forming cells (GM-CFC) were investigated. Distinct biologic responses were stimulated by ligand binding to these different tyrosine kinase receptors in enriched GM-CFC. M-CSF stimulated GM-CFC to proliferate and develop into macrophages. SCF, on the other hand, stimulated GM-CFC to develop into neutrophils. Flt3 ligand had a relatively small proliferative effect on enriched GM-CFC compared to SCF and M-CSF and had no ability to either stimulate colony formation or synergize with these two cytokines in promoting DNA synthesis, colony formation, or expansion in liquid culture. Flt3 ligand, however, was capable of maintaining the clonogenic potential of GM-CFC and acted as an anti-apoptotic agent as assessed using the Annexin-V apoptosis assay. GM-CFC cultured in Flt3 ligand eventually formed macrophages and neutrophils in liquid culture. Labeling with the membrane-associated cell tracker dye PKH26 indicated that the majority of the enriched GM-CFC responded to Flt3 ligand by undergoing limited proliferation and macrophage development, whereas other cells survived but did not proliferate and differentiate into macrophages. Thus, Flt3 ligand promoted survival and stimulated development without proliferation in primary-enriched myeloid progenitor cells.

Preventative exercises in golf: arm, leg, and back

In summary, a sport-specific exercise program for golfers includes warming up, stretching, strengthening, and cardiovascular conditioning. The goals of such a program incorporated with playing the game of golf are to optimize performance and prevent injuries. The integration of each of these components represents a well-balanced fitness approach to sport and enhances the enjoyment of the game.