A quantitative assay for transformation of bone marrow cells by Abelson murine leukemia virus

A quantitative Abelson murine leukemia virus (A-MuLV) lymphoid cell transformation assay has been developed using a semisolid agarose culture system. Under these conditions lymphoid cell transformation was shown to vary linearly with the dose of A-MuLV used. The susceptibility of bone marrow cells from different strains of mice to A-MuLV-induced transformation can be estimated using the agarose assay. Strains with bone marrow cells of high, medium, and low susceptibility to A-MuLV can be identified. The assay has been used to study the susceptibility of cells from lymphoid organs of fetal and adult mice to A-MuLV. Cell suspensions from fetal liver, adult bone marrow, and adult spleen are susceptible to A-MuLV, while thymocytes are resistant to A-MuLV-induced transformation. Bovine serum albumin gradient fractionation of bone marrow cells before infection with A-MuLV demonstrates that the majority of A-MuLV-sensitive cells are recovered in a broad band partially overlapping the majority of the nucleated cells. The agarose assay system allows study of A-MuLV-lymphoid cell interaction at the level of single cell-single virus particle interaction

The effect of helper virus on Abelson virus-induced transformation of lymphoid cells

Abelson murine leukemia virus (A-MuLV)-transformed fibroblast nonproducer cells were used to prepare A-MuLV stocks containing a number of different helper viruses. The oncogenicity of the A-MuLV stocks was tested by animal inoculation and their ability to transform normal mouse bone marrow cells was measured in vitro. All of the A-MuLV stocks transformed fibroblast cells efficiently. However, only A-MuLV stocks prepared with helper viruses that are highly oncogenic were efficient in vivo and in vitro in hematopoietic cell transformation. In addition, inefficient helpers did not establish a stable infection in lymphoid nonproducer cells. Thus, helper virus has a more central role in lymphoid cell transformation than in fibroblast cell transformation

Galaxy Formation: Was There A Big Bang Shell?

The tight correlation of galactic velocity distribution to both luminosity and its black hole mass and the relation of halo parameters to luminous mass distribution, can not be due to collapse dynamics. A big bang shell can solve galaxy formation problems by forming the supermassive black holes necessary to capture the initial blast wave in a coordinated pattern.Comment: 7 pages late

Demographic Change and Economic Growth in South Asia

Identifying factors that influence the pace of national economic growth is a time-worn activity of economists. Strangely, demographic change has often been absent from consideration. But new thinking and evidence have highlighted the powerful contribution that demographic change can make to economic growth, and this line of inquiry has some salient implications for understanding past growth in South Asia and assessing and shaping its future prospects.economic growth, South Asia, demographic change

The Future of South Asia: Population Dynamics, Economic Prospects, and Regional Coherence

What do we foresee for South Asia in 2060, in light of the significant changes it has undergone in the past few decades? India has experienced rapid economic growth, but continues to suffer widespread, extreme poverty as well. Afghanistan, Nepal, and Sri Lanka have seen major conflicts, with Pakistan always seeming on the verge of a major eruption. Nepal and Sri Lanka finally seem to have moved toward peace. As elsewhere, the region's many developments and crosscurrents make reliable predictions difficult, but one relatively neglected set of factors – demographic change – may shed some light on the region's future. Throughout the world, falling mortality rates and declining birth rates have been predictive of growing per-capita incomes, and theoretical reasoning and related evidence are sufficiently compelling to think that the links may indeed be causal. In this vein, this essay explores South Asia's economic prospects through a demographic lens. In addition, as we will see, there are some similar demographic trends across the countries of South Asia, but there are also a number of extreme differences. Regional heterogeneity bears on the question, "to what extent is South Asia a coherent region?"South Asia, demographic change, economic prospects, demographic trends, regional heterogeneity

In vitro transformation of lymphoid cells by Abelson murine leukemia virus

Cell cultures prepared from fetal murine liver were infected by Abelson murine leukemia virus. After about 2 weeks, proliferating cells of lymphoid morphology appeared in some of the cultures. Addition of 2-mercaptoethanol to the initial culture medium greatly enhanced the appearance of the lymphoid cells. Immunoglobulin determinants were evident on the cells in some cultures. Continuous passage of the cells in certain cultures was possible and the passaged cells could form tumors after animal inoculation. Because Abelson murine leukemia virus is able to induce in vitro malignant transformation of lymphoid cells, it probably causes leukemia by directly affecting cellular growth control

Protein stabilization explains the gag requirement for transformation of lymphoid cells by Abelson murine leukemia virus

The single protein encoded by Abelson murine leukemia virus is a fusion of sequence from the retroviral gag genes with the v-abl sequence. Deletion of most of the gag region from the transforming protein results in a virus capable of transforming fibroblasts but no longer capable of transforming lymphoid cells. Smaller deletions in gag reveal that p15 gag sequences are responsible for this effect, whereas deletion of p12 sequences had no effect on lymphoid transformation. In transformed fibroblasts, p15-deleted and normal proteins had similar activities and subcellular localization. When the p15-deleted genome was introduced into previously transformed lymphoid lines, its protein product exhibited a marked instability. The tyrosine-specific autophosphorylation activity per cell was less than 1/20th that of the nondeleted protein. Although pulse-Ia-beling showed that the p15-deleted protein was synthesized efficiently, immunoblotting demonstrated that its steady-state level was less than 1/10th that of the nondeleted Abelson protein. The specific instability of the p15-deleted protein in lymphoid cells explains the requirement of these sequences for lymphoid but not fibroblast transformation

Finite domination and Novikov rings. Iterative approach

Suppose C is a bounded chain complex of finitely generated free modules over the Laurent polynomial ring L = R[x,1/x]. Then C is R-finitely dominated, ie, homotopy equivalent over R to a bounded chain complex of finitely generated projective R-modules, if and only if the two chain complexes C((x)) and C((1/x)) are acyclic, as has been proved by Ranicki. Here C((x)) is the tensor product over L of C with the Novikov ring R((x)) = R[[x]][1/x] (also known as the ring of formal Laurent series in x); similarly, C((1/x)) is the tensor product over L of C with the Novikov ring R((1/x)) = R[[1/x]][x]. In this paper, we prove a generalisation of this criterion which allows us to detect finite domination of bounded below chain complexes of projective modules over Laurent rings in several indeterminates.Comment: 15 pages; diagrams typeset with Paul Taylor's "diagrams" macro package. Version 2: clarified proof of main theorem, fixed minor typos; Version 3: expanded introduction, now 16 pages; Version 4: corrected mistake on functoriality of mapping tor