Properties of a nuclear protein marker of human myeloid cell differentiation

The Mr 55,000 nuclear antigen present in the human promyelocytic cell line HL-60 is a basic protein that is extracted from nuclei or chromatin by 0.35 M NaCl. The antigen is confined to the nucleus of the interphase HL-60 cell as judged by immunocytochemical localization but disperses throughout the cell during mitosis. The antigen was not detected in leukemic cell lines with blast cell properties or in cell lines representing other lineages. Additional cell lines (ML-1, ML-2, and U937) with myeloid cell characteristics similar to those of the HL-60 cells, which also differentiate in vitro, express the antigen. The presence of antigen in normal human myeloid cells in peripheral blood and bone marrow is consistent with its proposed role in nuclear events associated with normal human myeloid cell differentiation.     

Chromium-induced cross-linking of nuclear proteins and DNA

The in vivo cross-linking of proteins to DNA in intact Novikoff ascites hepatoma cells exposed to the chromium salt K2CrO4 was studied. DNA-protein complexes were assayed by high speed centrifugation of cells solubilized in buffered 4% sodium dodecyl sulfate and by electrophoretic identification of proteins associated with DNA-containing pellets. Further evidence of DNA-protein complexes, not dissociable in this buffer, was obtained by CsCl gradient centrifugation. Time dependence experiments showed that detectable cross-linking occurred after cells were exposed to chromium salt for at least 4 h, and the amount of DNA-protein complexes increased with longer incubation times. Complex formation occurred only with chromium salt concentrations of 200 microM or greater, and maximal cross-linking was effected at 5 mM. Immunotransfer methodology employing antibodies to nuclear matrix fraction and lamins was used to identify some of the polypeptides comprising the cross-linked complexes. These studies indicated specificity of chromium-induced complex formation within the nuclear protein fractions assayed. Our results document the ability of chromate to produce specific DNA-protein cross-links in living cells.     

Crosslinking of chromosomal proteins to DNA in HeLa cells by UV gamma radiation and some antitumor drugs

Immunochemical techniques were used to investigate the protein-DNA crosslinking by ultraviolet (UV) and gamma radiation as well as 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) or cis- and trans-diamminedichloroplatinum II (cis-DDP and trans-DDP). Antisera to 0.35 M NaCl extract and 0.35 M NaCl residue of HeLa nuclei were employed. Both gamma and UV irradiation, exposure to cis- or trans-DDP and, to a lesser extent, BCNU, resulted in crosslinking of various antigens to the DNA. Although several antigens were crosslinked by all the employed agents, other exhibited agent-specific crosslinking patterns.     

Phosphorylation of nonhistone chromatin proteins during sea urchin development

The phosphorylation of nonhistone chromatin proteins during development was studied in the sea urchin, $\text{Strongylocentrotus purpuratus}$. The rate of phosphorylation was found to be maximal during gastrula, slightly lower during prism and almost 70% lower in pluteus stage embryos. Analysis of the phosphorylated nonhistone chromatin proteins by SDS-acrylamide gel electrophoresis showed significant variations in the labeling pattern during different stages of development. A specific protein which is actively phosphorylated during gastrula and prism stages is nearly absent from the pluteus stage.     

Large old trees increase growth under shifting climatic constraints: Aligning tree longevity and individual growth dynamics in primary mountain spruce forests

In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree-level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~5000 Norway spruce (Picea abies [L.] H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed-linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e., competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modeled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (>400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks.     

Human granulocyte specific nuclear antigen(s). I: Production of antisera and determination of specificity.

Non-histone protein-DNA complexes isolated from human lung tissue were used to immunize New Zealand rabbits. Quantitative microcomplement fixation and immunocytochemistry revealed a specific chromatin antigen(s) in the human granulocyte nucleus. The study demonstrates the feasibility of employing antisera against chromosomal non-histone protein-DNA complexes for the immunochemical identification of cell types.     

Nuclear phosphoprotein kinase activities in normal and neoplastic tissues.

Nuclear phosphoprotein kinases from normal rat liver and transplantable neoplasms were fractionated and compared. A phosphoprotein kinase fraction activated by Mn2+ was found to be present only in the neoplasms. This nuclear protein kinase phosphorylated nuclear proteins represented by one major and several minor bands as determined by polyacrylamide gel electrophoresis (M approximately 50,000).     

From Microscopic to Macroscopic Descriptions of Cell Migration on Growing Domains

Cell migration and growth are essential components of the development of multicellular organisms. The role of various cues in directing cell migration is widespread, in particular, the role of signals in the environment in the control of cell motility and directional guidance. In many cases, especially in developmental biology, growth of the domain also plays a large role in the distribution of cells and, in some cases, cell or signal distribution may actually drive domain growth. There is an almost ubiquitous use of partial differential equations (PDEs) for modelling the time evolution of cellular density and environmental cues. In the last 20 years, a lot of attention has been devoted to connecting macroscopic PDEs with more detailed microscopic models of cellular motility, including models of directional sensing and signal transduction pathways. However, domain growth is largely omitted in the literature. In this paper, individual-based models describing cell movement and domain growth are studied, and correspondence with a macroscopic-level PDE describing the evolution of cell density is demonstrated. The individual-based models are formulated in terms of random walkers on a lattice. Domain growth provides an extra mathematical challenge by making the lattice size variable over time. A reaction–diffusion master equation formalism is generalised to the case of growing lattices and used in the derivation of the macroscopic PDEs.