Cell concentration and the staining properties of nuclear deoxyribonucleoprotein

DNA stainability in aneuploid breast tumors: comparison of four DNA fluorochromes differing in binding properties

The aim of this study was to evaluate whether or not the differences in chromatin structure between diploid stromal cells or lymphocytes, which are often used as DNA ploidy standard, and aneuploid breast tumor cells can significantly affect the estimates of the DNA index of these tumors. To this end, the DNA content estimates of 34 aneuploid breast tumors, differing in size, degree of differentiation, and presence or absence of estrogen and progesterone receptors and metastases, were compared using four common DNA fluorochromes: DAPI, Hoechst 33342, propidium iodide, and acridine orange. These dyes differ in their mode of interaction with DNA (binding to minor groove or intercalation) and for each of them binding to DNA is restricted to a different degree by nuclear proteins. It was expected, therefore, that if differences in chromatin structure play a role in DNA content estimates, the DNA index of the measured tumors may vary depending on the dye. The cell nuclei were isolated from the tumors using a detergent-based procedure and stained with each of the dyes and the DNA index was estimated using peripheral blood lymphocytes as a DNA content standard. For each of the tumors, the DNA index estimates with all four dyes correlated very well. When the results obtained with individual dyes were compared in pairs, the correlation coefficients (r) of DNA indices were all above 0.96 (correlation at p less than 0.001). The best concordance was seen between specimens stained with Hoechst 33342 and DAPI (r = 0.99), and the least between those stained with Hoechst 33342 and propidium iodide (r = 0.96). The data indicate that DNA content analysis of unfixed nuclei, utilizing the above fluorochromes, is not significantly biased by differences in chromatin structure of the measured cells.

Chromatin structure and nucleic acid synthesis in human lymphocyte activation by phytohemagglutinin

Alterations in chromatin structure were explored as a function of time following phytohemagglutinin (PHA) activation of human lymphocytes. Nuclear refringency (related to chromatin status), ultrastructural changes, and modifications of nucleic acid synthesis were compared. Chromatin dispersion was observed within 20 min of stimulation, with a concomitant increase in [3H]uridine incorporation; both were inhibited by actinomycin D. Recondensation of chromatin had occurred at 60 min when RNA synthesis was still increasing. The early chromatin dispersion thus was a reversible step and one of the most striking cellular events during the first phase of PHA activation. Late chromatin dispersion of blastic cells during the second phase of PHA response (after 24 h) was related to DNA synthesis in mitotic cells. This step was also inhibited by actinomycin D. These results suggest a relationship between the morphological changes in chromatin structure and the induction of RNA and DNA syntheses. The regulation of transcriptional and replicational states of the nucleus is discussed in terms of modifications of chromatin structure, considering PHA-induced calcium and cyclic nucleotide metabolism and interleukin II receptor expression.

DNase--a likely probe of juxtatranscriptional DNP

The acridine orange-DNase sequences applied to rat lymphoid cells resulted in granular products within the cell nucleus. Staining with uranyl acetate rendered the granules very opaque. Most of the coarse deposits lay adjacent to condensed chromatin. Minute granules were found in dispersed chromatin as well as in the nucleolus and in heterochromatin regions. Phosphotungstic acid staining revealed the protein constituents of these deposits. The procedure is suggested an electron microscopic demonstration of DNase protein bound to acridine orange modified beaded chromatin juxtaposed to transcription units.

Lymphocyte activation and the increase of nuclear birefringence

Nuclear birefringence of neutral red or rivanol stained cell suspensions from rat spleen has been investigated. Polyclonal or monoclonal mitogens produced an increased birefringence of the nucleus following 30 min in vitro stimulation at 37 degrees C. The nuclear birefringence increased by 62.2% [p less than 0.001], when the cells were incubated in the supernatants of a previously phytohemaglutinin stimulated culture. Amantadine, a potent phytohemagglutinin inhibitor, was unable to prevent the effect of the supernatant, but heating for 1 h at 56 degrees C destroyed its activity. The results suggest that increase in nuclear birefringence is mediated by a soluble factor which is released in the course of lymphocyte activation. The nuclear birefringence of surviving cells from human spleens obtained within 6 to 24 h post mortem increases after in vitro stimulation.

Substrate-attached serum and cell proteins in adhesion of mouse fibroblasts

The effects of serum and coatings of substrate-attached material (SAM, which remains tightly adherent to the substrate after EGTA-mediated removal of cells) on the kinetics of attachment of DNA-radiolabeled BALB/c 3T3. SV40-transformed 3T3, and concanavalin A-selected revertant cells to glass coverlips were studied. The presence of serum in the medium of attaching cells had a marked effect on (1) the initial time lag before stable attachment of cells, (2) the maximum level of attached cells, (3) the stability of attachment, and (4) pseudopodial spread of the cell over the substrate. These serum effects could be mimicked by measuring attachment in medium without serum and with use of serum-preadsorbed or 3T3 SAM-coated coverslips. Enzymatic treatment of serumpreadsorbed substrates indicated that the factor(s) in serum which affects attachment is very trypsin-sensitive. Serum preadsorption of substrates stimulated attachment of SVT2 cells in medium with serum in a manner very similar to the effects of 3T3 SAM coating, while attachment of 3T3 SAM coating, while attachment of 3T3 or revertant cells was unaffected. Slab gel electrophoretic analysis (PAGE-SDS gels) identified eight major serum proteins by Coomassie blue staining (a) which bind to the substrate in the absence of cells and (b) which persist on the substrate after growth to confluence of 3T3 or SVT2 cells; this suggests that major breakdown or serum-adsorbed components does not occur during growth of normal or transformed cells. Seven radioactive SAM proteins were detected by autoradiography in 3T3 or SVT2 SAM electropherograms -- two of which are high molecular weight components which correspond to the glucosamine-radiolabeled hyaluronate proteoglycans observed previously; the remaining five are newly-identified proteins in SAM (one of these proteins appears to be actin). 3T3 and SVT2 cells have unique proportions of these seven components. The data are consistent with the idea that normal or virus-transformed cells do not attach directly to the culture substrate, but to specific classes of substrate-adsorbed serum proteins via deposition of specific classes of cell surface proteins and polysaccharides.

Growth of mammalian cells on substrates coated with cellular microexudates. I. Effect on cell growth at low population densities

Mammalian and avian cells cultured on glass or plastic substrates produce microexudates of cellular macromolecules which remain bound to the substrate when the cells are detached. The gross macromolecular composition of microexudates from a range of diploid, heteroploid, and virus-transformed cells was determined with cells labeled with radioisotopes. Significant differences in the amounts of cellular glycoproteins, proteins, and RNA present in microexudates were found between different cell types and between cells of the same type at different stages of growth. Inoculation of cells onto substrates "coated" with microexudates altered their growth behavior. Microexudates from exponentially growing subconfluent homotypic and heterotypic cell populations enhanced the growth of mouse and chick embryo cells seeded at very low densities, but similar microexudates had no effect on the proliferation of cells seeded at higher densities. The enhanced growth of low-density cell populations seeded on microexudates was compared with the growth enhancement produced by feeder cell layers and conditioned medium.