Studies on nucleic acid metachromasy. I. The effect of certain fixatives on the dye stacking properties of nucleic acids in solution

A method for simultaneous nuclear immunofluorescence and DNA content quantitation using monoclonal antibodies and flow cytometry

A preparative technique for the two-parameter flow cytometric study of nuclear antigen expression is reported. This method employs a brief sequential treatment of cells at 4 degrees C first with 0.5% paraformaldehyde and second with 0.1% Triton X-100 in phosphate-buffered saline followed by cellular staining with indirect immunofluorescence and propidium iodide. Using this technique, cellular morphology is preserved, cell clumping is minimized, and high-quality indirect immunofluorescence and DNA staining are obtained with a minimum of nonspecific labeling. Utilizing nuclear antigen-specific monoclonal antibodies in conjunction with this technique, the cell-cycle phase-dependent expression of such antigens is examined. From these data, the utility of two-parameter flow cytometry in the identification and quantification of cell-cycle-dependent modulation of nuclear antigens is discussed.

Interaction of macrophages and lymphocytes in rat skin allografts

Light microscopy of 2 microgram sections of rejecting rat skin allografts, embedded in hydroxyethyl methacrylate, revealed among the cells infiltrating the graft base extravascular macrophages containing a small lymphocyte. Toluidine blue staining indicated DNA degradation in some of these phagocytosed lymphocytes. More frequently small lymphocytes were in intimate contact with the surface of the macrophages, resembling "Periopolesis', which others have previously observed in vitro. These macrophage-lymphocyte interactions were not seen in sections of autografts. Despite a previous report that diphenylhydantoin (phenytoin) impairs macrophage function, these macrophage-lymphocyte interactions were present in grafts placed in rats receiving this drug. This treatment did not hasten or delay the onset of graft rejection. These in vivo findings both accord with recent in vitro studies on the mechanisms of phagocytosis and with reports that phagocytosis is one of the effector mechanisms in allograft rejection. However, macrophage phagocytosis of lymphocytes has also been observed in testicular lymph collected from conscious normal sheep.

Microspectrophotometric studies of Romanowsky stained blood cells. I. Subtraction analysis of a standardized procedure

This paper describes a microspectrophotometric study of blood smears stained by a simple, standardized Romanowsky technique, using only the dyes azure B and cosin. Absorbance spectra are presented for twenty-two classes of cellular object, and for the two dyes in solution, together with tabulations of spectral maxima, and suitable wavelengths for use in automated image processing. The colours of objects stained with azure B/eosin are discussed in terms of absorbance spectra. By a spectral subtraction technique, it is shown that the differential colouration of various cell structures may be explained satisfactorily in terms of the varying proportions of only four dye components. These are the monomers and dimers of azure B and eosin. Polymerization was found to occur both in solution and on binding to biopolymers. A similar analysis of a conventional Romanowsky stain would present much greater difficulties, due to the greater number of dye components, which, however, contribute little to the colours observed.

A methodological study for the quantification and the control of the physico-chemical processes occurring during cell fixation. I. The development of a new technology

Fixation in a traditional sense means the immersion of biological material into a chemical fluid. For permanent preservation the fixative is always "offered" (1) in excess of the cell sample, and the process of fixation is influenced by (2) chemical impurities of the fixative fluid. Both factors influence the succeeding dyeing of cells. In order to avoid these uncontrolled criteria, a new technology for controlled cell fixation has been developed, whereby freshly prepared formaldehyde and methanol gas in an "inert" gas-flow of helium was applied to thin membranes by aid of a capillary flow-in technique. The instrumental equipment consists of (1) an ultra-high vacuum flow-apparatus with a total-pressure measuring unit, (2) a gas-supply device, (3) a mass spectrometer including a pump system, and (4) a Teflon and/or glass-gas chamber for the treatment of synthetic (Hostaphan foils) or biological membranes (mesenterium) with formaldehyde as the fixative gas. The amount of "offered", adsorbed, absorbed, diffused, and desorbed fixative gas could be absolutely estimated after the saturation of the membranes with an "on-line" operating "inert" mass spectrometer of the Omegatron type. The gas treatment of the Hostaphan foils with formaldehyde showed that nearly all adsorbed gas molecules could be desorbed. In contrast to native membranes the greatest proportion of the gas molecules adhered to the biological surface, and only a small quantity were desorbable. Physisorption or physisorption and chemisorption occured depending on the adsorber surface property. A monolayer of formaldehyde of 5.10(14) to 1.10(15) molecules per 10(16) A2 surface area can be postulated on the basis of these preliminary results. This value corresponds to a mass of about 5.10(-8) g CH2O. It resulted in an area-coverage ratio of CH2O molecules per cell of 10(9):1. The membrane surface facing the gas side always amounted to 1 cm2. A fixative gas concentration of 10(6) molecules/cm3, and therefore a degree of coverage of less than 1/1000 monolayer can be estimated absolutely. For a precise determination of the degree of fixation, further experiments and the evaluation of additional physico-chemical parameters are necessary.

Effect of temperature of aldehyde fixation on the radioautographic localization of ribonucleoprotein in nucleoli of HeLa cells. Inhibition by puromycin and actinomycin D

In efforts to clarify the role of the nucleolus and substructures thereof in the assembly or synthesis of protein associated with formation of the complete ribosome, the effect of variation of some conditions of aldehyde fixation on the intranuclear distribution of lysine-(3)H, arginine-(3)H, and uridine-(3)H was studied by differential grain count in radioautographs of PPLO-free HeLa cells. It was found that the nucleolus is a site of rapid assembly or synthesis of a protein, the synthesis of which is inhibited equally by puromycin (200 microg/ml) and by actinomycin D under conditions inhibitory for ribosomal precursor RNA synthesis (P < 0.01). This protein is fixed by phosphate-buffered formalin or glutaraldehyde at pH 7.3, but the label is diminished by fixation in customarily employed acetic ethanol or in formalin at acid pH. Elevation of temperature of formalin or glutaraldehyde fixatives to 37 degrees C consistently reduces the nucleolar protein label, but not the RNA label, by a proportion identical with that incurred by puromycin or actinomycin inhibition. This proportional reduction of nucleolar protein label occurs without evident loss of total grain count and is independent of length of fixation between 30 min and 4 hr, but it is not observed at 23 degrees C. The data support the interpretation that the proportion of nucleolar protein not fixed at 37 degrees C is associated with nucleolar ribosomal RNA but that it is dissociated at 37 degrees C in formalin or glutaraldehyde fixatives, probably on the basis of ionic dissociation of a conjugated ribonucleoprotein.

DNA-protein binding in interphase chromosomes

The metachromatic dye, azure B, was analyzed by microspectrophotometry when bound to DNA fibers and DNA in nuclei with condensed and dispersed chromatin. The interaction of DNA and protein was inferred from the amount of metachromasy (increased beta/alpha-peak) of azure B that resulted after specific removal of various protein fractions. Dye bound to DNA-histone fibers and frog liver nuclei fixed by freeze-methanol substitution shows orthochromatic, blue-green staining under specific staining conditions, while metachromasy (blue or purple color) results from staining DNA fibers without histone or tissue nuclei after protein removal. The dispersed chromatin of hepatocytes was compared to the condensed chromatin of erythrocytes to see whether there were differences in DNA-protein binding in "active" and "inactive" nuclei. Extraction of histones with 0.02 N HCl, acidified alcohol, perchloric acid, and trypsin digestion all resulted in increased dye binding. The amount of metachromasy varied, however; removal of "lysine-rich" histone (extractable with 0.02 N HCl) caused a blue color, and a purplish-red color (micro-peak absorption) resulted from prolonged trypsin digestion. In all cases, the condensed and the dispersed chromatin behaved in the same way, indicating the similarity of protein bound to DNA in condensed and dispersed chromatin. The results appear to indicate that "lysine-rich" histone is bound to adjacent anionic sites of a DNA molecule and that nonhistone protein is located between adjacent DNA molecules in both condensed and dispersed chromatin.

Studies on nucleic acid metachromasy. II. Metachromatic and orthochromatic staining by toluidine blue of nucleic acids in tissue sections

Acrolein-fixed, polyester wax-embedded tissue sections showed excellent preservation of light microscopic architecture and, when stained with toluidine blue, intense color contrast between DNA, which stained orthochromatically, and RNA, which stained metachromatically. This method has practical value for differentiating DNA from RNA in the same section. The color contrast was impaired by substituting formaldehyde for acrolein or paraffin for polyester wax, and was negligible in tissues fixed in formaldehyde or Carnoy's fluid and embedded in paraffin. Quality of structural preservation paralleled degree of color contrast. Metachromatic staining can be analysed, by the quantitative parameters of Bradley and colleagues, to provide inferences regarding the conformation of biopolymers in tissue sections. Comparison of the nucleic acid color contrasts in toluidine blue-stained sections with titrations of fixative-treated nucleic acids against toluidine blue in solution indicated a greater difference in conformation between DNA- and RNA-protein in acrolein-polyester sections than between acrolein-treated free DNA and RNA in solution. This is supported by recent evidence that the conformation of ribosomal RNA is quite different in whole ribosomes from that assumed by the same RNA free in solution. The acrolein-polyester method may enhance color contrast by providing superior preservation of ordered nucleoprotein conformations.