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

Loss of Drosophila nucleostemin 2 (NS2) blocks nucleolar release of the 60S subunit leading to ribosome stress

Four nucleostemin-like proteins (nucleostemin (NS) 1-4) were identified previously in Drosophila melanogaster. NS1 and NS2 are nucleolar proteins, while NS3 and NS4 are cytoplasmic proteins. We showed earlier that NS1 (homologous to human GNL3) enriches within the granular components (GCs) of Drosophila nucleoli and is required for efficient maturation or nucleolar release of the 60S subunit. Here, we show that NS2 is homologous to the human nucleostemin-like protein, Ngp1 (GNL2), and that endogenous NS2 is expressed in both progenitor and terminally differentiated cell types. Exogenous GFP-NS2 enriched within nucleolar GCs versus endogenous fibrillarin that marked the dense fibrillar components (DFCs). Like NS1, depletion of NS2 in midgut cells blocked the release of the 60S subunit as detected by the accumulation of GFP-RpL11 within nucleoli, and this likely led to the general loss of 60S subunits as shown by immunoblot analyses of RpL23a and RpL34. At the ultrastructural level, nucleoli in midgut cells depleted of NS2 displayed enlarged GCs not only on the nucleolar periphery but interspersed within the DFCs. Depletion of NS2 caused ribosome stress: larval midgut cells displayed prominent autophagy marked by the appearance of autolysosomes containing mCherry-ATG8a and the appearance of rough endoplasmic reticulum (rER)-derived isolation membranes. Larval imaginal wing disc cells depleted of NS2 induced apoptosis as marked by anti-caspase 3 labeling; loss of these progenitor cells resulted in defective adult wings. We conclude that nucleolar proteins NS1 and NS2 have similar but non-overlapping roles in the final maturation or nucleolar release of 60S ribosomal subunits.

Deletion of Drosophila Nopp140 induces subcellular ribosomopathies

The nucleolar and Cajal body phosphoprotein of 140 kDa (Nopp140) is considered a ribosome assembly factor, but its precise functions remain unknown. To approach this problem, we deleted the Nopp140 gene in Drosophila using FLP-FRT recombination. Genomic PCR, reverse transcriptase-PCR (RT-PCR), and immunofluorescence microscopy confirmed the loss of Nopp140, its messenger RNA (mRNA), and protein products from all tissues examined. Nopp140-/- larvae arrested in the second instar stage and most died within 8 days. While nucleoli appeared intact in Nopp140-/- cells, the C/D small nucleolar ribonucleoprotein (snoRNP) methyltransferase, fibrillarin, redistributed to the nucleoplasm in variable amounts depending on the cell type; RT-PCRs showed that 2'-O-methylation of ribosomal RNA (rRNA) in Nopp140-/- cells was reduced at select sites within both the 18S and 28S rRNAs. Ultrastructural analysis showed that Nopp140-/- cells were deficient in cytoplasmic ribosomes, but instead contained abnormal electron-dense cytoplasmic granules. Immunoblot analysis showed a loss of RpL34, and metabolic labeling showed a significant drop in protein translation, supporting the loss of functional ribosomes. Northern blots showed that pre-RNA cleavage pathways were generally unaffected by the loss of Nopp140, but that R2 retrotransposons that naturally reside within the 28S region of normally silent heterochromatic Drosophila ribosomal DNA (rDNA) genes were selectively expressed in Nopp140-/- larvae. Unlike copia elements and the related R1 retrotransposon, R2 expression appeared to be preferentially dependent on the loss of Nopp140 and not on environmental stresses. We believe the phenotypes described here define novel intracellular ribosomopathies resulting from the loss of Nopp140.

A novel MSC-seeded triphasic construct for the repair of osteochondral defects

Mesenchymal stem cells (MSC) are increasingly replacing chondrocytes in tissue engineering based research for treatment of osteochondral defects. The aim of this work was to determine whether repair of critical-size chronic osteochondral defects in an ovine model using MSC-seeded triphasic constructs would show results comparable to osteochondral autografting (OATS). Triphasic implants were engineered using a beta-tricalcium phosphate osseous phase, an intermediate activated plasma phase, and a collagen I hydrogel chondral phase. Autologous MSCs were used to seed the implants, with chondrogenic predifferentiation of the cells used in the cartilage phase. Osteochondral defects of 4.0 mm diameter were created bilaterally in ovine knees (n = 10). Six weeks later, half of the lesions were treated with OATS and half with triphasic constructs. The knees were dissected at 6 or 12 months. With the chosen study design we were not able to demonstrate significant differences between the histological scores of both groups. Subcategory analysis of O'Driscoll scores showed superior cartilage bonding in the 6-month triphasic group compared to the autograft group. The 12-month autograft group showed superior cartilage matrix morphology compared to the 12-month triphasic group. Macroscopic and biomechanical analysis showed no significant differences at 12 months. Autologous MSC-seeded triphasic implants showed comparable repair quality to osteochondral autografts in terms of histology and biomechanical testing.

Cell Death by Autoschizis in TRAMP Prostate Carcinoma Cells as a Result of Treatment by Ascorbate: Menadione Combination

A prostate carcinoma cell line derived from the transgenic murine prostate cancer model (TRAMP) was treated with ascorbate (VC) alone, menadione (VK(3)) alone, or a combination of ascorbate:menadione (VC + VK(3)) for 1, 2, and 4 h. Cytotoxic cell alterations examined by light and electron microscopy were treatment-dependent with VC + VK(3) > VC > VK(3). Induced by oxidative stress, these alterations included cytokeletal changes conducive to cytoplasmic blebbing, self-excisions, and progressive nuclear alterations. While the excised parts contained ribosomes, they were devoid of nuclear fragments or other organelles. The organelle-free self-excisions caused an extreme reduction in cell size as well as chromatolysis and karyolysis that were consistent with cell death by autoschizis, but not with apoptosis.

Distribution of DNA and alginate in purulent cystic fibrosis sputum: implications to pulmonary targeting strategies

Cystic fibrosis (CF) patients frequently experience recurring airway infections characterized by thick, viscous sputum. The consistency and nature of these purulent secretions may produce a significant barrier to the successful delivery of drugs and gene therapy vectors designed to treat CF. We have carried out a series of in vitro studies to determine the distribution of two macromolecular components typically present in purulent sputum, bacterial alginate and neutrophil-derived DNA. Sputum samples were obtained from hospitalized CF patients. DNA and alginate were disrupted, respectively, by the in vitro additions of human recombinant deoxyribonuclease I (rhDNase) or alginate lyase prepared from a mucoid strain of Pseudomonas aeruginosa. N-acetyl-L-cysteine (acetylcysteine) was similarly used to collapse the mucin matrix of these samples for comparison. Using a centrifugation-based rheological method known as the compaction assay, a greater maximal response was observed for rhDNase compared to alginate lyase treatment. A simultaneous addition of these enzymes to purulent sputum produced an additive compaction response. Electron microscopy was used to identify alginate and DNA components within the mucin matrix of sputa and to evaluate changes following treatment with high concentrations of alginate lyase or rhDNase. DNA was more widely distributed throughout purulent samples than alginate. Differences in the distribution of DNA and alginate may explain, at least in part, the larger compaction response to rhDNase versus alginate lyase treatment. An improved understanding of DNA and alginate distribution within purulent CF sputum may lead to improvements in drug and vector delivery to airway epithelial cells.

Early cellular events in an actinomycin D-created dentin niche in the rat incisor

Administration of actinomycin D at a dose level of 0.375 microgram/g resulted in the selective disruption of developing odontoblasts at a critical stage of morphogenesis. A dentin niche was formed which was later repaired by cellular reparative dentin. The cellular changes which resulted in dentin niche formation were studied histologically and ultrastructurally in serial longitudinal and transverse sections from tissues obtained 10 h to 80 h following injection of the drug. Five stages were identified: initial destruction (10-20 h), rapid destruction (30-40 h), debris removal (50-60 h), proliferation (60-80 h) and matrix deposition (post 80 h). The cellular changes found in the dental papilla were considerably different from those found in inflammation, resolution and repair of fibrous connective tissue. These early stages were dominated by apoptosis and heterophagy, and after 80 h by disordered dentin matrix formation. The three-dimensional morphology of the defect was reconstructed from serial sections. The shape of the niche was the result of interference by actinomycin D in the patterns of proliferation and migration of the cells in the apical region of the rat incisor tooth.

Perception and response to gravity in higher fungi--a critical appraisal

Considering that research on gravitropism in higher fungi has a history of over 100 years, the harvest of established fact is disappointingly meagre. We can be reasonably certain of the following. Hymenomycete 'mushroom' fruit bodies (polypore and agaric) exhibit a number of tropisms of which anemotropism, gravitropism, phototropism and thigmotropism have been clearly demonstrated. At any one time one tropism usually predominates but the inferior tropisms can be demonstrated if the predominating ones can be removed by manipulation of the growth conditions. In ascending order, the hierarchy appears to be: thigmotropism, gravitropism, anemotropism, phototropism. During the course of development of a fruit body different tropisms predominate at different times. The youngest fruit body initials grow perpendicularly away from their substratum. The nature of this tropism is completely unknown but perpendicular growth of fruit body initials has been remarked upon in experiments at a variety of light intensities and in gravitational fields from +/- 0 to 4.5 g. The fruit-body primordium then becomes first positively phototropic but later negative gravitropism predominates. The switch between predominance of the two tropisms has been associated with the onset of sporulation in a number of different studies. The major adjustment of the direction of growth in response to a tropic stimulus is made by the mushroom stem. It is the apex of the stem which makes the most immediate gravitropic response. Gravitropic growth curvatures are limited to the normal growth zones of the stem and seem to depend on re-allocation of available growth resources. If the fruit body is reoriented late in the growth of the stem, it may not be able to respond fully. In these cases gravitropic movements of the cap may still be able to bring the hymenophore back to the vertical. Mechanical forces may influence and contribute to the 'gravitropic' response but this has not been experimentally examined. The hymenophore (gill, tube or tooth) is positively gravitropic and responds independently of the stem. Bracket polypores do not show tropisms but exhibit gravimorphogenetic responses such that gross disturbance leads to renewal of growth to produce and entirely new fruiting structure suitably reoriented to the new spatial position. One experiment performed on an orbiting space station suggests that, in the absence of a light stimulus, gravity may be required for initiation of fruiting in Polyporus brumalis. Otherwise, the indications from both clinostat and space-borne experiments are that the basic form of the mushroom (overall tissue arrangement of stem, cap, gills, hymenium, veil) in agaric and polypore alike is established independently of the gravity vector. Abnormal stem growth has been observed in clinostat cultures of Panus (= Lentinus) tigrinus and Polyporus brumalis, but the morphogenetic event which seems most dependent on gravity is sporulation (in the broadest sense). Cultures of P. brumalis on orbiting space craft fail to produce the poroid hymenophore and in clinostat experiments on the ground even karyogamy was rare in similar cultures. Coprinus cinereus grown on the clinostat was able to produce apparently normal fruit body primordia which failed to produce spores and then aborted, forming a new flush of primordia on the old. Taken together with the clear association between observation of gravitropism and the onset of sporulation, the implication is that commitment to the meiosis-sporulation pathway both requires the gravity vector and couples it in some way to fruit-body growth. There is no convincing evidence for a graviperception mechanism in fungi. There is no evidence for any organised means of communicating the gravitropic stimulus once it has been perceived. Reports of three different experimental studies reveal the authors' conviction that the apparently coordinated expression of gravitropic response is in truth a common, but independent, response by the individual component hyphae of the structure concerned. There is some evidence that in the negatively gravitropic Phycomyces sporangiophore the vacuole floats in the protoplasm. If this is generally true it could affect protoplasmic volumes above and below the vacuole such that a greater proportion of the cell's potential for wall growth was adjacent to the lower wall. This is not only an attractive way of accounting for asymmetric wall growth, but since the relative density of the vacuole can presumably be controlled by regulation of water influx and efflux, it is also an attractive means of accounting for the control of gravitropic responses. Phycomyces also exhibits a response to the mechanical consequences of reorientation which is additional to (and different from) the longer term gravitropic response. [TRUNCATED]

Monomerizing effect of caffeine, o-phenanthroline, and tannin on cationic dyes: a model system to analyze spectral characteristics of the intercalative binding to nucleic acids

If used as co-solutes in concentrated solutions of cationic planar dyes, caffeine, o-phenanthroline, and tannin induce striking hyperchromic and bathochromic shifts in their absorption spectra. Likewise, the fluorescence of acridine orange at high concentration greatly increases in the presence of caffeine, the emission peak appearing at a shorter wave-length. These spectral changes, which are similar to those produced by organic solvents, detergents, and alpha-cyclodextrin, reflect the disaggregating (monomerizing) capacity of the co-solutes on stacked chromophores. After washing with saturated solutions of caffeine or o-phenanthroline, the chromatin fluorescence by intercalating fluorochromes is reduced or abolished, which suggests competition effects for intercalative binding modes. These results support the use of caffeine, o-phenanthroline, and tannin in spectroscopic and histochemical studies of dye-stuff interactions with DNA and chromatin.

Metachromatic staining and electron dense reaction of glycosaminoglycans by means of cuprolinic blue

The cationic phthalocyanin-like dye Cuprolinic Blue, unlike phthalocyanin dyes such as Alcian Blue or Astra Blue, can definitely exhibit a clear metachromatic reaction with appropriate substrates. The application of Cuprolinic Blue to epoxy-embedded semithin sections revealed that mast cell cytoplasmic granules, goblet cell mucin and cartilage matrix stained in violet shades (metachromatic), whereas nuclear chromatin presented a bright blue coloration (orthochromatic). The metachromatic structures showed a high degree of contrast when ultrathin sections treated with Cuprolinic Blue were examined by electron microscopy. Cytophotometric measurements of stained components from the large intestine showed different absorption maxima: at 580 nm for mucin and at 640 nm for nuclei. The spectroscopical analysis revealed a clear-cut metachromatic shift when the dye was in the presence of chondroitin-4-sulphate. The addition of aluminium metal to Cuprolinic Blue solutions resulted in a striking spectral change; under such conditions the dye showed absorption maximum at 530 nm.

Orthochromatic and metachromatic staining reactions by pyronin Y on Epon semithin sections

Semithin sections from glutaraldehyde-fixed, Epon-embedded tissues were stained by aqueous solutions of pyronin Y at increasing concentrations (from 10(-6) to 10(-3) mol). Mucopolysaccharide containing structures (e.g. mucin) were found stained in orange, meanwhile the chromatin and remaining tissue components appeared in a bright pink-red color. Cytophotometric measurements showed that a metachromatic shift occurs in the mucin content from goblet cells after pyronin Y staining at 10(-3) mol. Some features of the metachromatic reactions by cationic dyes are briefly discussed.

On the nature of Romanowsky--Giemsa staining and its significance for cytochemistry and histochemistry: an overall view

The chances of Romanowsky---Giemsa (RG) staining becoming a reliable and useful histochemical procedure are reviewed, based on the now proven fact that RG staining requires two dyes only, namely, cationic Azure B and anionic Eosin Y. These two dyes differ from otherwise similar dye combinations in that they give, on distinct biological substrates, one additional colour, purple, which cannot be obtained by the use of either dye alone. The purple colour characterizes the Romanowsky--Giemsa effect (RGE), which is the essential feature of RG staining. Consideration is given to the physico-chemical and morphological implications of RGE. Of primary importance is the nature of the biological substrates where RGE occurs, and also of those where it has never been observed. The way substrates react to RG stains largely depends on the kind of pretreatment they have received; for instance, alcoholic fixation preserves RGE but formaldehyde may inhibit it. Physico-chemical factors are considered which, by altering either the biological substrates or the composition of the staining solutions, may modify the RG staining pattern. This review also serves as an introduction for a series of experimental papers that will follow and which are intended to consolidate the basis of RG staining, a method which holds much promise as a useful histochemical tool.

Cuprolinic Blue: a specific dye for single-stranded RNA in the presence of magnesium chloride. I. Fundamental aspects

Qualitative and quantitative aspects of the cationic dye Cuprolinic Blue were investigated with model films of polyacrylamide gel in which RNA, DNA and other biological polyanionic compounds had been incorporated. In the presence of 1 M MgCl2, Curpolinic Blue was found to bind specifically to single-stranded RNA, leaving native DNA, proteins, (acid) polysaccharides and phospholipids completely unstained. Under these conditions, Cuprolinic Blue is complexed by non-electrostatic bonds with non-stacke purine bases, mainly adenine. Optimal conditions for dye binding and differentiation have been defined. Both the Cuprolinic Blue-MgCl2 staining of single-stranded RNA and the Cuprolinic Blue staining of RNA and DNA in the absence of MgCl2 were found to obey the Lambert-Beer law. The advantages and possible applications of Cuprolinic Blue are compared with well-known (indirect) histochemical RNA staining procedures.

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.

The morphology of erythroid cells separated by density gradient centrifugation through Ficoll

The regenerating blood of geese injected with phenylhydrazine was subjected to large scale, zonal centrifugation through density gradients of Ficoll. In this way, erythroid cells were fractionated according to their respective stages of development. Highly enriched fractions were obtained, containing cells that were well preserved as assessed by both light and electron microscopy. The separated cells exhibited ribosome density and nucleic acid and protein staining patterns typically associated with erythrocyte differentiation. Morphometric analysis of nuclei indicated that despite an apparent net increase in the amount of compact chromatin during development, comparatively little difference existed between the volumes of condensed chromatin present in immature and mature cells. Instead, there was a three fold decrease in nuclear volume between young erythroblasts and reticulocytes, coupled with a concomitant decrease in the volume occupied by dispersed chromatin, RNP and nucleoli. These observations are discussed in relation to molecular changes associated with nuclear differentiation in erythroid cells.

Cytokinins and nuclear RNA levels in onion root tips

Onion root tips were grown in water, kinetin or 6-benzyladenine and levels of RNA in the chromatin region of nuclei were analyzed using visible light microscopy with basic-dye staining, and ultraviolet microscopy of unstained material. No evidence was found for a significant increase in nuclear RNA in response to cytokinin treatment.

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

The stacking coefficients (K's) of nucleic acids have been thought to influence the color contrast between DNA and RNA in tissue sections stained with metachromatic dyes. This idea was tested by titrating toluidine blue (TB) and acridine orange (AO) in solution against DNA and RNA, native or treated with formaldehyde, acrolein, or Carnoy's fluid. Absorption spectra at varying polymer-dye ratios were used to compute K values by the methods of Bradley and colleagues. Results with both dyes fit Bradley's stacking equations. Fixatives did not block dye-binding sites but markedly altered K values. K of DNA was low, unaffected by aldehyde fixative, increased by Carnoy's fluid or heat denaturation. K of RNA was higher than that of DNA and was increased greatly by formaldehyde, almost as much by acrolein, considerably less by Carnoy's fluid. Aldehyde effects were partially reversed upon removal of aldehyde by dialysis. These observations accord with known effects of aldehydes and denaturation upon nucleic acid conformation. Differences between K's of DNA and RNA were greater after aldehyde treatment than after Carnoy's, and were greater with AO than with TB. This is generally consistent with the magnitude of the color contrasts observed in tissues. Additional factors must contribute to the intense color contrast observed in acrolein-fixed tissues stained with TB.