Carbol Fuchsin as A Stain for Human Chromosomes

Cells derived from cultures of bone marrow or leucocytes were treated with hypotonic citrate solution, squashed in 45% acetic acid frozen with CO₂ to allow removal of the cover glass without disturbing the smear, and stained by the following schedule: absolute alcohol, 5 min; coat with 0.2% parlodion and air dry; 70% alcohol, 5 min; distilled water, 5 min; stain 2-5 min in a mixture of 45 ml of a 0.3% solution of basic fuchsin in 5% phenol, 6 ml of glacial acetic acid, and 6 ml of 37% formaldehyde. Differentiate and dehydrate in absolute alcohol, clear in xylene and cover. The stain is durable for several weeks if slides are stored in darkness when not in use. Results resemble those obtained by Feulgen or aceto-orcein methods.     

Hydrochloric acid as a Fixative for root Tip Chromosomes

After pretreatment with 0.2 to 0.3% colchicine at 26° C. for 2 hours root tips are fixed and macerated in a 1/10 dilution of concentrated hydrochloric acid at 60° C. for 10 to 14 minutes, washed, transferred to a staining dish with aceto-orcein or another aceto-stain for about 10 minutes, immersed in a drop of the stain, covered and squashed. The preparations may subsqeuently be made permanent.     

Coumarin in Chromosome Analysis

Root tips of monocotyledons were soaked 2.5-3.0 hours at 25-27° C. in saturated aqueous coumarin solution and stained in a mixture of N HC 1 and 2% aceto-orcein (1:9 by volume) 3-4 seconds over a flame. They were then squashed in 1% orcein under a cover glass, the excess stain blotted and the cover sealed. Preparations could be kept about one week. Good chromosome morphology was secured.     

An Assessment of Routine Chromosomal Staining Procedures in Radioautography

Unlabeled human chromosome preparations were treated with commonly employed chromosome stains as follows: (I) they were stained, destained, coated with liquid emulsion, developed, fixed, and restained; (II) stained and coated directly; or (III) coated and then stained. Of the stains tested, the methylene blue-eosin type (Giemsa, MacNeal's, Wright's) was useful for application after coating, although a similar stain (eosin-Stevenel's blue) caused formation of a heavy precipitate in the emulsion when so used. None of these stains could be employed before coating, however, even though they were removed with acid alcohol prior to dipping, because they caused chemographic grain formation in the emulsion. Aceto-orcein and Feulgen could not be employed after coating because the procedures removed the emulsion from the slides. Safranin was also found to be ineffective for staining coated preparations due to chemical changes caused by the photographic processing. The only stain which did not cause chemography, and hence can be used before coating slides, is aceto-orcein. Since this stain fades during radioautographic processing and cannot be employed after coating, we recommend secondary use of one of the methylene blue-eosin type stains for revisualization of the chromosome spread.     

Notes on Technic

This report details a whole mount technique which allows rapid assessment of meiotic stages in large numbers of mammalian oocytes using an aceto-orcein stain.

Previous studies of mammalian oocyte meiosis have been hampered by the use of time-consuming staining techniques. Temporary preparations have been produced using squashes of oocytes with fixative and stain drawn under the coverslip by diffusion (Austin 1961). An air-drying technique requires less attention by the technician and allows permanent preparations to be made (Tarkowski 1966). However, these methods require that each slide be treated individually. The improvements outlined below permit many slides to be processed together, allowing surveys of larger numbers of oocytes than before.     

Permanent Mounting of Unstained and Aceto-Orcein Stained Cells in the Water-Soluble Medium, Abopon

For cellular morphology, mammalian cells were grown on cover slips in Leigh ton tubes, fixed in 1% osmic acid vapor for 2 min, decolorized with 30% H₂O₂ in 5% ammonium oxalate solution (1:7) for 2 min, then washed thoroughly, and finally mounted in a water-soluble medium consisting of a saturated solution of Abopon in 0.2 M phosphate buffer, pH 7.0. For chromosomal analysis of similarly cultured cells, aceto-orcein preparations were made by conventional methods, with the following minor modifications: following pretreatment with colchicine and hypotonic expansion, the cells on the cover slips were fixed in acetic-alcohol (1:3), air dried, incubated at 37° C for 15 min in 2% orcein in 45% acetic acid, rinsed in 45% acetic acid, washed several times in distilled water, and finally mounted in Abopon mounting medium. Both kinds of preparations were allowed to harden for 24 hr before being handled. Such slides will keep for years at room temperature. Studies requiring frequent comparisons of cellular and chromosomal morphology of cultured cells can thus be extended over long periods of time.     

Permanent Smears of Leaf Tips for the Study of Chromosomes

Young leaf tips are soaked in a saturated aqueous esculin (aesculine) solution at 10-12° C for 15 min to 24 hr and fixed in acetic-alcohol, 1:1. The materials are then stained in a mixture of 2% aceto-orcein and 12V HCl (9:1), 3-4 sec over a flame followed by 30 min or longer at 30° C and then smeared in 1% aceto-orcein. Preparations are made permanent by loosening the cover glass in tertiary butyl alcohol and mounting directly in Canada balsam.     

Permanent Mounting of Unstained and Aceto-Orcein Stained Cells in the Water-Soluble Medium,Abopon

For cellular morphology, mammalian cells were grown on cover slips in Leigh ton tubes, fixed in 1% osmic acid vapor for 2 min, decolorized with 30% H₂O₂ in 5% ammonium oxalate solution (1:7) for 2 min, then washed thoroughly, and finally mounted in a water-soluble medium consisting of a saturated solution of Abopon in 0.2 M phosphate buffer, pH 7.0. For chromosomal analysis of similarly cultured cells, aceto-orcein preparations were made by conventional methods, with the following minor modifications: following pretreatment with colchicine and hypotonic expansion, the cells on the cover slips were fixed in acetic-alcohol (1:3), air dried, incubated at 37° C for 15 min in 2% orcein in 45% acetic acid, rinsed in 45% acetic acid, washed several times in distilled water, and finally mounted in Abopon mounting medium. Both kinds of preparations were allowed to harden for 24 hr before being handled. Such slides will keep for years at room temperature. Studies requiring frequent comparisons of cellular and chromosomal morphology of cultured cells can thus be extended over long periods of time.     

Aceto-Orcein and Feulgen Stains for Anatomy and Cytology of Trematodes

Dicrocoelium dendriticum and Fasciola hepatica were killed in the extended condition without anesthetization by dropping them into 40% acetic acid or into aceto-orcein. By using aceto-orcein (La Cour, 1941), killing, fixing and staining were accomplished simultaneously: staining time 24 hr or more. Whole mounts were made by dehydrating, clearing and mounting in Canada balsam, or testes or the upper part of the uterus could be removed for squash preparations after as long as 2 mo in the fixing and staining fluid. For Feulgen staining, living specimens were placed in 40% acetic acid for 10—15 min and then transferred to either Gilson's fluid, for sections, or to acetic-ethanol (1:3) for squashes. Hydrolysis was either by 10% perchloric acid at 25°C for 12 hr or in 12V HCl at 60° for 10 min. The time for Feulgen staining (De Tomasi, 1936) was 1.5-4.0 hr. Squashes were made from testes and uterus in the same manner as after aceto-orcein or sections obtained after embedding in paraffin.     

Brilliant Cresyl Blue as a Stain for Plant Chromosomes

Methods are proposed for staining plant chromosomes with the dye brilliant cresyl blue, and for making these stained preparations permanent by using polyvinyl alcohol mounting medium.

The stain, which is composed of 2% brilliant cresyl blue in 45% aqueous acetic or propionic acid, is used with fixed material in making smear preparations. The technics for staining are similar to those employed in the aceto-carmine method.

The mounting medium is made by mixing 56% polyvinyl alcohol, which is diluted in water to the consistency of thick molasses, with 22% lactic acid and 22% phenol by volume. The permanent slides are made by floating off the cover slip of the temporary slide in 70% alcohol, then applying the mounting medium and replacing the cover slip.

The chief advantages of the methods described are:

1)The preparation of the stain is rapid and simple. The batch of stain will be good with the first try.

2)The staining procedure in some instances is shorter than when using aceto-carmine.

3)The stain shows a high degree of specificity for nuclear structures and gives better results than aceto-carmine when used on certain plant tissues.

4)A minimum number of cells is lost in making the slides permanent when using polyvinyl alcohol mounting medium as the slide and cover slip are run through only one solution prior to mounting.

5)The mounting medium dries rapidly and this shortens the time required before critical examination of the permanent mounts can be made.     

Sudan Black B And Acetocarmine as a Combination Stain

Epidermis stripped from either fresh or fixed plant organs, or sections of paraffin-embedded or fresh material are placed on a slide and covered with a drop or two of iron-acetocarmine. The stain is intensified by warming the slide over a flame. After a few minutes a drop or two of a saturated solution of Sudan black B in 45% acetic acid is added and a cover slip applied. The preparations cannot be made permanent, but last a few weeks if sealed with a compound such as gum mastic-paraffin, or if the combined stain is drained off and a drop of Karo syrup is added before the cover slip is applied. The acetocarmine produces its usual staining effects, i.e., nuclei dark red and some components of the cytoplasm of certain cells a less intense red. The Sudan black B colors lipid structures an intense blue.     

Prefixing with Paradichlorobenzene to Facilitate Chromosome Study

A technic was developed which resulted in preparations containing many mitotic divisions with chromosomes well fixed and stained, rod-shaped, and spread throughout the cell. This technic has given good results with guayule (Parthenium argentatum), Crepis, Allium, Pisum, Lycopersicon, Tradescantia, and other plants. Material is prefixed in a saturated solution of paradichlorobenzene for 1-4 hours, fixed in 65% acetic acid (or other suitable fixative) for 12-24 hours, hydrolyzed in 10% HCl for 10-30 minutes at 60° C, rinsed in water, transferred to a drop of 45% acetic acid on a slide, and smeared and stained in aceto-orcein. The preparation may be made permanent by separating slide and cover glass in 1 part glacial acetic acid to 1 part absolute alcohol, putting them in absolute alcohol, and then recombining them with a drop of euparol.     

A Formalin-Wright Staining Technique for Avian Blood Cells

A rather concentrated alcoholic staining solution, an aqueous formalin-containing diluent, and a mixture of ethyl ether and absolute methyl alcohol are required. Formulas: A. Wright's stain (Harleco, Cert. No. LWr-52 was used), 3.3 gm; methyl alcohol, 500 ml. B. Formaldehyde solution 40% USP (Fisher's used), 0.25 ml; distilled water, 500 ml with its pH adjusted to 6.8 by addition of either 0.25% Na₂CO₂ or 0.25% HCl, as needed. C. A I:I mixture of ethyl ether and absolute methyl alcohol. Procedure: Prepare thin smears of normal or pathological avian blood, air dry, place the slides on a drying rack, cover with solution A, and let stand for about 8 min. Dilute the stain by dropping on a volume of B estimated to be equal to the volume of the partially evaporated stain, and let stand for 2-5 min, or until the surface is well covered by a metallic sheen. Wash with distilled water adjusted to pH 6.8 with the 0.25% Na₂CO₂ solution or 0.25% HCl. Dry the preparations quickly by blotting with filter paper. Differentiate and adjust the color intensities by dipping 6-10 times into C. Check the results microscopically and differentiate further if the colors are not properly balanced. Dry, uncovered preparations may be examined under oil; or, a cover glass can be applied with balsam or a synthetic resin for permanent mount. Results are similar to those described in textbooks, but have been more consistent than those obtained with other techniques for blood cells of chicken, pheasants, American and Indian partridge, quail, pigeon, turkey, goose, canary, and the Himalayan snow partridge.     

Aceto-Iron-Haematoxylin-Chloral Hydrate for Chromosome Staining

Aceto-iron-haematoxylin can be used combined with the clearing agent chloral hydrate for the squash method. The stain is prepared by dissolving 2 gm of chloral hydrate in 5 ml of a stock solution of 4% haematoxylin and 1% iron alum in 45% acetic acid, which has been allowed to ripen for 24 hr to 1 wk. Heat must not be used to hasten solution. The material (fixed in 1:3 acetic-alcohol) is put on a slide, the fixative removed and a drop of stain added; if necessary the material is crushed before the cover slip is placed in position. The preparations are now carefully heated until a slight colour change occurs. Squashing needs more pressure than in other techniques. This stain gives best results in zoological and botanical material not requiring hydrolysis, e.g., leucocytes, ascites cells, and cells undergoing spermatogenesis and microsporogenesis. Well-spread and selectively stained mitotic and meiotic figures can be obtained.     

Rapid in situ cytochemical classification of CFU-C colonies in soft agar culture: permanent whole culture preparations

Soft agar culture CFU-C (colony-forming units in culture) are rapidly classified in situ as eosinophil, macrophage, and neutrophil-monocyte types by whole culture staining with luxol fast blue for eosinophil specific granules and acetoorcein for nuclei. Stained colonies may be picked and examined individually as wet mount cover slip preparations, or the agar culture may be air dried and mounted permanently. The whole culture stain has been variously modified for the enzyme markers alpha-naphthyl acetate esterase and peroxidase and for nuclear staining alone with acetoorcein.     

Simple Aids to Microscope Illumination

The following rapid but reliable method of making permanent preparations from temporary mounts has proved to be very useful.

Pollen mother-cell smears: Smeared anthers are treated hi the usual way with Belting's acetocarmine, except that the cover slip is left off. When correct differentiation is attained the stain is thoroly washed off with 50% acetic acid and the slide flooded with dioxan. This is followed by 2 changes of dioxan for 2 minutes each. A drop of Canada balsam dissolved in dioxan is added and a cover slip applied. In cases where a cover slip has been used at the acetocarmine stage it can be floated off in a staining jar of 50% acetic acid and dehydration with dioxan carried out as above.

Insect salivary gland chromosome smears: The glands are crushed under a cover slip in acetocarmine on a slide coated with dried egg albumen. After 20 minutes the area around the cover slip is flooded with 50% acetic acid and the cover slip floats loose so that it can be removed. The above described dioxan dehydrating procedure is then employed.

Squash preparations: Root tips are fixed in some suitable fixative and the Feulgen technic applied. The stained root tips can either be dehydrated by passing thru 3 changes of dioxan and mounting in dioxan-balsam where they are divided into small longitudinal sections by sharp needles, or they can be put immediately into a mixture of 1 part of 50% acetic acid to 1 part of corn syrup where shredding with needles is carried out. A cover slip is put on and separation of the cells completed by tamping or by applying pressure to the cover. This squash method is useful with anthers which are difficult to smear when in the early prophase stages of meiosis.     

Permanent Preparations from Rapid Cytological Technics

The following rapid but reliable method of making permanent preparations from temporary mounts has proved to be very useful.

Pollen mother-cell smears: Smeared anthers are treated hi the usual way with Belting's acetocarmine, except that the cover slip is left off. When correct differentiation is attained the stain is thoroly washed off with 50% acetic acid and the slide flooded with dioxan. This is followed by 2 changes of dioxan for 2 minutes each. A drop of Canada balsam dissolved in dioxan is added and a cover slip applied. In cases where a cover slip has been used at the acetocarmine stage it can be floated off in a staining jar of 50% acetic acid and dehydration with dioxan carried out as above.

Insect salivary gland chromosome smears: The glands are crushed under a cover slip in acetocarmine on a slide coated with dried egg albumen. After 20 minutes the area around the cover slip is flooded with 50% acetic acid and the cover slip floats loose so that it can be removed. The above described dioxan dehydrating procedure is then employed.

Squash preparations: Root tips are fixed in some suitable fixative and the Feulgen technic applied. The stained root tips can either be dehydrated by passing thru 3 changes of dioxan and mounting in dioxan-balsam where they are divided into small longitudinal sections by sharp needles, or they can be put immediately into a mixture of 1 part of 50% acetic acid to 1 part of corn syrup where shredding with needles is carried out. A cover slip is put on and separation of the cells completed by tamping or by applying pressure to the cover. This squash method is useful with anthers which are difficult to smear when in the early prophase stages of meiosis.     

A New Stain Mixture: Aceto-Orcein-Fast-Green

A new mixture consisting of aceto-orcein, fast green, and salt is described. The mixture provides contrast between nuclear material, nucleoli and cytoplasm without differentiation. We have found it most useful in the staining of teased tissues, squashes, smears and suspensions (fixed and unfixed). We recommend it for the great speed and simplicity with which it provides a stain having the contrast of much more laborious histological technics.     

Electron microscopy of free-floating cells: thin-layering technique, and selection of individual cells for ultramicrotomy.

A rapid and accurate procedure for electron microscopy of individual cells from suspensions (blood, peritoneal exudate, etc.) is described. After fixation of the sample with standard techniques, the particulate constituents are suspended in buffered 5% bovine serum albumin, thin-layered by gravity on clear supports (cover glasses or polyester slips) in which an orientation grid had been scored, and then immobilized by exposure of the preparations to acrolein vapors. The specimens are examined for cells of interest under a light microscope using interference or phase contrast; individual cells to be sectioned are documented in three photomicrographs taken at different magnifications. After this the specimens are embedded like ordinary cover slip preparations. When examining the face of the polymerized block under a light microscope, the position of the selected cell beneath the orientation grid relief can readily be relocated by the aid of the pre-embedding reference micrographs.     

Electron Microscopy of Free-Floating Cells: Thin-Layering Technique, and Selection of Individual Cells for Ultramicrotomy

A rapid and accurate procedure for electron microscopy of individual cells from suspensions (blood, peritoneal exudate, etc.) is described. After fixation of the sample with standard techniques, the particulate constituents are suspended in buffered 5% bovine serum albumin, thin-layered by gravity on clear supports (cover glasses or polyester slips) in which an orientation grid had been scored, and then immobilized by exposure of the preparations to acrolein vapors. The specimens are examined for cells of interest under a light microscope using interference or phase contrast; individual cells to be sectioned are documented in three photomicrographs taken at different magnifications. After this the specimens are embedded like ordinary cover slip preparations. When examining the face of the polymerized block under a light microscope, the position of the selected cell beneath the orientation grid relief can readily he relocated by the aid of the pre-embedding reference micrographs.