A Paradichlorobenzene, Saponin, Iron Mordant Sequence in the Staining of Meiotic Chromosomes of Ipomea

For the meiotic study of Ipomea spp., flower buds were stripped of the calyx and corolla and soaked in saturated aqueous paradichlorobenzene at about 28° C for 3 hr, transferred to acetic-alcohol (1:3) for 6 hr, then into 1% saponin solution and left overnight. They were mordanted in 1:3 acetic-alcohol saturated with ferric oxide for 24 hr and stained in a mixture of 1% aceto-carmine and 2% aceto-orcein with 1 N HCl in the proportion of 9:9:1. The preparations were mounted in 1% aceto-carmine for temporary use and made permanent by dehydration through the n-butanol schedule. The pollen mother cells had clear cytoplasm with deeply stained chromosomes.     

Differentiated Staining of Osmium Tetroxide-Fixed, Vestopal-w-Embedded Tissue in thin Sections

Tissues were fixed at 20° C for 1 hr in 1% OsO₄, buffered at pH 7.4 with veronal-acetate (Palade's fixative), soaked 5 min in the same buffer without OsO₄, then dehydrated in buffer-acetone mixtures of 30, 50, 75 and 90% acetone content, and finally in anhydrous acetone. Infiltration was accomplished through Vestopal-W-acetone mixtures of 1:3, 1:1, 3:1 to undiluted Vestopal. After polymerisation at 60° C for 24 hr, 1-2 μ sections were cut, dried on slides without adhesive, and stained by any of the following methods. (1) Mayer's acid hemalum: Flood the slides with the staining solution and allow to stand at 20°C for 2-3 hr while the water of the solution evaporates; wash in distilled water, 2 min; differentiate in 1% HCl; rinse 1-2 sec in 10% NH,OH. (2) Iron-trioxyhematein (of Hansen): Apply the staining solution as in method 1; wash 3-5 min in 5% acetic acid; restain for 1-12 hr by flooding with a mixture consisting of staining solution, 2 parts, and 1 part of a 1:1 mixture of 2% acetic acid and 2% H₂SO₄ (observe under microscope for staining intensity); wash 2 min in distilled water and 1 hr in tap water. (3) Iron-hematoxylin (Heidenhain): Mordant 6 hr in 2.5% iron-alum solution; wash 1 min in distilled water; stain in 1% or 0.5% ripened hematoxylin for 3-12 br; differentiate 8 min in 2.5%, and 15 min in 1% iron-alum solution; wash 1 hr in tap water. (4) Aceto-carmine (Schneider): Stain 12-24 hr; wash 0.5-1.0 min in distilled water. (5) Picrofuchsin: Stain 24-48 hr in 1% acid fuchsin dissolved in saturated aqueous picric acid; differentiate for only 1-2 sec in 96% ethanol. (6) Modified Giemsa: Mix 640 ml of a solution of 9.08 gm KH₂PO₄ in 1000 ml of distilled water and 360 ml of a solution of 11.88 gm Na₂HPO₄-2H₂O in 1000 ml of distilled water. Soak sections in this buffer, 12 hr. Dissolve 1.0 gm of azur I in 125 ml of boiling distilled water; add 0.5 gm of methylene blue; filter and add hot distilled water until a volume of 250 ml is reached (solution “AM”). Dissolve 1.5 gm of eosin, yellowish, in 250 ml of hot distilled water; filter (solution “E”). Mix 1.5 ml of “AM” in 100 ml of buffer with 3 ml of “E” in 100 ml of buffer. Stain 12-24 hr. Differentiate 3 sec in 25 ml methyl benzoate in 75 ml dioxane; 3 sec in 35 ml methyl benzoate in 65 ml acetone; 3 sec in 30 ml acetone in 70 ml methyl benzoate; and 3 sec in 5 ml acetone in 95 ml methyl benzoate. Dehydrated sections may be covered in a neutral synthetic resin (Caedax was used).     

Rapid Schedules for Koh Clearing and Alizarin Red S Staining of Fetal Rat Bone

Various schedules for staining fetal rat skeleton with alizarin red S were tested to determine a procedure that would produce a completely cleared and well-stained specimen in a short period of time. A 2 day procedure is presented which can produce specimens that are satisfactory but not completely transparent. A 7 day procedure produces cleared and stained specimens which can be well visualized with a dissecting microscope (30×). Fetal rats of 21 days gestation were fixed in 10% formalin for at least 1 wk. The specimens were skinned and eviscerated and then dehydrated in 2 changes of acetone for 12 hr (8 ml per gram body weight). The specimens were then placed in 1% KOM-alizarin red S (6 mg/liter) or 3 days, followed by 10% KOH-alizarin red S for 3 days. Finally, the specimens were placed in a mixture of benzyl alcohol, ethanol, and glycerol (1:2:2) (4 ml per gram body weight) for 12 hr, and then transferred to pure glycerol for storage.     

The influence of formaldehyde fixation time on the rate of nitrous acid deamination of erythrocytes and spinal cord proteins

Summary Alcohol fixed blood films and fresh blocks of spinal cord were immersed in phosphate buffered neutral 10% formol for graded intervals, the films for 10, 30 min, 1, 2, 4, 8, 24 hr; the blocks for 2, 4, 6, 24 hr at 3 and 24° C; 1, 3, 7, 14, 21, 28, 42, 56 da, 3 and 14 mo at 24–26°. Graded deaminations in 2 N NaNO₂/HAc at 3° C were applied: 1, 2, 5, 10, 20, 30 min; 1, 2, 4, 6, 8, 12, 18, 24, 36 hr. Blood films were stained at pH 6 and 6.5, tissue at pH 4.5 and 5.0, both in azure A eosin B. The point at which erythrocytes reached a slightly bluish green was taken as the end point, since no further color change occurred on further exposure and erythrocytes were the last of usually deamination susceptible tissue elements to lose their oxyphilia on deamination. Deamination of alcohol fixed blood films is completed in about 2 min, of sublimate fixed spinal cord in about 1 hr. Progressive formaldehyde exposure increased deamination time of blood films to 10–20 min in 1 hr, to 6–8 hr in 4 hr and to 12 hr in 24 hr. The tissue deamination showed similar progressive increase of deamination time, slower with 3° C fixation than with 24–26°, reaching 18–36 hr by about 3 days formol, and remaining about the same thereafter.Supported by National Cancer Institute Grant No. C-04816, National Institutes of Health.     

Selective Staining of Neurosecretory Material in Semithin Epoxy Sections by Gomori's Aldehyde Fuchsin

The epoxy resin was removed from semithin (1 μm) sections by immersing them for 30 sec in sodium methoxide (Mayor et al., J. Biophys. Biochem. Cytol., 9: 909-10, 1961) and then processed as follows: (1) left for 1-3 hr at 60 C in a mixture of formalin, 25 ml; glacial acetic acid, 5 ml; CrO₃, 3 gm; and distilled water, 75 ml: (2) oxidized 10 min in a 1:1:6 v/v mixture of 2.5% KMnO₄, 5% H₂SO₄ and distilled water: (3) bleached in 1% oxalic acid, and (4) stained for 15 min in aldehyde fuchsin, 0.125% in 70% alcohol, or in a 1% aqueous solution of toluidine blue. The neurosecretory material is selectively stained.     

Quad-Type Stain for the Simultaneous Demonstration of Intracellular and Extracellular Tissue Components

This technic for the simultaneous demonstration of several different tissue components works equally well on invertebrate and vertebrate tissue if they have been treated with nonchromate fixatives Sections 4-7 μ thick are stained 30 min in 1% Alcian blue, then treated with alkaline alcohol for 2 hr. They are stained in Verhoeff's hematoxylin for 4-6 hr, and rinsed in alcohol; stained in woodstain scarlet-acid fuchsin for 3 min, decolorized in 5% phosphotungstic acid for 20 min and finally stained 5-8 min in alcoholic saffron. Collagen and bone are stained yellow; elastin, myelin and nucleic acids, purple to black; muscle, chitin, cytoplasm, fibrinoid and acid secretion, bright red to lavender; ground substances and mucus, blue-green. Fibrous connective tissue, cartilage, bone and glandular epithelia are exceptionally well demonstrated by this method. Slides stained in this manner are well suited for color photomicrography and as demonstrations in the classroom.     

Staining Mitochondria With Hematoxylin After Formalin-Sublimate Fixation; A Rapid Method

Mitochondria were stained in liver, kidney, pancreas, adrenal and intestinal mucosa of rat and mouse. Tissues 1 mm thick, were fixed in a mixture of saturated aqueous HgCl₂, 90 ml; formalin (37-38% HCHO), 10 ml, at room temperature (25°C) for 1 hr. Deparaffinized sections 3-4μ thick were treated with Lugol's iodine (U.S.P.) followed by Na₂S₂O₃ (5%), rinsed in water and the ribonucleic acid removed by any of the following procedures: 0.2 M McIlavaine's buffer, pH 7.0, 2 hr, or 0.2 M phosphate buffer, pH 7.0, 2 hr at 37°C; 0.1% aqueous ribonuclease, 2 hr at 37°C; 5% aqueous trichloracetic acid overnight at 37°C; or 1% KOH at room temperature for 1 hr. After washing in water, sections were treated with a saturated solution of ferric ammonium alum at 37°C for 8-12 hr and colored by Regaud's ripened hematoxylin for 18 hr. They were then differentiated in 1% ferric ammonium alum solution while under microscopic observation.     

Pyridine-silver methods for the study of optic axons in retinal whole mounts.

The optic fibers in the retinas of diverse species may be selectively stained and viewed en bloc in the embryonic and adult states. Treat the eye as follows: 1) 50% pyridine for at least 16 hr, 2) distilled water 3--4 hr, 3) 20% H2O2 until the eye is a light brown, 4) 95% ethanol overnight, 5) 1.5% AgNO3 for 2--6 days at 37 C, 6) in water, remove the vitreous, then direct 0.25% pyrogallic acid in 1.25% formalin against the retina for 2--5 secs until the optic fibers are reduced to a coffee-copper color (1--4 minutes), 7) dissect the retina and mount flat on a glass slide, 8) cover with glycerin, apply a coverslip, and fix in place with nail polish. Variants for particular species are given. The technique offers an advantage over Golgi and methylene blue methods which tend to stain only a small percentage of fibers and frequently do not work at the earliest stages of development.     

Camwood (Baphia nitida) Extract as a Histological Stain for Interglobular Dentine, Striated Muscle, and Counterstaining

The shavings of the dried heartwood of the tree Baphia nitida are ground to a fine powder, and 6 gm of the powder are extracted in 100 ml absolute ethanol at 27-30 for 6-24 hr. The extract is filtered with Whatman No. 1 paper and stored in a screw-capped bottle. For staining the interglobular dentine of nondecalcified sections of formlin-fixed teeth, sawed cross sections 20-30 μ thick were dehydrated in ethanol and stained in the undiluted extract for 6-12 hr at room temperature. The interglobular dentine was stained a bright golden brown on a pale brown background. For staining striated muscle, the extract was diluted 1:1 with distilled water and filtered. After mordanting formalin-fixed paraffin sections with 0.25% KMnO₄ for 5 min, and bleaching with 5% oxalic acid for 10 min, they were washed in water and stained for 2-24 hr at room temperature. The striations were stained light to deep golden brown. For use as a counterstain, a 1:6 dilution of the original extract was required. When applied after haematoxylin for 15-30 min, it stained tissue components in varying shades of golden brown with distribution comparable to that produced by 1% eosin.     

Rapid Detection and Identification of Respiratory Viruses by Direct Immunofluorescence

The use of fluorescein-conjugated antiserum against respiratory syncytial (RS) and parainfluenza 1 and 3 viruses was compared with conventional techniques in the rapid detection of virus in tissue cultures inoculated with pharyngeal specimens known to contain these viruses. Twenty-three specimens were tested: 9 RS, 8 parainfluenza 1, and 6 parainfluenza 3. The fluorescent-antibody technique (FA) detected virus in 52% of the tissue cultures in 24 hr, and, by 72 hr, 22 of the 23 cultures were FA-positive whereas only 5 were positive by conventional techniques. Additionally, conjugated antisera were prepared against herpes simplex, influenza A₂, and adenovirus type 5. All conjugates stained only the homologous virus and were 100- to 10,000-fold more sensitive than conventional techniques in detecting descending dilutions of virus inocula by 24 hr. With the procedures described, several antisera could be conjugated and ready for use within 24 hr. Serum fractionation was by ammonium sulfate precipitation, and with the procedure outlined virtually complete recovery of the globulin fraction and elimination of all of the albumin were accomplished.     

Staining Mitochondria With Hematoxylin After Formalin-Sublimate Fixation; A Rapid Method

Mitochondria were stained in liver, kidney, pancreas, adrenal and intestinal mucosa of rat and mouse. Tissues 1 mm thick, were fixed in a mixture of saturated aqueous HgCl₂, 90 ml; formalin (37-38% HCHO), 10 ml, at room temperature (25°C) for 1 hr. Deparaffinized sections 3-4μ thick were treated with Lugol's iodine (U.S.P.) followed by Na₂S₂O₃ (5%), rinsed in water and the ribonucleic acid removed by any of the following procedures: 0.2 M McIlavaine's buffer, pH 7.0, 2 hr, or 0.2 M phosphate buffer, pH 7.0, 2 hr at 37°C; 0.1% aqueous ribonuclease, 2 hr at 37°C; 5% aqueous trichloracetic acid overnight at 37°C; or 1% KOH at room temperature for 1 hr. After washing in water, sections were treated with a saturated solution of ferric ammonium alum at 37°C for 8-12 hr and colored by Regaud's ripened hematoxylin for 18 hr. They were then differentiated in 1% ferric ammonium alum solution while under microscopic observation.     

Alkaline Phosphatase Activity in Skin, as Shown by Staining En Bloc1

A modification of Gomori's method for alkaline phosphatase was applied to 5-7 mm cubes of fresh, unfixed human skin. Exposure to the substrate of buffered Na-β·glycerophosphate was varied from 8-36 hr, to the 2% Co(NO₃)₃, 2-12 hr; and to ammonium sulfide (containing approximately 1% NH₃), 1-2 hr. Optimum timing for these treatments were found to be 24, 4 and 1 hr, respectively. After staining, blocks were embedded in paraffin and serial sections were made. In such small blocks, the staining was uniform throughout the block. Alkaline phosphatase activity was seen in the walls of the subepidermal and periappendageal capillaries, as well as in the eccrine sweat glands, and did not differ from that seen in stained frozen sections. In particular, there was no loss of specificity and no diffusion of the enzyme.     

The Histological Examination of Mummified Material

Tissue from Egyptian mummy material is extremely brittle; hence it was handled in perforated glass tubes during processing. The first (softening) fluid consisted of 96% ethyl alcohol, 30 vol; 1% aqueous formalin, 50 vol; 5% aqueous Na₂CO₃, 20 vol. It was used in a fluid to tissue volume ratio of 100:1 and allowed to act overnight. A special dehydrating sequence: 80% alcohol, 3-6 hr; 8% phenol in 96% alcohol, and absolute alcohol followed by 3 changes of amyl acetate, 6-18 hr each; 3 changes of 1 % celloidin in methyl benzoate, 24 hr each; then through benzene and embedding in paraffin completed the special technic. This allowed regular sectioning and staining to be done successfully.     

Effects of either glucose or fructose and metabolic regulators on bovine embryo development and lipid accumulation in vitro

Our objective was to determine if replacing glucose with fructose would decrease cytoplasmic lipid accumulation during culture of embryos with or without regulators of metabolism. In vitro-produced bovine zygotes were cultured 60 hr in chemically defined medium-1 (CDM-1) plus 0.5% BSA and 0.5 mM fructose or glucose in Experiment 1, and glucose in Experiment 2. In both experiments, 8-cell embryos were next cultured 135 hr in CDM-2 plus 2 mM fructose or glucose in factorial combination with five treatments: (Experiment 1: control, 10% fetal calf serum (FCS), 0.3 microM phenazine ethosulfate (PES), 30 microM dinitrophenol (DNP), and PES + DNP), and (Experiment 2: control, PES, PES + DNP, and 1 and 3 microg/ml cerulenin (C1 and C3)). Day 7.5 blastocysts were stained with Sudan Black B to quantify cytoplasmic lipid droplets as small (SD, <2 microm), medium (MD, 2-6 microm), or large (LD, >6 microm). Blastocyst rates per oocyte were 22% (Experiment 1) and 15% (Experiment 2) higher (P < 0.05) for fructose than glucose. For Experiment 1, numbers of MD were lower for PES, DNP, and PES + DNP than control and FCS (P < 0.05). LD were lower for PES and DNP than control, and higher for FCS than all other treatments (P < 0.05). For Experiment 2, MD were lower (P < 0.05) for PES, and PES + DNP than C1, C3, and control. For LD, PES was lower (P < 0.05) than control, C1, and C3, but not different from PES + DNP. The only effect of hexose on lipids was that fructose resulted in fewer MD (P < 0.01) in Experiment 2. In conclusion, fructose produced more blastocysts than glucose, and PES reduced lipid accumulation.     

Correlation of immunochemical detection of HPV L1 capsid protein in pap smears with regression of high-risk HPV positive mild/moderate dysplasia

OBJECTIVE: To immunostain Pap smears of high-risk (hr) HPV DNA-positive early squamous lesions for detecting HPV L1 protein. STUDY DESIGN: Routinely stained archival slides from 84 mild and moderate hrHPV DNA-positive dysplasias were immunostained using a panreactive HPV L1 antibody. Follow-up smears were taken from women with remission for a mean period of 22.8 months (range, 6-46). Conization was done in patients with persistence or progression (3 and 48 patients, respectively) after a mean time of 12 months (range, 9-48). RESULTS: Twenty-nine of 84 smears (34.5%) had positively stained squamous epithelial cell nuclei. In 9 of 29 (31%) women progressive disease occurred (2 cervical intraepithelial neoplasia [CIN] 2 and 7 CIN 3 lesions on conization) 20 (69%) had remission. Of the 55 L1-negative cases, 13 (23.6%) had remission, 42 (76.4%) progressed (3 CIN 2, 38 CIN 3, 1 microinvasive carcinoma). The difference in follow-up between L1 positive and negative cases was statistically significant (chi2 test, p< or =0.001). CONCLUSION: Low and moderate dysplastic squamous lesions without immunochemically detectable HPV L1 protein are significantly more likely to progress than are L1-positive cases. Immunochemical L1 capsid detection in routine Pap smears thus offers prognostic information about early dysplastic lesions.     

Azure a-Schiff, Alcian Blue, HIO4-Schiff, Naphthol Yellow S—A Sequential Staining Method for Paraffin Sections

Paraffin sections from tissue fixed 4-12 hr in 10% formalin containing 0.5% cetyl pyridinium chloride, and washed 2 hr, were stained as follows: (1) Hydrolyze in 5 N HCl at room temperature for 8.5-9 min, or use standard Feulgen hydrolysis at 60 C. (2) Stain in azure A-Schiff, 0.5% in bisulfite bleach (1 N HCl, 5; 10% Na₂S₂O₅, 5; and distilled water 90—parts by volume) for 10 min. (3) Place in bisulfite bleach 2 changes, 2 min each; wash in water, 1-2 min. (4) Stain in Alcian blue (0.1% in 0.01 2V HCl, pH 2.0) for 10 min. (5) Place in 0.01 N HCl for 2-3 min; wash in water for 1-2 min. (6) Oxidize in 0.5% HIO₄ for 5 min; wash in water, 1-2 min. (7) Stain in Schiff's leucofuchsiu, 10 min. (8) Treat with bisulfite bleach as in step 3; wash in running water, 10 min. (9) Stain in naphthol yellow S (0.01% in 1% acetic acid) for 1-2 min. (10) Place in 1% acetic acid for 2 min, dehydrate in tertiary butanol, clear and cover. Result: DNA is deep blue; acidic mucins are light blue; neutral polysaccharides, red to magenta; and proteins, yellow. Proper timing of the hydrolysis for the Feulgen reaction is the most critical step. Overhydrolysis results in green nuclei (staining by naphthol yellow S) whereas purplish nuclei are the results of insufficient hydrolysis.     

Double Staining of Plant Materials in Bulk

Ovaries and ovules of Oryza sativa and Zea mays were collected between 9-30 and 10-30 AM, fixed in formalin-acetic-alcohol, stained in Delafield's hematoxylin for 2-4 hr, dehydrated through graded ethanol, counterstained for 3-4 hr either in light green, orange G or fast green (0.05-0.1%) at the 1:1 alcohol-xylene stage and embedded. A few ovaries were hydrolysed in 1 N HCI for 25 min at 60 C, stained in leuco basic fuchsin for 60-90 min, rinsed 3 times with a mixture of: 10% Na₂S₂O₅, 1; N HC1, 1; and distilled water, 18; washed repeatedly in distilled water, dehydrated through graded ethanol, counter-stained for 3-4 hr either with light or fast green (0.05-0.1%) at the 1:1 alcohol-xylene stage and embedded. Microtome sections were cut, ribbons mounted, dried, paraffin removed with xylene, and mounted in balsam. Uniformly stained preparations resulted and the dilute stains gave vivid color contrasts. Large numbers of ovules and ovaries can be processed in a short time, and reliable percentages of viable embryo sacs in normal, sterile and semisterile plants obtained.     

Acid Orcein-Iron and Acid Orcein-Copper Stains for Elastin

Paraffin sections of formol-fixed tissues stained 4-18 hr in 70% alcohol containing 1% orcein and 1% of concentrated (12 N) HCl by volume yield the familiar purple brown elastin and red nuclei on a pink background. When sections so stained are transferred directly from the stain to 70% alcohol containing 0.02% ferric chloride (FeCl₃·6 H₂O) or 0.02% copper sulfate (CuSO₄·5 H₂O) for a 15 sec to 3 min period, elastin coloration is changed to black or reddish black and chromatin staining to reddish black. The procedure can be counterstained with picro-methyl blue to yield blue collagen and reticulum or with our flavianic acid, ferric chloride, acid fuchsin mixture to give deep yellow background and deep red collagen.     

Isolation and Restriction Mapping of a Pseudomonas Plasmid

The effects of the injection of a large amount of N¹ -methylnicotinamide (MNA) (500 mg per kg body weight) on the ratio of N¹ -methyl-4-pyridone-3-carboxamide (4-py) to N¹ -methyl-2-pyridone-5- carboxamide (2-py) excretion, and the activities of 2-py and 4-py forming MNA oxidases were investigated in rats. The injected MN A was excreted very rapidly into the urine; 46 % of the dose was excreted from 0~3hr post-injection, 15% from 3~6hr, 6% from 6~9hr and 1.5% from 9~ 12hr. The ratio of 4-py to 2-py also decreased rapidly; the ratio being about 0.6, 0.4, 0.4 and 0.6 from 0~3hr, 3~6hr, 6~9hr and 9~ 12hr post-injection, respectively. This ratio then recovered rapidly; being about 2, 5.5, 8.5 and 9.7 from 12~24 hr, 24 ~48 hr, 48~72 hr and 72 ~96 hr post-injection, respectively. The normal range of 4-py to 2-py excretion ratio is 8~14. So, this ratio returned to a normal level by day 3 post-injection. The rats were killed 5 hr after the MNA injection. At this time (the lowest ratio was observed around this time), the activities of 2-py and 4-py forming MNA oxidases in the injected group were 59 % and 11 % of the normal levels, respectively. Therefore, it was found that the decreased ratio of 4-py to 2-py excretion with the MNA injection was mainly due to the higher inhibition of the 4-py forming MNA oxidase than of the 2-py forming MNA oxidase by the MNA injection.     

Brazilin-Toluidine Blue O and Hematoxylin-Darrow Red Methods for Brain and Spinal Cord

Tissue fixed in 10% formalin, formalin-95% ethanol 1:s CaCO₂ or phosphate buffer neutralized formalin, or methanol-chloroform 2:1, was dehydrated and embedded in paraffin or double-embedded by infiltration in 1% celloidin followed by a chloroform-paraffin sequence. Sections were attached to slides with either albumen or gelatine adhesive and processed throughout at room temperature of 24-26 C. For either method, mordanting 30-60 min in 1% iron alum was followed by a 10 min wash in 4 changes of distilled water. For brazilin-toluidne blue O, myelin was stained for 20-60 min, depending upon section thickness, in a self-differentiating solution consisting of: 0.15% Li₂CO₃ 75 ml; 6% brazilin in 95% ethanol, 25 ml; and NaIO₃ 75 mg. After a thorough washing, Nissl material was stained for 3-8 min in a solution consisting of: 0.1 M acetic acid, 90 ml; 0.1 M sodium acetate, 10 ml; and 1% toluidine blue 0, 2.5 ml. For hematoxylin-Darrow red, myelin was stained for 2-6 hr in a self-differentiating solution consisting of: 0.15% Li₂,CO₃ 95 ml; 10% hematoxylin in 95% ethanol, 5 ml; and NaIO₃ 25 mg. After a thorough washing, Nissl material was stained for 20 min or less in a solution consisting of: 0.1 M acetic acid, 90 ml; 0.1 M sodium acetate, 10 ml; Darrow red, 25 mg. This mixture was first boiled, cooled to room temperature and filtered. In both methods, washing, dehydration, clearing, and mounting completed the process. In the brazilin-toluidine blue technic, myelin sheaths were stained reddish purple; neuronal nuclei light blue with dark granules of chromatin; nucleoli dark blue; and cytoplasm blue with dark blue Nissl granules. In the hematoxylin-Darrow red procedure, myelin sheaths were blue-black; nuclei light red with dark granules of chromatin; nucleoli almost black; and cytoplasm red with bright red Nissl granules.