A technique for fluorescence microscopy in semithin sections

We describe here a procedure to improve contrast and resolution in fluorescence microscopy of sectioned tissues. Tissue fragments were fixed in ethanol-glacial acetic acid, embedded in diethylene glycol distearate, and semithin sectioned. This method maintains tissue antigenicity while preserving the structure of cells and tissues. The thinness of the sections eliminates scattered and emitted light from tissue structures outside the plane of focus. The procedure is simple and quick, and works excellently with fluorescein-conjugated lectins and antibodies.     

Improved staining procedures for semithin epoxy sections of plant tissues.

Improved and reliable methods are described for staining semithin sections of plant materials fixed in glutaraldehyde-osmium and embedded in epoxy resins. One-micron sections are fixed to slides, stained with a two-solution hematoxylin procedure or with a methylene blue-azure A combination, counterstained in aqueous safranin O, cleared, and mounted permanently. Basophilic tissue components are stained gray to black by the hematoxylin and blue or purple by the methylene blue-azure A combination; cell wall structures are colored by the safranin. With the procedures recommended, stains are sharp and intense, sections are flat, wrinkling and loss are held to a minimum, and unsightly precipitates do not form.     

A simple impregnation technique for thin and semithin enterochromaffin cells in sections

Constant, intense and precise impregnation of enterochromaffin (EC) cells was achieved simply by floating thin or semithin sections of gut mucosa, fixed in osmium tetroxide or in glutaraldehyde with postfixation in osmium, on a silver nitrate or proteinate solution. EC cells alone showed impregnation in the light microscope. In the electron microscope, impregnation affected not only the secretory granules of EC cells but also, although much more faintly, those of other, non-EC cells (D, X, D1, G and other cells). Lysosomes also showed partial or total reactivity. Oxidation reduced but did not entirely suppress EC cell staining and had no effect on non-EC endocrine cell staining. Since the reaction did not occur with glutaraldehyde alone, osmium appeared to be a crucial component of the process. These findings should be borne in mind in applying Thiery's method for vicinal glycol groups to the type of study material used in these experiments.     

A simple impregnation technique for thin and semithin enterochromaffin cells in sections

Summary Constant, intense and precise impregnation of enterochromaffin (EC) cells was achieved simply by floating thin or semithin sections of gut mucosa, fixed in osmium tetroxide or in glutaraldehyde with postfixation in osmium, on a silver nitrate or proteinate solution. EC cells alone showed impregnation in the light microscope. In the electron microscope, impregnation affected not only the secretory granules of EC cells but also, although much more faintly, those of other, non-EC cells (D, X, D₁, G and other cells). Lysosomes also showed partial or total reactivity. Oxidation reduced but did not entirely suppress EC cell staining and had no effect on non-EC endocrine cell staining. Since the reaction did not occur with glutaraldehyde alone, osmium appeared to be a crucial component of the process. These findings should be borne in mind in applying Thiery's method for vicinal glycol groups to the type of study material used in these experiments.     

A simple polychrome stain for conventionally fixed Epon-embedded tissues.

The described technique, based upon a one-step Mallory-Heidenhain stain, can be applied as a routine stain for glutaraldehyde or OsO4 fixed, Epon embedded tissues of various organs. The technique consists of a short treatment of the sections with H2O2, a nuclear staining with celestine blue B and a final staining in a modified Cason's solution. The different tissue and cell components are displayed as follows: dark brown nuclei, yellow cytoplasm, red collagen fibers and blue elastic fibers. Intracytoplasmic components as glycogen and mucus are stained respectively blue and violet, whereas other inclusions such as leucocyte granules are colored orange to red.     

Immunocytochemical technique for protein localization in sections of plant tissues

There is a growing demand for methods that allow rapid and reliable in situ localization of proteins in plant cells. The immunocytochemistry protocol presented here can be used routinely to observe protein localization patterns in tissue sections of various plant species. This protocol is especially suitable for plant species with more-complex tissue architecture (such as maize, Zea mays), which makes it difficult to use an easier whole-mount procedure for protein localization. To facilitate the antibody-antigen reaction, it is necessary to include a wax-embedding and tissue-sectioning step. The protocol consists of the following procedures: chemical fixation of tissue, dehydration, wax embedding, sectioning, dewaxing, rehydration, blocking and antibody incubation. The detailed protocol, recommended controls and troubleshooting are presented here, along with examples of applications.     

Use of semithin sections for the histochemical study of carbohydrate-containing biopolymers in cells and tissues with the aid of lectins

A sensitive method of histochemical analysis of cellular and tissue glycoconjugates on semithin sections using lectins is suggested. For fixation tissue bioptates were incubated for 4 h in a 2.5% glutaraldehyde in phosphate buffered saline (PBS) at 4 degrees C, then washed for 1 h in 0.2 M glycine in PBS. After epon-araldite embedment and preparation of semithin sections, the resin was removed in saturated ethanol-KOH solution during 5-10 s. Endogenous perooxidase was inactivated in methanol containing 0.3% H2O2. For identification of lectin-binding sites semithin sections were incubated for 30 min in a 0.005% solution of lectin-peroxidase conjugate in PBS and visualized by 0.05% diaminobezidine solution in PBS, containing 0.015% H2O2. The method described ensures good preservation of cellular and tissue glycoconjugates and is highly specific and sensitive.     

A rapid method for staining semithin tissue sections embedded in araldite

A new rapid method is proposed for staining of semithin sections. The method involves the treatment of sections with a methylene blue solution with a slight heating for 1-3 minutes. The method allows to receive polychromatic contrast preparations, to save time and reagents. It also permits to avoid restaining effect. The preparations can be preserved for a long time in plastic media (e.g. in polystyrene) for light microscopy. A comparative analysis of the staining methods used in the electron microscopic practice is given.     

A rapid method for resectioning of semithin large epoxy sections for electron microscopy

A simple and rapid method is described for resectioning semithin large epoxy tissue sections. Six-micron thick sections are cut, floated on a polystyrene coverslip, and stained with toluidine blue. The coverslip is trimmed to the size of a BEEM capsule cap and placed section face-up inside the cap. A BEEM capsule with the conical end cut off is fitted onto the cap, filled with plastic and polymerized. The capsule and coverslip are trimmed off and thin sectioning is performed. This method allows the study of multiple tissue lesions in their entirety, i.e. serially from beginning to end, without sacrificing any part during trimming as in conventional thin sectioning.     

Transmission light microscopy of structurally colored semithin cartilage sections

 Conversion of osmified tracheal cartilage constituents into an array of laminar interference gratings has been attained by three tandem reactions. Oxidation of semithin, LR white-embedded cartilage sections by acetic anhydride in dimethyl sulfoxide is the first step in the conversion process. Subsequent addition reactions of oxidized cartilage pyranoses and furanoses with thiocarbohydrazide constitutes the second step. Reduction of silver proteinate by thiocarbohydrazones and the concomitant coating of cartilage constituents with silver gratings completes the conversion of cartilage sections into a system of layered interference filters. In transmitted light, all components of converted cartilage display vivid structural colors, which allow detailed microscopic analysis of structurally colored cellular and extracellular cartilage constituents. Accepted: 10 June 1997     

Postmortem diagnostics of renal diseases from semithin sections.

For the light microscopic postmortem study of mostly glomerular renal diseases, in addition to the paraffin technique, 0.5 mu thick (semithin) sections from material fixed in buffered formaldehyde and embedded in methacrylate or Durcupan ACM were used. The method allows for eventual electron microscopic examinations. The semithin sections were stained with methylene blue combined with basic fuchsin, as well as with periodic acid-silver methamine. The method is not a substitution, but the supplementation of the paraffin technique and is suited for the clarification of numerous fine details: in some cases the exact diagnosis was made in this way.     

Bromobimanes--fluorescent labeling agents for histochemical detection of sulfur containing neuropeptides in semithin sections

Sulfur containing neuropeptides could be demonstrated in semithin sections of invertebrate nervous tissue, especially of gastropods, by using the bromobimanes as fluorescent labeling agents for thiol groups. Semithin sections showed a brilliant fluorescence of labeled peptides and should be used if an excellent resolution is important. The three bromobimanes (MB: monobromobimane, DB: dibromobimane, MQ: monobromotrimethylammoniobimane) gave positive results under our experimental conditions. Dibromobimane (DB) was selected because the application is more convenient. In gastropods, the bromobimane technique seems to be the most specific and sensitive one compared to the classical neurosecretory staining methods. Neuropeptides with sulfur containing amino acids could be demonstrated in perikarya, axons, and axon swellings easily. We suppose that there are neurons--not stainable by the classical methods--which can be identified as peptidergic ones by the bromobimane technique. A slight reduction of fluorescence intensity (fading) was observed. So, the fading rate was determined for dibromobimane reaction products; a decrease in the fluorescence intensity of 50% was only reached after 1 h using a Neofluar objective 10/0.30. Nevertheless, we suppose that a comparative quantification of the labeled neuropeptides should be possible if special parameters are considered.