Biomedical subjects

R W Horobin

Publications and source records attributed to R W Horobin.

At least 73 records · Page 4Linked to original sources

PubMed1976

An alcohol-soluble Schiff's reagent: a histochemical application of the complex between Schiff's reagent and phosphotungstic acid.

A schedule for staining partially hydrated PAS-positive structures using non-aqueous solutions has been devised. Tissues are dewaxed, taken down to 70% alcohol, oxidised for 10 min in a 1% w/v alcoholic solution of periodic acid, treated with an alcoholic solution of phosphotungstic acid-Schiff reagent complex (PTA-Schiff reagent) for 25 min, washed in alcohol, cleared in xylene and mounted in a synthetic medium. The PTA-Schiff reagent complex prepared from de Tomasi Schiff reagent by precipitation with PTA may be stored in the deep freeze for many months and dissolved freshly in alcohol for use. The PTA-Schiff reagent used as above allows staining of highly water soluble materials such as dextran. From blocking and digestion studies the mode of action seems similar to de Tomasi Schiff reagent. The partial hydration of the tissues prior to reaction was found to be essential for effective staining.

Alcohols↗

PubMed1976

The influence of the embedding medium when staining for electron microscopy: the penetration of stains into plastic sections.

Using a sectioned-section procedure it was found that only a few structures, e.g. the connective tissue elements, were deeply penetrated by phosphotungstic acid (PTA) and uranyl acetate (UA). Reynold's lead citrate appeared to penetrate more generally. Using stains selective for the embedding medium, and also observing the surfaces of shadowed sections, it was concluded that structures readily penetrated by polar stains were only poorly infiltrated by non-polar embedding media. It is argued that this differential infiltration leading to differential penetration by polar stains largely controls the pattern of staining of ultrathin sections by PTA and UA.

Animals↗

PubMed1975

Staining banded human chromosomes with Romanovsky dyes: some practical consequences of the nature of the stain.

Chromatographic analyses of commercial samples of Romanovsky stains were followed by various chemical and staining studies. Strong banding of chromosomes was found to be favoured by the presence in the stain of high concentrations of methylene violet Bernthsen and its immediate homologues. Chromatographic analysis showed that these dyes are present in dry Leishman and Giemsa powders only in small proportion. However, additional active dye may be generated during the process of making up staining solutions from the dry powders, if the methanol used is not contaminated with formic acid and if the period of heating is not too brief.

Chromatography↗

PubMed1975

Thin layer chromatography of certain preformed metal complex dyes used in biological staining.

Thin-layer chromatographic systems are described for the analysis of various performed metal complex dyes (aluminon-chromium (III), carminic acid-aluminum, carminic acid-chromium (III), carminic acid-iron (III), celestine blue-chromium (III), gallamine blue-chromium (III), gallocyanin-chromium (III), hematein-aluminum, hematein-chromium (III), purpurin-aluminum) and their parent dyes. Certain of these dyes have also been analysed by agar-gel electrophoresis or gel-filtration chromatography. The merits of the three analytical methods are discussed.

Aluminum↗

PubMed1975

The use of a basic dye (azure A or toluidine blue) plus a cationic surfactant for selective staining of RNA: a technical and mechanistic study.

Selective purple staining of RNA-rich structures such as basophilic cytoplasms of exocrine pancreas and plasma cells, Nissl substance, and nucleoli was achieved by treating tissue sections as follows. Stain dewaxed sections for 1/2 hour in a dyebath containing 0.1% w/v axure A or toluidine blue and 1% cationic surfactant (Hyamine 2389, a 50% w/v aqueous solution of diisobutylphenoxyethoxyethyldimethylbenzylammonium chloride; or benzyldimethylammonium chloride, or cetylpyridinium bromide, or cetyltrimethylammonium bromide) buffered to pH 7 with phosphate. Rinse in water, blot, air dry and mount in synthetic resin. Intense purple staining of RNA-rich regions occurred after fixation in neutral formalin or in Carnoy's or Gendre's fluids, though satisfactory results were also found after fixation in acetone or alcohol. Chromatin generally stained a very pale azure after all fixations, though occasionally nuclei were unstained (Gendre's or Zenker's fluids). Subjecting tissue sections to acid hydrolysis or to digestion by RNAase eliminated or reduced the purple staining, but left the azure staining of nuclei unaffected. Satisfactory staining of RNA-rich structures was not critically dependent on the precise concentrations of dye, surfactant or inorganic salts in the dyebath, nor on pH, staining time or chemical nature of the surfactant. The staining patterns can be rationalized with a tissue model that considers both surface charge and permeability factors, since present in the dyebath are small dye cations and large cationic surfactant micelles. As micelles and dye will both quickly penetrate basophilic structures considered to be porous, such as chromatin, competition will then greatly reduce staining of such substrates. But the large micelles will only slowly penetrate regions considered to be more impermeable, such as basophilic cytoplasms, so consequently small fast moving dye ions may enter and stain without competition.

Animals↗

PubMed1974