{"id":476,"date":"2017-05-17T17:00:22","date_gmt":"2017-05-17T20:00:22","guid":{"rendered":"http:\/\/en-mol.icb.usp.br\/?page_id=476"},"modified":"2026-03-22T19:30:17","modified_gmt":"2026-03-22T22:30:17","slug":"1-23-basic-concepts","status":"publish","type":"page","link":"https:\/\/mol-en.icb.usp.br\/index.php\/1-23-basic-concepts\/","title":{"rendered":"1-23 Basic concepts"},"content":{"rendered":"

STAINS USED IN LIGHT MICROSCOPY – 1<\/strong><\/p>\n

Most histological sections must be stained in order to be studied under a light microscope.
\nFor this purpose, numerous dye solutions and dye combinations have been developed. The ones that became most commonly used are those that distinguish the various components of cells as well as of the extracellular matrix (ECM). Many dyes that demonstrate specific cell types or specific cell components were also developed and became very useful. Some dye solutions are composed of one molecule whereas others are solutions of salts in which a part of their molecules exhibits a color. <\/p>\n

One of the most widely used staining procedure, which will be briefly discussed ahead, combines two dyes called hematoxylin<\/strong> and eosin<\/strong>. This technique is called Hematoxylin and eosin staining <\/strong>, very commonly abridged as HE staining<\/strong>.
\nDuring this staining technique the sections are stained initially with a solution of hematoxylin followed by a solution of eosin (the whole staining procedure is actually more complex and will not be discussed here).<\/p>\n

Basic stains<\/strong>
\nLets us imagine a solution of a dye made of salts in which their cation (i.e. the positive part of the salt) has a color. Chemically speaking, these dyes are said to have a basic nature. Examples of cationic or basic dyes: toluidine blue and methylene blue. Hematoxylin<\/strong> is not such a kind of molecule, not even a salt, but in solution it behaves as a basic stain.
\nA solution of toluidine blue, methylene blue or hematoxylin stains components of cells and of the extracellular matrix in a purple\/blue<\/strong> color.
\nWhats happens during the staining procedure of sections?
\nMost commonly, the components of the cells and extracellular matrix that contain many acidic (negative) chemical groups exhibit affinity for the (positive) basic dyes. For this reason, these cell and extracellular structures of the sections are called basophilic<\/strong>, meaning that they are friendly to basic dyes and stain blue\/bluish with the above mentioned stains.
\nExamples of basophilic structures stained by hematoxylin and by basic dyes:
\n– Nuclei<\/strong> and nucleoli<\/strong> are rich in nucleic acids. They have affinity for basic stains and become stained in blue-purple by hematoxylin and by basic dyes.
\n– the ergastoplasm<\/strong> of the citoplasm (the granular endoplasmic reticulum when observed by electron microscopy) contains a lot of ribonucleic acid in its ribosomes and is a basophilic component of the cytoplasm of many cell types. It stains blue\/bluish by hematoxylin.
\n– the extracellular matrix of the hyaline cartilage<\/strong> contains many molecules that have acidic groups and stains blue\/bluish with hematoxylin.<\/p>\n

Acidic stains<\/strong>
\nThe negatively charged acidic dyes, also called acid dyes<\/strong>, are another important group of stains. The (negative) anionic portion of their salt is colored or it is a molecule that behaves as an acid. Examples: eosin, orange G.
\nComponents of sections that are stained by acidic dyes are called acidophilic<\/strong> structures or eosinophilic<\/strong> when stained with eosin.<\/p>\n

Examples of acidophilic structures:
\n– the cytoplasm<\/strong> is aproximately basic as well as its mitochondria<\/strong> and some other organelles.
\nFor this reason, the cytoplasm of most cells stains pink, red or orange by eosin after being stained with hematoxylin and eosin.
\nSimilarly the collagen fibers<\/strong> of the connective tissue. For this reason the extracellular matrix, which in most tissues contains much collagen protein, is stained pink-orange by eosin.<\/p>\n

A warning:<\/strong>
\nThe classification of acidic and basic dyes mentioned above does not apply to all dyes and dye mixtures.
\nIn addition, HE staining is generic and does not distinguish the components of cells known as organelles, except for the nucleus, nucleolus and the ergastoplasm. Other organelles (lysosomes, Golgi complex, etc.) need to be treated with special stains or techniques in order to be observed under a light microscope.<\/p>\n

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STAINS USED IN LIGHT MICROSCOPY – 1 Most histological sections must be stained in order to be studied under a light microscope. For this purpose, numerous dye solutions and dye combinations have been developed. The ones that became most commonly used are those that distinguish the various components of cells as well as of the […]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-476","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/pages\/476","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/comments?post=476"}],"version-history":[{"count":76,"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/pages\/476\/revisions"}],"predecessor-version":[{"id":21188,"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/pages\/476\/revisions\/21188"}],"wp:attachment":[{"href":"https:\/\/mol-en.icb.usp.br\/index.php\/wp-json\/wp\/v2\/media?parent=476"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}