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Laboratory Procedures and Management
Published in Jeremy R. Jass, Understanding Pathology, 2020
The solution into which tissue samples are placed usually includes formaldehyde. First introduced in 1893 (Bracegirdle, 1993), formaldehyde penetrates tissues rapidly and alters the structure of molecules so that all biological activity is destroyed. In particular, enzymes are denatured. This is important, because dying tissues would normally release their own enzymes and digest themselves, a process called autolysis. Dying tissues are also colonised by bacteria, but these are also destroyed by formaldehyde. Formaldehyde thereby preserves normal cellular structure and acts as a mordant, i.e. it facilitates the subsequent staining of the tissues with dyes. The entire process is called tissue fixation (since it attempts to ‘fix’ tissue in a lifelike state) and takes a few hours to a day or two, depending on the size of the specimen. Fixation can be speeded up by microwaving the tissue.
Symptom flowcharts and testing guidelines
Published in Sarah Bekaert, Alison White, Integrated Contraceptive and Sexual Healthcare, 2018
Sarah Bekaert, Alison White, Kathy French, Kevin Miles
Staining bottles containing:– crystal violet (the primary stain)– iodine solution (the mordant by forming a crystal violet-iodine complex)– decolouriser (ethanol is a good choice)– safranin (the counterstain)– water (preferably in a squirt bottle or from a specified tap).
Catalog of Herbs
Published in James A. Duke, Handbook of Medicinal Herbs, 2018
Gambir is widely used as a tanning material and is employed medicinally as an astringent. Gambir is the dried, aqueous extract prepared from the leaves and twigs. The drug contains catechutannic acid (22 to 50%) which resembles the tannin in kino (Pterocarpus marsupium Roxb.) and Krameria. Gambir is also used as a mordant in dyeing. In Malaya, it is used for chewing with the betel leaf; some believe it causes the reddening of the mouths of betel chewers. It is often planted in Malaya as well for the aromatic flowers.
Evaluation of different haematoxylin stain subtypes for the optimal microscopic interpretation of cutaneous malignancy in Mohs frozen section histological procedure
Published in British Journal of Biomedical Science, 2021
JA Gabriel, M Shams, GE Orchard
As a part of the Mohs procedure, H&E staining remains the staple method for microscopic evaluation for pathological diagnosis and interpretation of these tumour types. In most cases, the haematoxylin nuclear staining plays an essential role in determining neoplastic disease. The presence of basophilic, hyperchromatic nuclei, apoptotic bodies, mitotic figures and pleomorphism all rely on clear staining to allow the generation of unequivocal diagnoses. The haematoxylin dye is extracted from the bark of the logwood tree Haematoxylin Campechianum, originally located in the Mexican state Campeche [6]. The conversion of haematoxylin to haematin, vital for its ability to bind to nuclear components, is aided by the use of mordants. There are a broad range of mordants which can impact the tissue components stained and colour of staining, which is visualised. The mordants are usually a metal cation such as iron, aluminium, molybdenum, lead and tungsten [7].
Haematoxylin – the story of the blues
Published in British Journal of Biomedical Science, 2018
Hematein is anionic with poor affinity for tissue. It therefore requires the presence of a mordant to impart a positive charge to the dye–mordant complex thus enabling binding to anionic tissue components like nuclear chromatin. The word mordant is derived originally from the word mordere which is Latin and translated to mean ‘to bite’. The French equivalent word is mordre. Mordants are derived from heavy metals such as aluminium, iron, lead, tungsten and molybdenum, etc. [2–4]. They are di/tri valent salts or hydroxides of metals which combine as hydroxides with the dye by displacing a hydrogen atom from the dye (Figure 3). The remaining valences of the mordant serve to attach/bind the dye–mordant complex to the tissue components such as phosphate groups to nucleic acids. The result is a more permanent dye colour [6].
Canalicular system reorganization during mouse platelet activation as revealed by 3D ultrastructural analysis
Published in Platelets, 2021
Irina D. Pokrovskaya, Michael Tobin, Rohan Desai, Smita Joshi, Jeffrey A. Kamykowski, Guofeng Zhang, Maria A. Aronova, Sidney W. Whiteheart, Richard D. Leapman, Brian Storrie
We used state-of-the-art, 3D ultrastructural imaging techniques to examine the reorganization of the canalicular system (CS) in mouse platelets during their isolation and thrombin-induced activation. The CS has been assumed for decades to be 1) an inward, invaginated tubular membrane channel that supports protein and virus entry into and exit from the platelet, 2) a structure that is static during platelet isolation, and 3) the predominant, if not exclusive, source of membrane for platelet surface area expansion during platelet activation. Morphologically, in electron micrographs of thin sections, there is little that intrinsically distinguishes CS from other small, electron lucent, single membrane enclosed structures within the platelet cytoplasm. Emphasis has been placed on interconnections, network properties, and connection to the plasma membrane; all properties that are difficult to detect in electron micrographs of thin sections. Previously studies used mordants (e.g., tannic acid) to coat the platelet plasma membrane and its invaginations to establish cell surface connectivity. That criterion led to ambiguity in assigning platelet fusion events to the plasma membrane vs. canalicular system, since mordants can incompletely stain structures or can be endocytosed. The use of newer 3D-methodologies, recent work with STEM tomography [9] or serial block face imaging [10,11] has yielded results that question the relative importance of CS in granule release during platelet activation. Here, we have used serial block face imaging to generate 3D data sets to test the other assumptions about CS, namely, its stability during platelet isolation and the extent to which it is the membrane source for platelet surface area expansion. Because our image sets were collected in 3D, we were able to filter our quantification of SBF-SEM images on the basis of the added parameter of spatial extension over at least 3 Z-planes, ~100 nm, and hence excluded membrane trafficking and/or other small vesicles from our analysis. Together our qualitative analysis from both SBF- and FIB-SEM images and our quantitative SBF-SEM data strongly indicate that the CS, even in the presence of activation inhibitors, reorganizes during platelet isolation and that the CS redistribution into the plasma membrane can account for only about half the plasma membrane, cell surface expansion seen with thrombin induced platelet activation in vitro.