1.
Eosin
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In addition to staining proteins in the cytoplasm, it can be used to stain collagen and muscle fibers for examination under the microscope. Structures that stain readily with eosin are termed eosinophilic, the name Eosin comes from Eos, the Ancient Greek word for dawn and the name of the Ancient Greek goddess of the dawn. There are actually two closely related compounds commonly referred to as eosin. Most often used is Eosin Y, it has a slightly yellowish cast. The other eosin compound is eosin B, it has a faint bluish cast. The two dyes are interchangeable, and the use of one or the other is a matter of preference, Eosin Y is a tetrabromo derivative of fluorescein. Eosin B is a dibromo dinitro derivative of fluorescein, Eosin is most often used as a counterstain to hematoxylin in H&E staining. H&E staining is one of the most commonly used techniques in histology, tissue stained with haematoxylin and eosin shows cytoplasm stained pink-orange and nuclei stained darkly, either blue or purple. Eosin also stains red blood cells intensely red, for staining, eosin Y is typically used in concentrations of 1 to 5 percent weight by volume, dissolved in water or ethanol. For prevention of growth in aqueous solutions, thymol is sometimes added. A small concentration of acetic acid gives a deeper red stain to the tissue. It is listed as an IARC class 3 carcinogen, romanowsky stain Merbromin Jocelyn H. Bruce-Gregorios, M. D. Histopathologic Techniques, JMC Press Inc
2.
Toxoplasma gondii
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Toxoplasma gondii is an obligate intracellular, parasitic alveolate that causes the disease toxoplasmosis. For example, previous estimates have shown the highest prevalence of persons infected to be in France, although mild, flu-like symptoms occasionally occur during the first few weeks following exposure, infection with T. gondii produces no readily observable symptoms in healthy human adults. This asymptomatic state of infection is referred to as a latent infection and has recently been associated with numerous subtle adverse or pathological behavioral alterations in humans, in infants, HIV/AIDS patients, and others with weakened immunity, infection can cause a serious and occasionally fatal illness, toxoplasmosis. T. gondii has been shown to alter the behavior of infected rodents in ways that increase the chances of being preyed upon by felids. Support for this hypothesis stems from studies showing T. gondii-infected rats have a decreased aversion to cat urine. The rats would not shy away from areas where cats live, widespread histone-lysine acetylation in cortical astrocytes appears to be another epigenetic mechanism employed by T. gondii. Differences in aversion to cat urine are observed between non-infected and infected humans and sex differences within these groups were apparent, as well, because T. gondii can sexually reproduce only within cats, they are defined as the definitive host of T. gondii. All other hosts – hosts in which asexual reproduction can occur – are defined as intermediate hosts. When a member of the cat family is infected with T. gondii, inside these intestinal cells, the parasites undergo sexual development and reproduction, producing millions of thick-walled, zygote-containing cysts known as oocysts. Infected epithelial cells eventually rupture and release oocysts into the intestinal lumen, oocysts can then spread to soil, water, food, or anything potentially contaminated with the feces. Highly resilient, oocysts can survive and remain infective for many months in cold, ingestion of oocysts by humans or other warm-blooded animals is one of the common routes of infection. Humans can be exposed to oocysts by, for example, consuming unwashed vegetables or contaminated water, although cats can also be infected by ingesting oocysts, they are much less sensitive to oocyst infection than are intermediate hosts. T. gondii is considered to have three stages of infection, the stage of rapid division, the bradyzoite stage of slow division within tissue cysts. Tissue cysts in tissues such as brain and muscle tissue, form approximately 7–10 days after initial infection, inside host cells, the tachyzoites replicate inside specialized vacuoles created during parasitic entry into the cell. Tachyzoites multiply inside this vacuole until the host cell dies and ruptures, releasing and spreading the tachyzoites via the bloodstream to all organs and tissues of the body, inside host cells, clusters of these bradyzoites are known as tissue cysts. The cyst wall is formed by the vacuole membrane. Although bradyzoite-containing tissue cysts can form in any organ, tissue cysts predominantly form and persist in the brain, the eyes. Cysts usually range in size between five and 50 µm in diameter, consumption of tissue cysts in meat is one of the primary means of T. gondii infection, both for humans and for meat-eating, warm-blooded animals
3.
American and British English spelling differences
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Many of the differences between American and British English date back to a time when spelling standards had not yet developed. For instance, some spellings seen as American today were once used in Britain. But English-language spelling reform has rarely been adopted otherwise, and thus modern English orthography varies somewhat between countries and is far from phonemic in any country, in the early 18th century, English spelling was inconsistent. These differences became noticeable after the publishing of influential dictionaries, todays British English spellings mostly follow Johnsons A Dictionary of the English Language, while many American English spellings follow Websters An American Dictionary of the English Language. Webster was a proponent of English spelling reform for reasons both philological and nationalistic, in A Companion to the American Revolution, John Algeo notes, it is often assumed that characteristically American spellings were invented by Noah Webster. He was very influential in popularizing certain spellings in America, rather he chose already existing options such as center, color and check for the simplicity, analogy or etymology. William Shakespeares first folios, for example, used spellings like center and color as much as centre, Webster did attempt to introduce some reformed spellings, as did the Simplified Spelling Board in the early 20th century, but most were not adopted. In Britain, the influence of those who preferred the Norman spellings of words proved to be decisive, later spelling adjustments in the United Kingdom had little effect on todays American spellings and vice versa. For the most part, the systems of most Commonwealth countries. Australian spelling has also strayed slightly from British spelling, with some American spellings incorporated as standard, New Zealand spelling is almost identical to British spelling, except in the word fiord. There is also an increasing use of macrons in words that originated in Māori, most words ending in an unstressed -our in British English end in -or in American English. Wherever the vowel is unreduced in pronunciation, e. g. contour, velour, paramour and troubadour the spelling is the same everywhere, most words of this kind came from Latin, where the ending was spelled -or. They were first adopted into English from early Old French, after the Norman conquest of England, the ending became -our to match the Old French spelling. The -our ending was not only used in new English borrowings, however, -or was still sometimes found, and the first three folios of Shakespeares plays used both spellings before they were standardised to -our in the Fourth Folio of 1685. After the Renaissance, new borrowings from Latin were taken up with their original -or ending, Websters 1828 dictionary had only -or and is given much of the credit for the adoption of this form in the United States. Johnson, unlike Webster, was not an advocate of spelling reform and he preferred French over Latin spellings because, as he put it, the French generally supplied us. In Jeffersons original draft it is spelled honour, Honor and honour were equally frequent in Britain until the 17th century, honor still is, in the UK, the usual spelling as a persons name and appears in Honor Oak, a district of London. In derivatives and inflected forms of the words, British usage depends on the nature of the suffix used
4.
Staining
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Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image. Stains and dyes are used in biology and medicine to highlight structures in biological tissues for viewing. Stains may be used to define and examine bulk tissues, cell populations, in biochemistry it involves adding a class-specific dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes, biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Simple staining is staining with only one stain/dye, there are various kinds of multiple staining, many of which are examples of counterstaining, differential staining, or both, including double staining and triple staining. In vivo staining is the process of dyeing living tissues—in vivo means in life, by causing certain cells or structures to take on contrasting colour, their form or position within a cell or tissue can be readily seen and studied. In vitro staining involves colouring cells or structures that have removed from their biological context. Certain stains are often combined to reveal more details and features than a single stain alone, combined with specific protocols for fixation and sample preparation, scientists and physicians can use these standard techniques as consistent, repeatable diagnostic tools. A counterstain is stain that makes cells or structures more visible, for example, crystal violet stains only Gram-positive bacteria in Gram staining. A safranin counterstain is applied that stains all cells, allowing identification of Gram-negative bacteria, while ex vivo, many cells continue to live and metabolize until they are fixed. Some staining methods are based on this property and those stains excluded by the living cells but taken up by the already dead cells are called vital stains. Those that enter and stain living cells are called supravital stains, however, these stains are eventually toxic to the organism, some more so than others. To achieve desired effects, the stains are used in very dilute solutions ranging from 1,5000 to 1,500000, note that many stains may be used in both living and fixed cells. The preparatory steps involved depend on the type of analysis planned, fixation–which may itself consist of several steps–aims to preserve the shape of the cells or tissue involved as much as possible. Sometimes heat fixation is used to kill, adhere, and alter the specimen so it accepts stains, most chemical fixatives generate chemical bonds between proteins and other substances within the sample, increasing their rigidity. Common fixatives include formaldehyde, ethanol, methanol, and/or picric acid, pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices. Permeabilization involves treatment of cells with a mild surfactant and this treatment dissolves cell membranes, and allows larger dye molecules into the cells interior. Mounting usually involves attaching the samples to a microscope slide for observation
5.
Histology
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Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is commonly performed by examining cells and tissues under a microscope or electron microscope, the specimen having been sectioned, stained. Histological studies may be conducted using tissue culture, where human or animal cells are isolated and maintained in an artificial environment for various research projects. The ability to visualize or differentially identify microscopic structures is frequently enhanced through the use of histological stains, histology is an essential tool of biology and medicine. Trained physicians, frequently licensed pathologists, are the personnel who perform histopathological examination and their field of study is called histotechnology. In the 17th century, Italian Marcello Malpighi invented one of the first microscopes for studying tiny biological entities, Malpighi analysed several parts of the organs of bats, frogs and other animals under the microscope. Malpighi, while studying the structure of the lung, noticed its membranous alveoli and his discovery established how the oxygen we breathe enters the blood stream and serves the body. In the 19th century, histology was a discipline in its own right. The French anatomist Bichat introduced the concept of tissue in anatomy in 1801, the 1906 Nobel Prize in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal. They had dueling interpretations of the structure of the brain based in differing interpretations of the same images. Cajal won the prize for his theory and Golgi for the staining technique he invented to make it possible. There are four types of animal tissues, muscle tissue, nervous tissue, connective tissue. All tissue types are subtypes of these four basic tissue types and their structure is very different from animal tissues. The most common fixative for light microscopy is 10% neutral buffered formalin, for electron microscopy, the most commonly used fixative is glutaraldehyde, usually as a 2. 5% solution in phosphate buffered saline. These fixatives preserve tissues or cells mainly by irreversibly cross-linking proteins and this can be detrimental to certain histological techniques. Further fixatives are often used for electron microscopy such as osmium tetroxide or uranyl acetate Formalin fixation leads to degradation of mRNA, miRNA and DNA in tissues, however, extraction, amplification and analysis of these nucleic acids from formalin-fixed, paraffin-embedded tissues is possible using appropriate protocols. Frozen section procedure is a way to fix and mount histology sections using a refrigeration device called a cryostat. It is often used after surgical removal of tumors to allow determination of margin
6.
Medical diagnosis
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Medical diagnosis is the process of determining which disease or condition explains a persons symptoms and signs. It is most often referred to as diagnosis with the context being implicit. The information required for diagnosis is typically collected from a history, often, one or more diagnostic procedures, such as diagnostic tests, are also done during the process. Sometimes Posthumous diagnosis is considered a kind of medical diagnosis, Diagnosis is often challenging, because many signs and symptoms are nonspecific. For example, redness of the skin, by itself, is a sign of many disorders, thus differential diagnosis, in which several possible explanations are compared and contrasted, must be performed. This involves the correlation of various pieces of information followed by the recognition and differentiation of patterns, occasionally the process is made easy by a sign or symptom that is pathognomonic. Diagnosis is a component of the procedure of a doctors visit. From the point of view of statistics, the procedure involves classification tests. The first recorded examples of medical diagnosis are found in the writings of Imhotep in ancient Egypt, a Babylonian medical textbook, the Diagnostic Handbook written by Esagil-kin-apli, introduced the use of empiricism, logic and rationality in the diagnosis of an illness or disease. Traditional Chinese Medicine, as described in the Yellow Emperors Inner Canon or Huangdi Neijing, specified four diagnostic methods, inspection, auscultation-olfaction, interrogation, hippocrates was known to make diagnoses by tasting his patients urine and smelling their sweat. This article uses diagnostician as any of these person categories, a diagnostic procedure does not necessarily involve elucidation of the etiology of the diseases or conditions of interest, that is, what caused the disease or condition. Such elucidation can be useful to optimize treatment, further specify the prognosis or prevent recurrence of the disease or condition in the future, the initial task is to detect a medical indication to perform a diagnostic procedure. Indications include, Detection of any deviation from what is known to be normal, such as can be described in terms of, for example, anatomy, physiology, pathology, psychology, a complaint expressed by a patient. The fact that a patient has sought a diagnostician can itself be an indication to perform a diagnostic procedure, even during an already ongoing diagnostic procedure, there can be an indication to perform another, separate, diagnostic procedure for another, potentially concomitant, disease or condition. A diagnostic test is any kind of medical test performed to aid in the diagnosis or detection of disease, Diagnostic tests can also be used to provide prognostic information on people with established disease. Processing of the answers, findings or other results, consultations with other providers and specialists in the field may be sought. There are a number of methods or techniques that can be used in a diagnostic procedure, in reality, a diagnostic procedure may involve components of multiple methods. The final result may also remain a list of possible conditions, the resultant diagnostic opinion by this method can be regarded more or less as a diagnosis of exclusion
7.
Pathology
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Pathology is a significant component of the causal study of disease and a major field in modern medicine and diagnosis. Similarly, a condition is one caused by disease, rather than occurring physiologically. A physician practicing pathology is called a pathologist, as a field of general inquiry and research, pathology addresses four components of disease, cause, mechanisms of development, structural alterations of cells, and the consequences of changes. Further divisions in specialty exist on the basis of the involved sample types, organs, the sense of the word pathology as a synonym of disease or pathosis is very common in health care. The persistence of this usage despite attempted proscription is discussed elsewhere, the study of pathology, including the detailed examination of the body, including dissection and inquiry into specific maladies, dates back to antiquity. Notably, many advances were made in the era of Islam, during which numerous texts of complex pathologies were developed. By the 17th century, the study of microscopy was underway and examination of tissues had led British Royal Society member Robert Hooke to coin the word cell, setting the stage for later germ theory. However, pathology as an area of specialty was not fully developed until the late 19th and early 20th centuries. This realization led to the understanding that diseases are able to replicate themselves. To determine causes of diseases, medical experts used the most common and widely accepted assumptions or symptoms of their times, by the late 1920s to early 1930s pathology was deemed a medical specialty. The modern practice of pathology is divided into a number of subdisciplines within the discrete but deeply interconnected aims of biological research, anatomical pathology is itself divided into subfields, the main divisions being surgical pathology, cytopathology, and forensic pathology. Sometimes, pathologists practice both anatomical and clinical pathology, a known as general pathology. Cytopathology is a branch of pathology that studies and diagnoses diseases on the cellular level, however, cytology samples may be prepared in other ways, including cytocentrifugation. Dermatopathology is a subspecialty of pathology that focuses on the skin. It is unique, in there are two paths a physician can take to obtain the specialization. The completion of this allows one to take a subspecialty board examination. Dermatologists are able to recognize most skin diseases based on their appearances, anatomic distributions, sometimes, however, those criteria do not lead to a conclusive diagnosis, and a skin biopsy is taken to be examined under the microscope using usual histological tests. One of the greatest challenges of dermatopathology is its scope, more than 1500 different disorders of the skin exist, including cutaneous eruptions and neoplasms
