The document discusses tissue fixation and fixatives. It defines a fixative as a substance that prevents post-mortem changes and preserves the morphological and chemical characteristics of cells and tissues. The aims of fixation include preserving tissues as close to their living state as possible and preventing autolysis and bacterial attack. Common methods of fixation discussed are immersion, perfusion, heat, and vapor fixation. Types of fixatives covered include formaldehyde, alcohols, picric acid, mercuric chloride, and glutaraldehyde. Factors that influence fixation quality like fixation time and temperature are also addressed.
Fixatives are chemicals used to preserve biological tissues from decay. They terminate biochemical reactions and may increase mechanical strength. Fixatives disable enzymes and protect samples from damage. Common fixatives include formaldehyde, glutaraldehyde, osmium tetroxide, alcohols, and picric acid. Fixation aims to inhibit autolysis, preserve tissues, harden them, and improve staining. Factors like temperature, concentration, and duration impact fixation quality. Different tissues require specific fixatives for optimal preservation. An ideal fixative kills cells quickly without damage, penetrates rapidly, prevents decay, hardens tissues, and allows long-term storage.
This document discusses tissue processing and fixation. It begins by introducing tissue fixation and its objectives, such as preventing degradation and maintaining morphology. It then describes various fixation methods and factors that affect fixation quality. Common fixatives are discussed, including formaldehyde, glutaraldehyde, Zenker's solution and Bouin's solution. Fixation protocols for specific tissues like brain, breast, lung and kidney are also reviewed. The document emphasizes the importance of proper fixation for histological examination.
The document provides information on cerebrospinal fluid (CSF) examination including indications, collection, analysis, and findings in different conditions like meningitis. It discusses three clinical cases. For case 1, the diagnosis is bacterial meningitis based on cloudy CSF, low glucose, and high neutrophil count. Further tests would include cultures and sensitivity. For case 2, the diagnosis is viral meningitis (measles) based on clear CSF, normal glucose, and lymphocytic pleocytosis; complications include encephalitis. For case 3, the diagnosis is tuberculous meningitis based on low glucose, low chloride, and lymphocytic pleocytosis; confirmation requires microbiological tests.
This method is used to visualise the localisation and quantity of a protein of interest. The target protein is bound to by a specific primary antibody, which in turn is detected by a secondary antibody conjugated to a fluorophore. A fluorescent or confocal microscope is used to visualise the protein.
Immunocytochemistry (ICC) differs from immunohistochemistry (IHC) in that the former is performed on samples of intact cells that have had most, if not all, of their surrounding extracellular matrix removed. In contrast, immunohistochemical samples are sections of biological tissue, where each cell is surrounded by tissue architecture and other cells normally found in the intact tissue. These differences cause the samples to be prepared differently. For ICC, the sample requires permeabilisation so that the antibodies can reach the intracellular targets. Depending on the thickness of the sample, IHC samples do not require this.
Do you have a technical question? Get in touch: info@stjohnslabs.com
This document discusses enzymes and enzyme histochemistry techniques. It defines enzymes and their classifications including hydrolases, oxidoreductases, transferases, and lyases. It then demonstrates the histochemical localization of alkaline phosphatase and acid phosphatase in tissues. The optimal fixation, incubation, and interpretation of results are described. Finally, it lists some diagnostic applications of enzyme histochemistry and provides sample multiple choice questions.
This document discusses cytopreparatory techniques for cytology samples. It describes the different types of cytology samples like exfoliative cytology, aspiration cytology, and body fluids. The key steps in cytopreparatory techniques are outlined as evaluation of specimens, preparation of smears, fixation, and staining. Factors that can affect optimal cytological preparation like quality of specimen, fixative used, and stains are also summarized. Different fixation techniques including dry, wet, liquid-based, and lysing fixation for bloody samples are explained.
This document provides an overview of the process of histopathology. It discusses the key steps: sample collection and fixation, processing including dehydration, clearing, infiltration and embedding, sectioning of samples, and staining. Common techniques and agents used at each step are outlined, such as formalin for fixation, alcohol and acetone for dehydration, xylene for clearing, and paraffin for infiltration and embedding. Hematoxylin and eosin staining is described as the standard staining method, along with Pap staining and Toluidine blue staining. Finally, storage of slides and blocks in refrigerated boxes is mentioned.
The document discusses tissue fixation and fixatives. It defines a fixative as a substance that prevents post-mortem changes and preserves the morphological and chemical characteristics of cells and tissues. The aims of fixation include preserving tissues as close to their living state as possible and preventing autolysis and bacterial attack. Common methods of fixation discussed are immersion, perfusion, heat, and vapor fixation. Types of fixatives covered include formaldehyde, alcohols, picric acid, mercuric chloride, and glutaraldehyde. Factors that influence fixation quality like fixation time and temperature are also addressed.
Fixatives are chemicals used to preserve biological tissues from decay. They terminate biochemical reactions and may increase mechanical strength. Fixatives disable enzymes and protect samples from damage. Common fixatives include formaldehyde, glutaraldehyde, osmium tetroxide, alcohols, and picric acid. Fixation aims to inhibit autolysis, preserve tissues, harden them, and improve staining. Factors like temperature, concentration, and duration impact fixation quality. Different tissues require specific fixatives for optimal preservation. An ideal fixative kills cells quickly without damage, penetrates rapidly, prevents decay, hardens tissues, and allows long-term storage.
This document discusses tissue processing and fixation. It begins by introducing tissue fixation and its objectives, such as preventing degradation and maintaining morphology. It then describes various fixation methods and factors that affect fixation quality. Common fixatives are discussed, including formaldehyde, glutaraldehyde, Zenker's solution and Bouin's solution. Fixation protocols for specific tissues like brain, breast, lung and kidney are also reviewed. The document emphasizes the importance of proper fixation for histological examination.
The document provides information on cerebrospinal fluid (CSF) examination including indications, collection, analysis, and findings in different conditions like meningitis. It discusses three clinical cases. For case 1, the diagnosis is bacterial meningitis based on cloudy CSF, low glucose, and high neutrophil count. Further tests would include cultures and sensitivity. For case 2, the diagnosis is viral meningitis (measles) based on clear CSF, normal glucose, and lymphocytic pleocytosis; complications include encephalitis. For case 3, the diagnosis is tuberculous meningitis based on low glucose, low chloride, and lymphocytic pleocytosis; confirmation requires microbiological tests.
This method is used to visualise the localisation and quantity of a protein of interest. The target protein is bound to by a specific primary antibody, which in turn is detected by a secondary antibody conjugated to a fluorophore. A fluorescent or confocal microscope is used to visualise the protein.
Immunocytochemistry (ICC) differs from immunohistochemistry (IHC) in that the former is performed on samples of intact cells that have had most, if not all, of their surrounding extracellular matrix removed. In contrast, immunohistochemical samples are sections of biological tissue, where each cell is surrounded by tissue architecture and other cells normally found in the intact tissue. These differences cause the samples to be prepared differently. For ICC, the sample requires permeabilisation so that the antibodies can reach the intracellular targets. Depending on the thickness of the sample, IHC samples do not require this.
Do you have a technical question? Get in touch: info@stjohnslabs.com
This document discusses enzymes and enzyme histochemistry techniques. It defines enzymes and their classifications including hydrolases, oxidoreductases, transferases, and lyases. It then demonstrates the histochemical localization of alkaline phosphatase and acid phosphatase in tissues. The optimal fixation, incubation, and interpretation of results are described. Finally, it lists some diagnostic applications of enzyme histochemistry and provides sample multiple choice questions.
This document discusses cytopreparatory techniques for cytology samples. It describes the different types of cytology samples like exfoliative cytology, aspiration cytology, and body fluids. The key steps in cytopreparatory techniques are outlined as evaluation of specimens, preparation of smears, fixation, and staining. Factors that can affect optimal cytological preparation like quality of specimen, fixative used, and stains are also summarized. Different fixation techniques including dry, wet, liquid-based, and lysing fixation for bloody samples are explained.
This document provides an overview of the process of histopathology. It discusses the key steps: sample collection and fixation, processing including dehydration, clearing, infiltration and embedding, sectioning of samples, and staining. Common techniques and agents used at each step are outlined, such as formalin for fixation, alcohol and acetone for dehydration, xylene for clearing, and paraffin for infiltration and embedding. Hematoxylin and eosin staining is described as the standard staining method, along with Pap staining and Toluidine blue staining. Finally, storage of slides and blocks in refrigerated boxes is mentioned.
CYTOLOGY AND CYTOGENITICS MCQS BY IKRAM ULLAH Ikram Ullah
This document contains 60 multiple choice questions about cytology and cytogenetics. It covers topics like the structures and functions of cells and their organelles, cell membrane models, the role of mitochondria and lysosomes, fixation techniques used in cytology including different fixatives and their properties, staining methods like Papanicolaou staining, and normal cytology of organs like the uterus and cervix. The questions are multiple choice with a single correct answer for each question.
Papanicolaou staining, also known as a Pap smear, is a screening technique used to detect cervical cancer. It involves differentially staining cell components using multiple dyes. George Papanicolaou first developed the Pap stain technique in 1942 to distinguish cell types under a microscope. The stain uses basic and acidic dyes that bind to different cell components, allowing nuclei, cytoplasm, and cell types to be identified by their colors. A Pap smear can detect pre-cancerous changes in the cervix so that cancer treatment can begin early. It has significantly reduced cervical cancer rates in countries with widespread screening programs.
leucodepletion is the removal of 99% leucocytes from the whole blood, pcv or platelets before transfusing into the donor.
this process many infections, transfusion reactions..
Quality Control In Histopathology Dr.Rami amawi.pptxRami Al Amawi
This document discusses quality control in histopathology. It defines quality assurance, quality control, and quality improvement. It outlines the pre-analytic, analytic, and post-analytic phases of quality control and common problems and solutions in each phase. It also discusses approaches to quality control like intradepartmental consultation, random case review, clinical indicators, pathology turnaround times, and monitoring specimen adequacy.
This document discusses histotechniques related to fixation and decalcification of tissues for microscopic examination. It describes the objectives and ideal properties of fixatives, as well as common fixatives used such as formaldehyde, glutaraldehyde, and picric acid. Factors that influence fixation quality like temperature, concentration, and duration are addressed. The document also covers decalcification techniques and factors that affect the decalcification process. Special considerations for fixing different tissues are outlined.
This document discusses histology and histopathology techniques. It defines histology as the study of normal tissue structure and histopathology as the study of diseased tissue structure. It describes various histopathological techniques including tissue fixation, processing, staining and microscopic examination. Several commonly used fixatives are described along with their mechanisms and appropriate tissue and time requirements. Decalcification techniques are also summarized.
This document discusses tissue fixation in histopathology. It describes the various stages of histopathology including fixation, processing, embedding, sectioning and staining of tissues. It explains the importance of fixation in preventing autolysis and putrefaction of tissues. The key properties and reactions of common fixatives like formaldehyde and glutaraldehyde are outlined. Factors that can affect fixation quality including temperature, pH, concentration and duration of fixation are also summarized. Finally, different classifications of fixatives are presented based on their structural and functional properties.
This document discusses cytopreparatory techniques, including fixation of cytological samples, staining methods, and interpretation. It focuses on fixation, explaining that fixation preserves cells in a lifelike state after death by preventing autolysis and putrefaction. The key properties of a good fixative are outlined, and various fixatives are classified and examples are provided, including alcohols, formalin, and mercuric chloride, which are commonly used for cytological preparations.
Apheresis is a technique where whole blood is collected from a donor or patient and separated into its components. The desired component is retained while the rest are returned. It is commonly used to collect platelets, leukocytes, erythrocytes, and plasma through centrifugation or membrane filtration methods. Therapeutic apheresis uses this technique to remove pathogenic substances from the blood to treat various conditions like thrombocythemia or autoimmune diseases. Procedural elements include venous access, anticoagulation, replacement fluids, and monitoring for complications.
This document discusses the importance of cell block preparation from cytological specimens. It provides several key points:
1) Cell blocks allow cytological material to be processed, sectioned, stained, and viewed like histology specimens, providing additional diagnostic information.
2) Cell blocks have both diagnostic sensitivity and specificity. They can be stored easily and require minimal effort and cost.
3) Various methods for cell block preparation are described, including plasma thrombin, histogel, collodion bag, and automated methods.
4) Cell blocks increase diagnostic yield by providing additional cells and better preservation of morphological patterns compared to smears alone.
The PAS stain demonstrates carbohydrates and carbohydrate-rich compounds in tissues through oxidizing glycol groups with periodic acid and forming a magenta-colored complex with Schiff's reagent. It is useful for detecting conditions like glycogen storage disease and assessing thickness of the glomerular basement membrane. The PAS stain demonstrates substances like mucins, fungi cell walls, gangliosides, lipofuscin, Russell bodies and the basement membranes of various tissues.
1. The document describes the process of embedding plant materials in paraffin wax for microscopic examination. Tissues are infiltrated with molten paraffin wax using a paper tray method before being solidified into blocks.
2. Sections are cut from the wax blocks using a rotary microtome and mounted on microscope slides. The ribbons of sections are stretched on a heated plate to remove folds before being dried overnight.
3. Proper trimming, section thickness, and stretching are important to obtain intact ribbons of sections for microscopic analysis of plant materials.
Tissue processing involves removing water from tissue and replacing it with paraffin wax to provide rigidity for microscopic examination. The main steps are fixation, dehydration using increasing concentrations of alcohol, clearing with xylene to remove alcohol, and impregnation with molten paraffin wax. Automated tissue processors complete this process overnight using different stations for each step. Factors like tissue size, agitation, heat, and vacuum pressure influence effective processing. Ethyl alcohol is most commonly used for dehydration, while xylene is used for clearing prior to paraffin wax impregnation and embedding.
Agarose gel electrophoresis is a method to separate DNA fragments by size using an electric current applied across an agarose gel. DNA samples are loaded into wells in the gel and subjected to an electric field, causing the negatively charged DNA fragments to migrate through the agarose matrix. Shorter DNA fragments travel farther and faster through the gel than longer fragments. After a set period of time, the DNA fragments are visualized under UV light after staining with ethidium bromide, allowing their sizes to be determined by comparison with a DNA ladder of known fragment sizes.
This document discusses tissue fixation in pathology. It begins by describing the overall tissue processing steps and importance of fixation. The main types of fixatives are then outlined, including coagulant, cross-linking, and compound fixatives. Formalin and glutaraldehyde fixation are discussed in depth. Key factors that influence fixation quality like buffer pH, fixation duration, tissue size, and temperature are also summarized. The document provides a comprehensive overview of fixation in pathology.
Apheresis is a medical technology in which blood is withdrawn from a donor or patient, separated into components, and at least one component is retained while the remainder is returned to the circulation. It is used to collect blood components like platelets, plasma, and stem cells for transfusion or therapeutic purposes. Apheresis can be performed manually or using automated machines that utilize centrifugation or filtration to separate components. It has various applications including collection of platelets, plasma exchange to remove antibodies or toxins, and stem cell collection for transplantation. Complications are usually minor but may include hypocalcemia, hypotension, and allergic reactions.
Liquid based cytology is a method to collect and prepare cervical cell samples for microscopic examination. The sample is collected from the cervix using a spatula or broom and transferred to a preservative solution. The cells are then dispersed in the fluid and either centrifuged or filtered onto a slide to form a thin monolayer for staining and examination under a microscope. The two most widely used liquid based cytology systems are Sure Path and Thin Prep. Liquid based cytology offers advantages like immediate cell fixation, evaluation of all collected material, and preparation of representative samples, but it can alter smear patterns and dispersion of abnormal cells.
The document discusses the history, utility, and methods of preparing cell blocks from fine needle aspiration cytology samples. Cell blocks allow examination of histological structure and use of ancillary tests. Key methods include the fixed sedimentation method using a 1:1 ratio of 100% alcohol and 40% formalin, the plasma thrombin method using equal parts plasma and thrombin, and the bacterial agar method using 3% agar. Cell blocks provide increased diagnostic sensitivity and specificity compared to cytology alone through examination of tissue architecture and ability to perform special stains and molecular testing.
This document discusses decalcification, which is the process of removing calcium from bone and other calcified tissues prior to sectioning and microscopic examination. It defines decalcification and lists the criteria for an ideal decalcifying agent. Various factors that affect the rate of decalcification are described, including concentration, temperature, agitation, and suspension of the tissue. The main methods of decalcification are outlined as well as the principles, types, compositions, and procedures for different decalcifying agents such as acids, ion exchange resins, and chelating agents.
This document provides an overview of histotechniques, specifically tissue fixation. It discusses the goals of fixation including preventing autolysis and bacterial decomposition. Common fixatives like formalin, Bouin's fluid, and Zenker's fluid are described. Formalin is the most widely used fixative and its mechanisms of protein cross-linking and denaturation are explained. Factors that influence fixation like temperature, concentration, and duration are also summarized. Overall, the document provides a comprehensive introduction to the processes and chemicals used in tissue fixation for microscopic examination.
This document discusses fixatives used in histopathology. It describes the process of fixation and how fixatives preserve tissue by denaturing or precipitating proteins. The ideal properties of a fixative are described, including preventing autolysis and allowing for staining. Common fixatives are classified and their mechanisms and uses are explained. Factors that affect fixation such as temperature, size, volume ratio, time, choice of fixative, and penetration are also summarized.
CYTOLOGY AND CYTOGENITICS MCQS BY IKRAM ULLAH Ikram Ullah
This document contains 60 multiple choice questions about cytology and cytogenetics. It covers topics like the structures and functions of cells and their organelles, cell membrane models, the role of mitochondria and lysosomes, fixation techniques used in cytology including different fixatives and their properties, staining methods like Papanicolaou staining, and normal cytology of organs like the uterus and cervix. The questions are multiple choice with a single correct answer for each question.
Papanicolaou staining, also known as a Pap smear, is a screening technique used to detect cervical cancer. It involves differentially staining cell components using multiple dyes. George Papanicolaou first developed the Pap stain technique in 1942 to distinguish cell types under a microscope. The stain uses basic and acidic dyes that bind to different cell components, allowing nuclei, cytoplasm, and cell types to be identified by their colors. A Pap smear can detect pre-cancerous changes in the cervix so that cancer treatment can begin early. It has significantly reduced cervical cancer rates in countries with widespread screening programs.
leucodepletion is the removal of 99% leucocytes from the whole blood, pcv or platelets before transfusing into the donor.
this process many infections, transfusion reactions..
Quality Control In Histopathology Dr.Rami amawi.pptxRami Al Amawi
This document discusses quality control in histopathology. It defines quality assurance, quality control, and quality improvement. It outlines the pre-analytic, analytic, and post-analytic phases of quality control and common problems and solutions in each phase. It also discusses approaches to quality control like intradepartmental consultation, random case review, clinical indicators, pathology turnaround times, and monitoring specimen adequacy.
This document discusses histotechniques related to fixation and decalcification of tissues for microscopic examination. It describes the objectives and ideal properties of fixatives, as well as common fixatives used such as formaldehyde, glutaraldehyde, and picric acid. Factors that influence fixation quality like temperature, concentration, and duration are addressed. The document also covers decalcification techniques and factors that affect the decalcification process. Special considerations for fixing different tissues are outlined.
This document discusses histology and histopathology techniques. It defines histology as the study of normal tissue structure and histopathology as the study of diseased tissue structure. It describes various histopathological techniques including tissue fixation, processing, staining and microscopic examination. Several commonly used fixatives are described along with their mechanisms and appropriate tissue and time requirements. Decalcification techniques are also summarized.
This document discusses tissue fixation in histopathology. It describes the various stages of histopathology including fixation, processing, embedding, sectioning and staining of tissues. It explains the importance of fixation in preventing autolysis and putrefaction of tissues. The key properties and reactions of common fixatives like formaldehyde and glutaraldehyde are outlined. Factors that can affect fixation quality including temperature, pH, concentration and duration of fixation are also summarized. Finally, different classifications of fixatives are presented based on their structural and functional properties.
This document discusses cytopreparatory techniques, including fixation of cytological samples, staining methods, and interpretation. It focuses on fixation, explaining that fixation preserves cells in a lifelike state after death by preventing autolysis and putrefaction. The key properties of a good fixative are outlined, and various fixatives are classified and examples are provided, including alcohols, formalin, and mercuric chloride, which are commonly used for cytological preparations.
Apheresis is a technique where whole blood is collected from a donor or patient and separated into its components. The desired component is retained while the rest are returned. It is commonly used to collect platelets, leukocytes, erythrocytes, and plasma through centrifugation or membrane filtration methods. Therapeutic apheresis uses this technique to remove pathogenic substances from the blood to treat various conditions like thrombocythemia or autoimmune diseases. Procedural elements include venous access, anticoagulation, replacement fluids, and monitoring for complications.
This document discusses the importance of cell block preparation from cytological specimens. It provides several key points:
1) Cell blocks allow cytological material to be processed, sectioned, stained, and viewed like histology specimens, providing additional diagnostic information.
2) Cell blocks have both diagnostic sensitivity and specificity. They can be stored easily and require minimal effort and cost.
3) Various methods for cell block preparation are described, including plasma thrombin, histogel, collodion bag, and automated methods.
4) Cell blocks increase diagnostic yield by providing additional cells and better preservation of morphological patterns compared to smears alone.
The PAS stain demonstrates carbohydrates and carbohydrate-rich compounds in tissues through oxidizing glycol groups with periodic acid and forming a magenta-colored complex with Schiff's reagent. It is useful for detecting conditions like glycogen storage disease and assessing thickness of the glomerular basement membrane. The PAS stain demonstrates substances like mucins, fungi cell walls, gangliosides, lipofuscin, Russell bodies and the basement membranes of various tissues.
1. The document describes the process of embedding plant materials in paraffin wax for microscopic examination. Tissues are infiltrated with molten paraffin wax using a paper tray method before being solidified into blocks.
2. Sections are cut from the wax blocks using a rotary microtome and mounted on microscope slides. The ribbons of sections are stretched on a heated plate to remove folds before being dried overnight.
3. Proper trimming, section thickness, and stretching are important to obtain intact ribbons of sections for microscopic analysis of plant materials.
Tissue processing involves removing water from tissue and replacing it with paraffin wax to provide rigidity for microscopic examination. The main steps are fixation, dehydration using increasing concentrations of alcohol, clearing with xylene to remove alcohol, and impregnation with molten paraffin wax. Automated tissue processors complete this process overnight using different stations for each step. Factors like tissue size, agitation, heat, and vacuum pressure influence effective processing. Ethyl alcohol is most commonly used for dehydration, while xylene is used for clearing prior to paraffin wax impregnation and embedding.
Agarose gel electrophoresis is a method to separate DNA fragments by size using an electric current applied across an agarose gel. DNA samples are loaded into wells in the gel and subjected to an electric field, causing the negatively charged DNA fragments to migrate through the agarose matrix. Shorter DNA fragments travel farther and faster through the gel than longer fragments. After a set period of time, the DNA fragments are visualized under UV light after staining with ethidium bromide, allowing their sizes to be determined by comparison with a DNA ladder of known fragment sizes.
This document discusses tissue fixation in pathology. It begins by describing the overall tissue processing steps and importance of fixation. The main types of fixatives are then outlined, including coagulant, cross-linking, and compound fixatives. Formalin and glutaraldehyde fixation are discussed in depth. Key factors that influence fixation quality like buffer pH, fixation duration, tissue size, and temperature are also summarized. The document provides a comprehensive overview of fixation in pathology.
Apheresis is a medical technology in which blood is withdrawn from a donor or patient, separated into components, and at least one component is retained while the remainder is returned to the circulation. It is used to collect blood components like platelets, plasma, and stem cells for transfusion or therapeutic purposes. Apheresis can be performed manually or using automated machines that utilize centrifugation or filtration to separate components. It has various applications including collection of platelets, plasma exchange to remove antibodies or toxins, and stem cell collection for transplantation. Complications are usually minor but may include hypocalcemia, hypotension, and allergic reactions.
Liquid based cytology is a method to collect and prepare cervical cell samples for microscopic examination. The sample is collected from the cervix using a spatula or broom and transferred to a preservative solution. The cells are then dispersed in the fluid and either centrifuged or filtered onto a slide to form a thin monolayer for staining and examination under a microscope. The two most widely used liquid based cytology systems are Sure Path and Thin Prep. Liquid based cytology offers advantages like immediate cell fixation, evaluation of all collected material, and preparation of representative samples, but it can alter smear patterns and dispersion of abnormal cells.
The document discusses the history, utility, and methods of preparing cell blocks from fine needle aspiration cytology samples. Cell blocks allow examination of histological structure and use of ancillary tests. Key methods include the fixed sedimentation method using a 1:1 ratio of 100% alcohol and 40% formalin, the plasma thrombin method using equal parts plasma and thrombin, and the bacterial agar method using 3% agar. Cell blocks provide increased diagnostic sensitivity and specificity compared to cytology alone through examination of tissue architecture and ability to perform special stains and molecular testing.
This document discusses decalcification, which is the process of removing calcium from bone and other calcified tissues prior to sectioning and microscopic examination. It defines decalcification and lists the criteria for an ideal decalcifying agent. Various factors that affect the rate of decalcification are described, including concentration, temperature, agitation, and suspension of the tissue. The main methods of decalcification are outlined as well as the principles, types, compositions, and procedures for different decalcifying agents such as acids, ion exchange resins, and chelating agents.
This document provides an overview of histotechniques, specifically tissue fixation. It discusses the goals of fixation including preventing autolysis and bacterial decomposition. Common fixatives like formalin, Bouin's fluid, and Zenker's fluid are described. Formalin is the most widely used fixative and its mechanisms of protein cross-linking and denaturation are explained. Factors that influence fixation like temperature, concentration, and duration are also summarized. Overall, the document provides a comprehensive introduction to the processes and chemicals used in tissue fixation for microscopic examination.
This document discusses fixatives used in histopathology. It describes the process of fixation and how fixatives preserve tissue by denaturing or precipitating proteins. The ideal properties of a fixative are described, including preventing autolysis and allowing for staining. Common fixatives are classified and their mechanisms and uses are explained. Factors that affect fixation such as temperature, size, volume ratio, time, choice of fixative, and penetration are also summarized.
The document discusses fixatives used in histopathology. It describes the process of fixation and how fixatives preserve tissue by denaturing or precipitating proteins. The ideal properties of a fixative are also outlined, including preventing autolysis and allowing for staining. Common fixatives are described such as formalin, Bouin's fluid, Zenker's solution and their mechanisms and appropriate uses. Factors that affect fixation like temperature, size, volume ratio, time and choice of fixative are also summarized.
This document discusses the process of tissue processing in histology and histopathology laboratories. [1] Tissue samples are obtained from biopsies and autopsies and undergo histotechniques to prepare them for microscopic examination. [2] The key steps include fixation, processing, embedding in paraffin wax, sectioning, staining, and mounting. [3] Automated equipment is now commonly used to improve efficiency at many steps such as tissue processing, sectioning, and staining.
Fixatives used in tissue processing - Histopath techniques.Kaaviya Subramaniam
This document discusses various types of fixatives used to preserve cell and tissue structure. It begins by explaining how living cells require oxygen and nutrients from blood circulation, and will die when cut off from this supply. Fixation is needed to preserve tissues as they were in life for histological examination. Various fixatives are then described, including physical, chemical, simple, compound, dehydrant, coagulant, cross-linking, and osmium tetroxide fixatives. The ideal properties and mechanisms of several common fixatives like formaldehyde, glutaraldehyde, picric acid, acetic acid, and mercuric chloride are also summarized.
This document discusses tissue fixation techniques and histochemical staining methods. It begins by defining tissue fixation as a process that preserves tissues from decay through chemical means. It then describes various types of fixatives including simple fixatives like formalin and compound fixatives. Specific fixatives discussed include 10% neutral buffered formalin, Bouin's fluid, Zenker's fluid, and osmium tetroxide. Modes of action and uses of these fixatives are provided. The document concludes by outlining various histochemical staining techniques for identifying elements like glycogen, calcium, iron, uric acid crystals and amyloid. Specific stains discussed are PAS, Best's carmine, von Kossa's, Prussian blue, de Gal
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This document provides an overview of decalcification in histopathology. It discusses the need to decalcify bony tissue specimens to make them thin enough for microscopic examination. The key aspects of decalcification covered include the criteria for good decalcifying agents, factors that affect the process, common techniques and decalcifiers used, potential artifacts, and assessing the endpoint of decalcification. The techniques described aim to remove calcium from bone while minimizing damage to tissue morphology and antigenicity.
FIXATIVES in Pathology for Postgraduate and DMLTjenishJebadurai1
This document discusses various fixatives used in histology and cytology techniques. It begins by defining fixation as the process of preserving cells and tissue using physical or chemical methods. Commonly used fixatives include formaldehyde, glutaraldehyde, osmium tetroxide, mercury salts, picric acid, and alcohols. An ideal fixative would be non-toxic, low-cost, and effectively preserve tissue morphology, antigens, and nucleic acids while allowing for long-term storage. Factors like temperature, pH, concentration, and duration impact fixation quality. Proper fixation is important for minimizing artifacts and ensuring high quality staining.
3 Fixation and fixatives all about the filhooyo7295
This document discusses fixation and fixatives used in histopathology. It defines fixation as a chemical process that preserves tissues from decay by terminating biochemical reactions and increasing stability. The objective of fixation is to preserve cells and tissues in a lifelike state to allow for further processing without change. It then discusses various types of fixatives, how to choose a fixative, fixation methods, and factors that affect fixation quality. Key fixatives mentioned include formaldehyde, glutaraldehyde, mercuric chloride, picric acid, and osmium tetroxide.
The document discusses fixation and processing of tissue specimens. It describes fixation as a process that preserves cells and tissues in a physical and chemical state to prevent biochemical changes and morphological distortion. The goals of fixation are to maintain the original tissue structure and prevent autolysis and bacterial growth. Common fixatives include formaldehyde and ethanol. The document outlines various types of fixatives and factors that influence fixation like buffer, pH, duration, temperature and concentration. It also discusses processing of fixed tissue, which provides rigidity for sectioning. Processing is influenced by viscosity, agitation, heat, vacuum and pressure. The document notes potential artifacts from improper fixation like formalin pigment or prolonged fixation effects.
Histopathology studies the diseased tissues. As 300-level students at Alex Ekwueme Federal University in Ndufu Alike, Nigeria, it's a requirement to pass with a degree in human anatomy.
This document discusses histopathology and the process of tissue fixation. It defines histopathology as the study of diseased tissues to examine changes in structure from disease. The key steps in tissue fixation are described, including the objectives to preserve tissue structure and prevent decomposition. Various types of fixatives are classified and their mechanisms and properties explained, with examples like formalin, glutaraldehyde, alcohol, picric acid and osmium tetraoxide. Compound fixatives are also mentioned.
This document discusses various methods of decalcification used to remove calcium from bones and calcified tissues for histological examination. It describes the main decalcification methods including acid decalcification using strong acids like hydrochloric acid and nitric acid or weak acids like formic acid. Other methods discussed are chelating agents like EDTA, ion-exchange resins, and electrolysis. The document also covers factors affecting decalcification rate and various tests to determine the endpoint of decalcification including radiographic, chemical, and physical examination of the tissue.
This document provides an overview of histopathology and the process of tissue fixation and preparation for microscopic examination. It defines histopathology and describes the various steps tissues undergo, including fixation, to arrive at a diagnosis. It discusses the aims and principles of fixation, including preventing autolysis and putrefaction. Various fixatives are described, including formalin, alcohol, mercuric chloride and picric acid. The document also covers tissue processing, including sectioning and staining, as well as the roles and responsibilities of laboratory technicians in specimen handling.
This document provides an introduction to histopathology and the process of tissue sample preparation and analysis. It defines histopathology and describes the steps tissues undergo, including fixation, processing, sectioning and staining. It discusses the types of samples obtained, including biopsies and autopsy tissues. It explains the responsibilities of laboratory technicians in handling, labeling and storing samples. Finally, it provides details on fixation, including the goals, common fixatives used, and how to properly prepare tissue samples for fixation.
Histopathology is examination of tissues for presence or absence of changes in their structure due to disease processes. We go through various steps in the process of converting gross sample to microscopic slides.
Histological techniques involve preparing tissue for microscopic examination through a series of procedures to retain the tissue's microscopic anatomy and allow for good staining. This involves fixing, processing, embedding, sectioning, and staining the tissue. The key steps are fixation to prevent deterioration, dehydration and clearing to infiltrate the tissue with wax, sectioning thin slices, and staining, most commonly with hematoxylin and eosin, to highlight structures. The goal is to represent the tissue's structure as closely as possible to its in vivo state.
The document discusses fixation in histology and cytology. It describes the aims of fixation as preserving tissue structure and preventing autolysis and bacterial growth. Fixation causes some changes like tissue shrinkage and hardening. The types of fixation include immersion, coating, vapor and perfusion. Formalin and alcohol are common fixatives. Factors like pH, temperature, duration and osmolarity influence fixation quality. The choice of fixative depends on the tissue and technique used, for example glutaraldehyde for electron microscopy. Useful fixative formulas are also provided.
Industrial centrifuges separate or purify large quantities of materials using centrifugal force. They spin samples at high speeds to separate components based on density, size, or shape. There are three main types - decanter, filter, and sedimentation centrifuges. Decanter centrifuges continuously separate solids from liquids or two immiscible liquids. Filter centrifuges retain particulates while allowing liquid to pass through. Sedimentation centrifuges accumulate solids around the bowl wall while liquid exits through an output passage. Industrial centrifuges are used across industries such as fuel processing, water treatment, chemicals, pharmaceuticals, mining, and food/dairy processing.
Flotation is a separation technique used in downstream processing to purify minerals from an ore mixture. It works by selectively attaching air bubbles to the surfaces of desired minerals using chemicals, causing them to float to the top while heavier unwanted minerals remain suspended below. The process involves conditioning the ore, feeding it into a flotation cell with aeration, and collecting the froth containing concentrated valuable minerals separated from waste material. Flotation offers high selectivity, scalability, and recovery rates but requires optimization and incurs costs associated with reagents and froth handling.
This document discusses downstream processing techniques used in biopharmaceutical industries. It describes downstream processing as purifying and concentrating target products from biological mixtures after fermentation or cell culture. The key steps include cell harvesting, disruption, clarification, purification using techniques like chromatography, concentration, and formulation. Filtration is commonly used for clarification, pre-purification, and polishing. Specific filtration techniques discussed include surface filtration, depth filtration, centrifugal filtration, and rotating drum vacuum filtration.
Pox viruses can be diagnosed clinically or through laboratory tests. Common symptoms include fever, characteristic raised skin lesions that progress to fluid-filled blisters and pus-filled pustules usually appearing on the face and extremities. Swollen lymph nodes and general symptoms like muscle aches and fatigue may also be present. Travel history and animal contact can provide clues to the specific virus. Polymerase chain reaction testing of lesions or body fluids is the most sensitive method to detect poxvirus DNA. Virus isolation grows the virus for identification but takes longer. Electron microscopy can visualize virus particles less sensitively than PCR.
Parvoviruses are a diverse group of small DNA viruses that infect humans and animals. They include canine parvovirus which infects dogs and causes parvo, feline panleukopenia virus which infects cats, B19 parvovirus which causes fifth disease in humans, and rodent parvoviruses which infect rodents. Parvoviruses are categorized as either autonomous, which can replicate independently, or dependoviruses which require coinfection with another virus like adenovirus.
1. Parvovirus B19 causes a range of clinical manifestations from asymptomatic infection to transient erythroblastopenia or aplastic crisis depending on the host's immune status and underlying medical conditions.
2. The virus binds to the P blood group antigen receptor on erythroid progenitor cells and causes their lysis, resulting in transient red cell aplasia. This causes a temporary anemia in healthy individuals but can cause a severe aplastic crisis in those with hemolytic anemia.
3. Diagnosis involves detecting B19 viral DNA by PCR or antibodies such as IgM, which indicates a current infection, and IgG which persists for life after infection and confers immunity.
Arboviruses are a group of viruses transmitted by arthropods like mosquitoes and ticks. They cause a wide range of diseases from mild fevers to serious encephalitis. There are three main families of arboviruses: Flaviviridae which includes yellow fever, dengue, Zika, and West Nile viruses; Togaviridae which includes chikungunya and equine encephalitis viruses; and Bunyaviridae which includes Rift Valley fever and hantavirus pulmonary syndrome. Arboviruses are transmitted via arthropod bites and their transmission can be seasonal depending on climate and vector life cycles. Prevention includes avoiding bites, vaccination, and vector control.
Coronaviruses are enveloped viruses with distinctive spike proteins that give them a crown-like appearance. They can infect humans and animals, causing respiratory and gastrointestinal illness. SARS-CoV-2 is the coronavirus that causes COVID-19. It spreads efficiently between people and has caused a global pandemic. COVID-19 symptoms range from mild to severe, and complications can include pneumonia, respiratory failure, blood clots, and organ damage. Diagnosis involves molecular tests, antigen tests, imaging, and clinical evaluation.
Rhabdoviruses are enveloped viruses with bullet-shaped particles that contain single-stranded RNA. They replicate by entering host cells and using their RNA polymerase to transcribe and replicate their genome. New virus particles then bud from the host cell. Rhabdoviruses can infect many species and are transmitted by arthropods or bites. Rabies virus causes fatal neurological disease in humans and other mammals by traveling along nerves to the brain. It evades immunity and commonly causes fear of water, paralysis, and death from respiratory failure. Diagnosis involves clinical evaluation, exposure history, and fluorescent antibody or PCR testing of brain or saliva samples.
The rubella virus causes German measles and belongs to the Togaviridae family. It is a small, enveloped RNA virus that is highly contagious and spreads through respiratory droplets. Rubella infection typically causes a mild illness in children and adults characterized by fever, rash, and lymphadenopathy. However, infection during pregnancy can lead to congenital rubella syndrome in the fetus, resulting in birth defects. Rubella is diagnosed through clinical evaluation, patient history, and serological tests. It can be prevented through vaccination with the MMR or MMRV vaccines.
A nosocomial infection, also known as a healthcare-associated infection, is an infection acquired by a patient during their stay in a healthcare facility like a hospital or nursing home, rather than being present or incubating upon admission. These infections can affect various parts of the body and be caused by a variety of microorganisms. They are transmitted through direct contact or airborne routes and pose increased risks of health complications, prolonged hospitalization, and mortality for patients. Preventing nosocomial infections requires rigorous infection control measures in healthcare settings.
The Hospital Infection Control Committee (HICC) is responsible for preventing and managing infections within healthcare facilities. The HICC is composed of healthcare professionals from various disciplines who work together to develop infection control policies, educate staff, monitor infections, and ensure regulatory compliance. Key duties of the HICC include creating protocols for hand hygiene, outbreak management, and antimicrobial stewardship programs to safeguard patients, workers, and visitors from healthcare-associated infections.
Antiviral agents work by interfering with different stages of the viral lifecycle such as attachment, entry, replication, and release. There are several classes of antiviral drugs that target specific viral processes including entry inhibitors, nucleoside/nucleotide analogues, protease inhibitors, polymerase inhibitors, and neuraminidase inhibitors. While antiviral drugs aim to disrupt viral replication selectively, they can cause side effects like gastrointestinal issues, fatigue, headaches, and liver/kidney problems. Viruses may also develop resistance to antiviral medications over time through genetic mutations.
These toxins damage the blood. Some examples that damage red blood cells include E. coli verotoxin which destroys red blood cells and causes kidney damage, and Vibrio vulnificus toxin which destroys tissue and causes inflammation. Staphylococcal alpha-toxin produced by Staphylococcus aureus disrupts blood clotting and causes toxic shock syndrome through inflammation. Hemotoxins damage the blood through mechanisms such as disrupting clotting, destroying red blood cells, and other harmful effects.
Paramyxoviruses are enveloped viruses that range in size from 100-300 nanometers in diameter. They have a single-stranded, negative-sense RNA genome and can have spherical, oval, or bullet shapes. Paramyxoviruses attach to and fuse with the host cell membrane, releasing their genetic material. The RNA is then transcribed and the proteins are assembled into new viral particles, which bud from the cell to infect others. Common cell lines used to culture paramyxoviruses include Vero, HEL, and MDCK cells. Cytopathic effects include syncytia formation, cell rounding, death, and foci of infection.
Orthomyxoviruses are enveloped viruses with helical nucleocapsids and pleomorphic shapes. They contain two main glycoproteins, hemagglutinin and neuraminidase. Hemagglutinin attaches the virus to host cells while neuraminidase releases the virus. Orthomyxoviruses can be cultivated using cell culture, animal models like chickens and ferrets, or in ovo injection into chicken embryos. Replication involves transcription of viral RNA into DNA, integration into the host genome, then replication and release of new virions.
Microbial Pathogenicity-bacteria,fungi,virus and parasites along with key factors-Host invasion, invading immune response,virulence factors, systemic spread and transmission
Or: Beyond linear.
Abstract: Equivariant neural networks are neural networks that incorporate symmetries. The nonlinear activation functions in these networks result in interesting nonlinear equivariant maps between simple representations, and motivate the key player of this talk: piecewise linear representation theory.
Disclaimer: No one is perfect, so please mind that there might be mistakes and typos.
dtubbenhauer@gmail.com
Corrected slides: dtubbenhauer.com/talks.html
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
Unlocking the mysteries of reproduction: Exploring fecundity and gonadosomati...AbdullaAlAsif1
The pygmy halfbeak Dermogenys colletei, is known for its viviparous nature, this presents an intriguing case of relatively low fecundity, raising questions about potential compensatory reproductive strategies employed by this species. Our study delves into the examination of fecundity and the Gonadosomatic Index (GSI) in the Pygmy Halfbeak, D. colletei (Meisner, 2001), an intriguing viviparous fish indigenous to Sarawak, Borneo. We hypothesize that the Pygmy halfbeak, D. colletei, may exhibit unique reproductive adaptations to offset its low fecundity, thus enhancing its survival and fitness. To address this, we conducted a comprehensive study utilizing 28 mature female specimens of D. colletei, carefully measuring fecundity and GSI to shed light on the reproductive adaptations of this species. Our findings reveal that D. colletei indeed exhibits low fecundity, with a mean of 16.76 ± 2.01, and a mean GSI of 12.83 ± 1.27, providing crucial insights into the reproductive mechanisms at play in this species. These results underscore the existence of unique reproductive strategies in D. colletei, enabling its adaptation and persistence in Borneo's diverse aquatic ecosystems, and call for further ecological research to elucidate these mechanisms. This study lends to a better understanding of viviparous fish in Borneo and contributes to the broader field of aquatic ecology, enhancing our knowledge of species adaptations to unique ecological challenges.
Remote Sensing and Computational, Evolutionary, Supercomputing, and Intellige...University of Maribor
Slides from talk:
Aleš Zamuda: Remote Sensing and Computational, Evolutionary, Supercomputing, and Intelligent Systems.
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Inter-Society Networking Panel GRSS/MTT-S/CIS Panel Session: Promoting Connection and Cooperation
https://www.etran.rs/2024/en/home-english/
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The use of Nauplii and metanauplii artemia in aquaculture (brine shrimp).pptxMAGOTI ERNEST
Although Artemia has been known to man for centuries, its use as a food for the culture of larval organisms apparently began only in the 1930s, when several investigators found that it made an excellent food for newly hatched fish larvae (Litvinenko et al., 2023). As aquaculture developed in the 1960s and ‘70s, the use of Artemia also became more widespread, due both to its convenience and to its nutritional value for larval organisms (Arenas-Pardo et al., 2024). The fact that Artemia dormant cysts can be stored for long periods in cans, and then used as an off-the-shelf food requiring only 24 h of incubation makes them the most convenient, least labor-intensive, live food available for aquaculture (Sorgeloos & Roubach, 2021). The nutritional value of Artemia, especially for marine organisms, is not constant, but varies both geographically and temporally. During the last decade, however, both the causes of Artemia nutritional variability and methods to improve poorquality Artemia have been identified (Loufi et al., 2024).
Brine shrimp (Artemia spp.) are used in marine aquaculture worldwide. Annually, more than 2,000 metric tons of dry cysts are used for cultivation of fish, crustacean, and shellfish larva. Brine shrimp are important to aquaculture because newly hatched brine shrimp nauplii (larvae) provide a food source for many fish fry (Mozanzadeh et al., 2021). Culture and harvesting of brine shrimp eggs represents another aspect of the aquaculture industry. Nauplii and metanauplii of Artemia, commonly known as brine shrimp, play a crucial role in aquaculture due to their nutritional value and suitability as live feed for many aquatic species, particularly in larval stages (Sorgeloos & Roubach, 2021).
Current Ms word generated power point presentation covers major details about the micronuclei test. It's significance and assays to conduct it. It is used to detect the micronuclei formation inside the cells of nearly every multicellular organism. It's formation takes place during chromosomal sepration at metaphase.
2. Aim of fixation
(a) To preserve the tissues as close to their living
state as possible
(b) To prevent autolysis and bacterial attack
(c) To prevent tissues from changing their shape
and size during processing
(d) To harden the tissues
(e) To allow clear staining of sections
subsequently
(f) To improve the optical differentiation of cells &
tissues
3. Principle of fixation
Fixation results in denaturation and coagulation of
protein in the tissues.
The fixatives have a property of forming cross links
between proteins, thereby forming a gel, keeping
everything in vivo relation to each other.
4. Factors affecting fixation
1. Coagulation and precipitation of proteins in tissues.
2. Penetration rate differs with different fixatives
depending on the molecular weight of the fixative
3. pH of fixatives – Satisfactory fixation occurs between
pH 6 and 8. Outside this range, alteration in structure of
cell may take place.
4. Temperature – Room temperature is alright for fixation.
At high temperature there may be distortion of tissues.
5. Volume changes – Cell volume changes because of
the membrane permeability and inhibition of respiration.
6. An ideal fixative should be cheap, nontoxic and non-
inflammable. The tissues may be kept in the fixative for a
5. Types of fixation
• Immersion fixation
• Perfusion fixation
• Vapour fixation
• Coating/Spray fixation
• Freeze drying
• Microwave fixation/Stabilization
The most commonly used technique is simple
immersion of tissues/smears in an excess of
fixative.
For all practical purposes immersion fixatives are
most useful. These may be divided into routine and
6. Preparation of the specimen for
fixation
1. For achieving good fixation it is important that
the fixative penetrates the tissue well hence the
tissue section should be > 4mm thick, so that
fixation fluid penetrates from the periphery to the
centre of the tissue. For fixation of large organs
perfusion method is used i.e. fixative is injected
through the blood vessels into the organ. For
hollow viscera fixative is injected into the cavity
e.g. urinary bladder, eyeball etc.
7. 2. Ratio of volume of fixative to the specimen
should be 1:20.
3. Time necessary for fixation is important routinely
10% aqueous formalin at room temperature takes
12 hours to fix the tissue. At higher temperature i.e.
60-65°C the time for fixation is reduced to 2 hours.
8. Fixatives are divided into three main groups
A. Microanatomical fixatives - such fixatives preserves the
anatomy of the tissue.
B. Cytological fixatives - such fixation are used to
preserve intracellular structures or inclusion.
Cytological fixatives Subdivided into
(A) Nuclear fixatives (B) Cytoplasmic fixatives
C. Histochemical fixatives : Fixative used to preserve the
chemical nature of the tissue for it to be demonstrated
further. Freeze drying technique is best suited for this
9. Microanatomical Fixatives
10% (v/v) formalin in 0.9% sodium chloride (normal
saline).
This has been the routine fixative of choice for
many years, but this has now been replaced by
buffered formal or by formal calcium acetate.
10. Buffered formalin
(a) Formalin 10ml
(b) Acid sodium phosphate - 0.4 gm (monohydrate)
(c) Anhydrous disodium - 0.65 gm phosphate
(d) Water to 100 ml -
Best overall fixative
11. Formal calcium (Lillie : 1965)
(a) Formalin : 10 ml
(b) Calcium acetate 2.0 gm
(c) Water to 100 ml
• Specific features - They have a near neutral pH -
Formalin pigment (acid formaldehyde haematin) is
not formed.
12. Buffered formal sucrose (Holt and Hicks, 1961)
(a) Formalin : 10ml
(b) Sucrose : 7.5 gm
(c) M/15 phosphate to 100 ml buffer (pH 7.4)
• Specific features - This is an excellent fixative for
the preservation of fine structure phospholipids and
some enzymes. - It is recommended for combined
cytochemistry and electron microscopic studies. - It
should be used cold (4°C) on fresh tissue.
13. Alcoholic formalin
Formalin 10 ml
70-95% alcohol 90 ml
Acetic alcoholic formalin
Formalin 5.0ml
Glacial acetic acid 5.0 ml
Alcohol 70% 90.0 ml
14. Formalin ammonium bromide
Formalin 15.0 ml
Distilled water 85.0 ml
Ammonia bromide 2.0 gm
• Specific features : Preservation of neurological
tissues especially when gold and silver
impregnation is employed
15. Heidenhain Susa
(a) Mercuric chloride 4.5gm
(b) Sodium chloride 0.5 gm
(c) Trichloroacetic acid 2.0 gm
(d) Acetic acid 4.0 ml
(e) Distilled water to 100 ml
17. Nuclear fixative
• Specific features -
It penetrates very rapidly and gives excellent
nuclear fixation.
- Good fixative for carbohydrates.
- Nissil substance and glycogen are preserved.
- It causes considerable shrinkage.
- It dissolves most of the cytoplasmic elements.
Fixation is usually complete in 1-2 hours. For
small pieces 2-3 mm thick only 15 minutes in
needed for fixation.
18. Nuclear fixative
Clarke’s Fluid
(a) Absolute alcohol 75 ml
(b) Glacial acetic acid 25 ml.
• Specific features
- Rapid, good nuclear fixation and good
preservation of cytoplasmic elements.
- It in excellent for smear or cover slip preparation
of cell cultures or chromosomal analysis.
19. Nuclear fixative
New Comer's fluid.
(a) Isopropanol 60 ml
(b) Propionic acid 40ml
(c) Petroleum ether 10 ml.
(d) Acetone 10 ml. (e) Dioxane 10 ml.
• Specific features
- Devised for fixation of chromosomes
- It fixes and preserves mucopolysacharides.
-Fixation in complete in 12-18 hours.
20. Cytoplasmic fixative
Champy's fluid
(a) 3g/dl Potassium dichromate 7ml.
(b) 1% (V/V) chromic acid 7 ml.
(c) 2gm/dl osmium tetraoxide 4 ml.
• Specific features
- This fixative cannot be kept hence prepared
fresh.
- It preserves the mitochondrial fat and lipids.
- Penetration is poor and uneven.
- Tissue must be washed overnight after fixation.
21. Cytoplasmic fixative
Formal saline and formal Calcium
Fixation in formal saline followed by
postchromatization gives good cytoplasmic
fixation.
22. Histochemical fixative
For a most of the histochemical methods. It is best
to use cryostat. Sections are rapidly frozen or
freeze dried. Usually such sections are used
unfixed but if delay is inevitable then vapour
fixatives are used.
23. Vapour fixatives
1. Formaldehyde- Vapour is obtained by heating
paraformaldehyde at temperature between 50° and
80°C. Blocks of tissue require 3-5 hours whereas
section require ½- 1 hours.
2. Acetaldehyde- Vapour at 80°C for 1-4 hours.
3. Glutaraldehyde- 50% aqueous solution at 80°C
for 2 min to 4 hours.
4. Acrolein /chromyl chloride- used at 37°C for 1-2
24. Other more commonly used fixatives are
(1) formal saline
(2) Cold acetone Immersing in acetone at 0-4°C is
widely used for fixation of tissues intended to study
enzymes esp. phosphates.
(3) Absolute alcohol for 24 hours.
25. Simple fixatives-
Formaldehyde
Commercially available solution contains 35%-40%
gas by weight, called as formalin.
Formaldehyde is commonly used as 4% solution,
giving 10% formalin for tissue fixation.
Formalin is most commonly used fixative.
It is cheap, penetrates rapidly and does not over-
harden the tissues.
The primary action of formalin is to form additive
compounds with proteins without precipitation.
Formalin brings about fixation by converting the free
amine groups to methylene derivatives.
26. Formaldehyde
If formalin is kept standing for a long time, a large
amount of formic acid is formed due to oxidation of
formaldehyde and this tends to form artefact which
is seen as brown pigment in the tissues. To avoid
this buffered formalin is used.
27. • Specific features
- Excellent fixative for routine biopsy work
- Allows brilliant staining with good cytological
detail
- Gives rapid and even penetration with minimum
shrinkage
- Tissue left in its for over 24 hours becomes
bleached and excessively hardened.
- Tissue should be treated with iodine to remove
mercury pigment
28. Absolute Alcohol
It may be used as a fixative as it coagulates
protein.
Due to its dehydrating property it removes water
too fast from the tissues and produces shrinkage of
cells and distortion of morphology.
It penetrates slowly and over-hardens the tissues.
29. Acetone
Sometimes it is used for the study of enzymes
especially phosphatases and lipases.
Disadvantages are the same as of alcohol.
30. Mercuric chloride
It is a protein precipitant.
However it causes great shrinkage of tissues
hence seldom used alone.
It gives brown colour to the tissues which needs to
be removed by treatment with Iodine during
dehydration.
31. Potassium dichromate
It has a binding effect on protein similar to that of
formalin. Following fixation with Potassium
dichromate tissue must be well washed in running
water before dehydration
. 7. Chromic acid – 8. Osmium tetraoxide –. 9.
Picric acid –
33. Chromic acid
It precipitates all proteins and preserves
carbohydrates. Tissues fixed in chromic acid also
require thorough washing with water before
dehydration.
34. Osmium tetra oxide
It gives excellent preservation of cellular details,
hence used for electron-microscopy
35. Picric acid
It precipitates proteins and combines with them to
form picrates.
Owing to its explosive nature when dry; it must be
kept under a layer of water.
Tissue fixed in picric acid also require thorough
washing with water to remove colour. Tissue can
not be kept in picric acid more than 24 hrs
36. Formal Saline
It is most widely used fixative.
Tissue can be left in this for long period without excessive
hardening or damage.
Tissues fixed for a long time occasionally contain a
pigment (formalin pigment).
This may be removed in sections before staining by
treatment with picric alcohol or 10% alcoholic solution of
sodium hydroxide. The formation of this pigment can be
prevented by neutralising or buffering the formal saline.
37. Formal calcium
Useful for demonstration of phospholipids.
Fixation time-24 hours at room temperature
38. Zenker’s fluid
It contains mercuric chloride, potassium-di-
chromate, sodium sulphate and glacial acetic acid.
Advantages – even penetration, rapid fixation
Disadvantages – After fixation the tissue must be
washed in running water to remove excess
dichromate. Mercury pigment must be removed
with Lugol’s iodine.
39. Zenker’s formal
In stock Zenker’s fluid, formalin is added instead of
acetic acid.
Advantages – excellent microanatomical fixative
especially for bone marrow, spleen & kidney
40. Bouin’s Fluid
It contains picric acid, glacial acetic acid and 40%
formaldehyde.
Advantages –
(a) Rapid and even penetration without any
shrinkage.
(b) Brilliant staining by trichrome method. It is
routinely used for preservation of testicular
biopsies.
41. 1.10% buffered formalin is the commonest fixative.
2. Tissues may be kept in 10% buffered formalin for long
duration.
3. Volume of the fixative should be atleast ten times of the
volume of the specimen. The specimen should be
completely submerged.
4. Special fixatives are used for preserving particular
tissues.
5. Formalin vapours cause throat/ eye irritation hence
42. Secondary Fixation
Following fixation in formalin it is sometimes useful
to submit the tissue to second fixative eg. mercuric
chloride for 4 hours.
It provides firmer texture to the tissues and gives
brilliance to the staining
43. Post chromatization
It is the treatment and tissues with 3% potassium
dichromate following normal fixation.
Post chromatization is carried out either before
processing, when tissue is for left for 6-8 days in
dichromate solution or after processing when the
sections are immersed in dichromate solution, In
for 12-24 hours, in both the states washing well in
running water is essential.
This technique is used a mordant to tissues.
44. Washing Out
After the use of certain fixative it in urgent that the
tissues be thoroughly washed in running water to
remove the fixative entirely.
Washing should be carried out ideally for 24 hours.
Tissues treated with potassium dichromate,
osmium tetraoxide and picric acid particularly need
to be washed thoroughly with water prior to
treatment with alcohol (for dehydration).
45. 6. Tissues should be well fixed before dehydration.
7. Penetration of fixatives takes some time. It is necessary
that the bigger specimen should be given cuts so that the
central part does not remain unfixed.
8. Mercury pigment must be removed with Lugol’s iodine.
9. Biopsies cannot be kept for more than 24 hours in
bouin’s fluid without changing the alcohol.
10. Glutaraldehyde and osmion tetraoxide are used as