Immunohistochemistry in the context of "Cytochemistry"

Anatomical pathology (Commonwealth) or anatomic pathology (U.S.) is a medical specialty that is concerned with the diagnosis of disease based on the macroscopic, microscopic, biochemical, immunologic and molecular examination of organs and tissues. Over the 20th century, surgical pathology has evolved tremendously: from historical examination of whole bodies (autopsy) to a more modernized practice, centered on the diagnosis and prognosis of cancer to guide treatment decision-making in oncology. Its modern founder was the Italian scientist Giovanni Battista Morgagni from Forlì.

Anatomical pathology is one of two branches of pathology, the other being clinical pathology, the diagnosis of disease through the laboratory analysis of bodily fluids or tissues. Often, pathologists practice both anatomical and clinical pathology, a combination known as general pathology. Similar specialties exist in veterinary pathology.

Hematopathology or hemopathology (both also spelled haem-, see spelling differences) is the study of diseases and disorders affecting and found in blood cells, their production, and any organs and tissues involved in hematopoiesis, such as bone marrow, the spleen, and the thymus. Diagnoses and treatment of diseases such as leukemia and lymphoma often deal with hematopathology; techniques and technologies include flow cytometry studies and immunohistochemistry.

In the United States, hematopathology is a board-certified subspecialty by the American Board of Pathology. Board-eligible or board-certified hematopathologists are usually pathology residents (anatomic, clinical, or combined) who have completed hematopathology fellowship training after their pathology residency. The hematopathology fellowship lasts either one or two years. A physician who practices hematopathology is called a hematopathologist.

Amyloid plaques (also known as neuritic plaques, amyloid beta plaques or senile plaques) are extracellular deposits of amyloid beta (Aβ) protein that present mainly in the grey matter of the brain. Degenerative neuronal elements and an abundance of microglia and astrocytes can be associated with amyloid plaques. Some plaques occur in the brain as a result of aging, but large numbers of plaques and neurofibrillary tangles are characteristic features of Alzheimer's disease.

The plaques are highly variable in shape and size; in tissue sections immunostained for Aβ, they comprise a log-normal size distribution curve, with an average plaque area of 400–450 square micrometers (μm). The smallest plaques (less than 200 μm), which often consist of diffuse deposits of Aβ, are particularly numerous. Plaques form when Aβ misfolds and aggregates into oligomers and longer polymers, the latter of which are characteristic of amyloid.

Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of ions across the cell membrane, controlling the flow of ions across secretory and epithelial cells, and regulating cell volume. Ion channels are present in the membranes of all cells. Ion channels are one of the two classes of ionophoric proteins, the other being ion transporters.

The study of ion channels often involves biophysics, electrophysiology, and pharmacology, while using techniques including voltage clamp, patch clamp, immunohistochemistry, X-ray crystallography, fluoroscopy, and RT-PCR. Their classification as molecules is referred to as channelomics.

Lewy bodies are inclusion bodies – abnormal aggregations of protein – that develop inside neurons affected by Parkinson's disease, the Lewy body dementias (Parkinson's disease dementia and dementia with Lewy bodies (DLB)), and in several other disorders such as multiple system atrophy. The defining proteinaceous component of Lewy bodies is alpha-synuclein (α-synuclein), which aggregates to form Lewy bodies within neuronal cell bodies, and Lewy neurites in neuronal processes (axons or dendrites). In some disorders, alpha-synuclein also forms aggregates in glial cells that are referred to as 'glial cytoplasmic inclusions'; together, diseases involving Lewy bodies, Lewy neurites and glial cytoplasmic inclusions are called 'synucleinopathies'.

Lewy bodies appear as spherical masses in the neuronal cytoplasm that can displace other cellular components such as the nucleus and neuromelanin. A given neuron may contain one or more Lewy bodies. There are two main kinds of Lewy bodies – classical (brainstem-type) and cortical-type. Classical Lewy bodies occur most commonly in pigmented neurons of the brainstem, such as the substantia nigra and locus coeruleus, although they are not restricted to pigmented neurons. They are strongly eosinophilic structures ranging from 8-30 microns in diameter, and when viewed with a light microscope they are seen to consist of a dense core that is often surrounded by a pale shell. Electron microscopic analyses found that the core consists of a compact mass of haphazard filaments and various particles surrounded by a diffuse corona of radiating filaments. In contrast, cortical-type Lewy bodies are smaller, only faintly eosinophilic, and devoid of a surrounding halo with radial filaments. Cortical-type Lewy bodies occur in multiple regions of the cortex and in the amygdala. Cortical Lewy bodies are a distinguishing feature of dementia with Lewy bodies, but they may occasionally be seen in ballooned neurons characteristic of behavioural variant frontotemporal dementia and corticobasal degeneration, as well as in patients with other tauopathies.

In situ hybridization (ISH) is a type of hybridization that uses a labeled complementary DNA, RNA or modified nucleic acid strand (i.e., a probe) to localize a specific DNA or RNA sequence in a portion or section of tissue (in situ) or if the tissue is small enough (e.g., plant seeds, Drosophila embryos), in the entire tissue (whole mount ISH), in cells, and in circulating tumor cells (CTCs). This is distinct from immunohistochemistry, which usually localizes proteins in tissue sections.

In situ hybridization is used to reveal the location of specific nucleic acid sequences on chromosomes or in tissues, a crucial step for understanding the organization, regulation, and function of genes. The key techniques currently in use include in situ hybridization to mRNA with oligonucleotide and RNA probes (both radio-labeled and hapten-labeled), analysis with light and electron microscopes, whole mount in situ hybridization, double detection of RNAs and RNA plus protein, and fluorescent in situ hybridization to detect chromosomal sequences. DNA ISH can be used to determine the structure of chromosomes. Fluorescent DNA ISH (FISH) can, for example, be used in medical diagnostics to assess chromosomal integrity. RNA ISH (RNA in situ hybridization) is used to measure and localize RNAs (mRNAs, lncRNAs, and miRNAs) within tissue sections, cells, whole mounts, and circulating tumor cells (CTCs). In situ hybridization was invented by American biologists Mary-Lou Pardue and Joseph G. Gall.