Precursor cell in the context of "Myoblasts"

In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.

In mammals, roughly 50 to 150 cells make up the inner cell mass during the blastocyst stage of embryonic development, around days 5–14. These have stem-cell capability. In vivo, they eventually differentiate into all of the body's cell types (making them pluripotent). This process starts with the differentiation into the three germ layers – the ectoderm, mesoderm and endoderm – at the gastrulation stage. However, when they are isolated and cultured in vitro, they can be kept in the stem-cell stage and are known as embryonic stem cells (ESCs).

A muscle cell, also known as a myocyte, is a mature contractile cell in the muscle of an animal. In humans and other vertebrates there are three types: skeletal, smooth, and cardiac (cardiomyocytes). A skeletal muscle cell is long and threadlike with many nuclei and is called a muscle fiber. Muscle cells develop from embryonic precursor cells called myoblasts.

Skeletal muscle cells form by fusion of myoblasts to produce multinucleated cells (syncytia) in a process known as myogenesis. Skeletal muscle cells and cardiac muscle cells both contain myofibrils and sarcomeres and form a striated muscle tissue.

Myogenesis is the formation of skeletal muscular tissue, particularly during embryonic development.Muscle fibers generally form through the fusion of precursor myoblasts into multinucleated fibers called myotubes. In the early development of an embryo, myoblasts can either proliferate, or differentiate into a myotube. What controls this choice in vivo is generally unclear. If placed in cell culture, most myoblasts will proliferate if enough fibroblast growth factor (FGF) or another growth factor is present in the medium surrounding the cells. When the growth factor runs out, the myoblasts cease division and undergo terminal differentiation into myotubes.

Myoblast differentiation proceeds in stages. The first stage involves cell cycle exit and the commencement of expression of certain genes. The second stage of differentiation involves the alignment of the myoblasts with one another. Studies have shown that even rat and chick myoblasts can recognise and align with one another, suggesting evolutionary conservation of the mechanisms involved. The third stage is the actual cell fusion itself. In this stage, the presence of calcium ions is critical. Fusion in humans is aided by a set of metalloproteinases coded for by the ADAM12 gene, and a variety of other proteins. Fusion involves recruitment of actin to the plasma membrane, followed by close apposition and creation of a pore that subsequently rapidly widens.

Leukemia (also spelled leukaemia; pronounced /luːˈkiːmiːə/ loo-KEE-mee-ə) is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells. These blood cells are not fully developed and are called blasts or leukemia cells. Symptoms may include bleeding and bruising, bone pain, fatigue, fever, and an increased risk of infections. These symptoms occur due to a lack of normal blood cells. Diagnosis is typically made by blood tests or bone marrow biopsy.

The exact cause of leukemia is unknown. A combination of genetic factors and environmental (non-inherited) factors are believed to play a role. Risk factors include smoking, ionizing radiation, petrochemicals (such as benzene), prior chemotherapy, and Down syndrome. People with a family history of leukemia are also at higher risk. There are four main types of leukemia—acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML)—and a number of less common types. Leukemias and lymphomas both belong to a broader group of tumors that affect the blood, bone marrow, and lymphoid system, known as tumors of the hematopoietic and lymphoid tissues.

A lipoblast is a precursor cell for an adipocyte. Alternate terms include adipoblast and preadipocyte. Early stages are almost indistinguishable from fibroblasts.

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  Lipoblasts (white arrow) and lipocytes (black arrow), in a case of lipoblastoma
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  Micrograph showing a lipoblast (left-bottom of image) in a liposarcoma. H&E stain.
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  Histopathology of liposarcoma, H&E stain, with the main features:
  - Spindle cells with enlarged, hyperchromatic nuclei.
  - Apparently univacuolated adipocytes (may look normal).
  - Lipoblasts (multivacuolated), but neither necessary nor sufficient for diagnosis of liposarcoma.
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  Lipid-laden histiocytes may mimic lipoblasts, but have lightly eosinophilic cytoplasm and a small normochromatic nuclei which are not hollowed out from the lipid vacuoles.