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Encyclopedia > Mitochondrial disease

Mitochondrial diseases are a group of disorders relating to the mitochondria, the organelles that are the "powerhouses" of the eukaryotic cells that comprise higher-order lifeforms (including humans). The mitochondria convert the energy of food molecules into the ATP that powers most cell functions. Electron micrograph of a mitochondrion showing its mitochondrial matrix and membranes In cell biology, a mitochondrion (plural mitochondria) (from Greek μιτος or mitos, thread + χονδριον or khondrion, granule) is a membrane-enclosed organelle, found in most eukaryotic cells. ... Schematic of typical animal cell, showing subcellular components. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...


Mitochondrial diseases comprise those disorders that in one way or another affect the function of the mitochondria and/or are due to mitochondrial DNA. Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function. The subclass of these diseases that have neuromuscular disease symptoms are often referred to as a mitochondrial myopathy. Mitochondrial DNA (some captions in German) Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. ... Mitochondrial myopathy is typically caused by defects in part of the mitochondrion (the power plant of the cell) known as the respiratory chain. ...


Mitochondrial inheritance

Mitochondrial inheritance behaves differently from autosomal and sex-linked inheritance. Nuclear DNA has two copies per cell (except for sperm and egg cells). One copy is inherited from the father and the other from the mother. Mitochondria, however, contain their own DNA, and contain typically from five to ten copies (see Heteroplasmy), all inherited from the mother (for more detailed inheritance patterns, see Human mitochondrial genetics). When mitochondria divide, the copies of DNA present are divided randomly between the two new mitochondria, and then those new mitochondria make more copies. As a result, if only a few of the DNA copies inherited from the mother are defective, mitochondrial division may cause most of the defective copies to end up in just one of the new mitochondria. Mitochondrial disease begins to become apparent once the number of affected mitochondria reaches a certain level; this phenomenon is called 'threshold expression'. Nuclear DNA is DNA contained within a nucleus of eukaryotic organisms. ... Heteroplasmy is the presence of a mixture of more than one type of an organellar genome (mitochondrial DNA (mtDNA) or plastid DNA) within a cell or individual. ... // Mitochondrial genetics is the study of the genetics of the DNA contained in mitochondria. ... The phenomenon within molecular biochemistry when more than half of the Mitochondrial DNA copies are defective, causing mitochondrial disease to become more pronounced and unavoidable. ...


Not all of the enzymes and other components necessary for proper mitochondrial function are encoded in the mitochondrial DNA. Most mitochondrial function is controlled by nuclear DNA instead.


Mutations to mitochondrial DNA occur frequently, due to the lack of the error checking capability that nuclear DNA has. This means that mitochondrial disorders often occur spontaneously and relatively often. Sometimes the enzymes that control mitochondrial DNA duplication (and which are encoded for by genes in the nuclear DNA) are defective, causing mitochondrial DNA mutations to occur at a rapid rate.


Defects and symptoms

The effects of mitochondrial disease can be quite varied. Since the distribution of defective DNA may vary from organ to organ within the body, the mutation that in one person may cause liver disease might in another person cause a brain disorder. In addition, the severity of the defect may be great or small. Some minor defects cause only "exercise intolerance", with no serious illness or disability. Other defects can more severely affect the operation of the mitochondria and can cause severe body-wide impacts. As a general rule, mitochondrial diseases are worst when the defective mitochondria are present in the muscles or nerves, because these are the most energy-hungry cells of the body. Exercise Intolerance is a medical term used to describe a condition where the patient who is unable to do physical exercise at the level that would be expected of someone in his or her general physical condition, or who experiences unusually severe post-exercise pain, fatigue, or other negative effects. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... Nerves (yellow) Nerves redirects here. ...


However, even though mitochondrial disease varies greatly in presentation from person to person, several major categories of the disease have been defined, based on the most common symptoms and the particular mutations that tend to cause them:


Types

In addition to the Mitochondrial myopathies, other examples include: Mitochondrial myopathy is typically caused by defects in part of the mitochondrion (the power plant of the cell) known as the respiratory chain. ...

  • Leigh syndrome, subacute sclerosing encephalopathy
    • after normal development the disease usually begins late in the first year of life, but the onset may occur in adulthood
    • a rapid decline in function occurs and is marked by seizures, altered states of consciousness, dementia, ventilatory failure
  • Neuropathy, ataxia, retinitis pigmentosa, and ptosis (NARP)
    • progressive symptoms as described in the acronym
    • dementia
  • Myoneurogenic gastrointestinal encephalopathy (MNGIE)
Diabetes mellitus and deafness (DAD) or maternally inherited diabetes and deafness (MIDD) is a mitochondrial disease associated with the gene Leu-UUR. diabetes deafness Maassen J, t Hart L, Janssen G et al (2006). ... For the disease characterized by excretion of large amounts of very dilute urine, see diabetes insipidus. ... This article discusses the way the word deaf is used and how deafness is perceived by hearing and Deaf communities. ... Leber’s hereditary optic neuropathy (LHON) or Leber optic atrophy is a maternally inherited form of acute or subacute loss of central vision that may lead to degeneration of retinal ganglion cells (RGCs) and their axons; this affects predominantly young adult males. ... Wolff-Parkinson-White syndrome (WPW) is a syndrome of pre-excitation of the ventricles of the heart due to an accessory pathway known as the Bundle of Kent. ... Leighs Disease, a form of Leigh syndrome, is a rare neurometabolic disorder that affects the central nervous system. ... Neuropathy, ataxia, and retinitis pigmentosa (NARP) is a condition that causes a variety of signs and symptoms chiefly affecting the nervous system. ... For other uses, see Dementia (disambiguation). ... Myoneurogenic gastrointestinal encephalopathy or MNGIE is a rare mitochondrial disease typically appearing between the second and fifth decades of life. ... Neuropathy is usually short for peripheral neuropathy, meaning a disease of the peripheral nervous system. ...

  Results from FactBites:
 
Mitochondrial Disease (1299 words)
The common factor among these diseases is that the mitochondria are unable to completely burn food and oxygen in order to generate energy.
Mitochondrial diseases might affect the cells of the brain, nerves (including the nerves to the stomach and intestines), muscles, kidneys, heart, liver, eyes, ears, or pancreas.
It is important to determine which type of mitochondrial disease inheritance is present, in order to predict the risk of recurrence for future children.
Reference.com/Encyclopedia/Mitochondrial disease (667 words)
Mitochondrial diseases are a group of disorders relating to the mitochondria, the organelles that are the "powerhouses" of the eukaryotic cells that comprise higher-order lifeforms (including humans).
Mitochondrial diseases comprise those disorders that in one way or another affect the function of the mitochondria and/or are due to mitochondrial DNA.
Mitochondrial disease begins to become apparent once the number of affected mitochondria reaches a certain level; this phenomenon is called 'threshold expression'.
  More results at FactBites »

 
 

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