Mitochondrial myopathy with a defect of mitochondrial-protein transport

Article Abstract:

MItochondria are organelles located in the cytoplasm of cells that provide energy to the cell. They are involved in diverse biochemical reactions and contain many enzymes that facilitate life-sustaining chemical reactions. These tiny bodies even possess their own DNA. Mitochondria in muscle are now known to be responsible for several kinds of myopathy (muscle disease), and the molecular bases of some of these have been characterized. The case history of a 14-year-old girl with weakness and exercise intolerance of lifelong duration is discussed. The patient's intelligence appeared normal, but she had been unable to run or play normally in school. Her symptoms had been attributed to asthma. Biopsy specimens from a leg muscle were evaluated to determine the source of the muscle weakness. The levels of several enzymes important in the mitochondrial respiratory chain (the series of chemical events that leads to energy production) were abnormally low. An analysis of the specific deficits is provided. Similar cases reported in the medical literature are compared with the present case. People with deficits in mitochondrial enzymes of a magnitude equivalent to the patient's, but not confined to muscle, usually die in infancy. (Consumer Summary produced by Reliance Medical Information, Inc.)

Case studies, Physiological aspects, Metabolic regulation, Mitochondrial myopathies

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A defect in mitochondrial electron-transport activity (NADH-coenzyme Q oxidoreductase) in Leber's hereditary optic neuropathy

Article Abstract:

The nucleus of the cell contains DNA, genetic material inherited from both parents, while the mitochondria, the energy producing organ of the cell, has its own separate DNA, responsible for the production of proteins required for cellular activities, which is contributed solely by the mother during the fertilization process. Diseases due to mutations in mitochondrial DNA can be passed to both male and female children, but only the daughters will continue to pass on the disease. Leber's optic neuropathy is inherited from the mother and causes rapid loss of vision in both eyes during the late teenage and early adult years. The possibility that a mechanism of mitochondrial inheritance was responsible for Leber's optic neuropathy has been discussed. Evidence supporting the hypothesis that a mitochondrial genetic defect is responsible for this disease has been presented. Examination of four members of the same family all suffering from Leber's disease found a decrease in the activity of the Complex I electron transport activity suggesting that the mutation is associated with a gene in the mitochondria that is responsible for making the proteins needed for that complex to function.

Analysis, Electron transport, column, Leber's congenital amaurosis

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Epidemic optic neuropathy in Cuba - clinical characterization and risk factors

Article Abstract:

The outbreak of peripheral and optic neuropathy in Cuba from 1991 to 1993 may have been caused by poor nutrition resulting from poor economic conditions and widespread tobacco use. Neuropathy is a disturbance of nerves outside of the central nervous system. Researchers interviewed and administered physical examinations and blood tests to 123 people who had severe optic neuropathy during the epidemic and 123 matched people who showed no signs of optic neuropathy. Neuropathy patients had a lower median income and tended to be less educated. Common symptoms among the neuropathy group included partial loss of vision, reduced visual field, and poor color vision. Significant risk factors included cigar smoking, cassava consumption, low lycopene levels, and low dietary intake of animal protein, animal fat, methionine, vitamin B12, riboflavin, niacin, and pyridoxine. Risk of disease was reduced by raising chickens, possibly resulting in an increased availability of food. Most patients conditions during the epidemic improved with vitamin supplementation.

Health aspects, Risk factors, Cuba, Vision disorders, Peripheral nerve diseases, Peripheral nervous system diseases

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