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RRM2B
Ribonucleotide-diphosphate reductase subunit M2 B is an enzyme that in humans is encoded by the ''RRM2B'' gene. The gene encoding the RRM2B protein is located on chromosome 8, at position 8q23.1. The gene and its products are also known by designations MTDPS8A, MTDPS8B, and p53R2. Function RRM2B codes for one of two versions of the R2 subunit of ribonucleotide reductase, which generates nucleotide precursors required for DNA replication by reducing ribonucleoside diphosphates to deoxyribonucloside diphosphates. The version of R2 encoded by RRM2B is induced by p53, and is required for normal DNA repair and mtDNA synthesis in non-proliferating cells. The other form of R2 is expressed only in dividing cells. Interactions RRM2B has been shown to interact with Mdm2 and Ataxia telangiectasia mutated. Clinical relevance Abnormalities in this gene are one of the causes of mitochondrial DNA depletion syndrome (MDDS). Neonatal hypotonia, developmental delay, encephalopathy, with sei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitochondrial DNA Depletion Syndrome
Mitochondrial DNA depletion syndrome (MDS or MDDS), or Alper's disease, is any of a group of autosomal recessive disorders that cause a significant drop in mitochondrial DNA in affected tissues. Symptoms can be any combination of myopathic, hepatopathic, or encephalomyopathic. These syndromes affect tissue in the muscle, liver, or both the muscle and brain, respectively. The condition is typically fatal in infancy and early childhood, though some have survived to their teenage years with the myopathic variant and some have survived into adulthood with the SUCLA2 encephalomyopathic variant. There is currently no curative treatment for any form of MDDS, though some preliminary treatments have shown a reduction in symptoms. Signs and symptoms All forms of MDDS are very rare. MDDS causes a wide range of symptoms, which can appear in newborns, infants, children, or adults, depending on the class of MDDS; within each class symptoms are also diverse. In MDDS associated with mutations ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ribonucleotide Reductase
Ribonucleotide reductase (RNR), also known as ribonucleoside diphosphate reductase (rNDP), is an enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides. It catalyzes this formation by removing the 2'-hydroxyl group of the ribose ring of nucleoside diphosphates. This reduction produces deoxyribonucleotides. Deoxyribonucleotides in turn are used in the synthesis of DNA. The reaction catalyzed by RNR is strictly conserved in all living organisms. Furthermore, RNR plays a critical role in regulating the total rate of DNA synthesis so that DNA to cell mass is maintained at a constant ratio during cell division and DNA repair. A somewhat unusual feature of the RNR enzyme is that it catalyzes a reaction that proceeds via a free radical mechanism of action. The substrates for RNR are ADP, GDP, CDP and UDP. dTDP (deoxythymidine diphosphate) is synthesized by another enzyme ( thymidylate kinase) from dTMP (deoxythymidine monophosphate). Structure Ribonucleoti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gemcitabine
Gemcitabine, with brand names including Gemzar, is a chemotherapy medication. It treats cancers including testicular cancer, breast cancer, ovarian cancer, non-small cell lung cancer, pancreatic cancer, and bladder cancer. It is administered by intravenous infusion. It acts against neoplastic growth, and it inhibits the replication of Orthohepevirus A, the causative agent of Hepatitis E, through upregulation of interferon signaling. Common side effects include bone marrow suppression, liver and kidney problems, nausea, fever, rash, shortness of breath, mouth sores, diarrhea, neuropathy, and hair loss. Use during pregnancy will likely result in fetal harm. Gemcitabine is in the nucleoside analog family of medication. It works by blocking the creation of new DNA, which results in cell death. Gemcitabine was patented in 1983 and was approved for medical use in 1995. Generic versions were introduced in Europe in 2009 and in the US in 2010. It is on the WHO Model List of Essentia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ataxia Telangiectasia Mutated
ATM serine/threonine kinase or Ataxia-telangiectasia mutated, symbol ATM, is a serine/threonine protein kinase that is recruited and activated by DNA double-strand breaks. It phosphorylates several key proteins that initiate activation of the DNA damage checkpoint, leading to cell cycle arrest, DNA repair or apoptosis. Several of these targets, including p53, CHK2, BRCA1, NBS1 and H2AX are tumor suppressors. In 1995, the gene was discovered by Yosef Shiloh who named its product ATM since he found that its mutations are responsible for the disorder ataxia–telangiectasia#Cause, ataxia–telangiectasia. In 1998, the Shiloh and Michael B. Kastan, Kastan laboratories independently showed that ATM is a protein kinase whose activity is enhanced by DNA damage. Introduction Throughout the cell cycle DNA is monitored for damage. Damages result from errors during DNA replication, replication, by-products of metabolism, general toxic drugs or ionizing radiation. The cell cycle has diffe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypotonia
Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases and disorders that affect motor nerve control by the brain or muscle strength. Hypotonia is a lack of resistance to passive movement, whereas muscle weakness results in impaired active movement. Central hypotonia originates from the central nervous system, while peripheral hypotonia is related to problems within the spinal cord, peripheral nerves and/or skeletal muscles. Severe hypotonia in infancy is commonly known as floppy baby syndrome. Recognizing hypotonia, even in early infancy, is usually relatively straightforward, but diagnosing the underlying cause can be difficult and often unsuccessful. The long-term effects of hypotonia on a child's development and later life depend primarily on the severity of the muscle weakness and the na ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophthalmoplegia
Ophthalmoparesis refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic, ophthalmologic, and endocrine disease. Internal ophthalmoplegia means involvement limited to the pupillary sphincter and ciliary muscle. External ophthalmoplegia refers to involvement of only the extraocular muscles. Complete ophthalmoplegia indicates involvement of both. Causes Ophthalmoparesis can result from disorders of various parts of the eye and nervous system: * Infection around the eye. Ophthalmoplegia is an important finding in orbital cellulitis. * The orbit of the eye, including mechanical restrictions of eye movement, as in Graves' disease. * The muscle, as in progressive external ophthalmoplegia or Kearns–Sayre syndrome. * The neuromuscular junction, as in myasthenia gravis. * The relevant cranial nerves (specifically the oculomotor, trochlear, and abducens), as in ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acute Liver Failure
Acute liver failure is the appearance of severe complications rapidly after the first signs (such as jaundice) of liver disease, and indicates that the liver has sustained severe damage (loss of function of 80–90% of liver cells). The complications are hepatic encephalopathy and impaired protein synthesis (as measured by the levels of serum albumin and the prothrombin time in the blood). The 1993 classification defines ''hyperacute'' as within 1 week, ''acute'' as 8–28 days, and ''subacute'' as 4–12 weeks; both the speed with which the disease develops and the underlying cause strongly affect outcomes. Signs and symptoms The main features of acute liver failure are rapid-onset jaundice, weakness, and eventually, changes in mental status that can begin as mild confusion but progress to coma, known as hepatic encephalopathy. Encephalopathy and cerebral edema In ALF, hepatic encephalopathy leads to cerebral edema, coma, brain herniation, and eventually death. Detection of e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Respiratory Failure
Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes increased respiratory rate, abnormal blood gases (hypoxemia, hypercapnia, or both), and evidence of increased work of breathing. Respiratory failure causes an altered mental status due to ischemia in the brain. The typical partial pressure reference values are oxygen Pa more than 80 mmHg (11 kPa) and carbon dioxide Pa less than 45 mmHg (6.0 kPa). Cause Several types of conditions can potentially result in respiratory failure: * Conditions that reduce the fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lactic Acidosis
Lactic acidosis is a medical condition characterized by a build-up of lactate (especially -lactate) in the body, with formation of an excessively low pH in the bloodstream. It is a form of metabolic acidosis, in which excessive acid accumulates due to a problem with the body's oxidative metabolism. Lactic acidosis is typically the result of an underlying acute or chronic medical condition, medication, or poisoning. The symptoms are generally attributable to these underlying causes, but may include nausea, vomiting, Kussmaul breathing (laboured and deep), and generalised weakness. The diagnosis is made on biochemical analysis of blood (often initially on arterial blood gas samples), and once confirmed, generally prompts an investigation to establish the underlying cause to treat the acidosis. In some situations, hemofiltration (purification of the blood) is temporarily required. In rare chronic forms of lactic acidosis caused by mitochondrial disease, a specific diet or dichloro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deafness
Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written with a lower case ''d''. It later came to be used in a cultural context to refer to those who primarily communicate through sign language regardless of hearing ability, often capitalized as ''Deaf'' and referred to as "big D Deaf" in speech and sign. The two definitions overlap but are not identical, as hearing loss includes cases that are not severe enough to impact spoken language comprehension, while cultural Deafness includes hearing people who use sign language, such as children of deaf adults. Medical context In a medical context, deafness is defined as a degree of hearing difference such that a person is unable to understand speech, even in the presence of amplification. In profound deafness, even the highest intensity sound ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seizures
An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or neural oscillation, synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with loss of consciousness (tonic-clonic seizure), to shaking movements involving only part of the body with variable levels of consciousness (focal seizure), to a subtle momentary loss of awareness (absence seizure). Most of the time these episodes last less than two minutes and it takes some time to return to normal. Urinary incontinence, Loss of bladder control may occur. Seizures may be provoked and unprovoked. Provoked seizures are due to a temporary event such as low blood sugar, alcohol withdrawal, abusing alcohol together with prescription medication, low blood sodium, fever, brain infection, or concussion. Unprovoked seizures occur without a known or fixable cause such that ongoing seizures are likely. Unprovoked seizur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encephalopathy
Encephalopathy (; from grc, ἐνκέφαλος "brain" + πάθος "suffering") means any disorder or disease of the brain, especially chronic degenerative conditions. In modern usage, encephalopathy does not refer to a single disease, but rather to a syndrome of overall brain dysfunction; this syndrome has many possible organic and inorganic causes. Signs and symptoms The hallmark of encephalopathy is an altered mental state or delirium. Characteristic of the altered mental state is impairment of the cognition, attention, orientation, sleep–wake cycle and consciousness. An altered state of consciousness may range from failure of selective attention to drowsiness. Hypervigilance may be present; with or without: cognitive deficits, headache, epileptic seizures, myoclonus (involuntary twitching of a muscle or group of muscles) or asterixis ("flapping tremor" of the hand when wrist is extended). Depending on the type and severity of encephalopathy, common neurological sym ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
