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Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This paper reviews present knowledge on the etiology, pathophysiology, complications, prevention, and therapy of the disorders induced by iodine deficiency. The recommended dietary allowances of iodine are 100 micrograms/day for adults and adolescents, 60-100 micrograms/day for children aged 1 to 10 years, and 35-40 micrograms/day in infants aged less than 1 year. When the physiological requirements of iodine are not met in a given population, a series of functional and developmental abnormalities occur including thyroid function abnormalities and, when iodine deficiency is severe, endemic goiter and cretinism, endemic mental retardation, decreased fertility rate, increased perinatal death, and infant mortality. These complications, which constitute a hindrance to the development of the affected populations, are grouped under the general heading of iodine deficiency disorders (IDD). At least one billion people are at risk of IDD. Iodine deficiency, therefore, constitutes one of the most common preventable causes of mental deficiency in the world today. Most of the affected populations live in mountainous areas in preindustrialized countries, but 50 to 100 million people are still at risk in Europe. The most important target groups to the effects of iodine deficiency from a public health point of view are pregnant mothers, fetuses, neonates, and young infants because the main complication of IDD, i.e., brain damage resulting in irreversible mental retardation, is the consequence of thyroid failure occurring during pregnancy, fetal, and early postnatal life. The main cause of endemic goiter and cretinism is an insufficient dietary supply of iodine. The additional role of naturally occurring goitrogens has been documented in the case of certain foods (milk, cassava, millet, nuts) and bacterial and chemical water pollutants. The mechanism by which the thyroid gland adapts to an insufficient iodine supply is to increase the trapping of iodide as well as the subsequent steps of the intrathyroidal metabolism of iodine leading to preferential synthesis and secretion of triiodotyronine (T3). They are triggered and maintained by increased secretion of TSH, which is ultimately responsible for the development of goiter. The acceleration of the main steps of iodine kinetics and the degree of hyperstimulation by TSH are much more marked in the pediatric age groups, including neonates, than in adults, and the development of goiter appears as an unfavorable side effect in the process of adaptation to iodine deficiency during growth. The most serious complication of iodine deficiency is endemic cretinism, a syndrome characterized by irreversible mental retardation together with either a predominant neurological syndrome or predominant hypothyroidism, or a combination of both syndromes.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The disorders induced by iodine deficiency. 805 57

Effects of a 10-week aerobic exercise program on maximal oxygen consumption (VO2max), oxygen pulse (O2 pulse), maximum ventilation (max vent), exercise stress test duration (max time), flexibility, weight and body composition (percentage body fat, percentage lean mass, and percentage body water) were investigated in 14 community-based adults with mental retardation. Supervised optional training sessions were held 4 days per week. Subjects were assessed for VO2 max, O2 pulse, max vent, and max time before and after the training program. Flexibility, weight, and body composition changes were assessed before, midway through, and after the training program. Subjects had a 91.3% attendance rate, and all safely completed the program. The treatment produced significant increases in VO2 max, O2 pulse, max vent, max time, and flexibility. However, no significant change was observed in weight or body composition changes.
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PMID:Effects of an aerobic exercise program on community-based adults with mental retardation. 808 74

Hyponatremia, an electrolyte disturbance usually without clinical significance, may sometimes lead to serious complications when overlooked or not treated appropriately. One cause of hyponatremia, the syndrome of inappropriate antidiuretic hormone (SIADH) secretion, has been associated with some drugs, including carbamazepine (CBZ). Because of its antidiuretic effects, CBZ has been used successfully to treat diabetes insipidus centralis. Possible mechanisms for the antidiuretic effects of CBZ have been proposed. Altered sensitivity to serum osmolality by the hypothalamic osmoreceptors appears likely, but an increased sensitivity of the renal tubules to circulating ADH cannot be excluded. CBZ has led to hyponatremia in patients with epilepsy, neuralgia, mental retardation, and psychiatric disorders with a frequency varying from 4.8 to 40%. Oxcarbazepine (OCBZ), which is structurally related to CBZ, has shown similar hyponatremic effects, but whether hyponatremia occurs more often than with CBZ is not yet clear. Experience with OCBZ is still limited, and there is no definite explanation for a possible difference in antidiuretic potency. Most patients with CBZ/OCBZ-induced hyponatremia are asymptomatic. In rare cases, water intoxication has been reported, necessitating treatment discontinuation.
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PMID:Hyponatremia associated with carbamazepine and oxcarbazepine therapy: a review. 811 43

Normal development of the CNS requires adequate thyroid hormone exposure. Since iodine is an essential component of the thyroid hormone molecule, its deficiency during fetal development can cause hypothyroidism and irreversible mental retardation. The full-blown syndrome, called cretinism, includes deaf-mutism, short stature, spasticity, and profound mental retardation. The clinical spectrum can vary in degree and combination of these features. Screening programs in iodine-deficient countries show that up to 10% of neonates have elevated serum TSH levels, putting them at theoretical risk for permanent brain damage. About one billion people worldwide risk the consequences of iodine deficiency, all of which can be prevented by adequate maternal and infant iodine nutrition. Iodized salt is usually the preferred prophylactic vehicle, but iodized vegetable oil, iodized water, and iodine tablets are also occasionally used. The United Nations and the heads of state of most countries have pledged the virtual elimination of iodine deficiency by the year 2000. This goal is technically feasible if pursued with sufficient vigor and resources.
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PMID:Iodine supplementation and the prevention of cretinism. 849 59

The adverse effects of the maternal consumption of alcohol on the fetus have been recognized for centuries. Fetal alcohol syndrome is characterized by pre- and postnatal growth retardation, mental retardation, behavioral deficits, and facial deformities. Despite numerous animal studies, the biochemical mechanism(s) by which alcohol produces teratogenic effects on the developing fetus are not well understood. Several studies have shown that administration of alcohol to adult rats produces a decrease in hepatic levels of glutathione (GSH). In utero administration of alcohol has also been shown to produce a decrease in GSH levels, as well as prenatal growth retardation and intrauterine death. In an effort to determine if GSH may have a vital role in protecting the fetus against the teratogenic effects of alcohol, buthionine (SR)-sulfoximine (BSO) was used to deplete GSH levels in the mother and fetus. Timed pregnant Sprague-Dawley rats were placed on a liquid BioServ diet containing either 0%, 11%, 23%, 29%, 31%, 33%, or 35% ethanol-derived calories, with or without BSO (888 mg/kg/24 hr), starting on day 1 of pregnancy. Another set of mothers were fed lab chow and water as a control group for the liquid diet. The mothers were maintained on the diet until gestation day 21 when they were anesthetized with sodium pentobarbital and the pups delivered by cesarean section. The offspring were counted, weighed, killed, and the brain and liver weighed. The effects of BSO on the alcohol dose-response curves (body weights, brain weights, and litter number) were then determined to ascertain if a depletion in GSH potentiated the effects of alcohol. In utero administration of BSO, aside from the depletion of GSH in the liver and brain in the developing fetus, produced a shift to the left in the alcohol dose-response curve.
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PMID:Effects of buthionine sulfoximine on the outcome of the in utero administration of alcohol on fetal development. 890 78

In this study, we report on a 12-year-old boy with autism, mental retardation, and a history of severe gastrointestinal problems who presented with total liquid and food refusal. Backward chaining was used to shape drinking from a cup, and a fading procedure was used to increase the quantity of water he was required to drink.
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PMID:Treating total liquid refusal with backward chaining and fading. 899 38

Fmr1 knockout mice constitute a putative model of fragile X syndrome, the most common form of heritable mental disability in humans. We have compared the performance of transgenic mice with an Fmr1 knockout with that of normal littermates in hidden- and visible-platform water maze learning, and showed that knockouts exhibit subnormal spatial learning abilities and marginal motor performance deficits. During 12 training trials of the hidden-platform task, escape latency and path length decreased significantly in knockouts and control littermates, and no effect of genotype was found. During four ensuing reversal trials, however, significant differences were found between knockouts and control littermates both in escape latency and path length. During the visible-platform condition, the reversal trials also revealed a difference between knockouts and normal littermates in escape latency, but not in path length. Possibly due to marginal motor incapacity, knockouts swam significantly slower than controls during these latter trials. During both probe trials of the hidden-platform task, knockouts as well as normal littermates spent more time in the target quadrant than in the other quadrants, and percent of time spent in the target quadrant was the same in both groups; swimming velocity was not significantly different between knockouts and normal littermates during these trials. Entries in the target area during the probe trials did show a significant effect of genotype on number of entries. The present results largely confirm and extend our previous findings. Impaired spatial abilities in Fmr1 knockouts might have been due to relatively low response flexibility or high memory interference in Fmr1 knockouts. It remains unclear, however, which brain region or neurochemical system might be involved in these disabilities. We conclude that Fmr1 knockout mice might be a valid model of fragile X mental retardation.
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PMID:Mildly impaired water maze performance in male Fmr1 knockout mice. 901 22

In a normal adult subject, 12 liters of tubular urine with an osmolality of 100 mmol/kg exit per 24 hours from the loop of Henle. The antidiuretic hormone arginine-vasopressin increases the water permeability of the renal collecting ducts and induces the reabsorption of 11 liters of water: the final urinary osmolality is 1200 mmol/kg for a urinary flow rate of 1 litre per 24 hours. In nephrogenic diabetes insipidus the urine cannot be concentrated maximally. Congenital nephrogenic diabetes insipidus is secondary to either mutations in the AVPR2 gene (Xq28) that codes for the vasopressin antidiuretic (V2) receptor or to mutations in the AQP2 gene (12q13) that codes for the vasopressin dependent water channel. AVPR2 mutations are numerous and diverse: 72 different putative disease causing mutations in the AVPR2 gene have been reported in 102 unrelated families with X-linked nephrogenic diabetes insipidus. AQP2 mutations are rare. Nephrogenic diabetes insipidus could also be secondary to lithium or demeclocycline administration and to hypokaliemia. Some of these conditions are inducing, experimentally, a downregulation of aquaporin II. We encourage physicians who follow families with hereditary nephrogenic diabetes insipidus to recommend molecular genetic analysis because early diagnosis and treatment of infants can avert the physical and mental retardation associated with episodes of dehydration.
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PMID:[Pathological aspects of water transport in the collecting ducts]. 901 68

Aspartyglucosaminuria (AGU) is a lysosomal storage disease with autosomal recessive inheritance that is caused by deficient activity of aspartylglucosaminidase (AGA), a lysosomal enzyme belonging to the newly described enzyme family of N-terminal hydrolases. An AGU mouse model was generated by targeted disruption of the AGA gene designed to mimic closely one human disease mutation. These homozygous mutant mice have no detectable AGA activity and excrete aspartylglucosamine in their urine. Analogously to the human disease, the affected homozygous animals showed storage in lysosomes in all analyzed tissues, including the brain, liver, kidney and skin, and lysosomal storage was already detected in fetuses at 19 days gestation. Electron microscopic studies of brain tissue samples demonstrated lysosomal storage vacuoles in the neurons and glia of the neocortical and cortical regions. Magnetic resonance images (MRI) facilitating monitoring of the brains of living animals indicated cerebral atrophy and hypointensity of the deep gray matter structures of brain-findings similar to those observed in human patients. AGU mice are fertile, and up to 11 months of age their movement and behavior do not differ from their age-matched littermates. However, in the Morris water maze test, a slow worsening of performance could be seen with age. The phenotype mimics well AGU in humans, the patients characteristically showing only slowly progressive mental retardation and relatively mild skeletal abnormalities.
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PMID:Mice with an aspartylglucosaminuria mutation similar to humans replicate the pathophysiology in patients. 942 33

Mucopolysaccharidosis type VII (MPS VII; Sly syndrome) is one of a group of lysosomal storage diseases that share many clinical features, including mental retardation and hearing loss. Lysosomal storage in neurons of the brain and the associated behavioral abnormalities characteristic of a murine model of MPS VII have not been shown to be corrected by either bone marrow transplantation or gene therapy. However, intravenous injections of recombinant beta-glucuronidase initiated at birth reduce the pathological evidence of disease in MPS VII mice. In this study we present evidence that enzyme replacement initiated at birth improved the behavioral performance and reduced hearing loss in MPS VII mice. Enzyme-treated MPS VII mice performed similarly to normal mice and significantly better than mock- treated MPS VII mice in every phase of the Morris Water Maze test. In addition, the auditory function of treated MPS VII mice was dramatically improved, and was indistinguishable from normal mice. These data indicate that some of the learning, memory, and hearing deficits can be prevented in MPS VII mice if enzyme replacement therapy is initiated early in life. These data also provide functional correlates to the biochemical and histopathological improvements observed after enzyme replacement therapy.
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PMID:Enzyme replacement therapy for murine mucopolysaccharidosis type VII leads to improvements in behavior and auditory function. 952 82


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