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

Maternal phenylketonuria (PKU) is teratogenic and results in birth defects that include microcephaly, mental retardation, congenital heart disease, and intrauterine growth retardation. Treatment with a low phenylalanine diet can prevent or reduce the severity of the complications. Optimal benefit, however, requires frequent monitoring with fetal ultrasonography as a critical element. We have studied ultrasonography in 39 pregnancies enrolled in the Maternal PKU Collaborative Study and followed at our centre. First-trimester examinations in 24 pregnancies resulted in the discovery of non-viability in five. In each, this led to discontinuation of the difficult and expensive diet. Among the 33 pregnancies with second-trimester evaluation, congenital heart disease was identified in five. Two of these pregnancies were terminated. Microcephaly as determined by biparietal diameter (BPD) was identified in the second trimester in only one of nine fetuses who had microcephaly at birth. Among 20 pregnancies with third-trimester ultrasound, fetal microcephaly was identified by BPD in three of seven who had birth microcephaly. We conclude that fetal ultrasonography in maternal PKU is valuable during the first trimester in identifying non-viable pregnancies and determining gestational age and is also valuable during the second trimester in identifying congenital heart disease and perhaps other major anomalies, but not in identifying fetal microcephaly. Third-trimester ultrasound seems to be of limited usefulness.
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PMID:Fetal ultrasonography in maternal PKU. 884 68

We attempted to evaluate the role of maternal hyperphenylalaninaemia (HPA) as an isolated cause of mental retardation and microcephaly in children. This transversal study observed the plasma phenylalanine from mothers of 161 children with mental retardation and/or microcephaly of unknown origin. In this sample, we found two women with previously undiagnosed HPA, a frequency (2/161) higher than expected for our general population (1:12 500) (p < 0.001). We concluded that the plasma phenylalanine levels should be determined during preconceptional evaluation of every woman of reproductive age that already has had a child affected either by mental retardation or microcephaly of unknown cause. It is particularly significant where women currently having their pregnancies have not been screened for phenylketonuria as newborns, as happens in most developing countries.
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PMID:Maternal hyperphenylalaninaemia as a cause of microcephaly and mental retardation. 886 76

Phenylalanine hydroxylase (PAH) is the enzyme which converts phenylalanine into tyrosine. In case of its deficiency, hyperphenylalaninemia is observed, which leads to phenylketonuria (PKU), a disease causing mental retardation, unless treated with a low-phenylalanine diet since early childhood. In Estonia, PKU is among the most common inherited metabolic diseases. The data from retrospective study and newborn screening show an approximate incidence of 1 in 6,000 newborns. Molecular analysis of 34 Estonian patients has revealed high genotypic homogeneity in this group, as 84% of the mutant alleles carry the R408W mutation. The high rate of this mutation in the Estonian population rises the speculation of Finno-Ugric contribution to the East European pool of mutant PAH alleles. Five more mutations-IVS12nt1, R261Q, R252W, R158Q, S349P-have been detected. The mutation detection rate was 92% among the studied patients.
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PMID:Phenylalanine hydroxylase gene mutation R408W is present on 84% of Estonian phenylketonuria chromosomes. 894 76

Maternal phenylketonuria (PKU) in untreated women has resulted in offspring with microcephaly, mental retardation, congenital heart disease (CHD), and intrauterine growth retardation. The Maternal Phenylketonuria Collaborative Study (MPKUCS) was designed to determine the effect of dietary control of blood phenylalanine (Phe) during pregnancy in preventing damage to the fetus associated with untreated Maternal PKU. A cohort of offspring from MPKUS pregnancies was ascertained and examined to evaluate malformations, including CHD, craniofacial abnormalities, microcephaly, intrauterine and postnatal growth retardation, other major and minor defects, and early abnormal neurological signs. For analysis, the women were grouped according to their mean Phe levels in mumol/liter, < or = 360, 361-600, 601-900, or > 900, during critical gestational weeks of 0-8 (N = 203) and 8-12 (N = 190), and average for Phe exposure throughout pregnancy (N = 183). Frequencies of congenital abnormalities increased with increasing maternal Phe levels. Significant relationships included average Phe 0-8 weeks and CHD (P = 0.001); average Phe 8-12 weeks and brain, fetal, and postnatal growth retardation (P < 0.0005 for all), wide nasal bridge (P < 0.0005), and anteverted nares (P = 0.001); and average Phe exposure during the entire pregnancy and neurological signs (P < 0.0005). Although 14% of infants had CHD, none of the CHD occurred at 120-360 mumol/liter and only one (3%) at 361-600 mumol/liter. At levels of 120-360 mumol/liter, there were three infants (6%) with microcephaly, two (4%) with postnatal growth, and none with intrauterine growth retardation, in contrast to 85%, 51%, and 26%, respectively, with Phe above 900 mumol/liter. These data support the concept that women with PKU should begin a low-phenylalanine diet to achieve Phe levels of < 360 mumol/liter prior to conception and should maintain this throughout pregnancy.
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PMID:Maternal Phenylketonuria Collaborative Study (MPKUCS) offspring: facial anomalies, malformations, and early neurological sequelae. 906 90

To begin to study the importance of dopamine for executive function abilities dependent on prefrontal cortex during early childhood, the present investigation studied children in whom we predicted reduced dopamine in prefrontal cortex but otherwise normal brains. These are children treated early and continuously for the metabolic disorder phenylketonuria (PKU). Untreated PKU is the most common biochemical cause of mental retardation. The root problem is an inability to convert one amino acid, phenylalanine (Phe), into another, tyrosine (Tyr), the precursor of dopamine. Phe levels in the bloodstream soar; Tyr levels fall. Treatment with a diet low in Phe reduces the Phe:Tyr imbalance but cannot eliminate it. We hypothesized that the resultant modest elevation in the ratio of Phe to Tyr in the blood, which results in slightly less Tyr reaching the brain, uniquely affects the cognitive functions dependent on prefrontal cortex because of the special sensitivity of prefrontally projecting dopamine neurons to small decreases in Tyr. In a 4-year longitudinal study, we found that PKU children whose plasma Phe levels were three to five times normal (6-10 mg/dl) performed worse than other PKU children with lower Phe levels, matched controls, their own siblings, and children from the general population on tasks that required the working memory and inhibitory control abilities dependent on dorsolateral prefrontal cortex. The impairment was as evident in our oldest age range (3 1/2-7 years) as it was in the youngest (6-12 months). The higher a child's Phe level, the worse that child's performance. Girls were more adversely affected than boys. The deficit appears to be selective, affecting principally one neural system, since even PKU children with Phe levels three to five times normal performed well on the 13 control tasks. Clinical implications for the treatment of PKU and other neurodevelopmental disorders are discussed.
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PMID:Prefrontal cortex cognitive deficits in children treated early and continuously for PKU. 942 21

Behavior disorders frequently are associated with mental retardation. The most common interventions involve psychotropics, behavior modification, or both. Etiologically based treatments, derived from an understanding of underlying disease pathogeneses, are infrequent. However, several genetic diseases are associated with elevated rates of destructive responding. The hyperphenylalaninemias provide an excellent model for alternative interventions that have clear biological plausibility. A literature review is undertaken that provides the biochemical rationale for treatment with a low-phenylalanine diet. Several phenylalanine dietary control studies designed to manage aberrant responding among patients with hyperphenylalaninemia are summarized. Together they provide strong evidence that dietary phenylalanine restriction is the treatment of choice among patients ranging from classic phenylketonuria to milder hyperphenylalaninemia. Corroborating evidence derived from phenylalanine loading, magnetic resonance imaging, and dietary amino acid supplementation studies is presented.
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PMID:Dietary treatment of destructive behavior associated with hyperphenylalaninemia. 957 81

Acetylcholinesterase (AChE) is a significant component of the membrane contributing to the permeability changes during synaptic transmission and conduction. Phenylketonuria is a group of metabolic disorders in which phenylalanine (Phe) is highly elevated in blood (up to 0.1 M) resulting in mental retardation etc. AChE activity was measured spectrophotometrically after incubation with various Phe concentrations. Phe interaction with DNA was evaluated with an established HPLC method. Phe was found to inhibit AChE almost 40%, at a concentration of 5 mM, whereas a 62.5% DNA peak exclusion (molecular interaction) was observed when Phe was incubated with DNA at a concentration of 3 mM. In addition the ratio of DNA: Phe determined the potency of the observed molecular effect.
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PMID:In vitro influence of phenylalanine on acetylcholinesterase activity and DNA. 961 43

Phenylalanine hydroxylase (PheOH) catalyzes the conversion of L-phenylalanine to L-tyrosine, the rate-limiting step in the oxidative degradation of phenylalanine. Mutations in the human PheOH gene cause phenylketonuria, a common autosomal recessive metabolic disorder that in untreated patients often results in varying degrees of mental retardation. We have determined the crystal structure of human PheOH (residues 118-452). The enzyme crystallizes as a tetramer with each monomer consisting of a catalytic and a tetramerization domain. The tetramerization domain is characterized by the presence of a domain swapping arm that interacts with the other monomers forming an antiparallel coiled-coil. The structure is the first report of a tetrameric PheOH and displays an overall architecture similar to that of the functionally related tyrosine hydroxylase. In contrast to the tyrosine hydroxylase tetramer structure, a very pronounced asymmetry is observed in the phenylalanine hydroxylase, caused by the occurrence of two alternate conformations in the hinge region that leads to the coiled-coil helix. Examination of the mutations causing PKU shows that some of the most frequent mutations are located at the interface of the catalytic and tetramerization domains. Their effects on the structural and cellular stability of the enzyme are discussed.
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PMID:Structure of tetrameric human phenylalanine hydroxylase and its implications for phenylketonuria. 964 59

The tetrahydrobiopterin (BH4) cofactor is essential for the aromatic amino acid hydroxylases that are involved in phenylalanine degradation and catecholamine and serotonin biosynthesis. Furthermore, BH4 is an essential and limiting cofactor for all types of nitric oxide synthases. BH4 deficiency results in hyperphenylalaninemia and monoamine neurotransmitter depletion associated with progressive mental retardation and is most commonly due to autosomal recessive mutations in 6-pyruvoyltetrahydropterin synthase (PTPS), the second enzyme for cofactor biosynthesis. Due to the relatively poor blood-brain barrier penetration of the cofactor, conventional therapy requires, besides oral doses of synthetic BH4, administration of neurotransmitter precursors and an aromatic amino acid decarboxylase inhibitor. The outcome of this therapy is not always beneficial. In this study we transduced into primary patient fibroblasts the human cDNAs for the BH4 biosynthetic enzymes GTP cyclohydrolase I and PTPS, expressed from different retroviral vectors. This allowed BH4 biosynthesis in originally PTPS-deficient cells. Moreover, the double-transduced fibroblasts released between 200 and 800 pmol of BH4/10(6) cells/day. Such engineered fibroblasts may be grafted into the central nervous system and used as depository cells for constitutive delivery of BH4.
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PMID:Retrovirus-mediated double transduction of the GTPCH and PTPS genes allows 6-pyruvoyltetrahydropterin synthase-deficient human fibroblasts to synthesize and release tetrahydrobiopterin. 964 48

The phenylalanine-free diet is needed for the treatment of phenylketonuria. Phenylketonuria is an inherited metabolic condition in which there is a deficiency of the enzyme phenylalanine hydroxylase. Lack of this enzyme means the body cannot metabolise the essential amino acid phenylalanine, which then builds up in the blood and causes mental retardation and other abnormalities. Retardation can be prevented if phenylketonuria is diagnosed in the first three weeks of infancy and dietary treatment started straightaway. There is a universal screening test in the UK (the Guthrie test). Heel-prick blood samples are taken from all babies between 6-14 days old and analysed at a regional screening centre. For infants, a phenylalanine-free formula is needed, either as a supplement before breast feeds or following a formula feed. The diet must continue during weaning and childhood, with a low protein diet. Foods such as meat, fish, eggs, milk, cheese, nuts and pulses are excluded as they contain high levels of phenylalanine. Vegetables and fruit are allowed in measured amounts only! Special low protein bread, pasta, biscuits and flour are used to supplement the diet and ensure adequate calorie intake. Whether the diet can be stopped at the end of adolescence is debatable. If stopped, it should be re-started at conception and maintained during pregnancy, as high levels of phenylalanine in the mother can affect the fetus.
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PMID:Treating phenylketonuria by a phenylalanine-free diet. 981 66


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