Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0025362 (mental retardation)
 15,878 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The offspring of mothers with untreated classic phenylketonuria (PKU) have shown a high frequency of microcephaly, mental retardation, pre- and postnatal growth retardation, and birth defects. The aim of this study was to determine whether phenylalanine (phe) is the teratogenic agent in maternal PKU. To observe the direct effects of phe on organogenesis, embryos of 9.5-day pregnant rats were cultured for 48 h in the presence of phe at concentrations of 0.1 to 6.0 mM. Within this range no morphological abnormalities occurred in exposed embryos, when compared to control embryos. However there was a reduction (P less than or equal to 0.05) in embryonic protein content and somite number at the highest concentration of phe (6.0 mM). This does not preclude the longer-term effects of phe at later stages of gestation. To examine phe transport into the embryo in response to elevated serum phe levels, 3H-phe uptake studies were undertaken. These showed that 3H-phe from the culture serum is incorporated rapidly into the free amino acid pools and embryonic protein. At serum concentrations of 1.4 mM or higher, phe saturation occurs in the cellular pools of the embryo. Amino acid analysis of the exocoelomic fluid showed that when embryos were cultured for 48 h in serum containing 3.45 mM phe, the total amino acid concentration was maintained near the control levels (16 mM). Of this, 27% (4.26 mM) was contributed by phe, and all other amino acids, except methionine, were decreased with respect to control levels.
 ...
PMID:The effects of phenylalanine on cultured rat embryos. 615 Dec 61

Experimental phenylketonuria was induced in male rats by daily injections of alpha-methylphenylalanine and phenylalanine on postnatal Days 3-31. Beginning at 8 weeks of age, the animals were subjected to a test of observational learning followed by a test of latent learning (two tests of "advantageous" learning). The animals subjected to the PKU treatment early in life showed significant learning deficits in both tests. The importance of these studies lies in the fact that unlike conventional tests of learning, tests of advantageous learning are sensitive to the kinds of biological insults which cause mental retardation in humans. This differential sensitivity evident in studies of animal models of cognitive pathology is analogized to the areas of dysfunction which characterize human mental retardation. Suggestions for the development of appropriate models of intellectual development are made.
 ...
PMID:PKU, learning, and models of mental retardation. 653 25

We studied the effects of maternal phenylketonuria and hyperphenylalaninemia on 53 offspring from untreated pregnancies in 22 mothers who were identified by routine screening of umbilical-cord blood. The IQ of the offspring was significantly correlated with both maternal IQ (r = 0.83, P less than 0.001) and maternal blood phenylalanine level (r = 0.82, P less than 0.001), but with one exception, mental retardation in offspring was present only when the maternal blood phenylalanine level exceeded 1100 mumol per liter (18 mg per deciliter). Microcephaly in offspring was consistently present only when the maternal blood phenylalanine level exceeded 1200 mumol per liter (20 mg per deciliter). Congenital heart disease and other congenital anomalies were rare among offspring. The data suggest that severe atypical or classic phenylketonuria (blood phenylalanine level, greater than 1100 mumol per liter) in the mother has a substantial cognitive effect on her offspring but that the effect of mild hyperphenylalaninemia may have been overstated in the past.
 ...
PMID:Effects of untreated maternal phenylketonuria and hyperphenylalaninemia on the fetus. 663 85

The mRNA for phenylalanine hydroxylase (phenylalanine 4-monooxygenase, EC 1.14.16.1) has been purified from total rat liver mRNAs, of which it constitutes less than 0.25%, to greater than 10% purity in a single step by specific polysome immunoprecipitation. The purified mRNA was used for synthesis and cloning of its cDNA. Recombinant colonies containing phenylalanine hydroxylase DNA sequences were identified by differential hybridization, hybrid-selected translation, and blot hybridization analysis. The rat cDNA clone was capable of hybridizing with human phenylalanine hydroxylase mRNA, which will permit the isolation of the corresponding human gene for analysis of phenylketonuria, a hereditary disorder in phenylalanine metabolism that causes permanent mental retardation in humans.
 ...
PMID:Polysome immunoprecipitation of phenylalanine hydroxylase mRNA from rat liver and cloning of its cDNA. 675 Jun 7

The "justification hypothesis" attributes mental retardation in phenylketonuria (PKU) to an inability of the heterozygous mother to deliver an appropriate amount of tyrosine to the PKU fetus who, in turn, is unable to correct for this deficiency because of its genetic constitution. We tested this hypothesis by measuring concentrations of tyrosine and phenylalanine in cord blood obtained at delivery from nine infants with PKU and five infants with persistent (non-PKU) hyperphenylalaninemia (PHP). For each of these specimens there were four control cord-blood specimens from infants born on the same day and, generally, in the same hospital. PKU and PHP groups were similar with respect to cord-blood tyrosine and phenylalanine values. There was no biologically significant deficiency of tyrosine in cord blood of the pooled PKU and PHP deficiency of tyrosine in cord blood of the pooled PKU and PHP groups (54 +/- 10 microM, mean +/- SD) compared with controls (61 +/- 16 microM, P = 0.13). On the other hand, phenylalanine in cord blood of the pooled PKU and PHP groups was significantly increased (144 +/- 30 microM, mean +/- SD) compared with controls (128 +/- 24, P = 0.004). The mangitude of the differences in cord-blood tyrosine and phenylalanine between control and PKU subjects are so small that it is unlikely that they have any consequences for physical and mental development. The justification hypothesis, as it pertains to blood tyrosine at term, is not upheld.
 ...
PMID:Cord-blood tyrosine levels in the full-term phenylketonuric fetus and the "justification hypothesis". 693 44

Untreated maternal phenylketonuria (PKU) may result in nonphenylketonuric offspring with mental retardation, microcephaly, congenital heart disease, and low birth weight. We obtained information about 34 pregnancies in which dietary therapy was instituted to lower the concentration of phenylalanine in maternal blood in an attempt to avoid fetal damage. The outcomes varied from mental normality with no evidence of fetal effect to neonatal death due to congenital heart disease. Dietary therapy with control of the maternal biochemical abnormalities is not yet of proved efficacy in preventing these fetal effects. The available data tend to support initiation of dietary therapy prior to conception for best results, but the number of cases is small and points to the need for further research.
 ...
PMID:Maternal phenylketonuria--results of dietary therapy. 705 57

Maternal hyperphenylalaninemia constitutes a potential hazard to the fetus for whom the risks of postnatal mental retardation, microcephaly, and congenital malformations are elevated. Preconception and intragestational dietary treatment can apparently improve the outcome of such pregnancies. In the absence of predictive mechanisms for pregnancies at risk and preventive measures involving reproductive counseling and treatment, there could be a rebound in the population frequency of mental retardation related to disorders of phenylalanine metabolism in subsequent generations. We describe a program serving a population of six million that includes screening, diagnosis, treatment, and counseling of the hyperphenylalaninemias. The program has recently added a simple dedicated register for males and females with hyperphenylalaninemia to supplement traditional methods for continuous surveillance of probands. We registered 153 patients: 43 females and 56 males with phenylketonuria, 23 females and 31 males with benign hyperphenylalaninemia, of which 22, 7, 27 and 5, respectively, had reached their 12th birthday in an 1981. Regional centers in the program provided counseling about the consequences of maternal hyperphenylalaninemia and the options to prevent them. No family has rejected the principle or fact of the Register and its goals.
 ...
PMID:Prevention of mental retardation in offspring of hyperphenylalaninemic mothers. 713 36

Although the enzymatic etiology and the link between this and the accumulation of phenylalanine and its metabolites in phenylketonuria has been amply established, the pathogenesis of the brain dysfunction accompanying this inherited metabolic disease is still under research. Effects of phenylalanine and its metabolites, some leading to irreversible defective structural features in the nervous system, and others to reversible defective neurotransmission, are described as responsible of the mental retardation and other neurological and behavioural symptoms characteristic of phenylketonuria.
 ...
PMID:[Pathogenesis of cerebral dysfunction in phenylketonuria]. 714 76

Recent work has shown that in phenylketonuria, PKU, in which phenylalanine accumulates in the blood, the damage to the brain, which so often leads to mental retardation, is not solely due to the large quantities of phenylalanine that enter the brain. The raised levels of phenylalanine in the blood lead to a partial exclusion of various other amino acids from the brain and this exclusion in itself damages the brain. Based on this evidence, that in PKU some amino acids are partially excluded from entering the brain, proposals are made for a modified dietary treatment of this disease. In this diet the phenylalainine is not so greatly reduced as in the standard diet for PKU, whilst supplements of other amino acids are added. The rationale for this new diet is that the partial exclusion from the brain of various amino acids (methionine, tryptophan, histidine, tryosine, isoleucine, leucine and valine) by the raised level of phenylalanine in the blood, acting as a competitive inhibitor, can be largely prevented by increasing the blood levels of these excluded amino acids. Raising slightly their blood levels overcomes the excluding effect of moderately raised levels of phenylalanine in the blood. The advantages of the new diet are that not only is it more palatable than a diet very low in phenylalanine, so that it is more likely to continue to prove acceptable to older children and adolescents, as well as to PKU women who expect to become pregnant, but also that its margin of safety is greater if the patient does take unsuitable food.
 ...
PMID:A new approach to the treatment of phenylketonuria. 719 42

This report documents the outcome of two pregnancies is a woman with phenylketonuria (PKU) who was treated with a low phenylalanine diet before conception and during pregnancy. Her first pregnancy resulted in an abortion at 17 wk. During the second pregnancy the patient was unable to maintain the right diet consistently, and her blood phenylalanine levels in the first and second trimester were elevated. This pregnancy ended in the birth of a growth retarded microcephalic infant after an amenorrhea of 42 wk. The infant has maintained a normal growth velocity below the tenth percentile, and has not shown signs of mental retardation.
 ...
PMID:Maternal phenylketonuria: the outcome of pregnancy. 733 7


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>