[Clinical findings and mutational spectrum in Venezuelan patients with delayed diagnosis of phenylketonuria]. / Hallazgos clínicos y espectro mutacional en pacientes venezolanos con diagnóstico tardío de fenilcetonuria.

INTRODUCTION: Massive neonatal screening for phenylketonuria (PKU) began in developed countries in 1963, and eventually disappeared as a cause of mental retardation. Yet, this is not the case in most developing countries. AIM: To describe the phenotype and the genotype of PKU patients with a delayed diagnosis in order to draw attention to the importance of neonatal studies and molecular diagnosis. PATIENTS AND METHODS: Clinical data were collected from five unrelated patients by means of a medical assessment. The molecular study was conducted using the DGGE, sequencing and/or restriction analysis techniques to search for mutations in the PAH gene. RESULTS. Owing to the delayed diagnosis all the patients presented severe clinical manifestations, such as psychomotor retardation, atypical behaviours and language disorders. Four of them presented epilepsy and there were two cases of microcephaly. The phenotype was as expected, given the genotype. Seven different mutations were detected in the 10 alleles that were studied. The IVS10nt +5 g>t mutation was the most frequent, followed by the Venezuelan mutation S349L. Furthermore, two patients presented mutated proteins with residual activity, and good results were obtained using BH4 therapy. CONCLUSIONS: In our country, as in most developing countries, PKU neonatal studies are performed but the programme does not cover the whole neonatal population. In this work, we want to stress the importance of neonatal studies in the welfare of children, as well as the use of molecular diagnosis to improve the therapeutic orientation and genetic counselling of the families involved.

Hallazgos clínicos y espectro mutacional en pacientes venezolanos con diagnóstico tardío de fenilcetonuria / Clincial findings and mutational spectrum in Venezuelan patients with delayed diagnosis of phenylketonuria

Introducción. En 1963 comenzó el cribado neonatal masivo de fenilcetonuria (PKU) en países desarrollados, queacabó desapareciendo como causa de retraso mental. Sin embargo, éste no es el caso en la mayoría de los países en vías de desarrollo. Objetivo. Describir el fenotipo y el genotipo de pacientes con diagnóstico tardío de PKU, con el fin de resaltar la importancia del estudio neonatal y el diagnóstico molecular. Pacientes y métodos. Se recogieron datos clínicos de cinco pacientes no relacionados mediante evaluación médica. El estudio molecular se realizó empleando las técnicas de DGGE, secuenciación y/o análisis de restricción para la búsqueda de mutaciones en el gen PAH. Resultados. Todos los pacientes presentaronmanifestaciones clínicas graves debidas al diagnóstico tardío, como retraso psicomotor, conductas atípicas y trastornos del lenguaje. Cuatro de ellos presentaron epilepsia y dos, microcefalia. El fenotipo fue el esperado de acuerdo con el genotipo. Se detectaron siete mutaciones diferentes en los 10 alelos estudiados. La mutación IVS10nt+5g>t fue la más frecuente,seguida de la mutación venezolana S349L. Por otra parte, dos pacientes presentan proteínas mutadas con actividadresidual, y pudieron verse beneficiados de la terapia con BH4. Conclusiones. En Venezuela, al igual que en gran parte de los países en vías de desarrollo, se realiza el estudio neonatal de PKU pero el programa no cubre toda la población neonatal. En este trabajo se quiere destacar la importancia del estudio neonatal en el bienestar de los niños, y el uso del diagnóstico molecular para mejorar la orientación terapéutica y la asesoría genética de la familia

Introduction. Massive neonatal screening for phenylketonuria (PKU) began in developed countries in 1963, and eventually disappeared as a cause of mental retardation. Yet, this is not the case in most developing countries. Aim. To describe the phenotype and the genotype of PKU patients with a delayed diagnosis in order to draw attention to the importance of neonatal studies and molecular diagnosis. Patients and methods. Clinical data were collected from five unrelated patients by means of a medical assessment. The molecular study was conducted using the DGGE, sequencing and/or restriction analysis techniques to search for mutations in the PAH gene. Results. Owing to the delayed diagnosis all thepatients presented severe clinical manifestations, such as psychomotor retardation, atypical behaviours and language disorders. Four of them presented epilepsy and there were two cases of microcephaly. The phenotype was as expected, given the genotype. Seven different mutations were detected in the 10 alleles that were studied. The IVS10nt+5g>t mutation was themost frequent, followed by the Venezuelan mutation S349L. Furthermore, two patients presented mutated proteins with residual activity, and good results were obtained using BH4 therapy. Conclusions. In our country, as in most developingcountries, PKU neonatal studies are performed but the programme does not cover the whole neonatal population. In this work, we want to stress the importance of neonatal studies in the welfare of children, as well as the use of molecular diagnosis to improve the therapeutic orientation and genetic counselling of the families involved

N-methyl-D-aspartate (NMDA) and non-NMDA (metabotropic) type glutamate receptors modulate the membrane potential of the Schwann cell of the squid giant nerve fibre.

L-Glutamate application can produce three different responses in the membrane potential of the Schwann cell of the tropical squid, Sepioteuthis sepioidea, which appear to be mediated by three pharmacologically distinct classes of receptor. A class of non-NMDA-type receptors, with some similarities to metabotropic glutamate receptors, mediates the development of a rapid and long-lasting hyperpolarization. Two pharmacologically distinct classes of NMDA-type receptor are present. One mediates the development of a slow depolarization accompanied by a long-lasting change in responsiveness of the Schwann cell. The second produces rapid depolarizing responses during the period of this changed responsiveness. All three types of receptor can be activated by dipeptides containing excitatory amino acids.

The effect of a glutamate uptake inhibitor on axon-Schwann cell signalling in the squid giant nerve fibre.

The glutamate uptake blocker p-chloromercuriphenylsulphonic acid (PCMS) (100 mumol l-1) does not block any of the membrane potential changes induced by the application of L-glutamate to the adaxonal Schwann cells of the giant axon of the tropical squid Sepioteuthis sepioidea. This indicates that these potential changes are not due to the activation of an electrogenic glutamate uptake system and supports the idea that they are due to the activation of specific glutamate receptors. The presence of PCMS (100 mumol l-1) reduces the activity of the glutamate uptake system sufficiently for the extracellular level of axonally released glutamate to exceed the threshold for the activation of the NMDA-type glutamate receptors in this preparation.

Substance P modulation of the membrane potential of the Schwann cell of the squid giant nerve fibre.

Substance P produced a dose-dependent, long-lasting hyperpolarization of the membrane of the Schwann cells of the giant nerve fibre of the tropical squid. A survey of the effectiveness of a range of other naturally occurring tachykinin agonists suggested that the receptors present on the squid Schwann cell belong to the subtype SP-P or NK1, for which substance P is the preferred agonist. A survey of the effectiveness of a range of substance P fragments indicated that the direct hyperpolarizing effects of the substance P molecule were mediated by peptides with an intact amidated C-terminal. However, a second subset of receptors that can be activated by N-terminal fragments and analogues lacking an amidated C-terminal was also present in this preparation. The non-subtype-specific antagonist D-Arg1,D-Trp7,9,Leu11 substance P (spantide) was a potent blocker of the effects of substance P in this preparation. Activation of the substance P receptors did not interact with the effects induced by activation of either the nicotinic cholinergic receptors or octopaminergic receptors present in this preparation. However, it did potentiate the effects of activation of the receptors for vasoactive intestinal peptide (VIP), either in response to bath application of the peptide or due to their activation by the release of an endogenous VIP-like peptide after stimulation of the giant axon.