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Biomedical subjects

I C Lyon

Publications and source records attributed to I C Lyon.

At least 19 recordsLinked to original sources
PubMed1990

Maternal phenylketonuria.

A mother with phenylketonuria and hyperphenylalaninaemia of 960 mumol/L with four intellectually deficient offspring is described. In addition a mother with hyperphenylalaninaemia of 2100 mumol/L and two intellectually deficient microcephalic children is described. None of the affected children exhibited elevations of blood phenylalanine. In utero phenylalanine toxicity was considered a factor causing the handicaps.

Child↗
PubMed1989

Transient neonatal tyrosinaemia.

Children who had presented with transient neonatal tyrosinaemia (TNT) were compared with a group of unaffected controls at 7-9 years of age. A comprehensive psychometric assessment revealed significant differences between the groups in adaptive behaviour, psycholinguistic abilities, and speed of learning. In nearly all components of the tests used, higher levels of TNT were associated with lower levels of performance. This study demonstrates that TNT, a condition commonly regarded as benign in the short term, has long-term effects which may be detrimental to the child in school.

Adaptation, Psychological↗
PubMed1988

Worldwide experience in newborn screening for classical congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

The need for a reliable screening test for classical congenital adrenal hyperplasia prompted development of newborn screening programs. Worldwide incidence of classical congenital adrenal hyperplasia in this report was taken from newborn screening programs in France, Italy, Japan, New Zealand, Scotland, and the United States. Two populations in which the occurrence of congenital adrenal hyperplasia among live births has been reported with greater than usual frequency are the Yupik Eskimos of southwestern Alaska (1:282) and the people of La Reunion, France (1:2,141). Aside from these populations, 1,093,310 newborns were screened between 1980 and 1988, of whom 77 had congenital adrenal hyperplasia. Thus, worldwide incidence of this disorder was estimated at 1:14,199 live births for homozygous patients, 1:60 for heterozygous subjects, with a gene frequency of 0.0083. Incidence of congenital adrenal hyperplasia among whites was estimated to be 1:11,909 (41:488,279) for homozygous patients, 1:55 for heterozygous subjects with a gene frequency of 0.0091. Incidence for the salt-wasting form of congenital adrenal hyperplasia was 1:18,850 (58:1,093,310) compared with 1:57,543 (19:1,093,310) for congenital adrenal hyperplasia in the simple virilizing form. Thus, salt-wasting congenital adrenal hyperplasia was three times more common than simple virilizing congenital adrenal hyperplasia. Estimated incidence of congenital adrenal hyperplasia in white populations in Italy and France (1:10,866) was higher than in Scotland (1:17,098), New Zealand (1:14,500). The incidence in an Asian population (Japan) (1:15,800) did not differ significantly from that of the white population. In four of five populations, overall incidence was higher than previously reported, as was the frequency of the salt-wasting form (75% v 50% to 66%), suggesting improved case detection by newborn screening.(ABSTRACT TRUNCATED AT 250 WORDS)

17-alpha-Hydroxyprogesterone↗
PubMed1985

Outcome of pregnancy in the rat with mild hyperphenylalaninaemia and hypertyrosinaemia: implications for the management of "human maternal PKU".

In attempting to determine the effects of mildly elevated maternal phenylalanine (Phe) blood levels on the developing fetal rat brain, a dietary supplement of Phe was given, under taste cover of Aspartame. Phe and tyrosine (Tyr) levels were mildly elevated throughout pregnancy without evidence of malnutrition. Mild hyperphenylalaninaemia with concurrent hypertyrosinaemia induced in rats prior to conception resulted in microcephaly and lasting behavioural problems in the offspring, specifically hyperactivity and learning difficulties. Dams fed Tyr to produce Tyr levels equivalent to the Phe-fed animals showed only the learning difficulties among the offspring. alpha-Methyl Phe, a Phe hydroxylase inhibitor, fed in conjunction with Phe, at the level relevant to these experiments, resulted in raised Tyr levels and does not provide a better method of determining whether mildly elevated maternal Phe levels alone, or Phe and Tyr in combination, cause the abnormality found in the offspring of Phe-supplemented dams. Therapeutic addition of Tyr to diets of mothers with even mild hyperphenylalaninaemia should be approached with caution as mild co-elevation of Phe and Tyr in the fetus may be harmful. In the face of such a possible therapeutic dilemma alternatives, such as dietary additions of other essential amino acids to limit fetal brain damage, need to be explored.

Animals↗
PubMed1984

Screening for congenital hypothyroidism: a three year experience.

Experience with a nationwide screening programme for congenital hypothyroidism in New Zealand is reported. Using radio-immune assays for thyroxine (T4) on all newborns, and thyroid stimulating hormone (TSH) determinations on samples with T4 levels below the 5th percentile, 160 899 babies were screened and 33 cases of primary hypothyroidism were detected (incidence 1: 4875). Screening resulted in treatment beginning within the first three weeks of life.

Congenital Hypothyroidism↗
PubMed1983

Screening for cystic fibrosis.

During a 12 month period all New Zealand newborns were screened for cystic fibrosis using the Crossley test. Of 49 056 babies tested 522 had a raised blood immunoreactive trypsin level and follow-up testing indicated 19 persistent elevations. Clinical and laboratory studies indicated 14 cases of cystic fibrosis giving an apparent incidence of 1:3500.

Cystic Fibrosis↗
PubMed1975

Galactosaemia: estimated live birth incidence in New Zealand.

194 cord blood samples were studied in both a fluorimetric assay and an electrophoresis method for Gal-1-PUT. From this the expected live birth incidence was 1:37000. The New Zealand neonatal screening programme has detected 5 cases in 223326 live births--an apparent incidence of 1:44600. The Beutler testing of dried blood spots collected on filter paper cards is a satisfactory method of detecting galactosaemia in the neonate.

Fetal Blood↗