Prenatal diagnosis of isovaleric acidaemia by enzyme and metabolite assay in the first and second trimesters.

Isovaleric acidaemia (IVA) is caused by a deficiency of isovaleryl CoA dehydrogenase. The diagnosis can be established biochemically by the demonstration of increased levels of isovalerylglycine (IVG) and 3-hydroxyisovaleric acid in urine and by the deficiency of incorporation of radiolabel from [14C]isovaleric acid in macromolecules in cultured fibroblasts. This paper reports a consecutive series of 24 prenatal diagnoses in pregnancies at high risk, using both methods--metabolite and indirect enzyme assay. Affected fetuses were diagnosed in four pregnancies: three in the second trimester and one recent case in the first trimester. The latter represents the first reported case of a first-trimester diagnosis of IVA by direct analysis of chorionic villi. We also report the first demonstration of strongly accumulated IVG in the amniotic fluid in the 12th week of an affected pregnancy.

Pre- and postnatal diagnosis of peroxisomal disorders using stable-isotope dilution gas chromatography--mass spectrometry.

Quantitative analysis of the following peroxisomal metabolites is reported: very long-chain fatty acids (VLCFA), pipecolic acid, bile acid intermediates, phytanic and pristanic acid, in plasma, urine, cerebrospinal fluid (CSF), blood spots collected at neonatal screening and amniotic fluid. An overview is given of the concentrations of these metabolites in body fluids from control subjects and all patients investigated so far in this laboratory. The method of choice is gas chromatography -- mass spectrometry (GC-MS) with electron capture detection, combined with the use of stable-isotope-labelled internal standards.

Diagnosis of peroxisomal disorders by analysis of phytanic and pristanic acids in stored blood spots collected at neonatal screening.

Concentrations of phytanic acid and pristanic acid were measured in stored dried blood spots collected at neonatal screening from patients with peroxisomal disorders, and compared with concentrations in control blood spots. In blood spots from two patients with Zellweger syndrome both phytanic acid and pristanic acid concentrations were increased but their concentration ratio was normal. In the blood spot from a patient with rhizomelic chondrodysplasia punctata, the concentration of phytanic acid was increased, whereas pristanic acid was within the control range, resulting in a low pristanic acid/phytanic acid ratio. In the blood spot from a patient with X-linked adrenoleukodystrophy, the concentrations of the acids and their ratio were normal. These findings are consistent with results for these acids in plasma from such patients. Measurement of phytanic acid and pristanic acid and their ratios in stored dried blood collected at neonatal screening can therefore be used in the diagnosis of peroxisomal disorders, especially for those cases in which, owing to early death of the patient, no other material is available for biochemical investigations.

Pristanic acid and phytanic acid in plasma from patients with peroxisomal disorders: stable isotope dilution analysis with electron capture negative ion mass fragmentography.

A sensitive and selective stable isotope dilution method was developed for the accurate quantitation of pristanic acid and phytanic acid using electron capture negative ion mass fragmentography on pentafluorobenzyl derivatives. This technique allows detection of 1 pg of each compound and was applied to plasma from healthy controls and patients suffering from various peroxisomal disorders. The age-dependency of phytanic and pristanic acid levels in plasma from healthy controls was demonstrated. The involvement of peroxisomes in the beta-oxidation of pristanic acid was concluded from its accumulation in plasma from patients with peroxisomal deficiencies. Pristanic acid/phytanic acid ratios were markedly increased in bifunctional protein and/or 3-oxoacyl-CoA thiolase deficiency, indicating their role in the (differential) diagnosis of disorders of peroxisomal beta-oxidation.

Picrotoxin microinjections into the brain: a model of abrupt withdrawal 'jumping' behaviour in rats not exposed to any opiate?

Picrotoxin microinjections (0.5 microliter per side) given into the locus coeruleus, superior colliculus and central grey of freely moving Wistar rats produced an accelerating galloping locomotion, most often forwards but also upwards. Systemic administration of apomorphine (0.7-2.0 mg/kg s.c.) given 20 min earlier increased the number of rats that displayed the so-called 'running and jumping' behaviour after picrotoxin (0.1-0.2 microgram). The dose-effect curve, however, varied according to the brain structure selected. Systemic administration of morphine (1.0-10.0 mg/kg i.p.) was found to reduce the occurrence of running and jumping behaviour when it was elicited via the locus coeruleus, but not the superior colliculus and central grey. It is suggested that the running and jumping behaviour which is elicited via the locus coeruleus might be a suitable model of a partial morphine abstinence syndrome, i.e. withdrawal jumping, in experimental animals not exposed to any opiate. The superior colliculus and central grey appear to be involved in mediating an opiate-unrelated phenomenon of 'withdrawal' jumping in rats not exposed to any opiate.

Behavioural responses to novelty in two inbred mouse strains after intrahippocampal naloxone and morphine.

Male C57BL/6 and DBA/2 mice were injected intrahippocampally with either naloxone (0.5 microgram) or morphine (1.0 microgram), or saline vehicle alone and, after 15 min, some 12 behavioural components carried out in a novel environment were recorded for 20 min. Naloxone reduced exploratory rearing responses, wall-leaning and object-sniffing in strain C57BL/6 and augmented these behaviours in strain DBA/2, while morphine depressed the scores in both. In conjunction with previously obtained evidence that the mouse hippocampus contains a genotype-dependent cholinergic mechanism which regulates responses to novelty, these findings support the hypothesis that hippocampal opioid peptides modulate the cholinergic control of exploration in mice, possibly indirectly through GABAergic pathways. In contrast, locomotor activity, defaecation and tail elevation remained practically unaffected by the two drugs, and grooming showed another kind of genotype-treatment interaction, that is to say, after morphine.