A high-resolution polarimeter formed from inexpensive optical parts.

We describe a high resolution laser polarimeter built from commodity optical components. The optical rotation angle is determined by measuring the phase difference between two harmonically modulated polarised laser beams - an 'object beam' that passes through the sample under test and a 'reference beam' that bypasses the sample. The complete polarimeter may be assembled from low cost off-the-shelf parts for less than £300 (UK Sterling). Data acquisition and analysis are carried out on a microcontroller running an efficient algorithm based on the sliding Discrete Fourier Transform. Despite its low cost, the polarimeter is a fully automatic, research-grade instrument with an accuracy of ±0.0013° and a precision of ±0.0028° - comparable to far costlier commercial instruments. The polarimeter's ease of use, compact size, fast measurement times and high angular resolution make it a capable and versatile tool for analytical science, while its low cost means it is ideally suited for use in resource-constrained environments and process monitoring. The polarimeter is released here as open hardware, with technical diagrams, a full parts list, and source code for its firmware included as Supplementary Information.

Antisocial behaviour orders: the need to consider underlying neuropsychiatric disease.

Antisocial behaviour orders are legally constituted civil orders which aim to stop undesirable behaviour as part of United Kingdom government plans for crime reduction. They have been increasingly used since their introduction in 1999 and have attracted much media attention. The need to consider neurological illness as a possible cause of behaviour deemed anti-social is illustrated by a patient eventually diagnosed with neuroacanthocytosis.

Neuropsychological outcome of experimental manipulation of phenylalanine intake in treated phenylketonuria.

Blood phenylalanine concentrations were experimentally increased for 3 months by means of a phenylalanine-complemented amino acid supplement in a group of 16 children aged 10-16 years with classical phenylketonuria who had been treated early and who had remained on the restricted diet. Average concentrations achieved during challenge were between 1000 and 1300 mumol/L. Psychological outcome was measured by a neuropsychological battery consisting of tests of verbal and spatial memory, attention and fine motor coordination. A triple-blind, repeated measures, randomized, crossover design was adopted to control for practice and expectancy effects. Subjects were assessed at baseline and at the end of the first and second phenylalanine manipulation periods. Significant interactions (ANOVA) emerged as predicted for phenylalanine concentrations, but similar crossover effects were not found for any of the neuropsychological tests. The results suggested that medium-term hyperphenylalaninaemia in treated PKU is not harmful to psychological functioning in older children and adolescents who have been continuously treated up to and beyond age 10 years, though the susceptibility of executive functions needs to be further researched. The findings add some weight to the idea that by late childhood the vulnerability of the nervous system to the neurotoxic influence of phenylalanine may be much reduced.

Transitory hyperphenylalaninaemia in children with continuously treated phenylketonuria.

Cognitive and behavioral effects of temporarily challenging the CNS with elevated levels of phenylalanine in treated phenylketonuria (PKU) were investigated in a triple-blind, cross-over study. A high phenylalanine supplement was given over 3 months to sixteen 10- to 16-year-old early and continuously treated children with classical PKU. We used the WISC and Rivermead tests to measure cognitive function and the Rutter Scales to assess disordered behavior. Parents and children guessed at the condition imposed. The Group x Phase interaction for phenylalanine level was statistically significant, but this pattern was not mirrored in the psychological test data, and guessing was random. Results suggest that intellectual ability, memory, and conduct are not affected by medium-term hyperphenylalaninaemia in PKU after 10 or more years of treatment.

Sequence variation at the phenylalanine hydroxylase gene in the British Isles.

Using mutation and haplotype analysis, we have examined the phenylalanine hydroxylase gene in the phenylketonuria populations of four geographical areas of the British Isles: the west of Scotland, southern Wales, and southwestern and southeastern England. The enormous genetic diversity of this locus within the British Isles is demonstrated in the large number of different mutations characterized and in the variety of genetic backgrounds on which individual mutations are found. Allele frequencies of the more common mutations exhibited significant nonrandom distribution in a north/south differentiation. Differences between the west of Scotland and southwestern England may be related to different events in the recent and past histories of their respective populations. Similarities between southern Wales and southeastern England are likely to reflect the heterogeneity that is seen in and around two large capital cities. Finally, comparison with more recently colonized areas of the world corroborates the genealogical origin by range expansion of several mutations.

Discordant phenylketonuria phenotypes in one family: the relationship between genotype and clinical outcome is a function of multiple effects.

Four members spanning three generations of one family have phenylketonuria of varying degrees of severity. Two first cousins were screened in the neonatal period and have had dietary phenylalanine restriction since diagnosis, the older patient having been classified as having more severe PKU and the younger one as having mild PKU. Their mutual grandfather and his older brother also have a significant hyperphenylalaninaemia and are of normal intelligence despite never having had restricted phenylalanine intake. Mutation analysis of the phenylalanine hydroxylase (PAH) gene has established that there are four different mutations, two in exon 2 (F39L and L48S) and two in exon 3 (R111X and S67P), which give rise to PKU in this family. In order to establish their relative severity, we screened the PKU populations of western Scotland and the south west of England for these mutations. The exon 3 mutations are rare; however, F39L is relatively common in Scotland and L48S in England. A comparison of diagnostic blood phenylalanine concentrations in subjects carrying L48S/null or F39L/null mutations with those carrying two null mutations suggest that these exon 2 mutations are less deleterious. Thus, in this family, the different biochemical phenotypes can be explained, in part, by different genotypes at the PAH locus but our results show that the relationship between genotype and clinical outcome is more complex and is a function of multiple effects.

Neuropsychological effects of subsequent exposure to phenylalanine in adolescents and young adults with early-treated phenylketonuria.

Severe mental handicap in phenylketonuria (PKU) can be prevented if dietary treatment is implemented at birth. Controversy remains about the optimum age for terminating treatment. A group of adolescents and young adults with PKU from the West of Scotland Register was identified which had received early treatment, been well-controlled on diet, ceased treatment at 10 years old and subsequently were hyperphenylalaninaemic for 3 years or more. They were given a battery of neuropsychological tests and their results were compared with those of on-diet subjects with PKU and normal controls. The findings generally supported the view that dietary cessation at age 10 is sufficient to prevent a substantial reduction of cognitive and motor ability, and that the central nervous system is probably mature enough to withstand the toxic effects of high blood phenylalanine by then. However, there were minor indications, in keeping with Welsh et al.'s hypothesis [M.C. Welsh, B.F. Pennington, S. Ozonoff, B. Rouse & E.R.B. McCabe (1990) Neuropsychology of early-treated phenylketonuria: specific executive function deficits.

Mutation analysis of the phenylalanine hydroxylase gene using heteroduplex analysis with synthetic DNA constructs.

Using heteroduplex analysis generated with synthetic PCR-amplifiable DNA we have screened the PKU populations of southwest England and Wales, western Scotland, and southeast and central England for mutations in exons 3, 7 and 12 of the phenylalanine hydroxylase (PAH) gene. The technique characterized three mutations in exon 12, two in exon 3 and five in exon 7. Altogether over 370 PKU chromosomes were screened. In all geographical regions exon 12 mutations (R408W, IVS12nt1g- > a and Y414C) accounted for about 40% of mutant chromosomes. Exon 3 mutations (principally I65T) were found on between 9 and 12% of mutant alleles and exon 7 mutations accounted for a further 5-7%. Heteroduplex analysis is rapid, simple and safe and three constructs covering three exons can identify between 55 and 60% of mutations in various PKU populations of the UK.

Hyperphenylalaninemia due to defects in tetrahydrobiopterin metabolism: molecular characterization of mutations in 6-pyruvoyl-tetrahydropterin synthase.

A variant type of hyperphenylalaninemia is caused by a deficiency of tetrahydrobiopterin (BH4), the obligatory cofactor for phenylalanine hydroxylase. The most frequent form of this cofactor deficiency is due to lack of 6-pyruvoyl-tetrahydropterin synthase (PTPS) activity, the second enzyme in the biosynthetic pathway for BH4. The human liver cDNA for PTPS was previously isolated, and the recombinant protein was found to be active when expressed in Escherichia coli. We now have investigated two patients for their molecular nature of this autosomal recessive disorder. Both patients were diagnosed as PTPS deficient, one with the central and one with the peripheral form, on the basis of an elevated serum phenylalanine concentration concomitant with lowered levels of urinary biopterin and PTPS activity in erythrocytes. Molecular analysis was performed on the patients' cultured primary skin fibroblasts. PTPS activities were found in vitro to be reduced to background activity. Direct cDNA sequence analysis using reverse transcriptase-PCR technology showed for the patient with the central from a homozygous G-to-A transition at codon 25, causing the replacement of an arginine by glutamine (R25Q). Expression of this mutant allele in E. coli revealed 14% activity when compared with the wild-type enzyme. The patient with the peripheral form exhibited compound heterozygosity, having on one allele a C-to-T transition resulting in the substitution of arginine 16 for cysteine (R16C) in the enzyme and having on the second allele a 14-bp deletion (delta 14bp), leading to a frameshift at lysine 120 and a premature stop codon (K120-->Stop). Heterologous expression of the enzyme with the single-amino-acid exchange R16C revealed only 7% enzyme activity, whereas expression of the deletion allele delta 14bp exhibited no detectable activity. All three mutations, R25Q, R16C, and K120-->Stop, affect evolutionarily conserved residues in PTPS, result in reduced enzymatic activity when reconstituted in E. coli, and are thus believed to be the molecular cause for the BH4 deficiency. This is the first report describing mutations in PTPS that lead to BH4 deficiency.

Copper deficiency in the preterm infant of very low birthweight. Four cases and a reference range for plasma copper.

Four preterm infants of very low birthweight (less than 1500 g) developed signs of copper deficiency between age 8 and 10 weeks. All had required prolonged ventilatory support, parenteral nutrition, and nasojejunal feeding. The clinical features, which included osteoporosis, oedema, anaemia, neutropenia, and late apnoea improved when the oral copper intake was increased. Diagnosis was made more difficult because a suitable reference range for plasma copper was not available. Serial measurements of plasma copper in 39 preterm infants who had no important medical problems were used to produce a reference range for plasma copper from 30 weeks' gestation to term plus seven weeks. This information will aid recognition of hypocupraemia in the very low birthweight infant who is particularly at risk of copper deficiency.

Successful trigeminal thermocoagulation for paroxysmal trigeminal neuralgia in a patient with severe haemophilia.

Neurosurgical procedures in patients with severe haemophilia carry a major risk of bleeding. We describe successful thermocoagulation of the trigeminal nerve for neuralgia in a severe haemophiliac, under cover of factor VIII concentrate. This is the first case report of such an operation in severe haemophilia.

National Post-Perinatal Infant Mortality and Cot Death Study, Scotland 1981-82.

Throughout 1981 and 1982 all deaths of infants aged 8-365 days (post-perinatal infant mortality, PPIM) in Scotland were studied. During this period there were 135 250 live births and 1533 infant deaths (infant mortality rate 11.3), including 763 PPIM deaths (5.6 per 1000 live births). These 763 deaths fell into three main categories: birth-determined (329), accident or acquired disease (65), and cot deaths (369). Birth-determined deaths included 109 preterm, 199 congenital disorders, and 21 miscellaneous deaths. 61 of the cot deaths were fully explained on necropsy, in 141 an associated finding which might or might not be relevant was found, and in the remaining 167 no explanation was found. The cot death rate was 2.7 per 1000 live births overall (3.3 for boys, 2.1 for girls), and more second-born than first-born children died (approximately 3:2). Excluding "explained" cot deaths the rate was 2.3 per 1000 live births.

Activation of the kallikrein-kinin system in premature infants with respiratory distress syndrome (RDS).

Plasma prekallikrein levels, kallikrein activity and antikallikrein levels were investigated in nine premature infants with respiratory distress syndrome (RDS) and six premature infants without. Plasma prekallikrein and kallikrein were determined with a chromogenic substrate measuring amidolytic activity. Antikallikrein was measured with a functional assay. In infants with severe RDS, prekallikrein levels were significantly reduced (median 58% of initial values (p less than 0.01) about 48 hours after onset of symptoms. In infants with moderate RDS prekallikrein level was reduced less, while in babies without RDS there were no significant changes in prekallikrein levels the first 5-7 days of life. Antikallikrein levels did not change significantly in any babies. The results suggest that the kallikrein-kinin system might be involved in RDS. This could explain several features of this syndrome such as hypotension and edema. Furthermore the findings show that homeostatic functions are altered in this disease, and they suggest that other cascade systems as the coagulation, fibrinolytic and complement system may be involved as well. The findings emphasize that trauma might be a significant pathogenetical factor for development of this syndrome and indicate that RDS is not simply a biochemical disease with lack of surfactant as the only pathogenetic factor.

Post-perinatal infant mortality in Glasgow 1979-81.

Post-perinatal infant mortality (PPIM; deaths from the 8th day to the end of the 1st year of life) was studied in Glasgow over the 3-year period 1979-81. The 244 deaths were divided into three main categories--those determined at birth, those due to accidents and acquired disease, and cot deaths. 50% of deaths were determined at birth, and of these 46% were due to prematurity and 49% to congenital disorder. Cot deaths accounted for 44% of the total (88% of deaths not determined at birth) and a definite cause could be identified in only 10% of these. The PPIM rate was 6.1 per 1000 livebirths, a significant part of the infant mortality rate of 12.6. The significance of these findings is discussed in relation to the possible reduction of these figures.

Milk protein concentrations in neonatal milk (witch's milk).

Milk protein concentrations were determined in five samples of neonatal milk (witch's milk) by either double antibody radioimmunoassay (IgA) or by single radial immunodiffusion (IgG, lactoferrin, lysozyme and albumin). Neonatal milk IgA concentrations ranged from 0.43 to 118.2 mg/l; the corresponding mean neonatal serum IgA concentration was 2.6 +/- s.e. 1.45 mg/l (n = 48). Sucrose density gradient ultracentrifugation indicated that the IgA detected was of the 11S type. IgG, lactoferrin, lysozyme and albumin were detected in neonatal milk in similar concentrations to those found in maternal milk.

Intraspinal bleeding in haemophilia: successful treatment with factor VIII concentrate.

A severely affected haemophilic boy became tetraparetic as a result of a spontaneously occurring intraspinal haematoma. Myelography defined the extent of the lesion and showed it to be extradural in site. Infusion of large doses of factor VIII concentrate led to dramatic improvement and avoided the need to operate.