The implication of phenylketonuria on oral health

PURPOSE

This study was performed to evaluate the oral health of children with PKU and to assess, in vitro, the erosive potential of 5 amino acid supplements commonly prescribed in the management of these children.

METHODS

Forty children with phenylketonuria underwent a full dental examination and were compared with an age and sex matched control group. The erosive potential of the supplements was assessed by comparing their pH and titratable acidity to those of Coca Cola and orange juice.

RESULTS

There was no significant difference between the affected and control groups in the level of dental caries, with over 75% of the children examined being caries free. However significantly more (33%) children with phenylketonuria exhibited signs of tooth wear compared with 24% of the controls (P < 0.05). While Coca Cola had the lowest pH (2.46), the titratable acidity of the flavoured supplements (92.86-126.8 mEq/l) was significantly higher than both their unflavored counterparts (4.18-14.0 mEq/l) and Coca Cola (38.56 mEq/l).

CONCLUSIONS

Despite the potentially damaging nature of their diet, significantly less children with PKU had ever seen a dentist. Health professionals involved in the care of these patients should be aware of the implications of management and provide appropriate dental advice and referral.

Rett syndrome: clinical update and review of recent genetic advances

Rett syndrome, a severe neurodevelopmental disorder occurring almost exclusively in females, is thought to be the second most common cause of profound mental retardation in females after Down syndrome. Recent genetic advances suggest the gene for Rett syndrome to be located on the distal arm of the X chromosome, Xq28. This manuscript reviews the clinical phenotype, natural history and current genetic understanding of the disorder.

Patient with a 22q11.2 deletion with no overlap of the minimal DiGeorge syndrome critical region (MDGCR)

The apparent lack of genotype/phenotype correlation in patients with the DiGeorge anomaly and velocardiofacial syndrome (DGA/VCFS; the "22q11 deletion syndrome") indicates a complex genetic condition. Most cases, whatever the phenotype, have a 1.5-3 Mb chromosomal deletion that includes the minimal DiGeorge critical region (MDGCR). Another potential critical region on 22q11 has been suggested based on two patients with distal deletions outside the MDGCR. We report on a patient with a VCFS phenotype who has a deletion, mapped by short tandem repeat polymorphic loci and fluorescence in situ hybridization analysis, distal to and not overlapping the MDGCR. This patient is deleted for several genes, including the T-box 1 gene (TBX1; a transcription regulator expressed early in embryogenesis) and catechol-O-methyltransferase (COMT; involved in neurotransmitter metabolism). We discuss the role these two genes may play in the clinical phenotype of the patient.

A novel system for assigning the mode of inheritance in mitochondrial disorders using cybrids and rhodamine 6G

When normal human cultured skin fibroblasts were treated with the fluorescent dye rhodamine 6G (R6G), there was a drastic reduction in numbers of intact mitochondria and electron transport chain enzyme activities, despite the fact that mitochondrial DNA (mtDNA) was still present in treated cells. We used this observation to develop a novel system for generating cybrids. When cultured skin fibroblast cells from a patient with the mitochondrial encephalopathy and ragged-red fibers (MERRF) syndrome harboring the A8344G mtDNA mutation and which showed a severe reduction in cytochrome c oxidase activity were treated with R6G and fused to enucleated HeLaCOT cells, the resulting cybrid clones showed recovery of cytochrome c oxidase activity, and were shown to have mtDNA derived solely from the HeLaCOT cell line. R6G has significant advantages over ethidium bromide in removing the mitochondrial elements from cultured cells, and the results reported here demonstrate that this strategy can be used to determine the origin of the genetic defect in patients with electron transport chain abnormalities.

Flow cytometric evaluation of defects of the mitochondrial respiratory chain

Cultured human skin fibroblasts from 12 patients with a variety of mitochondrial respiratory chain defects were examined for their capacity to oxidize dihydrorhodamine-123 to the fluorescent molecule rhodamine-123 using a flow cytometer. We found that cells from patients with functional defects in respiratory chain enzymes were less able to oxidize dihydrorhodamine-123 than those of healthy controls. Ten of the cell strains had reduced activity in at least one of the respiratory chain complexes and also showed significantly reduced fluorescence when compared to the mean of eight normal control cell strains. One patient had mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (with the A3243G mutation) and reduced respiratory chain activities in muscle and liver. Molecular analysis did not show the mutation in cultured skin fibroblasts, and had correspondingly normal fluorescence. The 12th cell strain showed reduced fluorescence but did not reach statistical significance. This strategy could be of use in helping direct further investigations in patients, and in studying the biochemical pathogenesis of mitochondrial DNA mutations in cybrid studies.

The molecular basis of malonyl-CoA decarboxylase deficiency

We characterized a 2.1-kb human cDNA with a 1362-bp (454-amino acid) open reading frame showing 70.3% amino acid identity to goose malonyl-CoA decarboxylase (MCD). We have identified two different homozygous mutations in human MCD (hMCD) by using RT-PCR analysis of fibroblast RNA from two previously reported consanguineous Scottish patients with MCD deficiency. The first mutation is a 442C-->G transversion resulting in a premature stop codon (S148X) in the N-terminal half of the protein. The second is a 13-bp insertion in the mature RNA, causing a frameshift with predicted protein truncation. This insertion is the result of an intronic mutation generating a novel splice acceptor sequence (IVS4-14A-->G). Both mutations were found to segregate appropriately within the families and were not found in 100 normal unrelated individuals. These mutations would be predicted to cause MCD deficiency, thus confirming this transcript as the hMCD ortholog. The peptide sequence of hMCD revealed a C-terminal peroxisomal targeting sequence (-SKL). This targeting signal appears to be functional in vivo, since the distribution of MCD enzymatic activity in rat liver homogenates-as measured by means of subcellular fractionation-strongly suggests that MCD is localized to peroxisomes in addition to the mitochondrial localization reported elsewhere. These data strongly support this cDNA as encoding human MCD, an important regulator of fatty acid metabolism.

Prolonged QT interval in Rett syndrome

Rett syndrome is a severe neurodevelopmental disorder of unknown aetiology. A prolonged QT interval has been described previously in patients with Rett syndrome. To investigate QT prolongation and the presence of cardiac tachyarrhythmias in Rett syndrome electrocardiography and 24 hour Holter monitoring were performed prospectively in a cohort of 34 girls with Rett syndrome. The corrected QT value was prolonged in nine patients. Compared with a group of healthy controls of a similar age range, the patients with Rett syndrome had significantly longer corrected QT values. Clinical severity was not a predictor for prolonged QT intervals in the Rett syndrome cohort. The prolonged QT syndrome is a serious and potentially lethal cardiac disorder and should be considered in all girls with Rett syndrome.

A population-based approach to the investigation of osteopenia in Rett syndrome

This study compares bone mass in a national sample of girls with Rett syndrome (RS) with a sample of control children. The Australian RS Database was the source of cases for this population-based study. Hand radiographs were available from 101 of 137 subjects (74% of the known Australian population of girls with RS aged < or = 20 years). Control radiographs matched for age, sex, and laterality were obtained from hospital radiology departments. A measure of cortical thickness was made from the difference between the outer diameter and the medullary space in the second metacarpal bone. A mean z-score value for cortical thickness and percentage cortical area for each individual was calculated. The mean cortical thickness (z score) for girls with RS was -1.94 compared with -0.38 for control children (P<0.001). In girls with RS, the mean cortical thickness decreased with age (P<0.001). In girls who were taking epilepsy medication it was -2.21 compared with -1.23 in those not taking epilepsy medication (P<0.001). There was no evidence of a beneficial effect of increased calcium intake on cortical thickness. A similar pattern was obtained when percentage cortical area was estimated. In multivariate analysis, increasing age and use of anticonvulsant medication were associated with decreased cortical thickness and only use of anticonvulsant medication with decreased percentage cortical area. Fractures had occurred in one-third of cases and it was estimated that just over 40% of girls would sustain a fracture by the age of 15 years. Girls with RS may be at increased risk of fractures and their bone quality compromised as determined by cortical thickness and percentage cortical area measurements from the second metacarpal.

Surfactant protein B deficiency: clinical, histological and molecular evaluation

Congenital alveolar proteinosis due to surfactant protein B deficiency is an inherited disease which results in severe respiratory failure in term infants soon after birth. The pathophysiologic basis of this disease is now known to be an inability to synthesise adequate quantities of normally functioning surfactant protein B. We report a male infant with fatal respiratory failure of neonatal onset, and histopathological features typical of those seen in congenital alveolar proteinosis. Molecular analysis of genomic DNA revealed two mutations, the 'common' 121ins2 mutation in exon 4, and a novel 2bp frameshift mutation in exon 5. We believe this is the first Australian case of surfactant protein B deficiency confirmed by molecular analysis.

Metacarpophalangeal pattern profile and bone age in Rett syndrome: further radiological clues to the diagnosis

Hand radiographs of 100 girls representing 73% of the known Australian population of girls with Rett syndrome, age 20 years or less, were available for this study. Control radiographs were matched for age, sex, and laterality. Bone age was assessed against standard radiographs in Greulich and Pyle [1959: Radiographic Atlas of Skeletal Development of the Hands and Wrist, 2nd ed.]. A metacarpophalangeal pattern (MCPP) profile comparing the relative lengths of the hand bones with mean population norms by age was produced by converting the length of each of the 19 metacarpal and phalangeal bones into a Z score. In girls less than 15 years old, bone age was more advanced in Rett syndrome than in age-matched control girls (left hand P = 0.03, right hand 0.004), but was most advanced in the younger group and normalized with age. In Rett syndrome, the mean Z score for the 19 metacarpal and phalangeal bones was 1.0 in children under 5 years, -0.27 in those aged 5-11 years, and -1.7 in those aged 12 years and over. This variation between age groups was much greater than in the controls. The dips in the MCPP profile occurred at MC2 and D1, and the peaks at M5, P5, and M4. An MCPP profile may provide an additional aid to diagnosis in cases of Rett syndrome where all the criteria are not met, but in children under age 5 years, advanced bone age may be more helpful as a marker.

Rett syndrome: randomized controlled trial of L-carnitine

Rett syndrome is a severe neurodevelopmental disorder of unknown etiology, occurring almost exclusively in female patients. The etiology and functional significance of plasma carnitine deficiency seen in some patients with Rett syndrome is unknown. To investigate whether L-carnitine might be of benefit in Rett syndrome, a randomized, placebo-controlled, double-blind crossover trial of L-carnitine has been completed in 35 subjects. Eight-week treatment phases were completed for both a placebo and L-carnitine. Outcome was measured by parents/caregivers and at medical follow-up using three established tools: the Rett Syndrome Motor Behavioral Assessment, the Hand Apraxia Scale, and the Patient Well-Being Index. Analysis comparing change between baseline and week 8 of treatment for L-carnitine and the placebo showed that both parents/caregivers and medical follow-up detected improvements in the subjects' well-being. In addition, medical review showed an improvement on the Hand Apraxia Scale for a higher proportion of girls on L-carnitine. Identification of predictors of clinical improvement has been limited by the power of the study. These findings suggest that L-carnitine is of benefit in some patients with Rett syndrome. While L-carnitine did not lead to major functional changes in ability, the type of changes reported could still have a substantial impact on the girls and their families. Information is still needed, however, to determine if only subgroups of girls with the disorder are responsive to L-carnitine and the appropriate duration of therapy.

Respiratory chain complex III [correction of complex] in deficiency with pruritus: a novel vitamin responsive clinical feature

We report a child with an isolated complex III respiratory chain deficiency and global developmental delay who had severe pruritus with elevated plasma bile acid levels. A liver biopsy showed micronodular cirrhosis, and enzymologic evaluation demonstrated an isolated complex III deficiency in both liver and muscle. His pruritus improved and serum bile acid levels decreased after treatment with menadione and vitamin C.

Non-invasive estimation of pulmonary arterial hypertension in chronic obstructive pulmonary disease

The feasibility and reliability of the combination of several noninvasive methods using a multivariate method of analysis to predict pulmonary artery hypertension (PAH) is evaluated in 20 patients with chronic obstructive pulmonary disease. These methods comprised arterial blood gases (Pao2, Paco2), pulmonary functional parameters (FEV1), echo-Doppler parameters (tricuspid regurgitation jets, acceleration time on pulmonary valve), computed tomography measurements (transhilar distance, hilar thoracic index, and measurement of the descending branch of the right pulmonary artery to the lower lobe). A multiple stepwise regression analysis (including one Doppler parameter, two parameters of arterial blood gases, and one functional parameter) revealed a coefficient of determination (R2) equal to 0.954 for mean pulmonary artery pressure (MPAP) with a standard error of estimate (S.E.E.) of 5.25 mmHg. A stepwise regression analysis including computed tomography and radiographic parameters revealed an R2 equal to 0.970 for PAP with a S.E.E. of 4.26 mmHg. Logistical regression analysis classified correctly 80% of patients with PAH using noninvasive methods such as the diameter of the main pulmonary artery and the diameter of the left pulmonary arterial branch calculated by computed tomography. Not only the presence of PAH but also the level of MPAP can be estimated by the combination of multiple stepwise and logistical regression analyses.

Autonomic cardiovascular neuropathy in Sjögren's syndrome. A controlled study

OBJECTIVE

To test patients with primary Sjögren's syndrome (SS) for evidence of autonomic neuropathy.

METHODS

Thirty-two patients with primary SS and 22 age and sex matched healthy individuals were asked specific questions about symptoms suggestive of autonomic neuropathy, and were subjected to a battery of 5 cardiovascular tests: response of blood pressure to sustained hand grip, Valsalva maneuver, heart rate response to deep breathing, and heart rate and blood pressure response to standing up. The chi-squared test with Yates' correction and 95% confidence intervals were used for statistical analysis of the results.

RESULTS

Sixteen patients (50%) had symptoms of autonomic neuropathy when specifically asked versus none of the controls (p < 0.0005). The frequency of abnormal responses to the tests was 68.8% in patients and 12.7% in controls (p < 0.0001). Severe autonomic cardiovascular neuropathy was found in 87.5% of the patients but in none of the healthy individuals (p < 0.0001).

CONCLUSION

Our results suggest that autonomic neuropathy is a feature of a significant portion of the SS population, and such patients should have appropriate evaluation. Similarly, patients with unexplained autonomic neuropathy should be investigated for evidence of SS.

Diagnosis of Rett syndrome: can a radiograph help?

Rett syndrome (RS), a neurodevelopmental disorder almost exclusively affecting girls, is associated with severe intellectual and motor disability. In the absence of biological markers, diagnosis is determined by a set of clinical criteria. In a previous study in Scotland, shortening of the fourth metatarsal was reported clinically in 20% of classical RS cases aged 5 years or older. The Australian Rett Syndrome Study database has facilitated a population-based radiological study of the hands and feet of girls with RS. Straight radiographs of hands and feet were available from 94 cases, representing 70.1% of the known RS population in Australia. Control radiographs were matched for age, sex, and laterality. Relative shortening of the fourth metacarpal/metatarsal was assessed using the sign method. A short ulna (negative ulna variance) was defined as the distal articular surface of the ulna being at least 5mm proximal to the distal articular surface of the radius. A positive metacarpal sign was twice as common in verified cases of RS than in controls in the right but not the left hand. A short ulna was more common in subjects with RS than in controls. A short fourth metatarsal was also more common among subjects with RS. More than half (56.6%) the girls with RS over the age of 4 years had a negative ulnar variance in either wrist or a metatarsal sign in either foot. These findings will assist with the diagnosis of RS and may help direct research towards the location of the molecular defect.

Rett syndrome: significant clinical overlap with Angelman syndrome but not with methylation status

Rett syndrome and Angelman syndrome are neurodevelopmental disorders characterized by severe intellectual disability, microcephaly, speech disturbance, movement disorders with gait and/or truncal ataxia, and occasionally a similar facial appearance. Both conditions can be difficult to diagnose in girls early in their clinical course and can be difficult to distinguish from each other. Genomic imprinting is a known association in Angelman syndrome and previously has been suggested in Rett syndrome. Our aim was to evaluate the methylation status in a cohort of classical patients with Rett syndrome, using a methylation system for chromosome 15q11-13. Methylation analysis of chromosome 15 has not been previously reported in Rett syndrome. Furthermore, we document the clinical features of 31 girls with classical Rett syndrome and confirm the phenotypic similarities between Rett syndrome and Angelman syndrome. The methylation studies in these girls with Rett syndrome were normal. This excludes an imprinting error of the Angelman syndrome critical region on chromosome 15 (15q11-13) as an association with Rett syndrome, and indicates that methylation studies may be useful in distinguishing Rett syndrome from Angelman syndrome in young patients with an overlapping clinical phenotype. A normal methylation pattern, however, does not exclude the diagnosis of Angelman syndrome and clear distinction between the two syndromes will evolve over time.

Cisplatin binding sites on human albumin

Reactions of cisplatin (cis-[PtCl2(NH3)2]) with albumin are thought to play an important role in the metabolism of this anticancer drug. They are investigated here via (i) labeling of cisplatin with 15N and use of two-dimensional 1H,15N NMR spectroscopy, (ii) comparison of natural human serum albumin with recombinant human albumin (higher homogeneity and SH content), (iii) chemical modification of Cys, Met, and His residues, (iv) reactions of bound platinum with thiourea, and (v) gel filtration chromatography. In contrast to previous reports, it is shown that the major sulfur-containing binding site involves Met and not Cys-34, and also a N ligand, in the form of an S,N macrochelate. Additional monofunctional adducts involving other Met residues and Cys-34 are also observed. During the later stages of reactions of cisplatin with albumin, release of NH3 occurs due to the strong trans influence of Met sulfur, which weakens the Pt-NH3 bonds, and protein cross-linking is observed. The consequences of these findings for the biological activity of cisplatin-albumin complexes are discussed.

Automated analysis of mitochondrial enzymes in cultured skin fibroblasts

We report automated methods for assaying the activities of the mitochondrial respiratory chain enzyme cytochrome c oxidase (COX), the matrix enzyme citrate synthase (CS), and the cytoplasmic enzyme lactate dehydrogenase (LDH) on a random access analyzer, the Roche Mira S. COX activity was assayed by measuring the initial rate of oxidation of reduced cytochrome c. The CS assay was based on the reaction of this enzyme with oxaloacetate and acetyl-CoA to produce CoASH, which further reacts with dithionitrobenzoic acid producing a free thionitrobenzoate ion. LDH activity was assayed by measuring the reduction of nicotinamide adenine dinucleotide during the oxidation of lactate to pyruvate. Precision of the COX assay was 2. 3%, CS assay 0.7%, and LDH 5.6%. These automated methods were faster by as much as 80%, cheaper by 50%, and used less than half the sample material needed for traditional manual methods. While these assays are often performed by specialized laboratories using dedicated staff, the automated methods presented here are easily performed by staff trained in the regular diagnostic laboratory.

Multi-metal binding site of serum albumin

Circular dichroism and electron spin resonance spectroscopy are used to investigate the second specific metal binding site on human, bovine and porcine albumins. Ni(II), Zn(II) and Cd(II) can displace Cu(II) from the second Cu(II) site but not from the first strong site of human and bovine albumins (the N-terminal site). The second Cu(II) binds more strongly than the other metal ions to the second site of all three proteins, except Zn(II) binding to porcine albumin which is ca. 10 x stronger than Cu(II). The second Cu(II) site appears to be a tetragonal ¿2N, 4O¿ site.

Early treatment of Menkes disease with parenteral copper-histidine: long-term follow-up of four treated patients

We report on the long-term clinical course of 4 boys with Menkes disease, treated from early infancy with parenteral copper-histidine, with follow-up over 10-20 years. Three of the 4 had male relatives with a severe clinical course compatible with classical Menkes disease. As a consequence of early treatment, our patients have normal or near-normal intellectual development, but have developed many of the more severe somatic abnormalities of the related disorder, occipital horn syndrome, including severe orthostatic hypotension in 2. In addition, 1 boy developed a previously unreported anomaly, namely, massive splenomegaly and hypersplenism as a consequence of a splenic artery aneurysm. Previously reported molecular studies in 2 of these patients had shown gene defects which would have predicted a truncated and probably nonfunctional gene product. Despite the favorable effects on the neurological symptoms, parenteral copper treatment for Menkes disease should still be regarded as experimental. The development of more effective treatments must await a more precise delineation of the role which the Menkes protein plays in intracellular copper trafficking.

The association of protein-losing enteropathy with cobalamin C defect

We report a male infant with cobalamin C defect whose clinical course was complicated by diarrhoea suggestive of a protein-losing enteropathy, failure to thrive, macrocytosis and thrombocytopenia which resolved with hydroxocobalamin treatment. Protein-losing enteropathy has not previously been reported in association with cobalamin C defect and, if unrecognized, could cause considerable morbidity.

Intragenic complementation at the argininosuccinate lyase locus: reconstruction of the active site

Intragenic complementation has been observed at the argininosuccinate lyase (ASL) locus and the ASL alleles in the ASL-deficient cell strains of two complementation phenotypes have been identified. The frequent complementers, strains that participate in the majority of the complementation events, were found to be either homozygous or heterozygous for the Q286R allele, while the high-activity complementers, those strains in which complementation is associated with a high restoration of activity, were found to be either homozygous or heterozygous for the D87G allele. Direct proof of the intragenic complementation observed at the ASL locus has been obtained with the co-expression of the D87G and Q286R alleles in COS cells. A significant increase in the ASL activity was observed when the two alleles were co-expressed relative to the expression of each mutant allele alone. The increase in activity was comparable to that observed previously in the fibroblast complementation studies. The structure determinations of ASL and the homologous eye lens protein, duck delta II crystallin, have revealed that the active site of ASL is made up of residues from three different monomers. The structural mapping of the Q286 and D87 residues shows that both are located near the active site but that, in any one active site, each is contributed by a different monomer. The molecular symmetry of the ASL protein is such that when mutant monomers combine randomly, one active site will contain both mutations and at least one active site will contain no mutations at all. It is these 'native' active sites in the hybrid Q286R/D87G proteins that give rise to the partial recovery of enzymatic activity observed during intragenic complementation.

Progressive myoclonic epilepsies: recent genetic advances

The progressive myoclonic epilepsies are a rare group of debilitating epileptic encephalopathies characterized by myoclonic seizures, progressive neurological dysfunction and dementia. In the past year advances in gene mapping have isolated gene loci for the majority of progressive myoclonic disorders, paving the way for specific diagnosis, more accurate prognosis and risk calculation, as well as opening the potential for prenatal and pre-symptomatic diagnosis in at risk families.

Automated quantitation of total protein in cultured skin fibroblasts

An automated Coomassie Blue method of measuring total protein in cultured skin fibroblasts using a random access analyzer, the Roche MIRA, was compared to a manual dye binding method using bicinchoninic acid. The automated Coomassie Blue method is in common use in many routine laboratories for measurement of total protein in urine and CSF, and was found by us to be significantly faster than a manual protein method, with an average assay time of 2 min per sample. In addition, intra- and inter-run precision were comparable for the automated and manual methods, and compared favourable with other automated methods. We recommend that where the MIRA apparatus is available, consideration be given to its use for protein quantitation of cell or tissue extracts.