[Defects of pyruvate metabolism in cultured lymphoblastoid cells of 20 patients with Leigh syndrome]

Lymphoblastoid cells are useful materials for the diagnosis and basic studies of many human genetic disorders. To elucidate the etiology of Leigh syndrome, biochemical analyses and mitochondrial DNA analyses were performed on cultured lymphoblastoid cells from 20 patients with the clinical characteristics of this disorder. In 9 of 20 cases, we were able to define the following defects. Eight patients had biochemical defects, including 3 with pyruvate dehydrogenase complex (PDHC), 3 with cytochrome c oxidase (complex IV), and 2 with NADH-cytochrome c reductase (complex I) deficiencies. Two of 3 patients with PDHC deficiency were diagnosed with thiamine-responsive PDHC deficiency. One patient had a point mutation (T-->G) of mitochondrial DNA at nucleotide position 8993. These results indicate that the underlying defects in Leigh syndrome are heterogeneous and cultured lymphoblastoid cells are very useful materials for diagnosis of the etiology of Leigh syndrome.

Movement-related potentials associated with motor inhibition under different preparatory states during performance of two visual stop signal paradigms in humans

The motor-inhibition process was examined in humans by monitoring reaction times (RTs), electromyograms (EMGs), and movement-related potentials. Eight subjects performed two types of visual stop signal paradigm, one with ongoing motor activity and the other without background motor activity. NO-GO-specific negative potentials were consistently recorded from subjects with constant onset and duration relative to the onset of the NO-GO stimulus in both tasks and the spatial distribution of amplitudes was also invariant between the tasks. Sustained background muscle activity was not influenced by the inhibitory command. The constant features of NO-GO-specific potentials during performance of both tasks imply that temporally and spatially similar inhibition processes might specifically suppress the execution of a new motor process without any significant effect on the ongoing motor programme, regardless of differences in preparatory states.

Changes in rCBF during grasping in humans examined by PET

To identify the functional fields involved in grasping for objects, we measured regional cerebral blood flow (rCBF) by positron emission tomography (PET) in eight normal volunteers. In the reaching and grasping tasks, the subjects were asked to touch or grasp one of five cylinders with their finger(s). Compared with reaching, grasping specifically increased the rCBF in the fields located in the bilateral premotor area (PMA), the posterior parietal area (PPA) and the prefrontal area (PFA). These results indicate that PMA, PPA and PFA might be key structures for the performance of grasping movements.

Elevated cerebrospinal fluid lactate/pyruvate ratio in Machado-Joseph disease

To identify the metabolic alterations related to mitochondrial functions in Machado-Joseph disease (MJD), we analyzed the cerebrospinal fluid (CSF) levels of lactate, pyruvate, and citric acid cycle intermediates by high performance liquid chromatography (HPLC) in 7 Japanese patients with that disease and then measured some mitochondrial enzymes. Their mean age was 46 years. Diseased controls were matched by age to the patients studied. The CSF level of lactate was significantly elevated, pyruvate was significantly decreased, and the lactate/pyruvate (L/P) ratio was significantly elevated in the patients with MJD. There were no significant differences of citric acid cycle intermediates of the CSF between the patients and the controls. We measured the native and dichloroacetate (DCA)-activated pyruvate dehydrogenase complex (PDHC) activities, and mitochondrial electron transport activities in 3 patients with MJD, and found these activities to be normal. Therefore, the increased CSF lactate, increased lactate/pyruvate ratio, and decreased pyruvate may reflect the decreased regional cerebral blood flow rather than metabolic derangement of the mitochondria.

Surface-coil magnetic resonance imaging of the internal auditory canal and the inner ear. Preliminary report

Parasagittal surface-coil magnetic resonance imaging of the internal auditory canal and the inner ear was performed. We used T2-weighted fast spin-echo sequences to visualize the inner ear and the individual nerves in the internal auditory canal with high contrast in a short acquisition time. Computer-assisted quantitative measurement of the nerves was performed to estimate the cross-sectional areas and the diameters of the nerves. The average diameters of the facial nerve, the cochlear nerve, and the vestibular nerve of normal-hearing individuals were, respectively, 1.1 +/- 0.2 mm (mean +/- SD), 1.2 +/- 0.2 mm, and 1.5 +/- 0.2 mm. In the cerebellopontine angle, the average diameter of the eighth nerve was 1.8 +/- 0.2 mm. Two patients with unilateral and bilateral hearing loss were also presented. In the patient with unilateral deafness, the cochlear nerve of the diseased side was not identified and the eighth cranial nerve diameter was smaller than that of the normal side. In the patient with bilateral deafness, fibrosis of the inner ear and atrophy of the eight nerve were demonstrated in the ear with posttraumatic deafness. The present method may represent a new approach to the assessment of pathologic processes involving the inner ear and the nerves in the internal auditory canal.

Effect of vestibular nerve section on cytochrome oxidase activity in the vestibular ganglion cells of the squirrel monkey

Cytochrome oxidase (CO) activity of the vestibular ganglion cells of the squirrel monkey was demonstrated histochemically under normal and experimental conditions. Under general anesthesia, right vestibular nerve section was performed on adult squirrel monkeys between the vestibular ganglion and brain stem. The left side was left intact and was used as a within-animal normal control. One squirrel monkey that did not undergo vestibular nerve section was also included in the normal group. Following a survival period of seven months, neurons in the vestibular ganglion of both sides were examined. In the normal control sides, a significant negative correlation between the size of the neuron and its optical density for CO stain was observed. Many neurons in the vestibular ganglion survived after vestibular nerve section, but their cell sizes and optical densities of CO stain decreased compared with those of the control side.

Three short tandem repeat loci in Japanese population

Allele frequencies of three short tandem repeat loci, vWF, TH and GCG, were examined for 210 unrelated Japanese individuals. Eight alleles were identified with PCR and gel electrophoresis for vWF, 7 for TH and 13 for GCG, indicating that these loci are highly polymorphic. Combined discrimination power of the 3 STRs was 0.995. These results imply that the loci are useful as probes for the identification of Japanese individuals. Thus, we applied the probes to the identification of a forensic specimen that was decomposed severely. The vWF and TH probes successfully gave clear bands in gel electrophoresis, but GCG failed to be typed because of a lot of shadow bands. The results suggests the usefulness of at least the former two probes in forensic studies.

Molecular genetic analysis of a female patient with pyruvate dehydrogenase deficiency: detection of a new mutation and differential expression of mutant gene product in cultured cells

A new 18 bp insertion mutation in the gene for the alpha subunit of pyruvate dehydrogenase (E1 alpha) was found in a female patient with congenital lactic acidaemia. Cultured skin fibroblasts and Epstein-Barr virus-transformed lymphoblastoid cells from this patient showed decreased and normal pyruvate dehydrogenase complex (PDHC) activity, respectively. This 18 bp insertion was a de novo mutation, because it was not present in her parents. Although this female patient was heterozygous for the normal and the mutant alleles, 97% of cultured skin fibroblasts expressed the mutant allele, while 100% of cultured lymphoblastoid cells, 94% of peripheral blood lymphocytes and 98% of IL-2-activated T-cells expressed the normal allele. These results suggest that in this patient the X chromosome containing the normal allele was predominantly inactivated in fibroblasts and the X chromosome containing the mutant allele was predominantly inactivated in lymphocytes. The diagnosis of E1 alpha deficiency is usually established by measurement of PDHC activity and the level of immunoreactive proteins. However, these methods are not sufficient to diagnose the disorder in female patients with E1 alpha deficiency due to differential inactivation of the X chromosome. Therefore, it is necessary to develop a new method to firmly establish the diagnosis of E1 alpha deficiency.

DNA diagnosis of pyruvate dehydrogenase deficiency in female patients with congenital lactic acidaemia

The diagnosis of pyruvate dehydrogenase (PDH) E1 alpha deficiency, which is an X-linked inborn error of metabolism, is usually established by the measurement of PDH complex activity in cultured cells. However, heterozygous female patients with PDH E1 alpha deficiency may be misdiagnosed when the normal X chromosome is predominantly expressed in the cultured cells. Therefore, in female patients with convincing clinical presentations of PDH E1 alpha deficiency and the normal enzyme activity, the X-inactivation pattern should be analysed and the PDH E1 alpha gene screened for mutations. For this screening, we applied the method of single-strand conformational polymorphism (SSCP) and DNA sequencing and examined 11 female patients with congenital lactic acidaemia whose PDH complex activity was normal in cultured cells. In 2 of the 11 female patients, we found distinct pathogenic missense mutations in the PDH E1 alpha gene (G89S and G291R). Both affected patients showed a similar clinical presentation and had been diagnosed as West syndrome. In 3 of the 11 patients, we found a polymorphic base-pair substitution in exon 9 of the PDH E1 alpha gene which resulted in a changed amino acid residue (M282L). We conclude that PCR-SSCP analysis of the PDH E1 alpha gene, followed by DNA sequencing, is a useful method to screen for mutations of the PDH E1 alpha gene in female patients with congenital lactic acidaemia who have normal enzyme activities in available samples, normal ratio of lactate to pyruvate, and predominantly raised lactate concentration in cerebrospinal fluid.

Vitamin D-dependent rickets type II: regulation of human osteocalcin gene expression in cells with defective vitamin D receptors by 1,25-dihydroxyvitamin D-3, retinoic acid, and triiodothyronine

The vitamin D receptor (VDR) is a nuclear transcription factor which binds to the vitamin D response element (VDRE) of the human osteocalcin gene and regulates its expression. Humans with VDR gene mutations, ever among those with the same point mutation in their VDR gene, demonstrate clinical heterogeneity. In addition, in some patients with these mutations, rickets has not recurred following cessation of therapy during follow-up ranging from 6 to 24 years. While important, it is likely that the VDR protein is not the sole factor in the development of rickets. To try to understand these clinical findings, the complex formed between the VDRE and one or more proteins in the nuclear extracts of cultured skin fibroblasts treated with 1,25-dihydroxyvitamin D-3 (1,25(OH)2D3), retinoic acid (RA), and/or triiodothyronine (T3) was investigated since such complexes are likely to precede the transcription of the VDR gene. Complex formation in the control cells with an intact VDR was increased by treatment with either 0.1 nM, 1 nM, 10 nM 1,25(OH)2D3, 100 nM RA, or 100 nM T3; however, combinations of these compounds did not produce an additive effect. In cells of affected patients, 1,25(OH)2D3, RA, or T3 increased complex formation, while no combination had an additive effect. These results indicate that 1,25(OH)2D3, RA, and T3 play a role in the regulation of bone remodeling through modulating the formation of protein complexes on the VDRE. Therefore, the clinical observations in patients with a VDR mutation might be explained at least in part by the overlapping control of osteocalcin expression by 1,25(OH)2D3, RA and T3.

Movement-related slow potentials during motor imagery and motor suppression in humans

Electro-encephalograms (EEGs) associated with motor imagery and motor suppression were recorded from motor-related frontal regions in humans. A negative potential was observed both during motor imagery and during NO-GO responses, as well as in movement trials. The negative potentials observed in the motor imagery trials had a similar pattern to those observed in the movement trials, although the potentials were different from those during NO-GO responses. The peak amplitude of the negative potential recorded at FCz was significantly larger than those recorded at F3, F4, C3 and C4 in the imagery task. The peak amplitude of the negative component in movement trials was larger than that in the imagery trials of all recording positions. By contrast, during the GO/NO-GO task, the peak amplitude during NO-GO responses was larger than that during the GO responses at every position. It appears, therefore, that motor imagery and motor suppression are associated with their own specific internal processes which are reflected by specific EEG patterns in motor-related frontal areas.

Molecular analysis of abnormal pyruvate dehydrogenase in a patient with thiamine-responsive congenital lactic acidemia

A patient who responded to thiamine therapy with reduction of lactate in the blood and cerebrospinal fluid and clinical improvement was studied. Cultured lymphoblastoid cells of this patient were found to show reduced activities of pyruvate dehydrogenase complex (PDHC) and pyruvate dehydrogenase, decreased affinity of PDHC for thiamine pyrophosphate, and defective activation of PDHC by pyruvate dehydrogenase phosphatase. PDHC deficiency in fibroblasts and biopsied muscle of this patient was also due to the decreased affinity of PDHC for thiamine pyrophosphate. A mutation in the E1 alpha subunit containing the thiamine binding site and serine phosphorylation site regulating the activation/inactivation of PDHC was characterized by the polymerase chain reaction and DNA sequencing. A single A-->G transition was identified at position 131, resulting in the substitution of Arg-44 for His-44. This mutation must be a de novo mutation because it was not found in either parent's genomic DNA. In this study, we have obtained the first evidence at the molecular level for a mutation of thiamine-responsive PDHC deficiency.

Movement-related potentials associated with motor inhibition as determined by use of a stop signal paradigm in humans

The motor inhibition process was examined in humans by monitoring reaction times, electromyograms, and movement-related potentials. Four subjects performed a simple visual Stop Signal Paradigm. The results were as follows. (1) The EEG waveform pattern was remarkably consistent among subjects. NO-GO-specific negative-positive potentials were observed under all experimental conditions. (2) The timing of the onset and the peak latency of the negative potential relative to the second stimulus, S2, were constant (about 200-210 ms and 250-260 ms for each) regardless of changes in the S2 delay. The time interval between the initial onset of the negative potential and its peak latency was constant (about 50 ms). (3) By contrast, the peak-to-peak time between the negative potential and the positive potential became smaller as the S2 delay was increased. It is suggested, therefore, that the motor inhibition process might consist of different sub-processes and that some part of the inhibition process might be of constant and specific duration.

Sex typing of forensic DNA samples using male- and female-specific probes

Forensic DNA samples have been examined to ascertain the feasibility of a sex-typing procedure that we have recently developed. This uses two sets of primers complementary to the DXZ4 and SRY genes for polymerase chain reaction (PCR). PCR target in the DXZ4, an 80-bp sequence within the 130-bp fragment specific to females, is generated from inactive chromosome X by the DNA digestion with a methylation-sensitive restriction enzyme, HpaII. Therefore, the DXZ4 amplification and subsequent agarose gel electrophoresis detect the 80-bp fragment from female DNA. On the other hand, the SRY probe identifies a male-specific sequence on chromosome Y. Testing DNAs from fresh Turner's blood and from postmortem tissues exhibited band-signals confirming the sex identification. Degraded DNAs isolated from severely decomposed specimens were also identifiable when high-molecular-weight DNA was isolated before the assay. This demonstrates the usefulness of this method in forensic identification.

Controllability of motor imagery and transformation of visual imagery

This study examined the relation between control of motor imagery and generation and transformation of visual imagery by testing 54 subjects. We used two measures of the Controllability of Motor Imagery test to evaluate the ability to control motor imagery. One was a recognition test on which the subject imagines as if one sees another's movement, and the other was a regeneration test on which one imagines as if one moves one's own body. The former test score was related to processing time of a mental rotation task and the latter one was not but would reflect sport experience. It was concluded that two meanings of the test could reflect different aspects such as observational motor imagery and body-centered motor imagery.

Mutation of the p53 gene in gallbladder cancer

Genetic alteration of the p53 gene was examined in tissue specimens of primary gallbladder cancer (GBC) using PCR-single strand conformation polymorphism (SSCP) and direct sequencing analyses. The p53 gene mutation was detected in five of the 16 GBC cases examined (31%). All five cases showed single point mutations; four were mutations resulting in amino acid substitution and the other was one base-pair deletion. Of the five mutations detected, four occurred at evolutionarily conserved regions and the remaining one at a well conserved region among species. Our result is similar to those of previous reports for various human cancers in mutation scattering over four of the five conserved domains.

Sex determination using the hypomethylation of a human macro-satellite DXZ4 in female cells

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Leigh encephalopathy: histologic and biochemical analyses of muscle biopsies

To elucidate the pathogenesis of Leigh encephalopathy, histologic, biochemical, and mitochondrial DNA analyses were performed on biopsied muscles from 33 patients with the clinical characteristics of this disorder. On muscle histochemistry, cytochrome c oxidase activity was decreased or absent in 7 patients (21%), although none had ragged-red fibers. In 2 patients with cytochrome c oxidase deficiency, staining for this enzyme was poor in the muscle fibers and fibroblasts but was normal in the arterial wall, indicating tissue-specific involvement. Ten patients (30%) had biochemical defects, including 2 with pyruvate dehydrogenase complex, 4 with cytochrome c oxidase, 1 with NADH-cytochrome c reductase (complex I), and 3 with multiple complex deficiencies. None of the 28 patients in whom muscle mitochondrial (mt)DNA was analyzed had DNA deletions or point mutation at nucleotide positions 3,243 or 8,344. These results indicate that the underlying defect in Leigh encephalopathy is heterogeneous because only 30% of patients had enzyme defects demonstrable in muscle biopsy material.

Decrease of pyruvate dehydrogenase phosphatase activity in patients with congenital lactic acidemia

We developed an assay method for pyruvate dehydrogenase phosphatase activity using [1-14C]pyruvate and measured pyruvate dehydrogenase phosphatase activity in cultured skin fibroblasts from three patients with congenital lactic acidemia due to a defect in activation of the pyruvate dehydrogenase complex. The enzyme activity of their fibroblasts was significantly reduced to 50.7%, 64.6% and 63.1% of that of control fibroblasts. These observations suggest that the defect in activation of the pyruvate dehydrogenase complex in these patients might be due to a reduction in pyruvate dehydrogenase phosphatase activity.

Ribosomal ribonucleic acid (rRNA) gene typing for species identification

Deoxyribonucleic acid (DNA) typing of ribosomal ribonucleic acid (rRNA) genes was performed with a polymerase chain reaction (PCR) assay for species identification. A variable region of the 28S ribosomal RNA gene was amplified with primers complementary to flanking sequences phylogenetically well conserved. The products of twelve animal DNAs (human, Japanese monkey, dog, cattle, pig, cat, rabbit, mouse, rat, chicken, frog, and fish) were separated by polyacrylamide gel electrophoresis, each revealing a few bands ranging from 150 to 100 base pairs. The band patterns obtained from each DNA sample differed in number and size, which indicates the applicability of the method to species identification. Samples containing either as little as 1 pg of DNA or degraded DNA of 0.2 to 0.5 kb in length were able to give detectable bands. Postmortem human tissue DNAs were tested as an example. They showed a pattern identical to the human control one, which was distinct from those of the other animals examined.

The Rett syndrome and CSF lactic acid patterns

We investigated both blood and cerebrospinal fluid (CSF) lactate and pyruvate levels in seven girls with the Rett syndrome (RS) and evaluated the relationship between CSF lactate and pyruvate levels and the clinical manifestations, particularly seizures, anticonvulsant medication, and breathing dysfunction including breath holding, apnea and hyperventilation. Elevated lactate and pyruvate levels in CSF with normal serum lactate were found in two RS patients. Elevated CSF lactate correlated significantly with the clinical occurrence of hyperventilation (P0 = 0.048, Fisher exact probability). We measured native and dichloroacetate (DCA)-activated pyruvate dehydrogenase (PDH) complex activities in two patients (#1 and 2) using cultured lymphoblastoid cell lines which were transformed by EB virus and the results were normal. We also analyzed CSF citric acid intermediates from 7 RS patients including citric acid, cis-aconitate, alpha-ketoglutarate, succinate, fumarate, malate and oxaloacetate. These concentrations were not significantly different from those control patients (N = 21). An elevated lactate level may be a clue to clarify the etiology of RS.