RESUMO
The ageing process is associated with the accumulation of somatic mutations of mitochondrial DNA (mtDNA). The aged human skeletal muscle tissue presents a mosaic of fibers when stained histochemically for cytochrome c oxidase (COX) activity with a proportion of COX negative fibers. Given the potential relevance of any alteration in the mtDNA control region for replication, we analysed the correlation between the presence of mutations and their degree of heteroplasmy and the COX phenotype in individual muscle fibers of aged healthy donors.A region of the mtDNA D-loop was cloned from single fiber-derived DNA and multiple clones were analysed. This strategy showed that a high level of mutational burden is present in all fibers and that several types of mtDNA rearrangements are detectable: recurrent (A189G, T408A and T414G) and rare point mutations, length variations affecting the homopolymeric tract and the (CA)(n) repeat and macrodeletions. The aggregate mutational load in the D-loop region correlated with the single fiber COX phenotype, suggesting that the cumulative burden of multiple, individually rare, mtDNA alterations might functionally impair the mitochondrial genetic machinery.
Assuntos
Idoso/fisiologia , DNA Mitocondrial/genética , Complexo IV da Cadeia de Transporte de Elétrons/genética , Fibras Musculares Esqueléticas/fisiologia , Músculo Esquelético/fisiologia , Idoso de 80 Anos ou mais , Biópsia , Análise Mutacional de DNA , DNA Mitocondrial/metabolismo , Humanos , Fibras Musculares Esqueléticas/enzimologia , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/enzimologia , Músculo Esquelético/patologia , Mutação Puntual , Valores de ReferênciaRESUMO
In some patients, Campylobacter jejuni infection has been associated with the development of multifocal motor neuropathy (MMN) and high titers of antiganglioside antibodies. The authors measured anti-C. jejuni antibodies by ELISA and immunoblot in 20 patients with MMN, and correlated their presence with antiganglioside reactivity and a history of recent diarrhea. Only one patient had high titers of anti-C. jejuni antibodies, indicating that C. jejuni is unlikely to be involved in the pathogenesis of MMN in most patients.
Assuntos
Anticorpos Antibacterianos/sangue , Infecções por Campylobacter/complicações , Campylobacter jejuni/imunologia , Gangliosídeos/imunologia , Polineuropatias/microbiologia , Infecções por Campylobacter/imunologia , Infecções por Campylobacter/microbiologia , Infecções por Campylobacter/fisiopatologia , Diarreia/microbiologia , Ensaio de Imunoadsorção Enzimática , Humanos , Imunoglobulina A/sangue , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Polineuropatias/imunologia , Polineuropatias/fisiopatologiaRESUMO
Glatiramer acetate (GLAT) is a mixture of basic polypeptides that have been shown to suppress experimental autoimmune encephalomyelitis (EAE). As Copaxone, GLAT is approved for the treatment of relapsing-remitting multiple sclerosis (MS). Different immunomechanisms have been suggested to contribute to the beneficial effects of GLAT which rely on blockade of MHC class II molecules or cross-recognition with myelin basic protein (MBP). Because GLAT could also inhibit experimental autoimmunity not related to myelin proteins, we searched for additional, less-restricted immunomodulatory actions of GLAT. Using freshly isolated resident peritoneal macrophages from naive Lewis rats, it is shown that GLAT profoundly modulates cytokine secretion of the cells. In unseparated macrophages (MPhi) and MPhi of low density, GLAT enhanced constitutive and LPS-induced production of interleukin 10 (IL-10) while LPS-induced synthesis of tumor necrosis factor-alpha (TNF-alpha) was dose-dependently suppressed by GLAT. Although both basic proteins GLAT and MBP facilitated adherence of MPhi, MBP had opposite effects on cytokine production suggesting unique properties of GLAT. In contrast to MPhi, peritoneal mast cells produced only little amounts of cytokines. The inductive effect of GLAT on IL-10 production by antigen-presenting cells was also observed in bone marrow-derived rat dendritic cells (DCs) which, unlike MPhi, were not suppressed in their production of TNF-alpha. Induction of IL-10 in different antigen-presenting cells is a new immunomodulatory mechanism of GLAT. In part, it goes along with the inhibition of TNF-alpha and may be a common basis for the known beneficial effects of GLAT on various cellular autoimmune responses including MS.
Assuntos
Antígenos CD , Antígenos de Neoplasias , Antígenos de Superfície , Proteínas Aviárias , Proteínas Sanguíneas , Células Dendríticas/efeitos dos fármacos , Interleucina-10/metabolismo , Macrófagos Peritoneais/efeitos dos fármacos , Peptídeos/farmacologia , Animais , Antígenos de Diferenciação/metabolismo , Basigina , Células Cultivadas , Células Dendríticas/metabolismo , Relação Dose-Resposta a Droga , Interações Medicamentosas , Ensaio de Imunoadsorção Enzimática/métodos , Citometria de Fluxo/métodos , Acetato de Glatiramer , Proteínas de Grupo de Alta Mobilidade/farmacologia , Imunossupressores/farmacologia , Lipopolissacarídeos/farmacologia , Macrófagos Peritoneais/metabolismo , Mastócitos/efeitos dos fármacos , Glicoproteínas de Membrana/metabolismo , Proteína Básica da Mielina/metabolismo , Ratos , Ratos Endogâmicos Lew , Fator de Necrose Tumoral alfa/metabolismoRESUMO
This study reports that in Schwann cell tissue culture the administration of the two pro-inflammatory cytokines, interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma), at different dosages, singly or in combination, can induce apoptosis and/or mitosis. Schwann cell apoptosis was maximal within 24 h of stimulation with 50 U/ml of IFN-gamma, while proliferation was at its peak within 24 h with 10 U/ml IL-1 beta, and both processes decreased progressively by 48 and 72 h. Moreover, the combination of the two cytokines did not show any synergistic effect. These data can be interpreted as a possible involvement of pro-inflammatory cytokines not only in myelin disruption but also in promoting remyelination.
Assuntos
Apoptose , Interferon gama/farmacologia , Interleucina-1/farmacologia , Células de Schwann/citologia , Células de Schwann/fisiologia , Animais , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Combinação de Medicamentos , Mediadores da Inflamação/farmacologia , Microscopia Eletrônica , Ratos , Ratos Sprague-Dawley , Células de Schwann/efeitos dos fármacos , Células de Schwann/ultraestrutura , Fatores de TempoRESUMO
OBJECTIVES: To estimate the incidence of dementia, Alzheimer's disease (AD), and vascular dementia (VaD) in older Italians and evaluate the relationship of age, gender, and education to developing dementia. DESIGN: Cohort incidence study in the context of the Italian Longitudinal Study on Aging. SETTING: Population sample from eight Italian municipalities. PARTICIPANTS: A dementia-free cohort of 3,208 individuals (aged 65-84), individuated after a baseline evaluation performed in 1992 / 93, aimed at detecting prevalent cases. MEASUREMENTS: The dementia-free cohort was reexamined in 1995 to identify incident cases. The Mini-Mental State Examination (cutoff 23 / 24) was employed to screen for dementia. Trained neurologists evaluated the individuals who screened positive. Final diagnoses had to meet Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised criteria for dementia, National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for AD, and International Classification of Diseases, Tenth Revision criteria for VaD. RESULTS: Before the follow-up examination, 382 individuals had died (232 had reliable information). Of the 2,826 survivors, 2,266 completed the study. Overall, 127 new dementia cases were identified. Average incidence rates per 1,000 person-years were 12.47 (95% confidence interval (CI)=10.23-14.72) for dementia, 6.55 (95% CI=4.92-8.17) for AD, and 3.30 (95% CI=2.14-4.45) for VaD. Both AD and VaD showed age-dependent patterns. Education was protective against dementia and AD. Women carried a significantly higher risk of developing AD (hazard ratio=1.67, 95% CI=1.02-2.75), and men of developing VaD (hazard ratio=2.23, 95% CI=1.06-4.71). CONCLUSIONS: Incidence of dementia in Italy paralleled that in most industrialized countries. About 150,000 new cases per year are expected. A significant gender effect was evidenced for major dementia subtypes. The burden of VaD, especially in men, offers opportunities for prevention.
Assuntos
Demência/epidemiologia , Distribuição por Idade , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/epidemiologia , Estudos de Coortes , Demência Vascular/epidemiologia , Escolaridade , Feminino , Humanos , Incidência , Itália/epidemiologia , Masculino , Modelos de Riscos Proporcionais , Distribuição por Sexo , Fatores SexuaisRESUMO
Stem cell populations have been shown to be extremely versatile: they can generate differentiated cells specific to the tissue in which they reside and descendents that are of different germ layer origin. This raises the possibility of obtaining neuronal cells from new biological source of the same adult human subjects. In this study, we found that epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) cooperated to induce the proliferation, self-renewal, and expansion of neural stem cell-like population isolated from several newborn and adult mouse tissues: muscle and hematopoietic tissues. This population, in both primary culture and secondary expanded clones, formed spheres of undifferentiated cells that were induced to differentiate into neurons, astrocytes, and oligodendrocytes. Brain engraftment of the somatic-derived neural stem cells generated neuronal phenotypes, demonstrating the great plasticity of these cells with potential clinical application.
Assuntos
Células-Tronco Hematopoéticas/citologia , Células-Tronco Mesenquimais/citologia , Células-Tronco Multipotentes/citologia , Neuroglia/fisiologia , Neurônios/fisiologia , Envelhecimento , Animais , Animais Recém-Nascidos , Diferenciação Celular , Divisão Celular/efeitos dos fármacos , Linhagem da Célula , Separação Celular , Células Cultivadas , Técnicas de Cocultura , Corpo Estriado/citologia , Corpo Estriado/metabolismo , Corpo Estriado/cirurgia , Sinergismo Farmacológico , Fator de Crescimento Epidérmico/farmacologia , Fator 2 de Crescimento de Fibroblastos/farmacologia , Corantes Fluorescentes , Imuno-Histoquímica , Camundongos , Camundongos Endogâmicos C57BL , Compostos OrgânicosRESUMO
Recently, a frequent prion protein gene (PRNP) polymorphism consisting of a methionine (M) for valine (V) substitution at codon 129 has been associated with cognitive impairment in elderly individuals. Down syndrome (DS) is associated with mental retardation and development of Alzheimer-like brain abnormalities. In the present study, we investigated the role of the PRNP polymorphism in 122 relatively young Italian DS patients. Allele frequencies of DS subjects did not differ from those in the general population. However, we found a significantly faster rate of decline in intellectual ability in the subgroup of DS patients carrying at least one V allele compared with the M/M DS subjects. An additive deleterious effect of apolipoprotein E epsilon 4 allele was detected after stratifying by APOE gene status. Our findings provide evidence that variability of the PRNP gene at codon 129 might contribute to accelerating the rate of earlier cognitive decline in DS subjects.
Assuntos
Transtornos Cognitivos/genética , Síndrome de Down/genética , Polimorfismo Genético , Príons/genética , Adolescente , Adulto , Fatores Etários , Alelos , Substituição de Aminoácidos , Apolipoproteína E4 , Apolipoproteínas E/classificação , Apolipoproteínas E/metabolismo , Criança , Pré-Escolar , Códon , Transtornos Cognitivos/etiologia , Síndrome de Down/fisiopatologia , Feminino , Seguimentos , Frequência do Gene , Genótipo , Humanos , Testes de Inteligência , Masculino , Metionina/genética , Mutação , Valina/genéticaRESUMO
UNLABELLED: A retrospective evaluation of asymptomatic subjects with persistent elevation of serum creatine kinase (CK) levels (hyperCKemia) was made in order to verify the presence of subclinical myopathy or idiopathic hyperCKemia and to define the most appropriate diagnostic pathway. Persistently increased serum CK levels are occasionally encountered in healthy individuals. In 1980 Rowland coined for them the term idiopathic hyperCKemia. Despite the increase of scientific knowledge, several healthy subjects with hyperCKemia still represent a problem for the clinician. We made a retrospective evaluation of 114 asymptomatic or minimally symptomatic individuals with incidentally detected persistent hyperCKemia. They underwent neurological examination and laboratory/instrumental evaluation. Skeletal muscle biopsy was performed and thoroughly investigated. Biochemical and genetic investigations were added in selected cases. Logistic regression analysis was applied. We diagnosed a neuromuscular disorder in 21 patients (18.4%), and found, by muscle biopsy and/or EMG, pathological but not conclusive findings in 57 subjects (50%). The statistic correlation between elevated serum CK levels and the probability of making a diagnosis changed according to the age of the patient. CONCLUSIONS: Muscle biopsy is the basic tool for screening asymptomatic subjects with hyperCKemia. It allowed us to make a diagnosis of disease in 18.4% of patients, and to detect skeletal muscle abnormalities in 38.6% of the subjects. Interestingly, 31.6% of individuals had completely normal muscle findings. These best fit the "diagnosis" of idiopathic hyperCKemia.
Assuntos
Creatina Quinase/sangue , Doenças Neuromusculares/enzimologia , Adolescente , Adulto , Idoso , Aminoácidos/urina , Biópsia , Criança , Pré-Escolar , Creatina Quinase/genética , Eletromiografia , Exercício Físico/fisiologia , Feminino , Humanos , Imuno-Histoquímica , Ácido Láctico/sangue , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Contração Muscular/fisiologia , Músculo Esquelético/enzimologia , Músculo Esquelético/patologia , Doenças Neuromusculares/sangue , Doenças Neuromusculares/diagnóstico , Razão de Chances , Estudos Retrospectivos , Medição de RiscoRESUMO
Interferon-gamma-inducible Protein-10 (IP-10) and Monocyte Chemotactic Protein-1 (MCP-1) levels were measured by enzyme-linked immunosorbent assay (ELISA) in the CSF and in the serum from 74 patients affected by different clinical forms of Multiple Sclerosis (MS), including 39 patients with Relapsing Remitting (RR) MS in an active phase, 14 patients in a stable phase of the disease, 12 patients with Secondary Progressive (SP) MS and 9 patients with Primary Progressive (PP) MS. IP-10 and MCP-1 levels were also determined in 19 subjects with no neurological diseases or major systemic disorders, 18 patients with non-inflammatory neurological diseases, as well as in 15 patients with other inflammatory neurological diseases.IP-10 levels were significantly elevated in CSF and serum from RR and SP, but not PP-MS patients. On the contrary, MCP-1 levels were decreased in CSF and serum of all MS patients. CSF concentrations of IP-10 and MCP-1 did not significantly correlate neither with each other, nor with CSF mononuclear cell count, albumin quotient or CSF IgG index. No correlation between disease duration, clinical course or EDSS score and chemokine levels was found.IP-10 and MCP-1 undergo modifications in different subtypes of the disease: IP-10 levels in CSF and serum samples are markedly increased when inflammation is prominent, and not in PP--MS patients, where inflammation is less evident. MCP-1 decrease in CSF and serum from MS patients could be related to the regulation of T-cell polarization.
Assuntos
Quimiocina CCL2/líquido cefalorraquidiano , Quimiocina CXCL10/análise , Esclerose Múltipla Crônica Progressiva/metabolismo , Esclerose Múltipla Recidivante-Remitente/metabolismo , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças do Sistema Nervoso/metabolismo , Valores de ReferênciaRESUMO
This study describes the infiltration and death of monocyte/macrophages and concomitant endoneurial expression of the pro-inflammatory cytokine interleukin-1beta (IL-1beta) and neurotrophin receptor p75 (p75NTR) in the sciatic nerve at the early phases of experimental diabetic neuropathy induced in Lewis rats by streptozotocin (STZ) intraperitoneal injection. Immunocytochemistry and single nerve fiber immunostaining showed the presence of macrophages in diabetic nerves by weeks 2 and 3 after STZ administration, and the 15% of these cells were TUNEL positive. IL-1beta was evident in scattered macrophages, and along few isolated nerve fibers until week 5, when it became undetectable, in concomitance with complete endoneurial clearance of macrophages. p75NTR showed an up-regulation in the sciatic nerve of diabetic rats that began by week 3 after STZ administration, reached its peak by week 5, and returned then to a barely detectable level by week 6. These findings seem to indicate that macrophages and IL-1beta may be involved in the pathogenesis of diabetic neuropathy, participating not only to nerve damage but also to the promotion of an attempt of regeneration via p75NTR induction.
Assuntos
Neuropatias Diabéticas/fisiopatologia , Interleucina-1/metabolismo , Macrófagos/fisiologia , Receptores de Fator de Crescimento Neural/metabolismo , Nervo Isquiático/fisiopatologia , Animais , Apoptose , Morte Celular , Movimento Celular , Diabetes Mellitus Experimental , Neuropatias Diabéticas/patologia , Imuno-Histoquímica , Ratos , Ratos Endogâmicos , Receptor de Fator de Crescimento Neural , Nervo Isquiático/patologiaRESUMO
The progressive accumulation of mitochondrial DNA (mtDNA) alterations, ranging from single mutations to large-scale deletions, in both the normal ageing process and pathological conditions is a relevant phenomenon in terms of frequency and heteroplasmic degree. Recently, two point mutations (A189G and T408A) within the Displacement loop (D-loop) region, the control region for mtDNA replication, were shown to occur in skeletal muscles from aged individuals. We evaluated the presence and the heteroplasmy levels of these two mutations in muscle biopsies from 91 unrelated individuals of different ages (21 healthy subjects and 70 patients affected by mitochondrial encephalomyopathies). Overall, both mutations significantly accumulate with age. However, a different relationship was discovered among the different subgroups of patients: a higher number of A189G positive subjects younger than 53 years was detected in the subgroup of multiple-deleted patients; furthermore, a trend towards an increased risk for the mutations was evidenced among patients carrying multiple deletions when compared to healthy controls. These findings support the idea that a common biological mechanism determines the accumulation of somatic point mutations in the D-loop region, both in healthy subjects and in mitochondrial myopathy patients. At the same time, it appears that disorders caused by mutations of nuclear genes controlling mtDNA replication (the "mtDNA multiple deletions" syndromes) present a temporal advantage to mutate in the D-loop region. This observation may be relevant to the definition of the molecular pathogenesis of these latter syndromes.
Assuntos
DNA Mitocondrial/genética , Mitocôndrias Musculares/fisiologia , Encefalomiopatias Mitocondriais/genética , Músculo Esquelético/fisiologia , Peptídeos Cíclicos/genética , Mutação Puntual , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Biópsia , Southern Blotting , Criança , Análise Mutacional de DNA , Deleção de Genes , Humanos , Pessoa de Meia-Idade , Músculo Esquelético/ultraestrutura , Reação em Cadeia da PolimeraseRESUMO
Assessment of feigned cognitive disorders is an important field of neuropsychology because of its applications to forensic settings. Strategies for detecting malingering in amnesia are available for anterograde amnesia. Less attention has been given to malingering in retrograde amnesia. The case of the 'Smemorato di Collegno' (The Collegno Amnesic) is probably the most famous case of malingered retrograde amnesia ever known in Italy. In 1926, a man who appeared to have lost all his autobiographical memories and identity spent nearly a year in the Collegno asylum of Turin without a name. He was later initially identified as Giulio Canella, Director of the 'Scuola Normale di Verona' who had disappeared during the war in 1916. He was suspected of later identified as being Mario Bruneri, a petty crook from Turin who played the part of an amnesic whose retrograde memory gradually returned. A lengthy investigation was required before this conclusion was reached. Several clinicians and renowned academics evaluated the case, but only Alfredo Coppola, diagnosed "malingered retrograde amnesia" using a method that was extremely innovative for the times. The aim of the present paper is to review the original cognitive evaluation and the strategies used for malingering detection in the "Collegno case". The outcome of the case is then discussed in the light of present-day forensic neuropsychology and the level of advancement of mental examination achieved in the 1920s in Europe is highlighted.
Assuntos
Amnésia Retrógrada/história , Pessoas Famosas , Simulação de Doença/história , Amnésia Retrógrada/diagnóstico , História do Século XX , Humanos , Entrevista Psicológica , Itália , Masculino , Simulação de Doença/diagnóstico , Testes Neuropsicológicos/históriaRESUMO
PURPOSE OF REVIEW: The inherited disorders of muscle metabolism affect both substrate utilization and the final intramitochondrial oxidation through the Krebs cycle and the respiratory chain. Almost every step of these complex biochemical pathways can be affected by inborn errors, whose expression depends on peculiar tissue-specific or systemic gene expression. This review updates current knowledge in this broad field. RECENT FINDINGS: New inherited defects are still being discovered, such as the beta-enolase deficiency in glycogenosis type XIII and mutations in the gene encoding an esterase/lipase/thioesterase protein in Chanarin-Dorfman syndrome, a multisystem triglyceride storage disease. SUMMARY: Therapeutic approaches to the metabolic myopathies are still lagging behind, although remarkable observations have been made on the rare coenzyme Q10 deficiency syndrome. However, transgenic animal models may offer the opportunity both to investigate muscle pathogenesis and explore therapeutic targets. Finally, human myotoxicity may provide novel paradigms for naturally occurring muscle disorders.
Assuntos
Hipolipemiantes/efeitos adversos , Erros Inatos do Metabolismo/metabolismo , Doenças Mitocondriais/metabolismo , Doenças Musculares/induzido quimicamente , Doenças Musculares/metabolismo , Ubiquinona/análogos & derivados , Animais , Animais Geneticamente Modificados , Antioxidantes/metabolismo , Coenzimas , Doença de Depósito de Glicogênio/metabolismo , Humanos , Hipolipemiantes/administração & dosagem , Metabolismo dos Lipídeos , Mitocôndrias Musculares/metabolismo , Mutação , Fosfopiruvato Hidratase/deficiência , Ubiquinona/deficiênciaRESUMO
We present the case of a 58-year-old man, who has suffered from type 1 diabetes mellitus since he was young. He had monoclonal IgM kappa gammopathy of undetermined significance and high anti-MAG antibody titer. He developed a polyneuropathic picture with the clinical and laboratory features of chronic inflammatory demyelinating polyneuropathy within the span of approximately 2 years. He benefited from IV administration of high doses of immunoglobulins. Investigation of all parameters, but particularly of the clinical phenotype, can lead to a better definition of the polyneuropathic picture, especially for therapeutic and prognostic purposes.
Assuntos
Diabetes Mellitus Tipo 1/complicações , Neuropatias Diabéticas/etiologia , Polineuropatias/etiologia , Doença Crônica , Diabetes Mellitus Tipo 1/patologia , Neuropatias Diabéticas/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Polineuropatias/patologiaRESUMO
Adenine nucleotide translocator-1 (ANT-1), encoded by chromosome 4 (4q34-35 locus), is a component of the mitochondrial permeability transition pores that are involved in apoptotic mechanisms. We studied muscle biopsies from seven individuals with autosomal dominant progressive external ophthalmoplegia caused by ANT-1 mutations. We found no instance of terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) positivity nor significant expression of apoptosis-related proteins. Furthermore, there was no morphological evidence of apoptosis at the ultrastructural level. Thus, degeneration of muscle in this disorder is nonapoptotic.
Assuntos
Apoptose , Translocases Mitocondriais de ADP e ATP/genética , Oftalmoplegia Externa Progressiva Crônica/genética , Oftalmoplegia Externa Progressiva Crônica/patologia , Adulto , Idoso , Feminino , Humanos , Marcação In Situ das Extremidades Cortadas , Masculino , Pessoa de Meia-Idade , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/patologia , Oftalmoplegia Externa Progressiva Crônica/etiologia , FenótipoRESUMO
A 13084 A->T missense mutation in the mitochondrial ND5 gene was identified in a 16-year-old boy affected with a progressive neurodegenerative disorder combining features of Leigh and MELAS (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes) syndromes. Muscle biopsy analysis revealed partial complex I deficiency. The mutation presented a variable degree of heteroplasmy in the patient's tissues. This finding underlines the contribution of mtDNA-encoded complex I subunits in the etiology of complex I deficiency associated with encephalopathy.