RESUMO
BACKGROUND: e-Health tools using validated questionnaires to assess outcomes may facilitate measurement-based care for psychiatric disorders. MoodFX was created as a free online symptom tracker to support patients for outcome measurement in their depression treatment. We conducted a pilot randomized evaluation to examine its usability, and clinical utility. METHODS: Patients presenting with a major depressive episode (within a major depressive or bipolar disorder) were randomly assigned to receive either MoodFX or a health information website as the intervention and control condition, respectively, with follow-up assessment surveys conducted online at baseline, 8 weeks and 6 months. The primary usability outcomes included the percentage of patients with self-reported use of MoodFX 3 or more times during follow up (indicating minimally adequate usage) and usability measures based on the System Usability Scale (SUS). Secondary clinical outcomes included the Quick Inventory of Depressive Symptomatology, Self-Rated (QIDS-SR) and Patient Health Questionnaire (PHQ-9). RESULTS: Forty-nine participants were randomized (24 to MoodFX and 25 to the control condition). Of the 23 participants randomized to MoodFX who completed the user survey, 18 (78%) used MoodFX 3 or more times over the 6 months of the study. The mean SUS score of 72.7 (65th-69th percentile) represents good usability. Compared to the control group, the MoodFX group had significantly better improvement on QIDS-SR and PHQ-9 scores, with large effect sizes and higher response rates at 6 months. There were no differences between conditions on other secondary outcomes such as functioning and quality of life. CONCLUSION: MoodFX demonstrated good usability and was associated with reduction in depressive symptoms. This pilot study supports the use of digital tools in depression treatment.
E-health tools may be useful for measuring and tracking symptoms and other outcomes during treatment for depression. This study is a randomized evaluation of MoodFX, a free web-based app that helps patients track their symptoms using validated questionnaires, and also offers depression information and self-management tips. A total of 49 participants with clinical depression were randomized to using MoodFX or a health information website, for 6 months. In a survey, the participants that used MoodFX found it easy and useful to use. In addition, the participants that used MoodFX had greater improvement in depressive symptoms after 6 months, compared to those who used the health information website. These results suggest that MoodFX may be a useful tool to monitor outcomes and support depression treatment.
Assuntos
Transtorno Bipolar , Transtorno Depressivo Maior , Avaliação de Resultados em Cuidados de Saúde , Telemedicina , Humanos , Feminino , Masculino , Adulto , Pessoa de Meia-Idade , Transtorno Depressivo Maior/terapia , Projetos Piloto , Transtorno Bipolar/terapiaRESUMO
OBJECTIVE: Bipolar disorder (BD) is challenging to treat, and fewer treatments are available for depressive episodes compared to mania. Light therapy is an evidence-based nonpharmacological treatment for seasonal and nonseasonal major depression, but fewer studies have examined its efficacy for patients with BD. Hence, we reviewed the evidence for adjunctive light therapy as a treatment for bipolar depression. METHODS: We conducted a systematic review of databases from inception to June 30, 2019, for randomized, double-blind, placebo-controlled trials of light therapy in patients with BD (CRD42019128996). The primary outcome was change in clinician-rated depressive symptom score; secondary outcomes included clinical response, remission, acceptability, and treatment-emergent mood switches. We quantitatively pooled outcomes using meta-analysis with random-effects models. RESULTS: We identified seven trials representing 259 patients with BD. Light therapy was associated with a significant improvement in Hamilton Depression Rating Scale score (standardized mean difference = 0.43, 95% confidence interval [CI], 0.04 to 0.82, P = 0.03). There was also a significant difference in favor of light therapy for clinical response (odds ratio [OR] = 2.32; 95% CI, 1.12 to 4.81; P = 0.024) but not for remission. There was no difference in affective switches between active light and control conditions (OR = 1.30; 95% CI, 0.38 to 4.44; P = 0.67). Study limitations included different light treatment parameters, small sample sizes, short treatment durations, and variable quality across trials. CONCLUSION: There is positive but nonconclusive evidence that adjunctive light therapy reduces symptoms of bipolar depression and increases clinical response. Light therapy is well tolerated with no increased risk of affective switch.
Assuntos
Transtorno Bipolar , Transtorno Depressivo Maior , Transtorno Bipolar/terapia , Método Duplo-Cego , Humanos , Fototerapia , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
Patients with major depressive disorder (MDD) often report that cognitive difficulties, such as memory problems or poor concentration, interfere with their work functioning. We examined the association between self-reported cognitive complaints and work functioning in employed patients with MDD treated with desvenlafaxine. A sample of 36 adult outpatients with MDD completed subjective cognition (British Columbia Cognitive Complaints Inventory [BC-CCI]) and functioning scales (Sheehan Disability Scale [SDS]; Lam Employment Absence and Productivity Scale [LEAPS]; and Health and Work Performance Questionnaire [HPQ]) before and after 8 weeks of open-label treatment with flexibly-dosed desvenlafaxine (50-100â¯mg/day). Multiple regression analyses were used to assess the relationship between subjective cognitive measures and work functioning scales. Patients showed significant improvements in clinical, cognitive, and work functioning measures following treatment with desvenlafaxine. A predictive association was found between the BC-CCI and both the SDS and LEAPS, but not with the HPQ, when adjusted for depression severity. Self-report cognitive questionnaires can provide useful information to monitor changes in cognitive functioning over time and to predict improvement in work functioning outcomes.
Assuntos
Antidepressivos/uso terapêutico , Disfunção Cognitiva/psicologia , Transtorno Depressivo Maior/psicologia , Succinato de Desvenlafaxina/uso terapêutico , Trabalho/psicologia , Adulto , Cognição , Transtorno Depressivo Maior/tratamento farmacológico , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Pacientes Ambulatoriais/psicologia , Análise de Regressão , AutorrelatoRESUMO
Fatigue and low energy are cardinal symptoms of major depressive disorder (MDD) that have an impact on work functioning. Antidepressants with noradrenergic activity have been hypothesized to improve symptoms of fatigue and low energy. We examined the impact of these symptoms on work functioning in patients with MDD treated with the serotonin and noradrenaline reuptake inhibitor, desvenlafaxine. A secondary analysis was carried out from a study of employed adult outpatients (n=35) with MDD and subjective cognitive complaints treated with desvenlafaxine 50-100 mg/day for 8 weeks. Multiple regression analyses modeled improvement in work functioning measures (Lam Employment Absence and Productivity Scale, Health and Work Performance Questionnaire, Sheehan Disability Scale) with measures of fatigue (Patient-Reported Outcomes Measurement Information System Fatigue scale and 20-item Hopkins Symptom Check List Energy scale). Patients showed a significant improvement in Montgomery-Åsberg Depression Rating Scale scores as well as in fatigue and work functioning measures following treatment. Fatigue measures were significantly associated with improvement in some (Lam Employment Absence and Productivity Scale, Sheehan Disability Scale), but not all (Health and Work Performance Questionnaire) work functioning measures, independent of improvement in overall depressive symptoms. The limitations of this study include the small sample size and the lack of a placebo or a comparison group. Fatigue and low energy are important symptoms that are associated with occupational impairment in MDD. Treatments that improve these symptoms are likely to improve work functioning.
Assuntos
Antidepressivos/uso terapêutico , Transtorno Depressivo Maior/psicologia , Succinato de Desvenlafaxina/uso terapêutico , Eficiência/efeitos dos fármacos , Emprego/psicologia , Fadiga/psicologia , Adulto , Transtorno Depressivo Maior/tratamento farmacológico , Transtorno Depressivo Maior/epidemiologia , Eficiência/fisiologia , Fadiga/tratamento farmacológico , Fadiga/epidemiologia , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do TratamentoRESUMO
Adenovirus has evolved strategies to usurp host-cell factors and machinery to facilitate its life cycle, including cell entry, replication, assembly and egress. Adenovirus continues, therefore, to be an important model system for investigating fundamental cellular processes. The role of adenovirus E1B-55k in targeting host-cell proteins that possess antiviral activity for proteasomal degradation is now well established. To expand our understanding of E1B-55k in regulating the levels of host-cell proteins, we performed comparative proteome analysis of wild-type, and E1B-55k-deletion, adenovirus-infected cancer cells. As such we performed quantitative MS/MS analysis to monitor protein expression changes affected by viral E1B-55k. We identified 5937 proteins, and of these, 69 and 58 proteins were down-regulated during wild-type and E1B-55k (dl1520) adenovirus infection, respectively. This analysis revealed that there are many, previously unidentified, cellular proteins subjected to degradation by adenovirus utilizing pathways independent of E1B-55k expression. Moreover, we found that ALCAM, EPHA2 and PTPRF, three cellular proteins that function in the regulation of cell-cell contacts, appeared to be degraded by E1B-55k/E4orf3 and/or E1B-55k/E4orf6 complexes. These molecules, like integrin α3 (a known substrate of E1B-55k/E4orf6), are critical regulators of cell signalling, cell adhesion and cell surface modulation, and their degradation during infection is, potentially, pertinent to adenovirus propagation. The data presented in this study illustrate the broad nature of protein down-regulation mediated by adenovirus.
Assuntos
Infecções por Adenoviridae/patologia , Adenoviridae/crescimento & desenvolvimento , Proteínas E1B de Adenovirus/genética , Deleção de Genes , Interações Hospedeiro-Patógeno , Proteoma/análise , Adenoviridae/genética , Infecções por Adenoviridae/virologia , Linhagem Celular Tumoral , Humanos , Proteômica , Espectrometria de Massas em Tandem , Fatores de TempoRESUMO
BACKGROUND: Major depressive disorder (MDD) is associated with staggering personal and economic costs, a major proportion of which stem from impaired psychosocial and occupational functioning. Few studies have examined the impact of depression-related cognitive dysfunction on work functioning. We examined the association between neurocognitive and work functioning in employed patients with MDD. METHODS: Employed adult outpatients (n=36) with MDD of at least moderate severity (≥23 on the Montgomery Asberg Depression Rating Scale, MADRS) and subjective cognitive complaints completed neurocognitive tests (CNS Vital Signs computerized battery) and validated self-reports of their work functioning (LEAPS, HPQ) before and after 8 weeks of open-label treatment with flexibly-dosed desvenlafaxine 50-100mg/day. Relationships between neurocognitive tests and functional measures were examined using bivariate correlational and multiple regression analyses, as appropriate. An ANCOVA model examined whether significant change in neurocognitive performance, defined as improvement of ≥1SD in the Neurocognition Index (NCI) from baseline to post-treatment, was associated with improved outcomes. RESULTS: Patients showed significant improvements in depressive symptom, neurocognitive, and work functioning measures following treatment with desvenlafaxine (e.g., MADRS response=77% and MADRS remission=49%). There were no significant correlations between changes in NCI or cognitive domain subscales and changes in MADRS, LEAPS, or HPQ scores. However, patients demonstrating significant improvement in NCI scores (n=11, 29%) had significantly greater improvement in clinical and work functioning outcomes compared to those without NCI improvement. LIMITATIONS: The limitations of this study include small sample size, lack of a placebo control group, and lack of a healthy comparison group. Our sample also had more years of education and higher premorbid intelligence than the general population. CONCLUSIONS: There were no significant correlations between changes in neurocognitive and work functioning measures in this study. However, meaningful improvement in neurocognitive functioning with desvenlafaxine was associated with greater improvement in both mood and occupational outcomes. This suggests that addressing cognitive dysfunction may improve clinical and occupational outcomes in employed patients with MDD. However, the relationship between neurocognitive and work functioning in MDD is complex and requires further study.
Assuntos
Antidepressivos/farmacologia , Cognição/efeitos dos fármacos , Transtorno Depressivo Maior/tratamento farmacológico , Succinato de Desvenlafaxina/farmacologia , Emprego/psicologia , Adulto , Antidepressivos/uso terapêutico , Transtorno Depressivo Maior/diagnóstico , Transtorno Depressivo Maior/psicologia , Succinato de Desvenlafaxina/uso terapêutico , Esquema de Medicação , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Testes Neuropsicológicos , Saúde Ocupacional , Escalas de Graduação Psiquiátrica , Autorrelato , Resultado do TratamentoRESUMO
BACKGROUND AND OBJECTIVES: A substantial proportion of the disease burden of major depressive disorder (MDD) results from impairments in occupational functioning, including disability and reduced productivity. Accumulating evidence suggests that antidepressants can improve functional as well as symptomatic outcomes in patients with MDD. We examined the treatment effects of newer antidepressants on occupational impairment in MDD, based on a systematic review and meta-analysis of randomized controlled trials (RCTs). METHODS: We searched MEDLINE, EMBASE, and ClinicalTrials.gov for the period 1 January 1992 to 15 June 2015 to identify RCTs of newer antidepressants (excluding tricyclic antidepressants and monoamine oxidase inhibitors), with or without a placebo condition, that included a validated measure of occupational functioning in patients with MDD. Abstracts were scanned for eligibility by two independent reviewers and investigators of unpublished studies were contacted to obtain data. Study data were extracted and double-entered for accuracy. We selected the Sheehan Disability Scale Work/School subscale (SDS-Work) for the meta-analysis because it was the most consistently used assessment of occupational impairment. Analysis employed a random-effects model. RESULTS: The systematic review initially identified 42 RCTs but only 28 (67 %) had data on occupational outcomes that were published or obtained from investigators. The SDS-Work subscale was used in 25 of 28 trials; five other assessments of occupational functioning were used in seven trials. Data were synthesized from 17 placebo-controlled studies (n = 7031) that used the SDS-Work subscale. Antidepressants (n = 4722) were significantly superior to placebo (n = 2309) in improving SDS-Work scores at 8 weeks, with a mean difference of 0.73 [95 % confidence interval (CI) 0.60-0.86] and a standardized mean difference of 0.28 (95 % CI 0.23-0.33), representing small effects. LIMITATIONS: Few included trials reported on the employment status of their samples, and most trials were of short-term treatment duration (8-12 weeks). Several RCTs that collected data on occupational outcomes were also excluded from the review and meta-analysis because their data were unpublished and unobtainable. CONCLUSIONS: Our meta-analysis suggests that newer antidepressants have a small, positive impact on occupational impairment in the short-term, but the clinical significance of this impact is questionable. To improve assessment of this important outcome, future research studies should use more comprehensive measures of occupational functioning, productivity and impairment, and longer treatment durations.
Assuntos
Antidepressivos/uso terapêutico , Transtorno Depressivo Maior/tratamento farmacológico , Avaliação de Resultados em Cuidados de Saúde , Ensaios Clínicos Controlados Aleatórios como Assunto , Inibidores Seletivos de Recaptação de Serotonina/uso terapêutico , Humanos , Resultado do TratamentoRESUMO
OBJECTIVE: Neurocognitive deficits are demonstrated in major depressive disorder (MDD) and most likely contribute to the functional impairment experienced by affected individuals. We systematically reviewed the evidence on neurocognitive deficits and their relationship(s) to psychosocial functioning in MDD. DATA SOURCES: English-language literature was searched in MEDLINE, EMBASE, Science Direct, and PsycInfo databases for the years 1980-October 15, 2013, with the following terms: (depressive disorder or depressive disorder, major) and permutations of (cognitive, neurocognitive, neuropsych*) with (impairment, deficit, performance, test) and (quality of life; functional outcomes; outcome assessment, health care) or (assessment, outcomes; assessment, patient outcomes; outcomes assessment; outcomes assessments, patient). STUDY SELECTION: Inclusion criteria were (1) nongeriatric adults (< 60 years) with a primary diagnosis of MDD by DSM-IV, ICD-9, or ICD-10 criteria; (2) use of neuropsychological tests; and (3) use of a specific measure of social, occupational, or daily functioning. Of 488 articles identified in the initial search, 10 met the inclusion criteria. DATA EXTRACTION: Two independent appraisers assessed eligibility of the studies. Substantial heterogeneity in the samples and methods precluded a quantitative meta-analysis, so we performed a narrative descriptive review. RESULTS: The included studies employed a variety of neurocognitive tests and assessments of psychosocial functioning. Overall, depressed samples had neurocognitive deficits in various domains that were associated with different measures of psychosocial functioning. However, these findings were constrained by methodological limitations of studies. CONCLUSIONS: The limited evidence base suggests that neurocognitive functioning appears to be broadly associated with functional impairment in individuals with MDD, but the quality of evidence is weak. Further studies to clarify the relationship(s) between neurocognitive and psychosocial functioning in MDD will benefit from larger and more homogeneous samples, prospective designs with multivariate analyses, and use of comprehensive assessments of psychosocial functioning that are validated in depressed populations.
Assuntos
Transtornos Cognitivos/psicologia , Transtorno Depressivo Maior/psicologia , Comportamento Social , Transtornos Cognitivos/complicações , Transtorno Depressivo Maior/complicações , Emprego , Humanos , Testes Neuropsicológicos , Qualidade de VidaRESUMO
Identification of proteins by tandem mass spectrometry requires a reference protein database, but these are only available for model species. Here we demonstrate that, for a non-model species, the sequencing of expressed mRNA can generate a protein database for mass spectrometry-based identification. This combination of high-throughput sequencing and protein identification technologies allows detection of genes and proteins. We use human cells infected with human adenovirus as a complex and dynamic model to demonstrate the robustness of this approach. Our proteomics informed by transcriptomics (PIT) technique identifies >99% of over 3,700 distinct proteins identified using traditional analysis that relies on comprehensive human and adenovirus protein lists. We show that this approach can also be used to highlight genes and proteins undergoing dynamic changes in post-transcriptional protein stability.
Assuntos
Proteoma/química , Proteômica/métodos , Transcriptoma , Adenoviridae/genética , Adenoviridae/metabolismo , Animais , Arginina/metabolismo , Células CHO , Isótopos de Carbono , Cromatografia Líquida , Cricetinae , Cricetulus , Bases de Dados de Proteínas , Células HeLa , Humanos , Lisina/metabolismo , Isótopos de Nitrogênio , Proteínas Nucleares/metabolismo , Polimorfismo de Nucleotídeo Único , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/metabolismo , Análise de Sequência de Proteína/métodos , Software , Espectrometria de Massas em Tandem/métodosRESUMO
BACKGROUND: Single-stranded DNA oligonucleotides (ssODNs) can introduce small, specific sequence alterations into genomes. Potential applications include creating disease-associated mutations in cell lines or animals, functional studies of single nucleotide polymorphisms and, ultimately, clinical therapy by correcting genetic point mutations. Here, we report feasibility studies into realizing this potential by targeting a reporter gene, mutated enhanced green fluorescent protein (mEGFP). METHODS: Three mammalian cell lines, CHO, HEK293T and HepG2, expressing multiple copies of mEGFP were transfected with a 27-mer ssODN capable of restoring fluorescence. Successful cell correction was quantified by flow cytometry. RESULTS: Gene editing in each isogenic cell line, as measured by percentage of green cells, correlated tightly with target protein levels, and thus gene expression. In the total population, 2.5% of CHO-mEGFP cells were successfully edited, although, remarkably, in the highest decile producing mEGFP protein, over 20% of the cells had restored green fluorescence. Gene-edited clones initially selected for green fluorescence lost EGFP expression during cell passaging, which partly reflected G2-phase cycle arrest and perhaps eventual cell death. The major cause, however, was epigenetic down-regulation; incubation with sodium butyrate or 5-aza-2'-deoxycytidine reactivated fluorescent EGFP expression and hence established that the repaired genotype was stable. CONCLUSIONS: Our data establish that ssODN-mediated gene editing is underestimated in cultured mammalian cells expressing nonfluorescent mutated EGFP, because of variable expression of this mEGFP target gene in the cell population. This conclusion was endorsed by studies in HEK293T-mEGFP and HepG2-mEGFP cells. We infer that oligonucleotide-directed editing of endogenous genes is feasible, particularly for those that are transcriptionally active.
Assuntos
Engenharia Genética/métodos , Proteínas de Fluorescência Verde/metabolismo , Mutagênese/genética , Oligonucleotídeos/genética , Animais , Células CHO , Cricetinae , Cricetulus , Citometria de Fluxo , Terapia Genética/métodos , Proteínas de Fluorescência Verde/genética , Células HEK293 , Células Hep G2 , Humanos , TransfecçãoRESUMO
Intramuscular injection of adeno-associated viral (AAV) vectors is potentially a safe, minimally invasive procedure for the long-term gene expression of circulating antiatherogenic proteins. Here, we compare secretion and atheroprotective effects of human apoE3 after injection of 3 pseudotyped AAV vectors (AAV2/7, AAV2/8, or AAV2/9), driven by the CMV enhancer/chicken ß-actin (CAG) promoter, into skeletal muscle of hyperlipidemic apolipoprotein E-deficient (apoEâ»/â») mice. Vector viabilities were verified by transducing cultured C2C12 mouse myotubes and assessing secretion of human apoE3 protein. Both hind limb tibialis anterior muscles of female C57BL/6 apoEâ»/â» mice, 2 months old and fed a high-fat diet, were each injected with 1 x 10¹° vector genomes of AAV vector. Identical noninjected mice served as controls; and blood was collected at weeks 0, 1, 2, 4, and 13. At termination (13 weeks), the brachiocephalic artery was excised; and after staining sections, plaque morphometry and fractional lipid content were quantified by computerized image analysis. Intramuscular injection of AAV2/7 and AAV2/8 vectors produced up to 2 µg human apoE3 per milliliter plasma, just below the threshold to reverse dyslipoproteinemia. AAV2/9 was notably less effective, mice having a 3-fold lower level of plasma apoE3 at 13 weeks and a 50% greater burden of atherosclerotic plaque lipid in their brachiocephalic arteries. We conclude that although vector refinement is needed to exploit fully apoE3 atheroprotective functions, AAV2/7 and AAV2/8 are promising gene transfer vectors for muscle-based expression of antiatherogenic circulating proteins.
Assuntos
Apolipoproteína E3/genética , Apolipoproteína E3/metabolismo , Aterosclerose/prevenção & controle , Dependovirus/genética , Músculo Esquelético/metabolismo , Animais , Aterosclerose/metabolismo , Linhagem Celular , Artérias Cerebrais/patologia , Meios de Cultura , Dependovirus/classificação , Dependovirus/imunologia , Ensaio de Imunoadsorção Enzimática , Terapia Genética , Vetores Genéticos , Humanos , Hipercolesterolemia/terapia , Metabolismo dos Lipídeos/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Sorotipagem , Transdução GenéticaRESUMO
Adenoviruses replicate primarily in the host cell nucleus, and it is well established that adenovirus infection affects the structure and function of host cell nucleoli in addition to coding for a number of nucleolar targeted viral proteins. Here we used unbiased proteomics methods, including high throughput mass spectrometry coupled with stable isotope labeling by amino acids in cell culture (SILAC) and traditional two-dimensional gel electrophoresis, to identify quantitative changes in the protein composition of the nucleolus during adenovirus infection. Two-dimensional gel analysis revealed changes in six proteins. By contrast, SILAC-based approaches identified 351 proteins with 24 proteins showing at least a 2-fold change after infection. Of those, four were previously reported to have aberrant localization and/or functional relevance during adenovirus infection. In total, 15 proteins identified as changing in amount by proteomics methods were examined in infected cells using confocal microscopy. Eleven of these proteins showed altered patterns of localization in adenovirus-infected cells. Comparing our data with the effects of actinomycin D on the nucleolar proteome revealed that adenovirus infection apparently specifically targets a relatively small subset of nucleolar antigens at the time point examined.
Assuntos
Adenoviridae/crescimento & desenvolvimento , Nucléolo Celular/metabolismo , Proteínas Nucleares/análise , Proteômica/métodos , Adenoviridae/fisiologia , Nucléolo Celular/efeitos dos fármacos , Nucléolo Celular/virologia , Dactinomicina/farmacologia , Eletroforese em Gel Bidimensional , Células HeLa , Interações Hospedeiro-Patógeno , Humanos , Marcação por Isótopo/métodos , Espectrometria de Massas , Inibidores da Síntese de Ácido Nucleico/farmacologia , Proteoma/análiseRESUMO
Previous reports have shown that adenovirus recruits nucleolar protein upstream-binding factor (UBF) into adenovirus DNA replication centres. Here, we report that despite having a different mode of viral DNA replication, herpes simplex virus type 1 (HSV-1) also recruits UBF into viral DNA replication centres. Moreover, as with adenovirus, enhanced green fluorescent protein-tagged fusion proteins of UBF inhibit viral DNA replication. We propose that UBF is recruited to the replication compartments to aid replication of HSV-1 DNA. In addition, this is a further example of the role of nucleolar components in viral life cycles.