Prevalence of vocal cord paralysis in patients with incidentally discovered enlarged lymph nodes along the expected course of the recurrent laryngeal nerve.

OBJECTIVES: We sought to determine the prevalence of vocal cord paralysis in patients with incidentally discovered lymphadenopathy along the expected course of the recurrent laryngeal nerve (RLN). METHODS: We reviewed the positron-emission tomographic (PET) and computed tomographic (CT) scans of 936 consecutive patients with a variety of diagnoses. Enlarged lymph nodes (short-axis diameter of more than 1 cm) along the expected course of the RLN were identified. Patients with lymphadenopathy were evaluated for CT signs of vocal cord paralysis. The medical records of patients with lymphadenopathy were reviewed for clinical signs of vocal cord paralysis. Patients with head and neck malignancies were excluded from the study. RESULTS: Lymphadenopathy along the course of the RLN was identified in 57 of the 936 patients studied. Fifty-three of the 57 patients (93%) were found to have a malignancy. Thirty-four enlarged nodes (60%) had FDG uptake as shown on a PET/CT scan. Twenty enlarged nodes (35%) had CT evidence of extracapsular spread. Four patients (7%) had CT evidence of vocal cord paralysis. One patient (2%) had clinical evidence of vocal cord paralysis. CONCLUSIONS: In asymptomatic patients with incidental lymphadenopathy along the course of the RLN, vocal cord paralysis is rare.

Metabolic networks: enzyme function and metabolite structure.

Metabolism is one of the most complex cellular processes. Connections between biochemical reactions via substrate and product metabolites create complex metabolic networks that may be analyzed using network theory, stoichiometric analysis, and information on protein structure/function and metabolite properties. These frameworks take into consideration different aspects of enzyme chemistry, enzyme structure and metabolite structure, and demonstrate the impact of metabolic biochemistry on the systemic properties of metabolism. The integration of these approaches and the systematic classification of enzyme function and the chemical structure of metabolites will enhance our understanding of metabolism, and could improve our ability to predict enzyme function and novel metabolic pathways.

Exploring the diversity of complex metabolic networks.

MOTIVATION: Metabolism, the network of chemical reactions that make life possible, is one of the most complex processes in nature. We describe here the development of a computational approach for the identification of every possible biochemical reaction from a given set of enzyme reaction rules that allows the de novo synthesis of metabolic pathways composed of these reactions, and the evaluation of these novel pathways with respect to their thermodynamic properties. RESULTS: We applied this framework to the analysis of the aromatic amino acid pathways and discovered almost 75,000 novel biochemical routes from chorismate to phenylalanine, more than 350,000 from chorismate to tyrosine, but only 13 from chorismate to tryptophan. Thermodynamic analysis of these pathways suggests that the native pathways are thermodynamically more favorable than the alternative possible pathways. The pathways generated involve compounds that exist in biological databases, as well as compounds that exist in chemical databases and novel compounds, suggesting novel biochemical routes for these compounds and the existence of biochemical compounds that remain to be discovered or synthesized through enzyme and pathway engineering. AVAILABILITY: Framework will be available via web interface at http://systemsbiology.northwestern.edu/BNICE (site under construction). CONTACT: vassily@northwestern.edu or broadbelt@northwestern.edu SUPPLEMENTARY INFORMATION: http://systemsbiology.northwestern.edu/BNICE/publications.