Nitrogenase reactivity with P-cluster variants

Nitrogenase is a multicomponent metalloenzyme that catalyzes the conversion of atmospheric dinitrogen to ammonia. For decades, it has been generally believed that the [8Fe-7S] P-cluster of nitrogenase component 1 is indispensable for nitrogenase activity. In this study, we identified two catalytically active P-cluster variants by activity assays, metal analysis, and EPR spectroscopic studies. Further, we showed that both P-cluster variants resemble [4Fe-4S]-like centers based on x-ray absorption spectroscopic experiments. We believe that our findings challenge the dogma that the standard P-cluster is the only cluster species capable of supporting substrate reduction at the FeMo cofactor and provide important insights into the general mechanism of nitrogenase catalysis and assembly.     

Projections to bimodal sites in the torus semicircularis of the toadfish, Opsanus tau

Bimodal cells in the torus semicircularis of the toadfish respond to both directional acoustic stimuli and hydrodynamic stimuli. Our previous physiological work indicated that bimodal cells may be distributed throughout the torus semicircularis. In this study, neurobiotin was used to compare the distribution of auditory-only and bimodal sites and to assess the inputs to those sites. A brief neurobiotin injection with short survival time was used to document the recording location. In other fish, a longer injection and survival time was used at an auditory-only or a bimodal site to fill the axons of the medullary inputs. Auditory-only sites were located in the most dorsal and medial sites in nucleus centralis. Bimodal sites were identified within both nucleus centralis and nucleus ventrolateralis. The greatest number of retrogradely filled cell bodies was found in the descending octaval nucleus following injection at auditory-only recording sites in nucleus centralis. In contrast, retrogradely filled cell bodies were found in both the descending octaval nucleus and the lateral line nucleus medialis following injection at bimodal sites in nucleus centralis or nucleus ventrolateralis. Retrogradely filled cell bodies were located in the dorsal and ventral divisions of the secondary octaval population from injections at either bimodal or auditory-only sites. The secondary octaval population has been implicated in auditory processing based on previous studies of both auditory specialist and auditory generalist fishes; however, this study is the first to reveal the potential role of the secondary octaval population in directional hearing in a fish. Relatively large numbers of retrogradely filled cells around the lateral lemniscus at consistent locations in the medulla indicate that a perilemniscal cell group also might be a component of the directional hearing circuit.     

Suicidal ideation and suicide attempts in body dysmorphic disorder

OBJECTIVE: Because suicidality in body dys-morphic disorder (BDD) has received little investigation, this study examined rates, correlates, predictors, and other aspects of suicidal ideation and suicide attempts in this disorder. METHOD: From January 2001 to June 2003, 200 subjects with DSM-IV BDD recruited from diverse sources were assessed with standard measures. RESULTS: Subjects had high rates of lifetime suicidal ideation (78.0%) and suicide attempts (27.5%). Body dysmorphic disorder was the primary reason for suicidal ideation in 70.5% of those with a history of ideation and nearly half of subjects with a past attempt. Suicidal subjects often did not reveal their BDD symptoms to their clinician. In univariate analyses, both suicidal ideation and suicide attempts were associated with lifetime functional impairment due to BDD (p < .001), current functional impairment (p < .001 to < .05), lifetime bipolar disorder (p < .05), any personality disorder (p < .05 to .001), and comorbid borderline personality disorder (p < .01 to < .001). A history of suicidal ideation (but not suicide attempts) was additionally associated with comorbid lifetime major depression (p = .001). A history of suicide attempts (but not suicidal ideation) was additionally associated with delusional appearance beliefs (p = .01) and lifetime posttraumatic stress disorder (PTSD), an eating disorder, or a substance use disorder (p < .001 to < .05). In logistic regression analyses, suicidal ideation was significantly predicted by comorbid major depression (p = .010) and greater lifetime impairment due to BDD (p = .003); suicide attempts were significantly predicted by PTSD (p = .011), a substance use disorder (p = .011), and greater lifetime impairment due to BDD (p = .005). CONCLUSION: Individuals with BDD have high rates of suicidal ideation and suicide attempts. Lifetime impairment due to BDD and certain comorbid disorders are associated with suicidality.