Acute toxicity assay using mysid as an alternative test organism in the assessment of the aqueous fraction of sediment

The evaluation of sediment quality through biological testing of the aqueous fraction can be applied in dredging situations and is associated with a small number of confounding factors. The use of test organisms that are relatively resistant to contaminants is recommended when working with complex mixtures such as sediments. In this study, the sensitivity of the mysid Mysidopsis juniae to ammonia (NH₃) and metals was investigated in acute toxicity laboratory tests and the results were compared to those obtained in the traditional test with sea urchin embryos and larvae. The ability of the toxicity identification and evaluation (TIE) technique, with the use of EDTA and sodium thiosulfate, to indicate the factors responsible for adverse effects was determined. The results indicate that mysids are almost 5 times more resistant than the sea urchin to ammonia (NH₃), more sensitive to Cd²⁺ and Ni²⁺ and more resistant to Zn²⁺ and Pb²⁺. With the TIE technique and with the use of EDTA as a complexing agent, a greater resolution was observed in the diagnosis of the presence of the metals Cd²⁺ and Ni²⁺, which could be applied to the aqueous fraction of the sediment.

Mood disorders and prospective suicidality in young adults: a population-based cohort study

OBJECTIVE

To assess the prospective associations of mood disorders and suicidality in a community sample of young adults from south Brazil.

METHOD

Prospective population-based cohort study. Young adults (18-24 years old) were recruited and followed up on 5 years later; people were interviewed at their homes. Suicidality, as well as mood and anxiety disorders, was assessed using the Mini-International Neuropsychiatric Interview. The impact of mood episodes on suicidality was both evaluated when they occurred in the same wave (a current episode) and when suicidality occurred prospectively, with suicidality measured at follow-up (a past episode).

RESULTS

The sample included 1560 young adults at baseline, with 1244 reassessed at follow-up (80.6%). Depressive episodes, both current and past, had a significant impact on suicidality in the final multivariable model. Manic episodes, however, were less consistently associated with suicidality.

CONCLUSION

Depressive episodes have a strong, independent, and robust association with prospective suicidality. The association between manic episodes and suicidality, on the other hand, was dependent on the analysis and deserves further exploration.

Effect of acetic acid on xylose fermentation to xylitol by Candida guilliermondii

The effect of acetic acid concentration on xylose-fermentation to xylitol by Candida guilliermondii FTI 20037 was evaluated in semisynthetic medium containing different concentrations of the acid. Increasing acetic acid concentration up to 1.0 g/l favored xylitol yield and productivity, with maximum values of 0.82 g/g and 0.57 g/l.h, respectively. The presence of acetic acid reduced cell production at all concentration. Furthermore, acetic acid was assimilated by the yeast together with the sugars and was depleted from the medium at concentrations of less than 3.0 g/l. The ability of this yeast to assimilate acetic acid suggests that these cells act as agents of medium detoxification. This behavior may lead to a viable microbiological process of xylitol production by C. guilliermondii FTI 20037 using xylose-rich lignocellulosic hydrolysates in which acetic acid is commonly present, causing inhibition of fermentative activity.