PhD Discussions Sessions: Helena Lozano and Martina Maier

Electrical and morphological characterization of bacterial polar flagella

The electric polarization of proteins in response to external electric fields plays an important role to understand the electrostatic interaction of proteins with charged biomolecules and ions [1]. Even if dielectric studies on individual proteins have not been reported, yet, there have been some studies on protein complexes involving a relatively small number of proteins, such as for instance, virus capsids and virus tails [2,3]. I am going to present the results of a dielectric study performed on a third protein complex system, the bacterial polar flagellum, which is composed of protein subunits called flagellin arranged in several intertwined chains [4]. In particular, we perform a comparative study of the dielectric properties of single flagella belonging to two different bacteria types, namely, Shewanella oneidensis MR-1 and Pseudomona aeruginosas PAO1. The dielectric properties (dielectric constant) have been obtained by combining Electrostatic Force Microscopy images [2] and 3D finite element numerical calculations. The values obtained are within the range of values obtained with macroscopic techniques [1].
References:
[1] Simonson, T., Rep. Prog. Phys. 66 (2003) 737–787.
[2] Fumagalli, L., Esteban-Ferrer, et al. Nature Materials 11 (2012) 743
[3] Cuervo, A., Dans, P. D., et al. PNAS 111 (2014) E3624.
[4] Lozano, H., Fábregas, R., Blanco-Cabra, N., Millán-Solsona, R. Torrents, E., Gomila, G. (in preparation).

Rehabilitation of cognitive deficits and depression after stroke

Cognitive deficits and depression are common consequences of stroke [1], [2]. Both have detrimental effects on quality of life and the activities of daily living [3]. In addition, they have been linked to poor functional outcome and more severe impairment [4], [5], [6] than observed in patients without cognitive deficit or depression. Post-stroke depression has been related to cognitive impairment [7], but the dynamics of that relationship are not well understood, as cognitive deficits and depression are typically studied and treated in isolation. The aim of our work is twofold. On one hand, we investigate in how depression modulates cognitive functioning after a stroke. On the other, we propose a new rehabilitation method that treats cognitive deficits and depression in conjunction. For this reason, we conducted a longitudinal randomized clinical trial with chronic stroke patients. All patients had a cognitive impairment as measured with the Montreal Cognitive Assessment. In addition, they expressed various degrees of depression expressed by varying scores on the Hamilton Depression Scale. Our results so far suggest that the presence of depression modulates attentional processing similarly to a cognitive load in a psychophysical task. Moreover, we see that depressive patients profited most of the conjunctive cognitive training and that the improvement was most evident in the attention domain. Further analysis will shed light on the underlying mechanisms of this improvement. We hope that this work will aid in not only find better rehabilitation methods, but also improve current diagnostic tools.

References:
[1] M. Lesniak, T. Bak, W. Czepiel, J. Seniów, and A. Czlonkowska, “Frequency and prognostic value of cognitive disorders in stroke patients,” Dement. Geriatr. Cogn. Disord., vol. 26, no. 4, pp. 356–363, 2008.
[2] M. L. Hackett and K. Pickles, “Part I: Frequency of depression after stroke: An updated systematic review and meta-analysis of observational studies,” Int. J. Stroke, vol. 9, pp. 1017–1025, 2014.
[3] L. Mercier, T. Audet, R. Hébert, A. Rochette, and M. F. Dubois, “Impact of motor, cognitive, and perceptual disorders on ability to perform activities of daily living after stroke.,” Stroke., vol. 32, no. 11, pp. 2602–2608, 2001.
[4] R. G. Robinson and R. E. Jorge, “Post-stroke depression: A review,”Am. J. Psychiatry, vol. 173, pp. 221–23, 2016.
[5] R. Gillen, H. Tennen, T. E. McKee, P. Gernert-Dott, and G. Affleck, “Depressive symptoms and history of depression predict rehabilitation efficiency in stroke patients,” Arch. Phys. Med. Rehabil., vol. 82, pp. 1645–1649, 2001.
[6] S. Paolucci, G. Antonucci, E. Gialloreti, M. Traballesi, S. Lubich, L. Pratesi, and L. Palombi, “Predicting Stroke Inpatient Rehabilitation Outcome: The Prominent Role of Neuropsychological Disorders,” Eur. Neurol., vol. 36, no. 6, pp. 385–390, 1996.
[7] M. L. Kauhanen, J. T. Korpelainen, P. Hiltunen, E. Brusin, H. Mononen, R. Maatta, et al., “Poststroke depression correlates with cognitive impairment and neurological deficits,” Stroke, vol. 30, pp. 1875–1880, 1999.

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