Suicide Among Adolescents in Center Tunisia: An 18-Year Autopsy Study

Background: Suicide and suicide attempts are more common among adolescents. Many factors are known to influence suicide in particular: region and culture. Adolescent suicide has been widely studied in many countries, but there are, currently, no data relating to adolescent suicide in Tunisia. Aim: The aims of this study were to describe epidemiological aspects of death related to adolescent suicide in Sousse, a city in central Tunisia. Methods: Data of forensic autopsies from 1998 to 2015 related to suicide of adolescents were retrospectively examined considering age, gender, method of death, year and risk factor. Results: 70 cases were reported with female predominance (62, 8%). The age range was from 10 to 19 and most of the suicides occurred in the 15-to-19 age group (75, 7%). Most victims were from rural zones (70%). Self-poisoning was the most used method (47, 1 %) followed by hanging (35, 7%). Hanging was the most common method used by males (17/26) and self-poisoning by females (29/44). Self-poisoning was related to pesticides in the vast majority of cases (29 cases among 33). The identified precipitating factors were chronic family problems in 51.4%, sentimental deception in 8.6%. Conclusion: This retrospective study raises concerns regarding the use of pesticides and the urgent need to provide rural areas with structures and medical equipment. This will ensure adequate suicide prevention in the region

Concentration Dependent Ion Selectivity in VDAC: A Molecular Dynamics Simulation Study

The voltage-dependent anion channel (VDAC) forms the major pore in the outer mitochondrial membrane. Its high conducting open state features a moderate anion selectivity. There is some evidence indicating that the electrophysiological properties of VDAC vary with the salt concentration. Using a theoretical approach the molecular basis for this concentration dependence was investigated. Molecular dynamics simulations and continuum electrostatic calculations performed on the mouse VDAC1 isoform clearly demonstrate that the distribution of fixed charges in the channel creates an electric field, which determines the anion preference of VDAC at low salt concentration. Increasing the salt concentration in the bulk results in a higher concentration of ions in the VDAC wide pore. This event induces a large electrostatic screening of the charged residues promoting a less anion selective channel. Residues that are responsible for the electrostatic pattern of the channel were identified using the molecular dynamics trajectories. Some of these residues are found to be conserved suggesting that ion permeation between different VDAC species occurs through a common mechanism. This inference is buttressed by electrophysiological experiments performed on bean VDAC32 protein akin to mouse VDAC

Lipid Dynamics and Protein–Lipid Interactions in 2D Crystals Formed with the β-Barrel Integral Membrane Protein VDAC1

We employ a combination of [superscript 13]C/[superscript 15]N magic angle spinning (MAS) NMR and [superscript 2]H NMR to study the structural and functional consequences of different membrane environments on VDAC1 and, conversely, the effect of VDAC1 on the structure of the lipid bilayer. MAS spectra reveal a well-structured VDAC1 in 2D crystals of dimyristoylphosphatidylcholine (DMPC) and diphytanoylphosphatidylcholine (DPhPC), and their temperature dependence suggests that the VDAC structure does not change conformation above and below the lipid phase transition temperature. The same data show that the N-terminus remains structured at both low and high temperatures. Importantly, functional studies based on electrophysiological measurements on these same samples show fully functional channels, even without the presence of Triton X-100 that has been found necessary for in vitro-refolded channels. [superscript 2]H solid-state NMR and differential scanning calorimetry were used to investigate the dynamics and phase behavior of the lipids within the VDAC1 2D crystals. [superscript 2]H NMR spectra indicate that the presence of protein in DMPC results in a broad lipid phase transition that is shifted from 19 to ~27 °C and show the existence of different lipid populations, consistent with the presence of both annular and bulk lipids in the functionally and structurally homogeneous samples.National Institutes of Health (U.S.) (Grant EB001960)National Institutes of Health (U.S.) (Grant EB002026)National Institutes of Health (U.S.) (Grant GM075879