Transmission of parasites in the coastal waters of the Arctic seas and possible effect of climate change

The review deals with the biodiversity, life cycles, distribution and temperature adaptations of parasites circulating in the coastal waters of northern polar seas. Special attention is given to helminths of marine birds, which are the most common parasites in the coastal waters. Among them, the focus is on trematodes. Factors responsible for the impoverished species composition of parasites in the Arctic are analyzed. It is shown that species without free-living larvae in the life cycle have an advantage in this environment. The abundance of cestodes and acanthocephalans in Arctic seabirds is linked with the high proportion of crustaceans in their diet. The phenomenon of nonspecific parasitism (occurrence of parasites in atypical host species) is analyzed from an evolutionary viewpoint. Characteristic features in the spatial distribution of infection of marine coastal invertebrates with parasite larvae are considered, and factors that determine it are specified. The prevalence of infection in intermediate hosts is closely connected with the abundance of final hosts, which makes it possible to estimate the abundance of final hosts in a given region and reveal trends in its changes. Trematodes have a high potential for temperature acclimation. This facilitates their transmission in the northern seas but, on the other hand, makes it unlikely that the transmission process would be intensified upon an increase in summer temperatures resulting from climate warming. However, intensification of transmission may well occur due to the prolongation of the warm season (“transmission window”), which has been predicted and is already observed. It is suggested that warming in the Arctic promotes both the entry of certain “southern” species into the Arctic and the trans-Arctic interpenetration of the North Atlantic and North Pacific parasitic faunas. A case is made for the necessity to broaden the scope of parasitological research in the Arctic and Subarctic, including parasitological monitoring at the reference sites of the sea coast.     

Mannitol Does Not Enhance Tobramycin Killing of Pseudomonas aeruginosa in a Cystic Fibrosis Model System of Biofilm Formation

Cystic Fibrosis (CF) is a human genetic disease that results in the accumulation of thick, sticky mucus in the airways, which results in chronic, life-long bacterial biofilm infections that are difficult to clear with antibiotics. Pseudomonas aeruginosa lung infection is correlated with worsening lung disease and P. aeruginosa transitions to an antibiotic tolerant state during chronic infections. Tobramycin is an aminoglycoside currently used to combat lung infections in individuals with CF. While tobramycin is effective at eradicating P. aeruginosa in the airways of young patients, it is unable to completely clear the chronic P. aeruginosa infections in older patients. A recent report showed that co-addition of tobramycin and mannitol enhanced killing of P. aeruginosa grown in vitro as a biofilm on an abiotic surface. Here we employed a model system of bacterial biofilms formed on the surface of CF-derived airway cells to determine if mannitol would enhance the antibacterial activity of tobramycin against P. aeruginosa grown on a more clinically relevant surface. Using this model system, which allows the growth of robust biofilms with high-level antibiotic tolerance analogous to in vivo biofilms, we were unable to find evidence for enhanced antibacterial activity of tobramycin with the addition of mannitol, supporting the observation that this type of co-treatment failed to reduce the P. aeruginosa bacterial load in a clinical setting.     

The ABC’s of Suicide Risk Assessment: Applying a Tripartite Approach to Individual Evaluations

There is considerable need for accurate suicide risk assessment for clinical, screening, and research purposes. This study applied the tripartite affect-behavior-cognition theory, the suicidal barometer model, classical test theory, and item response theory (IRT), to develop a brief self-report measure of suicide risk that is theoretically-grounded, reliable and valid. An initial survey (n = 359) employed an iterative process to an item pool, resulting in the six-item Suicidal Affect-Behavior-Cognition Scale (SABCS). Three additional studies tested the SABCS and a highly endorsed comparison measure. Studies included two online surveys (Ns = 1007, and 713), and one prospective clinical survey (n = 72; Time 2, n = 54). Factor analyses demonstrated SABCS construct validity through unidimensionality. Internal reliability was high (α = .86-.93, split-half = .90-.94)). The scale was predictive of future suicidal behaviors and suicidality (r = .68, .73, respectively), showed convergent validity, and the SABCS-4 demonstrated clinically relevant sensitivity to change. IRT analyses revealed the SABCS captured more information than the comparison measure, and better defined participants at low, moderate, and high risk. The SABCS is the first suicide risk measure to demonstrate no differential item functioning by sex, age, or ethnicity. In all comparisons, the SABCS showed incremental improvements over a highly endorsed scale through stronger predictive ability, reliability, and other properties. The SABCS is in the public domain, with this publication, and is suitable for clinical evaluations, public screening, and research.     

Diffusion of extracellular K+ can synchronize bursting oscillations in a model islet of Langerhans.

Electrical bursting oscillations of mammalian pancreatic beta-cells are synchronous among cells within an islet. While electrical coupling among cells via gap junctions has been demonstrated, its extent and topology are unclear. The beta-cells also share an extracellular compartment in which oscillations of K+ concentration have been measured (Perez-Armendariz and Atwater, 1985). These oscillations (1-2 mM) are synchronous with the burst pattern, and apparently are caused by the oscillating voltage-dependent membrane currents: Extracellular K+ concentration (Ke) rises during the depolarized active (spiking) phase and falls during the hyperpolarized silent phase. Because raising Ke depolarizes the cell membrane by increasing the potassium reversal potential (VK), any cell in the active phase should recruit nonspiking cells into the active phase. The opposite is predicted for the silent phase. This positive feedback system might couple the cells' electrical activity and synchronize bursting. We have explored this possibility using a theoretical model for bursting of beta-cells (Sherman et al., 1988) and K+ diffusion in the extracellular space of an islet. Computer simulations demonstrate that the bursts synchronize very quickly (within one burst) without gap junctional coupling among the cells. The shape and amplitude of computed Ke oscillations resemble those seen in experiments for certain parameter ranges. The model cells synchronize with exterior cells leading, though incorporating heterogeneous cell properties can allow interior cells to lead. The model islet can also be forced to oscillate at both faster and slower frequencies using periodic pulses of higher K+ in the medium surrounding the islet. Phase plane analysis was used to understand the synchronization mechanism. The results of our model suggest that diffusion of extracellular K+ may contribute to coupling and synchronization of electrical oscillations in beta-cells within an islet.