Production of Fluorescent Dissolved Organic Matter by Microalgae Strains from the Ob and Yenisei Gulfs (Siberia).

Dissolved organic matter (DOM) is an important component of aquatic environments; it plays a key role in the biogeochemical cycles of many chemical elements. Using excitation-emission matrix fluorescence spectroscopy, we examined the fluorescent fraction of DOM (FDOM) produced at the stationary phase of growth of five strains of microalgae sampled and isolated from the Ob and Yenisei gulfs. Based on the morphological and molecular descriptions, the strains were identified as diatoms (Asterionella formosa, Fragilaria cf. crotonensis, and Stephanodiscus hantzschii), green microalgae (Desmodesmus armatus), and yellow-green microalgae (Tribonema cf. minus). Three fluorescent components were validated in parallel factor analysis (PARAFAC): one of them was characterized by protein-like fluorescence (similar to peak T), two others, by humic-like fluorescence (peaks A and C). The portion of fluorescence intensity of humic compounds (peak A) to the total fluorescence intensity was the lowest (27 ± 5%) and showed little variation between species. Protein-like fluorescence was most intense (45 ± 16%), but along with humic-like fluorescence with emission maximum at 470 nm (28 ± 14%), varied considerably for different algae strains. The direct optical investigation of FDOM produced during the cultivation of the studied algae strains confirms the possibility of autochthonous production of humic-like FDOM in the Arctic shelf regions.

Repolarizing potassium currents in working myocardium of Japanese quail: a novel translational model for cardiac electrophysiology.

Birds developed endothermy and four-chambered high-performance heart independently from mammals. Though avian embryos are extensively studied and widely used as various models for heart research, little is known about cardiac physiology of adult birds. Meanwhile, cardiac electrophysiology is in search for easily accessible and relevant model objects which resemble human myocardium in the pattern of repolarizing currents (IKr, IKs, IKur and Ito). This study focuses on the configuration of electrical activity and electrophysiological phenotype of working myocardium in adult Japanese quails (Coturnix japonica). The resting membrane potential and action potential (AP) waveform in quail atrial myocardium were similar to that in working myocardium of rodents. Using whole-cell patch clamp and sharp glass microelectrodes, we demonstrated that the repolarization of quail atrial and ventricular myocardium is determined by voltage-dependent potassium currents IKr, IKs and Ito - the latter was previously considered as an exclusive evolutionary feature of mammals. The specific blockers of these currents, dofetilide (3 µmol l-1), HMR 1556 (30 µmol l-1) and 4-aminopyridine (3 mmol l-1), prolonged AP in both ventricular and atrial myocardial preparations. The expression of the corresponding channels responsible for these currents in quail myocardium was investigated with quantitative RT-PCR and western blotting. In conclusion, the described pattern of repolarizing ionic currents and channels in quail myocardium makes this species a novel and suitable experimental model for translational cardiac research and reveals new information related to the evolution of cardiac electrophysiology in vertebrates.

Two known and one new species of Draconematidae and Epsilonematida (Nematoda, Desmodorida) from the White Sea, North Russia.

Morphological descriptions of three "walking nematode" species found for the first time in the White Sea are presented. Draconema ophicephalum (Claparède, 1863) (Draconematidae) and Epsilonema steineri Chitwood, 1935 (Epsilonematidae), both known from insufficient material and females only, are re-described and problems of their taxonomic identification as well as species compositions of respective genera are discussed. The new species Prochaetosoma marisalbi sp. n. (Draconematidae) differs from other Prochaetosoma species except P. longicapitatum (Allgén, 1935) in that the pharyngeal bulb lumen is not cuticularised, from P. longicapitatum by shape of body and rostrum, greater number of cephalic adhesive tubes, and from P. maertensi Decraemer, 1989 by having a relatively longer tail, fewer anterior adhesive tubes and longer spicules, besides lacking cuticular thickening in the pharyngeal bulb. Draconema hoonsooi, D. youngeouni, P.rochaetosoma beomseomense, P. brevicaudatum, P. byungilli, P. cracense, P. saheungi, P. sujungi, P. supseomense erected by Rho & Min (2011) are considered as invalid species while Prochaetosoma arcticum, P. lugubre and Epsilonema cygnoides are assumed as species inquirenda. From a phylogenetic tree based on the 18S rRNA gene, all three White Sea species adjoin to unidentified species of their respective genera.

Genomic study of the Ket: a Paleo-Eskimo-related ethnic group with significant ancient North Eurasian ancestry.

The Kets, an ethnic group in the Yenisei River basin, Russia, are considered the last nomadic hunter-gatherers of Siberia, and Ket language has no transparent affiliation with any language family. We investigated connections between the Kets and Siberian and North American populations, with emphasis on the Mal'ta and Paleo-Eskimo ancient genomes, using original data from 46 unrelated samples of Kets and 42 samples of their neighboring ethnic groups (Uralic-speaking Nganasans, Enets, and Selkups). We genotyped over 130,000 autosomal SNPs, identified mitochondrial and Y-chromosomal haplogroups, and performed high-coverage genome sequencing of two Ket individuals. We established that Nganasans, Kets, Selkups, and Yukaghirs form a cluster of populations most closely related to Paleo-Eskimos in Siberia (not considering indigenous populations of Chukotka and Kamchatka). Kets are closely related to modern Selkups and to some Bronze and Iron Age populations of the Altai region, with all these groups sharing a high degree of Mal'ta ancestry. Implications of these findings for the linguistic hypothesis uniting Ket and Na-Dene languages into a language macrofamily are discussed.

Carbon monoxide modulates electrical activity of murine myocardium via cGMP-dependent mechanisms.

Carbon monoxide (CO) is critical in cell signaling, and inhalation of gaseous CO can impact cardiovascular physiology. We have investigated electrophysiological effects of CO and their potential cGMP-dependent mechanism in isolated preparations of murine myocardium. The standard microelectrode technique was used to record myocardial action potentials (APs). Exogenous CO (0.96 × 10(-4)-4.8 × 10(-4) M) decreased AP duration in atrial and ventricular tissue and accelerated pacemaking activity in sinoatrial node. Inhibitors of heme oxygenases (zinc and tin protoporphyrin IX), which are responsible for endogenous CO production, induced the opposite effects. Inhibitor of soluble guanylate cyclase (sGC), ODQ (10(-5) M) halved CO-induced AP shortening, while sGC activator azosidnone (10(-5) M-3 × 10(-4) M) and cGMP analog BrcGMP (3 × 10(-4) M) induced the same effects as CO. To see if CO effects are attributed to differential regulation of phosphodiesterase 2 (PDE2) and 3 (PDE3), we used inhibitors of these enzymes. Milrinone (2 × 10(-6) M), selective inhibitor of cGMP-downregulated PDE3, blocked CO-induced rhythm acceleration. EHNA(2 × 10(-6) M), which inhibits cGMP-upregulated PDE2, attenuated CO-induced AP shortening, but failed to induce any positive chronotropic effect. Our findings indicate that PDE2 activity prevails in working myocardium, while PDE3 is more active in sinoatrial node. The results suggest that cardiac effects of CO are at least partly attributed to activation of sGC and subsequent elevation of cGMP intracellular content. In sinoatrial node, this leads to PDE3 inhibition, increased cAMP content, and positive chronotropy, while it also causes PDE2 stimulation in working myocardium, thereby enhancing cAMP degradation and producing AP shortening. Thus, CO induces significant alterations of cardiac electrical activity via cGMP-dependent mechanism and should be considered as a novel regulator of cardiac electrophysiology.

Carbon monoxide modulates electrical activity of murine myocardium via cGMP-dependent mechanisms

Carbon monoxide (CO) is critical in cell signaling, and inhalation of gaseous CO can impact cardiovascular physiology. We have investigated electrophysiological effects of CO and their potential cGMP-dependent mechanism in isolated preparations of murine myocardium. The standard microelectrode technique was used to record myocardial action potentials (APs). Exogenous CO (0.96 × 10−4–4.8 × 10−4 M) decreased AP duration in atrial and ventricular tissue and accelerated pacemaking activity in sinoatrial node. Inhibitors of heme oxygenases (zinc and tin protoporphyrin IX), which are responsible for endogenous CO production, induced the opposite effects. Inhibitor of soluble guanylate cyclase (sGC), ODQ (10−5 M) halved CO-induced AP shortening, while sGC activator azosidnone (10−5 M-3 × 10−4 M) and cGMP analog BrcGMP (3 × 10−4 M) induced the same effects as CO. To see if CO effects are attributed to differential regulation of phosphodiesterase 2 (PDE2) and 3 (PDE3), we used inhibitors of these enzymes. Milrinone (2 × 10−6 M), selective inhibitor of cGMP-downregulated PDE3, blocked CO-induced rhythm acceleration. EHNA(2 × 10−6 M), which inhibits cGMP-upregulated PDE2, attenuated CO-induced AP shortening, but failed to induce any positive chronotropic effect. Our findings indicate that PDE2 activity prevails in working myocardium, while PDE3 is more active in sinoatrial node. The results suggest that cardiac effects of CO are at least partly attributed to activation of sGC and subsequent elevation of cGMP intracellular content. In sinoatrial node, this leads to PDE3 inhibition, increased cAMP content, and positive chronotropy, while it also causes PDE2 stimulation in working myocardium, thereby enhancing cAMP degradation and producing AP shortening. Thus, CO induces significant alterations of cardiac electrical activity via cGMP-dependent mechanism and should be considered as a novel regulator of cardiac electrophysiology