Response of meiobenthos to migrating ripples in sandy lowland streams

Hydrobiologia - Stream sediments move at low flow forming migrating ripples. These ripples can cover substantial areas where benthic communities experience erosion-resting cycles of sand grains....     

Osmotic parameters of red blood cells from umbilical cord blood

The transfusion of red blood cells from umbilical cord blood (cord RBCs) is gathering significant interest for the treatment of fetal and neonatal anemia, due to its high content of fetal hemoglobin as well as numerous other potential benefits to fetuses and neonates. However, in order to establish a stable supply of cord RBCs for clinical use, a cryopreservation method must be developed. This, in turn, requires knowledge of the osmotic parameters of cord RBCs. Thus, the objective of this study was to characterize the osmotic parameters of cord RBCs: osmotically inactive fraction (b), hydraulic conductivity (L_p), permeability to cryoprotectant glycerol (P_glycerol), and corresponding Arrhenius activation energies (E_a). For L_p and P_glycerol determination, RBCs were analyzed using a stopped-flow system to monitor osmotically-induced RBC volume changes via intrinsic RBC hemoglobin fluorescence. L_p and P_glycerol were characterized at 4 °C, 20 °C, and 35 °C using Jacobs and Stewart equations with the E_a calculated from the Arrhenius plot. Results indicate that cord RBCs have a larger osmotically inactive fraction compared to adult RBCs. Hydraulic conductivity and osmotic permeability to glycerol of cord RBCs differed compared to those of adult RBCs with the differences dependent on experimental conditions, such as temperature and osmolality. Compared to adult RBCs, cord RBCs had a higher E_a for L_p and a lower E_a for P_glycerol. This information regarding osmotic parameters will be used in future work to develop a protocol for cryopreserving cord RBCs.     

The Chromatin Extrusion Phenomenon in Amoeba proteus Cell Cycle

Amoeba proteus is possibly the best known of all unicellular eukaryotes. At the same time, several quintessential issues of its biology, including some aspects of the cell cycle, remain unsolved. Here, we show that this obligate agamic amoebae and related species have a special type of cyclic polyploidy. Their nucleus has an euploid status only for a small fraction of the cell cycle, during metaphase and telophase. The rest of the time it has an aneuploid status, which is a consequence of polyploidization. Extrusion of “excess” chromatin from the nucleus in late interphase and during prophase results in depolyploidization. Such a strategy of life cycle in unicellular eukaryotes is thought to be the main mechanism of “resetting” the Muller's ratchet and is a satisfactory alternative to the meiotic recombination for agamic protists.     

Liposomal quercetin potentiates maxi-K channel openings in smooth muscles and restores its activity after oxidative stress

The effects of quercetin-loaded liposomes (PCL-Q) and their constituents, that is, free quercetin (Q) and ‘empty’ phosphatidylcholine vesicles (PCL), on maxi-K channel activity were studied in single mouse ileal myocytes before and after H₂O₂-induced oxidative stress. Macroscopic Maxi-K channel currents were recorded using whole-cell patch clamp techniques, while single BK_Ca channel currents were recorded in the cell-attached configuration. Bath application of PCL-Q (100?μg/ml of lipid and 3?μg/ml of quercetin) increased single Maxi-K channel activity more than threefold, from 0.010?±?0.003 to 0.034?±?0.004 (n?=?5; p?<?0.05), whereas single-channel conductance increased non-significantly from 138 to 146?pS. In the presence of PCL-Q multiple simultaneous channel openings were observed, with up to eight active channels in the membrane patch. Surprisingly, ‘empty’ PCL (100?μg/ml) also produced some channel activation, although it was less potent compared to PCL-Q, that is, these increased NPo from 0.010?±?0.003 to 0.019?±?0.003 (n?=?5; p?<?0.05) and did not affect single-channel conductance (139?pS). Application of PCL-Q restored macroscopic Maxi-K currents suppressed by H₂O₂-induced oxidative stress in ileal smooth muscle cells. We conclude that PCL-Q can activate Maxi-K channels in ileal myocytes mainly by increasing channel open probability, as well as maintain Maxi-K-mediated whole-cell current under the conditions of oxidative stress. While fusion of the ‘pure’ liposomes with the plasma membrane may indirectly activate Maxi-K channels by altering channel’s phospholipids environment, the additional potentiating action of quercetin may be due to its better bioavailability.     

Tyrosine nitration as a key event of signal transduction that regulates functional state of the cell

This review is dedicated to the role of nitration of proteins by tyrosine residues in physiological and pathological conditions. First of all, we analyze the biochemical evidence of peroxynitrite formation and reactions that lead to its formation, types of posttranslational modifications (PTMs) induced by reactive nitrogen species, as well as three biological pathways of tyrosine nitration. Then, we describe two possible mechanisms of protein nitration that are involved in intracellular signal transduction, as well as its interconnection with phosphorylation/dephosphorylation of tyrosine. Next part of the review is dedicated to the role of proteins nitration in different pathological conditions. In this section, special attention is devoted to the role of nitration in changes of functional properties of actin—protein that undergoes PTMs both in normal and pathological conditions. Overall, this review is devoted to the main features of protein nitration by tyrosine residue and the role of this process in intracellular signal transduction in basal and pathological conditions.