The effect of magnesium ions on the two-stage kinetics of superprecipitation and ATPase activity of natural actomyosin

The effect of magnesium ions on the two-stage kinetics of superprecipitation (SPP) and ATP activity of natural skeletal muscle actomyosin was studied. It was found that the changes in the ratios of two independent steps of SPP and ATPase activity are mainly induced by the Mg-ATP2- complex, but not by free Mg2+. These changes in the kinetics of SPP and ATPase are regarded as being due to the shift in the dynamic equilibrium between the two types of the actomyosin complexes in solution, each of which is characterized by different reaction mechanisms. The role of the Mg-ATP2(-)-induced alteration of at least two structural-and-functional states of actomyosin in muscle contractibility is discussed.     

The role of the voltage-dependent anion channels in the outer membrane of mitochondria in the regulation of cellular metabolism

The role of the voltage-dependent anion channels (VDAC) harbored in the outer membrane of mitochondria in the regulation of cellular metabolism was investigated using an experimental model of ethanol toxicity in cultured hepatocytes. It was demonstrated that ethanol inhibits State 3 and uncoupled mitochondrial respirations, decreases the accessibility of mitochondrial adenylate kinase localized in the intermembrane space of mitochondria, and suppresses ureagenic respiration and synthesis of urea in cultured hepatocytes. Increasing the permeability of the outer mitochondrial membrane with closed VDAC with high concentrations of digitonin (> 80 microM), which creates pores in the membrane, allowing the alternative bypass of closed VDAC, and restores all reactions suppressed with ethanol. It is concluded that the effect of ethanol in hepatocytes leads to global loss of mitochondrial functions due to the closure of VDAC, which limits the free diffusion of metabolites into the intermembrane space of mitochondria. Our studies demonstrated that ethanol affects the main mitochondrial functions and revealed the role of VDAC channels in the outer mitochondrial membrane in the regulation of liver specific intracellular processes such as ureagenesis. The data obtained can be used for the development of pharmaceutical drugs that prevent the closure of VDAC in mitochondria of ethanol oxidizing liver, thus protecting liver tissue from the hepatotoxic action of alcohol.     

Forest transitions in Eastern Europe and their effects on carbon budgets

Forests often rebound from deforestation following industrialization and urbanization, but for many regions our understanding of where and when forest transitions happened, and how they affected carbon budgets remains poor. One such region is Eastern Europe, where political and socio‐economic conditions changed drastically over the last three centuries, but forest trends have not yet been analyzed in detail. We present a new assessment of historical forest change in the European part of the former Soviet Union and the legacies of these changes on contemporary carbon stocks. To reconstruct forest area, we homogenized statistics at the provincial level for ad 1700–2010 to identify forest transition years and forest trends. We contrast our reconstruction with the KK11 and HYDE 3.1 land change scenarios, and use all three datasets to drive the LPJ dynamic global vegetation model to calculate carbon stock dynamics. Our results revealed that forest transitions in Eastern Europe occurred predominantly in the early 20th century, substantially later than in Western Europe. We also found marked geographic variation in forest transitions, with some areas characterized by relatively stable or continuously declining forest area. Our data suggest extensive deforestation in European Russia already prior to ad 1700, and even greater deforestation in the 18th and 19th centuries than in the KK11 and HYDE scenarios. Based on our reconstruction, cumulative carbon emissions from deforestation were greater before 1700 (60 Pg C) than thereafter (29 Pg C). Summed over our entire study area, forest transitions led to a modest uptake in carbon over recent decades, with our dataset showing the smallest effect (<5.5 Pg C) and a more heterogeneous pattern of source and sink regions. This suggests substantial sequestration potential in regrowing forests of the region, a trend that may be amplified through ongoing land abandonment, climate change, and CO₂ fertilization.     

Parasternal intercostal muscle remodeling in severe chronic obstructive pulmonary disease.

Studies in experimental animals indicate that chronic increases in neural drive to limb muscles elicit a fast-to-slow transformation of fiber-type proportions and myofibrillar proteins. Since neural drive to the parasternal intercostal muscles (parasternals) is chronically increased in patients with severe chronic obstructive pulmonary diseases (COPDs), we carried out the present study to test the hypothesis that the parasternals of COPD patients exhibit an increase in the proportions of both slow fibers and slow myosin heavy chains (MHCs). Accordingly, we obtained full thickness parasternal muscle biopsies from the third interspace of seven COPD patients (mean +/- SE age: 59 +/- 4 yr) and seven age-matched controls (AMCs). Fiber typing was done by immunohistochemistry, and MHC proportions were determined by SDS-PAGE followed by densitometry. COPD patients exhibited higher proportions of slow fibers than AMCs (73 +/- 4 vs. 51 +/- 3%; P < 0.01). Additionally, COPD patients exhibited higher proportions of slow MHC than AMCs (56 +/- 4 vs. 46 +/- 4%, P < 0.04). We conclude that the parasternal muscles of patients with severe COPD exhibit a fast-to-slow transformation in both fiber-type and MHC proportions. Previous workers have demonstrated that remodeling of the external intercostals, another rib cage inspiratory muscle, elicited by severe COPD is characterized by a slow-to-fast transformation in both fiber types and MHC isoform proportions. The physiological significance of this difference in remodeling between these two inspiratory rib cage muscles remains to be elucidated.     

Virus-induced gene silencing in detached tomatoes and biochemical effects of phytoene desaturase gene silencing

Virus-induced gene silencing (VIGS) is a technology that has rapidly emerged for gene function studies in plants. Many advances have been made in applying this technique in an increasing number of crops. Recently, VIGS has been successfully used to silence genes in tomato fruit through agroinfiltration of fruit attached to the plant. The phytoene desaturase (Pds) gene has been widely used as a reporter gene in VIGS experiments, although little is known about the changes that occur due to its silencing in plants. In this paper, we describe the efficient silencing of the Pds gene through the VIGS approach in detached tomato fruits, which makes the VIGS procedure even more versatile and applicable. After 16 days of agroinfiltration, approximately 75% of the tomatoes showed Pds silencing symptoms, although the distribution of silenced areas was variable among fruits. To study the potential effects caused by Pds silencing in detached tomatoes, carotenoids and other semi-polar secondary metabolites were analyzed using Liquid Chromatography-Mass Spectrometry. In addition, potential differences in primary metabolites were analyzed using Gas Chromatography-Mass Spectrometry. The results indicated that the yellow phenotype observed in Pds-silenced fruit was mainly due to the lack of the red-colored lycopene and therefore to a more pronounced contribution of the yellow-orange carotenoids (lutein, violaxanthin, and zeaxanthin) to the final color of the fruits. Furthermore, the biochemical changes observed in Pds-silenced detached tomatoes suggested that carotenoid and other pathways, e.g. leading to alkaloids and flavonoids, might be affected by the silencing of this reporter gene, and this should be taken into consideration for future experimental designs.     

Role of voltage-dependent anion channels of the mitochondrial outer membrane in regulation of cell metabolism

The role of voltage-dependent anion channels (VDAC/porins) of the mitochondrial outer membrane in the regulation of cell metabolism is assessed using an experimental model of ethanol toxicity in cultured hepatocytes. It is demonstrated that ethanol inhibits the phosphorylating and the uncoupled mitochondrial respiration, decreases the accessibility of mitochondrial adenylate kinase in the intermembrane space, and suppresses ureagenic respiration in the cells. Treatment with digitonin at high concentrations (>80 μM)—which creates pores in the mitochondrial outer membrane, allowing bypass of closed VDAC—restores all the processes suppressed with ethanol. It is concluded that the effect of ethanol in hepatocytes leads to global loss of mitochondrial function because of closure of VDAC, which limits the free diffusion of metabolites into the intermembrane space. Our studies also reveal the role of VDAC in the regulation of liver-specific intracellular processes such as ureagenesis. The data obtained can be used in development of pharmaceuticals that would prevent VDAC closure in mitochondria of ethanol-oxidizing liver, thus protecting liver tissue from the hepatotoxic action of alcohol.