Hormone regulation of cardiac energy metabolism. I. Creatine transport across cell membranes of euthyroid and hyperthyroid rat heart

Hyperthyroid rat heart was studied with the purpose of identifying the mechanism for the significant decrease in total creatine (free creatine plus phosphocreatine) observed in this pathology and its consequences on heart function. Administration of L-thyroxine in doses of 50-100 micrograms/100 g of body weight during a week resulted in a reversible decrease of the total creatine by 40-50%. Simultaneously, remarkable changes in the creatine transport system across the cardiac cell membranes were observed: both the maximal rate of its active uptake and its passive movement along its concentration gradient were enhanced. In euthyroid hearts, the parameters of creatine uptake (Km approximately or equal to 0.05 mM, Vmax = 20 nmole/min/g dry weight) were similar to those for skeletal muscle and the passive movement of creatine was negligible. In hyperthyroid hearts the latter rate was enhanced to 0.4 mumole min/g dry weight, this showing reversible damages in the cell membrane structure induced by L-thyroxine. This conclusion is consistent with observed penetration of colloidal lanthanum into the cells of hyperthyroid hearts. Perfusion of hyperthyroid rat hearts with 50 mM creatine significantly restored creatine content in the cells, Hyperthyroid hearts with decreased creatine content were found to develop ischemic contracture more rapidly and in higher extent than the euthyroid hearts. Increased sensitivity to ischemic damage may be related to decreased efficiency of energy channeling via phosphocreatine pathway.     

Population Dynamics of the Bream Abramis brama in Lake Peipus

Journal of Ichthyology - Population dynamics of the bream Abramis brama in lakes Peipsi and Pihkva for the period from 1980 to 2009 has been studied by means of cohort models. Bream stock increased...     

4-Alkyl and 4,4'-dialkyl 1,2-bis(4-chlorophenyl)pyrazolidine-3,5-dione derivatives as new inhibitors of bacterial cell wall biosynthesis

Over 195 4-alkyl and 4,4-dialkyl 1,2-bis(4-chlorophenyl)pyrazolidine-3,5-dione derivatives were synthesized, utilizing microwave accelerated synthesis, for evaluation as new inhibitors of bacterial cell wall biosynthesis. Many of them demonstrated good activity against MurB in vitro and low MIC values against gram-positive bacteria, particularly penicillin-resistant Streptococcus pneumoniae (PRSP). Derivative 7l demonstrated antibacterial activity against both gram-positive and gram-negative bacteria. Derivatives 7f and 10a also demonstrated potent nanomolar Kd values in their binding to MurB.     

Isolation of Staphylococcus aureus protoplasts using lysoamidase

The effect of the bacteriolytic enzyme preparation, lysoamidase, on Staphylococcus aureus 209P cells was studied. The protoplast formation was examined by spectrophotometric, biochemical and electron microscopic methods. Optimal conditions for isolation of S. aureus protoplasts were chosen. The susceptibility of S. aureus cells to lysoamidase depended on the culture age: the maximum effect was observed in the logarithmic growth phase. The protoplast yield was 80% when 1 M sucrose was used as an osmotic stabilizer. Lysoamidase caused local disruptures of the staphylococcus cell walls, which resulted in the formation of osmotically fragile spheroplasts and the release of protoplasts into the medium. The protoplasts obtained could retain 85-90% of the respiration activity and were able of cell wall regeneration.     

Specificity of hydrolysis of S. aureus 209P cell walls by a lytic preparation of Pseudomonas lytica

Specificity of Staphylococcus aureus 209P cell wall hydrolysis by a lytic preparation isolated from the culture liquid filtrate of Pseudomonas lytica VKM V-1454D was studied by the dansylation method. The lytic preparation was found to contain the lytic proteinase lysing the cells of Gram-positive microorganisms. The enzyme hydrolysed the cell walls of S. aureus 209P releasing N-terminal glycine and alanine in amounts of 0.73 and 0.34 mumoles per 1 mumole of lysine, respectively, which indicated the cleavage of the bonds in the pentaglycine bridge and, apparently, of the bond between N-acetylmuramic acid.     

Inhibition of 2'-phosphodiesterase by cAMP-dependent protein kinase. Involvement of phosphorylation of protein inhibitor

2'-Phosphodiesterase from NIH 3T3 cells was purified about 530-fold. Treatment of the cell lysate with the cAMP-dependent protein kinase causing the 2'-phosphodiesterase inhibition did not result in phosphorylation of the enzyme itself. The kinase was found to phosphorylate a specific 18-kDa protein, the phosphorylated form of this protein being the inhibitor of 2'-phosphodiesterase.     

Oxygen Degradation in Mesoporous Al2O3/CH3NH3PbI3‐xClx Perovskite Solar Cells: Kinetics and Mechanisms

The rapid pace of development for hybrid perovskite photovoltaics has recently resulted in promising figures of merit being obtained with regard to device stability. Rather than relying upon expensive barrier materials, realizing market‐competitive lifetimes is likely to require the development of intrinsically stable devices, and to this end accelerated aging tests can help identify degradation mechanisms that arise over the long term. Here, oxygen‐induced degradation of archetypal perovskite solar cells under operation is observed, even in dry conditions. With prolonged aging, this process ultimately drives decomposition of the perovskite. It is deduced that this is related to charge build‐up in the perovskite layer, and it is shown that by efficiently extracting charge this degradation can be mitigated. The results confirm the importance of high charge‐extraction efficiency in maximizing the tolerance of perovskite solar cells to oxygen.