Results suggest that the observed lower shortening velocity of type 2B fibres following unloading could be related to slowing of acto-myosin kinetics in the presence of MLC phosphorylation.
Short-term dexamethasone administration in healthy subjects elicits quantitative and qualitative adaptations of muscle fibers that precede (and may predict) the clinical appearance of myopathy in glucocorticoid-treated subjects.
The present work reports on the biological activity of alfalfa (Medicago sativa) saponins on white poplar (Populus alba, cultivar 'Villafranca') cell suspension cultures. The extracts from alfalfa roots, aerial parts and seeds were characterized for their saponin content by means of thin layer chromatography (TLC) and electrospray ionisation coupled to mass spectrometry. The quantitative saponin composition from the different plant extracts was determined considering the aglycone moieties and determined by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) analyses. Only soyasapogenin I was detected in the seed extract while several other saponins were found in the root and leaf extracts. Actively proliferating white poplar cell cultures were challenged with the different saponin extracts. Only alfalfa root saponins, at 50 µg ml⁻¹, induced significant cell death rates (75.00 ± 4.90%). Different cell subpopulations with peculiar cell death morphologies were observed and the programmed cell death (PCD)/necrosis ratio was reduced at increasing saponin concentrations. Enhancement of nitric oxide (NO) production was observed in white poplar cells treated with root saponins (RSs) at 50 µg ml⁻¹ and release of reactive oxygen species (ROS) in the culture medium was also demonstrated. Saponin-induced NO production was sensitive to sodium azide and N(G)-monomethyl-L-arginine, two specific inhibitors of distinct pathways for NO biosynthesis in plant cells.
The number of every enzyme is the result of many mechanisms of regulation, at transcriptional and translational levels. We asked if the presence of rare amino acids in the sequence of an enzyme could represent a limiting factor in the balance between enzymes synthesis and enzymes efficiency. To try to find a correlation we analyzed the amino acids sequences of different housekeeping and metabolic enzymes.Like in economical model of pricing there is an equilibrium point between marginal cost and marginal revenue curves in the quantity vs price plot, similarly these concepts can be applied to enzymes synthesis and its energetic cost.The number of copies of a certain enzyme is the result of many mechanisms of translational, transcriptional and post-translational modification regulation.Gene expression can be regulated at several different levels, for example (1-17): Initiation of transcription by repressor or activator proteins Premature termination of transcription by attenuation Initiation of translation by an antisense RNA Chromatin domains Modification of DNA RNA transport mRNA degradation Post-translational by proteolysis or modification of the gene product
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