Metabolism actin

Vitamin D3 (VD3) and retinoids synergistically inhibit the growth and progression of squamous cell carcinomas and actinic keratoses in chronically sun exposed skin. One reason for this synergism may be the direct influence of VD3 on the isomerization and the metabolism of RA. Here, VD3 inhibits the isomerization of 13-cis-RA to the more receptor active all-trans and 9-cis-isomers. Moreover, the VD3 derivative secocholestra-trien-l,3,24-triol (tacalcitol), used for the treatment of severe keratinizing disorders inhibits 4-hydroxylation of all-ri ans-RA. 

A three-dimensional meshwork of proteinaceous filaments of various sizes fills the space between the organelles of all eukaryotic cell types. This material is known collectively as the cytoskeleton, but despite the static property implied by this name, the cytoskeleton is plastic and dynamic. Not only must the cytoplasm move and modify its shape when a cell changes its position or shape, but the cytoskeleton itself causes these movements. In addition to motility, the cytoskeleton plays a role in metabolism. Several glycolytic enzymes are known to be associated with actin filaments, possibly to concentrate substrate and enzymes locally. Many mRNA species appear to be bound by filaments, especially in egg cells where they may be immobilized in distinct regions thereby becoming concentrated in defined tissues upon subsequent cell divisions. 

Ginis, I., Zaner, K., Wang, J.-S., Pavlotsky, N., Tauber, A. I. (1992). Comparison of actin changes and calcium metabolism in plastic- and fibronectin-adherent human neutrophils. J. Immunol. 149, 1388-94. 

RPMI 2650 is the only human nasal epithelial cell line derived from a spontaneously formed tumor. This particular cell line has been mostly used for nasal metabolism studies, since it grows into a multilayer and does not form confluent monolayers (although perijunctional actin rings are present). Thus, RPMI 2650 cell monolayer is rarely used for nasal transport studies [44, 58],... 

Aminolevulinic acid (ALA HCl, Levulan Kerastick) is indicated for the treatment of nonhyperkeratotic actinic keratosis of the face and scalp. It has two components, an alcohol solution vehicle and ALA HCl as a dry solid. The two are mixed prior to application to the skin. When applied to human skin, ALA is metabolized to protoporphyrin, which accumulates and on exposure to visible light produces a photodynamic reaction that generates reactive oxygen species (ROS).The ROS produce cytotoxic effects that may explain therapeutic efficacy. Local burning and stinging of treated areas of skin due to photosensitization can occur. 

The stem cells of the basal cells are located at the level of the limbus, which come from centripetal migration. The daughter cells migrate to form the intermediate cells. Their cytoplasm, which is rich in glycogen and mitochondria, shows their high metabolic activity. It also contains a Golgi s apparatus, some microtubules, and some keratin filaments connected to each other by desmosomes and hemidesmo-somes. Most of all this cytoplasm contains some actin... 

Simulation of glucose transport and glucose transporter translocation from intracellular stores to the plasma membrane in muscle cells by vanadate and peroxovan-adate involve a mechanism independent of PI-3K and protein kinase C systems utilized for stimulation of these processes by insulin. The transport of GLUT4 to the plasma membrane in muscle cells growing in culture after stimulation by vanadate, peroxovanadate, or insulin all require an intact actin network [138], Sometimes, the insulin-like action of vanadium is accompanied by overall stimulation of actual metabolic pathways. One example of this is the stimulation of the pentose phosphate pathway observed when vanadate promotes the incorporation of glucose into lipids, an antilipogenic effect [139],... 

Skeletal muscle is composed of muscle cells, thin and thick filaments, and endomysium, a connective tissue containing fibroblasts that holds the fibers together. Mechanical loading regulates normal muscle metabolism in the absence of normal tensile loading muscle atrophy results. Interactions between thick (myosin) and thin (actin) filaments result in lines or bands containing one or more of the muscle fiber components. The H band represents overlap of only the thick filaments whereas the I band represents the area of overlap of thin and thick filaments. The z lines are the points at which the sarcomere repeats itself. 

Studies involving fluid shear, hydrostatic compression, biaxial and uniaxial stretch, or a combination of two or more of these factors indicate that fluid shear is a major factor affecting bone cell metabolism and cells subjected to mechanical stress reshape and align themselves with their long axis perpendicular to the axis of force. Cells also exhibited remodeling of the actin cytoskeleton and increases in PKC levels, processes thought to be involved in the early phase of mechanochemical transduction. 

In mammals, 25% of the protein in the body is collagen it provides the scaffold that holds the entire body together. Movement is provided almost entirely by interactions of actin with myosin (making muscle) or of kinesin/dynein with microtubules (see also Chapter 21). Few animal materials have the chemical stability of cellulose probably only chitin (primarily in arthropods and fungi, but also part of the metabolic pathway of other animals including man) and elastin. 

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