Mammalian cells contraction

Goodwin Biotechnology, Inc. (GBI) is a fully integrated GMP contract manufacturer of mammalian cell products providing process development (upstream and downstream) and cell banking through production, purification, and sterile fill. The downstream... 

Glycogen, a major source of energy for muscle contraction, is the principle storage form of glucose in mammalian cells. Glycogen consists mainly of glucose... 

Actin is one of the most abundant cellular proteins and is present in all mammalian cells. F-actin is physically crosslinked to form the cellular cytoskeleton and its contraction allows cell deformation and movement... 

Kirkland, D. J., and Dean, S. W. On the need for confirmation of negative genotoxicity results in vitro and on the usefulness of mammalian cell mutation tests in a core battery Experiences of a contract research laboratory. Mutagenesis 9, 491-501,1994. 

In telophase, nuclei for each daughter cell form at the two poles, and the mitotic spindle apparatus disappears. Furthermore, nuclear membranes, nuclear lamina, nuclear pores, and nucleoli are reformed. The cell is now ready for cytokinesis, which is physical division of the cytoplasm. The cytoplasm divides as actin/myosin filaments contract and pinch off the plasma membrane, which results in two daughter cells that enter into Go or Gi for another round of division. The main checkpoint that exists during M phase in mammalian cells is the spindle checkpoint it is in place to ensure proper microtubule assembly, proper cell division, and that each daughter cell receives one copy of DNA. 

Comparison of Four Types of Mammalian Cells Specialized for Contraction... 

The answer is b. (Murray, pp 199-207. Scriver, pp 1521-1552. Sack, pp 121-138. Wilson, pp 287-31 77) In the presence of low blood glucose, epinephrine or norepinephrine interacts with specific receptors to stimulate adenylate cyclase production of cyclic AMP Cyclic AMP activates protein kinase, which catalyzes phosphorylation and activation of phosphorylase kinase. Activated phosphorylase kinase activates glycogen phosphorylase, which catalyzes the breakdown of glycogen. Phosphorylase kinase can be activated in two ways. Phosphorylation leads to complete activation of phosphorylase kinase. Alternatively, in muscle, the transient increases in levels of Ca" associated with contraction lead to a partial activation of phosphorylase kinase. Ca" " binds to calmodulin, which is a subunit of phosphorylase kinase. Calmodulin regulates many enzymes in mammalian cells through Ca" binding. 

Actin. This is one of the most important components in the cytoskeletal architecture, and in the movement of cytoplasm in eukaryotic cells. In addition to muscle contraction, actin is involved in cellular processes such as phagocytosis, secretion, cell migration, and the maintenance of cell shape. A recent report shows that a mammalian cell arginine-specific ADP-ribosyl transferase can ADP-ribosylate actin molecules, suggesting that this could be a regulatory mechanism in the above cellular functions (Terashima et al., 1992). 

More complex proteins have been produced in mammalian cell culture using recombinant DNA techniques. The gene for Factor VIII, a protein involved in blood clotting, is defective in individuals with hemophilia. Before genetically engineered Factor VIII became available, a number of hemophiliac patients died of AIDS or hepatitis that they contracted from transfusions of contaminated blood or from Factor VIII isolated from contaminated blood. 

The synthesis of prostaglandin and thromboxane hormones by cyclooxygenase enzymes is another important target of NO. With the exception of red blood cells, all mammalian cells release prostaglandins, which have an important role in inflammatory response, formation of blood clots, regulation of blood pressure, and muscle contraction. 

There are many examples in mammalian cells in which the effectuation of hormone action is associated with variations in calcium concentration in the different cellular compartments. Such hormonal actions include stimulation of corticosteroid secretion in the adrenal, the effect of parathyroid hormone on renal tubules, reabsorption and release of calcium from the bone, the effect of melanocyte hormone on melano-phores, the stimulation of smooth muscle contraction by acetylcholine and its retraction by epinephrine, the effect of epinephrine on heart contraction, etc. The role of calcium in the sequence of steps following the hormonal stimulus is often difficult to interpret. 

Sorcin (soluble resistance-related calcium binding protein) was isolated from multidrug-resistant cells and is expressed in a few mammalian tissues such as skeletal muscle, heart, and brain. In the heart, sorcin interacts with the ryanodine receptor and L-type Ca2+-channels regulating excitation in contraction coupling. 

Key findings that demonstrated that the 0 subunit is the essential component of L-type channels have come from studies of the channel activity of the expressed protein. Expression studies performed in mammalian liver fibroblasts have demonstrated that the oti subunit alone can form a channel [77] and contains the receptors for the DHPs, PAAs and diltiazem [64]. In very elegant studies using a mouse model of muscular dysgenesis it has been demonstrated that the ] subunit DNA can restore Ca currents and the charge movement that arises from the voltagesensing function of the channels to the mutant cells that normally lack these activities [21,78,79]. The restoration of these activities restores excitation-contraction coupling. Thus it is clear that the aj subunit is the major functional unit of L-type Ca channels. 

Lipoxygenases catalyse the regio-specific and stereoselective oxygenation of unsaturated fatty acids. The mammalian enzymes have been detected in human platelets, lung, kidney, testes and white blood cells. The leukotrienes, derived from the enzymatic action of the enzyme on arachidonic acid, have effects on neutrophil migration and aggregation, release of lysosomal enzymes, capillary permeability, induction of pain and smooth muscle contraction (Salmon, 1986). 

Devine CE, Somlyo AV, Somlyo AP 1971 Sarcoplasmic reticulum and excitation-contraction coupling in mammalian smooth muscles. J Cell Biol 52 690-718 Ebashi S 1991 Excitation—contraction coupling and the mechanism of muscle contraction. Annu Rev Physiol 53 1—16... 

The gastrointestinal system of zebrafish presents clear differences from the human system. The zebrafish does not possess a stomach, the intestine is continuous with the pharynx through a short esophagus, and no sphincters are present [61]. However, zebrafish have most of the cell types observed in the small intestine -absorptive, endocrine, goblet, and interstitial cells of Cajal, although Paneth cells are absent. Gut contractions are under the control of the enteric nervous systems, which respond to different pharmaceuticals in similar way as the mammalian counterpart. For example, zebrafish embryos can be used as predictor of emetic response to pharmaceuticals, one of the most commonly reported clinical adverse effects to be considered in the development of new dmgs [61]. 

In ihe mammalian body, calcium is required to insure the integrity and permeability of cell membranes. 10 regulate nerve and muscle excitubiliiy. to help maintain normal muscular contraction, and to assure cardiac rhvthmicity. Calcium plays an essential role in several of ihe enzymatic steps involved in blood coagulation and also activates certain other enzyme-catalyzed reactions not involved in any of ihe foregoing processes. Calcium is ihe niosi important element of bone sail. Together with phosphate and carbonate, calcium confers on bone most of its mechanical and structural properties. 

The cell body of a mammalian motor neuron has an extended process termed an axon that branches at its tip to make multiple contacts (synapses) with a muscle cell (fig. S1.1). Some axons actually reach lengths of several meters. Much of the axon may be encased in myelin sheaths, which are multilayered membranes formed by other cells that wrap themselves around the neuron. Shorter processes (dendrites) extend from the cell body to make contacts with other neurons. If a motor neuron is stimulated electrically or is triggered by its connecting neurons, an electric signal called an action potential sweeps down the axon and is transmitted to the muscle cell, which then proceeds to contract. Other... 

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