Calcium ions transport

This can be accomplished either by reducing the load on the heart, or by lowering systemic venous and arterial pressure (nitrates and nitrites), or by partial suppression of adrenergic innervation of the heart (j3-adrenoreceptors), or by suppressing calcium ion transport in myocardial cells since the contraction of smooth muscles vessels is controlled by the concentration of calcinm ions in the cytoplasm (Ca channel blockers). The resulting effect of the aforementioned drngs is that they reduce the need for oxygen in the heart. 

The acute toxic properties of all the organochlorine pesticides in humans are qualitatively similar. These agents interfere with inactivation of the sodium channel in excitable membranes and cause rapid repetitive firing in most neurons. Calcium ion transport is inhibited. These events affect repolarization and enhance the excitability of neurons. The major effect is central nervous system stimulation. With DDT, tremor may be the first manifestation, possibly continuing to convulsions, whereas with the other compounds convulsions often appear as the first sign of intoxication. There is no specific treatment for the acute intoxicated state, and management is symptomatic. 

Neuropeptides Y (NFY) and YY are 36-residue amidated peptides that are members of the pancreatic polypeptide (PP) family (Fig. 30-5). NPY is produced both in the peripheral nervous system and in the brain,110 134 where it is one of the most abundant neuropeptides. Another member of the PP family is semi-nalplasmin, a regulator of calcium ion transport in bovine sperm.135 NPY is best known for its stimulation of appetite. It also inhibits anxiety and increases memory retention. It has a vasoconstrictive effect on blood vessels, participating in cardiovascular regulation.136 137 Peptide YY is formed in endocrine cells of the intestine, while NPY is formed in neurons of the parasympathetic system.138 Both participate in regulation of fluid and electrolyte secretion. Both are found in other vertebrate species.139... 

Rugolo, M., Pistocchi, R., and Zannoni, D., Calcium ion transport in higher plant mitochondria (Helianthus tuberosus), Physiol. Plant., 79, 297-302, 1990. 

Sarcoplasmic reticulum Ca + ATPase, responsible for calcium ion transport. See Martonosi, A.N. and Pikula, S., The structure of the Ca +-ATPase of sarcoplasmic reticulum, Acta Biochim. Pol. 50, 337-365, 2003 Strehler, E.E. and Treiman, M., Calcium pumps of plasma membrane and cell interior, Curr. Mol. Med. 4, 323-335, 2004. 

Wodzki R and Klosinski P. Magnesium and calcium ions transport by synthetic analogs of teichoic acids with 1,2- and 1,3-hnked phosphodiester units. Makromol Chem, 1990 191(4) 921-931. 

Nucleation of calcium phosphate precipitation within the matrix vesicles is mediated by phosphatidylserine, which comprises about 8% of the phospholipids of the inner cytosolic membrane surface (Fig. 9.5a). Calbindin in the vesicle (Fig. 9.5b) may also contribute. Rapid mineral growth within the vesicle keeps the concentration of dissolved calcium and inorganic phosphate ions so low that additional Ca2+ and Pi ions spontaneously enter from the extracellular fluid via their respective transporters. Attached type II and type X collagens from cartilage in the growth plate enhance calcium ion transport and calcification during endochondral ossification (Fig. 9.5b). 

The type El sodium-dependent phosphate (Na/Pi) transporters involved in mineralization are members of the inorganic phosphate transporter (PiT) family, which is conserved in all biology. El osteoclasts, a proton (H+) gradient instead of a sodium (Na+) gradient transports Pi. These transporters are antiports the Na+ or H+ is transported out as the Pi is transported in (Sects. 2.2.3 and 10.1.4). All these transporters are composed of repeating alpha helices that weave in and out of a membrane with intra- and extracellular turns (Fig. 9.7). A similar kind of structure is proposed for the annexins that mediate calcium ion transport. 

Vitamin D is a fat soluble vitamin related to cholesterol. In the skin, sunlight spontaneously oxidizes cholesterol to 7-dehydrocholesterol. 7-Dehydrocholesterol spontaneously isomerizes to cholecalciferol (vitamin D3), which is oxidized in the liver to 25-hydroxy cholecalciferol and, under the influence of PTH in the kidney, to 1,25-dihy-droxy cholecalciferol (calcitriol), the active form of vitamin D. Vitamin D induces the expression of calcium ion transport proteins (calbindins) in intestinal epithelium, osteoclasts, and osteoblasts. Calbindins and transient receptor potential channels (TRPV) are responsible for the uptake of calcium from the diet. In children, the absence of sunlight provokes a deficiency of vitamin D, causing an absence of calbindins and inadequate blood calcium levels. Osteoid tissue cannot calcify, causing skeletal deformities (rickets). In the elderly, there is a loss of intestinal TRPV receptors and decreased calbindin expression by vitamin D. In both cases, the resultant low blood calcium levels cause poor mineralization during bone remodeling (osteomalacia). Rickets is the childhood expression of osteomalacia. Osteoclast activity is normal but the bone does not properly mineralize. In osteoporosis, the bone is properly mineralized but osteoclasts are overly active. 

The antibiotic calcimycin (or A23187) is a widely used probe for calcium ion transport in biological systems. A synthesis of the core of this antibiotic has been developed [15]. Although little stereoselectivity is associated with this method it is rather remarkable in that two ring closures are involved, the first involving hemi-acetal formation and the second an electrophilic closure (Fig. 12). 

Protons are pumped in living systems to establish a proton gradient, and the energy necessary for this pumping is frequently provided by the hydrolysis of ATP, in which ADP and phosphate are formed [7]. In this section, we study a model of a proton pump found in the plasma membrane of plants [8-12] and include the coupling of potassium and calcium ion transport. As in prior examples, we calculate the thermodynamic efficiency [13] of the proton pump with a constant influx of ATP and compare that to the thermodynamic efficiency with an oscillatory influx of ATP, the average of which is the same as the constant concentration of ATP. 

Calcium ion transport Metabolic process Amino acid transport Cell redox omeostasis Lipidic metabolic process... 

This area also has been covered recently. Several techniques, including Li NMR, have been used to study sarcoplasmic reticular calcium ion transport adenosine triphosphatase. The lithium relaxation rate is high in the presence of the Gd " form of the enzyme because the two ions are close together. Adding Ca " reduces the lithium relaxation rate as Gd " is displaced. Ion-ion distances are estimated. Comparison of the relaxation rates of Li with Li on the Mn " form of pyruvate kinase allows the molecular correlation time to be estimated at 3700 ps so that the Mn-Li distance must be 570 20 pm. Na NMR in the presence of DNA favors the theory that the... 

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